JP2002193120A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize a shock generated at the time of regulating the steering of a wheel for steering at the maximum steering angle. SOLUTION: A torque integrating part 72 integrates steering torque added to a steering wheel 1 after a steering neutral state is detected. When the integrated value of the steering torque integrated at this torque integrating part 72 is out of a specified range, the wheel for steering is judged to be steered to the neighbourhood of the maximum steering angle, and an assist limiting electric current is set at an assist limiting electric current setting part 73. Thereafter, a motor indicating electric current is set by subtracting the assist limiting electric current from the assist electric current specified at the assist electric current setting part 71, and driving control of an electric motor 4 is carried out in accordance with this motor indicating electric current. Consequently, it is possible to restrain the shock at the time when the steering of the wheel for steering is regulated at the maximum steering angle small.

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 steering by using a driving force generated by an electric motor.

[0002]

2. Description of the Related Art Conventionally, there has been used an electric power steering device which assists steering by transmitting a driving force generated by an electric motor to a steering mechanism of a vehicle. In this type of electric power steering device, a motor instruction current is set according to a steering torque applied to a steering wheel, and the electric motor is feedback-controlled based on the set motor instruction current. The motor instruction current is set to be larger as the steering torque is larger, whereby a steering assist force corresponding to the magnitude of the steering torque is applied to the steering mechanism.

[0003]

By the way, a general steering mechanism is so constructed that when the steering angle of the steering wheel reaches a predetermined maximum steering angle, the steering wheel cannot be further turned. I have. Nevertheless, in the conventional power steering device, even if the steering wheel is turned to near the maximum turning angle, a large steering assist force is applied to the steering mechanism if the steering torque applied to the steering wheel is large. However, there is a problem that the impact when the turning of the steering wheel is restricted is large, and the driver feels discomfort. In addition, if the impact when the steering of the steering wheel is restricted is large, there is a possibility that parts constituting the steering mechanism may be damaged.

It is an object of the present invention to solve the above-mentioned technical problems and to provide an electric power steering apparatus capable of reducing an impact generated when steering of a steering wheel is regulated at a maximum steering angle. is there.

[0005]

Means for Solving the Problems and Effects of the Invention According to the first aspect of the present invention, a driving force generated by an electric motor (4) is given to a steering mechanism (3) to assist steering. A steering torque detecting means (6) for detecting a steering torque input to a steering mechanism, and a neutral for detecting that the steering mechanism has entered a neutral state when the vehicle is traveling straight. An integrated value (積 算 T) of the steering torque detected by the steering torque detecting means after the neutral state of the steering mechanism is detected by the state detecting means and the neutral state detecting means (for example, until the neutral state is detected again).
And a motor instruction current to be supplied to the electric motor based on the steering torque detected by the steering torque detecting means and the integrated value of the steering torque obtained by the torque integrating means. Motor instruction current setting means (7, 71, 73, 7)
4) An electric power steering apparatus comprising:

According to a second aspect of the present invention, the motor instruction current setting means includes an assist current setting means (71) for setting an assist current according to a steering torque detected by the steering torque detection means. An assist limiting current setting unit (73) for setting an assist limiting current for reducing and correcting the assist current set by the assist current setting unit, wherein the integrated value of the steering torque obtained by the torque integrating unit is predetermined. Range (-T
If H ≦ ΣT ≦ + TH), the assist current set by the assist current setting means is determined as the motor instruction current, and the integrated value of the steering torque obtained by the torque integration means is set in the predetermined range. If it is outside, the motor instruction current is set by subtracting the assist limit current set by the assist limit current setting means from the assist current set by the assist current setting means. The electric power steering apparatus according to claim 1.

[0007] Alphanumeric characters in parentheses indicate corresponding components in the embodiment described later. Hereinafter, the same applies in this section. According to the above invention, the motor instruction current is set based on the steering torque and the integrated torque value. Since the torque integrated value obtained by the torque integrating means is the sum of the steering torques input after the neutral state of the steering mechanism is detected, when the steering wheel of the vehicle is near the maximum steering angle, it exceeds a certain range. Should be. Therefore, when the torque integrated value obtained by the torque integrating means exceeds a predetermined range, it can be determined that the steering wheel has been turned to near the maximum steering angle.

