JPH04314903A - Tappet - Google Patents

Abstract

PURPOSE:To provide a tappet which suppresses scattering of crowning rates at the time of production within an allowable range, and reduction of whose crowning rate is small even under influence of heat at the time of operation. CONSTITUTION:A tappet I is composed of a reversed mashroom-like, metal tappet main body 1 on a lower end of whose slider part 2 a flange 5 is formed, and a ceramic plate 2 connected to a bottom wall of the tapped main body 1 on which plate crowning shape is formed by utilizing difference of a thermal expansion coefficient from that of the tapped main body 1. The relation between a maximum thickness A2 of the flange 5 of the tapped main body 1 and a flange diameter D1 is indicated by an equation of A2/D1>=0.1. The relation between a maximum thickness A2 of the flange 5 and a thickness A1 of the ceramic plate 2 is indicated by an equation of A2/A1>=2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tappets used in internal combustion engines such as automobile engines and other industrial machines.

0002

[Prior Art] Conventionally, the sliding surfaces of sliding parts such as tappets have so-called crowning, which has a gentle bulge of several μm to several tens of μm toward the center in order to prevent uneven contact with cams, etc. It has a shape. Since this crowning shape is a three-dimensional curved surface, it is difficult to form it by methods such as polishing, and the cost is high. Therefore, a technique is disclosed in Japanese Patent Laid-Open No. 63-225728, filed by the present applicant, in which a ceramic plate is brazed to a metal and a crowning shape is applied to the surface of the ceramic plate by utilizing the difference in thermal expansion coefficient between the two. Disclosed in the issue.

0003

[Problem to be solved by the invention] The above-mentioned Japanese Patent Application Laid-Open No. 63-22
The technology of No. 5728 has two problems: firstly, there are slight differences in temperature and cooling rate depending on the location in the welding furnace during brazing, and secondly, the amount of shrinkage differs slightly depending on the lot of steel material. There is a possibility that the variation in the amount of crowning becomes large due to this reason. If the amount of crowning required for the tappet is too small, it will cause uneven contact with the cam, and if it is too large, the surface pressure will be too high and cause abnormal wear.
It needs to be managed very strictly. Therefore, an important issue in the above-mentioned Japanese Patent Application Laid-Open No. 63-225728 was how to suppress the variation in the amount of crowning within an allowable range. Furthermore, when the temperature of the tappet increases during operation of an engine, etc., the metal expands more due to the difference in thermal expansion coefficient between the metal and the ceramic, resulting in a decrease in the amount of crowning. If this decrease in the amount of crowning exceeds the initial amount of crowning, an inverted crowning shape occurs, causing uneven contact with the cam. especially,
In a so-called inverted mushroom-shaped tappet in which a flange is formed at the lower end of the slider, the flange has less rigidity than the slider, so it is easily deformed, and there is a high risk of the tappet forming an inverted crowning shape due to heat during operation. Therefore, it is equally important to find out how to reduce the amount of crowning due to heat during operation.

[0004] The present invention has been made to overcome the problems existing in the prior art as described above, and is capable of suppressing variations in the amount of crowning during production to an acceptable range, and further reducing the amount of crowning due to heat during use (during operation). The purpose is to provide tappets with less

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an inverted mushroom-shaped metal tappet body with a flange formed at the lower end of a slider portion, and a metal tappet body that is bonded to the bottom wall of the tappet body. In a tappet made of a ceramic plate which is provided with a crowning shape by utilizing the difference in thermal expansion coefficient with the tappet body, the dimensional ratio between the maximum thickness A2 of the flange of the tappet body and the flange diameter D1 is (A2 /D1≧0.
1), and a tappet in which the dimensional ratio between the maximum thickness A2 of the collar and the thickness A1 of the ceramic plate is (A2/A1≧2). More preferably, the dimensional ratio between the maximum thickness A2 of the flange of the tappet body and the flange diameter D1 is (0.1≦A2/D1≦0.4). Note that the maximum thickness A2 of the flange section here refers to the thickness from the lower end of the flange section to a portion having the same diameter as the slider section.

