JP2002106309A - Roller type cam follower device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roller-type cam follower device capable of reducing the abrasion of a contact face of a roller and a cam lobe. SOLUTION: The crowning 53 continuously changing its radius of curvature, is applied onto an outer peripheral face 51 of the roller 45. The crowning 53 can be comparatively easily obtained by utilizing, for example, a logarithmic curve or the like. Both end faces 55 of the roller 45, and the crowning 53 are connected with continuous curvature, and circular flanges 57 having an outer diameter smaller than the roller are projected from both end faces 55 of the roller 45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller type cam follower device constituting a valve train of an internal combustion engine, and more particularly, to a technique for suppressing wear of a contact surface between a roller and a cam lobe.

[0002]

2. Description of the Related Art A roller type cam follower having a roller which comes into contact with a cam lobe is often used in a valve mechanism of an internal combustion engine in order to suppress power loss due to friction with a cam shaft and wear of a contact surface. Generally, the outer peripheral surface of a roller used in a roller type cam follower is crowned so that its axial cross section (profile) has a middle height in order to reduce the contact surface pressure with the cam lobe. The type of crowning formed on the roller is shown in FIG.
There are known a single arc crowning as shown in FIG. 7 and a partial crowning as shown in FIG. The former (first
In the prior art), a single arc crowning 61 having a predetermined radius of curvature R1 (for example, 600 to 3000 mm) is applied to the entire outer peripheral surface 51 of the roller 45, and the latter (the second conventional art) is applied to the center of the outer peripheral surface 51 of the roller 45. A predetermined radius of curvature R2 (for example, 600
(5500 mm) arc crowning 65 is provided. 1 and 2, reference numeral 5 denotes a cam lobe.

[0003]

By the way, the above-mentioned 2
Each type of crowned roller has its own problems. That is, in the single-arc crowning type of the first prior art, the fluctuation of the contact surface pressure P caused by the inclination of the roller 45 with respect to the cam lobe 5 (FIG. 8 shows the surface pressure distribution when facing directly, and FIG. Surface pressure distribution) is relatively small, but the effective contact area (contact ellipse) with the cam lobe 5 is extremely small. Therefore, the maximum contact surface pressure between the cam lobe 5 and the roller 45 is constantly increased, and the abrasion of the contact portion between the two tends to progress. Further, in the partial crowning type of the second prior art, the maximum contact surface pressure can be reduced normally because the effective contact area is large (FIG. 10 shows the surface pressure distribution when facing directly). On the other hand, when the roller 45 is greatly inclined, the cylindrical portion 63 and the arc crowning 65
The contact surface pressure P locally increases at the joint Q between
The surface pressure distribution at the time of inclination is shown in FIG.
There is a possibility that the surface may be worn or damaged.

In order to solve such a problem, Japanese Utility Model Application Laid-Open No.
In Japanese Patent Application Publication No. 36005/1995, a composite arc crowning type roller (third prior art) as shown in FIG. 12 is proposed. In this method, a central circular arc crowning 71 having a relatively large radius of curvature R3 is applied to a central portion of the roller 45, and an end circular arc crowning 73 having a relatively small radius of curvature R4 is applied to an end of the central circular arc crowning 71. Things. However, also in the roller 45 of the third prior art, the contact surface pressure P locally increases at the boundary R (ie, the point of change in curvature) between the center arc crowning 71 and the end arc crowning 73 (see FIG. 13). In particular, when the roller 45 is greatly inclined with respect to the cam lobe 5 (FIG. 14 shows the surface pressure distribution when inclined), the surface of the cam lobe 5 and the roller 45 are worn or damaged. May be caused.

On the other hand, no matter which crowning is applied, since the chamfer 81 is formed between the outer peripheral surface 51 and the end surface 55 of the roller 45, the effective contact length with the cam lobe 5 is reduced. Also, crowning 61, 65, 7
Since the curvature greatly changes at the boundary S between the edge 3 and the chamfer 81, when the roller 45 is greatly inclined with respect to the cam lobe 5, as shown in FIG. 9, FIG. 11, and FIG. Thus, the cam lobe 5 may be damaged.
Furthermore, in such a site that requires crowning,
Since the thrust force is generated on the roller 45 due to the large inclination, friction between the tappet and the rocker arm holding the roller 45 increases, and the end face of the roller 45 and the holding portion such as the tappet may be worn. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a roller-type cam follower device that suppresses abrasion of a contact surface between a roller and a cam lobe.

