Vehicle stop-holding device

Abstract

To provide a vehicle stop holding device capable of maintaining a vehicle stop holding state in a reliable manner.SOLUTION: A vehicle stop holding device 100 for holding a stop of a vehicle 1 includes an ECU 10 for executing turning-over control to turn over an operation of a brake device 5 to a driver when it is determined that backup control for holding a stop state of the vehicle 1 by a brake holding device 6 cannot be achieved after the vehicle 1 is stopped by the brake device 5, and a getting-off operation by the driver is detected, and executing turning-over control when a grace time necessary for the turning-over control elapses from the reference time after the undermentioned determination when it is determined that the backup control cannot be achieved after the vehicle 1 is stopped by the brake device 5, and a getting-off operation by the driver is not detected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle stop-holding device. [Background technology]

[0002] As a technical document related to a vehicle stop-holding device, for example, Patent Document 1 discloses a driving control device that, if an abnormal condition is detected in the stop-holding device while the vehicle is stopped, maintains the vehicle stopped using hydraulic brakes until the driver operates the brakes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4788354 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vehicle stop-holding device described above, if the hydraulic brakes reach their limit after the driver gets off the vehicle without applying the brakes, there is a risk that the vehicle will not be able to maintain its stopped state.

[0005] Therefore, an object of one aspect of the present invention is to provide a vehicle stop-holding device that can reliably maintain a vehicle stopped state. [Means for solving the problem]

[0006] A vehicle stop-maintaining device according to one aspect of the present invention is a vehicle stop-maintaining device that maintains a stop of a vehicle, and if it determines that backup control for maintaining the vehicle's stopped state by the brake-maintaining device cannot be realized after the vehicle has been stopped by the brake device and detects that the driver has dismounted, it executes handover control to hand over operation of the brake device to the driver, and if it determines that backup control cannot be realized after the vehicle has been stopped by the brake device and does not detect that the driver has dismounted, it is equipped with a control unit that executes handover control when a grace period required for handover control has elapsed from a reference time after the determination.

[0007] In a vehicle stop-holding device according to one aspect of the present invention, the control unit controls the braking force applied to the vehicle by the brake device during handover control, and may change the braking force in a first pattern during handover control after the vehicle is stopped by the brake device, and may change the braking force in a second pattern different from the first pattern during handover control before the vehicle is stopped by the brake device. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to provide a vehicle stop-holding device that can reliably maintain a vehicle stopped state. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a vehicle stop-holding device according to an embodiment of the present invention; [Figure 2] 10 is a flowchart illustrating an example of a process for keeping a vehicle stopped. [Figure 3] 10 is a flowchart illustrating an example of a process for keeping a vehicle stopped. [Figure 4] 10 is a flowchart illustrating an example of a process for keeping a vehicle stopped. [Figure 5] 10 is a flowchart showing another example of a process for maintaining a stop of the vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] Fig. 1 is a block diagram showing a vehicle stop-maintaining device 100 according to this embodiment. The vehicle stop-maintaining device 100 shown in Fig. 1 is a device that maintains the vehicle 1 at a stop when the vehicle 1 comes to a stop. The vehicle 1 is not particularly limited and may be various devices.

[0012] The vehicle stop-holding device 100 includes an ECU (Electronic Control Unit) 10 (controller) that controls the entire system. The ECU 10 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a CAN (Controller Area Network) communication circuit, etc. The ECU 10 performs various functions by, for example, loading a program stored in the ROM into the RAM and executing the program loaded into the RAM with the CPU.

[0013] The ECU 10 may be configured with multiple electronic units. Some of the functions of the ECU 10 described below may be executed by a server that can communicate with the vehicle. The functional configuration and processing of the ECU 10 will be described in detail later. The ECU 10 is connected to an internal sensor 2, an external sensor 3, an accelerator device 4, a brake device 5, a brake holding device 6, and an HMI (Human Machine Interface) 7.

[0014] The internal sensors 2 are detection devices that detect the driving state of the vehicle 1 and the internal state of the vehicle 1. The internal sensors 2 transmit the detection results to the ECU 10. The internal sensors 2 include an accelerator sensor and a brake sensor. The accelerator sensor detects the amount of operation of the accelerator device 4 by the driver and transmits the detected amount of operation to the ECU 10. The brake sensor detects the amount of operation of the brake device 5 by the driver and transmits the detected amount of operation to the ECU 10.

