JP2001106099A - Electric power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To well detect an abnormal torque sensor by means of an inexpensive constitution and to materialize steering assistance in the presence of the abnormal torque sensor. SOLUTION: In diagnosis treatment for a torque sensor, firstly, the presence of possibility is determined that a torque sensor 63 has an abnormality when a current detection value in each phase motor based on an output signal from a motor current detection circuit 70 is an established value of 1x or higher, and a torque detection value based on an output signal from a torque sensor is an established value of Xt or higher. Secondly, when the abnormal torque sensor 63 is detected, a current value of interest is established in accordance with a steering angle detection value based on an output signal from a steering angle sensor 61.

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 for assisting a steering mechanism mounted on a vehicle by using an electric motor as a drive source.

[0002]

2. Description of the Related Art Conventionally, an electric power steering device that assists steering by transmitting a torque generated by an electric motor to a steering mechanism of a vehicle has been used. Such an electric power steering device is provided with a torque sensor for detecting a steering torque applied to a steering wheel, and is determined according to a torque detection value based on an output signal from the torque sensor. The electric motor is controlled based on the target current. Therefore, when an abnormality such as a failure occurs in the torque sensor, the target current is not set to a value corresponding to the steering torque applied to the steering wheel, and there is a possibility that steering assistance unrelated to the operation of the steering wheel is performed.

Therefore, in the above-described electric power steering apparatus, an abnormality (failure) of the torque sensor is caused.
Is detected. That is, in the conventional electric power steering device, two main and sub torque sensors are provided, and the microcomputer compares the output signal of the main torque sensor with the output signal of the sub torque sensor, and It is determined whether an abnormality has occurred in the main or sub torque sensor based on the comparison result. When no abnormality occurs in any of the main and sub torque sensors, the microcomputer determines a target current based on an output signal of the main torque sensor and controls a current flowing through the electric motor. I have.

[0004]

However, in the conventional electric power steering apparatus described above, a circuit for inputting the output signal of the main torque sensor to the microcomputer and the output signal of the sub torque sensor to the microcomputer. A separate circuit for inputting is required. Therefore, the cost is high to detect the abnormality of the torque sensor.

Further, in the conventional electric power steering apparatus, when an abnormality of the torque sensor is detected, a current is supplied to the electric motor in order to prevent a steering assist unrelated to the operation of the steering wheel. It is to be stopped immediately. For this reason, there is a possibility that the steering wheel becomes suddenly heavy and the steering feeling is remarkably reduced. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems and to provide an electric power steering device capable of satisfactorily detecting an abnormality of a torque sensor with an inexpensive configuration.

Another object of the present invention is to provide an electric power steering apparatus capable of performing steering assist according to operation of an operation means when an abnormality occurs in a torque sensor. Still another object of the present invention is to provide an electric power steering device capable of improving a steering feeling when an abnormality occurs in a torque sensor.

[0007]

According to a first aspect of the present invention, an electric motor is used as a drive source, and a steering mechanism mounted on a vehicle is operated in response to an operation of an operating means. An electric power steering device that provides a steering assist force, comprising: a motor detection unit that detects a motor current flowing through an electric motor and outputs a signal corresponding to the detected motor current; and a steering torque applied to the operation unit. A torque sensor for detecting and outputting a signal corresponding to the detected steering torque; and a motor current detection value based on an output signal from the current detection means being equal to or greater than a predetermined current value, and an output from the torque sensor. When the torque detection value based on the signal is equal to or greater than a predetermined torque value, an abnormality determination unit that determines that an abnormality has occurred in the torque sensor. Mukoto an electric power steering apparatus according to claim.

When the torque sensor is normal and the motor current flowing through the electric motor increases to assist the steering of the steering mechanism, the steering torque applied to the operating means decreases. Therefore, a torque sensor for detecting the steering torque The torque detection value based on the output signal from the controller becomes smaller. Therefore, if the detected torque value based on the output signal from the torque sensor remains large even though the detected motor current value based on the output signal from the current detecting means has increased, an abnormality may occur in the torque sensor. Can be determined.

Therefore, according to the present invention, it is determined whether or not the torque sensor is abnormal based on the motor current detection value and the torque detection value. Therefore, it is possible to detect the abnormality of the torque sensor required for the motor control without requiring a torque sensor separately from the torque sensor required for the motor control. Therefore, two torque sensors are required to detect the abnormality of the torque sensor. The cost can be reduced as compared with a conventional electric power steering apparatus provided with the power steering apparatus.

