JP2006022692A - Assembling type cam shaft structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact assembling type cam shaft structure for an internal combustion engine comprising a small number of components and having simple structure, in the assembling type cam shaft structure for the internal combustion engine, which comprises a cam shaft main body having a cam ridge formed thereon and a rotating member which is integral with the cam shaft main body and to which drive force from a crankshaft is input, and in which the cam shaft main body and the rotating member are detachably jointed via a fastening member. <P>SOLUTION: One side of the rotating member has a jointed face jointed to the cam shaft main body, and the other side of the rotating member has a rotational bearing part. In a base circle part of the cam rise of the cam shaft main body, a phase positioning part with respect to the rotating member is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an assembled camshaft structure for an internal combustion engine.

  The conventional assembly type camshaft has a structure composed of three members: a camshaft main body, a rotating member, and a bearing member provided between the two members (see, for example, Patent Document 1). For this reason, the number of members is large, the number of spigot joints for coupling each of them increases, and there are also problems in phase positioning accuracy and assemblability between the camshaft body and the rotating member.

Japanese Patent No. 3285915 (FIG. 1).

  The present invention is intended to solve the above-mentioned problems and to provide a compact assembly type camshaft for an internal combustion engine that is configured with a simple structure with a small number of members.

The present invention solves the above problems, and the invention according to claim 1
The camshaft main body is formed with a camshaft main body and a rotating member that is integrated with the camshaft main body and receives driving force from the crankshaft. The camshaft main body and the rotating member are interposed via a fastening member. In an assembled camshaft structure for an internal combustion engine that is detachably coupled,
The rotating member relates to an assembly type camshaft structure for an internal combustion engine comprising a coupled surface coupled to the camshaft body on one side and a rotating bearing portion on the other side.

The invention according to claim 2 is the assembled camshaft structure for the internal combustion engine according to claim 1,
A phase positioning portion for the rotating member is formed in a base circle portion of the cam crest of the camshaft body.

According to a third aspect of the present invention, in the assembled camshaft structure for the internal combustion engine according to the first aspect,
The rotating member includes a boss portion, a pulley portion around which a timing belt is wound, and a connecting portion that connects the boss portion and the pulley portion.
A decompression mechanism having a centrifugal weight supported by the joint portion and a decompression cam that extends through the joint portion and extends to the cam peak portion of the camshaft main body is disposed at a position inside the pulley portion. It is a feature.

The invention according to claim 4 is the assembled camshaft structure for the internal combustion engine according to claim 2,
The cylinder head side cover of the internal combustion engine includes a cam shaft support portion and a rocker arm shaft support portion,
The bearing on the rotating member side of the assembly type cam shaft is supported by a cam shaft support portion of the cylinder head side cover.

According to the invention of claim 1,
The assembly type camshaft is formed by a simple structure with a small number of members.
In addition, since the rotating member is formed independently of the camshaft body and is connected by providing a bearing portion at each one end, the length of the assembled camshaft is divided into two in the axial direction. It can be shortened and the degree of freedom of assembly to the internal combustion engine is improved.

According to the invention of claim 2,
Since the phase positioning portion is formed using the thickness of the cam crest, the length of the assembly type cam shaft can be shortened.

According to the invention of claim 3,
Since the decompression mechanism is arranged using the empty space inside the pulley portion, the decompression mechanism can be miniaturized and the length of the assembled camshaft provided with the decompression mechanism can be shortened.

According to the invention of claim 4,
Since the cam shaft support portion and the rocker arm shaft support portion are formed on the cylinder head side cover, the structure of the cylinder head can be simplified.

  FIG. 1 is a side view of a motorcycle 1 with a pedal according to an embodiment of the present invention. A body frame 3 having a sheet metal box-shaped cross section extends rearward and obliquely downward from the head pipe 2. A steering shaft 4 is pivotally supported on the head pipe 2, a handle 5 that extends left and right is provided on the steering shaft 4, and a front wheel 7 is pivotally supported on a front fork 6 that extends downward from the steering shaft 4. The pipe seat post 8 is made of a U-shaped pipe, and both lower end portions thereof are coupled to the rear end portion of the vehicle body frame 3, and a seat 9 is attached to the upper U-shaped bent portion.

