JPS6182389A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To stop a head at the position where an output becomes maximum by supplying a voltage in which an envelope of an output of the head wabbled, to a pulse motor for driving a head. CONSTITUTION:A bimorph plate 19 is driven by the output of a driving circuit 25 and a head 4 is wabbled in the track direction. Simultaneously, when the head is shifted in the inner circumference and outer circumference by wabbling by means of FF27 which is operated in response to the output of the circuit 25, gate circuits 28 and 29 are opened respectively. An envelope signal of the detecting output of the head 4 are differentially processed at a differentiating circuit 23 by an envelope detecting circuit 21 and a filter 22, supplied through the circuit 28 or the circuit 29 to a charging circuit 30 and to the position where an envelope signal becomes maximum, the voltage necessary to drive a pulse motor 2 is charged. Thus, without influencing the track, head rotary angle, feeding mechanism, etc., the head is always stopped at the output maximum position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk device in which a head is moved using a pulse motor.

[Prior Art] FIGS. 8 and 9 are both schematic diagrams showing a head positioning mechanism in a conventional static magnetic disk device.

Fig. 8 shows a one-type lead screw type, and in the figure, (1) is the lead screw, (2) is the pulse motor for rotating this lead screw (1), and (
3) is a head arm that moves in the direction of arrow a by the rotation of the lead screw (1), and (4) is a head arm (
The head (5) attached to the top of the disk (3) is a magnetic disk on which image information and the like are recorded and can be written and read by the head (4).

FIG. 9 shows a steel belt system, in which (6) is a pulley rotated by a pulse motor (2), (7) is a pulley that rotates around a shaft (8),
(8) is the shaft that is the rotation center of pulley (7), (9) is the steel belt that is hung between pulley (6) and pulley (7), and (10) is the shaft that is connected to the steel belt (8). ,”
The head (4) is attached to two parts and is a head moving table movable in the direction of the arrow.

I will explain the operation in detail.

In Fig. 8, when the pulse motor (2) rotates, the lead screw (1) rotates by the rotation angle of the pulse motor (2).
) is rotated, and the female threaded head arm (3) is t/(0
/ 380) (mm). However, 0:
Rotation angle of pulse motor (2) (deg': J,
t: Pitch (mm) of the lead screw (1).

As a result, head positioning is performed according to the take-up rotation angle of the pulse motor (2).

Also in FIG. 9, when the pulse motor (2) rotates, the pulley (6) and the pulley (7) rotate, and the head moving table (10) is moved by the pulse motor (2) as the steel belt (9) moves. Move according to the rotation angle.

The head feeding mechanism shown in Figs. 8 and 9 above is capable of positioning at a predetermined position within the rotation angle error of the pulse motor (2) and the error of the lead screw (1) or steel belt (8). is possible.

[Problems to be Solved by the Invention] Since the head positioning device in a conventional magnetic disk device is configured as described above, the head can only be stopped at a predetermined position, and it is not possible to deal with track misalignment. Even at the stop position, there are drawbacks such as errors in the rotation angle of the pulse motor (2), errors in the lead screw (1) or the steel belt (8), etc.

The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a magnetic disk device that can stop the head at a position where its output is maximum.

[Means for Solving the Problems] In the present invention, a pulse motor is driven in a closed loop by a wobbling type embedded servo. That is, a wobbling mechanism is provided to wobble the head in the track direction of the disk, and an increase/decrease in the envelope of the head output is detected, and a voltage that maximizes the envelope output is supplied to the pulse motor drive circuit to drive the pulse motor to a predetermined value. The angle is rotated to perform tracking.

[Operation] In this invention, closed loop control is performed so that the pulse motor rotates at a predetermined angle based on the voltage that maximizes the envelope output, so the pulse motor always stops at the maximum head output point. It becomes possible to do so.

[Embodiment] FIG. 5 is a diagram showing an embodiment of a head feeding mechanism in a magnetic disk device according to the present invention. In the figure, (1
) is the lead screw, (2) is the pulse motor for rotating this lead screw (1), (3) is the head arm that moves by the rotation of the lead screw (1), and the lead screw (1) and helad arm ( 3) constitutes a feeding mechanism. (4) is a head attached to a bimorph (18), which will be described later; (5)
is a magnetic disk on which image information and the like are recorded and can be written and read by a head (4). (19
) is a bimorph that constitutes a wobbling mechanism,
It is connected to the head arm (3), supports the head (4), and has the function of swinging the head (4) in the inner and outer circumferential directions of the magnetic disk (5).

Figure 6 is a diagram showing a four-phase drive pulse motor.
2) is the α phase of the coil of the pulse motor (2), (1
3) has no β phase, (14) has no α phase, and (15) has no β phase. Note that (11) is the rotor of the pulse motor.

FIG. 7 shows the electromagnetic force within the pulse motor as a vector, and one rotation 36o0 represents one step.

