JP3500517B2 - 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 drives and controls a steering force assisting motor on the basis of the detected torque detected by a torque sensor, and when the detected torque is within a predetermined range, the steering force in the direction opposite to the detected torque. The present invention relates to an improvement in an electric power steering device that prohibits driving of an auxiliary motor.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional electric power steering apparatus, which the applicant of the present invention has already filed in Japanese Patent Application No. 6-2465.
FIG. 37 is a block diagram showing a schematic configuration of an electric power steering device proposed in Japanese Patent No. 36. In this electric power steering device, a detected torque signal representing the detected torque detected by the torque sensor 1 is given to the CPU 2. The CPU 2 receives the detected torque signal, reads a target current corresponding to the detected torque signal from a built-in target current table (not shown), differentiates the detected torque signal, and differentiates the differentiated value and the target current. Is added (PD control) to determine the motor current target value of the steering force assisting motor 4.

The CPU 2 controls the motor drive circuit 3 to drive the motor 4 by using this motor current target value as the target value for automatic control, and at that time, the right drive motor current detection circuit 5
a, the motor 4 detected by the left drive motor current detection circuit 5b
C drive current as a feedback value for automatic control
Inputting to PU2. The drive current of the motor 4 detected by the right drive motor current detection circuit 5a and the left drive motor current detection circuit 5b is also given to an abnormal current determination circuit 6 described later.

The detected torque signal from the torque sensor 1 is also input to the direction prohibited area determination circuit 8a. As shown in FIG. 3, the direction prohibited area determination circuit 8a has a predetermined detected torque in each of the left and right directions. When the value is larger than the value, the motor drive prohibition region in which the motor 4 is not driven in the direction opposite to the detected torque is set, and whether or not the detected torque is in this motor drive prohibition region is determined by a drive logic determination circuit described later. 9 and the dead zone detection circuit 10 are notified. The detection signal of the dead zone detection circuit 10 is given to the abnormal current determination circuit 6 which determines that the detected torque is within the dead zone and the drive current of the motor is larger than a predetermined value. Here, the predetermined value of the drive current of the motor is larger than the maximum value of the return current of the steered wheels, and is set to a value at which the electric power steering device does not become unstable. From the CPU 2, the motor current target value (size and direction) is sent to the motor drive circuit 3, the drive logic determination circuit 9 and the motor non-drive detection circuit 11 described later.

A drive logic determination circuit 9 and an abnormal current determination circuit for determining that the detected torque is outside the dead zone and the direction in which the motor 4 should be driven and the detected torque direction are opposite directions according to the target value of the motor current. The determination result of No. 6 is given to the drive abnormality detection circuit 7, and when the drive abnormality detection circuit 7 detects an abnormality from these determination results, the detection timer 12 and the confirmation timer 15 have predetermined time T1 and Start timing of T2. When the detection timer 12 completes counting the predetermined time T1, the latch circuit 13 holds the abnormality detection signal from the drive abnormality detection circuit 7. While the latch circuit 13 holds the abnormality detection signal from the drive abnormality detection circuit 7, the diagnostic lamp 19 lights up and
The motor drive prohibition circuit 14 stops the operation of the motor drive circuit 3.

The latch circuit 13 is cleared when the motor non-drive detection circuit 11 which detects that the motor current target value is zero detects zero. When the confirmation timer 15 has finished measuring the predetermined time T2, the latch circuit 16
Holds the abnormality detection signal from the drive abnormality detection circuit 7. While the latch circuit 16 holds the abnormality detection signal from the drive abnormality detection circuit 7, the diagnostic lamp 19 lights up and the relay drive inhibition circuit 17 causes the motor drive circuit 3 to operate.
The fail-safe relay 18 that connects the power supply to the power source is turned off.

In the electric power steering apparatus having such a structure, the assist current and the steering wheel return current based on the torque signal are determined in the CPU 2 and the angular velocity difference control (differential control of the detected torque signal) is performed. Therefore, depending on the target value of the motor current, the direction in which the motor 4 should be driven and the direction of the detected torque are opposite to each other, or a large drive current of the motor flows even though the detected torque is in the dead zone. Occurring momentarily, the drive abnormality may be detected even though the CPU 2 is normal (not runaway). Therefore, it is necessary to set the predetermined time T1 of the detection timer 12 to be longer than the time when the drive abnormality detection circuit 7 operates in the normal state. Further, the predetermined time T1 of the detection timer 12 needs to be as short as possible when the CPU 2 runs out of control. Therefore, the detection timer 12
The role of is to turn off the motor 4 in the shortest possible time when the CPU 2 runs away without erroneously detecting that the CPU 2 runs out of control.

