JP2012210900A - Electric power steering device and setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology to balance the right and left steering characteristics considering manufacturing variance as the whole apparatus without using a measuring instrument such as a torque meter.SOLUTION: An electric power steering apparatus includes: a relative angle detection device for outputting an electric signal corresponding to relative rotation angle of two coaxially arranged rotary shaft: an electric motor imparting driving force to one of two rotary shafts; a torque detection part for detecting the steering torque based on the output value of the relative angle detection device and a correction value stored in a storage region; and a neutral correcting value set part for setting the correction value. The neutral correction setting part sets the correction value based on a right side output value which is an output value from the relative angle detection device when the electric motor is rotated in the right direction at a predetermined rotational speed and a left side output value which is an output value from the relative angle detection device when the electric motor is rotated in the left direction at a predetermined rotational speed.

Description

  The present invention relates to an electric power steering apparatus and a setting method.

In recent years, in electric power steering devices that assist the driver's steering force with the power of the electric motor, a technique has been proposed to improve the steering feeling by correcting the deviation of the neutral point of the sensor and balancing the left and right steering characteristics. Yes.
For example, the power steering control device described in Patent Document 1 is configured as follows. That is, the electric power steering apparatus is based on the steering torque reference value that defines the neutral point of the steering position, and the steering torque neutral point signal that is detected by the steering torque detection means in a state in which the steering torque is regarded as zero (0). And control means having torque correction means for correcting a steering torque signal in a normal steering state.

Japanese Patent Laid-Open No. 10-278816

Whether or not the steering torque is zero is difficult to grasp unless a measuring instrument such as a torque meter is used. In addition, the neutral point of the sensor varies from product to product due to variations in component manufacturing, component fastening variations, or friction between components.
Therefore, in order to easily improve the steering feeling of the electric power steering device, without using a measuring instrument such as a torque meter, the manufacturing variability of the entire device, the variability of component fastening or the friction generated between the components is taken into consideration. It is desirable that the left and right steering characteristics be balanced.

  For this purpose, the present invention provides a relative angle detection means for outputting an electrical signal corresponding to the relative rotation angle of two rotation shafts arranged coaxially, and one of the two rotation shafts. An electric motor for applying a driving force to the motor, torque detection means for detecting a steering torque based on an output value from the relative angle detection means and a correction value stored in a storage area, and a correction value for setting the correction value Setting means, and the correction value setting means includes a right output value that is an output value from the relative angle detection means when the electric motor rotates in the right direction at a predetermined rotational speed, An electric power steering apparatus, wherein the correction value is set based on a left output value that is an output value from the relative angle detection means when the electric motor rotates leftward at the predetermined rotation speed. .

Here, the correction value setting means includes a reference value that is an intermediate value between the maximum value and the minimum value of the electrical signal output by the relative angle detection means, and an intermediate value between the right output value and the left output value. The correction value may be set based on a difference from the intermediate output value that is a value.
In addition, first target current determining means for determining a target current to be supplied to the electric motor based on the steering torque detected by the torque detecting means, and the rotational speed of the electric motor to be the predetermined rotational speed. A second target current determining means for determining a target current to be supplied to the electric motor; a target current determined by the first target current determining means or a target current determined by the second target current determining means; Supply means for supplying to the electric motor, the correction value setting means from the relative angle detection means when the supply means supplies the electric motor with the target current determined by the second target current determination means. The correction value may be set based on the output value.

  From another point of view, the present invention provides a detection unit that detects a relative rotation angle between two coaxially arranged rotation axes, and a correction value that stores a correction value for correcting the detection value of the detection unit. A storage unit, and a relative angle detection unit that outputs an electrical signal corresponding to a value obtained by correcting the detection value with the correction value, a correction value setting unit that sets the correction value, and the two An electric motor that applies a driving force to one of the rotating shafts, and the correction value setting means is configured to perform the relative operation when the electric motor rotates in the right direction at a predetermined rotational speed. The correction is based on a right output value that is an output value from the angle detection means and a left output value that is an output value from the relative angle detection means when the electric motor rotates leftward at the predetermined rotation speed. Electricity characterized by setting a value It is a word steering apparatus.

  From another point of view, the present invention relates to a relative angle detection means for outputting an electrical signal corresponding to the relative rotation angle between two coaxially arranged rotating shafts, and the rotation of one of the two rotating shafts. An electric motor for applying a driving force to the shaft, a torque detection means for detecting a steering torque based on an output value from the relative angle detection means and a correction value stored in the storage area, and a correction for setting the correction value A setting method for setting the correction value in an electric power steering apparatus comprising: a value setting means, wherein the electric motor is rotated from the relative angle detection means when the electric motor rotates in a right direction at a predetermined rotation speed. Obtaining a right output value as an output value, and obtaining a left output value as an output value from the relative angle detection means when the electric motor rotates in the left direction at the predetermined rotation speed; Calculating the correction value based on the right side output value and the left side output value, and storing the correction value calculated in the step of calculating the correction value in the storage area. It is the setting method characterized by including.

  According to the present invention, it is possible to balance the left and right steering characteristics in consideration of manufacturing variations, component fastening variations, friction between components, and the like without using a measuring instrument such as a torque meter.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is sectional drawing which shows the inside of a steering gear box. It is an enlarged view of the X section in FIG. It is a schematic block diagram of the main components of a torque detection apparatus. It is the figure which looked at the torque detection apparatus from the Y direction in FIG. It is a figure which shows the state of the torque detection apparatus before a lower connection shaft and a pinion shaft make relative displacement. FIG. 6 is a diagram illustrating a state in which the magnet rotates in the clockwise direction with respect to the yoke when viewed in FIG. 5. FIG. 6 is a diagram illustrating a state in which the magnet rotates counterclockwise with respect to the yoke when viewed in FIG. 5. It is a figure which shows the relationship between the relative angle of a magnet and a yoke, and the magnetic flux density which a 1st magnetic sensor and a 2nd magnetic sensor detect. It is a figure which shows the relationship between steering torque and a 1st voltage signal and a 2nd voltage signal. It is a schematic block diagram of the control apparatus of an electric power steering apparatus. It is a schematic block diagram of a target current calculation part. It is a schematic block diagram of a control part. It is a schematic block diagram of a neutral correction value setting part. It is a flowchart which shows the procedure of the neutral correction value setting process which a neutral correction value calculation part performs. It is a figure which shows the process in which a neutral correction value is set by the neutral correction value setting process.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment. FIG. 2 is a cross-sectional view showing the inside of the steering gear box 107.
An electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle. In the present embodiment, the configuration applied to an automobile is used. Illustrated.

  The steering device 100 includes a wheel-like steering wheel (handle) 101 operated by a driver, and a steering shaft 102 provided integrally with the steering wheel 101. The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.
The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is coupled to the above-described lower coupling shaft 108 via the torsion bar 140 (see FIG. 2) in the steering gear box 107.

  As shown in FIG. 2, the pinion shaft 106 and the lower connection shaft 108 are rotatably supported by the housing 120. The housing 120 is a member that is fixed to a body frame (hereinafter also referred to as “vehicle body”) of a vehicle such as an automobile, and the first housing 121 and the second housing 122 are coupled by, for example, a bolt or the like. Configured. The lower connecting shaft 108 is rotatably supported by the first housing 121 via a bearing, and the pinion shaft 106 is coaxially coupled to the lower connecting shaft 108 via a torsion bar 140 and is connected to the second via the bearing. The housing 122 is rotatably supported.

