JP2002070508A - Method for fitting tip in tappet made of synthetic resin for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To firmly fit a tip to the inner bottom of a tappet body formed of synthetic resin without error. SOLUTION: An upward recessed fitting hole 5 is formed in the center of the lower surface of a top wall 1a in the tappet body 1 shaped like a cylinder and made of synthetic resin. A hard tip 3 having a thickness smaller than the depth of the fitting hole 5 is fitted in the hole 5, the periphery of an opening part of the fitting hole 5 is pressed by a pressing head 10 heated lower than a melting point of the synthetic resin constituting the tappet body 1 to be plastically deformed inward, and the peripheral end part of the outer surface of the opening part side of the tip 3 is pressed to hold the tip 3 in the fitting hole 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine in which a hard tip is firmly fixed to a contact portion with an engine valve on a lower surface of a top wall of a cylindrical toppet body made of synthetic resin. The present invention relates to a method for mounting a tip on a synthetic resin tappet for use in a vehicle.

[0002]

2. Description of the Related Art In recent years, tappets used in direct-acting valve trains in internal combustion engines have been formed of hard synthetic resins such as engineering plastics and fiber-reinforced plastics instead of ordinary steel ones. Attempts have been made to reduce the inertial mass of the system.

A tappet made of such a synthetic resin is inferior in hardness to a tappet body as a base material as compared with an iron-made tappet and cannot withstand a high surface pressure. Therefore, as shown in FIG. A hard metal tip (3) is fitted into the center of the lower surface of the top wall (1a) of the synthetic resin tappet body (1) having a top cylindrical shape, that is, the portion where the upper end of the engine valve (2) abuts. There is a need.

A thin metal cover tube (4) as shown by a two-dot chain line in FIG. 7 is provided on the entire surface of the tappet body (1).
May be fitted to prevent wear of the outer peripheral surface and the top surface that are in sliding contact with the guide hole and the cam (both not shown) of the cylinder head.

[0005]

In order to mount the chip, when the tappet body is formed by a mold, a fitting hole for the chip is also formed at the same time, and the chip is pressed into the fitting hole or an appropriate bonding is performed. A method has been considered in which the tappet body is fixed with an agent, or a tip is inserted into a mold, and the tappet body is molded and simultaneously integrated.

However, in the press-fitting method or the mounting method using an adhesive, since a load larger than that of the engine valve is repeatedly applied to the chip, the fitting hole is plastically deformed to increase the diameter, and the adhesive is peeled off. And the chip may rattle or fall off in the fitting hole.

On the other hand, in the method of mounting the tappet at the same time as the molding of the tappet body, when the molten resin is injected into the mold, the chip may be displaced in the mold, and an error is likely to occur in the mounting accuracy. In addition, a difference is generated between the shrinkage rate when the resin is solidified and the shrinkage rate when the chip heated in the mold cools, so that a gap is generated between the chip and its fitting hole, and the chip comes off. It may be easier or rattle may occur.

The present invention has been made in view of the above-mentioned problems, and a tip is inserted into a fitting hole on an inner bottom surface of a tappet body.
It is an object of the present invention to provide a method of mounting a tip in a synthetic resin tappet for an internal combustion engine, which can be firmly fixed without error.

[0009]

According to the present invention, the above-mentioned problem is solved as follows. (1) A concave upward fitting hole is formed at the center of the lower surface of the top wall of the synthetic resin tappet body having a cylindrical shape with a top,
After fitting a hard chip having a thickness smaller than its depth into the fitting hole, pressing around the opening of the fitting hole to a temperature not higher than the melting point of the synthetic resin constituting the tappet body. The chip is plastically deformed inward by being pressed by the head, and the chip is held in the fitting hole by pressing the peripheral end of the outer surface on the opening side of the chip.

(2) In the above item (1), a thick portion having a tapered outer peripheral surface is formed at the center of the lower surface of the top wall, and a chip is fitted into a fitting hole formed in the thick portion. Thereafter, the outer peripheral surface of the opening of the fitting hole in the thick portion is plastically deformed inward by the tapered pressing surface formed at the tip of the pressing head.

(3) In the above item (1) or (2), the tip has a shape having a receiving portion with which the engine valve comes in contact and an enlarged diameter engaging portion, and the enlarged diameter engaging portion is formed in the fitting hole. To be kept.

