Deceleration support control device for vehicle

Abstract

To provide a deceleration support control device improved so as to control vehicle speed to necessary vehicle speed more easily than before.SOLUTION: A deceleration support control device 10 for a vehicle comprises a control unit 50 that when a deceleration target is detected under a situation where an accelerator aperture is over a reference value, performs deceleration-support control in an accelerator aperture mode in which a deceleration device 30 is controlled so that a vehicle 16 is decelerated in accordance with the accelerator aperture. The control unit calculates target deceleration for making vehicle speed of the vehicle to be equal to target vehicle speed that is determined depending on a type of the deceleration target when the vehicle reaches a position of the deceleration target; sets a timing for changing the mode in accordance with the type of the deceleration target; and changes the mode from the accelerator aperture mode to a non-accelerator aperture mode in which the vehicle is decelerated on the basis of the target deceleration, when setting the timing for changing the mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a deceleration assistance control device for a vehicle such as an automobile. [Background technology]

[0002] As one type of driving assistance control for vehicles such as automobiles, there is known a deceleration assistance control that automatically decelerates the vehicle when it detects an object in front of the vehicle that needs to be decelerated, that is, an object that requires the vehicle to slow down in order to approach it, such as an intersection without traffic lights.

[0003] For example, the following Patent Document 1 describes a deceleration assistance device that is configured to perform deceleration assistance when a deceleration target is detected, a deceleration assistance start condition is met, and the accelerator is not on, i.e., when the accelerator pedal is not depressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-116000 Summary of the Invention

[0005] [Problem to be solved by the invention] A deceleration assist device is known that performs deceleration assistance according to the accelerator pedal depression amount when the accelerator pedal is released and the accelerator pedal depression amount is reduced, even if the accelerator pedal is on. This type of deceleration assist device can start deceleration control early to improve the effectiveness of the deceleration assist.

[0006] However, when deceleration assistance is performed according to the accelerator pedal depression while the accelerator is on, the driver must control the vehicle speed by controlling the accelerator pedal depression amount. Therefore, depending on the type of deceleration target and the vehicle driving conditions, it is not easy to control the vehicle speed to the required speed.

[0007] For example, when the deceleration target is a deceleration target that requires the vehicle to stop, such as a red light, the vehicle speed must be controlled so that it becomes 0 when the vehicle reaches the deceleration target. Also, when the road is an uphill road, the deceleration of the vehicle may be higher than the deceleration desired by the driver due to the deceleration caused by the inclination of the road acting on the vehicle in addition to the deceleration caused by the deceleration assistance. Furthermore, when the driver performs a steering operation while reducing the accelerator opening, the driver must control the vehicle speed by controlling the accelerator opening while controlling the traveling direction of the vehicle by the steering operation.

[0008] The present invention provides an improved deceleration assistance control device that improves the effectiveness of deceleration assistance by starting deceleration control early, while making it easier than conventional devices to control the vehicle speed to the required vehicle speed regardless of the type of deceleration target.

[0009] [Means for solving the problems and effects of the invention] According to the present invention, there is provided a deceleration assist control device (10) for a vehicle, which includes an accelerator opening detection device (accelerator opening sensor 64) that detects an accelerator opening (Acc), a deceleration object detection device (56) that detects a deceleration object (such as a T-junction 80) in front of a vehicle (16), a deceleration device (30) that decelerates the vehicle, and a control unit (driving assist ECU 50) that controls the deceleration device, wherein when a deceleration object is detected (S10) in a situation in which the accelerator opening exceeds a reference value (Accc) (S40), the control unit performs deceleration assist control (S80) in an accelerator opening mode that decelerates the vehicle in accordance with the accelerator opening by controlling the deceleration device.

[0010] The control unit (driving assistance ECU 50) is configured to calculate a target deceleration (Gbt) for making the vehicle speed (V) when the vehicle reaches the position of the deceleration target reach a target vehicle speed (Vt) determined by the type of deceleration target, set the timing (tc) for changing the mode according to the type of deceleration target, and when it is determined that it is time to change the mode (S70), change the mode from the accelerator opening mode to a non-accelerator opening mode (S90) in which the vehicle is decelerated based on the target deceleration (S100).

