WO2018180558A1

WO2018180558A1 - Internal combustion engine

Info

Publication number: WO2018180558A1
Application number: PCT/JP2018/010294
Authority: WO
Inventors: 平山　周二; 泰弘森本
Original assignee: 本田技研工業株式会社
Priority date: 2017-03-28
Filing date: 2018-03-15
Publication date: 2018-10-04
Also published as: EP3604748A1; JPWO2018180558A1; EP3604748B1; JP6706388B2; EP3604748A4; CN110506151A; CN110506151B

Abstract

Provided is an internal combustion engine that comprises: a decompression cam (112) that causes a curved protruding surface (129), which has a generating line that is parallel to a rotational axis of a cam shaft, to protrude from an imaginary cylindrical surface (122), which is coaxial with the camshaft, at a rotational speed less than a preset rotational speed; a convex decompression follower surface (133) that is a convex curved surface that is provided on an exhaust-side rocker arm (97b) outside the imaginary cylindrical surface (122), and that faces the imaginary cylindrical surface (122) and contacts the curved protruding surface (129) at a position closest to the imaginary cylindrical surface (122); and a concave decompression follower surface (134) that is provided upstream from the convex decompression follower surface (133) in the positive rotation direction of the camshaft, that is formed into a concave curved surface having a generating line that is parallel to the rotational axis of the camshaft, and that contacts the curved protruding surface (129). Due to this configuration, provided is an internal combustion engine that can further reduce a collision sound between a decompression cam and an exhaust-side rocker arm and a seat sound of an exhaust valve.

Description

Internal combustion engine

The present invention relates to a decompression device for an internal combustion engine.

Patent Document 1 discloses a decompression device for an internal combustion engine. The decompression device includes a decompression cam having a small-diameter partial cylindrical surface having an axis parallel to the rotation axis of the camshaft. The decompression cam causes a part of the partial cylindrical surface to protrude from the virtual cylindrical surface coaxial with the camshaft at a rotation speed less than a preset value. The slipper of the exhaust side rocker arm contacts the protruding decompression cam and opens the exhaust valve. By opening the exhaust valve during the compression stroke in the low rotation range, the driving resistance of the piston is reduced and the vibration of the internal combustion engine is suppressed.

Japanese Unexamined Patent Publication No. 2014-129794

¡When the piston rotates over the compression top dead center and the camshaft reverses, the collision noise between the decompression cam and the exhaust side rocker arm is reduced. In addition to reducing the impact noise, it is required to reduce the impact noise between the decompression cam and the exhaust side rocker arm and the seating noise of the exhaust valve when the camshaft rotates forward.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an internal combustion engine that can further reduce the collision noise between the decompression cam and the exhaust-side rocker arm and the seating noise of the exhaust valve.

According to the first aspect of the present invention, a base surface having a shape of a partial cylindrical surface coaxial with the rotation axis of the camshaft, and the base surface is provided on the camshaft continuously to the base surface in the rotation direction. A lift surface that swells outward in the radial direction and defines the lift amount of the exhaust valve, and an exhaust-side rocker arm that maintains contact with the base surface and the lift surface to maintain the exhaust-side rocker arm. A cam follower that causes rocking, a decompression cam that projects a curved projecting surface having a generatrix parallel to the rotational axis of the camshaft from a virtual cylindrical surface that is coaxial with the camshaft and is less than a preset number of revolutions, and Provided on the exhaust-side rocker arm outside the virtual cylindrical surface, facing the virtual cylindrical surface at a position closest to the virtual cylindrical surface and contacting the curved projecting surface A curved convex convex follower surface and a concave curved surface provided in the forward rotation direction of the camshaft and upstream of the convex decompression follower surface and having a generatrix parallel to the rotational axis of the camshaft. An internal combustion engine is provided that includes a concave decompressor follower surface that contacts the projecting surface.

According to the second side surface, in addition to the configuration of the first side surface, the upstream end of the concave decompression follower surface is provided at a position farther from the rotational axis of the camshaft than the curved projecting surface.

According to the third aspect, in addition to the configuration of the first or second side surface, the concave decompression follower surface moves away from the rotation axis of the camshaft as the distance from the convex decompression follower surface increases.

According to the fourth aspect, in addition to the configuration of any one of the first to third aspects, the internal combustion engine is formed between the convex decompression follower surface and the concave decompression follower surface, and more than the curved projecting surface. An auxiliary concave decompressor follower surface composed of a concave curved surface having a small curvature is further provided.

According to the fifth aspect, in addition to the configuration of the fourth side surface, the auxiliary concave decompression follower surface is formed by a part of a cylindrical surface having a larger curvature than the concave decompression follower surface.

According to the sixth aspect, in addition to the configuration of any one of the first to fifth aspects, the internal combustion engine is provided downstream of the convex decompression follower surface in the forward rotation direction of the camshaft, It further includes a second concave decompression follower surface that is formed on a concave curved surface having a generatrix parallel to the rotation axis and contacts the curved convex surface.

According to the seventh aspect, the base surface having a shape of a partial cylindrical surface coaxial with the rotation axis of the camshaft, and the camshaft is provided on the camshaft continuously to the base surface in the rotation direction, and has a diameter larger than that of the base surface. A lift surface that swells outward in the direction and defines the lift amount of the exhaust valve, and an exhaust-side rocker arm that maintains contact with the base surface and the lift surface to swing the exhaust-side rocker arm. A cam follower, a decompression cam projecting a curved projecting surface having a generatrix parallel to the rotation axis of the camshaft from a virtual cylindrical surface coaxial with the camshaft at a rotation speed less than a preset rotational speed, and the virtual cylindrical surface A convex decon that is provided on the exhaust-side rocker arm on the outer side and contacts the curved projecting surface facing the virtual cylindrical surface at a position closest to the virtual cylindrical surface A follower surface is provided downstream of the convex decompression follower surface in the forward rotation direction of the camshaft, and is formed as a concave curved surface having a generatrix parallel to the rotation axis of the camshaft and contacts the curved projecting surface An internal combustion engine having a concave decompressor follower surface is provided.

According to the eighth aspect, in addition to the configuration of the seventh side surface, the downstream end of the concave decompression follower surface is provided at a position farther from the rotational axis of the camshaft than the curved projecting surface.

According to the ninth aspect, in addition to the configuration of the seventh or eighth aspect, the concave decompression follower surface is further away from the rotational axis of the camshaft as the distance from the convex decompression follower surface is increased.

According to the tenth aspect, in addition to the configuration of any one of the seventh to ninth aspects, the internal combustion engine is formed between the convex decompression follower surface and the concave decompression follower surface, and more than the curved projecting surface. An auxiliary concave decompressor follower surface composed of a concave curved surface having a small curvature is further provided.

According to the eleventh aspect, in addition to the configuration of the tenth side surface, the auxiliary concave decompression follower surface is formed by a part of a cylindrical surface having a larger curvature than the concave decompression follower surface.

According to the twelfth aspect, in addition to the structure of any one of the first to eleventh aspects, the internal combustion engine is coupled to the crankshaft and generates electric power in accordance with the rotation of the crankshaft, and the supplied electric power. Accordingly, an AC generator for driving the crankshaft around its rotational axis is further provided.

According to the thirteenth aspect, a base surface having a shape of a partial cylindrical surface coaxial with the rotation axis of the camshaft, and provided on the camshaft continuously to the base surface in the rotation direction, the diameter is larger than the base surface. A lift surface that swells outward in the direction and defines the lift amount of the exhaust valve, and an exhaust-side rocker arm that maintains contact with the base surface and the lift surface to swing the exhaust-side rocker arm. A cam follower, a decompression cam projecting a curved projecting surface having a generatrix parallel to the rotation axis of the camshaft from a virtual cylindrical surface coaxial with the camshaft at a rotation speed less than a preset rotational speed, and the virtual cylindrical surface A convex decompression follower surface of the convex curved surface that is provided on the exhaust-side rocker arm on the outer side and faces the virtual cylindrical surface and contacts the curved convex surface. The curved projecting surface has a top surface that protrudes most from the virtual cylindrical surface, and a generatrix that is provided upstream of the top surface in the forward rotation direction of the camshaft and is parallel to the rotation axis of the camshaft. There is provided an internal combustion engine having a buffer surface formed on a concave curved surface and contacting the convex decompression follower surface.

According to the fourteenth aspect, in addition to the configuration of the thirteenth side surface, the curved projecting surface is provided downstream of the top surface in the normal rotation direction of the camshaft and is parallel to the rotation axis of the camshaft. And a second buffer surface formed on the concave curved surface.

