Braking control device

Abstract

A processing circuit 51 of a braking control device 50 functions as: a reduction control unit M13 that, when stopping a vehicle 10 traveling on an uphill road by applying braking force to the vehicle 10, executes braking force reduction processing in which a vehicle body speed of the vehicle 10 is set to 0 (zero) after reducing the vehicle braking force to a first braking force that is a braking force equal to or greater than 0 (zero) and is smaller than a stop maintaining braking force which is a braking force for counteracting a force acting on the vehicle 10 in a downhill direction and a force acting on the vehicle 10 in an uphill direction; and a degeneration control unit M17 that executes braking force increase processing that increases the vehicle braking force to a second braking force greater than or equal to the stop maintaining braking force from a point in time when the vehicle 10 is switched from the forward movement to the backward movement by the execution of the braking force reduction processing.

Description

Braking control device

[0001] The present invention relates to a braking control device that controls braking force applied to a vehicle.

[0002] Patent Document 1 discloses a vehicle control device that performs stopping control to suppress changes in the vehicle's posture when the vehicle is stopped by reducing the braking force applied to the vehicle just before the vehicle stops. When the vehicle is traveling uphill, the braking control device performs the stopping control while the motor generator, which is the power source of the vehicle, is powered.

[0003] JP 2016-28913 A

[0004] In the above vehicle control device, when the vehicle is stopped on an uphill road, the motor generator is made to perform power running when the vehicle is stopped. Therefore, when the vehicle is stopped on an uphill road, although the change in the vehicle's posture when stopped can be suppressed, the energy efficiency of the vehicle deteriorates.

[0005] A braking control device for solving the above problem includes a first control unit that, when applying braking force to a vehicle traveling on an uphill road to stop the vehicle, reduces the braking force applied to the vehicle to a first braking force that is smaller than a stop-maintenance braking force that is a braking force for balancing a downhill force acting on the vehicle and an uphill force acting on the vehicle and is greater than or equal to 0 (zero), and then executes a braking force reduction process to set the vehicle's body speed to 0 (zero); and a second control unit that executes a braking force increase process to increase the braking force applied to the vehicle to a second braking force that is greater than or equal to the stop-maintenance braking force, from the point at which the vehicle switches from forward movement to reverse movement as a result of execution of the braking force reduction process.

[0006] The braking control device described above has the effect of suppressing deterioration in the energy efficiency of the vehicle when stopping the vehicle on an uphill road, while suppressing changes in the vehicle's attitude when stopping the vehicle.

[0007] FIG. 1 is a schematic diagram showing a vehicle equipped with a brake control device according to an embodiment. FIG. 2 is a schematic diagram showing a state in which a vehicle traveling on an uphill road is stopped by applying a braking force to the vehicle. FIG. 3 is a schematic diagram showing a state in which a vehicle is stopped on an uphill road by applying a braking force. FIG. 4 is a schematic diagram showing the relationship between forces acting on the vehicle when the vehicle is decelerating on an uphill road. FIG. 5 is a timing chart for stopping the vehicle on a level road. FIG. 6 is a flowchart showing a series of processes executed by the brake control device of FIG. 1. FIG. 7 is a timing chart for stopping the vehicle on an uphill road.

[0008] An embodiment of a brake control device will be described below with reference to Figs. 1 to 7. Fig. 1 illustrates a vehicle 10 equipped with a brake control device 50. The vehicle 10 includes a brake operating member 11, a plurality of wheels, a plurality of friction brakes 20, and a brake actuator 30. The brake operating member 11 is a member that is operated by the driver when applying a braking force to the vehicle 10. An example of the brake operating member 11 is a brake pedal. The plurality of wheels include two front wheels 12 and two rear wheels 13.

[0009] <Friction Brake> The multiple friction brakes 20 each apply a braking force to a corresponding wheel. The friction brake 20 has a wheel cylinder 21, a rotating body 22, and a friction portion 23. The rotating body 22 rotates integrally with the wheel. Therefore, braking force is applied to the wheel by pressing the friction portion 23 against the rotating body 22. The force pressing the friction portion 23 against the rotating body 22 increases as the wheel hydraulic pressure, which is the hydraulic pressure in the wheel cylinder 21, increases. Therefore, the friction brake 20 can apply a greater braking force to the wheel as the wheel hydraulic pressure increases.

[0010] <Brake Actuator> The brake actuator 30 controls the wheel hydraulic pressure in the plurality of wheel cylinders 21 to control the braking force applied to the wheels 12, 13. For example, the brake actuator 30 has a pressure source that supplies brake fluid to the plurality of wheel cylinders 21. The pressure source is, for example, an electric pump and an electric cylinder. The brake actuator 30 can individually adjust the wheel hydraulic pressure in the wheel cylinder 21 for the front wheels 12 and the wheel hydraulic pressure in the wheel cylinder 21 for the rear wheels 13.

[0011] In the following description, the sum of the braking forces applied to the multiple wheels 12, 13 will also be referred to as the "vehicle braking force BPAl." <Regarding the relationship of forces acting on a vehicle on an uphill road> With reference to Figures 2 and 3, the relationship of forces acting on the vehicle 10 when the vehicle 10 is on an uphill road will be described. Figure 2 shows the relationship of forces acting on the vehicle 10 when the vehicle 10 is decelerating due to the application of braking force. Figure 3 shows the relationship of forces acting on the vehicle 10 when the vehicle 10 is stopped on an uphill road due to the application of braking force. Note that the downhill direction Z1 is the direction toward the downhill side of the slope. The uphill direction Z2 is the direction toward the uphill side of the slope, opposite to the downhill direction Z1.

[0012] 2, before the vehicle 10 stops, the forces acting on the vehicle 10 in the uphill direction Z2 include the driving force FD of the vehicle 10. Meanwhile, the forces acting on the vehicle 10 in the downhill direction Z1 include a gravitational acceleration component Gg, a vehicle braking force BPAl, and a running resistance Gr of the vehicle 10. The gravitational acceleration component Gg is the component of gravity acting on the vehicle 10 in the downhill direction Z1.

[0013] 3, when the vehicle 10 stops, the forces acting on the vehicle 10 in the uphill direction Z2 include the driving force FD of the vehicle 10 and the vehicle braking force BPAl. On the other hand, the forces acting on the vehicle 10 in the downhill direction Z1 include the gravitational acceleration component Gg and the running resistance Gr of the vehicle 10.

[0014] In other words, the direction of the vehicle braking force BPAl acting on the vehicle 10 changes between immediately before and after the vehicle 10 stops. <Detection System> As shown in Fig. 1 , the detection system of the vehicle 10 includes a plurality of sensors that output detection signals to the braking control device 50. The plurality of sensors includes a brake sensor 101, a plurality of wheel speed sensors 102, and a longitudinal acceleration sensor 103.

