JPH08282522A - Electric power steering device - Google Patents

Abstract

PURPOSE: To materialize the sufficient maximum torque and the maximum revolution speed, and concurrently make the device small in size and light in weight by determining a gap width based on information on a steering condition or a vehicle running condition. CONSTITUTION: When detected values from a steering force sensor 12, a steering speed sensor 14 and a vehicle speed sensor 13 are received by a controller 7, the controller 7 informs a gap width control section 16 only of the detected value from the steering force sensor 12. The gap width control section 16 obtains a gap width command value based on the detected value by the steering force sensor 12, and gives it to an actuator. In this case, when a great assist force is required, namely, when steering force for a steering wheel is great, the maximum torque is made great with the gap width of an assist motor 8 narrowed. On the other hand, when the assist force is not required so much, namely, when a steering force for the steering wheel 1 is small, the maximum torque is made small with the gap width of the assist motor 8 widened.

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 force applied to steering a vehicle with a rotation output of an electric motor.

[0002]

2. Description of the Related Art A power steering device for a vehicle is a device for assisting a steering force necessary for a driver to rotate a steering wheel and reducing a burden on the driver.

Conventionally, the power steering device is generally of a hydraulic type, but it is difficult to reduce the size, weight and cost of the power steering device. It is becoming more and more popular.

In an electric power steering system, an input shaft connected to a steering wheel and an output shaft connected to an operating portion for turning a wheel via a pinion gear or the like are connected via an elastic member such as a torsion bar. There is. Further, the electric power steering apparatus includes an electric motor that assists the rotational force of the output shaft, and a switch circuit that switches the rotational direction of the electric motor according to the rotational direction of the input shaft.

Here, it is preferable that the electric motor used in the power steering device has a large rotational torque and a high allowable rotational speed. In other words, when the vehicle is stationary,
In the case of low-speed garage entry, if the assist torque is large, the driver can steer with a small force. Further, when the steered steering is performed, if the maximum allowable rotation speed of the electric motor is high, the steering can be smoothly performed without feeling a catch.

In order to meet this requirement, there is a device for controlling the rotational position, speed control and acceleration control of the motor output in consideration of inertia, viscosity, friction, etc. of the motor and steering mechanical system. As a conventional example, there are the devices described in JP-A-62-34846 and JP-A-61-11947.

[0007]

By the way, the above-mentioned conventional apparatus requires an electric motor having a large maximum torque and a high maximum allowable rotation speed.

FIG. 8 shows an equivalent circuit of the electric motor. The characteristic of the electric motor can be expressed by a mathematical expression based on FIG. _{V Batt = RI + V Back V} Back = k e · N (V Batt; battery voltage, R; motor internal resistance, I; motor current, V _Back; counter electromotive force, k _e; back electromotive force coefficient,
N: Motor rotation speed) FIG. 9 shows the motor characteristics based on the above equation. As shown in the figure, in the electric motor, the counter electromotive force increases and the torque decreases as the rotation speed increases. on the other hand,
As the rotation speed decreases, the counter electromotive force decreases and the torque increases. Further, when the capacity of the electric motor is increased, the maximum torque is increased and the maximum allowable rotation speed can be increased.

The electric motor is provided with a rotor and a stator, and the relationship between the gap width, the maximum torque, and the maximum allowable rotation speed is shown in FIG. As shown in the figure, the electric motor has a characteristic that the maximum allowable rotation speed increases when the gap width is widened and the maximum torque increases when the gap width is narrowed. Therefore, in an electric motor having a constant gap width, the maximum allowable rotation speed and the maximum torque are uniquely determined. Then, in order to obtain sufficient maximum torque and maximum allowable rotation speed by using an electric motor with a fixed gap width, as in the above-mentioned conventional example, the capacity of the electric motor must be increased, and the entire device is There is a problem that the size becomes large and the weight becomes heavy.

