JPS62159710A - Intake and exhaust valve driving device for internal combustion engine - Google Patents

Abstract

PURPOSE:To make the device compact, by converting a torque of a cam control shaft on a prime motor side to an axial force to compress an elastic member, and rotating an unlocked lift control cam by a force of the elastic member at a predetermined timing. CONSTITUTION:A lift control cam 21 is formed at its outer periphery with a plurality of substantially flat cam surfaces so as to stepwise change a lift characteristic of suction and exhaust valves 2. A cam control shaft 26 to be rotated by a stepping motor 18 is inserted through a central portion of the lift control cam 21. A cylindrical stopper 27 is fixed to the cam control shaft 26. A cylindrical collar 28 is axially slidably mounted on the cam control shaft 26, and a compression coil spring 32 is interposed between the stopper 27 and the collar 28. One cylindrical portion 21b of the cam 21 is formed at its side wall with a recess 30a forming an inclined portion, and the collar 28 is provided at its side wall with a projection 31 projecting into the recess 30a. Thus, a spring force of the spring 32 is converted to a torque at the inclined portion 30a, thereby rotating the cam 21.

Description

[Detailed Description of the Invention] <Industrial Application Fields> 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 the intake/exhaust valves according to engine operating conditions. Regarding.

<Prior Art> As a conventional example of an intake/exhaust valve drive device for an internal combustion engine, there is one as shown in FIGS.
(See Publication No. 09 and Japanese Patent Application No. 59-81052).

That is, a rocker arm 3 is provided with both ends abutting an intake/exhaust valve drive cam 1 that rotates in synchronization with engine rotation and a stem end of the intake/exhaust valve 2, and a curved back surface of the rocker arm 3. 3a in fulcrum contact, and the shaft 3b protruding from both side walls of the rocker arm 3 with the holding member 4.
A lever 5 is provided which is held in the groove 5a via the lever 5a.

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.

Further, the spherical lower end surface of the hydraulic pivot 9, which is fitted and held by a bracket 8 interposed in the cylinder head 7, is in a concave portion 5C formed on the top wall of the other end of the lever 5 on the stem end side of the intake/exhaust valve 2. The lift control cam 10, which is fitted into the bracket 8 to freely swing and support the lever 5 around the fitting part, is connected to the intake/exhaust valve of the lever 5. The swinging position of the lever 5 is regulated by coming into contact with the top wall of the end portion on the drive cam 1 side.

The hydraulic pivot 9 has a lower end surface that is connected to the concave portion 5 of the lever 5.
an outer cylinder 9a that fits into the bracket C and whose peripheral surface is slidably inserted into a mounting hole 8a formed in the bracket 8;
The hydraulic pressure chamber 9C is formed between the inner cylinder 9b and the inner cylinder 9b, which is inserted into the inner cylinder 9b, and a check valve 9d is provided in the hydraulic chamber 9C formed between the two. 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 via 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 attached to the bracket 8. A first gear 13 is rotatably attached to the support shaft 11, and one end of a coil spring 14 is locked to the side of the first gear 13. 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 connector 1.
The rotating shaft of the stepping motor 18 is connected to the rotating shaft of the stepping motor 18 via the motor 7. 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, and rotates the cam control shaft 16. ing. Note that 20 is a valve spring, and 20a and 2Qb are snap rings, respectively.

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. For this reason, the lower surface of the lever 5, which is in fulcrum contact with the back surface 3a of the rocker arm 3, is also lowered, and the fulcrum contact point A moves toward the intake/exhaust valve drive cam 1 side and is transmitted to the intake/exhaust valves 2, increasing the amount of lift. In addition, the valve opening timing is early and the valve closing timing is late.

On the other hand, when the lift control cam 10 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. Intake/exhaust valve drive cam 1 that rises by rocking
The initial position of the fulcrum when it is in contact with the rocker arm 3 at the base circle is to the right in Fig. 8 compared to when the lever 5 is in contact with the cam surface with the large lift amount, that is, the fulcrum moves after the lift. Move away from the direction.

