JPH07102912A - Tappet in internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a side wall from becoming fatigued so far as to be broken without making the thickness of the side wall of a tappet large. CONSTITUTION:The part from the top end to the lower end of a clearance groove 11 in a side wall 1B is made to a tapered face 12 wherein its diameter becomes small gradually upward so that the offset load F0 to a rotary cam 5 works on a tappet body 1. As a result, even if the shaft line of the tappet body 1 tilts, a gap is formed between the side wall 1B and fitting hole 2a. Therefore, a lateral load will not work on the side wall 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents a side wall of a shim fitting portion formed on an upper surface of a tappet used in a direct-acting valve operating mechanism in an internal combustion engine from causing fatigue damage or the like. Regarding tappets.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional direct-acting valve operating mechanism, which is widely used in a DOHC engine. (1) is a cylindrical tappet body (valve lifter) whose upper surface is closed, and a cylinder head ( It is fitted in the fitting hole (2a) of 2) so as to be vertically slidable. The circular recess (3) formed on the upper surface of the upper wall (1a) of the tappet body (1) has a shim (4) for adjusting the valve clearance.
However, it is inserted as removable.

On the upper surface of the shim (4), a rotary cam (5) having a center of rotation substantially on the axis of the tappet body (1) is in contact. (6) is a wear-resistant tip that is press-fitted into the center of the lower end surface of the upper wall (1a).

Inside the tappet body (1) is an engine valve.
The shaft end of (7) is housed, and the shaft end is in contact with the lower end surface of the tip (6). A spring retainer (9) is attached to the upper end of the engine valve (7) via a pair of cotters (8) fitted on the outer peripheral surface of the engine valve (7).
Is constantly urged upward by a valve spring (10) contracted between the spring retainer (9) and the upper surface of the cylinder head (2), and a port (not shown) formed in the cylinder head (2). ) Is closed.

In the tappet body (1) used in the direct-acting valve operating mechanism as described above, the peripheral edge corner of the recess (3) into which the shim (4) is inserted, that is, the tappet body (1). ) The annular side wall (1b) for holding the shim (4) projecting upward at the upper end of the) and the connecting corner of the upper wall (1a) have an annular cross section. It is common to form a relief groove (11)
This relief groove (11) prevents stress from concentrating on the corners,
Moreover, it prevents the seating property of the shim (4) on the upper wall (1a) of the lower end corner from being impaired.

[0006]

In recent years, in order to further reduce the weight of the valve train, the tappet body (1) described above is
Instead of the conventional iron-based metal, it is becoming more common to form it with a light alloy such as an aluminum alloy. Since the tappet body (1) made of such a light alloy has lower strength and rigidity than that made of iron, the side wall (1) is formed near the escape groove (11) described above.
b) may cause fatigue failure.

That is, the tappet body (1) is replaced by the shim (4).
When it is driven by the nose portion (5a) of the rotary cam (5) via the, as shown in an enlarged view in FIG. 5 (slightly exaggerated), the tappet main body (1) is A strong offset load (F ₀ ) off the central axis acts vertically. Due to this eccentric load (F ₀ ), the tappet body (1) is pushed while tilting toward the nose portion (5a) side, and immediately after the nose portion (5a) is thrust into the fitting hole (2a) of the cylinder head (2). The reaction force received from the upper end of the inner wall of the cylinder head (2) acts as a lateral load (F ₁ ) on the side wall (1b) on the lower side of the slope facing the top end of), and acts in the direction of the arrow.

As a result, a large repetitive bending stress is applied to the relief groove (11), and the side wall (1b) will be exposed to the relief groove after long-term operation.
Fatigue failure will occur mainly in (11). In order to prevent this, it is conceivable to increase the rigidity of bending by increasing the wall thickness of the side wall (1b), but if this is done, the weight of the tappet body (1) increases, which is contrary to the weight reduction. .

The present invention has been made to solve the above-mentioned problems, and it is possible to prevent fatigue damage to the side wall portion without increasing the thickness of the side wall in which the shim is fitted. It is intended to provide tappets for institutions.

