JPH07243308A - Mutual sliding device of both metal materials and valve system for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress abrasion of a counterpart sliding surface by preventing surface roughness while preventing both fatigue damages of a surface starting point and an inner part starting point by applying remaining stress in a wide range under the surface of a sliding surface. CONSTITUTION:Shot peening treatment is carried out on at least either one of sliding surface 10a, 13a in a cam 10 and a roller 13, and then, barrel finishing is carried out. The value of surface roughness of the sliding surface 10a, 13a which is generated by barrel finishing after shot peeling treatment may be set to 1mumRz and less. Not only sufficient remaining stress is applied on a deep part under surface in the sliding surfaces 10a, 13a, but also it is applied on a most surface part. Since surface roughness at the time of shot is eliminated by barrel finishing so as to form the smooth sliding surfaces 10a, 13a (for example, 1mumRz and less), it is possible to suppress generation of abrasive loss of the counterpart sliding surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding device for metal members, for example, a valve operating device of an internal combustion engine provided with various valve driving means, for sliding metal members such as a cam and a roller. It is related to the improvement of the moving surface.

[0002]

2. Description of the Related Art As a valve operating system for an internal combustion engine, for example,
There is a rod type OHV shown in Japanese Utility Model Laid-Open No. 62-173509, a swing arm type OHC shown in Japanese Utility Model Laid-Open No. 62-111914, and the like. In order to reduce fuel consumption, roller type devices (roller lifters and roller rocker arms shown in the above two publications) have been adopted as these valve operating devices.

In transmitting the motion between the cam and the roller, a large stress (about 100) is generated between the sliding surfaces of the cam and the roller.
kgf / mm ² ) is acting. Further, while the angular velocity of the cam constantly changes on its sliding surface, it tries to rotate at a constant speed due to the influence of the inertial force of the roller itself, so that a slight slip occurs between both sliding surfaces. Therefore, both sliding surfaces are required to have high rolling contact fatigue characteristics. Therefore, for example, as a roller, a bearing hole (SUJ
2) is mainly used, and for the cam, spheroidal graphite cast iron (FCD70) subjected to quenching and tempering treatment is mainly used. However, since a slight slip occurs between the cam and the roller as described above, wear due to seizure may occur in the cam in a new state that is not familiar. As a countermeasure, manganese phosphate treatment, which is a type of chemical conversion treatment, is applied to improve the initial conformability. When this manganese phosphate treatment is performed, the base material under the manganese phosphate crystals is etched and the base material becomes rough. Then, the manganese phosphate-treated crystal on the cam is almost worn in the initial stage of sliding with the roller, and the base material is exposed to form a rough sliding surface of roughness (about 10 μmRz).

During the transmission of the motion between the cam and the roller, the rough cam nose portion and the roller come into contact with each other, and a local high stress acts on the outermost surface thereof, and at the same time, in addition to the stress, the cam and the roller. The high stress acting on the entire sliding surface of the element acts on a portion deeper than the outermost surface portion. For this reason, rolling fatigue damage (peeling) originating from the surface and rolling fatigue damage (pitting) originating from an interior deeper than that occur in the roller.

As a measure for preventing peeling occurring on the outermost surface portion, the present applicant specifies the surface roughness of cams and rollers in the patent application of Japanese Patent Application No. 5-40144 and suppresses mutual adverse effects based on those roughnesses. is doing.

[0006] In addition, as a means for improving the fatigue strength of metal materials, there is a shot peening method as disclosed in, for example, Japanese Patent Laid-Open No. 2-185369. Generally, blasting is a process in which innumerable iron or other material particles are collided with the surface of the work piece at a high speed.Blasting is generally called shot. Called blasting. When this processing is performed on the metal surface, the hardening effect of the surface is remarkable and the fatigue strength of the metal part to be processed is increased. Therefore, when such an effect is aimed, it is called shot peening. The most remarkable effect of shot peening is the improvement of fatigue strength. When shot peening is performed, a compressive residual stress is generated on the surface layer side, and the surface hardening by cold working improves fatigue strength. This point has been clarified by various documents.

