JP2015196421A - Vehicular brake control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stability of a vehicle when travelling on a split road.SOLUTION: A vehicular brake control device includes: differential pressure setting means 150 for setting a difference between a braking force of the wheel brake of a high friction coefficient side and a braking force of the wheel brake of a low friction coefficient side, on a split road on which friction coefficients of road surfaces contacted with right and left wheels are different by a predetermined value or more, in such a manner that an actual yaw rate Y follows a target yaw rate YT; target yaw rate setting means 121 for setting the target yaw rate YT; and steering angle fixed state determination means 120 for determining a steering angle fixed state of a driver. The target yaw rate setting means 121 sets a first target yaw rate as a target yaw rate YT, at which a vehicle is turned to a high friction coefficient side, and when the steering angle fixed state determination means 120 determines that a steering angle is in a fixed state, the target yaw rate setting means 121 changes the target yaw rate YT to a second target yaw rate set in such a manner that an absolute value is smaller than the first target yaw rate just before the steering angle is determined to be in a fixed state.

Description

  The present invention relates to a vehicle brake control device, and more particularly to brake control corresponding to split roads in which the road surface friction coefficient of the road on which the vehicle is traveling differs on the left and right.

  Conventionally, as a vehicle brake control device that performs brake control corresponding to a split road, the target yaw rate is set to a value that turns the vehicle to the high friction coefficient side based on the rudder angle and vehicle speed, and the actual yaw rate is set There is known one that sets a difference in brake fluid pressure (difference in braking force) applied to the left and right wheel brakes so as to follow the set target yaw rate (see Patent Document 1).

JP 2013-193479 A

  By the way, in the prior art, when the driver operates the steering and the steering angle increases, the target yaw rate is set to be small, so when the driver cannot operate the steering and the steering angle is fixed, The target yaw rate will be maintained at a certain level. If the difference in braking force is set so that the actual yaw rate follows the target yaw rate when this rudder angle is fixed, there is a possibility that the vehicle will gradually turn to the high friction coefficient side. Further improvement is desired for improvement.

  Accordingly, an object of the present invention is to provide a vehicle brake control device that can improve the stability of the vehicle when traveling on a split road.

  The present invention for solving the above-mentioned problems is the difference between the braking force of the wheel brake on the high friction coefficient side and the braking force of the wheel brake on the low friction coefficient side on the split road where the friction coefficient of the ground contact surface of the wheel is different from the left and right by a predetermined amount or more. Braking force difference setting means for setting the actual yaw rate to follow the target yaw rate, target yaw rate setting means for setting the target yaw rate, and steering angle fixed state determination means for determining the steering angle fixed state of the driver, The target yaw rate setting means sets, as the target yaw rate, a first target yaw rate at which the vehicle turns to the high friction coefficient side, and the rudder angle fixed state determination means determines that the rudder angle is fixed. The second target yaw rate set so that the absolute value of the target yaw rate is smaller than the first target yaw rate immediately before the steering angle is determined to be fixed. And changes to the over door.

  According to such a configuration, the target yaw rate is reduced when the rudder angle is fixed, so that the optimum difference in braking force can be set when the rudder angle is fixed. Thereby, in the case where the steering angle is fixed, it is possible to prevent the vehicle from turning too far to the high friction coefficient side, so that it is possible to improve the stability of the vehicle when traveling on the split road.

  In the above-described apparatus, the second target yaw rate may be a preset value.

  According to such a configuration, the target yaw rate can be changed to a dedicated target yaw rate when the rudder angle is fixed, so that appropriate brake control can be performed and the stability of the vehicle can be further improved. .

  In the above-described apparatus, when the target yaw rate setting means determines that the steering angle is not fixed when the steering angle fixed state determination means determines that the steering angle is fixed, the target yaw rate setting means A configuration in which the target yaw rate is changed to the first target yaw rate can be employed.

  According to such a configuration, the optimum braking force difference can be set continuously while traveling on the split road regardless of the steering angle state, thereby further improving the stability of the vehicle. be able to.

  In the above-described apparatus, when the target yaw rate setting means changes the target yaw rate from the first target yaw rate immediately before it is determined to be in the rudder angle fixed state to the second target yaw rate, the change limit is gradually reduced. It can be set as the structure changed by the predetermined gradient by.

  According to such a configuration, since a rapid change in the difference in braking force can be suppressed before and after the target yaw rate is changed, the stability of the vehicle can be further improved.

  In the above-described device, the rudder angle fixed state determination means can be configured to determine that the rudder angle is fixed when a state where the absolute value of the rudder angle is equal to or smaller than the rudder angle threshold value continues for a predetermined time.

  According to such a configuration, the steering angle fixed state can be appropriately determined, so that appropriate brake control can be performed and the stability of the vehicle can be further improved.

