JPH0322673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a head positioning device for a magnetic recording/reproducing device, and particularly to a magnetic head positioning device that uses a stepping motor to improve the positioning accuracy. , relates to a head positioning device for a magnetic recording/reproducing device. [Background of the Invention] In conventional magnetic recording and reproducing devices with removable magnetic disks such as floppy disks, the positioning error of the magnetic head must be below a certain tolerance in order to maintain compatibility between devices. is required. This tolerance varies depending on the number of tracks per unit length (track density) and the configuration and dimensions of the magnetic head, but if a tunnel erase type head with guard bands on both sides of the data is used,
The value roughly corresponds to the tunnel erase gap width. Therefore, as track density increases, higher head positioning accuracy is required. FIG. 1 is a schematic perspective view of a conventional example of a head positioning device that has been widely used in floppy disks. In FIG. 1, 1 is a stepping motor, 2 is a pulley press-fitted into the shaft of the stepping motor, 3 is a steel belt, 4 is a rail fixed to the chassis (not shown) of a floppy disk drive, and 5 is a pulley press-fitted into the shaft of the stepping motor. is the carriage, 6 is the head arm, 7 is the upper magnetic head, 8 is the lower magnetic head, 9
1 is a chucking device for fixing a magnetic recording medium (floppy disk) (not shown) to a floppy disk drive, and 10 is a reference track position sensor. In the operation of the head positioning device having such a structure, first, the rotation angle of the stepping motor 1 fixed to the chassis is changed stepwise in response to a control signal. Therefore, the pulley 2 also rotates in a stepwise manner. This rotation of the pulley 2 causes the carriage 5 to move linearly along the rail 4 via the steel belt 3. That is, the carriage 5 moves linearly in accordance with the stepwise changing rotation of the stepping motor 1. That is, since the stepping motor 1 rotates at regular intervals, the carriage 5 performs linear motion at regular intervals. Therefore, the carriage 5 and the upper and lower magnetic heads 7, 8 attached to the head arm 6 fixed to the carriage 5 move linearly at regular intervals. This interval is used as the reciprocal of the track density.
When set, the upper and lower magnetic heads 7 and 8 are positioned at the track position. The reference track position sensor 10 is used to detect when the upper and lower magnetic heads 7 and 8 have reached the reference track position (usually the outermost track position) by detecting the position of the carriage 5. . Positioning error factors in a magnetic recording/reproducing device using such a magnetic head positioning device include (1) angular error due to rotation of the stepping motor in one direction (usually about ±2.5% of the rotation angle); (2) Angle error due to the rotation direction of the stepping motor (usually about ±1% of the rotation angle), (3) Absolute accuracy of pulley diameter, (4) Accuracy of mounting the rail to the chassis, (5)
There are factors such as the tracking accuracy of the magnetic disk, and (6) expansion and contraction of the magnetic disk due to temperature and humidity. In the current magnetic recording/reproducing device using a 3-inch diameter magnetic disk, the total of these is about 80 μm, and due to the tunnel erase width limit mentioned above,
The limit of track density is about 100 Tpi (tracks/inch: number of tracks per inch) to 150 Tpi, and this is an obstacle to higher density. Next, the angular error due to the rotational direction of the stepping motor will be explained in more detail. Here, FIG. 2 is a diagram showing the relationship between the rotation angle and output torque of the stepping motor, and FIG. 3 is a diagram illustrating the angular error of the stepping motor. In the figure, M indicates the output torque when rotating in the clockwise direction, and N indicates the output torque when rotating in the counterclockwise direction. A stepping motor stops when the output torque becomes 0, but when a load is connected to the stepping motor, hysteresis occurs in the output torque due to frictional torque. Therefore, depending on the direction of rotation, the stationary position differs as shown in the figure, and as shown in FIG. 3, there is a difference in angular error, and this angular error differs from track to track. [Object of the Invention] The present invention provides a head positioning device for a magnetic recording/reproducing device, which improves head positioning accuracy and realizes high-density recording in a magnetic head positioning device using a stepping motor. That is the purpose. [Summary of the Invention] The configuration of the head positioning device for a magnetic recording and reproducing device according to the present invention includes at least a head positioning device for a magnetic recording and reproducing device in which a stepping motor is used to position the magnetic head. and a non-volatile data storage means in which a value for correcting head positioning error for each track due to the moving direction of the stepping motor is stored in advance, and the stepping motor is controlled by the correction value of the data storage means. It is configured to control. The details are as follows. That is, the present invention reduces the magnetic head positioning error mainly caused by factor (2) among the positioning error factors mentioned above.
