JPH0357283B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is directed to a multi-cylinder engine having a plurality of intake valves or exhaust valves each of which is driven to open via a rocker arm by a cam that rotates in synchronization with a crankshaft for each cylinder. It relates to a valve mechanism for an internal combustion engine.

<Conventional technology> Regarding the internal combustion engine described above, in order to optimize the intake and exhaust efficiency over the entire rotation range from low speed to high speed, the number of activated intake and exhaust valves is changed according to the engine speed. Valve deactivation mechanisms are known. In addition, Japanese Patent Application Laid-Open No. 1986-61 by the applicant of the present application
The specification of No. 19911 proposes a method for improving the filling efficiency of air-fuel mixture into the combustion chamber over a wide operating range by changing the timing of valve operation between low-speed and high-speed engine operation. has been done.

These devices operate a solenoid valve in response to the rotational speed of the engine to open and close a hydraulic circuit, thereby moving a piston built into one rocker arm to connect or disconnect the other adjacent rocker arm. These plurality of rocker arms are operated integrally or separately.
In order for this piston to move smoothly, it is necessary that both adjacent rocker arms be in a stationary state, that is, both rocker arms must be in sliding contact with the base circle of the cam. However, in reality, there is a considerable delay in operation depending on the oil pressure, oil temperature, etc., from when the solenoid valve receives an operation command signal to switch the spool and when the hydraulic circuit opens until the piston operates. When the locker arm is sliding in the valve opening direction, it is difficult for the piston to engage the adjacent locker arm, and even if the locker arm is slightly engaged, it is difficult to engage the adjacent locker arm, especially in the initial stage of the valve opening operation. This will cause the development to occur and be released midway through, resulting in loud noises and damage.

Therefore, in Japanese Patent Application Laid-Open No. 61-31614, the applicant of the present application has constructed a piston that is extendable and retractable, is biased in the direction of extension by a built-in spring, and has a timing that allows engagement with the piston. By providing the plate on the rocker arm, the operation of the piston is also restricted after the operation command signal is output, unless sufficient hydraulic pressure is applied to the piston and the adjacent rocker arm is in a state that allows the piston to move. The present invention proposes a valve operation stop device equipped with a control means configured to do the following. However, this device has a complicated structure and is expensive, so when such a device is installed in the rocker arms of all cylinders of a multi-cylinder internal combustion engine, there is a problem in that the manufacturing cost increases significantly.

On the other hand, in consideration of the delay in the operation of the hydraulic circuit, a method may be considered in which the hydraulic circuit and its opening/closing are controlled so that the piston moves excluding the period when the above-mentioned peeling development may occur. However, in the case of a multi-cylinder engine, the timing at which dusting and development occurs is different for each cylinder, and they arrive sequentially based on the rotation angle of the crankshaft or cam, so if any cylinder is Scattering and development will definitely occur.

<Problems to be Solved by the Invention> Therefore, an object of the present invention is to provide an inexpensive valve switching control system that can always smoothly connect or release the rocker arm in the above-mentioned valve mechanism for a multi-cylinder internal combustion engine. It is about providing.

<Means for Solving the Problems> According to the present invention, the above-mentioned object is achieved by providing a plurality of intake valves or exhaust valves biased in the valve opening direction, and a rock shaft corresponding to the intake valves or exhaust valves. A plurality of rocker arms that are swingably supported and swingably driven by a cam that rotates in synchronization with the crankshaft, and a connecting means that can selectively connect or release the adjacent rocker arms by the action of hydraulic pressure are connected to each cylinder. a hydraulic circuit for selectively supplying hydraulic pressure to each of the connecting means by opening and closing in accordance with the rotational speed of the engine; and a control means for controlling the operating timing of the connecting means. In the valve switching control system for a valve train for a multi-cylinder internal combustion engine, the output timing of the opening/closing command signal to the hydraulic circuit is fixed based on the stroke position of a specific cylinder, and the opening/closing command signal is output. This is achieved by providing a valve switching control system characterized in that the control means is provided in a cylinder having a rocker arm that is in the vicinity of the initial valve opening position when the connection means is ready to start actual operation after the valve is opened.

