JPH0634616B2 - Motor speed monitoring circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a DC brushless motor that determines a current direction and a current amount to flow in a driving coil based on detection signals from a plurality of Hall elements. The present invention relates to a magnetic disk device used as the above, and more particularly to a motor speed monitoring circuit that detects abnormal rotation of the DC brushless motor with high accuracy.

The magnetic disk device used as an external storage device of an information processing device has been improved and devised so that a large amount of data can be recorded / reproduced accurately and quickly, the data transfer speed is high, and the density is high. Recording is becoming possible.

In order to maintain such a function accurately, the rotation speed of the DC brushless motor used as a spindle motor is controlled accurately, and if a rotation abnormality should occur,
Highly accurate detection is a necessary condition.

[Problems to be solved by conventional technology and invention]

FIG. 2 shows a conventional motor speed monitoring circuit of a magnetic disk device, and FIG. 3 shows a motor rotation speed monitoring situation.

A DC brushless motor used as a spindle motor of a magnetic disk device includes a rotor a made of a permanent magnet (FIG. 2 shows the case of two poles) and a plurality of Hall elements c for detecting the rotational position of the rotor a. , A coil (b) of a stator (not shown) that produces a rotating magnetic field of the rotor a by passing a multiphase current.

The rotation of the DC brushless motor starts when the motor control circuit 5 which receives a start signal from a control unit (not shown) sends a drive current to the coil b, and the Hall element c changes depending on the rotation position of the rotor a. The output changes,
The output is amplified and pulsed by the amplification and waveform shaping circuit 1,
The motor control circuit 5 controls the rotation direction of the DC brushless motor by controlling the direction and amount of current flowing through the coil b through the power amplifier 13 by the hall signal converted into the electric signal by the rotor position detection circuit 2.

That is, the rotating magnetic field in the direction of increasing the rotation speed of the rotor a or the rotor a by controlling the direction of the current flowing between the plurality of coils b wound around the plurality of stators (not shown), the timing and the amount of the current. Generates a rotating magnetic field in a direction that reduces the rotation speed of the.

On the other hand, the Hall signal is also sent to the one-revolution-pulse creating circuit 12, and the one-revolution-pulse creating circuit 12 creates a pulse ′ that is generated once for one revolution of the rotor a from this Hall signal.
It is sent to the comparators 9 and 10 and the counting circuit 4.

The pulse 'sent to the counting circuit 4 is used as a signal for resetting the counting circuit 4.

The signal from the motor control circuit 5 is a signal that is turned on after a fixed time from the start signal, and this signal causes the signal from the counting circuit 4 to be output via the AND circuits 6, 7, and 8.

While the signal is off, the signals from the AND circuits 6, 7, 8 are not output.

When the signal is turned on, the rotation gradually increases after starting with the start signal, and if the DC brushless motor and its drive circuit are normal, the motor rotation speed falls within the upper and lower limit ranges described below. It's time to enter.

When the signal is turned on, if it is not within the range between the upper limit value and the lower limit value, the motor drive is immediately stopped as a rotation abnormality at the start.

The counting circuit 4 starts counting after reset by the output pulse of the predetermined cycle output from the oscillator 3, and reaches the preset count value T (this is the reference rotation cycle of the DC brushless motor) when the count value is reached. The T is output to the motor control circuit 5 via the AND circuit 7.

The motor control circuit 5 compares the count value T with the pulse ', and controls the rotation speed (rotation speed) of the DC brushless motor based on the difference, and when the difference becomes substantially zero, the motor control circuit 5 keeps a predetermined constant value. It is determined that the rotation speed (rotation speed) has been reached.

In addition to the reference count value T, the counting circuit 4 has setting terminals for the count value (count value T-Δt) and the count value (count value T + Δt), and the count value is set to (count value T-Δt). When it reaches, it goes to the comparator 9, and after counting up to (count value T + Δt), the comparator
Output signals to 10 respectively.

The comparator 9 compares the period of this signal with the period of the pulse ', and outputs a signal if the period of the pulse' is shorter than the count value (count value T-Δt). Similarly, the comparator 10 also compares the period of the pulse 'and outputs a signal if the period of the pulse' exceeds the count value (count value T + Δt).

Further, the signal is an alarm signal for the rotation speed (rotation speed) of the motor being too fast, and the signal is an alarm signal for being too slow. The OR circuit 11 sends this signal to the motor control circuit 5 as a speed abnormality signal. To do.

The motor control circuit 5 controls to stop the motor drive immediately upon receiving the speed abnormality signal, and also sends an abnormality signal to a control unit (not shown).