According to the fifteenth aspect, the base surface having the shape of a partial cylindrical surface coaxial with the rotation axis of the camshaft, and the camshaft is provided on the camshaft continuously to the base surface in the rotation direction, and has a diameter larger than that of the base surface. A lift surface that swells outward in the direction and defines the lift amount of the exhaust valve, and an exhaust-side rocker arm that maintains contact with the base surface and the lift surface to swing the exhaust-side rocker arm. A cam follower, a decompression cam projecting a curved projecting surface having a generatrix parallel to the rotation axis of the camshaft from a virtual cylindrical surface coaxial with the camshaft at a rotation speed less than a preset rotational speed, and the virtual cylindrical surface A convex decompression follower surface of the convex curved surface that is provided on the exhaust-side rocker arm on the outer side and faces the virtual cylindrical surface and contacts the curved convex surface. The curved projecting surface has a top surface that protrudes most from the virtual cylindrical surface and a generatrix that is provided downstream of the top surface in the normal rotation direction of the camshaft and is parallel to the rotation axis of the camshaft. There is provided an internal combustion engine having a buffer surface formed on a concave curved surface and contacting the convex decompression follower surface.

According to the first aspect, the curved protrusion surface of the decompression cam protrudes in the centrifugal direction of the camshaft in a low rotation range less than the set rotation speed. During forward rotation of the camshaft, the curved protrusion surface of the decompression cam contacts the concave decompression follower surface and the convex decompression follower surface of the exhaust side rocker arm one after another. Since the concave decompression follower surface is formed into a concave curved surface, the curved convex surface of the decompression cam can slide in a tangential direction with respect to the concave curved surface at the start of contact. Therefore, the collision sound between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the second aspect, at the start of contact, the curved protrusion surface of the decompression cam contacts the concave curved surface. The collision noise between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the third aspect, even if the curved surface of the decompression cam is slightly displaced due to dimensional tolerances or assembly errors, the curved surface of the decompression cam slides in the tangential direction with respect to the concave curved surface at the start of contact. Can do. Therefore, the collision sound between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the fourth aspect, since the concave decompression follower surface, the auxiliary concave decompression follower surface and the convex decompression follower surface are continuous, the curved convex surface of the decompression cam can smoothly follow the convex decompression follower surface from the concave decompression follower surface. it can. The collision noise between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the fifth aspect, the curved protrusion surface of the decompression cam can smoothly follow the convex decompression follower surface from the concave decompression follower surface in accordance with the change in curvature. The collision noise between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the sixth aspect, during the forward rotation of the camshaft, the curved convex surface of the decompression cam contacts the second concave decompression follower surface following the convex decompression follower surface. Since the second concave decompression follower surface is formed as a concave curved surface, the lift amount of the exhaust valve changes gently when the decompression cam is detached from the second concave decompression follower surface. As a result, the seating sound of the exhaust valve is reduced. In addition, during the reverse rotation of the camshaft, the curved protrusion surface of the decompression cam successively contacts the second concave decompression follower surface and the convex decompression follower surface. Since the second concave decompression follower surface is formed into a concave curved surface, the curved convex surface of the decompression cam can slide in a tangential direction with respect to the concave curved surface at the start of contact. Therefore, when the camshaft reverses without overcoming the compression top dead center, the collision noise between the decompression cam and the exhaust-side rocker arm can be suppressed.

According to the seventh aspect, during the forward rotation of the camshaft, the curved protrusion surface of the decompression cam contacts the concave decompression follower surface following the convex decompression follower surface. Since the concave decompression follower surface is formed as a concave curved surface, the lift amount of the exhaust valve changes gently when the decompression cam is detached from the concave decompression follower. As a result, the seating sound of the exhaust valve is reduced. In addition, during the reverse rotation of the camshaft, the curved protrusion surface of the decompression cam contacts the concave decompression follower surface and the convex decompression follower surface one after another. Since the concave decompression follower surface is formed into a concave curved surface, the curved convex surface of the decompression cam can slide in a tangential direction with respect to the concave curved surface at the start of contact. Therefore, when the camshaft reverses without overcoming the compression top dead center, the collision noise between the decompression cam and the exhaust-side rocker arm can be suppressed.

According to the eighth aspect, according to the rotation of the camshaft, the curved projecting surface of the decompression cam separates from the rocker arm with a concave curved surface. When lifted, the lift amount of the exhaust valve surely changes slowly. Thus, the seating noise of the exhaust valve can be reduced.

According to the ninth aspect, the lift amount of the exhaust valve changes gently when seated even if the curved protrusion surface of the decompression cam is slightly displaced based on dimensional tolerance or assembly error. Thus, the seating noise of the exhaust valve can be reduced.

According to the tenth aspect, since the convex decompression follower surface, the auxiliary concave decompression follower surface, and the concave decompression follower surface are continuous, the curved convex surface of the decompression cam can smoothly follow the convex decompression follower surface to the concave decompression follower surface. it can. The collision noise between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the eleventh aspect, the curved protrusion surface of the decompression cam can smoothly follow the concave decompression follower surface from the convex decompression follower surface in accordance with the change in curvature. The collision noise between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the twelfth aspect, such an alternator can establish an idling state of the internal combustion engine. In idling, the AC generator can realize the reciprocating motion of the piston without going through the combustion stroke. Fuel consumption is suppressed and exhaust noise of the internal combustion engine is reduced.

According to the thirteenth aspect, the curved protrusion surface of the decompression cam protrudes in the centrifugal direction of the camshaft in a low rotation range less than the set rotation speed. During the forward rotation of the camshaft, the curved protrusion surface of the decompression cam successively contacts the convex decompression follower surface of the exhaust side rocker arm at the buffer surface and the top surface. Since the buffer surface of the decompression cam is formed as a concave curved surface, the convex decompression follower surface can slide in a tangential direction with respect to the concave curved surface of the decompression cam at the start of contact. Therefore, the collision sound between the decompression cam and the exhaust side rocker arm can be suppressed.

According to the fourteenth aspect, during the forward rotation of the camshaft, the curved protrusion surface of the decompression cam contacts the convex decompression follower surface at the second buffer surface following the top surface. Since the second buffer surface is formed as a concave curved surface, the lift amount of the exhaust valve changes gently when the convex decompression follower surface is detached from the second buffer surface. As a result, the seating sound of the exhaust valve is reduced. In addition, during the reverse rotation of the camshaft, the curved protrusion surface of the decompression cam successively contacts the second buffer surface and the top surface. Since the second buffer surface is formed as a concave curved surface, the convex decompression follower surface can slide in the tangential direction with respect to the second buffer surface at the start of contact. Therefore, when the camshaft reverses without overcoming the compression top dead center, the collision noise between the decompression cam and the exhaust-side rocker arm can be suppressed.

According to the fifteenth aspect, the curved protrusion surface of the decompression cam protrudes in the centrifugal direction of the camshaft in a low rotation range less than the set rotation speed. During the forward rotation of the camshaft, the curved surface of the decompression cam successively contacts the top surface and the buffer surface. Since the buffer surface is formed as a concave curved surface, the lift amount of the exhaust valve changes gently when the convex decompression follower surface is detached from the buffer surface. As a result, the seating sound of the exhaust valve is reduced. In addition, during the reverse rotation of the camshaft, the curved protrusion surface of the decompression cam successively contacts the buffer surface and the top surface. Since the buffer surface is formed as a concave curved surface, the convex decompression follower surface can slide in a tangential direction with respect to the buffer surface at the start of contact. Therefore, when the camshaft reverses without overcoming the compression top dead center, the collision noise between the decompression cam and the exhaust-side rocker arm can be suppressed.

FIG. 1 is a side view schematically showing a scooter type motorcycle according to an embodiment of a saddle-ride type vehicle. (First embodiment) FIG. 2 is a horizontal sectional view taken along line 2-2 in FIG. (First embodiment) 3 is an enlarged vertical sectional view of the cylinder head taken along line 3-3 in FIG. (First embodiment) 4 is a cross-sectional view taken along line 4-4 of FIG. (First embodiment) FIG. 5 is an enlarged vertical sectional view of a part of FIG. (First embodiment) FIG. 6 is an enlarged vertical sectional view of a part of FIG. (First embodiment) FIG. 7 corresponds to FIG. 5 and is a vertical sectional view showing the position of the decompression cam when the cam pin is displaced from the first position to the second position in the decompression device according to the first embodiment. (First embodiment) FIG. 8 corresponds to FIG. 6 and is an enlarged vertical sectional view schematically showing the configuration of the decompression device according to the second embodiment. (Second Embodiment) FIG. 9 corresponds to FIG. 6 and is an enlarged vertical sectional view schematically showing the configuration of the decompression device according to the third embodiment. (Third embodiment)

49 ... Alternator (alternator starter)
89 ... Exhaust valve 95 ... Cam shaft 97b ... Exhaust-side rocker arm 101 ... Cam follower 108a ... Base surface 108b ... Lift surface 109 ... (functioning as a convex decompression follower surface) Roller 112 ... Decompression cam 122 ... Virtual cylindrical surface 129 ... Curved projection Surface (partial cylindrical surface)
133 ... Convex decompression follower surface 134 ... Concave decompression follower surface 134a ... Upstream end 135 ... (Second) concave decompression follower surface 135a ... Downstream end 136 ... Auxiliary concave decompression follower surface 137 ... (Second) supplementary concave decompression follower surface 143 ... convex decompression follower surface 144 ... decompression cam 145 ... curved projection surface 146 ... top surface 147 ... cushioning surface 148 ... (second) cushioning surface 151 ... decompression device Xc ... rotation axis (of the camshaft)

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the following description, front and rear, up and down, and left and right directions refer to directions viewed from a passenger on a motorcycle.

