JPH06169591A - Starting method for sensorless multiphase dc motor - Google Patents

Abstract

PURPOSE:To provide a method of starting a sensorless multiphase DC motor which improves the starting probability. CONSTITUTION:According to this starting method, an exciting counter is set S1, and the first step process S2 is executed. When the first step process S2, which has a specified inside step, is executed, a current preserving process S3 is executed for a specified time. Subsequently, the second step process S4 is executed. For the inside step pattern in this process, reverse excitation drive action, in which the direction of current application reverses without including the pause period, is performed, in the early stage of the process, in u phase. As regards v and w phases, the inside step pattern, where these are replaced with each other, is executed in the second step process s4. According to the second step process s4 like this, reverse excitation drive action, where the direction of current application reverses from negative to positive without including pause period, is performed in u phase and w phase. And, after that, it goes to acceleration process s5, and next it shifts to a constant velocity process s6, and if there is no abnormality in its condition, the condition is maintained, and also if abnormality occurs in the constant velocity process s6, and it is detected, it returns to s1 and the processing at start is executed again.

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 starting.

[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.

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

[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 an inconvenience and improve the starting reliability, the present applicant has developed a starting method in which a part of the stepping is a double drive system. In this starting method, at the time of starting the sensorless motor, the starting method includes a reverse excitation drive operation in which the energization direction is reversed from positive to negative or from negative to positive without including a down time, and according to this method, A large variation range of the magnetic flux density is generated, the dead point of starting is eliminated, high torque is generated, and starting reliability is improved.

However, even in such a double drive system, for example, if the positional relationship between the rotor and the stator happens to be a position where 0 torque is generated by energization at the start of the first stepping process, it is started. Even if the step sequence is repeated in a state where the rotor does not move much and the second step process for surely rotating the rotor in the predetermined direction is performed, for example, the reverse excitation drive operation is performed in a single direction. In the case of only the phase coils, there is a problem that the torque cannot be increased sufficiently.

The present invention has been made in view of the above problems, and an object of the present invention is to perform reverse excitation driving operation in a plurality of phases in the second step process. With this, you can significantly increase the torque,
As a result, it is an object of the present invention to provide a method for starting a sensorless multi-phase DC motor that improves the starting probability.

[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. And a step of supplying an exciting current for rotating the rotor in a predetermined direction to the stator coil by applying an exciting current to the stator coil in a predetermined internal step pattern. In the method for starting a sensorless multi-phase DC motor having first and second stepwise steps of supplying the reverse step, the second stepwise step is the reverse in which the energization direction reverses initially in any phase without including a pause period. An exciting drive operation is performed, and the stator coil is excited by an internal step pattern in which phases other than the above-mentioned phases are exchanged with respect to the internal step pattern in the first step step. And supplying the current.

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

[0012]

In general, in a multi-phase DC motor, an internal step pattern for supplying an exciting current to each phase is determined in a step step. For example, in a three-phase DC motor, the exciting current is 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, if such an internal step pattern is adopted in the first step step and nine steps are repeated, the present invention provides the second step step. In the initial stage of, the reverse excitation drive operation is performed in the u phase, for example, and the exciting current is supplied in a state in which the v step and the w phase are interchanged in the internal step pattern of the second step step.

That is, for example, if the motor is at the position of zero torque at the time of start-up, since the exciting current is supplied from u to v in the first step of the first step, the u phase is positive. , V phase is negative and w phase is 0. 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 Be positive.

In such an excited state, in the initial stage of the second step process, the u phase becomes the reverse excitation drive operation, so that the u phase is positive and the v phase and the w phase are exchanged, so that the v phase is changed. Is 0 and the w phase is negative. Therefore, when the phases are exchanged, the reverse excitation drive operation in which the energization direction reverses from positive to negative without the pause period is performed in the initial stage of the second step even 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 operation, which shortens the starting time and allows the motor to be started in a short time.

[0015]

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 4 show an embodiment of a method for starting a sensorless polyphase DC motor according to the present invention. The starting method shown in the same figure is one in which the present invention is applied to a three-phase sensorless DC motor, and FIG. 1 shows the entire configuration including a control system of the motor. And a stator outside the figure that generates
It has a rotor (not shown) that obtains a rotational force by electromagnetic interaction with the magnetic field of this stator.

The stator has three-phase stator coils u,
The back electromotive force which detects the back electromotive force induced in each stator coil u, v, w during the rest time when the exciting current is not supplied to each stator coil u, v, w. The detection circuit 1 is connected. The control system of this embodiment includes a control unit 2 to which the detection signal of the back electromotive force detection circuit 1 is input, and a driver circuit 3 connected to the output side of the control unit 2.
And a control signal from the power circuit 4 and the control unit 2,
It has a sequencer 5 for outputting an output signal of a preset internal stepping 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 section 2 and supplies an exciting current in a pattern set for each stator coil u, v, w. The control unit 2 controls the start-up of the motor and the steady operation after the start-up based on a signal from the back electromotive force detection circuit 1. FIG. 2 shows a control flow at the time of starting performed by the control unit 2, and FIG. 3 shows a time chart of the step process at the time of starting.

In the step process shown in FIG. 3, the first and second step processes and the acceleration process after the second step process are set so that the step process is repeated twice. Therefore, in each step, an internal step pattern in which nine internal step steps are performed is set. Further, in this embodiment, the internal step pattern of the first step is, as shown in FIG. 4, a cycle in which the exciting current is u → v in the stator coils u, v, w in synchronization with the inertia of the motor. , W → v,
repeated in the order of w → u, v → u, v → w, u → w,
It is set such that nine internal stepping steps 1 to 9 are performed.

