JP6382553B2 - Brake control device for vehicle - Google Patents

Description

  The present invention relates to a vehicle brake control device capable of estimating a road surface friction coefficient of a ground contact surface of a wheel.

  2. Description of the Related Art Conventionally, as a vehicle brake control device, a device that estimates vehicle deceleration based on wheel speed and estimates a road surface friction coefficient based on the estimated vehicle deceleration during braking of the vehicle is known (Patent Document 1). reference).

JP 2013-71657 A

  However, in the prior art, in order to accurately estimate the vehicle deceleration, it is estimated from a plurality of timings at which the wheels return in the anti-lock brake control, and there is a problem that the timing for estimating the road surface friction coefficient is delayed. .

  Accordingly, an object of the present invention is to provide a vehicle brake control device that can quickly estimate a road surface friction coefficient when braking a vehicle.

In order to solve the above problems, a vehicle brake control device according to the present invention includes a plurality of wheel brakes provided corresponding to a plurality of wheels, and a vehicle brake having a control unit that controls the braking force of each wheel brake. A control device, wherein the control unit acquires a road surface friction coefficient estimating unit that estimates a road surface friction coefficient, a braking force acquisition unit that acquires a braking force of a wheel brake for each wheel, and a wheel deceleration for each wheel. Wheel deceleration acquisition means, and the road surface friction coefficient estimation means is configured to control each wheel brake on condition that the slip amount or slip ratio of the wheel is equal to or greater than a predetermined threshold value and the wheel is decelerating. The road surface friction coefficient corresponding to each wheel is estimated based on the power and the wheel deceleration of each wheel.

According to this configuration, since the road surface friction coefficient is estimated based on the braking force of each wheel brake and the wheel deceleration of each wheel, it is estimated from a plurality of timings at which the wheel returns in conventional antilock brake control. Compared with the method of estimating the road surface friction coefficient based on the vehicle deceleration, the road surface friction coefficient can be estimated at an earlier timing. In the situation where the slip amount is generated to some extent (predetermined threshold) when the wheel is decelerating, the wheel deceleration and the road surface friction coefficient correspond to each other. By estimating the road surface friction coefficient based on the deceleration, the road surface friction coefficient can be accurately estimated.

  Further, in the above-described configuration, the road surface friction coefficient estimating means may be configured to estimate the road surface friction coefficient to the low friction coefficient side as the absolute value of the wheel deceleration is larger.

  Since the absolute value of the wheel deceleration when the driver depresses the brake pedal with a predetermined stroke increases as the road surface friction coefficient is on the low friction coefficient side, the vehicle is estimated by estimating the road surface friction coefficient as described above. Based on the deceleration, the road surface friction coefficient can be accurately estimated.

  Further, in the above-described configuration, the road surface friction coefficient estimating means may be configured to estimate the road surface friction coefficient to the low friction coefficient side as the braking force is smaller.

  Since the braking force of the wheel brake becomes smaller as the road surface friction coefficient is lower, the road surface friction coefficient can be accurately estimated based on the braking force by estimating the road surface friction coefficient as described above. .

  In the above-described configuration, the road surface friction coefficient estimating means estimates the road surface friction coefficient when the condition that the antilock brake control mode is not the pressure reduction mode for reducing the braking force is met in addition to the above condition. It can be constituted as follows.

  In the decompression mode that reduces the braking force, the relationship between the wheel deceleration and the road surface friction coefficient may be disrupted, so the road surface friction coefficient is estimated accurately by estimating the road surface friction coefficient when not in such a decompression mode. It can be estimated well.

  In the above-described configuration, the road surface friction coefficient estimating means can be configured to hold the previous value of the road surface friction coefficient when the wheel is not decelerating.

  When the wheel is not decelerating, the wheel tends to return (acceleration), and the relationship between the wheel deceleration and the road surface friction coefficient may be disrupted. In this case, the road surface friction coefficient is not estimated. By maintaining the previous value of the road surface friction coefficient, the road surface friction coefficient can be used by the control unit even when the wheel is not decelerating.

  Further, in the above-described configuration, the road surface friction coefficient estimating means can be configured to hold the previous value of the road surface friction coefficient when the slip amount or slip ratio of the wheel is less than a predetermined threshold. .

  If the slip amount is less than the predetermined threshold, the slip is shallow, and the relationship between the wheel deceleration and the road surface friction coefficient may be disrupted. In this case, the road surface friction coefficient is not estimated and the road surface friction coefficient is not estimated. By holding the previous value of the coefficient, the road surface friction coefficient can be used by the control unit even when the slip amount is less than the predetermined threshold.

  In the above-described configuration, the road surface friction coefficient estimating means can be configured to hold the previous value of the road surface friction coefficient when the antilock brake control mode is the pressure reduction mode.

  When the anti-lock brake control mode is the decompression mode, the wheel tends to return (acceleration), and the relationship between the wheel deceleration and the road surface friction coefficient may be lost. By maintaining the previous value of the road surface friction coefficient without estimating the road surface friction coefficient, the control unit can use the road surface friction coefficient even in the decompression mode.

The vehicle brake control device according to the present invention is a vehicle brake control device having a plurality of wheel brakes provided corresponding to a plurality of wheels, and a control unit that controls the braking force of each wheel brake. The control unit includes a road surface friction coefficient estimating unit that estimates a road surface friction coefficient, a braking force acquisition unit that acquires a braking force of a wheel brake for each wheel, and a wheel deceleration acquisition unit that acquires a wheel deceleration for each wheel. And the difference between the two road surface friction coefficients corresponding to the left and right wheels on the same axis is not less than the first threshold value, and the second smallest road surface friction coefficient among the plurality of road surface friction coefficients corresponding to the plurality of wheels is the first. If it is less than the second threshold value, the vehicle is provided with a split road judging means for judging the road surface friction coefficient of the road surface that is currently traveling is a predetermined value or more different split road in the right and left, and the road surface friction coefficient estimating means , The braking force of the wheel brakes, on the basis of the wheel deceleration of each wheel, and estimates the road surface friction coefficient corresponding to each wheel.