[0011] According to the above configuration, a target deceleration is calculated to set the vehicle speed when the vehicle reaches the position of the deceleration target to the target vehicle speed determined according to the type of the deceleration target, and the timing of the mode change is set according to the type of the deceleration target. Furthermore, when it is determined that it is time to change the mode, deceleration support control is performed from the accelerator opening mode to the non-accelerator opening mode in which the vehicle is decelerated based on the target deceleration.

[0012] Therefore, the vehicle deceleration is first controlled according to the accelerator opening in the accelerator opening mode, and when it is determined that it is time to change the mode, it is automatically controlled based on the target deceleration in the non-accelerator opening mode. Therefore, when the mode is changed, the driver can control the vehicle speed to the required vehicle speed without controlling the amount of depression of the accelerator pedal. Therefore, by starting the deceleration control early, the effect of the deceleration assistance is improved, and the vehicle speed can be controlled to the required vehicle speed more easily than in the past.

[0013] According to the above configuration, the target deceleration for bringing the vehicle speed to the target vehicle speed determined by the type of deceleration object is calculated, and the timing of the mode change is set according to the type of deceleration object. Therefore, the vehicle speed can be easily controlled to a required vehicle speed regardless of the type of deceleration object, and the mode change can be performed at a timing according to the type of deceleration object.

[0014] [Mode of the invention] In one aspect of the present invention, the control unit (driving assistance ECU 50) is configured to, when it determines that the deceleration target is an object that requires the vehicle (16) to be stopped (S22), and when it determines that a predetermined time has elapsed since the deceleration target was first detected, determine that it is time to change modes (S70).

[0015] According to the above aspect, when it is determined that the deceleration target is an object that requires the vehicle to be stopped, the mode can be changed from the accelerator opening mode to the non-accelerator opening mode when a predetermined time has elapsed from the time when the deceleration target was first detected.

[0016] In another aspect of the present invention, the control unit (driving assistance ECU 50) is configured to variably set the predetermined time period depending on at least one of the type of deceleration target and the vehicle running conditions (S22, S24, S30).

[0017] According to the above aspect, the timing of the mode change from the accelerator opening mode to the non-accelerator opening mode can be variably set according to at least one of the type of deceleration target and the traveling conditions of the vehicle.

[0018] Furthermore, in another aspect of the present invention, the control unit (driving assistance ECU 50) is configured to, when it is determined that a steering operation is being performed (S30), advance the timing of the mode change (S36) compared to when it is not determined that a steering operation is being performed.

[0019] According to the above aspect, when a steering operation is being performed, the timing of the mode change can be advanced compared to when the steering operation is not being performed, and the timing at which the vehicle decelerates based on the target deceleration can be advanced. Therefore, compared to when the timing of the mode change is not advanced, the driver can concentrate on the steering operation without controlling the accelerator opening.

[0020] Furthermore, in another aspect of the present invention, when the control unit (driving assistance ECU 50) determines that there are multiple deceleration targets (S32), it is configured to advance the timing of the mode change (S36) compared to when it determines that there is only one deceleration target.

[0021] According to the above aspect, when there are multiple deceleration targets, the timing of the mode change can be advanced compared to when there is only one deceleration target, and the timing at which the vehicle decelerates based on the target deceleration can be advanced. Therefore, the driver can be relieved from having to control the accelerator opening earlier than when the timing of the mode change is not advanced.

[0022] Other objects, other features and attendant advantages of the present invention will become readily apparent from the following description of the embodiments of the present invention which is given with reference to the accompanying drawings. [Brief description of the drawings]

[0023] [Figure 1] 1 is a schematic configuration diagram showing a deceleration support device according to an embodiment. [Diagram 2] 4 is a flowchart showing a deceleration assistance control routine according to the embodiment. [Diagram 3] 10 is a flowchart showing a subroutine for determining a ratio Rec in the first embodiment. [Figure 4] 10 is a flowchart showing a subroutine for determining a ratio Rec in the second embodiment. [Diagram 5] 11A and 11B are diagrams illustrating an example of changes in vehicle speed V when a deceleration target is detected ahead of the vehicle with the accelerator on. [Figure 6] FIG. 2 is a diagram showing a situation in which a vehicle is approaching a T-junction as a deceleration target. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025] The vehicle deceleration assist control device 10 according to the embodiment shown in FIG. 1 is applied to a vehicle 16 having wheels 14FL, 14FR, 14RL, and 14RR. The vehicle 16 may be an autonomous vehicle. In the embodiment, the left and right front wheels 14FL and 14FR are steered wheels and driven wheels, and the left and right rear wheels 14RL and 14RR are non-steered wheels and driven wheels. The front wheels 14FL and 14FR are steered via a rack bar 22 and tie rods 24L and 24R by an electric power steering device 20 driven in response to the operation of a steering wheel 18 by a driver. In the following description, the electronic control device is referred to as an ECU (abbreviation of Electronic Control Unit).

