JPH06129434A - Outer ring of cam follower device for valve system of engine - Google Patents

Abstract

PURPOSE:To secure the extent of excellent peeling resistance even in the case where a lubricating condition is so severe. CONSTITUTION:When a range of 0 to 50mum in depth from the surface of an outer diametral surface is defined as a surface layer part, a maximum compressive residual stress in this surface layer part is set down to 50 to 110kgf/mm<2>. Likewise hardness in this surface layer part is defined as Hv830 to Hv960. In addition, a rate of residual austenite in the surface layer part should be set to more than 7 capacity percent. Then, minute and successive jogs are formed on the surface. Each roundness conversion diameter of projections 2, 2 constituting the aforesaid jogs in the case of supposing that each area of recesses 1, 1 constituting these jobs accounts for 80% of the whole surface area should be set to less than 15mum. In addition, superfinishing is applied to an inner diametral surface.

Description

Detailed Description of the Invention

[0001]

The outer ring of a cam follower device for a valve operating mechanism of an engine according to the present invention is used, for example, in a state where it is incorporated in a valve operating mechanism of an automobile engine.

[0002]

2. Description of the Related Art There are various types of automobile engines, but in the case of a reciprocating piston type engine, a part of
Except for the cycle engine, all intake valves and exhaust valves are opened and closed in synchronization with the rotation of the crankshaft.

There are various types of valve operating mechanisms for driving the intake valve and the exhaust valve, but for example, the SOHC type shown in FIG. 4 will be described. With one camshaft 17 that rotates at a speed of / 2 (for a 4-cycle engine),
The intake valve 19 and the exhaust valve 20 are reciprocally driven via the rocker arms 18, 18. The cams 21, 21 fixed to the cam shaft 17, which rotates in synchronization with the crankshaft 16, slidably contact the end portions of the rocker arms 18, 18 and reciprocally drive the intake valve 19 and the exhaust valve 20.

By the way, in recent years, the frictional force between the peripheral surfaces of the cams 21 and 21 and the facing portions of the other members such as the rocker arms 18 and 18 during engine operation is reduced to reduce the fuel consumption rate during engine operation. In order to reduce the number of cams, a cam follower device that rotates with the rotation of the cams 21, 21 is provided at the facing portion.

That is, as shown in FIGS. 5 to 7, a pair of support wall portions 22, 22 provided at the end of the rocker arm 18 facing the cam 21 with a space therebetween are provided on both ends of the shaft 23. Is supported and fixed around the shaft 23, and has a short cylindrical outer ring 25 that is in contact with the shaft 23 through the rollers 24, 24 or directly.
Is provided, and the outer diameter surface of the outer ring 25 and the outer diameter surface of the cam 21 are brought into contact with each other, and the outer ring 25 is rotated as the cam 21 rotates.
However, it is designed to rotate about the shaft 23.

By providing such an outer ring 25 and changing the friction between the cam 21 and the member facing it from sliding friction to rolling friction, the fuel consumption rate is reduced.

By the way, when the cam follower device as described above is incorporated in the valve operating mechanism of the engine, as it is, due to the fluctuating load applied to the outer diameter surface of the cam 21 by the outer diameter surface of the outer ring 25, Damage such as pitching is likely to occur on the outer peripheral surface of the cam 21.

For this reason, the magazine "Automotive Engineering" 1989 7
As described on page 39 of the special issue “Roller Rocker Arm and Friction Reduction Effect” in the monthly issue, the cam 2
The camshaft 17 including 1 is made of a high-strength, high-hardness metal material such as hardened cast iron, chilled cast iron, hardened steel, or a sintered alloy having excellent pitting resistance. There is.

On the other hand, Japanese Patent Publication No. 1-30008 discloses that
An invention relating to a bearing rolling element in which a scratch is formed in a random direction with R _max of 0.3 to 1.5 μm on the surface of the rolling surface and a residual stress layer of 50 kgf / mm ² or more is formed on the surface layer is described. There is.

Further, in Japanese Patent Laid-Open No. 3-117723-5, a large number of dents are randomly formed on the surface by barreling to increase the hardness of the surface layer portion as compared with the internal hardness and to compress the surface layer portion. Inventions that cause residual stress are described.

Further, Japanese Patent Laid-Open No. 3-199716 discloses that
A bearing in which a surface hardening treatment layer is provided on the surface in contact with a mating member, and the depth of the peak value of the compressive residual stress and the depth of the peak value of the shear stress distribution are matched is described.

