Title of Invention

"AN OVERHEAD CAM ENGINE, PROVIDED WITH A CYLINDER SECTION"

Abstract

An overhead cam engine, provided with a cylinder section, slidably housing a piston, a head section, having an ignition chamber, intake and exhaust valves, and a cam chamber rotatably housing a cam shaft provided with cam for driving the intake and exhaust valves, and a head cover section for covering the cam chamber, wherein, an open end is formed on cam chamber in the axial direction of the cam shaft, the cylinder section, the head section and head cover section are integrally formed in a state where least a part of the head cover section is covering an upper part of the cam shaft.

Full Text

[Detailed Description Of The Invention] [0001] [Technical Field] This invention relates to an overhead cam engine formed by die casting. [0002] [Related Art] A typical engine has a structure in which a cylinder block, a cylinder head and a cylinder head cover formed are individually cast, and are assembled by being stacked on top of one another. There is also known the case of integrally die casting part of the cylinder block, cylinder head and cylinder head cover (Japanese patent laid open No. Hei. 4-17759) , and in this case not (the entire cylinder head cover but only a part of it is integrally formed. [0003] Further, an overhead cam type valve mechanism is adopted, and in the case where a cam shaft is supported by metal bearings, the bearing portion must be divided into upper and lower section, and also, a cam chamber and valve lifter holes are integrally formed using sand cores. Similarly, intake and exhaust ports, and in the case of a water cooled engine a water jacket, must also be formed using sand cores. [0004] [Problems To Be Solved By The Invention] In the above described structure of the related art, where a cylinder block, cylinder head and cylinder head cover are divided, there is an increase in the number of components, and packing surfaces increase in number, which means that the number of manufacturing steps is increased. Also, there is a need for gaskets at the packing surfaces, and the reliability of the seals must be very high. On top of this, the sealing surfaces of the gaskets must be guaranteed, and the thickness between the cylinder and the water jacket etc. is restricted by the bore diameter. [0005] Further, even in the case where the cylinder block, cylinder head and up to a part of the cylinder head cover are integrally die cast, sand cores are used in making the cam chamber and valve lifter holes, and the intake and exhaust ports and water jacket, which means that a large number of processes are required for the formation of the cores and sand casting. On top of'this, the cylinder head cover must be divided into upper and lower parts at the cam shaft section, and substantially all of the cylinder head cover including a section for covering an upper part of the cam shaft can not be die cast connected to the cylinder head. Still further, because of the metal bearings being caused to be split in to upper and lower parts, cam holders are required, and the cam holders and cylinder head must be processed together on the same axis. This means that the cam shaft bearing structure is complicated and processing also takes a lot of labor. The object of this invention is to solve these problems. [0006] [Means Of Solving The Problems] In order to solve the above problems, an over head cam engine of a first invention is provided with a cylinder section, slidably housing a piston, a head section, having an ignition chamber, intake and exhaust valves, and a cam chamber rotatably housing a cam shaft provided with cams for driving the intake and exhaust valves, and a head cover section for covering the cam chamber, wherein, the cam chamber is formed by die stamping in the axial direction of the cam shaft, and the cylinder section, head section and head cover section are integrally formed by die casting in a state where least a part of the head cover section is covering an upper part of the cam shaft. [0007] A second invention is the same as the first invention, wherein the engine is a die cast component, a die for forming the cam chamber is integral with a die for forming one side of the outside of the engine, and the engine is formed by extracting from the die in the same direction. [0008] A third invention is the same as the first invention, wherein valve lifter holes for housing valve lifters are formed in the head cover, crossing the cam shaft, by die casting. [0009] A fourth invention is the same as the