JP2015010595A - Engine, and saddle-riding type vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine capable of suppressing noises from a decompression mechanism, and a saddle-riding type vehicle.SOLUTION: An engine 1 comprises a decompression mechanism 70 and an oil supply mechanism 80. The decompression mechanism 70 is mounted on an exhaust cam shaft 62. In the case where the exhaust camshaft 62 is at or lower than a predetermined rotation number, the decompression mechanism 70 drives a pair of first exhaust valves 53 and a pair of second exhaust valves 55 through four exhaust valve cams 62a thereby opening the exhaust flows from first and second cylinders 21 and 22. An oil supply mechanism 80 feeds oil to the internal space 62S of the exhaust cam shaft 62 thereby force-feeding oil to the decompression mechanism 70.

Description

  The present invention relates to an engine having a decompression mechanism and a saddle-ride type vehicle.

  2. Description of the Related Art Conventionally, for the purpose of reducing engine starting load, a decompression mechanism that opens an exhaust valve for opening and shutting off an exhaust flow from a cylinder when starting the engine has been used (see, for example, Patent Document 1). The decompression mechanism is configured to operate smoothly with a small force by providing a sufficient clearance between the constituent members.

JP 2008-19845 A

  However, since the clearance is provided between the members of the decompression mechanism, there is a problem that noise is likely to be generated from the decompression mechanism during traveling.

  The present invention has been made in view of the above situation, and an object thereof is to provide an engine and a saddle-ride type vehicle that can suppress noise from the decompression mechanism.

  The engine according to the first aspect of the present invention includes a cylinder, an exhaust valve, an exhaust camshaft, a decompression mechanism, and an oil supply mechanism. The cylinder houses the piston. The exhaust valve opens and shuts off the exhaust flow from the cylinder. The exhaust camshaft is formed in a hollow shape and includes a valve cam for driving the exhaust valve. The decompression mechanism is attached to the exhaust camshaft. The decompression mechanism releases the exhaust flow from the cylinder by driving the exhaust valve via the valve operating cam when the exhaust cam shaft has a predetermined rotational speed or less. The oil supply mechanism feeds oil to the decompression mechanism by supplying oil to the internal space of the exhaust camshaft.

  An engine according to a second aspect of the present invention relates to the first aspect, and further includes an exhaust valve lifter that is driven by a valve cam and opens and closes the exhaust valve. The decompression mechanism includes a weight portion, a decompression shaft portion, and a decompression pin portion. The weight portion moves due to centrifugal force when the exhaust camshaft rotates at a rotational speed greater than a predetermined rotational speed. The decompression shaft portion is disposed in the internal space of the exhaust cam shaft, and rotates according to the movement of the weight portion. The decompression pin portion protrudes from a pin hole formed on the side surface of the exhaust camshaft and comes into contact with the exhaust valve lifter. The decompression pin portion retreats from the exhaust valve lifter according to the rotation of the decompression shaft portion.

  An engine according to a third aspect of the present invention relates to the second aspect, and the exhaust camshaft is formed on the first end portion, the second end portion, the central portion, and a side surface of the central portion. An oil inflow hole. The oil supply mechanism supplies oil to the internal space through the first oil inflow hole.

  An engine according to a fourth aspect of the present invention relates to the third aspect, and the exhaust camshaft has a second oil inflow hole facing the first oil inflow hole on the basis of the axis of the exhaust camshaft. The oil supply mechanism supplies oil to the internal space through the second oil inflow hole.

  An engine according to a fifth aspect of the present invention relates to the third or fourth aspect, and the exhaust camshaft has a sprocket fixed to the first end. The weight portion is attached to the sprocket and is in contact with the sprocket.

  An engine according to a sixth aspect of the present invention relates to the fifth aspect, and when the sprocket is viewed from the axial direction of the exhaust camshaft, the first end portion is disposed in the shaft hole opened on the central axis of the sprocket. The opening formed in is located.

  The engine according to the seventh aspect of the present invention is related to the fifth or sixth aspect, and the weight portion is located between the sprocket and the inner wall surface of the engine case where the sprocket faces.

  A saddle riding type vehicle according to an eighth aspect of the present invention relates to any one of the third to seventh aspects, and the exhaust camshaft has a closing plug that closes an opening formed at the second end.

  A saddle-ride type vehicle according to a ninth aspect of the present invention relates to any one of the third to eighth aspects, and the oil supply mechanism has a bearing portion that supports the exhaust camshaft. The bearing portion has an internal oil passage formed inside and an oil supply port facing the first oil inflow hole.

  A saddle-ride type vehicle according to a tenth aspect of the present invention relates to any one of the second to ninth aspects, and the decompression shaft portion includes a plurality of decompression shafts connected in the axial direction of the exhaust camshaft. The decompression pin portion includes a plurality of decompression pins connected to each of the plurality of decompression shafts.

  A saddle riding type vehicle according to an eleventh aspect of the present invention relates to any one of the fifth to tenth aspects, wherein the weight portion includes a first support shaft, a first weight body, a second support shaft, A second weight body. The first support shaft is parallel to the axial center of the exhaust cam shaft. The first weight body is rotatable about the first support shaft and is formed in a fan shape. The second support shaft is arranged in parallel with the rotation shaft and symmetrically with the first support shaft about the rotation shaft. The second weight main body is rotatable about the second support shaft and is formed in a fan shape. The first weight body and the second weight body are arranged symmetrically with respect to the axis.

  A saddle-ride type vehicle according to a twelfth aspect of the present invention includes the engine according to the first aspect of the present invention and a vehicle body frame that supports the engine.

  According to the engine according to the first aspect of the present invention, oil can be supplied to the decompression mechanism by the forced lubrication method, so that generation of mechanical noise from the decompression mechanism can be effectively suppressed. Therefore, it is possible to prevent the mechanical noise of the decompression mechanism from being noticeable even when the driving sound is low because the engine speed is low. In addition, for example, if a non-forced lubrication method that sprays oil droplets on the decompression mechanism is adopted, the oil is scattered by centrifugal force, so the decompression mechanism cannot be lubricated effectively. Can be lubricated up to.

  According to the engine of the second aspect of the present invention, the decompression pin can be forcibly retracted in response to the exhaust camshaft becoming larger than the predetermined rotational speed. Therefore, after the engine is started, the normal compression state can be restored accurately and promptly.

  According to the engine according to the third aspect of the present invention, the oil is supplied from the first oil inflow hole formed in the central portion of the exhaust camshaft, so that the oil can be efficiently filled into the internal space. At this time, since the oil is being pumped, the oil can flow toward the first and second weight portions even if the first oil inflow hole is formed in the central portion.

  According to the engine according to the fourth aspect of the present invention, oil can be continuously supplied from two opposing oil inflow holes. Therefore, compared to a case where oil is intermittently supplied from only the first oil inflow hole, A stable oil supply can be achieved.

