JPH08296412A - Roller tappet - Google Patents

Abstract

PURPOSE: To reduce contact face pressure between a cam and a roller by preventing half abutting of the roller on the cam caused by misalignment between the roller of a roller tappet and the cam. CONSTITUTION: An inner roller 1A whose outer circumferential face is formed into a projecting curved face R1 with its central part set as an apex is pivotally supported in a tappet main body 4 via a roller shaft 5 and its internal and outer circumferential faces have flat faces parallel to a cam shaft 3. An outer roller 1B whose internal circumferential face is fitted in the projecting curved face R1 of the inner roller 1A and outer circumferential face abuts on the cam 2 of the cam shaft 3 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller tappet for converting rotational movement of a valve lift cam of an engine into reciprocating movement.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, a roller tappet 6 of this type has a tappet body 4 in which a roller 1 having a convex curved surface R1 having an outer peripheral surface having a central portion as an apex is rotatable via a roller shaft 5. It has a structure in which the convex curved surface R1 (crowning) of the roller 1 is in contact with the cam 2 of the cam shaft 3.

[0003]

In the conventional roller tappet 6 described above, since the contact with the cam is a point contact, stress concentration is large, and pitching or fretting occurs on the rolling contact surface. Further, when the roller shaft 5 and the cam shaft 3 of the roller tappet 6 have an error in processing or assembling with the lift amount being zero, as shown in FIG.
The roller 1 tilts to hit the cam 2 on one side (edge contact), and the tilting of the roller 1 causes a rotational force T on the tappet body 4 to increase the surface pressure of the roller end.

An object of the present invention is to provide a roller tappet which takes advantage of the rolling contact of a roller with a cam due to a convex curved surface and also realizes contact with the cam by line contact to prevent uneven contact with the cam. is there.

[0005]

The object of the present invention to achieve the above object is to provide a roller that comes into contact with a cam of a cam shaft for valve lift of an engine and that is rotated by the rotation of the cam shaft, and the roller. A roller tappet having a roller shaft pivotally supported and reciprocating by rotation of the cam shaft, wherein the cam shaft and the roller shaft are arranged in parallel with each other, and the outer peripheral surface has a central portion. An inner roller pivotally supported on the roller shaft, which is formed on a convex curved surface as an apex, and inner and outer peripheral surfaces having a plane parallel to the cam shaft, and the inner peripheral surface is fitted to the convex curved surface of the inner roller, And an outer roller having an outer peripheral surface in contact with the cam of the cam shaft.

Further, according to the present invention, there is provided a roller that abuts on a cam of a valve lift cam shaft of an engine and rotates by the rotation of the cam shaft, and a roller shaft that pivotally supports the roller. In a roller tappet having a reciprocating tappet body, wherein the cam shaft and the roller shaft are arranged in parallel with each other, an outer peripheral surface is formed into a convex curved surface having a central portion as an apex and pivotally supported on the roller shaft. The inner roller has an inner peripheral surface having a plane parallel to the cam shaft, and the outer peripheral surface is formed into a convex curved surface having a central portion as an apex, and the inner peripheral surface is fitted to the convex curved surface of the inner roller, And an outer roller whose surface contacts the cam of the cam shaft.

[0007]

With the above construction, the inner roller and the outer roller can be brought into rolling contact by the convex curved surface of the inner roller,
Further, the outer roller and the cam can be brought into line contact with each other, which prevents one-sided contact with the cam and reduces the contact surface pressure between the cam and the roller.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of the present invention. In FIGS. 1 and 2, 3 is a cam shaft, 2 is a cam, 6 is a roller tappet, and 4 is a tappet body.

The tappet body 4 has an inner roller 1A whose outer peripheral surface is formed into a convex curved surface R1 having a central portion as an apex.
Is rotatably supported via a roller shaft 5, and the inner roller 1A
A double roller structure in which the inner and outer peripheral surfaces of the convex curved surface R1 have planes parallel to the cam shaft 3, and the outer peripheral surface of the outer roller 1B is in contact with the cam 2 of the cam shaft 3. Is.

In the configuration of the first embodiment of the invention described above, the outer peripheral surface of the outer roller 1B having a plane parallel to the cam shaft 3 makes line contact with the cam 2 of the cam shaft 3 to prevent uneven contact with the cam 2. , The contact surface pressure between the cam 2 and the outer roller 1B is reduced.

Further, the inner roller 1A and the outer roller 1B which is fitted in contact with the convex curved surface R1 of the inner roller 1A in a plane are different in rotational peripheral speed, and as shown in FIG. 3, the apex of the convex curved surface R1 depends on the relative speed. The Hertzian stress PV (P = stress, V = slip velocity) at the point is reduced to prevent the occurrence of pitching and fretting on the rolling contact surface.