The steering device 100 also includes an electric motor 110 fixed to the steering gear box 107 and a worm wheel 130 fixed to the pinion shaft 106. The worm gear 111 and the worm wheel 130 connected to the output shaft of the electric motor 110 mesh with each other, and the rotational force of the electric motor 110 is decelerated by the worm wheel 130 and transmitted to the pinion shaft 106. It can be exemplified that the electric motor 110 is a three-phase brushless motor.
Inside the steering gear box 107 is a relative angle detection device 20 as an example of a relative angle detection means for detecting the torsion amount of the torsion bar 140 based on the relative angle between the lower connecting shaft 108 and the pinion shaft 106. Is provided. The relative angle detection device 20 will be described in detail later.
In addition, the steering device 100 includes a control device 10 that controls the operation of the electric motor 110. The control device 10 receives the output value of the relative angle detection device 20 and the output value of the vehicle speed sensor 170 that detects the vehicle speed V, which is the moving speed of the automobile.

  The steering device 100 configured as described above detects the steering torque T applied to the steering wheel 101 based on the output value from the relative angle detection device 20, and the control device 10 responds to the detected steering torque T. The electric motor 110 is driven and controlled, and torque generated by the electric motor 110 is transmitted to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101. That is, the pinion shaft 106 rotates with the steering torque T generated by the rotation of the steering wheel 101 and the auxiliary torque applied from the electric motor 110.

Next, the relative angle detection device 20 will be described in detail.
FIG. 3 is an enlarged view of a portion X in FIG. FIG. 4 is a schematic configuration diagram of main components of the relative angle detection device 20. FIG. 5 is a view of the relative angle detection device 20 as viewed from the Y direction in FIG. In FIG. 4, a bracket 60 described later is omitted.

The relative angle detection device 20 includes, as an example of two coaxially arranged rotating shafts, a lower connection shaft 108 rotatably supported by a housing 120 and a pinion shaft 106 also rotatably supported by the housing 120. And a relative rotation angle (a twist amount of the torsion bar 140).
The relative angle detection device 20 includes a magnet 21 attached to the lower connecting shaft 108, a yoke 30 disposed in a magnetic field formed by the magnet 21, and a magnetic sensor 40 that detects a magnetic flux density generated in the yoke 30. Yes.

  The magnet 21 has a cylindrical shape, and as shown in FIG. 4, N poles and S poles are alternately arranged in the circumferential direction of the lower connecting shaft 108 and are magnetized in the circumferential direction. The magnet 21 is attached to the lower connecting shaft 108 via the collar 22. That is, the magnet 21 is fixed to the collar 22, and the collar 22 is fixed to the lower connection shaft 108. The magnet 21 rotates together with the lower connecting shaft 108. The axial length of the lower connecting shaft 108 of the magnet 21 is longer than the length of the yoke 30.

  The yoke 30 includes a first yoke 31, a second yoke 32, and a third yoke 33 provided between the first yoke 31 and the second yoke 32 in the axial direction of the lower connecting shaft 108. It consists of and. The first yoke 31, the second yoke 32 and the third yoke 33 are attached to the pinion shaft 106.

The first yoke 31 includes a disk-shaped first annular portion 31a in which a hole having a diameter larger than the outer diameter of the magnet 21 is formed, and the lower connecting shaft 108 from the first annular portion 31a. And a plurality of first protrusions 31b formed so as to extend in the axial direction.
The same number of first protrusions 31b as the N poles and S poles of the magnet 21 are formed. That is, when the number of N poles and S poles of the magnet 21 is 12, for example, 12 first protrusions 31b are also formed. The first protrusion 31b is slightly outside of the outer peripheral surface so as to face the outer peripheral surface of the magnet 21 in the rotational radius direction of the lower connecting shaft 108 as shown in FIGS. The surface of the first protrusion 31b facing the magnet 21 is rectangular when viewed in a direction perpendicular to the rotation axis of the lower connecting shaft 108.

The second yoke 32 includes a disc-shaped second annular portion 32a in which a hole having a diameter larger than the outer diameter of the magnet 21 is formed on the inside, and the lower connecting shaft 108 from the second annular portion 32a. And a plurality of second protrusions 32b formed to extend in the axial direction.
The same number of second protrusions 32b as the N and S poles of the magnet 21 are formed. The second protrusion 32b is slightly outside the outer peripheral surface so as to face the outer peripheral surface of the magnet 21 in the rotational radius direction of the lower connecting shaft 108 as shown in FIGS. The surface of the second protrusion 32b facing the magnet 21 is rectangular when viewed in a direction perpendicular to the rotation axis of the lower connecting shaft 108.

The third yoke 33 includes a disk-shaped third annular portion 33a in which a hole having a diameter larger than the outer diameter of the magnet 21 is formed, and the lower connecting shaft 108 from the third annular portion 33a. A plurality of third protrusions 33b formed to extend toward the first yoke 31 and a plurality of fourth protrusions 34b formed to extend toward the second yoke 32 in the axial direction. have.
The same number of third protrusions 33b and fourth protrusions 34b as the N poles and S poles of the magnet 21 are formed. The third protrusion portion 33b and the fourth protrusion portion 34b are arranged so as to face the outer peripheral surface of the magnet 21 in the rotational radius direction of the lower connecting shaft 108 as shown in FIGS. The surface of the third protrusion portion 33b and the fourth protrusion portion 34b facing the magnet 21 is disposed slightly outside the outer peripheral surface, and is rectangular when viewed in a direction perpendicular to the rotation axis of the lower connecting shaft 108. It is.

Further, the first protrusions 31 b of the first yoke 31 and the third protrusions 33 b of the third yoke 33 are alternately arranged in the circumferential direction of the lower connecting shaft 108. The second protrusions 32 b of the second yoke 32 and the fourth protrusions 34 b of the third yoke 33 are alternately arranged in the circumferential direction of the lower connecting shaft 108.
Note that, in the third yoke 33 according to the present embodiment, the third projecting portion 33 b and the fourth projecting portion 34 b are integrally formed continuously in the axial direction of the lower connecting shaft 108.

  In the relative angle detection device 20 according to the present embodiment, in the initial state where the torsion bar 140 is not twisted, as shown in FIG. , The boundary line between the N pole and the S pole of the magnet 21 and the center of the first protrusion 31b of the first yoke 31 in the circumferential direction coincide with each other.

  The second protrusion 32 b of the second yoke 32 is disposed so as to be at the same position as the first protrusion 31 b of the first yoke 31 in the circumferential direction of the lower connecting shaft 108. That is, in the initial state where the torsion bar 140 is not twisted, the boundary line between the N pole and the S pole of the magnet 21 facing the first protrusion 31b and the circumferential direction of the second protrusion 32b. It is arranged so that the centers coincide. That is, as shown in FIG. 5, when viewed in the clockwise direction, the boundary line between the N pole and the S pole of the magnet 21 and the center in the circumferential direction of the second protrusion 32b coincide with each other. . When the steering torque T is applied to the torsion bar 140 and the torsion bar 140 is twisted, and the first protrusion 31b faces the north or south pole of the magnet 21, the second protrusion 32b One protrusion 31b faces a magnetic pole having the same polarity as the opposite polarity.

