JP5660488B2 - Brushless DC motor and drive circuit thereof - Google Patents

Description

  The present invention relates to a brushless DC motor and a drive circuit thereof, and more particularly to a brushless DC motor and a drive circuit thereof capable of controlling forward rotation and reverse rotation with a simple configuration.

Brushless DC motors have a large starting torque even at low speeds, can operate at high speeds with a stable rotation at a constant speed, and since there are no brushes or commutators, no sparks are generated during operation, so no radio waves causing noise are generated. Taking advantage of this feature, it is widely used as an industrial motor for medical machines, office equipment, OA equipment, automatic control equipment and the like.
In particular, since a single-phase or two-phase brushless DC motor can be realized at a low cost by a relatively simple configuration of the motor itself and its drive circuit, for example, a demanding application such as a fan motor for cooling an electronic device. Suitable for

  Conventionally, in a single-phase or two-phase brushless DC motor, in order to ensure stable self-startability in a predetermined rotation direction, the rotor magnetic pole center is the center of the salient pole of the stator core when the motor is not energized. In many cases, it is configured to stop in a state of moving to the positive direction side (with respect to the predetermined rotation direction). Such a configuration is achieved, for example, by forming the shape of the salient pole of the stator core asymmetrically with respect to the center line of the salient pole (for example, Patent Document 1).

JP 11-332193 A

However, the brushless DC motor described in Patent Document 1 is supposed to rotate the rotor only in one direction set in advance as a predetermined rotation direction because of its configuration, and the rotor is driven by a drive circuit. It is not possible to control forward and reverse rotation.
On the other hand, a three-phase brushless DC motor, for example, can control forward rotation and reverse rotation by changing the commutation pattern of the coil current flowing in each phase under the control of the drive circuit. Compared with the two-phase brushless DC motor, the configuration of the motor itself and its drive circuit are complicated, leading to an increase in cost.

  The present invention has been made in view of the above problems, and an object thereof is to provide a brushless DC motor capable of controlling forward rotation and reverse rotation with a simple configuration and a drive circuit thereof.

  The following aspects of the present invention exemplify the configuration of the present invention, and will be described separately for easy understanding of various configurations of the present invention. Each section does not limit the technical scope of the present invention, and some of the components of each section are replaced, deleted, or further, while referring to the best mode for carrying out the invention. Those to which the above components are added can also be included in the technical scope of the present invention.

(1) A stator having a plurality of salient poles, a coil wound around all the salient poles of the stator, and a rotor having a permanent magnet disposed to face the stator. In the brushless DC motor, the tips of all the salient poles of the stator are formed in an asymmetric shape with respect to the center line of the salient pole, and all the salient poles of the stator have The brushless DC motor according to claim 1, wherein the adjacent salient poles face each other on the same shape side of the tip portion.

In the brushless DC motor described in this section, preferably, the rotor has permanent magnets magnetized to even poles so that different poles are alternately arranged on a surface facing the stator, The stator has the same number of salient poles as the number of poles of the permanent magnet, and more preferably, the rotor is magnetized to four poles, and the stator has four salient poles. is there.

(2) In the brushless DC motor according to item (1), the salient pole is formed such that a gap between the tip and the rotor is asymmetrical with respect to the center line of the salient pole. A brushless DC motor (claim 2).

(3) In the brushless DC motor according to item (1), the salient pole is formed such that a thickness of the tip is asymmetrical with respect to a center line of the salient pole. motor.

(4) A drive circuit for driving the brushless DC motor according to any one of (1) to (3), wherein the brushless DC motor performs forward rotation and reverse rotation. Item 3).

