JPH0320571B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake/exhaust valve drive device for an internal combustion engine that variably controls the opening/closing timing and valve lift amount of intake/exhaust valves according to operating conditions.

Various intake and exhaust valve control devices have been proposed in the past that variably control the opening/closing timing of the intake and exhaust valves and the amount of valve lift according to engine operating conditions so that valve overlap and fresh air charging efficiency can always be optimally achieved. One example is the U.S. Patent No. 1 shown in Figure 1.
No. 3413965 is known.

In this valve drive device, the back surface 4 of a rocker arm 3 whose one end abuts the valve drive cam 1 and whose other end is fitted and supported by the stem end of the intake/exhaust valve 2 is curved. By swinging the left and right sides of the rocker arm 3 while contacting the fulcrum,
The lift of the cam 1 is transmitted to the intake and exhaust valves 2, and in particular, the lever 5 is pivotably supported at one end thereof, and its inclination is regulated by a control cam 6. ing. The control cam 6 is rotationally driven in an appropriate phase according to engine operating conditions by a drive mechanism such as a hydraulic actuator, thereby variably controlling the opening/closing timing and lift amount of the intake/exhaust valve 2. That is, for example, if the lever 5 is pushed down by a large amount by the control cam 6, the free end of the lever 5 and the rocker arm 3 are close to each other in the base circle state of the valve drive cam 1, and therefore the intake and exhaust valves 2 are pushed down by a large amount. As the valve opening timing becomes earlier, the valve lift amount increases, and if the amount of depression by the control cam 6 is small, the free end of the lever 5 and the rocker arm 3 will move even if the valve drive cam 1 is in the same base circle state.
Therefore, the opening timing of the intake and exhaust valves is delayed and the amount of valve lift becomes small.

However, in such a conventional valve drive device, when applied to a multi-cylinder engine with four or more cylinders, one of the intake and exhaust valves 2 is always lifted, so the valve spring 7 is not strong enough. A large torque acts on the shaft 6a of the control cam 6 due to the reaction force, and in order to resist this force and rotate the shaft 6a, a large and powerful actuator is required. Therefore, for example, in an automobile engine, it is difficult to arrange a large actuator within a limited space, and there is also a problem in terms of responsiveness of control of the control cam 6. Moreover, the power loss and wear on the cam surface caused by driving the control cam 6 become large.

In view of these conventional drawbacks, the present invention aims to solve the above-mentioned conventional drawbacks by configuring the lever to individually control the inclination of the levers using hydraulic actuators that expand and contract according to the control hydraulic pressure. do.

That is, the intake and exhaust valve drive device for an internal combustion engine according to the present invention includes a valve drive cam that rotates in synchronization with engine rotation, and a rocker arm that has one end in contact with the valve drive cam and the other end that is linked to a valve stem. , a lever that is disposed approximately along the back surface of the rocker arm and has a rocker arm support surface with which the back surface makes fulcrum contact; a bracket that supports one end of the lever on the valve side; and a bracket that supports one end of the lever on the cam side. and a hydraulic actuator that controls the inclination of the lever by expanding and contracting in accordance with the control hydraulic pressure.

Hereinafter, a specific embodiment of the present invention will be described in detail based on the drawings.

FIG. 2 is a sectional view showing one embodiment of the present invention, in which 11 is a valve drive cam that rotates in synchronization with engine rotation, 12 is an intake and exhaust valve, 13 is a valve spring, and 14 is a bolt attached to a cylinder head 15. The bracket is shown secured at 16. 17 is
One end 17a is connected to the valve drive cam 11, the other end 17b
are in contact with the stem ends 12b of the valve stem 12a, respectively, and have a support shaft 18 rotatably inserted approximately in the center, and have a back surface 19 curved to a predetermined profile; A lever provided with a rocker arm support surface 21 disposed substantially along a back surface 19 and with which the back surface 19 makes fulcrum contact;
0 has a bifurcated rocker guide part 22 on both sides of its substantially central part, and the support shaft 18 of the rocker arm 17 is slidably fitted into the rocker guide part 22, and the support shaft 18 and the lever 20 A coil spring 23 for biasing the lever 20 toward the bracket 14 is compressed and disposed between the lever 20 and the bracket 14. Further, one end 20a of the lever 20 on the valve side is supported in contact with an adjusting screw 24 at the tip edge of the bracket 14, and one end 20b on the cam side is supported by the adjustment screw 24 on the front edge of the bracket 14.
The lever 20 is supported by a hydraulic actuator 25 embedded therein, and the inclination of the lever 20 is controlled by the expansion and contraction of the hydraulic actuator 25.

The hydraulic actuator 25 is attached to the bracket 1
The overall length of the cylinder barrel 27 is slidably fitted into the cylinder barrel 27 recessed in the bracket 14. An outer cylinder part 28 having a cylindrical bottom shape and an oil gear lary 26 disposed slidably within the outer cylinder part 28.
An inner cylinder part 30 having an oil reservoir chamber 29 in constant communication with
and a coil spring 31 which is compressed and disposed between the two and urges the outer cylinder part 28 in the projecting direction.
A hydraulic chamber 32 is partitioned by 0, and this hydraulic chamber 32 communicates with the oil reservoir chamber 29 via a check valve 33. And the outer cylinder part 28
A hemispherical pivot portion 28a is formed at the top of the lever 20, and the pivot portion 28a is pivotally fitted to one end 20b of the lever 20.