  When the third protrusion 33b and the fourth protrusion 34b of the third yoke 33 are viewed in the clockwise direction as shown in FIG. 5 in the circumferential direction of the lower connecting shaft 108 in the initial state. The boundary line between the S pole and the N pole of the magnet 21 and the center in the circumferential direction of the third protrusion portion 33b and the fourth protrusion portion 34b coincide with each other. When the steering torque T is applied to the torsion bar 140 and the torsion bar 140 is twisted, and the first protrusion 31b faces the north or south pole of the magnet 21, the third protrusion 33b and the fourth protrusion The protruding portion 34b faces a magnetic pole having a polarity different from that of the magnetic pole opposed to the first protruding portion 31b.

  In the yoke 30 according to the present embodiment, as shown in FIG. 3, the first yoke 31, the second yoke 32, and the third yoke 33 are integrated by insert molding. The bracket 60 is also integrally formed when insert molding is performed. The bracket 60 has a thin cylindrical axial part 61 extending in the axial direction of the pinion shaft 106 and a disk-shaped radial part 62 extending from the axial part 61 in the rotational radial direction of the pinion shaft 106. The axial portion 61 of the bracket 60 is fixed to the pinion shaft 106 by being press-fitted, welded, or screwed to the pinion shaft 106. Thereby, the yoke 30 is fixed to the pinion shaft 106.

  The first magnetic sensor 41 is fixed to the housing 120, and the first annular portion 31 a of the first yoke 31 and the third annular ring of the third yoke 33 in the axial direction of the lower connecting shaft 108. It arrange | positions between the parts 33a. The first magnetic sensor 41 operates when the power supply voltage is supplied from the control device 10, detects the magnetic flux density between the first yoke 31 and the third yoke 33, and uses the detected magnetic flux density. A sensor that converts an electrical signal (for example, a voltage signal) and outputs it, and examples thereof include a magnetoresistive element, a Hall IC, and a Hall element.

The second magnetic sensor 42 is fixed to the housing 120, and the second annular portion 32 a of the second yoke 32 and the third of the third yoke 33 in the axial direction of the lower connecting shaft 108. It arrange | positions between the annular parts 33a. The second magnetic sensor 42 operates when the power supply voltage is supplied from the control device 10, detects the magnetic flux density between the second yoke 32 and the third yoke 33, and detects the detected magnetic flux density. A sensor that converts an electrical signal (for example, a voltage signal) and outputs it, and examples thereof include a magnetoresistive element, a Hall IC, and a Hall element.
The first magnetic sensor 41 and the second magnetic sensor 42 are arranged so as to detect the magnetic flux density with the same sign when, for example, magnetic fields having the same direction are generated in the axial direction of the lower connecting shaft 108. Has been.

The relative angle detection device 20 configured as described above operates as described below.
FIG. 6 is a diagram illustrating a state of the relative angle detection device 20 before the lower connection shaft 108 and the pinion shaft 106 are relatively displaced. FIG. 6A is a diagram showing the relationship between the magnet 21 and the yoke 30 in the Y direction in FIG. FIG. 6B is a diagram of the magnet 21 and the yoke 30 viewed in the Z direction in FIG.

  When the torsion bar 140 is in an initial state in which no torsion occurs, as shown in FIGS. 5 and 6A, first protrusions that are all protrusions of the yoke 30 in the circumferential direction of the lower connecting shaft 108. The center in the circumferential direction of the portion 31b to the fourth protrusion 34b coincides with the boundary line between the N pole and the S pole of the magnet 21. In such a case, the same number of magnetic lines of force enter and exit from each of the first and fourth protrusions 31b to 34b from the N and S poles of the magnet 21. Therefore, between the first annular portion 31a of the first yoke 31 and the third annular portion 33a of the third yoke 33, and between the second annular portion 32a and the third annular portion of the second yoke 32. Since there is no magnetic flux density difference with the third annular portion 33a of the yoke 33, the outputs of the first magnetic sensor 41 and the second magnetic sensor 42 become zero.

When the steering torque T is input to the steering wheel and the torsion bar 140 is twisted, the relative position in the circumferential direction between the magnet 21 and the yoke 30 changes.
FIG. 7 is a diagram illustrating a state in which the magnet 21 (lower connection shaft 108) rotates in the clockwise direction with respect to the yoke 30 (pinion shaft 106) when viewed in FIG. FIG. 8 is a diagram illustrating a state in which the magnet 21 is rotated counterclockwise with respect to the yoke 30 when viewed in FIG. 5. In each figure, (a) is the figure which looked at the relationship between the magnet 21 and the yoke 30 from the Y direction in FIG. (B) is the figure which looked at the magnet 21 and the yoke 30 in the Z direction in (a).
FIG. 9 shows the relative angle between the magnet 21 (lower connection shaft 108) and the yoke 30 (pinion shaft 106) (the torsion angle θ of the torsion bar 140), the first magnetic sensor 41, and the second magnetic sensor 42. It is a figure which shows the relationship with the magnetic flux density to detect.

  As shown in FIGS. 7 and 8, when the torsion bar 140 is twisted, in the circumferential direction of the lower connecting shaft 108, the circumferential center of the first protrusion 31 b to the fourth protrusion 34 b of the yoke 30, The boundary line between the N pole and the S pole of the magnet 21 does not match. That is, compared with the initial state, the area | region where any one magnetic pole of the magnet 21 opposes the 1st projection part 31b-the 4th projection part 34b of the yoke 30 increases.

  More specifically, in the state of FIG. 7, the first protrusion 31 b of the first yoke 31 and the second protrusion 32 b of the second yoke 32 have regions that face the north pole of the magnet 21. As a result, the third protrusion 33 b and the fourth protrusion 34 b of the third yoke 33 increase in the area facing the S pole of the magnet 21. Therefore, the magnetic lines of force from the N pole of the magnet 21 toward the first protrusion 31b and the second protrusion 32b are more than the lines of magnetic force from the first protrusion 31b and the second protrusion 32b toward the S pole of the magnet 21. To increase. In addition, the magnetic lines of force from the third protrusion 33b and the fourth protrusion 34b toward the S pole of the magnet 21 are more than the magnetic lines of force from the N pole of the magnet 21 toward the third protrusion 33b and the fourth protrusion 34b. To increase. As a result, the magnetic flux density from the first annular portion 31a of the first yoke 31 toward the third annular portion 33a of the third yoke 33 increases, and the second annular portion of the second yoke 32 increases. The magnetic flux density from 32 a toward the third annular portion 33 a of the third yoke 33 increases.

  When the direction from the first annular portion 31a of the first yoke 31 toward the third annular portion 33a of the third yoke 33 is a plus direction, when viewed from the initial state in FIG. As the magnet 21 (lower coupling shaft 108) rotates in the clockwise direction with respect to the yoke 30 (pinion shaft 106), the magnetic flux density B1 detected by the first magnetic sensor 41 increases in the positive direction. On the other hand, the magnetic flux density B2 detected by the second magnetic sensor 42 increases in the negative direction. 5, when the magnet 21 (lower connection shaft 108) rotates clockwise relative to the yoke 30 (pinion shaft 106) from the initial state, the steering torque T in the “right direction”. Is assumed to occur.