[0012] Further, JP-A-4-54312, by shot peening, the compressive residual stress and 100 kgf / mm ² or more in the surface portion, bearing component was 40 kgf / mm ² or more at a portion of the subsurface 300μm The invention relating to is described.

Further, Japanese Patent Publication No. 2-17607 discloses that
A shot of 40 to 200 μm having a hardness equal to or higher than the hardness of the product is ejected onto the surface of the metal product at an injection speed of 100 m /
injected above sec, increasing the temperature in the vicinity of the surface than A ₃ transformation point, the invention has been described for surface processing method.

[0014]

However, as described in the above-mentioned magazine "Automotive Engineering", the camshaft 17 including the cam 21 is simply formed of hardened metal such as hardened cast iron. When manufactured by, peeling is likely to occur on the outer diameter surface of the outer ring 25 that comes into contact with the outer diameter surface of the cam 21.

That is, it is more difficult to finish the outer diameter surface of the cam 21 made of a hard metal material such as hardened cast iron as compared with the usual finish processing of cast iron. As shown in FIG. 9, a large number of minute projections are formed on the outer diameter surface of the cam 21, and the surface roughness of the outer diameter surface becomes relatively rough at about 0.4 μmRa to 0.8 μmRa. . On the other hand, although the outer ring 25 is made of bearing steel that is harder than the cam 21, the outer ring 25 has a simpler shape than the camshaft 17 provided with the cam 21, and therefore the surface can be easily superfinished, and The outer diameter surface of the outer ring 25 is shown in FIG.
As shown in FIG. 9, the surface roughness is about 0.05 μmRa and the finish is smooth. Therefore, the amount of the lubricating oil 26 retained on the outer diameter surface of the outer ring 25 is limited.

When the amount of the lubricating oil 26 is limited as described above, in the case of an outer ring which constitutes a cam follower device and comes into rolling contact with the outer diameter surface of the cam during operation of the engine, the life is shortened due to the occurrence of peeling. There is. That is, SO
When the valve operating mechanism is present in the upper part of the engine like the HC type engine and the DOHC type engine, the lubricating oil is not always sufficiently supplied to this valve operating mechanism, and the lubrication conditions during operation become severe. Under such conditions, when the outer diameter surface of the outer ring 23 and the outer diameter surface of the cam 19 make rolling contact with each other while sliding, peeling with a depth of 2 to 10 μm occurs on the outer diameter surface of the outer ring 23. However, the life of the outer diameter surface of the outer ring 23 is shortened.

In this case, even if the invention relating to the bearing component described in Japanese Patent Laid-Open No. 4-54312 is applied to the outer ring 23, if the lubrication condition is severe, the peeling resistance is insufficient regardless of the friction condition. Becomes In addition, JP-A-3-19971
The material described in Japanese Patent No. 6 has no particular problem when the friction condition is only rolling friction, but when sliding friction occurs, the peeling resistance becomes poor. Also, Tokuhei 1-30
The materials described in Japanese Patent Application Laid-Open No. 008 and Japanese Patent Application Laid-Open No. 3-117723-5 also have insufficient peeling resistance when the operating conditions become strict, such as the lubrication conditions being severe and the load on the contact portion being large. Further, the one described in Japanese Patent Publication No. 2-17607 cannot still obtain sufficient peeling resistance as it is.

Furthermore, in addition to the above-mentioned respective publications, JP-A-52-1
No. 7525, No. 56-150622, and Japanese Patent Publication No. 63-44505 disclose a processing method for injecting a shot having a minute particle diameter onto a surface to be processed at a high speed, or an invention relating to a processed product. However, none of these publications describes a technique for obtaining an outer ring having sufficient peeling resistance.

In view of such circumstances, the present inventor has previously found that when the surface layer has a depth from the surface of 0 to 50 μm, the maximum compressive residual stress of the surface layer is 50 to 110 kgf /.
mm ² , the hardness is Hv830 to Hv960, the proportion of retained austenite is 7% by volume or more, and fine and continuous irregularities are formed on the surface. An invention (Japanese Patent Application No. 4-216562) relating to a rolling / sliding component in which the true circle equivalent diameter of the convex portion constituting the above-mentioned unevenness is set to 15 μm or less, assuming that the proportion of the entire area is 80%. I did.

