JP2018043543A - Braking force control device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel economy by efficiently performing regeneration without causing an interruption of deceleration of a vehicle and making braking force unstable due to an intervention of an ABS.SOLUTION: A braking force control device of a vehicle has function of ABSs by which braking force during braking the vehicle is controlled so as to prevent a wheel lock state for each wheel; calculates ABS affordable intervention degrees PABS at which respective ABSs are activated on the basis of moving states of wheels to be controlled by respective ABSs; compares the ABS affordable intervention degrees PABS calculated until respective ABSs are activated; and sets, for wheels whose ABS affordable intervention degrees PABS are smaller, delay time (regenerative braking force-decrease start delay time) tk during which switching of braking force for decreasing regenerative braking force and increasing hydraulic braking force to shorter time.SELECTED DRAWING: Figure 2

Description

  The present invention is an antilock brake system (Antilock Brake System: hereinafter abbreviated as ABS) that can perform regenerative braking and hydraulic braking, and can control the braking force of the wheel to be controlled independently for each wheel. The present invention relates to a vehicle braking force control device having a function.

  Conventionally, an ABS that prevents a wheel from being locked is used in many vehicles, and is also used in an electric vehicle and a hybrid vehicle that can perform a regenerative brake and a hydraulic brake. For example, in Japanese Patent Laying-Open No. 2015-85792 (hereinafter referred to as Patent Document 1), when the braking slip amount of the front wheel on which the regenerative brake is operated exceeds a reference value, the regenerative brake of the front wheel at the reference time is set as the reference time. The hydraulic brake is controlled so that the hydraulic brake of the front wheel increases while controlling the regenerative brake of the front wheel so that the provisional target regenerative braking force is lower than the braking force by a predetermined value. There is disclosed a technique of a vehicle braking force control method for gradually decreasing a regenerative brake and gradually increasing a hydraulic brake when it is determined that the increase amount of the brake has become a predetermined value or more.

Japanese Patent Laying-Open No. 2015-85792

  By the way, the regenerative brake is excellent in control responsiveness compared with the hydraulic brake, but the regenerative braking force has a different characteristic that it varies depending on the situation and is unstable. For this reason, as in the technique of the vehicle braking force control method disclosed in Patent Document 1 described above, the switching from the regenerative brake to the hydraulic brake is performed by the operation of the ABS during braking by the regenerative brake and the hydraulic brake. If it happens, even if ABS does not intervene on all four wheels, if the regenerative brake and hydraulic brake are switched simultaneously on all four wheels, the difference in characteristics between the regenerative brake and hydraulic brake, etc. There is a problem that the deceleration is lost from the brake or the braking force becomes unstable. Also, if the regenerative brake and hydraulic brake are switched simultaneously on all four wheels, the regenerative brake is switched to the hydraulic brake up to wheels that do not require ABS intervention and do not need to replace the regenerative brake and hydraulic brake. Therefore, there is a problem that the regeneration cannot be performed efficiently.

  The present invention has been made in view of the above circumstances, and the braking force of a vehicle with high fuel efficiency and efficient regeneration without causing deceleration omission of the vehicle or instability of braking force due to the intervention of ABS. The object is to provide a control device.

  One aspect of a vehicle braking force control device according to the present invention is a vehicle braking force control device that can be freely braked by a regenerative brake and a hydraulic brake of an electric motor. A plurality of wheel braking force control means that are controlled in accordance with the movement state of each wheel, and each wheel braking force control means that is operated based on the movement state of each wheel that is controlled by the plurality of wheel braking force control means. The operating margin calculation means for calculating the operating margin until operation is compared with the operating margin until each of the wheel braking force control means is operated, and the regenerative brake is lowered for the wheel with the smaller operating margin. There is provided braking force switching means for setting a short delay time until switching of the braking force for increasing the hydraulic brake is started and executing switching of the braking force.

  According to the braking force control device for a vehicle according to the present invention, it is possible to improve the fuel efficiency by efficiently performing the regeneration without causing the deceleration of the vehicle to be lost or the braking force becoming unstable due to the intervention of ABS. It becomes.

1 is a schematic configuration diagram of a regenerative brake system and a hydraulic brake system for a vehicle according to an embodiment of the present invention. It is a flowchart of the braking force control program which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the characteristic of the slip ratio correction | amendment gain which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the characteristic of the regenerative brake reduction start delay time which concerns on one Embodiment of this invention. It is a time chart which shows an example of the change of the regenerative braking force by the regenerative brake of each wheel when ABS operates to four wheels concerning one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes a vehicle, and a left front wheel 2fl, a right front wheel 2fr, a left rear wheel 2rl, and a right rear wheel 2rr of the vehicle 1 are supported by the vehicle body via suspensions (not shown).

