JPH1089018A - Tappet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the structure of a tappet main body easily, thereby reducing costs. SOLUTION: In a tappet in which a ceramic plate is brazed to a bottom surface of a steel tappet body, the tappet body is divided into an upper half and a lower half, and the lower half is brazed to the ceramic plate. A tappet formed of a steel material that can be hardened under heating conditions during the heat treatment, and having an upper half and a lower half joined by a brazing material that does not contain phosphorus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tappet used for an automobile engine or the like.

[0002]

2. Description of the Related Art In recent years, a technique of brazing and joining a ceramic plate to the bottom surface of a steel tappet body in order to improve the abrasion resistance of the tappet in response to an increase in the output of an engine has been disclosed in, for example, Japanese Unexamined Patent Publication No. No. 55809 and the like. The tappet body described in Japanese Unexamined Patent Publication No. 2-55809 is integrally formed of a steel material such as JIS SNCM630 or SKC24, and the steel material is cured under heating conditions when brazing a ceramic plate. The heating conditions refer to brazing temperature, brazing time, cooling after brazing, and the like.

[0003]

However, the steel materials such as JIS SNCM630 and SKC24 applicable to the prior art have a drawback that their workability is poor. Therefore, if the above-mentioned prior art is applied as it is, the processing cost of the tappet body is high, and the tappet becomes very expensive due to the high value of the material itself. This tendency is particularly strong in tappets that require deep hole processing.

An object of the present invention is to provide a tappet having a composite structure of ceramic and steel, which is excellent in all aspects of strength (durability), workability and cost.

[0005]

According to the present invention, there is provided a tappet in which a ceramic plate is brazed to a bottom surface of a tappet body made of steel. The lower half is formed of a steel material having a property that can be hardened under heating conditions when brazing the ceramic plate, and the upper half and the lower half are joined with a brazing material that does not contain phosphorus. A tappet is provided.

[0006]

The ceramic plate smoothly slides with the cam and improves the durability of the tappet due to its high abrasion resistance. Also,
The lower half of the tappet body can be hardened by the heat of brazing the ceramic plate and thus has a high strength, and absorbs the shock caused by sliding with the cam to prevent the ceramic plate from cracking. In addition, since the upper half of the tappet body only slides in the axial direction within the guide hole of the cylinder block, it is possible to use an inexpensive steel material that is easy to process, and the shape is simplified. Therefore, the processing itself becomes easy and the cost is reduced. Furthermore, when the upper half and the lower half are brazed and joined with a brazing material that does not contain phosphorus, a tappet body having practically sufficient strength can be obtained even with a divided structure.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is an exploded perspective view showing a half section of the tappet of the first embodiment, and FIG. 2 is a longitudinal sectional view of the tappet. As shown in FIGS. 1 and 2, the tappet includes a tappet body 1 made of a steel material and a ceramic plate 2 joined to the bottom surface of the tappet body 1.

The tappet main body 1 has an inverted mushroom shape by an upper half 1a having a bottomed cylindrical shape and a lower half 1b having a substantially truncated cone shape. A hemispherical recess 4 for receiving the lower end of the push rod is formed in the center of the inner surface of the bottom wall 3 of the upper half 1a.

Since the upper half 1a only slides up and down in the guide hole of the cylinder block, the required level of wear resistance is low. Therefore, it is sufficient to use a steel material which is inexpensive and has good workability. For example, JIS SNCM616 and SNC
815 and the like. When the slidability, abrasion resistance or rigidity of the steel material is insufficient, a hardening treatment such as carburization, induction hardening, and electron beam quenching may be performed as necessary.

On the other hand, the lower half 1b must have high strength because it is necessary to absorb the shock caused by sliding with the cam to prevent the ceramic plate 2 from cracking. For this reason, a steel material having a property of being hardened under heating conditions for brazing the ceramic plate 2 is used. For example, JIS SNCM
630 is preferred.

The upper half 1a and the lower half 1b are joined by brazing with a brazing material 5 not containing phosphorus. This is because, if a brazing filler metal containing phosphorus is used, the iron in the steel and the phosphorus in the brazing filler metal may form an intermetallic compound and significantly lower the joining strength. Further, impurities such as silicon, aluminum, iron, and yttrium are mixed into the brazing material 5 during the manufacturing process, and it is preferable that these are suppressed to 0.1% by weight or less. When a silver braze containing copper is used as the brazing material 5, it is preferable to increase the copper content because brazing strength can be improved. This is because steel and copper react well. Furthermore, it is desirable that the brazing material does not include elements that are not suitable for brazing in a furnace, such as zinc and cadmium. This is because the brazing of the lower half 1b and the ceramic plate 2, which will be described later, may be adversely affected by a non-oxidizing atmosphere such as vacuum or argon.

The ceramic plate 2 to be joined to the bottom surface of the tappet body 1 is used to enhance the slidability with the cam and the abrasion resistance, and any material can be used as long as such an object can be achieved. For example, normal pressure silicon nitride is suitable.

