JPH09242512A - Tappet - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To improve workability when brazing a ceramic chip, to improve the bonding strength by reducing blow holes, and to prevent chipping of the ceramic chip, and reliability when using a tappet. Improve sex. SOLUTION: A ceramic chip 22 that comes into contact with a cam is brazed to a bottom surface of a tappet body 21a so as to cover the bottom surface 21b. Chamfering C is applied to the entire peripheral edge of the bottom surface. It is also possible to form a radial pattern from the center of the bottom surface of the tappet body toward the periphery, and the surface roughness of the bottom surface due to the pattern is preferably 2 to 15 μm. It is more preferable that the entire periphery of the surface of the ceramic chip that contacts the cam be rounded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tappet used in an engine having a cam structure. More specifically,
The present invention relates to a tappet in which a ceramic tip that contacts a cam is brazed so as to cover the bottom surface of the tappet body.

[0002]

2. Description of the Related Art A four-cycle engine is usually equipped with a valve system. The valve is generally shaped like a mushroom and is closed by the force of a coil spring. By opening this valve, it is possible to perform intake and exhaust in the operation process of 4 cycles,
Gas can be exchanged between the combustion chamber and the cylinder from the opened valve. The device that opens the valve by pressing it connects the rotation of the crankshaft to the camshaft with a timing belt, chain, or gear, and opens and closes the valve via a rocker arm by rotating the substantially oval cam provided on the camshaft with the shaft. Let The valve system can be classified according to the position where the camshaft is provided. The so-called overhead camshaft system and the overhead valve system (hereinafter referred to as OH
V).

As shown in FIG. 5, in an OHV, one end of a rocker arm 18 is pushed up through a pair of push rods 17 that are upright by the rotation of a cam shaft 12 positioned horizontally on the cylinder side, and the arm 18 is a seesaw type. The valve 19 is pushed down and opened.
The cam 1 of the camshaft 12 is located below the push rod 17.
A tappet 21 that abuts 6 is mounted, and the push rod 17 is configured to move up and down by rotation of the cam 16 via the tappet 21. According to this OHV, valve 1
Since 9 can be located above the head of the cylinder, the combustion chamber can be formed in a hemispherical shape or a wedge shape, so that the degree of freedom in design can be increased.

On the other hand, since the tappet 21 provided under the push rod 17 is in constant contact with the rotating cam 16 and rubs against each other, abrasion resistance is required. In particular, in order to cope with higher engine output in recent years, the tappet 21 is required to have very high wear resistance. In order to satisfy this requirement of wear resistance, a technique of brazing a ceramic chip so as to cover the bottom surface of the tappet body has been developed. The brazing of the ceramic chip to the bottom surface of the tappet body is performed by interposing a brazing material between the bottom surface of the tappet body and the ceramic chip, locating them concentrically and pressing their peripheral edges, and in this state. It is carried out by applying an appropriate load to the heat treatment. By brazing the ceramic tip to the bottom surface of the tappet body in this manner, the durability of the tappet 21 that abuts on the cam 16 can be improved by utilizing the excellent wear resistance of the ceramic.

[0005]

However, when the ceramic chip is brazed to the bottom surface of the tappet body, a brazing material is interposed therebetween and the brazing is performed at a predetermined temperature. Therefore, a blow hole is provided between the ceramic chip and the bottom surface. Could remain. In order to eliminate this point and obtain a highly reliable tappet, the joining surface is loaded with a slightly larger amount of brazing material than necessary, and excess brazing material is applied to the outer peripheral edge of the joining surface during heating brazing. Is made to protrude. However, in the brazing material near the center of the ceramic chip, the surface roughness of the bottom surface of the ceramic chip and the tappet body becomes a resistance and does not effectively protrude from the peripheral edge, and it is impossible to prevent blowholes near this center. was there. Further, since the peripheral edge of the ceramic chip is usually pressed by the base plate or the like, the protruding brazing material adheres to the base plate. Processing after brazing may be difficult.

On the other hand, the Young's modulus of the ceramic chip is 30,000 to 500, as compared with 21,000 kg / mm ^{2 of} iron.
It is as high as 00 kg / mm ² . Especially in the influence on the Hertzian surface pressure used for the reliability evaluation of the valve train, as the Young's modulus increases, 2
It is said to rise by 0 to 50%. Therefore, it is necessary to reduce the curvature of the ceramic chip as much as possible to bring the crowning shape closer to a flat shape. However, when this flatness is applied to the peripheral edge of the ceramic chip, there are corners on the peripheral edge of the ceramic chip, and stress concentrates on the peripheral edge of the surface of the ceramic chip that contacts the cam, and the peripheral corners may be chipped. . In particular, when the valve is opened, the external force tends to concentrate near the periphery of the ceramic tip with which the cam abuts, and the tappet may be damaged during use. It is an object of the present invention to provide a highly reliable tappet with improved workability during brazing of ceramic chips and improved bonding strength by reducing blow holes. Another object of the present invention is to provide a tappet capable of preventing chipping of the ceramic chip and improving reliability when the tappet is used.