[0006]

According to the present invention, there is provided a roller-type roller having a roller interposed between a camshaft of an internal combustion engine and an intake / exhaust valve and rotatably contacting a cam lobe of the camshaft. A cam follower device, wherein the outer peripheral surface of the roller is subjected to crowning of continuously changing curvature, and both end surfaces of the roller and the crowning are connected with a continuous curvature, and the outer diameter of the roller is attached to the both end surfaces. We propose one with a smaller flange.

In this cam follower device, since the curvature of the crowning changes continuously, the surface pressure does not locally increase when the cam follower comes into contact with the cam lobe. Further, since both end surfaces of the roller and the crowning are connected at a continuous curvature, even when the roller is greatly inclined, edge load unlike the conventional device does not occur. Further, since flanges smaller than the outer diameter of the roller are protrudingly provided on both end surfaces of the roller, even if a thrust force is generated on the roller due to its inclination, an increase in friction between the tappet and the rocker arm is suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a roller tappet of an OHV engine will be described with reference to the drawings. FIG. 1 is a partial cross-sectional side view of the valve train according to the embodiment, and FIG. 2 is a cross-sectional view along AA in FIG. As shown in these figures, the valve train of the present embodiment includes a roller tappet 7 slidably held by a cylinder block 1 and driven by a cam lobe 5 of a camshaft 3, and a valve sleeve on a cylinder head 11. An intake (or exhaust) valve 15 slidably held through a push rod 13, a push rod 21 engaged with the upper end of the roller tappet 7,
The rocker arm 23 is rotatably supported by the rocker shaft 23 and transmits the movement of the push rod 21 to the intake valve 15. In FIG. 1, reference numeral 27 denotes a combustion chamber.

The cylinder block 1 has a detent bolt 3
1 is screwed in, and a shank portion of a detent bolt 31 is inserted into a long hole 33 formed in the roller tappet 7 in order to prevent the rotation of the roller tappet 7. Also,
A valve spring 37 is interposed between the upper valve seat 35 fixed to the upper end of the intake valve 15 and the cylinder head 11, and the valve spring 37 urges the intake valve 15 in the closing direction. A member indicated by reference numeral 39 in FIG. 1 is an adjusting screw mounted on the push rod 21 side of the rocker arm 25, and is used for adjusting tappet clearance.

The roller tappet 7 has a cylindrical tappet body 41 and a roller shaft 4 at the lower end of the tappet body 41.
The roller 45 is rotatably held through the roller 3, and the outer peripheral surface of the roller 45 is in rolling contact with the cam lobe 5. Note that the roller shaft 43 is arranged in parallel with the camshaft 3. Reference numeral 47 in FIG. 2 denotes an oil hole, and lubricating oil is supplied from the tappet body 41 to the roller shaft 43 through the oil hole 47.

In the case of this embodiment, the roller 45 has a structure shown in FIG.
As shown in the enlarged view of the main part, a crowning 53 whose curvature continuously changes is applied to the outer peripheral surface 51. The crowning 53 can be relatively easily obtained by using, for example, a logarithmic curve or the like. Further, both end faces 55 of the roller 45 and the crowning 53 are connected at a continuous curvature, while a circular flange 57 having a diameter smaller than the outer diameter of the roller is projected from the both end faces 55 of the roller 45.

Hereinafter, the operation of the present embodiment will be described. When the engine starts, a crankshaft (not shown) rotates, and the camshaft 3 also rotates at half the rotational speed of the crankshaft. Then, the roller tappet 7 moves up and down according to the profile of the cam lobe 5, and the push rod 2
The movement is transmitted to the upper end of the intake valve 15 via the lock valve 1 and the rocker arm 25. Then, the intake valve 15
Lifts at a predetermined timing against the spring force of the valve spring 37, and fresh air is sucked into the combustion chamber 27 from the intake pipe (not shown) under a negative pressure.

The roller 45 of the roller tappet 7 is
When the intake valve 15 is lifted, it rolls in a state of being pressed against the cam lobe 5, and contacts the outer peripheral surface 51 of the roller 45 with the cam lobe 5.
And a relatively large compressive stress is generated between them. However, in the roller 45 of the present embodiment, the outer peripheral surface 51 is provided with the crowning 53 whose curvature continuously changes, so that a portion where the contact surface pressure P locally increases as shown in FIG. It does not appear.