The ceramic plate 2 and the lower half 1b are brazed with a brazing material 6. The brazing material 6 may have the same composition as the brazing material 5 used for brazing the upper half 1a and the lower half 1b, or may have a completely different composition.

Samples A to I shown below were prepared based on the tappet of Example 1 as described above, and the strength of the joint was measured as shown in FIG. For comparison with the present invention, samples J and K were prepared and the same strength measurement was performed.

The size of each sample A to K is 5 mm
0mm, maximum diameter of lower half 1b 35mm, height 13m
m, the outer diameter of the upper half 1a is 21 mm, the inner diameter is 15 mm, the diameter of the ceramic plate 2 is 35 mm, and the thickness is 2 mm.

The ceramic plate 2 of each of the samples A to K was prepared by mixing a Y2O3-Al2O3-based sintering aid with 90% by weight of silicon nitride.
A molding binder was added, the mixture was molded into a disk shape by a mold press, and after firing, both surfaces were polished. The upper half 1a and the lower half 1b were made by cutting the steel materials shown in Table 1. Sample A ~
In E and GI, after the upper half 1a and the lower half 1b were brazed with the brazing material of Table 1, the lower half 1b and the ceramic plate 2 were brazed with the brazing material of Table 1. The samples F and K are the upper half 1a.
And the lower half 1b and the ceramic plate 2 were simultaneously brazed. The respective brazing temperatures are as shown in Table 1. The sample J was prepared by welding the upper half 1a and the lower half 1b by electron beam welding and then lowering the lower half 1b.
And the ceramic plate 2 were brazed at the brazing material and temperature shown in Table 1.

The measurement of the bonding strength of each of the samples A to K is performed by fixing each of the samples A to K horizontally as shown in FIG. 3 and attaching the samples A to K to the lower half 1b and the ceramic plate 2 at a speed of 0.5 mm / min. A load W was applied up to 000 kg. Table 1 shows the results.

[0018]

[Table 1]

The following items were confirmed from Table 1. From the results of Samples D and J, the upper half 1a and the lower half 1 were welded.
b, the JIS SNCM447 cannot be used, but when the upper half 1a and the lower half 1b are joined by brazing, the JIS SNCM447 can be sufficiently used. Sample I consisted of an upper half 1a and a lower half 1 with a load of 3,500 kg.
b has broken from the brazing surface (however, withstand load 3,
500 kg is a strength with no practical problem. ), Sample F → sample E → samples A to D, the bonding strength gradually increases. Therefore, in a silver solder containing copper, the bonding strength is increased by increasing the content of copper. Sample K contains 5% by weight of phosphorus in the brazing material 5 of the upper half 1a and the lower half 1b, but breaks from the brazing surfaces of the upper half 1a and the lower half 1b under a load of 500 kg. Therefore, when phosphorus is contained in the brazing material 5, the brazing strength is reduced.

[0020]

Second Embodiment FIG. 4 is a longitudinal sectional view of a tappet according to a second embodiment. The tappet body 1 of this tappet has an upper half 1a
Is formed in the shape of a pipe, and the upper half 1a is tightly fitted to a circular projection 7 protruding from the upper surface of the lower half 1b, brazed with a brazing material 5, and further receives a lower end of a push rod. Is provided in the circular projection 7 of the lower half 1b.
By forming the upper half 1a in a pipe shape in this way, it is possible to use a commercially available pipe material to save processing costs, and to fit the upper half 1a into the lower half 1b (tight fit). By performing brazing, the joining strength of the brazed portion is increased, and there are advantages that the thickness of the upper half 1a can be reduced.

Samples L to R as shown below were prepared based on the tappet of Example 2 as described above, and the strength of the joint was measured by the same method as described above. In addition, in order to make a comparison with the present invention, a sample S was prepared and the strength was measured.

The dimensions of each of the samples L to S correspond to the total length of the tappet.
0 mm, the maximum diameter of the lower half 1b is 35mm, the height of the lower half 1b up to the circular projection 7 is 13mm, and the height of the circular projection 7 is 5
mm, the outer diameter of the upper half 1a is 21 mm, the inner diameter is 15 mm, the diameter of the ceramic plate 2 is 35 mm, and the thickness is 2 mm.

The ceramic plate 2 of each of the samples L to S is the same as the sample A and the like. The upper half 1a is made of a metal material as shown in Table 2, and the samples Q and R using JIS S40C are made of commercially available pipes, and the other samples are made by cutting round bars. The upper half 1a of each of the samples P, Q, and S was subjected to induction hardening to a depth of 0.5 mm on the outer periphery of the upper half 1a after completion. The lower half 1b was cut using JIS SNCM630 for each sample. Samples L, N, and O were prepared by brazing the upper half 1a and the lower half 1b with the brazing material shown in Table 2 and then lowering the lower half 1b and the ceramic plate 2.
Was brazed with the brazing material in Table 2. Samples M, P,
As for Q and R, the brazing of the upper half 1a and the lower half 1b and the brazing of the lower half 1b and the ceramic plate 2 were simultaneously performed. The respective brazing temperatures are as shown in Table 2. Also,
For sample S, the upper half 1a and the lower half 1b were welded by electron beam welding, and then the lower half 1b and the ceramic plate 2 were brazed at the same temperature as the brazing material in Table 2.

