JP6172675B2 - Internal combustion engine - Google Patents

Description

  According to the present invention, at least one of an intake valve and an exhaust valve arranged to be openable and closable on a cylinder head of an engine body is radially arranged with respect to one combustion chamber, and the intake valve and the exhaust valve are individually provided. Correspondingly, a driven gear is provided on at least one of a pair of camshafts that are rotatably supported by the cylinder head, and a driven wheel that is rotatably supported by the cylinder head is rotatable by a crankcase of the engine body. The present invention relates to an internal combustion engine in which an endless transmission band for transmitting rotational power from a crankshaft supported by a coil is wound, and a drive gear meshing with the driven gear is provided coaxially with the driven wheel.

  An internal combustion engine in which rotational power from a crankshaft is transmitted to a driven sprocket via a cam chain, and a drive gear that rotates together with the driven sprocket meshes in common with driven gears provided on a pair of camshafts. It is known from Document 1 and the like, in which the driven sprocket and the driving gear are arranged at substantially the same height as the pair of driven gears.

Japanese Utility Model Publication No. 58-127107

  Incidentally, in the internal combustion engine disclosed in Patent Document 1, a pair of intake valves and exhaust valves are arranged radially with respect to the combustion chamber, and a pair of camshafts individually corresponding to the intake valves and the exhaust valves are provided. In order to avoid interference with the intake valve and the exhaust valve, the bearing portion provided on the cylinder head so as to support the normal valve arrangement in which the intake valve and the exhaust valve are arranged along a plane perpendicular to the crankshaft. Compared to the internal combustion engine, it must be disposed radially outside the combustion chamber. Then, in the structure disclosed in Patent Document 1 in which the driven sprocket and the drive gear are arranged at substantially the same height as the pair of driven gears, in order to avoid interference between the bearing portion and the driven sprocket. It is necessary to widen the distance between the pair of camshafts so as to ensure a space for accommodating the driven sprocket between the pair of camshafts. However, when such a camshaft arrangement structure is adopted, in addition to the increase in the cylinder head width in the direction along the camshaft axis due to the radial arrangement of at least one of the intake valve and the exhaust valve, the camshaft arrangement structure is orthogonal to the camshaft axis. This causes an increase in the width of the cylinder head in the direction in which the cylinder head is enlarged, and the cylinder head becomes larger.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine in which an increase in the distance between a pair of camshafts is avoided and a cylinder head can be miniaturized.

  In order to achieve the above object, according to the present invention, at least one of an intake valve and an exhaust valve arranged to be openable and closable on a cylinder head of an engine body is radially arranged with respect to one combustion chamber, A driven gear is provided on at least one of a pair of camshafts rotatably supported by the cylinder head corresponding to the valve and the exhaust valve individually, and a driven wheel rotatably supported by the cylinder head includes In an internal combustion engine in which an endless transmission band that transmits rotational power from a crankshaft rotatably supported by a crankcase of an engine body is wound, and a drive gear that meshes with the driven gear is provided coaxially with the driven wheel. The driven wheel and the drive gear are disposed closer to the crankshaft than a straight line connecting between the central axes of the pair of camshafts, A bearing wall that constitutes a part of the inner wall of the accommodating chamber formed in the engine body so as to accommodate the gear, the driven wheel, and the driving gear and travel in the endless transmission band is formed of the pair of camshafts. At least one of the driven wheels provided on the cylinder head so as to have a pair of camshaft sliding contact supporting surfaces that are slidably contacted and supported on at least a part of the outer periphery, and disposed closer to the bearing wall than the drive gear. The first feature is that a driven wheel housing recess for housing the portion is formed in the bearing wall.

  Further, according to the present invention, in addition to the configuration of the first feature, one of the intake valve and the exhaust valve is radially arranged, and the other valve is disposed on the axis of the intake side and the exhaust side camshaft. It is a second feature that they are arranged along an orthogonal plane.

  According to the present invention, in addition to the structure of the second feature, the cylinder head has the same number of mounting boss portions as the number of the intake valves and the exhaust valves, and through bolts for fastening the cylinder head to the crankcase One cam shaft sliding contact is provided around the intake valve and the exhaust valve so that the bearing wall is disposed on the one valve side of the pair of cam shaft sliding contact support surfaces. A third feature is that the support surface is formed so as to be offset from the other camshaft sliding contact support surface toward the storage chamber.

  According to the present invention, in addition to the configuration of the third feature, a cam holder fixed to the bearing wall so as to sandwich the pair of camshafts between the bearing walls is bent corresponding to the shape of the bearing wall. A fourth feature is that the first shape is formed so as to have an integral shape.

  According to the present invention, in addition to the configuration of the fourth feature, a gear that houses a part of the drive gear on an inner surface of an outer wall of the cylinder head that forms a part of the housing chamber with the bearing wall. A housing recess is formed, and a projecting portion having a shape corresponding to the gear housing recess is projected on the outer surface of the outer wall.

  According to the present invention, in addition to the configuration of the fifth feature, the pair of camshafts corresponding to the arrangement shape of the pair of driven gears and the drive gears, wherein the gear receiving recesses are respectively provided in the pair of camshafts. A sixth feature is that it is formed in a V shape that is open to the side.

  According to the present invention, in addition to the configuration of the fifth or sixth feature, the camshaft is provided between one stem end of the intake valve and the exhaust valve and a cam provided on one of the pair of camshafts. A rocker arm that is swingably supported by a rocker shaft that is inserted and fixed in the cylinder head with an axis parallel to the cylinder head, and an insertion hole through which the rocker shaft is inserted has one end in the driven wheel housing recess. A through hole that is opened and provided in the cylinder head and sandwiches the storage chamber with the insertion hole is provided on the outer wall so that the rocker shaft can be inserted into the insertion hole from the through hole. The seventh feature is provided.

  Further, according to the present invention, in addition to any one of the first to seventh features, the bearing wall is provided with a pair of through holes that sandwich the drive gear from both sides below the driven wheel housing recess. Is the eighth feature.

  The driven sprocket 90 of the embodiment corresponds to the driven wheel of the present invention, the cam chain 91 of the embodiment corresponds to the endless transmission band of the present invention, and the sprocket housing recess 131 of the embodiment corresponds to the driven wheel of the present invention. Corresponds to the housing recess.

  According to the first aspect of the present invention, the rotational power is transmitted from the crankshaft via the endless transmission band to the driven wheel that rotates together with the drive gear that meshes with the driven gear provided on at least one of the pair of camshafts. Thus, the pair of camshaft sliding support surfaces are supported while being rotatably supported by the cylinder head on the crankshaft side with respect to the straight line connecting the central axes of the pair of camshafts, and constituting a part of the inner wall of the storage chamber. Since a driven wheel receiving recess for receiving at least a part of the driven wheel arranged on the bearing wall side of the drive gear is formed in the bearing wall provided on the cylinder head, the camshaft of the camshaft by the radial arrangement of the valve is formed. While suppressing an increase in the cylinder head width in the direction along the axis, the distance between the shafts of the pair of camshafts can be shortened, thereby reducing the size of the cylinder head. Can.

  Further, according to the second feature of the present invention, one of the intake valve and the exhaust valve is radially arranged, and the other valve is normally arranged along a plane perpendicular to the axis of the camshaft. The normal drive system can be used as it is on the valve side, and the manufacturing cost can be reduced by making the valve drive structure complicated by the radial arrangement only on one valve side.

  According to the third aspect of the present invention, the cylinder head around the intake valve and the exhaust valve is provided with the same number of attachment boss portions as the number of the intake valve and the exhaust valve, and is arranged on the radially arranged valve side. Since the bearing wall is formed so that the camshaft sliding contact support surface is offset to the storage chamber side relative to the camshaft sliding contact support surface arranged on the valve side, which is not radially arranged, the depth of the driven wheel housing recess is reduced. Further, it is possible to reduce the processing man-hour at the time of forming the processing by shallowing the valve side which is not in the radial arrangement.

  According to the fourth aspect of the present invention, the cam holder having an integral shape bent corresponding to the shape of the bearing wall is fixed to the bearing wall with the pair of camshafts sandwiched between the bearing walls. Although the wall has a bent shape, it is possible to avoid separate cam holders on the intake side and exhaust side, and to reduce costs without increasing the number of parts.

  According to the fifth feature of the present invention, a gear housing recess for housing a part of the drive gear is formed on the inner surface of the outer wall of the cylinder head so that a part of the housing chamber is formed between the bearing wall. Since the protrusion having a shape corresponding to the gear receiving recess is protruded from the outer surface of the outer wall, only the portion corresponding to the gear receiving recess for receiving a part of the drive gear on the outer wall of the cylinder head is provided. By projecting in the axial direction of the camshaft, it is possible to avoid an increase in the size of the entire cylinder head.

