JPH0742845B2 - Valve drive controller for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve train control device for an internal combustion engine that variably controls lift characteristics of intake and exhaust valves according to engine operating conditions.

<Prior Art> An example of a valve operating system for an internal combustion engine that variably controls lift characteristics of intake and exhaust valves according to engine operating conditions is disclosed in Japanese Utility Model Laid-Open No. 55-110758.

In this system, two stages of cams having different valve lift characteristics are provided, and the cams engaged with the intake valve are switched between the low load region and the high load region of the engine.

Specifically, as shown in FIG. 6A in the high load region of the engine, intake charging efficiency is improved as a characteristic of a large valve lift amount, and in the low load region of the engine, as shown in FIG. 6B. ,
The intake amount is suppressed by advancing the intake valve closing timing before bottom dead center to shorten the effective intake stroke. That is, when controlling the load, the intake amount can be suppressed without relying on the throttle valve, so that the throttle valve opening can be increased, the intake pipe internal pressure can be reduced, and the pump loss can be reduced.

<Problems to be Solved by the Invention> However, when the lift characteristic shown in FIG. 6A in the low load range is switched to the characteristic shown in FIG. 6B in the high load range, the intake capacity of the intake valve is changed. The torque increases from the difference,
A torque difference as shown in the figure is produced. This torque difference increases as the intake pipe negative pressure decreases, that is, as the throttle valve opening increases, and as a result, as shown in FIG. Because the valve opening is large,
There has been a problem that the torque difference becomes large and the shock at the time of switching becomes large.

The present invention has been made in view of such a conventional situation, and the time required from the start of the switching control until the valve lift characteristics of all cylinders are switched, that is, the switching speed of the valve lift amount is controlled by the intake control during the switching control. By performing variable control according to the pipe negative pressure equivalent value, it is possible to improve the responsiveness in the region where the torque change is small when switching the valve lift amount, while reducing the shock in the region where the torque change is large. An object is to provide a control device.

<Means for Solving Problems> Therefore, according to the present invention, the operation of the internal combustion engine provided with the valve lift characteristic changing means for variably controlling the lift characteristics of the intake and exhaust valves according to the operating conditions of the multi-cylinder internal combustion engine. In the valve control device, when the intake pipe negative pressure equivalent value detecting means for detecting a value corresponding to the intake pipe negative pressure of the engine and the valve lift characteristic switching control under the condition that the intake pipe negative pressure equivalent value is small are performed. In order to increase the time required from the start of the switching control until the valve lift characteristics of all the cylinders are switched, as compared with the case where the switching control of the valve lift characteristics is performed under the condition that the intake pipe negative pressure equivalent value is large. A switching control means for reducing the switching speed of the valve lift characteristic by the valve lift characteristic changing means is provided.

<Operation> As described above, when the intake pipe negative pressure during the switching control of the valve lift characteristic is small, the difference in torque before and after the switching is larger than when the intake pipe negative pressure is large.

Therefore, when the valve lift characteristic switching control is performed under the condition where the intake pipe negative pressure equivalent value detected by the intake pipe negative pressure equivalent value detecting means is small, the valve lift characteristic is increased under the condition that the intake pipe negative pressure equivalent value is large. As compared with when the switching control is performed, the switching speed is decreased so as to increase the time required from the start of the switching control until the valve lift characteristics of all the cylinders are switched, so that the torque change due to the switching is moderated. Try to reduce the shock as a thing.

<Example> An example of the present invention will be described below with reference to the drawings.

1 to 3 showing the configuration of an embodiment, both ends of an intake / exhaust valve drive cam 11 that rotates in synchronization with engine rotation and a stem end of the intake / exhaust valve 12 are brought into contact with both ends of the rocker arm. A rocker arm 13 is provided with a curved back surface 13a which is brought into fulcrum contact with a lever 15 supported at one end thereof by a hydraulic pivot 19 to be freely rocked. Further, the lever 15 holds the shaft 13b protruding from both side walls of the rocker arm 13 through the holding member 14 in the groove 15a, and between the spring seat 15b formed on the lever 15 and the holding member 14. A spring 16 having a small spring constant is interposed to bias the rocker arm 13 downward.

