JP4671923B2 - Internal combustion engine camshaft structure - Google Patents

Description

  The present invention relates to a camshaft structure of an internal combustion engine having a camshaft disposed on a side of a cylinder chamber and disposed through a chain chamber formed in a cylinder block.

  An intake / exhaust port that opens to the combustion chamber of the internal combustion engine is opened and closed by an intake / exhaust valve attached to the cylinder head, and a valve mechanism that drives the intake / exhaust valve by the action of a cam piece that rotates integrally with the camshaft is installed in the cylinder head. Be contained. As a configuration example of the valve mechanism, a cam shaft is arranged in a chain chamber on the side of the cylinder chamber and supported by the cylinder block, and as a component member of the valve mechanism, a push that extends vertically in the cylinder head and follows the rotation of the cam piece The form provided with the rod is known (for example, refer to patent documents 1). The camshaft is rotated by transmitting the power of the crankshaft via a chain transmission mechanism housed in a chain chamber, and a sprocket for the chain transmission mechanism is provided.

JP 2004-100550 A

  In the conventional camshaft, the cam piece is disposed outside the sprocket, and there is a possibility that the constituent members of the valve mechanism such as the push rod are arranged so as to protrude to the side of the internal combustion engine. . For this reason, in the form in which the camshaft is arranged in the chain chamber, a structure capable of reducing the size of the internal combustion engine by the optimum arrangement of the valve operating mechanism has been demanded.

  Further, if the lateral extension amount of the chain chamber is reduced, the internal combustion engine can be reduced in size, while the camshaft arrangement space is reduced, and assembling of the camshaft and peripheral members becomes a problem. For this reason, the structure which can assemble these easily also in the narrow arrangement | positioning space was calculated | required.

  Conventionally, an internal combustion engine having an air pump that discharges compressed air supplied to an air assist type injector or the like is known, but this air pump is attached to the periphery of the camshaft and rotation of the camshaft serves as a drive source. May be used. At this time, it is preferable that the air pump is optimally arranged in accordance with the structure and arrangement of the camshaft and the valve mechanism so that the desired discharge amount can be ensured and the entire engine can be downsized.

  In view of such problems, the present invention provides a camshaft structure in which the internal combustion engine is downsized and the camshaft is improved in an internal combustion engine in which the camshaft is disposed through the chain chamber. With the goal.

To achieve the above object, a camshaft structure for an internal combustion engine according to a first aspect of the present invention is formed in a cylinder block in which a cylinder chamber into which a piston is inserted is formed, and a cylinder block that is located on the side of the cylinder chamber. The camshaft is disposed through the chain chamber and has one end rotatably supported by the inner wall of the cylinder block defining the cylinder chamber and the chain chamber, and the other end rotatably supported by the side wall of the cylinder block. A camshaft structure of an internal combustion engine configured to include a cam piece of a valve mechanism for driving an intake / exhaust valve in an intermediate portion of the camshaft located in a chain chamber, and a camshaft to be rotated And a chain transmission mechanism sprocket. In addition, the cam piece is disposed on the cylinder chamber side with respect to the sprocket. In addition, an air pump that discharges compressed air supplied to a predetermined location of the internal combustion engine is attached to the cylinder block, and this air pump extends in parallel with the camshaft and is rotatably connected to the drive shaft. The swash plate member is arranged adjacent to the cam piece when it is composed of a swash plate member that extends radially outward of the drive shaft and a pump piston that reciprocates linearly in conjunction with the swash plate member. is doing. Further, the pump piston is arranged on the side of the cylinder chamber so as to be offset in the axial direction with respect to the camshaft in the direction of sliding in the axial direction of the camshaft, and the swash plate member is connected to the pump piston and the cylinder chamber. It is arranged between the sprocket.

The camshaft structure of the internal combustion engine according to the first aspect of the present invention has a pump gear train that transmits the rotation of the camshaft to a drive shaft and a swash plate member coupled to the drive shaft. And a pump driven gear meshed with the pump drive gear and coupled to the drive shaft, and the peripheral portion of the swash plate member is disposed so as to overlap the outer peripheral side of the pump drive gear as seen from the axial direction of the camshaft. It is preferable.
In the camshaft structure of the internal combustion engine according to the first aspect of the present invention, a cam chain for rotating the camshaft is wound around the sprocket, and the peripheral portion of the swash plate member is the axis of the camshaft. As viewed from the direction, it is preferable that the cam chain is arranged so as to overlap with the outer peripheral side of the sprocket in a state where the cam chain is wound.
Further, the camshaft structure of the internal combustion engine according to the first aspect of the present invention has an operating member fastened to the left end face of the pump piston, and the operating members are located on the central axis of the pump piston and are respectively hemispherical. It is preferable that a holding portion for slidably receiving and holding the two shoes formed in a shape is provided, and the peripheral portion of the swash plate member is sandwiched between the two shoes received and held by the holding portion.
According to a first aspect of the present invention, there is provided a camshaft structure for an internal combustion engine, wherein an air pump includes a pump body having a pump cylinder chamber formed therein, and a pump head coupled to the pump body so as to cover an opening of the pump cylinder chamber. A pump piston having an operating member at the left end is slidably inserted in the inside of the pump cylinder chamber, and a groove extending in the left-right direction is formed on the front surface of the operating member. The end of the bolt inserted from the front outer side of the pump body is preferably received in the groove.

