Vehicle brake system

Abstract

To provide a brake device for a vehicle which is capable of enhancing stability of vehicle behavior at regenerative cooperative brake control in a hybrid vehicle or an electric vehicle which is provided with a motor for driving to generate driving force of the vehicle on each of front wheels and rear wheels.SOLUTION: In a brake control for a vehicle which comprises a front wheel hydraulic pressure brake (38a), a rear wheel hydraulic pressure brake (38b) and a control device (90) which controls brake force generated by a motor (125F) for driving the front wheels and a motor (125R) for driving the rear wheels, respectively, the control device (90) sets shortage to front wheel target hydraulic pressure brake force generated by the front wheel hydraulic pressure brake (38a) when at least either of the shortage of front wheel maximum regenerative brake force which the electric motor (125F) for driving the front wheels makes it possible to generate with respect to front wheel ideal brake force according to longitudinal distribution or the shortage of rear wheel maximum regenerative brake force which the electric motor (125R) for driving the rear wheels makes it possible to generate with respect to rear wheel ideal brake force according to longitudinal distribution is caused.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a brake device for a vehicle. [Background technology]

[0002] Conventionally, a vehicle brake device has been known that includes a hydraulic brake that generates hydraulic braking force by utilizing hydraulic pressure generated in response to the driver's brake operation, and a regenerative brake that generates regenerative braking force, and that is capable of performing control to distribute braking force between the hydraulic braking force and the regenerative braking force (hereinafter also referred to as "regenerative cooperative brake control").

[0003] The purpose of regenerative braking used in vehicle brake devices is to convert the kinetic energy of the wheels during braking into electrical energy and to utilize energy effectively. The maximum regenerative braking force that can be generated by regenerative braking is limited by factors such as the vehicle speed during braking and the battery charge state. Therefore, from the perspective of effective energy utilization, it is preferable to increase the proportion of regenerative braking by varying the ratio of braking force by hydraulic brakes to braking force by regenerative brakes according to the maximum regenerative braking force even while hydraulic brakes are operating.

[0004] Various methods have been proposed for performing regenerative cooperative brake control. For example, Patent Document 1 discloses a vehicle brake device that is provided between the hydraulic brakes of the front wheels and the hydraulic brakes of the rear wheels and includes a regulating valve that is capable of continuously adjusting the flow rate of brake fluid from the hydraulic brakes of the front wheels to the hydraulic brakes of the rear wheels, and a pressure reducing valve that is capable of reducing the pressure of the brake fluid supplied to the hydraulic brakes of the rear wheels, and that continuously increases the opening of the regulating valve and opens the pressure reducing valve when reducing the braking force of the hydraulic brakes of the front wheels. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 086290 Summary of the Invention [Problem to be solved by the invention]

[0006] When regenerative cooperative brake control is implemented, an ideal value (ideal front / rear distribution) of the distribution of braking force generated on the front wheels and braking force generated on the rear wheels (front / rear distribution) is set based on the desired energy efficiency or stability of vehicle behavior. For example, if an electric motor that generates regenerative braking force on the front wheels and an electric motor that generates regenerative braking force on the rear wheels have the same level of output characteristics, a 50:50 front / rear regenerative braking distribution may be considered to maximize regenerative efficiency. However, in reality, increasing the proportion of rear wheels in the front / rear regenerative braking distribution may reduce the stability of vehicle behavior.

[0007] The present invention has been made in consideration of the above problems, and provides a vehicle brake device that can improve the stability of vehicle behavior during regenerative cooperative brake control in a hybrid vehicle or an electric vehicle equipped with a drive motor that generates drive force for the front wheels and rear wheels, respectively. [Means for solving the problem]

[0008] According to one aspect of the present invention, in a vehicle brake device including a first hydraulic brake that generates hydraulic braking force on a front wheel, a second hydraulic brake that generates hydraulic braking force on a rear wheel, a first electric motor that converts kinetic energy of the front wheels to generate regenerative braking force, a second electric motor that converts kinetic energy of the rear wheels to generate regenerative braking force, and a control device that controls the braking forces generated by the first hydraulic brake, the second hydraulic brake, the first electric motor, and the second electric motor, when there is a shortage of the maximum front wheel regenerative braking force that can be generated by the first electric motor with respect to the front wheel ideal braking force according to the front / rear distribution, the control device: andA vehicle brake device is provided, characterized in that when a shortage occurs in the maximum rear wheel regenerative braking force that can be generated by the second electric motor relative to the rear wheel ideal braking force according to the front / rear distribution, the shortage is set as the front wheel target hydraulic braking force to be generated by the first hydraulic brake. [Effects of the Invention]

[0009] As described above, according to the present invention, the stability of vehicle behavior during regenerative cooperative brake control can be improved in a hybrid vehicle or an electric vehicle equipped with a drive motor that generates drive force for the front wheels and rear wheels, respectively. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing a configuration example of a vehicle brake device according to an embodiment of the present invention; [Figure 2] 2 is an explanatory diagram of a hydraulic circuit that constitutes a hydraulic brake in the vehicle brake device according to the embodiment; FIG. [Figure 3] FIG. 2 is an explanatory diagram illustrating an example of the configuration of a brake ECU. [Figure 4] FIG. 10 is an explanatory diagram showing an example of a calculation process of a front wheel braking force distribution rate. [Figure 5] 10 is a flowchart illustrating an example of a process for calculating a front wheel braking force distribution rate. [Figure 6] FIG. 4 is an explanatory diagram showing an example of a calculation process of a front wheel braking force distribution rate set based on a required braking force and a vehicle body deceleration. [Figure 7] FIG. 4 is an explanatory diagram showing an example of a calculation process of a front wheel braking force distribution rate set based on the possibility of intervention in the front wheel braking force by ABS control. [Figure 8] FIG. 10 is an explanatory diagram showing a transition of the front wheel braking force distribution rate when filtering is performed. [Figure 9] FIG. 10 is an explanatory diagram showing another example of the filtering process of the front wheel braking force distribution rate. [Figure 10] 5 is an explanatory diagram showing an example of a calculation process for calculating a maximum regenerative braking force, a front wheel ideal regenerative braking force, and a rear wheel ideal regenerative braking force. FIG. [Figure 11] 10 is a flowchart showing an example of a calculation process for calculating a maximum regenerative braking force, a front wheel ideal regenerative braking force, and a rear wheel ideal regenerative braking force. [Figure 12] 10 is a flowchart showing a process of calculating a total target regenerative braking force, a front wheel target hydraulic pressure braking force, and a rear wheel target hydraulic pressure braking force by a regenerative braking force calculation unit and a target hydraulic pressure braking force calculation unit. [Figure 13] 5 is an explanatory diagram showing an example of a calculation process for calculating a front wheel target regenerative braking force and a rear wheel target regenerative braking force; FIG. [Figure 14] 10 is a flowchart illustrating an example of a calculation process for calculating a front wheel target regenerative braking force and a rear wheel target regenerative braking force. [Figure 15] FIG. 10 is an explanatory diagram showing an example of an operation of regenerative emphasis brake control. [Figure 16] FIG. 10 is an explanatory diagram showing an example of an operation of regenerative emphasis brake control. [Figure 17] FIG. 10 is an explanatory diagram showing an example of an operation of regenerative emphasis brake control. [Figure 18] FIG. 10 is an explanatory diagram showing an example of an operation of regenerative emphasis brake control. [Figure 19] FIG. 10 is an explanatory diagram showing an example of an operation of regenerative emphasis brake control. [Figure 20] FIG. 10 is an explanatory diagram showing an example of an operation of regenerative emphasis brake control. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0012] <1. Overall configuration of vehicle brake device> First, the overall configuration of the vehicle brake device according to this embodiment will be described. Fig. 1 is a schematic diagram showing an example of the configuration of a vehicle brake device 100. In Fig. 1, only one front wheel F and one rear wheel R are shown for ease of understanding.

[0013] The vehicle brake device 100 according to this embodiment includes a hydraulic brake and a regenerative brake that utilizes the kinetic energy of the wheels. In the vehicle brake device 100, braking force is distributed between the hydraulic brake force and the regenerative brake force in response to the brake force requested by the driver.

