Brake control device and brake control method

Abstract

A brake control device (100) comprises: a first control unit (3) that drives a hydraulic brake for braking a vehicle; a failure detecting unit that detects failure of the first control unit (3); a second control unit (4) that causes a motor responsible for driving the vehicle to function as an electricity generator, and that drives a regenerative brake that applies a braking force by means of resistance; a third control unit (5) that drives an electric parking brake that brakes the vehicle by means of an electric signal; and a target braking amount calculating unit that detects an amount of depression of a brake pedal (11) and calculates a target braking amount. If the failure detecting unit detects a failure of the first control unit (3), the third control unit (5) determines a first instruction for controlling the electric parking brake in accordance with the target braking amount. The second control unit (4) determines a second instruction for controlling the regenerative brake on the basis of the target braking amount and the first instruction.

Description

Brake control device and brake control method

[0001] The present invention relates to a brake control device and a brake control method.

[0002] Hydraulic brakes may become ineffective due to reasons such as vapor lock, in which brake fluid pressure cannot be secured, or brake fade, in which air bubbles are introduced into the brake fluid. When hydraulic brakes are ineffective, the vehicle must be braked using other braking means. For example, Patent Document 1 discloses a technology for braking the vehicle by activating an electric parking brake (EPB) in response to the amount of depression of the brake pedal when a hydraulic brake malfunctions.

[0003] Japanese Patent Application Laid-Open No. 2021-142833

[0004] In the technology disclosed in Patent Document 1, when the brake pedal is depressed, the EPB performs braking by pressing the pads against the brake disc using a motor. However, because the EPB presses the pads against the brake disc via a motor, there is a problem in that controllability is low due to variations in responsiveness and motor performance.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a brake control device and a brake control method that can perform braking with high controllability even when braking cannot be performed with hydraulic brakes.

[0006] To achieve the above object, the brake control device of the present invention includes a first control unit that drives a hydraulic brake that brakes a vehicle, a failure detection unit that detects a failure of the first control unit, a second control unit that causes a motor that drives the vehicle to function as a generator and drives a regenerative brake that applies braking force through resistance, a third control unit that drives an electric parking brake that brakes the vehicle using an electric signal, and a target braking amount calculation unit that detects the amount of depression of the brake pedal and calculates a target braking amount.If the failure detection unit detects a failure of the first control unit, the third control unit determines a first instruction to control the electric parking brake in accordance with the target braking amount.Furthermore, the second control unit determines a second instruction to control the regenerative brake based on the target braking amount and the first instruction.

[0007] According to the present invention, if the first control unit that controls the hydraulic brake fails, the vehicle is braked using the electric parking brake and the regenerative brake, so that braking with high controllability can be performed even when braking cannot be performed using the hydraulic brake.

[0008] 2A to 2C are diagrams illustrating an overview of a brake control device according to a first embodiment of the present invention. FIG. 1 is a diagram illustrating an example configuration of a first control unit of the brake control device shown in FIG. 1. FIG. 2B is a diagram illustrating an example configuration of a second control unit of the brake control device shown in FIG. 1. FIG. 2C is a diagram illustrating an example configuration of a third control unit of the brake control device shown in FIG. 1. FIG. 2C is a diagram illustrating an example configuration of hardware of electronic control units of the first control unit to the third control unit shown in FIGS. 2A to 2C. FIG. 2B is a diagram illustrating an overview of each brake according to the first embodiment. FIG. 2C is a diagram illustrating a relationship between braking forces of each brake according to the first embodiment. FIG. 2D is a diagram illustrating an overview of an EPB actuator according to the first embodiment. FIG. 2D is a diagram illustrating control of braking force when a vehicle is traveling at low speed according to the first embodiment. FIG. 2E is a diagram illustrating control of braking force when a vehicle is traveling at high speed according to the first embodiment. FIG. 2F is a diagram illustrating control of braking force within a specified speed of the vehicle according to the first embodiment. FIG. 2G is a flowchart of vehicle control processing according to the first embodiment. FIG. 2H is a flowchart of failure detection processing according to the first embodiment. FIG. 2H is a flowchart of braking amount determination processing according to the first embodiment. FIG. 2H is a flowchart of battery management processing according to the second embodiment. FIG. 2I is a diagram illustrating an overview of a brake control device according to a third embodiment. FIG. 2I is a diagram illustrating operation of an EPB actuator according to the third embodiment. FIG. 2I is a diagram illustrating change in current flowing in a motor of an electric parking brake according to the third embodiment. 10 is a flowchart of a braking control process according to Embodiment 3. FIG. 11 is a flowchart of a multiple failure detection process according to Embodiment 3. FIG. 12 is a diagram for explaining brake control during pop-in braking according to a modified example.

[0009] A brake control device and a brake control method according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent parts are designated by the same reference numerals.

[0010] (Embodiment 1) A brake control device 100 according to Embodiment 1 of the present invention is a device that controls vehicle braking. FIG. 1 shows an overview of the brake control device 100 according to Embodiment 1. The brake control device 100 includes a first control unit 3, a second control unit 4, and a third control unit 5. The first control unit 3 controls a hydraulic brake that brakes the wheels 2 in accordance with the amount of depression of the foot brake 1. The wheels 2 collectively refer to a left front wheel 21, a left rear wheel 22, a right front wheel 23, and a right rear wheel 24. The left front wheel 21 and the right front wheel 23 are collectively referred to as front wheels. The left rear wheel 22 and the right rear wheel 24 are collectively referred to as rear wheels. The second control unit 4 controls a regenerative brake that applies braking force due to the resistance of a motor 421 caused by the rotation of the front wheels. The third control unit 5 sends an electric signal in accordance with the amount of depression of the foot brake 1 to control an electric parking brake 26 that brakes the wheels 2.

[0011] The configurations of the first control unit 3, the second control unit 4, and the third control unit 5 will be described below with reference to Figures 2A to 2C. Figure 2A is a diagram showing an example configuration of the first control unit 3. The first control unit 3 includes a first electronic control unit (hereinafter referred to as first ECU (Electronic Control)) 31 and a hydraulic circuit unit 32. The first ECU 31 controls the hydraulic circuit unit 32 in accordance with the amount of depression of the foot brake 1.

[0012] The foot brake 1 includes a brake pedal 11 and a brake housing 12. The brake pedal 11 is a pedal that is depressed by a user. The brake housing 12 includes a first stroke sensor 121 and a second stroke sensor 122 that detect the amount of depression of the brake pedal 11.

[0013] The first ECU 31 includes a communication unit 311, a memory unit 312, a failure detection unit 313, a drive circuit unit 314, and a calculation unit 315. The communication unit 311 is connected to the first stroke sensor 121 of the brake housing 12. The communication unit 311 acquires the depression amount of the brake pedal 11 from the first stroke sensor 121. The memory unit 312 stores programs and various data for various controls executed by the first ECU 31. The failure detection unit 313 detects a failure of the first control unit 3. The drive circuit unit 314 drives the hydraulic circuit unit 32 in accordance with the depression amount of the brake pedal 11 acquired by the communication unit 311. The calculation unit 315 executes the programs stored in the memory unit 312 and performs various controls of the first ECU 31.

