INTERNAL COMBUSTION ENGINE AND VEHICLE

Abstract

An internal combustion engine allows easy installment of a support that pivotally supports a rocker arm while preventing fretting wear due to rising of the support. The internal combustion engine includes the support, at least a portion of which is located in a hole of a cylinder head, a rocker arm that is pivotally supported on the support, and a ball plunger that secures the support inside the hole. The ball plunger includes a spring seat that contacts with the support, a ball that contacts with the cylinder head, and a spring interposed between the spring seat and the ball.

Claims

1-14. (canceled)

15. An internal combustion engine comprising: a cylinder including a hole; a port in the cylinder; a valve in the cylinder to open/close the port; a cam shaft rotatably supported on the cylinder; a cam provided on the cam shaft; a columnar support at least a portion of which is located in the hole of the cylinder; a rocker arm including a supported portion pivotally supported on the columnar support, a pressed portion pressed by the cam, and an abutting portion that abuts on the valve; and a retainer that includes a first contact portion that contacts with the columnar support, a second contact portion that contacts with the cylinder, and an elastic portion interposed between the first contact portion and the second contact portion; wherein the retainer secures the columnar support inside the hole.

16. The internal combustion engine according to claim 15, wherein the retainer includes a plunger including a spring located inside the columnar support, and a presser at least a portion of which is located outside the columnar support and that is connected to the spring.

17. The internal combustion engine according to claim 15, wherein the retainer includes a snap ring that is fitted to the columnar support.

18. The internal combustion engine according to claim 15, wherein the retainer includes a ring-shaped coil spring that is wound around the columnar support.

19. The internal combustion engine according to claim 16, further comprising a groove provided on an inner surface of the hole of the cylinder and that engages with the retainer.

20. The internal combustion engine according to claim 19, wherein, in a cross section that passes through the groove and includes a center line of the hole, the groove includes a sloped surface that is inclined relative to the center line of the hole so as to extend towards the center line of the hole as the sloped surface extends toward the rocker arm along a direction of the center line of the hole.

21. The internal combustion engine according to claim 19, wherein the groove is cone-shaped or circular columnar-shaped and has an axis that is inclined relative to the center line of the hole.

22. The internal combustion engine according to claim 19, wherein the hole and the columnar support each have a circular columnar shape; and the groove is a circumferential groove provided on an inner circumferential surface of the hole.

23. The internal combustion engine according to claim 15, wherein the retainer includes a plunger including a spring located inside the cylinder, and a presser at least a portion of which is located inside the hole of the cylinder and that is connected to the spring.

24. The internal combustion engine according to claim 15, wherein the retainer includes a snap ring that is fitted to an inner surface of the hole of the cylinder.

25. The internal combustion engine according to claim 15, wherein the retainer includes a ring-shaped coil spring that is fitted to an inner surface of the hole of the cylinder.

26. The internal combustion engine according to claim 15, wherein the retainer includes a leaf spring that is secured to an edge of the hole of the cylinder.

27. The internal combustion engine according to claim 15, wherein the rocker arm includes a first arm that includes the supported portion and the abutting portion, and a second arm that includes the pressed portion and is pivotally connected to the first arm; and the internal combustion engine includes a connector that removably connects the first arm to the second arm; and the columnar support is not able to expand/contract in an axial direction of the columnar support.

28. A vehicle comprising the internal combustion engine according to claim 15.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a view showing an example of an internal combustion engine according to a preferred embodiment of the present invention installed in an automobile.

[0036] FIG. 2 is a partial cross-sectional view of the internal combustion engine.

[0037] FIG. 3 is a partial enlarged cross-sectional view of the internal combustion engine.

[0038] FIG. 4 is a side view of a rocker arm and a support.

[0039] FIG. 5 is a plan view of the rocker arm and the support.

[0040] FIG. 6 is an exploded perspective view of a first arm and a second arm of the rocker arm.

[0041] FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 4.

[0042] FIG. 8 is equivalent to FIG. 7, showing the rocker arm in the connected state.

[0043] FIG. 9 is a side view showing the rocker arm in the connected state that has pivoted relative to the support.

[0044] FIG. 10 is equivalent to FIG. 7, showing the rocker arm when the second arm pivots relative to the first arm.

[0045] FIG. 11 is a side view showing the rocker arm and the support when the second arm pivots relative to the first arm.

[0046] FIG. 12A is a side view of a support.

[0047] FIG. 12B is a cross-sectional view taken along line XIIb-XIIb of FIG. 12A.

[0048] FIG. 13 is a cross-sectional view of a hole of a cylinder head.

[0049] FIG. 14 is a side view of a support according to an alternative preferred embodiment of the present invention.

[0050] FIG. 15A is a cross-sectional view of a support according to an alternative preferred embodiment of the present invention.