Further, since the electric motor adopts the magnetic pole structure, torque fluctuation (cogging torque) occurs during one rotation of the rotor, and the cogging torque is amplified by the reduction ratio and transmitted to human beings, which is smooth. There is a problem that it causes a loss of steering feeling. The cogging torque depends on the structure of the motor (number of magnetic poles, arrangement of magnetic poles, etc.), and particularly depends on the gap width. Here, the relationship between the cogging torque and the gap width is shown in FIG. As shown in the figure, the magnitude of the cogging torque is inversely proportional to the width of the gap width, and the magnitude of the cogging torque is uniquely determined in an electric motor with a fixed gap width, which is difficult to reduce. .

Therefore, the present invention has been made in view of the above-mentioned problems, and provides a technique for changing the gap width according to the steering state to realize a sufficient maximum torque and maximum rotation speed, and at the same time, to realize the apparatus. The challenge is to reduce the size and weight. Furthermore, it is an object to control the gap width and suppress the generation of cogging torque to improve the steering feeling.

[0012]

The present invention has the following structure in order to solve the above problems. (1) The electric power steering apparatus of the present invention includes an electric motor that assists the steering force that turns the wheels of the vehicle, and a control unit that drives the electric motor based on information about the steering state of the steering wheel. In an electric power steering apparatus, a variable gap mechanism that changes a gap width between a rotor and a stator of the electric motor and a gap width is determined based on information about the steering state or the traveling state of the vehicle, and the gap width is determined according to the gap width. Gap width control means for driving the variable gap mechanism is provided (corresponding to claim 1).

(2) Further, the gap width control means is
The gap width is determined based on the steering force of the steering wheel, and the larger the steering force of the steering wheel, the narrower the gap width may be (corresponding to claim 2).

(3) Further, the gap width control means determines the gap width on the basis of the turning speed of the steering wheel. The higher the turning speed of the steering wheel, the wider the gap width. (Corresponding to claim 3).

(4) Further, the gap width control means is
The gap width is determined based on the vehicle speed of the vehicle, and the higher the vehicle speed of the vehicle, the wider the gap width (corresponding to claim 4).

(5) Further, the gap width control means determines the gap width based on a value obtained by differentiating the steering force of the steering wheel. The larger the differential value of the steering force, the narrower the gap width. You may make it perform (corresponding to Claim 5).

(6) Further, the gap width control means is
The gap width is determined based on the turning acceleration of the steering wheel, and the gap width may be narrowed as the turning acceleration of the steering wheel increases (corresponding to claim 6).

[0018]

According to the electric power steering apparatus of the present invention, the gap width control means determines the gap width of the electric motor based on the information regarding the steering wheel. Then, the gap width control means notifies the variable gap mechanism of the command value corresponding to the determined gap width.

The variable gap mechanism changes the gap width between the rotor and the stator according to the command value from the gap width control means. Here, the gap width control means narrows the gap width to increase the torque generated by the electric motor when increasing the assist torque, and widens the gap width when rapid steering of the steering wheel is required. Increase the maximum permissible speed of the electric motor.

For example, when determining the gap width based on the steering force of the steering wheel, the gap width control means makes the magnitude of the steering force and the width of the gap width inversely proportional. That is, the gap width control means narrows the gap width as the steering force increases. At this time, the torque generated by the electric motor increases. Further, the gap width control means widens the gap width as the steering force becomes smaller.
At this time, the torque generated by the electric motor is reduced and the cogging torque is also reduced.

When the gap width is determined based on the turning speed, the gap width control means makes the height of the turning speed proportional to the width of the gap width. That is, the gap width control means widens the gap width as the turning speed increases. At this time, the maximum allowable rotation speed of the electric motor becomes high. Further, the gap width control means narrows the gap width as the turning speed becomes lower. At this time, the torque generated by the electric motor increases.

Further, when the gap width is determined based on the vehicle speed, the gap width control means makes the width of the gap width and the height of the vehicle speed proportional. That is, the gap width control means widens the gap width as the vehicle speed increases. At this time, the torque generated by the electric motor becomes small,
Cogging torque also decreases. Further, the gap width control means narrows the gap width as the vehicle speed decreases. At this time,
The torque generated by the electric motor increases.

