Vehicle travel control apparatus, method, and program

Abstract

To early terminate override control as desired by a driver.SOLUTION: A vehicle travel control apparatus 100 includes: a driving control device 26 for controlling driving force of a vehicle 102; a braking control device 36 for applying braking force to wheels 34; and a driving support ECU 10 for executing vehicle speed limit control to execute limitation on the driving force by controlling the driving control device when a vehicle speed exceeds a limit vehicle speed. When an accelerator opening ACC is increased by a driver during execution of the vehicle speed limit control, the driving support ECU executes override control to cancel execution of the limitation on the driving force, until the vehicle speed becomes equal to or lower than the limit vehicle speed. The driving support ECU decelerates the vehicle by controlling the braking control device when a time during which the accelerator opening is 0 becomes equal to or longer than a reference time during execution of the override control.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cruise control device, method, and program that are applied to vehicles such as automobiles. [Background technology]

[0002] A known driving control for vehicles such as automobiles is a speed limit control that limits the driving force of the vehicle when the vehicle speed exceeds a speed limit (a set speed).It is also known that if the driver performs a predetermined driving operation while the driving force is being limited by the speed limit control, an override control is executed to cancel the limit on the driving force, allowing the vehicle speed to exceed the speed limit, and the override control is terminated when the vehicle speed falls below the speed limit.

[0003] For example, Patent Document 1 below, filed by the applicant of the present application, describes an example of a vehicle speed limiting device configured to perform vehicle speed limiting control and override control. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-144571 Summary of the Invention

[0005] [Problem to be solved by the invention] In conventional cruise control devices that perform vehicle speed limit control and override control, the override control is terminated when the driver reduces the amount of drive operation and the vehicle speed falls below the vehicle speed limit. Even if the driver attempts to reduce the vehicle speed by, for example, reducing the amount of drive operation until the accelerator pedal position becomes zero while the override control is being executed, the vehicle speed can only be reduced by engine braking, etc., and it takes time for the vehicle speed to fall below the vehicle speed limit. Therefore, there are cases where the override control cannot be terminated as early as the driver desires.

[0006] Furthermore, if the driver wishes to terminate the override control, he or she must switch from driving with the accelerator pedal to braking with the brake pedal, which is cumbersome for the driver.

[0007] The present invention provides a cruise control device, method, and program that can terminate override control during vehicle speed limit control earlier than conventional methods without shifting driving operations from driving operations to braking operations. [Means for solving the problems and effects of the invention]

[0008] According to the present invention, there is provided a vehicle travel control device (100) including: a drive control device (26) that controls the drive force of a vehicle (102) in accordance with at least an accelerator pedal position (ACC); a braking control device (36) that decelerates the vehicle by applying braking force to wheels (34); and a control unit (driving assistance ECU 10) that executes vehicle speed limit control (S150, S170) that controls the drive control device to limit the drive force when the vehicle speed (V) exceeds a limit vehicle speed (Vlim), wherein the control unit is configured to execute override control (S20, S140, S150) that releases the limit on the drive force when the accelerator pedal position is increased by the driver during the execution of the vehicle speed limit control (S10) until the vehicle speed becomes equal to or less than the limit vehicle speed (S80).

[0009] The control unit (driving assistance ECU 10) is configured to control the braking control device (36) to decelerate the vehicle (S70) when the time (T) during which the accelerator opening is 0 becomes equal to or exceeds a reference time (Tc) (S30, S50, S60) while the override control is being executed.

[0010] Furthermore, according to the present invention, there is provided a vehicle driving control method that is applicable to a vehicle equipped with a drive control device (26) that controls the drive force of a vehicle (102) in accordance with at least an accelerator pedal position (ACC) and a braking control device (36) that decelerates the vehicle by applying braking force to wheels (34), and includes steps (S150, S170) of executing vehicle speed limit control that controls the drive control device to limit the drive force when the vehicle speed (V) exceeds a limited vehicle speed (Vlim), and steps (S20, S140, S150) of executing override control that releases the limit on the drive force when the driver increases the accelerator pedal position (S10) during the execution of the vehicle speed limit control until the vehicle speed becomes equal to or less than the limited vehicle speed (S80).

