JP2000224885A - Position-detecting device of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the position detector of a motor with a simple configuration and a high detection system. SOLUTION: A magnetization part 95d of a ring magnet 95 is magnetized with strength in the rotary direction of a motor for arranging so that parts adjacent to the magnetization part 95d have different polarities. Comparators OP1, OP2, and OP3 detect the absolute position of the motor based on the polarity of the magnetization part 95d being detected by Hall elements 64U, 64V, and 64W, and at the same time a comparator OP4 detects the relative position of the motor based on the strength of the magnetization of the detected magnetization part 95d, thus accurately detecting the position of the motor by using the output of the comparators OP1-OP4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for magnetically detecting the position of a motor.

[0002]

2. Description of the Related Art Conventionally, in an electric vehicle, a motor drive device for a vehicle is provided, and the motor is driven by supplying current to the motor from a battery mounted on the vehicle. Among them, a wheel motor type electric vehicle is provided with a motor for each wheel, and travels by transmitting rotation generated by each motor to driving wheels.

[0003]

In this wheel motor type electric vehicle, a motor is housed in a wheel.
Although it has the advantage of high efficiency without transmission loss, it has a problem that the unsprung weight becomes heavy to accommodate the motor, and it is difficult to improve the riding comfort. For this reason, the weight reduction of the motor is the biggest issue for the practical use of the wheel motor type electric vehicle.

A DC brushless motor is generally used as the wheel motor. To drive the DC brushless motor, it is necessary to detect a rotational position and excite a coil. Here, in order to control the DC brushless motor with high efficiency, it is required to perform position detection with high accuracy. However, in order to increase the accuracy, it is necessary to increase the number of sensors and the like, and the structure is complicated. And the weight increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a motor position detector having a simple configuration and a high detection accuracy.

[0006]

According to a first aspect of the present invention, a plurality of permanent magnets are arranged on one of a rotor and a stator so that polarities different from each other are adjacent to each other, and a magnetic detection sensor is provided on one of the other. Attachment, in a motor position detection device that detects the direction of the magnetic flux passing through the detection unit of the magnetic detection sensor in a specific direction and detects the relative position of the rotor with respect to the stator, the permanent magnet, the magnitude of the magnetic flux density It is formed so that it occurs alternately in the arrangement direction,
Binarization means for binarizing the magnitude of the magnetic flux density detected by the magnetic detection sensor with a threshold value, a direction of the magnetic flux detected by the magnetic detection sensor, and the binarized signal. And a computing device for detecting a relative position of the rotor with respect to the stator in each of the permanent magnets based on the calculation.

A second aspect of the present invention is characterized in that, in the first aspect, the permanent magnet formed so that the magnitude of the magnetic flux density alternately occurs is formed by the strength of magnetization.

According to a third aspect of the present invention, in the position detecting device for magnetically detecting the position of a motor, a permanent magnet, a portion forming a magnetic path by the permanent magnet, and a portion not forming a magnetic path are provided. A rotating body that rotates together with the output shaft of the motor, the rotating body having a portion where the magnetic flux is easily formed and a portion that hardly passes a magnetic flux at a portion forming the magnetic path; and a magnetic flux at the portion forming the magnetic path is detected. A plurality of magnetic detection sensors, a first position detector for detecting a position of a motor based on a magnetic flux of a portion forming the magnetic path detected by the magnetic detection sensors, and a magnetic sensor detected by the magnetic detection sensors. It is a technical feature of the present invention to include a second position detector that detects a position of the motor based on a change in magnetic flux between a portion where a magnetic flux of a portion forming a path easily passes and a portion where the magnetic flux does not easily pass.

According to a fourth aspect of the present invention, in the third aspect, the second position detector includes a portion where the magnetic flux of the portion forming the magnetic path detected by each magnetic detection sensor is easy to pass and a portion where the magnetic flux is difficult to pass. The technical feature is that the position of the motor is detected by selecting a detection signal based on the change in magnetic flux of the motor.

