JP2015085729A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which can protect a transmission mechanism for transmitting a rotary operation force of a steering wheel to a wheel even if a member for buffering a shock is not provided.SOLUTION: An electric power steering device includes: a steering angle sensor for detecting a steering angle; a rack and pinion mechanism for transmitting a rotary operation force in one direction of a steering wheel as a rolling force in one direction of a wheel; an electric motor to which a rotational driving force in one direction is given as the rolling force in one direction of the wheel via the rack and pinion mechanism; and a control unit for controlling drive of the electric motor. Electric power is supplied to the steering angle sensor and the control unit even if an ignition switch provided on a vehicle is turned off. The control unit controls rotation of the electric motor in one direction when a displacement magnitude with respect to a middle point of a steering angle in one direction of the steering wheel, which is detected by the steering angle sensor, is equal to or more than a predetermined limit angle.

Description

  The present invention relates to an electric power steering apparatus.

Conventionally, in order to prevent an excessive impact load from being applied to the rack and pinion of the electric power steering apparatus, shock absorbing elastic members such as rubber are provided at both ends of the rack shaft.
For example, in the rack and pinion type power steering device described in Patent Document 1, the rack shaft is an annular stopper rubber made of synthetic resin, rubber, or the like having a predetermined width at positions adjacent to the ball joint portions at both left and right ends thereof. It has. The stopper rubber is at the end of the stopper piece that is fitted into the inner peripheral portion of the right-extending cylindrical housing of the gear housing at the moving end of the leftward movement in the stroke of the forward / backward movement of the rack shaft in the left-right direction. Further, the moving end of the rightward movement is in contact with the left end of the left housing. As a result, it is possible to prevent an excessive impact load from being generated on the rack and pinion due to the rack shaft hitting the housing. As described above, the stopper rubber serves to protect a transmission mechanism (reduction gear mechanism) such as a rack and pinion that transmits the rotational operation force of the steering wheel (handle) to the wheel.

JP 2006-117221 A

From the viewpoint of weight reduction and cost reduction, it is desirable not to provide an impact buffer member when a rack shaft such as a stopper rubber hits the housing.
An object of the present invention is to provide an electric power steering device that can protect a transmission mechanism that transmits a rotational operation force of a steering wheel to a wheel without providing an impact buffer member.

  For this purpose, the present invention provides an angle detection means for detecting a steering angle, which is a rotation angle of a steering wheel of a vehicle, and a rotational operation force in one direction of the steering wheel as a rolling force in one direction of the wheel of the vehicle. A transmission mechanism that transmits the motor as an electric motor to which a rotational driving force in one direction is applied as a rolling force in one direction of the wheel via the transmission mechanism, and a control unit that controls the driving of the electric motor. The angle detection means and the control means are supplied with electric power even when an ignition switch provided in the vehicle is off, and the control means detects the one direction of the steering wheel detected by the angle detection means. When the amount of displacement with respect to the midpoint of the rudder angle is equal to or greater than a predetermined limit angle, rotation of the electric motor in one direction is suppressed. A Steering apparatus.

Here, when the ignition switch is OFF, the control means rotates the electric motor in one direction when a displacement amount with respect to a midpoint of the steering angle in one direction of the steering wheel is equal to or greater than the limit angle. It is good to suppress.
Moreover, the said control means is good to short-circuit the said electric motor, when the displacement amount with respect to the midpoint of the steering angle of the one direction of the said steering wheel becomes more than the said predetermined limit angle.
Alternatively, the control means may supply a current that rotates the electric motor in the other direction when the amount of displacement of the steering wheel with respect to the midpoint of the steering angle in one direction becomes equal to or greater than the predetermined limit angle.