[0026] The deceleration assistance control device 10 includes a deceleration device 30 that decelerates the vehicle 16, and a driving assistance ECU 50 as a control unit that controls the deceleration device. The deceleration device 30 includes a braking device 32 that applies friction braking force to the wheels 14FL to 14RR, and a braking ECU 34 that controls the braking device. The braking device 32 includes a hydraulic circuit 36, friction braking force generating devices 38FR, 38FL, 38RR, and 38RL provided on the wheels 14FL to 14RR, and a master cylinder 42 that pumps brake oil in response to the driver's depression of a brake pedal 40. Although not shown in detail in FIG. 1, the hydraulic circuit 36 ​​includes a reservoir, an oil pump, various valve devices, and the like, and functions as a brake actuator.

[0027] The braking device 32 applies to the wheels 14FL-14RR a braking force proportional to the pressure in the wheel cylinder corresponding to the friction braking force generating device 38FR-38RL. The pressure in the wheel cylinder is normally controlled according to the pressure in a master cylinder 42 (master cylinder pressure Pm) which is actuated in response to the depression of a brake pedal 40 by the driver. That is, the master cylinder pressure Pm is detected by a pressure sensor 44, and the brake ECU 34 controls the pressure in each wheel cylinder based on the master cylinder pressure Pm. Furthermore, the brake ECU 34 controls an oil pump and various valve devices as necessary, so that the pressure in each wheel cylinder is controlled regardless of the amount of depression of the brake pedal 40 by the driver, thereby performing automatic braking.

[0028] The vehicle 16 has a drive device 60, such as an engine, that applies drive force to the left and right front wheels 14FL, 14FR, which are drive wheels. The amount of depression of an accelerator pedal 62 by the driver is detected as an accelerator opening Acc by an accelerator opening sensor 64. The output of the drive device 60 is normally controlled by a drive ECU 66 based on the accelerator opening Acc, and is controlled independently of the accelerator opening Acc as necessary. The drive device 60 may be any device that can apply drive force to the drive wheels, and may be, for example, an electric motor, a hybrid system, or the like. The drive wheels may be the left and right rear wheels 14RL and 14RR, or may be the four wheels 14FL to 14RR.

[0029] 1, the drive device 60 may further include a regenerative device 66 that generates a regenerative braking force by converting the rotational energy of the drive wheels into electric energy. The regenerative device 66 is controlled by the drive ECU 66 based on a control command from the brake ECU 34. The regenerative device 66 functions as a part of the reduction gear 30 when generating a regenerative braking force.

[0030] Each ECU has a microcomputer as its main component, which includes a CPU, ROM, RAM, a readable / writable 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 connected to each other via a Controller Area Network (CAN) to enable data exchange (communication). Therefore, the detection values ​​of sensors (including switches) connected to a specific ECU are also transmitted to other ECUs. Note that multiple ECUs may be integrated into one ECU.

[0031] The driving assistance ECU 50 is a central control device that performs driving assistance control such as deceleration assistance control, following distance control, lane departure prevention control, etc. In the embodiment, the driving assistance ECU 50 executes deceleration assistance control by automatic braking in cooperation with other ECUs, as will be described in detail later.

[0032] A camera sensor 52 and a radar sensor 54 are connected to the driving assistance ECU 50. The camera sensor 52 and the radar sensor 54 may include a plurality of camera devices and a plurality of radar devices, respectively. The camera sensor 52 and the radar sensor 54 function as a deceleration object detection device 56 that detects a deceleration object at least in front of the vehicle 16. Note that instead of the radar sensor 14 or in addition to the radar sensor 14, a LiDAR (Light Detection And Ranging) may be used.