  As shown in FIG. 1, an overhead valve type four-stroke single cylinder internal combustion engine 10 is mounted and fixed to the lower part of the vehicle body frame 3, and a human-powered pedal shaft 11 is provided in front of the internal combustion engine 10 and at the lower part of the vehicle body frame 3. Is equipped for rotation. A power transmission case 12 is fixed to the left side surface of the internal combustion engine 10, and a rear wheel 13 is rotatably supported at the rear end thereof. The vehicle body frame 3, the internal combustion engine 10, and the power transmission case 12 are integrally coupled to each other.

  The power transmission case 12 houses a power transmission mechanism 14 that transmits the power of the internal combustion engine 10 to the rear wheel 13. The pedal transmission force transmission that transmits the pedal depression force to the rear wheel 13 is outside the power transmission case 12. A mechanism 15 is provided. A fuel tank 16, an air cleaner 17, and a carburetor 18 are provided at the lower part of the seat post 8, and a portion sandwiched between the left and right pipe portions of the seat post 8 is a place 19 for the helmet. In addition, 26 is a pedal arm and 27 is a pedal.

  FIG. 2 is an external view of the internal combustion engine 10 and the power transmission case 12 in the above embodiment, FIG. 3 is a diagram showing a cross section in the horizontal direction of the power unit viewed from above, and FIG. 4 is a vertical cross section of the internal combustion engine viewed from the left side. It is a figure. As shown in FIGS. 2 and 4, the outer shell of the internal combustion engine 10 includes a crankcase 20, a cylinder head 21, and a cylinder head cover 22. As shown in FIG. 3, the cylinder 30 is housed in the crankcase 20 and is not visible in FIG. A generator housing portion 23 shown in FIG. 3 is integrally provided on the right side of the crankcase 20, and a generator cover 24 is provided outside the generator housing portion 23 in FIG. 2. A spark plug 25 is visible in the center of the front surface of the cylinder head 21 in FIG.

  3 is a diagram showing a cross section of the power unit in a substantially horizontal direction from above, FIG. 4 is a diagram showing a longitudinal section of the internal combustion engine as seen from the left side, and FIG. 5 is a view of removing the cylinder head cover of the internal combustion engine. It is the front view which made the inside visible.

  In FIG. 4, the crankcase 20 houses a cylinder 30 that is inclined in a substantially horizontal direction, and an oil pan portion 80 having an opening in the front of the cylinder axis is formed below the cylinder 30. Covers the opening of the oil pan 80. The cylinder 30 is fixed to the cylinder head 21 with bolts 31, and the cylinder head 21 is fixed to the crankcase 20 with bolts 28. Accordingly, the cylinder 30 is held in the crankcase 20 in a cantilevered manner substantially in the horizontal direction by the cylinder head 21. In the cylinder head 21, the joint surface with respect to the crankcase 20 and the joint surface with respect to the cylinder 30 are formed on the same plane. A plurality of fins 32 parallel to the cylinder axis are provided on the outer periphery of the cylinder 30. Bolt insertion holes 125 for attaching the internal combustion engine 10 to the vehicle body are formed integrally with the upper and lower portions of the crankcase 20.

  In FIG. 3, a crankshaft 35 is rotatably held by the crankcase 20 via ball bearings 36A and 36B at the rear portion of the crankcase 20. The ball bearing 36B that supports the left end portion of the crankshaft 35 is held by the crankcase 20 via a power transmission case base end member 40 that covers the crankcase left wall opening provided at the center of the left surface of the crankcase 20. The crank pin 37 supports the large end portion of the connecting rod 38, and the small end portion of the connecting rod 38 supports the piston 39. The piston 39 is slidable in the cylinder 30.

