JP2007160997A - Travel controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the risks for a driver to feel sense of incongruity caused by the reason that a vehicular traveling direction is different from the traveling direction, corresponding to the position of a steering input means, even when abnormality is generated in a steering transmission variable device and when there is relative displacement left between a steering input means side member and a steering wheel side member. <P>SOLUTION: A yaw moment Mt required to prevent excessive yaw moment from acting on a wheel is computed (S140), when abnormality is generated in the steering transmission variable device 24 (S120), a yaw moment is applied onto the wheel based on the yaw moment Mt (S250, 260), when it is steered to be returned (S150); and a level of the yaw moment Mt is reduced gradually (S220, 230), when steering angle θ goes to zero once (S180), so as to surely reduce the risk of the driver receiving a sense of incongruity caused due to that the vehicular traveling direction does not match the traveling direction that corresponds to the position of a steering wheel 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle travel control device, and more specifically, a steering transmission ratio variable for changing a steering transmission ratio that is a ratio of a steering wheel turning angle change amount to a steering operation change amount of a steering input means by a driver. The present invention relates to a vehicle travel control device including the device.

  In vehicles such as automobiles, steering transmission that changes the steering transmission ratio (corresponding to the reciprocal of the steering gear ratio) by turning the steering wheel relative to the steering input means such as the steering wheel by the steering driving means. 2. Description of the Related Art A vehicle that includes a ratio variable device and controls the steering transmission ratio by the steering transmission ratio variable device is conventionally known.

  Further, as described in, for example, Patent Document 1 below, as one of travel control devices including a steering transmission ratio variable device, an electric motor that makes the steering angle ratio of the steering system variable, and an actual steering angle ratio of the steering system The deviation between the target steering angle ratio of the steered wheels and the detected actual steering angle ratio is a predetermined value in a situation where the steering angle ratio of the steering system is changed by an electric motor. A travel control device including a failure detection unit that determines that the actual steering angle ratio sensor is abnormal when the above situation continues for a predetermined time or longer is already known.

According to such a traveling control device, when a failure or abnormality occurs in the actual steering angle ratio sensor, the failure or abnormality of the actual steering angle ratio sensor is detected by the failure detection means. When this occurs and the steering angle ratio of the steering system cannot be properly controlled by the steering transmission ratio variable device, appropriate measures such as stopping the control of the steering angle ratio can be taken.
JP-A-11-91604

  In general, in a travel control device including a steering transmission ratio variable device, as described in Patent Document 1, a failure or an abnormality occurs in an actual steering angle ratio sensor or the like, and the steering angle ratio of the steering system is increased. When proper control is no longer possible, the steering input means side member and the steering wheel side member are locked to each other so that the steering wheel side member is not displaced relative to the steering input means side member of the steering transmission ratio variable device. Therefore, even if a failure or abnormality occurs in the actual steering angle ratio sensor or the like, it is possible to ensure a situation where the steering operation amount of the driver can be reliably transmitted from the steering input means side member to the steering wheel side member.

  However, if an abnormality occurs in the steering transmission ratio variable device in a situation where the vehicle is in a turning state and the steering wheel side member is displaced relative to the steering input means side member, the steering input means side member and the steering wheel Since the side members are mutually locked in a state where an unnecessary relative displacement amount remains between them, the steering wheel has an angle corresponding to the relative displacement amount between the steering input means side member and the steering wheel side member. It becomes a steered state. Therefore, an unnecessary yaw moment acts on the vehicle, and it is inevitable that the driver feels uncomfortable due to the traveling direction of the vehicle not matching the traveling direction corresponding to the position of the steering input means. It becomes more prominent as the position of the steering input means approaches the neutral position (the straight position of the vehicle).

  The above-mentioned problem is that the steering transmission ratio variable device is incorporated in, for example, a steering shaft, and the steering transmission ratio is changed by rotating the steering wheel side member relative to the steering input means side member. Not only the variable device but also a steering transmission ratio variable device is incorporated in, for example, a tie rod, and a linear displacement type in which the steering transmission ratio is changed by linearly moving the steering wheel side member relative to the steering input means side member. The same applies to the steering transmission ratio variable device.

  According to the present invention, in a vehicle travel control device having a steering transmission ratio variable device, when an abnormality occurs in the steering transmission ratio variable device, relative displacement of the steering wheel side member with respect to the steering input means side member is prevented. The main problem of the present invention is that when an abnormality occurs in the steering transmission ratio variable device and the steering input means side member and the steering wheel side member are locked to each other, Even when a relative displacement remains between the steering input means side member and the steering wheel side member by giving the vehicle a yaw moment so that the traveling direction of the vehicle approaches the traveling direction corresponding to the position of the steering input means, This is to reduce the possibility that the driver feels uncomfortable due to the vehicle traveling direction being different from the traveling direction corresponding to the position of the steering input means.

  According to the present invention, the main problem described above is that the structure of claim 1, that is, the steering wheel side member relative to the steering input means side member is displaced relative to the steering input amount of the steering wheel. Steering transmission ratio variable means for changing a steering transmission ratio, which is a ratio of the steering amount, detection means for detecting a relative displacement amount of the steering wheel side member with respect to the steering input means side member, and for the steering input means side member Means for calculating a target relative displacement amount of the steering wheel side member, control means for controlling the steering transmission ratio variable means so that the relative displacement amount becomes the target relative displacement amount, and abnormality in the steering transmission ratio variable means In a vehicle steering control device having a locking means for preventing relative displacement of the steering wheel side member with respect to the steering input means side member, an abnormality occurs in the steering transmission ratio variable means, and When the steering means is operated, the yaw moment necessary to counter the extra yaw moment acting on the vehicle is calculated based on the relative displacement, and the left and right wheels are controlled so as to apply the necessary yaw moment to the vehicle. This is achieved by a vehicle travel control device having braking / driving force control means for controlling the driving force difference.

