Title of Invention	A LUBRICATION STRUCTURE FOR A DISTRIBUTOR
Abstract	A lubrication structure for a distributor (46) comprises : camshaft-supporting walls (16) provided in cam chambers (14) surrounded by a peripheral head wall of a cylinder head (6) of an I.C. engine (2), a camshaft (18) provided on the camshaft-supporting walls and rotatably supported on cam housings (20) ; a gear chamber (40) provided between a part of the peripheral head wall located at one end of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall (10), the camshaft-supporting wall axially supporting one end of the camshaft and also partitioning the gear chamber (40) from the cam chamber (14) ; a driving gear (42) axially disposed at one end of the camshaft and positioned in the gear chamber ; a mounting hole (44) extending through part of the peripheral head wall and communicating with the gear chamber ; and a driven gear (54) meshing with the driven gear and disposed on a distributor shaft of the distributor, mounted on the cylinder head so that part of the distributor is fitted in the mounting hole, characterized in that at least one return hole (60) extending through the camshaft-supporting wall (16) through which return hole lubricating oil in the gear chamber is returned to the cam chamber.

Title of Invention

A LUBRICATION STRUCTURE FOR A DISTRIBUTOR

Abstract

A lubrication structure for a distributor (46) comprises : camshaft-supporting walls (16) provided in cam chambers (14) surrounded by a peripheral head wall of a cylinder head (6) of an I.C. engine (2), a camshaft (18) provided on the camshaft-supporting walls and rotatably supported on cam housings (20) ; a gear chamber (40) provided between a part of the peripheral head wall located at one end of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall (10), the camshaft-supporting wall axially supporting one end of the camshaft and also partitioning the gear chamber (40) from the cam chamber (14) ; a driving gear (42) axially disposed at one end of the camshaft and positioned in the gear chamber ; a mounting hole (44) extending through part of the peripheral head wall and communicating with the gear chamber ; and a driven gear (54) meshing with the driven gear and disposed on a distributor shaft of the distributor, mounted on the cylinder head so that part of the distributor is fitted in the mounting hole, characterized in that at least one return hole (60) extending through the camshaft-supporting wall (16) through which return hole lubricating oil in the gear chamber is returned to the cam chamber.

