JPH06237595A - Controlling method of revolution of sensorless multiphase dc motor - Google Patents

Abstract

PURPOSE:To provide a controlling method of revolution of a sensorless multiphase DC motor which enables increase of a torque in starting and also cancels a starting dead point. CONSTITUTION:In a controlling method of revolution, an exciting current for which steps of (u) (w), (w) (v) and (v) (u) are repeated is supplied only for a period T, and in coils (u), (v) and (w), a reverse excitation drive operation in which the exciting current is reversed from minus to plus is conducted sequentially, not inclusive of a period of stop. Besides, a stop period (t) in which supply of the exciting current to all phases of a motor is stopped after internal steps are repeated twice is provided and each stop period (t) is set between the reverse excitation drive operations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control method for a sensorless multi-phase DC motor, and more particularly to a technique for increasing torque during rotation and avoiding a starting dead point.

[0002]

2. Description of the Related Art Conventionally, a brushless polyphase DC motor has been used as a motor for rotating a magnetic disk drive. This kind of motor is also called a spindle motor, and for example, a stator including a stator coil that generates a magnetic field in an excited state, and a rotor including a rotor magnet that obtains a rotational force by electromagnetic interaction with the magnetic field of the stator coil. , A structure having a sensor for detecting the rotational position of the rotor magnet is well known,
In the spindle motor with such a structure, in many cases,
Rotation control is performed by an electronic circuit formed into a semiconductor chip.

In this case, the magnetic field generation timing on the stator side is controlled by detecting the rotational position of the rotor magnet by a sensor, and a Hall element has been conventionally used for this type of sensor. However, in recent years, in order to avoid downsizing of motors and deterioration of sensor characteristics, the position of the rotor magnet is detected by using the induced voltage (or induced current) generated in the coil while it is idle, without using the sensor. The so-called sensorless multi-phase DC motor is becoming popular.

At the time of starting the sensorless motor, when the motor is stopped, a counter electromotive voltage cannot be obtained, so that the rotor is first oscillated. For example, in a three-phase coil spindle motor, a step process of sequentially supplying an exciting current to a stator coil is repeated, and during this step process,
Normally, there is included a step of supplying a positive direction, a pause, and a reverse direction of exciting current to each phase, and a magnetic field generated by causing a predetermined pattern of exciting current containing such steps to flow between the rotor magnet and The driving torque is generated by the attraction and repulsive force between them, and the motor is started.

On the other hand, when the motor is started, the counter electromotive voltage is detected, and the rotation control of the motor is performed based on the detected value. However, such a rotation control method for a sensorless multi-phase DC motor has the following technical problems.

[0006]

That is, in the above sensorless multi-phase DC motor, the position of the rotor magnet is detected by the induced voltage due to the magnetic flux interlinking with the coil, but there is no induced voltage when the motor is stopped. Also,
Since the polarity of the magnet is unknown, it is forced to start when starting. However, depending on the position of the rotor, a start failure may occur due to low torque, or a magnetic field due to energization may occur in the opposite direction, causing a reverse rotation of 60 degrees or more at the start-up.

Therefore, in order to avoid such inconvenience and improve the starting reliability, the present applicant has developed a starting control method in which a part of the step is a double drive system. In this control method, when the sensorless motor is started, the energization direction is a method including reverse excitation drive operation in which the energization direction reverses from positive to negative or from negative to positive without including a down time, and according to this control method, A large variation range of magnetic flux density is generated, high torque is generated, and starting reliability is improved.

However, even in such a double drive system, for example, when the positional relationship between the rotor and the stator happens to be a position where the generated torque happens to be small with respect to the energization, that is, the starting dead point, the starting current is particularly large. If the number is small, there is a problem that the step sequence is repeated while the rotor does not move much. Further, even in the control after the motor is started and rotated, generally, the method is to supply the exciting current to the stator coils of multiple phases sequentially. I was also dissatisfied with the torque.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sensorless multiphase system capable of sufficiently increasing the torque at the time of starting and eliminating the starting dead point. It is to provide a rotation control method for a DC motor.

[0010]

In order to achieve the above object, the present invention provides a rotating force by electromagnetic interaction between a stator having a stator coil for generating a current magnetic field in an excited state and the current magnetic field of the stator coil. In a rotation control method of a sensorless multi-phase DC motor, the method comprising: a rotor having a rotor magnet for obtaining the above; and a control device that supplies an exciting current for rotating the rotor in a predetermined direction to the stator coil. The step process includes a reverse excitation drive operation in which the energization direction reverses substantially without including a rest period, the reverse excitation drive operation is sequentially performed in a plurality of phases, and an excitation current is supplied during the reverse excitation drive operation. Is provided in all of the plurality of phases.