  In the state of FIG. 8, the first protrusion 31 b of the first yoke 31 and the second protrusion 32 b of the second yoke 32 have an increased area facing the S pole of the magnet 21. In the third protrusion 33 b and the fourth protrusion 34 b of the three yokes 33, the area facing the north pole of the magnet 21 increases. Therefore, the magnetic lines of force from the first protrusion 31b and the second protrusion 32b toward the S pole of the magnet 21 are more than the magnetic lines of force from the N pole of the magnet 21 toward the first protrusion 31b and the second protrusion 32b. To increase. Further, the magnetic lines of force from the N pole of the magnet 21 toward the third protrusion 33b and the fourth protrusion 34b are more than the lines of magnetic force from the third protrusion 33b and the fourth protrusion 34b toward the S pole of the magnet 21. To increase. As a result, the magnetic flux density from the third annular portion 33a of the third yoke 33 toward the first annular portion 31a of the first yoke 31 increases and the third annular portion of the third yoke 33 increases. The magnetic flux density from 33a toward the second annular portion 32a of the second yoke 32 increases. Therefore, the first magnetic sensor 41 as the magnet 21 (lower connection shaft 108) rotates counterclockwise with respect to the yoke 30 (pinion shaft 106) when viewed from the initial state in FIG. Detects the magnetic flux density B1 in the negative direction. On the other hand, the magnetic flux density B2 detected by the second magnetic sensor 42 increases in the positive direction. Hereinafter, as seen in FIG. 5, when the magnet 21 (the lower connecting shaft 108) rotates counterclockwise with respect to the yoke 30 (the pinion shaft 106) from the initial state, the “leftward” steering torque Assume that T is generated.

  FIG. 9 shows a change in magnetic flux density when the lower connecting shaft 108 and the pinion shaft 106 are relatively rotated by one magnetic pole (α degree) in both directions. The first magnetic sensor 41 and the second magnetic sensor 42 are configured to allow the torsion bar 140 to be twisted by 1/3 × α degrees in both directions. It is possible to detect a change in magnetic flux density that is proportional to the relative rotation angle between the shaft 108 and the pinion shaft 106.

  The first magnetic sensor 41 converts the detected magnetic flux density B1 into a first voltage signal V1s indicating a voltage value corresponding to the magnetic flux density B1, and outputs it. The second magnetic sensor 42 detects the detected magnetic flux. The density B2 is converted into a second voltage signal V2s indicating a voltage value corresponding to the magnetic flux density B2 and output. The torsion amount of the torsion bar 140 (the relative rotation angle between the lower connecting shaft 108 and the pinion shaft 106) and the steering torque T of the steering wheel 101 are in a proportional relationship. That is, the first magnetic sensor 41 and the second magnetic sensor 42 output the first voltage signal V1s and the second voltage signal V2s that indicate voltage values corresponding to the steering torque T.

FIG. 10 is a diagram illustrating a relationship between the steering torque T and the first voltage signal V1s and the second voltage signal V2s.
In FIG. 10, the horizontal axis represents the steering torque T, and the vertical axis represents the first voltage V1 of the first voltage signal V1s and the second voltage V2 of the second voltage signal V2s. In the horizontal axis, the state in which the steering torque T is zero, in other words, the state in which the torsion bar 140 has a zero twist amount is set to the middle point, the right steering torque T is positive, and the left steering torque is negative.
As shown in FIG. 10, the first magnetic sensor 41 and the second magnetic sensor 42 according to the present embodiment have a first voltage V1 and a second voltage signal V2s indicated by the first voltage signal V1s. Is configured to change between the maximum voltage VHi and the minimum voltage VLo. The maximum voltage VHi is slightly lower than the output upper limit value that the first magnetic sensor 41 and the second magnetic sensor 42 can output as the first voltage signal V1s and the second voltage signal V2s, and the minimum voltage VLo is The output lower limit value is set slightly higher. This is because the voltages output as the first voltage signal V1s and the second voltage signal V2s become unstable near the output upper limit value and the output lower limit value of the first magnetic sensor 41 and the second magnetic sensor 42. This is because the detection accuracy of the steering torque T may be lowered.

  As shown by the solid line in FIG. 10, the first voltage signal V1s output from the first magnetic sensor 41 increases the magnitude of the steering torque T in the right direction (the rotation of the torsion bar 140 in the right direction). The voltage increases as the amount increases). That is, when the steering wheel 101 rotates rightward, the first voltage V1 of the first voltage signal V1s increases. Further, as shown by the broken line in FIG. 10, the second voltage V2 of the second voltage signal V2s changes between the same maximum voltage VHi and the minimum voltage VLo as the first voltage V1 of the first voltage signal V1s. In addition, it has a characteristic (negative correlation) opposite to that of the first voltage signal V1s, and the second voltage signal V2s decreases as the steering torque T increases in the right direction. Have. That is, when the steering wheel 101 rotates rightward, the second voltage V2 of the second voltage signal V2s decreases.

At the middle point, the first voltage V1 of the first voltage signal V1s is equal to the second voltage V2 of the second voltage signal V2s (hereinafter, sometimes referred to as “middle point voltage Vc”). It is comprised so that it may become. The midpoint voltage Vc is, for example, an intermediate voltage (Vc = (VHi + VLo) / 2) between the maximum voltage VHi and the minimum voltage VLo.
Further, the rate of change of the first voltage signal V1s with respect to the change of the steering torque T is equal to the rate of change (absolute value) of the second voltage signal V2s, and the first voltage signal V1s indicating the same steering torque T has the same value. The total voltage Vt obtained by summing up the first voltage V1 and the second voltage V2 of the second voltage signal V2s (hereinafter simply referred to as “total voltage Vt”) is always a predetermined voltage. Have. In the present embodiment, the total voltage Vt is configured to be a constant voltage (VHi + VLo), and “VHi + VLo” is a predetermined voltage.

For example, when the 1st magnetic sensor 41 and the 2nd magnetic sensor 42 have the performance which can output the voltage value between 0-5 [V] as the 1st voltage signal V1s and the 2nd voltage signal V2s. That is, when the output lower limit value is 0 [V] and the output upper limit value is 5 [V], the first voltage V1 of the first voltage signal V1s and the second voltage V2 of the second voltage signal V2s. When the maximum voltage VHi is set to 4.5 [V] and the minimum voltage VLo is set to 0.5 [V], the midpoint voltage Vc is 2.5 [V] and the predetermined voltage is 5 [V].
Therefore, at the middle point where the steering torque T is zero, the first voltage V1 of the first voltage signal V1s and the second voltage V2 of the second voltage signal V2s are both 2.5 [V]. The total voltage Vt of the voltage V1 and the second voltage V2 is always 5 [V]. When the steering torque T increases in the right direction, the first voltage V1 increases from 2.5 [V], and the second voltage V2 decreases from 2.5 [V]. On the other hand, when the steering torque T increases in the left direction, the first voltage V1 decreases from 2.5 [V], and the second voltage V2 increases from 2.5 [V].

Next, the control device 10 will be described.
The control device 10 includes a CPU 11 that performs arithmetic processing when controlling the electric motor 110, a ROM 12 that stores programs executed by the CPU 11, various data, and the like, and a RAM 13 that is used as a work memory for the CPU 11, and the like. EEPROM (Electrically Erasable & Programmable Read Only Memory) 14.
The control device 10 receives an output value from the relative angle detection device 20 described above, a vehicle speed signal v obtained by converting the vehicle speed V detected by the vehicle speed sensor 170 into an output signal, and the like.

