JP5313714B2 - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily cancel a yaw moment by properly controlling an electric power steering device which can provide a steering reaction force when a rear toe control device fails. <P>SOLUTION: When the failure of the rear toe control device 11 is determined by inputting a failure signal Sf in step 1 (Yes) and the toe angles &delta;rl, &delta;rr of right and left rear wheels 5l, 5r are determined asymmetrical in step 6 (No), a yaw rate reaction force component Tb&gamma;is set larger than normal referring to a yaw rate reaction force component map for use in failure (step 7), and a steer angle reaction force component Tb&theta; is set smaller than normal referring to a steer angle reaction force component map for use in failure (step 8). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering device that can apply a steering reaction force to a steering wheel by a steering assist motor, and is applied to a vehicle including a vehicle behavior control device such as a rear toe control device.

  In order to reduce a driver's steering operation load, an electric power steering device that generates an assist torque by an electric motor is widely known. This assist torque is generally determined based on the steering torque by the driver and detected values such as the vehicle speed and road surface condition.

  On the other hand, a technique for setting a steering reaction torque based on a detection value related to a motion state quantity such as a yaw rate or a lateral acceleration of a vehicle body, and adjusting the assist torque according to the motion state quantity by adding the steering reaction force torque. Is known (see Patent Document 1). According to this, the deflection suppression performance when disturbances such as crosswinds and rusty roads are applied to the vehicle can be improved, the running stability of the vehicle can be improved, and the friction coefficient with tires such as snowy roads is low. The steering operation load applied to the driver is reduced even on the road surface (hereinafter referred to as a low μ road) or at low speeds.

  On the other hand, in order to improve the turning performance and steering stability of the vehicle, there is provided a rear toe control device that is provided with actuators for the left and right rear wheels and variably controls the toe angle of the rear wheels by driving the actuators. Various wheel steering vehicles have been developed (see, for example, Patent Document 2). In a four-wheel steered vehicle, for example, the ratio of the rear wheel rudder angle (rear wheel toe angle) to the front wheel rudder angle is set in advance to be in reverse phase at low speed and in phase at high speed, and various control parameters (front wheel rudder angle, In general, the target yaw rate of the vehicle body is set based on the vehicle speed and the rear wheel steering angle is set so that the actual yaw rate approaches the target yaw rate.

JP-A-5-105100 Japanese Patent Laid-Open No. 9-30438

  However, when the rear toe control device fails in the rear wheel steering state and the rear wheel steering angle cannot be controlled, if the driver holds the steering wheel at the steering angle 0, the tire lateral force of the rear wheel will cause yaw moment on the vehicle body. And the vehicle will not go straight ahead. Therefore, in order to maintain straight traveling, it is necessary to operate the steering wheel in a direction that cancels the yaw moment. On the other hand, the electric power steering device that sets the steering reaction torque according to the amount of motion state as described in Patent Document 1, for example, a steering wheel that is generated according to the yaw rate of the vehicle body and the steering angle of the steering wheel. By adding the return force (steering reaction force) to the normal assist torque, the straightness of the vehicle is improved. A control law is established for this steering reaction force on the assumption that the yaw rate is zero and the steering angle is zero when the vehicle is in a straight traveling state.

  However, when an electric power steering device based on such a control law is applied to a four-wheel steering vehicle, when the rear toe control device becomes uncontrollable in a steering state, the steering angle of the steering wheel is maintained at zero. Since the yaw moment acts on the vehicle body when traveling, the reaction force control and the driver that the yaw moment acts on the vehicle body as the steering reaction force is applied to the steering wheel so that the electric power steering device returns the steering angle to 0. There was a problem of interference with the steering intention.

  The present invention has been made in view of such a background. When a vehicle behavior control device that controls a vehicle behavior by generating a yaw moment, such as a rear toe control device, malfunctions, the steering reaction force is reduced. An object is to appropriately control the electric power steering device that can be applied and to easily cancel the yaw moment.