[0033] The deceleration target may be a red light, a stop road sign and pavement markings, an intersection without a traffic light (a crossroad, a T-junction, or a forking road where the road on which the vehicle is traveling is not a priority road), a stopped vehicle, a curved road, a preceding vehicle, etc. In this application, a red light, a stop road sign and pavement markings, and an intersection without a traffic light are referred to as a stopping target as necessary. A stopping target is an object where a vehicle needs to stop.

[0034] Furthermore, a steering angle sensor 70, a vehicle speed sensor 72, and a deceleration assist switch 74 are connected to the driving assist ECU 50. The steering angle sensor 70 detects a steering angle θ as an amount of operation of the steering wheel 18 by the driver. The vehicle speed sensor 72 detects a vehicle speed V as a traveling speed of the vehicle 16. The deceleration assist switch 74 is operated by the driver, and when the deceleration assist switch is on, deceleration assist control is executed by the driving assist ECU 50 as described below. Although not shown in FIG. 1, a display device that displays the status of driving assist control such as deceleration assist control may be connected to the driving assist ECU 50.

[0035] When a deceleration target is detected in a situation where the accelerator opening Acc exceeds a reference value Acc (0 or a positive constant), the driving assistance ECU 50 performs deceleration assistance control in an accelerator opening mode in which the vehicle 16 is decelerated according to the accelerator opening by controlling the reduction gear 30. In Fig. 2, the accelerator opening mode is indicated as an ACC mode.

[0036] The driving assistance ECU 50 calculates a target deceleration Gbt for making the vehicle speed of the vehicle 16 when it reaches the position of the deceleration target a target vehicle speed Vt determined by the type of the deceleration target, and sets the timing of the mode change according to the type of the deceleration target. If the deceleration target is a preceding vehicle, the position of the deceleration target is the position of the preceding vehicle when the preceding vehicle is first detected. Furthermore, when the driving assistance ECU 50 determines that it is time to change the mode, it changes the mode of the deceleration assistance control from the accelerator opening mode to a non-accelerator opening mode in which the vehicle is decelerated based on the target deceleration. In FIG. 2, the non-accelerator opening mode is denoted as a non-ACC mode.

[0037] The target vehicle speed Vt determined by the type of deceleration object is the vehicle speed Vf of the preceding vehicle when the deceleration object is a preceding vehicle, and is 0 when the deceleration object is a stopped object, i.e., a red light, a stop road sign or pavement marking, or an intersection without a traffic light.

[0038] For example, if the vehicle speed of the vehicle 16 when the deceleration target is detected is Vp and the distance between the vehicle 16 and the deceleration target is Dr, the target deceleration Gbt is calculated according to the following formula (1). Note that the distance Dr between the vehicle 16 and the deceleration target is estimated based on the detection result of the deceleration target detection device 56. Gbt=(Vp-Vt) / Dr (1)

[0039] Furthermore, when the deceleration target detection device 56 detects a deceleration target in a situation where the accelerator opening Acc is equal to or greater than the reference value Accc, the deceleration control mode is set to the accelerator opening mode, and the vehicle 16 is decelerated according to the accelerator opening. When the mode of the deceleration assistance control is changed to a non-accelerator opening mode in which the vehicle 16 is decelerated based on the target deceleration Gbt, the mode of the deceleration assistance control is changed from the accelerator opening mode to a non-accelerator opening mode in which the vehicle 16 is decelerated based on the target deceleration Gbt.

[0040] In this embodiment, the ROM of the driving assistance ECU 50 stores a deceleration assistance control program corresponding to the flowchart shown in Fig. 2. The CPU of the driving assistance ECU 50 performs deceleration assistance control in accordance with this program.

[0041] <Deceleration support control> Next, a deceleration support control routine in the embodiment will be described with reference to the flowchart shown in Fig. 2. The deceleration support control according to the flowchart shown in Fig. 2 is repeatedly executed at predetermined time intervals when the deceleration support switch 74 is on.

[0042] In the following description, the deceleration support control according to the flowchart shown in Fig. 2 will simply be referred to as "this control". Prior to the start of this control, a flag Foff indicating whether or not the mode of the deceleration support control has been changed is reset to 0 (indicating that the mode has not been changed).