[0011] The driving control method further includes a step (S70) of decelerating the vehicle by controlling the brake control device (36) when the time (T) during which the accelerator opening is 0 becomes equal to or exceeds a reference time (Tc) in a situation where override control is being executed.

[0012] Furthermore, according to the present invention, there is provided a driving control program that is applicable to a vehicle including a drive control device (26) that controls the drive force of a vehicle (102) in accordance with at least an accelerator pedal position (ACC) and a braking control device (36) that decelerates the vehicle by applying a braking force to wheels (34), and causes an electronic control device (driving assistance ECU 10) mounted on the vehicle to execute the following steps (S150, S170): executing vehicle speed limit control that controls the drive control device to limit the drive force when the vehicle speed (V) exceeds a limited vehicle speed (Vlim); and, when the accelerator pedal position is increased by the driver during the execution of the vehicle speed limit control (S10), executing override control (S20, S140, S150) until the vehicle speed becomes equal to or less than the limited vehicle speed (S80).

[0013] The driving control program further includes a step (S70) of decelerating the vehicle by controlling the brake control device (36) when the time (T) during which the accelerator opening (ACC) is 0 becomes equal to or exceeds a reference time (Tc) while the override control is being executed (S30, S50, S60).

[0014] According to the above-described cruise control device, method, and program, when override control is being executed, if the time during which the accelerator opening is 0 exceeds a reference time, the braking control device is activated to decelerate the vehicle. Therefore, compared to conventional cruise control devices in which the vehicle is decelerated by engine braking, the vehicle deceleration can be increased, and the override control during vehicle speed limit control can be terminated earlier.

[0015] In addition, it is sufficient that the driving operation is maintained in the accelerator-off state so that the time during which the accelerator opening is 0 is equal to or longer than the reference time, and there is no need to perform a braking operation. Therefore, the driver does not need to switch driving operations from driving operation using the accelerator pedal to braking operation using the brake pedal in order to terminate the override control as desired, which reduces the risk of the driver feeling annoyed. [Mode of the Invention]

[0016] In one aspect of the present invention, the control unit (driving assistance ECU 10) is configured to, when the time (T) during which the accelerator pedal position (ACC) is 0 becomes equal to or exceeds a reference time (Tc) while override control is being executed, calculate a target deceleration (Gbt) of the vehicle so that the deceleration gradually increases from the deceleration of the vehicle at the time when the time during which the accelerator pedal position is 0 becomes equal to or exceeds the reference time (S70), and decelerate the vehicle by controlling the braking control device (36) so that the deceleration (Gb) of the vehicle becomes the target deceleration (S70, S230, S250, S260).

[0017] According to the above aspect, the target deceleration of the vehicle is calculated so as to gradually increase from the deceleration of the vehicle at the time when the time during which the accelerator opening is 0 becomes equal to or exceeds the reference time, and the vehicle is decelerated by controlling the brake control device so that the deceleration of the vehicle becomes the target deceleration. Therefore, when deceleration of the vehicle is started by controlling the brake control device, it is possible to prevent a sudden change in the deceleration of the vehicle and a resulting discomfort felt by the vehicle occupants.

[0018] In another aspect of the present invention, the control unit (drive assist ECU 10) is configured to calculate (S70) a target deceleration (Gbt) of the vehicle so that the target deceleration gradually increases up to a preset maximum target deceleration.

[0019] According to the above aspect, the target deceleration of the vehicle is calculated so as to gradually increase up to a preset maximum target deceleration, thereby preventing a sudden change in the target deceleration of the vehicle and a resulting sudden change in the deceleration of the vehicle, and also preventing the target deceleration of the vehicle from becoming excessive and resulting in an excessively large deceleration of the vehicle.

[0020] In the above description, to facilitate understanding of the present invention, the names and / or symbols used in the embodiments described below are enclosed in parentheses for the configurations of the invention corresponding to those embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or symbols enclosed in parentheses. Other objects, features, and attendant advantages of the present invention will be easily understood from the following description of the embodiments of the present invention, which will be given with reference to the drawings. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic configuration diagram showing an embodiment of a vehicle travel control device according to the present invention; [Figure 2] 10 is a flowchart corresponding to an override control program. [Figure 3]4 is a flowchart corresponding to a driving force control program for limiting vehicle speed. [Figure 4] 4 is a flowchart corresponding to a braking force control program. [Figure 5] FIG. 10 is a diagram illustrating an example of the operation of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cruise control device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] 1, a cruise control device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driving assistance ECU 10. The vehicle 102 is an autonomously driven vehicle and includes a drive ECU 20, a brake ECU 30, and a meter ECU 50. The ECU stands for an electronic control unit that includes a microcomputer as its main component.