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 1, the braking / driving force control means is configured so that the steering wheel side member is not moved toward the steering input means side member. A target relative displacement amount is calculated, and the necessary yaw moment is calculated based on a deviation between the target relative displacement amount and the relative displacement amount when an abnormality occurs in the steering transmission ratio variable means ( Configuration of claim 2).

  According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 2, the braking / driving force control means is provided on the basis of the deviation of the relative displacement amount and the vehicle speed. A simple yaw moment is calculated (configuration of claim 3).

  According to the present invention, in order to effectively achieve the main problems described above, the braking / driving force control means determines the driver's steering operation in order to effectively achieve the driver's steering operation. When the steering operation is a switchback operation, the braking / driving force difference between the left and right wheels is controlled so as to apply the necessary yaw moment to the vehicle (configuration of claim 4).

  According to the present invention, in order to effectively achieve the above main problems, the braking / driving force control means is configured such that the magnitude of the steering operation amount is once a reference value. When it becomes below, it is comprised so that the magnitude | size of the yaw moment given to a vehicle may be gradually reduced based on the said required yaw moment (structure of Claim 5).

  According to the present invention, in order to effectively achieve the above-mentioned main problems, the braking / driving force control means is a vehicle based on the braking / driving operation amount of the driver. The target braking / driving force of each wheel and the target driving force of the vehicle necessary for making the braking / driving force of the vehicle the target braking / driving force are applied to the vehicle. And calculating and controlling the braking force of each wheel based on the target braking force and controlling the driving force of the vehicle based on the target driving force.

  According to the first aspect of the present invention, when an abnormality occurs in the steering transmission ratio variable means and the lock means is actuated, the yaw moment necessary to counter the extra yaw moment acting on the vehicle based on the relative displacement is obtained. Since the difference in braking / driving force between the left and right wheels is controlled so that the necessary yaw moment is applied to the vehicle, an abnormality occurs in the steering transmission ratio variable device, and the difference between the steering input means side member and the steering wheel side member is calculated. Even if the steering wheel is steered by an angle corresponding to the relative displacement between the steering input means side member and the steering wheel side member. The necessary yaw moment can be reduced, thereby effectively reducing the possibility that the driver will feel uncomfortable due to the vehicle traveling direction differing from the traveling direction corresponding to the position of the steering input means. Can .

  According to the second aspect of the present invention, the target relative displacement amount of the steering wheel side member with respect to the steering input means side member is calculated, and the relative displacement amount when the abnormality occurs in the target relative displacement amount and the steering transmission ratio variable means. Since the necessary yaw moment is calculated based on the deviation from the above, the magnitude of the necessary yaw moment suddenly increases immediately after the abnormality occurs in the steering transmission ratio variable means, and the driver It can be surely prevented from feeling uncomfortable.

  According to the third aspect of the present invention, since the necessary yaw moment is calculated based on the deviation of the relative displacement amount and the vehicle speed, it is possible to accurately counter the excess yaw moment acting on the vehicle regardless of the vehicle speed. Necessary yaw moment can be calculated as the yaw moment, whereby unnecessary yaw moment acting on the vehicle can be reduced without excess or deficiency.

  Also, in general, the uncomfortable feeling caused by the occurrence of an abnormality in the steering transmission ratio variable device and the unnecessary relative displacement remaining between the steering input means side member and the steering wheel side member is increased and switched back compared to the operation. It is large during operation and increases as the position of the steering input means approaches the neutral position.

  According to the configuration of claim 4 above, the difference in braking / driving force between the left and right wheels is determined so as to give the vehicle the necessary yaw moment when the driver's steering operation is determined and the driver's steering operation is a switchback operation. Therefore, the possibility that the driver will feel uncomfortable at the time of the switchback operation can be reliably reduced, and the right and left wheels can be compared with the case where the necessary yaw moment is applied to the vehicle at the time of the switchover operation. The energy consumed by controlling the braking / driving force difference can be reduced.

  According to the fifth aspect of the present invention, once the magnitude of the steering operation amount becomes equal to or less than the reference value, the necessary yaw moment is gradually reduced. For example, the magnitude of the steering operation amount becomes equal to or less than the reference value. Then, the driver may feel uncomfortable due to a sudden change in the necessary yaw moment, compared to when the necessary yaw moment is finished or the magnitude of the necessary yaw moment is drastically reduced. Can be reliably reduced.

  According to the sixth aspect of the present invention, the target braking / driving force of the vehicle is calculated based on the braking / driving operation amount of the driver, the necessary yaw moment is applied to the vehicle, and the braking / driving force of the vehicle is set to the target braking / driving. The target braking force of each wheel and the target driving force of the vehicle necessary for making the force are calculated, the braking force of each wheel is controlled based on the target braking force, and the driving force of the vehicle is calculated based on the target driving force. Because it is controlled, the necessary yaw moment can be reliably applied to the vehicle, and the braking / driving force of the vehicle is reliably controlled to the target braking / driving force even in the situation where the necessary yaw moment is applied. be able to.

[Preferred embodiment of problem solving means]
According to a preferred aspect of the present invention, in the configuration of the first to sixth aspects, the steering input means side member is an upper steering shaft, the steering wheel side member is a lower steering shaft, and steering transmission ratio control is performed. The means is configured to change the steering transmission ratio by rotationally displacing the lower steering shaft relative to the upper steering shaft (preferred aspect 1).

