JP3120003B2 - Electric power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus in which the power of an electric motor is directly applied to a steering system as a steering assist force to reduce a driver's steering force.

[0002]

2. Description of the Related Art In a conventional electric power steering apparatus, a target current IMS is set based on a steering torque detected by a steering torque sensor, and the motor is driven by a motor voltage VM corresponding to the target current IMS. Detecting the flowing motor current IM, applying negative feedback (NFB), controlling the motor voltage VM based on a deviation signal between the target current IMS and the motor current IM, and driving the motor with the motor current IM equal to the target current IMS; 2. Description of the Related Art An arrangement configured to apply a steering assist force to a steering system is known.

Further, a conventional electric power steering apparatus employs a motor driving means for driving an electric motor as a power FET.
(Field effect transistor) and a bridge circuit using a switching element such as a power transistor. The duty ratio of the pulsed power supply voltage supplied to the motor is changed by control (for example, PWM control) from the control means. ing.

FIG. 4 is an overall configuration diagram of a conventional electric power steering device, and FIG. 5 is a block diagram of a main part of the conventional electric power steering device. In FIG. 4, the electric power steering device 1 includes a steering wheel 2,
A rack and pinion mechanism 5 including a steering shaft 3, a hypoid gear 4, a pinion 5a and a rack shaft 5b, a tie rod 6, a front wheel 7 of a steering wheel, an electric motor 8 for generating a steering assist force, and a steering torque acting on the steering wheel 2. A steering torque sensor 10 that outputs a steering torque signal T that is detected and converted into an electric signal corresponding to the steering torque, a control unit 12 that drives and controls the electric motor 8 based on the steering torque signal T, an electric motor driving unit 13, an electric motor It includes a current detecting means 14 and the like.

[0005] When the steering wheel 2 is steered, a steering torque sensor 10 provided on the steering shaft 3 detects the steering torque, converts it into a corresponding electric signal, and sends a steering torque signal T to the control means 12. In addition, in the rotation applied to the steering shaft 3, the rotational force of the pinion 5 a is converted into the axial linear motion of the rack shaft 5 b via the rack & pinion mechanism 5, and the steering of the front wheel 7 is changed via the tie rod 6. Let it.

The control means 12 supplies a motor control voltage VO to the motor drive means 13 based on the steering torque signal T,
The motor driving means 13 drives the motor 8 by supplying a motor voltage VM corresponding to the motor control voltage VO.

The electric motor 8 driven by the electric motor voltage VM
Is configured to apply a steering assist force corresponding to the level and sign of the motor voltage VM to the steering system via the hypoid gear 4 to reduce the steering force applied to the steering wheel 2.

In FIG. 5, the control means 12 of the electric power steering apparatus 1 controls the steering torque (T) shown in FIG. 6 based on the steering torque signal T from the steering torque sensor 10.
A target current setting means 15 for converting to a target current IMS in a target current (IMS) characteristic diagram, a target current IMS, and a motor detection current IM of the motor current IM detected by the motor current detection means 14.
A deviation determining means 16 for calculating a deviation signal ΔI from D, converts the deviation signal ΔI into a voltage, and sets the motor driving means 13 to PWM.
There is provided a drive control means 17 for generating a motor control voltage VO for controlling the deviation signal ΔI to quickly converge to zero.

The motor driving means 13 is, for example, a power FE.
A motor control voltage VO composed of a switch-on / off signal and a PWM control signal provided from the drive control means 17 is composed of a bridge circuit using four switching elements such as T (field effect transistor). By driving and controlling each pair of the two power FETs, the voltage value and the direction of the motor voltage VM to be supplied to the motor 8 are set. The direction of the motor voltage VM is
It is determined according to the polarity of the motor control voltage VO output from the drive control means 17.

For example, when a rightward steering operation is performed, a positive-polarity steering torque signal T is input to the target current setting means 15, and a positive-polarity target current corresponding to the positive-polarity steering torque signal T shown in FIG. IMS is output, and a positive polarity motor current IM also flows through the motor 8 to generate a steering assist force in the right direction. In this state, the motor detection current IMD detected by the motor current detection means 14 also has a positive polarity, and the deviation signal Δ
I is the difference between the motor current IM and the motor detection current IMD (IM-
IMD), and the deviation signal ΔI quickly converges to 0 under the control of the drive control means 17.