[0015] The internal sensor 2 includes a sensor that detects an exit operation by the driver. The exit operation is an operation by an occupant of the vehicle 1 to exit the vehicle 1. For example, the internal sensor 2 includes a seat belt sensor that detects an operation to release a seat belt as an exit operation, and a door opening / closing sensor that detects an operation to open a door as an exit operation. Note that the operation to open a door may be, for example, an operation to unlock the door (unlocking operation), or may be an operation other than those described above. The internal sensor 2 may also include a vehicle speed sensor, an acceleration sensor, and a yaw rate sensor.

[0016] The external sensor 3 is a detection device for detecting obstacles and the like around the vehicle 1. The external sensor 3 transmits the detection results to the ECU 10. The external sensor 3 includes at least one of a camera, a radar, and a LIDAR (Laser Imaging Detection and Ranging).

[0017] The accelerator device 4 operates a drive device such as a motor or an engine. The accelerator device 4 is controlled by, for example, the driver or the ECU 10. The brake device 5 controls the braking force applied to the wheels of the vehicle 1. The brake device 5 is, for example, a hydraulic brake. The brake device 5 is controlled by, for example, the driver or the ECU 10.

[0018] The brake holding device 6 holds the vehicle 1 in a stopped state. The brake holding device 6 is controlled, for example, by the driver or the ECU 10. As an example, the brake holding device 6 controls the parking brake 6a in response to a control signal from the ECU 10, and activates or releases the parking brake 6a. The parking brake 6a may be, for example, an electric parking brake (EPB).

[0019] The HMI 7 is an interface for transmitting and receiving information between an occupant (e.g., a driver) of the vehicle 1 and the vehicle stop-maintenance device 100. The HMI 7 includes a display 7a that displays image information to the occupant, a speaker that transmits audio to the occupant, etc. In response to a control signal from the ECU 10, the HMI 7 displays image information on the display 7a and transmits audio via the speaker.

[0020] The ECU 10 controls the accelerator device 4, the brake device 5, the brake holding device 6, and the HMI 7 based on the detection results of the internal sensor 2 and the external sensor 3, and executes the following control.

[0021] The ECU 10 performs vehicle speed adjustment assistance for the vehicle 1. The vehicle speed adjustment assistance is driving assistance that automatically adjusts the vehicle speed of the vehicle 1 according to the surrounding environment of the vehicle 1 and the driving conditions of the vehicle 1. The vehicle speed adjustment assistance is, for example, adaptive cruise control (ACC). For example, ACC control is constant speed control that causes the vehicle 1 to travel at a predetermined set speed when there is no preceding vehicle ahead of the vehicle 1. For example, ACC control is follow-up control that adjusts the vehicle speed of the vehicle 1 so that the inter-vehicle distance from the preceding vehicle becomes a predetermined set distance when there is a preceding vehicle ahead of the vehicle 1. The ACC control works in conjunction with a brake hold function that operates the brake device 5 to apply automatic brakes, and allows the vehicle 1 to travel or stop so as to follow the preceding vehicle.

[0022] The ECU 10 executes backup control to maintain the vehicle 1 in a stopped state using the brake holding device 6. Specifically, the ECU 10 executes control to activate the parking brake 6a in the backup control. For example, if the vehicle 1 is a vehicle equipped with (or configured with) an electric parking brake, the ECU 10 activates the electric parking brake in the backup control. Note that, for example, if the vehicle 1 is a vehicle equipped with (or configured with) a shift-by-wire (SBW) system, the ECU 10 activates an auto P lock (automatic parking lock) in the backup control.

[0023] The ECU 10 determines whether or not backup control can be realized by the brake holding device 6. A case in which backup control cannot be realized may be, for example, when the parking brake 6a has malfunctioned. Also, a case in which backup control cannot be realized may be, for example, when the vehicle 1 is stopped on a steep slope and the brake device 5 is no longer able to maintain the stopped state of the vehicle 1. Note that backup control may be impossible to realize in cases other than those described above.

[0024] The ECU 10 executes takeover control (brake operation handover control) to allow the driver to take over (hand over) the operation of the brake device 5. If the ECU 10 determines that backup control cannot be realized before the vehicle 1 is stopped by the brake device 5, the ECU 10 executes the takeover control. In this takeover control, the ECU 10 changes the braking force of the brake device 5 in a predetermined pattern.