[0051] FIG. 15B is a cross-sectional view taken along line XVb-XVb of FIG. 15A.

[0052] FIG. 16 is a cross-sectional view of a support according to an alternative preferred embodiment of the present invention.

[0053] FIG. 17A is a cross-sectional view of a support according to an alternative preferred embodiment of the present invention.

[0054] FIG. 17B is a cross-sectional view taken along line XVIIb-XVIIb of FIG. 17A.

[0055] FIG. 18 is a cross-sectional view of a support according to an alternative preferred embodiment of the present invention.

[0056] FIG. 19 is a side view of a support according to an alternative preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] Preferred embodiments of the present invention will now be described with reference to the drawings. An internal combustion engine according to the present preferred embodiment is installed in a vehicle and used as the drive source of the vehicle. There is no limitation on the type of the vehicle, which may be a straddled vehicle such as a motorcycle, an auto tricycle or an ATV (All Terrain Vehicle) or may be an automobile. For example, an internal combustion engine 10 may be provided in the engine room of an automobile 5 as shown in FIG. 1.

[0058] The internal combustion engine 10 according to the present preferred embodiment is preferably a multi-cylinder engine including a plurality of cylinders. The internal combustion engine 10 is a 4-stroke engine that goes through the intake stroke, the compression stroke, the combustion stroke, and the exhaust stroke. FIG. 2 is a partial cross-sectional view of the internal combustion engine 10. As shown in FIG. 2, the internal combustion engine 10 includes a crankcase (not shown), a cylinder body 7 connected to the crankcase, and a cylinder head 12 connected to the cylinder body 7. A crankshaft (not shown) is located inside the crankcase. A plurality of cylinders 6 are provided inside the cylinder body 7. A piston 8 is located inside each cylinder 6. The piston 8 and the crankshaft are connected by a connecting rod (not shown).

[0059] An intake cam shaft 23 and an exhaust cam shaft 21 are rotatably supported on the cylinder head 12. Intake cams 23A are provided on the intake cam shaft 23, and exhaust cams 21A are provided on the exhaust cam shaft 21.

[0060] Intake ports 16 and exhaust ports 14 are provided in the cylinder head 12. An intake opening 18 is provided at one end of the intake port 16. An exhaust opening 17 is provided on one end of the exhaust port 14. The intake port 16 communicates with a combustion chamber 15 through the intake opening 18. The exhaust port 14 communicates with the combustion chamber 15 through the exhaust opening 17. The intake port 16 guides the mixed gas of the air and the fuel into the combustion chamber 15. The exhaust port 14 guides the exhaust gas discharged from the combustion chamber 15 to the outside.

[0061] Intake valves 22 and exhaust valves 20 are installed in the cylinder head 12. The intake valve 22 opens/closes the intake opening 18 of the intake port 16. The exhaust valve 20 opens/closes the exhaust opening 17 of the exhaust port 14. The intake valve 22 and the exhaust valve 20 are so-called poppet valves. The intake valve 22 includes a shaft portion 22a and an umbrella portion 22b, and the exhaust valve 20 includes a shaft portion 20a and an umbrella portion 20b. The configuration of the intake valve 22 and the configuration of the exhaust valve 20 are similar to each other, and the configuration of the intake valve 22 will be described below while omitting the description of the configuration of the exhaust valve 20. The shaft portion 22a of the intake valve 22 is slidably supported on the cylinder head 12 with a cylinder-shaped sleeve 24 therebetween. A valve stem seal 25 is attached to one end of the sleeve 24 and the shaft portion 22a of the intake valve 22. The shaft portion 22a of the intake valve 22 extends through the sleeve 24 and the valve stem seal 25. A tappet 26 is fitted to the tip of the shaft portion 22a.

[0062] As shown in FIG. 3, a cotter 28 is attached to the shaft portion 22a of the intake valve 22. The cotter 28 is fitted to a valve spring retainer 30. The valve spring retainer 30 is secured to the intake valve 22 with the cotter 28 therebetween. The valve spring retainer 30 is able to move, together with the intake valve 22, in an axial direction of the intake valve 22. The intake valve 22 extends through the valve spring retainer 30.

[0063] The internal combustion engine 10 includes a valve spring 32 that provides the intake valve 22 with a force in the direction of closing the intake opening 18 (the upward direction in FIG. 3). The valve spring 32 is preferably a compression coil spring, and includes a first spring end portion 32a supported on the valve spring retainer 30 and a second spring end portion 32b supported on the cylinder head 12.

[0064] The internal combustion engine 10 includes a rocker arm 40 that receives a force from the intake cam 23A to open/close the intake valve 22. The rocker arm 40 is pivotally supported on the cylinder head 12 with a support 35 therebetween. FIG. 4 is a side view of the rocker arm 40 and the support 35, and FIG. 5 is a plan view of the rocker arm 40 and the support 35. The rocker arm 40 includes a first arm 41 and a second arm 42 including a roller 43.