Here, if the motor non-driving detection circuit 11 does not detect that the motor current target value is zero (non-driving), the latch circuit 13 is not cleared. Defect occurs. When the CPU 2 runs out of control and the motor current target value becomes excessive, a large current flows through the motor 4 while the detection timer 12 measures the predetermined time T1 even when the detected torque is within the dead zone. , The steering wheel rotates. By turning the steering wheel,
Since the detected torque is generated in the direction opposite to the direction in which the motor drive current drives the motor 4, the drive logic determination circuit 9 determines and notifies the abnormality. Therefore, the driving of the motor 4 is prohibited, the assist is turned off, and the steered wheels return in the opposite direction. At this time, the determination of the drive logic determination circuit 9 becomes normal, and a large current flows again. Hereinafter, the same operation is repeated, and the operation of the electric power steering device becomes unstable.

The drive logic determination circuit 9 is normal during a period in which the detected torque is outside the dead zone and the logic indicating that the direction in which the motor 4 should be driven and the direction of the detected torque are opposite to each other is not established according to the motor current target value. Therefore, the drive abnormality detection circuit 7 is not notified of the abnormality. Further, the abnormal current determination circuit 6 does not notify the drive abnormality detection circuit 7 of an abnormality during the period when the detected torque is within the dead zone and the condition that the motor drive current is larger than the predetermined value is not satisfied. The drive abnormality detection circuit 7 stops the detection timer 12 and the confirmation timer 15 while no abnormality is notified from the drive logic determination circuit 9 or the abnormal current determination circuit 6. Therefore, the latch circuits 13 and 16
Does not hold the abnormality notification and does not operate the motor drive prohibition circuit 14 and the relay drive prohibition circuit 17.

[0010]

As described above, this electric power steering apparatus determines the assist current and the steering wheel return current based on the torque signal in the CPU 2, and also performs the differential control of the detected torque signal (angular velocity difference control). However, if the gain of this differential control is made large, the direction in which the motor 4 should be driven and the direction of the detected torque are opposite directions depending on the target value of the motor current, or the detected torque is in the dead zone. Instead, a state in which a large amount of motor drive current flows momentarily occurs, and a drive abnormality may be detected even though the CPU 2 is normal (not runaway). Therefore, a predetermined time T of the detection timer 12 is longer than the time when the drive abnormality detection circuit 7 operates in the normal state.
It is necessary to set 1 but if it is set to a long time, the CPU 2 will be allowed to runaway during that time, which may not be a safety measure during runaway.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric power steering apparatus capable of detecting runaway of a CPU in a short time.

[0012]

According to a first aspect of the present invention, there is provided an electric power steering apparatus, wherein a motor for a steering force assisting motor is based on the detected torque when the detected torque detected by the torque sensor is outside the dead zone. A torque change direction detection circuit that detects a change direction of the detected torque in an electric power steering device that drives and controls the motor by setting a current target value and using the motor current target value as a target value for automatic control; The torque is outside the dead zone, the direction in which the motor should be driven by the motor current target value is opposite to the direction in which the detected torque is, and the motor should be driven by the motor current target value. A drive abnormality detection circuit for detecting a state in which the direction and the change direction detected by the torque change direction detection circuit indicate opposite directions, When moving the abnormality detecting circuit detects the state, characterized in that are no in order to prohibit the driving of the motor.

An electric power steering apparatus according to a second aspect of the present invention comprises an abnormal current determination circuit for determining that the drive current of the motor is larger than a predetermined value and the drive current of the motor is in the direction of driving the motor. The drive abnormality detection circuit, in addition to the above state, the detected torque is within the dead zone, and the abnormal current determination circuit determines that the drive current of the motor is larger than the predetermined value. It is designed to detect a state in which the determined direction and the change direction detected by the torque change direction detection circuit indicate opposite directions, and when the drive abnormality detection circuit detects this state, the motor is driven. It is characterized by being prohibited.

