JPH0159403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sealed hydraulic latch adjuster suitable for an engine valve drive mechanism, that is, a valve train.

(Prior Art) FIG. 2 shows a typical example of an engine valve train.

1 is a cylinder head, 2 is a valve guide formed in the cylinder head 1, 3 is a valve stem inserted into the valve guide 2, 4 is a valve, 5 is a spring receiver fixed to the end of the valve stem 3, and 6 is a A valve spring compressed and interposed between a spring receiver 5 and a spring seat 7 formed on the upper surface of the cylinder head 1.
The valve 4 is always urged to be seated on the valve seat 8. Reference numeral 9 denotes a rocker arm, one end of which is supported by the top of the valve stem 3, and the other end engaged with a latching adjuster to be described later. The cam lobe 10 is driven by a crankshaft mounted on the upper surface of the rocker arm 9 and rotates so as to press the rocker arm 9. As the cam lobe 10 rotates, the rocker arm 9 swings its left end up and down using the lash adjuster 12 as a fulcrum, thereby opening and closing the valve 4.

FIG. 3 shows an example of a sealed hydraulic lash adjuster that has been widely used as a lash adjuster used in such valve trains. This example includes a hollow cylindrical bottomed plunger 36 that slides within a hole 35 of a body 34, a bottom outer surface of the plunger 36 as a pressure receiving surface, a pressure chamber 37 exposed on this pressure receiving surface, and a pressure chamber 37 inside the cylindrical plunger 36. Reservoir 3
8 and a diaphragm 39 sealing the reservoir 38.
and the reservoir 38 and the pressure chamber 37.
The end of the plunger 36 exposed from the body 34 is engaged with the rocker arm 9 as a fulcrum 24.

Next, the operation will be explained. In FIG. 2, if there is a clearance in any part of the drive system of the valve stem 3, that is, the valve train, the lower spring 41 in FIG. Delete this rash by transmitting it sequentially. At this time, the volume within the chamber 37 increases due to the upward movement of the plunger 36. An amount of oil commensurate with this volume increase is compensated for in the pressure chamber 37 from the reservoir 38 via the check valve 40. When the engine is stopped for a certain period of time, if the nose of the cam is engaged with the rocker arm 9, the strong spring 6
As a result, the spring 41 shown in FIG. 3 is defeated, and the fulcrum 24 is pushed down in the downward direction as shown in the drawing, and the oil in the chamber 37 is pressurized. Therefore, the oil in the chamber 37 returns to the reservoir 38 through the leak clearance 42 on the outer periphery of the plunger 36 and through the through hole 43. If the Valklum does not return quickly, a lump corresponding to the amount of oil returned to this reservoir will be created in the valve train when the engine is started, but during the first cycle of operation when the engine is restarted next time, the above-mentioned A lash elimination operation is performed, and the engine valve 4 is driven with the lash always at zero. Even if a similar phenomenon occurs due to thermal expansion of the valve train, engine block, etc., the return of oil to the reservoir and the lash elimination upon re-operation are performed in the same manner as described above.

(Problems to be Solved by the Present Invention) Since the above type of latch adjuster has a reservoir in the plunger, that is, the fulcrum,
In order to secure the required amount of oil storage, the plunger cannot be made small in diameter. Therefore, by setting the pressure receiving surface to a small diameter, the stroke of the plunger can be made longer.
It is difficult to increase the lash adjuster ability. That is, it is not suitable for adjusting large lashes due to errors in valve train assembly or wear of various parts. Furthermore, it is difficult to hope that the damper effect of the operation will be enhanced by reducing the diameter of the pressure receiving surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sealed hydraulic latch adjuster which avoids the above-mentioned drawbacks of the prior art.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention basically does not provide a reservoir in the plunger, but separates the reservoir from the plunger and places the reservoir in a separate bore. By providing a pressure receiving surface of the plunger, a means is adopted that allows the pressure receiving surface of the plunger to be set to a small diameter without affecting the oil storage capacity of the reservoir. That is, separate first and second spaces are provided in the body, a plunger having a pressure receiving surface is reciprocated within the first space, the second space is used as a reservoir, and this reservoir is connected to the outside via a diaphragm. Adopt a means of sealing from Of course, as described above in connection with the prior art, a check valve mechanism that allows hydraulic oil to be supplied from the reservoir to the pressure chamber and blocks the flow of hydraulic oil from the pressure chamber to the reservoir;
Furthermore, since a leak clearance that communicates the pressure chamber with the reservoir is essential for achieving the function as a lash adjuster, the adjuster according to the present invention also has this function. The check valve mechanism is arranged at a position where it can open and close the communication passage between the pressure chamber and the reservoir.

