Vehicle brake control device

Abstract

Each of a multitude of electric braking devices corresponds to one of a multitude of wheels and has a motor. A brake ECU, which controls the electric braking devices, determines whether there is an overheating motor whose temperature T is greater than or equal to a first set threshold Tth1. Additionally, if there is only one overheating motor, the brake ECU reduces a current value Ix for the overheating motor, with a more gradual gradient when the temperature T of the overheating motor is low than when the temperature is high.

Description

TECHNICAL AREA

[0001] The present invention relates to a vehicle brake control device that controls a plurality of electric brake devices, each corresponding to one of a plurality of wheels. STATE OF THE ART

[0002] Traditionally, the development of a device comprising a plurality of electric brake devices, each individually corresponding to a plurality of wheels, and a brake control device controlling each of the electric brake devices, was pursued as a braking system mounted on a vehicle (see patent document 1). Each of the electric brake devices comprising such a system has a motor driven on the basis of command signals from the brake control device and applies a braking force to the corresponding wheel according to the current value for the motor.

[0003] If the motor provided in any electric braking device is used continuously, even if its temperature exceeds or is equal to a predetermined thermal resistance temperature, it is likely that the motor will exhibit abnormalities. In the braking system described above, if any abnormal motor is present, a motor protection control is implemented to protect the abnormal motor. In the motor protection control, the current to the abnormal motor corresponding to a first wheel (for example, the right front wheel) is rapidly reduced, and another motor (hereinafter referred to as the "normal motor") is actuated, corresponding to a second wheel (for example, the left front wheel) positioned opposite the first wheel in the lateral direction of the vehicle.This means that even if the braking force applied to the first wheel is reduced, the braking force applied to the second wheel is not reduced. Therefore, the reduction in the braking force applied to the entire vehicle is limited, and the malfunctioning engine is adequately protected.

[0004] However, if the engine protection control described above is activated, a braking force differential is generated between the braking force of the first wheel and the braking force of the second wheel (referred to below as the "right-left braking force differential"). As a result, the vehicle's yaw moment becomes large, making it likely that the vehicle's behavior will become unstable. Accordingly, in the braking system described above, the engine protection control is activated if the abnormal engine is present, even if the vehicle's driving condition is stable. The determination of "whether the vehicle's driving condition is stable" is made, for example, by determining "whether it is unlikely that lateral slip of the vehicle will occur." Document in accordance with the state of the art Patent document

[0005] Patent document 1: JP 2001 - 158 336 A SUMMARY OF THE INVENTION Problems that the invention is intended to solve

[0006] As described above, if the motor is used continuously, even if its temperature exceeds its thermal resistance temperature, it is likely to be damaged. For motor protection, it is preferable to protect the motor before it is damaged. Accordingly, the braking system shown below has been devised in recent years.

[0007] This means that the temperature of each motor is periodically monitored, and it is determined whether any motor is overheating, with a temperature equal to or greater than a temperature reference value set below the thermal resistance temperature. If any motor is found to be overheating, motor protection is initiated, rapidly reducing the current to the overheating motor while the normal motors continue to operate. This control limits the temperature rise of the overheating motor, thus preventing it from exceeding or exceeding its thermal resistance temperature.

[0008] However, even in this case, the difference in braking force between the left and right wheels—the braking force applied to the first wheel (corresponding to the overheated engine) and the braking force applied to the second wheel (corresponding to the normal engine)—is caused by the engine protection control. The greater this difference, the greater the vehicle's yaw moment, making it more likely that the vehicle will become unstable. Therefore, it is necessary to tighten the criteria for determining whether the vehicle's driving condition is stable in order to prevent the phenomenon of the vehicle spinning due to the engine protection control. This means that the opportunities for the engine protection control to activate are limited.

[0009] One object of the present invention is to provide a vehicle brake control device which, if any of the engines overheats, can increase the opportunity to implement engine protection control to protect the overheated engine, and to facilitate vehicle operation to correct any change in vehicle behavior that accompanies the engine protection control. Means of solving the problems

[0010] To solve the problem described above, a vehicle brake control device is specified that controls a plurality of electric brake devices. Each of the electric brake devices corresponds to one of a plurality of wheels provided in a vehicle, and each electric brake device has a motor and is configured to apply a braking force according to a current value for the wheel corresponding to the motor. The vehicle brake control device has a temperature acquisition section, a determination section, and a motor control section. The temperature acquisition section acquires a temperature reading for each motor. The determination section determines whether a motor is overheating, i.e., whether its acquired temperature is greater than or equal to a temperature reference value, which is set as a criterion for determining whether the motor is prone to overheating.If any of the motors is identified as the overheated motor, the motor control section performs a motor protection control to reduce a current value for the overheated motor to a more gradual (flatter) gradient in the case where the temperature of the overheated motor is low than in a case where the temperature of the overheated motor is high.

[0011] According to the configuration described above, if any of the motors overheats, the current value for the overheated motor is reduced to protect it. Since the temperature of the overheated motor is relatively low at the time it is determined to be overheating, the current value for the overheated motor is reduced gradually. Accordingly, if the temperature of the overheated motor is relatively low, the rapid increase in the braking force differential between the braking force applied to the first wheel and the braking force applied to the second wheel, which accompanies the execution of the motor protection control, is limited. The first wheel corresponds to the wheel that receives the braking force from the overheated motor. The second wheel corresponds to a wheel positioned opposite the first wheel in the transverse direction of the vehicle.This means that at the time the engine protection control is initiated, it is not likely that the vehicle's behavior will become unstable when the engine protection control is performed, compared to a conventional case where the current value for the overheated engine is rapidly reduced regardless of the engine's temperature.

[0012] As a result, when the engine protection control according to the present invention is initiated, the vehicle's behavior changes gradually. However, since the change in behavior is slower than in the conventional case, the driver is able to easily operate the vehicle to compensate for the change in behavior that accompanies the initiation of the engine protection control described above. Accordingly, compared to the conventional case, where the current value for the overheated engine is rapidly reduced regardless of whether the overheated engine is at high or low temperature, the opportunity for the engine protection control to be initiated is increased, and the vehicle operation to correct the change in vehicle behavior that accompanies the engine step control is facilitated.

[0013] In contrast, if the temperature of the overheated motor is continuously increased, even if the motor protection control is configured to allow the temperature to remain relatively high, the current for the overheated motor will be reduced more rapidly than if the temperature were low. Accordingly, the overheated motor is protected appropriately.

[0014] A wheel corresponding to the electric brake device with the overheating motor is defined as the first wheel, and a wheel located on the opposite side of the first wheel in the transverse direction of the vehicle is defined as the second wheel. The electric brake device corresponding to the second wheel has a standard motor. When implementing motor protection control, it is preferable for the motor protection section to perform an adjustment control to increase the current value for the standard motor attached to the electric brake device corresponding to the second wheel.

