TWI605189B - Engine - Google Patents

Description

engine

The present invention relates to an engine.

In the prior art, an engine in which the joint surface of the cylinder head and the head cover is disposed at the same height as the cam shaft is known (for example, refer to Japanese Laid-Open Patent Publication No. 2009-52475). In addition, the "height" herein refers to the height in the case where the cylinder axis direction is viewed from the cylinder head toward the head cover. In such an engine, the shaft end of the intake or exhaust valve driven by the camshaft is disposed at a position higher than the joint surface.

On the other hand, for ease of maintenance, it is preferable that the accessibility to the axial end of the valve is good. As a method for improving the accessibility to the shaft end of the valve, it is considered to ensure a large gap between the side wall of the cylinder head and the valve. However, in this case, there is a problem of engine size.

In this regard, in the case of the above-described engine, the shaft end of the valve is located higher than the end of the cylinder head in the state in which the head cover has been removed. Therefore, the accessibility to the axial end of the valve can be improved even if the gap between the side wall of the cylinder head and the valve is not ensured. Therefore, the engine can be miniaturized.

However, if the joint surface is disposed at the same height as the cam shaft, the head of the fastening bolt that fastens the cylinder head and the crank axle box is located higher than the joint surface. Due to manufacturing It is required that the inner surface of the side surface of the head cover is inclined, so that if the head is located at a higher position than the joint surface, the head may interfere with the side of the head cover.

In order to avoid interference between the head of the fastening bolt and the side of the head cover, it is preferable to ensure a large distance between the fastening bolt and the side of the head cover. However, in this case, the engine will be large.

An object of the present invention is to reduce the size of the engine and improve the accessibility to the axial end of the valve.

An engine of an aspect of the present invention includes a crank shaft, a crankcase, a cylinder block, a cylinder head, a valve, a camshaft, a head cover, a first fastening bolt, and a second fastening bolt. The crankcase houses the crankshaft. The cylinder block is connected to the crankcase. The cylinder head is connected to the cylinder block. The valve is mounted to the cylinder head. The camshaft is supported on the cylinder head. The head cover includes an end portion that is disposed opposite the end of the cylinder head and is mounted to the cylinder head.

The first fastening bolt fastens the cylinder head, the cylinder block, and the crankcase. The first fastening bolt includes a first head fixed to the cylinder head. The second fastening bolt fastens the cylinder head, the cylinder block, and the crankcase. The second fastening bolt includes a second head fixed to the cylinder head. The first imaginary plane including the end portion of the cylinder head and the second imaginary plane including the end portion of the head cover overlap the cam shaft.

The cylinder head includes a first cylinder side wall and a second cylinder side wall that are disposed opposite to each other in the axial direction of the cam shaft. The head cover includes a first outer casing side wall connected to the first cylinder side wall and a second outer casing side wall connected to the second cylinder side wall. The inner surface of the first outer casing side wall is inclined in the cylinder axis direction of the cylinder block toward the head cover from the cylinder head (hereinafter referred to as "head cover side"), the first outer casing side wall and the second outer casing side wall. Narrowed between.

The first head portion is disposed between the first cylinder side wall and the second head portion in the axial direction of the cam shaft. The second head portion is disposed between the second cylinder side wall and the first head portion in the axial direction of the cam shaft. The distance between the first cylinder side wall and the first head in the axial direction of the camshaft is less than convex The distance between the second cylinder side wall and the second head in the axial direction of the axle. The distance from the third imaginary plane including the axis of the crankshaft and perpendicular to the cylinder axis to the first head in the cylinder axis direction is smaller than the distance from the third imaginary plane to the second head in the cylinder axis direction.

In the engine of this aspect, the end portion of the cylinder head which is the joint surface between the cylinder head and the head cover and the end portion of the head cover are disposed at a height overlapping with the cam shaft. Therefore, the accessibility to the shaft end of the valve can be improved.

Further, the first head portion is disposed at a position close to the first cylinder side wall, and the inner surface of the first outer casing side wall connected to the first cylinder side wall is separated from the end portion of the first outer casing side wall in the axial direction of the cam shaft The upper direction is inclined toward the first head. Therefore, the position of the first head portion is located on the side of the head cover, and the distance between the first head portion and the inner surface of the side wall of the first outer casing is smaller. In this case, in order to ensure a gap between the inner surface of the first outer casing side wall and the first head portion, the engine is enlarged. However, in the engine of the present aspect, the distance from the third imaginary plane to the first head in the cylinder axis direction is smaller than the distance from the third imaginary plane to the second head in the cylinder axis direction. Therefore, the first head portion is located closer to the cylinder block side than the second head portion in the cylinder axis direction. Therefore, the engine can be miniaturized. Further, the cylinder block side refers to the direction from the cylinder head toward the cylinder block in the cylinder axis direction.

Further, the second head portion is disposed apart from the second cylinder side wall than the position of the first head portion with respect to the first cylinder side wall. Therefore, even if the second head portion is disposed closer to the head cover than the first head portion, it is possible to suppress an increase in size of the engine and to secure a gap between the second casing side wall and the second head portion. Further, by arranging the second head portion closer to the head cover than the first head portion, the rigidity of the cylinder head can be improved as compared with the case where the second head portion is disposed at the same height as the first head portion. According to the above, the engine can be miniaturized and the accessibility to the shaft end of the valve can be improved.

Preferably, the first fastening bolt does not overlap the head cover when viewed from the axial direction of the cam shaft. In this case, the first fastening bolt is disposed closer to the cylinder block side than the end portion of the head cover. Thereby, the engine can be miniaturized.

Preferably, the engine further includes a camshaft drive portion disposed on the camshaft. Cam The camshaft drive unit is disposed between the second cylinder side wall and the second head portion in the axial direction of the shaft. Thereby, since the second head portion and the second cylinder side wall are disposed apart from each other, the distance between the second head portion and the second cylinder side wall can be ensured compared with the distance between the first head portion and the first cylinder side wall. Larger. Thereby, even if the rigidity of the engine is ensured to be large, the engine can be miniaturized.

Preferably, the cylinder head includes a support wall that supports the camshaft. The support wall includes a through hole for the second fastening bolt. In this case, since the second fastening bolt is disposed in the through hole of the support wall, it is possible to suppress an increase in the size of the support wall and to increase the strength of the support wall. Thereby, the engine can be miniaturized.

Preferably, the engine further includes a rocker shaft, a first rocker arm, a second rocker arm, a switching pin member, and an actuator. The rocking shaft is supported by the cylinder head and is parallel to the camshaft. The first rocker arm is supported on the rocking shaft. The second rocker arm is supported by the rocking shaft and arranged in parallel with the first rocker arm in the axial direction of the camshaft. The switching pin member is movable in the axial direction of the cam shaft and is provided to be movable to the first position and the second position. The switching pin member connects the first rocker arm and the second rocker arm at the first position, and swings together with the first rocker arm and the second rocker arm. The switching pin member disconnects the first rocker arm from the second rocker arm at the second position. The actuator presses the switching pin member in the axial direction of the cam shaft, and switches the position of the switching pin member to the first position and the second position. The actuator is attached to the head cover outside the engine.