When braking while turning the vehicle on a road surface with a relatively high coefficient of friction, the load applied to each wheel is affected by the effect of centrifugal force due to the vehicle body turning forward due to braking. The outer ring gradually decreases in the order of the front inner ring and the rear inner ring. As a result, the magnitude of the wheel deceleration gradually decreases in the order of the rear inner ring, the front inner ring, the rear outer ring, and the front outer ring in the order opposite to the load order. In contrast to this order, the road surface friction coefficient estimated in this way gradually decreases in the order of the front outer ring, the rear outer ring, the front inner ring, and the rear inner ring. Therefore, the wheel corresponding to the second smallest road surface friction coefficient is the front inner ring. On the other hand, when braking a vehicle on a split road, the wheel deceleration of each wheel on the low friction coefficient side is larger than each wheel on the high friction coefficient side, and the vehicle body is turned forward by braking. The wheel deceleration gradually decreases in the order of the rear wheel on the low friction coefficient side, the front wheel on the low friction coefficient side, the rear wheel on the high friction coefficient side, and the front wheel on the high friction coefficient side. Contrary to this order, the front wheel on the high friction coefficient side, the rear wheel on the high friction coefficient side, the front wheel on the low friction coefficient side, and the rear wheel on the low friction coefficient side gradually decrease. Therefore, the wheel corresponding to the second smallest road surface friction coefficient is the front wheel on the low friction coefficient side.
Therefore, by determining the size of the second smallest road friction coefficient, the size of the road surface friction coefficient corresponding to the wheel with the larger slip amount among the left and right front wheels of the vehicle that is loaded during braking is determined. Therefore, it can be accurately determined whether or not the road surface is a split road.

The vehicle brake control device according to the present invention is a vehicle brake control device having a plurality of wheel brakes provided corresponding to a plurality of wheels, and a control unit that controls the braking force of each wheel brake. The control unit includes a road surface friction coefficient estimating unit that estimates a road surface friction coefficient, a braking force acquisition unit that acquires a braking force of a wheel brake for each wheel, and a wheel deceleration acquisition unit that acquires a wheel deceleration for each wheel. If the vehicle deceleration acquisition means for acquiring vehicle deceleration, the difference between the two road friction coefficient corresponding to the left and right wheels of the coaxial is the third threshold value or more, the vehicle deceleration is within a predetermined range in some cases, the vehicle is provided with a split road judging means for judging the road surface friction coefficient of the road surface that is currently traveling is a predetermined value or more different split road in the right and left, and the road surface friction coefficient estimation means, each wheel brake And the braking force, based on the wheel deceleration of each wheel, and estimates the road surface friction coefficient corresponding to each wheel.

  According to this, since the vehicle deceleration is used as the determination condition, the split road can be determined not only at the start of the antilock brake control but also at an arbitrary time point during the antilock brake control.

The vehicle brake control device according to the present invention is a vehicle brake control device having a plurality of wheel brakes provided corresponding to a plurality of wheels, and a control unit that controls the braking force of each wheel brake. The control unit includes a road surface friction coefficient estimating unit that estimates a road surface friction coefficient, a braking force acquisition unit that acquires a braking force of a wheel brake for each wheel, and a wheel deceleration acquisition unit that acquires a wheel deceleration for each wheel. And the difference between the two road surface friction coefficients corresponding to the left and right front wheels is not less than the fourth threshold value, and the smaller one of the two road surface friction coefficients corresponding to the left and right front wheels is less than the fifth threshold value. in some cases, the vehicle is provided with a split road judging means for judging the road surface friction coefficient of the road surface that is currently traveling is a predetermined value or more different split road in the right and left, and the road surface friction coefficient estimation means, each wheel Bed Based braking force over key, to a wheel deceleration of each wheel, and estimates the road surface friction coefficient corresponding to each wheel.

  According to this, since the magnitude of the road surface friction coefficient corresponding to the wheel with the larger slip amount among the left and right front wheels of the vehicle that is loaded during braking is determined, it is determined whether or not the road surface is a split road. The determination can be performed with high accuracy.

  According to the present invention, it is possible to quickly estimate a road surface friction coefficient when braking a vehicle.

It is a lineblock diagram of vehicles provided with a brake control device for vehicles concerning a 1st 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 flowchart which shows operation | movement of a control part. It is a time chart which shows an example of the estimation method of a road surface friction coefficient, and the determination method of a split road. It is a block diagram which shows the structure of the control part which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the control part which concerns on 2nd Embodiment. It is a time chart which shows an example of the determination method of the split road by the control part which concerns on 2nd Embodiment.

[First Embodiment]
Next, a first 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. In normal times, the brake hydraulic pressure generated in the master cylinder MC in response to the depression force of the brake pedal BP (driver's braking operation) is supplied to the wheel cylinder H after being controlled by the control unit 100 and the hydraulic unit 10. Is done.

  A pressure sensor 91 that detects the pressure of the master cylinder MC and a wheel speed sensor 92 that detects the wheel speed of each wheel W are connected to the control unit 100. 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 and 92, a 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 in which 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 increases. 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 wheel deceleration acquisition unit 112, a brake hydraulic pressure acquisition unit 113 as an example of a braking force acquisition unit, and a road surface friction coefficient estimation. Means 120, anti-lock brake control means 130, split road determination means 140, differential pressure setting means 150, control execution means 160, and storage means 190 are mainly provided.

  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 antilock brake control means 130.