[0025] When the ECU 10 determines that backup control cannot be realized after the vehicle 1 is stopped by the brake device 5 and detects an operation by the driver to get off the vehicle, the ECU 10 executes takeover control. In this takeover control, the ECU 10 changes the braking force of the brake device 5 in a first pattern. For example, the ECU 10 gradually reduces the braking force of the brake device 5 to zero.

[0026] If the ECU 10 determines that backup control cannot be realized after the vehicle 1 is stopped by the brake device 5 and does not detect an operation by the driver to get out of the vehicle, the ECU 10 executes takeover control when a grace period required for takeover control has elapsed from a reference time after the determination. In this takeover control, the ECU 10 changes the braking force of the brake device 5 in a second pattern. For example, the ECU 10 repeatedly increases and decreases the braking force of the brake device 5. Note that the second pattern may be any pattern that draws the driver's attention to driving operations when the braking force of the brake device 5 is changed in this pattern.

[0027] The ECU 10 notifies the driver of the remaining time until the grace period expires. The ECU 10, for example, displays the remaining time in a countdown format on the display 7a, and executes a notification requesting a brake operation. The ECU 10 may also notify the driver of the remaining time by voice, for example, through a speaker.

[0028] Next, a processing method of the vehicle stop-holding device 100 according to this embodiment will be described. Figures 2 to 4 are flowcharts showing an example of processing for holding the vehicle 1 at a stop. The ECU 10 periodically executes processing for determining whether or not backup control can be achieved by the brake holding device 6. More specifically, in the processing for holding the vehicle 1 at a stop, the processing of S10 to S27 is repeatedly executed.

[0029] 2, in S10, the ECU 10 determines whether or not ACC control is being executed. If the ECU 10 determines that ACC control is being executed (S10: YES), the ECU 10 proceeds to S11. If the ECU 10 determines that ACC control is not being executed (S10: NO), the ECU 10 ends the process of keeping the vehicle 1 stopped for this cycle and proceeds to S10 for the next cycle.

[0030] Next, in S11, the ECU 10 determines whether the vehicle 1 is stopped (following stopped). For example, the ECU 10 acquires information indicating the vehicle speed of the vehicle 1 from a vehicle speed sensor included in the internal sensor 2, and determines whether the vehicle 1 is stopped. If the ECU 10 determines that the vehicle 1 is stopped (S11: YES), the ECU 10 proceeds to S12. If the ECU 10 determines that the vehicle 1 is not stopped (S11: NO), the ECU 10 ends the process of keeping the vehicle 1 stopped for this cycle, and proceeds to S10 for the next cycle.

[0031] Next, in S12, the ECU 10 determines whether or not it has determined that backup control cannot be executed before the vehicle 1 is stopped by the braking device 5. If the ECU 10 determines that backup control cannot be executed before the vehicle 1 is stopped by the braking device 5 (S12: YES), the ECU 10 proceeds to S13. If the ECU 10 has not determined that backup control cannot be executed before the vehicle 1 is stopped by the braking device 5 (S12: NO), the ECU 10 proceeds to S15 (see FIG. 3).

[0032] Next, in S13, the ECU 10 ends the ACC control. Finally, in S14, the ECU 10 executes the takeover control, then ends the process of keeping the vehicle 1 stopped for this cycle and proceeds to S10 for the next cycle. In this way, if it is determined that backup control cannot be realized before the vehicle 1 stops, the braking force of the brake device 5 is changed and the operation of the brake device 5 is handed over to the driver.

[0033] 3, in S15, the ECU 10 determines whether or not it has determined that backup control cannot be executed after the vehicle 1 has been stopped by the braking device 5. If the ECU 10 determines that backup control cannot be executed after the vehicle 1 has been stopped by the braking device 5 (S15: YES), the ECU 10 proceeds to S16. If the ECU 10 has not determined that backup control cannot be executed after the vehicle 1 has been stopped by the braking device 5 (S15: NO), the ECU 10 proceeds to S25.

