JP2011169181A - Timing belt driving engine - Google Patents

Abstract

In a timing belt drive engine in which an inter-axis dimension of a driving pulley and a driven pulley is set so that tension is applied to a timing belt of a timing transmission means provided between a crankshaft and a camshaft, the engagement by the timing belt Suppresses noise generation and enhances the durability of the timing belt.
A cylinder block 36 which is a separate body from a crankcase 35 is formed of a material having a smaller coefficient of thermal expansion than the crankcase 35.
[Selection] Figure 2

Description

  The present invention relates between a crankshaft rotatably supported by a crankcase and a camshaft rotatably supported by a cam holder fixed to a cylinder head having a cylinder block interposed between the crankcase and the crankshaft. In addition, a timing transmission means comprising: a driving pulley provided on the crankshaft; a driven pulley provided on the camshaft; and a timing belt formed endlessly by a synthetic resin and wound around the driving pulley and the driven pulley. And a timing belt drive engine in which the dimension between the axes of the drive pulley and the driven pulley is set so that tension is applied to the timing belt.

  The timing transmission means comprises an endless timing belt wound around a driving pulley provided on the crankshaft and a driven pulley provided on the camshaft, and the tensioner is configured by setting an inter-axis dimension between the driving pulley and the driven pulley. A timing belt drive engine in which tension is applied to a timing belt without applying tension by a pulley is known from Patent Document 1, Patent Document 2, and the like.

JP 2003-65009 A JP 2007-2740 A

  In such an engine, when the engine is further increased in size, the tension of the timing belt changes due to the difference in thermal expansion between the timing belt and the engine body, which may cause a meshing sound due to the tension change, There is a possibility of increasing the load on the belt.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a timing belt drive engine that suppresses the generation of meshing noise by the timing belt and reduces the load on the timing belt. .

  In order to achieve the above-mentioned object, the present invention can be rotated by a crankshaft rotatably supported by a crankcase and a cam holder fixed to a cylinder head having a cylinder block interposed between the crankcase and the crankshaft. A drive pulley provided on the crankshaft, a driven pulley provided on the camshaft, and an endless shape made of a synthetic resin between the supported camshaft and wound around the drive pulley and the driven pulley. In a timing belt drive engine provided with timing transmission means including a timing belt, and the inter-axis dimension of the drive pulley and the driven pulley is set so that tension is applied to the timing belt, the timing belt drive engine is separate from the crankcase. The cylinder block, which is a body, heats more than the crankcase. The first being formed by a material having small Zhang rate.

  According to the present invention, in addition to the configuration of the first feature, the crankcase is made of aluminum or an aluminum alloy, and a metal gasket is interposed between the cylinder block made of cast iron and the crankcase. This is the second feature.

  According to the third aspect of the present invention, in addition to the configuration of the first or second feature, the cam holder made of cast iron is fixed to the cylinder head so as to rotatably support the cam shaft. Features.

  According to the present invention, in addition to the configuration of the first feature, a flange projecting radially outward from the camshaft to attach the driven pulley to one end side of the camshaft, and a center of the driven pulley coaxially A pulley bearing boss having a circular cross section protruding from the flange so as to be fitted into the hole is provided coaxially, and a tapered guide having a smaller diameter as the distance from the flange is increased at the outer peripheral edge of the pulley bearing boss. A fourth feature is that a surface is formed.

  The fifth feature of the present invention is that, in addition to the configuration of the fourth feature, the camshaft is provided with an intake cam and an exhaust cam aligned in the axial direction.

  In addition to the configuration of the fifth feature, the present invention provides a first journal portion that sandwiches the intake cam and the exhaust cam between the flange and the intake cam and the exhaust cam between the first journal portion. A sixth feature is that a second journal portion sandwiching the shaft is provided on the camshaft so as to be supported by the cam holder.

  In addition to any of the configurations of the fourth to sixth features, the driven pulley includes a ring portion having a plurality of tooth portions around which the timing belt is wound, and the center hole. A disc portion that is integrally connected to the inner periphery of the ring portion and fastened to the flange, and the thickness of the disc portion along the axial direction of the camshaft is A pair of recesses for disposing at least a part and at least a part of a bolt for fastening the disk part to the flange are formed so that both side surfaces of the disk part cooperate with the inner periphery of the ring part. Thus, the seventh feature is that the length is set to be smaller than the axial length of the ring portion.

  The eighth feature of the present invention is that, in addition to the seventh feature, the driven pulley is formed symmetrically.

  In addition to any of the first to eighth features, the present invention provides a cam holder that rotatably supports the camshaft and is fixed to the cylinder head, the cylinder head, and the cylinder block, A ninth feature is that the crankcase is coupled by a plurality of fasteners disposed around the shaft.

  According to the present invention, in addition to any of the first to ninth features, an engine body including the crankcase, the cylinder block, and the cylinder head is supported so as to be swingable on a body frame of a saddle-ride type vehicle. This is a tenth feature.

  Furthermore, in addition to any of the first to tenth features of the present invention, the driven pulley is formed in a shape in which valleys between a plurality of teeth on the outer periphery of the driven pulley are open on both sides in the axial direction. This is an eleventh feature.

  In addition, the stud bolt 103 of embodiment corresponds to the fastener of this invention.

  According to the first feature of the present invention, the coefficient of thermal expansion of the cylinder block, which is a separate member from the crankcase, is made smaller than that of the crankcase, so It is possible to suppress the change during the hot time, thereby preventing the change in the tension of the timing belt, thereby suppressing the generation of the meshing noise caused by the timing belt and reducing the load on the timing belt. it can.

  According to the second feature of the present invention, the crankcase is made of aluminum or an aluminum alloy, and the cylinder block is made of cast iron, so that the crankcase and the cylinder block can be formed without using a special material. Since the metal gasket is interposed between the cylinder block and the crankcase with different hardness, the variation in surface pressure is suppressed compared to the paper gasket, and the sealing performance of the connecting surface of the crankcase and the cylinder block is improved. Can do.

  According to the third feature of the present invention, since the cam holder fixed to the cylinder head so as to rotatably support the camshaft is made of cast iron, thermal expansion is suppressed even on the cylinder head side, and engagement with the timing belt is performed. Generation of noise can be more effectively suppressed, and the load on the timing belt can be further reduced.

