Braking control device

Abstract

To provide a braking control device, which is configured to suppress a change in attitude of a vehicle which is stopped, while suppressing deterioration in energy efficiency of the vehicle, when stopping the vehicle on an upslope road.SOLUTION: A processing circuit 51 of a braking control device 50 functions as: a decrease control part M13 that decreases vehicle braking force down to first braking force which is smaller than braking force for keeping vehicle stop that is braking force for balancing force in a downslope direction acting on a vehicle 10 and force in an upslope direction acting on the vehicle 10 and is equal to or more than 0 (zero), and then executes a braking force decreasing process for decreasing the speed of a vehicle body of the vehicle 10 down to 0 (zero), when applying braking force to the vehicle 10 running on an upslope road to stop the vehicle; and a degeneracy control part M17 that executes a braking force increasing process for increasing the vehicle barking force up to second braking force that is equal to or more than the braking force for keeping vehicle stop, after a time point when the vehicle 10 is switched from a forward running mode to a backward running mode by executing the braking force decreasing process.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a vehicle control device that performs stop control for suppressing a change in the posture of a vehicle at the time of stopping by reducing the braking force applied to the vehicle immediately before stopping. When the vehicle is traveling on an uphill road, the braking control device performs the above stop control with the motor generator, which is a power source of the vehicle, in a power running state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above vehicle control device, when performing stop control when the vehicle stops on an uphill road, the motor generator is made to perform power running. Therefore, when stopping on an uphill road, although a change in the posture of the vehicle at the time of stopping can be suppressed, the energy efficiency of the vehicle deteriorates.

Means for Solving the Problems

[0005] When stopping a vehicle traveling on an uphill road by applying a braking force, a braking control device reduces the braking force applied to the vehicle to a first braking force that is smaller than a parking maintenance braking force, which is a braking force for balancing the downhill force acting on the vehicle and the uphill force acting on the vehicle, and is a braking force of 0 (zero) or more, and then executes a braking force reduction process for setting the vehicle body speed of the vehicle to 0 (zero). The braking control device includes a first control unit and a second control unit. The second control unit executes a braking force increase process for increasing the braking force applied to the vehicle to a second braking force that is equal to or greater than the parking maintenance braking force from the time when the vehicle switches from forward movement to backward movement due to the execution of the braking force reduction process.

Advantages of the Invention

[0006] The braking control device can suppress a change in the posture of the vehicle during parking while suppressing a deterioration in the energy efficiency of the vehicle when stopping the vehicle on an uphill road.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0008] Hereinafter, an embodiment of the braking control device will be described with reference to FIGS. 1 to 7. FIG. 1 illustrates a vehicle 10 including a braking control device 50. The vehicle 10 includes a braking operation member 11, a plurality of wheels, a plurality of friction brakes 20, and a braking actuator 30. The braking operation member 11 is a member that a driver operates when applying a braking force to the vehicle 10. An example of the braking operation member 11 is a brake pedal. The plurality of wheels includes two front wheels 12 and two rear wheels 13.

[0009] <Friction brake> The plurality of friction brakes 20 respectively apply a braking force to the corresponding wheels. 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, by pressing the friction portion 23 against the rotating body 22, a braking force is applied to the wheel. The force for 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, becomes higher. Therefore, the friction brake 20 can apply a greater braking force to the wheel as the wheel hydraulic pressure increases.

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

[0011] In the following description, the sum of the braking forces applied to the plurality of wheels 12, 13 is also referred to as "vehicle braking force BPAl". <Regarding the relationship of forces acting on a vehicle located on an uphill road> Referring to FIGS. 2 and 3, the relationship of the forces acting on the vehicle 10 when the vehicle 10 is located on an uphill road will be described. FIG. 2 shows the relationship of the forces acting on the vehicle 10 when the vehicle 10 is decelerating due to the application of braking force. FIG. 3 shows the relationship of the forces acting on the vehicle 10 when the vehicle 10 stops on the uphill road due to the application of braking force. Note that the downhill direction Z1 is the direction on the lower side of the slope of the slope road. The uphill direction Z2 is the direction on the upper side of the slope of the slope road and is the opposite direction of the downhill direction Z1.

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

[0013] As shown in FIG. 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] That is, immediately before and after the vehicle 10 stops, the direction of the vehicle braking force BPAl acting on the vehicle 10 changes. <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 include a brake sensor 101, a plurality of wheel speed sensors 102, and a front and rear acceleration sensor 103.

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

[0016] The wheel speed sensors 102 are provided for each of the plurality of wheels. The plurality of wheel speed sensors 102 respectively detect the rotational speed of the corresponding wheels. The rotational speed of the wheels based on the detection signal of the wheel speed sensor 102 is referred to as "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 "vehicle body speed VS".

[0017] The longitudinal acceleration sensor 103 detects the acceleration in the longitudinal direction of the vehicle 10 among the accelerations acting on the vehicle 10. The acceleration in the longitudinal direction 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, as the longitudinal acceleration sensor 103, a sensor 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, which is the detected value of the longitudinal acceleration sensor 103, becomes a positive value. When the vehicle 10 decelerates on a horizontal road, the longitudinal acceleration Gx becomes a negative value. When the vehicle 10 is stopped on a horizontal road, the longitudinal acceleration Gx becomes 0 (zero).

