Brake control system

Abstract

To suppress the shock when switching between regenerative braking torque and friction braking torque in a vehicle that uses a motor generator as a drive source.SOLUTION: A brake control device includes: a detection unit which detects that a request value of a first braking torque generated by regenerative power generation has changed to a value greater than a predetermined threshold torque in such a state that the acceleration operation is not performed in a vehicle in the braking torque generated by the regenerative power generation; a friction brake control unit which controls the hydraulic pressure supplied to a brake mechanism and adjusts the friction brake braking torque generated by the friction brake; and a regenerative brake control unit which gradually reduces a second braking torque equivalent to a portion obtained by removing the first braking torque from the braking torque generated by the regenerative power generation at a predetermined reduction rate in a case where the brake operation is performed and it is detected that the request value of the first braking torque has changed to a value greater than the threshold torque.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a braking control device used in a vehicle.

Background Art

[0002] In vehicles using a motor generator capable of regenerative power generation, such as electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs), it may be necessary to cooperate the braking torque generated by regenerative power generation and the braking torque generated by a friction brake to achieve required braking. While the regenerative braking force obtained by the regenerative braking torque can change rapidly, a shock may occur when switching between the regenerative braking force and the friction braking force due to a response delay in the friction braking force obtained by the friction brake caused by a delay in the change of hydraulic pressure or the like. Therefore, a technique has been proposed to mitigate the change in the regenerative braking force during the period from the detection of a predetermined operation by the driver to the interruption of power supply to the motor generator (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, various vehicles have been put into practical use that allow the driver to actively increase engine braking torque. "Engine braking torque" is the braking torque generated by regenerative power generation when the driver is not operating the accelerator. For example, there are vehicles that have a brake (B) position in addition to drive (D) as a shift position, and increase engine braking torque when the shift is changed from D to B; vehicles that have a dedicated operation button, and increase engine braking torque when this button is operated; and vehicles that have a pedal that integrates the accelerator and brake pedals, and greatly increase engine braking torque when the driver takes their foot off this pedal. In such vehicles, if the engine braking torque is increased while the driver is operating the brakes, a shock may occur when the torque is switched. However, the above technologies do not take into consideration how to suppress the shock when the torque is switched in such situations.

[0005] The above problem is common not only to configurations in which the driver actively increases engine braking torque, but also to any configuration in which engine braking torque can be increased. For this reason, in vehicles driven by a motor generator capable of regenerative power generation, when braking is performed and engine braking torque increases, there is a need for a technology that can suppress the shock when switching between regenerative braking torque and friction braking torque. [Means for solving the problem]

[0006] This disclosure can be implemented in the following forms:

