JP2008002669A - Chain tensioner structure of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner structure of an internal combustion engine, which exhibits excellent assemblability. <P>SOLUTION: A cam shaft 60F driven by an endless chain 73F is arranged to pass through a chain chamber 27F having opening both ends of a cylinder block 3F. A chain tensioner 80 is constituted of: a fixing member 81 fixed by a case body 1 and extending in the chain chamber 27F from a base end opening side to a distal end opening side; a movable member 82 movably attached in an extending direction of the fixing member 81; an energizing member 83 for energizing the movable member 82 to the base end opening side; and a tensioner member 85 curved in an arc shape accompanied by movement of the movable member 82 to the base end opening side and brought into contact with the endless chain 73F. Extending parts extending to the distal end opening side is provided on the fixing member and the movable member respectively, and a position maintaining mechanism for positioning the movable member against energizing force of the energizing member and maintaining the state where the tensioner member extends in the almost straight line is provided on each end of the extending parts in such a manner as to protrude from the end opening of the chain chamber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chain tensioner structure for an internal combustion engine.

  The internal combustion engine is configured to transmit the power of the crankshaft to the camshaft via an endless chain, and at this time, a chain tensioner that eliminates the relaxation of the endless chain is provided to reduce noise and the like. As an example of the camshaft arrangement, a configuration is known in which the camshaft is arranged on the side of the cylinder chamber so as to pass through a chain chamber in which an endless chain and a chain tensioner are arranged (see, for example, Patent Document 1). . The chain chamber formed in the cylinder block has a base end portion and a distal end portion opened so as to wind the endless chain around the sprocket on the crankshaft side and to communicate with the valve operating chamber formed in the cylinder head.

  As a chain tensioner, a movable member that is movable in the extending direction of the fixed member fixed to the case body is urged, and is straddled between the fixed member and the movable member as the movable member moves in the urging direction. A configuration is known in which the tensioner member is elastically deformed to be bent in an arcuate shape, and the bending tensioner member is brought into contact with the endless chain from the outside (see, for example, Patent Document 2). The chain tensioner is provided in the chain chamber in parallel to the linear portion between the sprockets in the endless chain.

JP 2004-108271 A Japanese Utility Model Publication No. 58-36915

  A conventional chain tensioner is disposed between sprockets provided on a crankshaft and a camshaft. When the camshaft is arranged as shown in Patent Document 1, it is necessary to position the tip of the chain tensioner deep inside the chain chamber with respect to the sprocket on the camshaft side, which may make assembly difficult. .

  In view of such a problem, an object of the present invention is to provide a chain tensioner structure with good assemblability in an internal combustion engine in which a camshaft is disposed so as to pass through a chain chamber formed on a side of a cylinder chamber. And

  In order to achieve the above object, a chain tensioner structure for an internal combustion engine according to the present invention includes a cylinder block in which a chain chamber having both ends opened in a side of a cylinder chamber into which a piston is inserted, and a cylinder chamber and a chain chamber. A case body having a cylinder head that covers the front end opening and is coupled to the cylinder block, and is disposed through the chain chamber, and the power of the crankshaft is transmitted through an endless chain disposed in the chain chamber. A chain tensioner structure of an internal combustion engine having a camshaft and a chain tensioner disposed in a chain chamber and applying tension to the endless chain, the chain tensioner being fixed to the case body and extending along the endless chain in the chain chamber A fixing member that extends from the proximal opening side to the distal opening side, and a fixing portion on the fixing member. A movable member attached movably in the extending direction, a biasing member for biasing the movable member toward the proximal end opening side, a straddling member between the fixed member and the movable member, and extending toward the proximal end opening side of the movable member. The tensioner member is curved in an arcuate shape along with the movement and contacts the endless chain. In addition, the fixed member and the movable member are respectively provided with a fixed-side extension portion and a movable-side extension portion that extend toward the tip opening side, and are provided at the tip portions of the fixed-side extension portion and the movable-side extension portion. A position holding mechanism that holds the state in which the movable member is positioned on the tip opening side against the urging force of the urging member and the tensioner member extends substantially in a straight line; It protrudes from the front end opening.

  Further, a base end side mounting portion and a tip end side mounting portion for mounting the fixing member to the case body are provided at the base end portion and the tip end portion of the fixing member, respectively, and the base end side mounting portion is positioned in the vicinity of the crankshaft. It is preferable that the distal end side mounting portion be positioned between the tensioner member and the connecting portion of the movable member and the movable side extending portion. Moreover, it is preferable to perform a drawing process to the movable side extension part.

