JP4363316B2 - Steering control device for vehicle - Google Patents

Description

  The present invention relates to a vehicle steering control device, and more specifically, controls a steering transmission ratio, which is a ratio of a turning angle change amount of a steering wheel to a steering operation change amount of a steering input means by a driver, and a steering wheel. The present invention relates to a vehicle steering control device that performs behavior control so that the behavior of the vehicle becomes a target behavior state by correcting the steering.

  In a vehicle such as an automobile, the steering wheel side rotation member is driven to rotate relative to the steering wheel side rotation member by the steering drive device, thereby turning the steering wheel relative to the steering wheel and steering transmission. A steering control device that includes a transmission ratio variable mechanism that changes a ratio (steering gear ratio) and is configured to control the steering transmission ratio by the transmission ratio variable mechanism has been conventionally known.

  Further, as described in, for example, the following Patent Document 1 relating to the application of the present applicant, as one of the steering control devices provided with a transmission ratio variable mechanism, the steered drive device is relative to the steering wheel side rotating member. Has a motor that rotationally drives the steering wheel side rotation member. When the load on the motor increases, the rotation of the motor stops and the lock device is activated to rotate the steering wheel side rotation member and the steering wheel side rotation member relative to each other. Steering control devices that prevent this are already known.

According to such a steering control device, when the load on the electric motor becomes high, the rotational drive of the electric motor is stopped, so that the high load on the electric motor can be reliably prevented from becoming abnormal and the lock device can be prevented from becoming abnormal. Since the relative rotation of the steering wheel side rotation member and the steering wheel side rotation member is prevented by the operation, the steering operation of the steering wheel by the driver can be reliably transmitted to the steering wheel.
JP 2004-58787 A

  However, in the case of a vehicle in which behavior control is performed to correct and steer the steered wheels by the steering drive device so that the behavior of the vehicle becomes the target behavior state when the behavior of the vehicle is unstable, the steering wheel is activated by the operation of the lock device. If the relative rotation of the side rotation member and the steering wheel side rotation member is prevented, the steering wheel cannot be corrected and steered by the steering drive device, and the behavior control by the correction steering of the steering wheel cannot be performed. End up.

  According to the present invention, when the load of the steering drive device that rotationally drives the steering wheel side rotation member relative to the steering wheel side rotation member becomes high, the operation of the steering drive device is stopped and the steering wheel is operated by the lock device. The present invention has been made in view of the above-described problems in the vehicle steering control device configured to prevent the relative rotation of the side rotation member and the steering wheel side rotation member. When the behavior control by the modified steering of the wheel is performed, the operation of the steering drive device is performed until the load of the steering drive device becomes higher than when the behavior control by the modified steering of the steered wheel is not performed. By not operating the stop and lock device, the behavior control by the modified steering of the steered wheels is performed as effectively as possible while reducing the possibility of excessive load acting on the steering drive device continuously. Is Rukoto.

  According to the present invention, the main problem described above is the structure of claim 1, that is, the steering driving means capable of steering the steering wheel independently of the driver's steering operation, and the steering by the steering driving means. A steering transmission ratio control unit that controls a steering transmission ratio that is a ratio of a steering amount of a steering wheel to a steering operation amount of a steering input unit by a driver by steering the wheel, and steering by the steering driving unit Steering by the steering driving means when the load of the steering driving means exceeds an allowable reference value by behavior control means for performing behavior control so that the behavior of the vehicle becomes a target behavior state by correcting and steering the wheels. In a vehicle steering control device having a steering drive amount reduction means for reducing the steering drive amount of a wheel, the steering drive amount reduction means is used when the steering wheel is corrected and steered by the behavior control means. By the behavior control means It is achieved by a vehicle steering control apparatus characterized by increasing the allowable reference value as compared with when the modified steering of the steering wheel is not performed.

  According to the present invention, in order to effectively achieve the above-mentioned main problem, in the configuration of claim 1, the steered drive means is a steering wheel side member relative to the steering input means side member. The steered wheels are steered by relatively driving the steered wheels, and the steered drive amount reducing means reduces the relative drive amount by the steered drive means to 0 to thereby steer the steered wheels. Is reduced to 0 (configuration of claim 2).

  According to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 2, the steered drive means is configured such that the steering wheel side member is relative to the steering input means side member. The steering drive amount reducing means is configured to reduce the steering drive amount of the steered wheels by the steering drive means to 0 and to operate the lock device (claim). Configuration of Item 3).

  According to the present invention, in order to effectively achieve the above main problems, in the configuration of the above claims 1 to 3, when the steered wheels are corrected and steered by the behavior control means, It is comprised so that it may be when the correction turning amount of a steered wheel is not 0 (structure of Claim 4).