[0007] (1) According to one embodiment of the present disclosure, a braking control device is provided for use in a vehicle having a motor generator capable of regenerative power generation and which is driven by the driving force output by the motor generator. The braking control device includes: a detection unit that detects when the required value of the first braking torque, which is the braking torque generated by regenerative power generation when the vehicle is not being operated on the accelerator, becomes greater than a predetermined threshold torque; a friction brake control unit that controls the hydraulic pressure supplied to a brake mechanism mounted on the vehicle that generates friction brakes by hydraulic pressure, and adjusts the friction brake braking torque, which is the braking torque generated by the friction brake; and a regenerative brake control unit that, when a brake operation is performed on the vehicle and it is detected that the required value of the first braking torque has changed to a value greater than the threshold torque, gradually reduces the second braking torque, which is equivalent to the amount obtained by subtracting the first braking torque from the braking torque generated by regenerative power generation when the accelerator is being operated, at a predetermined reduction rate. According to this type of braking control device, when braking is performed in the vehicle and it is detected that the required value of the first braking torque has changed to a value greater than the threshold torque, the second braking torque, which is equivalent to the amount obtained by subtracting the first braking torque from the braking torque generated by regenerative braking, is gradually reduced at a predetermined rate. Therefore, even if there is a delay in the increase of friction braking torque when the second braking torque decreases due to the required value of the first braking torque becoming greater than the threshold torque, it is possible to suppress a sudden change in the total torque of the second braking torque and the friction braking torque, and thus suppress the shock (switching shock) associated with such a sudden change in total torque. (2) In the braking control device of the above form, the regenerative brake control unit identifies the rechargeable power value of the battery mounted on the vehicle, which is charged by the power obtained by the regenerative power generation, and the target value of the first braking torque, and sets the target value of the second braking torque based on the value obtained by subtracting the power corresponding to the target value of the first braking torque from the rechargeable power value, and the second braking control unit motionThe control circuit, which includes an inverter that supplies power to the motor generator according to the target torque value, controls the control circuit, and when the brake operation is performed and it is detected that the required value of the first braking torque has become greater than the threshold torque, the first braking torque is increased at a predetermined rate until it reaches the required value of the first braking torque. motion The second braking torque may be gradually reduced by the aforementioned reduction rate by gradually increasing the target value of the torque. According to this type of braking control device, when a braking operation is performed and the required value of the first braking torque is detected to have changed to a value greater than the threshold torque, the regenerative braking control unit applies the first braking torque at a predetermined rate of increase until it reaches the required value of the first braking torque. motion By gradually increasing the target torque value, the second braking torque is gradually reduced at a predetermined rate of decrease. Therefore, with a simple configuration, the second braking torque can be gradually reduced at a predetermined rate of decrease. (3) In the braking control device of the above form, the detection unit may detect that the required value of the first braking torque has changed to a value greater than the threshold torque when the shift of the vehicle is changed from drive (D) to brake (B). According to this type of braking control device, the detection unit detects when the vehicle's shift is changed from drive (D) to brake (B) and the required value of the first braking torque becomes greater than the threshold torque, thus enabling accurate detection of when the required value of the first braking torque becomes greater than the threshold torque. (4) In the braking control device of the above embodiment, the friction brake control unit may control the hydraulic pressure by setting the value obtained by subtracting the target value of the second braking torque from the required braking torque specified based on the amount of the brake operation as the target value of the friction brake braking torque. According to this type of braking control device, the friction brake control unit controls the hydraulic pressure using a value obtained by subtracting the target value of the second braking torque from the required braking torque, which is determined based on the amount of brake operation and the vehicle speed, as the target value of the friction brake braking torque. Therefore, the required braking torque can be satisfied by coordinating the regenerative braking force and the friction braking force. [Brief explanation of the drawing]

[0008] [Figure 1] This block diagram shows a schematic configuration of a vehicle equipped with a braking control device as one embodiment of the present disclosure. [Figure 2] This is a branch office showing the functional configuration centered on the braking control system. [Figure 3] This flowchart shows the procedure for the braking control process performed by the braking control device. [Figure 4] This flowchart shows the procedure for the second braking torque reduction process. [Figure 5] This is a schematic diagram illustrating an example of how braking power changes before and after changing the shift position. [Modes for carrying out the invention]

[0009] A. First Embodiment: A-1. System Configuration: Figure 1 is a block diagram showing the schematic configuration of a vehicle 10 equipped with a braking control device 100 as one embodiment of the present disclosure. Figure 2 is a block diagram showing the functional configuration centered on the braking control device 100. As shown in Figure 1, the vehicle 10 is configured as a hybrid vehicle equipped with a motor generator 51 and an engine 90 as the driving power source. In addition to the motor generator 51 and the engine 90, the braking control device 100 includes four wheels 21, a brake mechanism 39, a reduction gear 41, a power split mechanism 42, a motor generator control circuit 52 (hereinafter referred to as "MG control circuit 52"), a battery 61, a battery monitoring unit 62, a sensor group 70, and the braking control device 100.

