JP2761508B2 - Tappet for internal combustion engine and manufacturing method thereof - Google Patents

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 direct-acting valve train in an internal combustion engine and a method of manufacturing the tappet.

[0002]

2. Description of the Related Art Recently, there has been a tendency to adopt a DOHC type valve operating mechanism due to a demand for high rotation and high output of an engine.
Further, for the purpose of further reducing the valve train, the tappet (valve lifter) used in the valve train tends to be made of aluminum alloy from conventional iron (see, for example, JP-A-1-315607). .

[0003] Tappets made of aluminum alloy have low strength and rigidity and are inferior in wear resistance as compared with those made of iron. Therefore, a wear-resistant metal material is attached to the contact surface between the rotating cam and the shaft end of the engine valve. It is generally used.

FIG. 3 shows a conventional tappet incorporated in a direct-acting type valve operating mechanism. (1) is a cylinder head, and (2) is a tappet slidably fitted to the cylinder head (1). The main body has a cylindrical shape with a closed top surface, a large-diameter recess (2a) formed on the upper end surface and the inner bottom surface, and a small-diameter fitting hole (2
In b), a disk-shaped shim (3) and a small-diameter tip (4) each made of a wear-resistant metal material are fitted.

[0005] The lower end face of the chip (4) has a pair of cotters (5).
(5), spring retainer (6), valve spring (7)
It is in contact with the shaft end of the engine valve (8) attached to the cylinder head (1) by the above method. The upper end surface of the shim (3) is in sliding contact with a rotary cam (9) disposed substantially on the axis of the engine valve (8).

[0006]

In the tappet used in the above-described direct-acting type valve operating mechanism, a rotary cam is used.
The driving force according to (9) becomes a strong compressive load on the chip (4) and acts repeatedly. Therefore, the upper and lower surfaces of the chip (4) are formed as flat surfaces,
Further, if the peripheral edge of the chip (4) fitted in the fitting hole (2b) is formed in a right angle, stress concentrates on the corner, and a crack (FIG. 3) shown in FIG. 10) may occur.

Further, the outer peripheral surface of the tappet body (2) is worn to cause backlash, or the engine valve (8) causes an improper movement due to a surging phenomenon or the like.
When the axes of (2) and the engine valve (8) are inclined with respect to each other, the shaft end of the engine valve (8) and the lower end face of the chip (4) are biased, so that the contact surfaces of the two come into contact with each other. May cause uneven wear.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and prevents stress from being concentrated on a tip fitting portion of a tappet body, and at the same time, a contact surface between a tip and an engine valve. An object of the present invention is to provide a tappet excellent in durability and reliability by preventing uneven wear and a method for manufacturing the same.

[0009]

In order to achieve the above object, a tappet of the present invention comprises a cylindrical tappet body having a closed upper surface, the upper and lower end surfaces of which are spherically bulged at the center of the inner bottom surface. A chip having a roundness with a required curvature is fitted to a peripheral corner of the upper end surface.

In the manufacturing method, a fitting hole of a required size having a flat inner surface is formed at the center of an inner bottom surface of a plastically deformable cylindrical tappet body whose upper surface is closed,
After the upper and lower end surfaces are swelled into a spherical shape in the fitting hole, and a chip having a rounded corner of a required curvature formed at the peripheral edge of the upper end surface is inserted, the chip is inserted into the inner side of the fitting hole. The surface is strongly pressed until it is plastically deformed into a spherical shape having the same shape as the upper end of the chip, and the opening end of the fitting hole is caulked inward.

[0011]

[Function] Since the upper and lower end surfaces of the chip fitted to the center of the inner bottom surface of the tappet main body bulge spherically and have a rounded corner at the upper end surface, a strong compressive load is applied to the chip. Even if it acts, stress does not concentrate on the fitting corner of the tip in the tappet body.

Further, since the lower end surface of the chip is spherical, even if the axes of the tappet body and the engine valve are inclined with respect to each other, there is no possibility that the shaft end of the engine valve will be biased against the lower end surface of the chip.

According to the manufacturing method of the present invention, the inner surface of the fitting hole of the chip formed at the center of the inner bottom surface of the tappet body is formed into a spherical shape by forcibly compressing and deforming the chip. The machining of the part can be omitted.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. Note that the same members as those in the above-described conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, the outer shape of a tappet body (2) formed of an aluminum alloy or the like has substantially the same shape as that of a conventional tappet body, and has a recess formed on an upper end surface thereof.
A shim (3) similar to the above shim is fitted in (2a).

