Lane departure prevention device

Abstract

The present invention relates to a lane departure prevention device, which, when it is determined that a vehicle is in danger of deviating from a lane, issues an alarm and steers a steering wheel to prevent the vehicle from deviating. When an electronic control device determines that a vehicle is shifting obliquely relative to a lane based on a position of the vehicle detected by a CCD camera and determines that a steering torque detected by a torque sensor is greater than a reference steering torque, the device starts prohibiting the issuance of an alarm and prohibiting the steering of the steering wheel. When it is determined that the vehicle has completed the oblique shift relative to the lane, the device cancels the prohibition of the issuance of an alarm and the prohibition of the steering of the steering wheel.

Description

Technical Field

[0001] The present invention relates to a lane departure prevention device for vehicles such as automobiles. Background Art

[0002] Lane departure prevention control is known that automatically turns the steering wheel to prevent the vehicle from leaving the lane when there is a risk (danger, possibility) that the vehicle will leave the lane. Even if lane departure prevention control is performed, if the driver drives the vehicle out of the lane by steering (steering) operation based on his own will in order to change lanes (lane change), it is necessary to restrict (control according to rules) the steering of the steering wheel based on the lane departure prevention control.

[0003] For example, Japanese Patent Application Laid-Open No. 09-142327 describes a lane departure prevention device that automatically turns the steering wheel and activates the alarm device to sound an alarm when the vehicle is detected to be likely to deviate from the lane. In this lane departure prevention device, in order to prevent the lane departure prevention control from interfering with the steering operation based on the driver's intention, even if the vehicle is detected to be likely to deviate from the lane, if a sudden steering operation by the driver is detected, the steering of the steering wheel based on the lane departure prevention control and / or the alarm are restrained. Summary of the invention

[0004] In a situation where there is a risk that the driver may cause the vehicle to deviate from the lane on his own will, in order to prevent the driver from becoming annoyed (annoyed) by alarms, etc., it is preferred to determine whether the driver has the intention to deviate from the lane before detecting the risk of the vehicle deviating from the lane, and to restrict the steering of the steering wheel and / or alarm.

[0005] In the conventional lane departure prevention device described in the above-mentioned public gazette, when the possibility of the vehicle deviating from the lane is detected, the steering wheel is steered by the lane departure prevention control and an alarm is sounded. Thus, the steering of the steering wheel and the alarm are restrained by the lane departure prevention control when a sudden steering operation based on the driver's intention is detected in the situation where the possibility of the vehicle deviating from the lane is detected. Therefore, in the conventional lane departure prevention device, it is impossible to restrain the steering of the steering wheel and / or the alarm before the possibility of the vehicle deviating from the lane is detected, and the driver will inevitably feel annoyed by the alarm.

[0006] The main subject of the present invention is to prevent the driver from being annoyed by the alarm, etc. when the driver causes the vehicle to deviate from the lane based on his own will, by determining the driver's intention to deviate from the lane before detecting the possibility of the vehicle deviating from the lane and prohibiting the issuance of the alarm and / or the steering of the steering wheel.

[0007] According to the present invention, a lane departure prevention device is provided, which includes a vehicle position detection device for detecting the position of a vehicle relative to a lane, an alarm device, a steering device for steering a steering wheel, and a control unit for controlling the alarm device and the steering device. The control unit is configured to perform at least one of issuing an alarm by the alarm device and steering the steering wheel to prevent the vehicle from deviating from the lane when it is determined that the vehicle is in danger of deviating from the lane based on the position of the vehicle detected by the vehicle position detection device.

[0008] The lane departure prevention device also includes a steering torque detection device for detecting steering torque. The control unit is configured to prohibit the issuance of an alarm and the steering of the steering wheel when it is determined that the vehicle is shifting obliquely (driving diagonally) relative to the lane based on the position of the vehicle detected by the vehicle position detection device, and when it is determined that the steering torque detected by the steering torque detection device is above a reference steering torque.

[0009] When the driver intentionally deviates the vehicle from the lane in order to change lanes, the vehicle starts to shift obliquely relative to the lane and the steering torque increases before the vehicle is likely to deviate from the lane. Therefore, by determining whether the vehicle is shifting obliquely relative to the lane and determining whether the steering torque is large, it is possible to determine whether the driver is about to deviate the vehicle from the lane intentionally.

[0010] According to the above configuration, when it is determined that the vehicle is shifting obliquely relative to the lane and the steering torque is determined to be greater than the reference steering torque, the issuance of an alarm and the steering of the steering wheel are prohibited. Thus, it is possible to determine whether the driver is about to deviate the vehicle from the lane based on his / her own will before the risk of the vehicle deviating from the lane occurs. Therefore, since it is possible to determine the driver's intention to deviate from the lane and prohibit the issuance of an alarm and the steering of the steering wheel before the risk of the vehicle deviating from the lane is detected, it is possible to prevent the driver from being annoyed by the alarm and the steering of the steering wheel when the driver deviates from the lane based on his / her own will.

[0011] In addition, when the vehicle deviates from the lane due to the driver's inattention, even if the vehicle moves obliquely relative to the lane, the steering torque will not become a large value. Therefore, even if it is determined that the vehicle is moving obliquely relative to the lane, since the steering torque is not determined to be greater than the reference steering torque, the issuance of an alarm and the prohibition of steering the steering wheel will not be started. Therefore, the issuance of an alarm or the steering of the steering wheel can be performed, thereby calling the driver's attention or preventing the vehicle from deviating from the lane by steering the steering wheel.

[0012] As described above, in the conventional lane departure prevention device described in the above-mentioned publication, even if the possibility of the vehicle deviating from the lane is detected, if a sudden steering operation by the driver is detected, the alarm is suppressed. Therefore, according to the setting of the threshold value for detecting the sudden steering operation, the sudden steering operation is detected when the vehicle is traveling in a curve, so even if the vehicle is likely to deviate from the lane when the vehicle is traveling in a curve, the driver's attention cannot be called by the alarm and the steering wheel cannot be turned to prevent the vehicle from deviating from the lane.

[0013] According to the above configuration, when it is determined that the vehicle is shifting obliquely relative to the lane and the steering torque is determined to be greater than the reference steering torque, the issuance of an alarm and the prohibition of steering the steering wheel are started. Therefore, when the vehicle deviates from the lane to the outside of the curve while traveling in a curve, it is not determined that the steering torque is greater than the reference steering torque, and the issuance of an alarm and the prohibition of steering the steering wheel are not started. As a result, it is possible to issue an alarm to call attention to the danger of the vehicle deviating from the lane or to turn the steering wheel to prevent the vehicle from deviating from the lane.

[0014] In another technical solution of the present invention, the control unit is configured to, under a condition where the issuance of an alarm and the steering of a steering wheel are prohibited, lift the prohibition on the issuance of an alarm and the steering of a steering wheel when it is determined based on the position of the vehicle detected by a vehicle position detection device that the oblique shift of the vehicle relative to the lane has ended.

[0015] According to the above technical solution, when the alarm is prohibited and the steering of the steering wheel is prohibited, the prohibition of the alarm is lifted when it is determined that the vehicle has ended its oblique displacement relative to the lane based on the position of the vehicle detected by the vehicle position detection device. In this way, it is possible to prevent the alarm from being prohibited and the steering of the steering wheel from being prohibited unnecessarily, and to perform the necessary alarm and steering when there is a risk of the vehicle deviating from the lane.