[0010] The motor-generator 51 is configured as a three-phase synchronous generator-motor that functions as an electric motor when power (electrical energy) is supplied from the battery 61, and as a generator when driving force is transmitted from the engine 90 or rotational force (kinetic energy) is transmitted from the wheels 21. More specifically, the motor-generator 51 functions as a generator when the driving force (kinetic energy) of the engine 90, which has been split by the power split mechanism 42, is transmitted to it, and also functions as a starter motor that can start the engine 90. In addition, the motor-generator 51 functions as an electric motor (power source) that drives a group of gears and a reduction gear 41 (not shown) that transmit driving force to the drive shaft 22, and also functions to generate regenerative braking force by converting the rotation of the wheels 21, i.e., the kinetic energy of the vehicle, into power (electrical energy). The engine 90 outputs driving force by burning hydrocarbon fuels, such as gasoline or ethanol, stored in a fuel tank (not shown).

[0011] In this embodiment, of the four wheels 21, the front wheels rotate as drive wheels due to the driving force supplied by the motor generator 51 and the engine 90, while the rear wheels function as driven wheels. The brake mechanism 39 includes a brake actuator 30, four friction brake units 32 provided corresponding to each wheel 21, and piping for hydraulic fluid connecting the brake actuator 30 and the friction brake units 32. The brake actuator 30 generates braking force by operating each friction brake unit 32. The friction brake units 32 generate braking torque by converting kinetic energy into thermal energy. The brake actuator 30 is equipped with a hydraulic adjustment unit 31. When a brake pedal (not shown) provided on the vehicle 10 is pressed by the driver, the hydraulic adjustment unit 31 increases the hydraulic fluid supplied to each friction brake unit 32 via the piping, thereby increasing the hydraulic pressure and increasing the braking torque generated in each friction brake unit 32. The braking torque generated by the friction brakes of the friction brake units 32 is also called "friction braking torque".

[0012] The reduction gear 41 adjusts the rotational speed of the wheels 21 (front wheels) connected via the drive shaft 22. The power split mechanism 42 is coupled to the engine 90, the motor generator 51, and the reduction gear 41, and distributes power among them. The power split mechanism 42 is configured as a planetary gear having three rotating shafts, for example, a sun gear, a planetary carrier, and a ring gear, and these three rotating shafts are connected to the rotating shafts of the engine 90, the motor generator 51, and the reduction gear 41, respectively.

[0013] The MG control circuit 52 constitutes an energizing path that supplies power from the battery 61 to the motor generator 51 and an energizing path that supplies regenerative power generated by the motor generator 51 to the battery 61. The MG control circuit 52 is equipped with an inverter circuit 53, and by controlling the operation of this inverter circuit 53, the amount of current supplied to the motor generator 51 and the amount of current supplied to the battery 61 are controlled. This allows the driving force supplied to the wheels 21 to be adjusted, thereby adjusting the vehicle speed of the vehicle 10. In addition, by adjusting the amount of current supplied to the battery 61 (amount of regenerative power), the charge level of the battery 61 can be adjusted, and the braking torque generated by regenerative power generation can also be adjusted. In regenerative power generation, the rotational resistance of the rotor in the motor generator 51 generates braking torque. The braking torque generated by regenerative power generation is also called "regenerative braking torque".

[0014] The battery 61 receives and stores electricity generated by the regenerative power generation of the motor generator 51 via the motor generator control circuit 52. In this embodiment, the battery 61 is made of a secondary battery formed of nickel-metal hydride or lithium-ion material. However, instead of a secondary battery, it may be made of any type of power supply device that can temporarily store and supply power to the outside, such as a large-capacity capacitor.

[0015] The battery monitoring unit 62 monitors the state of the battery 61. Specifically, it acquires information regarding the charging and power supply capabilities of the battery 61, such as the terminal voltage of the battery 61, the input current to the battery 61, the output current from the battery 61, the SOC (State Of Charge) of the battery 61, and the chargeable power (electric power). The battery monitoring unit 62 is electrically connected to the braking control device 100 and notifies the braking control device 100 of the acquired battery-related information.

[0016] As shown in FIG. 2, the sensor group 70 includes an accelerator operation amount sensor 71, a brake operation amount sensor 72, and a shift position sensor 73. The accelerator operation amount sensor 71 detects the operation amount (depression amount) of an accelerator pedal (not shown) mounted on the vehicle 10. The brake operation amount sensor 72 detects the operation amount (depression amount) of a brake pedal (not shown) mounted on the vehicle 10.