  The wheel deceleration acquisition unit 112 is a unit that calculates and acquires the wheel deceleration WD of each wheel W based on the information on the wheel speed WS acquired from each wheel speed sensor 92. Specifically, the wheel deceleration acquisition unit 112 calculates the wheel deceleration WD of the wheel W by subtracting the previous wheel speed WS from the current wheel speed WS. That is, when the vehicle is decelerated, the wheel deceleration WD is a negative value. When the wheel deceleration acquisition unit 112 calculates the wheel deceleration WD for each wheel W, the wheel deceleration acquisition unit 112 outputs the calculated wheel deceleration WD to the road surface friction coefficient estimation unit 120.

  The brake fluid pressure obtaining unit 113 obtains the brake fluid pressure Pb in each wheel cylinder H corresponding to each wheel W as an example of the braking force of the wheel brakes FL, RR, RL, FR corresponding to each wheel W. It is. Specifically, the brake fluid pressure acquisition unit 113 is configured to select each wheel based on the master cylinder pressure acquired from the pressure sensor 91 and the control history of each inlet valve 1 and each outlet valve 2 acquired from the antilock brake control unit 130. The brake fluid pressure Pb in the cylinder H is estimated and acquired. When the brake fluid pressure acquisition unit 113 estimates the brake fluid pressure Pb in each wheel cylinder, the brake fluid pressure acquisition unit 113 outputs the estimated brake fluid pressure Pb to the road surface friction coefficient estimation unit 120.

  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 a means for determining for each wheel W an instruction for the pressure control mode (indication of whether the hydraulic pressure in the wheel cylinder H is to be increased, held or reduced). Specifically, for example, the anti-lock brake control unit 130 determines that the slip amount SL determined based on the vehicle speed V and the wheel speed WS is equal to or greater than a predetermined threshold value TH1 (see FIG. 5), and the wheel acceleration is increased. When it is less than or equal to 0 (decelerated), it is determined that the wheel W is about to lock, and the instruction of the hydraulic pressure control mode is determined to be the pressure reduction mode. Here, the wheel acceleration is calculated from the wheel speed WS, for example.

  Further, when the wheel acceleration is larger than 0, the antilock brake control means 130 determines the hydraulic pressure control mode instruction as the holding mode. Further, the antilock brake control means 130 determines the instruction of the hydraulic pressure control mode to the pressure increasing mode when the slip amount SL is less than the predetermined threshold value TH1 and the wheel acceleration is 0 or less. When it is determined that the antilock brake control is to be executed, the antilock brake control means 130 outputs information indicating that the antilock brake control is to be executed to the split road determination means 140, and calculates the calculated slip amount SL and the determination. The hydraulic pressure control mode instruction is output to the road surface friction coefficient estimating means 120 and the control execution means 160.

  The road surface friction coefficient estimation unit 120 is based on the wheel deceleration WD of each wheel W acquired from the wheel deceleration acquisition unit 112 and the brake hydraulic pressure Pb in each wheel cylinder H acquired from the brake hydraulic pressure acquisition unit 113. The means for estimating the road surface friction coefficient corresponding to each wheel W. Specifically, the road surface friction coefficient estimating means 120 is a road surface corresponding to each wheel W based on the wheel deceleration WD of each wheel W, the brake fluid pressure Pb in each wheel cylinder H, and the road surface friction coefficient estimation map. The coefficient of friction is estimated.

  Here, the road surface friction coefficient estimation map is a map set in advance for associating the magnitude (absolute value) of the wheel deceleration WD, the brake fluid pressure Pb, and the road surface friction coefficient. It is set in advance. In this road surface friction coefficient estimation map, the larger the wheel deceleration WD, the smaller the road surface friction coefficient (lower friction coefficient side), and the smaller the brake hydraulic pressure Pb, the smaller the road surface friction coefficient. Is set.

  The road surface friction coefficient estimating means 120 estimates the road surface friction coefficient by linear interpolation when the brake fluid pressure Pb and the wheel deceleration WD are values other than those shown in the road surface friction coefficient estimation map.

  Further, the road surface friction coefficient estimating unit 120 acquires the master cylinder pressure acquired from the pressure sensor 91, the hydraulic pressure control mode instruction and the slip amount SL for each wheel W acquired from the antilock brake control unit 130, and the wheel deceleration acquisition. Based on the wheel deceleration WD of each wheel W acquired from the means 112, it also has a function of determining whether or not to estimate the road surface friction coefficient. Specifically, the road surface friction coefficient estimating means 120 has a first condition that the master cylinder pressure is larger than 0, that is, there is a brake input, and a predetermined threshold TH2 in which the slip amount SL is smaller than the predetermined threshold TH1 (FIG. 5). Reference) The second condition that the above is the above, the third condition that the wheel deceleration WD is negative, that is, the wheel W is decelerating, and the instruction of the fluid pressure control mode is not the decompression control as an example of the decompression mode. When all the fourth conditions are satisfied, the road surface friction coefficient is estimated based on the road surface friction coefficient estimation map.

  Here, the predetermined threshold value TH2 can be appropriately set by experiment, simulation, or the like.

  In addition, the road surface friction coefficient estimation unit 120 satisfies the first condition and does not satisfy any one of the second condition, the third condition, and the fourth condition, the road surface friction coefficient estimation map. The previous value of the road surface friction coefficient is held without estimating the road surface friction coefficient based on the above. Further, when the first condition described above is not satisfied, the road surface friction coefficient estimating means 120 sets the road surface friction coefficient to a fixed value for high μ, which is a relatively large fixed value corresponding to the dry road surface. It is configured.

  Then, when the road surface friction coefficient estimating unit 120 estimates the road surface friction coefficient corresponding to each wheel W, the road surface friction coefficient estimating unit 120 outputs the estimated road surface friction coefficient to the split road determination unit 140.