  In order to solve the above-mentioned problem, the first invention is mounted on a vehicle (1) including a vehicle behavior control device (11) for controlling a vehicle behavior by generating a yaw moment in the vehicle body (2), and for steering assist. In the electric power steering device (21) capable of applying the steering reaction force (Tb) to the steering wheel (22) by the motor (27), the yaw rate detecting means (15) for detecting the yaw rate (γ) of the vehicle body (2), Among the steering reaction forces, the yaw rate reaction force component (Tbγ) for setting the yaw rate to be reduced based on the yaw rate is set, and the steering assist motor is set based on at least the yaw rate reaction force component. Motor control means (35) for driving control, and the yaw rate component setting unit is configured to control the vehicle behavior control device when the vehicle behavior control device fails. It is characterized in that the yaw rate reaction force component is set larger than in the case where the position is normal.

  According to the present invention, when the vehicle behavior control device breaks down, the electric power steering device sets the yaw rate reaction force component that reduces the yaw rate of the vehicle body to be large and controls the driving of the steering assist motor. It is possible to facilitate corrective steering that cancels the yaw moment resulting from the failure.

  The second invention is mounted on a vehicle (1) having a vehicle behavior control device (11) for controlling the vehicle behavior by generating a yaw moment in the vehicle body (2), and is provided by a steering assist motor (27). In the electric power steering device (21) capable of applying the steering reaction force (Tb) to the steering wheel (22), the steering angle detection means (9) for detecting the steering angle (θ) of the steering wheel, and the steering reaction force A steering angle component setting unit (32b) for setting a steering angle reaction force component (Tbθ) in a direction for decreasing the steering angle based on the steering angle, and a steering assist motor based on at least the steering angle reaction force component. Motor control means (35) for driving control, and the steering angle component setting unit has a smaller steering angle reaction force component when the vehicle behavior control device fails than when the vehicle behavior control device is normal. It is characterized by setting.

  According to the present invention, when the vehicle behavior control device breaks down, the electric power steering device sets the steering angle reaction force component that decreases the steering angle of the steering wheel to drive and controls the steering assist motor. It is possible to facilitate corrective steering that cancels the yaw moment caused by the failure of the behavior control device.

  According to a third aspect of the invention, in the electric power steering device (21) according to the first or second aspect of the invention, the vehicle behavior control device variably controls the toe angle (δr) of the rear wheel (5) independently on the left and right. It is a rear toe control device (11).

  According to this invention, when the rear toe control device breaks down, the electric power steering device sets the yaw rate reaction force component that reduces the yaw rate of the vehicle body to a large value, or the steering angle reaction force component that reduces the steering angle of the steering wheel. Since the steering assist motor is driven and controlled with a small value, correction steering for canceling the yaw moment caused by the failure of the rear toe control device can be facilitated.

  According to a fourth aspect of the present invention, in the electric power steering device (21) according to the first aspect of the invention, the vehicle behavior control device variably controls the toe angle (δr) of the rear wheel (5) independently on the left and right. (11), and further includes a rear wheel toe angle detecting means (17) for detecting a toe angle (δr) of the rear wheel (5), and the steering angle component setting unit (32a) is provided when the rear toe control device fails. The yaw rate reaction force component is set large only when the toe angle of the rear wheel detected by the wheel toe angle detecting means is not symmetrical. As shown in FIG. 6, (A) the left and right rear wheels 5l and 5r are in the same direction, one rear wheel 5l is on the toe-in side, and the other rear wheel 5r is on the toe-out side. Steering state, (B) left and right rear wheels 5l, 5r are toe-in, but if the amount of steering is different, (C) left and right rear wheels 5l, 5r are toe-out When the turning amounts are different, (D) one rear wheel 5l has a steering angle 0 and the other rear wheel 5r is toe-out, and (E) one rear wheel 5l has a steering angle 0 and the other A state where the rear wheel 5r is toe-in can be mentioned.

