JPH02176129A - Valve head characteristic control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To attempt improvement in driving performance and so on of a vehicle by changing a valve head characteristic which should be selected according to the driving state of an engine by a valve head characteristic selecting means. CONSTITUTION:A valve timing (valve head characteristic) control unit 2 selects a valve head characteristic according to the driving state of an engine 1 detected by a revolution sensor 6 and a throttle sensor 7. In this case, a driving wheel slip control unit 3 detects a slip state of driving wheels by signals from driving wheel and driven wheel speed sensors 4 and 5, the selected valve head characteristic is changed corresponding to it. That is, when an over-slip state occurs, a valve head characteristic is changed to further reduce output of the engine 1. In this way, driving performance and so on of a vehicle can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve head characteristic control device for an internal combustion engine in which the valve head characteristics of an intake valve and/or an exhaust valve can be switched, and particularly to a device equipped with a driving wheel slip control device. The present invention relates to a valve lift characteristic control device for a vehicle.

(Prior art) The valve head characteristics of at least one of the intake valve and the exhaust valve can be switched between a low-speed lift characteristic suitable for the low-speed range of an internal combustion engine and a high-speed lift characteristic suitable for the high-speed range. Conventionally, there has been known a valve head characteristic control device for an internal combustion engine that detects an engine operating state (e.g. engine speed) and selects a valve head characteristic suitable for the detected engine operating state (e.g. , Special public official 1977-332
Publication No. 89).

According to this valve head characteristic control device, the valve head characteristic (
valve timing) is selected.

That is, when the engine speed Ne is less than the predetermined rotation speed Neo, the low-speed requirement lift characteristic (low-speed valve timing) is selected, and when the engine rotation speed Ne is higher than the predetermined rotation speed Neo, the high-speed requirement lift characteristic (high-speed valve timing) is selected. is selected. Here, the predetermined rotation speed Ne.

is the engine rotation speed at which the engine output torque obtained when the low speed requirement lift characteristic is selected and the engine output torque obtained when the high speed requirement lift characteristic is selected are approximately equal. Therefore, as a result of selecting the valve head characteristics as described above, the valve head characteristics that result in a relatively large engine output torque are always selected.

Generally, when the vehicle starts or accelerates, the driving force of the driving wheels is the I'i1' friction force between the tires and the road surface [friction coefficient between the tires and the road surface x load on the driving wheels of vehicle weight (vehicle load)] If the wheel speed deviation exceeds ΔV, the driving wheels will slip, but the extent of this slip is detected by the difference ΔV between the driving wheel speed and the driven wheel speed of the vehicle, and when an excessive slip state in which the wheel speed deviation ΔV becomes large is detected, Drive wheel slip control devices have been known that reduce the output torque (driving force) of the engine by reducing the amount of fuel supplied to the engine by cutting off the fuel, etc.
Publication No.). According to this drive wheel slip control device, the more the degree of excessive slip increases, the more control is performed to increase the number of cylinders in which fuel is cut off.

(Problem to be Solved by the Invention) In a vehicle equipped with the drive wheel slip control device described above, when an excessive slip state of the drive wheels is detected, control is performed to reduce the engine output, but the valve lift characteristics can be switched. In the case of an engine, the valve head characteristic that provides a relatively large engine output is selected as described above.

As a result, a situation occurs in which controls are performed in opposite directions at the same time, such as controlling to reduce the engine output on one hand and increasing the engine output on the other hand. For this reason, there remains room for improvement in aspects such as vehicle drivability.

The present invention has been made in view of the above points, and includes a driving wheel slip control device. An object of the present invention is to provide a valve head characteristic control device that can more appropriately select the valve head characteristic in an engine of a vehicle and improve the drivability of the vehicle.

(Means for Solving the Problems) In order to achieve the above object, the present invention sets a plurality of valve head characteristics of at least one of an intake valve and an exhaust valve of an internal combustion engine, and uses the set valve head characteristics of the engine. Valve lift characteristic selection means for selecting according to the operating state; driving wheel slip detection means for detecting slip of the driving wheels driven by the engine; and reducing engine output in accordance with the output of the driving wheel slip detection means. In the valve head characteristic control device for an internal combustion engine, the valve head characteristic selection means should select a valve head characteristic,
A valve head characteristic selection and change means is provided for changing the valve lift characteristic according to the output of the drive wheel slip detection means.

