Brake control device

Abstract

A braking control device (10) performs pre-stop braking control for adjusting braking force when the vehicle stops. The pre-stop braking control includes reduction control for reducing braking force and increase control that is executed before the start of the reduction control and increases braking force. The braking control device (10) includes an increase unit (12) that executes the increase control and a reduction unit (13) that executes the reduction control. The braking control device (10) includes a calculation unit (14). The calculation unit (14) calculates the distance by which the braking distance is extended by the reduction control as the extension distance, and calculates the distance by which the braking distance is shortened by the increase control as the shortening distance. When the operation amount of the braking operation member operated by the driver decreases during braking, the calculation unit (14) calculates the extension distance to be longer than when the operation amount does not decrease. When the difference between the extension distance and the shortening distance is less than a determination value, the reduction unit (13) starts the reduction control.

Description

Technical Field

[0001] The present invention relates to a braking control device for a vehicle. Background Art

[0002] A control device for controlling braking force when a vehicle stops is disclosed in Patent Document 1. The control device reduces the change amount of the longitudinal acceleration of the vehicle immediately before stopping by reducing the braking force immediately before the vehicle stops.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-28913 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] In the control device described in Patent Document 1, since the braking force immediately before the vehicle stops is reduced, there is a risk that the braking distance becomes longer. Further, when controlling the braking force immediately before the vehicle stops, the change in the operation amount by the driver is not sufficiently considered.

[0008] Solution for Solving the Technical Problem

[0009] One way of the braking control device for solving the above technical problems is a braking control device which, when a braking operation member is operated by a driver of a vehicle, performs pre-stop braking control for adjusting the braking force of the vehicle when the vehicle stops by braking. The braking control device is characterized by comprising: a reducing unit that performs reducing control in the pre-stop braking control to reduce the braking force applied to the vehicle compared to the required braking force, where the required braking force is the braking force corresponding to the operation amount of the braking operation member; an increasing unit that performs increasing control in the pre-stop braking control to increase the braking force compared to the required braking force before the start of the reducing control in such a manner that the extended distance becomes longer, where the extended distance is a value obtained by estimating the distance by which the braking distance in the case of reducing the braking force by executing the reducing control is extended compared to the case of not executing the reducing control; and a calculating unit that calculates a shortening distance and the extended distance during the execution of the increasing control, where the shortening distance is a value obtained by estimating the distance by which the braking distance in the case of increasing the braking force by executing the increasing control is shortened compared to the case of not executing the increasing control; the calculating unit calculates the extended distance in such a manner that the extended distance becomes longer when the operation amount decreases during the braking of the vehicle compared to the case where the operation amount does not decrease, the increasing unit ends the increasing control when the difference between the extended distance and the shortening distance is less than a specified determination value, and the reducing unit starts the reducing control when the difference between the extended distance and the shortening distance is less than the determination value.

[0010] According to the above structure, by performing the increasing control before the reducing control, it is possible to suppress the extension of the extended distance. That is, it is possible to suppress the extension of the braking distance and to reduce the change amount of the longitudinal acceleration of the vehicle immediately before stopping. Further, in the above structure, the increasing control is ended and the reducing control is started when the difference between the extended distance and the shortening distance is less than a specified determination value. Since the driver's operation is reflected in the calculation of the extended distance, it is possible to reflect the driver's operation of the vehicle at the time point when the reducing control starts. Thus, it is easy to achieve a braking distance that reflects the driver's operation.

[0011] One way of the braking control device for solving the above technical problems is a braking control device that performs a reduction control and an increase control on the vehicle decelerated by the operation of the braking operation member by the driver of the vehicle. The reduction control reduces the braking force applied to the vehicle regardless of the operation of the braking operation member during the vehicle stop in order to suppress the vehicle movement accompanying the vehicle stop. The increase control increases the braking force applied to the vehicle regardless of the operation of the braking operation member during a period earlier than the execution period of the reduction control in order to compensate for the braking distance of the vehicle extended by the execution of the reduction control. The braking control device is characterized in that it includes an accumulation unit that accumulates the operation amount of the braking operation member before the start of the execution of the reduction control, and a control unit that starts the execution of the reduction control based on the operation amount of the braking operation member accumulated by the accumulation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 FIG. is a block diagram showing an embodiment of a braking control device applied to a braking device.

[0013] Figure 2 FIG. is a flowchart showing a process flow when performing pre-stop braking control in the braking control device.

[0014] Figure 3 FIG. is a flowchart showing a process flow executed by the braking control device during the execution of the increase control in the pre-stop braking control.

[0015] Figure 4 FIG. is a flowchart showing a process flow executed by the braking control device during the execution of the increase control in the pre-stop braking control.

[0016] Figure 5 FIG. is a flowchart showing a calculation process of the shortened distance executed by the braking control device.

[0017] Figure 6 FIG. is a timing chart showing the transition of the braking force controlled by the braking control device when the vehicle stops.

[0018] Figure 7 FIG. is a timing chart showing the transition of the braking force controlled by the braking control device when the vehicle stops.

[0019] Figure 8 FIG. is a timing chart showing the transition of the braking force controlled by the braking control device when the vehicle stops.

[0020] Figure 9 FIG. is a timing chart showing the transition of the braking force controlled by the braking control device when the vehicle stops. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, with reference to Figures 1 to 9 , an embodiment of the braking control device will be described.

[0022] Figure 1 The braking device 20 shown is mounted on a vehicle. The braking device 20 includes a braking control device 10 and a brake actuator 21. The braking control device 10 can adjust the braking force applied to the wheels of the vehicle by controlling the operation of the brake actuator 21.

