JP2010202104A - Vehicular behavior control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular behavior control device capable of ensuring the safety of a vehicle by improving the intervention level of the behavior control if the possibility of dropping the friction coefficient of a road surface is high even when a driver drops the intervention level of the behavior control. <P>SOLUTION: The vehicular behavior control device 20 includes a behavior detection means for detecting the over-steer state or the under-steer state of a vehicle, a behavior control means for performing the behavior control to reduce the over-steer state or the under-steer state by generating the controlled power difference between right and left wheels according to the result of detection of the behavior detection means, a behavior control mode selecting means for changing the intervention level of the behavior control means according to the operation by a driver, and a friction coefficient drop determination means for determining a symptom of the friction coefficient drop of a road surface when the vehicle travels. The behavior control means improves the intervention level of the behavior control if the intervention level of the behavior control is dropped by the input from the behavior control mode changing means, and the friction coefficient drop determination means determines the symptom of the friction coefficient drop. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle behavior control device that stabilizes the behavior of a vehicle by generating a yaw moment in a recovery direction when the vehicle such as an automobile is oversteered or understeered.

A vehicle behavior control device provided in a vehicle such as an automobile generates a yaw moment in the restoring direction by generating a braking / driving force difference between the left and right wheels when an oversteer behavior or understeer behavior occurs. Is to secure.
Such a vehicle behavior control device includes a cancel switch for stopping the behavior control described above by a driver's operation in order to cope with special traveling conditions such as sports traveling and muddy ground traveling and to comply with legal regulations. .

The behavior control described above is particularly effective when traveling on a low friction coefficient road surface such as a snowy road or a frozen road, so even if the driver stops the behavior control for some reason, the friction of the road surface When the coefficient decreases, it is preferable to resume the behavior control.
As a conventional technique for varying the vehicle control state in consideration of the friction coefficient of the road surface, for example, Patent Document 1 discloses that the fastening force of the transfer clutch of a four-wheel drive vehicle is increased when the outside air temperature is lowered or the wiper is operated. A technique for ensuring running stability is described.

JP 2004-359213 A

When the driver stops the behavior control when traveling on a road surface having a high friction coefficient, the vehicle behavior control device normally maintains the state in which the behavior control is stopped even when the environment changes. For this reason, for example, the driver has forgotten that the behavior control has been stopped, and if the friction coefficient of the road surface decreases due to changes in temperature or weather, even if oversteer behavior or understeer behavior occurs Control does not intervene and it becomes difficult to ensure the stability of the vehicle.
The same problem occurs not only when the behavior control is completely stopped, but also when the intervention level in the behavior control device capable of selecting a plurality of intervention levels is lowered. Such behavior control with a low intervention level includes, for example, delaying the start of yaw moment generation compared to the normal control mode, reducing the generated yaw moment, and engine output control (traction control) performed during normal operation. Something that is not done.
The problem of the present invention is that even if the driver reduces the intervention level of the behavior control, if there is a high possibility that the friction coefficient of the road surface is reduced, the intervention level of the behavior control is improved to improve the stability of the vehicle. It is providing the vehicle behavior control apparatus which can ensure.

The present invention solves the above-described problems by the following means.
According to a first aspect of the present invention, there is provided behavior detection means for detecting an oversteer state or an understeer state of a vehicle, and a braking / driving force difference between right and left wheels is generated according to a detection result of the behavior detection means. A behavior control means having a first control mode for performing behavior control for reducing an understeer state and a second control mode having an intervention level lower than that of the first control mode; and A vehicle behavior control device comprising behavior control mode selection means for selecting the first control mode and the second control mode, and friction coefficient decrease determination means for determining a sign of a decrease in friction coefficient of the road surface while the vehicle is traveling Wherein the behavior control means has the second control mode selected by the input from the behavior control mode selection means and the friction control means. If the coefficient drop judging means determines the sign of the friction coefficient decreases, a vehicle behavior control device, characterized in that switching the behavior control means to said first control mode.
In addition, as the control in the second control mode, for example, the behavior control is turned off, the start of generation of the braking / driving force difference is delayed with respect to the first control mode, and the generation amount of the braking / driving force difference is reduced. The engine output restriction that is performed simultaneously with the occurrence of the braking / driving force difference can be used.