[0065] FIG. 6 is an exploded perspective view of the first arm 41 and the second arm 42. The first arm 41 includes a plate 41A, a plate 41B, an abutting plate 41C, and a connecting plate 41D. The plate 41A and the plate 41B are parallel or substantially parallel to each other. The abutting plate 41C and the connecting plate 41D extend across the plate 41A and the plate 41B. The abutting plate 41C and the connecting plate 41D connect together the plate 41A and the plate 41B. The plate 41A includes a hole 46A and a hole 48. The plate 41B includes a hole 46B (see FIG. 7) and the hole 48. The holes 46A, 46B, and 48 extend in the direction parallel or substantially parallel to the axial line direction of the intake cam shaft 23 (see FIG. 3).

[0066] FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 4. As shown in FIG. 7, a cylinder-shaped boss portion 49A is provided around the hole 46A of the plate 41A. A connecting pin 60A is slidably inserted inside the hole 46A. A bottomed cylinder-shaped cover portion 49B is provided around the hole 46B of the plate 41B. The cover portion 49B is provided with a hole 47 having a smaller diameter than the hole 46B, but the hole 47 may be omitted. A connecting pin 60B is slidably inserted inside the hole 46B. A spring 64 is located inside the hole 46B. The spring 64 is present between the cover portion 49B and the connecting pin 60B, and urges the connecting pin 60B toward the plate 41A.

[0067] The second arm 42 is located on the inner side of the first arm 41. That is, the second arm 42 is located between the plate 41A and the plate 41B. As shown in FIG. 6 the second arm 42 includes a plate 42A, a plate 42B, an abutting plate 42C, and a connecting plate 42D. The plate 42A and the plate 42B are parallel or substantially parallel to each other. The abutting plate 42C and the connecting plate 42D extend across the plate 42A and the plate 42B. The abutting plate 42C and the connecting plate 42D connect together the plate 42A and the plate 42B. The plate 42A and the plate 42B include a hole 50 and a hole 52, respectively.

[0068] As shown in FIG. 7, the cylinder-shaped roller 43 is rotatably supported on the hole 50 of the plate 42A and the hole 50 of the plate 42B. Specifically, a cylinder-shaped collar 54 is inserted through the holes 50 of the plate 42A and the plate 42B. The roller 43 is rotatably supported on the collar 54. A connecting pin 62 is slidably inserted inside the collar 54. Since the collar 54 is located inside the holes 50, the connecting pin 62 is slidably inserted inside the holes 50. Note that the collar 54 is not always necessary. The connecting pin 62 may rotatably support the roller 43.

[0069] An outer diameter of the connecting pin 60B is less than or equal to an inner diameter of the collar 54. The connecting pin 60B is able to be inserted inside the collar 54. An outer diameter of the connecting pin 62 is less than or equal to an inner diameter of the hole 46A. The connecting pin 62 is able to be inserted inside the hole 46A. In the present preferred embodiment, the inner diameter of the collar 54 and the inner diameter of the hole 46A are equal or substantially equal to each other. The outer diameter of the connecting pin 60B, the outer diameter of the connecting pin 62 and an outer diameter of the connecting pin 60A are equal or substantially equal to each other.

[0070] As shown in FIG. 4, the support 35, the first arm 41, and the second arm 42 are connected together by a support pin 56. The support pin 56 is inserted through the hole 48 of the plate 41A and the hole 48 of the plate 41B of the first arm 41, and the hole 52 of the plate 42A and the hole 52 of the plate 42B of the second arm 42. The first arm 41 and the second arm 42 are pivotally supported on the support 35 by the support pin 56. The second arm 42 is pivotally supported on the first arm 41 by the support pin 56.

[0071] As shown in FIG. 7, a connection switch pin 66 is located on the side of the rocker arm 40. The connection switch pin 66 is movable in the direction toward the connecting pin 60A and in the direction away from the connecting pin 60A.

[0072] As shown in FIG. 8, when the connection switch pin 66 moves in the direction away from the connecting pin 60A, the connecting pins 60A, 62 and 60B slide leftward in FIG. 8 due to the force of the spring 64. Thus, the connecting pin 60B is located inside the hole 46B and inside the hole 50 (specifically, inside the collar 54), and the connecting pin 62 is located inside the hole 50 (specifically, inside the collar 54) and inside the hole 46A. This state will hereinafter be referred to as the connected state. In the connected state, the first arm 41 and the second arm 42 are connected together by the connecting pin 60B and the connecting pin 62. As a result, as shown in FIG. 9, the first arm 41 and the second arm 42 are, as a single unit, pivotable about the axis of the support pin 9.