[0007]

However, in such a shot peening method, a sufficient compressive residual stress can be applied in a depth range of about 50 to 150 μm below the surface, but it is about 0 to 50 μm below the surface. Sufficient compressive residual stress cannot be applied to the outermost surface portion in the depth range, particularly to the depth range of about 0 to 10 μm below the surface. In addition, the surface that has been shot peened will have a rough surface at the time of shot, and 1.5 to 3
The surface roughness becomes μmRz.

When this shot peening is applied to the roller, since sufficient compressive residual stress is not applied to the outermost surface portion, the improvement of the fatigue strength at the outermost surface portion is insufficient, and rolling fatigue from the surface starting point is caused. Peeling, which is damage, is likely to occur. In particular, the surface roughness remaining on the roller easily causes peeling of the cam contacting the surface.

An object of the present invention is to provide means for preventing not only pitting which is deep rolling fatigue damage originating from the inside, but also peeling which is rolling fatigue damage originating from the surface.

[0010]

INDUSTRIAL APPLICABILITY The present invention can be applied to a sliding device provided with metal members that slide with each other, for example, an internal combustion engine valve operating device of various valve drive systems. As this member,
For example, a cam and a roller are included. The cam is fixed to a camshaft that rotates in synchronization with the crankshaft rotational movement of the internal combustion engine. The roller is provided on a roller follower such as a roller lifter or a roller rocker arm, and contacts the cam to convert its rotational movement into linear movement. The mechanism for converting the linear movement of the roller and the roller follower into the opening / closing movement of the intake / exhaust valve differs depending on various valve drive systems.

The sliding surfaces of the metal members, for example, at least one of the cam and the roller, are subjected to shot peening treatment, and then subjected to barrel polishing treatment. The surface roughness of the sliding surface produced by the barrel polishing process after the shot peening process is preferably 1 μmRz or less.

[0012]

By such a treatment, sufficient residual stress is applied not only to the deep portion under the surface of the sliding surface but also to the outermost surface portion. Further, since the surface roughness at the time of shot is removed by the barrel polishing to form a smooth sliding surface (for example, 1 μmRz or less), abrasion of the sliding surface on the other side hardly occurs.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A valve operating system for an internal combustion engine according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 (a) schematically shows one cylinder of a 4-cycle in-line 4-cylinder gasoline engine, 1 is a cylinder, 2 is a piston, 3 is a combustion chamber, 4 is an intake port, 5 is an intake valve, 6 Is an exhaust port, 7 is an exhaust valve, 8 is a fuel injection nozzle, and 9 is a spark plug.

FIG. 1 (b) shows a protruding rod type OHV, to which the intake valve 5 and the exhaust valve 7 are respectively connected.
This thrust bar type OHV includes a cam 10 and a roller lifter 11 as a reciprocating roller follower. The cam 10 as a sliding metal member is fixed to the cam shaft 12 so as to be rotatable integrally therewith, and is rotated in synchronization with a crank shaft rotational movement (not shown). Roller lifter 11
A roller 13 as a sliding metal member is rotatably supported by the sliding surface 13 a of the roller 13 and a sliding surface 1 a of the cam 10.
The rotational movement of the cam 10 is transmitted as a reciprocating linear movement of the roller lifter 11 in contact with 0a. The motion converting mechanism 14 includes a projecting rod 15, a rocker arm 16, a retainer 17, and a valve spring 18. The retainer 17 is attached to the stems 19 of the intake valve 5 and the exhaust valve 7. The valve spring 18 urges the stem 19 to close the intake valve 5 and the exhaust valve 7, and at the same time, the rocker arm 1
Roller 13 of roller lifter 11 via 6 and projecting rod 15
Is pressed against the cam 10. The reciprocating linear motion of the roller lifter 11 is transmitted to the retainer 17 via the projecting rod 15 and the rocker arm 16, and the stem 19 reciprocates linearly as the valve spring 18 expands and contracts to open and close the intake valve 5 and the exhaust valve 7. It has become so.

For the cam 10, casting is mainly used in consideration of cost and mass productivity. In that case, since fatigue peeling easily occurs in chilled cast iron and flake graphite cast iron that has been subjected to quenching and tempering treatment, spheroidal graphite cast iron (FCD70) that has been subjected to quenching and tempering treatment is used. The cam 10 is subjected to the manganese phosphate treatment described above. The surface roughness is 8 to 10 μmRz.