First embodiment

FIG. 1 schematically shows a scooter type motorcycle according to an embodiment of a saddle type vehicle. The motorcycle 11 includes a body frame 12 and a body cover 13. The vehicle body frame 12 includes a head pipe 14 at the front end, a main frame 15 coupled to the head pipe 14 at the front end, a cross pipe 16 coupled to the rear portion of the main frame 15 and extending in the vehicle width direction, and the cross pipe 16 And a pair of left and right rear frames 17 extending in the vehicle front-rear direction. The head pipe 14 supports a front fork 18 that supports the front wheel WF so as to be rotatable about a horizontal axis, and a rod-shaped steering handle 19 that can be steered.

The body cover 13 is attached to the body frame 12. An occupant seat 21 is mounted on the vehicle body cover 13 above the rear frame 17. The body cover 13 includes a front cover 22 that covers the head pipe 14 from the front, a leg shield 23 that is continuous from the front cover 22, and a main frame 15 between the passenger seat 21 and the front wheel WF that is continuous from the lower end of the leg shield 23. And a step floor 24 disposed above.

A unit swing type drive unit 25 is disposed in a space below the rear frame 17. The drive unit 25 is coupled to a bracket 26 coupled to the front end of the rear frame 17 via a link 27 so as to be swingable in the vertical direction. A rear wheel WR is supported at the rear end of the drive unit 25 so as to be rotatable about a horizontal axis. A rear cushion unit 28 is disposed between the rear frame 17 and the drive unit 25 at a position away from the link 27 and the bracket 26. The drive unit 25 includes an air-cooled single-cylinder internal combustion engine 29 and a transmission 31 that is connected to the internal combustion engine 29 and the rear wheel WR and transmits the output of the internal combustion engine 29 to the rear wheel WR. A transmission case 31 a of the transmission device 31 is coupled to the engine body 29 a of the internal combustion engine 29.

An engine main body 29a of the internal combustion engine 29 includes a crankcase 33 that supports a crankshaft 32 so as to be rotatable about a rotation axis, a cylinder block 34 coupled to the crankcase 33, and a cylinder head 35 coupled to the cylinder block 34. And a head cover 36 coupled to the cylinder head 35. An intake device 37 and an exhaust device 38 are connected to the cylinder head 35. The intake device 37 includes an air cleaner 39 supported by the transmission case 31 a and a throttle body 41 disposed between the air cleaner 39 and the cylinder head 35. A fuel injection valve 42 is attached to the upper side wall of the cylinder head 35. The exhaust device 38 includes an exhaust pipe 43 extending rearward from the lower side wall of the cylinder head 35 through the lower part of the engine body 29a, and an exhaust muffler (not shown) connected to the downstream end of the exhaust pipe 43 and coupled to the crankcase 33. Z)).

As shown in FIG. 2, a cylinder bore 44 is defined in the cylinder block 34. A piston 45 is fitted into the cylinder bore 44 so as to be slidable along the cylinder axis C. The cylinder axis C is slightly inclined upward. The crankshaft 32 is connected to the piston 45. The rotation axis Xis of the crankshaft 32 is directed in the vehicle width direction.

A combustion chamber 46 is defined in the cylinder head 35. The combustion chamber 46 continues from the cylinder bore 44. The piston 45 faces the cylinder head 35 and partitions the combustion chamber 46 between the piston 45 and the cylinder head 35. An air-fuel mixture is introduced into the combustion chamber 46 via an intake device 37. The exhaust gas in the combustion chamber 46 is discharged through the exhaust device 38.

The crankcase 33 is divided into a first case half 33a and a second case half 33b. The first case half 33a and the second case half 33b cooperate to partition the crank chamber 47. A crank of the crankshaft 32 is accommodated in the crank chamber 47. The first case half 33 a has a bearing 48 a that rotatably supports the crankshaft 32, while the second case half 33 b has a bearing 48 b that rotatably supports the crankshaft 32.

The AC generator starter 49 is coupled to the crankcase 33. The alternator starter 49 includes an outer rotor 51 that is fixed to the crankshaft 32 that passes through the first case half 33a of the crankcase 33 and protrudes from the first case half 33a, and is surrounded by the outer rotor 51. 32 and an inner stator 52 disposed around 32. The inner stator 52 is fixed to a support plate 53 fastened to the first case half 33a. An electromagnetic coil 52 a is wound around the inner stator 52. A magnet 51 a is fixed to the outer rotor 51. When the outer rotor 51 rotates relative to the inner stator 52, electric power is generated by the electromagnetic coil 52a. On the other hand, when a current flows through the electromagnetic coil 52a, a magnetic force is generated in the electromagnetic coil 52a, causing the outer rotor 51 to rotate. At this time, the AC generator starter 49 functions as a motor. The AC generator starter 49 can rotationally drive the crankshaft 32 without using a gear or the like.

The AC generator starter 49 is connected to a control circuit (ECU). The control circuit controls the supply of power to the electromagnetic coil 52a. The driving force of the alternator starter 49 may be used, for example, as a starter when the internal combustion engine 29 is started to rotate the crankshaft 32, and is used when the motorcycle 11 is smoothly restarted at an idle stop. Also good. Here, the control circuit includes, for example, an idle stop determination unit, an idle stop control unit, and a motor idle drive processing unit.

The idle stop determination unit has a function of determining whether or not to perform idle stop control when the vehicle stops temporarily during traveling. The throttle stop calculated by the throttle opening calculator and the traveling speed of the vehicle calculated by the vehicle speed calculator are input to the idle stop determination unit while traveling. The idle stop determination unit outputs an instruction signal for idle stop control to the idle stop control unit when the throttle opening and the traveling speed are equal to or less than predetermined values. An instruction signal is supplied to the idle stop determination unit from the idle stop SW determination unit. When it is confirmed by the instruction signal that the idle stop switch is ON, the idle stop determination unit prompts the execution of the idle stop control.

The idle stop control unit performs idle stop control based on the instruction signal from the idle stop determination unit. The idle stop control unit stops the operation of the fuel injection valve 42 and the operation of the spark plug. Thereby, the combustion operation of the internal combustion engine 29 is interrupted. When the motorcycle 11 restarts from the temporary stop, the idle stop control unit performs the reverse rotation driving of the crankshaft 32 based on the rotation angle of the crankshaft 32 and performs the control to ensure the forward rotation driving of the crankshaft 32.

The motor idle drive processing unit maintains the engine rotational speed at a predetermined rotational speed while the motorcycle 11 is stopped in a state where the combustion operation of the internal combustion engine 29 is stopped by the idle stop determination unit and the idle stop control unit. Carry out motor idle control. The motor idle drive processing unit stops the motor idle control when an accelerator request is not detected after a predetermined time has elapsed. If an accelerator request is detected before a predetermined time elapses, the crankshaft 32 is rotationally driven by the alternator starter 49 to start the motorcycle 11. Simultaneously with the start of the motorcycle 11, the combustion stroke of the internal combustion engine 29 is restarted.

A cylindrical generator cover 54 surrounding the AC generator starter 49 is coupled to the first case half 33a. An air inlet 54 a is defined at the open end of the generator cover 54. A radiator 55 is disposed at the air inlet 54a. A cooling fan 56 is coupled to the outer surface of the outer rotor 51. The cooling fan 56 rotates in accordance with the rotation of the crankshaft 32, and the cooling air flows through the radiator 55.

The transmission device 31 is housed in a transmission case 31a, and an electronically controlled V-belt continuously variable transmission (hereinafter referred to as "transmission") 57 that continuously changes the rotational power transmitted from the crankshaft 32, and a transmission A reduction gear mechanism 59 that is housed in the case 31a and decelerates the rotational power of the transmission 57 and transmits it to the axle 58 of the rear wheel WR. The rear wheel WR is disposed between the transmission case 31 a and the support arm 61. The support arm 61 extends continuously from the crankcase 33 toward the rear of the vehicle. The aforementioned exhaust muffler is attached to the support arm 61. The axle 58 of the rear wheel WR is supported at both ends by the transmission case 31a and the support arm 61 so as to be rotatable about the axis.

