JPH0587643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a valve control device for an internal combustion engine that variably controls the lift characteristics of intake and exhaust valves according to engine operating conditions.

<Prior Art> Valve control devices for internal combustion engines that variably control the lift characteristics of intake and exhaust valves according to engine operating conditions are disclosed in, for example, JP-A-60-26109 or JP-A-60-224909. As shown in , there is a device in which the lift amount of the intake/exhaust valve is controlled by changing the fulcrum position of the rocker arm provided between the intake/exhaust valve and its driving cam. As the lift amount decreases, the opening timing is delayed, the closing timing is advanced, and the opening period is shortened.

Therefore, when this is applied to the intake valve, the lift amount and opening/closing timing of the intake valve can be adjusted as shown in Fig. 11, for example.
I ₁ and I ₂ can be controlled as I 1 and I ₂ when the engine is at low speed and low load.
By controlling the lift amount to decrease as shown in the figure, the overlap with the exhaust valve can be reduced or eliminated, and combustion can be improved by reducing residual gas.
Further, benefits such as enhanced gas flow (improved combustion) due to the reduced intake valve opening area, and reduced drive loss of the valve train due to the reduced lift amount can be obtained. However, it is also true that the pump loss increases as the lift amount decreases, canceling out the above advantages.

For this reason, as proposed by the present applicant in Japanese Patent Application No. 59-269429, a rotational phase control device is installed on the camshaft to control the rotational phase of the intake/exhaust valve drive cam according to engine operating conditions. , it is considered to be used in combination.

That is, at the same time as the lift control of the intake valve, the rotational phase of the intake valve and exhaust valve drive cams is controlled, and when the lift amount decreases, the rotational phase is advanced as shown, for example, at I ₃ and E ₃ in FIG. By reducing the effective suction stroke of the intake valve and suppressing the amount of intake air, the throttling by the engine throttle valve is reduced to control the load, thereby reducing the suction negative pressure and reducing pump loss.

<Problems to be solved by the invention> However, when performing lift amount control and rotational phase control simultaneously in this way, a large lift amount is required when the engine accelerates, but when the rotational phase is on the leading side, When the lift amount is greatly controlled (12th
_I4 ) in the figure, the opening timing of the intake valve was extremely advanced, and there was a risk of interference between the piston head and the valve head.

Furthermore, if interference is avoided in the design, problems such as the maximum lift amount and rotational phase control angle will be restricted, or a large recess will be required in the piston head, which will adversely affect combustion.

In view of these problems, it is an object of the present invention to make it possible to avoid the problem of interference with the piston when lift amount control and rotational phase control are performed simultaneously.

<Means for Solving the Problems> For this reason, the present invention, as shown in FIG. a lift amount control device 10 that controls the lift amount of the intake/exhaust valves 12 by changing the fulcrum position of the engine; and a rotational phase control device 40 that controls the rotational phase of the intake/exhaust valve drive cam 11 according to engine operating conditions. A valve control device for an internal combustion engine, comprising a rotational phase amount detection means A for detecting the rotational phase amount of the cam 11, and a lift amount of the intake/exhaust valve 12 according to the detected rotational phase amount. This configuration includes a lift amount regulating means B.

<Operation> In the above configuration, since the rotational phase amount is detected by the rotational phase amount detection means and the lift amount is regulated by the lift amount regulating means based on this, interference with the piston can be avoided. The advantages of lift amount control and rotational phase control can be maximized.

<Example> An embodiment of the present invention will be described below.

The intake valve and exhaust valve are each driven by a cam attached to the same camshaft via a rocker arm, but the lift amount (and opening) of the intake valve is controlled by a lift amount control device as shown in Figures 2 to 4. period) is variable.