[0023] The vehicle on which the braking device 20 is mounted is equipped with various sensors for detecting the state of the vehicle. Detection signals from the various sensors are input to the braking control device 10. The vehicle is equipped with a monitoring device 50 for monitoring the driver. Information obtained by the monitoring device 50 is input to the braking control device 10.

[0024] As Figure 1 shown, the vehicle is equipped with an operation amount sensor 30 as one of the various sensors. The operation amount sensor 30 detects the operation amount BR of a braking operation member operated by the driver of the vehicle. The braking operation member is operated by the driver when braking the vehicle. An example of the braking operation member is a brake pedal. In this case, the operation amount sensor 30 is a stepping force sensor that detects the force with which the brake pedal is depressed as the operation amount BR. The required braking force is calculated as a target value of the braking force corresponding to the operation amount BR based on the detection signal from the operation amount sensor 30.

[0025] The vehicle is equipped with a wheel speed sensor 40 as one of the various sensors. The wheel speed sensor 40 is installed corresponding to each wheel of the vehicle. The speed of each wheel of the vehicle is calculated based on the detection signal from the wheel speed sensor 40. The vehicle speed, that is, the speed of the vehicle, is calculated based on the speed of each wheel.

[0026] The monitoring device 50 has a function of obtaining information about the driver of the vehicle. The monitoring device 50 is equipped with a camera disposed inside the vehicle. The monitoring device 50 is equipped with an information processing unit for processing the image captured by the camera. For example, the monitoring device 50 can estimate the age of the driver by analyzing the captured image by the information processing unit. The monitoring device 50 can also determine whether the driver is in a lax state based on the captured image. The monitoring device 50 is not limited to a camera and may also be equipped with a device for monitoring the driver. For example, the monitoring device 50 may also be equipped with a measuring device for measuring the pulse of the driver. The pulse of the driver can be used as an index of the driver's state of tension. The pulse can also be used as an index of the driver's health state. That is, the monitoring device 50 may also obtain the driver's state of tension. The monitoring device 50 may also obtain the driver's health state.

[0027] The information processing units included in the braking control device 10 and the monitoring device 50 may have any one of the following structures (a) to (c). (a) It includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memories such as a RAM and a ROM. The memory stores program codes or instructions configured to cause the CPU to execute processes. The memory, i.e., the computer-readable medium, includes all available media that can be accessed by a general-purpose or special-purpose computer. (b) It includes one or more dedicated hardware circuits that execute various processes. The dedicated hardware circuits are, for example, application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs) for specific purposes. (c) It includes a processor that executes a part of various processes according to a computer program and a dedicated hardware circuit that executes the remaining processes in the various processes.

[0028] The braking control device 10 includes a pre-stop control unit 11 and a calculation unit 14 as functional units. The pre-stop control unit 11 includes an increasing unit 12 and a decreasing unit 13.

[0029] The pre-stop control unit 11 performs pre-stop braking control for adjusting the braking force of the vehicle when the vehicle stops due to braking. The pre-stop control unit 11 performs pre-stop braking control when a braking operation member is operated by the driver of the vehicle. The pre-stop braking control includes decreasing control executed by the decreasing unit 13 and increasing control executed by the increasing unit 12. The pre-stop control unit 11 executes increasing control before the start of the decreasing control.

[0030] The decreasing unit 13 reduces the braking force applied to the vehicle compared to the required braking force during the decreasing control. The decreasing control includes a control for maintaining the braking force at a value less than the required braking force.

[0031] The increasing unit 12 increases the braking force applied to the vehicle compared to the required braking force during the increasing control. The increasing control includes a control for maintaining the braking force at a value greater than the required braking force.

[0032] The calculation unit 14 calculates the reaction time Tith. The reaction time Tith represents a value obtained by estimating the time required for the driver to recognize the change in the braking force relative to the required braking force when the adjustment of the braking force is started by the braking control device 10. The calculation unit 14 calculates the reaction time Tith based on a preset standard value and the information of the driver that can be obtained by the monitoring device 50. An example of the standard value is a value less than 1 second. For example, the older the estimated age of the driver, the larger the value the calculation unit 14 sets the reaction time Tith to be than the standard value. The calculation unit 14 can also set the reaction time Tith to a value greater than the standard value when the driver is in a lax state. In addition, when information such as the driver's tension state and health state is obtained by the monitoring device 50, the calculation unit 14 can also calculate the reaction time Tith based on the standard value and the information obtained by the monitoring device 50. The calculation unit 14 can also calculate the reaction time Tith based on a combination of the standard value and a plurality of information that can be obtained by the monitoring device 50. In addition, the calculation unit 14 can use the standard value as the reaction time Tith.

[0033] The calculation unit 14 can calculate the jerk as the rate of change of the acceleration of the vehicle. The calculation unit 14 can calculate the stop position obtained by estimating the position where the vehicle stops during the braking of the vehicle. The stop position can be calculated based on the vehicle speed, deceleration, etc. The distance from the position where braking starts to the stop position is the braking distance. The calculation unit 14 can predict the longitudinal and lateral accelerations of the vehicle at the time point when the vehicle reaches the stop position. The calculation unit 14 can calculate the longitudinal and lateral accelerations at the stop position based on the required jerk.

[0034] The calculation unit 14 calculates the extension distance Di1 during the execution of the increase control. The calculation unit 14 repeats the calculation of the extension distance Di1 for each specified cycle. The extension distance Di1 is a value obtained by estimating the distance by which the braking distance when the braking force is reduced by the execution of the reduction control is extended compared to the case where the reduction control is not executed, assuming that the reduction control starts from the calculation time point of this extension distance Dil. For example, the extension distance Di1 can be calculated as follows. First, the calculation unit 14 calculates the braking distance in the case where the reduction control is executed as the first braking distance. In addition, the calculation unit 14 calculates the braking distance in the case where the reduction control is not executed as the second braking distance. Then, the calculation unit 14 calculates the difference between the first braking distance and the second braking distance as the extension distance Di1.