  According to the chain tensioner structure for an internal combustion engine according to the present invention, when the chain tensioner is inserted into the chain chamber while the position of the movable member is held by the position holding mechanism, the movable side extension portion or the like protrudes from the end opening of the chain chamber. In this state, the fixing member can be fixed to the case body, and the chain tensioner can be easily assembled to the case body. Next, when the position holding state due to the action of the position holding mechanism is released, the movable member is urged and the tensioner member presses against the endless chain, but this release operation can be performed outside the cylinder block. Can be easily set against the chain.

  Further, by providing the extension portion, the chain tensioner becomes larger on the tip opening side as compared with the conventional case, whereby the tip portion attaching portion is located in a newly formed space on the tip opening side. For this reason, the chain tensioner can be stably fixed to the case body. Further, the extension portion can be reduced in weight by drawing the extension portion to increase the rigidity. Thereby, in providing an extension part, the enlargement of the whole weight can be avoided and the operability of a member connected to the movable side extension part such as a tensioner member can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 to 3 show an engine E equipped with a chain tensioner for an internal combustion engine according to the present invention. In the following, the directions of the arrow F and the arrow U in the figure are the forward and upward directions, and these directions correspond to the directions viewed by the driver when the engine E is mounted on the vehicle.

  The engine E is a four-stroke / V-type two-cylinder reciprocating engine mounted on a vehicle such as a motorcycle, and a crankcase 2 that rotatably supports the crankshaft 11 and a V-shape above the crankcase 2. The cylinder blocks 3F and 3R before and after the pistons 12F and 12R are slidably inserted into the cylinder chambers 21F and 21R that are tilted forward and backward and fastened and opened up and down, and above the cylinder blocks 3F and 3R. The case body 1 is composed of front and rear cylinder heads 4F and 4R fastened to each other. Note that head covers 5F and 5R are attached to the cylinder heads 4F and 4R so as to cover the openings on the upper surface.

  The case body 1 of the engine E is V-shaped in a side view by the front and rear cylinder blocks 3F and 3R and the front and rear cylinder heads 4F and 4R above the crankcase 2, and these are collectively referred to as V bank 1B below. Called. The front cylinder block 3F and the front cylinder head 4F are collectively referred to as a front bank 1F, and the rear cylinder block 3R and the rear cylinder head 3R are collectively referred to as a rear bank 1R.

  The crankcase 2 includes left and right case halves 2A and 2B, the left journal portion 11a of the crankshaft 11 is rotatably supported on the side wall of the left case half 2A, and the right journal portion 11b is the side wall of the right case half 2B. Is supported rotatably. The crank webs 11c, 11c and the crank pin 11d provided between the journal portions 11a, 11b are accommodated in the internal space (crank chamber 22) of the crankcase 2. The crankshaft 11 and the pistons 12F and 12R are connected via connecting rods 13F and 13R.

  The cylinder heads 4F and 4R are attached so as to cover the openings of the cylinder chambers 21F and 21R, and are surrounded by the inner peripheral surfaces of the cylinder chambers 21F and 21R, the pistons 11F and 11R, and the cylinder heads 4F and 4R. 23R is formed. The combustion chambers 23F, 23R communicate with the intake ports 32F, 32R extending inwardly of the V bank 1B through the intake ports 31F, 31R and the cylinders via the exhaust ports 36F, 36R. Exhaust ports 37F and 37R that extend inside the heads 4F and 4R toward the outside of the V bank 1B communicate with each other. Intake pipes 33F and 33R are connected to the intake ports 32F and 32R. The upstream side of the intake pipes 33F and 33R is gathered in the V bank 1B, and a throttle valve for adjusting the intake air amount and an air cleaner for cleaning external air are connected to the gathered part (not shown). Exhaust pipes 38F and 38R are connected to the exhaust ports 37F and 37R.

  The cylinder heads 4F and 4R are provided with intake valves 15F and 15R and exhaust valves 16F and 16R that open and close the intake ports 31F and 31R and the exhaust ports 36F and 36R. The intake / exhaust valves 15F, 15R, 16F, and 16R are energized in a direction to close the intake / exhaust ports 31F, 31R, 36F, and 36R by the valve spring 14, and are driven by valve operating mechanisms 50F and 50R that are driven by the crankshaft 11. The intake / exhaust ports 33F and 33R are opened and closed.

  In the engine E, the pistons 12F and 12R reciprocate in the cylinder chambers 21F and 21R with a phase difference corresponding to the angle formed by the V bank 1B, and intake, compression, combustion, and exhaust strokes are performed. When the pistons 12F and 12R move downward, the air that has passed through the air cleaner and the throttle valve is introduced into the intake pipes 33F and 33R, and enters the combustion chambers 23F and 23R via the intake ports 31F and 31R opened from the intake ports 32F and 32R. Supplied and compressed as the pistons 12F and 12R move upward. During compression, fuel is injected from injectors 17F and 17R attached to the cylinder heads 4F and 4R so that the injection ports face the central portions of the combustion chambers 23F and 23R, thereby forming an air-fuel mixture. When the pistons 12F and 12R are in the vicinity of the top dead center, the air-fuel mixture is ignited and burned by a spark plug 18 (the rear cylinder head 4R side is not shown) attached to the cylinder heads 4F and 4R, and the pistons 12F and 12R. Move down again. The burned gas is discharged to the outside through the opened exhaust ports 36F, 36R, exhaust ports 37F, 37R, and exhaust pipes 38F, 38R when the pistons 12F, 12R move up again.