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

[0020] Referring to FIG. 4, the transition of the longitudinal acceleration Gx when the vehicle 10 decelerates and stops on the uphill road will be described. Note that the gravitational acceleration component Gg is a positive value. When the vehicle 10 is decelerating on the uphill road, a deceleration inertial force DI, which is an inertial force caused by the deceleration, acts on the vehicle 10. The deceleration inertial force DI acts on the vehicle 10 in the uphill direction Z2. That is, the direction of the deceleration inertial force DI is opposite to the direction of the gravitational acceleration component Gg. Therefore, the deceleration inertial force DI has a negative value. And the value corresponding to the sum of the gravitational acceleration component Gg and the deceleration inertial force DI becomes the longitudinal acceleration Gx.

[0021] After that, when the vehicle 10 substantially stops on the uphill road, the deceleration inertial force DI becomes 0 (zero). As a result, the 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, the vehicle 10 may move in the downhill direction Z1. That is, when the vehicle 10 switches from forward to backward on the uphill road, the longitudinal acceleration Gx shifts from a negative value to a positive value.

[0022] <Braking control device> As shown in FIG. 1, the braking control device 50 includes a processing circuit 51. An example of the processing circuit 51 is an electronic control unit. In this case, the processing circuit 51 has 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 the calculation results of the CPU 52 and the like. By the CPU 52 executing the control program in the first memory 53, the processing circuit 51 controls the braking actuator 30 to operate the plurality of friction brakes 20. That is, the processing circuit 51 can adjust the vehicle braking force BPAl by operating the plurality of friction brakes 20.

[0023] <Outline of braking control at stop> The processing circuit 51 performs braking control at stop when the driver operates the braking operation member 11. The braking control at stop is braking control for suppressing changes in the posture of the vehicle 10 accompanying stopping.

[0024] Referring to FIG. 5, the stop-time braking control will be described. FIG. 5 shows an example of the case where the vehicle 10 is stopped on a horizontal road. At timing t11 when the vehicle 10 is running, the driver starts to operate the braking operation member 11. In this case, as shown in FIG. 5(B), the processing circuit 51 derives the required braking force BPRq. The required braking force BPRq is the required value of the vehicle braking force BPAl. For example, the processing circuit 51 derives the required braking force BPRq such that the value becomes larger as the operation amount X of the braking operation member 11 is larger. When the vehicle body speed VS of the vehicle 10 is larger than the first vehicle body speed determination value VSth1 as before timing t12, as shown in FIG. 5(D), the processing circuit 51 sets the required braking force BPRq as the instructed braking force BPTr. Then, the processing circuit 51 controls the braking actuator 30 so that the vehicle braking force BPAl becomes the instructed braking force BPTr.

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

[0026] When the vehicle body speed VS reaches the first vehicle body speed determination value VSth1 at timing t12, the processing circuit 51 starts the stop-time braking control. The first vehicle body speed determination value VSth1 is an example of a threshold value for setting the start timing of the stop-time braking control. From timing t12, the processing circuit 51 starts the supplementary correction processing of the stop-time braking control. In the supplementary correction processing, the processing circuit 51 sets a braking force larger than the required braking force BPRq as the instructed 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 instructed braking force BPTr. Then, the processing circuit 51 controls the braking actuator 30 so that the vehicle braking force BPAl becomes the instructed braking force BPTr. Thereby, even if the required braking force BPRq is the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 becomes larger than before timing t12 by the amount of the offset value ΔBP.

[0027] At timing t13, the vehicle body speed VS becomes the second vehicle body speed determination value VSth2. A vehicle body speed smaller than the first vehicle body speed determination value VSth1 is set as the second vehicle body speed determination value VSth2. When the vehicle body speed VS is equal to or lower than the second vehicle body speed determination value VSth2, it can be considered that the vehicle 10 has approached the stop position PS. The stop position PS is the predicted position where the vehicle 10 stops. The processing circuit 51 shifts the processing of the stop-time braking control from the addition correction process to the subtraction correction process. In the subtraction correction process, the processing circuit 51 decreases the commanded braking force BPTr at a constant speed. Then, the processing circuit 51 controls the braking actuator 30 so that the vehicle braking force BPAl becomes the commanded braking force BPTr. By executing the subtraction correction process in this way by the processing circuit 51, the vehicle braking force BPAl becomes smaller than the required braking force BPRq. As a result, even if the required braking force BPRq is the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually becomes smaller.

[0028] At timing t14, the commanded braking force BPTr becomes equal to the stop-maintaining braking force BPth. As the stop-maintaining braking force BPth, the minimum braking force required to maintain the stop of the vehicle 10 on the current traveling road surface of the vehicle 10, or a braking force slightly larger than the braking force, is set. At timing t14, in the subtraction correction process, the processing circuit 51 holds the commanded braking force BPTr at the stop-maintaining braking force BPth.

[0029] At timing t15, the processing circuit 51 determines that the vehicle 10 has stopped, and thus shifts the processing of the stop-time braking control from the subtraction correction process to the degradation process. In the degradation process, the processing circuit 51 increases the commanded braking force BPTr. For example, the processing circuit 51 increases the commanded braking force BPTr to the required braking force BPRq. By controlling the braking actuator 30 based on the commanded braking force BPTr by the processing circuit 51, the vehicle braking force BPAl increases. When the commanded braking force BPTr becomes equal to the required braking force BPRq at timing t16, the processing circuit 51 ends the stop-time braking control.