  In the engine according to the fifth aspect of the present invention, mechanical noise is likely to be generated when the weight portion hits the sprocket, so that the effect of suppressing the mechanical noise by the forced lubrication method is particularly great.

  According to the engine of the sixth aspect of the present invention, oil can flow out from the opening, and oil can be efficiently supplied between the weight portion and the sprocket using centrifugal force.

  According to the engine of the seventh aspect of the present invention, even if oil supply to the weight portion sandwiched between the inner wall surface of the engine and the sprocket is difficult due to oil splashes, the weight portion is effective by the forced lubrication method. Can be lubricated.

  According to the engine of the eighth aspect of the present invention, oil can be prevented from flowing out of the opening even when the opening is directed downward when the saddle-ride type vehicle is made to stand on its side stand.

  According to the engine of the ninth aspect of the present invention, the oil can be pumped by using an oil supply mechanism that is generally used for lubricating the outer peripheral surface of the exhaust camshaft. An increase in the number of parts can be suppressed.

  With the engine according to the tenth aspect of the present invention, the operations of the plurality of decompression pins corresponding to the multiple cylinders can be synchronized.

  According to the engine of the eleventh aspect of the present invention, the exhaust camshaft can be rotated in a well-balanced manner by the first and second weight main bodies, so that the decompression is less than when the exhaust camshaft is driven by one weight main body. The mechanism can be driven smoothly.

  According to the saddle-ride type vehicle according to the eleventh aspect of the present invention, oil can be supplied to the decompression mechanism by the forced lubrication method, and therefore it is possible to effectively suppress the occurrence of mechanical noise from the decompression mechanism.

Top view of engine Top view of engine Exploded side view of engine partially seen through AA sectional view of FIG. BB sectional view of FIG. Cross section of exhaust camshaft and decompression mechanism Three views of the first decompression shaft Side view of the first decompression pin Three views of the second decompression shaft Side view of the second decompression pin Side view of decompression mechanism when engine 1 is started Side view of decompression mechanism after engine 1 is started CC sectional view of FIG. DD sectional view of FIG. Schematic diagram showing the configuration of the oil supply mechanism FIG. 4 is a partial enlarged view of the main part of FIG. FF sectional view of FIG. Left side view of saddle riding type vehicle

(Overall configuration of engine 1)
The overall configuration of the engine 1 according to the embodiment will be described with reference to the drawings. 1 and 2 are top views of the engine 1. In FIG. 1, the head cover 40 is omitted, and in FIG. 2, the head cover 40, the valve mechanism 50, and the valve mechanism 60 are omitted. FIG. 3 is an exploded side view of the engine 1 partially seen through. In FIG. 3, the cylinder body 20 is omitted. 4 is a cross-sectional view taken along line AA in FIG. 5 is a cross-sectional view taken along the line BB in FIG. 4 and 5, the spark plug is shown in the center of the drawing for easy understanding.

  The engine 1 is mounted on a saddle-ride type vehicle such as a motorcycle, an all-terrain vehicle, or a snowmobile. An example of the configuration of the saddle riding type vehicle equipped with the engine 1 will be described later. The engine 1 is supported by the body frame. The engine 1 according to this embodiment is a two-cylinder four-cycle engine that employs a four-valve DOHC system.

  The engine 1 includes a crankcase 10, a cylinder body 20, a cylinder head 30, a cylinder head cover 40, a valve mechanism 50, a valve mechanism 60, a decompression mechanism 70, and an oil supply mechanism 80.

  The crankcase 10 accommodates the crankshaft 11. The cylinder body 20 is connected to the crankcase 10. As shown in FIGS. 4 and 5, the cylinder body 20 includes a first cylinder 21 and a second cylinder 22. The first cylinder 21 accommodates the first piston 23 and forms a first combustion chamber 21S. The second cylinder 22 accommodates the second piston 24 and forms a second combustion chamber 22S. The crankshaft 11 is rotated by the reciprocating motion of the first piston 23 and the second piston 24. In FIGS. 1 and 2, a portion below the cylinder head 30 (including the first piston 23 and the second piston 24) is schematically illustrated.

  The cylinder head 30 is connected on the cylinder body 20. The cylinder head 30 has a first intake port 31, a first exhaust port 32, a second intake port 33, and a second exhaust port 34.

  The first intake port 31 has a pair of first intake ports 31S connected to the first combustion chamber 21S. The first exhaust port 32 has a pair of first exhaust ports 32S connected to the first combustion chamber 21S. The second intake port 33 has a pair of second intake ports 33S connected to the second combustion chamber 22S. The second exhaust port 34 has a pair of second exhaust ports 34S connected to the second combustion chamber 22S.

  The cylinder head 30 supports a head cap 86 that constitutes a part of the valve mechanism 50, the valve mechanism 60, the decompression mechanism 70, and the oil supply mechanism 80 on the top. A shaft support groove 30a (see FIG. 17) having a semicircular groove section is formed on the upper surface of the cylinder head 30 in order to rotatably support the exhaust camshaft 62.

  The cylinder head cover 40 is connected to the cylinder head 30. The cylinder head cover 40 covers the valve mechanism 50, the valve mechanism 60, the decompression mechanism 70, and the head cap 86.

  4 and 5, the valve mechanism 50 includes a pair of first intake valves 51, a pair of first intake valve lifters 52, a pair of first exhaust valves 53, and a pair of first exhaust valve lifters. 54, a pair of second intake valves 55, a pair of second intake valve lifters 56, a pair of second exhaust valves 57, and a pair of second exhaust valve lifters 58.

  The first intake valve 51 opens and blocks the air flow to the first cylinder 21. The first intake valve lifter 52 opens the first intake valve 51 each time it is pushed by the valve operating mechanism 60. The first exhaust valve 53 opens and blocks the exhaust flow from the first cylinder 21. The first exhaust valve lifter 54 opens the first exhaust valve 53 each time it is pushed by the valve mechanism 60.

  The second intake valve 55 opens and closes the air flow to the second cylinder 22. The second intake valve lifter 56 opens the second intake valve 55 each time it is pushed by the valve mechanism 60. The second exhaust valve 57 opens and blocks the exhaust flow from the second cylinder 22. The second exhaust valve lifter 58 opens the second exhaust valve 57 each time it is pushed by the valve mechanism 60.

  The valve mechanism 60 includes an intake cam shaft 61, an exhaust cam shaft 62, a first sprocket 63, a second sprocket 64, and a cam chain 65.

  The intake camshaft 61 is disposed above the pair of first intake valve lifters 52 and the pair of second intake valve lifters 56. Four intake valve cams 61 a are attached to the intake cam shaft 61. The four intake valve cams 61 a press the pair of first intake valve lifters 52 and the pair of second intake valve lifters 56. Thereby, opening and closing of the pair of first intake valves 51 and the pair of second intake valves 55 is controlled.

