JP2006159991A - Steering control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately determine abnormality of a transfer ratio variable mechanism without erroneous determination and appropriately cope with the abnormality by performing the abnormality determination for the transfer ratio variable mechanism in consideration of the operating state of the transfer ratio variable mechanism. <P>SOLUTION: The steering control device confirms (S10 to 30) that a steered angle variable device 24 is normal, and determines (S60) that a vehicle is during traveling and whether or not the fixation condition during traveling of the vehicle is enacted regarding a rotation angle sensor 64. It determines (S70) that the vehicle is during operation of steering by a driver and whether or not the fixation condition during operation of steering is enacted regarding the rotation angle sensor 64. It determines (S80) that the vehicle is in a limit travel state and whether or not the fixation condition during limit travel is enacted regarding the rotation angle sensor 64. When it is determined that the fixation abnormal occurs in the rotation angle sensor 64, the fixation determination flag Fn is reset, the steered angle variation device 24 is locked by the locking device, and the turning control of the right and left front wheel is prohibited (S90). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle steering control device, and more specifically, to a vehicle steering control for controlling 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. Related to the device.

  In vehicles such as automobiles, there is provided a transmission ratio variable mechanism for changing a steering transmission ratio (steering gear ratio) by turning a steering wheel relative to a steering input means such as a steering wheel by a steering driving means. A steering control device that controls a steering transmission ratio by a transmission ratio variable mechanism has been conventionally known.

  Further, as described in, for example, Patent Document 1 below, as one of the steering control devices having a transmission ratio variable mechanism, an electric motor that makes the steering angle ratio of the steering system variable, and an actual steering angle ratio of the steering system And a deviation between the target steering angle ratio of the steered wheel and the detected actual steering angle ratio is a predetermined value or more in a situation where the steering angle ratio of the steering system is changed by an electric motor. A steering control device having a failure detection means for determining that the actual steering angle ratio sensor is abnormal when the above condition continues for a predetermined time or more is already known.

According to such a steering control device, when a failure or abnormality occurs in the actual steering angle ratio sensor, the failure detection means detects the failure or abnormality of the actual steering angle ratio sensor. When this occurs and the steering angle ratio of the steering system cannot be properly controlled, it is possible to take appropriate measures such as stopping the control of the steering angle ratio.
JP-A-11-91604

  Generally, in a steering control device equipped with a transmission ratio variable mechanism, as described in Patent Document 1, a transmission ratio such as a deviation between a target steering angle ratio of a steered wheel and a detected actual steering angle ratio. The abnormality of the sensor can be detected based on the deviation between the target rotation angle in the variable mechanism and the detected rotation angle or the electrical signal of the sensor that detects the rotation angle in the transmission ratio variable mechanism.

  However, depending on the operating condition of the transmission ratio variable mechanism, it may not be possible to detect the abnormality of the rotation angle sensor by the abnormality determination based on the deviation of the rotation angle or the electric signal of the rotation angle sensor, and the rotation angle sensor is normal. Nevertheless, it may be erroneously determined that the rotation angle sensor is abnormal, which may make it impossible to properly control the steering gear ratio and the steering angle of the steered wheels, and if the rotation angle sensor becomes abnormal Necessary measures such as stopping the transmission ratio variable mechanism cannot be taken.

  For example, in a situation where the speed increasing ratio of the transmission ratio variable mechanism is 0, the target relative rotation angle of the transmission ratio variable mechanism is 0, and the relative rotation angle detected by a normal rotation angle sensor is also 0. On the other hand, the detected value of the rotational angle sensor becomes 0 even when a sticking abnormality occurs in the rotational angle sensor, and therefore the deviation between the target relative rotational angle and the detected value of the rotational angle sensor is abnormal even when the rotational angle sensor is normal. The case is also 0, and abnormality of the rotation angle sensor cannot be detected by abnormality determination based on the deviation of the rotation angle. The same applies to the abnormality determination based on the electrical signal of the rotation angle sensor.

  The present invention has been made in view of the above-described problems relating to abnormality determination of a transmission ratio variable mechanism of a vehicle steering control device for controlling a steering transmission ratio, particularly its rotation angle sensor. By determining the abnormality of the transmission ratio variable mechanism in consideration of the operating condition of the transmission ratio variable mechanism, the abnormality of the transmission ratio variable mechanism is accurately determined without erroneous determination, and the abnormality of the transmission ratio variable mechanism is appropriately dealt with. That is.

  According to the present invention, the main problem described above is the steering transmission ratio for controlling the steering transmission ratio which is the ratio of the steered amount of the steered wheel to the steering operation amount of the steering input means by the driver according to the configuration of claim 1. In a vehicle steering control device having a control means and a steering transmission ratio detecting means for detecting an actual steering transmission ratio, a means for determining a traveling state of the vehicle, and a predetermined condition that causes the vehicle to change the steering transmission ratio. When the steering transmission ratio detected by the steering transmission ratio detection means does not change more than the steering transmission ratio change determination reference value for a reference time or longer, the steering transmission ratio by the steering transmission ratio control means This is achieved by a vehicle steering control device that reduces the control amount of the vehicle.

  According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 1, the vehicle is brought into the predetermined traveling state when the steering input means is being steered. It is configured to be determined that there is (configuration of claim 2).

  Further, according to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 2, the magnitude of the steering angular velocity or the magnitude of the steering torque is not less than the steering operation determination reference value. It is sometimes configured that it is determined that the steering input means is in a steering operation state (configuration of claim 3).

  According to the present invention, in order to effectively achieve the above main problems, in the configuration of claim 1, the steering transmission ratio control means is used to bring the vehicle behavior into a target behavior state. The vehicle is determined to be in the predetermined traveling state when behavior control for correcting and steering the steered wheel relative to the steering input means is performed (configuration of claim 4) .

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1, a situation in which an external force that steers the steered wheels acts is determined, and the steered wheels are steered. The vehicle is determined to be in the predetermined traveling state when it is determined that the external force acting is applied (configuration of claim 5).

