JPH04304192A - Drive control method for motor - Google Patents

Abstract

PURPOSE:To prevent head sticking and to improve starting performance of a spindle motor for magnetic disc unit. CONSTITUTION:The drive control circuit for the spindle motor of magnetic disc unit comprising a stator and a rotor comprises a first step oscillator 1, a second step oscillator 2, a timer 3, a step timing generating circuit 4, a conduction switching logic 5, an output driver 6 and a reverse electromotive force detecting circuit 7, wherein the output driver 3 is connected with three-phase driving stator coils 8-10. At the time of starting, first stepping operation takes place at first and after inversion to reverse excitation during a predetermined pause interval, second stepping operation takes place and normal rotation control takes place subsequently upon detection of reverse electromotive force during normal rotation.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a drive control technology for a sensorless motor, and in particular to a motor drive control method that can prevent head stiction and improve starting performance in a spindle motor for a magnetic disk device. Concerning applied and effective techniques.

0002

[Prior Art] Conventionally, a spindle motor for a magnetic disk drive is a DC brushless motor that includes a stator that generates an electromagnetic field in an excited state and a rotor that obtains rotational force through electromagnetic interaction with the stator. Type motors are often used, and their rotation is controlled by electronic circuits on semiconductor chips. For this rotation control, a Hall sensor method using a Hall element as a magneto-electric conversion element is currently most commonly used.

However, with the rapid miniaturization and increase in capacity in recent years, HDD (Hard Disc Drive)
ive) and other magnetic disks are becoming smaller,
As a result, sensorless systems that do not use Hall elements are being adopted in motors for small-diameter disks, and are expected to become the main drive system in the future.

For example, in a motor drive control circuit using this sensorless method, electromagnetic energy is generated by a stepping operation at the same frequency as the natural frequency of the motor, that is, an operation that applies rotational force to the extent that a back electromotive force of the motor appears. After converting the rotor into mechanical vibration, the vibration is amplified and rotated by substantially matching the period to the resonance frequency, and after the rotational speed reaches a predetermined number of rotations or after a predetermined period of time has passed after startup. By processing the back electromotive force generated by the stator coil into a waveform, it is used as a rotational position signal of the rotor, thereby making it possible to control the rotation of the rotor without using a Hall element.

[0005] In this case, the CPU (Central P
In the control type drive control circuit, a software measure is taken to prevent head stiction, that is, damage to the surface of the magnetic disk caused by the head, under the control of the CPU.

[0006]

[Problem to be Solved by the Invention] However, although the above-mentioned conventional technology takes measures against head stiction, it has the disadvantage that software control by an external CPU is slow. .

[0007] Therefore, the inventors of the present invention came up with the idea of speeding up the head stiction prevention function and incorporating it into a semiconductor chip to prevent head stiction on an electronic circuit without external control.

That is, an object of the present invention is to provide a motor drive control method that can prevent head stiction particularly in a spindle motor for a magnetic disk device.

Another object of the present invention is to provide a motor drive control method that can improve the starting performance when starting the motor.

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

[0011]

[Means for Solving the Problems] Among the inventions disclosed in this application, a brief overview of typical inventions will be as follows.
It is as follows.

That is, the motor drive control method of the present invention includes a stator that generates an electromagnetic field in an excited state and a rotor that obtains rotational force through electromagnetic interaction with the stator, and the rotor's natural frequency The rotor is rotated by applying rotational force to the rotor by performing a stepping motion with approximately the same frequency as the
This is a sensorless motor drive control method that controls rotation by detecting a back electromotive force of a stator coil after the rotor reaches a predetermined rotational speed. An initial step motion is performed to generate only slight vibrations in the rotor, and a step motion is performed after this initial step motion.

In this case, the frequencies of the initial stepping motion and the stepping motion are set to desired frequencies that can be varied linearly within a predetermined range.

