JP2012205355A - Motor - Google Patents

Abstract

A rotational position is detected with high accuracy while suppressing a dimensional limitation of a rotor in the radial direction and a decrease in torque performance.
A motor includes a stator that generates a rotating magnetic field by energizing a winding, and a rotor that rotates in synchronization with the rotating magnetic field. The motor includes a position detection magnet embedded in the rotor so that the magnetic poles are reversed at predetermined first angles along the circumferential direction of the rotor core, and the magnetic flux generated from the magnetic poles leaks to the outside of the rotor. And a magnetic flux detection means provided on the stator side for detecting magnetic flux leaking from the position detection magnet to the outside of the rotor.
[Selection] Figure 1

Description

  Embodiments described herein relate generally to a motor that rotates in synchronization with a rotating magnetic field.

  In order to detect the position (rotational position) of the rotor of the motor, a magnetic or optical encoder, a resolver, or the like is used. Further, in a permanent magnet motor provided with a permanent magnet for generating a driving main magnetic flux, the rotational position can be detected by detecting the magnetic flux of the permanent magnet. Further, in recent years, the rotational position is estimated based on the motor voltage information or the motor current information without using such position detecting means.

JP 2006-191738 A

  Of the various position detection methods described above, when position detection means such as an encoder or resolver is employed, the structure becomes complicated and the number of parts increases, resulting in an increase in the number of assembly steps. Further, since these position detecting means are arranged on the inner peripheral side of the rotor, the inner diameter of the rotor is increased, and the thickness of the rotor core in the radial direction is limited. For example, in a reluctance motor, the d-axis reluctance is increased, the q-axis reluctance is decreased, and the reluctance torque is generated by utilizing the gap magnetic flux density difference between the d-axis and q-axis portions of the rotor core and the stator. I am letting. However, if the radial thickness of the rotor core is limited, the reluctance torque is reduced because the q-axis magnetic path is narrowed.

  Further, when detecting the magnetic flux of the driving permanent magnet, the distance between the adjacent magnetic poles of the permanent magnet is wide, making it difficult to detect the position with high accuracy. Further, in the case of sensorless driving, there are problems that the estimation accuracy decreases when the load suddenly changes, or the position cannot be estimated during start-up and low-speed rotation.

  Therefore, a motor capable of detecting a rotational position with high accuracy while suppressing a dimensional limitation of the rotor in the radial direction and a decrease in torque performance is provided.

  The motor of the embodiment is a motor including a stator that generates a rotating magnetic field by energizing a winding, and a rotor that rotates in synchronization with the rotating magnetic field. The motor includes a position detection magnet embedded in the rotor so that the magnetic poles are reversed at predetermined first angles along the circumferential direction of the rotor core, and the magnetic flux generated from the magnetic poles leaks to the outside of the rotor. And a magnetic flux detecting means provided on the stator side for detecting magnetic flux leaking from the position detecting magnet to the outside of the rotor.

The top view which shows the state which combined the stator and rotor by 1st Embodiment The perspective view which shows the state which combined the stator and the rotor A longitudinal side view showing a part cut along the line AA in FIG. 1 including the rotating shaft. The figure which shows the example of arrangement of a division magnet (A) The figure which shows the hysteresis characteristic of a Hall sensor, and (b) The wave form diagram which matches and shows magnetic flux density and signal Hs Schematic explanatory drawing which shows the arrangement of divided magnets and signal Hs in association with each other (A) Partial plan view and (b) Partial perspective view showing a state where the stator and the rotor are combined when the position detection magnets are continuously arranged Diagram showing magnetic flux density detected by Hall sensor with respect to rotation position FIG. 3 equivalent view according to the second embodiment

(First embodiment)
The first embodiment will be described with reference to FIGS. 1 and 2 show a state in which a stator and a rotor are combined in a permanent magnet motor. FIG. 3 is a partial vertical side view showing a part cut along the line AA in FIG. 1 in a state in which the rotating shaft is further fitted. The permanent magnet motor 1 (hereinafter referred to as a motor) is an inner rotor type flat motor, and is used, for example, as a vehicle driving motor.