The transmission case 31 a includes a case main body 62 that is continuous from the second case half 33 b of the crankcase 33, a case cover 64 that is fastened to the case main body 62 and divides the transmission chamber 63 between the case main body 62, A gear cover 66 is provided that is fastened to the case main body 62 and defines a gear chamber 65 between the case main body 62 and the case main body 62. A transmission 57 is accommodated in the transmission chamber 63. A reduction gear mechanism 59 is accommodated in the gear chamber 65. The case main body 62 and the case cover 64 together constitute a mission case.

The transmission 57 is disposed in the transmission chamber 63 and is installed in the transmission chamber 63 and the drive pulley device 67 attached to the crankshaft 32 as a drive shaft. The transmission chamber 63 is moved from the transmission chamber 63 to the gear chamber 65. And a driven pulley device 69 attached to the protruding driven shaft 68. In the drive pulley device 67, a fixed sheave 73 fixed to the crankshaft 32 and a movable sheave 74 supported by the crankshaft 32 so as to be movable in the axial direction of the crankshaft 32 while facing the fixed sheave 73. The V belt 71 is wound around. Similarly, in the driven pulley device 69, a V-belt 71 is provided between a fixed sheave 78 that is coaxially mounted on the driven shaft 68 and a movable sheave 79 that is coaxially mounted on the driven shaft 68 while facing the fixed sheave 78. Is wrapped around. The belt pulley diameter is variably electronically controlled in the drive pulley device 67 by the action of the actuator unit 72. The belt winding diameter of the driven pulley device 69 changes according to the change in the belt winding diameter of the driving pulley device 67.

In the driving pulley device 67, the movable sheave 74 is disposed between the second case half 33 b of the crankcase 33 and the fixed sheave 73. The movable sheave 74 has a movable sheave boss 74 a that receives the crankshaft 32. The movable sheave boss 74 a extends from the sheave body that receives the V-belt 71 toward the second case half 33 b of the crankcase 24. The transmission 57 includes a first shift mechanism 75a including a centrifugal weight and a cam plate, and a second shift mechanism 75b including the actuator unit 72 described above. In accordance with the functions of the first shift mechanism 75a and the second shift mechanism 75b, the axial movement of the movable sheave 74 is realized, and the winding radius of the V-belt 71 changes.

The driven pulley device 69 has a cylindrical shape coaxial with the driven shaft 68, and has an inner cylinder 76 attached to the coaxial driven shaft 68, a cylindrical shape coaxial with the driven shaft 68, and coaxially with the inner cylinder 76. And an outer cylinder 77 to be mounted. The inner cylinder 76 is supported by the driven shaft 68 so as to be relatively rotatable. The outer cylinder 77 is supported by the inner cylinder 76 so as to be relatively rotatable and axially displaceable. A fixed sheave 78 is coaxially fixed to the inner cylinder 76. The inner cylinder 76 and the fixed sheave 78 are integrally formed from a material lighter than steel, such as aluminum. A movable sheave 79 is coaxially fixed to the outer cylinder 77. The outer cylinder 77 and the movable sheave 79 are integrally formed from a material lighter than steel, such as aluminum. The movable sheave 79 approaches or moves away from the fixed sheave 78 in accordance with the axial relative displacement of the outer cylinder 77 and the inner cylinder 76.

A centrifugal clutch 81 is attached to the driven shaft 68. The centrifugal clutch 81 includes a clutch plate 81 a fixed to the inner cylinder 76. A string spring 82 is disposed between the clutch plate 81a and the movable sheave 79. The string spring 82 exerts an elastic force that presses the movable sheave 79 toward the fixed sheave 78. When the winding radius of the V belt 71 is increased by the driving pulley device 67, the movable sheave 79 is moved away from the fixed sheave 78 against the elastic force of the string winding spring 82 in the driven pulley device 69, and the winding radius of the V belt 71 is decreased. .

The centrifugal clutch 81 includes an outer plate 81b fixed to the driven shaft 68. The outer plate 81b is opposed to the clutch plate 81a. When the clutch plate 81a rotates, the outer plate 81b is coupled to the clutch plate 81a by the action of centrifugal force. Thus, the rotation of the driven pulley device 69 is transmitted to the driven shaft 68. When the engine speed exceeds the set speed, the centrifugal clutch 81 establishes a power transmission state.

The reduction gear mechanism 59 is disposed between the drive gear 83 fixed to the driven shaft 68 protruding into the gear chamber 65, the final gear 84 fixed to the axle 58 of the rear wheel WR, and the drive gear 83 and the final gear 84.

Idle gears

85a and 85b. The

idle gears

85a and 85b are fixed to a common intermediate shaft 86. The drive gear 83 meshes with the idle gear 85a, and the final gear 84 meshes with the idle gear 85b. Thus, the rotation of the driven shaft 68 is decelerated and transmitted to the axle 58 of the rear wheel WR.

As shown in FIG. 3, the internal combustion engine 29 has a valve operating mechanism 87. The valve operating mechanism 87 includes an intake valve 88 supported by the cylinder head 35 so as to be axially displaceable by a valve shaft 88 b extending from the valve body 88 a while disposing the valve body 88 a in the combustion chamber 46, and the combustion chamber 46. An exhaust valve 89 is supported by the cylinder head 35 so as to be axially displaceable by a valve shaft 89b extending from the valve body 89a while disposing the valve body 89a. The valve body 88a of the intake valve 88 is seated on a valve seat 92a that is embedded in the cylinder head 35 at the opening of the intake port 91a connected to the combustion chamber 46 and partitions the intake port. The valve body 89 a of the exhaust valve 89 is seated on a valve seat 92 b that is embedded in the cylinder head 35 at the opening of the exhaust port 91 b connected to the combustion chamber 46 and defines an exhaust port.

The

valve shafts

88b and 89b are supported by the cylinder head 35 so as to be slidable in the axial direction. The

valve shafts

88 b and 89 b have one end (outer end) that penetrates the cylinder head 35 and is disposed outside the combustion chamber 46. A flange 93 is fixed to the outer ends of the

valve shafts

88b and 89b. A string-wound spring 94, which is an elastic member, is sandwiched between the flange 93 and the outer surface of the cylinder head 35. The string spring 94 exerts an elastic force in the extending direction that keeps the flange 93 away from the outer surface of the cylinder head 35. Based on the elastic force of the string spring 94, the

valve bodies

88a and 89a are seated on the

valve seats

92a and 92b.

The valve operating mechanism 87 has a camshaft 95 supported by the cylinder head 35 so as to be rotatable about an axis Xc parallel to the rotation axis Xis of the crankshaft 32, and an axis Xk parallel to the rotation axis Xis of the crankshaft 32. The pair of rocker shafts 96 are supported by the cylinder head 35, and the intake side rocker arm 97a and the exhaust side rocker arm 97b are supported by the rocker shaft 96 so as to be swingable about the axis Xk. Each

rocker arm

97a, 97b extends from the rocker shaft 96 in the centrifugal direction and has a first arm 99 having an operating point 98 at the tip, and extends from the rocker shaft 96 in the centrifugal direction in the opposite direction to the first arm 99. And a second arm 102 having a cam follower 101. The

rocker arms

97a and 97b are in contact with the outer ends of the intake valve 88 and the exhaust valve 89, respectively, at the operating point 98 of the first arm 99. The

rocker arms

97a and 97b come into contact with the camshaft 95 by the cam follower 101, respectively. Details of the camshaft 95 and the

rocker arms

97a and 97b will be described later.

As shown in FIG. 4, the valve operating mechanism 87 includes a timing chain 103. The timing chain 103 is wound around a crank sprocket (not shown) fixed to the crankshaft 32 and a cam sprocket 104 fixed to the camshaft 95. The timing chain 103 transmits the rotation of the crankshaft 32 to the camshaft 95. The camshaft 95 rotates in synchronization with the rotation of the crankshaft 32.

The internal combustion engine 29 includes a spark plug 105. The spark plug 105 is supported by the cylinder head 35. The spark plug 105 passes through the cylinder head 35 so that the electrode 105 a at the tip is exposed in the combustion chamber 46. The spark plug 105 ignites the air-fuel mixture in the combustion chamber 46 by a spark generated at the electrode 105a in accordance with the supplied electric signal.

