JPH07118832A - Sliding member and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a sliding member capable of shortening the time required to mirror-finish a contact surface and a method for manufacturing the sliding member. [Structure] After the surface of a shim substrate 50 is finished to about 0.3 μm Rz, a coating layer 51 of titanium nitride is formed by an arc ion plating method. By adjusting the current density during the treatment to 60 to 90 MA / cm ² , the height on the surface relative to the substrate area is 0.5 μ.
The ratio of the total areas of the cross sections when cut at m is 0.7 to 5.2.
% Droplets are formed. The cam contact surface has a roughness of 0.2 by performing the sliding operation for about 10 hours.
It can be mirror-finished down to μmRz or less, and the droplets are broken off by the sliding operation, and the shim surface is 0.01 to 0.30 which is the same level as the coating base roughness.
It is mirror-finished up to μmRz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member such as a shim that contacts a cam to transmit a motion to a valve and the like, and a method for manufacturing the sliding member. Sliding member and its manufacturing method.

[0002]

2. Description of the Related Art An intake valve or an exhaust valve of an internal combustion engine is driven by a shim that is displaced according to the shape of a cam installed on a cam shaft driven by the internal combustion engine. Therefore, since the contact resistance between the cam and the shim causes a loss of the internal combustion engine, the surface roughness of the contact surface of the cam and the shim is the thickness of the oil film formed by the lubricating oil supplied to the contact portion between the cam and the shim. It is necessary to reduce it to the same level as the above.

However, while the thickness of the oil film is about 0.1 μm, the surface roughness of the contact surface of the cam is at most 1.6 to 3.2 μmRzm according to known processing techniques, and a sufficient contact resistance is obtained. Could not be reduced. Therefore, the present applicant provides a coating layer, for example, titanium nitride, on the contact surface of the shim that has been mirror-finished in advance so that the contact surface with the shim of the cam is mirror-finished during the initial sliding operation. A cam contact portion structure has already been proposed (see Japanese Patent Laid-Open No. 163909/1993).

[0004]

However, the sliding action of the shim becomes weaker as the sliding surface of the shim becomes a mirror surface. Therefore, the effect of reducing the contact resistance is not sufficiently exhibited until the mirror surface of the cam is completed. Create challenges. The present invention has been made in view of the above problems, and an object of the present invention is to provide a sliding member capable of shortening the time required for mirroring a contact surface and a method for manufacturing the sliding member.

[0005]

A sliding member according to a first aspect of the present invention is a sliding member that slides on a cam, and a contact surface of the sliding member is finished to be smoother and smoother than a contact surface of the cam. A coating layer having fine irregularities made of a material having an Hv hardness of 1,000 or more is provided on the finished contact surface.

In the sliding member according to the second aspect of the present invention, the ratio of the cut area when fine irregularities are cut at a height of 0.5 μm from the surface of the coating layer to the area of the contact surface of the sliding member is 0.7 to. It is set to 5.2%. A method of manufacturing a sliding member according to a third aspect of the present invention is a method of manufacturing a sliding member that slides on a cam, wherein the contact surface of the sliding member is finished to 0.3 μmRz or less and the contact surface has an Hv hardness of 1 Over 1,000 materials are coated by the arc ion plating method.

In the method for manufacturing the sliding member according to the fourth aspect of the present invention, the current density when the coating layer is provided by the arc type ion plating method is 60 to 90 MA (megaamps) per square centimeter.

[0008]

In the sliding member according to the first aspect of the invention, the cam contact surface is mirror-finished by the fine irregularities during the sliding operation and the fine irregularities on the surface of the sliding member are broken off by the cam. The surface of the sliding member is also mirror-finished. In the sliding member according to the second aspect of the present invention, the cam contact surface is mirror-finished in a short time with a wear amount of a predetermined value or less.

In the method of manufacturing the sliding member according to the third aspect of the present invention, the droplets are formed on the surface of the sliding member by the arc ion plating method. In the method of manufacturing the sliding member according to the fourth aspect of the invention, the droplet is formed so that the cam contact surface can be mirror-finished in a short time with a wear amount of a predetermined value or less.

[0010]

1 is a partial cross-sectional view of an internal combustion engine having a direct drive valve train to which the present invention is applied. That is, two cam shafts 12 and 14 are provided above the cylinder head 10, and one cam shaft 12 is driven by a crank shaft (not shown) via a timing pulley and a timing belt (both not shown). .

