JPH07322589A - Brushless motor and control method for its rotation - Google Patents

Abstract

PURPOSE:To obtain advantages of both the motor with a brush and the brushless motor, eliminate their disadvantages, and obtain desired levels of characteristics, such as starting reliability. CONSTITUTION:A brushless motor includes a stator 26 formed by winding a coil around each tooth 38 of a stator core 22, having a plurality of slots; an annular rotor magnet 30 that is opposed to the stator in such a way that it is freely rotatable, and that is composed of different poles alternately positioned in the direction of circumference; and a sensor 36 that detects the magnetic flux of the rotor magnet 30. The coil wound around of each of the teeth comprise one circuit, and these circuits are simultaneously driven by bi-directional power application via a single-phase power supply. The number of magnetic poles of the rotor magnet is set to a value different from the number of slots in the stator. Further, the sensor is placed in a position opposite to the rotor magnet, outside any adjacent teeth of the stator core in the radial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet type compact motor in general, a brushless motor suitable for a spindle motor and various micromotors, and a rotation control method thereof.

[0002]

2. Description of the Related Art Conventionally, various types of brushless motors such as small magnet type motors and spindle motors have been adopted, but most of them have a coil on each tooth of a stator core having a plurality of slots. Is wound around to form a stator, and an annular rotor magnet having different poles arranged alternately in the circumferential direction is rotatably provided facing the stator, and electromagnetic interaction between the coil current and the magnetic field of the rotor magnet is provided. Thus, the rotor provided with the rotor magnet is rotated.

[0003]

By the way, in the brushless motor having such a configuration, in the case of starting the brushless motor, for example, a shading plate is required in the case of a single-phase inductor motor, and in the case of the single-phase induction motor, a starting rotating magnetic field is generated. Is required, and there is a drawback that switching of the rotation direction requires switching of the switch. Also, in the case of a hall motor, switching of the output polarity is required to switch the rotating direction, and in the case of a two-phase inductor motor and a three-phase spindle motor, switching of terminals is required to switch the rotating direction. .

On the other hand, in the brushed motor, a coil current is supplied by sliding a brush connected to a power source to a commutator connected to a coil of the armature, and the coil current is changed in accordance with the rotation of the armature. Although the configuration is such that switching is performed, the above-described switching is not necessary for switching the rotation direction, and the rotation output can be changed according to the polarity of the power supply output. Therefore, it is simple, inexpensive, and widely used for applications in which the drawbacks described later do not pose a problem.

On the other hand, in the case of this brushed motor, there are problems such as short life and generation of noise because a mechanical contact by a commutator and a brush is required to rotate the armature, and the motor has an axial direction. It has the drawback that the length is large and the number of parts is large.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to retain the advantages of both the brush motor and the brushless motor, and at the same time, to solve various problems. It is an object of the present invention to provide a brushless motor and a rotation control method for the same, which can solve the above problems and obtain a predetermined performance with respect to various characteristics such as starting reliability.

[0007]

In order to achieve the above object, in the brushless motor of the present invention, a stator constituted by winding a coil around each tooth of a stator core having a plurality of slots, and this stator. A rotor magnet that is rotatably provided facing each other and in which different poles are alternately arranged in the circumferential direction, and a sensor that detects the magnetic flux of the rotor magnet, and is wound around each tooth. One network is formed, and this network is driven simultaneously by bidirectional energization from a single-phase power source.
The number of magnetic poles of the rotor magnet and the number of slots of the stator are set to different numbers, and the sensor is arranged at a position facing the rotor magnet radially outside between any two adjacent teeth in the stator core. I am trying.

In this case, it is desirable to dispose one sensor at a position facing the rotor magnet radially outside between any two adjacent teeth in the stator core, and each coil wound around each tooth. It is desirable that the polarities of the two are different in the number of magnetizing and demagnetizing. Further, it is preferable that the coil is energized by reverse excitation when the energization direction reverses, substantially without including a rest period. Further, it is more desirable to form the stator core from a grain-oriented steel plate.