  Inside the left front wheel 2fl, right front wheel 2fr, left rear wheel 2rl, and right rear wheel 2rr are a left front wheel in-wheel motor 3fl, a right front wheel in-wheel motor 3fr, a left rear wheel in-wheel motor 3rl, and a right rear wheel in-wheel. A motor 3rr is incorporated so that power can be transmitted to each wheel.

  In the present embodiment, the driving force described below, which is generated in each wheel 2fl, 2fr, 2rl, 2rr by independently controlling the torque of each in-wheel motor 3fl, 3fr, 3rl, 3rr, and The regenerative braking force (regenerative brake) can be independently controlled.

  Each in-wheel motor 3fl, 3fr, 3rl, 3rr is connected to an inverter 4 provided corresponding to each motor, and converts the direct current power supplied from the battery 5 into alternating current power. Are supplied independently to each in-wheel motor 3fl, 3fr, 3rl, 3rr. Thereby, each in-wheel motor 3fl, 3fr, 3rl, 3rr is drive-controlled, and a driving force is provided with respect to each wheel 2fl, 2fr, 2rl, 2rr.

  Each in-wheel motor 3fl, 3fr, 3rl, 3rr also functions as a generator, generates electric power by the rotational energy of each wheel 2fl, 2fr, 2rl, 2rr, and regenerates the generated power to the battery 5 via the inverter 4. The regenerative energy generated by the power generation of each in-wheel motor 3fl, 3fr, 3rl, 3rr gives regenerative braking force (regenerative braking) to each wheel 2fl, 2fr, 2rl, 2rr. Give.

  On the other hand, each wheel 2fl, 2fr, 2rl, 2rr is provided with a friction brake mechanism 6fl, 6fr, 6rl, 6rr. These friction brake mechanisms 6fl, 6fr, 6rl, 6rr are, for example, disc brakes, This is a known brake device such as a drum brake.

  These friction brake mechanisms 6fl, 6fr, 6rl, 6rr are connected to the brake drive unit 7, and the pistons of the wheel cylinders are actuated by the hydraulic pressure supplied from the brake drive unit 7, and the wheels 2fl, 2fr, 2rl, A braking force (hydraulic brake) is applied to 2rr.

  The brake drive unit 7 includes a hydraulic pressure generator including a booster pump, an accumulator, etc., a pressure adjustment control valve that adjusts the pressure of the brake hydraulic oil and supplies it to the wheel cylinders of the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr, and a friction brake The hydraulic unit includes an open / close control valve that opens and closes a hydraulic circuit that supplies brake hydraulic oil to the mechanisms 6fl, 6fr, 6rl, and 6rr.

  And the above-mentioned inverter 4 and the brake drive part 7 are each connected to the control unit 10. FIG.

  The control unit 10 includes a microcomputer including a CPU, a ROM, a RAM, and the like, and executes various programs to control the in-wheel motors 3fl, 3fr, 3rl, and 3rr, and the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr. Control the operation independently. For this reason, the control unit 10 includes an accelerator sensor 11 that detects the driver's accelerator operation amount, a brake sensor 12 that detects the driver's brake operation amount, and wheel speeds ωfl, ωfr, ωrl of each wheel 2fl, 2fr, 2rl, and 2rr. , Ωrr for detecting wheel speed sensors 13fl, 13fr, 13rl, 13rr, a longitudinal acceleration sensor 14 for detecting longitudinal acceleration Gx, and a lateral acceleration sensor 15 for detecting lateral acceleration Gy. Further, the control unit 10 controls each in-wheel motor 3fl, 3fr, 3rl, 3rr, such as a signal representing a current value flowing from the inverter 4 to each in-wheel motor 3fl, 3fr, 3rl, 3rr, a signal representing a voltage value, and the like. The sensor signal necessary for this is input from the inverter 4.

  Based on the above-mentioned signals, the control unit 10 requests the required driving force (target driving force) according to the driver's accelerator operation amount or the required braking force (target braking force) according to the driver's brake operation amount, that is, The required braking / driving force required for running or braking the vehicle 1 is calculated with reference to a preset map, table, etc., for each wheel 2fl, 2fr, 2rl, 2rr. The in-wheel motors 3fl, 3fr, 3rl, and 3rr are allotted to each wheel demand braking / driving force generated. When the required braking / driving force value is positive, the driving force is requested, and when the requested braking / driving force is negative, the braking force is requested.

