JP4233950B2 - Brushless motor - Google Patents

Description

  The present invention relates to a stator that generates a rotating magnetic field, a rotor that supports a plurality of permanent magnets radially on a rotor core that is rotatably housed inside the stator, and a rotational position of the rotor based on leakage magnetic flux from the rotor. The present invention relates to a brushless motor including a hall element to be detected.

  A brushless motor in which four permanent magnets are attached radially to the rotor housed in the stator at 90 ° intervals, and a hole constituting a flux barrier is formed on the outer peripheral surface of the rotor core facing the radially outer end surface of each permanent magnet. It is known from Patent Document 1 below. This hole is for preventing leakage and short circuit of magnetic flux from the permanent magnet of the rotor, thereby reducing the eddy current loss without reducing the reluctance torque and improving the efficiency of the motor.

Further, a brushless motor that detects the rotational position of a rotor by attaching a sensing permanent magnet to a rotating shaft of a rotor disposed on the outer periphery of the stator and detecting the sensing permanent magnet with a Hall element is known from Patent Document 2 below. is there.
JP 2001-86673 A JP-A-11-2899736

  By the way, the brushless motor described in Patent Document 2 requires a special sensing permanent magnet for detecting the rotational position of the rotor, which is an obstacle to making the motor thinner and increases the number of parts. There was a problem to do. Therefore, a method of detecting the magnetic flux leaking from the magnetic path of the rotor core to the outside by the Hall element and detecting the rotational position of the rotor is also adopted, but if a certain amount of magnetic flux is not generated at the position where the Hall element is arranged There was a problem that sufficient detection accuracy could not be obtained.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to accurately detect the rotational position of the rotor of a brushless motor using leakage magnetic flux.

  To achieve the above object, according to the first aspect of the present invention, a rotor that generates a rotating magnetic field, and a rotor in which a plurality of permanent magnets are radially supported by a rotor core that is rotatably housed inside the stator. And a Hallless element that detects the rotational position of the rotor based on the leakage magnetic flux from the rotor, the rotor core has a circumferential width smaller than the radial width between adjacent permanent magnets. There is proposed a brushless motor characterized in that a hall element is provided at a position facing the magnetic path.

  Further, according to the invention described in claim 2, in addition to the configuration of claim 1, a brushless motor is proposed, in which a space for increasing the magnetic resistance of the magnetic path is formed in the rotor core. .

  According to the invention described in claim 3, in addition to the configuration of claim 2, a brushless motor is proposed in which the space is formed in the magnetic path.

  According to a fourth aspect of the present invention, a stator that generates a rotating magnetic field, a rotor that is rotatably housed inside the stator, and a plurality of permanent magnets that are circumferentially disposed on the outer periphery of the rotor core. And a plurality of sensing permanent magnets arranged circumferentially on the inner peripheral portion of the rotor core, and a Hall element that detects the rotational position of the rotor based on leakage magnetic flux from the sensing permanent magnet A brushless motor is proposed in which a space for increasing the leakage magnetic flux from the sensing permanent magnet is formed in the rotor core.

  In addition, the 1st space part 24c-the 6th space part 24h of an Example respond | correspond to the space part of this invention.

  According to the first aspect of the present invention, since the magnetic path whose circumferential width is narrower than the radial width is formed between the plurality of permanent magnets radially supported by the rotor core, the magnetic resistance of the magnetic path increases. Leakage magnetic flux is likely to be generated, and it is possible to detect the rotational position of the rotor with high accuracy by increasing the leakage magnetic flux passing through the Hall element arranged at the position facing the magnetic path. Moreover, since a sensing permanent magnet for detecting the rotational position of the rotor is not required, it is possible to contribute to a reduction in the number of parts and a reduction in the size and thickness of the motor.

  According to the second aspect of the present invention, the space portion is formed in the rotor core, so that the magnetic flux does not easily pass and the magnetic resistance of the magnetic path increases. Therefore, the leakage flux is increased and the rotational position of the rotor is detected by the Hall element. The accuracy can be further increased.

