JPH09119304A - Rocker arm with cam follower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it difficult to generate failure such as seizure and easy to follow the outer periphery of a three-dimensional cam for the outer periphery of a cam follower. SOLUTION: This rocker arm 1 oscillates around a pivoted shaft inserted in a through hole 2. Inside a storage recessed part 4 formed in the middle of the rocker arm 1, a holding case 7 is supported so as to oscillate around locking protruding parts 8, 8 formed at both ends on the front/rear side of the holding case 7. A cam follower 13 is rotatingly-supported around the middle part of a supporting shaft 11 supported by the holding case 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The rocker arm with a cam follower according to the present invention is used in a state of being incorporated in a valve opening / closing device of an engine having a variable valve timing mechanism.

[0002]

2. Description of the Related Art In order to maximize the performance of an engine from low rotation speed to high rotation speed, the opening / closing timing and lift amount (opening degree) of the intake valve and the exhaust valve at low speed and high speed Is changing in some car engines. Variable valve timing mechanisms used for such purposes include, for example, Japanese Patent Laid-Open No. 3-160104, Japanese Utility Model Laid-Open No. 60-65307, and Japanese Utility Model Laid-Open No. 1-159.
Nos. 106 to 7 describe a structure using a cam whose profile continuously changes in the axial direction.

In the case of the variable valve timing mechanism using such a cam, the cam and the rocker arm are relatively displaced in the axial direction according to the rotation speed of the engine. As a result, on the outer peripheral surface of the cam, the profile of the portion of the outer peripheral surface of the cam follower (roller) rotatably supported by the rocker arm changes, and the opening / closing timing of the valve driven according to the rotation of the cam and Lift amount changes.
That is, the cam rotates together with the cam shaft, and the rocker arm reciprocally swings about a pivot axis arranged in parallel with the cam shaft as the outer peripheral surface of the cam follower follows the outer peripheral surface of the cam. When the cam and the rocker arm are relatively displaced in the axial direction to change the outer peripheral surface shape (cam profile) of the cam that the cam follower follows, the opening / closing timing of the valve and the lift amount change.

In the case of the variable valve timing mechanism constructed and operated as described above, the rotation center axis of the camshaft and a part of the outer peripheral surface of the cam in the circumferential direction are not parallel to each other. Therefore, unless some measures are taken, the outer peripheral surface of the cam follower and a part of the outer peripheral surface of the cam in the circumferential direction come into partial contact. When such a one-sided contact occurs, an excessive surface pressure acts on a part of the outer peripheral surface of the cam follower and the cam, which may cause abnormal wear such as early peeling or a failure such as seizure. Increase. Especially in recent engines, it is considered that the cam profile is changed more complicatedly in the three-dimensional direction in order to improve the engine performance (torque at each rotation speed, fuel consumption rate, etc.). There is. In the case of a variable valve timing mechanism incorporating a cam having such a complicated outer peripheral surface shape, the above-mentioned problems become more prominent.

On the other hand, the above-mentioned actual Kaihei 1-151010
Japanese Unexamined Patent Publication (Kokai) No. 7 describes a structure in which an aligning sleeve is provided between the inner peripheral surface of the cam follower and the outer peripheral surface of the pivot. The inner peripheral surface of the cam follower is a spherical concave surface, and the outer peripheral surface of the pivot is a spherical convex surface. I am making it. Therefore, even when the outer peripheral surface of the cam follower is brought into contact with the outer peripheral surface of the cam whose profile in the axial direction continuously changes, the outer peripheral surface of the cam follower is almost the entire width of the outer peripheral surface of the cam. Abut substantially evenly.

[0006]

However, the actual Kaihei 1-
Due to the structure described in Japanese Patent No. 159107, when the cam follower is provided with self-centering property, it becomes difficult to lubricate the sliding surface between the inner peripheral surface of the cam follower and the outer peripheral surface of the aligning sleeve. Seizure easily occurs between both peripheral surfaces. That is, during operation of the engine, the cam follower swings while rotating with respect to the centering sleeve.
In such a state, an oil film is hard to be formed between the both peripheral surfaces, and the above-mentioned seizure is likely to occur. The rocker arm with a cam follower of the present invention is invented in order to eliminate the above-mentioned inconvenience.

[0007]

A rocker arm with a cam follower according to the present invention, like the rocker arm with a cam follower of the related art, has a rocker arm which is swingable and displaceable, and a support supported by a part of the rocker arm. Axis and
A cam follower rotatably supported around the support shaft is provided. The cam follower is used in a state in which the outer peripheral surface of the cam is brought into contact with the outer peripheral surface of the cam whose profile in the axial direction continuously changes.