Further, the valve lift characteristic selection and change means is configured to control the I/O when the driving wheel slip detection means detects an excessive slip state.
H. It is desirable that the valve head characteristic to be selected by the valve distribution head characteristic selection means be changed to a valve head characteristic that further reduces the engine output.

Further, it is preferable that the valve head characteristic selection and change means operate to change when the engine operating state reaches a predetermined operating state when the valve head characteristic is changed by the valve head characteristic selection means.

Further, it is preferable that the predetermined operating state is a state in which the engine rotation speed matches a predetermined rotation speed.

Further, the valve head characteristic selection and change means performs the change operation when the engine operating state reaches a predetermined operating state of 011 when the drive wheel slip detection means detects that the drive wheel is not in an excessive slip state. It is desirable to cancel it.

Further, it is preferable that the valve head characteristic selection and change means cancels the change operation when detecting a deceleration operating state of the engine.

Note that the valve lift characteristics as used herein refers to both or one of the valve opening period and the valve lift amount.

(Operation) The valve lift characteristic selected according to the engine operating state is changed according to the slip state of the driving wheels.

When the drive wheels enter an excessive slip state, the valve head characteristic selected according to the engine operating state is changed to a valve head characteristic that further reduces the engine output.

Changes to the valve head characteristics selected according to the engine operating state are made when the engine operating state reaches a predetermined operating state, and changes are canceled when the engine operating state reaches the predetermined operating state or when the engine operating state reaches the predetermined operating state. This is done when a deceleration driving condition is detected.

(Example) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Note that "valve timing" in the description of this embodiment has the same meaning as the above-mentioned "valve head characteristic".

Figure f51 is an overall configuration diagram of a valve timing control device according to the present invention, and numeral 1 in the figure is a DOIIC internal combustion engine in which each cylinder is provided with one pair of intake valves and one pair of exhaust valves.

The engine 1 is equipped with an engine rotation speed sensor 6 that detects the engine rotation speed Ne, and a thrower valve It) degrees (θ
An electronic control unit (hereinafter referred to as rVTC-ECU) 2 for controlling valve timing li' is provided with a throttle valve opening sensor 7 for detecting Tl+).
The detection signal is supplied to

Further, an electronic control unit (hereinafter referred to as r'rcs-ECUJ) 3 for driving wheel slip control is connected to the VTC-ECU 2. This 'rC3-ECU3 includes a driving wheel speed sensor 4 that detects the driving wheel speed Vw,
A driven wheel speed sensor 5 that detects the driven wheel speed Vv (this driven wheel speed corresponds to the vehicle speed, that is, the vehicle body speed) is connected, and these sensors 4 and 5 transmit their detection signals.
rcs - Supplied to ECU3. TCS-ECU3
calculates the slip ratio λ of the driving wheels by applying the detected driving wheel speed Vw and driven wheel speed Vv to the following equation (1), and sends a signal representing the calculated slip ratio λ to the VTC knee ECU.
Supply to 2.

^= (Vw-Vv)/Vw-(1) Furthermore, TC
The S-ECtJ3 calculates a base driving wheel speed, that is, a target value Vrer of the driving wheel speed, according to the vehicle body speed Vv, and calculates the drive wheel speed based on the difference ΔV between the reference driving wheel speed Vre and the actual driving wheel speed Vw. Drive width slip control is performed based on the
When V increases to the above-mentioned speed difference, that is, when an excessive slip state of the drive wheels is detected, the control (hereinafter referred to as "control") that reduces the engine output by cutting off the fuel supplied to engine l (hereinafter referred to as "tuning cut") (referred to as "traction control"). In this l-traction control, the larger the speed difference ΔV, that is, the degree of excessive slip of the driving wheels, the more the number of cylinders to be phenyl cut is increased, and the engine output is further reduced. The TCS-ECU 3 sends a signal indicating that traction control is in progress to VT.
Supplied to C-ECU2.

The VTC-ECU 2 outputs a valve opening/closing command signal to the solenoid valve 11 based on signals from the engine speed sensor 6, throttle valve opening sensor 7, and TCS-ECU 3, and controls valve timing switching. I do.

