ENGINE

Abstract

 A coupling pin (51) includes a receiver portion (56) that receives an urging force applied by an urging member (52). The receiver portion (56) is located outside a first coupling hole (422). The urging member (52) is disposed between the receiver portion (56) and a first rocker arm (42). A cylinder head (4) includes a retainer portion (58) disposed downstream of the receiver portion (56) in a first direction (XI). The retainer portion (58) overlaps at least part of the coupling pin (51) as seen from an axis direction. The coupling pin (51) has a length (LI) greater than a distance (L2) between the first coupling hole (422) and the retainer portion (58) in the axis direction.

Description

[0001] The present invention relates to an engine.

[0002] An engine includes a valve actuating mechanism for opening and closing an intake valve and an exhaust valve. For example, Japan Laid-open Patent Application Publication No. 2015-90098 describes a type of valve actuating mechanism that includes a rocker shaft, a first rocker arm, a second rocker arm and a decoupling device. The rocker shaft is supported by a cylinder head. The first rocker arm and the second rocker arm are supported by the rocker shaft. The second rocker arm is disposed in alignment with the first rocker arm in the axis direction of the rocker shaft. The decoupling device switches coupling and decoupling between the first rocker arm and the second rocker arm.

[0003] The decoupling device includes a coupling pin, an actuator and an urging member. The coupling pin is disposed in a first coupling hole provided in the first rocker arm. The actuator presses the coupling pin so as to insert the coupling pin into a second coupling hole provided in the second rocker arm. The urging member is disposed in the first coupling hole. The urging member urges the coupling pin to the side remote from the second coupling hole in the axis direction.

[0004] When the coupling pin is not being pressed by the actuator, the end of the coupling pin is disposed outside the second coupling hole by the urging force of the urging member. A decoupled state is thereby made between the first rocker arm and the second rocker arm. Contrarily, when the coupling pin is being pressed by the actuator, the end of the coupling pin is disposed inside the second coupling hole against the urging force of the urging member. A coupled state is thereby made between the first rocker arm and the second rocker arm.

[0005] The coupling pin includes a stopper member having a flange shape. A stopper, having a ring shape, is attached to the inner peripheral surface of the first coupling hole provided in the first rocker arm. In assembling or disassembling the engine, the stopper member of the coupling pin is configured to make contact with the stopper attached to the first coupling hole so as to prevent the coupling pin from coming off.

[0006] Incidentally, in changing a valve lift curve to enhance fuel efficiency, for instance, there are chances of increase in acceleration of each rocker arm. In general, with increase in acceleration of each rocker arm, each rocker arm or the peripheral structure thereof requires higher stiffness. However, when each rocker arm or the peripheral structure thereof is increased in thickness so as to reliably obtain required stiffness, increase in size of the engine is inevitable.

[0007] The aforementioned stiffness of each rocker arm is reduced with reduction in equivalent mass thereof. In view of this, the inventor of the present invention conceived of reducing the equivalent mass of each rocker arm such that each rocker arm can be driven with high acceleration while increase in size of the engine can be avoided. It is an object of the present invention to reduce the equivalent mass of a rocker arm in a valve actuation mechanism including a decoupling device. According to the present invention said object is solved by an engine having the features of the independent claim 1. Preferred embodiments are laid down in the dependent claims.

[0008] An engine according to an aspect includes a cylinder head and a valve actuating mechanism. The valve actuating mechanism is provided in the cylinder head. The valve actuating mechanism includes a valve, a rocker shaft, a first rocker arm, a second rocker arm and a decoupling device. The rocker shaft is supported by the cylinder head. The first rocker arm is supported by the rocker shaft. The second rocker arm is supported by the rocker shaft, and is disposed in alignment with the first rocker arm in an axis direction of the rocker shaft. The decoupling device switches coupling and decoupling between the first rocker arm and the second rocker arm. The first rocker arm includes a first coupling hole extending in the axis direction. The second rocker arm includes a second coupling hole that extends in the axis direction and overlaps the first coupling hole as seen from the axis direction.

[0009] The decoupling device includes a coupling pin, an urging member and an actuator. The coupling pin is disposed at least in part inside the first coupling hole. The coupling pin is movable in the axis direction. The urging member urges the coupling pin in a first direction. The first direction is oriented from the second coupling hole to the first coupling hole in the axis direction. The actuator presses the coupling pin in a second direction. The second direction is oriented from the first coupling hole to the second coupling hole in the axis direction.

[0010] The coupling pin includes a receiver portion receiving an urging force applied by the urging member. The receiver portion is located outside the first coupling hole. The urging member is disposed between the receiver portion and the first rocker arm. The cylinder head includes a retainer portion disposed downstream of the receiver portion in the first direction. The retainer portion overlaps at least part of the coupling pin as seen from the axis direction. The coupling pin has a length greater than a distance between the first coupling hole and the retainer portion in the axis direction.

[0011] In the engine according to the present aspect, the receiver portion of the coupling pin is located outside the first coupling hole of the first rocker arm. Additionally, the urging member is disposed between the receiver portion and the first rocker arm. Therefore, the first rocker arm can be herein made compact compared to a configuration that the receiver portion and the urging member are disposed inside the first coupling hole. Because of this, the equivalent mass of the first rocker arm can be reduced.

[0012] Additionally, the retainer portion overlaps at least part of the coupling pin as seen from the axis direction, and the length of the coupling pin is greater than the distance between the first coupling hole and the retainer portion in the axis direction. Therefore, in assembling or disassembling the engine, the coupling pin can be prevented from coming off while in contact with the retainer portion. Furthermore, the retainer portion is included in the cylinder head. Therefore, the first rocker arm can be herein made more compact compared to a configuration that a structure for preventing the coupling pin from coming off is disposed inside the first coupling hole, whereby the equivalent mass of the first rocker arm can be reduced.

[0013] The coupling pin may include a lateral surface portion overlapping the retainer portion as seen from the axis direction. In this case, the coupling pin can be prevented from coming off, while making contact at the lateral surface portion thereof with the retainer portion.

[0014] The first rocker arm may include a first shaft boss portion and a first pin boss portion. The first shaft boss portion may include a first rocker shaft hole in which the rocker shaft is disposed. The first pin boss portion may include the first coupling hole. The first pin boss portion may have a smaller thickness than the first shaft boss portion in the axis direction. The first coupling hole may have a smaller length than the first rocker shaft hole in the axis direction.

[0015] In this case, the first pin boss portion disposed away from the rocker shaft has a small thickness, whereby the equivalent mass of the first rocker arm can be reduced. Additionally, a portion of the first rocker arm, which is located about the first coupling hole disposed away from the rocker shaft, has a small thickness, whereby the equivalent mass of the first rocker arm can be reduced.