In this case, an actuator is attached to the head cover. Therefore, even if the actuator is disposed close to the switching pin member, the thermal influence of the combustion chamber from the combustion chamber in the cylinder head on the actuator can be suppressed as compared with the case where the actuator is attached to the cylinder head. Thereby, the thermal influence on the actuator can be suppressed and the engine can be miniaturized.

Preferably, at least a portion of the actuator overlaps the end of the head cover when viewed from the cylinder axis direction. In this case, the distance between the actuator and the switching pin member is shortened, whereby the driving force required to switch the pin member can be reduced. Thereby, the actuator can be miniaturized and the engine can be further miniaturized.

Preferably, at least a portion of the first fastening bolt is viewed from the direction of the cylinder axis It overlaps with the actuator. In this case, the engine can be further miniaturized.

According to the present invention, the engine can be miniaturized and the accessibility to the shaft end of the valve can be improved.

1‧‧‧ engine

2‧‧‧ crankshaft

3‧‧‧ crankcase

4‧‧‧Cylinder Department

5‧‧‧Cylinder block

6‧‧‧ cylinder head

7‧‧‧ head cover

8‧‧‧Piston

9‧‧‧ Connecting rod

11‧‧‧ combustion chamber

12‧‧‧Mars plug

13‧‧‧Valve mechanism

14‧‧‧Camshaft

15‧‧‧Cam chain

16‧‧‧Cam chain room

17‧‧‧Water pump

18‧‧‧ coolant hose

19‧‧‧ radiator

21‧‧‧shims

22‧‧‧1st bearing

23‧‧‧2nd bearing

24‧‧‧Exhaust valve

25‧‧‧Exhaust valve

26‧‧‧Intake valve

27‧‧‧Intake valve

31‧‧‧Exhaust rocking shaft

32‧‧‧Exhaust rocker arm

33‧‧‧Intake shaft

34‧‧‧Intake rocker

35‧‧‧Switch pin member

36‧‧‧1st rocker

37‧‧‧2nd rocker

38‧‧‧ force components

39‧‧‧Actuator

41‧‧‧1st support member

42‧‧‧2nd support member

44‧‧‧Flexible components

51‧‧‧ bolt

52‧‧‧Bolts

61‧‧‧1st fastening bolt

62‧‧‧2nd fastening bolt

65‧‧‧1st head

66‧‧‧2nd head

67‧‧‧3rd head

68‧‧‧4th head

141‧‧‧1st camshaft end

142‧‧‧2nd camshaft end

143‧‧‧1st camshaft drive

144‧‧‧1st intake cam

145‧‧‧2nd intake cam

146‧‧‧Exhaust cam

201‧‧‧2nd camshaft drive unit

241‧‧‧Exhaust valve spring

242‧‧‧The end of the first exhaust valve

251‧‧‧Exhaust valve spring

252‧‧‧ the end of the second exhaust valve

261‧‧‧Intake valve spring

262‧‧‧The end of the first intake valve

271‧‧‧Intake valve spring

272‧‧‧ the end of the second intake valve

321‧‧‧arm body

322‧‧‧Roll support

323‧‧‧roll

324‧‧‧Exhaust valve pusher

325‧‧‧1st adjustment screw

326‧‧‧2nd adjustment screw

327‧‧‧through holes

361‧‧‧1st arm body

362‧‧‧1st roller support

363‧‧‧1st roll

364‧‧‧Intake valve pusher

365‧‧‧1st link

366‧‧‧through holes

367‧‧‧1st adjustment screw

368‧‧‧2nd adjustment screw

369‧‧‧through holes

371‧‧‧2nd arm body

372‧‧‧2nd roller support

373‧‧‧2nd roller

374‧‧‧2nd link

375‧‧‧through holes

376‧‧‧through holes

391‧‧‧ rod

392‧‧‧ Body Department

393‧‧‧Flange

601‧‧‧1st end

602‧‧‧2nd end

603‧‧‧1st cylinder side wall

604‧‧‧2nd cylinder side wall

605‧‧‧1st protruding wall

606‧‧‧2nd protruding wall

607‧‧‧ recess

608‧‧‧3rd cylinder side wall

609‧‧‧4th cylinder side wall

610‧‧‧Connecting pipe connection

611‧‧‧Connecting pipe connection

612‧‧‧1st support wall

613‧‧‧2nd support wall

614‧‧‧Intake 埠

615‧‧‧Exhaust gas

619‧‧‧ Section

620‧‧‧ recess

621‧‧‧1st through hole

622‧‧‧2nd through hole

701‧‧‧ end of the head cover

702‧‧‧1st outer casing side wall

703‧‧‧2nd casing side wall

704‧‧‧through holes

705‧‧‧1st seat

706‧‧‧2nd seat

Ax1‧‧‧Cylinder axis

Ax2‧‧‧ crank axis

Ax3‧‧‧ cam axis

D1‧‧‧ distance

D2‧‧‧ distance

P1‧‧‧1st imaginary plane

P2‧‧‧2nd imaginary plane

P3‧‧‧3rd imaginary plane

Figure 1 is a cross-sectional view of a portion of the engine.

Figure 2 is a view of the cylinder head and the head cover viewed from a direction perpendicular to the cylinder axis and the cam axis.

Figure 3 is a cross-sectional view of the cylinder head and the head cover viewed from a direction perpendicular to the cylinder axis and the cam axis.

Figure 4 is a perspective view of the inside of the cylinder head.

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

Fig. 6 is a view showing the inside of the cylinder head viewed from the cylinder axis direction.

Fig. 7 is a cross-sectional view showing the inside of the cylinder head viewed from the direction of the cam axis.

Fig. 8 is a cross-sectional view showing the vicinity of the second support wall and the urging member.

Figure 9 is a cross-sectional view showing the inside of the cylinder head viewed from the direction of the cam axis.

Fig. 10 is a view showing the cylinder head and the head cover viewed from the cylinder axis direction.

Figure 11 is a cross-sectional view of a portion of the engine as viewed from a direction perpendicular to the cam axis and the cylinder axis.

Figure 12 is a cross-sectional view of a portion of the engine as viewed from a direction perpendicular to the cam axis and the cylinder axis.

Hereinafter, the engine 1 of the embodiment will be described with reference to the drawings. The engine 1 of the present embodiment is a water-cooled single cylinder engine. Figure 1 is a cross-sectional view of a portion of the engine 1. As shown in FIG. 1, the engine 1 includes a crankshaft 2, a crankcase 3, and a cylinder portion 4. The crankcase 3 houses the crankshaft 2. The cylinder portion 4 includes a cylinder block 5, a cylinder head 6, and a head cover 7. Cylinder block 5 connected to crankshaft Box 3. The cylinder block 5 may be integral with the crankcase 3 or may be separate from the crankcase 3. The cylinder block 5 houses the piston 8. The piston 8 is coupled to the crankshaft 2 via a connecting rod 9.