  According to the present invention, the stability of the vehicle when traveling on a split road can be improved.

It is a lineblock diagram of vehicles provided with a brake control device for vehicles concerning an embodiment. It is a block diagram which shows the structure of a hydraulic unit. It is a block diagram which shows the structure of a control part. It is a map which shows the relationship between the vehicle speed for setting a 1st target yaw rate, and the target yaw rate based on a vehicle speed. It is a map which shows the relationship between the steering angle for setting a 1st target yaw rate, and the target yaw rate based on a steering angle. It is a block diagram which shows the structure of a differential pressure setting means. It is a map which shows the relationship between the steering angle for setting a feedforward differential pressure, and the differential pressure based on a steering angle. It is a map which shows the relationship between the ratio of a vehicle speed and a target yaw rate for setting a feedforward differential pressure, and the differential pressure based on the ratio of a vehicle speed and a target yaw rate. It is a map which shows the relationship between vehicle speed and differential pressure for setting differential pressure. It is a flowchart which shows the process at the time of antilock brake control by a control part. It is a flowchart which shows the process of a target yaw rate setting. 6 is a timing chart showing changes in vehicle speed, steering angle, yaw rate, differential pressure, and steering angle fixed state determination flag when the steering angle is not fixed during split road travel in the embodiment. 10 is a timing chart showing changes in vehicle speed, steering angle, yaw rate, and differential pressure when the steering angle is fixed during traveling on a split road in a comparative example. 7 is a timing chart showing changes in vehicle speed, steering angle, yaw rate, differential pressure, and steering angle fixed state determination flag when the steering angle is fixed during traveling on a split road in the embodiment.

Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the vehicle brake control device A according to the present embodiment is a device that appropriately controls the braking force applied to each wheel W of the vehicle CR. The vehicle brake control device A mainly includes a hydraulic unit 10 provided with an oil passage and various parts, and a control unit 100 for appropriately controlling various parts in the hydraulic unit 10.

  Each wheel W is provided with a wheel brake FL, RR, RL, FR, and each wheel brake FL, RR, RL, FR is braked by a hydraulic pressure supplied from a master cylinder MC as a hydraulic pressure source. Is provided. Master cylinder MC and wheel cylinder H are each connected to hydraulic unit 10. During normal times (when the hydraulic pressure unit 10 is not controlled), the brake hydraulic pressure generated in the master cylinder MC in response to the depression force of the brake pedal BP (the driver's braking operation) is the control unit 100 and the hydraulic pressure unit. 10 is supplied to the wheel cylinder H.

  The control unit 100 includes a pressure sensor 91 that detects the pressure of the master cylinder MC, a wheel speed sensor 92 that detects the wheel speed of each wheel W, a steering angle sensor 93 that detects the steering angle θ of the steering ST, and a vehicle. A yaw rate sensor 94 that detects an actual yaw rate Y that is an actual yaw rate of the CR is connected. The control unit 100 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an input / output circuit, and inputs from the sensors 91 to 94 and the ROM The control is executed by performing various arithmetic processes based on the programs and data stored in. Details of the control unit 100 will be described later.

  As shown in FIG. 2, the hydraulic unit 10 is disposed between the master cylinder MC and the wheel brakes FL, RR, RL, FR. The two output ports M1, M2 of the master cylinder MC are connected to the inlet port 10a of the hydraulic unit 10, and the outlet port 10b is connected to each wheel brake FL, RR, RL, FR. In normal times, the oil pressure path of the brake pedal BP is transmitted to the wheel brakes FL, RR, RL, and FR because the oil passage communicates from the inlet port 10a to the outlet port 10b in the hydraulic unit 10. It has become so.

  The hydraulic pressure unit 10 is provided with four inlet valves 1, four outlet valves 2, and four check valves 1a corresponding to the wheel brakes FL, RR, RL, FR. The hydraulic unit 10 is also provided with a reservoir 3, a pump 4, and an orifice 5a in each of the hydraulic pressure paths 11 and 12 corresponding to the output ports M1 and M2 of the master cylinder MC. The hydraulic unit 10 is provided with a common motor 6 for driving the pumps 4.

  The inlet valve 1 is a normally open proportional solenoid valve provided between each wheel brake FL, RR, RL, FR and the master cylinder MC. The inlet valve 1 is normally opened to allow the brake hydraulic pressure to be transmitted from the master cylinder MC to the wheel brakes FL, RR, RL, FR. In addition, the inlet valve 1 is blocked by the control unit 100 when the wheel W is about to be locked, thereby cutting off the hydraulic pressure transmitted from the brake pedal BP to each wheel brake FL, RR, RL, FR.

