JPS6085207A - Valve operation transfer device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To gain large driving force at the time of movement by restricting movement of an actuator until the negative pressure within the actuator is increases in a transfer device which transfers valve operations by moving a rocker arm in a rocker shaft direction using intake negative pressure of an engine. CONSTITUTION:A rocker arm 5 is arranged on a rocker shaft 2 movably in the axis direction or oscillating freely, and it makes slidable contact with a cam for low speed 3 or a cam for high speed 4. Movement of the rocker arm 5 is performed by an actuator 20 into which intake negative pressure of an engine or the atmosphere is introduced. At an ordinary time, movement of the rod 21 of the actuator 20 is restricted by a restriction means 30. And at the time of transfer of valve operation, a transfer signal is given to a transfer valve 27. Then after the predetermined time, the restriction means 30 is released. Thus, movement of the rod 21 begins after large negative pressure is accumulated in a negative pressure chamber 25 of the actuator 20, and large driving force can be obtained, thereby transfer is performed rapidly.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a device for switching valve operation of intake and exhaust valves of an internal combustion engine.

Background technology> The valve operation of intake and exhaust valves can be switched using, for example, a cylinder number control engine that suspends the operation of some cylinders depending on operating conditions, or a two-stage cam switching engine that switches the lift height or opening/closing timing of the valve. The rocker arm installed on the camshaft 1 is moved in the axial direction of the camshaft.
This is achieved by selectively engaging one of a pair of cams having different profiles formed in -.

An example of this type of valve operation switching device is the one disclosed in Japanese Patent Application Laid-Open No. 140015/1983.

When the hydraulic actuator for moving the rocker arm is activated, it moves when the rocker arm is in the cam's heath circle. During the lift, the spring stores the biasing force of the hydraulic actuator, and immediately after the lift ends, the cam moves. The rocker arm is designed to move while in a heath circle state. Furthermore,
The movement timing of the rocker arm in the cam head circle is limited by a stopper guide attached to the camshaft. In other words, the camshaft is equipped with a guide that is easy to bend in the radial direction and relatively rigid in the axial direction.
By providing the outer periphery of the camshaft between the two cams so as to protrude from the cam surface in the latter half of the cam base circle, the area in which the rocker arm can start moving is limited in the base circle area of the cam.

However, in this case, since the camshaft rotates even at high speeds, there is a possibility that the stopper guide will fall off due to centrifugal force at that time, and if the urging force for moving the rocker arm is increased, there is a risk that the stopper guide will be damaged. There is a big problem in terms of reliability.

Furthermore, there is a possibility that the movement timing of the rocker arm may be shifted due to deformation of the stosobacite or the like.

Further, since a hydraulic actuator is used to move the rocker arm, there are disadvantages in that a special pressure source is required and the configuration of the hydraulic circuit etc. is complicated.

<Purpose of the Invention> The present invention has been made in view of the above-mentioned problems, and has a rocker arm movement actuator with high reliability and a simple configuration. The object of the present invention is to provide a valve actuation switching device.

<Summary of the Invention> Therefore, the present invention provides a structure in which the urging force of the stopper that restricts the movement of the rocker arm and the urging means that urges the rocker arm in the axial direction of the rocker shaft based on the valve operation switching signal acts on the rocker arm. The structure is such that a stationary part such as the Ronca shaft is provided with a release means that locks and interlocks with the rocker arm when the cam is lifted, and releases the restriction by the stopper described in njj at the end of the cam lift, so that the movement timing of the rocker arm can be adjusted. In addition, the suction negative pressure of the engine is used as the source of the urging force of the urging means, and a regulating means is provided for regulating the movement of the urging means in the axial direction of the rocker shaft. t111 is released after a predetermined period of time has elapsed since the output of the valve operation switching signal.

<Example> Hereinafter, an example in which the present invention is applied to an internal combustion engine with an exhaust turbo supercharger will be described.

Before explaining the main structure of this embodiment, the valve operating characteristics of a supercharged internal combustion engine to which the present invention is applied will be explained.

In a supercharged internal combustion engine, the compression ratio is reduced at high speeds and high loads when supercharging is performed to prevent non-king and ensure output, while at low speeds and high loads when supercharging is not effective, the output is reduced. It is desirable to be able to variably control the compression ratio to increase it, and also to improve fuel efficiency during partial loads where supercharging is not effective. However, it is substantially difficult to variably control the compression ratio by making the piston stroke amount variable.

Incidentally, the intake valve closes at an appropriate time during the compression stroke, and substantial compression starts from this point.

Therefore, the actual compression ratio (hereinafter referred to as the actual compression ratio) with respect to the compression ratio determined from the specifications of the engine is determined by the specifications of the engine and the intake valve closing timing.