When determining the gap width based on the differential value of the steering torque, the gap width control means makes the width of the gap width and the magnitude of the differential value of the steering force inversely proportional. That is, the gap width control means narrows the gap width as the differential value of the steering force increases. At this time, the torque generated by the electric motor increases. Further, the gap width control means widens the gap width as the differential value of the steering force is smaller. At this time, the torque generated by the electric motor is reduced and the cogging torque is also reduced.

Further, when the gap width is determined based on the turning acceleration obtained by differentiating the turning speed, the gap width control means makes the width of the gap width and the turning acceleration inversely proportional. . That is, the gap width control means narrows the gap width as the turning acceleration increases.
At this time, the torque generated by the electric motor increases. Further, the gap width control means widens the gap width as the turning acceleration becomes smaller. At this time, the torque generated by the electric motor is reduced and the cogging torque is also reduced.

[0025]

【Example】

Embodiment 1 FIG. 1 is a drawing showing an example of a steering mechanism of a vehicle to which an electric power steering device of the present invention is applied.

In this steering mechanism, a steering wheel 1 is attached to one end of a handle shaft 2, and a pinion gear 3 is attached to the other end of the handle shaft 2. The pinion gear 3 is a knuckle of left and right wheels 6L and 6R. It meshes with the rack 4 that operates the arm 5.

In this structure, the rotational force of the steering wheel 1 is transmitted to the pinion gear 3 via a torsion bar or the like, and the rotational force of the pinion gear 3 is transmitted to the rack 4. At this time, the rotational movement of the pinion gear 3 is converted into the linear movement of the rack 4, the left and right knuckle arms 5 are operated, and the left and right wheels 6L and 6R are turned. A ring gear 11 is provided in the middle of the handle shaft 2.
Is attached to the worm gear 1 which is attached to the motor shaft 9 of the assist motor 8.
It meshes with 0. Then, the rotational force of the assist motor 8 is transmitted to the worm gear 10 and the ring gear 11 to assist the rotational force of the handle shaft 2.

Further, a steering force sensor 12 for detecting the steering force of the steering handle 1 and a steering speed sensor 14 for detecting the steering speed of the steering handle 1 are attached in the middle of the steering shaft 2. The outputs of the steering force sensor 12 and the steering speed sensor 14 are connected to the controller 7. The controller 7 is also connected to the output of the vehicle speed sensor 13 attached to the vehicle body. Furthermore, the input terminal of the controller 7 is connected to the positive / negative terminals of the battery 15, and the output terminal of the controller 7 is connected to the positive / negative terminals of the assist motor 8.

A gap width control unit 16 is attached to the controller 7. Here, the controller 7 inputs signals from the steering force sensor 12, the turning speed sensor 14, and the vehicle speed sensor 13, and determines a current value supplied from the battery 15 to the assist motor 8 based on these signals. The controller 7 includes a current detector, a voltage detector, a drive circuit that drives the assist motor 8, a microprocessor that manages the overall control of the assist motor 8, a memory, an interface circuit with each of the above devices, and the like. It

The assist motor 8 is a motor provided with a variable gap mechanism 17 capable of changing the gap width between the rotor and the stator. The gap width control unit 16 inputs the detection value of the steering force sensor 12 from the controller 7 and determines the gap width of the assist motor 8 based on this detection value. The gap width control unit 16 drives the variable gap mechanism 17 described later. The circuit, a microcomputer for determining a gap width command value for the variable gap mechanism 17, a memory, an input / output interface circuit, and the like.

FIG. 2 shows an example of the assist motor 8. In the figure, the assist motor 8 has a disk-shaped flange 18A, 18B on both end surfaces of a cylindrical outer cylinder 21.
Is installed. A convex portion 19 is provided on the peripheral edge portion of the flanges 18 </ b> A and 18 </ b> B so as to fit with a concave portion 22 provided on the inner surface of the outer cylinder 21. These ridges 1
The outer cylinder 21 is fitted with the flange 1 by the fitting of the groove 9 and the recess 22.
8A and 18B cannot rotate in the circumferential direction and can slide in the axial direction. The flange 18A
18B is assumed to be fixed to the vehicle body.

Further, the motor shaft 9 penetrates through the central portions of the flanges 18A and 18B. This motor shaft 9
The flanges 18A and 18B are held via bearings 20A and 20B so as to be rotatable.