  According to the present invention, it is possible to protect the transmission mechanism that transmits the rotational operation force of the steering wheel to the wheels without separately providing an impact buffer member.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a figure which shows schematic structure of the motor vehicle to which a steering device is applied, and schematic structure of the control apparatus of a steering device. It is a figure which shows schematic structure of a motor control part. It is a flowchart which shows the procedure of the impact suppression control process which a motor control part performs.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
The electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of the vehicle. In the present embodiment, the configuration is applied to the automobile 1. Is illustrated.

  The steering device 100 includes a wheel-like steering wheel (handle) 101 operated by a driver, and a steering shaft 102 provided integrally with the steering wheel 101. The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is coupled to the lower coupling shaft 108 via a torsion bar (not shown) in the steering gear box 107. Inside the steering gear box 107, a torque sensor 109 that detects the steering torque of the steering wheel 101 based on the relative rotation angle between the lower connecting shaft 108 and the pinion shaft 106, in other words, based on the torsion amount of the torsion bar. Is provided.

  In the steering gear box 107, rack teeth 105a formed at the center of the rack shaft 105 are placed, and both end portions of the rack shaft 105 protrude from the steering gear box 107, respectively. Further, the both ends of the rack shaft 105 are provided with protruding portions 105b having outer shapes larger than the openings on both end surfaces of the steering gear box 107 in the left-right direction when viewed in FIG. Then, the amount of movement of the rack shaft 105 is restricted when the protruding portion 105b hits the end surface of the steering gear box 107 in the left-right direction.

  Further, the steering device 100 includes an electric motor 110 supported by the steering gear box 107 and a speed reduction mechanism 111 that reduces the driving force of the electric motor 110 and transmits it to the pinion shaft 106. Electric motor 110 according to the present embodiment is a three-phase brushless motor.

  The steering device 100 includes a control device 10 as an example of a control unit that controls the operation of the electric motor 110. The control device 10 includes a CPU that performs arithmetic processing when controlling the electric motor 110, a ROM that stores programs executed by the CPU, various data, and the like, and a RAM that is used as a working memory of the CPU, and the like. It is equipped with. The control device 10 includes a torque signal Td obtained by converting the steering torque detected by the torque sensor 109 described above into an output signal, and a moving speed of the automobile 1 detected by a vehicle speed sensor 170 provided in the automobile 1. A vehicle speed signal v obtained by converting the vehicle speed Vc into an output signal is input.

  The steering device 100 includes a steering angle sensor 180 as an example of an angle detection unit that detects a steering angle that is a rotation angle of the steering wheel (handle) 101. The steering angle sensor 180 is attached to the steering shaft 102 itself and rotates in synchronization with the steering shaft 102, and a second rotating member (not shown) that rotates in conjunction with the rotation of the first rotating member. And a magnetoresistive element (not shown) for detecting the magnetic field change of the magnetized portion fixed to the second rotating member, and a sine wave and a cosine wave corresponding to the rotation angle of the steering wheel 101. It is a sensor that outputs a signal.

  In the steering device 100 configured as described above, the steering torque applied to the steering wheel 101 is detected by the torque sensor 109, and the control device 10 drives and controls the electric motor 110 in accordance with the detected torque. The generated torque 110 is transmitted to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

FIG. 2 is a diagram illustrating a schematic configuration of the automobile 1 to which the steering device 100 is applied and a schematic configuration of the control device 10 of the steering device 100.
In addition to the steering device 100, the automobile 1 includes a known ignition (IG) switch 11, a generator 12, and a battery 13.
The control device 10 includes a motor control unit 40 that controls driving of the electric motor 110. The motor control unit 40 is mainly composed of the CPU, ROM, and RAM described above. As shown in FIG. 2, the motor control unit 40 is supplied with power from the battery 13 even when the IG switch 11 is off.
In addition, the control device 10 includes a motor driving unit 50 that drives the electric motor 110 based on a control signal from the motor control unit 40, a motor current detection unit 60 that detects an actual current Im that actually flows through the electric motor 110, have.