[0073] As shown in FIG. 7, the connection switch pin 66 moves toward the connecting pin 60A, the connecting pins 60A, 62 and 60B are pushed by the connection switch pin 66 and slide rightward in FIG. 7. Thus, the connecting pin 60B is located inside the hole 46B and not located inside the hole 50, and the connecting pin 62 is located inside the hole 50 and not located inside the hole 46A. This state will hereinafter be referred to as the non-connected state. In the non-connected state, as shown in FIG. 10, the connecting pin 62 is slidable relative to the connecting pin 60A and the connecting pin 60B. As a result, as shown in FIG. 11, the second arm 42 is pivotable about the axis of the support pin 56 relative to the first arm 41. Therefore, the second arm 42 pivots about the axis of the support pin 56 while the first arm 41 does not pivot.

[0074] As shown in FIG. 3, the portion of the first arm 41 that is supported by the support pin 56 (specifically, the portion of the plate 41A around the hole 48 and the portion of the plate 41B around the hole 48) defines a supported portion 41S that is pivotally supported on the cylinder head 12. The abutting plate 41C defines an abutting portion that abuts on the intake valve 22 with the tappet 26 therebetween. The roller 43 defines a pressed portion that is in contact with the intake cam 23A and is pressed by the intake cam 23A.

[0075] As shown in FIG. 3, the support 35 that pivotally supports the rocker arm 40 is inserted into a hole 37 in the cylinder head 12. In the present preferred embodiment, the cylinder head 12 corresponds to the cylinder. Note, however, that a cam carrier (not shown) may be attached to the cylinder head 12, and the hole 37, through which the support 35 is inserted, may be provided in the cam carrier. In such a case, the cylinder head 12 and the cam carrier, combined together, correspond to the cylinder. Thus, another member may be attached to the cylinder head 12, and the hole 37 may be provided in that member. In such a case, the cylinder head 12 and the other member, combined together, correspond to the cylinder. In the present preferred embodiment, the support 35 preferably has a circular columnar shape. Note, however, that the support 35 is not limited to a circular columnar shape, but may have a polygonal columnar shape, for example, or any other columnar shape. The hole 37 preferably has a cross-sectional shape that corresponds to the cross-sectional shape of the support 35.

[0076] FIG. 12A is a side view of the support 35. FIG. 12B is a cross-sectional view taken along line XIIb-XIIb of FIG. 12A. As shown in FIG. 12A, the support 35 includes a shaft portion 35A at least a portion of which is inserted into the hole 37, and a ring portion 35B includes a hole 35C through which the support pin 56 (see FIG. 3) is inserted. A ball plunger 39 is provided inside the shaft portion 35A as a retainer that secures the support 35 in the hole 37.

[0077] As shown in FIG. 12B, the shaft portion 35A of the support 35 includes a hole 35D extending in the radial direction. The ball plunger 39 is fitted in the hole 35D. The ball plunger 39 includes a spring 39A that is a compression coil spring, a spring seat 39B that is connected to one end of the spring 39A, and a ball 39C that is connected to the other end of the spring 39A. While the ball 39C is an example of a presser of a plunger, the presser is not limited to the ball 39C but may be a pin, etc. A portion of the ball 39C is exposed on the outside of the hole 35D. The inner circumferential surface of the hole 37 of the cylinder head 12 includes a groove 37a that engages with the ball 39C.

[0078] Although there is no limitation on the shape of the groove 37a, the groove 37a preferably includes a sloped surface 37b as shown in FIG. 13 in the present preferred embodiment. As shown in FIG. 13, in a cross section that passes through the groove 37a and includes a center line 37c of the hole 37, the sloped surface 37b is inclined relative to the center line 37c and extends toward the center line 37c as it extends toward the rocker arm 40 along the direction of the center line 37c of the hole 37 (i.e., upward in FIG. 13).

[0079] The groove 37a is cone-shaped or circular columnar-shaped and includes an axis 13c that is inclined relative to the center line 37c of the hole 37. The groove 37a according to the present preferred embodiment is easily machined by inserting a tool 13 such as a drill or an endmill into the hole 37 in a direction that is slanted relative to the center line 37c.

[0080] With the internal combustion engine 10 according to the present preferred embodiment, the support 35 is not screwed onto the cylinder head 12. The support 35 is easily attached to the cylinder head 12 by inserting the support 35 into the hole 37. Specifically, by positioning the shaft portion 35A of the support 35 above the hole 37 and inserting the shaft portion 35A into the hole 37, the ball 39C is pushed by the inner circumferential surface of the hole 37, thus compressing the spring 39A. When the shaft portion 35A is inserted to a predetermined position, the ball 39C engages with the groove 37a. Then, the operator feels a clicking feel and thus easily knows that the shaft portion 35A has been inserted to a predetermined position. Therefore, the support 35 is easily positioned, and the support 35 is unlikely to come out of the hole 37. With the elastic force generated by the compression of the spring 39A, the ball 39C is pressed against the inner circumferential surface of the hole 37. The pressure with which the ball 39C presses the inner circumferential surface of the hole 37 secures the support 35 inside the hole 37.