  The outlet valve 2 is a normally closed electromagnetic valve provided between each wheel brake FL, RR, RL, FR and the reservoir 3. Although the outlet valve 2 is normally closed, the hydraulic pressure applied to the wheel brakes FL, RR, RL, FR is applied to the reservoir 3 by being released by the control unit 100 when the wheel W is about to be locked. Let it go.

  The check valve 1a is connected to each inlet valve 1 in parallel. This check valve 1a is a valve that only allows the brake fluid to flow from the wheel brakes FL, RR, RL, FR side to the master cylinder MC side, and the inlet valve when the input from the brake pedal BP is released. Even when 1 is closed, the flow of brake fluid from each wheel brake FL, RR, RL, FR side to the master cylinder MC side is allowed.

The reservoir 3 has a function of temporarily storing brake fluid that is released when each outlet valve 2 is opened.
The pump 4 is provided between the reservoir 3 and the master cylinder MC, and has a function of sucking the brake fluid stored in the reservoir 3 and returning the brake fluid to the master cylinder MC through the orifice 5a. ing.

  The inlet valve 1 and the outlet valve 2 control the brake fluid pressure of the wheel cylinders H of the wheel brakes FL, RR, RL, FR by the control unit 100 controlling the open / close state. For example, in a normal state where the inlet valve 1 is open and the outlet valve 2 is closed, if the brake pedal BP is depressed, the hydraulic pressure from the master cylinder MC is transmitted to the wheel cylinder H as it is, and the pressure is increased. When the valve 1 is closed and the outlet valve 2 is opened, the brake fluid flows out from the wheel cylinder H to the reservoir 3 side to be in a reduced pressure state, and when both the inlet valve 1 and the outlet valve 2 are closed, the brake fluid pressure is increased. It becomes a holding state to be held.

Next, details of the control unit 100 will be described.
The control unit 100 is a device that performs control to stabilize the vehicle by controlling the hydraulic unit 10 and applying the braking force set to each wheel brake FL, RR, RL, FR. Therefore, as shown in FIG. 3, the control unit 100 includes a vehicle speed acquisition unit 111, a steering angle acquisition unit 112, an actual yaw rate acquisition unit 113, a steering angle fixed state determination unit 120, and a target yaw rate setting unit 121. And anti-lock brake control means 130, split road determination means 140, differential pressure setting means 150 as an example of braking force difference setting means, control execution means 160, and storage means 190. ing.

  The vehicle speed acquisition unit 111 acquires wheel speed WS information (pulse signal of the wheel speed sensor 92) from the wheel speed sensor 92, and calculates the vehicle speed V by a known method based on the information of the wheel speed WS. It is a means to acquire. The calculated vehicle speed V is output to the target yaw rate setting means 121, the antilock brake control means 130, and the differential pressure setting means 150.

  The steering angle acquisition unit 112 is a unit that acquires information on the steering angle θ from the steering angle sensor 93. The acquired steering angle θ is output to the steering angle fixed state determination means 120, the target yaw rate setting means 121, and the differential pressure setting means 150. In the present specification, the steering angle θ is positive when the steering ST is operated in the direction in which the vehicle CR turns to the low friction coefficient side on the split road.

  The actual yaw rate acquisition unit 113 is a unit that acquires information on the actual yaw rate Y that is the actual yaw rate of the vehicle CR from the yaw rate sensor 94. The acquired actual yaw rate Y is output to the differential pressure setting means 150. In this specification, the actual yaw rate Y and the target yaw rate YT, which will be described later, are positive in the direction in which the vehicle CR turns to the high friction coefficient side on the split road.

  The anti-lock brake control means 130 determines, for each wheel W, whether or not to execute the anti-lock brake control by a known method based on the wheel speed WS and the vehicle speed V, and the liquid during the anti-lock brake control. This is means for determining for each wheel W an instruction for pressure control (instruction on whether the hydraulic pressure in the wheel cylinder H is to be in a pressure-increasing state, a holding state, or a pressure-reducing state). Information indicating that the anti-lock brake control is to be executed is output to the split road determination unit 140, and the determined hydraulic pressure control instruction is output to the control execution unit 160.

  The split road determination means 140 is a means for determining whether or not the split road has a friction coefficient different from the left and right by a predetermined amount or more when the antilock brake control is executed. In the present invention, the split road determination method is not particularly limited. As an example, when the antilock brake control is executed, the maximum value (the value at which the deceleration is least) is shown among the decelerations of the wheels W. When the deceleration of the wheel W is equal to or greater than the first threshold and the difference in deceleration between the left and right wheels W is equal to or greater than the second threshold, it can be determined that the road is a split road. Further, when the split road determination unit 140 determines that the road is a split road, the split road determination unit 140 determines which of the left and right wheels W is on the high friction coefficient side and which is on the low friction coefficient side. As an example, of the left and right wheels W, the wheel W having the smaller deceleration is determined as the high friction coefficient side, and the wheel W having the larger deceleration is determined as the low friction coefficient side. Information indicating that the road is a split road is output to the steering angle fixed state determination means 120 and the differential pressure setting means 150.