Further, as shown in FIG. 2, the control device 10 includes a large-capacity capacitor 71 for absorbing a ripple component of the current flowing through the electric motor 110, various relays 72 for energizing and interrupting the current, It has. The relay 72 is connected to a power relay 721 for energizing / cutting off the current to the motor drive unit 50 and two paths among three motor terminals arranged in parallel to drive the motor. A motor relay 722 is provided for energizing and interrupting the current supplied from the unit 50 to the electric motor 110.
In addition, as shown in FIG. 2, the control device 10 includes diodes D1, D2, D3, D4, resistors R1, R2, and switching elements S1, S2 in order to perform stable current control.

First, the motor control unit 40 will be described.
FIG. 3 is a diagram illustrating a schematic configuration of the motor control unit 40.
The motor control unit 40 calculates a target auxiliary torque based on the torque signal Td (steering torque) and calculates a target current IT necessary for the electric motor 110 to supply the target auxiliary torque. And a motor drive control unit 30 that controls the drive of the electric motor 110 based on the target current calculated by the target current calculation unit 20.

In addition, the motor control unit 40 includes a relay operating unit 37 that operates a relay 72 described later, that is, switches the relay 72 from off (open state) to on (closed state) or switches from on to off. Yes.
Further, the motor control unit 40 drives the steering angle sensor 180 by supplying power to the steering angle sensor 180, and the steering angle signal obtained by converting the steering angle detected by the steering angle sensor 180 into an output signal. The steering angle sensor drive unit 38 for acquiring
In addition, the motor control unit 40 includes a short circuit unit 39 that short-circuits the electric motor 110.

  The target current calculation unit 20 calculates a base current calculation unit 21 that calculates a base current Ib that serves as a reference for setting the target current, and an inertia compensation current Is that is a current for canceling the inertia moment of the electric motor 110. An inertia compensation current calculation unit 22 and a damper compensation current calculation unit 23 that calculates a damper compensation current Id, which is a current that limits the rotation of the motor, are provided. The target current calculation unit 20 includes a target current determination unit 25 that determines the target current IT based on outputs from the base current calculation unit 21, the inertia compensation current calculation unit 22, the damper compensation current calculation unit 23, and the like. . Further, the target current calculation unit 20 includes a phase compensation unit 26 that performs phase compensation of the torque signal Td.

  The target current calculation unit 20 receives the torque signal Td, the vehicle speed signal v, and the rotation speed signal Nms obtained by converting the rotation speed Nm of the electric motor 110 into an output signal. The rotation speed signal Nms is provided in the electric motor 110 that is, for example, a three-phase brushless motor, and a sensor that detects the rotation angle of the rotor (rotor) of the electric motor 110 (for example, a resolver that detects the rotation position of the rotor, It can be exemplified that it is obtained by differentiating the output signal of a rotor position detection circuit comprised of a rotary encoder or the like.

The base current calculation unit 21 calculates a base current Ib based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170.
The inertia compensation current calculation unit 22 calculates an inertia compensation current Is for canceling the moment of inertia of the electric motor 110 and the system based on the torque signal Ts and the vehicle speed signal v.
The damper compensation current calculation unit 23 calculates a damper compensation current Id for limiting the rotation of the electric motor 110 based on the torque signal Ts, the vehicle speed signal v, and the rotation speed signal Nms of the electric motor 110.

  The target current determination unit 25 is based on the base current Ib calculated by the base current calculation unit 21, the inertia compensation current Is calculated by the inertia compensation current calculation unit 22, and the damper compensation current Id calculated by the damper compensation current calculation unit 23. The current IT is determined. The target current determination unit 25, for example, previously creates a compensation current obtained by adding the inertia compensation current Is to the base current Ib and subtracting the damper compensation current Id based on an empirical rule, and stores it in the ROM. The target current IT is calculated by substituting it into a map showing the correspondence between the compensation current and the target current IT.

