JP2002081961A - Rotary angle detector, brushless motor and motor operated power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary angle detector, a brushless motor and a motor operated power steering system capable of deciding the presence or absence of an own fault in the case of detecting a rotary angle and detecting an auxiliary rotary angle when the fault is detected. SOLUTION: The rotary angle detector comprises a resolver 22 for outputting a signal corresponding to the rotary angle of a rotary shaft 6, a plurality of pairs of poles cooperatively rotated with the shaft 6 and provided on a magnet plate 20 having the shaft 6 as a center, a magnetism detecting element provided on a board 21 to detect magnetism of the pole, a means for comparing a signal t1 corresponding to the rotary angel of the shaft 6 based on the magnetism detected by the detecting element with a signal t2 corresponding to the rotary angle of the shaft 6 output from the resolver 22, and a means for deciding the presence or absence of a fault of the signal t2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation angle detection device for detecting a rotation angle of a rotation shaft, a brushless motor that is driven to rotate based on the rotation angle detected by the rotation angle detection device, and a steering system using the brushless motor. The present invention relates to an assisted electric power steering device.

[0002]

2. Description of the Related Art As a brushless motor used in an electric power steering device, a rotation angle detecting device using a resolver is used for detecting a rotation angle of a rotor. The rotation angle detection device is constituted by a resolver and an R / D converter (resolver signal / digital signal converter), and the resolver outputs a resolver signal corresponding to the rotation angle of the rotor. The signal is converted into a digital signal by the D converter and output. The motor drive circuit is based on the digital signal corresponding to the rotation angle of the rotor,
A magnetic field is generated in the stator of the brushless motor to control the rotation of the rotor.

[0003]

However, according to the rotation angle detecting device described above, the resolver or R
If an abnormality occurs in the / D converter, the rotation angle of the rotor cannot be accurately detected, and the brushless motor may rotate in an unintended direction or may not be able to rotate. There is a need for a rotation angle detection device capable of determining the presence or absence of an abnormality in a signal to be detected.

[0004] Among the rotational position detecting devices, those that determine an abnormality include encoders for detecting the relative position of the phase of the rotating body and magnetic poles for detecting the absolute position of the rotating body, which are mainly used for synchronous machines. A rotation sensor having a position sensor and capable of performing its own failure determination is disclosed in
It is disclosed in Japanese Patent Application Publication No. 160101 and can be applied to detection of a rotation angle of a rotor of a brushless motor and abnormality detection.

However, according to this device, there is no auxiliary means for detecting the rotation angle of the rotor after the abnormality is detected.
The possibility that rotation control of the rotor becomes impossible when an abnormality occurs cannot be solved. Particularly, in a brushless motor used in an electric power steering device, it is necessary to continuously assist the steering even after the abnormality is detected. Therefore, when the abnormality is detected, the rotation angle can be detected auxiliary. It is desirable to have a device.

Therefore, it is conceivable to use two sets of resolvers and R / D converters. In this case, by outputting a signal corresponding to the rotation angle of the rotor by one of the sets during normal times, detecting the rotation angle of the rotor based on the signal, and comparing the signals output from both sets. It is possible to determine the presence or absence of an abnormality, and if an abnormality is detected, output a signal corresponding to the rotation angle of the rotor by the other set, and detect the rotation angle of the rotor based on the signal. However, the resolver and the R / D converter are both expensive, and using two sets of them increases the cost.

The present invention has been made in view of the above circumstances, and has a resolver and a magnetic sensing element.
It is an object of the present invention to provide a relatively inexpensive rotation angle detection device that can determine the presence or absence of abnormality of a signal output by a resolver by comparing signals corresponding to rotation angles of rotation shafts obtained from the respective devices. . If it is determined that there is an abnormality in the signal output by the resolver, a rotating magnetic field of the rotor is generated based on a signal corresponding to the rotation angle of the rotating shaft based on the magnetism detected by the magnetic detection element instead of the resolver. It is an object of the present invention to provide a rotation angle detecting device capable of performing the following. It is another object of the present invention to provide a brushless motor including the rotation angle detection device and an electric power steering device including the brushless motor.