In the fitting hole (2b) formed at the center of the inner bottom surface of the tappet body (2), the back surface of which is recessed into a spherical shape, the upper and lower end surfaces are bulged into a spherical shape, and the upper end surface is Peripheral corner (1
The tip (11) made of a wear-resistant metal material with the required radius of curvature (R) is fitted to 1a), and the open end (12) of the fitting hole (2b) is caulked in the centripetal direction. Has been prevented by. The lower end surface of the tip (11) is in contact with the shaft end of the engine valve (8).

Next, a method for manufacturing the tappet, that is, a procedure for attaching the tip (11) to the tappet body (2) will be described with reference to FIG.
A description will be given based on (A) to (C). First, as shown in FIG. 2 (A), the inner surface of the tappet body (2) is substantially equal in diameter to the outer shape of the chip (11) to be fitted at the center of the inner bottom surface, and the inner surface is flat. An annular projection (2c) in which a fitting hole (2b ') is formed and the lower end is gradually thinner at the opening end.
After that, insert the chip (11) into the rounded corner (1
1a) Insert into the fitting hole (2b ') with the side facing upward.

Next, as shown in FIG. 2 (B), with the upper end of the tappet body (2) held by an immovable support (13), the lower end surface of the tip (11) is pressed by a pressing jig. The tip (11) itself plastically deforms the inner surface of the fitting hole (2b ') upward by a high pressure by (14), and is recessed into a spherical shape having the same shape as the upper end surface of the tip (11).

Finally, as shown in FIG. 2 (C), when the jig (15) for caulking is raised and the annular projection (2c) is bent inward, the tip (11) is caulked. It is firmly fixed in the fitting hole (2b).

Thus, the fitting hole on the tappet body (2) side
Forming the spherical portion at the back of (2b) by forcibly pressing the tip (11) itself and plastically deforming the tappet body (2),
The troublesome machining of the spherical portion can be omitted, and the productivity is improved and the manufacturing cost is reduced. In the above manufacturing process, if the shape of the upper end of the pressing jig (14) is changed,
The high pressure of the tip (11) and the caulking can be performed simultaneously.

[0021]

According to the present invention, the following effects can be obtained. (a) Since the upper end surface of the tip is formed in a spherical shape and its peripheral edge is rounded with a required curvature, stress is prevented from being concentrated on the tip fitting corner in the tappet body, and therefore, that portion is There is no danger of cracks, etc.
A tappet with excellent reliability can be provided. (b) As the lower end surface of the tip is spherical, even if the axis of the tappet body or the engine valve is inclined, the shaft end of the engine valve and the tip do not hit each other, and the contact surfaces of each other are unevenly worn. Is prevented. (c) Since the spherical portion on the inner surface of the fitting hole in the tappet body is formed by strongly pressing the chip itself, the manufacturing process is simplified and the productivity is improved.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional front view showing a tappet of the present invention and a direct-acting type valve operating mechanism.

FIG. 2 is a process chart sequentially showing the manufacturing procedure of the tappet of the present invention.

FIG. 3 is a front view in the center longitudinal section showing a conventional tappet and a direct-acting type valve operating mechanism.

[Explanation of symbols]

(1) Cylinder head (2) Tappet body (2a) Recess (2b) (2b ') Fitting hole (2c) Annular protrusion (3) Shim (5) Cotta (6) Spring retainer (7) Valve spring ( 8) Engine valve (9) Rotating cam (11) Tip (11a) Peripheral corner (12) Open end (13) Support (14) Pressing jig (15) Jig for caulking

Claims (2)

(57) [Claims] At the center of the inner bottom surface of a cylindrical tappet body having a closed upper surface, an upper and lower end surface is swelled in a spherical shape, and a tip having a required curvature formed at a peripheral corner of an upper end surface. A tappet for an internal combustion engine, which is fitted. 2. A method for manufacturing a tappet according to claim 1, wherein the inner surface of the tappet body having a closed upper surface is formed into a plastically deformable cylindrical shape. After forming a fitting hole, the upper and lower end faces are swelled in a spherical shape in the fitting hole, and a chip having a rounded corner of a required curvature formed at the peripheral edge of the upper end face is inserted. ,
A method of manufacturing a tappet for an internal combustion engine, wherein the inner surface of the fitting hole is strongly pressed until it is plastically deformed into a spherical shape having the same shape as the upper end of the chip, and the opening end of the fitting hole is caulked inward. .