Referring to FIGS. 2 to 4, lift amount control device 1
0, a rocker arm 13 is provided with both ends in contact with the cam 11 and the stem end of the intake valve 12, and the curved back surface 13a of the rocker arm 13 is connected to a hydraulic pivot 19 (described later).
Lever 1 is freely supported at one end by
The fulcrum is in contact with 5. Further, the lever 15 is connected to the shaft 1 protruding from both side walls of the rocker arm 13.
3b is held in the concave groove 15a via the holding member 14, and between the spring seat 15b formed on the lever 15 and the holding member 14, there is a spring constant spring that biases the rocker arm 13 downward. A spring 16 is interposed.

The hydraulic pivot 19 includes an outer cylinder 19a that is slidably inserted into a mounting hole 18a formed in a bracket 18 attached to the cylinder head, and
an inner cylinder 19b fitted into the inner cylinder 9a, and
A check valve 19d is provided in a hydraulic chamber 19c formed between the two. The hemispherical lower end of the outer cylinder 19a is fitted into a recess 15c on the upper surface of one end of the lever 15 on the stem end side of the intake valve 12, supporting the lever 15 in a freely swingable manner. Hydraulic pressure is supplied from a hydraulic pressure supply passage 18b formed inside the bracket 18 to the hydraulic chamber 19c through the inside of the inner cylinder 19b and the check valve 19d to keep the bubble clearance constant.

Further, a lift control cam 20 rotatably attached to the bracket 18 as described later engages with the upper surface of the other end of the lever 15 on the cam 11 side, thereby regulating the swinging position of the lever 15. .

The lift control cam 20 has a polygonal shape and is attached to the intake valve 1.
A plurality of substantially flat cam surfaces 20a to 20e each having a different height so as to change the lift amount of step 2 in stages.
It also has a hole 20g in the center through which a control shaft 23, which will be described later, is inserted. Further, a cylindrical portion 2 formed to protrude from both ends of the lift control cam 20 is provided.
0h is the difference between the lower arcuate groove 18c formed on the bracket 18 and the upper arcuate groove 22a formed on the pair of caps 22 fastened to the bracket 18 with bolts 21, as shown in FIGS. 3 and 4. It is held freely rotatable in between.

Then, one control shaft 23 is inserted into the hole 20g formed by penetrating the center of the lift control cam 20 provided with several cylinders in a loose fit state.
One end of the torsion coil spring 24 fitted into both sides of each lift control cam 20 of No. 3 is locked to a set screw 23a screwed into the outer peripheral surface of the control shaft 23, and the other end of the coil spring 24 is connected to the lift control cam 20. It is fitted and locked into a hole 20i formed in the end surface of the cylindrical portion 20h of 20.

One end of the control shaft 23 is connected to a drive shaft 26a of a stepping motor 26 via a joint 25. The stepping motor 26 has an engine speed N,
It is driven by a control circuit 27 to rotate the control shaft 23 to a predetermined rotation position based on engine operating conditions such as throttle valve opening degree α.

29 is a valve spring.

Therefore, when the lift control cam 20 is in contact with the lever 15 with the cam surface 20a having the largest lift amount, the lever 15 is pushed down the most towards the cam 11. For this reason, the lever 15 is brought into fulcrum contact with the back surface 13a of the rocker arm 13.
The lower surface of the valve also lowers, and the fulcrum contact point A moves toward the cam 11 while being transmitted to the intake valve 12, resulting in a large lift amount and characteristics that the opening timing is early and the closing timing is late.

On the other hand, when the lift control cam 20 is rotated so that, for example, the cam surface 20e with the smallest lift comes into contact with the lever 15, the end of the lever 15 on the cam 11 side swings about the concave portion 15c as a fulcrum. The lever 15 then moves upward and retreats upward from the bottom surface of the lever 15.

The lower surface of the lever 15 is connected to the locking arm 13 by the cam 1.
The initial position of the fulcrum when the cam 11 is in contact with the rocker arm 13 at the base circle is when the lever 15 is in contact with the cam surface 20a with the large lift amount. Compared to when they are in contact, they move to the right in FIG. 2, 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, and the opening timing is late and the closing timing is early.

In this way, by rotating the lift control cam 20, any one of the cam surfaces 20a to 20e is attached to the lever 15.
By bringing the valve into contact with the intake valve 12, the lift amount characteristic of the intake valve 12 can be changed stepwise.