By utilizing this phenomenon, at low speeds and partial load regions where supercharging is not effective, the intake valve close timing can be advanced to improve the actual compression ratio and prevent deterioration of fuel efficiency, while at high speeds and high load regions, the intake valve closing timing can be advanced. By delaying the engine speed and lowering the actual compression ratio and sliding the non-king region to overwhelmingly high supercharging, it is possible to operate under sufficient supercharging pressure and thereby secure output.

On the other hand, regarding the opening timing of the intake valve, if you try to advance the opening timing during high-speed operation to take advantage of the inertia effect of the intake air, the overlap period with the exhaust valve will increase, resulting in a large exhaust pressure at high speed υ1 In the case of a turbocharger, exhaust gas flows back into the intake system during the overramp period, which actually reduces the charging efficiency.
There is a risk that the exhaust efficiency will decrease and the output will decrease.

, ] Therefore, it is desirable that the advance in the opening timing of the intake valve be relatively small, and that the change due to rotational speed be small (including no change).

From the above points, in the valve operation switching device described below, a high-speed cam with a profile that greatly delays the intake valve closing timing and a small advance in the intake valve opening timing, and A low-speed cam with a profile that has a small delay in intake valve opening timing and a small advance in intake valve opening timing (same as or slightly smaller than a high-speed cam) is used, and the rocker arm is moved to combine these two types of cams. The valve operation is switched by switching the engagement of the valve.

Next, the configuration of the valve operation switching device according to the present invention will be explained based on FIGS. 1 to 4.

In the figure, a camshaft 1 is rotatably supported in a locker room, and a rotor shaft l-
2 is fixedly supported. #1 for cam shirts 1-1
A pair of intake valve operating cams having different profiles, namely a low speed cam 3 and a high speed cam 4, are formed to switch the intake valve operating characteristics for each cylinder of #4.

As mentioned above, the low-speed cam 3 has a profile that reduces the delay in the closing timing of the intake valve (about 25 degrees after bottom dead center) and the small advance in the opening timing (about 5 degrees before top dead center). Similarly, the high-speed cam 4 has a large delay in the intake valve closing timing (approximately 65 degrees after bottom dead center), and the advance in the opening timing is slightly larger than that of the low-speed cam, but the change is small compared to the change in the closing timing. (approximately 10 degrees before top dead center).

A rocker arm 5 for driving an intake valve is freely rotatably and axially slidably supported in each cylinder #1 to #44ii on the rocker shaft 2. The rocker arm 5 is freely rotated and axially slidable in each cylinder #1 to #44ii. It is adapted to be selectively engaged.

A frame 6 provided to partition these rocker arms 5 is fitted onto the rocker shaft 2 so as to be able to slide freely in the axial direction, and one end of the frame 6 is provided with a frame 6 that allows the rocker arm 5 to move in the axial direction of the rocker shaft based on a valve operation switching signal. A rod 2] of a negative pressure actuator 20, which will be described later, is engaged and fixed, and can be switched and shifted in the axial direction by the negative pressure actuator 20. Sliders 8.9 are provided on both sides of each rocker arm 5, and the rocker arm side is formed to have a large diameter and is fitted into the rocker shaft 2 so as to freely slide in the rocker shaft axial direction.
The stopper 10.11 is configured to be engageable with a stopper 10.11 implanted as shown in FIG. Further, on the end surface of each slider 8, 9 on the rocker arm side, a pin is provided on both sides of the rocker arm 5, as shown in FIG. Pin holes 8a and 9a into which the pins 14 and 15 can be inserted are formed.

A leaf spring 16 has one end fixed to one slider 8 so as to straddle the rocker arm 5, and the other end abuts on the other slider 9 so as to be able to freely rotate relative to each other.

Springs 17 and 18 are interposed between the large diameter portions of the sliders 8 and 9 and the partition wall 6A of the frame 6, respectively.

Next, the aforementioned negative pressure actuator will be explained in detail.

The negative pressure actuator 20 is connected to the opening 2 by a diaphragm 22 connected to the other end of the rod 21 that engages with the frame 6.
3, and a negative pressure chamber 25, which can communicate with the atmosphere or an engine suction negative pressure source through a first electromagnetic directional gate valve 27. A return spring 26 is provided in the negative pressure chamber 25 to elastically bias the diaphragm 22 toward the atmospheric chamber 24 at all times.

Further, the negative pressure circuit between the first electromagnetic directional switching valve 27 and the suction negative pressure source includes an accumulator 28 and a check valve 29 that only allows flow from the switching valve 27 side to the suction negative pressure source side. It has been intervened.