  Recirculation passages 39F and 39R extending toward the inside of the V bank 1B communicate with the exhaust ports 37F and 37R. An exhaust gas introduction pipe 35 is connected to the recirculation passages 39F and 39R via reed valves 34F and 34R which are opened when the combustion chambers 23F and 23R become negative pressure. The exhaust introduction pipe 35 is disposed below the intake pipes 33F and 33R in the V bank 1B, and is connected to the control valve 19 of the exhaust gas recirculation device provided at the collection part of the intake pipes 33F and 33R. By this exhaust gas recirculation device, the gas in the exhaust ports 37F and 37R is caused to flow into the intake pipes 33F and 33R via the recirculation passages 39F and 39R, the reed valves 34F and 34R, the exhaust introduction pipe 35 and the control valve 19, and the combustion chamber It can be refluxed to 23F and 23R.

  A left cover 6 is fastened to the left case half 2A so as to cover the outside of the side surface, and the left end portion 11e of the crankshaft 11 is accommodated in a space (left auxiliary device chamber) 24 surrounded by the left cover 6. ing. A generator 41 driven by the crankshaft 11 is provided at the left end portion 11e, and a gear 43 is connected via a one-way clutch 42. A driving force of a starter motor (not shown) that operates when the engine E is started is transmitted to the gear 43. Two balancer shafts 44 and 45 arranged parallel to the crankshaft 11 with the crankshaft 11 sandwiched in the front-rear direction are rotatably supported on the crankcase 2. The crankshaft 11 is provided with a drive gear 46a of a gear train 46 that rotates the front balancer shaft 44 in synchronization with the crankshaft 11 between the left journal portion 11a and the left crank web 11c. Further, the right case 7 is also fastened to the right case half 2B so as to cover the outside of the side surface, and the right end portion 11f of the crankshaft 11 is accommodated in a space (right accessory chamber) 25 surrounded by the right cover 7. ing. A driving gear 47a of a gear train 47 that rotates the rear balancer shaft 45 in synchronization with the crankshaft 11 is provided at the right end portion 11f. The rear balancer shaft 45 is provided with a driven gear 47b of the gear train 47 and a drive gear 49a of a gear train 49 that transmits the rotation of the crankshaft 11 to the main shaft 48 at a reduced speed. The main shaft 48 is a rotating shaft of a power transmission device that shifts and transmits power to a rear wheel (not shown). Behind the crankcase 2 is integrally provided a transmission case 9 that houses the power transmission device.

  As shown in FIGS. 3 to 5, the valve operating mechanisms 50 </ b> F and 50 </ b> R are swayed by the camshafts 60 </ b> F and 60 </ b> R rotating with the intake and exhaust side cams 63 and 64 and the intake side cam 63. An intake-side first rocker arm 51 that moves, an exhaust-side first rocker arm 52 that swings following the exhaust-side cam 64, an intake-side second rocker arm 53 that has one end contacting the upper ends of the intake valves 15F and 15R, One end portion is provided between the exhaust side second rocker arm 54 contacting the upper ends of the exhaust valves 16F and 16R, and the intake side first and second rocker arms 51 and 53, and the swinging motion of the intake side first rocker arm 51 is inhaled. Provided between the intake-side push rod 55 that transmits to the side second rocker arm 53 and the exhaust-side first and second rocker arms 52 and 54, and swings the exhaust-side first rocker arm 52. Composed of the exhaust-side push rod 56 to transfer the gas-side second rocker arm 54.

  Of these, the upper portions of the intake side and exhaust side push rods 55, 56 and the intake side and exhaust side second rocker arms 53, 54 are surrounded by the cylinder heads 4F, 4R and the head covers 5F, 5R, and the valve operating chamber 26F is formed. , 26R. In addition, chain chambers 27F and 27R are formed in the cylinder blocks 3F and 3R so as to extend vertically on the sides of the cylinder chambers 21F and 21R. The chain chambers 27F and 27R communicate with the valve operating chambers 26F and 26R via the upper end opening 27a, and the cylinder heads 4F and 4R are attached so as to cover the upper end openings 27a of the chain chambers 27F and 27R. The front chain chamber 27F formed in the front cylinder block 3F is formed on the left side of the cylinder chamber 21F, communicates with the left chain chamber 28A formed in the left case half 2A via the lower end opening 27b, and further to the left It communicates with the chamber 24. Similarly, the rear chain chamber 27R formed in the rear cylinder block 3R is formed on the right side of the cylinder chamber 21R and communicates with the right chain chamber 28B formed in the right case half 2B via the lower end opening 27b. Furthermore, it communicates with the right accessory chamber 25.