4 and 5 show a second embodiment of the present invention. The second embodiment is basically the same as the double roller structure of the first embodiment. In the second embodiment, the outer peripheral surface of the inner roller 1A is fitted with the inner peripheral surface of the outer roller 1C having a flat inner peripheral surface and the outer peripheral surface having a convex curved surface R2.

In this case, there are two convex curved surfaces R1 (crowning) on the outer periphery of the inner roller 1A and convex curved surface R2 (crowning) on the outer peripheral surface of the outer roller 1C.
Although the radius of curvature of crowning (R400 to 600 mm) by one roller 1 shown in FIG.
The radius of curvature (R1000 to 1500 mm) of the convex curved surface R1 on the outer periphery of A and the convex curved surface R2 on the outer peripheral surface of the outer roller 1C can be increased, and thus the radius of curvature can be increased by reducing the amount of crowning. It is possible to reduce the contact surface pressure while lowering the Hertzian stress PV (P = stress, V = slip velocity).

FIG. 6 shows a third embodiment of the present invention. The third embodiment is basically the same as the double roller structure of the second embodiment. In the third embodiment, the outer peripheral surface of the inner roller 1A is fitted with the inner peripheral surface of the outer roller 1C having a flat inner peripheral surface and the outer peripheral surface having a convex curved surface R2. In the example, Inner Roller 1A
The outer periphery of the supporting surface of the inner roller 1A of the roller shaft 5 that pivots is a convex curved surface R3, and the curved inner surface of the inner roller 1A is in curved contact.

In the structure of the third embodiment, in addition to the operation of the second embodiment, the one-sided contact prevention by the curved surface contact between the roller shaft 5 and the inner roller 1A is improved, and the supporting surface of the inner roller 1A of the roller shaft 5 is improved. By forming the convex curved surface R3 on the outer circumference, concave portions 7 in which lubricating oil is accumulated are formed at both ends of the roller shaft 5, and the lubricating oil accumulated in the concave portions 7 serves to prevent seizure of the roller shaft 5.

[0016]

As described above, according to the present invention, the inner roller and the outer roller have a double roller structure, and the inner roller and the outer roller have a rolling contact due to the convex curved surface of the inner roller, so that the outer roller and the cam are in line contact, and the roller tappet is provided. It absorbs the misalignment of, prevents one-sided contact with the cam, and reduces the contact surface pressure between the cam and roller.

Further, in the structure in which the outer circumference of the support surface of the inner roller of the roller shaft is made into a convex curved surface and the inner peripheral surface of the inner roller is in curved contact, the friction resistance is reduced and the lubrication accumulated in the concave portions formed at both ends of the roller shaft. Prevents seizure of the roller shaft with oil.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1;

FIG. 3 is an explanatory view of the operation of the present invention

FIG. 4 is a sectional view of a main part of a second embodiment of the present invention.

5 is a sectional view taken along line BB of FIG.

FIG. 6 is a cross-sectional view of the essential parts of a third embodiment of the present invention.

FIG. 7 is a sectional view of a main part of a conventional roller tappet.

FIG. 8 is a view showing a state in which a roller of a conventional roller tappet hits one side of a cam.

[Explanation of symbols]

 1A Inner roller 1B Outer roller 1C Outer roller 2 Cam 3 Cam shaft 4 Tappet body 5 Roller shaft 6 Roller tappet R1 Inner roller convex curved surface R2 Outer roller convex curved surface R3 Roller shaft convex curved surface

Claims (2)

[Claims] 1. A tappet that has a roller that abuts on a cam of a valve lift cam shaft of an engine and that rotates by the rotation of the cam shaft, and a roller shaft that pivotally supports the roller, and that reciprocates by the rotation of the cam shaft. A roller tappet having a main body, wherein the cam shaft and the roller shaft are arranged in parallel with each other, wherein an inner roller is formed in a convex curved surface having a central portion as an apex and pivotally supported by the roller shaft, An outer roller having an outer peripheral surface having a plane parallel to the cam shaft, the inner peripheral surface fitted to a convex curved surface of the inner roller, and the outer peripheral surface contacting a cam of the cam shaft. And Lola Tappet. 2. A tappet that has a roller that abuts on a cam of a camshaft for valve lift of an engine and that rotates by the rotation of the camshaft, and a roller shaft that pivotally supports the roller, and that reciprocates by the rotation of the camshaft. A roller tappet having a main body, wherein the cam shaft and the roller shaft are arranged in parallel with each other, wherein an inner roller is formed in a convex curved surface having a central portion as an apex and pivotally supported by the roller shaft, The outer peripheral surface has a flat surface parallel to the cam shaft, the outer peripheral surface is formed into a convex curved surface having a central portion as an apex, the inner peripheral surface is fitted to the convex curved surface of the inner roller, and the outer peripheral surface is the cam. A roller tappet, comprising an outer roller that comes into contact with a cam of a shaft.