On the other hand, as the roller 13, a bearing hole (SUJ2) subjected to quenching and tempering treatment is used. In this embodiment, the sliding surface 13a of the roller 13 is improved. This improving means is characterized in that after the sliding surface 13a of the roller 13 is ground with a grindstone, the sliding surface 13a is ground.
The point is that not only the shot peening treatment is performed on a, but also the barrel polishing treatment is further performed thereafter. Here, shot peening refers to shot peening that uses a small steel ball called shot to hit the machined surface at high speed to cause work hardening on the surface of the workpiece to cause residual stress and increase fatigue strength. Say. or,
Barrel polishing means that a mixture of particles and liquid called media and a large number of workpieces are put in the barrel of a barrel processing apparatus and surface-treated while being rotated and stirred for a long time.

Therefore, not only sufficient compressive residual stress is applied in the depth range of about 50 to 150 μm below the surface by shot peening, but also 0 below the surface by barrel polishing.
Sufficient compressive residual stress can be applied to the outermost surface portion in the depth range of about 50 μm. In particular, barrel polishing is effective in that it is easy to apply compressive residual stress even in a depth range of about 0 to 10 μm below the surface, where sufficient compressive residual stress cannot be applied by shot peening. The proof is shown by the experimental results described later.

In shot peening, the surface roughness at the time of shot remains on the sliding surface 13a of the roller 13. However, when barrel polishing is performed as the final processing, the surface roughness of the sliding surface 13a is removed and the surface roughness is 1 μmRz. The following is a smooth surface. Therefore, abrasion development hardly occurs on the sliding surface 10a of the plate cam 10 that contacts the sliding surface 13a of the roller 13.

The roughness is expressed by a ten-point average roughness.
This ten-point average roughness is 5 from the maximum measured in the direction of longitudinal magnification from a straight line that does not cross the cross-section curve and is parallel to the average line in the portion where the reference length is extracted from the cross-section curve.
The value of the difference between the average value of the peaks up to the th and the average value of the elevations of the valley bottom from the deepest to the fifth is measured in micrometers (μ
It means the one represented by m). Since this roughness varies from place to place, it is measured at several points and determined by averaging the measured values. The above "1 μm Rz or less" is usually indicated by "1Z".

Shot peening and barrel polishing were performed on the sliding surface 13a of the roller 13 under the following conditions. As shot peening conditions, the injection method is direct pressure air blast, the diameter of the injection nozzle is 7 mm, and the injection pressure is 7 kg.
/ Cm ² , the injection distance is about 50 mm, the shot hardness is Vickers hardness Hv 700 to 800, and the shot particles are 0.
Steel beads of about 5 to 1 mm. On the other hand, barrel polishing is performed separately in the first step and the second step. As the barrel polishing conditions in the first step, the stirring method is a rotating barrel, the medium is a 6 × 5 mm regular triangular columnar alumina, the compound is polymerized phosphate, surfactant and water, the stirring time is 1 hour, and the stirring rotation speed is 150 rpm. Is. Also, as the barrel polishing conditions of the second step, the stirring method is a centrifugal barrel,
The media is 50% spherical alumina with a diameter of 5 mm and a diameter of 3 m.
m spherical alumina 50%, compound is fatty acid salt and water, stirring time is 2 hours, stirring rotation speed is 100 rpm.

This roller-type OHV was installed in a 2000 cc in-line 4-cylinder gasoline engine, and the roller 13 was evaluated. In order to speed up the evaluation, the load of the valve spring 18 was increased by 20% from the design specifications. 2 for operating conditions
The method was carried out by driving the engine at 000 rpm for 5000 hours. Regarding the determination of damage, after 5,000 hours of operation, the sliding surface 13a of the roller 13 was visually observed for damage,
When the damaged area was 0 to 10%, it was evaluated as O, when it was 11 to 50%, and when it was 51 to 100%. As described above, the roller 13 according to the present embodiment is obtained by grinding the bearing steel that has been quenched and tempered with a grindstone and then sequentially performing shot peening and barrel polishing. A comparison was made with six types of rollers. The roller according to the comparative example is the bearing steel that has been subjected to quenching and tempering treatment as it is after grinding with a grindstone, the roller according to the comparative example is the roller according to the comparative example only subjected to shot peening, and the roller according to the comparative example is The roller according to the comparative example is only barrel-polished, the roller according to the comparative example is the roller according to the comparative example only shot blasted, and the roller according to the comparative example is shot blasted on the roller according to the comparative example. After that, barrel polishing is performed, and the roller according to the comparative example is subjected to the same treatment as that of this example, but has a rough surface.