The camshaft 95 is rotatably supported by the cylinder head 35 via a pair of bearings 106. For example, a ball bearing is used for the bearing 106. A first cam 107 for the intake side rocker arm 97a and a second cam 108 for the exhaust side rocker arm 97b are formed on the camshaft 95 between the bearings 106. The first cam 107 and the second cam 108 are arranged so as to be shifted in the axial direction of the cam shaft 95.

Referring also to FIG. 5, the cam follower 101 includes a roller 109 that is supported by the second arm 102 so as to be rotatable about a rotation axis parallel to the axis Xc of the camshaft 95. The outer peripheral surface of the roller 109 is in contact with the first cam 107 and the second cam 108, respectively. In response to the rotation of the first cam 107 and the second cam 108, the roller 109 can rotate. The roller 109 follows the profiles of the first cam 107 and the second cam 108 while rotating. The opening and closing of the intake valve 88 and the exhaust valve 89 are controlled as the roller 109 approaches or moves away from the axis Xc of the camshaft 95.

The first cam 107 is provided on the camshaft 95 so as to be continuous with the base surface 107a in the rotation direction, and has a base surface 107a having a shape of a partial cylindrical surface coaxial with the axis Xc of the camshaft 95. And a lift surface 107b that rises radially outward and defines the lift amount of the intake valve 88. The cam follower 101 of the intake side rocker arm 97a maintains contact with the base surface 107a and the lift surface 107b and causes the intake side rocker arm 97a to swing.

The second cam 108 is provided on the camshaft 95 continuously to the base surface 108a in the rotational direction and is formed on the camshaft 95 in a rotational direction, and is more than the base surface 108a. And a lift surface 108b that swells radially outward and defines the lift amount of the exhaust valve 89. The cam follower 101 of the exhaust side rocker arm 97b maintains the contact with the base surface 108a and the lift surface 108b and causes the exhaust side rocker arm 97b to swing.

4 and 5, the valve mechanism 97 includes a decompression device 111 according to the first embodiment. The decompression device 111 is assembled to the camshaft 95, the decompression cam 112 assembled to the camshaft 95, the decompression follower 113 defined on the exhaust-side rocker arm 97b so as to be in contact with the decompression cam 112, and the camshaft 95. And a drive arm 114 for driving the decompression cam 112 therebetween.

The decompression cam 112 and the driving arm 114 are supported by a step surface 115 formed on the camshaft 95 between the second cam 108 and the bearing 106. The step surface 115 is partitioned between a large-diameter shaft 116a that defines the second cam 108 and a small-diameter shaft 116b that is continuous with the large-diameter shaft 116a and has a smaller diameter than the large-diameter shaft 116a and is received by the bearing 106, It faces the bearing 106. The step surface 115 is connected to the edges of the base surface 108a and the lift surface 108b of the second cam 108 perpendicular to the axis Xc of the cam shaft 95.

The decompression cam 112 includes a shaft body 117 having an axis parallel to the axis Xc of the camshaft 95. The shaft body 117 is formed in the camshaft 95 and is received in a through hole 118 that defines a cylindrical space coaxial with the shaft body 115 so as to be rotatable about an axis (= rotation axis Xd). In this way, the decompression cam 112 is supported by the camshaft 95 so as to be rotatable about the rotation axis Xd.

The decompression cam 112 includes a cam body 119 that is coaxial with the shaft body 117. The cam body 119 has a cylindrical surface 121 that is concentric with the shaft body 117 and is continuous around the axis of the shaft body 117. The cylindrical surface 121 is arranged at a position shifted in the axial direction of the camshaft 95 from the virtual cylindrical surface 122 drawn coaxially with the axis Xc of the camshaft 95 and facing the decompression follower 113. Here, the virtual cylindrical surface 122 is a cylindrical surface coaxial with the cylindrical surface 121 and continuous from the cylindrical surface 121 in the axial direction.

The decompression cam 112 has a cam groove 124 that receives the cam pin 123. The cam pin 123 is configured by a cylindrical body having an axis parallel to the axis Xc of the camshaft 95. The cam groove 124 is formed on the end surface of the cam body 119 and extends linearly from the cylindrical surface 121 toward the axis. When the cam pin 123 moves in the circumferential direction around the axis Xc of the camshaft 95, the decompression cam 112 changes its posture between its operating position and non-operating position about its axis.

The drive arm 114 is supported by the camshaft 95 so as to be swingable about the swing shaft 125. The swing shaft 125 has an axis parallel to the axis Xc of the camshaft 95. The swing shaft 125 is pushed into the step surface 115 by press-fitting, for example. A spacer 126 is mounted on the swing shaft 125 between the step surface 115 and the drive arm 114. The size of the spacer 126 in the axial direction of the camshaft 95 corresponds to the size of the virtual cylindrical surface 122. Thus, the virtual cylindrical surface 122 is disposed between the drive arm 114 and the step surface 115.

The oscillating shaft 125 is disposed at a position away from the rotational axis Xd of the decompression cam 112 at least in the circumferential direction of the camshaft 95. It is desirable that the swing shaft 125 be separated from the decompression cam 112 as much as possible. Here, the rotation axis Xd of the swing shaft 125 and the decompression cam 112 is arranged on both sides of the axis Xc on one diameter line.

The cam pin 123 is fixed to the tip of the drive arm 114. The cam pin 123 moves between a first position that establishes the operating position of the decompression cam 112 and a second position that establishes the non-operating position of the decompression cam 112. A torsion spring 127 is attached to the spacer 126. One end of the torsion spring 127 is hooked on the drive arm 114. The other end of the torsion spring 127 is hooked on the small diameter shaft 116b. The torsion spring 127 exhibits an elastic force that drives the cam pin 123 toward the first position.

The drive arm 114 is curved between the swing shaft 125 and the cam pin 123, bypassing the small diameter shaft 116b. A centrifugal weight 128 is attached to the drive arm 114 between the swing shaft 125 and the cam pin 123. The centrifugal weight 128 exerts a centrifugal force that moves the cam pin 123 from the first position to the second position against the elastic force of the torsion spring 127 when the rotation of the camshaft 95 reaches a preset number of rotations.

The cam body 119 of the decompression cam 112 is disposed in a space inside the virtual cylindrical surface 122, and a partial cylindrical surface 129 that is coaxially continuous with the shaft body 117 from the cylindrical surface 121, and buses at both ends of the partial cylindrical surface 129. And a plane 131 to be connected. The decompression cam 112 projects a part of the partial cylindrical surface 129 outward from the virtual cylindrical surface 122 at the operating position. The partial cylindrical surface 129 corresponds to a curved projecting surface having a generatrix parallel to the axis Xc of the camshaft 95.

As shown in FIG. 6, the decompression follower 113 is provided on the exhaust-side rocker arm 97 b outside the virtual cylindrical surface 122, and faces the virtual cylindrical surface 122 at a position closest to the virtual cylindrical surface 122. A convex decompression follower surface 133 having a convex curved surface in contact with the camshaft 95 and a concave curved surface provided upstream of the convex decompression follower surface 133 in the forward rotation direction of the camshaft 95 and having a generatrix parallel to the axis Xc of the camshaft 95. A first concave decompression follower surface 134 that is formed and contacts the partial cylindrical surface 129 and a downstream line of the convex decompression follower surface 133 in the forward rotation direction of the camshaft 95, and generates a bus parallel to the axis Xc of the camshaft 95. And a second concave decompress follower surface 135 that contacts the partial cylindrical surface 129. In the decompression follower 113, a first auxiliary concave decompression follower surface 136 configured by a concave curved surface having a smaller curvature than the partial cylindrical surface 129 is formed between the convex decompression follower surface 133 and the first concave decompression follower surface 134. . Similarly, a second auxiliary concave decompression follower surface 137 is formed between the convex decompression follower surface 133 and the second concave decompression follower surface 135. The second auxiliary concave decompression follower surface 137 is a concave curved surface having a smaller curvature than the partial cylindrical surface 129.

The upstream end 134a of the first concave decompression follower surface 134 is disposed at a position away from the axis Xc of the camshaft 95 in the radial direction as compared with the partial cylindrical surface 129. The downstream end 135a of the second concave decompression follower surface 135 is disposed at a position radially away from the axis Xc of the camshaft 95 as compared to the partial cylindrical surface 129. The first concave decompression follower surface 134 moves away from the axis Xc of the camshaft 95 as it moves away from the convex decompression follower surface 133 in the circumferential direction of the virtual cylindrical surface 122. The second concave decompression follower surface 135 moves away from the axis Xc of the camshaft 95 as it moves away from the convex decompression follower surface 133 in the circumferential direction of the virtual cylindrical surface 122. The first concave decompression follower surface 134 is formed by a part of a cylindrical surface having a smaller curvature than the partial cylindrical surface 129. The second concave decompression follower surface 135 is formed by a part of a cylindrical surface having a smaller curvature than the partial cylindrical surface 129. The first auxiliary concave decompression follower surface 136 is formed by a part of a cylindrical surface having a smaller curvature than the partial cylindrical surface 129. The second auxiliary concave decompression follower surface 137 is formed by a part of a cylindrical surface having a smaller curvature than the partial cylindrical surface 129. The first auxiliary concave decompression follower surface 136 is formed of a part of a cylindrical surface having a larger curvature than the first concave decompression follower surface 134. The second auxiliary concave decompression follower surface 137 is formed of a part of a cylindrical surface having a larger curvature than the second concave decompression follower surface 135. The first auxiliary concave decompression follower surface 136 and the second auxiliary concave decompression follower surface 137 may be formed of a part of a cylindrical surface having a smaller curvature than the convex decompression follower surface 133, and have a larger curvature than the convex decompression follower surface 133. You may form with a part of cylindrical surface which has.