[0014] The hydraulic circuit unit 32 includes a motor 321, a reservoir 322, a gear 323, and a hydraulic pressure generating unit 324. The motor 321 is driven by instructions from the drive circuit unit 314 of the first ECU 31. The reservoir 322 stores brake fluid for hydraulic braking. The gear 323 transmits the driving force of the motor 321 to the hydraulic pressure generating unit 324. The hydraulic pressure generating unit 324 compresses the brake fluid in the reservoir 322 using the driving force of the motor 321 transmitted via the gear 323, thereby generating hydraulic pressure. The hydraulic pressure is transmitted to a hydraulic circuit unit 52 of the third control unit 5, which will be described later.

[0015] Next, the second control unit 4 will be described. Fig. 2B is a diagram showing an example configuration of the second control unit 4. The second control unit 4 includes a second ECU 41 and a regenerative braking mechanism 42. The second ECU 41 controls the operation of the regenerative braking mechanism 42. The second ECU 41 includes a communication unit 411, a memory unit 412, a failure detection unit 413, a drive circuit unit 414, a vehicle speed detection unit 415, a battery state control unit 416, a power consumption unit 417, and a calculation unit 418.

[0016] The communication unit 411 is connected to the third control unit 5 and acquires from the third control unit 5 a target braking amount required to control the regenerative braking mechanism 42. The memory unit 412 stores programs and various data for various controls executed by the second ECU 41. The failure detection unit 413 detects a failure of the second control unit 4. The drive circuit unit 414 drives the regenerative braking mechanism 42 in accordance with the target braking amount acquired from the third control unit 5 by the communication unit 411.

[0017] The vehicle speed detection unit 415 detects the speed of the vehicle using the speed sensor 6. The battery state control unit 416 checks the charge state of the battery 7. The battery 7 is charged by an external power source and stores power to drive the motor 421. The battery 7 can also store power generated by driving the regenerative braking mechanism 42. The battery state control unit 416 checks the charge state of the battery 7 and thereby calculates the chargeable amount of the battery 7. The power consumption unit 417 consumes the power stored in the battery 7.

[0018] When the charge rate of the battery 7 reaches 100%, the battery 7 cannot store the power generated by driving the regenerative braking mechanism 42. In this case, braking by the regenerative braking mechanism 42 becomes less effective, resulting in regeneration failure. Therefore, a power consumption unit 417 is provided that consumes the power stored in the battery 7. For example, the power consumption unit 417 changes the internal temperature of the vehicle by controlling an air conditioner in accordance with the temperature outside the vehicle detected by the outside air temperature sensor 8. In this way, the power consumption unit 417 can consume the power stored in the battery 7.

[0019] The calculation unit 418 executes the programs stored in the storage unit 412 and performs various controls of the second ECU 41. The regenerative braking mechanism 42 includes a motor 421, a gear 422, and a torque transmission unit 423. The motor 421 rotates using power supplied from the battery 7 or an internal power source of the vehicle, and generates rotational torque to rotate the wheels 2.

[0020] Furthermore, the motor 421 functions as a generator by operating in response to the rotational energy of the wheels 2. When the motor 421 functions as a generator, the rotational resistance increases during power generation. The increased rotational resistance can be used as a braking force for the vehicle. Therefore, the rotational resistance can function as a regenerative brake. The electric power generated by the motor 421 is stored in the battery 7.

[0021] The gear 422 transmits the rotational torque of the motor 421 to the torque transmission unit 423. The torque transmission unit 423 drives the wheels 2 of the vehicle shown in Fig. 1 using the rotational torque of the motor 421 obtained via the gear 422. This causes the vehicle to move.

[0022] Next, the third control unit 5 will be described. Fig. 2C is a diagram showing an example of the configuration of the third control unit 5. The third control unit 5 includes a third ECU 51 and a hydraulic circuit unit 52. The third control unit 5 includes a communication unit 511, a storage unit 512, a target braking amount calculation unit 513, a drive circuit unit 514, an EPB drive circuit 515, and a calculation unit 516. Note that the hydraulic circuit unit 52 may be independent from the third control unit 5, or may be included in the first control unit 3.

[0023] The communication unit 511 is connected to the second stroke sensor 122 of the brake housing 12. The communication unit 511 acquires the depression amount of the brake pedal 11 from the second stroke sensor 122. The storage unit 512 stores programs and various data for various controls executed by the third ECU 51. The target braking amount calculation unit 513 calculates the braking amount for braking the vehicle according to the depression amount of the brake pedal 11 acquired by the communication unit 511.

[0024] The drive circuit unit 514 drives the hydraulic circuit unit 52 to brake the wheels 2 using hydraulic brakes. The EPB drive circuit 515 sends electrical signals to and controls the first EPB 261 arranged on the left rear wheel 22 and the second EPB 262 arranged on the right rear wheel 24 of the wheels 2. This allows the EPB drive circuit 515 to electrically brake each of the left rear wheel 22 and the right rear wheel 24. Therefore, the EPB drive circuit 515 can brake the rear wheels of the vehicle. The calculation unit 516 executes programs stored in the memory unit 512 and performs various controls of the third ECU 51. Note that hereinafter, the first EPB 261 and the second EPB 262 are collectively referred to as EPB 26.

[0025] The hydraulic circuit unit 52 includes a first hydraulic valve 521a, a second hydraulic valve 521b, and a motor 522. Hereinafter, the first hydraulic valve 521a and the second hydraulic valve 521b will be collectively referred to as the hydraulic valve 521. The hydraulic valve 521 is a valve that can be opened and closed. The hydraulic valve 521 opens when there is a difference between the hydraulic pressure on the upstream side and the hydraulic pressure on the downstream side, and closes when there is no difference between the hydraulic pressure on the upstream side and the hydraulic pressure on the downstream side. Therefore, when the hydraulic pressure transmitted from the hydraulic pressure generating unit 324 included in the hydraulic circuit unit 32 of the first control unit 3 shown in FIG. 2A, i.e., the hydraulic pressure on the upstream side is higher than the hydraulic pressure on the downstream side, the hydraulic valve 521 opens to allow brake fluid to flow from the upstream side to the downstream side.

[0026] A first brake disc 251 for braking by brake fluid pressure is disposed on the left front wheel 21 of the wheels 2. The first brake disc 251 includes a first brake pad 251a (not shown). A second brake disc 252 is disposed on the left rear wheel 22. The second brake disc 252 includes a second brake pad 252a (not shown). A third brake disc 253 is disposed on the right front wheel 23. The third brake disc 253 includes a third brake pad 253a (not shown). A fourth brake disc 254 is disposed on the right rear wheel 24. The fourth brake disc 254 includes a fourth brake pad 254a (not shown).

[0027] The motor 522 operates in response to instructions from the drive circuit unit 514 of the third ECU 51. The motor 522 is also connected to the drive circuit unit 414 of the first ECU 31, and may also operate in response to instructions from that unit. When driven, the motor 522 causes the brake fluid that has flowed in via the hydraulic valve 521 to flow out toward the first brake disc 251 to the fourth brake disc 254. This increases the hydraulic pressure of the brake fluid, which presses the first brake disc 251 to the fourth brake disc 254 via the first brake pad 251 a to the fourth brake pad 254 a (not shown). This enables the wheels 2 to be braked.