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 the driving of the stepping motor 18 on the cam control shaft 16. 2nd gear 1
5. This is done via the first gear 13 and the coil spring 14. That is, the control circuit 19 outputs a drive pulse set to the stepping motor 18 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, the fulcrum of contact between the rocker arm 3 and the lever 5 is moving toward the intake/exhaust valve drive cam 1 in the cylinder where the intake/exhaust valve 2 is in lift. Therefore, a large reaction force of the pulp spring 20 is applied to the rocker arm 3. Lift control cam 1 via lever 5
Acts on 0. Therefore, while the lift control cam 10 remains stationary and twists the coil spring 14, the cam control shaft 16. The second gear 15 and the first gear 13 rotate. 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, and 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 force and the amount of rotation of the control shaft 16 are stored as the torsional torque of the coil spring 14, the force is stored at a predetermined timing. The stored torsional torque rotates the lift control cam 10 to change the lift characteristics, and the lift control cam 10 is rotated clockwise and counterclockwise in FIG. 8, so that the coil spring 14 The coil spring 14 has a so-called double-sided structure in which the coil springs alternately tear on the insertion side and the unwinding side.As a result, the fatigue strength of the coil spring 14 is significantly reduced, and there is a risk that the coil spring 14 may 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) Therefore, 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 with a predetermined spacing between the lift control cam and the cam control shaft. 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;
formed on the other of the collar and the lift control cam so as to engage the protrusion by the expansion force of the elastic member and move the collar in the axial direction so that the engagement surface compresses the elastic body; The engine is provided with an inclined portion that slopes, and a drive means that rotates the cam control shaft by a predetermined amount depending on the engine operating state.

<Operation> In this way, the rotational force of the driving side cam control shaft is converted into an 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. Incidentally, the same elements as in the conventional example are given the same reference numerals as in FIGS. 8 and 9, and the explanation thereof will be omitted.

1 to 4 show one 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 Y characteristics of the intake/exhaust valves 2 in stages, as in the conventional example. One of the two contacts the top wall of the end of the lever 5 on the side of the intake/exhaust valve drive cam 1 to restrict 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.

Further, the lift control cam 21 has cylindrical portions 21b on both sides.

21c is formed protrudingly, and these cylindrical parts 21b and 21C are connected to a lower circular groove 23a formed in the bracket 23 and a bolt 2 on the bracket 23, as shown in FIGS. 2 and 3.
The caps 25 are held freely rotatably between the upper arcuate grooves 25a formed in the pair of caps 25 that are fastened together.

A cam control shaft 26 is inserted into the hole 21a formed through the center of the lift control cam 21 provided with several cylinders.
is inserted. A cylindrical stopper 27 is fastened to the cam control shaft 26 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 can be freely slid in the axial direction of the cam control shaft 26 by means of a key 29, as shown in FIGS. 2 and 5. installed.

The side wall of one cylindrical portion 21b of the lift control cam 21 is provided with a recess 30 as an inclined portion, as shown in FIGS. 2 and 3.
A and 30b are formed at two locations. A pair of protrusions 31 are formed on the side wall of the collar 28, facing the recesses 3Qa and 30b, respectively. The stopper 27 and the collar 2
8 is a compression coil spring 3 as an elastic member.
2 is interposed, and the expansion force of the compression coil spring 32 causes the protrusion 31 of the collar 28 to be pushed into the recesses 30a, 30.
b It is designed to be pressed against the inner wall.

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 via a connector 17 to a rotating wheel of a stepping motor 18 serving as a driving means. 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.
The cam control shaft 26 is rotated. In addition, 3
3 is a stopper that restricts movement of the lift control cam 21;
23a is a hydraulic pressure supply passage.

Next, the effect will be explained.

In order to change the contact position between the lever 5 and the back surface 3a of the rocker arm 3 to change the lift characteristics of the intake/exhaust valves, the lift control cam 21 is rotated and the intake/exhaust valve drive cam 1 of the lever 5 is rotated.
Although it is necessary to change the side height, 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 in operation. For this reason, 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 is closed, the reaction force of the valve spring 20 is small. , 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 done.

The collar 28 is also rotated with the rotation of the cam control shaft 26, and the recess 3 that the protrusion 31 formed on the collar 28 comes into contact with
Since 0a and 30b are inclined, the recessed portion 30a.

Due to the reaction force of 30b, the collar 28 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 compression coil spring 32
Due to the expanding force of
Since the inner wall 30b is pressed upward in FIG. 6, the lift control cam 21 tends to be rotated by this pressing force. still,
Recessed portion 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, the intake and exhaust valves 2 are in the opening operation, so the reaction force of the valve spring 20 is large and the lift control cam 21
remains stationary 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 intake/exhaust valve 2
The valve characteristics can be changed.

