JP3208506B2 - Tip mounting method for tappets for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for attaching a tip of an internal combustion engine tappet, in which a tip provided at a contact portion with an engine valve on an inner bottom surface of a tappet body is firmly fixed.

[0002]

2. Description of the Related Art In recent years, attempts have been made to further reduce the weight of a valve train by using a tappet (valve lifter) made of an aluminum alloy for a direct acting valve train such as a DOHC type to further improve engine performance.

[0003] Tappets made of aluminum alloy have lower strength and rigidity and lower abrasion resistance than ordinary iron tappets. Therefore, a wear-resistant metal material is attached to a contact surface with a rotating cam or an engine valve. used.

FIG. 4 shows an aluminum alloy tappet incorporated in a direct acting type valve operating mechanism. (101) is a cylinder head, (102) is slidably fitted to a cylinder head (101). The tappet body has a cylindrical shape with a closed upper surface, and a large-diameter recess (102) formed on the upper surface of its upper wall (102a).
In (b), a disc-shaped shim (103) made of a wear-resistant metal material that comes into contact with the rotating cam (105), and a bottomed fitting hole formed in the center of the inner bottom surface of the upper wall (102a). (102c) has an engine valve
Small-diameter tips (104), also made of wear-resistant metal material, that are in contact with the shaft ends of (106) are fitted respectively.

When the chip (104) is fixed in the fitting hole (102c), the chip (104) may fall off due to a difference in the coefficient of thermal expansion between the two members if the member is simply press-fitted.
As shown in (upside down), the periphery of the fitting hole (102c) in which the chip (104) is fitted is provided with a caulking (caulking) blade (107) having an inverted triangular cross section at the lower end. The tip (104) is prevented from falling off by strongly pressing with the punch (108) and plastically deforming (109) the peripheral edge inward (centripetally).

[0006]

In the above-described conventional method for mounting a chip, the peripheral edge of the chip (104) is formed at a right angle, so that the portion (104) engages with the plastic deformation (109). (Contact) area is small, and the crimping force of the chip (104) is weak.

Further, since the depth of the concave groove (110) formed by the caulking blade (107) is relatively shallow, the amount of inward deformation of the plastically deformed portion (109) is small, and sufficient crimping force is obtained. I can't.

If the tip (104) is not firmly fixed in the fitting hole (102c), the tip (104) and the tappet body (102), or the tip (104) and the engine valve (106) may not be connected. A gap is generated between the two, and a driving sound is generated during operation or abnormal wear is caused, so that durability and reliability are impaired.

As one means for firmly fixing the chip (104), it is conceivable to increase the pressing force of the punch (108) to increase the caulking force and to increase the holding force of the chip (104). When crimping is performed with a strong force, as shown in FIG. 5, a crack (111) may be formed at the top of the concave groove (110).

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the chip is firmly fixed in a fitting hole by greatly increasing the caulking force of the chip, thereby improving durability and reliability. It is an object of the present invention to provide an excellent tapping method for a tappet for an internal combustion engine.

In order to achieve the above object, the present invention provides a tip provided with a chamfer at the lower peripheral edge in a fitting hole formed at the center of the inner bottom surface of a cylindrical tappet body having a closed upper end. After the fitting, the peripheral edge of the fitting hole in the inner bottom surface has a substantially triangular cross section, and a punch having a circular caulking blade whose base ends of both oblique sides are continuous with a flat surface is provided at the top end of the caulking blade. Presses to a depth exceeding the upper edge of the chamfered portion to complement the caulking blade.
By forming a concave groove having a triangular cross section, the chip is plastically deformed inward, and the chip is caulked in the fitting hole.

[0012]

[Action] A chamfer is formed at the lower peripheral edge of the chip, and the caulking blade is pressed to a depth where the top end exceeds the upper edge of the chamfer, thereby increasing the engagement area between the plastically deformed portion and the chip. As a result, the chip holding force is increased, and the starting point of the plastic deformation portion is higher than the upper end edge of the chamfered portion, and the entire chamfered portion is pressed with a uniform and large load, so that the caulking force of the chip increases.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, (1) is a tappet body made of an aluminum alloy similar to the conventional one and has a downward opening at the center of a thick portion (2a) formed at the center of the inner bottom surface of an upper wall (2). A bottom fitting hole (4) is formed.

The tip (5) is made of a wear-resistant metal material.
The plate is formed in a disk shape whose thickness is slightly smaller than the depth of the fitting hole (4), and a chamfer (5a) of approximately 45 ° is provided on the lower peripheral edge. . Tip (5) has a fitting hole
It is fixed in (4) as follows.