The invention according to claim 2 is characterized in that the friction coefficient decrease determining means determines the sign of the friction coefficient decrease when the outside air temperature of the vehicle becomes lower than a predetermined threshold value. It is a behavior control device.
The invention according to claim 3 is characterized in that the friction coefficient decrease determining means calculates an estimated friction coefficient of a road surface by comparing an estimated vehicle behavior calculated using the model of the vehicle with an actual vehicle behavior. A vehicle behavior control device according to claim 1.
According to a fourth aspect of the present invention, when the behavior control unit selects the second control mode by the behavior control mode selection unit after switching to the first control mode, the friction coefficient decrease determination unit The vehicle behavior control device according to any one of claims 1 to 3, wherein the second control mode is maintained regardless of a determination result.

According to the present invention, the following effects can be obtained.
(1) When the second control mode is selected by the input from the behavior control mode selection means and the friction coefficient lowering determination means determines the sign of the lowering of the friction coefficient, the behavior control means has a higher intervention level. By switching to the control mode 1, the driver can prevent the vehicle from traveling on a low friction coefficient road surface with the behavior control intervention level lowered, such as turning off the behavior control unintentionally. Can be ensured.
(2) By determining the sign of a decrease in the coefficient of friction when the outside air temperature decreases, it is possible to detect signs of road surface freezing or the like with a very simple configuration and to ensure the stability of the vehicle.
(3) By calculating the estimated friction coefficient of the road surface by comparing the estimated vehicle behavior calculated using the model of the vehicle with the actual vehicle behavior, the friction coefficient of the road surface can be accurately estimated. The stability of the vehicle can be ensured by restarting the behavior control when the coefficient is low.
(4) When the second control mode is selected by the behavior control mode selection unit after switching to the first control mode, the second control mode is maintained regardless of the determination result of the friction coefficient decrease determination unit. Thus, the driver can respect the intention to continue driving by lowering the intervention level of behavior control, and the trouble of the driver changing the behavior control mode many times can be eliminated.

It is a figure which shows the structure of the Example of the vehicle behavior control apparatus to which this invention is applied. It is a flowchart which shows operation | movement at the time of behavior control restart of the vehicle behavior control apparatus of FIG.

  Even if the driver reduces the intervention level of the behavior control, the present invention improves the intervention level of the behavior control and ensures the stability of the vehicle if the road surface friction coefficient is likely to decrease. The problem of providing a vehicle behavior control device that can perform the problem is solved by resuming the behavior control when the outside air temperature falls below a threshold value after the driver performs the behavior control cancel operation.

Embodiments of a vehicle behavior control apparatus to which the present invention is applied will be described below. The vehicle behavior control device according to the embodiment is provided in an automobile such as a passenger car, for example.
FIG. 1 is a diagram illustrating a configuration of a vehicle behavior control apparatus according to an embodiment.
The vehicle behavior control device 1 includes a hydraulic control unit (HCU) 10 and a behavior control control unit 20.
The behavior control control unit 20 includes a behavior control cancel switch 21, vehicle speed sensors 31 to 34, a steer angle sensor 40, a yaw rate sensor 50, a lateral G sensor 60, an outside air temperature sensor 70, an engine control unit (ECU) 80, and the like. Directly or indirectly via a communication means such as an in-vehicle LAN such as a CAN communication system.

