JPH04168995A - Starting method for brushless two-phase dc motor and brushless 2-phase dc motor circuit - Google Patents

Abstract

PURPOSE:To effectively start a motor by judging the position of a rotor from a detected induced electromotive force, and sequentially supplying a current to first, second driving coils based on the position of the rotor. CONSTITUTION:When the position of a rotor 1 is detected by electromotive forces induced in coils 2a, 2b, the position of the rotor 1 at the time of starting is not known. When a current flows to the first driving coil 2a, the rotor 1 is started to be rotated forward or reversely according to where and which pole of the rotor 1 exhaust near the coil 2a. In this case, an electromotive force is induced in the second driving coil 2a, and the position of the rotor 1 can be known by knowing the polarity and magnitude of the electromotive force. Accordingly, driving currents are sequentially fed to the coils 2a, 2b based on the detected position of the rotor 1 to start to rotate the rotor 1 forward.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC brushless motor, and more particularly to a method for starting a two-phase brushless DC motor and a brushless two-phase DC motor circuit.

[Prior Art] Since a DC brushless motor does not have brushes, it is highly reliable, has a long life, and generates low noise.

For example, electronic equipment and control equipment are sensitive to heat and must be cooled when they generate heat. If natural cooling is insufficient in cooling power, forced cooling using a fan such as an axial fan, cross-flow fan, or centrifugal fan is effective for ensuring normal operation of the equipment.

The characteristics of a DC brushless motor are very suitable for use, for example, in driving a fan for cooling such equipment.

FIG. 2 shows an example of a conventional brushless two-phase DC motor circuit.

The rotor 1 combined with the impeller has a coil 2a.

It is driven by the current flowing through 2b and rotates in the direction of the arrow. The current flowing through the coils 2a and 2b is controlled by transistors Tri and Tr2, and flows through backflow prevention diodes D2 and D3.

The rotation of the rotor 1 is detected by the Hall element 18,
The detection signal is supplied to logic circuit 16.

The logic circuit 16 operates the coil 2a based on the detection signal.
It is calculated whether the current flowing through 2b should be controlled as shown in FIG. 2b, and a control signal is supplied to the bases of transistors Trl and Tr2 via resistors R2 and R3.

Note that capacitors C1 and C2 connected to the bases of transistors TR1 and Tr2 are for voltage stabilization and high frequency short circuit. In addition, D1 in the figure is a backflow prevention guioto;
R1 is a protection resistor, and C3 and C4 are voltage stabilizing high frequency short circuit capacitors.

At startup, the rotational position of the rotor 1 is detected by the Hall element 18, and the drive coil 2a is activated.

Rotation of the rotor 1 is started by supplying a drive current to the rotor 2b. In addition, in applications such as a cooling fan, even if the rotor 1 rotates slightly in the reverse direction, there is no problem as long as the rotor 1 then starts rotating in the normal direction. However, when manufacturing a motor, it is necessary to control the mounting position of the circuit member so that the Hall element 18 is mounted at an appropriate position relative to the rotor 1. This imposes limitations on automatic assembly;
This will cause problems in mass production.

[Problems to be Solved by the Invention] According to the conventional technology described above, InSb is used in the control circuit.
A Hall element formed by the following methods is used.

Such a Hall element has a finite life and has limited temperature characteristics. Furthermore, there are variations in the characteristics of individual elements, and means for correcting the characteristics is required. Furthermore, single-chip integration with silicon integrated circuits is not possible.

Furthermore, since a Hall element is used in the control circuit, it is necessary to individually adjust the position of the pole element relative to the rotor of the motor during manufacturing.

An object of the present invention is to provide a method for starting a brushless two-phase DC motor without using a Hall element.

Another object of the present invention is to provide a brushless 2 that can be manufactured automatically.
The purpose of the present invention is to provide a phase-to-direct current motor.

[Means for Solving the Problems] A method for starting a brushless two-phase DC motor according to the present invention includes a rotor having a permanent magnet, and first and second drive motors each passing a current in a unidirectional direction and driving the rotor. A method for starting a two-phase DC motor having a coil circuit and no brushes, the method comprising the steps of: flowing a drive current through a first drive coil without detecting the position of the rotor; and a second drive coil. A process of detecting the induced electromotive force generated in the drive coil, a process of determining the position of the rotor from the detected induced electromotive force, and a process of controlling the current flowing through the first and second drive coils based on the position of the rotor. and accelerating the rotor.

[When detecting the position of the working rotor using the induced electromotive force of the coil,
At startup, the rotor position cannot be determined. When a current is applied to the first drive coil, the rotor starts rotating forward or reverse depending on whether the front pole of the rotor is nearby or where it is located. At this time, an induced electromotive force is generated in the second drive coil. By knowing the polarity and magnitude of this induced electromotive force, the position of the rotor can be known. By sequentially passing a drive current through the drive coils based on the detected rotor position, rotation of the rotor can be started in the forward direction.

