Vehicle driving assistance device, vehicle driving assistance method, and vehicle driving assistance program

Abstract

To provide a vehicle driving support device capable of suppressing an own vehicle from getting too close to a preceding vehicle after starting coasting of the own vehicle when executing follow-up traveling control.SOLUTION: When the following travel control is executed, the vehicle driving support device 10 causes the host vehicle to travel such that the inter-vehicle distance between the host vehicle and the preceding vehicle 200 falls within a predetermined range while repeating power running and coasting of the host vehicle 100. When the following travel control is executed, the vehicle driving support device sets a lower limit value of the predetermined range as a target inter-vehicle distance, predicts a minimum value of the inter-vehicle distance after the host vehicle starts coasting at the present time as a minimum inter-vehicle distance when the host vehicle is being powered by the following travel control, and starts coasting of the host vehicle when the minimum inter-vehicle distance is equal to or less than the target inter-vehicle distance. The minimum inter-vehicle distance is predicted as a shorter distance when the size of the preceding vehicle is large than when the size of the preceding vehicle is small.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vehicle driving assistance device, a vehicle driving assistance method, and a vehicle driving assistance program. [Background technology]

[0002] A follow-up cruise control is known in which a host vehicle travels while following a preceding vehicle. Also known is a vehicle driving assistance device that, when performing such follow-up cruise control, causes the host vehicle to travel while repeatedly powering and coasting so that the inter-vehicle distance between the host vehicle and the preceding vehicle falls within a predetermined range. Furthermore, a vehicle driving assistance device is also known that is configured to decelerate the host vehicle when the brake pedal is depressed while the host vehicle is coasting during follow-up cruise control (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6577668 Summary of the Invention

[0004] When the following cruise control is performed, the host vehicle approaches the preceding vehicle immediately after the host vehicle's driving state is switched from a powered state to a coasting state. At this time, if the preceding vehicle is a large vehicle, the air resistance force on the host vehicle is small. Therefore, the host vehicle approaches the preceding vehicle even closer. At this time, if the driver of the host vehicle feels that the host vehicle is getting too close to the preceding vehicle and depresses the brake pedal, the conventional vehicle driving assistance device described above will decelerate the host vehicle. Therefore, the energy efficiency related to the driving of the host vehicle will decrease accordingly.

[0005] An object of the present invention is to provide a vehicle driving assistance device, a vehicle driving assistance method, and a vehicle driving assistance program that can prevent a vehicle from getting too close to a preceding vehicle after the vehicle starts coasting when following cruise control is being performed.

[0006] A vehicle driving assistance device according to the present invention includes a control device that executes follow-distance control to cause a host vehicle to travel while following a preceding vehicle. The control device, when executing the follow-distance control, is configured to repeatedly power and coast the host vehicle, causing the host vehicle to travel so that the inter-vehicle distance between the host vehicle and the preceding vehicle falls within a predetermined range. The control device, when executing the follow-distance control, sets a lower limit of the predetermined range as a target inter-vehicle distance, and, while powering the host vehicle through the follow-distance control, predicts the minimum inter-vehicle distance after the host vehicle starts coasting at the current time as a minimum inter-vehicle distance, and starts coasting of the host vehicle if the minimum inter-vehicle distance is equal to or less than the target inter-vehicle distance. The predicted minimum inter-vehicle distance is shorter when the preceding vehicle is large than when the preceding vehicle is small.

[0007] When the host vehicle starts to coast, the acceleration of the host vehicle decreases. However, at the point when the host vehicle starts to coast, the acceleration of the host vehicle is a positive value. Therefore, the host vehicle approaches the preceding vehicle for a short time after the host vehicle starts to coast. The degree to which the host vehicle approaches the preceding vehicle increases as the air resistance force against the host vehicle decreases. Here, the air resistance force against the host vehicle decreases as the size of the preceding vehicle increases.

[0008] The vehicle driving assistance system according to the present invention predicts the minimum inter-vehicle distance taking into account the size of the preceding vehicle. That is, the system predicts the minimum inter-vehicle distance taking into account the effect of the preceding vehicle in reducing the air resistance force on the host vehicle. The system then uses this minimum inter-vehicle distance to determine the timing for starting coasting of the host vehicle. Therefore, the system can prevent the host vehicle from getting too close to the preceding vehicle after starting coasting.

