Vehicle operation support device

Abstract

To provide a vehicle operation support device capable of utilizing information on a recognized speed limit with improved efficiency.SOLUTION: When a collision determination condition is met for a predicted collision between an own vehicle HV and a target, an operation support ECU 10 executes a collision avoidance support operation to prevent a collision between the own vehicle and the target. The operation support ECU recognizes a speed limit applied to a lane in which the own vehicle is traveling. When the current speed limit, newly recognized at the present time, is lower than the previous speed limit recognized up to just before the present time, the operation support ECU modifies the collision determination condition to make the same more likely to be met, allowing the collision avoidance support operation to be executed at an earlier timing compared to when the current speed limit is not lower than the previous speed limit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vehicle driving support device that performs driving support control for reducing the possibility of a host vehicle colliding with an object target.

Background Art

[0002] Conventional devices acquire image data by photographing a scene in front of the host vehicle using an in-vehicle camera, and recognize road signs from the image data. Further, conventional devices extract a speed limit (maximum speed) from the recognized road signs and notify the vehicle occupants of the speed limit (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] However, since conventional devices only notify the speed limit, the driver of the host vehicle may not immediately notice that the speed limit has changed. For example, when the speed limit drops significantly and the leading vehicle decelerates significantly in response to the drop in the speed limit, if the driver of the host vehicle does not notice the drop in the speed limit, the timing of operating the brakes will be delayed. As a result, there is a risk that the host vehicle will approach the leading vehicle extremely closely. Conventional devices have not been able to effectively utilize the information about the recognized speed limit in such a situation.

[0005] The present invention has been made to solve such problems. That is, one of the objects of the present invention is to provide a vehicle driving support device that can more effectively utilize the information about the recognized speed limit.

[0006] One aspect of the driving assistance device for a vehicle according to the present invention includes a controller (10, 50, 70) configured to execute a collision avoidance assistance operation (S450, S470) for avoiding a collision between the host vehicle and the target object when a collision determination condition that is established when it is predicted that the host vehicle will collide with the target object is satisfied (S440, S460).

[0007] Furthermore, the controller recognizes a speed limit applicable to the lane in which the host vehicle is traveling, and when the current speed limit (S210), which is the newly recognized speed limit at the current time, has decreased from the past speed limit recognized until immediately before the current time (S250: Yes), the collision determination condition is changed to a condition that is more likely to be satisfied so that the collision avoidance assistance operation is executed at an earlier timing compared to when the current speed limit has not decreased from the past speed limit (S250: No) (S290). It is configured as described above.

[0008] When the newly recognized speed limit (current speed limit) at the current time has decreased from the speed limit (past speed limit) recognized until then, there is a high possibility that the preceding vehicle will decelerate rapidly. Therefore, in such a case, the above aspect changes the collision determination condition to a condition that is more likely to be satisfied so that the collision avoidance assistance operation is executed at an earlier timing. More specifically, the collision determination condition is a condition that is established when a collision index value indicating the possibility of the host vehicle colliding with the target object reaches a threshold value. In this case, by changing the threshold value or correcting the collision index value, the collision determination condition can be changed to a condition that is more likely to be satisfied. For example, when the collision determination condition is a condition that is established when the "collision required time as a collision index value", which is the time required for the host vehicle to collide with the target object, is equal to or less than a collision determination time threshold value, the collision determination time threshold value is increased or the collision required time is corrected to be smaller, whereby the collision determination condition is changed to a condition that is more likely to be satisfied.

[0009] As a result, even if the driver of the host vehicle overlooks the decrease in the speed limit and the response to the sudden deceleration of the preceding vehicle is delayed, the collision determination condition is satisfied early and the collision avoidance support operation is executed early, so that the host vehicle can be prevented from approaching the preceding vehicle extremely closely.

[0010] In the above description, for the purpose of assisting the understanding of the present invention, the names and / or reference numerals used in the embodiments are attached in parentheses to the configurations of the invention corresponding to the embodiments described later. However, each component of the present invention is not limited to the embodiments defined by the above names and / or reference numerals. The present invention also extends to a vehicle driving support method and its program.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] The "driving support device DS for vehicles (hereinafter referred to as the 'device DS')" according to an embodiment of the present invention includes the components shown in FIG. 1 and is applied (mounted) to the host vehicle HV. The host vehicle HV may be any of a vehicle powered by an internal combustion engine, a vehicle powered by an electric motor (i.e., an electric vehicle), a hybrid vehicle, and the like.