  FIG. 5 is a front view of the internal combustion engine with the cylinder head cover removed. 4, a combustion chamber 45 is formed in a portion of the cylinder head 21 that faces the piston 39, and an intake valve 46 and an exhaust valve 47 shown in FIG. In the internal space in front of the top of the cylinder 30 in the cylinder head 21, shaft end portions of the intake valve 46 and the exhaust valve 47 protrude, and an overhead valve type valve mechanism 48 for driving them is housed. As shown in FIGS. 4 and 5, the valve mechanism 48 includes a cam shaft 49 and a rocker arm shaft 52. An intake cam 50 and an exhaust cam 51 are integrally provided on the cam shaft 49, and an intake rocker arm 53 and an exhaust rocker arm 54 are pivotally supported on the rocker arm shaft 52. A driven pulley 55 is integrally provided at the end of the camshaft 49, and a timing belt 57 (FIG. 4) is wound around a drive pulley 56 provided integrally with the crankshaft 35. The shaft 49 is driven to rotate. The timing belt 57 is a toothed belt. In FIG. 4, 60 is an intake port, and in FIG. 5, 61 is an exhaust port. Although the details of the structure of the cam shaft 49 will be described later, the cam shaft 49 is formed by fastening a cam shaft main body 145 having cams 50 and 51 and a rotating member 146 having a driven pulley 55 in FIG. The assembled camshaft is connected by a bolt 147, and the camshaft 49 here is the name of the whole of the above-mentioned parts connected together.

  In FIG. 4, a cylinder head cover 22 is attached to the top of the cylinder head 21 with a bolt 29 and covers the top of the cylinder head 21. A gas-liquid separation chamber 58 of a breather mechanism is formed inside the cylinder head cover 22. Reference numeral 59 denotes a partition wall that constitutes one wall surface of the gas-liquid separation chamber 58 and partitions the valve mechanism 48.

  3 and 4, an oil pump 70 is attached to the base end member 40 of the power transmission case 12 covering the left surface of the crankcase 20 from the inside thereof. The oil pump shaft 71 is provided with a driven gear 72 and meshes with a drive gear 73 provided on the crankshaft 35 so that the oil pump 70 is driven by the crankshaft 35.

  In FIG. 4, an oil pan portion 80 is formed in the lower portion of the crankcase 20, and a strainer 82 is mounted in the strainer mounting groove 81. A suction oil passage 85 and a discharge oil passage 86 are formed by an oil passage forming member 83 and an oil passage cover member 84 at a portion of the cylinder head 21 that covers the oil pan portion 80. A suction pipe 87 is bridged between the suction oil passage 85 and the suction port 74 of the oil pump 70, and a discharge pipe 88 is provided between the discharge oil passage 86 and the discharge port 75 of the oil pump 70. It is laid over. The suction pipe 87 and the discharge pipe 88 are both provided below the cylinder 30 and are disposed along the axis of the cylinder 30. The oil that flows into the oil pan section 80 and passes upward through the strainer 82 is sucked into the oil pump 70 through the oil suction hole 95, the suction oil passage 85, and the suction pipe 87, and is added by the oil pump 70. Compressed and discharged via the discharge pipe 88 and the discharge oil passage 86.

  In FIG. 5, the discharged oil is injected to the valve operating mechanism 48 via oil passages 89, 90, 91, 92, 93, 94 following the discharge oil passage 86. The oil passage is connected from the end of the discharge oil passage 86 to the oil passage 90 provided on the end surface of the crankcase 20 by the wall oil passage 89, and from the end of the oil passage 90 by the wall oil passage 91 to the cylinder head 21. Is connected to an oil passage 92 provided on the end face, and reaches the oil injection hole 94 through the oil passage 93 in the wall. Oil is injected from the oil injection hole 94 to the valve mechanism 48.

  4, the oil pump is provided with an oil pump internal oil passage 76 connected to the discharge port 75 on the joint surface to the power transmission case base end member 40, and an oil injection hole 77 connected to the end thereof. . The pressurized oil is injected from the oil injection hole 77 toward the large end portion of the connecting rod 38, and the sliding portion between the crankshaft 35 is lubricated. The oil injected to the valve operating mechanism 48, the large end of the connecting rod 38, the crankshaft 35, etc. flows down in the cylinder head 21 and the crankcase 20, drops into the oil pan 80 and accumulates, and again the oil pump 70 Inhaled, pressurized and circulated.

  In FIG. 5, the internal combustion engine 10 is provided with a cooling air passage 63 extending from the front surface of the cylinder head 21 to the rear surface of the crankcase 20 substantially parallel to the suction pipe 87 and the discharge pipe 88. The cooling air passage 63 is composed of a cylinder head portion 63A and a crankcase portion 63B. A plurality of fins 64 extending in the front-rear direction are provided on the inner surface of the crankcase portion 63B so as to cool the oil scattered or flowing down in the crankcase. 4 and 5, fins 65 are also provided on the front surface of the wall portion of the cylinder head 21 that covers the oil pan portion 80, and this serves to cool the inside of the crankcase 20 and the oil passage. . Also, fins 66 are provided on the front surface of the cylinder head cover 22 (FIG. 4), which helps cool the oil in the gas-liquid separation chamber 58.

