TWI611095B - Engine and vehicle - Google Patents

Abstract

In the present invention, the pressure reducing mechanism is disposed between both end portions in the axial direction of the camshaft. The decompression mechanism includes a weight body and a decompression cam. The weight is rotatably supported relative to the camshaft. According to the rotation of the weight body, the decompression cam is switched into a state in which it is in contact with the valve mechanism and a state in which it is not in contact with the valve mechanism. The weight includes an inner wheel contact portion. The inner wheel contact portion is arranged side by side with the inner wheel of the bearing in the axial direction of the camshaft. The inner wheel contact portion is located radially inward of the inner peripheral surface of the outer wheel of the bearing.

Description

Engines and vehicles

The present invention relates to an engine and a vehicle having a decompression mechanism (hereinafter referred to as a "decompression mechanism").

When starting the engine, it is necessary to rotate the engine by external force until the start is completed. For example, there are those who use a starter motor to rotate, or those who use a foot starter to rotate. On the other hand, during the compression step of the engine, the air in the cylinder is compressed, so the resistance to rotation increases. In order to reduce such resistance, a pressure reducing mechanism is known which is used to reduce the pressure in the cylinder in a compression step when the engine is rotated by an external force.

For example, the decompression mechanism of the engine disclosed in Japanese Patent Laid-Open No. 2008-128171 has a decompression cam, and the decompression cam is switched to an activated state and a released state by the rotation of the weight body. The decompression mechanism is supported on a sprocket of a cam chain. Therefore, there is a problem that the cam shaft including the pressure reducing mechanism becomes large in the axial direction.

In the engine disclosed in Japanese Patent Laid-Open No. 2009-180104, the pressure reducing mechanism is disposed between the two ends of the camshaft. Therefore, compared with a case where a pressure reducing mechanism is provided outside the camshaft, the cam shaft including the pressure reducing mechanism may be simplified in the axial direction in some cases.

However, if the pressure reducing mechanism is disposed between both ends of the camshaft, the camshaft itself It is easy to lengthen in the axial direction. If the cam shaft becomes longer in the axial direction, there is a problem that the engine becomes larger.

An object of the present invention is to provide a simplified engine and a vehicle provided with the engine.

An aspect of the invention is an engine including a cylinder head, an exhaust valve, a valve operating mechanism, a camshaft, a bearing, and a pressure reducing mechanism. The exhaust valve is housed in the cylinder head. The valve action mechanism opens and closes the exhaust valve. The camshaft drives the valve mechanism by being in contact with the valve mechanism. The bearing includes an inner wheel and an outer wheel, and a camshaft is rotatably supported by a cylinder head. The inner wheel is in contact with the camshaft. The outer wheel is in contact with the cylinder head. The decompression mechanism is disposed between both end portions in the axial direction of the cam shaft. The decompression mechanism includes a weight body and a decompression cam. The weight is rotatably supported relative to the camshaft. According to the rotation of the weight body, the decompression cam is switched into a state in which it is in contact with the valve mechanism and a state in which it is not in contact with the valve mechanism. The weight includes an inner wheel contact portion. The inner wheel contact portion is arranged side by side with the inner wheel in the axial direction of the camshaft. The inner wheel contact portion is located radially inward of the inner peripheral surface of the outer wheel.

The inventors of the present case have studied a configuration in which a pressure reducing mechanism is arranged between both ends of a cam shaft, and the cam shaft is simplified as much as possible in the axial direction. Among them, the inventors have studied and arranged a bearing supporting a camshaft and a counterweight in the axial direction. This can simplify the camshaft in the axial direction. However, it can be seen that, in this case, if the weight body is not inhibited from sliding in the axial direction, the bearing may come into contact with the weight body. In order to suppress the contact between the bearing and the weight body, it is considered that a member such as a washer is sandwiched between the bearing and the weight body. However, the provision of such a member prevents the cam shaft from being simplified.

Therefore, the inventors focused on a configuration in which an inner wheel which does not rotate with respect to the camshaft and an outer wheel which rotates with respect to the camshaft exist in the bearing. Furthermore, the inventors have found that by providing an inner wheel contact portion on the weight body, it is possible to suppress damage caused by the contact. That is, since the inner wheel contact portion is located radially inward of the inner peripheral surface of the outer wheel, it does not contact the outer wheel. Therefore, damage caused by contact with the outer wheel can be suppressed. In addition, the inner wheel rotates together with the cam shaft in the same manner as the weight body, so that even if the weight body contacts the inner wheel, damage can be suppressed.

Preferably, at least a part of the inner wheel contact portion is disposed closer to the rotation center of the weight body than the rotation center of the cam shaft as viewed from the axial direction of the cam shaft. In this case, the amount of movement of the contact portion of the inner wheel when the weight body rotates is small, so that the contact portion of the inner wheel can be made larger in a range where it does not contact the outer wheel. In addition, by increasing the inner wheel contact portion, the weight of the weight can be increased.

Preferably, at least a part of the contact portion of the inner wheel is located between the rotation center of the weight body and the cam shaft as viewed from the axial direction of the cam shaft. In this case, by positioning the center of gravity of the weight body close to the center of rotation of the weight body, the opening of the weight body caused by gravity can be suppressed. In addition, the contact portion of the inner wheel can be brought closer to the center of rotation of the weight.

Preferably, when viewed from the axial direction of the camshaft, the portion of the inner wheel contact portion that is closer to the center of rotation of the weight body than the center of gravity of the weight body is larger than the portion of the inner wheel contact portion that is further away from the center of gravity of the weight body The center of rotation of the weight. In this case, by positioning the center of gravity of the weight body close to the center of rotation of the weight body, the opening of the weight body caused by gravity can be suppressed. In addition, the contact portion of the inner wheel can be brought closer to the center of rotation of the weight.