Here, the lift control cam 20 is rotated by a stepping motor 26 via a control shaft 23 and a torsion coil spring 24.

Now, at the timing when the control shaft 23 rotates, in the cylinder where the intake valve 12 is in the lift state, the fulcrum of contact between the rocker arm 13 and the lever 15 is at the cam 11.
The large reaction force of the valve spring 29 acts on the lift control cam 20 via the rocker arm 13 and lever 15. Therefore, the lift control cam 20 remains fixed and only the control shaft 23 rotates while twisting the torsion coil springs 24 on both sides thereof. Next, after the cam 11 rotates and the intake valve 12 closes, the contact fulcrum between the rocker arm 13 and the lever 15 is located approximately above the intake valve 12, and the reaction force of the valve spring 29 disappears. The only force acting on the lift control cam 20 is the weak force of the spring 16 attached between the rocker arm 13 and the lever 15. Therefore, the torque stored in the torsion coil spring 24 during the lift of the intake valve 12 overcomes the weak force of the spring 16, and the lift control cam 2
0 can be rotated.

Next, a rotational phase control device 40 for controlling the rotational phase of the intake valve and exhaust valve driving cams will be explained with reference to FIGS. 5 and 6.

That is, as shown in FIG. 5, the intake valve driving cam 1
1, a timing pulley 38 is connected to one end of a camshaft 37 that forms an exhaust valve driving cam (not shown), and this timing pulley 38 is connected to an engine crank (not shown) via a toothed timing belt 39. Linked to the axis. Then, the cam 1 is attached to the connecting part (fixed part) between the timing preamp 38 and the camshaft 37.
Rotational phase control device 40 that controls the rotational phase of the first class
is incorporated.

The rotational phase control device 40 includes a timing pulley 3
An annular piston 42 that slidably reciprocates within an annular cylinder 38A formed within the cylinder 38A to define a hydraulic chamber 41 within the cylinder 38A; The camshaft 3 resists the biasing force of the coil spring 43.
7, and a stopper member 45 fixed to the end surface of the camshaft 37 with a bolt 50, which restricts the movement of the slider 44 via a coil spring 43. As shown in FIG. 6, the slider 44 has a torsion spline 44A formed on the inner surface of its hollow part, and has a flange 44B at one end on which the piston 42 comes into contact, and a cylinder 38A at the other end. A protrusion 44C is formed to be slidably supported in a groove 38B formed in the inner wall. Further, as shown in FIG. 6, a torsion spline A is formed at one end of the camshaft 37, and this torsion spline 37A is connected to the slider 4.
It is designed to mesh with the torsion spline 44A of No. 4.

5 is a hydraulic passage formed in the camshaft 37 and the timing pulley 38. One end of this hydraulic passage 46 communicates with the hydraulic chamber 41, and the other end communicates with an external hydraulic pressure supply passage 47. are doing. The other end of this hydraulic supply passage 47 is
One passage 47A is for oil pump 4
8, the other passage 47B communicates with the hydraulic control valve 49, respectively. This hydraulic control valve 49 is of an electromagnetic type and controls the hydraulic pressure supplied from the oil pump 48 to the hydraulic chamber 41 in accordance with an electric signal.

Therefore, the hydraulic pressure control valve 49 controls the hydraulic pressure chamber 41.
The hydraulic pressure is controlled, and the slider 44 is positioned in the axial direction in accordance with this hydraulic pressure. Then, the torsion splines 37A, 44A slide in the axial direction in accordance with the position of the slider 44, thereby rotating the camshaft 37 by a predetermined amount, thereby controlling the rotational phase of the cam 11, etc.

The hydraulic control valve 49 is controlled by the control circuit 5 based on the engine operating conditions such as the engine speed N and the throttle valve opening α.
2.