[0081] Note that in the present preferred embodiment, the spring seat 39B is an example of the first contact portion in contact with the support 35. The ball 39C is an example of the second contact portion in contact with the cylinder head 12. The spring 39A is present between the spring seat 39B and the ball 39C, and is an example of the elastic portion.

[0082] As shown in FIG. 3, the internal combustion engine 10 includes a compression coil spring 68, as a lost motion spring, that urges the rocker arm 40 toward the intake cam 23A. A shaft 70 that extends along a winding axis 68d of the compression coil spring 68 is located inside the compression coil spring 68. The shaft 70 includes a first end portion 70a, and a second end portion 70b that is located on the second arm 42 side relative to the first end portion 70a. A spring seat 72 that receives the compression coil spring 68 is provided at the first end portion 70a.

[0083] The compression coil spring 68 includes a first end portion 68a, and a second end portion 68b that is located on the second arm 42 side relative to the first end portion 68a. A spring retainer 74 is supported at the second end portion 68b. The spring retainer 74 includes a disc-shaped top plate portion 74a and a cylinder-shaped tube portion 74b. The tube portion 74b extends from the top plate portion 74a along the axial direction of the shaft 70 toward the compression coil spring 68. The top plate portion 74a is supported on the second end portion 68b of the compression coil spring 68. The top plate portion 74a is in contact with the abutting plate 42C of the second arm 42 of the rocker arm 40.

[0084] The spring seat 72, at least a portion of the shaft 70, at least a portion of the compression coil spring 68, and at least a portion of the tube portion 74b of the spring retainer 74 are located inside a hole 76 in the cylinder head 12.

[0085] The intake valve 22, the valve spring 32, the shaft 70, the spring retainer 74, the compression coil spring 68, and the support 35 are parallel or substantially parallel to each other. The spring retainer 74 is located between the valve spring 32 and the support 35. The shaft 70 is located between the valve spring 32 and the support 35.

[0086] As shown in FIG. 2, as with the intake valve 22, the valve spring 32, the valve spring retainer 30, the rocker arm 40, the support 35, the compression coil spring 68, etc., are provided also for the exhaust valve 20. These elements are similar to those described above, and will not be described in detail below.

[0087] With the internal combustion engine 10 according to the present preferred embodiment, it is possible to switch the operation state of the intake valve 22 and the exhaust valve 20 by switching the state of the connection switch pin 66.

[0088] That is, when the connection switch pin 66 is switched to the connected state, the first arm 41 and the second arm 42 of the rocker arm 40 are connected together by the connecting pin 60B and the connecting pin 62 (see FIG. 8). When the intake cam 23A pushes the roller 43 of the rocker arm 40 following the rotation of the intake cam shaft 23, the first arm 41 and the second arm 42, as a single unit, pivot about the axis of the support pin 56 (see FIG. 9). As a result, the abutting plate 41C of the first arm 41 pushes the intake valve 22, thus opening the intake opening 18 of the intake port 16. Similarly, when the exhaust cam 21A pushes the roller 43 of the rocker arm 40 following the rotation of the exhaust cam shaft 21, the first arm 41 and the second arm 42, as a single unit, pivot about the axis of the support pin 56. As a result, the abutting plate 41C of the first arm 41 pushes the exhaust valve 20, thus opening the exhaust opening 17 of the exhaust port 14.

[0089] When the connection switch pin 66 is switched to the non-connected state, the connection between the first arm 41 and the second arm 42 by the connecting pin 60B and the connecting pin 62 is disconnected (see FIG. 7). The second arm 42 becomes pivotable relative to the first arm 41 (see FIG. 10). When the intake cam 23A pushes the roller 43 following the rotation of the intake cam shaft 23, the second arm 42 pivots about the axis of the support pin 56 while the first arm 41 does not pivot (see FIG. 11). Therefore, the abutting plate 41C of the first arm 41 will not push the intake valve 22, and the intake opening 18 remains closed by the intake valve 22. Similarly, when the exhaust cam 21A pushes the roller 43 following the rotation of the exhaust cam shaft 21, the second arm 42 pivots about the axis of the support pin 56 while the first arm 41 does not pivot. Therefore, the abutting plate 41C of the first arm 41 will not push the exhaust valve 20, and the exhaust opening 17 remains closed by the exhaust valve 20. Thus, in the present preferred embodiment, one or more of a plurality of cylinders are able to be brought to the inoperative state by switching the connection switch pin 66 to the non-connected state. For example, by making one or more cylinders inoperative while the load is small, it is possible to improve the fuel efficiency.

