Vehicle driving assistance system

Abstract

The present invention provides a vehicle driving assistance device that can prevent the vehicle's speed from temporarily falling below the legal minimum speed, even when performing driving assistance control that allows the vehicle to coast. [Solution] The vehicle driving support device 10 performs a first driving support control to drive the vehicle 100 by autonomously alternating between accelerating and coasting the vehicle so that the vehicle's speed is maintained within a range between a target upper speed and a target lower speed. The vehicle driving support device sets the target upper speed by adding a predetermined upper limit to the set vehicle speed set by the vehicle's user as the target value for the vehicle's speed, and sets the target lower speed by subtracting a predetermined lower limit from the set vehicle speed. When the first driving support control is executed, if the target lower speed is lower than the legally mandated minimum speed applicable to the vehicle, the predetermined lower limit is changed so that the target lower speed is equal to or greater than the legally mandated minimum speed.

Description

Technical Field

[0001] The present invention relates to a vehicle driving support device.

Background Art

[0002] There is known a vehicle driving support device that executes driving support control for driving a host vehicle by autonomously accelerating and decelerating the host vehicle so that the host vehicle speed is maintained at a set vehicle speed. Here, the host vehicle speed is the traveling speed of the host vehicle. Also, the set vehicle speed is a speed set as a target value of the host vehicle speed by the driver of the host vehicle.

[0003] As such a vehicle driving support device, there is also known a vehicle driving support device that changes the set vehicle speed to a speed not lower than the legal minimum speed when the set vehicle speed is lower than the legal minimum speed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] By the way, there is known a vehicle driving support device that executes driving support control for driving a host vehicle by autonomously repeating the power running and the coasting of the host vehicle alternately so that the host vehicle speed is maintained within a predetermined range. Also, in such a vehicle driving support device, there is known a vehicle driving support device that sets a value obtained by adding a predetermined upper limit width to the set vehicle speed as the upper limit value of the predetermined range, and sets a value obtained by subtracting a predetermined lower limit width from the set vehicle speed as the lower limit value of the predetermined range. In such a vehicle driving support device, even when the set vehicle speed is changed to a speed not lower than the legal minimum speed when the set vehicle speed is lower than the legal minimum speed, when the host vehicle is coasting, the host vehicle speed may temporarily become lower than the legal minimum speed.

[0006] The object of the present invention is to provide a vehicle driving assistance device that can prevent the vehicle's speed from temporarily falling below the legal minimum speed, even when performing driving assistance control that coasts the vehicle.

[0007] The vehicle driving support device according to the present invention includes a control device that performs a first driving support control to drive the vehicle by autonomously alternating between accelerating the vehicle and coasting the vehicle, so that the vehicle's driving speed is maintained within a range between a target upper speed limit and a target lower speed limit. The control device is configured to set the target upper speed limit as the set vehicle speed plus a predetermined upper limit range, and to set the target lower speed limit as the set vehicle speed minus a predetermined lower limit range. Furthermore, when the first driving support control is executed, if the target lower speed limit is lower than the legally mandated minimum speed applicable to the vehicle, the control device is configured to change the predetermined lower limit range so that the target lower speed limit becomes equal to or greater than the legally mandated minimum speed limit.

[0008] According to the present invention, if the target lower limit speed is lower than the legal minimum speed, the target lower limit speed is changed to a speed equal to or greater than the legal minimum speed. Therefore, even when the first driving support control, which is a driving support control that coasts the vehicle, is being executed, it is possible to prevent the vehicle's driving speed from temporarily falling below the legal minimum speed.

[0009] Furthermore, in the vehicle driving support device according to the present invention, the control device may be configured to execute a second driving support control, which, if the difference between the target lower speed set by the changed predetermined lower limit width and the target upper speed is smaller than a predetermined value, cancels the first driving support control and autonomously accelerates and decelerates the vehicle to drive it so that the vehicle's driving speed is maintained at the set vehicle speed or the distance between the vehicle and the preceding vehicle is maintained at a predetermined distance.

[0010] If the difference between the target lower speed limit and the target upper speed limit is small, the distance over which the vehicle can coast becomes shorter, which may actually reduce the energy efficiency of driving the vehicle. According to the present invention, if the difference between the target lower speed limit and the target upper speed limit is smaller than a predetermined value, the first driving support control is canceled. Therefore, the decrease in energy efficiency of driving the vehicle can be suppressed.

[0011] Furthermore, in the vehicle driving support device according to the present invention, the control device may be configured to change the predetermined upper limit width so that the difference between the target lower limit speed and the target upper limit speed, which are set by the changed predetermined lower limit width, becomes equal to or greater than the predetermined value, within a range in which the target upper limit speed is maintained at or below the legal maximum speed.

[0012] As mentioned above, if the difference between the target lower speed limit and the target upper speed limit is small, the distance over which the vehicle can coast becomes shorter, which may actually reduce the energy efficiency of driving the vehicle. According to the present invention, if the difference between the target lower speed limit and the target upper speed limit is smaller than a predetermined value, that difference is increased. Therefore, the decrease in energy efficiency of driving the vehicle can be suppressed.

[0013] Furthermore, in the vehicle driving support device according to the present invention, the control device may be configured to perform a second driving support control in which, when the driving speed of the preceding vehicle is lower than the set vehicle speed, the value obtained by subtracting the target lower limit speed set by the changed predetermined lower limit width from the driving speed of the preceding vehicle is less than a predetermined value, the first driving support control is canceled and the vehicle is driven by autonomously accelerating and decelerating the vehicle so that the driving speed of the vehicle is maintained at the set vehicle speed or the distance between the vehicle and the preceding vehicle is maintained at a predetermined distance.

[0014] When the difference between the target lower speed limit and the speed of the preceding vehicle is small, the distance over which the vehicle can coast becomes shorter, which may actually reduce the energy efficiency of driving the vehicle. According to the present invention, when the difference between the target lower speed limit and the speed of the preceding vehicle is smaller than a predetermined value, the first driving support control is canceled. Therefore, the decrease in energy efficiency of driving the vehicle can be suppressed.

[0015] Furthermore, in the vehicle driving support device according to the present invention, the control device may be configured to set the target upper limit speed as a value obtained by adding half the sum of the predetermined upper limit and predetermined lower limit to the driving speed of the preceding vehicle when the driving speed of the preceding vehicle is lower than the average value of the driving speed of the own vehicle achieved by the first driving support control, and to set the target lower limit speed as a value obtained by subtracting half the sum of the predetermined upper limit and predetermined lower limit from the driving speed of the preceding vehicle. In this case, the control device may be configured to change the target lower limit speed so that the target lower limit speed is equal to or greater than the legal minimum speed when the driving speed of the preceding vehicle is lower than the average value of the driving speed of the own vehicle achieved by the first driving support control during the execution of the first driving support control, and the target lower limit speed is lower than the legal minimum speed. Furthermore, in this case, the control device may be configured to execute a second driving support control, which, if the value obtained by subtracting the modified target lower speed limit from the target upper speed limit is less than a predetermined value, cancels the first driving support control and autonomously accelerates and decelerates the vehicle to drive it so that the vehicle's speed is maintained at the set speed or the distance between the vehicle and the preceding vehicle is maintained at a predetermined distance.

[0016] As mentioned above, if the difference between the target lower speed limit and the target upper speed limit is small, the distance over which the vehicle can coast becomes shorter, which may actually reduce the energy efficiency of driving the vehicle. According to the present invention, if the difference between the target lower speed limit and the target upper speed limit is smaller than a predetermined value, the first driving support control is canceled. Therefore, the decrease in energy efficiency of driving the vehicle can be suppressed.

[0017] Furthermore, in the vehicle driving support device according to the present invention, the control device may be configured to determine the width by which the predetermined lower limit width is changed based on the legal minimum speed obtained from the legal minimum speed information included in the information on the road on which the vehicle is traveling when the first driving support control is executed.

[0018] According to the present invention, a predetermined lower limit is changed based on the legal minimum speed obtained from the legal minimum speed information included in the information on the road on which the vehicle is traveling. Therefore, it is possible to more reliably suppress the temporary decrease in the vehicle's speed below the legal minimum speed.