[0016] The cylinder head may include a first support wall and a second support wall. The first and second support walls may be disposed away from each other in the axis direction, and may support the rocker shaft. The coupling pin may be entirely located between the first support wall and the second support wall in the axis direction. In this case, the coupling pin can be located close to the rocker shaft without being hindered by the first support wall. Because of this, the equivalent mass of the first rocker arm can be reduced.

[0017] The actuator may include a pressing pin making contact with the coupling pin. The pressing pin may further protrude than the retainer portion in the second direction. In this case, the coupling pin can be prevented from making contact with the retainer portion in actuation of the rocker shaft.

[0018] The urging member may be a coil spring. The coupling pin may be disposed inside the urging member. In this case, the urging member and the coupling pin can be compactly disposed.

[0019] The cylinder head may include the first support wall. The first support wall may be disposed downstream of the first rocker arm in the first direction, and may support the rocker shaft. The retainer portion may be part of the first support wall. In this case, the retainer portion can be provided with use of the first support wall for supporting the rocker shaft.

[0020] The cylinder head may include the first support wall and an attachment component. The first support wall may be disposed downstream of the first rocker arm in the first direction, and may support the rocker shaft. The attachment component may be provided separately from the first support wall, and may be attached to the first support wall. The retainer portion may be part of the attachment component. In this case, the retainer portion can be provided by the attachment component. Additionally, the attachment component is provided separately from the first support wall, whereby flexibility in layout of the retainer portion can be enhanced.

[0021] The retainer portion may overlap a first directional end of the coupling pin as seen from the axis direction. In this case, when moved in the axis direction, the coupling pin makes contact at the end thereof with the retainer portion, whereby the coupling pin is prevented from coming off.

[0022] The coupling pin may include a shaft portion and a flange portion. The shaft portion may be disposed at least in part inside the first coupling hole. The flange portion may be disposed outside the first coupling hole, and may radially protrude from the shaft portion. The retainer portion may overlap at least part of the flange portion as seen from the axis direction. The receiver portion may be part of the flange portion. In this case, when moved in the axis direction, the coupling pin makes contact at the flange portion with the retainer portion, whereby the coupling pin is prevented from coming off.

[0023] The actuator may include the pressing pin making contact with the coupling pin. The retainer portion and the coupling pin may overlap in a smaller range than the pressing pin and the coupling pin do as seen from the axis direction. In this case, the pressing pin and the coupling pin can reliably make contact with each other in a large contact area.

[0024] The urging member may overlap the receiver portion and the first rocker arm as seen from the axis direction. The urging member may be located second-directionally downstream of the receiver portion in the axis direction. The urging member may include a first end and a second end in the axis direction. The second end may be located second-directionally downstream of the first end in the axis direction. The first end may urge the receiver portion. In this case, the urging force of the urging member (e.g., a restoring stroke when the urging member is a spring) can be sufficiently utilized.

[0025] The valve actuating mechanism may have an SOHC (Single OverHead Camshaft) configuration. In this case, the decoupling device can be employed without impairing lightweight properties of the SOHC valve actuating mechanism.

FIG. 1 is a side view of a straddled vehicle according to a preferred embodiment.

FIG. 2 is a side view of part of an engine for the straddled vehicle.

FIG. 3 is a cross-sectional view of a cylinder head and a head cover as seen from a perpendicular direction to both a cylinder axis and a cam axis.

FIG. 4 is a perspective view of the interior of the cylinder head.

FIG. 5 is a perspective view of the interior of the cylinder head.

FIG. 6 is a view of the interior of the cylinder head as seen from a cylinder axis direction.

FIG. 7 is a cross-sectional view of the interior of the cylinder head as seen from a cam axis direction.

FIG. 8 is a perspective view of an intake rocker unit.

FIG. 9 is a view of the intake rocker unit as seen from a perpendicular direction to an intake rocker shaft axis.

FIG. 10 is a perspective view of a decoupling device and the surroundings thereof.

FIG. 11 is a view of the decoupling device and the surroundings thereof as seen from the cylinder axis direction.

FIG. 12 is a view of the decoupling device and the surroundings thereof as seen from the cylinder axis direction.

FIG. 13 is a view of part of the decoupling device as seen from an intake rocker shaft axis direction.

FIG. 14 is a view of the decoupling device and the surroundings thereof in a removed state of an actuator as seen from the cylinder axis direction.

FIG. 15 is a view of a decoupling device according to a first modification and the surroundings thereof as seen from the cylinder axis direction.

FIG. 16 is a view of a decoupling device according to a second modification and the surroundings thereof as seen from the cylinder axis direction.

FIG. 17 is a view of a decoupling device according to a third modification and the surroundings thereof as seen from the cylinder axis direction.

FIG. 18 is a view of part of a decoupling device according to a fourth modification as seen from the intake rocker shaft axis direction.

FIG. 19 is a view of the decoupling device according to the fourth modification and the surroundings thereof as seen from the cylinder axis direction.

[0026] A straddled vehicle according to a preferred embodiment and an engine for the straddled vehicle will be hereinafter explained with reference to drawings. FIG. 1 is a side view of a straddled vehicle 100 according to the preferred embodiment. The straddled vehicle 100 is a motorcycle of a so-called scooter type. As shown in FIG. 1, the straddled vehicle 100 includes a front wheel 101, a seat 102, a rear wheel 103, a power unit 104, a steering device 105 and a vehicle body cover 106.

[0027] The front wheel 101 is rotatably supported by the steering device 105. A handle 113 is attached to the upper end of the steering device 105. The seat 102 is disposed behind the steering device 105. The power unit 104 is disposed below the seat 102. The power unit 104 includes an engine 1 and a transmission 107. The power unit 104 supports the rear wheel 103 such that the rear wheel 103 is rotatable.

[0028] The vehicle body cover 106 includes a rear cover 108, a lower cover 109 and a front cover 110. The rear cover 108 is disposed below the seat 102. The front cover 110 covers the surroundings of the steering device 105. The lower cover 109 is disposed between the front cover 110 and the rear cover 108.

[0029] The lower cover 109 includes a foot rest 111 on the upper surface thereof. The foot rest 111 is provided for allowing a rider to put his/her feet thereon. The foot rest 111 has a flat shape extending in the right and left direction. It should be noted that the shape of the foot rest 111 is not limited to the flat shape. For example, the foot rest 111 may be provided with an upwardly protruding tunnel portion in the middle thereof.

[0030] FIG. 2 is a cross-sectional view of part of the engine 1. In the present preferred embodiment, the engine 1 is a single-cylinder engine of a water cooling type. As shown in FIG. 2, the engine 1 includes a crankcase 2, a cylinder body 3, a cylinder head 4 and a head cover 5.

[0031] The crankcase 2 accommodates a crankshaft 6. The cylinder body 3 is connected to the crankcase 2. The cylinder body 3 may be integrated with or separated from the crankcase 2. The cylinder body 3 accommodates a piston 7. The piston 7 is coupled to the crankshaft 6 through a connecting rod 8.