[0014] Vehicle brake device 100 is equipped with a front-wheel drive motor (first electric motor) 125F as a first regenerative brake. This motor functions as a drive source for driving front wheels F when the vehicle is running, and functions as a generator during braking to generate regenerative braking force on the front wheels F. Vehicle brake device 100 is also equipped with a rear-wheel drive motor (second electric motor) 125R as a second regenerative brake. This motor functions as a drive source for driving rear wheels R when the vehicle is running, and functions as a generator during braking to generate regenerative braking force on the rear wheels R. Hereinafter, unless a distinction is required, front-wheel drive motor 125F and rear-wheel drive motor 125R will be referred to as drive motors 125.

[0015] The driving of the drive motor 125 is controlled by the motor ECU 110. Specifically, the motor ECU 110 controls the operation of the inverter 123F of the front-wheel drive motor 125F and the inverter 123R of the rear-wheel drive motor 125R. As a result, the motor ECU 110 supplies electric power from the battery 121 to the drive motor 125, or charges the battery 121 with regenerative electric power from the drive motor 125.

[0016] The vehicle brake device 100 is also equipped with hydraulic brakes 38F, 38R that generate hydraulic brake forces corresponding to the hydraulic pressure supplied to each of the front wheels F and rear wheels R. The hydraulic pressure of the brake fluid supplied to each of the hydraulic brakes 38F (first hydraulic brake) 38F of the front wheels F and the hydraulic brakes 38R (second hydraulic brake) 38R of the rear wheels R is controlled by a brake ECU 90. Specifically, the brake ECU 90 adjusts the hydraulic pressure supplied to each of the hydraulic brakes 38F of the front wheels F and the hydraulic brakes 38R of the rear wheels R by controlling the operation of the hydraulic unit 20. In other words, the vehicle brake device 100 according to this embodiment can generate regenerative braking force and hydraulic braking force for each of the front wheels F and the rear wheels R.

[0017] The brake ECU 90 and the motor ECU 110 are connected to each other so as to be able to communicate with each other via a network such as a CAN (Controller Area Network). The brake ECU 90 controls the regenerative braking force generated on each of the front wheels F and the rear wheels R by providing a regenerative braking command value to the motor ECU 110. The motor ECU 110 transmits to the brake ECU 90 information on the maximum value of the regenerative braking force that can be output at that time.

[0018] The brake ECU 90 or the motor ECU 110 may be partially or entirely configured with, for example, a microcomputer or a microprocessor unit, or may be configured with updatable firmware, etc. Furthermore, the brake ECU 90 or the motor ECU 110 may be partially or entirely configured with a program module or the like that is executed by commands from a CPU or the like.

[0019] The brake ECU 90 receives as input a stroke signal supplied from the electric booster 13, a sensor signal from a master cylinder hydraulic pressure sensor 24 that detects the hydraulic pressure (master cylinder pressure) in the master cylinder 14, as well as sensor signals from wheel speed sensors (not shown) that indicate the rotational speeds of the respective wheels RF, LR, LF, and RR (see FIG. 2).

[0020] <2. Hydraulic circuit> Next, with reference to FIG. 2, an example of a hydraulic circuit 1 that constitutes a hydraulic brake in the vehicle brake device according to this embodiment will be briefly described.

[0021] The hydraulic circuit 1 shown in Figure 2 is a hydraulic circuit for a brake system for a four-wheeled vehicle. The hydraulic circuit 1 is applied to a hydraulic circuit with two brake systems, each of which brakes one front wheel and a rear wheel diagonally opposite the front wheel as a set, a so-called X-piping system. The brake hydraulic circuit 1 can be applied to a wide range of vehicles, including not only four-wheeled vehicles but also two-wheeled vehicles.

[0022] In the hydraulic circuit 1, the depression force applied to the brake pedal 11 is amplified by a booster 13 and transmitted to a master cylinder 14, which serves as a hydraulic pressure generating source. Two pressure chambers are formed in the master cylinder 14, defined by a primary piston and a secondary piston. When the driver depresses the brake pedal, each piston is pressed, and brake fluid moves into the hydraulic circuit 1 through hydraulic ports that communicate with each pressure chamber.

[0023] The booster 13 is connected to the brake pedal 11 side via an input rod 15, and the amplified pedal force is transmitted to a master cylinder 14 via a push rod connected to a primary piston. In this embodiment, an electric booster is used as the booster 13.

[0024] A first hydraulic circuit 28 and a second hydraulic circuit 30 extend from hydraulic ports communicating with the two pressurizing chambers of the master cylinder 14 toward hydraulic brakes 38a to 38d of the respective wheels RF, LR, LF, and RR. The hydraulic circuit 1 of the vehicle brake device according to this embodiment employs an X-piping system, and brake fluid is supplied to the wheel cylinder of hydraulic brake 38a of the front right wheel RF and the wheel cylinder of hydraulic brake 38b of the rear left wheel LR via the first hydraulic circuit 28. Brake fluid is also supplied to the wheel cylinder of hydraulic brake 38c of the front left wheel LF and the wheel cylinder of hydraulic brake 38d of the rear right wheel RR via the second hydraulic circuit 30.

[0025] As a result, each of the hydraulic brakes 38a to 38d can generate a braking force on each of the wheels RF, LR, LF, and RR by hydraulic pressure. The hydraulic brakes 38a and 38c correspond to the first hydraulic brake 38F. The hydraulic brakes 38b and 38d correspond to the second hydraulic brake 38R.

[0026] The hydraulic circuit 1 includes a first hydraulic circuit 28 and a second hydraulic circuit 30 having the same configuration. Brake fluid is supplied to the first hydraulic circuit 28 and the second hydraulic circuit 30 from the master cylinder 14. Below, the first hydraulic circuit 28 will be briefly described, and a description of the second hydraulic circuit 30 will be omitted.

[0027] The first hydraulic circuit 28 includes solenoid valves, such as a normally open, linearly controllable circuit control valve 36a, a normally closed, on / off controlled suction valve 34a, normally open, linearly controllable pressure increase valves (adjustment valves) 58aa, 58ba, and normally closed, on / off controlled pressure reduction valves 54aa, 54ba. The first hydraulic circuit 28 also includes a pump 44a driven by a pump motor 96, a low-pressure accumulator 71a, and a damper 73a. The number of pumps 44a is not limited to one.

[0028] A first pressure increase valve 58aa and a first pressure reduction valve 54aa provided adjacent to the hydraulic brake 38a of the right front wheel RF are used for ABS (Antilock Brake System) control or ESC (Electronic Stability Control) control of the right front wheel RF. A second pressure increase valve 58ba and a second pressure reduction valve 54ba provided adjacent to the hydraulic brake 38b of the left rear wheel LR are used for ABS control or ESC control of the left rear wheel LR.

[0029] The first pressure-increasing valve 58aa for the right front wheel RF is located between the circuit control valve 36a and the hydraulic brake 38a for the right front wheel RF. The linearly controllable first pressure-increasing valve 58aa continuously adjusts the flow rate of brake fluid from the circuit control valve 36a to the wheel cylinder of the hydraulic brake 38a for the right front wheel RF. When the first pressure-increasing valve 58aa is closed, the first pressure-increasing valve 58aa allows brake fluid to flow from the hydraulic brake 38a to the circuit control valve 36a, while also providing a bypass flow path with a check valve that restricts reverse flow.

[0030] The first pressure-reducing valve 54aa for the right front wheel RF is a solenoid valve that can be switched between a fully open and a fully closed state, and is located between the wheel cylinder of the hydraulic brake 38a for the right front wheel RF and the low-pressure accumulator 71a. When the first pressure-reducing valve 54aa is open, it reduces the pressure of brake fluid supplied to the wheel cylinder of the hydraulic brake 38a for the right front wheel RF. By repeatedly opening and closing the valve intermittently, the first pressure-reducing valve 54aa can adjust the flow rate of brake fluid flowing from the wheel cylinder of the hydraulic brake 38a for the right front wheel RF to the low-pressure accumulator 71a.