More specifically, the present invention provides a body having a separate first space and a second space therein, a plunger that slides within the first space, and a body made around the outer peripheral surface of the plunger. an annular groove sealed from the outside by a sealing member; a pressure chamber defined within the first space by the plunger;
a reservoir disposed within the space and communicating with the annular groove; a diaphragm disposed inside the reservoir to seal the reservoir from the outside; an inner circumferential surface of the first space and an outer circumferential surface of the plunger; a leak clearance formed between the pressure chamber and the annular groove to connect the pressure chamber and the annular groove; a communication path that communicates the reservoir and the pressure chamber; A check valve mechanism that allows oil supply and blocks the flow of hydraulic oil from the pressure chamber to the reservoir, and a compression spring that is disposed within the pressure chamber and biases the plunger in a direction to protrude from the body. The present invention provides a sealed hydraulic lash adjuster in which one end of the plunger is a pressure receiving surface that receives the pressure of the pressure chamber, and the other end is a working surface on which an external force acts.

(Function) When a clearance, or lash, occurs in the valve train as shown in Figure 2 due to temperature changes, the fulcrum and plunger come out of the body by the amount corresponding to this lash, but at this time, the check valve mechanism in the communication passage is activated. Then, hydraulic oil is supplied from the reservoir to the pressure chamber to compensate for changes in the volume of the pressure chamber. Additionally, if the nose of the cam is locked to the Fulcrum even when the engine is stopped, the external pressure acting on the Fulcrum will be transmitted to the pressure chamber via the pressure receiving surface of the plunger, increasing the pressure inside the pressure chamber. However, this pressure escapes to the reservoir via the leak clearance. During normal engine operation, the fulcrum forms a fulcrum for the rocker arm in a locked form.

In this way, even if the reservoir is provided separately from the plunger, the plunger has a small diameter, and its stroke is increased, the basic function of the lash adjuster remains unchanged.

(Example) A sealed lash adjuster 12 as an example of the present invention will be described with reference to FIG. The body 13 of the lash adjuster 12 is supported in the blind hole 11 of the cylinder head 1 as shown in FIG. This body 1
3 includes a first space 2 in which a plunger 25 with a Fulcrum 24 and a reduced diameter moves reciprocally.
3, and a second space 15 which is open upward and has a partition wall 14 at its bottom. The second space 15 is sealed from the outside by expanding the mouth edge of the bag-shaped diaphragm 17 and fixing the diaphragm 17 to the inner peripheral surface of the second space 15 using a ring 18. Ru. This second space is utilized as a reservoir 15 for hydraulic oil.

A plunger 25 with a Fulcrum 24 is slidably fitted into the first space 23 of the body 13, and a so-called leak clearance A is maintained between the inner circumferential surface of the first space 23 and the plunger 25, and a liquid passage circuit described below is maintained. do. The plunger 25 has an annular groove 26 on its circumferential surface, and a stopper 27 protruding from its lower end. The compression coil spring 28 is manufactured by Fulcrum 24.
force upward. As is well known, by making the chamber 29 in which the spring 28 is housed a pressure chamber into which hydraulic oil enters, and by making this chamber 29 face the pressure-receiving surface on the lower surface of the plunger 25, the sliding movement of the plunger 25 is controlled by the flow of the hydraulic oil. It has the function of converting. Hence,
The pressure chamber 29 is in contact with one end of the plunger 25 and is configured so that a volume change occurs as the plunger 25 slides.