  According to the sixth aspect of the present invention, since the gear receiving recess is formed in a V shape that is open to the camshaft side, the drive gear is made into the gear receiving recess when the drive gear and the cylinder head of the driven wheel are assembled. By dropping, approximate positioning becomes possible, and assemblability can be improved.

  According to the seventh feature of the present invention, one end of the insertion hole through which the rocker shaft for swingably supporting the rocker arm is inserted is opened in the driven wheel housing recess, and the rocker shaft can be inserted into the insertion hole. Since the through hole is provided on the outer wall with the accommodation chamber sandwiched between the insertion hole, when inserting the rocker shaft inserted into the through hole into one end of the insertion hole, it is easy to confirm the position of one end of the insertion hole, The assembling property of the rocker shaft to the cylinder head can be improved.

  Further, according to the eighth feature of the present invention, the bearing wall is provided with a pair of through holes that sandwich the drive gear from both sides below the driven wheel housing recess, so that the cylinder is connected in the direction connecting the axis of the crankshaft and the driven wheel. While a load is applied to the head from the driven wheel and the drive gear side, by arranging a through hole at a position that avoids the direction of the load operation, a reduction in rigidity can be avoided and the weight of the cylinder head can be reduced.

1 is a side view of a motorcycle. It is a principal part vertical side view of the internal combustion engine which notches and shows a part of engine body. It is a left side view of the upper part of the engine body. FIG. 4 is a plan view of a cylinder head taken along line 4-4 of FIG. It is sectional drawing which follows the 5-5 line of FIG. It is sectional drawing which follows the 6-6 line of FIG. FIG. 7 is a sectional view taken along line 7-7 in FIG. 3. FIG. 8 is a sectional view taken along line 8-8 in FIG. 3. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 4. It is the perspective view which looked at the left side principal part of the cylinder head from back diagonally upward. It is the 11-11 line sectional view of Drawing 4. FIG. 12 is a sectional view taken along line 12-12 of FIG. 4. FIG. 13 is a sectional view taken along line 13-13 of FIG. FIG. 14 is a cross-sectional view taken along line 14-14 of FIG. FIG. 15 is a cross-sectional view taken along line 15-15 in FIG. 4. FIG. 16 is a cross-sectional view taken along line 16-16 in FIG. FIG. 17 is a cross-sectional view taken along line 17-17 in FIG. 13. It is the figure which looked at the 1st cam holder from the 18-18 line arrow direction of FIG.

  The embodiment of the present invention will be described with reference to FIGS. 1 to 18 attached herewith. First, in FIG. 1, a body frame F of a motorcycle supports a front fork 21 that pivotally supports a front wheel WF so as to be steerable. From the head pipe 22, a pair of left and right main frames 23 extending rearwardly downward from the head pipe 22, a pair of left and right hangers 24 hanging downward from the front portion of the main frames 23, A pair of left and right pivot frames 25 that extend downward, a pair of left and right seat rails 27 that are supported by the upper ends of columns 26 that are erected at the rear of the main frame 23 and extend rearward, and the main frame 23 And a rear stay 28 connecting the rear portion and the rear portion of the seat rail 27.

  An engine main body 29 of the internal combustion engine E is supported on a rear portion of the main frame 23 in the vehicle body frame F, a lower portion of the hanger 24, and a lower portion of the pivot frame 25. Further, the front end portion of the swing arm 30 that pivotally supports the rear wheel WR driven by the power exerted by the internal combustion engine E at the rear end portion is supported by the pivot frame 25 so as to be swingable up and down. A link 31 and a rear cushion unit 32 are provided between the column 26 of the vehicle body frame F.

  A fuel tank 33 disposed above the engine body 29 is mounted on the main frame 23, and a riding seat 34 disposed behind the fuel tank 33 is supported by the seat rail 27. Further, a radiator 35 is disposed in front of the engine body 29, and the radiator 35 is supported by the vehicle body frame F and the engine body 29.

  A part of the internal combustion engine E and a part of the body frame F are covered with a body cover 37, and the body cover 37 extends from the front of the head pipe 22 to the rear part of the main frame 23. And a front cowl 38 that covers the upper part of the internal combustion engine E, a pair of left and right side cowls 39 that are connected to the rear sides of the front cowl 38 and cover the lower part of the internal combustion engine E, and a rear cowl 40 that covers the seat rail 27 and the rear stay 28. With.

  2 and 3, the engine main body 29 of the internal combustion engine E includes a crankcase 43 that rotatably supports a crankshaft 42 having an axis extending in the vehicle width direction, and a cylinder axis C slightly tilted rearward. A cylinder body 44 coupled to the front upper end of the crankcase 43, a cylinder head 45 coupled to the upper end of the cylinder body 44, and a head cover 46 coupled to the upper end of the cylinder head 45; Consists of a single cylinder.

  A mission case 47 extending rearward is connected to the crankcase 43. A transmission (not shown) for shifting the rotational power from the crankshaft 42 is accommodated in the transmission case 47, and the output shaft 48 of the transmission protrudes from the left side wall of the transmission case 47. . A driving sprocket 49 is fixed to the output shaft 48. As shown in FIG. 1, a driven sprocket 50 is fixed to the axle of the rear wheel WR. The driven sprocket 49 and the driven sprocket 50 are endless. The chain 51 is wound around.

  4 to 7 together, combustion between the cylinder body 44 and the cylinder head 45 faces the top of a piston (not shown) slidably fitted to the cylinder body 44. A chamber 52 is formed, and a front intake side wall 45 a of the cylinder head 45 is provided with a single intake port 53 that can communicate with the combustion chamber 52. A rear side wall 45 b of the cylinder head 45 is provided with the combustion chamber 52. A pair of exhaust ports 54 that can communicate with each other is provided. The cylinder head 45 also controls an intake valve 55 for switching communication / blocking between the combustion chamber 52 and the intake port 53 to control intake air to the combustion chamber 52 and exhaust gas from the combustion chamber 52. Accordingly, an exhaust valve 56 that switches between communication and blocking between the combustion chamber 52 and the exhaust port 54 is disposed so as to be openable and closable for each combustion chamber 52.

  On the rear side wall 45 b of the cylinder head 45, an exhaust side connection cylinder portion 58 constituting a part of the pair of exhaust ports 54 is integrally projected so as to protrude rearward. The upstream end of the exhaust pipe 59 that communicates is connected to the exhaust side connecting cylinder portion 58. The exhaust pipe 59 is bent from the rear side wall 45 b of the cylinder head 45 to the left side of the engine body 29 and extends forward of the engine body 29, and is bent downward from the front of the engine body 29 to be below the crankcase 43. The downstream end of the exhaust pipe 59 is connected to an exhaust muffler 60 disposed below the mission case 47.

  On the front side wall 45a of the cylinder head 45, an intake side connection cylinder portion 61 that constitutes a part of the intake port 53 is projected integrally so as to protrude forward, and the intake side connection cylinder The downstream end of the throttle body 62 communicating with the intake port 53 is connected to the portion 61. A frame trap 63 is attached to the throttle body 62 and is formed in a hemispherical shape bulging upward by a metal mesh, and covers the upstream end opening of the throttle body 62. The throttle body 62 including the frame trap 63 is attached to the throttle body 62. The upstream portion is accommodated in an intake chamber 64 (see FIG. 1) disposed below the fuel tank 33.

  A first fuel injection valve 65 is attached to the throttle body 62 outside the intake chamber 64, and a second fuel injection valve 66 that injects fuel from the frame trap 63 toward the throttle body 62 is a support frame 67. The second fuel injection valve 66 is disposed in the intake chamber 64.

  At least one of the pair of intake valves 55 and exhaust valves 56 is arranged radially with respect to one of the combustion chambers 52. In this embodiment, the pair of intake valves 55 is radially arranged. The pair of exhaust valves 56 is normally disposed along a plane perpendicular to the axis of the crankshaft 42.

  Referring to FIG. 5, the stems 55a of the pair of intake valves 55 are slidable on a guide cylinder 68 provided in the cylinder head 45 in a radial arrangement so as to be separated from each other as the distance from the combustion chamber 52 increases. The intake valve 55 is biased in the valve closing direction by a retainer 69 fitted to the stem end 55 b of the intake valve 55 and a valve spring 70 provided between the cylinder head 45.

  Focusing on FIG. 6, the stems 56 a of the pair of exhaust valves 56 are slidable on a guide cylinder 71 that is disposed along a plane perpendicular to the axis of the crankshaft 42 and embedded in the cylinder head 45. The exhaust valve 56 is biased in the valve closing direction by a retainer 72 fixed to the stem end 56 b of the exhaust valve 56 and a valve spring 73 provided between the cylinder head 45.

