ROCKER ARM STRUCTURE
A rocker arm arranged between a camshaft and a valve which opens/closes an intake port or an exhaust port. A rolling bearing for supporting a support hole formed in a rocker arm is of a type of bearing wherein a plurality of needles are mounted on an inner side of an outer peripheral shell, and the outer peripheral shell is fixed to the support hole, the cam follower includes an outer ring which is supported on a periphery of a cam follower shaft which is held by a pair of left and right arm portions of the rocker arm by way of a plurality of rollers, a position of the outer ring and a position of the rollers in the lateral direction are restricted by the arm portion, and an outer diameter of the outer ring is set equal to or less than an inner diameter of the support hole.
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The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2011-024854 filed on Feb. 8, 2011 the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to the rocker arm structure.
2. Description of Background Art
For reducing friction in a valve system, efforts have been made to miniaturize a size of a cam follower portion or to reduce a weight of the cam follower portion by forming the cam follower into a shell structure having needle bearings. See, for example, JP-A-2004-346760. However, to realize the comprehensive miniaturization and reduction of weight of the cam follower portion or the reduction of friction in a valve system in the combination of the cam follower portion and a support portion of a rocker arm per se, further improvements with respect to the rocker arm structure are necessary.
SUMMARY AND OBJECTS OF THE INVENTIONThe task of the present invention lies in the reduction of friction of a rocking part or a rotary part, the miniaturization of a rocker arm and the miniaturization of a decompression cam.
The present invention has been made to overcome the above-mentioned drawbacks. According to an embodiment of the present invention, a structure of a rocker arm (57) of a valve system is provided which is arranged between a camshaft (53) and a valve (45, 47) which opens/closes an intake port (42) or an exhaust port (43) in an internal combustion engine (15).
The rocker arm (57) includes a support hole (67) for enabling rockable supporting of the rocker arm 57 by way of a rocker shaft (56) which is supported on a cylinder head (22). A cam follower (58) receives a pushing force from a cam (54A, 54B) of the camshaft (53). The support hole (67) and the cam follower (58) are supported by a rolling bearing structure.
A rolling bearing (68) which supports the support hole (67) is of a type of bearing where a plurality of needles (70) are mounted on an inner side of an outer peripheral shell (69) with the outer peripheral shell (69) being fixed to the support hole (67).
The cam follower (58) includes an outer ring (74) which is supported on a periphery of a cam follower shaft (72) which is held by a pair of left and right arm portions (66) of the rocker arm (57) by way of a plurality of rollers (73). The positioning of the outer ring (74) and the positioning of the rollers (73) in the lateral direction are restricted by the arm portion (66).
An outer diameter (Dr) of the outer ring (74) is set equal to or less than an inner diameter (Dh) of the support hole (67).
According to an embodiment of the present invention, in the structure of the rocker arm (57), an escape portion (78) is formed on the rocker arm (57) so that the rocker arm (57) does not obstruct the movement of a distal end of a cam nose (54a) when the camshaft (53) is rotated.
According to an embodiment of the present invention, an exhaust-side rocker arm (57B) out of the rocker arm (57), a decompression device (65) which is engaged with the exhaust-side rocker arm (57B) is mounted on the camshaft (53), a decompression shaft portion (86) of a decompression cam (84) which the decompression device (65) includes is supported on an inner side of an outer peripheral surface of a base circle portion (54b) of the exhaust cam (54B) on a side opposite to the cam nose (54a). The decompression cam (84) applies a decompression action to a projecting portion (66Ea) of an arm portion (66E) of the exhaust-side rocker arm (57B).
According to an embodiment of the present invention, the arm portions (66) of the exhaust-side rocker arm (57B) are formed such that, compared to a width of the arm portion (66E) on a side where the arm portions (66) are brought into contact with the decompression cam, a width of the arm portion (66I) on the other side is set small.
According to an embodiment of the present invention, the internal combustion engine (15) is an internal combustion engine (15) where the camshaft (53) and the rocker shaft (56) are arranged in front of a combustion chamber (40), and in a planar projection view as viewed in the cylinder axis direction (
According to an embodiment of the present invention, the rocker shaft (56) is fixed to the cylinder head (22) by fastening in a non-rotatable manner.
According to an embodiment of the present invention, the cam follower shaft (72) of the cam follower (58) is formed of a solid small-diameter shaft, and a thickness of the outer ring (74) in the radial direction is set smaller than a diameter of the roller (73).