The hydraulic pivot 19 includes an outer cylinder 19a slidably inserted in a mounting hole 18a formed in a bracket 18 mounted on the cylinder head, and an inner cylinder 19b fitted in the outer cylinder 19a. In addition, 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 intake / exhaust valve 12 on the stem end side of the lever 15 to swingably support the lever 15. Then, from the hydraulic pressure supply passage 18b formed inside the bracket 18 to the inside of the inner cylinder 18b and the check valve 19b.
Hydraulic pressure is supplied to the hydraulic chamber 19c via d to keep the valve 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 intake / exhaust valve drive cam 11 of the lever 15 to move the swing position of the lever 15. Regulated.

The lift control cam 20 has a hexagonal shape, and six substantially flat cams so that the distance from the rotation center axis increases stepwise in one rotation direction so as to change the lift amount of the intake / exhaust valve 12 stepwise. surface
In addition to having 20a to 20f, it has a hole 20g at the center for inserting a control shaft 23 described later. Also, the lift control cam 20
The cylindrical portion 20h formed by projecting from both ends is formed in the lower arc groove 18c formed in the bracket 18 and the pair of caps 22 fastened on the bracket 18 by the bolts 21 as shown in FIGS. 2 and 3. It is rotatably held between it and the upper arc groove 22a.

Then, one control shaft 23 is inserted in a clearance fit state into a hole 20g formed through the central portion of the lift control cam 20 provided in several cylinders, and both sides of each lift control cam 20 of the control shaft 23 are inserted. One end of the torsion coil spring 24 inserted in each is locked to a stop screw 23a screwed into the outer peripheral surface of the control shaft 23, and the torsion coil spring 24 and the other end are connected to the side wall of the cylindrical portion 20h of the lift control cam 20. It is fitted and locked in the hole 20i formed in the.

One end of the control shaft 23 is connected to the stepping motor via a joint 25.
It is connected to a drive shaft 26a of 26. Stepper motor 26
Is driven by the signal output from the control circuit 27,
23 is rotated to a predetermined rotation position.

28 is a valve spring.

The control circuit 27 includes a throttle sensor 31 as intake pipe negative pressure equivalent value detecting means for detecting an intake pipe negative pressure equivalent value by detecting an opening of a throttle valve 30 provided in an intake passage 29 of the engine. And a signal from a crank angle sensor 32 including a toothed signal plate 32a and a pickup 32b.

The control circuit 27 sets the valve lift amount of the intake / exhaust valve 12 according to the operating conditions detected based on these signals, sets the switching speed at the time of switching the valve lift amount, and responds to these set values. By outputting a drive pulse to the stepping motor 26 to drive it, the valve lift amount can be switch-controlled.

Specifically, as shown in FIG. 4, as the opening degree of the throttle valve 30 increases, that is, as the intake amount increases, the valve lift amount is switched to be controlled stepwise. However, since the hammering sound at the time of switching the cam surface becomes large in the high speed range, the characteristics are such that the maximum lift amount is kept constant without switching at the predetermined speed V or higher.

On the other hand, as the opening degree of the throttle valve 30 increases, that is, under the condition where the intake pipe negative pressure equivalent value decreases, the time required from the start of the switching control until the valve lift characteristics of all the cylinders are switched is increased. Control is performed so that the switching speed is reduced as much as possible.