  The split road determination means 140 is a means for determining whether or not the road surface friction coefficient of the ground road surface of the left and right wheels W on the same axis is different from the predetermined road when executing anti-lock brake control. Specifically, the split road determination means 140 has a difference between two road surface friction coefficients corresponding to the left and right front wheels equal to or greater than a first threshold TH3 (see FIG. 5), and a plurality of road surfaces corresponding to a plurality of wheels W. When the second smallest road friction coefficient among the friction coefficients is less than the second threshold value TH4 (see FIG. 5), the road friction coefficient of the road surface on which the vehicle CR is currently traveling is different on the left and right by a predetermined or different split road. Judge that there is.

  Here, when the vehicle CR is braked while turning on a road surface having a relatively high friction coefficient corresponding to a dry road surface (hereinafter also referred to as “high μ turning braking”), the vehicle body is caused by braking. The load applied to each wheel W is gradually reduced in the order of the front outer ring, the rear outer ring, the front inner ring, and the rear inner ring due to the forward turning and the centrifugal force. As a result, the wheel deceleration WD gradually decreases in the order of the rear inner ring, the front inner ring, the rear outer ring, and the front outer ring in the order opposite to the load order. Contrary to this order, the road surface friction coefficient estimated based on is gradually decreased in the order of the front outer ring, the rear outer ring, the front inner ring, and the rear inner ring. Therefore, the wheel W corresponding to the second smallest road surface friction coefficient is the front inner ring.

  On the other hand, when the vehicle CR is braked on a split road, the wheel deceleration WD of each wheel W on the low friction coefficient side is larger than each wheel W on the high friction coefficient side, and the vehicle body is turned forward by braking. As a result, the wheel deceleration WD gradually decreases in the order of the rear wheel on the low friction coefficient side, the front wheel on the low friction coefficient side, the rear wheel on the high friction coefficient side, and the front wheel on the high friction coefficient side. Therefore, on the contrary, the road surface friction coefficient gradually decreases in the order of the front wheel on the high friction coefficient side, the rear wheel on the high friction coefficient side, the front wheel on the low friction coefficient side, and the rear wheel on the low friction coefficient side. . Therefore, the wheel W corresponding to the second smallest road surface friction coefficient is the front wheel on the low friction coefficient side.

  Therefore, the split road determination means 140 determines the second smallest road surface friction coefficient so that the road surface friction coefficient corresponding to the wheel W having the larger slip amount among the left and right front wheels to which a load is applied during braking is substantially applied. The size of is to be determined. As a result, it is possible to satisfactorily distinguish between two situations in which the slip states of the left and right wheels W on the same axis are similar (during braking on a split road and during high μ turning braking).

  The first threshold value TH3 and the second threshold value TH4 can be set in advance to values that can distinguish between high-μ turning braking and braking on a split road by experiments and simulations.

  When the split road determination unit 140 determines that the road is a split road, it outputs information indicating that to the differential pressure setting unit 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 the present embodiment, an allowable differential pressure DP that is a 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 set as a value corresponding to the braking force difference. .

  As a method for setting the allowable differential pressure, a publicly known method may be adopted. The pressure can be set.

  The differential pressure setting means 150 sets the allowable differential pressure DP by receiving information indicating that the road is a split road from the split path determination means 140, and outputs the set allowable differential pressure DP to the control execution means 160.

  The control execution unit 160 uses a known method to determine the wheel brakes FL, RR, and the like based on the hydraulic pressure control mode instruction determined by the antilock brake control unit 130 and the allowable differential pressure DP set by the differential pressure setting unit 150. It is means for controlling the brake fluid pressure of RL and 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 mode instruction determined by the antilock brake control means 130. Also, when it is determined that the road is split, 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 allowable differential pressure DP Controls the hydraulic pressure unit 10 so that the brake fluid pressure of the wheel brake on the high friction coefficient side becomes a value obtained by adding the allowable 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 and constants necessary for the operation of the control unit 100, a road surface friction coefficient estimation map, calculation results, and the like.

Next, the road surface friction coefficient estimation method and split road determination method by the control unit 100 will be described in detail with reference to FIG.
As shown in FIG. 4, the control unit 100 first acquires the wheel speed WS of each wheel W, the vehicle speed V, the wheel deceleration WD of each wheel W, and the brake hydraulic pressure Pb of each wheel cylinder H (S11). . After step S11, the control unit 100 determines whether there is a brake input (S12).

  If it is determined in step S12 that there is no brake input (NO), the control unit 100 sets all the road surface friction coefficients corresponding to the wheels W to fixed values for high μ (S13), and ends this control. If it is determined that there is a brake input in step S12 (YES), the control unit 100 determines for each wheel W whether or not the wheel W is decelerating (S14). In addition, the control part 100 performs a process for every wheel W about the process which estimates the road surface friction coefficient of step S14-S18.

  If it is determined in step S14 that a certain wheel W is not decelerating (NO), the control unit 100 holds the road surface friction coefficient corresponding to the wheel W at the previous value (S15). If it is determined in step S14 that a certain wheel W is decelerating (YES), the control unit 100 determines whether or not the slip amount SL corresponding to the wheel W is equal to or greater than a predetermined threshold value TH2 (S16). .

  If it is determined in step S16 that the slip amount SL corresponding to a certain wheel W is less than the predetermined threshold value TH2 (NO), the control unit 100 holds the road surface friction coefficient corresponding to that wheel W at the previous value (S15). ). If it is determined in step S16 that the slip amount SL corresponding to a certain wheel W is greater than or equal to the predetermined threshold TH2 (YES), the control unit 100 determines whether the instruction of the hydraulic pressure control mode corresponding to that wheel W is not the depressurization mode. It is determined whether or not (S17).