A rotor having a conical outer periphery is fixed to the motor shaft 9 located inside the outer cylinder, and the rotor passes through a conical iron core 24 and a slot of the iron core 24. And the coil 25 that is formed. Further, a commutator 28 is attached to the apex portion of the rotor, and the commutator 28, the iron core 24 and the coil 25 are attached.
And are electrically connected to.

On the other hand, a magnet 23 surrounding the rotor is fixed to the inner peripheral surface of the outer cylinder 21. The inner peripheral surface of the magnet 23 is made parallel to the outer peripheral surface of the rotor. A brush 26 is attached to one of the flanges 18A via a spring 27, and the brush 26 is pressed against the commutator 28 by the spring 27.

Here, the current from the battery 15 is transmitted to the brush 26 through a wire (not shown), and further transmitted from the brush 26 to the commutator 28 so that the coil 2
5 is energized.

Further, a variable gap mechanism 17 is attached to the outer cylinder 21 of the assist motor 8. The variable gap mechanism 17 includes a link mechanism 30, an actuator 29, and a stroke sensor 31.

The link mechanism 30 slides the outer cylinder 21 in the axial direction. The stroke sensor 31 is the outer cylinder 2
The amount of movement of 1 is detected. Actuator 29
When receiving the gap width command value from the gap width control unit 16, drives the link mechanism 30 so that the gap width command value and the detection value of the stroke sensor 31 match.

Here, the control procedure of the gap width control section 16 will be described. First, in the memory of the gap width control unit 16, a map showing the relationship between the steering force and the gap width command value, or a calculation formula for calculating the gap width command value using the value of the steering force as a variable is registered. Here, the relationship between the steering force and the gap width command value k ₁ is shown in FIG. As shown in the figure, the gap width control unit 16 decreases the gap width command value k ₁ to decrease the gap width as the steering force increases. On the other hand, the smaller the steering force, the gap width command value k ₁
To increase the gap width. this is,
This is because the driver is more likely to feel the torque fluctuation transmitted to the steering wheel 1 as the steering force is smaller. Therefore, when the steering force is small, the gap width is widened to reduce the torque generated by the assist motor 8.

The operation and effect of this embodiment will be described below. When the controller 7 receives the detection values from the steering force sensor 12, the turning speed sensor 14, and the vehicle speed sensor 13, the controller 7 notifies the gap width control unit 16 of only the detection values of the steering force sensor 12.

The microcomputer of the gap width control unit 16 accesses the memory based on the detection value of the steering force sensor 12 and obtains the gap width command value k ₁ by using a map or a calculation formula. Then, the gap width control unit 16
Is the calculated gap width command value k ₁ for the actuator 29
Notify to

The actuator 29 drives the link mechanism 30 while comparing the detection value of the stroke sensor 31 and the gap width command value k ₁ . The link mechanism 30 moves the outer cylinder 21 of the assist motor 8 in the axial direction by the driving force from the actuator 29. Here, the actuator 29 stops the driving of the link mechanism 30 when the detection value of the stroke sensor 31 and the gap width command value k ₁ match.

Here, the electric power steering device narrows the gap width of the assist motor 8 to increase the maximum torque when a large assist force is required, that is, when the steering force of the steering wheel 1 is large. This allows the driver to steer the steering wheel 1 with a small force. On the other hand, when the assist torque is not required so much, that is, when the steering force of the steering wheel 1 is small, the gap width of the assist motor 8 is widened to reduce the maximum torque. As a result, the generation of cogging torque can be suppressed and the steering feeling can be improved.

Therefore, according to the electric power steering apparatus of the present embodiment, the maximum torque can be improved without increasing the capacity of the assist motor by changing the gap width according to the necessity of the generated torque. The cogging torque can be suppressed and the device can be downsized.

[0044]

Second Embodiment In the electric power steering apparatus according to the second embodiment, the gap width control unit 16 has the above-described first embodiment.
On the other hand, the gap width command value for the actuator 29 is determined based on the turning speed.

