Lane departure prevention device

Abstract

The lane departure prevention device includes a control unit that performs lane departure prevention control (automatic steering of the steering wheel and / or issuance of an alarm) when it is determined that the vehicle is likely to deviate from the lane. The control unit aborts the execution of the lane departure prevention control until it is determined that the control restoration condition is satisfied when the intention of the driver to deviate from the lane, which is determined to have crossed the first white line, changes from none to sometimes. Even when it is determined that the control restoration condition is satisfied, the control unit continues to abort the execution of the lane departure prevention control when it is determined that the speed at which the vehicle approaches the second white line located ahead of its travel is equal to or higher than the reference speed.

Description

Technical Field

[0001] The present invention relates to a lane departure prevention device for a vehicle such as an automobile. Background Art

[0002] The lane departure prevention device performs lane departure prevention control of at least one of automatic steering of the steering wheel and issuance of an alarm when the vehicle position detection device detects the position of the vehicle relative to the lane and determines that the vehicle is likely to deviate from the lane based on the detected vehicle position.

[0003] If lane departure prevention control interferes with a driver's lane change intention or a control that reduces the vehicle's turning level, lane departure prevention control needs to be limited. For example, Japanese Patent Application Laid-Open No. 2019-177762 states that lane departure prevention control is limited when a steering speed exceeding a reference value, a steering torque exceeding a reference value, and / or a steering torque change exceeding a reference value is detected. Summary of the Invention

[0004] In lane departure prevention devices such as the one described in Japanese Patent Application Laid-Open No. 2019-177762, when the vehicle moves into an adjacent lane, the lane departure prevention control is determined to have been resumed, and the lane departure prevention control is restarted. Therefore, even if the driver attempts to make a continuous lane change from an adjacent lane to another adjacent lane or a roadside strip, the automatic steering of the steering wheel prevents the driver from making the second lane change smoothly, inevitably causing a feeling of discomfort.

[0005] The present invention provides an improved lane departure prevention device capable of smoothly performing a second lane change when a driver intends to change lanes to an adjacent lane and then continuously change lanes to an adjacent lane or a roadside strip.

[0006] The lane departure prevention device of the scheme of the present invention is constructed to include: a vehicle position detection device (camera sensor), which detects the position of the vehicle relative to the lane; and a control unit (LDA·ECU), which, when determining that the vehicle is likely to deviate from the lane based on the position of the vehicle detected by the vehicle position detection device, executes lane departure prevention control of at least one of automatic steering of the steering wheel and issuance of an alarm, and when determining that the driver's intention to depart from the lane after crossing the first lane boundary changes from no intention to some intention, the control unit suspends the execution of the lane departure prevention control until it is determined that a predetermined control recovery condition is met.

[0007] In the above solution, even if the control unit (LDA·ECU) determines that the control restoration condition is satisfied, when it is determined that the speed at which the vehicle approaches the second lane boundary (white line) in front of its traveling direction is equal to or higher than the reference speed, the suspension of the execution of the lane departure prevention control is continued.

[0008] According to the above structure, even if it is determined that the control restoration condition is satisfied, when it is determined that the speed at which the vehicle approaches the second lane boundary in front of its traveling direction is equal to or higher than the reference speed, the suspension of the execution of the lane departure prevention control is continued. Therefore, the automatic steering of the steering wheel based on the lane departure prevention control and the issuance of an alarm are not performed, so that the vehicle can cross the second lane boundary in front of its traveling direction and perform a lane change or the like of a lane departure. Therefore, it is possible to avoid a situation where the driver feels a sense of discomfort because the driver cannot smoothly perform the second lane change, and in addition, it is possible to avoid a situation where the driver feels bored due to the issuance of an unnecessary alarm.

[0009] In the above solution, before the control restoration condition is satisfied, even if it is determined that the driver has canceled the intention of lane departure across the second lane boundary (white line), when it is determined that the speed at which the vehicle approaches the second lane boundary is equal to or higher than the reference speed, the execution of the lane departure prevention control is suspended.

[0010] According to the above solution, before the control restoration condition is satisfied, even if it is determined that the driver has canceled the intention of lane departure across the second lane boundary, when it is determined that the speed at which the vehicle approaches the second lane boundary is equal to or higher than the reference speed, the execution of the lane departure prevention control is suspended. Therefore, the automatic steering of the steering wheel based on the lane departure prevention control and the issuance of an alarm are not performed, so that the vehicle can cross the second lane boundary in front of its traveling direction and perform a lane change or the like of a lane departure. Therefore, it is possible to avoid a situation where the driver feels a sense of discomfort because the driver cannot smoothly perform the second lane change, and in addition, it is possible to avoid a situation where the driver feels bored due to the issuance of an unnecessary alarm.