[0030] <Functional configuration of the processing circuit> Referring to FIG. 1, the functional configuration of the processing circuit 51 will be described. By the CPU 52 executing the control program of the first memory 53, the processing circuit 51 functions as a plurality of functional units. These plurality of functional units are functional units for stopping the vehicle 10 by applying braking force thereto. The plurality of functional units include, for example, an increase control unit M11, a decrease control unit M13, a determination unit M15, a degradation 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 additional 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 instructed braking force BPTr. Then, the increase control unit M11 operates the brake actuator 30 based on the instructed braking force BPTr. Thereby, the increase control unit M11 can make the vehicle braking force BPAl larger than the required braking force BPRq.

[0032] <Decrease control unit> The decrease control unit M13 executes a reduction correction process for the stop-time braking control. The decrease control unit M13 gradually decreases the instructed braking force BPTr. Then, the decrease control unit M13 holds the instructed braking force BPTr. Also, the decrease control unit M13 operates the brake actuator 30 based on the instructed braking force BPTr at that time. Thereby, the decrease control unit M13 can make the vehicle braking force BPAl smaller than when the additional correction process is executed.

[0033] When the vehicle 10 is traveling on a horizontal road, the decrease control unit M13 decreases the instructed braking force BPTr to the stop-maintaining braking force BPth. When the instructed braking force BPTr reaches the stop-maintaining braking force BPth, the decrease control unit M13 holds the instructed braking force BPTr at the stop-maintaining braking force BPth.

[0034] Here, when the vehicle 10 is traveling on an uphill road, the parking maintenance braking force BPth corresponds to the braking force for balancing the force in the downhill direction Z1 acting on the vehicle 10 and the force in the uphill direction Z2 acting on the vehicle 10. When the vehicle 10 stops on an uphill road as shown in FIG. 3, the 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 in the downhill direction Z1 acting on the vehicle 10. On the other hand, the 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 in the uphill direction Z2 acting on the vehicle 10. Therefore, the value obtained by subtracting the driving force FD of the vehicle 10 from the first sum becomes the parking maintenance braking force BPth.

[0035] When the vehicle 10 is traveling on an uphill road, the decrease control unit M13 decreases the commanded braking force BPTr to a first braking force BPC1 that is smaller than the parking maintenance braking force BPth and greater than 0 (zero), and then sets the vehicle body speed VS to 0 (zero). Therefore, the deceleration correction process executed when the vehicle 10 is traveling on an uphill road corresponds to the "braking force decrease process". Also, when the vehicle 10 is traveling on an uphill road, the decrease control unit M13 functions as the "first control unit".

[0036] When the vehicle 10 is traveling on an uphill road, the decrease control unit M13 decreases the commanded braking force BPTr to the first braking force BPC1. And even when the commanded braking force BPTr reaches the first braking force BPC1, if the transition condition from the deceleration correction process to the degradation process is not satisfied, the decrease control unit M13 holds the commanded braking force BPTr at the first braking force BPC1.

[0037] <Determination unit> When the determination unit M15 executes the deceleration correction process, that is, when the braking force reduction process is being executed, under the condition that the vehicle 10 is traveling on an uphill road, it determines whether or not the vehicle 10 has switched from forward to reverse at the moment. Specifically, when the longitudinal acceleration Gx, which is the detected value of the longitudinal acceleration sensor 103, transitions from a state where it is less than the reference value to a state where it is greater than or equal to the reference value, the determination unit M15 determines that this is the moment when the vehicle 10 has switched from forward to reverse. For example, when 0 (zero) is set as the reference value, the determination unit M15 determines that this is the moment when the vehicle 10 has switched from forward to reverse when the longitudinal acceleration Gx switches from a negative value to a positive value.

[0038] When the vehicle 10 stops, as described above, the deceleration inertial force DI becomes 0 (zero). 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 or not the deceleration inertial force DI has become 0 (zero).

[0039] <Degradation control unit> The degradation control unit M17 executes the degradation process of the braking control during stop. The degradation control unit M17 increases the commanded braking force BPTr. Then, the degradation control unit M17 operates the brake actuator 30 based on the commanded braking force BPTr. Thereby, the degradation control unit M17 maintains the state where the vehicle 10 is stopped.

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

[0041] When the vehicle 10 is traveling on an uphill road, the degradation control unit M17 executes the degradation process from the time when the vehicle 10 switches from forward movement to backward movement by executing the subtraction correction process (i.e., the braking force reduction process). That is, when it is determined by the determination unit M15 that the vehicle 10 has switched from forward movement to backward movement, the degradation control unit M17 executes the degradation process. In this case, in the degradation process, the degradation control unit M17 increases the commanded 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 parking maintenance braking force BPth. Therefore, the degradation process executed when the vehicle 10 is traveling on an uphill road corresponds to the "braking force increase process". Also, when the vehicle 10 is traveling on an uphill road, the degradation control unit M17 functions as the "second control unit".

[0042] After that, when the commanded braking force BPTr reaches the second braking force BPC2, the degradation control unit M17 ends the degradation process, that is, the braking control during parking. <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 within a range that is 0 (zero) or more and less than the parking 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 required for the passengers (e.g., the driver) of the vehicle 10 at the time of parking, 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 the uphill road, the first braking force setting unit M19 may set a larger value as the first braking force BPC1 as the gradient of the uphill road is steeper.