  According to another preferred aspect of the present invention, the steering input means side member is a tie rod member on the steering input means side, and the steering wheel side member is a steering wheel side member. The steering transmission ratio control means is configured to change the steering transmission ratio by linearly displacing the tie rod member on the steering wheel side member side relative to the tie rod member on the steering input means side ( Preferred embodiment 2).

  According to another preferred aspect of the present invention, in the configuration of the above-described claims 1 to 6 or the preferred aspect 1 or 2, the magnitude of the relative displacement when the abnormality occurs in the steering transmission ratio variable means. Is less than the control start determination reference value, it is configured not to control the braking / driving force difference between the left and right wheels that imparts the necessary yaw moment to the vehicle (preferred aspect 3).

  According to another preferred aspect of the present invention, in the configuration of the first to sixth aspects or the preferred aspects 1 to 3, an abnormality occurs in the steering transmission ratio variable means, and the driver performs the switching back operation. When the driver's steering operation after this is not a switch-back operation, the necessary yaw moment is configured to be set to the previous value (preferred aspect 4).

  According to another preferred aspect of the present invention, in the configuration of the first to sixth aspects or the preferred aspects 1 to 4, the means for calculating the target relative displacement is the speed increasing ratio of the steering transmission ratio varying means. Is configured to calculate the target relative displacement amount so as to obtain a desired speed increase ratio (preferred aspect 5).

  According to another preferred embodiment of the present invention, in the configuration of the above-described claims 1 to 6 or the preferred embodiments 1 to 4, the means for calculating the target relative displacement amount has a desired steering gear ratio. The target relative displacement amount is calculated so as to satisfy (preferred aspect 6).

  The present invention will now be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing one embodiment of a vehicle travel control device according to the present invention applied to a rear wheel drive vehicle equipped with a turning angle varying device.

  In FIG. 1, 10FL and 10FR respectively indicate left and right front wheels as driven steering wheels of the vehicle 12, and 10RL and 10RR respectively indicate left and right rear wheels as drive wheels of the vehicle. The left and right front wheels 10FL and 10FR, which are steering wheels, are rotated via a rack bar 18 and tie rods 20L and 20R by a rack-and-pinion type power steering device 16 driven in response to an operation of the steering wheel 14 by a driver. Steered.

  The steering wheel 14 is drivingly connected to the pinion shaft 30 of the power steering device 16 through an upper steering shaft 22, a turning angle varying device 24, a lower steering shaft 26, and a universal joint 28. In the illustrated embodiment, the turning angle varying device 24 is connected to the lower end of the upper steering shaft 22 on the housing 24A side, and is connected to the upper end of the lower steering shaft 26 on the rotor 24B side. An electric motor 32 for turning driving is included.

  Thus, the steering angle varying device 24 drives the lower steering shaft 26 to rotate relative to the upper steering shaft 22, so that the ratio of the steering angles of the left and right front wheels 10 FL and 10 FR, which are the steering wheels, with respect to the rotation angle of the steering wheel 14. That is, it functions as a steering transmission ratio variable device that changes the steering transmission ratio (corresponding to the reciprocal of the steering gear ratio) and is controlled by the electronic control unit 34.

  In particular, the turning angle varying device 24 is configured so that the lower steering shaft 26 is driven by the electric motor 32 so that the speed increasing ratio of the rotation of the lower steering shaft 26 with respect to the rotation of the upper steering shaft 22 is a predetermined speed increasing ratio corresponding to the vehicle speed V. By rotating relative to the upper steering shaft 22, the steering gear ratio is controlled to be a gear ratio that achieves a predetermined steering characteristic.

  FIG. 1 shows an abnormality in the turning angle varying device 24 in which the lower steering shaft 26 cannot be driven to rotate relative to the upper steering shaft 22 so that the speed increasing ratio becomes a predetermined speed increasing ratio. Thus, the relative rotation of the housing 24 </ b> A and the rotor 24 </ b> B is mechanically prevented so that the locking device that is not operated is activated and the relative rotation angle of the lower steering shaft 26 with respect to the upper steering shaft 22 does not change.

  The power steering device 16 may be either a hydraulic power steering device or an electric power steering device. However, the power steering device 16 is generated by the auxiliary steering driving of the front wheels by the steering angle varying device 24 and transmitted to the steering wheel 14. A rack coaxial type electric motor having, for example, an electric motor and a conversion mechanism such as a ball screw type that converts the rotational torque of the electric motor into a reciprocating force of the rack bar 18 so that an auxiliary steering torque for reducing the force torque is generated. A power steering apparatus is preferable.

  The braking force of each wheel is controlled by controlling the pressure Pi (i = fl, fr, rl, rr) in the wheel cylinders 40FL, 40FR, 40RL, 40RR, that is, the braking pressure, by the hydraulic circuit 38 of the braking device 36. The Although not shown in the drawing, the hydraulic circuit 38 includes an oil reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven in response to the depression operation of the brake pedal 42 by the driver. It is controlled by the master cylinder 44 and individually controlled by the electronic control unit 34 as will be described in detail later if necessary.

  In the illustrated embodiment, the upper steering shaft 22 is provided with a steering angle sensor 50 for detecting the rotation angle of the upper steering shaft as a steering angle θ. The steering angle variable device 24 includes a housing 24A and A rotation angle sensor 52 that detects the relative rotation angle of the rotor 24B as the relative rotation angle θre of the lower steering shaft 26 with respect to the upper steering shaft 22 is provided, and the output of these sensors is supplied to the electronic control unit 34. The steering angle sensor 52 may be replaced with a sensor that detects the rotation angle θs of the lower steering shaft 28B, and the relative rotation angle θre may be obtained as a steering angle difference θs−θ.