[0015] According to the configuration described above, when the motor protection control is performed, the braking force applied to the second wheel is increased by increasing the current value for the normal motor connected to the electric brake device corresponding to the second wheel. Even if the braking force applied to the second wheel is increased when the braking force applied to the first wheel is reduced as described above, the rapid increase in the braking force difference between the braking force applied to the first wheel and the braking force applied to the second wheel is limited because the rate of reduction of the braking force applied to the first wheel is lower than the rate of reduction in the conventional case described above.As a result, even when the adjustment control is performed in parallel with the engine protection control, the vehicle's behavior changes more gradually when both control systems are activated than in the conventional case of activating the engine protection control and the adjustment control separately. This allows the driver to easily adjust the vehicle's operation to compensate for the change in behavior that accompanies the activation of the aforementioned engine protection and adjustment control systems. Therefore, compared to the conventional case, the opportunity to activate the engine protection and adjustment control systems is increased, and the ability to adjust the vehicle's behavior is facilitated.The magnitude of the change in braking force compared to the braking force applied to the entire vehicle before the start of the engine protection control and the adjustment control is reduced.

[0016] When implementing motor protection control, it is preferable for the motor control section to perform the adjustment control in such a way that the current value for the normal motor is increased to compensate for the magnitude of the reduction in braking force applied to the entire vehicle caused by the implementation of motor control.

[0017] According to the configuration described above, when the engine protection control is activated, the braking force applied to the second wheel is increased by the adjustment control in such a way as to limit the reduction in the braking force applied to the entire vehicle. Furthermore, when the engine protection control is activated, the rate of increase in the braking force applied to the second wheel is lower than the rate of increase in the conventional case described above, and the rate of decrease in the braking force applied to the first wheel is also lower than the rate of decrease in the conventional case. Accordingly, the rapid increase in the braking force difference between the braking force applied to the first wheel and the braking force applied to the second wheel, which accompanies the execution of the engine protection control and the adjustment control, is limited.As a result, even when the adjustment control is performed in parallel with the engine protection control, the vehicle's behavior changes more gradually when the controls are activated than in the conventional case of activating both the engine protection control and the adjustment control. This allows the driver to easily adjust the vehicle's operation to compensate for the change in behavior that accompanies the activation of the aforementioned engine protection control and adjustment control. Therefore, the opportunity for the engine protection control and adjustment control to activate is increased compared to the conventional case, while compensating for the reduction in the overall braking force applied to the vehicle.

[0018] When implementing motor protection control and adjustment control, it is preferable that the motor control section adjusts the braking force applied to all wheels except the first wheel.

[0019] The vehicle brake control device further includes a yaw rate procurement section which procures an estimated value of a yaw rate generated on the vehicle by performing the engine protection control and the adjustment control.

[0020] When implementing motor protection control and adjustment control, it is preferable for the motor control section to control the motors attached to the electric brake devices in order to apply a braking force to the wheels other than the first and second wheels, in order to adjust the braking force applied to the wheels other than the first and second wheels so that the estimated value of the yaw rate obtained by the yaw rate acquisition section approaches zero.

[0021] When both the engine protection control and the adjustment control are activated, the yaw rate in the vehicle is generated according to the difference in braking force between the braking force applied to the first wheel and the braking force applied to the second wheel. Accordingly, according to the present invention, the estimated value of the yaw rate generated in connection with the implementation of the two control systems described above is obtained, and the braking force applied to the wheels other than the first and second wheels is adjusted such that the estimated value of the yaw rate approaches zero. Consequently, the change in vehicle behavior associated with the engine protection control and the adjustment control is limited.Since it is unlikely that the vehicle's behavior will become unstable when the overheated engine is protected, the opportunity to implement engine protection control and adjustment control is increased, and vehicle operation is facilitated to correct the change in vehicle behavior that accompanies the engine protection control. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a block diagram illustrating a braking system with a vehicle brake control device according to the present invention. Fig. Figure 2 shows a characteristic map used to set a rate of change of a current value according to the temperature of an overheated motor. Fig. 3(a) and Fig. 3(b) show characteristic maps used to determine whether the driving condition of a vehicle is stable, Fig. Figure 4 shows a time-series diagram illustrating a motor protection control where the current value for the overheated motor is reduced. Fig. Figure 5 shows a first half-section of a flowchart illustrating a current value correction processing routine according to the present embodiment, and Fig. Figure 6 shows a second half of the flowchart, which shows the current value correction processing routine according to the present embodiment. WAYS TO IMPLEMENT THE INVENTION

[0022] Below is an embodiment of the present invention with reference to Fig. Figures 1 to 6 illustrate this. In the following description, the direction of travel (lead direction) of a vehicle is defined as the front (vehicle forward direction).

[0023] As it is in Fig. As shown in Figure 1, a plurality of wheels (according to the present embodiment 4) FR, FL, RR, and RL are provided in the vehicle. The front wheels FR and FL are arranged in front of the rear wheels RR and RL in the longitudinal direction of the vehicle. The right front wheel FR and the right rear wheel RR are each arranged opposite the left front wheel FL and the left rear wheel RL in the transverse direction of the vehicle. A braking system 11 attached to the vehicle comprises a plurality of electric braking devices 12 (12a, 12b, 12c, and 12d) (four according to the present embodiment), each corresponding to the wheels FR, FL, RR, and RL, respectively; an actuation force sensing device 14 for sensing an actuation force (also referred to as the "operating variable") of a brake pedal 13 by a driver; and a brake ECU 15, as an example of a brake control device, which individually controls the electric braking devices 12a to 12d.

[0024] The electric braking devices 12 are described below.

[0025] As it is in Fig. As shown in Figure 1, each brake device 12 has a motor 21, a motor drive circuit 22 which is driven according to command signals from the brake ECU 15 to drive current through the motor 21, and a temperature sensor 23a to detect the temperature of the motor 21. Detection signals based on the temperature of the motor 21 are supplied to the brake ECU 15 from the temperature sensors 23.

[0026] The electric brake devices 12 include ring-shaped brake rotors (not shown) that rotate integrally with the wheels FR, FL, RR, and RL, and brake pads (not shown) arranged to face the friction surfaces of the brake rotors. When the motor 21 is driven, the corresponding brake pad reaches the brake rotor by the driving force from the motor 21. The brake pad slides on the corresponding brake rotor by a pressing force corresponding to the driving force transmitted from the motor 21. That is to say, according to the present embodiment, the driving force generated by the motors 21, i.e., the braking force corresponding to the current values ​​for the motors 21, is applied to the wheels FR, FL, RR, and RL.

