WO2012043257A1

WO2012043257A1 - Valve mechanism for internal-combustion engine

Info

Publication number: WO2012043257A1
Application number: PCT/JP2011/071121
Authority: WO
Inventors: 真昭福田; 前野　栄二
Original assignee: Ntn株式会社
Priority date: 2010-09-28
Filing date: 2011-09-15
Publication date: 2012-04-05
Also published as: JP2012072688A

Abstract

Provided is a low cost valve mechanism having a stable valve lift amount, which is used in an internal-combustion engine. A valve mechanism for an internal-combustion engine comprises a tappet (2) reciprocating while being in sliding contact with a cam (15) of a camshaft (1), and a lash adjuster (16) provided in the middle of a power transmission path which transmits a valve opening/closing force to a valve stem (9) from the cam (15) through the tappet (2), the lash adjuster (16) comprising a nut member (18) having an internal thread (17), an adjust screw (20) having an external thread (19), and a return spring (21) biasing the adjust screw (20), wherein the center in the width direction of the cam (15) is arranged to be deviated from the center of the tappet (2) so as to generate a rotational force in the tappet (2), and screwing directions of the external thread (19) and the internal thread (17) are selected so that the direction of the rotational force to be transmitted to the lash adjuster (16) becomes the direction to project the adjust screw (20) from the nut member (18).

Description

Valve operating device in internal combustion engine

This invention relates to a valve operating apparatus that operates intake and exhaust valves of an internal combustion engine.

BACKGROUND ART Generally, a valve operating apparatus that operates an intake valve or an exhaust valve of an internal combustion engine has a cam shaft that is rotationally driven and a cam driven member that reciprocates in contact with the cam of the cam shaft. A valve opening / closing force is transmitted to the valve stem of the intake valve or the exhaust valve via the driven member.

As an internal combustion engine to which such a valve operating system is applied, for example, a DOHC (Double Over Head) having a lifter body that reciprocates in sliding contact with a cam of a camshaft and that pushes down a valve stem with the lifter body. Camshaft) An engine and a tappet that reciprocates in contact with the camshaft cam, and the valve stem is pushed down by the valve opening / closing force transmitted from the tappet via the push rod and rocker arm. Head valve) engine.

In these internal combustion engines, a gap between constituent members of the valve operating device changes due to a difference in thermal expansion that occurs between the constituent members of the valve operating device during engine operation, and noise or compression leakage may occur due to the change in the clearance. There is. Further, even if the sliding portion of the valve operating device is worn, the gap between the constituent members of the valve operating device changes, and there is a possibility that abnormal noise is generated due to the change in the gap.

In order to prevent this abnormal noise and compression leakage, a lash adjuster that absorbs changes in the gaps between the structural members is generally provided in the middle of the power transmission path of the valve opening / closing force from the cam to the valve stem.

As such a lash adjuster, for example, a hydraulic lash adjuster using engine oil as a working fluid is known. However, the hydraulic lash adjuster is susceptible to changes in oil pressure due to engine speed, contamination and bubbles contained in engine oil. In addition, the structure is complicated, requiring a lot of man-hours for manufacturing and assembly, which is disadvantageous in terms of cost.

As a lash adjuster for solving this problem, there is a mechanical lash adjuster as described in Patent Documents 1 to 3. The mechanical lash adjuster includes a nut member having an internal thread on the inner periphery, an adjustment screw having an external thread that engages with the internal thread on the outer periphery, and a return spring that urges the adjustment screw in a direction protruding from the nut member. Therefore, when the gap between the components of the valve operating device changes due to thermal expansion of the valve operating device, etc., the adjusting screw moves in the axial direction while rotating in the nut member in accordance with the change in the clearance. The clearance between the constituent members of the valve gear is adjusted.

Here, in

Patent Documents

1 and 2, a compression coil spring that applies an axial force in a direction protruding from the nut member to the adjustment screw is used as the return spring. Moreover, in patent document 3, the torsion spring which provides the adjusting screw with the rotational force of the direction which protrudes from a nut member is used as a return spring.

By the way, when a mechanical lash adjuster is employed in the DOHC engine, a rotational force is generated in the lifter body due to misalignment between the cam and the lifter body that is in sliding contact with the cam, and the rotational force may be transmitted to the lash adjuster. In addition, even when a mechanical lash adjuster is used for the OHV engine, a rotational force is generated in the tappet due to the misalignment between the cam and the tappet that is in sliding contact with the cam, and the rotational force is lashed through the push rod. It may be transmitted to the adjuster.