[0028] The functions of the first ECU 31 of the first control unit 3, the second ECU 41 of the second control unit 4, and the third ECU 51 of the third control unit 5 are realized by executing a program. Fig. 3 is a diagram showing an example of the hardware configuration for executing the program. For example, the first ECU 31 includes a processor 1002, a storage device 1003, a communication interface (referred to as "communication I / F" in the figure) 1004, and a drive circuit device 1005, which are connected to each other via a bus 1001.

[0029] The processor 1002 includes, for example, one or more central processing units (CPUs) and their peripheral circuits, and executes various types of arithmetic processing. The processor 1002 executes various programs stored in the storage device 1003. The processor 1002 may include a volatile semiconductor memory such as a random access memory (RAM) that functions as a working memory for the CPU. The processor 1002 may also include arithmetic circuits such as a logic operation unit and a numerical operation unit.

[0030] The storage device 1003 includes a non-volatile semiconductor memory such as an EEPROM (Electrically Erasable and Programmable Read Only Memory), a flash memory, etc. The storage device 1003 stores various programs executed by the processor 1002 and various data used in the processing of the processor 1002.

[0031] The communication interface 1004 includes an interface circuit for connecting the processor 1002 to an in-vehicle network that complies with standards such as CAN (Controller Area Network). The communication interface 1004 also connects to various sensors, hydraulic circuits, and other ECUs provided in the vehicle to transmit and receive various signals. The communication interface 1004 passes the transmitted and received signals to the processor 1002.

[0032] The drive circuit device 1005 includes a switching element and the like, and supplies power to a motor provided in the vehicle to operate the motor based on a control signal from the processor 1002. Note that the second ECU 41 of the second control unit 4 and the third ECU 51 of the third control unit 5 also have similar hardware configuration examples.

[0033] Next, a vehicle braking method using the brake control device 100 according to the first embodiment will be described. FIG. 4A is a diagram illustrating an overview of each brake according to the first embodiment. Of the vehicle's wheels 2, the left front wheel 21 and the right front wheel 23 are connected by a front-wheel drive shaft 27. Furthermore, the left rear wheel 22 and the right rear wheel 24 of the wheels 2 are connected by a rear-wheel drive shaft 28. A torque transmission unit 423 included in the regenerative brake mechanism 42 of the second control unit 4 is connected to the front-wheel drive shaft 27. The torque transmission unit 423 transmits the rotational torque of the motor 421 to the front-wheel drive shaft 27. This rotational torque rotates the front-wheel drive shaft 27, causing the left front wheel 21 and the right front wheel 23, which are located at both ends of the front-wheel drive shaft 27, to rotate. As the left front wheel 21 and the right front wheel 23 rotate, the left rear wheel 22 and the right rear wheel 24, which are located at both ends of the rear-wheel drive shaft 28, rotate. This causes the vehicle to move. The second control unit 4 may be connected to the rear wheel drive shaft 28 for rear wheel drive.

[0034] Furthermore, when the motor 421 of the regenerative braking mechanism 42 functions as a generator, the braking force due to the rotational resistance during power generation weakens the rotation of the front wheel drive shaft 27. This weakens the rotation of the left front wheel 21 and the right front wheel 23. Therefore, the braking in the regenerative braking mechanism 42 brakes the front wheels of the vehicle.

[0035] A first EPB 261 is disposed on the left rear wheel 22, and a second EPB 262 is disposed on the right rear wheel 24. The EPB drive circuit 515 drives the first EPB 261 and the second EPB 262 to electrically brake the left rear wheel 22 and the right rear wheel 24, respectively. Therefore, the EPB drive circuit 515 can brake the rear wheels of the vehicle.

[0036] When a user depresses the brake pedal 11 shown in Figure 1, the hydraulic circuit unit 32 of the first control unit 3 and the hydraulic circuit unit 52 of the third control unit 5 increase the hydraulic pressure in the first brake disc 251 to the fourth brake disc 254. This causes the wheels 2 to brake. There are cases where the hydraulic brakes are unable to brake the vehicle due to reasons such as vapor lock, in which the brake fluid pressure cannot be secured, or brake fade, in which air bubbles get into the brake fluid due to excessive use of the foot brake 1, such as when going downhill or during sudden acceleration or deceleration. In such cases, the vehicle can be braked by a mechanical backup mechanism that directly links the failed hydraulic brake with the brake pedal 11.

[0037] However, not all vehicles are equipped with a mechanical backup mechanism. For this reason, it is desirable to perform braking by the regenerative brake mechanism 42 or the EPB 26 rather than by a mechanical backup mechanism. Therefore, the vehicle according to the first embodiment is not equipped with a mechanical backup mechanism.

[0038] However, because the regenerative braking mechanism 42 brakes the front wheels of the vehicle, there is a possibility that the rear wheels of the vehicle may skid. Also, because braking by the EPB 26 brakes the rear wheels of the vehicle, there is a possibility that the front wheels of the vehicle may skid. For this reason, if only one of the mechanisms is used, there is a higher possibility that the vehicle will spin out, and the vehicle may not be able to be braked safely.

[0039] Furthermore, the EPB 26 has poor responsiveness and cannot quickly respond to commands from the foot brake 1. Figure 4B is a diagram for explaining the relationship between the response speeds of the braking forces of each brake. In Figure 4B, the vertical axis represents braking force and the horizontal axis represents time. In Figure 4B, the braking force of the foot brake 1 is shown by a dashed line. The braking force of the EPB 26 is shown by a solid line. The braking force of the regenerative brake mechanism 42 is shown by a two-dot chain line. The combined braking force of the EPB 26 and the regenerative brake mechanism 42 is shown by a dashed line.

[0040] First, when the foot brake 1 is depressed by the user, if the foot brake 1 (hydraulic brake) is normal, a braking force as shown by the dashed line is exerted. If the foot brake 1 (hydraulic brake) fails, braking is performed by the regenerative brake mechanism 42 and the EPB 26, and in response to depression, １ The braking force of the regenerative brake mechanism 42 starts to increase at the time t １ Delayed from ２ The braking force of the EPB 26 then starts to increase gradually from the time t ３ The braking force reaches a peak value at time t and then remains constant. As a result, the EPB 26 can exert a braking force as shown by the solid line. This is because when the EPB 26 brakes the wheels 2, it operates the EPB actuator 263 using current.

[0041] 4C is a diagram for explaining an outline of the EPB actuator 263. Here, the explanation will be given taking as an example the first EPB 261 arranged on the left rear wheel 22. As shown in FIG. 1, the left rear wheel 22 is provided with a second brake disc 252 including a second brake pad 252a.

[0042] 4C includes a motor 2631, a gear 2632, a piston bearing 2633a, and a piston shaft 2633b. The piston bearing 2633a and the piston shaft 2633b are hereinafter collectively referred to as the piston 2633.