Further, in the present embodiment, the direction from the cylinder head 6 toward the head cover 7 in the cylinder axis Ax1 direction of the cylinder block 5 is referred to as "head cover side". Further, the direction from the cylinder head 6 toward the cylinder block 5 in the cylinder axis Ax1 direction is referred to as "cylinder block side".

The cylinder head 6 is disposed on the head cover side of the cylinder block 5. The cylinder head 6 is mounted to the cylinder block 5. The head cover 7 is disposed on the head cover side of the cylinder head 6. The head cover 7 is mounted to the cylinder head 6. The cylinder axis Ax1 is perpendicular to the central axis Ax2 of the crankshaft 2 (hereinafter referred to as "crank axis Ax2"). The cylinder head 6 includes a combustion chamber 11. A spark plug 12 is mounted to the cylinder head 6. The front end of the spark plug 12 is disposed facing the combustion chamber 11. The base end of the Mars plug 12 is disposed outside of the engine 1. A valve gear 13 is housed in the cylinder head 6 and the head cover 7.

The valve mechanism 13 is a mechanism for opening and closing the following exhaust valves 24 and 25 and the intake valves 26 and 27. A mechanism of a SOHC (Single OverHead Camshaft) type is employed for the valve actuation mechanism 13. The valve mechanism 13 is a so-called variable valve mechanism that switches the timing of opening and closing of the intake valves 26 and 27. The valve actuation mechanism 13 includes a camshaft 14. The camshaft 14 is supported by the cylinder head 6. The central axis Ax3 of the camshaft 14 (hereinafter referred to as "cam axis Ax3") is perpendicular to the cylinder axis Ax1. The cam axis Ax3 is parallel to the crank axis Ax2.

The camshaft 14 includes a first camshaft end 141 and a second camshaft end 142. The first camshaft drive unit 143 is provided at the first camshaft end portion 141. The first camshaft drive unit 143 is a sprocket. The first camshaft drive unit 143 meshes with the cam chain 15 , and the cam chain 15 is coupled to the camshaft 14 . The second camshaft drive unit 201 is provided on the crankshaft 2 . The second camshaft drive unit 201 is a sprocket. The second camshaft drive unit 201 meshes with the cam chain 15 , and the cam chain 15 is coupled to the crankshaft 2 . That is, the cam chain 15 is wound around the first camshaft drive unit 143 of the camshaft 14 and the second camshaft drive unit 201 of the crankshaft 2. The rotation of the crankshaft 2 is transmitted to the camshaft 14 via the cam chain 15, whereby the camshaft 14 is rotated.

A cam chain chamber 16 is provided in the cylinder head 6 and the cylinder block 5. The cam chain 15 is disposed in the cam chain chamber 16. The cam chain chamber 16 is disposed in a direction perpendicular to the cylinder axis Ax1 with respect to the combustion chamber 11. That is, the cam chain chamber 16 and the combustion chamber 11 are arranged side by side in the direction of the cam axis Ax3.

A water pump 17 is coupled to the first camshaft end portion 141. The water pump 17 is disposed in the cam axis Ax3 direction of the cam shaft 14. The water pump 17 is connected to a coolant passage (not shown) and a radiator 19 in the engine 1 via a coolant hose 18. The water pump 17 is driven by the rotation of the cam shaft 14, whereby the coolant of the engine 1 is circulated.

2 is a view showing the cylinder head 6 and the head cover 7 viewed from a direction perpendicular to the cylinder axis Ax1 and the cam axis Ax3. 3 is a cross-sectional view showing the cylinder head 6 and the head cover 7 viewed from a direction perpendicular to the cylinder axis Ax1 and the cam axis Ax3. Further, in Figs. 2 and 3, the water pump 17 is removed from the cylinder head 6 and the head cover 7.

The cylinder head 6 includes a first end portion 601 and a second end portion 602. The first end portion 601 is disposed to face the end portion 701 of the head cover 7 in the cylinder axis Ax1 direction. The second end portion 602 is disposed to face the end portion of the cylinder block 5 in the cylinder axis Ax1 direction. The first end portion 601 and the second end portion 602 extend in a direction perpendicular to the cylinder axis Ax1.

As shown in FIG. 3, the first imaginary plane P1 including the first end portion 601 of the cylinder head 6 and the second imaginary plane P2 including the end portion 701 of the head cover 7 are overlapped with the cam shaft 14. Specifically, the first imaginary plane P1 and the second imaginary plane P2 are located closer to the head cover than the cam axis Ax3. Further, a spacer 21 is interposed between the first end portion 601 of the cylinder head 6 and the end portion 701 of the head cover 7.

The cylinder head 6 includes a first cylinder side wall 603 and a second cylinder side wall 604. The first cylinder side wall 603 and the second cylinder side wall 604 are arranged to face each other in the direction of the cam axis Ax3. The second cylinder side wall 604 is closer to the cam chain chamber 16 than the first cylinder side wall 603. The second cylinder side wall 604 is closer to the first cam shaft driving portion 143 than the first cylinder side wall 603.

The head cover 7 includes a first outer casing side wall 702 and a second outer casing side wall 703. The first outer casing side wall 702 and the second outer casing side wall 703 are disposed to face each other in the direction of the cam axis Ax3. First outer casing sidewall 702 It is located on the head cover side of the first cylinder side wall 603 and is connected to the first cylinder side wall 603. The second outer casing side wall 703 is located on the head cover side of the second cylinder side wall 604 and is connected to the second cylinder side wall 604. The second outer casing side wall 703 is closer to the cam chain chamber 16 than the first outer casing side wall 702. The second outer casing side wall 703 is closer to the first cam shaft driving portion 143 than the first outer casing side wall 702.

4 and 5 are perspective views of the inside of the cylinder head 6. Fig. 6 is a view showing the inside of the cylinder head 6 as viewed from the cylinder axis Ax1 direction. As shown in FIG. 6, the first cylinder side wall 603 includes a first protruding wall portion 605, a second protruding wall portion 606, and a recessed portion 607. The first protruding wall portion 605 and the second protruding wall portion 606 have a shape that protrudes outward in the direction of the cam axis Ax3 toward the cylinder head 6 . The recessed portion 607 is located between the first protruding wall portion 605 and the second protruding wall portion 606. The recess 607 has a shape recessed toward the inside of the cylinder head 6 in the direction of the cam axis Ax3. The Mars plug 12 is attached to the first cylinder side wall 603. The base end portion of the Mars plug 12 is disposed in the recess 607 of the first cylinder side wall 603. That is, the base end portion of the spark plug 12 is disposed between the first protruding wall portion 605 and the second protruding wall portion 606 when viewed from the cylinder axis Ax1 direction.