[0031] The second pressure-increasing valve 58ba for the left rear wheel LR is provided between the circuit control valve 36a and the hydraulic brake 38b for the left rear wheel LR. The linearly controllable second pressure-increasing valve 58ba continuously adjusts the flow rate of brake fluid from the circuit control valve 36a to the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR. When the second pressure-increasing valve 58ba is closed, it allows brake fluid to flow from the hydraulic brake 38b to the circuit control valve 36a, while also providing a bypass flow path with a check valve that restricts reverse flow.

[0032] The second pressure-reducing valve 54ba for the left rear wheel LR is a solenoid valve that can be switched between a fully open and a fully closed state, and is located between the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR and the low-pressure accumulator 71a. When the second pressure-reducing valve 54ba is open, it reduces the pressure of the brake fluid supplied to the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR. By repeatedly opening and closing the valve intermittently, the second pressure-reducing valve 54ba can adjust the flow rate of brake fluid flowing from the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR to the low-pressure accumulator 71a.

[0033] The circuit control valve 36a is provided to establish or block communication between the pressure increase valves 58aa, 58ba and the master cylinder 14. The suction valve 34a is provided to establish or block communication between the master cylinder 14 and the suction side of the pump 44a. A master cylinder hydraulic pressure sensor 24 is provided in the conduit between the circuit control valve 36a and the master cylinder 14, as well as between the suction valve 34a and the master cylinder 14. These are similar to the components for conventional ESC control, so detailed description will be omitted.

[0034] The second hydraulic circuit 30 controls a hydraulic brake 38c for the left front wheel LF and a hydraulic brake 38d for the right rear wheel RR. The second hydraulic circuit 30 is configured in the same manner as the first hydraulic circuit 28, except that the wheel cylinder of the hydraulic brake 38a for the right front wheel RF in the description of the first hydraulic circuit 28 is replaced with the wheel cylinder of the hydraulic brake 38c for the left front wheel LF, and the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR is replaced with the wheel cylinder of the hydraulic brake 38d for the right rear wheel RR.

[0035] <3. Control device> Next, a configuration example of the brake ECU 90 provided in the vehicle brake device 100 according to this embodiment will be described. The control device may be configured with only the brake ECU 90, or may be configured with multiple ECUs including other ECUs such as the motor ECU 110.

[0036] 3 is a block diagram showing an example of the functional configuration of the brake ECU 90. The brake ECU 90 includes a required braking force calculation unit 91, a regenerative braking force calculation unit 93, a target regenerative braking force calculation unit 95, and a target hydraulic pressure braking force calculation unit 97. In this embodiment, these units are functions realized by the execution of a program by a microcomputer or the like. In addition, the brake ECU 90 includes storage units (not shown) such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The storage units store programs executed by the microcomputer or the like, various parameters used in arithmetic processing, acquired information, calculation results, and the like.

[0037] The brake ECU 90 can acquire information on the maximum front wheel regenerative braking force bff_rg_pot and the maximum rear wheel regenerative braking force bfr_rg_pot that can be generated by the front-wheel drive motor 125F and the rear-wheel drive motor 125R, respectively, from the motor ECU 110. The maximum front wheel regenerative braking force bff_rg_pot and the maximum rear wheel regenerative braking force bfr_rg_pot vary depending on the specifications of the drive motor 125, the wheel rotation speed whl_spd, and the charge capacity SOC of the battery 121. For example, the motor ECU 110 calculates the maximum front wheel regenerative braking force bff_rg_pot and the maximum rear wheel regenerative braking force bfr_rg_pot for each of the front-wheel drive motor 125F and the rear-wheel drive motor 125R by referring to a regenerative braking force map that is stored in advance and that uses the wheel rotation speed whl_spd and the charge capacity SOC of the battery 121 as variables. When the front wheel drive motor 125F and the rear wheel drive motor 125R have the same specifications, there may be only one regenerative braking force map.

[0038] In addition, the brake ECU 90 is capable of acquiring information on the amount of brake pedal operation by the driver brk_str, information on the possibility of intervention in the braking force of each wheel by ABS control or ESP control esp_idx, information on the rotational speed of each wheel whl_spd, information on the vehicle deceleration dec, information on the vehicle yaw rate yaw, information on the steering wheel steering angle ang_ste, and information on the charging capacity SOC of the battery 121.

[0039] (Required braking force calculation section) The required braking force calculation unit 91 calculates a braking force (required braking force) bf_tgt required of the vehicle based on information on the brake pedal operation amount brk_str by the driver. The brake pedal operation amount brk_str can be obtained, for example, based on a detection signal from a stroke sensor provided in the booster 13. The required braking force brk_tgt may be set, for example, to increase proportionally with an increase in the brake pedal operation amount brk_str. Furthermore, the required braking force calculation unit 91 obtains information on the calculated required braking force bf_tgt when the vehicle is under automatic driving or ACC (Adoptive Cruise Control) control.

[0040] (Regenerative braking force calculation section) The regenerative braking force calculation unit 93 sets an ideal front / rear distribution of braking force. In this embodiment, the regenerative braking force calculation unit 93 sets the ideal front / rear distribution by increasing or decreasing a preset initial value of the ideal front / rear distribution in accordance with the stability of the vehicle behavior. The initial value of the ideal front / rear distribution is set in accordance with the purpose. For example, if emphasis is placed on energy use efficiency, the initial value of the ideal front / rear distribution is set to 50:50 (front wheel ideal braking force distribution ratio ratio_bff_ide is 50%). Alternatively, if emphasis is placed on the stability of the vehicle behavior, the initial value of the ideal front / rear distribution is set to, for example, 70:30 (front wheel ideal braking force distribution ratio ratio_bff_ide is 70%).

[0041] For example, when it is estimated that the vehicle behavior is unstable, the regenerative braking force calculation unit 93 increases the front wheel ideal braking force distribution ratio ratio_bff_ide to improve the stability of the vehicle behavior. On the other hand, when it is estimated that the vehicle behavior is stable, the regenerative braking force calculation unit 93 decreases the front wheel ideal braking force distribution ratio ratio_bff_ide with the initial value as the lower limit. This makes it possible to achieve both energy utilization efficiency and stability of the vehicle behavior.

[0042] The regenerative braking force calculation unit 93 may prevent the front wheel ideal braking force distribution ratio "ratio_bff_ide" from exceeding a preset upper limit. This makes it possible to prevent the front wheel ideal braking force distribution ratio "ratio_bff_ide" from becoming too large and causing the vehicle behavior to become unstable. The upper limit of the front wheel ideal braking force distribution ratio "ratio_bff_ide" can be set to, for example, 70 to 80%.

[0043] 4 and 5 are explanatory diagrams showing an example of the calculation process of the front wheel ideal braking force distribution ratio ratio_bff_ide by the regenerative braking force calculation unit 93. Fig. 4 is a logic circuit diagram showing an example of the calculation process of the front wheel ideal braking force distribution ratio ratio_bff_ide, and Fig. 5 is a flowchart showing an example of the calculation process of the front wheel ideal braking force distribution ratio ratio_bff_ide.

[0044] 4 and 5, first, the regenerative braking force calculation unit 93 calculates the front wheel ideal braking force distribution ratio ratio_bff_ide_C based on the vehicle speed veh_spd (step S31). The front wheel ideal braking force distribution ratio ratio_bff_ide_C set based on the vehicle speed veh_spd is set by, for example, referring to a preset map using the vehicle speed veh_spd as a parameter.

[0045] Next, the regenerative braking force calculation unit 93 calculates the front wheel ideal braking force distribution ratio ratio_bff_ide_D based on the required braking force bf_tgt and the vehicle body deceleration dec (step S33). Fig. 6 is an explanatory diagram showing an example of the calculation process of the front wheel ideal braking force distribution ratio ratio_bff_ide_D set based on the required braking force bf_tgt and the vehicle body deceleration dec. When the deceleration is small, the front wheel ideal braking force distribution ratio ratio_bff_ide_D is set to a constant value regardless of the required braking force bf_tgt, whereas when the deceleration is large, once the required braking force bf_tgt exceeds a certain value, the front wheel ideal braking force distribution ratio ratio_bff_ide_D is set to increase as the required braking force bf_tgt increases.