When the rotational force is transmitted to the lash adjuster in this way, if the direction of the rotational force is the direction in which the adjusting screw protrudes from the nut member, the gap between the components of the valve gear is kept at zero. However, if the direction of the rotational force transmitted to the lash adjuster is the direction in which the adjusting screw is pushed into the nut member, the adjusting screw moves in the pushing direction every time the cam rotates. There is a problem that gaps between the constituent members are enlarged and valve lift loss occurs. And if the magnitude of the valve lift loss exceeds the lamp height set on the cam, the valve may be shockedly seated on the valve seat, causing abnormal noise, or in the worst case, the valve may be damaged. .

Therefore, in order to prevent the rotational force generated in the lifter body from being transmitted to the lash adjuster in the DOHC engine, a lash adjuster described in Patent Document 4 has been proposed. In this lash adjuster, a spacer member is interposed between the adjusting screw and the valve stem, and the spacer member can be moved in the axial direction with respect to the nut member and constrained in the rotational direction, thereby The rotation is blocked from being transmitted to the adjusting screw.

Japanese Examined Patent Publication No. 62-33401 JP-T 61-502553 Japanese Patent Laid-Open No. 5-10109 JP 2003-227317 A

However, incorporating such a spacer member not only increases the number of parts of the valve operating device, but also complicates the structure for moving the spacer member in the axial direction relative to the nut member and restraining it in the rotational direction. There has been a problem that the processing cost and assembly cost of each part increase.

The problem to be solved by the present invention is to provide a valve operating apparatus for an internal combustion engine which is low in cost and has a stable valve lift.

In order to solve the above problems, a cam shaft that is rotationally driven, a cam driven member that reciprocates in contact with the cam of the cam shaft, and a valve stem of an intake valve or an exhaust valve from the cam via the cam driven member And a lash adjuster provided in the middle of the power transmission path for transmitting the valve opening / closing force. The lash adjuster has a nut member having an internal thread on the inner periphery and an external thread that engages with the internal thread on the outer periphery. In a valve operating apparatus for an internal combustion engine comprising an adjustment screw and a return spring that urges the adjustment screw in a direction protruding from a nut member, the cam width member and the cam follower are arranged with a center shifted from each other. Thus, a rotational force is generated in the cam follower member, and the rotational force is transmitted to the lash adjuster. The power transmission path to configure so, the direction of the rotational force transmitted to the lash adjuster selected the winding direction of the male screw and the female screw such that the direction to project the adjusting screw from the nut member.

In this case, the direction of the rotational force transmitted from the cam follower member to the lash adjuster is the direction in which the adjustment screw protrudes from the nut member. Therefore, the valve lift loss caused by the rotational force transmitted from the cam follower member to the lash adjuster. Thus, a stable valve lift amount can be obtained. Further, since a spacer member for interrupting transmission of the rotational force from the cam follower member to the lash adjuster is unnecessary, the structure is simple and the cost is low.

The present invention can be applied to, for example, the following valve gears.
1) The cam follower member is a tappet that is slidably supported up and down and has a cam sliding contact surface that slides on the cam at the lower end. A valve operating apparatus for an OHV engine, provided with a rocker arm, provided with a push rod that transmits power from the tappet and pushes up one end of the rocker arm, and pushes down the valve stem at the other end of the rocker arm.
2) The cam follower member is a lifter body including a cylindrical portion that is slidably supported by a guide hole formed in a cylinder head and an end plate provided at an upper end of the cylindrical portion. A valve operating device for a DOHC engine in which a cam sliding contact surface is provided on the upper surface of the end plate, the upper end of the valve stem is disposed in the cylindrical portion, and the cam pushes down the valve stem through a lifter body.

When the present invention is applied to the valve operating apparatus of 1), the lash adjuster is arranged such that the protruding direction from the nut member of the adjusting screw is downward at the end of the rocker arm that is pushed up by the push rod. It is possible to adopt a configuration in which the protruding end of the adjusting screw from the nut member is brought into contact with the upper end of the push rod.

In addition, when the present invention is applied to the valve operating device of 2), the lash adjuster is assembled to the lower surface of the end plate so that the protruding direction from the nut member of the adjusting screw is downward, and the adjusting screw of the adjusting screw A configuration in which the protruding end from the nut member is in contact with the upper end of the valve stem can be employed.