(5) In the drive circuit according to the item (4), the brushless DC motor is preliminarily operated before the forward rotation operation and the reverse rotation operation, and the rotor is moved to the preliminary operation at the end of the preliminary operation. The drive circuit according to claim 4, wherein the rotor is stopped at a position where the rotor is attracted to the salient pole on the rotation direction side by energizing the first coil after operation.
( 6 ) In the drive circuit according to (4) or (5) , the coil wound around the plurality of salient poles of the brushless DC motor is a two-phase coil of a first phase and a second phase. And the coils wound around the adjacent salient poles are in different phases, and the drive circuit energizes the first phase coil and the second phase coil alternately. After the preliminary operation, the rotor is stopped in a state where the first phase coil is energized, and then the rotor is started in one direction by energizing the second phase coil, or The rotor is stopped in a state where the second phase coil is energized, and then the rotor is started in a direction opposite to the one direction by energizing the first phase coil. Drive circuit.

  Since the brushless DC motor and its drive circuit according to the present invention are configured as described above, in the brushless DC motor and its drive circuit having a simple and low-cost configuration, the forward / reverse rotation of the motor can be controlled by the drive circuit. It becomes possible. According to the brushless DC motor and its drive circuit according to the present invention, a fan motor capable of both intake and exhaust can be realized at low cost.

It is a figure which shows typically the structure and operation | movement of the brushless DC motor in one Embodiment of this invention, (1) of (a), (2), (3) is each step in forward rotation operation | movement, (b) (1), (2), (3) are cross-sectional views showing each stage in the reverse rotation operation by cutting along a plane perpendicular to the rotation axis. It is a circuit block diagram which shows the example of the drive circuit of the brushless DC motor shown in FIG. It is a figure which shows typically the structure of the brushless DC motor in another embodiment of this invention, (a) is sectional drawing cut | disconnected and shown by the plane perpendicular | vertical to a rotating shaft, (b) is 1 of a stator. It is the front view which looked at the front-end | tip part of one salient pole along the centerline of the salient pole from the direction parallel to the paper surface of (a), and its both side views.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The brushless DC motor 10 in one embodiment of the present invention has a so-called outer rotor structure, and includes a stator 20 and a rotor 30 disposed on the outer peripheral side of the stator 20 as shown in FIG. Contains.
The stator 20 is formed of a laminated iron core, and has four salient poles 21 to 24 that extend radially from the rotation center O of the motor and are arranged at equiangular intervals in the circumferential direction. Coils 41 to 44 are wound around the salient poles 21 to 24, respectively, and these coils 41 to 44 are configured such that coils wound around adjacent salient poles are in different phases. It consists of two-phase coils. In the present embodiment, first-phase (A-phase) coils 41 and 43 are wound around salient poles 21 and 23, and second-phase (B-phase) coils 42 and 44 are wound around salient poles 22 and 24. ing.
The rotor 30 is formed by arranging four permanent magnets 31 to 34 magnetized in the radial direction in an annular shape at equal angular intervals in the circumferential direction, and these permanent magnets 31 to 34 are adjacent to each other. Magnetized in the opposite direction. In FIG. 1, magnetization of the inner surface of the rotor 30 facing the stator 20 (ie, N pole (region 31), S pole (region 32), N pole (region 33), S pole ( Region 34)) is shown.

Further, in the brushless DC motor 10, the tip portions 11 to 14 of the salient poles 21 to 24 of the stator 20 have shapes that are center lines of the salient poles 21 to 24 (center lines of the coils 41 to 44) c 1 to c 4. On the other hand, it is formed to be asymmetrical.
In the present embodiment, the left-right direction with respect to the center line c1 of the salient pole 21 is counterclockwise from the center line c1 of the salient pole 21 as shown by way of example in FIG. The directions are clockwise (CCW) and clockwise (CW). For example, in FIG. 1, the counterclockwise (CCW) direction is the left direction, and the clockwise (CW) direction is the right direction. The same applies to the other salient poles 22-24.

  Specifically, the tip portions 11 to 14 of the salient poles 21 to 24 are formed so as to protrude to the left and right in order to increase the facing area with the inner peripheral surface of the rotor 30, and the salient poles 21, 23, the right sides of the center lines c1 and c3 of the surfaces of the front end portions 11 and 13 facing the rotor 30 are formed into arc shapes 11b and 13b in the top view, and the left sides of the center lines c1 and c3 are linear in the top view 11a. , 13a. In the salient poles 22 and 24, the left sides of the center lines c2 and c4 of the surfaces facing the rotor 30 of the tip portions 12 and 14 are formed into arcuate shapes 12b and 14b in the top view, and the right sides of the center lines c2 and c4. Are formed in a straight line shape 12a, 14a in a top view.