  The motor drive control unit 30 is based on a deviation between the target current IT finally determined by the target current calculation unit 20 and the actual current Im supplied to the electric motor 110 detected by the motor current detection unit 60. A feedback (F / B) control unit 31 that performs feedback control, and a PWM signal generation unit 35 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110.

The feedback control unit 31 includes a deviation calculation unit 32 for obtaining a deviation between the target current IT finally determined by the target current calculation unit 20 and the actual current Im detected by the motor current detection unit 60, and the deviation is A feedback (F / B) processing unit 33 that performs feedback processing so as to be zero.
The PWM signal generation unit 35 generates a PWM signal based on the output value from the feedback control unit 31, and outputs the generated PWM signal to the motor driving unit 50.

  When the IG switch 11 is on, the relay actuating unit 37 turns on the relay 72 in a normal use state and turns off in the event of an abnormality. In addition, when the IG switch 11 is off, the relay operating unit 37 turns off the relay 72, but switches from off to on according to impact suppression control described later.

  The steering angle sensor drive unit 38 drives the steering angle sensor 180 by supplying power to the steering angle sensor 180, and the steering angle signal obtained by converting the steering angle detected by the steering angle sensor 180 into an output signal. To get the rudder angle. In the control device 10 according to the present embodiment, even when the IG switch 11 is off, power is supplied from the battery 13 to the rudder angle sensor drive unit 38, and power is supplied from the rudder angle sensor drive unit 38 to the rudder angle sensor 180. Is supplied.

Next, the motor drive unit 50 will be described.
The motor drive unit 50 is a so-called inverter, and includes six independent transistors (FETs) as switching elements, and three of the six transistors are between the positive-side line of the power source and the electric coil of each phase. The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.
The short-circuit unit 39 of the motor control unit 40 short-circuits the electric motor 110 by turning on all transistors (FETs) provided in the motor drive unit 50 in accordance with impact suppression control described later.

Next, the motor current detection unit 60 will be described.
The motor current detection unit 60 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor driving unit 50, and converts the detected actual current Im into a motor current signal. Output.

  In the steering device 100 configured as described above, electric power from the battery 13 is supplied to the motor control unit 40 of the control device 10 regardless of whether the IG switch 11 is on or off. Then, whether the IG switch 11 is on or off, the motor control unit 40 constantly supplies power to the steering angle sensor 180 and constantly acquires the steering angle detected by the steering angle sensor 180. . Further, when the IG switch 11 is turned on and the engine (not shown) of the automobile 1 is operated, the electric power from the generator 12 and the battery 13 is supplied to the motor control unit 40. Then, the relay actuating unit 37 of the motor control unit 40 turns on the power relay 721 so that electric power is supplied to the motor driving unit 50. In addition, when the relay operating unit 37 turns on the motor relay 722, current is supplied to the electric motor 110 by the operation of the motor driving unit 50, and the electric motor 110 is driven.

  Next, a description will be given of the impact suppression control that is performed by the motor control unit 40 of the control device 10 and that suppresses the impact when the protruding portion 105b of the rack shaft 105 hits the end surface of the steering gear box 107. The motor control unit 40 performs this impact suppression control when the IG switch 11 is turned off.

  First, the relay operation unit 37 of the motor control unit 40 has a displacement amount from a midpoint of the rudder angle detected by the rudder angle sensor 180 grasped by the rudder angle sensor drive unit 38 (a position where the automobile goes straight). When the angle exceeds the predetermined reference angle, the relay 72 is switched from OFF to ON, and electric power is supplied to the motor drive unit 50 and current can be supplied to the electric motor 110 by the operation of the motor drive unit 50. To do.

  And the short circuit part 39 of the motor control part 40 was provided in the motor drive part 50, when the amount of displacement from the middle point of the steering angle detected by the steering angle sensor 180 is not less than a predetermined limit angle. All the transistors (FET) are turned on to short-circuit the electric motor 110. The predetermined limit angle is an angle larger than the above-described predetermined reference angle, and can be exemplified as being closer to the midpoint by a predetermined angle than the rudder angle at which the rack shaft 105 abuts against the steering gear box 107.