[0009] In addition, in the vehicle driving assistance device of the present invention, the minimum inter-vehicle distance is predicted to be a shorter distance when the size of the preceding vehicle is large than when the size of the preceding vehicle is small, and when the target inter-vehicle distance is short, it can be predicted to be a shorter distance than when the target inter-vehicle distance is long.

[0010] The air resistance force on the host vehicle decreases as the size of the preceding vehicle increases and as the target inter-vehicle distance decreases.

[0011] The vehicle driving assistance system according to the present invention predicts the minimum inter-vehicle distance taking into account the size of the preceding vehicle and the target inter-vehicle distance. That is, the minimum inter-vehicle distance is predicted taking into account the effect of the preceding vehicle in reducing the air resistance force on the host vehicle. The system then determines the timing to start coasting the host vehicle using this minimum inter-vehicle distance. Therefore, it is possible to prevent the host vehicle from getting too close to the preceding vehicle after coasting has started.

[0012] Furthermore, in the vehicle driving assistance device according to the present invention, the control device may be configured to start powering the host vehicle when the inter-vehicle distance reaches the upper limit of the predetermined range while the host vehicle is coasting using the following cruise control.

[0013] According to the vehicle driving assistance device of the present invention, it is possible to start powering the host vehicle at an appropriate timing.

[0014] A vehicle driving assistance method according to the present invention is a method for performing follow-up cruise control to cause a host vehicle to travel while following a preceding vehicle, and during execution of the follow-up cruise control, the host vehicle is caused to travel such that an inter-vehicle distance between the host vehicle and the preceding vehicle falls within a predetermined range while repeatedly powering and coasting the host vehicle. The vehicle driving assistance method according to the present invention includes the steps of: during execution of the follow-up cruise control, setting a lower limit value of the predetermined range as a target inter-vehicle distance; while the host vehicle is being powered by the follow-up cruise control, predicting as a minimum inter-vehicle distance the smallest value of the inter-vehicle distance after coasting of the host vehicle has started at the present time, and starting coasting of the host vehicle if the minimum inter-vehicle distance is equal to or less than the target inter-vehicle distance; and predicting the minimum inter-vehicle distance as a shorter distance when the preceding vehicle is large than when the preceding vehicle is small.

[0015] For the reasons described above, the vehicle driving assistance method according to the present invention can prevent the host vehicle from getting too close to the preceding vehicle after the host vehicle starts coasting.

[0016] A vehicle driving assistance program according to the present invention is a program for executing follow-up cruise control that causes a host vehicle to travel while following a preceding vehicle, and during execution of the follow-up cruise control, causes the host vehicle to travel while repeatedly powering and coasting so that an inter-vehicle distance between the host vehicle and the preceding vehicle falls within a predetermined range. The vehicle driving assistance program according to the present invention is configured to, during execution of the follow-up cruise control, set a lower limit of the predetermined range as a target inter-vehicle distance, and, while the host vehicle is powered by the follow-up cruise control, predict as a minimum inter-vehicle distance a minimum value of the inter-vehicle distance after the host vehicle starts coasting at the current time, and, if the minimum inter-vehicle distance is equal to or less than the target inter-vehicle distance, start coasting of the host vehicle, and predict the minimum inter-vehicle distance as a shorter distance when the preceding vehicle is large compared to when the preceding vehicle is small.

[0017] For the reasons described above, the vehicle driving assistance program according to the present invention can prevent the host vehicle from getting too close to the preceding vehicle after the host vehicle starts coasting.

[0018] The components of the present invention are not limited to the embodiments of the present invention described below with reference to the drawings. Other objects, features, and attendant advantages of the present invention will be easily understood from the description of the embodiments of the present invention. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing a vehicle driving assistance device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the host vehicle and the preceding vehicle. [Figure 3] FIG. 3 is a flowchart showing a routine executed by the vehicle driving assistance device according to the embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing a routine executed by the vehicle driving assistance device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a vehicle driving assistance device, a vehicle driving assistance method, and a vehicle driving assistance program according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a vehicle driving assistance device 10 according to an embodiment of the present invention.