  According to the present invention, even if the rear toe control device fails, the rear wheel toe angle at the time of the failure is symmetrical, that is, the rear wheel toe angle is toe-in or toe-out for both the left and right wheels and the same turning amount. In some cases, or when there is a failure in the toe zero state, the yaw moment hardly acts on the vehicle body during straight running, so by setting the normal yaw rate reaction force component without increasing the yaw rate reaction force component, Appropriate control of the electric power steering device is possible.

  Further, according to a fifth aspect of the present invention, in the electric power steering device (21) according to the second aspect of the invention, the vehicle behavior control device is a rear toe control device that variably controls the toe angle (δr) of the rear wheel (5) independently on the left and right. (11), further comprising rear wheel toe angle detecting means (17) for detecting a toe angle (δr) of the rear wheel (5), wherein the steering angle component setting unit (32a) The steering angle reaction force component is set small only when the rear wheel toe angle detected by the rear wheel toe angle detecting means is not bilaterally symmetric. In addition, as a case where it is not left-right symmetric, the state of (A)-(E) shown in FIG. 6 is mentioned similarly to 4th invention.

  According to the present invention, even if the rear toe control device fails, if the toe angle of the rear wheel at the time of the failure is symmetrical, if the steering wheel is held in a substantially neutral position in order to travel straight ahead, Therefore, by setting the normal steering angle reaction force component without reducing the steering angle reaction force component, it is possible to appropriately control the electric power steering apparatus.

  According to a sixth aspect of the present invention, in the electric power steering device (21) according to the first or second aspect of the invention, the vehicle behavior control device is such that the front wheel and the steering wheel are mechanically connected, and the steering amount of the steering wheel is It is an active front steering device that variably controls the steering angle ratio of the front wheels to the front wheel.

  According to the present invention, when the active front steering device fails, the electric power steering device sets the yaw rate reaction force component that reduces the yaw rate of the vehicle body to a large value, or reduces the steering angle of the steering wheel. Since the steering assist motor is driven and controlled by setting the reaction force component small, it is possible to facilitate corrective steering that cancels the yaw moment caused by the failure of the active front steering device.

  According to a seventh aspect of the invention, in the electric power steering device (21) according to the first or second aspect of the invention, the vehicle behavior control device includes at least braking control for the left and right wheels and driving force distribution control for each wheel. It is a wheel longitudinal force control device that performs one side.

  According to this invention, similarly to the sixth invention, the electric power steering device sets the yaw rate reaction force component for reducing the yaw rate of the vehicle body large when the wheel longitudinal force control device breaks down, or the steering wheel Since the steering assist motor is driven and controlled by setting a small steering angle reaction force component that reduces the steering angle, it is possible to facilitate corrective steering that cancels the yaw moment caused by the failure of the wheel longitudinal force control device.

  According to the present invention, an electric power steering apparatus capable of applying a steering reaction force is a steering system that places importance on the driver's steering intention when a vehicle behavior control apparatus that controls the vehicle behavior by generating a yaw moment in the vehicle body fails. Since the drive control of the assist motor is performed, it becomes easy for the driver to perform the correction steering that cancels the yaw moment caused by the failure.

Schematic configuration diagram of an automobile provided with an electric power steering device according to an embodiment Block diagram of EPS / ECU according to embodiment Map showing yaw rate reaction component Map showing steering angle reaction force component Flowchart showing steering reaction torque setting processing procedure Schematic showing the state of rear wheel toe angle that is not symmetrical

  Hereinafter, an embodiment of an automobile 1 including an electric power steering device 21 according to the present invention will be described in detail with reference to the drawings. In the description, for the wheels and members arranged on them, such as tires and electric actuators, suffixes f or r indicating front and rear or suffixes l or r indicating left and right are added after the reference numerals, for example, rear The wheels 5l (left side), the rear wheels 5r (right side), the tires 3fl (front left side), and the tires 3rr (rear right side) are collectively referred to as rear wheels 5 or rear wheels 5l and 5r, for example.

