JPS6318724Y2 - - 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 opening/closing timing and valve lift amount of intake/exhaust valves according to operating conditions.

Various intake and exhaust valve drive devices have been proposed in the past, which variably control the opening/closing timing of the intake and exhaust valves and the amount of valve lift according to the engine operating conditions so that valve overlap, fresh air filling efficiency, etc. are always optimally achieved. 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 conventional intake/exhaust valve drive devices, the rocker arm is integrally molded from aluminum alloy, etc., and the curved surface on the back side is configured to make fulcrum contact with the flat part of the lever. , especially at maximum lift of the intake and exhaust valves.
Since the surface pressure at the fulcrum contact point increases, the rocker arm requires a relatively heavy metal such as a wear-resistant member, which increases the inertial force of the rocker arm, causing the problem of making high-speed rocking difficult. Ta.

The present invention was developed by focusing on these conventional problems.The rocker arm is made of a light metal such as an alloy, and a wear-resistant member is provided on the contact surface with the lever.This wear-resistant member is attached to the valve of the rocker arm. The intake/exhaust valve drive for internal combustion engines is designed to be thick on the drive cam side and tapered toward the valve stem side to ensure the wear resistance of the rocker arm while reducing the inertial mass as much as possible, thereby enabling high-speed rocking of the rocker arm. Provide equipment.

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

Figures 2a and 2b show an embodiment of an intake/exhaust valve drive device. In the same figure, 11 is a valve drive cam;
2 is a rocker arm that transmits the movement of the valve drive cam 11 to the intake and exhaust valves 13. The rocker arm 12 is made of a light metal such as an aluminum alloy, and has wear-resistant parts in the contact area with the valve drive cam, the valve head 13a of the intake/exhaust valve 13, and the lever described later. Members 12a, 12b, 12
c are each fixed by casting or the like.

Further, the rocker arm 12 is curved into a substantially dogleg shape, and a support shaft 14 is fitted into the substantially central portion thereof. Further, the back surface 16 of the rocker arm 12 is formed into a continuous predetermined gently convex curved surface.

A lever 17 has a linear support surface 18 and is brought into fulcrum contact with the back surface of the rocker arm 12. A U-shaped groove 17a is formed on the valve stem 13b side of the lever 17. A shaft 19 is fitted into this U-shaped groove 17a, and rotatably supports one end of the lever 17. An adjuster screw 19a and a lock nut 19b are attached to the shaft 19 for adjusting the clearance between the locker arm 12 and the valve head 13a, that is, the valve clearance.

On the other hand, a guide groove 20 having a pair of parallel guide surfaces is provided on the valve drive cam 11 side of the lever 17.
a, a rocker guide 20 having a spring holding portion 20b is formed. The support shaft 14 is slidably inserted into the guide groove 20a, and a coil spring 21 is interposed between the support shaft 14 and the spring holding portion 20b.

Further, the lever 1 is attached to the back surface 22 of the lever 17.
A control cam 23 that regulates the inclination of the shaft 2 is brought into contact with the shaft 2, which rotates according to the operating state of the engine.
It is supported by 4. 25 is a drive device for the shaft 24.

Furthermore, the wear-resistant member 12c is closer to the valve stem 13b than the linear support surface 18 of the lever 17.
The contact area is narrowed.

Next, the operation of this intake/exhaust valve drive device will be explained.

First, when the valve drive cam 11 rotates and pushes up the rocker arm 12, the rocker arm 12 swings while bringing its back surface 16 into support contact with the support surface 18 of the lever 17, and pushes the intake and exhaust valves 13 open. At this time, the fulcrum contact point A moves toward the valve drive cam side as the rocker arm 12 lifts.

Due to this movement, the contact surface between the support surface 18 and the wear-resistant member 12c gradually increases, and the valve lift becomes maximum. Furthermore, where the surface pressure at the fulcrum contact point is greatest, the contact width is also greatest.

On the other hand, when the valve lift is small, that is, the surface pressure at contact point A is small, the above point A is on the valve stem side, and the width of the wear-resistant member in this area becomes smaller, resulting in the optimal contact width depending on the surface pressure. is obtained. Therefore, the closer to the end of the rocker arm 12 there are fewer wear-resistant members, the moment of inertia of the rocker arm 12 becomes smaller, and therefore the equivalent inertial mass of the intake and exhaust valves 13 becomes smaller, making high-speed operation easier. Further, according to the shape of the wear-resistant member 12c, the equivalent inertial mass of the rocker arm 12 as a whole can be reduced.

In addition, control of the valve lift and lift timing is performed by setting the rotation angle of the control cam to the inclination of the lever 17, and when the lever 17 is pushed down by the control cam 13, it becomes the fulcrum of the rocker arm 12. The support surface 18 is also lowered, and the valve lift becomes larger and the period of the lift becomes longer. On the other hand, when the lever 18 is tilted upward, the support surface 1
8 retreats upward, even if the rocker arm 12 lifts, the valve lift is slight and its lift period is shortened.

As explained in detail above, a wear-resistant member is integrally provided on the contact surface of the rocker arm made of light metal such as aluminum alloy with the lever, and this wear-resistant member is wide in the direction of the valve drive cam and extends in the direction of the valve stem. By forming the locking arm so that its width is narrow, it is possible to maintain the weight of the locking arm while increasing the wear resistance of the contact surface with the lever, and also to obtain the advantages of allowing the locking arm to swing at high speed. can.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional intake and exhaust valve drive device for an internal combustion engine, and FIGS. 2a and 2b are a plan view and a sectional view of the intake and exhaust valve drive device of the present invention. 11... Valve drive cam, 12... Locker arm, 12c... Wear-resistant member, 13... Intake and exhaust valve,
14...Support shaft, 17...Lever, 23...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. The rocker arm is made of a light alloy, and the rocker arm is made of a light alloy, and the rocker arm makes contact with the lever. An intake and exhaust valve drive device for an internal combustion engine, characterized in that a wear-resistant member is integrally provided on a face side, and further, the wear-resistant member is provided so that its width becomes narrower from the valve drive cam side toward the valve stem side.