Title of Invention	FORCED AIR COOLING INTERNAL COMBUSTION ENGINE
Abstract	I [Document Name] Abstract of the Disclosure [Abstract] [Problem] To provide a forced air cooling internal combustion engine such that a plug part of a head cover gasket can be fitted in a machining recess on a mating surface of a cylinder head without being blocked by an annular elastic member and such that a cylinder head cover can be easily fitted to the cylinder head. [Solution] In a forced air cooling internal combustion engine in which a machining recess 33v is formed on a mating surface 33s of a cylinder head 33, a plug part 47p to be fitted in the machining recess 33v is integrally formed at a head cover gasket 47, and shrouds 68 are provided in such a manner that an annular elastic member 95 is placed between head penetration opening parts 68p and an outer peripheral surface of the cylinder head 33, the annular elastic member 95 is provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s, and an inner peripheral surface side of a portion corresponding to the machining recess 33v is notched to form a thin wall part 951c having a notched recess 95h on a side opposite to the machining recess 33v. [Selected Drawing] FIG. 15

Title of Invention

FORCED AIR COOLING INTERNAL COMBUSTION ENGINE

Abstract

I [Document Name] Abstract of the Disclosure [Abstract] [Problem] To provide a forced air cooling internal combustion engine such that a plug part of a head cover gasket can be fitted in a machining recess on a mating surface of a cylinder head without being blocked by an annular elastic member and such that a cylinder head cover can be easily fitted to the cylinder head. [Solution] In a forced air cooling internal combustion engine in which a machining recess 33v is formed on a mating surface 33s of a cylinder head 33, a plug part 47p to be fitted in the machining recess 33v is integrally formed at a head cover gasket 47, and shrouds 68 are provided in such a manner that an annular elastic member 95 is placed between head penetration opening parts 68p and an outer peripheral surface of the cylinder head 33, the annular elastic member 95 is provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s, and an inner peripheral surface side of a portion corresponding to the machining recess 33v is notched to form a thin wall part 951c having a notched recess 95h on a side opposite to the machining recess 33v. [Selected Drawing] FIG. 15

