JP2003328706A - Rocker arm and its bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rocker arm rarely generating dents on a transfer surface of a bearing outer ring acting as a cam follower and to provide a bearing of the rocker arm. <P>SOLUTION: An action part 14 operating a valve of an internal combustion engine and a roller bearing 10 in which an outer ring 22 acts as the cam follower are installed in a rockable arm body 4. The roller bearing 10 is equipped with a roller spindle 21 fit to the arm body 4; the outer ring 22; and a plurality of needle rollers 23. The material of the outer ring 22 is steel and the amount of retained austenite in the steel is specified to 8% or less. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocker arm which is swingably installed between a cam and a valve in a valve operating mechanism for driving an intake / exhaust valve of an internal combustion machine such as an automobile, and a roller serving as a cam follower thereof. It relates to bearings.

[0002]

2. Description of the Related Art In this type of rocker arm, a needle follower bearing is used as a cam follower. The bearing that serves as this cam follower is
The rocker arm is swung in contact with the rotating cam, and the shocking load due to the opening and closing of the valve that opens and closes at high speed repeatedly acts. Since the bearing outer ring, which is the cam follower of the rocker arm, is used in such a severe impact environment, the rollers tend to generate indentations, which are plastic deformations, on the rolling surface. These indentations affect the rolling life of rolling surfaces and rolling elements, that is, the rolling fatigue life, and become a factor that hinders the extension of the bearing life. Various studies have been made from the viewpoint of materials such as hardness, crystal grains, and compressive stress to reduce the indentation. However, due to various factors, we have yet to find a suitable material.

An object of the present invention is to provide a rocker arm and its bearing in which an indentation hardly occurs on the rolling surface of a bearing outer ring which is a cam follower.

[0004]

SUMMARY OF THE INVENTION A rocker arm of the present invention is a rocker in which an arm body which is swingably installed is provided with an operating portion for operating a valve of an internal combustion engine and a roller bearing whose outer ring serves as a cam follower. In the arm, the roller bearing includes a roller support shaft attached to the arm main body, an outer ring, and a plurality of needle rollers interposed between the roller support shaft and the outer ring, and the outer ring is made of steel. ,
The amount of retained austenite in this steel is 8% or less. The arm body may be pressed from a single steel plate.

The rocker arm roller bearing of the present invention is
A roller bearing comprising a roller support shaft and an outer ring, and a plurality of needle rollers interposed between the roller support shaft and the outer ring, wherein the roller support shaft is attached to a rocker arm and the outer ring serves as a cam follower. The outer ring is made of steel, and the amount of retained austenite in the steel is 8% or less.

When the amount of retained austenite in the steel of the outer ring is 8% or less, even when the hardness of the surface layer is about the same, and when various heat treatment methods are adopted,
It was confirmed by a test that an indentation is unlikely to occur on the rolling surface. That is, it was assumed that residual austenite was one of the factors influencing the susceptibility to indentation, and when the amount of retained austenite was studied, the above results were obtained. Therefore, the rolling life is excellent.
When the arm body of the rocker arm is formed by pressing a single steel plate, the rocker arm is lightweight, has a small number of processing steps, and can be manufactured at low cost. Therefore, in combination with the residual austenite amount of the outer ring that serves as the cam follower being 8% or less, a rocker arm having a long life and a light weight can be obtained at low cost.

[0007]

1 is a block diagram of a first embodiment of the present invention.
4 to FIG. This rocker arm 1
A roller bearing, which is mounted on an internal combustion engine, has an arm body 4 swingable about a predetermined swing center O, an acting portion 14 for operating a valve 3 of the internal combustion engine, and a cam follower rolling on the cam 2. And 10 are provided. Cam 2
It is driven to rotate around the support shaft 2a. Valve 3
Is movable up and down, and is urged upward by the spring member 13. The swing center O is an intermediate portion in the length direction of the arm body 4. The roller bearing 10 is attached to one end 1a of the arm body 4, and the acting portion 14 is provided to the other end 1b of the arm body 4. The action portion 14 is a component separate from the arm body 4 and has an adjuster screw portion 14a that is screwed into a screw hole 15 provided at the other end 1b of the arm body 4 and can be adjusted in and out of the arm body 4. It is installed freely.