  According to the fourth aspect of the present invention, a flange projecting radially outward from the camshaft and a pulley bearing boss having a circular cross section projecting from the flange are provided coaxially on one end side of the camshaft, The pulley is attached to the flange while the pulley bearing boss is fitted into the center hole that the driven pulley has coaxially, but a tapered guide surface is formed on the outer peripheral edge of the pulley bearing boss. On the other hand, when the driven pulley with the timing belt wound is attached to one end of the camshaft at a fixed position at a fixed distance, the driven pulley is camshafted while being guided by the guide surface while slightly pulling the timing belt. Can be assembled to one end of the camshaft. In can be prevented from becoming a state of tension than necessary timing belt has been applied.

  According to the fifth aspect of the present invention, since the intake cam and the exhaust cam are provided side by side in the axial direction on the camshaft, although the camshaft is elongated in the axial direction, it is possible to avoid a decrease in assemblability. . That is, in what is disclosed in Patent Document 1, the driven pulley / cam combined body in which the driven pulley and the cam are integrated is supported by the cylinder head via the support shaft, resulting in a decrease in assemblability. Although there is a possibility, a support shaft for supporting the camshaft on the cylinder head side becomes unnecessary, so that the assembling property is not lowered.

  According to the sixth aspect of the present invention, the first and second journal portions provided on the camshaft with the intake cam and the exhaust cam interposed therebetween are provided on the camshaft, and these journal portions are supported by the cam holder. Therefore, the portion of the camshaft where the intake cam and exhaust cam are provided can be stably supported from both sides, and the first journal portion is disposed between the intake cam and exhaust cam and the driven pulley. In this way, it is possible to stably support the portion of the camshaft where the driven pulley is attached.

  According to a seventh aspect of the present invention, the driven pulley includes a ring portion having a plurality of tooth portions on the outer periphery, and a disc portion that is fastened to the flange by integrally connecting the outer periphery to the inner periphery of the ring portion. And a pair of recesses in which at least a part of the flange and at least a part of the bolt for fastening the disk part to the flange are formed on both sides of the driven pulley. The enlargement in the axial direction due to the fastening to the camshaft can be avoided.

  According to the eighth feature of the present invention, since the driven pulley is formed symmetrically, the degree of freedom in the direction in which the driven pulley is assembled to the camshaft is increased, and the assemblability can be improved.

  According to the ninth aspect of the present invention, the cam holder, the cylinder block, and the cylinder head are fastened together with the crankcase by a plurality of fasteners around the camshaft, so that the space around the cylinder bore provided in the cylinder block is efficient. The crankcase, the cylinder block, and the cylinder head can be combined in a compact manner with a plurality of fasteners arranged, and the camshaft support rigidity of the cam holder can be increased.

  According to the tenth feature of the present invention, since the engine body is swingably supported on the body frame of the saddle-ride type vehicle, the transmission member for transmitting power from the crankshaft to the camshaft is not a metal chain. By using a belt, it is possible to reduce noise due to swing vibration.

  Further, according to the eleventh feature of the present invention, since the valleys between the plurality of teeth on the outer periphery of the driven pulley are open on both sides in the axial direction, the timing belt to which tension is applied is assembled to the driven pulley. Becomes easy.

It is a left view of a scooter type motorcycle. FIG. 2 is an enlarged sectional view taken along line 2-2 of FIG. FIG. 3 is an enlarged view of a main part of FIG. 2. FIG. 4 is an enlarged view taken along arrow 4 in FIG. 3 in a state in which the head cover is omitted. It is the front view which looked at the cam holder from the same direction as FIG. FIG. 6 is a cross-sectional view showing the engine body cut along line 6-6 in FIG. 3. FIG. 7 is an enlarged view of a portion indicated by arrow 7 in FIG. 2. It is the figure which looked at the drive pulley from the 8-8 line arrow direction of FIG. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 6. FIG. 10 is a cross-sectional view taken along line 10-10 of FIG. 9 for explaining the operation of the belt guide means. FIG. 11 is a cross-sectional view taken along line 11-11 in FIG. 9. FIG. 10 is a cross-sectional view illustrating Example 2 and corresponding to FIG. 9.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  A first embodiment of the present invention will be described with reference to FIGS. 1 to 11. First, in FIG. 1, a vehicle body frame 15 of a scooter type motorcycle includes a front fork 16 that pivotally supports a front wheel WF, and the front fork 16. A head pipe 18 that supports the steering handle 17 connected thereto so as to be steerable, a down tube 19 that extends rearward and downward from the head pipe 18, and a pair of left and right that has a front end fixed to both sides of the lower tube 19 and extends rearward. Lower frame pipes 20 and a pair of left and right rear frame pipes 21 integrally connected to the rear ends of the lower frame pipes 20. The rear frame pipe 21 includes an inclined portion 21a extending rearward from the rear end of the lower frame pipe 20 and a horizontal portion 21b extending substantially rearward from the rear end of the inclined portion 21a. The rear parts are connected to each other.

  A bracket 22 is provided at an integrally connected portion of the lower frame pipes 20 and the rear frame pipes 21 in the vehicle body frame 15. The front portion of the power unit P is supported on the bracket 22 via a link mechanism 23 so as to be able to swing up and down. The A rear cushion unit 24 is provided between the rear part of the left rear frame pipe 21 and the rear part of the power unit P among the rear frame pipes 21.

  A fuel tank 25 supported by the lower frame pipes 20 is disposed between the lower frame pipes 20 in front of the power unit P, and a storage box 26 is disposed above the power unit P. The storage box 26 is supported by the rear frame pipes 21.

  The vehicle body frame 15 is covered with a vehicle body cover 27 made of synthetic resin. The vehicle body cover 27 is provided under the leg shield 28 for covering the front of the driver's feet and the leg shield 28 for placing the rider's feet. A tandem type that includes a step floor 29 that continuously covers the fuel tank 25 and a side cover 30 that continues to the step floor 29 and covers the rear portion of the vehicle body from both sides. The storage box 26 can be opened and closed on the side cover 30 from above. Is provided.