  The control unit 10 generates a control signal (for example, a PWM control signal) so that a current corresponding to the required braking / driving force of each wheel 2fl, 2fr, 2rl, 2rr flows to each in-wheel motor 3fl, 3fr, 3rl, 3rr. And output to the inverter 4. When the required braking / driving force of each wheel 2fl, 2fr, 2rl, 2rr is negative, the control unit 10 sets the required braking / driving force of each wheel 2fl, 2fr, 2rl, 2rr by experiment, calculation or the like in advance. According to the ratio, the regenerative brakes generated by the in-wheel motors 3fl, 3fr, 3rl, and 3rr and the hydraulic brakes generated by the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr are distributed. At this time, the control unit 10 outputs a control signal for generating the regenerative brake to the inverter 4, and outputs a control signal for generating the hydraulic brake to the brake drive unit 7. Thereby, the target regenerative brake is generated in each of the in-wheel motors 3fl, 3fr, 3rl, and 3rr, and the target hydraulic brake is generated in the friction brake mechanisms 6fl, 6fr, 6rl, and 6rr.

  The control unit 10 also has an ABS function for controlling the braking force during braking to prevent the wheel from being locked for each wheel (that is, wheel braking force control means that can be operated independently of four. And an operation margin (ABS intervention margin) PABS until each ABS is operated based on a motion state of a wheel to be controlled by each ABS, and ABS until each ABS is operated. Delay time (regenerative brake reduction start delay time) tk before starting replacement of braking force to reduce the regenerative brake and increase the hydraulic brake as the wheel with a smaller ABS intervention margin PABS is compared with the intervention margin PABS Set to short and execute the braking force replacement. Specifically, the ABS of the present embodiment is, for example, when the preset wheel deceleration is reached, the increase of the brake fluid pressure is suppressed, and the brake fluid pressure is maintained. When the slip ratio exceeds a preset value, the brake fluid pressure is reduced, and thereafter, the brake fluid pressure is maintained, the brake fluid pressure is increased, and so on. Thus, the control unit 10 has functions as wheel braking force control means, operating margin calculation means, and braking force replacement means.

  Next, the braking force control of the present embodiment executed by the control unit 10 will be described with reference to the flowchart of FIG.

  First, in step (hereinafter abbreviated as “S”) 101, it is determined whether or not the host vehicle 1 is being braked. If the vehicle is not being braked, the program is exited, and if it is being braked, the process proceeds to S102.

  In S102, it is determined whether or not the braking being executed includes a regenerative brake (whether or not the regenerative brake and the hydraulic brake are applied). If the regenerative brake is not included, that is, only the hydraulic brake, The process jumps to S113 to continue the braking control as it is, and the ABS is activated as necessary.

  If it is determined in S102 that the regenerative brake is included (braking by regenerative brake and hydraulic brake), the process proceeds to S103, and it is determined whether or not there is a wheel on which the ABS intervenes. In addition, since it is only necessary to determine whether or not a condition that the ABS intervenes in the wheel is satisfied, even if the ABS does not intervene directly as in the present embodiment, a side slip during braking of the vehicle is prevented. Whether or not the side-slip prevention device is activated may be provided instead of the determination in S103.

  As a result of the determination in S103, if it is determined that there is no wheel in which the ABS has intervened, or that the condition in which the ABS intervenes in the wheel is not satisfied, the process jumps to S113 to continue the brake control as it is. In response, the ABS is activated.

  If there is a wheel intervened by ABS, the process proceeds to S104, the regenerative brake of the wheel intervening ABS is immediately reduced to 0, and the hydraulic brake is increased to a value (control pressure) set in advance by experiment, calculation, etc. As a result, a signal is output to the inverter 4 and the brake drive unit 7.

  Next, the process proceeds to S105, where the slip ratio λ (left front wheel slip ratio λfl, right front wheel slip ratio λfr, left rear wheel slip ratio λrl, right rear wheel slip ratio λrr) of each wheel is set to, for example, the following (1) to Calculated by equation (4).

λfl = ((vehicle speed−ωfl) / vehicle speed) · 100 (1)
λfr = ((vehicle speed−ωfr) / vehicle speed) · 100 (2)
λrl = ((vehicle speed−ωrl) / vehicle speed) · 100 (3)
λrr = ((vehicle speed−ωrr) / vehicle speed) · 100 (4)
Here, the vehicle body speed is a value (for example, the fastest value) calculated in advance based on the wheel speeds ωfl, ωfr, ωrl, ωrr, etc. of the wheels 2fl, 2fr, 2rl, 2rr.