On the other hand, when the steering operation in the left direction is performed, the target current IMS, the motor current IM and the motor detection current IMD shown in FIG. 6 become negative polarity, and the deviation signal ΔI output from the deviation determination means 16 becomes (−IMS + IMD). ), And the deviation signal ΔI quickly converges to zero.

As described above, the control means 12 provides the feedback loop of the motor detection current IMD and controls the deviation signal ΔI between the target current IMS and the motor detection current IMD. Is also the deviation signal Δ
It is configured such that I is converged to 0 and the motor current IM is quickly controlled to become the target current IMS.

[0013]

Since the conventional electric power steering apparatus is configured to control the driving of the electric motor 8 by feedback of the electric motor detection current IMD, for example, the steering wheel is used when the vehicle is stationary and stationary. When the hand is released from the steering wheel or when the steering wheel is returned, the motor rotates in the opposite direction due to the reaction force from the tire, and the regenerative current IK flows due to the back electromotive force generated by the regenerative action of the motor 8, and the regenerative current IK And the motor detection current IMD corresponding to the sum of the motor current IM is fed back, so that the deviation signal ΔI does not converge to 0, and diverges or vibrates to generate an unpleasant sound or to deteriorate the steering feeling. There are issues.

Next, the relationship between the motor current IM and the regenerative current IK will be described. Generally, the motor voltage VM ignores the inductance (L) of the motor 8, and the motor current IM,
Motor resistance Rm, motor rotation speed NM, induction voltage coefficient kS
Is represented by Equation 1.

[0015]

## EQU1 ## VM = Rm * IM + ks * NM

From the equation (1), the motor current IM is represented by the equation (2). On the other hand, the motor current IM when the motor 8 rotates in the reverse direction due to the reaction force from the tire is represented by the equation (3).

[0017]

## EQU2 ## IM = (VM-ks * NM) / Rm

[0018]

## EQU3 ## IM = {VM-(-kS * NM)} / Rm

As is apparent from Equation 3, at the time of the return operation of the steering, the motor current IM increases due to the generation of the regenerative current IK (= kS * NM / Rm), and the control means 12 outputs the deviation signal by the feedback of the motor current IM. ΔI is 0
Cannot be converged.

FIG. 3 is a diagram for explaining the operation of the motor driving means. In FIG. 3, the motor driving means 13 includes four power FETs (field effect transistors) Q1 to Q4 forming a bridge circuit. Each of the FETs Q1 to Q4 has diodes D1 to D4 between its source and drain. Q1 and Q2 are DC power supplies EO, Q2 and Q
Reference numerals 4 are respectively connected to a vehicle body ground (GND). On the other hand, a motor 8 is connected between a connection point of Q1 and Q2 and a connection point of Q3 and Q4, and each of FETs (field effect transistors) Q1 to Q4 is controlled by a motor control voltage VO supplied from the drive control means 17 in FIG. , The motor voltage VM and the motor current IM are supplied to the motor 8 by controlling the gates G1 to G4. The bridge circuit may be constituted by a power transistor in which a diode is connected in parallel instead of the power FET.

In the right steering direction,
For example, the ON signal VON of the motor control voltage VO is applied to the gate G1 of Q1, the PWM signal VPWM is applied to the gate G4 of Q4, and the OFF signal VOF is applied to the gates G2 and G3 of Q2.
3 to the motor 8, the motor current IM (in the direction of the dashed arrow) of the path of DC power supply EO → FET (field effect transistor) Q1 → motor 8 → FET (field effect transistor) Q4 → vehicle ground (GND) Supply.

On the other hand, when the steering wheel is in the left steering direction, the ON signal VON is applied to the gate G3 of Q3 and the PWM signal V3.
PWM is gate G2 of Q2, and OFF signal VOF is Q1
DC power supply EO → FET (field effect transistor) Q
3 → motor 8 → FET (field effect transistor) Q2 →
The motor current IM (in the direction opposite to the dashed arrow) in the path of the vehicle body ground (GND) is supplied to the motor 8.

As described above, the FETs (field effect transistors) Q1 and Q4, FE, which form the opposite side of the bridge circuit by the ON signal VON of the motor control voltage VO and the PWM signal VPWM.
By controlling T (field effect transistors) Q3 and Q2, the direction and magnitude of the motor current IM can be determined, and the rotation direction and rotation speed of the motor 8 can be controlled.

The resistance RD detects the direction and level of the motor current IM as a voltage VI (polarity and voltage value), and converts the voltage and current into a current by a motor current detecting means 14 to detect the motor detection current IMD.
Is output and fed back to the deviation determining means 16.