Here, the convex decompression follower surface 133 is further away from the axis Xc of the camshaft 95 than the outer peripheral surface of the roller 109. Since the cylindrical surface 121 and the virtual cylindrical surface 122 have the same diameter, the convex decompression follower surface 133 is maintained at a constant interval from the virtual cylindrical surface 122. As shown in FIG. 7, when the flat surface 131 continuing to the partial cylindrical surface 129 is disposed inside the virtual cylindrical surface 122 at the non-operating position of the decompression cam 112, contact between the decompression cam 112 and the decompression follower 113 is avoided. The

Next, the operation of the decompression device 111 will be described. In the internal combustion engine 29, the intake stroke, the compression stroke, the combustion stroke, and the exhaust stroke are repeated in order. In the intake stroke, the intake valve 88 is opened. The piston 45 is lowered by the inertial force of the crankshaft 32. An air-fuel mixture is introduced into the combustion chamber 46. Fuel is injected from the fuel injection valve 42 by the throttle body 41 into the air introduced from the intake device 37. In the compression stroke, the piston 45 is lifted by the inertial force of the crankshaft 32. The intake valve 88 and the exhaust valve 89 are kept closed. The air-fuel mixture is compressed in the combustion chamber 46. In the combustion stroke, the air-fuel mixture is ignited in the combustion chamber 46. The intake valve 88 and the exhaust valve 89 are kept closed. The piston 45 descends due to the explosion in the combustion chamber 46. A driving force is transmitted to the crankshaft 32. In the exhaust stroke, the exhaust valve 89 is opened. The piston 45 is raised by the inertial force of the crankshaft 32. The exhaust gas after combustion is released to the exhaust pipe 43. The intake stroke is performed again as the piston 45 continues to descend. When the internal combustion engine 29 is started, a driving force is transmitted from the alternator starter 49 to the crankshaft 32. The AC generator starter 49 generates a driving force in accordance with power supplied from, for example, a battery (not shown).

The valve mechanism 87 operates in conjunction with the rotation of the crankshaft 32. Opening and closing of the intake valve 88 is controlled by swinging of the intake side rocker arm 97a. The rocker arm 97 a swings according to the contact between the roller 109 and the first cam 107. While the roller 109 is in contact with the base surface 107a of the first cam 107, the rocker arm 97a maintains the closed state of the intake valve 88. When the roller 109 follows the lift surface 107b, the intake valve 88 opens. Opening and closing of the exhaust valve 89 is controlled by swinging of the exhaust side rocker arm 97b. The rocker arm 97 b swings according to the contact between the roller 109 and the second cam 108. While the roller 109 is in contact with the base surface 108 a of the second cam 108, the rocker arm 97 b maintains the exhaust valve 89 in the closed state. When the roller 109 follows the lift surface 108b, the exhaust valve 89 opens.

If the engine speed of the internal combustion engine 29 is less than a predetermined speed, the decompression device 111 does not generate sufficient centrifugal force in the centrifugal weight 128 according to the rotation of the camshaft 95. Therefore, the drive arm 114 maintains the cam pin 123 in the first position according to the elastic force of the torsion spring 127. The decompression cam 112 is located at the operating position. The partial cylindrical surface 129 protrudes from the virtual cylindrical surface including the virtual cylindrical surface 122. In response to the rotation of the camshaft 95, the partial cylindrical surface 129 becomes the first concave decompression follower surface 134, the first auxiliary concave decompression follower surface 136, the convex decompression follower surface 133, the second auxiliary concave decompression follower surface 137 and the first auxiliary concave decompression follower surface 137. The two-concave decompressor follower surface 135 is successively contacted. Thus, the exhaust valve 89 opens during the compression stroke. The pressure in the combustion chamber 46 is released. The driving resistance of the piston 45 is reduced, and the vibration of the internal combustion engine is suppressed.

When the engine speed of the internal combustion engine 29 reaches or exceeds a predetermined speed, the decompression device 111 generates a sufficient centrifugal force in the centrifugal weight 128 according to the rotation of the camshaft 95. Therefore, the drive arm 114 drives the cam pin 123 from the first position to the second position against the elastic force of the torsion spring 127. The decompression cam 112 changes its posture to the non-operating position. The decompression cam 112 fits inside the virtual cylindrical surface including the virtual cylindrical surface 122. Contact between the decompression follower 113 and the decompression cam 112 during the rotation of the camshaft 95 is avoided. The exhaust valve 89 is kept closed during the compression stroke. The driving force of the piston 45 based on the explosion is maximized. The internal combustion engine 29 generates power efficiently.

According to the present embodiment, the partial cylindrical surface 129 of the decompression cam 112 protrudes in the centrifugal direction of the camshaft 95 in a low rotational speed range less than the set rotational speed. During the forward rotation of the camshaft 95, the partial cylindrical surface 129 of the decompression cam 112 successively contacts the first concave decompression follower surface 134 and the convex decompression follower surface 133 of the exhaust side rocker arm 97b. Since the first concave decompression follower surface 134 is formed as a concave curved surface, the partial cylindrical surface 129 of the decompression cam 112 can slide in a tangential direction with respect to the concave curved surface at the start of contact. Therefore, the collision sound between the decompression cam 112 and the exhaust side rocker arm 97b can be suppressed.

The upstream end 134a of the first concave decompression follower surface 134 is disposed at a position farther from the axis Xc of the camshaft 95 than the partial cylindrical surface 129 of the rocker arm 97b. At the start of contact, the partial cylindrical surface 129 of the decompression cam 112 reliably contacts the concave curved surface of the first concave decompression follower surface 134. The collision sound between the decompression cam 112 and the exhaust side rocker arm 97b can be suppressed.

The first concave decompression follower surface 134 according to the present embodiment moves away from the axis Xc of the camshaft 95 as the distance from the convex decompression follower surface 133 increases. Therefore, even if the partial cylindrical surface 129 of the decompression cam 112 is slightly displaced based on dimensional tolerances or assembly errors, the partial cylindrical surface 129 of the decompression cam 112 is tangential to the first concave decompression follower surface 134 at the start of contact. You can slide into. Therefore, the collision sound between the decompression cam 112 and the exhaust side rocker arm 97b can be suppressed.

In addition, in the decompression follower 113, the first auxiliary concave decompression follower configured by a concave curved surface having a smaller curvature than the partial cylindrical surface 129 of the decompression cam 112 between the convex decompression follower surface 133 and the first concave decompression follower surface 134. A surface 136 is formed. Since the first concave decompression follower surface 134, the first auxiliary concave decompression follower surface 136 and the convex decompression follower surface 133 are continuous, the partial cylindrical surface 129 of the decompression cam 112 is changed from the first concave decompression follower surface 134 to the convex decompression follower surface 133. It can follow smoothly. The collision sound between the decompression cam 112 and the exhaust side rocker arm 97b can be suppressed.

The first auxiliary concave decompression follower surface 136 is formed by a part of a cylindrical surface having a larger curvature than the first concave decompression follower surface 134. As a result, the partial cylindrical surface 129 of the decompression cam 112 smoothly follows the convex decompression follower surface 133 from the first concave decompression follower surface 134 in accordance with the change in curvature. The collision sound between the decompression cam 112 and the exhaust side rocker arm 97b can be suppressed.

Furthermore, during the forward rotation of the camshaft 95, the partial cylindrical surface 129 of the decompression cam 112 contacts the second concave decompression follower surface 135 following the convex decompression follower surface 133. Since the second concave decompression follower surface 135 is formed as a concave curved surface, the lift amount of the exhaust valve 89 gradually changes when the decompression cam 112 is detached from the second concave decompression follower surface 135. As a result, the seating sound (seat noise) of the exhaust valve 89 is reduced. Moreover, the partial cylindrical surface 129 of the decompression cam 112 successively contacts the second concave decompression follower surface 135 and the convex decompression follower surface 133 when the piston 45 does not pass over the compression top dead center and the camshaft 95 reverses. Since the second concave decompression follower surface 135 is formed as a concave curved surface, the partial cylindrical surface 129 of the decompression cam 112 can slide in a tangential direction with respect to the concave curved surface at the start of contact. Therefore, when the camshaft 95 reverses without the piston 45 overcoming the compression top dead center, the collision noise between the decompression cam 112 and the exhaust-side rocker arm 97b can be suppressed.