[0008]

According to a first aspect of the present invention, there is provided a rotation angle detection device including a resolver that outputs a signal corresponding to a rotation angle of a rotation shaft. It is characterized by comprising a plurality of pairs of magnetic poles provided on a circumference around a rotation axis, and a magnetic detecting element for detecting the magnetism of the magnetic poles.

According to a second aspect of the present invention, in the rotation angle detecting device according to the first aspect, the first signal corresponding to the rotation angle of the rotation shaft output by the resolver is detected by the magnetic detection element. It is characterized by comprising means for comparing a second signal corresponding to the rotation angle of the rotating shaft based on magnetism, and means for determining whether or not the first signal is abnormal.

According to a third aspect of the present invention, there is provided a rotation angle detecting device according to the second aspect, wherein the first rotation angle detecting device comprises:
Means for outputting the first signal as a normal signal corresponding to the rotation angle of the rotating shaft when the signal is determined to be normal, and means for outputting the second signal when the first signal is determined to be abnormal. Means for outputting a normal signal corresponding to the rotation angle of the rotation shaft.

According to a fourth aspect of the present invention, there is provided a brushless motor including the rotation angle detection device according to the third aspect, wherein the motor is driven to rotate based on a signal output from the rotation angle detection device. I do.

According to a fifth aspect of the present invention, there is provided an electric power steering apparatus comprising a brushless motor which is driven and controlled in accordance with a signal output by the rotation angle detecting device according to claim 3 and steering of a steering means. It is characterized in that steering is assisted by a motor.

In the case of the rotation angle detecting device according to the first aspect of the present invention, since the resolver and the magnetic detecting element are provided, when the resolver breaks down, the magnetism of a plurality of pairs of magnetic poles rotating in conjunction with the rotating shaft is changed to the magnetic field. By detecting the detection element, an auxiliary rotation angle can be detected.

In the case of the rotation angle detection device according to the second invention, the rotation angle detection device according to the first invention corresponds to the rotation angle of the rotation shaft output by the resolver and the relatively durable magnetic detection element. And means for comparing the signals to be performed, and means for determining the presence or absence of an abnormality.
It is possible to determine at a relatively low cost whether there is an abnormality in the signal output by the resolver.

In the case of the rotation angle detection device according to the third invention, in the rotation angle detection device according to the second invention, when it is determined that there is an abnormality in the signal detected by the resolver, instead of the signal output by the resolver, The rotation angle can be detected based on a signal output from the magnetic detection element.

In the case of the brushless motor according to the fourth aspect of the present invention, the apparatus is provided with the rotation angle detecting device according to the third aspect of the present invention,
The output signal from the resolver is determined to be abnormal, and when an abnormality occurs, the rotation angle can be continuously detected based on the output signal from the magnetic detection element. It is possible to avoid the possibility of rotation or inability to rotate.

In the case of the electric power steering apparatus according to the fifth aspect of the present invention, the electric power steering apparatus includes a brushless motor that is driven and controlled in accordance with a signal output from the rotation angle detecting apparatus according to the third aspect of the present invention. Is improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment. FIG. 1 is a block diagram showing a rotation angle detection device according to the present invention. In the figure, reference numeral 2 denotes a rotor of a motor (brushless motor), and the rotation angle detecting device 10 includes a magnet plate 20, a substrate 21, and a resolver 22 provided coaxially with the rotation shaft 6 of the rotor 2. . The substrate 21 and the resolver 22 are connected to a rotation angle calculator 31 and an R / D converter 32, respectively, and both the rotation angle calculator 31 and the R / D converter 32 are connected to a microcomputer 40.

FIG. 2 is a side view of the magnet plate 20 and the substrate 21.
FIG. 3 is a plan view of the magnet plate 20 shown in FIG. 2, and FIG. 4 is a perspective view of the magnet plate 20 shown in FIG. As shown in FIG. 2, on the lower surface of the disk-shaped magnet plate 20 coaxially fixed to the rotating shaft 6, as shown in FIG. Pairs (six poles) of magnetic poles 20a, 20a,... Are arranged in parallel. As shown in FIG. 4, 48 pairs (96 poles) of magnetic poles 20b, 2 are arranged at equal intervals on the peripheral surface of the magnet plate 20.
0b,...