  A valve operating device 75 that opens and closes the intake valve 55 and the exhaust valve 56 has a pair of intake side cams 76 individually corresponding to the pair of intake valves 55 and is rotatably supported by the cylinder head 45. An intake side camshaft 77, an exhaust side camshaft 79 having a pair of exhaust side cams 78 individually corresponding to the pair of exhaust valves 56, and rotatably supported by the cylinder head 45, the intake valve 55, A pair of intake side rocker arms 80 interposed between the intake side cams 76 and a pair of exhaust side rocker arms 81 interposed between the exhaust valve 56 and the exhaust side cam 78 are provided.

  The intake side camshaft 77 has an axis parallel to the crankshaft 42 and is disposed so as to intersect with an axis extending upward from the stem 55a of the intake valve 55. The exhaust side camshaft 79 is The exhaust valve 56 has an axis parallel to the crankshaft 42 and the intake camshaft 77 and is arranged so as to intersect with an axial extension line above the stem 56a of the exhaust valve 56. In addition, the intake side camshaft 77 and the exhaust side camshaft 79 extending in parallel with each other are rotatably supported by first and second camshaft support portions 82 and 83 provided in the cylinder head 45.

  One end portion of the pair of intake side rocker arms 80 corresponds to each intake side rocker arm 80 individually, and the intake side camshaft 77 and the exhaust side camshaft 79 as viewed from the axial direction. A pair of intake-side rocker shafts 84 supported by the cylinder head 45 so as to be disposed between the exhaust-side camshafts 79 are swingably supported. While being individually associated with the side rocker arm 81, it is arranged between the intake side camshaft 77 and the exhaust side camshaft 79 as viewed from the axial direction of the intake side camshaft 77 and the exhaust side camshaft 79. A pair of exhaust-side rocker shafts 85 supported by the cylinder head 45 are supported so as to be swingable.

  The other end portion of the intake side rocker arm 80 has a cam slipper 80 a that is in sliding contact with the intake side cam 76, and is disposed between the stem end 55 b of the intake valve 55 and the intake side cam 76. Moreover, the outer periphery of the intake side cam 76 obliquely intersects with the axis of the intake side camshaft 77 based on the radial arrangement of the intake valves 55 with respect to the combustion chamber 52. The pair of intake-side rocker shafts 84 is also supported by the cylinder head 45 with an axis that obliquely intersects with a straight line parallel to the axis of the intake-side camshaft 77. The other end of the exhaust side rocker arm 81 has a cam slipper 81 a that is in sliding contact with the exhaust side cam 78 and is disposed between the stem end 56 b of the exhaust valve 56 and the exhaust side cam 78.

  Referring to FIG. 2, the rotational power from the crankshaft 42 is transmitted to the intake side camshaft 77 and the exhaust side camshaft 79 via a timing transmission mechanism 88. The transmission mechanism 88 is wound around a drive sprocket 89 provided on the crankshaft 42, a driven sprocket 90 as a driven wheel rotatably supported by the cylinder head 45, and the drive sprocket 89 and the driven sprocket 90. A cam chain 91 as an endless transmission band; driven gears 92 and 93 fixed to shaft ends of the intake-side camshaft 77 and the exhaust-side camshaft 79 protruding from the first camshaft support portion 82; Rotate with the driven sprocket 90 so as to rotate with the driven sprocket 90. And and a drive gear 94 meshing with the common to the driven gear 92 and 93 with integrally provided.

  In addition, the driven sprocket 90 and the drive gear 94 are disposed closer to the crankshaft 42 than a straight line L connecting the central axes of the intake side camshaft 77 and the exhaust side camshaft 79.

  The crankshaft 42 and the drive sprocket 89 rotate in the direction indicated by the arrow 95 in FIG. 2, and the driven sprocket 90 and the drive gear 94 rotate in the direction indicated by the arrow 96 in FIG. The pair of driven gears 92 and 93, that is, the intake side camshaft 77 and the exhaust side camshaft 79 rotate in the same cam rotation direction indicated by an arrow 97 in FIG.

  A slipper 98 is in contact with the outer periphery of the slack side of the cam chain 91 between the drive sprocket 89 and the driven sprocket 90, which is the side fed from the drive sprocket 89 to the driven sprocket 90. A tensioner 99 abutting from the opposite side of the cam chain 91 is attached to the cylinder body 44. Further, a cam chain guide 100 is brought into contact with the outer periphery of the tension side, which is the side pulled by the drive sprocket 89, of the cam chain 91 between the drive sprocket 89 and the driven sprocket 90.

  The slipper 98 is formed in an arc shape so that a convex curved surface is slidably contacted with the outer periphery of the cam chain 91 on the relaxation side, and one end of the slipper 98 on the crankshaft 42 side is connected to the crankcase 43 via the pivot 101. Is pivotally supported. The cam chain guide 100 is formed of a synthetic resin having appropriate rigidity and elasticity so as to form a substantially arcuate shape along the cam chain 91 side, and the cam chain guide 100 on the crankshaft 42 side is formed. The end is fixed to the crankcase 43 by a bolt 102. Further, an end portion of the cam chain guide 100 on the driven sprocket 90 side is brought into contact with a contact support portion 103 provided in the cylinder head 45.

  The crankcase 43, the cylinder body 44, and the cylinder head 45 in the engine body 29 include the pair of driven gears 92 and 93, the driven sprocket 90, and the drive that constitute a part of the timing transmission mechanism 88. A housing chamber 104 for housing the gear 94 and running the cam chain 91 is formed, and the slipper 98 and the cam chain guide 100 are also housed in the housing chamber 104.

  8 and 9, the first camshaft support portion 82 includes a first bearing wall 105 that forms a part of the inner wall of the storage chamber 104 and is formed integrally with the cylinder head 45, and the intake air. An intake side camshaft bearing portion 82 a that rotatably supports the side camshaft 77 and the exhaust side camshaft 79 and an exhaust side camshaft bearing portion 82 b are formed in cooperation with the first bearing wall 105. And a first cam holder 106 fixed to one bearing wall 105.

  Referring to FIGS. 10 and 11 together, the first bearing wall 105 is in sliding contact with at least a part of the outer periphery of the intake side camshaft 77 and the exhaust side camshaft 78, in this embodiment. The cylinder head 45 is provided with a pair of arcuate camshaft sliding support surfaces 107 and 108 to be supported, and the first cam holder 106 includes the intake side camshaft 77 and the exhaust side camshaft. Camshaft sliding contact surfaces 109 and 110 are formed which are in sliding contact with the remaining part of the outer periphery of 78.

  4 and 7, the intake valve 55 and the exhaust valve are connected to the cylinder head 45 on the cylinder body 44 side of the cam shaft sliding contact support surfaces 107 and 108 of the first bearing wall 105. The number of the mounting bosses 111, 112, 113, 114 is the same as the number of 56, so that the through bolts 115 for fastening the cylinder head 45 together with the cylinder body 44 to the crankcase 43 are inserted. Provided around the intake valve 55 and the exhaust valve 56.

  Moreover, since the intake valve 55 of the intake valve 55 and the exhaust valve 56 is radially disposed with respect to the combustion chamber 52, a pair of the mounting boss portions disposed outside the intake valve 55. In order to avoid interference with the intake valve 55, the distances 111 from the central axis of the intake-side rocker shaft 84 in the direction perpendicular to the axes of the intake-side and exhaust-side camshafts 77, 79 are set. The pair of mounting boss portions 113 and 114 disposed outside the exhaust valve 56 are disposed at positions larger than the distance L2 from the central axis of the exhaust rocker shaft 85. On the other hand, on the first bearing wall 105, the mounting boss portion 111 on the first bearing wall 105 side of the mounting boss portions 111 and 112 disposed outside the intake valve 55, and the exhaust valve 56. In order to allow the through bolt 115 to be inserted into the mounting boss portion 113 on the first bearing wall 105 side of the mounting boss portions 113 and 114 arranged on the outer side of the mounting boss portion 113, 114, Arc-shaped notches 116 and 117 are formed so as to cut out part of the contact support surfaces 107 and 108, but the mounting on the outside of the intake valve 55 and on the first bearing wall 105 side is performed. Of the pair of camshaft sliding contact support surfaces 107 and 108, in order to avoid the notch portion 116 that faces the boss portion 111 from becoming large and causing the rigidity of the first bearing wall 105 to decrease. One camshaft sliding contact support surface 107 disposed on the intake valve 55 side is offset to the storage chamber 104 side relative to the other camshaft sliding contact support surface 108 disposed on the exhaust valve 56 side. A first bearing wall 105 is formed for placement.