[0013] In this specification, the "ECU" is an electronic control device (control unit) including a microcomputer including a CPU (processor), a ROM, a RAM, a writable non-volatile memory for data, an interface, and the like. The ECU is also referred to as a controller or a computer. A plurality of ECUs shown in FIG. 1 are connected to be able to exchange information with each other through a CAN (Controller Area Network). Some or all of these plurality of ECUs may be integrated into one ECU.

[0014] The driving support ECU 10 executes driving support control, also referred to as "collision avoidance support control or collision damage reduction control", for reducing the possibility that the host vehicle collides with an object (obstacle) using the components shown in FIG. 1.

[0015] The camera device 20 includes a camera 21 and an image ECU 22. The camera 21 captures an image of the scene in front of the host vehicle HV every time a predetermined time elapses and acquires image data. The image ECU 22 generates "camera information including the image data itself, camera object information, and lane information" based on the image data from the camera 21 and transmits it to the driving support ECU 10.

[0016] The driving support ECU 10 extracts a "road sign indicating the speed limit (maximum speed)" included in the image data based on the image data acquired by the camera device 20, and recognizes (acquires) the numerical value indicated by the road sign as the speed limit (maximum speed) set / applied to the "lane in which the host vehicle HV is currently traveling (hereinafter also referred to as the 'host lane')". This recognition (acquisition) of the restricted vehicle speed may be performed by the image ECU 22.

[0017] The radar device 30 is a well-known device that acquires information about a target existing in front of the host vehicle HV using radio waves in the millimeter-wave band, and includes a radar 31 and a radar ECU 32. The radar 31 transmits millimeter waves within a predetermined detection range every time a predetermined time elapses, and receives the millimeter waves reflected by the target. The radar 31 transmits information about the transmitted and received millimeter waves to the radar ECU 32. The radar ECU 32 acquires radar information based on the information from the radar 31, and transmits the radar information to the driving support ECU 10. The radar information includes the distance to the target, the azimuth of the target, the relative speed of the target, and the like.

[0018] The power train ECU 40 controls a drive device including a power source of the host vehicle HV (not shown) by driving a power train actuator 41, thereby generating a driving force.

[0019] The brake ECU 50 controls a braking device of the host vehicle HV (not shown) by driving a brake actuator 51, thereby applying a braking force to the host vehicle HV. When the brake ECU 50 receives an instruction from the driving support ECU 10, it drives the brake actuator 51 to execute an automatic brake that automatically applies a braking force to the host vehicle HV.

[0020] The steering ECU 60 controls a steering device of the host vehicle HV (not shown) by driving a steering motor 61, thereby changing the steering angle of the host vehicle HV. When the steering ECU 60 receives an instruction from the driving support ECU 10, it drives the steering motor 61 to automatically change the steering angle of the host vehicle HV (that is, to execute automatic steering).

[0021] The notification ECU (alarm ECU) 70 is connected to a display 71 disposed at a position visible from the driver's seat and an alarm sound generator 72 that generates an alarm sound (notification sound), and controls these in accordance with an instruction (instruction signal) from the driving support ECU 10. The display 71 is provided with a region 71a for displaying a speed limit (maximum speed) and an alarm display region 71b for displaying an alarm mark for notifying that there is a risk of collision. The notification ECU 70 displays the speed limit included in the instruction from the driving support ECU 10 in the region 71a and displays an alarm mark in the alarm display region 71b in accordance with the instruction from the driving support ECU 10.

[0022] The navigation ECU 80 is connected to a GPS receiver 81, a map database 82 storing map information, and a display touch panel 83 for displaying touch buttons, and together with these, constitutes an in-vehicle navigation system. The navigation ECU 80 acquires the current position of the own vehicle HV based on the GPS signal received by the GPS receiver 81, and based on the acquired current position of the own vehicle HV and the map information stored in the map database 82, can acquire the speed limit set / applied to the own lane at the current time.

[0023] The communication ECU 90 performs wireless communication with a device outside the own vehicle HV (for example, a roadside unit and an information management center, etc.), and can acquire "various information including information about the speed limit" from the external device.