Particularly, in the rocker arm with cam follower of the present invention, both ends of the support shaft are swingably supported with respect to the rocker arm so that the outer periphery of the cam follower is irrespective of the rotation of the cam. A centering function is provided to evenly abut the surface and the outer peripheral surface of the cam.

[0009]

In the rocker arm with cam follower of the present invention constructed as described above, the moment the outer peripheral surface of the cam follower contacts a portion of the outer peripheral surface of the cam that is not parallel to the center of rotation of the cam shaft. When the support shaft swings, the center of the support shaft and the outer peripheral surface of the cam are parallel to each other.
Therefore, the outer peripheral surface of the cam follower rotatably supported by the rocker arm by the support shaft abuts the outer peripheral surface of the cam evenly over its entire width. As a result,
Excessive surface pressure does not act on the contact portion between the outer peripheral surface of the cam follower and the outer peripheral surface of the cam, the wear life of both peripheral surfaces can be secured, and troubles such as seizure can be prevented.

In particular, in the case of the rocker arm with a cam follower according to the present invention, the cam follower is rotatably supported on the support shaft. Therefore, lubrication of the rotary support portion between the cam follower and the support shaft is easy, and a failure such as seizure is unlikely to occur in the rotary support portion. Further, it suffices that the support shaft is swingably supported by the rocker arm. Therefore, it is easy to lubricate the rocking support portion between the support shaft and the rocker arm, and the rocking support portion is less likely to suffer a failure such as seizure.

[0011]

1 to 5 show a first embodiment of the present invention. The rocker arm 1 is made by forging a metal material such as steel, aluminum alloy, and magnesium alloy. A circular through hole 2 is formed at one end (the right end in FIGS. 1 to 3) of the rocker arm 1.
In the width direction (diagonal left and right direction in FIG. 1, vertical direction in FIG. 2, FIG.
It is formed so as to penetrate in the front and back direction. A pivot shaft (not shown) is inserted into the through hole 2, and the pivot shaft is supported and fixed to the cylinder head of the engine. Therefore, the rocker arm 1 is swingably displaceable around the pivot. The base end of the air supply valve or the exhaust valve is a pressing portion 3 formed at the other end of the rocker arm 1 (the left end in FIGS. 1 to 3).
1 is brought into contact with one surface (the lower surface in FIGS. 1 and 3 and the rear surface in FIG. 2), and the air supply port or the exhaust port is opened / closed as the rocker arm 1 swings. In the case of a so-called end pivot type rocker arm in which one end of the rocker arm 1 is brought into contact with the end of the lash adjuster and the other end is brought into contact with the base end of the air supply valve or the exhaust valve, The through hole 2 is omitted. Of course, the present invention can also be applied to such an end pivot type rocker arm.

On the other surface of the intermediate portion of the rocker arm 1 (the upper surface in FIGS. 1 and 3 and the front surface in FIG. 2), a storage recess 4 and locking recesses 5 and 5 continuous from both ends of the storage recess 4 are formed. Is formed. The back end surfaces of these locking recesses 5 and 5 are concave surfaces 6 and 6 having a substantially quarter spherical shape. Further, the rear end surface of the storage recess 4 is also a concave surface having an arcuate cross section.

A holding case 7 is provided inside the storage recess 4.
Is stored and held so that it can be swung slightly. The holding case 7 is formed by die-casting a metal material such as an aluminum alloy or a magnesium alloy, or by injection-molding a high-performance resin having heat resistance (see FIG. 1,
3 is formed, the front side of FIG. 2, the left side of FIG. 4) is formed in a box shape having an opening. Locking projections 8, 8 are formed concentrically on the outer surfaces of both ends of the housing 10 formed in the center of the holding case 7. Width W ₈ of the locking portions 8 is smaller than the width W ₅ of the respective engaging recesses _{5,5 (W 8 <W 5)} . Further, the outer peripheral surface of the tip end portion of each of the locking convex portions 8 is a quarter spherical convex surface 9, 9. The radius of curvature of each of these convex surfaces 9, 9 is
The radius of curvature of each of the concave surfaces 6, 6 is made smaller. In the state where the storage portion 10 of the holding case 7 is inserted into the storage concave portion 4, the respective convex surfaces 9 and 9 are formed into the concave surfaces 6 and 6.
Abut. Then, in this state, the holding case 7 is attached to the rocker arm 1 by the pair of locking projections 8,
8 is supported so as to be slightly swingable around a contact portion between the concave surface 8 and each of the concave surfaces 6, 6. Since the rear end surface of the storage concave portion 4 is a semi-cylindrical concave surface, and the outer peripheral surface of the distal end portion of the storage portion 10 is a convex surface having an arcuate cross section, the holding case 7 is somewhat centered around the locking convex portions 8 and 8. Even if it swings, the inner surface of the storage recess 4 does not interfere with the inner surface of the storage portion 10.