[0090] As described above, with the internal combustion engine 10 according to the present preferred embodiment, the support 35 that pivotally supports the rocker arm 40 is not only inserted into the hole 37 of the cylinder head 12 but is also secured inside the hole 37 by the ball plunger 39. While the internal combustion engine 10 is running, the cam 21A, 23A repeatedly presses the rocker arm 40, and a load in the axial direction is repeatedly generated on the support 35. However, since the support 35 is secured inside the hole 37 by the ball plunger 39, it is possible to prevent the support 35 from rising from the hole 37. Therefore, it is possible to prevent fretting wear, or the like, due to rising of the support 35.

[0091] With the internal combustion engine 10, when the support 35 is pushed into the hole 37, the support 35 is inserted into the hole 37 and is then secured inside the hole 37 by the elastic force of the spring 39A of the ball plunger 39. With the internal combustion engine 10 according to the present preferred embodiment, there is no need for an operation of securing the support 35 to the cylinder head 12 by using screws, bolts, or the like. This makes easy the installment of the support 35.

[0092] Thus, with the internal combustion engine 10 according to the present preferred embodiment, it is possible to prevent fretting wear, or the like, due to rising of the support 35 while maintaining the ease of installment of the support 35.

[0093] Now, where the support 35 is able to contract/expand in the axial direction, such as a lash adjuster, the position of the rocker arm 40 changes following the contraction/expansion of the support 35. For example, when the support 35 expands, the rocker arm 40 moves toward the cam 21A, 23A (upward in FIG. 3). As a result, the position of the pivot center of the second arm 42 moves toward the cam 21A, 23A. On the other hand, since the position of the cam 21A, 23A does not change, the contact position between the roller 43 and the cam 21A, 23A does not change. Therefore, if the support 35 expands when the rocker arm 40 is in the non-connected state, the second arm 42 may not be able to return to the position where the hole 50 and the hole 46A, 46B are aligned with each other (the position shown in FIG. 7). Then, it is possible that the first arm 41 and the second arm 42 may not be properly connected together by the connecting pin 60B and the connecting pin 62, and the connecting function of the rocker arm 40 may possibly be difficult. However, in the present preferred embodiment, the support 35, as opposed to a lash adjuster, cannot expand/contract in the axial direction. The rocker arm 40 does not move toward the cam 21A, 23A. Therefore, it is possible to prevent difficulty in connecting the first arm 41 and the second arm 42 of the rocker arm 40.

[0094] Although there is no limitation on the retainer that secures the support 35 inside the hole 37 of the cylinder head 12, the present preferred embodiment includes the ball plunger 39, which includes the spring 39A located inside the support 35, and the ball 39C at least a portion of which is located outside the support 35. Therefore, the retainer is simple and compact. By appropriately setting the spring constant, etc., of the spring 39A, the ease of operation of inserting the support 35 into the hole 37 and the prevention of rising of the support 35 are achieved in a well-balanced manner.

[0095] With the internal combustion engine 10 according to the present preferred embodiment, the groove 37a that engages with the ball 39C of the ball plunger 39 is provided on the inner circumferential surface of the hole 37 of the cylinder head 12. Thus, when the support 35 is inserted into the hole 37, the ball 39C engages with the groove 37a, and the support 35 is even less likely to rise. Therefore, the ease of installment of the support 35 and the prevention of fretting wear, or the like, due to rising of the support 35 are both realized at a high level.

[0096] In the present preferred embodiment, the groove 37a includes the sloped surface 37b (see FIG. 13). Since the groove 37a includes the sloped surface 37b, the ball 39C of the ball plunger 39 is unlikely to come out of the groove 37a, and the support 35 is even less likely to rise. Therefore, it is possible to even better prevent fretting wear, or the like, due to rising of the support 35.

[0097] In the present preferred embodiment, the groove 37a is preferably cone-shaped or circular columnar-shaped and includes the axis 13c that is inclined relative to the center line 37c of the hole 37. According to the present preferred embodiment, the groove 37a is able to be machined by inserting the tool 13 such as a drill or an endmill into the hole 37 from outside the hole 37. Therefore, the groove 37a is formed in a simple and inexpensive manner.

[0098] Note that while the groove 37a may be provided only at one point in the circumferential direction of the hole 37, it may be provided in a circumferential pattern (see the phantom line in FIG. 13). Where the groove 37a is provided only at one point in the circumferential direction of the hole 37, if the position at which the groove 37a is machined is shifted in the circumferential direction, the position at which the support 35 is attached in the circumferential direction may possibly be shifted. However, where the groove 37a is provided in a circumferential pattern, the position at which the support 35 is attached in the circumferential direction is prevented from being shifted. Therefore, even if the machining precision of the groove 37a is relatively low, it is possible to properly machine the groove 37a. Thus, the groove 37a is provided in a simple and inexpensive manner.