Next, the procedure of the impact suppression control process performed by the motor control unit 40 of the control device 10 will be described using a flowchart.
FIG. 4 is a flowchart showing the procedure of the impact suppression control process performed by the motor control unit 40. When the IG switch 11 is turned off, the motor control unit 40 repeatedly executes this impact suppression control process every predetermined period.

  First, the rudder angle sensor driving unit 38 of the motor control unit 40 determines whether or not the amount of displacement from the midpoint of the rudder angle detected by the rudder angle sensor 180 is equal to or greater than a predetermined reference angle (step (hereinafter referred to as “step”). , Simply “S”.) 101). When the displacement amount from the midpoint of the rudder angle detected by the rudder angle sensor 180 is equal to or greater than the predetermined reference angle (Yes in S101), the relay operating unit 37 turns the relay 72 on (closed state). (S102). On the other hand, when the amount of displacement from the midpoint of the steering angle is less than the predetermined reference angle (No in S101), the relay 72 is turned off (open state) (S103).

  After the relay 72 is closed (ON), the rudder angle sensor drive unit 38 determines whether or not the displacement amount from the midpoint of the rudder angle detected by the rudder angle sensor 180 is greater than or equal to a predetermined limit angle. A determination is made (S104). When the displacement amount from the midpoint of the steering angle is equal to or greater than the predetermined limit angle (Yes in S104), the short circuit unit 39 turns on all the transistors (FETs) provided in the motor drive unit 50, and the electric motor 110. Are short-circuited (S105). On the other hand, when the amount of displacement from the midpoint of the steering angle is less than the predetermined limit angle (No in S104), the execution of this process is terminated.

  Even when the motor control unit 40 performs the above-described impact suppression control, for example, when the front wheel 150 is replaced or serviced, the vehicle body is lifted and the front wheel 150 is rotated to change the direction of the front wheel 150. The impact when the rack shaft 105 hits the steering gear box 107 can be avoided or suppressed.

  That is, when the IG switch 11 is off and the engine (not shown) of the automobile 1 is not operating, if the front wheel 150 is rotated, the front wheel is moved with considerable momentum due to the influence of the moment of inertia due to the weight of the front wheel 150. 150 rotates and the rack shaft 105 may move vigorously. Even in such a case, when the amount of displacement from the midpoint of the steering angle detected by the steering angle sensor 180 exceeds a predetermined limit angle, all the transistors (FETs) provided in the motor drive unit 50 are turned on. Since the phases are short-circuited, the electric motor 110 is instantaneously stopped by the counter electromotive voltage generated when the electric motor 110 rotates. As a result, the rotation of the pinion shaft 106 mechanically connected to the electric motor 110 stops, and the movement of the rack shaft 105 stops instantaneously. As a result, the rack shaft 105 can be prevented from hitting the steering gear box 107, or even if it hits, the impact at that time can be suppressed. Accordingly, it is possible to prevent an excessive shock from being generated on the rack teeth 105a formed on the rack shaft 105 and the pinion 106a formed on the pinion shaft 106 due to the rack shaft 105 hitting the steering gear box 107. be able to.

  As described above, according to the control device 10 according to the present embodiment, even when the IG switch 11 is turned off, for example, even when the front wheel 150 is rotated to change the direction of the front wheel 150, the rack It is possible to suppress the occurrence of excessive impact on the rack teeth 105a and the pinion 106a due to the shaft 105 hitting the steering gear box 107. Therefore, there is no need to provide an elastic member such as a stopper rubber made of synthetic resin or rubber, which softens the impact when the rack shaft 105 hits the steering gear box 107. In other words, it is possible to suppress an excessive impact load from being generated on the rack teeth 105a and the pinion 106a without providing an impact buffer member when the rack shaft 105 hits the steering gear box 107. A rack and pinion mechanism having a rack tooth 105a, a pinion 106a, and the like, which is an example of a transmission mechanism that transmits a rotational operation force as a rolling force of the front wheel 150, can be protected.