Next, when the vehicle shifts from the steering forward state in the right direction of rotation to the return state, a counter electromotive force is generated in the motor 8 by the reaction force from the tire, and the regenerative current IK due to the counter electromotive force is changed from the motor 8 to the diode D3. → FET (field effect transistor) Q1 → flows through the closed loop of the motor 8, and the current flowing through the motor 8 increases as the sum (IM + IK) of the motor current IM and the regenerative current IK by the motor control voltage VO control.

The motor current detecting means 14 detects the increased motor current (IM + IK) and feeds back the motor detection current IMD corresponding to the motor current (IM + IK) to the deviation determining means 16, so that the motor current is generated by the back electromotive force of the motor 8. The regenerated current IK cannot be controlled, and the drive control means 17 in FIG. 5 cannot determine the motor control voltage VO, causing a parasitic oscillation or a hunting phenomenon in the motor current (IM + IK) and generating an unpleasant sound when the steering returns. Or the steering feeling may be degraded.

An object of the present invention is to solve such a problem, and an object of the present invention is to generate a steering assist force according to a target current even when the steering wheel returns, and to improve an electric power that can improve the steering feeling. An object of the present invention is to provide a steering device.

[0028]

In order to solve the above-mentioned problems, an electric power steering apparatus according to the present invention comprises a control means for providing a steering torque signal detected by a steering torque sensor and a motor rotation speed detected by the motor rotation speed detection means. A steering state detecting means for detecting a forward state and a return state of the steering system based on the signal; and a return state control means for generating a return state control signal whose level decreases as the motor rotation speed signal increases, the steering system comprising: Condition detection
The output means detects when the return state of the steering system is detected.
Return steering state signal related to tearing return state
Input to the time control means, the return time control means
Steering state signal is input from state detecting means
The return control signal corresponding to the motor speed signal.
ON signal input to the motion control means and generated by the drive control means
The pulse width modulation signal corresponding to the level of the return control signal.
It is characterized by changing to the number .

Further, in the electric power steering apparatus according to the present invention, the motor rotation speed detecting means includes a motor rotation speed signal based on the motor current signal detected by the motor current detection means and the motor voltage signal detected by the motor voltage detection means. Is provided.

Further, the electric power steering apparatus according to the present invention is characterized in that the motor current detecting means includes a non-contact type current detecting means using a Hall element.

[0031]

In the electric power steering apparatus according to the present invention, the control means controls the forward and return states of the steering system based on the steering torque signal detected by the steering torque sensor and the motor rotation speed signal detected by the motor rotation speed detection means. And a return control means for generating a return control signal that decreases as the motor rotational speed signal increases , so that the steering state detector detects the return state of the steering system. In this case, the ON signal generated by the drive control means is changed to a pulse width modulation signal corresponding to the motor rotation speed signal based on the return control signal, so that the regenerative current due to the back electromotive force of the motor is compensated for. The current can be made to converge to the target current.

Further, in the electric power steering apparatus according to the present invention, the motor rotation speed detecting means includes a motor rotation speed signal based on the motor current signal detected by the motor current detection means and the motor voltage signal detected by the motor voltage detection means. Is provided, the motor rotation speed can be detected without using a motor rotation speed sensor.

Further, in the electric power steering apparatus according to the present invention, since the motor current detecting means includes the non-contact type current detecting means using the Hall element, the motor current is detected without affecting the operation of the motor. can do.

[0034]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a main part of an electric power steering apparatus according to the present invention. In FIG.
The electric power steering device includes a steering torque sensor 1
0, a control means 20, a motor drive means 13, a motor 8, a motor current detection means 18 and a motor voltage detection means 19 which constitute a detection part of the motor rotation speed detection means 30. Further, a feedback loop of the motor current IM is formed via the motor current detecting means 18.

The control means 20 is a microprocessor, RO
It is composed of a memory such as an M / RAM, an interface circuit, and a software program. The target current setting means 15, the deviation determination means 16, the drive control means 21, the low-pass filters (LPF) 22A and 22B, the motor rotation speed calculation means 23, the steering A state detecting unit 24 and a return control unit 25 are provided. In addition, a low-pass filter (LPF) 2
2A and 22B and the motor rotation speed calculating means 23 constitute a motor rotation speed detecting means 30 together with the motor current detecting means 18 and the motor voltage detecting means 19.