Next, a series of operations of this embodiment will be described.When the lift control cam 20 is in contact with the lever 15 at the cam surface 20a having the largest lift amount at the time of high speed and high load with a large throttle valve opening, 15 is pushed down to the intake / exhaust valve drive cam 11 side most. Therefore, the lower surface of the lever 15 that is in fulcrum contact with the back surface 13a of the rocker arm 13 also lowers, and the fulcrum contact point A moves to the intake / exhaust valve drive cam 11 side while sucking /
It is transmitted to the exhaust valve 12 and has a characteristic that the lift amount is large and the valve opening timing is early and the valve closing timing is late as shown by a curve 20a in FIG. As a result, the intake / exhaust capacity of the intake / exhaust valve is sufficiently enhanced, and the maximum output can be increased as much as possible.

On the other hand, when the lift control cam 20 is rotated so as to contact the lever 15 with the cam surface 20f having the smallest lift amount, for example, the end portion of the lever 15 on the intake / exhaust valve drive cam 11 side is a recessed portion.
It rises by swinging around 15c as a fulcrum, and the lower surface of the lever 15 also retracts upward.

The lower surface of the lever 15 serves as a fulcrum for the rocker arm 13 to transmit the lift of the intake / exhaust valve drive cam 11 to the intake / exhaust valve 12, but the intake / exhaust valve drive cam 11 contacts the rocker arm 13 in the base circle. The initial position of the fulcrum in this state moves to the right side in FIG. 3, that is, to the side away from the direction in which the fulcrum moves after lifting, as compared with when the lever 15 is in contact with the cam surface 20a having the large lift amount. , Rear of rocker arm 13 13
Even if the intake / exhaust valve drive cam 11 is lifted, the gap between the a and the lower surface of the lever 15 becomes large, and the speed at which the fulcrum contact point between the rocker arm 13 and the lower surface of the lever 15 shifts to the drive cam side. As shown by the curve 20f in FIG. 5, the lift amount is small, the valve opening timing is delayed, and the valve closing timing is advanced. As a result, the effective intake stroke is shortened and the amount of intake air is suppressed, so that the opening of the throttle valve 30 can be increased correspondingly and the pump loss can be reduced to improve fuel efficiency.

In this way, the lift control cam 20 is rotated to rotate the cam surface 20.
By abutting any one of a to 20f on the lever 15,
The lift characteristic of the intake / exhaust valve 12 can be changed stepwise.

Here, the rotation of the lift control cam 20 is performed by driving the stepping motor 26 via the control shaft 23 and the torsion coil spring 24. That is, the control circuit 27 outputs the drive pulse set based on the signal corresponding to the engine operating state to the stepping motor 26 as described above. This drive pulse causes the drive shaft 26a of the stepping motor 26 to rotate by a preset angle, and the control shaft passes through the joint 25.
23 also rotates.

Now, at the timing when the control shaft 23 rotates, in the cylinder where the intake / exhaust valve 12 is being lifted, the contact fulcrum between the rocker arm 13 and the lever 15 moves to the intake / exhaust valve drive cam 11 side, Large reaction force of valve spring 28 is spring 1
3, acting on the lift control cam 20 via the lever 15. Therefore, while the lift control cam 20 remains fixed, only the control shaft 23 rotates while twisting the torsion coil springs 24 on both sides thereof. Next, after the intake / exhaust valve drive cam 11 rotates to close the intake / exhaust valve 12, the rocker arm 13 and the lever 15
Since the fulcrum of contact with is located substantially above the intake / exhaust valve 12 and the reaction force of the valve spring 28 disappears, the force acting on the lift control cam 20 is between the rocker arm 13 and the lever 15. There is only a weak force on the attached spring 16. Therefore, the torque accumulated in the torsion coil spring 24 during the lift of the intake / exhaust valve 12 is
The lift control cam 20 can be rotated by overcoming the weak force of the lift control cam 20. Therefore, the output required for the stepping motor 26 is small enough to twist the torsion coil spring 24 by the turning angle of the adjacent cam surface.

Then, as a function of the control circuit 27 according to the present invention, in a region where the throttle valve opening is small, when the cam surface is switched, that is, when the valve lift amount is switched, the generation frequency of the drive pulse output to the stepping motor 26. When the valve lift amount is switched in a region where the throttle valve opening is also large, the rotation frequency is increased by increasing the value of the drive pulse generation frequency to reduce the rotation speed of the stepping motor 26. To control.