Therefore, when the integrated value of the steering torque obtained by the torque integrating means is outside a predetermined range, the assist limiting current setting is performed based on the assist current set by the assist current setting means. By setting the motor instruction current by subtracting the assist limit current set by the means, it is possible to reduce the steering assist force given to the steering mechanism when the turning of the steering wheel is regulated at the maximum turning angle, The impact when the steering of the steering wheel is regulated at the maximum steering angle can be reduced.

According to a third aspect of the present invention, there is provided an electric motor (4).
Motor steering angle detecting means (1) for detecting a rotation angle of an electric motor by providing a steering force to the steering mechanism (3) to provide steering assist.
0) and turning angle determination means (11, 11) for determining whether or not the steering wheel of the vehicle has been turned to near the maximum turning angle.
T5), when the steering angle determination means determines that the steering wheel has been steered to near the maximum steering angle, and based on the rotation angle of the electric motor detected by the motor rotation angle detection means. And an end contact current setting means for setting a motor instruction current to be supplied to the electric motor.
T12).

According to the present invention, the motor instruction current is set based on the rotation angle of the electric motor in a state where the steered wheels are turned to the vicinity of the maximum turning angle. Since the rotation angle of the electric motor corresponds to the steering angle of the steering wheel, a motor instruction current is set based on the rotation angle of the electric motor, and the electric motor is driven and controlled based on the motor instruction current. Thus, control of the electric motor according to the turning angle of the steering wheel is achieved. Therefore, if the motor instruction current is appropriately set based on the rotation angle of the electric motor, the steering assist force applied to the steering mechanism when steering of the steering wheel is regulated at the maximum steering angle is reduced, and the steering assist force is reduced. It is possible to reduce the impact when the turning of the wheels is regulated at the maximum turning angle.

For example, as set forth in claim 4, the end contact current setting means sets the rotation angle of the electric motor detected by the motor rotation angle detection means to a value such that the steering wheel turns the maximum turning angle. If the motor instruction current is set smaller as the motor rotation angle of the electric motor approaches the maximum rotation angle of the electric motor when steered, as the steering wheel approaches the maximum steering angle, the electric motor switches to the steering mechanism. The applied steering assist force can be reduced, and the impact when the steering of the steering wheel is regulated at the maximum steering angle can be reduced.

Even if the steering wheel is steered to near the maximum steering angle, a steering torque for turning the steering wheel in a direction opposite to the maximum steering angle is applied to the steering mechanism. In such a case, the steering wheel is not steered to the maximum steering angle. In such a case, it is not necessary to set the motor instruction current based on the motor rotation angle. Therefore, as set forth in claim 5, the electric power steering apparatus further includes a steering torque detecting means (6) for detecting a steering torque input to a steering mechanism, and the end contact current setting means includes: When it is determined by the turning angle determining means that the steering wheel has been turned to the vicinity of the maximum turning angle, the direction of the steering torque detected by the steering torque detecting means changes the steering wheel to the maximum steering angle. Preferably, the motor instruction current is set based on the rotation angle of the electric motor detected by the motor rotation angle detection means, provided that the steering direction is to be turned toward a corner.

According to a sixth aspect of the present invention, in the electric power steering system, the steering angle determination means determines that the steering wheel has not been turned to near the maximum steering angle; When the steering wheel is determined by the steering angle determining means to have been turned to near the maximum steering angle, and the direction of the steering torque detected by the steering torque detecting means indicates that the steering wheel is moving straight ahead of the vehicle. In the normal direction of setting the motor instruction current based on the steering torque detected by the steering torque detecting means (preferably not depending on the rotation angle of the electric motor) when returning to the neutral position which is the state of Current setting means (11,
The electric power steering apparatus according to claim 5, further comprising T8).

According to the present invention, even when the steering wheel is not steered to near the maximum steering angle, or even when the steering wheel is steered to near the maximum steering angle, the steering wheel is not moved. When a steering torque for turning in the direction opposite to the maximum turning angle is applied to the steering mechanism, the electric motor can be controlled based on the steering torque applied to the steering mechanism.