Furthermore, circumferential grooves 21a and 21b are formed at two locations on the outer periphery of the rotor I' 21 of the negative pressure actuator 20, and the lot 2
A ball 31 of a regulating means 30 for regulating the movement of the ball 1 can be fitted therein. The regulating means 30 is arranged inside the case by a diaphragm 34, one end of which abuts the ball 31 and the other end of the slider F'33 connected, to an atmospheric chamber 35 which is open to the atmosphere through an opening 35a, and the first and second chambers. The negative pressure chamber 36 communicates with the atmosphere or an intake negative pressure source via two electromagnetic directional control valves 27 and 40, and the negative pressure chamber 36 is provided with a return spring 37. Further, a throttle 41 is interposed in the negative pressure circuit between the negative pressure chamber 36 of the regulating means 30 and the second electromagnetic directional switching valve 40, so that negative pressure is created in the negative pressure actuator 20 based on the valve operation switching signal. When the negative pressure is introduced, the throttle 41 causes a predetermined time delay in introducing the negative pressure into the negative pressure chamber 36 of the regulating means 30. The switching operation of the second electromagnetic directional switching valve 40 is performed using a fixed contact 42a fixed to a fixed body and a movable contact 42 provided on the frame 6.
The switch 42 is turned on and off by the movement of the frame 6 in the axial direction of the four shafts.

Next, the effect will be explained.

During low speed and partial load operation of the engine, the first electromagnetic directional control valve 27 is set to the position shown in FIG. 1 by a signal from a control circuit (not shown). 25 communicates with the atmosphere and is at atmospheric pressure. Therefore, the frame 6 is in the position shown in the first figure based on the elastic biasing force of the return spring 26. As a result, the switch 42 of the second electromagnetic directional control valve 40 is in the OFF state, and the second electromagnetic directional control valve 40 is centered at the position shown in the first diagram, and the inside of the negative pressure chamber 36 of the regulating means 30 is at atmospheric pressure, and its return spring Due to the elastic biasing force of 37, the ball 31 is rotated through the diaphragm 34 and the rod 33.
It fits into the circumferential groove 212 on the left side in the figure of 1.

Therefore, the spring 17 is compressed and presses the slider 8 with its compressive elastic force, and as the rocker arm 5 swings, the pin 14 of the rocker arm 5 enters the pin hole 8a, and the engagement with the stopper 10 is released. Due to rocker arm 5
is pressed toward the low speed cam 3 side and swings together with the lug arm 5. On the other hand, the other slider 9 is separated from the rocker arm 5 by the spring force of the leaf spring 16. Therefore, valve operation of the intake valve with a large actual compression ratio suitable for the operating range can be obtained, ensuring output and improving fuel efficiency.

Next, when the engine operating state shifts to high-speed, high-load operation, a switching signal from the control circuit causes the first electromagnetic directional control valve 27 to
is placed in a position opposite to that shown in the first diagram. Thereby, the negative pressure chamber 25 of the negative pressure actuator 20 communicates with the negative pressure source, and negative pressure is introduced. At that time, the second electromagnetic directional valve 40
Negative pressure is also introduced into the negative pressure chamber 36 of the regulating means 30 through the negative pressure circuit, but this is gradually done by the action of the throttle 41 installed in the negative pressure circuit, and the negative pressure chamber 25 of the negative pressure actuator 20 is gradually introduced. Until the negative pressure value becomes sufficient, the restricting force exerted by the restricting means 30 on the movement of the negative pressure actuator 20 is not released.

When the restriction of the restriction means 30 is released, the inside of the negative pressure chamber 25 of the negative pressure actuator 20 is in a sufficiently negative pressure state, so that the rod 21 is moved as shown in FIG. The circumferential groove 21 to the left
b moves until it comes to a position corresponding to the ball 31 of the regulating means 30, and the frame 6 also moves in the same direction accordingly. Then, the sliders 8 corresponding to the springs 17 and 18
The elastic bias against and 9 is reversed 7, and the slider 9, which had been separated from the rocker arm 5, moves to the left in the figure, but is stopped by the striker 11 and applies its pressing force to the rocker arm 5. 5's movement is restricted.

At this time, if the rocker arm 5 is located in the heath circle of the cam 3, the pin hole 9 of the slider 9 is
Since the positions of a and the pin 15 are misaligned, the pin 15 is pushed by the slider 9 and retracted into the rocker arm 5. On the other hand, the slider 8 engaged with the rocker arm 5 is pushed and moved to the left in the drawing by the leaf spring 16, and the pin 14 is disengaged and separated from the rocker arm 5 as shown in the fourth figure.