In order to achieve the above object, in the rotation control method for a brushless motor of the present invention, a stator having coils forming one circuit network is wound around each tooth of a stator core having a plurality of slots. And an annular rotor magnet rotatably opposed to the stator, having a number of magnetic poles different from the number of slots of the stator, and having different poles arranged alternately in the circumferential direction, and the magnetic flux of the rotor magnet is detected. At least one sensor for driving the circuit network simultaneously by bidirectional energization by a single-phase power source, and energizing the circuit network when the detection signal from the sensor exceeds a certain value range. It is characterized in that the energization direction is switched according to the direction in which the detection signal crosses the range of the constant value upon starting.

In this case, when the detection signal of the sensor is below a certain value at the time of start-up, or when the start-up torque is insufficient due to other reasons, the sequence of reversing the recognition of the polarity of the sensor and restarting is executed. Desirably, it is also desirable to insert at least one rest period at the time of reversal of the magnetic excitability in this restart sequence. Further, it is preferable to perform the step of determining the rotation direction of the rotor magnet after the startup or after the restart, and reverse the recognition of the polarity of the sensor at the time of reverse rotation to execute the restart sequence.

[0011]

According to the brushless motor of the present invention described above,
The coils of each tooth that make up one circuit network are simultaneously excited by the bidirectional energization in which the energization direction is reversed by the single-phase power source, so before the stator coil is magnetized and this residual magnetism disappears, this time in the opposite direction. Is excited, a so-called reverse excitation operation is obtained, the width of magnetic change in the stator core is increased, and a large torque can be generated.

During rotation, a sensor arranged radially outside between any two adjacent teeth in the stator core detects the rotational position of the boundary between the magnetic pole of the rotor magnet and the adjacent magnetic pole, and the sensor detects the rotational position. The rotation direction of the rotor magnet is determined by the detection signal, and the energization switching timing is set. Here, since the number of slots of the stator, that is, the number of poles and the number of magnetic poles of the rotor magnet are set to be different from each other, a dead point is rarely formed at the time of startup, and the startup is performed quickly. Further, if the stator core is composed of a directional core, the dead center can be further eliminated.

If the polarities of the coils wound around the teeth are set so that the numbers of magnetizing and demagnetizing are different, the rotor magnet is increased even if a dead point is formed at the time of starting. Starting is started based on the difference in magnetic field between the magnetic pole and the demagnetizing pole, and smooth starting is realized. Since each coil is excited simultaneously by bidirectional energization in which the energization direction is reversed by the single-phase power supply, even if the number of increasing poles and demagnetizing poles are different, the polarity of the coils for increasing magnetism and demagnetizing will alternate. Changes to
Less irregular rotation.

Further, according to the rotation control method of the brushless motor of the present invention described above, it is preferable that the coil 1 is composed of each coil.
A direction in which two circuits are driven simultaneously by bidirectional energization from a single-phase power supply, and when the detection signal from the sensor exceeds a certain value range, energization to the circuit network is started and the detection signal crosses the certain value range. By switching the energizing direction according to the above, reliable and smooth rotation of the rotor magnet can be obtained.

When the detection signal of the sensor is in the range of a constant value at the time of starting, the circuit network is not energized. In such a case, the sequence of reversing the polarity of the sensor and restarting is executed. The energization of the circuit network is started and the rotation of the rotor magnet is obtained. In this restart sequence, if the rest period is inserted at least once when reversing the excitation magnetic pole, one and the other rotation vectors are deviated, and the rotor magnet starts to rotate in the uneven distribution direction, enabling reliable start. Become.

Further, if the step of determining the rotation direction of the rotor magnet is carried out after the startup or after the restart, and the polarity of the sensor is reversed at the time of reverse rotation and the restart sequence is executed, the desired rotation direction can be obtained. Always get.

