JP2001158689A - Diamond coated sliding parts - Google Patents

Abstract

(57) [Summary] Lightweight and excellent wear resistance, along with prevention of wear of mating material,
Provided is a diamond-coated sliding part that is effective in reducing power loss. A sliding part such as an adjusting shim (4) used for a valve mechanism of an internal combustion engine such as an automobile engine. The sliding part is made of silicon nitride or sialon, and its surface is coated with diamond. It is. The surface of the diamond coating layer is not subjected to processing such as polishing, and the surface load length ratio (t _p ) on the sliding surface of the diamond coating layer is controlled to 60 at a cutting level of 0.1 μm by controlling the film forming conditions and the like. % Or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding part such as an adjusting shim used in a valve train of an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, in the field of automobiles, there is an urgent need to improve fuel efficiency from the viewpoint of energy saving.
As a countermeasure, reducing power loss of the engine and the like has become a major issue in parallel with reducing the weight of the vehicle body and improving the thermal efficiency of the engine. In particular, among the power loss of the engine, as measures to reduce the loss in the valve train, reduction of the weight of parts mainly for the purpose of reducing the inertial weight and reduction of the friction work in the sliding portion are being studied.

FIG. 3 shows a specific example of a valve mechanism of an automobile engine. In FIG. 3, reference numeral 1 denotes an engine cylinder head, 2 denotes a cam, 3 denotes a valve lifter, 4 denotes an adjusting shim, 5 denotes an intake / exhaust valve, 6 denotes a valve seat, and 7 denotes a valve spring. In the valve operating mechanism shown in FIG. 3, the displacement of the cam 2 is transmitted to the intake / exhaust valve 5 by driving the valve lifter 3 by the cam 2.

In the valve operating mechanism described above, the adjusting shim 4 is disposed between the cam 2 and the valve lifter 3, so that the adjusting shim 4 slides on the cam 2 and the valve lifter 3. The adjusting shim 4 is for adjusting the valve clearance, and is conventionally generally made of metal. In the adjusting shim 4 as well, a reduction in weight and an improvement in wear resistance are required to reduce power loss.

[0005]

As measures to reduce the power loss in the valve train described above, for example, Japanese Patent Application Laid-Open No. 6-294.
No. 307 discloses that the friction shim can be reduced, that is, the friction coefficient μ can be reduced by using an adjusting shim, which is a sliding component, as diamond or by depositing diamond on a substrate. Is disclosed.

However, in this adjusting shim, it is necessary to machine the surface of the diamond to a smooth mirror surface, and since diamond is a very difficult-to-cut material,
Processing costs are very high, and the overall cost is very high because diamond is a high cost material. Further, when the base material is a metal, there is a large difference in longitudinal elastic modulus between the metal and the diamond coated thereon, so that an internal stress is generated at an interface between the two and the diamond is peeled off from the metal base material. was there.

The present invention has been made in view of such a conventional situation,
It is an object of the present invention to provide a diamond-coated sliding part that is lightweight, has excellent wear resistance, prevents wear of a mating material, and is effective in reducing power loss.

[0008]

In order to achieve the above object, a diamond-coated sliding component provided by the present invention is a sliding component comprising silicon nitride or sialon as a base material and the base material surface coated with diamond. there, in its diamond coating layer has not been processed, the sliding surface of the diamond coating layer, the load length ratio conforming to JIS B 0601 (t _p) is 60% or more at the cutting level 0.1μm It is characterized by the following.

[0009]

Diamond-coated sliding part according to the present invention DETAILED DESCRIPTION OF THE INVENTION, the substrate is made of silicon nitride _(Si 3 _{N 4)} or sialon (Si-Al-O-N ). Silicon nitride and Sialon are both ceramic materials, and are extremely lightweight, have high hardness, and are excellent in wear resistance and heat resistance as compared with metals. In particular, the strength of silicon nitride and sialon as base materials is used as sliding parts,
The three-point bending strength (σ3 _b ) is preferably 1000 MPa or more.

The diamond coating layer provided on the substrate is preferably a vapor-phase synthetic diamond formed by a known PVD method or CVD method. Above all, according to the CVD method, it is possible to decompose a raw material gas such as a hydrocarbon-based gas and a hydrogen gas to deposit diamond from a gas phase on a base material. A method, a high frequency plasma method and the like are known.

[0011] In addition, diamond has high hardness and excellent thermal conductivity, and thus is suitable as a wear-resistant sliding coating. In addition, diamond has a small difference in thermal expansion coefficient and longitudinal elastic modulus from silicon nitride or sialon as the base material,
The diamond coating layer does not peel off from the substrate. The thickness of the diamond coating layer is preferably in the range of 0.5 to 20 μm. If the thickness is less than 0.5 μm, sufficient strength as a diamond cannot be obtained, and if it exceeds 20 μm, the cost increases. However, if there is an advantage corresponding to the cost, it may be formed thicker than 20 μm.

