FR2528213A1 - MEMORY DEVICE WITH MAGNETIC DISK - Google Patents

Abstract

THE INVENTION RELATES TO A MAGNETIC DISC MEMORY DEVICE, OF THE TYPE USING "FLYING" HEADS. ON DETECTION OF AN ELECTRICAL ENERGY SUPPLY FAILURE, THE WINDINGS 36, 38 OF THE MOTOR 30 OF THE SPINDLE 14 CARRYING A DISC 12 ARE SWITCHED SO AS TO BE CONNECTED DIRECTLY TO THE MOTOR 32 FOR POSITIONING THE HEADS 16, IN ORDER THAT THE ELECTROMOTOR FORCE PRODUCED BY THE WINDINGS 36, 38 SUPPLY THE MOTOR 32 TO QUICKLY MOVE OR RETRACT THE HEADS 16 TO A LAYING AREA. FIELD OF APPLICATION: DISC MEMORY UNITS.

Description

The invention relates generally to disk memories

magnetic type using

  "flying" transducer heads, and more particularly

  a device for moving the heads to a laying area following a failure of the power supply.

electrical power.

  In high-speed magnetic disk memories

  performance, the read / write heads are now

  naked out of contact with the surfaces corres-

  of the disks, the airflow induced by the fast-rotating disk being sufficient to support the flying heads, in fact, at a short distance from the surfaces of the disk. However, when the speed of the disk decreases, for example as a result a lack of power supply to the motor entraining the pin, the flow of air produced by the disk decreases and it arrives at a stage at which the support of the flying heads ceases In the case of "crushing" heads , which results, takes place on

  parts of the disk surfaces assigned to the memory

  data loss, data loss and

  Therefore, various arrangements have been devised to prevent any contact between the heads and the parts of the disk used for memorization.

  in the event of a failure of the food

  In general, these arrangements include a back-up power supply, either mechanical or electrical, which, in response to a detected failure of the power supply, is used to raise and maintain the heads away from the pins. corresponding surfaces of the disk, or to move the heads either to a laying area in which they can be safely brought into contact with the disk being slowed down, or to a station for resting the heads An example of a mechanical system using a spring as a power reserve for resting or raising the heads in the event of a power failure is described in United States Patent No. 3,702,997, while No. 4,237,501 gives an example of an electrical embodiment in which backup energy stored in a capacitor maintained under full load is t the operation

  normal, is used to power the position motor.

  heads to bring the heads, so

  ordered, to a resting station of the heads.

  The emergency removal or quenching devices of the heads used in the prior art are characterized by the fact that they are bulky and of a high cost, partly due to the fact that a relatively large number is required. mechanical, electromechanical and / or electrical components some of which tend to be expensive. For example, in order to store a suitable energy reserve, emergency withdrawal or quenching capacitors must be relatively

  large, which increases the cost and the size required.

  These two factors have become particularly important

  because there is always a steady increase in demand for inexpensive compact disk drives, using 13 cm disks and even

smaller discs.

  In general, according to the invention,

  following a detection of a failure of the food

  In this case, the windings of this motor are commutated and connected directly to the motor positioning the heads and the electromotive force produced by the rotating spindle motor is used, causing or reducing the speed of the spindle motor. to power the head positioning motor to rapidly move or remove the flying heads to a seating area where they can be safely brought into contact with the corresponding surfaces of the disc The term "power failure" used in this specification does not necessarily indicate a complete loss of energy, a relatively small fall in the voltage level of the power supply

  in motor energy of the spindle or power source

  The power supply of the control circuits of this motor is sufficient to trigger, in one embodiment of the invention, the emergency withdrawal.

  In any case, it is sufficient to

  tively few small and inexpensive components for

  implement the concept of the invention.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting example and in which: FIG. 1 is a diagram of part of a

  mechanism for driving a magnetic disk

  and a relatively simplified circuit, constituting an example of an embodiment of the invention; Figure 2 is a timing chart showing

  the voltage signals appearing across the windings

  spindle motor parts; and FIG. 3 is a diagram of a circuit of

  monitoring of the supply voltage.