  The camshafts 60F, 60R are disposed across the upper part of the chain chambers 27F, 27R from side to side, and one end portions of the camshafts 60F, 60R extend up and down in the cylinder blocks 3F, 3R, and the cylinder chambers 21F, 21R 27R is rotatably supported by a bearing 66 held on the inner wall 3a that partitions the left and right. An opening 3c is formed in the upper part of the side wall 3b of the cylinder block 3F, 3R that partitions the chain chambers 27F, 27R and faces the inner wall 3a. The other end portions of the camshafts 60F and 60R are rotatably supported by bearings 67 held by a shaft cover 8 attached so as to cover the opening 3c.

  The valve operating mechanisms 50F and 50R are provided with chain transmission mechanisms 70F and 70R that reduce the rotation of the crankshaft 11 by half and transmit it to the camshafts 60F and 60R. The front chain transmission mechanism 70F is wound around a front cam drive sprocket 71F provided at the left end portion 11e of the crankshaft 11, a front cam driven sprocket 72F coupled to the front camshaft 60F, and both sprockets 71F and 72F. It consists of a front cam chain 73F. The rear chain transmission mechanism 70R is wound around a rear cam drive sprocket 71R provided at the right end portion 11f of the crankshaft 11, a rear cam driven sprocket 72R coupled to the rear camshaft 60R, and both sprockets 71R and 72R. And a rear cam chain 73R.

  In the valve operating mechanisms 50F and 50R, when the crankshaft 11 rotates, the intake side first rocker arm is driven by the intake side cam 63 in accordance with the rotation of the camshafts 60F and 60R that are transmitted with power via the chain transmission mechanisms 70F and 70R. 51 swings and the intake side push rod 55 moves up and down, and the intake side second rocker arm 53 swings accordingly, and the intake valves 15F and 15R are driven to open and close in accordance with the strokes of the pistons 12F and 12R. . Further, the exhaust-side cam 64 swings the exhaust-side first rocker arm 52 and the exhaust-side push rod 54 moves up and down, and the exhaust-side second rocker arm 56 swings accordingly, and the pistons 12F and 12R travel. At the same time, the exhaust valves 16F and 16R are driven to open and close.

  The chain transmission mechanisms 70F and 70R are provided with chain tensioners 80 and 80 for applying tension to the cam chains 73F and 73R. The chain tensioner 80 eliminates the loosening of the cam chains 73F and 73R, maintains the function as a timing chain, reduces noise during operation, and extends the life of the cam chains 73F and 73R.

  In addition, the injectors 17F and 17R of this configuration example are of an air assist type that injects fuel using compressed air discharged from the air pump 100, and the air pump 100 is placed on the upper part of the front cylinder block 3F from the front. It is attached. The front camshaft 60F is provided with a pump drive gear 107a of a pump gear train that transmits power to the drive shaft 106 of the air pump 100. Further, a compressed air passage 130 that guides the compressed air discharged from the air pump 100 to the injectors 17F and 17R is formed inside the case main body 1.

  A cam pulser 150 for detecting the rotational position of the rear cam shaft 60R is attached to the upper part of the rear cylinder block 3R from the rear so that the sensing unit 151 is positioned inside the chain chamber 27R. The rear cam driven sprocket 72R is integrally formed with a plurality of arm portions 152, 152 extending in a tongue-like shape from the side surface, and the arm portions 152, 152 face the sensing portion 151 as the rear cam driven sprocket 72R rotates. In this case, the cam pulser 150 is configured to output a signal indicating the rotational position of the rear camshaft 60R.

  As shown in FIGS. 3 to 5, the chain tensioner 80 has a long outer shape, and is disposed in the front chain chamber 27F along the inner surface of the rear wall 3d of the cylinder block 3F. It is disposed along the inner surface of the rear wall 3e of the rear cylinder block 3R, and is provided substantially parallel to the linear portion between the sprockets in the cam chains 73F and 73R with the longitudinal direction thereof oriented substantially vertically.

  As shown in FIGS. 6 to 9, the chain tensioner 80 includes a metal base plate 81 that is fastened to the case body 1 by forming a guide groove 81 d extending in the longitudinal direction, and the base plate 81 slides in the guide groove 81 d. A metal slider plate 82 provided freely, a spring 83 straddling between both plates 81, 82 and biasing the slider plate 82 toward the base end side in the longitudinal direction, and between the plates 81, 82. It is composed of a tensioner 85 that is laid across and a lock mechanism 90 that restricts the movement of the slider plate 82.