[0027] The brake ECU 15 is described below according to the present embodiment.

[0028] As it is in Fig. As shown in Figure 1, wheel speed sensors 31a, 31b, 31c, and 31d for detecting the wheel speed of wheels FR, FL, RR, and RL are each electrically connected to the brake ECU 15 in addition to the temperature sensors 23. A steering angle sensor 32 for detecting the steering angle of a steering wheel (not shown) attached to the vehicle and a yaw rate sensor 33 for detecting the yaw rate of the vehicle are also electrically connected to the brake ECU 15. Furthermore, signals (i.e., actuation force signals) corresponding to the actuation force of the brake pedal 13 are supplied to the brake ECU 15 from the actuation force sensing device 14. The brake ECU 15 adjusts the current value for the motor 21 of each electric brake device 12 such that the braking force is applied to the entire vehicle in accordance with the braking force requested by the driver (hereinafter referred to as "the requested braking force").The brake ECU 15 then supplies command signals to each electric brake device 12 based on the set current value.

[0029] The requested braking force is set even if the driver does not operate the brake pedal 13. For example, in vehicle control systems, including brake control systems such as automatic stop control and constant speed control, the requested braking force is set to a value greater than zero.

[0030] The brake ECU 15 features a digital computer configured by a CPU, ROM, and RAM, which are not illustrated. Various control processes (for example, control processes according to) Fig. 5 and Fig. 6), various characteristic maps (for example, characteristic maps according to Fig. 2 and Fig. 3) and various threshold values ​​are pre-stored in the ROM of the brake ECU 15. Various pieces of information (such as vehicle speed, described below), which can be overwritten as necessary during a period of time when the (not shown) ignition switch in the vehicle is turned "ON", are temporarily stored in the RAM.

[0031] The motor 21 of each electric brake device 12 generates heat according to the current flowing through it. If the amount of heat generated exceeds the amount of heat dissipated from the motor 21, its temperature will increase. If the motor 21 is continuously operated in a condition where its temperature exceeds the preset thermal resistance temperature—that is, if current flows continuously through it—it is likely that the motor 21 will be damaged. Therefore, if the motor 21's temperature approaches the thermal resistance temperature, it is preferable to protect the motor, hereinafter referred to as the "overheated motor," before its temperature exceeds or equals the thermal resistance temperature.

[0032] According to the present embodiment, if it is determined that an overheated motor exists, motor protection control is implemented, whereby the current value for the overheated motor is reduced to mitigate the temperature increase of the overheated motor. The rate of change (decrease rate) of the current value for the overheated motor during motor protection control is determined based on a Fig. 2 shown map set.

[0033] When the engine protection control is activated, a braking force differential is generated between the first wheel (for example, the right front wheel), which receives the driving force from the overheated engine, and the second wheel (for example, the left front wheel), which is positioned opposite the first front wheel in the vehicle's transverse direction (hereinafter referred to as the "right-left braking force differential"). The greater the right-left braking force differential, the greater the yaw rate generated in the vehicle, making it more likely that the vehicle will skid. That is, the vehicle's behavior will exhibit an unstable tendency. Accordingly, the implementation of the engine protection control, which causes the generation of the right-left braking force differential, is only permitted if it is determined that the vehicle's driving condition is stable. Accordingly, according to the present embodiment, using the [reference to be added] Fig. 3(a) and Fig. The characteristic maps shown in 3(b) determine whether the vehicle's driving condition is stable. The following are the maps shown in Fig. 2, Fig. 3(a) and Fig. 3(b) described the characteristic curves shown.

[0034] First, this is in Fig. The two shown characteristic curves are described.

[0035] The first characteristic map serves to adjust the rate of change ΔIx of the current value for the overheated motor to a value that is smaller than that which occurs when the temperature T is high, in cases where the temperature T is low at that time. That is to say, as described in Fig. As shown in Figure 2, according to the present embodiment, a plurality (here three) preset threshold values ​​Tth1, Tth2, and Tth3 are set as temperatures that are lower than a maximum heat resistance temperature Tmax. If the temperature of the overheated motor is greater than or equal to the first preset threshold value Tth1, which is the smallest of the preset threshold values ​​Tth1, Tth2, and Tth3, and lower than the second threshold value Tth2 (Tth2 > Tth1), the rate of change ΔIx is set as a first gradient ΔIx1 (ΔIx1 > 0). Furthermore, if the temperature T of the overheated motor is greater than or equal to the second preset threshold value Tth2 and lower than the third preset threshold value Tth3 (Tth3 > Tth2), the rate of change ΔIx is set as a second gradient ΔIx that is greater than the first gradient ΔIx1.Furthermore, if the temperature T of the overheated motor is greater than or equal to the third setpoint Tth3 and lower than the thermal resistance temperature Tmax, the rate of change ΔIx is set as a third gradient ΔIx3, which is greater than the second gradient ΔIx2. The third gradient ΔIx3 is a value that is close to the rate of change of the current value for the overheated motor when using conventional motor protection control.

[0036] The second set of characteristic curves is described below. Fig. 3(a) and Fig. 3(b) are shown.

[0037] The second characteristic map serves to determine, based on the steering angle θ of the steering wheel and the vehicle body speed VS, whether the vehicle's driving state is stable. More precisely, this applies in Fig. 3(a) the second characteristic map shown in the case where the left front wheel FL or the left rear wheel RL corresponds to the first wheel. In contrast, the one shown in Fig. 3(b) shows the second map in the case where the right front wheel FR or the right rear wheel RR is defined as the first wheel. In every second map, a region with hatched lines corresponds to a region on an unstable side, and a region without hatched lines corresponds to a region on a stable side. That is, if the steering angle θ and the vehicle body speed VS belong to the region on the unstable side, the vehicle's driving state is determined to be unstable. Conversely, if the steering angle θ and the vehicle speed VS belong to the region on the stable side, the vehicle's driving state is determined to be stable.

[0038] As it is in Fig. As shown in Figure 3(a), in the case where the vehicle turns left, if the left front wheel FL or left rear wheel RL corresponds to the first wheel, the right front wheel FR or right rear wheel RR, which is positioned outside in the direction of rotation, corresponds to the second wheel. When the engine protection control is performed in this state, the braking force applied to the wheel inside in the direction of rotation is less than the braking force applied to the wheel outside in the direction of rotation. As a result, a yaw moment is generated, causing the vehicle to turn right, due to the difference between the right and left braking forces. The yaw moment is opposite in direction to the yaw moment generated based on the driver's steering input, so the vehicle's tendency to turn is not likely to be strong, even when the right-left braking force is generated.