The male screw and female screw of the lash adjuster are sawtooth screws in which the flank angle of the pressure flank that receives pressure when an axial load in the direction of pushing the adjustment screw into the nut member is applied is larger than the flank angle of the play flank. Can be adopted.

The return spring may be a compression coil spring that applies an axial force in a direction protruding from the nut member to the adjustment screw, and a twist that applies a rotational force in a direction protruding from the nut member to the adjustment screw. A spring may be employed.

When the present invention is applied to a valve operating apparatus for an internal combustion engine having a plurality of intake valves and exhaust valves, if a lash adjuster whose male screw and female screw are right-handed and a lash adjuster whose male screw and female screw are left-handed are mixed, When assembling the valve device, there is a risk that the right-handed lash adjuster and the left-handed lash adjuster are mistakenly assembled. Therefore, it is preferable to unify the winding direction of the male screw and the female screw of each lash adjuster corresponding to the intake valve and unify the winding direction of the male screw and the female screw of each lash adjuster corresponding to the exhaust valve.

In this case, the winding direction of the male screw and the female screw of each lash adjuster corresponding to the intake valve can be opposite to the winding direction of the male screw and the female screw of each lash adjuster corresponding to the exhaust valve. .

In the valve operating device according to the present invention, the direction of the rotational force transmitted from the cam driven member to the lash adjuster is the direction in which the adjusting screw protrudes from the nut member, so that the valve lift caused by the rotational force transmitted from the cam driven member to the lash adjuster There is no problem of loss, and a stable valve lift amount can be obtained. Further, since a spacer member for interrupting transmission of the rotational force from the cam follower member to the lash adjuster is unnecessary, the structure is simple and the cost is low.

The front view which shows the valve gear of 1st Embodiment of this invention Enlarged sectional view along line II-II in FIG. Enlarged cross-sectional view along line III-III in FIG. Enlarged cross-sectional view along line IV-IV in Fig. 2 The figure which shows the modification of the valve operating apparatus shown in FIG. The front view which shows the valve gear of 2nd Embodiment of this invention 6 is an enlarged sectional view of the vicinity of the lifter body in FIG. 6 as viewed from the right. Enlarged view of the adjusting screw shown in FIG. The figure which shows the modification of the valve operating apparatus shown in FIG. Enlarged view of the adjusting screw shown in FIG.

FIG. 1 shows a valve operating apparatus for an OHV (overhead valve) engine according to a first embodiment of the present invention. This valve operating apparatus is swingable about a camshaft 1 that is rotationally driven in synchronization with an engine crankshaft (not shown), a tappet 2 that is slidably supported in the vertical direction, and a rocker shaft 3. The rocker arm 4 is supported, the push rod 5 transmits power between the tappet 2 and the rocker arm 4, and the valve 8 opens and closes the intake port (or exhaust port) 7 of the cylinder head 6.

The valve 8 is integrally provided with a valve stem 9 extending upward from the valve 8. The valve stem 9 is supported by a cylindrical valve stem guide 10 fixed to the cylinder head 6 so as to be slidable up and down. An annular spring retainer 12 is fixed to the upper outer periphery of the valve stem 9 via a wedge-shaped cotter 11. A valve spring 13 is incorporated between the lower surface of the spring retainer 12 and the upper surface of the cylinder head 6. The valve spring 13 urges the valve stem 9 upward via the spring retainer 12 and seats the valve 8 on the valve seat 14 by the urging force.

The cam 15 is integrally formed with the cam shaft 1. The cam 15 has a base circle 15b and a cam peak portion 15a raised with respect to the base circle 15b on the outer periphery. The tappet 2 has a flat cam sliding contact surface 2 a that is in sliding contact with the outer periphery of the cam 15 at the lower end, and is adapted to reciprocate following the contour of the cam 15.

The rocker arm 4 disposed above the tappet 2 is supported by the rocker shaft 3 at the center, and can swing around the rocker shaft 3 as a fulcrum. A lash adjuster 16 is incorporated at one end of the rocker arm 4, and the other end of the rocker arm 4 is in contact with the upper end of the valve stem 9.

