JPH0323724B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake/exhaust valve drive device for an internal combustion engine that variably controls the opening/closing timing and valve lift amount of intake/exhaust valves according to operating conditions.

Various intake and exhaust valve drive devices have been proposed in the past, which variably control the opening/closing timing of the intake and exhaust valves and the amount of valve lift according to the engine operating conditions so that valve overlap, fresh air filling efficiency, etc. are always optimally achieved. One example is the U.S. Patent No. 1 shown in Figure 1.
No. 3413965 is known.

In this valve drive device, the back surface 4 of a rocker arm 3 whose one end abuts the valve drive cam 1 and whose other end is fitted and supported by the stem end of the intake/exhaust valve 2 is curved. By swinging the left and right sides of the rocker arm 3 while contacting the fulcrum,
The lift of the cam 1 is transmitted to the intake and exhaust valves 2, and in particular, the lever 5 is pivotably supported at one end thereof, and its inclination is regulated by a control cam 6. ing. The control cam 6 is rotationally driven in an appropriate phase according to engine operating conditions by a drive mechanism such as a hydraulic actuator, thereby variably controlling the opening/closing timing and lift amount of the intake/exhaust valve 2. That is, for example, if the lever 5 is pushed down by a large amount by the control cam 6, the free end of the lever 5 and the rocker arm 3 are close to each other in the base circle state of the valve drive cam 1, and therefore the intake and exhaust valves 2 are pushed down by a large amount. As the valve opening timing becomes earlier, the valve lift amount increases, and if the amount of depression by the control cam 6 is small, the free end of the lever 5 and the rocker arm 3 will move even if the valve drive cam 1 is in the same base circle state.
Therefore, the opening timing of the intake and exhaust valves is delayed and the amount of valve lift becomes small.

However, in such a conventional intake/exhaust valve drive device, the valve lift is controlled by rotating the support shaft 6a having the control cam 6 by a hydraulic actuator, so that the repulsion of the valve spring 7 is Based on force, Rotsuka arm 4,
A periodically fluctuating load applied to the control cam 6 is applied to the hydraulic actuator via the lever 5, acting to leak oil from the hydraulic actuator, forcing the control cam 6 to rotate.
For this reason, there was a problem in that the valve drive cam 1 could not stably obtain the valve lift characteristics, and the output performance, high-speed drivability, etc. were impaired.

This invention was made in view of such conventional problems, and by forming at least two flat cam surfaces on the control cam and rotating the control cam according to the engine operating condition, The purpose is to prevent the lever from forcibly rotating the control cam.

For this reason, the present invention includes a valve drive cam that rotates in synchronization with engine rotation, a rocker arm that has one end in contact with the valve drive cam and the other end that is linked to the valve stem, and a rocker arm that is disposed approximately along the back surface of the rocker arm. a lever provided with a rocker arm support surface whose back surface is in fulcrum contact; a bracket supporting one end of the lever on the valve stem side; and at least two flat cam surfaces; It consists of a control cam that supports the other end of the lever on the cam side, a support shaft that supports this control cam, and an actuator that rotates this support shaft in accordance with the operating conditions of the engine.

Below, drawings of embodiments of this invention will be specifically described.

FIG. 2 is a sectional view of one embodiment. In the figure, 11 is a valve drive cam synchronized with engine rotation, 12 is an intake and exhaust valve, 13 is a valve spring,
14 is a bracket fixed to the cylinder head 15, and 16 is a bracket that connects the lift of the valve drive cam to the intake and exhaust valve 1.
2 is the Rotsuka arm, 17 is the Rotsuka arm 1.
This is a lever that supports the rear surface 16a of 6 as a fulcrum and holds the rocker shaft 18. Lever 1
The valve stem side end of the valve stem 7 is supported as a fulcrum by the hydraulic pivot 19, and the valve drive cam side end is supported by the control cam 2.
It is supported in contact with 0.