[0039] In contrast, if the vehicle is turning right, and the left front wheel (FL) or left rear wheel (RL) corresponds to the first wheel, then the right front wheel (FR) or right rear wheel (RR), positioned inside in the direction of rotation, corresponds to the second wheel. When the engine protection control is activated in this state, the braking force applied to the wheel inside in the direction of rotation becomes greater than the braking force applied to the wheel outside in the direction of rotation. As a result, a yaw moment is generated, causing the vehicle to turn right, due to the difference in braking force between the left and right wheels. The direction of this yaw moment is the same as the direction of the yaw moment generated by the driver's steering input. Accordingly, when the difference in braking force between the left and right wheels is generated, the vehicle's tendency to turn right becomes pronounced.

[0040] Accordingly, if the left front wheel (FL) or the left rear wheel (LR) is the first wheel when the vehicle turns left, a vehicle speed determination value (KS) is set as a constant and comparatively large value to determine whether the vehicle's driving condition is stable, even if the absolute value of the steering angle (θ) of the steering wheel increases. Conversely, if the left front wheel (FL) or the left rear wheel (RL) is the first wheel when the vehicle turns right, the vehicle speed determination value (KS) is set as a smaller value if the absolute value of the steering angle (θ) of the steering wheel increases.As a result, if the motor 21 overheats according to the left front wheel FL or the left rear wheel RL, the opportunity to carry out the engine protection control is increased more in the case where the vehicle turns to the left than in the case where the vehicle turns to the right.

[0041] As it is in Fig. As shown in Figure 3(b), if the right front wheel FR or the right rear wheel RR corresponds to the first wheel, the left front wheel FL or the left rear wheel RL, positioned outside in the direction of rotation, corresponds to the second wheel. When the engine protection control is performed in this state, the braking force applied to the wheel inside in the direction of rotation becomes less than the braking force applied to the wheel outside in the direction of rotation. As a result, a yaw moment is generated, causing the vehicle to rotate to the left, due to the right-left braking force difference. This yaw moment is in the opposite direction to the yaw moment generated based on the driver's steering input. Accordingly, even if the right-left braking force difference is generated, the vehicle's tendency to rotate will not be severe.

[0042] In contrast, if the vehicle is turning left, and the right front wheel (FR) or right rear wheel (RR) corresponds to the first wheel, the left front wheel (FL) or left rear wheel (RL), positioned inwards in the direction of rotation, corresponds to the second wheel. When the engine protection control is activated in this state, the braking force applied to the wheel inwards in the direction of rotation becomes greater than the braking force applied to the wheel on the outside in the same direction. As a result, a yaw moment is generated, causing the vehicle to turn left, due to the difference in right-left braking forces. The direction of this yaw moment is the same as the direction of the yaw moment generated by the driver's steering input. Accordingly, when the right-left braking force difference is generated, the vehicle's tendency to turn sharply is pronounced.

[0043] Accordingly, if the right front wheel FR or the right rear wheel RR is the first wheel when the vehicle turns right, the vehicle speed determination value KS is set to a constant and comparatively large value, even if the absolute value of the steering wheel angle θ increases. Conversely, if the right front wheel FR or the right rear wheel RR is the first wheel when the vehicle turns left, the vehicle speed determination value KS is set to a smaller value if the absolute value of the steering wheel angle θ increases. As a result, if the engine 21 overheats, depending on the right front wheel FR or the right rear wheel RR, the likelihood of the engine protection control being activated is increased more when the vehicle turns right than when it turns left.

[0044] Accordingly, in the present embodiment, the vehicle speed VS corresponds to a stability index value that represents the stability of the vehicle's driving condition as a numerical value. Furthermore, the vehicle speed determination value KS corresponds to a stability reference value, serving as a criterion for determining whether the driving condition is stable.

[0045] Below is an operation in the case where one of the four motors 21 overheats, with reference to the in Fig. The time-series diagram shown in section 4 is described. The dashed line shown in Fig. Figure 4 shows the case where the overheated engine is protected by the conventional method. It is assumed that the vehicle's driving condition remains stable even if any of the wheels FR, FL, RR, and RL overheat.

[0046] As shown in the time history diagram according to Fig. As shown in Figure 4, during a period of time after the initial time T1, at which a requested braking force Breq is gradually increased from zero by the driver, for example, operating the brake pedal 13, the braking force BP_all applied to the entire vehicle is increased until it approaches the requested braking force Breq. During this process, the current value for the motor 21 of each electric brake device 12 gradually increases in accordance with the requested braking force Breq. Then, the braking force is applied to each of the wheels FR, FL, RR, and RL according to the current value for the corresponding motor 21.

[0047] During a period of time after a second time point t2, while the force applied to the brake pedal 13 by the driver remains constant, the requested braking force Breq also becomes constant. The current value for each motor 21 is then also set to a constant in order to maintain the braking force applied to each of the wheels FR, FL, RR, and RL. During a period of time after a subsequent third time point t3, if the temperature T of any of the motors 21 (for example, the motor 21 for the right front wheel FR) becomes greater than or equal to the first set threshold value Tth1, the corresponding motor 21 is determined to be overheating. The temperatures T of the other motors 21, except for the overheated motor, are sufficiently lower than the first set threshold value Tth1.

[0048] Then the engine protection control, to protect the overheated engine, and the adjustment control, to limit the reduction in the braking force BP_all applied to the entire vehicle, which accompanies the execution of the engine protection control, are started. The conventional engine protection control and the adjustment control are described first.

[0049] That is, as indicated by the dotted line in Fig. As shown in Figure 4, in conventional motor protection control, the protection of the overheated motor is given top priority, so the current Ix for the overheated motor is rapidly reduced. The rate of change of the current Ix is equal to or close to the third gradient ΔIx3 described above. Then, the braking force BPx applied to the first wheel X is rapidly reduced in line with the rapid decrease in the current Ix for the overheated motor. As a result, the lower the current Ix becomes, the less heat is generated by the overheated motor. Consequently, the rate of temperature rise T of the overheated motor is low.At a fifth time point t5, when the rate of temperature increase of the overheated motor becomes less than or equal to a preset prescribed rate, the probability that the temperature of the overheated motor will exceed the maximum heat resistance temperature Tmax is determined to be low. The reduction of the current value Ix for the overheated motor is then stopped. Accordingly, for a period of time after the fifth time point t5, the temperature T of the overheated motor is maintained at the temperature immediately before the fifth time point t5, or at a value close to that temperature.