  Further, according to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 5, the magnitude of the lateral acceleration of the vehicle or the magnitude of the yaw rate of the vehicle is greater than a reference value. In some cases, it is determined that an external force to steer the steered wheel is applied (configuration of claim 6).

  According to the present invention, in order to effectively achieve the main problems described above, the load of the steering transmission ratio control means is determined and the steering transmission ratio control means is determined. When the load of the steering transmission ratio is high, the steering transmission ratio change determination reference value is configured to be larger than when the load of the steering transmission ratio control means is low (configuration of claim 7).

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of the above-described first to seventh aspects, the steering transmission ratio controlled by the steering transmission ratio control means is small when the steering transmission ratio is small. The steering transmission ratio change criterion value is configured to be smaller than when the steering transmission ratio is large (configuration of claim 8).

  According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 4, the vehicle controls the braking / driving force of each wheel and the behavior of the vehicle as the target behavior. Means for calculating the target correction turning amount of the steered wheels and the target braking / driving force of each wheel for setting the state, means for controlling the correction turning amount of the steered wheels based on the target correction turning amount, and the target Means for controlling the braking / driving force of each wheel based on the braking / driving force, and the vehicle steering control device reduces and corrects the target correction turning amount when reducing the control amount of the steering transmission ratio. In addition, the target braking / driving force is increased and corrected (structure of claim 9).

  In general, when the vehicle is in a predetermined traveling state that causes a change in the steering transmission ratio, the steering transmission ratio changes. Therefore, a situation in which the steering transmission ratio detected by the steering transmission ratio detecting means does not change more than a predetermined reference value is predetermined. Accurately determining whether the steering transmission ratio is detected by the steering transmission ratio detecting means and the steering transmission ratio is controlled normally by the steering transmission ratio control means. Can do.

  According to the configuration of claim 1, the vehicle is in a predetermined traveling state that causes a change in the steering transmission ratio, and the steering transmission ratio detected by the steering transmission ratio detecting means does not change more than the steering transmission ratio change determination reference value. Is continued for a reference time or longer, the amount of control of the steering transmission ratio by the steering transmission ratio control means is reduced, so that the detection of the steering transmission ratio by the steering transmission ratio detection means and the control of the steering transmission ratio by the steering transmission ratio control means Whether or not the operation is normally performed can be accurately determined without erroneous determination, and steering is detected when the detection of the steering transmission ratio by the steering transmission ratio detection unit and the control of the steering transmission ratio by the steering transmission ratio control unit are abnormal. By reducing the control amount of the steering transmission ratio by the transmission ratio control means, it is possible to reliably reduce the possibility of inappropriate control of the steering transmission ratio being excessively performed.

  According to the second aspect of the present invention, since it is determined that the vehicle is in the predetermined traveling state when the steering input means is being steered, the steering transmission ratio is changed by the steering input means being steered. Thus, it can be reliably determined that the vehicle is in a predetermined traveling state.

  According to the third aspect of the present invention, when the magnitude of the steering angular velocity or the magnitude of the steering torque is greater than or equal to the steering operation determination reference value, it is determined that the steering input means is in a steering operation state. When the steering input means is being steered, this can be determined with certainty.

  According to the fourth aspect of the present invention, the behavior control for correcting and steering the steered wheels relative to the steering input means is performed using the steering transmission ratio control means to bring the vehicle behavior into the target behavior state. Since it is determined that the vehicle is in a predetermined traveling state when the vehicle is in a closed state, it is determined that the vehicle is surely in the predetermined traveling state in a situation where the steering transmission ratio changes as the steering wheel is corrected. be able to.

  According to the fifth aspect of the present invention, when a situation in which an external force that steers the steered wheels is applied is determined, and when it is determined that an external force that steers the steered wheels is applied, the vehicle travels a predetermined amount. Since it is determined that the vehicle is in the state, it is possible to reliably determine that the vehicle is in the predetermined traveling state in a situation where the steering transmission ratio changes due to the action of an external force that steers the steered wheels.

  According to the sixth aspect of the present invention, when the lateral acceleration of the vehicle or the yaw rate of the vehicle is greater than or equal to a reference value, it is determined that an external force for turning the steered wheel is applied. Therefore, it is possible to reliably determine a situation in which a lateral force as an external force acts on the steered wheel and the steering transmission ratio changes.

  In general, when the load of the steering transmission ratio control means is high, the amount of change in the steering transmission ratio under the control of the steering transmission ratio control means is smaller than when the load of the steering transmission ratio control means is low. In order to prevent an erroneous determination as to whether or not the steering transmission ratio detected by the means does not change, the steering transmission ratio change criterion value used for the determination is the steering transmission ratio when the load on the steering transmission ratio control means is high. It is preferable that the ratio control means is larger than when the load is low.

  According to the seventh aspect of the present invention, the load of the steering transmission ratio control means is determined, and when the load of the steering transmission ratio control means is high, the steering transmission ratio change determination is made compared to when the load of the steering transmission ratio control means is low. Since the reference value is increased, the steering transmission ratio detection means regardless of the load of the steering transmission ratio control means as compared with the case where the steering transmission ratio change determination reference value is constant regardless of the load of the steering transmission ratio control means. It is possible to accurately determine whether or not the steering transmission ratio is detected normally and the steering transmission ratio is controlled by the steering transmission ratio control means.

  In general, when the steering transmission ratio controlled by the steering transmission ratio control means is small, the amount of change in the steering transmission ratio under the control of the steering transmission ratio control means is smaller than when the steering transmission ratio is large. In order to prevent erroneous determination as to whether or not the steering transmission ratio detected by the detection means does not change, the steering transmission ratio change determination reference value used for the determination is large when the steering transmission ratio is small. It is preferable that it is smaller than the case.