The electric power steering apparatus according to the third aspect of the invention starts timing when the drive abnormality detection circuit detects the state, and is reset when the drive abnormality detection circuit stops detecting the state. Is provided with a detection timer, and the drive of the motor is prohibited when the detection timer completes counting the first predetermined time.

The electric power steering apparatus according to the fourth aspect of the invention starts timing when the drive abnormality detection circuit detects the state, and is reset when the drive abnormality detection circuit stops detecting the state. A determination timer, an abnormality detection signal holding circuit that holds an abnormality detection signal from the drive abnormality detection circuit when the determination timer completes measuring a second predetermined time, and the abnormality detection signal holding circuit Includes a relay drive prohibition circuit that turns off a fail-safe relay that connects the drive circuit of the motor and a power supply while holding the abnormality detection signal.

[0016]

In the electric power steering apparatus according to the first aspect of the present invention, the torque change direction detection circuit detects the change direction of the detected torque. Then, the drive abnormality detection circuit detects that the detected torque is outside the dead zone, the motor current target value indicates the direction in which the motor should be driven and the detected torque direction is opposite, and the motor current target value indicates that the motor should be driven. When the state in which the direction to be driven and the change direction detected by the torque change direction detection circuit indicate opposite directions is detected, the drive of the motor is prohibited.

In the electric power steering apparatus according to the second aspect of the invention, the abnormal current determination circuit determines that the motor drive current is larger than a predetermined value and the motor drive current is in the direction in which the motor is driven. Then, the drive abnormality detection circuit detects that the detected torque is within the dead zone, and the abnormal current determination circuit determines that the motor drive current is larger than a predetermined value, and detects the direction and the torque change direction determined by the abnormal current determination circuit. When a state in which the direction of change detected by the circuit indicates a reverse direction is detected, the drive of the motor is prohibited.

In the electric power steering apparatus according to the third aspect of the present invention, when the drive abnormality detection circuit detects the above state, the detection timer starts counting time. Then, when the drive abnormality detection circuit stops detecting the above state, the detection timer is reset. On the other hand, when the detection timer completes counting the first predetermined time, the drive of the motor is prohibited.

In the electric power steering apparatus according to the fourth aspect of the present invention, the confirmation timer starts counting when the drive abnormality detection circuit detects the above state, and when the drive abnormality detection circuit stops detecting the state. Will be reset. Further, when the confirmation timer completes the counting of the second predetermined time, the abnormality detection signal holding circuit holds the abnormality detection signal from the drive abnormality detection circuit. Then, while the abnormality detection signal holding circuit holds the abnormality detection signal, the relay drive inhibition circuit turns off the fail-safe relay that connects the drive circuit of the motor and the power supply.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments. FIG. 1 is a block diagram showing the configuration of one embodiment of an electric power steering device according to the present invention.
In this electric power steering device, the detected torque signal representing the detected torque detected by the torque sensor 1 is the CPU 2
Given to. The CPU 2 receives the detected torque signal,
By reading the target current corresponding to the detected torque signal from the built-in target current table (not shown), differentiating the detected torque signal and adding the differential value and the target current (PD control), A motor current target value (size and direction) of the steering force assisting motor 4 is determined.

The CPU 2 controls the motor drive circuit 3 to drive the motor 4 by using this motor current target value as the target value for automatic control, and at that time, the right drive motor current detection circuit 5
a, the motor 4 detected by the left drive motor current detection circuit 5b
CP drive current as a feedback value for automatic control
Input to U2. The motor current target value is also sent from the CPU 2 to the drive logic determination circuit 9a and the motor non-drive detection circuit 11 described later.

The detected torque signal from the torque sensor 1 is also input to the direction prohibited area determination circuit 8a, and the direction prohibited area determination circuit 8a has predetermined values for the left and right directions of the detected torque as shown in FIG. Has set a value,
Whether the detected torque is within this predetermined value is notified to the drive logic determination circuit 9a and the dead zone detection circuit 10 described later. The detected torque signal from the torque sensor 1 is also input to the differentiating circuit 20, and the differentiation result of the differentiating circuit 20 is given to the torque changing direction detecting circuit 21 to detect the changing direction of the detected torque. The signal indicating the changing direction of the detected torque is given to the abnormal current determination circuit 6a and the drive logic determination circuit 9a described later.