[0015] The brake sensor 101 detects information related to the operation of the brake operating member 11 by the driver. An example of the brake sensor 101 is a stroke sensor that detects the amount of operation of the brake operating member 11 by the driver. The amount of operation based on the detection signal of the brake sensor 101 is referred to as the "operation amount X." The detection system may also include a sensor that detects the operating force of the brake operating member 11 by the driver.

[0016] A wheel speed sensor 102 is provided for each of the plurality of wheels. Each of the plurality of wheel speed sensors 102 detects the rotational speed of the corresponding wheel. The rotational speed of the wheel based on the detection signal of the wheel speed sensor 102 is referred to as the "wheel speed VW." The traveling speed of the vehicle 10 calculated based on the wheel speeds VW of the plurality of wheels 12, 13 is referred to as the "vehicle speed VS."

[0017] The longitudinal acceleration sensor 103 detects the longitudinal acceleration of the vehicle 10 out of the accelerations acting on the vehicle 10. The longitudinal acceleration of the vehicle 10 based on the detection signal of the longitudinal acceleration sensor 103 is referred to as "longitudinal acceleration Gx."

[0018] The detection system employs a sensor as the longitudinal acceleration sensor 103 that detects the inertial force acting on the vehicle 10 in the longitudinal direction of the vehicle 10. When the vehicle 10 accelerates on a horizontal road, the longitudinal acceleration Gx detected by the longitudinal acceleration sensor 103 is a positive value. When the vehicle 10 decelerates on a horizontal road, the longitudinal acceleration Gx is a negative value. When the vehicle 10 is stopped on a horizontal road, the longitudinal acceleration Gx is 0 (zero).

[0019] When the vehicle 10 is traveling uphill, the longitudinal acceleration sensor 103 can detect the gravitational acceleration component Gg, which is the component of gravity acting on the vehicle 10 in the downhill direction Z1. In other words, when the vehicle 10 is traveling uphill, the detection signal of the longitudinal acceleration sensor 103 reflects the gravitational acceleration component Gg. Therefore, when the vehicle 10 is stopped on an uphill road, the longitudinal acceleration Gx will be a positive value. On the other hand, when the vehicle 10 is stopped on a downhill road, the longitudinal acceleration Gx will be a negative value.

[0020] Referring to Figure 4, the transition of the longitudinal acceleration Gx when the vehicle 10 decelerates and stops on an uphill road will be described. Note that the gravitational acceleration component Gg has a positive value. When the vehicle 10 decelerates on an uphill road, a deceleration inertia force DI, which is an inertial force resulting from deceleration, acts on the vehicle 10. The deceleration inertia force DI acts on the vehicle 10 in the uphill direction Z2. In other words, the direction of the deceleration inertia force DI is opposite to the direction of the gravitational acceleration component Gg. Therefore, the deceleration inertia force DI takes a negative value. The value corresponding to the sum of the gravitational acceleration component Gg and the deceleration inertia force DI becomes the longitudinal acceleration Gx.

[0021] Thereafter, when the vehicle 10 substantially stops on an uphill road, the deceleration inertia force DI becomes 0 (zero). As a result, a value corresponding to the gravitational acceleration component Gg becomes the longitudinal acceleration Gx. If no braking force is applied to the vehicle 10 in this state, there is a possibility that the vehicle 10 will move in the downhill direction Z1. In other words, when the vehicle 10 switches from forward to reverse on an uphill road, the longitudinal acceleration Gx transitions from a negative value to a positive value.

[0022] <Brake Control Device> As shown in FIG. 1 , the brake control device 50 includes a processing circuit 51. One example of the processing circuit 51 is an electronic control device. In this case, the processing circuit 51 includes a CPU 52, a first memory 53, and a second memory 54. The first memory 53 stores a control program executed by the CPU 52. The second memory 54 stores calculation results of the CPU 52, etc. When the CPU 52 executes the control program in the first memory 53, the processing circuit 51 controls the brake actuator 30 to activate the plurality of friction brakes 20. In other words, the processing circuit 51 can adjust the vehicle braking force BPAl by activating the plurality of friction brakes 20.

[0023] <Outline of braking control at a stop> The processing circuit 51 performs braking control at a stop when the driver is operating the brake operating member 11. The braking control at a stop is braking control for suppressing changes in the posture of the vehicle 10 due to stopping.

[0024] Braking control during a stop will be described with reference to FIG. 5 . FIG. 5 shows an example of stopping the vehicle 10 on a level road. While the vehicle 10 is traveling, the driver begins to operate the brake operating member 11 at timing t11. In this case, as shown in FIG. 5B, the processing circuit 51 derives a required braking force BPRq. The required braking force BPRq is a required value of the vehicle braking force BPAl. For example, the processing circuit 51 derives the required braking force BPRq so that the greater the operation amount X of the brake operating member 11, the greater the required braking force BPRq. When the vehicle speed VS of the vehicle 10 is greater than the first vehicle speed determination value VSth1, as before timing t12, the processing circuit 51 sets the required braking force BPRq as the command braking force BPTr, as shown in FIG. 5D. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes equal to the command braking force BPTr.

[0025] When a braking force is applied to the vehicle 10 in this manner, the vehicle speed VS decreases as shown in Fig. 5A. Also, as shown in Fig. 5C, the absolute value of the longitudinal acceleration Gx increases as the vehicle braking force BPAl increases.

[0026] When the vehicle speed VS reaches the first vehicle speed determination value VSth1 at timing t12, the processing circuit 51 starts stop braking control. The first vehicle speed determination value VSth1 is an example of a threshold value for setting the start timing of stop braking control. From timing t12, the processing circuit 51 starts an increase correction process for the stop braking control. In the increase correction process, the processing circuit 51 sets a braking force greater than the required braking force BPRq as the command braking force BPTr. For example, the processing circuit 51 sets the sum of the required braking force BPRq and the offset value ΔBP as the command braking force BPTr. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr. As a result, even if the required braking force BPRq remains the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 becomes greater by the amount of the offset value ΔBP than before timing t12.

[0027] At timing t13, the vehicle speed VS becomes the second vehicle speed determination value VSth2. A vehicle speed smaller than the first vehicle speed determination value VSth1 is set as the second vehicle speed determination value VSth2. When the vehicle speed VS is equal to or smaller than the second vehicle speed determination value VSth2, it is determined that the vehicle 10 is approaching the stop position PS. The stop position PS is a predicted position where the vehicle 10 will stop. The processing circuit 51 shifts the processing of the stop-time braking control from an increase correction processing to a decrease correction processing. In the decrease correction processing, the processing circuit 51 decreases the command braking force BPTr at a constant rate. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr. By performing the decrease correction processing in this manner, the processing circuit 51 causes the vehicle braking force BPAl to become smaller than the required braking force BPRq. As a result, even if the required braking force BPRq remains the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually decreases.

[0028] At timing t14, the command braking force BPTr becomes equal to the stop-maintenance braking force BPth. The stop-maintenance braking force BPth is set to the minimum braking force necessary to maintain the stop of the vehicle 10 on the current road surface on which the vehicle 10 is traveling, or to a braking force slightly greater than that braking force. At timing t14, in the decrease correction process, the processing circuit 51 maintains the command braking force BPTr at the stop-maintenance braking force BPth.

