JP6050102B2 - Brushless motor and blower - Google Patents

Description

  The present invention relates to a brushless motor.

  The brushless motor rotates the motor by detecting the position of the rotor magnet and switching the coil current. As a method for detecting the position of the rotor magnet, a structure using a Hall element is known. For example, Patent Document 1 discloses a technique for providing a groove between magnetic poles of a rotor magnet and providing a section where the Hall element does not react as a structure for detecting the rotational position of the rotor with a plurality of Hall elements.

JP 2005-124368 A

  Patent Document 1 describes a technique for clarifying an off section of a Hall element by providing a groove between magnetic poles. However, with this technology, the off interval of the Hall element changes depending on the magnetized state of the magnet, and when the off interval becomes short, a negative torque (reverse torque) is generated in the direction to cancel the cogging torque, and the motor efficiency There is a problem that decreases.

  In such a background, an object of the present invention is to provide a technique in which the efficiency of a motor does not decrease in a structure in which the position of a rotor magnet in a brushless motor is detected by magnetic detection means.

The invention according to claim 1 includes a radially magnetized rotor magnet, and magnetic detection means for detecting the polarity of the magnetic pole of the rotor magnet at the end face of the rotor magnet, and the end face of the rotor magnet includes: A notch serving as an off section of the magnetic detection means is formed so as to include at least a part between the magnetic poles between adjacent magnetic poles in the circumferential direction, and the circumferential distance between the notches is W2, and the circumferential direction between the magnetic poles When the distance is W1, W2 is (the maximum dimension of W1) + (the phase angle of the section where the combined torque in the state where the notch is not formed is smaller than the cogging torque in the state where the notch is not formed) The brushless motor is set to a value corresponding to a circumferential distance × 1 to 5) .

  According to the first aspect of the present invention, since the off section of the magnetic detection means is set in consideration of fluctuations in the size and position between the magnetic poles, the supply of drive current in the section in which the negative torque is generated is suppressed, Generation of negative torque is suppressed.

  The invention described in claim 2 is characterized in that, in the invention described in claim 1, a section where the combined torque is lower than the cogging torque does not exist over the entire circumference. The invention described in claim 3 is the invention described in claim 1 or 2, characterized in that the circumferential center of the notch and the circumferential center between the magnetic poles are substantially the same.

  The invention according to claim 4 is the invention according to claim 1 or 2, characterized in that the circumferential center of the notch and the circumferential center between the magnetic poles are at different positions. According to the fourth aspect of the present invention, the advance angle that determines the timing for supplying the drive current can be set to a desired value.

  A fifth aspect of the present invention is a blower comprising the brushless motor according to any one of the first to fourth aspects.

  ADVANTAGE OF THE INVENTION According to this invention, the technique in which the efficiency of a motor does not fall is provided in the structure which detects the position of the rotor magnet in a brushless motor with a magnetic detection means.

It is a sectional side view of the axial blower using the brushless motor of an embodiment. It is sectional drawing (A) which cut | disconnected some rotors of embodiment , and the figure (B) seen from the opening side of the motor yoke. It is a characteristic of the brushless motor of an embodiment. It is a characteristic of the brushless motor of a comparative example. It is sectional drawing which cut | disconnected a part of rotor of the modification in the axial direction.

(Constitution)
FIG. 1 shows an axial blower 100. The axial blower 100 includes a brushless motor 101 in which blades 113 are integrated. The brushless motor 101 is an outer rotor type single-phase brushless motor, and includes a rotor 110, a stator 120, and other components integrated with the stator 120.

The rotor 110 rotates with respect to the stator 120. The rotor 110 includes an impeller 111. The impeller 111 includes a resin hub 112, a blade 113 formed integrally with the hub 112, a shaft 114 embedded and fixed in the center of the hub 112 , and a magnetic material fixed inside the hub 112. The motor yoke 115 and the magnet 116 which is a rotor magnet fixed inside the motor yoke 115 are provided.

  The stator 120 includes a stator core 121, an insulator 122, and a coil 123 made of a magnetic material. The stator core 121 has a structure in which a plurality of magnetic materials such as electromagnetic steel plates are laminated, and has the same shape as a stator core of a normal outer rotor type brushless motor. In this example, the stator core 121 has four salient poles arranged at equiangular positions when viewed from the axial direction. The salient pole extends in a direction away from the axial center, and has a structure in which a tip portion thereof is opened in a substantially T shape when viewed from the axial direction.

  A resin insulator 122 is attached to the stator core 121. The insulator 122 insulates the salient pole of the stator core 121. A coil 123 serving as a drive coil is wound around a salient pole of the stator core 121 via an insulator 122. These structures are the same as those of a normal outer rotor type brushless motor.

  The stator core 120 is fixed to a resin bearing housing 131. The bearing housing 131 is formed integrally with the motor base 132 and the casing 133. Bearings 134 and 135 are attached to the bearing housing 131, and the shaft 114 is rotatably held by the bearings 134 and 135. A circuit board 136 is fixed to the bearing housing 131, and a hall element 137 that is a magnetic detection unit is attached to the circuit board 136.