An intake cam 16 disposed on the cam shaft 12 is provided with an intake valve spring 20 via an intake valve lifter 18.
The intake valve 21 is driven against. The gear 22 provided on the cam shaft 12 is fitted with the gear 24 provided on the other one cam shaft 14 to drive the other one cam shaft 14. The exhaust cam 25 arranged on the cam shaft 14 drives the exhaust valve 30 against the exhaust valve spring 28 via the exhaust valve lifter 26.

Adjusting shims (hereinafter referred to as shims) 34 and 36 are installed on the contact surface of the intake valve lifter 18 with the intake cam 16 and the contact surface of the exhaust valve lifter 26 with the exhaust cam 25, respectively. And sim 3
The sliding members according to the present invention are used for 4 and 36. FIG. 2 is a side sectional view of the shims 34 and 36. The upper and lower surfaces of the base material 50, which is, for example, chrome molybdenum steel, is finished to have a surface roughness of 0.3 μmRz or less.

A coating layer 51 is formed on the surface of the substrate 50 by a well-known arc type ion plating method using a material having an Hv hardness of 1,000 or more. In this embodiment, titanium is used as the coating material,
Nitrogen gas with a pressure of 10 millitricheri was used as the atmosphere gas, and the bias voltage was 50V. The processing time is 90 minutes.

FIG. 3 shows the results of measuring the surface roughness after coating. As can be understood from this figure, a droplet formed by coating titanium nitride on titanium that has been scattered as metal lump 52 by the arc spot generated during processing and adhered to substrate 50,
Minute protrusions are present on the surface of the base material 50.

4A and 4B are schematic diagrams for explaining the droplets. FIG. 4A is a side sectional view and FIG. 4B is a sectional view taken along line XX. The droplets are randomly generated on the base material 50, and the size, height, or generation position cannot be controlled, but the generation density can be controlled to some extent by the current density.

When the number of droplets per unit area is small, the cam contact surface cannot be sufficiently mirror-finished during the sliding operation, while when the number is large, excessive wear is caused on the cam contact surface. . Therefore, in order to complete the mirroring of the cam contact surface and the mirroring of the shim surface itself in a short time sliding operation, it is necessary to set the number of droplets per unit area within an appropriate range.

However, since the size or height of the droplet cannot be controlled as described above,
Even when using a shim with a few large droplets, the cam contact surface can wear excessively. Therefore, not the number of droplets per unit area, but the cross-sectional area of the droplets (total area of the hatched portions in FIG. 3B) when the droplets are cut at a constant height with respect to the area of the base material 50 is appropriate. It is necessary to set the range.

In the present invention, 0.5 on the surface of the substrate 50.
The number of droplets per unit area is defined by the cross-sectional area of droplets (hereinafter referred to as droplet area ratio) with respect to the area of the base material 50 when cut at μm. Five types of shims having different droplet ratios (Droplet ratio = 0.7, 3.0, 5.2, 7.2, 8.0) for determining the optimum droplet ratio.
%) Was manufactured, and the time required for mirroring and the contact resistance reduction effect were tested.

FIG. 5 is a graph showing the relationship between the droplet ratio and the current density of the arc type ion plating. The vertical axis represents the droplet ratio and the horizontal axis represents the current density. That is, the droplet ratio also increases as the current density increases. Five types indicated by black circles in this graph and 0% droplet ratio (surface roughness 0.01 to 0.30 μm Rz)
The following tests were conducted on a total of 6 types of shims.

FIG. 6 is a graph showing the amount of wear of the cam contact surface when three types of shims having droplets are applied, where the horizontal axis is the droplet ratio and the vertical axis is the cam wear amount. That is, the larger the droplet ratio, the larger the cam wear amount.However, if the cam wear amount is too large, a predetermined valve displacement cannot be obtained and intake / exhaust loss becomes large. Exists.

Therefore, it is necessary to set the droplet ratio to 5.2% or less in order to keep the cam wear amount to the predetermined upper limit value or less. FIG. 7 is a graph showing the contact resistance reduction rate when six types of shims are applied, where the horizontal axis represents the droplet ratio and the vertical axis represents the contact resistance reduction rate. As shown in this graph, when the droplet ratio is 0.7% or less, the contact resistance reduction rate increases according to the increase of the droplet ratio, and when it is 0.7% or more, the contact resistance reduction rate is about the same. Saturate at 30%.

Therefore, it is necessary to set the droplet ratio to 0.7% or more in order to make the surface roughness mirror-finished to 0.2 μmRz or less. That is, the droplet ratio is 0.7
It is preferable to set it to ˜5.2%. Therefore, from FIG. 4, the current density when the droplet ratio is 0.7% is 60 MA per square centimeter, and the droplet ratio is 5.2.
% Current density is 90M per square centimeter
It becomes A.