[0046] Next, the regenerative braking force calculation unit 93 calculates the front wheel ideal braking force distribution ratio ratio_bff_ide_B based on the possibility esp_idx of intervention in the braking force of the front wheels by ESP control (step S35). The front wheel ideal braking force distribution ratio ratio_bff_ide_B, which is set based on the possibility esp_idx of intervention in the braking force of the front wheels by ESP control, is calculated by referring to a pre-stored map using the possibility esp_idx of intervention in the braking force of the front wheels by ESP control as a parameter.

[0047] Next, the regenerative braking force calculation unit 93 calculates a front wheel braking force distribution rate based on the possibility of intervention in the front wheel braking force by ABS control (steps S37 to S43). Fig. 7 is an explanatory diagram showing an example of a calculation process for the front wheel braking force distribution rate set based on the possibility of intervention in the front wheel braking force by ABS control. The regenerative braking force calculation unit 93 calculates a first intervention possibility state value abs_st_idx_split based on a value obtained by subtracting a value obtained by adding a value abs_idx_FR indicating the possibility of intervention in the braking force of the right front wheel by ABS control to a value abs_idx_RR indicating the possibility of intervention in the braking force of the right rear wheel by ABS control from a value obtained by adding a value abs_idx_FL indicating the possibility of intervention in the braking force of the left front wheel by ABS control to a value abs_idx_RL indicating the possibility of intervention in the braking force of the left rear wheel by ABS control (step S37).

[0048] In addition, the regenerative braking force calculation unit 93 calculates a second intervention possibility state value abs_idx_μlump based on the value obtained by adding the value abs_idx_RL indicating the possibility of ABS control intervening in the braking force of the left rear wheel to the value abs_idx_RR indicating the possibility of ABS control intervening in the braking force of the right rear wheel, minus the value obtained by adding the value abs_idx_FL indicating the possibility of ABS control intervening in the braking force of the left front wheel to the value abs_idx_FR indicating the possibility of ABS control intervening in the braking force of the right front wheel (step S39).

[0049] Next, the regenerative braking force calculation unit 93 calculates a first front wheel ideal braking force distribution ratio ratio_bff_ide_Aa based on the first intervention possibility state value abs_idx_split (step S41). Furthermore, the regenerative braking force calculation unit 93 calculates a second front wheel ideal braking force distribution ratio ratio_bff_ide_Ab based on the second intervention possibility state value abs_idx_μlump (step S43). Then, the regenerative braking force calculation unit 93 sets the maximum value of the calculated front wheel ideal braking force distribution ratios ratio_bff_ide_Aa to ratio_bff_ide_D as the front wheel ideal braking force distribution ratio ratio_bff_ide_raw (step S45).

[0050] Next, the regenerative braking force calculation unit 93 determines whether or not the previous value of the front wheel ideal braking force distribution rate, ratio_bff_ide_K1, is greater than the currently calculated front wheel ideal braking force distribution rate, ratio_bff_ide_raw (step S47). If the previous value of the front wheel ideal braking force distribution rate, ratio_bff_ide_K1, is greater than the currently calculated front wheel ideal braking force distribution rate, ratio_bff_ide_raw (S47 / Yes), the regenerative braking force calculation unit 93 determines whether or not the value of the delay timer is positive (step S49). The delay timer is used to fix the maximum value of the front wheel ideal braking force distribution rate, ratio_bff_ide, for a certain period of time so that the set front wheel ideal braking force distribution rate, ratio_bff_ide, does not decrease suddenly.

[0051] If the value of the delay timer is a positive value (S49 / Yes), the regenerative braking force calculation unit 93 subtracts 1 from the value of the delay timer and sets the previous value ratio_bff_ide_K1 of the front wheel ideal braking force distribution rate as the current front wheel ideal braking force distribution rate ratio_bff_ide (step S51). On the other hand, if the value of the delay timer is not a positive value (S49 / No), the regenerative braking force calculation unit 93 subtracts 1 from the value of the delay timer and sets the current front wheel ideal braking force distribution rate ratio_bff_ide to the larger of the previous value ratio_bff_ide_K1 of the front wheel ideal braking force distribution rate minus a preset allowable value or the currently calculated front wheel ideal braking force distribution rate ratio_bff_ide_raw (step S53).

[0052] Furthermore, in the above-mentioned step S47, if the previous value ratio_bff_ide_K1 of the front wheel ideal braking force distribution rate is not greater than the currently calculated front wheel ideal braking force distribution rate ratio_bff_ide_raw (S47 / No), the regenerative braking force calculation unit 93 sets the value of the delay timer to a preset value and sets the currently calculated front wheel ideal braking force distribution rate ratio_bff_ide_raw to the current front wheel ideal braking force distribution rate ratio_bff_ide (step S55). After the front wheel ideal braking force distribution rate ratio_bff_ide is set in step S51, step S53, or step S55, the regenerative braking force calculation unit 93 updates the set value of the current front wheel ideal braking force distribution rate ratio_bff_ide to the previous value ratio_bff_ide_K1 (step S57).

[0053] Fig. 8 is an explanatory diagram showing an example of the transition of the front wheel ideal braking force distribution ratio ratio_bff_ide set by the filtering process performed in steps S47 to S57 of Fig. 5. The dotted line shows the transition of the front wheel ideal braking force distribution ratio ratio_bff_ide when filtering process is not performed, and the solid line shows the transition of the front wheel ideal braking force distribution ratio ratio_bff_ide when filtering process is performed. By repeatedly performing the processes of steps S47 to S57 described above, the regenerative braking force calculation unit 93 can calculate the front wheel ideal braking force distribution ratio ratio_bff_ide so that the front wheel ideal braking force distribution ratio ratio_bff_ide does not decrease suddenly.

[0054] The filtering process of the front wheel ideal braking force distribution ratio ratio_bff_ide is not limited to the above example. Fig. 9 is an explanatory diagram showing another example of the filtering process of the front wheel ideal braking force distribution ratio ratio_bff_ide. In the example shown in Fig. 9, the filtering process is performed using the inverted value crb_ratio_bff_ide of the front wheel ideal braking force distribution ratio.

[0055] Specifically, the regenerative braking force calculation unit 93 subtracts the previous value of the inverted value of the front wheel ideal braking force distribution rate crb_ratio_bff_ide_K1 from the calculated inverted value of the front wheel ideal braking force distribution rate crb_ratio_bff_ide_raw, multiplies the result by a preset filtering coefficient P_ratio_bff_LPF, and then adds the previous value crb_ratio_bff_ide_K1. The regenerative braking force calculation unit 93 compares the result of this addition, the previous value crb_ratio_bff_ide_K1 with the result of the addition and selects the smaller value from among these, and the calculated inverted value of the front wheel ideal braking force distribution rate crb_ratio_bff_ide_raw, and sets the inverted value crb_ratio_bff_ide of the current set value of the front wheel ideal braking force distribution rate. This filtering process also makes it possible to prevent a sudden decrease in the front wheel ideal braking force distribution rate ratio_bff_ide.

[0056] Although not shown, when terminating the regenerative control, the regenerative braking force calculation unit 93 stores the front wheel ideal braking force distribution ratio ratio_bff_ide set at the start of the terminating control and maintains this setting until the regenerative control is terminated. Therefore, until the regenerative control is terminated, the regenerative braking force calculation unit 93 executes the regenerative control in accordance with the front / rear distribution according to the stored front wheel ideal braking force distribution ratio ratio_bff_ide.

[0057] In addition, the regenerative braking force calculation unit 93 calculates the total maximum regenerative braking force bf_rg_pot_total and the front wheel ideal regenerative braking force bff_rg_ide and rear wheel ideal regenerative braking force bfr_rg_ide to be generated by the front wheel drive motor 125F and the rear wheel drive motor 125R, respectively, based on the front wheel maximum regenerative braking force bff_rg_pot and rear wheel maximum regenerative braking force bfr_rg_pot, the required braking force bf_tgt, and the calculated front wheel ideal braking force distribution ratio ratio_bff_ide.

