JP2005112203A - Treading strength estimating device and vehicle behavior control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treading strength estimating device for detecting the treading strength without a master cylinder pressure sensor, and a vehicle behavior control device using the device. <P>SOLUTION: A control device ECU estimates that a brake pedal BP is stepped more strongly in the case where a time difference from the on-state of a stop switch STP to the on-state of an end switch PMC (the change time to the state BS0 to BS2: the period of the state BS1) is small as compared with the case of a large time difference. In order to quickly move the brake pedal BP, the treading strength should be large. When the time difference (the period of BS1) is small, it is estimated that the brake pedal BP is stepped strongly. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pedaling force strength estimation device and a vehicle behavior control device, and more particularly to a pedaling force strength estimation device and a vehicle behavior control device that can detect pedaling strength even when there is no master cylinder pressure sensor.

Conventionally, as described in, for example, Patent Document 1 below, a master cylinder pressure sensor that detects the pressure in the master cylinder has been used to detect the depression strength of the brake pedal, in other words, the driver's intention to brake. It was. A vehicle behavior control device using such a master cylinder pressure sensor is also known.
JP 11-124022 A

  However, the conventional pedal force intensity estimation device and vehicle behavior control device require a master cylinder pressure sensor that directly detects the pressure in the master cylinder, which increases the number of parts and increases the product price. .

  The present invention has been made in view of the above problems, and provides a pedal force intensity estimating device capable of detecting a pedal force strength without using a master cylinder pressure sensor, and a vehicle behavior control device using the same. Objective.

  In order to solve the above-described problem, a pedal effort strength estimating apparatus according to claim 1 is a pedal effort strength estimating apparatus for estimating a pedal pedal depression strength, wherein the first detection means detects that the brake pedal is at a front position or more. And the second detection means for detecting that the brake pedal is at the rear position or more, and the time difference between when the first detection means generates an output and when the second detection means generates an output is large. As compared with the case, it is characterized by comprising estimation means for estimating that the brake pedal is strongly depressed.

  Each detection means generates an output at each position or more. When the time difference due to these detection means is small, it is equivalent to the brake pedal quickly moving from the front position to the back position. Therefore, in order to move the brake pedal quickly, the pedaling force needs to be large. In this case, it can be estimated that the estimation means depresses the brake pedal more strongly than when the time difference is large.

  According to a second aspect of the present invention, there is provided a vehicle behavior control device according to the first aspect, a pedal force intensity estimating device according to the first aspect, a master cylinder linked to a brake pedal, a wheel cylinder communicating with the master cylinder, and a hydraulic pressure between the master cylinder and the wheel cylinder. A switching valve provided in the path, a pressure adjusting valve for increasing, reducing, or holding the inside of the wheel cylinder with the switching valve closed, and a control device for controlling the pressure adjusting valve. The pressure regulating valve is controlled based on the pedal effort output from the strength estimating device.

  When controlling vehicle behavior, the vehicle behavior is usually controlled by the pressure regulating valve of the wheel cylinder with the switching valve closed. By using the braking control by the adjusting valve, the braking control reflecting the driver's braking intention can be performed.

  The pedal effort intensity estimating device according to claim 3, when the first detection means detects that the position is equal to or greater than the near position, and the second detection means detects that the position is equal to or greater than the back position. Further, the present invention is characterized in that a failure determination means for determining that any one of the detection means is a failure is provided.

  If it is detected that the brake pedal is in the rear position without detecting that the brake pedal is in the front position or higher, this is physically impossible. Can be determined.

  The vehicle behavior control device according to claim 4, when the first detection means detects that the second detection means is above the back position without detecting that the first detection means is above the front position. The control device prohibits the control of the pressure regulating valve based on the output of the pedal effort intensity estimating device.

  As described above, if it is detected that the brake pedal is at the back position or more without detecting that the brake pedal is at the front position or more, this is presumed that the detecting means is out of order. The device prohibits control of the pressure regulating valve based on the output of the pedal effort intensity estimating device, and improves safety.

  In the vehicle behavior control apparatus according to the fifth aspect, the pressure adjustment valve is a valve for adjusting the braking force of the reference wheel in the vehicle behavior control mode. In this case, the braking intention of the driver can be reflected in the braking force of the reference wheel, and the braking force of the other wheels can be determined according to the braking force of the reference wheel.