  In step S17, when it is determined that the instruction of the hydraulic pressure control mode corresponding to a certain wheel W is the pressure reduction mode (NO), the control unit 100 holds the road surface friction coefficient corresponding to the wheel W at the previous value (S15). ). If it is determined in step S17 that the hydraulic pressure control mode instruction corresponding to a certain wheel W is not the pressure reduction mode (YES), the control unit 100 calculates the road surface friction coefficient corresponding to the wheel W, the wheel deceleration WD, and the brake fluid. Estimation is performed based on the pressure Pb and the road surface friction coefficient estimation map (S18).

  After step S18, the control unit 100 determines whether or not the difference between the two road surface friction coefficients corresponding to the left and right front wheels is equal to or greater than the first threshold value TH3 (S19). If it is determined in step S19 that the difference between the two road surface friction coefficients is equal to or greater than the first threshold value TH3 (YES), the control unit 100 determines whether or not the second smallest road surface friction coefficient among the plurality is smaller than the second threshold value TH4. Is determined (S20).

  If it is determined in step S20 that the second smallest road surface friction coefficient is smaller than the second threshold TH4 (YES), the control unit 100 determines that the road is a split road (S21) and ends this control. When determining NO in steps S19 and S20, the control unit 100 ends this control without determining that the road is a split road.

  Next, an example of a road surface friction coefficient estimation method and a split road determination method performed by the control unit 100 when the vehicle CR is traveling on a split road will be described in detail with reference to FIG. In the following description, the method for estimating the road surface friction coefficient will be described on behalf of the left and right front wheels, and the description of the left and right rear wheels will be omitted.

  Further, in the following description, the wheel speed, the brake fluid pressure, and the road surface friction coefficient corresponding to the front wheel that contacts the road surface on the low friction coefficient side of the split road are respectively expressed as the low μ side wheel speed WSL, the low μ side hydraulic pressure PL, and Also called the low μ side road surface friction coefficient CL. Also, the wheel speed, brake fluid pressure, and road surface friction coefficient corresponding to the front wheel that contacts the road surface on the high friction coefficient side of the split road are respectively set to the high μ side wheel speed WSH, the high μ side hydraulic pressure PH, and the high μ side road surface friction. Also called coefficient CH.

  As shown in FIGS. 5A and 5B, when the driver steps on the brake pedal BP when the vehicle CR is traveling on a split road (time t1), the low μ-side hydraulic pressure PL and the high μ As the side hydraulic pressure PH increases, each wheel W decelerates, and the vehicle speed V gradually decreases. The low μ side wheel speed WSL is significantly lower than the high μ side wheel speed WSH with respect to the vehicle speed V, and the low μ side wheel speed WSL is lower than the vehicle speed V by a predetermined threshold TH2 or more at time t2. That is, when the slip amount SL on the low μ side becomes equal to or greater than the predetermined threshold value TH2, as shown in FIG. 5C, the control unit 100 estimates the low μ side road surface friction coefficient CL based on the road surface friction coefficient estimation map. Start. In FIG. 5C, for the sake of convenience, the range in which the road surface friction coefficient is changed indicates that the road surface friction coefficient is estimated based on the road surface friction coefficient estimation map, and the range indicated by the straight line is It shall indicate that the road surface friction coefficient is maintained at the previous value.

  Thereafter, as shown in FIG. 5A, when the slip amount SL on the low μ side becomes equal to or greater than a predetermined threshold value TH1 (time t3), as shown in FIGS. The anti-lock brake control is started, specifically, the pressure reduction mode is started, the low μ side hydraulic pressure PL is reduced, and the low μ side road surface friction coefficient CL is held at the previous value.

  At time t3, as shown in FIG. 5A, the high μ side wheel speed WSH is lower than the vehicle speed V by a predetermined threshold value TH2, that is, the high μ side slip amount SL is a predetermined threshold value TH2 or more. Then, as shown in FIG. 5C, the control unit 100 starts estimating the high μ side road surface friction coefficient CH based on the road surface friction coefficient estimation map. That is, in this embodiment, when antilock brake control is started (time t3), the road surface friction coefficient of each front wheel is estimated based on the road surface friction coefficient estimation map. Compared with a method in which the road surface friction coefficient is estimated from a plurality of timings at which the wheels return in control, the road surface friction coefficient can be estimated quickly. In FIG. 5, the timing for starting the estimation of the high μ road surface friction coefficient CH based on the road surface friction coefficient estimation map is the same as that at the start of the antilock brake control. Even if the timing for starting CH estimation is somewhat delayed from the start of antilock brake control, the road surface friction coefficient can be estimated more quickly than in the conventional method.

  In addition, when the low μ side road surface friction coefficient CL is estimated based on the road surface friction coefficient estimation map (time t2), the control unit 100 determines whether the road is a split road. Specifically, as shown in FIG. 5C, at time t2, the difference between the road surface friction coefficients CL and CH is equal to or greater than the first threshold value TH3, and the low μ side road surface friction coefficient CL (second Since the small road surface friction coefficient) is smaller than the second threshold value TH4, the control unit 100 determines that the road is a split road.

  Here, a graph G1 indicated by a two-dot chain line in FIG. 5C is a low μ side road surface friction coefficient during high μ turning braking. Thus, the low μ side road surface friction coefficient is larger than the second threshold value TH4 at the time of high μ turning braking, and therefore the control unit 100 may erroneously determine that the road is a split road at the time of high μ turning braking. Absent.

  Thereafter, as shown in FIGS. 5A and 5B, when the wheel acceleration of the front wheel on the low μ side becomes larger than 0 (time t4), the control unit 100 controls the hydraulic pressure of the low μ side hydraulic pressure PL. The mode is switched from the decompression mode to the holding mode. In the holding mode, when only a part of the friction coefficient of the ground road surface of the front wheel on the low μ side is a smaller friction coefficient (time t6), as shown in FIG. The low μ wheel speed WSL may decrease. In this case, since the control unit 100 determines that the front wheel on the low μ side is decelerating, all the above three conditions (steps S14, S16, and S17) are satisfied, and FIG. As shown, the low μ side road surface friction coefficient CL is estimated again based on the road surface friction coefficient estimation map.