[0035] When the operation amount BR during braking decreases, that is, when the driver releases the braking operation member, the calculation unit 14 calculates the extended distance Di1 in such a way that the extended distance Di1 becomes longer than when the operation amount BR does not decrease. When the operation amount BR during braking increases, that is, when the driver steps on the braking operation member, the calculation unit 14 calculates the extended distance Dil in such a way that the extended distance Di1 becomes shorter than when the operation amount BR does not increase.

[0036] The calculation unit 14 calculates the shortened distance Di2 during the execution of the increasing control. The calculation unit 14 repeats the calculation of the shortened distance Di2 for each specified cycle. The shortened distance Di2 is a value obtained by estimating the distance by which the braking distance in the case where the braking force is increased by the execution of the increasing control is shorter than the braking distance in the case where the increasing control is not executed. The shortened distance Di2 can be calculated based on the increase value of the braking force with respect to the required braking force and the time during which the increasing control is continuously performed. For example, the larger the increase value of the braking force, the longer the shortened distance Di2 is calculated. The longer the time during which the increasing control is continuously performed, the longer the shortened distance Di2 is calculated. In addition, as will be described in detail later, the calculation unit 14 performs processing to suppress the increase of the shortened distance Di2 or decrease the shortened distance Di2 according to conditions.

[0037] The details of the increasing control and the decreasing control will be described.

[0038] The increasing unit 12 starts the calculation of the elapsed time Ti1 as the duration of the increasing control at the start of the increasing control. The elapsed time Ti1 may also consider the response delay from the start of the increasing control until the braking force applied to the wheel actually increases, and start counting from a starting point after a certain period has elapsed from the start time point of the increasing control. In this case, the period from the start time point until the certain period has elapsed is taken as the standby time.

[0039] The increasing unit 12 increases the braking force in such a way that the difference between the extended distance Di1 and the shortened distance Di2 becomes less than a specified determination value α until the duration of the increasing control reaches the reaction time Tith. The determination value α is a determination value for determining whether the difference between the extended distance Dil and the shortened distance Di2 becomes smaller. An example of the determination value α is a value slightly larger than "0". For example, at the start of the increasing control, the increasing unit 12 sets the increase value of the braking force with respect to the required braking force in such a way that the difference between the extended distance Di1 and the shortened distance Di2 becomes less than the determination value α at the time point when the elapsed time Ti1 reaches the reaction time Tith.

[0040] When the operation amount BR decreases during the execution of the increase control in the increasing section 12, the braking amount is maintained in a state of increasing relative to the required braking force, and the braking force is decreased according to the decreasing speed of the operation amount BR. When the operation amount BR increases during the execution of the increase control in the increasing section 12, the braking amount is maintained in a state of increasing relative to the required braking force, and the braking force is increased according to the increasing speed of the operation amount BR.

[0041] The decreasing section 13 executes the decrease control in accordance with the configuration data that defines the decrease value of the braking force that is less than the required braking force and the speed at which the braking force is decreased during the decrease control. The decreasing section 13 sets the configuration data for controlling the braking force in such a way as to reduce the change amount of the longitudinal acceleration when the vehicle stops. The decreasing section 13 sets the configuration data based on the vehicle speed and deceleration at the start of braking. The decreasing section 13 updates the configuration data based on the vehicle speed and deceleration at the time point when the decrease control starts. That is, the configuration data can also be updated based on the wheel speed at the time point when the decrease control starts. As the updated configuration data, not limited to the decrease value of the braking force and the speed at which the braking force is decreased being changed, it can also be that the decrease value of the braking force is changed and the speed at which the braking force is decreased is changed, etc.

[0042] The decreasing section 13 ends the decrease control when the vehicle stops. In addition, after the vehicle stops, the pre-stop control section 11 executes the holding control for applying the braking force for maintaining the stopped state of the vehicle.

[0043] Use Figures 2 to 4 , the process of the processing executed by the pre-stop control section 11 will be described. Figure 2 The shown processing process is executed during the braking of the vehicle. This processing process is repeatedly executed for each specified cycle until the start of the increase control.

[0044] When this processing process starts, first in step S101, the pre-stop control section 11 determines whether the execution condition of the pre-stop braking control is satisfied. An example of the execution condition will be described. Here, the pre-stop control section 11 determines that the execution condition is satisfied when the target value of the deceleration is less than the specified value when the vehicle speed becomes lower than the specified start determination value due to the braking of the vehicle. On the other hand, the pre-stop control section 11 determines that the execution condition is not satisfied when the vehicle speed is greater than or equal to the specified start determination value. In addition, the pre-stop control section 11 also determines that the execution condition is not satisfied when the target value of the deceleration is greater than or equal to the specified value.

[0045] When the execution condition of the pre-stop braking control is not satisfied (S101: No), the pre-stop control unit 11 ends this processing routine. On the other hand, when the execution condition of the pre-stop braking control is satisfied (S101: Yes), the pre-stop control unit 11 transfers the processing to step S102. In step S102, the pre-stop control unit 11 causes the increasing unit 12 to start the increasing control. As a result, the braking force of the vehicle increases more than the required braking force. After that, the pre-stop control unit 11 ends this processing routine.