third invention, wherein cam peep holes penetrating through to a cam chamber on an extension of the valve lifter holes are provided in part of the head cover section, and a cap member for closing off the cam chamber is attached to the cam peep holes so as to be-freely attachable and detachable. [0010] [Effects of the Invention] According to the first invention, the cam chamber is formed by die stamping in the direction axial of the cam shaft, which means that the cylinder head section, head section and part of the head cover section including a portion for covering an upper part of the cam shaft can be integrally formed by die casting. As a result, it is possible to reduce the number of components and packing surfaces that are required for engaging portion of these components are no longer required which leads to a reduction in the number of processing steps, there is also no longer any need for packing surface seals, and there is no restriction on the thickness between the water jacket and the cylinder, or bore diameter accompanying guaranteeing of the seal surfaces. [0011] Further, sand cores are not used in the formation of the cam chamber, which means that the large number of processes usually required for making the sand cores and sand casting are no longer necessary. As well as this, the whole of the cylinder head cover can be integrally die cast by being connected to the cylinder head, which means that there is no need to divide bearings into upper and lower parts in the cam shaft section, cam holders can be done away with and the processes needed to put the cam holders and the cylinder head on the same axis are no longer required. This means that the bearing structure can be simplified and the labor required in manufacturing the bearing structure is not too intensive. [0012] According to the second invention, ca-sting is die casting, among the dies used, a die for forming the cam chamber is integral with a die for forming the outer shape of the engine and the extraction is carried out in the same direction. This means that when the outer shape of the engine is formed, it is also possible to integrally form the cam chamber by die stamping in the direction of the cam shaft, and the formation of the cam chamber u.s made easy. [0013] According to the third invention, since valve lifter holes for housing valve lifters are formed by die stamping across the cam shaft, it is possible to form the valve lifter holes at the same time as the cam chamber of the head section is formed, and also, since the cores are done away with it is possible to significantly reduce the number of processes. [0014] According to the fourth invention, since cam peep holes penetrating through to a cam chamber on an extension of the valve lifter holes are provided in part of the head cover section, the cam lifter holes cam be formed at the same time as the die stamping of the valve lifter holes. Also, by attaching a cap member for closing off the cam chamber to the cam peep holes so as to be freely attachable and detachable, it is possible for them to act as maintenance holes. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 is a cross sectional drawing of the whole engine in an embodiment of the invention. Fig. 2 is a drawing showing a right side surface with an inlet cover removed. Fig. 3 is a drawing showing a left side surface with a cam chain cover removed. Fig. 4 is a cross sectional drawing along line 4-4 in Fig. 1. Fig. 5 is a cross sectional drawing of a body portion along line 5-5 in Fig. 1. Fig. 6 is cross sectional drawing of a body. Fig. 7 is a drawing showing a connecting surface side of the inlet cover. Fig. 8 is a drawing showing a connecting surface side of the cam chain cover. Fig. 9 is a cross sectional drawing showing cast metal dies for the body portion. Fig. 10 is a cross sectional drawing of a die showing the method of forming a cam chamber and valve lifter holes. Fig. 11 is a cross sectional drawing of metal dies showing the method of forming the water jacket. Fig. 12 is a drawing of a second embodiment, equivalent to Fig. 1. Fig. 13 is a drawing of a third embodiment, equivalent to Fig. 1. [0015] [Embodiment of the Invention] An embodiment that has been applied to a 4-cycle water cooled low displacement engine for a small type motorcycle will be described below based on the drawings. Fig. 1 is a cioss sectional drawing of the whole engine in an embodiment of the invention; Fig. 2 is a drawing showing a right side surface with an inlet cover removed; Fig. 3 is a drawing showing a left side surface