[0024] The driving support ECU 10 inputs the detection values (output values) of the following "sensors and switches". · An accelerator pedal operation amount sensor 91 that detects the accelerator pedal operation amount AP of the own vehicle HV. · A brake pedal operation amount sensor 92 that detects the brake pedal operation amount BP of the own vehicle HV. · A vehicle speed sensor 93 that detects the speed of the own vehicle HV (that is, the own vehicle speed).

[0025] The setting input device 94 is provided at a position operable by the driver and includes a display touch panel that displays touch buttons. By the driver operating the setting input device 94, the "collision determination time threshold TTCth, execution start timing correction time dTTCth of collision avoidance support control, magnitude of the restricted speed reduction amount threshold VLth for control switching, and length of the control switching period (change time threshold) Tth, etc." described later can be changed.

[0026] (Outline of operation) The device DS acquires (recognizes) the restricted speed (maximum speed) VLT of the lane in which the host vehicle HV is traveling from the image data. When the restricted speed VLT drops significantly, the collision determination time threshold TTCth for starting the collision avoidance support operation (here, automatic braking) is increased by the timing correction time dTTCth for the period (correction period) until the time corresponding to the change time threshold Tth has elapsed from that point. That is, the device DS changes the collision determination conditions for starting the collision avoidance support operation (automatic braking) to conditions that are more likely to be satisfied during the correction period.

[0027] (Specific operation) The CPU 10a of the driving support ECU 10 (hereinafter simply referred to as "CPU") executes the routine shown by the flowchart in FIGS. 2 to 4 and FIG. 6 every time a predetermined time (operation cycle) dt elapses. In the following, "step" is denoted as "S".

[0028] <Correction of collision determination time threshold (correction of execution start timing of collision avoidance support operation)> At a predetermined timing, the CPU starts processing from S200 in FIG. 2 and proceeds to S210, and determines whether the restricted speed set for the host lane has been newly acquired (recognized from the image) based on the image data transmitted from the camera device 20. Note that the CPU may acquire the restricted speed set for the host lane from the current position of the host vehicle HV and the map information via the navigation ECU 80.

[0029] When the speed limit is newly acquired, the CPU proceeds from S210 to S220 and stores the newly acquired speed limit in RAM10c (hereinafter referred to as "RAM") as the current speed limit VLTnow. At this time, the CPU changes the speed limit displayed in the area 71a of the display 71 to the current speed limit VLTnow.

[0030] Next, the CPU proceeds to S230 and reads the speed limit reduction amount threshold VLTth from the non-volatile memory 10d (hereinafter referred to as "non-volatile memory"). Next, the CPU proceeds to S240 and reads the reference threshold TTCthStd from the non-volatile memory.

[0031] Next, the CPU proceeds to S250 and determines whether the speed limit reduction amount dV1, which is the value obtained by subtracting the current speed limit VLTnow from the past speed limit (past speed limit) VLTold recognized so far, is greater than the speed limit reduction amount threshold VLTth read from the non-volatile memory. That is, at S230, the CPU determines whether the speed limit has decreased by more than the speed limit reduction amount threshold Vth.

[0032] When the speed limit reduction amount dV1 is less than or equal to the speed limit reduction amount threshold VLTth (that is, when the speed limit has not decreased by more than the speed limit reduction amount threshold Vth), the CPU proceeds from S250 to S260, reads the collision determination time threshold TTCth from the non-volatile memory, sets it to the reference threshold TTCthStd read from the non-volatile memory, and stores it in the RAM. Note that S260 may be omitted. The collision determination time threshold TTCth is set to the "reference threshold TTCthStd read from the non-volatile memory" when the host vehicle HV is started. Next, the CPU proceeds to S270 and sets the past speed limit VLTold to the current speed limit VLTnow. That is, the CPU stores the current speed limit VLTnow stored in the RAM at S220 as the past speed limit VLTold in the RAM. Thereafter, the CPU proceeds to S295 and temporarily ends this routine.

[0033] On the other hand, when the CPU proceeds to S250, if the restricted speed reduction amount dV1 is greater than the restricted speed reduction amount threshold VLTth (i.e., if the restricted speed has decreased by more than the restricted speed reduction amount threshold VLTth), the CPU proceeds from S250 to S280. At S280, the CPU reads the timing correction time dTTCth from the non-volatile memory. Next, the CPU proceeds to S290 and sets the collision determination time threshold TTCth to "the value obtained by adding the timing correction time dTTCth to the reference threshold TTCthStd" and stores it in the RAM. "The value obtained by adding the timing correction time dTTCth to the reference threshold TTCthStd" is also referred to as the corrected collision determination time threshold. Thereafter, the CPU proceeds to S270 and then to S295.