[0044] When setting the first braking force BPC1 based on an index indicating the degree of comfort required for the occupants during parking, the first braking force setting unit M19 may set a larger value as the first braking force BPC1 as the degree of comfort required for the occupants is smaller. The greater the vehicle braking force BPAl at the time of parking, the greater the likelihood of a large change in the posture of the vehicle 10 during parking. The vehicle braking force BPAl is more likely to increase as the operation amount X of the braking operation member 11 by the driver increases. Therefore, the first braking force setting unit M19 may adopt the operation amount X as the above index. In this case, the first braking force setting unit M19 sets the first braking force BPC1 so that the value increases as the operation amount X increases.

[0045] When setting the first braking force BPC1 based on the force that moves the vehicle 10 acting on the vehicle 10, the first braking force setting unit M19 may set a larger value as the first braking force BPC1 as the force that moves the vehicle 10 is smaller. An example of the 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 without increasing the vehicle braking force BPAl. Therefore, the first braking force setting unit M19 sets a larger value as the first braking force BPC1 as the driving force FD is smaller.

[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 first braking force BPC1 as the weight is larger. This is because the larger the weight, the larger the magnitude of the gravitational acceleration component Gg, and the easier it is 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 within a range equal to or greater than the parking 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 required for the occupants during parking, the force that moves the vehicle 10 acting on the vehicle 10, and the weight of the vehicle 10.

[0048] When setting the second braking force BPC2 based on the gradient of the ascending slope road, the second braking force setting unit M21 may set a larger value as the second braking force BPC2 as the gradient of the ascending slope road is steeper.

[0049] When setting the second braking force BPC2 based on an index indicating the degree of comfort required for the passengers during parking, the second braking force setting unit M21 may set a larger value as the degree of comfort required for the passengers is smaller as the second braking force BPC2. When adopting the operation amount X as the above index, the second braking force setting unit M21 may set a larger value as the second braking force BPC2 as the operation amount X is larger.

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

[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 is larger as the second braking force BPC2. This is because as the weight increases, the magnitude of the gravitational acceleration component Gg increases and it becomes more difficult to maintain parking.

[0052] <Flow of processing during vehicle braking> Referring to FIG. 6, a series of processes when the processing circuit 51 executes parking braking control will be described. The processing circuit 51 repeatedly executes a series of processes shown in FIG. 6 during vehicle braking.

[0053] In step S11, the processing circuit 51 determines whether the traveling road surface of the vehicle 10 is an uphill road. For example, the processing circuit 51 can determine whether the traveling road surface is an uphill road based on the difference between the differential value of the vehicle body speed VS of the vehicle 10 and the longitudinal acceleration Gx. Also, the processing circuit 51 may determine whether the traveling road surface is an uphill road based on the information about the road surface obtained from the navigation device. Further, when the vehicle 10 is equipped with a sensor for detecting the inclination degree of the vehicle body, the processing circuit 51 may determine whether the traveling road surface is an uphill road based on the detection value of the sensor. Additionally, the processing circuit 51 may determine whether the traveling road surface is an uphill road by analyzing the image captured by the in-vehicle camera.

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

[0055] In step S13, the processing circuit 51 sets the parking maintenance braking force BPth as the first braking force BPC1. In the subsequent step S15, the processing circuit 51 determines whether the start condition for the first braking control at stop is satisfied. The first braking control at stop is the braking control at stop that is implemented when the traveling road surface is not an uphill road. For example, as shown in FIG. 5, when the vehicle body speed VS decreases from a state where it is greater than the first vehicle body speed determination value VSth1 to a value less than or equal to the first vehicle body speed determination value VSth1, the processing circuit 51 determines that the start condition is satisfied. When the processing circuit 51 determines that the start condition is satisfied (S15: YES), the process proceeds to step S17. On the other hand, when the processing circuit 51 determines that the start condition is not satisfied (S15: NO), the series of processes shown in FIG. 6 is temporarily terminated.

[0056] In step S17, the processing circuit 51 performs the first braking control at stop. Specifically, in step S19, the processing circuit 51 executes a first augmentation correction process. The first augmentation correction process is an augmentation correction process for the first stop-time braking control. In the first augmentation correction process, the processing circuit 51 sets a braking force greater than the required braking force BPRq as the indicated braking force BPTr in order to compensate for the extension of the braking distance of the vehicle 10 caused by the execution of the first reduction correction process described later. That is, the offset value ΔBP shown in FIG. 5(D) is the correction amount of the braking force for compensating for the extension of the braking distance of the vehicle 10 caused by the execution of the first reduction correction process. The processing circuit 51 operates the brake actuator 30 based on the indicated braking force BPTr.

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

[0058] In step S23, the processing circuit 51 executes the first reduction correction process. In the first reduction correction process, the processing circuit 51 reduces the indicated braking force BPTr to the first braking force BPC1 (that is, the parking maintenance braking force BPth). After the indicated braking force BPTr reaches the first braking force BPC1, the processing circuit 51 holds the indicated braking force BPTr at the first braking force BPC1. Then, the processing circuit 51 operates the brake actuator 30 based on the indicated braking force BPTr.

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

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

[0061] In the next step S29, the processing circuit 51 determines whether the end condition of the first degradation process is satisfied. For example, when the commanded braking force BPTr becomes equal to the required braking force BPRq, it is considered that the end condition is satisfied. On the other hand, when the commanded braking force BPTr is less than the required braking force BPRq, it is considered that the end condition is not satisfied. If the processing circuit 51 determines that the end condition is not satisfied (S29: NO), the process proceeds to step S27. That is, the processing circuit 51 executes the first degradation process. On the other hand, if the processing circuit 51 determines that the end condition is satisfied (S29: YES), the first degradation process is terminated. Then, the processing circuit 51 terminates the first stop-time braking control and terminates the series of processes shown in FIG. 6.