Full Text	[Document Name] Specification [Title of the Invention] FORCED AIR COOLING INTERNAL COMBUSTION ENGINE [Technical Field] [0001] The present invention relates to a forced air cooling internal combustion engine (including an internal combustion engine of an air-cooling and water-cooling combined type) for cooling a cylinder and a cylinder head by a cooling fan driven by rotation of a crankshaft. [Background Art] [0002] For internal combustion engines of this type, already adopted has been a structure in which a shroud surrounding a cylinder and a cylinder head is provided and in which the shroud guides cooling air suctioned from the outside by a cooling fan directly connected to a crankshaft to the cylinder and the cylinder head to thereby efficiently cool the cylinder and the cylinder head (see Patent Document 1, for example). [0003] The cylinder head penetrates through a head penetration opening part of the shroud covering the surrounding of the cylinder head, and between the head penetration opening part of this shroud and the cylinder head, an annular elastic member is set for sealing so as to minimize cooling air uselessly coming out through the head penetration opening part, thereby evenly cooling the cylinder and the cylinder head and also avoiding shaking and noise caused by vibration. [0004] On the other hand, there is an internal combustion engine having a structure such that a machining recess for forming a camshaft bearing hole through machining is formed on a mating surface of a cylinder head mating with a cylinder head cover and a plug part covering the machining recess on the mating surface of the cylinder head is formed at an annular head cover gasket placed between the cylinder head and cylinder head cover in a manner such as to project therefrom (for example, see Patent Document 2). [0005] The head cover gasket, while being fitted in a groove formed on the mating surface of the cylinder head cover and thereby integrally attached to the cylinder head cover, is brought to abut on the mating surface of the cylinder head, and the plug part is fitted and sandwiched in a recess, the cylinder head cover is assembled to the cylinder head. [0006] [Patent Document 1] JP-A NO. H7-253019 [Patent Document 2] JP-A NO. 2003-343372 [Disclosure of the Invention] [Problem to be Solved by the Invention] [0007] As disclosed in Patent Document 2, when the plug part is formed at the head cover gasket in a manner such as to project therefrom, the annular elastic member is disposed along the outer surface of the plug part covering the recess on the mating surface of the cylinder head. [0008] Therefore, upon assembling a cylinder head cover with a shroud attached to a cylinder head during fabrication, maintenance, or the like, an annular elastic member as an elastic body makes contact with a machining recess on a mating surface of the cylinder head from outside, and in some cases possibly enters into the machining recess as result of fastening by a head penetration opening part of the shroud. [0009] Thus, upon assembling to the cylinder head the cylinder head cover with a mating surface thereof integrally fitted with a head cover gasket, the annular elastic member making contact with or entering into the machining recess on the mating surface of the cylinder head becomes an obstacle. Thus, it is not easy to fit the plug part of the head cover gasket in the machining recess, making it difficult to assemble the cylinder head cover. [0010] In view of the points described above, the present invention has been made, and it is an object of the invention to provide a forced air cooling internal combustion engine such that a plug part of a head cover gasket can be fitted in a machining recess on a mating surface of a cylinder head without being blocked by an annular elastic member and such that a cylinder head cover can be easily assembled to the cylinder head. [Means for Solving the Problem] [0011] To address the object described above, the invention according to Claim 1 refers to a forced air cooling internal combustion engine in which a machining recess for forming a camshaft bearing hole through machining is formed on a mating surface of a cylinder head, the mating surface mating with a cylinder head cover, in which a plug part fitted in the machining recess is integrally formed at a head cover gasket placed between the cylinder head cover and the cylinder head, and in which shrouds surrounding a cylinder and the cylinder head and guiding cooling air are provided in such a manner that an annular elastic member is placed between head penetration opening parts through which the cylinder head penetrates and an outer peripheral surface of the cylinder head near the mating surface, wherein the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, and an inner peripheral surface side of a portion corresponding to the machining recess is notched to form a thin wall part having a notched recess on a side opposite to the machining recess. [0012] The invention according to Claim 2 is characterized by the forced air cooling internal combustion engine according to Claim 1 in that the notched recess of the annular elastic member is formed so that a notched width narrows down from both sides thereof to a center thereof. [0013] The invention according to Claim 3 is characterized by the forced air cooling internal combustion engine according to Claim 1 or 2 in that both side portions of the notched recess of the annular elastic member are formed in such a manner that inner peripheral surfaces thereof swell inward from both ends to the notched recess with a gradually larger wall thickness. [Effect of the Invention] [0014] According to the forced air cooling internal combustion engine according to Claim 1, when the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, the notched recess of the annular elastic member is located oppositely to the machining recess on the mating surface of the cylinder head. Thus, the thin wall part of the annular elastic member separates from the machining recess and thus does not make contact with or enter into the machining recess, so that the plug part of the head cover gasket can be fitted in the machining recess on the mating surface of the cylinder head without being blocked by the annular elastic member, thereby permitting easy assembly of the cylinder head cover to the cylinder head. [0015] According to the forced air cooling internal combustion engine according to Claim 2, the notched recess of the annular elastic member is formed in such a manner that the notched width narrows down from both the sides thereof to the center thereof. Thus, even when an external force is added to the annular elastic member, the center of the thin wall part is always so deformed as to move to the outside separating from the machining recess, thereby preventing an influence exerted on the fitting of the plug part of the head cover gasket in the machining recess of the cylinder head. [0016] According to the forced air cooling internal combustion engine according to Claim 3, both the side portions of the notched recess of the annular elastic member are formed in such a manner that inner peripheral surfaces thereof swell inward from both ends to the notched recess with a gradually larger wall thickness. Thus, when the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, both the side portions of the notched recess of the annular elastic member are widened outward by a part swelling inward, and the thin wall part moves further away from the matching recess on the mating surface of the cylinder head, thereby reliably preventing the fitting of the plug part of the head cover gasket in the machining recess from being blocked. [Best Mode of Carrying out the Invention] [0017] Hereinafter, one embodiment according to the present invention will be described, based on FIGS. 1 through 15. An internal combustion engine 30 according to this embodiment is loaded as a swing-type power unit 10 in a motorcycle. In this specification, the front, rear, left, and right are determined with reference to a body with a forward direction of the motorcycle defined as the front. [0018] FIG. 1 shows a side view of the power unit 10. The power unit 10 has at the front thereof a single cylinder, four-stroke forced air cooling internal combustion engine 30 provided in such a posture as to lean forward to an extent such that a cylinder 32 and a cylinder head 33 are oriented in a substantially horizontal state, has a belt type continuously variable transmission 35 so formed as to extend backward from the internal combustion engine 30, and has a speed reduction mechanism 38 provided at the rear thereof and journaled by a rear wheel (not shown). [0019] Disposed at the top of the power unit 10 are: a carburetor 24 connected to a suction pipe 23 extending from the top of the cylinder head 33 of the internal combustion engine 30; and an air cleaner 25 coupled to this carburetor 24 . [0020] FIG. 2 is a sectional view of a front side portion of the power unit 10 (sectional view taken along line II-II of FIG. 1). A unit case 31 is formed by combining together a left unit case 31L and a right unit case 31R divided into the left and right. The right unit case 31R forms a half part of a crank case part. The Left unit case 31L is elongated in an anteroposterior direction, and is composed of a crank case part 31a at the front, a transmission case part 31b at the center, and a speed reducer case part 31c at the back (see FIG. 1). [0021] The left side open face of this left unit case 31L is covered with a transmission case cover 36 as a part of a transmission case, and the belt-type continuously variable transmission 35 is stored inside. The right side open face of the speed reducer case part 31c at the back is covered with a speed reducer case, and a speed reduction mechanism 38 is stored inside. [0022] In- the crank case part 31a and the so-called crank case of the right unit case 31R, a crankshaft 40 is rotatably supported by right and left main bearings 41 and 41. A connecting rod 43 connects together a piston 42 reciprocating in a cylinder liner 44 of the cylinder 32 and a crank pin 40a of the crankshaft 40. Of extending parts of the crankshaft 40, extending horizontally leftward and rightward, the rightward extending part is provided with an AC generator 60, and the leftward extending part is provided with a cam chain driving sprocket 55 and a belt driving pulley 76 of the belt-type continuously variable transmission 35. [0023] The AC generator 60 provided on the right side surface of the right unit case 31R has an outer rotor 62 of a bowl-like shape firmly fixed via ACG bosses 61 to an end part of a crankshaft 40 projecting from a central cylindrical part 31d of the right unit case 31R, and has, inside magnets 63 disposed circumferentially over the inner peripheral surface of the outer rotor 62, stators 64 each wound with a stator coil 65 and fixed to the central cylindrical part 31d. [0024] On the right side surface of the outer rotor 62, a forced air cooling fan 66 is attached, the side of which is covered with a fan cover 67, to which a shroud 58 is connected and so provided as to cover the surrounding of the cylinder 32 and the cylinder head 33. [0025] On the other hand, the belt driving pulley 76 at the left end part of the crankshaft 40 is composed of a stationary pulley half body 77 and a movable pulley half body 78. The stationary pulley half body 77 is spline-fitted to the left end part of the crankshaft 40 and firmly fixed thereto via bosse's 79. To the right thereof, the movable pulley half body 78 is journaled by the crankshaft 40 via bosses. This movable pulley half body 78 can axially slide to approach or separate from the stationary pulley half body 77. Between both the pulley half bodies 77 and 78, a V belt 75 is sandwiched and wound. [0026] At a fixed position on the right side of the movable pulley half body 78 near aforementioned annular seal members 72, a cam plate 80 is provided. A slide piece 80a provided at the outer peripheral end thereof slidably engages with a cam plate sliding boss 78a axially formed at the outer peripheral end of the movable pulley half body 78. The side surface of the movable pulley half body 78 on the cam plate 80 side is tapered toward the cam plate 80, and a dry weight roller 81 is stored in such a manner as to be sandwiched between the inside of this tapered surface and the cam plate 80. [0027] Therefore, as the rotation speed of the crankshaft 40 increases, the dry weight roller 81 located between the movable pulley half body 78 and the cam plate 80 and rotating therewith moves in a centrifugal direction due to a centrifugal force, and the movable pulley half body 78 is pressed by this dry weight roller 81 and thereby moves leftward to approach