According to an embodiment of the present invention, the respective rocker arms (57) arranged adjacent to each other are formed such that a width of the arm portion (66) on a left side and a width of the arm portion (66) on a right side differ from each other, and the width of the inner arm portion (66I) is set smaller than a width of the outer arm portion (66E).
According to an embodiment of the present invention, the internal combustion engine (15) is a frontwardly-inclined engine where a cylinder axis extends frontwardly and upwardly, and oil supply guide walls (76A, 76B) which lead to an end surface of the support hole (67) of the rocker arm (57) from the rocker shaft support boss portion (55) in a vehicle mounted state are formed in the vicinity of the rocker shaft support boss portions (55) of the cylinder head (22).
According to an embodiment of the present invention, the oil supply guide walls (76A, 76B) are arranged close to the rocker shaft support boss portions (55) which are positioned laterally outside the intake-side rocker arm (57A) and the exhaust-side rocker arm (57B) which are arranged parallel to each other in the lateral direction toward an oil supply hole (75) formed in the cylinder head cover (23).
According to an embodiment of the present invention, both the support hole (67) and the cam follower (58) have the rolling bearing structure. Thus, a friction loss can be reduced. Further, a size of the outer diameter (Dr) of the outer ring (74) of the cam follower (58) is set equal to or less than a size of the inner diameter (Dh) of the support hole (67). Thus, a wall thickness (80) between the support hole 67 and an outer ring housing portion (79) can be ensured while keeping a length of the rocker arm (57) short. In addition, the required rigidity for press-fitting of the shell-needle-type rolling bearing (68) can be ensured. Further, circularity of an inner surface of the shell after press-fitting can be enhanced so that durability of the rocker arm (57) can be enhanced. Thus, the center of gravity of the rocker arm (57) can be made to approach a rocking fulcrum so that a load applied to the shell (69) can be reduced.
According to an embodiment of the present invention, the escape portion (78) is formed on the rocker arm (57) and hence, also in the cam follower (58) having the small-diameter outer ring (74). Thus, it is possible to prevent the cam nose (54a) and the rocker arm (57) from being brought into contact with each other.
According to an embodiment of the present invention, a stepped portion between the projecting portion (66Ea) of the arm portion (66E) of the rocker arm (57) and the outer ring (74) can be made small. Thus, a projection amount of the decompression cam (84) from the outer peripheral surface of the base circle portion (54b) of the exhaust cam (54B) can be made small whereby the decompression cam (84) can be miniaturized.
According to an embodiment of the present invention, compared to the width of the arm portion (66E) of the exhaust-side rocker arm (57B) on a side where the arm portions (66) are brought into contact with the decompression cam (84), the width of the arm portion (66I) of the exhaust-side rocker arm (57B) on the other side is set small. Thus, the arm portion to which a load is not applied can be made light-weighted.
According to an embodiment of the present invention, the cam follower shafts (72) of the respective rocker arms (57) are arranged close to the corresponding rocker shafts (56). Thus, a length of the rocker arm (57) can be shortened. Further, a lever ratio (a ratio between the distance from the rocker shaft (56) to the tappet screw (59) and the distance from the rocker shaft (56) to the cam follower shaft (72)) can be set large. Thus, a cam height can be set low. Still further, since irregularities in the direction of a cam-crest reaction force which is applied to the rolling bearing (68) by way of the rocker arm (57) can be set in the fixed direction, the irregular movement of the rocker arm (57) can be suppressed. Accordingly, vibrations of the respective parts generated by rocking of the rocker arm can be also reduced thus further enhancing the durability of the bearing.
According to an embodiment of the present invention, the rocker shaft (56) is fixed and hence, the needles inside the shell (69) can be surely rotated. Accordingly, it is possible to prevent the needles (70) and the rocker shaft (56) from local abutting caused by the co-rotation of the needles (70) and the rocker shaft (56). Thus, the durability of the needles (70) and the rocker shaft (56) can be enhanced.
According to an embodiment of the present invention, the size of the outer diameter (Dr) of the outer ring (74) can be set small. Thus, the rocker arm (57) can be miniaturized.
According to an embodiment of the present invention, a distance between the cam followers (58) of both rocker arms (57) can be decreased. Thus, a distance between the cams (54A, 54B) of the camshaft (53) can be decreased whereby the valve gear (51) can be miniaturized.
