JP3382379B2 - Hydraulic lash adjuster - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic lash adjuster for automatically correcting a valve clearance in a valve train of an internal combustion engine.

[0002]

2. Description of the Related Art As a conventional hydraulic lash adjuster, as shown in FIG. 3, there is a plunger 3 slidably fitted in a cup-shaped cylinder body 2 having an upper opening, and a lower end of the plunger 3 is provided. And a bottom end of the cylinder body 2 constitute a high pressure chamber S ₁ , and a return coil spring 7 set to an appropriate load is provided between the lower end of the plunger 3 and the bottom wall of the cylinder body 2, and the lower end of the plunger 3 in the chamber S ₁ has a structure in which a check ball valve 5 for opening and closing the orifice 4 for communicating the reservoir chamber R ₁ and the high pressure chamber S ₁ in the plunger 3.

However, in such a conventional technique, since the check ball valve 5 is composed of the three parts of the check ball 6, the retainer 8 which is a ball cage, and the check ball spring 9, the high pressure chamber S ₁
Has a structure in which a total of four parts of the return coil spring 7 are accommodated in addition to the above-mentioned three members constituting the check ball valve, the number of parts is large, it takes a lot of time for assembly, and part management is difficult There was a drawback.

Therefore, Japanese Utility Model No. 2-38002 and Japanese Utility Model No. 2-38003 have been proposed. The former are shown in Figs.
As shown in FIG. 3, the lower end of the plunger 3 or the bottom wall of the cylinder body 2 is provided with a protrusion 3a (2a).
By using (2a) as the retainer portion of the check ball 6, among the components of the check ball valve in the conventional structure shown in FIG. 3, the retainer 8 and the check ball spring 9 are eliminated so that the components are housed in the high pressure chamber S _1. The number of is reduced.

On the other hand, in the latter, as shown in FIG. 6, the upper end portion of the return coil spring 7 is bent inward to form the retainer portion 7a of the check ball 6, thereby forming the check ball valve structure of the conventional structure shown in FIG. Of the parts, retainer 8
By eliminating the check ball spring 9, the number of parts accommodated in the high pressure chamber S ₁ is reduced.

[0006]

In any of the structures shown in FIGS. 4 to 6, since the number of parts accommodated in the high pressure chamber is small, the assembling property is excellent and the parts are easy to manage. It is valid. However, in the structure shown in FIGS. 4 and 5, there is a problem in that the processing of the protrusion 3a (2a) is troublesome and the cost is high.

On the other hand, in the structure shown in FIG. 6, since the check ball 6 is supported by the retainer portion 7a formed at the upper end of the return coil spring 7, the check ball 6 is provided around the orifice 4 at the lower end of the plunger 3. It is necessary to form a concave portion (a concave portion as a retainer portion for restraining the horizontal movement of the check ball 6) 3b into which the check ball 6 enters, and to change the specification of the plunger in order to apply it to the conventional structure shown in FIG. Is necessary, and the cost becomes higher.

Further, since the vertical height of the high pressure chamber S ₁ is expanded by the amount equivalent to the check ball 6, the high pressure chamber S ₁
Is increased, and the total amount of air contained in the hydraulic oil in the high-pressure chamber S ₁ is increased accordingly, and as a result, the rigidity of the hydraulic oil in the high-pressure chamber is extremely reduced (so-called sponge state).
There is also a problem that the recovery from the valve may be delayed and the valve clearance may not be properly corrected.

The present invention has been made in view of the above problems of the prior art, and its object is to reduce the number of parts accommodated in the high pressure chamber and to change the specifications of the plunger (enlarge the volume of the high pressure chamber). An object of the present invention is to provide a hydraulic lash adjuster having a check ball valve structure without a valve.

[0010]

To achieve the above object, in a hydraulic lash adjuster according to a first aspect of the present invention, a plunger is slidably fitted in a cup-shaped cylinder body having a closed lower end, A high pressure chamber is formed between the lower end of the plunger and the bottom wall of the cylinder body, and a check ball valve for opening and closing an orifice that connects the reservoir chamber in the plunger with the high pressure chamber is provided at the lower end of the plunger. In a hydraulic lash adjuster in which a return coil spring is provided between the bottom end of the body and the lower end of the plunger, the return coil spring has a lower end extending upward inward and a return surrounding the extending portion and a check ball. configure retainer portion for holding the check ball in the orifice near by the coil spring , The extending portion is in charge of the check ball
If you hold it and limit the downward movement of the check ball,
Check ball of the return coil spring
The check bow in which the area surrounding the
It is configured to limit the amount of horizontal movement of the tool . According to a second aspect of the present invention, in the hydraulic lash adjuster according to the first aspect, the extending portion is constituted by a spring for biasing the check ball in the orifice closing direction and having a spring constant smaller than that of the return coil spring. Is.