  The base plate 81 has a rectangular belt-like base wall 81a and two side walls 81b and 81c that extend perpendicularly from the edges extending in the longitudinal direction of the base wall 81a and face each other, and are formed in a U-shaped cross section. A guide portion 81A in which a guide groove 81d surrounded by a base wall 81a and side walls 81b and 81c is formed at an intermediate portion in the longitudinal direction, and an extension portion 81B provided to extend to the distal end side of the guide portion 81A And the receiving part 81C extended to the base end side of 81 A of guide parts, and the opposing space | interval of the side walls 81b and 81c larger than the guide groove 81d is united.

  The slider plate 82 includes a main body portion 82A having a U-shaped cross section and an extending portion 82B integrated with the main body portion 82A. The main body portion 82A has a rectangular belt-shaped base wall 82a and two side walls 82b and 82c that extend perpendicularly from edges extending in the longitudinal direction of the base wall 82a and face each other. The extending portion 82B has two side walls 82b and 82c of the main body portion 82A extending from the distal end of the base wall 82a further to the distal end side, and is formed in a tuning fork shape. 82b and 82c.

  The body portion 82A of the slider plate 82 is fitted and received in the guide groove 81d of the base plate 81, and the slider plate 82 is slidable in the longitudinal direction with respect to the base plate 81. In the guide portion 81A of the base plate 81, a plurality of projecting pieces 81e are formed that project from the side walls 81b and 81c in a tongue-like shape in the direction perpendicular to the base wall 81a. In a state where the slider plate 82 is received in the guide groove 81d, the protruding piece 81e is bent so as to cover the base wall 82a of the slider plate 82, and the slider plate 82 is prevented from dropping in the opening direction of the guide groove 81d. To do.

  At this time, the extension portion 82B of the slider plate 82 is received inside the extension portion 81B of the base plate 81, and slides in the longitudinal direction inside the extension portion 81B. The extending portions 81B and 82B of both the plates 81 and 82 are formed by partially drawing the side walls 81b, 81c, 82b, and 82c to form drawn portions 81E and 82E extending in the longitudinal direction. The slider plate throttle portion 82E is located inside the throttle portion 81E where the opposing distance between the side walls 81b and 81c in the extension portion 81B of the base plate 81 is narrow, and the backlash when the extension portion 82B of the slider plate 82 slides. Sticking is prevented.

  In addition, at the lower end portion of the guide portion 81A of the base plate 81, a tongue piece formed so as to protrude from the side wall 81b in the vertical direction of the base wall 81a is bent vertically, and is opposed to the base wall 81a in parallel above the guide groove 81d. Ribs 81f are formed. On the other hand, on the upper part of the base wall 82a of the slider plate 82, a tongue piece formed by punching in a cantilever manner is bent vertically, and a rib 82d extending perpendicularly to the base wall 82a and the side walls 82b and 82c is provided. Is formed. The spring 83 has a base end portion 83a locked in a support hole 81g passing through the rib 81f of the base plate 81, and a tip end portion 83b locked in a support hole 82e passing through the rib 82d of the slider plate 82. It arrange | positions outside with respect to the base wall 82a, and urges | biases the slider plate 82 to a base end side. Note that the rib 81f of the base plate 81 is welded with a metal backing plate 84a to ensure strength. Further, the spring 83 is clinched at both ends 83a and 83b to maintain the locking state with respect to the support holes 81g and 82e, and the coil portion 83c is accommodated inside the tube 84b.

  The tensioner 85 has a skeleton formed by a main body plate 86 formed by curving an elastically deformable band-shaped metal plate material, and a rubber shoe 87 is baked on the outer surface of the intermediate portion 86 c in the longitudinal direction of the main body plate 86. A synthetic resin sheet material that forms a sliding contact surface with the cam chains 73F and 73R is attached to the outer surface of the shoe 87 to protect the shoe 87 and reduce the frictional resistance when the chain slides. A cylindrical collar 88 is attached to both end portions 86a and 86b of the main body plate 86 via a rubber material baked on the inner surface.

  The tensioner 85 has a base end received inside the accommodating portion 81C of the base plate 81, a tip end sandwiched by the base end of the extending portion 82B of the slider plate 82, and a pin loosely inserted into the collars 88, 88. And is pivotally connected to the side walls 81b, 81c, 82b, 82c of both plates 81, 82. The intermediate portion 86c of the main body plate 86 is positioned outside the spring 83, and the intermediate portion 86c is elastically deformed following the sliding of the slider plate 82. When the slider plate 82 is on the distal end side, the intermediate portion 86c extends linearly substantially parallel to the base wall 81a, and the shoe 87 is pulled toward the base wall 81a. When the slider plate 82 slides to the base end side, the distance between both end portions 86a and 86b is shortened, the intermediate portion 86c is curved and deformed in an arcuate shape, and the shoe 87 protrudes outward with respect to the base wall 81b.

