FR2699719A1 - Unit for operating magnetic disks, especially a memory unit. - Google Patents

Abstract

The invention relates to a fast and large capacity memory unit comprising a disk cartridge and an electronic unit. The disk cartridge has a stationary pin on which is fixed a motor stator; a motor rotor is constituted by a rotatable hub mounted around the stator, the hub containing a motor magnet; at least one upper or lower bearing is disposed between the stator and the rotor; this assembly is preloaded by at least one curved spring which is arranged around the spindle and bears against the floating ring of at least one of the upper bearings; preloading the assembly produced in this manner avoids abrupt contact between the bearing and the spindle shaft during vibration.

Description

UNIT FOR OPERATING MAGNETIC DISCS,

IN PARTICULAR UNIT OF NEMOIRE

  The present invention relates to the field of magnetic disk memory units. More particularly, this invention relates to a magnetic disk memory unit of robust structure and suitable for use in hostile or severe environments and capable of withstanding loads or The unit according to the present invention is particularly suitable for use in military applications, but it can also be used in a variety of situations, such as shocks, vibrations and extreme temperatures. used in other demanding environments, such as drilling oil and gas wells and

seismic explorations.

  Magnetic tape recording units and magnetic disk storage units have been known in the prior art for many years. Band units suitable for use in difficult applications are available but there is a need for An Advanced Disk Unit Examples of such disk drives of the prior art have been described in US Pat. Nos. 4,791,508, 4,870.

703 and 4,965,686.

  The object of the present invention is to create a magnetic disk memory unit that is capable of withstanding loads and constraints, such as

  shocks, vibrations and extreme temperatures.

  According to this object, the invention relates to a disk unit comprising: a support plate; a spindle shaft attached to said support plate at one end of said spindle shaft; a stator disposed around said spindle shaft; mounting means for mounting said stator on said spindle shaft; a rotor disposed around said stator; a first bearing positioned between said spindle shaft and said rotor for rotatably supporting said rotor to rotate about said stator and said spindle shaft; a plurality of discs mounted spaced from each other on said unit rotor characterized in that biasing means are disposed between said spindle shaft and said first

bearing.

  Preferably, the system comprises a disk cartridge and an electronic unit. The disk cartridge comprises five magnetic hard disks having a usable capacity of 300 megabytes and housed in an independent unit, hermetically sealed and suitable for use in vibration environments, shocks and extreme temperatures The electronic unit comprises a metal structure in which the elements are housed

electronic system.

  The disk cartridge has a stationary pin on which is fixed a motor stator assembly. An engine rotor assembly is constituted by a rotary drum mounted around the stator, the drum containing a

magnetic motor system.

  Upper and lower bearings are arranged between the stator and the rotor. This assembly is preloaded by a pair of curved springs which are arranged around the spindle and which bear against the floating ring of the upper bearing. A preload of all of this This avoids abrupt contact between the bearing and the spindle during vibration. It has been found that such sudden contacts produce errors in positioning the heads during vibrations. These head positioning errors are out of the bandwidth.

  a servo-closed loop typical of the prior art.

  However, because of the increased capacity of the present invention, greater bandwidth is utilized. Correspondingly, the curved springs of the present invention prevent abrupt contacts, thereby eliminating otherwise head errors. The disk cartridge also has a temperature sensor mounted on a circuit board of the spindle assembly The temperature sensor measures the internal temperature of the disk cartridge This temperature information is used to modify a search algorithm, more specifically to modify excitation current levels applied to the voice coil (since the resistance of a voice coil varies with temperature), to modify a head charge / discharge operation, to modify a temperature drift in order to readings of Hall-effect devices, and to better take into account bending stresses of flexible circuits of

type "capton".