  Next, the process proceeds to S106, and the contact loads Fz (left front wheel contact load Fzfl, right front wheel contact load Fzfr, left rear wheel contact load Fzrl, right rear wheel contact load Fzrr) of each wheel are set as follows, for example: 11) Calculated by the equation.

  That is, the front wheel ground load Fzf and the rear wheel ground load Fzr can be calculated by, for example, the following equations (5) and (6).

Fzf = Wf − ((m · Gx · h) / L) (5)
Fzr = W−Fzf (6)
Here, Wf is the front wheel static load, m is the vehicle mass, h is the height of the center of gravity, L is the wheelbase, and W is the vehicle weight (= m · g).

  Further, the left wheel side load ratio WRl can be calculated by the following equation (7).

WRl = 0.5− (Gy / g) · (h / Ltred) (7)
Here, Ltred is the average tread value of the front and rear wheels.

  From these equations (5), (6), and (7), Fzfl, Fzfr, Fzrl, and Fzrr can be calculated by the following equations (8) to (11).

Fzfl = Fzf · WRl (8)
Fzfl = Fzf · (1-WRl) (9)
Fzrl = Fzr · WRl (10)
Fzrr = Fzr · (1−WR1) (11)
Next, in S107, slip ratio correction gains KABS (left front wheel slip ratio correction gain KABSfl, right front wheel slip ratio correction gain KABSfr, left rear wheel slip ratio correction gain KABSrl, right rear wheel slip ratio correction gain KABSrr) are processed. For example, the setting is made by referring to a map as shown in FIG.

  This slip ratio correction gain KABS is set according to the contact load Fz of each wheel, and is set to a smaller value as the contact load Fz of each wheel becomes larger as shown in FIG. This reflects that it can be determined that the wheel having a larger ground load Fz has a greater gripping force on the road surface, the slip is small, and the ABS intervention margin PABS until the ABS described later is activated is large. is there.

  Next, in S108, the ABS intervention margin PABS (left front wheel ABS intervention margin PABSfl, right front wheel ABS intervention margin PABSfr, left rear wheel ABS intervention margin PABSrl, right rear wheel until the ABS of each wheel is activated. The ABS intervention margin PABSrr) is calculated by, for example, the following equations (12) to (15).

PABSfl = 100−λfl · KABSfl (12)
PABSfr = 100−λfr · KABSfr (13)
PABSrl = 100−λrl · KABSrl (14)
PABSrr = 100−λrr · KABSrr (15)
As described above, the ABS intervention margin PABS is set to be smaller as the slip ratio λ increases and the slip ratio correction gain KABS increases.

  Next, in S109, the regenerative brake reduction start delay time limit value tklim for each wheel (left front wheel regenerative brake reduction start delay time limit value tklimfl, right front wheel regenerative brake reduction start delay time limit value tklimfr, left rear wheel regenerative brake reduction start) The delay time limit value tklimrl and the right rear wheel regenerative brake reduction start delay time limit value tklimrr) are calculated by the following equations (20) to (23), for example.

  In other words, the regenerative brake reduces the regenerative braking force Fk linearly with a slope α set in advance by experiment, calculation, etc., and reduces it from the regenerative brake reduction start delay time tk (Fk ≦ Fk0, t−tk ≧ If it is 0), the following equations (16) and (17) are established.

Fk = Fk0−α · (t−tk) (16)
Therefore, the wheel speed ω is
ω0−ω = ∫ (Fk0−α · (t−tk)) dt
= (Fk0 + α · tk) · t- (1/2) · α · t 2 ... (17)
Here, Fk0 is an initial regenerative braking force, and ω0 is an initial wheel speed (in the present embodiment, the initial indicates a value when an ABS intervention occurs in any wheel).

