JPH07111791A - Controlling method for brushless dc motor - Google Patents

Abstract

PURPOSE:To improve the efficiency of utilization of coils and magnetism by forming a circuit only with exciting coils, connecting the resultant circuit to an energization circuit, and simultaneously exciting all the exciting coils. CONSTITUTION:A Hall element 3 detects the rotational position of a rotor magnet, and an exciting current control circuit 6 turns on/off transistors Tr1-Tr4 based on the detection signal to feed exciting current to stator coils 1, 2. For example, the transistors Tr1 and Tr4 are turned on and then the transistors Tr2 and Tr3 are turned off according to a detection signal from the Hall element 3. As a result exciting current in the direction of the arrow A is fed to the coils 1, 2 connected in series with each other. This state is maintained for a specified period, and then Tr1 and Tr4 are turned off and Tr2 and Tr3 are turned on. As a result exciting current in the direction of the arrow B is fed to the coils 1, 2. Thereafter, these states are alternately repeated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor including a permanent magnet, and more particularly to a control method of a brushless DC motor applied to a driving motor for a micro motor, a fan motor, a CD, a printer and the like.

[0002]

2. Description of the Related Art A brushless DC motor is, for example, a CD.
It is used in a relatively wide range as a fan motor for driving electronic equipment such as a printer and printer, and for heat dissipation of electronic equipment. 4 and 5 show an example of a control method of the brushless DC motor. The control method shown in the figure is for a two-phase brushless DC motor, and FIG. 4 shows a control circuit of a motor used in this control method, in which a plurality of current magnetic fields are generated in an excited state. Phase first and second phase stator coils 1 and 2 and a rotor magnet (not shown) that obtains a rotational force by electromagnetic interaction between the current magnetic fields of the stator coils 1 and 2, and the rotational position of the rotor magnet. Hall element 3 for detection, and a power supply control unit 4 whose output side is connected to one end side of each stator coil 1, 2.
And a DC power supply 5 connected to the input side of the power supply control unit 4.
And transistors Tr1 and Tr2 having collectors connected in series to the other ends of the stator coils 1 and 2, and an exciting current controller 6 for controlling the Hall element 3 connected to the bases of the transistors Tr1 and Tr2. It consists of

By the way, in the aforementioned DC motor, a dead point may be formed depending on the relative position of the rotor and the stator. Therefore, a part of the teeth of the stator is cut out so that the rotor and the stator die in a stationary state. The point is mechanically deviated, and the start is applied from this state. After the motor is started, the rotation position of the rotor magnet is detected by the hall element 3, and the exciting current control circuit 6 turns on and off the transistors Tr1 and Tr2 based on the detection signal, as shown in FIG. A unidirectional half-wave exciting current is supplied to the first and second phase stator coils 1 and 2 to obtain a rotating torque. However, the following technical problems have been pointed out in such a conventional brushless DC motor control method.

[0004]

That is, in the control method shown in FIGS. 4 and 5, since the cores around which the first and second phase stator coils 1 and 2 are wound are alternately driven by the unipolar type. At least one of the coils 1 and 2 will be inactive, and the utilization efficiency of the coils 1 and 2 will be 1
Not only becomes 1/2, but the utilization efficiency of the stator core around which the coils 1 and 2 are wound is also 1/2 of the whole, and there is a problem that the utilization efficiency is extremely low.

By the way, in the case of the conventionally provided commutator motor, the utilization efficiency of magnetism is higher than that of the circuit of FIG. 6 and 7 show an example of the structure and electric circuit of such a commutator motor.
The commutator motor shown in the figure is a three-phase motor, has an armature 8 and a field 9, and has coils 1 to 3 wound around the armature 8. There is.

The coil 10 is formed of three coils,
A pair of brushes that are connected in a Δ shape and each vertex is connected to a commutator 11 divided into three parts provided on the rotating shaft of the armature 8, and the side surface of the commutator 11 is always in contact with the two commutators 11. 12 are arranged, and both ends of the brush 12 are connected to a DC power supply. In the commutator motor configured as described above, the exciting current is constantly supplied to all of the three coils 10 and the directions thereof are alternated by the same coil, so that the utilization efficiency of the coils and the utilization efficiency of magnetism are high. Become.

However, the commutator motor having such a structure uses the commutator 11 and the brush 12 in order to supply the exciting current to each coil 10, and the brush 12 and the commutator 11 accompanying the rotation. There are various problems such as contact with and changes in its area, scattering of carbon powder of the brush 12, kick voltage due to coil inductance, voltage drop due to brush loss, noise, and life.