The detection signal of the dead zone detection circuit 10 for detecting the dead zone of the detected torque for which the motor current target value should be zero is such that the detected torque is within the dead zone, and the drive current of the motor exceeds a predetermined value (for example, 10 A). It is supplied to the abnormal current determination circuit 6a that determines that the direction in which the motor is driven by the motor drive current is opposite to the direction in which the detected torque changes. Here, the predetermined value of the drive current of the motor is larger than the maximum value of the return current of the steered wheels, and is set to a value at which the electric power steering device does not become unstable.

The drive logic determination circuit 9a has the detected torque outside the dead zone, the direction in which the motor should be driven according to the target value of the motor current is opposite to the detected torque, and the motor is driven according to the target value of the motor current. It is determined that the power direction and the changing direction of the detected torque are opposite directions. The determination results of the drive logic determination circuit 9a and the abnormal current determination circuit 6a are
The drive abnormality detection circuit 7a receives the drive abnormality detection circuit 7a.
When a detects an abnormality from these determination results, the predetermined time T1 (for example, 10 msec.) and T2 (for example, 1) of the detection timer 12 and the confirmation timer 15 are detected.
sec. ) To start timing. When the detection timer 12 has finished counting the predetermined time T1, the latch circuit 13
Holds the abnormality detection signal from the drive abnormality detection circuit 7a. While the latch circuit 13 holds the abnormality detection signal from the drive abnormality detection circuit 7a, the diagnostic lamp 19 lights up and the motor drive prohibition circuit 14 causes the motor drive circuit 3 to operate.
Stop the operation of.

The latch circuit 13 is cleared when the motor non-drive detection circuit 11 which detects that the motor current target value is zero detects zero. When the confirmation timer 15 completes counting the predetermined time T2, the latch circuit (abnormality detection signal holding circuit) 16 holds the abnormality detection signal from the drive abnormality detection circuit 7a. While the latch circuit 16 holds the abnormality detection signal from the drive abnormality detection circuit 7a, the diagnostic lamp 19 lights up, and the relay drive inhibition circuit 17 causes the fail-safe relay that connects the motor drive circuit 3 and the power supply. Turn off 18.

The operation of the electric power steering apparatus having such a structure will be described below. The detected torque detected by the torque sensor 1 is input to the direction prohibited area determination circuit 8a,
The direction prohibited area determination circuit 8a determines the direction and magnitude of the detected torque, and a signal indicating the direction of the detected torque is sent to the drive logic determination circuit 9a. As for the magnitude of the detected torque, as shown in FIG. 3, a signal notifying the magnitude of the detected torque with respect to each of the left and right directions (inside the dead zone or outside the dead zone) is sent to the dead zone detection circuit 10. . The dead zone detection circuit 10 sends a notification signal indicating whether the detected torque is within the dead zone or outside the dead zone to the abnormal current determination circuit 6a. Further, the detected torque detected by the torque sensor 1 is also input to the differentiating circuit 20, and the differentiating circuit 20
The calculation result of is given to the torque change direction detection circuit 21, and the change direction of the detected torque is detected. The signal indicating the changing direction of the detected torque is given to the abnormal current determination circuit 6a and the drive logic determination circuit 9a.

Here, the drive logic determination circuit 9a indicates that the detected torque is outside the dead zone, the direction in which the motor should be driven and the detected torque direction are opposite to each other according to the motor current target value, and the motor current is The abnormality is notified to the drive abnormality detection circuit 7a during a period in which the direction in which the motor should be driven by the target value and the direction in which the detected torque changes are opposite directions. Further, the abnormal current determination circuit 6a detects that the detected torque is within the dead zone, the drive current of the motor is larger than a predetermined value, and the direction in which the motor is driven by the drive current of the motor and the change direction of the detected torque are opposite directions. The drive abnormality detection circuit 7a continues to be notified of the abnormality for a certain period.