In the control method, the reverse excitation drive operation is performed even during rotation after the stepping step, the reverse excitation drive operation is sequentially performed in the plurality of phases, and the reverse excitation drive operation is performed. The stop period can be provided in between.

[0012]

According to the rotation control method of the sensorless multi-phase DC motor having the above configuration, the exciting current includes the reverse excitation driving operation in which the energization direction is reversed without the rest period, and the reverse excitation driving operation is performed in the plurality of phases. Since the steps are sequentially performed, the reverse excitation drive operation causes a large variation range of the magnetic flux density at the time of start-up, and high torque is generated. Further, according to the above rotation control method, since the stop section for stopping the supply of the exciting current in all the phases is provided during the reverse excitation driving operation, the motor is reset to the initial value at the time of starting, In other words, the dead center elimination operation is repeated, and even if the dead center is reached at the first start, the rotor and the stator are not operated at the next start time (the next reverse excitation drive operation after reset). Due to the difference in the variation width of the magnetic flux density due to the asymmetry of the positional relationship, the dead point is avoided, and such an operation is continuously repeated during the stepping process.

[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. 1 to 5 show an embodiment of a method for starting a sensorless polyphase DC motor according to the present invention. The start-up method shown in the figure applies the present invention to a three-phase sensorless DC motor, and FIG. 1 shows the overall configuration including a motor control device. And a rotor (not shown) that obtains a rotational force by electromagnetic interaction with the magnetic field of the stator.

The stator has three-phase stator coils u,
v, w, and each stator coil u, v, w
Are commonly connected at one end side. The control device 10 includes a power circuit 10a to which one end side of each stator coil u, v, w is connected, a driver circuit 10b whose output side is connected to the power circuit 10a, and a control section 10c whose output side is connected to the driver circuit 10b. And a sequencer 10d connected to the output side of the control unit 10c, and an excitation counter 1
0e and a stepping timer 10f.

The power circuit 10a receives the output signal of the driver circuit 10b which operates based on a command from the control unit 10c, and applies an exciting current to each of the stator coils u, v, w in a pattern set by the exciting counter 10e. Supply.
The control unit 10c controls the activation of the motor and the rotation control after the activation. The sequencer 10d receives a control signal from the controller 10c and sends out an exciting current having a preset step pattern, and as shown in FIG. 2, the stator coils u, v, w u → w, u → v, w
An exciting current pattern is set in which six internal steps of → v, w → u, v → u, v → w are repeated.

The excitation counter 10e receives a signal from the control section 10c and changes the step pattern of the sequencer 10d based on this signal. For example, when this is set to 1, the step counter is stepped. The progressive pattern is the driver circuit 10b that generates an exciting current that repeats the steps of
When the excitation counter 10e is set to +2, the excitation current in which the internal steps are repeated in the stepping pattern shown in FIG.

The step-up timer 10f is an excitation counter 10e.
The energizing time T of the exciting current and the stop period t set in step 1 are individually set based on the signal from the controller 10c. FIG. 3 shows an example of a control procedure executed by the control unit 10c, and FIG. 4 shows a time chart of exciting currents in the respective stator coils u, v, w at the time of starting and steady rotation of the motor. It is shown.

In the control procedure shown in FIG. 3, when the control unit 10c operates by receiving a start signal, first, step s1.
In step s2, the excitation counter 10e is set to +2. In step s3, the energization period T, the stop period t, and the number of repetitions n of the step timer 10f are set, and the step step is started. In the next step s4, it is determined whether or not the internal step is repeated twice, and when it is determined that this is repeated twice, the process proceeds to step s5.

In step s5, it is determined whether or not the stop period t set in step s3 has elapsed. When the period t has elapsed, in step s6 the number of repetitions n of the stop period is determined, and the number of times n ends. If it is, it is determined in step s7 whether or not it is a zero cross. If it is not zero cross, the process returns to step s2, and if it is determined that a zero cross is performed, the stepping process is ended and step s8 After shifting to the acceleration step, the steady operation of the motor is performed.