The head positioning accuracy is improved. The head positioning error due to the above factors differs for each stepping motor and each part, and as a result, it varies for each magnetic recording/reproducing device, for each track, and for each direction of rotation of the stepping motor. It's on. In the present invention, the head positioning error after assembly of the head positioning device is measured in advance for each head positioning device, and
By equipping the floppy disk drive with a means to correct the error, storing the correction value for each drive, and controlling the head position using the value,
This absorbs head positioning errors and improves head positioning accuracy. As a means of error correction, the rest position of the stepping motor after the stepwise rotation is controlled by controlling the internal magnetic field of the stepping motor.
This method takes advantage of minute changes and can be easily realized. In other words, the PROM outputs data for correcting the positioning error of the magnetic head for each track due to the direction of movement based on the signal that determines the rotation direction of the track counter and the stepping motor, thereby causing the stepping motor to slightly deviate. be. [Embodiments of the Invention] Examples of the present invention will be described with reference to the drawings. First, FIG. 4 is a circuit diagram of a head positioning device for a magnetic recording/reproducing apparatus according to an embodiment of the present invention. The illustrated configuration is a new addition to the stepping motor 1 shown in FIG. In the figure, 1 is a stepping motor, 11
12 is a PROM (Programmable Read Only Memory) as a data storage means; 13 is a converter; 14 is a stepping motor driver;
is an oscillator, and 16 is a frequency divider. First, to explain the input signal, STEP
is a signal sent from a higher-level controller to move the magnetic head by one track. In this embodiment, the stepping motor 1 rotates by a certain angle every time STEP falls. DIRECTION is also a signal from a higher-level controller that instructs the direction of rotation of the stepping motor 1. When this signal is at a low level, the magnetic head moves toward the inner track of the magnetic disk. TKφφ is the reference track position sensor 1 in Fig. 1.
With an output of 0, it becomes a low level when the upper and lower magnetic heads 7 and 8 reach the reference track position. Further, the POWER ON signal is a signal that becomes high level when the power of this system is turned on. Next, the operation of each part will be explained. When the power is turned on, the track counter 11 is
While the lower magnetic heads 7 and 8 are moved to the reference track position (the outermost track of the magnetic disk, the track number is usually set to 0 and the track number increases by 1 each time the head moves one track inward). It is reset (set to 0). And usually from a higher level controller
Counting by STEP and DIRECTION signals
The count is UP or DOWN to indicate the output track number. The outputs Q ₀ and Q ₁ of the lower two bits of the binary value of the track counter 11 are applied to the D ₁ terminal of the stepping motor driver 14 through the EOR gate, and the above Q ₁ is similarly applied to the D ₂ terminal. be done. Therefore, the stepping motor driver 14
At the D ₁ and D ₂ terminals of the track counter 1
When counting up 1, the change in (D ₂ , D ₁ ) is
(0, 0) → (0, 1) → (1, 1) → (1, 0)
→ (0, 0) →... is repeated. Conversely, when the count is DOWN, (0, 0)
→(1,0)→(1,1)→(0,1)→(0,
0)... is repeated. This stepping motor driver 14 is, for example, an IC manufactured by Hitachi, Ltd., HA13421P.
The figure is a rotation principle diagram showing the operating principle of a stepping motor. Therefore, when the _D1 terminal is at low level, the current corresponding to the input voltage of the input terminal _E1 in Fig. 4 is as follows.
When the switch transistors T ₂ and T ₃ are turned on, the current flows in the a direction of the A-phase winding of the stepping motor 1, and when the D ₁ terminal is at a high level, the switch transistors T ₁ and T ₄ are turned on. According to
It is flown in direction b. The switching transistors T ₅ to _{T 8} perform the same operation regarding the current according to the input voltage of the input terminal E ₂ . That is, the voltage applied to the input terminals E ₁ and E ₂ is caused by the input signals to the D ₁ and D ₂ terminals,
It is applied to the A-phase and B-phase windings of the stepping motor 1 with its direction controlled. Therefore, if a commercially available hybrid stepping motor, for example, is used as the stepping motor 1, the count of the track counter 11 will be reduced.
