JP2003226235A - Vehicle control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle control device for changing the control characteristics of a vehicle stability control system to complement a change in braking force resulting from lower air pressure in wheels (tires) by changing the control characteristics regarding the steering of a vehicle in response to the lower air pressure in addition to issuing an alarm when the air pressure in the wheels (the tires) deviates from a preset range. <P>SOLUTION: The vehicle control device comprises air pressure alarming systems 20, 32 for detecting air pressure in the wheels 2 and issuing the alarm when the air pressure in any of wheels deviates from the preset range, the vehicle stability control system 22 for independently controlling the braking force on the wheels to control the attitude of the vehicle in its yawing direction, and control characteristic changing means 22, 28 for changing the control characteristics of the vehicle stability control system when the air pressure is detected to be lower. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle control device, and more particularly, it issues an alarm when the air pressure of wheels (tires) deviates from a predetermined range and stabilizes the vehicle in response to a decrease in air pressure. The present invention relates to a vehicle control device that changes the control characteristics of a safety control system.

[0002]

2. Description of the Related Art A vehicle equipped with an air pressure alarm system which measures the air pressure of a wheel and issues an alarm to notify the driver when the measured air pressure deviates from a predetermined range has been proposed. A vehicle stability control system has also been proposed in which the braking force on each wheel is independently controlled to control the attitude of the vehicle in the yawing direction.

[0003]

When the air pressure of the wheel decreases, the grip force of the tire, the cornering force, etc. also change. As a result, even if the same braking hydraulic pressure is applied to the wheels from the vehicle side, the braking force actually generated by the tire differs from that when the air pressure is normal. Therefore, if a vehicle stability control system that controls the attitude of the vehicle in the yawing direction by controlling the braking force on the wheels is installed, this system cannot exert its original function due to the decrease in air pressure of the wheels, There are problems such as unstable running of the vehicle.

The present invention has been made paying attention to this point, and in addition to issuing an alarm when the air pressure of wheels (tires) deviates from a predetermined range, steering the vehicle in accordance with the decrease of the air pressure. It is an object of the present invention to provide a vehicle control device that changes the control characteristics of the vehicle stability control system so that the control characteristics of the vehicle stability control system are changed so as to compensate for changes in braking force caused by a decrease in air pressure of wheels (tires).

[0005]

According to the present invention, an air pressure alarm system for detecting the air pressure of each wheel and issuing an alarm when the air pressure of any wheel deviates from a predetermined range, and a control for each wheel. A vehicle stability control system that independently controls power and controls the attitude of the vehicle in the yawing direction, and control that changes control characteristics of the vehicle stability control system when it is detected that the air pressure is low. There is provided a vehicle control device comprising: a characteristic changing unit.

According to this structure, the function of the vehicle stability control system is suppressed from being lowered due to the decrease in the air pressure of the wheels.

According to a preferred aspect of the present invention, the control characteristic changing means changes the control characteristic of the vehicle stability control system in accordance with the reduced state of air pressure and the control content of the vehicle stability control system. To do. The "lowering state" means, for example, at which position the air of the wheel is lowering, and the "control content" is, for example, the control content such as oversteer control for suppressing oversteer or understeer control for suppressing understeer. Means

According to another preferred aspect of the present invention, the control characteristic changing means starts control by the vehicle stability control system in accordance with a reduced state of air pressure and control contents of the vehicle stability control system. Advance the timing of. When the air pressure of the wheels decreases, the braking force that can be generated by the tire decreases, so the timing of starting the control is advanced.

According to another preferred aspect of the present invention, the control characteristic changing means controls the control amount of the vehicle stability control system in accordance with a decrease state of the air pressure and a control content of the vehicle stability control system. Increase. When the air pressure of the wheel decreases, the braking force that can be generated by the tire decreases, so the control amount is increased.

According to another preferred aspect of the present invention, the control characteristic changing means is responsive to the reduced state of the air pressure and the control contents of the vehicle stability control system.
The timing for releasing the control by the vehicle stability control system is advanced.