[0017]

Embodiments of the present invention will be described with reference to the drawings. First, the first embodiment will be described with reference to FIGS.

FIG. 2 shows a case where the recording medium such as a CD-ROM is applied to a micromotor for rotationally driving the same. In FIG. 2, a substrate 10 made of an isotropic or directional silicon steel plate is fixed to a driving device. A cylindrical sleeve 14 is fixed in the mounting hole 12 of the shaft 10 with its axis perpendicular to the substrate 10 and protruding downward, and the shaft 20 is inserted inside the sleeve 14 via a pair of oil-impregnated bearings 16 and 18. Is rotatably supported. The upper and lower ends of the shaft 20 are led out from the sleeve 14 in the vertical direction.

A stator 26 constituted by winding a coil 24 around a stator core 22 is fixed to the outer periphery of the lower half of the sleeve 14, and the stator 2 is attached to the lower end of the shaft 20.
A cup-shaped rotor holder 28 arranged so as to surround the outer periphery of 6 is fixed by caulking or the like.
An annular rotor magnet 30 is fixed to the inner peripheral surface of the cylindrical wall. The rotor magnet 30 faces the outer peripheral surface of the stator 26 with a slight gap. A rotor 32 is constituted by the rotor holder 28 and the rotor magnet 30.

At the upper end of the shaft 20, a turntable 34 located above the substrate 10 is press-fitted and fixed, and a CD (recording medium) (not shown) is placed on the turntable 34. A sensor 36 including one Hall element is arranged at a position corresponding to the rotor magnet 30 on the lower surface of the substrate 10 and detects a boundary between magnetic poles of the rotor magnet 30.

FIG. 1 shows the relationship between the stator 26 and the rotor 32 in the micromotor. The coil 24 is omitted.

The stator core 22 of the stator 26 has a six-slot structure, and six teeth 38 are arranged at equal intervals in the circumferential direction. The coils 24 are wound around the teeth 38, respectively.
In each tooth 38 in the order of constant rotation direction,
,,, and the coils 24 of the teeth 38 are magnetized (or demagnetized), and the coils 2 of the teeth 38 of
4 is wound so as to be demagnetized (or increased), and these are connected in series to form one circuit network.

Therefore, by energizing the coil 24,
,,, each tooth 38, and, each tooth 38
The respective tip portions, namely, the tip 40 are magnetized so that their magnetic poles are opposite to each other.

On the other hand, the rotor magnet 30 has a 4-pole structure, which is different from the number of slots of the stator core 22.
N poles and S poles are alternately arranged in the circumferential direction to form four magnetic poles. The sensor 36 is arranged on the lower surface of the substrate 10 so as to face the rotor magnet 30 between the increased magnetic pole and the depolarized magnetic pole of the stator core 22, that is, radially outside the center between the teeth 38.

FIG. 3 shows a schematic configuration of the motor control circuit 42. The motor control circuit 42 is connected to a DC power supply 44 and supplies a DC current to the coil 24, and an exciting current control unit 48 that controls switching of a switching element connected to the coil 24, for example, transistors T1 to T4. And have. The detection signal from the sensor 36 is input to the exciting current controller 48 through the hysteresis amplifier 50.

The power supply control unit 46 controls the current supplied to the coil 24 by the CLV signal obtained when reproducing the CD, and controls the rotation speed of the rotor 32. In addition, the exciting current control unit 48 drives the coil 24 at the same time by bidirectional energization in which the energizing direction is reversed while the magnetization of the stator core 22 remains substantially without including the rest period, and the sensor 36 is operated.
When the detection signal from 1 exceeds the constant value range, energization to the circuit network is started, and the energization direction is switched according to the direction in which the detection signal crosses the constant value range.

In the thus constructed micromotor, the excitation current control section 48 of the motor control circuit 42 carries out the rotation control shown in the flow chart of FIG.