  In the base plate 81, side walls 81b and 81c further protrude toward the base end side with respect to the base end of the base wall 81a. This protruding portion is bent so that the side walls 81b and 81c are aligned and extend from the receiving portion 81C to the base end side, thereby forming a base end side mounting bracket 81D. A bolt insertion hole 81h is formed through the proximal end mounting bracket 81D. On the other hand, a bolt insertion hole 81i is formed in the extending portion 81B through the base wall 81a, and a nut 89 is welded to the inner surface of the base wall 81a so as to be coaxial with the bolt insertion hole 81i. . In the assembled state, the nut 89 is disposed on the distal end side with respect to the joint portion of the slider plate 82 and the tensioner 85, and is disposed on the proximal end side with respect to a lock mechanism 90 described later.

  The lock mechanism 90 is provided at the distal end portion of the extending portion 81 B of the base plate 81 and the distal end portion of the extending portion 82 B of the slider plate 82, and is attached to the base side wedge piece 91 attached to the base plate 81 and the slider plate 82. And a slider-side wedge piece 92 that engages with the base-side wedge piece 91. The slider-side wedge piece 92 is pivotally connected to the distal end portion of the extending portion 82B of the slider plate 82, and is disposed on the distal end side with respect to the extending portion 82B.

  A receiving member 95 having a U-shaped cross section is welded to the distal end portion of the base plate 81 in a state where the receiving member 95 is fitted and accommodated inside the extension portion 81B. A receiving space 95A having a substantially rectangular cross section for receiving and holding both wedge pieces 91 and 92 is formed by being surrounded by the wall surface. The receiving member 95 forms, as an inner wall surface facing the base wall 81a in a state attached to the base plate 81, a tapered surface 95d that inclines in a direction approaching the base wall 81a of the base plate 81 toward the distal end side.

  The two wedge pieces 91 and 92 are fitted and received in the receiving space 95A by bringing the wedge contact surfaces 91a and 92a into surface contact with each other, and the base surface 91b of the base-side wedge piece 91 is brought into contact with the tapered surface 95d of the receiving member 95. The base surface 92 b of the slider-side wedge piece 92 is in contact with the inner surface of the base wall 81 a of the base plate 81. In a state where both the wedge pieces 91 and 92 are received and held, the wedge mating surfaces 91a and 92a are inclined toward the base wall 81a of the base plate 81 toward the distal end side.

  The side wall 95b of the receiving member 95 is formed with a hook portion 95e formed by bending a tongue piece projecting toward the base end side. The base-side wedge piece 91 has a long hole extending in parallel to the base surface 91b. 91c is formed. A compression spring 93 locked to the hook portion 95e is accommodated in the long hole 91c, and the base-side wedge piece 91 is urged toward the distal end side by the compression spring 93.

  Therefore, when the slider-side wedge piece 92 moves to the base end side together with the slider plate 81, the base surface 91b moves along the inner surface of the base wall 81a, so that the wedge mating surfaces 91a and 92a are separated from each other. The wedge piece 91 is urged toward the distal end side by the urging force of the compression spring 93, the wedge engagement surfaces 91a, 92a are brought into contact with each other, and both the wedge pieces 91, 92 are wedged in the receiving space 95A. In this wedged state, the movement of the slider plate 81 toward the tip side is restricted. In addition, if the wedge side state is released by moving the base side wedge piece 91 to the proximal end side, the slider plate 81 can be moved again to the distal end side.

  Further, a pin mounting hole 92c is formed at the tip of the slider-side wedge piece 92 through the wedge mating surface 92a and the base surface 92b. By sliding the slider plate 82 toward the tip side against the biasing force of the spring 83, the pin mounting hole 92c can be exposed from the tip of the base wall 81a of the base plate 81 to the tip side. By inserting the lock pin 94 into the pin mounting hole 92c in this state, the lock pin 94 comes into contact with the distal end edge of the base wall 81a of the base plate 81 and the movement of the slider plate 82 toward the proximal end side is restricted. The movement of the slider plate 82 is restricted with respect to both the distal end side and the proximal end side by the lock mechanism 90 with the lock pin 94 attached in this manner.

  The chain tensioner 80 is assembled in such a state that the cylinder blocks 3F and 3R are assembled to the crankcase 2, the camshafts 60F and 60R are supported by the cylinder blocks 3F and 3R, and the chain transmission mechanisms 70F and 70R are assembled. Suppose you do. The cylinder heads 4F and 4R and the left and right covers 6 and 7 are removed.