The push rod 5 has a hemispherical convex surface 5b formed at the lower end thereof supported by a hemispherical concave surface 2b formed at the upper end of the tappet 2, and pushes together with the tappet 2 when the tappet 2 reciprocates. The lower end of the rod 5 reciprocates. The upper end of the push rod 5 supports one end portion of the rocker arm 4 via a lash adjuster 16, and when the tappet 2 is raised, the push rod 5 transmits the power of the tappet 2 and one end portion of the rocker arm 4. The other end of the rocker arm 4 pushes down the valve stem 9. Here, the valve opening / closing force of the valve 8 is transmitted from the cam 15 to the valve stem 9 through the tappet 2, the push rod 5, and the rocker arm 4 in this order, and a lash adjuster 16 is provided in the middle of the power transmission path.

As shown in FIG. 2, the lash adjuster 16 includes a cylindrical nut member 18 having an internal thread 17 on the inner periphery, an adjustment screw 20 having an external thread 19 that engages with the female thread 17 on the outer periphery, and the adjustment screw 20. The return spring 21 is urged in a direction protruding from the nut member 18. A convex spherical surface 20 a is formed at the projecting end of the adjusting screw 20 from the nut member 18, and the convex spherical surface 20 a is in contact with a concave spherical surface 5 a formed at the upper end of the push rod 5.

The nut member 18 is provided by being inserted through a fitting hole 22 penetrating the end of the rocker arm 4 in the vertical direction. A flange 23 that contacts the lower surface of the rocker arm 4 is integrally provided at the lower end of the nut member 18. As shown in FIG. 4, a flat surface 23 a is formed on the outer periphery of the flange 23, and the flat surface 23 a engages with a stopper surface 4 a formed on the lower surface of the rocker arm 4 to prevent the nut member 18 from rotating. is doing. The locking of the nut member 18 may be performed by other methods such as connecting the nut member 18 and the rocker arm 4 with a pin.

As shown in FIG. 2, a retaining ring 24 that prevents the nut member 18 from coming off from the fitting hole 22 is attached to a portion of the nut member 18 protruding upward from the fitting hole 22. A wave spring 25 is incorporated between the retaining ring 24 and the rocker arm 4 in order to absorb axial backlash of the nut member 18.

The return spring 21 is a torsion coil spring. The lower end of the return spring 21 is locked in a locking hole 26 formed on the outer periphery of the nut member 18, and the upper end of the return spring 21 is a locking groove 27 formed in the upper end of the adjusting screw 20 as shown in FIG. 3. Due to the torsional deformation, the adjusting screw 20 is given a rotational force in a direction in which the adjusting screw 20 protrudes downward from the nut member 18.

As shown in FIG. 2, the male screw 19 and the female screw 17 are configured such that the flank angle of the pressure side flank 28 that receives pressure when a load in the direction of pushing the adjusting screw 20 into the nut member 18 is applied is that of the play side flank 29. It is formed in a sawtooth shape larger than the flank angle.

When the lead angle of the male screw 19 and the female screw 17 is α and the flank angle of the pressure side flank 28 is θ, the magnitude of the lead angle α is the flank angle θ and the static friction coefficient μ between the male screw 19 and the female screw 17. In contrast, tan α · cos θ <μ is set. That is, the self-supporting friction coefficient (= tan α · cos θ) on the pushing side determined by the flank angle θ of the pressure side flank 28 and the lead angle α of the male screw 19 and the female screw 17 is the static friction coefficient μ between the male screw 19 and the female screw 17. Smaller than. Therefore, when a static load in the pushing direction is applied to the adjustment screw 20, the rotation of the adjustment screw 20 is prevented by the frictional resistance between the

pressure side flank

28, 28 of the male screw 19 and the female screw 17.

The diameter of the cam sliding contact surface 2 a of the tappet 2 is larger than the width of the cam 15. The center of the cam sliding contact surface 2 a of the tappet 2 is arranged so as to be shifted from the center of the cam mountain portion 15 a of the cam 15 in the width direction. As a result, when the cam 15 rotates, the frictional force acting between the cam crest 15a and the tappet 2 becomes asymmetric with respect to the axis of the tappet 2 so that a rotational force around the axis is generated in the tappet 2. It has become. Here, the direction of deviation between the tappet 2 and the cam 15 is a direction in which the direction of the rotational force generated in the tappet 2 is clockwise when viewed from above.