  The disk cartridge further includes a head bias sensor assembly. A magnetic flux sensor is disposed on a circuit board that extends over a portion of an arm assembly. The arm assembly includes a permanent magnet positioned In this way, when the arm assembly moves, the magnetic flux from the permanent magnet and detected by the flux sensor will vary. determined that this corresponded to a generally linear relationship As a result, the position of the arm assembly (more particularly of the permanent magnet incorporated in this arm assembly) is followed by the flux sensor In addition, the set of same as the arm assemblies of the prior art, has a stowage or stopping position. However, unlike the arm assemblies of the prior art, the present set arm is completely moved (fully retracted) from the disc to its storage position In this fully retracted position, the heads and the disc are protected from impact and

vibrations.

  The electronic unit has a new peak detection circuit In the prior art, individual peak detectors were used to retrieve each

  servo burst (for head positioning, is it

  ie a location and a center of track) The use of a single peak detector, as in the present invention, requires fast operation With a single circuit, temperature-induced variations are compensated for each servo The circuit includes a

  precision rectifier for straightening a servo burst.

  The rectified signal is then integrated by an integrator.

  The integrated signal passes through a multiplexer and is converted into an eight-bit word by a converter

analog / digital fast.

  The features and advantages defined above and others of the present invention will be appreciated and well understood by the specialists of this field from the

  detailed description which follows and accompanying drawings

  wherein: Figure 1 is a perspective view of a disk cartridge and an associated electronic unit which are arranged in accordance with the present invention;

2699719

  Fig. 2 is a block diagram illustrating interconnections between the disk cartridge and the electronic unit of Fig. 1; Fig. 3 is an exploded perspective view of the disk cartridge of Fig. 1 with the cover removed; Fig. 4A is a plan view of the disk cartridge of Fig. 1 with the cover removed; Figure 4B is a side elevational view, partly broken away, of the disk cartridge of Figure 1; Figure 4C is a rear elevational view, partly broken away, of the disk cartridge of Figure 1; Fig. 4D is a view taken along line 4D-4D with the arm and sensor removed to clarify the drawing; Fig. 4E is a schematic plan view of a flexible circuit used in the disk cartridge of Fig. 1; Fig. 5 is a side elevational view, partly in section, of a spindle motor assembly used in the disc drive system of Fig. 1; FIGS. 6A-B are views of a curved spring used in the motor assembly of FIG. 5, FIG. 6A being a plan view of this spring and FIG. 6B is a sectional view taken along the line. 6 B-6 B of Figure 6A; Figs. 7AB are views of a circuit board assembly used in the spindle assembly of the disk cartridge of Fig. 1, Fig. 7A being a plan view of this assembly and Fig. 7B a sectional view taken along line 7B-7B of Figure 7A; Fig. 8 is a block diagram of the pin servo circuit used in the electronic unit of Fig. 1; Figs. 9A-B are views of the arm assembly used in the disk cartridge of Fig. 1, Fig. 9A being a plan view of this assembly and Fig. 9B a side elevational view; Figs. 1 OA-B are views of the magnetic assembly occurring in the arm assembly of Figs. 9A-B, Fig. 10A being a plan view of the assembly and Fig. 1B showing an elevational view; Figs. 11AA are views of the pickup assembly used in the disk cartridge of Fig. 1, Fig. 11A being a bottom view of this assembly, Fig. 11B is an end view, Fig. 11C a plan view and FIG. 11D a view taken along the line 11D-11D of FIG. 1A; Fig. 12 is a block diagram of a closed-loop system used by the electronic unit of Fig. 1; Figure 13 is a block diagram of the circuits involved in the electronic unit of Figure 1; Fig. 14 is a diagram showing preferred servo burst information used for centering and track positioning in accordance with the present invention; Fig. 15 is a timing chart for burst information of privileged servos of Fig. 14; Figs. 16A-C show schematics of the servo recovery circuit according to the present invention; and Fig. 17 is a high level structural flow chart of the software used in accordance with the present invention. In Figs. 1 and 2, a disk storage system is shown generally in the form of a disk storage system. This disk storage system is a fast, high capacity memory system that is designed to operate in demanding environments (eg a military plane). The memory system 50 includes a disk cartridge 52 and an electronic unit 54. The disk cartridge 52 comprises five magnetic hard disks having a usable capacity of 300 megabytes. The disks use a Winchester disk technology and are housed in an independent and hermetically sealed unit. As a result, the disk cartridge 52 is completely interchangeable and can be handled, transported and used without care in environments of vibrations, shocks and extreme temperatures. The disk cartridge 52 comprises a casing 58, a main portion 60 of which is provided with a plate 62 forming a removable cover and which is fastened to the main casing part 60 by means of several screws 64. The casing part 60 and the casing plate 60 cover 62 are formed of a metal, preferably aluminum A front cover 66 has a triggerable locking mechanism 68 for locking the housing in an anti-vibration cradle, or for disengaging it from this cradle (not shown), which The housing portion 60 has a mounting notch 70 along the length of its two opposite sides and its grooves are arranged in correspondence with guides provided in the cradle. so that the unit is correctly mounted in the cradle (and to ensure proper alignment with electrical connectors provided on the rear end of the unit), the grooves staggered on both sides of the unit (as are the corresponding guides provided in the cradle) Since the grooves and the corresponding guides are asymmetrical,