[0024] The microcomputer of each ECU includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU performs various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are interconnected via a Controller Area Network (CAN) 104 to enable data exchange (communication). Therefore, the detected values ​​of sensors (including switches) connected to a specific ECU are transmitted to other ECUs.

[0025] The driving assistance ECU 10 is a central control device that performs driving assistance control such as vehicle speed limit control, adaptive cruise control, lane keeping control, etc. In the embodiment, the driving assistance ECU 10 cooperates with other ECUs to perform driving control for the vehicle 102, as will be described in detail later.

[0026] In this embodiment, the driving assistance ECU 10 sets a vehicle speed limit Vlim, and when it determines that the vehicle speed V of the vehicle 102 exceeds the vehicle speed limit Vlim, it executes vehicle speed limit control that automatically limits the driving force of the vehicle so that the vehicle speed is equal to or less than the vehicle speed limit. Furthermore, if a driving operation that overrides the automatic limit on the driving force is performed while the vehicle speed limit control is being executed, the automatic limit on the driving force is canceled. Thus, the cruise control device 100 functions as an adjustable speed limiter (abbreviated as ASL).

[0027] The driving assistance ECU 10 is connected to a camera sensor 12, a radar sensor 14, and a setting operation device 16. The camera sensor 12 and the radar sensor 14 each include a plurality of camera devices and a plurality of radar devices. The camera sensor 12 and the radar sensor 14 function as a target information acquisition device 18 that acquires target information around the vehicle 102.

[0028] Although not shown, each camera device of the camera sensor 12 includes a camera unit that captures images of the surroundings of the vehicle 102 and a recognition unit that analyzes image data captured by the camera unit to recognize targets such as white lines on the road and road signs (including road surface marks). The recognition unit supplies information about the recognized targets to the driving assistance ECU 10 at predetermined time intervals. When the road sign information supplied from the camera sensor 12 is information about a road sign that indicates a vehicle speed limit, the driving assistance ECU 10 determines the vehicle speed limit Vlimc based on the information.

[0029] Each radar device of the radar sensor 14 includes a radar transmitting / receiving unit and a signal processing unit (not shown). The radar transmitting / receiving unit emits millimeter-wave radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves reflected by a three-dimensional object (e.g., another vehicle, a bicycle, etc.) within the emission range (i.e., reflected waves). The signal processing unit supplies information indicating the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, and the relative position (direction) of the three-dimensional object with respect to the vehicle to the driving assistance ECU 10 at predetermined time intervals, based on the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the time from transmitting the millimeter waves to receiving the reflected waves. Note that a LiDAR (Light Detection and Ranging) may be used instead of or in addition to the radar sensor 14.

[0030] The setting operator 16 is located at a position accessible to the driver, such as a steering wheel (not shown in FIG. 1), and is operated by the driver. Although not shown in FIG. 1, the setting operator 16 includes an ASL operator 16A that functions as a vehicle speed limit setting device. As will be described in detail later, the driving assistance ECU 10 executes vehicle speed limit control when the main switch of the ASL operator 16A is on. The ASL operator 16A changes and sets the vehicle speed limit Vlima by operating a button. For details of the ASL operator, please refer to, for example, Japanese Patent Application Laid-Open No. 2017-1406, filed by the applicant of the present application, if necessary.

[0031] The drive ECU 20 is connected to a drive unit 22 that accelerates the vehicle 102 by applying drive force to drive wheels 24. The drive ECU 20 normally controls the drive unit 22 so that the drive force generated by the drive unit 22 changes in response to the driving operation by the driver, and when it receives a command signal from the driving assistance ECU 10, it controls the drive unit 22 based on the command signal. Thus, the drive ECU 20 and the drive unit 22 work together to function as a drive control device 26.

[0032] The drive device may be any drive device known in the art, such as a so-called hybrid system which is a combination of an engine and a transmission, an engine and a motor, a so-called plug-in hybrid system, a combination of a fuel cell and a motor, or a motor.