According to the first aspect of the present invention, the permanent magnets are formed so that the magnitude of the magnetic flux density is generated alternately in the arrangement direction, and the permanent magnets are arranged such that different polarities are adjacent to each other. Then, the arithmetic unit detects the relative position of the rotor with respect to the stator based on the direction of the magnetic flux of the permanent magnet detected by the magnetic detection sensor and the magnitude of the magnetic flux density binarized by the binarizing means. That is, since each permanent magnet is detected in the direction of the magnetic flux and the position of the motor is detected based on the magnitude of the magnetic flux density of one permanent magnet, it has a higher resolution than detection in the direction of the magnetic flux. . Therefore, the position of the motor can be detected with high accuracy by using the direction of the magnetic flux and the magnitude of the magnetic flux density.

According to the second aspect of the present invention, the permanent magnet formed so that the magnitude of the magnetic flux density alternately occurs is formed by the strength of the magnetization, and thus can be easily formed.

According to the third aspect of the present invention, a rotating body provided with a portion where a magnetic path is formed by a permanent magnet and a portion where a magnetic path is not formed is used. Then, portions where the magnetic flux is easily formed and portions where the magnetic flux is not easily passed are provided at portions where the respective magnetic paths of the rotating body are formed. Then, the first position detector detects the position of the motor based on the magnetic flux of the portion forming the magnetic path detected by the magnetic detection sensor, and the second position detector is detected by the magnetic detection sensor. The position of the motor is detected based on a change in magnetic flux between a portion where a magnetic path is formed and a portion where the magnetic flux is difficult to pass. That is, the first position detector detects a portion forming each magnetic path, and the second position detector detects a portion where a magnetic flux easily passes through and a portion that does not easily pass through the portion forming one magnetic path. Therefore, it has higher resolution than the first position detector. Therefore, the position of the motor can be detected with high accuracy by using the first and second position detectors.

According to the third aspect of the present invention, when only one magnetic detection sensor is used to detect a part forming a magnetic path, the one magnetic detection sensor corresponds to a part not forming a magnetic path. In this case, it is impossible to detect a portion through which the magnetic flux easily passes and a portion through which the magnetic flux does not easily pass. For this reason, in claim 4, by using a detection signal based on a change in magnetic flux between a portion where magnetic flux is easily detected and a portion where magnetic flux is difficult to pass, the detection signal is selected by using a detection signal. A second position detector detects the motor position. This makes it possible to detect the position of the motor with high accuracy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wheel motor provided with a detection device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a wheel motor 10 according to an embodiment of the present invention, and FIG. 2 is a sectional view of a main part of the wheel motor 10 shown in FIG. As shown in the figure,
The drive unit case 11 has a two-part structure including two dish-shaped first and second casings 12 and 13 disposed inside and outside the vehicle. By connecting the first and second casings 12 and 13 with bolts (not shown), a motor chamber 15 having a substantially circular cross section is formed between the first and second casings 12 and 13. You. The motor chamber 15 houses a motor 24. The drive device case 11 is attached to a chassis of the vehicle via a wishbone type suspension device (not shown).

A planetary gear unit 31 as a transmission gear device is disposed radially inward of the motor 24.
The rotation of the motor 24 is reduced by a factor of 7.2 by the planetary gear unit 31 and output to the output shaft 38.
A wheel hub 39 is connected to the output shaft 38. A wheel disk 45 is fixed to the outer periphery of the flange 39b of the wheel hub 39 by a bolt b2. The wheel disc 45 has a cup-like shape, and includes a flat bottom 45a and a cylindrical portion 45b integrally formed on the outer periphery of the bottom 45a, and an outer edge of the cylindrical portion 45b. Is fixed to the tire 47.

FIG. 2 shows the structure of this wheel motor.
This will be described in more detail with reference to FIG. Second casing 13
An opening is formed at the center of the wheel hub 39, and the sleeve portion 39a of the wheel hub 39 is inserted into the opening.
Is rotatably supported by the bearing 40 with respect to the second casing 13. Then, the sleeve portion 39a
An output shaft 38 is provided in the inside, and the sleeve portion 39a and the output shaft 38 are spline-engaged. A flange portion 38a is integrally formed at an outer end portion of the output shaft 38, a screw portion 38b is formed at an inner end portion of the output shaft 38, and a nut 42 is screwed to the screw portion 38b. The output shaft 38 and the wheel hub 39 are prevented from moving in the axial direction with respect to each other. In addition, the motor chamber 1 is provided through the opening.
A seal 59 is provided between the opening and the sleeve portion 39a so that the oil inside 5 does not leak out of the drive device case 11.