  In FIG. 3, a generator storage section 23 is provided on the right side of the crankcase 20, and a generator 68 is stored. The generator 68 is rotationally driven by the end of the crankshaft 35 that protrudes outward from the right side surface of the crankcase 20. The generator housing 23 is covered with a generator cover 24 having a ventilation gap.

  In FIG. 3, the power transmission case 12 is formed by an inner member 41, an outer member 42, and a rear member 43 that are sequentially assembled to the base end member 40. The base end member 40 forms part of the power transmission case 12 and also serves as a lid for the opening of the left wall of the crankcase.

  In FIG. 3, the motorcycle 1 is provided with five rotating shafts of a pedal shaft 11, a crankshaft 35, a driven shaft 96, an intermediate shaft 97, and a rear axle 98 in order from the front. The pedal shaft 11 is rotatably supported by the vehicle body frame 3. The crankshaft 35 is rotatably supported on the right wall of the crankcase and the base end member 40 of the power transmission case 12 via ball bearings 36A and 36B, respectively. The driven shaft 96, the intermediate shaft 97, and the rear axle 98 are all rotatably supported by the inner member 41 and the rear member 43 of the power transmission case 12. The driven shaft 96 and the rear axle 98 are supported via ball bearings.

  In FIG. 3, a crankshaft 35, a driven shaft 96, an intermediate shaft 97, and a rear axle 98 are axes related to power transmission from the internal combustion engine 10 to the rear wheel 13. A drive pulley 100 is provided at the left end of the crankshaft 35, a driven pulley 101 is rotatably provided on the driven shaft 96, and an endless V-belt 102 is bridged between both pulleys to provide a V-belt type continuously variable transmission. A machine 103 is configured. A centrifugal clutch 104 provided at the left end of the driven shaft 96 disconnects the system between the driven pulley 101 and the driven shaft 96. The small-diameter gear 105 provided on the driven shaft 96 and the large-diameter gear 106 provided on the intermediate shaft 97 mesh with each other, and the small-diameter gear 107 provided on the intermediate shaft 97 and the rear axle 98 are mounted via the one-way clutch 108. The reduction gear mechanism 110 is configured by meshing with the large-diameter gear 109. The V-belt continuously variable transmission 103 and the reduction gear mechanism 110 constitute a power transmission mechanism 14.

  In FIG. 3, a drive sprocket 112 is attached to the left end portion of the pedal shaft 11. The driver's pedaling force of the pedal 27 is transmitted through the pedal arm 26 and the pedal shaft 11, and the drive sprocket 112 is driven to rotate. A driven sprocket 114 is pivotally supported on the rear axle 98 via a one-way clutch 113. An endless chain 115 is bridged between the two sprockets, and the pedaling force is transmitted to the rear wheel 13 through the endless chain 115. The rotation of the rear wheel 13 is not transmitted to the pedal 27 by the action of the one-way clutch 113. As shown in FIG. 1, tension is applied to the endless chain 115 by the action of the idle pulley 116 and the tensioner pulley 117. The pedal depression force transmission mechanism 15 is configured by the above members.

  FIG. 6 is a left side view of the valve operating chamber above the cylinder head 21. Arrow F points forward. In FIG. 6, there is a large opening 140 on the upper left surface of the cylinder head 21. This is a portion covered with a cylinder head side cover 141 (details will be described later, FIGS. 7 and 8) provided with a bearing support portion and a rocker arm support portion on the pulley portion side of the cam shaft. Through the opening 140, the cam shaft support portion 135 and the rocker arm shaft support portion 133 can be seen. A periphery of the opening 140 is an abutting surface 140a with which the cylinder head side cover 141 abuts. An exhaust port 61 is open at the bottom of the valve operating chamber.

  7 is a view of the cylinder head side cover 141 covering the left opening of the cylinder head 21 as viewed from the right side (inside the cylinder head), and FIG. 8 is a sectional view taken along line VIII-VIII in FIG. The arrow L in FIG. 8 points to the left, and the arrow R points to the right. A cam shaft support portion 142 and a rocker arm shaft support portion 143 are provided on a portion of the cylinder head side cover 141 facing the right side (inner side) of the cylinder head 21.