According to the camshaft structure of the internal combustion engine according to the first aspect of the present invention configured as described above, the cam piece constituting the valve mechanism is provided on the cylinder chamber side with respect to the sprocket. It can be arranged close to the cylinder chamber side. Thereby, the valve mechanism is accommodated in a compact manner, and the internal combustion engine can be downsized.
Further, when a swash plate type air pump is attached to the cylinder block, if a swash plate member extending radially outward of the drive shaft is provided adjacent to the cam piece, the outer peripheral space of the cam piece is effectively utilized, and the cam shaft and the drive shaft The air pump can be attached without increasing the size of the internal combustion engine, such as shortening the distance between the shafts.
Further, the camshaft and the pump piston are arranged on the side of the cylinder by offsetting the swash plate member with respect to the camshaft on the side of the cylinder chamber and between the pump piston and the cylinder and the sprocket. In this case, the swash plate member can be efficiently arranged without interfering with these members by utilizing the empty space.
Thus, in the camshaft structure for an internal combustion engine according to the first aspect of the present invention, the internal combustion engine can be downsized.

The camshaft structure of the internal combustion engine according to the first aspect of the present invention has a pump gear train that transmits the rotation of the camshaft to a drive shaft and a swash plate member coupled to the drive shaft. And a pump driven gear meshed with the pump drive gear and coupled to the drive shaft, and the peripheral portion of the swash plate member is disposed so as to overlap the outer peripheral side of the pump drive gear as seen from the axial direction of the camshaft. It is preferable. With such an arrangement, the distance between the camshaft and the swash plate member can be shortened, and the arrangement space of these members can be reduced, that is, the internal combustion engine can be reduced in size.
In the camshaft structure of the internal combustion engine according to the first aspect of the present invention, a cam chain for rotating the camshaft is wound around the sprocket, and the peripheral portion of the swash plate member is the axis of the camshaft. As viewed from the direction, it is preferable that the cam chain is arranged so as to overlap with the outer peripheral side of the sprocket in a state where the cam chain is wound. With such an arrangement, the sprocket around which the cam chain is wound and the peripheral portion of the swash plate member can be brought closer to each other, so that the arrangement space of these members can be reduced, that is, the internal combustion engine can be reduced.
Further, the camshaft structure of the internal combustion engine according to the first aspect of the present invention has an operating member fastened to the left end face of the pump piston, and the operating members are located on the central axis of the pump piston and are respectively hemispherical. It is preferable that a holding portion for slidably receiving and holding the two shoes formed in a shape is provided, and the peripheral portion of the swash plate member is sandwiched between the two shoes received and held by the holding portion. By sandwiching the swash plate member between the two shoes in this way, the pump piston moves smoothly (linearly) following the peripheral edge of the swash plate member while ensuring the slidability of the swash plate member. Can do.
According to a first aspect of the present invention, there is provided a camshaft structure for an internal combustion engine, wherein an air pump includes a pump body having a pump cylinder chamber formed therein, and a pump head coupled to the pump body so as to cover an opening of the pump cylinder chamber. A pump piston having an operating member at the left end is slidably inserted in the inside of the pump cylinder chamber, and a groove extending in the left-right direction is formed on the front surface of the operating member. The end of the bolt inserted from the front outer side of the pump body is preferably received in the groove. Thereby, although it is a simple structure, the operation member is restricted from rotating around the axis of the pump piston.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 and 2 show an engine E having a camshaft structure for an internal combustion engine according to the present invention. In the following description, the directions of the arrow F and the arrow U in the drawings 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 4-stroke V-type 2-cylinder reciprocating engine mounted on a vehicle such as a motorcycle, and has a crankcase 2 that rotatably supports the crankshaft 11 and a V-shape above the crankcase 2. The cylinder blocks 3F, 3R and the cylinder blocks 3F, 3R before and after the pistons 12F, 12R are slidably inserted into the cylindrical cylinder chambers 21F, 21R which are tilted forward and backward and are opened up and down. The case body 1 is composed of front and rear cylinder heads 4F and 4R fastened to the top. Head covers 5F and 5R are attached to the cylinder heads 4F and 4R so as to cover the opening 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 repeatedly 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 near top dead center, the air-fuel mixture is ignited and burned by spark plugs 18F and 18R (see FIG. 5 for the rear cylinder head 4R side) attached to the cylinder heads 4F and 4R. 12F and 12R are moved 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. 2 to 6, the valve operating mechanisms 50 </ b> F and 50 </ b> R are swung by the camshafts 60 </ b> F and 60 </ b> R rotating with the intake-side and exhaust-side cams 63 and 64 and the intake-side cam 63. An intake side first rocker arm 51, an exhaust side first rocker arm 52 that swings following the exhaust side cam 64, an intake side second rocker arm 53 whose one end is in contact with the upper ends of the intake valves 15 F and 15 R, and one end Is provided between the exhaust-side second rocker arm 54 and the intake-side first and second rocker arms 51 and 53, the portion of which is in contact with the upper ends of the exhaust valves 16F and 16R. Provided between the intake-side push rod 55 that transmits to the second rocker arm 53 and the exhaust-side first and second rocker arms 52 and 54, the swinging motion of the exhaust-side first rocker arm 52 is eliminated. Composed of the exhaust-side push rod 56 for transmitting to the 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 intake-side and exhaust-side first rocker arms 51, 52 are provided with rollers 51a, 52a that come into contact with the intake-side and exhaust-side cams 63, 64 from above at one end, and the other ends are above the camshafts 60F, 60R. It is supported by rocker shafts 57a and 58a extending in parallel with the camshafts 60F and 60R. The intake-side and exhaust-side second rocker arms 53, 54 are swingably supported at their central portions by rocker shafts 57b, 58b disposed in the valve operating chambers 26F, 26R. Also, hook-shaped pressure receiving portions 51b and 52b that are open upward are provided at one end portions of the intake side and exhaust side first rocker arms 51 and 52, and the other ends of the intake side and exhaust side second rocker arms 53 and 54 are provided. The portion is provided with bowl-shaped pressure receiving portions 53b and 54b that open downward. On the other hand, both ends of the intake-side and exhaust-side push rods 55, 56 are spherical, and their lower ends are slidably fitted and received by the pressure-receiving portions 51b, 52b of the intake-side and exhaust-side first rocker arms 51, 52. Is slidably fitted and received by the pressure receiving portions 53b and 54b of the intake side and exhaust side second rocker arms 53 and 54.