The surface condition of the diamond coating layer formed on the substrate varies depending on the surface condition of the substrate and film forming conditions by a vapor phase synthesis method or the like. Therefore, in the present invention,
By controlling these conditions, on the sliding surface of the diamond coating layer, the surface load length ratio (t _p ) is adjusted to 60% or more at a cutting level of 0.1 μm, and the surface becomes smooth or has a surface profile. The surface should be free of peaks.

The load length ratio at the cutting level of 0.1 μm
By setting (t _p ) to 60% or more, the loss torque becomes smaller than that of the conventional metal sliding part, and the loss torque itself becomes smaller with the increase in the load length ratio, and the wear amount of the mating material is reduced. Decrease. However, even if the load length ratio (t _p ) is increased beyond 85% at a cutting level of 0.1 μm,
No further reduction in loss torque can be obtained, and the amount of wear of the mating material becomes substantially constant.

In the present invention, the “load length ratio (t _p )” is defined as a value obtained by cutting a roughness curve of a reference length at a cutting level parallel to a peak line, as defined in JIS B0601. The ratio of the sum of the obtained cut lengths (load length) to the reference length is expressed as a percentage. The load length ratio (t
The measurement of _p ) is carried out in accordance with the above JIS, and the reference length is set to 0.
25 mm, and the evaluation length was 1.25 mm.

The diamond-coated sliding part of the present invention has a diamond coating layer in which the load length ratio (t _p ) at a cutting level of 0.1 μm is adjusted and the surface is smooth or has no peak portion in the surface profile. As a result, it is possible to reduce the friction loss generated with the counterpart material and improve the power loss, and therefore, it is extremely excellent as a sliding component used for a valve train of an internal combustion engine such as an automobile engine. Also, by using silicon nitride or sialon for the base material, it can be made lighter than those made of metal or metal.
In addition, since the difference between the modulus of longitudinal elasticity and the coefficient of thermal expansion between the substrate and the diamond is reduced, the adhesion of the diamond coating layer is improved.

[0016]

The present invention will be specifically described below with reference to examples. In each of the following embodiments, an adjusting shim was used as an example of a sliding component.

[0017]Example 1  By the known filament CVD method, the three-point bending strength is different.
Become Si₃N₄Vapor phase synthesis die on each substrate consisting of sintered body
Precipitate the almonds and adjust each adjusting shim
Produced. Adjusting shim dimensions for all samples
Is 30 mm in diameter and 5 mm in thickness.

At the time of the above-mentioned vapor phase synthesis, the film forming conditions were changed, and as shown in FIG.
At the contact surface 4a with the cam at a cutting level of 0.1 μm
The load length ratio in the (labeled t _p 0.1 in Table 1), respectively adjusted to the values shown in Table 1 below. Reference numerals 4b and 4c in FIG. 1 indicate contact surfaces with the valve lifter.

Each of the adjusting shims 4 manufactured as described above is incorporated in a motoring apparatus shown in FIG. 4 which reproduces a direct-hitting OHC valve operating mechanism, and is driven under a certain rotation speed by a motor 8 (in terms of engine rotation speed, 2000 rpm). 4000r
pm) was measured to evaluate the power loss. The results obtained are shown in Table 1 below.

For comparison, an adjusting shim made of a conventional Cr-Mo steel and an adjusting shim made only of a Si ₃ N ₄ sintered body were subjected to the same test as above, and the results were obtained. The results are shown in Table 1.

[0021]

[Table 1] t_p0.1 Base material strength Diamond layerMotor power consumption sample Shim material (%) (MPa) Thickness (μm) 2000rpm 4000rpm  1 Diamond coating 60 1200 5.0 0.71 0.81 2 Diamond coating 65 1150 5.0 0.62 0.67 3 Diamond coating 75 1200 15.0 0.55 0.59 4 Diamond coating 80 1050 2.0 0.47 0.50 5 Diamond coating 85 1300 5.0 0.35 0.40 6 Diamond coating 90 1200 1.0 0.29 0.33 7 Diamond Coating 95 1200 2.0 0.27 0.31 8 * Diamond coating 50 1200 0.3 Diamond coating layer peeled 9 * Diamond coating 55 800 3.0 Shim damaged 10 * Si₃N₄ 40 (1200)-1.35 1.52 11 * Cr-Mo steel 90--1.17 1.30 (Note) Samples marked with * in the table are comparative examples.