[0058] 10 and 11 are explanatory diagrams showing an example of a calculation process for calculating the total maximum regenerative braking force bf_rg_pot_total, the front wheel ideal regenerative braking force bff_rg_ide, and the rear wheel ideal regenerative braking force bfr_rg_ide. Fig. 10 shows a logic circuit diagram for calculating the total maximum regenerative braking force bf_rg_pot_total, the front wheel ideal regenerative braking force bff_rg_ide, and the rear wheel ideal regenerative braking force bfr_rg_ide, and Fig. 11 shows a flowchart for calculating the total maximum regenerative braking force bf_rg_pot_total, the front wheel ideal regenerative braking force bff_rg_ide, and the rear wheel ideal regenerative braking force bfr_rg_ide.

[0059] The regenerative braking force calculation unit 93 compares the smaller of the rear wheel maximum regenerative braking force bfr_rg_pot and the total maximum regenerative braking force bf_rg_pot_total of the front and rear wheels with the required braking force bf_tgt minus the front wheel ideal braking force multiplied by the front wheel ideal braking force distribution rate ratio_bff_ide (front wheel ideal braking force), and sets the smaller value as the rear wheel ideal regenerative braking force bfr_rg_ide (step S61). Next, the regenerative braking force calculation unit 93 determines whether an upper limit is imposed on the rear wheel ideal regenerative braking force bfr_rg_ide (step S63). If there is no upper limit value limit imposed on the rear wheel ideal regenerative braking force bfr_rg_ide (S63 / No), the process proceeds directly to step S67. On the other hand, if there is an upper limit value limit imposed on the rear wheel ideal regenerative braking force bfr_rg_ide (S63 / Yes), the regenerative braking force calculation unit 93 sets the smaller of the rear wheel ideal regenerative braking force bfr_rg_ide set in step S61 or the previous value bfr_rg_ide_K1 of the rear wheel ideal regenerative braking force as the current rear wheel ideal regenerative braking force bfr_rg_ide (step S65), and then proceeds to step S67.

[0060] In step S67, the regenerative braking force calculation unit 93 sets an upper limit value bff_UL of the braking force to be generated on the front wheels based on the vehicle speed Veh_spd (step S67). Next, the regenerative braking force calculation unit 93 sets an upper limit value bff_rg_UL of the front wheel regenerative braking force (step S69). The upper limit value bff_rg_UL of the front wheel regenerative braking force can be calculated, for example, by adding a value obtained by multiplying the upper limit value bff_UL of the front wheel braking force by a mechanical braking distribution to the upper limit value bff_UL, and then subtracting a value obtained by multiplying the mechanical braking distribution by the value obtained by subtracting the rear wheel ideal regenerative braking force bfr_rg_ide from the required braking force bf_tgt. Here, the "mechanical braking distribution" refers to the ratio of the braking effect provided by the hydraulic brake (first hydraulic brake) 38F of the front wheels F and the hydraulic brake (second hydraulic brake) 38R of the rear wheels R.

[0061] Next, the regenerative braking force calculation unit 93 compares the upper limit value bff_rg_UL of the front wheel regenerative braking force with the front wheel maximum regenerative braking force bff_rg_pot, and selects the smaller value (step S71). Next, the regenerative braking force calculation unit 93 determines whether or not an upper limit value is imposed on the selected front wheel regenerative braking force bff_rg (step S73). If an upper limit value is not imposed on the front wheel regenerative braking force bff_rg (S73 / No), the process proceeds directly to step S77. On the other hand, if an upper limit value is imposed on the front wheel regenerative braking force bff_rg (S73 / Yes), the regenerative braking force calculation unit 93 compares the upper limit value bff_rg_UL of the front wheel regenerative braking force with the previous value bff_rg_tgt_K1 of the front wheel regenerative braking force, and sets the smaller of the two as the upper limit value bff_rg_UL of the front wheel regenerative braking force (step S75), and proceeds to step S77.

[0062] In step S77, the regenerative braking force calculation unit 93 compares the value obtained by subtracting the rear wheel ideal regenerative braking force bfr_rg_ide from the required braking force bf_tgt with the front wheel maximum regenerative braking force bff_rg_pot, and sets the smaller value as the front wheel ideal regenerative braking force bff_rg_ide (step S77).

[0063] Next, the regenerative braking force calculation unit 93 compares the value obtained by adding the front wheel ideal regenerative braking force bff_rg_ide set in step S77 to the rear wheel ideal regenerative braking force bfr_rg_ide with the total maximum regenerative braking force bf_rg_pot_total of the front and rear wheels, and sets the smaller value as the maximum regenerative braking force (step S79).

[0064] Next, the regenerative braking force calculation unit 93 determines whether the upper limit value bff_rg_UL of the front wheel regenerative braking force, which is set based on the required braking force bf_tgt, and the front wheel ideal regenerative braking force bff_rg_ide are the same value (step S81). If the upper limit value bff_rg_UL of the front wheel regenerative braking force and the front wheel ideal regenerative braking force bff_rg_ide are the same value (S81 / Yes), the regenerative braking force calculation unit 93 imposes a limit so that the front wheel ideal regenerative braking force bff_rg_ide does not exceed the previous value bff_rg_ide_K1 until the front wheel ideal regenerative braking force bff_rg_ide becomes zero (step S83). On the other hand, if the upper limit value bff_rg_UL of the front wheel regenerative braking force and the front wheel ideal regenerative braking force bff_rg_ide are not the same value (S81 / No), the regenerative braking force calculation unit 93 terminates the control that restricts the front wheel ideal regenerative braking force bff_rg_ide so that it does not exceed the previous value bff_rg_ide_K1 until the front wheel ideal regenerative braking force bff_rg_ide becomes zero (step S85).

[0065] In the above example, instead of using the value of the front wheel maximum regenerative braking force bff_rg_pot as is, an upper limit is set for the front wheel regenerative braking force. In other words, the regenerative braking force calculation unit 93 may set the front wheel ideal regenerative braking force bff_rg_ide or the rear wheel ideal regenerative braking force bfr_rg_ide so that the rate of change of the front wheel ideal regenerative braking force bff_rg_ide or the rear wheel ideal regenerative braking force bfr_rg_ide is equal to or less than a predetermined threshold. This prevents the specification of the drive motor 125 from making it impossible to achieve the desired change in regenerative braking force, and enables the generation of braking force with the desired front / rear distribution.

[0066] (Target hydraulic braking force calculation section) The target hydraulic braking force calculation unit 97 calculates the front wheel target hydraulic braking force bff_hy_tgt and the rear wheel target hydraulic braking force bfr_hy_tgt based on the front wheel ideal braking force distribution ratio ratio_bff_tgt, the front wheel ideal regenerative braking force bff_rg_ide and the rear wheel ideal regenerative braking force bfr_rg_ide, and the front wheel maximum regenerative braking force bff_rg_pot and the rear wheel maximum regenerative braking force bfr_rg_pot. When at least one of a shortfall in the front wheel maximum regenerative braking force bff_rg_pot relative to the front wheel ideal regenerative braking force bff_rg_ide or a shortfall in the rear wheel maximum regenerative braking force bfr_rg_pot relative to the rear wheel ideal regenerative braking force bfr_rg_ide occurs, the target hydraulic braking force calculation unit 97 sets the shortfall to the target value (front wheel target hydraulic braking force) bff_hy_tgt of the first hydraulic brake 38a.

[0067] In other words, in the vehicle brake device 100 according to this embodiment, when the front wheel ideal regenerative braking force bff_rg_ide and the rear wheel ideal regenerative braking force bfr_rg_ide calculated based on the set front / rear brake distribution are insufficient to achieve the required braking force bf_tgt, the brake device 100 controls the front wheel hydraulic braking force to compensate for the braking force shortfall. This makes it possible to achieve the required braking force bf_tgt while suppressing a decrease in the stability of the vehicle behavior. In this case, when the rear wheel target regenerative braking force bfr_rg_tgt is insufficient compared to the rear wheel ideal regenerative braking force bfr_rg_ide, if there is a surplus in the front wheel regenerative braking force generated by the front wheel drive motor 125F, the front wheel regenerative braking force is used preferentially, and the front wheel hydraulic braking force is also used. This makes it possible to stabilize the vehicle behavior and improve energy utilization efficiency.