When the rolling sliding component according to the present invention is used as the outer ring constituting the cam follower device, it is possible to prevent peeling having a depth of 2 to 10 μm from occurring.
While the life of the outer diameter surface of the outer ring can be increased, a new problem to be solved occurs as described below.

That is, when the entire surface of the outer ring whose outer diameter surface is in contact with the cam 21 and whose inner diameter surface is in contact with the shaft 23 or the rollers 24 has the properties as in the above invention, the outer diameter surface of the cam 21 and The roller 2 can prevent peeling from occurring on the outer surface of the outer ring, but the surface is smoothed by super finishing.
At the rolling surface part of 4, peeling is likely to occur,
Alternatively, the outer diameter surface of the shaft 23 is easily worn.

The outer ring of the cam follower device for the valve operating mechanism of the engine of the present invention was invented in view of the above circumstances.

[0023]

An outer ring of a cam follower device for a valve train of an engine according to the present invention has a metal cam fixed to a camshaft which rotates in synchronization with a crankshaft of the engine, and a metal cam opposed to the cam. And a pair of support wall portions formed at intervals in the member that receives the movement of the cam, a shaft fixed in a state of being suspended between the pair of support wall portions, and a shaft of this shaft. A cam follower device for a valve train of an engine, which is composed of an outer ring rotatably supported around its periphery.

In particular, the outer ring of the cam follower device for the valve train of the engine according to the present invention has a depth of 0 to 5 from the outer diameter surface.
When the range of 0 μm is set as the surface layer, the maximum compressive residual stress of this surface layer is 50 to 110 kgf / mm ² , the hardness of the surface layer is Hv830 to Hv960, and the ratio of retained austenite in the surface layer is 7 The volume% or more, fine and continuous irregularities are formed on the outer diameter surface, and the area of the concave portions forming the irregularities accounts for 80% of the total area of the outer diameter surface.
%, It is characterized that the diameter of the convex portion forming the irregularities is reduced to 15 μm or less, and the inner diameter surface is superfinished.

When assuming that the area of the concave portion forming the unevenness occupies 80% of the entire area of the outer diameter surface, the diameter of a perfect circle of the convex portion forming the unevenness is 15 μm or less. Is the following concept. That is, the surface roughness curve is expressed, for example, as shown in FIG. 3. Considering an imaginary straight line a parallel to the surface, recesses 1 and 1 are located below the straight line a and projections 2 are located above the straight line a. Set to 2. Then, the straight line a is located at a position where the total opening area of the large number of recesses 1 and 1 is 80% of the area of the entire outer diameter surface where the recesses 1 and 1 are present.
Is set, the surface irregularities represented by the roughness curve are regulated so that the true circle equivalent diameter of the convex portions 2 and 2 existing above the straight line a is 15 μm or less.

[0026]

First, the outer ring of the present invention can effectively prevent peeling having a depth of about 2 to 10 .mu.m from occurring on the outer diameter surface thereof to improve the durability.

More specifically, in order to prevent the occurrence of peeling, the oil film should not be broken at the contact portion even when it is used under severe lubrication conditions. In that case, it is necessary to prevent the occurrence of peeling. That is, when the oil film is cut off at the contact portion, the contact surfaces directly contact (metal contact), and most of the load applied to the outer peripheral surface of the outer ring is a small number of small protrusions (contact) with the surface of the mating component. It is supported by the convex portion), so that large stress is concentrated on each minute protrusion and tangential force is applied.

Based on the stress concentration and the tangential force, minute cracks are generated on the outer diameter surface of the outer ring,
This crack develops and causes peeling. The hardness of the surface of the component should be increased to simply prevent wear,
If the hardness is excessively high, cracks associated with peeling are likely to occur due to stress concentration.

In the case of the outer diameter surface of the outer ring of the present invention, by making it easy to form an oil film on the surface, oil film breakage is less likely to occur even under severe lubrication conditions, and even if oil film breakage occurs. , It is possible to prevent cracks that may lead to peeling from occurring for a short time.