Preferably, the engine further includes a sprocket and a cam chain. The sprocket is mounted on the camshaft. The cam chain is wound around a sprocket. The camshaft includes a first end portion and a second end portion. The sprocket is attached to the first end portion. The bearing is disposed closer to the first end portion than the second end portion in the axial direction of the camshaft. Generally, a bearing provided with a cam chain is easily enlarged. Therefore, by making the inner wheel with the bearing provided with the inner wheel contact portion larger, the degree of freedom in designing the inner wheel contact portion can be improved.

A vehicle according to another aspect of the present invention includes the engine described above.

According to the present invention, a simplified engine and a vehicle equipped with the engine can be provided.

1‧‧‧ vehicle

2‧‧‧vehicle body

2a‧‧‧flat pedal

3‧‧‧ front wheel

4‧‧‧ rear wheel

5‧‧‧handle

6‧‧‧ seat

7‧‧‧ Engine

8‧‧‧ Gearbox

11‧‧‧ crankshaft

12‧‧‧ crankcase

13‧‧‧ cylinder block

14‧‧‧ Cylinder head

15‧‧‧Piston

16‧‧‧ connecting rod

17‧‧‧combustion chamber

18‧‧‧ Mars Plug

19‧‧‧ head cover

21‧‧‧air inlet

22‧‧‧ exhaust port

23‧‧‧ exhaust valve

24‧‧‧Air inlet valve

25‧‧‧Valve action mechanism

26‧‧‧camshaft

27‧‧‧The first bearing

28‧‧‧ 2nd bearing

29‧‧‧ cam chain

31‧‧‧1st sprocket

32‧‧‧Second sprocket

33‧‧‧Exhaust rocker shaft

34‧‧‧Exhaust rocker arm

35‧‧‧Inlet rocker shaft

36‧‧‧Inlet rocker arm

40‧‧‧ Decompression mechanism

41‧‧‧ flange

42‧‧‧ weight

42a‧‧‧1st locking part

42b‧‧‧ 2nd locking part

43‧‧‧ Decompression cam

44‧‧‧ Decompression Pin

45‧‧‧ reply spring

46‧‧‧ pivot pin

47‧‧‧ 1st weight body

48‧‧‧Second weight body

141‧‧‧The first support wall

142‧‧‧ 2nd support wall

143‧‧‧The first bearing support hole

144‧‧‧1st recess

145‧‧‧2nd recess

146‧‧‧3rd recess

231‧‧‧Exhaust valve spring

232‧‧‧ Rod End

241‧‧‧Intake valve spring

242‧‧‧ Rod End

261‧‧‧The first camshaft end

262‧‧‧ 2nd camshaft end

263‧‧‧Air intake cam

264‧‧‧Exhaust Cam

265‧‧‧Concave

266‧‧‧base circle

267‧‧‧ cam protrusion

271‧‧‧Inner wheel

272‧‧‧outer

341‧‧‧arm body

342‧‧‧Exhaust roller

343‧‧‧Exhaust valve pushing part

361‧‧‧arm body

362‧‧‧Air intake roller

363‧‧‧Intake valve pushing part

411‧‧‧hole

412‧‧‧1st protrusion

413‧‧‧ 2nd convex part

414‧‧‧hole

421‧‧‧Part 1

421a‧‧‧Inner diameter section

421b‧‧‧outer diameter

422‧‧‧Part 2

423‧‧‧ pivot pin support department

423a‧‧‧Storage

423b‧‧‧ convex seat

423c‧‧‧hole

424‧‧‧ 1st protrusion

424a‧‧‧More recent

424b

425‧‧‧ protrusion

426‧‧‧Inner wheel contact

426a‧‧‧1st contact

426b‧‧‧2nd contact

426c‧‧‧3rd contact

431‧‧‧Head

432‧‧‧Shaft

433‧‧‧Slot

434‧‧‧Cam

451‧‧‧1st spring end

452‧‧‧ 2nd spring end

471‧‧‧ tip

481‧‧‧ tip

A1‧‧‧Area 1

A2‧‧‧ Zone 2

A3‧‧‧Region 3

A4‧‧‧Area 4

C1‧‧‧ center of rotation of camshaft 26

C2‧‧‧ weight center of rotation 42

Center of gravity of G1‧‧‧ weight body 42

G2 ‧‧‧ Center of gravity of weight body 42 without first protrusion 424

X‧‧‧ horizontal axis

x1‧‧‧ 1st horizontal direction

x2‧‧‧ 2nd horizontal direction

Y‧‧‧Vertical axis

y1‧‧‧1st vertical direction

y2‧‧‧ 2nd vertical direction

Figure 1 is a side view of the vehicle.

Figure 2 is a sectional view of a part of the engine.

Figure 3 is a sectional view of the cylinder head in a plane perpendicular to the camshaft.

Fig. 4 is an enlarged sectional view of a camshaft assembly.

Fig. 5 is a perspective view of a camshaft assembly.

Fig. 6 is an exploded view of a camshaft assembly.

Fig. 7 is a view showing a weight body in a closed state.

Fig. 8 is a view showing a weight body in an opened state.

Figures 9 (A) and (B) are enlarged views of the exhaust cam.

Fig. 10 is a side view of a camshaft assembly.

FIG. 11 is a view showing a camshaft assembly viewed from the cam axis direction.

Fig. 12 is a view showing a weight body viewed from the cam axis direction.

Fig. 13 is a perspective view of a weight body.

FIG. 14 is a side view of the camshaft assembly viewed from the direction of arrow XIV in FIG. 10.

FIG. 15 is a view showing a flange, a weight body, and a return spring viewed from the cam axis direction.

Fig. 16 is a view showing a cylinder head in a state where a head cover is removed.

FIG. 17 is a diagram showing a weight body according to a modification.

Hereinafter, the vehicle 1 according to the embodiment will be described with reference to the drawings. FIG. 1 is a side view of the vehicle 1. The vehicle is a Scooter locomotive. The vehicle 1 includes a vehicle body 2, a front wheel 3, a rear wheel 4, a handle 5, and a seat portion 6. The vehicle body 2 includes a flat footrest 2a. The vehicle body 2 supports front wheels 3 and rear wheels 4. The handle 5 and the seat portion 6 are attached to the vehicle body 2. The flat footrest 2 a is disposed in front of and below the seat portion 6.