Full Text	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a lubrication structure for a distributor. More particularly, it relates to a lubrication structure for a distributor, which is designed to provide a reduced mechanical loss, while maintaining the function of lubricating gears that drive the distributor, to prevent deterioration of lubricating oil, to provide improved maintainability of the distributor, to absorb vibrations from a camshaft, and to prevent a reduced efficiency of transmittance of driving force from the camshaft to the distributor. 2. Description of the Related Art In multi-cylinder internal combustion engines disposed in vehicles, there is such an engine provided with a distributor in order to ignite and combust a mixture in each cylinder. The distributor is driven in synchronism with a rotating crankshaft, and then distributes high electric voltage to an ignition plug for each cylinder. Figs. 9 - 12 illustrates a lubrication structure for such a distributor. In Figs. 9 and 10, reference numeral 102 denotes an internal combustion engine; 104 a cylinder block; 106 1A a cylinder head; and, 108 a head cover. The cylinder head 106 is formed into a substantially rectangular shape, in which the cylinder head 106 is greater in length in a longitudinal direction thereof than in a transverse direction of the cylinder head 106. A peripheral head wall 110 extends around the periphery of the cylinder head 106. The cylinder head 106 has cam chambers 114 disposed above a head body 112 inside the peripheral head wall 110. The cam chambers 114 are surrounded by the peripheral head wall 110. The cam chambers 114 have a plurality of camshaft-supporting walls 116 serially provided in a row in the longitudinal direction of the cylinder head 106. The camshaft-supporting walls 116 are oriented in the transverse direction of the cylinder head 106. A camshaft 118 is provided on the camshaft-supporting walls 116 in a state of being rotatably supported on camshaft housings 120. A gear chamber 122 is provided between part of the peripheral head wall 110 located at one end of the cylinder head 106 in the longitudinal direction thereof (i.e., the right side in Fig. 10) and the camshaft-supporting wall 116 that opposes the aforesaid part of the peripheral head wall 110, which camshaft-supporting wall 116 supports one axial end of the camshaft 118 (i.e., one end of the camshaft 118 on the right side in Fig. 10). The above-identified camshaft-supporting wall 116 partitions the gear chamber 122 from the cam chamber 114. A driving 2 gear 124 is disposed on the camshaft 118 at one axial end thereof. The drive gear 124 is positioned inside the gear chamber 122. A mounting hole 126 is provided through part of the peripheral head wall 110 located at one end of the cylinder head 106 in the transverse direction thereof (the upper side in Fig. 10), which transverse direction is perpendicular to the axial direction of the camshaft 118. The mounting hole 126 is communicated directly to the gear chamber 122. A distributor 128 is mounted on the cylinder head 106 in a state of part of the distributor 128 being fitted in the mounting hole 126. The distributor 128 includes a distributor shaft 130. The distributor shaft 130 is provided with a driven gear 132 that meshes with the driving gear 124. As illustrated in Fig. 11, in this lubrication structure for the distributor 128, when the engine 102 is driven into operation, then lubricating oil flowing upward from the cylinder block 104 is introduced into a first oil passage 136 through a venturi 134. The first oil passage 136 is oriented in the transverse direction of the cylinder block 104. Then, the lubricating , oil in the first passage 136 is led into a second oil passage 138. The second oil passage 138 is directed in the longitudinal direction of the cylinder head 106. As shown in Fig. 12, the lubricating oil in the second oil passage 138 is caused to reach head-side rotatable support portions 142 of the camshaft-supporting walls 116 through sup- 3 port wall oil passages 140. The support wall oil passages 140 are provided on the camshaft-supporting walls 116. Then, the lubricating oil lubricates journal portions 146 of the camshaft 118 between the head-side rotatable support portion 142 and housing-side rotatable support portions 144 of the camshaft housings 120. The camshaft-supporting wall 116 and the camshaft housing 120, both of which oppose the part of the peripheral head wall 110 located at one end of the cylinder head 106 in the longitudinal direction thereof, rotatably support the journal portion 146 of the camshaft 118; and, the lubricating oil, which has lubricated the journal portion 146, is then caused to flow into the cam chamber 114 and the gear chamber 122 through a void space between the head-side rotatable support portion 142, the housing-side rotatable support portion 144, and the journal portion 146. The lubricating oil, which has flowed into the gear chamber 122, lubricates the driving gear 124 and the driven gear 132, both of which drive the distributor 128. One example of the above-described distributor lubrication structure is disclosed in published Japanese Patent Application Laid-Open No. Hei 9-53427. According to the structure in this publication, an engine has a distributor mounted at one ena of a cylinder head in the longitudinal direction thereof by means of a distributor-supporting member. The 4 distributor is connected to a camshaft through an Oldham coupling. The Oldham coupling is located in a coupling chamber inside the distributor-supporting member. In order to lubricate the Oldham coupling, lubricating oil leaking from a leakage hole of an inner intake rocker shaft oil passage is introduced into the aforesaid coupling chamber throu'gh two different oil holes, in which one hole is formed at a portion above the cylinder head, while another hole is defined at a portion above the distributor-supporting member. After such lubrication, the lubricating oil is discharged from the oil hole that is formed at the above-mentioned portion above the distributor-supporting member. In conventional lubrication structures for distributors as shown in Figs. 9 — 12, the gear chamber 122 is isolated from the cam chamber 118 by means of the camshaft-supporting wall 116 that opposes the previously mentioned part of the peripheral head wall 110 located at one end of the cylinder head 106 in the longitudinal direction thereof. As a result, the lubricating oil flowing into the gear chamber 122 is reserved in excess of the full capacity of the gear chamber 122, as illustrated in Fig. 9. This causes an inconvenience in that the lubricating oil is deteriorated because of interruptions in the flow of the lubricating oil into the cam chamber 118. A further inconvenience arises in that the driven gear 132 immersed in the lubricating oil results in an increased mechanical loss. 5 In addition, there occurs a problem in that the lubricating oil held excessively in the gear chamber 122 as previously mentioned escapes out of the mounting hole 126 when the distributor 128 is removed from the mounting hole 126 during practice of maintenance. This means that removal of the distributor 128 involves operations to drain off the lubricating oil from the gear chamber 122 and further to block the escape of the lubricating oil from the mounting hole 126. This brings about another inconvenience of reduced maintainability. A yet further inconvenience is that the lubricating oil discharged outside contaminates the engine 102. SUMMARY OF THE INVENTION In order to obviate the above-described disadvantages, the present invention provides a lubrication structure for a distributor comprising : a plurality of camshaft-supporting walls provided in cam chambers that are surrounded by a peripheral head wall of a cylinder head of an internal combustion engine, said camshaft-supporting walls being arranged in a row in series along a longitudinal direction of the cylinder head, and the camshaft-supporting walls being oriented in a transverse direction of the cylinder head ; a camshaft provided on the camshaft-supporting walls so as to be rotatably supported on cam housings ; -6- a gear chamber provided between a part of the peripheral head wall located at one end of the cylinder head in the longitudinal direction of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall, said camshaft supporting wall supporting one end of the camshaft in an axial direction of the camshaft and also partitioning the gear chamber from the cam chamber ; a driving gear disposed on the camshaft at one end of the camshaft in the axial direction of the camshaft, the driving gear being located in the gear chamber ; a mounting hole extending through part of the peripheral head wall located at one end of the cylinder head in the transverse direction of the cylinder head, which transverse direction is perpendicular to the axial direction of the camshaft, said mounting hole communicating directly with the gear chamber ; and a driven gear disposed on a distributor shaft of said distributor, said distributor being mounted on the cylinder head so that part of the distributor is fitted in said mounting hole, said driven gear being in mesh with said driving gear, characterized in that at least one return hole is provided to extend through said camshaft-supporting wall which partitions said gear chamber from said cam chamber, through which return hole lubricating oil in the gear chamber is returned to the cam chamber. In a first preferred embodiment of the present invention, said return hole comprises a substantially polygonal-shaped return hole extending through the camshaft-supporting wall ; and a bottom surface portion of the return hole is positioned parallel to a horizontal line when the engine is disposed in a vehicle, said bottom surface -7- portion being located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication of the driving gear and the driven gear in the gear chamber, and the bottom surface portion having an enlarged width. In a second embodiment, said return hole comprises a circular return hole extending through the camshaft-supporting wall ; and a curved bottom surface portion of the circular return hole is positioned at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving gear and the driven gear in the gear chamber, and a curved side surface portion of the circular return hole is located outside a revolving course of a tooth width of the driven gear. In a third embodiment, said at least one return hole comprises a plurality of reduced circular return holes having different heights extending through the camshaft-supporting wall, and the lowest one of the circular return holes has a curved bottom surface portion located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving ear and the driven gear in the gear chamber. In a fourth embodiment, said return hole comprises a substantially elliptic return hole extending through the camshaft-supporting wall ; and a bottom surface portion of the return hole extends parallel to a horizontal line when the engine is disposed in a vehicle, said bottom surface portion of the return hole being located at an oil surface level of a required lubricating oil quantity that is -8- necessary for lubrication to the driving gear and the driven gear in the gear chamber, and said bottom surface portion having an enlarged width. In a fifth embodiment, said return hole comprises a substantially inverted triangular-shaped return hole extending through the camshaft-supporting wall ; and a tapered basic angle portion of the return hole is located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving gear and the driven gear in the gear chamber. In the lubrication structure for a distributor, the return hole extends through the camshaft-supporting wall that partitions the gear chamber from the cam chamber, through which return hole the lubrication oil in the gear chamber is returned to the cam chamber. As a result, the lubricating oil is prevented from being retained in the gear chamber in excess of the full capacity of the gear chamber. In addition the lubricating oil can flow smoothly from the gear chamber into the cam chamber without being lodged in the gear chamber. Consequently, no lubricating oil escapes out of the mounting hole when the distributor is removed from the mounting hole. In the lubrication structure for the distributor according to one aspect of the present invention, the substantially polygonal-shaped return hole is provided through the camshaft-supporting wall. In addition, the bottom surface portion of the -9- return hole is positioned parallel to the horizontal line when the internal combustion engine is disposed in the vehicle. This structural feature provides an improved efficiency of outflow when the engine is disposed in the vehicle. Furthermore, the bottom surface portion is located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as mentioned above, and then reliably provides lubricating function. In the lubrication structure for the distributor pursuant to another aspect of the present invention, the circular return hole is provided through the camshaft-supporting wall. This structural feature avoids concentration of stresses, and thus provides improved durability of the camshaft-supporting wall. In addition, the curved bottom surface portion of the return hole is positioned at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as described above, and reliably provides lubricating function. Further, the curved side surface portion of the circular return hole is situated outside the revolving course of a tooth width of the driven gear. This structural feature prevents the lubricating oil stirred up by the drivengear from flowing directly into the 10 cam chamber through the return hole, and then prevents a decrease in such a required lubricating oil quantity as above, with the result that lubricating function is insured. In the lubrication structure for the distributor according to a further aspect of the present invention, a plurality of the smaller circular return holes having different heights are provided through the cam shaft-supporting wall. This structural feature disperses concentration of stresses, and provides improved durability of the camshaft-supporting wall. In addition, the lowest one of the circular return holes has the curved bottom surface portion located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as above, and positively provides lubricating function. In the lubrication structure for the distributor according to yet another aspect of the present invention, the substantially elliptic return, hole is provided through the camshaft-supporting wall. As a result, the camshaft at one axial end thereof can elastically be supported, and such a feature absorbs vibrations from the camshaft, and prevents a reduction in efficiency of transmittance of driving force from the camshaft to the distributor. Furthermore, the bottom surface portion of the return hole is positioned parallel to the horizontal line when the engine is disposed in the vehicle. This structural feature 11 an improved efficiency of outflow when the engine is disposed in the vehicle. Moreover, the bottom surface portion of the return hole is located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature ensures such a required lubricating oil quantity as above, and securely provides lubricating function. In the lubrication structure for the distributor in accordance with yet another aspect of the present invention, a substantially inverted triangular-shaped return hole is provided through the camshaft-supporting wall. As a result, when the lubricating oil in the gear chamber increases in quantity beyond the oil surface level of the required lubricating oil quantity, then an outflow of the lubricating oil to be led into the cam chamber is increased. Consequently, the level of the lubricating oil in the gear chamber can promptly be lowered back to the oil surface level of the required lubricating oil quantity. In addition, a tapered basic angle portion of the return hole is located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as previously described, and thus reliably provides lubricating function. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS -12- Fig. 1 is a cross-sectional view taken along line I-I of Fig. 2, illustrating a cylinder head according to a first embodiment of this invention; Fig. 2 is a plan view, showing the cylinder head, with a head cover of an internal combustion engine being partially broken away; Fig. 3 is a plan view, showing the cylinder head; Fig. 4 is a cross-sectional view taken along line IV-IV of Fig. 3, illustrating the cylinder head; Fig. 5 is a cross-sectional view, illustrating a cylinder head according to a second embodiment; Fig. 6 is a cross-sectional view, illustrating a cylinder head according to a third embodiment; Fig. 7 is a cross-sectional view, showing a cylinder head according to a fourth embodiment; Fig. 8 is a cross-sectional view, showing a cylinder head according to a fifth embodiment; Fig. 9 is a cross-sectional view taken along line IX-IX of Fig. 10, illustrating a cylinder head according to the prior art; Fig. 10 is a plan view, showing the cylinder head, with a head cover of an internal combustion engine being partially broken away; Fig. 11 is a cross-sectional view taken along line 13 XI-XI of Fig. 10, illustrating the cylinder head; and, Fig. 12 is a cross-sectional view taken along line XII-XII of Fig. 10, illustrating the cylinder head. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of this invention will now be described with reference to the drawings. Figs. 1-4 illustrates a first embodiment. In Fig. 1, reference numeral 2 denotes an internal combustion engine; 4 a cylinder block; 6 a cylinder head; and, 8 a head cover. In the engine 2 disposed in a vehicle (not shown), the cylinder head 6 is mounted on the cylinder block 4; and, the head cover 8 is fitted on the cylinder head 6. The cylinder head 6 is formed in a substantially rec-tangular shape, in which the cylinder head 6 is greater in length in a longitudinal direction thereof (i.e., in the rightward and leftward directions in Fig. 2) than in a transverse direction of the cylinder head 6 (i.e., in the upward and downward directions in Fig. 2). A peripheral head wall 10 having a substantially square-cornered tower configuration extends around the periphery of the cylinder head 6. A head body 12 extends inside the peripheral head wall 10. The peripheral head wall 10 surrounds cam chambers 14 that are arranged above the head body 12. As illustrated in Figs. 3 and 4, the cam chambers 14 have a plurality of camshaft-supporting walls 16 arranged in a row in 14 series along the longitudinal direction of the cylinder head 6. The camshaft-supporting walls 16 are oriented in the transverse direction of the cylinder head 6. A camshaft 18 is provided on the camshaft-supporting walls 16 in a state of being rotatably supported on camshaft housings 20. As shown in Figs. 3 and 4, the camshaft-supporting walls 16 are provided with head-side rotatable suprport portions 22. The camshaft housings 20 are provided with housing-side rotatable support portions 24. The camshaft housings 20 are mounted on the camshaft-supporting walls 16 by means of housing-mounting bolts 26. The head-'side rotatable portions 22 and the housing-side rotatable portions 24 rotatably carry journal portions 28 of the camshafts 18. In order to open and close each intake valve and ex-haust valve (not shown), the camshaft 18 causes a seesaw type of an intake rocker arm 34 and a swing type of an exhaust rocker arm 38 to be swung by means of an intake cam 30 and an exhaust cam 36, respectively. The intake rocker arm 34 is rotatably supported on a rocker shaft 32. A gear chamber 40 is provided between part of the peripheral head wall 10 located at one end of the cylinder head 6 in the longitudinal direction thereof (i.e., the right side in Fig. 2) and the camshaft-supporting wall 16 that opposes the aforesaid part of the peripheral head wall 10, which camshaft-supporting wall 16 supports one axial end of the camshaft 18 (i.e., 15 one end of the camshaft 18 on the right side in Fig. 2). The above camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. A driving gear 42 is disposed on the camshaft 18 at one axial end thereof. The driving gear 42 is located in the gear chamber 40. As seen from Fig. 1, a mounting hole 44 is provided through part of the peripheral head wall 10 located at one end of the cylinder head 6 in the transverse direction thereof (i.e., the upper side in Fig. 2), which transverse direction is perpendicular to the axial direction of the camshaft 18. The mounting hole 44 is communicated directly to the gear chamber 40. ¦ A distributor 46 is mounted on the cylinder head 6 in a state of a mounting shaft portion 48 of the distributor 46 being fitted in the mounting hole 44. A mounting flange 50 is mounted on the cylinder head 6 around the hole 44 by means of mounting bolts (not shown). The distributor 46 is provided with a distributor shaft 52 that projects from the mounting shaft 'portion 48 into the gear chamber 40. The distributor shaft 52 is provided with a driven gear 54 that meshes with the driving gear 42. The camshaft 18 is driven in synchronism with a rotating crankshaft (not shown), and then the revolving force of the camshaft 18 is transmitted to the distributor 46 through the driving gear 42 and the driven gears 54. The distributor 46 then distributes high electric voltage to an ignition plug (not 16 shown) for each cylinder. Reference numeral 56 denotes a camshaft pulley disposed on the camshaft 18 at the other axial end thereof. The pulley 56 is communicated to the crankshaft through a timing belt (not shown). Reference numeral 58 denotes a cap. In this lubrication structure for the distributor 46, a return hole 60 is provided through the camshaft-supporting wall 16 that supports one axial end of the camshaft 18 (i.e., one end of the camshaft 18 on the right side in Fig. 2), and further that partitions the gear chamber 40 from the cam chamber 14. Then, the lubricating oil in the gear chamber 40 flows back to the cam chamber 14 through the return hole 60. Pursuant to the first embodiment, the camshaft-supporting wall 16 is provided with the return hole 60 having a "substantially polygonal shape, as shown in Fig. 1. The return hole 60 includes a bottom surface portion 62 that has an enlarged width. The bottom surface portion 62 is positioned parallel to horizontal line "H" when the engine 2 is disposed in a vehicle (not shown). Further, the bottom surface portion 62 is located at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrication to the driving gear 42 and the driven gears 54 in the gear chamber 40. The engine 2 is disposed in the vehicle at angle 0 1 which is formed between cylinder center line "C" of the engine 2 and vertical line "V." In consideration of this angle 01, the bottom surface portion 62 is positioned par- 17 allel to horizontal line "H" at angle 8 2 with reference to cylinder center line "C." Next, the operation of the first embodiment will be . described. As illustrated in Figs. 3 and 4, in the lubrication structure for the distributor 44, when the engine 2 is driven into operation, then a first oil passage causes the lubricating oil flowing upward from the cylinder block 4 to be introduced into a second oil passage 64 through a venturi (not shown). The first oil passage is oriented in the transverse direction of the cylinder head 6. The second oil passage 64 is directed in the longitudinal direction of the cylinder head 6. Then, the lubricating oil in the second oil passage 64 is caused to reach the head-side rotatable support portions 22 through support wall oil passages 66. The support wall oil passages 66 are provided on the camshaft-supporting walls 16. Then, the lubricating oil lubricates the journal portions 28 of the camshaft 18 between the head-side rotatable support portions 22 and the housing-side rotatable support portions 24. The camshaft-supporting wall 16 and the camshaft housing 20, both of which oppose the part of the peripheral head wall 10 located at one end of the cylinder head 6 in the longitudinal direction thereof, rotatably supports the journal portion 28 of the camshaft 18; and, the lubricating oil, which has lubricated the aforesaid journal portion 28, is then caused to 18 flow into the cam chamber 14 and the gear chamber 40 as well through a void space that is formed between the head-side ro-tatable support portion 22, the housing-side rotatable support portion 24, and the journal portion 28. The lubricating oil, which is led into the gear chamber 40, lubricates the driving gear 42 and the driven gears 54, both of which gears drive the distributor 46. The lubricating oil in the gear chamber 40 is then returned to the cam chamber 14 through the return hole 60. As previously described, in the present lubrication structure for the distributor 46, the return hole 60 is provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. The lubricating oil in the gear chamber 40 is caused to flow back into the cam chamber 14 through the return hole 60. As a result, in the above-described lubrication structure for the distributor 46, the lubricating oil is prevented from being reserved in the gear chamber 40 in excess of the full capacity of the gear chamber 40. In addition, the lubricating oil can flow smoothly from the gear chamber 40 into the cam chamber 14 without being lodged in the gear chamber 40. Consequently, no lubricating oil escapes out of the mounting hole 44 when the distributor 46 is removed from the mounting hole 44. Accordingly, the present lubrication structure for 19 the distributor 46 precludes the driven gear 54 from being immersed in the lubricating oil, and thus provides a reduced mechanical loss, while maintaining the function of providing lubrication to the gears 42 and 54, both of which gears 42 and 54 drive the distributor 46. In addition, the present lubrication structure for the distributor 46 precludes the lubricating oil from staying in the gear chamber 40, and thus prevents deterioration of the lubricating oil. Furthermore, the present lubrication structure for the distributor 46 eliminates the need to take steps of: draining off the lubricating oil from the gear chamber 40 before the distributor 46 is removed from the mounting hole 44; and, blocking escape of the lubricating oil from the mounting hole 44. As a result, improved maintainability is provided. In addition, no lubricating oil discharge occurs, which otherwise would contaminate the engine 2. Furthermore, in the lubrication structure for the distributor 46 according to the first embodiment, the substan- tially polygonal-shaped return hole 60 is provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 separates the gear chamber 40 from the cam chamber 14. The bottom surface portion 62 of the return hole 60 is positioned parallel to horizontal line "H" when the engine 2 is disposed in the vehicle. At the same time, the bottom surface portion 62 is located at oil surface level "L" of the required lubricating oil quantity neces- 20 sary for lubrication to the driving gear 42 and the driven gear 54 in the gear chamber 40. In the lubrication structure for the distributor 46 according to the first embodiment, the bottom surface portion 62 is positioned parallel to horizontal line "H" when the engine 2 is disposed in the vehicle. This structural feature provides an improved efficiency of outflow when the engine 2 is disposed in the' vehicle. In addition, the bottom surface portion 62 is located at the aforesaid oil surface level "L". This structural feature insures such a required lubricating oil quantity as mentioned above, and then reliably provides lubricating function. Fig. 5 illustrates a second embodiment "SG1". In a lubrication structure for a distributor 46 according to this embodiment, a circular return hole 68 is provided through a cam-shaft-supporting wall 16 that is located at one axial end of a camshaft 18, which camshaft-supporting wall 16 partitions a gear chamber 40 from a cam chamber 14. The return hole 68 has a curved bottom surface portion 70 and a curved side surface portion 72. The bottom surface portion 70 is positioned at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrication to a driving gear 42 and a driven gear 54 in the gear chamber 40. The side surface portion 72 lies outside a revolving course of tooth width "W" of the driven gear 54. As previously described, in the lubrication structure 21 for the distributor 46 pursuant to the second embodiment, the return hole 68 is provided through the aforesaid camshaft-supporting wall 16, through which hole 68 the lubricating oil in the gear chamber 40 is delivered back to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while maintaining the function of providing lubrication to the gears 42 and 54. In addition, the'above structural feature prevents deterioration of the lubricating oil, and further provides improved maintainability, with the result that no lubricating oil discharge contaminates the engine 2. In the lubrication structure for the distributor 46 according to the second embodiment, the circular return hole 68 is provided through the camshaft-supporting wall 16 that is lo-cated at one axial end of the camshaft 18, which camshaft-supporting wall 16 separates the gear chamber 40 from the cam chamber 14. This structural feature avoids concentration of stresses, and thus provides improved durability of the camshaft-supporting wall 16. Furthermore, the bottom surface portion 70 of the return hole 68 is positioned at the aforesaid oil surface level "L". This structural feature insures such a re-quired lubricating oil quantity as described above, and reliably provides lubricating function. Further, in the lubrication structure for the distributor 46 according to the second embodiment, the side surface 22 , portion 72 of the circular return hole 68 is situated outside the revolving course of tooth width "W" of the driven gear 54. This structural feature prevents the lubricating oil stirred up by the driven gear 54 from flowing directly into the cam chamber 14 through the return hole 68, and then prevents a decrease in such a required lubricating oil quantity as above, with the result that lubricating function is insured. Fig. 6 illustrates a third embodiment "SG2". In a lubrication structure for a distributor 46 according to this embodiment, a plurality of smaller circular return holes 74 having different heights are provided through a camshaft-supporting wall 16 that is located at one axial end of a camshaft 18, which camshaft-supporting wall 16 partitions a gear chamber 40 from a cam chamber 14. The return holes 74 are arranged and slanted at angle 0 3 with reference to oil surface level "L" of a required lubricating oil quantity. The lowest one of the return holes 74 has a curved bottom surface portion 76 positioned at oil surface level "L" of the required lubricating oil quantity that is necessary for lubrication to a driving gear 42 and a driven gear 54 in the gear chamber 40. As described above, in the lubrication structure for the distributor 46 according to the third embodiment, the plurality of the' smaller circular return holes 74 are arranged through the aforesaid camshaft-supporting wall 16, through which holes 74 the lubricating oil in the gear chamber 40 is 23 caused to flow back to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while sustaining the function of providing lubrication to the gears 42 and 54. In addition, the above structural feature prevents deterioration of the lubricating oil, and further provides improved maintainability, with the result that no lubricating oil discharge contaminates the engine 2. In the lubrication structure for the distributor 46 according to the third embodiment, the plurality of the smaller circular return holes 74 are provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. This structural feature disperses concentration of stresses, and provides improved durability of the camshaft-supporting wall 16. In addition, since the return holes 74 are arranged at different heights, then the lubricating oil is caused to flow into the cam chamber 14 in stages in greater amounts when the lubricating oil in the gear chamber 44 increases in quantity beyond the aforesaid oil surface level "L". As a result, the level of the lubricating oil in the gear chamber 44 can promptly be lowered back to oil surface level "L". Furthermore, in the lubrication structure for the distributor 46 according to the third embodiment, the lowest one of the circular return holes 74 has the curved bottom surface 24 . portion 76 located at the aforesaid oil surface level "L". This structural feature insures such a required lubricating oil quantity as above, and positively provides lubricating function. Fig. 7 illustrates a fourth embodiment "SG3". In a lubrication structure for a distributor 46 according to this embodiment, a substantially elliptic return hole 78 is provided through a camshaft-supporting wall 16 that is positioned at one axial end of a camshaft 18, which camshaft-supporting wall 18 partitions a gear chamber 40 from a cam chamber 14. The return hole 78 includes a bottom surface portion 80 having an enlarged width, and a ceiling surface portion 82 having an enlarged width. The ceiling surface portion 82 is parallel to the bottom surface portion 80 in an opposed relationship with one another. The bottom surface portion 80 is positioned parallel to horizontal line "H" when the engine 2 is disposed in a vehicle. Further, the bottom surface portion 80 is located at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrica-. tion to a driving gear 42 and a driven gear 54 in the gear chamber 40. The engine 2 is disposed in the vehicle at angle 0 1 which is formed between cylinder center line "C" of the engine 2 and vertical line "V". In consideration of the above angle 0 1, the bottom surface portion 80 is positioned parallel to horizontal line "H" at angle 0 2 with reference to cylinder center line "C". As previously described, in the lubrication structure for the distributor 46 according to the fourth embodiment, the 25 - return hole 78 is provided through the above-described camshaft-supporting wall 16, through which hole 78 the lubricating oil in the gear chamber 40 is returned to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while retaining the function of providing lubrication to the gears 42 and 54. In addition, the above structural feature prevents deterioration of the lubricat-ing oil, provides improved maintainability, and eliminates lubricating oil discharge that otherwise would contaminate the engine 2. In the lubrication structure for the distributor 46 according to the fourth embodiment, the substantially elliptic return hole 78 is provided through the camshaft-supporting wall 16 that is positioned at one axial end of the camshaft 18, which camshaft-supporting wall 18 partitions the gear chamber 40 from the cam chamber 14. This structural feature allows for elastic deformation of the camshaft-supporting wall 16 that supports one axial end of the camshaft 18, and the camshaft 18 can elastically be supported. Such a feature absorbs vibrations from the camshaft 18, and prevents a reduction in efficiency of transmittance of driving force from the camshaft 18 to the distributor 46. Furthermore, the bottom surface portion 80 of the return hole 78 is positioned parallel to horizontal line "H" when the engine 2 is disposed in the vehicle. This structural feature provides an improved efficiency of outflow when the engine 2 is 26 disposed in the vehicle. Furthermore, in the lubrication structure for the distributor 46 according to the fourth embodiment, the bottom surface portion 80 of the return hole 78 is located at the above-described oil surface level "L". This structural feature insures such a required lubricating oil quantity as above, and securely provides lubricating function. Fig. 8 illustrates a fifth embodiment "SG4". In a lubrication structure for a distributor 46 according to this embodiment, a substantially inverted triangular-shaped return hole 84 is provided through a camshaft-supporting wall 16 that is positioned at one axial end of a camshaft 18, which camshaft-supporting wall 16 partitions a gear chamber 40 from a cam chamber 14. The return hole 84 includes a tapered basic angle portion 86 and a ceiling surface portion 88, the latter having an enlarged width. The ceiling surface portion 88 is positioned in an opposed relationship to the basic angle portion 86. The ba-sic angle portion 86 is located at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrication to a driving gear 42 and a driven gear 54 in the gear chamber 40. In addition, the ceiling surface portion 88 is positioned parallel to horizontal line "H" when the engine 2 is disposed in a vehicle. As previously mentioned, in the lubrication struc-ture for the distributor 46 according to the fifth embodiment, the return hole 84 is provided through the above-described cam- 27 shaft-supporting wall 16, through which hole 84 the lubricating oil in the gear chamber 40 is returned to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while retaining the function of providing lubrication to the gears 42 and 54. In addition, the above feature prevents the deterioration of the lubricating oil, and provides improved maintainability. Yet further, no lubricating oil escape occurs, which otherwise would contaminate the engine 2. In the lubrication structure for the distributor 46 according to the fifth embodiment, the substantially inverted triangular-shaped return hole 84 is provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. As a result, when the lubricating oil in the gear chamber 40 increases in quantity beyond the aforesaid oil surface level "L", then an outflow of the lubricating oil to be fed into the cam chamber '14 is increased. Consequently, the level of the lubricating oil in the gear chamber 40 can promptly be lowered back to oil surface level "L", In addition, the basic angle portion 86 of the return hole 84 is located at the above-described oil surface level "L". This structural feature insures such a required lubricating oil quantity as previously described, and thus reliably provides lubricating function. 28 As evidenced by the above description, the lubrication structure for the distributor according to this invention precludes the driven gear from being immersed in the lubricating oil, and then provides a reduced mechanical loss, while maintaining the function of providing lubrication to the gears that drive the distributor. In addition, the present lubrication structure for the distributor precludes the lubricating oil from staying in the gear chamber, and thus prevents deterioration of the lubricating oil by virtue of smooth circulation of the lubricating oil. Further, the present lubrication structure for the distributor eliminates operations to drain off the lubricating oil from the gear chamber when the distributor is removed from the mounting hole, and further to block escape of the lubricating oil from the mounting hole. Such a feature provides improved maintainability. In addition, no lubricating oil discharge occurs, which otherwise would contaminate the engine. 29 WE CLAIM : 1. A lubrication structure for a distributor comprising : a plurality of camshaft-supporting walls provided in cam chambers that are surrounded by a peripheral head wall of a cylinder head of an internal combustion engine, said camshaft-supporting walls being arranged in a row in series along a longitudinal direction of the cylinder head, and the camshaft-supporting walls being oriented in a transverse direction of the cylinder head ; a camshaft provided on the camshaft-supporting walls so as to be rotatably supported on cam housings ; a gear chamber provided between a part of the peripheral head wall located at one end of the cylinder head in the longitudinal direction of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall, said camshaft-supporting wall supporting one end of the camshaft in an axial direction of the camshaft and also partitioning the gear chamber from the cam chamber ; a driving gear disposed on the camshaft at one end of the camshaft in the axial direction of the camshaft, the driving gear being located in the gear chamber ; a mounting hole extending through part of the peripheral head wall located at one end of the cylinder head in the transverse direction of the cylinder head, which transverse direction is perpendicular to the axial direction of the camshaft, said mounting hole communicating directly with the gear chamber ; and -30- a driven gear disposed on a distributor shaft of said distributor, said distributor being mounted on the cylinder head so that part of the distributor is fitted in said mounting hole, said driven gear being in mesh with said driving gear, characterized in that at least one return hole is provided to extend through said camshaft-supporting wall which partitions said gear chamber from said cam chamber, through which return hole lubricating oil in the gear chamber is returned to the cam chamber. 2. A lubrication structure for a distributor as claimed in claim 1, wherein said return hole comprises a substantially polygonal-shaped return hole extending through the camshaft-supporting wall ; and a bottom surface portion of the return hole is positioned parallel to a horizontal line when the engine is disposed in a vehicle, said bottom surface portion being located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication of the driving gear and the driven gear in the gear chamber, and the bottom surface portion having an enlarged width. 3. A lubrication structure for a distributor as claimed in claim 1, wherein said return hole comprises a circular return hole extending through the camshaft-supporting wall ; and a curved bottom surface portion of the circular return hole is positioned at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving gear and the driven gear in the gear chamber, and a curved side surface portion of the circular return hole is located outside a revolving course of a tooth width of the driven gear. -31- 4. A lubrication structure for a distributor as claimed in claim 1, wherein said at least one return hole comprises a plurality of reduced circular return holes having different heights extending through the camshaft-supporting wall, and the lowest one of the circular return holes has a curved bottom surface portion located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving ear and the driven gear in the gear chamber. 5. A lubrication structure for a distributor as claimed in claim 1, wherein said return hole comprises a substantially elliptic return hole extending through the camshaft-supporting wall ; and a bottom surface portion of the return hole extends parallel to a horizontal line when the engine is disposed in a vehicle, said bottom surface portion of the return hole being located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving gear and the driven gear in the gear chamber, and said bottom surface portion having an enlarged width. 6. A lubrication structure for a distributor as claimed in claim 1, wherein said return hole comprises a substantially inverted triangular- shaped return hole extending through the camshaft-supporting wall ; and a tapered basic angle portion of the return hole is located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving gear and the driven gear in the gear chamber. -32- -33- 7. A lubrication structure for a distributor, substantially as herein described, particularly with reference to and as illustrated in figures 1 to 8 of the accompanying drawings. 8. A distributor incorporating a lubrication structure, as claimed in any of claims 1 to 6. A lubrication structure for a distributor (46) comprises : camshaft-supporting walls (16) provided in cam chambers (14) surrounded by a peripheral head wall of a cylinder head (6) of an I.C. engine (2), a camshaft (18) provided on the camshaft-supporting walls and rotatably supported on cam housings (20) ; a gear chamber (40) provided between a part of the peripheral head wall located at one end of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall (10), the camshaft-supporting wall axially supporting one end of the camshaft and also partitioning the gear chamber (40) from the cam chamber (14) ; a driving gear (42) axially disposed at one end of the camshaft and positioned in the gear chamber ; a mounting hole (44) extending through part of the peripheral head wall and communicating with the gear chamber ; and a driven gear (54) meshing with the driven gear and disposed on a distributor shaft of the distributor, mounted on the cylinder head so that part of the distributor is fitted in the mounting hole, characterized in that at least one return hole (60) extending through the camshaft-supporting wall (16) through which return hole lubricating oil in the gear chamber is returned to the cam chamber.