  Thereafter, as shown in FIG. 5 (a), when the front wheel on the low μ side accelerates (time t7), the control unit 100 determines that the front wheel on the low μ side is not decelerating. Keep CL at the previous value. Thereafter, similarly, the control unit 100 estimates the low μ side road surface friction coefficient CL based on the road surface friction coefficient estimation map when all of the above-described three conditions (steps S14, S16, and S17) are satisfied. (Time t8 to t9, t12 to t13), and when any one of the three conditions described above is not satisfied, the low μ side road surface friction coefficient CL is held at the previous value (time t9 to t12, after time t13). .

  In addition, after starting the anti-lock brake control of the low μ side hydraulic pressure PL (time t3), the control unit 100 performs the difference between the high μ side hydraulic pressure PH and the low μ side hydraulic pressure PL by a known differential pressure control. The high μ side hydraulic pressure PH is reduced, held, and increased so that the pressure does not exceed the set allowable differential pressure DP. Furthermore, during the differential pressure control, the control unit 100 reduces the high μ hydraulic pressure PH by the antilock brake control when the anti-lock brake control conditions are met even on the high μ wheel. Time t11).

  That is, the anti-lock brake control is performed on the high μ side front wheel based on the anti-lock brake control on the low μ side. In this case, the control unit 100 estimates the high μ side road surface friction coefficient CH as follows.

  As described above, the control unit 100 starts to estimate the high μ side road surface friction coefficient CH based on the road surface friction coefficient estimation map at time t3. Thereafter, as shown in FIGS. 5A and 5C, when the high μ-side wheel speed WSH increases (time t5), the control unit 100 determines that the high μ-side front wheel is not decelerating, and the high μ-side wheel speed WSH increases. The μ-side road surface friction coefficient FH is held at the previous value.

  Thereafter, when the front wheel on the high μ side is in a decelerating state and the high μ side wheel speed WSH is lower than the vehicle speed V by a predetermined threshold value TH2, that is, the slip amount SL on the high μ side becomes equal to or higher than the predetermined threshold value TH2. (Time t10), the control unit 100 again estimates the high μ side road surface friction coefficient CH based on the road surface friction coefficient estimation map. Thereafter, when the slip amount SL on the high μ side becomes equal to or greater than the predetermined threshold value TH1 (time t11), the control unit 100 starts the pressure-reducing mode of antilock brake control for the front wheel on the high μ side.

  As a result, the condition that the pressure reduction mode is not selected among the three conditions described above is not satisfied, and therefore the control unit 100 stops estimating the high μ side road surface friction coefficient CH based on the road surface friction coefficient estimation map, and increases the high μ value. The side road surface friction coefficient CH is held at the previous value (after time t11).

As described above, according to the present embodiment, the following effects can be obtained in addition to the effects described above.
When the wheel W is not decelerating, when the slip amount SL is less than the predetermined threshold value TH2, or when the hydraulic pressure control mode is the reduced pressure mode, the relationship between the wheel deceleration WD and the road surface friction coefficient may be disrupted. However, in the present embodiment, in such a situation, the road surface friction coefficient is estimated based on the wheel deceleration WD, so that the road surface friction coefficient can be estimated with high accuracy.

  In addition, when there is a possibility that the relationship between the wheel deceleration WD and the road surface friction coefficient as described above may be lost, the previous value of the road surface friction coefficient is maintained without estimating the road surface friction coefficient. Even when the relationship between the speed WD and the road surface friction coefficient is broken, the road surface friction coefficient can be used by the control unit 100.

  Since the split road is determined using the second smallest road surface friction coefficient, that is, the road surface friction coefficient corresponding to the wheel with the larger slip amount SL among the left and right front wheels of the vehicle CR that is loaded during braking, the road surface is split. It is possible to accurately determine whether or not the road.

  For example, compared to the method of determining split roads based on the lateral acceleration applied to the vehicle at the start of antilock brake control, the road surface friction coefficient is used as the determination condition. Therefore, not only at the start of antilock brake control, but also antilock brake A split path can be determined at any time during control.

[Second Embodiment]
Next, a second embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In addition, since this embodiment is obtained by changing a part of the structure of the control unit 100 according to the first embodiment described above, the same reference numerals are given to substantially the same components as those in the first embodiment. The description is omitted.

  As shown in FIG. 6, the control unit 100 according to the second embodiment newly includes a vehicle deceleration acquisition unit 114 that does not exist in the first embodiment, and a split road determination unit according to the first embodiment. A split road determination unit 141 having a split road determination method different from that of 140 is provided. The vehicle deceleration acquisition unit 114 is a unit that calculates and acquires the vehicle deceleration CD applied to the vehicle CR based on the information on the wheel speed WS acquired from each wheel speed sensor 92. Specifically, the vehicle deceleration acquisition means 114 calculates the wheel deceleration WD of each wheel W based on each wheel speed WS, and calculates the average value of each wheel deceleration WD as the vehicle deceleration CD. When the vehicle deceleration acquisition unit 114 calculates the vehicle deceleration CD, the vehicle deceleration CD is output to the split road determination unit 141.

  The split road determination means 141 determines that the vehicle CR is currently traveling when the difference between the two road surface friction coefficients corresponding to the left and right front wheels is equal to or greater than the third threshold TH5 and the vehicle deceleration CD is within a predetermined range. The road surface friction coefficient of the road surface is determined to be a split road that differs from the left and right by a predetermined amount or more. Specifically, the split road determination means 141 determines the difference between two road surface friction coefficients corresponding to the left and right front wheels (hereinafter also referred to as “coaxial wheel μ difference”), the vehicle deceleration CD, and the split level map. Based on this, the split level is calculated, and when the split level is equal to or higher than a predetermined value, it is determined that the road is split.