Note that the driving wheel slip control in this embodiment is performed by reducing the engine output by the engine cut as described above, but is not limited to this, for example, by making the air-fuel ratio of the air-fuel mixture supplied to the engine leaner, or by reducing the throttle valve. This may be done by reducing the engine output by reducing the opening degree, or by applying brakes to the drive wheels.

In this embodiment, the VTC-ECU 2 constitutes a part of the valve head characteristic selection means and the valve head characteristic selection change means,
Te3-ECU3 constitutes a part of drive wheel slip detection means and engine output reduction means.

Although FIG. 2 shows an intake valve side valve train 20 that drives the intake valve r30 of each cylinder of the engine 1, a valve train having basically the same configuration as this is also provided on the exhaust valve side. This valve train 20 includes a camshaft 21 that is rotationally driven from a crankshaft (not shown) of an engine 1 at a speed ratio of 1/2, and high-speed cams provided on the camshaft 21 corresponding to each cylinder. 24 and low-speed cams 22 and 23, a rocker shaft 25 fixedly arranged parallel to the camshaft 21, and a rocker shaft 25 corresponding to each cylinder.
5, a first drive rocker arm 26, a second drive rocker arm 27, and a free rocker arm 28, and a connection switching mechanism 29 provided between each rocker arm 26, 27, and 28 corresponding to each cylinder.

In FIG. 2(b), the connection switching mechanism 29 includes a first switching bin 31 that can connect the first drive rocker arm 26 and the free rocker arm 28, and a first switch bin 31 that can connect the free rocker arm 28 and the second drive rocker arm 27. 2 switching bin 3
2, a regulation bin 33 that regulates the movement of the first and second switching bins 31 and 32, and a return spring 34 that urges each of the bins 31 to 33 toward the disconnection side.

The first driving rocker arm 26 has a bottomed first guide hole 35 opened to the rocker shaft 25 and parallel to the rocker shaft 25.
A first switching bin 31 is slidably fitted into the first switching bin 31 , and a hydraulic chamber 36 is defined between one end of the first switching bin 31 and the closed end of the first guide hole 35 . Moreover, the first driving rocker arm 2
A passage 37 communicating with the hydraulic chamber 36 is bored in the rocker shaft 25, and an oil supply passage 38 is provided in the rocker shaft 25.
is the path 3 regardless of the swinging state of the first drive rocker arm 26.
It is constantly communicated with the hydraulic chamber 36 via 7.

A guide hole 39 corresponding to the first guide hole 35 is formed in the free rocker arm 28 in parallel with the rocker shaft 25 and extends between both sides, and one end is brought into contact with the other end of the first switching pin 31. The second switching bin 32 is in the guide hole 39
is slidably fitted to.

The second drive rocker arm 27 has a bottomed second guide hole 40 corresponding to the guide hole 39 in the free rocker arm 27.
A disc-shaped regulation pin 33, which is opened to the side and is bored parallel to the rocker shaft 25 and comes into contact with the other end of the second switching pin 35, is slidably fitted into the second guide hole 40. Moreover, a guide tube 41 is fitted into the closed end of the second guide hole 40, and a shaft portion 42 that is slidably fitted into the guide tube 41 is integrally provided with the regulation bin 32 at the same angle +111I+. be done. In addition, the return spring 34 is connected to the guide cylinder 41 and the regulation bin 3.
The return spring 34 urges each bottle 31, 32, 33 toward the hydraulic chamber 36.

In this connection switching mechanism 27, as the hydraulic pressure in the hydraulic chamber 36 increases, the first switching bin 31 fits into the guide hole 39, and the second switching bin 32 fits into the second guide hole 40, so that each Rocker arms 26, 28, 27 are connected. When the oil pressure in the hydraulic chamber 36 becomes low, the spring force of the return spring 34 causes the first switching pin 31 to return to the position where the contact surface with the 21st switching pin 32 corresponds between the first drive rocker arm 26 and the free rocker arm 28. , second switching bin 3
2 is the contact surface with the regulation bottle 33 is 1! (2) Since it returns to the position where it corresponds between the 110 lever arm 28 and the second drive rocker arm 27, the connection state of each rocker arm 26, 28° 27 is released.