  According to the pedal effort intensity estimating device and the vehicle behavior control device using the same according to the present invention, the pedal effort strength can be detected without using a master cylinder pressure sensor.

  Hereinafter, a pedal effort intensity estimating device and a vehicle behavior control device according to an embodiment will be described. Note that the same reference numerals are used for the same elements, and redundant description is omitted.

  FIG. 1 is a block diagram of a vehicle including a vehicle behavior control apparatus according to an embodiment.

This vehicle includes two front wheels W _FL and W _FR attached to the vehicle body, and two rear wheels W _RL and W _RR . Foil cylinders H _FL , H _FR , H _RL , H _RR are respectively attached to the wheels W _FL , W _FR , W _RL , W _RR correspondingly. The wheel cylinders H _FL , H _FR , H _RL , H _RR are connected to the master cylinder M through a hydraulic path. A brake pedal BP is linked to the piston of the master cylinder M.

When the brake pedal BP is depressed, the hydraulic pressure in the master cylinder M increases, and in principle, the master cylinder pressure is transmitted to the wheel cylinders H _FL , H _FR , H _RL , H _RR via the hydraulic path. This hydraulic path is composed of X-shaped piping, and there is a hydraulic path OP1 of one system corresponding to the wheel cylinders _HFR , _HRL of the right front wheel and the left rear wheel, and the wheel of the left front wheel and the right rear wheel Corresponding to the cylinders H _FL and H _RR , there is a hydraulic path OP2 of another system, and these hydraulic paths OP1 and OP2 intersect with the X type.

(Wheel cylinders _H FR of the right front wheel and left rear _wheel, a hydraulic passage including _{H RL)} master cylinder M and one hydraulic path on the upstream side of the OP1 is first root valve _{V ROOT1} is provided. (Wheel cylinders _H FL of the left front wheel and right rear _wheel, a hydraulic passage including _{H RR)} master cylinder M and the other hydraulic pressure passage on the upstream side of the OP2 is the second root valve _{V Root2} is provided. A route for transmitting the master cylinder pressure to the wheel cylinder without passing through the root valve is also set separately.

On the end side corresponding to the right front wheel of one hydraulic path OP1, end valves V _FR1 and V _FR2 for increasing pressure, holding, and reducing pressure during ABS control are provided, and the end valve corresponding to the left rear wheel is provided. On the side, end valves V _RL1 and V _RL2 are provided for increasing, holding, and reducing pressure during ABS control. On the end side corresponding to the left front wheel of the other hydraulic path OP2, end valves V _FL1 and V _FL2 for increasing, holding, and reducing pressure during ABS control are provided, and the end corresponding to the right rear wheel is provided. On the side, end valves V _RR1 and V _RR2 are provided for increasing, holding, and reducing pressure during ABS control.

The master cylinder M is provided with a reservoir RS for containing brake fluid (oil), and the hydraulic pressure P is forcibly supplied from the reservoir RS into hydraulic paths OP1 and OP2 by a motor (not shown). When each of the end valves V _FR1 , V _FL1 , V _RR1 , V _RL1 is connected to the pressure reducing side, the wheel cylinder pressure is reduced and the hydraulic pressure R is returned to the reservoir RS.

Here, the root valves V _ROOT1 and V _ROOT2 are linear valves capable of controlling the valve closing pressure by an electric signal supplied from the outside, but the present invention is not limited to the linear valves. This electric signal is a current supplied from the electronic control unit ECU, and the higher the current value, the higher the valve closing pressure of the linear valve. The pressure applied to each end valve from the upstream side is a pressure obtained by adding the valve closing pressure of the linear valve to the master cylinder pressure. That is, if the amount of current supplied to the linear valve is increased, the pressure on the end side increases.

The electronic control unit ECU receives signals from the yaw rate sensor S1, the steering wheel angle sensor S2, the acceleration sensor S3, and the wheel speed sensor S4, and based on the received detection values, the root valves _VROOT1 , _VROOT2 and the end valves Controls the opening and closing of V _FR1 , V _FL1 , V _RR1 , V _RL1 , V _FR2 , V _FL2 , V _RR2 , V _RL2 .