According to an embodiment of the present invention, due to the formation of the oil guide walls (76A, 76B), an amount of oil supplied to the rolling bearing (68) of the support hole (67) can be increased. Thus, the durability of the rolling bearing (68) of the support hole (67) can be enhanced.
According to an embodiment of the present invention, although the rocker shaft support boss portions (55) are separated from each other in the lateral direction toward the oil supply hole (75) of the valve system which is formed in the cylinder head cover (23) at one place positioned approximately right above the top portion of the intake valve (45), a lubrication oil which is supplied from the oil supply hole (75) and is splashed by hitting the tappet screw (59) on the top portion of the intake valve (45) is received by the supply oil guide walls (76A, 76B) and is supplied to the support hole (67) formed in the rocker arm (57). Thus, the lubrication oil can be supplied to the support hole (67) formed in the rocker arm (57) whereby an amount of the lubrication oil supplied to the rolling bearing (68) in the support hole (67) can be increased while simplifying the oil supply structure in the inside of the cylinder head cover (23).
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
The power unit 5 includes an internal combustion engine 15 which is arranged on a front side of the power unit 5 and a power transmission device 16 which extends rearwardly from a left side of the internal combustion engine 15. The power transmission device 16 includes a V-belt-type continuously variable transmission 17 and a final reduction gear 18.
A shell body of the above-mentioned internal combustion engine 15 includes a crankcase 20, and a cylinder block 21, a cylinder head 22 and a cylinder head cover 23 which are joined to a front portion of the crankcase 20 in order in a frontward direction. The internal combustion engine 15 is a rocker-arm-type overhead-valve-type 4-stroke-cycle single cylinder water-cooled-type internal combustion engine. A throttle body 26 is mounted on an intake pipe 25 which is mounted on an intake port formed on an upper side of the cylinder head 22. Further, an air cleaner 8 (
A drive shaft of the V-belt-type continuously variable transmission 17 is a crankshaft 28 of the internal combustion engine 15 itself, and a drive pulley 29 of the V-belt-type continuously variable transmission 17 is mounted on a leftwardly extending portion of the crankshaft 28. A driven shaft 30 of the V-belt-type continuously variable transmission 17 is pivotally and rotatably supported on a transmission case 33 by way of a bearing. A driven pulley 31 is mounted on the driven shaft 30 by way of a centrifugal clutch. An endless V belt 32 extends between the drive pulley 29 and the driven pulley 31.
The final reduction gear 18 is arranged in a rear portion of the V-belt-type continuously variable transmission 17. An input shaft of the final reduction gear 18 is the above-mentioned driven shaft 30. A rear axle 6 to which the rear wheel 7 (
In these drawings, the cylinder head 22 is joined to the cylinder block 21 and the crankcase 20 using bolts 36A and nuts 36B, and the cylinder head cover 23 is joined to the cylinder head 22 using bolts not shown in the drawing. A piston 37 is slidably fitted in a cylinder bore 38 which is formed in a cylinder liner 24 inside the cylinder block 21. The above-mentioned piston 37 is connected to a crank pin (not shown in the drawing) of the crankshaft 28 (
In
In
In
omitted from the drawing. The intake-side rocker arm 57A and the exhaust-side rocker arm 57B are arranged parallel to each other (
The intake-side rocker arm 57A and the exhaust-side rocker arm 57B have the same shape with respect to portions other than the projecting portion 66Ea which is subject to a decompression action of the decompression device 65. When it is unnecessary to explain both rocker arms 57A, 57B in a differentiated manner, both rocker arms 57A, 57B are simply referred to as “rocker arm 57”. Further, also with respect to the rocker shafts 56A, 56B and the cams 54A, 54B, when it is unnecessary to differentiate an intake side and an exhaust side from each other, these rocker shafts 56A, 56B and these cams 54A, 54B are simply referred to as “rocker shaft 56” and “cam 54” respectively.