  The chain tensioner 80 for the rear chain transmission mechanism 70R is inserted into the rear chain chamber 27R along the inner surface of the rear wall 3e of the rear cylinder block 3R through the base wall 81a of the base plate 81 from the upper end opening 27a of the rear chain chamber 27R. Opposing the rear linear portion of the chain 73R, the base end side mounting bracket 81D is exposed downward from the lower end opening 27b. The base end side mounting bracket 81D is opposed to the outer surface of the right case half 2B near the lower side of the crankshaft 11, and a bolt 96 is inserted into the bolt insertion hole 81h, whereby the base plate 81 is fastened to the right case half 2B. Further, a bolt 96 is inserted from the outside of the rear wall 3e of the rear cylinder block 3R and screwed into the nut 89, and the base plate 81 is fastened to the upper portion of the rear cylinder block 3R. The cam pulser 150 is attached to the rear wall 3e of the rear cylinder block 3R. However, the chain tensioner 80 and the cam pulser 150 are provided side by side without interference according to the offset of the arm portions 152, 152,.

  In a state of being fixed to the case main body 1, the front end side of the lock mechanism 90 such as the lock pin 94 is exposed upward from the upper end opening 27a of the rear chain chamber 27R. When the lock pin 94 is removed, the slider plate 82 is moved downward by the urging force of the spring 83, the tensioner 85 is bent, the shoe 87 is projected outward, and is pressed against the rear cam chain 73R, and the rear cam chain 73R The rear straight part is pushed forward. A support member 97 that supports the front straight portion of the rear cam chain 73R is disposed inside the rear chain chamber 27F. As a result, the tension is applied to the rear cam chain 73R and the relaxation is eliminated. When the slider plate 82 is moved downward, the base-side wedge piece 91 is moved upward by the urging force of the compression spring 93 so as to maintain the contact state of the wedge mating surfaces 91a and 92a. When the wedge surfaces 91a and 92a come into contact with each other, the slider plate 82 is restricted from moving upward, and a state in which tension is applied to the rear cam chain 73R is maintained.

  On the other hand, since the air pump 100 is attached to the front cylinder block 3F from the front, the chain tensioner 80 for the front chain transmission mechanism 70F has the base wall 81a of the base plate 81 along the inner surface of the rear wall 3d of the front cylinder block 3F. It is disposed in the front chain chamber 27F. A support member 99 similar to the above is disposed in the front chain chamber 27F so as to support the front straight portion of the front cam chain 73F. Then, it is fastened to the left case half 2 </ b> A via the base end mounting bracket 81 </ b> D, and fastened to the upper portion of the front cylinder block 3 </ b> F by a bolt 98 screwed to the nut 89. Next, when the lock pin 94 exposed from the upper end opening 27a of the front cylinder block 3F is removed, the slider plate 82 is moved downward, the shoe 87 of the tensioner 85 is protruded to the front side, and the loosening of the front cam chain 73F is eliminated. The base-side wedge piece 91 moves upward and the upward movement of the slider plate 82 is restricted.

  Thus, in this chain tensioner 80, in the assembled state, the locking mechanism 90 and the like are extended to the front ends of the plates 81 and 82 so as to protrude from the upper end openings 27a of the chain chambers 27F and 27R. 81b and 82B are provided. Note that the base end portion also protrudes downward from the lower end opening 27b. In addition, the slider plate 81 is positioned on the distal end side by the lock pin 94 and is held in a state in which the shoe 87 is retracted. For this reason, the fastening operation | work to the case main body 1 can be performed easily. Further, the operation of removing the lock pin 94 after fastening can be performed outside the cylinder blocks 3F and 3R, and the chain tensioner 80 can be easily set to the cam chains 73F and 73R.

  The lock mechanism 90 is configured by overlapping two wedge pieces 91 and 92 moving in the longitudinal direction in the direction in which the cam chains 73F and 73R are disposed. In this configuration example, a receiving space 95A that accommodates the lock mechanism 90 is formed at the distal ends of the extending portions 81B and 82B, and the receiving space 95A is disposed above the cam driven sprockets 72F and 72R in the assembled state. For this reason, the space of the receiving space 95A can be easily secured with respect to the moving direction and the overlapping direction of the wedge pieces 91 and 92, and the operability can be improved by the optimum design of the lock mechanism 90. At the same time, operability from the outside is improved.

  Further, the fastening point of the chain tensioner 80 is vertically separated, and the chain tensioner 80 is stably fixed to the case body 1. Note that the nut 89 can be provided above the conventional arrangement by providing the extending portions 81B and 82B, and there are no members that obstruct the assembly, so that the fastening operation can be easily performed. In particular, in the chain tensioner 80 for the rear chain transmission mechanism 70R, the bolt can be inserted in the space above the transmission case 9 without other members around it, and the fastening operation can be easily performed.

