JPH0585725B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an intake/exhaust valve drive device for an internal combustion engine that variably controls the lift characteristics (opening/closing timing and lift amount) of intake/exhaust valves according to engine operating conditions. Regarding.

<Prior Art> Conventional examples of intake/exhaust valve drive devices for internal combustion engines include those shown in FIGS. 8 and 9. (Refer to Japanese Patent Application Laid-Open No. 60-26109 and Japanese Patent Application No. 81052-1982).

That is, a rocker arm 3 is provided with both ends in contact with an intake/exhaust valve driving cam 1 that rotates in synchronization with engine rotation and a stem end of the intake/exhaust valve 2, and a curved rear surface of the rocker arm 3 is provided. A lever 5 is provided that brings the shaft 3a into fulcrum contact and holds the shaft 3b protruding from both side walls of the rocker arm 3 in the groove 5a via the holding member 4. A spring 6 with a small spring constant is interposed between the spring seat 5b formed on the lever 5 and the holding member 4 to bias the rocker arm 3 downward.

Also, a bracket 8 interposed in the cylinder head 7
The spherical lower end surface of the hydraulic pivot 9 fitted and held in the lever 5 fits into the recessed part 5c formed in the top wall of the other end on the stem end side of the intake/exhaust valve 2, and the fitting part is opened. A lift control cam 10, which supports the lever 5 at its center so that it can freely swing and is rotatably attached to the bracket 8 as described later, touches the top wall of the end of the lever 5 on the side of the intake/exhaust valve drive cam 1. The swing position of the lever 5 is regulated by contacting the lever 5.

The hydraulic pivot 9 has a lower end surface that fits into the concave portion 5c of the lever 5, and a peripheral surface that fits into the bracket 8.
An outer cylinder 9a that is slidably inserted into a mounting hole 8a formed in the outer cylinder 9a, and an inner cylinder 9b that is fitted into the outer cylinder 9a.
and a hydraulic chamber 9 formed between the two.
c is provided with a check valve 9d. Then, from the hydraulic pressure supply passage 8b formed inside the bracket 8 to the inside of the inner cylinder 9b and the check valve 9d.
The valve clearance is kept constant by supplying hydraulic pressure to the hydraulic chamber 9c through the hydraulic pressure chamber 9c.

The lift control cam 10 is keyed to a hollow support shaft 11, and the hollow portion of the support shaft 11 serves as a passage for lubricating oil. The support shaft 11 is rotatably supported by a bearing 12, and the bearing 12 is supported by the bracket 8.
installed on. A first gear 13 is rotatably attached to the support shaft 11, and the first gear 13
One end of a coil spring 14 is locked to the side of the coil spring 14. The other end of the coil spring 14 is locked to the side of the lift control cam 10.

Further, a second gear 15 is meshed with the first gear 13, and this second gear 15 is fixed to a cam control shaft 16. The cam control shaft 16 is rotatably supported by the bracket 8 or the bearing 12, and one end of the cam control shaft 16 is connected to the rotating shaft of a stepping motor 18 via a connector 17. The stepping motor 18 is driven by a control circuit 19 based on engine operating conditions such as engine speed, throttle valve opening, cooling water temperature, intake air flow rate, and intake negative pressure, so as to rotate the cam control shaft 16. It's summery.
In addition, 20 is a valve spring, and 20a and 20b are respective snap springs.

When the lift control cam 10 is in contact with the lever 5 at the cam surface with the largest lift amount, the lever 5 is pushed down the most toward the intake/exhaust valve drive cam 1 side. Therefore, the lower surface of the lever 5, which is in fulcrum contact with the back surface 3a of the rocker arm 3, also lowers, and the fulcrum contact point A is brought into contact with the intake/exhaust valve drive cam 1.
It is transmitted to the intake/exhaust valve 2 while moving to the side, and the lift amount is large, and the valve opening timing is early and the valve closing timing is late.

On the other hand, when the lift control cam 1 rotates and, for example, comes into contact with the lever 5 with a cam surface having a small lift amount, the end of the lever 5 on the intake/exhaust valve drive cam 1 side uses the concave portion 5c as a fulcrum. The initial position of the fulcrum, which is raised by rocking and in which the intake/exhaust valve driving cam 1 is in contact with the rocker arm 3 at the base circle, is when the lever 5 is in contact with the cam surface with the large lift amount. In comparison, it moves to the right in FIG. 8, that is, to the side away from the direction in which the fulcrum moves after the lift. As a result, the lift amount is small, the valve opening timing is delayed, and the valve closing timing is advanced.