[0099] While preferred embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to the above-described preferred embodiments. Next, examples of alternative preferred embodiments will be described. First, an example of an alternative preferred embodiment using a different configuration of the retainer will be described.

[0100] With the internal combustion engine 10 according to an alternative preferred embodiment shown in FIG. 14, the retainer includes the ball plunger 39 including the spring 39A and the spring seat 39B that are located inside the cylinder head 12, and the ball 39C at least a portion of which is located inside the hole 37. The spring 39A is a compression coil spring, wherein one end of the spring 39A is connected to the spring seat 39B and the other end thereof is connected to the ball 39C. A groove 35a that engages with the ball 39C is provided on the outer circumferential surface of the shaft portion 35A of the support 35. Note, however, that the groove 35a is not always necessary and may be omitted. In the present preferred embodiment, the ball 39C, the spring seat 39B, and the spring 39A correspond to the first contact portion, the second contact portion, and the elastic portion, respectively.

[0101] Also in the present preferred embodiment, the support 35 is able to be secured inside the hole 37 by the ball plunger 39 simply by inserting the support 35 into the hole 37. It is possible to prevent fretting wear, or the like, due to rising of the support 35 while maintaining the ease of installment of the support 35. It is possible to prevent a negative impact on the connecting function of the rocker arm 40. By appropriately setting the spring constant, etc., of the spring 39A, the ease of operation of inserting the support 35 into the hole 37 and the prevention of rising of the support 35 are realized in a well-balanced manner. According to the present preferred embodiment, there is no need to install the ball plunger 39 inside the support 35, and it is possible to increase the degree of freedom in the position of installment of the retainer.

[0102] As shown in FIG. 15A and FIG. 15B, with the internal combustion engine 10 according to an alternative preferred embodiment, the retainer includes a snap ring 139 fitted to the support 35. In the present preferred embodiment, a groove 35F is provided on the outer circumferential surface of the shaft portion 35A of the support 35, and the snap ring 139 is fitted to the groove 35F. The groove 37a that engages with the snap ring 139 is provided on the inner circumferential surface of the hole 37 of the cylinder head 12. Note, however, that the groove 37a is not always necessary and may be omitted. When the shaft portion 35A of the support 35 is inserted into the hole 37 of the cylinder head 12, the snap ring 139 is pressed by the inner circumferential surface of the hole 37 so as to elastically deform radially inward. In other words, the radius of the snap ring 139 decreases. By the elastic force generated following the deformation of the snap ring 139, the support 35 is pressed against the inner circumferential surface of the hole 37 with the snap ring 139 therebetween. Thus, the support 35 is secured inside the hole 37. According to the present preferred embodiment, the retainer includes the snap ring 139, and therefore the retainer is simple and compact.

[0103] As shown in FIG. 16, the snap ring 139 may be fitted to the inner circumferential surface of the hole 37 of the cylinder head 12 so that the snap ring 139 defines and functions as the retainer that secures the support 35. In the present preferred embodiment, a groove 37F is provided on the inner circumferential surface of the hole 37, and the retainer includes the snap ring 139 fitted into the groove 37F. The groove 35F that engages with the snap ring 139 is provided on the outer circumferential surface of the support 35. Note, however, that the groove 35F is not always necessary and may be omitted. In the present preferred embodiment, when the shaft portion 35A of the support 35 is inserted into the hole 37, the snap ring 139 elastically deforms radially outward by being pressed by the outer circumferential surface of the support 35. In other words, the radius of the snap ring 139 increases. By the elastic force generated following the deformation of the snap ring 139, the support 35 is pressed against the inner circumferential surface of the hole 37 with the snap ring 139 therebetween. Thus, the support 35 is secured inside the hole 37. Also in the present preferred embodiment, the retainer includes the snap ring 139, and therefore the retainer is simple and compact.

[0104] As shown in FIG. 17A and FIG. 17B, with the internal combustion engine 10 according to an alternative preferred embodiment, the retainer includes a ring-shaped coil spring 239 wound around the support 35. In the present preferred embodiment, the groove 35F is provided on the outer circumferential surface of the shaft portion 35A of the support 35, and the ring-shaped coil spring 239 is fitted to the groove 35F. The groove 37a that engages with the coil spring 239 is provided on the inner circumferential surface of the hole 37 of the cylinder head 12. Note, however, that the groove 37a is not always necessary and may be omitted. When the shaft portion 35A of the support 35 is inserted into the hole 37, the ring-shaped coil spring 239 elastically deforms radially inward by being pressed by the inner circumferential surface of the hole 37. By the elastic force generated following the deformation of the coil spring 239, the support 35 is pressed against the inner circumferential surface of the hole 37 with the coil spring 239 therebetween. Thus, the support 35 is secured inside the hole 37. According to the present preferred embodiment, the retainer includes the ring-shaped coil spring 239, and therefore the retainer is simple and compact.