[0016] In another aspect of the present invention, the control unit is configured to obtain information on the vehicle speed and variably set the reference steering torque according to the vehicle speed so that the reference steering torque is set smaller as the vehicle speed increases.

[0017] The higher the vehicle speed, the smaller the steering resistance when the steering wheel is turned by the driver's steering operation. According to the above technical solution, the reference steering torque is variably set according to the vehicle speed in a manner that the reference steering torque is set smaller as the vehicle speed increases. Thus, compared with the case where the reference steering torque is constant, it is possible to appropriately determine whether the driver intends to change the direction of travel of the vehicle regardless of the vehicle speed.

[0018] In one technical solution of the present invention, the control unit is configured to obtain vehicle speed information, estimate the vehicle's moving speed in a direction perpendicular to the lane based on the vehicle speed and the position of the vehicle detected by a vehicle position detection device, and determine whether the vehicle is moving obliquely relative to the lane based on at least one of the moving speed and the time rate of change of the moving speed.

[0019] According to the above technical solution, the moving speed of the vehicle in the direction perpendicular to the lane is estimated based on the position and speed of the vehicle, and whether the vehicle is moving obliquely with respect to the lane is determined based on at least one of the moving speed and the time rate of change of the moving speed. Thus, for example, compared with the case where whether the vehicle is moving obliquely with respect to the lane is determined based on changes in image information in front of the vehicle obtained by a camera, etc., it is possible to easily and accurately determine whether the vehicle is moving obliquely with respect to the lane.

[0020] Furthermore, in another aspect of the present invention, the control unit is configured to determine that the vehicle is obliquely shifting relative to the lane when a linear sum of the moving speed and the time change rate of the moving speed is equal to or greater than an oblique shift start reference value.

[0021] According to the above technical solution, when the linear sum of the moving speed and the time change rate of the moving speed is greater than the starting reference value of the slanting, it is determined that the vehicle is slanting relative to the lane. Thus, compared with the case where the slanting relative to the lane is determined based on either the moving speed or the time change rate of the moving speed, it is possible to appropriately determine whether the vehicle is slanting relative to the lane.

[0022] Furthermore, in another aspect of the present invention, the control unit is configured to variably set the tilt start reference value according to the vehicle speed so as to be larger as the vehicle speed is higher.

[0023] Even if the degree of the vehicle's tilt is the same, the higher the vehicle speed, the greater the linear sum of the moving speed and the time rate of change of the moving speed. According to the above technical solution, the tilt start reference value is variably set according to the vehicle speed in such a way that it is set larger as the vehicle speed increases. As a result, compared with the case where the tilt start reference value is a constant, it is possible to appropriately determine whether the vehicle is tilting relative to the lane regardless of the vehicle speed.

[0024] Furthermore, in another technical solution of the present invention, the control unit is configured to determine that the vehicle's oblique shift relative to the lane has ended when the linear sum of the moving speed and the time rate of change of the moving speed becomes below a reference value for the end of oblique shift when the issuance of an alarm and the steering of the steering wheel are prohibited.

[0025] According to the above technical solution, when the issuance of an alarm and the steering of the steering wheel are prohibited, when the linear sum of the moving speed and the time change rate of the moving speed becomes less than the slant end reference value, it is determined that the slant movement of the vehicle with respect to the lane has been completed. Therefore, compared with the case where the slant movement of the vehicle with respect to the lane is determined based on either the moving speed or the time change rate of the moving speed, it is possible to appropriately determine whether the slant movement of the vehicle with respect to the lane has been completed.

[0026] Furthermore, in another aspect of the present invention, the control unit is configured to variably set the tilt shift end reference value according to the vehicle speed so as to be larger as the vehicle speed is higher.

[0027] As described above, even if the degree of the vehicle's tilt is the same, the higher the vehicle speed, the greater the linear sum of the moving speed and the time rate of change of the moving speed. According to the above technical solution, the tilt end reference value is variably set according to the vehicle speed in such a manner that it is set larger as the vehicle speed increases. Thus, compared with the case where the tilt end reference value is a constant, it is possible to appropriately determine whether the vehicle's tilt relative to the lane has ended regardless of the vehicle speed.

[0028] Furthermore, in another technical solution of the present invention, the control unit is configured to, under a condition where the issuance of an alarm and the steering of the steering wheel are prohibited, determine that the oblique shift of the vehicle relative to the lane has ended when it is determined that the vehicle is traveling along the lane based on the position of the vehicle detected by the vehicle position detection device.

[0029] According to the above technical solution, when the vehicle is determined to be traveling along the lane in a condition where the issuance of an alarm and the steering of the steering wheel are prohibited, it is determined that the vehicle has completed the oblique movement relative to the lane. Thus, for example, compared with the case where the oblique movement of the vehicle relative to the lane is determined to be completed when the linear sum of the moving speed and the time rate of change of the moving speed becomes less than the oblique movement completion reference value, the timing of lifting the prohibition of the issuance of an alarm and the prohibition of the steering wheel can be delayed.

[0030] Furthermore, in another technical solution of the present invention, the lane departure prevention device also includes an obstacle detection device for detecting obstacles in front of the vehicle, and the control unit is configured such that, under a condition in which the issuance of an alarm and the steering of the steering wheel are prohibited, when an obstacle is detected in front of the vehicle by the obstacle detection device, even if it is determined based on the position of the vehicle detected by the vehicle position detection device that the oblique shift of the vehicle relative to the lane has ended, the prohibition of the issuance of the alarm and the prohibition of the steering wheel are not lifted.

[0031] According to the above technical solution, when an obstacle is detected in front of the vehicle under the condition that the alarm is prohibited and the steering of the steering wheel is prohibited, even if it is determined that the vehicle has completed its oblique shift relative to the lane, the prohibition of the alarm is not lifted. This can prevent the driver from being annoyed by the alarm and / or the steering of the steering wheel when the prohibition of the alarm is lifted while the driver is driving to avoid the obstacle in front of the vehicle based on his own will.

[0032] Furthermore, in another technical solution of the present invention, the lane departure prevention device also includes an obstacle detection device for detecting obstacles in front of the vehicle, and the control unit is configured to, under a condition where the issuance of an alarm and the steering of the steering wheel are prohibited, when an obstacle is detected in front of the vehicle by the obstacle detection device, the prohibition of the issuance of the alarm and the prohibition of the steering wheel are not lifted from the time when the oblique displacement of the vehicle relative to the lane is determined to have ended based on the position of the vehicle detected by the vehicle position detection device until a time period exceeding a reference time has passed.

[0033] According to the above technical solution, in a situation where the alarm is prohibited and the steering of the steering wheel is prohibited, when an obstacle is detected in front of the vehicle, the prohibition of the alarm and the steering of the steering wheel is not lifted from the time when it is determined that the vehicle has completed the oblique displacement relative to the lane until a time greater than the reference time has passed. As a result, in a situation where the vehicle is traveling to avoid an obstacle (obstacle avoidance), the alarm can be effectively prohibited from being issued and the steering of the steering wheel from the time when it is determined that the vehicle has completed the oblique displacement relative to the lane until a time greater than the reference time has passed.