  In FIG. 2, the power unit P includes an OHC type engine E that is a four-cycle forced air-cooled single cylinder disposed in front of the rear wheel WR, and a transmission device T provided between the engine E and the rear wheel WR. Consists of.

  The engine body 34 of the engine E is slidable with a crankcase 35 that rotatably supports a crankshaft 45 having a rotation axis parallel to the rotation axis of the rear wheel WR, and a piston 41 coupled to the crankshaft 45. A cylinder block 36 having a cylinder bore 40 fitted to the cylinder case 36 and coupled to the crankcase 35, a cylinder head 37 coupled to the cylinder block 36 on the opposite side of the crankcase 35, and a cylinder on the opposite side of the cylinder block 36 The head cover 38 is coupled to the head 37. When mounted on a motorcycle, the axis of the cylinder bore 40, that is, the cylinder axis C is inclined slightly upward until it becomes substantially horizontal.

  A combustion chamber 42 that faces the top of the piston 41 is formed between the cylinder block 36 and the cylinder head 37, and the piston 41 is connected to the crankshaft 45 via a connecting rod 43 and a crankpin 44.

  The crankcase 35 includes a pair of case halves 35a and 35b that include the axis of the cylinder bore 40 and are coupled by a plane orthogonal to the axis of the crankshaft 45. The crankshaft 45 is formed by both case halves 35a and 35b. It is supported rotatably. Thus, a ball bearing 47 is interposed between the crankshaft 45 and the one case half 35a, and a ball bearing 48 is interposed between the crankshaft 45 and the other case half 35b.

  An intake port (not shown) that can communicate with the combustion chamber 42 is provided on the upper side surface of the cylinder head 37, and an exhaust port (not shown) that can communicate with the combustion chamber 42 is provided on the lower side surface of the cylinder head 37. It is done.

  As shown in FIG. 1, the upper side surface of the cylinder head 37 includes an air cleaner 49 disposed above the power unit P on the left side of the rear wheel WR, and a vaporizer 50 having an upstream end connected to the air cleaner 49. An intake device 51 is connected to be connected to the intake port, and an upstream end of an exhaust pipe 52 communicating with the exhaust port is connected to a lower side surface of the cylinder head 37. A downstream end of the exhaust pipe 52 is connected to a rear wheel WR. Is connected to an exhaust muffler 53 disposed on the right side of the. A spark plug 54 (see FIG. 2) facing the combustion chamber 42 is attached to the right side surface of the cylinder head 37 with the motorcycle facing forward in the direction of travel.

  One end of the crankshaft 45 is linked and connected to the axle 55 of the rear wheel WR via the transmission device T, and a generator 56 and a cooling fan 57 are connected to the other end of the crankshaft 45.

  The generator 56 includes an outer rotor 58 fixed to the other end portion of the crankshaft 45 outside the crankcase 35, and a stator surrounded by the outer rotor 58 and fixed to the case half 35 b of the crankcase 35. 59. The cooling fan 57 is fixed to the crankshaft 45 outside the generator 56.

  Of the engine body 34, a part of the crankcase 35, the cylinder block 36 and the cylinder head 37 are covered with a shroud 60, and a cooling air passage 61 formed between the engine body 34 and the shroud 60 is connected to the cooling fan 57. Discharged forced air cooling air flows. In addition, a plurality of cooling fins 36a, 37a,... Protrude from the outer surfaces of the cylinder block 36 and the cylinder head 37 in order to enable efficient cooling by the cooling air flowing through the cooling air passage 61.

  A fan cover 62 that covers the cooling fan 57 is coupled to the shroud 60, and a suction port 63 for sucking air from the outside is formed in the fan cover 62 toward the cooling fan 57 side. A suction cylinder 64 is provided so as to correspond to the cooling fan 57 outside, and a louver 65 is provided at the suction port 64.

  The crankcase 35 is connected to a transmission case 66 that extends to the left side of the rear wheel WR while facing the front in the running direction of the motorcycle. The transmission case 66 is formed by forming a transmission chamber 70 between a case main body 67 integrally connected to the case half 35 a of the crankcase 35 and extending rearward, and the case main body 67. The left cover 68 is fastened to the main body 67 from the left side, and the right cover 69 is formed on the right rear portion of the case main body 67 by forming a gear chamber 71 between the case main body 67 and the rear wheel WR. The axle 55 is rotatably supported by the rear portion of the case main body 67 and the right cover 69.

  The transmission device T includes a V-belt type continuously variable transmission 72 accommodated in the transmission chamber 70, and a reduction gear mechanism 73 provided between the continuously variable transmission 72 and the axle 55 and accommodated in the gear chamber 71. It consists of.

  The continuously variable transmission 72 has a drive pulley 74 connected to one end portion of the crankshaft 45 outside the crankcase 35, an axis parallel to the crankshaft 45, and the rear portion of the case main body 67 and the right cover 69. It is a well-known one that includes a driven pulley 77 that is mounted on a driven shaft 75 that is rotatably supported via a centrifugal clutch 76, and a drive pulley 74 and an endless V-belt 78 that is wound around the driven pulley 77. .

  Thus, the drive pulley 74 includes a ramp plate 79 fixed to the crankshaft 45 and a plurality of weight rollers 80 housed in a floating state between the drive pulleys 74 in accordance with an increase in the rotational speed of the crankshaft 45. It operates to increase the contact radius to the V-belt 78 as it moves radially outward at 45.

  On the other hand, the driven pulley 77 operates so that the contact radius of the V-belt 78 becomes smaller as the contact radius of the V-belt 78 to the drive pulley 74 becomes larger, whereby the driven pulley 77 is connected between the crankshaft 45 and the driven shaft 75. A continuously variable transmission according to the rotation of the crankshaft 45 is performed.

  The reduction gear mechanism 73 is provided between the driven shaft 75 and the axle 55 and is housed in the gear chamber 71. After the rotational power of the driven shaft 75 in the continuously variable transmission 72 is decelerated by the reduction gear mechanism 73, It is transmitted to the axle 55 of the wheel WR.

