JPH06200715A - Hollow tappet - Google Patents

Abstract

PURPOSE:To provide a hollow tappet of a mushroom type, light in weight and excellent in abrasion resistance. CONSTITUTION:A tappet main body 3 having a hollow 2 opened toward a shade 6 is made of steel. A sliding portion 51 with respect to a cam is composed of a sintered chip 5. A steel back plate 4 is interposed between the main body 3 and the sintered chip 5, so as to close the opening of the tappet main body 3. The sintered chip 5 is diffusion-joined to the steel back plate 4, which is brazed to the main body 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is one of valve operating mechanism parts for an internal combustion engine, and is of an overhead valve type (hereinafter, referred to as O
HV system), a tappet provided between a cam and a push rod.

[0002]

2. Description of the Related Art A tappet in an OHV type engine slides on a cam surface of a cam shaft and converts the rotational movement of the cam into a reciprocating movement of a push rod to smoothly transmit it to a valve. Since wear resistance is required for the sliding portion of the tappet with the cam, chill cast iron, high alloy steel, sintered alloy or carburized steel has been conventionally used. For example, as shown in FIG. 4, in a mushroom type tapet, the base material is steel material 3 having excellent strength, and liquid phase sintered material chip 5 is firmly bonded by diffusion bonding to the cam contact surface that slides under high surface pressure. It was joined to improve the wear resistance.

On the other hand, due to the recent social situation, it is more and more necessary to increase the engine rotation speed and reduce the weight. Among the valve mechanism components, reducing the weight of the tappet having a large inertial weight means increasing the engine rotation speed. This is the most effective means for achieving this. In order to reduce the weight, it is conceivable to make the tappet hollow. For example, in Japanese Utility Model Laid-Open No. 60-6803 and Japanese Unexamined Patent Publication No. 4-71705, the lower half portion (shaft portion) of the tappet and abrasion resistance There is disclosed a technique in which a hollow portion is provided to reduce the weight by joining an upper half portion having a sliding portion with a cam that requires the above. In cast iron tappets, tappets that are hollow and lightened using a core are partially used.

[0004]

However, since the mushroom type tappet has a thin shaft portion structurally, it is necessary to use a core during casting or hollow the shaft portion by machining. Has a problem of poor workability and productivity. Furthermore, as described above, when the sliding parts with the upper half and lower half cams are formed respectively, and then they are joined and integrated, the man-hour There was also a problem that it took a lot of time. Further, as shown in FIG. 5, it is conceivable to perform a plastic working such as drilling or forging in advance on the base material of the steel material to provide the hollow portion 2 and to join the sintered material chips 5, but this structure is high. Since the cam slides on the sintered material tip when the load rotates at high speed, stress is applied to the part that contacts the hollow portion of the sintered material tip, and because the sintered material tip is weak against impact force, problems such as cracking occur. It may occur. The present invention has been made in view of these problems, and an object thereof is to provide a mushroom type hollow tappet which is lightweight and has excellent wear resistance.

[0005]

In order to achieve the above object, the present invention is a mushroom type tappet used in a valve operating system of an internal combustion engine, wherein a tappet body (shaft portion) having a hollow portion opening to the umbrella side. Is made of steel, a sintered material tip is used for the sliding part with the cam, and a steel back plate is inserted between the main body and the sintered material tip to cover the opening of the tappet body. The hollow tappet is characterized in that the sintered material chip and the steel back plate are joined by diffusion bonding, and the main body and the steel back plate are joined by brazing.

[0006]

According to the present invention, the sintered material chip is reinforced by inserting the steel back plate between the sintered material chip and the main body, and there is no fear of cracking even when a high load and an impact load are applied. It was possible to provide a tappet with excellent wear resistance. In addition, the diameter of the hollow part can be increased to the required value for the strength of the shaft part. Further, when the sintered material chip and the steel back plate are baked, the steel back plate and the main body can be brazed at the same time, and the productivity is high.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a tappet according to a first embodiment of the present invention. The tappet 1 has a surface 7 that is in sliding contact with the push rod.
And a sliding portion 51 between the main body 3 having the hollow portion 2 and the cam
And an umbrella portion 6 having. The main body 3 is made of steel, and the hollow portion 2 is formed by cutting, plastic working or the like so as to open to the umbrella portion side. The umbrella portion 6 is composed of a steel back plate 4 arranged so as to cover the opening of the tappet body, and a sintered material chip 5 provided on the back plate. Here, the steel back plate serves to reinforce the sintered material chips. A convex portion 52 and a concave portion 41 are provided on the sintered material chip and the back plate respectively for positioning. Further, a convex portion 42 and a concave portion 31 are provided for positioning the back plate and the main body, respectively.

The sintered material chip and the back plate are connected by diffusion bonding through a sintering furnace. Also, the back plate and the body are joined by brazing. Since brazing is performed at the same time as diffusion bonding, it can be supplied inexpensively in a small number of steps. As the brazing material used for brazing, pure copper or the like is used, but a brazing material selected according to the temperature of the sintering material is selected. The brazing material is
Paste, ring or foil is brazed between the back plate and the body. An example of a ring-shaped brazing material set is shown in FIG.

Next, FIG. 2 shows a sectional view of a tappet according to a second embodiment of the present invention. Similar to the first embodiment, a steel tappet body 3 having a hollow portion 2 that opens to the umbrella side.
And a steel back plate 4 disposed so as to cover the tappet body, and a sintered material chip 5 provided on the back plate. The main body, the back plate, and the sintered material chip are sequentially installed in a lid shape for positioning between the sintered material chip, the back plate, and the main body.

[0010]

As described above, in the mushroom type tappet for an internal combustion engine, a steel base material is previously subjected to plastic working such as drilling or forging to form a hollow portion opening to the umbrella portion side. By doing so, it is possible to increase the diameter of the hollow part and achieve a significant weight reduction. Further, by inserting a steel back plate between the sintered material chip and the main body, reinforcement was achieved, and it was possible to provide a hollow tappet with excellent wear resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a tappet according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a tappet according to a second embodiment of the present invention.

FIG. 3 is a partially enlarged sectional view of the tappet showing a brazing state according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a conventional mushroom type tappet.

FIG. 5: Of conventional mushroom type hollow tappet,
It is sectional drawing which shows an example.

[Explanation of symbols]

 1. Tappet 2. Hollow part 3. Main body 31. Recess 4. Back plate 41. Recess 42. Convex portion 5. Sintered material chip 51. Sliding part with cam 52. Convex portion 6. Umbrella part 7. Push rod sliding surface 8. Brazing material ring

Claims (1)

[Claims] 1. A mushroom-type tappet used in a valve train of an internal combustion engine, comprising a steel tappet body having a hollow portion opening to the umbrella side, and a steel bag arranged so as to cover the opening of the tappet body. A plate and a sintered material chip provided on the back plate, and a steel body and a steel back plate are joined by brazing,
A tappet for an internal combustion engine, characterized in that a sintered material chip and a steel back plate are joined by diffusion bonding.