FIG. 11 is a schematic configuration diagram of the control device 10 of the steering device 100.
The control device 10 detects a steering torque T based on a signal input from the relative angle detection device 20, and supplies the electric motor 110 based on the steering torque T detected by the torque detection unit 210. A target current calculation unit 220 that calculates a target current to be calculated. The target current calculation unit 220 includes a first target current determination unit 225 described later.
In addition, the control device 10 includes a neutral correction value setting unit 250 that sets a neutral correction value ΔV used by the torque detection unit 210 to detect the steering torque T. As will be described later, the neutral correction value setting unit 250 calculates a target current to be supplied to the electric motor 110 so that the deviation between the actual rotational speed of the electric motor 110 and the target rotational speed becomes zero. A determination unit 254 is included.

  In addition, the control device 10 includes a control unit 230 that performs feedback control based on the target current determined by the first target current determination unit 225 or the second target current determination unit 254, and an input to the control unit 230. A switching unit 270 that switches between the output value from the first target current determination unit 225 and the output value from the second target current determination unit 254. In addition, the control device 10 calculates a rotation angle of the electric motor 110 (hereinafter also referred to as “motor angle θ”), and a motor angle θ calculated by the motor angle calculation unit 36. And a motor rotation speed calculation unit 37 that calculates the actual rotation speed of the electric motor 110 (hereinafter also referred to as “actual rotation speed Nma”).

First, the target current calculation unit 220 will be described in detail.
FIG. 12 is a schematic configuration diagram of the target current calculation unit 220.
The target current calculation unit 220 includes a base current calculation unit 221 that calculates a base current that serves as a reference for setting the target current, and an inertia compensation current calculation unit 222 that calculates a current for canceling the moment of inertia of the electric motor 110. And a damper compensation current calculation unit 223 for calculating a current for limiting the rotation of the motor. The target current calculation unit 220 includes a first target current determination unit 225 that determines a target current based on outputs from the base current calculation unit 221, the inertia compensation current calculation unit 222, the damper compensation current calculation unit 223, and the like. ing. Furthermore, the target current calculation unit 220 includes a phase compensation unit 226 that performs phase compensation of the torque signal Td.

  The target current calculation unit 220 receives the torque signal Td, the vehicle speed signal v, and the rotation speed signal Nms from the motor rotation speed calculation unit 37. Since a signal from the vehicle speed sensor 170 or the like is input to the control device 10 as an analog signal, the analog signal is converted into a digital signal by an A / D conversion unit (not shown) and is taken into the target current calculation unit 220.

  The base current calculation unit 221 calculates a base current based on the torque signal Ts in which the torque signal Td is phase-compensated by the phase compensation unit 226 and the vehicle speed signal v from the vehicle speed sensor 170, and information on this base current is obtained. A base current signal Imb including the same is output. For example, the base current calculation unit 221 generates a torque signal detected on a map indicating the correspondence between the torque signal Ts, the vehicle speed signal v, and the base current, which is previously created based on an empirical rule and stored in the ROM 12. The base current is calculated by substituting Ts and the vehicle speed signal v.

  The inertia compensation current calculation unit 222 calculates an inertia compensation current for canceling the inertia moment of the electric motor 110 and the system based on the torque signal Td and the vehicle speed signal v, and generates an inertia compensation current signal Is including information on this current. Output. Note that the inertia compensation current calculation unit 222, for example, displays the torque signal Td on a map indicating the correspondence between the torque signal Td and the vehicle speed signal v and the inertia compensation current, which is previously created based on an empirical rule and stored in the ROM 12. And the inertia compensation current is calculated by substituting the vehicle speed signal v.

  The damper compensation current calculation unit 223 calculates a damper compensation current for limiting the rotation of the electric motor 110 based on the torque signal Td, the vehicle speed signal v, and the motor angular speed ω, and a damper compensation current including information on the current. The signal Id is output. The damper compensation current calculation unit 223, for example, is a map that shows the correspondence between the torque signal Td, the vehicle speed signal v, the motor angular velocity ω, and the damper compensation current that are created based on empirical rules and stored in the ROM 12 in advance. The damper compensation current is calculated by substituting the torque signal Td, the vehicle speed signal v, and the motor angular velocity ω.

  The first target current determination unit 225 outputs the base current signal Imb output from the base current calculation unit 221, the inertia compensation current signal Is output from the inertia compensation current calculation unit 222, and the damper compensation current calculation unit 223. A final target current is determined based on the damper compensation current signal Id, and a target current signal IT1 including information on this current is output. The first target current determination unit 225, for example, previously creates a compensation current obtained by adding the inertia compensation current to the base current and subtracting the damper compensation current based on an empirical rule, and stores the compensation current in the ROM 12. The final target current is calculated by substituting it into a map showing the correspondence between the compensation current and the final target current.

Next, the control unit 230 will be described in detail.
FIG. 13 is a schematic configuration diagram of the control unit 230.
The control unit 230 includes a motor drive control unit 231 that controls the operation of the electric motor 110, a motor drive unit 232 that drives the electric motor 110, and a motor current detection unit 233 that detects the actual current Im that actually flows through the electric motor 110. And have.
The motor drive control unit 231 detects the target current determined by the first target current determination unit 225 or the target current determined by the second target current determination unit 254 and the motor current detection unit 233. A feedback (F / B) control unit 240 that performs feedback control based on a deviation from the actual current Im supplied to the electric motor 110 and a PWM (pulse width modulation) signal for PWM driving the electric motor 110 are generated. And a PWM signal generation unit 260.

The feedback control unit 240 includes a deviation calculating unit 241 for obtaining a deviation between the target current finally determined by the target current calculating unit 220 and the actual current Im detected by the motor current detecting unit 233, and the deviation is zero. A feedback (F / B) processing unit 242 for performing feedback processing.
Deviation calculation section 241 outputs a deviation value between target current signal IT, which is an output value from target current calculation section 220, and motor current signal Ims, which is an output value from motor current detection section 233, as deviation signal 241a.

The feedback (F / B) processing unit 242 performs feedback control so that the target current and the actual current Im coincide with each other. For example, a signal obtained by performing proportional processing on the input deviation signal 241a with a proportional element. Is output, a signal obtained by integration processing by the integration element is output, and these signals are added by an addition operation unit to generate and output a feedback processing signal 242a.
The PWM signal generation unit 260 generates the PWM signal 260a based on the output value from the feedback control unit 240, and outputs the generated PWM signal 260a.

The motor driving unit 232 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.
The motor current detection unit 233 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 232, and converts the detected actual current Im into a motor current signal Ims. And output.

  The motor angle calculation unit 36 calculates the motor angle θ based on the output signal of the resolver provided in the electric motor 110. This motor angle θ is an angle of the rotor (field) with respect to the position of the U-phase armature winding of the electric motor 110. The motor rotation speed calculation unit 37 calculates the actual rotation speed Nma based on the motor angle θ calculated by the motor angle calculation unit 36, converts the calculated actual rotation speed Nma into a rotation speed signal Nms, and outputs it. The signs of the motor angle θ and the actual rotation speed Nma are determined as follows. That is, when the user rotates the steering wheel 101 so that the sign of the steering torque T becomes positive with the force received from the front wheel 150 side being zero, the direction in which the electric motor 110 rotates is determined by the motor angle θ and the actual rotational speed Nma. Plus direction.