(4) In the above item (3), an annular groove is provided on a surface of the enlarged diameter locking portion on the opening side of the fitting hole.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The same members as those in the related art will be described with the same reference numerals.

FIG. 1 shows a completed tappet (6) obtained by applying the first embodiment of the present invention. The tappet has a cylindrical shape whose upper surface is closed by a top wall (1a). Body
(1) is a thermoplastic synthetic resin (engineering plastic) such as polyamide (nylon), polyacetal, or polycarbonate, or a composite composite containing reinforcing fibers such as glass fiber, carbon fiber, and aramid (Kevlar) fiber, and ceramic whiskers. It is formed of resin or the like.

If necessary, a thin (for example, 0.1 to 0.2 mm) metal cover tube (4) is fitted over the entire surface of the tappet body (1), and the lower end thereof is bent inward. It may be prevented from falling off.

An upwardly concave fitting hole (5) formed in the thick portion (1b) at the center of the lower surface of the top wall (1a) of the tappet body (1).
Inside, a hard metal circular tip (3) against which the upper end of the engine valve (2) abuts is plastically deformed (7) inwardly at the open end of the fitting hole (5), so that it is firmly formed. Fixed.

FIGS. 2 to 4 show a first embodiment of a method for mounting the chip (3).

First, the above-mentioned resin material in a molten state is placed in a mold.
(Not shown), as shown in FIG. 2, a fitting hole (5) for mounting the chip (3) was provided in the thick portion (1b) at the center of the lower surface of the top wall (1a). The tappet body (1) is formed.

At this time, the inclination angle of the tapered outer peripheral surface of the thick part (1b) is made slightly larger than the inclination angle of the thick part (1b) of the finished product, and the inclination of the top wall (1a) is increased. Thick section from bottom (1
The projecting dimension (H) of b) is made slightly larger than that of the finished product of FIG. 1 so that the depth of the fitting hole (5) is deeper than the thickness of the chip (3).

Then, as shown in FIG. 3, the tappet body (1) is placed on a support (not shown) in an inverted state, and then the tip (3) is fitted into the fitting hole (5).

Next, as shown in FIG. 3, the upper part (lower part in FIG. 2) of the thick part (1b) is upwardly fitted in the cylindrical part of the tappet body (1). A cylindrical pressing head (10) having a concave hole (8) and having a heating means such as a coiled sheath heater (9) embedded therein is inserted thereinto, and an inner peripheral surface of the concave hole (8) is inserted. The tapered pressing surface (8a), which is slightly inclined from the tapered surface of the thick portion (1b),
To the outer periphery of the upper end of

At this time, the lower end of the pressing head (10) is preliminarily heated to a temperature lower than the melting point of the thermoplastic synthetic resin as a material of the tappet body (1) (for example, a temperature lower by 10 to 20 ° C. than the melting point). Keep it.

Next, as shown in FIG.
0) is gradually lowered by a predetermined stroke to
While heating (1b), the outer peripheral portion of the upper end is pressed. Then, due to the heat of the pressing head (10), the upper end of the thick portion (1b) is softened and becomes plastic, so that the upper end is plastically deformed inward as shown (7), While pressing the outer peripheral portion of the upper surface of the chip (3), the entire chip (3) is strongly tightened.

If the thick portion (1b) is cooled and hardened in this state, the chip (3) is prevented from coming off and is firmly mounted in the fitting hole (5).

Finally, a cover cylinder is provided on the entire surface of the tappet body (1).
By fitting (4) (see FIG. 1), a completed tappet (6) as shown in FIG. 1 is obtained.

FIG. 5 shows a second embodiment of the present invention, in which the shape of the tip (11) is changed to the enlarged diameter locking portion (11) at the lower end of the receiving portion (11a) with which the engine valve (2) comes into contact. 11b) into a substantially inverted T-shape, and after inserting the enlarged diameter locking portion (11b) side into the fitting hole (5) of the tappet body (1), the thick portion (1b ) Is plastically deformed (7) by pressing the upper end portion with a pressing head (10). The pressing head
In the center of the lower surface of (10), an escape recess (12) for preventing interference with the receiving portion (11a) is formed.

According to the second embodiment, the inner peripheral end of the plastically deformed portion (7) also comes into pressure contact with the receiving portion (11a) and the contact area becomes large. Therefore, the mounting strength of the chip (11) increases.

FIG. 6 shows a third embodiment of the present invention. In the same chip (11) as the second embodiment, an annular groove (11) is formed on the upper surface of the base of the enlarged diameter locking portion (11b). 13) to form
The thick part (1b) is pressed by the same pressing head (10) as described above.