On the lower surface side of the magnet plate 20, a magnet plate 20
A disk-shaped substrate 21 is provided in parallel with an appropriate interval, and the rotation shaft 6 is rotatably penetrated through the center of the substrate 21. The magnetic poles 20a, 20a,
, 20b, 20b,... Are provided with magnetic detecting elements 21a to 21e such as Hall elements or MR elements.

FIG. 5 is a schematic plan view showing the positional relationship between the magnetic sensing elements 21a to 21e on the substrate 21 and the magnet plate 20. The magnetic detection elements 21a to 21c for detecting the magnetic poles 20a, 20a,... Each have a phase of 1/3 of an electric angle formed by the three pairs of magnetic poles 20a ((36 in the spatial angle).
0 ° / 3) / 3) differently, it is attached to the upper surface of the substrate 21 so as to face the lower surface of the magnet plate 20. Further, the two magnetic detecting elements 21d and 21e for detecting the magnetic poles 20b, 20b,... Have a phase of 1/4 (electrical angle of (360
゜ / 48) / 4) Differently, it is attached to the tip of a column erected on the upper surface of the substrate 21 so as to face the peripheral surface of the magnet plate 20.

FIG. 6 is an axial sectional view showing a state where the magnet plate 20 and the substrate 21 shown in FIG. 2 and the resolver 22 are attached to the brushless motor 7. Brushless motor 7
The rotary shaft 6 is supported on both bottoms of a bottomed cylindrical housing 7a by bearings (not shown). An intermediate portion of the rotary shaft 6 has three magnets 20 corresponding to the three pairs of magnetic poles 20a of the magnet plate 20.
A rotor 2 composed of a pair of permanent magnets is coaxially fixed to a rotating shaft 6. A rotor 2 is provided on the inner peripheral surface of the housing 7a.
, A stator 8 composed of three coils is fixed.

The substrate 21 is internally fixed to the bottom between the rotor 2 and one bottom of the housing 7a, and the other surface of the magnet plate 20 faces the rotor 2. A resolver 22 is provided on an outer surface of one bottom of the housing 7a. The rotor 22 a of the resolver 22 is fixed to the rotating shaft 6.

When the rotating shaft 6 of the brushless motor 7 rotates, the magnet plate 20 rotates in conjunction with the rotating shaft 6, and the magnetic detecting elements 21 a to 21 e on the substrate 21 are provided with magnetic poles 20 a, 20 a provided on the magnet plate 20. ,..., 20b, 20b,. The analog signals output from the magnetic detection elements 21 a to 21 e are respectively provided to the rotation angle calculation unit 31 by the lead lines from the substrate 21.

FIG. 7 is a block diagram showing the internal configuration of the rotation angle calculator 31. FIG.
It is a timing chart which shows operation | movement of the signal which a-21e outputs. The analog signals output from the magnetic detection elements 21a to 21c are input to pulse generation circuits 310a to 310c included in the rotation angle calculation unit 31.
As shown in FIGS.
The electrical angle of a differs by 1/3 phase and the spatial angle is 360
The signal is converted into a pulse signal having three periods in ゜. Since the pulse signals are different in phase by ３ from each other, they have six-level resolution for identifying the rotation angle at intervals of a spatial angle of 20 ° (electrical angle of 60 °) and are input to the first decoder 313.

The analog signals output from the magnetic detection elements 21d and 21e are input to pulse generation circuits 310d and 310e provided in the rotation angle calculator 31, and as shown in FIGS. 8 (d) and 8 (e). , Each other magnetic pole 2
The electrical angle of 0b differs by 1/4 phase and the spatial angle is 36
At 0 °, it is converted into a pulse signal having 48 periods and output. The pulse signal is input to a pulse conversion device 311 for performing differentiation or the like, and 64 (= (48) at a spatial angle 120 ° (electrical angle 360 °) as shown in FIG.
/ 3) × 4) It is synthesized and converted into one pulse signal having a period. The pulse signal is input to a counter 312 and counted by counting the number of pulses. The pulse signal is converted into a count signal, output from the counter 312 and input to a first decoder 313.