  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 inside the cylinder blocks 3F, 3R, and the cylinder chambers 21F, 21R and the chain chambers 27F, 27F, 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 ends of the camshafts 60F and 60R are rotatably supported by bearings 67 that are attached to cover the openings 3c and are held by a shaft cover 8 that integrally forms the side walls 3b of the cylinder blocks 3F and 3R.

  Further, the valve operating mechanisms 50F and 50R are provided with chain transmission mechanisms 70F and 70R that reduce the rotation of the crankshaft 11 to 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 to maintain the function as a timing chain, and also 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 107 that transmits power to the drive shaft of the air pump 100.

  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 rear chain chamber 27R. The rear cam driven sprocket 72R is integrally formed with a plurality of arm portions 152, 152,... Extending from the side surface in a tongue-like shape, and the arm portions 152, 152 are sensed by the rotation of the rear cam driven sprocket 72R. The cam pulser 150 is configured to output a signal indicating the rotational position of the rear cam shaft 60R.

  By the way, the connecting rod 13F connected to the piston 12F of the front cylinder block 3F is pivotally connected to the right portion of the crank pin 11d, and the connecting rod 13R connected to the piston 12R of the rear cylinder block 3R is connected to the left portion of the crank pin 11d. The cylinder chamber 21F of the front cylinder block 3F is offset to the right with respect to the cylinder chamber 21R of the rear cylinder block 3R. That is, the front and rear chain chambers 27F and 27R are formed on the opposite sides with respect to the offset direction of the cylinder chambers 21F and 21R, respectively. On the other hand, the cam drive sprockets 71F and 71R are provided close to the outer surface of the crankcase 2, and the cam chains 73F and 73R extending in the axial direction of the cylinder chambers 21F and 21R are also connected to the left and right auxiliary chambers. 24, 25 and the left and right chain chambers 28A, 28B are provided along the wall surface of the crankcase 2.

  As described above, cam drive sprockets 71F and 71R are provided so as to avoid an increase in the shaft length of the crankshaft 11, but in the chain chambers 27F and 27R, cylinders are provided with respect to the cam driven sprockets 72F and 72R. A predetermined large space is secured on the side of the chambers 21F and 21R in combination with the offset of the cylinder chambers 21F and 21R.

  The intake side and exhaust side cams 63 and 64 and cam driven sprockets 72F and 72R are provided at intermediate portions of the camshafts 60F and 60R located in the chain chambers 27F and 27R. In this configuration example, the intake side and exhaust side cams 63 and 64 are provided on the cylinder chambers 21F and 21R side with respect to the cam driven sprockets 72F and 72R using the space, and the intake side and exhaust side first Other members constituting the valve operating mechanisms 50F, 50R such as the rocker arms 51, 52 and the intake side and exhaust side push rods 55, 56 are also arranged close to the cylinder chambers 21F, 21R.

  On the other hand, on the opposite side of the cylinder chambers 21F, 21R with respect to the cam driven sprockets 72F, 72R, a pump drive gear 107a is provided in the front camshaft 60F, and arm portions 152, 152, in the rear camshaft 60R. ... is extended. However, when these pump drive gears 107a and arm portions 152, 152,... Are provided on the camshafts 60F, 60R, the camshafts 60F, 60R are cams compared to the cylinder chambers 21F, 21R on which the components of the valve operating mechanisms 50F, 50R are disposed. There is no need to ensure a large shaft length of the shafts 60F and 60R, and the cam shafts 60F and 60R have a shorter protruding length from the cam driven sprockets 72F and 72R to the outside.

  As described above, in the configuration in which the camshafts 60F and 60R are supported on the sides of the cylinder chambers 21F and 21R, when the intake side and exhaust side cams 63 and 64 are arranged on the cylinder chambers 21F and 21R side, the valve operating mechanisms 50F and 50R. Can be disposed without projecting left and right outside. As a result, downsizing in the left-right direction is achieved mainly in the upper part of the engine E, such as the cylinder blocks 3F, 3R that support the camshafts 60F, 60R and the cylinder heads 4F, 4R in which the valve operating chambers 27F, 27R are formed. . In particular, in a V-type internal combustion engine in which a plurality of connecting rods 13F, 13R are pivotally connected to one crankpin 11d as in the engine E of this configuration example, the chain chambers 27F, 27R are arranged in the offset direction of the cylinder chambers 21F, 21R. On the other hand, by forming the intake side and exhaust side cams 63 and 64 on the cylinder chambers 21F and 21R side after being formed on the opposite side, it is possible to avoid an increase in the axial length of the crankshaft 11 and to avoid the V bank 1B. Can be prevented from increasing in size in the left-right direction.

  The air pump 100 driven by the front camshaft 60F is a swash plate type / reciprocating type pump, and includes a pump body 101 having a pump cylinder chamber 101a formed therein, and an opening of the pump cylinder chamber 101a in the pump body 101. And a pump piston 103 is slidably inserted in the pump cylinder chamber 101a.