In this way, by rotating the lift control cam 10 and bringing either of the cam surfaces into contact with the lever 5, the lift characteristics of the intake/exhaust valves 2 can be changed in stages.

Here, the rotation of the lift control cam 10 is caused by driving the cam control shaft 18 by the stepping motor 18.
6, through the second gear 15, the first gear 13, and the coil spring 14. That is, the control circuit 19 outputs a drive pulse to the stepping motor 18, which is set based on a signal corresponding to the engine operating state. This drive pulse rotates the rotating shaft of the stepping motor 18 by a preset angle, and also rotates the cam control shaft 16 via the connector 17.

Now, at the timing when the cam control shaft 16 rotates, in the cylinder where the intake/exhaust valve 2 is in lift, the contact fulcrum between the rocker arm 3 and the lever 5 is moving toward the intake/exhaust valve drive cam 1 side. Therefore, a large reaction force of the valve spring 20 acts on the lift control cam 10 via the rocker arm 3 and lever 5. Therefore, while the lift control cam 10 remains stationary, the cam control shaft 16, second gear 15, and first gear 13 rotate while twisting the coil spring 14. Next, after the intake/exhaust valve drive cam 1 rotates and the intake/exhaust valves 2 are closed, the contact fulcrum between the rocker arm 3 and the lever 5 is located approximately above the intake/exhaust valves 2. The reaction force of the spring 20 does not act on the lift control cam 10, and the only force acting on the lift control cam 10 is the weak force of the spring 6 attached between the rocker arm 3 and the lever 5. Therefore, the torsional torque stored in the coil spring 14 during the lift of the intake/exhaust valve 2 overcomes the weak force of the spring 6,
The lift control cam 10 and the support shaft 11 can be rotated.

<Problems to be Solved by the Invention> However, in such a conventional intake/exhaust valve drive device, after the amount of rotation of the cam control shaft 16 is stored as the torsional torque of the coil spring 14, the amount of rotation is stored at a predetermined timing. The lift control cam 10 is rotated by torsional torque to change the lift characteristics, and the lift control cam 10 is rotated clockwise and counterclockwise in FIG. It was twisted alternately on the insertion side and the rewind side, so-called double-sided. For this reason, the fatigue strength of the coil spring 14 was significantly reduced, and there was a risk that the coil spring 14 would break.

The present invention was made in view of the above circumstances, and provides an intake/exhaust valve drive device for an internal combustion engine that rotates a lift control cam at a predetermined timing to vary the lift characteristics and improve the durability of the spring. The purpose is to provide.

<Means for Solving the Problems> For this reason, the present invention provides a cam control shaft of the lift control cam, a stopper fixed to the cam control shaft, and a stopper fixed to the cam control shaft at a predetermined distance from the stopper. a collar mounted to be freely movable in the axial direction of the cam control shaft; an elastic member provided in contact with the collar and the stopper; and a protrusion formed on one of the collar and the lift control cam; The elastic member formed on the other of the collar and the lift control cam engages with the protrusion by an expanding force, and the engagement surface moves the collar in the axial direction to compress the elastic body. an inclined part inclined to;
A drive means for rotationally driving the cam control shaft by a predetermined amount depending on the engine operating condition is provided.

<Operation> In this way, the rotational force of the drive-side cam control shaft is converted into axial force by the inclination of the engagement surface, and the elastic body connected to the lift control cam in the locked state is compressed. The lift control cam, which is released from the locked state at a predetermined timing, is rotated by the rotational force converted from the compressive restoring force of the elastic body by the inclination of the engagement surface, thereby changing the lift characteristics.

<Example> Below, an example of the present invention will be described based on the drawings. Note that the same elements as the conventional example are shown in Figures 8 and 9.
The same reference numerals as those in the figure are used to omit the explanation.

1 to 4 show an embodiment of the present invention.

In the figure, a plurality of substantially flat cam surfaces are formed on the outer circumferential surface of the lift control cam 21 so as to change the lift characteristics of the intake/exhaust valves 2 in stages, as in the conventional example. One is lever 5
The lever 5 contacts the top wall of the end on the intake/exhaust valve drive cam 1 side to regulate the swinging position of the lever 5.

