JPH0416873B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic head feeding device in a magnetic recording/reproducing device using a disk-shaped recording medium, and its purpose is to adjust the position of the head during signal recording (writing) to the magnetic head during reproduction. This is to correct the deviation of the head position (during reading). Conventionally, head positioning devices (positioners) used in this type of magnetic recording/reproducing apparatus include those that normally perform positioning using a closed loop system, and those that perform positioning using a closed loop system. A conventional closed-loop head positioning system is shown in FIG. As shown in the figure, a pulse motor 3 is used as a drive source, a control circuit 1 generates pulses as many times as necessary to move the bed to a predetermined position, and a pulse motor drive circuit 2 supplies current to each phase of the pulse motor. The pulse motor is rotated by a predetermined amount by changing the direction of the pulse motor. As the shaft of the pulse motor rotates, the metal belt 4, which is wound around the shaft of the motor in an α-shape and fixed at both ends to the moving table, wraps around to either side, and the moving table is moved accordingly. One end of the magnetic head 5 was pulled by the belt and moved to one side (toward the disk or the opposite direction), and the position of the magnetic head 6 was thereby moved. The positioning accuracy of this method is determined by a combination of factors such as the stopping angle accuracy of the pulse motor, gaps in the mechanism, and changes in the dimensions of each element and component due to temperature changes.It is a closed loop that feeds back the head signal and applies the servo. Compared to the positioning method, the disadvantage was that the positioning accuracy was poor. but,
It is widely used because it is considerably cheaper than the closed-loop method and allows for a more compact positioning mechanism. The present invention was devised in view of the drawbacks of the conventional closed-loop system, and it is an object of the present invention to provide a magnetic head feeding device that has a simple configuration and can provide unprecedented positioning accuracy. Conventional magnetic recording and reproducing devices send and receive data while constantly checking with the host system whether or not the data contains errors when reading a necessary part of the data already recorded on the disk. If it is determined that there is an error, the magnetic recording/reproducing device repeats the readout of that location, and if the correct readout signal is still not obtained even after rereading several times, it is treated as a system error. ing. The present invention is a specific method for correcting such a situation by moving the head position in small steps and then gradually in large steps until it reaches a position where data can be read correctly. The gist of the present invention will be explained below with reference to the drawings. FIG. 2 shows how the pulse motor shaft is moved to correct an off-track head to on-track according to the present invention. FIG. 3 is a block diagram showing a specific implementation method for realizing the movement shown in FIG. 2. Assume that in conventional closed loop head positioning, the motor is advanced by one step (one track interval) and stopped at position 0 in FIG. However, even if the stop position is slightly shifted from the track position at the time of writing due to the reasons mentioned above, there is no choice but to reproduce the data at the shifted position. Therefore, in the case of a relatively large off-track, the reproduction level becomes low or the signal of an adjacent track is also reproduced, making it often impossible to read out the signal correctly. In such a case, the present invention slightly changes the phase current of the pulse motor, moves the motor shaft from the 0 position as shown in Figure 2, and reads the data on the disk again at that position. If the reproduced signal still contains an error, move the corner to the position and read the data again. If the error still exists, continue from corner to corner...
...while gradually increasing the stopping angle by a predetermined amount,
The present invention proposes that by vibrating the shaft of the pulse motor so that the head moves back and forth, the phase current of the pulse motor can be changed little by little until the signal on the track can be read correctly. Figure 2a shows a method of moving the motor shaft by a predetermined amount alternately back and forth with reference to the initial stop position 0, and Figure 2b shows a method that is a further improvement of Figure 2a, starting from position 0'. If you use it as a reference, but once you move it a certain amount in one direction and cannot read the signal correctly at that position, move it a certain amount in the same direction immediately next to it, and if you still cannot read the signal correctly, next time. , 0' as a reference and moves the shaft in the opposite direction.This method requires less time to move the motor shaft in small increments than the method shown in FIG. 2a. How to concretely realize this idea,
This will be explained with reference to FIG. Third to realize the present invention
The diagram shows the pulse motor drive circuit, pulse motor, head moving table, magnetic head, and amplifier.
A correction signal controller 20, a correction signal generation circuit 21, and a phase current variable circuit 22 are newly added to a conventional open-loop head positioning device consisting of a signal processing circuit including a recording/reproducing signal processing circuit, a disk drive circuit, etc. This is a head positioning configuration. Under normal conditions, the pulse motor 13 rotates by a predetermined angle by switching the phase current supplied from the pulse motor drive circuit 12 to the target track according to a command from the signal processing circuit 18, and the head carriage 15 rotates according to the command from the signal processing circuit 18. slides,
The magnetic head 16 moves to a predetermined position on the magnetic disk and stops. When the positioning of the magnetic head 16 is completed, the signals on the disk are read out by the magnetic head 16, processed by a signal processing circuit 18, and sent to a host system (host computer) 19. host system 19
Then, it constantly checks whether there is an error in the ID field or DATA field of the read signal that is sent, and if an error is found, the host system 19 sends a request for re-reading. A signal indicating a request or an error is returned to the signal processing circuit 18. When the signal processing circuit 18 receives a reread request or an error signal, it immediately transmits this to the correction signal controller 20. At this time, the correction signal controller 20
In order to move the pulse motor shaft as shown in the figure, the A-phase side 21a of the correction signal generation circuit 21a sends a signal indicating how much the current of either phase A or B phase should be varied.
or B phase side 21b and outputs it.
In response to this signal, the corresponding correction signal generation circuit generates a signal to reduce the phase current required for the pulse motor shaft to slightly rotate by a predetermined amount, and transmits the signal to the corresponding phase current variable circuit 22a or 22b. The corresponding phase current variable circuit 22 varies the phase current according to the correction signal. When the amount of current in one of the two phases changes, the stationary stable point of the motor rotor changes accordingly, and the stopping position of the motor shaft changes accordingly. The head carriage 15 moves slightly in proportion to this movement, and the head position also moves by a predetermined amount, reading out a signal at a position slightly different from the track read last time, processing it again in the signal processing circuit 18, and sending the signal to the host system 19. send. In this way, by repeating the above operations until the data can be read correctly, the data that was not read correctly by off-track can be transferred to the head until it can be read correctly. It becomes possible to correct the displacement. The determination of whether there is an error does not need to be performed by the host system 19 as described above, but a determination circuit may be provided within the signal processing circuit 18, or even without the method of checking read data for errors. It is determined that correction is necessary depending on whether the playback level of the read signal is abnormally low.
It is also possible to carry out the head position correction operation described above. Specific circuit configurations of a phase current variable circuit for varying the motor phase current in small increments are shown in FIGS. 4, 5, 6, and 7, respectively. Figure 4 shows a circuit system in which shunt circuits with slightly different shunt flows are installed in parallel with the motor phases, and circuits with gradually increasing shunt flows are sequentially selected to gradually reduce the motor phase current. be. In Fig. 4, the four transistors Q _A1 to Q _A4 and Q _B1 to Q _B4 connected in a bridge configuration are switching transistors for driving the pulse motor in a bipolar manner. Table 1 shows the operating states of each transistor for step feeding.