Further, the roller 45 may be greatly inclined with respect to the cam lobe 5 for some reason. In the case of the present embodiment, the both end surfaces 55 of the roller 45 and the crowning 53 are connected with a continuous curvature. As shown in FIG. 5, there is no portion where the contact surface pressure P locally increases. As a result, even if the operation is performed for a long period of time, the rollers 45 and the cam lobes 5 are not abnormally worn or damaged, and the life of the apparatus can be greatly improved.

Further, since flanges 57 smaller than the outer diameter of the roller are projected from both end surfaces 55 of the roller 45,
Even if the roller 45 is greatly inclined with respect to the cam lobe 5, the friction between the tappet main body 41 and the roller 45 is extremely small, and the wear of the sliding contact portion is suppressed to a negligible level.

The description of the specific embodiment has been completed.
Aspects of the present invention are not limited to this embodiment.
For example, in the above embodiment, the present invention is applied to a roller tappet of an OHV engine, but may be applied to a roller rocker arm of an OHC engine. The shape of the crowning applied to the outer peripheral surface of the roller is not limited to the shape using the logarithmic curve described above, but may be any shape as long as the curvature continuously changes. In addition, the specific configuration of the valve operating mechanism, such as interposing a needle bearing between the roller and the roller pin or incorporating a hydraulic lash adjuster, can be appropriately changed without departing from the gist of the present invention.

[0017]

As described above, according to the present invention, there is provided a roller type cam follower device having a roller interposed between a camshaft of an internal combustion engine and an intake / exhaust valve, and which is in contact with a cam lobe of the camshaft. The outer peripheral surface of the roller is continuously crowned so that the curvature changes, and both end surfaces of the roller and the crowning are connected with a continuous curvature, and the both end surfaces have a flange smaller than the outer diameter of the roller. As a result, the contact pressure does not rise locally when the cam follower comes into contact with the cam lobe, making it difficult for the rollers and the cam lobe to be worn or damaged. The increase in friction between them and the wear of the sliding contact portion are suppressed.

[Brief description of the drawings]

FIG. 1 is a side view showing a valve train according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is an enlarged view of a main part of a roller in the embodiment.

FIG. 4 is a diagram illustrating a surface pressure distribution of a roller at the time of facing directly in the embodiment.

FIG. 5 is a diagram showing a surface pressure distribution of a roller at the time of inclination in the embodiment.

FIG. 6 is an enlarged view of a main part showing a roller of the first related art.

FIG. 7 is an enlarged view of a main part showing a roller of the second conventional technique.

FIG. 8 is a diagram showing a surface pressure distribution of a roller when facing directly in the first prior art.

FIG. 9 is a diagram showing a surface pressure distribution of a roller at the time of inclination in the first prior art.

FIG. 10 is a diagram showing a surface pressure distribution of a roller when facing directly in the second related art.

FIG. 11 is a diagram showing a surface pressure distribution of a roller at the time of inclination in the second conventional technique.

FIG. 12 is an enlarged view of a main part showing a roller of the third related art.

FIG. 13 is a diagram showing a surface pressure distribution of a roller when facing directly in the third related art.

FIG. 14 is a diagram showing a surface pressure distribution of a roller at the time of inclination in the third conventional technique.

[Explanation of symbols]

 3 Camshaft 5 Cam lobe 7 Roller tappet 41 Tappet body 43 Roller shaft 45 Roller 51 Outer peripheral surface 53 Crowning 55 End surface 57 Flange

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kuki 3-1-1, Hinodai, Hino-shi, Tokyo Hino Motors Co., Ltd. (72) Miki Ihara 3-1-1, Hinodai, Hino-shi, Tokyo Hino Automobile Co., Ltd. F-term (reference) 3G016 AA05 AA19 BA47 BA50 BB03 BB06 CA07 CA08 CA09 CA22 FA13 GA02 3J030 EA02 EA08 EC07

Claims (1)

[Claims] 1. A roller-type cam follower device having a roller interposed between a camshaft of an internal combustion engine and an intake / exhaust valve and rotatably contacting a cam lobe of the camshaft, wherein the roller-type follower is continuously provided on an outer peripheral surface of the roller. A roller type cam follower characterized in that a crown having a variable curvature is applied, both end faces of the roller and the crowning are connected at a continuous curvature, and flanges smaller than the outer diameter of the roller are protruded at the both end faces. apparatus.