[0021] The vehicle driving assistance device 10 is mounted on the host vehicle 100. Hereinafter, the vehicle driving assistance device 10 will be described using as an example a case where the operator of the host vehicle 100 is a person who gets into the host vehicle 100 and drives the host vehicle 100 (i.e., the driver of the host vehicle 100). However, the operator of the host vehicle 100 may also be a person who drives the host vehicle 100 remotely without getting into the host vehicle 100 (i.e., a remote operator of the host vehicle 100). The present invention is also applicable to vehicles that run by automatic driving without requiring driving by a driver or a remote operator.

[0022] As shown in FIG. 1, the vehicle driving assistance device 10 includes an ECU (electronic control unit) 90 as a control device. The ECU 90 includes a microcomputer as a main component. The microcomputer includes a CPU, storage media such as a ROM, a RAM, and a non-volatile memory, as well as an interface. The CPU executes instructions, programs, or routines stored in the storage media to realize various functions. In particular, in this example, the vehicle driving assistance device 10 stores programs in the storage media that realize various controls executed by the vehicle driving assistance device 10.

[0023] In this example, the vehicle driving assistance device 10 includes only one ECU 90. However, the vehicle driving assistance device 10 may be configured to include multiple ECUs, with each ECU performing a respective function of the vehicle driving assistance device 10 described below. Furthermore, the vehicle driving assistance device 10 may be configured to be able to update a program stored in a storage medium via wireless communication with an external device (for example, via the Internet).

[0024] The host vehicle 100 is equipped with a power unit 20, a braking unit 30, and a surrounding information detection device 50.

[0025] The power unit 20 is a device that generates power to be applied to the host vehicle 100 (particularly, the drive wheels of the host vehicle 100). In this example, the power unit 20 includes an internal combustion engine 21 and an electric motor 22. The power unit 20 is electrically connected to the ECU 90. The vehicle driving assistance device 10 can control the power applied to the host vehicle 100 by controlling the operation of the internal combustion engine 21 and the electric motor 22.

[0026] The braking device 30 is a device that applies braking force to the host vehicle 100 (particularly, the wheels of the host vehicle 100). In this example, the braking device 30 is equipped with a hydraulic brake device 31. The braking device 30 is electrically connected to the ECU 90. The vehicle driving assistance device 10 can control the braking force applied to the host vehicle 100 by controlling the operation of the hydraulic brake device 31.

[0027] The surrounding information detection device 50 is a device that detects information about the surroundings of the host vehicle 100. In this example, the surrounding information detection device 50 includes an electromagnetic wave sensor 51 and an image sensor 52. The surrounding information detection device 50 is electrically connected to the ECU 90. The electromagnetic wave sensor 51 is, for example, a radar sensor such as a millimeter wave radar. The vehicle driving assistance device 10 acquires information about objects present in the surroundings of the host vehicle 100 as surrounding information IS using the electromagnetic wave sensor 51. Furthermore, the image sensor 52 is, for example, a camera sensor. The vehicle driving assistance device 10 acquires image information about the surroundings of the host vehicle 100 as surrounding information IS using the image sensor 52.

[0028] <Operation of vehicle driving assistance device> Next, a description will be given of the operation of the vehicle driving assistance device 10. The vehicle driving assistance device 10 is configured to execute follow-up cruise control when execution of follow-up cruise control is requested. On the other hand, the vehicle driving assistance device 10 is configured to stop follow-up cruise control when stop of follow-up cruise control is requested.

[0029] As shown in FIG. 2, follow-up cruise control is a type of automatic driving control that causes the host vehicle 100 to travel while following the preceding vehicle 200. In other words, follow-up cruise control is a type of automatic driving control that causes the host vehicle 100 to travel by autonomously accelerating and decelerating so that the host vehicle 100 travels while following the preceding vehicle 200. In this example, the follow-up cruise control has a coasting mode and a powering mode as control modes. The preceding vehicle 200 is another vehicle traveling in the host vehicle's travel lane within a certain distance D200 ahead of the host vehicle 100. The host vehicle's travel lane is the lane in which the host vehicle 100 is traveling. The preceding vehicle 200 is detected based on surrounding information IS.

[0030] The coasting mode is a control mode in which the host vehicle 100 is decelerated by coasting the host vehicle 100 by disconnecting the power unit 20 from the drive wheels of the host vehicle 100. The powering mode is a control mode in which the host vehicle 100 is accelerated. In particular, the powering mode is an optimal powering mode in which the host vehicle 100 is powered by operating the power unit 20 with optimal energy efficiency.