[0043] First, in step S10, the CPU determines whether or not there is a deceleration target ahead of the vehicle 16, i.e., whether or not a deceleration target has been detected by the deceleration target detection device 56. If the CPU makes a negative determination, it temporarily ends this control, and if the CPU makes a positive determination, it advances this control to step S20. In particular, if the CPU makes a negative determination when the flag Foff is 1, it resets the flag Foff to 0.

[0044] When the deceleration target is a preceding vehicle and the relative speed Vr of the vehicle 16 with respect to the preceding vehicle is a negative value, a negative determination is made in step S10. When a negative determination is made, such as when the preceding vehicle changes course, and there is a target deceleration Vbt calculated in step S20 described later, the target deceleration Vbt is erased. When the road is a curved road, it may be determined that the curved road is a deceleration target when the radius of curvature of the curved road is equal to or smaller than a reference radius. The reference radius may be variably set according to the vehicle speed so that the higher the vehicle speed, the smaller the reference radius.

[0045] In step S20, the CPU calculates a target deceleration Gbt for changing the vehicle speed V of the vehicle 16 when it reaches the position of the deceleration target to a target vehicle speed Vt determined by the type of deceleration target, and sets the timing of the mode change according to the type of deceleration target.

[0046] The time from when the deceleration target is first detected until the vehicle 16 is decelerated at the target deceleration Gbt and reaches the position of the deceleration target is defined as te, and the time from when the deceleration target is first detected until the timing of the mode change is defined as tc. A ratio Rec of the time tc to the time te is preset for each deceleration target.

[0047] In the embodiment, the time te is calculated based on the detection result of the deceleration object detection device 56, and the ratio Rec is determined according to the flowchart shown in Fig. 3 or 4. Furthermore, the time tc is determined as the product of the time te and the ratio Rec, and the timing of the mode change is determined according to the type of the deceleration object.

[0048] In this embodiment, the ratio Rec for the preceding vehicle on a level road is 1, and the ratio Rec for the preceding vehicle on an uphill road is 0.8. The ratio Rec for the stopped object is 0.7 when the driver is not performing a steering operation, and is 0.5 when the driver is performing a steering operation. Whether or not the driver is performing a steering operation may be determined in a manner known in the art based on the steering angle θ and the steering angular velocity θd, which is the rate of change of the steering angle θ.

[0049] In step S40, the CPU determines whether the accelerator is on, i.e., whether the accelerator opening Acc exceeds a reference value Acc. If the CPU makes a positive determination, the control proceeds to step S60, and if the CPU makes a negative determination, the control proceeds to step S50.

[0050] In step S50, the CPU performs deceleration control while the accelerator is off, i.e., deceleration control when the accelerator opening Acc is equal to or smaller than the reference value Acc. For example, the CPU calculates a target braking force Fbt of the vehicle 16 based on the target deceleration Gbt, and controls the reduction gear 30 so that the braking force Fb of the vehicle becomes the target braking force Fbt, thereby performing deceleration control so that the deceleration of the vehicle becomes the target deceleration Gbt.

[0051] In step S60, the CPU determines whether or not the flag Foff is 1, that is, whether or not the mode of the deceleration support control has been changed. If the CPU makes a positive determination, the control proceeds to step S100, and if the CPU makes a negative determination, the control proceeds to step S70.

[0052] In step S70, the CPU determines whether or not a change in the mode of the deceleration support control is necessary by determining whether or not the elapsed time from the time when the deceleration target was first detected is equal to or longer than time tc. If the CPU makes a positive determination, it advances this control to step S90, and if the CPU makes a negative determination, it advances this control to step S80.

[0053] In step S80, the CPU performs deceleration control of the vehicle in accordance with the accelerator opening so that the greater the amount of decrease in the accelerator opening Acc, the greater the deceleration of the vehicle 16. This mode of deceleration support control using deceleration control is referred to as ACC mode in Fig. 2 and Fig. 5, which will be described later. Note that in a situation where the accelerator opening Acc increases, the vehicle deceleration control is not performed.

[0054] In step S90, the CPU sets flag Foff to 1, and in step S100, the CPU controls the deceleration so that the vehicle deceleration becomes the target deceleration Gbt, similar to the deceleration control during accelerator release. This mode of deceleration support control by controlling the deceleration is referred to as non-ACC mode in Fig. 2 and Fig. 5 described later.