  The exhaust camshaft 62 is disposed above the pair of first exhaust valve lifters 54 and the pair of second exhaust valve lifters 58. Four exhaust valve cams 62 a are attached to the exhaust cam shaft 62. The four exhaust valve cams 62 a press the pair of first exhaust valve lifters 54 and the pair of second exhaust valve lifters 58. Thereby, opening / closing of the pair of first exhaust valves 53 and the pair of second exhaust valves 57 is controlled.

  The exhaust cam shaft 62 is formed in a hollow shape. A decompression mechanism 70 is attached to the exhaust camshaft 62. The detailed configuration of the exhaust camshaft 62 will be described later.

  The first sprocket 63 is attached to the first end 611 of the intake camshaft 61. The second sprocket 64 is attached to the first end 621 of the exhaust camshaft 62. The cam chain 65 is wound around the first sprocket 63, the second sprocket 64, and the crankshaft 11.

  When the cam chain 65 is rotated by the crankshaft 11, the intake camshaft 61 connected to the first sprocket 63 rotates, and the exhaust camshaft 62 connected to the second sprocket 64 rotates. In response, the pair of first intake valves 51 opens and closes the pair of second intake valves 55, and the pair of first exhaust valves 53 and the pair of second exhaust valves 57 opens and closes.

  The decompression mechanism 70 is attached to the exhaust camshaft 62. A part of the decompression mechanism 70 is accommodated in the exhaust camshaft 62. The decompression mechanism 70 reduces the compression pressure in the first combustion chamber 21S and the second combustion chamber 22S when the engine 1 is started. Thereby, since the force required for cranking is reduced, a small and light starter motor or battery can be used. The decompression mechanism 70 returns the inside of the first combustion chamber 21S and the second combustion chamber 22S to a normal compression state after the engine 1 is started.

  Specifically, the decompression mechanism 70 drives the pair of first exhaust valves 53 via the two exhaust valve cams 62a in the compression stroke by the first piston 23 when the exhaust cam shaft 62 has a predetermined rotation speed or less. The exhaust flow from the first cylinder 21 is released. The decompression mechanism 70 drives the pair of second exhaust valves 57 via the remaining two exhaust valve cams 62a in the compression stroke by the second piston 24 when the exhaust cam shaft 62 has a predetermined rotation speed or less. The exhaust flow from the cylinder 22 is released. The decompression mechanism 70 stops the release of the exhaust flow during the compression stroke of the first and second cylinders 21 and 22 when the exhaust camshaft 62 becomes larger than the predetermined rotational speed. A detailed configuration of the decompression mechanism 70 will be described later.

  A head cap 86 constituting the oil supply mechanism 80 is disposed on the valve operating mechanism 60. The oil supply mechanism 80 supplies oil to the decompression mechanism 70 by supplying oil to the internal space 62S (see FIG. 6) of the exhaust camshaft 62 from the start of the engine 1. That is, the oil supply mechanism 80 supplies oil to the decompression mechanism 70 by a forced lubrication method.

  The oil supply mechanism 80 supplies oil not only to the decompression mechanism 70 but also to the outer surfaces of the intake cam shaft 61 and the exhaust cam shaft 62. Thereby, smooth rotation driving of the intake cam shaft 61 and the exhaust cam shaft 62 is maintained. The configuration of the decompression mechanism 70 and the oil supply mechanism 80 will be described later.

(Configuration of exhaust camshaft 62 and decompression mechanism 70)
Next, the configuration of the exhaust camshaft 62 and the decompression mechanism 70 will be described with reference to the drawings. 6 is a cross-sectional view of the exhaust camshaft 62 and the decompression mechanism 70 (cross-sectional view taken along line EE in FIG. 11). 7 to 10 are single views of components constituting the decompression mechanism 70. FIG. FIG. 11 is a side view of the decompression mechanism 70 when the engine 1 is started. 6 and 11 illustrate a state when the engine 1 is stopped or started, that is, a state where the exhaust camshaft 62 is equal to or lower than a predetermined rotational speed.

  In the following description, the direction in which the axial center AX of the exhaust cam shaft 62 extends is referred to as “axial direction”, and the direction orthogonal to the axial center AX is referred to as “radial direction”. Hereinafter, the configuration of the exhaust camshaft 62 and the decompression mechanism 70 will be described, and the operation of the decompression mechanism 70 will be described later.

1. Configuration of Exhaust Cam Shaft 62 The exhaust cam shaft 62 includes a first end 621, a second end 622, a central portion 623, a through hole 624, and a closing plug 625.

  A second sprocket 64 is attached to the outer periphery of the front end of the first end 621. As shown in FIG. 6, the end surface of the first end 621 is positioned slightly inside the outer surface of the second sprocket 64. The first end 621 has a first journal side surface 621S.

  The second end 622 is provided opposite to the first end 621 with the central portion 623 interposed therebetween. Two exhaust valve cams 62 a for driving the pair of first exhaust valves 53 are attached to the second end portion 622. The second end 622 has a second journal side surface 622S formed between the two exhaust valve cams 62a.

  The central portion 623 is continuous with the first end 621 and the second end 622. Two exhaust valve cams 62 a for driving the pair of second exhaust valves 57 are attached to the central portion 623. The central portion 623 has a third journal side surface 623S formed between the two exhaust valve cams 62a. A first oil inflow hole OH1 and a second oil inflow hole OH2 are formed in the third journal side surface 623S. The first oil inflow hole OH1 and the second oil inflow hole OH2 are formed at symmetrical positions so as to face each other with respect to the axis AX. Oil is pumped from the oil supply mechanism 80 (see FIG. 3) to the first oil inflow hole OH1 and the second oil inflow hole OH2.

  A pair of first pin holes PH1 are formed on the side surface of the central portion 623 so as to be adjacent to the exhaust valve cam 62a. The pair of first pin holes PH1 are formed at symmetrical positions with respect to the axis AX. That is, the pair of first pin holes PH1 are formed in a straight line along the radial direction.

  Similarly, a pair of second pin holes PH2 is formed so as to be adjacent to the exhaust valve cam 62a located on the central portion 623 side of the second end portion 622. The pair of second pin holes PH2 are formed at symmetrical positions with respect to the axis AX. That is, the pair of second pin holes PH2 are formed on a straight line along the radial direction.

  The through hole 624 penetrates the first end 621, the second end 622, and the center 623 in the axial direction. A first opening 621P of the through hole 624 is formed in the first end 621, and a second opening 622P of the through hole 624 is formed in the second end 622. The first opening 621P is located inside the shaft hole 64S (see FIG. 11) of the second sprocket 64 when the second sprocket 64 is viewed from the axial direction. The through hole 624 forms an internal space 62S extending in the axial direction. A part of the decompression mechanism 70 is accommodated in the internal space 62S. Oil is pumped into the internal space 62S from the first oil inflow hole OH1 and the second oil inflow hole OH2.