[0046] Figure 3 The processing routine shown Figure 2 During the execution of the increasing control that starts in the processing of step S102, the pre-stop control unit 11 repeats the execution for each prescribed period.

[0047] When this processing routine starts, first in step S201, the pre-stop control unit 11 determines whether the difference between the extension distance Di1 and the shortening distance Di2 is less than a prescribed determination value α.

[0048] When the difference between the extension distance Di1 and the shortening distance Di2 is greater than or equal to the determination value α (S201: No), the pre-stop control unit 11 transfers the processing to step S205. On the other hand, when the difference between the extension distance Di1 and the shortening distance Di2 is less than the determination value α (S201: Yes), the pre-stop control unit 11 transfers the processing to step S202.

[0049] In step S202, the pre-stop control unit 11 determines whether the prohibition flag F1 is "0". The pre-stop control unit 11 permits the start of the decreasing control when the prohibition flag F1 is "0". The pre-stop control unit 11 prohibits the start of the decreasing control when the prohibition flag F1 is "1". The initial value of the prohibition flag F1 is set to "0". The prohibition flag F1 is set to "0" or "1" in the Figure 4 processing routine shown later. The prohibition flag F1 is set to the initial value "0" when the vehicle stops. When the prohibition flag F1 is "1" (S202: No), the pre-stop control unit 11 transfers the processing to step S205.

[0050] In step S205, the pre-stop control unit 11 causes the increasing unit 12 to continue the execution of the increasing control. After that, the pre-stop control unit 11 ends this processing routine.

[0051] On the other hand, in the processing of step S202, when the prohibition flag F1 is "0" (S202: Yes), the pre-stop control unit 11 transfers the processing to step S203.

[0052] In step S203, the pre-stop control unit 11 causes the reduction unit 13 to set the configuration data. The reduction unit 13 sets the configuration data using the vehicle speed at that time. After that, the pre-stop control unit 11 transfers the process to step S204.

[0053] In step S204, the pre-stop control unit 11 causes the increase unit 12 to end the increase control and causes the reduction unit 13 to start the reduction control. The reduction unit 13 starts the reduction control based on the configuration data set in the process of step S203. As a result, the braking force of the vehicle is reduced compared to the required braking force. After that, the pre-stop control unit 11 ends this processing procedure.

[0054] Figure 4 The processing procedure shown Figure 2 is repeatedly executed by the pre-stop control unit 11 for each specified cycle during the execution of the increase control started in the processing of step S102.

[0055] When this processing procedure starts, first in step S301, the pre-stop control unit 11 determines whether the elapsed time Ti1 is greater than the reaction time Tith. When the elapsed time Ti1 is less than or equal to the reaction time Tith (S301: No), the pre-stop control unit 11 ends this processing procedure. On the other hand, when the elapsed time Ti1 is greater than the reaction time Tith (S301: Yes), the pre-stop control unit 11 transfers the process to step S302.

[0056] In step S302, the pre-stop control unit 11 causes the calculation unit 14 to calculate the required jerk. The calculation unit 14 calculates the required jerk as the rate of change of the acceleration of the vehicle per unit time. After that, the pre-stop control unit 11 transfers the process to step S303.

[0057] In step S303, the pre-stop control unit 11 causes the calculation unit 14 to calculate the longitudinal acceleration at the stop position of the vehicle. The calculation unit 14 calculates the longitudinal acceleration at the stop position as a predicted value estimated based on the required jerk. After that, the pre-stop control unit 11 transfers the process to step S304.

[0058] In step S304, the pre-stop control unit 11 determines whether the longitudinal acceleration at the stop position is within the allowable range. The pre-stop control unit 11 determines that the longitudinal deceleration is within the allowable range when the magnitude of the longitudinal acceleration is less than the allowable value. On the other hand, the pre-stop control unit 11 determines that the longitudinal acceleration is outside the allowable range when the magnitude of the longitudinal acceleration is greater than or equal to the allowable value. In order to determine whether the change amount of the longitudinal acceleration when the vehicle stops is suppressed to be small, the allowable value is set to a value calculated in advance through experiments or the like.

[0059] When the front and rear accelerations are within the allowable range (S304: Yes), the pre-stop control unit 11 transfers the process to step S305. In step S305, the pre-stop control unit 11 sets the prohibition flag F1 to "1". As a result, the reduction control is no longer started. After that, the pre-stop control unit 11 ends this processing procedure.

[0060] On the other hand, when the front and rear accelerations are outside the allowable range (S304: No), the pre-stop control unit 11 transfers the process to step S306. In step S306, the pre-stop control unit 11 sets the prohibition flag F1 to "0". After that, the pre-stop control unit 11 ends this processing procedure.

[0061] Next, Figure 5 is used to explain the calculation process of the shortening distance Di2 executed by the calculation unit 14. During the execution of the increasing control started in the processing of step S102 of Figure 2 , it is repeatedly executed by the calculation unit 14 for each specified cycle.

[0062] When this processing procedure starts, first in step S401, the calculation unit 14 determines whether the elapsed time Ti1 is greater than the reaction time Tith. The reaction time Tith corresponds to a specified determination time. When the elapsed time Ti1 is greater than the reaction time Tith (S401: Yes), the calculation unit 14 transfers the process to step S402.

[0063] In step S402, the calculation unit 14 stops the accumulation of the shortening distance Di2. After that, the calculation unit 14 transfers the process to step S403. In step S403, the calculation unit 14 starts subtracting the shortening distance Di2. After that, the calculation unit 14 ends this processing procedure.