The cylinder head 6 includes a third cylinder sidewall 608 and a fourth cylinder sidewall 609. The third cylinder side wall 608 and the fourth cylinder side wall 609 are arranged side by side in a direction perpendicular to the cam axis Ax3 and the cylinder axis Ax1. A connection portion 610 of an exhaust pipe (not shown) is provided in the third cylinder side wall 608. As shown in FIG. 4, a connection portion 611 of an intake pipe (not shown) is provided in the fourth cylinder side wall 609.

The cylinder head 6 includes a first support wall 612 and a second support wall 613. The first support wall 612 and the second support wall 613 are arranged side by side in the direction of the cam axis Ax3. The first support wall 612 and the second support wall 613 support the cam shaft 14 to be rotatable. As shown in FIG. 3, the first support wall 612 supports the cam shaft 14 via the first bearing 22. The second support wall 613 supports the cam shaft 14 via the second bearing 23 . The first support wall 612 and the second support wall 613 are disposed between the first camshaft drive unit 143 and the first cylinder side wall 603. The second support wall 613 is closer to the first camshaft drive unit 143 than the first support wall 612. The second support wall 613 is disposed between the first support wall 612 and the first camshaft drive unit 143 in the cam axis Ax3 direction. The ridge of the first support wall 612 is located on the cylinder head 6 The first end portion 601 is closer to the head cover side. The ridge portion of the second support wall 613 is located closer to the head cover than the first end portion 601 of the cylinder head 6.

Fig. 7 is a cross-sectional view showing the inside of the cylinder head 6 from the direction of the cam axis Ax3. As shown in FIGS. 4 to 7, the intake valves 26 and 27 and the exhaust valves 24 and 25 are attached to the cylinder head 6. As shown in FIG. 7, the cylinder head 6 includes an intake port 614 and an exhaust port 615 that communicate with the combustion chamber 11. The intake valves 26 and 27 open and close the intake port 614. As shown in FIG. 6, the intake valves 26 and 27 include a first intake valve 26 and a second intake valve 27. The first intake valve 26 and the second intake valve 27 are arranged side by side in the direction of the cam axis Ax3. As shown in FIG. 7, an intake valve spring 261 is attached to the first intake valve 26. The intake valve spring 261 biases the first intake valve 26 in a direction in which the first intake valve 26 closes the intake port 614. Similarly to the second intake valve 27, the intake valve spring 271 (see FIG. 4) is attached, and the second intake valve 27 is biased in the direction in which the second intake valve 27 closes the intake port 614.

The exhaust valves 24 and 25 open and close the exhaust port 615. As shown in FIG. 6, the exhaust valves 24 and 25 include a first exhaust valve 24 and a second exhaust valve 25. The first exhaust valve 24 and the second exhaust valve 25 are arranged side by side in the direction of the cam axis Ax3. As shown in FIGS. 5 and 7, an exhaust valve spring 241 is attached to the first exhaust valve 24. The exhaust valve spring 241 biases the first exhaust valve 24 in a direction in which the first exhaust valve 24 closes the exhaust port 615. The exhaust valve spring 251 is attached to the second exhaust valve 25, and the second exhaust valve 25 is biased in a direction in which the second exhaust valve 25 closes the exhaust port 615.

As shown in FIG. 3, the camshaft 14 includes 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 arranged side by side in the cam axis Ax3 direction. Among the first intake cam 144, the second intake cam 145, and the exhaust cam 146, the exhaust cam 146 is closest to the first camshaft drive unit 143. Among the first intake cam 144, the second intake cam 145, and the exhaust cam 146, the first intake cam 144 is the farthest from the first camshaft drive unit 143. The second intake cam 145 is disposed on the first intake cam 144 and the exhaust in the cam axis Ax3 direction. Use between cams 146.

As shown in FIG. 7, the valve actuation mechanism 13 includes an exhaust rocker shaft 31 and an exhaust rocker arm 32. The exhaust rocking shaft 31 is disposed in parallel with the cam shaft 14. The exhaust rocking shaft 31 is supported by the cylinder head 6. Specifically, the exhaust rocker shaft 31 is supported by the first support wall 612 and the second support wall 613. The center axis of the exhaust rocker shaft 31 is located closer to the head cover than the cam axis Ax3.

The exhaust rocker arm 32 is supported by the exhaust rocker shaft 31 so as to be swingable about the exhaust rocking shaft 31. The exhaust rocker arm 32 is provided to operate the exhaust valves 24 and 25. The exhaust rocker arm 32 includes an arm body 321, a roller support portion 322, a roller 323, and an exhaust valve pressing portion 324.

The arm body 321 includes a through hole 327 through which the exhaust rocking shaft 31 is inserted. The roller support portion 322 protrudes from the arm body 321 toward the cam shaft 14 side. The roller support portion 322 supports the roller 323 to be rotatable. The central axis of rotation of the roller 323 is parallel to the cam axis Ax3. The roller 323 is located on the cam shaft 14 side of the exhaust rocker shaft 31. The roller 323 is in contact with the exhaust cam 146 and is rotated by the rotation of the exhaust cam 146.

The exhaust valve pressing portion 324 protrudes from the arm body 321 toward the side opposite to the cam shaft 14. In other words, the exhaust valve pressing portion 324 protrudes from the arm main body 321 toward the stem end 242 side (hereinafter referred to as "exhaust valve side") of the first exhaust valve 24. As shown in FIGS. 5 and 6, a first adjusting screw 325 and a second adjusting screw 326 are provided at the front end of the exhaust valve pressing portion 324. The front end of the first adjusting screw 325 faces the column end 242 of the first exhaust valve 24. The front end of the second adjustment screw 326 is opposed to the column end 252 of the second exhaust valve 25.

When the roller 323 is pushed up by the exhaust cam 146, the exhaust rocker arm 32 swings, whereby the exhaust valve pressing portion 324 connects the column end 242 of the first exhaust valve 24 and the second exhaust valve 25 The column end 252 is pressed down. Thereby, the first exhaust valve 24 and the second exhaust valve 25 are pressed down to open the exhaust port 615. When the roller 323 is not pushed up by the exhaust cam 146, the first exhaust valve 24 and the second exhaust valve 25 are pushed up by the exhaust valve springs 241 and 251 to close the exhaust port 615.

As shown in FIG. 3, the valve mechanism 13 includes an intake rocking shaft 33, an intake rocker arm 34, and switching. Pin member 35 and actuator 39. The intake rocking shaft 33 is disposed in parallel with the cam shaft 14. The intake rocking shaft 33 is supported by the cylinder head 6. Specifically, the intake rocking shaft 33 is supported by the first support wall 612 and the second support wall 613. The center axis of the intake rocking shaft 33 is located closer to the head cover than the cam axis Ax3.