[0033] The braking ECU 30 is connected to a braking device 32 that applies braking force to wheels 34 to decelerate the vehicle 102. The braking ECU 30 normally controls the braking device so that the braking force generated by the braking device 32 changes in response to the braking operation by the driver, and when it receives a command signal from the driving assistance ECU 10, it controls the braking device 32 based on the command signal to perform automatic braking.

[0034] Therefore, the brake ECU 30 and the brake device 32 work together to function as a brake control device 36. When braking force is applied to the wheels by vehicle speed limit control or the like, a brake lamp (not shown in FIG. 1) is turned on.

[0035] A touch panel display 52 that displays the status of control by the driving assistance ECU 10 is connected to the meter ECU 50. The display 52 may be, for example, a multi-information display that displays meters and various information, or may be a display of a navigation device 80 described below. As described below, when the display 52 receives a signal from the driving assistance ECU 10, it displays the status of vehicle speed limit control, the vehicle speed limit Vlim, etc.

[0036] The driving operation sensors 60 and the vehicle condition sensors 70 are also connected to the CAN 104. Information detected by the driving operation sensors 60 and the vehicle condition sensors 70 (referred to as sensor information) is transmitted to the CAN 104. The sensor information transmitted to the CAN 104 can be used appropriately in each ECU. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted to the CAN 104 from that specific ECU.

[0037] The driving operation sensor 60 includes an accelerator opening sensor 60A that detects an accelerator opening ACC, which is a driving operation amount; a braking operation amount sensor that detects master cylinder pressure or a brake pedal depression force; and a brake switch that detects whether the brake pedal is being operated. The driving operation sensor 60 also includes a kickdown switch 60B. The kickdown switch 60B switches on when the accelerator opening ACC becomes equal to or greater than a start reference value (a positive constant), and switches off when the accelerator opening ACC becomes equal to or less than a termination reference value (a positive constant smaller than the start reference value). The driving operation sensor 60 also includes a steering angle sensor that detects a steering angle, a steering torque sensor that detects a steering torque, etc.

[0038] The vehicle state sensor 70 includes a vehicle speed sensor that detects the vehicle speed V of the vehicle 102, a longitudinal acceleration sensor that detects the longitudinal acceleration of the vehicle, a lateral acceleration sensor that detects the lateral acceleration of the vehicle, and a yaw rate sensor that detects the yaw rate of the vehicle.

[0039] Furthermore, the navigation device 80 is also connected to the CAN 104. The navigation device 80 includes a GPS receiver that detects the position of the vehicle 102, a storage device that stores map information and road information, and a communication device that acquires the latest map information and road information from an external device. In particular, the road information includes information on the vehicle speed limit Vlimn. The navigation device 80 extracts information on the vehicle speed limit Vlimn that indicates the vehicle speed limit for the road on which the vehicle is currently traveling, based on the vehicle's position on the map and the road information, and outputs the extracted information on the vehicle speed limit to the driving assistance ECU 10 via the CAN 104. Note that the navigation device 80 does not necessarily have to be provided.

[0040] The driving assistance ECU 10 sets the vehicle speed limit Vlim based on the vehicle speed limit Vlimc set based on road sign information supplied from the camera sensor 12, the vehicle speed limit Vlima set by the ASL operation device, and the vehicle speed limit Vlimn extracted by the navigation device 80. For example, the vehicle speed limit Vlim may be set by selecting one of Vlimc, Vlima, and Vlimn in accordance with a preset priority order.

[0041] In this embodiment, the ROM of the driving assistance ECU 10 stores an override control program and a driving force control program for limiting vehicle speed, which correspond to the flowcharts shown in Figures 2 and 3. Furthermore, the ROM of the braking ECU 30 stores a braking force control program for limiting vehicle speed, which corresponds to the flowchart shown in Figure 4.

[0042] The vehicle driving control method in this embodiment is carried out by executing override control, driving force control for limiting vehicle speed, and braking force control for limiting vehicle speed in accordance with the flowcharts shown in FIGS. <Override control (Fig. 2)>

[0043] Next, the override control in this embodiment will be described with reference to the flowchart shown in Fig. 2. The override control according to the flowchart shown in Fig. 2 is repeatedly executed at predetermined time intervals by the CPU of the driving assistance ECU 10 while the main switch of the ASL operator 16A is on. Note that a flag For is initialized to 0 when the override control starts.