A hole 21a is formed in the center of the lift control cam 21, into which a cam control shaft 22, which will be described later, is inserted. Furthermore, cylindrical portions 21b and 21c are formed protruding from both sides of the lift control cam 21, and these cylindrical portions 21b and 21c are connected to a lower arcuate groove 23 formed in a bracket 23, as shown in FIGS.
a, and an upper arcuate groove 2 formed in a pair of caps 25 fastened to the bracket 23 with bolts 24.
5a, and are each held rotatably.

A cam control shaft 26 is inserted into a hole 21a formed through the center of the lift control cams 21 provided in several cylinders. Cam control axis 2
6 has a cylindrical stopper 27 tightened with a screw. Further, a cylindrical collar 28 is provided on the cam control shaft 26 at a predetermined distance from the stopper 27, and is freely slidable in the axial direction of the cam control shaft 26 by means of a key 29, as shown in FIGS. 2 and 5. installed.

One cylindrical portion 21b of the lift control cam 21
As shown in FIGS. 2 and 3, two recessed portions 30a and 30b are formed as inclined portions on the side wall. The side wall of the collar 28 has the recess 30a,
A pair of protrusions 31 are formed respectively facing 30b. A compression coil spring 32 as an elastic member is interposed between the stopper 27 and the collar 28, and the expansion force of the compression coil spring 32 causes the protrusion 31 of the collar 28 to be pushed into the recess 30.
a, 30b are pressed against the inner walls.

As shown in FIG. 2, the inner walls of the recesses 30a and 30b that come into contact with the protrusion 31 are formed to be inclined so as to gradually protrude toward the protrusion 31 from the center toward both sides.

One end of the cam control shaft 26 is connected to a stepping motor 18 as a driving means via a connector 17.
It is connected to the rotating shaft of. The stepping motor 18 is driven by a control circuit 19 based on engine operating conditions such as engine speed, throttle valve opening, cooling water temperature, intake air flow rate, and intake negative pressure.
It is designed to rotate 6. In addition, 33 is
This is a stopper that restricts the movement of the lift control cam 21.

Next, the action will be explained.

In order to change the lift characteristics of the intake/exhaust valves by changing the contact position between the lever 5 and the back surface 3a of the rocker arm 3, the lift control cam 21 is rotated to change the height of the lever 5 on the intake/exhaust valve drive cam 1 side. Although it needs to be changed, in a multi-cylinder internal combustion engine such as a four-cylinder engine, the intake and exhaust valves of one of the cylinders are always operating. Therefore, a strong reaction force of the valve spring 20 acts on one of the lift control cams 21 provided in each cylinder, so when the intake/exhaust valve 2 with a small reaction force of the valve spring 20 is closed, , the lift control cam 21 is rotated with a small control force.

That is, the stepping motor 18 is driven by a signal from the control circuit 19 based on engine operating conditions such as engine speed, throttle valve opening, cooling water temperature, intake air flow rate, and intake negative pressure, and the cam control shaft 26 is rotated. be moved.

The collar 28 is also rotated with the rotation of the cam control shaft 26, but since the recesses 30a and 30b that the protrusion 31 formed on the collar 28 abuts are inclined, the reaction force of the recesses 30a and 30b causes the collar 28 to rotate.
moves in the axial direction of the cam control shaft 26 (downward in FIG. 6) along the key 29, as shown in FIG. As a result, the compression coil spring 32 is compressed. Therefore, the expansion force of the compression coil spring 32 causes the protrusion 31 of the collar 28 to move into the recess 30.
In order to press the inner walls a and 30b upward in FIG.
This pressing force tends to rotate the lift control cam 21. Note that the recesses 30a in FIG.
The engagement state between 30b and the protrusion 31 is a state in which the compression coil spring 32 is hardly compressed.

During the above period, since the intake/exhaust valves 2 are in the opening operation, the reaction force of the valve spring 20 is large and the lift control cam 21 is maintained in a stationary state without being rotated.

Then, as the closing timing of the intake/exhaust valve 2 approaches, the reaction force of the valve spring 20 weakens, so the lift control cam 21 is rotated by the pressing force of the protrusion 31 generated by the expansion force of the compression coil spring 32. The valve characteristics of the intake/exhaust valve 2 can be changed by moving the intake/exhaust valve 2.

As explained above, compression coil spring 3
2 is compressed and the compression force is converted into rotational force by the inclination of the engagement surface to rotate the lift control cam 21. Compared to conventional coil springs, fatigue caused by torsional rotation in the opposite direction is eliminated. Therefore, breakage of the compression coil spring 32 can be prevented and durability can be improved.