  the unit can only be mounted in one position (ie

  ie the correct position) in the cradle.

  The electronic unit 54 comprises a hermetic metal structure 72 in which are housed the electronic elements of the system. The structure 72 comprises a main housing part 74 which is provided with a removable cover 76, fixed on the housing part 74 to the The housing portion 74 and the cover 76 are formed of a metal, preferably aluminum. Several connectors 78 are mounted at the forward end of the housing portion 74 to create interface means. between the electronic unit 54 and the disk cartridge 52, a main computer 85 (FIG. 2) is a current source. The electronic unit 54 also comprises an elapsed time indicator 75, a bit engagement switch 77 and an indicator of

bit 79.

  The disk cartridge 52 is interconnected with the electronic unit 54, more particularly an electronic drive control system 80, by signal transmission lines 82 (i.e., cables). The electronic system disk drive control unit 80 communicates with the electronic interface system 84 (described below), provided inside the electronic unit 54, by signal transmission lines 86. The electronic unit 54, more particularly the electronic interface unit 84, communicates with the main computer 85 via a bus 88 (ie cables) for

  small computer system interface (SCSI).

  With reference to FIGS. 3 and 4 AE, the disk cartridge 52 comprises a pin assembly 90 (hereinafter described). The pin assembly 90 has at its lower end a circuit board 96. An actuating plate 100 is mounted. within the housing portion 60 in an area adjacent to the pin assembly 90 An arm pivot 102 extends upwardly from the actuator plate 100 An inductor assembly 104, on which is mounted a head loading assembly 106 is installed on the actuating plate 100 The inductor assembly comprises a core 104a, an upper inductor 104b and a lower inductor 104c Two limiters 108 of adjustable arm strokes are mounted to opposite ends of the inductor assembly 104 by means of

fixation 109.

  A first bearing assembly 110 is disposed on the pivot 102 and is supported by the plate 100. An arm assembly 111 includes a central arm 112 having upper and lower arms 114, 116, which are secured thereto by fasteners 117. The arm assembly 111 is disposed on the pivot 102 and is supported by the bearing 110 to allow the arm assembly 111 to rotate relative to the pivot 102. The central arm assembly 112 includes a housing portion 118 in which which is housed a voice coil unit 120 The voice coil 120 has a central opening 120a in which is disposed a motor core 104a The current flowing in the voice coil unit 120 provides, in cooperation with the inductor assembly 104 a linear drive of the arm assembly A feed zone indicator 117 and a feed position indicator 119 are mounted on the housing 118 The indicators 117 and 119 are detected by an optical assembly Each arm 112, 114, 116 has a plurality of flexible portions 121. The flexible portions 121 comprise on at least one surface a protuberance or projection 122 and a head assembly 124 is disposed at one end.

  bearing assembly 126 is disposed on the pivot 102 to

  Above the arm assembly Nipples and preload washers 128 are attached to the pivot 102 to exert a retaining action and to produce a precharge force on the arm assembly An adapter plate 130, preferably composed of of a metal, is fixed on the housing portion 60, on the pin assembly 90 on the pivot 102 to

using several screws 132.