  The electronic control unit 34 also includes a signal indicating the vehicle speed V detected by the vehicle speed sensor 54, a signal indicating the master cylinder pressure Pm detected by the pressure sensor 56, and the braking pressure Pi of each wheel detected by the pressure sensors 58FL to 58RR. A signal indicating the accelerator opening φ is input from an accelerator opening sensor 62 provided on the accelerator pedal 60.

  Although not shown in detail in FIG. 1, the electronic control unit 34 includes a turning control unit that controls the turning angle varying device 24, a braking force control unit that controls the braking force of each wheel, and an engine 64. The engine control unit includes a CPU, a ROM, a RAM, and an input / output port device, each of which includes a microcomputer connected to each other via a bidirectional common bus. . Further, the steering angle sensor 50 and the rotation angle sensor 52 detect the steering angle θ and the relative rotation angle θre, respectively, when the vehicle is steered or steered in the left turn direction.

  As will be described later, the steering control device 34 has a positive target acceleration ratio Kvgt of the turning angle varying device 24 in a region where the vehicle speed V is low, and a target acceleration ratio in a region where the vehicle speed V is high. The target acceleration ratio Kvgt of the turning angle varying device 24 is calculated based on the vehicle speed V so that Kvgt becomes a negative value, the target relative rotation angle θret is calculated based on the target acceleration ratio Kvgt, and the target relative rotation is calculated. The electric motor 32 of the turning angle varying device 24 is controlled so that the deviation between the angle θret and the relative rotation angle θre becomes zero.

  Further, the electronic control unit 34 is in a manner known in the art based on the accelerator opening φ and the master cylinder pressure Pm detected by the accelerator opening sensor 62 at the normal time when the turning angle varying device 24 operates normally. The target braking / driving force Fvt of the vehicle is calculated, and when the target braking / driving force Fvt is the driving force, the target throttle opening φt of the engine 64 is calculated based on the accelerator opening φ, and based on the target throttle opening φt The engine 64 is controlled.

  Further, the electronic control unit 34 is configured so that when the turning angle varying device 24 is normally operated, when the target braking / driving force Fvt is a braking force, the electronic control unit 34 has a predetermined pressure increase coefficient Ki (i = fl, fr, A value obtained by multiplying (rl, rr) is calculated as a target braking pressure Pti (i = fl, fr, rl, rr) of each wheel, and control is performed so that the braking pressure Pi becomes the corresponding target braking pressure Pti.

  On the other hand, when an abnormality occurs in the turning angle varying device 24 and the lock device is activated, the electronic control unit 34 deviates between the target relative displacement amount and the relative displacement amount at the time when the turning angle varying device 24 becomes abnormal. Based on the vehicle speed V, a yaw moment Mt necessary to give the vehicle a yaw moment that opposes the extra yaw moment acting on the vehicle is calculated. The yaw moment Mt is calculated as a moment opposite in direction to the extra yaw moment and having the same magnitude as or smaller than the extra yaw moment.

  The electronic control unit 34 calculates the target braking force Fbti of each wheel and the target driving force Fvdt of the vehicle for achieving the target braking / driving force Fvt and the yaw moment Mt, and the target braking of each wheel based on the target braking force Fbti. The pressure Pti is calculated and controlled so that the braking pressure Pi becomes the corresponding target braking pressure Pti, and the target throttle opening φt of the engine 64 is calculated based on the target driving force Fvdt, and based on the target throttle opening φt. The engine 64 is controlled.

  The control of the steering angle varying device 24, the control of the braking force, and the control of the engine itself do not form the gist of the present invention, and these controls are performed in any manner known in the art. May be executed.

  Next, the control routine of the turning angle varying device in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals.

  First, at step 10, a signal indicating the steering angle θ detected by the steering angle sensor 60 is read, and at step 20, the graph shown in FIG. The target speed increase ratio Kvgt of the turning angle varying device 30 is calculated from the map, and in step 30, the target relative rotation angle θret of the turning angle varying device 24 is obtained as the product of the target speed increasing ratio Kvgt and the steering angle θ. In step 40, a rotation angle deviation Δθre is calculated as a deviation between the target relative rotation angle θret and the relative rotation angle θre of the turning angle varying device 30.

In step 50, the differential value Δθred of the rotation angle deviation Δθre is calculated as, for example, a time differential value, and Kp and Kd are set as a proportional term gain and a differential term gain (both are positive constants), respectively. Accordingly, the target control voltage Vst for the electric motor 36 of the turning angle varying device 30 is calculated.
Vst = KpΔθre + KdΔθred (1)

  In step 60, it is determined whether or not an abnormality determination condition for the turning angle varying device 30 is satisfied. If an affirmative determination is made, the process proceeds to step 80. If a negative determination is made, step 70 is performed. Proceed to The abnormality determination condition itself does not form the gist of the present invention, and may be any condition known in the art. For example, the absolute value of the rotation angle deviation Δθre is a reference value Δθreo (a positive constant). When the above state continues for the reference time To (positive constant) or more, it may be determined that the abnormality determination condition for the turning angle varying device 30 is satisfied.

  In step 70, a control current is applied to the motor 32 of the turning angle varying device 24 at the target control voltage Vst, so that the relative rotation angle θre of the turning angle varying device 24 becomes the target relative rotation angle θret. In step 80, the turning angle varying device 24 is locked by the locking device so that the relative rotation of the lower steering shaft 28B with respect to the upper steering shaft 28A is mechanically blocked, and at that time. The relative rotation angle θrea is stored in a storage means such as a RAM.