[0019] The components of the present invention are not limited to the embodiments described below with reference to the drawings. Other objects, features, and incidental advantages of the present invention will be readily apparent from the description of the embodiments. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a diagram showing a vehicle driving assistance device according to an embodiment of the present invention. [Figure 2] Figure 2 shows a scenario where a preceding vehicle is present. [Figure 3] Figure 3 is a flowchart showing the routine executed by a vehicle driving assistance device according to an embodiment of the present invention. [Figure 4] Figure 4 is a flowchart showing the routine executed by a vehicle driving assistance device according to an embodiment of the present invention. [Figure 5]FIG. 5 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention. [Figure 6] FIG. 6 is a time chart for explaining the control of the traveling speed of the host vehicle when the target lower limit speed is changed and the first traveling speed control is continued. [Figure 7] FIG. 7 is a time chart for explaining the control of the traveling speed of the host vehicle when the first traveling speed control is stopped. [Figure 8] FIG. 8 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention. [Figure 10] FIG. 10 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention. [Figure 11] FIG. 11 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention. [Figure 12] FIG. 12 is a flowchart showing a process that replaces the process of step S810 and the like in the routine shown in FIG. 8. [Figure 13] FIG. 13 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention. [Figure 14] FIG. 14 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention. [Figure 15] FIG. 15 is a flowchart showing a routine executed by a vehicle driving support device according to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0021] The vehicle driving support device according to an embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows the vehicle driving support device 10 according to an embodiment of the present invention. The vehicle driving support device 10 is mounted on the vehicle 100. The vehicle driving support device 10 will be described below using the case where the operator or user of the vehicle 100 is the driver of the vehicle 100 (i.e., a person who is in the vehicle 100 and drives the vehicle 100) as an example. However, the operator or user of the vehicle 100 may also be a remote operator of the vehicle 100 (i.e., a person who does not ride in the vehicle 100 and drives the vehicle 100 remotely). In the following description, the driver of the vehicle 100 may be simply referred to as "driver".

[0022] As shown in Figure 1, the vehicle driving assistance system 10 is equipped with an ECU (Electronic Control Unit) 90 as a control device. The ECU 90 mainly consists of a microcomputer. The microcomputer includes a CPU, a computer-readable storage medium, and an interface, etc. The storage medium is ROM, RAM, and non-volatile memory, etc. The CPU realizes various functions by executing instructions, programs, or routines stored in the storage medium. In particular, in this example, the vehicle driving assistance system 10 stores programs that realize the various controls that the vehicle driving assistance system 10 performs in the storage medium.

[0023] In this example, the vehicle driving assistance system 10 is equipped with only one ECU 90, but it may also be equipped with multiple ECUs, and the functions of the vehicle driving assistance system 10 described below may be divided among the ECUs.

[0024] Furthermore, the vehicle driving assistance device 10 may be configured to update the program stored in the storage medium via wireless communication with an external device (for example, internet communication).

[0025] Furthermore, the vehicle driving assistance system 10 can be applied not only to vehicles driven by manual operation by an operator, but also to vehicles driven by automated driving.

[0026] As shown in Figure 1, the vehicle 100 is equipped with a drive unit 20, a braking unit 30, a power transmission unit 40, and a notification unit 50.

[0027] The drive unit 20 is a device that generates the driving force supplied to the vehicle 100 (particularly to the drive wheels of the vehicle 100). In this example, the drive unit 20 comprises an internal combustion engine 21 and an electric motor 22. The drive unit 20 is electrically connected to the ECU 90. The vehicle driving support device 10 can control the driving force supplied to the vehicle 100 by controlling the operation of the drive unit 20 (i.e., the internal combustion engine 21 and the electric motor 22).

[0028] The braking device 30 is a device that applies braking force to the vehicle 100 (particularly to the wheels of the vehicle 100). In this example, the braking device 30 includes a hydraulic brake system 31. The braking device 30 is electrically connected to the ECU 90. The vehicle driving support system 10 can control the braking force applied to the vehicle 100 by controlling the operation of the braking device 30 (more specifically, the operation of the hydraulic brake system 31).

[0029] The power transmission device 40 is a device that transmits the power output from the drive unit 20 to the drive wheels of the vehicle 100. The power transmission device 40 is, for example, a transmission. The power transmission device 40 is electrically connected to the ECU 90. The vehicle driving support device 10 can establish a power transmission path and transmit the power output from the drive unit 20 to the drive wheels of the vehicle 100 by controlling the operation of the power transmission device 40. The power transmission path is the path that transmits power from the drive unit 20 to the drive wheels of the vehicle 100. The vehicle driving support device 10 can also block the power transmission path by controlling the operation of the power transmission device 40, preventing power from being transmitted from the drive unit 20 to the drive wheels of the vehicle 100.

[0030] The notification device 50 is a device that provides various notifications to the driver. In this example, the notification device 50 includes a display device 51 and an audio device 52.

[0031] The display device 51 is a device that displays various images. The display device 51 includes, for example, a display. The display device 51 is electrically connected to the ECU 90. The vehicle driving assistance system 10 displays various images using the display device 51.

[0032] The sound device 52 is a device that outputs various sounds and / or voices. The sound device 52 is equipped with, for example, a speaker. The sound device 52 is electrically connected to the ECU 90. The vehicle driving assistance system 10 outputs various sounds and / or voices through the sound device 52.

[0033] Furthermore, the vehicle 100 is equipped with a driver assistance control unit 61, a vehicle speed setting control unit 62, a vehicle speed width setting control unit 63, a vehicle distance setting control unit 64, a vehicle speed detection device 65, a surrounding information detection device 70, a GPS signal receiver 81, and a map database 82.

[0034] The driver assistance control unit 61 is a device operated by the driver. By operating the driver assistance control unit 61, the driver can request the execution or cessation of the driver assistance control described later. The driver assistance control unit 61 is electrically connected to the ECU 90. When the driver assistance control unit 61 is operated while the driver assistance control is not being executed, the vehicle driver assistance system 10 determines that the execution of the driver assistance control has been requested. On the other hand, when the driver assistance control unit 61 is operated while the driver assistance control is being executed, the vehicle driver assistance system 10 determines that the cessation of the driver assistance control has been requested.

[0035] The vehicle speed setting device 62 is a device operated by the driver. By operating the vehicle speed setting device 62, the driver can set the target vehicle speed Vset, which is used for the driver assistance control described later. The target vehicle speed Vset is the speed set by the driver as the target value of the vehicle speed V1. The vehicle speed V1 is the driving speed of the vehicle 100.

[0036] The vehicle speed width setting device 63 is a device operated by the driver. By operating the vehicle speed setting device 62, the driver can set the set vehicle speed width WVset, which will be used for the driver assistance control described later.

[0037] The following distance setting device 64 is a device operated by the driver. By operating the following distance setting device 64, the driver can set the set following distance Dset, which is used for the driver assistance control described later. In this example, by operating the following distance setting device 64, the driver can set one of the following distances, a long distance, a medium distance, or a short distance as the set following distance Dset. If a long distance is set as the set following distance Dset, a relatively long distance Dlong will be set as the set following distance Dset. If a medium distance is set as the set following distance Dset, a medium distance Dmid will be set as the set following distance Dset. If a short distance is set as the set following distance Dset, a relatively short distance Dshort will be set. The set following distance Dset is set to a longer distance the higher the vehicle speed V1 is. Note that if the vehicle speed V1 is the same, the relatively long distance Dlong is longer than the medium distance Dmid. Furthermore, assuming the same vehicle speed V1, the medium distance Dmid is longer than the relatively short distance Dshort.

[0038] The vehicle speed detection device 65 is a device for detecting the vehicle speed V1. The vehicle speed detection device 65 is equipped with, for example, wheel speed sensors provided on each wheel of the vehicle 100. The vehicle speed detection device 65 is electrically connected to the ECU 90. The vehicle driving support system 10 acquires the vehicle speed V1 using the vehicle speed detection device 65.