[0034] Next, in S16, the ECU 10 ends the ACC control. Next, in S17, the ECU 10 turns on the warning lamp. Next, in S18, the ECU 10 determines whether or not a vehicle exit operation by the driver has been detected. For example, the ECU 10 determines whether or not a vehicle exit operation by the driver has been detected based on information acquired from a seat belt sensor, a door opening / closing sensor, etc. included in the internal sensor 2. If the ECU 10 determines that a vehicle exit operation by the driver has been detected (S18: YES), the ECU 10 proceeds to S14 (see FIG. 2). If the ECU 10 determines that a vehicle exit operation by the driver has not been detected (S18: NO), the ECU 10 proceeds to S19.

[0035] Next, in S19, the ECU 10 determines whether or not an accelerator operation (operation of the accelerator device 4) or a brake operation (operation of the brake device 5) by the driver has been detected. For example, the ECU 10 determines whether or not an accelerator operation or a brake operation by the driver has been detected based on the operation amount of the accelerator device 4 acquired from an accelerator sensor included in the internal sensor 2 or the operation amount of the brake device 5 acquired from a brake sensor. If the ECU 10 determines that an accelerator operation or a brake operation by the driver has been detected (S19: YES), the ECU 10 proceeds to S24. If the ECU 10 determines that an accelerator operation or a brake operation by the driver has not been detected (S19: NO), the ECU 10 proceeds to S20.

[0036] Next, in S20, the ECU 10 determines whether a grace period required for the takeover control has elapsed since the reference time. The reference time is the time after the vehicle 1 stops. The reference time may be, for example, the time after it is determined in S16 that backup control cannot be realized. The reference time is, for example, the time when the warning lamp is turned on in S17. The reference time may be any time other than the above. The grace period is a predetermined period. The grace period may be any period set to ensure the driver's attention to driving operations (driver engagement: driver adaptability). For example, the grace period may be a period that allows the driver to reliably and safely take over operation of the brake device when takeover control is executed after the grace period has elapsed. The grace period may be longer than the time required for the driver to get out of the vehicle (for example, 2 seconds).

[0037] When the ECU 10 determines that the grace period required for the takeover control has elapsed since the reference time (S20: YES), the ECU 10 proceeds to S21. Subsequently, the ECU 10 executes the takeover control in S21 and proceeds to S24. In this way, the ECU 10 gives the driver a grace period before taking over the operation of the brake device 5 (requesting a handover) in consideration of changes in the driver's attention to driving operations while the vehicle 1 is stopped.

[0038] If the ECU 10 determines that the grace time required for takeover control has not elapsed since the reference time (S20: NO), the ECU 10 proceeds to S23. In S23, the ECU 10 controls the brake device 5 to hold the vehicle 1 in a stopped state, and then proceeds to S18. Finally, in S24, the ECU 10 releases the brake of the brake device 5, and then ends the process of holding the vehicle 1 stopped for this cycle, and proceeds to S10 for the next cycle.

[0039] As shown in FIG. 4, in S25, the ECU 10 determines whether a predetermined time has elapsed since the vehicle 1 entered a stopped state (following stopped state). If the ECU 10 determines that the predetermined time has elapsed since the vehicle 1 entered a stopped state (YES in S25), the ECU 10 proceeds to S26. If the ECU 10 determines that the predetermined time has not elapsed since the vehicle 1 entered a stopped state (NO in S25), the ECU 10 ends the process of keeping the vehicle 1 stopped in this cycle and proceeds to S10 in the next cycle. In this case, in step S25, the ECU 10 ends the process of keeping the vehicle 1 stopped while maintaining the state in which the vehicle 1 is kept stopped (while keeping the vehicle 1 stopped). Thereafter, the ECU 10 executes S10 in the next cycle.

[0040] Subsequently, in S26, the ECU 10 ends the ACC control. Finally, after executing the backup control in S27, the ECU 10 ends the process of keeping the vehicle 1 stopped in this cycle and proceeds to S10 in the next cycle.

[0041] As described above, the vehicle stop-maintaining device 100 is a device for maintaining the stop of the vehicle 1, and includes an ECU 10 that, after stopping the vehicle 1 with the brake device 5, determines that backup control for maintaining the stopped state of the vehicle 1 with the brake-maintaining device 6 cannot be realized and, if a driver's dismounting operation is detected, executes handover control to hand over operation of the brake device 5 to the driver; and, if, after stopping the vehicle 1 with the brake device 5, determines that backup control cannot be realized and, if a driver's dismounting operation is not detected, executes handover control when a grace period required for handover control has elapsed from a reference time after the determination. This makes it possible to quickly hand over operation of the brake device 5 to the driver when backup control cannot be realized. As a result, it becomes possible to reliably maintain the stopped state of the vehicle 1.