FIG. 2 shows a cross-sectional view (A) in which the member with the magnet 116 attached inside the motor yoke 115 is cut in the axial direction and a view (B) viewed from the opening side of the motor yoke. The magnet 116 is a permanent magnet having a thin and substantially cylindrical shape, and is radially magnetized to the NSNS and four poles along the circumferential direction. FIG. 2 shows S poles 21 and N poles 22 arranged alternately along the circumferential direction. Between the adjacent S poles and N poles, there is a magnetic pole space 23 which is a region between magnetized regions of different polarities. Between the magnetic poles 23 is an area in which the magnetic force generated between adjacent magnetic poles of different polarities is small, and the direction of the magnetic field cannot be detected by the Hall element 137 .

The edge portion of one end of the magnet 116 in the axial direction ( the lower end of FIG. 2A ) includes the gap 23 in the circumferential direction, and the dimension in the circumferential direction is larger than the dimension W1 of the gap 23. Cutouts 24 that are W2 are provided at four locations. That is, the rotation position of the S pole 21 and the N pole 22 of the magnet 116 is detected by the Hall element 137 in FIG. 1, but at the position between the magnetic poles 23 on the end face side portion of the magnet 116 detected by the Hall element 137 A notch 24 (circumferential distance W2) longer than the circumferential distance W1 between the magnetic poles 23 is provided. Here, the center position of the notch 24 and the center position between the magnetic poles 23 in the circumferential direction substantially coincide with each other.

  Although how much W2 is made larger than W1 depends on various conditions, the dimension of W2 may be determined so that a phenomenon in which the combined torque shown in FIG. 4 described later becomes smaller than the cogging torque does not occur. For example, the cogging torque and the combined torque of the motor are measured in the state where the notch 24 is not formed, and the dimension of W2 is obtained by adding a circumferential distance corresponding to a phase angle of a section where the combined torque is smaller than the cogging torque to W1. I can do it. Since W1 varies and has a certain width, the maximum value of a plurality of samples (for example, 10 brushless motors (total of 40 locations)) manufactured under the same conditions is adopted. Further, since the magnets are magnetized in multiple poles and the central angles of adjacent W1s vary, a value larger than the circumferential distance corresponding to the phase angle of the section where the combined torque is smaller than the cogging torque is set to W1. It is desirable that the added value be the dimension of W2.

Specifically, in the present invention, the circumferential dimension W2 of the notch 24 is expressed as follows : (maximum dimension of W1) + (circumferential distance × 1-5 corresponding to a phase angle in a section where the combined torque is smaller than the cogging torque) Set to a value. If W2 is smaller than this range, the effect of suppressing the generation of negative torque, which will be described later, is not sufficient, and the phenomenon that the combined torque becomes smaller than the cogging torque cannot be ignored. Further, when W2 is larger than the above range, the section in which the drive current is OFF becomes longer, and the tendency for the drive power as the motor to decrease becomes obvious.

  Although not shown, an advance angle adjustment circuit is mounted on the circuit board 136. The advance angle adjustment circuit is a circuit that sets the relationship between the output of the Hall element 137 and the supply timing of the drive current to the coil 123. The relationship between the output of the Hall element 137 and the supply timing of the drive current to the coil 123 is determined based on data experimentally obtained in advance. The advance angle adjustment circuit determines which value of the output of the wheel element 137 is to be turned ON or OFF when the drive current is supplied to the coil 123.

(Function)
In the brushless motor, the position of the magnetic pole of the rotor-side magnet is detected by a Hall element, and the switching timing of the drive current supplied to the stator-side coil is determined based on the detected position. Here, when the switching of the drive current supplied to the stator side coil deviates from the ideal state, the magnetic force for pulling the rotor back in the reverse direction acts on the rotor type magnet from the stator side coil. As a result, although it is a short section, negative torque is generated, and the efficiency of the motor is reduced accordingly.

Consider a case where the notch 24 is not formed, or a case where the circumferential dimension W2 is equal to or less than W1. In general, the range between the magnetic poles 23 is strongly affected by subtle fluctuations in the magnetization of the magnet 116 and the material of the magnet 116, and variations in the position and range thereof occur. Therefore, when the dimension is set to satisfy W2 ≦ W1, the possibility that the Hall element 137 detects the magnet 116 at a timing that should not be detected by design increases. In this case, switching of the drive current supplied to the above-described stator side coil is shifted from an ideal state, and negative torque is generated.

  On the other hand, when W1 <W2, the section where the Hall element 137 does not detect magnetism (off section) at the timing when the distance between the magnetic poles 23 passes near the Hall element 137 can be lengthened. Even if the range fluctuates, detection of magnetism by the unintended Hall element 137 described above can be avoided. For this reason, the switching of the drive current supplied to the stator-side coil described above deviates from an ideal state, and a situation in which negative torque is generated is prevented.

(Measurement result)
Figure 3 is a graph of the measurement of the phase (rotational angle) and torque relationships in the brushless motor 101 shown in FIGS. 1 and 2 are shown. FIG. 3 shows data when W2 = W1 + (circumferential distance corresponding to 2 ° × 2) = circumferential distance corresponding to 11 degrees. Further, in FIG. 4, in the brushless motor 101 shown in FIGS. 1 and 2, graph of the measurement of the phase (rotational angle) and the torque relationship in a comparative example in which W1 = W2 is shown.

