JPS61149510A - Engine valve operation control device - Google Patents

Abstract

PURPOSE:To effectively prevent always the jumping action of a valve, by urging intake and exhaust valves with the used of valve springs, and by providing an oil chamber so that the hydraulic pressure in the chamber selectively urges the intake and exhaust valves in their closing directions. CONSTITUTION:When the rotational speed of an engine is lower than a predetermined value, a control device 17 closes a shut-off valve 15 but open a shut-off valve 16, and therefore, the hydraulic oil in an oil chamber 8 flows into an oil pan 11 through a drain passage 14. Accordingly, the urging force of a valve spring 10 alone acts upon a movable member 5. Meanwhile the shut-off valve 15 is opened but the shut-off valve 16 is closed upon high speed operation, and therefore the hydraulic oil from an oil pump 12 is fed into the oil chamber 8 through an oil supply passage 13. Accordingly, a movable member 5 is exerted with an urging force by hydraulic pressure in addition to the urging force of a valve spring 10 so that the movable member 5 is made into press-contact with a cam 7 under great urging force, thereby it is possible to restrain the jumping action of valves.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve operation control device that controls the opening and closing operations of an intake valve or an exhaust valve of an engine.

(Prior art) Generally, the intake or exhaust valve of an engine is biased in the closing direction by a valve spring, and the intake or exhaust valve is pushed in the opening direction in accordance with the cam shape of the camshaft of the valve drive mechanism. It is configured to open and close with predetermined lift characteristics. However, when opening and closing the intake or exhaust valves, when the engine speed increases, there is a problem in that the opening and closing movements of the valves cannot follow the cam shape and move apart, resulting in a jumping phenomenon.

That is, as shown in FIG. 4, the cam acceleration changes as shown in curve B with respect to the cam lift characteristic shown in curve A. Jumping phenomenon is likely to occur during period C when the amount of change in cam acceleration B is large, and when cam acceleration B suddenly decreases or increases, the valve moves away from the cam shape due to its inertia force. As a result, followability deteriorates.

In order to improve the followability of the cam and valve as described above, it is possible to use a strong valve spring to press the cam follower against the cam surface with a large biasing force, but at low rotation speeds where there is little jumping phenomenon, This means that excessive spring force is acting, increasing resistance to opening and closing.
There are problems such as wear of the cam surface, and there is a limit to the increase in spring force.

Therefore, as a conventional method for suppressing the above-mentioned jumping phenomenon, as shown in Utility Model Application No. 57-148003, for example, a hydraulic mechanism is used to move the retainer of the valve spring according to the engine speed, and when the engine speed is low, the valve spring retainer is moved according to the engine speed. A known technique is to sometimes reduce the set load of a valve spring, and then increase this set load as the engine speed increases, thereby improving the followability of the valve.

However, in the case of changing the set load of the valve spring as described above, since the spring force is large, it is necessary to supply high oil pressure to the hydraulic mechanism, and a dedicated oil pump is required separately from the oil pump required for lubrication. There are practical problems such as the need for

(Object of the Invention) In view of the above circumstances, the present invention uses hydraulic pressure in an oil gear rally used for normal lubrication to increase the biasing force in the valve closing direction of the valve only when necessary to achieve a predetermined jumping suppressing effect. It is an object of the present invention to provide a valve actuation control device for an engine which provides advantages.

(Structure of the Invention) The valve operation control device of the present invention biases the intake or exhaust valve in the closing direction using a valve spring, and is provided with an oil chamber, and uses the oil pressure in the oil chamber to bias the intake or exhaust valve in the closing direction. Further, a pressure-responsive member is provided for absorbing a volume change accompanying a valve lift with respect to the oil chamber, and this pressure-responsive member is provided to be biased toward the oil chamber by an elastic member. It is characterized by this.

(Effects of the Invention) According to the present invention, when the engine rotates at high speed, the intake or exhaust valve is urged in the closing direction by the valve spring, and is also urged by the oil pressure of the oil chamber to increase the urging force. This can improve the valve jumping phenomenon.