The rotational force generated in the tappet 2 is transmitted from the tappet 2 to the push rod 5 by the friction between the concave surface 2b and the convex surface 5b shown in FIG. 1, and further, the friction between the concave spherical surface 5a and the convex spherical surface 20a shown in FIG. Is transmitted from the push rod 5 to the adjusting screw 20. At this time, the direction of the rotational force transmitted to the adjusting screw 20 is clockwise as viewed from above. The winding direction of the male screw 19 and the female screw 17 is the direction in which the adjusting screw 20 protrudes downward from the nut member 18 when the adjusting screw 20 is rotated clockwise as viewed from above, that is, the direction of the right screw. It has become.

Next, an example of the operation of the valve gear described above will be described.

When the camshaft 1 is rotated by the operation of the engine and the cam crest 15a of the cam 15 pushes up the tappet 2, the valve 8 is separated from the valve seat 14 and the intake port 7 is opened. At this time, an axial load in the pushing direction is applied to the adjusting screw 20, but the pressure side flank 28 of the male screw 19 is received by the pressure side flank 28 of the female screw 17, and the axial position of the adjusting screw 20 is fixed. .

When the cam 15 further rotates and the cam crest 15 a passes the position of the tappet 2, the valve stem 9 is raised by the urging force of the valve spring 13, the valve 8 is seated on the valve seat 14, and the intake port 7 is close.

Strictly speaking, when the cam crest 15a of the cam 15 pushes up the tappet 2, a slight slip occurs between the

pressure side flank

28, 28 of the male screw 19 and the female screw 17, and the adjustment screw 20 slightly moves in the pushing direction by the slip. However, when the cam crest 15a passes the position of the tappet 2 and the load in the push-in direction is released, the adjustment screw 20 moves in the protruding direction due to the load applied from the return spring 21. Return to position.

Immediately after the start of the engine when the engine is cold, the valve (especially the exhaust valve) 8 and the valve stem 9 among the components of the valve operating device first rise in temperature and thermally expand, so the difference in thermal expansion from the other components This may cause a gap between the valve 8 and the valve seat 14. However, at this time, even when the base circle 15b of the cam 15 is in the position of the tappet 2, the urging force of the valve spring 13 acts on the adjustment screw 20, so that the cam peak portion 15a of the cam 15 pushes up the tappet 2. The protruding amount of the adjusting screw 20 when the cam 15 further rotates and the load in the pressing direction is released is smaller than the pressing amount of the adjusting screw 20. As a result, each time the cam 15 rotates, the adjustment screw 20 gradually moves in the pushing direction, and no gap is generated between the valve 8 and the valve seat 14.

Also, when the contact portion between the valve stem 9 and the rocker arm 4, the contact portion between the adjustment screw 20 and the push rod 5, the contact portion between the push rod 5 and the tappet 2, the contact portion between the tappet 2 and the cam 15, etc. As a result of the wear, a gap is generated between the components of the valve operating device, and the valve lift amount of the valve 8 may be insufficient. However, at this time, the protrusion of the adjusting screw 20 when the cam 15 rotates and the load in the pressing direction is released is larger than the pressing amount of the adjusting screw 20 when the cam crest 15a of the cam 15 pushes up the tappet 2. The amount increases. As a result, each time the cam 15 rotates, the adjusting screw 20 gradually moves in the protruding direction, so that the gap between the constituent members of the valve operating device is kept at zero, and the valve lift loss of the valve 8 does not occur.

In this valve operating device, a rotational force is generated in the tappet 2 by shifting the center of the cam 15 in the width direction and the center of the tappet 2, and the direction of the rotational force transmitted from the tappet 2 to the lash adjuster 16 is changed. Since the adjustment screw 20 protrudes from the nut member 18, the problem of valve lift loss due to the rotational force transmitted from the tappet 2 to the lash adjuster 16 does not occur, and a stable valve lift amount can be obtained. it can. Further, since a spacer member that blocks transmission of rotational force from the tappet 2 to the lash adjuster 16 is unnecessary, the structure is simple and the cost is low.

In the above embodiment, the valve operating device in which the male screw 19 and the female screw 17 are incorporated with the right-handed lash adjuster 16 has been described. However, as shown in FIG. The present invention can also be applied to a valve gear incorporating 16. In this case, the direction of the rotational force generated in the tappet 2 is such that the direction of the rotational force transmitted from the tappet 2 to the adjusting screw 20 is counterclockwise as viewed from above. The direction must be counterclockwise when viewed from above.