[0034] <End of correction of collision determination time threshold> At a predetermined timing, the CPU starts processing from S300 in FIG. 3 and proceeds to S310, and determines whether the collision determination time threshold TTCth stored in the RAM is equal to the corrected determination time threshold (i.e., "the value obtained by adding the timing correction time dTTCth to the reference threshold TTCthStd") (whether the collision determination time threshold TTCth has been corrected).

[0035] If the collision determination time threshold TTCth is the corrected determination time threshold (=TTCthStd + dTTCth), the CPU proceeds from S310 to S320 and reads the change time threshold Tth from the non-volatile memory.

[0036] Next, the CPU proceeds to S330 and determines whether the elapsed time since the collision determination time threshold TTCth was changed to the corrected determination time threshold (=TTCthStd + dTTCth) is equal to or greater than the change time threshold Tth. That is, at S330, the CPU determines whether the change time threshold Tth has elapsed since the time when the restricted speed decreased by more than the restricted speed reduction amount threshold VLTth.

[0037] When the change time threshold Tth has elapsed since the conflict determination time threshold TTCth was changed to the corrected determination time threshold (= TTCthStd + dTTCth), the CPU proceeds from S330 to S340 and sets the conflict determination time threshold TTCth to the reference threshold TTCthStd. That is, the CPU returns the conflict determination time threshold TTCth to the value before the change (before the change) to which the timing correction time dTTCth is added. Thereafter, the CPU proceeds to S395 and once ends this routine.

[0038] Note that when the CPU proceeds to S310 and the conflict determination time threshold TTCth is not the corrected determination time threshold (= TTCthStd + dTTCth) (that is, when the conflict determination time threshold TTCth has not been corrected), the CPU proceeds directly from S310 to S395.

[0039] Furthermore, when the CPU proceeds to S330 and the change time threshold Tth has not elapsed since the conflict determination time threshold TTCth was changed to the corrected determination time threshold (= TTCthStd + dTTCth), the CPU proceeds directly from S330 to S395. As described above, the conflict determination time threshold TTCth is maintained at the corrected determination time threshold (= TTCthStd + dTTCth) during the period from the time when the restricted speed has decreased by more than the restricted speed decrease amount threshold VLTth until the change time threshold Tth elapses.

[0040] <Collision Avoidance Support Control> At a predetermined timing, the CPU starts processing from S400 in FIG. 4 and proceeds to S410, and determines whether there is a target (obstacle) in the area where the host vehicle HV will travel within a certain time based on the camera information and the radar information. When there is no target (obstacle) in the area where the host vehicle HV will travel within a certain time, the CPU proceeds directly from S410 to S495 and once ends this routine.

[0041] On the other hand, if there is an object (obstacle) in the area where the host vehicle HV will travel within a certain period of time, the CPU proceeds from S410 to S420 and calculates the time to collision TTC by dividing the distance between the obstacle and the host vehicle HV by the relative speed of the obstacle. That is, the CPU calculates the time required for the host vehicle to collide with the obstacle as the time to collision TTC. Next, the CPU proceeds to S430 and reads the collision determination time threshold value TTCth from the RAM.

[0042] Next, the CPU proceeds to S440 and determines whether the time to collision TTC is less than or equal to "the value obtained by adding the warning difference time DTW to the collision determination time threshold value TTCth". That is, at S440, the CPU determines whether the first collision determination condition (warning generation condition) that holds when it is predicted that the host vehicle will collide with the object is satisfied. If the time to collision TTC is less than or equal to "the value obtained by adding the warning difference time DTW to the collision determination time threshold value TTCth", the CPU proceeds from S440 to S450 and sends an instruction signal to the notification ECU 70 to display a warning mark in the warning display area 71b of the display 71 and generate a warning sound with the warning sound generator 72. The display of this warning mark and / or the generation of the warning sound is one of the collision avoidance support operations for avoiding a collision between the host vehicle and the object. After that, the CPU proceeds to S460.

[0043] On the other hand, if the time to collision TTC is longer than "the value obtained by adding the warning difference time DTW to the collision determination time threshold value TTCth", the CPU proceeds directly from S440 to S460.