In the configuration according to the present invention, as shown in FIG.
A position sensor 60 is fixed to the belt cover 55 and serves as rotational phase amount detection means so that the bar-shaped iron piece 61 moves as the iron bar 61 moves. Of course, this position sensor 60 is provided with a cylindrical coil inside.

Then, the signal from this position sensor 60 is transferred to a third
As shown in the figure, it is input to the control circuit 27 of the lift amount control device 10.

Then, in this control circuit 27, the stepping motor 26 is controlled according to the flowchart shown in FIG.
It is designed to control the operation of the

To explain the flowchart in Figure 7,
Step 1 (marked as S1 in the diagram. The same applies below)
In step 2, engine operating conditions such as engine speed N and throttle valve opening degree α are detected, and in step 2, an optimum lift amount is set based on the detected engine operating conditions.

Next, in step 3, the amount of rotational phase is read based on the signal from the position sensor 60, and in step 4, the maximum allowable lift amount is set based on the read amount of rotational phase.

Next, in step 5, the set lift amount is compared with the allowable maximum lift amount, and if the set lift amount exceeds the allowable maximum lift amount, the process proceeds to step 6, where the set lift amount is changed to the allowable maximum lift amount. The steps 5 and 6 correspond to lift amount regulating means.

Thereafter, in step 7, the stepping motor 26 is driven to select the cam surfaces 20a to 20e corresponding to the set lift amount.

As a result, at low speeds and low loads, by reducing the lift amount of the intake valve and advancing the rotational phase of the intake valve and exhaust valve driving cams, as shown in Figure 8, the pump loss is reduced and combustion is improved. etc.

Furthermore, during acceleration, as shown in FIG. 9, the lift amount of the intake valve is increased to improve the filling efficiency. At this time, if the lift amount is increased when the rotational phase amount of the cam is controlled to be large, the opening timing of the intake valve will advance greatly, making it easier to interfere with the piston. However, by detecting the rotational phase amount of the cam, the lift amount is regulated and the lift amount is set to the states A to B in Fig. 9 to avoid interference with the piston.

Incidentally, FIG. 10 shows the lift characteristics at high-speed loading.

<Effects of the Invention> As explained above, according to the present invention, the amount of rotational phase is detected and the amount of lift is regulated to avoid interference with the piston, so the maximum lift amount and rotational phase control angle are set small in advance. Also, there is no need to form a large recess in the piston head, and the advantages of lift amount control and rotational phase control can be maximized.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of the present invention, Figure 2 is a block diagram showing the configuration of the present invention.
The figure is a sectional view showing an example of a lift amount control device.
FIG. 3 is a plan view of FIG. 2, FIG. 4 is a perspective view of the lift control cam portion in FIG. 2, FIG. 5 is a sectional view showing an embodiment of the rotational phase control device, and FIG. Fifth
7 is a flowchart showing the control contents of the control circuit in FIG. 3, FIGS. 8 to 10 are lift characteristic diagrams in the same embodiment, and FIG. 11 and 12 are lift characteristic diagrams of conventional examples. 10...lift amount control device, 11...cam, 12...
Intake valve, 13...Rotsuka arm, 15...Lever, 2
0... Lift control cam, 23... Control shaft, 24... Torsion coil spring, 26... Stepping motor,
27... Control circuit, 37... Camshaft, 37A... Torsion spline, 38... Timing pulley, 40... Rotation phase control device, 41... Hydraulic chamber, 44... Slider,
44A...Torsion spline, 49...Hydraulic control valve, 5
2...Control circuit, 60...Position sensor.

Claims (1)

[Claims] 1. A lift amount control device that controls the lift amount of the intake/exhaust valves by changing the fulcrum position of a rocker arm provided between the intake/exhaust valves and their driving cams according to engine operating conditions, and Suction and
A valve control device for an internal combustion engine, comprising: a rotational phase control device for controlling a rotational phase of an exhaust valve driving cam; a rotational phase amount detection means for detecting a rotational phase amount of the cam; 1. A valve control device for an internal combustion engine, comprising a lift amount regulating means for regulating the lift amount of an intake/exhaust valve accordingly.