[0011] In the above solution, the control unit (LDA·ECU) determines that the control restoration condition is satisfied at an earlier time point among when a time equal to or longer than the reference time has elapsed since the time point when the driver's intention of lane departure across the first lane boundary has changed from none to some, and when it is determined that the vehicle has crossed the first lane boundary.

[0012] According to the above solution, when the time elapsed since the time point when the intention of lane departure of the driver crossing the first lane boundary is determined to have changed from none to some exceeds the reference time, and when it is determined that the vehicle has crossed the first lane boundary, at the earlier time point, it is determined that the control recovery condition is satisfied. Therefore, it is possible to prevent a situation where the automatic steering of the steering wheel and the issuance of an alarm based on lane departure prevention control are not performed from continuing unnecessarily for a long time, and it is possible to execute lane departure prevention control of the steering wheel when the vehicle is likely to deviate from the lane, preventing the vehicle from deviating from the lane.

[0013] Moreover, in the above solution, the control unit (LDA·ECU) variably sets the reference time according to the vehicle speed in such a way that the higher the vehicle speed, the shorter the reference time.

[0014] According to the above solution, the reference time is variably set according to the vehicle speed in such a way that the higher the vehicle speed, the shorter the reference time. Therefore, compared with the case where the reference time is constant regardless of the vehicle speed, it is possible to appropriately determine whether the control recovery condition is satisfied.

[0015] Moreover, in the above solution, the control unit (LDA·ECU) variably sets the reference speed according to the vehicle speed in such a way that the lower the vehicle speed, the higher the reference speed.

[0016] According to the above solution, the reference speed is variably set according to the vehicle speed in such a way that the lower the vehicle speed, the higher the reference speed. Therefore, compared with the case where the reference speed is constant regardless of the vehicle speed, it is possible to appropriately determine whether the control recovery condition is satisfied.

[0017] Moreover, in the above solution, the control unit (LDA·ECU) variably sets the reference speed according to the tilt angle of the vehicle in such a way that the larger the tilt angle of the vehicle in the longitudinal direction of the lane, the smaller the reference speed.

[0018] According to the above solution, the reference speed is variably set according to the tilt angle of the vehicle in such a way that the larger the tilt angle of the vehicle in the longitudinal direction of the lane, the smaller the reference speed. Therefore, compared with the case where the tilt angle of the vehicle in the longitudinal direction of the lane is not considered, it is possible to appropriately determine whether the control recovery condition is satisfied.

[0019] Moreover, in the above solution, the control unit (LDA·ECU) determines that the driver has the intention of lane departure when at least one of an operation of tilting the turn signal lever in the direction of lane departure of the vehicle and an operation of steering in the direction of lane departure of the vehicle is performed by the driver.

[0020] According to the above solution, when at least one of the tilting movement operation of the turn signal lever in the direction of lane departure of the vehicle and the steering operation in the direction of lane departure of the vehicle is performed by the driver, it is determined that the driver has the intention of lane departure across the first lane boundary. Therefore, compared with the case of only determining one of the tilting movement operation of the turn signal lever in the direction of lane departure of the vehicle and the steering operation in the direction of lane departure of the vehicle, it is possible to appropriately determine whether the driver has the intention of lane departure.

[0021] In the above description, in order to facilitate the understanding of the present invention, for the configuration of the invention corresponding to the embodiments described later, the names and / or reference numerals used in the embodiments are marked in parentheses. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or reference numerals marked in parentheses. Other objects, other features, and attendant advantages of the present invention will be easily understood from the description of the embodiments of the present invention with reference to the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Hereinafter, the features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described with reference to the drawings, in which like reference numerals denote like elements, and in the drawings:

[0023] Figure 1 is a schematic configuration diagram showing an embodiment of a lane departure prevention device of the present invention.

[0024] Figure 2 is a flowchart showing a lane departure prevention control routine in the embodiment.

[0025] Figure 3 is a map for calculating a reference time Tc with respect to the elapsed time based on the vehicle speed V.

[0026] Figure 4 is a map for calculating a reference speed Vyc with respect to the lateral speed Vy of the vehicle based on the vehicle speed V.

[0027] Figure 5 is a diagram showing a state in which the vehicle is traveling obliquely in the longitudinal direction of the lane.