  FIG. 1 is a plan view showing a schematic configuration of an automobile 1 provided with a rear toe control device (RTC) 11 according to the embodiment. The automobile 1 includes front wheels 4l and 4r to which tires 3fl and 3fr are mounted, and rear wheels 5l and 5r to which tires 3rl and 3rr are mounted. The front wheels 4l and 4r and the rear wheels 5l and 5r are It is suspended from the vehicle body 2 by left and right front suspensions 6l and 6r and rear suspensions 7l and 7r.

  The vehicle 1 also includes an electric power steering device 21 that applies assist torque to the steering system to reduce manual steering force, and directly steers the front wheels 4 as steering wheels by steering the steering wheel 22. 20, and rear toe control devices that independently change the toe angles (steering angles) δrl and δrr of the rear wheels 5l and 5r by extending and retracting the left and right electric actuators 12l and 12r provided on the rear suspensions 7l and 7r. 11.

  The front wheel steering device 20 includes a pinion 24 integrally connected to the steering wheel 22 via a steering shaft 23, and both ends connected to the left and right front wheels 4 via tie rods 25 and the like. A rack and pinion mechanism including a rack shaft 26 reciprocating in the width direction, and an electric power steering device 21 including an electric motor 27 coaxially provided on the rack shaft 26 to generate a steering assist force. It is a major component.

  The steering shaft 23 is provided with a steering angle sensor 9 for detecting the steering angle θ of the steering wheel 22, and in the vicinity of the pinion 24, a steering torque sensor 10 for detecting the steering torque T by the driver acting on the pinion 24 is provided. The output signals of these sensors are input to the EPS / ECU 28 via a later-described main ECU (Electronic Control Unit) 8, whereby the current flowing through the electric motor 27 is controlled by the EPS / ECU 28. A steering assist force for generating the is applied to the rack shaft 26.

  On the other hand, although detailed illustration is omitted, the electric actuator 12 includes a housing connected to the vehicle body 2 side, a motor housed in the housing, a speed reducer, a feed screw mechanism using a trapezoidal screw, and a female screw of the feed screw mechanism. It constitutes a member and is composed of an output rod or the like connected to the rear wheel 5 side, and linearly expands and contracts by converting the rotational motion of the motor into a thrust motion by a feed screw mechanism. Note that the feed screw mechanism has a self-locking function and has a structure that does not reverse-differentiate even if there is an input from the output rod side.

  In addition, the automobile 1 includes a main ECU 8 that performs overall control of various systems, an RTC / ECU 13 that drives and controls the rear toe control device 11, a yaw rate sensor 15 that detects the yaw rate of the vehicle body 2, a vehicle speed sensor 16, and the like (not shown). Various sensors are installed at appropriate positions, and detection signals from these sensors are input to the main ECU 8 for various control of the vehicle.

  Each ECU 8, 13, 28 comprises a CPU, ROM, RAM, peripheral circuit, input / output interface, various drivers, etc., and is connected to each other via a communication line such as a vehicle local area network CAN (Controller Area Network). Thus, the control amount and the control state can be monitored each other. The main ECU 8 calculates a target toe angle δrt of the target rear wheel 5 based on the detection results of the sensors 9 and 16 and outputs a drive control signal to the RTC / ECU 13.

  The left and right electric actuators 12 are provided with stroke sensors 17l and 17r (rear wheel toe angle detecting means) for detecting the stroke amount of each electric actuator 12 by detecting the positions of magnets arranged in proximity from the differential transformer. ing. The RTC / ECU 13 calculates the target stroke amount of each electric actuator 12 based on the drive control signal output from the main ECU 8, and controls the current flowing through the electric actuator 12 so that the actual stroke amount matches the target stroke amount. By doing so, the rear wheels 5l and 5r are steered independently on the left and right. Further, the RTC / ECU 13 controls the electric actuator 12 with high accuracy by performing feedback control based on the stroke amount detected by the stroke sensor 17, and steers the rear wheels 5l and 5r to the target toe angle δrt. .