The target current setting means 15 is constituted by a memory such as a ROM or the like. The target current signal IMS corresponding to the steering torque signal T is obtained from the steering torque (T) -target current (IMS) characteristic shown in FIG. And the deviation determining means 16
To provide. The deviation determining means 16 calculates the target current signal IMS,
Motor current detecting means 18 and a low-pass filter (LP
F) Motor current I fed back via 22A
The deviation of the M current signal IMF is calculated, and the deviation signal ΔI is supplied to the drive control means 21.

The drive control means 21 has a PID (proportional / integral /
Differential) compensating means, current-voltage converting means, PWM control signal generating means, and the like. After the PID control of the deviation signal ΔI, the current signal is converted into a voltage signal, and the motor control voltage VO
(VON, VPWM, VOF) are supplied to the motor driving means 13. The drive control means 21 includes a control voltage changing means. When a control signal VX (for example, an encoding level signal) is supplied at the time of steering return from the return control means 25 described later, the motor control voltage VO is turned on. The signal VON is changed to a PWM signal VOPMW corresponding to a control signal VX (for example, an encoding level signal) and output.

The low-pass filter 22A is constituted by an active filter or a filter of software processing, and the motor detection current IM of the motor current IM detected by the motor current detection means 18 is used.
An unnecessary band level including a noise level which is equal to or higher than the predetermined frequency of D is attenuated, and a current signal IMF corresponding to the motor current IM is supplied to the deviation determining means 16 and the motor rotation speed calculating means 23. The low-pass filter 22B is also constituted by an active filter or a filter of software processing, and attenuates an unnecessary band level including a noise level which is equal to or higher than a predetermined frequency of the motor detection voltage VMD of the motor voltage VM detected by the motor voltage detection means 19, for example. A voltage signal VMF corresponding to the voltage VM is supplied to the motor rotation speed calculating means 23.

The motor rotation speed calculating means 23 has a function of calculating a software program, and calculates the motor rotation speed NM represented by the equation 4 based on the current signal IMF from the low-pass filter 22A and the voltage signal VMF from the low-pass filter 22B. , The motor rotational speed signal NM is provided to the steering state detecting means 24 and the return control means 25.

[0040]

NM = (VM−Rm * IM) / kS

The motor rotational speed detecting means 30 comprises a motor current detecting means 18 and a motor voltage detecting means 19 as circuits, and a low-pass filter 22A, a low-pass filter 22B and a motor rotational speed which constitute a part of the control means 20. Since the noise component of the motor current IM and the motor voltage VM is attenuated using the calculation means 23 and the motor rotation speed NM is calculated and detected, the detection accuracy is reduced by a relatively simple configuration instead of a sensor such as a tachogenerator. Construct a good detector.

FIG. 2 is a block diagram of a main part of a non-contact type motor current detecting means. In FIG. 2, the motor current detecting means 18 comprises a non-contact type Hall element 18A and a current converting means 18B.
Is detected as a Hall voltage VHO, and the current converting means 18B is configured to convert the Hall voltage VHO into a motor detection current IMD and output the same.

Since the motor current detecting means 18 detects the motor current IM without affecting the measured system of the motor 8 and the motor driving means 13, it constitutes a motor current detecting means with high detection accuracy and little change over time. .

The steering state detecting means 24 has a comparison / judgment function. Based on the sign signal F of the steering torque signal T detected by the steering torque sensor 10 and the result calculated by the motor rotational speed calculating means 23, the steering state is returned or returned. The state is detected, and a steering state signal ST is provided to the return control means 25.

When the sign signal F of the steering torque signal T and the sign (polarity) signal G of the motor rotation speed signal NM match, it is determined that the steering is in the forward state.
For example, an L-level steering state signal ST is output,
When the sign signal F and the sign (polarity) signal G do not match, it is determined that the steering is in a return state, and for example, an H level steering state signal ST is output.

The return control means 25 is a memory such as a ROM,
A switching function is provided. Corresponding data between the motor rotation speed NM and a control signal VX (for example, an encoding level signal) as shown in FIG. 7 is stored in advance, and the motor rotation speed signal NM is output from the motor rotation speed calculation means 23. When supplied, a corresponding control signal VX (for example, an encoding level signal) is provided to the drive control means 21, and the ON signal VON of the motor control voltage VO output from the drive control means 21 corresponds to the control signal VX. Control is performed so that the PWM signal is changed to V0PWM (VON → V0PWM).

