Patent Publication Number: US-6712031-B2

Title: Support device for rocker arm

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a support device for a rocker arm used as a component of a valve mechanism for actuating an engine valve of an internal combustion engine. 
     2. Description of the Prior Art 
     A rocker arm of the above-mentioned kind has been conventionally proposed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 2000-303806, which includes a rocker shaft supported between a pair of supporting portions formed in a cylinder head, and a rocker arm pivotally movably supported on the rocker shaft via its supported portion. Further, a wave washer is mounted on one end of the supported portion of the rocker arm. The wave washer is comprised of a resilient annular portion bent in an outwardly curved manner, and a pair of engaging pieces extending inward from diametrically opposite portions of the annular portion. Each engaging piece has a predetermined bent shape and is resilient. On the other hand, the supported portion of the rocker arm has a pair of engaging holes formed at respective locations corresponding to the pair of engaging pieces. The wave washer has its engaging pieces precisely fitted in the engaging holes, respectively, and sandwich the supported portion of the rocker arm from opposite sides by the resilience of the engaging pieces, whereby the wave washer is unrotatably held on the supported portion of the rocker arm. The rocker shaft is inserted through the supported portion of the rocker arm and the annular portion of the wave washer, and in the assembled state of these members, the wave washer is sandwiched between the supported portion of the rocker arm and one of the aforementioned supporting portions, and the annular portion urges the rocker arm by the resilience thereof toward the other of the supporting portions, whereby the rattling of the rocker arm in the thrust direction is prevented. 
     In the conventional support device for the rocker arm, however, in assembling the wave washer to the rocker arm, it is necessary to circumferentially align the pair of engaging pieces of the wave washer with the pair of engaging holes of the rocker arm, respectively, which degrades the working efficiency in assembling the wave washer to the rocker arm. Further, since the engaging pieces of the wave washer are engaged with the engaging holes of the rocker arm, the wave washer is unrotatable with respect to the rocker arm, and further, since the wave washer is sandwiched between the rocker arm and the one of the supporting portions by the reactionary force of its own resilience, the rotation thereof is restricted. Therefore, as the rocker arm is pivotally moved, part of large load acting from the cam and the valve spring on the rocker arm acts on the wave washer. This makes the wave washer, particularly the engaging pieces, susceptible to deformation or wear. Further, since the supported portion of the rocker arm receiving large load from the cam and the valve spring is formed with the engaging holes, the resulting decrease in the cross-sectional area of the supported portion lowers the rigidity and strength of the supported portion. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a support device for a rocker arm, which is capable of suppressing deformation or wear of a washer, and greatly improving the working efficiency in assembling the washer to the rocker arm. 
     To attain the above object, the invention provides a support device for supporting a rocker arm that includes a supported portion and actuates an engine valve of an internal combustion engine having a cylinder head, 
     the support device comprising: 
     a plurality of shaft holders arranged in the cylinder head; 
     a rocker shaft supported by the plurality of shaft holders, for supporting the rocker arm thereon via the supported portion of the rocker arm between a pair of the shaft holders, such that the rocker arm can pivotally move thereabout; and 
     a washer attached to one of respective opposed ends of the supported portion of the rocker arm and one of the shaft holders, in a manner interposed between the one of the opposed ends and the other of the opposed ends, the washer having an engaging piece, 
     wherein the one of the opposed ends is formed with an annular engaging portion for having the washer engaged thereon via the engaging piece. 
     According to this support device for a rocker arm, a washer is attached to one of respective opposed ends of a supported portion of the rocker arm and one of shaft holders, in a manner interposed between the opposed ends. Further, the washer has an engaging piece, and the one of the opposed ends to which the washer is attached is formed with an annular engaging portion. The washer is latched or engaged on the supported portion of the rocker arm or the shaft holder by the engagement between the engaging piece and the annular engaging portion. Thus, the engaging piece of the washer is engaged with the annular engaging portion, which enables the washer to be assembled to the rocker arm or the shaft holder at any relative rotational angle thereto. This makes it absolutely unnecessary to carry out an operation for aligning the engaging piece with an engaging hole, which has been conventionally necessary, thereby greatly improving the working efficiency in assembling the washer to the associated component. 
     Preferably, the washer is engaged with the annular engaging portion via the engaging piece in a manner rotatable relative to the annular engaging portion. 
     According to this preferred embodiment, the rotation of the washer relative to the rocker arm or the shaft holder is permitted, whereby load applied from a cam or a valve spring via the rocker arm to the washer becomes very small, which makes it possible to suppress deformation or wear of the washer. 