[0032] It should be noted that in the present preferred embodiment, the term "head cover side" is one side of the direction of a cylinder axis Ax1 of the cylinder body 3, and indicates a direction from the cylinder head 4 to the head cover 5. On the other hand, the term "cylinder body side" is the other side of the direction of the cylinder axis Ax1, and indicates a direction from the cylinder head 4 to the cylinder body 3.

[0033] The cylinder head 4 is disposed on the head cover side of the cylinder body 3. The cylinder head 4 is attached to the cylinder body 3. The cylinder head 4 may be separated from or integrated with the cylinder body 3. The head cover 5 is attached to the cylinder head 4.

[0034] As shown in FIG. 2, the cylinder axis Ax1 is arranged perpendicular to a center axis Ax2 of the crankshaft 6 (hereinafter referred to as "crank axis Ax2"). The cylinder head 4 includes a combustion chamber 11. A spark plug 12 is attached to the cylinder head 4. The tip end of the spark plug 12 is disposed to face the combustion chamber 11. The base end of the spark plug 12 is disposed outside the engine 1. A valve actuating mechanism 13 is accommodated in the cylinder head 4 and the head cover 5.

[0035] The valve actuating mechanism 13 is a mechanism for opening and closing an exhaust valve 25 (to be described) and an intake valve 27 (to be described). The valve actuating mechanism 13 employs an SOHC (Single OverHead Camshaft) mechanism. The valve actuating mechanism 13 also employs a so-called variable valve timing actuating mechanism that switches timing of opening and closing the intake valve 27.

[0036] The valve actuating mechanism 13 includes a camshaft 14. The camshaft 14 is supported by the cylinder head 4. A center axis Ax3 of the camshaft 14 (hereinafter referred to as "cam axis Ax3") is arranged perpendicular to the cylinder axis Ax1. The cam axis Ax3 is arranged in parallel to the crank axis Ax2.

[0037] FIG. 3 is a cross-sectional view of the cylinder head 4 and the head cover 5 as seen from a perpendicular direction to both the cylinder axis Ax1 and the cam axis Ax3. As shown in FIG. 3, the camshaft 14 includes a first camshaft end 141 and a second camshaft end 142.

[0038] A sprocket 29 is attached to the first camshaft end 141. A cam chain 15 shown in FIG. 2 is wound about the sprocket 29. The camshaft 14 is coupled to the crankshaft 6 through the cam chain 15. Rotation of the crankshaft 6 is transmitted to the camshaft 14 through the cam chain 15, whereby the camshaft 14 is rotated.

[0039] As shown in FIG. 3, the camshaft 14 includes a rod portion 143, a first intake cam 144, a second intake cam 145 and an exhaust cam 146. The first intake cam 144, the second intake cam 145 and the exhaust cam 146 are disposed on the outer periphery of the rod portion 143. The first intake cam 144, the second intake cam 145 and the exhaust cam 146 are disposed in alignment in the direction of the cam axis Ax3.

[0040] FIGS. 4 and 5 are perspective views of the interior of the cylinder head 4. FIG. 6 is a view of the interior of the cylinder head 4 as seen from the direction of the cylinder axis Ax1. As shown in FIGS. 3 to 6, the cylinder head 4 includes a first support wall 21 and a second support wall 22. The first and second support walls 21 and 22 are integrated with the cylinder head 4. It should be noted that the first and second support walls 21 and 22 may be provided separately from the cylinder head 4. The first and second support walls 21 and 22 are disposed away from and in alignment with each other in the cam axis Ax3 direction.

[0041] The first and second support walls 21 and 22 support the cam shaft 14 such that the cam shaft 14 is rotatable. As shown in FIG. 3, the first support wall 21 includes a first camshaft hole 211 into which the camshaft 14 is inserted. A first bearing 24 is attached to the first camshaft hole 211. The first support wall 21 supports the camshaft 14 through the first bearing 24. The second support wall 22 includes a second camshaft hole 221 into which the camshaft 14 is inserted. A second bearing 23 is attached to the second camshaft hole 221. The second support wall 22 supports the camshaft 14 through the second bearing 23.

[0042] As shown in FIG. 6, the exhaust valve 25 and the intake valve 27 are attached to the cylinder head 4. FIG. 7 is a cross-sectional view of the interior of the cylinder head 4 as seen from the cam axis Ax3 direction. As shown in FIG. 7, the cylinder head 4 includes an intake port 31 and an exhaust port 32, both of which communicate with the combustion chamber 11.

[0043] The intake valve 27 opens and closes the intake port 31. An intake valve spring 271 is attached to the intake valve 27. The intake valve spring 271 urges the intake valve 27 in a direction to cause the intake valve 27 to close the intake port 31.

[0044] The exhaust valve 25 opens and closes the exhaust port 32. An exhaust valve spring 251 is attached to the exhaust valve 25. The exhaust valve spring 251 urges the exhaust valve 25 in a direction to cause the exhaust valve 25 to close the exhaust port 32.

[0045] The valve actuating mechanism 13 includes an exhaust rocker unit 33 and an intake rocker unit 34. The exhaust rocker unit 33 opens/closes the exhaust valve 25 by pressing down/up the exhaust valves 25. The intake rocker unit 34 opens/closes the intake valve 27 by pressing down/up the intake valve 25. The exhaust rocker unit 33 and the intake rocker unit 34 are driven by the camshaft 14.

[0046] As shown in FIG. 7, the exhaust rocker unit 33 includes an exhaust rocker shaft 35, an exhaust rocker arm 36, a roller 37 and a pressing arm 38. The exhaust rocker shaft 35 is disposed in parallel to the camshaft 14. The exhaust rocker shaft 35 is supported by the cylinder head 4. Detailed, the exhaust rocker shaft 35 is supported by the first and second support walls 21 and 22.

[0047] The exhaust rocker arm 36 is supported by the exhaust rocker shaft 35 and is thereby pivotable about the exhaust rocker shaft 35. The exhaust rocker arm 36 is disposed to be capable of actuating the exhaust valve 25. The exhaust rocker arm 36 includes a through hole 364. The exhaust rocker shaft 35 is inserted through the through hole 364. As shown in FIG. 6, the exhaust rocker arm 36 supports the roller 37 such that the roller 37 is rotatable. The rotational center axis of the roller 37 is arranged in parallel to the cam axis Ax3. The roller 37 makes contact with the exhaust cam 146, and is rotated by rotation of the exhaust cam 146.

[0048] The pressing arm 38 is integrated with the exhaust rocker arm 36. The pressing arm 38 is provided with an adjuster screw 365 on the tip thereof. The tip end of the adjuster screw 365 faces the stem end of the exhaust valve 25.

[0049] When the roller 37 is pressed and lifted up by the exhaust cam 146, the exhaust rocker arm 36 pivots. In conjunction with this, the pressing arm 38 downwardly presses the exhaust valve 25. Accordingly, the exhaust port 32 is opened. When the roller 37 is not being pressed and lifted up by the exhaust cam 146, the exhaust valve 25 is upwardly pressed by the exhaust valve spring 251. Accordingly, the exhaust port 32 is closed.

