JP3132779B2 - 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 brushless multi-phase DC motor of a sensorless type. For example, in a spindle motor for a magnetic disk drive, the starting reliability is improved by repeating a plurality of starting steps by a plurality of reverse excitations in a plurality of phases. The present invention relates to a technique that is effective when applied to a startup method of a sensorless multi-phase DC motor capable of improving performance.

[0002]

2. Description of the Related Art Conventionally, as a spindle motor for a magnetic disk drive, for example, a brushless sensorless type having a stator for generating a magnetic field in an excited state and a rotor magnet for obtaining a rotational force by electromagnetic interaction with the stator. DC motors are often used, and in many cases, rotation control is performed by an electronic circuit formed into a semiconductor chip.

For example, in a three-phase coil sensorless multiphase DC motor, the direction of rotation is unknown at the time of stoppage.
A step of sequentially supplying a drive current to the stator and energizing the same is repeated. Thus, the coils are intermittently and synchronously energized by passing forward, resting, and reverse exciting currents through the respective phases, so that the rotor is reliably rotated in a predetermined direction.

Further, the motor can be driven by generating a driving torque due to the attraction or repulsion of the electromagnet and the permanent magnet, and the generation timing is different from the detection of the rotor magnet by a conventional Hall sensor or the like, and the induced voltage of the coil is different. It is performed using. In this case, the magnitude of the torque is directly proportional to the current and the magnetic flux density change width if the number of turns is constant. Therefore, to increase the torque, increase the current or
Alternatively, the change width of the magnetic flux density may be increased.

[0005]

By the way, in the sensorless start, an induced voltage due to a magnetic flux linked to the coil is used. However, there is a drawback that there is no induced voltage at the time of stop, and the polarity of the magnet is unknown. For this reason, at first, stepping is forcibly performed without a signal, but depending on the rotor position, start-up failure may occur due to low torque, or reversal may occur due to the opposite direction of the magnetic field from the energization.

Therefore, in order to enhance the starting reliability, conventionally, retry is repeated, a double drive system is used,
Further, it is necessary to improve the starting characteristics by using both of them. Here, the double starting method is a starting method separately filed by the present applicant, and changes the upper current direction that gives an initial value for energization at the time of starting the motor, performs reverse excitation to increase the starting torque, The method includes a step of generating a high torque by obtaining a large magnetic flux density change width.

However, if the start is performed when the positional relationship between the rotor and the stator happens to be at a position where zero torque is generated by energization, the step sequence is repeated with the rotor not moving much. . At this time,
The step is repeated in order to surely rotate the rotor in a predetermined direction. However, for example, if only one-phase coil in a single direction develops high torque by double driving, there is a problem that torque increase is insufficient. .

Accordingly, an object of the present invention is to perform a start-up process by performing reverse excitation in a forward direction or a reverse direction or in a reverse direction in a forward direction a plurality of times in a plurality of phases and repeating the start-up process a plurality of times. It is an object of the present invention to provide a method of starting a sensorless multi-phase DC motor capable of improving characteristics in a multiplex or cumulative manner.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0010]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, according to a first aspect of the present invention, there is provided a method for starting a sensorless multi-phase DC motor, wherein a stator having a multi-phase coil that generates a magnetic field when energized, and a rotation caused by electromagnetic interaction between the stator and the stator. A sensorless multi-phase DC motor comprising a rotor for obtaining a force, and starting by repeating a starting step consisting of a series of steps of sequentially supplying a current to the coil so as to rotate the rotor in a predetermined direction. , The step of performing the reverse excitation for converting the current in the reverse direction from the forward direction or from the reverse direction to the forward direction without including the idle period by the two-phase coil simultaneously a plurality of times.

According to a second aspect of the present invention, in the first aspect of the present invention, when the starting step is repeated, an initial value of a current supplied to the coil is changed.

[0013]

According to the above-described method of starting the sensorless multi-phase DC motor, a plurality of phases include reverse excitation during the starting step, and the starting step is repeated a plurality of times, so that a high torque is generated. Since the operation is performed a plurality of times in the phase, the ability of the magnetic body can be sufficiently exhibited, and the starting torque can be increased. As a result, the starting time is shortened, and the motor can be started up in a short time by the high torque.