[0028] Figure 6 is a diagram showing a specific example of the operation of the embodiment in the case where the recovery condition of the lane departure prevention control is not satisfied, the intention of lane departure is canceled, and the lateral speed Vy is less than the reference speed Vyc.

[0029] Figure 7 is a diagram showing a specific example of the operation of the embodiment in the case where the recovery condition of the lane departure prevention control is satisfied and the lateral speed Vy is equal to or higher than the reference speed Vyc. Detailed Embodiment

[0030] Hereinafter, a lane departure prevention device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0031] <Structure>

[0032] As Figure 1 shown, the lane departure prevention device 100 of the embodiment is applicable to a vehicle 50 and includes a lane departure prevention ECU 10, an electric power steering ECU 20, and a steering ECU 40. In this specification, lane departure prevention is referred to as LDA (abbreviation for Lane Departure Alert with Control) as needed, and electric power steering is referred to as EPS (abbreviation for Electric Power Steering) as needed.

[0033] These ECUs are electronic control devices (Electronic Control Unit) having a microcomputer as a main part, and are connected via a CAN (Controller Area Network) 52 so as to be able to communicate with each other. Each microcomputer includes a CPU, a ROM, a RAM, a non-volatile memory, an interface, and the like. The CPU realizes various functions by executing instructions (programs, routines) stored in the ROM. These ECUs may also combine several or all of the ECUs into one ECU.

[0034] As will be described in detail later, the ROM of the LDA·ECU 10 stores a program for lane departure prevention control corresponding to the Figure 2 shown flowchart, and the CPU executes lane departure prevention control according to this program. A camera sensor 12, a vehicle speed sensor 14, an LDA switch 16, and an alarm device 18 are connected to the LDA·ECU 10.

[0035] The camera sensor 12 includes a camera unit and a lane recognition unit that analyzes image data captured by the camera unit to identify the white lines of the road. The camera sensor 12 (camera unit) captures the scenery in front of the vehicle 50. The camera sensor 12 (lane recognition unit) repeatedly supplies information related to the identified white lines to the LDA·ECU 10 every time a predetermined operation cycle elapses.

[0036] As Figure 5As shown, the camera sensor 12 can recognize white lines 56L and 56R that are the boundaries of the lane 54 (referred to as lane boundaries), and can detect the relative position relationship of the vehicle with respect to the lane 54 based on the relationship between the white lines and the position of the vehicle 50. Here, the position of the vehicle 50 refers to the position of the center of gravity 50A of the vehicle, but it can also be the center position when the vehicle is viewed from above. The lateral position of the vehicle described later represents the position of the center of gravity of the vehicle in the lane width direction, and the lateral speed of the vehicle represents the speed of the center of gravity of the vehicle in the lane width direction. They are obtained based on the relative position relationship between the white lines detected by the camera sensor 12 and the vehicle.

[0037] The vehicle speed sensor 14 detects the vehicle speed V of the vehicle 50 and repeatedly supplies a signal representing the vehicle speed V to the LDA·ECU 10 at a predetermined control cycle. The LDA switch 16 is operated by the driver and supplies a signal indicating whether it is turned on (ON) to the LDA·ECU 10. The LDA switch 16 being turned on means that lane departure prevention control is executed.

[0038] The alarm device 18 operates when the LDA·ECU 10 determines that the vehicle 50 is likely to deviate from the lane 54, and issues an alarm as a lane departure prevention control, that is, issues an alarm about the content that the vehicle 50 is likely to deviate from the lane. The alarm device 18 can be any one of an alarm device that issues a visual alarm such as an alarm lamp, an alarm device that issues an auditory alarm such as an alarm buzzer, an alarm device that issues a somatic sensation alarm such as the vibration of a seat, or any combination thereof.

[0039] The EPS·ECU 20 can control the EPS device 22 to steer the steering wheel 24 as needed. Therefore, the EPS·ECU 20 and the EPS device 22 constitute a steering device 26 that automatically steers the steering wheel 24 as needed. When the LDA·ECU 10 determines that the vehicle 50 is likely to deviate from the lane, the EPS·ECU 20 performs automatic steering of the steering wheel 24 for preventing the vehicle from deviating from the lane as another lane departure prevention control.