In this state, as the camshaft 1 rotates, the low-speed cam 3 lifts, and the mouth and rear arms 5 rotate to rotate the pin 1.
When the positions of the rocker arm 5 and the pin hole 9a match, the pin 15 is pushed into the pin hole a by the spring force at this point, and the slider 9 rotates together with the rocker arm 5. Then, when the low-speed cam 3 has finished lifting and becomes a heath circle, the slider 9 and the stopper 11 are disengaged as shown in the fourth figure, and the slider 9 and the rocker arm 5 are moved together by the elastic force of the spring 18. Then, the engagement can be switched from the low speed cam 3 to the high speed cam 4. Therefore, a valve operating characteristic with a small actual compression ratio can be obtained, and the supercharging effect can be fully exerted and the maximum output can be secured. The switch 42 is turned on by the movement of the frame 6, and the second electromagnetic directional control valve 40 is moved to a position opposite to that shown in the first figure, and atmospheric air is introduced into the negative pressure chamber 36 of the regulating means 30 and into the circumferential groove 21b. Movement of the negative pressure actuator 20 is restricted by pressing the ball 31.

According to this configuration, no matter when the switching signal is output, the rocker arm automatically switches and moves in the section where the cam is in the Heas circle, and the movement always starts immediately after the cam lift ends. Furthermore, movement of the actuator is prevented until the negative pressure within the negative pressure actuator increases sufficiently, and the actuator is moved when the effect of the negative pressure on the actuator becomes sufficient. Therefore,
Even if the engine rotation becomes high speed and the available switching time is shortened, sufficient switching movement is possible, and damage to the cam etc. can be prevented.

Furthermore, since the stopper mechanism is provided on a non-rotating rocker shaft or the like, reliability is improved compared to the conventional one provided on the cam shirt 1 side. Furthermore, since there is a certain amount of time between the application of the biasing force of the actuator and the start of movement of the rocker arm, the response speed of the actuator may be relatively slow.

Moreover, since the engine suction negative pressure is used instead of hydraulic pressure as the force generating source for the actuator for moving the rocker arm, a special pressure source is not required, and the configuration is simplified and costs can be reduced.

Note that the switching of the second electromagnetic directional switching valve is not limited to the configuration of this embodiment, and may be configured to be delayed using a timer circuit or the like. Although this example is applied to an internal combustion engine with an exhaust turbo supercharger, it can also be applied to other two-stage cam switching engines or cylinder number control engines that switch the valve operation of exhaust valves. Of course.

<Effects of the Invention> As described above, according to the present invention, the rocker arm can be sufficiently switched within the cam base circle section even in the high speed range of engine rotation, and the accuracy of valve operation switching can be improved. can. Furthermore, since the stopper mechanism is provided on a non-rotating rocker shaft or the like, there is no danger of the stopper falling off, and reliability can be greatly improved. Furthermore, the actuator is not a hydraulic type but a negative pressure type that uses engine suction negative pressure, and the movement of the actuator is restricted until the negative pressure inside the actuator increases sufficiently, so a special pressure source is not required. At the same time, the configuration is simple, so
(Cost can be reduced and regulations are still in place) N: The biasing force of the actuator during release is increased, and the moving speed of the rocker arm can be increased.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing one embodiment of the present invention, Fig. 2 is a detailed view of the pin take-up portion of the Ronoka arm of the same embodiment, Fig. 3
The figure is an explanatory view of the positional relationship between the pin and the pin hole in the embodiment, and FIG. 4 is an enlarged view of the engaging portion between the cam and the rocker arm in the embodiment. 1...Camshaft 2...Rocker shaft 3...
□・Low speed cam 4...High speed cam 5...Rocker arm 6...Frame 8.9...Slider 17
, 18... Spring 20... Negative pressure actuator 27... First electromagnetic directional control valve 30... Regulating means 40... Second electromagnetic directional control valve 41... Throttle patent applicant Nissan Motor Co., Ltd. Company agent Patent attorney Fujio Sasashima

Claims (1)

[Claims] Move the rocker arm in the axial direction of the rocker shaft,
A valve that is driven via this rocker arm by selectively engaging one of the cams of different profiles arranged in parallel in the axial direction of a camshaft disposed parallel to the rocker shaft. The valve operation switching device for an internal combustion engine is configured to switch the operation of a valve operation switching device, comprising: a biasing means for biasing the rocker arm in the axial direction of the rocker shaft based on a valve operation switching signal; a stopper for regulating movement of the rocker arm; and a release means that engages with the rocker arm when the cam is lifted when the cam is engaged with the rocker arm while the biasing force of the biasing means is applied, and releases the restriction by the stopper when the cam lift ends;
While the engine suction negative pressure is used as a source of the urging force of the urging means, the movement of the urging means in the axial direction of the rocker shaft is restricted during operation, and when the valve operation is switched, a predetermined period of time is elapsed from the output of the switching signal. 1. A valve operation switching device for an internal combustion engine, comprising a regulating means for canceling the regulation after a period of time has elapsed.