  Further, the RTC / ECU 13 compares the current passed through the electric actuator 12 with the detected value of the stroke sensor 17 to determine whether or not the rear wheels 5l and 5r are normally steered, that is, the rear toe control device 11 It is determined whether or not the vehicle is operating normally. When the rear wheels 5l and 5r are not normally steered and a failure determination of the rear toe control device 11 is performed, a failure signal Sf is output to the main ECU 8. It is like that.

  According to the vehicle 1 configured as described above, the left and right electric actuators 12l and 12r are simultaneously symmetrically displaced to freely control the toe-in / to-out of the left and right rear wheels 5l and 5r under appropriate conditions. In addition, if one of the left and right electric actuators 12l and 12r is extended and the other is contracted, the left and right rear wheels 5l and 5r can be steered left and right. For example, the automobile 1 changes the rear wheel 5 to toe-out during acceleration, the rear wheel 5 to to-in during braking, and the rear wheel 5 during high-speed turning, based on the motion state of the vehicle grasped by various sensors, in order to improve steering stability. The wheel 5 is in phase with the front wheel rudder angle, the rear wheel 5 is in reverse phase with the front wheel rudder angle during low-speed turning, or the rear outer wheel 5 is turned into the toe-in during high-side G turning.

  Next, the EPS / ECU 28 according to the embodiment will be described with reference to the block diagram shown in FIG. The EPS / ECU 28 has an input interface 29 through which various signals from the sensors and the main ECU 8 are input, the steering torque T detected by the steering torque sensor 10, the vehicle speed V detected by the vehicle speed sensor 16, and the rotational speed N of the electric motor 27. Based on the above, the assist torque setting unit 30 that sets the normal assist torque Ta, the assist current setting unit 31 that sets the assist current Ia necessary to generate the set assist torque Ta, and the behavior of the vehicle A steering reaction force torque setting unit 32 that sets the steering reaction force torque Tb to be normalized, and a steering reaction force current setting unit 33 that sets the steering reaction force current Ib necessary to generate the set steering reaction force torque Tb. And the assist current Ia set by the assist current setting unit 31 and the steering reaction force current setting unit 33, respectively. A target current setting unit 34 that sets the target current It by adding the reaction force current Ib, an output current control unit 35 (motor control means) that controls an output current to the electric motor 27 according to the target current It, and an output And an interface 36.

  The steering reaction force torque setting unit 32 includes a yaw rate component setting unit 32a for setting a yaw rate reaction force component Tbγ in a direction to reduce the yaw rate based on the yaw rate γ of the steering reaction force torque Tb, and a steering reaction force torque Tb. Among these, a steering angle component setting unit 32b that sets a steering angle reaction force component Tbθ in a direction that decreases the steering angle θ based on the steering angle θ, that is, a direction that returns the steering wheel 22 to the neutral position is provided. Then, the steering reaction force torque setting unit 32 outputs the steering reaction force torque Tb obtained by adding the yaw rate reaction force component Tbγ and the steering angle reaction force component Tbθ to the steering reaction force current setting unit 33.

  Here, when the rear toe control device 11 is operating normally, the yaw rate reaction force component Tbγ is based on the normal yaw rate reaction component map shown in FIG. Search and set. When the rear toe control device 11 is operating normally, the steering angle reaction force component Tbθ is determined based on the normal steering angle reaction force component map shown in FIG. Searched and set as an address.

  In the present embodiment, only the yaw rate reaction force component Tbγ and the steering angle reaction force component Tbθ will be described. However, the steering reaction force torque Tb includes a damping reaction force component based on the steering speed, 2 may be calculated as a sum of a plurality of reaction force components, such as a vehicle body behavior suppression reaction force component based on the lateral acceleration of 2 and a road surface reaction force component based on the steering reaction force of the front wheels 4. It is not limited.