[0039] The surrounding information detection device 70 is a device for detecting information about the surroundings of the vehicle 100. In this example, the surrounding information detection device 70 is equipped with a plurality of electromagnetic wave sensors 71 and a plurality of image sensors 72.

[0040] The electromagnetic wave sensor 71 is electrically connected to the ECU 90. The electromagnetic wave sensor 71 is, for example, a radar sensor such as a millimeter-wave radar. The vehicle driving support system 10 acquires information (object information IO) related to objects present around the vehicle 100 as surrounding information IS using the electromagnetic wave sensor 71.

[0041] The image sensor 72 is electrically connected to the ECU 90. The image sensor 72 is, for example, a camera sensor. The vehicle driving assistance system 10 acquires image information ICs related to the surroundings of its own vehicle 100 as surrounding information IS using the image sensor 72.

[0042] The GPS signal receiver 81 is a device that receives GPS signals. The GPS signal receiver 81 is electrically connected to the ECU 90. The vehicle driving assistance system 10 receives GPS signals via the GPS signal receiver 81. The vehicle driving assistance system 10 obtains the current position of its own vehicle 100 based on the GPS signals.

[0043] The map database 82 is a device that stores map information IM. The map database 82 is electrically connected to the ECU 90. The vehicle driving assistance system 10 obtains road information IR from the current position of the vehicle 100 and the map information IM. Road information IR is information about the road on which the vehicle 100 is traveling.

[0044] Next, the operation of the vehicle driving support system 10 will be described. The vehicle driving support system 10 executes the routines shown in Figure 3 at predetermined time intervals. As a result, when predetermined conditions are met, the vehicle driving support system 10 executes driving support control. In this example, the driving support control includes first driving support control and second driving support control.

[0045] The first driver assistance control includes a first driving speed control and a first inter-vehicle distance control.

[0046] The first driving speed control is performed when there is no preceding vehicle 200. As shown in Figure 2, the preceding vehicle 200 is another vehicle that is traveling in the vehicle's lane LN1 ahead of the vehicle 100 and is within a predetermined distance Dth ahead of the vehicle 100. The preceding vehicle 200 is detected based on surrounding information IS.

[0047] The first speed control is a control that drives the vehicle 100 by repeatedly and alternately autonomously performing acceleration and coasting of the vehicle 100 so that the vehicle speed V1 is maintained within the target speed range RVtgt. In other words, the first speed control is a control that drives the vehicle 100 by repeatedly and alternately performing acceleration control and coasting control autonomously so that the vehicle speed V1 is maintained within the target speed range RVtgt.

[0048] Power control is a control method that enables the vehicle 100 to exert power. When power control is performed, the vehicle driving support device 10 enables the vehicle 100 to exert power by applying driving force from the drive unit 20 to the vehicle 100. Alternatively, optimal power control may be used as the power control method. Optimal power control is a control method that enables the vehicle 100 to exert power by applying driving force from the drive unit 20 to the vehicle 100 while controlling the operation of the drive unit 20 to maximize the driving energy efficiency. Driving energy efficiency is the energy efficiency when the drive unit 20 generates driving force.

[0049] Coasting control is a control method that allows the vehicle 100 to coast. When coasting control is performed, the vehicle driving support device 10 allows the vehicle 100 to coast by stopping the application of driving force from the drive unit 20 to the vehicle 100. In this example, when coasting control is performed, the vehicle driving support device 10 stops the application of driving force from the drive unit 20 to the vehicle 100 by disconnecting the driving force transmission path. As described above, the driving force transmission path is the path through which driving force is applied from the drive unit 20 to the vehicle 100. The vehicle driving support device 10 disconnects the driving force transmission path by controlling the operation of the driving force transmission device 40.

[0050] When the vehicle driving support device 10 is executing the first driving speed control, if the vehicle speed V1 increases due to the execution of power control and reaches the target upper limit speed Vtgt_max, it terminates power control and starts coasting control. The target upper limit speed Vtgt_max is the upper limit of the target vehicle speed range RVtgt. The target upper limit speed Vtgt_max is the set vehicle speed Vset plus a predetermined upper limit width ΔVmax. In this example, the predetermined upper limit width ΔVmax is zero, except for the exceptions described later. Therefore, in this example, except for the exceptions described later, the set vehicle speed Vset set by the driver is set as the target upper limit speed Vtgt_max (Vtgt_max = Vset).

[0051] On the other hand, when the vehicle driving support device 10 is executing the first driving speed control, if the vehicle speed V1 decreases due to the execution of coasting control and reaches the target lower limit speed Vtgt_min, it terminates coasting control and starts power control. The target lower limit speed Vtgt_min is the lower limit of the target vehicle speed range RVtgt. The target lower limit speed Vtgt_min is the speed obtained by subtracting a predetermined lower limit width ΔVmin from the set vehicle speed Vset. In this example, the predetermined lower limit width ΔVmin is the target vehicle speed width WVtgt. Therefore, in this example, the value obtained by subtracting the target vehicle speed width WVtgt from the target upper limit speed Vtgt_max is set as the target lower limit speed Vtgt_min. Also, except for the exceptions described later, the set vehicle speed width WVset set by the driver is set as the target vehicle speed width WVtgt.

[0052] The first inter-vehicle distance control is performed when a preceding vehicle 200 is present. The first inter-vehicle distance control is a control that drives the vehicle 100 by repeatedly and autonomously alternating between accelerating and coasting the vehicle 100 so that the inter-vehicle distance D is maintained within the target inter-vehicle distance range RDtgt. In other words, the first inter-vehicle distance control is a control that drives the vehicle 100 by repeatedly and autonomously alternating between accelerating control and coasting control so that the inter-vehicle distance D is maintained within the target inter-vehicle distance range RDtgt.

[0053] The following distance D is the distance between the vehicle 100 and the preceding vehicle 200. The following distance D is obtained based on surrounding information IS.

[0054] When the vehicle driving support device 10 is performing the first inter-vehicle distance control, if the inter-vehicle distance D is shortened by the execution of the power control and reaches the target lower limit inter-vehicle distance Dtgt_min, it terminates the power control and starts coasting control. The target lower limit inter-vehicle distance Dtgt_min is the lower limit of the target inter-vehicle distance range RDtgt. In this example, the set inter-vehicle distance Dset set by the driver is set as the target lower limit inter-vehicle distance Dtgt_min (Dtgt_min = Dset).

[0055] On the other hand, when the vehicle driving support device 10 is performing the first inter-vehicle distance control, if the inter-vehicle distance D increases due to the execution of coasting control and reaches the target upper limit inter-vehicle distance Dtgt_max, it terminates coasting control and starts power control. The target upper limit inter-vehicle distance Dtgt_max is the upper limit of the target inter-vehicle distance range RDtgt. In this example, the value obtained by adding the target lower limit inter-vehicle distance Dtgt_min to the target inter-vehicle distance width WDtgt is set as the target upper limit inter-vehicle distance Dtgt_max (Dtgt_max = Dtgt_min + WDtgt). In this example, the target inter-vehicle distance width WDtgt is set according to the set inter-vehicle distance Dset and the vehicle speed V1.

[0056] Furthermore, during power control, if the vehicle speed V1 reaches the target upper limit speed Vtgt_max before the inter-vehicle distance D reaches the target lower limit inter-vehicle distance Dtgt_max, power control will continue to maintain the vehicle speed V1 at the target upper limit speed Vtgt_max. Also, during coasting control, if the vehicle speed V1 reaches the target lower limit speed Vtgt_min before the inter-vehicle distance D reaches the target upper limit inter-vehicle distance Dtgt_max, coasting control will be terminated, and power control will be performed to maintain the vehicle speed V1 at the target lower limit speed Vtgt_min.

[0057] Therefore, the first inter-vehicle distance control can also be described as a control that drives the vehicle 100 by repeatedly and alternately autonomously performing acceleration and coasting of the vehicle 100 so that the vehicle speed V1 is maintained within the range between the target upper speed Vtgt_max and the target lower speed Vtgt_min.