  The blocking plug 625 is attached to the second end 622 so as to block the second opening 622P. As the closing plug 625, for example, a metal or rubber cap can be used. In the present embodiment, the axis AX substantially coincides with the vehicle width direction (that is, the left-right direction) of the saddle riding type vehicle, and when the saddle riding type vehicle is self-supported by the side stand, the second end 622 is the first It is assumed that it is lower than the end 621. Since the blocking plug 625 blocks the second opening 622P, oil does not flow out from the second opening 622P even if the saddle-ride type vehicle is made to stand on its own by the side stand.

2. Configuration of Decompression Mechanism 70 The decompression mechanism 70 includes a first decompression shaft 71, a first decompression pin 72, a second decompression shaft 73, a second decompression pin 74, a first weight portion 75, a second weight portion 76, Have The first decompression shaft 71 and the second decompression shaft 73 constitute a “decompression shaft portion” according to this embodiment, and the first decompression pin 72 and the second decompression pin 74 constitute a “decompression pin portion” according to this embodiment.

2-1. First decompression shaft 71 and first decompression pin 72
As shown in FIG. 6, the first decompression shaft 71 is arranged along the axial direction in the internal space 62 </ b> S. As shown in FIG. 7A, the first decompression shaft 71 has a base end portion 71a, a rod 71b, and a disk 71c.

  The base end portion 71 a is disposed in the first opening 621 </ b> P of the exhaust cam shaft 62. However, since the outer diameter of the base end portion 71 a is smaller than the inner diameter of the through hole 624, a gap is provided between the outer peripheral surface of the base end portion 71 a and the inner peripheral surface of the exhaust cam shaft 62. As shown in FIG. 7B, an engagement groove 71d is formed on the end surface of the base end portion 71a. The engaging groove 71d is formed linearly along the radial direction.

  The rod 71b is connected to the base end portion 71a and extends in the axial direction. The rod 71b has a smaller diameter than the base end 71a and the disk 71c.

  The disc 71c is connected to the tip of the rod 71b. Since the outer diameter of the disc 71 c is substantially equal to the outer diameter of the base end portion 71 a, a gap is provided between the outer peripheral surface of the disc 71 c and the inner peripheral surface of the exhaust cam shaft 62. A locking projection 71e is formed on the end surface of the disk 71c. As shown in FIG. 7C, the locking projection 71e is arranged at a position eccentric from the axis AX. As shown in FIG. 7C, a connecting groove 71f is formed on the side surface of the disk 71c. The connecting groove 71f is formed so as to penetrate the disk 71c in the axial direction. The connecting groove 71f is formed at a position away from the locking projection 71e in the circumferential direction centered on the axis AX.

  The first decompression pin 72 is formed in a rod shape. As shown in FIG. 6, the first decompression pin 72 is adjacent to the exhaust valve cam 62a. The first decompression pin 72 is inserted through a pair of first pin holes PH1 formed in the exhaust camshaft 62. The first decompression pin 72 projects outward from each of the pair of first pin holes PH1. As shown in FIG. 8, a locking recess 72 a is formed on the side surface of the first decompression pin 72. The locking convex portion 71e of the first decompression shaft 71 is locked to the locking concave portion 72a. The distal end portion 72E of the first decompression pin 72 is subjected to curved surface processing.

2-2. Second decompression shaft 73 and second decompression pin 74
As shown in FIG. 6, the second decompression shaft 73 is arranged along the axial direction in the internal space 62 </ b> S. As shown in FIG. 9A, the second decompression shaft 73 has a base end portion 73a, a rod 73b, and a disk 73c.

  The base end portion 73 a is disposed so as to face the disk 71 c of the first decompression shaft 71. A first decompression pin 72 is disposed between the base end portion 73a and the disk 71c. Since the outer diameter of the base end portion 73 a is smaller than the inner diameter of the through hole 624, a gap is provided between the outer peripheral surface of the base end portion 73 a and the inner peripheral surface of the exhaust cam shaft 62. A connection pin 73d is formed on the end surface of the base end portion 73a. As shown in FIG. 9B, the connecting pin 73d is disposed at a position eccentric from the axis AX. The connecting pin 73d extends from the end surface of the base end portion 73a toward the first decompression shaft 71 side. The connection pin 73 d passes through the side of the first decompression pin 72 and is inserted into the connection groove 71 f of the first decompression shaft 71.

  The rod 73b is connected to the base end portion 73a and extends in the axial direction. The rod 73b has a smaller diameter than the base end portion 73a and the disk 73c. A first oil inflow hole OH1 and a second oil inflow hole OH2 are located on the side of the rod 73b.

  The disk 73c is connected to the tip of the rod 73b. Since the outer diameter of the disk 73 c is substantially equal to the outer diameter of the base end portion 73 a, a gap is provided between the outer peripheral surface of the disk 73 c and the inner peripheral surface of the exhaust cam shaft 62. On the end surface of the disk 73c, as shown in FIG. 9C, a locking projection 73e is formed.

  The second decompression pin 74 is formed in a rod shape. As shown in FIG. 6, the second decompression pin 74 is adjacent to the exhaust valve cam 62a. The second decompression pin 72 is inserted through a pair of second pin holes PH <b> 2 formed in the exhaust camshaft 62. The second decompression pin 74 projects outward from each of the pair of second pin holes PH2. On the side surface of the second decompression pin 74, a locking recess 74a is formed as shown in FIG. The locking convex portion 73e of the second decompression shaft 73 is locked to the locking concave portion 74a. The distal end portion 74E of the second decompression pin 74 is subjected to curved surface processing.

2-3. First weight portion 75 and second weight portion 76
The first weight portion 75 and the second weight portion 76 are located between the inner wall surface of the engine 1 and the second sprocket 64 (see FIG. 3). The first weight portion 75 and the second weight portion 76 are close to the inner wall surface of the engine 1 and abut against the second sprocket 64.

  As shown in FIG. 11, the first weight portion 75 includes a first weight body 75a, a first support shaft 75b, a first return spring 75c, a first elongated hole 75d, and a first drive pin 75e. Have.

  The first weight main body 75 a is disposed on the outer surface of the second sprocket 64. The first weight body 75a is a stepped plate-like member formed in a fan shape or a blade sickle shape. The first stage 75a1 of the first weight body 75a is rotatably supported by the first support shaft 75b and is inserted through the first drive pin 75e so as to be relatively rotatable. The second stage 75a2 of the first weight body 75a is disposed so as to avoid the first support shaft 75b and the fixing bolt 62a that fixes the second sprocket 64 to the exhaust camshaft 62.