A support shaft 11 is provided in the storage portion 10 of the holding case 7, and a pair of support walls 1 constituting the storage portion 10.
It is supported so that it can be hung between two and twelve. The cam follower 13 is provided around the middle portion of the support shaft 11.
Are rotatably supported via a needle bearing 14. Support shaft 11 which is the center of rotation of the cam follower 13
Is parallel to the pivot inserted through the through hole 2 when the holding case 7 is in the neutral position. However,
When the holding case 7 swings around the locking projections 8 and 8, the support shaft 11 and the pivot shaft have a twisted positional relationship. That is, in the rocker arm with a cam follower of the present embodiment, both ends of the support shaft 11 are swingably supported by the rocker arm 1 via the holding case 7 so that the rocker arm 1 can be axially moved (left and right in FIG. 5). Despite the rotation of the cam 15 whose profile (direction) changes continuously, it has a centering function to evenly contact the outer peripheral surface of the cam follower 13 and the outer peripheral surface of the cam 15.

A rocker arm with a cam follower according to this embodiment has a cam follower 1 as shown in FIG.
It is incorporated and used in a valve opening / closing device of an engine provided with a variable valve timing mechanism in a state where the outer peripheral surface of 3 is in contact with the outer peripheral surface of the cam 15. In the case of the rocker arm with a cam follower of the present embodiment configured as described above and incorporated in the valve opening / closing device in this way, the outer peripheral surface of the cam follower 13 is a part of the outer peripheral surface of the cam 15 and is the center of rotation of the cam shaft 16. At the moment of contact with a portion that is not parallel to, the support shaft 11 swings together with the holding case 7, so that the center of the support shaft 11 and the outer peripheral surface of the cam 15 are parallel to each other.

That is, the profile of the outer peripheral surface of the cam 15 to which the rocker arm with a cam follower of the present invention faces is shown in FIG.
As shown in FIG. 5, the cam shaft 16 continuously changes in the axial direction (the horizontal direction in FIG. 5). To close the valve,
As shown in FIG. 5 (A), while the outer peripheral surface of the cam follower 13 is in contact with a part of the outer peripheral surface of the cam 15 which is parallel to the rotation center and has a small diameter, the support shaft 11 and the cam shaft are in contact with each other. While the center of rotation of 16 remains parallel, the cam follower 13 rotates about the support shaft 11 as the cam 15 rotates.

On the other hand, in order to open the valve, as shown in FIG.
As shown in (B), attach the outer peripheral surface of the cam follower 13 to the cam 1
When a part of the outer peripheral surface of 5 is brought into contact with a large-diameter portion that is not parallel to the rotation center, the holding case 7 supporting the support shaft 11 swings around the locking projections 8 and 8. To do. Then, the support shaft 11 is inclined with respect to the rotation center by the same angle θ as the inclination angle θ between the outer peripheral surface of the cam 15 and the rotation center of the cam shaft 16. The cam follower 13
In this way, the support shaft 11 tilted by the angle θ is rotated. Therefore, the outer peripheral surface of the cam follower 13 abuts the outer peripheral surface of the cam 15 evenly over its entire width. As a result, the outer peripheral surface of the cam follower 13 and the cam 1
Excessive surface pressure does not act on the contact portion of the outer peripheral surface of the outer peripheral surface 5 with the outer peripheral surface of the inner peripheral surface of the outer peripheral surface 5, and the wear life of these peripheral surfaces can be secured, and the occurrence of a failure such as seizure can be prevented.

Particularly, in the case of the rocker arm with a cam follower of the present invention, the cam follower 13 is supported by the needle shaft 14 on the support shaft 11 so as to be rotatable only. Therefore, lubrication of the needle bearing 14 is easy, and failure such as seizure is unlikely to occur in the rotation support portion. The holding case 7 supporting the support shaft 11 is
It is sufficient if the rocker arm 1 is swingably supported. Therefore, it is easy to lubricate the abutting portions of the locking concave portions 5 and 5 and the locking convex portions 8 and 8 which are the rocking supporting portions of the support shaft 11 and the rocker arm 1, and the rocking is performed. It is unlikely that a failure such as seizure will occur on the support. If the both concave surfaces 6, 6 are spherical concave surfaces having a single center, the degree of freedom of displacement of the holding case 7 and the support shaft 11 supported by the holding case 7 can be increased. For example,
Even when the outer peripheral surface of the cam 15 has a complicated shape in which the profile of the outer peripheral surface of the cam 15 changes in the circumferential direction at the same time as the axial direction, the support shaft 11 is made parallel to the outer peripheral surface of the cam 15 and the cam follower. The outer peripheral surface of 13 and the outer peripheral surface of the cam 15 can be evenly contacted.