[0015]

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 one embodiment of the present invention. The steering torque applied to the steering wheel 1 is transmitted to the steering mechanism 3 via the steering shaft 2. The driving force generated from the electric motor 4 is transmitted to the steering mechanism 3 as a steering assist force via a driving force transmission mechanism such as a gear mechanism or a ball screw mechanism.

The steering shaft 2 is divided into an input shaft 2A connected to the steering wheel 1 and an output shaft 2B connected to the steering mechanism 3;
The input shaft 2A and the output shaft 2B are connected to each other by a torsion bar 5. Torsion bar 5
Generates twist according to the steering torque. By detecting the direction and amount of twist of the torsion bar 5, the steering torque applied to the steering wheel 1 can be detected.

The direction and amount of twist generated in the torsion bar 5 are detected by a torque sensor 6. The torque sensor 6 outputs a positive / negative detection signal according to, for example, the direction of the steering torque (the direction of the torsion of the torsion bar 5). For example, the torque for turning the steering wheel to the right is detected. When it is applied to the steering wheel 1, it outputs a positive detection signal,
When a torque for turning the steering wheel to the left is applied to the steering wheel 1, a negative detection signal is output.

The detection signal output from the torque sensor 6 is input to a controller (ECU) 7. In addition to the detection signal of the torque sensor 6, the detection signal of the motor current sensor 8 for detecting the motor current flowing through the electric motor 4 and the detection signal of the vehicle speed sensor 9 for detecting the traveling speed (vehicle speed) of the vehicle are input to the controller 7. I have. Controller 7
Is an assist current setting unit 71 for setting an assist current according to the vehicle speed and the steering torque by executing an operation program stored in a storage medium (ROM or the like) not shown, an integrated value of the steering torque (torque integrated value) , An assist limiting current setting unit 73 that sets an assist limiting current for reducing and correcting the assist current based on the integrated value of the steering torque given from the torque integrating unit 72; Each function processing unit of the motor control unit 74 that sets a motor instruction current based on the assist limit current and performs feedback control of the electric motor based on the motor instruction current is substantially provided. The operation of each of the function processing units controls the drive of the electric motor 4 so that a steering assist force corresponding to the steering of the steering wheel 1 is applied to the steering mechanism 3.

FIG. 2 is a flowchart for explaining the drive control of the electric motor 4 by the controller 7.
The process shown in FIG. 2 is repeatedly executed at a constant control cycle. First, the steering torque and the vehicle speed are taken from the torque sensor 6 and the vehicle speed sensor 9, respectively (steps S1 and S2). Then, the assist current setting unit 71 determines an assist current according to the vehicle speed and the steering torque (step S3). More specifically, a plurality of assist tables in which different steering torque-assist current characteristics are determined for each vehicle speed range are prepared in advance, and an assist table according to the vehicle speed is selected from the plurality of assist tables. In accordance with the selected assist table, an assist current corresponding to the steering torque taken from the torque sensor 6 is determined.

Next, after the IG (ignition) switch of the vehicle is turned on, it is checked whether or not the neutral state of the steering mechanism 3 has been detected (step S4). The neutral state of the steering mechanism 3 (steering neutral state) refers to a state of the steering mechanism 3 when the vehicle is traveling straight. The neutral state of the steering mechanism 3 is, for example, when the vehicle speed is equal to or more than a certain value, the steering torque is equal to or less than a certain value, and the steering angle movement amount per certain time is equal to or less than a certain set value. It can be estimated that the steering angle is at the middle point. In addition, it may be detected by a neutral position sensor (not shown) provided in association with the steering wheel 1 or the steering shaft 2. This neutral position sensor can be constituted by, for example, a proximity sensor including a magnet attached to the steering shaft 2 and a detector that detects the magnet when the rotational position of the steering wheel 1 reaches the neutral position and outputs a signal. .

If the steering neutral state has not been detected since the IG switch was turned on (NO in step S4), the assist current determined by the assist current setting section 71 is directly used as the motor instruction current (step S4). S5) The drive control of the electric motor 4 is performed based on the motor instruction current set in this way (step S6).
If the steering neutral state has been detected (YES in step S4), it is checked whether the steering neutral state is currently detected, that is, whether the steering mechanism 3 is in the neutral state (step S4).
7). When the steering mechanism 3 is in the neutral state,
The torque integrated value integrated by the torque integrating unit 72 up to that time is cleared to zero (step S8).