Due to UP or count DOWN, the signals at the D ₁ and D ₂ terminals change as described above, so the magnetic field inside the stepping motor 1 rotates as shown in Figure 5, and the stepping motor 1 rotates. That will happen. Therefore, the magnetic head moves one track at a time. Next, correction of positioning errors will be explained. FIG. 6 is an explanatory diagram of a control method showing actual measured values of minute changes in stationary position when the voltage of the winding of the stepping motor is controlled. That is, Figure A shows the rest position of the stepping motor when the voltage ratio applied to the A-phase winding and the B-phase winding is changed. The horizontal axis is the A phase winding, B
The vertical axis shows the voltage of the phase winding and the rest position. This shows that by controlling the voltage, the rest position can be controlled by ±1/2 steps from the balanced position when the same voltage is applied. Therefore, by controlling the voltages of the A-phase winding and the B-phase winding, the magnetic head can be positioned at any desired position. Further, B in the figure shows the rest position when the duty ratio is changed by PWM modulation (pulse width modulation) of the voltage applied to the A-phase winding and the B-phase winding. As a result, the A phase winding, B
It can be seen that by changing the duty ratio of the phase winding, the rest position can be controlled in the same way as by changing the voltage ratio. Correction of positioning errors is performed as follows. First, after assembly, on each individual truck,
Depending on the rotational direction of the stepping motor 1, measure the voltage (or duty ratio) that should be applied to the A-phase winding and the B-phase winding in order to make the positioning error zero (usually in order to measure the positioning error on the disk). It is known to measure the positioning error by writing a special signal in advance and reading this signal with a magnetic head.) The data corresponding to this voltage value or duty is shown in Figure 4.
Write to PROM12. As a result, the correction data for setting the positioning error to 0 for each drive, each track, and each rotation direction of the stepping motor is stored in the PROM1.
This means that it is written inside 2. Therefore, when using this drive, the signal for setting the positioning error to 0 for each track is the output of the track counter 11.
The stepping motor 1 is read out from the PROM 12 according to the DIRECTION signal, and is controlled by the converter 13 and the stepping motor driver 14.
It is made to stand still at a position where the positioning error becomes 0. Depending on the rotation direction of stepping motor 1
The data to be written into the PROM 12 is determined as follows. Here, FIG. 7 is a distribution diagram of the resting position of the stepping motor according to the rotation direction, and is an actual measurement of the degrees of the resting position of the stepping motor during clockwise rotation (A) and counterclockwise rotation (B) in a certain track. It indicates the value. In this way, the rest position is almost constant, although there is some variation. If the center values of these A and B are written in the PROM 12 shown in FIG. 4 in advance as a voltage value or data corresponding to duty that will result in a positioning error of 0, the positioning error can be reduced. Next, specific configuration examples of the converter 13 shown in FIG. 4 will be explained with reference to the circuit diagrams shown in FIGS. 8 and 9. First, Figure 8 shows D/A (digital/analog)
This is an example of a configuration using a converter. As mentioned above, 12 is a PROM, 14 is a stepping motor driver, and 17 is a D/A converter. That is, the data written in the PROM 12 is converted into an analog voltage value by the D/A converter 17, and the input terminals E 1 and E ₁ of the stepping driver 14 are converted by the driver transistors T ₉ and T ₁₀ .
E ₂ is driven at constant voltage. Therefore, this is a suitable method for controlling with the voltage shown in A of FIG. 6 above. Next, FIG. 9 is a circuit diagram relating to a method of changing the duty in another configuration example. In the figure, 12 is a PROM, 14 is a stepping motor driver, 15 is an oscillator, 16 is a frequency divider,
18 is a digital comparator, which is used in common with the oscillator 15 and frequency divider 16 in FIG. 4, which will be described later. That is, the frequency divider 16 always divides the pulse of the oscillator 15 into binary values. Therefore, a carry occurs every certain pulse, and flip-flops FF2 and FF3 are reset. The digital comparator 18 is
The output value of the PROM 12 and the output value of the frequency divider 16 are compared, and if they match, the respective flip-flops are
Set FF2 or FF3. Therefore, a signal with a duty according to the value of PROM 12 is generated in flip-flops FF2 and FF3 to switch driver transistors _T11 and _T12 . Therefore, the stepping motor driver 14
V _CC having a duty ratio according to the data of PROM 12 is applied to input terminals E ₁ and E ₂ of . This method uses driver transistors T ₁₁ , T ₁₂
is a saturated operation, so it is efficient. Next, although it is a bit of a back and forth, in the system described in FIG.