[0044] First, in step S10, the CPU determines whether the kickdown switch 60B is on, i.e., whether the accelerator opening ACC is equal to or greater than the start reference value. If a negative determination is made, the override control is temporarily terminated, and if a positive determination is made, the override control proceeds to step S20.

[0045] In step S20, the CPU sets the flag For to 1, and resets to 0 the time T that has elapsed since the accelerator opening ACC became 0%.

[0046] In step S30, the CPU determines whether the accelerator opening ACC is 0%, i.e., whether the accelerator is off. If a negative determination is made, the override control is temporarily terminated, and if a positive determination is made, the override control proceeds to step S40.

[0047] In step S40, the CPU determines whether or not the driver is performing a braking operation. If a positive determination is made, the override control proceeds to step S80, and if a negative determination is made, the override control proceeds to step S50.

[0048] In step S50, the CPU increments the elapsed time T after the accelerator opening ACC becomes 0% by ΔT, where ΔT is the cycle time (positive constant) of the override control according to the flowchart shown in FIG.

[0049] In step S60, the CPU determines whether the elapsed time T is equal to or greater than a reference value Tc (a positive constant such as 3 seconds), i.e., whether deceleration of the vehicle 102 by automatic braking should be started. If a negative determination is made, the override control returns to step S30, and if a positive determination is made, the override control proceeds to step S70.

[0050] In step S70, the CPU increments the target deceleration Gbt of the vehicle 102 by ΔGb (negative constant) and outputs an automatic braking command signal based on the target deceleration Gbt to the brake ECU 30. Note that the target deceleration Gbt is a negative value because it is a target value for negative acceleration. Furthermore, if the target deceleration Gbt exceeds the maximum value Gbtmax (negative constant) of the deceleration due to the increment, it is limited to the maximum value Gbtmax.

[0051] In step S80, the CPU determines whether the vehicle speed V is equal to or less than the limit vehicle speed Vlim. If a negative determination is made, the override control returns to step S30, and if a positive determination is made, the override control proceeds to step S90.

[0052] In step S90, the CPU resets the flag For to 0, and then temporarily ends the override control. <Drive force control for limiting vehicle speed (Fig. 3)>

[0053] Next, the driving force control for limiting the vehicle speed will be described with reference to the flowchart shown in Fig. 3. The driving force control for limiting the vehicle speed according to the flowchart shown in Fig. 3 is also repeatedly executed by the CPU of the driving assistance ECU 10 at predetermined time intervals when the main switch of the ASL operation device 16A is on.

[0054] In step S110, the CPU calculates the driver's requested driving force Fdd based on the accelerator pedal position ACC in a manner known in the art.

[0055] In step S120, the CPU calculates the limiting drive force Fdlim of the vehicle 102 for limiting the vehicle speed V to less than or equal to the limiting vehicle speed Vlim based on the current vehicle speed V, the limiting vehicle speed Vlim, the current acceleration, etc., in a manner known in the art.

[0056] In step S130, the CPU determines whether the required driving force Fdd is greater than the limiting driving force Fdlim, i.e., whether the driving force needs to be limited by the limiting driving force Fdlim. If a negative determination is made, the driving force control proceeds to step S150, and if a positive determination is made, the driving force control proceeds to step S140.

[0057] In step S140, the CPU determines whether the flag For is 1, i.e., whether an override that releases the limit on the driving force is in progress. If a positive determination is made, the CPU proceeds to step S150, where the target driving force Fdt of the vehicle 102 is set to the required driving force Fdd. If a negative determination is made, the CPU proceeds to step S160, where the target driving force Fdt of the vehicle 102 is set to the limited driving force Fdlim.

[0058] In step S170, the CPU outputs a command signal to the drive ECU 20 to set the driving force Fd of the vehicle 102 to the target driving force Fdt. As a result, the drive ECU 20 controls the drive device 22 so that the driving force Fd of the vehicle 102 becomes the target driving force Fdt.