The supply i+lj path 38 in the rocker shaft 25 is connected to the oil pump 13 via a switching valve 12, and the switching operation of the switching valve 12 changes the oil pressure in the oil supply path 38, and therefore the connection switching machine (1' The hydraulic pressure in the hydraulic chamber 36 of 1129 is switched between high and low.
1, and the switching operation of the switching valve 12 is controlled by the VTC.
- Controlled by ECU 2 via electromagnetic valve 11.

The intake tilting device 20 of the engine I configured as described above operates as follows.The exhaust side tilting device 20 also operates in the same manner.

When a valve opening command signal is output from the VTC-ECU 2 to the solenoid valve 11, the solenoid valve 11 is operated to open, and the switching valve 1 is opened.
2 opens the valve, and the oil pressure of the feed-11 passage 38 increases. As a result, the connection switching device jR29 is operated and each rocker arm 26, 28.27 is in a connected state.The lever high speed cam 24 causes each rocker arm 26, 28.27 to be operated integrally, and No. 3121(a) is in this state. ), the pair of intake valves 30 are opened and closed at high-speed valve timing with a relatively large valve opening period and lift amount.

On the other hand, when a valve closing command signal is output from the VTC-ECU 2 to the solenoid valve 11, the solenoid valve 11 and the switching valve 12 are operated to close, and the oil pressure in the oil supply path 38 is reduced. As a result, the connection switching mechanism 29 operates in the opposite direction to the direction indicated by -, the connection state of each rocker arm 26, 28, 27 is released, and the low speed cam 2
2.23 respectively corresponding rocker arms 26.27
is activated, and the pair of intake valves 30 are activated at low valve timing with a relatively small valve opening period and reflux l-claw.

FIG. 3 is a flowchart showing a method of valve timing control by the VTC-ECU 2.

In the same figure, normal valve timing control (step 3
08) means that the engine rotational speed Ne is a predetermined rotational speed Neo (for example, s, oo) as shown by the solid line in FIG.

When the rpm is less than ) (Ne<Neo), low-speed valve timing is selected, and when it is over Neo (Ne≧Neo), high-speed valve timing is selected, that is, the valve timing that provides a relatively large engine output horn is selected. control (hereinafter referred to as "normal control"). - Force, reverse valve timing control all (step 307)
As shown by the broken line in the figure, when Ne (Neo), high-speed valve timing is selected, and when Ne≧Neo, low-speed valve timing is selected. In other words, the control selects valve timing that provides a relatively small engine output. be(
(hereinafter referred to as "reverse control"). In addition, the predetermined rotation speed Nco is
This is the engine rotation speed at which the engine output torque obtained when low-speed valve timing is selected and the engine output torque obtained when high-speed valve timing is selected are approximately equal.

In step 301, it is determined whether T CHil1gg is in progress, that is, whether excessive slip control of the drive wheels (hereinafter referred to as "traction control") is in progress, and if the answer is negative (NO), whether the valve timing has been reversed or not. That is, it is determined whether reverse rotation control is being performed (step 305). Step 30
If both answers to 1.305 are negative (No), that is, traction control is not in progress and normal control is in progress, normal control is continued (step 308). If the answer to step 305 is affirmative (Yes), that is, if reverse control is being performed, it is determined whether or not engine speed Ne is equal to the predetermined speed Nco (step 306).

When this answer is negative (No), that is, Ne-I:Nco, the reverse control is continued (step 307), while when this answer is set to 1'' (Yes), that is, when Ne = Noo, normal control is started. Migrate (step 308).

niJ Step 301) The answer is tT (Y OS)
, during the fllJll action control, it is determined whether the slip rate ^ is greater than or equal to a predetermined slip rate λ0 (for example, 8%) (step 302). This answer is negative (NO),
That is, when λ is less than λ0, the process proceeds to step 305,
Control is performed in the same way as when traction control is not in progress. As the slip ratio λ increases, the driving force F due to the frictional force between the tires and the road surface changes as shown in Figure 5, but as λ increases
This is because good drive characteristics can be obtained by traction control in the 0 range.

The answers to steps 301 and 302 are both 11t constant (Y
es), that is, when traction control is in progress and ^≧λ0 becomes 1, it is determined whether or not reverse rotation control is in progress (step 303). If this answer is affirmative (Yes), that is, if the reverse rotation control is in progress, the reverse rotation control continues as it is (step 30).
7). When the answer to step 303 is negative (No), that is, during normal control, the engine rotation speed Ne is set to the predetermined rotation speed N.
It is determined whether it is equal to eo (step 304). When the answer is negative (No), that is, Ne≠Neo, normal control is continued (step 308), while when the answer is positive (Yes), that is, No=Neo, the control is shifted to reverse (step 308). Step 307).