Full Text

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a lubrication structure for a distributor. More particularly, it relates to a lubrication structure for a distributor, which is designed to provide a reduced mechanical loss, while maintaining the function of lubricating gears that drive the distributor, to prevent deterioration of lubricating oil, to provide improved maintainability of the distributor, to absorb vibrations from a camshaft, and to prevent a reduced efficiency of transmittance of driving force from the camshaft to the distributor.
2. Description of the Related Art
In multi-cylinder internal combustion engines disposed in vehicles, there is such an engine provided with a distributor in order to ignite and combust a mixture in each cylinder. The distributor is driven in synchronism with a rotating crankshaft, and then distributes high electric voltage to an ignition plug for each cylinder.
Figs. 9 - 12 illustrates a lubrication structure for such a distributor. In Figs. 9 and 10, reference numeral 102 denotes an internal combustion engine; 104 a cylinder block; 106
1A

a cylinder head; and, 108 a head cover. The cylinder head 106 is formed into a substantially rectangular shape, in which the cylinder head 106 is greater in length in a longitudinal direction thereof than in a transverse direction of the cylinder head 106. A peripheral head wall 110 extends around the periphery of the cylinder head 106. The cylinder head 106 has cam chambers 114 disposed above a head body 112 inside the peripheral head wall 110. The cam chambers 114 are surrounded by the peripheral head wall 110.
The cam chambers 114 have a plurality of camshaft-supporting walls 116 serially provided in a row in the longitudinal direction of the cylinder head 106. The camshaft-supporting walls 116 are oriented in the transverse direction of the cylinder head 106. A camshaft 118 is provided on the camshaft-supporting walls 116 in a state of being rotatably supported on camshaft housings 120.
A gear chamber 122 is provided between part of the peripheral head wall 110 located at one end of the cylinder head 106 in the longitudinal direction thereof (i.e., the right side in Fig. 10) and the camshaft-supporting wall 116 that opposes the aforesaid part of the peripheral head wall 110, which camshaft-supporting wall 116 supports one axial end of the camshaft 118 (i.e., one end of the camshaft 118 on the right side in Fig. 10). The above-identified camshaft-supporting wall 116 partitions the gear chamber 122 from the cam chamber 114. A driving
2

gear 124 is disposed on the camshaft 118 at one axial end thereof. The drive gear 124 is positioned inside the gear chamber 122.
A mounting hole 126 is provided through part of the peripheral head wall 110 located at one end of the cylinder head 106 in the transverse direction thereof (the upper side in Fig. 10), which transverse direction is perpendicular to the axial direction of the camshaft 118. The mounting hole 126 is communicated directly to the gear chamber 122.
A distributor 128 is mounted on the cylinder head 106 in a state of part of the distributor 128 being fitted in the mounting hole 126. The distributor 128 includes a distributor shaft 130. The distributor shaft 130 is provided with a driven gear 132 that meshes with the driving gear 124.
As illustrated in Fig. 11, in this lubrication structure for the distributor 128, when the engine 102 is driven into operation, then lubricating oil flowing upward from the cylinder block 104 is introduced into a first oil passage 136 through a venturi 134. The first oil passage 136 is oriented in the transverse direction of the cylinder block 104. Then, the lubricating , oil in the first passage 136 is led into a second oil passage 138. The second oil passage 138 is directed in the longitudinal direction of the cylinder head 106.
As shown in Fig. 12, the lubricating oil in the second oil passage 138 is caused to reach head-side rotatable support portions 142 of the camshaft-supporting walls 116 through sup-
3

port wall oil passages 140. The support wall oil passages 140 are provided on the camshaft-supporting walls 116. Then, the lubricating oil lubricates journal portions 146 of the camshaft 118 between the head-side rotatable support portion 142 and housing-side rotatable support portions 144 of the camshaft housings 120.
The camshaft-supporting wall 116 and the camshaft housing 120, both of which oppose the part of the peripheral head wall 110 located at one end of the cylinder head 106 in the longitudinal direction thereof, rotatably support the journal portion 146 of the camshaft 118; and, the lubricating oil, which has lubricated the journal portion 146, is then caused to flow into the cam chamber 114 and the gear chamber 122 through a void space between the head-side rotatable support portion 142, the housing-side rotatable support portion 144, and the journal portion 146.
The lubricating oil, which has flowed into the gear chamber 122, lubricates the driving gear 124 and the driven gear 132, both of which drive the distributor 128.
One example of the above-described distributor lubrication structure is disclosed in published Japanese Patent Application Laid-Open No. Hei 9-53427. According to the structure in this publication, an engine has a distributor mounted at one ena of a cylinder head in the longitudinal direction thereof by means of a distributor-supporting member. The
4

distributor is connected to a camshaft through an Oldham coupling. The Oldham coupling is located in a coupling chamber inside the distributor-supporting member. In order to lubricate the Oldham coupling, lubricating oil leaking from a leakage hole of an inner intake rocker shaft oil passage is introduced into the aforesaid coupling chamber throu'gh two different oil holes, in which one hole is formed at a portion above the cylinder head, while another hole is defined at a portion above the distributor-supporting member. After such lubrication, the lubricating oil is discharged from the oil hole that is formed at the above-mentioned portion above the distributor-supporting member.
In conventional lubrication structures for distributors as shown in Figs. 9 — 12, the gear chamber 122 is isolated from the cam chamber 118 by means of the camshaft-supporting wall 116 that opposes the previously mentioned part of the peripheral head wall 110 located at one end of the cylinder head 106 in the longitudinal direction thereof.
As a result, the lubricating oil flowing into the gear chamber 122 is reserved in excess of the full capacity of the gear chamber 122, as illustrated in Fig. 9. This causes an inconvenience in that the lubricating oil is deteriorated because of interruptions in the flow of the lubricating oil into the cam chamber 118. A further inconvenience arises in that the driven gear 132 immersed in the lubricating oil results in an increased mechanical loss.
5

In addition, there occurs a problem in that the lubricating oil held excessively in the gear chamber 122 as previously mentioned escapes out of the mounting hole 126 when the distributor 128 is removed from the mounting hole 126 during practice of maintenance.
This means that removal of the distributor 128 involves operations to drain off the lubricating oil from the gear chamber 122 and further to block the escape of the lubricating oil from the mounting hole 126. This brings about another inconvenience of reduced maintainability. A yet further inconvenience is that the lubricating oil discharged outside contaminates the engine 102.
SUMMARY OF THE INVENTION
In order to obviate the above-described disadvantages, the present invention provides a lubrication structure for a distributor comprising :
a plurality of camshaft-supporting walls provided in cam chambers that are surrounded by a peripheral head wall of a cylinder head of an internal combustion engine, said camshaft-supporting walls being arranged in a row in series along a longitudinal direction of the cylinder head, and the camshaft-supporting walls being oriented in a transverse direction of the cylinder head ;
a camshaft provided on the camshaft-supporting walls so as to be rotatably supported on cam housings ;
-6-

a gear chamber provided between a part of the peripheral head wall located at one end of the cylinder head in the longitudinal direction of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall, said camshaft supporting wall supporting one end of the camshaft in an axial direction of the camshaft and also partitioning the gear chamber from the cam chamber ;
a driving gear disposed on the camshaft at one end of the camshaft in the axial direction of the camshaft, the driving gear being located in the gear chamber ;
a mounting hole extending through part of the peripheral head wall located at one end of the cylinder head in the transverse direction of the cylinder head, which transverse direction is perpendicular to the axial direction of the camshaft, said mounting hole communicating directly with the gear chamber ; and
a driven gear disposed on a distributor shaft of said distributor, said distributor being mounted on the cylinder head so that part of the distributor is fitted in said mounting hole, said driven gear being in mesh with said driving gear,
characterized in that at least one return hole is provided to extend through said camshaft-supporting wall which partitions said gear chamber from said cam chamber, through which return hole lubricating oil in the gear chamber is returned to the cam chamber.
In a first preferred embodiment of the present invention, said return hole comprises a substantially polygonal-shaped return hole extending through the camshaft-supporting wall ; and a bottom surface portion of the return hole is positioned parallel to a horizontal line when the engine is disposed in a vehicle, said bottom surface
-7-

portion being located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication of the driving gear and the driven gear in the gear chamber, and the bottom surface portion having an enlarged width.
In a second embodiment, said return hole comprises a circular return hole extending through the camshaft-supporting wall ; and a curved bottom surface portion of the circular return hole is positioned at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving gear and the driven gear in the gear chamber, and a curved side surface portion of the circular return hole is located outside a revolving course of a tooth width of the driven gear.
In a third embodiment, said at least one return hole comprises a plurality of reduced circular return holes having different heights extending through the camshaft-supporting wall, and the lowest one of the circular return holes has a curved bottom surface portion located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving ear and the driven gear in the gear chamber.
In a fourth embodiment, said return hole comprises a substantially elliptic return hole extending through the camshaft-supporting wall ; and a bottom surface portion of the return hole extends parallel to a horizontal line when the engine is disposed in a vehicle, said bottom surface portion of the return hole being located at an oil surface level of a required lubricating oil quantity that is
-8-

necessary for lubrication to the driving gear and the driven gear in the gear chamber, and said bottom surface portion having an enlarged width.
In a fifth embodiment, said return hole comprises a substantially inverted triangular-shaped return hole extending through the camshaft-supporting wall ; and a tapered basic angle portion of the return hole is located at an oil surface level of a required lubricating oil quantity that is necessary for lubrication to the driving gear and the driven gear in the gear chamber.
In the lubrication structure for a distributor, the return hole extends through the camshaft-supporting wall that partitions the gear chamber from the cam chamber, through which return hole the lubrication oil in the gear chamber is returned to the cam chamber. As a result, the lubricating oil is prevented from being retained in the gear chamber in excess of the full capacity of the gear chamber. In addition the lubricating oil can flow smoothly from the gear chamber into the cam chamber without being lodged in the gear chamber. Consequently, no lubricating oil escapes out of the mounting hole when the distributor is removed from the mounting hole.
In the lubrication structure for the distributor according to one aspect of the present invention, the substantially polygonal-shaped return hole is provided through the camshaft-supporting wall. In addition, the bottom surface portion of the
-9-