  The HCU 10 includes a motor pump that pressurizes the brake fluid, and a solenoid valve that performs flow path switching and pressure adjustment of the pressurized brake fluid. Further, the HCU 10 is connected to a wheel cylinder FR (front right) 11, a wheel cylinder FL (front left) 12, a wheel cylinder RR (back right) 13, and a wheel cylinder RL (back left) 14 via line pipes. . Each of the wheel cylinders 11 to 14 is provided in a caliper of a service brake that brakes a wheel at each position, and presses the brake pad against the disc rotor by the pressure of the brake fluid. The HCU 10 can individually control the brake fluid pressures of the wheel cylinders 11 to 14 in accordance with a control signal from the behavior control unit 20.

The behavior control unit 20 detects the understeer state and the oversteer state of the vehicle based on information from each sensor, and controls the HCU 10 to generate a braking force difference between the left and right wheels to generate a yaw moment in the restoring direction. The behavior control is performed.
That is, the behavior control unit 20 functions as a behavior detection unit that detects an understeer state or an oversteer state of the vehicle, and a behavior control unit that generates a braking force difference between the left and right wheels according to the detection result of the behavior detection unit. .
The behavior control unit 20 includes an information processing device such as a CPU, a storage device such as a RAM and a ROM, an input / output interface, and the like.

The behavior control unit 20 determines whether or not the vehicle is currently in an understeer state based on the outputs of the vehicle speed sensors 31 to 34, the steer angle sensor 40, the yaw rate sensor 50, and the lateral G sensor 60. It is determined whether or not there is.
Then, when the vehicle is in an understeer state, the behavior control control unit 20 generates a yaw moment in the recovery direction by increasing the braking force of the rear wheel on the turning inner wheel side, for example. In addition, when the vehicle is in an oversteer state, the behavior control control unit 20 increases the braking force of the front wheel on the turning outer wheel side to generate a yaw moment in the recovery direction, for example. At this time, the behavior control control unit 20 outputs a control signal to the ECU 80, and executes control for reducing the output of the engine as necessary.
The behavior control control unit 20 includes a behavior control cancel switch 21. The behavior control cancel switch 21 is behavior control stop operation means (behavior control mode selection means) that is provided on, for example, an instrument panel in a cabin, and for which the driver inputs the behavior control stop operation described above. That is, the driver can select the first control mode according to the present invention in which the behavior control is turned on and the second control mode according to the present invention in which the behavior control is turned off by the behavior control cancel switch 21. ing.

  The vehicle speed sensor FR (front right) 31, the vehicle speed sensor FL (front left) 32, the vehicle speed sensor RR (back right) 33, and the vehicle speed sensor RL (back left) 34 are provided in a hub portion that rotatably supports the wheels at the respective positions. The vehicle speed pulse signal corresponding to the rotational speed of the wheel is output. The vehicle speed of the vehicle can be calculated based on the interval of the vehicle speed pulse signal.

The steering angle sensor 40 detects the steering angle of the front wheels by the driver's steering operation. The steering angle sensor 40 includes, for example, an encoder that detects an angular position of a steering shaft (column) to which a steering wheel is connected.
The yaw rate sensor 50 detects the rotational speed of the vehicle body around the vertical axis.
The lateral G sensor 60 detects acceleration in the vehicle width direction that acts on the vehicle body.
The outside air temperature sensor 70 detects outside air temperature around the vehicle body. The behavior control control unit 20 described above determines a sign of a decrease in the friction coefficient of the road surface on the assumption that the road surface is likely to be frozen or snowfall when the outside air temperature becomes, for example, 0 ° C. or less. In other words, the outside air temperature sensor 70 functions as the friction coefficient reduction determining means in the present invention in cooperation with the behavior control unit 20.

  The ECU 80 comprehensively controls an engine (not shown) that is a driving power source for the vehicle and its auxiliary equipment. The ECU 80 provides the behavior control control unit 20 with information related to the operating state such as on / off of the engine, and controls the electric throttle valve of the engine in accordance with the control signal from the behavior control control unit 20 to suppress the engine output. Etc.