  The iron core 3 (stator iron core) of the stator 2 has an annular yoke portion 4 and a large number of teeth 5 provided so as to protrude toward the inner peripheral side, and is a magnetic steel sheet punched into the shape, for example, silicon A large number of steel plates are laminated. A winding 6 is wound around the tooth 5. Although not shown, the stator core 3 is fixed in a frame formed in a flat bottomed cylindrical shape. The rotor 7 has a rotor core 8 formed by laminating a plurality of silicon steel plates punched in an annular shape, and a rotating shaft 9 that is rotatably supported by a bearing (not shown). The rotor 7 rotates with a slight gap between its outer peripheral surface and the teeth 5 of the stator 2.

  On the outer peripheral side of the rotor core 8, a plurality of pairs (for example, ten pairs) of magnet insertion holes 10 whose separation distance increases toward the outer peripheral side are provided at regular intervals in the circumferential direction. The magnet insertion hole 10 penetrates the rotor core 8 in the stacking direction, and a permanent magnet 11 for driving is embedded in the magnet insertion hole 10.

  The pair of magnet insertion holes 10 are arranged in a V shape when viewed from the inner peripheral side of the rotor 7, and a bridge portion 12 is formed between the V-shaped abutting portions having a minimum separation distance. ing. The bridge portion 12 is formed to be narrow as long as strength against centrifugal force can be secured in order to reduce short-circuiting of magnetic flux. A center line passing through the bridge portion 12 is a d-axis direction that is a magnetic flux axis direction. In a region extending from the pair of magnet insertion holes 10 to the outer peripheral surface of the rotor core 8, a through hole 13 that expands toward the outer peripheral side is provided. This through hole 13 also penetrates the rotor core 8 in the stacking direction, and has the effect of increasing the magnetic resistance in the d-axis direction. Thereby, the difference between the d-axis inductance Ld and the q-axis inductance Lq is increased, and the reluctance torque can be increased.

  The permanent magnet 11 is actually embedded in the magnet insertion hole 10 in an almost half region on the inner peripheral side. The almost half area on the outer peripheral side acts to prevent a short circuit of the magnetic flux. In order to prohibit the movement of the permanent magnet 11 due to centrifugal force, a locking portion 14 is formed at the center of the magnet insertion hole 10. The permanent magnet 11 embedded in the pair of magnet insertion holes 10 has the same polarity on the side facing the outer peripheral side of the rotor core 8 and is different from the permanent magnet 11 embedded in the pair of adjacent magnet insertion holes 10. It is considered as a pole.

  The rotating shaft 9 is formed so that the outer diameter thereof is smaller than the inner diameter of the rotor core 8 except for the coupling portion with the rotor 7. A fitting portion 15 having the same outer diameter as the inner diameter of the rotor core 8 and an outer diameter of the rotor core 8 are provided on the coupling portion of the rotating shaft 9 continuously with the fitting portion 15 in the axial direction. A disk-shaped support plate portion 16 that is slightly smaller than the shape is formed. The fitting portion 15 of the rotating shaft 9 is press-fitted into the rotor core 8 until the support plate portion 16 and the axial end surface (lower surface) of the rotor core 8 come into contact with each other.

  The fitting portion 15 is shorter than the axial length of the rotor core 8. Therefore, in the fitted state, an annular groove is formed between the inner peripheral surface of the rotor core 8 and the rotary shaft 9 on the upper surface side of the rotor core 8, that is, on the non-contact side with the support plate portion 16. The gap portion 17 is secured. An accommodating portion 20 is formed in the rotor core 8 by using this gap portion 17, and a position detecting magnet 18 is embedded therein.