It is necessary to reset the track counter 11 when the power is turned on. Here, FIG. 10 is a timing chart when the power is turned on. That is, when the POWER ON signal rises, the flip-flop FF1 shown in FIG. 4 is set, and the track counter 11 consisting of an up-down counter enters the count DOWN mode. Further, the output pulse of the oscillator 15 is frequency-divided by a frequency divider 16, passes through NA1 and NA2 in the figure, and is applied to the CLK terminal of the track counter 11.
At this time, the STEP signal is kept at a high level by a gate (not shown). The output pulse period of the frequency divider 16 may normally be set to about several mSec. Therefore, the track counter 11 counts down every few mSec, and the stepping motor 1 also rotates to move the magnetic head in the direction of the reference track. When the magnetic head reaches the reference track position, the signal TKφφ from the reference track position sensor 10 becomes low level, resetting the flip-flop FF1 and the track counter 11. Therefore, the value of the track counter 11 and the actual track position match, and from now on, STEP ,
In response to the DIRECTION input, the upper and lower magnetic heads 7 and 8 are positioned at positions with little positioning error by the above-described correction operation. According to the present invention according to the embodiments described above, it was possible to improve the positioning error of an open loop head positioning device using a stepping motor. In other words, the positioning error has been improved from the conventional ±20 μm to ±4 μm, and even for a 3-inch floppy disk, the sum of all error factors can be improved to approximately ±21 μm.
It has become possible to increase the recording density to 200Tpi, which is twice as high as that of conventional technology. Although the above explanation was based on a floppy disk, the present invention is not limited to use only with a floppy disk, but can be widely used in open-loop position control systems using stepping motors. It is something. In addition, in the example of the converter that changes the duty ratio shown in FIG. 9, the input terminals E ₁ and E ₂ are operated complementary, so that the number of digital comparators 18 is reduced to one, and the flip-flop
It is also possible to exclude FF3. Furthermore, PROM can be any non-volatile storage means, regardless of whether it is an ultraviolet erasable ROM or a mask ROM, or a RAM backed up by a battery.
(Random access memory) is obviously possible. [Effects of the Invention] According to the present invention, the head positioning accuracy can be improved simply by adding electronic components to the conventional device without using a new head positioning device.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a conventional head positioning device, FIG. 2 is a diagram showing the relationship between the rotation angle and output torque of the stepping motor, and FIG. 3 is a diagram explaining the angular error of the stepping motor. Fig. 4 is a circuit diagram of a head positioning device for a magnetic recording/reproducing apparatus according to an embodiment of the present invention, Fig. 5 is a diagram of the rotation principle of a stepping motor, and Fig. 6 is an explanation of a method of controlling the stepping motor. Figure 7 is a distribution diagram of the rest position of the stepping motor according to the rotation direction, Figures 8 and 9 are
The figures are circuit diagrams of the converter, and FIG. 10 is a timing chart when the power is turned on. DESCRIPTION OF SYMBOLS 1... Stepping motor, 7... Upper magnetic head, 8... Lower magnetic head, 10... Reference track position sensor, 11... Track counter, 12...
...PROM, 13 ... converter, 14 ... stepping motor driver, 15 ... oscillator, 16 ...
Frequency divider, 17...D/A converter, 18...digital comparator.

Claims (1)

[Scope of Claims] 1. At least a head positioning device for a magnetic recording/reproducing apparatus in which a magnetic head is positioned by a stepping motor, which includes means for counting tracks, and means for counting tracks in advance according to the moving direction of the stepping motor. A magnetic recording and reproducing apparatus characterized in that the magnetic recording and reproducing apparatus is provided with a non-volatile data storage means in which a value for correcting a head positioning error is stored, and the stepping motor is controlled by the correction value of the data storage means. head positioning device. 2. In what is stated in claim 1,
A head positioning device for a magnetic recording/reproducing device, which is configured to control a stepping motor by controlling the driving voltage of its winding. 3 In what is stated in claim 1,
A head positioning device for a magnetic recording/reproducing device, which is configured to control a stepping motor by controlling the duty ratio of the driving voltage of its winding. 4 In what is stated in claim 1,
When the power is turned on, the magnetic head is moved in the direction of the reference track, and when the magnetic head reaches the reference track position, the means for counting tracks is reset by the reference track position sensor,
A head positioning device for a magnetic recording/reproducing device configured to match the value with the actual track position.