Driving assistance systems

Abstract

The present invention provides a driver assistance system equipped with a deceleration support function and a collision risk reduction function, which can efficiently reduce the risk of collision between the vehicle and a preceding vehicle in a scenario where the collision risk reduction function is activated after the braking of the vehicle by the deceleration support function has finished. [Solution] The processor of the driving support device 1 can terminate the execution of the deceleration support process and perform a condition relaxation process to relax the conditions for executing the collision risk reduction process when the speed sp0 of the vehicle decreases to a threshold by continuing the deceleration support process under conditions where the conditions for executing the deceleration support process are met and the conditions for executing the collision risk reduction process are not met.

Description

Technical Field

[0001] The present invention relates to a driving support device having a function of braking the host vehicle so as to prevent the host vehicle from approaching the preceding vehicle excessively, and a function of controlling the host vehicle so as to reduce the collision risk when the collision risk between the host vehicle and the preceding vehicle becomes high.

Background Art

[0002] A driving support device having a function of controlling the host vehicle so that the inter-vehicle distance between the host vehicle and the preceding vehicle matches a target value has been proposed (see, for example, Patent Document 1 below). The processor of this device (hereinafter referred to as the "conventional device") determines the target value of the inter-vehicle distance based on the speeds of the host vehicle and the preceding vehicle. Then, the processor controls the drive device or the braking device of the host vehicle so that the measured value of the inter-vehicle distance between the host vehicle and the preceding vehicle matches the target value.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

[0004] Well-known functions of this type of driving support device include a deceleration assist function (DA = Deceleration Assist) and a collision risk reduction function (PCS = Pre Crush Safety).

[0005] The deceleration support function is a feature in which the driver assistance system automatically brakes the vehicle when there is a preceding vehicle, the vehicle's speed is relatively high, and both the accelerator and brake pedals are released. In other words, in the above scenario, the processor executes a process (deceleration support process) to control the vehicle's braking system so that the vehicle brakes gradually. The processor terminates the deceleration support process when the vehicle's speed decreases to a threshold as a result of executing the deceleration support process. In this way, in scenarios where the driver is behind a preceding vehicle and is not performing any driving operations to adjust the speed, the vehicle is automatically braked (gradually decelerated), and the vehicle's speed becomes somewhat low. This prevents the vehicle from getting too close to the preceding vehicle.

[0006] The collision risk reduction function includes a warning function. The warning function issues a predetermined warning to the driver of the vehicle to prompt them to initiate manual driving operations (collision avoidance actions) to avoid a collision when the time to collision (TTC) is below a threshold. The threshold for the time to collision to trigger the warning function is relatively small. It is rare for the time to decrease to reach this threshold while the processor is performing deceleration support processing, but if this situation occurs, the processor will prioritize the execution of collision risk reduction processing. The collision risk reduction function also includes an emergency braking function. The emergency braking function applies the brakes to the vehicle when the collision risk increases further from the time the warning function issues a warning (when the time to collision decreases further and the amount of decrease reaches a threshold).

[0007] Incidentally, the deceleration assistance function is designed on the premise that the driver will press the brake pedal and brake the vehicle while the vehicle is being braked (gently braked) by the function. In other words, the deceleration assistance function is merely a function that assists the braking operation in the event that the start of the braking operation of the vehicle is slightly delayed. In contrast, the collision risk reduction function is a function that reduces the risk of collision when an emergency situation occurs in which there is a high risk of collision between the vehicle and the vehicle in front.