  Here, a stop switch (first detection means) STP is provided at the front position in the stroke of the brake pedal BP, and a termination switch (second detection means) PMC is provided at the back position. The stop switch STP generates an output above the near position (turns on), and the end switch PMC generates an output above the back position (turns on).

  FIG. 2 is an explanatory diagram showing the position of the brake pedal BP.

  BS0 indicates the range from the stroke = 0 state to the stop switch STP, and BS1 indicates the range from the stop switch STP to the end switch PMC, and the range beyond the end switch PMC. The state shown is BS2.

  FIG. 3 is a table showing the states of the stop switch STP, the end switch PMC, and the pedal position.

  When the brake pedal BP is in the state BS0, the stop switch STP is OFF, the end switch PMC is OFF, and when the brake pedal BP is in the state BS1, the stop switch STP is ON, the end switch PMC is OFF, the brake pedal When the BP is in the state BS2, the stop switch STP is ON and the termination switch PMC is ON.

  Note that BS3 is defined as a state of the brake pedal BP which is not possible normally. In the state BS3, the stop switch STP is OFF and the termination switch PMC is ON.

  This pedal force intensity estimating device is a pedal force strength estimating device that estimates the depression strength of the brake pedal BP. However, the stop switch STP that detects that the brake pedal BP is at the front position or higher, and the brake pedal BP is at the rear position or higher. And a termination switch PMC for detecting the fact.

  Here, the control device ECU compares the case where the time difference from when the stop switch STP is turned on to when the end switch PMC is turned on (change time from state BS0 to BS2: period of state BS1) is small or large. Then, it is estimated that the brake pedal BP is stepped on strongly (estimating means).

  Here, in order to move the brake pedal BP quickly, it is necessary that the pedal effort is large. The stop switch STP and the end switch PMC generate outputs at the front position and the back position, but when the time difference between these switches (the period of BS1) is small, the brake pedal BP moves from the front position to the back position. In this case, it can be estimated that the estimation means has stepped on the brake pedal BP more strongly than when the time difference (the period of BS1) is large.

  In short, if the period of the state BS1 is measured, this period is inversely proportional to the pedal effort.

At the time of vehicle behavior control, the root valves (switching valves) V _ROOT1 and V _ROOT2 are _usually closed and the wheel cylinder end valves V _FR1 , V _FL1 , V _RR1 , V _RL1 , V _FR2 , V _FL2 , V _RR2 , V _The vehicle behavior is controlled by _RL2 (pressure regulating valve) (pressure increase, pressure reduction, hold).

At the time of pressure increase, terminal valves V _FR1 , V _FL1 , V _RR1 , V _RL1 as pressure increase valves are connected in a state where terminal valves V _FR2 , V _FL2 , V _RR2 , V _RL2 as connection valves are connected, and the master valve The cylinder M and the wheel cylinders H _FL , H _FR , H _RL , H _RR are connected, but the hydraulic release time (connection time) with respect to the unit time of the end valves V _FR1 , V _FL1 , V _RR1 , V _RL1 as the pressure increasing valve is Duty ratio. Note that the terminal valve is connected to the pressure reducing side during pressure reduction, and the terminal valves V _FR2 , V _FL2 , V _RR2 , and V _RL2 as holding valves are disconnected during holding.

  FIG. 4 is a graph showing the relationship between the master cylinder pressure change rate (Dpmc) and the duty ratio (duty).

When the period of the state BS is long (when the driver's intention to brake is weak), the pedal force is small and the master cylinder pressure gradually increases (Dpmc = small), so the end valves V _FR1 , V _FL1 , V _RR1 , V _RL1 By reducing the duty ratio in the pressure increasing mode, the rate of increase in the wheel cylinder pressure is reduced (duty = minimum duty ratio Dmin side).

When the period of the state BS is short (when the driver's intention to brake is strong), the pedal force is large and the master cylinder pressure increases rapidly (Dpmc = high), so the end valves V _FR1 , V _FL1 , V _RR1 , V _RL1 The increase rate of the wheel cylinder pressure is increased by increasing the duty ratio in the pressure increasing mode (duty = maximum duty ratio Dmax side).

In any control, the driver's intention to brake is reflected. In the present invention, the pedaling force intensity that is the driver's intention to brake is estimated by the pedaling force intensity estimation device, and this value is estimated as the end valves _VFR1 , _VFL1 , _VRR1 , _VRL1 , _VFR2 , _VFL2 , _VRR2 , _VRL2. By using this for the braking control, the braking control reflecting the driver's braking intention can be performed.