the stationary pulley half body 77, moving the V belt 75 sandwiched between both the pulley half bodies 77 and 78 in the centrifugal direction and thereby increasing the winding diameter. [0028] • Referring to FIG. 2, to the stationary pulley half body 77, cooling fan plates 118 are attached by being spline-fitted to the crankshaft 40. Opposite to this cooling fan 118, a case air suction port 36c is formed at the front of a transmission case cover 36, and an outside air introduction duct 150 communicating with the case air suction port 36c is attached at the front of the transmission case cover 36. The outside air introduction duct 150 extends upward from the front side surface of the transmission case cover 36 and has an outside air introduction port 154 at the top thereof (see FIG. 1). [0029] As a result of rotation of the cooling fan plates 118 attached to the stationary pulley half body 77 of the belt-type continuously variable transmission 35, outside air is introduced to the case air suction port 36c from the outside air introduction port 154 of the outside air introduction duct 150 via an outside air passage 160 and is suctioned as cooling air into the chamber of the belt-type continuously variable transmission, so that the cooling air cools down the belt-type continuously variable transmission 35 and is discharged to the outside from a case air exhaust duct 36d (see FIG. 1). [0030] Referring to FIGS. 4 and 5, the cylinder head 33 superimposed on and fastened to the cylinder 32 has a mating surface 33s of a substantially rectangular annular shape mating with a cylinder head cover 34 further shrouded over the cylinder head 33, and has swelling walls 33BL and 33BR formed inside the mating surface 33s oppositely and in bilateral symmetry with each other in a manner such that a ceiling wall portion of a combustion chamber 46 opposing a top surface of the piston 42 greatly swells (see FIG. 2). [0031] These swelling walls 33BL and 33BR project more than the mating surface 33s. On these left and right swelling walls 33BL and 33BR, a valve train 50 formed of an SOHC model valve system is provided. Since the cylinder head 33 leans forward to a great extent such that it is oriented substantially horizontally, the left and right swelling walls 33BL and 33BR project forward from the mating surface 33s. In these left and right swelling walls 33BL and 33BR, camshaft bearing holes 33cL and 33cR are drilled coaxially at a position in the same plane with the mating surface 33s. At the diagonally upper front and lower front, rocker arm shaft bearing holes 33iL and 33iR and rocker arm shaft bearing holes 33eL and 33eR are respectively drilled coaxially. All of these bearing holes 33cL, 33cR, 33iL, 33iR, 33eL, and 33eR are so formed as to be oriented horizontally in the lateral direction. [0032] Then between the left side wall of the cylinder head 33 and the left side swelling wall 33BL, a cam chain chamber 52 is formed (see FIG. 4). On the left side wall of the cylinder head 33 opposing the left side swelling wall 33BL spaced apart therefrom by the cam chain chamber 52, a machining recess 33v of a semicircular-arc shape for machining the camshaft bearing holes is formed in the mating surface 33s while lacking a semicircular portion opposing the camshaft bearing hole 33cL since the central axis of the camshaft bearing hole 33cL is in the same plane with the mating surface 33s (see FIGS. 4 and 5). [0033] In the camshaft bearing holes 33cL and 33cR of the left and right swelling walls 33BL and 33BR, a camshaft 53 is rotatably provided via bearings 53bL and 53bR in a manner such as to be oriented horizontally in the lateral direction. To the left end part of the camshaft 53 projecting to the cam chain chamber 52, a driven sprocket 54 is attached. On the other hand, between a driving sprocket 55 attached to the crankshaft 40 and the aforementioned driven sprocket 54, a cam chain 51 is provided in a manner such as to penetrate through the cam chain chamber 52 which is so provided as to communicate with the crank case part 31a, the cylinder 32, and the cylinder head 33, so that rotation of the crankshaft 40 is transmitted to the camshaft 53 at a half rotation speed. [0034] In upper rocker arm shaft bearing holes 33i and 33i of the right and left swelling walls 33B and 33B, a suction ■ rocker shaft 58i is provided, and in the lower rocker arm shaft bearing holes, an exhaust rocker shaft 58e is provided. The suction rocker shaft 58i and the exhaust rocker shaft 58e are oriented in parallel to the camshaft 53 horizontally in the lateral direction. [0035] Referring to FIGS. 3 and 11, to the suction rocker shaft 58i, a suction rocker arm 59i is freely swingably and pivotably fitted, and to the exhaust rocker shaft 58e, an exhaust rocker arm' 59e is freely swingably and pivotably fitted. One of the rocker arms, the suction rocker arm 59i, has a roller 59ir at one end thereof in contact with a suction cam lobe of the camshaft 53 and has the other end thereof in contact with a valve stem head part of a suction valve 56 located above the camshaft 53. The other rocker arm, the exhaust rocker arm 59e, has a roller 59er at one end thereof in contact with an exhaust cam lobe of the camshaft 53 and has the other end thereof in contact with a valve stem head part of an exhaust valve 57 located below the camshaft 53. [0036] Therefore, in this valve train 50, rotation of the camshaft 53 in synchronization with rotation of the crankshaft 40 oscillates the suction rocker arm 59i and the exhaust rocker arm 59e, and at predetermined timing, the suction valve 56 opens and closes a suction port opening of the combustion chamber 4 6 and the exhaust valve 57 opens and closes an exhaust port opening of the combustion chamber 46. A spark plug 45 is inserted diagonally into the cylinder head 33 from a side opposite to the cain chain chamber 52 (right side) toward the combustion chamber 46. [0037] The cylinder head cover 34 covering the valve train 50 as described above is formed in a rectangular bowl-like shape. As shown in FIG. 15, on a mating surface 34s of a substantially annular shape mating with the cylinder head 33, grooved lines 34sv are formed, and a head cover gasket 47 of a substantially rectangular annular shape is fitted therein at its ridges 47r, whereby the cylinder head cover 34 is joint and fastened to the cylinder head 33 with the head cover gasket 47 therebetween. [0038] Since, on the mating surface 33s on the cylinder head 33 side, the machining recess 33v of a semicircular arc shape is formed on the left side wall as described above, a plug part 47p of a semicircular arc shape to be fitted in this machining recess 33v for closing is formed integrally with the head cover gasket 4-7 in a manner such as to project therefrom (see FIGS. 14 and 15). [0039] As shown in FIGS. 14 and 15, the plug part 47p projecting to the left side edge in the head cover gasket 47 of a substantially rectangular annular shape is formed into a vessel-like shape having a semicircular cylindrical wall part 47ps whose inner end opens and whose outer end opening is closed by a semicircular wall part 47pw, and this shape is maintained by a metal tool 48 of the same shape fitted in such a manner as to make contact with a bottom surface of this semicircular wall part 47pw and an inner peripheral surface of the semicircular cylindrical part 47ps. At inner and outer ends of the semicircular cylindrical part 47ps, flanges 47pf and 47pf are formed in a manner such as to project therefrom. [0040] Therefore, when the head cover gasket 47 is sandwiched between the mating surfaces 33s and 34s of the cylinder head 33 and the cylinder head cover 34, the plug part 47p of the head cover gasket 47 is fitted in the machining recess 33v of a semicircular arc shape formed on the mating surface 33s on the cylinder head 33 side and thereby closes the machining recess 33v. [0041] On the other hand, the shroud 68 surrounding the cylinder 32 and the cylinder head 33 is composed of an upper shroud s 68U and a lower shroud 68L that are divided into an upper half and a lower half, respectively. The upper and lower shroud 68U and 68L are provided in a manner such that head penetration opening parts 68Up and 6BLp through which the cylinder head 33 penetrates sandwich a rubber annular elastic member 95 with an outer peripheral surface of the cylinder head 33 near the mating surface 33s. [0042] As shown in FIG. 4, ribs 33r are formed separately at the top and bottom and circumferentially on the outer peripheral surface of the cylinder head 33 near the mating surface 33s in a manner such as to project therefrom. The upper and lower ribs 33r and 33r project outward from the outer peripheral surface of the cylinder head 33 along the mating surface 33s, with left ends (right ends in FIG. 4) thereof orthogonally bent and right ends (left ends in FIG. 4) thereof curved in the form of a circular arc and further extending around on the right side surface. [0043] The annular elastic member 95 formed into a substantially rectangular annular shape, as shown in FIGS. 6 through 10, is U-shaped in cross section (see FIG. 7) in a manner such as to be fitted to the ribs 33r from the upper and lower side edges to the right side edge (left side edge in FIG. 6). A center part 95r on the right side edge swells inward in a manner such as to be fitted between the upper and lower end parts of the right side part of the upper and lower ribs 33r and 33r. The left side edge is so formed as to be solid and vertically symmetrical. A center part of this left side edge has its inner surface notched to be thereby formed into a thin wall part 951c having a notched recess 95h opening inward (see FIG. 9). A left upper part 951u and a left lower part 9511 above and below the thin wall part 951c located at this left side center are so formed as to gradually swell inward with a gradually increased wall thickness from the upper and lower bending parts to the notched recess 95h located at the center (FIGS. 6 and 10). i The notched recess 95h on the inner side of the thin wall part 951c is formed with tilted surfaces 95s and 95s such that a notched width w becomes narrower from both the upper and lower sides toward the center. [0044] This annular elastic member 95, while being extended with a tensile force, is provided around an outer peripheral surface of the cylinder head 33 near the mating surface 33s in a manner such as to be engaged with the upper and lower ribs 33r and 33r of the cylinder head 33. Referring to FIG. 11, when the annular elastic member 95 is provided around the outer peripheral surface of the cylinder head 33 in a manner such that a portion of a U shape in cross section from the upper and lower sides to the right side of the annular elastic member 95 is fitted to the ribs 33r, the left upper part 951u and the left lower part 9511 gradually swelling inward from the upper and lower bending parts of the annular elastic member 95 to the thin wall part 951c at the left center abut on the left outer side surface of the cylinder head 33 and widens in a manner such as to open outward, whereby the thin wall part 951c at the left center of the annular elastic member 95 separates outward from the left outer side surface of the cylinder head 33. [0045] Therefore, in the annular elastic member 95, the notched recess 95h originally formed on the inner side of the thin wall part 951c at the left center is consequently located on the outer side of the semicircular-arc-shaped machining recess 33v on the left outer side surface of the cylinder head 33 (see FIG. 11), thereby forming space on the outer side of the machining recess 33v. [0046] Under the condition that the annular elastic member 95 is provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s, the upper shroud 68U and the lower shroud 68L covering the surrounding of the cylinder 32 and the cylinder head 33 are shrouded. The head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L through which the cylinder head 33 penetrates are each formed into a U shape, in cross section, fitted to the annular elastic member 95 from the outer side (see FIG. 3). [0047] FIG. 12 is a front view of the cylinder 32 and the cylinder head 33 shrouded with the upper shroud 68U and the lower shroud 68L from the above and below before the cylinder head cover 34 is attached, as viewed from the front. [0048] Split surfaces of the upper and lower shrouds 68U and 68L are located at a substantially vertical center. When the upper shroud 68U and the lower shroud 68L are shrouded from the above and below, the head penetration opening parts 68Up and 68Lp cover the cylinder 32 and the cylinder head 33 from the above and below in a manner such as to be fitted to the annular elastic member 95, from the above and below, provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s, their split surfaces are aligned with each other, and both are combined together with joining parts 68Uc and 68Lc. [0049] As shown in FIG. 12, the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L fit to the annular elastic member 95 provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s and almost cover it. Left side parts 68Upl and 68Lpl of the head penetration opening parts 68Up and 68Lp in the upper and lower shrouds 68U and 68L are formed into a shape similar to that of the left side part of the annular elastic member 95, with a recess 68h formed on the inner side of its center part. [0050] On the outer side of the machining recess 33v on the mating surface 33s of the cylinder head 33, in a front view shown in FIG. 12, the recess 68h of the upper and lower shrouds 68U and 68L together with the notched recess 95h of the annular elastic member 95 is located, thereby forming space. The annular elastic member 95 has the tilted surfaces 95s and 95s such that the notched recess 95h at the center on the_left side edge has a notched width vj narrowing down from both the upper and lower sides toward the center. Thus, even when the annular elastic member 95 receives an external force by being sandwiched between the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L, it is deformed in a bending manner so as to move the center of the thin wall part 951c to the outside separating from the machining recess 33v. [0051] Therefore, between the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L and the outer peripheral surface of the cylinder head 33 near the mating surface 33s, the annular elastic member 95 is placed, whereby the head penetration opening parts 68Up and 68Lp are almost sealed. However, part of the notched recess 95h of the annular elastic member 95, together with the recess 68h of the head penetration opening parts 68Up and 68Lp, communicates with the outside. Note, however, that the recess 68h of the head penetration opening parts 68Up and 68Lp is partially covered with the plug part 47p of the head cover gasket 47 fitted in the machining recess 33v of the cylinder head 33. Placing this annular elastic member 95 permits absorbing vibration caused by driving of the internal combustion engine 30, prevents shaking of the upper and lower shrouds 68U and 68L, and suppressing occurrence of noise. [0052] The upper and lower shrouds 68U and 68L covering th surrounding of the cylinder 32 and the cylinder head 33 of the internal combustion engine 30 in this manner have an upper side wall, a lower side wall, and a left side wall extending backward along the side surfaces of the cylinder 32 and the cylinder head 33 and have a right side wall greatly swelling rightward in a manner such as to separate gradually from the cylinder 32 and the cylinder head 33 to be coupled to the fan cover 67 (see FIGS. 2 and 12). [0053] For the fan cover 67, a front part of the peripheral edge of an annular frame 67a, having the crankshaft 40 as its central axis, is screwed with a screw 120 into the back end edge of the right side walls of the upper and lower shrouds 68U and 68L to be thereby coupled thereto, and a portion other than the front part of the peripheral edge of the annular frame 67a is screwed with a bolt 121 into the right end edge of the right unit case 31R to be thereby fixed thereto. Thus, the fan cover 67 corresponds to an extending member of the upper and lower shrouds 68U and 68L, and has a cooling air inlet 67i provided at its right side wall oppositely to the forced air cooling fan 66 (see FIG. 2) . [0054] On the other hand, at the left side wall of the lower shroud 68L, a cooling air outlet 68e opens in the lower half near the back, and to this cooling air outlet 68e, the front end of an exhaust air duct 69 is coupled (see FIGS. 1, 2, and 12) . The exhaust air duct 69 first extends leftward from the cooling air outlet 68e at the left side wall of the lov;er shroud 68L, bends diagonally downward and backward, then extends along the lower end surface of the outside air introduction duct 150, reaching a back end exhaust air port 69e (see FIG. 1). [0055] For the upper and lower shrouds 68U and SBL surrounding the cylinder 32 and the cylinder head 33, the cooling air inlet 57i is provided in the fan cover 67 as the backward extension of the right side wall that swells rightward, and the cooling air outlet 68e is formed in the left side wall opposing this right side wall. Therefore, referring to FIG. 2, cooling air suctioned through the cooling air inlet 67i as a result of rotation of the forced air cooling fan 66 integral to rotation of the crankshaft forcibly cools the cylinder 32 and the cylinder head 33 by flowing leftward around the cylinder 32 and the cylinder head 33 while being guided diagonally forward by the bent right side wall. Since the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L are almost sealed by the annular elastic member 95, the cooling air directly flows out to the cooling air outlet 68e in the left side wall without changing its direction, is guided diagonally downward and backward by the exhaust air duct 69, and is discharged from the back end exhaust air port 69e. [0056] Note that the sealing of the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L by the annular elastic member 95 is not complete, and a gap between the inner surface of the recess 68h on the left side of the head penetration opening parts 68Up and 68Lp and the plug part 47p of the head cover gasket 47 is not sealed, causing concern of cooling air leak from the gap, although this gap is located at the downstream side (left side) of the cylinder head 33 with respect to the cooling air flow, which does not have great influence on the cooling performance of the internal combustion engine. [0057] However, since the temperature inside an engine room surrounded by the body is not increased by hot air leak, a gap between the inner surface of the recess 68h and the plug part 47p of the head cover gasket 47 is set as minimum as possible within a range such that the head cover gasket 47, together with the cylinder head cover 34, can be assembled to the cylinder head 33 in a manner such as to penetrating through the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L. [0058] On the other hand, the annular elastic member 95 is hidden inside the upper and lower shrouds 68U and 68L and thus cannot be visually checked when the head cover gasket 47 is assembled together with the cylinder head cover 34. Thus, to preferentially facilitate assembly, a gap between' the inner surface of the notched recess 95h of the annular elastic member 95 and the plug part 47p of the head cover gasket 47 is set larger than the gap between the inner surface of the recess 68h of the upper and lower shrouds 68U and 68L and the plug part 47p of the head cover gasket 47. [0059] Under the condition that the upper and lower shrouds 68U and 68L guiding the cooling air from the forced air cooling fan 66 to the cylinder 32 and the cylinder head 33 in this manner are so attached as to cover the cylinder 32 and the cylinder head 33 as described above, as shown in the front view of FIG. 12, the notched recess 95h of the annular elastic member 95 and the recess 68h of the upper and lower shrouds 68U and 68L are located on the outer side of the machining recess 33v on the mating surface 33s of the cylinder head 33, thereby providing a space. Thus, upon attaching the cylinder head cover 34 together with the head cover gasket 47 to the cylinder head 33, the plug part 47p of the head cover gasket 47 can be easily fitted in the machining recess 33v on the mating surface 33s without being blocked by the thin wall part 951c of the annular elastic member 95. [0060] Specifically, upon assembling the cylinder head cover 34 with the upper and lower shrouds 68U and 68L attached to the cylinder head 33 and the cylinder 32 during fabrication, maintenance, or the like, the notched recess 95h of the > r annular elastic member 95 is located oppositely to the machining recess 33v on the mating surface '33s of the cylinder head 33, the thin wall part 951c of the annular elastic member 95 is kept separated from the machining recess 33v, and the thin wall part 951c neither makes contact with nor enters into the machining recess. Thus, the plug part 47p of the head cover gasket 47 attached to the cylinder head cover 34 can be fitted in the machining recess 33v on the mating surface 33s of the cylinder head 33 without being blocked by the annular elastic member 95, thereby permitting easy assembly of the cylinder head cover 34 to the cylinder head 33. [0061] Since the plug part 47p of the head cover gasket 47 maintains its shape by having the metal tool 48 fitted thereinside, it can be easily fitted in the machining recess 33v of the cylinder head 33 without being deformed, and the plug part 47p can be reliably fitted in the machining recess 33v through positioning such that the flanges 47pf and 47pf at the inner and outer ends of the semicircular cylindrical part 47ps in the plug part 47p sandwich both the sides of the semicircular arc surface of the machining recess 33v. [Brief Description of the Drawings] [0062] [FIG. 1] FIG. 1 is a side view of a power unit according to one embodiment of the present invention. [FIG. 2] FIG. 2 is a sectional view of a front side portion of the same power unit (sectional view taken along line II-II of FIG. 1). [FIG. 3] FIG. 3 is a sectional view of a front side portion of the same power unit (sectional view taken along line III-III of FIG. 2) . [FIG. 4] FIG. 4 is a plan view of a cylinder head. [FIG. 5] FIG. 5 is a left side view of the same (view, along arrow V of FIG. 4). [FIG. 6] FIG. 6 is a plan view of an annular elastic member. [FIG. 7] FIG. 7 is a sectional view taken along line VII- VII of FIG. 6. [FIG. 8] FIG. 8 is a sectional view taken along line VIII- VIII of FIG. 6. [FIG. 9] FIG. 9 is a sectional view taken along line IX-IX of FIG. 6. [FIG. 10] FIG. 10 is a sectional view taken along line X-X of FIG. 6. [FIG. 11] FIG. 11 is a front view showing the annular elastic member provided around the cylinder head. [FIG. 12] FIG. 12 is a front view of a cylinder and the cylinder head covered with shrouds before a cylinder head cover is attached, as viewed from the front. [FIG. 13] FIG. 13 is a plan view of a head cover gasket. [FIG. 14] FIG. 14 is a disassembled side view of the disassembled cylinder head cover and head cover gasket at the front of an internal combustion engine. [FIG. 15] FIG. 15 is a sectional view of the same. [Description of Reference Numerals] [0063] 10 . . .Power unit 30 ...Internal combustion engine 31. . .Unit case 32 . ..Cylinder 33...Cylinder head 33s..Mating surface 33v...Machining recess 34 ...Cylinder head cover 35...Belt-type continuously variable transmission 36...Transmission case cover 40."Crankshaft 65...Forced air cooling fan 67 ...Fan cover 67i...Cooling air inlet 68...Shroud 68U...Upper shroud 68L...Lower shroud 68Up, 68Lp...Head penetration opening part 68e...Cooling air outlet 69...Exhaust air duct 69e...Back end exhaust air port 95...Annular elastic member 95h...Notched recess 951c...Thin wall part 95s...Tilted surface 951u...Left upper part 9511...Left lower part [Document Name] Scope of Claims [Claim 1] A forced air cooling internal combustion engine in which: a machining recess for forming a camshaft bearing hole through machining is formed on a mating surface of a cylinder head, the mating surface mating with a cylinder head cover; a plug part fitted in the machining recess is integrally formed at a head cover gasket placed between the cylinder head cover and the cylinder head; and shrouds surrounding a cylinder and the cylinder head and guiding cooling air are provided in such a manner that an annular elastic member is placed between head penetration opening parts through which the cylinder head penetrates and an outer peripheral surface of the cylinder head near the mating surface, wherein the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, and an inner peripheral surface side of a portion corresponding to the machining recess is notched to form a thin wall part having a notched recess on a side opposite to the machining recess. [Claim 2] The forced air cooling internal combustion engine according to Claim 1, wherein the notched recess of the annular elastic member is formed in such a manner that a notched width narrows down from both sides thereof to a center thereof. [Claim 3] The forced air cooling internal combustion engine according to Claim 1 or 2, wherein both side portions of the notched recess of the annular elastic member are formed in such a manner that inner peripheral surfaces thereof swell inward from both ends to the notched recess with a gradually larger wall thickness.

