JP4206898B2 - Vehicle behavior control device - Google Patents

Description

  The present invention relates to a vehicle behavior control device that controls the behavior of a vehicle.

Conventionally, as described in Japanese Patent Application Laid-Open No. 6-280633, as a control device for controlling the behavior of a vehicle, a decrease in the tire air pressure of the vehicle is detected, and the engine output is suppressed when the tire air pressure decreases. A device that changes the control amount in the traction control is known. This control device is intended to reduce tire load by reducing the engine output when the tire air pressure is reduced, thereby reducing the tire load by reducing the air pressure.
JP-A-6-280633

  In the control device described above, there is a problem that control is started early. That is, when the tire air pressure decreases, the wheel speed sensor cannot accurately detect the speed of the tire ground contact surface, and as a result, the behavior control of the vehicle is started early, and there is a possibility that appropriate control cannot be performed.

  Accordingly, the present invention has been made to solve such problems, and an object of the present invention is to provide a vehicle behavior control device that can prevent inappropriate vehicle behavior control when tire air pressure decreases. .

That is, the vehicle behavior control device according to the present invention is a vehicle behavior control device that controls the behavior of the vehicle based on the output of the wheel speed sensor, and performs behavior control when the tire pressure of the vehicle is lower than the first air pressure value. The threshold value for starting is set so that the behavior control is less likely to start than when the tire air pressure is greater than or equal to the first air pressure value, and the control amount of the behavior control is greater than when the tire air pressure is greater than or equal to the first air pressure value. Is set to be large . Here, the vehicle behavior control includes, for example, ABS (Antilock Brake System) control, TRC (Traction Control) control, and VSC (Vehicle Stability Control) control.

According to this invention, when the tire air pressure is lower than the first air pressure value, the threshold value for starting the behavior control is set so that the behavior control is less likely to start than when the tire air pressure is greater than or equal to the first air pressure value. Thereby, even if the output value of the wheel speed sensor deviates from the actual wheel speed due to a decrease in tire air pressure, it is possible to prevent the behavior control from starting early. In addition, when the tire pressure of the vehicle is lower than the first air pressure value, the start of behavior control is delayed by setting the control amount for behavior control to be larger than when the tire air pressure is greater than or equal to the first air pressure value. As a result, the effect of the control can be exhibited quickly.

  The vehicle behavior control device according to the present invention is characterized in that the drift-out suppression control is prohibited when the tire pressure of the vehicle is lower than a second air pressure value set lower than the first air pressure value.

  According to the present invention, the drift-out suppression control is prohibited when the tire air pressure greatly decreases. For this reason, when the tire air pressure drops significantly, the deviation of the steering angle sensor increases, and the target yaw rate value is set inappropriately based on the output of the steering angle sensor, so that inappropriate drift-out suppression control is performed. Can be prevented.

The vehicle behavior control device according to the present invention starts behavior control when the vehicle tire pressure is lower than the first air pressure value in the vehicle behavior control device that controls the vehicle behavior based on the output of the wheel speed sensor. Is set so that behavior control is less likely to start than when the tire air pressure is greater than or equal to the first air pressure value, and if the tire pressure of at least three wheels is lower than the first air pressure value, the wheel speed is set to All the control start threshold values of the behavior control for performing the control based on the control are changed so that the control is less likely to be started than in the case where the air pressure of the tires of at least three wheels is equal to or higher than the first air pressure value.

  According to the present invention, it is difficult to accurately estimate the vehicle body speed based on the wheel speed when the air pressure of three or more tires is reduced. Therefore, all of the behavior control that performs the control based on the wheel speed is performed. It is possible to suppress inappropriate behavior control from being performed by changing the control start threshold value so that control is difficult to start.

  According to the present invention, inappropriate vehicle behavior control can be prevented when the tire air pressure decreases.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram of a vehicle behavior control device according to an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram of a brake system in the vehicle behavior control device.

As shown in FIG. 1 and FIG. 2, the vehicle behavior control apparatus according to the present embodiment includes the wheels 15 _FL , 15 _FR , 15 _RR , 15 _RL (subscripts FL, FR, RR, RL are the left front wheel, the right wheel, respectively) The components corresponding to the front wheel, the left rear wheel, and the right rear wheel are represented. Hereinafter, the components corresponding to all four wheels are represented at a time such as wheels 15 _FL to 15 _RR . A brake ECU 1 that controls the hydraulic pressure supplied to the provided wheel cylinders 31 _{FL to} 31 _RR is provided. Further, the vehicle behavior control device includes a hydro booster 2 that generates hydraulic pressure to be supplied to each of the wheel cylinders 31 _{FL to} 31 _RR , and a brake actuator 3 that controls the hydraulic pressure based on an instruction from the brake ECU 1.