In the first decoder 313, FIG.
(C), a pulse signal having a six-value resolution is input, and the count value signal is input at each interval (spatial angle 20 ° interval) of the six values of the pulse signal. Two 6-bit signals are generated.
By referring to the rotation angle / digital signal table 314, the 6-bit signal allocates three pairs of magnetic pole positions of the rotor 2 at an electrical angle of 5.625 ° (= 360 ° / 64), and has an electrical angle resolution of 6 °. It is converted into a digital signal having bits.

Further, in the second decoder 315, a predetermined 2-bit digital signal (for example, (00)) is assigned to the lower two digits of the digital signal having the electrical angle resolution of 6 bits, with the upper six digits of the digital signal. The signal is converted into an 8-bit digital signal t1 and input to the microcomputer 40. Also, the second decoder 315
Outputs a reset signal for resetting the count of the counter 312 at every space angle of 20 ° (electrical angle of 60 °), and the reset signal is input to the counter 312.

A resolver signal indicating the output voltage of the resolver 22 is supplied to the R / D converter 32 through a lead from the stator 22b of the resolver 22. R / D converter 32
Converts the resolver signal into a digital signal t2 having an electrical angle resolution of 8 bits (a spatial angle of 120 ° is divided into 256) by referring to a rotation angle / digital signal table 320 provided in the R / D converter 32. 4
Enter 0. The digital signals t1, t2
However, when indicating the rotation angle of the rotation shaft 6, the rotation angle is 0.
The rotation reference positions of the rotating shafts 6 are the same as each other.

The rotation angle detecting device using the magnetic detecting element has a higher durability because of its simple structure as compared with the rotating angle detecting device using the resolver. Therefore, the signal based on the magnetism detected by the magnetic detecting element is used. The microcomputer 40 compares the signal t1 with the signal t2 based on the signal output from the resolver, thereby obtaining the signal t2.
Can be determined whether or not there is an abnormality.

The operation of the microcomputer 40 will be described below with reference to the flowchart shown in FIG.
The microcomputer 40 includes a digital signal t1, output from the rotation angle calculation unit 31 and the R / D converter 32.
t2 is read (S1), and the absolute value t of the difference between the digital signal values of the signals t1 and t2 is calculated (S2). Signal t2
Represents the resolution of the rotation angle of the rotation shaft 6 (120 in space angle).
゜ / 256) is θ, the rotation axis 6 indicated by the signal t1
Is 4θ (120 ° / 6 in spatial angle)
4). Therefore, when the signal t2 is normal, the angle indicated by the difference value t is not less than 0 and not more than 3θ.

The magnitude of the angle indicated by the difference value t and 3θ is compared (S3). If the angle indicated by the difference value t is 3θ or less (YES in S3), the microcomputer 40 sends the signal t2 to the rotor 2 Is output as a normal rotation angle signal (S4). The signal t2 output from the microcomputer 40 is input to the motor drive circuit 5, and the motor drive circuit 5 drives the motor 7 to rotate based on the signal t2.

On the other hand, if the angle indicated by the difference value t is larger than 3θ (NO in S3), the microcomputer 40
Outputs a signal t1 as a normal rotation angle signal of the rotor 2 (S5), and the motor drive circuit 5 rotates the motor 7 based on the signal t1.

Such a rotation angle detection device includes magnetic detection elements 21a to 21e and a resolver 22,
A rotation angle detection device using a magnetic detection element has a higher durability because of a simpler configuration than a rotation angle detection device using a resolver. Therefore, the rotation angle detection device output from the rotation angle calculator 31 and the R / D converter 32 is used. By comparing the signals t1 and t2, it is possible to determine whether or not the signal t2 is abnormal. If it is determined that the signal t2 is abnormal, the signal t1 can be output as a normal rotor rotation angle signal. A relatively inexpensive rotation angle detection device can be realized.

FIG. 10 is a block diagram showing a main configuration of a brushless motor and an electric power steering apparatus according to an embodiment of the present invention. In this electric power steering device, a torque detection signal detected by a torque sensor 50 that detects a torque applied to a steering shaft (not shown) is supplied to a microcomputer 52 via an interface circuit 51, while the vehicle speed is controlled. A vehicle speed signal detected by the detected vehicle speed sensor 60 is provided to the microcomputer 52 via the interface circuit 61.
The motor current flowing when the brushless motor 7 rotates is detected by a motor current detection circuit 57 and is supplied to the microcomputer 52 as a motor current signal.