return hole is positioned parallel to the horizontal line when the internal combustion engine is disposed in the vehicle. This structural feature provides an improved efficiency of outflow when the engine is disposed in the vehicle. Furthermore, the bottom surface portion is located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as mentioned above, and then reliably provides lubricating function.
In the lubrication structure for the distributor pursuant to another aspect of the present invention, the circular return hole is provided through the camshaft-supporting wall. This structural feature avoids concentration of stresses, and thus provides improved durability of the camshaft-supporting wall. In addition, the curved bottom surface portion of the return hole is positioned at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as described above, and reliably provides lubricating function. Further, the curved side surface portion of the circular return hole is situated outside the revolving course of a tooth width of the driven gear. This structural feature prevents the lubricating oil stirred up by the drivengear from flowing directly into the
10

cam chamber through the return hole, and then prevents a decrease in such a required lubricating oil quantity as above, with the result that lubricating function is insured.
In the lubrication structure for the distributor according to a further aspect of the present invention, a plurality of the smaller circular return holes having different heights are provided through the cam shaft-supporting wall. This structural feature disperses concentration of stresses, and provides improved durability of the camshaft-supporting wall. In addition, the lowest one of the circular return holes has the curved bottom surface portion located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as above, and positively provides lubricating function.
In the lubrication structure for the distributor according to yet another aspect of the present invention, the substantially elliptic return, hole is provided through the camshaft-supporting wall. As a result, the camshaft at one axial end thereof can elastically be supported, and such a feature absorbs vibrations from the camshaft, and prevents a reduction in efficiency of transmittance of driving force from the camshaft to the distributor. Furthermore, the bottom surface portion of the return hole is positioned parallel to the horizontal line when the engine is disposed in the vehicle. This structural feature
11

an improved efficiency of outflow when the engine is disposed in the vehicle. Moreover, the bottom surface portion of the return hole is located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature ensures such a required lubricating oil quantity as above, and securely provides lubricating function.
In the lubrication structure for the distributor in accordance with yet another aspect of the present invention, a substantially inverted triangular-shaped return hole is provided through the camshaft-supporting wall. As a result, when the lubricating oil in the gear chamber increases in quantity beyond the oil surface level of the required lubricating oil quantity, then an outflow of the lubricating oil to be led into the cam chamber is increased. Consequently, the level of the lubricating oil in the gear chamber can promptly be lowered back to the oil surface level of the required lubricating oil quantity. In addition, a tapered basic angle portion of the return hole is located at the oil surface level of the required lubricating oil quantity that is necessary for lubrication to the driving and driven gears in the gear chamber. This structural feature insures such a required lubricating oil quantity as previously described, and thus reliably provides lubricating function.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
-12-

Fig. 1 is a cross-sectional view taken along line I-I of Fig. 2, illustrating a cylinder head according to a first embodiment of this invention;
Fig. 2 is a plan view, showing the cylinder head, with a head cover of an internal combustion engine being partially broken away;
Fig. 3 is a plan view, showing the cylinder head;
Fig. 4 is a cross-sectional view taken along line IV-IV of Fig. 3, illustrating the cylinder head;
Fig. 5 is a cross-sectional view, illustrating a cylinder head according to a second embodiment;
Fig. 6 is a cross-sectional view, illustrating a cylinder head according to a third embodiment;
Fig. 7 is a cross-sectional view, showing a cylinder head according to a fourth embodiment;
Fig. 8 is a cross-sectional view, showing a cylinder head according to a fifth embodiment;
Fig. 9 is a cross-sectional view taken along line IX-IX of Fig. 10, illustrating a cylinder head according to the prior art;
Fig. 10 is a plan view, showing the cylinder head, with a head cover of an internal combustion engine being partially broken away;
Fig. 11 is a cross-sectional view taken along line
13

XI-XI of Fig. 10, illustrating the cylinder head; and,
Fig. 12 is a cross-sectional view taken along line XII-XII of Fig. 10, illustrating the cylinder head.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of this invention will now be described with reference to the drawings. Figs. 1-4 illustrates a first embodiment. In Fig. 1, reference numeral 2 denotes an internal combustion engine; 4 a cylinder block; 6 a cylinder head; and, 8 a head cover. In the engine 2 disposed in a vehicle (not shown), the cylinder head 6 is mounted on the cylinder block 4; and, the head cover 8 is fitted on the cylinder head 6.
The cylinder head 6 is formed in a substantially rec-tangular shape, in which the cylinder head 6 is greater in length in a longitudinal direction thereof (i.e., in the rightward and leftward directions in Fig. 2) than in a transverse direction of the cylinder head 6 (i.e., in the upward and downward directions in Fig. 2). A peripheral head wall 10 having a substantially square-cornered tower configuration extends around the periphery of the cylinder head 6. A head body 12 extends inside the peripheral head wall 10. The peripheral head wall 10 surrounds cam chambers 14 that are arranged above the head body 12. As illustrated in Figs. 3 and 4, the cam chambers 14 have a plurality of camshaft-supporting walls 16 arranged in a row in
14

series along the longitudinal direction of the cylinder head 6. The camshaft-supporting walls 16 are oriented in the transverse direction of the cylinder head 6.
A camshaft 18 is provided on the camshaft-supporting walls 16 in a state of being rotatably supported on camshaft housings 20. As shown in Figs. 3 and 4, the camshaft-supporting walls 16 are provided with head-side rotatable suprport portions 22. The camshaft housings 20 are provided with housing-side rotatable support portions 24. The camshaft housings 20 are mounted on the camshaft-supporting walls 16 by means of housing-mounting bolts 26. The head-'side rotatable portions 22 and the housing-side rotatable portions 24 rotatably carry journal portions 28 of the camshafts 18.
In order to open and close each intake valve and ex-haust valve (not shown), the camshaft 18 causes a seesaw type of an intake rocker arm 34 and a swing type of an exhaust rocker arm 38 to be swung by means of an intake cam 30 and an exhaust cam 36, respectively. The intake rocker arm 34 is rotatably supported on a rocker shaft 32.
A gear chamber 40 is provided between part of the peripheral head wall 10 located at one end of the cylinder head 6 in the longitudinal direction thereof (i.e., the right side in Fig. 2) and the camshaft-supporting wall 16 that opposes the aforesaid part of the peripheral head wall 10, which camshaft-supporting wall 16 supports one axial end of the camshaft 18 (i.e.,
15

one end of the camshaft 18 on the right side in Fig. 2). The above camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. A driving gear 42 is disposed on the camshaft 18 at one axial end thereof. The driving gear 42 is located in the gear chamber 40.
As seen from Fig. 1, a mounting hole 44 is provided through part of the peripheral head wall 10 located at one end of the cylinder head 6 in the transverse direction thereof (i.e., the upper side in Fig. 2), which transverse direction is perpendicular to the axial direction of the camshaft 18. The mounting hole 44 is communicated directly to the gear chamber 40. ¦ A distributor 46 is mounted on the cylinder head 6 in a state of a mounting shaft portion 48 of the distributor 46 being fitted in the mounting hole 44. A mounting flange 50 is mounted on the cylinder head 6 around the hole 44 by means of mounting bolts (not shown).
The distributor 46 is provided with a distributor shaft 52 that projects from the mounting shaft 'portion 48 into the gear chamber 40. The distributor shaft 52 is provided with a driven gear 54 that meshes with the driving gear 42.
The camshaft 18 is driven in synchronism with a rotating crankshaft (not shown), and then the revolving force of the camshaft 18 is transmitted to the distributor 46 through the driving gear 42 and the driven gears 54. The distributor 46 then distributes high electric voltage to an ignition plug (not
16

shown) for each cylinder. Reference numeral 56 denotes a camshaft pulley disposed on the camshaft 18 at the other axial end thereof. The pulley 56 is communicated to the crankshaft through a timing belt (not shown). Reference numeral 58 denotes a cap.
In this lubrication structure for the distributor 46, a return hole 60 is provided through the camshaft-supporting wall 16 that supports one axial end of the camshaft 18 (i.e., one end of the camshaft 18 on the right side in Fig. 2), and further that partitions the gear chamber 40 from the cam chamber 14. Then, the lubricating oil in the gear chamber 40 flows back to the cam chamber 14 through the return hole 60.
Pursuant to the first embodiment, the camshaft-supporting wall 16 is provided with the return hole 60 having a "substantially polygonal shape, as shown in Fig. 1. The return hole 60 includes a bottom surface portion 62 that has an enlarged width. The bottom surface portion 62 is positioned parallel to horizontal line "H" when the engine 2 is disposed in a vehicle (not shown). Further, the bottom surface portion 62 is located at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrication to the driving gear 42 and the driven gears 54 in the gear chamber 40. The engine 2 is disposed in the vehicle at angle 0 1 which is formed between cylinder center line "C" of the engine 2 and vertical line "V." In consideration of this angle 01, the bottom surface portion 62 is positioned par-
17