  Further, the extending portions 81B and 82B are integrally provided at the tip portions of the plates 81 and 82, but the narrowed portions 81E and 82E extending in the longitudinal direction are formed on the side walls 81b, 81c, 82b and 82c. The section modulus is increased and the rigidity is increased. For this reason, the extension parts 81B and 82B are reduced in weight, and the overall weight of the chain tensioner 80 is not increased. Further, the extension portion 82B of the slider plate 82 slides under the urging force of the spring 83. Since the extension portion 82B is reduced in weight, the operability of the tensioner 85, the slider-side wedge piece 92, and the like connected thereto can be improved.

  So far, the embodiment of the chain tensioner structure of the internal combustion engine according to the present invention has been described, but it is not necessarily limited to the above-described configuration. As long as the camshaft is disposed through the chain chamber of the cylinder block and at least the cylinder block and the cylinder head have a divided structure, the present invention can be similarly applied to a parallel type or a single cylinder.

1 is a right side sectional view of an engine including a chain tensioner for an internal combustion engine according to the present invention. It is sectional drawing of the engine shown along the arrow II-II direction shown in FIG. It is a right side sectional view of an engine which shows the composition of a valve operating mechanism. It is a top view of the front cylinder block which shows the attachment structure of a front camshaft. It is a top view of the back cylinder block which shows the attachment structure of a back camshaft. It is a sectional side view which shows the structure of a chain tensioner. It is a figure which shows the structure of a baseplate, (a) is a top view of a baseplate, (b) is sectional drawing shown along arrow VIIb-VIIb shown to Fig.7 (a). It is a figure which shows the structure of a slider plate, (a) is a top view of a slider plate, (b) is sectional drawing shown along arrows VIIIb-VIIIb shown to Fig.8 (a). It is a front end side enlarged view of a chain tensioner.

Explanation of symbols

E Engine 1 Case body 2 Crankcase 3F, 3R Cylinder block 4F, 4R Cylinder head 11 Crankshaft 12F, 12R Piston 21F, 21R Cylinder chamber 27F, 27R Chain chamber 60F, 60R Camshaft 70F, 70R Chain transmission mechanism 73F, 73R Cam Chain (endless chain)
80 Chain tensioner 81 Base plate (fixing member)
81B extension part (fixed side extension part)
81D Base end mounting bracket (base end mounting part)
82 Slider plate (movable member)
82B extension part (movable side extension part)
81E, 82E Restriction part 83 Spring (biasing member)
85 Tensioner (Tensioner member)
89 Nut (tip mounting part)
90 Locking mechanism (position holding mechanism)
94 Lock pin

Claims (3)

A cylinder block in which a chain chamber having both ends opened on the side of the cylinder chamber into which the piston is inserted is formed, and a cylinder head that covers the cylinder chamber and the end opening of the chain chamber and is coupled to the cylinder block. A case body,
A camshaft that is disposed through the chain chamber and in which the power of the crankshaft is transmitted through an endless chain disposed in the chain chamber;
A chain tensioner structure for an internal combustion engine having a chain tensioner that is disposed in the chain chamber and applies tension to the endless chain,
The chain tensioner is
A fixing member fixed to the case body, and arranged to extend from the proximal opening side to the distal opening side along the endless chain in the chain chamber;
A movable member attached to the fixed member movably in the extending direction of the fixed member;
A biasing member that biases the movable member toward the base end opening;
A tensioner member straddling the fixed member and the movable member, curved in a bow shape with the movement of the movable member toward the proximal end opening side, and contacted with the endless chain;
Consisting of
The fixed member and the movable member are each provided with a fixed side extending portion and a movable side extending portion extending to the tip opening side,
The movable member is positioned on the distal end opening side against the urging force of the urging member at the distal end portions of the fixed side extending portion and the movable side extending portion, and the tensioner member extends substantially linearly. A chain tensioner structure for an internal combustion engine, wherein a position holding mechanism for holding the projecting state is provided so as to protrude from the tip opening of the chain chamber when in the position holding state. A base end side mounting portion and a front end side mounting portion for mounting the fixing member to the case body are provided at the base end portion and the tip end portion of the fixing member, respectively.
2. The chain tensioner structure for an internal combustion engine according to claim 1, wherein the base end side mounting portion is positioned in the vicinity of the crankshaft, and the tip end side mounting portion is positioned in the fixed side extending portion.   3. The chain tensioner structure for an internal combustion engine according to claim 1, wherein the fixed side extending portion and the movable side extending portion are drawn.

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