  The first support shaft 75b is disposed at a position away from the axis AX. The first support shaft 75b is a shaft member centering on a first shaft 75P parallel to the axis AX. The first support shaft 75b supports the first weight body 75a so as to be rotatable about the first shaft 75P.

  The first return spring 75c is connected to the second sprocket 64 and the first weight body 75a. The first return spring 75c biases the first weight body 75a and holds it in the initial position shown in FIG. However, as will be described later, the biasing force of the first return spring 75c is smaller than the centrifugal force applied to the first weight body 75a after the engine 1 is started.

  The first elongated hole 75d is formed in the first weight main body 75a along a direction that obliquely intersects the radial direction. A stopper 64b protruding from the outer surface of the second sprocket 64 is inserted into the first long hole 75d. The stopper 64b abuts against the inner surface of the first long hole 75d, so that the rotation width of the first weight body 75a is restricted.

  The first drive pin 75e is inserted through the first weight body 75a. The first drive pin 75e is disposed near the axis AX. The first drive pin 75e protrudes toward the first opening 621P of the exhaust camshaft 62. The distal end portion of the first drive pin 75 e is engaged with the engagement groove 71 d of the first decompression shaft 71.

  As shown in FIG. 11, the second weight portion 76 includes a second weight body 76a, a second support shaft 76b, a second return spring 76c, a second long hole 76d, and a second drive pin 76e. Have. The second weight portion 76 has the same configuration as the first weight portion 75. The second weight portion 76 is disposed at a position obtained by rotating the first weight portion 75 by 180 ° around the axis AX. Accordingly, the second weight main body 76a is arranged point-symmetrically with the first weight main body 75a with the axis AX as the center.

(Operation of decompression mechanism 70)
The operation of the decompression mechanism 70 will be described with reference to the drawings. FIG. 12 is a side view of the decompression mechanism 70 after the engine 1 is started. 13 is a cross-sectional view taken along the line CC of FIG. 14 is a cross-sectional view taken along the line DD of FIG. FIGS. 13A and 14A show a state when the engine 1 is stopped or started, that is, a state where the exhaust camshaft 62 is equal to or lower than a predetermined rotational speed. FIGS. 13B and 14B show a state after the engine 1 is started, that is, a state in which the exhaust camshaft 62 is larger than a predetermined rotational speed.

  First, while the exhaust camshaft 62 is equal to or lower than the predetermined rotation speed, the first and second weight bodies 75a and 76a are held at the initial positions by the urging forces of the first and second return springs 75c and 76c (FIG. 11). reference).

  At this time, as shown in FIG. 13A, the first decompression pin 72 protrudes outward from the exhaust valve cam 62a, and the tip 72E of the first decompression pin 72 pushes the second exhaust valve lifter 58. . As a result, the second exhaust valve 57 is opened in the compression stroke, and the exhaust flow is released from the second cylinder 22.

  Similarly, as shown in FIG. 14A, the second decompression pin 74 projects outward from the exhaust valve cam 62a, and the tip 74E of the second decompression pin 74 pushes the first exhaust valve lifter 54. . As a result, the first exhaust valve 53 is opened in the compression stroke, and the exhaust flow is released from the first cylinder 21.

  Next, when the rotational speed of the exhaust camshaft 62 increases and becomes larger than the predetermined rotational speed, the centrifugal force applied to the first and second weight bodies 75a and 76a is biased by the first and second return springs 75c and 76c. Bigger than. Due to this centrifugal force, the first and second weight bodies 75a and 76a cause the first and second support shafts 75b and 76b to move until the stopper 64b abuts against the inner surface of the first elongated hole 75d, as shown in FIG. Move outward as the center.

  When the first and second weight bodies 75a and 76a move, the first and second drive pins 75e and 76e attached to the first and second weight bodies 75a and 76a rotate around the axis AX. When the first and second drive pins 75e and 76e rotate, the first decompression shaft 71 engaged with the first and second drive pins 75e and 76e rotates about the axis AX. When the first decompression shaft 71 rotates, the second decompression shaft 73 connected to the first decompression shaft 71 via the connection pin 73d (see FIG. 9) rotates about the axis AX.

  At this time, when the first decompression shaft 71 rotates, as shown in FIG. 13 (b), the first decompression pin 72 locked to the locking projection 71e of the first decompression shaft 71 becomes the second exhaust valve lifter. Retreat from 58. That is, the first decompression pin 72 is retracted inside the exhaust valve cam 62a, and the tip 72E of the first decompression pin 72 is not in contact with the second exhaust valve lifter 58. As a result, the second exhaust valve 57 is closed in the compression stroke, and the second cylinder 22 returns to the normal compression state.

  Similarly, when the second decompression shaft 73 rotates, as shown in FIG. 14 (b), the second decompression pin 74 latched to the latching convex portion 73e of the second decompression shaft 73 becomes the first exhaust valve lifter. Retreat from 54. That is, the second decompression pin 74 is retracted inside the exhaust valve cam 62a, and the tip end portion 74E of the second decompression pin 74 does not contact the first exhaust valve lifter 54. As a result, the first exhaust valve 53 is closed in the compression stroke, and the first cylinder 21 returns to the normal compression state.

  As described above, the decompression mechanism 70 reduces the compression pressure in the first and second cylinders 21 and 22 when the engine 1 is started, and after the engine 1 is started, normally the inside of the first and second cylinders 21 and 22 is maintained. Return to the compressed state.

(Configuration of oil supply mechanism 80)
The configuration of the oil supply mechanism 80 will be described with reference to the drawings. FIG. 15 is a schematic diagram showing the configuration of the oil supply mechanism 80. FIG. 16 is an enlarged view of a main part of FIG. 3 and a partial cross-sectional view showing the configuration of the oil supply mechanism 80. 17 is a cross-sectional view taken along line FF in FIG. 16 corresponds to the GG cross-sectional view of FIG.

  The oil supply mechanism 80 includes an oil pump 81, an external oil passage 82, a gasket 83, and a bearing portion 84.

  The oil pump 81 is accommodated in the crankcase 10. The oil pump 81 sucks up oil from an oil tank (not shown) and pumps it to the external oil passage 82.

  The external oil passage 82 is formed inside the crankcase 10, the cylinder body 20, and the cylinder head 30. The external oil passage 82 is connected to the oil pump 8 and the internal oil passage 90. The oil pumped from the oil pump 81 is supplied to the bearing portion 84 via the external oil passage 82. The external oil passage 82 is also connected to the intake camshaft 61.

  The gasket 83 is provided in the middle of the external oil passage 82. The gasket 83 has a function of restricting the flow rate of oil flowing through the external oil passage 82. Thereby, even if the capacity of the oil pump 81 fluctuates, the pressure of the oil supplied to the internal oil passage 90 can be kept constant.