According to another preferred aspect of the present invention, the control characteristic changing means makes different changes when the air pressure of the turning inner wheel is lower and when the air pressure of the turning outer wheel is lower. To do. Since the running characteristics of the vehicle are greatly different between when the air pressure of the turning inner wheel is low and when the air pressure of the turning outer wheel is low, the vehicle stability control system is controlled by performing control according to the situation. Maximize the functions.

According to another preferred aspect of the present invention, the control characteristic changing means advances the control release timing by the vehicle stability control system when the air pressure of the turning outer wheel is reduced.

According to another preferred aspect of the present invention, the control characteristic changing means controls the timing of release of control by the vehicle stability control system in oversteer control when the air pressure of the turning inner wheel or the rear wheel is reduced. Speed up.

According to another preferred aspect of the present invention, the control characteristic changing means increases the control amount by the vehicle stability control system in the oversteer control when the air pressure of the rear wheel on the outside of the turning is reduced. In addition, the control release timing is advanced.

According to another preferred aspect of the present invention, the control characteristic changing means advances the control release timing in the oversteer control when the air pressure of the rear wheel on the inside of the turn is reduced.

According to another preferred aspect of the present invention, the control characteristic changing means advances the control start timing by the vehicle stability control system in the oversteer control when the air pressure of the front wheel on the outside of the turning is reduced. ,
Moreover, the control release timing is advanced.

According to another preferred aspect of the present invention, the control characteristic changing means changes the control characteristic of the vehicle stability control system in the oversteer control when the air pressure of the front wheel on the inside of the turn is reduced. Not performed.

According to another preferred aspect of the present invention, the control characteristic changing means sets the control start timing by the vehicle stability control system in the understeer control when the air pressure of the rear wheel on the outside of the turning is decreased. Delay and accelerate the control release timing.

According to another preferred aspect of the present invention, the control characteristic changing means sets the control start timing by the vehicle stability control system in the understeer control when the air pressure of the rear wheels on the inside of the turn is decreased. Delay and reduce the control amount.

According to another preferred aspect of the present invention, the control characteristic changing means does not change the control characteristic of the vehicle stability control system in the understeer control when the air pressure of the front wheels is low.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail with reference to the drawings. First, the configuration of the vehicle control device according to the embodiment of the present invention will be described. Figure 1
It is a block diagram showing a schematic structure of a vehicle in which vehicle control device 1 of this embodiment is carried. The vehicle control device 1 of the present embodiment detects the air pressure of the wheels (tires) 2 and issues an alarm when the air pressure deviates from an appropriate range, and
The vehicle control device is capable of correcting the control characteristics of the vehicle in accordance with changes in air pressure.

As shown in FIG. 1, the vehicle control device 1 includes a detection device 4 attached to each wheel 2 of the vehicle and a processing device 6 arranged on the vehicle body side. The vehicle of the present embodiment has a vehicle stability control (DSC: Dynamic Stabilit) functioning as an anti-lock brake system (ABS) and a traction control system (TRC).
y Control) device. This DSC device is a device that independently controls the braking force applied to each wheel to control the attitude of the vehicle in the yawing direction.

Further, the vehicle of this embodiment is provided with an electric power steering (EPS) device 7 having a variable gear ratio (Variable Gear Ratio) mechanism. Further, the vehicle of the present embodiment is equipped with a suspension device capable of changing the steering characteristics by changing the hardness of the damper and changing the vehicle height by changing the length of the damper.

The detection device 4 is mounted near the air valve of the wheel of each wheel 2, detects the pressure and temperature of the air in each wheel (inside the tire), and processes the detection result as an air pressure signal on the vehicle body side. It is configured to send to the device 6.

As shown in FIG. 2, the detection device 4 includes a pressure sensor 8 for detecting the air pressure inside each wheel (tire) and a temperature sensor 10 for detecting the temperature of the air inside the wheel (tire). , An acceleration sensor 12 for detecting an acceleration applied to the wheel 2, and a memory 14 storing a tire identification ID.
Is equipped with. The detection device 4 further includes each sensor 8,
Transmission C that generates an air pressure signal including the detection values of 10 and 12 and the tire identification ID and transmits this to the processing device 6 side.
A PU 16 and a transmitter 18 that performs transmission are provided.
The detection device 4 is configured to be operated by a built-in battery (not shown).

