JPH034730Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a variable valve timing device that can change the opening and closing timing of poppet valves used in intake valves, exhaust valves, etc. of automobile engines, depending on low and high speeds. It is.

In general, the opening/closing timing (valve timing) of both the intake and exhaust valves of an automobile engine is such that, for example, the intake and exhaust valves in high-speed models have a relatively early valve opening timing, and a relatively early valve closing timing. It is set to be slow.

This valve timing is set to have the best intake and exhaust efficiency near the engine speed at maximum torque, but when the engine is at low speed,
In particular, during idling, when the intake valve starts to open and the exhaust valve closes, the overlap between the two valves causes the intake air-fuel mixture to flow into the exhaust system, causing so-called raw gas suction and exhaust gas blowback, which deteriorates the combustion state. This results in deterioration of exhaust components, which is not only extremely disadvantageous in terms of exhaust purification measures, but also unfavorable in terms of fuel efficiency.

Therefore, the valve timing is switched between high engine speed and low engine speed.As such, for example, two cams, one for low speed and one for high speed, are used, and the valve timing is driven by these cams. It has been proposed that the locker arm is moved to selectively engage either of the two cams. However, this method not only requires a driving means to move the rocker arm, but also causes interference between the rocker arm and the cam when it slides, and in some cases, the rocker arm and cam may interfere with each other. There is a malfunction that may cause damage to the

The purpose of the present invention is to provide a variable valve timing device that has a simple configuration and can change valve timing in response to low and high engine speeds without having to slide a rocker arm or the like. .

The present invention will be explained below based on one embodiment.

Therefore, in the apparatus according to the embodiment of the present invention, a valve operation stopping mechanism is used, and an example of such a valve operation stopping mechanism will be explained in advance.

4 and 5, which illustrate the valve actuation stop mechanism, show hydraulic pressure being communicated to actuator 48 through oil passages 84, 82 and 80 via appropriate hydraulic switching devices. In this state, the piston 46 and the rod 50 are pressed to the rightmost position by the hydraulic pressure against the return spring 52, and the engagement/disengagement member 42 is also moved to the rightmost position and the plunger 2
It is engaged with the upper end of 6. As a result, when a cam lift occurs due to the cam located at the lower end of the plunger 26, the plunger 26 cannot slide within the cylinder 18, so the rocker arm 10 is swung and the poppet valve 12 is operated.

From this state, in order to stop the operation of the poppet valve 12 according to the operating state of the engine, when the hydraulic pressure in the actuator 48 is discharged through the oil passages 80, 82 and 84 by the operation of the hydraulic pressure switching device, the poppet valve 12 is stopped. The rod 50 and the piston 46 are pushed to the left by the spring 52, but the locking portion 68 of the timing plate 62 is engaged with the recess 70 of the rod 50 during a period when no cam lift is occurring. , the rod 50 cannot slide to the left.

Next, when the cam lift occurs and reaches the maximum value or near it, the rocker arm 10 rotates counterclockwise around the rocker shaft 14, and the protrusion 74 of the timing plate 62 moves toward the timing cam 7.
2, move the timing plate 62 to the pivot 60.
Since the timing plate is rotated counterclockwise around the timing plate locking portion 68 and the rod recess 70,
The rod 50 and the piston 46 are moved to the left by the pressing force of the return spring 52. However, in this state, the locker arm 10 swings and the poppet valve 12
, the engaging/disengaging member 42 is held between the upper end of the plunger 26 and the upper surface of the elongated hole 40 by the valve spring load and cannot slide. Therefore, the piston 46 and the rod 50 slide by the dimension of the gap 58 provided at the connecting portion with the locking/disengaging member 42, and the recess 70 of the rod 50 and the locking portion 68 of the timing plate 62 do not engage. position. Thereafter, when the cam lift is completed, the engaging and disengaging member 42 is released from the spring load and becomes slidable, so that the piston 46 and the rod 5 are connected by the return spring 52.
0 moves to the left, the engaging/disengaging member 42 is removed from the elongated hole 40, allowing the plunger 26 to slide. As a result, even if a cam lift occurs next time, the poppet valve 12 and the rocker arm 10 will be held back by the spring 32.
is biased by a valve spring that is stronger than the
Plunger 26 only moves freely relative to cylinder 18, rocker arm 10 is not swung, and poppet valve 12 is not actuated.

In this state, the locking portion 68 of the timing plate 62 engages with the right end surface of the rod 50.

In order to operate the poppet valve 12 again depending on the operating condition of the engine, hydraulic pressure is supplied into the cylinder 44 of the actuator 48 via the oil passages 84, 82 and 80 by the operation of the hydraulic switching device.
The piston 46 and the rod 50 are pushed to the right against the return spring 52 by the same hydraulic pressure, but the locking portion 68 of the timing plate 62 is pressed against the rod 50.
Since the piston 46 and the rod 50 are engaged with the right end surface of the piston 46, the piston 46 and the rod 50 cannot slide to the right.

Next, when the cam lift occurs and reaches the maximum value or near it, the plunger 26 moves to the cylinder 18.
The lower edge of the slot 64 formed in the plunger 26 is inserted into the timing plate 6.
2 and presses upward to rotate the timing plate 62 counterclockwise around the pivot 60, so that the engagement between the timing plate locking portion 68 and the right end surface of the rod 50 is prevented. Once removed, the piston 46 and rod 50 are moved to the right by hydraulic pressure. However, in this state, a cam lift occurs and the plunger 26 is slid inside the cylinder 18, so the stopper 42 slides as the inner edge of its forked portion abuts against the cylindrical wall surface of the plunger 26. Can not. Therefore, piston 4
6 and the rod 50 slide by the size of the gap 58 provided at the connecting portion with the locking/disengaging member 42, and reach a position where the locking portion 48 of the timing plate and the right end surface of the rod 50 do not engage.