<Function> Since the response delay time from when the actuation command signal is issued until the piston of the coupling device actually operates can be estimated in advance within a certain range, the output timing of the actuation command signal can be adjusted to suit the specific cylinder. If it is fixed at a specific stroke position, it is possible to specify the cylinder in which the rocker arm starts swinging after the above-mentioned response delay time after the activation command signal is issued. Therefore, if the control means is provided only for this cylinder, it is possible to avoid the occurrence of flutter development in all cylinders of a multi-cylinder internal combustion engine.

<Examples> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, an engine main body (not shown) is provided with a pair of intake valves 1 and 2, which are biased in the valve closing direction by springs 3 and 4. Both of these intake valves 1 and 2 are connected to a cam 6 having an oval cross section and a cam 6 which is parallel to the camshaft 5 and which is provided in a pair on a camshaft 5 which is driven synchronously at a rotation speed of 1/2 with a crankshaft (not shown). It is designed to be opened and closed by rocker arms 8 and 9 which are swingably supported by rocker arms 7 and 7. Further, this engine is equipped with a pair of exhaust valves (not shown), which are driven to open and close in the same manner as the intake valves 1 and 2 described above.

Both rocker arms 8 and 9 are arranged adjacent to each other, and tappet screws 10 and 11 that come into contact with the upper ends of each valve 1 and 2 can be moved forward and backward at the free ends that extend above both intake valves 1 and 2. The tappet screws 10 and 11 are secured by lock nuts 12 and 13 to prevent them from loosening. A cam slipper 14 that comes into sliding contact with the cam 6 is formed on the upper surface of the first rocker arm 8 .

As clearly shown in FIG. 2, a first guide hole 15 that opens toward the second rocker arm 9 in parallel with the axial direction of the rocker shaft 7 is bored inside the first rocker arm 8, so that the piston 16 can move along the axis. It is housed so as to be slidable along the direction. A small diameter portion 17 is formed at the bottom side of the first guide hole 15, and a hydraulic chamber 18 is defined therein. The hydraulic chamber 18 is a first
No matter what position the rocker arm 8 is in, it always communicates with an oil passage 20 provided in the rocker shaft 7 via a passage 19. Oil road 2
0 communicates with the oil pump via a solenoid valve. A second guide hole 21 corresponding to the guide hole 15 of the first rocker arm 8 is bored inside the second rocker arm 9 . Inside the second guide hole 21, a stopper 22 is biased toward the first rocker arm side by a coil spring 23, and a guide rod 22a drilled in the center is inserted through the stopper 22, which is drilled at the bottom of the second guide hole 21. It protrudes from the hole 24 to the outside.

In the middle and low speed range of the engine, the hydraulic chamber 18
Since no hydraulic pressure is supplied to the piston 16 and the piston 16 is within the first guide hole 15, the rocker arms 8 and 9 are not connected and can be displaced relative to each other in an angular manner. In this case, as shown in FIG.
Since a cam slipper 14 is formed on only one of the shafts and is in sliding contact with the cam 6, only the first rocker arm 8 swings as the camshaft 5 rotates, and only one intake valve 1 is driven to open.

When the engine is operated at high speed, hydraulic pressure is supplied to the hydraulic chamber 18. Specifically, as clearly shown in FIG. 3, when the engine speed reaches a predetermined speed, the solenoid 27 of the solenoid valve 26 is operated by the control unit 25, and the oil passage 20 is opened from the oil pump 28. A hydraulic circuit communicating with the hydraulic chamber 18 via the hydraulic circuit is opened. As a result, the piston 16 is pushed out toward the second rocker arm 9,
It moves into the second guide hole 21 while pressing the stopper 22 against the biasing force of the coil spring 23. In this way, the first rocker arm 8 and the second rocker arm 9 are integrally connected. Furthermore,
An accumulator 29 is provided in front of the solenoid valve 26,
By applying the stored hydraulic pressure simultaneously with the hydraulic pressure supplied from the oil pump 28, the responsiveness of the piston 16 can be improved.

After connecting the first rocker arm 8 and the second rocker arm 9, when the engine speed becomes below the predetermined speed, the solenoid 27 is turned off, and the solenoid valve 2
6 closes the hydraulic circuit from the oil pump 28.
The hydraulic pressure acting on the piston 16 is released, and the oil flows in the opposite direction through the oil passage 20 and into the oil tank 3.
Return to 0. Since the piston 16 is pushed back into the guide hole 15 of the first rocker arm 8 by the action of the coil spring 23, the connection state between the first rocker arm 8 and the second rocker arm 9 is released, and the second rocker arm 9 returns to the resting state. Become.