[0034] Furthermore, in another aspect of the present invention, the control unit is configured to obtain information on the vehicle speed and to variably set the reference time in accordance with the vehicle speed so that the reference time is set shorter as the vehicle speed increases.

[0035] When a vehicle avoids an obstacle, the vehicle will move diagonally to bypass the obstacle, move along the lane, and then move diagonally to return to the original lane. The higher the vehicle speed, the shorter the time required for the vehicle to return to the original lane after completing the diagonal movement and moving along the lane.

[0036] According to the above technical solution, the reference time is variably set according to the vehicle speed so that it is set shorter as the vehicle speed increases. Therefore, compared with the case where the reference time is constant, it is possible to appropriately determine whether the lane departure prevention prohibition should be maintained regardless of the vehicle speed.

[0037] Furthermore, in another technical solution of the present invention, the control unit is configured to, when it is determined that the vehicle has changed lanes based on the position of the vehicle detected by the vehicle position detection device, prohibit the issuance of an alarm and the prohibition on the steering of the steering wheel, even if a time greater than a reference time has not elapsed since it was determined that the oblique shift of the vehicle relative to the lane has ended.

[0038] According to the above technical solution, when it is determined that the vehicle has changed lanes, even if the time not exceeding the reference time has passed since it is determined that the vehicle has ended its oblique movement relative to the lane, the prohibition of issuing the alarm and the prohibition of turning the steering wheel are cancelled. Thus, when the oblique movement of the vehicle relative to the lane ends, such as when the vehicle changes lanes to avoid an obstacle, the prohibition of issuing the alarm and the prohibition of turning the steering wheel can be cancelled, thereby avoiding the prohibition of issuing the alarm and the prohibition of turning the steering wheel for an unnecessary long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Hereinafter, features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which like reference numerals represent like elements, and wherein:

[0040] Figure 1 It is a schematic diagram showing the configuration of a lane departure prevention device according to an embodiment of the present invention.

[0041] Figure 2 1 is a flowchart showing a lane departure prevention control routine in the first embodiment.

[0042] Figure 3 1 is a flowchart showing a control routine for warning and prohibition of steering in the first embodiment.

[0043] Figure 4 1 is a flowchart showing a main part of a control routine for warning and prohibition of steering in the second embodiment.

[0044] Figure 5 1 is a flowchart showing a main part of a control routine for warning and prohibition of steering in the third embodiment.

[0045] Figure 6 This is a flowchart showing a main part of a control routine for warning and prohibition of steering in a modification of the third embodiment.

[0046] Figure 7 This is a diagram for showing the key points of calculating the moving speed Vy of the vehicle in the direction perpendicular to the longitudinal direction of the lane.

[0047] Figure 8 : This is a diagram showing the relationship between the vehicle speed V and the tilt start reference value Vys.

[0048] Fig. 9 It is a diagram showing the relationship between the vehicle speed V and the reference steering torque Tsc.

[0049] Fig.10 2 is a diagram showing the relationship between the vehicle speed V and the tilt shift end reference value Vye.

[0050] Fig.11 It is a diagram showing the relationship between the vehicle speed V and the reference time Tpc.

[0051] Fig.12 This is a diagram showing an operation example of the first embodiment when a vehicle changes lanes.

[0052] Fig.13 This is a diagram showing an operation example of the first embodiment in a case where the vehicle overtakes the preceding vehicle (the preceding vehicle).

[0053] Fig.14 This is a diagram showing an operation example of the first embodiment when the vehicle avoids an obstacle. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0055] [First embodiment]

[0056] like Figure 1 As shown, the lane departure prevention device 10 according to the embodiment includes a CCD camera 12, an alarm device 14, and an electronic control unit for lane departure prevention (hereinafter referred to as "the lane departure prevention ECU") 16 as a control unit for controlling the alarm device and a steering device described later. The CCD camera 12 functions as an information acquisition device, which is a part of the vehicle position detection device, and the image information in front of the vehicle 18 acquired by the CCD camera 12 is input to the lane departure prevention ECU 16. In addition, a signal indicating the vehicle speed V is input to the lane departure prevention ECU 16 from the vehicle speed sensor 20, and a signal indicating the steering torque Ts is input to the lane departure prevention ECU 16 from the electronic control unit for electric power steering (hereinafter referred to as "the EPS ECU") 22.

[0057] In the illustrated embodiment, the information acquisition device is a CCD camera 12, but the information acquisition device may be other cameras known in the art such as a CMOS camera as long as it can acquire image information in front of the vehicle 18. In addition, the alarm device 14 may be any one of an alarm device that issues a visual alarm such as an alarm light, an alarm device that issues an auditory alarm such as an alarm buzzer, and an alarm device that issues a physical alarm such as seat vibration, or any combination thereof.

[0058] As will be described in detail later, the deviation prevention ECU 16 determines the lane based on the image information in front of the vehicle 18 obtained by the CCD camera 12, and determines the positional relationship of the vehicle 18 relative to the lane. Thus, the CCD camera 12 and the deviation prevention ECU 16 cooperate with each other to function as a vehicle position detection device that detects the position of the vehicle 18 relative to the lane. Furthermore, the deviation prevention ECU 16 performs lane departure prevention control: based on the determined positional relationship, it determines whether the vehicle 18 is likely to deviate from the lane according to the principles known in the technical field, and when it is determined that there is a risk of deviation, an alarm is issued by operating the alarm device 14. This lane departure prevention control is also called LDA (Lane Departure Alert) control.

[0059] like Figure 1 As shown, a torque sensor 28 for detecting a steering torque Ts is provided on a steering shaft 26 integrally connected to a steering wheel 24 operated by a driver. A signal indicating the steering torque Ts detected by the torque sensor 28 is input to an EPS ECU 22. The EPS ECU 22 controls an electric power steering device (hereinafter referred to as "EPS") 30 in accordance with a method known in the art based on the steering torque Ts and the vehicle speed V detected by the vehicle speed sensor 20, thereby controlling the steering assist torque.

[0060] The EPS ECU 22 can steer the steering wheel 32 as needed by controlling the EPS 30. Thus, the EPS ECU 22 and the EPS 30 constitute a steering device 34 that automatically steers the steering wheel 32 as needed. When the lane departure prevention device 10 determines that the vehicle 18 is likely to deviate from the lane, it performs lane departure prevention control by steering the steering wheel. The lane departure prevention control based on the steering of the steering wheel 32 can be, for example, any LKA (Lane Keeping Assist) control known in the technical field.

[0061] In addition, although not Figure 1 Although shown in detail in the figure, the deviation prevention ECU 16 and the EPS ECU 22 each include a microcomputer and a drive circuit, and exchange (send and receive) the required information with each other. Each microcomputer has a CPU, ROM, RAM, and an input / output port device, and has a general structure in which these parts are interconnected through a bidirectional common bus.

[0062] In particular, the ROM of the deviation prevention ECU 16 stores Figure 2 The lane departure prevention control procedure corresponding to the flowchart shown in FIG. Figure 3The flowchart shown in the figure corresponds to the alarm and steering prohibition control program. The CPU of the deviation prevention ECU 16 is respectively Figure 2 and Figure 3 The flowchart shown performs lane departure prevention control and prohibition control of warning and steering.