The stator 25 of the motor 24 in the motor chamber 15 is fixed to the cylindrical portion 12a of the first casing 12 by bolts bll. The stator 25 includes a stator core 25a and a stator coil 26 wound around the stator core 25a. A rotor 27 is rotatably disposed inside the stay core 25a in the radial direction with a predetermined gap (gap) therebetween with respect to the drive device case 11. The rotor 27 includes a rotor shaft 21, a rotor hub 29 fixed to the rotor shaft 21, and a rotor core 30 fixed to an outer peripheral edge of the rotor hub 29.
And permanent magnets 50 are arranged at a plurality of locations in the circumferential direction of the rotor core 30.

The outer end of the rotor shaft 21 is rotatably supported by the bearing 28 with respect to the first casing 12, and the inner end of the rotor shaft 21 is connected to the flange 38a of the output shaft 38. Is rotatably supported by a bearing 33.

As described above, the planetary gear unit 31 as a transmission gear device is provided radially inward of the motor 24.
Is arranged. In this case, since the motor 24 and the planetary gear unit 31 are overlapped in the axial direction, the axial dimension of the vehicle motor drive device can be reduced. The planetary gear unit 31 is rotatably supported by the sun gear S and the ring gear R spline-engaged with the rotor shaft 21, the carrier CR formed by the flange portion 38a, and the sun gear S. S and a gear element of a pinion P meshed (engaged) with the ring gear R,
The rotation generated by the motor 24 is the sun gear S
And the reduced rotation is output to the output shaft 38. The ring gear R is connected to the second casing 13
Gear flange 14 fixed by bolts bl
Fixed to

In order to detect the rotation speed of the rotor 27, an annular projection 94 is formed at a predetermined position of the rotor 27, and the inner periphery of the annular projection 94 is magnetized in correspondence with the permanent magnet 50. A ring magnet 95 is provided. And
A detection device 62 that detects the rotational position of the rotor 27 is provided in the drive device case 11 so as to face the ring magnet 95. The detection device 62 is fixed to the first casing 12 by a bolt (not shown).

FIG. 3 shows the ring magnet 95 and the detecting device 62.
FIG. 3 is a diagram showing the correspondence relationship with the arrow A in FIG. 2.
The ring magnet 95 is formed by forming a resin containing a magnetic material such as soft iron into a cylindrical shape. The ring magnet 95 has twelve magnetized portions 95d in accordance with the polarities of the twelve permanent magnets 50. Here, by applying a strong magnetic field to the soft iron included in the ring magnet 95, the magnetized portion 95 shown in FIG.
d is formed. That is, by providing the 12-pole magnetized portion 95d such that the mechanical angle of 60 degrees shown in the drawing corresponds to the electrical angle of 360 degrees from the N pole to the N pole, the permanent magnet 50 of the motor 24 is provided. Respectively. here,
Each of the magnetized portions 95d is magnetized so as to have strength relative to the rotation direction of the motor.

The detection device 62 for detecting the magnetized portion 95d is provided with three Hall elements 64U, 64V and 64W. That is, the Hall elements 64U, 64V, 6
The lower surface of the 4W faces the inner periphery of the ring portion 95b of the ring magnet 95, and detects the polarity of the magnetized portion 95d.

The Hall elements 64U, 64V, 64W are:
The motors 24 are arranged at intervals of 10 mechanical angles. That is, as described above, the motor 24 has a mechanical angle of 60
Since the degree is set to the electrical angle of 360 degrees, the Hall elements 64U, 64V, and 64W are arranged at the electrical angle of 60 degrees. In the first embodiment, the output is inverted by attaching the central Hall element 64V of the three Hall elements to the other two magnetic detection sensors 64U and 64W in the opposite detection direction. . That is, since the output waveform is inverted by inverting and arranging the center Hall element 64V, the outputs of the Hall elements 64U, 64V, and 64W do not become the same regardless of the position of the rotor. For this reason, the presence or absence of a failure can be determined by detecting the same output.