The vehicle 1 includes an engine 7 according to the embodiment. Fig. 2 is a sectional view of a part of the engine 7. As shown in FIG. 2, the engine 7 includes a crankshaft 11, a crankcase 12, a cylinder block 13, a cylinder head 14, and a head cover 19. The cylinder block 13 is connected to a crankcase 12. The cylinder block 13 may be integrated with the crankcase 12 or may be separated from the crankcase 12. The cylinder block 13 houses a piston 15. The piston 15 is connected to the crankshaft 11 via a connecting rod 16. The crankshaft 11 is connected to the transmission 8.

The cylinder head 14 is connected to a cylinder block 13. The cylinder head 14 includes a combustion chamber 17. A spark plug 18 is mounted on the cylinder head 14. The front end of the spark plug 18 is disposed facing the combustion chamber 17. The head cover 19 is attached to the cylinder head 14.

The engine 7 includes a valve mechanism 25 and a camshaft 26. The valve mechanism 25 and the camshaft 26 are housed in the cylinder head 14. The cam shaft 26 drives the valve mechanism 25 by being in contact with the valve mechanism 25.

The camshaft 26 is supported by the cylinder head 14. The cylinder head 14 includes a first support wall 141 and a second support wall 142. The first support wall 141 and the second support wall 142 are arranged side by side in the axial direction of the cam shaft 26 (hereinafter referred to as the "cam axis direction"). The first support wall 141 supports the camshaft 26. The first support wall 141 supports the camshaft 26 via a first bearing 27. The second support wall 142 supports the camshaft 26. The second support wall 142 supports the camshaft 26 via a second bearing 28. The first bearing 27 and the second bearing 28 rotatably support the camshaft 26 to the cylinder head 14. The outer diameter of the first bearing 27 is larger than the outer diameter of the second bearing 28. The first support wall 141 may support the camshaft 26 without passing through the first bearing 27. The second support wall 142 may support the camshaft 26 without passing through the second bearing 28.

The camshaft 26 includes a first camshaft end portion 261 (first end portion) and a second camshaft end portion 262 (second end portion). The first bearing 27 is disposed closer to the first camshaft end portion 261 than the second camshaft end portion 262 in the cam axis direction. The second bearing 28 is disposed closer to the second camshaft end portion 262 than the first camshaft end portion 261 in the cam axis direction.

A cam chain 29 is wound around the camshaft 26 and the crankshaft 11. Specifically, the first sprocket 31 is attached to the camshaft 26. The first sprocket 31 is attached to the first camshaft end portion 261. A second sprocket 32 is attached to the crankshaft 11. The cam chain 29 is wound around the first sprocket 31 and the second sprocket 32.

The rotation of the crankshaft 11 is transmitted to the camshaft 26 via the cam chain 29, whereby the camshaft 26 is rotated. The camshaft 26 includes an intake cam 263 and an exhaust cam 264. Intake cam 263 with The exhaust cams 264 are arranged side by side in the cam axis direction. The camshaft 26 rotates to rotate the intake cam 263 and the exhaust cam 264. The intake cam 263 and the exhaust cam 264 are in contact with the valve mechanism 25, and the intake cam 263 and the exhaust cam 264 rotate to drive the valve mechanism 25.

FIG. 3 is a sectional view of the cylinder head 14 in a plane perpendicular to the camshaft 26. As shown in FIG. 3, the engine 7 includes an exhaust valve 23 and an intake valve 24. The cylinder head 14 includes an intake port 21 and an exhaust port 22 in communication with the combustion chamber 17. The exhaust valve 23 and the intake valve 24 are housed in the cylinder head 14. The intake valve 24 opens and closes the intake port 21. The exhaust valve 23 opens and closes the exhaust port 22. The valve mechanism 25 opens and closes the intake valve 24 and the exhaust valve 23.

An intake valve spring 241 is attached to the intake valve 24. The intake valve spring 241 urges the intake valve 24 in a direction in which the intake valve 24 closes the intake port 21. An exhaust valve spring 231 is attached to the exhaust valve 23. The exhaust valve spring 231 urges the exhaust valve 23 in a direction in which the exhaust valve 23 closes the exhaust port 22.

The valve moving mechanism 25 includes an exhaust rocking shaft 33 and an exhaust rocking arm 34. The exhaust rocking shaft 33 is arranged parallel to the cam shaft 26. The exhaust rocking shaft 33 is supported by the cylinder head 14. The exhaust rocking arm 34 can be supported by the exhaust rocking shaft 33 while swinging about the exhaust rocking shaft 33 as a center. The exhaust rocker arm 34 is provided to operate the exhaust valve 23. The exhaust rocking arm 34 includes an arm body 341, an exhaust roller 342, and an exhaust valve pressing portion 343.

The arm body 341 is swingably supported by the exhaust swing shaft 33. One end of the arm body 341 rotatably supports the exhaust roller 342. The other end of the arm body 341 supports an exhaust valve pressing portion 343. The exhaust roller 342 is in contact with the exhaust cam 264 and is rotated by the rotation of the exhaust cam 264. The front end of the exhaust valve pressing portion 343 faces the rod end 232 of the exhaust valve 23.

When the exhaust roller 342 is pushed up by the exhaust cam 264, the exhaust rocking arm 34 is rocked, whereby the exhaust valve pressing portion 343 presses the rod end 232 of the exhaust valve 23. Thereby, the exhaust valve 23 is depressed and the exhaust port 22 is opened. When the exhaust roller 342 is not pushed up by the exhaust cam 264, the exhaust valve 23 is pushed up by the exhaust valve spring 231 to close the exhaust port 22.