Full Text

[Document Name] Specification
[Title of the Invention] FORCED AIR COOLING INTERNAL
COMBUSTION ENGINE
[Technical Field]
[0001]
The present invention relates to a forced air cooling internal combustion engine (including an internal combustion engine of an air-cooling and water-cooling combined type) for cooling a cylinder and a cylinder head by a cooling fan driven by rotation of a crankshaft. [Background Art] [0002]
For internal combustion engines of this type, already adopted has been a structure in which a shroud surrounding a cylinder and a cylinder head is provided and in which the shroud guides cooling air suctioned from the outside by a cooling fan directly connected to a crankshaft to the cylinder and the cylinder head to thereby efficiently cool the cylinder and the cylinder head (see Patent Document 1, for example). [0003]
The cylinder head penetrates through a head penetration opening part of the shroud covering the surrounding of the cylinder head, and between the head penetration opening part of this shroud and the cylinder head, an annular elastic member is set for sealing so as to minimize cooling air uselessly coming out through the head penetration opening part, thereby evenly cooling the

cylinder and the cylinder head and also avoiding shaking
and noise caused by vibration.
[0004]
On the other hand, there is an internal combustion engine having a structure such that a machining recess for forming a camshaft bearing hole through machining is formed on a mating surface of a cylinder head mating with a cylinder head cover and a plug part covering the machining recess on the mating surface of the cylinder head is formed at an annular head cover gasket placed between the cylinder head and cylinder head cover in a manner such as to project therefrom (for example, see Patent Document 2). [0005]
The head cover gasket, while being fitted in a groove formed on the mating surface of the cylinder head cover and thereby integrally attached to the cylinder head cover, is brought to abut on the mating surface of the cylinder head, and the plug part is fitted and sandwiched in a recess, the cylinder head cover is assembled to the cylinder head. [0006]
[Patent Document 1] JP-A NO. H7-253019
[Patent Document 2] JP-A NO. 2003-343372 [Disclosure of the Invention] [Problem to be Solved by the Invention] [0007]
As disclosed in Patent Document 2, when the plug part is formed at the head cover gasket in a manner such as to project therefrom, the annular elastic member is disposed

along the outer surface of the plug part covering the recess on the mating surface of the cylinder head. [0008]
Therefore, upon assembling a cylinder head cover with a shroud attached to a cylinder head during fabrication, maintenance, or the like, an annular elastic member as an elastic body makes contact with a machining recess on a mating surface of the cylinder head from outside, and in some cases possibly enters into the machining recess as result of fastening by a head penetration opening part of the shroud. [0009]
Thus, upon assembling to the cylinder head the cylinder head cover with a mating surface thereof integrally fitted with a head cover gasket, the annular elastic member making contact with or entering into the machining recess on the mating surface of the cylinder head becomes an obstacle. Thus, it is not easy to fit the plug part of the head cover gasket in the machining recess, making it difficult to assemble the cylinder head cover. [0010]
In view of the points described above, the present invention has been made, and it is an object of the invention to provide a forced air cooling internal combustion engine such that a plug part of a head cover gasket can be fitted in a machining recess on a mating surface of a cylinder head without being blocked by an annular elastic member and such that a cylinder head cover

can be easily assembled to the cylinder head.
[Means for Solving the Problem]
[0011]
To address the object described above, the invention according to Claim 1 refers to a forced air cooling internal combustion engine in which a machining recess for forming a camshaft bearing hole through machining is formed on a mating surface of a cylinder head, the mating surface mating with a cylinder head cover, in which a plug part fitted in the machining recess is integrally formed at a head cover gasket placed between the cylinder head cover and the cylinder head, and in which shrouds surrounding a cylinder and the cylinder head and guiding cooling air are provided in such a manner that an annular elastic member is placed between head penetration opening parts through which the cylinder head penetrates and an outer peripheral surface of the cylinder head near the mating surface, wherein the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, and an inner peripheral surface side of a portion corresponding to the machining recess is notched to form a thin wall part having a notched recess on a side opposite to the machining recess. [0012]
The invention according to Claim 2 is characterized by the forced air cooling internal combustion engine according to Claim 1 in that the notched recess of the annular elastic member is formed so that a notched width

narrows down from both sides thereof to a center thereof. [0013]
The invention according to Claim 3 is characterized by the forced air cooling internal combustion engine according to Claim 1 or 2 in that both side portions of the notched recess of the annular elastic member are formed in such a manner that inner peripheral surfaces thereof swell inward from both ends to the notched recess with a gradually larger wall thickness. [Effect of the Invention] [0014]
According to the forced air cooling internal combustion engine according to Claim 1, when the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, the notched recess of the annular elastic member is located oppositely to the machining recess on the mating surface of the cylinder head. Thus, the thin wall part of the annular elastic member separates from the machining recess and thus does not make contact with or enter into the machining recess, so that the plug part of the head cover gasket can be fitted in the machining recess on the mating surface of the cylinder head without being blocked by the annular elastic member, thereby permitting easy assembly of the cylinder head cover to the cylinder head. [0015]
According to the forced air cooling internal combustion engine according to Claim 2, the notched recess

of the annular elastic member is formed in such a manner that the notched width narrows down from both the sides thereof to the center thereof. Thus, even when an external force is added to the annular elastic member, the center of the thin wall part is always so deformed as to move to the outside separating from the machining recess, thereby preventing an influence exerted on the fitting of the plug part of the head cover gasket in the machining recess of the cylinder head. [0016]
According to the forced air cooling internal combustion engine according to Claim 3, both the side portions of the notched recess of the annular elastic member are formed in such a manner that inner peripheral surfaces thereof swell inward from both ends to the notched recess with a gradually larger wall thickness. Thus, when the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, both the side portions of the notched recess of the annular elastic member are widened outward by a part swelling inward, and the thin wall part moves further away from the matching recess on the mating surface of the cylinder head, thereby reliably preventing the fitting of the plug part of the head cover gasket in the machining recess from being blocked. [Best Mode of Carrying out the Invention] [0017]
Hereinafter, one embodiment according to the present

invention will be described, based on FIGS. 1 through 15.
An internal combustion engine 30 according to this embodiment is loaded as a swing-type power unit 10 in a motorcycle.
In this specification, the front, rear, left, and right are determined with reference to a body with a forward direction of the motorcycle defined as the front. [0018]
FIG. 1 shows a side view of the power unit 10.
The power unit 10 has at the front thereof a single cylinder, four-stroke forced air cooling internal combustion engine 30 provided in such a posture as to lean forward to an extent such that a cylinder 32 and a cylinder head 33 are oriented in a substantially horizontal state, has a belt type continuously variable transmission 35 so formed as to extend backward from the internal combustion engine 30, and has a speed reduction mechanism 38 provided at the rear thereof and journaled by a rear wheel (not shown). [0019]
Disposed at the top of the power unit 10 are: a carburetor 24 connected to a suction pipe 23 extending from the top of the cylinder head 33 of the internal combustion engine 30; and an air cleaner 25 coupled to this carburetor 24 . [0020]
FIG. 2 is a sectional view of a front side portion of the power unit 10 (sectional view taken along line II-II of

FIG. 1).
A unit case 31 is formed by combining together a left unit case 31L and a right unit case 31R divided into the left and right. The right unit case 31R forms a half part of a crank case part. The Left unit case 31L is elongated in an anteroposterior direction, and is composed of a crank case part 31a at the front, a transmission case part 31b at the center, and a speed reducer case part 31c at the back (see FIG. 1). [0021]
The left side open face of this left unit case 31L is covered with a transmission case cover 36 as a part of a transmission case, and the belt-type continuously variable transmission 35 is stored inside. The right side open face of the speed reducer case part 31c at the back is covered with a speed reducer case, and a speed reduction mechanism 38 is stored inside. [0022]
In- the crank case part 31a and the so-called crank case of the right unit case 31R, a crankshaft 40 is rotatably supported by right and left main bearings 41 and 41. A connecting rod 43 connects together a piston 42 reciprocating in a cylinder liner 44 of the cylinder 32 and a crank pin 40a of the crankshaft 40.
Of extending parts of the crankshaft 40, extending horizontally leftward and rightward, the rightward extending part is provided with an AC generator 60, and the leftward extending part is provided with a cam chain

driving sprocket 55 and a belt driving pulley 76 of the belt-type continuously variable transmission 35. [0023]
The AC generator 60 provided on the right side surface of the right unit case 31R has an outer rotor 62 of a bowl-like shape firmly fixed via ACG bosses 61 to an end part of a crankshaft 40 projecting from a central cylindrical part 31d of the right unit case 31R, and has, inside magnets 63 disposed circumferentially over the inner peripheral surface of the outer rotor 62, stators 64 each wound with a stator coil 65 and fixed to the central cylindrical part 31d. [0024]
On the right side surface of the outer rotor 62, a forced air cooling fan 66 is attached, the side of which is covered with a fan cover 67, to which a shroud 58 is connected and so provided as to cover the surrounding of the cylinder 32 and the cylinder head 33. [0025]
On the other hand, the belt driving pulley 76 at the left end part of the crankshaft 40 is composed of a stationary pulley half body 77 and a movable pulley half body 78. The stationary pulley half body 77 is spline-fitted to the left end part of the crankshaft 40 and firmly fixed thereto via bosse's 79. To the right thereof, the movable pulley half body 78 is journaled by the crankshaft 40 via bosses. This movable pulley half body 78 can axially slide to approach or separate from the stationary