[0050] If such engine protection control is implemented, the braking force BPx applied to the first wheel X is reduced. When the engine protection control is initiated, an adjustment control is also initiated to increase the braking force BPy applied to the second wheel Y, which is positioned opposite the first wheel X in the transverse direction of the vehicle. The magnitude of the increase in braking force BPy at this time is equivalent to the magnitude of the reduction in braking force BPx applied to the first wheel X. The reduction in the braking force BP_all applied to the entire vehicle is limited by adjusting the braking force applied to the second wheel Y, as described above.

[0051] However, in conventional engine protection control, the braking force BPx applied to the first wheel X is rapidly reduced. Accordingly, in the adjustment control, the braking force BPy applied to the second wheel Y is rapidly increased to match the rapid reduction of the braking force BPx applied to the first wheel X. As a result, the right-left braking force differential BPsub between the braking force applied to the first wheel X and the braking force applied to the second wheel Y increases rapidly. This means that the vehicle's behavior changes rapidly in line with the rapid increase in the right-left braking force differential BPsub.

[0052] With regard to this point, the method according to the present embodiment limits the rapid change in vehicle behavior, even if any of the motors 21 overheats. That is, the rate of change of the current value Ix for the overheated motor using the Fig. 2. The first characteristic map shown is set more gradually (flatter) in the case where the temperature T of the overheated engine is low at that time than in the case where the temperature T is high.

[0053] Accordingly, after the third time point t3, the current value Ix is reduced more gradually if the temperature T of the overheated motor is comparatively lower than in the case where conventional motor protection control is applied. As a result, the braking force BPx applied to the first wheel X is reduced more gradually than in the case where conventional motor protection control is applied. In the adjustment control, which is started simultaneously with the motor protection control, the braking force BPy applied to the second wheel Y is increased more gradually if the reduction rate of the braking force BPx applied to the first wheel X is low. That is, in the period immediately following the detection of the overheated motor, the right-left braking force differential BPsub is gradually increased. The vehicle behavior is thus gradually changed towards instability.

[0054] If the current value Ix for the overheated motor is gradually reduced as described above, the increase in the motor's temperature can continue. At the fourth time point t4, when the overheated motor's temperature T becomes greater than or equal to the second set threshold value Tth2, the rate of change ΔIx of the current value Ix for the overheated motor changes from the first gradient ΔIx1 to the second gradient ΔIx2. Then, after the fourth time point t4, when the rate of change ΔIx becomes greater than the rate of change ΔIx before the fourth time point t4, the decrease gradient of the braking force BPx applied to the first wheel X becomes greater. Correspondingly, the increase gradient of the braking force BPy applied to the second wheel Y becomes steeper than the increase gradient before the fourth time point t4.However, since the second gradient ΔIx2 is a value smaller than the conventional rate of change of the current value Ix, the magnitude of the change in the right-left braking force difference BPsub after the fourth time point t4 is smaller than in the conventional case. Accordingly, if the temperature T of the overheated engine is lower than the third set threshold value Tth3, the vehicle's behavior will change more gradually towards the unstable side than in the conventional case.

[0055] Although the amount of heat generated in the overheated motor is reduced by increasing the rate of change ΔIx of the current value Ix, as described above, the temperature of the overheated motor will continuously increase if the amount of heat generated exceeds the amount of heat dissipated. At the sixth time point t6, when the temperature T of the overheated motor becomes greater than or equal to the third set threshold value Tth3, the rate of change ΔIx of the current value Ix for the overheated motor is changed from the second gradient ΔIx2 to the third gradient ΔIx3. That is, when the temperature T of the overheated motor becomes greater than or equal to the third set threshold value Tth3, the protection of the overheated motor is assigned top priority.Then, after the sixth time t6, the decrease gradient of the braking force BPx applied to the first wheel X and the increase gradient of the braking force BPy applied to the second wheel Y become equivalent to those in the conventional case.

[0056] As a result, although the magnitude of the change in the right-left braking force differential BPsub becomes equivalent to that in the conventional case, the increase in the temperature of the overheated motor is limited. At the seventh time t7, when the increase in the temperature of the overheated motor is excessively small, the current value Ix for the overheated motor is maintained.

[0057] The following describes a current value correction processing routine executed by the brake ECU 15 during the execution of the motor protection control and adjustment control described above, with reference to the information in Fig. 5 and Fig. The 6 flowcharts shown are described.

[0058] The current value correction processing routine is executed at a preset interval (for example, every 0.01 seconds). In this routine, the brake ECU 15 obtains the requested braking force Breq (step S10) and determines whether the requested braking force Breq is a value other than zero (step S11). If the requested braking force Breq is zero (step S11: NO), the brake ECU 15 does not apply the braking force to any of the wheels FR, FL, RR, and RL. Accordingly, the current value correction processing routine is temporarily terminated. Conversely, if the requested braking force Breq is a value other than zero (step S11: YES), the brake ECU 15 obtains (calculates) the temperatures T of each of the motors 21 based on the sensing signals from each temperature sensor 23 of each of the electric brake devices 12a to 12d (step S12).Accordingly, in the present embodiment, the brake ECU 15 serves as a temperature supply section.

[0059] The brake ECU 15 then determines whether there is a motor with a temperature T that is greater than or equal to the first set threshold Tth1, i.e., an overheated motor (step S13). According to the present embodiment, the first set threshold Tth1 corresponds to a temperature reference value, which is a criterion for determining whether each motor 21 tends to overheat (that is, whether its temperature tends to reach the maximum heat resistance temperature Tmax). Accordingly, the brake ECU 15 also serves as a determination section that identifies whether there is an overheated motor among the motors 21.

[0060] If there is no overheated motor (step S13: NO), the brake ECU 15 temporarily terminates the current value correction processing routine, since all temperatures T of all motors 21 are lower than the first set threshold value Tth1. If, on the other hand, there is an overheated motor (step S13: YES), the brake ECU 15 determines whether there is only a single overheated motor (step S14). If there is more than one overheated motor (step S14: NO), the brake ECU 15 temporarily terminates the current value correction processing routine. If, on the other hand, there is only one overheated motor (step S14: YES), the brake ECU 15 calculates the rate of change of the temperature T of the overheated motor per unit of time as the rate of increase ΔT of the temperature of the overheated motor (step S15).The brake ECU 15 then determines whether the rate of increase ΔT of the calculated temperature is lower than or equal to a prescribed rate ΔTh, which is set as a determining criterion to ensure that the increase in temperature of the overheated engine is almost not observed (step S16).

[0061] If the temperature increase rate ΔT exceeds the prescribed rate ΔTh (step S16: NO), the brake ECU 15 determines that the temperature increase of the overheated engine will continue and proceeds to step S18, described below. Conversely, if the temperature increase rate ΔT is less than or equal to the prescribed rate ΔTth (step S16: YES), the brake ECU 15 determines that the temperature increase of the overheated engine will be almost negligible and proceeds to the next step, S17.