[0017] The shift position sensor 73 detects the current designated shift position of a shift lever (not shown) mounted on the vehicle 10. In the present embodiment, the vehicle 10 has "D" (Drive), "B" (Brake), "R" (Reverse), "N" (Neutral), and "P" (Parking) set as shift positions. "B" is a shift position that can be selected when the vehicle 10 is moving forward, and when such a shift position is designated, it is a shift position where a greater braking force is generated compared to when "D" is designated. In the present embodiment, the braking force generated in the case of "B" is due to the regenerative braking torque described above. Each sensor 71 to 73 constituting the sensor group 70 is electrically connected to the braking control device 100 and notifies the braking control device 100 of the detected information.

[0018] As shown in FIG. 2, the braking control device 100 includes a hybrid vehicle control unit 110 and a friction brake control unit 150 that are configured to be communicable with each other via a CAN (Control Area Network).

[0019] The braking control device 100 is configured as an ECU (Electronic Control Unit) comprising a CPU 120 and a memory 130. The CPU 120 functions as a detection unit 121 and a regenerative braking control unit 122 by executing a control program pre-stored in the memory 130.

[0020] The detection unit 121 detects when the required value of the braking torque generated by regenerative power generation (regenerative braking torque) when the vehicle is not operating the accelerator (hereinafter referred to as "first braking torque") exceeds a predetermined threshold torque. The vehicle 10 is configured to operate with a predetermined amount of regenerative braking torque (first braking torque) according to the shift position when the accelerator is not operating. In other words, it is configured to generate regenerative power and perform braking from the moment the driver takes their foot off the accelerator pedal. As for the required value of the first braking torque at this time, a larger braking torque is required when the shift position is "B" than when the shift position is "D". Therefore, by setting the shift position to "B", the driver can obtain greater braking when the accelerator pedal is released. The above-mentioned "threshold torque" is a value that is greater than the required value of the first braking torque set when the shift position is "D" and less than the required value of the first braking torque set when the shift position is "B". In this embodiment, the detection unit 121 detects when the shift position received from the shift position sensor 73 is "B" and the required value of the first braking torque has become greater than a predetermined threshold torque. The first braking torque is also called the "engine brake torque".

[0021] The regenerative braking control unit 122 adjusts the braking torque (hereinafter referred to as the "second braking torque") that is equivalent to the amount obtained by subtracting the first braking torque from the braking torque (regenerative braking torque) generated by regenerative power generation. The second braking torque is also called the "regeneratively coordinateable torque". The detailed processing performed by the regenerative braking control unit 122 will be described later.

[0022] The friction brake control unit 150 calculates the required friction braking torque and controls the brake actuator 30 to generate that braking torque. The "required friction braking torque" at this time is calculated in the regenerative cooperative braking process described later. The friction brake control unit 150, like the detection unit 121 and the regenerative brake control unit 122, may be implemented by a CPU of an ECU separate from the hybrid vehicle control unit 110 executing a control program.

[0023] A-2. Regenerative Coordination Braking Process: In vehicle 10, the total braking torque is generated by combining friction braking torque and regenerative braking torque. At this time, the hybrid vehicle control unit 110 and the friction brake control unit 150 work together to determine how much braking torque each will be responsible for, and control is performed to output the determined braking torque. Specifically, the following processes are performed.

[0024] The friction brake control unit 150 calculates the braking torque requested by the driver (requested braking torque) from information such as the amount of brake pedal depression and the current vehicle speed. The friction brake control unit 150 also notifies the hybrid vehicle control unit 110 of the requested braking torque and requests a target value for the regenerative braking torque that can be generated additionally in the current situation, i.e., the second braking torque.