     Preferably, the engaging piece comprises a plurality of engaging pieces arranged at intervals along a circumference of the washer, and the annular engaging portion is configured to be continuous along a circumference of the one of the opposed ends. 
     According to this preferred embodiment, the engaging piece of the washer comprises a plurality of engaging pieces circumferentially arranged, while the annular engaging portion is configured to be circumferentially continuous. This makes it possible to engage the plurality of engaging pieces on the annular engaging portion at any relative rotational angle without requiring any aligning work, and thereby maintain excellent working efficiency in assembling the washer to the rocker arm or the shaft holder. Further, since the engaging piece comprises a plurality of the engaging pieces, compared with a case in which the engaging piece is circumferentially continuous, it is easy to deform the engaging pieces, which further enhances working efficiency in assembling the washer to the rocker arm or the shaft holder. Moreover, when the washer is attached to the one of the opposed ends in a manner relatively rotatable, it is possible to reduce the rotational resistance of the washer. 
     Preferably, the annular engaging portion is formed by an annular protruding portion. 
     The supported portion of the rocker arm and the shaft holder are portions receiving large load from a cam or a valve spring when the rocker arm is pivotally moved, and therefore, it is preferred that they are configured to have as much rigidity and strength as possible. According to this preferred embodiment, the annular engaging portion for having the washer engaged thereon is configured as an annular protruding portion, and therefore, the resulting increase in cross-sectional area of the supported portion of the rocker arm or the shaft holder can make the rigidity and strength thereof much larger than in the case of the prior art in which engaging holes are formed therein. 
     Preferably, the washer is attached to the supported portion of the rocker arm, and at least part of the engaging piece is orthogonal to an axis of the rocker arm, and at the same time arranged at a location closer to a center of the supported portion than a plane passing on an outer end of an abutment portion of the rocker arm where the rocker arm is in abutment with the engine valve. 
     According to this preferred embodiment, at least part of the engaging piece is arranged by making effective use of space inside (not outward of) an abutment portion of the rocker arm where the rocker arm is in abutment with the engine valve. Therefore, the rocker arm can be made compact in size. 
     Preferably, the washer is attached to an end of the one of the shaft holders opposed to the rocker arm out of the respective opposed ends of the supported portion of the rocker arm and one of the shaft holders, and the annular protruding portion is formed at the end of the one of the shaft holders. 
     According to this preferred embodiment, since the shaft holder is formed with the annular protruding portion, it is possible to enhance not only the rigidity and strength of the shaft holders, but also the supporting rigidity of the rocker shaft supported by the shaft holders. 
     Preferably, the supported portion is formed with a projection corresponding to an overflow port used during casting of the rocker arm. 
     According to this preferred embodiment, the rigidity and strength of the supported portion can be further increased by the projection. 
     More preferably, the projection is formed on a flat surface of the supported portion radially inwardly offset from other peripheral portions of the supported portion. 
     According to this preferred embodiment, since the projection is formed on a flat surface of the supported portion radially inwardly offset from other peripheral portions of the supported portion, the engaging piece of the washer is prevented from being caught on the projection, thereby-ensuring rotation of the washer relative to the rocker arum. 
     Preferably, the washer comprises an annular portion having a central portion formed with a shaft hole through which the rocker shaft extends, and a plurality of the engaging pieces which extend from an outer periphery of the annular portion, and each of the engaging pieces comprises a perpendicular portion shortly extending perpendicularly from the annular portion and a curved portion having a semi-circular shape and extending inwardly from the perpendicular portion. 
     More preferably, the washer is attached to the supported portion of the rocker arm, and the supported portion has an outer peripheral surface formed with an annular concave portion which is adjacent to the annular protruding portion and with which the curved portion of the engaging piece is engaged. 
     According to this preferred embodiment, the washer can be stably held on the rocker arm by the engagement of the annular concave portion and the curved portion of the engaging piece. 