[0055] In step S110, the CPU determines whether or not the end condition of the deceleration support control is satisfied, i.e., whether or not the deceleration control should be terminated. If the CPU determines that the deceleration control should be terminated, the CPU temporarily terminates the control, whereas if the CPU determines that the deceleration control should be terminated, the CPU advances the control to step S120. Note that the end condition of the deceleration support control may be determined to be satisfied when the CPU determines that the vehicle speed V of the vehicle 16 is equal to or lower than the target vehicle speed Vt, or when the CPU determines that the duration of the deceleration control is equal to or longer than te.

[0056] In step S120, the CPU resets the flag Foff to 0, erases the target deceleration Gbt, the time te, and the time tc if they have been calculated, and then temporarily ends this control.

[0057] In addition, if the drive device 60 includes the regenerative device 66, at least a part of the braking force may be a regenerative braking force generated by the regenerative device 66 in the control of the deceleration in steps S50, S80 and S100.

[0058] <Control of Ratio Rec Determination in the First Embodiment> Next, a subroutine for determining the ratio Rec in the first embodiment will be described with reference to the flowchart shown in FIG.

[0059] In step S22, the CPU determines whether the vehicle to be decelerated is a preceding vehicle. If the CPU determines that the vehicle is not running, the CPU advances control to step S30. If the CPU determines that the vehicle is running, the CPU advances control to step S24.

[0060] In step S24, the CPU determines whether or not the road on which the vehicle 16 is traveling is an uphill road. If the CPU determines negatively, it sets the ratio Rec to 1 in step S26, and if the CPU determines positively, it sets the ratio Rec to 0.8 in step S28. The determination of whether or not the road is an uphill road may be made based on, for example, information from a navigation device not shown in FIG 1, or may be made based on the relationship between the braking / driving force of the vehicle 16 and the acceleration / deceleration of the vehicle.

[0061] In step S30, the CPU determines whether the deceleration target is an intersection and the driver is steering the vehicle. If the determination is negative, the CPU determines the ratio Rec to be 0.7 in step S34, and if the determination is positive, the CPU determines the ratio Rec to be 0.5 in step S36.

[0062] <Control of Ratio Rec Determination in the Second Embodiment> Next, a subroutine for determining the ratio Rec in the second embodiment will be described with reference to the flowchart shown in Fig. 4. As can be seen from a comparison between Fig. 4 and Fig. 3, steps S22 to S28 and steps S34 and S36 are executed in the same manner as the corresponding steps in the first embodiment.

[0063] In step S30, the CPU performs the same determination as in the first embodiment, but if an affirmative determination is made, the control proceeds to step S36, and if a negative determination is made, the control proceeds to step S32.

[0064] In step S32, the CPU determines whether there are multiple factors for the mode change. If the CPU determines that the mode change is caused by a curve, the CPU advances the control to step S34. If the CPU determines that the mode change is caused by a curve, the CPU advances the control to step S36. For example, if the road ahead of the vehicle is curved and there is a red light ahead, the CPU may determine that there are multiple factors for the mode change.

[0065] <Example of Operation of the First and Second Embodiments> Next, an example of the operation of the first and second embodiments will be described with reference to FIG. 5 as necessary when a deceleration target is detected in front of the vehicle 16 by the deceleration target detection device 56 while the accelerator is on.

[0066] 5A to 5C respectively show examples of changes in the vehicle speed V of the vehicle 16 in the cases of C1 to C3 below. In addition, in Fig. 5, the dashed line and the dashed dotted line show examples in which the average deceleration of the deceleration control in the accelerator opening mode is smaller and larger, respectively, than the target deceleration Gbt calculated when the deceleration target is detected.

[0067] C1. When the vehicle ahead is decelerating (Figure 5 (A)) If the road is not an uphill road, a positive determination and a negative determination are made in steps S22 and S24, respectively, and in step S26, the ratio Rec is determined to be 1. Therefore, since the time tc is the same as the time te, the deceleration assist control is performed in the accelerator opening mode, and the mode is not changed from the non-accelerator opening mode to the accelerator opening mode.