[0007]

The invention according to claim 1 is
As shown in FIG. 1, the ceramic tip 2 that contacts the cam
2b so that 2 covers the bottom surface of the tappet body 21a.
It is an improvement of the tappet brazed to. The characteristic structure is that chamfering C is applied to the entire peripheral edge of the bottom surface 21b. When the ceramic chip 22 is brazed, the brazing material flows out to the periphery of the bottom surface 21b. The brazing material that has flowed out is collected in the chamfered portion provided on the bottom surface 21b and does not leak to the outer periphery of the bottom surface 21b. Chamfer C is 0.
It is preferably in the range of 1 mm to 1.0 mm, and more preferably C is in the range of 0.3 mm to 0.5 mm. If C exceeds 1.0 mm, the brazing area with the ceramic chip 22 is reduced, and if C is less than 0.1 mm, all the brazing material that has flowed out cannot be collected.

The material of the tappet body 21a is JIS; S
NCM630 and SNCM616 are illustrated. The tappet body 21a is manufactured by forging or cutting such a steel material, and the bottom surface 21b is ground or polished in a post process. The ceramic chip 22 includes Si ₃ N ₄ , SiC, Al.
₂ O ₃ , zirconia, etc. are exemplified, and the plate thickness thereof is set so that at least the strength capable of withstanding the impact received from the cam is secured. It is preferable that the brazing means is heat-bonded by a silver braze containing Ti. Ag-as a brazing material system
Cu-Ti system, Ag-Cu-In-Ti system, Ag-Ti
A system, Cu-Ti system, and Ag-Cu-Ni-Ti system are especially preferable. Further, the brazing surface of the ceramic chip 22 may be preliminarily subjected to a metallizing process by a vapor deposition method or the like. In that case, Ag—Cu based and Ag—Cu—In based brazing materials are preferable. The atmosphere of the brazing material is preferably a non-oxidizing atmosphere such as vacuum, argon gas, hydrogen gas or nitrogen gas, and in the case of the brazing material containing Ti, it is particularly preferable to perform brazing in a vacuum or argon gas atmosphere.

In the invention according to claim 2, as shown in FIG. 2, in the invention according to claim 1, the tappet body 21a is provided.
A radial pattern M is formed from the center of the bottom surface 21b of the bottom surface 21b to the periphery, and the surface roughness of the bottom surface 21b due to the pattern M is 2
It is a tappet that is ˜15 μm. By forming the pattern M radially, the gas at the time of brazing is guided along the pattern and is effectively discharged to the outside from the peripheral edge of the bottom surface 21b. This processing is preferably performed by an eccentric milling cutter. If the surface roughness exceeds 15 μm, the gas is prevented from being discharged to the peripheral edge, and if it is less than 2 μm, processing becomes difficult.

The invention according to claim 3 is an improvement of the tappet, as shown in FIG. 1, in which the ceramic tip 22 contacting the cam is brazed to the bottom surface 21b so as to cover the bottom surface of the tappet body 21a. The characteristic structure is a tappet in which a rounded R is formed on the entire peripheral edge of the surface of the ceramic chip 22 that contacts the cam. The rounding R eliminates the presence of the corners of the peripheral edge of the ceramic chip 22 and prevents stress concentration on the peripheral edge of the surface of the ceramic chip 22 that contacts the cam.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. As shown in FIG. 5, in the OHV of this embodiment, the cam shaft 12 is horizontally arranged on the cylinder side where the piston 11 moves up and down. The camshaft 12 and the crankshaft 13 are connected by a gear 14, and when the crankshaft 13 rotates, the camshaft 12 rotates and a pair of substantially oval cams 16 provided on the camshaft 12 stand upright. It is configured to move the push rod 17 up and down. When the pair of push rods 17 moves upward, one end of the rocker arm 18 is pushed up, the arm 18 rotates in a seesaw manner, the other end pushes down the valve 19 to open it, and the valve 19 moves to the lower side of the coil spring 20. It is designed to close by force. A tappet 21 that comes into contact with the cam 16 of the camshaft 12 is attached to the lower portion of the push rod 17, and the push rod 17 is configured to move up and down by rotation of the cam 16 via the tappet 21. Since the pair of tappets 21 have the same structure, one tappet 21 will be described below.

As shown in FIGS. 1 and 3, the tappet 21
The ceramic chip 22 is the bottom surface 2 of the tappet body 21a.
It is brazed to cover 1b. Tappet body 21a
Is made by cutting a metal member such as JIS standard SNCM630, and push rod 17 is attached to the small diameter part.
Has a hole 21c into which the lower end thereof is inserted, and a recess 21d with which the lower part of the push rod 17 engages is formed in the lower part of the hole 21c. Examples of the ceramic chip 22 include Si ₃ N ₄ . That is, the ceramic chip 22 is a silicon nitride sintered body, and has a diameter of 38 mm and a thickness of 1.
The surface roughness Ra of the joint surface is 0.2-
Polished to 0.3 μm. Further, as shown in FIG.
As shown in the enlarged view of FIG. 1, rounding R having a radius of about 3 mm is performed.