The present invention has been made in view of the above conventional problems, and the object thereof is to eliminate the mechanical commutator and to improve the utilization efficiency in spite of being brushless. It is to provide a control method of a brushless DC motor that can be improved.

[0009]

In order to achieve the above object, the present invention obtains a rotational force by electromagnetic interaction between a plurality of exciting coils that generate a current magnetic field in an excited state and the current magnetic fields of the exciting coils. In a method of controlling a brushless motor including a rotor magnet and a sensor that detects a rotational position of the rotor magnet, a circuit network is formed only by the exciting coils, and the circuit network is connected to a current-carrying circuit. The exciting coils are simultaneously excited.

The exciting coil is bidirectionally driven and can supply an exciting current including a state in which the energizing direction is reversed without a rest period. Further, the exciting current can be accelerated and decelerated by changing the ratio of each energization time in bidirectional energization.

[0011]

According to the control method of the brushless DC motor having the above construction, the exciting current is supplied based on the detection output of the sensor for detecting the rotational position of the rotor magnet, so that the commutator is not required. At this time, since the circuit network consisting of only the exciting coils is energized at the same time, all the exciting coils are excited at the same time, and the utilization efficiency of the coils and magnetism is significantly improved.

Further, according to the second aspect of the invention, the exciting current is supplied in a state in which the energizing direction is reversed without including the rest period, so that the width of the magnetic change becomes large despite the brushless state, and the magnetic material The utilization efficiency of is greatly improved and high torque can be obtained. Further, according to the configuration of claim 3, since the energization ratio of the exciting current is changed in response to a shift request at the time of starting, even if a dead point is encountered in one phase, energization is performed in another phase next time. It will be. Therefore, the N / S angle changes according to the energization ratio without providing a missing portion in the stator, so that the phase positional relationship between the rotor and the stator can be changed, dead points are eliminated, and smooth startup is possible. become.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following description, the same or corresponding parts as those in the conventional example described above are designated by the same reference numerals. 1 and 2 show an embodiment of a method of controlling a brushless DC motor according to the present invention. The control method shown in the figure shows a case where the present invention is applied to a single-phase brushless DC motor, and FIG. 1 shows a control circuit of a motor used in this control method.

In the control circuit shown in FIG. 1, a plurality of phases of the first and second stator coils 1 and 2 that generate a current magnetic field in an excited state, and electromagnetic interaction between the current magnetic fields of the stator coils 1 and 2 are used. A rotor magnet (not shown) that obtains a rotational force, a Hall element 3 (position sensor) that detects the position of the N / S pole of the rotor magnet, and a power supply control unit 4 that supplies a DC current to each of the stator coils 1 and 2. A DC power source 5 connected to the input side of the power source control unit 4, a plurality of semiconductor switches connected to the stator coils 1 and 2, for example, transistors Tr1 to Tr4, and bases of these transistors Tr1 to Tr4. And an exciting current control unit 6 for controlling the Hall element 3 connected to.

In the control circuit thus constructed, the rotational position of the rotor magnet is detected by the hall element 3, the detection signal is received by the excitation current control section 6, and the excitation current control circuit 6 is based on this detection signal. , The transistor Tr1 ~
Exciting current is supplied to the stator coils 1 and 2 by turning Tr4 on and off, and the basic content of the control method of such a brushless DC motor is different from this type of conventional method.
It is performed without phase switching, and is characterized by the points described below.

That is, in the case of this embodiment, first, the first and second stator coils 1 and 2 are connected in series and operate in the same phase. The + terminal side of the power supply control section 4 is connected to the emitters of the transistors Tr1 and Tr3 and one end side of the exciting current control section 6. Further, the power control unit 4
The minus terminal side of the Hall element 3 is connected to the emitters of the transistors Tr2 and Tr4 and the one end side of the Hall element 3.

The hall element 3 and the exciting current controller 6 are connected in series. The collectors of the transistors Tr1 and Tr2 and the collectors of the transistors Tr3 and Tr4 are connected in series. Of these transistors Tr1 to Tr4, Tr1 and Tr3 are NPN transistors, and Tr2 and Tr4 are PNP transistors.