Next, the torque detector 210 will be described.
In the electric power steering device 100 configured as described above, the neutral point (zero point) of the relative angle detection device 20 (magnetic sensor 40) is in the normal state (the output from the magnetic sensor 40 when the steering torque T is zero). When the value deviates from the state where the voltage is the midpoint voltage Vc (2.5 V), the steering feeling may be deteriorated. This is because even if the steering wheel 101 is operated and the same steering torque T is applied in the left-right direction, the steering assist force of the electric power steering apparatus 100 is larger on one side and smaller on the other, causing an unbalance in the steering assist force. Because it ends up.

  When the neutral point (zero point) of the relative angle detection device 20 is in a normal state, the deviation (absolute value) from the midpoint voltage Vc of the relative angle detection device 20 is equal to the steering torque T having the same left and right magnitudes. The steering assist force by the electric motor 110 is equal in both the left and right directions and is balanced. On the other hand, when the neutral point (zero point) of the relative angle detection device 20 deviates from the normal state, the output value of the relative angle detection device 20 is neutral even when the steering torque T is zero. The point voltage Vc becomes a different value, and the steering assist force is applied by the electric motor 110 on the assumption that the steering torque T corresponding to the output value is acting. For example, in the case where the output value of the relative angle detection device 20 is the middle point voltage Vc is the steering torque shifted Ta to the right, the steering wheel has a steering wheel T in the range from 0 to Ta in the right direction. Even if 101 is operated in the right direction, the left side steering assist force is applied by the electric motor 110.

In view of such matters, the torque detection unit 210 according to the present embodiment is configured as follows.
The torque detection unit 210 calculates a steering torque T based on a signal input from the relative angle detection device 20, and outputs a torque signal Td obtained by converting the calculated steering torque T into an electric signal to the target current calculation unit 220. Unit 211 and a neutral correction value storage unit 212 for storing the neutral correction value ΔV.
The neutral correction value ΔV is a value set by the neutral correction value setting unit 250 as follows. Before being set by the neutral correction value setting unit 250, the initial value is set to zero. The neutral correction value storage unit 212 is constituted by a part of the area of the EEPROM 14, and the neutral correction value ΔV1 of the first magnetic sensor 41 and the neutral correction value ΔV2 of the second magnetic sensor 42 are written therein. Yes.

When the first magnetic sensor 41 of the magnetic sensor 40 is normal, the output unit 211 includes a first voltage V1 of the first voltage signal V1s from the first magnetic sensor 41 and a neutral correction value storage unit. A steering torque T is calculated based on the neutral correction value ΔV1 stored in 212, and a torque signal Td obtained by converting the calculated steering torque T into an electric signal is output to the target current calculation unit 220.
The following can be exemplified as a method for calculating the steering torque T based on the first voltage V1 and the neutral correction value ΔV1. That is, first, a map indicating the relationship between the corrected voltage V1f obtained by adding the neutral correction value ΔV1 to the first voltage V1 and the steering torque T is stored in the ROM 12, and the torque detector 210 The steering torque T is calculated by substituting the corrected voltage V1f into this map. Alternatively, a function indicating the relationship between the corrected voltage V1f and the steering torque T or a function indicating the relationship between the first voltage V1 and the neutral correction value ΔV1 and the steering torque T is incorporated, and the torque detection unit 210 The steering torque T may be calculated by substituting the first voltage V1 and the neutral correction value ΔV1 into this function.
Note that the output unit 211 outputs the second magnetic sensor 42 from the second magnetic sensor 42 as an emergency when an abnormality occurs in the first magnetic sensor 41 of the magnetic sensor 40 and only the second magnetic sensor 42 is normal. The steering torque T is calculated based on the second voltage V2 of the second voltage signal V2s and the neutral correction value ΔV2 stored in the neutral correction value storage unit 212, and the calculated steering torque T is converted into an electric signal. The signal Td is output to the target current calculation unit 220.

Next, the setting of the neutral correction value ΔV will be described.
In the electric power steering device 100, the neutral point (zero point) of the relative angle detection device 20 is set for each product due to manufacturing variation of components constituting the electric power steering device 100, variation of component fastening, friction generated between components, and the like. May be different.
Therefore, in the electric power steering device 100 according to the present embodiment, the control device 10 includes the neutral correction value setting unit 250, and after the electric power steering device 100 is assembled, or the electric power steering device 100 is assembled to the vehicle. Later, the neutral correction value ΔV was calculated, and the torque detection unit 210 was configured to be writable in the neutral correction value storage unit 212.
The method by which the neutral correction value setting unit 250 calculates the neutral correction value ΔV is as follows.
Based on the output value of the magnetic sensor 40 when the electric motor 110 is rotated in the right direction at a predetermined rotation speed and the output value of the magnetic sensor 40 when the electric motor 110 is rotated in the left direction at the predetermined rotation speed. An intermediate voltage value Vm of the output value is calculated. Then, the neutral correction value ΔV is calculated by subtracting the intermediate voltage value Vm from the midpoint voltage Vc (ΔV = Vc−Vm).

Next, the neutral correction value setting unit 250 will be described in detail.
FIG. 14 is a schematic configuration diagram of the neutral correction value setting unit 250.
The neutral correction value setting unit 250 receives a specific signal from the external device 300 and performs a neutral correction value setting process to be described later with the reception of the specific signal as a trigger, and a target rotational speed Nmt of the electric motor 110. And a target motor rotation speed setting unit 252 for setting. Further, the neutral correction value setting unit 250 calculates a deviation between the target rotation speed Nmt set by the target motor rotation speed setting unit 252 and the actual rotation speed Nma that is the actual rotation speed of the electric motor 110. 253 and a second target current determination unit 254 that calculates a target current to be supplied to the electric motor 110 based on the deviation calculated by the deviation calculation unit 253.
The external device 300 is installed in an assembly factory of the electric power steering apparatus 100, a vehicle production factory or a service factory equipped with the electric power steering apparatus 100, and transmits a specific signal for executing the neutral correction value setting process. Any device can be used.

The target motor rotation speed setting unit 252 determines a target rotation speed Nmt of the electric motor 110 based on the command output from the neutral correction value calculation unit 251, and generates a target rotation speed signal Nmts including information on the target rotation speed Nmt. Output.
The deviation calculation unit 253 calculates an actual rotation speed Nma that is an actual rotation speed of the electric motor 110 calculated by the motor rotation speed calculation unit 37 from the target rotation speed Nmt set by the target motor rotation speed setting unit 252. By subtracting, the deviation between the target rotational speed Nmt and the actual rotational speed Nma is calculated.

  The second target current determination unit 254 determines a target current to be supplied to the electric motor 110 based on the deviation calculated by the deviation calculation unit 253, and outputs a target current signal IT2 including information on this current. Second target current determination unit 254 determines a target current to be supplied to electric motor 110 so that the difference between target rotation speed Nmt and actual rotation speed Nma is zero. More specifically, the second target current determination unit 254 creates the deviation calculated by the deviation calculation unit 253 based on an empirical rule and stores it in the ROM 12 in advance and the deviation of the motor rotation speed and the target current. The target current is calculated by substituting it into a map indicating the correspondence to the above, and this target current is determined as the target current to be supplied to the electric motor 110.