That is, in the case of the outer diameter surface of the outer ring of the present invention, since fine and continuous unevenness is formed on the surface, an effective oil film can be formed on the contact surface portion even under severe lubrication conditions. It is possible to prevent the oil film from running out. or,
Since assuming that the area of the concave portion forming the irregularities occupies 80% of the entire area of the outer diameter surface, the diameter of the convex portion forming the irregularities converted to a perfect circle is 15 μm or less,
At the same time that the oil film formation is made efficient, the number of convex portions that are minute protrusions that come into contact with the surface of the counterpart component is increased, the load applied to each convex portion is reduced, and the peeling resistance can be improved.

That is, when the true circle equivalent diameter of the convex portion exceeds 15 μm, the number of convex portions and concave portions per unit area decreases, and the oil film formed on the outer diameter surface of the outer ring tends to become uneven. Not only that, the load from the mating part is received by the small convex portion, and cracks that lead to peeling are likely to occur on the convex portion. Therefore, in the case of the outer diameter surface of the outer ring of the present invention, the true circle equivalent diameter of the convex portion forming the unevenness is limited to 15 μm or less as described above.

Further, since the hardness of the surface layer is regulated within the range of Hv830 to Hv960, even if the oil film is cut off at the contact portion, the occurrence of cracks leading to peeling while suppressing wear for a short time Can be prevented. If the hardness is less than Hv830, the wear will be remarkable instead of cracks. If the hardness is more than Hv960, the wear will be suppressed and the cracks will be easily generated. Come of decline.

Increasing the maximum compressive residual stress is
Even if a crack is generated, it is important to prevent the crack from further developing and prevent the crack from causing peeling. However, when the outer diameter surface of the outer ring is processed so that the maximum compressive residual stress exceeds 110 kgf / mm ² , the hardness of this surface is Hv960.
The maximum value of the maximum compressive residual stress is 110
It was set to kgf / mm ² . On the contrary, the maximum compressive residual stress is 50 kgf /
If it is less than mm ^2, the effect of preventing the crack growth is too small, so the minimum value of the maximum compressive residual stress is 50 kgf / mm ²
And

Further, when a large amount of ductile austenite remains, the effect of preventing cracks can be expected, but when the residual rate is 7% by volume or less, the effect of preventing cracks can be expected to a great extent. Absent. In order to keep the values of the maximum compressive residual stress and hardness within the ranges described above, it is necessary to set the austenite residual rate to a value exceeding 7% by volume.

That is, as a sufficient condition that the maximum compressive residual stress and hardness of the surface layer portion do not exceed the upper limit values of 110 kgf / mm ² and Hv 960, respectively, the decomposition rate of austenite during processing ( The austenite reduction rate due to processing) may be suppressed to 30% or less. On the other hand, the ratio of austenite contained in the bearing steel such as SUJ2 before surface processing is about 11% by volume. Therefore, in order to prevent the maximum compressive residual stress and hardness from exceeding the upper limit values, the austenite ratio after processing should be 7
It is necessary to exceed the capacity%. In addition, when the processing by shot peening is too weak, the maximum compressive residual stress and hardness are the respective lower limit values, that is, 50 kgf / mm ² , Hv8.
Does not reach 30.

Further, since the outer ring of the cam follower device for the valve operating mechanism of the engine according to the present invention is superfinished on the inner diameter surface, this inner diameter surface and the outer diameter of the roller or shaft which has been superfinished. Oil film parameter Λ (= h / σ,
(h: EHL oil film thickness, σ: composite roughness) can be increased to prolong the service life with the inner diameter surface of the outer ring or the outer diameter surface of the shaft. That is, by processing the outer diameter surface and the inner diameter surface of the outer ring by the optimum processing method according to the properties of the mating surface, the durability of the entire outer ring and the roller or shaft can be improved.

[0037]

EXAMPLE Next, one example of a method of processing the outer diameter surface to a predetermined property for producing the outer ring of the present invention and an experiment conducted by the present inventor to confirm the effect of the present invention will be described. And explain.

Regarding the experiment, as shown in the table below,
A total of 12 types of test pieces, 5 types of the present invention products and 7 types of comparative products, were prepared. The materials of the test pieces were all bearing steel (SU
J2), and prior to performing the desired treatment on the outer diameter surface,
Quenching treatment similar to that normally performed (800-850 ° C
After heating in oil, cooling with oil), tempering treatment (150-200 ° C)
Was applied. The test piece has an outer diameter of 20 mm and an inner diameter of 1
It was a short cylinder with a thickness of 3 mm and a thickness (width) of 8 mm.