The brake ECU 1 includes output signals from the hydraulic pressure sensors 32, 33, wheel cylinder pressure sensors 34 _{FL to} 34 _RR , and accumulator pressure sensors 27, 28 for detecting the hydraulic pressure at various points in the brake system, which will be described later. And each sensor for detecting the vehicle state amount and the steering amount, for example, the wheel speed sensors 16 _{FL to} 16 _RR for detecting the wheel speed provided on each wheel, the yaw rate sensor 42 for detecting the yaw rate of the vehicle, Output signals of a lateral acceleration sensor 44 that detects lateral acceleration, a steering angle sensor 46 that detects a steering angle steered by the driver, and an air pressure sensor 47 that detects the tire air pressure of the vehicle are input. Further, the brake ECU 1 has a function of controlling the operation of the solenoid valves 35 _{FL to} 35 _RR , 36 _{FL to} 36 _RR , 37 to 40 and the pump 24 in the actuator 3.

  The hydro booster 2 is connected to the brake pedal 11 and generates a hydraulic pressure corresponding to the brake depression force, and is configured around a master cylinder 21 having a booster function for increasing the hydraulic pressure, and stores brake fluid as hydraulic oil. The reservoir 22, the electric pump 24 that increases the hydraulic pressure of the brake fluid supplied from the reservoir 22, the accumulator 23 that stores the high pressure generated by the pump 24, and the pressure generated by the pump 24 reaches a predetermined high pressure or higher. And a relief valve 25 for returning the brake fluid to the reservoir 22. Accumulator pressure sensors 27 and 28 are disposed between the accumulator 23 and the brake actuator 3. Accumulator pressure sensors 27 and 28 have different measurement ranges.

Brake actuator 3 is for controlling the hydraulic pressure supplied to each wheel cylinder 31 _FL ~31 _RR, vacuum and linear solenoid valves 35 _FL to 35 _RR for holding corresponding to the respective wheel cylinders 31 _FL ~31 _RR Linear solenoid valves 36 _{FL to} 36 _RR for wheel cylinders and wheel cylinder pressure sensors 34 _{FL to} 34 _RR for detecting wheel cylinder pressure are provided. Further, switching solenoid valves 37 to 40 for supplying hydraulic pressure supplied from the master cylinder 21 at the time of system failure, and master pressure sensors 32 and 33 for detecting the master cylinder pressure are provided.

The holding linear solenoid valve 35 _{FL to} 35 _RR and the pressure reducing linear solenoid valve 36 _{FL to} 36 _RR are all connected in series to each other, and the wheel cylinder 31 to which the pipe branched from the middle corresponds. Connected to _{FL to} 31 _RR . Wheel cylinder pressure sensors 34 _{FL to} 34 _RR are arranged on these pipes, respectively. Both ends of the holding linear solenoid valves 35 _{FL to} 35 _RR and the pressure reducing linear solenoid valves 36 _{FL to} 36 _RR are connected in parallel between the accumulator 23 and the reservoir 22, respectively.

Master pressure sensors 32 and 33 are respectively disposed on the two pipes extending from the master cylinder 21 and connected to the pipes extending to the wheel cylinders 31 _FR and 31 _RR through switching solenoid valves 37 and 38, respectively. Further, the front wheel wheel cylinders 31 _FR and 31 _FL are connected to each other via a switching solenoid valve 39, and the rear wheel wheel cylinders 31 _RR and 31 _RL are connected to each other via a switching solenoid valve 40.

Here, the linear solenoid valves 35 _{FL to} 35 _RR and 36 _{FL to} 36 _RR are all closed when OFF, and control the flow rate in proportion to the control current when ON, and the switching solenoid valves 37 to 40 are all. It opens when it is OFF, and closes when it is ON.

Therefore, at the time of system failure, the linear solenoid valves 35 _{FL to} 35 _RR and 36 _{FL to} 36 _RR are all closed, but the switching solenoid valves 37 to 40 are all open, so that they are generated by the master cylinder 2. The hydraulic pressure is supplied directly to each of the wheel cylinders 31 _{FL to} 31 _RR , so that a necessary braking force can be secured.