[0058] The second driver assistance control includes a second driving speed control and a second inter-vehicle distance control.

[0059] The second speed control is performed when there is no preceding vehicle 200. The second speed control is a control system that drives vehicle 100 by autonomously accelerating and decelerating vehicle 100 so that its own speed V1 is maintained at the set speed Vset.

[0060] The second inter-vehicle distance control is performed when a preceding vehicle 200 is present. The second inter-vehicle distance control is a control system that autonomously accelerates and decelerates the vehicle 100 so that the inter-vehicle distance D is maintained at the set inter-vehicle distance Dset.

[0061] When a predetermined timing occurs, the vehicle driving support system 10 starts processing from step S300 of the routine shown in Figure 3. Then, the vehicle driving support system 10 proceeds to step S305 and determines whether or not the support request condition C1 is met. The support request condition C1 is met when the execution of driving support control is requested.

[0062] If the vehicle driving assistance system 10 determines "Yes" in step S305, it proceeds to step S310 to determine whether the preceding vehicle condition C2 is met. The preceding vehicle condition C2 is met when a preceding vehicle 200 exists.

[0063] If the vehicle driving support system 10 determines "No" in step S310, it proceeds to step S315 and executes the routine shown in Figure 4. Therefore, when the vehicle driving support system 10 proceeds to step S315, it starts processing from step S400 of the routine shown in Figure 4. Then, the vehicle driving support system 10 proceeds to step S405 and determines whether the target value setting condition C3 has been met.

[0064] The target value setting condition C3 is met when the driver sets or changes the set vehicle speed Vset by operating the vehicle speed setting device 62. Furthermore, the target value setting condition C3 is also met when the driver sets or changes the set vehicle speed width WVset by operating the vehicle speed width setting device 63.

[0065] If the vehicle driving support system 10 determines "Yes" in step S405, it proceeds to step S410 and sets the target upper speed limit Vtgt_max, the target vehicle speed range WVtgt, and the target lower speed limit Vtgt_min.

[0066] In step S410, the set vehicle speed Vset, set by the driver, is set as the target upper speed Vtgt_max (Vtgt_max = Vset). Also, the set vehicle speed range WVset, set by the driver, is set as the target vehicle speed range WVtgt. Furthermore, the value obtained by subtracting the target upper speed Vtgt_max from the target upper speed Vtgt_max is set as the target lower speed Vtgt_min (Vtgt_min = Vtgt_max - WVtgt).

[0067] Next, the vehicle driving support device 10 proceeds to step S320 of the routine shown in Figure 3.

[0068] On the other hand, if the vehicle driving support device 10 determines "No" in step S405, it proceeds to step S415 to determine whether the minimum speed change condition C4 has been met.

[0069] Minimum speed change condition C4 is met when the legal minimum speed Vlaw_min is changed. The legal minimum speed Vlaw_min is the minimum speed legally required for a vehicle to travel at.

[0070] The legal minimum speed Vlaw_min is obtained from the information on the legal minimum speed Vlaw_min included in the information on the road on which the vehicle 100 is traveling. The information on the road on which the vehicle 100 is traveling includes at least one of the following: road information IR, surrounding information IS (especially image information IC), and destination information of the ECU 90 (i.e., information on the destination of the vehicle 100). Therefore, the legal minimum speed Vlaw_min is obtained from the information on the legal minimum speed included in the road information IR. Alternatively, the legal minimum speed Vlaw_min is obtained from the information on road signs indicating the legal minimum speed obtained from surrounding information IS (especially image information IC). Alternatively, the legal minimum speed Vlaw_min is obtained from the information on the legal minimum speed set at the destination of the ECU 90, obtained from the destination information of the ECU 90. Furthermore, the highest of the legal minimum speeds obtained from road information IR, road sign information, and destination information from ECU90 may be adopted as the legal minimum speed Vlaw_min.

[0071] If the vehicle driving support system 10 determines "Yes" in step S415, it proceeds to step S420 and sets the target upper speed limit Vtgt_max, the target vehicle speed range WVtgt, and the target lower speed limit Vtgt_min.

[0072] In step S420, the currently set vehicle speed Vset is set as the target upper speed Vtgt_max (Vtgt_max=Vset). Also, the currently set vehicle speed range WVset is set as the target vehicle speed range WVtgt. Furthermore, the value obtained by subtracting the target upper speed Vtgt_max from the target upper speed Vtgt_max is set as the target lower speed Vtgt_min (Vtgt_min=Vtgt_max-WVtgt).

[0073] Next, the vehicle driving support device 10 proceeds to step S320 of the routine shown in Figure 3.

[0074] On the other hand, if the vehicle driving assistance device 10 determines "No" in step S415, it proceeds directly to step S320 of the routine shown in Figure 3.

[0075] When the vehicle driving support system 10 proceeds to step S320, it executes the routine shown in Figure 5. Therefore, when the vehicle driving support system 10 proceeds to step S320, it starts processing from step S500 of the routine shown in Figure 5. Then, the vehicle driving support system 10 proceeds to step S505 and determines whether the minimum speed condition C5 is met. The minimum speed condition C5 is met when the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min.

[0076] If the vehicle driving support system 10 determines "Yes" in step S505, it proceeds to step S510 and changes the target lower limit speed Vtgt_min to a speed equal to or greater than the legal minimum speed Vlaw_min. In this example, the legal minimum speed Vlaw_min is set as the target lower limit speed Vtgt_min.

[0077] Thus, in this example, when the first driving speed control is executed, if the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min applicable to the vehicle 100, the predetermined lower limit width ΔVmin is changed so that the target lower limit speed Vtgt_min becomes equal to or greater than the legal minimum speed Vlaw_min.

[0078] Furthermore, as mentioned above, the legal minimum speed Vlaw_min is obtained from the legal minimum speed information included in the information about the road on which the vehicle 100 is traveling. Therefore, in this example, when the first driving speed control is executed, the amount by which the predetermined lower limit width ΔVmin is changed is determined based on the legal minimum speed Vlaw_min obtained from the legal minimum speed information included in the information about the road on which the vehicle 100 is traveling.

[0079] Furthermore, in step S510, the target lower limit speed Vtgt_min may be set as the value obtained by adding a predetermined value ΔV to the legal minimum speed Vlaw_min.

[0080] The predetermined value ΔV is set to an appropriate value for setting the target lower limit speed Vtgt_min so that power control is initiated at a timing when the vehicle speed V1 can be increased without the vehicle speed V1 falling below the legal minimum speed Vlaw_min. In particular, the predetermined value ΔV is set to the minimum of such an appropriate value. The predetermined value ΔV is set to a larger value the smaller the vehicle's acceleration capability. Also, the predetermined value ΔV is set to a larger value the lower the vehicle's acceleration responsiveness. Note that the vehicle's acceleration capability is greater the greater the acceleration of the vehicle achieved by power control. Also, the vehicle's acceleration responsiveness is higher the shorter the time between the start of power control and the actual start of vehicle acceleration.

[0081] Furthermore, in step S510, the set vehicle speed Vset is not changed. Therefore, the target upper speed Vtgt_max is also not changed.

[0082] Next, the vehicle driving support system 10 proceeds to step S515 and determines whether or not the minimum vehicle speed width condition C6 is met.

[0083] The minimum vehicle speed width condition C6 is met when the target vehicle speed width WVtgt is smaller than the minimum vehicle speed width WVmin. In other words, the minimum vehicle speed width condition C6 is met when the difference between the target lower speed limit Vtgt_min and the target upper speed limit Vtgt_max is smaller than the minimum vehicle speed width WVmin. The minimum vehicle speed width WVmin is the minimum value of the target vehicle speed width WVtgt that ensures an improvement in drive energy efficiency of a predetermined value or more by executing the first driver assistance control. Furthermore, the minimum vehicle speed width WVmin is determined according to the characteristics of the vehicle (especially the characteristics of the drive energy efficiency of the drive system), the average driving speed of the vehicle, and the gradient of the road on which the vehicle is traveling.