That is, in order to manufacture a shim having a droplet ratio of 0.7 to 5.2% by the arc type ion plating method, it is necessary to set the current density per square centimeter to 60 to 90 MA. 8 is 100
It is a graph showing the time required for mirroring a cam contact surface by a droplet in 0 rpm sliding, where the vertical axis is the contact resistance (N · m) and the horizontal axis is the time.

The broken line is the change over time in the contact resistance of a shim having a droplet ratio of 0%, and the solid line is a droplet of 0.7%.
It is a change with time of the contact resistance of the shim. As shown in this graph, according to the shim having the droplet ratio of 0.7%, the contact resistance is saturated at the minimum value (about 1.5 N · m) in the sliding time of about 10 hours, and the contact ratio of the droplet ratio is 0%. It is improved by about 30% as compared with the contact resistance of the shim.

That is, if the shim has a droplet ratio of 0.7%, it is possible to reduce the contact resistance in a short sliding time. FIG. 9 is a graph showing the effect of sliding, in which the vertical axis represents the surface roughness of the cam contact surface and the horizontal axis represents the shim surface roughness. That is, when a shim having a droplet ratio of 0% (surface roughness 0.01 to 0.30 μm Rz) is used as indicated by a white circle, the surface roughness of the cam contact surface is 2.8 μm Rz to 0.8 μm by sliding. Although it is mirror-finished to 8 μm Rz, it takes more than 200 hours for the rubbing.

On the other hand, when a shim having a droplet ratio of 0.7% (surface roughness of about 1.5 μmRz) is used as indicated by a black circle, the surface roughness of the cam contact surface is 2. It is mirror-finished from 8 μm Rz to 0.2 μm Rz or less in a rubbing time of about 10 hours. At the same time, the surface roughness of the shim is mirror-finished from about 1.5 μmRz to 0.01 to 0.30 μmRz, which is the same level as the coating base roughness.

[0027]

According to the sliding member of the first invention,
Not only can the cam contact surface be mirror-finished by the droplets formed on the surface, but also the droplets can be broken off on the surface of the sliding member to mirror-finish and the contact resistance can be reduced. According to the sliding member of the second aspect of the present invention, it is possible to reduce the sliding time for making a mirror surface.

According to the method for manufacturing a sliding member of the third invention, it is possible to form a coating layer having droplets on the surface of the base material. According to the manufacturing method of the sliding member of the fourth aspect of the present invention, it is possible to manufacture the sliding member having an appropriate droplet ratio, which makes it possible to reduce the sliding time during coating.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an internal combustion engine having a direct drive valve train.

FIG. 2 is a side sectional view of a shim.

FIG. 3 is a measurement result of surface roughness after coating.

FIG. 4 is a schematic diagram for explaining a droplet.

FIG. 5 is a graph showing the relationship between the droplet ratio and the current density of arc type ion plating.

FIG. 6 is a graph showing the amount of wear of the cam contact surface when three types of shims having droplets are applied.

FIG. 7 is a graph showing contact resistance reduction rates when four types of shims are applied.

FIG. 8 is a graph showing a time required to make a cam contact surface mirror-finished by a droplet.

FIG. 9 is a graph showing an effect of lapping.

[Explanation of symbols]

 50 ... Base material 51 ... Titanium nitride 52 ... Titanium block

Front Page Continuation (72) Inventor Hitoshi Ozawa 1 Toyota Town, Toyota City, Aichi Toyota Motor Co., Ltd.

Claims (4)

[Claims] 1. A sliding member that slides on a cam, wherein a contact surface of the sliding member is finished to be smoother than a contact surface of the cam, and the finished contact surface has an Hv hardness of 1,000 or more. A sliding member provided with a coating layer having fine irregularities in the material. 2. The ratio of the cutting area when fine irregularities are cut from the surface of the coating layer to a height of 0.5 μm with respect to the area of the contact surface of the sliding member is 0.7 to 5.2%. The sliding member according to 1. 3. A method of manufacturing a sliding member that slides on a cam, wherein the contact surface of the sliding member is finished to 0.3 μmRz or less, and a material having an Hv hardness of 1,000 or more is arced on the contact surface. A method for manufacturing a sliding member coated by the ion-plating method. 4. The method for producing a sliding member according to claim 3, wherein the current density when the coating layer is provided by the arc type ion plating method is 60 to 90 MA (megaampere) per square centimeter.