  An opening is formed in the front cylinder block 3F in front of the upper part of the front chain chamber 27F. Further, the pump mounting rib 3d is formed so as to protrude forward and surround in a substantially rectangular shape and to position the opening inside. Is formed. The pump body 101 is aligned with the mating surface of the pump mounting rib 3d and fastened in front of the cylinder block 3F. As a result, the pump cylinder chamber 101a is disposed with its axis directed left and right (that is, in a direction parallel to the front camshaft 60F and orthogonal to the axis of the cylinder chamber 21F). The pump head 102 covers the left end opening of the pump cylinder chamber 101a in front of the front cylinder block 3F and is fastened to the pump body 101 from the left side. Thereby, a compression chamber 100a surrounded by the inner peripheral surface of the pump cylinder chamber 101a, the pump piston 103, and the pump head 102 is formed.

  The rotation of the front camshaft 60F is transmitted to the pump piston 103 via the pump drive mechanism 105, and reciprocates in the pump cylinder chamber 101a in the axial direction. The pump drive mechanism 105 is accommodated in a space surrounded by the pump body 101 and the front cylinder block 3F. The pump drive mechanism 105 extends parallel to the front camshaft 60F and is rotatably supported by the front cylinder block 3F and the pump body 101, and transmits the rotation of the front camshaft 60F to the drive shaft 106. The pump gear train 107, the swash plate 108 provided on the drive shaft 106 so as to be integrally rotatable, and the operating member 110 fixed to the pump piston 103 and connected to the swash plate 108.

  The pump mounting rib 3d is formed such that the left piece projects forward from the side wall 3b of the front cylinder block 3F, and the right piece has a chain chamber slightly more than the center line of the cylinder chamber 21F on the wall surface defining the cylinder chamber 21F. It is formed to project forward from the position displaced to the 27F side. That is, when the pump body 101 is attached to the front cylinder block 3F, the left end surface is substantially flush with the side wall 3b of the front cylinder block 3F, and the right end surface is substantially at the same position as the center of the cylinder chamber 21F.

  The drive shaft 106 is rotatably held by a bearing 121 provided on the front cylinder block 3F at the left end 106a, and a bearing 127 held on the mating surface between the front cylinder block 3F and the pump cover 101 at the right end 106b. It is supported rotatably.

  The pump gear train 107 includes a pump drive gear 107 a and a pump driven gear 107 b that meshes with the pump drive gear 107 a and is coupled to the drive shaft 106. The pump drive gear 107a is supported on the cylinder chamber 21F side with respect to the bearing 67 held by the shaft cover 8 on the front camshaft 60F. The outer peripheral side where is formed is offset outward. The left end portion 106a of the pump drive shaft 106 protrudes leftward from the bearing 121 and faces the inner wall surface of the pump body 101, and the pump driven gear 107b protrudes leftward from the bearing 121 on the drive shaft 106. It is provided in the part. Thus, the meshing portion of the pump drive gear 107a and the pump driven gear 107b are disposed close to the side wall 3b of the front cylinder block 3F and the inner wall surface of the pump body 101.

  A swash plate 108 extending in a direction inclined at a predetermined angle with respect to the axis orthogonal direction from the axis center is provided at the intermediate portion 106 c of the drive shaft 106. The swash plate 108 is disposed adjacent to the intake side of the camshafts 60F and 60R and in front of the exhaust side cams 63 and 64, and the peripheral edge portion 108a is close to the intake side and exhaust side cams 63 and 64. Further, the peripheral edge portion 108a of the swash plate 108 overlaps with the other end portion of the intake side first rocker arm 51 in a plan view, but is positioned below it so as not to interfere.

  The operating member 110 is fastened to the left end surface of the pump piston 103. The actuating member 110 is positioned on the central axis of the pump piston 103 in the assembled state with the pump piston 103, and each of the two hemispherical shoes 111, 111 is slidably received and held. Is provided. A peripheral portion 108 a of the swash plate 108 is sandwiched between the two shoes 111 and 111 received and held by the holding portion 112. Further, a groove extending in the left-right direction is formed on the front surface of the operating member 110, and an end portion of the bolt 114 inserted from the outer front surface of the pump body 101 is received inside the groove. As a result, the operation member 110 is restricted from rotating around the axis of the pump piston 103.

  The compression chamber 100a communicates with a suction port 102a formed inside the pump head 102 via a suction port 100b, and communicates with a discharge port 102b formed inside the pump head 102 via a discharge port 100c. Communicate. The suction port 102a opens above the pump head 102 and communicates with the outside, and an air introduction member (not shown) extending from the air cleaner is connected to the opening. Note that two suction ports 100b are formed side by side, and a reed valve (not shown) that opens when the compression chamber 100a becomes negative pressure is provided in each suction port 100b. The discharge port 102b is formed so as to penetrate the inside of the pump head 102 to the left and right. The discharge port 102b is provided with a poppet valve 116 including a disc-shaped valve body 117 that can be seated on a seating surface that extends radially outward from the discharge port 100c, and a spring 118 that biases the valve body 117 in the seating direction. It has been.

  In the air pump 100 configured as described above, the rotation of the crankshaft 11 is transmitted to the front camshaft 60F via the front chain transmission mechanism 70F, and the rotation of the front camshaft 60F is transmitted to the drive shaft 106 via the pump gear train 107. When transmitted, the drive shaft 106 rotates at the same speed as the crankshaft 11. When the swash plate 108 rotates in accordance with the rotation of the drive shaft 106, the peripheral edge portion 108a of the swash plate 108 is displaced in the left-right direction, and this displacement is transmitted to the operating member 110 via the shoe 111. 103 is reciprocated linearly left and right. When the pump piston 103 moves to the left from the right dead center, the inside of the compression chamber 100a becomes negative pressure, the reed valve opens, and the air that has passed through the air cleaner passes through the suction port 102b and the suction port 100b. Inhaled into 100a. When the pump piston 103 moves to the right from the left dead center, the reed valve is closed and the air sucked in the compression chamber 100a is compressed. When the compressed air exceeds a predetermined pressure, the valve element 117 of the poppet valve 116 moves to the right against the urging force of the spring 118 to open the discharge port 100c, and the compressed air is discharged to the discharge port 102b.