As shown in FIG. 3, the oil gear rally 26 has its oil pressure reduced by releasing a part of the engine lubricating oil supplied from the oil pan 41 by the oil pump 42 through the electromagnetic relief valve 43. The electromagnetic relief valve 43 is controlled by a signal from a control unit 44 based on the intake air amount, rotational speed, engine temperature, etc. of the engine.
is controlled, and a control oil pressure is applied according to the engine operating conditions. Incidentally, 45 is a relief valve for preventing an excessive increase in hydraulic pressure.

Next, its effect will be explained.

First, when the control oil pressure supplied from the oil gear rally 26 to the hydraulic actuator 25 is low,
The overall length of the hydraulic actuator 25 is shortened by the biasing force of the coil spring 23, and one end 20a
The lever 20 supported by the adjusting screw 24 swings relatively upward, and the valve drive cam 11
At the base circle of ROTSUKA arm 17
The back side 19 of the lever 20 and the locking arm support surface 2 of the lever 20
It is in a state separated from 1. Therefore, when the valve drive cam 11 starts to lift from this state, the valve opening timing is delayed by a certain period of time from the rise of the valve drive cam 11, as shown in a in FIG. 11, and the maximum lift amount obtained at the peak lift of the valve drive cam 11 also becomes smaller.

Here, as the rocker arm 17 lifts, a rotational force acts on the lever 20 in the clockwise direction in the drawing, but the hydraulic pressure in the hydraulic chamber 32 is maintained by the action of the check valve 33 in the hydraulic actuator 25. Therefore, the overall length of the hydraulic actuator 25 hardly changes, and the inclination of the lever 20 remains unchanged.

Next, when the control oil pressure supplied to the hydraulic actuator 25 increases depending on the engine operating conditions, the rocker arm 17 is in contact with the base circle of the valve drive cam 11 during a period in which the reaction force of the valve spring 13 does not act on the lever 20. During this period, the outer cylinder portion 28 protrudes to the point where the resultant force of the control hydraulic pressure and the coil spring 31 balances the reaction force on the coil spring 23. Therefore, the lever 20 moves counterclockwise, and the back side 1 of the locking arm 17
9 and the rocker arm support surface 21 of the lever 20 are in close proximity. Therefore, when the valve drive cam 11 starts to lift from this state, the intake and exhaust valves 1
2 is a valve drive cam 11 as shown in FIG. 4b.
It opens and closes at approximately the same timing as the rise and fall of the , and its maximum lift amount is also large. Further, as described above, during this lift, the inclination of the lever 20 is maintained by the action of the check valve 33.

In the hydraulic actuator 25, the hydraulic chamber 32 is opened every time the valve drive cam 11 is lifted.
A small amount of oil leaks from the gap with the cylinder barrel 27, and the required amount of oil is replenished from the oil reservoir chamber 29 to the hydraulic chamber 32 at the end of the lift.
The total length can always be obtained according to the control oil pressure.

According to the configuration in which the hydraulic actuator 25 is used for each lever 20 as described above, the inclination of the lever 20 can be quickly controlled during the period when the reaction force of the valve spring 13 does not act.
The driving force required for the hydraulic actuator 25 is extremely small, there is no need to install a large and powerful hydraulic system as in the past, and power loss can be significantly reduced.
The response of 0 is also good. Further, there is no risk of premature wear on the lever 20 as in the conventional case.

Note that the valve clearance required to cope with thermal expansion of the valve stem 12a is determined by the lever 20.
Adjustment can be made extremely easily by moving the adjusting screw 24, one end of which is supported, back and forth.

As described in detail above, according to the present invention, the lever inclination position can be controlled for each valve by using the rest period when the intake and exhaust valves are not lifted, so the control driving force is small. This eliminates the need to use a large actuator, reduces power loss and wear of levers, etc., and improves transient response of control.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional intake/exhaust valve drive device, FIG. 2 is a sectional view of an intake/exhaust valve drive device according to the present invention, FIG. 3 is a hydraulic circuit diagram showing an example of a control hydraulic system, and FIG. 4 1 is a lift characteristic diagram showing an example of valve lift characteristics. 11... Valve drive cam, 12... Intake and exhaust valve,
14... Bracket, 17... Locker arm, 2
0...Lever, 23...Coil spring, 25
...Hydraulic actuator.

Claims (1)

[Claims] 1. A valve drive cam that rotates in synchronization with engine rotation, a rocker arm that has one end in contact with the valve drive cam and the other end that is linked to the valve stem, and a rocker arm that is disposed approximately along the back surface of the rocker arm and that a lever with a rocker arm support surface that makes fulcrum contact; a bracket that supports one end of the lever on the valve side; and a bracket that supports one end of the lever on the cam side. An intake/exhaust valve drive device for an internal combustion engine, comprising a hydraulic actuator for controlling.