[0008] As described above, the deceleration support function is a function that assists the driver's braking operation, but there is a risk that the driver may overestimate the function and not press the brake pedal. In this case, the processor terminates the deceleration support process when the vehicle's speed decreases and reaches a threshold, so there is a risk that the vehicle will proceed with little to no braking from that point onward. If the system were to notify the driver of the termination of the deceleration support process each time the vehicle's speed decreases and reaches a threshold, the driver may find the notification annoying. Therefore, the processor of this type of driver assistance system is configured not to notify the driver of the termination of the deceleration support process even when it has ended. Consequently, there is a risk that the driver may not notice that the deceleration support process has ended, and the vehicle will proceed with little to no braking (a state where it is braked very slowly by engine braking). In this case, the collision risk reduction function is activated when the collision margin time decreases and reaches a threshold. As described above, when the warning function for collision risk reduction is activated while the driver is unaware that their vehicle is moving with little to no braking (i.e., the driver's attention is reduced), there is a risk that the driver may not be able to react immediately to the warning (there is a risk of a delay in initiating collision avoidance actions). If the conditions for initiating collision risk reduction processing are relatively strict (i.e., a relatively small value is assigned to the threshold for collision margin time), the timing of the warning processing will be relatively delayed. In addition, the timing of the emergency braking processing will also be relatively delayed. Therefore, there is a risk that the reduction in collision risk by the driver's collision avoidance actions and emergency braking may not be very effective.

[0009] One of the objectives of the present invention is to provide a driver assistance device equipped with a deceleration support function and a collision risk reduction function, which can efficiently reduce the risk of collision between the vehicle and a preceding vehicle in a scenario in which the collision risk reduction function is activated after the braking of the vehicle by the deceleration support function has finished.

[0010] To achieve the above objective, the driving assistance device (1) of the present invention is: An on-board sensor (20) for acquiring information about a target located in front of the vehicle (V0), A processor (10) is capable of performing a deceleration support process that brakes the vehicle when a first condition (Xa) is met for determining that there is a high probability that the vehicle will approach the preceding vehicle excessively closely, and a collision risk reduction process that controls the vehicle to reduce the collision risk when a second condition (Y), which is a condition for determining that there is a high risk of collision between the vehicle and the preceding vehicle, is met, and is configured to terminate the execution of the deceleration support process if the first condition becomes unmet or the second condition is met while the deceleration support process is being executed. It is equipped with. The processor is configured to terminate the execution of the deceleration support process when the first condition is met and the second condition is not met, and the speed of the vehicle decreases as the deceleration support process continues until the speed reaches a threshold (sp0th), and at the same time execute a condition relaxation process to relax the second condition.

[0011] When a vehicle (the vehicle in question) to which the driver assistance system according to the present invention is applied has another vehicle (a preceding vehicle) in front of it, and the first condition is met, the deceleration assistance process is executed, causing the vehicle in question to automatically decelerate. Subsequently, when the speed of the vehicle in question reaches a threshold due to the deceleration assistance process, the deceleration assistance process is terminated. At this point, the processor relaxes the second condition, which is the initiation condition for the collision risk reduction process. If the driver of the vehicle in question does not notice the end of the deceleration assistance process, and the vehicle in question continues to move forward with little to no braking, approaching the preceding vehicle, the collision risk reduction process is started with a relatively large time buffer (at a relatively early timing). This makes it possible to efficiently reduce the risk of collision between the vehicle in question and the preceding vehicle.

[0012] In a driving support device according to one aspect of the present invention, The processor is capable of performing a customization process to set the strictness (TTCth) of the second condition according to the manner of operation when a predetermined operating device (26) is operated. The condition relaxation process includes, if the strictness of the second condition set according to the operation mode is the same as or stricter than a predetermined first strictness (TTCstd), the process of changing the strictness of the second condition to a second strictness (TTCmax, TTCex) which is less strict than the first strictness.

[0013] According to this, if the strictness of the second condition is the same as or stricter than the first strictness (e.g., the standard value) due to the condition relaxation process, the strictness of the second condition will be changed to a second strictness level that is less strict than the first strictness level. On the other hand, if the strictness of the second condition matches the second strictness level, the strictness of the second condition will not be changed.

[0014] In another aspect of the present invention, in a driving support device, After the processor relaxes the second condition through the condition relaxation process, it maintains the relaxed state of the second condition until the ignition switch of its own vehicle transitions to the off state, and when the ignition switch transitions from the off state to the on state, it returns the second condition to the state it was in before the condition relaxation process was performed.