The rocker arm 57 includes a support hole 67 for enabling the rockable supporting of the rocker arm 57 by way of the rocker shaft 56 and the cam follower 58 which receives a pushing force from the cam 54. The support hole 67 portion and the cam follower 58 portion are supported by the rolling bearing structure. A rolling bearing 68 which supports the support hole 67 is, as shown in
An outer diameter Dr of the outer ring 74 is set equal to or less than an inner diameter Dh of the support hole 67. More specifically, the outer diameter Dr of the outer ring 74 of the cam follower 58 is set small compared to a conventional outer ring. For example, when the inner diameter Dh of the support hole 67 is set to 13.4 mm, the outer diameter Dr of the outer ring 74 is set to 13.0 mm. Due to such outer diameter setting, in
In
In a planar projection view as viewed in the cylinder axis direction shown in
In
In
In
In
In
In
Due to the formation of the supply oil guide walls 76A, 76B, an amount of oil supplied to the rolling bearing 68 in the support hole 67 can be increased and hence, the durability of the rolling bearing 68 can be enhanced. A bold-line arrow in the drawing shows the flow of lubrication oil which reaches the end surface of the support hole 67 from the oil supply hole 75 above the valve rear chamber 50.
In
The rocker shaft 92 is formed of the tubular material has a center hole 92a. Thus, both ends of the rocker shaft 92 open toward a valve gear chamber 50. An oil hole 92b is in communication with a space defined by the above-mentioned pair of O-rings 93 and includes a triangular cross section from a center portion of the center hole 92a. When an internal combustion engine 15 is operated, a lubrication oil splashed in a valve gear chamber 50 is supplied to a space defined by the support hole 67, the rocker shaft 92 and the pair of O-rings 93 having a triangular cross section through the center hole 92a and the oil hole 92b and hence, the rocker arm 57 is supported on the rocker shaft 92 in a floating manner whereby the rocker arm 57 can be smoothly rocked with respect to the rocker shaft 92. Due to the above-mentioned structure, a strike sound of a tappet screw 59 which is transmitted to a cylinder head 22 or the like from the rocker arm 57 by way of the rocker shaft 92 can be reduced.
As described in detail heretofore, the following advantageous effects are brought about by the above-mentioned embodiment.
Both the support hole 67 and the cam follower 58 have the rolling bearing structure and hence, a friction loss can be reduced. Further, a size of the outer diameter Dr of the outer ring 74 of the cam follower 58 portion is set small, that is, is set equal to or less than a size of the inner diameter Dh of the support hole 67. Thus, a length of the rocker arm 57 can be shortened, a wall thickness 80 between the support hole 67 and an outer ring housing portion 79 can be ensured, and the center of gravity of the rocker arm 57 can be made to approach a rocking fulcrum so that a load applied to the shell 69 can be reduced.
The escape portion 78 is formed on the rocker arm 57 so that the rocker arm 57 does not obstruct the movement of the distal end of the cam nose 54a when the camshaft 53 is rotated and hence, also in the cam follower 58 having the small-diameter outer ring 74, it is possible to prevent the cam nose 54a and the rocker arm 57 from being brought into contact with each other.
The decomposition device 65 is mounted on the camshaft 53, and the decomposition cam 84 is configured to apply a decomposition action to the projecting portion 66Ea of the arm portion 66E of the exhaust-side rocker arm 57B. A stepped portion between the projecting portion 66Ea and the outer ring 74 of the cam follower 58 can be made small. Thus, a projection amount of the decompression cam 84 from the outer peripheral surface of the base circle portion 54b of the exhaust cam 54B can be made small whereby the decompression cam 84 can be miniaturized.
Compared to the width of the arm portion 66E of the exhaust-side rocker arm 57B on a side where the arm portion 66E is brought into contact with the decompression cam 84, the width of the arm portion 66I of the exhaust-side rocker arm 57B on the other side is set small. Thus, the arm portion to which a load is not applied can be made light in weight.
In a planar projection view as viewed in the cylinder axis direction, with respect to each rocker arm 57, a size F between an axis 56x of the rocker shaft 56 and an axis 72x of the cam follower shaft 72 is set smaller than a size C between the axis 56x of the rocker shaft 56 and an axis 53x of the camshaft 53. Accordingly, the cam follower shafts 72 can be set closer to the corresponding rocker shafts 56. Thus, a length of the rocker arm 57 can be shortened.
The rocker shaft 56 is fixed to the cylinder head 22. Thus, the needles 70 inside the shell 69 can be surely rotated. Accordingly, it is possible to prevent local abutting of the needles 70 and the rocker shaft 56 caused by the co-rotation of the needles 70 and the rocker shaft 56 thus enhancing the durability of the needles 70 and the rocker shaft 56.