The arm body 4 is made of a sheet metal that is pressed from a plate material such as a single steel plate, and as shown in FIG. 2, a pair of opposed side walls 5 and 5 and the opposed side walls 5 and 5. It has an inverted U-shaped cross-section with the connecting plate wall 6 connecting the upper edges. The part where the screw hole 15 of the arm body 4 is formed is
For reinforcement, a stacking piece 12 protruding from the connecting plate wall 6 is folded to form a double stacking portion. Opposing side walls 5 on both sides
Reference numeral 5 has a swinging fulcrum hole 7 into which a swinging fulcrum shaft 9 is fitted via a bush 8. The axis center of the swing fulcrum shaft 9 is the swing center O.

The roller bearing 10 comprises a roller support shaft 21 attached to the arm body 4, an outer ring 22, and a plurality of rollers 23 interposed between the roller support shaft 21 and the outer ring 22. The roller 23 is a needle roller. As shown in FIG. 3, both ends of the roller support shaft 21 are fitted into mounting holes 11 provided in the opposite side walls 5 and 5 on both sides of the arm body 4. The mounting holes 11 on both sides of the arm body 4 have countersunk portions 11a at the opening edge on the outer surface side, and plastic working portions 21a projecting to the outer diameter side are provided at both ends of the roller support shaft 21 to provide the countersunk portions 11a. It is engaged. The counterbore 11a has, for example, a tapered shape. Plastic working part 21a of roller support shaft 21
Is, for example, an annular projection that extends over the entire circumference and has a tapered divergent shape that fits into the counterbore 11a, and is formed by staking or the like. The roller shaft 21 is prevented from coming off by engaging the plastically processed portion 21a with the countersunk portion 11a. At least the surface of the roller shaft 21 that comes into contact with the rollers 23 is a surface that is subjected to a hardening treatment such as induction hardening. Both ends of the roller shaft 21 are preferably not hardened so that the plastically worked portion 21a can be easily worked. As shown in FIG. 4, the plurality of rollers 23 are provided on the roller support shaft 2
It is incorporated in the annular space between 1 and the outer ring 22 as a full complement type. That is, the rollers 23 are incorporated without interposing a cage, and the rollers 23 adjacent to each other are brought close to each other with a gap allowing the rolling.

The material of the outer ring 22 of the roller bearing 10 is
It is made of steel, and the amount of retained austenite in this steel is 8% or less. Roller support shaft 21
The material of the roller and the roller 23 is not particularly limited, and is made of, for example, steel, but the retained austenite amount may be 8% or less like the outer ring 22. For example, the outer ring 22, the roller support shaft 21, and the roller 23 may be made of the same material.

As a detailed example of the material of the outer ring 22, the steel type is a bearing steel (for example, SUJ2 material of JIS standard), and is heat treated. As the heat treatment, for example, Table 1
The processes of Examples 1 to 7 shown in can be adopted.

[0012]

[Table 1]

In Example 1, a sub-zero treatment was performed after the carbonitriding treatment. Subzero treatment is deep-chill treatment. The temperature of the sub-zero treatment was -196 ° C. Example 2 is an example in which tempering was performed after carbonitriding, and the tempering temperature was 230 ° C. Example 3 is an example in which tempering was performed after the high-concentration carbonitriding treatment, and the tempering temperature was 250 ° C. Example 4 is an example in which the subzero treatment was performed after the high-concentration carbonitriding treatment, and the temperature of the subzero treatment was −169 ° C. Example 5 is an example in which tempering was performed after quenching, and the tempering temperature was 230 ° C.
Example 6 is an example in which sub-zero treatment was performed after quenching and tempering was performed. The sub-zero treatment was -169 ° C and the tempering temperature was 230 ° C. Example 7 is an example in which sub-zero treatment was performed after quenching, and the temperature of the sub-zero treatment was −16.
The temperature was 9 ° C. The surface hardness and the retained austenite amount of each of Examples 1 to 7 are as shown in Table 1, and the retained austenite amount is 8% or less in each case.

According to the rocker arm 1 having this structure, the outer ring 22 of the roller bearing 10 serving as the cam follower has a retained austenite amount in the steel of 8% or less, so that the rolling contact surface 22a (see FIGS. 3 and 4). It is difficult for indentation to occur on the. Even if the hardness of the surface layer is about the same or when various heat treatment methods are adopted, indentations are less likely to occur on the rolling surface as compared with the case where the amount of retained austenite exceeds 8%. This can be confirmed by the following test.