allel to horizontal line "H" at angle 8 2 with reference to cylinder center line "C."
Next, the operation of the first embodiment will be . described.
As illustrated in Figs. 3 and 4, in the lubrication structure for the distributor 44, when the engine 2 is driven into operation, then a first oil passage causes the lubricating oil flowing upward from the cylinder block 4 to be introduced into a second oil passage 64 through a venturi (not shown). The first oil passage is oriented in the transverse direction of the cylinder head 6. The second oil passage 64 is directed in the longitudinal direction of the cylinder head 6.
Then, the lubricating oil in the second oil passage 64 is caused to reach the head-side rotatable support portions 22 through support wall oil passages 66. The support wall oil passages 66 are provided on the camshaft-supporting walls 16. Then, the lubricating oil lubricates the journal portions 28 of the camshaft 18 between the head-side rotatable support portions 22 and the housing-side rotatable support portions 24.
The camshaft-supporting wall 16 and the camshaft housing 20, both of which oppose the part of the peripheral head wall 10 located at one end of the cylinder head 6 in the
longitudinal direction thereof, rotatably supports the journal

portion 28 of the camshaft 18; and, the lubricating oil, which has lubricated the aforesaid journal portion 28, is then caused to
18

flow into the cam chamber 14 and the gear chamber 40 as well through a void space that is formed between the head-side ro-tatable support portion 22, the housing-side rotatable support portion 24, and the journal portion 28.
The lubricating oil, which is led into the gear chamber 40, lubricates the driving gear 42 and the driven gears 54, both of which gears drive the distributor 46. The lubricating oil in the gear chamber 40 is then returned to the cam chamber 14 through the return hole 60.
As previously described, in the present lubrication structure for the distributor 46, the return hole 60 is provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. The lubricating oil in the gear chamber 40 is caused to flow back into the cam chamber 14 through the return hole 60.
As a result, in the above-described lubrication structure for the distributor 46, the lubricating oil is prevented from being reserved in the gear chamber 40 in excess of the full capacity of the gear chamber 40. In addition, the lubricating oil can flow smoothly from the gear chamber 40 into the cam chamber 14 without being lodged in the gear chamber 40. Consequently, no lubricating oil escapes out of the mounting hole 44 when the distributor 46 is removed from the mounting hole 44.
Accordingly, the present lubrication structure for
19

the distributor 46 precludes the driven gear 54 from being immersed in the lubricating oil, and thus provides a reduced mechanical loss, while maintaining the function of providing lubrication to the gears 42 and 54, both of which gears 42 and 54 drive the distributor 46. In addition, the present lubrication structure for the distributor 46 precludes the lubricating oil from staying in the gear chamber 40, and thus prevents deterioration of the lubricating oil. Furthermore, the present lubrication structure for the distributor 46 eliminates the need to take steps of: draining off the lubricating oil from the gear chamber 40 before the distributor 46 is removed from the mounting hole 44; and, blocking escape of the lubricating oil from the mounting hole 44. As a result, improved maintainability is provided. In addition, no lubricating oil discharge occurs, which otherwise would contaminate the engine 2.
Furthermore, in the lubrication structure for the distributor 46 according to the first embodiment, the substan- tially polygonal-shaped return hole 60 is provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 separates the gear chamber 40 from the cam chamber 14. The bottom surface portion 62 of the return hole 60 is positioned parallel to horizontal line "H" when the engine 2 is disposed in the vehicle. At the same time, the bottom surface portion 62 is located at oil surface level "L" of the required lubricating oil quantity neces-
20

sary for lubrication to the driving gear 42 and the driven gear 54 in the gear chamber 40.
In the lubrication structure for the distributor 46 according to the first embodiment, the bottom surface portion 62 is positioned parallel to horizontal line "H" when the engine 2 is disposed in the vehicle. This structural feature provides an improved efficiency of outflow when the engine 2 is disposed in the' vehicle. In addition, the bottom surface portion 62 is located at the aforesaid oil surface level "L". This structural feature insures such a required lubricating oil quantity as mentioned above, and then reliably provides lubricating function.
Fig. 5 illustrates a second embodiment "SG1". In a lubrication structure for a distributor 46 according to this embodiment, a circular return hole 68 is provided through a cam-shaft-supporting wall 16 that is located at one axial end of a camshaft 18, which camshaft-supporting wall 16 partitions a gear chamber 40 from a cam chamber 14. The return hole 68 has a curved bottom surface portion 70 and a curved side surface portion 72. The bottom surface portion 70 is positioned at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrication to a driving gear 42 and a driven gear 54 in the gear chamber 40. The side surface portion 72 lies outside a revolving course of tooth width "W" of the driven gear 54.
As previously described, in the lubrication structure
21

for the distributor 46 pursuant to the second embodiment, the return hole 68 is provided through the aforesaid camshaft-supporting wall 16, through which hole 68 the lubricating oil in the gear chamber 40 is delivered back to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while maintaining the function of providing lubrication to the gears 42 and 54. In addition, the'above structural feature prevents deterioration of the lubricating oil, and further provides improved maintainability, with the result that no lubricating oil discharge contaminates the engine 2.
In the lubrication structure for the distributor 46 according to the second embodiment, the circular return hole 68 is provided through the camshaft-supporting wall 16 that is lo-cated at one axial end of the camshaft 18, which camshaft-supporting wall 16 separates the gear chamber 40 from the cam chamber 14. This structural feature avoids concentration of stresses, and thus provides improved durability of the camshaft-supporting wall 16. Furthermore, the bottom surface portion 70 of the return hole 68 is positioned at the aforesaid oil surface level "L". This structural feature insures such a re-quired lubricating oil quantity as described above, and reliably provides lubricating function.
Further, in the lubrication structure for the distributor 46 according to the second embodiment, the side surface
22 ,

portion 72 of the circular return hole 68 is situated outside the revolving course of tooth width "W" of the driven gear 54. This structural feature prevents the lubricating oil stirred up by the driven gear 54 from flowing directly into the cam chamber 14 through the return hole 68, and then prevents a decrease in such a required lubricating oil quantity as above, with the result that lubricating function is insured.
Fig. 6 illustrates a third embodiment "SG2". In a lubrication structure for a distributor 46 according to this embodiment, a plurality of smaller circular return holes 74 having different heights are provided through a camshaft-supporting wall 16 that is located at one axial end of a camshaft 18, which camshaft-supporting wall 16 partitions a gear chamber 40 from a cam chamber 14. The return holes 74 are arranged and slanted at angle 0 3 with reference to oil surface level "L" of a required lubricating oil quantity. The lowest one of the return holes 74 has a curved bottom surface portion 76 positioned at oil surface level "L" of the required lubricating oil quantity that is necessary for lubrication to a driving gear 42 and a driven gear 54 in the gear chamber 40.
As described above, in the lubrication structure for the distributor 46 according to the third embodiment, the plurality of the' smaller circular return holes 74 are arranged through the aforesaid camshaft-supporting wall 16, through which holes 74 the lubricating oil in the gear chamber 40 is
23

caused to flow back to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while sustaining the function of providing lubrication to the gears 42 and 54. In addition, the above structural feature prevents deterioration of the lubricating oil, and further provides improved maintainability, with the result that no lubricating oil discharge contaminates the engine 2.
In the lubrication structure for the distributor 46 according to the third embodiment, the plurality of the smaller circular return holes 74 are provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. This structural feature disperses concentration of stresses, and provides improved durability of the camshaft-supporting wall 16. In addition, since the return holes 74 are arranged at different heights, then the lubricating oil is caused to flow into the cam chamber 14 in stages in greater amounts when the lubricating oil in the gear chamber 44 increases in quantity beyond the aforesaid oil surface level "L". As a result, the level of the lubricating oil in the gear chamber 44 can promptly be lowered back to oil surface level "L".
Furthermore, in the lubrication structure for the distributor 46 according to the third embodiment, the lowest one of the circular return holes 74 has the curved bottom surface
24 .

portion 76 located at the aforesaid oil surface level "L". This structural feature insures such a required lubricating oil quantity as above, and positively provides lubricating function. Fig. 7 illustrates a fourth embodiment "SG3". In a lubrication structure for a distributor 46 according to this embodiment, a substantially elliptic return hole 78 is provided through a camshaft-supporting wall 16 that is positioned at one axial end of a camshaft 18, which camshaft-supporting wall 18 partitions a gear chamber 40 from a cam chamber 14. The return hole 78 includes a bottom surface portion 80 having an enlarged width, and a ceiling surface portion 82 having an enlarged width. The ceiling surface portion 82 is parallel to the bottom surface portion 80 in an opposed relationship with one another. The bottom surface portion 80 is positioned parallel to horizontal line "H" when the engine 2 is disposed in a vehicle. Further, the bottom surface portion 80 is located at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrica-. tion to a driving gear 42 and a driven gear 54 in the gear chamber 40. The engine 2 is disposed in the vehicle at angle 0 1 which is formed between cylinder center line "C" of the engine 2 and vertical line "V". In consideration of the above angle 0 1, the bottom surface portion 80 is positioned parallel to horizontal line "H" at angle 0 2 with reference to cylinder center line "C".
As previously described, in the lubrication structure for the distributor 46 according to the fourth embodiment, the
25 -

return hole 78 is provided through the above-described camshaft-supporting wall 16, through which hole 78 the lubricating oil in the gear chamber 40 is returned to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while retaining the function of providing lubrication to the gears 42 and 54. In addition, the above structural feature prevents deterioration of the lubricat-ing oil, provides improved maintainability, and eliminates lubricating oil discharge that otherwise would contaminate the engine 2.
In the lubrication structure for the distributor 46 according to the fourth embodiment, the substantially elliptic return hole 78 is provided through the camshaft-supporting wall 16 that is positioned at one axial end of the camshaft 18, which camshaft-supporting wall 18 partitions the gear chamber 40 from the cam chamber 14. This structural feature allows for elastic deformation of the camshaft-supporting wall 16 that supports one axial end of the camshaft 18, and the camshaft 18 can elastically be supported. Such a feature absorbs vibrations from the camshaft 18, and prevents a reduction in efficiency of transmittance of driving force from the camshaft 18 to the distributor 46. Furthermore, the bottom surface portion 80 of the return hole 78 is positioned parallel to horizontal line "H" when the engine 2 is disposed in the vehicle. This structural feature provides an improved efficiency of outflow when the engine 2 is
26