The microcomputer 52 determines a torque / torque based on the torque detection signal, the vehicle speed signal, and the motor current signal.
By referring to the current table 58, a motor current command value for causing a target current to flow through the brushless motor 7 is created. The microcomputer 52 provides a PWM command value for performing PWM control of the brushless motor 7 and a motor rotation direction instruction signal to the motor drive circuit 5 based on the motor current command value. The power supply voltage of the vehicle-mounted battery P is applied to the motor drive circuit 5, and the applied PWM
The brushless motor 7 for steering assist is rotationally driven based on the command value and the motor rotation direction instruction signal.

The motor drive circuit 5 controls the rotation of the brushless motor 7 based on the rotation angle of the rotor detected by the rotation angle detection device 10 described with reference to FIG. 1 when the brushless motor 7 rotates. When the resolver 22 or the R / D converter 32 is abnormal in the rotation angle detection device 10, the rotation angle is continuously and auxiliaryly detected by the magnetic detection elements 21a to 21e, and the sound / light is detected. The alarm 9 for issuing an alarm is activated.

FIG. 11 is a block diagram showing the configuration of the brushless motor 7 and the motor drive circuit 5. The brushless motor 7 includes a stator 8 in which coils A, B, and C are star-connected, a rotor 2 including three pairs of permanent magnets, and rotating by a rotating magnetic field generated by the coils A, B, and C; A rotation angle detection device 10 for detecting a rotation angle.

The motor drive circuit 5 includes a switching circuit 5
a and a gate control circuit 5b. In the switching circuit 5a, the transistors Q1 and Q2 connected in series between the positive terminal and the ground terminal and the diodes D1 and D2 connected in series in the opposite direction are connected in parallel, and the transistors Q3 and Q4 connected in series And the diodes D3 and D4 connected in series in the reverse direction are connected in parallel, and the transistors Q5 and Q6 connected in series and the diodes D5 and D6 connected in series in the reverse direction are connected in parallel.

The other terminal U of the star-connected coil A is connected to the common connection node of the transistors Q1 and Q2 and the common connection node of the diodes D1 and D2, and the common connection node of the transistors Q3 and Q4 is Diode D
The other terminal V of the star-connected coil B is connected to the common connection node of the transistors Q5 and Q4.
6 and the common connection node of the diodes D5 and D6 are connected to the other terminal W of the star-connected coil C.
Is connected.

The gate control circuit 5b is supplied with the rotation angle of the rotor 2 detected by the rotation angle detection device 10, the rotation direction instruction signal and the PWM command value of the rotor 2 output from the microcomputer 52. Gate control circuit 5
b turns on / off the gates of the transistors Q1 to Q6 in accordance with the rotation angle of the rotor 2 and the rotation direction instruction signal. For example, UV, UW, VW, VU, W-
The path of the current flowing through the stator 8 is switched as in U, WV, and UV to generate a rotating magnetic field.

The gate control circuit 5b controls the on / off of the transistors Q1 to Q6 in accordance with the PWM command value, thereby generating sine-wave voltages in the coils A, B, and C, respectively, and rotating the brushless motor 7. The torque is smoothly increased or decreased. The diodes D1 to D6 are:
This is for absorbing noise generated by turning on / off the transistors Q1 to Q6.

Hereinafter, the operation of the electric power steering apparatus having such a configuration will be described. The microcomputer 52 reads the torque detection signal detected by the torque sensor 50 via the interface circuit 51, and reads the vehicle speed signal detected by the vehicle speed sensor 60 into the interface circuit 61.
Read through. The microcomputer 52 determines a target motor current from the vehicle speed signal and the torque detection signal with reference to a torque / current table 58.

Next, the microcomputer 52 reads the motor current signal from the motor current detection circuit 57,
A difference between the target motor current and the motor current signal is calculated, and a motor current command value is determined based on the calculated difference so that the target motor current flows through the brushless motor 7.

