JP4959217B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering device mounted on an automobile, and more particularly to control of steering torque.

  A traveling vehicle has a restoring force that tries to bring the rudder angle closer to 0 (neutral position) due to the self-aligning torque received by the steered wheels from the road surface. The self-aligning torque is small especially at low vehicle speeds, and the actual position does not return to the neutral position due to steering system friction or the like.

Therefore, an example in which a vehicle equipped with an electric power steering device performs drive control even during steering of a steering wheel by using a motor that assists human power has been proposed (for example, see Patent Document 1).
JP 2002-145094 A

In the embodiment described in Patent Document 1, when the steering torque is within a threshold value, it is determined that the steering wheel is returned (substantially released), the steering wheel return current is added to the assist current, and the steering wheel is returned at low speed. Handle return control means for improving the characteristics are provided.
That is, the steering wheel return control means adds the steering wheel return current to the assist current and performs the steering wheel return drive so as to return to the neutral position by driving the motor when the steering torque is within the threshold.

However, when the driver tries to make a large turn at a low vehicle speed while maintaining a small steering angle, the driver holds the steering (holding the steering angle) with an extremely small force, and the steering torque becomes a very small value.
Therefore, as in Patent Document 1, when steering return driving is executed when the steering torque falls within the threshold value, the steering torque falls within the threshold value when the driver keeps steering with a very small force. Since the steering wheel returning drive is executed, the driver applies a force to keep the steering against this, and the steering torque is increased to exceed the threshold value, so that the steering wheel returning drive is stopped.

  Steering force can be reduced by stopping the steering wheel return drive, and when the driver removes the force, the steering torque falls within the threshold value, and the steering wheel return driving is executed. The means repeats execution and stop of the steering wheel return drive, so that it is difficult for the driver to stably perform steering at a small steering angle, particularly at a low vehicle speed.

  The present invention has been made in view of the above points, and the object of the present invention is to provide an electric power steering device capable of maintaining a stable steering state at a small steering angle while performing steering wheel return control.

In order to achieve the above object, the invention according to claim 1
Steering assist control means (31) for calculating an assist base current value (Ib) based on the steering torque (T) and the vehicle speed (v), and assisting according to the assist target current (Io) based on the assist base current value (Ib). In the electric power steering device in which the motor (M) is driven and assisted to assist human power,
Rudder angle detection means (34) for detecting the rudder angle (θ);
Hand release determining means (45) for determining whether or not the steering wheel is released based on the steering torque (T);
A handle for calculating a steering wheel return correction current value (Isb) based on the steering angle (θ), the vehicle speed (v), and the steering torque (T) when the hand release determining means (45) determines that the handle is released. Return correction current value calculation means (46),
The handle return correction current value (Isb) calculated by the handle return correction current value calculation means (46) only when it is determined that the hand release determination means (45) is the handle release state, the final handle return correction current value ( Is)) handle return control means (S) to add to the assist base current value (Ib),
Reaction force current calculation means (50) for calculating a reaction force current value (Ia) that gives a return reaction force in the steering angle neutral direction at a small steering angle based on the vehicle speed (v) and the steering angle (θ), and Torque ratio calculation means (51) for calculating a torque ratio (r) that regulates the reaction force current value (Ia) based on the steering torque (T), and the reaction force current value (Ia) includes the torque ratio ( reaction force current adding means (A) for adding the reaction force current value (IaR) multiplied by r) to the assist base current value (Ib) ,
The reaction force current calculation means (50) stores in advance a reaction force current storage for each vehicle speed (v) that the reaction force current value increases from 0 and then decreases to 0 as the steering angle increases from 0. Means (50a), the reaction force current value (Ia) is extracted and calculated from the vehicle speed (v) and the steering angle (θ) based on the reaction force current storage means (50a),
The torque ratio calculation means (51) indicates that when the steering torque (T) is 0, the torque ratio (r) is 1.0, and the torque ratio (r) decreases as the steering torque (T) increases from 0 to the left and right. The torque ratio storage means (51a) that memorizes the characteristic that gradually decreases and smoothly reaches 0, and extracts the torque ratio (r) from the steering torque (T) based on the torque ratio storage means (51a). The electric power steering device.

According to a second aspect of the invention, in the electric power steering device according to claim 1, the storage characteristics of the reaction force current storage means, characterized in that the reaction force current value as the vehicle speed is high is low.