[0043] Before braking, the piston 2633 is located at position L1, which is the end opposite the motor 2631. The second brake pad 252a is located at position L2. When current flows through the motor 2631, it rotates and generates rotational torque. The piston shaft 2633b is configured integrally with the gear 2632, for example, as a screw-type worm gear. Therefore, the rotational torque of the motor 2631 is transmitted to the piston 2633 via the gear 2632. The piston 2633 pushes out the piston bearing 2633a due to the kinetic energy of the rotational torque. The piston bearing 2633a moves from position L1 toward position L2. The piston bearing 2633a pushes the second brake pad 252a. The second brake pad 252a moves from position L2 toward the second brake disc 252. The second brake pad 252a is then pressed against the second brake disc 252. This brakes the wheel 2.

[0044] When the current flowing through the motor 2631 is constant, the generated rotational torque is constant. Therefore, the force with which the piston bearing 2633a presses the second brake pad 252a against the second brake disc 252 is constant. Therefore, a constant braking force can be applied to the second brake disc 252. Therefore, in the first embodiment, the poor responsiveness of the EPB 26 is compensated for by the braking force of the regenerative brake mechanism 42. This can substantially increase the braking force of the EPB 26.

[0045] In the first embodiment, the braking force of the EPB 26 and the braking force of the regenerative brake mechanism 42 are determined under the conditions shown in FIGS. 5 to 7. First, FIG. 5 is a diagram for explaining the control of the braking force when the vehicle is traveling at a low speed. For example, when the speed of the vehicle when traveling (hereinafter referred to as the vehicle speed) is 10 km / h or less, even if the vehicle is braked by the EPB 26, the vehicle speed is low, so vehicle deflection, such as skidding of the front wheels, is unlikely to occur. For this reason, it is desirable to brake the vehicle more reliably by mechanically braking the vehicle by the EPB 26.

[0046] Therefore, in Figure 5, the braking force of the EPB 26 is set to a first braking force as shown by the solid line in Figure 5 until the vehicle speed reaches a first speed. When the vehicle speed falls below the first speed, the braking force of the EPB 26 becomes a second braking force that is greater than the first braking force. Conversely, the braking force of the regenerative brake is the second braking force as shown by the two-dot chain line in Figure 5 until the vehicle speed falls below the first speed. When the vehicle speed falls below the first speed, the braking force of the regenerative brake becomes a first braking force that is smaller than the second braking force.

[0047] Next, FIG. 6 is a diagram for explaining the control of braking force when the vehicle is traveling at high speed. As the vehicle speed increases, the braking force of the regenerative brake decreases. For example, when the vehicle speed is high at 80 km / h, it is desirable to brake more reliably by mechanically applying the brake using the EPB 26 in this vehicle speed range.

[0048] Therefore, in Figure 6, the braking force of the EPB 26 is set to a second braking force that is greater than the first braking force until the vehicle speed reaches a second speed, as shown by the solid line in Figure 6. The second speed is set to be higher than the first speed shown in Figure 5. When the vehicle speed falls below the second speed, the braking force of the EPB 26 becomes a first braking force that is smaller than the second braking force. Conversely, the braking force of the regenerative brake is the first braking force until the second speed, as shown by the two-dot chain line in Figure 6. When the vehicle speed falls below the second speed, the braking force of the regenerative brake becomes a second braking force that is greater than the first braking force. Note that the first and second braking forces in Figure 5 may be different from the first and second braking forces in Figure 6.

[0049] FIG. 7 is a diagram illustrating the control of braking force within a specified vehicle speed. For example, a speed of 10 to 80 km / h is a vehicle speed commonly used on public roads. Furthermore, the weight of the front wheels of a vehicle is greater than that of the rear wheels. Therefore, when the vehicle speed is between 10 and 80 km / h, the braking force on the front wheels, which have a greater weight, is controlled to be greater than that on the rear wheels. That is, when the vehicle speed is between 10 and 80 km / h, the braking force of the regenerative brake that brakes the front wheels is made greater than the braking force of the EPB 26 that brakes the rear wheels. This stabilizes the braking of the vehicle. In the following description, the first speed of the vehicle is assumed to be 10 km / h and the second speed is assumed to be 80 km / h.

[0050] 7 , first, when the vehicle speed is equal to or less than a first speed, the vehicle is braked by the braking force of the EPB 26, as shown by the solid line in FIG. 7 . When the vehicle speed exceeds the first speed, the braking force of the EPB 26 is controlled to be smaller than the braking force when the vehicle speed is equal to or less than the first speed. The braking force of the regenerative brake is controlled to be larger than the braking force of the EPB 26, as shown by the two-dot chain line in FIG. 7 . Thereafter, when the vehicle speed exceeds a second speed, the braking force of the regenerative brake mechanism 42 is controlled to be smaller than the braking force of the EPB 26. Conversely, the braking force of the EPB 26 is controlled to be larger than the braking force of the regenerative brake mechanism 42.

[0051] Furthermore, instead of the second speed, a third speed higher than the second speed can be used. For example, if the second speed is 80 km / h, the third speed is 100 km / h. In this case, when the vehicle speed is equal to or lower than the first speed, the vehicle is braked by the braking force of the EPB 26. When the vehicle speed exceeds the first speed, the braking force of the EPB 26 becomes smaller than the braking force when the vehicle speed is equal to or lower than the first speed. The braking force of the regenerative braking mechanism 42 becomes greater than the braking force of the EPB 26. Thereafter, when the third speed is exceeded, the braking force of the regenerative braking mechanism 42 becomes smaller than the braking force of the EPB 26. Conversely, the braking force of the EPB 26 becomes greater than the braking force of the regenerative braking mechanism 42.

[0052] Next, a description will be given of the braking control processing executed by the brake control device 100. When the vehicle engine is started, the brake control device 100 activates a braking control processing program stored in the storage device 1003 by the processor 1002 of the first ECU 31 of the first control unit 3 shown in Fig. 3. Similarly, the second ECU 41 of the second control unit 4 and the third ECU 51 of the third control unit 5 each activate a braking control processing program stored in the storage device 1003 by the processor 1002.

[0053] That is, the first control unit 3 to the third control unit 5 cooperate to execute the braking control process, but any one of the control units may execute the process. Also, there may be a control unit that manages the first control unit 3 to the third control unit 5. Also, the first control unit 3 to the third control unit 5 may be a single microcomputer (physically a single unit, functionally separate). In any case, it is sufficient that the brake control device 100 executes the process.

[0054] The processing flow of the braking control processing program will be described below with reference to the flowchart of FIG.

[0055] The calculation unit 516 included in the third ECU 51 of the third control unit 5 determines whether the foot brake 1 has been operated (step S101). Specifically, the calculation unit 516 determines whether the amount of depression of the brake pedal 11 has been acquired from the second stroke sensor 122 of the brake housing 12 via the communication unit 511. If the foot brake 1 has not been operated (step S101; NO), the calculation unit 516 repeats step S101. If the foot brake 1 has been operated (step S101; YES), the calculation unit 516 executes a fault detection process (step S102). The fault detection process will be described below with reference to the flowchart shown in FIG. 9 .

[0056] The failure detection unit 313 included in the first ECU 31 of the first control unit 3 reads from the memory unit 312 the output of the calculation unit 315 to the drive circuit unit 314, which is stored in the memory unit 312 (step S201). The failure detection unit 313 reads the output from the drive circuit unit 314 to the hydraulic circuit unit 32 (step S202). The failure detection unit 313 determines whether the output of the calculation unit 315 read in step S201 and the output of the drive circuit unit 314 read in step S202 are equal (step S203). If the first control unit 3 is normal, the two are equal. Therefore, by determining whether the two are equal, it is possible to determine whether the first control unit 3 is abnormal.