[0050] FIG. 8 is a perspective view of the intake rocker unit 34. FIG. 9 is a view of the intake rocker unit 34 as seen from a perpendicular direction to the cam axis Ax3. As shown in FIGS. 8 and 9, the intake rocker unit 34 includes an intake rocker shaft 41, a first rocker arm 42, a second rocker arm 43, a pressing arm 44 (see FIG. 6), a first contact portion 45 and a second contact portion 46. The intake rocker shaft 41 is disposed in parallel to the camshaft 14. The intake rocker shaft 41 is supported by the cylinder head 4. Detailed, the intake rocker shaft 41 is supported by the first support wall 21 and the second support wall 22.

[0051] The first rocker arm 42 is supported by the intake rocker shaft 41 and is thereby pivotable about the intake rocker shaft 41. The first rocker arm 42 is disposed to be capable of actuating the intake valve 27. As shown in FIG. 3, the first rocker arm 42 includes a first rocker shaft hole 421. The intake rocker shaft 41 is disposed in the first rocker shaft hole 421.

[0052] The first contact portion 45, shown in FIG. 8, is disposed to be contactable with the first intake cam 144. The first contact portion 45 is a roller rotatably supported by the first rocker arm 42. The first contact portion 45 is rotated by rotation of the first intake cam 144. The rotational center axis of the first contact portion 45 is arranged in parallel to the cam axis Ax3. The first contact portion 45 makes contact with the first intake cam 144, whereby the first rocker arm 42 is rotated about the axis of the intake rocker shaft 41.

[0053] As shown in FIG. 7, the second rocker arm 43 is supported, while being pivotable about the intake rocker shaft 41. The second rocker arm 43 is disposed in alignment with the first rocker arm 42 in the cam axis Ax3 direction. The second rocker arm 43 includes a second rocker shaft hole 431. The second rocker shaft hole 431 is a hole provided in the second rocker arm 43. The intake rocker shaft 41 is inserted through the second rocker shaft hole 431.

[0054] As shown in FIG. 7, the second contact portion 46 is disposed to be contactable with the second intake cam 145. The second contact portion 46 is a roller rotatably supported by the second rocker arm 43. The second contact portion 46 is rotated by rotation of the second intake cam 145. The rotational center axis of the second contact portion 46 is arranged in parallel to the cam axis Ax3. The second contact portion 46 makes contact with the second intake cam 145, whereby the second rocker arm 43 is rotated about the axis of the intake rocker shaft 41.

[0055] As shown in FIG. 6, the pressing arm 44 is connected to the first rocker arm 42. The pressing arm 44 is integrated with the first rocker arm 42. The pressing arm 44 is provided with an adjuster screw 44 on the tip thereof. The tip end of the adjuster screw 441 faces the stem end of the first intake valve 27. The pressing arm 44 is rotated about the axis of the intake rocker shaft 41, and thereby presses the intake valve 27.

[0056] The intake rocker unit 34 includes an arm urging member 47. The arm urging member 47 urges the second rocker arm 43 in a direction that the second contact portion 46 is pressed onto the camshaft 14. In the present preferred embodiment, the arm urging member 47 is a coil spring into which the intake rocker shaft 41 is inserted.

[0057] As shown in FIG. 3, the first rocker arm 42 includes a first coupling hole 422. The first coupling hole 422 extends in the axis direction of the intake rocker shaft 41. It should be noted that the axis direction of the intake rocker shaft 41 is arranged in parallel to the cam axis Ax3. Therefore, in the following explanation, the term "axis direction" is defined as meaning the cam axis Ax3 direction and the axis direction of the intake rocker shaft 41.

[0058] In the axis direction, the length of the first coupling hole 422 is shorter than that of the first rocker shaft hole 421. The second rocker arm 43 includes a second coupling hole 432. The second coupling hole 432 extends in the axis direction. In the axis direction, the length of the second coupling hole 432 is shorter than that of the first coupling hole 422. A coupling pin 51 (to be described) is inserted into the first coupling hole 422. The second coupling hole 432 overlaps the first coupling hole 422 as seen from the axis direction. In more detail, when the intake valve 27 is being closed, the second coupling hole 432 overlaps the first coupling hole 422 as seen from the axis direction. Therefore, the coupling pin 51 is insertable into the second coupling hole 432.

[0059] As shown in FIGS. 8 and 9, the first rocker arm 42 includes a first shaft boss portion 61 and a first pin boss portion 62. The first shaft boss portion 61 includes the aforementioned first rocker shaft hole 421. The first pin boss portion 62 protrudes from the first shaft boss portion 61. The first pin boss portion 62 more protrudes toward the head cover 5 than the first shaft boss portion 61. The first pin boss portion 62 includes the aforementioned first coupling hole 422. As shown in FIG. 9, in the axis direction, thickness W2 of the first pin boss portion 62 is thinner than thickness W1 of the first shaft boss portion 61. In the axis direction, the first pin boss portion 62 is located closer to the second rocker arm 43 than the first support wall 21.

[0060] The second rocker arm 43 includes a second shaft boss portion 63 and a second pin boss portion 64. The second shaft boss portion 63 includes the aforementioned second rocker shaft hole 431. The second pin boss portion 64 protrudes from the second shaft boss portion 63. The second pin boss portion 64 more protrudes toward the head cover 5 than the second shaft boss portion 63. The second pin boss portion 64 includes the aforementioned second coupling hole 432. As shown in FIG. 9, in the axis direction, thickness W4 of the second pin boss portion 64 is thinner than thickness W3 of the second shaft boss portion 63. The thickness W4 of the second pin boss portion 64 is thinner than the thickness W2 of the first pin boss portion 62. The thickness W2 of the first pin boss portion 62 is thinner than the thickness W3 of the second shaft boss portion 63. It should be noted that the thickness of each boss portion 61, 62, 63, 64 is the size of that in in the axis direction.

[0061] In the axis direction, the second pin boss portion 64 is located closer to the first rocker arm 42 than the second support wall 22. Additionally, in the axis direction, the second pin boss portion 64 is located closer to the first rocker arm 42 than the arm urging member 47.

[0062] As shown in FIG. 6, the valve actuating mechanism 13 includes a decoupling device 50. The decoupling device 50 switches coupling and decoupling between the first rocker arm 42 and the second rocker arm 43. The decoupling device 50 includes the coupling pin 51, an urging member 52 and an actuator 53.

[0063] FIG. 10 is a perspective view of the decoupling device 50 and the surroundings thereof. FIGS. 11 and 12 are views of the decoupling device 50 and the surroundings thereof as seen from the cylinder axis direction. As shown in FIGS. 11 and 12, the coupling pin 51 is disposed at least in part inside the first coupling hole 422. The coupling pin 51 is movable in the axis direction, and is disposed to be movable to a decoupled position shown in FIG. 11 and a coupled position shown in FIG. 12.