  According to the eighth aspect of the present invention, when the steering transmission ratio controlled by the steering transmission ratio control means is small, the steering transmission ratio change determination reference value is made smaller than when the steering transmission ratio is large. Compared to the case where the steering transmission ratio change determination reference value is constant irrespective of the steering transmission ratio controlled by the ratio control means, the steering transmission ratio detection means detects the steering transmission ratio regardless of the magnitude of the steering transmission ratio, and It is possible to accurately determine whether or not the steering transmission ratio is normally controlled by the steering transmission ratio control means.

  According to the configuration of claim 9, when the control amount of the steering transmission ratio is reduced, the magnitude of the target correction turning amount is reduced and corrected, and the target braking / driving force is increased and corrected. The possibility of improper vehicle behavior control by turning can be reliably reduced, and the vehicle behavior can be effectively brought to the target behavior state by behavior control by controlling the braking / driving force of each wheel. Can do.

[Preferred embodiment of problem solving means]
According to one preferable aspect of the present invention, in the configuration of the first to ninth aspects, the steering transmission ratio control means drives the steering wheel relative to the steering input means, thereby driving the driver. It is comprised so that the steering drive means which carries out steering drive of the steering wheel independently of steering operation may be included (Preferred aspect 1).

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 1 described above, the steered driving means can steer the first steering shaft and the steered wheels connected to the steering input means. The second steering shaft is provided between the second steering shaft and the second steering shaft relative to the first steering shaft (preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration of the above-mentioned claims 1 to 9 or the preferred aspect 1 or 2, the control amount of the steering transmission ratio is reduced to a value corresponding to the speed increasing ratio of 0. In addition, it is configured to prevent relative rotation of the first and second steering shafts (preferred aspect 3).

  According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 3, the steered drive means has a lock device that prevents relative rotation of the first and second steering shafts. Is configured to prevent relative rotation of the first and second steering shafts (preferred aspect 4).

  According to another preferred embodiment of the present invention, in the configuration of the above-mentioned claims 1 to 9 or the preferred embodiments 1 to 4, the steering transmission ratio control means controls the steering gear ratio to a desired value. It is configured to control the transmission ratio (preferred aspect 5).

  According to another preferred aspect of the present invention, in the configuration of claim 4, the steering control device calculates a target yaw moment to be applied to the vehicle in order to set the vehicle behavior to the target behavior state, Steering transmission ratio control means based on the target yaw moment by correcting the steering wheel and by distributing the target yaw moment to the target yaw moment by controlling the braking / driving force of each wheel and the target yaw moment by correcting the steering wheel It is comprised so that the target turning control amount by may be calculated (Preferred aspect 6).

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

  FIG. 1 shows a vehicle steering control according to the present invention configured as a part of a behavior control device that controls the steering gear ratio, controls the braking / driving force of each wheel, and controls the steering angle of the left and right front wheels. It is a schematic block diagram which shows the Example of an apparatus.

  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 the steering wheels, are driven via a rack bar 18 and tie rods 20L and 20R by a rack-and-pinion type electric power steering device 16 driven in response to an operation of the steering wheel 14 by a driver. Steered.

  The steering wheel 14 is connected to a pinion shaft 30 of the power steering device 16 via an upper steering shaft 22 as a first steering shaft, a turning angle varying device 24, a lower steering shaft 26 as a second steering shaft, and a universal joint 28. Drive connected. 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 turning angle varying device 24 rotationally drives the lower steering shaft 26 relative to the upper steering shaft 22 so that the left and right front wheels 10FL and 10FR are turned to the steering wheel 14 for the purpose of steering gear ratio control and behavior control. On the other hand, it functions as an automatic steering device that drives the auxiliary steering relatively, and is controlled by the steering angle control electronic control device 34.

  If an abnormality in which the lower steering shaft 26 cannot be driven to rotate relative to the upper steering shaft 22 occurs in the turning angle varying device 24, a lock device not shown in FIG. The relative rotation of the housing 24A and the rotor 24B is mechanically prevented so that the relative rotation angle of the lower steering shaft 26 with respect to 22 does not change.

  In the illustrated embodiment, the electric power steering device 16 is a rack coaxial type electric power steering device, and converts the electric motor 36 and the rotational torque of the electric motor 36 into a force in the reciprocating direction of the rack bar 18. For example, it has a ball screw type conversion mechanism 38. The electric power steering device 16 is controlled by an electric power steering device (EPS) control electronic control device 40, and generates an auxiliary steering force that drives the rack bar 18 relative to the housing 42, so that the driver's It functions as an auxiliary steering force generator that reduces the steering burden. The auxiliary steering force generator may be of any configuration known in the art.

  The braking force of each wheel is controlled by controlling the pressure Pi (i = fl, fr, rl, rr) in the wheel cylinders 46FL, 46FR, 46RL, 46RR, that is, the braking pressure, by the hydraulic circuit 44 of the braking device 42. It has become so. Although not shown in the drawing, the hydraulic circuit 44 includes an oil reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven according to the depression operation of the brake pedal 48 by the driver. It is controlled by the master cylinder 50 and individually controlled by the behavior control electronic control device 52 as will be described in detail later.

  In the illustrated embodiment, the upper steering shaft 22 is provided with a steering angle sensor 60 for detecting the rotation angle of the upper steering shaft as a steering angle θ. As shown in FIG. A signal indicating θ is input to the steering angle control electronic control unit 34 and the behavior control electronic control unit 52 via the CAN 62. The turning angle varying device 24 is provided with a rotation angle sensor 64 that detects the relative rotation angle of the housing 24A and the rotor 24B as the relative rotation angle θre of the lower steering shaft 26 with respect to the upper steering shaft 22, and the relative rotation angle θre. Is input to the steering angle control electronic control unit 34. The rotation angle sensor 64 may be replaced with a sensor that detects the rotation angle θs of the lower steering shaft 26, and the relative rotation angle θre may be obtained as a steering angle difference θs−θ.