This hydraulic pivot 19 consists of a bottomed outer cylindrical part 19a and an inner cylindrical part 19b, and a high pressure chamber 19 is arranged between them.
c is formed. Disposed within the high pressure chamber 19c are a coil spring 19d, a check valve 19e, a spring 19f that supports the check valve 19e, and a housing 19g that supports the check valve 19e and the spring 19f. An oil reservoir 19h is formed in the inner cylinder portion 19b, and communicates with the high pressure chamber 19c through a communication hole 19i. Oil reservoir 19h is communication hole 19
It communicates with a communication hole 14a, which will be described later, via j.

The control cam 20 has six substantially flat cam surfaces 20a, 20b, 20c, 20d, 20e,
20f, and the lift amount can be changed in stages. The control cam 20 is fixed to a support shaft 21 by a key 21a, and a hollow portion of the support shaft 21 serves as a passage 21b for lubricating oil. This passage 21b leads to an external oil supply source, and
It communicates with the oil reservoir 19h of the hydraulic pivot 19 through the communication hole 14a. 22 is the support shaft 21
This is another bracket for holding the bracket 14 on the bracket 14, and is fixed to the bracket 14 by bolts 23.

FIG. 3 shows a control system diagram of the hydraulic actuator. That is, a vane 31b of a hydraulic actuator 31 is fixed to one end of the support shaft 21, and the vane 31b can rotate within the housing 31a. Further, a rotation angle sensor 32 is attached to the other end of the support shaft 21 . This rotation angle sensor 32 has an insulator 32e attached to a housing 32a.
The brush 32c is attached to the support shaft 21 and includes a number of terminals 32b corresponding to the number of flat cam surfaces, a brush 32c fixed to the end of the support shaft 21, and a screw 32d for fixing the brush 32c to the support shaft 21. Note that the valve train shown in FIG. 2 is arranged between the hydraulic actuator 31 and the rotation angle sensor 32.

34 is an electrohydraulic switching valve, the A and B ports of which are the two intake and exhaust ports 31 of the hydraulic actuator 31.
c, 31d, the P port communicates with the oil pump, and the R port communicates with the oil pan 36. 3
7 is a check valve provided in the middle of the oil supply pipe, 38 is an accumulator connected between the check valve 37 and the P port, and 39 and 40 are relief valves. Further, 41 is a control unit that sends a control current to the electrohydraulic switching valve 34 in accordance with output signals of the rotation angle sensor 32, engine throttle opening, rotation speed, cooling water temperature, intake air amount, intake negative pressure, etc. It is a circuit.

Next, the effect will be explained.

Now, in FIG. 2, when the control cam 20 is in contact with the end of the lever 17 on the valve drive cam 11 side at the cam surface 20a with the largest lift, the lever 17 is pushed down toward the valve drive cam 11 side. The state will be as follows. Therefore, the lower surface 17a of the lever 17 makes fulcrum contact with the back surface 16a of the rocker arm 16.
As the fulcrum contact point A moves toward the valve drive cam side, the swing of the rocker arm 16 due to the lift of the valve drive cam 11 is transmitted to the intake and exhaust valves 12, and the movement is transmitted to the intake and exhaust valves 12, as shown by the curve X in FIG. The valve lift characteristics are large, the valve lift rises quickly, and falls slowly.

On the other hand, when the control cam 20 rotates and comes into contact with the lever 17 with the cam surface 20b with a small lift, for example, the end of the lever 17 on the valve drive cam 11 side rises, and the lower surface 17a of the lever 17 also retreats upward. . Therefore, the fulcrum contact point A moves to the side opposite to the valve drive cam 11 side, and as shown by the curve Y in FIG. 4, the valve lift amount is small, and the lift rises slowly and falls quickly.

In this way, by rotating the control cam 20, the valve lift can be changed in stages.