  The discharge port 102b communicates with a discharge passage (not shown) that is formed inside the pump head 102 and guides compressed air. The discharge passage extends downward from the discharge port 102b and bends to the right. And open to the outside. The lower part of the pump head 102 is fastened to the front cylinder block 3F, and the discharge passage communicates with an internal passage 130 formed in the front cylinder block 3F. The internal passage 130 extends rearward in the crankcase 2 and is bent upward to be divided into two. The two branched internal passages respectively extend inside the V bank 1B and open from the cylinder heads 4F, 4R to the valve operating chambers 26F, 26R. A piping member housed inside the valve operating chambers 26F, 26R is connected to the opening, and the piping member is connected to the compressed air inlets of the injectors 17F, 17R. Thus, fuel is injected from the injectors 17F and 17R into the combustion chambers 23F and 23R at high pressure using the compressed air discharged from the air pump 100.

  Now, the intake side and exhaust side cams 63 and 64 are in contact with the rollers 51a and 52a from the upper side, but the front, rear and lower sides are dead spaces. The intake-side first rocker arm 51 extends forward and upward from one end where the roller 51a is provided toward the other end supported by the rocker shaft 57a. In the air pump 100 configured as described above, the swash plate 108 uses the dead space formed on the outer periphery of the intake side and exhaust side cams 63 and 64 to avoid interference with the intake side first rocker arm 51 as much as possible to the peripheral portion 108a. Are arranged close to the intake side and exhaust side cams 63 and 64. As a result, the distance between the front camshaft 60F and the drive shaft 106 is shortened, so that the air pump 100 can be attached without reducing the forward protrusion amount of the air pump 100 and increasing the size of the engine E, and the pump gear train 107. Can be reduced in size and weight.

  The air pump 100 is of a swash plate type, and can secure a large amount of lateral movement of the pump piston 103 with respect to an air pump provided with, for example, a Scotch-yoke mechanism as a pump drive mechanism, and has a large stroke volume and a large discharge amount. An air pump can be provided. Further, the axis of the pump cylinder chamber 101a extends to the left and right (perpendicular to the axis of the cylinder chamber 21F), and even if the air pump 100 is made a swash plate type to ensure a large stroke volume, it does not protrude from the case body 1 to the left and right sides. As described above, both the discharge amount of the compressed air is ensured and the enlargement of the engine E is avoided.

  Next, the structure of the camshaft of the first configuration example will be described with reference to FIGS. The camshafts 60F and 60R are composed of a shaft member 61 whose outer shape is formed in a stepped cylindrical shape and a sprocket member 62 that forms cam-driven sprockets 72F and 72R.

  The shaft member 61 has both end portions 61a and 61b smaller in diameter than the intermediate portion 61c. The intermediate portion 61c of the shaft member 61 is integrally provided with the intake side and exhaust side cams 63 and 64 side by side in the axial direction at a position offset to the one end portion 61a side, and on the other end portion 61b side. A flange portion 61d protruding outward in the radial direction at the offset position is integrally formed. The shaft member 61 is formed with an axial hole 61e penetrating in the axial direction. The shaft member 61 extends in the radial direction from the axial hole 61e and has two diameters opened to the outer peripheral surfaces of the intake side and exhaust side cams 63 and 64. Direction holes 61f and 61f are formed.

  The sprocket member 62 is formed with a through-hole 62a having a diameter that allows the intake side and exhaust side cams 63 and 64 to be inserted in the center thereof and having a diameter smaller than that of the flange portion 61d. The sprocket member 62 of the front camshaft 60F is integrally provided with a pump drive gear 107a via an extending portion 62Fa that extends in the axial direction from the side surface of the front cam-driven sprocket 72F. Similarly, a plurality of arm portions 152, 152,... Are integrally formed on the sprocket member 62 of the rear camshaft 60R via extension portions 62Ra extending from the side surface of the rear cam driven sprocket 72R.

  In assembling the camshafts 60F and 60R, the cylinder blocks 3F and 3R are fastened to the crankcase 2, and the cam driven sprockets 72F and 72R around which the cam chains 73F and 73R are wound are attached to the chain chambers 27F and 27R. The bearing 66 is held on the inner wall 3a of the cylinder block 3F. Then, one end portion 61a of the shaft member 61 is inserted into the chain chambers 27F and 27R from the outside of the cylinder blocks 3F and 3R through the opening 3c. At this time, the shaft member 61 is inserted into the through hole of the sprocket member 62, the flange portion 61d is abutted against the side surfaces of the cam driven sprockets 72F and 72R, and one end portion 61a of the shaft member 61 is inserted into the bearing 66 to The member 61 is supported. At this time, the opening of the axial hole 61e of the shaft member 61 communicates with the lubricating oil passage extending inside the inner wall 3a of the cylinder block 3F, and the lubricating oil can be supplied to the axial hole 61e of the shaft member 61. The contact portions between the intake side and exhaust side cams 63 and 64 and the rollers 51a and 52a are lubricated through the holes 61f and 61f.