A test example will be described. The test was carried out according to Example 1 above.
7 to 7 and Comparative Examples 1 to 4 shown in Table 1 above. Comparative Example 1 is an example in which standard heat treatment was performed, and the tempering temperature after quenching is 180 ° C. Comparative Example 2 is an example of tempering at 200 ° C. after quenching. Comparative Example 3
Is an example of carbonitriding. Comparative Example 4 is an example of tempering at 200 ° C. after carbonitriding. The surface hardness and the amount of retained austenite in each of Comparative Examples 1 to 4 are as shown in Table 1, and the amount of retained austenite exceeds 8% in each case.

The roller bearings used in the tests are the same except that the outer ring material is different, and the bearing specifications are as follows. Outer ring: Inner diameter φ18.64 x Outer diameter φ24 x Width 6.9 (Unit: mm) Roller: Outer diameter φ2 x Length 6.8 (Unit: mm), 26 rollers Shaft: Outer diameter φ14.64 x Length 17.3 (Unit: mm) C (Basic dynamic load rating) = 8600N C ₀ (Basic static load rating) = 12900N

In the test method, both ends of the shaft are received by V blocks, and a static load is applied from the outer diameter of the outer ring. At this time, the roller was placed at the maximum load position (upper end), and an indentation was made on the rolling surface of the outer ring by the surface pressure between the roller and the outer ring. Under this condition, a load was applied when a load of 12900N corresponding to the basic static load rating C ₀ was applied and evaluated. The test results are shown in Table 2.

[0018]

[Table 2]

From Table 2, each of Examples 1 to 7, that is, an example in which the amount of retained austenite was 8% or less, was 2.0 μm even in the case of the maximum indentation depth (Example 5), and Comparative Example 1 It can be seen that the indentation depth of the outer raceway rolling surface is shallower than that of the example in which the amount of retained austenite exceeds 8%. The surface hardness is as shown in Table 1 in each Example 1
7 to 7 and Comparative Examples 1 to 4 are substantially the same,
The retained austenite content is 8 regardless of the heat treatment method.
It is recognized that indentations are less likely to occur when the percentage is less than or equal to%. Comparing examples (Example 2 and Comparative Example 4) having the same heat treatment method but different tempering temperatures, the indentation depth of Comparative Example 4 in which the retained austenite amount was 17.0% was 2.3 μm. On the other hand, in Example 2 in which the amount of retained austenite was 7.0%, the indentation depth was 1.6 μm.
It is shallow as m. Surface hardness is 780 HV of Comparative Example 4
On the other hand, Example 2 has a low 730 HV, but the indentation depth is shallow. From this, it is understood that the amount of retained austenite has a greater effect on the likelihood of indentation than the surface hardness.

Next, Examples 1 to 7 in which the amount of retained austenite is 8% or less are compared with each other. Example 6 and Example 7 in which the amount of retained austenite was as low as 0.5% and 3.5% and a medium value, respectively.
Indentation depths of 1.3 μm and 1.4 μm, respectively, and retained austenite amounts of 7.0% and 8.0%.
In Comparative Examples 2 and 4, which are relatively large, the indentation depths are 1.6 μm and 0.8 μm, respectively, which are about the same or rather shallow. From this, when the amount of retained austenite is 8% or less, no proportional relationship or positive correlation is observed between the amount of retained austenite and the indentation depth. When the amount of retained austenite is 8% or less, those having a high surface layer hardness tend not to cause indentation.

As described above, when the amount of retained austenite is set to 8% or less, indentation hardly occurs even when various heat treatment methods are used.

5 to 7 show a rocker arm according to another embodiment of the present invention. This rocker arm 1A is an example in which the arm body 4A is installed so as to be swingable at one end, that is, an end pivot type. The arm body 4A has a pivot mounting portion 18 at one end in the lengthwise direction, an action portion 14A for operating the valve 3 at the other end, and a roller bearing 10 serving as a cam follower rolling on the cam 2 in the middle thereof. ing. Arm body 4
A is pressed from a single steel plate, has an inverted U-shaped cross section over substantially the entire length, and has opposing plate walls 5 on both sides of the connecting plate wall 6. The pivot mounting portion 18 is provided with a female screw 19 on the connecting plate wall 6 of the arm body 4A. An adjuster screw 31, which is a male screw portion of the pivot part 30, is screwed onto the female screw 19. The pivot part 30 has a spherical pivot part 3 at the tip.
0a and is swingably supported by the pivot receiving member 33. The swing center of the pivot portion 30a, that is, the spherical center of the pivot portion 30a is the swing center O of the arm body 4A. In the portion where the female screw 19 is formed, the distance between the opposite plate walls 5 on both sides is smaller than the inner diameter of the female screw, and a part 19a of the female screw 19 is formed on the inner surface of the opposite plate wall 5. The acting portion 14A includes a part of the connecting plate wall 6,
In a cross section along the length direction of the arm body 4A, the arm body 4A has a curved plate shape that is convex toward the valve 3 side.