[0006]

[Function] The maximum thickness A2 of the flange is 0.1 with respect to the flange diameter D1.
If it is less than twice that, the stiffness of the flange will be insufficient and the variation in the amount of crowning will increase. Therefore, excessive crowning occurs, causing abnormal wear, or crowning is too small, causing uneven contact with the cam, which also causes abnormal wear. If the maximum thickness A2 of the flange is less than twice the thickness A1 of the ceramic plate, the flange will be deformed, making it difficult to obtain the specified amount of crowning. The crowning shape cannot be maintained because the crowning part expands a lot. Further, if the thickness A1 of the ceramic plate is small, the flange cannot absorb the impact force acting on the ceramic plate during operation, and the ceramic plate may break. on the other hand,
As the dimensional ratio between the maximum thickness A2 of the flange and the diameter D1 of the flange increases, a large tensile stress acts on the joint between the flange and the ceramic plate, causing some problems such as cracking and peeling of the ceramic plate. However, if the maximum thickness A2 of the flange of the tappet body is set to 0.4 times or less the flange diameter D1, such cracking and peeling of the ceramic plate can be prevented. Furthermore, with the size ratio set according to the present invention, the variation in the amount of crowning during production is small, but this means that changes in the amount of crowning of the tappet are insensitive to changes in temperature. Therefore, it shows an insensitive response to temperature changes during operation, and the decrease in the amount of crowning is extremely small.

[0007]

Embodiment 1 FIG. 1 is a longitudinal sectional view of a tappet I showing Embodiment 1. The tappet I has a ceramic plate 2 bonded to the bottom wall of a metal tappet body 1. The tappet body 1 includes a cylindrical slider portion 4 having a hemispherical concave portion 3 formed at the top that serves as a contact surface with the push rod, and a collar portion 5 having a substantially truncated conical diameter formed at the lower end of the slider portion 4.
The overall shape is an upside-down mushroom. The material is J.
ISSNCM630, and is machined and molded from a round bar made of such material. Ceramic plate 2 is made of 90% silicon nitride by weight.
A Y2O3-Al2O3-based sintering aid was mixed with the mixture, a molding binder was added thereto, and the material was molded into a disk shape using a mold press. After firing, both surfaces were polished. Tappet body 1 and ceramic plate 2
were heated and bonded in vacuum at 800° C. for 30 minutes using silver solder containing Ti. Ag-Cu-In-Ti based silver solder was used. The shape of the tappet I is such that the dimensional ratio between the maximum thickness A2 of the flange 5 and the flange diameter D1 satisfies (A2/D1≧0.1), and the maximum thickness A2 of the flange 5 and the ceramic plate 2 are The dimensional ratio with the thickness A1 is set to be (A2/A1≧2).

Next, a large number of test samples based on tappet I were manufactured and the amount of crowning was investigated. The dimensions of each part of the test sample are: total length L = 80 mm, flange diameter D1
= φ40 mm, slider diameter D2 = 25 mm, thickness A1 of ceramic plate 2 = 2 mm, 3 mm, taper angle α of flange 5 = 10°, 30°, and in order to confirm the effect of the present invention, the maximum thickness of flange 5 was determined. Various changes were made to A2. Then, a total of 100 test samples were prepared using 20 pieces each of 5 types of steel lots (melted steel lots) for each shape.
Each piece was produced, and the amount of crowning was measured for all 100 pieces. This work was performed for every test sample. The variation in the amount of crowning for each shape is expressed as a standard deviation value (±3σ), and the results are shown in the graph of FIG. In addition, it has been confirmed in other tests that the amount of crowning allowed in the test sample is 15 μm to 45 μm. That is, a value other than this will cause problems such as uneven contact with the cam and an increase in surface pressure, resulting in abnormal wear of the cam. Therefore, the width of the allowable crowning amount is 30 μm or less.

From the graph of FIG. 2, the maximum thickness A2 of the flange 5
It can be seen that those in which the ratio of the diameter D1 and the diameter D1 of the flange is (A2/D1<0.1) are problematic because of large variations in the amount of crowning. Furthermore, if the ratio of the maximum thickness A2 of the flange 5 to the thickness A1 of the ceramic plate 2 is (A2/A1<2), if the flange 5
The ratio of the maximum thickness A2 and the flange diameter D1 is (A2/D1≧0.
Even for 1), there were many that did not fall within the specified values. On the other hand, the ratio of the maximum thickness A2 of the flange 5 to the flange diameter D1 is (A2/
D1>0.4), the cracking of the ceramic plate 2 and the peeling of the joint surface were 2% for the ceramic plate 2 with a thickness A1 of 2 mm, and 8% for the ceramic plate 2 with a thickness A1 of 3 mm.
%there were. This result is the maximum thickness A2 of the flange and the diameter D of the flange.
It is shown that the effects of the present invention can be more fully achieved by setting the size ratio to (A2/D1≦0.4). At the same time, even if the ratio of the maximum thickness A2 of the flange 5 to the flange diameter D1 is (A2/D1>0.4), the defect rate is small, so the upper limit of (A2/D1) is It can be seen that even the invention of claim 1, which is not limited, can sufficiently achieve the intended purpose.