The intake rocker arm 34 includes a first rocker arm 36 and a second rocker arm 37. The first rocker arm 36 is supported by the intake rocking shaft 33 so as to be swingable about the intake rocking shaft 33. The first rocker arm 36 is provided to operate the intake valves 26 and 27. The first rocker arm 36 includes a first arm body 361 shown in FIG. 3, a first roller support portion 362 shown in FIG. 6, a first roller 363, an intake valve pressing portion 364, and a first connecting portion 365.

As shown in FIG. 3, the first arm body 361 includes a through hole 366 through which the intake rocking shaft 33 passes. The first roller support portion 362 protrudes from the first arm body 361 toward the cam shaft 14 side. The first roller support portion 362 supports the first roller 363 so as to be rotatable. The central axis of rotation of the first roller 363 is parallel to the cam axis Ax3. The first roller 363 is located on the cam shaft 14 side of the intake rocking shaft 33. The first roller 363 is in contact with the first intake cam 144 and is rotated by the rotation of the first intake cam 144.

The intake valve pressing portion 364 protrudes from the first arm body 361 to the side opposite to the cam shaft 14. In other words, the intake valve pressing portion 364 protrudes from the first arm body 361 toward the column end 262 side of the first intake valve 26 (hereinafter referred to as "intake valve side"). As shown in FIG. 6, the first adjustment screw 367 and the second adjustment screw 368 are provided at the front end of the intake valve pressing portion 364. The front end of the first adjustment screw 367 is opposed to the column end 262 of the first intake valve 26. The front end of the second adjustment screw 368 is opposed to the column end 272 of the second intake valve 27.

The first connecting portion 365 is connected to the intake valve pressing portion 364. The first joint portion 365 is located closer to the head cover than the intake rocking shaft 33. The first joint portion 365 is located closer to the intake valve side than the intake rocking shaft 33. The first joint portion 365 is located closer to the head cover than the intake valve pressing portion 364. As shown in FIG. 3, the first connecting portion 365 includes a through hole 369. The through hole 369 extends in the direction of the cam axis Ax3. A switching pin member 35 is inserted into the through hole 369.

As shown in FIG. 7, the second rocker arm 37 is supported to be swingable about the intake rocking shaft 33. The second rocker arm 37 is arranged side by side with the first rocker arm 36 in the direction of the cam axis Ax3. The second rocker arm 37 is disposed on the cam chain chamber 16 side of the first rocker arm 36. In other words, the second rocker arm 37 is closer to the first camshaft drive unit 143 than the first rocker arm 36. The second rocker arm 37 includes a second arm body 371 , a second roller support portion 372 , a second roller 373 , and a second coupling portion 374 .

The second arm body 371 includes a through hole 375 through which the intake rocking shaft 33 passes. The second roller support portion 372 protrudes from the second arm body 371 toward the cam shaft 14 side. The second roller support portion 372 supports the second roller 373 to be rotatable. The central axis of rotation of the second roller 373 is parallel to the cam axis Ax3. The second roller 373 is located on the camshaft 14 side of the intake rocking shaft 33. The second roller 373 is in contact with the second intake cam 145 and is rotated by the rotation of the second intake cam 145.

The second coupling portion 374 protrudes from the second arm body 371 on the side opposite to the cam shaft 14 . In other words, the second connecting portion 374 protrudes from the second arm body 371 toward the intake valve side. The second joint portion 374 is located closer to the head cover than the intake rocking shaft 33. The second joint portion 374 is located closer to the head cover than the intake valve pressing portion 364. As shown in FIG. 3, the second joint portion 374 includes a through hole 376. The through hole 376 extends in the direction of the cam axis Ax3. The through hole 376 of the second connecting portion 374 and the through hole 369 of the first connecting portion 365 are arranged side by side in the direction of the cam axis Ax3. Therefore, the switching pin member 35 can be inserted into the through hole 376 of the second coupling portion 374.

The valve actuation mechanism 13 includes a force applying member 38 as shown in FIG. The urging member 38 biases the second rocker arm 37 in a direction in which the second roller 373 is pressed against the cam shaft 14. In the present embodiment, the urging member 38 is a coil spring, and the intake rocking shaft 33 passes through the urging member 38. The second rocker arm 37 includes a first support member 41. The first support member 41 supports one end of the urging member 38. The first support member 41 has a pin shape and protrudes from the second rocker arm 37 in the cam axis Ax3 direction. FIG. 8 is a cross-sectional view of the vicinity of the second support wall 613 and the urging member 38.

As shown in FIG. 8, the valve mechanism 13 includes a second support member 42. The second support member 42 supports the other end of the urging member 38. The second support member 42 is composed of a curved plate and has L The cross-sectional shape of the shape. A segment portion 619 is provided in the second support wall 613, and the second support member 42 is supported by the segment portion 619.

As shown in FIG. 3, the switching pin member 35 is movable in the axial direction of the cam shaft 14, and is provided to be movable to the first position and the second position. The switching pin member 35 is disposed at the first position through the through hole 369 of the first connecting portion 365 and the through hole 376 of the second connecting portion 374. Thereby, the switching pin member 35 connects the first rocker arm 36 and the second rocker arm 37, and the first rocker arm 36 and the second rocker arm 37 are integrally swung. In this state, the switching pin member 35 swings together with the first rocker arm 36 and the second rocker arm 37.

The switching pin member 35 is disposed in the through hole 369 of the first connecting portion 365 at the second position, and is not disposed in the through hole 376 of the second connecting portion 374. Thereby, the switching pin member 35 is in the second position, and the first rocker arm 36 and the second rocker arm 37 are disconnected, and the first rocker arm 36 and the second rocker arm 37 are independently swung. In this state, the switching pin member 35 swings together with the first rocker arm 36.

The elastic member 44 is provided in the first joint portion 365. The elastic member 44 is disposed in the through hole 369 of the first connecting portion 365 . The elastic member 44 urges the switching pin member 35 in a direction from the first position toward the second position. Therefore, when the switching pin member 35 is not pressed by the actuator 39, the switching pin member 35 is held at the second position by the elastic member 44. When the switching pin member 35 is pressed by the actuator 39, the switching pin member 35 moves from the second position to the first position against the pressing force of the elastic member 44.

As shown in FIG. 7, the switching pin member 35 is located closer to the head cover than the first end portion 601 of the cylinder head 6 and the end portion 701 of the head cover 7. Therefore, the switching pin member 35 overlaps the head cover 7 when viewed from the axial direction of the cam shaft 14. As shown in FIG. 7, the switching pin member 35 is located on the intake valve side of the intake rocking shaft 33. That is, the switching pin member 35 is located between the intake rocking shaft 33 and the column end 262 of the first intake valve 26 in a direction perpendicular to the axis of the cylinder axis Ax1 and the cam shaft 14. When viewed from the axial direction of the camshaft 14, the distance between the axis of the intake rocking shaft 33 and the axis of the switching pin member 35 is smaller than the axis of the intake rocking shaft 33 and the first intake valve 26 The distance between the ends 262 of the column. Further, the intake rocking shaft 33 is located between the switching pin member 35 and the first roller 363 in a direction perpendicular to the axis of the cylinder axis Ax1 and the camshaft 14. Similarly, the intake rocking shaft 33 is located between the switching pin member 35 and the second roller 372 in a direction perpendicular to the axis of the cylinder axis Ax1 and the cam shaft 14.