[0029] At timing t15, the processing circuit 51 determines that the vehicle 10 has stopped, and therefore transitions the processing of the stop-time braking control from the reduction correction processing to the degeneration processing. In the degeneration processing, the processing circuit 51 increases the command braking force BPTr. For example, the processing circuit 51 increases the command braking force BPTr to the required braking force BPRq. The processing circuit 51 controls the brake actuator 30 based on the command braking force BPTr, thereby increasing the vehicle braking force BPAl. When the command braking force BPTr becomes equal to the required braking force BPRq at timing t16, the processing circuit 51 terminates the stop-time braking control.

[0030] <Functional Configuration of Processing Circuit> The functional configuration of the processing circuit 51 will be described with reference to Fig. 1. The CPU 52 executes the control program in the first memory 53, causing the processing circuit 51 to function as multiple functional units. These multiple functional units are functional units for applying braking force to the vehicle 10 to bring the vehicle 10 to a stop. The multiple functional units include, for example, an increase control unit M11, a decrease control unit M13, a determination unit M15, a reduction control unit M17, a first braking force setting unit M19, and a second braking force setting unit M21.

[0031] <Increase Control Unit> The increase control unit M11 executes an increase correction process for the stop-time braking control. The increase control unit M11 derives the sum of the required braking force BPRq and the offset value ΔBP as the command braking force BPTr. The increase control unit M11 then operates the brake actuator 30 based on the command braking force BPTr. This allows the increase control unit M11 to make the vehicle braking force BPAl greater than the required braking force BPRq.

[0032] <Decrease Control Unit> The decrease control unit M13 executes a decrease correction process for the stop-time braking control. The decrease control unit M13 gradually decreases the command braking force BPTr. After that, the decrease control unit M13 holds the command braking force BPTr. The decrease control unit M13 also operates the brake actuator 30 based on the command braking force BPTr at that time. This allows the decrease control unit M13 to reduce the vehicle braking force BPAl compared to when the increase correction process is executed.

[0033] When the vehicle 10 is traveling on a level road, the reduction control unit M13 reduces the command braking force BPTr to the stop-maintenance braking force BPth. When the command braking force BPTr reaches the stop-maintenance braking force BPth, the reduction control unit M13 maintains the command braking force BPTr at the stop-maintenance braking force BPth.

[0034] Here, when the vehicle 10 is traveling on an uphill road, the stop-maintenance braking force BPth corresponds to a braking force for balancing a force acting on the vehicle 10 in the downhill direction Z1 and a force acting on the vehicle 10 in the uphill direction Z2. When the vehicle 10 is stopped on an uphill road as shown in Figure 3, a first sum, which is the sum of the magnitude of the gravitational acceleration component Gg and the magnitude of the running resistance Gr of the vehicle 10, is the force acting on the vehicle 10 in the downhill direction Z1. Meanwhile, a second sum, which is the sum of the magnitude of the driving force FD of the vehicle 10 and the magnitude of the vehicle braking force BPAl, is the force acting on the vehicle 10 in the uphill direction Z2. Therefore, the value obtained by subtracting the driving force FD of the vehicle 10 from the first sum is the stop-maintenance braking force BPth.

[0035] When the vehicle 10 is traveling on an uphill road, the reduction control unit M13 reduces the command braking force BPTr to a first braking force BPC1, which is a vehicle braking force that is smaller than the vehicle-stop maintenance braking force BPth and greater than 0 (zero), and then sets the vehicle speed VS to 0 (zero). Therefore, the reduction correction process executed when the vehicle 10 is traveling on an uphill road corresponds to the "braking force reduction process." Furthermore, when the vehicle 10 is traveling on an uphill road, the reduction control unit M13 functions as the "first control unit."

[0036] When the vehicle 10 is traveling on an uphill road, the reduction control unit M13 reduces the command braking force BPTr to the first braking force BPC1. Then, even if the command braking force BPTr reaches the first braking force BPC1, if the condition for transitioning from the reduction correction process to the degeneration process is not met, the reduction control unit M13 maintains the command braking force BPTr at the first braking force BPC1.

[0037] <Determination Unit> When the reduction correction process is being executed while the vehicle 10 is traveling uphill, i.e., when the braking force reduction process is being executed, the determination unit M15 determines whether the vehicle 10 has switched from forward movement to reverse movement. Specifically, the determination unit M15 determines that the vehicle 10 has switched from forward movement to reverse movement when the longitudinal acceleration Gx, which is the detected value of the longitudinal acceleration sensor 103, transitions from a state in which it is less than a reference value to a state in which it is equal to or greater than the reference value. For example, when 0 (zero) is set as the reference value, the determination unit M15 determines that the vehicle 10 has switched from forward movement to reverse movement when the longitudinal acceleration Gx changes from a negative value to a positive value.

[0038] When the vehicle 10 stops, the deceleration inertia force DI becomes 0 (zero) as described above. As a result, the longitudinal acceleration Gx switches from a negative value to a positive value. Therefore, it can be said that the determination unit M15 determines whether the deceleration inertia force DI has become 0 (zero).

[0039] <Degeneration Control Unit> The degeneration control unit M17 executes degeneration processing of the stop-time braking control. The degeneration control unit M17 increases the command braking force BPTr. Then, the degeneration control unit M17 operates the brake actuator 30 based on the command braking force BPTr. In this way, the degeneration control unit M17 maintains the vehicle 10 in a stopped state.

[0040] When the vehicle 10 is traveling on a level road, the degeneration control unit M17 starts the degeneration process when it determines that the vehicle 10 has stopped. In this case, in the degeneration process, the degeneration control unit M17 increases the command braking force BPTr from the vehicle-stop maintenance braking force BPth to the required braking force BPRq. When the command braking force BPTr reaches the required braking force BPRq, the degeneration control unit M17 ends the degeneration process, i.e., the vehicle-stop braking control.

[0041] When the vehicle 10 is traveling on an uphill road, the degeneration control unit M17 executes the degeneration process from the point at which the vehicle 10 switches from forward to reverse due to the execution of the reduction correction process (i.e., the braking force reduction process). That is, the degeneration control unit M17 executes the degeneration process when the determination unit M15 determines that the vehicle 10 has switched from forward to reverse. In this case, in the degeneration process, the degeneration control unit M17 increases the command braking force BPTr to the second braking force BPC2. The second braking force BPC2 is a vehicle braking force equal to or greater than the stop-maintenance braking force BPth. Therefore, the degeneration process executed when the vehicle 10 is traveling on an uphill road corresponds to the "braking force increase process." Furthermore, when the vehicle 10 is traveling on an uphill road, the degeneration control unit M17 functions as the "second control unit."