That is, a process in which the energy stored in the stator by the reverse excitation is increased by the reversal of the excitation current and released as a high torque can be repeatedly and repeatedly stored in a short time. In this case, the effective current does not increase despite the torque increase, so that the drive circuit and the motor can be reduced in temperature and size. Conversely, when the motor is easily started and has high reliability, the starting current can be reduced for the same required torque.

In addition, when the current value of the drive current in the reverse excitation is varied, for example, when the drive current for the first startup is set to a low level and the drive is performed at a high level in the second startup, the first drive is performed. Energy can be suppressed at the start and almost no rotation of the motor, and the second start can increase the energy and rotate the motor reliably.

[0016]

FIG. 1 is a waveform diagram showing a model of a starting current of a sensorless multiphase DC motor which is an embodiment of a method of starting a sensorless multiphase DC motor according to the present invention, and FIG. 2 shows a startup procedure in the present embodiment. FIG. 3 is an explanatory diagram showing a startup sequence.

First, a starting current waveform in the sensorless multi-phase DC motor of this embodiment will be described with reference to FIG.

The sensorless multi-phase DC motor of the present embodiment is applied to, for example, a spindle motor for a magnetic disk drive, and although not shown, a stator having a multi-phase coil that generates a magnetic field when energized is provided. A starter comprising a rotor for obtaining a rotational force by an electromagnetic interaction with a stator or the like, and a series of steps of sequentially supplying a drive current to the coils of the respective phases and energizing the rotor so as to rotate the rotor in a predetermined direction; It is a sensorless multi-phase DC motor that is started by repeating the steps, and the starting step is a two-phase coil in which the reverse excitation that converts the current from the forward direction to the reverse direction or from the reverse direction to the forward direction without a pause is included. It has a plurality of steps to be performed simultaneously.

For example, as shown in FIG. 1, the current waveform (iu) to the U-phase coil is reversely excited in the negative direction in three steps, and the starting torque due to the high torque in the positive direction in four steps. Is released, and a high torque can be obtained in the forward direction in 7 steps, and also in the reverse direction in 13 steps and 16 steps.

Similarly, regarding the current waveform (iv) of the V-phase coil, a high torque is obtained in the reverse direction in 1 step and 4 steps, in the positive direction in 10 steps and 13 steps, and the current waveform (IV) of the W-phase coil iw)
With regard to, a high torque is obtained in the forward direction in steps 1 and 16 and in a reverse direction in steps 7 and 10.

In this way, in a step corresponding to the conventional starting step, a high-torque starting current is applied to each coil four times, thereby increasing the starting torque in the starting step and reliably starting up the motor. be able to.

The high torque is expressed in two phases in each step. For example, a V-phase coil and a W-phase coil in one step, a U-phase coil and a V-phase coil in four steps, and a U-phase coil and a W phase in seven steps Since a high torque can be simultaneously applied in the opposite direction as in the case of a coil, the motor can be started up in a short startup time. By the way, according to the measurement, a torque increase ratio of 1.7 times is obtained in one phase and a torque increase ratio of about 3 times is obtained in two phases simultaneously.

In this case, the timing of the Keep-on and the reverse excitation by the high torque to the starting process as described above is, for example, looped by a startup flow as shown in FIG. In the phase sequence of the first start-up, the detection period, the second start-up, and the acceleration period, after returning from the second start-up to before the first start-up,
It can be obtained by returning after starting to before the second starting.

Therefore, according to the method of starting the sensorless multi-phase DC motor of this embodiment, the motor can be started up reliably by repeating the start-up step by applying the reverse excitation current to the stator a plurality of times. Performance or power saving can be improved.

At the same time, during the start-up step, the reverse excitation for converting the current from the forward direction to the reverse direction or from the reverse direction to the forward direction is included a plurality of times in a plurality of phases, so that the capability of the magnetic material is sufficiently exhibited, and the start-up time is reduced. Can be shortened.