[0025] When the hybrid vehicle control unit 110 receives a request from the friction brake control unit 150 for a target value of the second braking torque, it first determines the required value of the first braking torque (engine braking torque) based on the current shift position, and then subtracts the braking force obtained from this first braking torque from the rechargeable power of the battery 61 to obtain a difference value. If this difference value is greater than or equal to the required braking torque, the hybrid vehicle control unit 110 sets the required braking torque as the target value of the second braking torque (regenerative coordinating torque). On the other hand, if the difference value is less than the required braking torque, it sets this difference value as the target value of the second braking torque (regenerative coordinating torque). The hybrid vehicle control unit 110 then notifies the friction brake control unit 150 of the target value of the second braking torque determined in this way.

[0026] The friction brake control unit 150 sets the target value of the friction brake torque as the braking torque obtained by subtracting the target value of the second braking torque received from the hybrid vehicle control unit 110 from the required braking torque. Therefore, as described above, if the difference obtained by subtracting the braking force obtained from the first braking torque from the rechargeable power of the battery 61 is greater than or equal to the required braking torque, the target value of the second braking torque will be the same as the required braking torque, and the target value of the friction brake torque will be "0". On the other hand, if the difference obtained by subtracting the braking force obtained from the first braking torque from the rechargeable power of the battery 61 is less than the required braking torque, the target value of the friction brake torque will be a value greater than "0". The friction brake control unit 150 controls the brake actuator 30 to generate friction brake torque according to the target value. Through this process, regenerative power can be generated as much as possible during braking to charge the battery 61, and only the insufficient braking torque can be generated by braking using the friction brake unit 32. Furthermore, the hybrid vehicle control unit 110 generates regenerative braking torque by controlling the MG control circuit 52 based on the target values ​​of the first braking torque and the second braking torque.

[0027] A-3. Braking control processing: Figure 3 is a flowchart showing the procedure for the braking control process performed by the braking control device 100. The braking control process is a process for controlling the braking in the vehicle 10 to suppress the shock (impact) caused by the sudden change in braking torque when the first braking torque (engine braking torque) increases rapidly, and can be performed in parallel with the regenerative cooperative braking process described above. The braking control process is performed when the ignition of the vehicle 10 is turned on.

[0028] The detection unit 121 determines whether or not a brake operation has been performed (step S105). If it is determined that a brake operation has been performed (step S105: YES), the detection unit 121 determines whether or not the required value of the first braking torque has changed to a value greater than a predetermined threshold torque (step S110). As described above, the detection unit 121 determines that the required value of the first braking torque has changed to a value greater than a predetermined threshold torque when the shift position received from the shift position sensor 73 changes from "D" to "B".

[0029] If it is determined that the required value of the first braking torque has changed to a value greater than a predetermined threshold torque (step S110: YES), the second braking torque reduction process is executed (step S115). If it is determined in step S105 that there was no brake operation (step S105: NO), if it is determined in step S110 that the required value of the first braking torque has not changed to a value greater than a predetermined threshold torque (step S110: NO), and after the completion of step S115 (second braking torque reduction process), the process returns to step S105.

[0030] Figure 4 is a flowchart showing the procedure for the gradual reduction of the second braking torque. The regenerative brake control unit 122 identifies the rechargeable power in the battery 61 and the required value of the first braking torque after the change (step S205). The rechargeable power in the battery 61 can be identified from information notified by the battery monitoring unit 62. The required value of the first braking torque after the change can be identified from the shift position information notified by the shift position sensor 73.

[0031] The regenerative braking control unit 122 increases the first braking torque at a predetermined rate until it reaches the required value of the first braking torque after the change. motion The target value of the torque is gradually increased (step S210). As described above, in the regenerative cooperative braking process, the hybrid vehicle control unit 110 calculates the target value of the second braking torque (regenerative cooperative torque) by subtracting the braking force obtained from the first braking torque from the rechargeable power of the battery 61. Therefore, the first braking is controlled by the braking control process. motion As the target torque gradually increases, the target value of the second braking torque will gradually decrease.