  FIG. 9 is an enlarged cross-sectional view of the cam shaft 49 and the cylinder head side cover 141 that supports the cam shaft 49. The camshaft 49 is connected to the camshaft main body 145 and the rotating member 146 via a fastening bolt 147 by bringing the coupling portion 145a on the camshaft main body 145 side into contact with the coupled surface 146a on the rotating member 146 side. It has an assembled camshaft structure. The cam shaft main body 145 includes a central shaft portion 148, an intake cam 50, and an exhaust cam 51. The rotating member 146 includes a central boss portion 149, a peripheral driven pulley 55, and a disc portion 150 connecting the two. A decompression mechanism 151, which will be described in detail later, is attached to the disc portion 150. In the cam shaft 49 configured as described above, the bearing portion 145 b at the right end of the cam shaft main body 145 is rotatably supported by the right cam shaft support portion 135 (FIG. 6) via the ball bearing 152, and the left end of the rotating member 146. The bearing portion 146b is rotatably supported by the cam shaft bearing support portion 142 of the cylinder head side cover 141 via the ball bearing 153.

  10 is a view of the camshaft main body 145 as viewed from the left side, and FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. A fastening bolt female screw 154 is provided in the center of the camshaft main body 145 in the axial direction. Each cam portion 50, 51 is provided with a base circle portion 155 having the same diameter. Since the rotation member 146 is provided with a decompression mechanism 151 closely related to the intake / exhaust cams 50 and 51, the rotation phase positioning between the rotation member 146 and the camshaft main body 145 is required. For this purpose, as a means on the camshaft main body 145 side, a phase positioning notch 156 (see FIG. 11 for a cross section) is provided on the base circle 155 of the exhaust cam 51 on the opposite side of the peak 51a of the exhaust cam 51. Is provided.

  12 is a view of a state in which the rotating member 146 and the camshaft main body 145 are combined in the rotational direction phase positioning as seen from the left side, and FIG. 13 is a sectional view taken along line XIII-XIII in FIG. In FIG. 12, in order to clearly show the relative positional relationship between the rotating member 146 and the camshaft main body 145, the fastening bolts, the decompression mechanism, and the like are removed because they are complicated. The left side surface of the rotating member disc 150 is provided with a hole 158 for rotatably mounting a decompression rotator 162 (described later), and a bottom surface is smoothed by an end mill for smooth sliding of the decompression rotator. A pin hole 161 for rotatably mounting a processed fan-shaped recess 159, a passage groove 160 of a pin tip caulking portion for driving the decompression rotator, and a centrifugal weight having a pin for driving the decompression rotator Is provided. A phase positioning projection 157 that matches the phase positioning notch 156 of the camshaft main body 145 is provided on the right side surface of the rotating member disk portion 150. In FIG. 12, the phase positioning projection 157 and the intake / exhaust cams 50 and 51 are behind the disc portion 150, and are indicated by chain lines. FIG. 13 shows a cross section of the protrusion 157. As shown in FIG. 13, by inserting the phase positioning projection 157 into the phase positioning notch 156 and fastening the camshaft main body 145 and the rotating member 146, the intake / exhaust cams 50, 51 and the decompression mechanism 151 are The phase is determined and positioning is performed.

  FIG. 14 is a sectional view of the decompression mechanism 151. The decompression mechanism 151 is fitted into the decompression rotor 162 rotatably mounted in the decompression rotor mounting hole 158, the centrifugal weight 163, and the pin hole 161 of the rotating member disk portion, and the centrifugal weight 163 can be rotated. The distal end of the centrifugal weight support pin 164 is supported in the distal end portion of the centrifugal weight 163, and the distal end is slidably inserted into a long hole 162d (details will be described later) of the arm portion of the decompression rotator. The decompression rotor driving pin 165 and the torsion coil spring 166 are constituted.