  Steering angle fixed state determination means 120 is a means for determining a driver's rudder angle fixed state, specifically, a state in which the steering ST is fixed with a small operation amount. Specifically, the steering angle fixed state determination unit 120 determines the absolute value of the steering angle θ after a first time T1 that is set in advance in a situation where the split road determination unit 140 determines that the road is a split road. Is determined to be the steering angle fixed state when the state below the steering angle threshold θth set in advance (the state of −θth ≦ θ ≦ θth) continues for the second time T2 as the predetermined time, and the steering angle fixed state The determination flag F is set to 0 to 1 which is an initial value. Further, the steering angle fixed state determination means 120 is a split road when the absolute value of the steering angle θ exceeds the steering angle threshold value θth when the steering angle fixed state determination flag F is 1, or when the split road determination means 140 determines the split road. Is not determined, the steering angle fixed state determination flag F is reset from 1 to 0. Information on whether or not the steering angle is fixed is output to the target yaw rate setting means 121.

  The target yaw rate setting means 121 is a means for setting a target yaw rate YT for setting a differential pressure DP described later.

Specifically, when the steering angle fixed state determination flag F is 0, the target yaw rate setting means 121 sets the vehicle CR to the high friction coefficient side of the split road based on the vehicle speed V and the steering angle θ as the target yaw rate YT. A first target yaw rate YT1 that turns is set. Specifically, the target yaw rate YT _V based on the vehicle speed V and the target yaw rate YT _θ based on the steering angle _θ are calculated, and the smaller one of the target yaw rates YT _V and YT _θ is calculated as the first target yaw rate YT1. . FIG. 4 is a map for setting the target yaw rate YT _V based on the vehicle speed V, and is determined so that the target yaw rate YT _V decreases as the vehicle speed V increases. FIG. 5 is a map for setting the target yaw rate YT _θ based on the steering angle θ, and is determined so that the target yaw rate YT _θ decreases as the steering angle θ increases. Specifically, the target yaw rate YT _θ is determined to be a constant value in a range where the steering angle θ is 0 or less, and the steering angle θ is set at a constant decrease rate from the above-described constant value when the steering angle θ is between 0 and a predetermined value θ1. larger as the target yaw rate YT _theta decreases, the steering angle theta is the target yaw rate YT as steering angle theta is larger with a large reduction ratio than during the period from the predetermined value θ1 to a predetermined value θ2 from 0 to a predetermined value θ1 _The target yaw rate YT _θ is determined to be 0 in the range where _θ is small and the steering angle θ is larger than the predetermined value θ2. The target yaw rate YT _V when the vehicle speed V is 0 in the map of FIG. 4 is set to a value smaller than the target yaw rate YT _θ when the steering angle θ is 0 in the map of FIG.

  Further, the target yaw rate setting means 121 has the second target yaw rate YT2 as the target yaw rate YT when the steering angle fixed state determination flag F is 1 (when the steering angle fixed state determination means 120 determines that the steering angle is fixed). And the target yaw rate YT is changed from the first target yaw rate YT1 immediately before the steering angle is fixed to the set second target yaw rate YT2. The second target yaw rate YT2 is a value set in advance so that the absolute value is smaller than the first target yaw rate YT1 immediately before the steering angle is fixed. In the present embodiment, the second target yaw rate YT2 is a fixed value and is stored in the storage unit 190. The second target yaw rate YT2 may be zero. When the target yaw rate setting means 121 changes the target yaw rate YT from the first target yaw rate YT1 immediately before it is determined to be in the rudder angle fixed state to the second target yaw rate YT2, the predetermined yaw rate setting means 121 has a predetermined gradient due to a change restriction that gradually decreases. Change with.

Further, the target yaw rate setting means 121 is not in the steering angle fixed state when the steering angle fixed state determination flag F is reset from 1 to 0 (when the steering angle fixed state determination means 120 determines that the steering angle is fixed). Is determined), the first target yaw rate YT1 is set as the target yaw rate YT, and the target yaw rate YT is changed from the second target yaw rate YT2 to the set first target yaw rate YT1. When the target yaw rate setting means 121 changes the target yaw rate YT from the second target yaw rate YT2 to the newly set first target yaw rate YT1, the target yaw rate setting means 121 changes the predetermined yaw rate YT1 with a predetermined gradient due to a change restriction that gradually increases the absolute value.
The set target yaw rate YT is output to the differential pressure setting means 150.