  Next, a travel control routine at the time of abnormality of the turning angle varying device in the embodiment will be described with reference to a flowchart shown in FIG. The control according to the flowchart shown in FIG. 4 is also started by closing an ignition switch not shown in the figure, and is repeatedly executed at predetermined time intervals. At the start of control according to the flowchart shown in FIG. 4, the flags Fe and Fc and the count value n of the counter are initialized to zero.

  First, in step 110, a signal indicating the relative rotation angle θre detected by the rotation angle sensor 52 is read, and in step 120, an abnormality occurs in the turning angle variable device 24, and the lock device is activated. It is determined whether or not it has been activated. If a negative determination is made, the process returns to step 110. If an affirmative determination is made, the process proceeds to step 130.

  In step 130, it is determined whether or not the absolute value of the relative rotation angle θre is greater than or equal to a reference value θreo (a positive constant), that is, whether or not the yaw moment needs to be controlled. When the determination is made, control of the yaw moment is unnecessary, so the control according to the flowchart shown in FIG. 4 is terminated, and when an affirmative determination is made, the routine proceeds to step 140.

  In step 140, the target relative rotation angle θret of the turning angle varying device 24 is calculated in the same manner as in steps 20 and 30 described above, and when an abnormality occurs in the turning angle varying device 24. The difference Δθre between the relative rotation angle θrea and the target relative rotation angle θret is calculated, and the excess yaw acting on the vehicle is calculated from the map corresponding to the graph shown in FIG. 5 based on the relative rotation angle deviation Δθre and the vehicle speed V. A yaw moment Mt necessary to give the vehicle a yaw moment that opposes the moment is calculated.

  In step 150, for example, based on a change in the steering angle θ, it is determined whether or not the driver is turning back. If an affirmative determination is made, the flag Fe is set to 1 in step 160. When it is set and a negative determination is made, the routine proceeds to step 170.

  In step 170, it is determined whether or not the flag Fe is 1, that is, the switchback steering is performed by the driver after an abnormality has occurred in the turning angle varying device 24. It is determined whether or not an affirmative determination has been made. If an affirmative determination has been made, the process proceeds to step 200. If a negative determination has been made, the process returns to step 140.

  In step 180, it is determined whether or not the absolute value of the steering angle θ is equal to or smaller than a reference value θo (positive constant), that is, whether or not the steering wheel 14 is substantially in the neutral position. If a negative determination is made, the process proceeds to step 200. If an affirmative determination is made, the flag Fc is set to 1 in step 190, and then the process proceeds to step 220.

  In step 200, it is determined whether or not the flag Fc is 1, that is, whether or not an affirmative determination has already been made in step 180 described above after an abnormality has occurred in the turning angle varying device 24. If a negative determination is made, the required yaw moment Mt is set to the previous value Mt in step 210, and then the process proceeds to step 250. If an affirmative determination is made, the process proceeds to step 220.

  In step 220, the count value n of the counter is incremented by 1. In step 230, ΔMt is a small positive constant, signMt is the sign of the required yaw moment Mt, and the required yaw moment Mt is decremented by nΔMt signMt. As a result, the magnitude of the necessary yaw moment Mt is gradually reduced.

  In step 240, it is determined whether or not the absolute value of the necessary yaw moment Mt is less than or equal to the reference value Mto (small positive constant), that is, the necessary yaw moment Mt is substantially zero. It is determined whether or not further reduction of the necessary yaw moment Mt is necessary. When an affirmative determination is made, the control according to the flowchart shown in FIG. 4 is terminated and a negative determination is made. If yes, go to Step 250.

  In step 250, the target braking force Fbti of each wheel and the vehicle target driving force Fvdt for achieving the target braking / driving force Fvt and yaw moment Mt are calculated, and in step 260, based on the target braking force Fbti. The target braking pressure Pti of each wheel is calculated and controlled so that the braking pressure Pi becomes the corresponding target braking pressure Pti, and the target throttle opening φt of the engine 64 is calculated based on the target driving force Fvdt, The engine 64 is controlled based on the target throttle opening φt.

  In step 250, when the yaw moment Mt is a positive value as the tread Tf of the front wheel, the target braking force Fbti of each wheel and the target driving force Fvdt of the vehicle are calculated according to the following equations 2-4. When the yaw moment Mt is a negative value, the target braking force Fbti of each wheel and the target driving force Fvdt of the vehicle may be calculated according to the following equations 5-7.

Fbtfl = Mt / Tf (2)
Fbtfr = Fbtrl = Fbtrr = 0 (3)
Fvdt = Fvt + Fbtfl (4)
Fbtfr = -Mt / Tf (5)
Fbtfl = Fbtrl = Fbtrr = 0 (6)
Fvdt = Fvt + Fbtfr (7)

  Thus, according to the illustrated embodiment, the target speed increase ratio Kvgt of the turning angle varying device 30 is calculated based on the vehicle speed V in step 20, and the target speed increase ratio Kvgt and the steering angle θ are calculated in step 30. The target relative rotation angle θret of the steered angle varying device 24 is calculated as the product of the rotation angle deviation Δθre as a deviation between the target relative rotational angle θret and the relative rotational angle θre of the steered angle varying device 30 in step 40. In step 50, the target control voltage Vst for the motor 36 is calculated based on the rotation angle deviation Δθre. When the turning angle varying device 24 is normal, a negative determination is made in step 60, and step 70 is performed. In this case, the relative rotation angle θre of the turning angle varying device 30 is controlled to become the target relative rotation angle θret.

