JPS6085206A - Valve operation transfer device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable simplification and lowering of cost of an actuator in a transfer device in which valve operation is transferred by moving a rocker arm in the rocker shaft direction, by gaining transfer force by the actuator which uses intake negative pressure of an engine. CONSTITUTION:A rocker arm 5 is arranged on a rocker shaft 2 movably in the axis direction and oscillating freely, and it makes slidable contact with a cam for low speed 3 or a cam for high speed 4. The rocker arm 5 is moved in the direction of the axis of the rocker shaft 2 through a slider 8, spring 17 and 18, and a frame 6 by actuators 20 and 21. Intake negative pressure of an engine or the atmosphere is introduced into negative pressure chambers 20E and 21E of actuators 20 and 21 according to the position of a transfer valve 22. Thus, there is no need for special source of pressure for the actuators, the structure is simplified, and the cost can be lowered.

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, a two-stage cam switching engine that switches the lift height or opening/closing timing of the valve, etc. This is achieved by moving the rocker arm provided on the rocker shaft in the axial direction of the rocker shaft and selectively engaging one of a pair of cams with different profiles formed on the camshaft. It is something.

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 pace circle of the cam, and during lift, the spring stores the biasing force of the hydraulic actuator, and immediately after the lift ends, the cam moves. 7 so that the rocker arm moves when the base circle is reached. Furthermore,
The movement timing of the rocker arm in the base circle of the cam is limited by a stopper guide attached to the camshaft. That is, a stopper guide that is easily bent in the radial direction of the camshaft and relatively rigid in the axial direction is provided on 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. In particular, 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 a shift in the movement timing of the Shirotsuka arm may occur due to deformation of the stopper guide or the like.

Furthermore, using a hydraulic actuator to move the rocker arm9 has the disadvantage that a special pressure source is required and the configuration of the hydraulic circuit etc. becomes complicated.

<Object of the Invention> The present invention has been made in view of the above points, and provides a low-cost valve for an internal combustion engine that has a rocker arm movement actuator with high reliability in rocker arm movement timing control and a simple structure. The purpose of the present invention is to provide an operation switching device.

<Summary of the Invention> Therefore, the present invention provides a stopper that restricts the movement of the rocker arm, and a biasing force of the biasing means that biases the rocker arm in the axial direction of the rocker shaft based on the valve operation switching signal.
A release means that engages and interlocks with the rocker arm when the cam reaches the 7th position while acting on the rocker arm, and releases the restriction by the stopper when the cam lift ends, and is provided on a stationary part such as all rocker shafts to move the rocker arm. In addition to timing, the engine's suction negative pressure is used as the source of the urging force of the urging means.

<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 an internal combustion engine with a supercharger, the compression ratio is reduced at high speeds and high loads, when supercharging is performed, to prevent knocking and ensure output, while at low speeds and high loads, when supercharging is not effective. Therefore, it is desirable to be able to perform variable control to increase the compression ratio in order to secure output and to improve fuel efficiency during partial loads where supercharging is not effective. However, it is substantially difficult to variably control the compression ratio by varying the piston/stroke amount.

By the way, the intake valve closes at an appropriate time in the compression stroke, and from this point on, the effective fishing force compression starts.

Therefore, compared to the compression ratio determined from the engine specifications, the actual compression ratio (hereinafter referred to as the actual compression ratio) is determined by the engine specifications 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 pressure-dynamic ratio and prevent deterioration of fuel efficiency, while at high speeds and high load regions, the intake valve can be closed. By delaying the timing and lowering the actual compression ratio and sliding the knocking region to the high boost pressure side, it is possible to operate under sufficient boost pressure and thereby secure the output.

On the other hand, regarding the opening timing of the intake valve, if you try to open the opening timing earlier 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 exhaust turbo overlapping, which increases the exhaust pressure at high speeds. In the case of a feeder, there is a risk that exhaust gas will flow back into the intake system during the overlap period, which will actually reduce the filling efficiency and exhaust efficiency, leading to a reduction in output.

For this reason, it is desirable that the advance of 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 minimizes the delay in the intake valve closing timing and a small advance in the intake valve opening timing, and a A low-speed cam with a profile that has a small retardation and a small advance in intake valve opening timing (same as or slightly smaller than a high-speed cam) is used, and these two types of cams are created by moving the rocker arm. The structure is such that the valve operation can be changed by switching the engagement between the valve and the valve.

Next, the configuration of the valve operation switching device according to the present invention will be explained based on FIGS. 1 to 5.

In the figure, a camshaft 1 is rotatably supported in a rocker room, and a rocker shaft 2 is located above it.
is fixedly supported. The camshaft 1 has a pair of intake valve operating cams with different profiles to switch the intake valve operating characteristics for each cylinder (number 1 to number 4), that is, a low speed cam 3 and a high speed cam 3.