On the other hand, if the steering mechanism 3 is not in the neutral state, it is determined whether or not the rotation speed of the electric motor 4 is zero (step S9). Whether or not the rotation speed of the electric motor 4 is zero can be determined, for example, based on the motor current taken from the motor current sensor 8. That is, if the motor current is zero, it can be determined that the rotation speed of the electric motor 4 is zero, and if the motor current is not zero, it can be determined that the rotation speed of the electric motor 4 is not zero. If the motor rotation speed is not zero, a new torque integrated value is calculated in the torque integrating section 72 by adding the steering torque taken in from the torque sensor 6 in the current process to the current integrated value of the torque. (Step S10).

The torque integrated value thus obtained by the torque integrating section 72 is the total sum of the steering torque applied to the steering wheel 1 after the detection of the steering neutral state. Therefore, while the steering wheel 1 is being turned in one direction from the neutral position, the absolute value of the torque integrated value obtained by the torque integrating unit 72 increases as the steering angle of the steering wheel 1 increases. . And
When the steering angle of the steering wheel 1 becomes close to the maximum steering angle corresponding to the maximum steering angle of the steering wheel of the vehicle, the absolute value of the integrated torque value becomes a certain constant value TH (where TH>
0).

Therefore, in the assist limit current setting section 73, the torque integrated value Σ given from the torque integrating section 72 is obtained.
T is defined as the upper limit value + TH in which the above-mentioned constant value is given a positive sign, and the lower limit value -TH is taken as the value in which the above-mentioned constant value is given a minus sign.
It is determined whether or not the predetermined range -TH ≦ ΔT ≦ + TH is satisfied (step S11). If the torque integrated value ΔT is out of the predetermined range −TH ≦ ΔT ≦ + TH,
It is determined that the steering wheel has been turned to near the maximum turning angle, and the assist limiting current setting unit 73 sets the assist limiting current. This assist limiting current is set to a larger value as the integrated torque value is larger. Therefore, the motor instruction current is set by subtracting the assist limit current from the assist current determined by the assist current setting unit 71 (step S12), and the drive control of the electric motor 4 is performed based on the motor instruction current, As the steering wheel approaches the maximum turning angle, the steering assist force can be reduced,
The impact when the steering of the steering wheel is regulated at the maximum steering angle can be reduced.

On the other hand, when the integrated torque value ΔT is within the predetermined range−
If TH ≦ ΔT ≦ + TH, it is determined that the steering wheel has not been turned to near the maximum turning angle, and the assist limiting current setting unit 73 does not set the assist limiting current. In this case, the assist current determined by the assist current setting unit 71 is directly used as the motor instruction current (step S5), and the drive control of the electric motor 4 is performed based on the motor instruction current (step S6). Thus, a steering assist force according to the steering torque and the vehicle speed can be given to the steering mechanism 3.

FIG. 3 is a block diagram showing an electric configuration of an electric power steering apparatus according to another embodiment of the present invention. In FIG. 3, parts that are the same as the parts shown in FIG. 1 are given the same reference numerals. The electric power steering apparatus according to this embodiment includes a torque sensor 6 that detects the direction and amount of twist generated in the torsion bar 5, a motor current sensor 8 that detects a motor current flowing through the electric motor 4, A motor rotation angle sensor 10 for detecting a rotation angle (motor rotation angle) and a vehicle speed sensor 9 for detecting a vehicle speed are provided. The detection signal of each of these sensors is sent to the controller (E
CU) 11, and the controller 11 controls the electric motor 4 based on a detection signal input from each sensor so that a steering assist force corresponding to the steering of the steering wheel 1 is applied to the steering mechanism 3. I do.