In this embodiment, the air pressure signal is, as shown in FIG. 3, a tire identification ID, a wheel air pressure signal, a wheel air temperature signal, an acceleration signal, an abnormal decrease code, a battery voltage signal and a failure code. Are transmitted in order from the detection device 4 to the processing device 6 side.

Tire identification ID included in the air pressure signal
Is a code used to identify that the air pressure signal is a signal from a wheel attached to the host vehicle, and is different for each processing device 4. This tire identification ID is collated with the tire identification ID registered on the processing device 6 side after being transmitted from the detection device 4. Further, the acceleration signal indicates the acceleration obtained by adding the acceleration due to the vertical movement of the wheel to the acceleration in the circumferential direction due to the rotation of the wheel. The abnormally low code is a code for notifying that the air pressure inside the wheels has dropped rapidly. Furthermore, the battery voltage signal and the failure code are signals used to notify the processing device 6 of the voltage of the built-in battery of the detection device 4 and the operating state of the detection device 4, respectively.

In this embodiment, the detection device 4 is configured to actively transmit an air pressure signal to the processing device 6 at predetermined time intervals, and this time interval changes according to the running condition of the vehicle and the like. ing. For example, when the vehicle is stopped, the air pressure signal transmission interval is set to be extremely long because the air pressure of the wheels is unlikely to change. The stop of the vehicle is determined by whether or not the output of the acceleration sensor 12 is zero. Further, during traveling, if the air pressure is within the proper range, it is transmitted at a first interval which is shorter than the vehicle stop interval but is relatively long, and when the air pressure deviates from the proper range, the first
Is transmitted at a second interval which is shorter than the interval. Further, when the air pressure changes suddenly, the air pressure signal is transmitted at the third interval shorter than the second interval.

As shown in FIG. 1, a dedicated antenna 19 for receiving the air pressure signal transmitted from each detection device 4 is arranged at a position near each wheel 2. The pneumatic signal received by each antenna 19 is transmitted to the processing device 4.

The processing device 6 includes an air pressure alarm CPU 20 and
ABS / TRC / DSC control CPU 22 and EPS /
VGR control CPU 24 and suspension control CP
A U26, a general control CPU 28, and a storage unit 30 are provided.

When the air pressure of the wheel calculated based on the air pressure signal transmitted from any of the detection devices 4 deviates from the proper range, the air pressure alarm CPU 20 determines that
Pneumatic warning light 3 located in the instrument panel
2 is turned on to notify the occupant that the air pressure of any wheel is abnormal. Since the proper range of the air pressure is related to the air temperature in the wheel, the in-wheel air temperature included in the air pressure signal is taken into consideration when determining whether or not it is the proper range.

ABS / TRC / DSC control CPU 22
Is based on various information from the steering angle sensor, throttle opening sensor, wheel speed sensor, yaw rate sensor, etc.
In-vehicle vehicle stability controller (DSC: Dynamic Stabilit
y Control) and determines the control characteristics of these devices based on the control characteristics.

Similarly, the EPS / VGR control CPU 24
Determines the control characteristics such as the change of the assist amount of the electric power steering (Electric Power Steering) device, the change of the gear ratio and the timing of these changes based on the running state and driving state of the vehicle. On the basis of,
The operation of the EPS device is controlled to obtain a predetermined steering characteristic.

Further, the suspension control CPU 26
Determines the control characteristics such as the travel characteristic control by changing the hardness of the suspension damper and the vehicle height control by changing the damper length based on the running state of the vehicle, and based on this control characteristic, the suspension device It is configured to control actuation.

Further, the total control CPU 28 is necessary for correcting changes in the running characteristics of the vehicle due to changes in the air pressure of the wheels, such as changes in grip force and cornering force, phase delay during steering, and changes in vehicle height. The amount of change in the control characteristics is calculated.