pulley half body 77. Between both the pulley half bodies
77 and 78, a V belt 75 is sandwiched and wound.
[0026]
At a fixed position on the right side of the movable pulley half body 78 near aforementioned annular seal members 72, a cam plate 80 is provided. A slide piece 80a provided at the outer peripheral end thereof slidably engages with a cam plate sliding boss 78a axially formed at the outer peripheral end of the movable pulley half body 78.
The side surface of the movable pulley half body 78 on the cam plate 80 side is tapered toward the cam plate 80, and a dry weight roller 81 is stored in such a manner as to be sandwiched between the inside of this tapered surface and the cam plate 80. [0027]
Therefore, as the rotation speed of the crankshaft 40 increases, the dry weight roller 81 located between the movable pulley half body 78 and the cam plate 80 and rotating therewith moves in a centrifugal direction due to a centrifugal force, and the movable pulley half body 78 is pressed by this dry weight roller 81 and thereby moves leftward to approach the stationary pulley half body 77, moving the V belt 75 sandwiched between both the pulley half bodies 77 and 78 in the centrifugal direction and thereby increasing the winding diameter. [0028] •
Referring to FIG. 2, to the stationary pulley half body 77, cooling fan plates 118 are attached by being

spline-fitted to the crankshaft 40. Opposite to this cooling fan 118, a case air suction port 36c is formed at the front of a transmission case cover 36, and an outside air introduction duct 150 communicating with the case air suction port 36c is attached at the front of the transmission case cover 36.
The outside air introduction duct 150 extends upward from the front side surface of the transmission case cover 36 and has an outside air introduction port 154 at the top thereof (see FIG. 1). [0029]
As a result of rotation of the cooling fan plates 118 attached to the stationary pulley half body 77 of the belt-type continuously variable transmission 35, outside air is introduced to the case air suction port 36c from the outside air introduction port 154 of the outside air introduction duct 150 via an outside air passage 160 and is suctioned as cooling air into the chamber of the belt-type continuously variable transmission, so that the cooling air cools down the belt-type continuously variable transmission 35 and is discharged to the outside from a case air exhaust duct 36d (see FIG. 1). [0030]
Referring to FIGS. 4 and 5, the cylinder head 33 superimposed on and fastened to the cylinder 32 has a mating surface 33s of a substantially rectangular annular shape mating with a cylinder head cover 34 further shrouded over the cylinder head 33, and has swelling walls 33BL and

33BR formed inside the mating surface 33s oppositely and in bilateral symmetry with each other in a manner such that a ceiling wall portion of a combustion chamber 46 opposing a top surface of the piston 42 greatly swells (see FIG. 2). [0031]
These swelling walls 33BL and 33BR project more than the mating surface 33s. On these left and right swelling walls 33BL and 33BR, a valve train 50 formed of an SOHC model valve system is provided.
Since the cylinder head 33 leans forward to a great extent such that it is oriented substantially horizontally, the left and right swelling walls 33BL and 33BR project forward from the mating surface 33s. In these left and right swelling walls 33BL and 33BR, camshaft bearing holes 33cL and 33cR are drilled coaxially at a position in the same plane with the mating surface 33s. At the diagonally upper front and lower front, rocker arm shaft bearing holes 33iL and 33iR and rocker arm shaft bearing holes 33eL and 33eR are respectively drilled coaxially. All of these bearing holes 33cL, 33cR, 33iL, 33iR, 33eL, and 33eR are so formed as to be oriented horizontally in the lateral direction. [0032]
Then between the left side wall of the cylinder head 33 and the left side swelling wall 33BL, a cam chain chamber 52 is formed (see FIG. 4).
On the left side wall of the cylinder head 33 opposing the left side swelling wall 33BL spaced apart

therefrom by the cam chain chamber 52, a machining recess 33v of a semicircular-arc shape for machining the camshaft bearing holes is formed in the mating surface 33s while lacking a semicircular portion opposing the camshaft bearing hole 33cL since the central axis of the camshaft bearing hole 33cL is in the same plane with the mating surface 33s (see FIGS. 4 and 5). [0033]
In the camshaft bearing holes 33cL and 33cR of the left and right swelling walls 33BL and 33BR, a camshaft 53 is rotatably provided via bearings 53bL and 53bR in a manner such as to be oriented horizontally in the lateral direction. To the left end part of the camshaft 53 projecting to the cam chain chamber 52, a driven sprocket 54 is attached.
On the other hand, between a driving sprocket 55 attached to the crankshaft 40 and the aforementioned driven sprocket 54, a cam chain 51 is provided in a manner such as to penetrate through the cam chain chamber 52 which is so provided as to communicate with the crank case part 31a, the cylinder 32, and the cylinder head 33, so that rotation of the crankshaft 40 is transmitted to the camshaft 53 at a half rotation speed. [0034]
In upper rocker arm shaft bearing holes 33i and 33i of the right and left swelling walls 33B and 33B, a suction ■ rocker shaft 58i is provided, and in the lower rocker arm shaft bearing holes, an exhaust rocker shaft 58e is

provided. The suction rocker shaft 58i and the exhaust rocker shaft 58e are oriented in parallel to the camshaft 53 horizontally in the lateral direction. [0035]
Referring to FIGS. 3 and 11, to the suction rocker shaft 58i, a suction rocker arm 59i is freely swingably and pivotably fitted, and to the exhaust rocker shaft 58e, an exhaust rocker arm' 59e is freely swingably and pivotably fitted.
One of the rocker arms, the suction rocker arm 59i, has a roller 59ir at one end thereof in contact with a suction cam lobe of the camshaft 53 and has the other end thereof in contact with a valve stem head part of a suction valve 56 located above the camshaft 53.
The other rocker arm, the exhaust rocker arm 59e, has a roller 59er at one end thereof in contact with an exhaust cam lobe of the camshaft 53 and has the other end thereof in contact with a valve stem head part of an exhaust valve 57 located below the camshaft 53. [0036]
Therefore, in this valve train 50, rotation of the camshaft 53 in synchronization with rotation of the crankshaft 40 oscillates the suction rocker arm 59i and the exhaust rocker arm 59e, and at predetermined timing, the suction valve 56 opens and closes a suction port opening of the combustion chamber 4 6 and the exhaust valve 57 opens and closes an exhaust port opening of the combustion chamber 46.

A spark plug 45 is inserted diagonally into the cylinder head 33 from a side opposite to the cain chain chamber 52 (right side) toward the combustion chamber 46. [0037]
The cylinder head cover 34 covering the valve train 50 as described above is formed in a rectangular bowl-like shape. As shown in FIG. 15, on a mating surface 34s of a substantially annular shape mating with the cylinder head 33, grooved lines 34sv are formed, and a head cover gasket 47 of a substantially rectangular annular shape is fitted therein at its ridges 47r, whereby the cylinder head cover 34 is joint and fastened to the cylinder head 33 with the head cover gasket 47 therebetween. [0038]
Since, on the mating surface 33s on the cylinder head 33 side, the machining recess 33v of a semicircular arc shape is formed on the left side wall as described above, a plug part 47p of a semicircular arc shape to be fitted in this machining recess 33v for closing is formed integrally with the head cover gasket 4-7 in a manner such as to project therefrom (see FIGS. 14 and 15). [0039]
As shown in FIGS. 14 and 15, the plug part 47p projecting to the left side edge in the head cover gasket 47 of a substantially rectangular annular shape is formed into a vessel-like shape having a semicircular cylindrical wall part 47ps whose inner end opens and whose outer end opening is closed by a semicircular wall part 47pw, and

this shape is maintained by a metal tool 48 of the same shape fitted in such a manner as to make contact with a bottom surface of this semicircular wall part 47pw and an inner peripheral surface of the semicircular cylindrical part 47ps.
At inner and outer ends of the semicircular cylindrical part 47ps, flanges 47pf and 47pf are formed in a manner such as to project therefrom. [0040]
Therefore, when the head cover gasket 47 is sandwiched between the mating surfaces 33s and 34s of the cylinder head 33 and the cylinder head cover 34, the plug part 47p of the head cover gasket 47 is fitted in the machining recess 33v of a semicircular arc shape formed on the mating surface 33s on the cylinder head 33 side and thereby closes the machining recess 33v. [0041]
On the other hand, the shroud 68 surrounding the cylinder 32 and the cylinder head 33 is composed of an upper shroud s 68U and a lower shroud 68L that are divided into an upper half and a lower half, respectively. The upper and lower shroud 68U and 68L are provided in a manner such that head penetration opening parts 68Up and 6BLp through which the cylinder head 33 penetrates sandwich a rubber annular elastic member 95 with an outer peripheral surface of the cylinder head 33 near the mating surface 33s. [0042]
As shown in FIG. 4, ribs 33r are formed separately at