[0031] When the following cruise control is being performed in powering mode, if it is predicted that the inter-vehicle distance D will become shorter and the minimum inter-vehicle distance Dm (described later) will become equal to or less than the target inter-vehicle distance Dtgt, the control mode is switched from powering mode to coasting mode. That is, when the vehicle 100 is being powered by the following cruise control, if the minimum inter-vehicle distance Dm (described later) is equal to or less than the target inter-vehicle distance Dtgt, the vehicle driving assistance device 10 starts coasting of the vehicle 100.

[0032] On the other hand, if the following distance D increases and reaches the upper limit of the following distance Du while the following cruise control is being performed in the coasting mode, the control mode is switched from the coasting mode to the powering mode. That is, when the following distance D reaches the upper limit of the predetermined range Rd while the host vehicle 100 is coasting under the following cruise control, the vehicle driving assistance device 10 starts powering the host vehicle 100.

[0033] Therefore, in this example, the lower limit of the predetermined range Rd is the target inter-vehicle distance Dtgt. Also, the upper limit of the predetermined range Rd is the upper limit inter-vehicle distance Du. Therefore, the following cruise control is a control that causes the host vehicle 100 to travel while repeatedly powering and coasting so that the inter-vehicle distance D between the host vehicle 100 and the preceding vehicle 200 falls within the predetermined range Rd.

[0034] The inter-vehicle distance D is the distance between the preceding vehicle 200 and the host vehicle 100. The inter-vehicle distance D is acquired based on the surrounding information IS.

[0035] Furthermore, in this example, the target inter-vehicle distance Dtgt is the set inter-vehicle distance Dset. However, the target inter-vehicle distance Dtgt may be a distance that is longer than the set inter-vehicle distance Dset by a predetermined distance ΔDtgt. Furthermore, the upper limit inter-vehicle distance Du is a distance that is longer than the set inter-vehicle distance Dset by a predetermined distance ΔDu. Here, the predetermined distance ΔDtgt is a very short distance. On the other hand, the predetermined distance ΔDu is a distance that is considerably longer than the predetermined distance ΔDtgt. Furthermore, the set inter-vehicle distance Dset is set in advance by the driver of the vehicle 100.

[0036] 3 at predetermined calculation intervals. As a result, when the following cruise control is being executed, if a predetermined condition is met while the host vehicle 100 is being powered, the vehicle driving assistance device 10 is configured to start coasting.

[0037] At a predetermined timing, the vehicle driving assistance device 10 starts processing from step S300 of the routine shown in Fig. 3. Then, the vehicle driving assistance device 10 proceeds to step S305, where it determines whether or not the follow-up cruise control is being executed in powering mode. That is, the vehicle driving assistance device 10 determines whether or not the host vehicle 100 is being powered by the follow-up cruise control.

[0038] If the vehicle driving assistance device 10 determines "No" in step S305, the process proceeds directly to step S395 and temporarily ends the process of this routine. On the other hand, if the vehicle driving assistance device 10 determines "Yes" in step S305, the process proceeds to step S310 and acquires the preceding vehicle size S.

[0039] In this example, the preceding vehicle size S is the size of the preceding vehicle 200. In particular, the preceding vehicle size S is the area of ​​the rear end portion of the preceding vehicle 200 when the rear end portion is cut by a vertical plane perpendicular to the front-to-rear direction of the preceding vehicle 200. Therefore, the preceding vehicle size S is larger for a large truck than for an ordinary passenger car. The preceding vehicle size S is acquired based on the surrounding information IS.

[0040] Next, the vehicle driving assistance device 10 advances the process to step S315 to acquire the target inter-vehicle distance Dtgt. Next, the vehicle driving assistance device 10 advances the process to step S320 to acquire the air resistance reduction rate R.

[0041] The air resistance reduction rate R represents the rate at which the air resistance force on the host vehicle 100 is reduced by the preceding vehicle 200, assuming that the air resistance force on the host vehicle 100 when the preceding vehicle 200 is not present is "100." When the preceding vehicle size S is large, the air resistance reduction rate R is acquired as a larger value than when the preceding vehicle size S is small. Furthermore, when the target inter-vehicle distance Dtgt is short, the air resistance reduction rate R is acquired as a larger value than when the target inter-vehicle distance Dtgt is long. In particular, the air resistance reduction rate R is acquired as a larger value the larger the preceding vehicle size S. Furthermore, the air resistance reduction rate R is acquired as a larger value the shorter the target inter-vehicle distance Dtgt. The vehicle driving assistance device 10 stores a map of the air resistance reduction rate R, which uses the preceding vehicle size S and the target inter-vehicle distance Dtgt as arguments. The vehicle driving assistance device 10 acquires the air resistance reduction rate R by applying the preceding vehicle size S and the target inter-vehicle distance Dtgt to the map.

