JPH06137406A - Adjusting shims and cams - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to reduce the friction loss of the valve operating type of the engine. [Composition] The hardness difference between the contact surfaces of the cam 2 and the adjusting shim 4 is 300 Vg / mm ² or more in Vickers hardness, and the hardness of the adjusting shim 4 is high, and the simple root mean square of the mutual surface roughness is between the cam 2 and the shim. The adjusting shim 4 and the cam 2 which fall within the range satisfying the following formula 1 with respect to the minimum oil film thickness (corresponding to the engine speed = 1000 to 5000 rpm) that occurs in 1). [Equation 1] R _c: the initial surface roughness of the cam, R _a: adjusting shim initial surface roughness h _min: minimum oil film thickness wherein adjusting shim and the surface roughness of the cam is evaluated by ten-point average roughness .

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a combination of adjusting shims and cams.

[0002]

2. Description of the Related Art Recently, in the field of automobiles, there is an urgent need to improve fuel efficiency from the viewpoint of energy saving. As a countermeasure against this, along with the reduction of the weight of the vehicle body and the improvement of the thermal efficiency of the engine, reduction of power loss of the engine and the like has become a major issue. Among the power loss of the engine, as a measure for reducing the loss in the valve train, the weight reduction of parts mainly for the purpose of reducing the inertial weight and the reduction of friction work of the sliding portion have been studied. FIG. 1 is a vertical sectional view of a valve train mechanism of an engine. In FIG. 1, 1 is a cylinder head of an engine, 2 is a cam, 3 is a valve lifter, 4 is an adjusting shim, 5 is an intake / exhaust valve, 6 is a valve seat, and 7 is a valve spring. In the structure shown in FIG. 1, the cam 2 drives the valve lifter 3 to transmit the displacement of the cam 2 to the intake / exhaust valve 5. As can be seen from FIG. 1, an adjusting shim 4 is arranged between the valve lifter 3 and the cam 2. The adjusting shim 4 is for adjusting the valve clearance. Conventionally, the adjusting shim 4 is mainly made of cast iron or a sintered alloy (Tribologist, Volume 34, No. 6, 1989, PP416), but it is made of ceramics for the purpose of weight reduction and wear resistance improvement. Some were made.

On the other hand, in recent years, due to the movement of fuel consumption regulation due to the exhaust gas problem of automobiles, it is an important development subject to reduce the weight of the vehicle body and reduce the friction loss of the valve train. Therefore, it may be possible to reduce the weight by using a ceramic material for this adjusting shim.However, since the ratio of this adjusting shim to the inertial weight of the valve train is very small, the improvement of the actual power loss is hardly recognized. There was a problem of not having. Furthermore, there is a problem in that the aggressivity of the cam 2 shown in FIG. 1, which is a mating component with which the ceramic adjusting shim comes into contact, is increased, resulting in severe wear.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to reduce the friction loss by maintaining the surface roughness of the cam and the adjusting shim in a specific relationship.

[0005]

Therefore, in the present invention, the difference in hardness between the contact surfaces of the cam and the adjusting shim is 300 kg / mm ² or more in Vickers hardness, and the hardness of the adjusting shim is high, and the mutual surface roughness is simple. The adjusting shim and cam are characterized in that the root mean square falls within a range satisfying the following expression with respect to the minimum oil film thickness generated between the cam and the shim (corresponding to engine speed = 1000 to 5000 rpm).

[0006]

[Equation 2]

R _c : initial surface roughness of the cam, R _a : initial surface roughness of the adjusting shim h _min : minimum oil film thickness Here, the surface roughness of the adjusting shim and the cam is a ten-point average roughness. Evaluate with.

When the above adjusting shim and cam are used, the sliding friction loss between the adjusting shim and the cam is significantly reduced, and it is possible to reduce the power loss of the engine, and at the same time, to the cam. The present inventors have come to the knowledge that the attacking power against the opponent is reduced and the wear of the cam can be remarkably improved. Here, when the value of the expression 1 exceeds 8, the direct contact between the adjusting shim and the cam is notably caused without passing through the oil film, so that the sliding friction loss may increase and the aggression to the cam may increase. It is not preferable. On the other hand, if the value of Expression 1 is less than 1, it is disadvantageous in terms of economical efficiency for machining for improving the surface roughness of the adjusting shim and the cam. Also, if the hardness difference between the contact surface of the adjusting shim and the cam is less than 300 kg / mm ^{2 in} Vickers hardness, the value of formula 1 may not be within the range, and the friction loss between the adjusting shim and the cam is reduced. do not do.