  Here, the split level map is a map set in advance for associating the coaxial wheel μ difference, the vehicle deceleration CD, and the split level, and is set in advance through experiments, simulations, or the like.

  In this split level map, the split level is set to be equal to or greater than a predetermined value when the coaxial wheel μ difference is equal to or greater than the third threshold TH5 and the vehicle deceleration is within the predetermined range Rp. Here, as shown in FIG. 8C, the predetermined range Rp of the vehicle deceleration CD includes the vehicle deceleration CDS calculated at the time of braking on the split road, and is calculated at the time of high μ turning braking. It can be set as appropriate by experiments, simulations, etc. so that the vehicle deceleration CDH deviates.

  More specifically, the split level map is set so that the split level decreases as the coaxial wheel μ difference decreases.

  Next, a split road determination method by the control unit 100 will be described in detail with reference to FIG. In the flowchart of FIG. 7, steps that are substantially the same as those in the flowchart of FIG.

  In the flowchart of FIG. 7, a new step S31 is provided instead of step S11 in the flowchart of FIG. 4, and new steps S32 and S33 are provided instead of steps S19 and S20 in the flowchart of FIG.

  In step S31, the control unit 100 acquires the wheel speed WS of each wheel W, the vehicle speed V, the wheel deceleration WD of each wheel W, and the brake hydraulic pressure Pb of each wheel cylinder H as in the first embodiment. In addition, the vehicle deceleration CD is also acquired. In step S32, the control unit 100 calculates the split level based on the coaxial wheel μ difference, the vehicle deceleration CD, and the split level map. In step S33, the control unit 100 determines whether or not the split level is greater than or equal to a predetermined value.

  In step S33, when the control unit 100 determines that the split level is equal to or higher than the predetermined value (YES), the control unit 100 determines that the split road is a split road (S21), and determines that the split level is lower than the predetermined value (NO). ) This control is finished as it is.

  Next, an example of a split road determination method performed by the control unit 100 when the vehicle CR is traveling on a split road will be described in detail with reference to FIG. In addition, since estimation of the road surface friction coefficient is the same as that of the first embodiment, the description thereof is omitted. In the following description, the control unit 100 calculates the value of the wheel deceleration WD as it is as the road surface friction coefficient.

  As shown in FIGS. 8A to 8C, the control unit 100 estimates the low μ side road surface friction coefficient CL based on the road surface friction coefficient estimation map at the time t21 by the same method as in the first embodiment. Then, the difference (coaxial wheel μ difference) between the high μ side road surface friction coefficient CH and the low μ side road surface friction coefficient CL is calculated, and the vehicle deceleration CDS is calculated from the wheel deceleration WD of each wheel W. Then, the control unit 100 calculates the split level based on the calculated coaxial wheel μ difference, the vehicle deceleration CDS, and the split level map.

  At this time, if the coaxial wheel μ difference is greater than or equal to the third threshold TH5 and the vehicle deceleration CDS is within the predetermined range Rp, the control unit 100 sets the split level to a value greater than or equal to the predetermined value, It is determined that Here, a graph G2 indicated by a thin two-dot chain line in FIG. 8C is a low μ road surface friction coefficient at the time of high μ turning braking, and a graph indicated by a thick two-dot chain line is at the time of high μ turning braking. Vehicle deceleration CDH. Thus, since the vehicle deceleration CDH is outside the predetermined range Rp during high μ turning braking, the control unit 100 does not set the split level to a predetermined value or higher, and splits during high μ turning braking. There is no misjudgment that it is a road.

  After time t22, the control unit 100 starts antilock brake control by the same method as in the first embodiment. Even after the anti-lock brake control is started in this way, the control unit 100 performs the split determination based on the coaxial wheel μ difference, the vehicle deceleration CDS, and the split level map. That is, the control unit 100 uses the coaxial wheel μ difference and the vehicle deceleration CDS as the determination conditions compared to the method of determining the split road based on, for example, the lateral acceleration applied to the vehicle at the start of the antilock brake control. The split road can be determined not only at the start of the lock brake control but also at an arbitrary time point during the anti-lock brake control.

  The present invention is not limited to the above embodiments, and can be used in various forms as exemplified below.

  In the first embodiment, as one of the split road determination conditions, there is provided a condition that the second smallest road surface friction coefficient among the plurality of road surface friction coefficients corresponding to the plurality of wheels W is less than the second threshold value TH4. However, the present invention is not limited to this, and instead of this condition, there is provided a condition that the smaller one of the two road surface friction coefficients corresponding to the left and right front wheels is less than a predetermined threshold value. Also good. In other words, the split road determination means is such that the difference between the two road surface friction coefficients corresponding to the left and right front wheels is equal to or greater than the fourth threshold value and the smaller of the two road surface friction coefficients corresponding to the left and right front wheels. When the coefficient is less than the fifth threshold value, the split road may be determined.

  In the first embodiment, one of the conditions for estimating the road surface friction coefficient based on the road surface friction coefficient estimation map is that the pressure reduction mode is not used. However, the present invention is not limited to this, and Instead, the condition may be that the slip amount SL is less than a predetermined threshold value TH1.

  In each of the above embodiments, in order to determine the split road, the difference between the two road surface friction coefficients corresponding to the left and right front wheels is compared with the respective threshold values TH3 and TH5, but the present invention is not limited to this, For example, a difference between two road surface friction coefficients corresponding to the left and right rear wheels may be compared with a threshold value.