According to a second aspect of the present invention, there is provided a motor control means for determining a target current value of an electric motor in accordance with a detected torque value based on an output signal from the torque sensor, and controlling the electric motor based on the target current value. The electric power steering apparatus according to claim 1, further comprising: According to the present invention, specifically, the target current value of the electric motor is determined according to the detected torque value, and the electric motor is controlled based on the determined target current value.

According to a third aspect of the present invention, there is provided an operation amount detecting means for detecting an operation amount of the operation means and outputting a signal corresponding to the detected operation amount, and an abnormality judging means for detecting an abnormality in the torque sensor. When it is determined that the electric motor has occurred, instead of controlling the electric motor based on the torque detection value by the motor control means, the target of the electric motor is controlled according to the operation amount detection value based on the output signal from the operation amount detection means. 3. The electric power steering apparatus according to claim 2, further comprising an abnormal-time control unit that determines a current value and controls the electric motor based on the target current value.

According to the present invention, when it is determined that the torque sensor is abnormal, the target current value is set based on the operation amount detection value based on the output signal from the operation amount detection means. Motor control is performed based on the target current value. Thus, even when an abnormality occurs in the torque sensor, steering assist according to the operation of the steering wheel can be performed. According to a fourth aspect of the present invention, in the electric power steering device, the supply current to the electric motor is determined by the abnormal time control means when the control by the motor control means shifts to the control by the abnormal time control means. 4. The electric power steering apparatus according to claim 3, further comprising a transition control means for gradually changing the current value to the target current value.

According to the present invention, immediately after the occurrence of the abnormality in the torque sensor, the current supplied to the motor is gradually changed to the target current value determined by the abnormality-time control means.
It is possible to prevent a sudden change in the steering assist force when an abnormality occurs in the torque sensor, and it is possible to improve the steering feeling.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an electric configuration of an electric power steering apparatus according to an embodiment of the present invention, together with a cross-sectional structure of a steering mechanism. The steering mechanism 1 includes a rack 11 arranged along the vehicle width direction, a pinion shaft 12 having a pinion portion at its tip for meshing with the rack 11 in a gear box 17, and rotatably coupled to both ends of the rack 11. And a knuckle arm 14 rotatably connected to the tip of the tie rod 13. The knuckle arm 14 is provided rotatably around the king pin 15.
The steering wheel 16 is attached to the.

The base end of the pinion shaft 12 is connected to the steering shaft via a universal joint.
A steering wheel as operating means is fixed to one end of the steering shaft. With this configuration,
By rotating the steering wheel, the rack 11 is displaced in the longitudinal direction, the knuckle arm 14 rotates around the king pin 15, and the direction of the steered wheels 16 changes. The electric power steering device 2 includes a rack 1
1 has a three-phase brushless motor M provided in connection with an intermediate portion thereof. The motor M includes a case 21 fixed to the vehicle.
Is arranged, and a stator 23 is arranged so as to surround the rotor 22.

A ball nut 3 is provided at one end of the rotor 22.
1 are connected. The ball nut 31 is screwed through a plurality of balls to a screw shaft portion 32 formed at an intermediate portion of the rack 11, whereby the ball screw mechanism 3
0 is formed. Bearings 33 and 34 are interposed between the ball nut 31 and the case 21 of the motor M, and a bearing 35 is interposed between the case 21 and the vicinity of the other end of the rotor 22. ing. With this configuration,
When the motor M is energized and torque is applied to the rotor 22, the applied torque is transmitted to the ball nut 31 connected to the rotor 22. The torque transmitted to the ball nut 31 is converted by the ball screw mechanism 30 into a driving force in the vehicle width direction of the rack 11. Thus, the force generated by the motor M is given to the steering mechanism 1.

The magnitude of the steering assist force is adjusted by controlling the drive current of the motor M. The drive current of the motor M is controlled by the controller 40 via the motor driver 50. Controller 40
Includes a steering angle sensor 61 for detecting a steering angle of a steering wheel and a vehicle speed sensor 6 for detecting a vehicle speed.
2. a torque sensor 63 for detecting a steering torque;
Output signals of a motor rotation angle sensor 64 for detecting the rotation angle of the motor M and a motor current detection circuit 70 for detecting the magnitude of the motor current flowing through the motor M are input. The controller 40 obtains a target current value based on each of the output signals, controls the motor driver 50 based on the target current value, and thereby controls the current flowing through each phase of the motor M.