[0010]

In order to achieve the above object, the present invention has an annular side wall on the outer peripheral edge of the upper end of a tappet body which is slidably fitted in a fitting hole of a cylinder head. In a tappet in an internal combustion engine in which a shim for valve clearance adjustment is inserted into a recess surrounded by the side wall, the upper end of the outer peripheral surface of the side wall of the tappet body to a substantially lower end of the recess is formed. The outer diameter is smaller than the outer diameter of the sliding surface of the tappet.

[0011]

When the outer diameter of the outer peripheral surface of the side wall of the tappet body is reduced from the upper end to almost the lower end of the recess, an eccentric load is applied to the tappet body by the rotating cam, and the upper end portion of the side wall is inclined to the side. Also, a slight gap is formed between the side wall and the fitting hole. Therefore, the lateral load from the cylinder head is prevented from acting on the side wall.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The same members as those of the above-described conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted. Figure 1
Shows a first embodiment of the present invention. In this embodiment, the outer peripheral surface of the upper end portion of the tappet body (1), that is, the side wall.
At the same position as the lower end of the escape groove (11) on the outer peripheral surface of (1b),
Or, the outer diameter of the portion from a position slightly lower than that to the upper end is a tapered surface (12) whose outer diameter gradually decreases toward the upper end, and the outer diameter of the sliding surface of the tappet body (1) is Also has a small diameter.

When such a taper surface (12) is formed, even if the tappet body (1) receives an eccentric load (F ₀ ) by the rotating cam (5) and is pushed at an inclination, as shown in the figure. Since there is a gap between the fitting hole (2a) at the upper end of the cylinder head (2) and the side wall (1b), the lateral load (F
₁ ) acts not on the side wall (1b) but slightly below the escape groove (11), and prevents a large bending stress from being applied to the escape groove (11).

As a result, the side wall (1b) is free from the risk of fatigue failure. 2 and 3 show the second and third aspects of the present invention, respectively.
FIG. 2 shows a third embodiment, which is an arc-shaped cross section in which the outer diameter of the outer peripheral surface of the side wall (1b) above the relief groove (11) is gradually curved toward the upper end. Curved surface
It is as (13). Moreover, what is shown in FIG. 3 is a small diameter surface (14) in which the outer diameter of the side wall (1b) above the clearance groove (11) is linearly reduced to the upper end. Also in the second and third embodiments, the same operational effects as those of the first embodiment can be obtained.

[0015]

According to the present invention, since the lateral load from the cylinder head does not act on the side wall surrounding the recess into which the shim is fitted, the side wall does not have to be made thick to increase the rigidity. Is prevented from fatigue failure.

[Brief description of drawings]

FIG. 1 is a central longitudinal front view of a direct-acting type valve operating device to which a first embodiment of the present invention is applied.

FIG. 2 is a vertical sectional view of a main part of the second embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of the main part of the third embodiment of the invention.

FIG. 4 is a central longitudinal front view showing a conventional example.

FIG. 5 is an enlarged vertical front view for explaining the action of the rotary cam during pushing.

[Explanation of symbols]

 (1) Tappet body (1a) Upper wall (1b) Side wall (2) Cylinder head (2a) Fitting hole (3) Recess (4) Shim (5) Rotating cam (5a) Nose part (6) Tip (7) ) Engine valve (8) Cotter (9) Spring retainer (10) Valve spring (11) Relief groove (12) Tapered surface (13) Curved surface (14) Small diameter surface

Claims (2)

[Claims] 1. A ring-shaped side wall is continuously provided on an outer peripheral edge of an upper end of a tappet body that is vertically slidably fitted in a fitting hole of a cylinder head, and is provided in a recess surrounded by the side wall. In a tappet in an internal combustion engine in which a shim for valve clearance adjustment is inserted, an outer diameter from an upper end of a sidewall outer peripheral surface of the tappet body to a substantially lower end of the recess is smaller than an outer diameter of a tappet sliding surface. A tappet in an internal combustion engine characterized by the above. 2. The outer surface of the outer peripheral surface of the side wall from the upper end to substantially the lower end of the recess is a curved surface having an arcuate cross section that gradually decreases in diameter toward the upper end. Tappet in the internal combustion engine described.