[0068] The deceleration of the vehicle 16 is controlled according to the accelerator pedal position Acc until the elapsed time reaches time te, at which point a positive determination is made in step S110 and the deceleration support control ends. In Fig. 5, the two-dot chain line indicates the change in the vehicle speed V when the deceleration of the vehicle is controlled in the non-accelerator pedal position mode based on the target deceleration Gbt calculated when the deceleration target is detected.

[0069] If the vehicle being decelerated is a preceding vehicle and the road is an uphill road, the time tc is set to 0.8te. Thus, although not shown in Fig. 5(A), the deceleration of the vehicle 16 is controlled according to the accelerator pedal depression Acc until the elapsed time reaches time tc. When the elapsed time reaches time tc, the mode is changed to the non-accelerator pedal depression mode, and the deceleration is controlled to the target deceleration Gbt until the elapsed time reaches time te.

[0070] C2. When the object to be decelerated is a stationary target (Figure 5 (B)) FIG. 6 shows an example of a case where the object to be decelerated is a stopping target, in which a T-junction 80 as the object to be decelerated is ahead of the vehicle 16, and the vehicle 16 is traveling on a non-priority road 82 and approaching a priority road 84.

[0071] If the object to be decelerated is a stopped target, negative determinations are made in steps S22 and S30, and in step S34, the ratio Rec is determined to be 0.7, and the time tc is set to 0.7te. Thus, as shown by the dashed and dashed lines in Fig. 5(B), the deceleration of the vehicle 16 is controlled according to the accelerator opening Acc until the elapsed time reaches time tc. When the elapsed time reaches time tc, the mode is changed to the non-accelerator opening mode, and the deceleration is controlled to be the target deceleration Gbt until the elapsed time reaches time te and the vehicle speed V becomes 0.

[0072] C3. When the driver is steering at an intersection (Figure 5(C)) In step S22, a negative determination is made, in step S30, an affirmative determination is made, and in step S36, the ratio Rec is determined to be 0.5 and the time tc is set to 0.5te. Therefore, as shown by the dashed line and the dashed dotted line in Fig. 5(C), the deceleration of the vehicle 16 is controlled in the same manner as in the case of C2, except that the mode change from the accelerator opening mode to the non-accelerator opening mode is earlier than in the case of C2.

[0073] C4. When the deceleration target is multiple stopped targets (Fig. 5(C)) 4, negative determinations are made in steps S22 and S30, and positive determinations are made in step S32, and the ratio Rec is determined to be 0.5 and the time tc is set to 0.5te in step S36. Thus, the deceleration of the vehicle 16 is controlled in the same manner as in the case of C3.

[0074] As can be seen from the above description, according to the embodiment, the target deceleration Gbt is calculated to make the vehicle speed V of the vehicle 16 when it reaches the position of the deceleration target reach the target vehicle speed Vt determined by the type of the deceleration target, and the timing of the mode change is set according to the type of the deceleration target. Furthermore, when it is determined that it is time to change the mode, the mode is changed from the accelerator opening mode to a non-accelerator opening mode in which the vehicle is decelerated based on the target deceleration.

[0075] Therefore, the vehicle deceleration is first controlled according to the accelerator opening in the accelerator opening mode, and when it is determined that it is time to change the mode, it is automatically controlled based on the target deceleration in the non-accelerator opening mode. Therefore, when the mode is changed, the driver can control the vehicle speed to the required vehicle speed without controlling the amount of depression of the accelerator pedal, so that the effect of deceleration assistance is improved by starting the deceleration control early, and the vehicle speed can be controlled to the required vehicle speed more easily than before.

[0076] According to the embodiment, the target deceleration for bringing the vehicle speed to the target vehicle speed determined by the type of deceleration object is calculated, and the timing of the mode change is set according to the type of deceleration object (S20). Therefore, regardless of the type of deceleration object, the vehicle speed can be easily controlled to a required vehicle speed, and the mode can be changed at a timing according to the type of deceleration object.

[0077] Furthermore, according to the embodiment, when it is determined that the deceleration target is a stopping target, that is, an object for which the vehicle needs to be stopped (S22), it is determined that it is time to change the mode when it is determined that a predetermined time tc has elapsed since the deceleration target was first detected (S70). Therefore, when the predetermined time has elapsed since the deceleration target was detected, the mode can be changed from the accelerator opening mode to the non-accelerator opening mode.