As described above, in the present embodiment, each magnetized portion 95d of the ring magnet 95 is magnetized so as to be strong or weak in the rotation direction of the motor. A magnetizing device for magnetizing in this way will be described with reference to FIG. FIG.
Shows a plan view of the magnetizing device 97. The magnetizing device 9
7 includes a pair of ring portions 97b and 97a that can accommodate the ring portion 95b of the ring magnet 95. The ring portions 97b and 97a are provided with N-pole magnetized portions 97N for performing N-polar magnetization and S-magnetized portions 97S for performing S-polar magnetization alternately. I have. Further, a groove 97c in the rotation axis direction of the motor is formed on the inner periphery of the outer ring portion 97b.
On the outer periphery of 7a, a groove 97d in the direction of the rotation axis of the motor is formed.

Here, when the ring magnet 95 is magnetized by the magnetizing device 97, a strong current flows through a coil (not shown) so that the N-pole magnetized portion 97N and the S-magnetized portion 97S become strong. A magnetic flux is generated, and as shown in FIG.
forming d. At this time, the passage of the generated magnetic flux to the ring magnet 95 is prevented by the groove 97c of the ring portion 97b and the groove 97d of the ring portion 97a, and in each magnetized portion 95d, the magnetization of the portion corresponding to the groove is weak. Magnetization of a portion not corresponding to the groove is increased. That is, the magnetized portion 95d is magnetized with the strength of the rotation direction of the motor. In this embodiment, the magnetization of the ring magnet 95 and the magnetization of the permanent magnet 50 are performed separately, but they can be performed simultaneously.

FIG. 5 shows a wheel motor 10 according to this embodiment.
And a control device 70. A detection signal from the detection device 62 disposed on the wheel motor 10 is input to the control device 70 via three signal lines 65U, 65V, and 65W. The control device 70 detects the relative position between the rotor 27 and the permanent magnet 50 based on the detection signal, and outputs the stator coil 26 via power lines 72U, 72V, 72W.
By exciting (see FIG. 2), the wheel motor 10 is driven.

Here, the operation of the control device 70 for detecting the position of the motor based on the signal from the detection device 62 will be described with reference to FIG.
This will be described with reference to FIG. FIG. 6A shows output waveforms of the Hall elements 64U, 64V, and 64W. This output waveform is +5 through a waveform amplification circuit (not shown).
V and -5V. Here, the Hall element 64
U and 64W output + 5V when detecting the magnetized portion 95d magnetized to the N polarity of the ring magnet 95, and output -5V when detecting the magnetized portion 95d magnetized to the S pole. Is output. On the other hand, as described above, the Hall element 64V, which is disposed to be inverted with respect to the Hall elements 64U and 64W, outputs -5V when detecting the magnetized portion 95d magnetized to the N polarity, and outputs S-5V. When the magnetized portion 95d magnetized at the pole is detected, + 5V is output. As described above, the magnetized portion 95
Since d is magnetized so as to be strong or weak with respect to the rotation direction of the motor, each output waveform oscillates in a wave shape.

The Hall elements 64U and 64 shown in FIG.
V, 64W output waveform is the comparator OP shown in FIG.
Waveforms shaped by 1, OP2, OP3 (absolute position signal)
Is shown in FIG. 6 (B). Comparators OP1, OP2, O
The inverting input terminal of P3 is connected to ground. The comparators OP1, OP2, OP3 output "high level" when a potential exceeding 0 V is applied to the non-inverting input terminal, and output "low level" when a potential lower than 0 V is applied. I do. Based on the absolute position signal, the arithmetic unit 74 of the control device 70 detects the absolute position of the motor.

FIG. 6C shows a waveform obtained by shaping the output waveform of the Hall element 64W shown in FIG. 6A by the comparators OP3 and OP4. The output waveform of the Hall element 64W is applied to the inverting input terminal of the comparator OP4, and the output waveform of the Hall element 64W is shaped to the non-inverting input terminal by the comparator OP3, divided by the resistors R1 and R2, and input. Is done. Using this divided potential as a threshold,
The comparator OP4 outputs a pulse (relative position pulse) corresponding to the wave-like swing of the output waveform of the Hall element 64W, that is, the magnitude of magnetization at the magnetized portion 95d of the ring magnet 95. By combining the absolute position signal with the relative position pulse, the arithmetic unit 74 can obtain high position accuracy and drive the wheel motor 10 with high efficiency. That is, by counting the number of pulses from the time when the absolute position signal has changed, a finer position can be detected.