[0068] The target hydraulic braking force calculation section 97 may set the front wheel target hydraulic braking force bff_hy_ide or the rear wheel target hydraulic braking force bfr_hy_ide so that the rate of change of the front wheel target hydraulic braking force bff_hy_ide or the rear wheel target hydraulic braking force bfr_hy_ide is equal to or less than a predetermined threshold value, thereby making it possible to suppress noise caused by an increase in hydraulic pressure.

[0069] FIG. 12 is a flowchart showing the process of calculating the total target regenerative braking force bf_rg_tgt_total, the front wheel target hydraulic braking force bff_hy_tgt, and the rear wheel target hydraulic braking force bfr_hy_tgt, performed by the regenerative braking force calculation section 93 and the target hydraulic braking force calculation section 97.

[0070] The regenerative braking force calculation unit 93 calculates a total target regenerative braking force bf_rg_tgt_total based on conditions such as the required braking force bf_tgt, the total maximum regenerative braking force bf_rg_pot_total, and restrictions on the rate of change of the regenerative braking force (step S91). Next, the regenerative braking force calculation unit 93 determines whether or not to execute control that limits the front wheel target regenerative braking force bff_rg_tgt so that it does not exceed the previous value bff_rg_tgt_K1 (step S93). Whether or not to execute this control is determined based on, for example, whether or not ABS control is being executed, whether or not regenerative cooperative brake control at low speeds is being executed, etc.

[0071] If the control is not to be executed (S93 / No), the regenerative braking force calculation unit 93 ends the control (step S117) and proceeds to step S97. On the other hand, if the control is to be executed (S93 / Yes), the regenerative braking force calculation unit 93 starts the control (step S95) and proceeds to step S97. In step S97, the regenerative braking force calculation unit 93 determines whether or not control is being executed to limit the front wheel target regenerative braking force bff_rg_tgt so that it does not exceed the previous value bff_rg_tgt_K1 (step S97). If the control is not being executed (S97 / No), the process proceeds directly to step S101. On the other hand, if the control is being executed (S97 / Yes), the regenerative braking force calculation unit 93 compares the total target regenerative braking force bf_rg_tgt_total calculated in step S91 with the previous value of the total target regenerative braking force bf_rg_tgt_total_K1, and sets the smaller of the two as the total target regenerative braking force bf_rg_tgt_total (step S99).

[0072] Next, the regenerative braking force calculation unit 93 updates the previous value bf_rg_tgt_total_K1 with the total target regenerative braking force bf_rg_tgt_total set in step S99 (step S101). Next, the target hydraulic braking force calculation unit 97 compares the value obtained by subtracting the total target regenerative braking force bf_rg_tgt_total from the required braking force bf_tgt with zero, and sets the larger of the two values ​​as the total target hydraulic braking force bf_hy_tgt_total (step S103). Next, the target hydraulic braking force calculation unit 97 compares the total target hydraulic braking force bf_hy_tgt_total with the upper limit value bf_hy_UL of the hydraulic braking force, and sets the smaller of the two values ​​as the front wheel target hydraulic braking force bff_hy_tgt (step S105). Furthermore, the target hydraulic braking force calculation section 97 sets the value obtained by subtracting the front wheel target hydraulic braking force bff_hy_tgt from the total target hydraulic braking force bf_hy_tgt_total as the rear wheel target hydraulic braking force bfr_hy_tgt (step S107).

[0073] Next, the target hydraulic braking force calculation unit 97 determines whether or not control is being executed to limit the front wheel target regenerative braking force bff_rg_tgt so that it does not exceed the previous value bff_rg_tgt_K1 (step S109). If this control is not being executed (S109 / No), the process proceeds directly to step S113. On the other hand, if this control is being executed (S109 / Yes), a limit is imposed on the front wheel target hydraulic braking force bff_hy_tgt or the rear wheel target hydraulic braking force bfr_hy_tgt, and the front wheel target hydraulic braking force bff_hy_tgt or the rear wheel target hydraulic braking force bfr_hy_tgt is adjusted (step S111).

[0074] Furthermore, the target hydraulic braking force calculation unit 97 adjusts the front wheel target hydraulic braking force bff_hy_tgt or the rear wheel target hydraulic braking force bfr_hy_tgt so that the increasing gradient of the front wheel target hydraulic braking force bff_hy_tgt or the rear wheel target hydraulic braking force bfr_hy_tgt does not exceed a preset gradient threshold value (step S113). Next, the target hydraulic braking force calculation unit 97 updates the previous value bff_hy_tgt_K1 of the front wheel target hydraulic braking force and the previous value bff_hy_tgt_K1 of the rear wheel target hydraulic braking force using the set front wheel target hydraulic braking force bff_hy_tgt or rear wheel target hydraulic braking force bfr_hy_tgt (step S115).

[0075] (Target regenerative braking force calculation unit) The target regenerative braking force calculation unit 95 calculates a front wheel target regenerative braking force bff_rg_tgt and a rear wheel target regenerative braking force bfr_rg_tgt based on the front wheel ideal braking force distribution rate ratio_bff_tgt, the front wheel ideal regenerative braking force bff_rg_ide and the rear wheel ideal regenerative braking force bfr_rg_ide, and the front wheel target hydraulic braking force bff_rg_tgt and the rear wheel target regenerative braking force bfr_hy_pot. For example, the target regenerative braking force calculation unit 95 sets the smaller of the front wheel maximum regenerative braking force bff_rg_pot and the front wheel ideal regenerative braking force bff_rg_ide as the front wheel target regenerative braking force bff_rg_tgt. The target regenerative braking force calculation unit 95 also sets the smaller of the rear wheel maximum regenerative braking force bfr_rg_pot and the rear wheel ideal regenerative braking force bfr_rg_ide as the rear wheel target regenerative braking force bfr_rg_tgt.

[0076] 13 and 14 are explanatory diagrams showing an example of a calculation process for calculating a front wheel target regenerative braking force bff_rg_tgt and a rear wheel target regenerative braking force bfr_rg_tgt. Fig. 13 is a logic circuit diagram showing an example of a calculation process for calculating a front wheel target regenerative braking force bff_rg_tgt and a rear wheel target regenerative braking force bfr_rg_tgt, and Fig. 14 is a flowchart showing an example of a calculation process for calculating a front wheel target regenerative braking force bff_rg_tgt and a rear wheel target regenerative braking force bfr_rg_tgt.

[0077] The target regenerative braking force calculation unit 95 determines whether or not control is being executed to limit the front wheel target regenerative braking force with an upper limit value (step S121). If such control is being executed (S121 / Yes), the target regenerative braking force calculation unit 95 calculates the rear wheel target regenerative braking force bfr_rg_tgt by multiplying the total target regenerative braking force bf_rg_tgt_total by the previous value bfr_rg_tgt_K1 of the rear wheel target regenerative braking force and dividing the result by the sum of the front wheel target regenerative braking force bff_rg_tgt and the rear wheel target regenerative braking force bfr_rg_tgt (step S123). Next, the target regenerative braking force calculation unit 95 sets the value obtained by subtracting the rear wheel target regenerative braking force bfr_rg_tgt from the total target regenerative braking force bf_rg_tgt_total as the front wheel target regenerative braking force bff_rg_tgt (step S125). Next, the target regenerative braking force calculation unit 95 updates the previous value bff_rg_tgt_K1 of the front wheel target regenerative braking force with the front wheel target regenerative braking force bff_rg_tgt, and updates the previous value bfr_rg_tgt_K1 of the rear wheel target regenerative braking force with the rear wheel target regenerative braking force bfr_rg_tgt (step S137).

[0078] On the other hand, if control to limit the front wheel target regenerative braking force with an upper limit value is not being executed in step S121 (S121 / No), the target regenerative braking force calculation unit 95 recalculates the required braking force bf_tgt_cal by adding the total target regenerative braking force bf_rg_tgt_total, the front wheel target hydraulic braking force bff_hy_tgt, and the rear wheel target hydraulic braking force bfr_hy_tgt (step S127). Next, the target regenerative braking force calculation unit 95 compares the product of the recalculated required braking force bf_tgt_cal and the front wheel ideal braking force distribution rate ratio_bff_ide minus the rear wheel target hydraulic braking force bfr_hy_tgt with the rear wheel ideal regenerative braking force bfr_rg_ide, and sets the smaller of the two values ​​as the rear wheel target regenerative braking force bfr_rg_tgt (step S129).