The annular groove 26 is communicated with the reservoir 15 through the through hole 31, and when an external force is applied through the Fulcrum 24 for a long time, the pressure in the pressure chamber 29 is cleared.
(A) to the reservoir 15. As already mentioned, the lash adjuster 12 includes the plunger 2.
Communication passages 16 and 30 for hydraulic oil are required to compensate for the volume of the pressure chamber 29 when the pressure chamber 29 protrudes from the body 13. In the illustrated example, these communication paths 16, 3
0 is composed of a space 16 facing the partition wall 14 at the bottom of the second space 15, a pressure chamber 29, and a through hole 30 connecting this space 16.

In the illustrated example, a check valve mechanism disposed at at least one of both ends of the communication passages 16, 30 is provided on the partition wall 14. The check valve mechanism consists of a valve seat 19 of the partition wall 14, a ball 20, a spring 21, and a cage 22. Spring 21 biases ball 20 against the valve seat. The cage 22 has its flange section connected to the partition wall 1.
4 and press against the step inside the body to support it. As a result, it is possible to supply hydraulic oil from the reservoir 15 to the pressure chamber 29, and from the pressure chamber 29 to the reservoir 1.
5, and fulfills the basic functions required of a lash adjuster.

Note that 32 represents a seal and 33 represents a ring.

(Effects) A feature of the present invention is that the reservoir 15 is provided separately from the plunger, without providing a reservoir within the plunger. Conventionally, in a sealed hydraulic latch adjuster, the plunger has a hollow cylindrical shape, the inside of which is used as a reservoir, and the outer end surface exposed within a pressure chamber to receive pressure. Therefore, the pressure-receiving cross section of the plunger cannot be made small in diameter due to the required amount of oil stored in the reservoir, and therefore a large stroke cannot be desired. Therefore, it was not possible to expect a large lash elimination ability. However, since the lash adjuster of the present invention is provided separately from the plunger reservoir 15, the pressure-receiving cross section of the plunger 25 can be set to a small diameter without affecting the oil storage capacity. This can increase the lash adjustment ability of the star. Furthermore, with the reduction in the diameter of the plunger portion, the internal pressure of the pressure chamber 29 is increased, resulting in an advantage that the damper effect can be increased.

Although the sealed hydraulic latch adjuster according to the present invention has been described for use in a valve drive mechanism of a combustion chamber of an engine, the use of this adjuster is, of course, not limited to this valve drive mechanism.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of the present invention, FIG. 2 is a partially omitted vertical cross-sectional view of an example of a valve opening/closing device for an internal combustion engine equipped with a latch adjuster, and FIG. FIG. 2 is a sectional view showing a conventional example of an adjuster. 13: Body, 15: Reservoir, 17: Diaphragm, 16, 30: Communication path, 24: Fulcrum, 29: Pressure chamber.

Claims (1)

[Scope of Claims] 1. A body having a separate first space and a second space therein, a plunger sliding in the first space, and a sealing member formed around the outer peripheral surface of the plunger. an annular groove sealed from the outside; a pressure chamber defined within the first space by the plunger; a reservoir disposed within the second space and communicating with the annular groove; a diaphragm disposed inside the reservoir; a leak clearance formed between the inner circumferential surface of the first space and the outer circumferential surface of the plunger and connecting the pressure chamber and the annular groove; a communication path that communicates between a reservoir and the pressure chamber; a check valve disposed in the communication path that allows hydraulic oil to be supplied from the reservoir to the pressure chamber and blocks the flow of hydraulic oil from the pressure chamber to the reservoir; a compression spring arranged in a pressure chamber and urging the plunger in a direction to protrude from the body, one end of the plunger serving as a pressure receiving surface receiving the pressure of the pressure chamber, and the other end receiving an external force. A sealed hydraulic latch adjuster with a working surface.