According to the electric power steering apparatus of the first aspect, when the hand release determining means determines that the handle is released, the handle return correction current value calculating means calculates the handle return correction current value based on the steering angle, the vehicle speed, and the steering torque. The steering wheel return control means adds the calculated steering wheel return correction current value to the assist base current value, so that when the steering wheel is released, the steering wheel return correction current value can return the steering wheel to the neutral position even at a low vehicle speed. When turning while keeping a small steering angle, the reaction force current adding means adds the reaction force current value to the assist base current value, so that the steering torque does not fall below the threshold value, and the steering wheel return control means The steering wheel return drive is not repeatedly executed and stopped by this, and steering at a small steering angle can be performed stably. .
In addition, while the handle release determination means determines that the hand release determination means is not in the substantially released state, the calculation process of the handle return correction current value calculation means is not performed, so the CPU burden associated with the calculation process is reduced.

The reaction force current adding means includes reaction force current storage means for preliminarily storing, for each vehicle speed, a characteristic that the reaction force current value increases from 0 and then decreases to 0 as the steering angle increases from 0. The reaction force current value that smoothly changes and is limited to a small steering angle is quickly extracted and added to the assist base current value, so that the steering angle change can be dealt with smoothly.
The reaction force current adding means regulates the reaction force current value when the steering torque is inputted and is equal to or higher than the predetermined steering torque, so that the reaction force current can be prevented from being influenced at the time of cutting or returning.

According to the electric power steering apparatus of the second aspect, the characteristic stored in the reaction force current storage means is that the reaction force current value is lower as the vehicle speed is higher. Therefore, the reaction force current value is higher when the vehicle speed is low and the self-aligning torque is low. In order to obtain a low reaction force current value at a high vehicle speed with a high self-aligning torque, when the vehicle turns while maintaining a small steering angle, an excessive reaction force torque is added to the self-aligning torque depending on the vehicle speed. This prevents a sense of incongruity (sensation of being excessively restored) from occurring.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 shows a schematic rear view of the entire electric power steering apparatus 1 according to the present embodiment.

  In the electric power steering apparatus 1, a rack shaft 3 is accommodated in a substantially cylindrical rack housing 2 oriented in the left-right direction of the vehicle (corresponding to the left-right direction in FIG. 1) so as to be slidable in the left-right axis direction.

  Tie rods are connected to both ends of the rack shaft 3 projecting from the openings at both ends of the rack housing 2 via joints, respectively, and the tie rod is moved by the movement of the rack shaft 3, and the steered wheels of the vehicle are rotated via the steering mechanism. Steered.

A steering gear box 4 is provided at the right end of the rack housing 2.
In the steering gear box 4, an input shaft 5 connected via a joint to a steering shaft to which a steering wheel (not shown) is integrally attached is rotatably supported via a bearing. As shown, the input shaft 5 is connected to the steering pinion shaft 7 via the torsion bar 6 in the steering gear box 4 so as to be capable of relative twisting.

The helical teeth 7 a of the steering pinion shaft 7 are engaged with the rack teeth 3 a of the rack shaft 3.
Therefore, the steering force transmitted to the input shaft 5 by the turning operation of the steering wheel rotates the steering pinion shaft 7 via the torsion bar 6 and meshes with the helical teeth 7a of the steering pinion shaft 7 and the rack teeth 3a. The rack shaft 3 is slid in the left-right axis direction.

  The rack shaft 3 is pressed from behind by a rack guide 9 biased by a rack guide spring 8.

  An assist motor M is attached to the upper portion of the steering gear box 4, and a worm reduction mechanism 10 that decelerates the driving force of the assist motor M and transmits it to the steering pinion shaft 7 is configured in the steering gear box 4.

  The worm speed reduction mechanism 10 is configured such that a worm wheel 11 fitted on the steering pinion shaft 7 is engaged with a worm 12 coaxially connected to a drive shaft of the assist motor M.

The driving force of the assist motor M is applied to the steering pinion shaft 7 via the worm reduction mechanism 10 to assist steering.
The assist motor M is provided with a rotation angle sensor 27 such as a rotary encoder or resolver that directly detects the rotation of the rotation drive shaft.

A steering torque sensor 20 is provided further above the worm reduction mechanism 10.
The twist of the torsion bar 6 is converted into the movement of the core 21 in the axial direction, and the movement of the core 21 is changed into the inductance change of the coils 22 and 23 to detect the steering torque T.
A torque sensor that optically detects torsion of the torsion bar 6 may be used.