As explained above, since the compression coil spring 32 is compressed and the compression force is converted into rotational force by the inclination of the engagement surface, and the lift control cam 21 is rotated, the rotational force is reversed compared to the conventional coil spring. Since fatigue caused by torsional rotation in the direction is eliminated, breakage of the compression coil spring 32 can be prevented and durability can be improved.

Furthermore, since the support shaft 11 and the cam control shaft 16 in the conventional example are integrated to form the cam control shaft 26, the first and second
Gears 13, 15, etc. are not required, and the device can be made smaller.

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 of the intake/exhaust valve 2, the rotational force of the lift control cam 21 increases, while the amount of lift of the intake/exhaust valve 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, the recess 3 is formed on the side of the cylindrical portion 21b of the lift control cam 21.
5 are formed at two locations in the same manner as in the previous embodiment. In the direction in which the lift control cam 21 is rotated to increase the lift amount of the intake/exhaust valve 2, the protrusion 31 of the collar 28
As shown in FIG. 7, the inner wall of the recess 35 that comes into contact with the inner wall of the recess 35 is formed into a steep slope 35a so as to protrude rapidly toward the protrusion 31 from the center toward one side. On the other hand, intake/exhaust valve 2
In the direction in which the lift control cam 21 is rotated to reduce the lift amount, the inner wall of the recess 35 gently protrudes toward the protrusion 31 from the center toward the other side, as shown in FIG. The gently sloped portion 35b is formed so as to.

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 the direction of increasing the lift t of the intake/exhaust valve 2, the collar 28 is moved in the axial direction by the steeply inclined portion 35a. The compressive force of the compression coil spring 32 becomes large because it is moved thickly. Therefore, the expansion force of the compression coil spring 32 becomes large.

Furthermore, 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 2I mentioned 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 of the elastic member, and the durability of the elastic member can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a plan view of the same, FIG. 3 is a perspective view of essential parts of the same, FIG. 4 is a view taken along the line IV-IV in FIG. Figure 5 is an exploded view of the main parts of the same as above, Figure 6
7 is a plan view of a main part showing another embodiment of the present invention, and FIG.
FIG. 9 is a sectional view showing a conventional example of an exhaust valve drive device, and FIG. 9 is a plan view of the same. ■...Suction/exhaust valve drive cam 2...Suction/exhaust valve 3
...Rocker arm 3a...Back 5...Lever I8...Stemping motor 19...'#
JI jHH road 21... Lift control cam 21a.
... Hole 22 ... Cam control shaft 27 ... Stopper 28 ... Collar 30a. 30b, 35... recess 31... protrusion 32
... Compression coil spring patent applicant Nissan Motor Co., Ltd. agent Patent attorney Fujio Sasashima 1... Intake/exhaust valve drive cam 2... Intake/exhaust valve 3... Rocker arm 3a... Back side 21a... ... Hole 22 ... Cam control shaft Fig. 1 Fig. 3 Fig. 4 Fig. 9

Claims (1)

[Claims] The back side of the rocker arm that engages the intake/exhaust valve drive cam and the intake/exhaust valve is brought into fulcrum contact with a lever that is swingably attached to the engine body along the back side, and is engaged with one end of the lever. An intake/exhaust valve drive for an internal combustion engine in which lift characteristics of the intake/exhaust valves are variably controlled by controlling the amount of rotation of a lift control cam to change the fulcrum position where the lever and the back surface of the rocker arm contact each other. In the device, a cam control shaft of the lift control cam, a stopper fixed to the cam control shaft, and a stopper attached to the cam control shaft with a predetermined distance from the stopper so as to be movable in the axial direction of the cam control shaft. a collar, an elastic member provided in contact with the collar and the stopper, a protrusion formed on one of the collar and the lift control cam, and a protrusion formed on the other of the collar and the lift control cam. an inclined part that engages with the protrusion by the expansion force of the elastic member and is inclined so that the engagement surface moves the collar in the axial direction to compress the elastic body;
An intake/exhaust valve drive device for an internal combustion engine, comprising: drive means for rotationally driving the cam control shaft by a predetermined amount depending on an engine operating state.