The rotation speed (revolution speed) of the motor is a count value (count value T-
If it is between Δt) and the count value (count value T + Δt), the motor control circuit 5 determines that the rotation speed (rotation speed) of the motor is normal. Therefore, the count value (count value T-Δt) and the count value (count value T + Δt) are set as the upper limit value and the lower limit value of the rotation speed (rotation speed) of the motor.

Incidentally, FIG. 3 shows a situation in which the motor rotation speed is monitored by the upper limit value and the lower limit value based on the reference rotation speed T.

The count value (count value T + Δt), the count value T, and the count value (count value T−Δt) are the signals output from the motor control circuit 5 after a fixed time from the start of rotation of the motor, and the count circuit 4 respectively. A logical product condition with a signal to be output when the count value is reached is taken, and output from each of the logical product circuits 6 to 8 with which the logical product condition matches.

The rotor a position detection of the hall element c detects the rotational position of the rotor a by detecting the direction of magnetic flux generated from the rotor a which is a permanent magnet. On the other hand, as described above, the control reference signal of the rotation speed (rotation speed) of the DC brushless motor is based on the detection output of the Hall element c, but the current is present in the coil b of the stator (not shown). When flowing, the magnetic flux from the rotor a is disturbed by this current.

That is, the magnetic flux distribution is different when the current is applied to the coil b and when it is not applied. As a result, in the Hall element c, the rotational position of the rotor a to be detected differs depending on the magnetic flux turbulence, and therefore the detection output of the Hall element c also becomes unstable, and the rotational speed (rotation speed) of the DC brushless motor is correspondingly increased.
However, there is a problem that the control accuracy of is decreased.

FIG. 3 shows such a state. Even if the rotation speed of the DC brushless motor is kept substantially constant near the target value T (not shown), only the detection output of the Hall element c shown by the solid line is shown. Outputs a signal that exceeds the upper limit value and the lower limit value to control the motor rotation speed in an unnecessary direction.

[Means for solving problems]

An object of the present invention is to realize a novel motor speed monitoring circuit that solves the above problems, and to detect the direction of current flowing through a drive coil based on the detection signals from a plurality of Hall elements and the current. A direct current motor that determines the amount is used as a spindle motor, and based on the detection signal from the Hall element, when the spindle motor is at a first predetermined speed or more or at a second predetermined speed or less, it is determined that the speed is abnormal. In a magnetic disk device for stopping the rotation of the spindle motor, a spindle motor rotation speed monitoring means based on a clock pulse obtained from a servo surface on a magnetic disk disk, and the spindle motor is at a first predetermined speed. And the second
Rotation speed determining means for determining that the predetermined rotation speed set during the predetermined speed is reached, and if the rotation speed determining means determines that the spindle motor has reached the predetermined rotation speed, the spindle motor It is solved by a motor speed monitoring circuit characterized by switching the rotation abnormality monitoring to the rotation speed monitoring means.

[Action]

That is, according to the present invention, both the detection output from the Hall element, which has a low detection accuracy but a detection output can be obtained even at a low rotation, and the detection output from the servo head, which has a high detection accuracy but has a narrow range of detectable revolutions, are provided. It is used by switching.

That is, the speed abnormality signal obtained by monitoring the speed abnormality signal input to the motor control circuit from the detection output of the Hall element and the speed abnormality signal obtained based on the clock pulse obtained by the servo head from the magnetic disk disk are used. An electronic switch for switching to is provided, and until the rotation speed (rotation speed) of the spindle motor reaches a predetermined constant rotation speed (rotation speed), for example, a constant rotation speed (rotation speed) when recording / reproducing data. The rotation speed (revolution speed) abnormality is monitored by the speed abnormality signal obtained from the detection output of the Hall element, and when the predetermined constant rotation speed (revolution speed) is reached, the rotation speed (revolution speed) abnormality is monitored by the magnetic disk circle. By switching to the speed abnormality signal obtained based on the clock pulse (eg index pulse) obtained by the servo head on the board, the rotation speed of the spindle motor ( The number) monitors have ten times the precision, made it possible to maintain.

〔Example〕

The gist of the present invention will be specifically described below with reference to the embodiment shown in FIG.

FIG. 1 is a block diagram showing an embodiment of a motor speed monitoring circuit according to the present invention. The same reference numerals denote the same objects throughout the drawings.

Next, the operation of this embodiment will be described focusing on the operation related to the present invention.