On the other hand, in a region where the valve jumping phenomenon is less likely to occur, such as during low rotation, it is possible to reduce resistance and prevent wear by biasing only with the valve spring.

In addition, the volume change in the oil chamber caused by the reciprocating movement of the intake or exhaust valve is absorbed by the pressure-responsive member, eliminating the need for supplying and discharging oil, making it possible to obtain the specified opening and closing operation even at high rotation speeds. Therefore, good followability can be ensured. Moreover, since the biasing force corresponding to the area of the movable member can be obtained, the predetermined biasing force can be obtained with low oil pressure, and the hydraulic pressure of the oil gear rally generated by a normal lubricant oil pump is sufficient. It provides power, has a simple structure, and is highly practical.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 schematically shows the overall configuration of a valve actuation control device 1. An intake or exhaust valve 4 for opening and closing an intake or exhaust boat 3 opened at the bottom of the cylinder head 2 is slidably mounted on the cylinder head 2. The valve stem 4a of the valve 4 passes through the cylinder head 2, and a movable member 5 made of a packet is provided at its upper end so as to reciprocate together with the valve stem 4a. The cam surface 7a of the camshaft 7 of the mechanism 6 is configured to abut against the cam surface 7a.

The movable member 5 is fitted into a cylindrical hole 2a formed in the cylinder head 2 on the upper outer periphery of the valve stem 4a to constitute an oil chamber 8, and the movable member 5 moves in accordance with the valve lift. Its volume changes depending on A valve spring 10 that biases the valve 4 in the closing direction is compressed in the oil chamber 8, and the valve 4 is biased in the closing direction by the hydraulic pressure supplied to the oil chamber 8 acting on the movable member 5. It is something that is energized.

That is, the oil chamber 8 includes an oil pan 11.
An oil supply passage 13 from an oil gear rally or the like via an oil pump 12 is connected thereto, and a drain passage 14 for returning oil in the oil chamber 8 to the oil pan 11 is connected. are each equipped with on-off valves 15 and 16.

The opening/closing valves 15 and 16 are opened and closed by control signals from the control device 17, and the supply of hydraulic pressure into the oil chamber 8 is controlled. The engine rotation speed signal from the rotation speed sensor 18 is input to the control device 17, and the control device 17 is controlled so as to supply oil pressure when the engine rotation is high.

Further, the oil chamber 8 is provided with a pressure adjustment mechanism 20 as shown in detail in FIG. This pressure adjustment mechanism 20 includes a piston-shaped pressure responsive member 22 in a communication path 21 that communicates with the oil chamber 8 , and the pressure responsive member 22 has a pressure receiving surface 22 a facing the oil chamber 8 to increase the hydraulic pressure in the oil chamber 8 . The elastic member 23 moves forward and backward to change the volume of the oil chamber 8, and an elastic member 23 is provided on the back thereof to bias the pressure responsive member 22 in the direction of the oil chamber 8.

The elastic member 23 is a first spring 2 arranged in series.
3a and a second spring 23b, and a spring seat 25 that engages with the stopper 24 is interposed between the two. Note that 26 is a plug. The first spring 23a has a lower set load and a larger spring constant than the second spring 23b. That is,
The first spring 23a has a large spring constant and is installed with a small set load, while the second spring 23b has a small spring constant and is installed with a large set load.

Therefore, according to the elastic member 23, the pressure responsive member 22
As shown in FIG. 3, when the pressure-responsive member 22 is not displaced, it receives the set load F1 of the first spring 23a, and the pressure-responsive member 22 is displaced. , until the displacement Pa of the second spring 23b reaches the set load F2, the first spring 23
The load increases due to the characteristic work due to the large spring constant of a, and the second
The structure is such that when the set load F2 of the spring 23b is exceeded, the load gradually increases due to the characteristic (2) due to the small spring constant of the second spring 23b in addition to the first spring 23a.