[0063] As described in detail later, the lane departure prevention device 10 determines whether the vehicle is shifting obliquely relative to the lane based on the image information in front of the vehicle 18 obtained by the CCD camera 12. When the lane departure prevention device 10 determines that the vehicle is shifting obliquely relative to the lane and determines that the absolute value of the steering torque Ts detected by the torque sensor 28 is greater than the reference steering torque Tsc, it starts to prohibit the issuance of an alarm and prohibit the steering of the steering wheel. Furthermore, when the lane departure prevention device 10 determines that the oblique shift of the vehicle relative to the lane has ended based on the image information obtained by the CCD camera 12, the prohibition of the issuance of an alarm and the prohibition of the steering of the steering wheel are released in the condition where the issuance of an alarm and the steering of the steering wheel are prohibited.

[0064] Next, refer to Figure 2 The flowchart shown in FIG. 1 is used to explain the lane departure prevention control routine in the first embodiment. Figure 2 The control flow chart shown is not in Figure 1 The CPU of the deviation prevention ECU 16 repeatedly executes the operation at a predetermined time when the ignition switch is turned on as shown in FIG.

[0065] First, in step S210 , the CPU reads in a signal or the like indicating image information in front of the vehicle 18 detected by the CCD camera 12 .

[0066] In step S220, the CPU determines the lane based on the image information in front of the vehicle 18, and determines whether the vehicle is in danger of deviating from the lane according to a method known in the art based on the change in the positional relationship of the vehicle 18 relative to the lane. The CPU advances the lane departure prevention control to step S250 when a negative determination is made, and advances the lane departure prevention control to step S230 when a positive determination is made.

[0067] In step S230, the CPU determines whether the lane departure prevention prohibition flag Fa is 1, that is, whether the alarm is prohibited and the steering wheel is prohibited. When the CPU makes a positive determination, that is, when it determines that the flag Fa is 1, the lane departure prevention control proceeds to step S250. When the CPU makes a negative determination, in step S240, the alarm is activated by activating the alarm device 14 and the steering wheel is turned. In addition, the flag Fa is set when the lane departure prevention control starts, that is, when it is not set. Figure 1 The ignition switch shown in FIG. 1 is initialized to 0 when it is switched from OFF to ON, and then, as described later, Figure 3 The flowchart shown is set to 0 or 1.

[0068] In step S250, the CPU stops the alarm device 14 when it is activated, stops steering the steering wheel, and then temporarily terminates the lane departure prevention control. The CPU temporarily terminates the lane departure prevention control when the alarm device 14 is not activated and the steering wheel is not turned.

[0069] Next, refer to Figure 3 The flowchart shown in FIG. 1 is used to explain the alarm and steering inhibition control routine in the first embodiment. Figure 3 The control flow chart shown is also not in Figure 1 When the ignition switch shown in FIG. is turned on, the CPU of the deviation prevention ECU 16 is repeatedly executed at a predetermined time. In addition, in the following description, the prohibition control of the alarm and the steering is simply referred to as "control". This is also the same for the prohibition control routines of the alarm and the steering in other embodiments described later.

[0070] First, in step S310 , the CPU reads in a signal or the like indicating image information in front of the vehicle 18 detected by the CCD camera 12 .

[0071] In step S320, the CPU determines the lane based on the image information in front of the vehicle 18 and determines whether the vehicle 18 is moving obliquely relative to the lane. The CPU temporarily ends the control when a negative determination is made, and advances the control to step S330 when a positive determination is made.

[0072] In this case, the determination of whether the vehicle 18 is shifting obliquely relative to the lane can be performed, for example, in the following manner. Figure 7 As shown, based on the image information in front of the vehicle 18, the angle θ between the traveling direction 54 of the vehicle 18 and the longitudinal direction 52 of the lane 50 is estimated. When the traveling direction 54 of the vehicle 18 is on the left side relative to the longitudinal direction 52 of the lane 50, the angle θ is a positive value. Based on the angle θ and the vehicle speed V, the moving speed Vy of the vehicle 18 in the direction perpendicular to the longitudinal direction 52 of the lane 50 is estimated as Vsinθ. With Ka and Kb as positive constant coefficients, when the absolute value |KaVy+KbdVy| of the linear sum of the moving speed Vy and its time change rate dVy is greater than the oblique shift start reference value Vys, it is determined that the vehicle 18 is obliquely shifting relative to the lane.

[0073] Furthermore, even if the degree of the tilt of the vehicle 18 is the same, the higher the vehicle speed V, the greater the absolute value of the linear sum |KaVy+KbdVy|. Therefore, although the tilt start reference value Vys may also be a positive constant, in the first embodiment and other embodiments described below, Figure 8 As shown, the bank shift start reference value Vys is variably set according to the vehicle speed so as to be larger as the vehicle speed V is higher. Therefore, compared with the case where the bank shift start reference value Vys is constant, it is possible to appropriately determine whether the vehicle 18 is banked relative to the lane regardless of the vehicle speed.

[0074] In step S330, the CPU determines whether the absolute value of the steering torque Ts is greater than or equal to the reference steering torque Tsc, thereby determining whether the driver intends to change the direction of the vehicle. If the CPU makes an affirmative determination, the control proceeds to step S350, and if the CPU makes a negative determination, the control proceeds to step S340.

[0075] In addition, the higher the vehicle speed V, the smaller the steering resistance when the steering wheel is turned by the driver's steering operation. Therefore, although the reference steering torque Tsc can also be a positive constant, in the first embodiment and other embodiments described later, Fig. 9 As shown, the reference steering torque Tsc is variably set according to the vehicle speed so as to be smaller as the vehicle speed V increases. Therefore, compared with a case where the reference steering torque Tsc is constant, it is possible to appropriately determine whether the driver intends to change the direction of travel of the vehicle regardless of the vehicle speed.

[0076] In step S340, the CPU determines whether the vehicle 18 is traveling along the lane, i.e., whether the vehicle 18 has completed the diagonal shift and returned to the normal driving state, based on the image information in front of the vehicle 18. If the CPU makes a negative determination, the control returns to step S330, and if the CPU makes an affirmative determination, the control is temporarily terminated.

[0077] In step S350, the CPU sets the flag Fa to 1 to prohibit lane departure prevention, so that issuance of an alarm and steering of the steering wheel are prohibited.

[0078] In step S360, the CPU performs the same determination as in step S340. When the CPU makes a negative determination, that is, when it determines that the vehicle 18 is not traveling along the lane, the control returns to step S350. On the other hand, when the CPU makes a positive determination, that is, when it determines that the vehicle 18 is traveling along the lane, in step S370, the flag Fa is reset to 0, the prohibition of issuing an alarm and the prohibition of steering the steering wheel are cancelled, and lane departure prevention is allowed.

[0079] [Second Embodiment]

[0080] In the second embodiment, the lane departure prevention control is performed in the same manner as in the first embodiment. Figure 2 The flowchart shown in the figure is executed, and the warning and steering inhibition control are performed according to Figure 4Execute the flowchart shown.

