JPH1150816A - Tappet for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fasten a tappet body and a cam receiving plate mutually with extreme ease and with large bonding strength by welding an abrasion resistant metal cam receiving plate having small protrusions formed on its bottom face to the top face of the tappet body through projection welding. SOLUTION: A tappet body 3 of a cylinder shape having a top face blocked by a top wall 3a is formed of aluminum alloy, and an abrasion resistant metal- made cam receiving plate 4 is joined to the top face of the top wall 3a. The cam receiving plate 4 is a disk formed of abrasion resistant hard metal such as, for example, an iron alloy, and small protrusions 5 are continuously provided on the circumference of its bottom face. The small protrusions 5 are concentrically formed, for example, on two circumferences, and are formed into an acutely sharpened shape of a triangular cross section. The cam receiving plate 4 equipped with such small protrusions 5 on the bottom face is joined to the top face of the top wall 3a of the tappet body 3 by projection welding so as to be integrated.

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 a valve train of an internal combustion engine.

[0002]

2. Description of the Related Art A general aluminum alloy tappet used for a direct-acting type valve train in an internal combustion engine is provided with a hard metal material having wear resistance in a recess formed in an outer surface of a top wall thereof. The shim is detachably fitted and fitted to prevent wear of the sliding contact surface with the cam. However, the use of the above-described shim is disadvantageous in terms of cost because parts management is troublesome and the engine assembly line is complicated.

Further, since the effective surface area of the portion of the outer surface of the top wall of the tappet where the cam contacts is reduced, when the lift amount of the engine valve is to be increased, the outer diameter of the tappet body is increased and a shim having a large diameter is mounted. And the degree of freedom in engine design is limited.

In order to solve such a problem, the entire outer surface of the top wall of a tappet body made of aluminum alloy is provided.
A tappet has been proposed in which a thin metal cam receiving plate having wear resistance is integrally fixed. As shown in FIG. 6, a tappet has also been proposed in which a disc (2) made of an iron-based alloy is fixed to an upper end opening of a cylindrical body (1) made of an aluminum alloy (for example, Japanese Patent Application Laid-Open No. 9-112217). Reference).

[0005]

Among the above-mentioned conventional tappets, the former is fixed to a cam receiving plate by means of heat welding such as welding or brazing. In such a case, it is necessary to strictly control the temperature of both materials so as to prevent variations in the bonding strength, which is cumbersome and increases the production cost. In the latter, unlike the shim, although the effective surface area of the portion where the cam comes into contact is large, it is necessary to support the pressing load from the cam by the iron-based alloy metal disk. It must be quite thick and strong. For this reason, there is a problem that the weight of the entire tappet increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is intended to fix a tappet body and a cam receiving plate very easily and with a large bonding strength.
It is an object of the present invention to provide a lightweight tappet that can significantly reduce manufacturing costs.

[0007]

According to the present invention, the above-mentioned problem is solved as follows. (1) An abrasion-resistant metal cam receiving plate having small projections formed on the lower surface is joined to the top surface of the tappet body by projection welding.

(2) In the above item (1), the tappet body is made of an aluminum alloy.

(3) In the above item (1) or (2), it is assumed that the small projection has a ring shape and is formed on at least two inner and outer circumferences.

(4) In the above item (3), it is assumed that the outermost small projection is formed on a circumference having a diameter equal to or larger than the cam travel diameter.

(5) In the above item (3) or (4), it is assumed that the innermost small projection is formed on a circumference having a diameter equal to or less than the cam width.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a tappet of the present invention, in which a cylindrical tappet body (3) whose upper surface is closed by a top wall (3a) is made of an aluminum alloy (for example, Al-S).
An abrasion-resistant metal cam receiving plate (4) is joined to the top surface (top surface) of the top wall (3a).

The cam receiving plate (4) is a disk having a thickness of about 1 mm and made of a wear-resistant hard metal such as an iron-based alloy. , Small projections (5) are continuously provided.

The small projection (5) may be formed on one circumference as shown in FIGS.
In the embodiment shown in FIG. 3, they are formed concentrically on two circles. In some cases, it may be formed on two or more circumferences.

The small projections (5) have a sharp pointed shape having a triangular cross section of about 1 mm in length. Even if the small projections (5) are ring-shaped and continuous on the circumference as described above, they may be intermittently formed on the circumference. It may be formed or a plurality of spots may be formed.