  The position detection magnet 18 includes a plurality of divided magnets 19. A portion of the inner peripheral surface of the rotor core 8 facing the gap portion 17 is formed with a bottomed accommodating portion 20 in which the divided magnet 19 is embedded at an interval of the first angle θ1 along the circumferential direction. The accommodating part 20 forms a part of the rotor core 8 and protrudes in a rectangular shape toward the axial direction. A split magnet 19 can be inserted into the housing portion 20 along the axial direction from the upper surface side. In the inserted state, the end surface of the rotor core 8 including the accommodating portion 20 and the end surface of the split magnet 19 are the same surface. In addition, the formation position of the accommodating part 20 will not be restricted to an axial direction edge part if it is a part which faces the clearance gap part 17. FIG.

  The silicon steel plate forming the accommodating portion 20 is formed thin so that the magnetic flux generated from the split magnet 19 leaks to the outside of the rotor core 8. Further, in the relationship with the driving permanent magnet 11, the center in the circumferential direction of each divided magnet 19 coincides with the q axis that is the torque axis. According to this arrangement, the segmented magnet 19 is positioned away from the magnetic path through which the magnetic flux in the q-axis direction passes, so that the influence on the q-axis magnetic flux can be reduced.

  In the position detection magnet 18 composed of a plurality of divided magnets 19, the magnetic poles are reversed every first angle θ <b> 1 along the circumferential direction of the rotor core 8. Each of the divided magnets 19 is located in a range of each second angle θ2 set to be smaller than θ1 / 2 in both circumferential directions around the magnetic pole inversion position, that is, in an angle range of 2 × θ2. FIG. 4 shows an arrangement example of the divided magnets 19. FIG. 4A shows a configuration in which two magnets having the same shape magnetized in the axial direction are arranged in the circumferential direction with opposite polarities and embedded in the accommodating portion 20. FIG. 4B shows a configuration in which one magnet magnetized in the circumferential direction is embedded in the accommodating portion 20.

  On the side of the stator 2, a hall sensor 21 (magnetic flux detection means) that detects magnetic flux generated by the position detection magnet 18 that leaks to the outside of the rotor 7 is provided. In FIG. 3, the support structure of the hall sensor 21 is omitted. The hall sensor 21 is fixed so as to face the housing portion 20 from the inside in the gap portion 17 described above.

  According to the above configuration, a rotating magnetic field is generated by energizing the winding 6, and the rotor 7 rotates in synchronization with the rotating magnetic field. The generated torque at this time is a reluctance torque due to a difference in magnetic attraction force and magnetic repulsion force acting between the permanent magnet 11 and the magnetic poles of the stator 2 and the magnetic resistance between the dq axes.

  Next, detection of the rotational position using the position detection magnet 18 and the hall sensor 21 will be described. As shown in FIG. 5A, the Hall sensor 21 has a hysteresis characteristic having a positive magnetic flux density Bop and a negative magnetic flux density Brp as threshold values, and outputs a binary signal Hs according to the magnetic flux density. . FIG. 5B shows the signal Hs when the magnetic flux density changes according to a sine wave.

  FIG. 6 is a schematic explanatory diagram showing the arrangement of the divided magnets 19 and the output signal Hs of the hall sensor 21 in association with each other. The figure also schematically shows the positional relationship between the driving permanent magnet 11 and the position detecting magnet 18. As the rotor 7 rotates, the signal Hs changes from L level to H level when the Hall sensor 21 faces one divided magnet 19 in order of N pole and S pole. Conversely, when the Hall sensor 21 faces one divided magnet 19 in the order of S pole and N pole, the signal Hs changes from H level to L level.

  After the level of the signal Hs is once changed by facing the divided magnet 19, the detected magnetic flux density of the Hall sensor 21 exceeds the positive magnetic flux density Bop until the rotor 7 rotates by the first angle θ1. The level of the signal Hs is maintained without falling below the negative magnetic flux density Brp.