That is, when the rotation control is performed, first, the sensor voltage is applied to set the conduction state of either polarity. This will be referred to as initial setting (step S).
1). At this time, depending on the position of the rotor magnet 30, the detection signal of the sensor 36 may not reach a certain value or more and the coil 24 may not be energized.
It is forcibly dropped to either polarity (S2). Then, the following first sequence is executed (S4).

In the first sequence, the energization of the coil 24 is based on bidirectional energization in which the energization direction is reversed by the single-phase power supply without substantially including the idle period as shown in FIG. In this case, it is more preferable to perform control such that the rest period t is inserted at least once (twice in the embodiment) at the time of reversing the exciting magnetic property. This rest period t
By including the above, it is possible to more reliably start the rotor 32 by modulating the variation width of the magnetic flux density due to single-phase excitation or the vibration period and restarting due to the vibration generated thereby. Although it is effective to provide the pause period t at the zero-cross at the time of polarity reversal, the exciting force decreases depending on the length of the pause period t.

When the starting torque of the motor is weak and the detection signal of the sensor 36 does not exceed a certain value within a certain time limit, that is, when a predetermined rotation cannot be obtained, the polarity of the sensor voltage is inverted (S5, S6). The second sequence is then executed (S7), and the coil 24 is energized. Second
In the sequence, for example, the same energization control as in the first sequence is performed.

Thereafter, the strong rotation direction of the rotor magnet 30 is determined based on the detection signal of the sensor 36 (S
8) In the case of the desired rotation direction, the next acceleration process is executed (S10), and in the case of the opposite of the desired rotation direction, after inserting the pause operation to stop or decelerate the rotation (S10).
9) Then, returning to step 2, the above-mentioned operation is performed. Here, although the rotation torque may differ with respect to the rotation direction, in the case where the rotation direction is changed in this state, the gain of the control system may be asymmetric.

This motor has one sensor, and the rotation direction (C
The torque differs depending on the energization timing depending on (W, CCW), but this can be compensated by making the servo gain asymmetric in the application including the acceleration / deceleration process. However, when it is desired to equalize the maximum torque in both directions, two sensors may be used and the optimum timing may be selected according to the rotation direction, or the output of one sensor may be delayed. In general, the former is used, in which case the outputs of the two sensors are selectively processed via operational amplifiers, or
One or both sensor outputs may be used by making the impedance and potential of the sensor terminals substantially equal.

In the acceleration step, as shown in FIG. 4, the single-phase power supply performs bidirectional energization in which the energization direction is reversed without substantially including a rest period, and the energization direction switching cycle is changed, that is, gradually. Then, the rotation speed of the rotor 32 is increased. The acceleration control of the child rotor 32 is performed until the rotor 32 reaches a constant speed (S11), and when the rotor 32 reaches a constant speed, control for maintaining this constant speed state is performed.
If the application is rotation in one direction, the relationship between the position of the stator and the sensor and the sensor voltage is uniquely determined in FIG.
The step (S8, S9) of FIG. 5 can be omitted.

When a stop command is issued during the rotation of the rotor 32 (S12), the energization of the coil 24 is stopped or the deceleration control is executed to stop the rotation of the rotor 32 (S13). ).

By the way, at the start-up described above, the stator 26
It is considered that the rotor 32 and the rotor 32 cannot be started by forming a so-called dead point. However, since the number of poles of the stator 26 and the number of magnetic poles of the rotor magnet 30 are different, it is possible to start them without forming a dead point. Is possible. Further, as shown in FIG. 4, in order to ensure the start-up reliability, the control for restarting after providing the resting period after supplying the excitation current for one cycle is executed, so that there is substantially no start-up failure. Can be considered.