[0084] Furthermore, when the first driver assistance control is executed, the larger the target vehicle speed width WVtgt, the higher the driving energy efficiency tends to be. Also, when the first driver assistance control is executed, if the target vehicle speed width WVtgt is too small, the driving energy efficiency may be lower than the driving energy efficiency achieved by the second driver assistance control. Therefore, when the first driver assistance control is executed, the vehicle driver assistance device 10 is configured to determine whether or not the minimum vehicle speed width condition C6 is met in order to ensure high driving energy efficiency.

[0085] If the vehicle driving support device 10 determines "No" in step S515, it proceeds to step S520 and executes or continues the first driving speed control. At this time, if the second driving speed control was being executed, the second driving speed control is canceled and the first driving speed control is executed. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0086] Furthermore, the vehicle driving support device 10 may be configured to issue a continuation notification when the first driving speed control is continued in step S520. In this example, the continuation notification informs the driver that the first driving speed control will be continued, but that the vehicle speed V1 may fall below the legal minimum speed Vlaw_min. Alternatively, the continuation notification will continue the first driving speed control, but because the vehicle speed V1 may fall below the legal minimum speed Vlaw_min, it will warn the driver to ensure that the vehicle speed V1 does not fall below the legal minimum speed Vlaw_min. Alternatively, the continuation notification will continue the first driving speed control, but because the vehicle speed V1 may fall below the legal minimum speed Vlaw_min, it will suggest to the driver to change the set vehicle speed Vset or set vehicle speed range WVset.

[0087] The continuation notification is implemented by the notification device 50. More specifically, the continuation notification is implemented by displaying a predetermined image by the display device 51 and / or by outputting a predetermined sound by the sound device 52.

[0088] On the other hand, if the vehicle driving support device 10 determines "Yes" in step S515, it proceeds to step S525 and executes or continues the second driving speed control. At this time, if the first driving speed control was being executed, the first driving speed control is canceled and the second driving speed control is executed. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0089] Thus, in this example, if the difference between the target lower speed Vtgt_min and the target upper speed Vtgt_max, which are set by the modified predetermined lower speed ΔVmin (target vehicle speed width WVtgt), is smaller than a predetermined value (minimum vehicle speed width WVmin), the first driving speed control is canceled and the second driving speed control is executed.

[0090] Furthermore, the vehicle driving support device 10 may be configured to issue a cancellation notification when the first driving speed control is discontinued in step S525. In this example, the cancellation notification informs the driver that the first driving speed control has been discontinued, but that in order to perform the first driving speed control, it is necessary to change the set vehicle speed Vset or the set vehicle speed range WVset. Furthermore, the cancellation notification may only inform the driver that the first driving speed control has been discontinued.

[0091] Cancellation notifications are provided by the notification device 50. More specifically, cancellation notifications are provided by displaying a predetermined image on the display device 51 and / or by outputting a predetermined sound on the sound device 52.

[0092] Furthermore, if the vehicle driving support device 10 determines "No" in step S505, it proceeds to step S530 and executes or continues the first driving speed control. At this time, if the second driving speed control was being executed, the second driving speed control is canceled and the first driving speed control is executed. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0093] Furthermore, if the vehicle driving assistance device 10 determines "No" in step S305 of the routine shown in Figure 3, or if it determines "Yes" in step S310 of the routine shown in Figure 3, it proceeds directly to step S395 and terminates the processing of this routine.

[0094] According to the control described above, the vehicle speed V1 is controlled as shown in Figure 6 or Figure 7.

[0095] In other words, in the example shown in Figure 6, at time t60, as a result of the legal minimum speed Vlaw_min increasing, the target lower limit speed Vtgt_min becomes lower than the legal minimum speed Vlaw_min. Therefore, the target lower limit speed Vtgt_min is set to the same speed as the legal minimum speed Vlaw_min. At this time, the target vehicle speed range WVtgt is greater than or equal to the minimum vehicle speed range WVmin. Consequently, the first driving speed control continues with the target lower limit speed Vtgt_min set to the same speed as the legal minimum speed Vlaw_min. In other words, the state in which coasting of the vehicle 100 is permitted continues.

[0096] On the other hand, in the example shown in Figure 7, at time t70, the legal minimum speed Vlaw_min increases, resulting in the target lower limit speed Vtgt_min becoming lower than the legal minimum speed Vlaw_min. Therefore, the target lower limit speed Vtgt_min is set to the same speed as the legal minimum speed Vlaw_min. At this time, the target vehicle speed range WVtgt becomes smaller than the minimum vehicle speed range WVmin. Consequently, the first driving speed control is discontinued. In other words, coasting of the vehicle 100 is prohibited.

[0097] Thus, according to the vehicle driving support device 10, if the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min, the target lower limit speed Vtgt_min is changed to a speed equal to or greater than the legal minimum speed Vlaw_min. Therefore, even when the first driving support control for coasting the vehicle 100 is being performed, it is possible to prevent the vehicle speed V1 from temporarily falling below the legal minimum speed Vlaw_min.

[0098] Alternatively, the routine shown in Figure 8 may be executed instead of the routine shown in Figure 5. In this case, the vehicle driving support system 10 proceeds to step S320 of the routine shown in Figure 3, and then starts processing from step S800 of the routine shown in Figure 8. The vehicle driving support system 10 then proceeds to step S805 to determine whether the minimum speed condition C5 is met.

[0099] If the vehicle driving support system 10 determines "Yes" in step S805, it proceeds to step S810 to change the target upper speed Vtgt_max and target lower speed Vtgt_min. Here, the value obtained by adding the target vehicle speed width WVtgt to the legal minimum speed Vlaw_min is set as the target upper speed Vtgt_max (Vtgt_max = Vlaw_min + WVtgt). Then, the value obtained by subtracting the target vehicle speed width WVtgt from the target upper speed Vtgt_max is set as the target lower speed Vtgt_min (Vtgt_min = Vtgt_max - WVtgt).

[0100] In step S805, the target upper speed Vtgt_max is changed, but the set vehicle speed Vset is not changed.

[0101] Thus, in this example as well, when the first driving speed control is executed, if the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min applicable to the vehicle 100, the predetermined lower limit width ΔVmin is changed so that the target lower limit speed Vtgt_min becomes equal to or greater than the legal minimum speed Vlaw_min.

[0102] Next, the vehicle driving support system 10 proceeds to step S812 and determines whether or not the maximum speed condition C7 is met. The maximum speed condition C7 is met when the target upper limit speed Vtgt_max is higher than the legal maximum speed Vlaw_max. The legal maximum speed Vlaw_max is the upper limit speed legally regulated for vehicle driving speed.

[0103] The legal maximum speed Vlaw_max is also obtained from the information on the legal maximum speed Vlaw_max included in the information on the road on which vehicle 100 is traveling. Here, the information on the road on which vehicle 100 is traveling is at least one of the road information IR and the surrounding information IS (in particular, image information IC). Therefore, the legal maximum speed Vlaw_max is obtained from the information on the legal maximum speed included in the road information IR. Alternatively, the legal maximum speed Vlaw_max is obtained from the information on road signs indicating the legal maximum speed obtained from the surrounding information IS (in particular, image information IC).

[0104] If the vehicle driving assistance device 10 determines "No" in step S812, it proceeds directly to step S815.

[0105] On the other hand, if the vehicle driving support system 10 determines "Yes" in step S812, it proceeds to step S814 and changes the target upper limit speed Vtgt_max. Specifically, the vehicle driving support system 10 changes the target upper limit speed Vtgt_max to a speed less than or equal to the legal maximum speed Vlaw_max. In this example, the legal maximum speed Vlaw_max is set as the target upper limit speed Vtgt_max. Next, the vehicle driving support system 10 proceeds to step S815.

[0106] When the vehicle driving support system 10 proceeds to step S815, it determines whether or not the minimum vehicle speed width condition C6 is met.