  A support 134 of pads and feed ramps is mounted on the actuating plate 100 A slide 136 for pads and feed ramps is mounted on the support 134 of the fasteners 137 The slide 136 comprises several feed ramps 138 and a plurality of feed pads 142 The feed ramps 138 comprise recesses 140 which are profiled to receive the protuberances 122.

  located on the flexible parts 121.

  A voice coil flexible circuit 144 is fixed on a mounting support 146 by means of two fasteners 148 The support 146 is mounted on the plate 100 by fasteners 150.

connection with voice coil 120.

  A hybrid circuit board 152 is mounted on a mounting bracket 153 which is attached to the inner surface of the housing portion 60. A flexible head circuit 151 is connected to the wafer 152 and retained by a suitable member 154 attached to the wafer. The circuit 151 is connected by its other end to the arm assembly Fixing members 156 also secure one end of the wafer 152 to the support 153. The other end of the wafer 152 is attached to the support 154 by securing members 158 The flexible circuit 151 includes a stiffening member 160 Another flexible circuit 162 connects the wafer 152 and a connector 164 through a rear end of the housing portion A assembly for flexible spindle motor circuits 166 establishes a connection between the wafer 96 and the

connector 164.

  The pin assembly 90 includes a plurality of magnetic recording disks 168 (e.g., five disks) disposed about a spindle motor assembly 170. The disks 168 are spaced from each other by a plurality of spacers 172 Disks 168 and the spacers 172 are held on the assembly 170 by

the retaining member 174.

  The spindle motor assembly 170 rotates the disks 168 in a precise rotational path such that the magnetic tracks on the disks remain in a concentric disposition established in the operating environment subjected to extreme temperatures and vibrations. degree of precision ultimately limits the minimum disk width that can be used as well as the maximum number of tracks per centimeter, which is directly related to the capacity

  of data (which will be defined later).

  Prior art commercial disc machines are subject to the influence of vibration and temperature. For example, during exposure to low levels of vibration, platters supporting discs begin to skewer and spindle bearings are subject to overloads by gravity forces and in some cases the actual pivot may bend and contribute to this. Displacements as small as 300 x 300 mm may produce defects In addition, when exposed to a temperature range of -550 C to + 710 C, there are significant differences in the positioning of the tracks, both because of the he design of the disk blocking system and the structure of the disk itself. With regard to the disk lock, a temperature coefficient adaptation deviation resulting from the fact that the pin pivot is in steel (which is necessary to absorb the backing load) and that the tray is made of aluminum causes the tray to expand and contract around one of the lock fixing screws, instead of doing so relative to the central axis of the spindle This produces at each turn a sway of the plateau which results in a gap

  track positioning and data errors.

  Also, a second effect produced by the temperature results from the nonuniformity of the coefficient of thermal expansion on the circumference of the plate. This lack of concentric dilation and contraction as a function of the anisotropy temperature also produces deviations in

  positioning of tracks and data errors.

  Pin set 90 solved these problems

of vibration.

  Referring now to FIG. 5, the spindle motor assembly 170 includes a hub 176 having a shaft 178 located at approximately its center. The shaft 178 (preferably a steel shaft) is mounted on a plate The spindle shaft 178 is secured to the support plate 180 by a thread 182 and this shaft 178 has a hollow interior defining a central passageway 185. The support plate 180 is in turn fixed to the bottom of the outer housing. 60 by means of several screws (not shown) The upper end of the spindle shaft 178 is held by the plate 130 by means of a screw 132 '(FIG. 4B). As a consequence, the two upper and lower ends lower of the spindle shaft 178

are held rigidly.