The microcomputer 52 determines a PWM command value and a rotation direction to perform the PWM control of the brushless motor 7 based on the motor current command value.
The WM command value and the instruction signal of the rotation direction are transmitted to the motor drive circuit 5.
Give to. Further, the rotation angle detection device 10 supplies a rotation angle signal to the motor drive circuit 5. The motor drive circuit 5
The drive of the brushless motor 7 is controlled based on the given PWM command value, rotation direction instruction signal, and rotation angle signal.

According to such a brushless motor and electric power steering apparatus, it is possible to prevent the rotor from being unable to rotate, to rotate in an unexpected direction, and the like, and to improve the resistance of the steering means to steering failure.

[0047]

In the case of the rotation angle detecting device according to the first aspect of the present invention, it is possible to use a magnetic detecting element as an emergency rotation angle detecting means when the resolver breaks down. In the case of the rotation angle detection device according to the second aspect of the present invention, the rotation angle detection device includes the resolver and the magnetic detection element, and can determine at a relatively low cost whether there is an abnormality in the signal output from the resolver. In the case of the rotation angle detection device according to the third invention, when it is determined that the signal detected by the resolver is abnormal, the rotation angle is detected based on the signal output by the magnetic detection element instead of the signal output by the resolver. It is possible to do. In the case of the brushless motor according to the fourth invention, it is possible to avoid the possibility that the rotor rotates in an unintended direction, becomes unrotatable, and the like. In the case of the electric power steering device according to the fifth invention, the resistance of the steering means to failure is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a rotation angle detection device according to the present invention.

FIG. 2 is a side view illustrating a configuration of a magnet plate and a substrate included in the rotation angle detection device according to the present invention.

FIG. 3 is a plan view illustrating a configuration of a magnet plate illustrated in FIG. 2;

FIG. 4 is a perspective view illustrating a configuration of a magnet plate illustrated in FIG. 3;

FIG. 5 is a schematic plan view showing a positional relationship between a magnetic detection element according to the present invention and a substrate and a magnet plate.

FIG. 6 is an axial sectional view showing a state in which a magnet plate, a substrate, and a resolver are attached to a brushless motor.

FIG. 7 is a block diagram illustrating an internal configuration of a rotation angle calculation unit included in the rotation angle detection device according to the present invention.

FIG. 8 is a timing chart showing the operation of a signal output by the magnetic detection element according to the present invention.

FIG. 9 is a flowchart illustrating an operation of a microcomputer of the rotation angle detection device according to the present invention.

FIG. 10 is a block diagram illustrating a main configuration of a brushless motor and an electric power steering device according to an embodiment of the present invention.

FIG. 11 is a block diagram illustrating a configuration of a brushless motor and a motor drive circuit.

[Explanation of symbols]

 Reference Signs List 2 rotor 5 motor drive circuit 6 rotating shaft 7 motor (brushless motor) 8 stator 9 alarm 10 rotation angle detection device 20 magnet plate 21 substrate 21a to 21e magnetic detection element 22 resolver 31 rotation angle calculation unit 32 R / D converter 40 Microcomputer

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Claims (5)

[Claims] 1. A rotation angle detection device including a resolver that outputs a signal corresponding to a rotation angle of a rotation shaft, wherein the plurality of pairs are rotated on the rotation shaft and provided on a circumference around the rotation shaft. And a magnetic detection element for detecting the magnetism of the magnetic pole. 2. A first signal corresponding to a rotation angle of the rotating shaft output from the resolver, and a second signal corresponding to a rotating angle of the rotating shaft based on magnetism detected by the magnetic detecting element.
2. The rotation angle detection device according to claim 1, further comprising: means for comparing the first signal with a signal; and means for determining whether or not the first signal is abnormal. 3. When it is determined that the first signal is normal,
Means for outputting the first signal as a regular signal corresponding to the rotation angle of the rotary shaft; and, when the first signal is determined to be abnormal, the second signal corresponding to the rotation angle of the rotary shaft. 3. A rotation angle detecting device according to claim 2, further comprising means for outputting a normal signal. 4. A rotation angle detection device according to claim 3, wherein the rotation angle detection device outputs a signal based on a signal output from the rotation angle detection device.
A brushless motor characterized by being driven to rotate. 5. A brushless motor that is driven and controlled based on a signal output by the rotation angle detection device according to claim 3 and steering of a steering unit, and assists steering by the brushless motor. An electric power steering device characterized by the above-mentioned.