  The steering angle control electronic control device 34 and the behavior control electronic control device 52 include a signal indicating the vehicle lateral acceleration Gy detected by the lateral acceleration sensor 66 and a signal indicating the vehicle yaw rate γ detected by the yaw rate sensor 68. A signal indicating the vehicle speed V detected by the vehicle speed sensor 70 is input via the CAN 62, a signal indicating the master cylinder pressure Pm detected by the pressure sensor 72, and the braking pressure Pi of each wheel detected by the pressure sensors 74FL to 74RR. Is input to the behavior control electronic control unit 52.

  The steering angle control electronic control device 34, the EPS control electronic control device 40, and the behavior control electronic control device 52 each have a CPU, a ROM, a RAM, and an input / output port device, which are connected by a bidirectional common bus. It may include microcomputers connected to each other. Further, the steering angle sensor 60, the rotation angle sensor 64, the lateral acceleration sensor 66, and the yaw rate sensor 68 are respectively set to the steering angle θ, the relative rotation angle θre, and the lateral acceleration when the vehicle is steered, steered, or turned in the left turn direction. Gy and yaw rate γ are detected.

  As will be described later, the behavior control electronic control unit 52 calculates a steering gear ratio Rg for achieving a predetermined steering characteristic based on the vehicle speed V according to a flowchart shown in FIG. The provisional target rudder angle δst is calculated based on the steering angle θ indicating the amount and the steering gear ratio Rg.

  Also, the behavior control electronic control unit 52 includes a spin state amount SS indicating the degree of spin of the vehicle based on a driving operation amount such as a steering angle θ and a vehicle state amount such as a lateral acceleration Gy of the vehicle that change as the vehicle travels. The vehicle's target yaw moment Mt and the vehicle's target deceleration for calculating the drift-out state quantity DS indicating the degree of drift-out of the vehicle and stabilizing the vehicle behavior based on the spin state quantity SS and the drift-out state quantity DS Calculate Gxbt.

  Then, the behavior control electronic control unit 52 distributes the target yaw moment Mt at a predetermined ratio to the target yaw moment Mts by the steering angle control of the left and right front wheels and the target yaw moment Mtb by the control of the braking force of each wheel. The target steering angle Δδmt of the left and right front wheels is calculated based on the yaw moment Mts, and the sum of the provisional target steering angle δst and the target steering angle Δδmt is calculated as the target steering angle δt of the left and right front wheels to indicate the target steering angle δt. The signal is output to the steering angle control electronic control unit 34 via the CAN 62.

  In particular, as is well known in the art, the behavior control electronic control unit 52 is designed to decelerate the vehicle and to apply a yaw moment in a turning suppression direction to the vehicle so as to decelerate the vehicle. Mt and the target deceleration Gxbt of the vehicle are calculated. Therefore, the turning direction of the target turning angle Δδmt in this case is the direction opposite to the turning direction, that is, the switchback direction, and the behavior of the vehicle is stabilized by behavior control. In the process, the left and right front wheels are steered relatively in the turning direction, that is, in the direction of additional turning.

  Further, as is well known in the art, the behavior control electronic control unit 52 decelerates the vehicle and applies a yaw moment in the turning assist direction to the vehicle when the vehicle is in a drift-out state. The moment Mt and the target deceleration Gxbt of the vehicle are calculated. In this case, the lateral force of the front wheels is saturated, and the lateral force cannot be increased even if the front wheels are turned and steered, so the target yaw moment Mt Are allotted to the target yaw moment Mtb by controlling the braking force of each wheel, and the target turning angle Δδmt is calculated to zero.

  The behavior control electronic control unit 52 calculates the target braking pressure Pti of each wheel based on the target deceleration Gxbt and the target yaw moment Mtb, and the hydraulic circuit so that the braking pressure Pi of each wheel becomes the corresponding target braking pressure Pti. 44 is controlled.

  Also, the behavior control electronic control unit 52 is based on the wheel speed Vwi of each wheel, and the vehicle body speed Vb and the braking slip amount SBi (i = fl, fr, rl, rr) of each wheel in a manner known in the art. When the braking slip amount SBi becomes larger than the reference value for starting the anti-skid control (ABS control) and the start condition for the anti-skid control is satisfied, the braking of the wheel is performed until the end condition for the anti-skid control is satisfied. Anti-skid control is performed by controlling the braking pressure Pi of the wheel so that the slip amount is within a predetermined range.

  The electronic controller 52 for behavior control is based on the wheel speed Vwi of each wheel, and the vehicle body speed Vb and the acceleration slip amount SAi (i = fl, fr, rl, rr) of each wheel in the manner known in the art. When the acceleration slip amount SAi becomes larger than the reference value for starting traction control (TRC control) and the traction control start condition is satisfied, the acceleration slip amount of the wheel is increased until the traction control end condition is satisfied. Traction control is performed by controlling the braking pressure Pi of the wheel so as to be within a predetermined range.

  Although not shown in the flowchart, the steering angle control electronic control unit 34 calculates the target relative rotation angle θret of the turning angle varying device 24 based on the target steering angle δt of the left and right front wheels, and calculates the target relative rotation angle θret. The electric motor 32 of the turning angle varying device 24 is controlled so that the deviation Δθre from the actual relative rotation angle θre detected by the rotation angle sensor 64 becomes zero.

  Accordingly, when the behavior of the vehicle is stable or the vehicle is in a drift-out state, the steering angle control electronic control unit 34 has a target turning angle Δδmt of 0, so that the steering angle of the left and right front wheels is a provisional target. The steered angle varying device 24 is controlled so as to be the steered angle δst, thereby performing steering gear ratio control for steering the left and right front wheels 10FL and 10FR with predetermined steering characteristics in accordance with the steering operation of the driver.

  The steering angle control electronic control unit 34 performs steering gear ratio control when the vehicle is in a spin state, and steers the left and right front wheels relative to the provisional target steering angle δst relative to the provisional target steering angle Δδmt. Thus, an anti-spin yaw moment is applied to the vehicle to reduce the spin state of the vehicle.