The assist motor M, which is controlled based on the steering torque and assists the steering, is driven and controlled by the CPU. A schematic block diagram of the steering torque control device 30 is shown in FIG.
The steering assist control means 31 calculates and outputs an assist base current Ib based on the steering torque T detected by the steering torque sensor 20 and the vehicle speed v detected by the vehicle speed sensor 25.

  The assist base current Ib is a current that serves as a base for driving the assist motor M. The assist base current Ib is calculated based on the fact that the assist base current Ib increases as the steering torque T increases to reduce the burden on the steering person. However, since the steering wheel becomes heavier when the vehicle speed is low than when the vehicle speed is high, the assist base current Ib is increased to reduce the steering torque.

The steering assist control means 31 calculates an appropriate assist base current Ib from the steering torque T and the vehicle speed v in consideration of the above.
For example, an optimal relationship between the assist base current Ib and the steering torque T is determined in advance for each predetermined vehicle speed, and the assist base current Ib is calculated from the steering torque T and the vehicle speed v based on the relationship.
Furthermore, the assist base current Ib may be obtained by adding a calculation for compensating the inertia torque of the steering system and the inertia torque of the motor.

  The assist base current Ib is added with a reaction force current value Ia by a reaction force current adding means A, which will be described later, and is further added with a target current value Is by the handle return control means S when the handle is released. The drive target current Id is calculated and output to the motor drive circuit 33. The drive current Id is controlled by the current feedback control means 32 so that the difference between the assist target current Io and the fed back motor current Im is zero. The assist motor M is driven by the PWM control of the motor drive circuit 33.

The assist motor M includes a motor current detection device 26 that detects a motor current Im, and a rotation angle sensor 27, and detects the rotation angle of the assist motor M, that is, the motor rotation number n.
The steering torque control device 30 includes a steering angle calculation means 34 for detecting the steering angle θ based on the motor rotation speed n detected by the rotation angle sensor 27.
A steering angle sensor that directly detects the steering angle θ may be provided.

Further, the steering torque control device 30 is provided with hand release determining means 45 for determining whether or not the handle is in the hand release state.
Based on the steering torque T detected by the steering torque sensor 20, the hand release determining means 45 can be set to a handle release state (including a substantially release state in which the hand can be released to the extent that the hand is touching the handle). Judgment is made based on whether or not it is equal to or less than the torque threshold Tp.

  When in the steering torque range of | T | ≦ Tp, it can be determined that the steering wheel is released, and in the steering torque range of | T |> Tp, it is determined that the steering wheel is being operated. This is transmitted to means S and handle return correction current value calculation means 46.

The handle return correction current value calculation means 46 operates and calculates only when a signal indicating the result of the determination that the handle is released from the hand release determination means 45 is input.
In the calculation process, the target rudder angular velocity with respect to the rudder angle θ is obtained in advance, and the relationship of the target rudder angular velocity ωmb with respect to the rudder angle θ is stored in advance in the target rudder angular velocity storage means 35a. A target steering angular velocity ωmb is extracted and calculated from the steering angle θ calculated by the steering angle calculation means 34 based on the relationship map.

  FIG. 4 shows coordinates indicating the relationship of the target rudder angular velocity ωmb with respect to the rudder angle θ stored in the target rudder angular velocity storage means 35a.

The horizontal axis indicates the steering angle θ, and on the horizontal axis, the origin is the neutral position of the steering angle 0, the right side from the origin is the right steering angle, and the left is the left steering angle.
The vertical axis represents the target rudder angular velocity ωmb, the origin is the target rudder angular velocity 0, the upper direction from the origin is the right rotation direction (the direction in which the handle is turned to the right), and the lower direction from the origin is the left rotation direction ( Direction to turn the handle to the left).

At the same coordinates, the relationship of the target rudder angular velocity ωmb with respect to the rudder angle θ is represented by a curve.
The relation curve is formed as a smooth curve symmetrical to the origin in the second quadrant and the fourth quadrant.

Looking at the right rudder angle, the larger the right rudder angle θ, the larger the target rudder angular velocity ωmb in the left steering direction, and the target rudder angular velocity ωmb increases rapidly at the beginning when the right rudder angle θ increases from the rudder angle 0. Then, a curve is drawn in which the rate of increasing becomes gradually smaller.
The left rudder angle is symmetrical with the right rudder angle, and the target rudder angular velocity ωmb increases in the right steering direction as the left rudder angle θ increases.