  The bearing portion 84 rotatably supports the journal of the exhaust cam shaft 62. The bearing portion 84 includes the above-described head cap 86 and journal bearings 85a, 85b, and 85c.

  As shown in FIG. 17, the head cap 86 has a cross section perpendicular to the axial direction, the beam section 87 having a bell-shaped cross section, and a lower part of the beam section 87, and the cross section has a gate shape. The arch portions 88a, 88b, 88c, the internal oil passage 90, and the first to third oil supply ports 84a to 84c are provided. As shown in FIG. 16, the arch portions 88a, 88b, 88c are formed at intervals in the axial direction, and are located at positions corresponding to the first journal side surface 621S, the second journal side surface 622S, and the third journal side surface 623S. They are formed in the above order. The arch portions 88a, 88b, 88c are formed with recesses 88S each having a semicircular shape in a cross section orthogonal to the axial direction (see FIG. 17). The head cap 86 is connected to the upper surface of the cylinder head 30.

  The journal bearings 85a, 85b, and 85c are configured by arch portions 88a, 88b, and 88c and a shaft support groove 30a on the upper surface of the cylinder head 30, respectively. The journal bearings 85 a, 85 b, 85 c have a perfect circular hole 89 formed by the respective recesses 88 </ b> S of the arch portions 88 a, 88 b, 88 c and the shaft support groove 30 a, and are inserted into the circular holes 89. The exhaust camshaft 62 thus supported is rotatably supported.

  The internal oil passage 90 includes a semicircular passage 91, a first introduction passage 92, a second introduction passage 93, a main passage 94, a second end branch passage 95, and a center portion branch passage 96. .

  The semicircular channel 91 extends in a semicircular arc shape along the exhaust camshaft 62 in the vicinity of the sprocket 64. The semicircular channel 91 communicates with the external oil channel 82.

  The first introduction channel 92 extends from the upper part of the semicircular channel 91 so as to be separated from the sprocket 64 along the axial direction.

  The second introduction flow path 93 extends from the upper part of the first introduction flow path 92 toward the beam portion 87.

  The main channel 94 communicates with the second introduction channel 93 and extends in the axial direction inside the beam portion 87. The main flow path 94 extends from one end portion of the beam portion 87 to the other end portion so as to be positioned above the arch portions 88a, 88b, 88c. The main flow path 94 is provided with a plug 97 at one end.

  The second end branch channel 95 extends in the radial direction from the main channel 94 and communicates with a second oil supply port 84b formed in the recess 88S of the arch 88b.

  The central branch channel 96 extends from the main channel 94 in the radial direction and communicates with a third oil supply port (oil supply port) 84c formed in the recess 88S of the arch portion 88c. The recess 88S is formed with an oil reservoir 88x that is formed in an arc shape when viewed in the cross section orthogonal to the axial direction and is further depressed toward the main flow path 94 side.

  The first oil supply port 84a allows the end portion of the first introduction flow path 92 and the oil reservoir 88x of the arch portion 88a to communicate with each other. The oil that has flowed out of the first oil supply port 84a into the journal bearing 85a lubricates the first journal side surface 621S.

  The second oil supply port 84b opens to the oil reservoir 88x in the recess 88S of the arch portion 88b, and faces the second journal side surface 622S of the exhaust camshaft 62. The oil that has flowed out of the second oil supply port 84b into the journal bearing 85b lubricates the second journal side surface 622S.

  The third oil supply port 84c opens to the oil reservoir 88x in the concave portion 88S of the arch portion 88c, and faces the third journal side surface 623S of the exhaust cam shaft 62. The oil flowing out from the third oil supply port 84c lubricates the third journal side surface 623S and is pumped to the internal space 62S from the first and second oil inflow holes OH1 and OH2 formed in the third journal side surface 623S. . The third oil supply port 84 c faces the second journal side surface 622 </ b> S of the exhaust cam shaft 62. The oil that flows out from the third oil supply port 84c lubricates the second journal side surface 622S.

  The oil pressure-fed into the internal space 62S from the first and second oil inflow holes OH1 and OH2 lubricates the first and second decompression shafts 71 and 73 and the first and second decompression pins 72 and 74 in the internal space 62S. It will be filled. After that, when the internal space 62S is filled with oil, the second opening 622P is blocked by the closing plug 625, so that the pumped oil is pushed out from the first opening 621P. The oil pushed out from the first opening 621P spreads in the gap between the second sprocket 64 and the first and second weight bodies 75a and 76a by centrifugal force. Thereby, the clearance gap between the 2nd sprocket 64 and the 1st and 2nd weight main bodies 75a and 76a is lubricated.

(Schematic configuration of the saddle riding type vehicle 100)
A schematic configuration of the saddle riding type vehicle 100 equipped with the engine 1 described above will be described with reference to the drawings. FIG. 18 is a side view of the saddle riding type vehicle 100.

  The saddle riding type vehicle 100 is a motorcycle. As shown in FIG. 18, the saddle riding type vehicle 100 includes a frame 110, a front fork 120, a front wheel 130, a swing arm 140, a rear wheel 150, and the engine 1.

  The frame 110 includes a head pipe 111, a front frame 112, and a pair of down tubes 113 and 113. The head pipe 111 is disposed at the center of the vehicle body in the vehicle width direction. The head pipe 111 extends in the vertical direction. The front frame 112 extends rearward and downward from the head pipe 111. The front frame 112 is arranged so as to go around from the upper side of the engine 1 to the rear side. A lower end portion of the front frame 112 is connected to the engine 1. The pair of down tubes 113 are connected to the head pipe 111 below the front frame 112. Each of the pair of down tubes 113 and 113 extends away from the head pipe 111 toward the rear and downward. A rear end portion of each of the pair of down tubes 113 and 113 is connected to a front portion of the engine 1.

  The front fork 120 is rotatably supported by the head pipe 111. A front wheel 130 is rotatably supported on the lower end portion of the front fork 120.

  The swing arm 140 is swingably supported on the lower end portion of the front frame 112. A rear wheel 150 is rotatably supported at the rear end of the swing arm 140.

  The engine 1 is supported by a lower end portion of the front frame 112 and a rear end portion of each of the pair of down tubes 113 and 113.

(Function and effect)
(1) The engine 1 according to this embodiment includes a decompression mechanism 70 and an oil supply mechanism 80. The decompression mechanism 70 is attached to the exhaust camshaft 62. The decompression mechanism 70 drives the pair of first exhaust valves 53 and the pair of second intake valves 55 via the four exhaust valve cams 62a when the exhaust cam shaft 62 has a predetermined number of revolutions or less. The exhaust flow from the first and second cylinders 21 and 22 is released. The oil supply mechanism 80 supplies oil to the decompression mechanism 70 by supplying oil to the internal space 62 </ b> S of the exhaust camshaft 62.