DC brushless motor is started by the start signal,
As described above, the signal is turned on from the motor control circuit 5 after a fixed time.

At this time, if the DC brushless motor is faulty and the rotation speed exceeds the upper limit value or falls below the lower limit value, the comparator circuits 9 and 10 on the Hall element side detect the abnormal rotation, and the electronic signal is output. It is sent to the motor control circuit 5 via the switch 23.

The Hall signal and the pulse ′ from the Hall element c are output even when the rotation speed is outside the range between the upper limit value and the lower limit value.
On the other hand, the signal output from the servo head, which will be described later, is limited in the number of revolutions within a certain range, and is not suitable for detecting a wide range of revolution abnormality such as rotation abnormality at the time of starting.

Next, when the signal turns on, if the rotation speed of the DC brushless motor is within the range between the upper limit value and the lower limit value, the motor control circuit 5 causes the rotation speed to gradually converge toward the count value T.

When a predetermined number of rotations between the upper limit value and the lower limit value is reached in the process, the motor control circuit 5 sends a signal to the electronic switch.
23, and switches the electronic switch 23 to the side of the OR circuit 22.

As a result, when the logical sum circuit 22 outputs a speed abnormality signal, the electronic switch 23 sends this signal to the motor control circuit 5.

As the speed abnormality signal, a signal obtained by reading the servo surface on the magnetic disk disk d with the servo head e (for example, an index signal that is read once to make one rotation of the magnetic disk disk d) is predetermined by the demodulation circuit 14. It is created as follows based on the signal 'which is demodulated into a waveform and shaped by the waveform shaping circuit 15 into a waveform that can be used in subsequent circuits (counter circuit 17, comparators 20, 21, etc.) .

That is, in the counting circuit 17, a lead for taking out the count value (count value T-Δt) and the count value (count value T + Δt) is set in the same way as the count circuit 4, and the count value (count value T-Δt) is set. Is connected to the AND circuit 18, and the lead for the count value (count value T + Δt) is connected to the AND circuit 19.

The counting circuit 17 resets the count value up to that point with a signal 'which becomes the reset signal of the counting circuit 17, and then starts counting by the pulse output from the oscillator 16 having the same period as the oscillator 3.

The signal sent from the motor control circuit 5 is turned on after the motor starts rotating and the count value of the counting circuit 17 is applied to the other terminals of the AND circuits 19 and 18 (count value T
+ Δt) and the count value (count value T−Δt) are reached, the AND circuits 19 and 18 send signals to the comparators 21 and 20, respectively.

The comparator 20 compares the signal from the logical product circuit 18 with the signal ', and outputs the signal to the logical sum circuit 22 when the speed is too fast, and also outputs the signal to the logical sum circuit 22 when the speed is too slow.

As described above, the rotation speed (rotation speed) of the DC brushless motor is monitored with higher accuracy during data recording / reproduction.

〔The invention's effect〕

According to the present invention as described above, it becomes possible to monitor the speed of the motor with a high accuracy of ten times or more.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a motor speed monitoring circuit according to the present invention, FIG. 2 is a conventional motor speed monitoring device diagram of a magnetic disk device, and FIG. 3 is a motor rotation speed monitoring status diagram. Show. In the figure, 1 is an amplification / waveform shaping circuit, 2 is a rotor position inspection circuit, 3 and 16 are oscillators, 4 and 17 are counting circuits, 5 is a motor control circuit, 6 to 8, 18 and 19 are AND circuits, 9 , 10, 20 and 21 are comparators, 11 and 22 are logical sum circuits, 12 is one rotation pulse generation circuit, 13 is a power amplifier, 14 is a demodulation circuit, 15 is a waveform shaping circuit, and 23 is an electronic switch. .

Claims (1)

[Claims] 1. A direct current motor for determining a current direction and a current amount to be passed through a drive coil based on detection signals from a plurality of Hall elements is used as a spindle motor, and based on the detection signals from the Hall elements. In a magnetic disk device that stops the rotation of the spindle motor as a speed abnormality when the spindle motor is equal to or higher than a first predetermined speed or equal to or lower than a second predetermined speed, it is obtained from a servo surface on a magnetic disk disk. Rotation speed monitoring means for the spindle motor based on a clock pulse;
Rotation speed determining means for determining that the predetermined rotation speed set during the predetermined speed is reached, and if the rotation speed determining means determines that the spindle motor has reached the predetermined rotation speed, the spindle motor The motor speed monitoring circuit is characterized in that the rotation abnormality monitoring is switched to the rotation speed monitoring means.