Under normal conditions, the brake ECU 1 refers to the detected values of the wheel cylinder pressure sensors 34 _{FL to} 34 _RR so that the hydraulic pressure applied to the wheel cylinders 31 _{FL to} 31 _RR becomes the set control oil pressure Pc, respectively. The valves 35 _{FL to} 35 _RR and 36 _{FL to} 36 _RR and the operation of the pump motor 24 are controlled.

Specifically, the case of the right front wheel 15 _FR will be described as an example. When the current wheel cylinder pressure Pm is lower than the control oil pressure Pc, that is, when pressure increase is necessary (hereinafter referred to as pressure increase mode), By closing the linear solenoid valve 36 _FL and opening the holding linear solenoid valve 35 _FR , the high pressure brake fluid on the accumulator 23 side is supplied to the wheel cylinder 31 _FR to increase its pressure.

Further, when the current wheel cylinder pressure Pm matches the control oil pressure Pc and needs to be held (hereinafter referred to as a holding mode), the brake fluid is turned off by closing the linear solenoid valves 35 _FL and 36 _FR. The cylinder 31 is held so as not to come off from the _FR side, and the pressure is held.

When the current wheel cylinder pressure Pm is higher than the control oil pressure Pc, that is, when pressure reduction is necessary (hereinafter referred to as pressure reduction mode), the pressure reducing linear solenoid valve 36 _FL is opened and the holding linear solenoid valve is opened. By closing the 35 _FR , a part of the brake fluid is returned to the reservoir 22 from the wheel cylinder 31 side to reduce the pressure.

  In the actuator 3 of FIG. 2, a linear solenoid valve is used for holding and decompressing, but control hydraulic pressure may be controlled by duty control using a switching solenoid valve. Further, the actuator for controlling the hydraulic pressure of the wheel cylinder 31 is not limited to the actuator 3 in FIG. 2, and may have other configurations and structures as long as the hydraulic pressure of the wheel cylinder 31 can be controlled. . Further, in the vehicle behavior control device, output control of an engine mounted on the vehicle can be performed by an engine ECU (not shown in FIG. 1).

  Next, the operation of the vehicle behavior control device of this embodiment will be described.

  The vehicle behavior control device according to the present embodiment controls the behavior of the vehicle based on the output of the wheel speed sensor 16, and appropriately changes the control start timing and the control content according to the tire pressure of the vehicle.

  3 and 4 show flowcharts of the operation of the vehicle behavior control apparatus according to this embodiment. As shown in S10 of FIG. 3, first, zero is set as the numerical value n. This numerical value n is a value from 0 to 3, for example, right front wheel FR when n = 0, left front wheel FL when n = 1, right rear wheel RR when n = 2, and left rear when n = 3. The control value of the wheel RL is set.

  Then, the process proceeds to S12, in which it is determined whether or not the tire air pressure P (n) P is lower than the air pressure decrease second threshold Thp2. The air pressure decrease second threshold Thp2 is a second air pressure value set in advance in the brake ECU 1. When it is determined in S12 that the tire air pressure P (n) P is not lower than the air pressure decrease second threshold Thp2, it is determined whether or not the tire air pressure P (n) P is lower than the air pressure decrease first threshold Thp1. Determination is made (S14).

  The air pressure decrease first threshold value Thp1 is a first air pressure value preset in the brake ECU 1, and is set to a value higher than the air pressure decrease second threshold value Thp2. When it is determined in S14 that the tire air pressure P (n) P is not lower than the air pressure decrease first threshold Thp1, the control start threshold and the control target value are set to normal values (S16).

  That is, ThAbs1 is set as an ABS (Antilock Brake System) control start threshold value P (n) ThAbs, ThTrc1 is set as a TRC (Traction Control) control start threshold value P (n) ThTrc, and VSC (Vehicle Stability Control) ) ThVsc1 is set as the control start threshold value P (n) ThVsc. Further, TsAbs1 is set as the ABS control target value TsAbs, and TsTrc1 is set as the TRC control target value TsTrc. These values ThAbs1, ThTrc1, ThVsc1, TsAbs1, and TsTrc1 are all set in advance in the brake ECU 1. Then, the process proceeds to S24.