[0039]

[Table 1]

The test piece 8 belonging to the comparative product was only polished by polishing the outer diameter surface of the outer ring with a polishing cloth, and was not subjected to shot peening for hardening the outer diameter surface of the outer ring. . Further, the 11 types of test pieces 1 to 7 and 9 to 12 belonging to the comparative product and the product of the present invention are all the same as the case of the invention described in JP-A-4-54312. Similarly, shot peening was performed using a device as shown in FIG. 1 to harden the outer diameter surface of the outer ring and generate a large compressive residual stress in the surface layer portion.

The structure and operation of the shot peening apparatus shown in FIG. 1 will be briefly described. The fine shot particles 5 introduced from the hopper 3 into the pressure tank 4 are supplied from the air supply pipe 6 to the fine shot particles 5. The compressed air sent into the pressure tank 4 pushes it into the mixer 7. Then, it is pushed by the compressed air sent to the mixer 7 through the branch pipe 8 and sent to the nozzle 9, and is blown vigorously from the nozzle 9 toward the surface to be processed. As a result, the work surface is hardened, a compressive residual stress is generated on the work surface, and minute irregularities are formed on the work surface.

As the shot grains 5, test pieces 2 to 1 were used.
In any of No. 2, alumina particles having an average particle size of 0.03 to 0.7 mm were used. Further, the projection speed of the shot particles 5 (the initial speed of the shot particles 5 ejected from the nozzle 9) is 3
It was set to 2 to 180 m / sec. The projection speed is adjusted by adjusting the opening of the adjusting valve 10 provided in the middle of the branch pipe 8. Based on the adjustment of the projection speed, each test piece 1
The compressive residual stress, hardness, and residual austenite amount generated on the surfaces of Nos. 7, 9 and 12 were adjusted.

Further, the test piece 8 and the test pieces 1 to 5 have superfinishing on the inner diameter surface after the shot peening processing. The test pieces 6 to 7 and 9 to 12 are still shot and peened. Shot peening is
Perform 8 test pieces at a time to obtain almost the same test pieces for all of the hardness of the surface layer, the maximum residual stress of the surface layer, the amount of retained austenite in the surface layer, the area ratio of the recesses, and the converted diameter of the true circle of the projections. Created 8 each.

8 pieces of 12 kinds obtained in this way,
A total of 96 test pieces 1 to 12 were subjected to a durability test by a test device as shown in FIG.

In this test apparatus, two mating rings 12 and 12 are fixed at two positions on the outer diameter surface of a rotary shaft 11 which is rotationally driven by a motor and spaced from each other. Each of the pair of support pieces 14, 14 provided on one surface of the pressing piece 13 in accordance with the distance between the mating rings 12, 12 has one
Each test piece 15, 15 is rotatably supported via a plurality of rollers, and the outer diameter surface of each test piece 15, 15 contacts the outer diameter surface of the mating ring 12, 12. I am letting you. As a result, the test pieces 15 and 15 rotate as the rotary shaft 11 rotates. Therefore, in the test apparatus shown in FIG. 2, the durability test of the two test pieces 15, 15 is simultaneously performed.

The rotation speed of the rotary shaft 11 is the same as that of each test piece 1.
The rotation speeds of 5 and 15 were adjusted to be 5100 rpm. Further, the pressing piece 13 faces the rotating shaft 11 and
Pressed with a force of kgf. Therefore, a radial load of 178 kgf is applied to the contact portion between the outer diameter surface of each test piece 15, 15 and the outer diameter surface of each mating ring 12, 12. or,
The properties of the outer diameter surface of each mating ring 12 and 12 were such that the surface hardness was H _R C 60 to 61 and the average roughness of the surface before the test was started.
_Ra was 0.38 to 0.45. Further, the lubrication of the contact portion was performed by splashing 10W-30 mineral oil.

The test was discontinued for 400 hours, interrupted at predetermined intervals in the middle, and the outer diameter surface of each test piece 15, 15 was observed to inspect whether peeling occurred. If peeling is observed, the test piece 1
The endurance test on 5 and 15 was completed. The results are shown in the above table as the test censoring time. When the censoring time was different for eight test pieces of the same type, the one with the shortest censoring time was described. or,
The test termination time of 400 hours means that peeling did not occur until the end.