  Further, the steering angle control electronic control unit 34 determines whether or not various fixing conditions are satisfied for the rotation angle sensor 64 according to the flowchart shown in FIG. 2 as described later, that is, appropriately detects the relative rotation angle θre. Therefore, it is determined whether or not the turning control of the left and right front wheels cannot be properly executed by the turning angle varying device 24, and any fixing condition is established for the rotation angle sensor 64. If it is determined that the steering angle is changed, the target relative rotation angle θret is reduced to 0, and the turning angle varying device 24 is mechanically locked by operating the locking device of the turning angle varying device 24 to perform upper steering. The relative rotation of the lower steering shaft 26 with respect to the shaft 22 is prevented.

  The behavior control electronic control unit 52 reduces all of the target yaw moment Mt when the target relative rotation angle θret is reduced to 0 by the steering angle control electronic control unit 34 and the steering control of the left and right front wheels is prohibited. Allocation is made to the target yaw moment Mtb by controlling the braking force of each wheel, and the yaw moment corresponding to the target yaw moment Mt is given to the vehicle by controlling the braking force of each wheel to stabilize the behavior of the vehicle.

  Further, the EPS control electronic control unit 40 indicates a signal indicating the steering torque Ts from a steering torque sensor not shown in FIG. 1, a signal indicating the steering angle θ from the steering angle sensor 60, and a vehicle speed V from the vehicle speed sensor 70. The electric power steering device 16 receives the signal, and the electronic control device 40 for EPS control generates a steering assist force that reduces the driver's steering burden in a manner known in the art based on the information. The electronic power steering device 16 is controlled so as to assist the control of the steering angle of the left and right front wheels by the steering angle control electronic control device 34 and to reduce the fluctuation of the steering reaction force due to the control of the steering angle of the left and right front wheels. To do.

  The steering gear ratio control and behavior control by the steering angle control of the steering wheel described above, the anti-skid control by the control of the braking force, the traction control, the behavior control, the steering assist force and the steering reaction force control itself are the gist of the present invention. Instead, these controls may be performed in any manner known in the art.

  Next, an abnormality determination routine for the rotation angle sensor 64 of the turning angle varying device 24 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. The sticking determination flag Fn relates to whether or not a sticking abnormality has occurred in the rotation angle sensor. 0 indicates that a sticking abnormality has occurred, and 1 indicates that a sticking abnormality has not occurred.

  First, in step 10, when the sticking determination flag Fn is reset to 0 as initialization, the lock device of the turning angle varying device 24 is unlocked, and the lock device is already unlocked. Is maintained in that state.

  In step 20, a command signal for rotating the lower steering shaft 26 relative to the upper steering shaft 22 by a predetermined rotation angle such as 360 ° is output to the turning angle varying device 24, and in step 30. It is determined whether or not the rotation angle sensor 64 has detected a rotation of a predetermined rotation angle in the turning angle varying device 24. If a negative determination is made, the sticking determination flag Fn is 0. After the signal is transmitted to the behavior control electronic control unit 52, the process returns to step 20, and when an affirmative determination is made, the sticking determination flag Fn is set to 1 in step 40.

  In step 50, reference values .theta.re1 to .theta.re3 in each determination in steps 60 to 80 described later are calculated from the map corresponding to the graph qualitatively shown in FIG. In this case, the reference values θre1 to θre3 become smaller as the speed increasing ratio of the turning angle varying device 24 (proportional to the difference Rg−Rgo between the steering gear ratio Rg and its initial value Rgo) is closer to 0, and the turning angle becomes smaller. The calculation is performed so as to increase as the load of the variable device 24 increases. In this case, the load of the turning angle varying device 24 may be detected in any manner known in the art.

  In step 60, it is determined whether or not the vehicle is traveling and the rotation angle sensor 64 is in a fixed condition during vehicle traveling. If an affirmative determination is made, the process proceeds to step 90. When the determination is made, the process proceeds to step 70. In this case, whether or not the vehicle is traveling may be determined by determining whether or not the vehicle speed V is equal to or higher than a reference value Vo (a positive constant), and the fixing condition during traveling of the vehicle is satisfied. For example, it is determined whether or not the situation in which the detected value θre of the rotation angle sensor 64 is equal to or less than the reference value θre1 set in step 50 continues for a reference time Tc1 (positive constant). May be performed.

  In step 70, it is determined whether the driver is performing a steering operation and the rotation angle sensor 64 is in a fixed condition during the steering operation. If an affirmative determination is made, the process directly proceeds to step 90. If the determination is negative, the process proceeds to step 80. In this case, it is determined whether or not the driver is performing a steering operation, for example, whether or not the magnitude of the steering angular velocity θd, which is a differential value of the steering angle θ, is equal to or greater than a reference value θdo (a positive constant). Alternatively, the determination may be made by determining whether the magnitude of the steering torque Ts is greater than or equal to a reference value Tso (positive constant), and determining whether the fixing condition during the steering operation is satisfied The determination may be made by determining whether or not the situation where the detection value θre of the angle sensor 64 is equal to or less than the reference value θre2 set in step 50 continues for a reference time Tc2 (positive constant).

  Further, for example, a driving torque for the lower steering shaft 26 by the turning angle varying device 24 is detected, and the rotation angle sensor 64 detects the turning angle varying device 24 even though the driving torque is applied to the lower steering shaft 26. When the value does not change, or the detected value θre of the rotation angle sensor 64 does not change more than the reference value θre3 even if the driving torque of the turning angle varying device 24 changes by a predetermined amount or more, the situation is more than the reference time Tc3 (positive constant) When it continues, it may be determined that the fixing condition during the steering operation is satisfied.