  On the other hand, when it is determined in S14 that the tire air pressure P (n) P is lower than the air pressure decrease first threshold Thp1, the process proceeds to S20. By the way, when it is determined in S12 that the tire air pressure P (n) P is lower than the air pressure lowering second threshold Thp2, the VSC drift-out control is prohibited (S18). When the tire air pressure P (n) P is lower than the air pressure decrease second threshold Thp2, it is determined that the tire is punctured, and only drift-out control is prohibited in the VSC control.

  Then, the process proceeds to S20, where zero is stored in the air pressure reduction flag P (n) F, and the low pressure flag is set. Then, the process proceeds to S22, and the control start threshold value is set so that the control is difficult to start with respect to the normal value. Further, the control target value is set so that the control amount is larger than the normal value.

  That is, ThAbs2 is set as the ABS control start threshold value P (n) ThAbs, and ThTrc2 is set as the TRC control start threshold value P (n) ThTrc. Further, TsVsc2 is set as the VSC control target value P (n) TsVsc, TsAbs2 is set as the ABS control target value TsAbs, and TsTrc2 is set as the TRC control target value TsTrc. These values ThAbs2, ThTrc2, TsVsc2, TsAbs2, and TsTrc2 are all preset in the brake ECU 1.

  ThAbs1 and ThAbs2 set as the ABS control start threshold value P (n) ThAbs are numerical values relating to wheel deceleration. ThAbs2 set when the tire air pressure decreases is set to a value lower than ThAbs1 set during normal time. As a result, when the tire air pressure decreases, the control is not started unless the wheel speed is significantly lower than the vehicle speed, and the ABS control is difficult to start.

  ThTrc1 and ThTrc2 set as the TRC control start threshold value P (n) ThTrc are numerical values related to the wheel speed difference. ThTrc2 set when the tire air pressure decreases is set to a value higher than ThTrc1 set during normal time. As a result, when the tire air pressure decreases, control is not started unless the wheel deceleration difference is large, and TRC control is difficult to start.

  TsVsc2 set as the VSC control target value P (n) TsVsc is set such that the control amount is larger than TsVsc1. Further, TsAbs2 set as the ABS control target value TsAbs is set so that the control amount is larger than TsAbs1. Further, TsTrc2 set as the TRC control target value TsTrc is set so that the control amount is larger than TsTrc1. Then, the process proceeds to S24.

  In S24, n + 1 is set as the numerical value n. Then, it is determined whether or not the numerical value n is larger than 3 (S26). When it is determined that the numerical value n is not greater than 3, the process returns to S12. On the other hand, when it is determined that the numerical value n is larger than 3, the process proceeds to S28 in FIG. 4 and it is determined whether or not the low pressure flag P (n) F is smaller than 2.

  When it is determined in S28 that the total value (ΣP (n) F) of the low pressure flag P (n) F is not smaller than 2, it is assumed that the number of tires in which the air pressure has decreased is two or less, and the tire pressure The vehicle speed calculation process is performed only with the wheels that have not decreased (P (n) F = 1) (S30). Then, ThVsc1 is set as the VSC control start threshold value P (n) ThVsc (S32). ThVsc1 is a control start threshold value at the normal time, and is preset in the brake ECU 1 in advance. Then, the process proceeds to S38.

  On the other hand, when it is determined in S28 that the total value (ΣP (n) F) of the low pressure flag P (n) F is smaller than 2, it is assumed that the number of tires in which the air pressure has decreased is three or more. Calculation processing of the vehicle body speed is performed from the wheel (S34). Then, ThVsc2 is set as the VSC control start threshold ThVsc, ThAbs3 is set as the ABS control start threshold P (n) ThAbs, and ThTrc3 is set as the TRC control start threshold P (n) ThTrc ( S36).

  ThVsc2 is a VSC control start threshold value at times other than normal, and is preset in the brake ECU 1 in advance. For example, ThVsc2 is set to a value larger than ThVsc1. ThAbs3 is set to a value lower than ThAbs2. For this reason, when the tire pressure of three or more wheels is reduced, the control is not started unless the wheel speed is much lower than the vehicle speed, and the ABS control becomes more difficult to start. ThTrc3 is set to a higher value than ThTrc2. As a result, when the tire pressure of three or more wheels is reduced, control is not started unless the wheel deceleration difference is further large, and TRC control is more difficult to start.