[0040] As Figure 1 shown, a torque sensor 32 that detects the steering torque Ts is provided on the steering shaft 30 integrally connected to the steering wheel 28 operated by the driver. A signal representing the steering torque Ts detected by the torque sensor 32 is input to the EPS·ECU 20. The EPS·ECU 20 controls the EPS device 22 based on the steering torque Ts and the vehicle speed V detected by the vehicle speed sensor 14 using a method well known in the art, thereby controlling the steering assist torque and reducing the driver's steering burden. The signal representing the steering torque Ts is input from the EPS·ECU 20 to the LDA·ECU 10 via the CAN 52.

[0041] The steering ECU 40 is connected to a turn signal lever 42 operated by a driver and turn signals 44L and 44R. When the turn signal lever 42 is tilted in the left turn direction of the vehicle 50, the steering ECU 40 causes the front and rear turn signals 44L on the left side of the vehicle 50 to flash. When the turn signal lever 42 is tilted in the right turn direction of the vehicle 50, the steering ECU 40 causes the front and rear turn signals 44R on the right side of the vehicle 50 to flash. The tilt movement information of the turn signal lever 42 is input from the steering ECU 40 to the LDA·ECU 10 via the CAN 52.

[0042] <Lane departure prevention control routine>

[0043] Next, refer to Figure 2 The flowchart shown to describe the lane departure prevention control routine in the embodiment. When the LDA switch 16 shown in Figure 1 is turned on, the CPU of the LDA·ECU 10 repeatedly executes the lane departure prevention control of the flowchart shown in Figure 2 at a predetermined control cycle. In addition, in the following description, the lane departure prevention control is simply referred to as "control".

[0044] First, in step S10, the CPU determines whether the flag Foff is 1, that is, determines whether it is in the non-execution period of the lane departure prevention control. When the CPU makes an affirmative determination, the control proceeds to step S60. When the CPU makes a negative determination, the control proceeds to step S20. In addition, the flag Foff is initialized to 0 at the start of the control, and then is set to 0 or 1 according to the flowchart shown in Figure 2 as described later.

[0045] In step S20, the CPU determines whether the vehicle is likely to deviate from the lane based on the relative position relationship between the vehicle 50 and the lane 54 detected by the camera sensor 12 using a method well known in the art. When the CPU makes a negative determination, the control is temporarily ended. When the CPU makes an affirmative determination, the control proceeds to step S30.

[0046] In this case, the determination of whether the vehicle 50 is likely to deviate from the lane can also be performed, for example, by the following method. First, as shown in Figure 5 based on the image information in front of the vehicle 50, the angle (tilt angle) θy formed by the traveling direction 62 of the vehicle with respect to the longitudinal direction 60 of the lane 54 is estimated. The angle θy is positive when the traveling direction 62 of the vehicle 50 is on the left side with respect to the longitudinal direction 60 of the lane 54. The moving speed (lateral speed) Vy of the vehicle 50 in the direction perpendicular to the longitudinal direction 60 of the lane 54 is estimated as Vsinθy based on the angle θy and the vehicle speed V.

[0047] In addition, the distance Dy (not shown) in the lane width direction between the white line 56L (the first lane boundary) on the approaching side of the vehicle 50 and the center of gravity 50A of the vehicle is estimated. Moreover, it is also possible that, taking Δt as a preset time, when Dy - VyΔt is equal to or less than a preset reference value Dyc (a positive constant), it is determined that the vehicle 50 may deviate from the lane.

[0048] In step S30, the CPU determines whether the driver has an intention of lane departure. When the CPU makes a negative determination, the control proceeds to step S50. When the CPU makes an affirmative determination, in step S40, the flag Foff is set to 1 in a manner that lane departure prevention control is not executed.

[0049] In this case, when the driver performs at least one of the tilting movement operation of the turn signal lever 42 in the lane departure direction and the steering operation in the lane departure direction, the CPU determines that the driver has an intention of lane departure across the first lane boundary. The steering operation can be determined based on whether the magnitude of the steering torque Ts detected by the torque sensor 32 is equal to or greater than the reference value Tsc or whether the magnitude of the rotation angle of the steering shaft 30, i.e., the steering angle θ, is equal to or greater than the reference value θsc.

[0050] In addition, the higher the vehicle speed V, the smaller the steering resistance when the steered wheels are steered by the driver's steering operation. Therefore, the reference value Tsc can be a positive constant, but the reference value Tsc is variably set according to the vehicle speed in such a way that the higher the vehicle speed V, the smaller the reference value Tsc. Therefore, compared with the case where the reference value Tsc is constant regardless of the vehicle speed, it is possible to appropriately determine whether the driver has an intention of lane departure across the lane boundary.