[0064] Here, an example of the process for the calculation unit 14 to calculate the shortening distance Di2 is explained. The calculation unit 14 calculates the value obtained by subtracting the subtraction value from the basic value as the shortening distance Di2. The basic value is calculated based on the increase value of the braking force increased relative to the required braking force by executing the increasing control and the time for continuously executing the increasing control. The calculation unit 14 increases the shortening distance Di2 by increasing the basic value during the execution of the increasing control. The subtraction value is calculated as the value for reducing the shortening distance Di2 as the increasing control continues. For example, the calculation unit 14 uses the value of the shortening distance Di2 at the time point obtained by tracing back the reaction time Tith from the time point when the subtraction value is calculated as the subtraction value. The calculation unit 14 can also use a preset constant as the subtraction value.

[0065] Return Figure 5, the stop of the accumulation of the shortening distance Di2 in the process of step S402 means stopping the process of calculating the basic value in the shortening distance Di2. When the process of step S402 is executed, the calculation unit 14 holds the previously calculated basic value and uses the held basic value to calculate the shortening distance Di2. That is, when the process of step S402 is executed, the increase of the shortening distance Di2 is suppressed. The subtraction of the shortening distance Di2 in the process of step S403 means starting the process of calculating the subtraction value in the shortening distance Di2. When the process of step S403 is executed, the calculation unit 14 starts the calculation of the subtraction value. In addition, until the process of step S403 is executed, the calculation unit 14 sets the subtraction value to "0".

[0066] On the other hand, in the process of step S401, when the elapsed time Ti1 is less than or equal to the reaction time Tith (S401: No), the calculation unit 14 transfers the process to step S404. In step S404, the calculation unit 14 continues to accumulate the shortening distance Di2. That is, the calculation unit 14 continues to calculate the basic value in the shortening distance Di2. After that, the calculation unit 14 ends this processing process.

[0067] The functions and effects of this embodiment will be described.

[0068] Figures 6 to 9 The change in the braking force controlled by stopping the execution of the pre-braking control is shown. In Figure 6 In the example shown, the operation amount BR is not changed during the execution of the pre-braking control. In Figure 6 In the example shown, the control starts to increase from time t11. The calculation of the elapsed time Til starts from time t12. The period from time t11 to time t12 shows the standby time. The period from time t12 to time t13 corresponds to the reaction time Tith. The vehicle stops at time t15.

[0069] In Figure 6 , the extension distance Di1 and the shortening distance Di2 are expressed as variable distances in (a). Figure 6 The solid line shown in (a) of Figure 6 represents the extension distance Di1.

[0070] As Figure 6 shown in (b) of

[0071] Figure 6 The solid line in (c) of Figure 6 represents the longitudinal acceleration of the vehicle. Figure 6The dashed line in (c) indicates the longitudinal acceleration before and after when the braking force is controlled with the required braking force corresponding to the operation amount BR as the target value.

[0072] Figure 6 The braking force correction amount shown in (d) is the increase or decrease value relative to the required braking force. When the braking correction amount is "0", the braking force is equal to the required braking force. When the braking force correction amount is positive, the braking force is increased compared to the required braking force. When the braking force correction amount is negative, the braking force is decreased compared to the required braking force.

[0073] When the control starts to increase at time t11, the braking force is increased as shown in (d). As a result, as shown in (c), the longitudinal acceleration decreases compared to the comparative example shown by the dashed line. Figure 6 As a result, as shown in (c), the longitudinal acceleration decreases compared to the comparative example shown by the dashed line. Figure 6 As shown in (c) of, the longitudinal acceleration is smaller than that of the comparative example shown by the dashed line.

[0074] As shown in Figure 6 As shown in (a), by performing the increase control, the shortening distance Di2 gradually increases after time t12. As a result, the difference between the lengthening distance Di1 and the shortening distance Di2 gradually decreases after time t12. At time t13, the difference between the lengthening distance Di1 and the shortening distance Di2 becomes small, and it is determined that this difference is less than the determination value α (S201: Yes). At this time, since the elapsed time Ti1 does not exceed the reaction time Tith (S301: No), the prohibition flag F1 is the initial value "0". That is, the configuration data in the decrease control is set (S203), the increase control is ended, and the decrease control is started (S204).

[0075] When the decrease control starts at time t13, the braking force is decreased as shown in (d). The braking force is maintained fixed during the period from time point t14 to time t15. As a result, as shown in (c), the longitudinal acceleration increases in a manner approaching "0". When the vehicle stops at time t15, the change amount of the longitudinal acceleration becomes small. When the vehicle stops at time t15, the holding control is executed by the pre-stop control unit 11, and the braking force is increased as shown in (d). Figure 6 As a result, as shown in (c), the longitudinal acceleration increases in a manner approaching "0". When the vehicle stops at time t15, the change amount of the longitudinal acceleration becomes small. When the vehicle stops at time t15, the holding control is executed by the pre-stop control unit 11, and the braking force is increased as shown in (d). Figure 6 As shown in (c), the longitudinal acceleration increases in a manner approaching "0". When the vehicle stops at time t15, the change amount of the longitudinal acceleration becomes small. When the vehicle stops at time t15, the holding control is executed by the pre-stop control unit 11, and the braking force is increased as shown in (d). Figure 6 As shown in (d), the braking force is increased.

[0076] According to the braking control device 10, the increase control is executed before the decrease control starts in the pre-stop braking control. As a result, the lengthening distance Di1 can be suppressed from becoming long. That is, the extension of the braking distance can be suppressed, and the change amount of the longitudinal acceleration before the vehicle stops can be reduced.