In a stationary state where the axes of the first guide hole 15 and the second guide hole 21 are aligned, that is, in a closed state where the cam slipper 14 of the first rocker arm 8 and the base circle of the cam 6 are in sliding contact, The piston 16 moves smoothly into the second guide hole 21 to integrally connect both the rocker arms 8 and 9, making it possible to smoothly and reliably switch the valve operation. Since the first rocker arm 8 is swinging during the opening operation of the intake valve, the piston 16 cannot be engaged with or released from the second rocker arm. In particular, near the initial position where the first locker arm 8 starts the valve opening operation, the first locker arm 8 is only slightly angularly displaced relative to the second locker arm 9, so the piston 16 is in contact with the second guide hole 21. There may be slight engagement. However, since the first rocker arm 8 further swings in the valve opening direction, so-called sagging occurs, and the engaged state is released midway, causing a loud noise or damage. Therefore, the first rocker arm 8 engages the piston 16 in the initial stage of the valve opening operation.
It is not desirable to move the

In a state where the first rocker arm 8 is angularly displaced to a considerable extent with respect to the second rocker arm 9, the piston 16 cannot engage with the second guide hole 21 at all, and the second rocker arm 8
It only engages the end face of the locker arm 9, and even if hydraulic pressure is applied to the piston 16 while the first locker arm is swinging in the valve closing direction, the first locker arm 8 enters a stationary state and the first locker arm Guide hole 1
5 and the second guide hole 21 are aligned in the axial direction, the piston 16 starts moving.

On the other hand, generally, after an operation command signal is sent from the control unit 25 to the solenoid valve 26, the hydraulic chamber 1
There is a certain delay until the hydraulic pressure supplied to piston 8 reaches a certain operating pressure and piston 16 operates. For example, as shown in FIG. 4, if the operation command signal is output at time _t0 , the solenoid valve 26 is activated to open the hydraulic circuit, and the oil pump 28 starts supplying hydraulic pressure at a constant level. Until the pressure reaches _t1 and the piston starts moving, a certain operation delay φ occurs based on the crankshaft rotation angle. Therefore, in order to prevent the so-called glaring phenomenon from occurring, it is necessary to output the operation command signal from the control unit 25 in consideration of the above-mentioned operation delay.

Further, FIG. 4 shows the lift amount of each intake valve of the first to fourth cylinders with respect to the rotation angle of the crankshaft or cam in a four-cylinder internal combustion engine. Regarding the first cylinder, there is a section _A1 near the initial position where the rocker arm starts opening the valve, in which the flutter phenomenon is expected to occur. This section _A1 is assumed to be a somewhat wide range in consideration of various factors such as oil pressure, oil temperature, and engine rotational speed that act depending on the operating conditions of the engine. In this way, in a series of intake strokes, each cylinder has a section where the flutter phenomenon occurs.
A ₁ to _{A 4} are continuous, and similar sections A' ₁ to A' ₄ are continuous in the next intake stroke. Therefore,
If the output timing of the operation command signal from the control unit 25 to the solenoid valve 26 is set randomly,
A flutter phenomenon occurs in one of the cylinders.

Here, the output timing of the operation command signal is determined based on the stroke position of a specific cylinder, for example, regardless of when the engine speed reaches a predetermined set rotation speed.
When fixed at time _t0 , which coincides with the top dead center of the cylinder, the means for connecting the rocker arms of each cylinder starts operating at time _t1 . Since this time _t1 is included in the interval _A3 in which the flutter phenomenon occurs in the third cylinder, in this case, the flutter phenomenon will definitely occur in the third cylinder.

Therefore, in this embodiment, it is sufficient to provide a control means capable of controlling the activation timing of the rocker arm coupling means only in the third cylinder. As such a control means, there is one disclosed in Japanese Patent Application Laid-open No. 31614/1983 by the applicant of the present invention.

An embodiment of this control means will be described with reference to FIGS. 5 and 6.