The valve moving mechanism 25 includes an intake rocking shaft 35 and an intake rocking arm 36. The intake rocking shaft 35 is arranged parallel to the cam shaft 26. The intake rocking shaft 35 is supported by the cylinder head 14. The intake rocker arm 36 is swingably supported by the intake rocker shaft 35 around the intake rocker shaft 35. The intake rocker arm 36 is provided to operate the intake valve 24. The intake rocker arm 36 includes an arm body 361, an intake roller 362, and an intake valve pressing portion 363.

The arm body 361 is swingably supported by the intake swing shaft 35. One end of the arm body 361 rotatably supports the air intake roller 362. The other end of the arm body 361 supports an intake valve pressing portion 363. The intake roller 362 is in contact with the intake cam 263 and is rotated by the rotation of the intake cam 263. The front end of the intake valve pressing portion 363 faces the rod end 242 of the intake valve 24.

When the air roller 362 is pushed on the intake cam 263, the intake rocker arm 36 is swung, whereby the intake valve pressing portion 363 pushes down the rod end of the intake valve 24. Thereby, the intake valve 24 is depressed and the intake port 21 is opened. When the air roller 362 is not pushed on the intake cam 263, the air valve 24 is pushed on the intake valve spring 241 to close the intake port 21.

As shown in FIG. 2, the engine 7 includes a decompression mechanism 40. FIG. 4 is an enlarged view of an assembly of the camshaft 26, the pressure reducing mechanism 40, and the first bearing 27 (hereinafter referred to as "camshaft assembly"). The decompression mechanism 40 is arranged between the first camshaft end portion 261 and the second camshaft end portion 262 in the cam axis direction. The pressure reducing mechanism 40 is disposed between the first support wall 141 and the second support wall 142 of the cylinder head 14.

Fig. 5 is a perspective view of a camshaft assembly. Fig. 6 is an exploded view of a camshaft assembly. As shown in FIGS. 5 and 6, the pressure reducing mechanism 40 includes a flange 41, a weight body 42, a pressure reducing cam 43, a pressure reducing pin 44, and a return spring 45.

As shown in FIG. 6, the flange 41 is separated from the cam shaft 26 and is fixed to the cam shaft 26. In detail, the flange 41 includes a hole 411. A camshaft 26 is inserted into a hole 411 of the flange 41, and the flange 41 is fixed to the camshaft 26 by press-fitting. The flange 41 is arranged between the weight body 42 and the exhaust cam 264 in the cam axis direction.

The flange 41 includes a first convex portion 412 and a second convex portion 413. A pivot is attached to the first convex portion 412 Pin 46. A hole 414 is provided in the second convex portion 413. A pressure reducing cam 43 is inserted into the hole 414 of the second convex portion 413.

The weight body 42 is arranged between the first bearing 27 and the flange 41 in the cam axis direction. The weight body 42 is rotatably supported with respect to the cam shaft 26 between a closed state and an open state.

7 and 8 are cross-sectional views taken along A-A in FIG. 4. FIG. 7 shows the weight body 42 in a closed state. FIG. 8 shows the weight body 42 in an opened state.

The decompression cam 43 is rotatably supported by the flange 41. Specifically, the weight body 42 is rotatably supported by the flange 41 via a pivot pin 46. The weight body 42 is switched to a closed state and an open state by rotating around the pivot pin 46 as a center.

The decompression cam 43 is connected to the weight body 42 via a decompression pin 44. Thereby, the decompression cam 43 rotates with the rotation of the weight body 42.

Specifically, as shown in FIGS. 4 and 6, the decompression cam 43 includes a head portion 431 and a shaft portion 432. The shaft portion 432 is inserted into the hole 414 of the flange 41. The head portion 431 is disposed between the flange 41 and the weight body 42. The outer diameter of the head 431 is larger than the inner diameter of the hole 414 of the flange 41. The head portion 431 includes a groove portion 433. The groove portion 433 has a shape recessed from an end surface of the head portion 431. The groove portion 433 extends from the outer peripheral surface of the head portion 431 toward the inside of the head portion 431. An end portion of the pressure reducing pin 44 is disposed in the groove portion 433. In addition, in this embodiment, the inner side means the inner side in the radial direction. The outer side means the outer side in the radial direction.

The shaft portion 432 includes a cam portion 434. The exhaust cam 264 includes a recessed portion 265. The recessed portion 265 has a shape that is recessed from the outer peripheral surface of the exhaust cam 264 toward the inside of the exhaust cam 264. FIG. 9 is an enlarged view of the exhaust cam 264. Fig. 10 is a side view of a camshaft assembly.

The cam portion 434 is disposed in the recessed portion 265 of the exhaust cam 264. The cross section of the cam portion 434 has a circular shape partially cut away. As described above, the decompression cam 43 rotates as the weight body 42 rotates. FIG. 9 (A) shows the decompression cam 43 when the weight body 42 is opened. FIG. 9 (B) shows the decompression cam 43 when the weight body 42 is closed. Decompression cam 43 with weight The rotation of the body 42 is switched between a state where it contacts the exhaust roller 342 of the valve mechanism 25 and a state where it does not contact the exhaust roller 342.

Specifically, when the weight body 42 is in an open state, as shown in FIG. 9A, the entire cam portion 434 of the decompression cam 43 is disposed in the recessed portion 265. That is, when the weight body 42 is in the open state, the cam portion 434 does not protrude outward from the outer peripheral surface of the exhaust cam 264. Thereby, when the weight body 42 is in the open state, the decompression cam 43 does not contact the exhaust roller 342.

When the weight body 42 is in a closed state, as shown in FIG. 9 (B), a part of the cam portion 434 of the decompression cam 43 is disposed outside the concave portion 265. That is, when the weight body 42 is in the closed state, a part of the cam portion 434 is in a state of protruding outward from the outer peripheral surface of the exhaust cam 264. Thereby, when the weight body 42 is in a closed state, the decompression cam 43 comes into contact with the exhaust roller 342.