[0079] Next, the target regenerative braking force calculation unit 95 compares the rear wheel target regenerative braking force bfr_rg_tgt with the rear wheel ideal regenerative braking force bfr_rg_ide, and sets the smaller of the two values ​​as the rear wheel target regenerative braking force bfr_rg_tgt (step S131). Next, the target regenerative braking force calculation unit 95 compares the larger of either the value obtained by subtracting the rear wheel target regenerative braking force bfr_rg_tgt from the recalculated required braking force bf_tgt_cal or zero with the front wheel ideal regenerative braking force bff_rg_ide, and sets the smaller of the two values ​​as the front wheel target regenerative braking force bff_rg_tgt (step S133).

[0080] Next, the target regenerative braking force calculation unit 95 updates the rear wheel target regenerative braking force bfr_rg_tgt with the front wheel target regenerative braking force bff_rg_tgt (step S135). Next, the target regenerative braking force calculation unit 95 updates the previous value bff_rg_tgt_K1 of the front wheel target regenerative braking force with the front wheel target regenerative braking force bff_rg_tgt, and updates the previous value bfr_rg_tgt_K1 of the rear wheel target regenerative braking force with the rear wheel target regenerative braking force bfr_rg_tgt (step S137).

[0081] According to the above-described calculation processing method, the required braking force bf_tgt is recalculated when a limit is imposed on the front wheel target hydraulic braking force bff_hy_tgt or the rear wheel target hydraulic braking force bfr_hy_tgt by the target hydraulic braking force calculation section 97. Therefore, the required braking force bf_tgt can be realized by utilizing regenerative braking force while suppressing noise caused by an increase in hydraulic braking force.

[0082] <4. Regenerative braking control operation> Next, an example of the operation of regenerative braking control by the vehicle brake device 100 according to this embodiment will be described. Figs. 15 to 20 show an example in which the initial value of the front wheel braking force distribution ratio is 50% (initial value of front / rear distribution is 50:50). In the following description, the front wheel ideal braking force refers to the value obtained by multiplying the required braking force bf_tgt by the front wheel ideal braking force distribution ratio ratio_bff_ide. Furthermore, the rear wheel ideal braking force refers to the value obtained by subtracting the product of the required braking force bf_tgt multiplied by the front wheel ideal braking force distribution ratio ratio_bff_ide from the required braking force bf_tgt. The vehicle brake device 100 according to this embodiment is configured to use regenerative braking preferentially, and the front wheel ideal braking force and rear wheel ideal braking force refer to the front wheel ideal regenerative braking force bff_rg_ide and rear wheel ideal regenerative braking force bfr_rg_ide.

[0083] 15 shows an example in which the front wheel ideal regenerative braking force (front wheel ideal braking force) bff_rg_ide is smaller than the front wheel maximum regenerative braking force bff_rg_pot, the rear wheel ideal regenerative braking force (rear wheel ideal braking force) bfr_rg_ide is smaller than the rear wheel maximum regenerative braking force bfr_rg_pot, and the required braking force bf_tgt is smaller than the sum bf_rg_pot of the front wheel maximum regenerative braking force bff_rg_pot and the rear wheel maximum regenerative braking force bfr_rg_pot. In this case, since both the front wheel ideal braking force and the rear wheel ideal braking force can be satisfied by regenerative braking force, the rear wheel ideal regenerative braking force bfr_rg_ide is set to the rear wheel target regenerative braking force bfr_rg_tgt, and the front wheel ideal regenerative braking force bff_rg_ide is set to the front wheel target regenerative braking force bff_rg_tgt.

[0084] 16 shows an example in which the front wheel ideal regenerative braking force (front wheel ideal braking force) bff_rg_ide is greater than the front wheel maximum regenerative braking force bff_rg_pot, the rear wheel ideal regenerative braking force (rear wheel ideal braking force) bfr_rg_ide is less than the rear wheel maximum regenerative braking force bfr_rg_pot, and the required braking force bf_tgt is less than the sum bf_rg_pot of the front wheel maximum regenerative braking force bff_rg_pot and the rear wheel maximum regenerative braking force bfr_rg_pot. In this case, the rear wheel ideal regenerative braking force bfr_rg_ide can be covered by regenerative braking force, so the rear wheel ideal regenerative braking force bfr_rg_ide is set to the rear wheel target regenerative braking force bfr_rg_tgt. On the other hand, since the front wheel maximum regenerative braking force bff_rg_pot is insufficient relative to the front wheel ideal regenerative braking force bff_rg_idle, the front wheel maximum regenerative braking force bff_rg_pot is set to the front wheel target regenerative braking force bff_rg_tgt, and the shortfall is set to the front wheel target hydraulic braking force bff_hy_tgt.

[0085] 17 shows an example in which the front wheel ideal regenerative braking force (front wheel ideal braking force) bff_rg_ide is smaller than the front wheel maximum regenerative braking force bff_rg_pot, the rear wheel ideal regenerative braking force (rear wheel ideal braking force) bfr_rg_ide is smaller than the rear wheel maximum regenerative braking force bfr_rg_pot, and the required braking force bf_tgt is larger than the sum bf_rg_pot of the front wheel maximum regenerative braking force bff_rg_pot and the rear wheel maximum regenerative braking force bfr_rg_pot. In this case, the rear wheel ideal regenerative braking force bfr_rg_ide can be covered by regenerative braking force, so the rear wheel ideal regenerative braking force bfr_rg_ide is set to the rear wheel target regenerative braking force bfr_rg_tgt. On the other hand, although the front wheel ideal regenerative braking force bff_rg_ide can be covered by regenerative braking force, if the front wheel ideal regenerative braking force bff_rg_ide is set to the front wheel target regenerative braking force bff_rg_tgt, the sum of the target regenerative braking forces will exceed the maximum regenerative braking force sum bf_rg_pot. Therefore, the value obtained by subtracting the rear wheel ideal regenerative braking force bfr_rg_ide from the maximum regenerative braking force sum bf_rg_pot is set as the front wheel target regenerative braking force bff_rg_tgt, and the shortfall is set as the front wheel target hydraulic braking force bff_hy_tgt.

[0086] 18 shows an example in which the front wheel ideal regenerative braking force (front wheel ideal braking force) bff_rg_ide is smaller than the front wheel maximum regenerative braking force bff_rg_pot, the rear wheel ideal regenerative braking force (rear wheel ideal braking force) bfr_rg_ide is greater than the rear wheel maximum regenerative braking force bfr_rg_pot, and the required braking force bf_tgt is smaller than the sum bf_rg_pot of the front wheel maximum regenerative braking force bff_rg_pot and the rear wheel maximum regenerative braking force bfr_rg_pot. In this case, the rear wheel maximum regenerative braking force bfr_rg_pot is insufficient compared to the rear wheel ideal regenerative braking force bfr_rg_ide, so the rear wheel maximum regenerative braking force bfr_rg_pot is set to the rear wheel target regenerative braking force bfr_rg_tgt. In addition, the remaining force obtained by subtracting the front wheel ideal regenerative braking force bff_rg_ide from the front wheel maximum regenerative braking force bff_rg_pot can cover the shortfall in the rear wheel ideal regenerative braking force bfr_rg_ide, so the value obtained by adding this shortfall to the front wheel ideal regenerative braking force bff_rg_ide is set as the front wheel target regenerative braking force bff_rg_tgt.