[0032] A-4. Suppression of shock during the transition between regenerative braking force and frictional braking force: The following explains how the shock during the switch between regenerative braking force and frictional braking force is suppressed by the gradual decrease in the second braking torque due to the braking control process described above.

[0033] Figure 5 is a schematic diagram illustrating an example of the change in braking power before and after a change in shift position. In Figure 5, the top row shows the change in accelerator operation, the second row shows the change in brake operation, the third row shows the change in braking torque, and the fourth row shows the time. In Figure 5, the accelerator operation and brake operation are shown as percentages (%) of the maximum possible operation amount, which is set to 100%. Note that in Figure 5, the accelerator operation amount is "0%", and the driver has taken their foot off the accelerator pedal.

[0034] Up to time t1, no brake operation has been performed, and in this case, only the first braking torque (engine braking torque), corresponding to the shift position "D", is generated. In Figure 5, the actual output value P1e, shown by the thick solid line, represents the actual output value of the first braking torque. This actual output value P1e matches the required value P1r of the first braking torque, shown by the dashed line, up to time t4. In Figure 5, the vertical range of the target value P1 of the first braking torque indicates the magnitude of the target value.

[0035] At time t1, braking is initiated, and as the amount of braking gradually increases, the target value P2 of the second braking torque gradually increases. However, even in this case, the required value P1r and the actual output value P1e of the first braking torque do not change. Then, at time t2, when the sum of the target value P1 of the first braking torque and the target value P2 of the second braking torque reaches the upper limit of the rechargeable power, friction braking torque is generated to achieve the required braking torque. Then, at time t3, the amount of braking reaches X%, and in the example in Figure 5, the amount of braking remains unchanged for a while at this level. In this case, the target value P1 of the first braking torque, the target value P2 of the second braking torque, and the actual output value P1e remain unchanged for a while.

[0036] In the example shown in Figure 5, at time t4, the driver changes the shift position from "D" to "B". In this case, the required value of the first braking torque P1r increases sharply to torque T2 simultaneously with the change in shift position. On the other hand, the actual output value of the first braking torque P1e gradually increases from time t4 to time t5. This is to suppress twisting of the drive shaft and the generation of abnormal noises from various gears caused by a sudden change in the first braking torque.

[0037] As described above, in this embodiment, when the braking control process is executed and the shift position changes from "D" to "B", the target value P1 of the first braking torque gradually increases. In the example in Figure 5, the target value P1 of the first braking torque has the same rate of increase as the rate of increase of the actual output value P1e of the first braking torque. As the target value P1 of the first braking torque gradually increases, the target value P2 of the second braking torque gradually decreases. As a result, the target value P3 of the friction braking torque gradually increases.

[0038] Here, the increase or decrease of the second braking torque is achieved by controlling the MG control circuit 52, resulting in relatively small response delays. Therefore, the actual output value of the second braking torque will be approximately equal to the target value P2 of the second braking torque. Generally, friction brakes have relatively large response delays due to the response delay in the increase or decrease of the hydraulic fluid pressure. However, as described above, the target value P3 of the friction braking torque increases gradually, so the actual output value of the friction braking torque will be approximately equal to the target value P3 of the friction braking torque. Therefore, even between times t4 and t5 when the shift position changes, the sum of the regenerative braking torque and the friction braking torque remains approximately constant. As a result, the shock associated with the switching between regenerative braking torque and friction braking torque is suppressed.

[0039] As a comparative example, we consider a configuration in which braking control processing is not performed. In this configuration, the target value of the first braking torque increases sharply to match the required value P1r simultaneously with the change in shift position. As a result, the target value P2 of the second braking torque decreases sharply, and the actual output value of the second drive torque decreases sharply to satisfy this target value P2. On the other hand, the actual output value P1e of the first braking torque increases gradually as described above, so the sum of the actual output value of the first braking torque and the actual output value of the second braking torque is lower than the required braking torque between time t4 and t5. In particular, at time t4 and immediately afterward, the actual output value decreases significantly compared to immediately before time t4, and a shock (impact) during the shift may occur instantaneously.