  The first cam holder 106 is formed to have an integrated shape bent corresponding to the shape of the first bearing wall 105, and the camshaft sliding contact support surface 107 and the camshaft on the intake valve 55 side. A pair of bolts 118 disposed on both sides of the sliding contact surface 110 and a pair of bolts 119 disposed on both sides of the camshaft sliding contact support surface 108 and the camshaft sliding contact surface 111 on the exhaust valve 56 side. Fixed to the first bearing wall 105.

  Referring to FIG. 8, the driven sprocket 90 and the drive gear 94 are arranged on the first bearing wall 105 such that the driven sprocket 90 is arranged on the first bearing wall 105 side of the drive gear 94. It is rotatably supported on a fixed support shaft 121 via a ball bearing 122.

  The support shaft 121 has a small-diameter cylindrical portion 121a whose one end is fitted and fixed to the first bearing wall 105 side, and a flange portion 121b projecting radially outward from the other end of the small-diameter cylindrical portion 121, A large-diameter cylindrical portion 121c whose one end is continuous with the outer periphery of the flange portion 121b is integrally formed to have a stepped cylindrical shape. On the other hand, the first bearing wall 105 is formed to have a larger diameter than the screw hole 123 so as to fit the bottomed screw hole 123 and one end of the small diameter cylindrical portion 121a of the support shaft 121. A support shaft fitting hole 124 and a spacer fitting hole 125 having a diameter larger than that of the support shaft fitting hole 124 are formed continuously in this order. In addition, the screw hole 123, the support shaft fitting hole 124, and the spacer fitting are formed in an outer wall 126 that forms a part of the storage chamber 104 between the cylinder head 45 and the first bearing wall 105. A fitting hole 127 corresponding to the hole 125 is provided, and the large-diameter cylindrical portion 121c of the support shaft 121 is fitted into the fitting hole 127, and the outer periphery of the large-diameter cylindrical portion 121c An annular seal member 128 that is in close contact with the inner periphery of the fitting hole 127 is attached.

  A bolt 129 that is screwed into the screw hole 123 is inserted into the small-diameter cylindrical portion 121a of the support shaft 121, and the enlarged-diameter head portion 129a of the bolt 129 is brought into contact with and engaged with the flange portion 112b. Until then, the support shaft 121 is fixed to the first bearing wall 105 by screwing the bolt 129 into the screw hole 123.

  An inner ring 122 a of the ball bearing 122 surrounds the small diameter cylindrical portion 121 a of the support shaft 121, and has a fitting cylinder portion 130 a that fits into the flange portion 121 b of the support shaft 121 and the spacer fitting hole 125. Thus, it is sandwiched between the spacer 130 and the first bearing wall 105.

  The first bearing wall 105 accommodates at least a part of the driven sprocket 90, in this embodiment, a part of the driven sprocket 90 on the driven gears 92 and 93 side, for example, on the head cover 46 side. A sprocket accommodating recess 131 formed in a bulging arc shape is formed. On the other hand, on the inner surface of the outer wall 126 of the cylinder head 45, a gear receiving recess 132 for receiving a part of the drive gear 94 is formed. The gear receiving recess 132 is formed by the pair of driven gears 92, 93. In correspondence with the arrangement shape of the drive gear 94, it is formed so as to have a V shape opened to the intake side and the exhaust side camshafts 77, 79 side. In addition, a protrusion 126 a having a shape corresponding to the gear receiving recess 132 is provided on the outer surface of the outer wall 126 corresponding to the gear receiving recess 132.

  Further, as shown in FIG. 11, the first bearing wall 105 is provided with a pair of through holes 133 that sandwich the driven sprocket 90 and the drive gear 94 from both sides below the sprocket housing recess 131.

  Referring to FIG. 12, the second camshaft support portion 83 includes the intake-side and the intake-side camshafts at a substantially central portion of the cylinder head 45 in a direction along the axes of the intake-side camshaft 77 and the exhaust-side camshaft 79. A second bearing wall 135 that extends in a direction perpendicular to the axis of the exhaust camshafts 77 and 79 and is formed integrally with the cylinder head 45, and the intake and exhaust camshafts 77 and 79 are rotatable. It comprises a second cam holder 136 fixed to the second bearing wall 135 so that the intake side and exhaust side camshaft bearing portions 83a, 83b to be supported are formed in cooperation with the second bearing wall 135.

  The second bearing wall 135 has a pair of arcuate camshaft sliding contact support surfaces 137 and 138 that are slidably supported on a part of the outer periphery of the intake side and exhaust side camshafts 77 and 79. Cam shaft sliding surfaces 139 and 140 are formed on the cylinder head 45, and the second cam holder 136 is in sliding contact with a part of the outer periphery of the intake side and exhaust side cam shafts 77 and 79. .

  The second cam holder 136 is formed so as to have an integral shape corresponding to the shape of the second bearing wall 135, and the camshaft sliding contact support surface 137 and the camshaft sliding contact surface on the intake valve 55 side. A pair of bolts 141 disposed on both sides of the 139 and a pair of bolts 142 disposed on both sides of the camshaft sliding contact surface 140 and the camshaft sliding contact surface 140 on the exhaust valve 56 side. It is fixed to the bearing wall 135.

  A spark plug (not shown) is attached to the second bearing wall 135 at the portion surrounded by the pair of intake valves 55 and the pair of exhaust valves 56 so that the tip of the combustion chamber 52 faces the tip. A plug mounting hole 143 is provided, and the second cam holder 136 is provided with a circular opening 144 leading to the plug mounting hole 143.

  The second bearing wall 135 is provided with a pair of through holes 145 disposed on both sides of the plug mounting hole 143 in order to reduce the weight of the cylinder head 45.

  In FIG. 13, the pair of exhaust-side rocker shafts 85 is inserted and fixed in an insertion hole 146 provided in the cylinder head 45 with an axis parallel to the exhaust-side camshaft 79. The insertion hole 146 is perforated from the side wall of the cylinder head 45 opposite to the accommodation chamber 104 while closing the end portion on the accommodation chamber 104 side, and the opening end of the insertion hole 146 is formed. A plug 147 that closes liquid tightly is screwed into the cylinder head 45.

  As shown in FIG. 14, an arc-shaped locking recess 148 is formed at a predetermined position on the outer periphery of the exhaust side rocker shaft 85, and the bolt 149 is engaged with the locking recess 148 so that the bolt 149 is engaged with the locking recess 148. Screwed onto the cylinder head 45. As a result, the pair of exhaust-side rocker shafts 85 are inserted and fixed at predetermined positions in the common insertion hole 146, and the slit 150 that faces a part of the exhaust-side rocker shafts 85 is formed in the cylinder head. 45. One end of the exhaust side rocker arm 81 is swingably supported by the exhaust side rocker shaft 85 in the slit 150.

  In FIG. 15, the pair of intake side rocker shafts 84 are arranged separately on both sides of the second camshaft support portion 83, and the second camshaft support of the pair of intake side rocker shafts 84 is arranged. One intake-side rocker shaft 84 disposed between the portion 83 and the storage chamber 104 has one end opened to the sprocket storage recess 131 formed in the first bearing wall 105 facing the storage chamber 104 and the other. The other intake-side rocker shaft 84 of the pair of intake-side rocker shafts 84 is opposite to the housing chamber 104 and is inserted into and fixed to an insertion hole 151 provided in the cylinder head 45 so as to close the end. Then, it is inserted through the bottomed insertion hole 152 to be drilled from the side wall side of the cylinder head 45 and fixed. Moreover, the insertion holes 151 and 152 are provided independently of each other in the cylinder head 45 so that the extension lines of the central axes C1 and C2 of the insertion holes 151 and 152 intersect each other.

  The pair of intake-side rocker shafts 84 are bolts that are screwed into the cylinder head 45 in a state where the intake-side rocker shafts 84 are inserted into predetermined positions of the pair of insertion holes 151 and 152 individually corresponding to the intake-side rocker shafts 84. By engaging 153 with the intake side rocker shaft 84, the insertion holes 151 and 152 are inserted and fixed.

  A slit 153 that faces a part of the intake side rocker shaft 84 is formed in the cylinder head 45, and one end portion of the intake side rocker arm 80 can swing to the intake side rocker shaft 84 within the slit 153. Supported by

  By the way, the outer wall 126 of the cylinder head 45 has a through hole 155 that sandwiches the storage chamber 104 with the insertion hole 151, and the intake side rocker shaft 84 is inserted into the insertion hole 151 from the through hole 155. A plug 156 that liquid-tightly closes the through hole 155 is screwed to the outer wall 126, and a plug 157 that liquid-tightly closes the outer end opening of the insertion hole 152 is screwed to the cylinder head 45. Combined.