For example, when the air pressure of one of the front wheels is reduced by a certain amount, the phase delay at the time of steering due to this decrease in air pressure is corrected, and in order to maintain the steering characteristics when the air pressure is not reduced, , Which control characteristics should be changed and how much should be changed. Similarly, D due to this decrease in air pressure
In order to correct or suppress the change in the effect of the SC device and secure the running stability of the vehicle, how to change the control characteristic of the DSC device is calculated.

The amount of change in the control characteristic calculated based on such calculation is the ABS / TRC / DS for performing each control.
C control CPU 22 and EPS / VGR control CPU 2
4, sent to the suspension control CPU 26, and the control characteristics of each device are changed.

The storage means 30 stores the tire identification ID of the tire mounted on the host vehicle, data necessary for issuing an air pressure warning such as the proper air pressure of the mounted tire, and the like. Further, the storage unit 30 stores data necessary for calculating the amount of change in the control characteristic that corrects the change in the traveling characteristic due to the change in air pressure.

Next, the operation of the vehicle control system of this embodiment will be described. At the time of vehicle completion, tire replacement, etc., the tire identification ID of the detection device 4 attached to each wheel is stored in the storage means 30 of the processing device 6. In the present embodiment, since the dedicated antenna 19 is arranged for each wheel 2, by causing each antenna 19 to receive the air pressure signal from each detection device 4, the wheel at which position has which tire identification ID. Can be registered.

During the use of the vehicle, as described above, the pneumatic signal is sent from the detection device 4 to the processing device 6 at time intervals according to the situation. Based on this air pressure signal, the air pressure warning CPU 20 determines whether or not the air pressure of each wheel is within the proper range stored in the storage means 30, and when the air pressure deviates from the proper range, the air pressure warning lamp 32 is provided. Light up. When the vehicle is equipped with a device having a display screen such as a navigation device, the display shown in FIG. 4 is displayed on the screen, and the air pressure of which wheel is insufficient (or excessive). Yes, each wheel (front left wheel: FL, front right wheel: FR, rear left wheel: RL, rear right wheel: R
You may comprise so that the relationship between the air pressure of R) and an appropriate air pressure zone may be notified. Furthermore, the dedicated wristwatch may be configured to display the current air pressure of each wheel and the proper air pressure on the display unit (FIG. 5).

Further, the total control CPU 28 calculates the change amount of each control characteristic of the vehicle necessary for correcting the change of the running characteristic due to the deviation of the air pressure of the wheel from the proper range, and this change amount. CPUs 2 and 2 for controlling
4 and 26 to change the control characteristics.

In this embodiment, ABS / TRC / DSC
Drift-out is avoided by the control CPU 22 etc.
Understeer control, which is control for suppressing, and oversteer control, which is control for avoiding / suppressing spin and the like, are performed. This understeer control reduces the engine output when the deviation between the control target yaw rate and the actual yaw rate is larger than the intervention threshold value, and when the understeer tendency is not improved, the understeer control is applied to the rear wheels (rear inner wheels) inside the turn. On the other hand, the control for applying the braking force is performed. Further, in the oversteer control, when the deviation between the control target yaw rate and the actual yaw rate is smaller than the intervention threshold value, control is performed to apply a braking force to the front wheel (front outer wheel) on the outside of the turn.

In such control, basically, the control amount (braking amount) is set on the assumption that the air pressure of the wheel to be controlled (braking target) is within an appropriate range. However, when the air pressure of the target wheel deviates from the proper range, the desired effect cannot be obtained by performing the same control as when the air pressure is in the proper range. For example, when the braking force is applied to the front outer wheel by oversteer control, if the air pressure of the front outer wheel is lower than the proper range, the air pressure will be based on the control amount set on the assumption that the air pressure is in the proper range. Even if the braking force is applied to the outside front wheel without sufficient grip force due to a decrease in air pressure, the outside front wheel cannot exert a predetermined braking force on the road surface, and as a result, the desired oversteer control is performed. There will be no. Also,
Even when the air pressure of the wheels other than the control (braking) target is lower than the proper range, the desired effect cannot be obtained by performing the same control as when the air pressure is in the proper range.