     The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary plan view showing the arrangement of a valve mechanism section of an internal combustion engine, including a support device for a rocker arm according to a first embodiment of the invention; 
     FIG. 2 is a cross-sectional view taken on line II—II of FIG. 1; 
     FIG. 3 is a perspective view showing the configurations of a rocker arm and washers, which is useful in explaining how the washers are attached to the rocker arm; 
     FIG. 4A is a plan view of the rocker arm; 
     FIG. 4B is a front view of the rocker arm; 
     FIG. 5A is a side view of a washer; 
     FIG. 5B is a front view of the washer; 
     FIG. 5C is a cross-sectional view taken on line C—C of FIG. 5B; 
     FIG. 6A is a partially-cutaway plan view of the rocker arm with the washers attached thereto; 
     FIG. 6B is a front view of the rocker arm with the washers attached thereto; 
     FIG. 7 is a partially-cutaway plan view similar to FIG. 6A, which shows a variation of the rocker arm; 
     FIG. 8 is a partially-cutaway plan view similar to the FIG. 6A, which shows another variation of the rocker arm; 
     FIG. 9 is a fragmentary plan view similar to the FIG. 1, which shows a second embodiment of the invention; 
     FIG. 10A is a sectional side elevation of a variation of the washer; and 
     FIG. 10B is a cross-sectional view taken on line B—B of FIG.  10 A. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention will now be described in detail with reference to the drawings showing preferred embodiments thereof. Referring first to FIGS. 1 and 2, there is schematically shown the arrangement of a valve mechanism section of an internal combustion engine, including a support device for a rocker arm, according to a first embodiment of the invention. The internal combustion engine (hereinafter simply referred to as “the engine”)  1  is, for instance, a four-cylinder four-valve DOHC engine, which includes a cylinder head  2  having intake ports  3  and exhaust ports  4  formed therein. A set of intake ports  3  and exhaust ports  4  communicate with a corresponding one of combustion chambers  5 , with intake valves  6  and exhaust valves  7  arranged as engine valves across respective communicating portions communicating between the intake ports  3  and the combustion chamber  5  and between the exhaust ports  4  and the combustion chamber  5 . Each intake valve  6  and each exhaust valve  7  include valve stems  6   a ,  7   a  having valve springs  9  attached to upper portions thereof via retainers  8 , respectively, such that the valve springs  9  urge the intake and exhaust valves  6 ,  7  upward in the valve-closing directions. 
     At respective locations above the intake valves  6  and the exhaust valves  7 , there are arranged an intake camshaft  10  and an exhaust camshaft  11  in parallel with each other (not shown in FIG.  1 ). The intake and exhaust camshafts  10 ,  11  are held by camshaft holders  12  bolted to an upper portion of the cylinder head  2 , and have two intake cams  10   a  (only one of which is shown in FIG. 2) and one exhaust cam  11   a  integrally formed therewith for each cylinder. 
     At respective locations below the intake and exhaust camshafts  10 ,  11 , there are arranged intake and exhaust rocker shafts  13 ,  13  in parallel with each other. The intake rocker shaft  13  pivotally supports two intake rocker arms  14 ,  15  associated with the respective intake valves  6  for each cylinder, while the exhaust rocker shaft  13  pivotally supports one exhaust rocker arm  16  common to the two exhaust valves  7  for the cylinder. The above rocker arms  14  to  16  have cam rollers  17  arranged in respective intermediate portions thereof such that the intake cams  10   a  and exhaust cam  11   a  associated with the rocker arms  14  to  16  are in sliding contact therewith. Further, each of the intake rocker arms  14 ,  15  has one adjuster screw  18  fixed to an end thereof by a locknut  19 , while the exhaust rocker arm  16  has two adjuster screws  18 ,  18  fixed to an end thereof by locknuts  19 , respectively. The adjuster screws  18  are in abutment with respective upper ends of the valve stems  6   a ,  7   a  of the intake valves  6  and exhaust valves  7  associated therewith. 
     As the intake and exhaust camshafts  10 ,  11  rotate in synchronism with rotation of a crankshaft, not shown, the intake cams  10   a  and exhaust cam  11   a  drive the rocker arms  14  to  16  associated therewith, so that the rocker arms  14  to  16  are pivotally moved about the rocker shafts  13  to thereby urge the valve stems  6   a ,  7   a  via the adjuster screws  18  against the respective urging forces of the valve springs  9 , causing the intake valves  6  and the exhaust valves  7  to be opened and closed. 
     Next, the configurations of the rocker arm and the support device therefor according to the present invention will be described in detail by taking the exhaust rocker arm  16  (hereinafter simply referred to as “the rocker arm  16 ”) as an example. As shown in FIGS. 1 and 2, the cylinder head  2  has a lot of exhaust-side shaft holders  21 ,  21  . . . (only two of which are shown in FIG. 1) formed at locations below and inward of the exhaust camshaft  11  such that they are arranged side by side in a row parallel with the camshaft  11 . The shaft holders  21  are made e.g. of cast aluminum, and the rocker shaft  13  is held by the shaft holders  21 . 