  Referring to FIG. 5, the pair of intake side rocker arms 80 includes a rocker arm for supplying oil to a sliding contact portion between the intake side rocker arms 80 and the intake side cam 76 of the intake side camshaft 77. A side oil passage 160 is provided, and the rocker arm side oil passage 160 opens to the upper portion of a passage portion 160a extending in the longitudinal direction of the intake side rocker arm 80 and an intermediate portion in the longitudinal direction of the intake side rocker arm 80, and the passage. It is formed so as to consist of an injection hole portion 160b communicating with the portion 160a.

  Referring to FIG. 6, the pair of exhaust side rocker arms 81 includes a rocker arm for supplying oil to a sliding contact portion between the exhaust side rocker arms 81 and the exhaust side cam 78 of the exhaust side camshaft 79. A side oil passage 161 is provided, and the rocker arm side oil passage 161 opens to an upper portion of a passage portion 161 a extending in the longitudinal direction of the exhaust side rocker arm 81 and a middle portion in the longitudinal direction of the exhaust side rocker arm 81. It is formed so as to be composed of an injection hole portion 161b communicating with the portion 161a.

  Each of the pair of intake side rocker shafts 84 is provided with a rocker shaft internal oil passage 162 communicating with the passage portion 160a in the rocker arm side oil passage 160 of the intake side rocker arm 80 individually corresponding to the intake side rocker shaft 84. The pair of exhaust side rocker shafts 85 have rocker shaft internal oil passages 163 communicating with the passage portions 161a in the rocker arm side oil passages 161 of the exhaust side rocker arms 81 individually corresponding to the exhaust side rocker shafts 85, respectively. Provided.

  Referring also to FIG. 16, the first camshaft support 82 provided on the cylinder head 45 by rotatably supporting the intake side and exhaust side camshafts 77 and 79 includes the intake side and the exhaust side camshafts 77 and 79. A communication oil passage 164 that bypasses the exhaust side camshafts 77 and 79 is provided so as to lead to an oil supply passage 165 provided in the cylinder head 45 so as to guide oil from the cylinder body 44 side. The intake-side and exhaust-side journal oil passages 166, 167 for guiding oil to the intake-side and exhaust-side camshaft bearing portions 82a, 82b formed in one camshaft support portion 82, and the rocker shaft inner oil passages 162, 163 The oil is guided to the oil passages 169 and 170 provided in the cylinder head 45 so as to communicate with each other. A branch oil passage 168 air side and communicating with the communication oil passage 164 in parallel with the exhaust-side journal oil path 166 and 167, provided on the first cam shaft support portion 82.

  In addition, the first camshaft support portion 82 is formed in cooperation with the first bearing wall 105 provided in the cylinder head 45, and a part of the oil supply passage 165 and the oil The communication oil passage 164 leading to the supply passage 165, the intake side and exhaust side journal oil passages 166, 167, and a part of the branch oil passage 168 are provided.

  Meanwhile, the pair of oil passages 169 and 170 communicate with the cylinder head 45 so as to individually communicate with the rocker shaft internal oil passages 162 and 163 provided in the intake side and exhaust side rocker shafts 84 and 85, respectively. The branched oil passage 168 is provided in the first camshaft support 82 so as to be branched and communicated with the pair of oil passages 169 and 170.

  In FIG. 17, the branch oil passage 168 includes a common oil passage portion 168a communicating with the communication oil passage 164, one end portion passing through the common oil passage portion 168a, and the other end portions individually connected to the oil passages 169 and 170. The individual oil passage portions 168b and 168c to be communicated with each other, and the individual oil passage portions 168b and 168c formed in the first bearing wall 105 in the first camshaft support portion 82 are the first oil passage portions 168b and 168c. The common oil passage portion 168 a formed on the first cam holder 106 in the camshaft support portion 82 communicates with the joint portion of the first bearing wall 105 and the first cam holder 106. That is, the branch portion 168 d of the branch oil passage 168 is provided at the joint between the first bearing wall 105 and the first cam holder 106.

  Referring also to FIG. 18, the communication oil passage 164 is formed in the first cam holder 106 so as to extend linearly in a direction orthogonal to the arrangement direction of the intake side and exhaust side camshafts 77 and 79, The intake-side and exhaust-side camshafts formed in the first cam holder 106 so that the intake-side and exhaust-side journal oil passages 166, 167 are in sliding contact with the intake-side and exhaust-side camshafts 77, 79, respectively. It is formed so as to connect the topmost portions of the sliding contact surfaces 109 and 110 and the communication oil passage 164.

  Further, grooves 171 and 172 for opening the intake side and exhaust side journal oil passages 166 and 169 are formed on the intake side and exhaust side camshaft sliding contact surfaces 109 and 110 of the first cam holder 106, respectively. The exhaust camshafts 77 and 79 are formed so as to extend in the axial direction.

  Of the intake side and exhaust side camshaft sliding surfaces 109, 110, the intake side camshaft sliding surface 109 disposed on the intake valve 55 side that is radially disposed with respect to the combustion chamber 52 is connected to the exhaust side camshaft. A first cam holder 106 is formed so as to be offset from the sliding contact surface 110 toward the timing transmission mechanism 88 and the storage chamber 104, and the communication oil passage 164 has the intake side and the exhaust side. The first cam holder 106 is provided so as to pass through the central portion in the width direction of the exhaust side camshaft sliding contact surface 110 on a projected view including the axis of the camshafts 77 and 79.

  The groove 171 formed on the intake side camshaft sliding contact surface 109 corresponding to the arrangement of the communication oil passage 164 is more than the groove 172 formed on the exhaust side camshaft sliding contact surface 110. , It is formed longer on the storage chamber 104 side.

  The oil passages 169 and 170 are provided in the cylinder head 45 in parallel with the intake side and exhaust side camshafts 77 and 79 so as to be disposed between the intake valve 55 and the exhaust valve 56. The oil passage 169 is disposed below a pair of insertion holes 151 and 152 provided in the cylinder head 45 so as to pass through the intake side rocker shaft 84, and the oil passage 170 is connected to the exhaust side rocker shaft. 85 is inserted below the insertion hole 146 provided in the cylinder head 45.

  The oil passages 169 disposed below a pair of insertion holes 151 and 152 provided in the cylinder head 45 so as to be inserted through the intake side rocker shaft 84 extend independently in the vertical direction. Oil connected to the pair of insertion holes 151 and 152 via a pair of communication paths 173 and 174 provided in the cylinder head 45, and the oil guided into the insertion holes 151 and 152 via the oil passage 162 in the rocker shaft. Guided to the rocker arm side oil passage 160.

  The oil passage 170 disposed below the insertion hole 146 provided in the cylinder head 45 so as to pass through the exhaust-side rocker shaft 85 extends in a pair so as to extend vertically. The oil communicated with the insertion hole 146 through the communication path 175 and guided into the insertion hole 146 is guided to the rocker arm side oil path 161 through the rocker shaft oil path 163.

  By the way, the rocker arms provided on the intake side and the exhaust side rocker arms 80 and 81 respectively at the sliding contact portions between the intake side and the exhaust side rocker arms 80 and 81 and the intake side and the exhaust side cams 76 and 78. Oil is supplied from the side oil passages 160 and 161, and the oil supply direction from the rocker arm side oil passage 160 to the sliding contact portions of the intake side cam 76 and the intake side rocker arm 80 among the sliding contact portions thereof. 5 is the same direction as the cam rotation direction 97 as shown in FIG. 5, the oil supply direction from the rocker arm side oil passage 161 to the sliding contact portion of the exhaust side cam 78 and the exhaust side rocker arm 81 is shown in FIG. 6, the direction opposite to the cam rotation direction 97 is such that a part of the oil supplied from the rocker arm side oil passage 161 is in the exhaust side cam 78. Will be repelled by the rolling oil supply amount is likely to be insufficient to sliding contact portion of the exhaust-side cam 78 and the exhaust-side rocker arm 81. Therefore, oil is supplied from the auxiliary oil supply means 176 in the same direction as the cam rotation direction 97 to the sliding contact portions of the exhaust side cam 78 and the exhaust side rocker arm 81.

  The auxiliary oil supply means 176 extends in parallel with the axis of the intake and exhaust side camshafts 77 and 79 and communicates with an auxiliary oil supply passage 177 provided in the cylinder head 45 and the auxiliary oil supply passage 177. The exhaust valve is provided with a pair of oil injection holes 178 provided in the cylinder head 45, and is disposed along a plane orthogonal to the axis of the intake side and the exhaust side camshafts 77 and 79. The cylinder head 45 is disposed on the 56 side.

