JP3223610B2 - How to start a sensorless multi-phase DC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a sensorless multi-phase DC motor, and more particularly to a technique for improving the reliability of the start.

[0002]

2. Description of the Related Art A brushless multi-phase DC motor has conventionally been used as a motor for rotating a magnetic disk drive. This type of motor is also called a spindle motor, and includes, for example, a stator having a stator coil that generates a magnetic field in an excited state, and a rotor having a rotor magnet that obtains 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 a spindle motor having such a structure, in many cases,
Rotation control is performed by an electronic circuit formed into a semiconductor chip.

In this case, the timing of generation of the magnetic field 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, recently, in order to avoid downsizing of the motor and deterioration of sensor characteristics, the position of the rotor magnet is detected using the induced voltage (or induced current) generated in the coil at rest without using the sensor. The so-called sensorless multi-phase DC motor is becoming popular.

When starting the sensorless motor, when the motor is stopped, a back electromotive force cannot be obtained, so that the rotor is first swung. For example, in a three-phase coil spindle motor, a step of sequentially supplying an exciting current to a stator coil is repeated, and during this step,
Normally, the method includes a step of passing an exciting current in a forward direction, a rest, and a reverse direction to each phase, and a magnetic field generated by flowing an exciting current of a predetermined pattern including such steps and a rotor magnet. The driving torque is generated by the suction and repulsive force during the operation, and the motor is started.

However, such a sensorless polyphase DC motor has a technical problem described below, particularly in its starting method.

[0006]

That is, in the above-mentioned sensorless multiphase DC motor, the position of the rotor magnet is detected by the induced voltage due to the magnetic flux linked to the coil. However, when the motor stops, there is no induced voltage. Also,
Since the polarity of the magnet is unknown, it is forcibly started when starting. However, depending on the position of the rotor, start-up failure may occur due to low torque, or a magnetic field due to energization may be generated in the opposite direction, causing a reverse rotation of the mechanical angle of 60 ° or more at the start-up.

Therefore, in order to avoid such inconveniences and to improve the starting reliability, the present applicant has developed a starting method in which a part of the step is made a double drive system. In this starting method, at the time of starting the sensorless motor, the starting method includes a reverse excitation driving operation in which the energizing direction is reversed from positive to negative or from negative to positive without including the pause time. A large change in the magnetic flux density occurs, eliminating the dead center of the start, generating a high torque, and improving the start reliability.

However, even in such a double drive system, for example, when starting at the start of the first stepping step, if the positional relationship between the rotor and the stator happens to be at a position where zero torque is generated with respect to energization, it is started. Even if the stepping sequence is repeated in a state where the rotor does not move much, and the second step for ensuring the rotation of the rotor in the predetermined direction is performed, for example, the reverse excitation driving operation is performed in one direction in one direction. When only the phase coils are used, there is a problem that the torque cannot be sufficiently increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to perform a reverse excitation driving operation in a plurality of phases in a second step. The torque can be increased significantly,
As a result, it is an object of the present invention to provide a method for starting a sensorless multi-phase DC motor in which the starting probability is improved.

[0010]

In order to achieve the above object, the present invention provides a stator having a stator coil for generating a current magnetic field in an excited state, and a rotational force generated by an electromagnetic interaction between the stator coil and the current magnetic field. And a step of supplying an excitation current for rotating the rotor in a predetermined direction to the stator coil in a predetermined internal step pattern. in the first and sensorless polyphase dc motor starting method having a second stepping step of supplying, at the beginning of the second stepping step, in any one phase
The energization direction is reversed without a pause and
Phase other than the internal phase of the first step
To the stator coil with the changed internal step pattern
By supplying the excitation current, the reverse excitation drive operation can be performed in multiple phases.
In this case, the power supply is performed simultaneously and in opposite directions .

In the second step, the reverse excitation driving operation can be performed in at least one phase after the initial reverse excitation driving operation.

[0012]

Generally, in a polyphase DC motor, an internal step pattern for supplying an exciting current to each phase in a stepping step is determined. For example, in a three-phase DC motor, the exciting current becomes u →
Six steps of v, w → v, w → u, v → u, v → w, u → w are repeated. In the start-up method having the above configuration, for example, assuming that such an internal stepping pattern is adopted in the first stepping step and that nine steps are repeated, the present invention provides the second stepping step. In the initial stage, for example, the reverse excitation driving operation is performed in the u-phase, and the excitation current is supplied in a state where the internal step pattern of the second step step exchanges the v-phase and w-phase.