     The rocker shaft  13  extends through respective supported portions  23  (only one of which is shown), referred to hereinafter, of the rocker arms  16  for the cylinders, for pivotally supporting the supported portions  23  thereon. Each supported portion  23  is arranged in a state interposed between two associated ones of the shaft holders  21 ,  21 . Each rocker arm  16  is also formed e.g. of cast aluminum. Further, the supported portion  23  of the rocker arm  16  has washers  22 ,  22  attached to opposite ends thereof. The washers  22 ,  22  serve as spacers for preventing the relatively soft rocker arm  16  and shaft holders  21 ,  21  from adhering to each other by seizure which might be caused if they were in direct contact with each other. The washers  22 ,  22  are formed e.g. of stainless steel. 
     Referring to FIGS. 3 and 4A,  4 B, the rocker arm  16  includes the above-mentioned supported portion  23 , and an arm portion  24  extending from the supported portion  23  in a direction orthogonal to the axis of the supported portion, as integral parts thereof. The supported portion  23  has a shape of a relatively thick hollow cylinder with a shaft hole  23   a  formed therethrough. The rocker shaft  13  is inserted through the shaft hole  23   a . Further, the opposite ends of the supported portion  23  are formed to have flat end faces and circumferentially continuous annular protruding portions  25 ,  25 , for having the washers  22 ,  22  fitted thereon, respectively, which will be described hereinafter. 
     The arm portion  24  is comprised of two forked portions  24   a ,  24   a  extending from the supported portion  23  with a gap therebetween, and a connecting portion  24   b  connecting between distal ends of the forked portions. The forked portions  24   a ,  24   a  extend up to intermediate portions thereof in parallel with each other, and the above-mentioned cam roller  17  is rotatably fitted in the gap therebetween in a manner slightly projecting upward. Further, from the intermediate portions, the forked portions  24   a ,  24   a  further extend obliquely more apart, and the distal ends thereof, that is, opposite ends of the connecting portion  24   b , are formed with screw holes  24   c ,  24   c  for screwing the above-mentioned adjuster screws  18  therein. 
     It should be noted that the screw holes  24   c ,  24   c  correspond to sprues used in casting the rocker arm  16 , and opposite end portions of the outer peripheral surface of the supported portion  23 , at respective locations opposite to the screw holes  24   c ,  24   c  correspond to overflow ports. As shown in FIGS.  4 A and  4 B, the opposite end portions are formed with protrusions  23   b ,  23   b  left as remains of the overflow ports. Further, an outer peripheral portion of the supported portion  23 , on which the protrusions  23   b ,  23   b  are formed, is formed as a flat surface  23   c  radially inwardly offset from the other peripheral portions of the supported portion  23  such that the protrusions  23   b  do not obstruct the washers  22 ,  22  attached to the opposite ends of the supported portion  23 . 
     The washers  22 ,  22  are formed of stainless steel or the like, as described hereinabove. As shown in FIGS. 5A to  5 C, each of the washers  22 ,  22  is comprised of an annular portion  26 , and a plurality of (six in the case of the illustrated example) engaging pieces  27  extending from an outer periphery of the annular portion  26 . The annular portion  26  is formed to be flat, with a shaft hole  26   a  formed through a central portion thereof, for having the rocker shaft  13  inserted therethrough. Further, the six engaging pieces  27  are arranged along the circumference of the annular portion  26 , at equally-spaced intervals, i.e. every 60 degrees about the center of the annular portion  26 . As shown in FIG. 5C, each engaging piece  27  is comprised of a perpendicular portion  27   a  extending perpendicularly from the annular portion  26  to a predetermined short length, and a substantially semicircular curved portion  27   b  extending radially inward from the perpendicular portion  27   a.    