[0051] In step S50, the CPU executes lane departure prevention control. That is, the CPU causes the alarm device 18 to operate, thereby issuing an alarm indicating that the vehicle 50 may deviate from the lane. In addition, the CPU outputs an automatic steering command signal to the EPS·ECU 20, thereby automatically steering the steered wheels 24 by the EPS device 22 in such a way that the vehicle 50 does not deviate from the lane.

[0052] In step S60, the CPU calculates a reference time Tc with respect to the elapsed time based on the vehicle speed V and referring to the Figure 3 shown map. As Figure 3 shown, the reference time Tc is variably set according to the vehicle speed in such a way that the higher the vehicle speed V, the shorter the reference time Tc.

[0053] In step S70, the CPU determines whether the recovery condition of the lane departure prevention control is satisfied. When the CPU makes an affirmative determination, the control proceeds to step S90. When the CPU makes a negative determination, the control proceeds to step S80.

[0054] In this case, the CPU determines that the control restoration condition is satisfied at the earlier of time points A and B described below.

[0055] Time point A: When the time elapsed since the determination in step S30 changed from a negative determination to an affirmative determination, that is, when the driver's intention to deviate from the lane changed from "none" to "yes", exceeds the reference time Tc

[0056] Time point B: When it is determined that the vehicle 50 has crossed the lane boundary and the lane change is completed, that is, when it is determined based on the relative positional relationship between the vehicle 50 and the white line that the entire vehicle 50 has moved to the lane of the lane change destination

[0057] In step S80, the CPU determines whether the driver has canceled the intention to deviate from the lane. When the CPU makes a negative determination, it temporarily ends the control. When it makes an affirmative determination, it advances the control to step S90. In addition, the CPU determines that the driver has canceled the intention to deviate from the lane when the driver returns the turn signal lever 42 to the non-tilted movement position (neutral position), or when the driver performs a steering operation to cancel the lane change.

[0058] In step S90, the CPU calculates a reference speed Vyc for the lateral speed Vy of the vehicle 50 based on the vehicle speed V and referring to the Figure 4 mapping shown. As shown in Figure 4 , the reference speed Vyc is variably set according to the vehicle speed such that the lower the vehicle speed V, the greater the reference speed Vyc. In addition, the reference speed Vyc is variably set according to the tilt angle θy of the vehicle such that the greater the tilt angle θy of the vehicle 50 in the longitudinal direction of the lane, the smaller the reference speed Vyc.

[0059] In step S100, the CPU determines whether the lateral speed Vy at which the vehicle 50 approaches the white line on the side where lane deviation is likely is equal to or higher than the reference speed Vyc. When the CPU makes an affirmative determination, it temporarily ends the control. When it makes a negative determination, in step S110, it resets the flag Foff to 0 in such a way that the lane departure prevention control is restored.

[0060] <Operation of the Embodiment>

[0061] <C1. Case where there is no possibility of the vehicle 50 deviating from the lane>

[0062] In steps S10 and S20, a negative determination is made. Therefore, the lane departure prevention control, that is, the operation of the alarm device 18 and the automatic steering of the steering wheel 24, is not performed.

[0063] <C2. Situation where vehicle 50 may deviate from the lane but the driver has no intention of lane departure>

[0064] In step S10, a negative determination is made. In step S20, an affirmative determination is made. In step S30, a negative determination is made. Therefore, in step S50, lane departure prevention control is executed. Thus, through the operation of the alarm device 18 and the automatic steering of the steering wheel 24, it is possible to prevent vehicle 50 from deviating from the lane. For example, even if vehicle 50 is subjected to a lateral force due to a crosswind, a lateral inclination of the road surface, etc., or if vehicle 50 unnecessarily skews relative to the lane 54 due to driver inattention, etc., resulting in the possibility of vehicle 50 deviating from lane 54, it is possible to prevent vehicle 50 from deviating from lane 54.

[0065] <C3. Situation where vehicle 50 may deviate from the lane and the driver has an intention of lane departure>

[0066] In step S10, a negative determination is made. In steps S20 and S30, affirmative determinations are made. In step S40, the flag Foff is set to 1. Therefore, when the turn signal 44L or 44R blinks and / or the steering torque Ts is above the reference value Tsc, the lane departure prevention control is not executed, and then an affirmative determination is made in step S10.

[0067] <C3-1. Situation where the recovery condition of the lane departure prevention control is not satisfied and the intention of lane departure is not cancelled>

[0068] In steps S70 and S80, negative determinations are made. Therefore, the automatic steering of the steering wheel 24 based on the lane departure prevention control is not executed, and thus the driver can perform a lane change or other lane departure as desired.