  A kick shaft 81 is rotatably supported on the left cover 68 of the transmission case 66, and a kick pedal 82 (see FIG. 1) is provided at the outer end of the kick shaft 81. A kick starter 83 is provided between the kick shaft 81 and the crankshaft 45 on the inner surface side of the left cover 68 so that the power of the kick shaft 81 according to the depression operation of the kick pedal 82 can be transmitted to the crankshaft 45. Provided.

  3 and 4 together, the cylinder head 37 is provided with an intake valve 86 and an exhaust valve 87 for opening and closing the intake port and the exhaust port, respectively, so that the valve spring can be opened and closed. The intake valve 86 and the exhaust valve 87 spring-biased in the valve closing direction by 88 and 89 are driven to open and close by the valve operating device 90.

  The valve operating device 90 is swung in accordance with a camshaft 92 rotatably supported by a cam holder 91 fixed to the cylinder head 37 and an intake cam 93 provided on the camshaft 92. The intake side rocker arm 95 that opens and closes the intake valve 86 and the exhaust cam 94 provided on the camshaft 92 at a position aligned with the intake cam 93 in the axial direction of the camshaft 92 swings. And an exhaust-side rocker arm 96 that opens and closes the exhaust valve 87, and a timing transmission means 97 that transmits the rotational power of the crankshaft 45 to the camshaft 92 while decelerating at a reduction ratio of 1/2.

  A valve operating chamber 98 is formed between the cylinder head 37 and the head cover 38, and the cam holder 91, which is a separate body from the cylinder head 37, is disposed in the valve operating chamber 98 and fixed to the cylinder head 37. .

  In FIG. 5, the cam holder 91 has first and second support walls 91a and 91b for rotatably supporting the camshaft 92 at a position where the intake cam 93 and the exhaust cam 94 are sandwiched therebetween. And formed into a rectangular frame shape.

  A first support hole 99 is provided in the first support wall portion 91 a of the cam holder 91, and the outer periphery of the first journal portion 92 provided on one end side of the cam shaft 92 and penetrating the first support hole 99 and the first support hole 99 are provided. A ball bearing 101 is interposed between the inner circumferences of the support holes 99. The second support wall portion 91b is provided with a second support hole 100 coaxially with the first support hole 99, and the second journal portion sandwiching the intake cam 93 and the exhaust cam 94 with the first journal portion 92a. 92b is provided at the other end of the camshaft 92 so as to be inserted into the second support hole 100, and a ball bearing 102 is interposed between the outer periphery of the second journal portion 92b and the inner periphery of the second support hole 100. Be dressed.

  A pair of rocker shafts (not shown) are provided between the first and second support wall portions 91a and 91b so as to be positioned on both sides of the camshaft 92, and one of the rocker shafts is connected to the intake side. The rocker arm 95 is swingably supported, and the exhaust rocker arm 96 is swingably supported by the other rocker shaft.

  The cylinder head 37 and the cylinder block 36 are coupled to the crankcase 35 by joint fastening with a plurality of fasteners arranged around the camshaft 92. In this embodiment, the cylinder block 36 .., And four stud bolts 103, 103... That are planted in the crankcase 35 so as to be arranged around the cylinder bore 40 in the cylinder bore 40, and the stud bolts 103, 103. The cam holder 91, the cylinder head 37, and the cylinder block 36 are coupled to the crankcase 35 by joint fastening with nuts 104, 104.

  Thus, a pair of insertion holes 105, 105... Are provided in the first and second support walls 91a, 91b of the cam holder 91 so as to sandwich the cam shaft 92 from both sides, and the nuts 104, 104. The cam holder 91 is brought into contact with and engaged with each of the insertion holes 105, 105.

  The first and second support wall portions 91a and 91b of the cam holder 91 are attached so as to protrude sideways from a portion where one of the insertion holes 105 is provided in each of the support wall portions 91a and 91b. Arm portions 91c and 91d are provided, and one mounting arm portion 91c is disposed at the upper left side in the valve operating chamber 98 when the engine body 34 is mounted on the vehicle body frame 15, whereas the other mounting arm portion 91d. Is arranged at the lower right side in the valve operating chamber 98, and screw holes 106, 106 are provided at the tip ends of the mounting arm portions 91c, 91d.

  Referring also to FIG. 6, the head cover 38 is coupled to the cam holder 91 such that a gasket 107 is sandwiched between the head cover 38 and the cylinder head 37. That is, a pair of stepped bolts 108 having stepped portions 108 a that abut and engage with the outer surface of the head cover 38 are inserted into the head cover 38, and these stepped bolts 108 are attached to the mounting arm portions 91 c and 91 d of the cam holder 91. Are screwed into the screw holes 106.

  The timing transmission means 97 is disposed between the ball bearing 47 interposed between the case half 35a of the crankcase 35 and the crankshaft 45, and a drive pulley 74 in the continuously variable transmission 72. A driving pulley 110 fixed to one end portion of the crankshaft 45, a driven pulley 111 fixed to one end portion of the camshaft 92, and the driving pulley 110 and the driven pulley formed endless by a synthetic resin. 111, and a timing belt 112 wound around the shaft 111. The inter-axis dimension of the driving pulley 110 and the driven pulley 111, that is, the axes of the crankshaft 45 and the camshaft 92, so that tension is applied to the timing belt 112. The inter dimension is set.

  Moreover, the cylinder block 36, which is a separate body from the crankcase 35, is formed of a material having a smaller coefficient of thermal expansion than the crankcase 35. Preferably, the crankcase 35 is made of aluminum or an aluminum alloy. The metal gasket 113 is interposed between the cylinder block 36 made of cast iron and the crankcase 35. The cylinder head 37 is made of aluminum or an aluminum alloy, whereas the cam holder 91 fixed to the cylinder head 37 is made of cast iron.

  With particular attention to FIG. 3, a small-diameter shaft portion 92c having a smaller diameter than the first journal portion 92a is coaxially and integrally provided at one end portion of the camshaft 92, and the small-diameter shaft portion 92c includes A flange member 115 having a flange 114 is press-fitted until the tip of the small diameter shaft portion 92c protrudes from the flange 114 as a pulley bearing boss 116 having a circular cross section until it contacts the first journal portion 92a. As a result, a flange 114 sandwiching the first journal portion 91a between the intake cam 93 and the exhaust cam 94 is provided on one end side of the camshaft 92 so as to be radially outward from the camshaft 92 so as to attach the driven pulley 111. A pulley bearing boss 116 having a circular cross section that protrudes from the flange 114 so as to be fitted in a central hole 117 that the driven pulley 111 has coaxially is provided coaxially. On the outer peripheral edge of the pulley bearing boss 116, a tapered guide surface 118 having a smaller diameter as the distance from the flange 114 increases.