  According to the present invention, in order to effectively achieve the above-mentioned main problems, in the configuration of the above-described claims 1 to 4, when the steered wheel is steered by the behavior control means, It is comprised so that the time of the correction | amendment steering of a steering wheel is anticipated (structure of Claim 5).

  Further, according to the present invention, in order to effectively achieve the above-mentioned main problem, in the configuration of the above-described claim 5, when the steering wheel is expected to be corrected, the vehicle running stability is It is comprised so that it may be a time when the braking / driving force of a wheel is controlled in order to ensure (Embodiment 6).

  According to the present invention, in order to effectively achieve the above-mentioned main problems, in the configuration of the above-described claims 1 to 6, the allowable reference value is obtained by correcting the steered wheels by the behavior control means. Even when the steering wheel is turned, it is configured so as to be smaller than the load when the steered wheel is steered beyond the maximum steerable position of the steered wheel.

  According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claims 1 to 7 described above, the vehicle loads the steering load of the steered wheels by the driver or the steering drive means. A steering assist force generating means for reducing is provided, and the steering assist force generating means is configured to stop the generation of the steering assist force when the load exceeds a reference value.

  According to the present invention, in order to effectively achieve the main problems described above, the vehicle according to any one of claims 1 to 8 includes means for controlling the braking / driving force of each wheel, and the behavior The control means calculates the target correction turning amount of the steered wheels and the target braking / driving force of each wheel for bringing the vehicle behavior into the target behavior state, and corrective steering of the steered wheels based on the target correction turning amount. Means for controlling the amount and means for controlling the braking / driving force of each wheel based on the target braking / driving force, and the vehicle steering control device corrects the target when reducing the steering driving amount of the steering wheel. The steering amount is reduced and corrected, and the target braking / driving force is increased and corrected (configuration of claim 9).

  According to the first aspect of the present invention, when the load of the steering driving means becomes equal to or greater than the allowable reference value, the steering driving amount of the steering wheel by the steering driving means is reduced, and the modified steering of the steering wheel by the behavior control means is reduced. Since the allowable reference value is increased when the steering wheel is corrected by the behavior control means, the behavior control means is used when the steering wheel is corrected by the behavior control means. Steering wheels can be steered to a region where the load of the steered driving means is high compared to when the steered wheels are not modified. As compared with the case where the permissible reference value is constant regardless of whether or not is performed, it is possible to effectively execute the behavior control by the modified turning of the steered wheels.

  According to the second aspect of the present invention, the steered drive means steers the steered wheel by driving the steered wheel side member relative to the steering input means side member. Since the steering drive amount of the steered wheels is reduced to 0 by reducing the relative drive amount by the rudder drive means to 0, the steered drive while effectively executing the behavior control by the modified steer of the steered wheels It is possible to reliably prevent an excessive load from acting on the means.

  According to the third aspect of the present invention, the lock device for preventing the relative movement of the steering wheel side member with respect to the steering input means side member is provided, and the steering drive amount of the steering wheel by the steering drive means is reduced to zero. In addition, since the locking device is operated, it is possible to reliably prevent an excessive load from acting on the steered drive means and to reliably steer the driver from the steering input means side member to the steered wheel side member. Can transmit the operation.

  According to the fourth aspect of the present invention, when the steered wheel is steered by the behavior control means, the steered wheel is steered by a corrected steered amount. When the amount is not 0, the allowable reference value is increased as compared with the case where the corrected turning amount of the steered wheel is 0, so that the behavior control by turning the steered wheel is performed until the load of the steered driving means is high. Can be done.

  According to the fifth aspect of the present invention, the time when the steering wheel is corrected by the behavior control means includes the time when the steering wheel is expected to be corrected. Even when it is expected, the allowable reference value is increased, so that it is possible to reliably prevent the increase of the allowable reference value from being delayed when behavior control by steering of the steered wheels is started.

  According to the sixth aspect of the present invention, the time when the steering wheel is expected to be corrected is the time when the braking / driving force of the wheel is controlled for the purpose of ensuring the running stability of the vehicle. When the braking / driving force of the wheel is controlled for the purpose of ensuring the running stability of the vehicle, the allowable reference value can be reliably increased.

  According to the seventh aspect of the present invention, when the steering wheel is steered beyond the maximum steerable position of the steered wheel even when the steered wheel is corrected and steered by the behavior control means, Therefore, it is possible to reduce the possibility that the steered wheel is steered beyond the maximum steerable position of the steered wheel by the behavior control by correcting the steered wheel. The possibility that the load acts can be reduced.

  Further, according to the configuration of the eighth aspect, the steering assist force generating means stops generating the steering assist force when the load exceeds the reference value. Therefore, the steering assist force generating means turns the steering by stopping the generation of the steering assist force. Even when the load on the drive means becomes high, the allowable reference value is increased when the steered wheel is steered by the behavior control means compared to when the steered wheel is not steered by the behavior control means. be able to.