  15 is an enlarged cross-sectional view of the decompression rotator 162 shown in FIG. 14, FIG. 16 is a cross-sectional view taken along XVI-XVI in FIG. 15 (the cross-sectional view is seen from the left), and FIG. 17 is a cross-sectional view taken along XVII-XVII in FIG. It is the figure which looked at the cross section from the right. FIG. 15 shows a cross section taken along line XV-XV in FIG. The decompression rotator 162 is formed integrally with three parts having different actions. In FIG. 15, the three portions are a shaft portion 162a having a central circular cross section, a left arm portion 162b, and a right decompression cam portion 162c. The decompression rotator 162 is rotatably supported by inserting the shaft portion 162a having a circular cross section into the rotator mounting hole 158 of the rotating member disc portion 150. The arm portion 162b is a portion that functions as an arm for rotating the decompression rotator 162 as a whole. A long hole 162d is provided along the center line B of the arm portion 162b. The decompression rotator 162 is rotationally driven by a decompression rotator driving pin 165 (FIG. 14) inserted through the elongated hole 162d. The decompression cam portion 162c has a shape in which one side portion of the cylinder is notched and removed in a V-shaped cross section. To do. An alternate long and short dash line A is a center line of the cross section (FIG. 17) of the decompression cam portion 162c, and the decompression cam is formed symmetrically with respect to a symmetry plane passing through this line.

  FIGS. 18 and 19 are views of the decompression mechanism as viewed from the left side. FIG. 18 shows the position of the decompression mechanism 151 with respect to the rotating member 146 when the internal combustion engine is stopped and at the start of the internal combustion engine. The position of the decompression mechanism 151 relative to the rotating member 146 after exceeding the decompression end rotational speed is shown. Arrow R is the direction of rotation of the camshaft. In FIG. 18, a curved centrifugal weight 163 is rotatably supported on the surface of the disc portion 150 via a centrifugal weight support pin 164. The centrifugal weight 163 is urged toward the center of the rotating member 146 by the torsion coil spring 166, whereby the inner side surface of the centrifugal weight 163 is in contact with the boss 149 of the rotating member 146. One end of the torsion coil spring 166 is locked to the spring receiving projection 146c of the rotating member 146, and the other end of the torsion coil spring 166 is locked to the centrifugal weight 163 itself.

  In FIG. 18, a decompression rotator 162 is mounted on the other side of the centrifugal weight 163. Since the decompression rotator 162 is hidden by the centrifugal weight 163, it is indicated by a chain line. The left-right positional relationship among the centrifugal weight 163, the decompression rotator 162, and the disc portion 150 is shown in FIG. 14 described above. A decompression rotator driving pin 165 fitted to the distal end portion of the centrifugal weight 163 is slidably fitted into the elongated hole 162 d of the decompression rotator 162.

  In FIG. 19, when the internal combustion engine reaches a predetermined decompression end rotational speed, the centrifugal weight 163 moves outward while rotating around the support pin 164 due to the centrifugal force accompanying the rotation of the rotating member 146. The side surface comes into contact with the stopper protrusion 146d of the rotating member 146 and stops. As the centrifugal weight 163 rotates, the decompression circuit is fitted to the distal end portion of the centrifugal weight 163 and is engaged with the elongated hole 162d (FIG. 16) of the arm portion 162b of the decompression rotor 162. The mover drive pin 165 drives the decompression rotator 162 to rotate, and the decompression rotator 162 rotates about its shaft portion 162a. While the rotational speed of the internal combustion engine is equal to or higher than the decompression end rotational speed, each member of the decompression mechanism maintains the position shown in FIG.

  20 and 21 are enlarged views of the decompression rotator 162 and intake / exhaust cams 50 and 51 viewed from the left side. FIG. 20 shows the intake cam 50 of the decompression rotator 162 when the internal combustion engine is stopped and at the start of the engine. FIG. 21 shows the positions of the decompression rotator 162 relative to the intake cam 50 and the exhaust cam 51 after the internal combustion engine exceeds a predetermined decompression end rotational speed. The decompression cam 162c of the decompression rotator 162 is provided adjacent to the base circle 155 of the exhaust cam 51, as shown in FIG. The positional relationship of the intake cam 50, the exhaust cam 51, and the decompression cam portion 162c as viewed from the cam shaft direction is determined by the phase positioning notch 156 and the phase positioning projection 157 shown in FIGS.

  When the internal combustion engine is stopped and in the initial start state shown in FIG. 20, the center line A of the decompression cam portion 162c is substantially in the tangential direction of the base circle portion 155 of the intake and exhaust cams 50 and 51. The operating surface 162e protrudes outward from the outer peripheral surface of the base circle portion 155.