[0042] Thereafter, when the command braking force BPTr reaches the second braking force BPC2, the degeneration control unit M17 terminates the degeneration process, i.e., the vehicle-stop braking control. <First Braking Force Setting Unit> The first braking force setting unit M19 sets the first braking force BPC1 when the vehicle 10 is traveling on an uphill road. Specifically, the first braking force setting unit M19 sets the first braking force BPC1 in a range greater than or equal to 0 (zero) and less than the vehicle-stop maintenance braking force BPth. For example, the first braking force setting unit M19 sets the first braking force BPC1 based on the gradient of the uphill road, an index indicating the degree of comfort desired by the occupants of the vehicle 10 (e.g., the driver) when the vehicle 10 is stopped, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10.

[0043] When setting the first braking force BPC1 based on the gradient of an uphill road, the first braking force setting unit M19 may set the first braking force BPC1 to a larger value the steeper the gradient of the uphill road.

[0044] When setting the first braking force BPC1 based on an index indicating the degree of comfort required by the occupants when the vehicle is stopped, the first braking force setting unit M19 should set a larger value for the first braking force BPC1 as the degree of comfort required by the occupants is smaller. The larger the vehicle braking force BPAl at the time of stopping, the more likely it is that the posture of the vehicle 10 will change significantly when stopped. The vehicle braking force BPAl is more likely to increase as the amount of operation X of the brake operating member 11 by the driver increases. Therefore, the first braking force setting unit M19 should use the amount of operation X as the index. In this case, the first braking force setting unit M19 sets the first braking force BPC1 so that the value increases as the amount of operation X increases.

[0045] When setting the first braking force BPC1 based on the force acting on the vehicle 10 to move the vehicle 10, the first braking force setting unit M19 should set a larger value as the force moving the vehicle 10 is smaller. One example of a force that moves the vehicle 10 is the driving force FD of the vehicle 10. The smaller the driving force FD, the more difficult it is for the vehicle 10 to stop unless the vehicle braking force BPAl is increased. Therefore, the smaller the driving force FD, the larger the value set by the first braking force setting unit M19 as the first braking force BPC1.

[0046] When setting the first braking force BPC1 based on the weight of the vehicle 10, the first braking force setting unit M19 may set a larger value as the weight of the vehicle 10 increases. This is because the greater the weight, the greater the magnitude of the gravitational acceleration component Gg, making it easier for the vehicle 10 to move in the downhill direction Z1.

[0047] <Second Braking Force Setting Unit> The second braking force setting unit M21 sets the second braking force BPC2 when the vehicle 10 is traveling on an uphill road. Specifically, the second braking force setting unit M21 sets the second braking force BPC2 in a range equal to or greater than the vehicle stop maintenance braking force BPth. For example, the second braking force setting unit M21 sets the second braking force BPC2 based on the gradient of the uphill road, an index indicating the degree of comfort desired by the occupants when stopped, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10.

[0048] When setting the second braking force BPC2 based on the gradient of an uphill road, the second braking force setting unit M21 may set the second braking force BPC2 to a larger value the steeper the gradient of the uphill road.

[0049] When the second braking force BPC2 is set based on an index indicating the degree of comfort required by the occupant when the vehicle is stopped, the second braking force setting unit M21 may set a larger value as the degree of comfort required by the occupant is smaller. When the operation amount X is used as the index, the second braking force setting unit M21 may set a larger value as the operation amount X is larger.

[0050] When setting the second braking force BPC2 based on a force acting on the vehicle 10 to move the vehicle 10, the second braking force setting unit M21 may set a larger value as the first braking force BPC1 the smaller the force to move the vehicle 10. An example of a force to move the vehicle 10 is the driving force FD of the vehicle 10. Therefore, the second braking force setting unit M21 sets a larger value as the second braking force BPC2 the smaller the driving force FD.

[0051] When setting the second braking force BPC2 based on the weight of the vehicle 10, the second braking force setting unit M21 may set a larger value as the weight of the vehicle 10 increases. This is because the larger the weight, the larger the magnitude of the gravitational acceleration component Gg, making it more difficult to maintain a stop of the vehicle.

[0052] <Processing Flow During Vehicle Braking> A series of processes performed by the processing circuit 51 when performing braking control during a stop will be described with reference to Fig. 6. The processing circuit 51 repeatedly performs the series of processes shown in Fig. 6 during vehicle braking.

[0053] In step S11, the processing circuit 51 determines whether the road surface on which the vehicle 10 is traveling is an uphill road. For example, the processing circuit 51 can determine whether the road surface on which the vehicle 10 is traveling is an uphill road based on the difference between the differential value of the vehicle body speed VS and the longitudinal acceleration Gx of the vehicle 10. The processing circuit 51 may also determine whether the road surface on which the vehicle is traveling is an uphill road based on information about the road surface obtained from a navigation device. If the vehicle 10 is equipped with a sensor that detects the degree of inclination of the vehicle body, the processing circuit 51 may also determine whether the road surface on which the vehicle is traveling is an uphill road based on the detection value of the sensor. The processing circuit 51 may also determine whether the road surface on which the vehicle is traveling is an uphill road by analyzing images captured by an on-board camera.

[0054] If the processing circuit 51 determines that the road surface is an uphill road (S11: YES), the processing proceeds to step S41. On the other hand, if the processing circuit 51 determines that the road surface is not an uphill road (S11: NO), the processing proceeds to step S13.

[0055] In step S13, the processing circuit 51 sets the stop-maintenance braking force BPth as the first braking force BPC1. In the following step S15, the processing circuit 51 determines whether a start condition for the first stop-state braking control is satisfied. The first stop-state braking control is performed when the road surface is not an uphill road. For example, as shown in FIG. 5 , the processing circuit 51 determines that the start condition is satisfied when the vehicle speed VS becomes equal to or less than the first vehicle speed determination value VSth1 from a state in which the vehicle speed VS is greater than the first vehicle speed determination value VSth1. If the processing circuit 51 determines that the start condition is satisfied (S15: YES), the processing circuit 51 proceeds to step S17. On the other hand, if the processing circuit 51 determines that the start condition is not satisfied (S15: NO), the processing circuit 51 temporarily terminates the series of processes shown in FIG. 6 .

[0056] In step S17, the processing circuit 51 executes the first stop braking control. Specifically, in step S19, the processing circuit 51 executes a first increasing correction process. The first increasing correction process is an increasing correction process for the first stop braking control. In the first increasing correction process, the processing circuit 51 sets a braking force greater than the required braking force BPRq as the command braking force BPTr to compensate for the extension of the braking distance of the vehicle 10 resulting from the execution of the first decreasing correction process, which will be described later. That is, the offset value ΔBP shown in FIG. 5D is the braking force correction amount for compensating for the extension of the braking distance of the vehicle 10 resulting from the execution of the first decreasing correction process. The processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0057] In the next step S21, the processing circuit 51 determines whether a transition condition from the first increasing correction process to the first decreasing correction process is satisfied. The first decreasing correction process is a decreasing correction process for the first stop-time braking control. For example, as shown in FIG. 5 , the processing circuit 51 determines that the transition condition is satisfied when the vehicle body speed VS becomes equal to or less than the second vehicle body speed determination value VSth2 after being greater than the second vehicle body speed determination value VSth2. If the processing circuit 51 determines that the transition condition is not satisfied (S21: NO), the processing circuit 51 proceeds to step S19. That is, the processing circuit 51 executes the first increasing correction process. On the other hand, if the processing circuit 51 determines that the transition condition is satisfied (S21: YES), the processing circuit 51 proceeds to step S23.