The work for obtaining the true circle equivalent diameter of the convex portion with the area ratio of the concave portion being 80% was performed by analyzing the image obtained by an optical microscope with a magnification of 200 times. At this time, the image obtained by the optical microscope is subjected to image processing for enhancing and clarifying the contour, and the work of setting the area ratio of the concave portion is performed by adjusting the brightness of the light source and the binarization level. It was Further, the quantification of the convex portion was performed on the binarized image extracted for the one (bright portion) exceeding the set binarization level.

As is apparent from the above table showing the results of the above durability test, the outer diameter surface of the outer ring of the present invention can obtain sufficient peeling resistance even under severe lubrication conditions.
Although not shown in the table, in the case of the product of the present invention, the time during which pitting occurs was 300 hours or more, which was longer than that of the comparative product, and it was confirmed that this product also has excellent durability. .

Among the symbols described after each numerical value in the above table, ◯ means that the numerical value is included in the limited range of the present invention, and × means that the numerical value is outside the limited range of the present invention. It means that each is. Further, among the maximum residual stresses in the surface layer portion, + means tensile residual stress, and − means compressive residual stress.

When the test was stopped, the test piece 1
5 and 15 were disassembled, and it was confirmed whether or not peeling occurred on the rolling surface (outer diameter surface) of the rollers supporting the test pieces 15 and 15. As a result, as shown in the above table, the one that only shot-peened the inner diameter surface of the outer ring,
Peeling occurred on the rolling surface of the rollers, but peeling did not occur on those with superfinishing.

Therefore, ◎ means that peeling did not occur on all rolling surfaces of all rollers, and x means that peeling occurred even on one roller. did.

[0053]

The outer ring of the cam follower device for a valve train of an engine of the present invention is constructed as described above, but the outer diameter surface of the outer ring is reinforced and a rough shape having an excellent oil film forming ability is formed. Since it is formed, it is possible to prevent peeling from occurring on the outer diameter surface of the outer ring and improve the durability of the outer ring. Further, since the inner diameter surface of the outer ring is superfinished, the roughness is small, the oil film parameter between the outer diameter surface of the roller or the shaft is large, and the life can be expected to be extended. Therefore, the durability of the cam follower device incorporating the outer ring can be improved.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a shot peening apparatus.

FIG. 2 is a longitudinal sectional view of a half portion of the durability test apparatus.

FIG. 3 is a roughness curve for explaining the concept of surface shape limitation.

FIG. 4 is a perspective view showing an example of a valve operating mechanism of an engine.

5 is a side view of a cam follower device incorporated in the valve mechanism shown in FIG.

6 is a sectional view taken along line AA of FIG. 5 (in the case of a rolling bearing).

7 is a sectional view taken along line AA of FIG. 5 (in the case of a sliding bearing).

FIG. 8 is a schematic view showing machining marks formed on the outer diameter surface of a conventional outer ring.

9 is a partially enlarged sectional view of FIG.

[Explanation of symbols]

 1 concave part 2 convex part 3 hopper 4 pressurized tank 5 shot grain 6 air supply pipe 7 mixer 8 branch pipe 9 nozzle 10 regulating valve 11 rotary shaft 12 mating ring 13 pressing piece 14 support piece 15 test piece 16 crankshaft 17 camshaft 18 rocker Arm 19 Intake valve 20 Exhaust valve 21 Cam 22 Support wall 23 Shaft 24 Roller 25 Outer ring 26 Lubricating oil

Claims (1)

[Claims] 1. A metal cam fixed to a camshaft that rotates in synchronization with a crankshaft of an engine, and a member that is provided so as to face the cam and that receives the movement of the cam, are formed with a space therebetween. A cam follower for a valve train of an engine, which includes a pair of support walls, a shaft fixed in a state of being hung between the pair of support walls, and an outer ring rotatably supported around the shaft. In the outer ring constituting the device, when the depth from the surface of the outer diameter surface is in the range of 0 to 50 μm as the surface layer portion, the maximum compressive residual stress of the surface layer portion is 50 to 110 kgf / mm ² . Similarly, the hardness of the surface layer
Hv830 to Hv960, the proportion of retained austenite in the surface layer portion is 7% by volume or more, and fine and continuous irregularities are formed on the outer diameter surface. When the ratio of the entire area to 80% is assumed to be 80%, the diameter of the convex portion forming the unevenness converted to a perfect circle is 15 μm or less, and the inner diameter surface is superfinished. The outer ring of the cam follower device for the valve operating mechanism of the engine.