In the figure, (16) represents the state in which the α phase (12) is excited, and (17) represents the state in which the α phase (12) is excited, and (17) represents the state in which the α phase (12) is excited.
) is driven in mini-steps by the output from the servo circuit, and the state in which it is slightly excited is represented by a vector. And the vector (18) is the vector (1
8) and vector (17), α phase (12)
This represents the rotation by O from the magnetic absorption position of .

FIG. 1 is a block diagram showing an embodiment of a magnetic disk device according to the present invention. In the figure, (4) and (18
) are the head and bimorph shown in Figure 5, respectively;
(20) is the head amplifier that amplifies the signal from the head (4), and (21) is the F from the head amplifier (20).
An envelope detection circuit that extracts only the envelope component from the M signal, (22) is a filter that cuts components above the rotation frequency and passes only DC-like components below the rotation frequency, and (23) is a filter that extracts only the envelope component of the envelope. This is a differentiating circuit for detecting whether it has increased or decreased.

(26) is an oscillation circuit for creating timing pulses and drive pulses for bimorph (19), and (25) is an oscillation circuit (
(26) is a frequency dividing circuit that shapes the pulse from the frequency dividing circuit (25) into a square wave and performs frequency division, and (24) is a bimorph drive circuit that drives the bimorph (19) with the pulse from the frequency dividing circuit (25). .

(27) is a flip-flop circuit that generates timing pulses for the movement of the bimorph (19) in the inner circumference direction of the disk and the timing pulses for movement in the outer circumference direction, based on the timing pulse from the frequency dividing circuit (25); Differential circuit (
(23) is a gate circuit that opens the gate when moving in the inner circumferential direction in response to the output of the differential circuit (23), (28) is a gate circuit that opens the gate when moving in the outer circumferential direction in response to the output of the differential circuit (23), and (30) is a gate circuit that opens the gate when moving in the outer circumferential direction in response to the output of the differential circuit (23). ) and the output of the gate circuit (28), the pulse motor (2) is controlled in a closed loop by the flip-flop circuit (27), the gate circuits (28), (28), and the charge circuit (3o). A control section is configured to do this.

(31) is a pulse motor drive circuit that drives the pulse motor (2) using the output of the charge circuit (3o) and a signal from the microcomputer (32), and (32) is a drive command and embedded servo circuit for the pulse motor (2). This is a microcomputer for generating a drive command signal for the output of the motor.

FIG. 2 is a timing chart for explaining the operation of FIG. 1. In Figure 2, (33) is the oscillation circuit (2
6) output, (34) is the output of the frequency divider circuit (25) and is a signal input to the bimorph drive circuit (24), (35)
is the drive signal for driving the bimorph (19), (3
6) is the signal from the flip-flop circuit (27), which is the gate pulse when moving to the outer circumference, (37) is the signal from the flip-flop circuit (27), which is the gate pulse when moving to the inner circumference, and (38) is the envelope detection. The head (4) is located at a position where the output of the circuit (21) increases toward the outer circumference and decreases toward the inner circumference.
This is the output of the differentiating circuit (23) when . (39
) is the signal obtained by gating the output (38) of the differentiating circuit (23) with the gate circuit (28) using the gate pulse (38) when moving to the outer circumference, and (40) is the gate pulse (37) when moving to the inner circumference.
The output (38) of the differentiator circuit (23) is gated and inverted by the gate circuit (29), and (41) is the signal obtained when each of the above signals (38) and (40) is charged by the charge circuit (30). shows the voltage.

FIG. 3 is a diagram showing the relationship between envelope output and head position, with the vertical axis representing the average envelope output voltage and the horizontal axis representing the head position. In the figure, arrow f indicates the inner circumferential direction, arrow g indicates the outer circumferential direction, C indicates the optimum head position, and d and e indicate positions shifted toward the inner and outer circumferences, respectively.

FIG. 4 shows the output waveforms when the initial stop position is at each position shown in FIG. 3, and (42) shows the output of the gate circuit (28) and the gate circuit (
A signal (43) which is a composite of the inverted outputs of (28) and (43) indicates the embedded servo output at that time, that is, the servo output voltage of the pulse motor drive circuit (31). (44) is a signal obtained by combining the output of the gate circuit (28) and the inverted output of the gate circuit (29) when the head is at the optimum position C;
(45) is the servo output voltage at that time, and (46) is the gate circuit (28) when the head is at position e due to a certain disturbance.
) and the inverted output of the gate circuit (28), and (47) indicates the servo output voltage at that time.

Next, the operation will be explained.

The pulse motor (2) is stopped by a command from the microcomputer (32), and its stop position is indicated by d in FIG. 3. The output (33) of the oscillation circuit (26) is divided into the frequency dividing circuit (2
A bimorph drive voltage (35) is generated in a bimorph drive circuit (24) by the signal (34) frequency-divided by 5), and this drive voltage causes the bimorph (18) to wobble in the inner and outer circumferential directions. At this time, the FM output signal from the head (4) is amplified by the head amplifier (20),
Only the envelope is extracted by the envelope detection circuit (21). Since the envelope during one rotation of the disk is actually quite non-uniform, a filter (22) cuts off components above the rotational frequency, and a differential circuit (23) differentiates the signal to obtain a signal like (38). The flip-flop circuit (27) generates a pulse (36) when the /kuimorph (18) moves from the inner circumference to the outer circumference, and a pulse (36) when it moves from the outer circumference to the inner circumference. Pulse (3
7), and gate circuit (28) and gate circuit (2) based on the timing of pulses (38) and (37).
9) gates the output (38) of the differentiating circuit (23).