[0062] In step S41, the processing circuit 51 sets a first braking force BPC1 for the uphill road. The processing circuit 51 sets a braking force that is smaller than the parking maintenance braking force BPth and is 0 (zero) or more as the first braking force BPC1. 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 for the passengers at the time of parking, the force acting on the vehicle 10 to move the vehicle 10, and the weight of the vehicle 10.

[0063] In the subsequent step S43, the processing circuit 51 sets a second braking force BPC2. The processing circuit 51 sets a braking force that is equal to or greater than the parking 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 for the passengers at the time of parking, 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 of the second stop-time braking control is satisfied. The second stop-time braking control is the stop-time braking control executed when the driving road surface is an uphill road. For example, when the magnitude of 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, the processing circuit 51 determines that the start condition is not satisfied. When the magnitude of the difference between the first braking force BPC1 and the required braking force BPRq is small, it can be presumed that the attitude of the vehicle 10 does not change significantly during stopping even if the second stop-time braking control is not executed. Therefore, when the magnitude of the difference between the first braking force BPC1 and the required braking force BPRq is less than the braking force difference determination value ΔBPth, the processing circuit 51 does not execute the second stop-time braking control. On the other hand, when the magnitude of the difference between the first braking force BPC1 and the required braking force BPRq is greater than or equal to the braking force difference determination value ΔBPth, and the vehicle body speed VS decreases from a state where the vehicle body speed VS is greater than the first vehicle body speed determination value VSth11 to a state where the vehicle body speed VS is less than or equal to the first vehicle body speed determination value VSth11, the processing circuit 51 determines that the start condition is satisfied. The first vehicle body speed determination value VSth11 may be the same as the first vehicle body speed determination value VSth1, or may be a value different from the first vehicle body speed determination value VSth11. When the processing circuit 51 determines that the start condition is satisfied (S45: YES), the process proceeds to step S47. On the other hand, when the processing circuit 51 determines that the start condition is not satisfied (S45: NO), the series of processes shown in FIG. 6 is temporarily terminated.

[0065] In step S47, the processing circuit 51 performs the second stop-time braking control. Specifically, in step S49, the processing circuit 51 executes a second augmentation correction process. The second augmentation correction process is an augmentation correction process for the second stop-time braking control. In the second augmentation correction process, the processing circuit 51 sets a vehicle braking force greater than the required braking force BPRq as the commanded braking force BPTr in order to compensate for the extension of the braking distance of the vehicle 10 caused by the execution of the second reduction correction process described later. For example, the processing circuit 51 sets the sum of the offset value ΔBP1, which is the correction amount of the braking force for compensating for the extension of the braking distance of the vehicle 10 caused by the execution of the second reduction correction process, and the required braking force BPRq as the commanded braking force BPTr. The processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr.

[0066] In the next step S51, the processing circuit 51 determines whether or not the transition condition from the second augmentation correction process to the second reduction correction process is satisfied. The second reduction correction process is a reduction correction process for the second stop-time braking control. For example, when the vehicle body speed VS changes from a state where it is greater than the second vehicle body speed determination value VSth21 to a state where it is less than or equal to the second vehicle body speed determination value VSth21, the processing circuit 51 determines that the transition condition is satisfied. The second vehicle body speed determination value VSth21 may be the same as the second vehicle body speed determination value VSth2, or may be a value different from the second vehicle body speed determination value VSth2. When the processing circuit 51 determines that the transition condition is not satisfied (S51: NO), the process proceeds to step S49. That is, the processing circuit 51 executes the second augmentation correction process. On the other hand, when the processing circuit 51 determines that the transition condition is satisfied (S51: YES), the process proceeds 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 commanded braking force BPTr to the first braking force BPC1. After the commanded braking force BPTr reaches the first braking force BPC1, the processing circuit 51 holds the commanded braking force BPTr at the first braking force BPC1. Then, the processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr.

[0068] In subsequent step S55, the processing circuit 51 determines whether the transition condition from the second deceleration correction process to the second degradation process is satisfied. The second degradation process is the degradation 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 is true: the vehicle 10 has switched from forward movement to reverse movement at the time when the second deceleration correction process (i.e., the braking force reduction process) is executed, and it can be 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 movement to reverse movement at the time when the second deceleration correction process (i.e., the braking force reduction process) is executed nor it can be determined that the vehicle 10 has stopped.

[0069] When the deceleration inertial force DI shown in FIG. 4 becomes 0 (zero) due to the vehicle 10 having substantially stopped, the vehicle 10 switches from forward movement to reverse movement. That is, the processing circuit 51 can determine that the transition condition is satisfied when it can be determined that the deceleration inertial force DI has become 0 (zero). In the present embodiment, the processing circuit 51 determines that the transition condition is satisfied when the longitudinal acceleration Gx changes from less than 0 (zero) to 0 (zero) or more.

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

[0071] In step S57, the processing circuit 51 executes a second degradation process (i.e., a braking force increasing process). In the second degradation 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 parking maintenance braking force BPth. In this case, the processing circuit 51 increases the commanded braking force BPTr to the parking maintenance braking force BPth early. After the commanded braking force BPTr reaches the parking maintenance braking force BPth, the processing circuit 51 gradually increases the commanded braking force BPTr to the second braking force BPC2. That is, the processing circuit 51 makes the increasing speed of the commanded braking force BPTr from the first braking force BPC1 to the parking maintenance braking force BPth greater than the increasing speed of the commanded braking force BPTr from the parking maintenance braking force BPth to the second braking force BPC2. Then, the processing circuit 51 operates the brake actuator 30 based on the commanded braking force BPTr.