[0042] Next, the vehicle driving assistance system 10 proceeds to step S325 to acquire the glide acceleration G.

[0043] The glide acceleration G is calculated using the air resistance force Fa, the rolling resistance force Fr, the grade resistance force Fg, and the vehicle weight Wego according to the following formula 1. The air resistance force Fa, the rolling resistance force Fr, and the grade resistance force Fg can be calculated using the air resistance reduction rate R, the host vehicle speed Vego, the gravitational acceleration g, and the road grade θ according to the following formulas 2, 3, and 4, respectively. The vehicle weight Wego is the weight of the host vehicle 100. The host vehicle speed Vego is the traveling speed of the host vehicle 100. The road grade θ is the grade of the road on which the host vehicle 100 is traveling. The symbol Ca is the air resistance coefficient. The symbols Cr_1 and Cr_2 are rolling resistance coefficients.

[0044] G = (Fa + Fr + Fg) / Wego … (1) Fa=Ca·Vego 2 ·(1-R / 100) …(2) Fr = Cr_1 · Vego + Cr_2 …(3) Fg=Wego·g·sinθ …(4)

[0045] Next, the vehicle driving assistance system 10 advances the process to step S330, and calculates the minimum inter-vehicle distance Dm.

[0046] When the host vehicle 100 starts to coast, the acceleration of the host vehicle 100 decreases at the glide acceleration G. However, at the point when the host vehicle 100 starts to coast, the acceleration of the host vehicle 100 is a positive value. Therefore, the host vehicle 100 approaches the preceding vehicle 200 for a short time after the host vehicle 100 starts to coast. The degree to which the host vehicle 100 approaches the preceding vehicle 200 increases as the air resistance force against the host vehicle 100 decreases. Here, the air resistance force against the host vehicle 100 decreases as the size of the preceding vehicle 200 increases and as the target inter-vehicle distance Dtgt decreases.

[0047] The minimum inter-vehicle distance Dm is the smallest value of the inter-vehicle distance D that is predicted taking these circumstances into consideration. That is, the minimum inter-vehicle distance Dm is the predicted value of the inter-vehicle distance D when the host vehicle 100 comes closest to the preceding vehicle 200 after coasting of the host vehicle 100 has started at the present time. In other words, the minimum inter-vehicle distance Dm is the predicted value of the inter-vehicle distance D when the acceleration of the host vehicle 100 decreases due to the glide acceleration G and becomes zero after coasting of the host vehicle 100 has started at the present time.

[0048] The vehicle driving assistance device 10 calculates the minimum inter-vehicle distance Dm using the glide acceleration G and the current acceleration of the host vehicle 100.

[0049] Therefore, in this example, when the preceding vehicle size S is large, the minimum inter-vehicle distance Dm is acquired as a shorter distance than when the preceding vehicle size S is small. Also, when the target inter-vehicle distance Dtgt is short, the minimum inter-vehicle distance Dm is acquired as a shorter distance than when the target inter-vehicle distance Dtgt is long. In particular, the larger the preceding vehicle size S, the shorter the minimum inter-vehicle distance Dm is acquired as a shorter distance. Also, the shorter the target inter-vehicle distance Dtgt, the shorter the minimum inter-vehicle distance Dm is acquired as a shorter distance.

[0050] In this example, the minimum inter-vehicle distance Dm is calculated taking into consideration both the size S of the preceding vehicle and the target inter-vehicle distance Dtgt. However, the minimum inter-vehicle distance Dm may be calculated taking into consideration only one of the size S of the preceding vehicle and the target inter-vehicle distance Dtgt.