[0058] In step S23, the processing circuit 51 executes a first decreasing correction process. In the first decreasing correction process, the processing circuit 51 reduces the command braking force BPTr to the first braking force BPC1 (i.e., the vehicle stop maintenance braking force BPth). After the command braking force BPTr becomes the first braking force BPC1, the processing circuit 51 maintains the command braking force BPTr at the first braking force BPC1. Then, the processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0059] In the following step S25, the processing circuit 51 determines whether a transition condition from the first decreasing correction processing to the first degenerate processing is satisfied. The first degenerate processing is a degenerate processing of the first stop-time braking control. For example, as shown in FIG. 5, the processing circuit 51 determines that the transition condition is satisfied when it is determined that the vehicle 10 has stopped. If the processing circuit 51 determines that the transition condition is not satisfied (S25: NO), the processing circuit 51 transitions the processing to step S23. That is, the processing circuit 51 executes the first decreasing correction processing. On the other hand, if the processing circuit 51 determines that the transition condition is satisfied (S25: YES), the processing circuit 51 transitions the processing to step S27.

[0060] In step S27, the processing circuit 51 executes a first degeneration process. In the first degeneration process, the processing circuit 51 increases the command braking force BPTr to the required braking force BPRq. Then, the processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0061] In the next step S29, the processing circuit 51 determines whether the termination condition of the first degeneration process is satisfied. For example, if the command braking force BPTr is equal to the required braking force BPRq, the termination condition is deemed to be satisfied. On the other hand, if the command braking force BPTr is less than the required braking force BPRq, the termination condition is deemed to be not satisfied. If the processing circuit 51 determines that the termination condition is not satisfied (S29: NO), the processing circuit 51 proceeds to step S27. That is, the processing circuit 51 executes the first degeneration process. On the other hand, if the processing circuit 51 determines that the termination condition is satisfied (S29: YES), the processing circuit 51 terminates the first degeneration process. Then, the processing circuit 51 terminates the first stop braking control and ends the series of processes shown in FIG. 6.

[0062] In step S41, the processing circuit 51 sets a first braking force BPC1 for an uphill road. The processing circuit 51 sets the first braking force BPC1 to a braking force that is smaller than the vehicle stop maintenance braking force BPth and is equal to or greater than 0 (zero). For example, the processing circuit 51 sets the first braking force BPC1 based on the gradient of the uphill road, an index indicating the degree of comfort required by the occupants when stopped, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10.

[0063] In the next step S43, the processing circuit 51 sets a second braking force BPC2. The processing circuit 51 sets a braking force equal to or greater than the vehicle stop maintenance braking force BPth as the second braking force BPC2. For example, the processing circuit 51 sets the second braking force BPC2 based on the gradient of the uphill road, an index indicating the degree of comfort required by the occupants when stopped, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10.

[0064] In the next step S45, it is determined whether the start condition for the second stop braking control is satisfied. The second stop braking control is executed when the road surface is an uphill road. For example, the processing circuit 51 determines that the start condition is not satisfied if the difference between the first braking force BPC1 set in step S41 and the required braking force BPRq is less than the braking force difference determination value ΔBPth. If the difference between the first braking force BPC1 and the required braking force BPRq is small, it can be assumed that the posture of the vehicle 10 will not change significantly when stopped even if the second stop braking control is not executed. Therefore, the processing circuit 51 does not execute the second stop braking control if the difference between the first braking force BPC1 and the required braking force BPRq is less than the braking force difference determination value ΔBPth. On the other hand, when the magnitude of the difference between the first braking force BPC1 and the required braking force BPRq is equal to or greater than the braking force difference determination value ΔBPth, the processing circuit 51 determines that the start condition is satisfied when the vehicle speed VS is greater than the first vehicle speed determination value VSth11 and then becomes equal to or less than the first vehicle speed determination value VSth11. The first vehicle speed determination value VSth11 may be the same as the first vehicle speed determination value VSth1 or may be a value different from the first vehicle speed determination value VSth11. If the processing circuit 51 determines that the start condition is satisfied (S45: YES), the processing circuit 51 proceeds to step S47. On the other hand, if the processing circuit 51 determines that the start condition is not satisfied (S45: NO), the processing circuit 51 temporarily terminates the series of processes shown in FIG. 6 .

[0065] In step S47, the processing circuit 51 executes the second stop braking control. Specifically, in step S49, the processing circuit 51 executes a second increasing correction process. The second increasing correction process is an increasing correction process for the second stop braking control. In the second increasing correction process, the processing circuit 51 sets a vehicle braking force greater than the required braking force BPRq as the command braking force BPTr to compensate for the extension of the braking distance of the vehicle 10 resulting from the execution of the second decreasing correction process, which will be described later. For example, the processing circuit 51 sets the command braking force BPTr to the sum of the required braking force BPRq and an offset value ΔBP1, which is a braking force correction amount for compensating for the extension of the braking distance of the vehicle 10 resulting from the execution of the second decreasing correction process. The processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0066] In the next step S51, the processing circuit 51 determines whether a transition condition from the second increasing correction process to the second decreasing correction process is satisfied. The second decreasing correction process is a decreasing correction process for the second stop-time braking control. For example, the processing circuit 51 determines that the transition condition is satisfied when the vehicle speed VS becomes equal to or less than the second vehicle speed determination value VSth21 after being greater than the second vehicle speed determination value VSth21. The second vehicle speed determination value VSth21 may be the same as the second vehicle speed determination value VSth2 or may be a value different from the second vehicle speed determination value VSth2. If the processing circuit 51 determines that the transition condition is not satisfied (S51: NO), the processing circuit 51 transitions the processing to step S49. That is, the processing circuit 51 executes the second increasing correction process. On the other hand, if the processing circuit 51 determines that the transition condition is satisfied (S51: YES), the processing circuit 51 transitions the processing to step S53.

[0067] In step S53, the processing circuit 51 executes a second reduction correction process (i.e., a braking force reduction process). In the second reduction correction process, the processing circuit 51 reduces the command braking force BPTr to the first braking force BPC1. After the command braking force BPTr becomes the first braking force BPC1, the processing circuit 51 maintains the command braking force BPTr at the first braking force BPC1. Then, the processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0068] In the following step S55, the processing circuit 51 determines whether a transition condition from the second decreasing correction process to the second degenerate process is satisfied. The second degenerate process is a degenerate process of the second stop-time braking control. For example, the processing circuit 51 determines that the transition condition is satisfied when at least one of the following conditions is satisfied: the vehicle 10 has switched from forward to reverse due to the execution of the second decreasing correction process (i.e., the braking force reduction process) and it has been determined that the vehicle 10 has stopped. In this case, the processing circuit 51 determines that the transition condition is not satisfied when neither the vehicle 10 has switched from forward to reverse due to the execution of the second decreasing correction process (i.e., the braking force reduction process) nor it has been determined that the vehicle 10 has stopped is satisfied.