That is, for example, if the motor is at the position of 0 torque at the time of starting, the exciting current is supplied from u to v in the first step of the first stepping step, so that the u phase is positive. , V-phase is negative, w-phase is 0, and in the final step, an exciting current is supplied from w to u. At this time, u-phase is negative, v-phase is 0, and w-phase is 0. Becomes positive.

In such an excited state, in the early stage of the second step, the u-phase is a reverse excitation driving operation, so that the u-phase is positive, and the v-phase and the w-phase are interchanged, so that the v-phase is switched. Is 0 and the w-phase is negative. Therefore, when the phases are switched, a reverse excitation driving operation in which the energization direction reverses from positive to negative without including the idle period is performed at the beginning of the second step in the w phase, and the reverse excitation of this phase is performed. The driving operation is in the opposite direction to that of the u-phase, so that the starting time is shortened and the motor can be started up in a short time.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 to 4 show an embodiment of a method for starting a sensorless multi-phase DC motor according to the present invention. The starting method shown in FIG. 1 applies the present invention to a three-phase sensorless DC motor, and FIG. 1 shows the entire configuration including a control system of the motor. An unillustrated stator that generates
And a rotor (not shown) that obtains rotational force by electromagnetic interaction with the magnetic field of the stator.

The stator has three-phase stator coils u,
v, w are applied to each of the stator coils u, v, w to detect a back electromotive force that is induced in each of the stator coils u, v, w during a pause time during which no exciting current is supplied. The detection circuit 1 is connected. The control system of the present embodiment includes a control unit 2 to which a detection signal of the back electromotive voltage detection circuit 1 is input, and a driver circuit 3 connected to an output side of the control unit 2.
And the power circuit 4 and the control signal of the control unit 2,
A sequencer 5 that outputs an output signal of a preset internal step pattern to the driver circuit 3 at the time of startup.

The power circuit 4 receives an output signal from the driver circuit 3 which operates based on a command from the control unit 2, and supplies an exciting current in a pattern set to each of the stator coils u, v, w. The control unit 2 controls the start of the motor and the steady operation after the start based on a signal from the back electromotive voltage detection circuit 1. FIG. 2 shows a control flow at the time of startup performed by the control unit 2, and FIG. 3 shows a time chart of a stepping process at the time of startup.

In the step shown in FIG. 3, a first step and a second step, and an acceleration step after the second step are set so that the step is repeated twice. In each step, an internal step pattern in which nine internal step steps are performed is set. Further, in this embodiment, as shown in FIG. 4, the internal step pattern of the first step step is such that the excitation current is u → v in the stator coils u, v, w in a cycle synchronized with the inertia of the motor. , W → v,
repeated in the order of w → u, v → u, v → w, u → w,
The first to ninth nine internal step steps are set to be performed.

In the control flow shown in FIG. 2, when the control unit 2 operates upon receiving a start signal, first, a start excitation counter is set in step s1, and a first step step is executed in step s2. In the first stepping step executed in step s2, the sequencer 5 is operated based on the control signal of the control unit 2, the output signal is input to the driver circuit 3, and the first In one internal step, current is supplied from the stator coil u to the coil v for a predetermined time, and in the next second internal step, power is supplied from the stator coil w to the coil v. Thereafter, the internal coil shown in FIG. The stator coils u,
v and w are excited.

When the first step up to nine internal step steps is performed, the current holding step is performed for a predetermined time in step s3. That is, the state of the exciting current in the internal step is maintained during the current holding step. In a succeeding step s4, a second step process is executed. At this time, in the present embodiment, the internal step pattern of the second step is set as follows in each phase u, v, w. First, for the u-phase, as shown in FIG. 4, in the initial stage of the second stepping step, the reverse excitation driving operation in which the energizing direction is reversed without including the idle period is performed.