[0042] Furthermore, in the prior art, if it is determined that backup control cannot be realized during ACC control, the stopped state of the vehicle 1 is maintained by the hydraulic brakes even if the driver gets off the vehicle. In this case, if the hydraulic brakes reach their limit after the driver gets off the vehicle without performing a brake operation, the stopped state of the vehicle 1 may not be maintained. In this regard, the vehicle stop-maintenance device 100 executes handover control after the vehicle 1 is stopped by the brake device 5, if backup control cannot be realized and an operation to detect that the driver is getting off the vehicle is detected. This makes it possible to reliably hand over operation of the brake device 5 to the driver before the driver gets off the vehicle. As a result, the stopped state of the vehicle 1 can be reliably maintained.

[0043] Furthermore, after the driver stops the vehicle 1, the driver's attention to driving operations temporarily decreases compared to when the vehicle 1 is traveling or immediately after the vehicle 1 is stopped, because the driver operates the car navigation system or the air conditioner, etc. In this case, when the vehicle stop maintenance device 100 determines that backup control cannot be realized after the vehicle 1 is stopped by the brake device 5 and does not detect an operation by the driver to get out of the vehicle, the vehicle stop maintenance device 100 executes handover control after the grace period has elapsed. As a result, when it is determined that backup control cannot be realized after the vehicle 1 has stopped, the grace period is appropriately changed, taking into account the driver's attention to driving operations, and the operation of the brake device 5 can be handed over to the driver at a timing when the driver's attention is restored, for example. As a result, the brake operation can be handed over safely and with peace of mind for the driver. Furthermore, when the vehicle 1 is stopped by the brake device 5 and backup control cannot be realized and an operation by the driver to get out of the vehicle is detected, the operation of the brake device 5 can be swiftly handed over to the driver. As a result, if the driver dismounts, it is determined that the driver's attention to driving operations is sufficiently high (driver engagement is ensured), and the operation of the brake device 5 can be swiftly handed over to the driver. As a result, it is possible to prevent the vehicle 1 from starting to move when unmanned. As a result, it is possible to more reliably maintain the stopped state of the vehicle 1 by taking into consideration changes in the driver's attention to driving operations before and after the vehicle 1 is stopped.

[0044] According to the vehicle stop-maintenance device 100, if the ECU 10 determines that backup control cannot be realized before the vehicle 1 is stopped by the brake device 5, it executes handover control. In this case, if backup control cannot be realized and the driver's attention is sufficiently high (driver engagement is ensured), the operation of the brake device 5 can be quickly handed over to the driver. This makes it possible to reliably maintain the stop-maintenance state of the vehicle 1.

[0045] According to the vehicle stop-holding device 100, the ECU 10 controls the braking force applied to the vehicle 1 by the brake device 5 during the handover control. In the handover control after the vehicle 1 is stopped by the brake device 5, the ECU 10 changes the braking force according to a first pattern. In the handover control before the vehicle 1 is stopped by the brake device 5, the ECU 10 changes the braking force according to a second pattern different from the first pattern. In this case, the braking force is changed during the handover control in consideration of the driver's attention to driving operations. For example, when the handover control is performed before the vehicle 1 is stopped, the ECU 10 gradually reduces the braking force of the brake device 5 to zero, taking into consideration that the driver's attention to driving operations is high (it is confirmed that driver engagement is ensured), and then hands over the operation of the brake device 5 to the driver. Furthermore, for example, when the handover control is performed after the vehicle 1 is stopped, the ECU 10 provides the driver with a sufficient grace period to wait for the driver's attention to driving operations to recover. However, since it is unclear (unconfirmed) whether the driver's attention to driving operations has been restored after the grace period has elapsed, the braking force of the brake device 5 is repeatedly increased and decreased to ensure that the driver's attention is restored, and then the operation of the brake device 5 is handed over to the driver. As a result, the operation of the brake device 5 can be reliably handed over to the driver. From the above, it is possible to reliably maintain the stopped state of the vehicle 1.