disposed in the vehicle.
Furthermore, in the lubrication structure for the distributor 46 according to the fourth embodiment, the bottom surface portion 80 of the return hole 78 is located at the above-described oil surface level "L". This structural feature insures such a required lubricating oil quantity as above, and securely provides lubricating function.
Fig. 8 illustrates a fifth embodiment "SG4". In a lubrication structure for a distributor 46 according to this embodiment, a substantially inverted triangular-shaped return hole 84 is provided through a camshaft-supporting wall 16 that is positioned at one axial end of a camshaft 18, which camshaft-supporting wall 16 partitions a gear chamber 40 from a cam chamber 14. The return hole 84 includes a tapered basic angle portion 86 and a ceiling surface portion 88, the latter having an enlarged width. The ceiling surface portion 88 is positioned in an opposed relationship to the basic angle portion 86. The ba-sic angle portion 86 is located at oil surface level "L" of a required lubricating oil quantity that is necessary for lubrication to a driving gear 42 and a driven gear 54 in the gear chamber 40. In addition, the ceiling surface portion 88 is positioned parallel to horizontal line "H" when the engine 2 is disposed in a vehicle.
As previously mentioned, in the lubrication struc-ture for the distributor 46 according to the fifth embodiment, the return hole 84 is provided through the above-described cam-
27

shaft-supporting wall 16, through which hole 84 the lubricating oil in the gear chamber 40 is returned to the cam chamber 18. Similarly to the first embodiment, this structural feature provides a reduced mechanical loss, while retaining the function of providing lubrication to the gears 42 and 54. In addition, the above feature prevents the deterioration of the lubricating oil, and provides improved maintainability. Yet further, no lubricating oil escape occurs, which otherwise would contaminate the engine 2.
In the lubrication structure for the distributor 46 according to the fifth embodiment, the substantially inverted triangular-shaped return hole 84 is provided through the camshaft-supporting wall 16 that is located at one axial end of the camshaft 18, which camshaft-supporting wall 16 partitions the gear chamber 40 from the cam chamber 14. As a result, when the lubricating oil in the gear chamber 40 increases in quantity beyond the aforesaid oil surface level "L", then an outflow of the lubricating oil to be fed into the cam chamber '14 is increased. Consequently, the level of the lubricating oil in the gear chamber 40 can promptly be lowered back to oil surface level "L", In addition, the basic angle portion 86 of the return hole 84 is located at the above-described oil surface level "L". This structural feature insures such a required lubricating oil quantity as previously described, and thus reliably provides lubricating function.
28

As evidenced by the above description, the lubrication structure for the distributor according to this invention precludes the driven gear from being immersed in the lubricating oil, and then provides a reduced mechanical loss, while maintaining the function of providing lubrication to the gears that drive the distributor. In addition, the present lubrication structure for the distributor precludes the lubricating oil from staying in the gear chamber, and thus prevents deterioration of the lubricating oil by virtue of smooth circulation of the lubricating oil. Further, the present lubrication structure for the distributor eliminates operations to drain off the lubricating oil from the gear chamber when the distributor is removed from the mounting hole, and further to block escape of the lubricating oil from the mounting hole. Such a feature provides improved maintainability. In addition, no lubricating oil discharge occurs, which otherwise would contaminate the engine.
29

WE CLAIM :
1. A lubrication structure for a distributor comprising :
a plurality of camshaft-supporting walls provided in cam chambers that are surrounded by a peripheral head wall of a cylinder head of an internal combustion engine, said camshaft-supporting walls being arranged in a row in series along a longitudinal direction of the cylinder head, and the camshaft-supporting walls being oriented in a transverse direction of the cylinder head ;
a camshaft provided on the camshaft-supporting walls so as to be rotatably supported on cam housings ;
a gear chamber provided between a part of the peripheral head wall located at one end of the cylinder head in the longitudinal direction of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall, said camshaft-supporting wall supporting one end of the camshaft in an axial direction of the camshaft and also partitioning the gear chamber from the cam chamber ;
a driving gear disposed on the camshaft at one end of the camshaft in the axial direction of the camshaft, the driving gear being located in the gear chamber ;
a mounting hole extending through part of the peripheral head wall located at one end of the cylinder head in the transverse direction of the cylinder head, which transverse direction is perpendicular to the axial direction of the camshaft, said mounting hole communicating directly with the gear chamber ; and
-30-

a driven gear disposed on a distributor shaft of said distributor, said distributor being mounted on the cylinder head so that part of the distributor is fitted in said mounting hole, said driven gear being in mesh with said driving gear,
characterized in that at least one return hole is provided to extend through said camshaft-supporting wall which partitions said gear chamber from said cam chamber, through which return hole lubricating oil in the gear chamber is returned to the cam chamber.
2. A lubrication structure for a distributor as claimed in claim 1,
wherein said return hole comprises a substantially polygonal-shaped
return hole extending through the camshaft-supporting wall ; and a
bottom surface portion of the return hole is positioned parallel to a
horizontal line when the engine is disposed in a vehicle, said bottom
surface portion being located at an oil surface level of a required
lubricating oil quantity that is necessary for lubrication of the driving
gear and the driven gear in the gear chamber, and the bottom surface
portion having an enlarged width.
3. A lubrication structure for a distributor as claimed in claim 1,
wherein said return hole comprises a circular return hole extending
through the camshaft-supporting wall ; and a curved bottom surface
portion of the circular return hole is positioned at an oil surface level
of a required lubricating oil quantity that is necessary for lubrication to
the driving gear and the driven gear in the gear chamber, and a
curved side surface portion of the circular return hole is located
outside a revolving course of a tooth width of the driven gear.
-31-

4. A lubrication structure for a distributor as claimed in claim 1,
wherein said at least one return hole comprises a plurality of reduced
circular return holes having different heights extending through the
camshaft-supporting wall, and the lowest one of the circular return
holes has a curved bottom surface portion located at an oil surface
level of a required lubricating oil quantity that is necessary for
lubrication to the driving ear and the driven gear in the gear chamber.
5. A lubrication structure for a distributor as claimed in claim 1,
wherein said return hole comprises a substantially elliptic return hole
extending through the camshaft-supporting wall ; and a bottom
surface portion of the return hole extends parallel to a horizontal line
when the engine is disposed in a vehicle, said bottom surface portion
of the return hole being located at an oil surface level of a required
lubricating oil quantity that is necessary for lubrication to the driving
gear and the driven gear in the gear chamber, and said bottom
surface portion having an enlarged width.
6. A lubrication structure for a distributor as claimed in claim 1,
wherein said return hole comprises a substantially inverted triangular-
shaped return hole extending through the camshaft-supporting wall ;
and a tapered basic angle portion of the return hole is located at an
oil surface level of a required lubricating oil quantity that is necessary
for lubrication to the driving gear and the driven gear in the gear
chamber.
-32-

-33-
7. A lubrication structure for a distributor, substantially as herein described, particularly
with reference to and as illustrated in figures 1 to 8 of the accompanying drawings.
8. A distributor incorporating a lubrication structure, as claimed in any of claims 1 to 6.
A lubrication structure for a distributor (46) comprises : camshaft-supporting walls (16) provided in cam chambers (14) surrounded by a peripheral head wall of a cylinder head (6) of an I.C. engine (2), a camshaft (18) provided on the camshaft-supporting walls and rotatably supported on cam housings (20) ; a gear chamber (40) provided between a part of the peripheral head wall located at one end of the cylinder head and the camshaft-supporting wall that opposes said part of the peripheral head wall (10), the camshaft-supporting wall axially supporting one end of the camshaft and also partitioning the gear chamber (40) from the cam chamber (14) ; a driving gear (42) axially disposed at one end of the camshaft and positioned in the gear chamber ; a mounting hole (44) extending through part of the peripheral head wall and communicating with the gear chamber ; and a driven gear (54) meshing with the driven gear and disposed on a distributor shaft of the distributor, mounted on the cylinder head so that part of the distributor is fitted in the mounting hole, characterized in that at least one return hole (60) extending through the camshaft-supporting wall (16) through which return hole lubricating oil in the gear chamber is returned to the cam chamber.

Documents:

00470-cal-1999 abstract.pdf

00470-cal-1999 claims.pdf

00470-cal-1999 correspondence.pdf

00470-cal-1999 description(complete).pdf

00470-cal-1999 drawings.pdf

00470-cal-1999 form-1.pdf

00470-cal-1999 form-18.pdf

00470-cal-1999 form-2.pdf

00470-cal-1999 form-3.pdf

00470-cal-1999 form-5.pdf

00470-cal-1999 g.p.a.pdf

00470-cal-1999 letters patent.pdf

00470-cal-1999 priority document others.pdf

00470-cal-1999 priority document.pdf

470-CAL-1999-FORM-27.pdf

« Previous Patent

Next Patent »

Patent Number

202672

Indian Patent Application Number

470/CAL/1999

PG Journal Number

09/2007

Publication Date

02-Mar-2007

Grant Date

02-Mar-2007

Date of Filing

19-May-1999

Name of Patentee

SUZUKI MOTOR CORPORATION

Applicant Address

300,TAKATSUKA-CHO,HAMAMATSU-SHI SHIZUOKA-KEN

Inventors:

#	Inventor's Name	Inventor's Address
1	SATOSHI KASAHARA	300,TAKATSUKA-CHO,HAMAMATSU-SHI SHIZUOKA-KEN

PCT International Classification Number

F 01 M 1/06

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10-166062	1998-05-30	Japan