In this case, when the rotation speed of the drive shaft 26a of the stepping motor 26 is high, the torsion speed of the torsion coil spring 24 is high, and therefore the time required for switching the valve lift amounts of all the cylinders in a short time increases. To do. In this case, the switching speed of the individual cylinders is fast, and even if the time required for the characteristic switching for each cylinder is short, the switching can be performed for each cylinder at intervals, so that the torque change per unit time of the entire engine can be reduced.

With this configuration, as described above, in the region where the throttle valve opening is small, the torque change due to the valve lift amount switching is small,
With a high switching speed, priority is given to improving responsiveness by switching, and in the region of the large throttle valve opening, the torque change due to the valve lift amount switching is large. Can be relaxed.

The switching speed is set in consideration of the stability when the cam surface is engaged during the switching.

By the function of the switching speed control by the control circuit 27,
The control means in the present invention is configured, and the valve lift characteristic varying means is configured by the function of the cam surface switching control according to the operating conditions of the control circuit 27 and the other mechanical configuration.

Further, it is needless to say that the present invention can be applied to the valve lift characteristic varying means as shown in the above-mentioned conventional example, in addition to the valve lift characteristic varying means in the above embodiment.

Further, in the present embodiment, the throttle valve opening is used as a substitute (equivalent value) of the intake pipe negative pressure, but the intake pipe negative pressure directly detected may be used, as a matter of course, and the intake air flow rate and the engine rotation speed may be changed. An estimated value obtained by estimating the intake pipe negative pressure from the velocity may be used.

<Effects of the Invention> As described above, according to the present invention, when the valve lift characteristic is switched by the valve lift characteristic varying means, the switching speed is variably controlled according to the intake pipe negative pressure equivalent value, so that a low load is achieved. It is possible to obtain the effect that the shock due to switching at the time of high load can be reduced while maintaining good switching responsiveness during switching.

[Brief description of drawings]

FIG. 1 is a diagram showing the overall construction of an embodiment of the present invention, and FIG.
FIG. 4 is a partial perspective view of the above-mentioned embodiment, FIG. 3 is a partial cross-sectional view of the above-mentioned embodiment, FIG. 4 is a diagram showing operating condition characteristics for switching the valve lift amount of the above-mentioned embodiment, and FIG. FIG. 6 is a diagram showing the valve lift characteristics of the embodiment, FIG. 6 is a diagram showing the valve lift characteristics of the conventional example, and FIG. 7 is a diagram showing operating conditions for switching the valve lift amount of the conventional example. FIG. 4 is a diagram showing a characteristic of a torque change amount at the time of switching the valve lift amount with respect to the throttle valve opening of the conventional example. 11 …… Intake / exhaust valve drive cam, 12 …… Intake / exhaust valve, 13 ……
Rocker arm, 15 …… Lever, 23 …… Control axis, 24 …… Torsion coil spring, 26 …… Stepping motor, 27
...... Control circuit, 30 ...... Throttle valve, 31 ...... Throttle sensor

Claims (1)

[Claims] 1. A valve train control device for an internal combustion engine, comprising: a valve lift characteristic changing means for variably controlling lift characteristics of intake and exhaust valves according to operating conditions of a multi-cylinder internal combustion engine. When the valve lift characteristic switching control is performed under conditions where the intake pipe negative pressure equivalent value is small and the intake pipe negative pressure equivalent value is small, when the intake pipe negative pressure equivalent value is large The valve lift characteristic of the valve lift characteristic changing means is increased so as to increase the time required until the valve lift characteristics of all the cylinders are switched after the switching control is started, as compared with when the valve lift characteristic is switched. A valve speed control device for an internal combustion engine, comprising: switching speed control means for reducing the switching speed;