Next, a neutral correction value setting process performed by the neutral correction value calculation unit 251 will be described with reference to a flowchart.
FIG. 15 is a flowchart illustrating the procedure of the neutral correction value setting process performed by the neutral correction value calculation unit 251. The neutral correction value calculation unit 251 executes the neutral correction value setting process when a command is acquired from the external device 300 via the interface provided in the control device 10. Hereinafter, a case where the neutral correction value ΔV1 of the first magnetic sensor 41 of the magnetic sensor 40 is set will be described as an example.

  First, the neutral correction value calculation unit 251 determines whether or not the electric power steering apparatus 100 is in a neutral state (step (hereinafter, simply referred to as “S”) 1501). This is a process for determining whether or not a load is applied from the steering wheel 101 or the front wheel 150. The voltage related to the output value from the magnetic sensor 40 is centered on the midpoint voltage Vc stored in the ROM 12 in advance. It is determined whether or not it is within a predetermined range, and if it is within the predetermined range, it is determined that it is in a neutral state, and if it is outside the predetermined range, it is determined that it is not in a neutral state. And if it is a neutral state (it is Yes at S1501), the switch part 270 will be switched so that the input to the control part 230 may be made into the output value from the 2nd target current determination part 254 (S1502).

Thereafter, a command for setting the rotational speed of the electric motor 110 to the target rotational speed Nmtr in the right direction is sent to the target motor rotational speed setting unit 252 (S1503).
And it is discriminate | determined whether the actual rotational speed Nma which is an actual rotational speed of the electric motor 110 is a predetermined rotational speed area | region of the right direction (S1504). This predetermined rotation speed region in the right direction can be exemplified as being not less than the right target rotation speed Nmtr-5 (rpm) and not more than the right target rotation speed Nmtr + 5 (rpm).

  If the actual rotational speed Nma is in a predetermined rightward rotational speed region (Yes in S1504), the first voltage signal V1s of the first magnetic sensor 41 is read, and the first neutral correction value setting process is performed first. After the actual rotational speed Nma falls within the predetermined rightward rotational speed region (after the first positive determination is made in S1504), the first voltage V1 indicated by the first voltage signal V1s acquired so far is averaged. The right average voltage V1r is calculated (S1505).

Thereafter, in the current neutral correction value setting process, after the actual rotational speed Nma first falls within a predetermined rightward rotational speed region (since an affirmative determination is first made in S1504), a predetermined specified time is set. It is determined whether or not it has elapsed (S1506). If the specified time has not elapsed (No in S1506), the processing after S1503 is performed.
If the actual rotation speed Nma is not in the predetermined rotation speed region (No in S1504), the processes after S1503 are performed.

When the specified time has elapsed (Yes in S1506), a command for setting the rotation speed of the electric motor 110 to the target rotation speed Nmtl in the left direction is sent to the target motor rotation speed setting unit 252 (S1507).
Then, it is determined whether or not the actual rotation speed Nma, which is the actual rotation speed of the electric motor 110, is in a predetermined left rotation speed region (S1508). This predetermined left rotation speed region can be exemplified as being a left target rotation speed Nmtl-5 (rpm) or more and a left target rotation speed Nmtl + 5 (rpm) or less.
If the actual rotational speed Nma is in the predetermined leftward rotational speed region (Yes in S1508), the first voltage signal V1s of the first magnetic sensor 41 is read, and the first neutral correction value setting process is performed first. After the actual rotational speed Nma falls within a predetermined leftward rotational speed region (after the first positive determination is made in S1508), the first voltage V1 indicated by the first voltage signal V1s acquired so far is averaged. The left average voltage V11 is calculated (S1509).

Thereafter, in the current neutral correction value setting process, after the actual rotational speed Nma first falls within the predetermined leftward rotational speed region (since an affirmative determination is first made in S1508), a predetermined specified time is set. It is determined whether or not it has passed (S1510). If the specified time has not elapsed (No in S1510), the processing after S1507 is performed.
If the actual rotational speed Nma is not in the predetermined leftward rotational speed region (No in S1508), the processing from S1507 is performed.

Thereafter, an intermediate voltage value (neutral voltage value) Vm1 (= (V1r + V1l) / 2) between the average voltage V1r in the right direction calculated in S1505 and the average voltage V1l in the left direction calculated in S1509 is calculated (S1511). ).
Then, the neutral correction value ΔV1 (= Vc−Vm1) is calculated by subtracting the intermediate voltage value Vm1 calculated in S1511 from the midpoint voltage Vc of the first magnetic sensor 41 (S1512).
Thereafter, the neutral correction value ΔV1 calculated in S1512 is written in the neutral correction value storage unit 212 of the torque detection unit 210 as a new neutral correction value ΔV1 (S1513).
Thereafter, the switching unit 270 is switched so that the input to the control unit 230 is the output value from the first target current determination unit 225 (S1514).

FIG. 16 is a diagram illustrating a process in which the neutral correction value ΔV1 is set by the neutral correction value setting process.
In S1503, when a command is sent to the target motor rotation speed setting unit 252 to set the rotation speed of the electric motor 110 to the target rotation speed Nmtr in the right direction, the target motor rotation speed setting unit 252 displays FIG. As shown in a), the target rotational speed Nmtr of the electric motor 110 is determined. Then, the second target current determination unit 254 determines the target current to be supplied to the electric motor 110 so that the difference between the target rotation speed Nmtr calculated by the deviation calculation unit 253 and the actual rotation speed Nma becomes zero. As a result, the actual rotational speed Nma of the electric motor 110 changes as shown in FIG.

If the actual rotational speed Nma is in a predetermined rightward rotational speed range (Yes in S1504), the first voltage signal V1s of the first magnetic sensor 41 is read, and the first voltage signal V1s acquired so far is read. Is averaged, and an average voltage V1r in the right direction is calculated (S1505). This process is performed until the specified time elapses after the actual rotational speed Nma is first within a predetermined rightward rotational speed region. As a result, the average voltage V1r in the right direction calculated in S1505 is 2.4 [V] as shown in FIG.
When the electric motor 110 rotates in the right direction, the rotational drive force of the electric motor 110 causes the pinion shaft 106 (yoke 30) to watch against the lower connecting shaft 108 (magnet 21) when viewed in FIG. Rotate in the direction of rotation. Therefore, the magnet 21 (lower connection shaft 108) rotates counterclockwise with respect to the yoke 30 (pinion shaft 106), and the first voltage V1 of the first voltage signal V1s from the first magnetic sensor 41 is It becomes lower than the midpoint voltage Vc.

  After the specified time has elapsed (Yes in S1506), in S1507, a command for setting the rotational speed of the electric motor 110 to the target rotational speed Nmtl in the left direction is sent to the target motor rotational speed setting unit 252. The target motor rotation speed setting unit 252 determines the target rotation speed Nmtl of the electric motor 110 as shown in FIG. Then, the second target current determination unit 254 determines the target current to be supplied to the electric motor 110 so that the difference between the target rotation speed Nmtl calculated by the deviation calculation unit 253 and the actual rotation speed Nma becomes zero. As a result, the actual rotational speed Nma of the electric motor 110 changes as shown in FIG.