[0081] In addition, although not Figure 4 , but steps S310 and S320 are respectively executed in the same manner as steps S310 and S320 of the first embodiment, and step S322 is executed when a positive determination is made in step S320. In addition, steps S330, S350, and S370 are respectively executed in the same manner as steps S330, S350, and S370 of the first embodiment. Therefore, the description of these steps is omitted.

[0082] In step S322, the CPU determines whether the flag Fo indicating the presence or absence of an obstacle is 1, that is, whether it is determined in step S324 described later that an obstacle exists in front of the vehicle 18. When the CPU makes a positive determination, that is, when it determines that the flag Fo is 1, the control proceeds to step S330, and when it makes a negative determination, the control proceeds to step S324. In addition, the flag Fo is set when the warning and steering prohibition control are started, that is, when it is not in Figure 1 When the ignition switch shown in FIG. 1 is switched from OFF to ON, it is initialized to 0, and then, as described later, Figure 4 The flowchart shown is set to 0 or 1.

[0083] In step S324, the CPU determines whether there is an obstacle in front of the vehicle 18 based on the image information in front of the vehicle 18 detected by the CCD camera 12. Thus, the CCD camera 12 and the deviation prevention ECU 16 cooperate with each other to function as an obstacle detection device for detecting obstacles in front of the vehicle 18. When the CPU makes a negative determination, the control proceeds to step S330, and when the CPU makes an affirmative determination, that is, when it is determined that there is an obstacle in front of the vehicle 18, the flag Fo is set to 1 in step S326.

[0084] Furthermore, obstacles are a concept that includes not only objects such as parked vehicles and fallen objects but also living things such as pedestrians and wild animals, and means objects that would hinder the travel of the vehicle if evasive steering is not performed.

[0085] In step S340, the CPU determines the lane based on the image information in front of the vehicle 18, and determines whether the oblique shift of the vehicle 18 relative to the lane has been completed. When the CPU makes a negative determination, the control returns to step S322, and when the CPU makes an affirmative determination, the flag Fo is reset to 0 in step S342, and then the control is temporarily terminated.

[0086] In step S360 executed immediately after step S350, similarly to step S340, the CPU determines the lane based on the image information in front of the vehicle 18, and determines whether the oblique displacement of the vehicle 18 relative to the lane has been completed. The CPU returns control to step S350 when a negative determination is made, and advances control to step S362 when an affirmative determination is made.

[0087] The determination of whether the oblique displacement of the vehicle 18 relative to the lane has been completed in steps S340 and S360 can be performed, for example, in the following manner. First, the absolute value of the linear sum of the moving speed Vy and its time change rate dVy |KaVy+KbdVy| is calculated as in the case of the above-mentioned step S330. Furthermore, when the absolute value of the linear sum |KaVy+KbdVy| is less than the oblique displacement completion reference value Vye, it is determined that the oblique displacement of the vehicle 18 relative to the lane has been completed.

[0088] Furthermore, as described above, even if the degree of the tilt of the vehicle 18 is the same, the higher the vehicle speed V, the greater the absolute value of the linear sum |KaVy+KbdVy|. Therefore, although the tilt end reference value Vye may also be a positive constant, in the second embodiment and the third embodiment described later, Fig.10 As shown, the bank shift end reference value Vye is variably set according to the vehicle speed so as to be larger as the vehicle speed V is higher. Therefore, compared with the case where the bank shift end reference value Vye is constant, it is possible to appropriately determine whether the bank shift of the vehicle 18 relative to the lane is completed regardless of the vehicle speed.

[0089] In step S362, the CPU determines whether the flag Fo is 1, that is, whether it is determined in step S324 that there is an obstacle in front of the vehicle 18. The CPU advances control to step S370 when the determination is negative, and advances control to step S364 when the determination is positive.

[0090] In step S364, the CPU determines whether the vehicle 18 is traveling along the lane, that is, whether it has returned to a normal driving state, based on the image information in front of the vehicle 18. When the CPU makes a negative determination, the control returns to step S350. When the CPU makes an affirmative determination, in step S370, the flag Fa is reset to 0 to cancel the prohibition of issuing an alarm and the prohibition of steering the steering wheel, and the flag Fo is reset to 0.

[0091] [Third Embodiment]

[0092] In the third embodiment, the lane departure prevention control is performed in the same manner as in the first embodiment. Figure 2 The flowchart shown in the figure is executed, and the warning and steering inhibition control are performed according to Figure 5 Execute the flowchart shown.

[0093] In addition, although not Figure 5 , but steps S310 and S320 are respectively executed in the same manner as steps S310 and S320 of the first embodiment, and step S322 is executed when a positive determination is made in step S320. In addition, steps S322 to S362 and step S370 are respectively executed in the same manner as steps S322 to S362 and step S370 of the second embodiment. Therefore, the description of these steps is omitted.

[0094] When the CPU makes an affirmative determination in step S362, the control proceeds to step S364. In step S364, the CPU determines whether the elapsed time Tp from the time when the vehicle 18 is determined in step S360 to have completed the oblique displacement relative to the lane is greater than the reference time Tpc. When the CPU makes a negative determination, the control returns to step S350, and when the CPU makes an affirmative determination, the control proceeds to step S370.

[0095] Furthermore, when the vehicle 18 avoids an obstacle, the vehicle will move diagonally to bypass the obstacle, thereby ending the diagonal movement and moving along the lane, and then moving diagonally to return to the original lane. The higher the vehicle speed V, the shorter the time required for the vehicle to return to the original lane after ending the diagonal movement and moving along the lane. Therefore, although the reference time Tpc can be a positive constant, in the third embodiment and the modified example of the third embodiment described later, as Fig.11 As shown, the reference time Tpc is variably set according to the vehicle speed so as to be set smaller as the vehicle speed V increases. Therefore, compared with the case where the reference time Tpc is constant, it is possible to appropriately determine whether the lane departure prevention prohibition should be maintained regardless of the vehicle speed.

[0096] [Modification of the Third Embodiment]

[0097] In this modification, the control for prohibiting lane departure prevention is performed according to Figure 6 In addition, although not in Figure 6 However, steps S310 to S362 and step S370 are respectively performed in the same manner as S310 to S362 and step S370 of the third embodiment.

[0098] In step S364, when the CPU makes an affirmative determination, the control proceeds to step S370, and when the CPU makes a negative determination, the control proceeds to step S366.

[0099] In step S366, the CPU determines whether the vehicle 18 has changed lanes. If the CPU makes a negative determination, the control returns to step S350, and if the CPU makes an affirmative determination, the control proceeds to step S370. In addition, the determination of whether the vehicle has changed lanes can be performed in any manner known in the art.

[0100] According to the above-mentioned embodiments and modifications, when the vehicle is in danger (probability) of deviating from the lane, Figure 2 In step S220 of the flowchart shown in the figure, an affirmative determination is made. When the warning and steering prohibition flag Fa is 0, a negative determination is made in step S230, and in step S240, a warning is issued and the steering wheel is turned.

[0101] On the other hand, when the warning and steering prohibition flag Fa is 1, an affirmative determination is made in step S230, and in step S250, the warning device 14 is not operated to issue a warning, and the steering wheel is not turned.