[0014]

[Operation] According to the above-described motor drive control method, before the step motion, the frequency of the step motion is set to a higher frequency than the frequency of the step motion, or to a desired step frequency that can be varied linearly within a predetermined range. By performing the initial stepping operation at a relatively high frequency, it is possible to generate only slight vibrations in the rotor, fly the head, and prevent head stiction against the magnetic disk.

Furthermore, when the stator coil is reversely excited in a predetermined rest period and then performs a stepwise operation, it is possible to perform open-loop activation by increasing the torque several times.

This is because the relationship between torque and rotation angle due to the initial step motion is approximately 90 degrees different from that during the subsequent step motion, so if the rotor is at the dead center during the initial step motion, the subsequent This is because the amplitude reaches its maximum during the step motion, and the width of change in magnetic flux density is doubled.

[0017] This makes it possible to prevent head stiction through the initial step motion, and to improve starting performance by increasing rotational torque through the step motion after reverse excitation.

[0018]

[Embodiment 1] FIG. 1 is a schematic configuration diagram showing a drive control circuit which is an embodiment of the motor drive control method of the present invention, and FIG. 2 is a waveform diagram showing each output waveform in the drive control circuit of this embodiment. FIG. 3 is an explanatory diagram showing starting characteristics in the drive control circuit of this embodiment, and FIG. 4 is an explanatory diagram showing torque characteristics in the drive control circuit of this embodiment.

First, the configuration of the motor drive control circuit of this embodiment will be explained with reference to FIG.

The drive control circuit of this embodiment is a magnetic sensorless brushless motor that includes a stator that generates an electromagnetic field in an excited state and a rotor that obtains rotational force through electromagnetic interaction with the stator. It is a drive control circuit for a spindle motor of a disk device, and 1
Stepping oscillator (OSC) 1,
It is composed of a second step oscillator (OSC) 2, a timer 3, a step timing generation circuit 4, an energization switching logic 5, an output driver 6, and a back electromotive force detection circuit 7. stator coil 8~10
is connected.

[0021] Then, at startup, as shown in FIG.
1, which is a feature of the present invention, before the second stepping motion (stepping motion)
The first step motion (initial step motion) is performed, and after being reversed to reverse excitation in a predetermined rest period, the second step motion is performed, and after reaching a predetermined rotation speed, the steady state is determined by detecting the back electromotive force. controlled by rotation.

In this embodiment, the first stepping oscillator 1 has a frequency of 55, which is approximately 10 times higher than the second stepping frequency.
A first stepping frequency (f1) of 0 Hz is generated to generate only slight vibrations in the rotor, which is a feature of the present invention, to fly the head and prevent head stiction between the magnetic disk and the head.

[0023] Note that the first step frequency (f1) is 2
Although it is set to approximately 10 times the step frequency (f2) of the second step, it can be set to 4 to 12 times, preferably 6 to 10 times.

The second step oscillator 2 divides the first step frequency by 1/10, generates a second step frequency (f2) of 55 Hz, which is approximately the same as the natural frequency of the motor, and It amplifies vibrations and rotates them.

The timer 3 is used to set the times for the first step, the second step, and a predetermined rest period between them.

The step timing generation circuit 4 generates the first step frequency by the first step oscillator 1, the second step frequency by the second step oscillator 2, the first step by the timer 3, the rest interval, and the second step frequency by the second step oscillator 2. This is to adjust the timing of the set time of the second step.

The energization switching logic 5 switches the energization time of the stator coils 8 to 10 between the first step, the second step, and the rest period by the step timing generation circuit 4, and at the same time controls the back electromotive force during steady rotation. Rotation is controlled by detection.

The output driver 6 energizes or de-energizes the stator coils 8 to 10 under the control of the energization switching logic 5, and momentarily switches the stator coils 8 to 10 to reverse excitation during the rest period.

The back electromotive force detection circuit 7 detects the back electromotive force of the stator coils 8 to 10 after reaching a predetermined rotation speed,
This feeds back to the energization switching logic 5 to maintain a predetermined steady rotation.

Next, the operation of this embodiment will be explained based on the waveform diagram shown in FIG.