  A knock pin 68 is provided in advance on the side surfaces of the cam driven sprockets 72F and 72R, and when the shaft member 61 is inserted through the through hole 62a, the knock pin 68 is fitted into a pin insertion hole formed in the flange portion 61d. The sprocket member 62 is positioned in the circumferential direction and the axial direction with respect to the shaft member 61, and the shaft of the shaft member 61 and the shaft of the sprocket member 62 are aligned. In addition, in the state positioned in this way, the flange portion 61d is fitted inside the extending portions 62Fa and 62Ra. The shaft member 61 and the sprocket member 62 are fastened by a plurality of bolts 69 inserted from the outside of the flange portion 61d.

  Then, the shaft cover 8 is fastened to the side walls 3b of the cylinder blocks 3F and 3R from the outside so as to cover the opening 3c. At this time, a bearing 67 is previously held inside the shaft cover 8, and the other end portion 61 b of the shaft member 61 is inserted into the bearing 67. As described above, the valve mechanisms 50F and 50R and the air pump 100 are assembled in a state where the camshafts 60F and 60R are supported by the cylinder blocks 3F and 3R.

  According to this configuration example, since the sprocket member 62 forming the cam driven sprockets 72F and 72R is divided from the shaft member 61, the cam member can be simply inserted into the chain chambers 27F and 27R from the outside in the axial direction. The assembly of the shafts 60F and 60R and the assembly to the cylinder blocks 3F and 3R are performed at the same time, and the camshafts 60F and 60R can be easily assembled even if the arrangement space in the axial direction is narrow. Moreover, the opening 3c formed in the side wall 3b of the cylinder blocks 3F and 3R should just be set to the size which can penetrate the collar part 61d, and the collar part 61d is smaller in diameter than the diameter of the sprocket member 62. The shaft cover 8 covering the opening 3c can be downsized.

  Further, in the structure in which the intake side and exhaust side cams 63, 64 are integrally provided on the shaft member 61, the intake side and exhaust side cams 63, 64 are moved to the cylinder chambers 21F, 21R side with respect to the sprocket member 62 by the above assembly method. In order to dispose the sprocket member 62, a through hole 62a having a diameter larger than that of the central portion 61c of the shaft member 61 is formed in the sprocket member 62. For this purpose, a flange portion 61d is formed in the shaft member 61 to form a shaft of the sprocket member 62. Positioning with respect to the member 61 is performed. In the present configuration example, since the flange portion 61d is fitted to the extending portions 62Fa and 62Ra of the sprocket member 62, the entire camshafts 60F and 60R are not enlarged in the axial direction and the radial direction along with the positioning. The extension portions 62Fa and 62Ra are supported by the outer peripheral edge of the flange portion 61d, and the strength of the sprocket member 62 is ensured.

  Next, the structure of the camshaft of the second configuration example will be described with reference to FIGS. The camshafts 160F and 160R of this configuration example are configured by a shaft member 161 whose outer shape is formed in a stepped cylindrical shape, and a cylindrical member 165 fitted to the shaft member 161.

  The cylindrical member 165 is integrally provided with an intake side cam 163, an exhaust side cam 164, and cam driven sprockets 72 </ b> F and 72 </ b> R in order in the axial direction. In the front camshaft 60F, a pump drive gear 107a is integrally provided on the opposite side of the cam-driven sprockets 72F and 72R from the cam arrangement side. Similarly, also in the rear camshaft 60R, arm portions 152, 152,... Are integrally formed on the opposite side of the cam-driven sprockets 72F, 72R from the cam placement side. The cylindrical member 165 has a through hole extending in the axial direction at the center, and has two diameters extending in the radial direction from the through hole and opening on the outer peripheral surfaces of the intake side and exhaust side cams 163 and 164. Direction holes 165f and 165f are formed. Further, two grooves 165g and 165g extending in the circumferential direction are formed on the inner peripheral surface of the through hole, and the openings on the through hole side in the radial holes 165f and 165f are located inside the grooves 165g and 165g. .

  In the shaft member 161, one end portion 161a and an intermediate portion 161c are integrally formed with substantially the same diameter as the inner diameter of the cylindrical member 165, and the other end portion 161b is larger in diameter than the intermediate portion 161c. Further, a flange portion 161d having a diameter larger than that of the other end portion 161b is formed so as to partition the other end portion 161b and the intermediate portion 161c. The shaft member 161 is formed with an axial hole 161e penetrating in the axial direction, and formed with radial holes 161f and 161f that open to the grooves 165g and 165g when assembled with the cylindrical member 165. ing.

  When the camshafts 160F and 160R are assembled, the cam chains 73F and 73R are wound around the cam-driven sprockets 72F and 72R in advance, and are accommodated in the chain chambers 27F and 27R. A bearing 66 is held on the inner wall 3a.

  Then, the shaft member 161 is inserted into the chain chambers 27F and 27R from the one end portion 161a through the opening 3c from the outside of the cylinder blocks 3F and 3R, and the intermediate portion 161c of the shaft member 161 is inserted into the through hole of the cylindrical member 165. The one end portion 161 a is inserted into the bearing 66. At this time, the cam-side end surface of the cylindrical member 165 is abutted against the outer surface of the bearing 66, and the flange portion 161 c of the shaft member 161 is abutted against the sprocket-side end surface of the cylindrical member 165. Thereby, insertion of the shaft member 161 is regulated.

  When the insertion of the shaft member 161 is restricted, the axial hole 161e of the shaft member 161 communicates with the lubricating oil passage extending inside the inner walls 3a of the cylinder blocks 3F, 3R, and the radial holes 161f, 161 f opens into the grooves 165 g and 165 g of the cylindrical member 165. Thus, by forming the groove 165g, the axial hole 161e of the shaft member 161 and the radial hole 161f of the cylindrical member 165 communicate with each other even if the shaft member 161 and the cylindrical member 165 are not positioned in the circumferential direction. Can be made. As a result, the intake side and exhaust side cams 163 and 164 and the rollers 51a and 52a are lubricated.