[Table] To rotate clockwise, change the conditions in Table 1 →
→→→→……, and to rotate it counterclockwise, do →→→→→……. Shunt phase current amount selection transistors Q _A5 to _{Q A10} ,
Q _B5 to Q _B10 and shunt transistor selection circuit 3
1, 32, 33, and 34 are circuits added to realize the present invention. The transistor selection circuit can actually be implemented with a decoder circuit or a microprocessor IO port circuit. Using the circuit shown in Figure 4 as an example where current flows through only one phase of the motor excitation coil, Figure 5 explains how to vary the phase current in small steps in order to correct the head position. do. A normal current loop is a current from a transistor
Q flows through _A1 to the motor coil and the transistor
Q Flows to GND via _A4 . If it is determined that there is an error in the data read on a certain track,
In order to vary the phase current, part of the current supplied from the power source may be shunted before the coil. To do this, it is sufficient to turn on any one of the transistors Q _A5 , Q _A6 , and Q _A7 . If you select the resistor connected to the collector in stages as R ₁ > R ₂ > R ₃ ,
When Q _A6 is selected over Q _A5 , and Q _A7 is selected over Q _A6 , the shunt current increases, the phase current decreases accordingly, and the motor resting position deviates by a predetermined amount from the deepest stopping position. will occur. Each transistor is
Since the switching operation is completely ON or OFF, each shunt current can be determined only by the resistor, and therefore it has the advantage of being able to determine the shunt current with considerable accuracy. Transistors Q _A5 , Q _A6 , and Q _A7 can be easily selected by decoding the binary code indicating how much the divided flow should be with a decoder, and the correction signal controller can be easily realized with a microcomputer. can. Similarly, other embodiments for varying the phase current are shown in FIGS. 6 and 7. Figure 6 shows a method of controlling the phase current with transistor Q _A2 , where Q _A11 , Q _A12 , and Q _A13 are bias current switching transistors, and R ₁ , R ₂ , and R ₃ are resistors that determine the bias current. . Figure 7 shows how to change the phase current flow time.
41 is a comparison circuit that compares the integrated value of the phase current with several set voltages as a reference, and 42 is a monostable multivibrator that cuts off the transistor Q _A1 for a certain period of time when the phase current exceeds a specified period of time. . 43 is a resistor for detecting phase current amount, and capacitor 44 and resistor 45 form an integrating circuit for converting the value detected by resistor 43 for detecting phase current amount into a level. According to the configuration of the present invention as described above, it is possible to practically perform head positioning that allows data to be read correctly without constructing a high-grade servo system.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a conventionally used open-loop magnetic head feeding device, and FIGS. 2a and 2b show a pulse motor shaft for correctly correcting the head onto the track according to the present invention. FIG. 3 is a block diagram showing the specific driving method of FIG. 2, FIG. 4 is a circuit diagram showing the specific embodiment of FIG. 3, and the fifth, sixth, and FIG. 7 is a circuit diagram showing a specific example of driving only one phase of a pulse motor. DESCRIPTION OF SYMBOLS 1... Control circuit, 2... Pulse motor drive circuit, 3... Pulse motor, 4... Belt, 5... Moving table, 6... Magnetic head, 7... Disk, 12... Pulse motor drive circuit, 1
3... Pulse motor, 15... Head carriage, 16... Magnetic head, 18... Signal processing circuit, 19... Host system, 20... Correction signal controller, 21... Phase correction signal generation circuit, 2
2... Phase current variable circuit, 31, 32, 33, 34
... Shunt transistor selection circuit, 41 ... Comparison circuit, 42 ... Monostable multivibrator, 43
... Phase current detection resistor, 45 ... Integrating resistor, 44
... Integral capacitor.

Claims (1)

[Claims] 1. In a magnetic head feeding device in a magnetic recording and reproducing device, the magnetic head feeding device includes a pulse motor drive circuit, a variable phase current circuit, a correction signal generation circuit, a correction signal controller, a pulse motor, a head moving stage, a magnetic head, etc. After rotating the pulse motor and moving the magnetic head to a predetermined position, if there is an error in the data read at that position, the scanning range is increased by a predetermined amount based on the initial stop position. A magnetic head feeding device characterized in that the phase current of a pulse motor is varied so that the magnetic head moves forward and backward on a track.