In the vehicle behavior control apparatus of the embodiment, even when the driver stops the behavior control by the behavior control control unit 20 by the behavior control cancel switch 21, the outside air temperature of the vehicle detected by the outside air temperature sensor 70 is equal to or less than a predetermined threshold value. In such a case, the behavior control is resumed assuming that there is a high possibility of snowfall or road surface freezing.
FIG. 2 is a flowchart illustrating an operation when the behavior control is resumed in the vehicle behavior control device of the embodiment. Hereinafter, the steps will be described step by step.

<Step S01: Judgment during vehicle travel>
The behavior control control unit 20 determines whether the engine is on and the vehicle is running based on the outputs of the ECU 80 and the vehicle speed sensors 31 to 34.
If the vehicle is traveling, the process proceeds to step S02. If the vehicle is not traveling, a series of processing ends (returns).

<Step S02: Behavior control cancel switch on determination>
The behavior control control unit 20 determines whether or not the behavior control cancel switch 21 is turned on by the driver.
If the behavior control cancel switch 21 is on (behavior control cancellation), the process proceeds to step S03. If the behavior control cancel switch 21 is off (behavior control maintained), a series of processing ends (returns).

<Step S03: External temperature judgment>
The behavior control unit 20 compares the outside air temperature of the vehicle detected by the outside air temperature sensor 70 with a predetermined threshold value (for example, 0 ° C.) set in advance.
If the outside air temperature is equal to or lower than the threshold value, the process proceeds to step S04 on the assumption that the road surface friction coefficient is likely to decrease due to road surface freezing or snowfall. If the outside air temperature exceeds the threshold value, the friction coefficient decreases. Since it is unlikely to be performed, the process proceeds to step S05.

<Step S04: Behavior Control Function Revival>
The behavior control unit 20 resumes the behavior control described above.
Thereafter, the process proceeds to step S06.

<Step S05: Behavior control off continuation>
The behavior control unit 20 maintains the state where the behavior control described above is stopped.
Thereafter, the process proceeds to step S09.

<Step S06: Judgment of presence or absence of behavior control cancel switch operation by driver>
The behavior control control unit 20 determines whether or not the behavior control cancel switch 21 is turned on again (behavior control cancel operation) by the driver after restarting the behavior control in step S04.
When there is an on operation, the process proceeds to step S07, and when there is no on operation, the process proceeds to step S08.

<Step S07: Change to behavior control off>
The behavior control unit 20 stops the behavior control described above again. The stop of the behavior control is maintained until the system is reset in step S10.
Thereafter, the process proceeds to step S09.

<Step S08: Maintain behavior control on>
The behavior control unit 20 maintains the state in which the behavior control described above is turned on.
Thereafter, the process proceeds to step S09.

<Step S09: Engine stop determination>
The behavior control unit 20 communicates with the ECU 80 to determine whether or not the engine has been stopped.
When the engine is stopped, the process proceeds to step S10. When the engine is not stopped, the series of processes is ended (returned).

<Step S10: Reset>
The behavior control control unit 20 resets the system so that behavior control is turned on at the next engine start, and then ends (returns) a series of processes.

