JPS6131128Y2 - - 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 of them is the US patent 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. In particular, the lever 5 is rotatably 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 driving 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 this conventional valve drive device, adjustment of valve clearance is not particularly considered, and the configuration is such that a certain valve clearance is given in advance, which causes problems such as increased noise and vibration. A shock absorbing curve is required on the profile of the back surface 4 of the rocker arm 3 as a countermeasure against shocks when standing up and sitting down, which has the disadvantage that the design and processing of the profile becomes complicated.

In view of these conventional drawbacks, this invention aims to solve the above-mentioned conventional drawbacks by providing a zero lash mechanism using an eccentric collar in the bearing portion of the lever where the back surface of the rocker arm makes fulcrum contact.

Hereinafter, one embodiment of this invention will be described in detail based on the drawings.

FIGS. 2 and 3 show an embodiment of this invention, and since the basic structure of this embodiment is not particularly different from the conventional one shown in FIG. 1, the same parts are given the same reference numerals. Duplicate explanations will be omitted.

In the figure, reference numeral 11 denotes a lever shaft fixed on an approximately extended line of the valve stem 2a to support the lever 5, and 12 denotes a cylindrical bearing portion formed at one end of the lever 5. A cylindrical eccentric collar 13 is interposed between the lever shaft 11 and the lever shaft 11, and as the eccentric collar 13 rotates, the center of rotation of the lever 5 changes.
O ₁ is configured to move up and down with respect to the center O ₂ of the lever shaft. The eccentric collar 13 protrudes to the side of the lever 5 as shown in FIG.
are integrally formed.

On the other hand, reference numeral 15 denotes a hydraulic actuator that is connected to the arm 14 via a push rod 16 and rotates the eccentric collar 13. a cylinder 18; a plunger 20 that is slidably fitted into the cylinder 18 and has an oil reservoir chamber 19 therein; and a plunger 20 that communicates with the oil reservoir chamber 19 via a check valve 21;
Hydraulic chamber 2 defined by and cylinder 18
2, and a coil spring 23 disposed within the hydraulic chamber 22 to bias the plunger 20 in the projecting direction.
The lower end of the arm 6 is fitted and supported on the upper surface of the plunger 20, and the upper end is fitted and supported on the tip of the arm 14, respectively.
An oil passage 24 is provided in the lever shaft 11 and communicates with the oil gear of the engine.
The oil reservoir chamber 19 is configured to be supplied with forced lubricating oil from an oil pump.

Next, its effect will be explained.

First, when the intake and exhaust valves 2 are not lifted,
That is, when the cam contact portion 3a of the rocker arm 3 is on the base circle of the valve drive cam 1, the eccentric collar 13 is rotated counterclockwise in the drawing by the biasing force of the coil spring 23 in the hydraulic actuator 15. As a result, the pivot center _O1 of the lever 5 is displaced downward, so that the valve clearance between the lever 5 and the rocker arm 3 or between the rocker arm 3 and the valve stem 2a is always maintained at zero. At this time, hydraulic actuator 1
The hydraulic chamber 22 of No. 5 is filled with oil through the passage 14a and the like.

Next, when the valve drive cam 1 rotates and the cam contact portion 3a of the rocker arm 3 is lifted, the rocker arm 3 tries to push the lever 5 upward with its back surface 4, but this pushing up force is applied to the eccentric collar 13 as shown in the figure. The rotation force in the clockwise direction, that is, is transmitted to the hydraulic actuator 15 as a compression force, and the hydraulic chamber 2
Compress the oil in 2. At this time, since the oil in the hydraulic chamber 22 is prevented from leaking to the oil reservoir chamber 19 by the check valve 21, the eccentric collar 13 receives a reaction force in the counterclockwise direction due to the hydraulic pressure in the hydraulic chamber 22. As a result, the eccentric collar 13 is prevented from rotating clockwise. Therefore, the rotation center _O1 of the lever 5 will not be displaced upward.