the top and bottom and circumferentially on the outer peripheral surface of the cylinder head 33 near the mating surface 33s in a manner such as to project therefrom.
The upper and lower ribs 33r and 33r project outward from the outer peripheral surface of the cylinder head 33 along the mating surface 33s, with left ends (right ends in FIG. 4) thereof orthogonally bent and right ends (left ends in FIG. 4) thereof curved in the form of a circular arc and further extending around on the right side surface. [0043]
The annular elastic member 95 formed into a substantially rectangular annular shape, as shown in FIGS. 6 through 10, is U-shaped in cross section (see FIG. 7) in a manner such as to be fitted to the ribs 33r from the upper and lower side edges to the right side edge (left side edge in FIG. 6). A center part 95r on the right side edge swells inward in a manner such as to be fitted between the upper and lower end parts of the right side part of the upper and lower ribs 33r and 33r. The left side edge is so formed as to be solid and vertically symmetrical. A center part of this left side edge has its inner surface notched to be thereby formed into a thin wall part 951c having a notched recess 95h opening inward (see FIG. 9). A left upper part 951u and a left lower part 9511 above and below the thin wall part 951c located at this left side center are so formed as to gradually swell inward with a gradually increased wall thickness from the upper and lower bending parts to the notched recess 95h located at the center (FIGS.

6 and 10).
i
The notched recess 95h on the inner side of the thin wall part 951c is formed with tilted surfaces 95s and 95s such that a notched width w becomes narrower from both the upper and lower sides toward the center. [0044]
This annular elastic member 95, while being extended with a tensile force, is provided around an outer peripheral surface of the cylinder head 33 near the mating surface 33s in a manner such as to be engaged with the upper and lower ribs 33r and 33r of the cylinder head 33.
Referring to FIG. 11, when the annular elastic member 95 is provided around the outer peripheral surface of the cylinder head 33 in a manner such that a portion of a U shape in cross section from the upper and lower sides to the right side of the annular elastic member 95 is fitted to the ribs 33r, the left upper part 951u and the left lower part 9511 gradually swelling inward from the upper and lower bending parts of the annular elastic member 95 to the thin wall part 951c at the left center abut on the left outer side surface of the cylinder head 33 and widens in a manner such as to open outward, whereby the thin wall part 951c at the left center of the annular elastic member 95 separates outward from the left outer side surface of the cylinder head 33. [0045]
Therefore, in the annular elastic member 95, the notched recess 95h originally formed on the inner side of

the thin wall part 951c at the left center is consequently located on the outer side of the semicircular-arc-shaped machining recess 33v on the left outer side surface of the cylinder head 33 (see FIG. 11), thereby forming space on the outer side of the machining recess 33v. [0046]
Under the condition that the annular elastic member 95 is provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s, the upper shroud 68U and the lower shroud 68L covering the surrounding of the cylinder 32 and the cylinder head 33 are shrouded.
The head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L through which the cylinder head 33 penetrates are each formed into a U shape, in cross section, fitted to the annular elastic member 95 from the outer side (see FIG. 3). [0047]
FIG. 12 is a front view of the cylinder 32 and the cylinder head 33 shrouded with the upper shroud 68U and the lower shroud 68L from the above and below before the cylinder head cover 34 is attached, as viewed from the front. [0048]
Split surfaces of the upper and lower shrouds 68U and 68L are located at a substantially vertical center. When the upper shroud 68U and the lower shroud 68L are shrouded from the above and below, the head penetration opening

parts 68Up and 68Lp cover the cylinder 32 and the cylinder head 33 from the above and below in a manner such as to be fitted to the annular elastic member 95, from the above and below, provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s, their split surfaces are aligned with each other, and both are combined together with joining parts 68Uc and 68Lc. [0049]
As shown in FIG. 12, the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L fit to the annular elastic member 95 provided around the outer peripheral surface of the cylinder head 33 near the mating surface 33s and almost cover it.
Left side parts 68Upl and 68Lpl of the head penetration opening parts 68Up and 68Lp in the upper and lower shrouds 68U and 68L are formed into a shape similar to that of the left side part of the annular elastic member 95, with a recess 68h formed on the inner side of its center part. [0050]
On the outer side of the machining recess 33v on the mating surface 33s of the cylinder head 33, in a front view shown in FIG. 12, the recess 68h of the upper and lower shrouds 68U and 68L together with the notched recess 95h of the annular elastic member 95 is located, thereby forming space.
The annular elastic member 95 has the tilted surfaces 95s and 95s such that the notched recess 95h at the center

on the_left side edge has a notched width vj narrowing down from both the upper and lower sides toward the center. Thus, even when the annular elastic member 95 receives an external force by being sandwiched between the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L, it is deformed in a bending manner so as to move the center of the thin wall part 951c to the outside separating from the machining recess 33v. [0051]
Therefore, between the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L and the outer peripheral surface of the cylinder head 33 near the mating surface 33s, the annular elastic member 95 is placed, whereby the head penetration opening parts 68Up and 68Lp are almost sealed. However, part of the notched recess 95h of the annular elastic member 95, together with the recess 68h of the head penetration opening parts 68Up and 68Lp, communicates with the outside.
Note, however, that the recess 68h of the head penetration opening parts 68Up and 68Lp is partially covered with the plug part 47p of the head cover gasket 47 fitted in the machining recess 33v of the cylinder head 33.
Placing this annular elastic member 95 permits absorbing vibration caused by driving of the internal combustion engine 30, prevents shaking of the upper and lower shrouds 68U and 68L, and suppressing occurrence of noise. [0052]

The upper and lower shrouds 68U and 68L covering th surrounding of the cylinder 32 and the cylinder head 33 of the internal combustion engine 30 in this manner have an upper side wall, a lower side wall, and a left side wall extending backward along the side surfaces of the cylinder 32 and the cylinder head 33 and have a right side wall greatly swelling rightward in a manner such as to separate gradually from the cylinder 32 and the cylinder head 33 to be coupled to the fan cover 67 (see FIGS. 2 and 12). [0053]
For the fan cover 67, a front part of the peripheral edge of an annular frame 67a, having the crankshaft 40 as its central axis, is screwed with a screw 120 into the back end edge of the right side walls of the upper and lower shrouds 68U and 68L to be thereby coupled thereto, and a portion other than the front part of the peripheral edge of the annular frame 67a is screwed with a bolt 121 into the right end edge of the right unit case 31R to be thereby fixed thereto. Thus, the fan cover 67 corresponds to an extending member of the upper and lower shrouds 68U and 68L, and has a cooling air inlet 67i provided at its right side wall oppositely to the forced air cooling fan 66 (see FIG. 2) . [0054]
On the other hand, at the left side wall of the lower shroud 68L, a cooling air outlet 68e opens in the lower half near the back, and to this cooling air outlet 68e, the front end of an exhaust air duct 69 is coupled (see FIGS. 1,

2, and 12) .
The exhaust air duct 69 first extends leftward from the cooling air outlet 68e at the left side wall of the lov;er shroud 68L, bends diagonally downward and backward, then extends along the lower end surface of the outside air introduction duct 150, reaching a back end exhaust air port 69e (see FIG. 1). [0055]
For the upper and lower shrouds 68U and SBL surrounding the cylinder 32 and the cylinder head 33, the cooling air inlet 57i is provided in the fan cover 67 as the backward extension of the right side wall that swells rightward, and the cooling air outlet 68e is formed in the left side wall opposing this right side wall. Therefore, referring to FIG. 2, cooling air suctioned through the cooling air inlet 67i as a result of rotation of the forced air cooling fan 66 integral to rotation of the crankshaft forcibly cools the cylinder 32 and the cylinder head 33 by flowing leftward around the cylinder 32 and the cylinder head 33 while being guided diagonally forward by the bent right side wall. Since the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L are almost sealed by the annular elastic member 95, the cooling air directly flows out to the cooling air outlet 68e in the left side wall without changing its direction, is guided diagonally downward and backward by the exhaust air duct 69, and is discharged from the back end exhaust air port 69e.