First, when starting the motor, 1
The first step frequency (waveform f1) outputted from the first step oscillator 1, for example, 16 ms, is used to perform the first step operation, and the start signal is input simultaneously. Timing signal (waveform T) adjusted by step timing generation circuit 4 during operation time
done by.

At this time, the stator coils 8 to 10 are supplied with current (waveforms U, V, W
), the vibration of the rotor is not amplified and only vibrates minutely, thereby making it possible to eliminate head stiction between the magnetic disk and the head.

Furthermore, in a state where the head stiction is released, the output driver 6 generates a predetermined rest interval (waveform t) set by the timer 3, for example, 10 m.
At s, the current direction to the stator coils 8 to 10 is switched, and the excitation direction of the first stepping operation is reversed to reverse excitation.

For example, as shown in the torque characteristics obtained by measuring the electrical angle and rotational torque of the motor shown in FIG. Accordingly, the second step movement described later can be rotated from a position several times larger than the rotational torque.

That is, in the first stepping operation, for example, the current polarity of the stator coils 8 to 10 is "+" or "-".
” to “0” and from “0” to “+” or “-”, in the second step operation, “+”
” to “-” or from “-” to “+”, the dead center is definitely avoided.The starting performance of the motor can be improved by increasing the torque.

Subsequently, after being reversed to reverse excitation, the second step frequency (waveform f2) output from the second step oscillator 2
) is performed in the same manner as the first step. At this time, unlike the first stepping operation, the stator coils 8 to 10 are supplied with a frequency that is almost the same as the natural frequency, so the vibrations of the rotor are amplified and rotational force is applied, which moves the rotor in a predetermined direction. It can be rotated with large rotational torque.

Furthermore, when the rotor reaches steady rotation,
The back electromotive force of the stator coils 8 to 10 is detected by the back electromotive force detection circuit 7, and the output signal of this back electromotive force is subjected to waveform processing to synchronize the rotor in the same way as when using a conventional sensor such as a Hall element. The rotation speed can be controlled to a constant speed by controlling the rotation speed and driving in accordance with the back electromotive force.

Therefore, according to the motor drive control circuit of this embodiment, the first step oscillator 1 and the second step oscillator 2 are provided, and the first step operation is performed before the second step operation. As a result, only vibration can be generated in the rotor during the first stepping operation, making it possible to prevent head stiction between the magnetic disk and the head. Furthermore, by performing a second stepping operation after the stator coils 8 to 10 are reversely excited in a predetermined rest period, starting performance can be improved by increasing the torque approximately several times that of the rotor.

[0039]

[Embodiment 2] FIG. 5 is a schematic configuration diagram showing the main parts of a drive control circuit which is another embodiment of the motor drive control method of the present invention.
FIG. 6 is a waveform diagram showing each output waveform in the main part of the drive control circuit of this embodiment.

The drive control circuit of this embodiment is a drive control circuit for a spindle motor of a magnetic disk device equipped with a stator and a rotor, as in the first embodiment, and as shown in FIG. Oscillator (VCO: Vol
stage Controlled Oscillato
r) 12, a timer 13, a changeover switch 14, etc., and the difference from Embodiment 1 is that the frequency of the first stepping operation (initial stepping operation) and the second stepping operation (stepping operation) is an integrator. 11 and voltage controlled oscillator 12.

That is, the output frequency of the voltage controlled oscillator 12 is varied in accordance with the output voltage from the integrator 11, and the oscillation frequency can be varied linearly within a predetermined range as shown in the waveform f shown in FIG. For example, set the first stepping frequency (f1) to substantially 550 Hz within that range,
Further, 55 Hz is substantially set as the second stepping frequency (f2). In this case, the timing signal of the waveform T is obtained by setting the time like the waveform t by the timer 13 and switching the changeover switch, and the timing signal of the waveform T is obtained for the first step and the second step.
The second step is set to a desired frequency.

Therefore, according to the motor drive control circuit of this embodiment, the first step frequency and the second step frequency can be set by the integrator 11, the voltage controlled oscillator 12, etc. Similarly, the first stepping operation prevents reverse rotation and stiction between the magnetic disk and the head, and the second stepping operation makes it possible to improve the starting performance by increasing the torque several times.