  The auxiliary oil supply path 177 leads to the oil supply path 165 provided in the cylinder head 45 so as to guide oil from the cylinder body 44 side, and the communication on the downstream side of the oil supply path 165 is performed. A pair of the oil passages 169 and 170 branched from the oil passage 164 and the auxiliary oil supply passage 177 extend in parallel with each other and are provided in the cylinder head 45.

  In addition, one of the pair of oil passages 169 and 170 is disposed at a position sandwiching the exhaust valve 56 between the auxiliary oil supply passage 177 and between the intake valve 55 and the exhaust valve 56. Placed in.

  Referring to FIG. 12, the cylinder head 45 is provided with a second camshaft support portion 83 that rotatably supports an intermediate portion between the intake side and the exhaust side camshafts 77 and 79. The camshaft support 83 and the camshaft lubrication passage 179 branched from the oil passage 169 corresponding to the intake valve 55 side of the pair of oil passages 169, 170 are the intake-side camshaft 77 and the second cam. The cylinder head 45 is provided so as to supply oil between the shaft support portion 83 and the camshaft lubrication passage 179 extends from the oil passage 169 to below the intake side camshaft 77. A passage portion 179a extending in the lateral direction, and an intake side camshaft of the second camshaft support portion 83 extending upward from the passage portion 179a. Comprising a passage 179b leading to the shift bearing portion 83a.

  A camshaft lubrication passage 180 branched from the auxiliary oil supply passage 177 is provided in the cylinder head 45 so as to supply oil between the exhaust camshaft 79 and the second camshaft support 83. The camshaft lubrication passage 180 is formed so as to extend obliquely upward from the auxiliary oil supply passage 177 and reach the exhaust camshaft bearing portion 83b of the second camshaft support portion 83.

  The pair of oil passages 169 and 170 and the auxiliary oil supply passage 177 are provided in the cylinder head 45 so as to be formed by processing from the same one side surface 45c of the cylinder head 45. The one side surface 45c accommodates a timing transmission mechanism 88 that transmits power from the crankshaft 42 to the intake side and exhaust side camshafts 77, 79 of all side surfaces of the cylinder head 45, and stores the engine body. In this embodiment, the storage chamber 104 is formed on the right side of the engine main body 29, so that the one side surface 45c is the right side surface. That is, the oil passages 169 and 170 and the auxiliary oil supply passage 177 are perforated from the side surface 45c which is the right side surface of the cylinder head 45, and the oil passages 169 and 170 and the auxiliary oil supply passage 177 at the side surface 45c are drilled. The open end of each is closed liquid-tightly by plugs 181, 182 and 183.

  Next, the operation of this embodiment will be described. Intake and exhaust side camshafts 77 and 79 individually corresponding to the intake valve 55 and the exhaust valve 56 are rotatably supported by the cylinder head 45, and A cam chain 91 that transmits rotational power from the crankshaft 42 is wound around a driven sprocket 90 that is rotatably supported, and a pair of shafts provided on the shaft ends of the intake side and exhaust side camshafts 77 and 79, respectively. A drive gear 94 that meshes in common with the driven gears 92 and 93 is provided coaxially with the driven sprocket 90, and the driven sprocket 90 and the drive gear 94 are center axes of the intake side and exhaust side camshafts 77 and 79. The pair of driven gears are disposed on the crankshaft 42 side of the straight line L connecting them 2 and 93, a first bearing wall that accommodates the driven sprocket 90 and the drive gear 94 and constitutes a part of the inner wall of the accommodating chamber 104 formed in the engine body 29 so that the cam chain 91 travels. 105 is provided on the cylinder head 45 so as to have a pair of camshaft sliding contact support surfaces 107 and 108 which are in sliding contact with and support at least a part of the outer periphery of the intake side and exhaust side camshafts 77 and 79. Since the sprocket accommodating recess 131 for accommodating at least a part of the sprocket 90 disposed on the first bearing wall 105 side with respect to the drive gear 94 is formed in the first bearing wall 105, the intake valve 55 and the exhaust gas are exhausted. At least one of the valves 56 is arranged radially with respect to the combustion chamber 52, and the intake side and exhaust side camshafts 7 are arranged. , 79 while suppressing an increase in the width of the cylinder head 45 in the direction along the axis, the distance between the intake and exhaust side camshafts 77, 79 can be shortened, and the cylinder head 45 can be reduced in size. be able to.

  The intake valve 55, which is one of the intake valve 55 and the exhaust valve 56, is radially arranged, and the exhaust valve 56 is along a plane orthogonal to the axis of the intake side and the exhaust side camshafts 77 and 79. Therefore, it is possible to adopt a normal drive system as it is on the exhaust valve 56 side, and to complicate the valve drive structure by the radial arrangement of at least one of the intake valve 55 and the exhaust valve 56. The manufacturing cost can be reduced only on the valve 55 side.

  Further, the cylinder head 45 has the same number of mounting bosses 111, 112, 113, 114 as the number of the intake valves 55 and the exhaust valves 56, and through bolts 115 for fastening the cylinder head 45 to the crankcase 43. Is inserted around the intake valve 55 and the exhaust valve 56, and the first bearing wall 105 is disposed on the intake valve 55 side of the pair of camshaft sliding support surfaces 107 and 108. Since one camshaft sliding contact support surface 107 is disposed so as to be offset from the other camshaft sliding contact support surface 108 toward the storage chamber 104, the depth of the sprocket storage recess 131 is increased. By reducing the depth on the exhaust valve 56 side, which is not in a radial arrangement, the number of processing steps at the time of processing formation can be reduced.

  Further, a first cam holder 106 fixed to the first bearing wall 105 so as to sandwich the intake side and exhaust side camshafts 77 and 79 between the first bearing wall 105 includes the first bearing wall. Since the first bearing wall 105 has a bent shape, the cam holder is provided separately on the intake side and the exhaust side, since the first bearing wall 105 has a bent shape. The cost can be reduced without increasing the number of parts.

  A gear housing recess 132 for housing a part of the drive gear 94 is formed on the inner surface of the outer wall 126 that forms a part of the housing chamber 104 between the cylinder head 45 and the first bearing wall 105. In addition, since a protrusion 126 a having a shape corresponding to the gear receiving recess 132 is provided on the outer surface of the outer wall 126, a gear housing that houses a part of the drive gear 94 in the outer wall 126 of the cylinder head 45. Only the portion corresponding to the recess 132 protrudes in the axial direction of the intake side and exhaust side camshafts 77 and 79, so that the entire cylinder head 45 can be prevented from being enlarged.

  The gear receiving recess 132 has a V-shape that is open to the intake side and the exhaust side camshafts 77 and 79 corresponding to the arrangement of the pair of driven gears 92 and 93 and the drive gear 94. Therefore, when the cylinder head 45 of the drive gear 94 and the driven sprocket 90 is assembled, the drive gear 94 is dropped into the gear receiving recess 132, so that approximate positioning is possible. Improvements can be made.

  Further, a stem end 55b of an intake valve 55 which is one of the intake valve 55 and the exhaust valve 56, an intake side cam 76 of the intake side camshaft 77 which is one of the intake side and the exhaust side camshafts 77 and 79, Between the intake side and the exhaust side camshafts 77, 79, and an intake side rocker arm that is swingably supported by an intake side rocker shaft 84 that is inserted into and fixed to the cylinder head 45. 80, an insertion hole 151 through which the intake side rocker shaft 84 is inserted is provided in the cylinder head 45 with one end opened in the sprocket housing recess 131, and the housing chamber 104 is formed between the insertion hole 151 and A through-hole 155 sandwiched between the intake-side rocker shaft 84 and the through-hole 151 can be inserted into the through-hole 151. Therefore, when the intake side rocker shaft 84 inserted through the through hole 155 is inserted into one end of the insertion hole 151, the position of one end of the insertion hole 151 can be easily confirmed. Assembling property to the cylinder head 45 can be improved.

  Further, since the first bearing wall 105 is provided with a pair of through holes 133 that sandwich the driven sprocket 90 and the drive gear 94 from both sides below the sprocket housing recess 131, the crankshaft 42 and the driven sprocket 90 While a load acts on the cylinder head 45 from the driven sprocket 90 and the drive gear 94 side in the direction connecting the axes, the through hole 133 is disposed at a position avoiding the load acting direction, thereby avoiding a decrease in rigidity. Thus, the weight of the cylinder head 45 can be reduced.