[0069] <C3-2. Situation where the recovery condition of the lane departure prevention control is not satisfied, the intention of lane departure is cancelled, and the lateral speed Vy is less than the reference speed Vyc>

[0070] In step S70, a negative determination is made, but in step S80, an affirmative determination is made. In step S100, a negative determination is made. Therefore, in step S110, the flag Foff is reset to 0 in a manner that enables the recovery of the lane departure prevention control. Thus, similar to the above situation C2, a negative determination is made in step S10, an affirmative determination is made in step S20, and a negative determination is made in step S30. Therefore, in step S50, the lane departure prevention control is executed. Thus, through the operation of the alarm device 18 and the automatic steering of the steering wheel 24, it is possible to prevent vehicle 50 from deviating from the lane.

[0071] <Case C3-3. The recovery condition for lane departure prevention control is not satisfied, the intention of lane departure is cancelled, and the lateral speed Vy is equal to or higher than the reference speed Vyc>

[0072] In step S70, a negative determination is made, but in steps S80 and S100, a positive determination is made. Therefore, the flag Foff is not reset to 0, and the automatic steering of the steering wheel 24 based on the lane departure prevention control is not performed. Thus, similar to the above Case C3-1, the driver can perform lane departures such as lane changes as desired.

[0073] <Case C3-4. The recovery condition for lane departure prevention control is satisfied and the lateral speed Vy is less than the reference speed Vyc>

[0074] In step S70, a positive determination is made, but in step S100, a negative determination is made. In step S110, the flag Foff is reset to 0 in a manner that allows the lane departure prevention control to resume. Therefore, in step S10, a negative determination is made, in step S20, a positive determination is made, and in step S30, a positive determination is made. Subsequently, in step S10, a positive determination is made, so the flag Foff is alternately set to 0 and 1, and the lane departure prevention control in step S50 is not performed. Thus, similar to the above Case C3-1, the driver can perform lane departures such as lane changes as desired.

[0075] <Case C3-5. The recovery condition for lane departure prevention control is satisfied and the lateral speed Vy is equal to or higher than the reference speed Vyc>

[0076] In steps S70 and S100, a positive determination is made. Therefore, even if the recovery condition for the lane departure prevention control is satisfied, the flag Foff is not reset to 0, and the automatic steering of the steering wheel 24 based on the lane departure prevention control is not performed. Thus, similar to the above Case C3-1, the driver can perform lane departures such as lane changes as desired.

[0077] <Specific example of operation>

[0078] Next, refer to Figure 6 and Figure 7 to describe specific examples of the operation of the embodiment for the above Cases C3-3 and C3-5. In addition, in the following description, each time point is the time point when the center of gravity 50A of the vehicle 50 is located at the displayed position.

[0079] <Case C3-3 ( Figure 6 )>

[0080] At time point t1 when the vehicle 50 is traveling on the lane 54, the flashing of the turn signal 44L starts. From time point t2 to time point t4, the steering torque Ts becomes equal to or greater than the reference value Tsc. If the vehicle 50 approaches the white line 56L (the first lane boundary) and the determinations in steps S20 and S30 become positive determinations at time point t3, then in step S40, the flag Foff is set to 1, and thus the automatic steering of the steering wheel 24 based on the lane departure prevention control is not executed. Therefore, the vehicle 50 can cross the white line 56L.

[0081] At time point t5, which is earlier than time point t6 when the recovery condition of the lane departure prevention control is established due to the completion of the movement of the vehicle 50 to the adjacent lane 64, the flashing of the turn signal 44L stops, and the determination in step S80 becomes a positive determination. Since the lateral speed Vy of the vehicle 50 is equal to or greater than the reference speed Vyc, the determination in step S100 becomes a positive determination, and the flag Foff is maintained at 1. Therefore, the situation where the lane departure prevention control is not executed continues. Therefore, the vehicle 50 can cross the white line 66 (the second lane boundary) and move to the adjacent lane or the roadside strip 68.

[0082] Moreover, at time point t7, the lateral speed Vy of the vehicle 50 is less than the reference speed Vyc, the determination in step S100 becomes a negative determination, and the flag Foff is reset to 0. At time point t8, the movement of the vehicle 50 to the lane or the roadside strip 68 is completed.