Thereby, about each salient pole 21-24, the gap between the front-end | tip parts 11-14 and the rotor 30 is narrow on the arcuate side 11b-14b, and is wide on the linear side 11a-14a side, It is asymmetrical with respect to the center lines c1 to c4 of the salient poles 21 to 24.
Furthermore, by forming the tip portions 11 to 14 of the salient poles 21 to 24 as described above, in the brushless DC motor 10, the adjacent salient poles are the same shape sides of the tip portions facing each other. is there. That is, the salient pole 21 faces the right-side salient pole 22 and the arc-shaped sides 11b and 12b of the tip portions 11 and 12, respectively, and the salient pole 22 and the right-side salient pole 23 respectively. The straight sides 12a and 13a of the tip portions 12 and 13 are opposed to each other, and the salient pole 23 is opposed to the salient pole 24 on the right side and the arc-shaped sides 13b and 14b of the tip portions 13 and 14 are opposed to each other. The salient pole 24 opposes the salient pole 21 on the right and the linear sides 14a and 11a of the tip portions 14 and 11 respectively.
Here, the tip shape of each of the salient poles 21 to 24 has been described as a combination of an arc shape and a linear shape. However, the shape is not limited to this shape, and the gap between the rotor and the stator is left and right. Any combination of shapes that are asymmetrical may be used.

  The brushless DC motor 10 includes means (not shown) for detecting the rotational position of the rotor 30 as in the case of the conventional brushless motor, and this means is preferably one magnetic sensor. (For example, a Hall element).

FIG. 2 shows an example of a drive circuit suitable for driving the brushless DC motor 10. Driving circuit shown in FIG. 2 50 is configured as a two-phase half-wave drive circuit so-called (corresponding to coil 41 and 43 in FIG. 1) phi _A coil of phases wound on the stator A, phi _B Is a B-phase coil wound around the stator (corresponding to the coils 42 and 44 in FIG. 1), Q1 and Q2 are output transistors for supplying current to the coils φ _A and φ _B , respectively. _a, common connection point of the phi _B is connected to the power supply voltage V. In the circuit example shown in FIG. 2, a clamp circuit including a diode D and a Zener diode ZD is connected in parallel to each of the two-phase coils φ _A and φ _B.

The drive circuit 50 includes a microcomputer 52 for controlling on / off of the output transistors Q1 and Q2, and a low voltage power source for stepping down the power supply voltage V and supplying a predetermined voltage to the microcomputer 52. A circuit 51 is also provided, and the microcomputer 52 energizes the two-phase coils φ A and φ B by controlling on / off of the output transistors Q1 and Q2 based on a signal from a magnetic sensor (not shown). The brushless DC motor 10 is driven by switching at an appropriate timing.

Furthermore, in the drive circuit 50, the microcomputer 52 performs forward rotation operation and reverse rotation operation of the brushless DC motor 10, and these operations will be described below. In the following description, in FIG. 1, the operation of rotating the rotor 30 clockwise (CW) is referred to as normal rotation operation, and the operation of rotating the rotor 30 counterclockwise (CW) is referred to as reverse rotation operation.
In the brushless DC motor 10, the coils 41 to 44 excite the tip portions 11 and 13 of the salient poles 21 and 23 to the N pole when energizing the A phase (41 and 43), and the B phase (42, 42 44), the tip ends 12, 14 of the salient poles 22, 24 are wound so as to excite the N pole.