  In step 80, it is determined whether or not the vehicle is in the limit running state and the rotation angle sensor 64 is in the limit running condition, and if a negative determination is made, the process returns to step 50. When an affirmative determination is made, in step 90, the sticking determination flag Fn is reset to 0, a signal indicating that the sticking judgment flag Fn is 0 is transmitted to the behavior control electronic control unit 52, and turning is performed. The angle varying device 24 is locked by the locking device, and the relative rotation of the lower steering shaft 26 with respect to the upper steering shaft 22 is mechanically prevented.

  Whether or not the vehicle is in the vehicle limit running state (whether or not an external force that steers the left and right front wheels is applied) is determined by behavior control or traction control or anti-noise control by steering angle control and braking force control. When any one of the skid controls is being executed, it may be determined that the vehicle is in the limit traveling state. Further, when the lateral acceleration Gy of the vehicle or the magnitude of the yaw rate γ of the vehicle is equal to or greater than the corresponding reference value, it may be determined that the vehicle is in the limit running state, and the vehicle includes a sensor that detects the vertical acceleration Gz. In this case, it may be determined that the vehicle is in the limit running state when the vertical acceleration Gz of the vehicle is equal to or greater than the corresponding reference value.

  Next, a vehicle behavior control routine based on the steering angle control of the left and right front wheels and the braking force control of each wheel in the illustrated embodiment will be described with reference to the 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.

First, at step 110, a signal indicating the steering angle θ is read, and at step 120, the steering gear ratio Rg is calculated from the map corresponding to the graph shown in FIG. The provisional target steering angle δst of the left and right front wheels for achieving a predetermined steering characteristic is calculated according to the following formula 1.
δst = θ / Rg (1)

  The provisional target rudder angle δst is the sum of the rudder angle δw (= θ / Rgo) corresponding to the driver's steering operation and the control turning angle δc for achieving a predetermined steering characteristic. Further, the control of the steering characteristic itself does not form the gist of the present invention, and the steering gear ratio Rg may be calculated in any manner known in the art, for example, improving the transient response of the vehicle to the steering. It may be changed depending on the steering speed.

  In step 130, a spin state quantity SS indicating the degree of vehicle spin and a drift-out state quantity DS indicating the degree of vehicle drift-out are calculated in a manner known in the art. In this case, the vehicle target yaw moment Mt and the vehicle target deceleration Gxbt for stabilizing the vehicle behavior based on the spin state quantity SS and the drift-out state quantity DS are calculated in a manner known in the art. The

  In step 150, the flag Fn set in accordance with the flowchart shown in FIG. 2 is 0, and the steering control of the left and right front wheels is prohibited, or other conditions for prohibiting the steering control known in the art are satisfied. If a negative determination is made, the process proceeds to step 180. If an affirmative determination is made, the process proceeds to step 160.

  In step 160, the target yaw moment Mtb obtained by controlling the braking force of each wheel is set as the target yaw moment Mt. In step 170, the target turning angle Δδmt of the left and right front wheels is set to 0, and then step 200 is performed. Proceed to

In step 180, based on the target yaw moment Mt and the distribution ratio Rb (a positive constant larger than 0 and smaller than 1), the target yaw moment Mts and each wheel by the steering angle control of the left and right front wheels according to the following formulas 2 and 3. A target yaw moment Mtb by controlling the braking force is calculated. The distribution ratio Rb may be variably set according to the traveling state of the vehicle.
Mts = (1-Rb) Mt (2)
Mtb = Rb ・ Mt (3)

In step 190, the target turning angle Δδmt of the left and right front wheels for achieving the target yaw moment Mts is calculated in a manner known in the art, and in step 200, the left and right according to the following equation 4 is calculated. The target rudder angle δt of the front wheels, that is, the target rudder angle δt of the left and right front wheels to achieve vehicle behavior control by controlling the steering characteristics and the rudder angle control of the left and right front wheels is calculated, and a signal indicating the target rudder angle δt is It is transmitted to the control electronic control unit 24.
δt = δst + Δδmt (4)

  In step 210, the target braking force of each wheel for achieving the target yaw moment Mtb and the target deceleration Gxbt of the vehicle is calculated as well known in the art, and the braking pressure of each wheel is calculated. Pi (i = fl, fr, rl, rr) is controlled to become the corresponding target braking pressure Pti.

  Thus, according to the illustrated embodiment, in step 60, it is determined whether or not the vehicle is traveling and whether the rotation angle sensor 64 is in a fixed condition during vehicle traveling. A determination is made as to whether or not the fixing condition during the steering operation is satisfied for the rotation angle sensor 64 while the driver is performing the steering operation. In step 80, the vehicle is in the limit running state and the rotation angle sensor 64 is detected. A determination is made as to whether or not the sticking condition during limit running is established.

  Whether or not the fixing condition is satisfied in steps 60 to 80 is determined based on a deviation Δθre between the target relative rotation angle θret and the actual relative rotation angle θre detected by the rotation angle sensor 64. Instead, the steering gear ratio Rg is set to its initial value because the determination is made based on whether or not the rotation angle sensor 64 has detected the relative rotation in the situation where the relative rotation should occur in the turning angle varying device 24. Rgo or a value close thereto, and when the target relative rotation angle θret of the turning angle varying device 24 and the deviation Δθre between the target relative rotation angle θret and the actual relative rotation angle θre are 0 or very small values, It is possible to accurately determine whether or not there is a sticking abnormality in the rotation angle sensor 64. With this, when there is a sticking abnormality in the rotation angle sensor 64, the abnormality is reliably determined. Preparative it is, it is possible to reliably prevent the at the situation where the fixation abnormality has not occurred in the rotational angle sensor 64 abnormally fixed to the rotation angle sensor 64 is erroneously determined to be occurring.

  Also, according to the illustrated embodiment, when a negative determination is made in any of steps 60 to 80, that is, when it is determined that there is no abnormality in the rotation angle sensor 64, the fixation determination flag Fn is set. As long as the other steering control prohibition conditions are not satisfied, a negative determination is made in step 150 of the flowchart shown in FIG. 4, and the processing of steps 110 to 140 and steps 180 to 200 is performed. Target steering to give the vehicle the required yaw moment by controlling the provisional target steering angle δst of the left and right front wheels and the steering angle of the left and right front wheels so that the target steering angle δt of the left and right front wheels achieves a predetermined steering gear ratio characteristic The steering angle variable device 2 is calculated so as to be summed with the angle Δδmt, a signal indicating the target steering angle δt is transmitted to the steering angle control electronic control device 24, and the steering angle of the left and right front wheels becomes the target steering angle δt. There is controlled.

  On the other hand, when an affirmative determination is made in any one of steps 60 to 80, that is, when it is determined that a fixing abnormality has occurred in the rotation angle sensor 64, a fixing determination flag Fn is set to 0 in step 90. And the turning angle varying device 24 is locked by the locking device, and the relative rotation of the lower steering shaft 26 with respect to the upper steering shaft 22 is mechanically prevented.

  In step 150 of the flowchart shown in FIG. 4, an affirmative determination is made. In step 160, the target yaw moment Mtb by controlling the braking force of each wheel is set as the target yaw moment Mt. At this time, the target turning angle Δδmt of the behavior control is set to 0, so that the steering control of the left and right front wheels is not executed, and the yaw moment corresponding to the target yaw moment Mt is applied to the vehicle by controlling the braking force of each wheel. It is given and the behavior of the vehicle is stabilized.

  Therefore, according to the illustrated embodiment, when a sticking abnormality occurs in the rotation angle sensor 64, the behavior control by the steering gear ratio control and the steering control of the left and right front wheels is improperly executed, and due to this. Steering due to the fact that the target relative rotation angle θret is forcibly achieved by the turning angle varying device 24 in a situation where the stability of the vehicle is lowered or it is difficult to achieve the target relative rotation angle θret. It is possible to reliably prevent an excessive load from acting on the angle variable device 24 and to reliably compensate that the behavior control by the steering control of the left and right front wheels is not executed by the behavior control by controlling the braking force of each wheel. In addition, the behavior of the vehicle can be reliably stabilized.

  In particular, according to the illustrated embodiment, the reference values θre1 to θre3 used in the discrimination of steps 60 to 80 become smaller as the speed increasing ratio of the turning angle varying device 24 becomes closer to 0 in step 50. Therefore, the rotation angle sensor 64 is normal in a region where the speed increase ratio is small as compared with the case where each reference value θre1 to θre3 is constant regardless of the speed increase ratio of the turning angle varying device 24. In spite of the above, it is erroneously determined that the rotation angle sensor 64 is abnormally fixed, or the rotation angle sensor 64 is normal in the region where the speed increase ratio is large, although the rotation angle sensor 64 is abnormal. Can be reliably reduced.

  Further, each reference value θre1 to θre3 is calculated so as to increase as the load of the turning angle varying device 24 increases, so that the load of the turning angle varying device 24 is high and the target relative rotation angle θret is difficult to achieve. Since the reference values θre1 to θre3 are constant regardless of the load of the turning angle varying device 24, the rotation angle is set when the load of the turning angle varying device 24 is low. Although the sensor 64 is abnormal, it is erroneously determined that the rotation angle sensor 64 is normal, or the rotation angle sensor 64 is normal in a situation where the load of the turning angle varying device 24 is high. It is possible to reliably reduce the possibility of erroneous determination that the rotation angle sensor 64 is stuck abnormally.

  Further, according to the illustrated embodiment, the sticking determination flag Fn is reset to 0 as initialization in step 10 and the lock device of the turning angle varying device 24 is unlocked. A command signal for rotating the rotation angle is output to the turning angle varying device 24. After the rotation angle sensor 64 detects the rotation of the predetermined turning angle in the turning angle varying device 24 in step 30, step 40 is performed. Since the subsequent steps are executed, it is possible to determine whether or not the rotation angle sensor 64 is normal after confirming that the turning angle varying device 24 itself is normal.

  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, in step 60, it is determined whether or not the vehicle is traveling and whether the rotation angle sensor 64 is in a fixed condition during vehicle traveling. It is determined whether or not the steering operation by the driver is being performed and the fixing condition during the steering operation is satisfied for the rotation angle sensor 64. In step 80, the vehicle is in the limit running state and the rotation angle sensor. 64 is determined whether or not the sticking condition during the limit running is established, but any of steps 60 to 80 may be omitted, and detailed determination of each step is performed. Any of these may be omitted.

  Further, in the above-described embodiment, the reference values θre1 to θre3 used in the discrimination of steps 60 to 80 are smaller as the speed increasing ratio of the turning angle varying device 24 is closer to 0 in step 50. The variability setting is made in accordance with the speed increasing ratio and the load of the turning angle varying device 24 so that the larger the load of the turning angle varying device 24 is, but any of the reference values θre1 to θre3 is set. Alternatively, the steering angle variable device 24 may be modified so as not to be variably set in accordance with the speed increasing ratio or the load.

  In the above-described embodiment, the reference values θdo and Tso as the steering operation determination reference values are positive constants, but the steering operation determination reference value is higher when the vehicle speed V is higher than when the vehicle speed V is low. It may be variably set according to the vehicle speed V so as to be a small positive value. In this case, it is determined at an early stage that the vehicle is in a predetermined traveling state when the vehicle is traveling at a high vehicle speed, and the steering transmission ratio is thereby determined. Can be reduced early.

  The steering operation determination reference value is a positive value that is smaller when each wheel braking force such as anti-skid control, traction control, and behavior control is individually controlled than when such control is not performed. In this case, when the behavior of the vehicle is unstable, it is possible to quickly determine that the vehicle is in a predetermined traveling state, thereby reducing the steering transmission ratio early. .