[0072] In the next step S59, the processing circuit 51 determines whether the end condition of the second degradation process is satisfied. For example, when the commanded braking force BPTr becomes equal to the second braking force BPC2, it is considered that the end condition is satisfied. On the other hand, when the commanded braking force BPTr is less than the second braking force BPC2, it is considered that the end condition is not satisfied. When the processing circuit 51 determines that the end condition is not satisfied (S59: NO), the process proceeds to step S57. That is, the processing circuit 51 executes the second degradation process. On the other hand, when the processing circuit 51 determines that the end condition is satisfied (S59: YES), the second degradation process is terminated. Then, the processing circuit 51 terminates the second stop-time braking control and terminates 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 reduction correction process in step S53 is executed by the processing circuit 51 functioning as the reduction control unit M13 (first control unit). The second degradation process in step S57 is executed by the processing circuit 51 functioning as the degradation control unit M17 (second control unit).

[0074] <Actions and effects of this embodiment> With reference to FIG. 7, the actions and effects when stopping a vehicle 10 traveling on an uphill road by applying a braking force will be described. FIG. 7 shows a time chart when the second braking control during stopping is implemented.

[0075] As shown in FIGS. 7(A), (B), (C), and (D), when a braking force is applied to the vehicle 10, the vehicle body speed VS decreases. Then, when the vehicle body speed VS reaches the first vehicle body speed determination value VSth11 at the timing t21, the processing circuit 51 starts the second braking control during stopping.

[0076] The processing circuit 51 executes the second increase correction process of the second braking control during stopping. In the second increase correction process, the processing circuit 51 sets the sum of the required braking force BPRq and the offset value ΔBP1 as the indicated braking force BPTr. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the indicated braking force BPTr. As a result, as shown in FIGS. 7(B) and (D), although the required braking force BPRq is constant, the vehicle braking force BPAl is increased. Specifically, the vehicle braking force BPAl becomes larger than the required braking force BPRq. As a result, as shown in FIG. 7(C), the magnitude of the longitudinal acceleration Gx becomes larger.

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

[0078] In the second reduction correction process, the processing circuit 51 reduces the commanded braking force BPTr to the first braking force BPC1 and then sets the vehicle body speed VS to 0 (zero). Specifically, the processing circuit 51 reduces the commanded braking force BPTr to the first braking force BPC1 at a constant speed. Then, the processing circuit 51 controls the brake actuator 30 so that the vehicle braking force BPAl becomes the commanded 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 is the same, the absolute value of the longitudinal acceleration Gx of the vehicle 10 gradually becomes smaller.

[0079] When the commanded braking force BPTr becomes equal to the first braking force BPC1 at timing t23 during the execution of the second reduction correction process, the processing circuit 51 holds the commanded 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 held.

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

[0081] Therefore, when the vehicle 10 switches from forward movement to backward movement, the processing circuit 51 shifts the process from the second reduction correction process to the second contraction process. This second contraction process corresponds to a "braking force increase process". In the example shown in FIG. 7, timing t24 is the point in time when the vehicle 10 switches from forward movement to backward movement. As shown in FIG. 7(C), timing t24 is the timing at which the longitudinal acceleration Gx, which is the detected 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 greater than or equal to the reference value (=0 (zero)).

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

[0083] Here, consider the case where the first stop-time braking control is performed when the vehicle 10 traveling on the uphill road is stopped by applying a braking force. In this case, the vehicle braking force BPAl is only decreased to the stop-maintaining braking force BPth. When the vehicle 10 is traveling on the uphill road, the stop-maintaining braking force BPth is larger than when the vehicle 10 is traveling on the flat road. Therefore, even if the vehicle braking force BPAl is decreased to the stop-maintaining braking force BPth, the vehicle braking force BPAl immediately before stopping is relatively large. As a result, the change in the posture of the vehicle 10 at the time of stopping is not suppressed so much.

[0084] In this regard, when the vehicle 10 traveling on the uphill road is stopped by applying a braking force, the braking control device 50 performs the second stop-time braking control. In the second stop-time braking control, the vehicle braking force BPAl is decreased to the first braking force BPC1 by the second subtraction correction process (braking force decrease process). The first braking force BPC1 set in the second stop-time braking control is smaller than the stop-maintaining braking force BPth. Therefore, compared with the case where the first stop-time braking control is performed, the vehicle braking force BPAl immediately before stopping becomes smaller. As a result, compared with the case where the first stop-time braking control is performed, the change in the posture of the vehicle 10 at the time of stopping becomes smaller.

[0085] If it is determined that the vehicle 10 has switched from forward to reverse during the execution of the second compensation process, even before it is determined that the vehicle 10 has stopped, the processing circuit 51 shifts the process from the second compensation process to the second degradation process (braking force increase process). In the second degradation process, the processing circuit 51 increases the commanded 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 commanded 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 parking maintenance braking force BPth. Therefore, by executing the second degradation process, the stop of the vehicle 10 is maintained.