[0059] Therefore, when the required driving force Fdd is greater than the limit driving force Fdlim and the flag For is 0, the target driving force Fdt is set to the limit driving force Fdlim, and the driving force Fd of the vehicle 102 is controlled to become the limit driving force Fdlim. On the other hand, even if the required driving force Fdd is greater than the limit driving force Fdlim, when the flag For is 1 and an override is in progress, the target driving force Fdt is set to the required driving force Fdd, and the driving force Fd of the vehicle 102 is controlled to become the required driving force Fdd, and is not limited by the limit driving force Fdlim. <Braking force control for limiting vehicle speed (Fig. 4)>

[0060] Next, braking force control for limiting vehicle speed will be described with reference to the flowchart shown in Fig. 4. The braking force control for limiting vehicle speed according to the flowchart shown in Fig. 4 is repeatedly executed by the CPU of the brake ECU 30 at predetermined time intervals while an ignition switch (not shown in Fig. 1) is on.

[0061] In step S210, the CPU determines whether the main switch of the ASL operator 16A is on. If a positive determination is made, the braking force control proceeds to step S240, and if a negative determination is made, the braking force control proceeds to step S220.

[0062] In step S220, the CPU determines whether or not the driver is applying the brakes. If a positive determination is made, the braking force control proceeds to step S240, and if a negative determination is made, the braking force control proceeds to step S230.

[0063] In step S230, the CPU determines whether or not a command signal for automatic braking based on the target deceleration Gbt has been input from the driving assistance ECU 10. If a negative determination is made, the braking force control proceeds to step S240, and if a positive determination is made, the braking force control proceeds to step S250.

[0064] In step S240, the CPU controls the brake device 32 based on the braking operation amount detected by the braking operation amount sensor of the driving operation sensor 60. For example, the CPU calculates a target braking force Fbt for the vehicle 102 based on the braking operation amount in a manner known in the art, calculates a target braking force for each wheel based on the target braking force Fbt, and controls the brake device 32 so that the braking force for each wheel becomes the corresponding target braking force.

[0065] In step S250, the CPU calculates the target braking force for each wheel in a manner known in the art based on the target deceleration Gbt calculated in step S70 and input from the driving assistance ECU 10.

[0066] In step S260, the CPU controls the brake control device 36 so that the braking force of each wheel becomes the corresponding target braking force, thereby decelerating the vehicle by automatic braking during override. <Operation and Effects of the Embodiment>

[0067] Next, as an example of the operation of the embodiment, the vehicle speed limit control in the embodiment will be described with reference to Fig. 5. The second row of Fig. 5 shows the change in acceleration of the vehicle 102, and negative values ​​of the acceleration indicate the deceleration Gb of the vehicle.

[0068] As shown in Fig. 5, assume that the driver suddenly depresses the brake pedal immediately before time t1, and at time t1, kick-down switch 60B is turned on. In step S10, a positive determination is made, and in step S20, flag For is set to 1, and override control is initiated. Vehicle speed V and acceleration change according to accelerator pedal position ACC, and vehicle speed V becomes a value higher than vehicle speed limit Vlim.

[0069] At time t2, the driver begins to reduce the brake pedal depression, causing the accelerator opening ACC to decrease from 100%, and at time t3, the accelerator opening ACC decreases to 0%, resulting in a positive determination in step S30. After time t3, the vehicle is decelerated by engine braking, and the vehicle speed V gradually decreases.

[0070] At time t4, the time elapsed since time t3 becomes equal to or greater than the reference elapsed time Tc, and the determination in step S60 is affirmative. The target deceleration Gbt of the vehicle 102 increases from time t4 to time t5, and reaches a maximum value Gbtmax at time t5. Since the vehicle is decelerated by automatic braking based on the target deceleration Gbt after time t4, the rate of decrease in vehicle speed V after time t4 is greater than the rate of decrease from time t3 to time t4.

[0071] If, at time t6, the vehicle speed V becomes equal to or less than the vehicle speed limit Vlim and the determination in step S80 is affirmative, the flag For is reset to 0 in step S90 and the override control ends. If a negative determination is made in step S130, step S150 is executed, and the deceleration Gb of the vehicle 102 decreases from the maximum value Gbtmax. The vehicle speed V becomes slightly lower than the vehicle speed limit Vlim and then increases, reaching the vehicle speed limit Vlim at time t7, for example.