  The differential pressure setting means 150 is a means for setting a braking force difference that is a difference between the braking force of the wheel brake on the high friction coefficient side and the braking force of the wheel brake on the low friction coefficient side on the split road. In this embodiment, the differential pressure setting means 150 is a difference corresponding to the braking force difference, which is the difference between the brake fluid pressure of the wheel brake on the high friction coefficient side and the brake fluid pressure of the wheel brake on the low friction coefficient side. The pressure DP is set so that the actual yaw rate Y follows the target yaw rate YT. For this control, as shown in FIG. 6, the differential pressure setting means 150 includes a feedforward differential pressure calculator 151, a deviation calculator 152, a feedback differential pressure calculator 153, and a differential pressure calculator 156. Have.

Feedforward pressure calculation unit 151, the vehicle speed V, based on the steering angle θ and the target yaw rate YT, a means for calculating the feedforward differential pressure DP _FF. Specifically, the feedforward differential pressure DP _FF is calculated by adding the differential pressure based on the vehicle speed V and the target yaw rate YT to the differential pressure based on the steering angle θ. FIG. 7 is a map for setting the differential pressure based on the steering angle θ, and is determined so that the differential pressure increases as the steering angle θ increases. FIG. 8 is a map for setting a differential pressure based on the vehicle speed V and the target yaw rate YT, and the differential pressure increases as the ratio (YT / V) between the vehicle speed V and the target yaw rate YT increases. It is decided so. The calculated feedforward differential pressure DP _FF is output to the differential pressure calculation unit 156.

  The deviation calculation unit 152 is a means for calculating a deviation ΔY (= Y−YT) between the actual yaw rate Y and the target yaw rate YT. The calculated deviation ΔY is output to the feedback differential pressure calculation unit 153.

The feedback differential pressure calculation unit 153 is means for calculating a feedback differential pressure DP _FB for setting the differential pressure DP by PID (Proportional Integral Derivative) control so that the actual yaw rate Y follows the target yaw rate YT. Specifically, feedback differential pressure DP _FB includes P term (proportional gain × current deviation ΔY), I term (previous I term + (integral gain × current deviation ΔY)), and D term (differential gain × (Previous deviation ΔY−current deviation ΔY)) is added. The calculated feedback differential pressure DP _FB is output to the differential pressure calculation unit 156.

The differential pressure calculation unit 156 is a means for calculating the differential pressure DP. Specifically, the differential pressure DP is determined based on the vehicle speed V and a preset map until the first time T1 (see FIG. 12 and the like) elapses after the split road is determined. calculate. FIG. 9 is a map for setting the differential pressure DP from when it is determined that the road is split until the first time T1 elapses, and the differential pressure DP decreases as the vehicle speed V increases. It is decided so. On the other hand, after the first time T1 after it is determined that the split road is elapsed, it calculates the differential pressure DP based on the feedforward differential pressure DP _FF and the feedback differential pressure DP _FB. Specifically, a value obtained by adding the feedforward differential pressure DP _FF and the feedback differential pressure DP _FB is calculated as the differential pressure DP. The calculated differential pressure DP is output to the control execution means 160.

  Based on the hydraulic pressure control instruction determined by the anti-lock brake control means 130 and the differential pressure DP set by the differential pressure setting means 150, the control execution means 160 uses a known method to cause the wheel brakes FL, RR, RL, It is means for controlling the brake fluid pressure of FR. Specifically, for the wheel brake that executes the antilock brake control, the hydraulic pressure unit 10 is controlled based on the hydraulic pressure control instruction determined by the antilock brake control means 130. Also, when it is determined that the road is split, if the difference between the brake fluid pressure of the wheel brake on the high friction coefficient side and the brake fluid pressure of the wheel brake on the low friction coefficient side is likely to exceed the differential pressure DP The hydraulic pressure unit 10 is controlled such that the brake fluid pressure of the wheel brake on the high friction coefficient side becomes a value obtained by adding the differential pressure DP to the brake fluid pressure of the wheel brake on the low friction coefficient side. The specific control of the hydraulic unit 10 is well known and will not be described in detail. However, in brief, the current output to the inlet valve 1 and the outlet valve 2 is adjusted, and the motor 6 is turned on as necessary. It controls to drive and drive the pump 4.

  The storage unit 190 is a unit that appropriately stores programs, constants, maps, calculation results, and the like necessary for the operation of the control unit 100.

  Next, processing during antilock brake control by the control unit 100 of the vehicle brake control device A will be described with reference to FIG. The process of FIG. 10 is repeatedly performed for each control cycle. The initial value of the steering angle fixed state determination flag F is zero. In the following description, the value of each parameter such as the steering angle θ and the target yaw rate YT means a magnitude (absolute value).

  First, the control unit 100 acquires the wheel speed WS from the wheel speed sensor 92, the steering angle θ from the steering angle sensor 93, and the actual yaw rate Y from the yaw rate sensor 94 (S101). Next, the control unit 100 calculates the vehicle speed V from the wheel speed WS (S102). Then, the antilock brake control means 130 determines a hydraulic pressure control instruction for the antilock brake control (S111).