4 is formed.

As mentioned above, the low-speed cam 3 reduces the delay in the closing timing of the intake valve by /J% (approximately 25 degrees after bottom dead center) and reduces the advance in the opening timing (by 5 degrees before top dead center). The high-speed cam 4 has a similar profile, and the high-speed cam 4 is designed to delay the intake valve closing timing (approximately 65 degrees after bottom dead center), while the low-speed cam has a slightly larger but closed timing profile. It has a profile with a smaller change (approximately 10 degrees before top dead center) than the change in .

A rocker arm 5 for driving an intake valve is rotatably supported on the rocker shaft 2 for each cylinder +1 to +4 so as to freely rotate and slide in the axial direction. It is adapted to selectively engage.

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 has a frame 6 at both ends that urges the rocker arm 5 in the axial direction of the rocker shaft based on a valve operation switching signal. Rods 20A and 21A of a pair of negative pressure actuators 20 and 21, which will be described later, are engaged and fixed so that they can be switched in the axial direction by the negative pressure actuators 20 and 21. . Sliders 8 and 9 are provided on both sides of each rocker arm 5 and have a large diameter on the rocker arm side and are fitted to the rocker shaft 2 to freely slide in the rocker shaft axial direction, as shown in FIG. 3. (The stopper 10.11 may extend from another stationary part). Further, the end faces of the sliders 8 and 9 on the rocker arm side are biased to protrude from both sides of the rocker arm 5 by springs 12 and are locked by stoppers 13, respectively, as shown in FIG. Pins 68a and 9a are formed into which the provided bottles 14 and 15 can be inserted. Reference numeral 16 denotes a plate whose one end is fixed to one slider 8 so as to straddle the rocker arm 5, and whose other end abuts on the other slider 9 so as to be able to freely rotate relative to each other. And each slider 8,
Springs 17 and 18 are interposed between the large diameter portion 90 and the partition wall 6A of the frame 6, respectively.

Next, the pair of negative pressure actuators 20 and 21 mentioned above are
Diaphragms 20B and 21B to which one ends of rods 20A and 21A are connected, respectively, atmospheric chambers 20D and 21D that are constantly in communication with the atmosphere through openings 20C and 21C, and an electromagnetic directional control valve 22 that operates to switch based on a valve actuation signal. It is divided into two chambers, negative pressure chambers 20E and 21E, into which engine suction negative pressure is introduced. In addition, as shown in FIG. 1, the negative pressure circuit between the electromagnetic directional control valve 22 and the suction negative pressure source includes:
An accumulator 23 and a check valve 24 that only allows flow from the electromagnetic directional switching valve 22 side to the suction negative pressure source side are interposed.

Furthermore, the rod 20A on the negative pressure actuator 20 side includes
Circumferential grooves 25 and 26 are formed at two locations on the outer periphery of the rod 20AI7) and the ball 2 of the regulating means 27 for regulating the movement of the rod 20AI7).
8 can be fitted. The regulating means 27 has a spring 30 inside the case 29, and the spring 3
0, the ball 28 is always pressed against the outer peripheral surface of the rod 20A of the negative pressure actuator 20 via the rod 31.

Next, the effect will be explained.

During low speed and partial load operation of the engine, a signal from a control circuit (not shown) causes the electromagnetic directional control valve 22 to close the negative pressure chamber 21K on the negative pressure actuator 21 side.

The negative pressure chamber 20E on the side of the negative pressure actuator 20 communicates with the atmosphere, so that the ball 2 of the regulating means 27 is in the position shown in the first figure.
8 fits into the circumferential groove 25 on the left side in the figure of the rod 20A.

Therefore, the spring 17 is compressed, and its elastic force moves the slider 8, and the pin 14 of the rocker arm 5 enters the pin hole 8a, and the rocker arm 5 is moved by the low-speed cam 311! I to engage the low speed cam 3 so that the slider 8 can swing together with the rocker arm 5.

On the other hand, the other slider 9 is affected by the spring force of the leaf spring 16.