  FIG. 7 shows another configuration example of the position detection magnet 18. In this example, the second angle θ2 is set equal to ½ of the first angle θ1, and the divided magnets 22 are continuously provided in the circumferential direction. FIG. 8 shows the detected magnetic flux density of the Hall sensor 21 with respect to the rotational position by the three-dimensional magnetic field analysis at this time. When the position detection magnet 18 is arranged over the entire circumference in this way, a substantially constant detected magnetic flux density is obtained within the range of the first angle θ1, and the detected magnetic flux density changes sharply at the change point of the magnetic pole. I understand that

  Although the configuration shown in FIG. 7 is one desirable mode, the amount of use of the magnet increases because the position detection magnet 18 is arranged over the entire circumference. In contrast, the motor 1 of the present embodiment in which the second angle θ2 is set to be smaller than ½ of the first angle θ1 can reduce the amount of the position detection magnet 18 used. In this case, since the Hall sensor 21 has hysteresis characteristics, the level of the signal Hs does not reverse within the range of the first angle θ1 as described above. Accordingly, even in the present embodiment in which the divided magnets 19 are arranged in the vicinity of the detection position for each first angle θ1, sufficiently stable position detection can be performed.

  According to the present embodiment described above, the position detection magnet 18 is embedded in the rotor core 8, and the magnetic flux of the position detection magnet 18 leaking to the outside of the rotor 7 is detected by the hall sensor 21, so an encoder, a resolver, etc. The rotational position can be detected without adding the position detecting means. In this case, since the accommodating part 20 is formed by laminating the punched silicon steel plates, and the position detecting magnet 18 (divided magnet 19) is inserted into the accommodating part 20, the structure is simple and the number of parts is small. In addition, the number of assembly steps can be reduced.

  In the rotor core 8, the magnet insertion hole 10 for inserting the permanent magnet 11 and the accommodating portion 20 for inserting the split magnet 19 are in a fixed positional relationship. For this reason, the relative positional accuracy between the magnetic pole of the permanent magnet 11 and the magnetic pole of the position detecting magnet 18 is increased, the displacement can be reduced, and the rotational position of the rotor 7 can be detected with high accuracy. In addition, since there is no limit on the radial thickness of the rotor core 8 that is received when position detecting means such as an encoder or resolver is added, a wide q-axis magnetic path can be secured and the reluctance torque can be increased. Furthermore, by embedding the position detection magnet 18 in the rotor core 8, the position detection magnet 18 can be reliably prevented from scattering during high-speed rotation, and sufficient strength against centrifugal force can be ensured.

  Except for the configuration shown in FIG. 7, the position detection magnet 18 has a second angle θ2 that is set smaller than ½ of the first angle θ1 in both circumferential directions around the magnetic pole reversal position for each first angle θ1. The segmented magnet 19 occupies an angle range. This utilizes the hysteresis characteristic of the hall sensor 21 and can reduce the magnet amount of the position detecting magnet 18. In this case, since the magnetic pole change position of the divided magnet 19 is detected, the position detection accuracy is remarkably increased as compared with the case where the magnetic flux of the driving permanent magnet 11 is detected.

  In the inner rotor type, a driving permanent magnet 11 is arranged on the outer peripheral side of the rotor 7, and a position detecting magnet 18 (divided magnet 19) is arranged along the inner peripheral surface of the rotor 7. According to this arrangement, the position detecting magnet 18 is located away from the magnetic path through which the magnetic flux in the q-axis direction passes, so that the magnetic path of the magnetic flux used for driving is not narrowed, and a decrease in reluctance torque can be prevented. . In this case, since the center of the split magnet 19 coincides with the q-axis direction, the influence on the q-axis magnetic flux can be further reduced.