The return control means 25 controls the supply / stop of the control signal VX based on the steering state signal ST supplied from the steering state detection means 24, and the steering state signal ST is at H level (steering return state). In this case, the control signal VX is output, and when the steering state signal ST is at the L level (steering going state), the control signal VX is stopped.

The calculated motor rotation speed NM corresponds to the motor current IM, and the control signal VX (for example, the encoding level signal) at the time of steering return is formed so as to correspond to the motor rotation speed NM. Since the PWM signal V0PWM of the motor control voltage VO is also formed so as to correspond to the control signal VX, even if the regenerative current IK is generated by the back electromotive force of the motor 8 when the steering returns as shown in FIG. The on signal VON of the motor control voltage VO applied to the gate G1 of the field effect transistor Q1 is changed to the PWM signal V0PWM, and the regenerative current I
The duty of the pulse width corresponding to K is changed (for example, when the regenerative current IK increases, the off-duty of the pulse width increases), and Q1 is controlled so as to reduce the current corresponding to the regenerative current IK.

Next, the operation of the electric power steering apparatus according to the present invention will be described with reference to FIG. In the forward steering state in the right direction of rotation, the motor control voltage VO corresponding to the target current IMS is output from the drive control means 21 of FIG. 1 to the motor drive means 13 shown in FIG. 3, and FETs (field effect transistors) Q1 to Q4 ON signals VO for forming the motor control voltage VO
N, the OFF signal VOF, the OFF signal VOF, and the PWM signal VPWM corresponding to the deviation signal ΔI are supplied, the motor current IM flows in the direction of the arrow (broken line), and the motor 8 is driven to apply a steering assist force in the steering direction. Let it.

When shifting from this state to the steering return state, a counter electromotive force is generated in the electric motor 8 by the reaction force from the tire, and the regenerative current I corresponding to the direction opposite to the steering torque is generated.
The current that flows in the motor 8 when K occurs in the direction of the arrow is the regenerative current IK plus the motor current IM corresponding to the target current IMS (IM + IK).

The added current (IM + IK) and the motor voltage VM are detected by the motor current detecting means 18 and the motor voltage detecting means 19 in FIG. 1, respectively, and the currents whose noise levels are attenuated via the low-pass filters 22A and 22B, respectively. The signal IMF and the voltage signal VMF are input to the motor rotation speed calculation means 23, and the motor rotation speed NM is calculated.

On the other hand, the steering state detecting means 23 detects the steering torque signal T (sign signal F) and the motor rotational speed NM.
A steering return state is detected from (code signal G) and a steering state signal ST is output.

When the steering state signal ST is input, the return control means 25 supplies a control signal VX corresponding to the motor rotation speed signal NM to the drive control means 21 to generate an ON signal VON of the motor control voltage VO. The signal is changed to the PWM signal V0PWM corresponding to the level of VX, and the gate G1 of the FET (field effect transistor) Q1 in FIG. 3 is subjected to PWM control in accordance with the control signal VX.

When the gate G1 is PWM-controlled, the FET
Body ground (GND) when Q1 and FET Q4 are off
→ Diode D2 → Electric motor 8 → Diode D3 → Electric motor 8 generates electric power by a current flowing through the path of DC power supply EO (+). Therefore, an increase in the electric motor current is suppressed, and a regenerative current IK is generated by the electric motor driving means in the steering return state. 13, the control means 20 compensates for the increase in the regenerative current IK and compensates for the motor current (IM +
IK) drives the electric motor 8 to apply a steering assist force to the steering system.

[0055]

As described above, in the electric power steering apparatus according to the present invention, the control means controls the steering based on the steering torque signal detected by the steering torque sensor and the motor rotation speed signal detected by the motor rotation speed detection means. a steering state detecting means for detecting a state return forward state of the system, accompanied to the motor rotation speed signal increases
Return control means for generating a return control signal that decreases, and when the steering state detection means detects a return state of the steering system, an on-state generated by the drive control means based on the return control signal is provided. Since the signal is changed to a pulse width modulation signal corresponding to the motor rotation speed signal, the regenerative current due to the back electromotive force of the motor can be compensated and the motor current can be made to converge to the target current, so unpleasant noise and hunting phenomenon of the motor current Can be prevented and the steering feeling can be improved.

Further, in the electric power steering apparatus according to the present invention, the motor rotation speed detecting means includes a motor rotation speed signal based on the motor current signal detected by the motor current detection means and the motor voltage signal detected by the motor voltage detection means. Is provided, and the motor rotation speed can be detected without using a motor rotation speed sensor, so that the configuration can be simplified and the detection accuracy can be improved.