[0044] The CPU determines at S460 whether the time to collision TTC is less than or equal to the collision determination time threshold TTCth. That is, the CPU determines at S460 whether the second collision determination condition (automatic brake execution condition) that holds when it is predicted that the host vehicle will collide with the target is satisfied. When the time to collision TTC is less than or equal to the collision determination time threshold TTCth, the CPU proceeds from S460 to S470 and transmits an instruction signal to the brake ECU 50 to execute the automatic brake so that the host vehicle HV stops in front of the obstacle (automatically applies braking force to the host vehicle HV). The execution of this automatic brake is one of the collision avoidance support operations for avoiding a collision between the host vehicle and the target. Thereafter, the CPU proceeds to S495 and temporarily ends this routine. On the other hand, when the time to collision TTC is longer than the collision determination time threshold TTCth, the CPU directly proceeds from S460 to S495 and temporarily ends this routine.

[0045] <Threshold setting> Incidentally, the setting input device 94 includes a display touch panel that displays touch buttons and normally displays the menu screen 500 shown in FIG. 5(A).

[0046] When the driver touches the display button 501 to change the "collision avoidance support timing", the setting input device 94 displays the collision avoidance support timing selection screen 510 shown in FIG. 5(B). The driver can change the reference threshold TTCthStd for determining the collision avoidance support timing by touching any one of the display buttons "earlier 511, normal 512, and later 513" from this selection screen 510 according to the routine shown in FIG. 6 described later. In the default state (initial state), "normal 512" is automatically selected, the reference threshold TTCthStd is set to the standard value TStdN, and is stored in the non-volatile memory of the driving support ECU 100.

[0047] When the driver touches the display button 502 on the menu screen 500 to change the "Collision Avoidance Support Timing after Correction", the setting input device 94 displays the collision avoidance support timing selection screen 520 after correction shown in Fig. 5(C). The driver can change the timing correction time dTTCth for determining the collision avoidance support timing after correction by touching any one of the display buttons "earlier 521, normal 522, and later 523" from this selection screen 520 according to the routine shown in Fig. 6 described later. In the default state (initial state), "normal 522" is automatically selected, and the timing correction time dTTCth is set to "2 / 3 times the value of the maximum correctable value TS" and stored in the non-volatile memory of the driving support ECU 100. The maximum correctable value TS is a value also referred to as the "difference value TS", and its details will be described later.

[0048] When the driver touches the display button 503 on the menu screen 500 to change the "Threshold Value of Restricted Speed Reduction Amount", the setting input device 94 displays the threshold value selection screen 530 of the restricted speed reduction amount shown in Fig. 5(D). The driver can change the threshold value VLTth of the restricted speed reduction amount by touching any one of the display buttons "larger 531, normal 532, and smaller 533" from this selection screen 530 according to the routine shown in Fig. 6 described later. In the default state (initial state), "normal 532" is automatically selected, and the threshold value Vth of the restricted speed reduction amount is set to the standard value VLTthN and stored in the non-volatile memory of the driving support ECU 100.

[0049] When the driver touches the display button 504 on the menu screen 500 to change the "length of the collision avoidance support timing correction period", the setting input device 94 displays the support timing correction period length selection screen 540 shown in (E) of FIG. 5. The driver can change the change time threshold Tth by touching any one of the display buttons "longer 541, normal 542, and shorter 543" from this selection screen 540 according to the routine shown in FIG. 6 described later. In the default state (initial state), "normal 542" is automatically selected, the change time threshold Tth is set to the standard value TthN, and it is stored in the non-volatile memory of the driving support ECU 100.

[0050] At a predetermined timing, the CPU starts processing from S600 in FIG. 6 and proceeds to S605, and determines which of the display buttons selected by the collision avoidance support timing selection screen 510 shown in (B) of FIG. 5 is "earlier 511, normal 512, or later 513".

[0051] If "earlier 511" is selected, the CPU performs the process of S610 described below. If "normal 512" is selected, the CPU performs the process of S615 described below. If "later 513" is selected, the CPU performs the process of S620 described below. After performing any of these processes, the CPU proceeds to S625.