  According to the ninth aspect of the present invention, when the steering drive amount of the steered wheels is reduced, the target correction steer amount is reduced and corrected, and the target braking / driving force is increased and corrected. The reduction in the behavior control effect due to the reduction of the steering drive amount can be compensated by the increase correction of the target braking / driving force, and the behavior of the vehicle can be stabilized effectively.

[Preferred embodiment of problem solving means]
According to one preferable aspect of the present invention, in the configuration of the above first to ninth aspects, the load of the turning drive means is based on a deviation between the target turning amount of the turning driving means and the actual turning amount. (Preferred aspect 1).

  According to another preferred aspect of the present invention, in the configuration of the first to ninth aspects, the steering drive means is electrically driven, and the load of the steering drive means is the steering drive. It is comprised so that it may determine based on the drive current supplied to a means (Preferred aspect 2).

  According to another preferred aspect of the present invention, in the configuration of claim 2, the steering drive means relatively drives the steering wheel side rotation member relative to the steering input means side rotation member. Thus, the steered wheels are steered and the steered drive amount reducing means reduces the relative rotational drive amount of the steered drive means to 0, thereby reducing the steered wheel drive amount to 0. (Preferred Aspect 3)

  According to another preferred aspect of the present invention, in the configuration of the preferred aspect 3, the steering drive means has a lock device that prevents relative rotation of the steering wheel side rotation member with respect to the steering input means side rotation member. The steered drive amount reducing means is configured to reduce the steered wheel drive amount of the steered wheels by the steered drive means to 0 and to activate the lock device (preferred aspect 4).

  According to another preferred aspect of the present invention, in the configuration of claim 4, the behavior control means calculates the target correction turning amount of the steered wheels for setting the vehicle behavior to the target behavior state. The steering drive means is controlled based on the target correction turning amount, and when the steering wheel correction turning is performed by the behavior control means, the target correction turning amount of the steering wheel is not zero. (Preferable aspect 5).

  According to another preferred aspect of the present invention, in the configuration of claim 6, when the braking / driving force of the wheel is controlled for the purpose of ensuring the running stability of the vehicle, the braking force is controlled. It is configured so that any one of behavior control by the above, anti-skid control for any wheel, and traction control for any wheel is performed (preferred aspect 6).

  According to another preferred aspect of the present invention, in the configuration of the above-mentioned claims 1 to 9 or the preferred aspects 1 to 6, the steering transmission ratio control means controls the steering gear ratio to obtain a desired value. It is configured to control the transmission ratio (preferred aspect 7).

  According to another preferred aspect of the present invention, in the configuration of claim 9, the behavior control means calculates a target yaw moment to be applied to the vehicle in order to bring the vehicle behavior into the target behavior state, The target yaw moment is distributed between the target yaw moment by controlling the braking / driving force of each wheel and the target yaw moment by correcting the steering wheel, and the target correction turning amount based on the target yaw moment by the correction steering of the steering wheel (Preferred aspect 8).

  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 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 driven to a pinion shaft 30 of the power steering device 16 via an upper steering shaft 22 as a steering input means side member, a turning angle varying device 24, a lower steering shaft 26 as a steering wheel side member, and a universal joint 28. It is connected. The turning angle varying device 24 includes an electric motor 32 for driving auxiliary steering, and by rotating the lower steering shaft 26 relative to the upper steering shaft 22, left and right for the purpose of steering gear ratio control and behavior control. The front wheels 10FL and 10FR function as an automatic steering device that drives the steering wheel 14 relatively to the steering wheel 14 and is controlled by the steering angle control electronic control device 34.

  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, as shown in FIG. 2, the turning angle varying device 24 includes an axis 56 of the upper steering shaft 22 as a steering input means side member and the lower steering shaft 26 as a steering wheel side member. The housing 58 is connected to the lower end of the upper steering shaft 22 at a connecting portion 58A at the upper end thereof.

  The electric motor 32 is accommodated in the housing 58 and fixed by press fitting. The electric motor 32 is rotatably supported by a stator 64 fixed to the electric motor housing 62 and bearings 66 and 68 disposed at both ends of the electric motor housing 62. And a rotor 70. The rotor 70 has a large-diameter permanent magnet portion 70A, and a coil 72 is wound around a stator 64 around the permanent magnet portion 70A.

  The lower shaft 70 </ b> B of the rotor 70 extends along the axis 56 through the bearing 68, and is connected to the upper end of the lower steering shaft 26 via the speed reducer 74. The upper shaft 70C of the rotor 70 extends along the axis 56 through the bearing 66, and a lock holder 76 having a plurality of lock grooves spaced apart from each other in the circumferential direction on the outer peripheral surface at the upper end of the upper shaft 70C. Is fixed.