FIG. 6 is a second embodiment showing a case of a 6-pole 9-slot configuration. The stator core 54 of the stator 52 has a nine-slot structure, and nine teeth 56 are arranged at equal intervals in the circumferential direction. Each tooth 5
Although coils not shown in the drawing are wound around 6 respectively, these coils are arranged in a certain rotation direction in order of each tooth 5 of.
6, the coils of the teeth 56 of ,,,, are magnetized (or demagnetized),
The coils of the teeth 56 are wound so as to be demagnetized (or magnetized), and these are connected in series to form one circuit network.

Therefore, by energizing the coil,
The tips 56 of the teeth 56 of ,,, and the teeth 56 of the teeth 56 of ,, and the tips 58 are magnetized so that their magnetic poles are opposite to each other.

On the other hand, the rotor magnet 60 has a 6-pole structure, unlike the number of slots of the stator core 54.
N poles and S poles are alternately arranged in the circumferential direction to form six magnetic poles. The sensor 62 such as a Hall element that detects the boundary between the magnetic poles of the rotor magnet 30 includes a stator core 54.
Between the increasing magnetic pole and the decreasing magnetic pole of, that is, both teeth 56 of
It is arranged to face the rotor magnet 60 on the outer side in the radial direction at the center of the space.

In the brushless motor having such a structure, the number of slots of the stator 52 and the number of poles of the rotor magnet 60 are different from each other, so that the coil is energized at the time of starting, as in the above-described embodiment. When started, the rotor magnet 60 starts rotating.

Further, by controlling the current to the coil by the same exciting current control section as described above, not only the start-up is sure but also the rotation of the rotor magnet 60 can be controlled in the desired rotation direction.

In the above embodiment, the stator cores 22 and 54 made of isotropic silicon steel sheets are assumed.
It is also possible to use a stator core of a grain-oriented silicon steel sheet or a grain-oriented silicon steel sheet. According to this, not only the starting torque can be increased by the inclination of the easy axis of magnetization, but also the effect of increasing the rotating torque due to the high saturation magnetic flux density, low noise, and low vibration can be obtained.

Although the embodiments of the brushless motor of the present invention have been described above, the present invention is not limited to these embodiments, and various changes and modifications can be made without departing from the gist of the present invention. It goes without saying that it is possible.

[0043]

Since the present invention is configured as described above, it has the following effects.

According to the brushless motor of the present invention, the number of slots of the stator core and the number of poles (number of magnetic poles) of the rotor magnet are set to different numbers, while one coil is wound around each tooth of the stator core to form one circuit network. Is formed and driven in a single phase, and only one sensor that detects the magnetic flux of the rotor magnet is used to control the energization to the circuit network by this detection signal. The object is to achieve the object of the present invention, which can be easily realized by a two-terminal circuit which can be easily switched, and has high starting reliability and controllability, low noise, low vibration, and long life.

Here, if the polarities of the coils wound around the teeth are set so that the numbers of magnetizing and demagnetizing are different, even if a dead center is formed at the time of starting, the rotor magnet is Starting is started based on the difference between the magnetic fields of the increasing magnetic pole and the decreasing magnetic pole, and smooth starting is realized.
Since each coil is excited at the same time by bidirectional energization in which the energization direction is reversed by the single-phase power supply, even if the number of the increasing pole and the demagnetizing pole is different, the polarity of the coil of the increasing magnetism and the demagnetizing force will change alternately However, uneven rotation can be prevented.

Further, according to the rotation control method of the brushless motor of the present invention, one circuit network constituted by each coil is simultaneously driven by bidirectional energization by the single-phase power source, and the detection signal from the sensor has a constant value. When the range is exceeded, energization to the network is started, the energization direction is switched according to the direction in which the detection signal crosses the range of a certain value, and the control gain is switched as necessary, so that a reliable and smooth rotor magnet The rotation is obtained.