[0026]

Embodiment 2 FIG. 4 is a waveform diagram showing a starting current of a sensorless multiphase DC motor which is another embodiment of the method for starting a sensorless multiphase DC motor of the present invention.

The sensorless multi-phase DC motor according to the present embodiment is applied to a spindle motor for a magnetic disk drive similarly to the first embodiment, and has a polyphase coil (not shown) that generates a magnetic field when energized. A stator,
A rotor that obtains a rotational force by electromagnetic interaction with the stator or the like, and sequentially supplies a drive current to the coils of the respective phases so as to rotate the rotor in a predetermined direction and energizes the rotor;
The sensorless multi-phase DC motor is started by repeating a starting step including a series of steps. The difference from the first embodiment is that, when the starting step is repeated, an initial value of a current supplied to the coil is changed. .

That is, as shown in FIG. 4, the sensing rate of each coil is changed, the first start is set to a low power rate, the initial value is increased in the second start after the detection period, and a torque greater than the first start is output. Thus, the second startup is performed, so that in the first startup, there is no reverse rotation and the motor hardly rotates, and in the second startup, the large current becomes the initial value and the motor can be surely rotated.

For example, as a method of changing the sensing rate, a current sensor, a timer, an adder, and the like are provided, and the adder changes the sensitivity of the current sensor only for the period of the timer, for example, 0.1.
The drive current can be reduced by recognizing A as 0.5 A, or can be set to a higher current value.

Therefore, according to the method for starting the sensorless multi-phase DC motor of the present embodiment, unlike the first embodiment, the energizing energy is suppressed at the first start and the second start is performed, unlike the repetition of the start process using the same energy. Since the energy can be increased to increase the energy, the driving reliability can be improved as in the first embodiment. In addition, the motor does not reverse at the time of starting, or the reverse rotation angle is reduced. As a result, for example, in a magnetic disk device, there is an effect that a head crash or stickion is avoided or the medium is not damaged.

[0031]

Third Embodiment FIG. 5 is a circuit diagram showing a main part of an energizing circuit of a sensorless multiphase DC motor which is another embodiment of the method for starting a sensorless multiphase DC motor according to the present invention, and FIG. It is explanatory drawing which shows a state.

The sensorless multi-phase DC motor of this embodiment is
Like the first and second embodiments, the present invention is applied to a spindle motor for a magnetic disk drive, and includes a stator that generates a magnetic field in an excited state (not shown), and a rotor that obtains a rotational force by electromagnetic interaction with the stator. A drive current for rotating in a predetermined direction is supplied to the stator, and a sensorless multi-phase DC motor is started up by repeating a start-up step of energizing the stator. The drive current in the reverse excitation when the start-up step is repeated in the same manner as in the second embodiment. The current value is varied, and the difference from the second embodiment is that a starting power supply is connected to the neutral point of the coil via a diode.

That is, as shown in FIG. 5, the neutral point of each coil connected to the connection point of the two transistors is Ei.
The power supply voltage is delayed by a predetermined time from the external power-on via a diode that corresponds to nstainer (one semiconductor element that converts the state function of the system) and serves to switch between conduction and two normal states. Is connected to the starting power supply to which the voltage is applied.

For example, if the impedance of each coil is 1.
Assuming that 5Ω, the starting power supply is + 3V, and the applied voltage is + 3V,
In the pre-excitation of the reverse excitation, as shown in FIG. 6A, only the transistor Q1 is turned on to allow a drive current of -2 A to flow through the U-phase coil.
As shown in (b), by turning on the transistors Q2 and Q5, a drive current of +1 A can flow through the U-phase coil, and a current of -1 A can flow through the W-phase coil.

Thus, in the U-phase coil, -2
Since a current change amount of 3 A can be obtained by a change from A to +1 A, conventionally, a current change amount of-
While only a change amount of 2A, such as 1A to + 1A, can be obtained, the start-up torque can be increased by a 1.5-fold change amount.

Therefore, according to the method of starting the sensorless multi-phase DC motor of this embodiment, the motor can be started up reliably as in the first and second embodiments, and the starting reliability can be improved.