Therefore, the control is changed based on which wheel the air pressure is decreasing so that the desired oversteer control is executed even when the air pressure is lower than the appropriate range. The objects to be changed are the intervention (braking start) timing of the control by the DSC device, the intervention strength (braking amount), and the release (braking removal) timing.

The characteristic change of the present embodiment is based on the control of detecting an oversteer state or an understeer state of the vehicle, braking the front outer wheel when the vehicle is oversteer, and braking the rear inner wheel when the vehicle is understeer. When is decreased, the content of this control is changed so as to compensate for the change in the traveling characteristics of the vehicle due to this decrease in air pressure.

This embodiment is shown in FIG. 6 in which the general control CPU 28 detects the air pressure of each wheel based on the air pressure of the wheel used for the air pressure alarm, and further, depending on which wheel the air pressure is decreasing. The calculation for changing the control characteristics is performed as described above. Then, this calculation result is sent to the ABS / TRC / DSC control CPU 22 that performs control, and the DSC device control with the changed content is executed.

The control characteristics of the modified DSC device are as follows. In oversteer control of spin prevention,
When the air pressure of the rear wheel on the outside of the turn is decreasing, the control amount by the vehicle stability control system is increased and the timing of releasing the control is advanced. In this state, the intervention timing does not change. However, since the rear wheel grip force and the like are relatively low and there is a tendency for oversteering, as a result, oversteer control is started at an early timing. Further, when the spinning starts, the grip of the rear wheels is suddenly lost, so a larger braking amount than usual is applied to the front outer wheels to prevent the spinning. Further, in this state, since the rear wheel grip force, cornering force, etc. are small, the lateral force generation at the rear wheel is delayed, and the vehicle body tends to return too much due to oversteer control. For this reason, the timing of releasing the braking is set earlier than usual. In this state, when the rear wheel load is large, the intervention timing is advanced. Such a load is preferably detected by a known means such as a vehicle height sensor.

In the oversteer control, when the air pressure of the rear wheels on the inside of the turn is decreasing, the timing for releasing the control by the vehicle stability control system is slightly advanced. It is preferable that the size of the advance is smaller than that when the air pressure of the rear inner ring is low. When returning from the spin state due to oversteer control, the grip force on the inner wheel side also recovers and the vehicle body returns too much (overshoot)
Tend. In order to prevent this overshoot, the timing for releasing the braking is set earlier than usual.

In the oversteer control, when the air pressure of the front wheels on the outside of the turn is decreasing, the control start timing by the vehicle stability control system is advanced and the control release timing is advanced. It is preferable that the size of the advance is smaller than that when the air pressure of the rear outer wheel is low. In this state, the air pressure of the front wheel on the outside of the turn, which is the target of oversteer control (braking), is decreasing, so control (braking) is performed at an early timing to compensate for the decrease in tire responsiveness due to the decrease in air pressure. There is. In addition, the brakes are released early to prevent excessive return due to a decrease in tire responsiveness due to a decrease in air pressure. In addition,
Intervention strength (braking force) when the vertical load on the front wheels is large
Is preferably smaller than usual. This is because the lateral force of the tire is less likely to be generated. The vertical load can be detected by various known methods. In the present embodiment, the vertical load is detected by a vehicle height sensor (not shown), and the detected value is sent to the general control CPU 28.

In the oversteer control, the control characteristic of the DSC device is not changed when the air pressure of the front wheel on the inside of the turn is reduced.

In the understeer control for braking the rear inner wheel, when the air pressure of the rear wheel on the outside of the turn is low, the control start timing is delayed and the control release timing is advanced. It is preferable that the amount of advance is smaller than that during oversteer control in which the air pressure of the rear outer wheel is reduced. The control start timing is delayed by setting the target yaw rate small. In this state, the grip force on the rear wheel side is relatively low, and the steering wheel tends to exceed the grip limit when the braking force is applied to the rear inner wheel by the understeer control. Therefore, the control start timing is delayed to prevent the rear wheel from exceeding the grip limit. For the same reason, the intervention amount (control amount) may be further reduced.
Further, the understeer control increases the side slip angle of the vehicle body and saturates the grip force of the rear outer wheel to prevent spin from occurring, so that the control is released earlier.