Thereafter, when the cam lift is completed, the plunger 26 is slid downward outside the cylinder 18 by the pressing force of the spring 32, and its upper end is located below the upper surface of the elongated hole 40, so that the stopper 42 is slid. Piston 46 with hydraulic pressure
As the rod 50 moves to the right, the engaging/disengaging member 42 enters the elongated hole 40 and comes into abutment engagement with the upper end of the plunger 26, thereby preventing the plunger 26 from sliding.
As a result, the next time a cam lift occurs, the plunger 26 cannot slide relative to the cylinder 18, so the rocker arm 10 is swung and the poppet valve 1
2 is activated.

As described above, in this valve operation stop mechanism, when the plunger is in a fixed state, the plunger is integrated with the rocker arm, the rocker arm begins to vibrate, the poppet valve is driven, and the plunger becomes in an idle state. When the locker arm is fully undone, the rocker arm no longer swings and the poppet valve stops driving.

The present invention is characterized in that such a valve operation stop mechanism is provided in one of the bifurcated arms of the rocker arm.

In FIG. 1, a rocker arm 2 swingably supported by a rocker shaft 1 has arm parts 2a and 2b that are bifurcated and integral with each other. Plunger 3 (Figure 2)
A valve operation stop mechanism 4 is provided in which the valve is selectively fixed and freely movable. The configuration of this valve operation stop mechanism 4 is basically the same as that shown in FIG. 4, so a detailed explanation of its configuration will be omitted.

The right end 2c of the rocker arm 2 has a poppet valve 12.
(Fig. 4), the lower end of the plunger 3 (Fig. 2) of the valve operation stop mechanism 4 provided on the arm portion 2a of the rocker arm 2 is the high-speed cam 5.
The lower end of the tip of the other arm 2b of the rocker arm 2 is in contact with the low-speed cam 6.

Both cams 5 and 6 are provided on a camshaft 7 at intervals, of which the low speed cam 6 is
As shown by the broken line in the figure, the cam profile is located inside the cam profile of the lift portion of the high-speed cam 5.

Both cams 5 and 6 are, for example, cams that actuate the intake valves. Of these, the valve timing by the low speed cam 6 is performed as shown in FIG. 3A, and the valve timing by the high speed cam 5 is shown in FIG. 3B. It is done as follows. For example, at low speeds, the valve timing for the intake valves is set so that the valve opening timing is later and the valve closing timing is earlier than at high speeds. Therefore, at low speeds, blow-by of raw gas and blow-back of exhaust gas do not occur, and functions such as a good combustion state are achieved.

Here, when in the mode that uses the high-speed cam,
The plunger 3 is fixed and integrated with the rocker arm 2, and as the high-speed cam 5 rotates, the rocker arm 2 swings through the integrated plunger 3.
This rocker arm 2 drives the intake valve. Of course,
In this case, the intake valve is opened and closed at the timing illustrated in FIG. 3B. At this time, the low speed cam 6
Since the cam profile of is located inside that of the high speed cam 5, the low speed cam 6 does not drive the rocker arm 2.

On the other hand, in the mode that uses the low speed cam 6,
Since the plunger 3 becomes free and freely movable, the lower end of the tip of the arm portion 2b of the rocker arm 2 directly engages with the low-speed cam 6, and in this state, due to the rotation of the low-speed cam 6, The rocker arm 2 swings, and this rocker arm drives the intake valve. The opening/closing timing of the intake valve at this time is controlled as shown in FIG. 3A. Note that depending on the shape of the cam contour of the low-speed cam relative to the high-speed cam, the valve operation stop mechanism may be provided on the arm portion 2b. In addition, the variable valve timing device according to this invention can be applied not only to intake valves but also to exhaust valves.

As described above, the present invention provides a variable valve timing device that can change valve timing in response to low engine speed and high engine speed with a simple configuration without sliding the rocker arm or cam. can do.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an embodiment of the device of the present invention, Fig. 2 is a configuration diagram of a low-speed cam and a high-speed cam that engages with a plunger, Fig. 3 is a valve timing diagram for low-speed and high-speed cams, and Fig. 4 is a diagram of the valve timing of the low-speed and high-speed cams. FIG. 5 is a sectional view taken along the - line in FIG. 5, showing an example of a valve operation stop mechanism, and FIG. 5 is a sectional view taken along the - line in FIG. 4. 2...Rotsuka arm, 2a, 2b...arm part, 3
...Plunger, 4...Valve operation stop mechanism, 5...
High speed cam, 6...low speed cam.

Claims (1)

[Claim for Utility Model Registration] A rocker arm for driving a poppet valve used in an engine intake valve, exhaust valve, etc., which has a bifurcated first arm and a second arm that are integral with each other. a rocker arm; a low-speed cam that drives the first arm to swing the rocker arm; and a cam that drives the second arm to rock the rocker arm, the cam being a lift portion of the low-speed cam. a high-speed cam having a cam profile higher than the cam profile; a plunger slidably provided on the second arm and in contact with the high-speed cam; A variable valve timing device comprising: a valve actuation stop mechanism having a locking/disengaging member selectively fixed or floating with respect to two arms.