The cam follower shaft 72 of the cam follower 58 is formed of a solid small-diameter shaft, and a thickness of the outer ring 74 in the radial direction is set smaller than a diameter of the roller 73. Thus, the rocker arm 57 can be miniaturized.
The respective rocker arms 57 arranged adjacent to each other are formed such that the width of the inner arm portion 66I is set smaller than the width of the outer arm portion 66E. Thus, a distance between the cam followers 58 can be decreased whereby the valve gear 51 can be miniaturized.
The oil supply guide walls 76A, 76B which lead to an end surface of the support hole 67 of the rocker arm 57 from the rocker shaft support boss portion 55 are formed. Thus, an amount of oil supplied to the rolling bearing 68 of the support hole 67 can be increased whereby the durability of the rolling bearing 68 of the support hole 67 can be enhanced.
Although the rocker shaft support boss portions 55 are separated from each other in the lateral direction toward the oil supply hole 75 of the valve system which is formed in the cylinder head cover 23 at one place positioned approximately right above the top portion of the intake valve 45, a lubrication oil which is splashed by hitting the tappet screw 59 on the top portion of the intake valve 45 is received by the supply oil guide walls 76A, 76B and is supplied to the support hole 67 formed in the rocker arm 57 and hence, an amount of the lubrication oil supplied to the rolling bearing 68 in the support hole 67 can be increased while simplifying the oil supply structure in the inside of the cylinder head cover 23.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
Claims
1. A structure of a rocker arm of a valve system arranged between a camshaft and a valve for opening/closing an intake port or an exhaust port in an internal combustion engine, wherein the rocker arm comprises:
- a support hole for enabling rockable supporting of the rocker arm by a rocker shaft supported on a cylinder head; and a cam follower receiving a pushing force from a cam of the camshaft, the support hole and the cam follower being supported by a rolling bearing structure; a rolling bearing for supporting the support hole includes a bearing having a plurality of needles mounted on an inner side of an outer peripheral shell, the outer peripheral shell being fixed to the support hole; the cam follower comprises an outer ring supported on a periphery of a cam follower shaft held by a pair of left and right arm portions of the rocker arm by a plurality of rollers, a position of the outer ring and a position of the rollers in the lateral direction being restricted by the arm portion, and an outer diameter of the outer ring is set equal to or less than an inner diameter of the support hole.
2. The structure of the rocker arm according to claim 1, wherein an escape portion is formed on the rocker arm so that the rocker arm does not obstruct the movement of a distal end of a cam nose when the camshaft is rotated.
3. The structure of the rocker arm according to claim 1, wherein in an exhaust-side rocker arm out of the rocker arm, a decompression device is engaged with the exhaust-side rocker arm and is mounted on the camshaft, a decompression shaft portion of a decompression cam which the decompression device includes is supported on an inner side of an outer peripheral surface of a base circle portion of the exhaust cam, and the decompression cam applies a decompression action to a projecting portion of an arm portion of the exhaust-side rocker arm.
4. The structure of the rocker arm according to claim 2, wherein in an exhaust-side rocker arm out of the rocker arm, a decompression device is engaged with the exhaust-side rocker arm and is mounted on the camshaft, a decompression shaft portion of a decompression cam which the decompression device includes is supported on an inner side of an outer peripheral surface of a base circle portion of the exhaust cam, and the decompression cam applies a decompression action to a projecting portion of an arm portion of the exhaust-side rocker arm.
5. The structure of the rocker arm according to claim 3, wherein the arm portions of the exhaust-side rocker arm are formed wherein, compared to a width of the arm portion on a side where the arm portions is brought into contact with the decompression cam, a width of the arm portion on the other side is set small.
6. The structure of the rocker arm according to claim 2, wherein the internal combustion engine is an internal combustion engine where the camshaft and the rocker shaft are arranged in front of a combustion chamber and in a planar projection view as viewed in the cylinder axis direction, with respect to each rocker arm, a size between an axis of the rocker shaft and an axis of the cam follower shaft is set smaller than a size between the axis of the rocker shaft and an axis of the camshaft.
7. The structure of the rocker arm according to claim 5, wherein the rocker shaft is fixed to the cylinder head by fastening in a non-rotatable manner.
8. The structure of the rocker arm according to claim 1, wherein the cam follower shaft of the cam follower is formed of a solid small-diameter shaft and a thickness of the outer ring in the radial direction is set smaller than a diameter of the roller.