[0107] If the vehicle driving support device 10 determines "No" in step S815, it proceeds to step S820 and executes or continues the first driving speed control, similar to step S520 of the routine shown in Figure 5. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0108] On the other hand, if the vehicle driving support device 10 determines "Yes" in step S815, it proceeds to step S825 and executes or continues the second driving speed control, similar to step S525 of the routine shown in Figure 5. At this time, if the first driving speed control was being executed, the first driving speed control is canceled and the second driving speed control is executed. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0109] Thus, in this example as well, if the difference between the target lower speed Vtgt_min and the target upper speed Vtgt_max set by the modified predetermined lower speed ΔVmin (target vehicle speed width WVtgt) is smaller than a predetermined value (minimum vehicle speed width WVmin), the first driving speed control is canceled and the second driving speed control is executed.

[0110] If the vehicle driving support device 10 determines "No" in step S805, it proceeds to step S830 and executes or continues the first driving speed control. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0111] Alternatively, the routine shown in Figure 9 may be executed instead of the routine shown in Figure 5. In this case, the vehicle driving support system 10 proceeds to step S320 of the routine shown in Figure 3, and then starts processing from step S900 of the routine shown in Figure 9. The vehicle driving support system 10 then proceeds to step S905 and determines whether the minimum speed condition C5 is met.

[0112] If the vehicle driving support system 10 determines "Yes" in step S905, it proceeds to step S910 to change the target upper speed Vtgt_max and target lower speed Vtgt_min. Here, the target upper speed Vtgt_max and target lower speed Vtgt_min are set, similar to step S810 of the routine shown in Figure 8.

[0113] Thus, in this example as well, when the first driving speed control is executed, if the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min applicable to the vehicle 100, the predetermined lower limit width ΔVmin is changed so that the target lower limit speed Vtgt_min becomes equal to or greater than the legal minimum speed Vlaw_min.

[0114] Next, the vehicle driving support system 10 proceeds to step S912 and determines whether or not the maximum speed condition C7 is met.

[0115] If the vehicle driving support device 10 determines "No" in step S912, it proceeds to step S920 and executes or continues the first driving speed control, similar to step S520 of the routine shown in Figure 5. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0116] On the other hand, if the vehicle driving support device 10 determines "Yes" in step S912, it proceeds to step S925 and executes or continues the second driving speed control, similar to step S525 of the routine shown in Figure 5. At this time, if the first driving speed control was being executed, the first driving speed control is canceled and the second driving speed control is executed. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0117] If the vehicle driving support system 10 determines "No" in step S905, it proceeds to step S930 and executes or continues the first driving speed control. Next, the vehicle driving support system 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0118] Alternatively, the routine shown in Figure 10 may be executed instead of the routine shown in Figure 5. In this case, the vehicle driving support system 10 proceeds to step S320 of the routine shown in Figure 3, and then starts processing from step S1000 of the routine shown in Figure 10. Then, the vehicle driving support system 10 proceeds to step S1005 and determines whether the minimum speed condition C5 is met.

[0119] If the vehicle driving support system 10 determines "Yes" in step S1005, it proceeds to step S1010 to change the target upper speed Vtgt_max and target lower speed Vtgt_min. Here, the target upper speed Vtgt_max and target lower speed Vtgt_min are set, similar to step S810 of the routine shown in Figure 8.

[0120] Thus, in this example as well, when the first driving speed control is executed, if the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min applicable to the vehicle 100, the predetermined lower limit width ΔVmin is changed so that the target lower limit speed Vtgt_min becomes equal to or greater than the legal minimum speed Vlaw_min.

[0121] Next, the vehicle driving support device 10 proceeds to step S1020 and executes or continues the first driving speed control, similar to step S520 of the routine shown in Figure 5. Then, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0122] On the other hand, if the vehicle driving support device 10 determines "No" in step S1005, it proceeds to step S1030 and executes or continues the first driving speed control. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0123] Alternatively, the minimum speed condition C5 used in step S805 of the routine shown in Figure 8 may be a condition that is met when the target lower limit speed Vtgt_min becomes lower than the legal minimum speed Vlaw_min due to an increase in the legal minimum speed Vlaw_min. Furthermore, the vehicle driving support device 10 may be configured to stop the first driving speed control and execute the second driving speed control when the target lower limit speed Vtgt_min becomes lower than the legal minimum speed Vlaw_min due to the driver lowering the set vehicle speed Vset.

[0124] In this case, the routine shown in Figure 8 becomes the routine shown in Figure 11. In this case, when the vehicle driving support system 10 proceeds to step S320 of the routine shown in Figure 3, it starts processing from step S1100 of the routine shown in Figure 11. Then, the vehicle driving support system 10 proceeds to step S1105 and determines whether the first minimum speed condition C51 is met. The first minimum speed condition C51 is met when the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min due to the legal minimum speed Vlaw_min being changed to a higher speed.

[0125] If the vehicle driving support system 10 determines "Yes" in step S1105, it proceeds to step S1110 to change the target upper speed limit Vtgt_max and target lower speed limit Vtgt_min. Here, the target upper speed limit Vtgt_max and target lower speed limit Vtgt_min are set, similar to step S810 of the routine shown in Figure 8.

[0126] Thus, in this example as well, when the first driving speed control is executed, if the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min applicable to the vehicle 100, the predetermined lower limit width ΔVmin is changed so that the target lower limit speed Vtgt_min becomes equal to or greater than the legal minimum speed Vlaw_min.

[0127] Next, the vehicle driving support device 10 proceeds to step S1112 and determines whether or not the maximum speed condition C7 is met.

[0128] If the vehicle driving assistance device 10 determines "No" in step S1112, it proceeds directly to step S1115.

[0129] On the other hand, if the vehicle driving support system 10 determines "Yes" in step S1112, it proceeds to step S1114 to change the target upper speed Vtgt_max. Here, the target upper speed Vtgt_max is set, similar to step S812 of the routine shown in Figure 8. Next, the vehicle driving support system 10 proceeds to step S1115.

[0130] When the vehicle driving support device 10 proceeds to step S1115, it determines whether or not the minimum vehicle speed width condition C6 is met.

[0131] If the vehicle driving support device 10 determines "No" in step S1115, it proceeds to step S820 and executes or continues the first driving speed control, similar to step S520 of the routine shown in Figure 5. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0132] On the other hand, if the vehicle driving support device 10 determines "Yes" in step S1115, it proceeds to step S1125 and executes or continues the second driving speed control, similar to step S525 of the routine shown in Figure 5. At this time, if the first driving speed control was being executed, the first driving speed control is canceled and the second driving speed control is executed. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0133] Thus, in this example as well, if the difference between the target lower speed Vtgt_min and the target upper speed Vtgt_max set by the modified predetermined lower speed ΔVmin (target vehicle speed width WVtgt) is smaller than a predetermined value (minimum vehicle speed width WVmin), the first driving speed control is canceled and the second driving speed control is executed.

[0134] Furthermore, if the vehicle driving support device 10 determines "No" in step S1105, it proceeds to step S1127 to determine whether the second minimum speed condition C52 is met. The second minimum speed condition C52 is met when the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min due to the set vehicle speed Vset being changed to a lower speed.

[0135] If the vehicle driving support device 10 determines "Yes" in step S1127, it proceeds to step S1129 and executes or continues the second driving speed control, similar to step S525 of the routine shown in Figure 5. At this time, if the first driving speed control was being executed, the first driving speed control is canceled and the second driving speed control is executed. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0136] On the other hand, if the vehicle driving support device 10 determines "No" in step S1127, it proceeds to step S1130 and executes or continues the first driving speed control. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0137] Similarly, the minimum speed condition C5 used in step S905 of the routine shown in Figure 9 and step S1005 of the routine shown in Figure 10 may be designated as the first minimum speed condition C51. Furthermore, the vehicle driving support device 10 may be configured to discontinue the first driving speed control and execute the second driving speed control when the target lower limit speed Vtgt_min falls below the legal minimum speed Vlaw_min due to the driver lowering the set vehicle speed Vset.

