Tappet in an internal combustion engine

Abstract: A tappet is used in an internal combustion engine. A cam receiving plate which contacts a cam is brazed on the upper surface of a top wall of a tappet body. The whole surface of the cam receiving plate can act as a cam follower surface, thereby making the outer diameter of the cam receiving plate to the minimum size corresponding to projected length of a nose of a rotary cam and lightening the tappet.

Description: The invention relates to a tappet in an internal combustion engine as per the preamble of claim 1. A tappet in an internal combustion engine of the said type has become known from 1. Patent Abstracts of Japan vol. 15, no. 120 (M-1096), 25 March 1991 & JP-A-03 011107 (YAMAHA MOTOR CO LTD), 18 January 1991, 2. Patent Abstracts of Japan vol. 15, no. 374 (M-1160), 20 Sept. 1991 & JP-A-03 149305 (NGK SPARK PLUG CO LTD), 25 June 1991, 3. JP-A-07 332 028 (MITSUBISHI MATERIALS CORP), 19 December 1995 4. DE-A-40 28 985 (BAYERISCHE MOTORENWERKE AG) 5. US-A-5 284 112 (NISSAN MOTOR CO LTD). To lighten a direkt acting type valve operating mechanism in an internal combustion engine, Al alloy tappets are widely used instead of conventional steel tappets. Al alloy tappets are lower than steel alloy tappets in strength and wear resistance, and thus, wear resistant material is applied on the upper surface of a tappet which is slidably engaged with a rotary cam. Fig. 4 illustrates a conventional Al tappet in which a cylindrical body 21 closed by an upper wall 21a at the upper end is molded from Al alloy. On the upper surface of the upper wall 21a, there is placed a wear resistant cam receiving plate 22 which has a smaller outer diameter than the body 21. The cam receiving plate 22 is fixed on the upper surface of the upper wall 22a by bending an annular protrusion 21b inwardly at the outer circumference of the upper end of the body 21. 23 denotes a rotary cam which contacts the upper surface of the cam receiving plate 22. The cam receiving plate 22 of the Al alloy tappet acts as a cam follower to a nose 23a of the rotary cam 23. To rotate the rotary cam 23 smoothly, the size or area of the cam receiving plate 22 must be equal or larger than a rotation trace of the nose 23a. The maximum lift length is determined depending on the projected length of the nose 23a from a base circle. Efficiency of intake and exhaust air is determined on the lift length. Thus, to obtain a desired intake and exhaust efficiency, it is necessary to determine the size of the projection of the nose 23a suitably and to keep the diameter of the cam receiving plate 22 in size which is corresponding to the projection of the nose 23a. As the conventional tappets, since the cam receiving plate 22 is fixed by caulking of the annular protrusion 22b to decrease an effective surface area of the cam receiving plate 22 having a relatively large diameter in the body 21 having a relatively large diameter to provide a surface area corresponding to the nose 23a of the cam 23. However, the tappet body increased in weight, the cylinder head increases in size, and flexibility in design of the engine decreases. It is the objective of the invention to provide a joint between the top ball of the body of the tappet and the cam receiving plate sufficiently strong during use, and to select an appropriate brazing filler material. This objective is achieved by the characterizing portion of claim 1. BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of the present invention will become more apparent from the following description with respect to the embodiment as shown in the drawing showing a central vertical sectional front view of the embodiment of the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The embodiment comprises concentric annular grooves 11 and projections 12 which are suitably engaged with each other are formed on the top wall la and the cam receiving plate 10 respectively, thereby joining the cam receiving plate 10 to the top wall la with the brazing filler material 4. Engagement of the annular grooves 11 and projections 12 prevents release of joining surfaces owing to difference in thermal expansion between the body 1 and the cam receiving plate 10. The present invention may be applied to a tappet which has a body made of Mg alloy. The foregoings merely relate to embodiments of the present invention. Various modifications and changes may be made by person skilled in the art without departing from the scope of claims wherein:

Claims: A tappet in an internal combustion engine, the tappet comprising: 1.1 a cylindrical body (1) made of light metal and having a top wall (1a); 1.2 a wear resistant cam receiving plate (2) which has roughly equal diameter to an outer diameter of the body (1); 1.3 the cam receiving plate (2) being brazed on an upper surface of the body (1); characterized by the following features: 1.4 there is provided a brazing filler material (4) with a melting point of 200 to 380° C; 1.5 concentric projections (12) and grooves (11) are formed on contact surfaces of the top wall (1a) and the cam receiving plate (10), the projections (12) being engaged with the grooves (11). A tappet as defined in claim 1 wherein the light metal comprises Al alloy.

Inventors: FUKUOKA SATOSHI, KANZAKI TATSUO, OHTSUBO KIZUKU, FUKUOKA, SATOSHI, KANZAKI, TATSUO, OHTSUBO, KIZUKU
Applicants: FUJI VALVE, FUJI OOZX INC.
Application year: 1996
Main classification: F01L1
IPC codes: F01L1