[0051] Next, the vehicle driving assistance device 10 proceeds to step S335 to determine whether the minimum inter-vehicle distance Dm is equal to or less than the target inter-vehicle distance Dtgt. If the vehicle driving assistance device 10 determines "No" in step S335, it proceeds directly to step S395 and temporarily ends the processing of this routine. On the other hand, if the vehicle driving assistance device 10 determines "Yes" in step S335, it proceeds to step S340 to end powering of the host vehicle 100 and start coasting of the host vehicle 100. In other words, the vehicle driving assistance device 10 switches the control mode from the powering mode to the coasting mode. Next, the vehicle driving assistance device 10 proceeds to step S395 to temporarily end the processing of this routine.

[0052] According to the vehicle driving assistance device 10, the minimum inter-vehicle distance Dm is predicted taking into consideration the preceding vehicle size S and the target inter-vehicle distance Dtgt. That is, the minimum inter-vehicle distance Dm is predicted taking into consideration the effect of the preceding vehicle 200 in reducing the air resistance force on the host vehicle 100. The timing to start coasting of the host vehicle 100 is then determined using this minimum inter-vehicle distance Dm. Therefore, it is possible to prevent the host vehicle 100 from getting too close to the preceding vehicle 200 after coasting has started.

[0053] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0054] For example, the vehicle driving assistance device 10 may be configured to execute the routine shown in FIG. 4 instead of the routine shown in FIG. 3. In this case, at a predetermined timing, the vehicle driving assistance device 10 starts processing from step S400 of the routine shown in FIG. 4. Then, the vehicle driving assistance device 10 proceeds to step S405, where it determines whether or not the following cruise control is being executed in powering mode. If the vehicle driving assistance device 10 determines "No" in step S405, it proceeds directly to step S495, where it temporarily ends the processing of this routine. On the other hand, if the vehicle driving assistance device 10 determines "Yes" in step S405, it proceeds to step S410, where it acquires the preceding vehicle size S.

[0055] Next, the vehicle driving assistance system 10 advances the process to step S415 to acquire the target inter-vehicle distance Dtgt, and then advances the process to step S420 to acquire the minimum inter-vehicle distance correction amount ΔDc.

[0056] The minimum inter-vehicle distance Dm when the preceding vehicle 200 has the effect of reducing the air resistance of the host vehicle 100 is shorter than the reference inter-vehicle distance Ds. The reference inter-vehicle distance Ds is the minimum inter-vehicle distance Dm when the preceding vehicle 200 has no effect of reducing the air resistance of the host vehicle 100. The minimum inter-vehicle distance correction amount ΔDc is used to correct the reference inter-vehicle distance Ds to the minimum inter-vehicle distance Dm when the preceding vehicle 200 has the effect of reducing the air resistance of the host vehicle 100.

[0057] Therefore, when the preceding vehicle size S is large, the minimum inter-vehicle distance correction amount ΔDc is acquired as a larger value than when the preceding vehicle size S is small. Also, when the target inter-vehicle distance Dtgt is short, the minimum inter-vehicle distance correction amount ΔDc is acquired as a larger value than when the target inter-vehicle distance Dtgt is long. In particular, the larger the preceding vehicle size S, the larger the acquired minimum inter-vehicle distance correction amount ΔDc. Also, the shorter the target inter-vehicle distance Dtgt, the larger the acquired minimum inter-vehicle distance correction amount ΔDc. The vehicle driving assistance device 10 stores a map of the minimum inter-vehicle distance correction amount ΔDc, which uses the preceding vehicle size S and the target inter-vehicle distance Dtgt as arguments. The vehicle driving assistance device 10 acquires the minimum inter-vehicle distance correction amount ΔDc by applying the preceding vehicle size S and the target inter-vehicle distance Dtgt to the map.

[0058] Next, the vehicle driving assistance device 10 proceeds to step S425 to calculate the minimum inter-vehicle distance Dm. Here, the minimum inter-vehicle distance Dm is calculated by subtracting the minimum inter-vehicle distance correction amount ΔDc from the reference inter-vehicle distance Ds (Dm=Ds-ΔDc). Therefore, in this example as well, when the preceding vehicle size S is large, the minimum inter-vehicle distance Dm is acquired as a shorter distance than when the preceding vehicle size S is small. Also, when the target inter-vehicle distance Dtgt is short, the minimum inter-vehicle distance Dm is acquired as a shorter distance than when the target inter-vehicle distance Dtgt is long. In particular, the larger the preceding vehicle size S, the shorter the acquired minimum inter-vehicle distance Dm. Also, the shorter the target inter-vehicle distance Dtgt, the shorter the acquired minimum inter-vehicle distance Dm.