In addition, the support shaft 11 and the cam control shaft 1 in the conventional example
6 is integrated to form the cam control shaft 26, the first and second gears 13, 15, etc. are unnecessary, and the device can be made more compact.

FIG. 7 shows another embodiment of the invention.

In this embodiment, when the lift control cam 21 is rotated in the direction of increasing the lift amount of the intake/exhaust valves 2, the rotational force of the lift control cam 21 increases, while the lift amount of the intake/exhaust valves 2 is decreased. This was proposed because the rotational force of the lift control cam 21 becomes smaller when the lift control cam 21 is rotated in the direction.

That is, two recesses 35 are formed on the side of the cylindrical portion 21b of the lift control cam 21, as in the previous embodiment. Then, the lift control cam 21 is connected to the intake/exhaust valve 2.
The recess 3 that contacts the protrusion 31 of the collar 28 in the direction of rotation to increase the amount of lift of the collar 28
As shown in FIG. 7, the inner wall 5 is formed into a steeply inclined part 35a so as to sharply protrude into the protruding part 31 from the center toward one side. On the other hand, intake/exhaust valve 2
lift control cam 2 to reduce the lift amount of
As shown in FIG. 7, the inner wall of the recess 35 is formed with a gentle slope 35b so as to gently protrude toward the protrusion 31 from the center toward the other side.

According to this configuration, in addition to producing the same effects as in the embodiment described above, when the lift control cam 21 is rotated in a direction to increase the lift amount of the intake/exhaust valve 2, the collar 28 is moved in the axial direction by the steeply inclined portion 35a. Since it is moved largely, the compression force of the compression coil spring 32 becomes large. Therefore, the expansion force of the compression coil spring 32 becomes large.

Further, when the lift control cam 21 is rotated to reduce the lift amount of the intake/exhaust valve 2, the collar 28 is moved in the axial direction by the gently inclined portion 35b, so that the moving force is small and the compression coil spring 32 is compressed. The force becomes smaller, and the spreading force becomes smaller.

As a result, it is possible to correspond to the rotational force of the lift control cam 21 described above.

In addition, contrary to each embodiment, the concave portion may be provided on the collar side, while the protrusion portion may be provided on the lift control cam side.

<Effects of the Invention> As explained above, the present invention compresses the elastic member by the rotational force of the cam control shaft of the lift control cam, and the lift control cam is rotated by this compression force. The fatigue strength of the elastic member can be improved while reducing the size, and the durability of the elastic member can be improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a plan view of the same as above, Figure 3 is a perspective view of the main part of the same as above,
4 is a view taken along the - arrow in FIG. 2, FIG. 5 is an exploded view of the main parts of the same, FIG. 6 is a diagram for explaining the operation of the same, and FIG. 7 is a view showing another embodiment of the present invention. 8 is a sectional view showing a conventional example of an intake/exhaust valve drive device for an internal combustion engine, and FIG. 9 is a plan view of the same. 1... Intake/exhaust valve drive cam, 2... Intake/exhaust valve, 3
...Lotsuka arm, 3a...back, 5...lever, 18
...Stepping motor, 19...Control circuit, 21...
Lift control cam, 21a... hole, 22... cam control shaft, 27... stopper, 28... collar, 30a, 3
0b, 35... recess, 31... protrusion, 32... compression coil spring.

Claims (1)

[Claims] 1. Bring the back side of the rocker arm that engages the intake/exhaust valve drive cam and the intake/exhaust valve into fulcrum contact with a lever that is swingably attached to the engine body along the back side, and engage one end of the lever. controlling the amount of rotation of the lift control cam so as to change the fulcrum position where the lever and the back surface of the rocker arm come into contact;
In an internal combustion engine intake/exhaust valve drive device configured to variably control the lift characteristics of the intake/exhaust valves, a cam control shaft of the lift control cam, a stopper fixed to the cam control shaft, and a stopper fixed to the stopper and a predetermined a collar attached to the cam control shaft with a space therebetween so as to be freely movable in the axial direction of the cam control shaft; an elastic member provided in contact with the collar and the stopper; and a link between the collar and the lift control cam. a protrusion formed on one side, and a protrusion formed on the other of the collar and lift control cam that engages with the protrusion due to the expansion force of the elastic member, and the engagement surface compresses the elastic body. An intake/exhaust valve for an internal combustion engine, comprising an inclined part that is inclined so as to move a collar in the axial direction, and a driving means that rotates the cam control shaft by a predetermined amount depending on the engine operating state. Drive device.