[0064] As shown in FIG. 11, when moved to the decoupled position, the coupling pin 51 is disposed in the first coupling hole 422 without being disposed in the second coupling hole 432 of the second rocker arm 43. Thus, when moved to the decoupled position, the coupling pin 51 decouples the first rocker arm 42 and the second rocker arm 43 from each other. Specifically, when moved to the decoupled position, the coupling pin 51 releases the second rocker arm 43 from the pressing arm 44. Accordingly, the pressing arm 44 and the first rocker arm 42 pivot independently from the second rocker arm 43.

[0065] As shown in FIG. 12, when moved to the coupled position, the coupling pin 51 is disposed in both the first coupling hole 422 and the second coupling hole 432. Accordingly, the coupling pin 51 couples the first rocker arm 42 and the second rocker arm 43 to each other. In other words, when moved to the coupled position, the coupling pin 51 couples the pressing arm 44 to the second rocker arm 43 through the first rocker arm 42. Accordingly, the pressing arm 44 pivots unitarily with the first and second rocker arms 42 and 43.

[0066] The urging member 52 urges the coupling pin 51 in a direction from the coupled position to the decoupled position. The urging member 52 is a coil spring. The coupling pin 51 is disposed in part inside the urging member 52.

[0067] The actuator 53 is an electromagnetic solenoid. The actuator 53 switches the position of the coupling pin 51 between the decoupled position and the coupled position. When the actuator 53 is not being electrified, the coupling pin 51 is held in the decoupled position by the urging member 52. When the actuator 53 is being electrified, the actuator 53 moves the coupling pin 51 from the decoupled position to the coupled position against the urging force of the urging member 52, and holds the coupling pin 51 in the coupled position. When the actuator 53 is stopped being electrified, the coupling pin 51 is returned to the decoupled position from the coupled position by the elastic force of the urging member 52.

[0068] When the coupling pin 51 is located in the coupled position, the first rocker arm 42 is coupled to the second rocker arm 43 and unitarily pivots therewith. Because of this, when the second contact portion 46 is pressed and lifted up by the second intake cam 145, the second rocker arm 43 pivots about the intake rocker shaft 41. In conjunction with this, the first rocker arm 42 also pivots in a direction that the pressing arm 44 tilts down.

[0069] Accordingly, the tip of the adjuster screw 441 presses down the intake valve 27. As a result, the intake valve 27 opens the intake port 31. Thus, when the coupling pin 51 is located in the coupled position, the pressing arm 44 presses the intake valve 27 in conjunction with rotation of the second rocker arm 43. When the second contact portion 46 is not being pressed and lifted up by the second intake cam 145, the intake valve 27 is pressed and lifted up by the intake valve spring 271, whereby the intake port 31 is closed.

[0070] When the coupling pin 51 is located in the decoupled position, the first rocker arm 42 pivots independently from the second rocker arm 43. Because of this, when the first contact portion 45 is pressed and lifted up by the first intake cam 144, the first rocker arm 42 pivots about the intake rocker shaft 41 in a direction that the pressing arm 44 tilts down.

[0071] Accordingly, the tip of the adjuster screw 441 presses down the intake valve 27. As a result, the intake valve 27 opens the intake port 31. Thus, when the coupling pin 51 is located in the decoupled position, the pressing arm 44 presses the intake valve 27 in conjunction with rotation of the first rocker arm 42. When the first contact portion 45 is not being pressed and lifted up by the first intake cam 144, the intake valve 27 is pressed and lifted up by the intake valve spring 271, whereby the intake port 31 is closed.

[0072] It should be noted that the shapes of the first and second intake cams 144 and 145 are designed such that the second intake cam 145 presses and lifts up the second contact portion 46 before the tip of the first intake cam 144 reaches the first contact portion 45. Because of this, when the coupling pin 51 is located in the coupled position, the first rocker arm 42 is actuated by rotation of the second intake cam 145. Accordingly, rotation of the first intake cam 144 is not transmitted to the first rocker arm 42.

[0073] Therefore, when the coupling pin 51 is located in the coupled position, the intake valve 27 performs opening and closing motions in conjunction with rotation of the second intake cam 145. On the other hand, when the coupling pin 51 is located in the decoupled position, rotation of the second intake cam 145 is not transmitted to the first rocker arm 42. Because of this, when the coupling pin 51 is located in the decoupled position, the intake valve 27 performs opening and closing motions in conjunction with rotation of the first intake cam 144.

[0074] Next, the structure of the decoupling device 50 will be explained in more detail. In the following explanation, one direction oriented from the second coupling hole 432 to the first coupling hole 422 in the axis direction will be referred to as a first direction (X1), whereas the other direction oriented from the first coupling hole 422 to the second coupling hole 432 in the axis direction will be referred to as a second direction (X2). The coupling pin 51 is moved from the decoupled position to the coupled position, when pressed by the actuator 53 in the second direction (X2). When the actuator 53 is not being electrified, the coupling pin 51 is pressed in the first direction (X1) by the urging force of the urging member 52, and is thus moved from the coupled position to the decoupled position.

[0075] As shown in FIG. 6, the coupling pin 51 is located between the first support wall 21 and the second support wall 22 in the axis direction. The coupling pin 51 is located second-directionally (X2) downstream of the first support wall 21 in the axis direction. The coupling pin 51 is located first-directionally (X1) downstream of the second support wall 22 in the axis direction.

[0076] As shown in FIG. 11, the coupling pin 51 includes a shaft portion 54 and a flange portion 55. The shaft portion 54 is disposed in part inside the first coupling hole 422. The shaft portion 54 extends in the axis direction. The flange portion 55 is connected to the first direction (X1) side end of the shaft portion 54. The flange portion 55 radially protrudes from the shaft portion 54. The flange portion 55 is disposed downstream of the first rocker arm 42 in the first direction (X1). The flange portion 55 is disposed outside the first coupling hole 422. The outer diameter of the flange portion 55 is larger than the inner diameter of the first coupling hole 422.

[0077] The coupling pin 51 includes a receiver portion 56 that receives the urging force applied thereto from the urging member 52. The urging member 52 is located second-directionally (X2) downstream of the receiver portion 56 in the axis direction. The receiver portion 56 is part of the flange portion 55, and is located outside the first coupling hole 422. Detailed, the receiver portion 56 is the second direction (X2) side lateral surface of the flange portion 55.

[0078] The urging member 52 first-directionally (X1) urges the coupling pin 51 in the axis direction. The urging member 52 is disposed between the receiver portion 56 and the first rocker arm 42 in the axis direction. Detailed, the urging member 52 is disposed between the receiver portion 56 and the first pin boss portion 62 in the axis direction. The outer diameter of the urging member 52 is larger than the inner diameter of the first coupling hole 422.