Fig. 9 shows a state in which the first rocker arm 36 and the second rocker arm 37 are swung by a broken line. When the switching pin member 35 is at the first position, the first rocker arm 36 is coupled to the second rocker arm 37 and swings integrally with the second rocker arm 37. Therefore, when the second roller 373 is pushed up by the second intake cam 145, the second rocker arm 37 swings around the intake rocking shaft 33, whereby the first rocker arm 36 also urges the intake valve. The portion 364 swings in the direction of the drop. Thereby, the front end of the first adjusting screw 367 presses the column end 262 of the first intake valve 26, and the front end of the second adjusting screw 368 presses the column end 272 of the second intake valve 27. Thereby, the first intake valve 26 and the second intake valve 27 open the intake port 614. When the second roller 373 is not pushed up by the second intake cam 145, the first intake valve 26 and the second intake valve 27 are pushed up by the intake valve springs 261 and 271 to close the intake port 614.

When the switching pin member 35 is at the second position, the first rocker arm 36 and the second rocker arm 37 swing independently. Therefore, when the first roller 363 is pushed up by the first intake cam 144, the first rocker arm 36 swings in the direction in which the intake valve pressing portion 364 is lowered around the intake rocking shaft 33. Thereby, the front end of the first adjusting screw 367 presses the column end 262 of the first intake valve 26, and the front end of the second adjusting screw 368 presses the column end 272 of the second intake valve 27. Thereby, the first intake valve 26 and the second intake valve 27 open the intake port 614. When the first roller 363 is not pushed up by the first intake cam 144, the first intake valve 26 and the second intake valve 27 are pushed up by the intake valve springs 261 and 271 to close the intake port 614.

In addition, the shape of the first intake cam 144 and the second intake cam 145 is set such that the second intake cam 145 is before the first end of the first intake cam 144 reaches the first roller 363. The second roller 373 is pushed up. Therefore, when the switching pin member 35 is at the first position, the first rocker arm 36 is operated by the rotation of the second intake cam 145, whereby the rotation of the first intake cam 144 cannot be transmitted to the first rocker arm. 36. Therefore, the switching pin member 35 is located at the first place. At the time of the setting, the first intake valve 26 and the second intake valve 27 are opened and closed in response to the rotation of the second intake cam 145. On the other hand, when the switching pin member 35 is at the second position, the rotation of the second intake cam 145 cannot be transmitted to the first rocker arm 36. Therefore, when the switching pin member 35 is at the second position, the first intake valve 26 and the second intake valve 27 are opened and closed in accordance with the rotation of the first intake cam 144.

The actuator 39 is an electromagnetic solenoid, and the switching pin member 35 is pressed in the axial direction of the cam shaft 14 by being energized, and the position of the switching pin member 35 is switched from the second position to the first position. When the energization of the actuator 39 is stopped, the position of the switching pin member 35 is returned from the first position to the second position by the elastic force of the elastic member 44.

As shown in FIG. 6, the actuator 39 overlaps the first end portion 601 of the cylinder head 6 when viewed in the cylinder axis Ax1 direction. That is, one portion of the actuator 39 is located closer to the inner side of the cylinder head 6 than the first end portion 601 of the cylinder head 6. The actuator 39 is disposed on the side opposite to the cam chain chamber 16 with respect to the cam shaft 14 when viewed from the cylinder axis Ax1 direction. The extension line of the cam axis Ax3 is located between the connection portion 610 of the exhaust pipe and the actuator 39 when viewed from the cylinder axis Ax1 direction. As shown in FIG. 3, the actuator 39 is located closer to the head cover than the first end portion 601 of the cylinder head 6.

The actuator 39 includes a rod 391 that pushes the switching pin member 35, and a body portion 392 that drives the rod 391. The central axis of the rod 391 is parallel to the cam axis Ax3. The rod 391 is disposed so as to overlap the switching pin member 35 when viewed in the direction of the cam axis Ax3 in the swing range of the switching pin member 35. The lever 391 is driven by the body portion 392, thereby pushing the switching pin member 35. The rod 391 is disposed close to the first support wall 612 described above. As shown in FIG. 4, the first support wall 612 includes a recess 620 that faces the side of the rod 391. The recess 620 has a shape that is recessed to avoid the rod 391.

The actuator 39 is disposed outside the engine 1. The actuator 39 is mounted to the head cover 7. In detail, the main body portion 392 is attached to the head cover 7. The rod 391 is supported by the head cover 7. As shown in FIG. 3, the head cover 7 is provided with a through hole 704, and the rod 391 passes through the through hole 704.

Fig. 10 is a view showing the cylinder head 6 and the head cover 7 as viewed from the cylinder axis Ax1 direction. As shown in FIGS. 2 and 10, the actuator 39 is attached to the head cover 7 outside the engine 1. The actuator 39 is attached to the first outer casing side wall 702. The actuator 39 is disposed so as not to overlap the extension line of the axis of the spark plug 12. The first boss portion 705 and the second boss portion 706 are provided on the first case side wall 702. The first boss portion 705 and the second boss portion 706 protrude from the first outer casing side wall 702 toward the outside of the cylinder head 6 in the direction of the cam axis Ax3. The first boss portion 705 and the second boss portion 706 are arranged side by side in a direction perpendicular to the cam axis Ax3 and the cylinder axis Ax1. The actuator 39 includes a flange portion 393 that protrudes from the body portion 392. The flange portion 393 is fixed to the first boss portion 705 and the second boss portion 706 by bolts 51 and 52. Thereby, the actuator 39 is fixed to the first outer casing side wall 702.

Figure 11 is a cross-sectional view of a portion of the engine 1 as seen from a direction perpendicular to the cam axis Ax3 and the cylinder axis Ax1. As shown in FIG. 11, the cylinder head 6, the cylinder block 5, and the crankcase 3 are fastened by the first fastening bolt 61 and the second fastening bolt 62. The cylinder head 6, the cylinder block 5, and the crank axle box 3 are fastened by a third fastening bolt and a fourth fastening bolt (not shown). The first fastening bolt 61 includes a first head portion 65. The second fastening bolt 62 includes a second head portion 66. The third fastening bolt includes a third head portion 67 as shown in FIG. The fourth fastening bolt includes a fourth head portion 68 as shown in FIG. The first to fourth heads 65 to 68 are fixed to the cylinder head 6. The first head portion 65 includes a nut that is partially open to the shaft of the first fastening bolt 61. However, the nut may be integral with the shaft portion of the fastening bolt 61. The second to fourth head portions 66-68 are also the same as the first head portion 65.