  Thus, since oil can be supplied to the decompression mechanism 70 by the forced lubrication method, it is possible to effectively suppress the generation of mechanical noise from the decompression mechanism 70. Therefore, the mechanical noise of the decompression mechanism 70 can be suppressed from being conspicuous even when the driving sound is low because the rotational speed of the engine 1 is low.

  Further, for example, if a non-forced lubrication method in which oil droplets are sprayed on the decompression mechanism 70, the splashed oil is repelled, and therefore the decompression mechanism 70 cannot be effectively lubricated. On the other hand, according to the engine 1 according to the present embodiment, it is possible to lubricate every corner of the decompression mechanism 70 by the forced lubrication method.

(2) The decompression mechanism 70 includes first and second weight portions 75 and 76, first and second decompression shafts 71 and 73 disposed in the internal space 62S, first and second decompression pins 72 and 74, Have The first and second weight portions 75 and 76 move by centrifugal force when the exhaust camshaft 62 rotates at a rotational speed greater than a predetermined rotational speed. The first and second decompression shafts 71 and 73 rotate according to the movement of the first and second weight portions 75 and 76. The first and second decompression pins 72 and 74 are retracted from the pair of first exhaust valve lifters 54 and the pair of second exhaust valve lifters 58 in accordance with the rotation of the first and second decompression shafts 71 and 73. The first and second decompression pins 72 and 74 can be forcibly retracted in response to the exhaust camshaft 62 becoming greater than the predetermined rotational speed. Therefore, the normal compression state can be restored accurately and promptly after the engine 1 is started.

  (3) The exhaust camshaft 62 has a first oil inflow hole OH1 formed in the side surface 623S of the central portion 623. The oil supply mechanism 80 supplies oil to the internal space 62S through the first oil inflow hole OH1.

  In this way, since the oil is supplied from the first oil inflow hole OH1 formed in the central portion 623 of the exhaust cam shaft 62, the oil can be efficiently filled into the internal space 62S. At this time, since the oil is being pumped, the oil can flow toward the first and second weight portions 75 and 76 even if the first oil inflow hole OH1 is formed in the central portion 623.

  Further, not the journal bearings 85a and 85b that support the first end 621 and the second end 622 of the exhaust cam shaft 62 but the journal bearing 85c that supports the central portion 623 of the exhaust cam shaft 62 is the first oil inflow hole OH1. , An oil supply function to the second oil inflow hole OH2 (hereinafter referred to as “noise reduction oil supply function”). In general, the bearing of the central portion 623 (journal bearing 85c) has a smaller acting load relative to the bearings of the shaft end portions (first end portion 621 and second end portion 622). In other words, the journal bearings 85a, 85b, 85c, which are required to reduce the lubricity, are not the journal bearings 85a, 85b that require relatively high lubricity. Oil can be pumped to the decompression mechanism 70 while ensuring lubrication performance.

  Further, since the journal bearing 85c has a sound-reducing oil supply function, it is easy to adjust the oil pressure of the bearing portion 84, and the oil can be quickly supplied to the decompression mechanism 70 at the time of starting the engine. For example, when the first oil inflow hole OH1 is formed in the first journal side surface 621S of the first end portion 621 and the sound reducing oil supply function is given only to the journal bearing 85a, the oil pressure to the journal bearings 85b and 85c. It becomes difficult to adjust. In addition, when the first oil inflow hole OH1 is formed in the second journal side surface 622S of the second end portion 622 and only the journal bearing 85b is provided with the sound-reducing oil supply function, when the side stand is used when the engine is stopped, Oil flows out from the first oil inflow hole OH1 positioned below, and the amount of oil in the internal space 62S becomes extremely small. For this reason, when the engine is started, oil supply to the decompression mechanism 70 is sufficiently performed after the internal space 62S is filled with oil. In particular, oil supply to the first weight portion 75 and the second weight portion 76 is performed. It takes time. According to the configuration of the present embodiment, the above-described adverse effects are not caused, and the journal bearing 85c has a sound-reducing oil supply function. Therefore, adjustment to the oil pressure of the bearing portion 84 is easy, and the decompression mechanism 70 at the time of engine start-up can be quickly performed. Can be supplied with oil.

  (4) The exhaust camshaft 62 has a second oil inflow hole OH2 that faces the first oil inflow hole OH1 with respect to the axis AX.

  Thus, since oil can be continuously supplied from the two opposing oil inflow holes OH1 and OH2, stable oil supply can be achieved compared to the case where oil is intermittently supplied only from the first oil inflow hole OH1. Can be achieved.

  (5) The first and second weight portions 75 and 76 are in contact with the second sprocket 64.

  In such a case, since the mechanical noise is likely to be generated when the first and second weight portions 75 and 76 hit the second sprocket 64, the effect of suppressing the mechanical noise by the forced lubrication method is particularly great.

  (6) The first opening 621P of the exhaust camshaft 62 is located inside the shaft hole 64S of the second sprocket 64 when the second sprocket 64 is viewed from the axial direction.

  Accordingly, the oil can be efficiently supplied between the first and second weight portions 75 and 76 and the second sprocket 64 by using the centrifugal force while allowing the oil to flow out from the first opening 621P.

  (7) The first and second weight portions 75 and 76 are located between the inner wall surface of the engine 1 and the second sprocket 64.

  As described above, even if it is difficult to supply oil to the first and second weight portions 75 and 76 sandwiched between the inner wall surface of the engine 1 and the second sprocket 64, the first and second oils are forcedly lubricated. The weight portions 75 and 76 can be effectively lubricated.

  (8) The exhaust camshaft 62 has a closing plug 625 that closes the second opening 622P formed in the second end 622.

  Therefore, even if the second opening 622P is directed downward when the saddle riding type vehicle is made to stand on the side stand, oil can be prevented from flowing out from the second opening 622P.

  Further, the second opening 622P is closed, so that the oil pressure-fed into the internal space 62 of the exhaust camshaft 62 flows out from the first opening 621P. That is, a large amount of oil flows out to the second sprocket 64 side arranged on the first opening 621P side. For this reason, oil can be sufficiently supplied to the first and second weight portions 75 and 76 and the second sprocket 64 where mechanical noise is likely to occur.

  (9) The oil supply mechanism 80 has a bearing portion 84 that supports the exhaust cam shaft 62. The bearing portion 84 has an internal oil passage 90 formed therein, and a second oil supply port 84b facing the first oil inflow hole OH1.

  Thus, since oil can be pumped using the oil supply mechanism 80 generally used to lubricate the outer peripheral surface of the exhaust camshaft 62, the increase in the number of parts due to the forced lubrication method is suppressed. Can do.