  A plunger-type locking device 78 is fixed to the inner surface of the housing 58 so as to face the lock holder 76. The locking device 78 extends in a radial direction perpendicular to the axis 56 and is fixed to the inner surface of the housing 58. A plunger 82 is disposed in the guide tube 80 so as to be able to reciprocate. A compression coil spring 84 that is urged inward in the radial direction, and a solenoid 86 wound around the guide tube 80.

  The lock device 78 is switched between a lock-on state and a lock-off state by controlling energization to the solenoid 86, and when the solenoid 86 is deenergized, the plunger 82 is inserted into the lock groove of the lock holder 76 and the motor 32 is turned off. By blocking the rotation of the rotor 70, a lock-on state is achieved in which the relative rotation of the upper steering shaft 22 and the lower steering shaft 26 is blocked. On the other hand, when the solenoid 86 is energized, the plunger 82 is driven radially outward against the spring force of the compression coil spring 84, so that it is detached from the lock groove of the lock holder 76 and the rotor of the electric motor 32. A lock-off state allowing 70 rotations is established.

  A permanent magnet disk 88 in which a plurality of N poles and S poles are alternately arranged on the outer peripheral surface is fixed to the upper shaft 70 </ b> C between the permanent magnet portion 70 </ b> A of the rotor 70 and the bearing 66. A rotation angle sensor 90 for detecting the rotation angle φ of the rotor 70 and thus the relative rotation angle θre between the upper steering shaft 22 and the lower steering shaft 26 in cooperation with the permanent magnet disk 88 is provided on the inner surface of the permanent magnet disk 88. It is fixed to face.

  In the illustrated embodiment, a spiral cable device 92 is disposed around the connecting portion 58 </ b> A of the housing 58. The spiral cable device 92 extends around the connecting portion 58A in an annular shape and is fixed to the vehicle body 94. Although not shown in FIG. 2, the spiral cable device 92 is fixed to the connecting portion 58A inside the outer power supplying member 96. An inner power supply member that is fixed to the outer power supply member 96 at the outer end, and a spiral cable 98 that is fixed to the inner power supply member at the inner end and wound around the inner power supply member several times in a spiral shape. ing.

  The spiral cable 98 incorporates a plurality of conductors 98A to 98C in an electrically insulating coating having elasticity such as rubber or resin, and one ends of the conductors 98A to 98C are a coil 72 of the motor 36, a solenoid 86 of the lock device 78, respectively. The other end of the conducting wires 98A to 98C is connected to the steering angle control electronic control device 34.

  Thus, when the locking device 78 is in the lock-off state, the turning angle varying device 24 rotates the lower steering shaft 26 relative to the upper steering shaft 22 by the rotation of the electric motor 32, so that the steering gear ratio as a steering transmission ratio is achieved. When the lock device 78 is in the lock-on state, the upper steering shaft 22 and the lower steering shaft 26 are integrally connected to prevent their relative rotation.

  In the illustrated embodiment, the upper steering shaft 22 is provided with a steering angle sensor 100 for detecting the rotation angle of the upper steering shaft as the steering angle θ. As shown in FIG. A signal indicating θ is input to the steering angle control electronic control device 34 and the behavior control electronic control device 52 via the CAN 102. A signal indicating the relative rotation angle θre detected by the rotation angle sensor 90 of the turning angle varying device 24 is also input to the steering angle control electronic control device 34. The rotation angle sensor 90 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 106 and a signal indicating the vehicle yaw rate γ detected by the yaw rate sensor 108. A signal indicating the vehicle speed V detected by the vehicle speed sensor 110 is input through the CAN 102, a signal indicating the master cylinder pressure Pm detected by the pressure sensor 112, and the braking pressure Pi of each wheel detected by the pressure sensors 114FL to 114RR. 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 100, the rotation angle sensor 90, the lateral acceleration sensor 106, and the yaw rate sensor 108 respectively indicate a steering angle θ, a relative rotation angle θre, and a lateral acceleration when the steering, turning, or turning in the left turn direction of the vehicle is positive. 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 102.

  In particular, as is well known in the art, the behavior control electronic control device 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.

  In addition, when the vehicle controls the skid control or the traction control for only one of the left and right wheels by the behavior control electronic control device 52, such as when the vehicle travels on a road with significantly different friction coefficients between the left and right road surfaces, the steering angle The control electronic control unit 34 calculates a target turning angle Δδmt of the left and right front wheels so as to give a vehicle deflection preventing yaw moment that cancels a yaw moment caused by a braking force difference or a driving force difference between the left and right wheels. The target turning angle Δδmt is steered relative to the provisional target rudder angle δst, thereby reducing the deflection of the vehicle.