  FIG. 1 shows in schematic form a magnetic disk unit 10 comprising at least one disk 12 mounted on a pin 14, electromagnetic transducer heads 16 for writing and reading data on the opposite magnetic surfaces of the disk 12, and a mobile mechanism 18 for supporting the heads for radially positioning the heads of

  reading / writing with respect to a series of concentrated tracks

  The radial travel of the mechanism 18 is limited by inner and outer stops 20 and 22, respectively, protruding from a base plate 24 which is part of the frame of the disk drive. 26, worn by the

  mechanism 18 and having a resilient outer surface

  The invention is intended to bear against the inner and outer abutments 20 and 22. In the particular embodiment described, a track or laying zone is provided on each surface of the disc, in close proximity to the inner tracks of data and, when the finger As a variant, the laying zones can be placed outside the outer data tracks, in which case the heads are in their positions. when the finger 26 is in contact with the end stop 22 of end

race.

  The disc 12 is rotated at a constant speed on its axis 28 by a motor 30 running

  which is connected to pin 14, while the

  head support canopy 18 is moved so as to move towards and away from the axis 28 under the action of a bidirectional bidirectional motor 32 for positioning heads operating with direct current The positioning of the heads can be carried out in various ways known in the art, for example by means of a system

closed loop servo.

  The spindle motor 30 comprises a permanent magnet rotor 34 and two stator shells 36 and 38 connected to a common ground point and energized by motor control circuits 40 controlling the application of power to the motor from the motor. a power supply supplying a voltage + V 2 (usually 12 volts) The circuits 40 precisely control the speed of rotation of the disks and they can consist of any one of the control circuits

  very different speeds, well known in the art.

  In the preferred embodiment of the invention, control pulses, suitably timed and shown schematically at 36 and 38 in FIG. 2, are applied to the windings 36 and 38 as shown in FIG.

  the action of logic signals, controlled by a micro-

  As is well known, the microprocessor and the associated logic elements (not shown) are generally powered by a + 5 volt source, designated generally.

in this case + V 1.

  The head positioning motor 32, which may be of the conventional moving-coil type, comprises terminals 50 and 52 connected to the terminals of a conventional bridge-type power amplifier circuit 54, powered by a voltage V 2 and comprising four transistors. power 55-58 A series 60 RC circuit, connected to the terminals of the motor 32, shunts the high voltage spikes which appear at the motor terminals during the

start-up.

  The transistors 55 and 56 of the power amplifier are controlled by a first amplifier transistor 62 which, when conducting, biases the transistors 55 and 56 in their conductive states, thus forming a current circuit extending from the + terminal. V 2 to a point 64 of mass passing through the transistor 56, the motor 32 and the transistor 55 The positive voltage thus applied to the terminal 50 of the motor 32 leads to

  the heads 16 read / write inward, that is to say

  In the same way, the conduction of the power transistors 57 and 58 is controlled by a second amplifier transistor 66 in order to supply energy from the + V 2 terminal to the other terminal 52 of the

  motor 32 to move the heads outward, that is,

  that is to say, to move them away from the axis 28 The transistors 62 and 66 are themselves controlled by suitable circuits 68 for controlling the direction of the speed of the positioning motor, these circuits comprising outputs connected to the bases of the transistors 62 and 66. circuits 68 are conventional and react to an input analog signal whose direction and amplitude of the deviation, with respect to a reference level, respectively determine the pair of transistors (55/56 or 57/58)

  of the bridge that leads and the amplitude of this conduction.

  As indicated previously, in the embodiment described by way of example, the tracks of

  16 heads are located radially towards the interior.

  data tracks on disk 12 By

  therefore, during a normal cycle of power failure

  tation, the transistors 55 and 56 are biased to drive to energize the motor 32 in a direction driving the finger 26 of the head support mechanism until it bears against the inner stopper 20, after which the motor 30 of the spindle is no longer powered, which ultimately results in the installation of

  heads To facilitate the description of this

  vention, the movement of the heads towards their respective laying areas, whether these areas are placed on the outside or

  within the data tracks, will be indicated globally

  as a "withdrawal" of the heads.