  A rocker arm side oil passage 160 for supplying oil to the intake side and the exhaust side rocker arms 80, 81 to the sliding contact portions between the rocker arms 80, 81 and the intake side cam 76 and the exhaust side cam 78. 161, and rocker shaft inner oil passages 162 and 163 communicating with the rocker arm side oil passages 160 and 161, respectively, are provided in the intake side and the exhaust side rocker shafts 84 and 85, respectively. The exhaust oil camshafts 77 and 79 are rotatably supported by a first camshaft support portion 82 provided in the cylinder head 45 to communicate oil that bypasses the intake and exhaust camshafts 77 and 79. A passage 164 is provided in the cylinder head 45 so as to guide oil from the cylinder body 44 side. And an intake side formed in the first camshaft support 82 so as to rotatably support the intake side and the exhaust side camshafts 77 and 79. An oil passage 169 provided in the cylinder head 45 so as to communicate with the intake-side and exhaust-side journal oil passages 166, 167 leading the oil to the exhaust-side camshaft bearing portions 82a, 82b and the rocker shaft inner oil passages 162, 163. , 170, a branch oil passage 168 connected to the communication oil passage 164 in parallel with the intake side and exhaust side journal oil passages 166, 167 so as to guide oil to the side of the first camshaft support portion 82. Therefore, oil is supplied to the rocker arm side oil passage through the communication passage branched from the camshaft bearing. Compared to the oil supply structure so, it is possible to secure the amount of oil supplied to the rocker arm side oil passage 160 and 161 regardless of the rotational speed of the intake side and the exhaust side cam shaft 77, 79.

  Further, the first camshaft support portion 82 is connected to the first bearing wall 105 provided integrally with the cylinder head 45, and the intake side and exhaust side camshaft bearing portions 82a and 82b are connected to the first bearing wall. 105, and a first cam holder 106 fixed to the first bearing wall 105 so as to be formed in cooperation with the first bearing wall 105. The first cam holder 106 includes a part of the oil supply path 165 and the oil. Since the communication oil passage 164 communicating with the supply passage 165, the intake side and exhaust side journal oil passages 166, 167, and a part of the branch oil passage 168 are provided, the cylinder passage 45 is smaller than the cylinder head 45 and has a cylinder. On the side of the first cam holder 106 that can be separated from the head 45, processing of the communication oil passage 164 and contact of the plurality of oil passages 166 to 168 with the communication oil passage 164 So as to perform the machining of parts, it is possible to facilitate the working of the oil passage.

  A pair of oil passages 169 and 170 are provided in the cylinder head 45 so as to individually communicate with the oil passages 162 and 163 in the rocker shaft provided in the intake side and exhaust side rocker shafts 84 and 85, respectively. The branch oil passage 168 is branched into the pair of oil passages 169, 170 so as to communicate with each other, and is provided in the first camshaft support portion 82. The exhaust side rocker shafts 84 and 85 are branched so as to directly communicate with a pair of oil passages 169 and 170 that individually communicate with the oil passages 162 and 163 in the rocker shaft. The oil supply amount to the rocker shaft oil passages 162 and 163 can be balanced.

  Further, since the branch portion 168d of the branch oil passage 168 is provided at the joint portion between the first bearing wall 105 and the first cam holder 106, the joint surface of the first bearing wall 105 with the first cam holder 106 is provided. Therefore, the branch passage portion 168d of the branch oil passage 168 can be processed, and the branch branch oil passage 168 can be easily processed.

  The first cam holder 106 is formed so as to integrally have a portion sandwiching the intake side and exhaust side camshafts 77, 79 between the first bearing wall 105, and the communication oil passage 164 is formed. The intake side and the exhaust side camshafts 77 and 79 are formed to extend linearly in a direction orthogonal to the arrangement direction of the exhaust side camshafts 77 and 79, and the intake side and the exhaust side journal oil passages 166 and 167 are formed on the intake side and the exhaust side. The uppermost portion of the intake side camshaft sliding contact surface 109 and the exhaust side camshaft sliding contact surface 110 formed on the first cam holder 106 so as to be in sliding contact with the camshafts 77 and 79 and the communication oil passage 164, respectively. Since they are formed so as to be connected, the intake side and exhaust side journal oil passages 166, 167 can be shortened to reduce the number of processing steps.

  Further, grooves 171 and 172 for opening the intake side and exhaust side journal oil passages 166 and 167 are formed on the intake side and exhaust side camshaft sliding contact surfaces 109 and 110, respectively. 79, the oil supplied from the intake-side and exhaust-side journal oil passages 166, 167 is diffused in the axial direction of the intake-side and exhaust-side camshafts 77, 79, so that the intake air The lubricity between the side and exhaust side camshafts 77 and 79 and the first camshaft support portion 82 can be improved.

  Incidentally, the intake valve 55 is arranged radially with respect to the combustion chamber 52, and the exhaust valve 56 is arranged along a plane orthogonal to the axis of the intake side and the exhaust side camshafts 77, 79, and the first A driven gear that constitutes a part of a timing transmission mechanism 88 that transmits rotational power from the crankshaft 42 to the shaft ends of the intake side and exhaust side camshafts 77 and 79 protruding from one camshaft support portion 82. 92 and 93 are fixed, and one of the intake side and the exhaust side camshaft sliding contact surfaces 109 and 110 is disposed on the intake valve 55 side with one camshaft sliding contact surface 109 as the other camshaft sliding contact surface. The first cam holder 106 is formed so as to be offset from the timing transmission mechanism 88 side than 110, and the one camshaft sliding contact surface 1 is formed. 9 is formed longer on the timing transmission mechanism 88 side than the groove 72 formed on the other camshaft sliding contact surface 110, so that the intake side and exhaust side camshafts are formed. The driven gear 92 is provided even if the communication oil passage 164 is disposed so as to pass through the center portion in the width direction of the other camshaft sliding contact surface 110 on the projection view including the axes 77 and 79. As a result, although the load in the direction orthogonal to the axis is larger at the shaft end of the intake camshaft 77, the intake camshaft 77 has a portion near the driven gear 92 between the first camshaft support portion 82 and the intake camshaft 77. Also, oil can be supplied effectively, and a good lubrication state can be ensured.

  Further, a pair of insertion holes 151 and 152 for inserting and fixing a pair of intake side rocker shafts 84 corresponding to the radially arranged intake valves 55 of the intake side and exhaust side rocker shafts 84 and 85 are inserted into these insertion holes. The extension lines of the central axes C1 and C2 of the 151 and 152 are provided independently of each other in the cylinder head 45 so as to intersect with each other, and oil is supplied from the oil passages 169 and 170 to the pair of insertion holes 151 and 152. Since a pair of communication passages 173 and 174 leading to the cylinder head 45 are provided in the cylinder head 45 independently of each other, oil is supplied to the insertion holes 151 and 152 without causing the pair of insertion holes 151 and 152 to communicate with each other. This makes it possible to shorten the overall length of the insertion holes 151 and 152 and ensure the rigidity of the cylinder head 45.

  The oil supply direction from the rocker arm side oil passages 160 and 161 in the sliding contact portions of the intake side and exhaust side cams 76 and 78 and the intake side and exhaust side rocker arms 80 and 81 is opposite to the cam rotation direction 97. Oil is supplied from the auxiliary oil supply means 176 in the same direction as the cam rotation direction 97 to the sliding contact portion on the direction side, in this embodiment, the sliding contact portions of the exhaust side cam 78 and the exhaust side rocker arm 81. Therefore, a sufficient oil supply amount to the sliding contact portion in which the cam rotation direction 97 is opposite to the oil supply direction from the exhaust side rocker arm 81 can be ensured.

  The auxiliary oil supply means 176 communicates with the auxiliary oil supply passage 177 provided in the cylinder head 45 and extending in parallel with the axis of the intake side and exhaust side camshafts 77 and 79, and the auxiliary oil supply passage 177. Thus, since the oil injection hole 178 provided in the cylinder head 45 is provided, it is possible to easily adjust the oil supply amount from the auxiliary oil supply means 176 only by adjusting the diameter of the oil injection hole 178.

  Further, the intake valve 55 is arranged radially with respect to the combustion chamber 52, and the exhaust valve 56 is arranged along a plane perpendicular to the axes of the intake side and exhaust side camshafts 77, 79, and the auxiliary oil Since the supply means 176 is provided in the cylinder head 45 so as to be disposed on the exhaust valve 56 side, the oil injection holes 178 of the auxiliary oil supply means 176 are arranged on the intake line and the exhaust camshafts 77 and 79. It is not necessary to form in a complicated direction so as to face along the direction, and the structure of the auxiliary oil supply means 176 can be simplified.