Generally, in the electric power steering apparatus, when the turning speed is high, the maximum rotation speed of the assist motor is increased to prevent the rotation delay of the assist motor 8 with respect to the rotation of the steering wheel 1, and the turning speed is slow. In this case, the maximum torque of the assist motor 8 is increased.
In response to this, the gap width control unit 16 is configured to perform control as shown in FIG. The figure shows the gap width command value k
_It shows the relationship between ₂ and the turning speed. When the steering speed is high, the gap width command value k ₂ is increased to widen the gap width in order to increase the maximum rotation speed of the assist motor 8. On the other hand, when the steered speed is slow, the gap width command value k ₂ is made smaller to make the gap width smaller in order to increase the maximum torque of the assist motor 8. These gap width command values k ₂
The relationship between the steering speed and the steering speed may be stored in a memory as a map, and the gap width command value k may be stored with the steering speed value as a variable.
A calculation formula for calculating ₂ may be stored in the memory.

The other structure is the same as that of the first embodiment, and the description thereof will be omitted. The operation and effect of the second embodiment will be described below. According to the electric power steering apparatus of the second embodiment, when quick steering is required, that is, when the turning speed is high, the gap width of the assist motor 8 is widened to increase the maximum rotation speed. As a result, the rotation delay of the assist motor 8 with respect to the rotation of the steering wheel 1 can be prevented, and the feeling of being caught during steering can be suppressed. On the other hand, when quick steering is not required, that is, when the turning speed is slow, a large steering force is required, so the gap width of the assist motor 8 is narrowed to increase the maximum torque. As a result, the driver can perform steering with a small steering force when slowly steering the steering wheel 1.

Therefore, according to the present embodiment, by changing the gap width according to the necessity of the maximum rotation speed, it is possible to improve the maximum rotation speed without increasing the capacity of the assist motor. At the same time, the size of the device can be reduced.

[0048]

Third Embodiment In the electric power steering apparatus according to the third embodiment, the gap width control unit 16 uses the detection value of the vehicle speed sensor 13 instead of the detection value of the steering force sensor 12 as compared with the first embodiment. Based on this, the gap width command value for the actuator 29 is determined.

Generally, in the electric power steering apparatus, in order to enhance the steering stability of the vehicle, the assist torque is suppressed when the vehicle speed is high, and the assist torque is increased when the vehicle speed is low. In response to this, the gap width control unit 16 is configured to perform control as shown in FIG. This figure shows the relationship between the gap width command value k ₃ and the vehicle speed. When the vehicle speed is high, in order to reduce the maximum torque of the assist motor 8, the gap width command value k ₃ is increased to widen the gap width. On the other hand, when the vehicle speed is low, the gap width command value k ₃ is increased in order to increase the maximum torque of the assist motor 8.
To make the gap width smaller.
The relationship between the gap width command value k ₃ and the vehicle speed may be stored in the memory as a map, or the formula for calculating the gap width command value k ₃ may be stored in the memory using the vehicle speed value as a variable. Good.

The rest of the configuration is similar to that of the first embodiment described above, and a description thereof will be omitted. The operation and effect of the third embodiment will be described below. According to the electric power steering apparatus of the third embodiment, when a large assist torque is not required, that is, when the vehicle speed is high, the gap width of the assist motor 8 is widened to reduce the maximum torque.
As a result, the generation of cogging torque can be suppressed and the steering feeling can be improved. On the other hand, when a large assist torque is required, that is, when the vehicle speed is low, the gap width of the assist motor 8 is narrowed to increase the maximum torque. As a result, the driver can perform steering with a small steering force when entering the garage at low speeds or when stationary with the vehicle stopped.

Therefore, according to the present embodiment, by changing the gap width according to the need for the maximum torque, the maximum torque can be improved without increasing the capacity of the assist motor and the size of the device can be reduced. Can be promoted.

[0052]

Fourth Embodiment In the electric power steering apparatus according to the fourth embodiment, the gap width control unit 16 differs from the above-described first embodiment in that the gap width command value is based on the differential value of the steering force instead of the steering force. I am trying to decide.