with a cam chain cover removed; Fig. 4 is a cross sectional drawing along line 4-4 in Fig. 1; Fig. 5 is a cross sectional drawing of a body portion along line 5-5 in Fig. 1; Fig. 6 is cross sectional drawing of a body; Fig. 7 is a drawing showing a connecting surface side of the inlet cover; Fig. 8 is a drawing showing a connecting surface side of the cam chain cover; Fig. 9 is a cross sectional drawing showing cast metal dies of the body portion; Fig. 10 is a cross sectional drawing of a die showing a method of forming the cam chamber and valve lifter holes; and Fig. 11 is a cross sectional drawing of metal dies showing the method of forming the water jacket. [0016] This engine is formed has a substantially cuboid body 1 that has been formed using a casting method such as die casting of a suitable metal such as aluminum alloy. The body 1 is formed by attaching an impeller cover 2 and a cam chain covex 3 to two substantially parallel side surfaces facing each other, and is attached to a crankcase (not shown). [0017] The body 1 is formed by integrating a cylinder portion 5, housing a piston 4 connected to a crank shaft (not shown) through a connecting rod 4, and a head portion 8 having a cam chamber 7 housing a cam shaft 6 in a rotatable manner. [0018] In this application, a portion for covering a cam chambe^ 7 in the head portion 8 will be specially termed the head cover portion 9, and for further convenience, for the respective surfaces of the body 1, a surface to which the impeller cover 2 is attached will be called the right side surface 10, a surface to which a cam chain cover 3 is attached will be called a left side surface 11 (Fig. 6) , of two opposed surfaces interposed between the left and right side surface, a surface to which a radiator (to be described later) is attached will be called a front surface 21, and the other of the two opposed surfaces will be called a rear surface 13. Also, an external ceiling surface will be called a top surface 14 and a surface to which a crankcase is attached will be called a bottom surface 15 (refer to Fig. 1). [0019] In the cylinder portion 5, a cylinder 16 is formed from the bottom surface 15 in a length direction to a substantially central portion of the body 1, and a combustion chamber 17 formed at the head portion 8 side, being the innermost portion of the cylinder 16, communicates with an intake port 18 and an exhaust port 19. Combustion chamber 17 side openings of each port are opened or closed by an intake valve 20 and an exhaust valve 21. The axes Cl, C2 of each of the valves form a fixed valve included angle with respect to the cylinder axis C. Reference numerals 20a and 21a are stem holders. [0020] The intake port 18 communicates with an intake passageway 22 formed on an inlet cover 2. This Intake passageway 22 extends to the outside diagonally along an extension of the intake port 18, and is connected to a carburetor (not shown in the drawings) via an inlet pipe 23. The exhaust port 21 extends substantially at a right angle to the inlet port 18, and is connected to an exhaust pipe 24 via its rear surface 13. In Fig. 2 and Fig. 3, reference numeral 29 is a spark plug. [0021] The driving of each valve is direct drive type, in which they are directly driven by cams 27, 28 via valve lifters 25, 26 provided on the ends of respective shafts. A cam shaft 6 constituting these cams 27, 28 is supported by bearings 30, 31 at both open ends of the cam chamber 7 penetrating between the right side surface 10 and the left side surface 11 and having a tapered shape. Each sliding surface of the cams 27, 28 forms an inclined plane corresponding to respective sliding surfaces of the valve lifters 25, 26. A refueling section 6a is also formed between one end of the cam shaft 6 and the inlet cover 2. [0022] The other end of the cam shaft 6 protrudes into a chain chamber 32 formed between a cam chain cover 3 and the left side surface 11, and a cam sprocket 33 is attached to this protruding end by bolts 34 . This cam sprocket 33 is linked to a drive sprocket provided on a crankshaft (not shown) via a cam chain 35. [0023] Cam peep holes 36 37 having substantially the same diameter as each of the valve lifters 25, 26, and the same axes as the valve shafts Cl and C2, are formed on extensions of each valve shaft Cl and C2 within the head cover portion 9, and caps 38, 39 for respectively opening and closing the cam chamber 7 are hermetically sealed via seals using screws . [0024] A water pump 40 is provided in the vicinity of the combustion chamber 17 of the body 1. As will