When the drive abnormality detection circuit 7a is notified of an abnormality from the drive logic determination circuit 9a or the abnormal current determination circuit 6a, the drive abnormality detection circuit 7a detects the abnormality and activates the detection timer 12 and the confirmation timer 15 to drive the drive logic. When the abnormality notification from the determination circuit 9a or the abnormal current determination circuit 6a is interrupted, the detection timer 12 and the confirmation timer 15 are reset. When the detection timer 12 completes the timing of the predetermined time T1 without interrupting the abnormality notification from the drive logic determination circuit 9a or the abnormal current determination circuit 6a to the drive abnormality detection circuit 7a, the detection logic 12 causes the drive logic determination circuit in the latch circuit 13. 9a or the abnormality notification from the abnormal current determination circuit 6a is held. The latch circuit 13 holds the diagnostic lamp 19 while holding the abnormality notification.
Is turned on and the motor drive prohibition circuit 14 is operated to prohibit the drive of the motor 4. During this time, the latch circuit 1
3 is cleared when the motor non-drive detection circuit 11 detects that the motor current target value is zero, the operation of the motor drive prohibition circuit 14 is stopped, and the drive prohibition of the motor 4 is released.

In the CPU 2, the assist current and the steering wheel return current based on the torque signal are determined, and the angular velocity difference control (differential control of the torque signal) is performed. Therefore, depending on the target value of the motor current, the direction in which the motor should be driven is opposite to the direction of the detected torque, or a large amount of motor drive current may flow even if the detected torque is in the dead zone. However, even if the CPU 2 is normal (not running out of control), a drive abnormality may be detected. Therefore, conventionally, the detection timer 1 is operated for a longer period of time than the drive abnormality detection circuit 7a operates in a normal state.
It was necessary to set the predetermined time T1 of 2.

However, in the electric power steering apparatus according to the present invention, as the conditions for detecting the drive abnormality, the relation condition between the direction in which the motor current target value should drive the motor and the changing direction of the detected torque, and the drive current of the motor are set. It becomes possible to set the predetermined time T1 of the detection timer 12 to be shorter by adding the relational condition between the direction in which the motor drives the motor and the direction in which the detected torque changes. Therefore, in the electric power steering apparatus according to the present invention, the detection timer 12 can promptly turn off the motor 4 when the CPU 2 runs out of control without erroneously detecting that the CPU 2 runs out of control when the CPU 2 is normal.

Here, if the motor non-driving detection circuit 11 does not detect that the motor current target value is zero (non-driving), the latch circuit 13 is not cleared. Defect occurs. When the CPU 2 runs out of control and the motor current target value becomes excessive, a large current flows through the motor 4 while the detection timer 12 measures the predetermined time T1 even when the detected torque is within the dead zone. , The steering wheel rotates. By turning the steering wheel,
Since the detected torque in the direction opposite to the drive current of the motor is generated, the drive logic determination circuit 9 determines and notifies the abnormality. Therefore, the driving of the motor 4 is prohibited, the assist is turned off, and the steered wheels return in the opposite direction. At this time, the determination of the drive logic determination circuit 9 becomes normal, and a large current flows again. Hereinafter, the same operation is repeated, and the operation of the electric power steering device becomes unstable.

The confirming timer 15 includes a drive logic determining circuit 9
a or the abnormal current determination circuit 6a to the drive abnormality detection circuit 7a
When the timing of the predetermined time T2 is completed without interruption of the abnormality notification to the drive logic determination circuit 9
a or the abnormality notification from the abnormal current determination circuit 6a is held. The latch circuit 16 lights up the diagnostic lamp 19 while holding the abnormality notification, and at the same time, the relay drive prohibiting circuit 1
7 is activated, the fail safe relay 18 is turned off,
The power supply of the motor drive circuit 3 is turned off. Latch circuit 16
Is cleared when the power of the electric power steering device is turned off (when the ignition key is turned off).

Since the detection timer 12 is reset by the motor non-driving detection of the CPU 2, depending on the runaway state of the CPU 2, detection and recovery may be repeated and there is a possibility of becoming unstable. Therefore, the predetermined time T of the detection timer 12
If the drive abnormality persists during the predetermined time T2 by setting the predetermined time T2 of the confirmation timer 15 sufficiently longer than 1, the failure is fixed.

The drive logic determination circuit 9a detects that the detected torque is outside the dead zone, and the motor 4 is driven by the motor current target value.
The period in which the direction in which the motor should be driven and the direction of the detected torque are opposite to each other and the direction in which the motor 4 is to be driven by the target value of the motor current and the direction in which the detected torque is changed are opposite to each other is not established. It is determined to be normal, and no abnormality is notified to the drive abnormality detection circuit 7a. Further, the abnormal current determination circuit 6a detects that the detected torque is within the dead zone, the drive current of the motor is larger than a predetermined value, and the direction in which the motor 4 is driven by the drive current of the motor and the change direction of the detected torque are opposite directions. During the period when the condition is not satisfied, the drive abnormality detection circuit 7a is not notified of the abnormality. The drive abnormality detection circuit 7a stops the detection timer 12 and the confirmation timer 15 while no abnormality is notified from the drive logic determination circuit 9a or the abnormal current determination circuit 6a. Therefore, the latch circuits 13 and 16 are
The motor drive prohibition circuit 14 and the relay drive prohibition circuit 17 are not operated without holding the abnormality notification.