[0072] In conventional cruise control devices, when the accelerator pedal position ACC is 0%, the vehicle is decelerated by engine braking, and deceleration by automatic braking is not performed even if the elapsed time since time t3 is equal to or exceeds the reference elapsed time Tc. Therefore, as shown by the dashed line in Figure 5, vehicle speed V continues to decrease from time t4 onwards at the same rate as the rate of decrease from time t3 to time t4. Therefore, vehicle speed V becomes equal to or less than vehicle speed limit Vlim at time t8, and override control continues from time t1 to time t8, so it takes a long time for vehicle speed V to decrease to or less than vehicle speed limit Vlim.

[0073] In contrast, according to this embodiment, the vehicle speed V drops to or below the limit vehicle speed Vlim at time t6, which is much earlier than time t8. Therefore, the override control during the vehicle speed limit control ends earlier than in the conventional case.

[0074] As can be seen from the above explanation, according to the cruise control device, method, and program of the present invention, when override control is being executed and the time T during which the accelerator opening ACC is 0% becomes equal to or exceeds the reference time Tc (S30, S50, S60), the braking control device 36 is controlled to automatically decelerate the vehicle 102 (S70). Therefore, compared to conventional cruise control devices in which the vehicle is decelerated by engine braking, the vehicle deceleration Gb can be increased, and the override control during vehicle speed limit control can be ended earlier.

[0075] In addition, the driving operation only needs to be maintained in the accelerator-off state so that the time T during which the accelerator opening ACC is 0% is equal to or longer than the reference time Tc, and there is no need to perform a braking operation. Therefore, the driver does not need to switch driving operations from driving operation using the accelerator pedal to braking operation using the brake pedal in order to terminate the override control as desired, which reduces the risk of the driver feeling annoyed.

[0076] In particular, according to this embodiment, the target deceleration Gbt of the vehicle 102 is calculated so as to gradually increase from the deceleration of the vehicle at the time when the time T during which the accelerator opening ACC is 0% becomes equal to or greater than the reference time Tc (S70), and the vehicle is decelerated by controlling the brake control device 36 so that the deceleration Gb of the vehicle becomes the target deceleration (S70, S230, S250, S260). Therefore, when deceleration of the vehicle begins due to control of the brake control device, it is possible to prevent a sudden change in the deceleration of the vehicle and any discomfort felt by the vehicle occupants due to this.

[0077] Furthermore, according to the embodiment, the target deceleration Gbt of the vehicle 102 is calculated so as to gradually increase up to a preset maximum target deceleration Gbtmax (S70). This makes it possible to prevent a sudden change in the target deceleration of the vehicle and a resulting sudden change in the deceleration Gb of the vehicle, and also to prevent the target deceleration of the vehicle from becoming excessive and the resulting excessive deceleration of the vehicle.

[0078] Furthermore, according to the embodiment, the vehicle speed limit Vlim is variably set based on the vehicle speed limit Vlimc set based on road sign information, the vehicle speed limit Vlima set by the ASL operation device, and the vehicle speed limit Vlimn extracted by the navigation device 80. Therefore, the vehicle speed limit Vlim can be set automatically according to the vehicle speed limit of the road on which the vehicle is traveling. Also, the driver can variably set the vehicle speed limit Vlimn according to his or her own will.

[0079] Although the present invention has been described in detail above with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and that various other embodiments are possible within the scope of the present invention.

[0080] For example, in the above-described embodiment, the vehicle speed limit Vlim is variably set based on the vehicle speed limit Vlimc set based on road sign information, the vehicle speed limit Vlima set by the ASL operation device, and the vehicle speed limit Vlimn extracted by the navigation device 80. However, the vehicle speed limit Vlim may also be a preset constant.

[0081] In the above-described embodiment, the vehicle speed limit Vlim is variably set based on the vehicle speed limits Vlimc, Vlima, and Vlimn. However, at least one of the variably setting of the vehicle speed limit Vlimc based on road sign information, the variably setting of the vehicle speed limit Vlimc based on road sign information Vlima using the ASL operation device, and the variably setting of Vlimn by the navigation device 80 may be omitted.