[0069] 4 becomes 0 (zero) as a result of the vehicle 10 substantially coming to a stop, the vehicle 10 switches from forward to reverse. That is, the processing circuit 51 can determine that the transition condition is met when it can determine that the deceleration inertia force DI has become 0 (zero). In this embodiment, the processing circuit 51 determines that the transition condition is met when the longitudinal acceleration Gx changes from less than 0 (zero) to 0 (zero) or greater.

[0070] If the processing circuit 51 determines that the transition condition is not met (S55: NO), the processing circuit 51 proceeds to step S53. That is, the processing circuit 51 executes the second subtraction correction process. On the other hand, if the processing circuit 51 determines that the transition condition is met (S55: YES), the processing circuit 51 proceeds to step S57.

[0071] In step S57, the processing circuit 51 executes a second degeneration process (i.e., a braking force increase process). In the second degeneration process, the processing circuit 51 increases the commanded braking force BPTr to the second braking force BPC2. The second braking force BPC2 set in step S43 may be greater than the stop-maintenance braking force BPth. In this case, the processing circuit 51 quickly increases the commanded braking force BPTr to the stop-maintenance braking force BPth. After the commanded braking force BPTr reaches the stop-maintenance braking force BPth, the processing circuit 51 gradually increases the commanded braking force BPTr to the second braking force BPC2. In other words, the processing circuit 51 increases the rate of increase of the commanded braking force BPTr from the first braking force BPC1 to the stop-maintenance braking force BPth faster than the rate of increase of the commanded braking force BPTr from the stop-maintenance braking force BPth to the second braking force BPC2. Then, the processing circuit 51 operates the brake actuator 30 based on the command braking force BPTr.

[0072] In the next step S59, the processing circuit 51 determines whether the termination condition for the second degeneration process is satisfied. For example, if the command braking force BPTr is equal to the second braking force BPC2, the termination condition is deemed to be satisfied. On the other hand, if the command braking force BPTr is less than the second braking force BPC2, the termination condition is deemed to be not satisfied. If the processing circuit 51 determines that the termination condition is not satisfied (S59: NO), the processing circuit 51 proceeds to step S57. That is, the processing circuit 51 executes the second degeneration process. On the other hand, if the processing circuit 51 determines that the termination condition is satisfied (S59: YES), the processing circuit 51 terminates the second degeneration process. Then, the processing circuit 51 terminates the second stop braking control and ends the series of processes shown in FIG. 6.

[0073] In this embodiment, the process of step S41 is executed by the processing circuit 51 functioning as the first braking force setting unit M19. The process of step S43 is executed by the processing circuit 51 functioning as the second braking force setting unit M21. The process of step S45 is executed by the processing circuit 51 functioning as the determination unit M15. The second decrease correction process of step S53 is executed by the processing circuit 51 functioning as the decrease control unit M13 (first control unit). The second degeneration process of step S57 is executed by the processing circuit 51 functioning as the degeneration control unit M17 (second control unit).

[0074] <Functions and Effects of the Present Embodiment> The functions and effects when applying a braking force to stop the vehicle 10 traveling on an uphill road will be described with reference to Fig. 7. Fig. 7 shows a time chart when the second vehicle-stop braking control is performed.

[0075] 7A, 7B, 7C, and 7D, the vehicle speed VS decreases when a braking force is applied to the vehicle 10. Then, when the vehicle speed VS reaches the first vehicle speed determination value VSth11 at timing t21, the processing circuit 51 starts the second stationary braking control.

[0076] The processing circuit 51 executes a second increasing correction process for the second stationary braking control. In the second increasing correction process, the processing circuit 51 sets the sum of the required braking force BPRq and the offset value ΔBP1 as the command braking force BPTr. The processing circuit 51 then controls the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr. As a result, as shown in FIGS. 7B and 7D, the vehicle braking force BPAl is increased even though the required braking force BPRq is constant. Specifically, the vehicle braking force BPAl becomes larger than the required braking force BPRq. As a result, the magnitude of the longitudinal acceleration Gx increases as shown in FIG. 7C.

[0077] When the vehicle speed VS reaches the second vehicle speed determination value VSth21 at timing t22, the processing circuit 51 shifts the processing from the second increasing correction processing to the second decreasing correction processing. That is, the processing circuit 51 executes the braking force decreasing processing.

[0078] In the second decrease correction process, the processing circuit 51 reduces the command braking force BPTr to the first braking force BPC1 and then sets the vehicle speed VS to 0 (zero). Specifically, the processing circuit 51 reduces the command braking force BPTr to the first braking force BPC1 at a constant rate. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes equal to the command braking force BPTr. As a result, the vehicle braking force BPAl becomes smaller than the required braking force BPRq. As a result, even if the required braking force BPRq remains the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually decreases.

[0079] When the command braking force BPTr becomes equal to the first braking force BPC1 at timing t23 during execution of the second decreasing correction process, the processing circuit 51 maintains the command braking force BPTr at the first braking force BPC1. The processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl is maintained.

[0080] Here, the first braking force BPC1 is smaller than the vehicle stop maintenance braking force BPth. Therefore, if the vehicle braking force BPAl continues to be maintained at the vehicle stop maintenance braking force BPth, the vehicle 10 switches from forward movement to reverse movement.

[0081] Therefore, the processing circuit 51 shifts the processing from the second decrease correction processing to the second degeneration processing when the vehicle 10 switches from forward movement to reverse movement. This second degeneration processing corresponds to the "braking force increase processing." In the example shown in FIG. 7 , timing t24 is the time when the vehicle 10 switches from forward movement to reverse movement. As shown in FIG. 7C , timing t24 is the time when the longitudinal acceleration Gx, which is the detection value of the longitudinal acceleration sensor 103, switches from a state where it is less than the reference value (=0 (zero)) to a state where it is equal to or greater than the reference value (=0 (zero)).

[0082] In the second degeneration process, the processing circuit 51 increases the command braking force BPTr to the second braking force BPC2. The processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr.

[0083] Consider a case where the first stop braking control is implemented when applying braking force to stop the vehicle 10 traveling on an uphill road. In this case, the vehicle braking force BPAl is only reduced to the stop-maintenance braking force BPth. When the vehicle 10 is traveling on an uphill road, the stop-maintenance braking force BPth is greater than when the vehicle 10 is traveling on a level road. Therefore, even if the vehicle braking force BPAl is reduced to the stop-maintenance braking force BPth, the vehicle braking force BPAl immediately before the vehicle 10 stops is relatively large. As a result, the change in the posture of the vehicle 10 when stopped is not significantly suppressed.