  On the other hand, when an abnormality occurs in the turning angle varying device 24, an affirmative determination is made in step 60, and in step 80, the turning angle varying device 24 is locked by the locking device, and the upper steering shaft 28A. The relative rotation of the lower steering shaft 28B is mechanically blocked, and the relative rotation angle θrea at that time is stored in a storage means such as a RAM.

  For example, assuming that the relationship between the steering angle θ and the target relative rotation angle θret at the time when an abnormality occurs in the turning angle varying device 24 is the relationship shown in FIG. 6, an abnormality occurs in the turning angle varying device 24. If the steering angle θ at this time is θ1, the relative rotation angle θre when the steering angle θ is θ1 becomes the relative rotation angle θrea.

  Even if the driver performs a turning-back steering operation after an abnormality occurs in the turning angle varying device 24 and the magnitude of the steering angle θ is reduced, the upper steering shaft 28A and the lower steering shaft 28B do not rotate relative to each other. The relative rotation angle θre of the turning angle varying device 24 does not change as the relative rotation angle θrea as indicated by the arrow in FIG. Therefore, the magnitude of the deviation Δθre between the target relative rotation angle θret and the actual relative rotation angle θre gradually increases as the steering angle θ decreases due to the return steering operation, and the relative value when the steering angle θ becomes zero. The rotation angle deviation Δθre is θrea.

  Therefore, as shown in FIG. 7 (A), even if the driver tries to drive the vehicle straight and operates the steering wheel 14 to the neutral position, the left and right front wheels are driven despite the steering angle θ being zero. 10FL and 10FR are steered in the left turning direction corresponding to the relative rotation angle θrea, and an excess yaw moment Ma acts on the vehicle 12, and the vehicle turns left without going straight. .

  According to the illustrated embodiment, when an abnormality occurs in the turning angle varying device 24, an affirmative determination is made in step 120 of the flowchart shown in FIG. 4, and the absolute value of the relative rotation angle θre is used as a reference. When the value is greater than or equal to the value θreo, an affirmative determination is made at step 130, and the deviation between the relative rotation angle θrea and the target relative rotation angle θret at the time when an abnormality occurs in the turning angle varying device 24 at step 140. Δθre is calculated, and a yaw moment Mt necessary to give the vehicle a yaw moment that opposes the excess yaw moment Ma acting on the vehicle based on the relative rotation angle deviation Δθre and the vehicle speed V is calculated.

  Then, if it is determined in step 150 that the driver is performing the turning-back steering operation, in step 180, the magnitude of the steering angle θ becomes equal to or smaller than the reference value θo, and the steering wheel 14 is substantially neutral. In step 250 and 260, the yaw moment Mc (= Mt) that opposes the extra yaw moment Ma is applied to the vehicle until it is determined that the vehicle has returned to the position. The possibility that the driver feels uncomfortable due to the fact that θrea remains and the traveling direction of the vehicle does not coincide with the traveling direction corresponding to the position of the steering wheel 14 is reliably reduced.

  FIG. 7B shows the situation of the vehicle when the yaw moment control according to the illustrated embodiment is performed, and a braking force Fbfl corresponding to the target braking force Fbtfl is added to the right front wheel, and the left and right front wheels are shown. Since the yaw moment Mc that opposes the excess yaw moment Ma is applied to the vehicle due to the braking / driving force difference, the vehicle can be driven in the straight direction corresponding to the neutral position of the steering wheel 14.

  In this case, the braking force Fbfl is applied to the right front wheel, but the output of the engine 64 is increased so that the sum of the additional driving forces of the left and right rear wheels 10RL and 10RR becomes equal to the braking force Fbfl. The driving forces Fdrl and Fdrr of the wheels 10RL and 10RR are increased, thereby preventing unnecessary vehicle deceleration due to yaw moment control.

  If an abnormality occurs in the turning angle varying device 24, the relative rotation angle θrea remains in the turning angle varying device 24 even when the driver performs additional steering operation, but the driver operates the steering wheel 14. Thus, the vehicle can be brought into a desired turning state, so that the driver can surely increase the rotation from the upper steering shaft 28A to the lower steering shaft 28B, and does not feel excessive discomfort during the steering operation.

  Further, according to the illustrated embodiment, once it is determined in step 180 that the steering angle θ is equal to or smaller than the reference value θo, the required yaw moment Mt is determined in steps 200 to 240. Since the magnitude of the necessary yaw moment Mt is gradually reduced until it becomes substantially zero, the magnitude of the yaw moment Mt is rapidly reduced to zero immediately after the steering wheel 14 is returned to the substantially neutral position. Compared to the case, it is possible to reduce the uncomfortable feeling that the driver feels due to the change of the yaw moment Mt, and the driver is opposite to the relative rotation angle θrea as shown in FIG. By gradually turning the steering wheel 14 in the direction of, the traveling direction of the vehicle can be surely set to the traveling direction desired by itself.

  FIG. 8 shows a steering angle when an abnormality occurs in the turning angle varying device 24 when the vehicle turns to the left, the steering wheel 14 is turned back to the neutral position by the driver, and the vehicle is steered to a straight traveling state. An example of changes in θ, relative rotation angle deviation Δθre, and yaw moment Mt is shown.