  In a state after the internal combustion engine shown in FIG. 21 exceeds the decompression end rotational speed, the center line A of the decompression cam portion 162c is orthogonal to the tangent to the base circle portion 155 as a result of the revolution of the decompression rotor 162. However, since the decompression notch 162f faces outward from the base circle portion 155, there is no portion protruding outward from the outer peripheral surface of the base circle portion 155.

  The valve mechanism 48 of this embodiment is an overhead valve type. As shown in FIGS. 4 and 5, the valve operating mechanism 48 is rotatable to an intake cam 50, an exhaust cam 51, and a rocker arm shaft 52 that rotate together with a camshaft 49 driven by a crankshaft 35. The intake rocker arm 53 and the exhaust rocker arm 54 are supported by each other. When the slipper that slides on the cam surface on one end of the rocker arm reaches the cam crest, the slipper is pushed up by the cam crest, and the tappet at the other end of the rocker arm pushes down the shaft end of the intake valve 46 and the exhaust valve 47 Thus, each valve is opened at a unique timing. FIG. 4 shows an intake rocker arm 53, a slipper 53a of the same arm, and a tappet 53b of the same arm.

  Although not shown, the exhaust rocker arm 54 is also provided with similar slippers and tappets. However, the slipper of the exhaust rocker arm 54 is formed in a wide shape so as to cover both the exhaust cam 51 and the decompression cam portion 162c provided close to one side thereof.

  In the initial stage of the internal combustion engine start-up, the slipper of the exhaust rocker arm is not only when it reaches the cam crest of the exhaust cam, but as shown in FIG. 20, the decompression operation surface 162e protruding outward from the base circle 155. The tappet at the other end of the exhaust rocker arm 54 pushes down the shaft end of the exhaust valve 47 to open the exhaust valve 47. Intake and exhaust are performed in the order of intake, compression, expansion, and exhaust. In particular, in the case of a manual start using a pedal depression force as in the present embodiment, a pedal depression force is required in the compression stroke at the initial stage of the internal combustion engine start. In order to reduce the pedal effort, the decompression (compression release) operation is performed. The timing is the latter half of the compression stroke.

  When the start of the internal combustion engine is achieved and the rotational speed of the internal combustion engine reaches a predetermined decompression end speed, the decompression cam portion 162c rotates to the position shown in FIG. 21, and the decompression notch 162f faces outward. Therefore, the decompression rotator 162 does not affect the slipper of the exhaust rocker arm. If the rotational speed of the internal combustion engine is equal to or higher than the decompression end speed, decompression is not performed and normal operation is performed.

As described in detail above, the present embodiment provides the following effects.
(1) The assembly type cam shaft is formed with a simple structure with a small number of members.
In addition, since the rotating member is formed independently of the camshaft body and is connected by providing a bearing at one end of each, the length of the assembled camshaft can be shortened, The degree of assembly freedom is improved.
(2) Since the phase positioning portion is formed using the thickness of the cam crest, the length of the assembled cam shaft can be shortened.
(3) Since the decompression mechanism is arranged using the empty space inside the pulley portion connected to the camshaft, the decompression mechanism can be downsized, and the length of the assembled camshaft provided with the decompression mechanism can be shortened. it can.
(4) Since the cam shaft support portion and the rocker arm shaft support portion are formed on the cylinder head side cover, the structure of the cylinder head can be simplified.