[0138] Similarly, the minimum speed condition C5 used in step S505 of the routine shown in Figure 5 may be designated as the first minimum speed condition C51. Furthermore, the vehicle driving support device 10 may be configured to discontinue the first driving speed control and execute the second driving speed control when the target lower limit speed Vtgt_min falls below the legal minimum speed Vlaw_min due to the driver lowering the set vehicle speed Vset.

[0139] Alternatively, the process shown in Figure 12 may be executed instead of the process in step S810 of the routine shown in Figure 8. In this case, if the vehicle driving support device 10 determines "Yes" in step S805 of the routine shown in Figure 8, it proceeds to step S1205 of the routine shown in Figure 12 and changes the target lower speed Vtgt_min. Here, the target lower speed Vtgt_min is set, similar to step S510 of the routine shown in Figure 5.

[0140] Next, the vehicle driving support device 10 proceeds to step S1210 and determines whether or not the minimum vehicle speed width condition C6 is met.

[0141] If the vehicle driving assistance system 10 determines "Yes" in step S1210, it proceeds to step S1215 and changes the target upper speed Vtgt_max. Here, the value obtained by adding the target vehicle speed range WVtgt to the legal minimum speed Vlaw_min is set as the target upper speed Vtgt_max (Vtgt_max = Vlaw_min + WVtgt). Note that the target lower speed Vtgt_min is not changed in step S1215.

[0142] Next, the vehicle driving support device 10 proceeds to step S812 of the routine shown in Figure 8.

[0143] On the other hand, if the vehicle driving support device 10 determines "No" in step S1210, it proceeds to step S1220 and executes or continues the first driving speed control, similar to step S520 of the routine shown in Figure 5. Next, the vehicle driving support device 10 proceeds to step S395 of the routine shown in Figure 3 and terminates the processing of this routine.

[0144] Thus, in this example, if the difference between the target lower speed Vtgt_min and the target upper speed Vtgt_max (target vehicle speed width WVtgt), which is set by the modified predetermined lower limit width ΔVmin, is smaller than a predetermined value (minimum vehicle speed width WVmin), the predetermined upper limit width ΔVmax is changed so that the above difference (target vehicle speed width WVtgt) becomes greater than or equal to the predetermined value (minimum vehicle speed width WVmin), while the target upper speed Vtgt_max is maintained at a speed less than or equal to the legal maximum speed Vlaw_max.

[0145] Similarly, the process shown in Figure 12 may be executed instead of the processes in steps S910, S1010, and S1110 of the routines shown in Figures 9, 10, and 11.

[0146] Furthermore, when a predetermined timing occurs, the vehicle driving support device 10 starts processing from step S1300 of the routine shown in Figure 13. Then, the vehicle driving support device 10 proceeds to step S1305 and determines whether or not the support request condition C1 is met.

[0147] If the vehicle driving assistance system 10 determines "Yes" in step S1305, it proceeds to step S1310 to determine whether the preceding vehicle condition C2 is met.

[0148] If the vehicle driving assistance system 10 determines "Yes" in step S1310, it proceeds to step S1312 to determine whether the preceding vehicle low-speed condition C8 is met.

[0149] The low-speed preceding vehicle condition C8 is met when the preceding vehicle speed V2 is lower than the set vehicle speed Vset. For example, the constant-speed preceding vehicle condition C8 is met when vehicle 100 is traveling on a congested road. The preceding vehicle speed V2 is the speed of the preceding vehicle 200. The preceding vehicle speed V2 is obtained from the surrounding information IS.

[0150] Alternatively, the preceding vehicle low-speed condition C8 may be set to be met when the preceding vehicle speed V2 is lower than the average vehicle speed Vave. The average vehicle speed Vave is the average value of the vehicle speed V1 achieved by the first inter-vehicle distance control. In this example, the average vehicle speed Vave is half the value obtained by adding the current target upper speed Vtgt_max to the target lower speed Vtgt_min (Vave = (Vtgt_max + Vtgt_min) / 2).

[0151] If the vehicle driving support system 10 determines "No" in step S1312, it proceeds to step S1315 and executes the routine shown in Figure 4. Next, the vehicle driving support system 10 proceeds to step S1320 and executes one of the routines shown in Figure 5 and Figures 8 to 11. Next, the vehicle driving support system 10 proceeds to step S1395 and terminates the processing of this routine.

[0152] On the other hand, if the vehicle driving support system 10 determines "Yes" in step S1312, it proceeds to step S1325 and executes the routine shown in Figure 14. Therefore, when the vehicle driving support system 10 proceeds to step S1325, it starts processing from step S1400 of the routine shown in Figure 14. Then, the vehicle driving support system 10 proceeds to step S1405 and sets the target vehicle speed range RVtgt.

[0153] In step S1405, the target vehicle speed range RVtgt is set by setting the target upper speed limit Vtgt_max and the target lower speed limit Vtgt_min as follows.

[0154] In other words, the vehicle driving support system 10 sets the target upper limit speed Vtgt_max as the value obtained by adding half of the target vehicle speed range WVtgt to the preceding vehicle speed V2 (Vtgt_max = V2 + WVtgt / 2). To put it another way, the vehicle driving support system 10 sets the target upper limit speed Vtgt_max as the value obtained by adding half of the sum of the predetermined upper limit range ΔVmax and the predetermined lower limit range ΔVmin to the preceding vehicle speed V2 (Vtgt_max = V2 + (ΔVmax + ΔVmin) / 2).

[0155] Furthermore, the vehicle driving support system 10 sets the target lower limit speed Vtgt_min as the value obtained by subtracting half the value of the target vehicle speed range WVtgt from the preceding vehicle speed V2 (Vtgt_min = V2 - WVtgt / 2). In other words, the vehicle driving support system 10 sets the target lower limit speed Vtgt_min as the value obtained by subtracting half the value of the sum of the predetermined upper limit range ΔVmax and the predetermined lower limit range ΔVmin from the preceding vehicle speed V2 (Vtgt_min = V2 - (ΔVmax + ΔVmin) / 2).

[0156] The vehicle driving support system 10 sets the range defined by the target upper speed limit Vtgt_max and the target lower speed limit Vtgt_min as the target vehicle speed width WVtgt.

[0157] Next, the vehicle driving support system 10 proceeds to step S1410 and determines whether or not the minimum speed condition C5 is met.

[0158] If the vehicle driving support system 10 determines "Yes" in step S1410, it proceeds to step S1415 and changes the target lower limit speed Vtgt_min to a speed equal to or greater than the legal minimum speed Vlaw_min, similar to step S510 of the routine shown in Figure 5.

[0159] Thus, in this example as well, when the first driving speed control is executed, if the target lower limit speed Vtgt_min is lower than the legal minimum speed Vlaw_min applicable to the vehicle 100, the predetermined lower limit width ΔVmin is changed so that the target lower limit speed Vtgt_min becomes equal to or greater than the legal minimum speed Vlaw_min.

[0160] Next, the vehicle driving support device 10 proceeds with the process to step S1420 and determines whether or not the minimum vehicle speed width condition C6 is satisfied.

[0161] When the vehicle driving support device 10 determines "No" in step S1420, the process proceeds to step S1425, and the first inter-vehicle distance control is executed or continued in the same manner as step S520 of the routine shown in FIG. 5. Next, the vehicle driving support device 10 proceeds with the process to step S1495 and once terminates the process of this routine.

[0162] Thus, in this example, the execution of the first inter-vehicle distance control (particularly, the coasting control) is permitted at least when the preceding vehicle speed V2 is equal to or greater than the value obtained by adding half of the target vehicle speed width WVtgt to the legal minimum speed Vlaw_min (V2≧Vlaw_min + WVtgt / 2).

[0163] Furthermore, in this example, the execution of the first inter-vehicle distance control (particularly, the coasting control) is permitted when the preceding vehicle speed V2 is equal to or greater than the value obtained by adding half of the minimum vehicle speed width WVmin to the legal minimum speed Vlaw_min (V2≧Vlaw_min + WVmin / 2).