  Then, the shaft cover 8 holding the bearing 67 in advance is fastened so as to cover the openings 3c of the cylinder blocks 3F and 3R. At this time, the shaft cover 8 holds the bearing 67 in advance, and the shaft cover 8 is attached so that the other end portion 161b of the shaft member 161 is inserted into the bearing 67. It abuts against the portion 161d. As a result, the camshafts 160F and 160R including the shaft member 161 and the cylindrical member 165 are held in the axial direction by the bearings 66 and 67.

  According to this configuration example, similarly to the first configuration example, since the cylindrical member 165 forming the cam driven sprockets 72F and 72R is divided from the shaft member 161, the cam shafts 160F and 160R can be easily assembled even in a narrow arrangement space. Can do. Further, since the shaft member 161 and the intake side and exhaust side cams 163 and 164 are divided, the intake side and exhaust side cams 163 and 164 are moved closer to the cylinder chambers 21F and 21R than the cam driven sprockets 72F and 72R. Even in the case of arrangement, it is not necessary to set the through hole provided in the cam driven sprockets 72F and 72R to a large diameter with respect to the intermediate portion 161c of the shaft member 161, and positioning fixing members such as knock pins and bolts are omitted, thereby reducing the number of parts. Can be reduced. In particular, since the sprocket member 162 and the intake side and exhaust side cams 163 and 164 are integrated as a cylindrical member 165, the shaft member 161 does not need to function as a member for transmitting power. For this reason, for example, a processing operation such as forming a spline groove for reliably transmitting the rotational driving force from the shaft side becomes unnecessary. In addition, since the outer peripheral surface of the shaft member 161 and the inner peripheral surface of the through hole of the cylindrical member 165 can be formed in a circular cross section, the lubricating oil path inside the shaft member 161 and the lubricating oil path inside the cylindrical member 165 Can be easily communicated. Moreover, the intake side and exhaust side cams 63 and 64 and the cam driven sprockets 72F and 72R are integrated, and it is not necessary to perform rotational alignment between them. Moreover, the opening 3c formed in the side wall 3b of the cylinder blocks 3F and 3R can be further reduced as compared with the first configuration example, and the shaft cover 8 can be further downsized.

  Next, the structure of the camshaft of the third configuration example will be described with reference to FIGS. The camshafts 260F and 260R in this configuration example are the same as the shaft member 261 in the second configuration example, the sprocket members 262 forming the cam driven sprockets 72F and 72R of the chain transmission mechanisms 70F and 70R, and the intake side and exhaust side cams 263. And a cam piece member 265 forming H.264.

  The sprocket member 262 and the cam piece member 265 are different from the cylindrical member 165 of the second configuration example in a portion where the cam drive sprockets 72F and 72R are provided and a portion where the intake side and exhaust side cams 63 and 64 are provided. Each is divided and has a through-hole extending in the axial direction at the center. In the sprocket member 262, the left and right mating surfaces with the cam piece member 265 and the side surfaces of the cam driven sprockets 72F and 72R on the cylinder chambers 21F and 21R side are substantially in the same plane. The pump drive gear 107a is integrally provided on the sprocket member 262 of the front camshaft 60F, and the arm portions 152, 152,... Are integrally formed on the sprocket member 262 of the rear camshaft 60R. In the cam piece member 265, radial holes 265f and 265f and grooves 265g and 265g are formed in the same manner as the cylindrical member 165 of the second configuration example.

  In assembling the camshafts 260F and 260R, the cam piece member 265 is previously accommodated in the cylinder chambers 21F and 21R in the chain chambers 27F and 27R, and the sprocket member 262 is accommodated outside in the chain chambers 27F and 27R. The bearing 66 is held on the inner wall 3a of the cylinder blocks 3F and 3R. Then, the shaft member 261 is inserted into the chain chambers 27F and 27R through the openings 3c formed in the side walls 3b of the cylinder blocks 3F and 3R. At this time, the intermediate portion 261 c of the shaft member 261 is inserted into the through hole of the cam piece member 265 and the sprocket member 262, and the one end portion 261 a is inserted into the bearing 66.

  Here, it is necessary to attach the sprocket member 262 and the cam piece member 265 by performing mutual rotation alignment. Spline grooves 261h, 261h are partially formed in the circumferential direction on the outer peripheral surface of the intermediate portion 261c of the shaft member 261, the inner peripheral surface of the through hole of the sprocket member 262, and the inner peripheral surface of the through hole of the cam piece member 265. 262h and 265h are formed, and the shaft member 261, the sprocket member 262, and the cam piece member 265 are coupled by spline fitting. Since the spline grooves 261h, 262h, and 265h are partially formed in this way, the sprocket member 262 and the cam piece member 265 are positioned in the rotational direction with respect to the shaft member 261 when the spline is fitted. In this manner, the rotational alignment of the sprocket member 262 and the cam piece member 265 is performed simultaneously with the passage of the shaft member 261 through the sprocket member 262 and the cam piece member 265.

  When the shaft member 261, the cam piece member 265, and the sprocket member 262 are spline-fitted in this manner, the cam piece member 265 and the sprocket member 262 are brought into contact with each other on the intermediate portion 261c of the shaft member 261, and the cam piece member 265 is contacted. The end surfaces of the cylinder chambers 21F and 21R are abutted against the side surface of the bearing 66, and the flange portion 261d of the shaft member 261 is abutted against the outer end surface of the sprocket portion 262. When the insertion of the shaft member 261 is restricted in this way, the shaft cover 8 that covers the opening 3c and holds the bearing 67 in advance is fastened to the cylinder blocks 3F and 3R. At this time, the other end portion 261b of the shaft member 261 is inserted into the bearing 67, and the side surface of the bearing 67 is abutted against the flange portion 261d.