     The washers  22  configured as above are fitted on the respective ends of the supported portion  23  of the rocker arm  16 , as shown in FIG.  3  and FIGS. 6A and 6B. In this state, as shown in FIG. 6A, the perpendicular portion  27   a  of each engaging piece  27  of the washer  22  is engaged with the annular protruding portion  25  of the supported portion  23  with a small gap, and the curved portion  27   b  is in abutment with the outer periphery of the supported portion  23 . This causes the washers  22  to be engaged on the supported portion  23  of the rocker arm  16  in a manner rotatable relative to the supported portion  23 . In the present embodiment, as described hereinbefore, the protrusions  23   b  of the supported portion  23  are formed on the flat surface  23   c  radially inwardly offset, so that the protrusions  23   b  are prevented from catching the washers  22  so as not to obstruct the relative rotation of the washers  22 . Further, as shown in FIG. 6A, each washer  22  is mounted such that part of each engaging piece  27  thereof is orthogonal to the axis of the rocker arm  16 , and at the same time arranged at a location closer to a center of the supported portion  23  than a plane X passing on an outer end of the connecting portion  24   b  of the arm portion  24 . 
     The rocker arm  16  after having the washers  22 ,  22  attached thereto, as described above, is assembled between the shaft holders  21 ,  21 , and the rocker shaft  13  is inserted through the shaft holes  23   a ,  26   a  of the rocker arm  16  and the washers  22 , whereby the rocker arm  16  is pivotally supported on the rocker shaft  13 . In this state, each washer  22  is held in a state rotatable with respect to the supported portion  23  of the rocker arm  16 , and interposed between the supported portion  23  and the shaft holder  21  in a state in which the washer  23  is in abutment with the shaft holder  21  opposed thereto. This makes it possible to prevent the supported portion  23  and the shaft holder  21  from adhering to each other by seizure which might be caused if they were in direct contact with each other. 
     As described hereinabove, according to the present embodiment, the washers  22  are rotatably attached to the rocker arm  16  through the engagement of the engaging pieces  27  thereof and the annular protruding portions  25  of the rocker arm  16 . Therefore, the washers  22  are permitted to rotate with respect to the rocker arm  16 , whereby when the rocker arm  16  is pivotally moved, load applied to the washers  22  from the exhaust cam  11   a  and the valve springs  9  via the rocker arm  16  becomes very small. As a result, it is possible to prevent deformation and wear of the washers  22 . 
     Further, since each washer  22  is formed with the plurality of engaging pieces  27 , and an engaging portion of the rocker arm  16  for having the engaging pieces  27  engaged therewith is formed by the circumferentially continuous annular protruding portion  25 , it is possible to engage the engaging pieces  27  of the washer  22  with the annular protruding portion  25  at any relative rotational angle when the washer  22  is attached to the rocker arm  16 . This makes it absolutely unnecessary to carry out an operation for aligning engaging pieces with engaging holes, which has been conventionally necessary, whereby the working efficiency in assembling the washers  22  to the rocker arm  16  can be greatly enhanced. 
     Further, the annular protruding portions  25  are formed on the supported portion  23  as portions protruding therefrom, so that when compared with the conventional case of engaging holes being formed in the supported portion  23 , an increase in cross-sectional area of the supported portion due to the provision of the protruding portions  25  makes it possible to largely enhance the rigidity and strength of the supported portion  23  which receives large load from the exhaust cam  11   a  and the like when the rocker arm  16  is pivotally moved. Further, as described above, since the supported portion  23  is formed with the protrusions  23   b ,  23   b  corresponding to overflow ports used in casting the rocker arm  16 , it is possible to further enhance the rigidity and strength of the supported portion  23  by the protrusions  23   b ,  23   b . Further, since the protrusions  23   b ,  23   b  are formed on the flat surface  23   c  radially inwardly offset from the other peripheral portions of the supported portion  23 , the engaging pieces  27  of the washers  22  are prevented from being caught on the protrusions  23   b , which positively permits the rotation of the washers  22  relative to the rocker arm  16 . 
     Further, as described hereinabove, part of each engaging piece  27  of the washer  22  is arranged at a location closer to the center of the supported portion  23  than the plane X passing on the outer end of the connecting portion  24   b  of the rocker arm  16 , i.e. in a space inside (not outward of) an abutment portion of the rocker arm  16  where the rocker arm  16  is in abutment with the exhaust valve  7 . This enables effective use of the space, thereby making it possible to make the rocker arm  16  compact in size in an axial direction. Further, differently from a conventional bent annular portion, the annular portion of the washer  22  is formed to be flat, whereby the rocker arm  16  can be made more compact in size in the axial direction. 