  In the control device 10 according to the above-described embodiment, the motor control unit 40 causes the motor to move when the amount of displacement from the middle point of the steering angle detected by the steering angle sensor 180 is equal to or greater than a predetermined limit angle. Although it has been described that all the transistors (FETs) provided in the drive unit 50 are turned on when the IG switch 11 is turned off, the present invention is not particularly limited to this mode. When the IG switch 11 is turned on and electric power is supplied to the motor drive unit 50, the motor control unit 40 has a displacement amount from the midpoint of the steering angle detected by the steering angle sensor 180 equal to or greater than a predetermined limit angle. In this case, all the transistors (FETs) provided in the motor drive unit 50 may be turned on.

  Further, in the control device 10 according to the above-described embodiment, it has been described that the CPU functions as the motor control unit 40 described above by executing a program stored in the ROM. It is not limited. The control device 10 has a main CPU and a sub CPU, and the sub CPU supplies power to the rudder angle sensor 180 to grasp the rudder angle detected by the rudder angle sensor 180. The main CPU may perform the functions as the target current calculation unit 20, the motor drive control unit 30, the relay operation unit 37, and the short circuit unit 39 described above.

Whether the IG switch 11 is on or off, the power from the battery 13 is always supplied to the sub CPU, and the sub CPU constantly supplies power to the rudder angle sensor 180. The steering angle detected at 180 is grasped. Then, the sub CPU activates the main CPU when the amount of displacement from the midpoint of the rudder angle detected by the rudder angle sensor 180 exceeds a predetermined reference angle. The activated main CPU switches the relay 72 from off to on to supply electric power to the motor driving unit 50 and to allow electric current to be supplied from the motor driving unit 50 to the electric motor 110. When the main CPU functioning as the short-circuit unit 39 acquires information from the sub CPU that the amount of displacement from the midpoint of the rudder angle detected by the rudder angle sensor 180 is equal to or greater than a predetermined limit angle, All the transistors (FETs) provided in the motor drive unit 50 are turned on to short-circuit the electric motor 110.
According to such a configuration, when the IG switch 11 is off, power is not supplied to the main CPU, so that power consumption can be reduced compared to a configuration in which power is supplied to the main CPU.

  Further, according to the control device 10 described above, in order to reduce the impact when the rack shaft 105 hits the steering gear box 107, the motor control unit 40 starts from the middle point of the steering angle detected by the steering angle sensor 180. In the case where the amount of displacement exceeds a predetermined limit angle, control is performed to turn on all the transistors (FETs) provided in the motor drive unit 50 and short-circuit, but the present invention is not particularly limited to this mode. For example, the motor control unit 40 may perform control so as to supply the electric motor 110 with a current that moves the rack shaft 105 in a direction opposite to the moving direction. In other words, the motor control unit 40 controls the electric motor 110 so as to supply the electric motor 110 with a current that rotates in a direction opposite to the direction in which the electric motor 110 rotates with the current movement of the rack shaft 105. Also good. More specifically, the target current calculation unit 20 of the motor control unit 40 is different from the determination of the target current IT at the normal time based on the torque signal Td (steering torque) when the IG switch 11 is on, A current that rotates in the direction opposite to the direction of rotation accompanying the current movement of the rack shaft 105 is determined as the target current IT to be supplied to the electric motor 110.

  Thus, by supplying current to the electric motor 110 that moves the rack shaft 105 in the direction opposite to the moving direction, the rotation speed of the electric motor 110 is reduced, and the movement speed of the rack shaft 105 is reduced. Get smaller. As a result, the rack shaft 105 can be prevented from hitting the steering gear box 107, or even if it hits, the impact at that time can be suppressed. Accordingly, it is possible to suppress an excessive impact load from being generated on the rack teeth 105a and the pinion 106a due to the rack shaft 105 abutting against the steering gear box 107. Therefore, it is possible to prevent an excessive shock from being generated on the rack teeth 105a and the pinion 106a without providing an impact buffer member when the rack shaft 105 abuts against the steering gear box 107. The transmission mechanism can be protected.