  When t is deleted from these equations (16) and (17), the regenerative brake reduction start delay time tk is solved, and the speed at which energy can be regenerated is ωlim (a value set in advance by experiment, calculation, etc.) Assuming that the brake reduction is completed (Fk = 0 when ω = ωlim), and the regenerative brake reduction start delay time limit tklim at this time is the regenerative brake reduction start delay time limit value tklim, the following equation (18) Is obtained.

tklim = ((2 · α · (ω0−ωlim)) ^1/2 −Fk0) / α (18)
Therefore, for each wheel, the start delay time of the regenerative brake is limited so that the reduction of the regenerative brake is completed by the time when the energy regenerative speed ωlim is reached (so that the regenerative braking force becomes 0). Then, the regenerative brake reduction start delay time limit value tklim (left front wheel regenerative brake reduction start delay time limit value tklimfl, right front wheel regenerative brake reduction start delay time limit value tklimfr, left rear wheel regenerative brake reduction start delay time limit value of each wheel. tklimrl and right rear wheel regenerative brake reduction start delay time limit value tklimrr) are calculated by the following equations (19) to (22).

tklimfl = ((2 · α · (ω0fl−ωlim)) ^1/2 −Fk0fl) / α (19)
tklimfr = ((2 · α · (ω0fr−ωlim)) ^1/2 −Fk0fr) / α (20)
tklimrl = ((2 · α · (ω0rl−ωlim)) ^1/2 −Fk0rl) / α (21)
tklimrr = ((2 · α · (ω0rr−ωlim)) ^1/2 −Fk0rr) / α (22)
Here, Fk0fl, Fk0fr, Fk0rl, and Fk0rr are initial regenerative braking forces of the respective wheels, and ω0fl, ω0fr, ω0rl, and ω0rr are initial wheel speeds of the respective wheels. As described above, in the present embodiment, the initial value indicates a value when an ABS intervention occurs in any wheel. In other words, if a low speed range where regenerative braking cannot be performed is reached, there is a risk that deceleration will be lost while the regenerative brake is being reduced. Thus, the regenerative brake reduction start delay time tk is limited to be long.

  Next, in S110, the regenerative brake reduction start delay time tk of each wheel (left front wheel regenerative brake reduction start delay time tkfl, right front wheel regenerative brake reduction start delay time tkfr, left rear wheel regenerative brake reduction start delay time tkrl, right The rear wheel regenerative brake reduction start delay time tkrr is set by, for example, experiments and calculations in advance, and by referring to a map as shown in FIG. 4, the ABS intervention margin until the ABS of each wheel is activated. Set according to degree PABS.

  As is clear from FIG. 4, the regenerative braking until the start of the replacement of the braking force that decreases the regenerative brake and increases the hydraulic brake as the ABS intervention margin PABS until the ABS of each wheel is activated decreases. The reduction start delay time tk is set to be short. The regenerative brake reduction start delay time tk of each wheel set in the map of FIG. 4 is limited by the regenerative brake reduction start delay time limit value tklim calculated in S109 described above (limited to be shorter than tklim). ) Is set.

  Next, in S111, the regenerative braking force Fk of the regenerative brake other than the ABS intervention wheel is calculated based on the above-described equation (16) and output to the inverter 4.

  Next, proceeding to S112, the hydraulic brakes Fb other than the ABS intervention wheels are calculated based on, for example, the following equation (23), and output to the brake drive unit 7.

Fb = Fx0−Fk (23)
Here, Fx0 is an initial braking force including a regenerative braking force of the wheel. As described above, in the present embodiment, the initial value indicates a value when an ABS intervention occurs in any wheel. That is, the sum of the braking force by the regenerative brake and the braking force by the hydraulic brake when the regenerative brake is replaced with the hydraulic brake is maintained at a constant Fx0. In addition, the replacement of the regenerative brake with the hydraulic brake is not performed simultaneously for each wheel, but is performed in order from the wheel having the smallest ABS intervention margin PABS. It is effectively prevented that speed loss occurs and braking force becomes unstable. At this time, when outputting the hydraulic brake Fb other than the ABS intervention wheel, a timing earlier than the regenerative brake reduction start delay time tk set for each wheel is taken into account in consideration of a delay in response of the hydraulic brake Fb. You may make it output by (value set beforehand).

  Subsequently, it progresses to S113 and brake control is continued.

  In other words, as shown in the time chart of FIG. 5, when the initial regenerative braking force Fk0, when ABS intervenes at a predetermined wheel at time t0, the regenerative braking force of the regenerative brake of this wheel is immediately 0 as shown by sk0. (S104). Note that the slope of sk0 indicates a mechanical delay in generating the regenerative braking force. Next, the ABS intervention margin PABS until the ABS of the other wheel is operated is calculated (S108), and the braking force is switched to reduce the regenerative brake and increase the hydraulic brake according to the ABS intervention margin PABS. The regenerative brake reduction start delay time tk (in FIG. 5, tk1, tk2, tk3) until the start is set (S110). The regenerative brake reduction start delay time tk is set to be shorter as the ABS intervention margin PABS is smaller (tk1 <tk2 <tk3), and the regenerative brake is lowered and the hydraulic brake is increased as the ABS is approaching. Replacement of the braking force to be performed is performed quickly. Further, although not shown in FIG. 5, the hydraulic brake that is equivalent to the reduced regenerative braking force is raised on the wheel where the regenerative brake is reduced.