  Reference numeral 70 denotes an emergency head removal circuit, which is operated when the voltages of either or both of the power sources + V 1 and + V 2 fall below levels. These voltage drops are detected by a voltage monitoring circuit 72, shown in FIG. 3 and described below, whose output signal VR is thus brought back to a potential close to that of the mass from a normally positive level of several volts The signal VR is applied to the direct input terminal 74 of a comparator 76 whose reference terminal 78 is maintained at about + 1.4 volts by the voltage divider constituted by a diode 80 (At which the voltage + V 2 is applied), a resistor 82 and a pair of diodes 84 A resistor 85 connects the terminal 74 to the ground When the voltage VR drops below the reference level established at the terminal 78, the voltage of the output 86 of the comparator 76 passes The output 86 is connected to the base of a power PNP transistor 88 which is normally biased in the off state when the comparator output 86 is high.

  transistor 88 is connected to the power supply + V 2 by the

  intermediate of the diode 80 and the stator windings of the motor 22 of the spindle by means of diodes 90 and 92 which are normally polarized in opposite direction The collector of the transistor 88 is connected to the terminal 50 of the motor 32 of positioning of heads by means of a diode 94 and at the base of the power amplifier transistor 55 of the bridge via a diode 96 and a resistor 98 connected in series. It appears that when VR falls below the reference voltage at terminal 78 of comparator 76, indicating a fall of + V 1 or + V 2 below a predetermined level, the resulting drop in voltage The output of the comparator 76 constitutes a control signal applied to the base of the transistor 88 to make the latter conductive. In the event of a partial or complete loss of the supply voltage + V 2, the energy supplied to the comparator circuit is The electromotive force signals induced in the spindle motor windings 36 and 38 resemble those shown in a relatively idealized form in FIG. e 36

  winding 36 consists of a series of pulses

  alternatively positive and negative,

  The negative direction pulses from the windings are stopped by the diodes 90 and 92, so that positive voltages are symmetrical with respect to the ground potential and in phase opposition. of a substantially constant level appear both at the terminal 50 of the motor 52 for positioning the heads and at the base of the transistor 55 of the power amplifier bridge in order to bias this transistor into the conducting state A complete circuit is thus established between the windings 36 and 38 of the spindle motor and the motor 32 for positioning the heads via the power amplification transistors 55, 88 which drive. When this emergency control circuit is closed, the motor 32 for positioning heads is driven in one direction causing the heads to move inwards, that is to say towards the axis 28 of the spindle, until the finger 26 bears be the

internal stop 20.

  As shown in FIG. 3, the voltage monitoring circuit 72, which produces the voltage VR, comprises the series connection of a resistor 110 and a zener diode 112, mounted between the + V 2 terminal and the ground in order to produce a reference voltage which is applied to the inverting terminals of three comparators 114, 116 and 118 forming part of a single integrated circuit package, for example a type 339 quad comparator, powered by the voltage + V 2 The outputs of the comparators 114 and 116 are both connected to the direct input terminal 120 of the third comparator

  118 A resistor 122 connects the input 120 to the power supply

  + V 2, while a small capacitor 124 is mounted between the terminal 120 and the ground. The voltage across a resistor 126, forming part of a divider

  voltage comprising the resistors 126 and 128 and

  monitoring the voltage + V 1, is applied to the input terminal of the comparator 116 Similarly, a resistor of a second voltage divider, including resistors 130 and 132, develops a proportional voltage

  to + V 2, applied to the input of the comparator 114.

  that when the input voltage of the comparator 114 or the comparator 116 falls below the reference voltage set by the Zener diode 112, the normally high voltage appearing at the input 120 of the

  comparator 118, is reduced to a value close to

  tial mass, thus also dropping VR to a

  value substantially equal to the ground potential.

  It goes without saying that many modifications can be made to the device described and shown

  without departing from the scope of the invention.

Claims (2)

  A magnetic disk memory device, characterized in that it comprises at least one disk   rotating member (12) having a surface   data storage means, a motor (30) for rotating the disk, at least one electromagnetic transducer head (16) for transferring the data to the data storage portion of the disk and in the opposite direction, means ( 18, 32) for moving the head relative to the disk surface, means (40) for supplying electrical energy   components of the magnetic disk memory device   and means which, in response to a failure of the electrical power supply, connect the motor to the means for moving the head, the electromotive force produced by the motor providing   the energy to keep the head away from the memory part   data from the disk to a laying area.   2 Magnetic disk memory device   according to claim 1, characterized in that the last   mentioned means include an element (76) for comparing the voltage level of the power supply.   electrical energy to a reference voltage, and to   to draw an output signal representative of a condition   of failure of the power supply, and a   switching device (70) for connecting the motor to the head moving means in response to the output signal produced by the comparison element Of voltage.