[0084] In this regard, the brake control device 50 performs a second vehicle-stop braking control when applying a braking force to the vehicle 10 traveling on an uphill road to stop the vehicle. In the second vehicle-stop braking control, the vehicle braking force BPAl is reduced to the first braking force BPC1 by a second reduction correction process (braking force reduction process). The first braking force BPC1 set in the second vehicle-stop braking control is smaller than the vehicle-stop maintenance braking force BPth. Therefore, the vehicle braking force BPAl immediately before stopping is smaller than when the first vehicle-stop braking control is performed. As a result, the change in the posture of the vehicle 10 when stopped is smaller than when the first vehicle-stop braking control is performed.

[0085] If it is determined that the vehicle 10 has switched from forward movement to reverse movement while the second reduction correction process is being executed, the processing circuit 51 transitions the process from the second reduction correction process to the second degeneration process (braking force increase process) even before it is determined that the vehicle 10 has stopped. In the second degeneration process, the processing circuit 51 increases the command braking force BPTr to the second braking force BPC2. The processing circuit 51 operates the brake actuator 30 so that the vehicle braking force BPAl becomes the command braking force BPTr. As a result, the vehicle braking force BPAl is increased from the first braking force BPC1 to the second braking force BPC2. The second braking force BPC2 is a braking force equal to or greater than the stop-maintenance braking force BPth. Therefore, by executing the second degeneration process, the vehicle 10 is maintained stopped.

[0086] Furthermore, the braking control device 50 does not increase the driving force FD of the vehicle 10 when stopping the vehicle 10 on an uphill road. For example, if the power source of the vehicle 10 is a motor generator, the motor generator does not need to perform power running.

[0087] Therefore, when stopping the vehicle 10 on an uphill road, the brake control device 50 can suppress a deterioration in the energy efficiency of the vehicle 10 and suppress a change in the posture of the vehicle 10 while stopping the vehicle 10. In this embodiment, the following effects can further be obtained.

[0088] (1) The stop-maintenance braking force BPth may vary depending on the gradient of an uphill road, the force acting on the vehicle 10 to move the vehicle 10, the weight of the vehicle 10, etc. Therefore, the brake control device 50 can change the first braking force BPC1 depending on the gradient of the uphill road, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10. This prevents the first braking force BPC1 from becoming too large or too small relative to the stop-maintenance braking force BPth. As a result, the brake control device 50 can simultaneously suppress changes in the posture of the vehicle 10 while stopped and suppress the occurrence of the vehicle 10 sliding downhill in the downhill direction Z1 by performing the second stop-time braking control when stopping the vehicle 10 on an uphill road.

[0089] (2) When the level of comfort required by an occupant (e.g., the driver) when the vehicle is stopped is low, it can be assumed that the occupant (e.g., the driver) wants the vehicle 10 to stop reliably rather than suppressing changes in the vehicle's posture when the vehicle is stopped. Therefore, the brake control device 50 sets the first braking force BPC1 according to the operation amount X of the brake operating member 11, which is an example of an index indicating the level of comfort required by the occupant when the vehicle is stopped. As a result, the brake control device 50 can execute braking control according to the level of comfort required by the occupant when the vehicle is stopped.

[0090] (3) If the deviation between the required braking force BPRq and the first braking force BPC1 is large before the second vehicle-stop braking control is stopped, not performing the second vehicle-stop braking control would result in a large change in the vehicle's posture when the vehicle is stopped. Therefore, when stopping the vehicle on an uphill road, if the brake control device 50 determines that the deviation between the required braking force BPRq and the first braking force BPC1 is large, the brake control device 50 performs the second vehicle-stop braking control. This allows the brake control device 50 to suppress changes in the vehicle's posture when stopping the vehicle 10 on an uphill road.

[0091] On the other hand, when stopping the vehicle on an uphill road, if it is determined that the deviation between the required braking force BPRq and the first braking force BPC1 is small, the brake control device 50 does not perform the second stationary braking control. In other words, if it is estimated that the change in the posture of the vehicle 10 while stopped is small even without performing the second stationary braking control, the second stationary braking control is not performed.

[0092] (4) When the deceleration inertia force DI ceases to act on the vehicle 10, the vehicle 10 switches from forward to reverse. When the deceleration inertia force DI ceases to act, the longitudinal acceleration Gx changes from less than the reference value to equal to or greater than the reference value. Therefore, when the longitudinal acceleration Gx changes from less than the reference value to equal to or greater than the reference value, the brake control device 50 can determine that the vehicle 10 has switched from forward to reverse, and therefore executes the second degeneration process to increase the vehicle braking force BPAl to the second braking force BPC2.

[0093] As a result, the brake control device 50 increases the vehicle braking force BPAl to the second braking force BPC2 earlier than when the second degeneration process is executed after it is determined that the vehicle 10 has stopped. As a result, even if the brake control device 50 reduces the vehicle braking force BPAl to suppress changes in the attitude of the vehicle 10 when stopped, it is possible to suppress the vehicle 10 from sliding downhill in the downhill direction Z1.

[0094] (5) As shown in FIG. 7 , the second braking force BPC2 may be set to a value greater than the vehicle stop maintenance braking force BPth. In the brake control device 50, in the second degeneration process, the rate of increase of the vehicle braking force BPAl from the first braking force BPC1 to the vehicle stop maintenance braking force BPth can be greater than the rate of increase of the vehicle braking force BPAl from the vehicle stop maintenance braking force BPth to the second braking force BPC2. In the example shown in FIG. 7 , timing t25 is the timing at which the command braking force BPTr reaches the vehicle stop maintenance braking force BPth. Timing t26 is the timing at which the command braking force BPTr reaches the second braking force BPC2. As a result, by executing the second degeneration process, the brake control device 50 can increase the vehicle braking force BPAl early until it reaches the vehicle stop maintenance braking force BPth. This allows the brake control device 50 to further enhance the effect of suppressing the vehicle 10 from rolling over.

[0095] On the other hand, after the vehicle braking force BPAl reaches the vehicle stop maintenance braking force BPth, the vehicle braking force BPAl is gradually increased. As a result, the brake control device 50 can shorten the period during which noise and vibration caused by the operation of the brake actuator 30 are high, compared to when the vehicle braking force BPAl continues to increase at a high rate.

[0096] <Modifications> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0097] The processing circuit 51 (i.e., the second braking force setting unit M21) may set the second braking force BPC2 based on any of the gradient of the uphill road, an index indicating the degree of comfort required by the occupants when stopped, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10.

[0098] The processing circuit 51 (i.e., the second braking force setting unit M21) may set the required braking force BPRq as the second braking force BPC2. However, if the required braking force BPRq is less than the vehicle stop maintenance braking force BPth, it is preferable that the processing circuit 51 sets the second braking force BPC2 to a vehicle braking force equal to or greater than the vehicle stop maintenance braking force BPth.