First, the forward rotation operation of the brushless DC motor 10 will be described with reference to FIG. The drive circuit 50 is in a non-energized state of the coils 41 to 44, and from the state where the rotor 30 is stationary with respect to the stator 20 (for example, the state shown in (1)), the A phase (41, 43). The preliminary operation is performed by switching between the energization to the B phase and the energization to the B phase (42, 44) several times, and finally the preparatory operation is terminated in the energized state to the A phase (41, 43).
It is generally uncertain whether the rotation of the rotor 30 during the preliminary operation is normal rotation or reverse rotation. However, at the end of the preliminary operation, the S poles 32 and 34 of the rotor 30 are attracted to the tips 11 and 13 of the salient poles 21 and 23 excited to the N pole, so that the rotor 30 has one S The magnetic pole center of the pole (32 in the illustrated example) and the center of the salient pole 21 substantially coincide, and the magnetic pole center of the other S pole (34 in the illustrated example) and the center of the salient pole 23 substantially coincide. It stops at the position ((2) in FIG. 1 (a)).

Next, the drive circuit 50 starts normal operation of the brushless DC motor by switching the energized coil to the B phase (42, 44) ((3) in FIG. 1A).
Thereby, the tip end portions 12 and 14 side of the salient poles 22 and 24 are excited to the N pole. Then, one S pole (32 in the illustrated example) of the rotor 30 is a tip portion of the tip portion 12 of the salient pole 22 and the tip portion 14 of the salient pole 24 that is close to the arcuate side 12b having a narrow gap. Similarly, the other S pole (34 in the example shown in the figure) is attracted to the tip portion 14 that is close to the arcuate side 14b with a narrow gap, thereby rotating forward (rotation in the CW direction). To start.
Thereafter, the drive circuit 50 switches between energization to the A phase (41, 43) and energization to the B phase (42, 44) at an appropriate timing based on the signal of the magnetic pole sensor, etc. Do the driving.

Next, the reverse rotation operation of the brushless DC motor 10 will be described with reference to FIG. The drive circuit 50 is in a non-energized state of the coils 41 to 44, and from the state where the rotor 30 is stationary with respect to the stator 20 (for example, the state shown in (1)), the A phase (41, 43). The preliminary operation is performed by switching between the energization to the B phase and the energization to the B phase (42, 44) several times, and finally the preparatory operation is completed in the energized state to the B phase (42, 44).
It is generally uncertain whether the rotation of the rotor 30 during the preliminary operation is normal rotation or reverse rotation. However, at the end of the preliminary operation, the S poles 32 and 34 of the rotor 30 are attracted to the tips 12 and 14 of the salient poles 22 and 24 excited to the N pole, so that the rotor 30 has one S The magnetic pole center of the pole (32 in the illustrated example) and the center of the salient pole 22 substantially coincide, and the magnetic pole center of the other S pole (34 in the illustrated example) and the center of the salient pole 24 substantially coincide. Stops at the position ((2) in FIG. 1B).

Next, the drive circuit 50 starts normal operation of the brushless DC motor by switching the energized coil to the A phase (41, 43) ((3) in FIG. 1B).
As a result, the tips 11 and 13 of the salient poles 21 and 23 are excited to the N pole. Then, one S pole (32 in the illustrated example) of the rotor 30 is a tip portion of the tip portion 11 of the salient pole 21 and the tip portion 13 of the salient pole 23 that is close to the arcuate side 11b having a narrow gap. Similarly, the other S pole (34 in the illustrated example) is attracted to the tip 13 that is close to the arcuate side 13b with a narrow gap, so that the reverse rotation (rotation in the CCW direction) is performed. Start.
Thereafter, the drive circuit 50 switches the energization to the A phase (41, 43) and the energization to the B phase (42, 44) at an appropriate timing based on the signal of the magnetic pole sensor, etc. Do the driving.

  In the drive circuit 50, the startup control procedure of the forward rotation operation and the reverse rotation operation of the brushless DC motor 10 as described above is preferably performed as a program for instructing the operation of the microcomputer 52. The microcomputer 52 is stored in the storage means, and executes the control procedure by controlling on / off of the output transistors Q1 and Q2 in accordance with this program. Further, at that time, switching between the forward rotation operation and the reverse rotation operation of the brushless DC motor 10 may be performed based on a rotation direction command signal (not shown) input to the microcomputer 52 from the outside. .