Next, from among the tappets I obtained in the above test, one with a small amount of crowning (approximately 15 μm) was extracted, and the amount of crowning was measured while heated to 150° C., which corresponds to the maximum temperature during operation. did. The results are shown in the graph of FIG. As a result of heating the tappet to 150°C and measuring it, it was found that even when crowning was formed within the allowable range at room temperature, the ratio of the maximum thickness A2 of the flange 5 to the flange diameter D1 was (A2/ For those with D1<0.1),
It was confirmed that the crowning shape was not maintained and became almost flat, or the crowning shape was reversed. Then, a part of the test sample was installed in an OHV diesel engine (displacement 15,000cc, 8 cylinders), and the engine speed was increased to 150% of the rated rotation speed (approximately 2,500 rpm).
When the tappet I was operated for 100 hours, the ceramic plate 2 became flat or had an inverted crowning shape, and abnormal wear occurred on the cam. On the other hand, in the case where the tappet I according to the present invention was used, the wear amount of both the tappet I and the cam was 3 μm or less, and there was no problem at all.

[0011]

Embodiment 2 FIG. 4 is a longitudinal sectional view showing a tappet II of Embodiment 2. The tappet II has a metal tappet body 1 divided into an upper half 1a and a lower half 1b which are welded together, and a ceramic plate 2 is brazed to the bottom wall of the tappet body 1. Upper half 1a is JIS S40
It is machined into a bottomed cylindrical shape from a round steel bar of No. C, and heated to 900°C and quenched in oil. The lower half 1b is JIS
It is machined and molded from SNCM630 steel. The ceramic plate 2 is the same as the tappet I described above. First, the lower half 1b and the ceramic plate 2 were brazed under the same conditions as the tappet I, and then the upper half 1a and the lower half 1b were joined by electron beam welding.

Next, test samples based on Tappet II were manufactured, and variations in the amount of crowning were investigated in the same manner as above. Variation in crowning amount for each shape (±3
σ) is shown in FIG. In addition, the dimensions of each part of Tappet II are as follows:
Total length L = 60 mm, flange diameter D1 = φ33 mm, slider part outer diameter D2 = 20 mm, same inner diameter D3 = 15 mm, thickness A1 of ceramic plate 2 = 1.5 mm, 2 mm, 3 mm,
Taper angle α of flange 5 = 20° (however, A2/D1<0.
1), and the maximum thickness A2 of the flange portion 5 was variously changed in order to confirm the effect of the present invention. This result also confirms that the crowning shape of the tappet II according to the present invention is within the permissible range.

[0013]

[Effects of the Invention] As is clear from the above test results using the test samples, the tappet of the present invention can minimize variations in the amount of crowning during production. As a result, the yield rate of tappet manufacturing can be significantly improved. In other words, since the amount of crowning itself can be controlled by changing the bonding temperature and cooling temperature of the ceramic plates, the bonding temperature and the like can be set so that the variation is within the range of the allowable crowning amount. Further, when the dimensional ratio of the present invention is set, the crowning amount changes are insensitive to temperature changes, and the crowning amount decreases very little even with temperature changes during operation. As described above, the present invention can significantly improve the productivity and reliability of the technique of forming a crowning shape by utilizing the difference in coefficient of thermal expansion between metal and ceramic plates. Furthermore, by limiting the maximum thickness of the flange to 0.4 times or less the diameter of the flange, defects such as cracking and peeling of the ceramic plate during production are prevented.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a tappet showing Example 1.

FIG. 2 is a graph showing the relationship between (maximum thickness of flange/diameter of flange) and (variation in crowning amount).

FIG. 3 is a graph showing the relationship between (maximum thickness of flange/diameter of flange) and (amount of crowning at 150° C.).

FIG. 4 is a longitudinal cross-sectional view of a tappet showing Example 2.

FIG. 5 is a graph showing the relationship between (maximum thickness of flange/diameter of flange) and (variation in crowning amount).

[Explanation of symbols]

I, II...Tappet １　　　　　…Tappet body 2… Ceramic plate ４　　　　　…Slider section 5…Trim section D1...Flame diameter A1...Thickness of ceramic plate A2...Maximum thickness of the flange

Claims (2)

[Claims] Claim 1: A metal tappet body having an inverted mushroom shape with a flange formed at the lower end of the slider portion, and a metal tappet body that is joined to the bottom wall of the tappet body and utilizes the difference in coefficient of thermal expansion between the tappet body and the tappet body. In a tappet consisting of a ceramic plate that is crowned with
0.1), and the dimensional ratio between the maximum thickness A2 of the collar portion and the thickness A1 of the ceramic plate is (A2/A1≧2). [Claim 2] Maximum thickness A of the flange portion of the tappet body
2 and the flange diameter D1 (0.1≦A2/D1≦0
．． 4) The tappet according to claim 1, wherein the tappet has the following features.