The return spring 45 urges the weight body 42 so that the weight body 42 returns from the open state to the closed state. In this embodiment, the return spring 45 is a coil spring. However, the return spring 45 may be another type of spring. As shown in FIG. 6, the return spring 45 includes a first spring end portion 451 and a second spring end portion 452. The first spring end portion 451 extends in the cam axis direction. The second spring end portion 452 extends in a direction crossing the cam axis direction. The second spring end portion 452 extends in the circumferential direction of the return spring 45. The first spring end portion 451 is locked to the flange 41. The second spring end portion 452 is locked to the weight body 42.

Next, the structure of the weight body 42 will be described in detail. As shown in FIG. 7, when viewed from the cam axis direction, a straight line passing through the rotation center C1 of the cam shaft 26 and the rotation center C2 of the weight body 42 is taken as the vertical axis Y. A straight line orthogonal to the vertical axis Y and passing through the rotation center C1 of the cam shaft 26 is referred to as a horizontal axis X. In the direction parallel to the longitudinal axis Y, the direction from the rotation center C1 of the cam shaft 26 toward the rotation center C2 of the weight body 42 is set to the first longitudinal direction y1. A direction opposite to the first vertical direction y1 is referred to as a second vertical direction y2. One of the directions parallel to the horizontal axis X is set to the first horizontal direction x1. A direction opposite to the first lateral direction x1 is referred to as a second lateral direction x2.

Further, it is positioned in the first longitudinal direction y1 with respect to the horizontal axis X, and is positioned in the first longitudinal direction with respect to the vertical axis Y. A region in the horizontal direction x1 is referred to as a first region A1. A region located in the second vertical direction y2 with respect to the horizontal axis X and in the first horizontal direction x1 with respect to the vertical axis Y is referred to as a second region A2. When viewed from the cam axis direction, a region located in the second vertical direction y2 with respect to the horizontal axis X and in the second horizontal direction x2 with respect to the vertical axis Y is referred to as a third region A3. A region located in the first vertical direction y1 with respect to the horizontal axis X and in a second horizontal direction x2 with respect to the vertical axis Y is referred to as a fourth region A4.

In addition, FIG. 7 shows the weight body 42 viewed from the first camshaft end portion 261 side in the cam axis direction. Therefore, the above directions x1, x2, y1, y2, and areas A1 to A4 are defined when the cam axis direction is viewed from the first camshaft end portion 261 side, but may be defined from the 2 When the camshaft end 262 is viewed from the side, the directions x1, x2, y1, y2, and areas A1 to A4 are defined.

As shown in FIG. 7, the weight body 42 has a shape extending in the circumferential direction of the cam shaft 26. The weight body 42 is arranged around the cam shaft 26 in the first area A1, the second area A2, and the fourth area A4. The weight body 42 has a shape that spans in the circumferential direction of the convex transmission shaft 26 and a plurality of areas in the first to fourth areas A1 to A4. When viewed from the cam axis direction, the weight body 42 does not have a portion arranged in the third area A3.

Specifically, the weight body 42 includes a first weight body portion 47 and a second weight body portion 48. The first weight body portion 47 extends from the rotation center C2 of the weight body 42 in the circumferential direction of the cam shaft 26 and in the first lateral direction x1. An end portion 471 in the circumferential direction of the first weight body portion 47 is located in the first lateral direction x1 with respect to the longitudinal axis Y. That is, the entire first weight body portion 47 is located in the first horizontal direction x1 with respect to the vertical axis Y. When viewed from the cam axis direction, the end portion 471 of the first weight body portion 47 is disposed in the second area A2.

The second weight body portion 48 extends from the rotation center C2 of the weight body 42 in the circumferential direction of the cam shaft 26 and in the second lateral direction x2. An end portion 481 in the circumferential direction of the second weight body portion 48 is located in the second lateral direction x2 with respect to the longitudinal axis Y. That is, the entire second weight body portion 48 is located in the second horizontal direction x2 with respect to the vertical axis Y. When viewed from the cam axis direction, the end portion 481 of the second weight body portion 48 is disposed in the fourth area A4.

In the circumferential direction of the cam shaft 26, the first weight body portion 47 is longer than the second weight body portion 48. That is, the angle of the rotation center C2 of the weight body 42 around the rotation center C1 of the cam shaft 26 to the end portion 471 of the first weight body portion 47 is larger than the rotation center C2 to the second weight body portion 48 of the weight body 42 Angle of the end 481.

The first weight body 47 includes a first portion 421 and a second portion 422. When viewed from the cam axis direction, the first portion 421 is disposed in the first region A1. When viewed from the cam axis direction, the second portion 422 is disposed in the second area A2. The second weight body 48 is arranged in the fourth area A4.

The weight body 42 includes a pivot pin support portion 423. The pivot pin support portion 423 is disposed across the first portion 421 and the second portion 422. The pivot pin 46 is attached to the pivot pin support portion 423.

The exhaust cam 264 includes a cam lobe 267 protruding toward the outside from the base circle 266. As viewed from the cam axis direction, a part of the pivot pin 46 does not overlap the cam projection 267. That is, when viewed from the cam axis direction, a part of the pivot pin 46 is located further outside than the outer peripheral surface of the exhaust cam 264. In addition, the pivot pin 46 includes a portion located further inside than the base circle 266 as viewed from the cam axis direction.

The pressure reduction pin 44 is connected to the first weight body 47. Specifically, the pressure reducing pin 44 is connected to the second portion 422. When viewed from the cam axis direction, the decompression pin 44 is arranged in the second area A2. Viewed from the cam axis direction, the distance between the rotation center C2 of the weight body 42 and the pressure reduction pin 44 is greater than the distance between the rotation center C2 of the weight body 42 and the rotation center C1 of the cam shaft 26.

FIG. 11 is a view showing a camshaft assembly viewed from the cam axis direction. As shown in FIG. 11, when viewed from the cam axis direction, the outer shape of the flange 41 includes a portion larger than the outer shape of the first bearing 27. Specifically, the first convex portion 412 protrudes further outward than the outer peripheral surface of the first bearing 27.