[0083] Therefore, as Figure 6 shown, even after the vehicle 50 has crossed the white line 56L and before the recovery condition of the lane departure prevention control is established due to the completion of the movement of the vehicle 50 to the adjacent lane 64, if the driver stops the flashing of the turn signal 44L and the lateral speed Vy of the vehicle 50 is equal to or greater than the reference speed Vyc, the vehicle can continuously change lanes to the adjacent lane or the roadside strip 68.

[0084] In addition, in the case of the conventional lane departure prevention control, steps S80 to S100 are not performed. Therefore, at time point t5, when the flashing of the turn signal 44L stops and the determination in step S70 becomes a positive determination, the flag Foff is reset to 0. Therefore, since the lane departure prevention control starts again, as Figure 6 shown by the imaginary line in, due to the automatic steering of the steering wheel 24, the vehicle 50 cannot deviate from the lane 64 and cannot continuously change lanes to the lane or the roadside strip 68.

[0085] <Case C3-5( Figure 7 ))>

[0086] Until the vehicle 50 crosses the white line 66 and moves toward the adjacent lane or the roadside strip 68, similar to the case C3-3, lane departure prevention control is not executed.

[0087] At time point t5, the recovery condition for lane departure prevention control is satisfied, and the determination in step S70 becomes a positive determination. At the subsequent time point t6, the flashing of the turn signal 44L stops.

[0088] Since the lateral speed Vy of the vehicle 50 is equal to or higher than the reference speed Vyc, the determination in step S100 becomes a positive determination, and the situation of not executing lane departure prevention control continues. Therefore, the vehicle 50 can cross the white line 66 (the second lane boundary) and move toward the adjacent lane or the roadside strip 68. After time point t7, lane departure prevention control is executed in the same manner as in case C3-3.

[0089] Therefore, automatic steering of the steering wheel 24 based on lane departure prevention control is not performed, and the vehicle 50 can move across the white line 56L (the first lane boundary) and the white line 66 (the second lane boundary). Therefore, the vehicle 50 can continuously change lanes from the lane 54 via the lane 58 to the adjacent lane or the roadside strip 68.

[0090] In addition, in the case of the conventional lane departure prevention control, at time point t5, when the recovery condition for lane departure prevention control is satisfied and the determination in step S70 becomes a positive determination, the flag Foff is reset to 0. Therefore, since lane departure prevention control is restarted, as Figure 7 shown by the imaginary line, due to the automatic steering of the steering wheel 24, the vehicle 50 cannot deviate from the lane 64 and cannot continuously change lanes to the lane or the roadside strip 68.

[0091] From the above description, according to the embodiment, even when automatic steering of the steering wheel 24 is performed as lane departure prevention control, the vehicle can continuously change lanes regardless of the temporal relationship between the time point when the recovery condition for lane departure prevention control is satisfied and the time point when the driver cancels the intention of lane departure. In addition, even when an alarm is issued by the alarm device 18 as lane departure prevention control, in a situation where the driver wants to continuously change lanes, it is possible to avoid the annoyance caused by the issuance of unnecessary alarms.

[0092] In addition, according to the embodiment, when the time elapsed since the time point when it is determined that the intention to deviate from the lane across the white line 56L as the first lane boundary changes from "none" to "yes" exceeds the reference time Tc, and when it is determined that the vehicle 50 has crossed the white line 56L, either one of them, it is determined that the control restoration condition is satisfied. Therefore, it is possible to prevent a situation where the automatic steering of the steering wheel based on the lane departure prevention control and the issuance of an alarm are not performed from continuing unnecessarily for a long time, and when the vehicle is likely to deviate from the lane, the automatic steering of the steering wheel based on the lane departure prevention control can be executed to prevent the vehicle from deviating from the lane.

[0093] Moreover, according to the embodiment, the reference time Tc is variably set according to the vehicle speed such that the higher the vehicle speed V, the shorter the reference time Tc. Therefore, compared with the case where the reference time Tc is constant regardless of the vehicle speed, it is possible to appropriately determine whether the control restoration condition is satisfied.

[0094] Moreover, according to the embodiment, the reference speed Vyc is variably set according to the vehicle speed such that the lower the vehicle speed V, the higher the reference speed Vyc. Therefore, compared with the case where the reference speed Vyc is constant regardless of the vehicle speed, it is possible to appropriately determine whether the control restoration condition is satisfied.

[0095] Moreover, according to the embodiment, the reference speed Vyc is variably set according to the inclination angle of the vehicle such that the larger the inclination angle θy of the vehicle in the longitudinal direction of the lane, the smaller the reference speed Vyc. Therefore, compared with the case where the inclination angle of the vehicle in the longitudinal direction of the lane is not considered, it is possible to appropriately determine whether the control restoration condition is satisfied.