The target rudder angular velocity ωmb is corrected by multiplying the vehicle speed multiplication coefficient kv based on the vehicle speed v.
The vehicle speed multiplication coefficient calculation means 36 for calculating the vehicle speed multiplication coefficient kv includes vehicle speed multiplication coefficient storage means 36a for storing the relationship of the vehicle speed multiplication coefficient kv with respect to the vehicle speed v as a map, and the vehicle speed multiplication coefficient storage means 36a is calculated from the vehicle speed v detected by the vehicle speed sensor 25. The vehicle speed multiplication coefficient kv is extracted and calculated based on the relationship map.

A map stored in the vehicle speed multiplication coefficient storage means 36a is shown in FIG.
The vehicle speed multiplication coefficient kv becomes larger with respect to the vehicle speed v as the vehicle speed v increases from the origin, the vehicle speed multiplication coefficient kv shows 1.0 at a vehicle speed of 10 km / h, increases rapidly when the vehicle speed v is lower, and then increases. The rate is gradually decreasing.

The vehicle speed multiplication coefficient kv is multiplied by the target steering angular speed ωmb by the multiplication correcting means 37 to calculate the final target steering angular speed ωm.
The vehicle speed multiplication coefficient kv works in a direction to suppress the target rudder angular speed ωmb with a value of less than 1.0 when the vehicle speed is less than 10 km / h, and works to increase the target rudder angular speed ωmb with a value of 1.0 or more when the vehicle speed is 10 km / h or more.

On the other hand, the steering angle θ calculated by the steering angle calculation means 34 is time-differentiated by the steering angular speed calculation means 40 to calculate the actual steering angular speed ω.
A deviation Δω (= ωm−ω) of the final target steering angular speed ωm with respect to the actual steering angular speed ω is obtained (see deviation calculating means 41 in FIG. 3), and the current conversion means 42 converts the deviation Δω into a current and returns the handle. A correction current value Isb is obtained.
This current conversion is calculated by multiplying the deviation Δω by a predetermined conversion coefficient, and is output to the handle return control means S.

The handle return control means S receives and processes the determination result signal from the hand release determination means 45 and the handle return correction current value Isb of the calculation result from the handle return correction current value calculation means 46 to process the final handle return correction current value. Is is output.
The final steering wheel return correction current value Is is added to the assist base current Ib calculated by the steering assist control means 31 (see addition means 47 in FIG. 3), and the assist base current Ib is corrected.

  When the determination result from the hand release determination means 45 is determined to be the handle release state, the handle return control means S uses the handle return correction current value Isb calculated by the handle return correction current value calculation means 46 as the final handle return correction current. When it is output as the value Is and it is determined that it is not in the hand-off state, the handle return correction current value calculation means 46 does not perform the calculation and outputs the final handle return correction current value Is as 0.

  The final steering wheel return correction current value Is is added to the assist base current Ib to correct the assist base current Ib. In the present steering torque control device 30, before the final steering wheel return correction current value Is is added. The reaction force current value Ia from the reaction force current adding means A is added.

Therefore, after the reaction force current value Ia is added to the assist base current Ib, the final handle return correction current value Is is added to obtain the assist target current Io.
The final handle return correction current value Is may be added to the assist base current Ib first, and the reaction force current value Ia may be added later.
The assist motor M is driven and controlled by the corrected assist target current Io.

The reaction force current adding means A will be described below.
A relationship map of the reaction force current value Ia with respect to the steering angle θ for each vehicle speed v is determined in advance and stored in the reaction force current storage means 50a. The reaction force current calculation means 50 stores the relationship stored in the reaction force current storage means 50a. Based on the map, the reaction force current value Ia is extracted and calculated from the steering angle θ calculated by the steering angle calculating means 34 and the vehicle speed v.

FIG. 6 shows coordinates indicating the relationship of the reaction force current value Ia to the steering angle θ for each vehicle speed v stored in the reaction force current storage means 50a.
The horizontal axis indicates the steering angle θ, and on the horizontal axis, the origin is the neutral position of the steering angle 0, the right side from the origin is the right steering angle, and the left is the left steering angle.
The vertical axis represents the reaction force current value Ia, the origin is the reaction force current value 0 on the vertical axis, and the current value that generates torque in the clockwise direction (the direction of turning the handle to the right) is above the origin. The value below the origin indicates the current value for generating torque in the left rotation direction (direction in which the handle is turned to the left).