[0079] The urging member 52 includes a first end 521 and a second end 522. The first end 521 is the first direction (X1) side end of the first urging member 52. The second end 522 is the second direction (X2) side end of the urging member 52. Both the first end 521 and the second end 522 are located downstream of the first rocker arm 42 in the first direction (X1). In other words, the entire urging member 52 is disposed outside the first coupling hole 422. It should be noted that the urging member 52 may be disposed in part inside the first coupling hole 422.

[0080] The actuator 53 includes a pressing pin 71 and a body 72. The pressing pin 71 protrudes from the body 72 in the second direction (X2). The body 72 includes a solenoid. The pressing pin 71 is moved in the axis direction with respect to the body 72. The pressing pin 71 makes contact with the coupling pin 51 in a pivot range of the coupling pin 51. When driven by the body 72, the pressing pin 71 presses the coupling pin 51.

[0081] The pressing pin 71 includes a rod portion 73 and a head portion 74. The head portion 74 is connected to the rod portion 73. The head portion 74 is located on the tip of the pressing pin 71. The outer diameter of the head portion 74 is larger than that of the rod portion 73. The head portion 74 makes contact with the coupling pin 51 in the pivot range of the coupling pin 51.

[0082] The coupling pin 51 includes a lateral surface portion 57. The lateral surface portion 57 is the first direction (X1) side end of the coupling pin 51. The lateral surface portion 57 is the first direction (X1) side lateral surface of the flange portion 55. The pressing pin 71 presses the lateral surface portion 57, while in contact therewith.

[0083] FIG. 13 is a view of part of the decoupling device 50 as seen from the axis direction. As shown in FIG. 13, the head portion 74 overlaps the coupling pin 51 in the pivot range of the coupling pin 51. The urging member 52 overlaps the receiver portion 56 as seen from the axis direction. The urging member 52 overlaps the first rocker arm 42 as seen from the axis direction. Detailed, the urging member 52 overlaps the first pin boss portion 62 as seen from the axis direction.

[0084] It should be noted that FIG. 13 illustrates components in a valve closed state that the intake valve 27 is closed, while dashed two-dotted line depicts the flange portion 55 (the lateral surface portion 57) in a valve opened state that the intake valve 27 is opened. The coupling pin 51 pivots in a range from a valve closing center axis P to a valve opening center axis P'.

[0085] As shown in FIG. 11, the cylinder head 4 includes a retainer portion 58 disposed downstream of the receiver portion 56 in the first direction (X1). The retainer portion 58 is part of the first support wall 21. The first support wall 21 is disposed downstream of the first rocker arm 42 in the first direction (X1). Therefore, the retainer portion 58 is disposed downstream of the coupling pin 51 in the first direction (X1).

[0086] As shown in FIGS. 10 and 11, in the present preferred embodiment, the retainer portion 58 is a recess provided on the first support wall 21 . The retainer portion 58 is provided on a sidewall 210 of the first support wall 21. The retainer portion 58 is recessed on the sidewall 210 of the first support wall 21 in the first direction (X1). The coupling pin 51 is disposed within the recess of the retainer portion 58 in the decoupled position. Therefore, as seen from the cylinder axis Ax1 direction, the coupling pin 51 in part overlaps the first support wall 21 in the decoupled position. Detailed, as seen from the cylinder axis Ax1 direction, the flange portion 55 in part overlaps the first support wall 21 in the decoupled position.

[0087] As shown in FIG. 13, the retainer portion 58 overlaps at least part of the coupling pin 51 as seen from the axis direction. The retainer portion 58 overlaps the first direction (X1) side end of the coupling pin 51 as seen from the axis direction. Detailed, the retainer portion 58 overlaps at least part of the flange portion 55 as seen from the axis direction. In other words, the lateral surface portion 57, at least in part, overlaps the retainer portion 58 as seen from the axis direction. In more detail, as seen from the axis direction, the lateral surface portion 57, at least in part, overlaps the retainer portion 58 in the entire pivot range of the coupling pin 51. The retainer portion 58 does not overlap the pressing pin 71 as seen from the axis direction.

[0088] The retainer portion 58 and the coupling pin 51 overlap in a smaller range than the pressing pin 71 and the coupling pin 51 do as seen from the axis direction. Detailed, the retainer portion 58 and the receiver portion 56 overlap in a smaller range than the head portion 74 and the receiver portion 56 do as seen from the axis direction. The pressing pin 71 overlaps the center of the coupling pin 51 as seen from the axis direction. The retainer portion 58 does not overlap the center of the coupling pin 51 as seen from the axis direction.

[0089] As shown in FIGS. 11 and 12, the pressing pin 71 further protrudes than the retainer portion 58 in the second direction (X2). Therefore, the coupling pin 51 is disposed away from the retainer portion 58 in the second direction (X2) while the pressing pin 71 of the actuator 53 makes contact with the coupling pin 51. In other words, the coupling pin 51 does not make contact with the retainer portion 58 in the condition that the pressing pin 71 of the actuator 53 makes contact with the coupling pin 51.

[0090] As shown in FIG. 11, in the axis direction, length L1 of the coupling pin 51 is greater than distance L2 between the first coupling hole 422 and the retainer portion 58. Therefore, as shown in FIG. 14, the coupling pin 51 is movable in the axis direction in a removed state of the actuator 53. However, the coupling pin 51 is restricted from moving in the axis direction, while in contact with the retainer portion 58. The coupling pin 51 is disposed in part inside the first coupling hole 422, while in contact with the retainer portion 58. Therefore, the coupling pin 51 is prevented from coming off even in the removed state of the actuator 53.

[0091] In the engine 1 for a straddled vehicle according to the present preferred embodiment explained above, the receiver portion 56 of the coupling pin 51 is located outside the first coupling hole 422 of the first rocker arm 42. Additionally, the urging member 52 is disposed between the receiver portion 56 and the first rocker arm 42. Therefore, the first rocker arm 42 can be herein made compact compared to a configuration that the receiver portion 56 and the urging member 52 are disposed inside the first coupling hole 422. For example, as described above, the first pin boss portion 62 of the first rocker arm 42 can be made thin. Because of this, the equivalent mass of the first rocker arm 42 can be reduced.

[0092] Additionally, the retainer portion 58 overlaps at least part of the coupling pin 51 as seen from the axis direction, and the length L1 of the coupling pin 51 is greater than the distance L2 between the first coupling hole 422 and the retainer portion 58 in the axis direction. Therefore, even when the actuator 53 is removed in assembling or disassembling the engine 1, the coupling pin 51 can be prevented from coming off while in contact with the retainer portion 58.

[0093] Furthermore, the retainer portion 58 is part of the cylinder head 4. Therefore, the first rocker arm 42 can be herein made more compact compared to a configuration that a structure for preventing the coupling pin 51 from coming off is disposed inside the first coupling hole 422, whereby the equivalent mass of the first rocker arm 42 can be reduced.