     FIG. 7 shows a variation of the rocker arm  16 . This rocker arm  16  has annular concave portions  23   d  formed in an outer peripheral surface of the supported portion  23  at a location adjacent to the annular protruding portions  25 . The curved portions  27   b  of the engaging pieces  27  of the washers  22  are engaged with the annular concave portions  23   d . Further, the protrusions  23   b  of the support device according to the first embodiment are omitted. Therefore, compared with the first embodiment, although this variation is slightly reduced in the rigidity or strength of the supported portion  23  due to the provision of the annular concave portions  23   d , it is possible to stably hold the washers  22  on the rocker arm  16  by engaging the annular concave portions  23   d  and the corresponding curved portions  27   b  of the engaging pieces  27  with each other. 
     FIG. 8 shows another variation of the rocker arm  16 . That is, this rocker arm  36  is of a type having a different shape from that of the rocker arm  16  described hereinabove. More specifically, in this rocker arm  36 , the two forked portions  24   a ,  24   a  of the arm portion  24  extend up to the connecting portion  24   b  at the distal ends of the arm portion  24  in parallel with each other. The other configurations are similar to those of the rocker arm  16 . Therefore, in this variation, although the axial length of the rocker arm  36  is slightly larger than that of the rocker arm  16 , it is possible to obtain the same advantageous effects as provided by the above embodiment in the other respects. Additionally, the annular protruding portions  25  are formed outward of the forked portions  24   a ,  24   a  of the arm portion  24 , which extend in parallel with each other. This can largely enhance the rigidity and strength of the rocker arm  36 . 
     FIG. 9 shows a second embodiment of the invention. In the second embodiment, the washers  22  are attached not to the rocker arms  16  but to the shaft holders  21 . To this end, each shaft holder  21  has an end formed with an annular protruding portion  45  similar to the annular protruding portion  25  of the rocker arm  16  according to the first embodiment. The engaging pieces  27  of the washers  22  are rotatably engaged with the annular protruding portions  45 . Therefore, in the present embodiment, the washers  22  are permitted to rotate with respect to the shaft holders  21 , whereby similarly to the first embodiment, when the rocker arm  16  is pivotally moved, load applied to the washers  22  can be made very small to prevent deformation and wear of the washers  22 . Further, since the shaft holders  21  are formed with the annular protruding portions  45 , it is possible to increase not only the rigidity and strength of the shaft holders  21  but also the supporting rigidity of the rocker shaft  13  supported by the shaft holders  21 . 
     FIGS. 10A and 10B show a variation of the washer. The washer  52  includes an annular portion  56  in the form of a flat plate having a shaft hole  56   a  formed therethrough, and only two engaging pieces  57  are formed on the annular portion  56  at diametrically opposite locations. Similarly to the engaging pieces  27  of the washers  22 , each engaging piece  57  is comprised of a perpendicular portion  57   a  shortly extending perpendicularly from the annular portion  56 , and a substantially semicircular curved portion  57   b  extending inward from the perpendicular portion  57   a . Further, as shown in FIG. 10B, the curved portion  57   b  is also curved circumferentially in a manner concentric with the annular portion  56 , and the curved inner surface forms an aligning surface  57   c.    
     As a result, according to the washer  52 , if a force is applied thereto in the direction of removing the same from the rocker arm  16  in the state of the washer  52  attached to the rocker arm  16 , the aligning function of the curved aligning surface  57   c  works, whereby the washer  52  can be stably held on the rocker arm  16 . Further, since it is required to form only two engaging pieces  57 , the machinability of the washers  52  can be increased. 
     It should be noted the present invention can be implemented in various forms without being limited to the above-described embodiments. For instance, although the above embodiments are described, by way of example, on the cases where the present invention is applied to the exhaust rocker arm  16 , it goes without saying that the present invention may be applied to the intake rocker arms  14 ,  15 . Further, although in the above embodiments, the annular portions  26 ,  56  of the washers  22 ,  52  are in the form of a flat plate, they may be in the form of an elastic curved plate. This makes it possible to urge the rocker arm  16  toward the shaft holder  21  on the opposite side by the elasticity of the annular portion, whereby it is possible to prevent the rocker arm  16  from being unstable or rattling. 
     Further, although in the above embodiments, the annular protruding portions  25 ,  45  are formed as the engaging portion of the rocker arm  16  or the shaft holder  21 , for having the engaging pieces of the washer engaged therewith, this is not limitative, but an annular groove may be formed in place of the annular protruding portion. Further, the number of the engaging pieces of the washers may be any number other than six or two exemplified in the above embodiments, e.g. four as a matter of course, so long as the engaging pieces can be positively held on the rocker arm or the like. 
     It is further understood by those skilled in the art that the foregoing are preferred embodiments of the invention, and that various changes and modifications may be made without departing from the spirit and scope thereof.