The invention made by the present inventor has been specifically explained based on Examples 1 and 2 above, but the present invention is not limited to the above embodiments, and various modifications may be made without departing from the gist thereof. Needless to say, it can be changed.

For example, in the motor drive control circuit of the above embodiment, the frequency of the first stepping operation is set to 550Hz.
, a case has been described in which the frequency of the second stepping operation is set to 55 Hz, but the present invention is not limited to the above embodiment. For example, the vibration is not amplified at the first stepping frequency, that is, the natural frequency It is only necessary to set the second step frequency within a larger frequency range than that of the motor.

Furthermore, the configuration of the drive control circuit is not limited to the configurations shown in FIGS. 1 and 5. In particular, the configuration of the first step frequency and second step frequency setting circuit is as follows.
Variable frequency oscillator (VFO)
It goes without saying that various changes can be made, such as the circuit configuration using a query oscillator.

In the above description, the invention made by the present inventor is mainly applied to a drive control circuit for a spindle motor for a magnetic disk drive, which is the field of application of the invention, but the present invention is not limited to this. The present invention can also be widely applied to drive control circuits for sensorless type breathless motors applied to other devices such as laser printers.

[0047]

[Effects of the Invention] Among the inventions disclosed in this application, the effects obtained by the typical inventions are briefly explained as follows.
It is as follows.

That is, before a stepping operation, an initial step is performed at a frequency higher than the frequency of this stepping operation, or with a frequency higher than the frequency of a desired stepping operation that can vary linearly within a predetermined range. By performing the forward movement, only slight vibrations can be generated in the rotor, so head stiction between the magnetic disk and the head can be prevented.

[0049] If the stator coil is inverted to reverse excitation in a predetermined rest period after the initial step operation and then the step operation is performed, the starting operation can be performed by increasing the torque approximately several times. Performance can be improved.

As a result, a motor drive control method that can prevent head stiction and improve starting performance by increasing rotational torque, especially when applied to a spindle motor for a magnetic disk drive. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a drive control circuit that is a first embodiment of a motor drive control method of the present invention.

FIG. 2 is a waveform diagram showing each output waveform in the drive control circuit of the first embodiment.

FIG. 3 is an explanatory diagram showing startup characteristics in the drive control circuit of Example 1.

FIG. 4 is an explanatory diagram showing torque characteristics in the drive control circuit of Example 1.

FIG. 5 is a schematic configuration diagram showing a main part of a drive control circuit which is a second embodiment of the motor drive control method of the present invention.

FIG. 6 is a waveform diagram showing each output waveform in a main part of the drive control circuit according to the second embodiment.

[Explanation of symbols]

1 First step (initial step) oscillator 2 Second step (stepping) oscillator 3. Timer 4 Step timing generation circuit 5 Energization switching logic 6 Output driver 7 Back electromotive force detection circuit 8 Stator coil 9 Stator coil 10 Stator coil 11 Integrator 12 Voltage controlled oscillator 13. Timer 14 Selector switch

Claims (3)

[Claims] 1. A rotor comprising: a stator that generates an electromagnetic field in an excited state; and a rotor that obtains rotational force through electromagnetic interaction with the stator; A method for controlling the drive of a sensorless motor, in which the rotor is rotated by applying a rotational force to the rotor, and after the rotor reaches a predetermined rotational speed, the rotation is controlled by detecting a back electromotive force of a stator coil, the method comprising: A motor characterized in that an initial stepping operation is performed at a frequency higher than the frequency of the stepping operation to generate only slight vibrations in the rotor, and further, the stepping operation is performed after the initial stepping operation. Drive control method. 2. The motor drive control method according to claim 1, wherein the frequency of the initial step motion and step motion is set to a desired frequency that can be varied linearly within a predetermined range. 3. The motor drive control method according to claim 1, wherein the stator coil is reversely excited during a predetermined rest period after the initial stepping operation.