[0011]

The check ball valve is composed of a check ball and a return coil spring having an extending portion that extends inwardly upward from the lower end. Only two parts, the check ball and the return coil spring, are provided in the high pressure chamber. Is housed. The check ball is a retainer portion that is supported by the retainer portion, that is, is surrounded by the return coil spring that is the retainer portion, is restricted from moving in the horizontal direction, and extends upward inward from the lower end of the return coil spring. The extension is restricted from moving downward and is held in the vicinity of the orifice, and hydraulic oil flows from the reservoir chamber into the high pressure chamber through a minute gap formed between the orifice and the check ball. Then, when a load is applied to the plunger and the volume of the high pressure chamber is about to be narrowed, the check ball closes the orifice and locks the plunger. Since the return coil spring constitutes the retainer part for restraining the horizontal movement of the check ball, there is no need to form a check ball catching recess at the lower end of the plunger, and the return coil spring, check ball, ball cage and Conventional structure for accommodating a check ball spring (see Fig. 3)
In addition, it can be applied as it is without changing the shape of the plunger. The vertical height of the high-pressure chamber can be made smaller than in the conventional structure (see FIG. 6) in which the check ball is supported by the retainer portion provided on the upper end of the return coil spring and the recess formed on the lower end of the plunger. In claim 2, since the check ball is urged in the direction of closing the orifice by a spring having a small spring constant,
The behavior of the check ball after the hydraulic fluid flows from the reservoir chamber to the high pressure chamber until the orifice is closed, that is, the responsiveness of the check ball valve is improved.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view of a valve operating mechanism of an overhead camshaft (OHC) type internal combustion engine to which the present invention is applied.
In this figure, reference numeral 10 is a cylinder head, and a valve body 14 is vertically inserted through an air supply (or exhaust) passage 12 formed in the cylinder head 10. Disc 14
Is biased by a valve body return spring 15 in a direction in which the air supply (or exhaust) passage 12 is closed, and an upper end portion of the valve body 14 is rocked by a cam 16 so that a rocker arm 17 swings.
Is in contact with.

Reference numeral 20 is a lash adjuster provided adjacent to the valve body 14. Lash adjuster 20
Has a structure in which the adjuster body 22 is inserted into an adjuster mounting hole 30 that opens upward.
Is mainly composed of a cup-shaped cylindrical cylinder body 24 that opens upward, and a plunger 26 that is fitted in the body 24 and is slidable in the vertical direction. A strip-shaped recessed groove 24a is provided around the outer peripheral surface of the body 24 at a substantially central position in the vertical direction, and an operating oil is supplied to the inner peripheral surface of the mounting hole 30 at a position facing the recessed groove 24a. A gallery 32 is formed.

The upper end portion of the plunger 26 carries the end portion of the rocker arm 17 on the side opposite to the contact portion of the rocker arm 17 with the valve body 14, and serves as a rocking fulcrum of the rocker arm 17. Plunger 26
A reservoir chamber R communicating with the oil gallery 32 through a small hole 27a formed in the side wall and a small hole 24b formed in the body 24 is formed inside. Also the reservoir R
Is communicated with the high pressure chamber S formed between the lower end of the plunger 26 and the bottom wall of the body 24 through the orifice 27b, and is open to the outside through a small hole 27c formed at the upper end of the plunger.

Reference numeral 40 denotes a return coil spring which is interposed between the lower end portion of the plunger 26 (the peripheral edge portion of the orifice 27b on the side of the high pressure chamber S) and the bottom wall of the cylinder body 24 to restore the plunger 26. The lower end of the return coil spring 40 is bent upward inward and extends to carry the check ball 25. That is, the extending portion 41 constitutes a retainer portion that limits the amount of downward movement of the check ball 25. Further, the check ball 25 is carried by the extending portion 41, is surrounded by the return coil spring 40, and is restricted from moving in the horizontal direction. That is, the area surrounding the check ball 25 of the return coil spring 40 is the check ball 2
The retainer portion that limits the amount of horizontal movement of the member 5 is configured. In other words, the return coil spring 4
0 and the extension portion 41 constitute a retainer portion that holds the check ball 25 near the orifice 27b.

In the state where high pressure does not act in the high pressure chamber S, a minute gap C is formed between the check ball 25 and the orifice 27b, and hydraulic oil is transferred from the reservoir chamber R to the high pressure chamber S through this minute gap C. It is ready for inflow. When a load is applied to the plunger 26 due to the rotation of the cam 16, the plunger 26 is lowered to cause the high pressure chamber S to move.
The inner volume becomes small, and the check ball 25 closes the orifice 27b, whereby the plunger 26 is locked and a rocking fulcrum of the rocker arm 17 is formed. Reference numeral 26a denotes an O-ring mounted on the outer peripheral surface of the body, which maintains the liquid tightness between the body 24 and the mounting hole 30 and prevents the hydraulic oil from leaking through the gap between the two and 24.