In the understeer control, when the air pressure of the rear wheel on the inside of the turn is decreasing, the control start timing is delayed and the control amount is decreased. The control start timing is delayed by setting the target yaw rate small. In this state, the gripping force on the rear wheel side is relatively low and oversteering tends to occur. Therefore, when the braking force is applied to the rear inner wheel by the understeer control, the rear wheel easily exceeds the grip limit. Therefore, the control start timing is delayed to prevent the rear wheel from exceeding the grip limit. Further, since the air pressure of the rear inner wheel to be controlled (braking) is low, if the braking force is applied by the control of the normal DSC device, the lateral force of the rear inner wheel may be suddenly lost, resulting in a spin. . Therefore, the strength of the intervention (braking) is weakened by reducing the gain. At the same time,
Control may be released earlier.

Further, the understeer control does not change the control characteristic of the control when the air pressure of the front wheel on the outer side or the inner side of the turning is reduced.

Further, when the air pressure of the steered wheels decreases, the steering wheel operation becomes heavy, and a phase delay occurs during steering. Therefore, in the present embodiment, the total control CPU 28 calculates the amount of change in the control of the EPS device necessary to compensate for the characteristic change at the time of steering due to the decrease in the air pressure in the wheels, and the calculated result is used to control the EPS device. CPU2 for EPS / VGR
4, the basic control characteristics of the EPS device are added to the calculated change amount, and the EPS device is controlled in consideration of the decrease in air pressure.

EPS control is performed based on the characteristics thus determined (changed). Specifically, the VGR gear ratio of the EPS device and / or the assist amount and assist timing of the EPS device are changed, the EPS device control with the changed contents is executed, and a predetermined steering characteristic is realized.

Furthermore, when the air pressure of the wheels becomes low,
Since the vehicle height decreases, in the present embodiment, the total control CPU2
8 calculates the amount of change in the control amount of the suspension that corrects the decrease in the air pressure based on the air pressure in the wheel, and the CPU 26 for the suspension that controls the calculated result.
Then, the suspension device is controlled in consideration of the change amount, and the vehicle is maintained horizontally at a predetermined vehicle height.

Further, when the air pressure of the wheel becomes high, the vibration characteristic changes and the riding comfort deteriorates. Therefore, in this embodiment,
The total control CPU 28 calculates the amount of change in the suspension control amount that corrects the air pressure that is too high, based on the in-wheel air pressure of each wheel, and sends the result of this calculation to the suspension CPU 26 that performs control, and changes the amount. Is performed to maintain the vibration characteristics of the vehicle in an appropriate state.

The above-mentioned change of the control characteristic is performed so as to correct the change in the characteristic of the vehicle caused by the air pressures of the plurality of wheels even when the air pressures of the plurality of wheels deviate from the proper ranges.

According to the present invention, the control characteristic of the DSC device of the vehicle is changed only when the wheel air pressure deviates from the proper range, or the wheel air pressure deviates from the optimum value. The configuration may be performed from time to time. Further, it is preferable that the degree of advancement or delay of the timing of intervention or cancellation of the control of the DSC device and the amount of change in the intervention strength are set according to the degree of decrease in the air pressure of the corresponding wheel.

The present invention is not limited to the above embodiment, but various changes and modifications can be made within the scope of the matters described in the claims.

In the above embodiment, a dedicated antenna is arranged for each detection device 4, but one antenna may be configured to receive the air pressure signal from each detection device 4. . In this case, when registering,
The tire identification ID is registered on the processing device side.

Further, in the above embodiment, each detecting device is configured to actively transmit an air pressure signal at a predetermined time interval. However, the detecting device processes the air pressure signal in response to a command from the processing device side. It may be configured to transmit to the side.