Next, the split road determination unit 140 determines whether or not the ground road surface of the wheel W is a split road (S112).
When it is determined that the road is not a split road (S112, NO), the control execution means 160 controls the hydraulic pressure unit 10 based on the hydraulic pressure control instruction of the antilock brake control, and controls the brake hydraulic pressure of the wheel brake. (Performs known antilock brake control) (S131).

  If it is determined in step S112 that the road is a split road (YES), the differential pressure setting unit 150 determines whether or not the first time T1 has elapsed since it was determined that the road is a split road (S121). . When the first time T1 has not elapsed (S121, NO), the differential pressure setting means 150 sets the differential pressure DP from the map of FIG. 9 based on the vehicle speed V (S122).

  On the other hand, when the first time T1 has elapsed in step S121 (YES), the control unit 100 first sets the target yaw rate YT in order to set the differential pressure DP (S200). As shown in FIG. 11, the control unit 100 determines whether or not the steering angle θ is equal to or smaller than the steering angle threshold θth (S210). If the steering angle θ is not less than or equal to the steering angle threshold θth (S210, NO), the steering angle fixed state determination means 120 maintains that state if the steering angle fixed state determination flag is 0, and the steering angle fixed state determination flag is If it is 1, it is reset to 0 (S211).

  The target yaw rate setting means 121 calculates the first target yaw rate YT1 from the maps of FIGS. 4 and 5 based on the vehicle speed V and the steering angle θ because the steering angle fixed state determination flag F is 0 (S231). ). Next, the target yaw rate setting means 121 calculates a third target yaw rate YT3 by adding a predetermined increment C1 to the previous target yaw rate YT (S232). Then, the target yaw rate setting means 121 sets the smaller one of the first target yaw rate YT1 calculated in step S231 and the third target yaw rate YT3 calculated in step S232 as the target yaw rate YT (S233). Thereby, the target yaw rate YT can be gradually increased with a predetermined gradient.

  In step S210, when the steering angle θ is equal to or smaller than the steering angle threshold θth (YES), the control unit 100 determines whether or not the steering angle fixed state determination flag F is 1 (S212). When the steering angle fixed state determination flag F is not 1 (when the steering angle fixed state determination flag F is 0) (S212, NO), the steering angle fixed state determination unit 120 determines that the steering angle θ is equal to or smaller than the steering angle threshold θth. It is determined whether or not the state lasts for the second time T2 (S220). If the second time T2 is not maintained (S220, NO), the target yaw rate setting unit 121 performs the processes of steps S231 to S233. On the other hand, when the state where the steering angle θ is equal to or less than the steering angle threshold θth continues for the second time T2 in step S220 (YES), the steering angle fixed state determination means 120 sets the steering angle fixed state determination flag from 0 to 1. (S221), the control unit 100 performs the processes of steps S241 to S243. Moreover, also when the steering angle fixed state determination flag F is 1 in step S212 (YES), the control unit 100 performs the processes of steps S241 to S243.

  In step S241, the target yaw rate setting means 121 acquires the second target yaw rate YT2 from the storage means 190 because the steering angle fixed state determination flag F is 1. Next, the target yaw rate setting means 121 calculates a fourth target yaw rate YT4 by subtracting a predetermined decrease C2 from the previous target yaw rate YT (S242). Then, the target yaw rate setting means 121 sets the larger value of the second target yaw rate YT2 acquired in step S241 and the fourth target yaw rate YT4 calculated in step S242 as the target yaw rate YT (S243). Thereby, the target yaw rate YT can be gradually reduced with a predetermined gradient.

Returning to FIG. 10, when the target yaw rate YT is set in step S200, the differential pressure setting means 150 calculates the feedforward differential pressure DP _FF based on the vehicle speed V, the steering angle θ, and the set target yaw rate YT. (S123). The differential pressure setting means 150 calculates a deviation ΔY between the actual yaw rate Y and the target yaw rate YT (S124), and calculates a feedback differential pressure DP _FB by PID control based on the deviation ΔY (S125). Then, the differential pressure setting means 150 calculates the sum of the feedforward differential pressure DP _FF and the feedback differential pressure DP _FB as the differential pressure DP (S126).

  When the differential pressure DP is calculated, the control execution means 160 controls the hydraulic pressure unit 10 based on the differential pressure DP and the hydraulic pressure control instruction of the antilock brake control, and controls the brake hydraulic pressure of the wheel brake. (S131). Specifically, the brake fluid pressure of the wheel brake on the low friction coefficient side is controlled based on the hydraulic control instruction of the anti-lock brake control, and the brake fluid pressure and the low friction coefficient of the wheel brake on the high friction coefficient side are controlled. If the difference from the brake fluid pressure of the wheel brake on the side is likely to exceed the differential pressure DP, the brake fluid pressure of the wheel brake on the high friction coefficient side becomes the differential pressure on the brake fluid pressure of the wheel brake on the low friction coefficient side. The brake fluid pressure of the wheel brake on the high friction coefficient side is controlled so as to be a value obtained by adding DP.