The downstream end 135a of the second concave decompression follower surface 135 is disposed at a position farther from the axis Xc of the camshaft 95 than the partial cylindrical surface 129 of the decompression cam 112. In response to the rotation of the camshaft 95, the partial cylindrical surface 129 of the decompression cam 112 moves away from the rocker arm 97b with a concave curved surface. When seated, the lift amount of the exhaust valve 89 changes gradually. Thus, the seating noise of the exhaust valve 89 can be reduced.

The second concave decompression follower surface 135 according to the present embodiment moves away from the axis Xc of the camshaft 95 as the distance from the convex decompression follower surface 133 increases. Therefore, even if the partial cylindrical surface 129 of the decompression cam 112 is slightly displaced based on dimensional tolerances, assembly errors, etc., the lift amount of the exhaust valve 89 changes gently upon seating. Thus, the seating noise of the exhaust valve 89 can be reduced.

In the decompression follower 113, a second auxiliary concave decompression follower surface 137 configured by a concave curved surface having a smaller curvature than the partial cylindrical surface 129 of the decompression cam 112 is provided between the convex decompression follower surface 133 and the second concave decompression follower surface 135. It is formed. Since the convex decompression follower surface 133, the second auxiliary concave decompression follower surface 137, and the second concave decompression follower surface 135 are continuous, the partial cylindrical surface 129 of the decompression cam 112 changes from the convex decompression follower surface 133 to the second concave decompression follower surface 135. It can follow smoothly. The collision sound between the decompression cam 112 and the exhaust side rocker arm 97b can be suppressed.

The second auxiliary concave decompression follower surface 137 is formed by a part of a cylindrical surface having a larger curvature than the second concave decompression follower surface 135. As a result, the partial cylindrical surface 129 of the decompression cam 112 can smoothly follow the second concave decompression follower surface 135 from the convex decompression follower surface 133 in accordance with the change in curvature. The collision sound between the decompression cam 112 and the exhaust side rocker arm 97b can be suppressed.

In this embodiment, the internal combustion engine 29 employs motor idling control. In the motor idling control, fuel is not injected from the fuel injection valve 42 into the air introduced from the intake device 37 into the combustion chamber 46 when the accelerator is off (the accelerator is not operated). A driving force is transmitted from the alternator starter 49 to the crankshaft 32 in maintaining idling. The AC generator starter 49 generates a driving force in accordance with power supplied from, for example, a battery (not shown). In idling, the AC generator starter 49 can realize the reciprocating motion of the piston 45 without going through a combustion stroke. Fuel consumption is suppressed and the exhaust noise of the internal combustion engine 29 is reduced.

Second embodiment

FIG. 8 schematically shows the configuration of the decompression device 141 according to the second embodiment. In the decompression device 141, the decompression follower 142 includes the first concave decompression follower surface 134, the first auxiliary concave decompression follower surface 136, the convex decompression follower surface 133, the second auxiliary concave decompression follower surface 137, and the second concave decompression follower surface. In place of 135, a convex decompression follower surface 143 having a single convex curved surface is provided. On the other hand, the curved projecting surface 145 of the decompression cam 144 is provided upstream of the top surface 146 that protrudes most from the virtual cylindrical surface 122 and the top surface 146 in the forward rotation direction of the camshaft 95, and the axis Xc of the camshaft 95. A first buffer surface 147 formed on a concave curved surface having a generatrix parallel to the camshaft 95, and provided downstream of the top surface 146 in the forward rotation direction of the camshaft 95 and having a generatrix parallel to the axis Xc of the camshaft 95 And a second buffer surface 148 formed on the concave curved surface. Other configurations are the same as those of the above-described embodiment.

Here, the convex decompression follower surface 143 of the decompression follower 142 is constituted by a part of a cylindrical surface that is coaxial with the rotation axis of the roller 109 and has a smaller diameter than the roller 109. Therefore, the convex decompression follower surface 143 faces the virtual cylindrical surface 122 at a set interval. On the other hand, the top surface 146 of the decompression cam 144 is configured as a part of a cylindrical surface having the same diameter as the partial cylindrical surface 129. The first buffer surface 147 and the second buffer surface 148 of the decompression cam 144 are each formed of a partial cylindrical surface having a smaller curvature than the convex decompression follower surface 143. The upstream end 147a of the first buffer surface 147 is disposed at a position closer to the axis Xc of the camshaft 95 than the convex decompression follower surface 143 when the decompression cam 144 is located at the operating position. The downstream end 148a of the second buffer surface 148 is disposed closer to the axis Xc of the camshaft 95 than the convex decompression follower surface 143 when the decompression cam 144 is located at the operating position.

During the forward rotation of the camshaft 95, the curved projecting surface 145 of the decompression cam 144 successively contacts the convex decompression follower surface 143 of the exhaust-side rocker arm 97b at the first buffer surface 147 and the top surface 146. Since the first buffer surface 147 of the decompression cam 144 is formed in a concave curved surface, the convex decompression follower surface 143 can slide in a tangential direction with respect to the first buffer surface 147 of the decompression cam 144 at the start of contact. Therefore, the collision sound between the decompression cam 144 and the exhaust side rocker arm 97b can be suppressed.

During the forward rotation of the camshaft 95, the curved projection surface 145 of the decompression cam 144 contacts the convex decompression follower surface 143 at the second buffer surface 148 following the top surface 146. Since the second buffer surface 148 is formed as a concave curved surface, when the convex decompression follower surface 143 is detached from the second buffer surface 148, the lift amount of the exhaust valve 89 gradually changes. As a result, the seating sound (seat noise) of the exhaust valve 89 is reduced. Moreover, during the reverse rotation of the camshaft 95, the curved projecting surface 145 of the decompression cam 144 contacts the second buffer surface 148 and the top surface 146 one after another. Since the second buffer surface 148 is formed as a concave curved surface, the convex decompression follower surface 143 can slide in the tangential direction with respect to the second buffer surface 148 at the start of contact. Therefore, when the piston 45 does not pass over the compression top dead center and the camshaft 95 is reversed, the collision noise between the decompression cam 144 and the exhaust-side rocker arm 97b can be suppressed.

Third embodiment

FIG. 9 schematically shows a configuration of a decompression device 151 according to the third embodiment. In the decompression device 151, the cam follower 101 also serves as the decompression follower 142. That is, the roller 109 of the cam follower 101 functions as the convex decompression follower surface 143 having the above-described convex curved surface over the entire circumference of the cylindrical surface. The roller 109 faces the virtual cylindrical surface 122 at a set interval. The top surface 146 of the decompression cam 144 is configured as a part of a cylindrical surface having the same diameter as the partial cylindrical surface 129. The first buffer surface 147 and the second buffer surface 148 of the decompression cam 144 are each configured by a partial cylindrical surface having a smaller curvature than the cylindrical surface of the roller 109. The upstream end 147a of the first buffer surface 147 is disposed at a position closer to the axis Xc of the camshaft 95 than the roller 109 when the decompression cam 144 is positioned at the operating position. The downstream end 148a of the second buffer surface 148 is disposed at a position closer to the axis Xc of the camshaft 95 than the roller 109 when the decompression cam 144 is positioned at the operating position. Other configurations are the same as those of the second embodiment.

During the forward rotation of the camshaft 95, the curved projecting surface 145 of the decompression cam 144 successively contacts the roller 109 of the exhaust-side rocker arm 97b at the first buffer surface 147 and the top surface 146. Since the first buffer surface 147 of the decompression cam 144 is formed in a concave curved surface, the roller 109 can slide in the tangential direction with respect to the first buffer surface 147 of the decompression cam 144 at the start of contact. Therefore, the collision sound between the decompression cam 144 and the exhaust side rocker arm 97b can be suppressed.

During the forward rotation of the camshaft 95, the curved projection surface 145 of the decompression cam 144 comes into contact with the roller 109 at the second buffer surface 148 following the top surface 146. Since the second buffer surface 148 is formed in a concave curved surface, when the roller 109 is detached from the second buffer surface 148, the lift amount of the exhaust valve 89 gradually changes. As a result, the seating sound (seat noise) of the exhaust valve 89 is reduced. Moreover, during the reverse rotation of the camshaft 95, the curved projecting surface 145 of the decompression cam 144 contacts the second buffer surface 148 and the top surface 146 one after another. Since the second buffer surface 148 is formed in a concave curved surface, the roller 109 can slide in the tangential direction with respect to the second buffer surface 148 at the start of contact. Therefore, when the piston 45 does not pass over the compression top dead center and the camshaft 95 is reversed, the collision noise between the decompression cam 144 and the exhaust-side rocker arm 97b can be suppressed.