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

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

[0088] (1) The parking maintenance braking force BPth can vary depending on the gradient of the uphill road, the force for moving the vehicle 10 acting on the vehicle 10, the weight of the vehicle 10, and the like. Therefore, the braking control device 50 can change the first braking force BPC1 according to the gradient of the uphill road, the force for moving the vehicle 10 acting on the vehicle 10, and the weight of the vehicle 10. As a result, it is suppressed that the first braking force BPC1 becomes too large or too small with respect to the parking maintenance braking force BPth. As a result, when stopping the vehicle 10 on an uphill road, the braking control device 50 can implement the second braking control at the time of stopping to suppress a change in the posture of the vehicle 10 at the time of stopping and to suppress the occurrence of slippage of the vehicle 10 in the downhill direction Z1.

[0089] (2) When the degree of comfort required for the occupant (e.g., the driver) during parking is low, it can be inferred that the occupant (e.g., the driver) requires the vehicle 10 to stop surely rather than suppressing the change in the posture of the vehicle 10 during parking. Therefore, in the braking control device 50, the first braking force BPC1 is set according to the operation amount X of the braking operation member 11, which is an example of an index indicating the degree of comfort required for the occupant during parking. As a result, the braking control device 50 can execute braking control according to the comfort required for the occupant during parking.

[0090] (3) Before the stop of the second parking braking control, if the deviation between the required braking force BPRq and the first braking force BPC1 is large, if the second parking braking control is not performed, the change in the posture of the vehicle 10 during parking will become large. Therefore, when stopping the vehicle 10 on an uphill road, the braking control device 50 performs the second parking braking control when it can be determined that the deviation between the required braking force BPRq and the first braking force BPC1 is large. Thereby, the braking control device 50 can suppress the change in the posture of the vehicle 10 during parking when stopping the vehicle 10 on an uphill road.

[0091] On the other hand, when stopping the vehicle 10 on an uphill road, if the braking control device 50 can determine that the deviation between the required braking force BPRq and the first braking force BPC1 is small, the second parking braking control is not performed. That is, when it can be inferred that the change in the posture of the vehicle 10 during parking is small even if the second parking braking control is not performed, the second parking braking control is not performed.

[0092] (4) When the deceleration inertial force DI no longer acts on the vehicle 10, the vehicle 10 switches from forward movement to backward movement. When the deceleration inertial force DI no longer acts, the longitudinal acceleration Gx changes from less than the reference value to greater than or equal to the reference value. Therefore, in the braking control device 50, when the longitudinal acceleration Gx changes from less than the reference value to greater than or equal to the reference value, it can be determined that the vehicle 10 has switched from forward movement to backward movement. Thus, by executing the second retraction process, the vehicle braking force BPAl is increased to the second braking force BPC2.

[0093] As a result, in the braking control device 50, the vehicle braking force BPAl increases to the second braking force BPC2 earlier than in the case where the second degradation process is executed after it is determined that the vehicle 10 has stopped. As a result, even if the braking control device 50 reduces the vehicle braking force BPAl to suppress the change in the posture of the vehicle 10 at the time of stopping, it is possible to suppress the vehicle 10 from slipping downward in the downhill direction Z1.

[0094] (5) As shown in FIG. 7, the second braking force BPC2 may be set to a value larger than the stop maintenance braking force BPth. In the braking control device 50, in the second degradation process, the increase rate of the vehicle braking force BPAl from the first braking force BPC1 to the stop maintenance braking force BPth can be made larger than the increase rate of the vehicle braking force BPAl from the stop maintenance braking force BPth to the second braking force BPC2. In the example shown in FIG. 7, the timing t25 is the timing when the commanded braking force BPTr reaches the stop maintenance braking force BPth. The timing t26 is the timing when the commanded braking force BPTr reaches the second braking force BPC2. Thereby, the braking control device 50 can increase the vehicle braking force BPAl earlier until the vehicle braking force BPAl reaches the stop maintenance braking force BPth by executing the second degradation process. Thereby, the braking control device 50 can increase the slipping suppression effect of the vehicle 10.

[0095] On the other hand, after the vehicle braking force BPAl reaches the stop maintenance braking force BPth, the vehicle braking force BPAl is gradually increased. Thereby, the braking control device 50 can shorten the state in which the noise and vibration caused by the operation of the brake actuator 30 are large as compared with the case where the state in which the increase rate of the vehicle braking force BPAl is large continues.

[0096] <Modification example> The above embodiment can be implemented with the following modifications. The above embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

[0097] ·The processing circuit 51 (i.e., the second braking force setting unit M21) may set the second braking force BPC2 based on any one of the gradient of the uphill road, an index indicating the degree of comfort required for the passengers during parking, the force for moving the vehicle 10 acting on 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, when the required braking force BPRq is less than the parking maintenance braking force BPth, it is preferable that the processing circuit 51 sets a vehicle braking force equal to or greater than the parking maintenance braking force BPth as the second braking force BPC2.

[0099] ·In the second degradation process, the processing circuit 51 (i.e., the degradation control unit M17) does not have to decrease the increasing speed of the commanded braking force BPTr even if the commanded braking force BPTr becomes equal to or greater than the parking maintenance braking force BPth.

[0100] ·In the above embodiment, 0 (zero) is set as the reference value for determining whether or not the vehicle 10 has switched from forward to reverse. However, if it is possible to determine whether or not it is the time when the vehicle 10 switches from forward to reverse, a value different from 0 (zero) may be set as the reference value.

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

[0102] ·When stopping the vehicle 10 on an uphill road, the processing circuit 51 may perform the second braking control during stopping regardless of whether or not the magnitude of the difference between the required braking force BPRq and the first braking force BPC1 is equal to or greater than the braking force difference determination 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 one of the gradient of the uphill road, an index indicating the degree of comfort required for the passengers during parking, the force that moves the vehicle 10 acting on the vehicle 10, and the weight of the vehicle 10.