  As shown in FIG. 8, an abnormality occurs in the turning angle varying device 24 at a time point t1, and the driver starts a switching back steering operation at a time point t2, and the steering angle θ at a time point t3. Is less than or equal to the reference value θo, and the steering angle θ becomes 0 at time t4. The magnitude of the relative rotation angle deviation Δθre increases from time t2 to time t4, and changes from time t4 according to the target relative rotation angle θret. Corresponding to the change in the deviation Δθre of the relative rotation angle, the yaw moment Mt increases in the right turn direction from the time point t2 to the time point t3, so that the traveling direction of the vehicle corresponds to the position of the steering wheel 14 during the switchback steering operation. The possibility that the driver feels uncomfortable due to the fact that it does not coincide with the traveling direction is reliably reduced.

  Further, since the magnitude of the yaw moment Mt is gradually decreased from the time t3 to the time t5 when the magnitude of the yaw moment Mt becomes equal to or less than the reference value Mto, the driver gradually turns the steering wheel 14 in the left turn direction so that the vehicle travels straight ahead. Steer to. Since the yaw moment Mc based on the yaw moment Mt is not applied after the time point t5, at least after the time point t5, the driver does not steer the steering wheel 14 and slightly steers leftward. maintain.

  In particular, according to the illustrated embodiment, in step 140, the deviation Δθre of the relative rotation angle is calculated as the deviation between the target relative rotation angle θret and the actual relative rotation angle θre, and the yaw moment Mt is calculated as the deviation Δθre of the relative rotation angle. Therefore, the magnitude of the yaw moment Mc suddenly increases immediately after an abnormality occurs in the turning angle varying device 24, and the uncomfortable feeling caused by this can be reliably prevented.

  Further, according to the illustrated embodiment, the yaw moment Mt is calculated so as to increase as the magnitude of the relative rotation angle deviation Δθre increases, and to increase as the vehicle speed V increases. Therefore, regardless of the vehicle speed V, the left and right front wheels 10FL and 10FR are steered by an angle corresponding to the relative rotation angle θrea remaining in the steered angle varying device 24. The yaw moment Mt can be calculated as a value corresponding to the yaw moment.

  Further, according to the illustrated embodiment, the yaw moment Mc corresponding to the yaw moment Mt is applied to the vehicle only at the time of switchback steering, and is not applied at the time of additional steering that the driver rarely feels uncomfortable. Therefore, the difference in braking / driving force between the left and right front wheels is not controlled at the time of additional steering, so that the yaw moment Mc is applied to the vehicle at the time of additional steering as well. Energy can be reduced.

  Further, according to the illustrated embodiment, the target braking / driving force Fvt of the vehicle is calculated based on the braking / driving operation amount of the driver, and the target braking force of each wheel for achieving the target braking / driving force Fvt and the yaw moment Mt. Fbti and the target driving force Fvdt of the vehicle are calculated, the braking force of each wheel is controlled based on the target braking force Fbti, and the output of the engine 64 is controlled based on the target driving force Fvdt, so that the yaw moment Mc is applied to the vehicle. It is possible to reliably avoid that the braking / driving force of the vehicle does not become the target braking / driving force Fvt due to the provision of.

  Further, according to the illustrated embodiment, if an affirmative determination is made in step 150, the flag Fe is set to 1 in step 160, so that the driver can subsequently hold or increase steering. However, since an affirmative determination is made in step 170 and step 200 and subsequent steps are executed, it is possible to reliably prevent the magnitude of the yaw moment Mt from increasing unnecessarily.

  Further, according to the illustrated embodiment, when an affirmative determination is made at step 180, the flag Fc is set to 1 at step 190, and an affirmative determination is made at step 200. In this case, even if the absolute value of the steering angle θ becomes larger than the reference value θo by the driver's steering after the affirmative determination is made, the magnitude of the yaw moment Mt can be gradually reduced.

  Further, according to the illustrated embodiment, even when an abnormality occurs in the turning angle varying device 24, an abnormality occurs in the turning angle varying device 24 in a situation where the speed increase ratio Kvg is substantially zero. As described above, when the absolute value of the relative rotation angle θre is less than the reference value θreo, a negative determination is made in step 130, and since step 140 and subsequent steps are not executed, the excess yaw moment Ma acting on the vehicle is slight. Under certain circumstances, it is possible to reliably prevent unnecessary control of the difference in braking / driving force between the left and right wheels.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the yaw moment Mt is calculated from the map corresponding to the graph shown in FIG. 5 based on the relative rotation angle deviation Δθre and the vehicle speed V. Since the target relative rotation angle θret of the angle varying device 24 is calculated based on the vehicle speed V, the yaw moment Mt is calculated based on the vehicle speed V and the vehicle speed Vc at the time when the abnormality occurs in the turning angle varying device 24. It may be modified so that.

  In the above-described embodiment, once the absolute value of the steering angle θ becomes equal to or smaller than the reference value θo, the magnitude of the yaw moment Mt is gradually reduced regardless of the value of the subsequent steering angle θ. However, once the absolute value of the steering angle θ becomes equal to or smaller than the reference value θo, the absolute value of the steering angle θ is equal to or smaller than the reference value θo or the direction in which the steering angle θ generates a yaw moment that opposes the excess yaw moment Ma. It may be modified so that the magnitude of the yaw moment Mt is gradually reduced only when it is increased to.

  In the above-described embodiment, the steering transmission ratio variable means is the turning angle variable device 24 that changes the steering transmission ratio by rotationally driving the lower steering shaft 28B relative to the upper steering shaft 28A. The steering transmission ratio variable means may be of any configuration known in the art as long as the steering transmission ratio can be changed. For example, the steering input means side member is a tie rod member on the steering input means side. The steering wheel side member is a tie rod member on the steering wheel side member side, and the steering transmission ratio control means linearly displaces the tie rod member on the steering wheel side member side relative to the tie rod member on the steering input means side. It may be configured to change the steering transmission ratio.