[0063]

According to the present invention, in addition to issuing an alarm when the air pressure of the wheels (tires) deviates from a predetermined range, the control characteristic relating to the steering of the vehicle is changed according to the decrease of the air pressure. There is provided a vehicle control device that changes a control characteristic of a vehicle stability control system so as to compensate for a change in a braking force caused by a decrease in air pressure of a (tire).

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a vehicle equipped with a vehicle control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a detection device.

FIG. 3 is a diagram showing a data format of a pneumatic signal.

FIG. 4 is an illustration of a wheel air pressure display.

FIG. 5 is a view showing a dedicated wristwatch displaying air pressure of wheels.

FIG. 6 is a table showing changes in control characteristics of the DSC device.

[Explanation of symbols]

1: Vehicle control device 2: Wheel 4: Detection device 6: Processing device

Claims (15)

[Claims] 1. An air pressure alarm system that detects the air pressure of each wheel and issues an alarm when the air pressure of any wheel deviates from a predetermined range, and the yawing of the vehicle by independently controlling the braking force for each wheel. A vehicle stability control system for controlling the attitude of the vehicle, and a control characteristic changing means for changing the control characteristic of the vehicle stability control system when it is detected that the air pressure is low. And a vehicle control device. 2. The control characteristic changing means changes the control characteristic of the vehicle stability control system in accordance with a reduced state of air pressure and the control content of the vehicle stability control system. Vehicle control device. 3. The control characteristic changing means accelerates the control start timing by the vehicle stability control system in accordance with the reduced state of the air pressure and the control content of the vehicle stability control system. 2. The vehicle control device according to item 2. 4. The control characteristic changing means increases the control amount of the vehicle stability control system in accordance with the reduced state of air pressure and the control content of the vehicle stability control system. The vehicle control device according to any one of 1. 5. The control characteristic changing means advances the timing of release of control by the vehicle stability control system in accordance with the state of decrease in air pressure and the control content of the vehicle stability control system. The vehicle control device according to any one of 4 above. 6. The control characteristic changing means makes different changes when the air pressure of the turning inner wheel is low and when the air pressure of the turning outer wheel is low. The vehicle control device according to Item 1. 7. The control characteristic changing means advances the timing of release of control by the vehicle stability control system when the air pressure of the turning outer wheel is lowered, according to any one of claims 1 to 6. Vehicle control device. 8. The control characteristic changing means advances the control release timing by the vehicle stability control system in oversteer control when the air pressure of the turning inner wheel or the rear wheel is lowered. The vehicle control device according to any one of claims. 9. The control characteristic changing means increases the control amount by the vehicle stability control system in the oversteer control when the air pressure of the rear wheels on the outside of the turn is decreased, and sets the control release timing. The vehicle control device according to any one of claims 1 to 7, which is advanced. 10. The control characteristic changing means advances the control release timing by the vehicle stability control system in oversteer control when the air pressure of the rear wheels on the inside of the turn is reduced. The vehicle control device according to any one of claims. 11. The control characteristic changing means advances the control start timing and the control release timing by the vehicle stability control system in the oversteer control when the air pressure of the front wheels on the outside of the turn is reduced. The vehicle control device according to any one of claims 1 to 7. 12. The control characteristic changing means does not change the control characteristic of the vehicle stability control system in the oversteer control when the air pressure of the front wheels on the inside of the turn is reduced. The vehicle control device according to any one of claims. 13. The control characteristic changing means delays the control start timing by the vehicle stability control system and sets the control release timing in the understeer control when the air pressure of the rear wheel on the outside of the turn is decreased. The vehicle control device according to any one of claims 1 to 7, which is advanced. 14. The control characteristic changing means delays the control start timing by the vehicle stability control system and reduces the control amount in the understeer control when the air pressure of the rear wheels on the inside of the turn is decreasing. The vehicle control device according to any one of claims 1 to 7. 15. The control characteristic changing means does not change the control characteristic of the vehicle stability control system in the understeer control when the air pressure of the front wheels is low. The vehicle control device described in the paragraph.