FIG. 4 is a flowchart for explaining the drive control of the electric motor 4 by the controller 11. The process shown in FIG. 4 is repeatedly executed at regular control intervals. First, the steering torque and the vehicle speed are taken from the torque sensor 6 and the vehicle speed sensor 9, respectively (steps T1 and T2). The rotation angle (motor rotation angle) of the electric motor 4 is detected based on the output signal of the motor rotation angle sensor 10 (step T3).
The rotation angle of the electric motor 4 is zero when the steering angle of the steering wheel is zero (when the vehicle is traveling straight), and takes a positive value when the steering wheel is steered to the right. When the steering wheel is steered to the left, a negative value is assumed.

Next, it is determined whether or not "1" is set in the end contact flag (step T4). The end contact flag is a flag indicating whether or not an end contact control for suppressing an impact when turning of the steering wheel of the vehicle is regulated at the maximum turning angle is being executed. Is reset to "0" immediately after is turned on. If the end contact flag remains reset to “0”, it is next determined whether or not it is necessary to perform the end contact control (step T5). Whether or not it is necessary to perform end contact control depends on the absolute value of the rotation angle of the electric motor 4 being the absolute value of the motor rotation angle (motor rotation maximum angle) when the steering wheel is steered to the maximum steering angle. From a predetermined angle (for example,
(10 degrees) is determined based on whether the angle is larger than a set reference angle. That is, if the absolute value of the motor rotation angle is larger than the determination reference angle, it is determined that the steering wheel has been turned to near the maximum steering angle, and it is determined that it is necessary to perform the end contact control. . On the other hand, if the absolute value of the motor rotation angle is equal to or less than the determination reference angle, it is determined that the steering wheel has not been turned to the vicinity of the maximum steering angle, and it is determined that it is not necessary to perform the end contact control. You. If it is determined that the end contact control needs to be performed, “1” is set to the end contact flag (step T6).

Thereafter, it is determined again whether or not "1" is set in the end contact flag (step T7). If the end contact flag remains reset to “0”, the motor instruction current is determined according to the vehicle speed and the steering torque (step T8), and the drive control of the electric motor 4 is performed based on the determined motor instruction current. Is performed (step T9). The motor instruction current according to the vehicle speed and the steering torque is, for example, the same as the assist current in the first embodiment described above, and selects an assist table corresponding to the vehicle speed from a plurality of prepared assist tables in advance. Then, it may be determined according to the selected assist table.

On the other hand, if "1" is set in the end contact flag (YES in step T7), the steering wheel is further steered from the current steering position toward the maximum steering angle ( It is determined whether or not the steering torque of the steering wheel 1 is applied to the steering wheel 1, that is, whether or not the turning direction of the steering wheel matches the direction of the steering torque applied to the steering wheel 1. (Step T10). Since the turning angle of the steering wheel and the motor rotation angle correspond to each other, if the sign given to the motor rotation angle and the sign of the detection signal of the torque sensor 6 match, the turning of the steering wheel is performed. It can be determined that the steering direction and the direction of the steering torque match, and if the sign of the motor rotation angle and the sign of the detection signal of the torque sensor 6 are different, the turning direction of the steering wheel and the steering torque are different. It can be determined that the directions do not match.

If the steering direction of the steering wheel and the direction of the steering torque match, it is determined that the steering wheel is further steered toward the maximum steering angle near the maximum steering angle. Then, end contact control for suppressing an impact when the turning of the steering wheel is regulated at the maximum turning angle is executed. In the end contact control, a motor instruction current corresponding to the motor rotation angle taken from the motor rotation angle sensor 10 is determined (step T12), and the drive control of the electric motor 4 is performed based on the determined motor instruction current. (Step T
9). The motor instruction current corresponding to the motor rotation angle is stored in a memory (not shown) in the form of a table for the motor rotation angle, for example, and is set smaller as the motor rotation angle approaches the maximum motor rotation angle. This allows
As the steering wheel approaches the maximum turning angle, the electric motor 4
, The steering assist force applied to the steering mechanism 3 can be reduced, and the impact when the turning of the steering wheel is regulated at the maximum turning angle can be suppressed.