Here, the control cam 20 is rotated by a hydraulic actuator 31. That is, the control circuit 41 generates an output current set based on the output of the rotation angle sensor 32 and other signals corresponding to the engine operating state. This current operates the electrohydraulic switching valve 34 to connect either the A port or the B port to the P port, and the oil pump 35
Alternatively, the hydraulic pressure discharged from the accumulator 38 is supplied to the hydraulic actuator 31 to control rotation of the vane 31b in either direction. Therefore, the support shaft 21 similarly rotates to perform lift control of the control cam 20. By this operation, when the target valve lift state is achieved via the lever 17, the brush 32
c contacts any of the terminals 32b, the output of the rotation angle sensor 32 is transferred to the control circuit 41.
is input, and feed dock control is performed to maintain the electrohydraulic switching valve 34 in a neutral state.

Therefore, after the target lift is controlled, the oil supply to the hydraulic actuator 31 is stopped, and the lever 17 stably contacts the cam surface 20b of the control cam 20, even if the valve lift amount becomes large. , this valve lift amount can be kept constant.

Note that the switching valve 34 is an ABT connection type,
In the neutral state, the P port is closed and the discharge pressure of the oil pump 35 is stored in the accumulator 38 via the check valve 37.
8 is regulated by a relief valve 39. The accumulated hydraulic pressure can be used as hydraulic oil for the hydraulic actuator 31 in the next control operation.
The discharge amount of the oil pump 35 is small, and the oil pump 35 can be made smaller. Furthermore, the responsiveness of the hydraulic actuator 31 when starting the engine is also improved.

Figures 5a and 5b show other embodiments. A small hole 20g is formed in the control cam 20, one end of the coil spring 40 is locked in the small hole 20g, and the other end is attached to the support shaft 20.
It is screwed to 1. Further, the support shaft 21 is provided with an oil supply hole 21c so that oil can be introduced between the control cam 20 and the support shaft 21 to provide lubrication. This allows the driving force of the control cam 20 to be reduced in a multi-cylinder engine with four or more cylinders. This is because in a multi-cylinder engine, the intake and exhaust valves 12 of at least one cylinder are lifted, and the reaction force of the valve spring 13 acts on the control cam.
Although the rotation of the control cam 20 is becoming heavy, the control cam 20 can be rotated when the valve lift is in a rest state by the elastic force stored in the coil spring 40 by the operation of the hydraulic actuator 31. This is because it can be done. In addition, the lever 17
Instead of the hydraulic pivot 19, an adjusting bolt screwed into the bracket 14 can be used at one end of the valve stem side, and the valve clearance can be adjusted by adjusting the screwing of the adjusting bolt. can do.

6 and 7 show cross-sectional and plan views of yet another embodiment of the invention. 51 is the support shaft 21
The first gear 51 is rotatably fitted into the first gear 51, and each end of a coil spring 52 is stopped between the first gear 51 and the same control cam 20 as described above. 53,
Reference numeral 54 denotes a snap ring that restricts the axial movement of the control cam 20 and the first gear 51. A second gear 55 meshes with the first gear 51, and the second gear 55 is fixed to a support shaft 56. This support shaft 56
is rotatably supported by a bracket 14, a bracket 22, etc. The end of the support shaft 56 is connected via a connector 57 to the rotating shaft of a stepping motor 58 as an actuator of the control cam 20, and the stepping motor 58 receives output from the control circuit 41 according to the engine operating state. The drive is controlled by the pulsed current.

According to this, when the stepping motor 58 operates and the second gear 55 is rotated counterclockwise in FIG. 6, the first gear 51 is rotated clockwise and the coil spring 52 is rotated. is applied with a clockwise rotational force, and attempts to rotate the control cam 20 clockwise. If the intake and exhaust valves 12 are lifted, the reaction force of the valve spring 13 will be applied to the lever 1.
7, the control cam 20 does not rotate. However, when the valve lift stops and the rocker arm 16 comes to the base circle of the valve drive cam, the reaction force of the valve spring 13 becomes extremely small and the control cam 20 rotates clockwise.

As a result, the stepping motor 58 is driven by the coil spring 5 through the second gear 55 and the first gear 54.
It is sufficient to have sufficient torque to store rotational force in the control cam 20, and compared to the case where the control cam 20 is directly driven, an extremely small driving force is required, which is economical.
Also in this embodiment, the lever 17 is stably supported by each cam surface of the control cam 20, and even when the reaction force of the valve spring 13 becomes high, the valve lift operation can be performed in a stable state. be.