  The steering angle control electronic control unit 34 controls the operation of the lock device 78 of the turning angle varying device 24 according to the flowchart shown in FIG. 3 as will be described later. In particular, the load of the turning angle varying device 24 is a reference value. When this is the case, the steering angle varying device 24 is mechanically locked by the lock device 78, thereby preventing relative rotation of the lower steering shaft 26 with respect to the upper steering shaft 22, but the reference value is a control of the steering angle of the left and right front wheels. When the behavior control by is performed, the value is set higher than that when only the steering gear ratio control is performed without performing the behavior control by the steering angle control.

  The behavior control electronic control device 52 sets the target relative rotation angle θret to 0 when the lock device 78 is set to the lock-on state by the steering angle control electronic control device 34 and the steering control of the left and right front wheels is prohibited. The target yaw moment Mt is allotted 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. Stabilize vehicle behavior.

  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 100, and a vehicle speed V from the vehicle speed sensor 110. 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 EPS control electronic control unit 40 determines the load of the electric power steering device 16 based on, for example, the steering torque Ts and the control current for the electric motor 36 of the electric power steering device 16, and the load of the electric power steering device 16 is determined. When the reference value is exceeded, the control current to the motor 36 is stopped and the steering assist by the electric power steering device 16 is stopped.

  Steering gear ratio control and behavior control by steering angle control of the steering wheel described above, behavior control by control of braking force, anti-skid control, traction control, anti-skid control or steering angle control of yaw moment cancellation during traction control, The control of the steering assist force and the steering reaction force itself does not form the gist of the present invention, and these controls may be executed in any manner known in the art.

  Next, a lock control routine 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. 3 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals. The lock determination flag Fn relates to whether or not the lock device 78 is in the lock-on state. 0 indicates that the lock device 78 is in the lock-on state, and 1 indicates that the lock device 78 is in the lock-off state. Indicates.

  First, in step 10, a signal indicating the steering angle θ is read, and in step 20, it is determined whether or not the lock determination flag Fn is 0, that is, the lock device 78 is in a lock-on state. If a negative determination is made, the process proceeds to step 60. If an affirmative determination is made, the process proceeds to step 30.

  In step 30, it is determined whether or not a condition for releasing the lock-on state of the lock device 78 is established in a manner known in the art, and if a negative determination is made, step 30 is performed. When the lock-on state of the lock device 78 is continued at 40 and an affirmative determination is made, the lock device 78 is switched to the lock-off state at step 50 and the lock determination flag Fn is set to 1.

  In step 60, for example, it is determined whether or not the absolute value of the target steering angle δt of the left and right front wheels calculated according to the flowchart shown in FIG. 4 is equal to or greater than the maximum possible turning angle δmax (positive constant). Thus, it is determined whether or not the left and right front wheels are steered beyond their maximum possible turning angle. If an affirmative determination is made, the process proceeds to step 140 and a negative determination is made. Sometimes go to step 70.

  In step 70, it is determined whether or not behavior control is being performed by controlling the steering angle of the left and right front wheels according to the flowchart shown in FIG. 4 described later, that is, the absolute value of the target turning angle Δδmt for behavior control described later. Whether or not is a positive value is determined. If an affirmative determination is made, the process proceeds to step 100 as it is, and if a negative determination is performed, the process proceeds to step 80.

  In step 80, it is determined whether or not the behavior control by the control of the steering angle of the left and right front wheels is highly likely to be started. When the reference value θreo in the determination in step 110 is set to the standard value θreon (positive constant) and an affirmative determination is made, in step 100, the reference value θreo is a value θreoh (a positive constant) higher than the standard value. ).

  Whether the behavior control by the control of the steering angle of the left and right front wheels is highly likely to be started is determined, for example, by controlling the braking force of each wheel performed according to the flowchart shown in FIG. Behavior control of spin suppression, behavior control of drift-out suppression by controlling braking force of each wheel, anti-skid control for any wheel, traction control for any drive wheel, anti-skid control for either left or right wheel Alternatively, it may be performed by determining whether or not any steering angle control for generating the vehicle deflection prevention yaw moment accompanying the execution of the traction control is being executed.

  In step 110, by determining whether the absolute value of the deviation Δθre between the target relative rotational angle θret of the lower steering shaft 26 with respect to the upper steering shaft 22 and the actual relative rotational angle θre is equal to or larger than a reference value θreo, the rotation is determined. It is determined whether or not the load on the steering angle varying device 24 is high. If a negative determination is made, the process proceeds to step 130. If an affirmative determination is made, the process proceeds to step 120.

