JPS5939909A - Locker arm having ceramic pad - Google Patents

Abstract

PURPOSE:To permit easy and strong joint of a pad onto a body by fitting a ceramic pad onto a U-shaped fixing fitting made of metal and welding said metal fixing fitting onto a locker arm body. CONSTITUTION:A ceramic pad 2 is fitted onto a U-shaped fixing fitting 3 made of metal, which is joined onto a locker arm body 1 through welding. Therefore, easy welding is permitted, and the pad 2 can be joined fixedly onto the body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a rocker arm with a ceramic pad.

BACKGROUND ART The problem of friction and wear on the sliding surfaces of the valve train of an automobile engine, particularly the camshaft and the rocker arm, is a major problem in terms of engine durability. Generally, both the camshaft and the rocker arm are made of cast iron, and the camshaft has its sliding surface made with a chill structure or heat treated to increase its hardness to improve its wear resistance. In addition, the sliding surfaces of the rocker arms are nitrided or hard chrome plated.
Efforts are being made to improve wear resistance. However, with the advancement of technology in recent years, even more extreme performance has become required of engines, and in accordance with this, the LJ 7 arm and camshaft have also been improved in terms of pitting resistance and scuffing resistance. It is desired to improve the wear resistance such as

Due to the above reasons, materials to be used for rocker arms and camshafts have recently been studied, and one of them is to combine a pad made of a material with excellent wear resistance on the sliding surface of the rocker arm. are being considered. That is, a composite rocker arm obtained by forming the rocker arm body from a cast iron or aluminum casting, manufacturing the pad from various materials, and joining these two materials is attracting attention.

A typical example of this is the use of a ceramic material having wear resistance. However, joining a ceramic material as a band material to a metal rocker arm body is difficult due to the large difference in thermal expansion between ceramic material and metal, and it is difficult to join the rocker arm body with a casting. Cracks may occur due to casting stress. Furthermore, unlike metals, it is not yet common to join ceramic materials by a joining method such as welding. Furthermore, ceramic materials have high hardness, and finishing processing after bonding to the rocker arm body is difficult, and the amount of finishing needs to be reduced as much as possible.

The present invention has been made to eliminate the above-mentioned drawbacks, and its purpose is to provide a rocker arm in which a ceramic pad is accurately and firmly joined to a rocker arm body.

The ceramic rocker arm of the present invention is characterized in that a cefmic pad is fitted into a U-shaped metal fixture, and this metal fixture is joined to the rocker arm body by welding.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a rocker with a ceramic pad according to the present invention will be explained below with reference to the drawings.

FIG. 1 is a small side view of the rocker arm of the present invention, FIG. 2 is a side view of an example of a ceramic band, and FIG. 3 is a side view of the metal fixture of the present invention.

In Figure ff41, reference numeral 1 denotes a rocker arm body cast from cast iron or aluminum, and the surface of the rocker arm body 1 that comes into contact with the cam has a curvature on the sliding surface 6 as shown in Figure 2. A pad 2 is provided which is shaped and made of ceramic material. This ceramic pad 2 is integrally formed by being fitted into a U-shaped metal fixture 3 as shown in FIG. 3 by lateral shrink fitting or heat tightening. The metal fixture 3 having the ceramic pad 2 is joined to the metal rocker arm body l by welding means.

To manufacture a rocker arm configured as above,
First, a rocker arm body 1 is manufactured by a conventional casting method, and then a rocker shaft insertion hole A1, a valve mounting hole B, etc. are formed in the rocker arm body 1. The metal fixture 3 is machined from a bar material and the inner dimension 4 of the U-shaped groove is formed to a predetermined dimension. Next, the pad 2 is manufactured by a normal ceramic manufacturing process and ground so that the flat portion 5 has a predetermined size. Then, this ceramic pad 2 is laterally fitted to the metal fixture 3 by shrink fitting or heat caulking at 300°C. Thereafter, the back surface 7 of the metal fixture 3 fitted with the ceramic pad 2 and the rocker arm body 1 are joined together by a commonly used welding method such as arc welding.

After joining the metal fixture with ceramic pad 2,
For the insertion hole A of the rocker shaft and the valve mounting hole B, which are pre-provided in the rocker arm body 1, the sliding surface 6 of the ceramic pad 2 is shaped into the final shape (kamabot shape) using #200 and #600 diamond grindstones. The final shape of the ceramic pad is preferably formed at an angle of 40° to 90° from the flat surface 5 of the semicircular shape. The dimensions of the flat surface 5 need to be finished with dimensional accuracy such that the minimum required tightening allowance can be secured even at the temperature at which the rocker arm is heated during engine operation (approximately 120° C.).

As the ceramic material used in the present invention, commonly used materials such as silicon nitride, silicon carbide, zirconia, alumina, and crystallized glass can be used. Cast iron, amber, etc. are suitable materials for the metal fixture.

Examples of the rocker arm with ceramic pad of the present invention will be described below, but the present invention is not limited to these examples.

Example 1 A pad previously formed of ceramic containing silicon nitride as a main component was integrally fitted into a U-shaped metal fixture with a thickness of las by shrink-fitting from carbon steel. Next, the metal fixture with the integrated ceramic pad was joined to the cast iron rocker arm body by arc welding to obtain a ceramic rocker arm.

Example 2 Using a normal caulking device, Example 1 was attached to a metal fixture similar to Example 1 while energizing the caulking rod of the device.
A ceramic pad similar to that was fitted. Next, the metal fixture with the integrated ceramic pad was joined to the cast iron rocker arm body by arc welding to obtain a ceramic rocker arm. When using this thermal caulking method, heat was generated in the metal fixture due to the energization, which prevented the metal fixture from cracking at the bent portion, and the ceramic pad could be sufficiently caulked.

Comparative Example A ceramic pad mainly composed of silicon nitride similar to that in Example 1 was made of cast iron and joined to an I-tsuka arm body using an adhesive (Sumitomo 3M 5W2214H), and a ceramic pad was attached to obtain an I-tsuka arm.

The rocker arms with Cefmic obtained in Example 1.2 and Comparative Example were each assembled into a 1800 cc engine, and a durability test was conducted at full load maximum rotation (6000 rpm). As a result, the rocker arm of the comparative example was 50
After 200 hours, the joint between the rocker arm body and the metal fixture separated, causing engine trouble, but no abnormality was observed in Examples 1 and 2, which correspond to the rocker arm of the present invention, even after 200 hours. Ta. There was also no wear on the ceramic pad surface.

As described above, in the rocker arm with ceramic of the present invention, the ceramic pad is fitted into the IJ-shaped metal fixture, and this metal fixture is joined to the rocker arm body by welding, so that the ceramic band is attached to the rocker arm body. The ceramic pads of the rocker arm body can be firmly joined, and the durability of the rocker arm can be significantly improved.

Furthermore, since a ceramic pad is provided on the sliding surface of the rocker arm with the cam, the wear resistance of the pad can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a side view of a rocker arm of the present invention, FIG. 2 is a side view of a ceramic pad, and FIG. 3 is a side view of a metal fixture of the present invention. 1-----1 Rotsuka arm body 2-----Ceramic pad 3----1 Metal fixing tool

Claims (1)

[Claims] A rocker arm with a ceramic pad, characterized in that a ceramic pad is fitted into a U-shaped metal fixture, and the metal fixture is joined to a rocker arm body by welding.