9. The structure of the rocker arm according to claim 2, wherein the cam follower shaft of the cam follower is formed of a solid small-diameter shaft and a thickness of the outer ring in the radial direction is set smaller than a diameter of the roller.
10. The structure of the rocker arm according to claim 4, wherein the respective rocker arms arranged adjacent to each other are formed such that a width of the arm portion on a left side and a width of the arm portion on a right side differ from each other and the width of the inner arm portion is set smaller than a width of the outer arm portion.
11. The structure of the rocker arm according to claim 1, wherein the internal combustion engine is a frontwardly-inclined engine wherein a cylinder axis extends frontwardly and upwardly and oil supply guide walls which lead to an end surface of the support hole of the rocker arm from the rocker shaft support boss portion in a vehicle mounted state are formed in the vicinity of the rocker shaft support boss portions of the cylinder head.
12. The structure of the rocker arm according to claim 9, wherein the oil supply guide walls are arranged close to the rocker shaft support boss portions positioned laterally outside the intake-side rocker arm and the exhaust-side rocker arm arranged parallel to each other in the lateral direction toward an oil supply hole formed in the cylinder head cover.
13. A rocker arm for a valve system arranged between a camshaft and a valve for opening/closing an intake port or an exhaust port in an internal combustion engine, comprising:
- a support hole formed for rockable supporting the rocker arm on a rocker shaft supported on a cylinder head; and a cam follower receiving a pushing force from a cam of the camshaft, the support hole and the cam follower being supported by a rolling bearing structure; a rolling bearing mounted within the support hole includes a plurality of needles mounted on an inner side of an outer peripheral shell, the outer peripheral shell being fixed to the support hole; the cam follower includes an outer ring supported on a periphery of a cam follower shaft held by a pair of left and right arm portions of the rocker arm by a plurality of rollers, a position of the outer ring and a position of the rollers in the lateral direction being restricted by the arm portion, and an outer diameter of the outer ring is set equal to or less than an inner diameter of the support hole.
14. The rocker arm according to claim 13, wherein an escape portion is formed on the rocker arm so that the rocker arm does not obstruct the movement of a distal end of a cam nose when the camshaft is rotated.
15. The rocker arm according to claim 13, wherein in an exhaust-side rocker arm out of the rocker arm, a decompression device is engaged with the exhaust-side rocker arm and is mounted on the camshaft, a decompression shaft portion of a decompression cam which the decompression device includes is supported on an inner side of an outer peripheral surface of a base circle portion of the exhaust cam, and the decompression cam applies a decompression action to a projecting portion of an arm portion of the exhaust-side rocker arm.
16. The rocker arm according to claim 14, wherein in an exhaust-side rocker arm out of the rocker arm, a decompression device is engaged with the exhaust-side rocker arm and is mounted on the camshaft, a decompression shaft portion of a decompression cam which the decompression device includes is supported on an inner side of an outer peripheral surface of a base circle portion of the exhaust cam, and the decompression cam applies a decompression action to a projecting portion of an arm portion of the exhaust-side rocker arm.
17. The rocker arm according to claim 15, wherein the arm portions of the exhaust-side rocker arm are formed wherein, compared to a width of the arm portion on a side where the arm portions is brought into contact with the decompression cam, a width of the arm portion on the other side is set small.
18. The rocker arm according to claim 14, wherein the internal combustion engine is an internal combustion engine where the camshaft and the rocker shaft are arranged in front of a combustion chamber and in a planar projection view as viewed in the cylinder axis direction, with respect to each rocker arm, a size between an axis of the rocker shaft and an axis of the cam follower shaft is set smaller than a size between the axis of the rocker shaft and an axis of the camshaft.
19. The structure of the rocker arm according to claim 17, wherein the rocker shaft is fixed to the cylinder head by fastening in a non-rotatable manner.
20. The structure of the rocker arm according to claim 13, wherein the cam follower shaft of the cam follower is formed of a solid small-diameter shaft and a thickness of the outer ring in the radial direction is set smaller than a diameter of the roller.
Type: Application
Filed: Feb 2, 2012
Publication Date: Aug 9, 2012
Applicant:
Inventors: Ryuji TSUCHIYA (Wako-shi), Nobutaka HORII (Wako-shi)
Application Number: 13/364,855