The measurement of the bonding strength of each of the samples L to S is performed by fixing each of the samples L to S horizontally as shown in FIG. A load W was applied up to 000 kg. Table 2 shows the results.

[0025]

[Table 2]

From the results of the samples P and S, the upper half 1a was welded.
JIS S50C cannot be used when the upper half 1a and the lower half 1b are joined by brazing, but it can be confirmed that JIS S50C can be sufficiently used when the upper half 1a and the lower half 1b are joined by brazing.

[0027]

As apparent from the above description, according to the present invention, the ceramic plate makes the sliding with the cam smooth and improves the durability of the tappet by high abrasion resistance. It can be hardened by the heat of brazing, so it has high strength and absorbs the shock caused by sliding with the cam to prevent cracking of the ceramic plate.The upper half is the shaft inside the guide hole of the cylinder block Because it only slides in the direction, it is possible to use an inexpensive steel material that is easy to process, and because the shape is simplified, the processing itself is easy and the cost is reduced. When the parts are brazed and joined with a brazing material that does not contain phosphorus, the tappet body has practically sufficient strength even if it is a split structure, and the elements interact organically, such as strength (durability). Excellent in all aspects of workability and cost Pets can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a tappet of a first embodiment in a half cross section.

FIG. 2 is a longitudinal sectional view of the tappet according to the first embodiment.

FIG. 3 is a cross-sectional view showing a bonding strength measurement test.

FIG. 4 is a longitudinal sectional view of a tappet according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tappet main body 1a ... Upper half 1b ... Lower half, 2 ... Ceramic plate 5 ... Brazing material

[Procedure amendment]

[Submission date] June 20, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005]

Means for solving the problems are as follows. In a tappet obtained by brazing a ceramic plate to the bottom surface of a tappet body made of steel material, the tappet body is divided into an upper half and a lower half, and the lower half is divided into two parts. A tappet formed of a steel material that can be hardened under heating conditions for brazing the ceramic plate, and having an upper half and a lower half joined with a brazing material that does not contain phosphorus. In the tappet, it is preferable that Cr contained in the lower half is equal to or more than Cr contained in the upper half. In the tappet, it is preferable that Mo contained in the lower half is equal to or more than Mo contained in the upper half. In the tappet, Cr and Mo contained in the lower half are replaced with Cr contained in the upper half.
It is preferable that Mo is contained equal to or more than Mo and Mo.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

The ceramic plate smoothly slides with the cam and improves the durability of the tappet due to its high abrasion resistance. Also,
The lower half of the tappet body can be hardened by the heat of brazing the ceramic plate and thus has a high strength, and absorbs the shock caused by sliding with the cam to prevent the ceramic plate from cracking. In addition, since the upper half of the tappet body only slides in the axial direction within the guide hole of the cylinder block, it is possible to use an inexpensive steel material that is easy to process, and the shape is simplified. Therefore, the processing itself becomes easy and the cost is reduced. Furthermore, when the upper half and the lower half are brazed and joined with a brazing material that does not contain phosphorus, a tappet body having practically sufficient strength can be obtained even with a divided structure. If the Cr contained in the lower half is equal to or greater than the Cr contained in the upper half, the hardening of the lower half is enhanced by Cr having an effect of improving workability. On the other hand, it is possible to enhance the workability of the upper half where the workability is required without requiring the curability. When the Mo contained in the lower half is equal to or more than the Mo contained in the upper half, the curability of the lower half is increased by Mo having an effect of improving workability. On the other hand, it is possible to enhance the workability of the upper half where the workability is required without requiring the curability. When Cr and Mo contained in the lower half are equal to or more than Cr and Mo contained in the upper half, C having an effect of improving workability is provided.
While the curability of the lower half can be enhanced by r and Mo, the workability of the upper half, which does not require curability and requires workability, can be enhanced.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

The measurement of the bonding strength of each of the samples A to K is performed by fixing each of the samples A to K horizontally as shown in FIG. 3 and attaching the samples A to K to the lower half 1b and the ceramic plate 2 at a speed of 0.5 mm / min. A load W was applied up to 000 kg. Table 1 shows the results. In addition, the contents of Cr and Mo in the materials constituting the upper half and lower half of each sample are shown below. Cr (% by weight) Mo (% by weight) JIS-SNC815 0.70 to 1.00 0.15 to 0.30 JIS-SNCM616 1.40 to 1.80 0.40 to 0.60 JIS-SNCM630 2.50 ３3.50 0.50 to 0.70 JIS-SNCM447 0.60 to 1.00 0.15 to 0.30 JIS-S40C 0.2 or less 0.2 or less

Claims (1)

[Claims] 1. A tappet in which a ceramic plate is brazed to a bottom surface of a steel tappet body, wherein the tappet body is divided into an upper half and a lower half, and the lower half is brazed to the ceramic plate. A tappet characterized by being formed of a steel material that can be hardened under heating conditions during attachment, and having an upper half and a lower half joined with a brazing material that does not contain phosphorus.