As shown in FIG. 2, the tip (5) is fitted in the fitting hole (4), and then the upper surface (2a) of the thick portion (2a) of the periphery of the fitting hole (4) is inserted. Hereinafter, the vertical direction refers to FIG. 2), and is formed in an inverted isosceles triangular cross section in which the angle of intersection of the inner and outer hypotenuses is substantially 90 ° , and the upper ends of both hypotenuses
Circular caulking blade (6 ) whose (base end) is continuous with a flat surface
By pressing strongly with a punch (6) provided at the lower end of (a), a concave groove (7) having an inverted triangular cross section complementary to the caulking blade (6a) is formed on the upper surface of the thick part (2a) and fitted. As shown in FIG. 3, the peripheral edge of the hole (4) is plastically deformed (8) inward over the entire circumference and caulked.

At this time, the top end (6b) of the caulking blade (6a) reaches a depth exceeding the lower edge (the upper edge in FIG. 1) (5b) of the chamfered portion (5a) of the chip (5). That is,
The depth (H ₁ ) of the top (7a) in the concave groove (7) from the upper end of the tip (5) is slightly larger than the axial dimension (H ₂ ) of the chamfer (5a). The pressing load of the punch (6) is set. The top end (6b) of the caulking blade (6a) has a groove.
It is slightly rounded so that stress does not concentrate on the top (7a) of (7).

In this manner, when the tip (5) is swaged, the engagement (contact) between the plastically deformed (8) part and the tip (5) is smaller than in the conventional example without the chamfered part (5a). ) As the area increases, the starting point of the plastic deformation (8) part is lower than the lower edge (5b) of the chamfered part (5a), so the amount of plastic deformation inward is large, and the chamfered part (5a) A large pressing load acts on the entire surface and the lower part of the substrate.

As a result, the caulking force (tightening force) of the tip (5)
Increases and is firmly fixed in the fitting hole (4).

When the magnitude of the caulking force is determined, the relative rotational force between the tip fitting portion (the tappet body) and the tip (5), that is, the slip torque is examined as a substitute characteristic. The applicant has confirmed that a large slip torque can be obtained by caulking the tip (5) in the manner of the above embodiment.

In the embodiment, the entire circumference of the chip (5) is caulked in a circular shape. However, a plurality of portions may be caulked using a punch having a plurality of discontinuous caulking blades.

The shape of the chip (5) is not limited to the above-mentioned circle, but may be elliptical or oval.

[0022]

According to the present invention, since the caulking force of the chip is greatly increased and the chip is firmly fixed in the fitting hole, a gap is generated between the chip and the tappet main body to generate an impact sound. And there is no danger of causing abnormal wear,
Durability and reliability are improved. Also, the periphery of the fitting hole is
A triangular cross-section groove that complements the caulking blade is formed.
When pressed and plastically deformed, the flat surface of the punch that is continuous with the base ends of both hypotenuses of the caulking blade abuts against the inner bottom surface of the tappet body, so that the biting depth of the top end of the caulking blade is always constant. This prevents the crimping force of the chips from varying.

[Brief description of the drawings]

FIG. 1 is a front view of a central longitudinal section of a main part of a tappet to which an embodiment of the present invention is applied.

FIG. 2 is a longitudinal sectional view showing a crimping point of the chip in an enlarged and inverted manner.

FIG. 3 is an enlarged bottom view of the chip fitting portion.

FIG. 4 is a central longitudinal sectional front view of a direct acting valve train and a conventional tappet incorporated therein.

FIG. 5 is a longitudinal sectional front view of a main part showing a caulking point of a conventional chip.

[Explanation of symbols]

(1) Tappet body (2) Upper wall (2a) Thick wall (4) Fitting hole (5) Tip (5a) Chamfer (5b) Lower edge (6) Punch (6a) Caulking blade (6b) Top ( 7) Groove (7a) Top (8) Plastic deformation (H ₁ ) Depth (H ₂ )

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01L 1/14 B21D 39/00

Claims (1)

(57) [Claims] 1. A chip having a chamfered portion at a lower peripheral edge is fitted into a fitting hole formed at the center of an inner bottom surface of a cylindrical tappet body having a closed upper end, and then fitted on the inner bottom surface. The peripheral edge of the hole is substantially triangular in cross section, and a punch having a circular caulking blade whose base ends of both hypotenuses are continuous with a flat surface is provided, and the top end of the caulking blade extends beyond the upper edge of the chamfer. by pressing in Somerset, said
Form a triangular cross-sectional groove that complements the caulking blade
Chip mounting method for an internal combustion engine tappet, characterized in that is plastically deformed inwardly, caulked the chip into the fitting hole by.