  That is, if the period of the state BS1 is measured, the braking force control can be performed by reflecting the driver's braking intention.

Here, the end valve can be applied to any wheel, but here, attention is paid to the right front wheel _WFR , which is a reference wheel when turning right.

In the vehicle behavior control mode (VSC), for example, when the vehicle is swollen outside the turn, the degree of steering of the steering wheel obtained from the output of the steering wheel steering angle sensor S2 and the wheel speed obtained from the wheel speed sensor S4 or The target yaw rate determined from the vehicle speed is set as the target vehicle state quantity, and the engine output is reduced, for example, so that the actual yaw rate (actual vehicle state quantity) matches the target yaw rate (target vehicle state quantity). The end valves V _FR1 and V _FR2 are connected so as to be in the pressure increasing mode (the wheel cylinder _HFR and the master cylinder M are communicated with each other with a predetermined duty ratio), and the deviation from the course of the vehicle is reduced.

In the case where the vehicle spins, the target yaw rate (target vehicle state quantity) determined based on the centrifugal force obtained from the output of the lateral acceleration sensor and the vehicle speed obtained from the output of the wheel speed sensor. The actual yaw rate (actual vehicle state quantity) increases. In such a case, apply a strong brake to the outer front wheel. That is, if the vehicle is turning right, the end valve V _FL1 wheel cylinder H _FL corresponding to the left front wheel and communicated with the wheel cylinders H _FL, boosts the wheel cylinder pressure, suppresses spin. When a braking force is applied to the reference wheel, the braking force of the turning outer wheel is uniquely determined so as to suppress course deviation and spin.

When the reference wheel is braked during the vehicle behavior control mode, the end valves V _FR1 and V _FR2 are set at a duty ratio (duty) derived from the rate of change Dpmc of the master cylinder pressure (proportional to the inverse of the period of the state BS1). The wheel cylinder _HFR and the master cylinder M may be communicated with each other by driving. As described above, the end valves V _FR1 and V _FR2 are valves for adjusting the braking force of the reference wheel in the vehicle behavior control mode, and can reflect the driver's braking intention in the braking force of the reference wheel. The braking force of the wheel can be determined according to the braking force of the reference wheel.

  Further, assuming that the period of the state BS1 is CT, the period of the control cycle is ΔT, and the constant is ΔP, Dpmc is given by the following (formula A). The constant ΔP is a difference between the master cylinder pressure Ppmc when the brake pedal BP is at the back position and the master cylinder pressure Pstp when the brake pedal BP is at the near position.

(Formula A)
Dpmc = ΔP / (CT × ΔT)

  The failure determination will be described.

  If the failure determination means in the control unit ECU detects that the end switch PMC is in the rear position or more without detecting that the stop switch STP is in the front position or more, one of the switches has failed. It is judged that. That is, when it is detected that the brake pedal BP is at the rear position or higher without detecting that the brake pedal BP is at the front position or higher, this is a physically impossible state (= BS3). It can be determined that one of the switches is faulty.

  In this case, the control device ECU prohibits control of the end valve based on the output of the pedal effort intensity estimating device, and improves safety.

  Hereinafter, various controls by the electronic control unit ECU will be described.

  5 and 6 are flowcharts of control by the electronic control unit ECU.

  Note that the wheel to be controlled in this example is a reference wheel, and basically the duty ratio at the time of pressure increase of the end valve is finally determined.

  First, in step S11, the current state of the brake pedal BP is determined from the outputs of the stop switch STP and the termination switch PMC according to the table shown in FIG. Note that the states BS0, BS1, BS2, and BS3 are represented by the values of the state BS being 0, 1, 2, and 3, respectively.

  Next, it is determined whether or not the state BS = 0 (S12). When BS = 0, the count value CT = 0 for measuring the period of the BS1 state, the holding mode request flag H = 0 (the holding mode is not executed), and for the pressure increase time measurement of this control by the variable duty ratio The count value AT = 0 is set (S13). Subsequently, it is determined whether or not VSC control is permitted (S14). When VSC control is permitted, it is determined whether or not VSC control is being performed (S15).

