JPH0347406B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an operation switching device for intake and exhaust valves of an internal combustion engine, and is applied to, for example, a cylinder number control engine that performs partial cylinder operation by suspending operation of some cylinders in a light load range, etc. It is something that will be done.

In a multi-cylinder internal combustion engine, when the engine load is light, the fuel supply to some cylinders is cut off to stop their operation, and the load on the remaining active cylinders is increased accordingly to improve fuel efficiency in the light load range. An engine with improved cylinder number control is known, but when cutting off fuel supply to some cylinders, for example, as shown in FIG. A device has been proposed that switches the operating state and regulates the intake and exhaust actions (Utility Model Opening in 1972).
124307 etc.).

In the figure, 3 is the rocker arm on the intake valve 1 side;
4 is a rocker arm on the exhaust valve 2 side, 5 is a rocker shaft, and 6 is a camshaft. The camshaft 6 includes a pair of cams 7 and 8 for the intake valve 1 and a pair of cams 9 and 10 for the exhaust valve 2. are formed adjacent to each other.

Of these, the first cams 7 and 9 are used for suction and exhaust through the rocker arms 3 and 4 during normal suction and exhaust strokes, respectively.
The exhaust valves 1 and 2 are formed in a predetermined profile to open and close, and the second cams 8 and 10 are connected to the first cams 7 and 10.
It is formed into a perfect circle with the same diameter as the base circle of No.9.

Further, the rocker arms 3 and 4 are supported not only so as to be able to swing relative to the rocker shaft 5, but also to move in the axial direction thereof, and the rocker arms 3 and 4 are supported so as to be movable in the axial direction of the rocker shaft 5.
A pump 17 is placed in pressure chambers 15 and 16 defined by
When pressure oil is selectively introduced through the directional control valve 18, the position changes from side to side.

This directional switching valve 18 is controlled by a control circuit 19.
The drive is controlled by the pilot oil pressure from the solenoid valve 20, which is switched by a signal from the
On the other hand, in the light load range of the engine based on the load signal from the accelerator sensor 21, pressure oil is guided to the pressure chamber 15 to move the rocker arms 3, 4 to the second cams 8, 10. move it.

As a result, when the engine load is small, the operation of the intake and exhaust valves 1 and 2 of some cylinders is switched and their operation is stopped, and partial cylinder operation is performed by operating only the other operating cylinders. During this partial cylinder operation, intake air is trapped in the cylinder on the idle side,
Since compression and expansion are repeated, not only does fuel efficiency improve, but torque fluctuations and rotational fluctuations are kept low.

In addition, 22 is a spacer, 23 is an accumulator for pilot oil pressure supply, 24 is a relief valve,
Reference numeral 25 denotes a clamping device for the directional control valve 18, which is used to control the control circuit 19 when switching the operation of the intake and exhaust valves 1 and 2.
When the electromagnetic actuator 26 is driven by a signal from
9 and 30 to fix the spool 28 and prevent it from shifting.

However, in such conventional devices, the locker arms 3 and 4 are simultaneously moved by hydraulic pressure to switch the operation of the intake and exhaust valves 1 and 2, so depending on the switching timing, The movement of the rocker arms 3 and 4 may overlap with the lift timing of the cams 7 and 9.

For example, when the conventional device is applied to the #2 and #3 cylinders of a 4-cylinder engine, the normal opening characteristics of the intake and exhaust valves 1 and 2 are as shown in a in Figure 2 (solid line portions). ), as shown in b and c in Figure 2, when attempting to shift from normal operation to partial cylinder operation,
When the directional control valve 18 is switched at a certain crank angle (for example, BDC), the rocker arms 3 and 4 move smoothly in the #2 cylinder, but the rocker arms 3 and 4 move smoothly in the #3 cylinder due to the lift of the cams 7 and 9.
4 is pushed up while moving. However, b in FIG. 2 shows the operating characteristics of the pump 17.

For this reason, an excessive frictional force is generated at the contact portion between the rocker arms 3, 4 and the cams 7, 9, resulting in a problem that damage or breakage may occur.

This invention was made by focusing on this problem, and includes a passage that opens at a predetermined cam angle (crank angle) in the middle of the passage that leads pressure oil from the directional control valve to each pressure chamber of the rocker arm. It is an object of the present invention to solve the above-mentioned problems by providing a valve and configuring the rocker arm to be moved at different times when the cam is lifted.