When the present invention is applied to a valve operating apparatus for an internal combustion engine having a plurality of intake valves 8, a male screw 19 and a female screw 17 are right-handed lash adjusters 16, and a male screw 19 and a female screw 17 are left-handed lash adjusters 16. Then, when assembling the valve gear, there is a possibility that the right-handed lash adjuster 16 and the left-handed lash adjuster 16 are mistakenly assembled. Therefore, it is preferable to unify the winding directions of the male screw 19 and the female screw 17 of each lash adjuster 16. The same applies to the exhaust valve 8. In this case, the size or shape of the rocker arm 4 is made different between the intake side and the exhaust side, and the winding direction of the screw of the lash adjuster 16 on the intake side is opposite to the winding direction of the screw of the lash adjuster 16 on the exhaust side. be able to.

In the above embodiment, the male screw 19 and the female screw 17 of the lash adjuster 16 are sawtooth screws in order to suppress the amount of movement of the adjusting screw 20 in the pushing direction and stabilize the valve lift, but the male screw 19 and the female screw 17 are It is also possible to employ vertically symmetrical triangular screws and trapezoidal screws.

In the above embodiment, the torsion coil spring is employed as the torsion spring that applies the rotational force in the direction protruding from the nut member 18 to the adjustment screw 20, but other torsion springs such as a mainspring spring instead of the torsion coil spring are employed. May be adopted. Further, instead of the torsion spring, a compression coil spring that applies an axial force in a direction protruding from the nut member 18 to the adjustment screw 20 may be employed.

FIG. 6 shows a valve operating apparatus for a DOHC (double over head camshaft) engine according to a second embodiment of the present invention. This valve operating apparatus includes a camshaft 31 that is rotationally driven in synchronization with an engine crankshaft (not shown), a lifter body 33 that reciprocates in contact with a cam 32 of the camshaft 31, and an intake air of a cylinder head 34. And a valve 36 for opening and closing a port (or exhaust port) 35.

A valve stem 37 similar to that of the first embodiment is integrally provided in the valve 36. A spring retainer 38 is fixed to the upper outer periphery of the valve stem 37. The spring retainer 38 is urged upward by a valve spring 39, and the valve 36 is seated on the valve seat 40 by the urging force.

As shown in FIG. 7, the lifter body 33 includes a cylindrical portion 42 that is slidably supported by a guide hole 41 formed in the cylinder head 34, and an end plate 43 provided at the upper end of the cylindrical portion 42. The upper end of the valve stem 37 is accommodated in the cylindrical portion 42.

On the upper surface of the end plate 43, a flat cam sliding contact surface 43a that is in sliding contact with the outer periphery of the cam 32 is formed, and the lifter body 33 reciprocates following the contour of the cam 32. A lash adjuster 44 is assembled to the lower surface of the end plate 43, and when the lifter body 33 reciprocates, the lifter body 33 pushes down the valve stem 37 via the lash adjuster 44. Here, the valve opening / closing force of the valve 36 is transmitted from the cam 32 to the valve stem 37 via the lifter body 33, and a lash adjuster 44 is provided in the middle of the power transmission path.

The lash adjuster 44 includes a cylindrical nut member 46 having an internal thread 45 on the inner periphery, an adjustment screw 48 having an external thread 47 that engages with the female thread 45 on the outer periphery, and a direction in which the adjust screw 48 projects from the nut member 46. And a return spring 49 that biases the spring. The nut member 46 is fixed to the lower surface of the end plate 43 with a retaining ring 50.

The return spring 49 is a compression coil spring. The return spring 49 is supported at its upper end by the end plate 43, and the lower end presses the adjusting screw 48. Due to the compression deformation, the axial force in the direction in which the adjusting screw 48 projects downward from the nut member 46 is adjusted. 48. The protruding end of the adjusting screw 48 from the nut member 46 is in contact with the upper end of the valve stem 37.

The male screw 47 and the female screw 45 have a sawtooth shape in which the flank angle of the pressure side flank 51 that receives pressure when a load in the direction of pushing the adjusting screw 48 into the nut member 46 is applied is larger than the flank angle of the play side flank 52. (See FIG. 8).

As shown in FIG. 7, the diameter of the cam sliding contact surface 43 a of the lifter body 33 is larger than the width of the cam 32. The center of the cam sliding contact surface 43 a of the lifter body 33 is shifted from the center of the cam 32 in the width direction. As a result, when the cam 32 rotates, the frictional force acting between the cam crest 32a and the lifter body 33 becomes asymmetric with respect to the axis of the lifter body 33, and a rotational force around the axis is generated in the lifter body 33. It has become. Here, the direction of displacement between the lifter body 33 and the cam 32 is a direction in which the direction of the rotational force generated in the lifter body 33 is clockwise when viewed from above.