  When the failure signal Sf of the rear toe control device 11 is input from the main ECU 8 to the steering reaction force torque setting unit 32, the yaw rate component setting unit 32a displays the yaw rate reaction force component map for failure shown in FIG. To set the yaw rate reaction force component Tbγ. In the yaw rate reaction force component map for failure, when the vehicle speed V and the yaw rate γ are the same value, the yaw rate reaction force component Tbγ is set so that its absolute value is larger than that of the normal map described above. Has been. That is, when the rear toe control device 11 fails, the yaw rate reaction force component Tbγ is set larger than that when the rear toe control device 11 is normal.

  Further, when the failure signal Sf of the rear toe control device 11 is input, the steering angle component setting unit 32b also switches to the steering angle reaction force component map for failure shown in FIG. Set. In the yaw rate reaction force component map for failure, when the vehicle speed V and the steering angle θ are the same value, the absolute value of the steering angle reaction force component Tbθ is smaller than that of the normal map described above. Is set to That is, when the rear toe control device 11 breaks down, the steering angle reaction force component Tbθ is set smaller than when the rear toe control device 11 is normal.

  Next, the steering reaction force torque setting process in the steering reaction force torque setting unit 32 will be described with reference to FIG. When the vehicle 1 starts the engine, the steering reaction force torque setting unit 32 repeatedly executes the processing described below at a predetermined cycle time.

  First, the steering reaction torque setting unit 32 determines whether or not the failure signal Sf of the rear toe control device 11 is input from the main ECU 8 (step 1). When the failure signal Sf is not input (No), the steering reaction force torque setting unit 32 refers to the yaw rate reaction force component map for normal time shown in FIG. 3A in the yaw rate component setting unit 32a. The reaction force component Tbγ is set (step 2), and then the steering angle reaction force component Tbθ is referred to in the steering angle component setting unit 32b with reference to the normal steering angle reaction force component map shown in FIG. Is set (step 3). Then, the steering reaction force torque setting unit 32 adds the yaw rate reaction force component Tbγ, the steering angle reaction force component Tbθ, and the like to obtain the steering reaction force torque Tb (step 4). The force torque Tb is output (step 5), and this process is repeated.

  On the other hand, when the failure signal Sf of the rear toe control device 11 is input in step 1 (Yes), the steering reaction force torque setting unit 32 determines whether the toe angles δrl and δrr of the left and right rear wheels 5l and 5r are symmetric. In other words, it is determined from the detection results of the stroke sensors 17l and 17r whether or not the toe angles δrl and δrr of the rear wheels 5l and 5r are toe-in or toe-out both on the left and right and have the same turning amount (step 6). When the toe angles δrl and δrr of the left and right rear wheels 5l and 5r are symmetric (Yes), the steering reaction torque setting unit 32 performs the processing from step 2 to step 5 and repeats this processing.

  When the toe angles δrl and δrr of the left and right rear wheels 5l and 5r are asymmetric in step 6 (No), the steering reaction force torque setting unit 32 is in the yaw rate component setting unit 32a at the time of failure shown in FIG. The yaw rate reaction force component Tbγ is set with reference to the yaw rate reaction force component map (step 7), and then the steering angle reaction force component for failure shown in FIG. A steering angle reaction force component Tbθ is set with reference to the map (step 8). Thereafter, the processing of step 4 and step 5 is performed, and this processing is repeated.

  In this way, when the rear toe control device 11 fails, the yaw rate component setting unit 32a switches to the failure yaw rate reaction component map shown in FIG. 3B, and the yaw rate reaction force component Tbγ is changed from the normal state. By setting a large value, the driver can easily perform corrective steering to cancel the yaw moment caused by the failure of the rear toe control device 11. Further, when the rear toe control device 11 fails, the steering angle component setting unit 32b switches to the steering angle reaction force component map for failure shown in FIG. 4B, and changes the steering angle reaction force component Tbθ from the normal time. Even if it is set to be small, the driver can easily perform the correction steering due to the failure of the rear toe control device 11.