[Embodiment] FIG. 1 shows a brushless two-phase DC motor circuit according to an embodiment of the present invention. The rotor 1 has a four-pole permanent magnet, and rotates in the direction of the arrow by passing a drive current through drive coils 2a and 2b. The currents flowing through the drive coils 2a and 2b are alternately switched by the power transistor circuit 4. The power transistor circuit 4 includes transistors of the same polarity or different polarity that supply two-phase drive currents, and is controlled by a control signal from the logic circuit 6.

When the rotor 1 is rotating, the drive coil 2a.

A driving current flows through one of the coils 2b, and induced electromotive force is detected from the connection points 5a and 5b of the other coil and is input to the logic circuit 6. Therefore, when the rotor 1 rotates, the rotational position of the rotor 1 is detected by the logic circuit 6, and the control signal supplied to the power transistor circuit 4 is controlled based on it. A signal is sent from the logic signal 6 to a flip-flop circuit 8 to form a timing signal.

When the rotor is rotating, an electromotive force is generated in the coil, but when the rotor is stationary, there is no means to detect the position of the rotor.

Therefore, the brushless two-phase DC motor shown in FIG. 1 is started as follows.

As shown in FIG. 3, a pair of drive coils 2a.

One of the two 2b, 2a, is a coil through which current flows during startup, and the other 2b is a coil for detecting induced electromotive force at startup. The rotor 1 has four permanent magnets, with north and south poles arranged alternately.

At startup, since the rotor 1 is stopped, no induced electromotive force is generated in any of the coils 2a, 2b. A current is passed through one coil 2a so that the upper side becomes the north pole as shown in the figure. At the position opposite to this N pole, there is an S pole or an N pole.
There are poles. Furthermore, depending on whether the S and N poles are on the right or left side of the N pole of the coil, the positions are PL,
It is expressed as P2. The adjacent permanent magnet poles of the rotor are Pl
.

Corresponding to P2, P3. Come to position P4. If Pl has an N pole, P3 has an S pole. An electromotive force as shown in the table below is generated in the other coil 2b depending on which position and which polarity of the magnetic pole is placed opposite the N pole of the starting coil 2a.

For example, S
When the pole exists at position P1, the north pole and the south pole attract each other, so the rotor starts rotating counterclockwise. That is, in this case, the rotation is reversed. At a position facing the detection end of the detection coil 2b, an N pole is arranged at position P3 corresponding to the S pole at position P1.

Since this north pole is reversed, a unipolar electromotive force is generated in the detection coil 2b.

Similarly, when the south pole of the rotor 1 is at position P2, the south pole and the north pole attract each other, and the rotor 1 starts rotating normally. At this time,
Since the N pole starts normal rotation from position P4, the detection coil 2
A ten-polar electromotive force is generated at b. In this way, depending on whether the rotor rotates forward or backward, the detection
generates an electromotive force of opposite polarity.

On the other hand, when the N pole of the rotor 1 is placed opposite to the N pole of the drive coil 2a, the S pole is placed opposite the detection coil 2b at position P3. It is placed at P4. Since the N poles repel each other, when the magnetic pole of the rotor 1 is at Pl, forward rotation is started, and when it is at position P21, reverse rotation is started. That is, the S pole at position P3 rotates in the normal direction, and the S pole at position P4 rotates in the reverse direction. When the magnetic pole facing the detection coil 2b is the south pole, the electromotive force generated in the detection coil 2b with respect to the rotation of the rotor 1 is opposite to that when the magnetic pole faces the north pole. That is,
When the S pole is placed at position P3, a negative electromotive force is generated, and when the S pole is placed at position P4, a ten polar electromotive force is generated.

In this way, electromotive force with different polarity is generated depending on whether the rotation is forward or reverse.

If it is known whether the magnetic pole facing the detection coil 2b is N pole or S pole, the position of the rotor can be determined based on the polarity of the induced electromotive force.

By the way, excitation in a two-phase DC motor is performed for each coil in one direction. For this reason, when a magnetic field H of positive polarity is generated by, for example, flowing a drive current, a magnetic flux of H>O is applied to the core of this coil, and even when the current is O, a residual magnetic flux Br remains. That is, magnetic flux in a certain direction remains in the detection coil 2b as well. Which polarity of the magnetic pole of the rotor 1 corresponds to this detection coil 2b?
The magnitude of the induced electromotive force differs depending on whether it is placed facing the In other words, if the magnetic pole (N pole) that reverses the polarity of the core is placed opposite the S pole, the induced electromotive force will be large, and if the other magnetic pole (S pole) is placed, the induced electromotive force will be large. The amount of power is small.

FIG. 5 schematically shows an example of changes in electromotive force when such a bias is present.