be clear from Fig. 5, a circular pump attachment hollow 41 is formed in a side wall facing the cam chain cover 3 of the body 1, and houses a flange 42 formed in part of a resin type cover constituting the profile of the water pump 40. This flange 42 is also substantially circular similarly to the pump attachment hollow 41, and sealing between the-pump attachment hollow 41 is carried out at a circumference wall portion of -the pump attachment hollow 41 via 0 rings 44 and using fluid coupling. [0025] Further, a pump body 43 is locked inside the water pump attachment hollow 41 further inside the flange 42, and covers the opening of the water jacket 45. An impeller 46 is arranged at a central portion of the pump body 43 and is supported so as to rotate integrally with a pump shaft 47, and a water way 43 a is defined by forming an opening connecting between the water jacket 45 and the impeller 46 at a position equivalent to the central portion of the impeller 46 inside the pump body 43. [0026] One end of the pump shaft 47 is rotatably supported by a boss 48 protruding into the waterway 43a, formed protruding to an outer circumference wall of the cylinder 16. The other end of the pump shaft 47 crosses over the cam chain 35, and protrudes into the chain chamber 32, and a magnet ring 49 is provided around the circumference of the shaft 47. The circumference of the shaft 47 is also formed into a small diameter portion 50 partially covered by a flange 42 and an integral resin cover. This small diameter portion 50 has a circular shape, and an end protruding to the cam chain cover 3 side is lockingly supported at a circular locking hollow 51 formed in the cam chain cover 3. [0027] As can be seen clearly in Fig. 3, the center of this small diameter portion 50 and the center of the flange 42 are different, and a locking hollow 51 having the same center as the small diameter portion 50, and a pump attachment hollow 41 having the same center as the flange 42, are on different centers. With the small diameter portion 50 in a state of being locked to the locking hollow 51, the flange 42 is locked to the pump attachment hollow 41, and the water pump 40 is fixed co the pump attachment hollow 41 by attaching a cam chain cover 3 to the left side surface 11 using bolts etc. [0028] As is clear from Fig; 5, a sprocket 53 for the water pump having a magnet ring 52 integrally formed on an inner circumference side is provided on an outer surface of the small diameter portion 50, and the sprocket 53 is driven by the cam chain 35. A boss outer circumference of the sprocket 53 is rotatably housed, via a bearing 54, inside a circular water pump housing 55 formed in the cam chain cover 3. [0029] When the magnet ring 52 is rotated integrally with the water pump sprocket 53, the magnet ring 49 inside the small diameter portion 50 is integrally rotated by magnetic coupling, and as a result the impeller 46 rotates via the pump shaft 47 integral with the magnet ring 49, and the water pump is put in a driven state. [0030] A water outlet 56 and a water inlet 57 are formed in the front surface 12 of the body 1 so as to protrude sideways. The water outlet 56 is formed in the vicinity of the cam chain cover 3, and is in communication with a discharge path 58 provided on the pump body 43. The discharge path 58 is connected to a substantially arc shaped passage 59 going around the circumference of the impeller 46 inside the pump body 43. The water inlet 57 is arranged in the vicinity of the inlet cover 2, and is connected to the water jacket 45. [0031] A return opening 61 and water main opening 62 of the radiator 60 directly and respectively communicate with the water outlet 56 and water inlet 57, and the return opening 61 connects the inside of the radiator 60 to an upper radiator 64 through a return passageway 63 extending in a straight line in the extension direction of the emission path 58. [0032] As shown in Fig. 6, valve lifter holes 84, 85 for housing each of the valve lifters 25, 26, and stem holder holes 86, 87 having a small diameter and extending so as to connect from the ends of the valve lifter holes 84, 85 to the inlet port 18 and the exhaust port 19, are formed in the head portion 8 of the body 1. Each of these holes runs along the axes of the valve shafts Cl and C2, and extensions of each valve shaft axes Cl and C2 extend orthogonally to the axis of the cam shaft 6 (the central axis of the cam chamber) , and cam peep holes 36, 37 are formed in the head cover portion 9 above these extensions. [0033] As shown in Fig. 7, a