In the closed state, the first portion 421 of the weight body 42 includes a first protruding portion 424. When viewed from the cam axis direction, the first protruding portion 424 projects further outward than the outer peripheral surface of the first bearing 27. When viewed from the cam axis direction, the outer peripheral surface of the second portion 422 is located more inward than the outer peripheral surface of the first bearing 27. Viewed from the cam axis direction, the outer periphery of the second weight body 48 The surface is located more inward than the outer peripheral surface of the first bearing 27.

The pivot pin support portion 423 includes a protruding portion 425, and the protruding portion 425 projects further outward than the outer peripheral surface of the first bearing 27 when viewed from the cam axis direction. The maximum value of the protruding length of the protruding portion 425 is larger than the maximum value of the protruding length of the first protruding portion 424. That is, the protruding portion 425 protrudes more radially than the first protruding portion 424 in the radial direction of the first bearing 27. The protruding length refers to a protruding length of the first bearing 27 in the radial direction from the outer peripheral surface of the first bearing 27.

As shown in FIG. 11, the first bearing 27 includes an inner wheel 271 and an outer wheel 272. The inner wheel 271 is in contact with the camshaft 26. The outer wheel 272 is in contact with the first support wall 141 of the cylinder head 14. As shown in FIG. 7, the weight body 42 includes an inner wheel contact portion 426. The inner wheel contact portion 426 is arranged side by side with the inner wheel 271 in the cam axis direction. The inner wheel contact portion 426 projects from the surface of the weight body 42 adjacent to the first bearing 27 toward the inner wheel 271.

As shown in FIG. 11, the inner wheel contact portion 426 is located more inward than the inner peripheral surface of the outer wheel 272. Moreover, the inner wheel contact portion 426 is located more inward than the inner peripheral surface of the outer wheel 272 regardless of the state of the weight body 42 in the closed state and the opened state. Viewed from the cam axis direction, at least a part of the inner wheel contact portion 426 is disposed closer to the rotation center C2 of the weight body 42 than the rotation center C1 of the cam shaft 26. Viewed from the cam axis direction, the inner wheel contact portion 426 is located between the rotation center C2 of the weight body 42 and the cam shaft 26. As shown in FIG. 4, in a state where the inner wheel contact portion 426 is in contact with the inner wheel 271, other parts of the weight body 42 are not in contact with the outer wheel 272.

Specifically, when the weight body 42 is in a closed state, the inner wheel contact portion 426 is disposed across the fourth area A4, the first area A1, and the second area A2. The inner-wheel contact portion 426 includes a first contact portion 426a, a second contact portion 426b, and a third contact portion 426c. When the weight body 42 is closed, the first contact portion 426a is disposed in the first area A1. When the weight body 42 is in a closed state, the second contact portion 426b is disposed in the second area A2. When the weight body 42 is closed, the third contact portion 426c is disposed in the fourth area A4. When viewed from the cam axis direction, the area of the first contact portion 426a is larger than the area of the second contact portion 426b. Viewed from the cam axis direction, the first contact portion 426a The area is larger than that of the third contact portion 426c.

G1 in FIG. 12 indicates the position of the center of gravity of the weight body 42. G2 indicates the position of the center of gravity of the weight body 42 when there is no first protruding portion 424. Note that in FIG. 12, the first protruding portion 424 is hatched. “When there is no first protruding portion 424” refers to a state after the portion marked with a hatched line in FIG. 12 is removed. In FIG. 12, the outer peripheral surface of the first bearing 27 is shown by a two-dot chain line. As shown in FIG. 12, when viewed from the cam axis direction, the center of gravity G1 of the weight body 42 is disposed in the first area A1. The distance between the center of gravity G1 of the weight body 42 and the center of rotation C1 of the cam shaft 26 is greater than the distance between the center of gravity G1 of the weight body 42 and the center of rotation C2 of the weight body 42. Viewed from the cam axis direction, the first protrusion 424 includes: a closer portion 424a, which is closer to the weight in the circumferential direction of the first bearing 27 than the center of gravity G2 of the weight body 42 without the first protrusion 424 The center of rotation C2 of the weight 42; and the farther portion 424b, which is farther away from the position of the center of gravity G2 of the weight body 42 than the weight body 42 when there is no first protrusion 424 in the circumferential direction of the first bearing 27 Rotation center C2. As for the amount of protrusion from the outer peripheral surface of the first bearing 27 to the outside, the closer portion 424a is larger than the farther portion 424b.

Also, as viewed from the direction of the cam axis, the portion of the inner wheel contact portion 426 that is closer to the center of rotation C2 of the weight body 42 than the center of gravity 42 of the weight body 42 is larger than the center of gravity of the weight body 42 in the inner wheel contact portion 426 G1 is further away from the center of rotation C2 of the weight body 42. For example, the maximum width of the first contact portion 426 a in the radial direction of the cam shaft 26 is larger than the maximum width of the second contact portion 426 b in the radial direction of the cam shaft 26.

FIG. 13 is a perspective view showing a surface on the second camshaft end portion 262 side of the weight body 42. 14 is a side view of the camshaft assembly viewed from the direction of arrow XIV in FIG. 10. As shown in FIG. 13, the maximum thickness of the first portion 421 in the cam axis direction is greater than the maximum thickness of the second portion 422 in the cam axis direction. The maximum thickness of the second weight body portion 48 in the cam axis direction is larger than the maximum thickness of the second portion 422 in the cam axis direction.

As shown in FIG. 13, the first portion 421 includes an inner diameter portion 421 a and an outer diameter portion 421 b. The inner diameter portion 421a is located inside the outer diameter portion 421b. The thickness of the outer diameter portion 421b in the cam axis direction is large The thickness of the inner diameter portion 421a in the cam axis direction. The outer diameter portion 421 b includes the first protruding portion 424. Therefore, the maximum thickness of the first protruding portion 424 in the cam axis direction is larger than the maximum thickness of the second portion 422 in the cam axis direction. The maximum thickness of the first protruding portion 424 in the cam axis direction is larger than the maximum thickness of the second weight body portion 48 in the cam axis direction. The thickness of the first protruding portion 424 in the cam axis direction is greater than the thickness of the pivot pin support portion 423 in the cam axis direction.