[0035]

According to the electric power steering apparatus of the present invention, the runaway of the CPU can be detected in a short time.
It is possible to prevent the steering from becoming unstable when the CPU goes out of control. Further, the runaway of the CPU can be monitored without disturbing the differential control of the torque detection signal.

[Brief description of drawings]

FIG. 1 is an electric power steering device 1 according to the present invention.
It is a block diagram showing a schematic structure of an example.

FIG. 2 is a block diagram showing a schematic configuration of an example of a conventional electric power steering device.

FIG. 3 is an explanatory diagram for explaining a relationship between a detected torque of the electric power steering device and a motor current target value.

[Explanation of symbols]

1 Torque sensor 2 CPU 3 Motor drive circuit 4 motor 5a Right drive motor current detection circuit 5b Left drive motor current detection circuit 6a Abnormal current determination circuit 7a Drive abnormality detection circuit 8a Direction prohibited area determination circuit 9a Drive logic determination circuit 10 Dead band detection circuit 11 Motor non-drive detection circuit 12 Detection timer 13 Latch circuit 14 Motor drive prohibition circuit 15 Confirmation timer 16 Latch circuit (abnormality detection signal holding circuit) 17 Relay drive prohibition circuit 18 Fail-safe relay 19 diagnostic lights 20 Differentiation circuit 21 Torque change direction detection circuit

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-5-112251 (JP, A) JP-A-63-180562 (JP, A) JP-A-7-137651 (JP, A) JP-A-6- 270823 (JP, A) JP-A-8-108856 (JP, A) JP-A-7-17423 (JP, A) JP-A-7-17424 (JP, A) JP-A-7-267108 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B62D 5/00-5/04 B62D 6/00-6/06

Claims (4)

(57) [Claims] 1. When the detected torque detected by the torque sensor is outside the dead zone, a target motor current value of the steering force assisting motor is determined based on the detected torque, and the target motor current value is automatically controlled. As a target value of the electric power steering device for driving and controlling the motor, a torque change direction detection circuit that detects a change direction of the detected torque, and the detected torque is outside the dead zone, and the motor current target value is The direction in which the motor should be driven and the direction of the detected torque are opposite directions, and the direction in which the motor should be driven by the motor current target value and the change direction detected by the torque change direction detection circuit are A drive abnormality detection circuit for detecting a state indicating a reverse direction, and when the drive abnormality detection circuit detects the state, the motor is driven. An electric power steering apparatus characterized by are none so as to prohibit. 2. An abnormal current determination circuit for determining that the drive current of the motor is larger than a predetermined value and a direction in which the drive current of the motor drives the motor, wherein the drive abnormality detection circuit is In addition, the detected torque is within the dead zone, the abnormal current determination circuit determines that the drive current of the motor is larger than the predetermined value, and the direction and the torque change direction determined by the abnormal current determination circuit. 2. A state in which the change direction detected by the detection circuit indicates a reverse direction, and when the drive abnormality detection circuit detects this state, the drive of the motor is prohibited. The electric power steering device described. 3. A detection timer is provided, which starts timing when the drive abnormality detection circuit detects the state, and is reset when the drive abnormality detection circuit stops detecting the state. The electric power steering apparatus according to claim 1 or 2, wherein the drive of the motor is prohibited when the timer for use has finished measuring the first predetermined time. 4. A confirmation timer that starts timing when the drive abnormality detection circuit detects the state and is reset when the drive abnormality detection circuit stops detecting the state, and a confirmation timer. An abnormality detection signal holding circuit for holding an abnormality detection signal from the drive abnormality detection circuit when the timer completes measuring the second predetermined time, and while the abnormality detection signal holding circuit holds the abnormality detection signal, The electric power steering apparatus according to claim 3, further comprising: a relay drive inhibition circuit that turns off a fail-safe relay that connects a drive circuit of the motor and a power supply.