[0059] Next, the vehicle driving assistance device 10 proceeds to step S430 to determine whether the minimum inter-vehicle distance Dm is equal to or less than the target inter-vehicle distance Dtgt. If the vehicle driving assistance device 10 determines "No" in step S430, it proceeds directly to step S495 and temporarily ends the processing of this routine. On the other hand, if the vehicle driving assistance device 10 determines "Yes" in step S430, it proceeds to step S435 to end powering of the host vehicle 100 and start coasting of the host vehicle 100. In other words, the vehicle driving assistance device 10 switches the control mode from the powering mode to the coasting mode. Next, the vehicle driving assistance device 10 proceeds to step S495 to temporarily end the processing of this routine.

[0060] This also makes it possible to prevent the host vehicle 100 from getting too close to the preceding vehicle 200 after the host vehicle 100 starts coasting. [Explanation of symbols]

[0061] 10...vehicle driving assistance device, 90...ECU, 100...own vehicle, 200...preceding vehicle

Claims

1. a control device that executes follow-up running control to make the host vehicle follow a preceding vehicle, The control device is configured to, when executing the following cruise control, cause the host vehicle to travel while repeatedly powering and coasting the host vehicle so that the inter-vehicle distance between the host vehicle and the preceding vehicle falls within a predetermined range. In a vehicle driving assistance device, The control device When the following cruise control is performed, a lower limit value of the predetermined range is set as a target inter-vehicle distance, When the host vehicle is powered by the following cruise control, a minimum value of the inter-vehicle distance after the host vehicle starts coasting at the current time is predicted as a minimum inter-vehicle distance, and when the minimum inter-vehicle distance is equal to or less than the target inter-vehicle distance, coasting of the host vehicle is started. It is structured as follows: The minimum inter-vehicle distance is predicted to be shorter when the size of the preceding vehicle is large than when the size of the preceding vehicle is small. Vehicle driving assistance device.

2. The vehicle driving assistance device according to claim 1, When the size of the preceding vehicle is large, the minimum inter-vehicle distance is predicted to be shorter than when the size of the preceding vehicle is small, and when the target inter-vehicle distance is short, the minimum inter-vehicle distance is predicted to be shorter than when the target inter-vehicle distance is long. Vehicle driving assistance device.

3. 3. The vehicle driving assistance device according to claim 1, the control device is configured to start powering the host vehicle when the inter-vehicle distance reaches an upper limit value of the predetermined range while the host vehicle is coasting under the following cruise control. Vehicle driving assistance device.

4. A vehicle driving assistance method for performing follow-up cruise control to cause a host vehicle to travel while following a preceding vehicle, wherein, during execution of the follow-up cruise control, the host vehicle is caused to travel while repeatedly powering and coasting so that an inter-vehicle distance between the host vehicle and the preceding vehicle falls within a predetermined range, setting a lower limit value of the predetermined range as a target inter-vehicle distance when the following cruise control is performed; a step of predicting, when the host vehicle is being powered by the following cruise control, a minimum value of the inter-vehicle distance after the host vehicle starts coasting at the current time as a minimum inter-vehicle distance, and starting coasting of the host vehicle if the minimum inter-vehicle distance is equal to or less than the target inter-vehicle distance; predicting the minimum inter-vehicle distance as a shorter distance when the preceding vehicle is large than when the preceding vehicle is small; A vehicle driving assistance method comprising:

5. A vehicle driving assistance program that executes follow-up cruise control to cause a host vehicle to travel while following a preceding vehicle, wherein, during execution of the follow-up cruise control, the host vehicle is caused to travel while repeatedly powering and coasting so that an inter-vehicle distance between the host vehicle and the preceding vehicle falls within a predetermined range, When the following cruise control is performed, a lower limit value of the predetermined range is set as a target inter-vehicle distance, When the host vehicle is being powered by the following cruise control, a minimum value of the inter-vehicle distance after the host vehicle starts coasting at the current time is predicted as a minimum inter-vehicle distance, and when the minimum inter-vehicle distance is equal to or less than the target inter-vehicle distance, coasting of the host vehicle is started; When the size of the preceding vehicle is large, the minimum inter-vehicle distance is predicted as a shorter distance than when the size of the preceding vehicle is small. A vehicle driving assistance program designed to:

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