Claims

A base surface (108a) having a shape of a partial cylindrical surface coaxial with the rotational axis (Xc) of the camshaft (95);
The camshaft (95) is provided on the camshaft (95) continuously to the base surface (108a) in the rotational direction, and rises radially outward from the base surface (108a) to define the lift amount of the exhaust valve (89). A lift surface (108b);
A cam follower (101) provided on the exhaust-side rocker arm (97b) and causing the exhaust-side rocker arm (97b) to swing while maintaining contact with the base surface (108a) and the lift surface (108b). When,
A curved projecting surface (129) having a generatrix parallel to the rotational axis (Xc) of the camshaft (95) from a virtual cylindrical surface (122) coaxial with the camshaft (95) at a rotational speed less than a preset value. A decompression cam (112) for projecting
Provided on the exhaust-side rocker arm (97b) outside the virtual cylindrical surface (122) and facing the virtual cylindrical surface (122) at a position closest to the virtual cylindrical surface (122), the curved projecting surface ( 129) a convex decompression follower surface (133) of a convex curved surface in contact with 129);
The camshaft (95) is formed in a concave curved surface provided upstream of the convex decompression follower surface (133) in the forward rotation direction of the camshaft (95) and having a generatrix parallel to the rotation axis (Xc) of the camshaft (95). An internal combustion engine comprising a concave decompression follower surface (134) that contacts the curved projecting surface (129).
The internal combustion engine according to claim 1, wherein the upstream end (134a) of the concave decompression follower surface (134) is separated from the rotational axis (Xc) of the camshaft (95) as compared to the curved projecting surface (129). An internal combustion engine characterized by being provided at a different position.
3. The internal combustion engine according to claim 1, wherein the concave decompression follower surface (134) moves away from the rotational axis (Xc) of the camshaft (95) as the distance from the convex decompression follower surface (133) increases. An internal combustion engine.
The internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is formed between the convex decompression follower surface (133) and the concave decompression follower surface (134), and more than the curved projecting surface (129). The internal combustion engine further comprising an auxiliary concave decompression follower surface (136) constituted by a concave curved surface having a small curvature.
5. The internal combustion engine according to claim 4, wherein the auxiliary concave decompression follower surface (136) is formed by a part of a cylindrical surface having a larger curvature than the concave decompression follower surface (134). organ.
The internal combustion engine according to any one of claims 1 to 5, wherein the camshaft (95) is provided downstream of the convex decompression follower surface (133) in a forward rotation direction of the camshaft (95). The internal combustion engine further comprising a second concave decompression follower surface (135) formed on a concave curved surface having a generatrix parallel to the rotation axis (Xc) and contacting the curved convex surface (129).
A base surface (108a) having a shape of a partial cylindrical surface coaxial with the rotational axis (Xc) of the camshaft (95);
The camshaft (95) is provided on the camshaft (95) continuously to the base surface (108a) in the rotational direction, and rises radially outward from the base surface (108a) to define the lift amount of the exhaust valve (89). A lift surface (108b);
A cam follower (101) provided on the exhaust-side rocker arm (97b) and causing the exhaust-side rocker arm (97b) to swing while maintaining contact with the base surface (108a) and the lift surface (108b). When,
A curved projecting surface (129) having a generatrix parallel to the rotational axis (Xc) of the camshaft (95) from a virtual cylindrical surface (122) coaxial with the camshaft (95) at a rotational speed less than a preset value. A decompression cam (112) for projecting
Provided on the exhaust-side rocker arm (97b) outside the virtual cylindrical surface (122) and facing the virtual cylindrical surface (122) at a position closest to the virtual cylindrical surface (122), the curved projecting surface ( 129) a convex decompressor follower surface (133) in contact with,
The cam shaft (95) is formed in a concave curved surface provided downstream of the convex decompression follower surface (133) in the forward rotation direction and having a generatrix parallel to the rotation axis (Xc) of the cam shaft (95). An internal combustion engine comprising a concave decompression follower surface (135) that contacts the curved projecting surface (129).
The internal combustion engine according to claim 7, wherein the downstream end (135a) of the concave decompression follower surface (135) is separated from the rotational axis (Xc) of the camshaft (95) as compared to the curved projecting surface (129). An internal combustion engine characterized by being provided at a different position.
9. The internal combustion engine according to claim 7, wherein the concave decompression follower surface (135) moves away from the rotational axis (Xc) of the camshaft (95) as the distance from the convex decompression follower surface (133) increases. An internal combustion engine.
The internal combustion engine according to any one of claims 7 to 9, wherein the internal combustion engine is formed between the convex decompression follower surface (133) and the concave decompression follower surface (135), and more than the curved projecting surface (129). An internal combustion engine, further comprising an auxiliary concave decompressor follower surface (137) composed of a concave curved surface with a small curvature.
The internal combustion engine according to claim 10, wherein the auxiliary concave decompression follower surface (137) is formed by a part of a cylindrical surface having a larger curvature than the concave decompression follower surface (135). organ.
The internal combustion engine according to any one of claims 1 to 11, wherein the internal combustion engine is coupled to a crankshaft (32) to generate electric power according to rotation of the crankshaft (32) and to generate electric power according to supplied electric power. An internal combustion engine further comprising an AC generator (49) for driving the crankshaft (32) about its rotational axis (Xis).
A base surface (108a) having a shape of a partial cylindrical surface coaxial with the rotational axis (Xc) of the camshaft (95);
The camshaft (95) is provided on the camshaft (95) continuously to the base surface (108a) in the rotational direction, and rises radially outward from the base surface (108a) to define the lift amount of the exhaust valve (89). A lift surface (108b);
A cam follower (101) provided on the exhaust-side rocker arm (97b) and causing the exhaust-side rocker arm (97b) to swing while maintaining contact with the base surface (108a) and the lift surface (108b). When,
A curved projecting surface (145) having a generatrix parallel to the rotational axis (Xc) of the camshaft (95) from a virtual cylindrical surface (122) coaxial with the camshaft (95) at a rotational speed less than a preset value. A decompression cam (144) for projecting
A convex decompression follower of a convex curved surface provided on the exhaust-side rocker arm (97b) outside the virtual cylindrical surface (122) and facing the virtual cylindrical surface (122) and contacting the curved convex surface (145). A surface (143),
The curved projecting surface (145) is provided upstream of the top surface (146) in the forward direction of the camshaft (95) and the top surface (146) that protrudes most from the virtual cylindrical surface (122). And a buffer surface (147) formed on a concave curved surface having a generatrix parallel to the rotational axis (Xc) of the camshaft (95) and in contact with the convex decompression follower surface (143). Internal combustion engine.
The internal combustion engine according to claim 13, wherein the curved projecting surface (145) is provided downstream of the top surface (146) in the forward rotation direction of the camshaft (95), so that the camshaft (95) The internal combustion engine further comprising a second buffer surface (148) formed on a concave curved surface having a generatrix parallel to the rotation axis (Xc).
A base surface (108a) having a shape of a partial cylindrical surface coaxial with the rotational axis (Xc) of the camshaft (95);
The camshaft (95) is provided on the camshaft (95) continuously to the base surface (108a) in the rotational direction, and rises radially outward from the base surface (108a) to define the lift amount of the exhaust valve (89). A lift surface (108b);
A cam follower (101) provided on the exhaust-side rocker arm (97b) and causing the exhaust-side rocker arm (97b) to swing while maintaining contact with the base surface (108a) and the lift surface (108b). When,
A curved projecting surface (145) having a generatrix parallel to the rotational axis (Xc) of the camshaft (95) from a virtual cylindrical surface (122) coaxial with the camshaft (95) at a rotational speed less than a preset value. A decompression cam (144) for projecting
A convex decompression follower of a convex curved surface provided on the exhaust-side rocker arm (97b) outside the virtual cylindrical surface (122) and facing the virtual cylindrical surface (122) and contacting the curved convex surface (145). A surface (143),
The curved projecting surface (145) is provided downstream from the top surface (146) in the forward rotation direction of the camshaft (95) with the top surface (146) most protruding from the virtual cylindrical surface (122). And a buffer surface (148) formed on a concave curved surface having a generatrix parallel to the rotational axis (Xc) of the camshaft (95) and contacting the convex decompression follower surface (143). Internal combustion engine.