When VSC control is being performed (“Yes” determination in S15), it is determined whether or not the state BS = 3 (failure) (S16). If BS = 3, the duty ratio (duty) is set to the time of failure. Value Df (S17), and thereafter, the end valve _VFR1 is controlled with this duty ratio (S29: see FIG. 6). If BS = 3, step S24 and subsequent steps are executed. Even when VSC control is not being performed in step S15 (“No” determination in S15), it is determined whether or not the state BS = 3 (failure) (S22). If BS = 3, VSC control is performed. Is prohibited (S23), and if BS = 3, the process returns to the start.

  In step S12, if BS = 0 is not satisfied, it is determined whether BS = 1 (S18). When BS = 1, the count value CT and the holding mode request flag H are set according to the previous BS (BSL) value. When previous BS = 0, set CT = 0, H = 0, and when previous BS = 1, add 1 to CT and set H = 0, previous BS = 2 Is set to H = 1 (S19). Thereafter, step S14 and subsequent steps are executed.

  In step S18, when BS is not 1, it is determined whether BS = 2 (S20). When BS = 2, the count value CT and the holding mode request flag H are set according to the previous BS (BSL) value. If the previous BS = 0, set CT = 0, H = 0, if the previous BS = 1, set H = 0, and if the previous BS = 2, CT = 1, H = 1 is set (S21). Thereafter, step S14 and subsequent steps are executed.

  That is, the count value CT increases every time the control cycle is repeated (sampling timing: ΔT) when the previous BS (BSL) is 1 and the current BS = 1.

  Next, step S24 and subsequent steps shown in FIG. 6 will be described.

It is determined whether or not the state of BS = 1 continues and then BS = 2 (S24). When BS = 2, it is determined whether the count value AT of the pressure increasing time has reached the specified value T1 (S25), and 1 is added to the count value AT (S26) until the pressure value reaches the specified value T1. . When the count value AT reaches the specified value T1 ("No" determination in step S25), the duty ratio (duty) is set to the minimum value Dmin (S32), and the end valve corresponding to the reference wheel is increased in pressure. The end valve V _FR1 is controlled with this duty ratio (S29).

After step S26, it is determined whether or not the count value CT = 0 for measuring the period of the BS1 state (S27). When the count value CT = 0 (when the duration of BS1 is short), the duty ratio is determined as the maximum value Dmax, and step S29 is executed. On the other hand, if the count value CT is not 0 (“No” determination in step S27), the change rate (estimated value) Dpmc of the master cylinder pressure is set as in the above (Equation A) (S30), The corresponding duty ratio (duty) is determined based on the graph (map 1) of the function f (Dpmc) shown in FIG. 4 (S31). Thereafter, the terminal valve _VFR1 is controlled with this duty ratio (S29).

If it is determined in step S24 that BS = 2 is not satisfied, it is determined whether or not BS = 1 (S33). If BS = 1, it is determined whether the holding mode request flag H = 0 (whether the holding mode is not set) (S34). If H = 0, the duty ratio is set to the minimum value Dmin. Thereafter, the terminal valve _VFR1 is controlled with this duty ratio (S29). If H = 0 is not satisfied (H = 1), the duty ratio (duty) is set to 0 in order to execute the holding mode (S36), and thereafter, the end valve _VFR1 is controlled with this duty ratio, that is, The holding mode is executed (S29).

If it is determined in step S33 that BS is not 1, since BS = 0 (when not braking), the duty ratio (duty) is set to the duty ratio Drel during execution of the decompression mode (S37). The end valve V _FR1 is controlled by the duty ratio (S29).

  FIG. 7 is a timing chart of the ON / OFF of the stop switch STP, the ON / OFF of the end switch PMC, the duty ratio (duty), and the oil pressure of the wheel cylinder of the reference wheel.

  The period from when the stop switch STP is turned on to when the end switch PMC is turned on is the period of the state BS1, and is also the product of the count value CT and the control cycle ΔT. The brake pedal BP is stepped on with a pedaling force that is inversely proportional to this period. When VSC control is started, BS = 0 until the stop switch STP is turned on, so the decompression mode is executed (S37), and when it is turned on, the minimum duty value Dmin is set. (S35). After that, when both switches STP and PMC are turned ON, the duty ratio is determined according to the period of BS1, and the control in the pressure increasing mode is executed with the duty ratio during the specified period T1 (S25). The

  When the specified period T1 has passed, the duty ratio is set to the minimum value Dmin (S32). After that, when the terminal switch PMC is turned off by weakening the depression of the brake pedal BP (from BS2 to BS1). 1 is assigned to the holding mode request flag H (S19), and the holding mode is executed (S36).