The relational curve of the reaction force current value Ia with respect to the steering angle θ is formed as a smooth convex curve symmetrical to the origin in the second quadrant and the fourth quadrant.
That is, the reaction force current value Ia is a current value that generates torque in a direction to return to the neutral position of the steering angle 0. As the steering angle increases from 0, the reaction force current value Ia increases from 0 and then decreases to 0. The characteristic which leads to is shown.

The relationship curve of the reaction force current value Ia with respect to the steering angle θ is set for each arbitrarily selected vehicle speed, and the reaction force current value decreases as the vehicle speed increases.
The rudder angle width in which the reaction force current value Ia appears is a fairly narrow width, and the reaction force current is output when the vehicle is turning at a small steering angle, particularly at a low vehicle speed.

The reaction force current calculation means 50 extracts and calculates the reaction force current value Ia from the steering angle θ and the vehicle speed v based on this relationship map.
The reaction force current value for the unselected vehicle speed v is calculated from the reaction force current values of the selected vehicle speed before and after the vehicle speed v.

Therefore, when turning at a small steering angle, the reaction force current value Ia that attempts to return the steering angle to the neutral position is output.
The reaction force current value Ia increases as the vehicle speed decreases.

The reaction force current value Ia is regulated by the torque ratio calculation means 51 based on the steering torque T.
The torque ratio calculation means 51 includes torque ratio storage means 51a for storing a predetermined relationship of the torque ratio r with respect to the steering torque T as a map.

A map stored in the torque ratio storage means 51a is shown in FIG.
From the origin of the horizontal axis, the right side (right side) is the right steering torque, the negative side (left side) is the left steering torque, and the vertical axis is the torque ratio r.
When the steering torque T is 0, the torque ratio r indicates 1.0. As the steering torque T increases from 0 to both the left and right, the torque ratio r decreases, gradually decreases, and smoothly reaches 0.

  The torque ratio r extracted and calculated by the torque ratio calculation means 51 based on the relationship map of the torque ratio r to the steering torque T stored in the torque ratio storage means 51a is multiplied by the reaction force current value Ia by the multiplication means 52. Thus, the reaction force current is regulated, and the reaction force current value Ia · r multiplied by the torque ratio r is added to the assist base current Ib by the adding means 53.

In this way, the reaction force current value Ia is regulated by the torque ratio r, so that the reaction force current is not affected when the steering wheel is actively cut or returned.
Therefore, the value of the steering torque T at which the torque ratio r becomes zero is a value that is clearly large enough to determine whether the steering wheel has been turned in or turned back, and the maximum steering torque that the hand release determining means 45 determines as the handle release state. Is a value considerably larger than the torque threshold value Tp.

  The reaction force current value Ia · r is added to the assist base current Ib, and the final handle return correction current value Is by the handle return control means S is added to obtain an assist target current Io (= Ib + Ia · r + Is). This is used for driving the motor M.

  Accordingly, when the steering torque T is equal to or less than the small torque threshold Tp that can be set to the handle release state by the handle return control means S, the handle is returned to the neutral position even at a low vehicle speed by the correction current Is added to the assist base current Ib. Can do.

  When turning while keeping a small steering angle, the reaction force current adding means A adds the reaction force current value Ia · r to the assist base current value Ib, so that the steering torque T is the torque threshold value. The steering wheel return control means S does not repeat execution and stop of the steering wheel return drive, and the steering at a small steering angle can be performed stably.

  The reaction force current value Ia of the reaction force current adding means A is limited to a required small steering angle and changes to a smooth convex shape with respect to the steering angle θ. Even if the angle changes, it can be handled smoothly.

  Further, since the reaction force current value Ia is lower as the vehicle speed is higher, the reaction force current value is lower when the self-aligning torque is lower and the reaction force current value Ia is lower, and the reaction force current value is lower when the self-aligning torque is high and the vehicle speed is high. Therefore, when turning while maintaining a small steering angle, it is possible to prevent a sense of incongruity (sensation of being returned excessively) from occurring due to excessive reaction force torque being added to the self-aligning torque depending on the vehicle speed. ing.

  Since it is determined that the steering torque T exceeds the small torque threshold value Tp that can be set to the handle release state and the steering wheel is operated, the steering wheel return correction current value calculation means 46 does not perform calculation processing. The burden on the CPU associated with the processing is reduced.