[0040] On the other hand, in this embodiment, as described above, even if a change in shift position occurs and the required value of the first braking torque (engine braking torque) increases sharply, the sum of the regenerative braking torque and the friction braking torque can be kept almost constant, thereby suppressing the shock associated with the substitution of regenerative braking torque and friction braking torque.

[0041] According to the braking control device 100 of the first embodiment described above, when a brake operation is performed in the vehicle 10 and it is detected that the required value of the first braking torque has changed to a value greater than the threshold torque, the second braking torque (regeneratively compatible torque), which is equivalent to the amount obtained by subtracting the first braking torque (engine brake torque) from the braking torque generated by regenerative power generation, is gradually reduced at a predetermined reduction rate. Therefore, when the second braking torque decreases due to the required value of the first braking torque becoming greater than the threshold torque, even if the increase in friction braking torque results in a response delay, it is possible to suppress a sudden change in the total torque of the second braking torque and friction braking torque, and thus suppress the shock (switching shock) associated with such a sudden change.

[0042] Furthermore, when the regenerative brake control unit 122 detects that a brake operation has been performed and that the required value of the first braking torque has changed to a value greater than the threshold torque, it increases the first braking torque at a predetermined rate until it reaches the required value of the first braking torque. motion By gradually increasing the target torque value, the second braking torque is gradually reduced at a predetermined rate of decrease. Therefore, with a simple configuration, the second braking torque can be gradually reduced at a predetermined rate of decrease.

[0043] Furthermore, the detection unit 121 detects when the vehicle 10's shift lever changes from drive "D" to brake "B" and the required value of the first braking torque becomes greater than the threshold torque, thus enabling accurate detection of when the required value of the first braking torque becomes greater than the threshold torque.

[0044] Furthermore, the friction brake control unit 150 controls the hydraulic pressure using a value obtained by subtracting the target value of the second braking torque from the required braking torque, which is determined based on the amount of brake operation and vehicle speed, as the target value of the friction brake braking torque. This allows the required braking torque to be satisfied by coordinating the regenerative braking force and the friction braking force.

[0045] B. Other embodiments: (B1) In the above embodiment, the detection unit 121 determined that the required value of the first braking torque had changed to a value greater than a predetermined threshold torque when the shift position received from the shift position sensor 73 changed from "D" to "B", but the disclosure is not limited thereto. For example, in a configuration in which an operating unit such as a button that instructs to increase the regenerative braking torque (regenerative boost) is provided in advance on the vehicle 10, the detection unit may determine that the required value of the first braking torque has changed to a value greater than a predetermined threshold torque when an instruction to perform regenerative boost is received from such an operating unit. Also, for example, in a configuration in which a pedal is provided in advance on the vehicle 10 that is set to exert a greater braking force when the foot is released from the pedal than on a normal vehicle, the detection unit may determine that the required value of the first braking torque has changed to a value greater than a predetermined threshold torque when it is detected that the foot has been released from such a pedal. Furthermore, in a configuration where an automated driving or advanced driver-assistance system (AD / ADAS) can instruct an increase in engine braking torque, when such an instruction command is received, it may be determined that the requested value of the first braking torque has changed to a value greater than a predetermined threshold torque. In addition, in a vehicle control device (not shown) that repeatedly calculates the current values ​​of output torque and output power at predetermined time intervals for driving control, it may be determined whether the amount of change from the previous value of the output torque or output power has become greater than a threshold.

[0046] (B2) In the above embodiment, the second braking torque was gradually decreased by gradually increasing the target value of the first braking torque, but the disclosure is not limited thereto. The target value of the first braking torque may remain the same, and the target value of the second braking torque may be decreased by a predetermined rate of decrease.

[0047] (B3) In the above embodiment, the vehicle 10 was configured as a hybrid electric vehicle (HEV), but the disclosure is not limited thereto. It may be configured as any type of vehicle that runs on the driving force output by the motor generator 51, such as a plug-in hybrid electric vehicle (PHEV) or an electric vehicle (EV).

