JPH063124B2 - Hydraulic tapes for internal combustion engines - Google Patents

Description

Detailed Description of the Invention A. Object of the Invention (1) Field of Industrial Application The present invention relates to a hydraulic tappet provided in a valve train for eliminating a valve head clearance in an internal combustion engine, particularly a bottomed cylinder and an inner peripheral surface of the cylinder. And a plunger defining a hydraulic chamber at the bottom of the plunger, the plunger being provided with an oil reservoir supplied from the outside and a valve hole communicating the oil reservoir with the hydraulic chamber. The hydraulic chamber is provided with a free ball valve that opens and closes the valve hole according to the pressure increase and decrease of the hydraulic chamber, a valve cage that accommodates the free ball valve, and an extension spring that urges the plunger in the extension direction. The present invention relates to improvement of a so-called free ball valve type hydraulic tappet.

(2) Conventional Technology Conventionally, in such a type of hydraulic tappet, the opening / closing stroke of the free ball valve is constantly regulated by the bottom wall of the valve cage.

(3) Problems to be solved by the invention With a free-ball valve type hydraulic tappet, when the plunger receives a compressive load, there is a slight time delay before the free-ball valve closes. Only after a small volume of oil that has flowed into the oil sump chamber, the plunger submerges in the cylinder and then exerts the stepping function. By utilizing such initial depression of the plunger, the center runout and bending of the cam shaft of the valve operating device are absorbed, the exhaust valve is prevented from being pushed up, and a reliable closed state is ensured.

By the way, the initial sinking of the plunger is greatly influenced by the oil temperature as well as being determined by the opening stroke of the free ball valve. That is, even if the opening / closing stroke of the freeball valve is constant, if the oil temperature rises and the viscosity of the oil decreases, the oil flows from the hydraulic chamber to the oil reservoir until the freeball valve closes after the plunger receives the compressive load. The amount of oil used increases, and the amount of initial sinking of the plunger increases by the increase. As described above, the fluctuation of the initial sinking amount of the plunger according to the change of the oil temperature causes the fluctuation of the valve opening lift amount of the intake and exhaust valves, which adversely affects the output performance of the engine.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide the hydraulic tappet capable of always obtaining the minimum required initial depression of the plunger regardless of the change in the oil temperature.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention supports the back surface of a freeball valve in a valve gauge and controls the opening / closing stroke of the valve to raise the oil temperature. It is characterized by accommodating a stroke control plate which is reduced in accordance with the above.

(2) Action The open / close stroke of the freeball valve is greatly controlled by the stroke control plate in the low oil temperature state, so even if the viscosity of the oil is high, the freeball valve will not be closed when the plunger receives a compressive load. In addition, a predetermined amount of oil can be made to flow out from the hydraulic chamber to the oil reservoir chamber, and therefore the required amount of initial sink can be given to the plunger.

When the oil temperature is high, the open / close stroke of the freeball valve is controlled to a small value by the control plate.Therefore, when the plunger receives a compressive load due to the decrease in the oil viscosity, the freeball valve must be closed before the hydraulic chamber closes. It is possible to suppress an increase in the amount of oil flowing into the oil sump chamber, and thus to keep the initial sinking amount of the plunger to a necessary minimum.

(3) Embodiment Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a combustion chamber 2 is provided in a cylinder head 1 of an internal combustion engine, and an intake (exhaust) air port opening to the combustion chamber 2. 3 is formed, and the intake (exhaust) air port 3 is intake (exhaust)
It is opened and closed by the air valve 4.

The valve 4 is movably supported by the cylinder head 1 via a valve guide 5 and driven by a valve operating device 6.

The valve train 6 includes a retainer 4a attached to the upper end of the valve 4.
A valve spring 7 that is compressed between the cylinder head 1 and the cylinder head 1 to urge the valve 4 in the closing direction, a hydraulic tappet 9 mounted in a support hole 8 of the cylinder head 1, and a base end portion of the hydraulic tappet 9. A cam follower 10 that is swingably supported to engage its tip with the upper end of the valve 4; On cam 1
It is composed of a cam shaft 11 for engaging 1a.

In FIG. 2, the hydraulic tappet 9 includes a cylinder 20 and
The main component is a plunger 22 that slides on the inner peripheral surface of the cylinder 22 and defines a hydraulic chamber 21 therein. The cylinder 20 is fitted in the support hole 8 of the cylinder head 1, and the plunger 22 is attached to the outer end of the cylinder 20. The spherical end 22a is engaged with the spherical recess 10b at the base end of the cam follower 10.

An oil reservoir chamber 23 and a valve hole 24 that connects the oil reservoir chamber 23 to the hydraulic chamber 21 are formed in the plunger 22,
The oil reservoir chamber 23 communicates with an oil supply passage 27 formed in the cylinder head 1 through an oil hole 25 on the side wall of the plunger 22 and an oil hole 26 on the side wall of the cylinder 20, and the oil sent from the oil supply passage 27. Is always filled with.

A hat-shaped valve cage 28 is fitted on the inner end of the plunger 22, and a free ball valve 29 that opens and closes the valve hole 24 and a back surface of the valve 29 are supported in the valve cage 28 to open and close s. And a stroke control plate 30 for controlling the.

Further, the hydraulic chamber 21 accommodates an extension spring 31 that urges the plunger 22 to project above the cylinder 20.

The free ball valve 29 opens when the pressure in the hydraulic chamber 21 is reduced and closes when the pressure is increased. The stroke control plate 30 is made of a shape memory alloy or bimetal and has a convex curved surface on the free ball valve 29. Make a dish shape with
The curvature of the convex curved surface is increased as the oil temperature rises. Therefore, the stroke control plate 30 operates so as to reduce the opening / closing stroke s of the free ball valve 29 according to the increase in the oil temperature.