To explain the operation of the above-mentioned embodiment, when the engine speed is low (lower than a set value), the opening/closing valve 15 of the oil supply passage 13 to the oil chamber 8 is closed, and the opening/closing valve 16 of the drain passage 14 is opened so that the engine can be moved. Only the biasing force of the valve spring 10 acts on the member 5, and the biasing force of the movable member 5 against the cam surface 7a is small.

When the engine speed increases beyond the set value, the control device 17 opens the on-off valve 15 of the oil supply passage 13, and closes the on-off valve 16 of the drain passage 14, supplying oil pressure at a predetermined pressure to the oil chamber 8. is,
In addition to the biasing force of the valve spring 10, the movable member 5 is acted on by a biasing force due to the hydraulic pressure in the oil chamber 8 corresponding to the pressure-receiving area of the movable member 5, and the movable member 5 is pressed against the cam surface 7a with a large biasing force. However, the tracking performance at high speeds has been improved to suppress the occurrence of jumping phenomena.

At this time, the movable member 5 reciprocates together with the valve 4 as the camshaft 7 rotates, and the volume of the oil chamber 8 changes depending on the valve lift amount, but this volume change is caused by the movement of the pressure responsive member 22 back and forth. absorbed by the movable member 5
The round trip movement will be ensured. Then, the pressure responsive member 2
The characteristics of the elastic member 23 that biases the first spring 2
3a and the second spring 23b, the set load at low lift is relatively high, while the load at maximum lift is reduced compared to the degree raised by a single spring. There is.

This increases the load at low lift without increasing the load at maximum lift, more reliably suppresses the jumping phenomenon, and counteracts wear and the like.

The movable member 5 provided on the valve stem 4a moves integrally with the valve stem 4a, has an oil sealing property for the oil chamber 8, and is provided in a structure that allows the valve spring 10 to be attached. ing. The diameter of the movable member 5 corresponds to the magnitude of the hydraulic pressure acting on the oil chamber 8. It is set so that the pressure-receiving area necessary to obtain the required urging force can be obtained.

Also, an oil supply passage 1 connected to the oil chamber 8
3 may be supplied via the opening/closing valve 15 from a gear rally or the like that conventionally supplies oil to the valve drive mechanism, etc., and its layout may be appropriately designed depending on the structure of each part.

Further, in the above embodiment, the elastic member 23 that biases the pressure responsive member 22 has two springs 23a and 23a having different characteristics.
23b is used to reduce the maximum load, it goes without saying that an elastic member made of a single spring may also be used.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the main parts of an engine showing a schematic configuration of a valve actuation control device in an embodiment of the present invention, Fig. 2 is an enlarged cross-sectional view showing the detailed structure of a pressure-responsive member, and Fig. 3 is a pressure-responsive member. FIG. 4 is a graph showing changes in cam lift and cam acceleration with respect to cam rotation angle. 1... Valve operation control device 4... Intake or exhaust valve 4a... Valve stem 5... Movable member 6... Valve drive mechanism 7...
Camshaft 8...Oil chamber 10...Valve spring 13...Oil supply passage 14...Drain passage 15.16...Open/close valve 17...Control device 2o...Pressure adjustment mechanism 21...Communication path 22...
...Pressure responsive member 22a...Pressure receiving surface
23...Elastic member 23a...First spring 23t)...Second spring Fig. 1 Fig. 2 Fig. 3 Fig. 4

Claims (2)

[Claims] (1) A valve spring biases the intake or exhaust valve in the closing direction, and a movable member that reciprocates with the valve stem of the intake or exhaust valve driven by the valve drive mechanism changes the volume as the valve lifts. An oil chamber is configured, and the intake or exhaust valve is biased in the closing direction by supplying hydraulic pressure into the oil chamber, and furthermore, a pressure receiving surface faces the oil chamber and is moved forward and backward by the hydraulic pressure in the oil chamber to provide oil. 1. A valve operation control device for an engine, comprising a pressure responsive member that absorbs changes in chamber volume, and an elastic member that urges the pressure responsive member toward an oil chamber. (2) The elastic member is composed of a first spring and a second spring arranged in series, and the first spring has a lower set load and a larger spring constant than the second spring. An engine valve operation control device according to claim 1, characterized in that: