Vehicle drive assistance device

Abstract

Provided is a drive assistance device that transmits an alarm to a driver when a first event is established in which another vehicle (2) preceding a vehicle (1) exists in a lane (R0) and the inter-vehicle distance is predicted to become less than a predetermined value within a predetermined time, a second event is established in which it is determined that an adjacent lane (R1, R2) can be a lane change destination, and a third condition is established in which another vehicle (3) is present in a lane change alarm area (B) set behind the vehicle (1) in the adjacent lane (R1, R2) that can be a lane change destination.

Description

Vehicle driving assistance device

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

[0002] In recent years, vehicles equipped with various driving assistance functions have become widespread. One of these driving assistance functions is a blind spot warning (BSW / Blind Spot Warning / Rear Side Vehicle Detection Alarm). This function allows a rear sensor equipped in the vehicle to detect a vehicle in an adjacent lane behind the vehicle, known as a blind spot. Therefore, for example, when a vehicle in the blind spot is detected and the driver turns on the turn signal in that direction, the system can alert the driver of the danger by lighting an indicator or sounding an alarm. The rear side vehicle detection alarm is described, for example, in Patent Document 1.

[0003] In addition, in Patent Document 2, it is determined whether or not it is necessary to change lanes to avoid a collision with a preceding vehicle based on the distance from the preceding vehicle, and further whether or not there is a lane to which the vehicle can change lanes on at least one of the right and left sides of the lane the vehicle is traveling in. When it is necessary to avoid a collision and there is a lane to which the vehicle can change lanes, the direction of the driver's line of sight is detected, and if it is determined that the driver intends to change lanes, steering is controlled to change lanes to the appropriate side, thereby enabling a lane change that matches the driver's intention.

[0004] JP 2020-135634 A (see paragraph 0022 of the specification) JP 2009-280015 A

[0005] Conventional driving assistance systems issue warnings based on the driver's behavior and operations. Therefore, depending on the driving conditions, there is a possibility that the warning may be delayed. For example, suppose a vehicle needs to change lanes to avoid a collision with a vehicle ahead, and another vehicle is traveling behind in the left lane. In this case, the warning is issued when the driver actually performs a lane-changing behavior (such as shifting the driver's line of sight) or operation (such as operating a turn signal), so the driver must stop changing lanes and slow down after receiving the warning. This raises concerns about the possibility of the vehicle getting too close to the vehicle ahead.

[0006] Therefore, an object of the present invention is to accurately alert the driver to the risk of changing lanes.

[0007] In order to solve the above-mentioned problems, the present invention provides a driving assistance device that includes a host vehicle speed detection means for detecting the speed of the host vehicle, a relative speed detection means for detecting the relative speed of other vehicles located around the host vehicle relative to the host vehicle, a other vehicle lane information acquisition means for acquiring information about the lane in which the other vehicle is traveling, a lane change destination determination means for determining whether an adjacent lane adjacent to the host vehicle's lane in which the host vehicle is traveling is a possible lane change destination, a vehicle distance prediction means for predicting a change in the inter-vehicle distance between the host vehicle and the other vehicle along the lane direction, and a warning control means for issuing a warning to the driver to notify them of the presence of the other vehicle, and that issues a warning to the driver when a first event occurs in which the other vehicle preceding the host vehicle is present in the host vehicle's lane and the inter-vehicle distance is predicted to become less than a predetermined value within a predetermined time, a second event occurs in which it is determined that the adjacent lane is a possible lane change destination, and a third event occurs in which the other vehicle is present in a lane change warning area set behind the host vehicle in the adjacent lane that is a possible lane change destination (Configuration 1).

[0008] In configuration 1, a first warning is issued when the other vehicle is present in a lane change warning area set behind the vehicle in the adjacent lane, and when the other vehicle is present in the lane change warning area set behind the vehicle in the adjacent lane, a second warning is issued when the driver's behavior or operation confirms an intention to change lanes to the adjacent lane on the side where the other vehicle is present, and a configuration can be adopted in which the methods for alerting the driver in the first warning, the rear vehicle warning, and the second warning are set to be different from each other (configuration 2).

[0009] In configuration 2, the method of alerting the driver can be set to at least one selected from the following, in the order of the first alarm, the rear vehicle warning alarm, and the second alarm: shortening the flashing interval of the flashing lamp; increasing the illuminance of the lit lamp; increasing the size of the lit lamp; moving the lit lamp closer to the front of the driver; increasing the volume of the alarm sound; shortening the period of the intermittent alarm sound; and increasing the vibration of a member that the driver touches (configuration 3).

[0010] In configuration 2 or 3, a configuration can be adopted in which the lane change warning area set for the third event when the following vehicle warning is issued is larger than the lane change warning area set for the third event when the second warning is issued (configuration 4).

[0011] In any one of configurations 1 to 4, a configuration can be adopted in which the presence of the other vehicle in the lane change warning area is determined based on an initial state at the time when the first event, the second event, and the third event occur, and a predicted state at the time when a predetermined time has elapsed from the initial state (configuration 5).

[0012] According to the present invention, it is possible to appropriately warn the driver when changing lanes.

[0013] Fig. 1 is a schematic diagram of a vehicle equipped with a driving assistance device according to an embodiment of the present invention. Fig. 2 is a schematic diagram showing an example of a case where a lane change space does not exist. Fig. 3 is a schematic diagram showing an example of a case where a lane change space exists. Fig. 4 is a schematic diagram showing an example of a lane change space and a lane change warning area, and showing a state of warning level 1.5. Fig. 5 is a schematic diagram showing a state of warning level 1. Fig. 6 is a schematic diagram showing a state of warning level 1.5. Fig. 7 is a flowchart showing an example of control of the present invention.

[0014] An embodiment of the present invention will be described with reference to the drawings. In this embodiment, a vehicle 1 (hereinafter referred to as "host vehicle 1") traveling on a highway, a motorway, or the like is equipped with a driving assistance device that alerts the driver of the vehicle 1 to the presence of other vehicles (hereinafter referred to as "other vehicles 2 and 3") traveling around the host vehicle 1 and to the risk of changing lanes. In this embodiment, the road on which the host vehicle 1 travels is a road with multiple lanes that can be traveled in the same direction. In this embodiment, three parallel lanes are used, but two or four lanes may also be used.

[0015] The vehicle 1 is equipped with a front sensor 12, a rear sensor 13, and a vehicle speed sensor 17 as information acquisition means. The vehicle speed sensor 17 is a sensor that detects the speed of the vehicle 1 and outputs a signal indicating the vehicle speed. For example, a radar sensor, an infrared sensor, a CCD camera, etc. can be used as the front sensor 12 and the rear sensor 13. The front sensor 12 and the rear sensor 13 are provided at the center, left end, and right end in the width direction of the front and rear of the vehicle 1, respectively. Information obtained by these information acquisition means is sent to an electronic control unit 20 mounted on the vehicle 1.

[0016] The driving assistance device comprises a vehicle speed detection means 21 for detecting the speed of the own vehicle, a relative speed detection means 22 for detecting the relative speed of other vehicles 2 and 3 located around the own vehicle 1 with respect to the own vehicle 1, an other vehicle lane information acquisition means 23 for acquiring information on the lanes in which the other vehicles 2 and 3 are traveling, a lane change destination determination means 24 for determining whether adjacent lanes R1 and R2 adjacent to the own lane R0 in which the own vehicle 1 is traveling can be a lane change destination, a vehicle distance prediction means 25 for predicting changes in the inter-vehicle distance between the own vehicle 1 and the other vehicles 2 and 3 along the lane direction, and an alarm control means 26 for issuing a warning to the driver.

[0017] The host vehicle speed detection means 21 can detect the speed v1 of the host vehicle 1 using information from the vehicle speed sensor 17. As the vehicle speed sensor 17, for example, a rotation sensor or the like can be used.

[0018] The relative speed detection means 22 uses information from the front sensor 12 and the rear sensor 13 to detect the inter-vehicle distance and relative speed between the vehicle 1 and the other vehicles 2 and 3. At this time, it can also detect the speeds V2 and V3 of the other vehicles 2 and 3. The inter-vehicle distance and relative speed between the vehicle 1 and the other vehicles 2 and 3 can be calculated by measuring the time and direction taken for millimeter wave radar or infrared light emitted toward the other vehicles 2 and 3 to reflect off the other vehicles 2 and 3 and return, or by image processing time-series images captured by a camera.

[0019] The inter-vehicle distance here means the distance along the direction of the lane of the road. Even when the vehicle 1 and the other vehicles 2 and 3 are in different lanes, or when they are in the same lane but are offset in the direction of the width of the road, the distance along the road is calculated based on information from sensors, or an approximation of the distance along the road is defined as the inter-vehicle distance.

[0020] The other vehicle's lane information acquisition means 23 uses information from the front sensor 12 and the rear sensor 13 to determine the positional relationship (lane distinction) between the host vehicle 1 and the other vehicles 2 and 3, i.e., whether the other vehicles 2 and 3 are in the same lane as the host vehicle 1 (referred to as the host vehicle's lane R0), the left lane R1 adjacent to the left side of the host vehicle's lane R0 in the direction of travel, or the right lane R2 adjacent to the right side of the host vehicle's lane R0 in the direction of travel. The lanes of the other vehicles 2 and 3 can be determined based on the inter-vehicle distance from the host vehicle 1 to the other vehicles 2 and 3 and their angle with respect to the direction of travel. Hereinafter, the other vehicle 2 preceding the host vehicle 1 in the host vehicle's lane R0 will be referred to as the preceding vehicle 2. In addition, in the adjacent lane on the left (left lane) R1 and the adjacent lane on the right (right lane) R2, other vehicles (adjacent lane vehicles) 3 located in front of or to the side of the vehicle 1 are referred to as adjacent lane front vehicles 3a, and other vehicles 3 located behind the vehicle 1 are referred to as adjacent lane rear vehicles 3b.

[0021] The lane change destination determination means 24 determines whether the left lane R1 and / or the right lane R2 are possible lane change destinations based on the inter-vehicle distances between the host vehicle 1 and the preceding vehicle 2, between the host vehicle 1 and the preceding vehicle 3a in the adjacent lane, and between the host vehicle 1 and the following vehicle 3b in the adjacent lane, and the relative speeds between the host vehicle 1 and the preceding vehicle 3a in the adjacent lane, and between the host vehicle 1 and the following vehicle 3b in the adjacent lane.Whether a lane change destination is possible is determined by whether or not another vehicle 3 (a preceding vehicle 3a in the adjacent lane) is present within the lane change space A, which is set according to predetermined requirements.

[0022] The inter-vehicle distance prediction means 25 determines whether the host vehicle 1 and the preceding vehicle 2 will collide within a predetermined time, i.e., whether the inter-vehicle distance will be less than a predetermined value (e.g., zero), based on the relative speed detected by the relative speed detection means 22. This predetermined time may be, for example, 5 seconds, 6 seconds, etc., and may be increased or decreased according to the speed of the host vehicle 1 (e.g., the faster the speed of the host vehicle 1, the shorter the predetermined time). "The host vehicle 1 and the preceding vehicle 2 will collide within a predetermined time" is not necessarily limited to the concept of the inter-vehicle distance being zero, but may also mean that the TTC (Time-To-Collision) will be less than a predetermined value. Note that TTC can be defined as inter-vehicle distance / (speed of host vehicle 1 - speed of preceding vehicle 2).

[0023] The warning control means 26 controls various devices to issue a warning that alerts the driver visually, audibly, and tactilely to the presence of other vehicles 2 and 3 around the vehicle 1 when predetermined conditions are met. Visual warnings can be issued, for example, by turning on warning lights 11 located around the driver's seat or near the door mirrors, or by displaying a warning on the screen of the navigation system 14, as shown in FIG. 1 . Audible warnings can be issued by sounding an alarm through a speaker 18. Tactile warnings can be issued by vibrating a component that the driver touches, such as the steering wheel 15 held by the driver. The steering wheel 15 is connected to a steering device 16, which not only performs normal steering functions based on driver operation but also vibrates the steering wheel 15 under predetermined conditions to perform automatic steering or to warn the driver.

[0024] The vehicle speed detection means 21, relative speed detection means 22, other vehicle lane information acquisition means 23, lane change destination determination means 24, inter-vehicle distance prediction means 25, and warning control means 26 are provided in the electronic control unit 20. In addition, overall control of the driving of the vehicle 1 including the steering device 16 and control of devices inside and outside the vehicle are controlled by control means 27 provided in the electronic control unit 20.

[0025] The control of this driving assistance device will be described below.

[0026] Suppose that while the host vehicle 1 is traveling, a preceding vehicle 2 is present in the host vehicle's lane R0, and an event has occurred in which it is predicted that the inter-vehicle distance between the host vehicle 1 and the preceding vehicle 2 will become less than a predetermined value within a predetermined time. This event will be referred to as a first event. Also, suppose that an event has occurred in which it is determined that the left lane R1 and / or the right lane R2 are possible lanes to change to. This event will be referred to as a second event.

[0027] In the state shown in Figure 2, the first event is established but the second event is not established, meaning that neither the left lane R1 nor the right lane R2 is determined to be a possible lane change destination.

[0028] 3, the first event is established, and the second event is also established. That is, the left lane R1 cannot be a destination lane for a lane change because a vehicle 3a ahead in the adjacent lane is present in the lane change space A (A1), but the right lane R2 can be a destination lane for a lane change because a vehicle 3a ahead in the adjacent lane is not present in the lane change space A (A2). Note that even if lane change spaces A (A1, A2) exist in both the left lane R1 and the right lane R2, the second event is also established.

[0029] Next, in the state shown in Figure 4, under the conditions where the first and second events are established, a vehicle 3b in the adjacent lane is present in the lane change warning area B set behind the vehicle 1 in the left lane R1 or the right lane R2, or one of the possible lane change destinations. This event is referred to as the third event. Note that in the second event, if lane change spaces A (A1, A2) exist in both the left lane R1 and the right lane R2, it is determined that the third event is established if a vehicle 3b in the adjacent lane is present in at least one of the left lane R1 or the right lane R2.

[0030] When the first, second, and third events described above occur, a rear vehicle warning is issued to the driver regardless of the driver's behavior or operation. The rear vehicle warning alerts the driver that a rear vehicle 3b in an adjacent lane is present in the blind spot behind the host vehicle 1 before the driver attempts to change lanes. Because the rear vehicle warning is issued regardless of the driver's behavior or operation, the driver can be notified of the presence of the rear vehicle 3b in the adjacent lane earlier than conventional warnings that are issued after the driver actually performs a lane change behavior (such as a change in the direction of the driver's eyes) or operation (such as operating a turn signal). In other words, the warning is issued by estimating the path of the host vehicle 1 from the environment surrounding the host vehicle 1, so the warning can be issued earlier than the driver's behavior or operation. This allows the driver to decide whether to change lanes earlier, enabling more accurate lane selection and speed adjustment. As a result, unnecessary warnings can be reduced, which is expected to reduce annoyance.

[0031] Regardless of whether a following vehicle warning is issued or not, if a following vehicle 3b in an adjacent lane is present in the lane change warning area B of at least one of the left lane R1 and the right lane R2 during normal driving, the first warning is issued regardless of the driver's behavior or operation. Since blind spots are located in positions that are difficult for the driver to see, the purpose of the first warning is to always alert the driver. The first warning is issued regardless of the occurrence of the first and second events.

[0032] Furthermore, when a rear vehicle 3b in the adjacent lane is present in the lane change warning area B of at least one of the left lane R1 and the right lane R2, a second warning is issued if the driver's behavior or operation indicates an intention to change lanes to the side where the rear vehicle 3b in the adjacent lane is located. The second warning is intended to warn the driver that the lane into which the driver is actually about to change lanes is dangerous, and is a stronger warning than the rear vehicle warning. The second warning is issued regardless of the occurrence of the first and second events. However, even if the above-mentioned rear vehicle warning has been issued, the second warning, which is a stronger warning than the rear vehicle warning, is also issued if the driver's behavior or operation indicates an intention to change lanes to the side where the rear vehicle 3b in the adjacent lane is located.

[0033] As described above, it is desirable to set different methods for alerting the driver for the three alerts, the first alert, the rear vehicle warning alert, and the second alert, because they each indicate different situations (levels of danger) of the vehicle 1. By providing different alert methods, it is easier to convey to the driver the difference in the level of urgency of the alerts.

[0034] For example, the first warning (warning level 1) simply notifies the driver that a vehicle requiring warning is present in the lane change warning area B, and is limited to lighting the warning light 11. In contrast, the second warning (warning level 2) is a high-risk warning because, in addition to the situation of the first warning (warning level 1), the driver has indicated his or her intention to change lanes in that direction. Therefore, the warning light 11 not only flashes, but also an audible warning (e.g., an intermittent audible warning with a short period) indicating the high risk alerts the driver. In contrast, the rear vehicle warning (warning level 1.5) is a warning that occurs when the situation of the first warning (warning level 1) occurs in the direction of the estimated path result (lane change estimated result) of the vehicle 1. Therefore, while the risk is not as high as that of the second warning (warning level 2), it is considered that the risk is close to that of the second warning (warning level 2) or will reach the level of risk of the second warning (warning level 2) within a short period of time. For this reason, it is advisable to issue a gentle warning (for example, a slowly flashing lamp) indicating approaching danger, as well as an inoffensive alarm sound (for example, a long, low-volume alarm sound).

[0035] Other methods for alerting the driver include, for example, when using the warning light 11, shortening the blinking interval of the flashing lamp, increasing the illuminance of the lit lamp, increasing the size of the lit lamp, and positioning the lit lamp closer to the front of the driver in order of increasing danger level from the first warning, rear vehicle warning, and second warning. Also, when using the speaker 18, for example, increasing the volume of the warning sound and shortening the period of the intermittent warning sound in order of increasing danger level from the first warning, rear vehicle warning, and second warning. Furthermore, when using vibration of a member that the driver touches, such as the steering wheel 15, increasing the vibration of the member in order of increasing danger level from the first warning, rear vehicle warning, and second warning.

[0036] Meanwhile, the size and range of the lane change warning area B can be changed depending on the situation. For example, it is desirable that the lane change warning area B set for the third event during a following vehicle warning be set larger than the lane change warning area B during a second warning. This is because a following vehicle warning issued based on the path estimation result of the vehicle 1 is more dangerous than a warning about a blind spot under normal circumstances, so it is effective to make the warning area wider and issue the warning earlier.

[0037] 4, the lane change warning area B during normal driving is indicated by C0, the lane change warning area B during the second warning is indicated by C1, and the lane change warning area B during the following vehicle warning (set for determining the third event) is indicated by C2. If the lengths of the lane change warning areas B indicated by C0, C1, and C2 in the lane direction (travel direction) are L0, L1, and L2, and the widths in the lane width direction are W0, W1, and W2, then the relationships L0<L1<L2 and W0≦W1≦W2 are satisfied.

[0038] Furthermore, the presence of the following vehicle 3b in the adjacent lane in the lane change warning area B may be determined not only in the initial state when the first, second, and third events occur, but also in the predicted state when a predetermined time (e.g., 1 second, 2 seconds, etc.) has elapsed from the initial state, which has the effect of widening the actual warning range.

[0039] Figure 5 shows a state (alarm state 1) in which a vehicle 3b in the adjacent lane behind is present in the lane change warning area B in the left lane R1, and the first alarm is issued regardless of whether the first or second event occurs.

[0040] 6 shows a state in which the first and second events have occurred, and the third event has also occurred, with the vehicle 3b in the adjacent lane being present in the lane change warning area B of the left lane R1. Therefore, a following vehicle advance warning is issued (warning state 1.5). In this state in FIG. 6, if the driver's behavior or operation indicates an intention to change lanes to the side where the vehicle 3b in the adjacent lane is present, the system transitions to a second warning (warning level 2).

[0041] In Figure 7, there is no rear vehicle 3b in the adjacent lane in either the left lane R1 or the right lane R2, and the third event does not occur. Therefore, regardless of whether the first and second events occur, the vehicle is not subject to a rear vehicle warning. Furthermore, neither the first nor the second warning is issued. Since neither warning is required, the warning level can be said to be 0.

[0042] FIG. 8 is a flowchart showing an example of this control.

[0043] First, control is started in step S1, and the surrounding environment (vehicles, lane markings, etc.) of the vehicle 1 is detected in step S2. In the following step S3, it is determined whether the inter-vehicle distance to the preceding vehicle 2 (preceding vehicle 2) will become less than a predetermined value (zero in FIG. 8) within a predetermined time. If the inter-vehicle distance does not become less than the predetermined value within the predetermined time, there is little risk of collision, and the process proceeds to step S7. If the inter-vehicle distance becomes less than the predetermined value within the predetermined time, a lane change is necessary, and the process proceeds to step S4.

[0044] In step S4, it is determined whether or not a lane-changing space A exists. If a lane-changing space A does not exist, no lane changes will be made thereafter. Therefore, the process proceeds to step S7. If a lane-changing space A exists, the process proceeds to step S5.

[0045] In step S5, it is determined whether or not there is a vehicle to be warned about in the vicinity of the vehicle 1. If there is no vehicle to be warned about, the process proceeds to step S11 and ends the control. If there is a vehicle to be warned about, the process proceeds to step S6, where a rear vehicle warning (warning level 1.5) is issued, and then the process proceeds to step S11 and ends the control.

[0046] In step S7, it is determined whether or not there is a vehicle to be warned about in the vicinity of the vehicle 1. If there is no vehicle to be warned about, the process proceeds to step S11 and ends the control. If there is a vehicle to be warned about, the process proceeds to step S8.

[0047] In step S8, it is determined whether the driver intends to change lanes. If the driver does not intend to change lanes, the process proceeds to step S10, where a first warning (warning level 1) is issued, and then the process proceeds to step S11, where the control is terminated. That is, during normal driving, regardless of the positional relationship with the preceding vehicle 2 or the presence or absence of a lane-changing space A, if a rear vehicle 3b in an adjacent lane is present in the lane-change warning area B of at least one of the left lane R1 and the right lane R2, the first warning is issued regardless of the driver's behavior or operation.

[0048] If the driver intends to change lanes in step S8, the process proceeds to step S9, where a second warning (warning level 2) is issued, and then the process proceeds to step S11, where the control is terminated. That is, when a rear vehicle 3b in an adjacent lane is present in the lane change warning area B of at least one of the left lane R1 and the right lane R2, and an intention to change lanes to the side where the rear vehicle 3b in the adjacent lane is present is confirmed based on the driver's behavior or operation, the second warning is issued.

[0049] The lane change space A can be set, for example, by the following method.

[0050] Symbol α shown in FIG. 3 is the distance at which the TTC (Time-To-Collision) between the host vehicle 1 and the preceding vehicle 2 reaches a certain value. The TTC (Time-To-Collision) is the value obtained by dividing the inter-vehicle distance between the host vehicle 1 and the preceding vehicle 2 by their relative speed. This TTC value is approximated to the distance required to change lanes. Symbol β shown in FIG. 3 is the distance traveled in a certain time period given the speed difference between the host vehicle 1 and the preceding vehicle 2. The width indicated by symbol γ may be set to the width between the left lane R1 and the right lane R2. This method of setting the lane change space A is one example, and other well-known methods may also be used.

[0051] The relative distance between the host vehicle 1 and the preceding vehicle 2 is ΔLego (see FIG. 4), and the relative speed between the host vehicle 1 and the preceding vehicle 2 is ΔVego. In this case, the time when the host vehicle 1 passes through the lane change space A is within the following range: {(ΔLego-α) / ΔVego} to {(ΔLego+β) / ΔVego} (Equation 1).

[0052] Next, the relative distance between the preceding vehicle 3a in the adjacent lane and the preceding vehicle 2 is ΔLother (see FIG. 4), and the relative speed is ΔVother. In this case, the time at which the preceding vehicle 3a in the adjacent lane passes through the lane change space A is within the following range: {(ΔLother-α) / ΔVother} to {(ΔLother+β+vehicle length of the preceding vehicle 3a in the adjacent lane) / ΔVother} (Equation 2).

[0053] If there is an overlap between the time ranges of (Equation 1) and (Equation 2), it is determined that there is no lane-changing space A. Note that if the relative speed ΔVother between the preceding vehicle 2 and the vehicle ahead in the adjacent lane 3a is lower than a predetermined speed (for example, less than 5 km / h), the presence or absence of lane-changing space A is determined based on their respective positions. In other words, the presence or absence of lane-changing space A is determined based on the relative distance (≒ΔLother) between the preceding vehicle 2 and the vehicle ahead in the adjacent lane 3a.

[0054] In the above embodiment, the first event "the preceding vehicle 2 is in the current lane R0" may refer to only a vehicle that is completely within the current lane R0, or may refer to a vehicle that is at least partially within the current lane R0. Furthermore, the lateral movement of a vehicle may be detected (predicted) and the target vehicle may be a vehicle that will enter the current lane R0 within a predetermined time. Furthermore, the presence or absence of lane-changing space A may be determined not only based on position information but also based on whether the preceding vehicle 2 will enter the area of ​​lane-changing space A within a specific time period (for example, TTC ±α seconds). When the preceding vehicle 2 is traveling across lanes, the preceding vehicle 2 itself may be replaced with a vehicle 3a ahead in an adjacent lane, and this may be used to determine the presence or absence of lane-changing space A.

[0055] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, the scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

[0056] 1 Own vehicle 2 Other vehicle (preceding vehicle) 3 Other vehicle (vehicle in adjacent lane) 20 Electronic control unit 21 Own vehicle speed detection means 22 Relative speed detection means 23 Other vehicle lane information acquisition means 24 Lane change destination determination means 25 Inter-vehicle distance prediction means 26 Warning control means 27 Control means A Lane change space B Lane change warning area R0 Own lane R1 Left lane (adjacent lane) R2 Right lane (adjacent lane)

Claims

1. A driving assistance device comprising: a vehicle speed detection means for detecting the speed of the host vehicle; a relative speed detection means for detecting the relative speed of other vehicles located around the host vehicle relative to the host vehicle; another vehicle lane information acquisition means for acquiring information about the lane in which the other vehicle is traveling; a lane change destination determination means for determining whether an adjacent lane adjacent to the host vehicle's lane in which the host vehicle is traveling is a possible lane change destination; an inter-vehicle distance prediction means for predicting a change in the inter-vehicle distance along the lane direction between the host vehicle and the other vehicle; and an alarm control means for issuing a warning to notify the driver of the presence of the other vehicle, wherein the driving assistance device issues a warning to the driver when a first event occurs in which the other vehicle preceding the host vehicle is present in the host vehicle's lane and the inter-vehicle distance is predicted to become less than a predetermined value within a predetermined time, a second event occurs in which it is determined that the adjacent lane is a possible lane change destination, and a third event occurs in which the other vehicle is present in a lane change warning area set behind the host vehicle in the adjacent lane that is a possible lane change destination.

2. A driving assistance device as described in claim 1, wherein a first warning is issued when the other vehicle is present in a lane change warning area set behind the vehicle in the adjacent lane, and a second warning is issued when, when the other vehicle is present in a lane change warning area set behind the vehicle in the adjacent lane, an intention to change lanes to the adjacent lane on the side where the other vehicle is present is confirmed based on the driver's behavior or operation, and the methods of alerting the driver in the first warning, the following vehicle warning, and the second warning are set to be different methods.

3. The driving assistance device of claim 2, wherein the method of alerting the driver is set to at least one selected from the following, in the order of the first warning, the rear vehicle warning, and the second warning: shortening the blinking interval of the blinking lamp, increasing the illuminance of the lit lamp, increasing the size of the lit lamp, moving the lit lamp closer to the front of the driver, increasing the volume of the warning sound, shortening the cycle of the intermittent warning sound, and increasing the vibration of a member that the driver can touch.

4. A driving assistance device as described in claim 2 or 3, wherein the lane change warning area set for the third event when the following vehicle warning occurs is set larger than the lane change warning area set for the third event when the second warning occurs.

5. A driving assistance device as described in any one of claims 1 to 4, wherein the presence of the other vehicle in the lane change warning area is determined based on an initial state at the time when the first event, the second event, and the third event occur, and a predicted state at the time when a predetermined time has elapsed from the initial state.

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