  After that, when the terminal switch PMC is turned on by depressing the brake pedal BP again (from BS1 to BS2), 0 is assigned to the holding mode request flag H (S21), and the duty ratio is minimized. The value Dmin is set (S32).

  Thereafter, when both switches STP and PMC are turned off (BS = 0), the duty ratio is set again to that in the pressure reduction mode (S37).

  INDUSTRIAL APPLICABILITY The present invention can be used for a pedaling force intensity estimation device and a vehicle behavior control device, and in particular, to be used for a pedaling force strength estimation device and a vehicle behavior control device that can detect a pedaling force strength even when there is no master cylinder pressure sensor. Can do.

It is a block diagram of the vehicle provided with the vehicle behavior control apparatus which concerns on embodiment. It is explanatory drawing which shows the position of the brake pedal BP. It is a table | surface which shows the state of stop switch STP, termination | terminus switch PMC, and a pedal position. It is a graph which shows the relationship between a master cylinder pressure change rate (Dpmc) and a duty ratio (duty). It is a flowchart of control by electronic control unit ECU. It is a flowchart of control by electronic control unit ECU. 5 is a timing chart of ON / OFF of a stop switch STP, ON / OFF of a termination switch PMC, a duty ratio (duty), and oil pressure of a wheel cylinder of a reference wheel.

Explanation of symbols

AT: count value, BP: brake pedal, CT: count value, Dmax: maximum duty ratio, Dmin: minimum duty ratio, Dpmc: rate of change in master cylinder pressure, Drel ..Duty ratio during decompression, ECU: Control device (electronic control unit), H: Holding mode request flag, H _FL , H _FR: Wheel cylinder, M: Master cylinder, OP1, OP2 ... Hydraulic path, PMC ... Terminal switch, Ppmc ... Master cylinder pressure at the back position, Pstp ... Master cylinder pressure at the front position, S1 ... Yaw rate sensor, S2 ... Steering angle sensor , S3 · · · acceleration sensor, S4 · · · wheel speed sensors, STP · · · stop _{switch, V FR1, V FL1, V} RR1, V RL1, _{FR2, V FL2, V RR2,} V RL2 ··· pressure regulating valve (end _{valve), V ROOT1,} V _ROOT2 ··· root _{valves, W FL,} W _FR ··· _{wheel, W RL,} W RR ··· Rear wheel, ΔP, constant, ΔT, control cycle.

Claims (5)

In the pedal force intensity estimation device that estimates the depression strength of the brake pedal,
First detecting means for detecting that the brake pedal is at or above the front position;
Second detection means for detecting that the brake pedal is at or above the back position;
An estimation means for estimating that the brake pedal is stepped on more strongly than when the time difference from when the first detection means generates an output to when the second detection means generates an output is small;
A treading force intensity estimating device comprising: In the vehicle behavior control device,
The pedal effort intensity estimating device according to claim 1;
A master cylinder linked to the brake pedal;
A wheel cylinder communicating with the master cylinder;
A switching valve provided in a hydraulic path between the master cylinder and the wheel cylinder;
A pressure regulating valve for increasing, reducing, or holding the inside of the wheel cylinder with the switching valve closed;
A control device for controlling the pressure regulating valve;
With
The vehicle behavior control device, wherein the control device controls the pressure regulating valve based on a pedaling force intensity output by the pedaling force strength estimating device.   If the second detection means detects that the position is greater than or equal to the back position without detecting that the first detection means is greater than or equal to the near position, one of the detection means fails. The treading force intensity estimating device according to claim 1, further comprising a failure determining unit that determines that   If the second detecting means detects that the position is equal to or greater than the back position without detecting that the first detection means is equal to or greater than the near position, the control device The vehicle behavior control device according to claim 2, wherein control of the pressure regulating valve based on an output of the estimation device is prohibited.   The vehicle behavior control device according to claim 2, wherein the pressure adjustment valve is a valve for adjusting a braking force of a reference wheel in a vehicle behavior control mode.

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