[0105] As shown in FIG. 18, the ring-shaped coil spring 239 may be fitted to the inner circumferential surface of the hole 37 so that the coil spring 239 defines and functions as the retainer that secures the support 35. In the present preferred embodiment, the groove 37F is provided on the inner circumferential surface of the hole 37, and the retainer includes the ring-shaped coil spring 239 fitted to the groove 37F. The groove 35F that engages with the coil spring 239 is provided on the outer circumferential surface of the support 35. Note, however, that the groove 35F is not always necessary and may be omitted. In the present preferred embodiment, when the shaft portion 35A of the support 35 is inserted into the hole 37, the ring-shaped coil spring 239 elastically deforms radially outward by being pressed by the outer circumferential surface of the support 35. By the elastic force generated following the deformation of the coil spring 239, the support 35 is pressed against the inner circumferential surface of the hole 37 with the coil spring 239 therebetween. Thus, the support 35 is secured inside the hole 37. Also in the present preferred embodiment, the retainer includes the ring-shaped coil spring 239, and therefore the retainer is simple and compact.

[0106] As shown in FIG. 19, the retainer may include a leaf spring 339 secured to the edge of the hole 37 of the cylinder head 12. Herein, the leaf spring 339 is secured to the cylinder head 12 by a pin 340. The leaf spring 339 includes a hole 339d through which the support 35 passes. The edge of the hole 339d of the leaf spring 339 is a first contact portion 339a that contacts with the support 35. A portion of the leaf spring 339 that is supported by the pin 340 is a second contact portion 339b that contacts with the cylinder head 12 with the pin 340 therebetween. A portion between the first contact portion 339a and the second contact portion 339b is an elastic portion 339c. According to the present preferred embodiment, the retainer includes the leaf spring 339, and therefore the retainer is simple.

[0107] In the preferred embodiments described above, the first arm 41 is configured so as not to be in contact with the cam 21A, 23A. In the preferred embodiments described above, the valve 20, 22 is brought into the inoperative state by switching the first arm 41 and the second arm 42 of the rocker arm 40 to the non-connected state. However, the first arm 41 may include a contact portion that contacts with the cam 21A, 23A after the second arm 42 starts pivoting as the roller 43 is pushed by the cam 21A, 23A. In such a case, it is possible to change the timing with which the valve 20, 22 is opened and closed by switching the first arm 41 and the second arm 42 to the non-connected state. Thus, it is possible to change the period in which the valve 20, 22 is open. For example, by extending the period in which the valve 20, 22 is open when the speed of the internal combustion engine 10 is high, it is possible to improve the performance at a high engine speed.

[0108] In the preferred embodiments described above, the internal combustion engine 10 is preferably a multi-cylinder engine. However, the internal combustion engine 10 may be a single-cylinder engine with which it is possible to change the timing with which the valve 20, 22 is opened/closed.

[0109] In the preferred embodiments described above, the internal combustion engine 10 includes a variable valve mechanism. That is, the rocker arm 40 includes the first arm 41, and the second arm 42 pivotally supported on the first arm 41. The internal combustion engine 10 includes the connection switch pin 66 as a connector that removably connects the first arm 41 and the second arm 42. However, the internal combustion engine 10 may not include a variable valve mechanism. The connector may be omitted. The second arm 42 may be integral with the first arm 41, and the rocker arm 40 may be a single-piece member. The internal combustion engine 10 may be unable to bring the valve 20, 22 to the inoperative state, and may be unable to change the timing with which the valve 20, 22 is opened/closed.

[0110] The terms and expressions used herein are used for explanation purposes and should not be construed as being restrictive. It should be appreciated that the terms and expressions used herein do not eliminate any equivalents of features illustrated and mentioned herein, but include various modifications falling within the claimed scope of the present invention. The present invention may be embodied in many different forms. The present disclosure is to be considered as providing examples of the principles of the present invention. These examples are described herein with the understanding that such examples are not intended to limit the present invention to preferred embodiments described herein and/or illustrated herein. Hence, the present invention is not limited to the preferred embodiments described herein. The present invention includes any and all preferred embodiments including equivalent elements, modifications, omissions, combinations, adaptations and/or alterations as would be appreciated by those skilled in the art on the basis of the present disclosure. The limitations in the claims are to be interpreted broadly based on the language included in the claims and not limited to examples described in the present specification or during the prosecution of the application.

[0111] While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.