Generally, in an electric power steering system, the assist torque is reduced when the differential value of the steering force is small and the assist torque is increased when the differential value of the steering force is large in order to improve the steering response. ing. In response to this, the gap width control unit 16 performs control as shown in FIG. The figure shows the gap width command value k ₄
And the steering force differential value are shown. When the steering force differential value is small, the gap width control unit 16 enlarges the gap width command value k ₄ so as to widen the gap width in order to reduce the maximum torque of the assist motor 8. On the other hand, when the steering force differential value is large, the gap width command value k ₄ is made small to narrow the gap width in order to increase the maximum torque of the assist motor 8. The relationship between the gap width command value k ₄ and the steering force differential value may be stored in a memory as a map, and a calculation formula for calculating the gap width command value k ₄ using the steering force differential value as a variable is stored in the memory. You may do it.

The rest of the structure is the same as that of the first embodiment described above, and the description thereof is omitted. The operation and effect of this embodiment will be described below. According to the electric power steering apparatus of the fourth embodiment, when a large assist torque is not required, that is, when the steering force differential value is small, the gap width of the assist motor 8 is widened to reduce the maximum torque. As a result, the generation of cogging torque can be suppressed, and the steering feeling can be improved. On the other hand, when a large assist torque is required, that is, when the steering force differential value is large, the gap width of the assist motor 8 is narrowed to increase the maximum torque. As a result, the driver can perform steering with a small steering force.

Therefore, according to the present embodiment, by changing the gap width according to the need for the maximum torque, the maximum torque can be improved without increasing the capacity of the assist motor, and the size of the apparatus can be reduced. Can be promoted.

[0056]

Fifth Embodiment In the electric power steering apparatus according to the fifth embodiment, the gap width control unit 16 differentiates the detection value of the steering speed sensor 14 from the first embodiment to calculate the steering acceleration. However, the gap width command value is determined based on this steering acceleration.

Generally, in the electric power steering apparatus, the assist torque is made small when the steering acceleration is small and the assist torque is made large when the total high speed is large in order to improve the steering response. In response to this, the gap width control unit 16 performs control as shown in FIG. This figure shows the relationship between the gap width command value k ₅ and the turning acceleration. The gap width control unit 16
When the turning acceleration is small, the gap width command value k ₅ is increased to widen the gap width in order to reduce the maximum torque of the assist motor 8. On the other hand, when the turning acceleration is large, the gap width command value k ₅ is made small to make the gap width narrow in order to increase the maximum torque of the assist motor 8. The relationship between the gap width command value k ₅ and the turning acceleration may be stored in the memory as a map, and the formula for calculating the gap width command value k ₅ using the turning acceleration as a variable may be stored in the memory. May be.

The rest of the configuration is similar to that of the first embodiment described above, and the description thereof is omitted. The operation and effect of this embodiment will be described below. According to the electric power steering apparatus of the fifth embodiment, when a large assist torque is not required, that is, when the steering acceleration is small, the gap width of the assist motor 8 is widened to reduce the maximum torque. As a result, the generation of cogging torque can be suppressed and the steering feeling can be improved. On the other hand, when a large assist torque is required, that is, when the steering acceleration is large, the gap width of the assist motor 8 is narrowed to increase the maximum torque. As a result, the driver can perform steering with a small steering force.

Therefore, according to the present embodiment, by changing the gap width according to the need for the maximum torque, the maximum torque can be improved without increasing the capacity of the assist motor, and the size of the device can be reduced. Can be promoted.

In each of the first to fifth embodiments, the gap width command value is determined based on a single element, but the gap width command value is determined based on a plurality of arbitrarily selected elements. You may do it.

[0061]

According to the electric power steering apparatus of the present invention, by varying the gap width of the electric motor, it is possible to increase the maximum torque or the maximum permissible rotation speed with the conventional motor size. The device can be downsized (corresponding to claim 1).

When a large steering force is required by determining the gap width based on the steering force,
The torque generated by the electric motor can be increased without increasing the capacity of the electric motor. When the steering force is small and the cogging torque is easily felt, the generated torque of the electric motor can be reduced to suppress the generation of the cogging torque to improve the steering feeling (corresponding to claim 2).

Furthermore, by determining the gap width based on the turning speed, when quick steering is required, the maximum rotation speed of the electric motor can be increased without increasing the capacity of the electric motor ( (Corresponding to claim 3).