Similar to the embodiment shown in the first diagram, the rock shaft 7
, a first rocker arm 31 and a second rocker arm 32 are pivotally supported so as to be able to move relative to each other in a relative angle while being in sliding contact with each other and to be swingable. 1st Rotsuka Arm 3
1 swings in response to the rotation of a cam 34 that is in sliding contact with a cam slipper 33, thereby driving the intake valve 35 to open. A coupling mechanism for connecting or disconnecting the first rocker arm 31 and the second rocker arm 32 includes a piston 36 that is movable between the two rocker arms, a stopper 37 that restricts the movement of the piston 36, and a stopper 37 that is connected to the first rocker arm 31 side. The piston 36 includes a coil spring 38 that biases the piston 36, and a timing plate 39 that controls the movement timing of the piston 36.

The piston 36 is slidably fitted into a first guide hole 40 formed in the first rocker arm 31, and is made up of a cylindrical connecting body 41 and a low cylindrical pressing body 42, which are combined to be expandable and retractable with each other, and a coil It is constantly urged in the direction of extension by a spring 43. The hydraulic chamber 44 defined on the lower side of the first guide hole is
It communicates with the oil passage 20 via a passage 45 as in the second illustrated embodiment. The pressing force 42 has a small diameter cylindrical portion 46, and an annular engagement groove 48 in which the timing plate 39 can be engaged is formed between the stepped portion 47 and the end of the connecting body 41. Pressing body 42
Another engagement groove 49 is provided on the outer peripheral surface of the timing plate 39 so that the timing plate 39 is engaged when the pressing body 42 is displaced to the maximum extent toward the second rocker arm 32 and both rocker arms 31 and 32 are completely connected. It is becoming possible to match.

The second rocker arm 32 has a first guide hole 40.
A second guide hole 50 is drilled corresponding to the second guide hole 50 , and the second guide hole 50 is opened until the disc-shaped stopper 37 comes into contact with the stepped portion 51 .
It is arranged to be slidable within the guide hole 50.

A timing plate 39 is slidably supported on the first rocker arm 31 by a pin 52 at the lower part of the first rocker arm 31, and a spring 53 surrounding the pin 52 is interposed. 39 is rotationally biased toward the piston 36. Furthermore, the end of the timing plate 39 is brought into contact with a cam surface 54 formed on the outer peripheral surface of the rocker shaft 7 by means of a spring 53.

The cam surface 54 is formed so that the timing plate 39 can be rotated by the swinging operation of the first rocker arm 31.
When it is in a stationary state sliding in contact with the base circle of
The timing plate 39 is moved to the sixth position by the urging force of the spring 53.
In the figure, the first locker arm 31 is rotated clockwise to engage the engagement grooves 48 and 49, and the first locker arm 31 is
While being pushed down and swinging in the valve opening direction, the piston 36 rotates counterclockwise. Therefore, even if hydraulic pressure is applied to the hydraulic chamber 44, the timing plate 39 is engaged with the engagement groove 48, so the pressing body 42 cannot move, and the first rotary arm 31 starts swinging in the valve opening direction. Then, the timing plate 39 is rotated counterclockwise, the engagement of the timing plate 39 is released, and the pressing body 42 moves until it comes into contact with the end of the connecting body 41. In this way, when the axes of the first guide hole 40 and the second guide hole 50 coincide with each other, that is, when the first rocker arm 31 enters a stationary state, the connecting body 41 slides into the second guide hole 50. Both rocker arms 31 and 32 are connected. When the connection by the piston 36 is completed, the timing plate 39 engages with the engagement groove 49.

When the hydraulic pressure acting on the hydraulic chamber 46 is released, the piston 36 is pressed toward the first rocker arm 31 by the spring 38, but the timing plate 3
9 is engaged with the engagement groove 49, so it cannot be moved immediately. When the first rocker arm 31 is driven in the valve opening direction, the timing plate 39 is released from the engagement groove 49 in accordance with its swinging motion, and the pressing body 42 moves toward the hydraulic chamber 44 side. At this time, the connecting body 41 is moved to the first position by sliding of the first rocker arm 31.
Due to the frictional force between the guide hole 40 and the second guide hole 50, it cannot return to the first guide hole 40, and the first
When the rocker arm enters the resting state, it moves to the first guide hole 40.