As can be seen from the results in Table 1 above, in each of the adjusting shims of Samples 1 to 7 provided with the diamond coating layer of the present invention, an adjusting shim made of a Si ₃ N ₄ sintered body having poor surface smoothness. Of course,
The load length ratio consists conventional Cr-Mo steel _t p 0.1
However, even when compared with an adjusting shim of 90%, the power consumption of the motor can be drastically reduced.

Further, even adjusting shim provided with a diamond coating layer on the surface of the Si ₃ N ₄ base material, said bearing length ratio t _p 0.1 is a reduction in motor power consumption is less than 60% yield In particular, in Sample 8 having a small diamond coating layer, the diamond coating layer was peeled off,
₃ strength N ₄ substrate is weak sample 9, an adjusting shim itself was broken.

[0024]Example 2  Each sample shown in Table 2 below prepared in the same manner as in Example 1 above
The adjusting shim shown in FIG.
Built-in to a turbocharger, under a certain speed (engine speed conversion)
200 hours continuous operation test at 6000 rpm)
Was.

After the continuous operation test, the wear amount of the valve lifter 3 sliding on the adjusting shim 4 was evaluated. As shown in FIG. 2, the amount of wear of the valve lifter 3 was measured by measuring the inner diameter R of the portion where the adjusting shim 4 was mounted before and after the test, and the amount of change was used to evaluate the wear of the valve lifter 3. Table 2 shows the obtained results.

For comparison, as in Example 1, an adjusting shim made of a conventional Cr-Mo steel (sample 11) and an adjusting shim made of only a Si ₃ N ₄ sintered body (surface polished) as in Example 1. The same test as described above was performed for the sample 20 and the unprocessed sample 19), and the results are shown in Table 2.

[0027]

[Table 2] t_p0.1 Base material strength Diamond layer R before and after testsample Shim material (%) (MPa) Thickness (μm) Dimension difference (μm)  12 Diamond coating 60 1200 3.0 6.7 13 Diamond coating 65 1250 10.0 6.2 14 Diamond coating 75 1100 1.5 5.8 15 Diamond coating 80 1150 2.5 5.1 16 Diamond coating 85 1100 8.0 4.5 17 Diamond coating 90 1030 2.0 4.3 18 Diamond coating 95 1200 2.0 4.2 19 * Si₃N₄ 50 (1200)-18 20 * Si₃N₄(Polishing) 60 (1200)-12 11 * Cr-Mo steel 90--20 (Note) The sample marked with * in the table is a comparative example.

As can be seen from the results in Table 2, by using the adjusting shim provided with the diamond coating layer of each of the samples 12 to 18 of the present invention, the adjusting shim made of the Si ₃ N ₄ sintered body and the conventional shim were used. Compared with the case of the adjusting shim made of Cr-Mo steel, the wear of the valve lifter, which is the mating material, can be drastically reduced. Further, the load length ratio t of the diamond coating layer
_p 0.1 is more Daii, it can be seen that the wear of the valve lifter is mating member is further reduced.

[0029]

According to the present invention, a diamond-coated sliding part which is lightweight, has excellent wear resistance, is capable of preventing abrasion of a mating material and dramatically reducing power loss, and has excellent reliability. Can be provided. By using this diamond-coated sliding component, the friction loss and wear resistance generated between the mating material and the diamond coating layer are improved, the power loss as a valve train of the internal combustion engine is reduced, and fuel consumption and Durability can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an adjusting shim.

FIG. 2 is a longitudinal sectional view of an adjusting shim mounted on a valve lifter.

FIG. 3 is a longitudinal sectional view showing a valve mechanism of an automobile engine.

FIG. 4 is a longitudinal sectional view showing a motoring device used in a test of an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Cam 3 Valve lifter 4 Adjusting shim 5 Intake / exhaust valve 6 Valve seat 7 Valve spring 8 Motor

Claims (5)

[Claims] Claims: 1. A silicon nitride or sialon base material,
A sliding component having the base material surface coated with diamond, wherein the diamond coating layer is not processed, and the sliding surface of the diamond coating layer is JIS B 060
Load length ratio that conforms to the 1 (t _p) is cut level 0.1μm
The diamond-coated sliding component is 60% or more. 2. The diamond-coated sliding part according to claim 1, wherein the three-point bending strength of silicon nitride or sialon as a base material is 1000 MPa or more. 3. The diamond-coated sliding component according to claim 1, wherein the diamond-coated layer is a vapor-phase synthetic diamond. 4. The diamond coating layer has a thickness of 0.5 to 2
The diamond-coated sliding part according to claim 1, wherein the diameter is 0 μm. 5. The diamond-coated sliding part according to claim 1, which is used for a valve train of an internal combustion engine.