JPS6318726Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an intake/exhaust valve drive device for an internal combustion engine that variably controls the valve lift amount of an intake/exhaust valve according to operating conditions.

Various intake and exhaust valve drive devices have been proposed in the past, which variably control the opening/closing timing or valve lift amount of intake and exhaust valves according to engine operating conditions so as to always achieve optimum valve overlap and fresh air filling efficiency. One example is the U.S. Patent No. 1 shown in Figure 1.
No. 3413965 is known.

This valve drive device has 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. The back surface 4 of the rocker arm 3 is curved, and the back surface 4 is connected to the lever 5. 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 lift control device, the support shaft of the lever 5 is located almost on the extension of the valve shaft of the intake and exhaust valve 2, so that the air-fuel mixture does not flow from the intake valve gap into the cylinder. If the valve lift is controlled to be quite small in order to increase the inflow speed or reduce the driving loss of the intake and exhaust valves, there is a problem that the valve opening/closing timing is also shortened and the pumping loss increases.

The present invention was developed by focusing on such conventional problems, and by positioning the pivot of the lever that makes fulcrum contact with the back of the rocker arm closer to the valve stem and closer to the valve drive cam than the valve stem extension line, To provide a valve lift control device for an internal combustion engine, which controls only the valve lift without changing the opening/closing timing of the valve, thereby preventing an increase in pump loss.

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIGS. 2a and 2b show in detail one embodiment of the valve lift control device. In the same figure, 11
12 is a valve drive cam, and 12 is a rocker arm having one end in contact with the valve drive cam. The rocker arm 12 is curved into a substantially doglegged shape, and a support shaft 14 is fitted into the substantially central portion thereof. Back side 1 of this Rotsuka arm 12
6 is a continuous, gently convex curved surface. Reference numeral 17 denotes a lever having a linear support surface, and the support surface of this lever comes into contact with a part of the convex curved surface of the rocker arm. Further, this lever 17 is rotatably supported by a shaft 19 fixed to a cylinder head or the like at a position closer to the valve drive cam 11 than the extension line of the valve stem 15. A U-shaped groove 17a is provided on the valve stem 15 side of the lever 17.
is formed, and the shaft 19 is fitted into this U-shaped groove 17a. An adjusting screw 19a and a nut 19b are attached to the shaft 19 installed in this U-shaped groove 17a. A rocker guide 22 having a pair of parallel guide portions 22a and a spring holding portion 22b is fixed to both end surfaces of the free end portion of the lever 17 by bolts 23.
A rocker arm support shaft 14 having a rectangular cross section is slidably inserted into the guide portion 22. A coil spring 24 is interposed in a compressed state between the support shaft 14 and the spring holding portion 22b.

Reference numeral 25 denotes a control cam that regulates the inclination of the lever 17, and is pivotally supported by the shaft 26.
is driven by a drive device shown in FIG. 6th
In the figure, 28 is a swing type hydraulic motor, 30 is a bracket, and 32 is a control unit. This control unit 32 controls a solenoid valve 35 connected to an oil pump 33 and an oil pan 34 based on signals such as an engine intake air amount signal, a rotational speed signal, an engine temperature signal, etc., and operates the hydraulic motor 28. The control cam 25 is positioned at a set angle according to engine operating conditions.

Next, the effect will be explained.

First, a case where the amount of depression of the lever 17 by the control cam 25 is large as shown in FIG. 3 will be described. In this case, the lever 17 is pushed down significantly toward the valve drive cam 11 side. Therefore, the supporting fulcrum A of the rocker arm 12 relative to the lever 17 moves to the left. Then, when the valve drive cam 11 rotates and moves to the position shown by the two-dot chain line, the support fulcrum A moves to the left, and the rocker arm 12 rotates clockwise about the support shaft 14. . Therefore, the intake and exhaust valves 13 are pushed down,
The amount of depression is as shown in _L1 in FIG.

On the other hand, the lever 17 by the control cam 25
If the amount of depression is small, the supporting fulcrum of the rocker arm 12 relative to the lever 17 moves to the right. When the valve drive cam 11 rotates, a clockwise force acts on the rocker arm 12 as described above. In this case, since the fulcrum A is located at the bottom of the shaft 19, the amount by which the intake and exhaust valves 13 are pushed down is small, and furthermore, even if the lift of the valve drive cam 11 becomes large, the lower surface 18 of the lever 17 retreats upward. Therefore, the bottom surface 1 of the lever 17
8 and the back surface 16 of the rocker arm 12 is delayed, the lift of the valve drive cam 11 is transmitted to the intake and exhaust valves 13 little by little, and the amount of depression of the intake and exhaust valves 13 is reduced as shown by L ₂ in FIG. 4. Become.

In this case, the coil spring 24
acts to cause the valve drive cam 11 to follow the rocker arm 12, but in the present invention, the force of the valve spring contributes to the following action, so the use of the coil spring 24 can be omitted. In addition, Figure 5 shows the valve lift characteristics,
The opening and closing periods of the intake and exhaust valves are set to be equal when the amount of depression of the intake and exhaust valves 13 is large (curve a) and when the amount of depression is small (curve b).

As explained in detail above, according to the present invention,
By locating the lever's spindle on the valve drive cam side rather than on the valve axis of the intake and exhaust valves, the lift of the intake and exhaust valves can be variably controlled according to engine operating conditions. It is possible to suppress the lift of the exhaust valve due to load to a small value, increase the inflow speed of the mixture from the valve gap, activate the gas flow of the mixture in the cylinder, and improve combustion efficiency. Driving loss of the valve portion can be reduced, and fuel efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional valve lift control device for an internal combustion engine, FIGS. A front view showing the state before and after the valve lift control device is activated,
FIG. 5 is a valve lift characteristic diagram, and FIGS. 6a and 6b are hydraulic control circuit diagrams of the control cam. DESCRIPTION OF SYMBOLS 11... Valve drive cam, 12... Locker arm, 13... Intake and exhaust valve, 14... Support shaft, 15...
...Valve stem, 16...Back, 17...Lever, 19...Shaft, 22...Rotsuka guide,
25...Control cam.

Claims (1)

[Scope of utility model registration request] A valve drive cam that rotates in synchronization with engine rotation, a rocker arm that has one end linked to the valve drive cam and the other end linked to the valve stem, and a support shaft provided in the middle, and a rocker arm that extends approximately along the back surface of the rocker arm. A lever is disposed along the shaft and is rotatably supported at a position on the valve drive cam side from the extension line of the valve stem, and the lever is attached to the lever and is slidably movable on the support shaft. A valve lift control device for an internal combustion engine, comprising a supporting rocker guide and a control cam that is provided in contact with the back surface of the lever and sets the inclination of the lever.