  In step 120, it is determined whether or not the affirmative determination in step 110 has been continuously performed for the reference time Tc (positive constant) or more, that is, the high load state of the turning angle varying device 24 continues for the reference time Tc or more. If a negative determination is made, the lock-off state of the lock device 78 is continued in step 130. If an affirmative determination is made, the lock device 78 is locked in step 140. The lock determination flag Fn is reset to 0 while being switched to the ON state.

  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 210, a signal indicating the steering angle θ is read, and at step 220, the steering gear ratio Rg is calculated from the map corresponding to the graph shown in FIG. The provisional target rudder 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 230, 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. Whether or not the vehicle behavior control is necessary is determined based on the spin state amount SS and the drift-out state amount DS, and if an affirmative determination is made, the process proceeds to step 260 and a negative determination is made. In step 250, the target turning angle Δδmt of the left and right front wheels is set to 0, and then the process proceeds to step 330.

  In step 260, the target yaw moment Mt of the vehicle and the target deceleration Gxbt of the vehicle for stabilizing the behavior of the vehicle based on the spin state quantity SS and the drift-out state quantity DS are well known in the art. It is calculated by.

  In step 270, 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 steering control prohibition conditions known in the art are established. If the determination is affirmative, the process proceeds to step 300. If the determination is negative, the process proceeds to step 280.

In step 280, 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 290, 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 then the process proceeds to step 330.

  In step 300, the target yaw moment Mtb obtained by controlling the braking force of each wheel is set to the target yaw moment Mt. In step 310, the target rudder angle δt of the left and right front wheels is set to the current rudder angle δa. In step 320, a signal indicating the target rudder angle δt is transmitted to the rudder angle control electronic control unit 34, and then the routine proceeds to step 340.

In step 330, the target rudder angle δt of the left and right 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 according to the following formula 4. Then, a signal indicating the target rudder angle δt is transmitted to the rudder angle control electronic control unit 34.
δt = δst + Δδmt (4)

  In step 340, the target braking force of each wheel for achieving the target yaw moment Mtb and the target deceleration Gxbt of the vehicle is calculated in the manner 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, when the lock device 78 is not in the lock-on state, a negative determination is made in step 20, and in step 70, behavior control is executed by controlling the steering angle of the left and right front wheels. When it is determined whether or not the behavior control by the control of the steering angle of the left and right front wheels is not executed, the reference value θreo is set to the standard value θreon in step 90, and the behavior by the control of the steering angle of the left and right front wheels is set. When the control is being executed, in step 100, the reference value θreo is set to a value θreoh that is higher than the standard value.

  In steps 110 and 120, the situation where the absolute value of the deviation Δθre between the target relative rotational angle θret of the lower steering shaft 26 relative to the upper steering shaft 22 and the actual relative rotational angle θre is equal to or greater than the reference value θreo is equal to or greater than the reference time Tc. It is determined whether or not the high load state of the turning angle varying device 24 continues for a reference time Tc or more by determining whether or not it continues, and if a negative determination is made, a lock is made in step 130. When the lock-off state of the device 78 is continued and an affirmative determination is made, the lock device 78 is switched to the lock-on state at step 140 and the lock determination flag Fn is reset to zero.

  When the lock-off state of the lock device 78 is continued and the lock determination flag Fn is 1, a negative determination is made in step 270 of the flowchart shown in FIG. 4, and steps 210 to 260 and steps 280 to 340 are performed. In order to give the vehicle the required yaw moment by controlling the provisional target rudder angle δst of the left and right front wheels and the rudder angle of the left and right front wheels so that the target rudder angle δt of the left and right front wheels achieves a predetermined steering gear ratio characteristic. The steering angle variable device is calculated so as to be summed with the target steering angle Δδmt, a signal indicating the target steering angle δt is transmitted to the steering angle control electronic control device 34, and the steering angle of the left and right front wheels becomes the target steering angle δt. 24 is controlled.

  On the other hand, when the lock determination flag Fn is reset to 0, an affirmative determination is made in step 270 of the flowchart shown in FIG. 4, and in step 300, the target yaw by controlling the braking force of each wheel is determined. The moment Mtb is set to the target yaw moment Mt, the target rudder angle δt of the left and right front wheels is set to the current rudder angle δa in step 310, and a signal indicating the target rudder angle δt is used for rudder angle control in step 320. This is transmitted to the electronic control unit 34, whereby the left and right front wheels are not steered by the steered angle varying device 24.

  Therefore, according to the illustrated embodiment, when behavior control is performed by controlling the steering angle of the left and right front wheels, the reference value θreo is set to a value θreoh higher than the standard value, so that only the control of the steering gear ratio is performed. Compared to the case where it is performed, the left and right front wheels can be steered to a region where the load of the steered angle varying device 24 is high, and thus the behavior control by controlling the steering angles of the left and right front wheels can be effectively performed. In the case where only the steering gear ratio control is performed, the reference value θreo is set to the standard value θreon, and the standard value θreon may be a low value, so that only the steering gear ratio control is performed. It is possible to reliably prevent an excessive load from acting on the turning angle varying device 24.