[0082] In the above embodiment, the driving operation sensor 60 includes a kickdown switch 60B, and when the kickdown switch is on, the override control is started (S10, S20). However, the kickdown switch may be omitted, and in step S10, it may be determined whether the accelerator opening ACC is equal to or greater than the start reference value, and the override control may be started when a positive determination is made.

[0083] In the above-described embodiment, in step S60, it is determined whether deceleration of the vehicle 102 by automatic braking should be started by determining whether the elapsed time T is equal to or greater than a reference value Tc, and the reference value Tc is a positive constant. However, the reference value Tc may be variably set according to the vehicle speed so that the higher the vehicle speed V, the smaller the reference value Tc becomes, so that deceleration by automatic braking starts earlier.

[0084] Furthermore, in the above-described embodiment, in step S70, the target deceleration Gbt of the vehicle 102 is incremented by ΔGb, where the increment ΔGb is a negative constant. However, the increment ΔGb may be variably set according to the vehicle speed so that the absolute value of the increment ΔGb increases as the vehicle speed V increases, so that the deceleration due to automatic braking increases as the vehicle speed V increases. [Explanation of symbols]

[0085] 10... driving assistance ECU, 12... camera sensor, 14... radar sensor, 18... target information acquisition device, 26... drive control device, 36... braking control device, 36... automatic braking device, 60A... accelerator opening sensor, 60B... kickdown switch, 100... driving control device, 102... vehicle

Claims

1. A vehicle travel control device including: a drive control device that controls the drive force of the vehicle in accordance with at least an accelerator opening; a braking control device that decelerates the vehicle by applying braking force to wheels; and a control unit that executes vehicle speed limit control that controls the drive control device to limit the drive force when the vehicle speed exceeds a vehicle speed limit, wherein the control unit is configured to execute override control that releases the limit on the drive force until the vehicle speed becomes equal to or less than the vehicle speed limit when the accelerator opening is increased by a driver while the vehicle speed limit control is being executed, The control unit is configured to control the braking control device to decelerate the vehicle when the time during which the accelerator opening is 0 becomes equal to or exceeds a reference time while the override control is being executed.

2. 2. The vehicle driving control device according to claim 1, wherein the control unit is configured to, when the time during which the accelerator opening degree is zero becomes equal to or exceeds a reference time while the override control is being executed, calculate a target deceleration of the vehicle so that the deceleration of the vehicle gradually increases from the deceleration of the vehicle at the time when the time during which the accelerator opening degree is zero becomes equal to or exceeds the reference time, and to decelerate the vehicle by controlling the brake control device so that the deceleration of the vehicle becomes equal to the target deceleration.

3. 2. The vehicle driving control device according to claim 1, wherein the control unit is configured to calculate the target deceleration of the vehicle so that the target deceleration gradually increases up to a preset maximum target deceleration.

4. A vehicle travel control method is applied to a vehicle equipped with a drive control device that controls the drive force of the vehicle in accordance with at least an accelerator pedal depression, and a braking control device that decelerates the vehicle by applying braking force to wheels, the method including the steps of: executing vehicle speed limit control that controls the drive control device to limit the drive force when the vehicle speed exceeds a vehicle speed limit; and executing override control that releases the limit on the drive force until the vehicle speed becomes equal to or less than the vehicle speed limit when the accelerator pedal depression is increased by the driver during execution of the vehicle speed limit control, The vehicle driving control method further includes a step of decelerating the vehicle by controlling the brake control device when the time during which the accelerator opening is 0 becomes equal to or exceeds a reference time while the override control is being executed.

5. A driving control program is applied to a vehicle equipped with a drive control device that controls the drive force of the vehicle in accordance with at least an accelerator pedal depression, and a braking control device that decelerates the vehicle by applying braking force to wheels, and causes an electronic control device mounted on the vehicle to execute the following steps: a step of controlling the drive control device to execute vehicle speed limit control to limit the drive force when the vehicle speed exceeds a vehicle speed limit; and a step of executing override control to release the limit on the drive force until the vehicle speed becomes equal to or less than the vehicle speed limit when the accelerator pedal depression is increased by the driver while the vehicle speed limit control is being executed, The vehicle driving control program further includes a step of decelerating the vehicle by controlling the brake control device when the time during which the accelerator opening is 0 becomes equal to or exceeds a reference time while the override control is being executed.

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