That is, in the present embodiment, with respect to the u phase, in the internal step of the first step, the u phase is
Since it is negative, the internal step pattern at the beginning of the second step is set to be positive. In the example shown in FIG. 4, the same internal step pattern as in the first step is used. Is set. For the v-phase, the internal step pattern replaced with the w-phase is set in the second step. That is, in the conventional start-up method, the same internal step pattern as in the first step is set for the v-phase.
Since the place where the v-phase becomes negative is replaced with the w-phase at the beginning of the stepping step, the v-phase becomes 0 at the beginning of the second stepping step, and thereafter the first step of the w-phase. Is executed.

Further, for the w phase, the internal step pattern replaced with the v phase is executed in the second step.
When the second step is performed in such a state, a reverse excitation driving operation in which the energization direction reverses from negative to positive without a pause period in the u phase is performed, and the energization direction also changes from positive in the w phase. Since the reverse excitation driving operations to reverse in the negative direction are performed, and the energization directions are opposite to each other in these reverse excitation driving operations, for example, even if the motor is started in a state of 0 torque, the performance of the magnetic body is reduced. It can be fully activated and can be started reliably with a very short startup time.

When the above-described second step is performed in step s4, an acceleration process is performed in step s5, and then a constant speed process is performed in step s6. If there is no abnormality in the state, the state is maintained and an abnormality occurs in the constant speed process. If this is detected in step s7, the process returns to step s1 and the processing at the time of starting is executed again. By the way, according to the above-described method of starting the multi-phase DC motor, even if the start fails in the first step, the reverse excitation driving operation is performed in a plurality of phases at the beginning of the second step. As a result, a large change width of the magnetic flux density is generated, the dead center of the start is eliminated, and a high torque is generated, so that the motor can be started reliably.

In the above embodiment, the execution time of each step of the internal step pattern in the second step is set to be approximately twice as long as the internal step pattern in the first step. However, implementation of the present invention is not limited to this.
In the above embodiment, at the start of the second step (initial stage)
In addition, a reverse excitation driving operation is performed in the two-phase coil,
Thereafter, the normal second stepping process is performed. However, in the motor of the specific model, even if the reverse excitation driving operation is performed at the start of the second stepping process, the motor is generated at a specific angular position of the rotor magnet. Sufficient drive torque cannot be obtained due to the cancellation of the torque, and there is a possibility that start-up failure may occur.

In such a case, it is preferable to switch the current as shown in FIG. That is, after the reverse excitation driving operation is performed in two phases at the start of the second stepping step, for example, the reverse excitation driving operation is performed in one phase (more preferably, it is performed subsequent to the two-phase reverse excitation driving operation). Is preferred. By doing so, the generated torque is offset at the time of the reverse excitation driving operation at the start of the second stepping step, so that even if the starting torque is hardly generated, the generated torque is offset at the subsequent reverse excitation driving operation. Escape, the rotor will rotate.

[0026]

As described above in detail in the embodiments,
According to the method for starting the sensorless multi-phase DC motor according to the present invention, the reverse excitation drive operation is performed in a plurality of phases at the beginning of the second stepping step. Becomes almost zero.

[Brief description of the drawings]

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

FIG. 2 is a flowchart illustrating an example of an activation method according to the present invention.

FIG. 3 is an explanatory diagram of a step process performed in the flowchart shown in FIG. 2;

FIG. 4 is an explanatory view of an internal step pattern in a step step shown in FIG. 3;

FIG. 5 is an explanatory diagram of an internal step pattern in a modification of the second step step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Back electromotive voltage detection circuit 2 Control part 3 Driver circuit 4 Power circuit 5 Sequencer u, v, w Stator coil

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 6/20 H02P 6/16

Claims (1)

(57) [Claims] 1. A stator for generating a current magnetic field in an excited state
Stator with coil and current in this stator coil
Rotor magnet that obtains rotational force by electromagnetic interaction with magnetic field
A rotor provided with a slot, and
An excitation current for rotating the motor is supplied to the stator coil.
Step is performed in a predetermined internal step pattern.
First and second step of supplying an exciting current to a coil
Method of starting sensorless multi-phase DC motor with
hand, At the beginning of the second step, the current is supplied in one phase.
The direction is reversed without a pause and other than the above-mentioned one phase
To the internal step pattern of the first step.
Exciting the stator coil with the changed internal step pattern
By supplying current, the reverse excitation drive operation can be performed in multiple phases.
At the same time and in opposite directions.
How to start a sensorless multi-phase DC motor.