  An annular motor winding 184, which forms the stator of an electric motor, is mounted on the shaft 178 by

  the upper sleeves 186 and lower 188.

  The sleeves 186 and 188 are fixed around the shaft 178 The sleeve 186 is fixed on the shaft 178 by a locking bar 189 and an adjusting screw 190. A washer 191 is placed on a shoulder 192 of the shaft 178. washer 191 and the shoulder 192 support the sleeve 188 and stop its downward movement along the axis of the shaft of

pin 178.

  The rotor structure in the motor includes an annular magnet 194 which is adhesively secured to a steel sleeve 196, which in turn is locked to the rotating steel outer hub 176. An annular cap 198 is fitted into the inner periphery of the rotor.

  hub 176 at its upper end.

  The magnet 194, the sleeve 196, the hub 176 and the cap 198 constitute a rotor structure which rotates around the stator structure mounted on the spindle shaft 178, so that the rotor structure must be mounted on As a result, the rotor structure is mounted on a lower bearing 200 and an upper bearing 202. The inner ring of the lower bearing 200 is held and prevented from rotating between a shoulder 204 provided on the spindle shaft 178 and a shoulder 206 provided. on the base plate 180 A flange 208 projecting radially inwardly from the hub 176 abuts against the rotating outer race of the bearing 200. The floating inner race 209 of the upper bearing 202 is held on the spindle shaft 178 by two curved springs 110 which are arranged in a groove 211 surrounding the shaft 178 The curved springs 210 are preferably made of a stainless steel wire the 302 corresponding to ASTM-A 580 The curved springs 210 eliminate an abrupt metal / metal contact (under the effect of vibrations and external shocks) between the ring 209 of the bearing 202 and the spindle shaft 178 This sudden contact would result in misalignment of the heads that would exit the typical closed loop servo bandwidth (eg, a normal bandwidth for a closed servo-loop is 250 Hz). However, in the present invention, densities are used. of tracks of about 817 tracks per cm (2075 tracks per inch) with a center spacing of about 1.2 x 10-2 cm (476 microinches). This corresponds to a much greater capacity than that obtained in the prior art ( for example about 344 tracks per cm (875 tracks per inch)> Sudden contact would produce head errors falling within the bandwidth of the closed servo-loop as described above As a result, the curved springs 110 would The curved springs 210 are an important feature, since they create a high axial and radial stiffness in the spindle motor assembly, and thus eliminate the misalignment of heads that would be caused by such contact. which in turn makes it possible to obtain high performances of resistance to vibrations / shocks / temperature The curved springs 210 also make it possible to obtain an appropriate axial movement for a precharging of the bearings This movement is necessary for the application of a constant precharge to the bearings as the materials expand and contract as a function of temperature variations One of the two identical curved springs 210 has been shown in Figs. 6AB. The spring 210 includes a plurality of continuous windings 212 which are configured to form a annular profile having an inside diameter

  allowing the engagement of the recessed portion of the shaft 178.

  The inner ring 209 of the bearing 202 is also

maintained by a washer 213.

  The washer 213 is held in place by an elastic washer 214, a washer 215 and a nut 216 which is screwed onto the upper part of the spindle shaft 178. The rotating outer race of the bearing 202 is applied against a rim 218, projecting radially inwardly on the cap 198 Accordingly, the rotor structure constituted by the magnet 194, the sleeve 196, the hub 176 and the cap 198 is supported for a movement

  rotation by bearings 200 and 202.