Further, in the electric power steering apparatus according to the present invention, the motor current detecting means includes a non-contact type current detecting means using a Hall element, and detects the motor current without affecting the operation of the motor. Therefore, detection accuracy and reliability can be improved.

Therefore, it is possible to provide an electric power steering apparatus having an excellent steering feeling that generates a steering assist force according to the target current even when the steering wheel returns.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of an electric power steering apparatus according to the present invention.

FIG. 2 is a block diagram of a main part of a non-contact type motor current detecting means.

FIG. 3 is an explanatory diagram of an operation of a motor driving unit.

FIG. 4 is an overall configuration diagram of a conventional electric power steering device.

FIG. 5 is a block diagram of a main part of a conventional electric power steering device.

FIG. 6 is a characteristic diagram of steering torque (T) -target current (IMS).

FIG. 7 is a characteristic diagram of a motor rotation speed (NM) -control signal (VX).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1: Electric power steering device, 2: Steering wheel, 3: Steering shaft, 4: Hypoid gear, 5
... Rack and pinion mechanism, 5a ... Pinion, 5b ... Rack shaft, 6 ... Tie rod, 7 ... Front wheel, 8 ... Electric motor, 10 ...
Steering torque sensor, 12, 30 ... control means, 13 ... motor drive means, 14, 18 ... motor current detection means, 15 ...
Target current setting means, 16: deviation determination means, 17: drive control means, 18A: Hall element, 18B: current conversion means,
19: motor voltage detecting means, 21: drive control means, 22
A, 22B: low-pass filter (LPF), 23: motor rotation speed calculation means, 24: steering state detection means, 25: return control means, 30: motor rotation speed detection means, D1 to D4: diodes, F, G ... Code signal, G
1 to G4: gate, IK: regenerative current, IM: motor current,
IMD: motor detection current, IMF: current signal, IMS: target current signal, ΔI: deviation signal, NM: motor rotation speed signal,
Q1 to Q4: power FET (field effect transistor),
ST: Steering state signal, VM: Motor voltage, VMD ...
Motor detection voltage, VMF: voltage signal, VHO: Hall voltage,
VO: electric motor control voltage, VOF: off signal, VON: on signal, VPWM, VOPWM: PWM signal, VX: control signal.

Continuation of the front page (56) References JP-A-6-144269 (JP, A) JP-A-6-8837 (JP, A) JP-A-6-219311 (JP, A) JP-A-1-101196 (JP) , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B62D 6/00 B62D 5/04

Claims (3)

(57) [Claims] 1. A steering torque sensor for detecting a steering torque of a steering system, a motor for applying a steering assist force to the steering system, a motor rotation speed detecting means for detecting a rotation speed of the motor, and a motor current of the motor. Motor current detecting means for detecting a target current signal corresponding to at least a steering torque signal detected by the steering torque sensor; a motor current signal detected by the target current signal and the motor current detecting means Control means including a drive control means for generating a pulse width modulation signal and an ON signal based on the deviation signal; and the pulse width modulation signal and the ON signal from the control means. Each of a pair of opposite sides of a switching element forming a bridge circuit based on a signal is simultaneously controlled. An electric power steering device comprising: a motor driving means for generating a drive signal for driving the electric motor to rotate forward and backward. The control means includes: a steering torque signal detected by the steering torque sensor; and a motor rotation speed detecting means. A steering state detecting means for detecting a forward state and a return state of a steering system based on the detected motor rotation speed signal, and a level as the motor rotation speed signal increases.
There is provided a return time control means for generating a return time control signal decreases, the steering state detecting means, return of the steering system
When the steering state is detected, the steering
Inputting the ringing state signal to the return state control means, wherein the return state control means comprises the steering state detection means
When the steering state signal is input from the
The return control signal corresponding to the motive rotation speed signal is
Input to the drive control means and before the drive control means
The ON signal corresponds to the level of the return control signal.
An electric power steering apparatus characterized by changing to a pulse width modulation signal . 2. A motor rotation speed for calculating the motor rotation speed signal based on the motor current signal detected by the motor current detection unit and a motor voltage signal detected by the motor voltage detection unit. The electric power steering apparatus according to claim 1, further comprising a calculation unit. 3. The electric power steering apparatus according to claim 1, wherein said motor current detecting means includes a non-contact type current detecting means using a Hall element.