  In each of the above embodiments, the wheel deceleration is treated as a negative value, but the present invention is not limited to this, and the wheel deceleration may be treated as a positive value.

  In each of the above embodiments, the vehicle brake control device A using the brake fluid is illustrated, but 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. It may be a vehicle brake control device for controlling the vehicle. In this case, the condition that the anti-lock brake control mode is not the pressure reducing mode for reducing the braking force is set as the condition that the pressure reducing mode is not one of the conditions for determining the split road in the first embodiment. It may be replaced with.

  In each said embodiment, although slip amount was used for estimation of a road surface friction coefficient, this invention is not limited to this, For example, you may use a slip ratio.

DESCRIPTION OF SYMBOLS 100 Control part 112 Wheel deceleration acquisition means 113 Brake fluid pressure acquisition means 120 Road surface friction coefficient estimation means A Vehicle brake control apparatus FL, RR, RL, FR Wheel brake W Wheel

Claims (10)

A vehicle brake control device having a plurality of wheel brakes provided corresponding to a plurality of wheels, and a control unit that controls a braking force of each wheel brake,
The controller is
Road surface friction coefficient estimating means for estimating a road surface friction coefficient;
Braking force acquisition means for acquiring the braking force of the wheel brake for each wheel;
Wheel deceleration acquisition means for acquiring wheel deceleration for each wheel, and
The road surface friction coefficient estimator is configured so that the braking force of each wheel brake, the wheel deceleration of each wheel, and the wheel deceleration, on the condition that the slip amount or slip ratio of the wheel is equal to or greater than a predetermined threshold value and the wheel is decelerating, A vehicle brake control device that estimates a road surface friction coefficient corresponding to each wheel on the basis of the above. A vehicle brake control device having a plurality of wheel brakes provided corresponding to a plurality of wheels, and a control unit that controls a braking force of each wheel brake,
The controller is
Road surface friction coefficient estimating means for estimating a road surface friction coefficient;
Braking force acquisition means for acquiring the braking force of the wheel brake for each wheel;
Wheel deceleration acquisition means for acquiring wheel deceleration for each wheel;
The difference between the two road surface friction coefficients corresponding to the left and right wheels on the same axis is equal to or greater than the first threshold value, and the second smallest road surface friction coefficient among the plurality of road surface friction coefficients corresponding to the plurality of wheels is the second threshold value. A split road determination means for determining that the road friction coefficient of the road surface on which the vehicle is currently traveling is a predetermined or different split road on the left and right ,
The road surface friction coefficient estimating means estimates a road surface friction coefficient corresponding to each wheel based on the braking force of each wheel brake and the wheel deceleration of each wheel. A vehicle brake control device having a plurality of wheel brakes provided corresponding to a plurality of wheels, and a control unit that controls a braking force of each wheel brake,
The controller is
Road surface friction coefficient estimating means for estimating a road surface friction coefficient;
Braking force acquisition means for acquiring the braking force of the wheel brake for each wheel;
Wheel deceleration acquisition means for acquiring wheel deceleration for each wheel;
Vehicle deceleration acquisition means for acquiring vehicle deceleration;
When the difference between the two road surface friction coefficients corresponding to the left and right wheels on the same axis is equal to or greater than a third threshold and the vehicle deceleration is within a predetermined range, the road surface of the road surface on which the vehicle is currently traveling Split road determination means for determining that the friction coefficient is a split road different in a predetermined difference between right and left, and
The road surface friction coefficient estimating means estimates a road surface friction coefficient corresponding to each wheel based on the braking force of each wheel brake and the wheel deceleration of each wheel. A vehicle brake control device having a plurality of wheel brakes provided corresponding to a plurality of wheels, and a control unit that controls a braking force of each wheel brake,
The controller is
Road surface friction coefficient estimating means for estimating a road surface friction coefficient;
Braking force acquisition means for acquiring the braking force of the wheel brake for each wheel;
Wheel deceleration acquisition means for acquiring wheel deceleration for each wheel;
The difference between the two road surface friction coefficients corresponding to the left and right front wheels is not less than the fourth threshold value, and the smaller one of the two road surface friction coefficients corresponding to the left and right front wheels is less than the fifth threshold value. Includes a split road determination means that determines that the road friction coefficient of the road surface on which the vehicle is currently traveling differs from the left and right by a predetermined distance or more ,
The road surface friction coefficient estimating means estimates a road surface friction coefficient corresponding to each wheel based on the braking force of each wheel brake and the wheel deceleration of each wheel. The road surface friction coefficient estimation means, as the absolute value of the wheel deceleration is large, the claim 1, characterized in that for estimating the road surface friction coefficient to a low friction coefficient side according to any one of claims 4 Brake control device for vehicles. The vehicle brake control according to any one of claims 1 to 5, wherein the road surface friction coefficient estimating means estimates the road surface friction coefficient to a lower friction coefficient side as the braking force is smaller. apparatus. The road surface friction coefficient estimating means estimates the road surface friction coefficient when a condition that the anti-lock brake control mode is not a pressure reduction mode for reducing the braking force is satisfied in addition to the above condition. the vehicle brake control device according to 1. The vehicular brake control device according to claim 1 or 7 , wherein the road surface friction coefficient estimating means holds a previous value of the road surface friction coefficient when the wheel is not decelerating. The road surface friction coefficient estimation unit, when the slip amount or the slip ratio of the wheel is less than the predetermined threshold value, according to claim 1, characterized in that to hold the previous value of the road surface friction coefficient, claim 7 or claim Item 9. The vehicle brake control device according to Item 8 . The road surface friction coefficient estimation unit, when the mode of the anti-lock brake control is vacuum mode, claim 1, characterized in that to hold the previous value of the road surface friction coefficient, claim 7, claim 8 or The vehicle brake control device according to claim 9 .

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