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

[0105] ·When stopping the vehicle 10 on an uphill road, the processing circuit 51 may set the first braking force BPC1 based on the parking maintenance braking force BPth. For example, the processing circuit 51 may set, as the first braking force BPC1, the larger value between the value obtained by subtracting a predetermined braking force from the parking maintenance braking force BPth and 0 (zero).

[0106] ·If the first stop-time braking control includes the first reduction correction process and the first fade-out process, it may not include the first increase correction process. ·If the second stop-time braking control includes the second reduction correction process and the second fade-out process, it may not include the second increase correction 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 reduction correction process of the stop-time braking control according to the change in the vehicle body speed VS. However, if it is a parameter whose value decreases as the vehicle 10 approaches the stop position PS, the processing circuit 51 may use a parameter other than the vehicle body speed VS to determine the start timing of each process. Examples of other parameters include the stop distance and the stop prediction time. The stop distance is the distance from the current position of the vehicle 10 to the stop position PS. The stop prediction time is the time required for the vehicle 10 to stop. An example of the stop prediction time is TTC. TTC is an abbreviation of "Time To Collision".

[0108] ·When executing the stop-time braking control, the braking 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 becomes the vehicle braking force BPAl.

[0109] ·In the above embodiment, when the vehicle is braked due to the operation of the braking operation member 11 by the driver, the processing circuit 51 executes the stop-time braking control. However, the processing circuit 51 may perform the stop-time braking control during automatic braking.

[0110] ·The processing circuit 51 can be configured as a circuit including one or more processors that operate according to a computer program, one or more dedicated hardware circuits such as dedicated hardware that executes at least a part of various processes, or a combination thereof. Examples of the dedicated hardware include, for example, an ASIC (Application Specific Integrated Circuit) which is an integrated circuit for a specific purpose. The processor includes a CPU and memories such as a RAM and a ROM, and the memories store program codes or instructions configured to cause the CPU to execute processes. The memory, that is, the storage medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0111] <Other technical ideas> The technical ideas that can be grasped from the above embodiment and modification examples will be described. [Appendix 1] The second braking force is set to a value greater than the parking maintenance braking force, In the braking force increasing process, it is preferable that the second control unit makes the increasing speed of the braking force applied to the vehicle from the first braking force to the parking maintenance braking force greater than the increasing speed of the braking force applied to the vehicle from the parking maintenance braking force to the second braking force.

[0112] [Appendix 2] It is preferable to include 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 for the passengers of the vehicle when stopped, the force for moving the vehicle acting on the vehicle, and the weight of the vehicle.

[0113] [Appendix 3] When stopping a vehicle traveling on an uphill road by applying a braking force, the braking force is made smaller than the parking maintenance braking force, which is a braking force for balancing the downhill force acting on the vehicle and the uphill force acting on the vehicle, and is a braking force of 0 (zero) or more. After reducing the braking force applied to the vehicle to the first braking force, a braking force reduction process for setting the vehicle body speed of the vehicle to 0 (zero) is executed. A first control unit; During the execution of the braking force reduction process, a determination unit that determines whether or not the deceleration inertial force, which is the inertial force acting on the vehicle due to deceleration, has become 0 (zero); When it is determined that the deceleration inertial force has become 0 (zero), a second control unit that executes a braking force increase process for increasing the braking force applied to the vehicle to a second braking force equal to or greater than the parking maintenance braking force. A braking control device comprising:

[0114] Note 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 the 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.

Explanation of Signs

[0115] 10…Vehicle 11, 12…Wheels 20…Friction Brake 30…Braking Actuator 50…Braking Control Device 51…Processing Circuit 103…Longitudinal and Lateral Acceleration Sensor M13… Reduction control unit (first control unit) M15… Judgment unit M17… Degeneration control unit (second control unit) M19… First braking force setting unit M21… Second braking force setting unit

Claims

1. When stopping a vehicle traveling on an uphill road by applying a braking force, the braking force is reduced to a first braking force that is smaller than the parking maintenance braking force, which is a braking force for balancing the downhill force acting on the vehicle and the uphill force acting on the vehicle, and is a braking force of 0 (zero) or more, and then a braking force reduction process for setting the vehicle body speed of the vehicle to 0 (zero) is executed. A first control unit; A second control unit that executes a braking force increase process for increasing the braking force applied to the vehicle to a second braking force equal to or greater than the parking maintenance braking force from the time when the vehicle switches from forward movement to backward movement due to the execution of the braking force reduction process. A braking control device.

2. A first braking force setting unit that 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 for the passengers of the vehicle when stopped, the force for moving the vehicle acting on the vehicle, and the weight of the vehicle. The braking control device according to claim 1.

3. The first control unit starts the braking force reduction process when the magnitude of the difference between the required value of the braking force applied to the vehicle and the first braking force is equal to or greater than a braking force difference determination value. The braking control device according to claim 1 or claim 2.

4. A determination unit that determines that the vehicle has switched from forward movement to backward movement when the detection value of a sensor that detects an inertial force acting on the vehicle in the longitudinal direction of the vehicle changes from a state where the detection value is less than a reference value or the lower limit of a reference range to a state where the detection value is equal to or greater than the reference value or the upper limit of the reference range. The braking control device according to claim 1.

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