[0057] If the two are equal (step S203; YES), the failure detection unit 313 determines that the drive circuit unit 314 is normal (step S204). If the two are not equal (step S203; NO), the failure detection unit 313 determines that the drive circuit unit 314 is abnormal (step S205). The failure detection unit 313 ends the failure detection process. Note that the failure detection process is not limited to this. Failures may also be detected by various sensors, or by comparing speed data with the operation history of the accelerator and brake pedals 11.

[0058] Returning now to FIG. 8 , the calculation unit 516 included in the third ECU 51 of the third control unit 5 determines whether the first control unit 3 has failed (step S103). Specifically, the calculation unit 516 determines whether the drive circuit unit 314 has been determined to be normal in the failure detection process of step S102. If the drive circuit unit 314 has been determined to be normal in the failure detection process, the calculation unit 516 determines that the first control unit 3 has not failed (step S103; NO). The calculation unit 516 performs normal braking (step S104). Normal braking is, for example, braking using a hydraulic brake. The calculation unit 516 performs braking using the hydraulic brake by having the drive circuit unit 514 drive the motor 522 of the hydraulic circuit unit 52.

[0059] Furthermore, if the drive circuit unit 314 is determined to be abnormal in the failure detection process of step S102, the calculation unit 516 determines that the first control unit 3 is faulty (step S103; YES). The calculation unit 516 then executes a braking amount determination process (step S105). The braking amount determination process will be described below with reference to the flowchart shown in FIG.

[0060] The target braking amount calculation unit 513 included in the third ECU 51 of the third control unit 5 calculates a target braking amount for braking the vehicle (step S301). Specifically, the target braking amount calculation unit 513 calculates the target braking amount based on conditions such as the depression amount of the brake pedal 11 and the vehicle speed acquired by the communication unit 511. The calculation unit 516 of the third ECU 51 determines a first instruction for controlling the EPB 26 based on the target braking amount (step S302). The first instruction indicates the braking amount of the EPB 26. The first instruction is determined based on the vehicle speed. For example, the first instruction is determined so that the braking amount of the EPB 26 is stronger than that of the regenerative brake mechanism 42 at a first speed less than 10 km / h and a second speed equal to or greater than 80 km / h. Furthermore, the first instruction is determined so that the braking amount of the EPB 26 is weaker than that of the regenerative brake mechanism 42 at a second speed (10 to 80 km / h). The calculation unit 516 controls the EPB 26 to generate the braking amount of the first command.

[0061] The calculation unit 516 determines whether the target braking amount is equal to the first command (step S303). If they are equal (step S303; YES), braking is possible using only the EPB 26, and the calculation unit 516 ends the braking amount determination process. If they are not equal (step S303; NO), the calculation unit 516 transmits the target braking amount and the first command to the second ECU 41 of the second control unit 4. The communication unit 411 of the second ECU 41 receives the target braking amount from the calculation unit 516.

[0062] The vehicle speed detection unit 415 of the second ECU 41 detects the vehicle speed using the speed sensor 6 (step S304). The calculation unit 418 of the second ECU 41 determines whether the detected vehicle speed is faster than a second speed or a third speed (step S305). For example, the second speed is 80 km / h, and the third speed is 100 km / h, which is faster than the second speed. If the detected vehicle speed is faster than the second speed or the third speed (step S305; YES), the calculation unit 418 determines a second instruction indicating a braking amount smaller than the first instruction (step S306). The second instruction is a braking amount for controlling the regenerative brake mechanism 42. The calculation unit 418 determines the second instruction based on the target braking amount and the first instruction for controlling the EPB 26.

[0063] Furthermore, in step S305, if the detected vehicle speed is slower than the second speed and the third speed (step S305; NO), the calculation unit 418 determines whether the detected vehicle speed is faster than the first speed (step S307). The first speed is set to a speed lower than the second speed or the third speed, for example, a speed low enough that braking by the EPB 26 is easy (less likely to cause a spin), or a speed range where regenerative braking is less effective. For example, if the second speed is 80 km / h and the third speed is 100 km / h, which is faster than the second speed, the first speed is set to 10 km / h.

[0064] If the detected vehicle speed is faster than the first speed (step S307; YES), the calculation unit 418 determines a second command that is greater than the first command (step S308). If the detected vehicle speed is slower than the first speed (step S307; NO), the calculation unit 418 determines a second command that is smaller than the first command (step S309). The calculation unit 418 then ends the braking amount determination process.

[0065] Returning to FIG. 8 , the third control unit 5 and the second control unit 4 brake the vehicle (step S106). Specifically, the EPB drive circuit 515 included in the third ECU 51 of the third control unit 5 drives the EPB 26 in accordance with the first instruction determined in the braking amount determination process to brake the rear wheels of the vehicle. The drive circuit unit 414 included in the second ECU 41 of the second control unit 4 drives the regenerative brake mechanism 42 in accordance with the second instruction determined in the braking amount determination process to brake the front wheels of the vehicle.

[0066] The calculation unit 418 included in the second ECU 41 of the second control unit 4 determines whether the vehicle has stopped (step S107). For example, the calculation unit 418 detects the vehicle speed from the speed sensor 6. If the detected vehicle speed is 0 km / h, the calculation unit 418 determines that the vehicle has stopped (step S107; YES). The calculation unit 418 ends the braking control process.

[0067] Furthermore, if the vehicle speed detected by the speed sensor 6 is not 0 km / h, the calculation unit 418 determines that the vehicle is not stopped (step S107; NO). The calculation unit 418 returns to step S105, executes the subsequent steps, and continues controlling the braking of the vehicle.

[0068] As described above, in the brake control device 100 according to the first embodiment, if the first control unit 3 that controls the hydraulic brakes fails, the vehicle can be braked by the EPB 26 and the regenerative brake mechanism 42. Therefore, even if braking cannot be performed by the hydraulic brakes, the vehicle can be braked with good controllability.

[0069] In the first embodiment, when the first control unit 3 that controls the hydraulic brake fails, the vehicle is braked by the EPB 26 and the regenerative braking mechanism 42. The regenerative braking mechanism 42 generates braking force by operating as a generator. The electric power generated by the regenerative braking mechanism 42 is stored in the battery 7.

[0070] If the charge rate of the battery 7 reaches 100%, the battery 7 cannot store the electric power generated by driving the regenerative braking mechanism 42. In this case, braking by the regenerative braking mechanism 42 becomes less effective, resulting in regeneration failure. Therefore, in the second embodiment, the electric power consumption unit 417 included in the second ECU 41 of the second control unit 4 periodically consumes the electric power stored in the battery 7. For example, the electric power consumption unit 417 operates the air conditioning of the vehicle driven by the electric power of the battery 7. This uses the electric power stored in the battery 7, thereby ensuring that the chargeable capacity is equal to or greater than a predetermined value.