A spring seat 28 of a return coil spring 40 is formed on the peripheral edge of the orifice 27b at the lower end of the plunger 26.
The return coil spring 4 having the same specifications as the plunger 3 in the related art shown in FIG.
Only 0 and the check ball 25 are different from the conventional structure shown in FIG.

FIG. 2 is an enlarged sectional view of the vicinity of the high pressure chamber of the lash adjuster which is the main part of the second embodiment of the present invention.
In this embodiment, a check ball spring 42 having a small spring constant as an extension is integrally provided inside the lower end of the return coil spring 40 for biasing the check ball 25 against the opening edge of the orifice 27b. ing. That is, the return coil spring 25 having a large wire diameter
And a check ball spring 42 having a small wire diameter and a small coil diameter (small spring constant) are integrally formed, and serve as a return spring for returning the plunger 26 and a check ball spring for urging the check ball in the valve closing direction. It has both functions of. Since the other points are the same as those in the first embodiment, the description thereof will be omitted.

Since the check ball 25 is always urged by the check ball spring 42 in the direction to close the orifice 27b, the check ball 25 closes the valve (orifice 27 after the hydraulic oil flows into the high pressure chamber S).
The operation b) is quick, that is, the responsiveness of the check ball valve is better than that of the first embodiment. The above-mentioned second
In the embodiment described above, the return coil spring 40 and the check ball spring 42 that is the extending portion that forms the retainer portion are integrally formed, but separate return coil springs and check ball springs are welded and brazed. It may be integrated by joining means such as caulking. Further, in the case of the structure in which the return coil spring 40 and the check ball spring 42 are joined and integrated, the check ball spring 42 may be a spring other than the coil spring such as a leaf spring.

[0020]

As is apparent from the above description, according to the hydraulic lash adjuster of the present invention, only the two parts of the check ball and the return coil spring are housed in the high pressure chamber, so that the assemblability is improved. It is excellent and the management of parts is easy. Further, according to the present invention, since the return coil spring and the check ball can be accommodated in the high pressure chamber having the conventional structure (see FIG. 3) without changing the shape of the plunger, the shape of the plunger can be changed. It is easier to change the specifications than the conventional structure (see FIG. 6) that must be used. Further, since the check ball is housed and arranged in the return coil spring, compared with the conventional structure in which the check ball is supported by the retainer portion provided at the upper end of the return coil spring (see FIG. 6), the upper and lower sides of the high pressure chamber The height can be reduced, the amount of air mixed in the high pressure chamber is small, and the valve clearance can be appropriately corrected. In the second aspect, since the check ball is always urged by the spring having a small spring constant in the direction of closing the orifice, the behavior of closing the orifice of the check ball, that is, the responsiveness of the check ball valve becomes good.

[Brief description of drawings]

FIG. 1 is a sectional view of a valve operating mechanism to which a hydraulic lash adjuster according to a first embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view of a main part of a hydraulic lash adjuster according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a valve mechanism including a conventional hydraulic lash adjuster.

FIG. 4 is a sectional view of a valve mechanism including another conventional hydraulic lash adjuster.

FIG. 5 is a cross-sectional view of a valve mechanism including still another conventional hydraulic lash adjuster.

FIG. 6 is a cross-sectional view of a valve mechanism including still another conventional hydraulic lash adjuster.

[Explanation of symbols]

20 hydraulic lash adjuster 24 cylinder body 26 Plunger 25 check balls 27b Orifice 28 Spring seat of return coil spring 30 Adjuster mounting hole 40 Return coil spring 41 Extension 42 check ball spring R reservoir chamber S high pressure chamber

Claims (2)

(57) [Claims] 1. A plunger is slidably fitted in a cup-shaped cylinder body whose lower end is closed, a high-pressure chamber is formed between the lower end of the plunger and the bottom wall of the cylinder body, and the lower end of the plunger is attached to the lower end of the plunger. A hydraulic lash adjuster provided with a check ball valve that opens and closes an orifice that connects the reservoir chamber in the plunger and the high-pressure chamber, and a return coil spring is provided between the bottom end of the cylinder body and the lower end of the plunger. In, the lower end of the return coil spring is extended upward inward,
Consists retainer portion for holding the check ball in the orifice near by a return coil spring that surrounds the extension portion and the check ball, the extending portion Choi
The amount of downward movement of the check ball carrying the check ball
Of the return coil spring
An area surrounding the check ball is carried on the extension.
A hydraulic lash adjuster that limits the amount of horizontal movement of the check ball . 2. The hydraulic lash adjuster according to claim 1, wherein the extending portion is constituted by a spring having a spring constant smaller than that of the return coil spring for urging the check ball in the orifice closing direction. .