[0046] According to the vehicle stop-holding device 100, the ECU 10 notifies the driver of the remaining time until the grace period expires. This allows the driver to focus his / her attention on the driving operation. This allows the driver to regain his / her attention to the driving operation. As a result, the stop-holding state of the vehicle 1 can be reliably maintained.

[0047] Although the embodiments have been described above, one aspect of the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the invention.

[0048] In the above embodiment, when the ECU 10 determines that backup control cannot be realized after the vehicle 1 is stopped by the brake device 5 and does not detect a driver's exit operation, the ECU 10 executes the takeover control when a grace period required for the takeover control has elapsed from the reference time after the determination. However, this is not limiting. For example, when the ECU 10 determines that backup control cannot be realized after the vehicle 1 is stopped by the brake device 5 and does not detect a driver's exit operation, the ECU 10 may execute the takeover control when it determines that the vehicle 1 cannot be continued to be stopped by the brake device 5. Note that the ECU 10 may determine that the vehicle 1 cannot be continued to be stopped when, for example, a limit time for maintaining the vehicle 1 in a stopped state by the hydraulic brake has elapsed. In this case, the limit time may be set for each type of vehicle 1. For example, the ECU 10 may determine that the vehicle 1 cannot be continued to be stopped when it detects that the hydraulic brake can no longer maintain the vehicle 1 in a stopped state.

[0049] 5, in the process of maintaining the stop of the vehicle 1 in the modified example, instead of determining whether the grace time required for the takeover control has elapsed from the reference time in S20, the ECU 10 may determine whether the braking device 5 can continue to stop the vehicle 1 in S28. If the ECU 10 determines that the braking device 5 can continue to stop the vehicle 1 (YES in S28), the ECU 10 may proceed to S23. If the ECU 10 determines that the braking device 5 cannot continue to stop the vehicle 1 (NO in S28), the ECU 10 may proceed to S24.

[0050] In the above embodiment, in the takeover control, the ECU 10 changes the braking force of the brake device 5 in a predetermined pattern (performs brake release control), but this is not limited to this. For example, in the takeover control, instead of or in addition to the brake release control, the ECU 10 may further perform notification control to control the HMI 7 to output a notification requesting the occupant to apply the brakes. For example, as the notification control, the ECU 10 may display a brake operation request to the driver on the display 7a.

[0051] The respective configurations in the above-described embodiments or modifications can be arbitrarily applied to the respective configurations in other embodiments or modifications. A part of the respective configurations in the above-described embodiments or modifications can be omitted as appropriate within the scope of the gist of one aspect of the present invention. [Explanation of symbols]

[0052] 1...vehicle, 5...brake device, 6...brake holding device, 10...ECU (control unit), 100...vehicle stop holding device

Claims

1. A vehicle stop maintaining device that maintains the stop of a vehicle, a control unit that determines, after the vehicle is stopped by the brake device, that backup control for maintaining the stopped state of the vehicle by a brake holding device cannot be realized and, if a driver's dismounting operation is detected, executes handover control to hand over operation of the brake device to the driver, and that determines, after the vehicle is stopped by the brake device, that backup control cannot be realized and, if a driver's dismounting operation is not detected, executes the handover control when a grace period required for the handover control has elapsed from a reference time after the determination.

2. The vehicle stop-maintaining device according to claim 1 , wherein the control unit executes the takeover control when it determines that the backup control cannot be realized before the vehicle is stopped by the brake device.

3. 3. The vehicle stop-holding device of claim 2, wherein the control unit controls the braking force applied to the vehicle by the brake device during the handover control, and during the handover control after the vehicle is stopped by the brake device, the control unit changes the braking force in a first pattern, and during the handover control before the vehicle is stopped by the brake device, the control unit changes the braking force in a second pattern different from the first pattern.

4. 4. The vehicle stop-maintaining device according to claim 1, wherein the control unit notifies the driver of the remaining time until the grace period elapses.

5. A vehicle stop maintaining device that maintains the stop of a vehicle, a control unit that determines, after the vehicle has been stopped by the brake device, that backup control for maintaining the stopped state of the vehicle by a brake holding device cannot be realized and, if a driver's dismounting operation is detected, executes handover control to hand over operation of the brake device to the driver; and, if, after the vehicle has been stopped by the brake device, it determines that the backup control cannot be realized and, if a driver's dismounting operation is not detected, it executes the handover control when it determines that the vehicle cannot continue to be stopped by the brake device.

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