  Then, the process proceeds to S38, and each control of VSC, ABS, and TRC is executed based on the set control start threshold value and control target value, and the control process ends.

  As described above, according to the vehicle behavior control apparatus according to the present embodiment, when the tire air pressure of the vehicle is lower than the air pressure decrease first threshold Thp1, the tire air pressure is equal to or higher than the air pressure decrease first threshold Thp1. The threshold value for starting the behavior control is set so that the behavior control is less likely to start than in the case. Thereby, even if the output value of the wheel speed sensor 16 deviates from the actual wheel speed due to a decrease in tire air pressure, it is possible to prevent the behavior control from being started early.

  In addition, when the tire pressure of the vehicle is lower than the first threshold value Thp1, the effect of the control is quickly exhibited by setting the control amount of the behavior control large so that the start of the behavior control is delayed. Can be made.

  Further, according to the vehicle behavior control device of the present embodiment, when the tire air pressure is lower than the air pressure decrease second threshold Thp2 set lower than the air pressure decrease first threshold Thp1, the drift-out suppression control is performed. Ban. For this reason, when the tire air pressure greatly decreases, the deviation of the steering angle sensor 46 increases, and the target yaw rate value is set inappropriately based on the output of the steering angle sensor 46, thereby improperly suppressing drift-out. Control can be prevented from being performed.

  Moreover, according to the vehicle behavior control apparatus according to the present embodiment, all of the behavior control that performs control based on the wheel speed when the air pressure of at least three or more tires is lower than the air pressure decrease first threshold Thp1. Change the control start threshold value so that control is difficult to start. When the air pressure of three or more tires is reduced, it is difficult to accurately estimate the vehicle body speed based on the wheel speed. For this reason, it is possible to suppress inappropriate behavior control from being performed by changing all the control start threshold values of behavior control that performs control based on the wheel speed so that the control is difficult to start.

1 is a schematic configuration diagram of a vehicle behavior control device according to an embodiment of the present invention. FIG. 2 is a hydraulic circuit diagram in the vehicle behavior control device of FIG. 1. It is a flowchart of the control processing in the vehicle behavior control apparatus of FIG. It is a flowchart of the control processing in the vehicle behavior control apparatus of FIG.

Explanation of symbols

1 ... brake ECU, 2 ... hydraulic booster, 3 ... brake actuator, 15 _FL to 15 _RR ... each wheel, 16 _FL ~ 16 _RR ... wheel speed sensor, 11 ... brake pedal, 21 ... master cylinder, 22 ... reservoir, 23 ... Accumulator, 24 ... Pump, 25 ... Relief valve, 27, 28 ... Accumulator pressure sensor, 31 _{FL to} 31 _RR ... Wheel cylinder, 32, 33 ... Master pressure sensor, 34 _{FL to} 34 _RR ... Wheel cylinder pressure sensor, 35 _FL to 35 _RR ... Linear solenoid valve for holding, 36 _{FL to} 36 _RR ... Linear solenoid valve for pressure reduction, 37 to 40 ... Switching solenoid valve, 42 ... Yaw rate sensor, 44 ... Lateral acceleration sensor, 46 ... Steering angle sensor, 47 ... Tire pressure Sensor.

Claims (3)

In a vehicle behavior control device that controls the behavior of a vehicle based on the output of a wheel speed sensor,
When the tire pressure of the vehicle is lower than the first air pressure value, a threshold value for starting the behavior control is set so that the behavior control is less likely to start than when the tire air pressure is equal to or higher than the first air pressure value. And setting the control amount of the behavior control to be larger than when the tire air pressure is equal to or higher than the first air pressure value,
A vehicle behavior control device. 2. The vehicle behavior control device according to claim 1 , wherein drift-out suppression control is prohibited when an air pressure of a tire of the vehicle is lower than a second air pressure value set lower than the first air pressure value . In a vehicle behavior control device that controls the behavior of a vehicle based on the output of a wheel speed sensor,
When the tire pressure of the vehicle is lower than the first air pressure value, a threshold value for starting the behavior control is set so that the behavior control is less likely to start than when the tire air pressure is equal to or higher than the first air pressure value. And
When the air pressure of at least three or more wheels is lower than the first air pressure value, all control start threshold values of behavior control for controlling based on the wheel speed are set, and the air pressure of at least three or more tires is the first air pressure. Change the control so that it is harder to start than when the air pressure is over 1
A vehicle behavior control device.

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