  (10) The decompression shaft portion according to the present embodiment includes first and second decompression shafts 71 and 72, and the decompression pin portion according to the present embodiment includes first and second decompression pins 72 and 74.

  Therefore, in the two-cylinder engine 1, the operations of the first and second decompression pins 72 and 74 can be synchronized.

  (11) The first weight portion 76 includes a first weight body 75a and a first support shaft 75b. The second weight portion 76 includes a second weight body 76a and a second support shaft 76b. The second weight body 76a is arranged point-symmetrically with the first weight body 75a, with the axis AX as the center.

  Thus, the exhaust cam shaft 62 can be rotated with good balance by the first and second weight bodies 75a, 76a, so that the decompression mechanism 70 can be made smoother than when the exhaust cam shaft 62 is driven by one weight body. Can drive.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  (A) In the above embodiment, the engine 1 is a two-cylinder four-cycle engine adopting the four-valve DOHC system, but the number of valves and the number of cylinders can be arbitrarily set.

  (B) In the above embodiment, the decompression mechanism 70 has the first and second weight portions 75 and 76, but may have only the first weight portion 75.

  (C) In the above embodiment, the first and second oil inflow holes OH1 and OH2 are formed in the central portion 623 of the exhaust camshaft 62, but in the first end 621 or the second end 622, It may be formed.

  (D) In the above embodiment, the exhaust camshaft 62 has the first and second oil inflow holes OH1 and OH2. However, the exhaust camshaft 62 may have only the first oil inflow hole OH1.

  (E) In the above embodiment, the exhaust camshaft 62 has the closing plug 625 that closes the second opening 622P, but the second opening 622P may not be closed. In particular, the exhaust camshaft 62 may not have the closing plug 625 if the second end 622 is not lowered when the saddle riding type vehicle is self-supported by the side stand.

  (F) In the above embodiment, the detailed shape of the parts constituting the decompression mechanism 70 has been described with reference to FIGS. 7 to 10, but the shape of the parts constituting the decompression mechanism 70 can be arbitrarily changed. . For example, a connection method between the first decompression shaft 71 and the first decompression pin 72, a connection method between the first decompression shaft 71 and the second decompression shaft 73, and an engagement method between the first and second drive pins 75e and 76e and the engagement groove 71d. Various variations can be added.

  (G) Although the detailed configuration of the oil supply mechanism 80 has been described with reference to FIGS. 15 to 17 in the above embodiment, the components of the oil supply mechanism 80 can be arbitrarily changed. In particular, various variations can be added to the cross-sectional shape and the extending direction of the flow path.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  According to the present invention, noise from the decompression mechanism can be suppressed, which is useful for the engine and saddle riding type vehicle fields.

DESCRIPTION OF SYMBOLS 1 Engine 20 Cylinder body 21 1st cylinder 23 1st piston 22 2nd cylinder 24 2nd piston 30 Cylinder head 50 Valve mechanism 53 1st exhaust valve 54 1st exhaust valve lifter 57 2nd exhaust valve 58 2nd exhaust valve lifter 60 Valve mechanism 62 Exhaust cam shaft 62a Exhaust valve cam 62S Internal space 623 Central portion 623S Third journal side surface OH1 First oil inlet hole OH2 Second oil inlet hole PH1 First pin hole PH2 Second pin hole 624 Through hole 621P first opening 622P second opening 64 second sprocket 70 decompression mechanism 71 first decompression shaft 72 first decompression pin 73 second decompression shaft 74 second decompression pin 75 first weight portion 76 second weight portion 80 oil supply mechanism 84 bearing portion 90 Internal oil flow path 84a First oil supply port 84b Second oil Supply port 84c third oil supply port

Claims (12)

A cylinder that houses the piston;
An exhaust valve for opening and shutting off the exhaust flow from the cylinder;
An exhaust camshaft that is hollow and includes a valve drive cam for driving the exhaust valve;
A decompression mechanism that is attached to the exhaust camshaft and opens the exhaust flow from the cylinder by driving the exhaust valve via the valve drive cam when the exhaust camshaft is equal to or lower than a predetermined number of revolutions;
An oil supply mechanism that supplies oil to the decompression mechanism by supplying oil to the internal space of the exhaust camshaft;
An engine equipped with. An exhaust valve lifter that is driven by the valve cam and opens and closes the exhaust valve;
The decompression mechanism is
A weight portion that moves by centrifugal force when the exhaust camshaft rotates at a rotational speed greater than the predetermined rotational speed;
A decompression shaft portion that is disposed in the internal space of the exhaust camshaft and rotates in accordance with the movement of the weight portion;
A decompression pin portion that protrudes from a pin hole formed on a side surface of the exhaust camshaft and contacts the exhaust valve lifter, and retracts from the exhaust valve lifter according to the rotation of the decompression shaft portion;
The engine according to claim 1. The exhaust camshaft includes a first end portion, a second end portion, a central portion, and a first oil inflow hole formed in a side surface of the central portion,
The oil supply mechanism supplies oil to the internal space through the first oil inflow hole;
The engine according to claim 2. The exhaust camshaft has a second oil inflow hole facing the first oil inflow hole on the basis of the axis of the exhaust camshaft;
The oil supply mechanism supplies oil to the internal space through the second oil inflow hole;
The engine according to claim 3. The exhaust camshaft includes a sprocket fixed to the first end;
The weight portion is attached to the sprocket and is in contact with the sprocket.
The engine according to claim 3 or 4. When the sprocket is viewed from the axial direction of the exhaust camshaft, an opening formed at the first end is located in a shaft hole that opens on the central axis of the sprocket.
The engine according to claim 5. The weight portion is located between the sprocket and the inner wall surface of the engine case that the sprocket faces.
The engine according to claim 5 or 6. The exhaust camshaft has a closing plug that closes an opening formed in the second end.
The engine according to any one of claims 3 to 7. The oil supply mechanism has a bearing portion that supports the exhaust camshaft,
The bearing portion includes an internal oil passage formed inside, and an oil supply port facing the first oil inflow hole.
The engine according to any one of claims 3 to 8. The decompression shaft portion includes a plurality of decompression shafts connected in the axial direction of the exhaust camshaft,
The decompression pin portion includes a plurality of decompression pins connected to each of the plurality of decompression shafts.
The engine according to any one of claims 2 to 9. The weight portion is
A first support shaft parallel to the axis of the exhaust camshaft;
A first weight body that is rotatable about the first support shaft and is formed in a fan shape;
A second support shaft that is parallel to the rotation shaft and that is arranged symmetrically with the first support shaft about the rotation shaft;
A second weight body that is rotatable about the second support shaft and formed in a fan shape;
Have
The first weight body and the second weight body are arranged symmetrically with respect to the axis.
The engine according to any one of claims 5 to 10. An engine according to claim 1;
A body frame that supports the engine;
A saddle-ride type vehicle equipped with

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