In this way, the plastically deformed portion (7) flows into the annular groove (13), the contact area with the chip (11) becomes larger, and the plastically deformed (7) portion itself becomes Since the flexural rigidity is also increased, the tip (11) is more firmly held in the fitting hole (5).

In the above embodiments, the chips (3) and (11) are made of a hard metal, but they may be made of fine ceramics or a titanium alloy.

The thick portion (1b) is plastically deformed at once by the pressing surface (8a) of the pressing head (10). For example, a heated spatula-shaped pressing jig is used. Then, the entire circumference of the thick portion (1b) may be pressed a plurality of times and plastically deformed.

[0032]

According to the first aspect of the present invention, since the chip is pressed by the inwardly plastically deforming portion, it is firmly fixed in the fitting hole, and rattling occurs or comes off. There is no fear. In addition, since the periphery of the fitting hole is plastically deformed while being heated by the pressing head, it can be plastically deformed with a small pressing force without any difficulty, and there is no possibility that a crack or the like is generated in the tappet body. Further, since the chip is mounted in the fitting hole formed in advance, no mounting error occurs.

According to the second aspect of the present invention, the periphery of the fitting hole can be easily and plastically deformed at one degree.

According to the third aspect of the invention, the plastically deformed inner peripheral end also comes into pressure contact with the outer peripheral surface of the receiving portion, and the contact area with the chip increases, so that the mounting strength of the chip increases. .

According to the fourth aspect of the present invention, the plastically deformed portion flows into the annular groove, so that the contact area with the chip becomes larger and the bending rigidity of the plastically deformed portion becomes higher. Is more firmly held in the fitting hole.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional front view of a tappet obtained by applying a first embodiment of the present invention.

FIG. 2 is a vertical sectional front view of the tappet main body before a tip is mounted in the first embodiment of the present invention.

FIG. 3 is an inverted vertical sectional front view showing a state before pressing by a pressing head in which a chip is inserted into a fitting hole of a tappet main body.

FIG. 4 is an inverted vertical sectional front view showing a state in which the pressing head is lowered to plastically deform a thick portion.

FIG. 5 is an inverted vertical sectional front view when a pressing head is lowered in a second embodiment of the present invention.

FIG. 6 is an inverted vertical sectional front view when a pressing head is lowered in a third embodiment of the present invention.

FIG. 7 is a front view in the center longitudinal section showing a conventional chip mounting method.

[Explanation of symbols]

 (1) Tappet body (1a) Top wall (1b) Thick part (2) Engine valve (3) Tip (4) Cover cylinder (5) Fitting hole (6) Tappet (7) Plastic deformation (8) Concave hole (8a) Pressing surface (9) Sheath heater (10) Pressing head (11) Tip (11a) Receiving part (11b) Large diameter locking part (12) Escape recess (13) Annular groove

Claims (4)

[Claims] An upwardly concave fitting hole is formed at the center of the lower surface of a top wall of a synthetic resin tappet body having a topped cylindrical shape, and a thickness smaller than the depth is formed in the fitting hole. After fitting the hard tip, the periphery of the opening of the fitting hole is plastically deformed inward by being pressed by a pressing head heated below the melting point of the synthetic resin constituting the tappet body, and A method for mounting a chip in a synthetic resin tappet for an internal combustion engine, wherein the chip is held in a fitting hole by pressing a peripheral end of an outer surface on an opening side of the chip. 2. A thick portion having a tapered outer peripheral surface formed at the center of the lower surface of the top wall, and a chip is fitted into a fitting hole formed in the thick portion, and then formed at the tip of the pressing head. 2. A tip mounting in a synthetic resin tappet for an internal combustion engine according to claim 1, wherein the outer peripheral surface of the opening of the fitting hole in the thick portion is inwardly plastically deformed by the tapered pressing surface. Method. 3. The chip according to claim 1, wherein the chip has a shape having a receiving portion with which the engine valve comes into contact and an enlarged diameter engaging portion, and the enlarged diameter engaging portion is held in the fitting hole. Mounting method for a synthetic resin tappet for an internal combustion engine according to the above. 4. The method for mounting a tip on a synthetic resin tappet for an internal combustion engine according to claim 3, wherein an annular groove is provided on a surface of the enlarged diameter locking portion on the opening side of the fitting hole.