1 is a schematic rear view of an entire electric power steering apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure in a steering gear box. It is a schematic block diagram of a steering torque control device. It is a coordinate which shows the relationship of target steering angular velocity (omega) mb with respect to steering angle (theta). It is a figure which shows the relationship map of the vehicle speed multiplication coefficient kv with respect to the vehicle speed v. It is a coordinate which shows the relationship of the reaction force electric current value Ia with respect to the steering angle (theta) for every vehicle speed v. It is a figure which shows the relationship map of the torque ratio r with respect to the steering torque T. FIG.

Explanation of symbols

M: Assist motor, 1 ... Electric power steering device, 2 ... Rack housing, 3 ... Rack shaft, 4 ... Steering gear box, 5 ... Input shaft, 6 ... Torsion bar, 7 ... Steering pinion shaft, 8 ... Rack guide spring, 9 ... Rack guide, 10 ... Worm reduction mechanism, 11 ... Worm wheel, 12 ... Worm,
20 ... Torque sensor, 21 ... Core, 22, 23 ... Coil, 25 ... Vehicle speed sensor, 26 ... Motor current detector, 27 ... Rotation angle sensor,
30 ... Steering torque control device, 31 ... Steering assist control means, 32 ... Current feedback control means, 33 ... Motor drive circuit, 34 ... Steering angle calculation means,
S: Handle return control means,
35 ... Target rudder angular speed calculation means, 35a ... Target rudder angular speed storage means, 36 ... Vehicle speed multiplication coefficient calculation means, 36a ... Vehicle speed multiplication coefficient storage means, 37 ... Multiplication correction means, 40 ... Rudder angular speed calculation means, 41 ... Deviation calculation means 42 ... current conversion means, 46 ... handle return correction current value calculation means,
45 ... Release control means, 47 ... Addition means,
A ... reaction force current addition means, 50 ... reaction force current calculation means, 50a ... reaction force current storage means, 51 ... torque ratio calculation means, 51a ... torque ratio storage means, 52 ... multiplication means, 53 ... addition means.

Claims (2)

Steering assist control means (31) for calculating an assist base current value (Ib) based on the steering torque (T) and the vehicle speed (v), and assisting according to the assist target current (Io) based on the assist base current value (Ib). In the electric power steering device in which the motor (M) is driven and assisted to assist human power,
Rudder angle detection means (34) for detecting the rudder angle (θ);
Hand release determining means (45) for determining whether or not the steering wheel is released based on the steering torque (T);
A handle for calculating a steering wheel return correction current value (Isb) based on the steering angle (θ), the vehicle speed (v), and the steering torque (T) when the hand release determining means (45) determines that the handle is released. Return correction current value calculation means (46),
The handle return correction current value (Isb) calculated by the handle return correction current value calculation means (46) only when it is determined that the hand release determination means (45) is the handle release state, the final handle return correction current value ( Is)) handle return control means (S) to add to the assist base current value (Ib),
Reaction force current calculation means (50) for calculating a reaction force current value (Ia) that gives a return reaction force in the steering angle neutral direction at a small steering angle based on the vehicle speed (v) and the steering angle (θ), and Torque ratio calculation means (51) for calculating a torque ratio (r) that regulates the reaction force current value (Ia) based on the steering torque (T), and the reaction force current value (Ia) includes the torque ratio ( reaction force current adding means (A) for adding the reaction force current value (IaR) multiplied by r) to the assist base current value (Ib) ,
The reaction force current calculation means (50) stores in advance a reaction force current storage for each vehicle speed (v) that the reaction force current value increases from 0 and then decreases to 0 as the steering angle increases from 0. Means (50a), the reaction force current value (Ia) is extracted and calculated from the vehicle speed (v) and the steering angle (θ) based on the reaction force current storage means (50a),
The torque ratio calculation means (51) indicates that when the steering torque (T) is 0, the torque ratio (r) is 1.0, and the torque ratio (r) decreases as the steering torque (T) increases from 0 to the left and right. The torque ratio storage means (51a) that memorizes the characteristic that gradually decreases and smoothly reaches 0, and extracts the torque ratio (r) from the steering torque (T) based on the torque ratio storage means (51a). An electric power steering device. The electric power steering apparatus according to claim 1, wherein the reaction force current storage means (50a) stores a characteristic that the reaction force current value (Ia) is lower as the vehicle speed (v) is higher.

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