[0052] S610: The CPU sets the reference threshold TTCthStd to a value (first value) TStdL corresponding to a relatively longer time and stores it in the non-volatile memory of the driving support ECU 100. S615: The CPU sets the reference threshold TTCthStd to the standard value TStdN corresponding to a medium time and stores it in the non-volatile memory of the driving support ECU 100. S620: The CPU sets the reference threshold TTCthStd to a value (second value) TStdS corresponding to a relatively shorter time and stores it in the non-volatile memory of the driving support ECU 100. Note that the above values are set so that the following inequalities hold. TStdL > TStdN > TStdS

[0053] When the CPU proceeds to S625, it subtracts the reference threshold value TTCthStd set in any of S610 to S620 from the value TStdL corresponding to a relatively long time, and stores the resulting value (TStdL - TTCthStd) as the correction margin TS in the non-volatile memory of the driving support ECU 100. Then, the CPU proceeds to S630.

[0054] At S630, the CPU determines which of the display buttons selected by the corrected collision avoidance support timing selection screen 520 shown in Fig. 5(C) is "earlier 521, normal 522, or later 523".

[0055] If "earlier 521" is selected, the CPU performs the process of S635 described below. If "normal 522" is selected, the CPU performs the process of S640 described below. If "later 523" is selected, the CPU performs the process of S645 described below. After performing any of these processes, the CPU proceeds to S650.

[0056] S635: The CPU sets the timing correction time dTTCth to the maximum correctable value TS corresponding to a relatively long time, and stores it in the non-volatile memory of the driving support ECU 100. S640: The CPU sets the timing correction time dTTCth to a value that is 2 / 3 times the maximum correctable value TS, which corresponds to a medium time, and stores it in the non-volatile memory of the driving support ECU 100. S645: The CPU sets the timing correction time dTTCth to a value that is 1 / 3 times the maximum correctable value TS, which corresponds to a relatively short time, and stores it in the non-volatile memory of the driving support ECU 100. Since the maximum correctable value TS is a positive value, the inequality "TS > (2 / 3)·TS > (1 / 3)·TS" naturally holds for each of the above values.

[0057] Since the timing correction time dTTCth is set in this way, the corrected determination time threshold (= TTCthStd + dTTCth) varies between "a value TStdL corresponding to a relatively long time" and "the reference threshold TTCthStd set in any of S610 to S620 (accurately, TTCthStd + (1 / 3)·TS)". Therefore, during the period from the time when the restricted speed drops below the restricted speed drop amount threshold VLTth until the change time threshold Tth elapses (correction period), the start timing of the collision avoidance support operation is set between the start timing of the collision avoidance support operation desired by the driver during normal driving and the earliest timing among the start timings of the collision avoidance support operation allowed by the system. For this reason, during the correction period, although the collision avoidance support operation is started at a timing earlier than the start timing of the collision avoidance support operation desired by the driver during normal driving, a situation where the collision avoidance support operation is started at an overly early timing is avoided.

[0058] At S650, the CPU determines which of the display buttons selected by the restricted speed drop amount threshold selection screen 530 shown in FIG. 5(D) is "large 531, normal 532, or small 533".

[0059] When "large 531" is selected, the CPU performs the process of S655 described below. When "normal 532" is selected, the CPU performs the process of S660 described below. When "small 533" is selected, the CPU performs the process of S665 described below. After performing any of these processes, the CPU proceeds to S670.

[0060] S655: The CPU sets the restricted speed drop amount threshold VLTth to a relatively large value VLTthL and stores it in the non-volatile memory of the driving support ECU 100. S660: The CPU sets the restricted speed drop amount threshold VLTth to a medium value VLTthN and stores it in the non-volatile memory of the driving support ECU 100. S665: The CPU sets the restricted speed reduction amount threshold value VLTth to a relatively small value VLTthS and stores it in the non-volatile memory of the driving support ECU100. Note that the above values are set so that the following inequality holds. VLTthL > VLTthN > VLTthS

[0061] At S670, the CPU determines which of the display buttons selected by the support timing correction period length selection screen 540 shown in (E) of FIG. 5 is "longer 541, normal 542, or shorter 543".

[0062] When "longer 541" is selected, the CPU performs the process of S675 described below. When "normal 542" is selected, the CPU performs the process of S680 described below. When "shorter 543" is selected, the CPU performs the process of S685 described below. After performing any of these processes, the CPU proceeds to S695 and temporarily ends this routine.