In order to achieve such an objective, the present invention
The rocker arm is moved in the axial direction of the rocker shaft depending on the engine operating conditions, and is selectively engaged with either one of a pair of cams with different profiles arranged in parallel in the axial direction of the camshaft. In a valve operation switching device for an internal combustion engine, which is provided with a mechanism for switching the valve operation of intake and exhaust valves for a plurality of cylinders, pressure chambers are formed on both sides of a rocker arm of each cylinder equipped with the switching mechanism, and both pressure chambers are A directional control valve is provided in the chamber for selectively introducing pressure oil from the pump via a hydraulic passage, and a hydraulic passage between the directional control valve and either one of the two pressure chambers is provided with a directional control valve for selectively introducing pressure oil from the pump through a hydraulic passage. An on-off valve that opens in the non-lift area of the cam of the cylinder is installed in synchronization.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 3, 3 is a rocker arm on the intake valve 1 side, 4 is a rocker arm on the exhaust valve 2 side, 5 is a rocker shaft, and 6 is a first and second cam 7 with different profiles corresponding to the rocker arms 3 and 4, respectively. - 10 are formed, and pressure chambers 15, 16 are formed on both sides of the rocker arms 3, 4 by brackets 11, 12 of the rocker shaft 5 and collars 13, 14.

A pump 17 is connected to the pressure chambers 15 and 16.
When pressure oil is selectively introduced through the directional control valve 18, the rocker arms 3, 4 move left and right, and move from the first cams 7, 9 to the second cams 8, 10 or the second cam 8. , 10 to the first cams 7, 9, and from this directional control valve 18 to the pressure chamber 15.
On-off valves 32 and 33, which open at a predetermined cam angle, are installed in the middle of a hydraulic passage 31 that guides pressure oil to the cam.

The on-off valves 32 and 33 have a valve body 35 that slides inside the valve housing 34 to open and close the hydraulic passage 31, a return spring 36 that biases the valve body 35 in the closing direction, and a return spring 36 that connects the valve body 35 in the axial direction. It consists of a tapepet-shaped rod 37 that is driven to open and close.
The distal end portion thereof is formed so as to penetrate the housing 34 and protrude to the outside.

Then, by engaging the tip of this rod 37,
Rotating cams 38 and 39 are provided which rotate synchronously with the camshaft 6 in a one-to-one manner, and open and close valves 32 and 33 according to their profiles.

Opening/closing valves 32, 3 by these rotary cams 38, 39
The opening timing of 3 is the corresponding intake and exhaust valve 1,
The cam profile is set for the cam angle of the camshaft 6 so that the cam angle of the camshaft 6 is excluded from the lift timing of 2, that is, during the compression stroke or expansion stroke of the corresponding cylinder.

Thereby, when switching the operation of the intake and exhaust valves 1 and 2, the lift timing by the cams 7 and 9 is removed, pressure oil is introduced into the pressure chamber 15, and the rocker arms 3 and 4 are moved.

Note that the rotating cams 38 and 39 may be formed integrally with the camshaft 6. Regarding other configurations, the same parts as in FIG. 1 are given the same reference numerals.

In such a configuration, the accelerator sensor 21
When the directional control valve 18 is switched in response to the solenoid valve 20 when the engine is in a light load range based on a signal from the pump 17, pressure oil from the pump 17 is supplied to the on-off valves 32 and 33 in the middle of the hydraulic passage 31. .

At this time, the pressure chamber 16 at one end of the rocker arms 3, 4 is opened to the tank return side via the directional control valve 18, and when the corresponding cylinder enters the compression stroke or expansion stroke, the rotary cams 38, 39 are opened. Therefore, the on-off valves 32 and 33 are opened, and pressure oil is introduced into the pressure chamber 15.

Therefore, the rocker arms 3 and 4 are connected to the cams 7 and 9.
The valves smoothly move toward the cams 8 and 10 without being pushed up, and the operations of the intake and exhaust valves 1 and 2 are switched (see c in FIG. 2).

When the rocker arms 3 and 4 are returned to the cams 7 and 9 side, the pressure chamber 16 is
Pressure oil is introduced into the on-off valves 32, 3.
The pressure oil previously introduced into the corresponding pressure chamber 15 is confined until the pressure chamber 3 is opened.