  The effects of the vehicle brake control device A of the present embodiment described above will be described with reference to FIGS. FIGS. 12 and 14 show the case of this embodiment. FIG. 13 shows a comparison in which the target yaw rate YT is not changed to a small value when the rudder angle is fixed (the first target yaw rate YT1 is always used as the target yaw rate YT). This is an example.

  As shown in FIG. 12, in the vehicle brake control device A, after the anti-lock brake control is started with the wheel W on the low friction coefficient side (time t1), the road surface on which the vehicle CR is currently traveling is a split road. (Time t2), the differential pressure DP is set from the vehicle speed V and the map of FIG. 9 until the first time T1 elapses (time t2 to t3). After the first time T1 has elapsed, the differential pressure DP is set so that the actual yaw rate Y follows the set target yaw rate YT (after time t3). As shown at times t3 to t4, the target yaw rate YT (first target yaw rate YT1) is set to a value that is large to some extent so that the vehicle CR turns to the high friction coefficient side when the steering angle θ is small. Then, by setting the differential pressure DP so that the actual yaw rate follows the target yaw rate YT, the differential pressure DP (the brake fluid pressure of the wheel brake on the high friction coefficient side) increases and the vehicle CR has a high friction coefficient. Try to turn to the side. The processing so far is the same in the case of the comparative example in FIGS.

  FIG. 12 shows a case where the driver operates the steering ST in a direction in which the vehicle CR turns to the low friction coefficient side in order to correct the turning of the vehicle CR to the high friction coefficient side. When the steering angle θ is increased by the operation of the steering ST, the target yaw rate YT is decreased (time t4 to t11) and finally becomes 0 (after time t11). As a result, after time t4, the increase in the differential pressure DP is suppressed, and the steering ST is operated in the direction of turning to the low friction coefficient side, so that the vehicle CR turns to the high friction coefficient side. In particular, it is possible to improve the stability of the vehicle CR when traveling on a split road with the wheel brake on the high friction coefficient side particularly effective.

  The comparative example of FIG. 13 and FIG. 14 show a case where the driver cannot operate the steering wheel ST and the steering angle θ is fixed below the steering angle threshold value θth.

  In the comparative example shown in FIG. 13, since the first target yaw rate YT1 is always used as the target yaw rate YT, when the steering angle θ is fixed, the target yaw rate YT continues to be maintained at a somewhat large value. When the differential pressure DP is set so that the actual yaw rate Y follows, the differential pressure DP becomes larger after time t4. Then, there is a possibility that the vehicle CR gradually turns to the high friction coefficient side because the steering ST is not operated in the direction to turn to the low friction coefficient side.

  On the other hand, in the present embodiment shown in FIG. 14, when the steering angle θ is fixed below the steering angle threshold θth and this state continues for the second time T2 (time t5), the steering angle fixed state determination flag F is set to 0. The target yaw rate YT is changed from the first target yaw rate YT1 to the second target yaw rate YT2 (time t21). As a result, as shown at times t5 to t23, the target yaw rate YT is reduced, so that the optimum differential pressure DP can be set in the case where the steering angle is fixed. Specifically, at times t5 to t23, the differential pressure DP is suppressed from increasing compared to the comparative example indicated by the broken line. As a result, since the vehicle CR is prevented from turning too far toward the high friction coefficient when the rudder angle is fixed, the stability of the vehicle CR when traveling on a split road even when the rudder angle is fixed. Can be improved.

  In the present embodiment, when the steering angle is fixed, the driver starts operating the steering ST in the direction in which the vehicle CR turns to the low friction coefficient side (time t22), and the steering angle θ is the steering angle threshold value. When θth is exceeded (time t23), the steering angle fixed state determination flag F is reset from 1 to 0, and the target yaw rate YT is changed from the second target yaw rate YT2 to the first target yaw rate YT1 (time t24). As a result, the setting of the target yaw rate YT based on the steering angle θ and the vehicle speed V is resumed, so that more appropriate brake control can be performed as compared with the case where the second target yaw rate YT2 is continuously used. That is, in the present embodiment, the steering angle θ is obtained by using the second target yaw rate YT2 as the target yaw rate YT when the steering angle is fixed, and using the first target yaw rate YT1 as the target yaw rate YT when the steering angle is not fixed. Regardless of the state, the optimum differential pressure DP can be set continuously while traveling on the split road. As a result, the stability of the vehicle CR when traveling on a split road can be further improved.