rectangular cooling water seal 65, a circular inlet seal 66 and a substantially "P' shaped oil section seal 67 are formed in a connecting surface side of the inlet cover 2 attached to the right side surface of the body 1. Water, air-fuel mixture and oil are separately sealed between the right side surface 10 and the inlet cover 2 by fitting the inlet cover 2 to the right side surface 10 of the body 1. [0034] Reference numeral 67 in Fig. 7 is a concave portion connecting an oilway 67a (see Fig. 5) to a main gallery (not shown), reference numeral 68 is an oil passageway for supplying oil to an oil supply section 6a (see Fig. 1 and Fig. 4) formed on the end of the cam shaft 6, and reference numeral 69 in Fig. 4 is a boss for attaching a spark plug 29. [0035] Fig. 9 shows the die structure for forming the cross sectional portion of the body 1 shown in Fig. 1, and comprises a right die 70 for forming the right side surface 10 of the body 1, a left die 71 for forming the left side surface 11, a cylinder die 72 for forming the cylinder portion 16, and an upper die 73 for forming the top surface 14. As shown in Fig. 11, a front surface die 92 and a rear surface die 97 are also used in the formation of the front surface 12 and the rear surface 13, respectively. [0036] A protruding portion 74 equivalent to a portion for receiving an end of the cam shaft is formed in the right die 70, as well as a protruding portion 75 for forming a lower hole 18a equivalent to part of the inlet port 18 and a protruding portion 76 etc. equivalent to the water jacket 45 at the inlet cover 2 side. [0037] A tapered protruding portion 77, for forming the cam chamber by casting, a pin 79 for forming a breather hole 78, and a protruding portion 80 equivalent to the pump attachment hollow 41 are formed in the left die 71, and'a formation portion 81 equivalent to the boss 48 is formed in the middle of this protruding portion 80. [0038] A protruding portion 82 equivalent to the lower hole 18b constituting part of the intake passage 18, and a protruding portion 83 equivalent to the lower hole 19a of the exhaust port 19 are formed in the cylinder die 72. [0039] Slide pins are provided in the upper die 73, for simultaneously forming valve lifter holes 84, 85 for housing each of the valve lifters 25 and 26, lower holes 86a, 87a of small diameter stem holder holes 86 and 87 extending to an intake port 18 and an exhaust port 19 connecting from tips of the valve lifter holes, and cam peep holes 36. 37 by die stamping. [0040] As shown in Fig. 10, these slide pins 88 and 89 move diagonally along respective valve shafts Cl, C2, and at the time of formation are made to cross the protruding portion 77. At that time, the tip of each slide pin 88, 89 is positioned in the vicinity of respective protruding portions 75, and 82 and 83. [0041] After formation, each slide pin 88 and 89 is made to slide along respective valve shafts Cl and C2, in the upward direction in the drawing, and when each die is opened the left side surface 11 of the body 1 is formed by opening the left die 71 to the left, and at the same time the cam chamber 7 is formed using the protruding portion 77 for being pulled out in the same direction. Also, valve lifter holes 84 and 85, lower holes 86a and 87a of stem holder holes 86 and 87, and cam peep holes 36 and 37 are formed by die casting using each of the slide pins 88 and 89. [0042] Subsequently, if a few mechanical process are carried out, such as drilling and internal hole surface cutting for each of the lower holes (18a, 19a, 86a, 87a) etc., and screw cutting of the peep holes 36, 37, a body 1 having the three major components of a cylinder portion 5, a head portion 8 and a head cover portion 9 covering up to the upper part of the cam chamber 7, is completed. [0043] Fig. 11 shows the die structure for forming the water jacket 45 section. Protruding portion 76 of a right die 70 and protruding portion 80 of left die 71 are provided with semicircular arc shaped formation surfaces 90, 91 having gaps to the extent of the thickness of the cylinder 16, so as to surround the cylinder die 72 like a ring. Casting pins 93 and 94 for casting the water outlet 56 and the water inlet 57, and a protrusion 96 for forming an intermediate concave portion 95, are provided on the front surface die 92. Reference numeral 97 is a rear surface die. [0044] Each of the formation surfaces 90, 91 form spaces for locking the guide portions 101, 102, 103 and 104 in the 4 nooks of the cylinder portion 5 surrounding the cylinder 16, as shown in Fig. 5. These guide