(Second Embodiment)
FIG. 9 is a longitudinal side view of the stator 2, the rotor 7, and a part of the rotating shaft 9 cut out in the same manner as in FIG. A split magnet 19 that is a position detection magnet 18 is inserted into a housing portion 20 that faces the gap portion 17 and is formed at an end portion in the axial direction on the inner peripheral surface of the rotor core 8. The hall sensor 21 is provided so as to face the position detection magnet 18 from the axial direction. In FIG. 9, the support structure of the hall sensor 21 is omitted. Other configurations are the same as those of the first embodiment. According to this embodiment, the same operation and effect as those of the first embodiment can be obtained.

(Other embodiments)
In addition to the plurality of embodiments described above, the following configuration may be adopted.
Any motor that rotates in synchronization with the rotating magnetic field may be used. For example, a reluctance motor may be used. The motor may be an outer rotor type. In this case, a housing portion may be formed on the outer peripheral side of the rotor core and a position detection magnet may be inserted. The number of poles of the motor is not limited to that shown in the drawing.

If the magnetic flux generated from the magnetic pole of the position detection magnet 18 leaks to the outside of the rotor 7 and can be detected by the Hall sensor 21, the manner of embedding the position detection magnet 18 in the rotor 7 is limited to the above embodiment. I can't.
As long as the q-axis magnetic flux is out of the magnetic path through which the magnetic flux passes, the divided magnets 19 may be arranged shifted from the q-axis direction.

  According to the embodiment described above, the structure for detecting the rotational position is simple, the number of parts is small, and the number of assembly steps is also small. Since there is no limit on the radial thickness of the rotor core 8, the reluctance torque can be increased by increasing the q-axis magnetic path. Since the relative position accuracy between the magnetic pole of the permanent magnet 11 and the magnetic pole of the position detecting magnet 18 is high in the rotor core 8, the rotational position can be detected with high accuracy. Since the position detection magnet 18 can be composed of the divided magnets 19, the amount of the position detection magnet 18 can be reduced.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  In the drawings, 1 is a permanent magnet motor (motor), 2 is a stator, 6 is a winding, 7 is a rotor, 8 is a rotor core, 9 is a rotating shaft, 18 is a position detection magnet, and 19 and 22 are divided. A magnet (position detecting magnet), 20 is a housing portion, and 21 is a hall sensor (magnetic flux detecting means).

Claims (5)

In a motor including a stator that generates a rotating magnetic field by energizing a winding, and a rotor that rotates in synchronization with the rotating magnetic field,
A position detecting magnet embedded in the rotor such that the magnetic poles are reversed at predetermined first angles along the circumferential direction of the rotor core, and the magnetic flux generated from the magnetic poles leaks outside the rotor;
A motor provided with magnetic flux detection means provided on the stator side and detecting magnetic flux leaking from the position detection magnet to the outside of the rotor.   The position detecting magnet is a split magnet positioned in an angular range of each second angle set smaller than ½ of the first angle in both circumferential directions around each inversion position of the magnetic pole in the rotor core. The motor according to claim 1, comprising:   It is an inner rotor type, and a rotating shaft is fitted to a part of the inner peripheral surface of the rotor core, and a housing portion into which the divided magnet can be inserted from the axial direction is provided in the circumferential direction on the remaining inner peripheral surface. 3. The motor according to claim 2, wherein the motor is formed at an interval of the first angle along the magnetic field, and the magnetic flux detection means is provided so as to face the position detection magnet from the inner peripheral side.   An inner rotor type, in which a rotating shaft is fitted to a part of the inner peripheral surface of the rotor core, and the split magnet can be inserted from the axial direction into the axial end portion of the remaining inner peripheral surface The part is formed at the first angular interval along the circumferential direction, and the magnetic flux detecting means is provided so as to face the position detecting magnet from the axial direction. motor.   5. The motor according to claim 1, wherein the position detection magnet is provided at a position off the magnetic path through which the magnetic flux in the q-axis direction passes in the rotor core. 6.

Images