Therefore, it is separated from the rocker arm 5. Therefore: Actual compression ratio suitable for cough driving region, over? Valve operation of the intake valve with small knobs can be achieved, 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 electromagnetic directional control valve 22 to switch to the first
It is set in the opposite position as shown. As a result, contrary to the above, the negative pressure chamber 20E on the negative pressure actuator 20 side communicates with the negative pressure source and is not under negative pressure, and the negative pressure chamber 21K on the negative pressure actuator 21 side communicates with the atmosphere. As a result, the diaphragms 20B and 21B are displaced, and the frame 6 is moved to the left in FIG. 1 via the rods 20A and 21A until the ball 2B of the regulating means 27 is fitted into the circumferential groove 26 on the right side. Then, the sliders 8 and 9 corresponding to the springs 1T and 18
The elastic biasing force against the rocker arm 5 is reversed until the rocker arm 5
The slider 9, which was separated from the slider 9, moves to the left in the figure.
P-locked by the stopper 11, no pressing force is applied to the rocker arm 5, and movement of the rocker arm 5 is restricted. At this time, if the rocker arm 5 is located at the base circle of the cam 3, as shown in FIG.
Since the positions of the bottle 15 and the bottle 15 are shifted, the bottle 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 connected to the plate 1
6, the bottle 14 is pushed and moved to the left in the figure, and the bottle 14 comes off and is separated from the rocker arm 5 as shown in the fourth figure.

In this state, as the camshaft rotates 10 times, the low-speed cam 3 lifts, the rocker arm 5 rotates, and the bin 1
5 and the bottle hole 9a, at this point the bottle 15 plunges into the shim hole a by the spring force of the spring, and the slider 9 rotates together with the rocker arm 5. When the low-speed cam 3 reaches the base circle after the lift is completed, the slider 9 and the stopper 11 are disengaged as shown in FIG. 4, and the elastic force of the spring 18 causes the slider 9 and the rocker arm 5 to move together, and the engagement can be switched from the low-speed cam 3 to the high-speed cam 4. Therefore, valve operating characteristics with a small actual compression ratio, low pressure and small pressure can be obtained, and the supercharging effect can be fully exerted to ensure maximum output.

With such a configuration, even if a switching signal is output at any time, the rocker arm automatically switches and moves in the section where the cam is in the base circle, and furthermore, this movement always starts immediately after the cam lift ends. Therefore, even if the engine rotation becomes high speed and the switching time is shortened, sufficient switching movement is possible, and damage to the cam etc. can be prevented.

Also, since the stopper mechanism is installed on a rocker shaft that does not rotate, it is installed on the conventional camshaft side.)
It also improves reliability. 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 engine suction negative pressure is used instead of hydraulic pressure as a source of biasing force 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. In addition, the configuration of the negative pressure actuator is not a spring offset type, but a pair of two actuators is used to switch and shift the rocker arm, and a regulating means is provided to prevent movement with small negative pressure, so it is possible to use a supercharger. If the internal combustion engine continues to operate in the supercharging region and little suction negative pressure is generated, or if the negative pressure inside the actuator leaks over time, the actuator will not operate and the rocker arm will not move. There is no possibility of so-called malfunctions such as stopping midway and engaging both cams. Furthermore, each rocker arm is configured to move automatically at the correct timing with a biasing force applied in advance, so even in the case of suction negative pressure, which has lower responsiveness than oil pressure, all cylinders can be moved at the same time. , since the actuator can be moved at any timing, there is an advantage that there is no critical timing to move the actuator.

Although this embodiment has been applied to an internal combustion engine with an exhaust turbo supercharger, it is possible that the present invention can also be applied to other two-stage cam switching engines and 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. Since the stopper mechanism is provided on a non-rotating rocker shaft, there is no risk of the stopper falling off, and reliability can be greatly improved. Furthermore, since the actuator is not a hydraulic type but a negative pressure type that utilizes engine suction negative pressure, a special pressure source is not required and the structure is simple, so that costs can be reduced.

[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 bottle attachment part of the rocker arm of the above embodiment, and Fig. 3 is an explanatory diagram of the positional relationship between the bottle and the bottle hole of the above embodiment. , FIG. 4 is an enlarged view of the engaging portion of the cam and rocker arm of the same embodiment as above;
FIG. 5 is an enlarged view of the negative pressure actuator portion. 1...Camshaft 2...Rocker shaft 3...
・Low speed cam 4...High speed cam 5...Rocker arm 6...Frame 8, 9...Slider 1
7.18 Spring 20.21 Negative pressure actuator 22 Electromagnetic directional valve patent applicant Fujio Sasashima, Patent attorney, Nissan Motor Co., Ltd.

Claims (1)

[Claims] Move the rocker arm in the axial direction of the rocker shaft,
A valve that is driven via the rocker arm by selectively engaging with either one of a pair of cams with different profiles arranged in parallel in the axial direction of a camshaft arranged 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 and interlocks with the rocker arm when the cam is lifted in a state of engagement with the rocker arm while the urging force of the urging means is applied, and releases the restriction by the stopper when the cam lift ends, and the urging means 1. A valve operation switching device for an internal combustion engine, characterized in that it is configured to use engine suction negative pressure as a source of biasing force.