According to the embodiment described above, the following effects can be obtained.
(1) When behavior control is stopped by the input from the behavior control cancel switch 21 and the outside air temperature becomes 0 ° C. or lower, the behavior control is resumed by unintentionally stopping the behavior control by the driver. In this state, it is possible to prevent the vehicle from traveling on a low friction coefficient road surface such as a frozen road or a snowy road, and to ensure the stability of the vehicle. As a result, for example, when the driver does not notice a decrease in temperature, forgets that the behavior control cancel switch 21 is operated, or when the behavior control cancel switch 21 is erroneously operated, safety is ensured. it can.
(2) By determining the sign of a decrease in the coefficient of friction when the outside air temperature decreases, it is possible to detect signs of road surface freezing or the like with a very simple configuration and to ensure the stability of the vehicle. Since such an outside air temperature sensor is generally installed in a vehicle, it is not necessary to add new hardware.
(3) When behavior control stop operation is input again from the behavior control cancel switch 21 after the behavior control is resumed, the driver dares to behave by maintaining the behavior control stopped regardless of the outside temperature. While respecting the intention to stop the control and continue traveling, it is possible to eliminate the trouble of the driver performing the behavior control stop operation many times.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configuration of the vehicle behavior control device is not limited to the above-described embodiment, and can be changed as appropriate. For example, the vehicle behavior control device of the embodiment generates a yaw moment due to a difference in braking force by varying the braking force of the left and right wheels. For example, a torque vectoring device that varies the left and right drive torque distribution is used. The yaw moment may be generated by the difference between the left and right driving forces. Further, the method for detecting the understeer state and the oversteer state is not particularly limited.
(2) In the embodiment, the sign of the decrease in the friction coefficient of the road surface is determined based on the decrease in the outside air temperature, but the present invention is not limited to this, and the sign of the decrease in the friction coefficient of the road surface is determined by other methods. You may judge. For example, the estimated friction coefficient of the road surface is calculated by comparing the estimated yaw rate calculated by giving the actual vehicle speed, steering angle, etc. to the model of the host vehicle and the actual yaw rate detected by the yaw rate sensor, and the estimated friction coefficient decreases. In this case, behavior control may be resumed.
(3) In the embodiment, the behavior control is resumed when the behavior control is turned off by the behavior control cancel switch and there is an indication of a decrease in the friction coefficient of the road surface. However, the present invention is not limited to this. When the control has a plurality of modes with different intervention levels and a control mode with a low intervention level is selected by the driver's selection operation, the mode is changed to a behavior control mode with a high intervention level according to the sign of a decrease in the friction coefficient of the road surface. You may make it switch.

1 Vehicle Behavior Control Device 10 Hydraulic Control Unit (HCU)
11 Wheel cylinder FR 12 Wheel cylinder FL
13 Wheel cylinder RR 14 Wheel cylinder RL
20 Behavior Control Control Unit 21 Behavior Control Cancel Switch 31 Vehicle Speed Sensor FR 32 Vehicle Speed Sensor FL
33 Vehicle speed sensor RR 34 Vehicle speed sensor RL
40 Steer angle sensor 50 Yaw rate sensor 60 Lateral G sensor 70 Outside air temperature sensor 80 Engine control unit (ECU)

Claims (4)

Behavior detecting means for detecting an oversteer state or understeer state of the vehicle;
Compared to the first control mode and the first control mode for performing behavior control for reducing the oversteer state or the understeer state by generating a braking / driving force difference between the left and right wheels according to the detection result of the behavior detection means. Behavior control means having a second control mode with a low intervention level;
Behavior control mode selection means for selecting the first control mode and the second control mode of the behavior control means in response to an operation by a driver;
A vehicle behavior control device comprising: a friction coefficient decrease determining means for determining a sign of a decrease in the friction coefficient of a road surface on which the vehicle is traveling,
The behavior control unit is configured to control the behavior control when the second control mode is selected by an input from the behavior control mode selection unit and the friction coefficient decrease determination unit determines the sign of the friction coefficient decrease. A vehicle behavior control device characterized by switching means to the first control mode. 2. The vehicle behavior control device according to claim 1, wherein the friction coefficient decrease determination unit determines an indication of the friction coefficient decrease when an outside air temperature of the vehicle becomes lower than a predetermined threshold value. 2. The vehicle according to claim 1, wherein the friction coefficient decrease determination unit calculates an estimated friction coefficient of a road surface by comparing an estimated vehicle behavior calculated using the model of the vehicle with an actual vehicle behavior. Behavior control device. The behavior control means, when the second control mode is selected by the behavior control mode selection means after switching to the first control mode, irrespective of the determination result of the friction coefficient decrease determination means. The vehicle behavior control device according to any one of claims 1 to 3, wherein two control modes are maintained.

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