On the other hand, when the turning direction of the steering wheel does not match the direction of the steering torque, the steering wheel is turned from the vicinity of the maximum turning angle to the turning position when the vehicle is traveling straight. Therefore, it is determined that the turning angle of the steering wheel does not reach the maximum turning angle and it is not necessary to perform the end contact control, and the end contact flag is reset to “0” (step T13). Then, a motor instruction current corresponding to the steering torque is determined according to the assist table corresponding to the vehicle speed (step T8), and the drive control of the electric motor 4 is performed based on the determined motor instruction current (step T9). . Thus, when the steering wheel is returned toward the steered position when the vehicle is traveling straight, the steering assisting force corresponding to the steering torque and the vehicle speed can be applied to the steering mechanism 3.

FIG. 5 is a flowchart for explaining another process executed by the controller 11. The process shown in FIG. 5 is, for example, a process performed in place of the process shown in FIG. 4 described above, and is repeatedly executed at a constant control cycle while the IG switch of the vehicle is turned on. You. First, the steering torque and the vehicle speed are taken from the torque sensor 6 and the vehicle speed sensor 9, respectively (steps E1 and E2). Then, a motor instruction current corresponding to the taken steering torque and vehicle speed is determined (step E3).

Subsequently, the rotation angle of the electric motor 4 is detected based on the output signal of the motor rotation angle sensor 10 (step E4), and the steering angle of the steering wheel is determined based on the detected motor rotation angle. Is determined to be near the maximum steering angle (step E5). Specifically, the absolute value of the rotation angle of the electric motor 4 is obtained by subtracting a predetermined angle from the absolute value of the motor rotation angle (maximum motor rotation angle) when the steering wheel is steered to the maximum steering angle. It is determined whether or not the angle is larger than the determination reference angle set by (1).

When the turning angle of the steering wheel is near the maximum turning angle, that is, when the motor rotation angle is larger than the above-mentioned reference angle, the steering wheel is turned to near the maximum turning angle. A signal is generated to warn the user (step E6). The generated warning signal is output from a warning light or warning buzzer placed on the instrument panel of the vehicle,
It is input to a control device for controlling warning means provided in the vehicle, such as a vibration mechanism for giving a slight vibration to the steering wheel 1 for warning. The warning device is controlled by the control device in response to the input of the warning signal, so that the driver is notified that the steering wheel has been turned to near the maximum turning angle. This allows
Since the driver can know that the steering wheel has been turned to the vicinity of the maximum steering angle, the steering torque applied to the steering wheel 1 before the steering wheel reaches the maximum steering angle is reduced, and the steering wheel The impact when the steering is regulated by the maximum steering angle can be reduced.

When the processing for generating the warning signal (warning signal generation processing) is performed, the drive control of the electric motor 4 is performed based on the motor instruction current set according to the assist table (step E7). The steering assist force according to the vehicle speed and the steering torque is applied to the steering mechanism 3.
Given to. On the other hand, if the steering angle of the steering wheel has not reached near the maximum steering angle, that is, if the motor rotation angle is equal to or smaller than the above-described determination reference angle, the above-described warning signal generation processing is not performed (step E6). Is skipped), and drive control of the electric motor 4 is performed based on the motor instruction current set according to the assist table.

Although several embodiments of the present invention have been described above, the present invention can be embodied in other forms. For example, in the above-described second embodiment, since the turning angle of the steering wheel corresponds to the rotation angle of the electric motor 4, the steering wheel moves to near the maximum turning angle based on the motor rotation angle. Although it is determined whether or not the vehicle is steered, since the steering angle of the steering wheel and the rotation angle (steering angle) of the steering shaft 2 correspond to each other, the steering is performed instead of the motor rotation angle sensor 10. An angle sensor may be provided, and it may be determined whether or not the steering wheel has been turned to near the maximum steering angle based on the steering angle detected by the steering angle sensor.

When the steering mechanism 3 is of a rack-and-pinion type, the position of the rack shaft in the vehicle width direction (rack position) corresponds to the steering angle of the steering wheel. Thus, it may be determined whether or not the steering wheel has been turned to the vicinity of the maximum turning angle. Specifically, for example, a rack position sensor for detecting the position of the rack shaft is provided, and the rack position detected by the rack position sensor is determined from the rack position when the steering wheel is turned to the maximum turning angle. If a predetermined distance (for example, 5 mm) has reached the judgment reference position in front,
If it is determined that the steering wheel has been turned to the vicinity of the maximum turning angle and the rack position detected by the rack position sensor has not reached the judgment reference position, the steering wheel is turned to near the maximum turning angle. It is only necessary to determine that it has not been done.