The cam receiving plate (4) having the small projections (5) on the lower surface is joined to the upper surface of the top wall (3a) of the tappet body (3) by projection welding.

That is, the cam receiving plate (4) is placed on the upper surface of the top wall (3a) of the tappet body (3) with its small projection (5) facing down, and then the cam receiving plate (4) is placed. An upper electrode (U) having a flat lower surface is provided on the upper surface side, and a lower electrode (L) having a shape conforming to the internal shape is provided inside the tappet body (3).
To each other and apply electricity between both electrodes.
Resistance heating is performed between (5) and the upper surface of the top wall (3a) of the tappet body (3) in contact with the tappet body (3), and the small protrusion (5) is formed in the tappet body (3).
Dive into the locally melted portion of the top wall (3a). FIG.
When the power is turned off and the cooling is performed in the state of (1), the small projections (5) are firmly welded in the material of the tappet body (3),
(4) and the tappet body (3) are joined.

As described above, the present invention basically includes the case where the small projections (5) are formed on one circumference, but as shown in FIGS. 4 and 5, When the cam (6) slides on the cam receiving plate (4) for a long time, the thin projection (5) of the thin cam receiving plate (4) is peeled off from the tappet body (3), There is a risk of rising as shown.

For this reason, in the present embodiment, the diameter (b) of the outer small projection (5) of the two small projections (5) formed on the concentric circumference is, as shown in FIG. It is set to be equal to or larger than the cam travel diameter (a), and as shown in FIG. 3, the diameter (d) of the inner small projection (5)
Is set to be the same as or within the width (c) of the cam (6).

When the small projections (5) are formed on three or more circumferences, the diameters of the outermost and innermost small projections are set so as to satisfy the above-described relationship. do it.

In FIGS. 1 to 5, reference numeral (7)
Indicates a wear-resistant metal tip fitted to the bulge (3b) on the inner surface of the top wall (3a) of the tappet body (3), and the symbol (8)
Indicates a sprayed abrasion resistant coating formed on the outer peripheral surface of the tappet body (3).

[0022]

According to the present invention, since the small projections formed on the circumference of the cam receiving plate bite into the material of the top surface of the tappet body and are firmly joined, even if the cam receiving plate is thin, , Has high shear strength and is hard to peel off from the tappet body. Further, the joining operation is cheaper and easier than conventional welding, brazing, or the like.

According to the second aspect of the present invention, a tappet having a light weight and a cam receiving plate firmly joined to the tappet body can be obtained.

According to the third aspect of the present invention, it is possible to uniformly and firmly join in the radial direction, and to have a large strength against a shear load by the cam.

According to the fourth and fifth aspects of the present invention, the peel strength of the cam receiving plate from the tappet body can be increased.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional front view showing an embodiment of a tappet of the present invention in which small projections are formed on two concentric circles on an inner surface of a cam receiving plate.

FIG. 2 is a front view of a central vertical section showing a travel direction of a cam.

FIG. 3 is a vertical front view of the center showing the width direction of the cam.

FIG. 4 is an explanatory view when a small projection is formed inside a cam travel.

FIG. 5 is also an explanatory view when a small projection is formed outside a cam width.

FIG. 6 is a front view of the center vertical section of a conventional tappet.

[Explanation of symbols]

 (3) Tappet body (3a) Top wall (3b) Swelling part (4) Cam receiving plate (5) Small protrusion (6) Cam (7) Tip (8) Thermal spray coating

Claims (5)

[Claims] 1. A tappet for an internal combustion engine, wherein a tapping-resistant metal cam receiving plate having a small projection formed on a lower surface is joined to a top surface of a tappet body by projection welding. 2. The tappet for an internal combustion engine according to claim 1, wherein the tappet body is made of an aluminum alloy. 3. The small projection according to claim 1, wherein the small projection has a ring shape and is formed on at least two inner and outer circumferences.
The tappet for an internal combustion engine according to the above. 4. The tappet for an internal combustion engine according to claim 3, wherein the outermost small projection is formed on a circumference having a diameter equal to or larger than the cam travel diameter. 5. The tappet for an internal combustion engine according to claim 3, wherein the innermost small projection is formed on a circumference having a diameter equal to or less than the cam width.