[0077] In the braking control device 10, the braking force is increased by increasing control in such a way that the difference between the extended distance Dil and the shortened distance Di2 until the reaction time Tith elapses is less than the determination value α. That is, the period during which the braking force is increased does not exceed the reaction time Tith. Therefore, it becomes difficult for the driver of the vehicle to recognize that the braking force has been increased. In other words, even if the braking force is increased by increasing control, it is difficult for the driver to feel the deviation between the driver's own operation and the acceleration of the vehicle. Assuming that the driver recognizes an increase in the braking force, there is a possibility of releasing the braking operation member to reduce the operation amount BR. In contrast, according to the braking control device 10, it is possible to suppress the operation amount BR from being changed by the driver during the execution of the increasing control.

[0078] Figure 7 The example shown and Figure 6 The difference from the example shown is that the operation amount BR is changed during the execution of the pre-stop braking control. In Figure 7 In the example shown, after the increasing control starts at time t21, the driver releases the braking operation member. That is, the operation amount BR is reduced, and as shown by the dotted line in Figure 7 (c), the longitudinal acceleration corresponding to the operation amount BR gradually increases.

[0079] In Figure 7 In the example shown, the calculation of the elapsed time Ti1 starts from time t21. The period from time t21 to time t22 shows the standby time. The period from time t22 to time t23 corresponds to the reaction time Tith. The vehicle stops at time t24.

[0080] Figure 7 The double-dot dash line shown in (a) of Figure 6 is a comparative example of the extended distance Di1 showing the case where the operation amount BR is not changed during the execution of the pre-stop braking control. Similar to the example shown in

[0081] In contrast, as shown by the solid line in Figure 7 (a), since the operation amount BR is reduced during the execution of the increasing control, the actual extended distance Di1 is calculated to be greater than the value of the comparative example shown by the double-dot dash line. Therefore, at the time point of time t23, the difference between the extended distance Di1 and the shortened distance Di2 becomes large, and this difference becomes greater than or equal to the determination value α. That is, the increasing control continues after time t23 (S205).

[0082] After time Ti1 elapses after time t23 and is greater than the reaction time Tith (S401: Yes), the accumulation of the shortened distance Di2 is stopped (S402), and the subtraction of the shortened distance Di2 is started (S403). Therefore, asFigure 7 As shown by the dashed line in (a) of, the shortening distance Di2 gradually decreases after time t23. After time t23, the extension distance Di1 and the shortening distance Di2 progress and the difference between the extension distance Di1 and the shortening distance Di2 is not less than the determination value α. Therefore, at time t24, the vehicle stops without starting the reduction control. As Figure 7 As shown in (c) of, the change amount of the longitudinal acceleration at the time of stopping becomes small.

[0083] As Figure 7 As shown in (d) of, the braking force that increases after the start of the increase control at time t21 continues to increase during the period until time t24. In addition, the braking force after the vehicle stops is maintained by the stop pre-control unit 11 during the period from time t24 to time point t25 and then decreases to the required braking force.

[0084] As Figure 7 In the example shown, it is considered that the operation amount BR is changed during the execution of the pre-stop braking control, which means that the driver intends to make the stop position farther than the case where the pre-stop braking control is not executed, or the driver performs the stop operation comfortably through his own operation. That is, when the pre-stop braking control intervenes during braking and causes a change in the longitudinal acceleration, the changed longitudinal acceleration may not conform to the driver's intention. The driver may also feel uncomfortable with the changed longitudinal acceleration. Therefore, in the braking control device 10, even if the elapsed time Ti1 is greater than the reaction time Tith, when the difference between the extension distance Di1 and the shortening distance Di2 is greater than or equal to the determination value α and the increase control continues, the shortening distance Di2 is subtracted. Thus, when the braking operation member is operated in such a way that the extension distance Di1 becomes "0" at the time point when the vehicle reaches the stop position, the difference between the extension distance Di1 and the shortening distance Di2 is difficult to become less than the determination value α. Moreover, by operating the braking operation member in such a way that the extension distance Di1 becomes "0" at the time point when reaching the stop position, it is possible to reduce the change amount of the longitudinal acceleration at the time of stopping without executing the reduction control as Figure 7 shown in (c) of. In this way, in the braking control device 10, according to the operation method of the driver on the braking operation member during the execution of the increase control, it is possible to perform braking centered on the driver's operation without executing the reduction control.

[0085] Figure 8 In the example shown, the operation amount BR is changed during the execution of the pre-stop braking control, but the way of changing the operation amount BR is different from Figure 7 the example shown in. In Figure 8 the example shown, after the start of the increase control at time point t31, the driver releases the braking operation member. However, the reduction amount of the operation amount BR caused by the release is smaller than Figure 7 the example shown in. Therefore, asFigure 8 As shown by the dashed line in (c) of, the inclination of the longitudinal acceleration corresponding to the operation amount BR is less than Figure 7 the inclination of the longitudinal acceleration in (c) of. Such an example is equivalent to a case where the correction of the stop position generated by the driver's operation is small, or a case where the feel is poor when the vehicle stops according to the driver's operation due to insufficient driving skills of the driver, etc.

[0086] In this Figure 8 example shown, as Figure 8 shown in (a) of, although the difference between the extended distance Di1 and the shortened distance Di2 at the time point t34 after the reaction time Tith has elapsed from the time point t32 is greater than or equal to the determination value α, the difference between the extended distance Di1 and the shortened distance Di2 at the time point t34 after the time point t33 is less than the determination value α. Therefore, the reduction control starts at the time point t34. By the reduction control, as Figure 8 shown in (d) of, the braking force is reduced during the period from the time point t34 to the time point t35. The braking force is maintained fixed during the period from the time point t35 to the time point t36. The reduction control ends when the vehicle stops at the time point t36. The holding control is executed after the time point t36.