A node in which the collectors of the transistors Tr1 and Tr2 are connected in series is connected to one end of the stator coils 1 and 2 connected in series, and the transistors Tr3 and Tr2 are connected.
A node in which collectors of 4 are connected in series is connected to the other ends of the stator coils 1 and 2. In the control circuit configured as described above, for example, based on the detection signal of the Hall element 3, first, the transistors Tr1 and Tr4 are controlled to be in the ON state, and the transistors Tr2 and Tr3 are controlled to be in the OFF state. As a result, the exciting current in the direction indicated by arrow A in FIG. 1 is supplied to the coils 1 and 2 connected in series.

After maintaining this state for a predetermined time, the transistors Tr1 and Tr4 are turned off,
Further, the transistors Tr2 and Tr3 are controlled to be in the ON state, whereby the exciting current in the direction shown by the arrow B in FIG. 1 is supplied to the coils 1 and 2 connected in series, and thereafter, each of these states. Is sequentially repeated. FIG. 2 shows a waveform diagram of the alternating excitation current supplied to the coils 1 and 2 by such control.

As is apparent from the figure, in the control method of this embodiment, the stator coils 1 and 2 are connected in series and all the stator coils 1 and 2 are excited at the same time, so that the utilization efficiency of the magnetic circuit is improved. Is greatly improved,
Unlike conventional commutator motors, commutators and brushes are not required, and the structure is simple and the number of parts does not increase. In particular, according to the control method of the present embodiment, the exciting current is supplied in a state in which the energization direction is reversed without including the pause period, as indicated by the thick arrow in FIG. Doubled,
High torque based on so-called reverse excitation can be obtained. Figure 3
6 shows another embodiment of the control method of the brushless DC motor according to the present invention. The example shown in the figure is the waveform of the exciting current used at the time of starting this type of DC motor. In this example, the supply time of the exciting current in the positive direction is gradually reduced and The excitation current is controlled so that the supply time is constant.

When the bidirectional energization ratio of the exciting current is changed at the time of starting in this way, the N / S ratio of the rotor magnet is constant, whereas the N / S ratio of the stator is changed, which causes the dead point to rise. It can be escaped and a smooth start-up becomes possible. In addition,
The pattern for changing the energization ratio of the exciting current is not limited to the pattern shown in FIG. 3, and a method of temporarily increasing the exciting current supply time, a method of repeatedly increasing and decreasing, or the like can be adopted. .

In the above embodiment, the case where the present invention is applied to a single-phase brushless DC motor has been illustrated, but the present invention is not limited to this and is also applied to other motors. be able to.

[0023]

As described above in detail in the embodiments,
According to the brushless DC motor control method of the present invention, the utilization efficiency of the magnetic circuit is doubled, the stator is not provided with notches and the like, and there is no noise or vibration. It is easy and inexpensive because it does not increase the number of parts.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a control circuit used in a method for controlling a brushless DC motor according to the present invention.

FIG. 2 is a waveform diagram showing an example of an exciting current supplied to a coil in the circuit of FIG.

FIG. 3 is a waveform diagram of an exciting current showing another embodiment of the control method of the brushless DC motor according to the present invention.

FIG. 4 is a circuit diagram showing an example of a control circuit used in a conventional method of controlling a brushless DC motor.

5 is a waveform diagram showing an example of an exciting current supplied to a coil in the circuit of FIG.

FIG. 6 is an explanatory diagram showing an example of a conventional commutator motor.

FIG. 7 is an explanatory diagram showing an electrical configuration of the commutator motor of FIG.

[Explanation of symbols]

 1 1st phase stator coil 2 2nd phase stator coil 3 Hall element (sensor) 4 Power supply control unit 5 DC power supply 6 Exciting current control unit Tr1 to Tr4 transistors

Claims (3)

[Claims] 1. A plurality of exciting coils that generate a current magnetic field in an excited state, a rotor magnet that obtains a rotational force by electromagnetic interaction with the current magnetic field of the exciting coils, and a sensor that detects a rotational position of the rotor magnet. In the method for controlling a brushless motor including the above, a brushless DC motor is characterized in that a circuit network is formed only by each of the exciting coils, the circuit network is connected to a current-carrying circuit, and all the exciting coils are simultaneously excited. Control method. 2. The brushless motor according to claim 1, wherein the exciting coil is bidirectionally driven, and the exciting current is supplied including a state in which the energizing direction is reversed without including a rest period. Control method. 3. The method of controlling a brushless DC motor according to claim 2, wherein the exciting current is accelerated or decelerated by changing a ratio of respective energization times in bidirectional energization.