  If the actual rotation speed Nma is in a predetermined left rotation speed region (Yes in S1508), the first voltage signal V1s of the first magnetic sensor 41 is read, and the first voltage signal V1s acquired so far is read. Is averaged to calculate a leftward average voltage V1l (S1505). This process is performed until the specified time elapses after the actual rotational speed Nma is first within a predetermined leftward rotational speed region. As a result, the average voltage V11 in the left direction calculated in S1509 is, for example, 2.7 [V] as shown in FIG.

After that, an intermediate voltage value Vm1 between the average voltage V1r = 2.4 [V] in the right direction calculated in S1505 and the average voltage V1l = 2.7 [V] in the left direction calculated in S1509 is Vm1 = It is calculated as (2.4 + 2.7) /2=2.55 [V] (S1511).
Then, the neutral correction value ΔV1 is obtained by subtracting the intermediate voltage value Vm1 = 2.55 [V] calculated in S1511 from the midpoint voltage Vc = 2.5 [V] of the first magnetic sensor 41, and ΔV1 = 2.5−2.55 = −0.05 [V] (S1512).
Thereafter, the neutral correction value ΔV1 = −0.05 [V] calculated in S1512 is written in the neutral correction value storage unit 212 of the torque detection unit 210 as a new neutral correction value ΔV1 (S1513).

  Since the neutral correction value setting unit 250 is configured as described above, in the electric power steering apparatus 100 according to the present embodiment, the manufacturing variation of parts constituting the electric power steering apparatus 100, the fluctuation of component fastening, Even if friction occurs between the parts, the neutral point when the steering torque T is zero can be derived, so that the steering feeling can be improved. Further, since the neutral point when the steering torque T is truly zero can be derived without using a measuring instrument such as a torque meter, the steering feeling can be improved with a simple configuration.

  In the neutral correction value setting process described above, the case where the neutral correction value ΔV1 of the first magnetic sensor 41 is set has been described as an example. However, the process of setting the neutral correction value ΔV2 of the second magnetic sensor 42 is described. Is the same as above, and after the neutral correction value setting process for setting the neutral correction value ΔV1 of the first magnetic sensor 41 is completed, the neutral correction for setting the neutral correction value ΔV2 of the second magnetic sensor 42 is completed. The value setting process may be executed continuously. Alternatively, after starting the execution of the neutral correction value setting process, after writing the neutral correction value ΔV1 in S1513 and before performing the process of S1514, S1503 is used to set the neutral correction value ΔV2 of the second magnetic sensor 42. After the subsequent processing is performed again and the neutral correction value ΔV2 of the second magnetic sensor 42 is written in S1513, the processing of S1514 may be performed to end the neutral correction value setting processing.

  In the neutral correction value setting process described above, in S1506 and S1510, it is first determined whether or not a specified time has elapsed since the actual rotation speed Nma is within the predetermined rotation speed region, and S1505 and S1509. In the above, the average voltage is calculated based on the sensor signal read within the specified time, but it is not particularly limited to such a mode. For example, in S1506 and S1510, it may be determined whether or not the sensor signal read in S1505 and S1509 has reached a predetermined number of times. That is, the average voltage for the specified number of times based on the sensor signal is set as the average voltage V1r in the right direction and the average voltage V1l in the left direction. In addition, the specified number of times is determined when the actual rotational speed Nma is continuously within a predetermined rotational speed region (firstly, when the actual rotational speed Nma is within the predetermined rightward rotational speed region, negative in S1504 or S1508). It may be the number of times). Further, the specified number of times does not necessarily need to be continuous, and may be the number of times that an affirmative determination is made in S1504 or S1508 after the actual rotational speed Nma first falls within a predetermined rightward rotational speed region. Good.

  In addition, the magnetic sensor 40 itself has an EEPROM and outputs it in consideration of the neutral correction value ΔV stored in the EEPROM, and the torque detector 210 calculates the steering torque T according to the output value from the magnetic sensor 40, When the torque signal Td obtained by converting the calculated steering torque T into an electric signal is output to the target current calculation unit 220, the neutral correction value ΔV calculated by the neutral correction value calculation unit 251 is used as the EEPROM of the magnetic sensor 40. It is good to have a configuration that can write to

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Torque detection apparatus, 21 ... Magnet, 30 ... Yoke, 40 ... Magnetic sensor, 41 ... 1st magnetic sensor, 42 ... 2nd magnetic sensor, 100 ... Electric power steering apparatus, 101 ... Steering Wheel (handle), 110 ... electric motor, 210 ... torque detection unit, 220 ... target current calculation unit, 230 ... control unit, 250 ... neutral correction value setting unit

Claims (5)

A relative angle detection means for outputting an electrical signal corresponding to the relative rotation angle of two rotation shafts arranged coaxially;
An electric motor for applying a driving force to one of the two rotating shafts;
Torque detection means for detecting a steering torque based on an output value from the relative angle detection means and a correction value stored in a storage area;
Correction value setting means for setting the correction value;
With
The correction value setting means includes a right output value that is an output value from the relative angle detection means when the electric motor rotates in the right direction at a predetermined rotational speed, and the electric motor in the left direction. An electric power steering apparatus, wherein the correction value is set based on a left output value that is an output value from the relative angle detection means when rotating at a predetermined rotational speed.   The correction value setting means is a reference value that is an intermediate value between the maximum value and the minimum value of the electrical signal output by the relative angle detection means, and an intermediate value between the right output value and the left output value. The electric power steering apparatus according to claim 1, wherein the correction value is set based on a difference from the intermediate output value. First target current determining means for determining a target current to be supplied to the electric motor based on the steering torque detected by the torque detecting means;
Second target current determining means for determining a target current to be supplied to the electric motor so that the rotational speed of the electric motor becomes the predetermined rotational speed;
Supply means for supplying the electric motor with the target current determined by the first target current determining means or the target current determined by the second target current determining means;
Further comprising
The correction value setting means sets the correction value based on an output value from the relative angle detection means when the supply means supplies the electric motor with the target current determined by the second target current determination means. The electric power steering device according to claim 1 or 2, wherein A detection unit that detects a relative rotation angle between two coaxially arranged rotation axes, and a correction value storage unit that stores a correction value for correcting a detection value of the detection unit; A relative angle detection means for outputting an electric signal corresponding to the value after correction with the correction value;
Correction value setting means for setting the correction value;
An electric motor for applying a driving force to one of the two rotating shafts;
With
The correction value setting means includes a right output value that is an output value from the relative angle detection means when the electric motor rotates in the right direction at a predetermined rotational speed, and the electric motor in the left direction. An electric power steering apparatus, wherein the correction value is set based on a left output value that is an output value from the relative angle detection means when rotating at a predetermined rotational speed. A relative angle detection means for outputting an electrical signal corresponding to the relative rotation angle of the two rotation shafts arranged coaxially; an electric motor for applying a driving force to one of the two rotation shafts; An electric power steering apparatus comprising: torque detection means for detecting a steering torque based on an output value from the relative angle detection means and a correction value stored in a storage area; and a correction value setting means for setting the correction value. A setting method for setting the correction value in
Obtaining a right output value that is an output value from the relative angle detection means when the electric motor rotates in the right direction at a predetermined rotation speed,
Obtaining a left output value that is an output value from the relative angle detection means when the electric motor rotates in the left direction at the predetermined rotation speed;
Calculating the correction value based on the right output value and the left output value;
Storing the correction value calculated in the step of calculating the correction value in the storage area;
The setting method characterized by including.

Images