[0071] The battery management processing executed by the power consumption unit 417 will be described below. After starting the vehicle engine, the brake control device 100 starts a battery management processing program stored in the storage device 1003 by the processor 1002 of the second ECU 41 of the second control unit 4 shown in Figure 3. The processing flow of the battery management processing program will be described below with reference to the flowchart shown in Figure 11.

[0072] The battery state control unit 416 included in the second ECU 41 of the second control unit 4 acquires the amount of stored power of the battery 7 (step S401). The power consumption unit 417 determines whether the chargeable amount of the battery 7 is equal to or less than a predetermined specified amount (step S402). In other words, the power consumption unit 417 determines whether the charging rate of the battery 7 is equal to or greater than a predetermined value. If the chargeable amount of the battery 7 exceeds the predetermined specified amount (step S402; NO), the power consumption unit 417 ends the battery management process.

[0073] If the chargeable amount of the battery 7 is equal to or less than a predetermined specified amount (step S402; YES), the power consumption unit 417 consumes the power of the battery 7. For example, by opening the window and turning the air conditioner to maximum volume and directing the air outward, the power of the battery 7 can be effectively discharged. This also prevents the driver and passengers in the vehicle from being exposed to the air.

[0074] The power consumption unit 417 reads the outside air temperature of the vehicle using the outside air temperature sensor 8 (step S403). The power consumption unit 417 sets the air conditioning set temperature according to the outside air temperature read by the outside air temperature sensor 8. For example, the power consumption unit 417 first determines whether to heat or cool based on the outside air temperature. The power consumption unit 417 calculates the absolute value of the outside air temperature. When the air conditioning is for heating, the power consumption unit 417 sets the air conditioning set temperature to a temperature higher than the outside air temperature. When the air conditioning is for cooling, the power consumption unit 417 sets the air conditioning set temperature to a temperature lower than the outside air temperature. The power consumption unit 417 also sets the air volume of the vehicle's air conditioning to maximum (step S404).

[0075] The power consumption unit 417 opens all windows attached to the vehicle doors (step S405). The power consumption unit 417 changes the air conditioning direction toward the windows (step S406). This makes it difficult for the temperature inside the vehicle to reach the air conditioning set temperature. The power consumption unit 417 performs air conditioning so that the temperature inside the vehicle becomes the air conditioning set temperature (step S407). This makes it possible for the user to recognize that it is difficult to perform braking by the regenerative brake mechanism 42 and that a dangerous situation exists.

[0076] The power consumption unit 417 determines whether the chargeable amount of the battery 7 has exceeded a predetermined specified amount (step S408). If the chargeable amount of the battery 7 has not exceeded the predetermined specified amount (step S408; NO), the power consumption unit 417 repeats step S407. This causes the power of the battery 7 to be discharged. This allows the power of the battery 7 to continue to be consumed to the maximum extent possible.

[0077] If the chargeable amount of the battery 7 exceeds a predetermined amount (step S408; YES), the power consumption unit 417 restores the air conditioning temperature setting, air volume, and air direction to their previous settings (step S409).The power consumption unit 417 then closes the door window (step S410).The power consumption unit 417 then ends the battery management process.

[0078] As described above, in addition to the effects of the first embodiment, the brake control device 100 causes the power consumption unit 417 of the second control unit 4 to consume power from the battery 7 when the chargeable amount of the battery 7 is equal to or less than a predetermined specified value. This allows the battery 7 to maintain a chargeable amount equal to or greater than the specified value.

[0079] (Embodiment 3) In the above-described embodiments 1 and 2, the brake control device 100 is described as including one first control unit 3. However, this is not limited to this, and there may be multiple first control units 3. FIG. 12 is a diagram showing an overview of a brake control device 100A including multiple first control units 3A, 3B. Each of the multiple first control units 3A, 3B has a configuration similar to that of the first control unit 3 shown in FIG. 2A. Furthermore, each of the multiple first control units 3A, 3B has a hardware configuration similar to that of the first ECU 31 of the first control unit 3 shown in FIG. 3. The multiple first control units 3A, 3B are connected to the first stroke sensor 121 of the brake housing 12 and the third control unit 5. Hereinafter, the multiple first control units 3A, 3B will be collectively referred to as multiple first control units 3′.

[0080] If any one of the first control units 3′ has a defect, the hydraulic brake becomes unusable. If the vehicle speed is too high, it becomes difficult to brake the vehicle. Therefore, in order to stabilize the braking performance of the vehicle, the vehicle speed is reduced to a predetermined speed or less. For example, the vehicle speed is reduced to a second speed or a third speed or less as shown in FIG. 7 .

[0081] Furthermore, if a defect occurs in one of the multiple first control units 3', the EPB 26 and the regenerative braking mechanism 42 brake the vehicle. However, as described in the first embodiment, the EPB 26 has poor applicability. Therefore, in the third embodiment, it is desirable to move the piston 2633 included in the EPB actuator 263 of the EPB 26 to a position closer to the second brake pad 252a. This can compensate for the poor applicability of the EPB 26.

[0082] For example, Figure 13A is a diagram for explaining the operation of the EPB actuator 263. The piston 2633 of the EPB actuator 263 is located at position L1 before braking. Here, the explanation will be given taking as an example the first EPB 261 located on the left rear wheel 22. As shown in Figure 1, the second brake disc 252 including the second brake pad 252a is located on the left rear wheel 22.

[0083] The second brake pad 252a is disposed at position L2. When a current is applied to the motor 2631, the motor 2631 rotates and generates a rotational torque. The rotational torque is transmitted to the piston 2633 via the gear 2632. The piston 2633 pushes out the piston bearing 2633a due to the kinetic energy of the rotational torque. The piston bearing 2633a moves from position L1 toward position L2.

[0084] If a defect occurs in one of the multiple first control units 3', the current flowing through the motor 2631 is not a constant current, but a current whose value increases in steps over time. For example, as shown in Fig. 13B, the current flowing through the motor 2631 of the EPB 26 changes in steps over time from threshold value Ta to threshold value Tb. Threshold value Ta is the current value when the EPB 26 has no play. Threshold value Tb is a value greater than threshold value Ta.

[0085] When one of the first control units 3′ is defective, the piston bearing 2633a approaches the second brake pad 252a in accordance with the current flowing through the motor 2631 of the EPB 26. For example, in Fig. 13A, the piston bearing 2633a is in contact with the second brake pad 252a. When braking the vehicle by the EPB 26 in this state, the piston bearing 2633a is in contact with the second brake pad 252a, resulting in better responsiveness than when they are not in contact.

[0086] Next, the braking control processing executed by the brake control device 100A will be described. When the vehicle engine is started, the brake control device 100A activates a braking control processing program stored in the storage device 1003 by the processors 1002 of the first ECUs 31A and 31B of the plurality of first control units 3'. Similarly, the second ECU 41 of the second control unit 4 and the third ECU 51 of the third control unit 5 each activate a braking control processing program stored in the storage device 1003 by the processors 1002. The processing flow of the braking control processing program will be described below with reference to the flowchart of FIG. 14.