The roller bearing 10 has a roller support shaft 21 mounted on the arm body 4A, as in the first embodiment.
An outer ring 22, and the roller support shaft 21 and the outer ring 22.
And a plurality of rollers 23 (FIG. 8) interposed therebetween. The roller 23 is a needle roller. The roller support shaft 21 is provided with mounting holes 11 provided on the opposite side walls 5 and 5 on both sides of the arm body 4A.
Both ends are fitted and attached. A part of the outer ring 22 projects from a roller projecting window 32 (FIG. 7) provided on the connecting plate wall 6 of the arm body 4A, and rolls on the cam 2 at the projecting portion. Other configurations of the roller bearing 10, for example, the full-roller type, and the fact that the outer ring 22 is made of steel and the amount of retained austenite in the steel is 8% or less , Are all the same as in the first embodiment.

Even in such an end pivot type rocker arm 1A, the bearing outer ring 2 serving as a cam follower is provided.
Since the amount of retained austenite of No. 2 is 8% or less, indentations are unlikely to occur on the rolling surface of the outer ring 22, and an excellent rolling life can be obtained.

In each of the above embodiments, the arm bodies 4 and 4A are formed by pressing a sheet metal, but the present invention can be applied regardless of the type of the arm bodies 4 and 4A. The arm bodies 4 and 4A may be machined products or welded assemblies. Further, the arm bodies 4 and 4A may be made of aluminum, and in that case, may be a cast product.

[0026]

According to the rocker arm of the present invention, the retained austenite amount of the bearing outer ring, which is the cam follower, is set to 8% or less, so that the rolling surface of the outer ring is less likely to be indented.
An excellent rolling life can be obtained. When the arm body is pressed from a single steel plate, it is light in weight, has a small number of processing steps, can be manufactured at low cost, and the retained austenite amount of the outer ring is set to 8% or less. A rocker arm that has a long life and is lightweight
Obtained at low cost. In the rocker arm roller bearing of the present invention, the residual austenite amount of the bearing outer ring, which serves as the cam follower, is set to 8% or less, so that indentations are unlikely to occur on the rolling surface of the outer ring and excellent rolling life can be obtained.

[Brief description of drawings]

FIG. 1 is a front view of a rocker arm according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the rocker arm.

FIG. 3 is a sectional view of a roller bearing portion of the rocker arm.

FIG. 4 is a cutaway front view of the roller bearing.

FIG. 5 is a cutaway front view of a rocker arm according to another embodiment of the present invention.

FIG. 6 is a plan view of the rocker arm.

FIG. 7 is a bottom view of the rocker arm.

FIG. 8 is a sectional view of a roller bearing portion of the rocker arm.

[Explanation of symbols]

1, 1A ... Rocker arm 2 ... cam 3 ... Valve 4, 4A ... Arm body 10 ... Roller bearing 14, 14A ... Working part 21 ... Roller support shaft 22 ... Outer ring 23 ...

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F16H 53/06 F16H 53/06 F term (reference) 3G016 AA06 AA19 BA18 BA49 BB16 BB18 BB22 CA06 CA10 CA11 CA12 CA21 CA22 CA25 CA52 EA04 FA07 FA16 FA20 GA02 3J030 EA22 EB05 EC04 EC07 3J101 AA14 AA24 AA42 AA52 AA62 AA72 BA54 BA70 EA02 EA31 GA01 GA21

Claims (3)

[Claims] 1. A rocker arm having a swingable arm body provided with an operating portion for operating a valve of an internal combustion engine and a roller bearing whose outer ring serves as a cam follower, wherein the roller bearing is the arm body. Equipped with a roller support shaft, an outer ring, and a plurality of needle rollers interposed between the roller support shaft and the outer ring. The outer ring is made of steel, and the amount of retained austenite in the steel is 8%. A rocker arm characterized in that: 2. The rocker arm according to claim 1, wherein the arm body is pressed from a single steel plate. 3. A roller comprising a roller support shaft and an outer ring, and a plurality of needle rollers interposed between the roller support shaft and the outer ring, wherein the roller support shaft is attached to a rocker arm and the outer ring serves as a cam follower. A roller bearing for a rocker arm, wherein the outer ring is made of steel and the amount of retained austenite in the steel is 8% or less.