Rotational force generated in the lifter body 33 is transmitted from the lifter body 33 to the nut member 46. At this time, the direction of the rotational force transmitted to the nut member 46 is clockwise as viewed from above. The winding direction of the male screw 47 and the female screw 45 is the direction in which the adjusting screw 48 protrudes downward from the nut member 46 when the nut member 46 is rotated clockwise as viewed from above, that is, the direction of the left screw (See FIG. 8).

When the camshaft 31 is rotated by the operation of the engine and the cam crest portion 32a of the cam 32 pushes down the lifter body 33, the valve 36 is separated from the valve seat 40 and the intake port 35 is opened. At this time, although the axial load in the pushing direction is applied to the adjusting screw 48, the pressure side flank 51 of the male screw 47 is received by the pressure side flank 51 of the female screw 45, and the axial position of the adjusting screw 48 is fixed. .

When the cam 32 further rotates and the cam crest 32a passes the position of the lifter body 33, the valve stem 37 is raised by the urging force of the valve spring 39, the valve 36 is seated on the valve seat 40, and the intake port 35 is close.

Strictly speaking, when the cam crest portion 32a of the cam 32 pushes down the lifter body 33, a slight slip occurs between the pressure side flanks 51, 51 of the male screw 47 and the female screw 45, and the adjustment screw 48 slightly moves in the pushing direction due to the slip. However, when the cam crest portion 32a passes the position of the lifter body 33 and the load in the pushing direction is released, the adjustment screw 48 moves in the protruding direction by the load applied from the return spring 49, Return to position.

As in the first embodiment, when the gap between the constituent members of the valve operating device changes due to thermal expansion of the valve operating device or the like, the adjusting screw 48 rotates in the nut member 46 according to the change in the clearance. By moving in the axial direction, the gap between the constituent members of the valve gear is adjusted.

In this valve operating apparatus, the center of the cam 32 in the width direction is shifted from the center of the lifter body 33 so that a rotational force is generated in the lifter body 33, and the direction of the rotational force transmitted from the lifter body 33 to the lash adjuster 44 is changed. Since the adjusting screw 48 protrudes from the nut member 46, there is no problem of valve lift loss due to the rotational force transmitted from the lifter body 33 to the lash adjuster 44, and a stable valve lift amount can be obtained. it can. Further, since a spacer member for blocking transmission of the rotational force from the lifter body 33 to the lash adjuster 44 is not necessary, the structure is simple and the cost is low.

In the above embodiment, the valve operating device in which the male screw 47 and the female screw 45 incorporate the left-handed lash adjuster 44 has been described. However, as shown in FIGS. 9 and 10, the male screw 47 and the female screw 45 have the right-handed lash adjuster 44. It can also be incorporated. In this case, the direction of deviation between the lifter body 33 and the cam 32 is a direction in which the direction of the rotational force generated in the lifter body 33 is counterclockwise when viewed from above.

When the male screw 47 and the female screw 45 are a right-handed lash adjuster 44 and the male screw 47 and the female screw 45 are a left-handed lash adjuster 44, the right-handed lash adjuster 44 and the left-handed screw lash are used when assembling the valve gear. There is a risk that the adjuster 44 may be mistakenly assembled. Therefore, it is preferable to unify the winding directions of the male screw 47 and the female screw 45 of each lash adjuster 44 on the intake side. The same applies to the exhaust side. In this case, the size or shape of the lifter body 33 is made different between the intake side and the exhaust side, and the winding direction of the screw of the lash adjuster 44 on the intake side is opposite to the winding direction of the screw of the lash adjuster 44 on the exhaust side. You can also

1 Camshaft 2 Tappet 2a Cam sliding contact surface 4 Rocker arm 5 Push rod 8 Valve 9 Valve stem 15 Cam 16 Rush adjuster 17 Female thread 18 Nut member 19 Male thread 20 Adjusting screw 21 Return spring 28 Pressure side flank 29 Play side flank 31 Cam shaft 32 Cam 33 Lifter body 34 Cylinder head 36 Valve 37 Valve stem 41 Guide hole 42 Tube portion 43 End plate 43a Cam slide contact surface 44 Rush adjuster 45 Female screw 46 Nut member 47 Male screw 48 Adjust screw 49 Return spring 51 Pressure side flank 52 Play side flank