[0094] The coupling pin 51 includes the lateral surface portion 57 that overlaps the retainer portion 58 as seen from the axis direction. Therefore, the coupling pin 51 can be prevented from coming off, while making contact at the lateral surface portion 57 thereof with the retainer portion 58.

[0095] In the axis direction, the thickness W2 of the first pin boss portion 62 is thinner than the thickness W1 of the first shaft boss portion 61. In the axis direction, the length of the first coupling hole 422 is smaller than that of the first rocker shaft hole 421. Therefore, the first pin boss portion 62 disposed away from the intake rocker shaft 41 has a small thickness, whereby the equivalent mass of the first rocker arm 42 can be reduced. Additionally, in the first rocker arm 42, the surrounding portion of the first coupling hole 422 disposed away from the intake rocker shaft 41 has a small thickness, whereby the equivalent mass of the first rocker arm 42 can be reduced.

[0096] The pressing pin 71 further protrudes than the retainer portion 58 in the second direction (X2). Therefore, in actuation of the intake rocker shaft 41, the coupling pin 51 can be prevented from making contact with the retainer portion 58.

[0097] The urging member 52 is a coil spring into which the coupling pin 51 is inserted. Therefore, the urging member 52 and the coupling pin 51 can be compactly disposed.

[0098] The retainer portion 58 is part of the first support wall 21. Therefore, the retainer portion 58 can be provided with use of the first support wall 21 for supporting the intake rocker shaft 41.

[0099] The retainer portion 58 overlaps the first direction (X1) side end of the coupling pin 51 as seen from the axis direction. Therefore, when moved in the axis direction, the coupling pin 51 makes contact at the end thereof with the retainer portion 58, whereby the coupling pin 51 is prevented from coming off

[0100] The retainer portion 58 overlaps at least part of the flange portion 55 as seen from the axis direction. The receiver portion 56 is part of the flange portion 55. Therefore, when moved in the axis direction, the coupling pin 51 makes contact at the flange portion 55 with the retainer portion 58, whereby the coupling pin 51 is prevented from coming off.

[0101] As seen from the axis direction, the retainer portion 58 and the coupling pin 51 overlap in a smaller range than the pressing pin 71 and the coupling pin 51 do. Therefore, the pressing pin 71 and the coupling pin 51 can reliably make contact with each other in a large contact area.

[0102] The second end 522 of the urging member 52 is located second-directionally (X2) downstream of the first end 521 in the axis direction. The first end 521 is located downstream of the first rocker arm 42 in the first direction (X1). Therefore, the urging force of the urging member 52 (e.g., a restoring stroke when the urging member 52 is a spring) can be sufficiently utilized.

[0103] The valve actuating mechanism has an SOHC configuration. Therefore, the decoupling device can be employed without impairing lightweight properties of the SOHC valve actuating mechanism.

[0104] One preferred embodiment of the present invention has been explained above. However, the present invention is not limited to the aforementioned preferred embodiment, and a variety of changes can be made without departing from the gist of the present invention.

[0105] The engine is not limited to a single-cylinder engine of a water cooling type. For example, the engine may be of an air cooling type. The engine may be a multiple-cylinder engine. The number of exhaust valves is not limited to one, and alternatively, may be two or greater. The number of intake valves is not limited to one, and alternatively, may be two or greater.

[0106] The configuration and layout of the valve actuating mechanism 13 may be changed. For example, the first contact portion 45 is not limited to the roller, and alternatively, may be another member such as a slipper that is fixedly provided on the first rocker arm 42 and slides against the first intake cam 144. The second contact portion 46 is not limited to the roller, and alternatively, may be another member such as a slipper that is fixedly provided on the second rocker arm 43 and slides against the second intake cam 145. In the aforementioned preferred embodiment, the mechanism for switching the timing of opening and closing the valve by the actuator 53 is employed for the intake valve. However, this mechanism may be employed for the exhaust valve.

[0107] The structure of the retainer portion 58 is not limited to that in the aforementioned preferred embodiment. For example, as shown in FIG. 15, the retainer portion 58 may be flush with the sidewall 210 of the first support wall 21. The entirety of the coupling pin 51 may be located between the first support wall 21 and the second support wall 22 in the axis direction. With the aforementioned configuration, the coupling pin 51 can be located close to the intake rocker shaft 41 without being hindered by the first support wall 21. As a result, the equivalent mass can be further reduced.

[0108] In the aforementioned preferred embodiment, the flange portion 55 makes contact with the pressing pin 71 of the actuator 53, and overlaps the retainer portion 58 as seen from the axis direction. However, a different portion from the flange portion 55 in the coupling pin 51 may make contact with the pressing pin 71 of the actuator 53, and may overlap the retainer portion 58 as seen from the axis direction.

[0109] For example, as shown in FIG. 16, the coupling pin 51 may include an end portion 59 protruding from the flange portion 55 in the first direction (X1). The end portion 59 may make contact with the pressing pin 71 of the actuator 53, and may overlap the retainer portion 58 as seen from the axis direction. The lateral surface portion 57 may be provided on the end portion 59, and may overlap the retainer portion 58 as seen from the axis direction. In this case, the actuator 53 may press the lateral surface portion 57 of the end portion 59 so as to move the coupling pin 51 between the coupled position and the decoupled position. Additionally, in the removed state of the actuator 53, the lateral surface portion 57 of the end portion 59 may make contact with the retainer portion 58 so as to prevent the coupling pin 51 from coming off.

[0110] Alternatively, a portion of the coupling pin 51, which overlaps the retainer portion 58 as seen from the axis direction, may be different from the portion making contact with the pressing pin 71 of the actuator 53. For example, as shown in FIG. 17, the end portion 59 protruded from the flange portion 55 may make contact with the pressing pin 71 of the actuator 53. As seen from the axis direction, the end portion 59 may not overlap the retainer portion 58, whereas the flange portion 55 may overlap the retainer portion 58.

[0111] Detailed, the flange portion 55 may include a first lateral surface portion 57a. The first lateral surface portion 57a is the first direction (X1) side lateral surface of the flange portion 55. The end portion 59 may include a second lateral surface portion 57b. The second lateral surface portion 57b may be located downstream of the first lateral surface portion 57a in the first direction (X1). The second lateral surface portion 57b is the first direction (X1) side lateral surface of the end portion 59. The second lateral surface portion 57b of the end portion 59 may make contact with the pressing pin 71 of the actuator 53. The first lateral surface portion 57a of the flange portion 55 may not make contact with the pressing pin 71 of the actuator 53, and may overlap the retainer portion 58 as seen from the axis direction.