  Also in the present configuration example, as in the second configuration example, a narrow arrangement space is provided even when the intake side and exhaust side cams 263 and 264 are disposed on the cylinder chambers 21F and 21R side with respect to the cam driven sprockets 72F and 72R. Even so, the camshafts 260F and 260R can be easily assembled, and the shaft cover 8 can be downsized. In this configuration example, it is necessary to align the rotational positions of the sprocket member 262 and the cam piece member 265, but the structure therefor is not limited to the above-described form. For example, a knock pin is provided between the surfaces where the sprocket member 262 and the cam piece member 265 are in contact with each other, and positioning in the rotational direction is performed between the sprocket member 262 and the cam piece member 265 in advance, and then the inside of the chain chamber. The form to accommodate may be sufficient.

  So far, the embodiment of the camshaft structure of the internal combustion engine according to the present invention has been described, but the present invention is not necessarily limited to the above configuration. For example, if it is an internal combustion engine in which the camshaft is disposed through the chain chamber of the cylinder block, it can be similarly applied to both a parallel type and a single cylinder.

1 is a right side sectional view of an engine provided with a cam chain tensioner mounting structure 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 plane sectional view of the front cylinder block which shows the attachment structure of the front camshaft of the 1st example of composition. It is sectional drawing of the rear bank which shows the attachment structure of the rear cam shaft of the 1st structural example. It is a plane sectional view of the back cylinder block which shows the attachment structure of the back camshaft of the 1st example of composition. It is sectional drawing of the front bank which shows the attachment structure of the front camshaft of the 2nd structural example. It is a plane sectional view of the rear cylinder block showing the mounting structure of the rear camshaft of the second configuration example. It is sectional drawing of the front bank which shows the attachment structure of the front camshaft of the 3rd structural example. It is a cross-sectional view of the rear cylinder block showing the mounting structure of the rear camshaft of the third configuration example.

Explanation of symbols

E Engine 1 Case body 3F, 3R Cylinder block 4F, 4R Cylinder head 11 Crankshaft 12F, 12R Piston 21F, 21R Cylinder chamber 26F, 26R Valve chamber 27F, 27R Chain chamber 50F, 50R Valve mechanism 60F, 60R Camshaft 61 Shaft member 62 Sprocket member 63 Intake side cam 64 Exhaust side cam 70F, 70R Chain transmission mechanism 80 Chain tensioner 100 Air pump 103 Pump piston 106 Drive shaft 108 Swash plate 160F, 160R Cam shaft 161 Shaft member 165 Cylindrical members 260F, 260R Cam shaft 261 Shaft member 262 Sprocket member 265 Cam piece member

Claims (5)

A cylinder block in which a cylinder chamber into which a piston is inserted is formed;
Located at the side of the cylinder chamber and disposed through a chain chamber formed in the cylinder block, one end portion thereof is rotatably supported by an inner wall of the cylinder block defining the cylinder chamber and the chain chamber. And a camshaft structure of an internal combustion engine having the other end portion rotatably supported on the side wall of the cylinder block,
A cam piece of a valve mechanism and a sprocket of a chain transmission mechanism that rotationally drives the camshaft are provided in an intermediate portion of the camshaft located in the chain chamber,
The cam piece is disposed on the cylinder chamber side with respect to the sprocket,
An air pump that discharges compressed air supplied to a predetermined location of the internal combustion engine is attached to the cylinder block,
A drive shaft provided parallel to the camshaft and rotatably provided; a swash plate member coupled to the drive shaft and extending radially outward of the drive shaft; and the swash plate It consists of a pump piston that reciprocates linearly in conjunction with the member,
The swash plate member is disposed adjacent to the cam piece;
The pump piston is arranged on the side of the cylinder chamber so as to be offset in the axial direction with respect to the camshaft in a direction sliding in the axial direction of the camshaft,
The camshaft structure for an internal combustion engine, wherein the swash plate member is disposed between the pump piston and the cylinder chamber and the sprocket. A pump gear train for transmitting rotation of the camshaft to the drive shaft and the swash plate member coupled thereto;
The pump gear train includes a pump drive gear and a pump driven gear meshed with the pump drive gear and coupled to the drive shaft.
2. The camshaft structure for an internal combustion engine according to claim 1, wherein a peripheral portion of the swash plate member is disposed so as to overlap an outer peripheral side of the pump drive gear when viewed from an axial direction of the camshaft. . A cam chain for rotating the camshaft is wound around the sprocket,
The peripheral portion of the swash plate member is disposed so as to overlap with the outer peripheral side of the sprocket in a state in which the cam chain is wound when viewed from the axial direction of the camshaft. The camshaft structure of the internal combustion engine according to 2. An actuating member fastened to the left end surface of the pump piston;
The actuating member is provided with a holding portion that is positioned on the central axis of the pump piston and that slidably receives and holds two shoes each formed in a hemispherical shape,
The cam of the internal combustion engine according to any one of claims 1 to 3, wherein a peripheral portion of the swash plate member is sandwiched between the two shoes received and held by the holding portion. Shaft structure. The air pump has a casing including a pump body in which a pump cylinder chamber is formed, and a pump head coupled to the pump body so as to cover an opening of the pump cylinder chamber. Inside the pump piston having the operating member on the left end is slidably inserted,
A groove extending in the left-right direction is formed on the front surface of the operating member,
The camshaft structure for an internal combustion engine according to any one of claims 1 to 4, wherein an end of a bolt inserted from the outside of the front surface of the pump body is received in the groove.

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