portions 101, 102, 103 and 104 are opposite to an external circumference of the cylinder 16 and face each other across substantially parallel R shaped curved guide surfaces, and the guide portions 101 and 102 are formed projecting from the pump body 43, while the guide portions 103 and 104 are formed on the water jacket 45 side of the inlet cover 2. [0045] Surfaces facing into the water jacket 45 of the pump body 43 define a hollow shaped guide surfaces surrounding the cylinder 16, and a water passageway 43a is defined between guide portions 101 and 102 within the guide surfaces, by making an opening facing into the water jacket 45. A curved connecting surface is also formed between the guide portions 103 and 104, and the surfaces at the water jacket 45 side of the inlet cover 2 together form a single guide surface 105. However, within this guide surface 105 a portion in the vicinity of the water inlet 57 partially forms a flank 106. Air-cooling fins 107 are integrally formed in an outer surfac'e side of the inlet cover 2. [0046] Next, the operation of this embodiment will be described. Because the cam chamber 7 is formed by die casting in the axial direction of the cam shaft 6, the cylinder section 5, head section 8 and head cover section 9 can be integrally made by die casting. As a result, it is possible to reduce the number of components, and packing surfaces that are required for engaging portions of these components are no longer required which leads to a reduction in the number of processing steps, there is also no longer any need for packing surface seals, and there is no restriction on the thickness between the water jacket and the cylinder, or bore diameter accompanying guaranteeing of the seal surfaces. Also, the overall strength of the engine can be increased. [0047] Further, since only simple mechanical processes are carried out as finishing processes for the body 1 after casting, and the cylinder section 5, head section 8 head cover section 9 for covering up to the upper part of the cam chamber 7 are easily formed into an integrated body 1, the productivity of the body 1 is improved. Moreover, since the body 1 is made by die casting using a die, the formation surfaces are comparatively nice and accurate, which means that finishing processing using these type of mechanical processes can often be done away with, and manufacture is more profitable. [0048] Further, sand cores are not used in the formation of the cam chamber 7, which means that the large number of processes usually required for making the sand cores and sand casting are no longer necessary. As well as this, substantially the entire head cover section 9, except for the sections of the peep holes 36 and 37, ca-n be integrally die cast by being connected to-the head section 8, which means that both ends of the cam shaft 6 can be supported on bearings 30 and 31 without the need to divide ball bearings etc. As a result, there is no need to divide metal bearings into upper and lower parts, cam holders can be done away with and the processes needed to put the cam holders and the cylinder head on the same axis are no longer required, which means that the bearing structure can be simplified. [0049] Further, the protruding portion 77- constituting the die for forming the cam chamber 7 is provided integrally with the left die 71 for forming the left side surface 11, and the cam chamber can also be integrally formed by die stamping in the cam shaft direction at the same time as forming the outer shape of the body 1 by extracting in the same direction as the opening direction of the left die 71, which simplifies the formation of the cam chamber 7. [0050] Still further, since the valve lifter holes 84 and 85 are formed by combining the slide pins 88 and 89 provided in the upper die 73 with the protruding portion 77, and die stamping across the cam shaft, the valve lifter holes 84 and 85 can be formed at the same time as the cam chamber 7 of the head section 8, and since it is possible to do away with the cores the number of processes cam be significantly reduced. [0051] As well as this, since cam peep holes 36 and 37 penetrating through to a cam chamber 7 on an extension of valve shafts Cl and C2 connecting to the valve lifter holes 84 and 85 are provided in part of the head cover section 9, the cam lifter holes can 36 and 37 be formed at the same time as the die stamping of the valve lifter holes 84 and 85. Also, by attaching cap members 38 and 39 for closing off the cam chamber to the cam peep holes 36 and 37 so as to be freely attachable