Then, even when the detection signal of the sensor is in the range of a constant value at the time of start-up, the sequence for reversing the polarity of the sensor and restarting is executed, so that energization to the network is started and the rotor magnet is started. Can be reliably rotated, and in this restart sequence, by inserting a pause period at least once when reversing the magnetic excitability, one and the other rotation vectors are biased, and the rotor magnet is It will start around and will be able to start reliably.

Further, in the case of bidirectional rotation, a step of discriminating the rotation direction of the rotor magnet is carried out after starting or restarting, and the polarity of the sensor is reversed at the time of reverse rotation to execute the restart sequence. Thus, the desired rotation direction can always be obtained.

[Brief description of drawings]

FIG. 1 is a plan view of a stator and a rotor showing essential parts of a brushless motor and a rotation control method thereof according to a first embodiment of the present invention.

FIG. 2 is a cut front view showing the overall configuration of the brushless motor of FIG.

FIG. 3 is a circuit diagram showing the coil drive circuit of FIG.

FIG. 4 is a waveform diagram of coil currents of CW and CCW in the drive circuit of FIG.

5 is a flowchart showing a sequence at startup in the drive circuit of FIG.

FIG. 6 is a plan view of a stator and a rotor showing a main part of a second embodiment of the present invention.

[Explanation of symbols]

 22, 54 Stator core 24 Coil 26, 52 Stator 30, 60 Rotor magnet 36, 62 Sensor 38, 56 Teeth 44 Single-phase power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Yamamoto, No. 10 Tsutsuimachi, Nishikyogoku, Ukyo-ku, Kyoto

Claims (9)

[Claims] 1. A stator formed by winding a coil around each tooth of a stator core having a plurality of slots, and a stator rotatably provided facing the stator and having different poles alternately arranged in the circumferential direction. An annular rotor magnet, and a sensor for detecting the magnetic flux of the rotor magnet,
In the brushless motor including: a coil wound around each tooth forms one circuit network, and the circuit networks are simultaneously driven by bidirectional energization by a single-phase power source, and the number of magnetic poles of the rotor magnet and the slot. What is a number?
The brushless motor is set to different numbers, and the sensor is arranged at a position facing the rotor magnet radially outside between any two adjacent teeth in the stator core. 2. The brushless motor according to claim 1, wherein one of the sensors is arranged at a position facing the rotor magnet radially outside between any two adjacent teeth of the stator core. 3. The brushless motor according to claim 1, wherein polarities of the coils wound around the teeth are different in the number of magnetizing and demagnetizing. 4. The brushless motor according to claim 1, wherein the coil is energized in a reverse excitation state in which the energization direction reverses substantially without a rest period. 5. The brushless motor according to claim 1, wherein the stator core is made of a grain-oriented steel plate. 6. A stator in which a coil forming one circuit network is wound around each tooth of a stator core having a plurality of slots, and a stator rotatably provided facing the stator and having a number of slots different from that of the stator. A rotation control method for a brushless motor, comprising: an annular rotor magnet having a number of magnetic poles and alternating different poles arranged in the circumferential direction; and at least one sensor for detecting a magnetic flux of the rotor magnet. The circuit network is simultaneously driven by bidirectional energization by a single-phase power source, and energization to the circuit network is started when the detection signal from the sensor exceeds a certain value range, and the detection is performed. A rotation control method for a brushless motor, wherein the energization direction is switched according to the direction in which the signal crosses the range of the constant value. 7. The rotation of the brushless motor according to claim 6, wherein at the time of start-up, when the detection signal of the sensor is in the range of the constant value, the sequence of reversing the recognition of the polarity of the sensor and restarting is executed. Control method. 8. The rotation control method for a brushless motor according to claim 7, wherein a rest period is inserted at least once when the exciting magnetic pole property is reversed in the restart sequence. 9. The method of determining the rotation direction of the rotor magnet after starting or after restarting, the polarity of the sensor is reversed during reverse rotation, and the restarting sequence is executed. 8. A rotation control method for a brushless motor according to item 8.