  In the above-described embodiment, the steering gear ratio Rg for achieving a predetermined steering characteristic is calculated based on the vehicle speed V, and provisional based on the steering angle θ indicating the driver's steering operation amount and the steering gear ratio Rg. The target rudder angle δst is calculated, and the target rudder angle δt for the left and right front wheels is set to the sum of the provisional target rudder angle δst for controlling the steering gear ratio and the target turning angle Δδt for vehicle behavior control by the rudder angle control for the left and right front wheels. However, the steering control device of the present invention may be applied to a vehicle in which behavior control by steering wheel steering control is not performed.

  Further, in the above-described embodiment, the turning angle varying device 24 rotates the lower steering shaft 26 relative to the upper steering shaft 22 by the electric motor 32 so that the left and right sides do not depend on the steering operation of the driver. The front wheels 10FL and 10FR are automatically steered. However, as long as the steering transmission ratio can be controlled and the actual steering transmission ratio can be detected by the detection means, the steering angle varying device is a technology of the related art. Any structure known in the art may be used.

  In the above-described embodiment, the lock device of the turning angle varying device 24 mechanically prevents the lower steering shaft 26 from rotating relative to the upper steering shaft 22. As long as the relative rotation in the turning angle varying device 24 can be prevented, the lock device may be, for example, an electromagnetic force that prevents the relative rotation.

  In the above embodiment, the vehicle target yaw moment Mt and the vehicle target deceleration Gxbt for stabilizing the vehicle behavior are calculated, and the target yaw moment Mt is steered to the left and right front wheels at a predetermined ratio. The target yaw moment Mts by angle control and the target yaw moment Mtb by control of the braking force of each wheel are distributed, and the target turning angle Δδt of the left and right front wheels is calculated based on the target yaw moment Mts. The target turning angle Δδt for stabilizing the behavior of the vehicle may be calculated in any manner known in the art.

  In the above-described embodiment, the behavior control by controlling the braking / driving force controls the behavior of the vehicle by controlling the braking force of each wheel and applying a required yaw moment to the vehicle. However, the behavior control by controlling the braking / driving force may be performed by controlling the braking force and driving force of each wheel, and the behavior control by controlling the braking / driving force may be omitted.

Implementation of a vehicle steering control device according to the present invention configured as part of a behavior control device that controls the steering gear ratio and controls the braking / driving force of each wheel and the steering angle of the left and right front wheels to control the behavior of the vehicle 1 is a schematic configuration diagram illustrating Example 1. FIG. 3 is a flowchart illustrating an abnormality determination routine of a rotation angle sensor of the turning angle varying device according to the first embodiment. It is a graph which shows the relationship between the speed increase ratio and load of a turning angle variable apparatus, and reference value (theta) re1- (theta) re3. 4 is a flowchart showing a vehicle behavior control routine by controlling the steering angle of the left and right front wheels and controlling the braking force of each wheel in the first embodiment. It is a graph which shows the relationship between the vehicle speed V and steering gear ratio Rg.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Steering wheel 16 Electric power steering device 24 Steering angle variable device 34 Steering angle control electronic control device 40 Electric power steering device (EPS) control electronic control device 42 Braking device 52 Behavior control electronic control device 60 Steering angle Sensor 62 CAN
64 Rotation angle sensor 66 Lateral acceleration sensor 68 Yaw rate sensor 70 Vehicle speed sensor 72 Pressure sensor 74FL to 74RR Pressure sensor

Claims (9)

  A steering transmission ratio control unit that controls a steering transmission ratio that is a ratio of a steering wheel turning amount to a steering operation amount of a steering input unit by a driver; and a steering transmission ratio detection unit that detects an actual steering transmission ratio. In the vehicle steering control device, a means for determining a traveling state of the vehicle, and a steering transmission ratio detected by the steering transmission ratio detecting means when the vehicle is in a predetermined traveling state in which the steering transmission ratio is changed. A vehicle steering control device, characterized in that when the situation where the steering transmission ratio change determination reference value does not change for more than a reference time continues for a reference time or longer, the control amount of the steering transmission ratio by the steering transmission ratio control means is reduced.   The vehicle steering control device according to claim 1, wherein the vehicle is determined to be in the predetermined traveling state when the steering input means is being steered.   The steering input means is determined to be in a steering operation state when the magnitude of the steering angular velocity or the magnitude of the steering torque is greater than or equal to a steering operation determination reference value. A steering control device for a vehicle.   When the behavior control for correcting and steering the steered wheels relative to the steering input means is performed using the steering transmission ratio control means to bring the vehicle behavior into the target behavior state, the vehicle is The vehicle steering control device according to claim 1, wherein the vehicle steering control device is determined to be in the traveling state.   A situation in which an external force that steers the steered wheel is applied is determined, and when it is determined that an external force that steers the steered wheel is applied, the vehicle is determined to be in the predetermined traveling state. The vehicle steering control device according to claim 1.   6. The vehicle according to claim 5, wherein when the lateral acceleration of the vehicle or the yaw rate of the vehicle is greater than or equal to a reference value, it is determined that an external force for turning the steered wheel is applied. A steering control device for a vehicle.   Determining the load of the steering transmission ratio control means, and increasing the steering transmission ratio change determination reference value when the load of the steering transmission ratio control means is high compared to when the load of the steering transmission ratio control means is low. The vehicle steering control device according to any one of claims 1 to 6.   8. The steering transmission ratio change determination reference value is made smaller when the steering transmission ratio controlled by the steering transmission ratio control means is smaller than when the steering transmission ratio is large. The vehicle steering control device described. The vehicle has a means for controlling the braking / driving force of each wheel, a means for calculating the target correction turning amount of the steered wheels and the target braking / driving force of each wheel for setting the vehicle behavior to the target behavior state, and the target correction. The vehicle steering control device has means for controlling the corrected turning amount of the steered wheel based on the turning amount, and means for controlling the braking / driving force of each wheel based on the target braking / driving force. 5. The vehicle control device according to claim 4, wherein when the ratio control amount is reduced, the target correction turning amount is corrected to be reduced and the target braking / driving force is increased to be corrected.

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