[0015] According to this, when the driver temporarily stops driving their vehicle and then resumes driving it, the second condition automatically returns to its original state.

[0016] In another aspect of the present invention, in a driving support device, The processor determines that the first condition is met when the vehicle's speed (sp0) exceeds a predetermined value (sp0th) and the vehicle's accelerator pedal and brake pedal are released.

[0017] When the speed of the host vehicle is relatively high and the driver is not performing an operation to adjust the speed of the host vehicle, the host vehicle travels in a state where it is hardly braked (a state where it decelerates extremely gently by engine braking). The processor of the driving support device according to this aspect determines that the first condition is satisfied in this situation and starts the deceleration support process. As a result, it is possible to prevent the host vehicle from approaching the preceding vehicle excessively.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a block diagram of a driving support device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view for explaining the positional relationship between the host vehicle and the preceding vehicle when the deceleration support process is not executed, and the positional relationship between the host vehicle and the preceding vehicle when the deceleration support process and the risk reduction process are executed. [Figure 3] FIG. 3 is an example of an image (A) displayed on an image display device in a state where the start timing (start condition) of the collision risk reduction process is set to "slow", and an image (B) displayed on the image display device in a state where the start timing is forcibly changed to "fast". [Figure 4] FIG. 4 is a flowchart of a first program executed by a CPU to realize a function of changing the start condition of the collision risk reduction process according to the scene. [Figure 5] FIG. 5 is a flowchart of a second program executed by a CPU to realize a function of changing the start condition of the collision risk reduction process according to the scene. [Figure 6] FIG. 6 is a flowchart of a third program executed by a CPU to realize a function of changing the start condition of the collision risk reduction process according to the scene.

[0019] (Overview) The driving support device 1 according to an embodiment of the present invention is applied to a vehicle V0 having an automatic driving function (hereinafter referred to as "the host vehicle"). The driving support device 1 has the deceleration support function and the collision risk reduction function described above. The driving support device 1 has a function of forcibly relaxing the condition for starting the collision risk reduction process when the deceleration support process is started and then terminated (completed) without interrupting the deceleration support process.

[0020] (Specific Configuration) As shown in FIG. 1, the driving support device 1 includes an ECU 10, an in-vehicle sensor 20, a notification device 30, a drive device 40, and a brake device 50.

[0021] The ECU 10 includes a microcomputer having a CPU 10a, a ROM 10b, a RAM 10c, a timer 10d, etc. The ECU 10 is connected to other ECUs via a CAN (communication network).

[0022] The in-vehicle sensor 20 includes a millimeter-wave radar 21, a camera 22, a speed sensor 23, an accelerator pedal sensor 24, a brake pedal sensor 25, and a user interface 26.

[0023] The millimeter-wave radar 21 includes a transmission / reception unit and a signal processing unit (not shown). The transmission / reception unit radiates radio waves in the millimeter-wave band (hereinafter referred to as "millimeter waves") to the front area of the host vehicle and receives the millimeter waves (reflected waves) reflected by a three-dimensional object (preceding vehicle V1) located within the radiation range. The signal processing unit calculates the distance between the host vehicle and the three-dimensional object (preceding vehicle V1), the speed of the three-dimensional object with respect to the host vehicle (relative speed vr), etc. based on the time from when the transmission / reception unit radiates the millimeter waves until it receives the reflected waves, the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, etc., and provides the calculation result to the ECU 10.

[0024] Camera 22 is equipped with an imaging device and an image analysis device. The imaging device incorporates a lens and an image sensor such as a CCD (charge coupled device) or CIS (CMOS image sensor). The imaging device is installed at the front of the vehicle and is directed forward. The imaging device captures the area in front of the vehicle at a predetermined frame rate and acquires image data. The imaging device transmits the image data to the image analysis device. The image analysis device analyzes the acquired image data and obtains information about targets located in front of the vehicle from the image. For example, the image analysis device identifies the preceding vehicle V1 from other targets. The image analysis device provides the identification result (recognition result) to the ECU 10.

[0025] The speed sensor 23 detects the rotational speed (wheel speed) of each wheel and calculates the vehicle's speed sp0 (measured value) based on the wheel speed. The speed sensor 23 provides the calculation result to the ECU 10.

[0026] The accelerator pedal sensor 24 detects the accelerator pedal depression depth AD (accelerator opening) and provides the detection result to the ECU 10. The brake pedal sensor 25 detects the brake pedal depression depth BD and provides the detection result to the ECU 10.

[0027] The user interface 26 includes an image display device, a touch panel, and the like. The user interface 26 is used to select the degree of strictness (sensitivity) of the conditions under which the ECU 10 initiates the collision risk reduction process, which will be described later.

[0028] The notification device 30 includes an image display device and an audio device. The image display device receives an image display command from the ECU 10 and displays an image (for example, an image indicating a high risk of collision between the vehicle and the preceding vehicle V1) according to the command. The image display device of the notification device 30 and the image display device of the user interface 26 may be used interchangeably. The audio device receives an audio playback command from the ECU 10 and plays an audio (for example, an audio indicating a high risk of collision between the vehicle and the preceding vehicle V1) according to the command.

[0029] The drive unit 40 applies driving force to the drive wheels. The drive unit 40 includes an engine ECU, an internal combustion engine, a transmission, and a driving force transmission mechanism that transmits driving force to the wheels. The engine ECU obtains information (target value) representing the target driving force from another ECU (ECU 10). The engine ECU drives the throttle valve of the internal combustion engine to match the driving force applied to the drive wheels to the target value.

[0030] Furthermore, if the vehicle to which the driver assistance system 1 is applied is a hybrid electric vehicle (HEV), the engine ECU can adjust the output (driving force) of either the internal combustion engine or the electric motor, or both, as the vehicle's power source. Also, if the vehicle to which the driver assistance system 1 is applied is an electric electric vehicle (BEV), an electric motor ECU that adjusts the output (driving force) of the electric motor, which is the vehicle's power source, is used instead of the engine ECU.

[0031] The braking system 50 applies braking force to the wheels (brake discs). The braking system 50 includes a brake ECU, brake calipers, etc. The brake calipers include actuators that press brake pads against the brake discs. The brake ECU obtains information (target value) representing the target braking force (or deceleration of the vehicle) from other ECUs. The brake ECU drives the actuator of the brake caliper to match the braking force (or deceleration of the vehicle) applied to the wheels (brake discs) to the target value. When the depression depth BD of the accelerator pedal and brake pedal is "0", braking force is applied to the vehicle by engine braking.

[0032] (Operation) The driver assistance device 1 has a deceleration assistance function (a function in which the ECU 10 performs deceleration assistance processing) and a collision risk reduction function (a function in which the ECU 10 performs warning processing and emergency braking processing).

[0033] (Deceleration Support Function (DA)) In a scene where a preceding vehicle V1 exists in front of the host vehicle, when the host vehicle travels in a state where it is hardly braked (a state where it decelerates very gently by engine braking), there is a risk that the host vehicle will approach the preceding vehicle V1 excessively. That is, as shown in Fig. 2(A), there is a risk that the inter-vehicle distance D will become too small (D = Da < Db (Db: a value predefined as a safe distance)). Therefore, when a predetermined condition X (the first condition of the present invention) is satisfied in a scene where the preceding vehicle V1 exists, the ECU 10 executes a deceleration support process for braking the host vehicle so that the host vehicle is prevented from approaching the preceding vehicle V1 excessively. The ECU 10 determines that the condition X is satisfied when the following conditions X1 and X2 are satisfied. Condition X1... The speed sp0 exceeds the threshold value sp0th (for example, 20 km / h). Condition X2: The driver of the vehicle is not performing any operation to adjust the speed sp0 (the accelerator pedal and brake pedal are released (AD=0, and BD=0)). As a deceleration support process, the ECU 10 performs a gentle braking process that controls the braking device 50 so that the vehicle is braked gradually. For example, the ECU 10 controls the drive system etc. so that the deceleration of the vehicle matches a predetermined value. In addition, in scenes where the distance between the vehicle and the preceding vehicle V1 tends to decrease, the ECU 10 may sequentially calculate (update) a target value of braking force (or a target value of the degree of deceleration of the vehicle) so that the speed sp0 matches the threshold sp0th when the vehicle reaches a predetermined position behind the preceding vehicle V1 (the point where the distance D matches a predetermined value Db (>Da)), and transmit the target value to the braking device 50. The ECU 10 detects the preceding vehicle V1 based on information acquired from the millimeter-wave radar 21 and camera 22, but its detectable distance (maximum value) is relatively large. For example, ECU10 can accurately detect the preceding vehicle V1 when the distance D between vehicles is 100 meters or less. In this way, ECU10 can start deceleration support processing even when the distance D between vehicles is relatively large. Therefore, the deceleration (absolute value) of the vehicle during deceleration support processing is, in most situations, only slightly greater than the deceleration when the vehicle is decelerated by engine braking alone, and it is rare for the braking to be so sudden that it causes discomfort to the occupants.

[0034] Furthermore, if the vehicle V0 (own vehicle) to which the driver assistance device 1 is applied is a hybrid vehicle or an electric vehicle, the vehicle may be decelerated by activating a well-known regenerative braking system instead of (or in addition to) the braking device 50.

[0035] The ECU10 continues the deceleration support process during the period when conditions X1 and X2 are met. When the speed sp0 decreases and condition X1 is no longer met, the deceleration support process terminates (completes).

[0036] Here, the deceleration support function is a function that assumes the driver will press the brake pedal to brake the vehicle before the speed sp0 reaches the threshold sp0th due to the automatic braking of the vehicle by the function. Therefore, there is a high possibility that the brake pedal will be pressed while the deceleration support process is being executed, causing condition X2 to be unmet. In this case, the ECU 10 will terminate (suspend) the execution of the deceleration support process. The ECU 10 will also terminate (suspend) the execution of the deceleration support process if it detects that the accelerator pedal has been pressed while the deceleration support process is being executed. In this case, the ECU 10 controls the drive unit 40 so that the vehicle accelerates with an acceleration corresponding to the depth of the accelerator pedal depression. Furthermore, as will be described in more detail later, the ECU 10 will also terminate (suspend) the execution of the deceleration support process if it starts the collision risk reduction process, which will be described next, while the deceleration support process is being executed.

[0037] (Collision Risk Reduction Function (PCS)) The ECU 10 controls the notification device 30 and the braking device 50 so as to reduce the risk of collision between its own vehicle and the preceding vehicle when the following condition Y (the second condition of the present invention) is met. Condition Y: The time it is predicted that your vehicle will need to reach the rear end of the preceding vehicle V1 (collision margin time TTC (=D / spr)) is less than or equal to the threshold TTCth. If condition Y is met, the ECU 10 performs risk reduction processing (see Figure 2(C)). Specifically, the ECU 10 displays an image on the notification device 30 indicating a high risk of collision between the vehicle and the preceding vehicle V1, and also plays an audio message indicating the high risk (warning processing). Furthermore, if the collision risk increases further from the time the warning processing is initiated (when the collision margin time TTC decreases further and the amount of decrease ΔTTC reaches the threshold ΔTTCth), the ECU 10 controls the braking device 50 so that a relatively large braking force is applied to the wheels of the vehicle (emergency braking processing).

[0038] Here, the threshold TTCth corresponds to the start timing Ts of the collision risk reduction process (the strictness of the start conditions for the collision risk reduction process). The driver can set (change) this start timing Ts using the user interface 26. That is, the ECU 10 performs a process (customization process) to change the start timing Ts in response to the driver's operation. Specifically, the ECU 10 displays icons ICN1, ICN2, and ICN3 on the image display device of the user interface 26, corresponding to the options "early," "normal," and "late" for the start timing Ts, as shown in Figures 3(A) and 3(B). If the driver selects "normal" (by tapping icon ICN2), the ECU 10 assigns the standard value TTCstd to the threshold TTCth. If the driver selects "early," the ECU 10 assigns a predetermined value TTCmax, which is larger than the standard value, to the threshold TTCth. As a result, the start conditions for the collision risk reduction process are relaxed compared to when "normal" is selected. If the driver selects "slow" (Figure 3(A)), the ECU 10 assigns a predetermined value TTCmin, which is smaller than the standard value TTCstd, to the threshold TTCth. This makes the conditions for starting the collision risk reduction process stricter compared to when "normal" is selected. If the driver selects the start timing Ts for the collision risk reduction process using the user interface 26, the selection result is stored in the ROM 10b. That is, the threshold TTCth is written to the ROM 10b (flash memory) as the threshold TTCmem. When the ignition switch transitions from the off state to the on state, the ECU 10 reads the threshold TTCmem from the ROM 10b and assigns the read threshold TTCmem to the threshold TTCth.

[0039] Incidentally, when deceleration support processing is executed, the collision margin time (TTC) decreases relatively slowly. Note that during the execution of deceleration support processing, the collision margin time (TTC) may become approximately constant (unchanged) or increase. It is rare for the collision margin time (TTC) to decrease to the threshold TTCth (a predetermined value TTCmax) while the ECU 10 is executing deceleration support processing, but if the collision margin time (TTC) reaches the threshold TTCth while the deceleration support processing is being executed, the ECU 10 will prioritize executing collision risk reduction processing.

[0040] If the deceleration support process is not interrupted (the brake pedal and accelerator pedal are not pressed during the deceleration support process, and the conditions for starting the collision risk reduction process are not met), the ECU 10 will terminate (complete) the execution of the deceleration support process when the speed sp0 reaches the threshold sp0th, but no information indicating the termination (completion) of the deceleration support process will be provided to the driver. Therefore, the driver may not notice that the deceleration support process has ended (completed), and the vehicle may continue moving forward with almost no braking (a state in which the vehicle is decelerated very slowly by engine braking). In this case, the collision risk reduction function will be activated at tpcs, the point at which the collision margin time TTC decreases and reaches the threshold TTCth. As described above, when the warning function as a collision risk reduction function is activated while the driver is unaware that the vehicle is moving forward with almost no braking (a state in which the driver's attention is reduced), the driver may not be able to react immediately to the warning (the collision avoidance action may be delayed). Therefore, as described above, in situations where the driver's attention is reduced due to the execution of deceleration support processing, it is preferable that the start timing Ts of the collision risk reduction processing be as early as possible.

[0041] Therefore, when condition X1 is not met while the deceleration support process is being executed, if "normal" or "late" is selected as the start timing for the collision risk reduction process, the ECU 10 executes a condition relaxation process (for example, a process that transitions from Figure 3(A) to Figure 3(B)) to forcibly change the start timing Ts to "early". In other words, the ECU 10 forcibly relaxes the start conditions for the collision risk reduction process. As a result, the warning process is started when there is still some margin before the vehicle reaches the rear end of the preceding vehicle V1. Therefore, even if some time is required between the time the warning is issued and the driver starts collision avoidance action, the collision margin time TTC at the start of the collision avoidance action is relatively large, and the collision risk is efficiently reduced as the collision avoidance action is continued. Even if the collision avoidance action is not started, the emergency braking process is started at a relatively early timing, so the collision risk is efficiently reduced.

[0042] If the ECU10 forcibly relaxes the start timing Ts of the collision risk reduction process, it maintains that state (TTCth = TTCmax) until the ignition switch is turned off. Then, when the ignition switch transitions from the off state to the on state, the ECU10 reads the threshold TTCmem (the start timing Ts previously selected by the driver) from the ROM10b and assigns that value to the threshold TTCth. However, if the driver changes the start timing Ts between the time the start timing of the collision risk reduction process is forcibly relaxed and the time the ignition switch transitions to the off state (if "normal" or "slow" is selected), the ECU10 changes the start timing Ts according to that operation.

[0043] Next, referring to Figures 4 to 6, we will describe the programs PR1 to PR3 executed by the CPU 10a of the ECU 10 (hereinafter simply referred to as "CPU") to realize the function of automatically changing the start timing Ts of the collision risk reduction process. The ECU 10 starts executing program PR1 when the ignition switch transitions from the off state to the on state. In addition, the ECU 10 starts executing programs PR2 and PR3 at predetermined intervals when it has detected a preceding vehicle V1. A flag F is used in programs PR2 and PR3. Flag F indicates whether the CPU is executing deceleration support processing or not. If the CPU is executing deceleration support processing, flag F is assigned "1". If the CPU is not executing deceleration support processing, flag F is assigned "0".

[0044] (Program PR1) The CPU starts executing Program PR1 from step 100 and proceeds to step 101.

[0045] In step 101, the CPU reads the collision margin time TTC threshold TTCmem (a value corresponding to the previously selected start timing Ts) from ROM 10b and assigns this value to the threshold TTCth. The CPU then proceeds to step 102.

[0046] In step 102, the CPU determines whether an operation to change the start timing Ts has been performed. If the CPU determines that the operation has been performed (102: Yes), it proceeds to step 103. On the other hand, if the CPU determines that the operation has not been performed (102: No), it returns to step 102.

[0047] In step 103, the CPU stores the threshold TTCth (TTCmin / TTCstd / TTCmax) corresponding to the current start timing Ts (start timing Ts selected by the driver) as the threshold TTCmem in ROM 10b (flash memory). Then, the CPU returns to step 102.

[0048] (Program PR2) The CPU starts executing Program PR2 from step 200 and proceeds to step 201.

[0049] In step 201, the CPU determines whether flag F is "0". If the CPU determines that flag F is "0" (201: Yes), it proceeds to step 202. On the other hand, if the CPU does not determine that flag F is "0" (201: No), it proceeds to step 205.

[0050] In step 202, the CPU determines whether condition X1 is true or false. If the CPU determines that condition X1 is true (202: Yes), it proceeds to step 203. On the other hand, if the CPU determines that condition X1 is not true (202: No), it proceeds to step 205.

[0051] In step 203, the CPU determines whether condition X2 is true or false. If the CPU determines that condition X2 is true (203: Yes), it proceeds to step 204. On the other hand, if the CPU does not determine that condition X2 is true (203: No), it proceeds to step 205.

[0052] In step 204, the CPU sets flag F to "1". In this case, the CPU executes a deceleration support program (not shown) to control the braking device 50 so that the vehicle's braking force (deceleration) matches the target value (gentle braking process). Next, the CPU proceeds to step 205, in which step 205, the execution of program PR2 is terminated.

[0053] (Program PR3) The CPU starts executing Program PR3 from step 300 and proceeds to step 301.

[0054] In step 301, the CPU determines whether flag F is "1". If the CPU determines that flag F is "1" (301: Yes), it proceeds to step 302. On the other hand, if the CPU does not determine that flag F is "1" (301: No), it proceeds to step 307.

[0055] In step 302, the CPU determines whether condition X1 is true or false. If the CPU determines that condition X1 is true (302: Yes), it proceeds to step 304. On the other hand, if the CPU does not determine that condition X1 is true (302: No), it proceeds to step 303.

[0056] In step 303, the CPU assigns a predetermined value TTCmax to the threshold TTCth. The CPU then proceeds to step 306.