When the rotation control of the motor is performed in the above procedure, first, in step s2, the excitation counter 10e is set to +2.
, And the energization period is set to T in step s3, each stator coil u, v, w has internal steps of u → w, w → v, v → u as shown in FIG. Is repeated for a period T, for example, 2 ms
Only supplied.

When such an exciting current is supplied, in the stator coils u, v, w, as shown by the thick arrows in FIG. 4, the exciting current is reversed from negative to positive without including a stop period. The excitation drive operation is performed by the stator coils w, u,
The steps are sequentially performed in the same v order, which causes a large magnetic flux density variation range, high torque is generated in the step process at the time of starting, and the starting probability of the motor is significantly improved, and the starting time is increased. Can be shortened.

In this embodiment, the stop period t is set in step s3, and the stop period t is provided after the internal steps are repeated twice in steps s4 and s5. 4, the stop period of time t is executed every time the internal step is repeated twice,
The stop period t is set during the reverse excitation drive operation. During this stop period, as is apparent from FIG. 4, the supply of the exciting current is stopped in all three phases, and the motor is substantially reset during this stop period.

In this case, for example, if the energization period T is 2 ms, the stop period t is set to about 2.5 ms, which is 5 ms, and a period of 500 μs or more is selected. In this way, when the stop period t is provided between the reverse excitation drive operations,
The residual magnetic flux density of the stator core becomes substantially zero, so the motor will start and reset at high speed at startup, and even if it is at the dead point at the first start, At this point, the dead point is avoided due to the asymmetry of the positional relationship between the rotor and the stator.

In other words, the variation width of the magnetic flux density generated when the current is applied in one direction is different from the variation width of the magnetic flux density generated when the reverse excitation drive operation is performed.
This operation is repeated every reset. Therefore, the starting characteristics of the motor can be improved. In the above embodiment, in the control procedure of FIG. 3, steps s6 and s7 are the same.
A step for detecting the number of rotations of the motor is provided between the step and the step, and even if it is determined in this step that the motor has rotated up to, for example, about 80% of the rated number of steps, the control method is not switched and the step is performed. The same operation as the progression process, that is,
Although the reverse excitation drive operation can be sequentially performed in three phases with a stop period in between, instead of this, a pattern for supplying a normal excitation current that does not include the reverse excitation drive operation after the step process is completed, for example, It is also possible to use the known unipolar control.

The energization period T and / or the stop period t set in step s3 do not necessarily have to be set to the same time during the repeated period. For example, these periods are gradually increased or decreased. It is also possible.

[0026]

As described above in detail in the embodiments,
According to the rotation control method for a sensorless multi-phase DC motor according to the present invention, it is possible to obtain an excellent effect that the starting probability of the motor is extremely high, the torque during operation is large, and the starting dead center is also eliminated. To be

[Brief description of drawings]

FIG. 1 is an overall configuration diagram including a control system of a sensorless polyphase DC motor to which a rotation control method according to the present invention is applied.

FIG. 2 is an explanatory diagram showing an example of a pattern of an exciting current in an energization process adopted in the rotation control method according to the present invention.

FIG. 3 is a flowchart showing an example of a control procedure in the rotation control method of the present invention.

FIG. 4 is a waveform diagram showing an example of an exciting current of the present invention.

[Explanation of symbols]

 10 control device 10a power circuit 10b driver circuit 10c control unit 10d sequencer 10e excitation counter 10f step timer u, v, w stator coil

Claims (2)

[Claims] 1. A stator including a stator coil that generates a current magnetic field in an excited state, a rotor including a rotor magnet that obtains a rotational force by electromagnetic interaction with the current magnetic field of the stator coil, and a predetermined rotor for the rotor. In a rotation control method of a sensorless polyphase DC motor having a control device for supplying an exciting current for rotating in a direction to the stator coil, the stepping step for starting the motor is substantially the energization direction without including a rest period. Including reverse excitation drive operation in which
The sensorless multi-phase DC, wherein the reverse excitation drive operation is sequentially performed in a plurality of phases, and a stop period is provided during which the supply of the excitation current is stopped in all the plurality of phases during the reverse excitation drive operation. Motor rotation control method. 2. The reverse excitation driving operation is performed even during rotation after the stepping step, the reverse excitation driving operation is sequentially performed in the plurality of phases, and the reverse excitation driving operation is performed during the reverse excitation driving operation. The rotation control method for a sensorless polyphase DC motor according to claim 1, wherein a stop period is provided.