In FIG. 3, when the head (4) moves from the position d in the direction g, the integral output of the envelope is in the increasing direction, so the output (38) of the differentiating circuit (23) is gated by the gate circuit (28). The resulting signal becomes as shown in (39). On the other hand, when the head (4) moves from the position d to the direction f, the integral output of the envelope is in the direction of decrease, so the output (38) of the differentiating circuit (23) is transferred to the gate circuit (
The gated and inverted signal in 28) becomes as in (40). Therefore, the voltage charged by each of the signals (38) and (40) increases with time as shown in (41).

Now, at the initial stop of the pulse motor (2), α in Fig. 6
Assuming that the phase (12) is excited, the charged voltage (41) excites the β phase (13) via the pulse motor drive circuit (31). The vector diagram at this time is as shown in Figure 7, assuming one pitch all around the circumference, and the vector (
17), it rotates slightly by θ and moves in the direction of the outer circumference of the helad arm (3) t± in FIG. 5.

When the head position moves to C in Figure 3, the gate circuit (
28) and the inverted output of the gate circuit (29) becomes (44) in FIG. 4, and the output voltage of the charge circuit (30) is kept constant as shown in (45).

Further, when the head (4) moves to the position e in FIG. 3 due to a certain disturbance, the input composite signal of the charge circuit (30) becomes as shown in (46),
) decreases and the head arm (3) moves in the direction of arrow f.

The process JR,l allows the head (4) to stop at position C where the envelope integral value is always the maximum. Further, when the initial stop position is e in Fig. 3, the charge circuit (30) is charged with a negative voltage, and if the β phase (13) is driven with a negative voltage, the pulse motor (2)
The head (4) rotates slightly in the inner circumferential direction, and through the process described above, the head (4) stops at the position C where the envelope integral value is maximum. Alternatively, if the input signal of the charge circuit (30) is negative, the signal is inverted and the β phase (1
It is also possible to adopt a method in which the servo output voltage is applied to 5).

[Effects of the Invention] As described above, according to the present invention, since the pulse motor is driven in a closed loop by the embedded servo, the pulse motor can be driven in a closed loop without being affected by the tracking accuracy, the head rotation angle accuracy, the accuracy of the feed mechanism, etc. This has the effect that the head can be stopped at the maximum output position of the head.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the magnetic disk device according to the present invention, FIG. 2 is a timing chart for explaining the operation of FIG. 1, and FIG. 3 is a characteristic showing the relationship between envelope output and head position. 4 is a waveform diagram showing the charge circuit input and servo output at each head position in FIG. 3, FIG. 5 is a diagram showing the head feeding mechanism in the embodiment of the present invention, and FIG. FIG. 7 is a diagram equivalently representing one pitch, FIG. 7 is a diagram representing one pitch of a pulse motor as a vector, and FIGS. 8 and 9 are diagrams showing a head feeding mechanism in a conventional magnetic disk device. . (1)...Lead screw, (2)...Pulse motor, (3)...Head arm, (4)...Head, (5)...Magnetic disk, (19)... Bimorph, (23)...Differential circuit, (24)...Bimorph drive circuit, (27)...Flip-flop circuit, (
28), (28)...gate circuit, (30)...
...Charge circuit, (31)...Pulse motor drive circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (4)

[Claims] (1) A head for reading information recorded on a magnetic disk, a wobbling mechanism that wobbles the head in the track direction of the disk, a feeding mechanism that moves the head in the track direction, and a feeding mechanism that moves the head in the track direction of the disk. a pulse motor to drive, a pulse motor drive circuit to drive the pulse motor, a differential circuit to detect an increase/decrease in the envelope of the head output due to the wobbling, and a differential circuit configured to maximize the envelope output based on the output of the differential circuit. a control unit that outputs a voltage, the output voltage of the control unit is supplied to the pulse motor drive circuit, and the pulse motor is rotated by a predetermined angle to perform tracking. . (2) The control unit includes a flip-flop circuit that generates timing pulses when the wobbling mechanism moves in the inner and outer circumferential directions of the disk, and a gate that opens the gate with the pulses when the wobbling mechanism moves in the inner circumferential direction, in response to the output of the differentiator circuit. 1 gate circuit, a second gate circuit that opens the gate with a pulse during the movement in the outer circumferential direction with respect to the output of the differentiating circuit, and
2. The magnetic disk device according to claim 1, further comprising a charge circuit for charging the output of the gate circuit. (3) A magnetic disk device according to claim 1 or 2, wherein the wobbling mechanism is constituted by a bimorph. (4) Claims 1 or 2, or The magnetic disk device according to item 3.