Next, FIGS. 6 to 8 show a second embodiment of the present invention. In the case of this embodiment, a holding hole 17 is formed in the intermediate portion of the rocker arm 1, and the support shaft 11 is swingably supported inside the holding hole 17. For this reason, the left and right sides of the inner peripheral surface of the holding hole 17 (diagonally up and down in FIG. 6, up and down in FIGS. 7 and 8) are spherical concave surfaces 18 and 18 concentric with each other. In addition, the front and rear of the holding hole 17 (oblique right and left in FIG. 6,
Parts on both sides (left and right in FIG. 7) apart from the spherical concave surfaces 18, 18 are processed into a shape that does not interfere with the cam follower 13. Both end surfaces of a support shaft 11 for supporting the cam follower 13 with respect to the rocker arm 1 are spherical convex surfaces 1
It is 9 and 19. The radius of curvature of the spherical convex surfaces 19, 19 is the same as or slightly smaller than the radius of curvature of the spherical concave surfaces 18, 18. The length dimension of the support shaft 11 (distance between the tips of the spherical convex surfaces 19, 19) is smaller than the interval between the spherical concave surfaces 18, 18 (= twice the radius of curvature of the spherical concave surfaces 18, 18). Small. Therefore, when the support shaft 11 is bridged between the pair of spherical concave surfaces 18, 18, the support shaft 11 is swingably supported inside the holding hole 17.

A cam follower 13 is rotatably supported via a needle bearing 14 around the intermediate portion of the support shaft 11 which is structured as described above and is swingably supported inside the holding hole 17. The support shaft 11, which is the center of rotation of the cam follower 13, can be slightly oscillated and displaced in any direction around a neutral position that is parallel to the pivot inserted through the through hole 2 at the end of the rocker arm 1. . That is, in the rocker arm with a cam follower of the present embodiment, both ends of the support shaft 11 are directly swingably supported with respect to the rocker arm 1 so that the profile in the axial direction continuously changes. Regardless of the rotation of the cam 15 (FIG. 5), the centering function is provided so that the outer peripheral surface of the cam follower 13 and the outer peripheral surface of the cam 15 contact each other evenly.

Therefore, as in the first embodiment described above, excessive contact pressure is prevented from acting on the contact portion between the outer peripheral surface of the cam follower 13 and the outer peripheral surface of the cam 15, and both peripheral surfaces are prevented. It is possible to secure the wear life of and prevent the occurrence of failures such as seizure. Further, the needle bearing 14 only rotatably supports the cam follower 13 with respect to the support shaft 11, and
Reference numeral 1 is supported inside the holding hole 17 so as to be freely swingable. Therefore, lubrication of the rotation support portion and the swing support portion is easy, and a failure such as seizure is unlikely to occur in the rotation support portion and the swing support portion. When the structure of this embodiment is assembled, the support shaft 11 and the cam follower 13 are
Is inserted into the holding hole 17 while rotating in a direction perpendicular to the axial direction. The structure of this embodiment can also be used as an end pivot type rocker arm by omitting the through hole 2. Further, in the case of the present embodiment, since the degree of freedom of displacement of the support shaft 11 is large, the cam 15 having a complicated outer peripheral surface profile.
The outer peripheral surface of the cam follower 13 and the outer peripheral surface of the cam follower 13 can be reliably brought into contact with each other.

[0022]

Since the rocker arm with the cam follower of the present invention is constructed and operates as described above, the reliability and durability of the valve opening / closing device of the engine incorporating the variable valve timing mechanism can be improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of the present invention.

FIG. 2 is a plan view showing an assembled state.

FIG. 3 is a side view of the same.

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a schematic plan view for explaining the function of following the outer peripheral surface of the cam.

FIG. 6 is an exploded perspective view showing a second embodiment of the present invention.

FIG. 7 is a plan view showing an assembled state.

FIG. 8 is a sectional view taken along line BB of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rocker arm 2 through-hole 3 pressing part 4 storage recess 5 locking recess 6 concave surface 7 holding case 8 locking projection 9 convex surface 10 storage part 11 support shaft 12 support wall 13 cam follower 14 needle bearing 15 cam 16 camshaft 17 holding hole 18 spherical concave surface 19 spherical convex surface

Claims (1)

[Claims] 1. A rocker arm swingably displaceable, a support shaft supported by a part of the rocker arm, and a cam follower rotatably supported around the support shaft, and an outer peripheral surface of the cam follower. In a rocker arm with a cam follower that is used in a state of being brought into contact with the outer peripheral surface of the cam whose profile in the axial direction changes continuously,
By supporting both ends of the support shaft with respect to the rocker arm so as to be swingable, a centering function for evenly contacting the outer peripheral surface of the cam follower and the outer peripheral surface of the cam regardless of the rotation of the cam is provided. A rocker arm with a cam follower characterized by having it.