Further, by determining the gap width based on the vehicle speed, when a large steering torque is required, such as when the vehicle is moving at a low speed, the electric motor can be generated without increasing the capacity of the electric motor. The torque can be increased (corresponding to claim 4).

Further, by determining the gap width based on the differential value of the steering force, when the large steering force is required, the torque generated by the electric motor can be increased without increasing the capacity of the electric motor. Can be done. When the steering force differential value is small and the cogging torque is easily felt, the generation torque of the electric motor can be reduced to suppress the generation of the cogging torque (corresponding to claim 5).

Further, by determining the gap width based on the turning acceleration, when the turning acceleration is small and a large steering torque is required, the maximum torque can be improved without increasing the size of the electric motor. It can be achieved (corresponding to claim 6).

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electric power steering device.

FIG. 2 is a diagram showing a configuration of an assist motor.

FIG. 3 is a diagram showing a relationship between a steering force and a gap width command value.

FIG. 4 is a diagram showing a relationship between a steering speed and a gap width command value.

FIG. 5 is a diagram showing a relationship between a vehicle immediate and a gap width command value.

FIG. 6 is a diagram showing a relationship between a steering force differential value and a gap width command value.

FIG. 7 is a diagram showing a relationship between a steering acceleration and a gap width command value.

FIG. 8: Equivalent circuit of electric motor

FIG. 9 is a diagram showing the relationship between the motor capacity, the maximum torque, and the maximum allowable rotation speed

FIG. 10 is a diagram showing the relationship between the gap width, the maximum torque, and the maximum allowable rotation speed.

FIG. 11 is a diagram showing the relationship between cogging torque and gap width.

[Explanation of symbols]

 1 ... Steering handle 2 ... Steering shaft 3 ... Pinion gear 4 ... Rack 5 ... Knuckle arm 6 ... Wheels (6L ... left wheel, 6R ... right wheel) 7 ... Controller 8 ... Assist motor 9・ ・ Motor shaft 10 ・ ・ Worm gear 11 ・ ・ Ring gear 12 ・ ・ Steering force sensor 13 ・ ・ Vehicle speed sensor 14 ・ ・ Steering speed sensor 15 ・ ・ Battery 16 ・ ・ Gap width controller 17 ・ ・ Variable gap mechanism 18 ・ ・Flange 19 ・ Convex portion 20 ・ Bearing 21 ・ Outer tube 22 ・ ・ Concave portion 23 ・ ・ Magnet 24 ・ ・ Iron core 25 ・ ・ Coil 26 ・ ・ Brush 27 ・ ・ Spring 28 ・ ・ Commutator 29 ・ ・ Actuator 30 ・.Link mechanism 31..Stroke sensor

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Claims (6)

[Claims] 1. An electric power steering apparatus comprising: an electric motor for assisting a steering force for turning a vehicle wheel; and a control means for driving the electric motor based on information about a steering state of a steering wheel. A variable gap mechanism that changes a gap width between a rotor and a stator of an electric motor, a gap width that is determined based on information about the steering state or the traveling state of the vehicle, and a gap that drives the variable gap mechanism according to the gap width. An electric power tearing device comprising: width control means. 2. The gap width control means determines the gap width based on the steering force of the steering wheel, and the gap width is narrowed as the steering force of the steering wheel increases. 1. The electric power steering device according to 1. 3. The gap width control means determines the gap width based on the turning speed of the steering handle, and the gap width is widened as the turning speed of the steering handle increases. The electric power steering device according to claim 1. 4. The gap width control means determines the gap width based on the vehicle speed of the vehicle, and the gap width is increased as the vehicle speed of the vehicle is increased. Electric power steering device. 5. The gap width control means determines the gap width based on a value obtained by differentiating the steering force of the steering wheel, and the gap width is narrowed as the differential value of the steering force is increased. The electric power steering apparatus according to claim 1, which is characterized in that. 6. The gap width control means determines the gap width based on the turning acceleration of the steering handle, and the gap width is narrowed as the turning acceleration of the steering handle increases. The electric power steering device according to claim 1.