The first head portion 65 and the second head portion 66 are arranged side by side in the direction of the cam axis Ax3. The third head portion 67 and the fourth head portion 68 are arranged side by side in the direction of the cam axis Ax3. The first head portion 65 and the third head portion 67 are arranged side by side in a direction perpendicular to the cam axis Ax3 and the cylinder axis Ax1. The second head portion 66 and the fourth head portion 68 are arranged side by side in a direction perpendicular to the cam axis Ax3 and the cylinder axis Ax1.

The first head portion 65 is disposed between the first cylinder side wall 603 and the second head portion 66 in the direction of the cam axis Ax3. The first cylinder side wall 603 is closer to the first head portion 65 than the second cylinder side wall 604. First head The portion 65 is disposed in the first protruding wall portion 605 of the first cylinder side wall 603. The first head portion 65 overlaps the actuator 39 when viewed from the cylinder axis Ax1 direction of the cylinder block 5. The axis of the switching pin member 35 is perpendicular to the cam axis Ax3 and the cylinder axis Ax1, and is located on the intake rocking shaft 33 side with respect to the center of the first head portion 65. The axis of the switching pin member 35 is located between the center of the first head portion 65 and the intake rocking shaft 33 in a direction perpendicular to the cam axis Ax3 and the cylinder axis Ax1.

The second head portion 66 is disposed between the second cylinder side wall 604 and the first head portion 65 in the direction of the cam axis Ax3. The second cylinder side wall 604 is closer to the second head portion 66 than the first cylinder side wall 603. The camshaft drive unit 143 is disposed between the second cylinder side wall 604 and the second head portion 66 in the cam axis Ax3 direction. The second head portion 66 is disposed on the second support wall 613. The first head portion 65 and the second head portion 66 are disposed on the intake valve side with respect to the cam axis Ax3. The distance between the first cylinder side wall 603 and the first head portion 65 in the cam axis Ax3 direction is smaller than the distance between the second cylinder side wall 604 and the second head portion 66 in the cam axis Ax3 direction.

The third head portion 67 is disposed between the first cylinder side wall 603 and the fourth head portion 68 in the cam axis Ax3 direction. The first cylinder side wall 603 is closer to the third head portion 67 than the second cylinder side wall 604. The third head portion 67 is disposed in the second protruding wall portion 606 of the first cylinder side wall 603.

The fourth head portion 68 is disposed between the second cylinder side wall 604 and the third head portion 67 in the cam axis Ax3 direction. The second cylinder side wall 604 is closer to the fourth head portion 68 than the first cylinder side wall 603. The camshaft drive unit 143 is disposed between the second cylinder side wall 604 and the fourth head portion 68 in the cam axis Ax3 direction. The fourth head portion 68 is disposed on the second support wall 613. The third head portion 67 and the fourth head portion 68 are disposed on the exhaust valve side with respect to the cam axis Ax3. The distance between the first cylinder side wall 603 and the third head portion 67 in the cam axis Ax3 direction is smaller than the distance between the second cylinder side wall 604 and the fourth head portion 68 in the cam axis Ax3 direction.

As shown in FIG. 11, the inner surface of the first outer casing side wall 702 and the inner surface of the second outer casing side wall 703 are inclined such that the first outer casing side wall 702 and the second outer casing side wall 703 are narrowed toward the head cover side.

The cylinder head 6 includes a first through hole 621 in which the first fastening bolts 61 are disposed, and a second through hole 622 in which the second fastening bolts 62 are disposed. The first through hole 621 and the second through hole 622 extend in the cylinder axis line Ax1 direction. The second through hole 622 is provided to pass through the second support wall 613. As shown in FIG. 12, the distance D1 from the third imaginary plane P3 including the crank axis Ax2 and perpendicular to the cylinder axis Ax1 of the cylinder block 5 to the first head 65 in the cylinder axis Ax1 direction is smaller than the distance from the third imaginary plane P3 to The distance D2 of the second head portion 66 in the cylinder axis Ax1 direction. That is, the first head portion 65 is located closer to the cylinder block side than the second head portion 66.

When viewed from the direction of the cam axis Ax3, the first fastening bolt 61 does not overlap the head cover 7. That is, the first head portion 65 is located closer to the cylinder block side than the first end portion 601 of the cylinder head 6. The second fastening bolt 62 overlaps the head cover 7 when viewed in the direction of the cam axis Ax3. That is, the second head portion 66 is located closer to the head cover than the first end portion 601 of the cylinder head 6.

Although not shown, the third head portion 67 is located at the same height as the first head portion 65, and the fourth head portion 68 is located at the same height as the second head portion 66. Therefore, the third head portion 67 is located closer to the cylinder block side than the fourth head portion 68.

In the engine 1 of the present embodiment, the first end portion 601 of the cylinder head 6 and the end portion 701 of the head cover 7 are disposed at a height overlapping the cam shaft 14. Therefore, the size of the engine 1 can be reduced, and the accessibility to the shaft ends of the exhaust valves 24 and 25 and the intake valves 26 and 27 can be improved.

Further, the inner surface of the first outer casing side wall 702 connected to the first cylinder side wall 603 is inclined toward the first head portion 65 in the cam axis direction as it goes away from the end portion of the first outer casing side wall 702 toward the head cover side. . Therefore, the position of the first head portion 65 is located on the side of the head cover, and the distance between the first head portion 65 and the inner surface of the first outer casing side wall 702 is smaller. In this case, in order to ensure a gap between the inner surface of the first outer casing side wall 702 and the first head portion 65, the engine 1 is increased in size.

However, in the engine 1 of the present aspect, the first head portion 65 is disposed closer to the cylinder block than the second head portion 66, whereby the engine 1 can be downsized.

Further, the second head portion 66 is spaced apart from the second cylinder side wall 604 than the position of the first head portion 65 with respect to the first cylinder side wall 603. Therefore, even if the second head 66 is disposed in comparison The first head portion 65 is further on the side of the head cover, and it is also possible to suppress an increase in size of the engine 1 and to secure a gap between the second outer casing side wall 703 and the second head portion 66. Further, by arranging the second head portion 66 on the side of the head cover from the first head portion 65, the rigidity of the cylinder head 6 can be improved.

As described above, in the engine 1 of the present embodiment, the engine 1 can be downsized, and the accessibility to the axial ends of the exhaust valves 24 and 25 and the intake valves 26 and 27 can be improved.

When viewed from the direction of the cam axis Ax3, the first fastening bolt 61 does not overlap the head cover 7. Thereby, the engine 1 can be miniaturized.

The second support wall 613 includes a through hole 622 in which the second fastening bolts 62 are disposed. Therefore, the increase in size of the second support wall 613 can be suppressed, and the strength of the second support wall 613 can be increased by the second fastening bolts 62. Thereby, the engine 1 can be miniaturized.