The tappet body 21a has a large diameter portion of 38.5 m.
m, the small diameter portion is 22.5 mm, and the height is 5.5 mm, and is processed into a substantially mushroom shape, and the lower surface of the large diameter portion, that is, the bottom surface 21b is polished to have a surface roughness Ra of 0.2 to 0.3 μm. The polishing is performed by an eccentric milling process, and as shown in FIG. 2, it is processed so as to form a radial pattern M from the center of the bottom face toward the periphery. The bottom surface 2 caused by the radial pattern M at this time
The surface roughness of 1b is adjusted to be in the range of 2 to 15 μm. After polishing the bottom surface 21b, as shown in the enlarged view of FIG. 1, a chamfer C of about 0.3 mm is further applied to the entire periphery of the bottom surface 21b.

As shown in FIG. 4, the ceramic chip 22
Of the ceramic chip 22 and the concave portion 31 formed slightly larger than the outer diameter of the bottom surface 21b.
The ceramic chip 22 is arranged on the base plate 32 having the tappet main body 21a so that the bottom surface 21b of the tappet main body 21a overlaps the ceramic chip 22 with the brazing material 23 interposed therebetween.
Carry out a. The brazing material 23 has a diameter of 38 mm and a thickness of 55.
In-Ti-C slightly larger than required formed in μm
Activated brazing material (foil) for u-Ag ceramic chip 23
And the bottom surface 21b are overlapped with each other. Recess 31
Has a depth for accommodating the ceramic chip 22 and the bottom portion of the tappet body 21a placed on the ceramic chip 22 so that the bottom surface 21b overlaps with each other, and these are concentrically positioned to press their peripheral edges. There is. In this state, a load P is applied to the upper portion of the tappet body 21a, and the ceramic chip 22 is brazed to the bottom surface 21b of the tappet body 21a by heat treatment.

In the tappet 21 thus constructed, the brazing material 23 that flows out when the ceramic chip 22 is brazed flows out and accumulates in the chamfered portion C provided on the peripheral edge of the bottom surface 21b. Also, the gas when brazing is the bottom surface 21b.
The sheet is guided along the pattern M formed on the bottom surface and is effectively discharged to the outside from the peripheral edge of the bottom surface 21b.

[0016]

As described above, according to the present invention, since the entire periphery of the bottom surface of the tappet body is chamfered, the brazing material that flows out when the ceramic chip is brazed is collected in this chamfered portion and the bottom surface is collected. Do not leak to the outer circumference. As a result, the workability at the time of brazing the ceramic chip can be improved without the brazing material adhering to the base plate or the like for brazing. Further, if a radial pattern having a surface roughness of 2 to 15 μm is formed, the gas at the time of brazing is guided to the outer periphery of the bottom surface along the pattern and is effectively discharged to the outside from the peripheral edge of the bottom surface. Blow holes can be reduced, and the bonding strength to the bottom surface of the ceramic chip can be improved. Furthermore, if the entire peripheral edge of the surface of the ceramic chip that contacts the cam is rounded, the corners of the peripheral edge of the ceramic chip are eliminated by this rounding, and stress concentration on the peripheral edge of the surface of the ceramic chip that contacts the cam is prevented. can do. As a result, it is possible to prevent chipping of the ceramic chip due to stress concentration and improve reliability when the tappet is used.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a tappet of the present invention.

FIG. 2 is a bottom view of the tappet.

FIG. 3 is a perspective view showing a relationship between a ceramic chip showing the tappet and a bottom surface.

FIG. 4 is a cross-sectional view showing a state in which a ceramic chip is brazed to the bottom surface.

FIG. 5 is a structural diagram showing an OHV using the tappet of the present invention.

[Explanation of symbols]

 16 Cam 21 Tappet 21a Tappet Body 21b Bottom 22 Ceramic Chip C Chamfer R Rounded M Pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayoshi Ohno, Mayor of Sodegaura, Chiba Prefecture, No. 2 580-99, Kasaya Seiko Co., Ltd. Within Automotive Industry Co., Ltd.

Claims (3)

[Claims] 1. The bottom surface (2) of the tappet body (21a) is covered with a ceramic tip (22) contacting the cam.
The tappet brazed to 1b), wherein the entire periphery of the bottom surface (21b) is chamfered (C). 2. The tappet body (21a) is formed with a radial pattern (M) from the center of the bottom surface (21b) toward the periphery thereof,
The surface roughness of the bottom surface (21b) due to (M) is 2 to 15 μm.
The tappet according to claim 1, wherein 3. The bottom surface (2) of the tappet body (21a) is covered so that the ceramic tip (22) contacting the cam covers the bottom surface (21b) of the tappet body (21a).
The tappet brazed to 1b), wherein the ceramic tip (22) is rounded (R) on the entire periphery of the surface in contact with the cam.