[0102] Warning and turn prohibition signs Fa are based on Figure 3 The flag Fa is set to 1 or 0 according to the control of the flowchart shown in FIG. 1. The flag Fa is set to 1 when an affirmative determination is made in steps S320 and S330, that is, when it is determined that the vehicle 18 is shifting obliquely relative to the lane and when it is determined that the absolute value of the steering torque Ts is greater than or equal to the reference steering torque Tsc.

[0103] According to the above-mentioned embodiments and modifications, when it is determined that the vehicle 18 is shifting obliquely relative to the lane and when it is determined that the absolute value of the steering torque Ts is greater than the reference steering torque Tsc, the issuance of an alarm and the steering of the steering wheel are prohibited. Thus, it is possible to determine whether the driver is about to deviate from the lane based on his own will before the risk of the vehicle 18 deviating from the lane occurs. Therefore, since it is possible to determine the driver's intention to deviate from the lane and prohibit the issuance of an alarm and the steering of the steering wheel before the risk of the vehicle deviating from the lane is detected, it is possible to prevent the driver from being annoyed by the alarm and the steering when the driver deviates from the lane based on his own will.

[0104] In addition, when the vehicle 18 deviates from the lane due to the driver's inattention, even if the vehicle is diagonally shifted relative to the lane, the steering torque will not become a large value. Therefore, even if it is determined that the vehicle is diagonally shifting relative to the lane, since the absolute value of the steering torque Ts is not determined to be greater than the reference steering torque Tsc, the issuance of the alarm and the prohibition of the steering wheel will not be started. Therefore, the alarm device can be operated to issue an alarm, thereby calling the driver's attention, or the vehicle can be prevented from deviating from the lane by turning the steering wheel.

[0105] As described above, in the conventional lane departure prevention device described in the above-mentioned publication, even if the possibility of the vehicle deviating from the lane is detected, if a sudden steering operation by the driver is detected, an alarm and the steering of the steering wheel are restrained. Therefore, according to the setting of the threshold value for detecting the sudden steering operation, the sudden steering operation is detected when the vehicle is traveling in a curve, so even if the vehicle is likely to deviate from the lane when the vehicle is traveling in a curve, it is impossible to call the driver's attention through an alarm and prevent the vehicle from deviating from the lane by steering the steering wheel.

[0106] According to the above-mentioned embodiments and modifications, when it is determined that the vehicle is shifting obliquely relative to the lane and the absolute value of the steering torque Ts is determined to be greater than the reference steering torque Tsc, the issuance of an alarm and the prohibition of steering the steering wheel are started. Therefore, when the vehicle deviates from the lane to the outside of the curve while traveling in a curve, it is not determined that the steering torque is greater than the reference steering torque, and the issuance of an alarm and the prohibition of steering the steering wheel are not started. As a result, an alarm that calls attention to the danger of the vehicle deviating from the lane can be issued and the steering wheel can be turned.

[0107] In addition, according to the above-mentioned embodiments and modifications, when the operation of the alarm device 14 is prohibited, when it is determined that the oblique displacement of the vehicle 18 relative to the lane has ended (step S360), the prohibition of the operation of the alarm device 14 is released (step S370). This prevents the operation of the alarm device from being prohibited from continuing unnecessarily, and when there is a risk that the vehicle 18 will deviate from the lane, a necessary alarm is issued.

[0108] Furthermore, according to the above-mentioned embodiments and modifications, the moving speed Vy of the vehicle 18 in the direction perpendicular to the lane is estimated, and when the absolute value of the linear sum of the moving speed Vy and its time change rate dVy |KaVy+KbdVy| is greater than the tilt start reference value Vys, it is determined that the vehicle is tilting relative to the lane. Thus, compared with the case where the tilting of the vehicle relative to the lane is determined based on either the moving speed Vy or its time change rate dVy, it is possible to appropriately determine whether the vehicle is tilting relative to the lane.

[0109] Furthermore, according to the above-mentioned embodiments and modifications, when the issuance of the alarm and the steering of the steering wheel are prohibited, when the absolute value of the linear sum of the moving speed Vy and its time change rate dVy |KaVy+KbdVy| becomes less than the oblique movement end reference value Vye, it is determined that the oblique movement of the vehicle with respect to the lane has ended. As a result, compared with the case where the end of the oblique movement of the vehicle with respect to the lane is determined based on either the moving speed Vy or its time change rate dVy, it is possible to appropriately determine whether the oblique movement of the vehicle with respect to the lane has ended.

[0110] Next, as specific examples of the operations of the above-described embodiments and modifications, a case where the vehicle 18 changes lanes and a case where the vehicle 18 overtakes a preceding vehicle will be described.

[0111] <Lane Change>

[0112] like Fig.12 As shown, from the state where the vehicle 18 is traveling along the lane 50 (P11), in response to the steering operation of the driver, the vehicle 18 begins to shift obliquely relative to the lane 50 (P12), and the front end of the vehicle 18 moves toward the adjacent lane 58 (P13). Furthermore, the main part of the vehicle 18 moves toward the adjacent lane 58 (P14), and the angle formed by the longitudinal direction of the vehicle 18 with respect to the direction of the lane 58 becomes very small (P15), and the vehicle 18 enters the state where it is traveling along the lane 58 (P16).

[0113] For example, when the vehicle 18 changes to the state of P12, an affirmative determination is made in steps S320 and S330, and the flag Fa is set to 1 in step S350 to start prohibiting the issuance of an alarm and prohibiting the turning of the steering wheel. In addition, when the state of the vehicle 18 changes to P15 or P16, an affirmative determination is made in step S360 or steps S360 and S364, and the flag Fa is reset to 0 in step S350 to cancel the prohibition of the issuance of an alarm and the prohibition of the turning of the steering wheel.

[0114] Thus, since the flag Fa is set to 1 from the state P12 to the state P15 or P16, even if it is determined after the state P12 that the vehicle 18 is in danger of deviating from the lane 50, no alarm is issued and the steering wheel is not turned. Therefore, it is possible to prevent the driver from being annoyed by the alarm and / or the steering when changing lanes on his own accord.

[0115] <Overtaking>

[0116] like Fig.13 As shown, the following case is described: in the lane 50 where the vehicle 18 is traveling, there is a preceding vehicle 60 traveling at a low speed in front of the vehicle 18 , and the vehicle 18 catches up with and overtakes the preceding vehicle 60 via the adjacent lane 58 .

[0117] From the state where the vehicle 18 is traveling along the lane 50 (P21), in response to the steering operation of the driver, the vehicle 18 begins to shift obliquely relative to the lane 50 (P22), and the front end of the vehicle 18 moves toward the adjacent lane 58 (P23). Furthermore, the vehicle 18 moves toward the adjacent lane 58, and the angle formed by the longitudinal direction of the vehicle 18 with respect to the direction of the lane 58 becomes extremely small (P24), and the vehicle 18 enters a state where it is traveling along the lane 58 (P25). Furthermore, the vehicle 18 begins to shift obliquely relative to the lane 58 (P26), and the front end of the vehicle 18 moves toward the original lane 50 (P27), and the angle formed by the longitudinal direction of the vehicle 18 with respect to the direction of the lane 50 becomes extremely small (P28), and the vehicle 18 enters a state where it is traveling along the lane 50 (P29).