The steering angle sensor 61 is provided, for example, in connection with a steering wheel, and outputs a pulse signal every time the steering wheel is rotated by a predetermined angle. Therefore, by counting the number of pulse signals output from the steering angle sensor 61, the steering angle of the steering wheel can be obtained. The vehicle speed sensor 62 is realized, for example, by a wheel speed sensor provided in connection with a wheel and outputting a pulse signal at a cycle corresponding to the rotation speed of the wheel. In this case, the vehicle speed, which is the speed of the vehicle, can be obtained by measuring the period or frequency of the pulse signal.

The torque sensor 63 divides the pinion shaft 12 into an input shaft on the steering wheel side and an output shaft on the rack 11 side, and connects the input shaft and the output shaft with a torsion bar. This is realized by a configuration for detecting the amount of twist of the bar. That is, since the torque applied to the steering wheel and the amount of twist of the torsion bar correspond one-to-one, the steering torque can be detected by detecting the amount of twist with an appropriate detection mechanism such as a potentiometer.

The motor rotation angle sensor 64 is constituted by a rotary encoder or the like, and is provided in association with the rotor 22. The rotation position of the rotor 22, that is, the rotation angle of the motor M can be detected based on the pulse signal output from the rotary encoder. FIG. 2 shows a controller 40, a motor driver 50, and a motor current detection circuit 7.
FIG. 3 is a block diagram showing a configuration of a 0. Controller 40
Is constituted by a microcomputer including, for example, a CPU, a RAM and a ROM, and its functions are shown by blocks in FIG.

The controller 40 includes a torque sensor diagnostic section 41 for determining whether or not the torque sensor 63 is normal based on the outputs of the torque sensor 63 and the motor current detection circuit 70, a steering angle sensor 61, a vehicle speed sensor 62, A target current calculator 42 for calculating a target current value based on the output of the torque sensor 63; and a three-phase splitter for performing a three-phase splitting process based on output signals of the target current calculator 42 and the motor rotation angle sensor 64 And a processing unit 43.

The result of the judgment by the torque sensor diagnosis section 41 is given to a target current calculation section 42. Target current calculator 4
2 is the torque sensor 6
3 is determined to be normal, the vehicle speed sensor 62
And a target current value based on the output signal of the torque sensor 63. On the other hand, when it is determined that the torque sensor 63 is abnormal, a target current value is calculated based on output signals of the steering angle sensor 61 and the vehicle speed sensor 62.

The target current value obtained by the target current calculator 42 is given to a three-phase splitter 43. The three-phase splitter 43 performs three-phase splitting on the target current value supplied from the target current calculator 42, and performs each motor phase (U phase, V phase, W phase) according to the rotation angle of the motor M. Phase) to find the target current value. The U-phase target current value, V-phase target current value, and W-phase target current value obtained by the three-phase phase separation processing unit 43 are given to subtraction units 44U, 44V, and 44W, respectively. These subtraction units 44U, 44V, 44W also have the U phase, V phase, W phase of the motor M detected by the motor current detection circuit 70.
The motor current value flowing through the phase is given. Subtraction unit 44
U, 44V, and 44W calculate the difference between each phase target current value and the motor current value for each phase of the motor, and calculate the calculation result as a U-phase PI (Proportional-Integral) control unit 45U and a V-phase PI control, respectively. Unit 45V and W-phase PI control unit 4
Give 5W.

The PI control units 45U, 45V, 45W perform PI calculations based on the outputs from the subtraction units 44U, 44V, 44W, respectively. The result of this PI operation is the U-phase PW
M (Pulse Width Modulation) control unit 46U, V-phase PWM
Control unit 46V and W-phase PWM control unit 46W. Each of the PWM control units 46U, 46V, and 46W creates a PWM control signal corresponding to the PI calculation result, and outputs the created PWM control signal to the motor driver 50.

The motor driver 50 has an FET (Field-Eff)
ect Transistor) 51U, 52U series circuit and FET
A series circuit of 51V and 52V and a series circuit of FETs 51W and 52W are connected in parallel, and a voltage (for example, 12 volts) from a battery mounted on a vehicle is applied to each series circuit. I have. And FET51
A connection point 53U between U and 52U is connected to the U-phase winding of the motor M, a connection point 53V between the FETs 51V and 52V is connected to the V-phase winding of the motor M, and a connection point 53W between the FETs 51W and 52W is connected to the motor. It is connected to the M W-phase winding.
The PWM control signals from the PWM control units 46U, 46V, 46W are transmitted to the FETs 51U, 52U,
V, 52V and FETs 51W, 52W.