In other words, the rotation center _O1 of the lever 5 remains set when the cam contact portion 3a of the rocker arm 3 is on the base circle of the valve drive cam 1, and is maintained during the opening period of the intake and exhaust valves 2. be done.

Here, while the intake and exhaust valves 2 are open, the hydraulic chamber 2
2 is compressed by the clockwise rotation of the eccentric collar 13, and some oil in the hydraulic chamber 22 leaks from the gap between the cylinder 18 and the plunger 20. Therefore, when the cam contact portion 3a of the rocker arm 3 returns to the base circle of the valve drive cam 1 after the valve drive cam 1 opens the intake and exhaust valves 2, the oil in the hydraulic chamber 22 leaks. The eccentric collar 13 is in a state of being rotated clockwise. However, at this point, the push-up force from Rotsuka arm 3 has already disappeared,
It is rotated counterclockwise again by the biasing force of the coil spring 23, and the valve clearance is adjusted to zero. At this time, there is a check valve 2 in the hydraulic chamber 22.
1, oil is supplied from the oil reservoir chamber 19 in an amount corresponding to the amount of leakage.

The above steps are repeated every revolution of the valve drive cam 1.

The hydraulic pressure of the oil supplied to the hydraulic chamber 22 is normally kept approximately constant by a regulator valve (not shown), but if this hydraulic pressure becomes too high, the oil in the hydraulic chamber 22 and the valve A small amount of leakage occurs each time the drive cam 1 rotates, and the rotation center O ₁ of the lever 5 is adjusted to the set position to keep the valve clearance at zero.

In addition, even when the valve stem 2a rises due to thermal expansion of the valve stem 2a or wear of the valve seat, oil in the hydraulic chamber 22 leaks with each rotation of the valve drive cam 1, thereby reducing the valve clearance. It can always be kept at zero.

Next, FIGS. 4 and 5 show different embodiments of this invention, in particular, the rocker arm 3.
A support shaft 31 is provided in the center of the lever 5, a rocker guide 32 for slidably holding the support shaft 31 is fixed to the lever 5, and a coil spring 33 is disposed between the lever 5 and the support shaft 31. be. Incidentally, the zero lash mechanism itself constructed in the bearing portion of the lever 5 is not particularly different from the above embodiment.

That is, with this configuration, compared to the embodiments shown in FIGS. 2 and 3, the bending moment applied to the valve stem 2a by the rocker arm 3 can be reduced, and the back surface 4 of the rocker arm 3 and the lever lower surface 5a can be Since the relative sliding speed of the steel is reduced, wear can be suppressed. Also, since the locking arm 3 is forcibly returned by the coil spring 33,
The ability of the rocker arm 3 to follow the valve drive cam 1 is improved, and phenomena such as jumps, bounces, or falling off of the lever 5 of the rocker arm 3 can be prevented.

As explained in detail above, with this invention, valve clearance can always be kept at zero, engine noise and vibration can be significantly reduced, and a buffer curve has been added to the profile on the back of the rocker arm that makes fulcrum contact with the lever. It is not necessary to provide the rocker arm, and the design and processing of the rocker arm becomes easier.

[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 this invention, Fig. 3 is a plan view of the same, and Fig. 4 is a different embodiment of this invention. FIG. 5 is a plan view of the same. 1... Valve drive cam, 2... Intake and exhaust valve, 3...
... Locker arm, 5 ... Lever, 6 ... Control cam, 11 ... Lever shaft, 12 ... Bearing section,
13...Eccentric collar, 15...Hydraulic actuator.

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 in contact with the valve drive cam and the other end that is linked to the valve stem; A lever that is in fulcrum contact and is rotatably supported at one end on the valve stem side, a control cam that comes into contact with the back surface of the lever to regulate the inclination of the lever, and a support shaft and a bearing of the lever. A cylindrical eccentric collar is interposed between the two cylinders and rotates to move the lever rotation center up and down with respect to the support shaft center. An intake/exhaust valve drive device for an internal combustion engine, comprising a hydraulic actuator for moving the valves.