[0118] For example, when the vehicle 18 changes to the state of P22, an affirmative determination is made in steps S320 and S330, thereby setting the flag Fa to 1 in step S350, and starting to prohibit the issuance of an alarm and prohibiting the turning of the steering wheel. In addition, when the state of the vehicle 18 changes to P24, an affirmative determination is made in step S360 or steps S360 and S364, thereby resetting the flag Fa to 0 in step S350, and canceling the prohibition of issuing an alarm and prohibiting the turning of the steering wheel.

[0119] In addition, when the vehicle 18 changes to the state of P26, an affirmative determination is made in steps S320 and S330, thereby setting the flag Fa to 1 in step S350, and starting to prohibit the issuance of the alarm and the prohibition of turning the steering wheel. Furthermore, when the vehicle 18 changes to the state of P15 or P16, an affirmative determination is made in step S360 or steps S360 and S364, thereby resetting the flag Fa to 0 in step S350, and canceling the prohibition of issuing the alarm and the prohibition of turning the steering wheel.

[0120] Thus, from state P22 to state P24 and from state P26 to state P28, the flag Fa is set to 1, and therefore, even if it is determined that the vehicle 18 is in danger of deviating from the lane 50 in these intervals, no alarm is issued and the steering wheel is not turned. Therefore, it is possible to prevent the driver from being annoyed by the alarm and / or the steering when he / she wants to overtake the vehicle ahead by his / her own will.

[0121] Furthermore, although the flag Fa is reset to 0 from the state P24 to the state P26, it is not determined that the vehicle 18 is in danger of deviating from the lane 50 in this section. Therefore, the driver will not feel annoyed by the warning and / or the steering in this section.

[0122] In particular, in the first embodiment, when the issuance of the alarm and the steering of the steering wheel are prohibited, when it is determined that the vehicle is traveling along the lane, it is determined that the oblique displacement of the vehicle relative to the lane has been completed. Therefore, according to the first embodiment, for example, compared with the case where the oblique displacement of the vehicle relative to the lane is determined to have been completed when the absolute value |KaVy+KbdVy| of the linear and becomes less than the oblique displacement completion reference value Vye, the timing of releasing the alarm prohibition can be delayed.

[0123] In addition, in the second embodiment, when an obstacle is detected in front of the vehicle under the condition that the issuance of the alarm and the steering of the steering wheel are prohibited, even if it is determined that the vehicle has completed its oblique displacement with respect to the lane, the prohibition of the issuance of the alarm and the prohibition of the steering wheel are not cancelled until it is determined that the vehicle is traveling along the lane. Thus, according to the second embodiment, it is possible to prevent the prohibition of the issuance of the alarm and the prohibition of the steering wheel from being cancelled while the driver is overtaking in front of the obstacle in front of the vehicle on his own will, thereby preventing the driver from being annoyed by the alarm and / or the steering.

[0124] Next, as a specific example of the operation of the second embodiment, a case where the vehicle 18 travels while avoiding the obstacle 60 on the lane will be described.

[0125] <Obstacle Avoidance>

[0126] like Fig.14 As shown, from the state where the vehicle 18 is traveling along the lane 50 (P31), in response to the steering operation of the driver, the vehicle 18 begins to shift obliquely relative to the lane 50 (P32), and the front end of the vehicle 18 moves toward the adjacent lane 58 (P33). Furthermore, the vehicle 18 travels along the two lanes in a state of straddling the lane 50 and the lane 58 (P34), and the front end of the vehicle 18 moves toward the original lane 50 (P35). Furthermore, the angle formed by the longitudinal direction of the vehicle 18 with respect to the direction of the lane 50 becomes very small (P36), and the vehicle 18 enters a state of traveling along the lane 50 (P37).

[0127] For example, when the vehicle 18 changes to the state of P32, an affirmative determination is made in steps S320 and S330, and thereby the flag Fa is set to 1 in step S350, and the issuance of the alarm and the prohibition of turning the steering wheel are prohibited. In addition, when the vehicle 18 changes to the state of P37, an affirmative determination is made in step S360, and thereby the flag Fa is reset to 0 in step S370, and the prohibition of issuing the alarm and the prohibition of turning the steering wheel are cancelled. In addition, in the interval from state P33 to state P35, the determination in step S360 will not become an affirmative determination.

[0128] Thus, from state P32 to state P37, the flag Fa is set to 1, so even if it is determined after state P32 that the vehicle 18 is in danger of deviating from the lane 50, no alarm is issued and the steering wheel is not turned. Therefore, it is possible to prevent the driver from being annoyed by the alarm and / or steering when the driver drives to avoid an obstacle based on his own will.

[0129] exist Fig.14 In FIG. 1 , range 62 indicates the imaging range of CCD camera 12. When vehicle 18 is in state P32, CCD camera 12 can image obstacle 60, but when the vehicle 18 advances to avoid obstacles as in state P33 and later, CCD camera 12 cannot image obstacle 60.

[0130] According to the second embodiment, if an obstacle is detected, a positive determination is made in step S324, and the driver performs a steering to avoid the obstacle, and a positive determination is made in step S330, step S324 is not executed, and only step S350 and subsequent steps are executed. Thus, once an obstacle is detected and the driver performs a steering to avoid the obstacle, it is determined that the vehicle is traveling along the lane regardless of whether the obstacle is detected, and the issuance of an alarm and the steering of the steering wheel are continuously prohibited until a positive determination is made in step S330. Therefore, the issuance of an alarm and the steering of the steering wheel can be effectively prohibited until the vehicle 18 completes the driving to avoid the obstacle.

[0131] Furthermore, in the third embodiment, when an obstacle is detected in front of the vehicle under a condition in which the issuance of an alarm and the turning of the steering wheel are prohibited, the prohibition of the issuance of an alarm and the prohibition of the turning of the steering wheel are not lifted from the time when it is determined that the vehicle has completed its oblique shift relative to the lane until a time greater than a reference time has passed. According to the third embodiment, when the vehicle 18 is traveling to avoid an obstacle, the issuance of an alarm and the turning of the steering wheel can be effectively prohibited from the time when it is determined that the vehicle has completed its oblique shift relative to the lane until a time greater than a reference time has passed.

[0132] Furthermore, in the modified example, when it is determined that the vehicle has changed lanes, even if the time not exceeding the reference time has elapsed since it was determined that the vehicle has ended its oblique movement relative to the lane, the prohibition of issuing the alarm and the prohibition of turning the steering wheel are cancelled. Thus, according to the modified example, when the oblique movement relative to the lane of the vehicle has ended, such as when the vehicle 18 changes lanes to avoid an obstacle, the prohibition of issuing the alarm and the prohibition of turning the steering wheel can be cancelled, thereby avoiding the prohibition of issuing the alarm and the steering wheel for an unnecessary long time.

[0133] The present invention has been described in detail above with respect to specific embodiments, but the present invention is not limited to the above-described embodiments, and it is obvious to those skilled in the art that various other embodiments can be implemented within the scope of the present invention.