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.

FIG. 2 is a flowchart for explaining drive control of an electric motor by a controller provided in the electric power steering device of FIG. 1;

FIG. 3 is a block diagram showing an electric configuration of an electric power steering device according to another embodiment of the present invention.

FIG. 4 is a flowchart for explaining drive control of an electric motor by a controller provided in the electric power steering device of FIG. 3;

FIG. 5 is a flowchart for explaining another process executed by a controller provided in the electric power steering device of FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steering wheel 2 steering shaft 3 steering mechanism 4 electric motor 5 torsion bar 6 torque sensor 7 controller 8 motor current sensor 9 vehicle speed sensor 10 motor rotation angle sensor 11 controller 71 assist current setting section 72 torque integrating section 73 assist limiting current setting section 74 Motor control section

Claims (6)

[Claims] 1. An electric power steering apparatus for assisting steering by applying a driving force generated by an electric motor to a steering mechanism, wherein a steering torque detecting means for detecting a steering torque input to the steering mechanism; Neutral state detecting means for detecting that a neutral state has been reached when the vehicle is traveling straight ahead; and a steering torque detected by the steering torque detecting means after the neutral state of the steering mechanism is detected by the neutral state detecting means. A torque instructing means for obtaining an integrated value; and a motor instruction current to be supplied to the electric motor is set based on the steering torque detected by the steering torque detecting means and the integrated value of the steering torque obtained by the torque integrating means. Electric power steering comprising motor instruction current setting means apparatus. 2. The motor command current setting means includes: an assist current setting means for setting an assist current corresponding to a steering torque detected by the steering torque detection means; and an assist current set by the assist current setting means. An assist limiting current setting unit for setting an assist limiting current for performing the reduction correction. If the integrated value of the steering torque obtained by the torque integrating unit is within a predetermined range, the assist current setting unit The set assist current is determined as the motor instruction current, and when the integrated value of the steering torque obtained by the torque integrating means is out of the predetermined range, the assist current set by the assist current setting means is used. The assist limit current set by the assist limit current setting means is reduced. The electric power steering apparatus according to claim 1, characterized in that for setting the motor command current by. 3. An electric power steering device for assisting steering by applying a driving force generated by an electric motor to a steering mechanism, comprising: a motor rotation angle detection means for detecting a rotation angle of the electric motor; Turning angle determining means for determining whether or not the steering wheel has been turned to near the maximum turning angle, and when it is determined by the turning angle determining means that the steering wheel has been turned to near the maximum turning angle. And electric current steering means for setting a motor instruction current to be supplied to the electric motor based on the rotation angle of the electric motor detected by the motor rotation angle detection means. apparatus. 4. The end contact current setting means according to claim 1, wherein said rotation angle of said electric motor detected by said motor rotation angle detection means is set to a value corresponding to a rotation of said electric motor when a steering wheel is turned to a maximum steering angle. As the angle approaches the motor maximum rotation angle,
4. The electric power steering apparatus according to claim 3, wherein the motor instruction current is set small. 5. The electric power steering apparatus according to claim 1, further comprising: a steering torque detecting means for detecting a steering torque input to a steering mechanism; When it is determined that the vehicle is steered to near the maximum steering angle, the direction of the steering torque detected by the steering torque detecting means is the direction in which the steering wheel is steered toward the maximum steering angle. 5. The electric power steering apparatus according to claim 3, wherein a motor instruction current is set based on a rotation angle of the electric motor detected by the motor rotation angle detection means on a condition. 6. The electric power steering apparatus according to claim 1, wherein the steering angle determining means determines that the steering wheel has not been turned to the vicinity of the maximum steering angle, and that the steering angle determining means performs steering. It is determined that the steering wheel has been turned to the vicinity of the maximum turning angle, and the direction of the steering torque detected by the steering torque detecting means is a neutral position where the steering wheel is in a state of straight traveling of the vehicle. 6. The electric power steering apparatus according to claim 5, further comprising a normal current setting means for setting a motor instruction current based on the steering torque detected by the steering torque detection means when the direction is returned to the normal direction. .