FIG. 8 shows a wavy portion 20h on one end surface of the control cam 20.
A collar 20j having a wavy portion 20i that contacts the collar 20j is shown fixed to a support shaft 21. In this case, the coil spring 5
2 is attached to a support shaft 21 so that the control cam 20 can be slid and rotated in the axial direction. In addition,
In a state in which the respective corrugated portions 20h and 20i are in mesh, each of the cam surfaces 20a, 20b, 20c of the control cam 20,
Either 20d, 20e or 20f is the lever 17
It is in a position where it makes stable contact with the

With such a configuration, even if the elastic force of the coil spring 52 stored during the valve lift is suddenly released when the valve lift is in a rest state, the control cam is still 20 can be prevented from exceeding the target rotation amount due to its elastic force. That is, in addition to providing the control cam 20 with at least two or more substantially flat cam surfaces, the wavy portion 20 is formed between the control cam 20 and the collar 20j.
By frictionally engaging at h, 20i,
Furthermore, the rotation of the control cam 20 can be controlled in a stable and stepwise manner.

FIG. 9 shows a belt 63 between a main drive wheel 61 fixed to the support shaft 56 and a driven wheel 62 fixed to the support shaft 21.
FIG. 10 shows a cog belt 66 suspended between a cog wheel 64 fixed to the support shaft 56 and a cog wheel 65 fixed to the support shaft 21, and FIG. A flat belt 69 is suspended between a main drive wheel 67 with a flange 67a fixed to the support shaft 56 and a driven wheel 68 fixed to the support shaft 21. And even in these three implementations, the seventh
It is possible to obtain the same functions and effects as those described in connection with the embodiment shown in FIG. 8 and FIG.

As explained above, according to the present invention, a plurality of flat cam surfaces are provided that stably contact the lever without applying rotational force to the control cam, and the support shaft of the control cam is connected to the hydraulic actuator or motor. Since the control cam is rotated by an actuator such as the above, there is no need to force the control cam to rotate due to the reaction force of the valve spring during valve lift, and the lift characteristics of the valve drive cam can be adjusted accurately to the intake and exhaust valves. It is possible to prevent a decrease in output performance due to a decrease in the lift amount during valve lift and an increase in the higher-order harmonic component of the valve lift amount, thereby achieving effects such as stably maintaining high-speed performance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional intake/exhaust valve drive device, FIG. 2 is a sectional view showing an embodiment of the intake/exhaust valve drive device according to the present invention, FIG. 3 is a hydraulic control system diagram of a hydraulic actuator, and FIG. Figure 4 is a valve lift characteristic diagram, Figure 5a is a sectional view of the main parts with improvements, and Figure 5
Fig. b is a plan view, Fig. 6 is a sectional view of another embodiment, Fig. 7 is a plan view, Fig. 8 is a partially improved plan view of the main part, Figs. 9, 10, and 1st
Figure 1 is a plan view of the main part with some improvements made. 11... Valve drive cam, 12... Intake and exhaust valve,
13... Valve spring, 14... Bracket, 16... Locker arm, 17... Lever, 1
9... Hydraulic pivot, 20... Control cam, 21...
... Support shaft, 31 ... Hydraulic actuator (actuator), 41 ... Control circuit, 58 ... Stepping motor (actuator).

Claims (1)

[Claims] 1. A valve drive cam that rotates in synchronization with engine rotation, a rocker arm that has one end in contact with the valve drive cam and the other end that is linked to the valve stem, and a rocker arm that is disposed approximately along the back surface of the rocker arm and that a lever having a rocker arm support surface that makes fulcrum contact with the lever, a bracket that supports one end of the lever on the valve stem side, and at least two substantially flat cam surfaces, and a lever that is located on the valve drive cam side of the bracket. An internal combustion engine comprising: a control cam that supports the other end of the lever; a support shaft that supports the control cam; and an actuator that rotates the support shaft in accordance with engine operating conditions. Intake and exhaust valve drive device.