[0062] In step S17, the brake ECU 15 sets the current value Ix for the overheated motor and the current value Iy for the motor (hereinafter referred to as the "normal motor") attached to the electric brake device 12 corresponding to the second wheel Y to the values ​​set during the preceding current value correction processing routine. The brake ECU then proceeds to step S27, described below.

[0063] In step S18, the brake ECU 15 obtains the vehicle body speed VS based on the detection signals from the wheel speed sensors 31a to 31d. The brake ECU 15 then obtains the steering angle Δ of the steering wheel based on the detection signals from the steering angle sensor 32 (step S19). According to the present embodiment, the vehicle body speed is a parameter for determining whether the vehicle's driving state is stable and corresponds to a stability index value. The steering angle θ is a parameter for adjusting the magnitude of the vehicle speed determination value KS, which is a stability reference value (compare Fig. 3) Accordingly, in the present embodiment, the brake ECU 15 also serves as an index value procurement section.

[0064] The brake ECU 15 then sets the current value for each motor 21 as a requested current value Im (step S20). The requested current value Im corresponds to a current value corresponding to the requested braking force Breq obtained in step S10. The brake ECU 15 then sets the rate of change ΔIx of the current value Ix for the overheated motor using the value obtained in Fig. The first characteristic map shown in step S21 is used. As a result, the rate of change ΔIx is more gradual when the temperature of the overheated engine is low at that time than when the temperature is high.

[0065] The brake ECU 15 then sets a candidate current value Ia as a candidate value for the current value for the overheated engine (step S22). Specifically, the brake ECU 15 reads the current value Ix for the overheated engine, which was set when the previous current value correction processing routine was executed, from RAM and sets the current value as a previous current value Ix(n-1). The value "n" is the number of times the current value correction processing routine has been executed since the vehicle's ignition switch (not shown) was turned on. The brake ECU 15 then subtracts the rate of change ΔIx, which was set in step S18, from the previous current value Ix(n-1) and sets the resulting calculation as the candidate current value Ia (Ia = Ix(n-1) - ΔIx).

[0066] Then, the brake ECU 15 sets a current value Ix for the overheated motor based on the comparison result between the requested current value Im for the overheated motor set in step S20 and the candidate current value Ia calculated in step S22 (step S23). According to the present embodiment, the brake ECU 15 sets the smaller of the requested current value Im and the candidate current value Ia as the current value Ix for the overheated motor.

[0067] The brake ECU 15 determines, using the information in Fig. 3(a) and Fig. 3(b) second maps shown, whether the vehicle's driving condition is stable (step S24). In particular, if the first wheel X is the left front wheel FL or the left rear wheel RL, corresponding to the overheated engine, the brake ECU 15 selects the one shown in Fig. 3(a) selects the second map shown. If the first wheel X, corresponding to the overheated engine, is the right front wheel FR or the right rear wheel RR, the brake ECU 15 selects the one shown in Fig. 3(b) shows the second map. The brake ECU 15 sets the vehicle speed determination value KS based on the steering angle θ obtained in step S19, using the selected second map. The brake ECU 15 then determines whether the vehicle body speed VS obtained in step S18 is less than the set vehicle speed determination value KS.

[0068] If the vehicle speed VS is less than the vehicle speed determination value KS (step S24: YES), the brake ECU 15 determines that the vehicle's driving condition is stable and proceeds to step S26, described below. Conversely, if the vehicle body speed is greater than or equal to the vehicle determination value KS (S24: NO), the brake ECU 15 determines that the vehicle's driving condition is unstable and proceeds to the next step S25.

[0069] In step S25, the brake ECU 15 adjusts the current value Iy for the normal motor, corresponding to the second wheel Y, so that it becomes the same value as the current value Ix for the overheated motor. The processing of the brake ECU 15 then proceeds to step S31, described below. In this case, the braking force BPy applied to the second wheel Y is equivalent to the braking force BPx applied to the first wheel X. Accordingly, the right-left braking force difference BPsub is almost zero. Therefore, although the braking force applied to the entire vehicle BP_all is reduced, the vehicle's behavior is prevented from becoming unstable by protecting the overheated motor.

[0070] In step S26, the brake ECU 15 adjusts the current value Iy for the normal motor to compensate for the reduction in the braking force BP_all applied to the entire vehicle, caused by the reduction in the current value Ix for the overheated motor. For example, the brake ECU 15 calculates a difference between the current value Ix set in step S23 and the previous current value Ix(n-1). The brake ECU 15 adds this calculated difference to the current value for the normal motor that was set when the previous current value correction processing routine was executed and sets the result of this addition as the current value Iy for the normal motor. The processing by the brake ECU 15 then proceeds to the next step S27.

[0071] In step S27, the brake ECU 15 obtains a yaw rate YR of the vehicle based on the acquired signals from the yaw rate sensor 33. The yaw rate YR is a value that represents the yaw moment based on the driver's steering and acceleration inputs, as well as the yaw moment based on the engine protection control and the adjustment control. The brake ECU 15 then calculates an estimated yaw rate YR1 based on the vehicle body speed VS and the steering angle θ, obtained in steps S18 and S19, using a relational expression (equation 1) shown below (step S28). The calculated estimated yaw rate YR1 is a value that corresponds to the yaw moment generated at the vehicle based on the driver's steering and acceleration inputs.This means that if the right-left braking force difference BPsub is zero, the estimated yaw rate YR1 is almost equal to the yaw rate YR. YR1=VS×θ(L×(A×VS2+1))

[0072] Here, the value L is the wheelbase (distance between the front wheels and the rear wheels), and the value A is a stability factor (constant).

[0073] The brake ECU 15 subtracts the estimated yaw rate YR1 calculated in step S28 from the yaw rate YR obtained in step S27 and sets the result of the subtraction as a generated yaw rate (estimated value of the yaw rate) YR2 (step S29). The generated yaw rate YR2 is a value that corresponds to the yaw moment that can be generated on the vehicle by the engine protection control and the adjustment control. Accordingly, in this embodiment, the brake ECU 15 also serves as a yaw rate acquisition section.

[0074] The brake ECU 15 adjusts a current value Iz for the motor 21 of each electric brake device 12 according to each of the wheels other than the first and second wheels of wheels FR, FL, RR, and RL such that the generated yaw rate YR2 calculated in step S29 is approximately zero (step S30). For example, if the right front wheel FR (or the left front wheel FL) is the first wheel X and the left front wheel FL (or the right front wheel FR) is the second wheel Y, then the rear wheels RR and RL correspond to the wheels other than the first and second wheels.When the braking force BPx applied to the right front wheel FR, which is the first wheel X, is reduced and the braking force applied to the left front wheel FL, which is the second wheel Y, is increased, the brake ECU 15 adjusts the current value Iz for each motor 21 such that the braking force applied to the left rear wheel RL becomes greater than the braking force applied to the right rear wheel RR in order to compensate for the rightward yaw moment.