FIGS. 2 and 3 show the residual stress, surface roughness, and rolling fatigue damage of these rollers, the average amount of wear of the cams that come into contact with these rollers, and the comprehensive judgment of quality. From the results, in each of the comparative examples, in particular, the degree of rolling fatigue damage is high, or the wear amount of the cam due to the rough roller surface roughness is large, the durability is insufficient in the overall judgment. I knew it was.
In comparison with this, it was found that all of them were good in this example. Although the comparative example was barrel-polished and then shot-peened, the evaluation as described above was not performed.However, since it is clear that the surface roughness at the shot remains, it was transferred to the cam side. Dynamic fatigue damage or wear occurs, resulting in insufficient durability.

Although the thrust rod type OHV is exemplified in the above-mentioned embodiment, it may be applied to a swing arm type OHC as shown in FIG. 4 as another valve driving method. In this swing arm type OHC, the rocker arm 21 as a roller follower has a lash adjuster 20.
Supported by the roller 22 on the rocker arm 21.
Is in contact with the plate cam 10. This roller 22 is subjected to the same processing as the roller 13 of the above embodiment. In this case, the retainer 17 and the valve spring 18 correspond to the motion conversion mechanism 14.

In addition, the processing according to this embodiment is performed by the roller 1.
Not only 3, 22 but also for cam 10, cam 1
It may be applied only to 0. It is also possible to apply the same treatment to a sliding metal member other than the rollers 13 and 22 and the cam 10, for example, a sliding metal member of a constant velocity joint provided between the tire of the vehicle and the mission.

[0026]

According to the present invention, by applying residual stress over a wide area below the surface of the sliding surface, it is possible to prevent both fatigue damage from the surface origin and the internal origin, and prevent surface roughness to prevent the mating sliding surface Wear can be suppressed.

[Brief description of drawings]

FIG. 1A is a schematic front view showing one cylinder of an engine, and FIG. 1B is a schematic partial sectional view showing a valve gear according to the present embodiment.

FIG. 2 is a diagram showing the relationship between the subsurface depth and the residual stress for a roller that has been subjected to the treatment according to the present embodiment and a roller that has been subjected to other treatment.

FIG. 3 is an evaluation diagram showing a comparison of such rollers.

FIG. 4 is a schematic partial cross-sectional view showing a valve gear according to another embodiment.

[Explanation of symbols]

5 ... Intake valve, 7 ... Exhaust valve, 10 ... Cam as sliding metal member, 10a ... Sliding surface, 11 ... Roller lifter as roller follower, 12 ... Cam shaft, 13 ... Roller as sliding metal member, 13a ... Sliding surface, 14 ... Motion conversion mechanism, 21 ... Roller rocker arm as roller follower, 22 ... Roller as sliding metal member.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area F01L 1/18 M 6965-3G

Claims (3)

[Claims] 1. A metal member comprising metal members that slide with each other, wherein at least one of the metal members is subjected to shot peening treatment and then barrel polishing treatment. Sliding device. 2. A cam fixed to a camshaft that rotates in synchronism with a crankshaft rotary motion of an internal combustion engine, a roller and a roller follower that contact the cam and convert the rotary motion into a linear motion, and the roller and the roller follower. In a valve train of an internal combustion engine having a mechanism for converting a linear motion into an opening / closing motion of an intake / exhaust valve, shot peening treatment is performed on a sliding surface of at least one of the cam and the lock, and then barrel polishing is performed. A valve operating device for an internal combustion engine, which has been subjected to a treatment. 3. The valve operating system for an internal combustion engine according to claim 2, wherein the surface roughness of the sliding surface is set to 1 μmRz or less by the barrel polishing process after the shot peening process.