[0096] Moreover, according to the embodiment, when the driver performs at least one of the tilting movement operation of the turn signal lever 42 in the direction of lane departure of the vehicle 50 and the steering operation in the direction of lane departure of the vehicle, it is determined that the driver has the intention of lane departure. Therefore, compared with the case where only one of the tilting movement operation of the turn signal lever in the direction of lane departure of the vehicle and the steering operation in the direction of lane departure of the vehicle is determined, it is possible to appropriately determine whether the driver has the intention of lane departure.

[0097] As described above, the present invention has been described in detail with respect to specific embodiments, but the present invention is not limited to the above-described embodiments, and various other embodiments can be made within the scope of the present invention for those skilled in the art.

[0098] For example, in the above-described embodiment, as the lane departure prevention control, the issuance of an alarm based on the operation of the alarm device 18 and the automatic steering of the steering wheel 24 based on the EPS device 22 are performed. However, either the issuance of the alarm or the automatic steering of the steering wheel 24 can be omitted.

[0099] In addition, in the above-described embodiment, as Figure 3 shown, for the reference time Tc with respect to the elapsed time, the reference time Tc is variably set according to the vehicle speed such that the higher the vehicle speed V, the shorter the reference time Tc. However, the reference time Tc may be constant regardless of the vehicle speed V.

[0100] In addition, in the above-described embodiment, as Figure 4 shown, for the reference speed Vyc with respect to the lateral speed Vy of the vehicle 50, the reference speed Vyc is variably set according to the vehicle speed such that the lower the vehicle speed V, the higher the reference speed Vyc. However, the reference speed Vyc may be constant regardless of the vehicle speed V.

[0101] Furthermore, in the above-described embodiment, as Figure 4 shown, the reference speed Vyc is variably set according to the inclination angle θy of the vehicle such that the larger the inclination angle θy of the vehicle 50 with respect to the longitudinal direction of the lane, the smaller the reference speed Vyc. However, the reference speed Vyc may not be variably set according to the inclination angle θy of the vehicle.

Claims

1. A lane departure prevention device, comprising: A vehicle position detection device that detects the position of a vehicle relative to a lane; And a control unit that, when it is determined based on the position of the vehicle detected by the vehicle position detection device that the vehicle is likely to deviate from the lane, performs at least one of automatic steering of the steering wheel and issuance of an alarm for lane departure prevention control. The control unit is configured to, when it is determined that the driver's intention to deviate from the lane by crossing the first lane boundary changes from none to being present, suspend the execution of the lane departure prevention control until it is determined that a preset control recovery condition is satisfied. The control unit is configured to, even when it is determined that the control recovery condition is satisfied, continue to suspend the execution of the lane departure prevention control when it is determined that the speed at which the vehicle approaches the second lane boundary located ahead of it in the traveling direction is equal to or higher than a reference speed. The control unit is configured to, even before the control recovery condition is satisfied, when it is determined that the driver has canceled the intention to deviate from the lane by crossing the second lane boundary and it is determined that the speed at which the vehicle approaches the second lane boundary is equal to or higher than the reference speed, suspend the execution of the lane departure prevention control.

2. The lane departure prevention device according to claim 1, The control unit is configured to determine that the control recovery condition is satisfied at an earlier time point among when a time equal to or longer than a reference time has elapsed since the time point when it is determined that the driver's intention to deviate from the lane by crossing the first lane boundary changes from none to being present, and when it is determined that the vehicle has crossed the first lane boundary.

3. The lane departure prevention device according to claim 2, The control unit is configured to variably set the reference time according to the vehicle speed such that the higher the vehicle speed, the shorter the reference time.

4. The lane departure prevention device according to any one of claims 1 to 3, The control unit is configured to variably set the reference speed according to the vehicle speed such that the lower the vehicle speed, the higher the reference speed.

5. The lane departure prevention device according to any one of claims 1 to 3, The control unit is configured to variably set the reference speed according to the tilt angle such that the larger the tilt angle of the vehicle in the longitudinal direction of the lane, the lower the reference speed.

6. The lane departure prevention device according to any one of claims 1 to 3, The control unit is configured to determine that the driver has an intention to deviate from the lane when the driver performs at least one of an operation of tilting the turn signal lever in the direction of lane departure of the vehicle and an operation of steering in the direction of lane departure of the vehicle.

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