[0087] 19 shows an example in which the front wheel ideal regenerative braking force (front wheel ideal braking force) bff_rg_ide is smaller than the front wheel maximum regenerative braking force bff_rg_pot, the rear wheel ideal regenerative braking force (rear wheel ideal braking force) bfr_rg_ide is greater than the rear wheel maximum regenerative braking force bfr_rg_pot, and the required braking force bf_tgt is greater than the sum bf_rg_pot of the front wheel maximum regenerative braking force bff_rg_pot and the rear wheel maximum regenerative braking force bfr_rg_pot. In this case, the rear wheel maximum regenerative braking force bfr_rg_pot is insufficient compared to the rear wheel ideal regenerative braking force bfr_rg_ide, so the rear wheel maximum regenerative braking force bfr_rg_pot is set to the rear wheel target regenerative braking force bfr_rg_tgt. Furthermore, the front wheel target regenerative braking force bff_rg_tgt is limited to the front wheel ideal regenerative braking force bff_rg_ide by the sum of the maximum regenerative braking forces bf_rg_pot. Therefore, the shortfall with respect to the required braking force bf_tgt is set as the front wheel target hydraulic braking force bff_hy_tgt.

[0088] 20 shows an example in which the front wheel ideal regenerative braking force (front wheel ideal braking force) bff_rg_ide is greater than the front wheel maximum regenerative braking force bff_rg_pot, the rear wheel ideal regenerative braking force (rear wheel ideal braking force) bfr_rg_ide is greater than the rear wheel maximum regenerative braking force bfr_rg_pot, and the required braking force bf_tgt is less than the sum bf_rg_pot of the front wheel maximum regenerative braking force bff_rg_pot and the rear wheel maximum regenerative braking force bfr_rg_pot. In this case, the rear wheel maximum regenerative braking force bfr_rg_pot is insufficient compared to the rear wheel ideal regenerative braking force bfr_rg_ide, so the rear wheel maximum regenerative braking force bfr_rg_pot is set to the rear wheel target regenerative braking force bfr_rg_tgt. Furthermore, since the front wheel maximum regenerative braking force bff_rg_pot is insufficient relative to the front wheel ideal regenerative braking force bff_rg_ide, the front wheel maximum regenerative braking force bff_rg_pot is set to the front wheel target regenerative braking force bff_rg_tgt. Therefore, the amount of the shortfall relative to the required braking force bf_tgt is set to the front wheel target hydraulic braking force bff_hy_tgt.

[0089] As described above, with the vehicle brake device according to this embodiment, the front wheel target regenerative braking force bff_rg_tgt and the rear wheel target regenerative braking force bfr_rg_tgt are set to achieve a predetermined front / rear braking force distribution, and if at least one of the front wheel maximum regenerative braking force and the rear wheel maximum regenerative braking force is insufficient relative to the ideal front wheel braking force or the ideal rear wheel maximum regenerative braking force is insufficient, the insufficiency is compensated for by the front wheel hydraulic braking force. This makes it possible to improve the stability of vehicle behavior while increasing energy utilization efficiency.

[0090] Furthermore, in the vehicle brake device according to this embodiment, when there is a surplus in the maximum front wheel regenerative braking force relative to the ideal front wheel regenerative braking force, the front wheel regenerative braking force is used preferentially to make up for the deficiency in the rear wheel regenerative braking force, thereby improving the stability of the vehicle behavior while increasing the energy utilization efficiency.

[0091] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0092] 28...first hydraulic circuit, 30...second hydraulic circuit, 38a...first hydraulic brake, 38b...second hydraulic brake, 90...brake ECU, 91...required braking force calculation unit, 93...regenerative braking force calculation unit, 95...target regenerative braking force calculation unit, 97...target hydraulic braking force calculation unit, 100...vehicle brake device, 110...motor ECU, 121...battery, 123F·123R...inverter, 125F...front wheel drive motor, 125R...rear wheel drive motor

Claims

1. A vehicle brake device comprising: a first hydraulic brake (38a) that generates hydraulic braking force on a front wheel; a second hydraulic brake (38b) that generates hydraulic braking force on a rear wheel; a first electric motor (125F) that converts kinetic energy of the front wheel to generate a regenerative braking force; a second electric motor (125R) that converts kinetic energy of the rear wheel to generate a regenerative braking force; and a control device (90) that controls the braking forces generated by the first hydraulic brake (38a), the second hydraulic brake (38b), the first electric motor (125F), and the second electric motor (125R), The control device (90) When a shortage occurs in the maximum front wheel regenerative braking force that can be generated by the first electric motor (125F) relative to the front wheel ideal braking force according to the front-rear distribution, and when a shortage occurs in the maximum rear wheel regenerative braking force that can be generated by the second electric motor (125R) relative to the rear wheel ideal braking force according to the front-rear distribution, the shortage is set as the front wheel target hydraulic pressure braking force to be generated by the first hydraulic pressure brake (38a). A vehicle brake device characterized by:

2. The control device (90) When a shortage of the rear wheel maximum regenerative braking force occurs, if there is a surplus in the front wheel maximum regenerative braking force, the shortage of the rear wheel ideal braking force is compensated for by the surplus, and if there is no surplus in the front wheel maximum regenerative braking force relative to the front wheel ideal braking force and the surplus cannot be compensated for entirely by the surplus, the shortage of the rear wheel ideal braking force is compensated for by the hydraulic braking force generated by the first hydraulic brake (38a).

2. A vehicle brake device according to claim 1.

3. The control device (90) When the front wheel ideal braking force is smaller than the front wheel maximum regenerative braking force, the rear wheel ideal braking force is smaller than the rear wheel maximum regenerative braking force, and the required braking force is smaller than the sum of the front wheel maximum regenerative braking force and the rear wheel maximum regenerative braking force, setting the rear wheel ideal braking force to a rear wheel target regenerative braking force; The front wheel ideal braking force is set to the front wheel target regenerative braking force.

3. The vehicle brake device according to claim 2, wherein:

4. The control device (90) When the front wheel ideal braking force is greater than the front wheel maximum regenerative braking force, the rear wheel ideal braking force is smaller than the rear wheel maximum regenerative braking force, and the required braking force is smaller than the sum of the front wheel maximum regenerative braking force and the rear wheel maximum regenerative braking force, setting the rear wheel ideal braking force to a rear wheel target regenerative braking force; setting the front wheel maximum regenerative braking force to a front wheel target regenerative braking force; A shortage of the front wheel maximum regenerative braking force relative to the front wheel ideal braking force is set as a target value of the front wheel target hydraulic braking force to be generated by the first hydraulic brake (38a).

3. The vehicle brake device according to claim 2, wherein:

5. The control device (90) When the front wheel ideal braking force is smaller than the front wheel maximum regenerative braking force, the rear wheel ideal braking force is larger than the rear wheel maximum regenerative braking force, and the required braking force is smaller than the sum of the front wheel maximum regenerative braking force and the rear wheel maximum regenerative braking force, setting the rear wheel maximum regenerative braking force to a rear wheel target regenerative braking force; The sum of the shortage of the maximum rear wheel regenerative braking force relative to the ideal rear wheel braking force and the ideal front wheel braking force is set as the target front wheel regenerative braking force.

3. The vehicle brake device according to claim 2, wherein:

6. When the sum of the shortage of the rear wheel maximum regenerative braking force with respect to the rear wheel ideal braking force and the front wheel ideal braking force is larger than the front wheel maximum regenerative braking force, The control device (90) setting the front wheel maximum regenerative braking force to a front wheel target regenerative braking force; The shortage of the maximum front wheel regenerative braking force with respect to the sum is set as the front wheel target hydraulic braking force to be generated by the first hydraulic brake (38a).

6. A vehicle brake device according to claim 5.

7. The control device (90) When terminating the regenerative control, the front / rear distribution at the start of the control to be terminated is stored; During the period until the regenerative control is completed, the regenerative control is executed in accordance with the stored front / rear distribution.

7. A vehicle brake device according to claim 1, wherein:

8. The control device (90) The front wheel target regenerative braking force or the rear wheel target regenerative braking force is set so that the change rate of the front wheel target regenerative braking force and the change rate of the rear wheel target regenerative braking force are equal to or less than a predetermined threshold value.

7. A vehicle brake device according to claim 3, wherein:

9. The control device (90) When it is estimated that the vehicle is in an unstable state, the distribution rate of the braking force generated on the front wheels is increased, When the vehicle is estimated to be in a stable state, the distribution rate of the braking force generated on the front wheels is reduced with the initial value of the front / rear distribution as the lower limit. A vehicle brake device according to any one of claims 1 to 8.

Images