  The driven pulley 111 has a ring portion 111a having a plurality of teeth 119, 119... Around which the timing belt 112 is wound, and a center hole 117, and an outer periphery integrally with the inner periphery of the ring portion 111a. The disc portion 111b is provided integrally with the flange portion 114 and is fastened to the flange 114, and the thickness d of the disc portion 111b along the axial direction of the camshaft 92 determines that the pair of recesses 120 and 120 is provided. It is set to be smaller than the axial length of the ring portion 111a so as to cooperate with both side surfaces of the disc portion 111b and the inner periphery of the ring portion 111a.

  Thus, at least a part of the flange 114 and at least a part of the bolts 121 and 121 for fastening the disc part 111b to the flange 114 are disposed in the recesses 120 and 120, In this embodiment, a part of the flange 114 is disposed in one recess 120, and the enlarged diameter heads 121 a of the bolts 121 are disposed in the other recess 120.

  Moreover, the driven pulley 111 has a shape in which valleys 122, 122... Between the plurality of tooth portions 119, 119. In addition, marks for timing adjustment are also provided on both surfaces of the driven pulley 111.

  Referring to FIG. 2, the crankcase 35, the cylinder block 36, and the cylinder head 37 of the engine body 34 are provided with a belt traveling passage 123 for traveling the timing belt 112 of the timing transmission means 34. The drive pulley 110 is fixed to one end of the crankshaft 45 by press-fitting, for example, at a position corresponding to the belt travel passage 123. The

  Also, oil is returned from the cylinder head 37 to the crankcase 35 below the cylinder head 37 and the cylinder block 36 in the engine main body 34 that is disposed with the cylinder axis C inclined substantially horizontally when mounted on the motorcycle. A dedicated oil return passage 127 is provided, and the belt travel passage 123 is provided in the cylinder head 37, the cylinder block 36, and the crankcase 35 of the engine body 34 along with the oil return passage 127.

  By the way, the ball bearing 47 is interposed between the left case half 35a and the crankshaft 45 of the pair of case halves 35a and 35b constituting the crankcase 35, and the transmission chamber 70 and the belt running are provided. An annular seal member 124 that seals between the passages 123 is interposed, and the drive pulley 110 is fixed to the camshaft 45 between the ball bearing 47 and the seal member 124, and the ball is more than the drive pulley 110. On the bearing 47 side, the crankshaft 45 is formed with an annular step 45a facing the drive pulley 110 as shown in FIG.

  The drive pulley 110 has a plurality of teeth 125, 125... That mesh with the inner periphery of the timing belt 112 on the outer periphery and surrounds the crankshaft 45, and a radius from one end of the cylinder 110a. A flange portion 110b that protrudes outward in the direction is integrally formed, and the flange portion 110b is disposed on the opposite side of the annular step portion 45a of the crankshaft 45 so as to be press-fitted and fixed to the crankshaft 45. .

  Thus, the timing belt 112 is wound around the outer periphery of the cylindrical portion 110a so that the movement to the opposite side of the annular step portion 45a is restricted by the flange portion 110b. Movement to the side opposite to the flange 110b is regulated by the annular step 45a of the crankshaft 45.

  In this way, the movement of the timing belt 112 in the axial direction of the drive pulley 110 is restricted by the flange portion 110b integrally formed with the drive pulley 110 and the annular step portion 45a formed on the crankshaft 45, whereby the drive pulley It is possible to prevent the timing belt 112 from dropping from 110 with a simple configuration that does not require dedicated parts.

  Referring also to FIG. 8, at the end of the drive pulley 110 opposite to the flange 110b of the cylindrical portion 110a, the cylindrical portion 110a has a plurality of teeth 125, 125. A plurality of oil drain grooves 127, 127, which respectively communicate with the bottoms of the formed valley portions 126, 126, are formed so as to approach the axis of the crankshaft 45 as they approach the annular step 45 a of the crankshaft 45. Provided.

  The oil accumulated in the troughs 126, 126 ... on the outer periphery of the drive pulley 110 can be discharged to the annular step 45a side of the crankshaft 45 by such oil drain grooves 127, 127 ..., and the timing belt to the drive pulley 110 can be discharged. It is possible to prevent an increase in resistance due to the oil biting into the winding portion of 112, and to suppress the generation of noise due to the timing belt 112 hitting the oil.

  Referring also to FIG. 9, the cylinder block 36 of the engine body 34 has a belt guide means for contacting the outer periphery of the timing belt 112 between the driving pulley 110 and the driven pulley 111 to guide the movement of the timing belt 112. 130A is disposed so that the contact portion of the belt guide means 130A with the timing belt 112 follows the running position of the timing belt 112 in a tension state.

  Thus, the crankshaft 45 and the driving pulley 110 rotate in the direction indicated by the arrow 129 in FIG. 6 and are pulled by the driven pulley 111 toward the driving pulley 110 to be in a tension state. The belt guide means 130 </ b> A is disposed in the lower part of the cylinder block 36 at an intermediate portion between the driven pulley 111 and the driving pulley 110 so as to contact the outer circumference of the cylinder block 36.

  With further reference to FIGS. 10 and 11, the belt guide means 130A is driven by a guide roller 131 disposed at the bottom of the belt travel path 123 so as to rotate in contact with the timing belt 112. A rotation support shaft 132 that can be rotated about an axis parallel to the pulley 110 and the driven pulley 111 and is supported by the cylinder block 36 of the engine body 34 is provided. The guide roller 131 extends from the axis of the rotation support shaft 132. The rotation support shaft 132 is rotatably supported so as to have a center of rotation at an eccentric position.