An actuator 39 is mounted to the head cover 7. Therefore, even if the actuator 39 is disposed close to the switching pin member 35, the combustion chamber 11 from the cylinder head 6 to the actuator 39 can be suppressed as compared with the case where the actuator 39 is attached to the cylinder head 6. The heat effect. Thereby, the thermal influence on the actuator 39 can be suppressed and the engine 1 can be miniaturized.

The actuator 39 overlaps the first end portion 601 of the cylinder head 6 and the end portion 701 of the head cover 7 when viewed from the cylinder axis Ax1 direction. In this case, the distance between the actuator 39 and the switching pin member 35 becomes short, whereby the driving force required to switch the pin member 35 can be reduced. Thereby, the actuator 39 can be miniaturized, and the engine 1 can be further miniaturized.

The first fastening bolt 61 overlaps the actuator 39 when viewed from the cylinder axis Ax1 direction. In other words, the actuator 39 can be disposed closer to the cylinder head 6 by the space on the head cover side of the first fastening bolt 61. Thereby, the engine 1 can be further miniaturized.

The embodiment of the present invention has been described above, but the present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit and scope of the invention.

The engine 1 is not limited to a water-cooled single cylinder engine. For example, the engine 1 can also be air-cooled. The engine 1 can also include a plurality of cylinders.

The number of valves for exhausting is not limited to two, and may be one or three or more. Intake The number of valves used is not limited to two, and may be one or three or more.

The positions of the first head portion 65, the second head portion 66, the third head portion 67, and the fourth head portion 68 are not limited to the positions of the above-described embodiments, and may be changed. For example, in the above-described embodiment, the first head portion 65 does not overlap the head cover 7 in the direction of the cam shaft 14, but the first head portion 65 may overlap the head cover 7 in the direction of the cam shaft 14. That is, the first head portion 65 may be located closer to the head cover than the end portion 701 of the head cover 7. Alternatively, the third head portion 67 may be located at a different height from the first head portion 65. For example, the third head portion 67 may be located at the same height as the second head portion 66. The fourth head portion 68 can also be located at a different height from the second head portion 66.

The first imaginary plane P1 including the first end portion 601 of the cylinder head 6 and the second imaginary plane P2 including the end portion 701 of the head cover 7 may be disposed in the same manner as the cam axis Ax3 as long as they overlap the cam shaft 14. The height or the arrangement is closer to the cylinder block side than the cam axis Ax3.

The configuration and arrangement of the valve actuation mechanism 13 are not limited to the above-described embodiments, and may be modified. For example, the actuator 39 can also be mounted to the cylinder head 6. Alternatively, the actuator 39 may be disposed so as not to overlap the end portion 701 of the head cover 7 when viewed from the direction of the cylinder axis Ax1. Alternatively, the actuator 39 may be disposed so as not to overlap the first head portion 65 when viewed from the cylinder axis Ax1 direction. It is not limited to one portion of the actuator 39, and all of the actuators 39 are located further inside than the first end portion 601 of the cylinder head 6.

In the above embodiment, the mechanism for switching the timing of opening and closing of the valve by the actuator can be used for the intake valve or the exhaust valve. That is, the same mechanism as the above-described mechanism including the first rocker arm 36, the second rocker arm 37, the switching pin member 35, and the actuator 39 may be provided to open and close the exhaust valve. Alternatively, the mechanism for switching the timing of opening and closing of the valve by the actuator may not be used for any of the intake valve and the exhaust valve.

7‧‧‧ head cover

12‧‧‧Mars plug

39‧‧‧Actuator

51‧‧‧ bolt

52‧‧‧Bolts

392‧‧‧ Body Department

393‧‧‧Flange

610‧‧‧ connection of the exhaust pipe

702‧‧‧1st outer casing side wall

703‧‧‧2nd casing side wall

705‧‧‧1st seat

706‧‧‧2nd seat

Claims (8)

An engine comprising: a crankshaft; a crankcase housing the crankshaft; a cylinder block coupled to the crankcase; a cylinder head coupled to the cylinder block; a valve mounted to the cylinder head; a cam a shaft supported by the cylinder head; a head cover including an end portion disposed opposite to an end portion of the cylinder head, and mounted to the cylinder head; and a first fastening bolt including a first fixing to the cylinder head a head portion that fastens the cylinder head, the cylinder block, and the crankcase; and a second fastening bolt that includes a second head fixed to the cylinder head, and the cylinder head, the cylinder block, and The crankcase is fastened; and the first imaginary plane including the end of the cylinder head and the second imaginary plane including the end of the head cover overlap with the camshaft; the cylinder head is included in the camshaft a first cylinder side wall and a second cylinder side wall disposed opposite to each other in the axial direction; the head cover includes a first outer casing side wall connected to the first cylinder side wall and a second outer casing side connected to the second cylinder side wall The inner surface of the side wall of the first outer casing is inclined in such a manner as to narrow between the side wall of the first outer casing and the side wall of the second outer casing in a direction from the cylinder head toward the head cover in the cylinder axis direction of the cylinder block The first head portion is disposed between the first cylinder sidewall and the second head portion in the axial direction of the cam shaft; The second head portion is disposed between the second cylinder side wall and the first head portion in the axial direction of the cam shaft; and between the first cylinder side wall and the first head portion in the axial direction of the cam shaft a distance smaller than a distance between the second cylinder side wall and the second head in the axial direction of the camshaft; and a third imaginary plane including an axis of the crankshaft and perpendicular to the cylinder axis to the cylinder axis direction The distance from the first head portion is smaller than the distance from the third imaginary plane to the second head portion in the cylinder axis direction. The engine of claim 1, wherein the first head portion is located closer to the cylinder block side than the second head portion in the cylinder axis direction. The engine of claim 1, wherein the first fastening bolt does not overlap the head cover when viewed from an axial direction of the cam shaft. The engine of claim 1, further comprising a camshaft drive unit provided on the camshaft, wherein the camshaft drive unit is disposed between the second cylinder sidewall and the second head in an axial direction of the camshaft . The engine of claim 4, wherein the cylinder head includes a support wall for supporting the cam shaft; and the support wall includes a through hole for arranging the second fastening bolt. The engine of any one of claims 1 to 5, further comprising: a rocking shaft supported by the cylinder head and parallel to the camshaft; a first rocker arm supported by the rocking shaft; and a second rocker arm Supporting the rocking shaft, and arranging in parallel with the first rocker arm in the axial direction of the camshaft; switching pin member movable in the axial direction of the camshaft and being movable to move to the first a first position in which the rocker arm is coupled to the second rocker arm, and a second position in which the first rocker arm and the second rocker arm are not connected, the second rocker swings together with the first rocker arm and the second rocker arm, and an actuator that switches the switch pin member Pressing in the axial direction of the camshaft switches the position of the switching pin member to the first position and the second position; and the actuator is attached to the head cover outside the engine. The engine of claim 6, wherein at least a portion of the actuator overlaps with the end of the head cover when viewed in the cylinder axis direction. The engine of claim 6, wherein at least a part of the first fastening bolt overlaps the actuator when viewed in the cylinder axis direction.