[0087] In addition, after the time point t33, the time Ti1 is greater than the reaction time Tith (S301: Yes), and thus the longitudinal acceleration at the stop position of the vehicle is estimated (S303). In Figure 8 the example shown, the longitudinal acceleration is estimated to be a value outside the allowable range. Therefore, the prohibition flag F1 is set to "0" (S306). Since the prohibition flag F1 is "0" (S202: Yes), the reduction control is not prohibited and the reduction control starts at the time point t34 when the difference between the extended distance Di1 and the shortened distance Di2 is less than the determination value α.

[0088] Assuming that the longitudinal acceleration is estimated to be a value within the allowable range around the time point t34, the prohibition flag F1 is set to "1" (S305). In this case, since the prohibition flag F1 is "1" (S202: No), the reduction control does not start and the increasing control continues. That is, Figure 7 as in the example shown, the increasing control continues until the vehicle stops. In this way, even if the difference between the extended distance Di1 and the shortened distance Di2 is less than the determination value α, when the longitudinal acceleration at the stop position of the vehicle is estimated to be a value within the allowable range, the increasing control can continue so that the reduction control does not start.

[0089] In the brake control device 10, the configuration data is updated at the time point when the reduction control starts. Therefore, in Figure 8 the example shown, as Figure 6The reduction value of the braking force becomes smaller compared to the example shown. Thus, in the braking control device 10, by calculating the configuration data based on the vehicle speed at the time when the reduction control starts, even if the timing of starting the reduction control changes, it is possible to reduce the change amount of the longitudinal acceleration before the vehicle stops.

[0090] In the braking control device 10, when the difference between the extension distance Di1 and the shortening distance Di2 is less than the determination value α, the increase control is ended and the reduction control is started. The driver's operation is reflected in the calculation of the extension distance Di1. Further, when the operation amount BR is changed during the execution of the increase control, the magnitude of the braking force is affected by the operation amount BR. That is, the shortening distance Di2 representing the distance shortened by the execution of the increase control varies depending on the operation amount BR. Thus, the operation amount BR is reflected in both the extension distance Di1 and the shortening distance Di2. Therefore, for example, when the operation amount BR is changed, it is possible to reflect the driver's operation on the vehicle at the time of starting the reduction control. Thereby, it is easy to achieve a braking distance that reflects the driver's operation. Figure 8 In addition, not limited to the driver's operation on the braking operation member, when other control other than the pre-stop braking control intervenes to change the braking force, by the braking control device 10 that changes the timing of starting the reduction control according to the extension distance Di1 and the shortening distance Di2, it is possible to start the reduction control in such a way as to reduce the change amount of the longitudinal acceleration before stopping.

[0091] In the example shown, after the increase control starts at time t41, the driver steps on the braking operation member. That is, the operation amount BR is increased, and as shown by the dotted line in (c) of, the longitudinal acceleration corresponding to the operation amount BR gradually decreases.

[0092] In Figure 9 the example shown, the calculation of the elapsed time Ti1 starts from time t41. The period from time t41 to time t42 shows the standby time. The period from time t42 to time t44 corresponds to the reaction time Tith. The vehicle stops at time t46. Figure 9 The double-dot chain line shown in (a) of is a comparative example of the extension distance Di1 showing the case where the operation amount BR is not changed during the execution of the pre-stop braking control. The comparative example shown by the double-dot chain line, similarly to the example shown in, at time t44 when the reaction time Tith has elapsed, the difference from the shortening distance Di2 is less than the determination value α.

[0093] In Figure 9 the example shown, the double-dot chain line shown in (a) of is a comparative example of the extension distance Di1 showing the case where the operation amount BR is not changed during the execution of the pre-stop braking control. The comparative example shown by the double-dot chain line, similarly to the example shown in, at time t44 when the reaction time Tith has elapsed, the difference from the shortening distance Di2 is less than the determination value α.

[0094] Figure 9 In contrast, as shown in Figure 6 the example shown, the double-dot chain line shown in (a) of is a comparative example of the extension distance Di1 showing the case where the operation amount BR is not changed during the execution of the pre-stop braking control. The comparative example shown by the double-dot chain line, similarly to the example shown in, at time t44 when the reaction time Tith has elapsed, the difference from the shortening distance Di2 is less than the determination value α.

[0095] In contrast, as Figure 9As shown by the solid line in (a), since the operation amount BR is increased during the execution of the increase control, the actual extension distance Di1 is calculated to be less than the value of the comparative example shown by the double-dashed line. Therefore, at time t43 before time t44, the difference between the extension distance Di1 and the shortening distance Di2 is less than the determination value α. That is, the reduction control starts at time t43. By the reduction control, as Figure 9 shown in (d), the braking force is reduced during the period from time t43 to time t45. The braking force is maintained fixed during the period from time t45 to time t46. The reduction control ends at the time t46 when the vehicle stops. The holding control is executed after time t46.

[0096] In addition, in Figure 9 the example shown, by stepping on the braking operation member during the execution of the increase control, as shown at times t41 to t43, the longitudinal acceleration significantly deviates from "0". In Figure 9 the reduction control in the example shown, in order to reduce the change amount of the longitudinal acceleration when the vehicle stops, the configuration data is calculated in such a way that the reduction value of the braking force becomes larger compared to the example shown in Figure 6 . The configuration data in the reduction control is updated by the reduction unit 13 at the time point when the reduction control starts.

[0097] As Figure 9 shown in the example, in the case where the operation amount BR is increased during the execution of the increase control, the braking control device 10 that changes the start time of the reduction control according to the extension distance Di1 and the shortening distance Di2 can execute the reduction control in such a way that the change amount of the longitudinal acceleration when the vehicle stops is reduced.