As described above, the invention made by the inventor has been specifically described based on the first to third embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the invention. Needless to say, it can be changed.

For example, in the sensorless multi-phase DC motor of each of the above embodiments, a change in the start-up flow in the first embodiment, a change in the sensing rate in the second embodiment, a change in the voltage value of the starting power supply in the third embodiment, etc. It is needless to say that various changes can be made to.

In the above description, a case has been described in which the invention made by the present inventor is mainly applied to a spindle motor for a magnetic disk drive, which is a field of application, but the invention is not limited to this. For example, the present invention can be widely applied to a sensorless multi-phase DC motor applied to other devices.

[0040]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

According to the first aspect of the present invention, a starting step consisting of a series of steps of sequentially supplying a drive current for rotating the rotor in a predetermined direction to the coils of each phase is repeated. By including a step of performing reverse excitation for converting a current in a reverse direction or a reverse direction to a forward direction simultaneously with a two-phase coil a plurality of times, the development of a high torque is performed a plurality of times in a start-up process. , The starting torque can be increased, and the motor can be reliably started.

In particular, since high torque can be expressed simultaneously by the two-phase coils, the starting torque can be increased and the starting time of the motor can be shortened.

Further, since the effective current value is not increased despite the increase in the torque, the drive circuit of the motor, the capacity of the power supply (including the battery) and the temperature rise value of the motor can be reduced and downsized. it can.

According to the second aspect of the present invention, when the starting step is repeated, the initial value of the current supplied to the coil is changed. For example, the driving current in the first starting step is set to a low level. When the rotor is driven with the drive current in the second start-up step at a high level, the energizing energy is suppressed in the first start-up step and the rotor is hardly rotated, and the energy is increased in the second start-up step to ensure the rotation. Can be rotated. As a result, a fatal head crash or stickion can be avoided in the magnetic disk drive.

In addition, since the starting torque can be increased by increasing the amount of change in the drive current in the reverse excitation, the motor can be reliably started.

As described above, the inventions according to both claims are surely started by the increase in the driving torque during the starting process, and a starting method of the sensorless multiphase DC motor with improved starting reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing a model of a starting current of a sensorless multiphase DC motor which is Embodiment 1 of a method for starting a sensorless multiphase DC motor of the present invention.

FIG. 2 is a flowchart illustrating a start-up procedure in the sensorless multiphase DC motor according to the first embodiment.

FIG. 3 is an explanatory diagram illustrating a startup sequence in the sensorless multiphase DC motor according to the first embodiment.

FIG. 4 is a waveform diagram showing a starting current of a sensorless multiphase DC motor which is Embodiment 2 of the method for starting a sensorless multiphase DC motor of the present invention.

FIG. 5 is a circuit diagram showing a main part of an energization circuit of a sensorless multiphase DC motor which is Embodiment 3 of a method for starting a sensorless multiphase DC motor according to the present invention.

FIG. 6 is an explanatory diagram showing an energized state in a sensorless multiphase DC motor according to a third embodiment.

[Explanation of symbols]

 iu Current waveform of U-phase coil iv Current waveform of V-phase coil iw Current waveform of W-phase coil Q1-Q6 Transistor D Diode E Starting power supply

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 6/20

Claims (2)

(57) [Claims] 1. A magnetic head which generates a magnetic field when energized.
A stator having a phase coil; and a rotor for obtaining a rotational force by electromagnetic interaction between the stator and the stator, and supplying a current to the respective phase coils so as to rotate the rotor in a predetermined direction.
Multiple start-up processes consisting of a series of steps that sequentially energize
A sensorless multi-phase DC motor that is started by repeating the same two times , and in the starting step, a reverse excitation that converts a current without a pause period from a forward direction to a reverse direction or from a reverse direction to a forward direction without a pause is performed by a two-phase coil. Multiple steps can be performed simultaneously
A method for starting a sensorless multi-phase DC motor characterized by having several times . 2. The method according to claim 1 , further comprising the step of :
2. The method for starting a sensorless multi-phase DC motor according to claim 1, wherein an initial value of a current supplied to the motor is changed.