Here, in this embodiment, since the configuration can be made without increasing the number of sensors and detection magnets, the rotational position can be detected with high accuracy without increasing the weight of the wheel motor, that is, the sprung weight. It is possible to do.
Furthermore, since the number of sensors is not increased, only three signal lines from the Hall element are required, the probability of occurrence of disconnection does not increase, and the reliability of the wheel motor does not decrease. In particular, as described above, the Hall elements 64U, 64V, 64W
By arranging in degrees, the detection device 62 is configured to be small and lightweight, so that the unsprung weight does not increase.

Next, a wheel motor according to a second embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the ring magnet 95 magnetized on the north pole and the south pole is attached to the rotor hub 29 of the motor 24. On the other hand, in the second embodiment, the rotor hub 29
The extension portion 29b is provided in itself to detect the position of the motor 24.

FIG. 8 shows the structure of the wheel motor, and FIG.
FIG. 8 shows a view of the rotor hub 29 in FIG. The rotor hub 29 is provided with a circumferential groove 29a, and the circumferential groove 2a is provided at a position corresponding to the N pole of the first embodiment.
A pair of extending portions 29b opposed to each other via 9a is provided. Here, the detection device 162 includes a Hall element 164.
8, a magnet 178 is provided, and a pair of extending portions 29b are provided at positions where the magnet 178 is provided as shown in FIG.
Is approaching, a magnetic path M is formed via the extending portion 29b, and the Hall element 164U detects this. Grooves 2 in the direction of the rotation axis of the motor are provided on the inner and outer circumferences of the extension 29b.
9c is formed. The groove 29c forms a portion that is difficult to pass through the magnetic path M. That is, in the extending portion 29b,
The portion where the groove 29c is not formed is easy for the magnetic flux of the magnetic path M to pass, and conversely, for the groove 29c, the magnetic flux is difficult to pass.

In the second embodiment, as in the first embodiment, the extension 29b is disposed at a mechanical angle of 60 degrees (electrical angle of 360 degrees).
64U, 164V, 164W (not shown) have a mechanical angle of 2
It is arranged at 0 degrees (120 degrees electrical angle).

Here, the operation of the controller 70 for detecting the position of the motor based on the signal from the detector 62 will be described with reference to FIG.
This will be described with reference to FIG. FIG. 10A shows output waveforms of the Hall elements 164U, 164V, and 164W. Here, the Hall elements 164U, 164V, 1
The 64 W outputs +5 V when the magnetic path M from the magnet 178 is detected, and outputs −5 V when the magnetic path M from the magnet 178 is not opposed to the extended portion 29 b. As described above, the extending portion 29b is provided in the groove 29 which is horizontal with respect to the rotation direction of the motor.
c is formed, and a portion through which magnetic flux easily passes and a portion through which magnetic flux does not easily pass are formed. For this reason, the waveform on the + 5V side fluctuates in a wave shape.

The Hall element 164U shown in FIG.
FIG. 10B shows a waveform (absolute position signal) obtained by shaping the output waveforms of 164 V and 164 W by the comparators OP1, OP2, and OP3 shown in FIG. The control device detects the absolute position of the motor based on the absolute position signal.

FIG. 10C shows a waveform (output of the comparator OP5) obtained by shaping the output waveform of the Hall element 164W shown in FIG. 10A by the comparators OP3 and OP5. Similarly, the comparators OP6 and OP7
Are shown in FIG. 10 (C). Comparator OP5,
OP6 and OP7 are Hall elements 164U, 164V, 1
While +5 V is output from 64 W, a pulse (relative position pulse) corresponding to the groove 29 c of the extending portion 29 b is output intermittently.

As described above with reference to FIG.
The comparators OP5, OP6, OP7 output relative position pulses intermittently. For this reason, the selection circuit 180
By selecting the outputs of the comparators OP5, OP6, and OP7 according to the +5 V outputs from the comparators OP1, OP2, and OP3, continuous relative position pulses are output (see FIG. 10D). By combining the absolute position signal with the relative position pulse, the control device can obtain high position accuracy and drive the wheel motor with high efficiency. Further, by counting the number of pulses from the time when the absolute position signal changes, a finer position can be detected.