As shown in FIG. 10, when viewed from the radial direction of the camshaft 26, a part of the weight body 42 overlaps the flange 41. Specifically, when viewed from the radial direction of the cam shaft 26, the outer diameter portion 421 b of the first portion 421 overlaps the flange 41. The surface of the second weight body portion 48 on the second camshaft end portion 262 side and the surface of the inner diameter portion 421a face the surface of the flange 41 on the first camshaft end portion 261 side. A head 431 of the pressure reducing cam 43 is disposed between the second portion 422 and the flange 41.

As shown in FIG. 13, the pivot pin support portion 423 includes a receiving portion 423 a and a convex portion 423 b. The boss portion 423b protrudes from the storage portion 423a in the cam axis direction. The thickness of the accommodating portion 423a in the cam axis direction is smaller than the thickness of the first portion 421 and the second weight body portion 48 in the cam axis direction. Therefore, the storage portion 423a has a shape recessed from the surface of the weight body 42 in the cam axis direction.

FIG. 15 is a view of the flange 41, the weight body 42, and the return spring 45 as viewed from the second camshaft end portion 262 side. As shown in FIG. 15, the storage portion 423 a stores the return spring 45. The boss portion 423b is inserted into the above-mentioned return spring 45. A hole 423c is provided in the convex portion 423b. A pivot pin 46 is inserted into the hole 423c of the boss portion 423b.

As shown in FIGS. 13 and 15, the weight body 42 includes a second locking portion 42 b. The second locking portion 42b is locked to the second spring end portion 452 of the return spring 45. The second locking portion 42b is included in the first portion 421. Specifically, the second locking portion 42 b is a stepped portion formed in the first portion 421 with respect to the pivot pin supporting portion 423.

As shown in FIGS. 14 and 15, the flange 41 includes a first locking portion 42 a. The first locking portion 42 a is locked to the first spring end portion 451 of the return spring 45. Specifically, the first locking portion 42a is the first A portion of the convex portion 412. The first locking portion 42 a is integrally formed on the flange 41. For example, the flange 41 includes the first locking portion 42 a and is integrally formed by a manufacturing method such as sintering, forging, or casting.

FIG. 16 is a diagram showing the cylinder head 14 in a state where the head cover 19 is removed. As shown in FIG. 16, the cylinder head 14 includes a first bearing support hole 143. The first bearing support hole 143 supports the first bearing 27. The first bearing support hole 143 is provided in the first support wall 141. The first bearing support hole 143 includes a first recessed portion 144, a second recessed portion 145, and a third recessed portion 146. The first recessed portion 144, the second recessed portion 145, and the third recessed portion 146 are located on the side opposite to the crankshaft 11 with respect to the center of the first bearing support hole 143. The first recessed portion 144 has a shape through which the first protruding portion 424 and the intake cam 263 can pass. The second concave portion 145 has a shape through which the exhaust cam 264 can pass. The third recessed portion 146 has a shape through which the pivot pin support portion 423 can pass. Furthermore, one part of the first recessed portion 144 may be located on the side opposite to the crankshaft 11 with respect to the center of the first bearing support hole 143, and the other part may be located on the same side as the crankshaft 11 with respect to the center of the first bearing support hole 143 The side. Alternatively, one part of the second recess 145 may be located on the side opposite to the crankshaft 11 relative to the center of the first bearing support hole 143, and the other part may be located on the same side as the crankshaft 11 relative to the center of the first bearing support hole 143 One side.

In the present embodiment, an inner wheel contact portion 426 is provided on the weight body 42. Since the inner wheel contact portion 426 is located radially inward of the inner peripheral surface of the outer wheel 272, it does not contact the outer wheel 272. Therefore, damage caused by contact with the outer wheel 272 can be suppressed. In addition, the inner wheel 271 rotates together with the cam shaft 26 in the same manner as the weight body 42, so that even if the weight body 42 contacts the inner wheel 271, damage can be suppressed.

As viewed from the cam axis direction, a part of the inner wheel contact portion 426 is disposed closer to the rotation center C2 of the weight body 42 than the rotation center C1 of the cam shaft 26. Therefore, the amount of movement of the inner wheel contact portion 426 is small when the weight body 42 rotates, so that the inner wheel contact portion 426 can be made larger in a range where it does not contact the outer wheel 272. In addition, by increasing the inner wheel contact portion 426, the weight of the weight body 42 can be increased.

Viewed from the cam axis direction, a part of the inner wheel contact portion 426 is located between the rotation center of the weight body 42 and the cam shaft 26. Therefore, by making the position of the center of gravity of the weight body 42 close to the center of rotation of the weight body 42, the opening of the weight body 42 caused by gravity can be suppressed. In addition, the inner wheel contact portion 426 can be brought closer to the center of rotation of the weight body 42.

Viewed from the direction of the cam axis, the portion of the inner wheel contact portion 426 that is closer to the center of rotation of the weight body 42 than the center of gravity of the weight body 42 is larger than the center of gravity of the weight portion 42 in the inner wheel contact portion 426 is farther away from the weight. The center of rotation of the weight 42. Therefore, by positioning the center of gravity of the weight body 42 close to the center of rotation of the weight body 42, the opening of the weight body 42 caused by gravity can be suppressed. In addition, the inner wheel contact portion 426 can be brought closer to the center of rotation of the weight body 42.

The first bearing 27 is disposed closer to the first camshaft end portion 261 than the second camshaft end portion 262 in the cam axis direction. Generally, the bearing provided with the cam chain 29 is easily enlarged. Therefore, by making the inner wheel 271 of the first bearing 27 provided with the inner wheel contact portion 426 larger, the degree of freedom in designing the inner wheel contact portion 426 can be increased.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, Various changes are possible in the range which does not deviate from the meaning of invention.