  According to the configuration of the third aspect, since the space portion of the rotor core is formed in the magnetic path between the adjacent permanent magnets, the magnetic resistance of the magnetic path can be effectively increased to further increase the leakage magnetic flux.

  According to the configuration of the fourth aspect, since the space portion is formed in the rotor core so as to increase the leakage magnetic flux from the plurality of sensing permanent magnets arranged in the circumferential direction on the inner peripheral portion of the rotor core, The magnetic resistance of the magnetic path increases and leakage magnetic flux is likely to be generated, and the rotational position of the rotor can be accurately detected by increasing the leakage magnetic flux passing through the Hall element arranged at the position facing the magnetic path. Become. In addition, since the sensing permanent magnet can be reduced in size, it can contribute to the reduction in size and thickness of the motor.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 4 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of the brushless motor (sectional view taken along line 1-1 in FIG. 2), and FIG. 2 is a sectional view taken along line 2-2 in FIG. FIG. 3 is a sectional view taken along line 3-3 in FIG. 1, and FIG. 4 is an enlarged sectional view taken along line 4-4 in FIG.

  As shown in FIGS. 1 and 2, the housing 11 of the thin brushless motor M includes a dish-like upper housing 12 and a disk-like lower housing 13 connected by a plurality of bolts 14. An output shaft 17 is rotatably supported by the lower housing 13 via bearings 15 and 16, respectively. The brushless motor M includes a stator 18 that is fixed to the inner peripheral surface of the housing 11, and a rotor 19 that is disposed on the radially inner side of the stator 18 and rotates with the output shaft 17.

  The stator 18 is formed by connecting 24 teeth 21 made of laminated steel plates in the circumferential direction at intervals of 15 ° and winding the coils 22 around each of the teeth 21. It faces the outer peripheral surface with a slight air gap.

  3 and 4, the rotor 19 includes a rotor boss 23 splined to the output shaft 17, a rotor core 24 made of a laminated steel plate fixed to the outer periphery of the rotor boss 23, and a rotor core 24. 20 permanent magnets 25 are held in the formed permanent magnet holding holes 24a. For example, the neodymium permanent magnets 25 have a rectangular shape when viewed in the direction of the axis L of the rotor 19, and are arranged at intervals of 18 ° in the circumferential direction with the longitudinal direction along the radial direction centered on the axis L. The

  The permanent magnets 25 are arranged so that the long sides facing each other are N poles or S poles. Sector-shaped magnetic paths 24b are defined between adjacent permanent magnets 25, and these magnetic paths 24b are arranged so that the circumferential maximum width W1 is smaller than the radial width W2. It is elongated in the radial direction.

  Twenty notch-shaped first space portions 24c are formed on the outer peripheral portion of the rotor core 24 facing the radially outer end of each permanent magnet 25, and the permanent space is made permanent via these first space portions 24c. The radially outer end surfaces of the magnets 25 are exposed to the air gap. Twenty hole-shaped second space portions 24d are formed between the radially inner ends of the adjacent permanent magnets 25 and adjacent to the outer peripheral surface of the rotor boss 23. The first and second space portions 24c, 24d, ... pass through the rotor core 24 in the axis L direction.

  Three openings 12a... Are formed in the upper housing 12 of the brushless motor M at intervals of 120 ° with the axis L as the center, and a Hall element 27 fixed to the substrate 26 is connected to the upper surface of the rotor 19 from each opening 12a. It faces. The hall elements 27 are for detecting the rotational position of the rotor 19 by detecting the leakage flux of the magnetic flux formed in the rotor core 24 by the permanent magnets 25, and the stator 18 at a predetermined timing based on the rotational position. The rotor 19 is driven by sequentially exciting the 24 coils 22.