FIG. 6 is a diagram showing a specific example of valve timing control using the above-mentioned method. As shown in FIG. This shows an example.

In the same figure (b), normal control is in progress at time to,
A case where traction control is not being performed or a case where traction control is being performed and the slip ratio λ is λ0 is shown. In this case, normal control is performed, and low-speed valve timing is selected until time L2, and high-speed valve timing is selected after time L2.

The same figure (c) shows the case where the commuting system (1) is in progress at time 10, and the conditions of traction control being in progress and slip rate ^≧λ0 at time L1 (hereinafter referred to as "reversal condition") are satisfied. In this case Normal control until 5th time L2,
After time L2, reverse control is performed, and low-speed valve timing is selected until time 2, and low-speed valve timing is selected even after time 2. In this way, even if the reversal condition is satisfied (time L1) during normal control, the reversal fli
Since the system does not shift to J control and shifts to reverse control at time t2 when Ne=Neo is established and the engine outputs are approximately equal (in this case, low-speed valve timing is continued), normal control is switched to reverse control. It is possible to prevent shocks caused by sudden changes in engine output during the transition to . Furthermore, after time L2, valve timing with a relatively small engine output is selected, so that the degree of excessive slip of the driving wheels can be further reduced.

As a result, it is possible to reduce the number of cylinders subjected to twin cut by the Te3-ECU3 described above, so it is possible to reduce the fluctuation component of output torque caused by twin cut to some cylinders of the engine, and improve drivability. can.

In the same figure (d), reverse control is being performed at time to,
A case is shown in which the reversal condition continues to hold true even after time to. In this case, reverse control is performed, and high-speed valve timing is selected until time L2, and low-speed valve timing is selected after time L2. In this way, when the reversal condition continues to hold true, valve timing with a relatively small engine output is always selected, so
It is possible to further reduce the degree of excessive slip of the drive wheels and reduce the number of twin cylinders cut, thereby improving drivability.

In the same figure (e), reverse control is being performed at time to,
This shows a case where the reversal condition is satisfied and the reversal condition is not satisfied because λ becomes λ0 at time (, 1).In this case, reverse control is performed until time t2, and normal control is performed after time L2. Therefore, high-speed valve timing is selected until time L2, and high-speed valve timing is selected even after time t2.

In this way, if the reversal condition is not met during reversal control (time series 1
), it does not immediately shift to normal control and N e =
Since the control is shifted to normal control at time 2 when Neo is established, it is possible to prevent shocks due to sudden changes in engine output even when switching from reverse rotation control to normal control.

Furthermore, as explained in the cases of (c) and (e) in the same figure, the transition from normal control to reverse control or vice versa is N e
= Neo, so even if the friction coefficient of the road surface changes as the vehicle travels and the slip ratio λ of the drive wheels fluctuates, and the above reversal condition is met or not met frequently, The frequency of valve timing switching is reduced, and the durability of the aforementioned valve timing switching mechanism, especially the connection switching mechanism 29, can be improved.

FIG. 7 shows a modification of the control method shown in FIG.
Only step 30G of 3M is changed to step 306'. In this modification, the reversal condition (during traction control and slip rate λ≧λ0) is not satisfied,
Reverse control is in progress (the answer to step 305 is ``Yes'').
)), it is determined whether the engine is decelerating (step 306').

The determination as to whether the engine is running at low speed is performed, for example, by determining whether the throttle valve is substantially fully closed or whether the rate of change ΔNe of the engine speed Ne is less than or equal to a predetermined value. Further, a sensor is provided that detects when the throttle valve is substantially fully open, or when the rate of change △Ne of the engine speed continues to be below a predetermined value for a predetermined period of time or more, or when the brake pedal is depressed. The deceleration may be detected based on the output.

If the answer to step 306' is negative (No), that is, if the deceleration is not in progress, reverse control is continued (step 307). Shift to normal control.