It should be noted that the present invention is not limited to the above-described embodiments, and can be implemented with various modifications and changes within the technical scope, as will be apparent to those skilled in the art. For example, the control means provided in the cylinder where the flutter phenomenon occurs may be any means as long as it can control the actuation timing of the coupling means regardless of the output timing of the actuation command signal.

<Invention and Effects> As described above, according to the present invention, in the valve mechanism of a multi-cylinder internal combustion engine, the output timing of the operation command signal to the solenoid valve that opens and closes the hydraulic circuit is adjusted to the stroke position of a specific cylinder. By fixing the cylinder based on the locking arm, it is possible to limit the cylinders in which the so-called sagging phenomenon occurs in consideration of the delay in the operation of the hydraulic circuit, and to provide a connecting means having a means for controlling the operation timing only to the rocker arm of the cylinder. By providing this, the connecting means for all the cylinders can be operated smoothly, and the number of rocker arms provided with a control device for controlling the operation timing of the connecting means can be minimized. Therefore, manufacturing of such a control system can be facilitated and manufacturing costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing a valve train to which the present invention is applied. FIG. 2 is a longitudinal cross-sectional view showing the coupling mechanism in the embodiment shown in the first figure. Third
The figure is a hydraulic system diagram showing a hydraulic circuit for operating the coupling mechanism shown in the second figure. FIG. 4 is a diagram showing the operation timing of valve switching according to the present invention.
FIG. 5 is a longitudinal sectional view showing an embodiment of a coupling mechanism with control means used in the present invention. FIG. 6 is a view taken along the line - in FIG. 5. 1, 2...Intake valve, 3, 4...Spring, 5...
...Camshaft, 6...Cam, 7...Rock shaft, 8...First rocker arm, 9...Second rocker arm, 10, 11... Tappet screw, 12,
13...Rocknut, 14...Kamsuritsupa,
15...First guide hole, 16...Piston, 17
...Reduced diameter section, 18...Hydraulic chamber, 19...Passage, 2
0...Oil passage, 21...Second guide hole, 22...Stopper, 22a...Guide rod, 23...Coil spring, 24...Through hole, 25...Control unit, 26...Solenoid valve, 27 ...Solenoid, 2
8... Oil pump, 29... Accumulator,
30... Oil tank, 31... First rocker arm, 32... Second rocker arm, 33... Cam slipper, 34... Cam, 35... Intake valve, 3
6... Piston, 37... Stopper, 38... Coil spring, 39... Timing plate, 40... First
Guide hole, 41... Connecting body, 42... Pressing body pressure, 4
3...Coil spring, 44...Hydraulic chamber, 45...Passway, 46...Small diameter cylinder part, 47...Step part, 48,4
9...Engagement groove, 50...Second guide hole, 51...
Stepped portion, 52...pin, 53...spring, 54...cam surface.

Claims (1)

[Scope of Claims] 1. A plurality of intake valves or exhaust valves biased in the valve-closing direction, pivotably supported on a rocker shaft corresponding to the intake valves or exhaust valves, and rotating synchronously with a crankshaft. Each cylinder has a plurality of rocker arms rockingly driven by a cam, and a connecting means that can selectively connect or release the adjacent rocker arms by the action of hydraulic pressure, and the locker arms can be opened and closed in accordance with the rotational speed of the engine. A valve switching control system for a valve mechanism for a multi-cylinder internal combustion engine, comprising a hydraulic circuit for selectively supplying hydraulic pressure to each of the coupling means, and a control means for controlling the operating timing of the coupling means. In this, the output timing of the opening/closing command signal to the hydraulic circuit is fixed based on the stroke position of a specific cylinder, and when the connecting means is ready to start actual operation after the opening/closing command signal is output. 1. A valve switching control system for a valve train for a multi-cylinder internal combustion engine, characterized in that the control means is provided in a cylinder having a rocker arm located near an initial valve opening position. 2. The connecting means includes a piston movable to connect or release adjacent rocker arms, the piston is formed to be extendable and retractable and is biased in the extension direction by a built-in spring means, and the control means The multi-cylinder internal combustion engine according to claim 1, further comprising a timing plate that engages or disengages the piston in accordance with the rocking angle of the rocker arm to control its movement. Valve switching control system for valve train mechanisms.