  In particular, according to the illustrated embodiment, it is determined in step 80 whether or not the behavior control by the control of the steering angle of the left and right front wheels is highly likely to be started. When the behavior control by the control is not executed and the possibility that the behavior control by the control of the steering angle of the left and right front wheels is not high is set, the reference value θreo is set to the standard value θreon in step 90, When the behavior control by the control of the steering angle of the left and right front wheels is not executed, but the behavior control by the control of the steering angle of the left and right front wheels is highly likely to start, the reference value θreo is a standard value in step 100 Is set to a higher value θreoh.

  Accordingly, the reference value θreo can be reliably set to a value θreoh higher than the standard value from the beginning when the behavior control by the control of the steering angle of the left and right front wheels is started, and the behavior control by the control of the steering angle of the left and right front wheels is started. Therefore, it is possible to reliably perform the steering control of the left and right front wheels up to the region where the load of the turning angle varying device 24 is high from the beginning.

  Further, according to the illustrated embodiment, when the behavior control by the control of the steering angle of the left and right front wheels is being executed, or when the possibility of the behavior control by the control of the steering angle of the left and right front wheels is high, the turning angle can be changed. Not only the steering drive of the left and right front wheels by the device 24 is not performed, in other words, the target steering angle Δδt of the steering angle varying device 24 is not only reduced to 0, but the upper steering is activated by the operation of the lock device 78. Since the relative rotation of the lower steering shaft 26 with respect to the shaft 22 is mechanically blocked, it is possible to reliably prevent the turning load from acting on the turning angle varying device 24 and to ensure the driver's steering operation. Can be transmitted to the left and right front wheels via the turning angle varying device 24.

  Further, according to the illustrated embodiment, when the lock device 78 is brought into the lock-on state, an affirmative determination is made in step 270 of the flowchart shown in FIG. In step 310, the target steering angle δt of the left and right front wheels is set to the current steering angle δta, so that the steering control of the left and right front wheels is executed. Instead, the yaw moment corresponding to the target yaw moment Mt is applied to the vehicle by controlling the braking force of each wheel, and the behavior of the vehicle is stabilized.

  Therefore, although behavior control is necessary, if behavior control is not performed by controlling the steering angle of the left and right front wheels to prevent an excessive load from acting on the steering angle varying device 24, the steering of the left and right front wheels is controlled. The fact that the behavior control by the control is not executed can be reliably compensated by the behavior control by controlling the braking force of each wheel, and the behavior of the vehicle can be reliably stabilized.

  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 high load determination of the turning angle varying device 24 is performed in steps 110 and 120 in which the target relative rotation angle θret of the lower steering shaft 26 with respect to the upper steering shaft 22 and the actual relative rotation angle θre are determined. This is performed by determining whether or not the situation where the absolute value of the deviation Δθre is equal to or greater than the reference value θreo continues for the reference time Tc or longer. May be executed.

  For example, the target relative rotational angular velocity θredt of the steering angle varying device 24 is estimated based on the voltage Vc of the command signal for the electric motor 32, and the actual relative rotational angular velocity of the lower steering shaft 26 with respect to the upper steering shaft 22, that is, the actual relative rotational angle. When the rate of change of θre is θred and the relationship between the actual relative rotational angular velocity θred and the target relative rotational angular velocity θredt is in the hatched area of FIG. 6 for a predetermined time Tc (positive constant) or more Alternatively, it may be determined that the turning angle varying device 24 is in a high load state. In FIG. 6, the dead zone when the target relative rotational angular velocity θredt is a value near 0 is erroneously determined that the turning angle varying device 24 is in a high load state in a situation where it is not actually in a high load state. This is to prevent this.

  In the above-described embodiment, when it is determined in step 70 that the behavior control by the control of the steering angle of the left and right front wheels is executed, or in step 80, the behavior by the control of the steering angle of the left and right front wheels. When it is determined that the control is likely to be started, the target turning angle Δδt of the turning angle varying device 24 is reduced to 0, and the lock device 78 is brought into the lock-on state. For example, in steps 90 and 100, the first and second reference values are set, and the absolute value of the deviation Δθre between the target relative rotation angle θret and the actual relative rotation angle θre is the first reference value. The target turning angle Δδt may be corrected so that the magnitude of the target turning angle Δδt is reduced when the value is greater than or equal to the value, and the target turning angle Δδt is reduced to 0 when the absolute value of the deviation Δθre is greater than or equal to the second reference value.