[0048] (B4) In each embodiment, some of the configurations implemented by hardware may be replaced with software, and conversely, some of the configurations implemented by software may be replaced with hardware. For example, at least some of the detection unit 121, the regenerative brake control unit 122, and the friction brake control unit 150 may be implemented by an integrated circuit, a discrete circuit, or a module combining such circuits. Furthermore, if some or all of the functions of this disclosure are implemented by software, the software (computer program) may be provided in the form of being stored on a computer-readable recording medium. "Computer-readable recording medium" is not limited to portable recording media such as flexible disks and CD-ROMs, but also includes various internal storage devices in a computer such as RAM and ROM, and external storage devices fixed to a computer such as hard disks. In other words, "computer-readable recording medium" has a broad meaning that includes any recording medium on which data packets can be fixed rather than temporary.

[0049] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in each embodiment corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-mentioned problems, or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0050] 10...Vehicle, 21...Wheel, 22...Drive shaft, 30...Brake actuator, 31...Hydraulic adjustment unit, 32...Friction brake unit, 39...Brake mechanism, 41...Reduction gear, 42...Power split mechanism, 51...Motor generator, 52...MG control circuit, 53...Inverter circuit, 61...Battery, 62...Battery monitoring unit, 70...Sensor group, 71...Accelerator operation amount sensor, 72...Brake operation amount sensor, 73...Shift position sensor, 90...Engine, 10 0... Brake control device, 110... Hybrid vehicle control unit, 120... CPU, 121... Detection unit, 122... Regenerative brake control unit, 130... Memory, 150... Friction brake control unit, P1... Target value of first braking torque, P1e... Actual output value of first braking torque, P1r... Required value of first braking torque, P2... Target value of second braking torque, P3... Target value of friction braking torque, T1... Torque, T2... Torque, t1... Time, t2... Time, t3... Time, t4... Time, t5... Time

Claims

1. A braking control device used in a vehicle that has a motor generator capable of regenerative power generation and is driven by the driving force output by the motor generator, A detection unit detects when the required value of the first braking torque, which is the braking torque generated by the regenerative power generation when the vehicle is not being operated on the accelerator, changes to a value greater than a predetermined threshold torque, among the braking torque generated by the regenerative power generation. A friction brake control unit controls the hydraulic pressure supplied to a brake mechanism mounted on the vehicle that generates friction brakes using hydraulic pressure, and adjusts the friction brake braking torque, which is the braking torque generated by the friction brake. When the brakes are applied to the vehicle and it is detected that the required value of the first braking torque has changed to a value greater than the threshold torque, the regenerative brake control unit gradually reduces the second braking torque, which is equivalent to the amount obtained by subtracting the first braking torque from the braking torque generated by regenerative power generation, at a predetermined reduction rate. A braking control device equipped with the following:

2. In the braking control device according to claim 1, The regenerative braking control unit, The rechargeable power value of the battery mounted on the vehicle, which is charged by the electricity obtained by the regenerative power generation, and the target value of the first braking torque are determined. Based on the value obtained by subtracting the power corresponding to the target value of the first braking torque from the rechargeable power value, the target value of the second braking torque is set, and a control circuit including an inverter that supplies power to the motor generator is controlled according to the target value of the second braking torque. A braking control device that, when the aforementioned braking operation is performed and it is detected that the required value of the first braking torque has become greater than the threshold torque, gradually increases the target value of the first braking torque at a predetermined rate of increase until it reaches the required value of the first braking torque, thereby gradually decreasing the second braking torque at the aforementioned rate of decrease.

3. In the braking control device according to claim 1 or claim 2, The detection unit is a braking control device that detects when the vehicle's shift is changed from drive (D) to brake (B) and the required value of the first braking torque changes to a value greater than the threshold torque.

4. In the braking control device according to claim 1 or claim 2, The friction brake control unit controls the hydraulic pressure, with the value obtained by subtracting the target value of the second braking torque from the required braking torque, which is determined based on the amount of the brake operation and the vehicle speed, being the target value of the friction brake braking torque.

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