When the S pole of the rotor 1 faces the N pole of the drive coil 2a, the N pole of the rotor 1 is placed at the N pole of the detection coil, a large electromotive force is generated, and the N pole of the rotor 1 is placed in the N pole of the detection coil. 2
When facing the north pole of b, the electromotive force becomes smaller. S pole, N
Each time the poles arrive alternately, the electromotive force changes its amplitude.

The magnitude of such electromotive force can be determined by a determination circuit as shown in FIG. That is, the reference voltage Vref at the intermediate position of the electromotive force shown in FIG. 5 is applied to the comparator 12 together with the detection voltage. Since the comparison result is reversed depending on whether the detected voltage is a high voltage indicated as S pole or a low voltage indicated as N pole, the polarity of the rotor can be determined.

When starting the motor, the logic circuit 6 thus causes a driving current to flow through one coil 2a, detects the induced electromotive force generated in the other coil 2b, and determines the position of the rotor. When the rotor position is determined, a current having a phase that rotates the rotor in the normal direction is passed through the power transistor circuit 4 to the drive coil 2a based on the determined rotor position.
, 2b alternately to rotate the rotor 1 in the forward direction.

In addition, during startup, not only one drive current is passed through the coil 2a, but also a startup mode is executed in which current is alternately passed through the coils 2a and 2b, and then the current is cut off in both coils for detection. is preferred. In this case, not only the electromotive force detected by the coil 2b described above but also the electromotive force detected by the coil 2a.
Since the electromotive force can also be detected by the method, the determination result becomes more reliable. When the rotor position is determined,
Accelerating current is alternately applied to the drive coils 2a and 2b again to accelerate the rotor 1, and the rotor 1 is accelerated to a low rotation speed.

In addition, in FIG. 1, the activation/detection time limit switching circuit 1
0 inputs a timing signal and generates a signal to switch the startup mode to the detection mode when the set startup time of two times has elapsed. Initially, the logic circuit 6 generates a control signal for causing current to flow through the drive coils 2a, 2b in a predetermined order without knowing the rotational position of the rotor 1. Such a starting mode is performed a predetermined number of times, and after a pause, the rotation of the rotor is detected and the starting mode is executed again. When a predetermined time has elapsed, a signal from the starting/detection time switching circuit 10 is supplied, and the logic circuit is activated. Transition from startup mode to discovery mode. In detection mode, connection point 5
The rotational position of the rotor 1 is detected by the detection signals supplied from the drive coils 2a and 5b, and the current supplied to the drive coils 2a and 2b is controlled.

Note that D1, R1, C1, C2, and C3 in the figure are parts equivalent to those shown in FIG. 2.

Note that even if the power transistor circuit 4 uses bipolar transistors of the same polarity as shown in FIG.
p) may also be used. It is also possible to use field effect transistors.

However, if the second startup mode is executed after the motor stops, the motor will definitely start rotating.

By adopting a sensorless configuration, the Hall element can be omitted, improving temperature characteristics and extending the circuit life.The number of external parts can be reduced, and the accuracy of circuit component installation can be improved. This eliminates the need for automatic assembly, making it possible to reduce costs.

Although the present invention has been described above with reference to Examples, the present invention is not limited thereto. For example, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

[Effects of the Invention] Omitting the Hall element circuit simplifies the configuration and simplifies the installation process.

Even if the Hall element is omitted, reliable startup can be achieved by executing the startup mode twice.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a brushless 2-phase DC motor circuit according to an embodiment of the present invention, Fig. 2 is a circuit diagram of a brushless 2-phase DC motor circuit according to the conventional technology, and Fig. 3 schematically shows the configuration of a 2-phase DC motor. Fig. 4 is a graph showing the history characteristics of the stator, Fig. 5 is a graph showing the electromotive force generated in the stator coil, and Fig. 6 is a circuit diagram of a judgment circuit that discriminates the electromotive force. . In the figure: 1 Rotor 2 Drive coil 4 Power transistor circuit 5 Connection point 6.16 Logic circuit 8 Flip-flop 10 Starting/detection time switching circuit 18
Hall element circuit R resistance D diode C capacitor Tr) transistor

Claims (2)

[Claims] (1). A method for starting a two-phase DC motor having no brushes and having a rotor having a permanent magnet, and first and second drive coil circuits each passing current in one direction to drive the rotor. a step of supplying a drive current to the first drive coil without detecting the position of the rotor; a step of detecting the induced electromotive force generated in the second drive coil; and a step of detecting the induced electromotive force generated in the second drive coil; A method for starting a brushless two-phase DC motor, comprising: determining the position of the rotor; and accelerating the rotor by controlling currents flowing through first and second drive coils based on the position of the rotor. (2). a rotor having permanent magnets;
and a second driving coil circuit, and the first and second driving coil circuits.
A current source that supplies a drive current to the drive coil; A current source that supplies a drive current to the drive coil, detects the induced electromotive force from the other drive coil to determine the rotor position, and then passes the drive current to the drive coil. A brushless two-phase DC motor circuit having a control circuit that controls current.