[0164] On the other hand, when the vehicle driving support device 10 determines "Yes" in step S1420, the process proceeds to step S1430, and the second inter-vehicle distance control is executed or continued in the same manner as step S525 of the routine shown in FIG. 5. At this time, when the first inter-vehicle distance control is being executed, the first inter-vehicle distance control is terminated, and the second inter-vehicle distance control is executed. Next, the vehicle driving support device 10 proceeds with the process to step S1495 and once terminates the process of this routine.

[0165] Thus, in this example, the execution of the first inter-vehicle distance control (particularly, the coasting control) is prohibited when the preceding vehicle speed V2 is lower than the value obtained by adding half of the minimum vehicle speed width WVmin to the legal minimum speed Vlaw_min (V2 < Vlaw_min + WVmin / 2).

[0166] Further, in this example, when the difference (target vehicle speed width WVtgt) between the target lower limit speed Vtgt_min and the target upper limit speed Vtgt_max set by the changed predetermined lower limit width ΔVmin is smaller than a predetermined value (minimum vehicle speed width WVmin), the first inter-vehicle distance control is terminated and the second inter-vehicle distance control is executed.

[0167] Further, in this example, when the leading vehicle speed V2 is lower than the set vehicle speed Vset, and the value obtained by subtracting the target lower limit speed Vtgt_min set by the changed predetermined lower limit width ΔVmin from the leading vehicle speed V2 is smaller than a predetermined value (minimum vehicle speed width WVmin) (V2 - Vtgt_min < WVmin), the first inter-vehicle distance control is terminated and the second inter-vehicle distance control is executed.

[0168] Further, in this example, when the value obtained by subtracting the changed target lower limit speed Vtgt_min from the target upper limit speed Vtgt_max is smaller than a predetermined value (minimum vehicle speed width WVmin) (Vtgt_max - Vtgt_min < WVmin), the first inter-vehicle distance control is terminated and the second inter-vehicle distance control is executed.

[0169] Further, when the vehicle driving support device 10 determines "No" in step S1410, the process proceeds to step S1425 to execute or continue the first inter-vehicle distance control. Next, the vehicle driving support device 10 proceeds the process to step S1495 to temporarily end the process of this routine.

[0170] [[ID=1S6]] [[ID=]17] Incidentally, when the vehicle driving support device 10 determines "No" in step S1305 or step S1310 of the routine shown in FIG. 13, the process directly proceeds to step S1395 to temporarily end the process of this routine.

[0171] Instead of the routine shown in FIG. 14, the routine shown in FIG. 15 may be executed. In this case, when the vehicle driving support device 10 proceeds with the process to step S1325 of the routine shown in FIG. 13, it starts the process from step S1500 of the routine shown in FIG. 15. Then, the vehicle driving support device 10 proceeds with the process to step S1505 and sets the target vehicle speed range RVtgt in the same manner as step S1405 of the routine shown in FIG. 14.

[0172] Next, the vehicle driving support device 10 proceeds with the process to step S1510 and determines whether the minimum speed condition C5 is satisfied.

[0173] When the vehicle driving support device 10 determines "Yes" in step S1510, it proceeds with the process to step S1530 and executes or continues the second inter-vehicle distance control in the same manner as step S525 of the routine shown in FIG. 5. At this time, when the first inter-vehicle distance control is being executed, the first inter-vehicle distance control is stopped and the second inter-vehicle distance control is executed. Next, the vehicle driving support device 10 proceeds with the process to step S1595 and temporarily ends the process of this routine.

[0174] Thus, in this example, the execution of the first inter-vehicle distance control (particularly, coasting control) is prohibited when the preceding vehicle speed V2 is lower than the value obtained by adding half of the target vehicle speed range WVtgt to the legal minimum speed Vlaw_min (V2 < Vlaw_min + WVtgt / 2).

[0175] On the other hand, when the vehicle driving support device 10 determines "No" in step S1510, it proceeds with the process to step S1535 and executes or continues the first inter-vehicle distance control. Next, the vehicle driving support device 10 proceeds with the process to step S1595 and temporarily ends the process of this routine.

[0176] Thus, in this example, the execution of the first inter-vehicle distance control (particularly, coasting control) is permitted when the preceding vehicle speed V2 is equal to or higher than the value obtained by adding half of the target vehicle speed range WVtgt to the legal minimum speed Vlaw_min (V2 ≥ Vlaw_min + WVtgt / 2).

[0177] Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be adopted within the scope of the present invention. [Explanation of symbols]

[0178] 10...Vehicle driving assistance system, 20...Drive system, 30...Braking system, 61...Driving assistance control unit, 62...Vehicle speed setting control unit, 63...Vehicle speed range setting control unit, 90...ECU, 100...Own vehicle, 200...Preceding vehicle

Claims

1. A vehicle driving support system comprising a control device that performs a first driving support control to drive the vehicle by repeatedly and alternately autonomously performing acceleration and coasting of the vehicle so that the vehicle's speed is maintained within a range between a target upper speed limit and a target lower speed limit, The control device is The target upper speed is set by adding a predetermined upper limit range to the set vehicle speed which is set as the target value for the vehicle's driving speed, and the target lower speed is set by subtracting a predetermined lower limit range from the set vehicle speed. When the first driving assistance control is executed, if the target lower limit speed is lower than the legally mandated minimum speed applicable to the vehicle, the predetermined lower limit range is changed so that the target lower limit speed is equal to or greater than the legally mandated minimum speed. It is structured in such a way. Vehicle driving assistance system.

2. In the vehicle driving support device according to claim 1, The control device is configured to, if the difference between the target lower speed limit set by the modified predetermined lower limit width and the target upper speed limit is smaller than a predetermined value, discontinue the first driving support control and execute a second driving support control that causes the vehicle to move by autonomously accelerating and decelerating the vehicle so that the vehicle's speed is maintained at the set vehicle speed or the distance between the vehicle and the preceding vehicle is maintained at a predetermined distance. Vehicle driving assistance system.

3. In the vehicle driving support device according to claim 1, The control device is configured such that, if the difference between the target lower speed and the target upper speed set by the modified predetermined lower limit width is smaller than a predetermined value, the difference becomes greater than or equal to the predetermined value while the target upper speed is maintained at or below the legal maximum speed. Vehicle driving assistance system.

4. In the vehicle driving support device according to claim 1, The control device is configured such that, when the speed of the preceding vehicle is lower than the set speed, if the value obtained by subtracting the target lower speed set by the modified predetermined lower limit range from the speed of the preceding vehicle is less than a predetermined value, it discontinues the first driving support control and executes a second driving support control that causes the vehicle to move by autonomously accelerating and decelerating the vehicle so that the vehicle's speed is maintained at the set speed or the distance between the vehicle and the preceding vehicle is maintained at a predetermined distance. Vehicle driving assistance system.

5. In the vehicle driving support device according to claim 1, The control device is If the speed of the preceding vehicle is lower than the average value of the vehicle's own speed achieved by the first driver assistance control, the target upper speed is set by adding half the sum of the predetermined upper limit and the predetermined lower limit to the speed of the preceding vehicle, and the target lower speed is set by subtracting half the sum of the predetermined upper limit and the predetermined lower limit from the speed of the preceding vehicle. When the first driving support control is executed, if the driving speed of the preceding vehicle is lower than the average value of the driving speed of the own vehicle achieved by the first driving support control, and the target lower limit speed is lower than the legal minimum speed, the target lower limit speed is changed so that the target lower limit speed is equal to or greater than the legal minimum speed. If the value obtained by subtracting the modified target lower speed limit from the target upper speed limit is smaller than a predetermined value, the first driving support control is discontinued, and a second driving support control is executed, which causes the vehicle to move by autonomously accelerating and decelerating the vehicle so that the vehicle's speed is maintained at the set speed or the distance between the vehicle and the preceding vehicle is maintained at a predetermined distance. It is structured in such a way. Vehicle driving assistance system.

6. In the vehicle driving support device according to claim 1, The control device is configured to determine the width by which the predetermined lower limit width is changed based on the legal minimum speed obtained from the legal minimum speed information included in the information on the road on which the vehicle is traveling, when the first driving assistance control is executed. Vehicle driving assistance system.

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