  In the present embodiment, when the target yaw rate YT is changed, the value is gradually decreased with a predetermined gradient (time t5 to t21) or gradually increased with a predetermined gradient (time t23 to t24). ), The rapid change of the differential pressure DP set based on the target yaw rate YT can be suppressed before and after the change of the target yaw rate YT. Thereby, the stability of the vehicle CR can be further improved.

  In the present embodiment, since the second target yaw rate YT2 is a preset value, the target yaw rate YT can be changed to an optimum value dedicated to the steering angle fixed state when the steering angle is fixed. Thereby, since appropriate brake control becomes possible, the stability of the vehicle CR can be further improved.

  In the present embodiment, since the steering angle fixed state is determined when the state where the steering angle θ is equal to or smaller than the steering angle threshold θth continues for the second time T2, the steering angle fixed state can be appropriately determined. . This also makes it possible to perform appropriate brake control, so that the stability of the vehicle CR can be further improved.

  Although the embodiment has been described above, the present invention is not limited to the above-described embodiment, and can also be implemented in the forms exemplified below.

  In the embodiment, the second target yaw rate YT2 is a fixed value, but the present invention is not limited to this. For example, the second target yaw rate is multiplied by a predetermined coefficient to the first target yaw rate immediately before the determination, or so that the absolute value is smaller than the first target yaw rate immediately before the determination that the steering angle is fixed. You may set for every control cycle by subtracting a predetermined value from the 1st target yaw rate.

  In the embodiment, when the target yaw rate YT is changed from the first target yaw rate YT1 to the second target yaw rate YT2, or when the target yaw rate YT2 is changed to the first target yaw rate YT1, the target yaw rate YT changes gradually. However, the present invention is not limited to this. For example, when the difference between the immediately preceding first target yaw rate and the set second target yaw rate is not so large, the first target yaw rate may be changed at a stroke.

  In the embodiment, the differential pressure setting means 150 as the braking force difference setting means is configured to set the differential pressure DP as the braking force difference. However, the present invention is not limited to this. For example, the braking force difference setting means May be configured to set the braking force difference itself.

  In the above embodiment, the target yaw rate setting means 121 is configured to set the target yaw rate YT based on the vehicle speed V and the steering angle θ, but is not limited to this. For example, the target yaw rate setting means may be configured to set the target yaw rate based only on the vehicle speed, or may be configured to set the target yaw rate based only on the steering angle. The target yaw rate may be a fixed value.

  In the above-described embodiment, the vehicle brake control device A using the brake fluid is exemplified. However, the present invention is not limited to this. For example, the electric brake device that generates the brake force by the electric motor without using the brake fluid is controlled. It may be a vehicle brake control device.

DESCRIPTION OF SYMBOLS 10 Hydraulic unit 100 Control part 111 Vehicle speed acquisition means 112 Steering angle acquisition means 113 Actual yaw rate acquisition means 120 Steering angle fixed state determination means 121 Target yaw rate setting means 130 Anti-lock brake control means 140 Split road determination means 150 Differential pressure setting means 160 Control Execution Unit A Vehicle Brake Control Device

Claims (5)

The actual yaw rate follows the target yaw rate in the difference between the braking force of the wheel brake on the high friction coefficient side and the braking force of the wheel brake on the low friction coefficient side on the split road where the friction coefficient of the ground contact surface of the wheel differs from left to right by a predetermined value or more. Braking force difference setting means for setting so as to
Target yaw rate setting means for setting the target yaw rate;
Rudder angle fixed state determining means for determining the driver's rudder angle fixed state,
The target yaw rate setting means includes
As the target yaw rate, a first target yaw rate is set such that the vehicle turns to the high friction coefficient side,
When the steering angle fixed state determination means determines that the steering angle is fixed, the target yaw rate is set to have an absolute value smaller than the first target yaw rate immediately before the steering angle fixed state is determined. A vehicle brake control device, wherein the vehicle brake control device is changed to a 2-target yaw rate.   The vehicular brake control device according to claim 1, wherein the second target yaw rate is a preset value.   The target yaw rate setting means determines the target yaw rate from the second target yaw rate to the second target yaw rate when it is determined that the steering angle is not fixed when the steering angle is fixed. 3. The vehicle brake control device according to claim 1, wherein the vehicle brake control device is changed to one target yaw rate.   The target yaw rate setting means, when changing the target yaw rate from the first target yaw rate immediately before it is determined to be in the rudder angle fixed state to the second target yaw rate, has a predetermined gradient due to a change restriction in which the absolute value gradually decreases. The vehicular brake control device according to any one of claims 1 to 3, wherein the vehicular brake control device is changed.   The steering angle fixed state determination means determines that the steering angle is fixed when the absolute value of the steering angle is equal to or less than a steering angle threshold value for a predetermined time. The vehicle brake control device according to claim 1.

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