[0057] In step 304, the CPU determines whether condition X2 is true or false. If the CPU determines that condition X2 is true (304: Yes), it proceeds to step 305. On the other hand, if the CPU does not determine that condition X2 is true (304: No), it proceeds to step 306.

[0058] In step 305, the CPU determines whether condition Y is false. If the CPU determines that condition Y is false (305: Yes), it proceeds to step 307. On the other hand, if the CPU does not determine that condition Y is false (305: No), it proceeds to step 306. When the CPU proceeds from step 305 to step 306, it executes an alarm program (not shown) to control the notification device 30 so that a predetermined alarm is issued. In addition, the CPU executes an emergency brake program to control the braking device 50 so that the vehicle is subjected to sudden braking.

[0059] In step 306, the CPU sets flag F to "0" and proceeds to step 307. In step 307, the CPU terminates the execution of program PR3.

[0060] (Effect) When the driver assistance device 1 is applied to a vehicle with a preceding vehicle V1 in front of it and condition X is met, the deceleration assistance process is executed. This causes the vehicle to automatically decelerate. When condition X1 is no longer met during the execution of the deceleration assistance process, the deceleration assistance process is terminated. At this point, if "normal" or "late" is selected as the start timing Ts for the collision risk reduction process, the ECU 10 changes the start timing Ts to "early". In other words, the ECU 10 forcibly relaxes condition Y, which is the start condition for the collision risk reduction process. As a result, if the driver of the vehicle does not notice the end of the deceleration assistance process and the vehicle proceeds with almost no braking and approaches the preceding vehicle V1, the collision risk reduction process is started with a relatively large amount of time (relatively early timing). Therefore, the risk of collision between the vehicle and the preceding vehicle V1 can be efficiently reduced.

[0061] (Modified Version) In the above embodiment, when the ECU 10 is executing the deceleration support process and condition X1 becomes unmet, in a scene where "early" is selected as the start timing Ts for the collision risk reduction process, the ECU 10 does not change the value assigned to the threshold TTCth. Alternatively, in the scene, the ECU 10 may assign a predetermined value TTCex that is greater than a predetermined value TTCmax to the threshold TTCth. [Explanation of Symbols]

[0062] 1...Vehicle control unit, 10...ECU, 20...On-board sensor, 30...Notification device, 40...Drive system, 50...Braking system

Claims

1. An on-board sensor for acquiring information about an object located in front of the vehicle, A processor capable of performing a deceleration support process that brakes the vehicle when a first condition is met for determining that there is a high probability that the vehicle will approach the preceding vehicle excessively closely, and a collision risk reduction process that controls the vehicle to reduce the collision risk when a second condition is met for determining that there is a high risk of collision between the vehicle and the preceding vehicle, and configured to terminate the execution of the deceleration support process if the first condition is not met or the second condition is met while the deceleration support process is being executed. A driver assistance device equipped with, The driver assistance device is configured such that, when the speed of the vehicle decreases and reaches a threshold by continuing the deceleration support process while the state in which the first condition is met and the second condition is not met is maintained, the execution of the deceleration support process is terminated and a condition relaxation process is executed to relax the second condition.

2. In the driving support device according to claim 1, The processor is capable of performing a customization process to set the strictness of the second condition according to the manner of operation when a predetermined operating device is operated. The aforementioned condition relaxation process includes a process of changing the strictness of the second condition, which is a less severe level than the first strictness, when the strictness of the second condition, which is set according to the operation mode, is the same as or stricter than a predetermined first strictness.

3. In the driving support device according to claim 2, The processor is configured to maintain the relaxed state of the second condition after relaxing the second condition through the condition relaxation process, until the ignition switch of the vehicle transitions to the off state, and then, when the ignition switch transitions from the off state to the on state, to return the second condition to the state it was in before the condition relaxation process was performed.

4. In the driving support device according to any one of claims 1 to 3, The aforementioned processor is a driver assistance device configured to determine that the first condition is met when the speed of the vehicle exceeds a predetermined value and the accelerator pedal and brake pedal of the vehicle are released.

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