  The cylinder block 36 is provided with third and fourth support holes 134 and 135 for supporting the rotation support shaft 132 coaxially with the belt travel path 123 interposed therebetween. Is formed so that a cylindrical portion 136 coaxial with the third support hole 134 protrudes outward, and an annular step portion 137 is formed between the inner periphery of the cylindrical portion 136. A third support hole 134 is provided in the cylinder block 36.

  The rotation support shaft 132 is rotatably and liquid-tightly inserted into the third support hole 134 so that its outer end protrudes from the third support hole 134 and is disposed in the cylindrical portion 136. An inner end portion of the rotation support shaft 132 is fitted into the fourth support hole 135 so as to be rotatable.

  In the step portion 137 in the cylindrical portion 136, a plurality of sets of, for example, four sets of locking recesses 138, 138... Arranged in pairs on the diameter line of the third support hole 134 are formed around the third support hole 134. Engagement pins 139 provided at equal intervals and extending along one diameter line at the outer end portion of the rotation support shaft 132 are selected at both ends of the locking recesses 138, 138. It is inserted so as to engage with the locking recesses 138 and 138 of the set. Thus, the rotation position of the rotation support shaft 132 is held in a state in which the engagement pin 139 is engaged with the pair of locking recesses 138, 138. It is possible to hold at a selected rotation position among a plurality of rotation positions set to.

  An eccentric piece 133 having an outer periphery that is eccentric from the outer periphery of the rotation support shaft 132 is mounted on the rotation support shaft 132 in the belt travel path 123 so as not to be relatively rotatable. The piece 133 is supported rotatably. That is, a flat surface 140 is formed on a part of the outer periphery of the rotation support shaft 132 so that a part of the rotation support shaft 132 is formed in a non-circular cross section. The portion having a non-circular shape penetrates the eccentric piece 133, so that the eccentric piece 133 is attached to the rotation support shaft 132 so as not to be relatively rotatable.

  Thus, as shown in FIGS. 10A and 10B, by changing the position of the engagement pin 139, the contact between the center of the rotation support shaft 132 and the timing belt 112 on the outer periphery of the eccentric piece 133 is achieved. The distances L1 and L2 to the contact portion can be changed.

  By the way, two ridges for inserting a pair of bolts 142 and 143 for connecting the cylinder head 37 to the crankcase 35 through the cylinder block 36 are mounted on the left side surface of the cylinder block 36 when mounted on the motorcycle. The portions 144 and 145 are integrally provided extending in parallel with the operation direction of the piston 41, and one of the raised portions 144 and 145 is provided at the outer end of the rotation support shaft 132 of the belt guide means 130A. In addition, a notch portion 146 is provided to allow the cylindrical portion 136 protruding from the cylinder block 36 to face outward so that the outer end portion of the rotation support shaft 132 is disposed.

  Thus, the bolt 142 is disposed in the notch 146 in the vicinity of and opposed to the outer end of the rotation support shaft 132 and is inserted into the cylinder block 36 so as to be detachable. The detachment of the shaft 132 from the cylinder block 36 is prevented by the bolt 142.

  Thus, when the bolt 142 is close to and opposed to the outer end of the rotation support shaft 132, the rotation support shaft 132 is prevented from being detached from the cylinder block 36, and the locking recesses 138, 138. The state where both ends of the engagement pin 139 are engaged with the selected set of the locking recesses 138, 138 is held.

  Next, the operation of the first embodiment will be described. In the timing transmission means 97, the dimension between the axes of the driving pulley 110 and the driven pulley 111 is set so that tension is applied to the timing belt 112. 35 is formed of a material having a smaller coefficient of thermal expansion than that of the crankcase 35, so that the dimension between the shafts of the driving pulley 110 and the driven pulley 111 in the timing transmission means 97 is hot. It is possible to suppress the change and thereby prevent the tension of the timing belt 112 from changing, thereby suppressing the meshing noise generated by the timing belt 112 and reducing the load on the timing belt 112. .

  Further, since the crankcase 35 is made of aluminum or an aluminum alloy and the cylinder block 36 is made of cast iron, the crankcase 35 and the cylinder block 36 are formed without using a special material to reduce the manufacturing cost, and the hardness is mutually reduced. Since the metal gasket 113 is interposed between the different cylinder blocks 36 and the crankcase 35, variations in surface pressure can be suppressed as compared with the paper gasket, and the sealing performance of the coupling surface of the crankcase 35 and the cylinder block 36 can be improved.

  In addition, since the cam holder 91 made of cast iron is fixed to the cylinder head 37 so as to rotatably support the camshaft 92, thermal expansion is suppressed even on the cylinder head 37 side, and a meshing noise is generated by the timing belt 112. Can be more effectively suppressed, and the load on the timing belt 112 can be further reduced. Moreover, in this embodiment, since the cylinder head 37 is made of aluminum or an aluminum alloy, it is possible to contribute to the weight reduction of the entire engine body 34.

  From one end of the camshaft 92, a flange 114 projecting radially outward from the camshaft 92 to attach the driven pulley 111, and a flange 114 so as to fit into a central hole 117 that the driven pulley 111 has coaxially. A protruding pulley bearing boss 116 having a circular cross section is provided coaxially, and a tapered guide surface 118 having a smaller diameter as the distance from the flange 114 is formed on the outer peripheral edge of the pulley bearing boss 116. 45, when the driven pulley 111 in which the timing belt 112 is wound is attached to one end portion of the camshaft 92 at a fixed position with respect to 45, the guide surface 118 guides the timing belt 112 while slightly pulling the timing belt 112. The driven pulley 111 is attached to one end of the camshaft 92 You see it can attach, as well as improving the assembling property can be prevented from becoming a state of excessive tension to the timing belt 112 is applied in a state assembled with the driven pulley 111 to the cam shaft 92.

  Further, since the driven pulley 111 is formed in a shape in which valleys 122 between the plurality of teeth 119 on the outer periphery of the driven pulley 111 are opened on both sides in the axial direction, the driven belt 111 is driven by a tension. Assembly to the pulley 111 becomes easier.

  In addition, since the camshaft 92 is provided with the intake cam 93 and the exhaust cam 94 arranged in the axial direction, the camshaft 92 becomes longer in the axial direction, but it is possible to avoid a decrease in assemblability. That is, in what is disclosed in Patent Document 1, the driven pulley / cam combined body in which the driven pulley and the cam are integrated is supported by the cylinder head via the support shaft, resulting in a decrease in assemblability. Although there is a possibility, a support shaft for supporting the camshaft 92 on the cylinder head 37 side becomes unnecessary, so that the assembling property is not lowered.