[0134] For example, in each of the above-mentioned embodiments and modifications, when it is determined that the vehicle 18 is shifting obliquely relative to the lane 50 and when it is determined that the steering torque Ts is greater than the reference steering torque Tsc, the issuance of an alarm and the steering of the steering wheel are prohibited. However, the lane departure prevention device of the present invention may also be applied to a vehicle that performs only one of the issuance of an alarm and the steering of the steering wheel when it is determined that the vehicle is in danger of deviating from the lane. In this case, the issuance of an alarm and the steering of the steering wheel are prohibited.

[0135] In addition, in each of the above-mentioned embodiments and modified examples, when it is determined that the vehicle is in danger of deviating from the lane, the alarm is issued and the steering wheel is turned at the same time. However, it can be modified so that when it is determined that the vehicle is in danger of deviating from the lane, the alarm is first issued, and when it is determined that the danger of deviation is further increased, the steering wheel is turned.

[0136] For example, in each of the above-mentioned embodiments and modified examples, the vehicle position detection device for detecting the position of the vehicle 18 relative to the lane 50 is the CCD camera 12 and the deviation prevention ECU 16 that work in cooperation with each other. However, the position of the vehicle 18 relative to the lane 50 may also be determined based on a combination of road map information stored in the navigation device and the current location of the vehicle obtained by the GPS device. Furthermore, the position of the vehicle 18 relative to the lane 50 may also be determined based on the relationship between the track of the vehicle 18 and the track of the preceding vehicle, and when the deviation of the track of the vehicle 18 relative to the track is greater than the reference value, it is determined that the vehicle is moving obliquely.

[0137] In the above-mentioned embodiments and modifications, in step S320, it is determined whether the vehicle 18 is shifting obliquely relative to the lane based on whether the linear sum |KaVy+KbdVy| is greater than the shift start reference value Vys. However, it is also possible to determine whether the vehicle 18 is shifting obliquely relative to the lane based on one of the moving speed Vy and its time change rate dVy. Furthermore, the determination of whether the vehicle 18 is shifting obliquely relative to the lane may also be performed based on changes in image information in front of the vehicle 18 acquired by an information acquisition device such as the CCD camera 12.

[0138] In addition, in each of the above-mentioned embodiments and modifications, the vehicle speed V is detected by the vehicle speed sensor 20. However, the vehicle speed V may be acquired based on information supplied from a GPS device.

[0139] Furthermore, in each of the above-mentioned embodiments and modifications, the warning and the prohibition control of the steering ( Figure 3 ) is different from lane departure prevention control ( Figure 2 However, the lane departure prevention control may be modified to execute the warning and the routine of prohibiting the steering between steps S220 and S230.

[0140] Furthermore, the determinations of steps S340 and S360 in the above-mentioned first embodiments may be replaced by the determinations of steps S340 and S360 in the second embodiment, the third embodiment and the modified example, respectively.

Claims

1. A lane departure prevention device, comprising a vehicle position detection device for detecting a position of a vehicle relative to a lane, an alarm device, a steering device for turning a steering wheel, and a control unit for controlling the alarm device and the steering device, wherein the control unit is configured to, when it is determined that the vehicle is in danger of deviating from the lane based on the position of the vehicle detected by the vehicle position detection device, at least one of issuing an alarm by the alarm device and turning the steering wheel for preventing the vehicle from deviating from the lane, The lane departure prevention device further includes a steering torque detection device for detecting a steering torque. The control unit is configured to, when it is determined that the vehicle is shifting obliquely relative to a lane based on the position of the vehicle detected by the vehicle position detection device and when it is determined that the steering torque detected by the steering torque detection device is greater than a reference steering torque, start prohibiting the issuance of the alarm and prohibiting the steering of the steering wheel, The control unit is configured to obtain information on the vehicle speed, estimate the moving speed of the vehicle in a direction perpendicular to the lane based on the vehicle speed and the position of the vehicle detected by the vehicle position detection device, and determine whether the vehicle is moving obliquely with respect to the lane based on at least one of the moving speed and the time change rate of the moving speed. The control unit is configured to determine that the vehicle is obliquely shifting with respect to a lane when a linear sum of the moving speed and the time change rate of the moving speed is equal to or greater than an oblique shift start reference value.

2. The lane departure prevention device according to claim 1, The control unit is configured to, under a condition where the issuance of the alarm and the steering of the steering wheel are prohibited, cancel the prohibition of the issuance of the alarm and the prohibition of the steering of the steering wheel when it is determined based on the position of the vehicle detected by the vehicle position detection device that the oblique displacement of the vehicle relative to the lane has ended.

3. The lane departure prevention device according to claim 1 or 2, The control unit is configured to obtain information on the vehicle speed and variably set the reference steering torque according to the vehicle speed so that the reference steering torque is set smaller as the vehicle speed increases.

4. The lane departure prevention device according to claim 1, The control unit is configured to variably set the tilt start reference value according to the vehicle speed so that the tilt start reference value becomes larger as the vehicle speed becomes higher.

5. The lane departure prevention device according to claim 1 or 4, The control unit is configured to determine that the vehicle has completed tilting relative to the lane when a linear sum of the moving speed and the time rate of change of the moving speed becomes less than a tilting completion reference value when issuance of the alarm and steering of the steering wheel are prohibited.

6. The lane departure prevention device according to claim 5, The control unit is configured to variably set the tilt end reference value according to the vehicle speed so as to increase the tilt end reference value as the vehicle speed increases.

7. The lane departure prevention device according to claim 1 or 2, The control unit is configured to determine that the oblique shift of the vehicle relative to the lane has ended when it is determined that the vehicle is traveling along the lane based on the position of the vehicle detected by the vehicle position detection device under the condition that the issuance of the alarm and the steering of the steering wheel are prohibited.

8. The lane departure prevention device according to claim 1 or 2, Also includes an obstacle detection device for detecting obstacles in front of the vehicle, The control unit is configured such that, under a condition in which the issuance of the alarm and the steering of the steering wheel are prohibited, when an obstacle is detected in front of the vehicle by the obstacle detection device, the prohibition of the issuance of the alarm and the prohibition of the steering of the steering wheel are not lifted even if it is determined based on the position of the vehicle detected by the vehicle position detection device that the oblique shift of the vehicle relative to the lane has ended.

9. The lane departure prevention device according to claim 1, Also includes an obstacle detection device for detecting obstacles in front of the vehicle, The control unit is configured such that, under a condition in which the issuance of the alarm and the steering of the steering wheel are prohibited, when an obstacle is detected in front of the vehicle by the obstacle detection device, the prohibition of the issuance of the alarm and the prohibition of the steering of the steering wheel will not be lifted from the time when it is determined that the oblique displacement of the vehicle relative to the lane has ended based on the position of the vehicle detected by the vehicle position detection device until a time greater than a reference time has passed.

10. The lane departure prevention device according to claim 9, The control unit is configured to obtain information on the vehicle speed and to variably set the reference time in accordance with the vehicle speed so that the reference time is set shorter as the vehicle speed increases.

11. The lane departure prevention device according to claim 9 or 10, The control unit is configured to, when it is determined that the vehicle has changed lanes based on the position of the vehicle detected by the vehicle position detection device, prohibit the issuance of the alarm and lift the prohibition on the steering of the steering wheel even if a time greater than the reference time has not elapsed since it was determined that the oblique shift of the vehicle relative to the lane has ended.

Images