  The cylinder head 45 is provided with an oil supply passage 165 for guiding oil from the cylinder body 44 side so as to communicate with the auxiliary oil supply passage 177 and a pair of branches branched from the downstream side of the oil supply passage 165. Oil passages 169 and 170 are provided in parallel with the auxiliary oil supply passage 177 so that the downstream side of the oil passages 169 and 170 communicates with the pair of rocker arm side oil passages 160 and 161, and the pair of oil passages One of the passages 169 and 170 is disposed at a position sandwiching the exhaust valve 56 between the auxiliary oil supply passage 177 and the both oil passages 169 and 170 are disposed between the intake valve 55 and the exhaust valve 56. The three passages 169, 170, 177 for guiding the oil are connected to the intake valve 55 and Are distributed on both sides of the exhaust valve 56 is arranged, it is possible to reduce the size of the cylinder head 45 by utilizing the space effectively.

  Further, the intake side and exhaust side rocker shafts 84 and 85 are inserted directly above the pair of oil passages 169 and 170 disposed below the branching portion 168d from the downstream side of the oil supply passage 165. Two sets of insertion holes 151, 152; 146 provided in the cylinder head 45 are arranged, and the oil passages 169, 170 are inserted into the rocker shaft oil passages 162, 163 via the insertion holes 151, 152; 146. The passages 173, 174, and 175 for guiding the oil are connected to the cylinder head 45 so as to extend vertically between the two sets of insertion holes 151, 152; 146 and the pair of oil passages 169, 170. Since the oil passage is provided, oil for guiding the oil to the rocker arm side oil passages 160 and 161 when the internal combustion engine E is stopped is provided in the oil passage. Can be left stored in 69,170, quickly on the rocker arm side oil passage 160 and 161 at the start of the internal combustion engine E can supply oil, it is possible to eliminate the possibility that oil shortage occurs.

  A second camshaft support portion 83 that rotatably supports the intake side and exhaust side camshafts 77, 79 is provided in the cylinder head 45, and the intake valve 55 of the pair of oil passages 169, 170 is provided. A pair of camshaft lubrication passages 179 and 180 branched from the oil passage 169 corresponding to the side and the auxiliary oil supply passage 177, respectively, are the intake side and exhaust side camshafts 77 and 79, and the second camshaft. Since oil is supplied to the cylinder head 45 so as to supply oil between the support portion 83 and the oil passage 169 and the auxiliary oil supply passage 177, the intake side and exhaust side camshafts 77 and 79 are lubricated. Therefore, the oil passage structure can be simplified.

  Further, the pair of oil passages 169 and 170 and the auxiliary oil supply passage 177 are provided in the cylinder head 45 so as to be formed by processing from the same one side surface 45c of the cylinder head 45. The pair of oil passages 169 and 170 and the auxiliary oil supply passage 177 can be continuously formed without changing the fixing direction of the cylinder head 45, and the number of processing steps can be reduced.

  Further, the one side surface 45c of the cylinder head 45 accommodates a timing transmission mechanism 88 that transmits power from the crankshaft 42 to the intake side and exhaust side camshafts 77, 79 of all side surfaces of the cylinder head 45. Since the side surface is disposed on the opposite side of the storage chamber 104 formed in the engine body 29, there is no need to form a processing through-hole penetrating the outer wall 126 of the storage chamber 104, and the cylinder head 45 The rigidity of the cylinder head 45 can be ensured without reducing the rigidity.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

  For example, in the above-described embodiment, the drive gear 94 is commonly engaged with the driven gears 92 and 93 provided on the pair of camshafts 77 and 79, respectively. The present invention can also be applied to a structure in which a drive gear is meshed with a driven gear provided in the shaft and a power transmission mechanism using a gear or a power transmission mechanism using an endless transmission band such as a chain is provided between both camshafts. it can.

29 ... Engine body 42 ... Crankshaft 43 ... Crankcase 45 ... Cylinder head 52 ... Combustion chamber 55 ... Intake valve 55b ... Stem end 56 ... Exhaust valve 76- ..Cam 80 ... Rocker arm 84 ... Rocker shaft 77, 79 ... Cam shaft 90 ... Driven sprocket 91, driven wheel ... Cam chain 92, 93 ... driven, endless transmission band Gear 94 ... Drive gear 104 ... Storage chamber 105 ... Bearing wall 106 ... Cam holder 107, 108 ... Cam shaft sliding contact support surface 111, 112, 113, 114 ... Mounting boss 115 ... Through bolt 126 ... Outer wall 126a ... Projection 131 ... Sprocket receiving recess 132 that is driven wheel receiving recess ... Gear receiving recess 133 ... Through hole 51 ... insertion hole 155 ... through hole L ... linear

Claims (8)

  At least one of an intake valve (55) and an exhaust valve (56) that are disposed in the cylinder head (45) of the engine body (29) so as to be openable and closable is radially arranged with respect to one combustion chamber (52). The driven gear (92) is attached to at least one of a pair of camshafts (77, 79) rotatably supported by the cylinder head (45) corresponding to the intake valve (55) and the exhaust valve (56) individually. 93) and a crankshaft (42) rotatably supported by a crankcase (43) of the engine body (29) on a driven wheel (90) rotatably supported by the cylinder head (45). ) Is wound around an endless transmission band (91) for transmitting rotational power from the drive gear (94), and a drive gear (94) meshing with the driven gear (92, 93) is provided coaxially with the driven wheel (90). The driven wheel (90) and the drive gear (94) are disposed closer to the crankshaft (42) than a straight line (L) connecting the central axes of the pair of camshafts (77, 79), A housing formed in the engine body (29) for housing the driven gear (92, 93), the driven wheel (90), and the drive gear (94) and running the endless transmission band (91). A pair of camshaft slidable contact surfaces (105) that are supported by a bearing wall (105) that constitutes a part of the inner wall of the chamber (104) in sliding contact with at least a part of the outer periphery of the pair of camshafts (77, 79). 107, 108) provided on the cylinder head (45), and at least one of the driven wheels (90) disposed closer to the bearing wall (105) than the drive gear (94). Internal combustion engine, wherein a driven wheels housing recess (131) for housing the formed in said bearing wall (105).   One of the intake valve (55) and the exhaust valve (56) is radially arranged, and the other valve (56) is provided on the intake side and the exhaust side camshaft (77, 79). The internal combustion engine according to claim 1, wherein the internal combustion engine is disposed along a plane perpendicular to the axis.   The cylinder head (45) has the same number of mounting bosses (111, 112, 113, 114) as the number of intake valves (55) and exhaust valves (56), and the cylinder head (45) is connected to the crankcase. A through bolt (115) for fastening to (43) is inserted around the intake valve (55) and the exhaust valve (56), and the bearing wall (105) is a pair of the cams. Of the shaft sliding contact support surfaces (107, 108), one cam shaft sliding contact support surface (107) arranged on the one valve (55) side is more than the other cam shaft sliding contact support surface (108). The internal combustion engine according to claim 2, wherein the internal combustion engine is formed so as to be offset from the storage chamber (104) side.   A cam holder (106) fixed to the bearing wall (105) so as to sandwich the pair of camshafts (77, 79) between the bearing wall (105) corresponds to the shape of the bearing wall (105). The internal combustion engine according to claim 3, wherein the internal combustion engine is formed to have a bent and integrated shape.   A part of the drive gear (94) is accommodated in an inner surface of an outer wall (126) that forms a part of the accommodating chamber (104) between the cylinder head (45) and the bearing wall (105). The gear receiving recess (132) is formed, and a protrusion (126a) having a shape corresponding to the gear receiving recess (132) is provided on the outer surface of the outer wall (126). The internal combustion engine described in 1.   The gear receiving recess (132) corresponds to the arrangement shape of the pair of driven gears (92, 93) and the drive gear (94) provided in the pair of camshafts (77, 79), respectively. 6. The internal combustion engine according to claim 5, wherein the internal combustion engine is formed to have a V-shape opened toward the camshaft (77, 79).   The camshaft is disposed between one stem end (55b) of the intake valve (55) and the exhaust valve (56) and a cam (76) provided on one of the pair of camshafts (77, 79). A rocker arm (80) having an axis parallel to (77, 79) and inserted into and fixed to the cylinder head (45) and supported rockably by a rocker shaft (84) is provided, and the rocker shaft ( 84) is inserted in the cylinder head (45) with one end opened in the driven wheel housing recess (131), and the housing chamber (104) is connected to the insertion hole (151). A through hole (155) sandwiched between the outer wall (126) and the outer wall (126) is provided so that the rocker shaft (84) can be inserted from the through hole (155) into the insertion hole (151). Internal combustion engine according to claim 5 or 6, characterized in.   The bearing wall (105) is provided with a pair of through holes (133) sandwiching the driven wheel (90) and the drive gear (94) from both sides below the driven wheel housing recess (131). The internal combustion engine according to any one of claims 1 to 7.

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