  In the above-described embodiment, it is determined in step 80 whether or not there is a high possibility of starting behavior control by controlling the steering angle of the left and right front wheels. This determination may be omitted.

  In the above-described embodiment, the reference value θreo set in steps 90 and 100 is a positive constant. For example, the turning angle varying device 24 has a smaller value as the temperature of the motor 32 is higher. The motor 32 may be modified so as to be variably set according to a parameter such as the temperature of the motor 32.

  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, the steering wheel can be steered relative to the steering input means to control the steering transmission ratio. As long as the transmission ratio can be detected by the detecting means, the turning angle varying device may be of any configuration known in the art.

  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 It is a schematic block diagram which shows an example. It is an expanded sectional view which shows the turning angle variable apparatus shown by FIG. It is a flowchart which shows the lock control routine of the turning angle variable apparatus in an Example. 5 is a flowchart showing a vehicle behavior control routine based on steering angle control of left and right front wheels and braking force control of each wheel in the embodiment. It is a graph which shows the relationship between the vehicle speed V and steering gear ratio Rg. It is a graph which shows the relationship between the target relative rotational angular velocity (theta) redt of a steering angle variable apparatus, and the change rate of actual relative rotational angle (theta) re (theta) red.

Explanation of symbols

DESCRIPTION OF SYMBOLS 14 Steering wheel 16 Electric power steering device 24 Steering angle variable device 32 Electric motor 34 Electronic control device for steering angle control 40 Electronic control device for electric power steering device (EPS) 42 Braking device 52 Electronic control device for behavior control 78 Lock device 90 Rotation angle sensor 100 Steering angle sensor 106 Lateral acceleration sensor 108 Yaw rate sensor 110 Vehicle speed sensor 112 Pressure sensor 114FL to 114RR Pressure sensor

Claims (9)

  Steering driving means that can steer the steering wheel independently of the driver's steering operation, and steering driving the steering wheel by the steering driving means, the amount of steering operation of the steering input means by the driver A steering transmission ratio control means for controlling a steering transmission ratio, which is a ratio of the steering amount of the steered wheels, and a behavior in which the behavior of the vehicle is brought into a target behavior state by correcting and steering the steered wheels by the steered drive means. For vehicle having behavior control means for performing control, and turning drive amount reduction means for reducing the turning drive amount of the steered wheels by the turning drive means when the load of the turning drive means exceeds an allowable reference value In the steering control device, the steered drive amount reducing means is less when the steered wheel is steered by the behavior control means than when the steered wheel is steered by the behavior control means. The acceptable reference value Vehicle steering control apparatus, characterized by listening.   The steering drive means drives the steering wheel by driving the steering wheel side member relative to the steering input means side member, and the steering drive amount reduction means is the steering 2. The vehicle steering control device according to claim 1, wherein the steering drive amount of the steered wheels is reduced to 0 by reducing the relative drive amount by the drive means to 0.   The steered drive means includes a lock device that prevents relative movement of the steered wheel side member with respect to the steering input means side member, and the steered drive amount reducing means is steered drive of steered wheels by the steered drive means. The vehicle steering control device according to claim 2, wherein the amount is reduced to 0 and the locking device is operated.   The vehicle steering control device according to any one of claims 1 to 3, wherein the time when the steering control of the steered wheels by the behavior control means is performed is when the amount of steered wheels to be corrected is not zero. .   5. The vehicle steering control device according to claim 1, wherein the time when the steered wheel is corrected by the behavior control means includes a time when the steered wheel is corrected.   6. The vehicle according to claim 5, wherein the time when the steering wheel is expected to be corrected is when the braking / driving force of the wheel is controlled for the purpose of ensuring the running stability of the vehicle. Steering control device.   The allowable reference value is smaller than a load when the steered wheel is steered beyond the maximum steerable position of the steered wheel even when the steered wheel is corrected by the behavior control unit. The vehicle steering control device according to claim 1.   The vehicle includes a steering assist force generating means that reduces a steering burden of the steering wheel by the driver or the steering drive means, and the steering assist force generating means stops generating the steering assist force when the load exceeds a reference value. The vehicle steering control device according to claim 1, wherein the vehicle steering control device is a vehicle steering control device. The vehicle has means for controlling the braking / driving force of each wheel, and the behavior control means calculates the target correction turning amount of the steered wheel and the target braking / driving force of each wheel to bring the vehicle behavior into the target behavior state. Means for controlling the correction turning amount of the steered wheel based on the target correction turning amount, and means for controlling the braking / driving force of each wheel based on the target braking / driving force. The steering control device according to any one of claims 1 to 8, wherein when the steering drive amount of the steered wheels is reduced, the target correction turning amount is reduced and corrected, and the target braking / driving force is increased and corrected. Vehicle control device.

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