[0087] The calculation unit 516 included in the third ECU 51 of the third control unit 5 determines whether the foot brake 1 has been operated (step S501). Specifically, the calculation unit 516 determines whether the communication unit 511 of the third ECU 51 has acquired the depression amount of the brake pedal 11 from the second stroke sensor 122 of the brake housing 12. If the foot brake 1 has not been operated (step S501; NO), the calculation unit 516 repeats step S501. If the foot brake 1 has been operated (step S501; YES), the calculation unit 516 executes multiple fault detection processing (step S502). The multiple fault detection processing will be described below with reference to the flowchart shown in FIG. 15 .

[0088] The failure detection unit 313 included in the first ECU 31A of the first control unit 3A among the multiple first control units 3′ reads from the storage unit 312 the output of the calculation unit 315 to the drive circuit unit 314, which is stored in the storage unit 312 (step S601). The failure detection unit 313 reads the output from the drive circuit unit 314 to the hydraulic circuit unit 32 (step S602). The failure detection unit 313 determines whether the output of the calculation unit 315 read in step S601 and the output of the drive circuit unit 314 read in step S602 are equal to each other (step S603).

[0089] If the two are equal (step S603; YES), the failure detection unit 313 determines that the drive circuit unit 314 is normal (step S604). The failure detection unit 313 determines whether or not a failure has been determined for all of the multiple first control units 3' (step S605). If a failure has been determined for all of the multiple first control units 3' (step S605; YES), the failure detection unit 313 ends the failure detection process. If a failure has not been determined for all of the multiple first control units 3' (step S605; NO), the failure detection unit 313 returns to step S601. The failure detection unit 313 performs failure determination for the remaining first control units 3B.

[0090] If the two are not equal in step S603 (step S603; NO), the failure detection unit 313 determines that the drive circuit unit 314 is abnormal (step S606). The failure detection unit 313 ends the failure detection process.

[0091] Returning now to FIG. 14 , the calculation unit 516 included in the third ECU 51 of the third control unit 5 determines whether any of the multiple first control units 3′ has failed (step S503). Specifically, the calculation unit 516 determines whether the drive circuit unit 314 is determined to be normal in the multiple failure detection process of step S502. If the drive circuit unit 314 is determined to be normal in the multiple failure detection process, the calculation unit 516 determines that none of the multiple first control units 3′ has failed (step S503; NO). The calculation unit 516 performs normal braking (step S504). Normal braking is, for example, braking using a hydraulic brake. The calculation unit 516 performs braking using the hydraulic brake by having the drive circuit unit 514 drive the motor 522 of the hydraulic circuit unit 52.

[0092] Furthermore, if the drive circuit unit 314 is determined to be abnormal in the multiple failure detection process of step S502, the calculation unit 516 determines that one of the multiple first control units 3' has a failure (step S503; YES). The vehicle speed detection unit 415 included in the second ECU 41 of the second control unit 4 detects the vehicle speed using the speed sensor 6 (step S505). The calculation unit 418 of the second ECU 41 determines whether the vehicle speed is equal to or greater than a third speed (step S506). The third speed is, for example, 100 km / h. If the vehicle speed is equal to or greater than the third speed (step S506; YES), the calculation unit 418 causes the drive circuit unit 414 of the second ECU 41 to operate the regenerative braking mechanism 42 as a regenerative brake. As a result, the calculation unit 418 changes the vehicle speed to be slower than the third speed (step S507).

[0093] If the vehicle speed is slower than the third speed (step S506; NO), the calculation unit 418 proceeds to step S508. The calculation unit 516 included in the third ECU 51 of the third control unit 5 executes a braking amount determination process (step S508). The braking amount determination process will be described below with reference to the flowchart shown in FIG. 10.

[0094] The target braking amount calculation unit 513 included in the third ECU 51 of the third control unit 5 calculates a target braking amount for braking the vehicle (step S301). Specifically, the target braking amount calculation unit 513 calculates the target braking amount based on conditions such as the depression amount of the brake pedal 11 and the vehicle speed acquired by the communication unit 511.

[0095] The calculation unit 516 of the third ECU 51 determines a first instruction for controlling the EPB 26 (step S302). In the third embodiment, the current supplied to the motor 2631 shown in FIG. 13A is increased in a stepwise manner. As a result, the piston bearing 2633a of the EPB actuator 263 approaches the second brake pad 252a, as shown in FIG. 13A. Therefore, the calculation unit 516 sets, as the first instruction for controlling the EPB 26, a current value that is increased in a stepwise manner to be supplied to the motor 2631.

[0096] The calculation unit 516 calculates the braking amount based on the first instruction. The calculation unit 516 determines whether the target braking amount is equal to the first instruction (step S303). If they are equal (step S303; YES), the calculation unit 516 ends the braking amount determination process. If they are not equal (step S303; NO), the calculation unit 516 transmits the target braking amount to the second ECU 41 of the second control unit 4. The communication unit 411 of the second ECU 41 receives the target braking amount from the calculation unit 516.

[0097] Steps S304 to S309 are the same as steps S304 to S309 in the flowchart shown in Figure 10. When the braking amount determination process is completed, the process returns to Figure 14. Steps S509 and S510 in Figure 14 are the same as steps S106 and S107 in the flowchart shown in Figure 8. When the calculation unit 418 determines that the vehicle has stopped (step S510; YES), it ends the braking control process.

[0098] As described above, in addition to the effects of embodiments 1 and 2, this embodiment 3 can brake the vehicle using the EPB 26 and the regenerative braking mechanism 42 even if one of the multiple first control units 3' fails.

[0099] (Modification) In the above-described first to third embodiments, the poor responsiveness of the EPB 26 is compensated for by the braking force of the regenerative brake mechanism 42. However, because the braking force of the EPB 26 is strong, there is a possibility that the rear wheels will lock when braking. If the rear wheels lock, the vehicle may slip, which is extremely dangerous. Therefore, when the vehicle speed is equal to or greater than a certain value (e.g., a first speed), the braking force of the EPB 26 can be controlled to periodically increase and decrease, thereby preventing the rear wheels from locking (popping braking).

[0100] Figure 16 is a diagram illustrating brake control during pop-and-play braking when the hydraulic brake fails. In Figure 16, the braking force of the foot brake 1 is shown by a dashed line. The braking force of the EPB 26 is shown by a solid line. The braking force of the regenerative brake mechanism 42 is shown by a two-dot chain line. The combined braking force of the EPB 26 and the regenerative brake mechanism 42 is shown by a dashed line.

[0101] The braking force of the EPB 26, indicated by a solid line, increases in accordance with the braking force (depression amount) of the foot brake 1, indicated by a dashed line. １ The braking force of the EPB 26 stops increasing and decays at the time t ２ The braking force is then attenuated until time t ３ At time t, the braking force of the EPB 26 increases. ４ After that, the braking force of the EPB 26 repeatedly increases and decreases periodically.

[0102] However, if the braking force of the EPB 26 repeatedly increases and decreases periodically, the user in the vehicle may feel uncomfortable with the braking. Therefore, the braking force of the regenerative brake mechanism 42 is used to perform braking so as to compensate for the popping braking of the EPB 26.

[0103] As shown in FIG. 16, the braking force of the regenerative brake mechanism 42 increases in accordance with the braking force (depression amount) of the foot brake 1. The braking force of the regenerative brake mechanism 42 increases from t １ The braking force of the EPB 26 further increases at time t ２The braking force of the EPB 26 is increased until the time t ３ At time t, the braking force of the regenerative brake mechanism 42 is attenuated. ４ At time point , the braking force of the regenerative braking mechanism 42 increases. After that, the braking force of the regenerative braking mechanism 42 periodically repeats an increase and a decrease.