  In order to accurately detect the rotational position of the rotor 19 with the Hall elements 27, it is necessary to increase the leakage magnetic flux leaking in the direction of the axis L from the rotor core 24 toward the Hall elements 27. In this embodiment, a large number (20 in the embodiment) of permanent magnets 25 are arranged in the radial direction at narrow intervals in the rotor core 24, so that the cross-sectional area of the magnetic paths 24b between the adjacent permanent magnets 25 is large. The magnetic flux is saturated as it becomes smaller, and the leakage magnetic flux passing through the Hall elements 27 is increased, so that the detection accuracy of the rotational position of the rotor 19 can be increased.

  In particular, the rotor core 24 has first and second space portions 24c, 24d,..., And the Hall element 27 is blocked by blocking the flow of magnetic flux in the first and second space portions 24c, 24d,. It is possible to further increase the detection accuracy of the rotational position of the rotor 19 by further increasing the leakage magnetic flux toward.

  As described above, since the rotational position of the rotor 19 is detected using the leakage magnetic flux from the magnetic paths 24b of the rotor core 24, a sensing permanent magnet for detecting the rotational position of the rotor 19 is not required, and the number of parts is reduced. In addition, the motor can be reduced in size and thickness.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  The second embodiment differs from the first embodiment in the arrangement of the Hall elements 27.

  In the first embodiment, the output direction of the three Hall elements 27 arranged at intervals of 120 ° is processed by a microcomputer to detect the rotational direction and rotational position of the rotor 19. In the second embodiment, three Hall elements 27a for detecting the clockwise rotation position of the rotor 19 and three Hall elements 27b for detecting the counterclockwise rotation position of the rotor 19 are provided. Separately provided.

  The three Hall elements 27a for detecting the rotational position of the rotor 19 in the clockwise direction are arranged at positions advanced by a predetermined angle θ (for example, 3.5 °) with respect to the phase of the teeth 21. Thus, when the coils 22 are excited based on the rotational position of the rotor 19 detected by the Hall elements 27a, the maximum torque is obtained when the rotor 19 rotates at the maximum rotational speed in the clockwise direction.

  On the other hand, the three Hall elements 27b for detecting the counterclockwise rotation position of the rotor 19 are arranged at positions delayed by a predetermined angle θ (for example, 3.5 °) with respect to the phase of the teeth 21. Thus, when the coils 22 are excited based on the rotational position of the rotor 19 detected by the Hall elements 27b, the maximum torque is obtained when the rotor 19 rotates at the maximum rotational speed in the counterclockwise direction. It has become.

  Other configurations and effects of the second embodiment are the same as those of the first embodiment.

  FIGS. 6 to 8 show the third to fifth embodiments of the present invention, respectively, which are different from the first embodiment only in the position of the space portion of the rotor core 24.

  In the third embodiment shown in FIG. 6, the third space portions 24e are formed so as to face both long sides of the permanent magnets 25 at positions near the radially inner ends of the magnetic paths 24b, and the vicinity thereof. Thus, by narrowing the cross-sectional area of the magnetic paths 24b and increasing the leakage magnetic flux, the detection accuracy of the rotational position of the rotor 19 by the Hall elements 27 is increased.

  In the fourth embodiment shown in FIG. 7, the fourth spaces 24f are formed at the central positions near the radially inner ends of the magnetic paths 24b, and the cross-sectional area of the magnetic paths 24b is narrowed in the vicinity thereof to cause leakage. Increasing the magnetic flux increases the detection accuracy of the rotational position of the rotor 19 by the Hall elements 27.

  In the fifth embodiment of FIG. 8, fifth space portions 24g are formed at positions radially inward from the radial inner ends of the magnetic paths 24b, and the radial inner ends of the magnetic paths 24b are formed. By narrowing the cross-sectional area and increasing the leakage magnetic flux, the detection accuracy of the rotational position of the rotor 19 by the Hall elements 27 is increased.

  6 to 8, the portion surrounded by the chain line is the portion where the leakage magnetic flux is maximized, and the detection accuracy can be maximized by arranging the Hall elements 27 at this position. In particular, in the embodiment shown in FIGS. 6 and 7, the third space portion 24e... Or the fourth space portion 24f... Is formed directly in the magnetic paths 24b, so that the cross-sectional area of the magnetic paths 24b. Can be increased effectively.