  As described above, according to the embodiment of the present invention, the ABS function of controlling the braking force during braking and preventing the locked state of each wheel is provided (that is, the four can be operated independently). Each of the ABSs has a braking force control means), and an operation margin (ABS intervention margin) PABS until each ABS is operated based on a motion state of a wheel to be controlled by each ABS is calculated. Compared to the ABS intervention margin PABS until the engine operates, the smaller the ABS intervention margin PABS is, the smaller the delay time until the braking force replacement starts to reduce the regenerative brake and increase the hydraulic brake (regenerative brake). Reduction start delay time) tk is set short, and braking force replacement is executed. For this reason, the replacement of the regenerative brake to the hydraulic brake during ABS operation is not performed all at once, but in order from the wheel with the smallest ABS intervention margin PABS. There will be no significant loss of speed or unstable braking force. In addition, in a wheel having a large ABS intervention margin PABS, replacement of the regenerative brake with the hydraulic brake is performed for as long as possible, so that regeneration is performed efficiently and fuel efficiency can be improved.

  In the present embodiment, an electric vehicle having an in-wheel motor on each of the four wheels has been described as an example. However, a vehicle that travels with two motors, an electric vehicle that travels with three motors, and a hybrid vehicle also have predetermined Needless to say, the present invention can also be applied to a vehicle having a plurality of ABS functions corresponding to wheels.

1 Vehicle 2fl, 2fr, 2rl, 2rr Wheel 3fl, 3fr, 3rl, 3rr In-wheel motor 4 Inverter 5 Battery 6fl, 6fr, 6rl, 6rr Friction brake mechanism 7 Brake drive 10 Control unit (wheel braking force control means, operating margin Degree calculation means, braking force replacement means)
11 Acceleration sensor 12 Brake sensor 13fl, 13fr, 13rl, 13rr Wheel speed sensor 14 Longitudinal acceleration sensor 15 Lateral acceleration sensor

Claims (7)

In a braking force control device for a vehicle that can be freely braked by a regenerative brake and a hydraulic brake of an electric motor,
A plurality of wheel braking force control means for controlling the braking force of the wheel to be controlled according to the movement state of the wheel;
An operation margin calculating means for calculating an operation margin until each wheel braking force control means is operated based on a motion state of each wheel to be controlled controlled by the plurality of wheel braking force control means;
Comparing the operating margins until the respective wheel braking force control means are operated, the delay until the braking force replacement is started to reduce the regenerative brake and increase the hydraulic brake as the operating margin is smaller. A braking force replacement means for setting the time short and executing the braking force replacement;
A braking force control device for a vehicle, comprising:   2. The vehicle braking force control device according to claim 1, wherein the wheel braking force control means is an anti-lock brake control device that controls a braking force during braking to prevent a wheel from being locked.   The operating margin calculating means calculates the operating margin according to at least a slip ratio of a wheel, and sets the operating margin smaller as the slip ratio of the wheel increases. The braking force control device for a vehicle according to claim 1 or 2.   The operating margin calculation means calculates the operating margin according to the slip ratio of the wheel and the contact load, and sets the operating margin smaller as the slip ratio of the wheel increases. 4. The braking force control device for a vehicle according to claim 3, wherein the operating margin is set to be larger as the ground contact load of the wheel is larger.   The braking force replacement means immediately turns off the regenerative brake without considering the delay time until the braking force replacement is started for the wheel in which the wheel braking force control by the wheel braking force control means is first activated. The braking force control device for a vehicle according to any one of claims 1 to 4, wherein the hydraulic brake is increased to a preset value.   The braking force replacement means reduces the regenerative brake to increase the hydraulic brake, and sums the braking force by the regenerative brake and the braking force by the hydraulic brake when the regenerative brake is replaced with the hydraulic brake. The vehicle braking force control device according to any one of claims 1 to 5, wherein the braking force is maintained constant.   The braking force replacement means completes replacement of the regenerative brake with the hydraulic brake before a preset wheel falls below a recyclable vehicle speed. A braking force control device for a vehicle according to claim 1.

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