[0104] Therefore, the timing of increase and decrease of the braking force of the EPB 26 and the regenerative braking mechanism 42 are opposite. Therefore, when the braking forces of the EPB 26 and the regenerative braking mechanism 42 are combined, the braking force changes smoothly, as shown by the dashed line in the graph of FIG. 16. This reduces the risk that the user riding in the vehicle will feel uncomfortable with the braking. In addition, it is possible to prevent the rear wheels from locking due to the braking force of the EPB 26.

[0105] The control of the third embodiment (vehicle speed limit, piston position, step-like current) may be performed by a single first control unit 3 in the event of a failure.

[0106] In the third embodiment, when the vehicle speed is equal to or greater than the third speed, the vehicle speed is set to be slower than the third speed. However, the present invention is not limited to this, and when the vehicle speed is equal to or greater than the second speed, which is slower than the third speed, the vehicle speed may be set to be slower than the second speed.

[0107] Furthermore, the hardware configurations and flowcharts shown in the above-described first to third embodiments are merely examples and can be modified or applied as desired. Furthermore, in the above-described first to third embodiments, examples have been described in which the processor 1002 executes various programs to realize each function, but the brake control device 100 may also be configured with dedicated hardware that realizes each function. Furthermore, the first to third embodiments can be combined as desired, and each configuration can be replaced, added, or omitted (particularly, the dependent claim configuration can be omitted).

[0108] Furthermore, the brake control device 100 may be configured to realize each function by storing and distributing various programs for executing the operations of the above-described first to third embodiments on a computer-readable recording medium such as a CD-ROM (Compact Disc Read-Only Memory), a DVD (Digital Versatile Disc), an MO (Magneto Optical Disc), or a memory card, and installing the programs on a computer. When each function is realized by sharing the work between an OS (Operating System) and an application, or by cooperation between the OS and an application, only the parts other than the OS may be stored on the recording medium.

[0109] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. In other words, the scope of the present invention is defined by the claims, not by the embodiments. Various modifications made within the scope of the claims and the meaning of the disclosure equivalent thereto are considered to be within the scope of the present invention.

[0110] The present invention can be suitably used in a brake control device.

[0111] L1, L2 position, Ta, Tb threshold value, 1 foot brake, 2 wheels, 3, 3A, 3B first control unit, 3' plural first control units, 4 second control unit, 5, 51 third control unit, 6 speed sensor, 7 battery, 8 outside air temperature sensor, 11 brake pedal, 12 brake housing, 21 left front wheel, 22 left rear wheel, 23 right front wheel, 24 right rear wheel, 26 EPB (electric parking brake), 27 front wheel drive shaft, 28 rear wheel drive shaft, 31, 31A first ECU (electronic control unit), 32, 52 hydraulic circuit unit, 41 second ECU, 42 regenerative brake mechanism, 51 third ECU, 100, 100A brake control device, 121 first stroke sensor, 122 second stroke sensor, 251 first brake disc, 251a first brake pad, 252 second brake disc, 252a Second brake pad, 253 Third brake disc, 253a Third brake pad, 254 Fourth brake disc, 254a Fourth brake pad, 261 First EPB, 262 Second EPB, 263 EPB actuator, 311, 411, 511 Communication unit, 312, 412, 512 Memory unit, 313, 413 Failure detection unit, 314, 414, 514 Drive circuit unit, 315, 418, 516 Calculation unit, 321, 421, 522, 2631 Motor, 322 Reservoir, 323, 422, 2632 Gear, 324 Hydraulic pressure generation unit, 415 Vehicle speed detection unit, 416 Battery state control unit, 417 Power consumption unit, 423 Torque transmission unit, 513 Target braking amount calculation unit, 515 EPB drive circuit, 521 Hydraulic valve, 521a first hydraulic valve, 521b second hydraulic valve, 1001 bus, 1002 processor, 1003 storage device, 1004 communication interface, 2633 piston, 2633a piston bearing, 2633b piston shaft.

Claims

1. A brake control device comprising: a first control unit that drives a hydraulic brake that brakes a vehicle; a failure detection unit that detects a failure of the first control unit; a second control unit that causes a motor that drives the vehicle to function as a generator and drives a regenerative brake that applies braking force through resistance; a third control unit that drives an electric parking brake that brakes the vehicle using an electric signal; and a target braking amount calculation unit that detects the amount of depression of the brake pedal and calculates a target braking amount, wherein when the failure detection unit detects a failure of the first control unit, the third control unit determines a first instruction to control the electric parking brake in accordance with the target braking amount, and the second control unit determines a second instruction to control the regenerative brake based on the target braking amount and the first instruction.

2. The brake control device according to claim 1, which does not have a mechanism that directly links the hydraulic brake with the brake pedal.

3. A brake control device as described in claim 1 or 2, further comprising a vehicle speed detection unit that detects vehicle speed, and when the vehicle speed detected by the vehicle speed detection unit is lower than a first speed, the braking amount of the electric parking brake is made greater than the braking amount of the regenerative brake.

4. The brake control device according to claim 3, wherein when the vehicle speed detected by the vehicle speed detection unit is greater than a second speed that is greater than the first speed, the braking amount of the electric parking brake is made greater than the braking amount of the regenerative brake.

5. A brake control device as described in claim 3, comprising a plurality of the first control units, and limiting the vehicle speed to a third speed or less when the failure detection unit detects that at least one of the plurality of first control units has failed.

6. The brake control device according to claim 5, wherein when the vehicle speed is between a first speed and a second speed, or between the first speed and a third speed, the braking amount of the regenerative brake is made larger than the braking amount of the electric parking brake.

7. The brake control device according to claim 1, wherein the electric parking brake includes a motor for driving the electric parking brake, and the third control unit determines the first instruction to increase the current supplied to the motor in a stepwise manner.

8. A brake control device as described in any one of claims 1 to 7, comprising a plurality of the first control units, and further comprising a battery status control unit that controls the status of the battery, wherein the battery status control unit controls the chargeable amount of the battery to a specified value or more so as to enable the regenerative brake to be operated when the failure detection unit detects that at least one of the plurality of first control units has failed.

9. A brake control device as described in claim 8, further comprising a power consumption unit that consumes power from the battery in order to control the chargeable amount of the battery to a specified value or more, wherein when the failure detection unit detects that at least one of the plurality of first control units has failed and when the battery status control unit determines that the chargeable amount of the battery is below a specified value, the power consumption unit sets the air conditioning set temperature and maximum airflow in the air conditioner based on the outside air temperature read by an outside air temperature sensor, and fully opens the windows of all doors.

10. The brake control device according to claim 9, wherein the power consumption unit directs the airflow direction of the air conditioner toward the window.

11. A brake control method executed by a brake control device, which, when a failure is detected in a first control unit that drives a hydraulic brake that brakes a vehicle, determines a first instruction to control an electric parking brake in accordance with a target braking amount, and determines a second instruction to control a regenerative brake based on the target braking amount and the first instruction.

Images