  Next, a sixth embodiment of the present invention will be described with reference to FIG.

  FIG. 9 shows the rotor 19 of the brushless motor M. The rotor core 24 includes a plurality of permanent magnets 25 arranged at predetermined intervals in the circumferential direction on the outer peripheral portion thereof, and the circumferential direction on the inner peripheral portion thereof. Are provided with a plurality of sensing permanent magnets 28 arranged at predetermined intervals. A plurality of sixth space portions 24h penetrating the rotor core 24 in the direction of the axis L is formed so as to block a part of the magnetic path surrounding each of the sensing permanent magnets 28, and magnetic saturation of the magnetic path is formed. The three Hall elements 27 face the portion where the magnetic flux is likely to occur, that is, the portion where the leakage magnetic flux from the sensing permanent magnets 28 tends to increase.

  Therefore, according to the sixth embodiment, the magnetic flux leakage from the sensing permanent magnets 28 is increased and the rotor 19 is reduced while the sensing permanent magnets 28 are downsized to reduce the size and thickness of the brushless motor M. The detection accuracy of the rotational position can be improved.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, the brushless motor M of the embodiment includes 24 coils 22 and 20 permanent magnets 25 (16 in the sixth embodiment), but the number is not limited to the embodiment. Absent.

  The first space portion 24c to the sixth space portion 24h do not need to be hollow, and may be embedded with a nonmagnetic material such as copper.

Longitudinal sectional view of brushless motor (sectional view taken along line 1-1 in FIG. 2) 2-2 sectional view of FIG. 3-3 line view of FIG. 4-4 enlarged sectional view of FIG. The figure which shows arrangement | positioning of the Hall element based on 2nd Example. The figure which shows the shape of the space part which concerns on 3rd Example The figure which shows the shape of the space part which concerns on 4th Example The figure which shows the shape of the space part which concerns on 5th Example The figure which shows the structure of the rotor which concerns on 6th Example

Explanation of symbols

18 Stator 19 Rotor 24 Rotor core 24b Magnetic path 24c First space (space)
24d 2nd space part (space part)
24e 3rd space part (space part)
24f 4th space part (space part)
24g 5th space part (space part)
24h 6th space part (space part)
25 Permanent Magnet 27 Hall Element 27a Hall Element 27b Hall Element 28 Sensing Permanent Magnet W1 Circumferential Width W2 Radial Width

Claims (4)

A stator (18) that generates a rotating magnetic field, a rotor (19) in which a plurality of permanent magnets (25) are radially supported by a rotor core (24) rotatably accommodated in the stator (18), and a rotor (19 In a brushless motor provided with Hall elements (27, 27b, 27c) for detecting the rotational position of the rotor (19) based on leakage magnetic flux from
The rotor core (24) has a magnetic path (24b) between the adjacent permanent magnets (25) whose circumferential width (W1) is narrower than the radial width (W2). A brushless motor characterized in that hall elements (27, 27a, 27b) are arranged at the facing positions.   The brushless motor according to claim 1, wherein a space (24c to 24g) for increasing the magnetic resistance of the magnetic path (24b) is formed in the rotor core (24).   The brushless motor according to claim 2, wherein the space (24f, 24g) is formed in the magnetic path (24b). A stator (18) that generates a rotating magnetic field, a rotor (19) rotatably accommodated inside the stator (18), and a plurality of permanent magnets (circumferentially arranged) on the outer periphery of the rotor core (24) ( 25), a plurality of sensing permanent magnets (28) disposed in the circumferential direction on the inner peripheral portion of the rotor core (24), and leakage flux from the sensing permanent magnet (28). In a brushless motor provided with a Hall element (27) for detecting the rotational position,
A brushless motor characterized in that a space (24h) for increasing leakage magnetic flux from the sensing permanent magnet (28) is formed in the rotor core (24).

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