[0099] In the second degeneration process, the processing circuit 51 (i.e., the degeneration control unit M17) does not have to reduce the rate of increase of the command braking force BPTr even when the command braking force BPTr becomes equal to or greater than the vehicle stop maintenance braking force BPth.

[0100] In the above embodiment, the reference value for determining whether the vehicle 10 has switched from forward movement to reverse movement is set to 0. However, as long as it is possible to determine whether the vehicle 10 has switched from forward movement to reverse movement, the reference value may be set to a value other than 0.

[0101] The processing circuit 51 (i.e., the determination unit M15) may determine that the vehicle 10 has switched from forward movement to reverse movement when the longitudinal acceleration Gx transitions from a state in which it is less than the lower limit of a predetermined reference range to a state in which it is equal to or greater than the upper limit of the reference range. In this case, the reference range is preferably a range that includes 0 (zero).

[0102] - When stopping the vehicle 10 on an uphill road, the processing circuit 51 may perform the second stationary braking control regardless of whether the magnitude of the difference between the required braking force BPRq and the first braking force BPC1 is greater than or equal to the braking force difference judgment value ΔBPth.

[0103] The processing circuit 51 (i.e., the first braking force setting unit M19) may set the first braking force BPC1 based on any of the gradient of the uphill road, an index indicating the degree of comfort required by the occupants when stopped, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10.

[0104] The processing circuit 51 may fix the first braking force BPC1 at a predetermined value when stopping the vehicle 10 on an uphill road. For example, the processing circuit 51 may fix the first braking force BPC1 at 0 (zero). Of course, the processing circuit 51 may fix the first braking force BPC1 at a value greater than 0 (zero).

[0105] The processing circuit 51 may set the first braking force BPC1 based on the vehicle stop maintenance braking force BPth when stopping the vehicle 10 on an uphill road. For example, the processing circuit 51 may set the first braking force BPC1 to the larger of 0 (zero) or a value obtained by subtracting a predetermined braking force from the vehicle stop maintenance braking force BPth.

[0106] The first braking control at a stop does not have to include the first increasing correction process as long as it includes the first decreasing correction process and the first degenerating process. The second braking control at a stop does not have to include the second increasing correction process as long as it includes the second decreasing correction process and the second degenerating process.

[0107] In the above embodiment, the processing circuit 51 determines the start timing of the increase correction process and the start timing of the decrease correction process of the stop braking control in accordance with changes in the vehicle body speed VS. However, the processing circuit 51 may determine the start timing of each process using a parameter other than the vehicle body speed VS, as long as the parameter value decreases as the vehicle 10 approaches the stop position PS. Examples of the other parameters include a stopping distance and a predicted stopping time. The stopping distance is the distance from the current position of the vehicle 10 to the stop position PS. The predicted stopping time is the time required for the vehicle 10 to stop. An example of the predicted stopping time is TTC. TTC is an abbreviation for "Time To Collision."

[0108] When executing braking control at a stop, the brake control device may control not only the frictional braking force but also the regenerative braking force. In this case, the sum of the total frictional braking force applied to the vehicle 10 and the total regenerative braking force applied to the vehicle 10 is the vehicle braking force BPAl.

[0109] In the above embodiment, the processing circuit 51 executes the braking control at a standstill when the driver brakes the vehicle in response to the operation of the brake operating member 11. However, the processing circuit 51 may execute the braking control at a standstill when automatic braking is performed.

[0110] The processing circuitry 51 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware for performing at least some of the various processes, or a combination thereof. Examples of dedicated hardware include an application-specific integrated circuit (ASIC). The processor includes a CPU and memory such as RAM and ROM, which store program code or instructions configured to cause the CPU to perform processes. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or dedicated computer.

[0111] <Other Technical Ideas> The following describes technical ideas that can be understood from the above embodiment and modified examples. [Supplementary Note 1] It is preferable that the second braking force is set to a value greater than the vehicle stop maintenance braking force, and that the second control unit, in the braking force increase process, increases the rate of increase of the braking force applied to the vehicle from the first braking force to the vehicle stop maintenance braking force greater than the rate of increase of the braking force applied to the vehicle from the vehicle stop maintenance braking force to the second braking force.

[0112] [Appendix 2] It is preferable to provide a second braking force setting unit that sets the second braking force based on at least one of the gradient of the uphill road, an index indicating the degree of comfort required by the occupants of the vehicle when stopped, a force acting on the vehicle to move the vehicle, and the weight of the vehicle.

[0113] [Supplementary Note 3] A brake control device comprising: a first control unit that, when applying braking force to a vehicle traveling on an uphill road to stop the vehicle, reduces the braking force applied to the vehicle to a first braking force that is smaller than a stop-maintenance braking force that is a braking force for balancing a downhill force acting on the vehicle and an uphill force acting on the vehicle and is greater than or equal to 0 (zero), and then executes a braking force reduction process to set the vehicle's body speed to 0 (zero); a determination unit that determines whether a deceleration inertia force that is an inertia force acting on the vehicle as it decelerates has become 0 (zero) during the braking force reduction process; and a second control unit that, when it is determined that the deceleration inertia force has become 0 (zero), executes a braking force increase process to increase the braking force applied to the vehicle to a second braking force that is greater than or equal to the stop-maintenance braking force.

[0114] It should be noted that the expression "at least one" used in this specification means "one or more" of the desired options. As an example, the expression "at least one" used in this specification means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used in this specification means "only one option" or "any combination of two or more options" if the number of options is three or more.

Claims

1. A braking control device comprising: a first control unit that, when applying braking force to a vehicle traveling on an uphill road to stop the vehicle, executes a braking force reduction process to reduce the braking force applied to the vehicle to a first braking force that is smaller than a stop-maintaining braking force that is a braking force for balancing a downhill force acting on the vehicle and an uphill force acting on the vehicle and is greater than or equal to 0 (zero), and then sets the vehicle's body speed to 0 (zero); and a second control unit that executes a braking force increase process to increase the braking force applied to the vehicle to a second braking force that is greater than or equal to the stop-maintaining braking force, from the point at which the vehicle switches from forward movement to reverse movement as a result of execution of the braking force reduction process.

2. A brake control device as described in claim 1, further comprising a first braking force setting unit which sets the first braking force based on at least one of the gradient of the uphill road, an index indicating the degree of comfort required by the occupants of the vehicle when stopped, a force acting on the vehicle to move the vehicle, and a weight of the vehicle.

3. A braking control device as described in claim 1 or claim 2, wherein the first control unit starts the braking force reduction process when the magnitude of the difference between the required value of the braking force to be applied to the vehicle and the first braking force is equal to or greater than a braking force difference judgment value.

4. A brake control device as described in claim 1, further comprising a judgment unit which judges that the vehicle has switched from forward to reverse when a detection value of a sensor which detects an inertial force acting on the vehicle in the fore-and-aft direction of the vehicle transitions from a state in which the detection value is less than a reference value or the lower limit of a reference range to a state in which the detection value is equal to or greater than the reference value or the upper limit of the reference range.

Images