  Even if the rear toe control device 11 breaks down, the steering reaction force torque setting unit 32 is normal in FIG. 3A when the toe angles δrl and δrr of the rear wheels 5l and 5r at the time of the failure are symmetrical. The steering reaction force torque Tb is set with reference to the normal yaw rate reaction force component map and the normal steering angle reaction force component map shown in FIG. Appropriate control can be performed without applying a moment to the vehicle body 2.

  Therefore, even if the rear toe control device 11 breaks down, the steering reaction force of the electric power steering device 21 is appropriately controlled with an emphasis on the driver's steering intention, and the driver can control the yaw moment resulting from the failure. Corrective steering can be easily performed to cancel out.

  Although the description of the specific embodiment is finished as described above, the present invention can be widely modified without being limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention. . For example, the automobile of the above embodiment is equipped with an RTC (rear toe control system), but this can be changed to an AFS (active front steering) device, or the driving force transmitted from the engine to the drive wheels can be changed. It may be changed to a wheel longitudinal force control device such as a left and right driving force distribution device (ATTS: Active Torque Transfer System). When AFS is installed, when the front wheel steering angle is shifted in a state where the steering steering angle is 0, that is, when the AFS is lost while the front wheel is steered when the steering wheel is in the neutral position. The electric power steering may be controlled similarly. On the other hand, when an ATTS or the like is mounted, the ATTS is lost when the driving force transmitted to the left and right driving wheels is not equal to the left and right, that is, when the yaw moment is generated in the vehicle body even when the steering amount is 0, and the vehicle cannot travel straight. In the event of a fall, the electric power steering may be controlled similarly.

1 Car 2 Car body 5 Rear wheel 8 Main ECU
9 Steering angle sensor 11 Rear toe control device 12 Electric actuator 15 Yaw rate sensor 17 Stroke sensor (rear wheel toe angle detecting means)
20 Front wheel steering device 21 Electric power steering device 22 Steering wheel 27 Electric motor (steering assist motor)
28 EPS / ECU
32 Steering reaction force torque setting unit 32a Yaw rate reaction force component setting unit 32b Steering angle reaction force component setting unit 35 Output current control unit (motor control means)

Claims (3)

An electric power steering device that is mounted on a vehicle equipped with a rear toe control device that variably controls the toe angle of the rear wheel independently on the left and right sides and that can apply a steering reaction force to the steering wheel by a steering assist motor,
A yaw rate detecting means for detecting the yaw rate of the vehicle body;
A yaw rate component setting unit for setting a yaw rate reaction force component in a direction to reduce the yaw rate based on the yaw rate out of the steering reaction force;
Motor control means for driving and controlling the steering assist motor based on at least the yaw rate reaction force component ;
Rear wheel toe angle detecting means for detecting the toe angle of the rear wheel ,
The yaw rate component setting unit is more than when the rear toe control device is normal only when the rear toe control device fails and the rear wheel toe angle detected by the rear wheel toe angle detecting means is not symmetrical. An electric power steering apparatus characterized by setting a yaw rate reaction force component large. Steering angle detection means for detecting the steering angle of the steering wheel;
A steering angle component setting unit configured to set a steering angle reaction force component in a direction of decreasing the steering angle based on the steering angle of the steering reaction force;
The motor control means further controls driving of the steering assist motor based on the steering angle reaction force component,
The steering angle component setting unit, when said rear toe control unit fails, characterized in that the rear toe control system is set small the steering angle reaction force component than the normal case, an electric according to claim 1 Power steering device.   The steering angle component setting unit sets the steering angle reaction force component small only when the toe angle of the rear wheel detected by the rear wheel toe angle detecting means when the rear toe control device fails is not symmetrical. The electric power steering apparatus according to claim 2, characterized in that:

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