  In the above-described embodiment, the target speed increase ratio Kvgt of the turning angle varying device 24 is calculated based on the vehicle speed V, and the turning angle varying device 24 is calculated as the product of the target speed increasing ratio Kvgt and the steering angle θ. The target relative rotation angle θret is calculated, but the target relative rotation angle θret of the turning angle varying device 24 is calculated by, for example, the target steering gear ratio Rsgt from a map corresponding to the graph shown in FIG. Then, it may be corrected so as to be calculated in a manner known in the art based on the target steering gear ratio Rsgt. In FIG. 9, Rsgo is a steering gear ratio at which the speed increasing ratio becomes zero.

  In the above-described embodiment, the vehicle is a rear-wheel drive vehicle, and the yaw moment Mc is applied to the vehicle by applying a braking force to one of the left and right front wheels. If the vehicle is a front-wheel drive vehicle, the yaw moment Mc may be applied to the vehicle by applying a braking force to one of the left and right rear wheels. If the vehicle is a four-wheel drive vehicle, the yaw moment Mc May be applied to the vehicle by applying a braking force to the left front wheel or the right front wheel.

It is a schematic block diagram which shows one Example of the traveling control apparatus of the vehicle by this invention applied to the rear-wheel drive vehicle provided with the turning angle variable apparatus. It is a flowchart which shows the control routine of the turning angle variable apparatus in an Example. It is a graph which shows the relationship between the vehicle speed V and the target speed increase ratio Kvgt. It is a flowchart which shows the traveling control routine at the time of abnormality of the turning angle variable apparatus in an Example. It is a graph which shows the relationship between deviation (DELTA) (theta) re of a relative rotation angle, and the target yaw moment Mt. It is a graph which shows the relationship between steering angle (theta), target relative rotation angle (theta) ret, and relative rotation angle (theta) re. In the conventional vehicle, when the abnormality occurs in the turning angle varying device, the explanatory diagram (A) showing the situation of the vehicle, in the case where abnormality occurs in the turning angle varying device in the illustrated embodiment It is explanatory drawing (B) which shows the condition of the vehicle in this, and explanatory drawing (C) which shows the condition where the steering wheel was correctively operated after abnormality occurred in the turning angle variable device in the illustrated embodiment. When the vehicle turns to the left, an abnormality occurs in the turning angle variable device, the steering wheel is turned back to the neutral position by the driver, and the steering angle θ and the relative rotation angle when the vehicle is steered to travel straight ahead. It is a graph which shows an example of change of deviation (DELTA) (theta) re of this, and yaw moment Mt. It is a graph which shows the relationship between vehicle speed V target steering gear ratio Rsgt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 16 Power steering apparatus 14 Steering wheel 24 Steering angle variable apparatus 34 Electronic control apparatus 36 Braking apparatus 44 Master cylinder 50 Steering angle sensor 52 Rotation angle sensor 54 Vehicle speed sensor 56, 58FL-58RR Pressure sensor 62 Accelerator opening sensor 64 Engine

Claims (6)

  A steering transmission ratio variable means for changing a steering transmission ratio that is a ratio of a steering wheel turning amount to a steering operation amount of the steering input means by displacing the steering wheel side member relative to the steering input means side member; Detecting means for detecting a relative displacement amount of the steering wheel side member relative to the steering input means side member; means for calculating a target relative displacement amount of the steering wheel side member relative to the steering input means side member; and the relative displacement amount Control means for controlling the steering transmission ratio variable means so that becomes the target relative displacement amount, and when an abnormality occurs in the steering transmission ratio variable means, the relative displacement of the steering wheel side member with respect to the steering input means side member is changed. In a vehicle steering control device having locking means for blocking, when an abnormality occurs in the steering transmission ratio variable means and the locking means is activated, the vehicle is controlled based on the relative displacement amount. A braking / driving force control means for calculating a yaw moment necessary to counter the excess yaw moment acting on the vehicle and controlling a braking / driving force difference between the left and right wheels so as to apply the necessary yaw moment to the vehicle. A vehicle travel control device.   The braking / driving force control means calculates a target relative displacement amount of the steering wheel side member with respect to the steering input means side member, and the relative displacement at the time when an abnormality occurs in the target relative displacement amount and the steering transmission ratio variable means. 2. The vehicle travel control apparatus according to claim 1, wherein the necessary yaw moment is calculated based on a deviation from the quantity.   3. The vehicle travel control apparatus according to claim 2, wherein the braking / driving force control means calculates the necessary yaw moment based on a deviation of the relative displacement amount and a vehicle speed.   The braking / driving force control means determines the driver's steering operation, and controls the braking / driving force difference between the left and right wheels so as to apply the necessary yaw moment to the vehicle when the driver's steering operation is a switchback operation. The vehicle travel control device according to any one of claims 1 to 3.   2. The braking / driving force control means gradually reduces the magnitude of a yaw moment to be applied to a vehicle based on the necessary yaw moment once the magnitude of the steering operation amount becomes a reference value or less. The vehicle travel control device according to any one of 4 to 4. The braking / driving force control means calculates a target braking / driving force of the vehicle based on the braking / driving operation amount of the driver, applies the necessary yaw moment to the vehicle, and uses the braking / driving force of the vehicle as the target braking / driving force. To calculate the target braking force of each wheel and the target driving force of the vehicle necessary to control the braking force of each wheel based on the target braking force and to control the driving force of the vehicle based on the target driving force The vehicle travel control apparatus according to claim 1, wherein the vehicle travel control apparatus is a vehicle travel control apparatus.

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