[0098] This embodiment can be modified as follows. This embodiment and the following modification examples can be implemented in combination with each other within a technically non-contradictory range.

[0099] · In the above embodiment, as Figure 5 shown, when the elapsed time Ti1 is greater than the reaction time Tith, the shortening distance Di2 is subtracted during the period of continuously increasing the control. Instead, the shortening distance Di2 can be kept fixed after the elapsed time Ti1 exceeds the reaction time Tith. In addition, the increase of the shortening distance Di2 can be continued, and the increase speed of the shortening distance Di2 can be reduced. That is, after the elapsed time Ti1 exceeds the reaction time Tith, the increase of the shortening distance Di2 can be suppressed or the shortening distance Di2 can be reduced.

[0100] For example, instead of executing the processes of step S402 and step S403 in Figure 5 , the process of step S402 or the process of step S403 can be executed.

[0101] · In the above-described embodiment, when there is a change in the operation amount BR during the execution of the increase control, the change in the operation amount BR is reflected in the adjustment of the extension distance Di1 and the braking force. The braking control device 10 may also determine whether to reflect the change in the operation amount BR based on the information acquired by the monitoring device 50. For example, the change in the operation amount BR may not be reflected when there is a possibility of a driver's misoperation. In addition, when it can be inferred that the driver is not used to driving the vehicle, the degree of reflecting the change in the operation amount BR can also be reduced.

[0102] · The braking control device may be, for example, a device that executes the reduction control and the increase control. The reduction control reduces the braking force applied to the vehicle regardless of the driver's braking operation during the vehicle stop for a vehicle decelerated by the driver's braking operation. The increase control increases the braking force applied to the vehicle regardless of the driver's braking operation during the period before the execution of the reduction control in order to compensate for the braking distance of the vehicle extended by the execution of the reduction control.

[0103] For example, the braking control device may be a device including an accumulation unit and a control unit. The accumulation unit accumulates the operation amount BR of the braking operation member before the start of the execution of the reduction control, and the control unit starts the reduction control based on the accumulated value of the operation amount BR.

[0104] · The pre-stop braking control in the above-described embodiment is not limited to braking when the vehicle is moving forward, and can also be applied to braking when the vehicle is moving backward.

Claims

1. A braking control device that, when a braking operation member is operated by a driver of a vehicle, performs pre-stop braking control for adjusting the braking force of the vehicle when the vehicle stops by braking. The braking control device includes: A reducing unit that performs reducing control in the pre-stop braking control to reduce the braking force applied to the vehicle compared to the required braking force, where the required braking force is the braking force corresponding to the operation amount of the braking operation member; An increasing unit that performs increasing control in the pre-stop braking control to increase the braking force compared to the required braking force before the start of the reducing control; And A calculating unit that calculates a shortening distance and an extension distance during the execution of the increasing control. The shortening distance is a value obtained by estimating the distance by which the braking distance is shortened when the braking force is increased by the execution of the increasing control compared to the case where the increasing control is not executed, and the extension distance is a value obtained by estimating the distance by which the braking distance is extended when the braking force is reduced by the execution of the reducing control compared to the case where the reducing control is not executed. The calculating unit calculates the extension distance in such a manner that the extension distance becomes longer when the operation amount decreases during the braking of the vehicle compared to the case where the operation amount does not decrease. The reducing unit starts the reducing control when the difference between the extension distance and the shortening distance is less than a determination value.

2. The braking control device according to claim 1, wherein the reducing unit performs the reducing control in accordance with configuration data that defines the reduction amount of the braking force and the speed at which the braking force is reduced in the reducing control, and sets the configuration data based on the wheel speed of the vehicle at the time point when the reducing control is started.

3. The braking control device according to claim 2, wherein after the duration of the increasing control exceeds a specified determination time, when the operation amount is reduced during the execution of the increasing control, the increasing unit maintains a state where the braking force is greater than the required braking force and reduces the braking force. The reducing unit does not start the reducing control when the difference between the extension distance and the shortening distance is greater than or equal to the determination value.

4. The braking control device according to claim 1 or 2, wherein the calculating unit predicts the longitudinal acceleration of the vehicle at the time point when the vehicle stops by braking based on at least one of the operation amount and the required braking force. When the operation amount is reduced during the execution of the increasing control, the increasing unit maintains a state where the braking force is greater than the required braking force and reduces the braking force. When the magnitude of the predicted value of the longitudinal acceleration at the time point when the vehicle stops by braking is less than a specified allowable value, even if the difference between the extension distance and the shortening distance is less than the determination value, the increasing control is continued. When the magnitude of the predicted value of the longitudinal acceleration at the time point when the vehicle stops by braking is less than the allowable value, the reducing unit does not start the reducing control even if the difference between the extension distance and the shortening distance is less than the determination value.

5. A braking control device performs a reduction control and an increase control on the vehicle that decelerates by the operation of a braking operation member by a driver of the vehicle. The reduction control reduces the braking force applied to the vehicle regardless of the operation of the braking operation member during the vehicle stop in order to suppress the movement of the vehicle accompanying the vehicle stop. The increase control increases the braking force applied to the vehicle regardless of the operation of the braking operation member during a period earlier than the execution period of the reduction control in order to compensate for the braking distance of the vehicle extended by the execution of the reduction control. It is characterized in that the braking control device includes: an accumulation unit that accumulates the operation amount of the braking operation member before the start of the execution of the reduction control; and a control unit that starts the reduction control based on the operation amount of the braking operation member accumulated by the accumulation unit.

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