  The cogging torque indicated by the broken line in FIGS. 3 and 4 is a torque caused by the magnetic force acting between the salient pole of the stator core 121 and the magnet 116 regardless of the drive current to the coil 123. As shown in the figure, the cogging torque is periodically reversed in polarity as the rotor 110 rotates. The combined torque in the solid line is a torque obtained by combining the driving torque caused by the driving current flowing through the coil 123 of the stator core 121 and the above-described cogging torque.

  As shown in FIG. 4, when W1 = W2, the off section of the hall element 137 is short, and the section in which the combined torque becomes smaller than the cogging torque immediately after the off section (the section has a phase of 82 degrees to 84 degrees). There is. Since the combined torque is the sum of the driving torque and the cogging torque caused by the driving current, FIG. 4 shows that a negative torque that makes the driving torque negative is generated in this section. On the other hand, in the case of FIG. 3 where W2> W1, the negative torque of FIG. 4 is not seen.

(Superiority)
As described above, the brushless motor 101 includes the radially magnetized magnet 116 and the Hall element 137 that detects the polarity of the magnetic pole of the magnet 116 at the end face in the axial direction of the magnet 116. Is formed so as to include a gap 23 between the magnetic poles adjacent to each other in the circumferential direction, and a circumferential distance W2 of the notch 24 is the circumference of the gap between the magnetic poles 23. It is set longer than the direction distance W1.

  According to this structure, it is possible to suppress the generation of negative torque as shown in FIG. 4 by satisfying W2> W1 and intentionally securing a long off section of the Hall element 137. Since the negative torque is a torque that causes the drive current to rotate in the direction opposite to the direction in which the rotor 110 should originally rotate, the drive current is wasted in this section. In the present embodiment, the generation of negative torque can be suppressed by setting W2> W1, and the efficiency of the motor can be increased.

(Modification)
FIG. 5 shows an example in which the center position of the notch 24 and the center position between the magnetic poles 23 are shifted, and the phase of the magnetic pole position of the rotor 110 and the magnetic pole detection position by the Hall element 137 is shifted. According to this structure, the advance angle that determines the timing for supplying the drive current can be set to a desired value. FIG. 5 shows an example in which the gap between the magnetic poles 23 is included in the range of the notch 24, but the notch 24 and the gap between the magnetic poles 23 partially overlap in the circumferential direction. A structure where the parts do not overlap is also possible.

(Other)
As means for detecting magnetism, in addition to the Hall element, a magnetoresistive effect element or a magneto-impedance element can be used. In the embodiment, an example of an outer rotor type single-phase brushless motor having a rotor on the outer side has been described, but the present invention can also be applied to an inner rotor type brushless motor having a rotor on the inner side. In the embodiment, an example in which the brushless motor using the present invention is used for an axial blower has been shown. However, the brushless motor using the present invention is not limited to the blower, and for other uses to which the brushless motor can be applied. It can also be used.

  The aspect of the present invention is not limited to the individual embodiments described above, and includes various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the contents described above. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

  The present invention can be used for a brushless motor provided with magnetic detection means.

DESCRIPTION OF SYMBOLS 100 ... Axial blower, 101 ... Brushless motor, 110 ... Rotor, 111 ... Impeller, 112 ... Hub, 113 ... Blade, 114 ... Shaft, 115 ... Motor yoke, 116 ... Magnet, 120 ... Stator, 121 ... Stator core, 122 ... Insulator, 123 ... Coil, 131 ... Bearing housing, 132 ... Motor base, 133 ... Casing, 134 ... Bearing, 135 ... Bearing, 136 ... Rotary substrate, 137 ... Hall element, 21 ... S pole (magnetic pole on the rotor side), 22 ... N pole (rotor side magnetic pole), 23 ... between magnetic poles, 24 ... notch.

Claims (5)

A radially magnetized rotor magnet;
Magnetic detection means for detecting the polarity of the magnetic poles of the rotor magnet at the end face of the rotor magnet,
On the end surface of the rotor magnet, a notch serving as an off section of the magnetic detection means is formed so as to include at least a part between the magnetic poles adjacent in the circumferential direction,
When the circumferential distance of the notch is W2 and the circumferential distance between the magnetic poles is W1, W2 is (the maximum dimension of W1) + (the combined torque in the state where the notch is not formed is the notch. A brushless motor characterized by being set to a value of a circumferential distance x 1 to 5) corresponding to a phase angle in a section smaller than a cogging torque in a state where it is not formed .   2. The brushless motor according to claim 1, wherein no section in which the combined torque is lower than the cogging torque exists over the entire circumference.   The brushless motor according to claim 1, wherein a circumferential center of the notch and a circumferential center between the magnetic poles are substantially the same.   The brushless motor according to claim 1 or 2, wherein the circumferential center of the notch and the circumferential center between the magnetic poles are at different positions.   A blower comprising the brushless motor according to any one of claims 1 to 4.

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