1 is a side view of a motorcycle 1 with a pedal according to an embodiment of the present invention. 2 is an external view of an internal combustion engine 10 and a power transmission case 12 in the embodiment. FIG. It is the figure which looked at the cross section of the substantially horizontal direction of the said power unit from the top. It is the figure which looked at the longitudinal cross-section of the said internal combustion engine from the left side. It is the front view which removed the cylinder head cover of the said internal combustion engine. 2 is a left side view of a valve operating chamber of a cylinder head 21. FIG. FIG. 3 is a view of a cylinder head side cover 141 covering the left opening of the cylinder head 21 as viewed from the right side (inside the cylinder head). It is VIII-VIII sectional drawing of FIG. 4 is an enlarged cross-sectional view of a cam shaft 49 and a cylinder head side cover 141 that supports the cam shaft 49. FIG. It is the figure which looked at the camshaft main body 145 from the left side. It is XI-XI sectional drawing of FIG. FIG. 5 is a view of a state in which a rotating member 146 and a camshaft main body 145 are combined in a rotational direction phase positioning as viewed from the left side. It is XIII-XIII sectional drawing of FIG. 4 is a sectional view of a decompression mechanism 151. FIG. 5 is an enlarged cross-sectional view of a decompression rotator 162. FIG. It is XVI-XVI sectional drawing of FIG. It is XVII-XVII sectional drawing of FIG. It is the figure which looked at the decompression mechanism at the time of an internal combustion engine stop and the start-up from the left side. It is the figure which looked at the decompression mechanism after an internal combustion engine exceeded predetermined decompression end rotation speed from the left side. FIG. 6 is a view of the decompression rotator 162 and intake / exhaust cams 50 and 51 when the internal combustion engine is stopped and at the start of the engine as viewed from the left side. FIG. 6 is a view of the decompression rotor 162 and intake / exhaust cams 50 and 51 viewed from the left side after the internal combustion engine exceeds a predetermined decompression end rotational speed.

Explanation of symbols

21 ... Cylinder head, 46 ... Intake valve, 47 ... Exhaust valve, 48 ... Valve mechanism, 49 ... Cam shaft, 50 ... Intake cam, 51 ... Exhaust cam, 52 ... Rocker arm shaft, 53 ... Intake rocker arm, 53a ... Slipper, 53b ... Tappet, 54 ... Exhaust rocker arm, 55 ... Drive pulley, 56 ... Drive pulley, 57 ... Timing belt, 140 ... Cylinder head left side opening, 141 ... Cylinder head side cover, 142 ... Cam shaft support, 143 ... Rocker arm shaft support part, 145 ... cam shaft body, 145a ... cam shaft body side coupling part, 145b ... cam shaft body right end bearing part, 146 ... rotating member, 146a ... coupled surface on rotating member side, 146b ... Rotating member left end bearing portion, 146c ... spring receiving projection, 146d ... stopper projection, 147 ... fastening bolt, 148 ... cam shaft main body shaft portion, 149 ... rotating member boss portion, 150 ... rotating member disk portion, 151 ... decompression mechanism , 152 ... Right ball bearing, 153 ... Left baud Bearing, 154 ... Female screw hole for fastening bolt, 155 ... Base circular part, 156 ... Notch for phase positioning, 157 ... Phase positioning protrusion, 158 ... Decompression rotor mounting hole, 159 ... Decompression rotor sliding recess 160 ... Decompression rotator drive pin tip passage groove, 161 ... Centrifugal weight mounting pin hole, 162 ... Decompression rotator, 162a ... Shaft part, 162b ... Arm part, 162c ... Decompression cam part, 162d ... Long hole , 162e ... decompression operating surface, 162f ... decompression notch, 163 ... centrifugal weight, 164 ... centrifugal weight support pin, 165 ... decompression rotor drive pin, 166 ... torsion coil spring, A ... center line of decompression cam portion 162c , B: center line of the arm portion 162b, R: rotation direction of the cam shaft 49.

Claims (4)

The camshaft main body is formed with a camshaft main body and a rotating member that is integrated with the camshaft main body and receives driving force from the crankshaft. The camshaft main body and the rotating member are interposed via a fastening member. In an assembled camshaft structure for an internal combustion engine that is detachably coupled,
An assembly type camshaft structure for an internal combustion engine, wherein the rotating member includes a coupled surface coupled to the camshaft body on one side and a rotating bearing portion on the other side. The assembled camshaft structure for an internal combustion engine according to claim 1, wherein a phase positioning portion for the rotating member is formed in a base circle portion of a cam crest of the camshaft body. The rotating member includes a boss portion, a pulley portion around which a timing belt is wound, and a connecting portion that connects the boss portion and the pulley portion.
A decompression mechanism having a centrifugal weight supported by the joint portion and a decompression cam that extends through the joint portion and extends to the cam peak portion of the camshaft main body is disposed at a position inside the pulley portion. 2. The assembled camshaft structure for an internal combustion engine according to claim 1 characterized by the above. The cylinder head side cover of the internal combustion engine includes a cam shaft support portion and a rocker arm shaft support portion,
The assembled camshaft structure for an internal combustion engine according to claim 2, wherein the bearing on the rotating member side of the assembled camshaft is supported by a camshaft support portion of the cylinder head side cover.

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