The motor current detection circuit 70 includes current transformers 71U, 71V, 71W using, for example, Hall elements. The current transformers 71U, 71V, and 71W are arranged so as to be able to detect motor currents flowing from the connection points 53U, 53V, and 53W to the respective phase windings of the motor M. Outputs of the current transformers 71U, 71V, and 71W are amplified by amplifiers (Amp) 72U, 72V, and 72W, respectively, and then amplified by a torque sensor diagnostic unit 41 and subtraction units 44U and 4U.
4V, 44W.

FIG. 3 is a flowchart for explaining the operation of the controller 40. The controller 40
When the ignition switch is turned on, first, an initialization process including an initial setting is performed, and a relay for turning on / off the power supply from the battery is turned on. Subsequently, the controller 40 captures each detection signal of the steering angle sensor 61, the vehicle speed sensor 62, the torque sensor 63, the motor rotation angle sensor 64, and the motor current detection circuit 70, and detects a steering angle based on each detection signal, The vehicle speed detection value, the torque detection value, the motor rotation angle detection value, and the motor current detection value are obtained (steps S1, S2, S3, S4, S
5). Then, a torque sensor diagnosis process is performed to determine whether or not the torque sensor 63 is normal based on the detected steering torque value and the detected motor current value (Step S).
6).

Next, a target current value is calculated based on the steering angle detection value and the vehicle speed detection value, or the torque detection value or the vehicle speed detection value according to the result of the torque sensor diagnosis processing (step S7). When the target current value is determined, the controller 40 performs a three-phase splitting process on the target current value, and calculates a target current value of each phase of the motor according to the rotation angle of the motor M (step S8). Then, PI calculation is performed based on the deviation between the target current value of each phase and the motor current value of each phase obtained from the output signal of the motor current detection circuit 70 (step S9), and further, a PWM control signal corresponding to the result of the PI calculation Is generated, and the generated PWM control signal is output to the motor driver 50 (step S10).

Thereafter, the controller 40 determines whether or not the ignition switch of the vehicle has been turned off (step S11). If the ignition switch remains on, the process returns to step S1, and the above-described processes after step S1 are performed. Then, when the ignition switch is turned off, the process ends. FIG. 4 is a flowchart showing a flow of the torque sensor diagnosis processing executed by the controller 40 (torque sensor diagnosis unit 41). In the torque sensor diagnosis processing, first, the motor current detection value of each phase based on the output signal from the motor current detection circuit 70 is set to a predetermined value Ix
It is determined whether or not this is the case (step S61). Then, for example, at least one of the motor current detection values for the U phase, V phase and W phase of the motor M is set to the specified value Ix
If so, it is determined whether the detected torque value based on the output signal from the torque sensor 63 is equal to or greater than the specified value Tx (step S62).

When the torque sensor 63 is normal, the motor current flowing through the motor M increases, and the steering assist force generated from the motor M increases. The increased steering assist force causes the steering mechanism 1 (see FIG. 1) to operate. When the steering assist is performed, the amount of torsion of the torsion bar interposed between the input shaft of the pinion shaft 12 on the steering wheel side and the output shaft of the rack 11 decreases, and therefore, the torque for detecting the amount of torsion of the torsion bar is reduced. The torque detection value based on the output signal from the sensor 63 decreases. Therefore, even though the motor current detection value based on the output signal from the motor current detection circuit 70 has increased, if the torque detection value based on the output signal from the torque sensor 63 remains large, the torque sensor 63 It can be determined that an abnormality has occurred.

If the detected motor current value is equal to or greater than the predetermined value Ix and the detected torque value is equal to or greater than the specified value Tx (YES in step S62), the torque sensor 6
When it is determined that there is a possibility that an abnormality has occurred in the microcomputer 3, the count value C of a counter provided in the RAM of the microcomputer constituting the controller 40 is incremented (+1) (step S63). The count value C of this counter has been reset to “0” at the start of the torque sensor diagnosis processing, and at this time, the count value C becomes “1”.

Subsequently, it is determined whether or not the count value C of the counter has reached a predetermined value N (N: natural number) (step S64). If the count value C has not reached the predetermined value N, the process returns to step S61, and it is determined again whether the magnitude of the motor current is equal to or greater than the predetermined value Ix. N times that the motor current detection value based on the output signal from the motor current detection circuit 70 is equal to or greater than the predetermined value Ix and the torque detection value based on the output signal from the torque sensor 63 is equal to or greater than the specified value Tx. It is performed continuously, and when the count value C of the counter reaches a predetermined value N, the controller 40 determines that the torque sensor 63 is abnormal (step S65). Then, the torque sensor diagnosis processing ends.