In order to prevent the stroke control plate 30 from vibrating, a groove 28a into which the peripheral edge of the stroke control plate 30 is fitted is formed on the peripheral edge of the bottom of the valve cage 28.

Next, the operation of this embodiment will be described.

When the cam 11a applies a pressing force to the slipper surface 10a of the cam follower 10 due to the lift action of the camshaft 11 due to its rotation, the plunger 22 of the hydraulic tappet 9 is pressed toward the hydraulic chamber 21, so that the valve moves from the hydraulic chamber 21. A small amount of oil flows out through the hole 24 into the oil reservoir 23, causing the plunger 22 to initially sink, and then the free ball valve 29.
Closes the valve hole 24 to generate hydraulic pressure in the hydraulic chamber 21, and the hydraulic pressure causes the plunger 22 to step on the cam follower 10.
As a result of supporting the base end of the valve, the carofollower 10 is swung downward by the cam 11a with the spherical end 22a of the plunger 22 as a fulcrum, and the valve 4 is opened against the force of the valve spring 7.

Next, when the cam 11a releases the lift action on the cam follower 10, the valve spring 7 pushes up the valve 4 together with the cam follower 10 to return the valve 4 to the closed position. On the other hand, in the hydraulic tappet 9, the extension spring 31 pushes up the plunger 22 to bring the slipper surface 10a of the cam follower 10 into contact with the cam 11a, thereby eliminating the valve head gap.

If the hydraulic chamber 21 is depressurized by the push-up action of the extension spring 31 on the plunger 22, the free ball valve 2
Since the valve 9 is opened, the oil in the oil reservoir 23 is supplied to the hydraulic chamber 21 through the valve hole 24, and the oil outflow from the hydraulic chamber 21 is replenished.

By the way, in the low oil temperature state, the stroke control plate 30
As shown in FIG. 2, the opening / closing stroke s of the freeball valve 29 is largely controlled by reducing the curvature of the convex curved surface that supports the back surface of the freeball valve 29. Therefore, even if the viscosity of the oil is high, the plunger 22 Is subjected to a compressive load, a predetermined amount of oil can be made to flow from the hydraulic chamber 21 to the oil reservoir 23 by the time the free ball valve 29 is closed, so that the plunger 22 can be provided with a required amount of initial sink. it can.

When the oil temperature rises from this state, the stroke control plate 30 increases the curvature of the convex curved surface as shown in FIG. 3 to decrease the opening / closing stroke of the free ball valve 29, so that the oil viscosity is increased. Even when the plunger 22 receives a compressive load due to the decrease, the increase in the amount of oil flowing out from the hydraulic chamber 21 to the oil sump chamber 23 is suppressed by the time the free ball valve 29 is closed, thereby reducing the initial sinking amount of the plunger 22. It can be kept to the minimum necessary.

Thus, the initial depression of the plunger 22 is shown in FIG.
As shown by, it is controlled appropriately in response to changes in oil temperature.

When setting the initial sinking amount of the plunger 22, the eccentric movement of the cam shaft 11 due to manufacturing error of each part is absorbed to prevent the valve 4 from being pushed up when the oil temperature is low (about -20 ° C). The required minimum sink amount is set on the condition that it is obtained, and the required maximum sink amount is set on the condition that the maximum inertial force of the valve operating device 6 can be supported at a high oil temperature (about + 130 ° C).

C. As described above, according to the present invention, since the stroke control plate that supports the back surface of the free ball valve and reduces the opening / closing stroke of the free ball valve according to the increase of the oil temperature is housed in the valve cage, The free ball valve opening stroke can be automatically controlled to be large when the oil temperature is low and small when the oil temperature is high, so that even if the oil temperature changes, the plunger must always be given a minimum initial sink. As a result, the valve operating device can always be operated properly regardless of whether the engine is cold or hot, and the output performance and quietness of the engine can be improved.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of the head of an internal combustion engine equipped with the hydraulic tappet of the present invention.
The figure shows an enlarged vertical cross-sectional view of the hydraulic tappet and its surroundings shown in a low oil temperature state, FIG. 3 is a cross-sectional view of the essential parts of the hydraulic tappet shown in a high oil temperature state, and FIG. 4 is a hydraulic tappet. It is a diagram which shows the relationship between oil temperature and the amount of initial sinks. 9 ... Hydraulic tappet, 20 ... Cylinder, 21 ... Hydraulic chamber, 2
2 ... Plunger, 23 ... Oil sump chamber, 28 ... Valve cage,
29 ... Free ball valve, 30 ... Stroke control plate, 31
… Extension spring

 ─────────────────────────────────────────────────── ───Continued from the front page (56) References Microfilm of Japanese Patent Application No. 59-189479 (No. 61-103509 of Actual Development) Microfilm of No. 60-33813 (No. 61-149707 of Actual Development)

Claims (1)

[Claims] 1. A bottomed cylinder, and a plunger that slides on the inner peripheral surface of the cylinder to define a hydraulic chamber at the bottom thereof. The plunger is provided with an oil reservoir chamber supplied with oil from the outside, and A valve hole is provided for communicating the oil reservoir with the hydraulic chamber, and the hydraulic chamber accommodates a free ball valve that opens and closes the valve hole according to decrease and increase in pressure of the hydraulic chamber. In a hydraulic tappet for an internal combustion engine, which is provided with a valve cage and an extension spring for urging the plunger in the extension direction, the back surface of the free ball valve is supported in the valve cage and the opening / closing stroke of the valve is controlled by the oil. A hydraulic tappet for an internal combustion engine, characterized by containing a stroke control plate which is reduced in response to an increase in temperature.