[0063] S675: The CPU sets the change time threshold value Tth to a value TthL corresponding to a relatively long time and stores it in the non-volatile memory of the driving support ECU100. S680: The CPU sets the change time threshold value Tth to a value TthN corresponding to a medium-length time and stores it in the non-volatile memory of the driving support ECU100. S685: The CPU sets the change time threshold value Tth to a value TthS corresponding to a relatively short time and stores it in the non-volatile memory of the driving support ECU100. Note that the above values are set so that the following inequality holds. TthL > TthN > TthS

[0064] As described above, when the current speed limit has decreased by more than the speed limit decrease threshold value VLTth from the past speed limit, the device DS changes the collision determination time threshold value TTCth to the corrected determination time threshold value (= TTCthStd + dTTCth), thereby changing the collision determination condition of the collision avoidance support operation to a condition that is more likely to be satisfied. Therefore, even if the driver of the host vehicle overlooks the decrease in the speed limit and the response to the sudden deceleration of the preceding vehicle is delayed, the collision determination condition is satisfied early and the collision avoidance support operation is executed early, so that the host vehicle can be prevented from approaching the preceding vehicle extremely closely.

[0065] Note that the present invention is not limited to the above-described embodiments and modified examples, and various modified examples can be adopted within the scope of the present invention. For example, in S210, the CPU may recognize the current speed limit by receiving the speed limit from the roadside unit via the communication ECU90. Further, the present invention is applicable to a host vehicle in a state where the driving mode has transitioned from automatic driving to driving by a driver in an autonomous vehicle. Although the number of types of each value changed by the operation of the setting input device 94 was three, it may be N types (N is an integer of 2 or more). Further, when the CPU determines "No" in S330, it may determine whether the current speed limit is greater than the past speed limit. If the current speed limit is greater than the past speed limit, the process may proceed to S340, and if it is not greater, the process may proceed to S395.

Explanation of Reference Numerals

[0066] 10... Driving support ECU, 20... Camera device, 30... Radar device, 50... Brake ECU.

Claims

1. In a driving support device for a vehicle including a controller configured to execute a collision avoidance support operation for avoiding a collision between the host vehicle and a target object when a collision determination condition that holds when it is predicted that the host vehicle will collide with the target object is satisfied, the controller recognizes a speed limit applicable to a lane in which the host vehicle is traveling, when a current recognized speed, which is a speed limit newly recognized at the current time, has decreased from a past speed limit, which is a speed limit recognized until immediately before the current time, the collision determination condition is changed to a condition that is more likely to be satisfied so that the collision avoidance support operation is executed at an earlier timing than when the current recognized speed has not decreased from the past speed limit, configured as a driving support device for a vehicle.

2. The driving support device for a vehicle according to claim 1, comprising a setting input device operated by an occupant of the host vehicle, the controller is configured to change the collision determination condition to a condition that is more likely to be satisfied when the current speed limit has decreased by a speed limit decrease amount threshold or more from the past speed limit, the controller further is configured to be able to change the speed limit decrease amount threshold based on an input to the setting input device, a driving support device for a vehicle.

3. The driving support device for a vehicle according to claim 1, comprising a setting input device operated by an occupant of the host vehicle, the controller is configured to return the collision determination condition to the condition before the change when an elapsed time from the time when the collision determination condition is changed to the condition that is more likely to be satisfied reaches a change time threshold, the controller further is configured to be able to change the change time threshold based on an input to the setting input device, Driving support device for a vehicle.

4. The vehicle driving support device according to claim 1, comprising a setting input device operated by an occupant of the host vehicle, wherein the controller further is configured to be able to change the degree of ease of establishment of the condition that is likely to be established based on an input to the setting input device, Driving support device for a vehicle.

5. The vehicle driving support device according to claim 1, comprising a setting input device operated by an occupant of the host vehicle, wherein the controller calculates a collision required time required until the host vehicle collides with the target, and is configured to determine that the collision determination condition is satisfied when the collision required time becomes equal to or less than a collision determination time threshold value, wherein the controller further based on an input to the setting input device, the collision determination time threshold value used to determine whether the collision determination condition is satisfied when the collision determination condition has not been changed is configured to be changeable between a first value and a second value smaller than the first value as a reference threshold value, and is configured to change the collision determination condition to the condition that is likely to be changed by changing the collision determination time threshold value to a value obtained by adding a timing correction time to the reference threshold value, based on an input to the setting input device, the timing correction time is configured to be changeable, and the timing correction time is set to be a value equal to or less than a difference value obtained by subtracting the reference threshold value from the first value, Driving support device for a vehicle.

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