  The camshaft 92 includes a first journal portion 92a that sandwiches the intake cam 93 and the exhaust cam 94 between the flange 114 and a second journal that sandwiches the intake cam 93 and the exhaust cam 94 between the first journal portion 92a. Portion 92b and the first and second journal portions 92a, 92b are supported by the cam holder 91, so that the portion of the camshaft 92 where the intake cam 93 and the exhaust cam 94 are provided can be stably provided from both sides. A portion of the camshaft 92 to which the driven pulley 111 is attached can be supported and the first journal portion 92a is disposed between the intake cam 93 and the exhaust cam 94 and the driven pulley 111. It can be supported stably.

  By the way, the driven pulley 111 has a ring portion 111a having a plurality of tooth portions 119 around which the timing belt 112 is wound, a center hole 117, and an outer periphery integrally connected to the inner periphery of the ring portion 111a. And a disc portion 111b fastened to 114, and the thickness d of the disc portion 111b along the axial direction of the camshaft 92 is set to be smaller than the axial length of the ring portion 111a. A pair of recesses 120 and 120 in which at least a part of the flange 114 and at least a part of the bolt 121 for fastening the disc part 111b to the flange 114 are disposed on both side surfaces of the part 111b and the inner periphery of the ring part 111a. Since they are formed in cooperation, an increase in the size in the axial direction due to the fastening of the driven pulley 111 to the camshaft 92 can be avoided. .

  In addition, since the driven pulley 111 is formed symmetrically, the degree of freedom in the direction in which the driven pulley 111 is assembled to the camshaft 92 is increased, and the assemblability can be improved.

  Further, the cam holder 91, the cylinder head 37, and the cylinder block 36, which are rotatably supported by the cam shaft 92 and fixed to the cylinder head 37, are cranked together by a plurality of stud bolts 103 arranged around the cam shaft 92. Since it is coupled to the case 35, the crankcase 35, the cylinder block 36, and the cylinder head 37 can be coupled in a compact manner by a plurality of stud bolts 103 that are efficiently disposed around the cylinder bore 40 provided in the cylinder block 36. In addition, the support rigidity of the camshaft 92 by the cam holder 91 can be increased.

  Since the engine body 34 including the crankcase 35, the cylinder block 36, and the cylinder head 37 is swingably supported on the body frame 15 of the motorcycle, a transmission member for transmitting power from the crankshaft 45 to the camshaft 92 is provided. By using the timing belt 112 instead of the metal chain, it is possible to reduce noise due to swing vibration.

  Further, belt guide means 130A that contacts the outer periphery of the timing belt 112 between the driving pulley 110 and the driven pulley 111 in the timing transmission means 97 and guides the movement of the timing belt 112 includes the timing belt 112 of the belt guide means 130A. Is arranged on the engine body 34 so as to be along the running position of the timing belt 112 in a tensioned state, so that the timing belt 112 is guided by the belt guide means 130A. Without bending, it is possible to reduce the load on the timing belt 112, suppress the generation of noise, and improve the durability of the timing belt 112.

  Further, since the belt guide unit 130A includes the guide roller 131 that rotates in contact with the timing belt 112, the friction of the contact portion between the belt guide unit 130A and the timing belt 112 can be reduced.

  The belt guide means 130A includes a rotation support shaft 132 that is supported by the engine body 34 so as to be rotatable around an axis parallel to the drive pulley 110 and the driven pulley 111, and the guide roller 131 supports the rotation. Since the rotation support shaft 132 is rotatably supported so as to have a center of rotation at a position eccentric from the axis of the shaft 132, the guide to the timing belt 112 is adjusted by adjusting the rotation position of the rotation support shaft 132. The contact position of the roller 131 can be adjusted, the belt guide means 130A can be simply configured without increasing the component accuracy, and the belt guide means 130A can be easily assembled.

  By the way, the engine main body 34 tilts the cylinder axis C substantially horizontally when mounted on a motorcycle. A dedicated engine for returning oil from the cylinder head 37 to the crankcase 35 is provided below the engine main body 34. Since the oil return passage 127 is provided and the guide roller 131 is disposed at the bottom of the belt running passage 123 provided in the engine body 34 along with the oil return passage 127 so as to run the timing belt 112, the guide roller 131. Can be prevented from being hindered by the oil returning from the cylinder head 37 to the crankcase 35, and the oil splashing by the guide roller 131 to the timing belt 112 can be prevented, and the driving pulley 110 and the driven pulley 111 can be prevented. Winding of the timing belt 112 The increase in resistance due to the oil biting can be prevented only part.

  In addition, a rotation support shaft 132 is formed on a cylinder block 36 that constitutes a part of the engine body 34 and is sandwiched between the crankcase 35 and the cylinder head 37. A bolt 142 which is inserted so as to be able to be inserted / removed in the axial direction while being able to hold the selected rotation position and which couples the cylinder head 37 to the crankcase 35 via the cylinder block 36 is provided with the rotation support shaft 132. The rotation support shaft 132 can be prevented from being detached from the cylinder block 36 by the bolt 142 connecting the cylinder head 37, the cylinder block 36 and the crankcase 35. The number of parts can be reduced.

  Further, an eccentric piece 133 that is disposed in the cylinder block 36 and has an outer periphery that is eccentric from the outer periphery of the rotation support shaft 132 is mounted on the rotation support shaft 132 so as not to be relatively rotatable. Since the rotary support shaft 132 is rotatably supported, the outer diameter of the rotation support shaft 132 can be set to be relatively small. The rotation support shaft 132 is provided in the cylinder block 36 so as to be detachably inserted. The diameters of the third and fourth support holes 134 and 135 can be reduced to suppress the strength reduction of the cylinder block 36 and the amount of eccentricity of the guide roller 131 can be increased.

  FIG. 12 shows a second embodiment of the present invention, and the portions corresponding to the first embodiment in FIGS. 1 to 11 are only given the same reference numerals and are not described in detail.