In the control flow shown in FIG. 2, when the control section 2 receives the start signal and operates, first, the start excitation counter is set in step s1, and the first step step is executed in step s2. In the first step step executed in step s2, the sequencer 5 is operated based on the control signal of the control unit 2, the output signal thereof is input to the driver circuit 3, and first, through the power circuit 4, In one internal step step, the stator coil u is energized to the same v for a predetermined time, and in the next second internal step step, the stator coil w is energized to the same v, and thereafter, the internal steps shown in FIG. 4 are performed. The stator coil u,
v and w are excited.

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

That is, in the present embodiment, regarding the u phase, in the internal step of the first step, the u phase is
Since it is negative, the initial internal step pattern of the second step process is set to be positive, and in the example shown in FIG. 4, the same internal step pattern as the first step process is set. It is set. In addition, regarding the v phase, the internal step pattern replaced with the w phase is set in the second step step. That is, in the conventional start-up method, the same internal stepwise pattern as in the first stepwise step is set for the v-phase.
At the beginning of the stepping process, the place where the v phase becomes negative is replaced with the w phase, so that the v phase becomes 0 at the beginning of the second stepping process, and thereafter, the first stepping process of the w phase. The internal step pattern of is executed.

Further, regarding the w phase, the internal step pattern replaced with the v phase is executed in the second step step.
When the second step process is executed in such a state, a reverse excitation drive operation is performed in which the energization direction reverses from negative to positive without including a pause period in the u phase, and also in the w phase, the energization direction changes from the positive direction. The reverse excitation drive operation is performed in the negative reverse direction, and the energization directions are opposite to each other by these reverse excitation drive operations. Therefore, for example, even if the motor is started in the state of 0 torque, the ability of the magnetic body is reduced. It is possible to make full use of it, and it is possible to reliably start it up with a very short start-up time.

When the above-described second step process is executed in step s4, the acceleration process is performed in step s5, and thereafter, the constant speed process is executed in step s6, and the process proceeds to the constant speed process. If there is no abnormality in the state, the state is maintained, and if an abnormality occurs in the constant speed process, and this is detected in step s7, the process returns to step s1 and the startup process is executed again. By the way, according to the starting method of the multi-phase DC motor as described above, even if the starting fails in the first step process, the reverse excitation drive operation is performed in a plurality of phases in the initial stage of the second step process. A large variation range of the magnetic flux density is generated, the dead point of starting is eliminated, and high torque is generated, so that the motor is reliably started.

In the above embodiment, the execution time of each step of the internal step pattern of the second step is set to be approximately twice as long as that of the internal step pattern of the first step. The implementation of the present invention is not limited to this.
Further, in the above embodiment, at the start of the second step process (initial stage)
, The reverse excitation drive operation is performed in the two-phase coil,
After that, the configuration is such that the normal second step process is performed, but in the motor of the specific model, even if the reverse excitation drive operation is performed at the start of the second step process, the motor is generated at the specific angular position of the rotor magnet. Due to the cancellation of the torque, a sufficient drive torque cannot be obtained, which may cause a start failure.

In such a case, it is preferable to switch the current as shown in FIG. That is, after the reverse excitation drive operation is performed in the two phases at the start of the second step process, for example, the reverse excitation drive operation is performed in one phase (more preferably, the reverse excitation drive operation is performed subsequent to the two phases). Is preferred. By doing so, the generated torque is canceled at the time of the reverse excitation drive operation at the start of the second step, and the generated torque is canceled at the subsequent reverse excitation drive operation even if the starting torque is hardly generated. It escapes and the rotor comes to rotate.

[0026]

As described above in detail in the embodiments,
According to the sensorless multi-phase DC motor start-up method of the present invention, since the reverse excitation drive operation is performed in a plurality of phases in the initial stage of the second step process, the start-up probability of the motor becomes very high and the start-up failure occurs. The probability of is almost zero.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing an example of a starting method according to the present invention.

FIG. 3 is an explanatory diagram of a stepping process performed by the flowchart shown in FIG.

FIG. 4 is an explanatory diagram of an internal step pattern in the step step shown in FIG.

FIG. 5 is an explanatory diagram of an internal step pattern in a modified example of the second step process.

[Explanation of symbols]

 1 Back Electromotive Voltage Detection Circuit 2 Control Section 3 Driver Circuit 4 Power Circuit 5 Sequencer u, v, w Stator Coil

Claims (2)

[Claims] 1. A rotor comprising: a stator including a stator coil that generates a current magnetic field in an excited state; and a rotor including a rotor magnet that obtains a rotational force by electromagnetic interaction with the current magnetic field of the stator coil. The stepless step of supplying an exciting current to the stator coil for rotating the stator coil in a predetermined direction includes first and second stepless steps of supplying an exciting current to the stator coil in a predetermined internal step pattern. In the method for starting a phase DC motor, the second step step has a reverse excitation drive operation in which the energization direction is reversed in any of the phases in the initial stage without including a rest period,
And, with respect to the internal step pattern of the first step,
A method for starting a sensorless multi-phase DC motor, comprising supplying an exciting current to the stator coil in an internal step pattern in which phases other than the above phases are exchanged. 2. The start-up of a sensorless multi-phase DC motor according to claim 1, wherein in the second step, the reverse excitation drive operation is performed in at least one phase after the reverse excitation drive operation in the initial stage. Method.