Here, in the second embodiment, since the configuration can be made without increasing the number of sensors and detection magnets, the rotational position can be adjusted with high accuracy without increasing the weight of the wheel motor, ie, the weight of the spring. It becomes possible to detect. Further, in the second embodiment, there is no need to separately attach the ring magnet 95, so that there is an advantage that the mechanical configuration can be simplified.

In the above-described embodiment, the Hall element is used as the magnetic detection sensor. However, various magnetic detection sensors such as a magnetic thin film may be used. In the above-described embodiment, an example in which the configuration of the present invention is used for detecting the position of a motor has been described. However, the position detecting device of the present invention can detect the positions of various types of rotating bodies.

[Brief description of the drawings]

FIG. 1 is a sectional view of a wheel motor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of the wheel motor shown in FIG.

FIG. 3 is a view of the ring magnet in FIG.

FIG. 4 is a plan view of a magnetizing device for magnetizing a ring magnet.

FIG. 5 is an explanatory diagram of a wheel motor and a control device.

FIG. 6 (A) is an output waveform diagram of a Hall element,
FIGS. 6B and 6C are output waveform diagrams of the comparator.

FIG. 7 is a block diagram of a waveform shaping circuit of the position detector according to the first embodiment.

FIG. 8 is a sectional view of a wheel motor according to a second embodiment of the present invention.

FIG. 9 is a view of the rotor hub in FIG. 8 as viewed from an arrow D side.

10A is an output waveform diagram of a Hall element, FIGS. 10B and 10C are output waveform diagrams of a comparator, and FIG. 10D is a diagram of a selection circuit. It is an output waveform diagram.

FIG. 11 is a block diagram of a waveform shaping circuit of the position detector according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Wheel motor 11 Drive case 24 Motor 25 Stator 27 Rotor 29 Rotor hub (rotary body) 29b Extension part (part which forms a magnetic path) 29c Groove (part where magnetic flux does not easily pass) 62 Detector 70 Control unit 74 Arithmetic unit 64U , 64V, 64W Hall element (magnetic detection sensor) 95 Ring magnet 95d Magnetized part (permanent magnet) 180 Selection circuit (second position detector) OP1, OP2, OP3 Comparator OP4 Comparator (Binarization means)

Claims (4)

[Claims] 1. A method according to claim 1, wherein one of the rotor and the stator is
A plurality of permanent magnets are arranged so that different polarities are adjacent to each other, and a magnetic detection sensor is attached to one of the other permanent magnets, and a direction of a magnetic flux passing in a specific direction through a detection unit of the magnetic detection sensor is detected. In the motor position detecting device for detecting the relative position of the permanent magnet, the permanent magnet is formed so that the magnitude of the magnetic flux density alternately occurs in the arrangement direction, and the magnitude of the magnetic flux density detected by the magnetic detection sensor Means for binarizing the rotor with a threshold value, the direction of the magnetic flux detected by the magnetic detection sensor, and the stator of the rotor in an individual permanent magnet based on the binarized signal. And a calculating device for detecting a relative position with respect to the motor. 2. The motor position detecting device according to claim 1, wherein the permanent magnet formed so that the magnitude of the magnetic flux density alternately occurs is formed by the strength of magnetization. 3. A position detection device for magnetically detecting a position of a motor, comprising: a permanent magnet; a portion forming a magnetic path by the permanent magnet; and a motor output shaft provided with a portion not forming a magnetic path. A rotating body having a portion that forms a magnetic path and a portion that easily passes magnetic flux and a portion that does not easily pass a magnetic flux, and a plurality of magnetic detection sensors that detect magnetic flux of the portion that forms the magnetic path. A first position detector for detecting a position of a motor based on a magnetic flux of a part forming the magnetic path detected by the magnetic detection sensor; and a part forming the magnetic path detected by the magnetic detection sensor. A second position detector for detecting a position of the motor based on a change in magnetic flux between a portion through which the magnetic flux easily passes and a portion through which the magnetic flux does not easily pass. 4. The second position detector selects a detection signal based on a change in magnetic flux between a portion where the magnetic flux is easily detected and a portion where the magnetic flux is difficult to pass, which is detected by each magnetic detection sensor. The motor position detecting device according to claim 3, wherein the position of the motor is detected.