  The target current calculation unit 20 exemplifies that the amount of the target current IT that is rotated in the direction opposite to the direction rotating with the current movement of the rack shaft 105 is a predetermined amount. be able to. Alternatively, the target current calculation unit 20 may be an amount corresponding to the rotation speed of the electric motor 110, for example, increasing the amount of current as the rotation speed of the electric motor 110 increases.

  Further, the steering device 100 described above includes a steering angle sensor 180 that is attached to the steering shaft 102 itself and has a first rotating member that rotates in synchronization with the steering shaft 102, and the IG switch 11 is connected to the steering angle sensor 180. Even when the power is off, the electric power is always supplied to detect the steering angle, and the electric motor 110 is controlled based on the detected steering angle, but the present invention is not particularly limited thereto. For example, a resolver that detects the rotational position of the rotor (rotor) of the electric motor 110 without providing the rudder angle sensor 180 may be provided, and the rudder angle may be detected based on an output value from the resolver. That is, the resolver may function as an example of an angle detection unit that detects the steering angle. And the steering angle sensor drive part 38 of the motor control part 40 always supplies electric power to a resolver, always acquires the rotational position of the rotor of the electric motor 110 detected by the resolver, and based on the acquired rotational position. Calculate the rudder angle. Then, the target current calculation unit 20, the short circuit unit 39, and the like may control the electric motor 110 based on the calculated steering angle. Thereby, without providing the rudder angle sensor 180 having the first rotating member, it is possible to suppress an excessive shock from being generated in the transmission mechanism having the rack teeth 105a, the pinion 106a, and the like, and to protect the transmission mechanism. Can do. As a result, it is not necessary to separately provide the steering angle sensor 180, and the cost can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Automobile, 10 ... Control apparatus, 20 ... Target electric current calculation part, 30 ... Motor drive control part, 37 ... Relay operation part, 38 ... Steering angle sensor drive part, 39 ... Short circuit part, 40 ... Motor control part, 50 ... Motor drive unit 72 ... Relay 100 ... Electric power steering device 101 ... Steering wheel (handle) 105 ... Rack shaft 106 ... Pinion shaft 110 ... Electric motor 180 ... Steering angle sensor

Claims (4)

An angle detection means for detecting a steering angle which is a rotation angle of a steering wheel of the vehicle;
A transmission mechanism for transmitting a rotational operation force in one direction of the steering wheel as a rolling force in one direction of the wheel of the vehicle;
An electric motor to which a rotational driving force in one direction is applied as a rolling force in one direction of the wheel, via the transmission mechanism;
Control means for controlling the drive of the electric motor;
With
The angle detection means and the control means are supplied with electric power even when an ignition switch provided in the vehicle is off,
The control means suppresses the rotation of the electric motor in one direction when the displacement detected by the angle detection means with respect to the midpoint of the steering angle in the one direction of the steering wheel exceeds a predetermined limit angle. An electric power steering device. The control means suppresses the rotation of the electric motor in one direction when the amount of displacement of the steering wheel with respect to the midpoint of the steering angle in one direction exceeds the limit angle when the ignition switch is off. The electric power steering apparatus according to claim 1. 3. The electric motor according to claim 1, wherein the control unit short-circuits the electric motor when the amount of displacement of the steering wheel with respect to the midpoint of the steering angle in one direction becomes equal to or greater than the predetermined limit angle. Power steering device. The control means supplies a current that rotates the electric motor in the other direction when a displacement amount of the steering wheel with respect to a middle point of a steering angle in one direction becomes equal to or greater than the predetermined limit angle. The electric power steering apparatus according to claim 1 or 2.

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