Claims

A cam shaft (1) that is rotationally driven, a cam driven member (2) that reciprocates in contact with the cam (15) of the cam shaft (1), and a cam driven member (2) from the cam (15). And a lash adjuster (16) provided in the middle of the power transmission path for transmitting the valve opening / closing force to the valve stem (9) of the intake valve (8) or the exhaust valve (8) via the lash adjuster (16 ) Includes a nut member (18) having an internal thread (17) on the inner periphery, an adjustment screw (20) having an external thread (19) threadedly engaged with the female thread (17), and an adjustment screw (20) thereof. In a valve operating apparatus for an internal combustion engine comprising a return spring (21) that urges the nut in a direction protruding from the nut member (18),
The cam driven member (2) is arranged so that the center of the cam (15) in the width direction is shifted from the center of the cam driven member (2) so that the cam driven member (2) generates a rotational force. The power transmission path is configured to transmit the male screw (19) so that the direction of the rotational force transmitted to the lash adjuster (16) is the direction in which the adjust screw (20) protrudes from the nut member (18). ) And the direction of winding of the female screw (17) are selected.
The cam follower member is a tappet (2) slidably supported up and down having a cam sliding contact surface (2a) in sliding contact with the cam (15) at the lower end, and a central portion above the tappet (2). Is provided with a rocker arm (4) supported so as to be able to swing, and a push rod (5) for transmitting power from the tappet (2) to push up one end of the rocker arm (4) is provided. 2. The valve operating apparatus for an internal combustion engine according to claim 1, wherein the valve stem (9) is pushed down at the other end of the internal combustion engine.
The lash adjuster (16) has a protruding direction from the nut member (18) of the adjustment screw (20) at the end of the rocker arm (4) on the side pushed up by the push rod (5). The valve gear for an internal combustion engine according to claim 2, wherein the protruding end of the adjustment screw (20) from the nut member (18) is brought into contact with the upper end of the push rod (5).
The cam follower includes a cylindrical portion (42) supported by a guide hole (41) formed in the cylinder head (34) so as to be slidable up and down, and an end plate provided at an upper end of the cylindrical portion (42). (43) is provided with a cam sliding contact surface (43a) slidably contacting the cam (32) on the upper surface of the end plate (43), and the valve in the cylindrical portion (42). The valve operating apparatus for an internal combustion engine according to claim 1, wherein an upper end of the stem (37) is disposed, and the cam (32) pushes down the valve stem (37) via a lifter body (33).
The lash adjuster (44) is assembled to the lower surface of the end plate (43) so that the protruding direction of the adjust screw (48) from the nut member (46) is downward, and the nut of the adjust screw (48). The valve operating apparatus for an internal combustion engine according to claim 4, wherein a protruding end from the member (46) is brought into contact with an upper end of the valve stem (37).
The male screw (19) and the female screw (17) of the lash adjuster (16) are pressure-side flank that receives pressure when an axial load is applied in the direction of pushing the adjusting screw (20) into the nut member (18). The valve gear for an internal combustion engine according to any one of claims 1 to 5, wherein the flank angle of 28) is a sawtooth screw larger than the flank angle of the play side flank (29).
The internal combustion engine according to any one of claims 1 to 6, wherein the return spring (49) is a compression coil spring that applies an axial force in a direction protruding from the nut member (46) to the adjustment screw (48). Valve operating device.
The valve according to any one of claims 1 to 6, wherein the return spring (21) is a torsion spring that applies a rotational force in a direction protruding from the nut member (18) to the adjustment screw (20). apparatus.
A plurality of intake valves (8) and exhaust valves (8) are provided, and the winding directions of the male screw (19) and female screw (17) of each lash adjuster (16) corresponding to the intake valve (8) are adjusted. In the internal combustion engine according to any one of claims 1 to 8, wherein the screw winding directions of the male screw (19) and the female screw (17) of each lash adjuster (16) corresponding to the exhaust valve (8) are unified. Valve operating device.
The winding direction of the male screw (19) and female screw (17) of each lash adjuster (16) corresponding to the intake valve (8), and the male screw (16) of each lash adjuster (16) corresponding to the exhaust valve (8) The valve gear for an internal combustion engine according to claim 9, wherein the winding direction of the screw of 19) and the female screw (17) is opposite.