According to the brushless DC motor 10 and its drive circuit 50 in the present embodiment, the drive circuit 50 allows the motor 10 to be used in a simple and low-cost configuration such as the two-phase half-wave drive type brushless DC motor 10 and its drive circuit 50. It becomes possible to control forward rotation and reverse rotation. According to the brushless DC motor 10 and its drive circuit 50, a fan motor capable of both intake and exhaust can be realized at low cost.

  Next, a brushless DC motor 60 according to another embodiment of the present invention will be described with reference to FIG. However, the brushless DC motor 60 in the present embodiment is different from the brushless DC motor 10 shown in FIG. 1 only in the shapes of the tip portions 71 to 74 of the salient poles 81 to 84 of the stator 70. The description of overlapping parts is omitted as appropriate, and the differences will be described below.

In the brushless DC motor 60, the tips 71 to 74 of the salient poles 81 to 84 of the stator 70 are formed so that the thickness thereof is asymmetric with respect to the center line of the salient poles 81 to 84. Specifically, as shown in FIG. 3B as an example of the tip 73 of the salient pole 83, the tip 73 has a surface 73c facing the rotor 30 parallel to the paper surface of FIG. When viewed from the center direction along the center line c3, one end side 73d in the left-right direction of the center line c3 is formed in a substantially trapezoidal shape having a long side and the other end side 73e being a short side. The thickness decreases toward the other end side 73e. The same applies to the other salient poles 71, 72, 74.
And the brushless DC motor 60 has a thick side and a thin side with respect to the center line of the salient pole, respectively, even if the gap between the tip portions 71 to 74 and the rotor 30 is uniform. By functioning equivalently to the narrow side and the wide side, the driving circuit 50 shown in FIG. 2 is used to achieve the same operational effects as the brushless DC motor 10 shown in FIG.
Of course, in the brushless DC motor 60, the adjacent salient poles are configured such that one end side forming the long side and the one end side forming the short side of each tip end face each other.
In the present embodiment, the shape of the salient pole is described as a substantially trapezoidal shape. However, the shape is not limited to this shape, and any shape can be used as long as the shape is asymmetric on the left and right of the center line c3. Also good.

  As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to embodiment mentioned above. For example, in the above-described embodiment, the brushless DC motors 10 and 70 and their drive circuits 50 are 4-pole 4-slot 2-phase half-wave drive type brushless DC motors and their drive circuits. The motor is applicable if the number of poles of the rotor magnetic pole and the number of salient poles of the stator (number of slots) are the same even number. Furthermore, the brushless DC motor and its drive circuit according to the present invention may be of a single phase full wave drive system.

10, 60: brushless DC motor, 11-14, 71-74: tip, 20: stator, 21-24: salient pole, 30: rotor, 31-34: permanent magnet, 41, 43: coil (A Phase), 42, 44: coil (phase B), 50: drive circuit, 51: low voltage power supply circuit, 52: microcomputer, c1 to c4: salient pole center line, Q1, Q2: output transistor, φA: coil (A phase), φ B : Coil (B phase), V: Power supply voltage

Claims (4)

A brushless DC motor comprising a stator having a plurality of salient poles, a coil wound around all the salient poles of the stator, and a rotor having a permanent magnet disposed facing the stator. In
The tips of all the salient poles of the stator are formed in an asymmetric shape with respect to the center line of the salient pole, and the salient poles adjacent to each other across all the salient poles of the stator. Is a brushless DC motor characterized in that the same shape sides of the tip end face each other.   2. The brushless DC according to claim 1, wherein the salient pole is formed such that a gap between the tip portion and the rotor is asymmetrical with respect to a center line of the salient pole. motor.   3. A drive circuit for driving the brushless DC motor according to claim 1, wherein the brushless DC motor performs a forward rotation operation and a reverse rotation operation. Before performing the forward rotation operation and the reverse rotation operation, a preliminary operation of the brushless DC motor is performed, and at the end of the preliminary operation, the rotor is energized by first energizing the coil after the preliminary operation. The driving circuit according to claim 3, wherein the driving circuit is stopped at a position attracted to the salient pole on the rotation direction side.

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