The shape of the weight body 42 is not limited to the shape of the embodiment described above, and may be changed. The circumferential length of the weight body may be shorter than the weight body 42 of the above embodiment. For example, the circumferential end portion 471 of the first weight body portion 47 may be disposed in the first region A1. Alternatively, the circumferential length of the weight body may be longer than the weight body 42 of the above embodiment. For example, the circumferential end portion 471 of the first weight body portion 47 may be disposed in the third region A3.

The first protruding portion 424 of the weight body 42 may be omitted. That is, the first portion 421 may be positioned further inside than the outer peripheral surface of the first bearing 27 when viewed from the cam axis direction.

In the above embodiment, the weight body 42 is supported by the camshaft 26 via the flange 41. However, the weight body 42 may be directly supported by the camshaft 26. In the above embodiment, the flange 41 is separated from the camshaft 26 and is fixed to the camshaft 26 by press-fitting, but may be fixed by a fixing method other than press-fitting. Alternatively, the flange may be formed integrally with the cam shaft 26.

The center of gravity G1 of the weight body 42 is not limited to the first area A1, and may be disposed in other areas. For example, the center of gravity G1 of the weight body 42 may be disposed in the second area A2.

The shape of the inner wheel contact portion is not limited to the shape of the embodiment described above, and may be changed. FIG. 17 is a view showing a weight body 42 according to a modification. As shown in FIG. 17, the inner wheel contact portion 426 of the modification is located in the first area A1 and the second area A2, and does not include a portion located in the third area A3.

Alternatively, the entire contact portion of the inner wheel may be arranged closer to the rotation center of the weight body than the rotation center of the cam shaft as viewed from the direction of the cam axis. Alternatively, the whole of the contact portion of the inner wheel may be located between the rotation center of the weight body and the cam shaft as viewed from the cam axis direction.

In the above-mentioned embodiment, a scooter type locomotive is used as an example of a vehicle. However, the vehicle of the present invention is not limited to a scooter type, and may be other types of locomotives such as a sports type, an off-road type, and a light type. Here, the locomotive is not limited to two-wheeled vehicles, and includes three-wheeled vehicles. The vehicle of the present invention is preferably a straddle type vehicle such as a locomotive, an all-terrain vehicle (ALL-TERRAIN VEHICLE), or a snowmobile, but may be a vehicle other than a straddle type vehicle.

The terms and expressions used herein are for the purpose of explanation and not for the purpose of limiting interpretation. It must be recognized that all equivalents of the characteristic matters shown and described herein are not excluded, and variations within the scope of the patent application of the present invention are also allowed. The invention can be implemented in many different forms. This disclosure should be regarded as an embodiment providing the principle of the present invention. Prior to understanding these embodiments, it is not intended to limit the present invention to the preferred embodiments described and / or illustrated herein, and the embodiments are described here. It is not limited to the embodiment described here. The present invention also includes all embodiments which can be recognized by the supplier based on the disclosure, including equal elements, corrections, deletions, combinations, improvements, and / or changes. The matters limiting the scope of the patent application shall be interpreted broadly based on the terms used in the scope of the patent application, and shall not be limited to the implementation forms described in the examination process of this specification or this case.

26‧‧‧camshaft

27‧‧‧The first bearing

41‧‧‧ flange

42‧‧‧ weight

46‧‧‧ pivot pin

47‧‧‧ 1st weight body

48‧‧‧Second weight body

263‧‧‧Air intake cam

264‧‧‧Exhaust Cam

271‧‧‧Inner wheel

272‧‧‧outer

412‧‧‧1st protrusion

421‧‧‧Part 1

422‧‧‧Part 2

423‧‧‧ pivot pin support department

424‧‧‧ 1st protrusion

425‧‧‧ protrusion

426‧‧‧Inner wheel contact

C1‧‧‧ center of rotation of camshaft 26

C2‧‧‧ weight center of rotation 42

Claims (6)

An engine includes: a cylinder head; an exhaust valve housed in the cylinder head; a valve operating mechanism that opens and closes the exhaust valve; and a camshaft that drives the valve by contacting the valve operating mechanism A valve mechanism; a first bearing including an inner wheel in contact with the camshaft and an outer wheel in contact with the cylinder head, and rotatably supporting the camshaft to the cylinder head; and a pressure reducing mechanism disposed in the above Between the two ends in the axial direction of the camshaft; the decompression mechanism includes: a weight body that is rotatably supported relative to the camshaft; and a decompression cam that switches according to the rotation of the weight body It is in a state of being in contact with the valve actuating mechanism and not in a state of being in contact with the valve actuating mechanism; the weight body includes an inner wheel contact portion which is arranged side by side with the inner wheel in the axial direction of the camshaft. And the inner wheel contact portion is located radially inward of the inner peripheral surface of the outer wheel. If the engine of claim 1 is viewed from the axial direction of the camshaft, at least a part of the inner wheel contact portion is disposed closer to the rotation center of the weight body than the rotation center of the camshaft. According to the engine of claim 1, wherein at least a part of the inner wheel contact portion is located between the center of rotation of the weight body and the camshaft as viewed from the axial direction of the camshaft. If the engine of claim 1 is viewed from the axial direction of the camshaft, the portion of the inner wheel contact portion that is closer to the center of rotation of the weight body than the center of gravity of the weight body is larger than the portion of the inner wheel contact portion. The middle part is farther from the center of gravity of the weight body than the center of gravity of the weight body. The engine according to claim 1, further comprising: a first sprocket, which is mounted on the camshaft; and a cam chain, which is wound on the first sprocket; the camshaft includes a first end portion and a second end portion The first sprocket is attached to the first end portion, and the first bearing is disposed closer to the first end portion than the second end portion in the axial direction of the camshaft. A vehicle comprising an engine as claimed in any one of claims 1 to 5.