[0078] Furthermore, according to the embodiment, the predetermined time tc is variably set depending on the type of deceleration object and the running conditions of the vehicle (S22, S24, S30). Therefore, the timing of the mode change from the accelerator opening mode to the non-accelerator opening mode can be variably set depending on the type of deceleration object and the running conditions of the vehicle.

[0079] Furthermore, according to the embodiment, when it is determined that a steering operation is being performed (S30), the timing of the mode change is advanced (S36) compared to when it is not determined that a steering operation is being performed. Therefore, when a steering operation is being performed, the timing of the mode change is advanced, and the timing at which the vehicle decelerates based on the target deceleration can be advanced. Therefore, it is possible for the driver to concentrate on the steering operation without controlling the accelerator opening earlier than when the timing of the mode change is not advanced.

[0080] Furthermore, according to the embodiment, when it is determined that there are multiple deceleration targets, the timing of the mode change is made earlier than when it is determined that there is only one deceleration target. Thus, when there are multiple deceleration targets, the timing of the mode change is made earlier than when there is only one deceleration target, and the timing at which the vehicle decelerates based on the target deceleration can be made earlier. Therefore, it is possible to prevent the driver from having to control the accelerator opening earlier than when the timing of the mode change is not made earlier.

[0081] 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.

[0082] For example, in the above embodiment, the predetermined time tc is variably set according to both the type of deceleration object and the vehicle driving conditions (S22, S24, S30). However, the predetermined time may be variably set according to either the type of deceleration object or the vehicle driving conditions. Also, the vehicle driving conditions in the embodiment are conditions in which the vehicle is driving on an uphill road, but may include other driving conditions such as the distance from the preceding vehicle and weather conditions.

[0083] For example, the order of execution of steps S22 and S30 in the first embodiment described above may be reversed, and the order of execution of step S22, and steps S30 and S32 in the second embodiment may be reversed.

[0084] In addition, the value of the ratio Rec in the above embodiment is an example, and is not limited to the above value. In addition, the ratio Rec is 1 when the deceleration target is a preceding vehicle, but may be a value smaller than 1 and larger than 0.8. [Explanation of symbols]

[0085] 10...vehicle deceleration assist control device, 14FL to 14RR...wheels, 16...vehicle, 30...deceleration device, 34...braking ECU, 50...driving assist ECU, 56...deceleration target detection device, 64...accelerator opening sensor, 66...drive ECU, 70...steering angle sensor

Claims

1. A deceleration assist control device for a vehicle includes an accelerator opening detection device that detects an accelerator opening, a deceleration target detection device that detects a deceleration target in front of the vehicle, a deceleration device that decelerates the vehicle, and a control unit that controls the deceleration device, wherein the control unit is configured to perform deceleration assist control in an accelerator opening mode that decelerates the vehicle in accordance with the accelerator opening by controlling the deceleration device when a deceleration target is detected in a situation in which the accelerator opening exceeds a reference value, The control unit is configured to calculate a target deceleration for making the vehicle speed when the vehicle reaches a position of a deceleration target a target vehicle speed determined by the type of deceleration target, set the timing of a mode change according to the type of deceleration target, and when it determines that it is time to change the mode, change the mode from the accelerator opening mode to a non-accelerator opening mode in which the vehicle is decelerated based on the target deceleration.

2. In the deceleration assistance control device for a vehicle as described in claim 1, the control unit is configured to determine that it is time to change modes when it determines that the deceleration target is an object that requires the vehicle to be stopped and when it determines that a predetermined time has elapsed since the deceleration target was first detected.

3. 3. The vehicle deceleration assistance control device according to claim 2, wherein the control unit is configured to variably set the predetermined time period depending on at least one of a type of an object to be decelerated and a driving condition of the vehicle.

4. 2. The deceleration assistance control device for a vehicle according to claim 1, wherein the control unit is configured to make the timing of the mode change earlier when it determines that a steering operation is being performed, compared to when it is not determined that a steering operation is being performed.

5. 2. The deceleration assistance control device for a vehicle according to claim 1, wherein the control unit is configured to advance the timing of the mode change when it determines that there are multiple deceleration targets, compared to when it determines that there is only one deceleration target.

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