[0075] If, in contrast, the right rear wheel RR (or the left rear wheel RL) corresponds to the first wheel X and the left rear wheel RL (or the right rear wheel RR) corresponds to the second wheel Y, then the front wheels FR and FL correspond to the wheels other than the first and second wheels. The processing of the brake ECU 15 then proceeds to the next step S31.

[0076] In step S31, the brake ECU 15 outputs command signals corresponding to the set current value for each of the motors 21 to each of the electric brake devices 12a to 12d. The current value for motor 21 of each of the electric brake devices 12a to 12d is then adjusted based on the input command signals. The braking force corresponding to the current value for each motor 21 is applied to each of the wheels FR, FL, RR, and RL. Accordingly, in this embodiment, the brake ECU 15 also serves as a motor control section. The brake ECU 15 then temporarily terminates the current value correction processing routine.

[0077] As described above, the present embodiment has the following advantages. (1) If any of the motors 21 overheats, the current value Ix for the overheated motor is reduced to protect it. The current value Ix for the overheated motor is reduced at a more gradual (flatter) gradient when the temperature of the overheated motor is lower than when the temperature T is high. Accordingly, compared to the conventional case where the current value Ix is reduced at a steep gradient regardless of the temperature T of the overheated motor, the rapid increase in the right-left braking force differential BPsub between the braking force applied to the first wheel X and the braking force applied to the second wheel Y immediately after the motor protection control is activated is limited. (2) Although such motor protection control is initiated, if the temperature T of the overheated motor continues to rise, the rate of change ΔIx of the current value Ix of the overheated motor is increased. That is, although the temperature T of one of the motors becomes greater than or equal to a first set threshold value Tth1, a sudden change in vehicle behavior is preferably limited if the temperature T of the motor is relatively low. However, if the temperature T of the overheated motor becomes high, protection of the overheated motor is preferably implemented. Accordingly, events in which the temperature T of the overheated motor becomes greater than or equal to the heat resistance temperature Tmax are limited in such a way that the overheated motor is adequately protected. (3) When the engine protection control is executed, the adjustment control is performed, which increases the braking force BPy applied to the second wheel Y. In the case where both the adjustment control and the engine protection control are performed, the right-left braking force difference BPsub between the braking force applied to the first wheel X and the braking force applied to the second wheel Y is increased more gradually than in the conventional case, since the rate of reduction of the braking force BPx applied to the first wheel X is low. This means that a sudden change in vehicle behavior, which accompanies the execution of the engine protection control and the adjustment control, is limited. (4) The reduction of the braking force BP_all applied to the entire vehicle is limited by increasing the braking force BPy applied to the second wheel Y by the same amount as the reduction in the braking force BPx applied to the first wheel X, by carrying out the engine protection control in parallel with the adjustment control. Accordingly, since the change in the braking force BP_all applied to the entire vehicle accompanying the execution of the engine protection control and the adjustment control is limited, the driver of the vehicle will hardly experience any sense of confusion associated with the execution of the engine protection control and the adjustment control. (5) The control configuration is applied in which the rate of change ΔIx is modified according to the temperature T of the overheated engine. The vehicle's behavior is thus gradually modified when the engine protection and adjustment controls are activated. This allows the driver to easily operate the vehicle to compensate for the change in behavior that accompanies the activation of the engine protection and adjustment controls. In other words, this facilitates the vehicle operation required by the driver to correct the change in behavior that accompanies the activation of the engine protection and adjustment controls. (6) Compared to the conventional case, a sudden change in vehicle behavior immediately after the start of the engine protection control and the adjustment control is limited. Thus, the determining criterion (according to the present embodiment, the vehicle speed determination value KS) for determining whether the vehicle's driving state is stable can be mild. As a result, the opportunity to implement the engine protection control is increased compared to the conventional case. (7) Furthermore, according to the present embodiment, when the engine protection control and the adjustment control are implemented, the braking force applied to the wheels other than the first wheel X and the second wheel Y is adjusted to counteract the yaw moment generated by the operation of the controls. Accordingly, the unstable state of vehicle behavior that accompanies the operation of the engine protection control and the adjustment control is limited. This means that, compared to the case where the adjustment of the braking force applied to the wheels other than the first and second wheels is not carried out, the criterion for determining whether the vehicle's driving condition is stable can be less stringent. As a result, the opportunity to implement the engine protection control is further increased. (8) When the rate of temperature increase ΔT of the first wheel X becomes less than or equal to the prescribed rate ATth due to the execution of the motor protection control, it is determined that the amount of heat generated in the overheated motor is essentially in equilibrium with the amount of heat dissipated from the overheated motor. As a result, the reduction of the current value Ix for the overheated motor due to the execution of the motor protection control is stopped. Accordingly, in contrast to the case where the reduction of the current value Ix continues even when the rate of temperature increase ΔT becomes less than or equal to the prescribed rate ΔTh, the increase in the right-left braking force differential BPsub, which accompanies the execution of the motor protection control and the adjustment control, is limited. (9) If the requested braking force Breq is reduced, for example because the force applied by the driver to the brake pedal 13 is weakened, the requested current value Im may be smaller than the candidate current value Ia calculated in step S22, corresponding to the overheated motor set in step S20. In this case, according to the present embodiment, the current value Ix for the overheated motor is set as the requested current value Im. Accordingly, the braking force BP_all applied to the entire vehicle is reduced appropriately in accordance with the reduction in the requested braking force Breq.