On the other hand, if the motor current detection value based on the output signal from the motor current detection circuit 70 is smaller than the predetermined value Ix (NO in step S61), or the motor current detection value is equal to or greater than the specified value Ix, If the torque detection value based on the output signal from the torque sensor 63 is less than the specified value Tx (NO in step S62), the controller 4
By 0, it is determined that the torque sensor 63 is normal (fail cancellation) (step S66). Then, the count value C of the counter is reset to “0”, and the torque sensor diagnosis processing ends.

As described above, in the electric power steering apparatus according to this embodiment, it is determined whether or not the torque sensor 63 is abnormal based on the motor current detection value and the torque detection value. I have. Therefore, since no separate torque sensor from the torque sensor 63 or a circuit for providing an output signal of the torque sensor to the controller 40 is required for detecting an abnormality of the torque sensor 63, two torque sensors are provided. The cost can be reduced as compared with the conventional electric power steering apparatus.

FIG. 5 is a diagram showing a map referred to by the controller 40 (the target current calculation section 42) for setting the target current value. FIG. 5A shows the setting of the target current value based on the detected torque value. FIG. 3B shows a torque-motor current map referred to when the setting is performed, and FIG. 4B shows a steering angle-motor current map referred when setting the target current value based on the detected steering angle. If it is determined in the torque sensor diagnosis process that the torque sensor 63 is normal, the controller 40 refers to the torque-motor current map shown in FIG. A target current value is determined based on the signal. That is, the vehicle speed range V1, V
2, different torque-motor current maps are prepared for each of V3 (V1>V2> V3), and one of the maps is selected based on the output signal of the vehicle speed sensor 62. Regardless of which torque-motor current map is referred to, the target current value is set to zero if the torque detection value based on the output signal from the torque sensor 63 is equal to or less than a predetermined lower limit T1. If the detected torque value is equal to or greater than a predetermined upper limit value T2, the target current value is set to a constant value, and the detected torque value is larger than the lower limit value T1 and the upper limit value T2.
Within the range smaller than 2, the target current value is set to be larger as the detected torque value is larger.

Based on the target current value set according to the torque-motor current map, the controller 40
By controlling the motor driver 50, the current flowing through each phase of the motor M is controlled. As a result, good steering assistance can be realized according to the magnitude of the steering torque applied to the steering wheel. On the other hand, when it is determined in the torque sensor diagnosis process that the torque sensor 63 has an abnormality,
The controller 40 refers to the steering angle-motor current map shown in FIG.
The target current value is determined on the basis of the output of (2). That is,
A different steering angle-motor current map is prepared for each of the vehicle speed ranges V1, V2, V3 (V1>V2> V3), and any one map is selected based on the output signal of the vehicle speed sensor 62. Whichever steering angle-motor current map is referred to, the larger the detected steering angle value based on the output signal from the steering angle sensor 61, the larger the target current value is set.

The controller 40 sets the supply current to the motor M according to the steering angle-motor current map from the detected motor current value at the time when it is determined that the torque sensor 63 has failed within a predetermined transition time. Motor driver 50 so that it gradually changes to the set target current value.
Control. As a result, the motor current and the steering angle-at the time when it is determined that the torque sensor 63 is abnormal have been calculated.
When the target current value largely differs from the target current value set in accordance with the motor current map, it is possible to prevent the steering assist force applied to the steering mechanism 1 from suddenly changing, and to improve the steering feeling.

The rate of change when the current supplied to the motor M is gradually changed to a target current value set according to the steering angle-motor current map can be changed by adjusting the length of the transition time. The transition time may be adjusted based on a deviation between a motor current detection value when the torque sensor 63 is determined to be abnormal and a target current value set according to a steering angle-motor current map. As described above, according to this embodiment, based on the motor current detection value based on the output signal from the motor current detection circuit 70 and the torque detection value based on the output signal from the torque sensor 63, the torque sensor 63 detects an abnormality. It can be determined whether or not it has occurred. As a result, the cost can be reduced as compared with a conventional electric power steering device having two torque sensors.