In this way, even if the reversal condition is not met, normal control will not be entered unless deceleration is in progress, so as with the control method shown in FIG. It is possible to prevent the frequency of timing switching from increasing, and also to avoid the occurrence of a shock due to a sudden change in engine output when transitioning from reverse control to normal control.

In the above embodiment, the valve timing is selected according to the engine rotation speed Ne, but the invention is not limited to this.
For example, the valve timing may be selected depending on the intake pressure, or both the engine speed and the intake pressure, or the engine speed, the intake pressure, the engine cooling water temperature, etc. Furthermore, the above embodiment is an example for an engine in which two valve timings, low-speed valve timing and high-speed valve timing, can be selected. The same control as described above is also possible.

(Effects of the Invention) As detailed above, according to the valve lift 4° characteristic control device of 817 claim 1 of the present invention, the valve lift characteristic in the engine of the vehicle equipped with the drive wheel slip control device can be controlled by the drive wheel slip control device. It can be appropriately selected depending on the degree of wheel slip.

According to the valve lift characteristic control device of claim 2, during excessive slip control of the drive wheels, the valve lift characteristic with a relatively smaller engine output angle is selected, thereby further reducing the degree of excessive slip of the drive wheels. be able to.

Further, as a result, the number of cylinders to be cut for excessive slip control can be reduced, and drivability can be improved.

According to the valve head characteristic control device of claims 3 to 6, it is possible to prevent a shock caused by a sudden change in engine output when changing the valve head characteristic and/or canceling the change, and furthermore, it is possible to prevent shocks due to sudden changes in engine output when changing the valve head characteristic and/or canceling the change. The frequency of switching the valve head characteristics due to changes in the slip ratio is reduced, and the durability of the mechanism for switching the valve head characteristics can be improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is an overall configuration diagram of a valve head characteristic control device according to the present invention, Fig. 2 is a diagram showing an engine moving valve p device and its control system, and Fig. 3 is a diagram showing valve head characteristics. Fig. 4 is a diagram showing changes in engine output torque for each valve lift characteristic and selection of valve lift characteristics with respect to engine speed, and Fig. 517I shows changes in driving force with respect to drive wheel slip ratio. 6 is a diagram showing a specific example of control by the control method of FIG. 3, and FIG. 7 is a diagram showing a modification of FIG. 3. l...Internal combustion engine, 2...Electronic control unit for valve timing (valve head characteristics) control (VTC-
ECU), 3...Electronic control unit for drive wheel slip control ("1'GS-ε[J]", 4...Drive wheel speed sensor, 5...Driven wheel speed sensor, 7...
Solenoid valve, 8... switching valve, 20... valve train, 29.
...Connection switching mechanism.

Claims (1)

[Claims] 1. Valve head characteristic selection in which a plurality of valve head characteristics are set for at least one of an intake valve and an exhaust valve of an internal combustion engine, and the set valve head characteristics are selected according to the operating state of the engine. an internal combustion engine, comprising: a driving wheel slip detecting means for detecting a slip of a driving wheel driven by the engine; and an engine output reducing means for reducing engine output in accordance with an output of the driving wheel slip detecting means. The valve head characteristic control device includes a valve head characteristic selection and change means for changing the valve head characteristic to be selected by the valve head characteristic selection means in accordance with the output of the drive wheel slip detection means. Lifting head characteristic control device. 2. The valve head characteristic selection and change means changes the valve head characteristic to be selected by the valve head characteristic selection means to a valve head at which the engine output is further reduced when the driving wheel slip detection means detects an excessive slip state. 2. The valve head characteristic control device according to claim 1, wherein the valve head characteristic control device changes the characteristic. 3. The valve head characteristic selection and change means operates to change when the engine operating state reaches a predetermined operating state when the valve head characteristic selection means switches the valve head characteristic. Valve head characteristic control device. 4. The valve head characteristic control device according to claim 3, wherein the predetermined operating state is a state in which the engine rotational speed matches a predetermined rotational speed. 5. The valve lift characteristic selection change means cancels the change operation when the engine operating state reaches the predetermined operating state when the drive wheel slip detection means detects that the drive wheel is not in an excessive slip state. The valve head characteristic control device according to claim 3 or 4, characterized in that: 6. The valve head characteristic control device according to claim 3 or 4, wherein the valve head characteristic selection and change means cancels the changing operation when a deceleration operating state of the engine is detected.