  In the cylinder block 36 of the engine body 34, belt guide means 130B that contacts the outer periphery of the timing belt 112 between the driving pulley 110 and the driven pulley 111 to guide the movement of the timing belt 112 is provided at the timing of the belt guide means 130B. The contact portion with the belt 112 is arranged so as to follow the running position of the timing belt 112 in a tension state.

  The belt guide means 130 </ b> B includes a guide roller 151 that rotates in contact with the timing belt 112, a rotation support shaft 132 supported by the cylinder block 36 of the engine body 34, and the rotation support in the belt travel path 123. The guide roller 151 is rotatably supported by the eccentric piece 133 and is disposed at the bottom of the belt travel path 123.

  In addition, the guide roller 151 is wider than the width of the timing belt 112, and flanges 151 a and 151 a that guide both side surfaces of the timing belt 112 are integrally provided at both ends of the guide roller 151.

  According to the second embodiment, the same effect as that of the first embodiment is obtained, and both side surfaces of the timing belt 112 are guided by the guide rollers 151 wider than the width of the timing belt 112. 45 and the timing belt 112 can be prevented from swinging in the axial direction of the camshaft 92, thereby contributing to an increase in the life of the timing belt 112.

  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 embodiment, the metal gasket 113 is interposed between the crankcase 35 made of aluminum or aluminum alloy and the cylinder block 36 made of cast iron. An O-ring housed in a recess provided in at least one of the crankcase 35 and the cylinder block 36 may be interposed.

  In the above embodiment, the engine E in which the cam holder 91 that is a separate body from the cylinder head 37 is fixed to the cylinder head 37 has been described. However, the present invention also applies to an engine in which the cam holder is formed integrally with the cylinder head. Applicable.

15 ... Body frame 34 ... Engine body 35 ... Crank case 36 ... Cylinder block 37 ... Cylinder head 45 ... Crank shaft 91 ... Cam holder 92 ... Cam shaft 92a ... First journal portion 92b ... second journal portion 93 ... intake cam 94 ... exhaust cam 97 ... timing transmission means 103 ... stud bolt 110 as a fastener ... drive pulley 111 ... driven pulley 111a ... ring part 111b ... disc part 112 ... timing belt 113 ... metal gasket 114 ... flange 116 ... pulley bearing boss 117 ... center hole 118 .... Guide surface 119 ... tooth part 120 ... concave part 121 ... bolt 122 ... valley part W ... engine

Claims (11)

  A cam holder (fixed to a cylinder head (37) having a cylinder block (36) interposed between the crankshaft (45) rotatably supported by the crankcase (35) and the crankcase (35). 91) a drive pulley (110) provided on the crankshaft (45) and a driven pulley (111) provided on the camshaft (92) between the camshaft (92) rotatably supported by 91). And a timing transmission means (97) provided with a timing belt (112) formed endlessly with synthetic resin and wound around the driving pulley (110) and the driven pulley (111). 112) The inter-shaft dimensions of the driving pulley (110) and the driven pulley (111) are set so that tension is applied to 112) In the timing belt drive engine, the cylinder block (36) separate from the crankcase (35) is formed of a material having a smaller coefficient of thermal expansion than the crankcase (35). Timing belt drive engine.   The crankcase (35) is made of aluminum or an aluminum alloy, and a metal gasket (113) is interposed between the cylinder block (36) made of cast iron and the crankcase (35). The timing belt drive engine according to claim 1.   The timing according to claim 1 or 2, wherein the cam holder (91) made of cast iron is fixed to the cylinder head (37) so as to rotatably support the cam shaft (92). Belt drive engine.   A flange (114) projecting radially outward from the camshaft (92) and the driven pulley (111) are coaxially provided on one end side of the camshaft (92) to attach the driven pulley (111). A pulley bearing boss (116) having a circular cross section protruding from the flange (114) so as to be fitted into the center hole (117) is provided coaxially, and on the outer peripheral edge of the front end of the pulley bearing boss (116), The timing belt drive engine according to claim 1, wherein a tapered guide surface (118) having a smaller diameter as the distance from the flange (114) increases.   The timing belt drive engine according to claim 4, wherein the camshaft (92) is provided with an intake cam (93) and an exhaust cam (94) arranged in the axial direction thereof.   The intake cam (93) between the first journal portion (92a) and the first journal portion (92a) that sandwich the intake cam (93) and the exhaust cam (94) between the flange (114). 6. The camshaft (92) according to claim 5, wherein a second journal portion (92b) sandwiching the exhaust cam (94) is provided on the camshaft (92) so as to be supported by the cam holder (91). Timing belt drive engine.   The driven pulley (111) includes a ring portion (111a) having a plurality of tooth portions (119) around which the timing belt (112) is wound, the center hole (117), and the ring portion (111a). ) And a disc portion (111b) fastened to the flange (114) with the outer periphery integrally connected to the inner circumference of the camshaft (92), and the disc portion along the axial direction of the camshaft (92) (111b) is a pair of recesses in which at least a part of the flange (114) and at least a part of a bolt (121) for fastening the disc part (111b) to the flange (114) are disposed. 120) is formed so that both side surfaces of the disk part (111b) cooperate with the inner periphery of the ring part (111a), and the axial length of the ring part (111a) Timing belt drive engine according to any one of claims 4-6, characterized in that the fence set.   The timing belt drive engine according to claim 7, wherein the driven pulley (111) is symmetrically formed.   The camshaft (91), the cylinder head (37), and the cylinder block (36) fixed to the cylinder head (37) by rotatably supporting the camshaft (92) are provided on the camshaft (92). The timing belt drive engine according to any one of claims 1 to 8, wherein the timing belt drive engine is coupled to the crankcase (35) by joint fastening with a plurality of fasteners (103) arranged around the periphery.   An engine body (34) including the crankcase (35), the cylinder block (36), and the cylinder head (37) is swingably supported by a body frame (15) of a saddle-ride type vehicle. The timing belt drive engine according to any one of claims 1 to 9.   The said driven pulley (111) is formed in the shape which open | released the trough part (122) between the some tooth | gear parts (119) of the outer periphery of this driven pulley (111) to the axial direction both sides. The timing belt drive engine according to any one of 1 to 10.

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