When an abnormality of the torque sensor 63 is detected, a target current value is set based on a steering angle detection value based on an output signal from the steering angle sensor 61, and a motor current is set based on the target current value. Control is performed. This allows
Even when an abnormality occurs in the torque sensor 63, steering assist according to the operation of the steering wheel can be performed. Further, immediately after the occurrence of the abnormality in the torque sensor 63, the supply current to the motor M is set to a target current value set according to the steering angle-motor current map from the detected motor current value at the time when it is determined that the abnormality in the torque sensor 63 occurs. Is controlled so as to gradually change up to. As a result, a sudden change in the steering assist force can be prevented, and the steering feeling can be improved.

Although the embodiment of the present invention has been described above, the present invention can be implemented in other embodiments. For example, in the above-described embodiment, when the torque sensor is abnormal, the target current value is set based on the steering angle and the vehicle speed of the steering wheel. However, for example, in order to detect the yaw rate and the lateral acceleration of the vehicle, May be additionally provided, and the yaw rate and the lateral acceleration may be added as parameters for setting the target current value.

In addition, various design changes can be made within the scope of the matters described in the claims.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electric configuration of an electric power steering device according to an embodiment of the present invention, together with a cross-sectional structure of a steering mechanism.

FIG. 2 is a block diagram illustrating a configuration of a controller, a motor driver, and a motor current detection circuit.

FIG. 3 is a flowchart for explaining the operation of the controller.

FIG. 4 is a flowchart illustrating a flow of a torque sensor diagnosis process.

FIG. 5 is a diagram showing a map referred to when a controller (a target current calculation unit) sets a target current value.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steering mechanism 2 Electric power steering device 40 Controller 41 Torque sensor diagnosis part (Abnormality judgment means) 42 Target current calculation part (Motor control means, Abnormality control means, Transition time control means) 43 Three-phase phase separation processing part (Motor control Means, abnormal time control means, transition time control means) 44U, 44V, 44W subtraction section (motor control means, abnormal time control means, transition time control means) 45U, 45V, 45W PI control section (motor control means, abnormal time control) Means, transition control means) 46U, 46V, 46W PWM control section (motor control means, abnormal control means, transition control means) 50 motor driver 61 steering angle sensor (operation amount detection means) 63 torque sensor 70 motor current detection Circuit (current detection means) M Motor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Takamatsu 3-5-8 Minamisenba, Chuo-ku, Osaka-shi Inside Koyo Seiko Co., Ltd. (72) Inventor Nobuyoshi Sugitani 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor In-house F term (reference) 3D032 CC08 CC28 CC33 CC46 CC48 DA03 DA15 DA24 DA29 DA33 DA63 DA64 DC01 DC02 DC08 DC21 DC33 DC34 DD02 DD10 DD17 EA01 EB11 EC23 GG01 3D033 CA03 CA13 CA14 CA16 CA17 CA20 CA21 CA31 CA32

Claims (4)

[Claims] 1. An electric power steering device that uses an electric motor as a drive source and applies a steering assist force to a steering mechanism mounted on a vehicle in accordance with an operation of an operation means, wherein a motor current flowing through the electric motor is detected. A current detection unit that outputs a signal corresponding to the detected motor current; a torque sensor that detects a steering torque applied to the operation unit and outputs a signal corresponding to the detected steering torque; If the motor current detection value based on the output signal is equal to or greater than a predetermined current value and the torque detection value based on the output signal from the torque sensor is equal to or greater than a predetermined torque value, an abnormality occurs in the torque sensor. An electric power steering apparatus, comprising: an abnormality determining unit configured to determine that the vehicle is in the off state. 2. A target current value for an electric motor is determined according to a torque detection value based on an output signal from the torque sensor.
2. The electric power steering apparatus according to claim 1, further comprising motor control means for controlling the electric motor based on the target current value. 3. An operation amount detection means for detecting an operation amount of the operation means and outputting a signal corresponding to the detected operation amount, and the abnormality determination means determines that an abnormality has occurred in the torque sensor. In this case, instead of controlling the electric motor based on the torque detection value by the motor control means, a target current value of the electric motor is determined according to an operation amount detection value based on an output signal from the operation amount detection means, 3. The electric power steering apparatus according to claim 2, further comprising an abnormal time control unit that controls the electric motor based on the target current value. 4. The electric power steering apparatus according to claim 1, wherein, at the time of transition from control by said motor control means to control by said abnormal control means, a current supplied to said electric motor is adjusted to a target current determined by said abnormal control means. The electric power steering apparatus according to claim 3, further comprising a transition control means for gradually changing the value to a value.