The on-off valves 32 and 33 are opened during the compression stroke and expansion stroke of the corresponding cylinder to release the pressure oil in the pressure chamber 15.

Therefore, the rocker arms 3 and 4 are connected to the cams 7 and 9.
It moves smoothly to cams 7 and 9 without conflicting with the lift timing.

By doing this, when switching the operation of the intake and exhaust valves 1 and 2, the movement of the rocker arms 3 and 4 and the lift by the cams 7 and 9 overlap, which could damage or damage them, as in the conventional example. This can be prevented, a good and stable switching operation can be obtained, and durability can be improved.

In addition, by providing on-off valves 32 and 33,
The switching timing of the directional switching valve 18 can be set arbitrarily, making control extremely easy.

Since there is no fear of damage to the rocker arms 3, 4 or cams 7, 9, the movement speed of the rocker arms 3, 4 can be increased by increasing the hydraulic pressure, etc., and the intake and exhaust valves can be adjusted accurately when the engine speed is high. 1 and 2 operation switching can be performed.

In addition, this embodiment is applicable even when the rocker arms 3 and 4 corresponding to the intake and exhaust valves 1 and 2 are moved separately, or when the rocker arms 3 and 4 corresponding to each cylinder are moved separately. It is only necessary to provide the on-off valves 32 and 33, and it is easily applied.

FIG. 4 shows another embodiment of the present invention, in which a hydraulic passage 31
The on-off valve is provided with valves 41 and 42 that are opened and closed in accordance with the rotation of the spool 40.

In this case, two substantially half-circular grooves 43 and 44 are formed on the outer periphery of the spool 40, and ports 46 and 47 that connect to each hydraulic passage 31 are provided in the valve housing 45 to face each other.

The spool 40 is connected to the camshaft 6 so as to rotate in one-to-one synchronization, and the grooves 43, 44 and ports 46, 4 are connected so that the valves 41, 42 open from the compression stroke to the expansion stroke of each corresponding cylinder.
7 position is set.

According to this, the structure of the on-off valves 41 and 42 becomes simple, and pressure fluctuations at the time of opening and closing can be reduced. As shown in FIG. 5, a passage 50 connected to a groove 49 is formed in the center of the spool 48, and as the groove 49 rotates, the groove 49 connects to each port 51, 5.
It may be an on-off valve 53 that communicates with 2 in a timely manner.

As explained above, according to the present invention, an on-off valve that opens at a predetermined cam angle is provided in the middle of the hydraulic passage that leads pressure oil from the directional control valve to each pressure chamber of the rocker arm, Since the locker arm is moved when the locker arm is moved, the operation of the intake and exhaust valves can be accurately switched without damaging the locker arm, cam, etc., and reliability is improved.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the configuration of a conventional device;
b, c are respective operation characteristic diagrams when switching the operation of the intake and exhaust valves, and FIG. 3 is a cross-sectional view of the configuration showing an embodiment of the present invention.
FIGS. 4 and 5 are sectional views showing other embodiments of the present invention. 1... Intake valve, 2... Exhaust valve, 3, 4... Rocker arm, 5... Rocker shaft, 6... Camshaft, 7-10... Cam, 11, 12... Bracket, 13, 14... Color, 15, 16...
Pressure chamber, 17...pump, 18...directional switching valve,
19...Control circuit, 21...Accelerator sensor, 3
1...Hydraulic passage, 32, 33...Opening/closing valve, 38,
39...Rotating cam, 41, 42...Opening/closing valve, 53
...Open/close valve.

Claims (1)

[Claims] 1. By moving the rocker arm in the axial direction of the rocker shaft according to the engine operating conditions and selectively engaging one of a pair of cams with different profiles arranged in parallel in the axial direction of the camshaft,
In a valve operation switching device for an internal combustion engine in which a mechanism for switching the valve operation of the intake and exhaust valves driven via the rocker arm is provided for a plurality of cylinders, pressure chambers are provided on both sides of the rocker arm of each cylinder equipped with the switching mechanism. a directional switching valve for selectively introducing pressure oil from the pump into both pressure chambers via a hydraulic passage; and a hydraulic passage between the directional switching valve and either one of the pressure chambers. A valve operation switching device for an internal combustion engine, characterized in that an on-off valve that opens in a non-lift region of the cam of the cylinder in synchronization with the rotation of the camshaft is interposed therein.