[0056]
Note that the sealing of the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L by the annular elastic member 95 is not complete, and a gap between the inner surface of the recess 68h on the left side of the head penetration opening parts 68Up and 68Lp and the plug part 47p of the head cover gasket 47 is not sealed, causing concern of cooling air leak from the gap, although this gap is located at the downstream side (left side) of the cylinder head 33 with respect to the cooling air flow, which does not have great influence on the cooling performance of the internal combustion engine. [0057]
However, since the temperature inside an engine room surrounded by the body is not increased by hot air leak, a gap between the inner surface of the recess 68h and the plug part 47p of the head cover gasket 47 is set as minimum as possible within a range such that the head cover gasket 47, together with the cylinder head cover 34, can be assembled to the cylinder head 33 in a manner such as to penetrating through the head penetration opening parts 68Up and 68Lp of the upper and lower shrouds 68U and 68L. [0058]
On the other hand, the annular elastic member 95 is hidden inside the upper and lower shrouds 68U and 68L and thus cannot be visually checked when the head cover gasket 47 is assembled together with the cylinder head cover 34. Thus, to preferentially facilitate assembly, a gap between'

the inner surface of the notched recess 95h of the annular elastic member 95 and the plug part 47p of the head cover gasket 47 is set larger than the gap between the inner surface of the recess 68h of the upper and lower shrouds 68U and 68L and the plug part 47p of the head cover gasket 47. [0059]
Under the condition that the upper and lower shrouds 68U and 68L guiding the cooling air from the forced air cooling fan 66 to the cylinder 32 and the cylinder head 33 in this manner are so attached as to cover the cylinder 32 and the cylinder head 33 as described above, as shown in the front view of FIG. 12, the notched recess 95h of the annular elastic member 95 and the recess 68h of the upper and lower shrouds 68U and 68L are located on the outer side of the machining recess 33v on the mating surface 33s of the cylinder head 33, thereby providing a space. Thus, upon attaching the cylinder head cover 34 together with the head cover gasket 47 to the cylinder head 33, the plug part 47p of the head cover gasket 47 can be easily fitted in the machining recess 33v on the mating surface 33s without being blocked by the thin wall part 951c of the annular elastic member 95. [0060]
Specifically, upon assembling the cylinder head cover 34 with the upper and lower shrouds 68U and 68L attached to the cylinder head 33 and the cylinder 32 during fabrication, maintenance, or the like, the notched recess 95h of the

>
r
annular elastic member 95 is located oppositely to the machining recess 33v on the mating surface '33s of the cylinder head 33, the thin wall part 951c of the annular elastic member 95 is kept separated from the machining recess 33v, and the thin wall part 951c neither makes contact with nor enters into the machining recess. Thus, the plug part 47p of the head cover gasket 47 attached to the cylinder head cover 34 can be fitted in the machining recess 33v on the mating surface 33s of the cylinder head
33 without being blocked by the annular elastic member 95, thereby permitting easy assembly of the cylinder head cover
34 to the cylinder head 33. [0061]
Since the plug part 47p of the head cover gasket 47 maintains its shape by having the metal tool 48 fitted thereinside, it can be easily fitted in the machining recess 33v of the cylinder head 33 without being deformed, and the plug part 47p can be reliably fitted in the machining recess 33v through positioning such that the flanges 47pf and 47pf at the inner and outer ends of the semicircular cylindrical part 47ps in the plug part 47p sandwich both the sides of the semicircular arc surface of the machining recess 33v. [Brief Description of the Drawings] [0062]
[FIG. 1] FIG. 1 is a side view of a power unit according to one embodiment of the present invention. [FIG. 2] FIG. 2 is a sectional view of a front side portion

of the same power unit (sectional view taken along line II-II of FIG. 1).
[FIG. 3] FIG. 3 is a sectional view of a front side portion of the same power unit (sectional view taken along line III-III of FIG. 2) .
[FIG. 4] FIG. 4 is a plan view of a cylinder head. [FIG. 5] FIG. 5 is a left side view of the same (view, along arrow V of FIG. 4).
[FIG. 6] FIG. 6 is a plan view of an annular elastic member. [FIG. 7] FIG. 7 is a sectional view taken along line VII-
VII of FIG. 6.
[FIG. 8] FIG. 8 is a sectional view taken along line VIII-
VIII of FIG. 6.
[FIG. 9] FIG. 9 is a sectional view taken along line IX-IX
of FIG. 6.
[FIG. 10] FIG. 10 is a sectional view taken along line X-X
of FIG. 6.
[FIG. 11] FIG. 11 is a front view showing the annular
elastic member provided around the cylinder head.
[FIG. 12] FIG. 12 is a front view of a cylinder and the
cylinder head covered with shrouds before a cylinder head
cover is attached, as viewed from the front.
[FIG. 13] FIG. 13 is a plan view of a head cover gasket.
[FIG. 14] FIG. 14 is a disassembled side view of the
disassembled cylinder head cover and head cover gasket at
the front of an internal combustion engine.
[FIG. 15] FIG. 15 is a sectional view of the same.
[Description of Reference Numerals]

[0063]
10 . . .Power unit
30 ...Internal combustion engine
31. . .Unit case
32 . ..Cylinder
33...Cylinder head
33s..Mating surface
33v...Machining recess
34 ...Cylinder head cover
35...Belt-type continuously variable transmission
36...Transmission case cover
40."Crankshaft
65...Forced air cooling fan
67 ...Fan cover
67i...Cooling air inlet
68...Shroud
68U...Upper shroud
68L...Lower shroud
68Up, 68Lp...Head penetration opening part
68e...Cooling air outlet
69...Exhaust air duct
69e...Back end exhaust air port
95...Annular elastic member
95h...Notched recess
951c...Thin wall part
95s...Tilted surface
951u...Left upper part
9511...Left lower part

[Document Name] Scope of Claims [Claim 1]
A forced air cooling internal combustion engine in which:
a machining recess for forming a camshaft bearing hole through machining is formed on a mating surface of a cylinder head, the mating surface mating with a cylinder head cover;
a plug part fitted in the machining recess is integrally formed at a head cover gasket placed between the cylinder head cover and the cylinder head; and
shrouds surrounding a cylinder and the cylinder head and guiding cooling air are provided in such a manner that an annular elastic member is placed between head penetration opening parts through which the cylinder head penetrates and an outer peripheral surface of the cylinder head near the mating surface,
wherein the annular elastic member is provided around the outer peripheral surface of the cylinder head near the mating surface, and an inner peripheral surface side of a portion corresponding to the machining recess is notched to form a thin wall part having a notched recess on a side opposite to the machining recess. [Claim 2]
The forced air cooling internal combustion engine according to Claim 1,
wherein the notched recess of the annular elastic member is formed in such a manner that a notched width

narrows down from both sides thereof to a center thereof. [Claim 3]
The forced air cooling internal combustion engine according to Claim 1 or 2,
wherein both side portions of the notched recess of the annular elastic member are formed in such a manner that inner peripheral surfaces thereof swell inward from both ends to the notched recess with a gradually larger wall thickness.

Documents:

2024-CHE-2008 CORRESPONDENCE OTHERS 22-04-2013.pdf

2024-CHE-2008 AMENDED PAGES OF SPECIFICATION 10-04-2013.pdf

2024-CHE-2008 AMENDED CLAIMS 10-04-2013.pdf

2024-CHE-2008 ENGLISH TRANSLATION OF CLAIMS 10-04-2013.pdf

2024-CHE-2008 EXAMINATION REPORT REPLY RECEIVED 10-04-2013.pdf

2024-CHE-2008 FORM-3 10-04-2013.pdf

2024-CHE-2008 FORM-5 22-04-2013.pdf

2024-CHE-2008 FORM-5 10-04-2013.pdf

2024-CHE-2008 POWER OF ATTORNEY 10-04-2013.pdf

2024-che-2008 abstract.jpg

2024-che-2008 abstract.pdf

2024-che-2008 claims.pdf

2024-che-2008 correspondence-others.pdf

2024-che-2008 description(complete).pdf

2024-che-2008 drawings.pdf

2024-che-2008 form-1.pdf

2024-che-2008 form-18.pdf

2024-che-2008 form-26.pdf

2024-che-2008 form-3.pdf

2024-che-2008 form-5.pdf

2024-che-2008 others.pdf

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Patent Number

256200

Indian Patent Application Number

2024/CHE/2008

PG Journal Number

20/2013

Publication Date

17-May-2013

Grant Date

15-May-2013

Date of Filing

20-Aug-2008

Name of Patentee

HONDA MOTOR CO., LTD,

Applicant Address

1-1 MINAMIAOYAMA 2-CHOME, MINATO-KU,

Inventors:

#	Inventor's Name	Inventor's Address
1	TSUCHIYA, RYUJI,	C/OHONDA R&D, CO., LTD, 4-1, 1- CHOME WAKO-SHI, SAITAMA 351-0193
2	KOBAYASHI, KOJI,	C/O HONDA R&D, CO., LTD, 4-1, 1- CHOME WAKO-SHI, SAITAMA 351-0193

PCT International Classification Number

F02M69/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2007-220108	2007-08-27	Japan