[0078] The embodiment can be modified as described in the other embodiments below. - In the embodiment described above, if the first wheel X corresponds to a wheel (the right front wheel FR or the right rear wheel RR) that is located inwards in the direction of rotation when the vehicle is turning right, it is not necessary to perform the brake control to counteract the yaw rate (i.e., the generated yaw rate YR2) produced by the execution of the engine protection control and the adjustment control. That is, it is not necessary to perform the operations in steps S27 to S30. Likewise, if the first wheel X corresponds to a wheel (the left front wheel FL or the left rear wheel RL) that is located inwards in the direction of rotation when the vehicle is turning left, it is not necessary to perform the brake control to counteract the yaw moment (i.e., the generated yaw rate YR2) produced by the execution of the engine protection control and the adjustment control.This means that it is not necessary to perform the processing operations in steps S27 to S30. - According to the embodiment described above, the operations in steps S27 to S30 can be omitted. Even with this configuration, the opportunity for motor protection control is increased more than in the conventional case, although the opportunity is lower than in the case where the operations in steps S27 to S30 are performed. - According to the embodiment described above, the adjustment control can correspond to a control in which the reduction of the braking force BP_all applied to the entire vehicle is limited by adjusting the braking force applied to the other wheels (including the second wheel Y) except the first wheel X. - According to the embodiment described above, the increase in the braking force BPy applied to the second wheel Y when the motor protection control is implemented does not have to correspond to the decrease in the braking force BPx applied to the first wheel X. - According to the embodiment described above, it is not necessary to perform the adjustment control when implementing the motor protection control. - According to the embodiment described above, the motor protection control can be carried out if the first wheel X corresponding to the overheated motor is the front wheel FR or FL.

[0079] In contrast, engine protection control can be performed if the first wheel X corresponding to the overheated engine is the rear wheel RR or RL. - According to the embodiment described above, the rate of change ΔIx of the current value Ix can be set such that it gradually increases as the temperature T of the overheated motor rises. In this case, the rate of change ΔIx can be set based on a linear or quadratic function with the temperature T of the overheated motor as a parameter. - According to the embodiment described above, the temperature of each motor 21 can be an estimated value calculated using the magnitude of the current value for the motor 21 and the line time as parameters. - According to the embodiment described above, the vehicle's yaw rate YR can be used to determine whether the vehicle's driving state is stable. For example, if the yaw rate YR is less than a yaw rate determination value, it can be determined that the vehicle's driving state is stable. In this case, the yaw rate determination value can be set lower as the vehicle's speed VS increases. In such a control configuration, the yaw rate YR corresponds to the stability index value, which represents the stability of the vehicle's driving state as a numerical value, and the yaw rate determination value corresponds to the stability reference value, which is a criterion for determining whether the driving state is stable.

[0080] - According to the embodiment described above, if the first wheel X corresponds to a wheel (the right front wheel FR or the right rear wheel RR) that is located inwards in the direction of rotation when the vehicle turns right, the engine protection control and the adjustment control can be performed without carrying out the determination process in step S24. Likewise, if the first wheel X corresponds to a wheel (the left front wheel FL or the left rear wheel RL) that is located inwards in the direction of rotation when the vehicle turns left, the engine protection control and the adjustment control can be determined without carrying out the determination process in step S24. In this case, the yaw moment generated by carrying out the engine protection control and the adjustment control corresponds to the moment in the direction opposite to the yaw moment generated by the steering input from the driver.Accordingly, even when the engine protection control and the adjustment control are in operation, the instability of the vehicle's behavior is limited. Description of reference symbols

[0081] 12, 12a to 12d... electric braking device, 15... brake ECU as a brake control device (temperature acquisition section, determination section, motor control section, yaw rate acquisition section, index value acquisition section), 21... motor, FR, FL, RR, RL... wheel, KS... vehicle speed determination value as an example of the stability reference value, Ix... current value for the overheated motor, Iy... current value for the normal motor, T... temperature, Tth1... first set threshold as temperature reference value, VS... vehicle speed as an example of a stability index value, X... first wheel, Y... second wheel, YR... yaw rate as an example of the stability index value, and YR2... generated yaw rate as an estimated value of the yaw rate.

Claims

[1] Vehicle brake control device controlling a plurality of electric brake devices (12, 12a, 12b, 12c, 12d), each corresponding to one of a plurality of wheels (FR, FL, RR, RL) provided on a vehicle, wherein each electric brake device (12, 12a, 12b, 12c, 12d) has a motor (21) and is configured to apply a braking force corresponding to a current value for the motor (21) to the corresponding wheel, wherein the vehicle brake control device comprises: a temperature procurement section that procures a temperature for each motor (21), a determination section that determines whether the motors (21) have an overheated motor (21) in which the obtained temperature is greater than or equal to a temperature reference value that is set as a determination criterion to determine whether the motor (21) tends to overheat, and a motor control section, characterized by, that, If any of the motors (21) is identified as the overheated motor (21), the motor control section performs a motor protection control to reduce a current value for the overheated motor (21) with a more gradual gradient in a case where the temperature of the overheated motor (21) is low than in a case where the temperature of the overheated motor (21) is high. [2] Vehicle brake control device according to claim 1, wherein a wheel corresponding to the electric braking device with the overheated motor (21) is defined as a first wheel, A wheel that is located on the opposite side to the first wheel in the transverse direction of the vehicle is defined as a second wheel. an electric braking device corresponding to the second wheel, comprising a normal motor (21), and During the motor protection control, the motor control section performs an adjustment control to increase a current value for the normal motor (21) attached to the electric brake device corresponding to the second wheel. [3] Vehicle brake control device according to claim 2, wherein, when the motor protection control is carried out, the motor control section performs the adjustment control such that the current value for the normal motor (21) is increased to compensate for a reduction in the braking force applied to the entire vehicle caused by the motor protection control. [4] Vehicle brake control device according to claim 2, wherein, during the implementation of the motor protection control and the adjustment control, the motor control section adjusts the braking force applied to all other wheels (FR, FL, RR, RL) except the first wheel. [5] Vehicle brake control device according to claim 4, further comprising a yaw rate acquisition section which obtains an estimated value of a yaw rate generated on the vehicle by carrying out the motor protection control and the adjustment control, wherein, when carrying out the motor protection control and the adjustment control, the motor control section controls the motors (21) attached to the electric brake devices (12, 12a, 12b, 12c, 12d) to apply the braking force to the other wheels (FR, FL, RR, RL) other than the first and second wheels, in order to adjust the braking force applied to the other wheels (FR, FL, RR, RL) other than the first and second wheels such that the estimated value of the yaw rate obtained by the yaw rate acquisition section approaches zero. [6] Vehicle brake control device according to claim 2, wherein, during the adjustment control, the motor control section adjusts the current values ​​for the motors (21) attached to the electric brake devices (12, 12a, 12b, 12c, 12d) corresponding to all wheels (FR, FL, RR, RL) except the first wheel in such a way that the braking force applied to all wheels (FR, FL, RR, RL) except the first wheel is increased in order to compensate for a reduction in the braking force applied to the entire vehicle caused by the motor protection control. [7] Vehicle brake control device according to one of claims 1 to 6, further comprising an index value procurement section which procures a stability index value which indicates stability of the vehicle's driving condition, wherein the engine control section allows the execution of the engine protection control if the stability index value obtained by the index value procurement section is lower than or equal to a stability reference value which is a determining criterion for determining whether the vehicle's driving condition is stable.

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