and detachable, it is possible for them to act as maintenance holes. [0052] Fig. 12 is a second embodiment, and in this embodiment a ceiling wall 110 of a chain chamber 32 and a side wall 111 are made to integrally protrude sideways beyond the circumference of a left side surface of a body 1, and a joint portion 112 of a chain cover 3 is located further outside than a cam chain 35. [0053] In this way, the chain chamber 32 can also be integrally formed with the body 1 by die stamping. Further, the structure of the joint portion 112 of the chain cover 3 is a single surface, which simplifies the joining process. Other processes are the same as in the previously described embodiment, and common components have the same reference numerals. (This also applies in the following). [0054] Fig. 13 is a third embodiment)of the present invention that has been applied to an air cooled engine. In this embodiment, the water pump and water jacket are omitted, as well as the inlet cover, and air cooling fins 120 are formed integrally with the cylinder section 5. This air cooling fins 120 can be formed by die stamping at the same time as the right side surface 10. In this way, using the air cooling fins 120 it is possible to obtain a more adequate cooling function than a cooling mechanism. [0055] However, the cam chamber 7 of this embodiment does not penetrate into the right side surface 10, but the formation is not different to each of the above described embodiments. Also, the chain chamber 32 has the same structure as the second embodiment, and an idling sprocket 121 is rotatably supported on the chain cover side 3. Chain passage holes 122 are also formed by die stamping a portion extending out of the side of the cylinder section 5. [0056] The present invention is not limited to the above described embodiments, and various modifications are possible thereto. For example, with respect to at least the first embodiment, the casting method does not have to be aluminum die casting, and it is possible to adopt other well known casting methods such as sand casting. Also, it is sufficient if at least a part of the head cover section 5 is covering the upper part of the cam shaft, but the portion covering the cam shaft must be made integrally with another frame formation part. [Description of the Numerals] body inlet cover cam chain cover cylinder portion cam shaft cam chamber head portion head cover portion 16: cylinder 32: chain chamber 35: cam chain 36.37 cam peep holes 40: water pump 41: pump attachment hollow 42: flange 43: pump body 45: water jacket 46: impeller 84.85 valve lifter holes [Claims] Claim I. An overhead cam engine, provided with a cylinder section, slidably housing a piston, a head section, having an ignition chamber, intake and exhaust valves, and a cam chamber rotatably housing a cam shaft provided with cams for driving the intake and exhaust valves, and a head cover section for covering the cam chamber, wherein, said cam chamber is formed by die stamping in the axial direction of the cam shaft, and the cylinder section, head section and head cover section are integrally formed by die casting, in a state where least a part of the head cover section is covering an upper part of the cam shaft. Claim 2. The overhead cam engine as disclosed in claim 1, wherein said engine is a die cast component, a die for forming the cam chamber is integral with a die for forming one side of the outside of the engine, and the engine is formed by extracting from the die in the same direction. Claim 3. The overhead cam engine as disclosed in claim 1, wherein valve lifter holes for housing valve lifters are formed in said head cover, crossing the cam shaft, by die casting. Claim 4. The overhead cam engine as disclosed in claim 2, wherein cam peep holes penetrating through to a cam chamber on an extension of said valve lifter holes are provided in part of said- head cover section, and a cap member for closing off the cam chamber is attached to the cam peep holes so as to be freely attachable and detachable. 5. An overhead cam engine substantially as herein described with reference to the accompanying drawings.

Documents:

2651-del-1998-abstract.pdf

2651-del-1998-claims.pdf

2651-del-1998-correspondence-others.pdf

2651-del-1998-correspondence-po.pdf

2651-del-1998-description (complete).pdf

2651-del-1998-drawings.pdf

2651-del-1998-form-1.pdf

2651-del-1998-form-13.pdf

2651-del-1998-form-19.pdf

2651-del-1998-form-2.pdf

2651-del-1998-form-29.pdf

2651-del-1998-form-4.pdf

2651-del-1998-form-6.pdf

2651-del-1998-gpa.pdf