[0112] In this case, the actuator 53 may press the second lateral surface portion 57b of the end portion 59 so as to move the coupling pin 51 between the coupled position and the decoupled position. Additionally, in the removed state of the actuator 53, the first lateral surface portion 57a of the flange portion 55 may make contact with the retainer portion 58 so as to prevent the coupling pin 51 from coming off

[0113] The retainer portion 58 may be provided separately from the first support wall 21. For example, as shown in FIGS. 18 and 19, the retainer portion 58 may be part of an attachment component 75 to be attached to the first support wall 21. The attachment component 75 may be made in the shape of, for instance, a plate. For example, the attachment component 75 may also function as a member for reinforcing the engine 1. Alternatively, the attachment component 75 may be part of a washer of a stud bolt for fixing the cylinder head 4. The attachment component 75 may be obtained by extending part of the washer to a position overlapping the coupling pin 51 as seen from the axis direction. In this case, the retainer portion 58 can be provided by the attachment component 75. Additionally, the attachment component 75 is provided separately from the first support wall 21, whereby flexibility in layout of the retainer portion 58 can be enhanced.

[0114] The lateral surface portion 57 of the coupling pin 51, at least in part, may overlap the retainer portion 58 in part of the pivot range of the coupling pin 51 as seen from the axis direction. The pivot position of the coupling pin 51, corresponding to the valve closed state, is desirably included as part of the pivot range thereof in which the both portions 57 and 58 overlap. This is because in assembling or disassembling the engine 1, workability is better in the valve closed state than in the valve opened state.

Claims

1. An engine (1) comprising:

a cylinder head (4); and

a valve actuating mechanism (13) provided in the cylinder head (4), wherein

the valve actuating mechanism (13) includes

a valve,

a rocker shaft (35) supported by the cylinder head (4),

a first rocker arm (42) supported by the rocker shaft (35),

a second rocker arm (43) supported by the rocker shaft (35), the second rocker arm (43) being disposed in alignment with the first rocker arm (42) in an axis direction of the rocker shaft (35), and

a decoupling device (50) switching coupling and decoupling between the first rocker arm (42) and the second rocker arm (43),

the first rocker arm (42) includes a first coupling hole (422) extending in the axis direction,

the second rocker arm (43) includes a second coupling hole (432) extending in the axis direction, the second coupling hole (432) overlapping the first coupling hole (422) as seen from the axis direction,

the decoupling device (50) includes

a coupling pin (51) disposed at least in part inside the first coupling hole (422), the coupling pin (51) being movable in the axis direction,

an urging member (52) urging the coupling pin (51) in a first direction (X1), the first direction (X1) being oriented from the second coupling hole (432) to the first coupling hole (422) in the axis direction, and

an actuator (53) pressing the coupling pin (51) in a second direction (X2), the second direction (X2) being oriented from the first coupling hole (422) to the second coupling hole (432) in the axis direction,

the coupling pin (51) includes a receiver portion (56) receiving an urging force applied by the urging member (52),

the receiver portion (56) is located outside the first coupling hole (422),

the urging member (52) is disposed between the receiver portion (56) and the first rocker arm (42),

the cylinder head (4) includes a retainer portion (58) disposed downstream of the receiver portion (56) in the first direction (X1),

the retainer portion (58) overlaps at least part of the coupling pin (51) as seen from the axis direction, and

the coupling pin (51) has a length (L1) greater than a distance (L2) between the first coupling hole (422) and the retainer portion (58) in the axis direction.

2. A engine (1) according to claim 1, wherein the coupling pin (51) includes a lateral surface portion (57) overlapping the retainer portion (58) as seen from the axis direction.

3. A engine (1) according to claim 1 or 2, wherein

the first rocker arm (42) includes

a first shaft boss portion (61) including a first rocker shaft hole (421) in which the rocker shaft (35) is disposed, and

a first pin boss portion (62) includes the first coupling hole (422),

the first pin boss portion (62) has a smaller thickness than the first shaft boss portion (61) in the axis direction, and

the first coupling hole (422) has a smaller length than the first rocker shaft hole (421) in the axis direction.

4. A engine (1) according to any of claims 1 to 3, wherein

the cylinder head (4) includes a first support wall (21) and a second support wall (22), the first and second support walls (21, 22) being disposed away from each other in the axis direction, the first and second support walls (21, 22) supporting the rocker shaft (35), and

the coupling pin (51) is entirely located between the first support wall (21) and the second support wall (22) in the axis direction.

5. A engine (1) according to any of claims 1 to 4, wherein

the actuator (53) includes a pressing pin (71) making contact with the coupling pin (51), and

the pressing pin (71) further protrudes than the retainer portion (58) in the second direction (X2).

6. A engine (1) according to any of claims 1 to 5, wherein

the urging member (52) is a coil spring, and

the coupling pin (51) is disposed inside the urging member (52).

7. A engine (1) according to any of claims 1 to 6, wherein

the cylinder head (4) includes a first support wall (21) disposed downstream of the first rocker arm (42) in the first direction (X1), the first support wall (21) supporting the rocker shaft (35), and

the retainer portion (58) is part of the first support wall (21).

8. A engine (1) according to any of claims 1 to 6, wherein

the cylinder head (4) includes

a first support wall (21) disposed downstream of the first rocker arm (42) in the first direction (X1), the first support wall (21) supporting the rocker shaft (35), and

an attachment component (75) provided separately from the first support wall (21), the attachment component (75) being attached to the first support wall (21), and

the retainer portion (58) is part of the attachment component (75).

9. The engine (1) according to any of claims 1 to 8, wherein the retainer portion (58) overlaps a first directional end of the coupling pin (51) as seen from the axis direction.

10. A engine (1) according to any of claims 1 to 9, wherein

the coupling pin (51) includes

a shaft portion (54) disposed at least in part inside the first coupling hole (422), and

a flange portion (55) disposed outside the first coupling hole (422), the flange portion (55) radially protruding from the shaft portion (54),

the retainer portion (58) overlaps at least part of the flange portion (55) as seen from the axis direction, and

the receiver portion (56) is part of the flange portion (55).

11. A engine (1) according to any of claims 1 to 10, wherein

the actuator (53) includes a pressing pin (71) making contact with the coupling pin (51), and

the retainer portion (58) and the coupling pin (51) overlap in a smaller range than the pressing pin (71) and the coupling pin (51) do as seen from the axis direction.

12. A engine (1) according to any of claims 1 to 11, wherein the urging member (52) overlaps the receiver portion (56) and the first rocker arm (42) as seen from the axis direction.

13. A engine (1) according to any of claims 1 to 12, wherein the urging member (52) is located second-directionally downstream of the receiver portion (56) in the axis direction.

14. A engine (1) according to any of claims 1 to 13, wherein

the urging member (52) includes a first end (521) and a second end (522) in the axis direction,

the second end (522) is located second-directionally downstream of the first end (521) in the axis direction, and

the first end (521) urges the receiver portion (56).

15. A engine (1) according to any of claims 1 to 14, wherein the valve actuating mechanism (13) has an SOHC (Single OverHead Camshaft) configuration.

Drawing