In order to make the effect of the present invention more remarkable, when the material of the adjusting shim is silicon nitride ceramics or zirconium oxide ceramics, the hardness difference from the cam material is 300 kg / m in Vickers hardness.
It is easy to maintain m ² or more, and it is possible to easily improve the surface roughness when the surface of the adjusting shim is machined. The initial ten-point average height roughness (R _z ) of the adjusting shim and the cam is 0.5 μm, respectively.
The following and 3 μm or less are preferable to satisfy the expression 1 when the engine is operating.

According to the present invention, the sliding friction loss can be significantly reduced, and the friction loss of the valve train can be significantly reduced.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Table 1 shows combinations for various surface roughnesses when silicon nitride (theoretical density of 99% or more) is used as the material of the adjusting shim and chill cast iron is used as the material of the cam. The hardness of the contact surface with the cam is shown by Vickers hardness. This was rotated from a commercially available 2000CC automobile gasoline engine by a motoring device equipped with a direct drive type OHC valve mechanism (cylinder head), which was rotated at an engine speed Ne = 2000 rpm. The power consumption of the camshaft drive motor was measured and evaluated. The evaluation results are shown in Table 1. This evaluation was carried out by performing a break-in operation for 2 hours after the start of the test, and then measuring the surface roughness of the adjusting shim and the cam immediately after the measurement. The minimum oil film thickness h _min
For Cheng's equation (ASME, J. Lub.
Tech. 92, No. 1, (1970), the result was 0.4 μm. The hardness difference between the adjusting shim and the cam is 650 kg / mm ^{2 in} Vickers hardness.
Met.

[0013]

[Table 1]

Example 2 Table 2 shows combinations of various surface roughnesses when silicon nitride and zirconium oxide (theoretical density of 99% or more) are used as the material of the adjusting shim and chill cast iron is used as the material of the cam. Show. The hardness of the contact surface with the cam is shown by Vickers hardness. This was rotated from a commercially available 2000CC automobile gasoline engine by a motoring device equipped with a direct drive type OHC valve mechanism (cylinder head), which was rotated at an engine speed Ne = 1000 rpm. The power consumption of the camshaft drive motor was measured and evaluated. The evaluation results are shown in Table 2.
Shown inside. This evaluation was carried out by performing a break-in operation for 100 hours after the start of the test and then measuring the surface roughness of the adjusting shim and the cam immediately after the measurement. still,
For the minimum oil film thickness h _min , the Cheng equation {AS
ME, J. Lub. Tech. , Volume 92, Issue 1 (197
0)}, and the result was 0.2 μm. The difference in hardness between the adjusting shim and the cam was 650 kg / mm ^{2 in the} Vickers hardness (in the case of silicon nitride adjusting shim) and 350 kg / mm ² (in the case of zirconium oxide).

[0015]

[Table 2]

Example 3 As a result of measuring the wear amount of the cam noses of Nos. 7 and 9 in Example 2, No. 7 was less than 1 μm, while No. 9 was 5 μm. It was confirmed that the invention reduced the attack on the opponent.

[0017]

As described above, the adjusting shim according to the present invention can improve the power loss and wear resistance of the valve train and can improve the fuel consumption, performance and durability of the internal combustion engine. is there.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a valve train system mechanism of an engine.

[Explanation of symbols]

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

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area F16H 53/02 Z

Claims (3)

[Claims] 1. The difference in hardness between the contact surfaces of the cam and the adjusting shim is 300 kg / mm ² or more in terms of Vickers hardness, and the hardness of the adjusting shim is high, and a simple root mean square of mutual surface roughness occurs between the cam and the shim. An adjusting shim and a cam having a minimum oil film thickness (corresponding to an engine speed of 1000 to 5000 rpm) satisfying the following formula (1). [Equation 1] R _c: the initial surface roughness of the cam, R _a: adjusting shim initial surface roughness h _min: minimum oil film thickness wherein adjusting shim and the surface roughness of the cam is evaluated by ten-point average roughness . 2. The adjusting shim and cam according to claim 1, wherein the material of the adjusting shim is silicon nitride-based or zirconium oxide-based ceramics. 3. The initial ten-point average height roughness (R _z ) of the adjusting shim and the cam is 0.5 μm or less and 3 μm or less, respectively. Adjusting shims and cams.