  A precharging force is also exerted on the bearing 202 by a nut 216 acting via a washer 210, an elastic washer 214 and a washer 213 to apply a load to the inner ring, this load being in turn transmitted through the balls of the bearing 202 so as to apply the outer ring against the flange 218 of the cap 198 The preload is also applied to the bearing 200 because it is transmitted from the cap 198 by the intermediate sleeve 196 and outer hub 176 to urge the outer ring of the bearing 200 and then react, through the balls of the bearing 200 on the plate 180 The preload acts to maintain contact through the assembly bearings, with a view to reducing the effects of

shocks and vibrations.

  Yarns 220 from the stator windings 184 enter the passage 185 provided in the spindle shaft 178 through two opposed openings 222 provided in this shaft 178. The wires 220 pass through an opening 224 provided in the plate 180 and The wafer 96 is spaced from the plate 180 and is secured thereto by a plurality of spacers 226 and a plurality of screws 228 which are screwed into the plate 180. intermediate wires 220 to stator windings 184 for driving the rotor associated with the disks 168. Referring to Fig. 7Ab, the spindle motor circuit board 96 has a plurality of Hall effect circuits 230, 232 and 234, each having a Hall effect sensor 236, resistors 238, 240 and a concentrator 241. The circuit 234 also comprises a capacitor 242. The sensors 236 and the capacitor 242 are fixed on The wafer 96 is generally round and has an outer diameter approximately the same as that of the disks 168. The wafer 96 also has an aperture 244 located approximately at its center and in which The Hall effect sensors 236 are used to obtain a rotating magnet position information that is applied to a spindle servo circuit 245 (FIG. 8). The rotational speed of the spindle is controlled. by the closed-loop speed servo-circuit 245 and the motor (previously described) A phase-locked loop 246 provided in the spindle servo-circuit uses the Hall signals to lock the spindle speed. The spindle servo-circuit 245 comprises a pilot member 247 which regulates the value of the excitation current, independently of variations in gain produced by the temperature. As a result, starting times are obtained. spindles that are predictable and repetitive throughout the operating range defined by values

extremes of temperature.

  A temperature sensor 247 is mounted on the circuit board 96 A mounting pad 248 is disposed between the sensor 247 and the wafer 96 The temperature sensor 247 corresponds to a significant characteristic The output signal of the temperature sensor 247 is used to To modify the search algorithm More specifically, excitation current levels that are applied to the voice coil 120 are adjusted according to changes in temperature (since the resistance of the voice coil varies with the temperature), in order to adjust loading / unloading of the head, modifying a temperature drift for Hall effect device readings, and to better take into account

  bending of flexible circuits of type "capton".

  The output signal of the temperature sensor 247 is used to modify the servo parameters during the head loading / unloading operations, and the search operations. The output signal of the temperature sensor 247 is converted by an analog / digital converter 456. (Figure 13 and described below in connection with the peak detection circuits), which is controlled by the controller 350 The corresponding servo and temperature dependent parameters are stored in a ROM memory consultation table. The following servo parameters are temperature dependent for loading / unloading operations: (1) Hall effect sensor gain; and (2) excitation current necessary to drive the actuating arm in the manner of an open loop and to a

constant acceleration.

  The following servo parameters are a function of the temperature for a search operation: (1) adaptation to a flexible head cable; and (2) excitation current needed to accelerate a

  actuating arm with constant acceleration.

  Typical commercial disc drive systems are subject to what is commonly called "head knocking" when subjected to vibration. The flying head is supported by a pneumatic bearing which is stable and stiff enough to oppose to contact with the surface of the disc due to the exponential profile of the curve representing the air support force as a function of the displacement It has been determined that head banging and recording medium damage generally occur when disc drive systems are exposed to vibration during the following operations Rapid head positioning by operating laterally from one track to another tends to produce pitching or rolling motion of the head causing the bearing to become unstable pneumatic, especially under the effect of vibrations By optimizing the point of attachment of the articulation of the head to the center of gravity of the head, the tendency to pitch or roll of the head under the effect of rapid positioning is eliminated, so that the stability of the pneumatic bearing is increased and the tolerance of vibrations in operation is improved Knocks occur also when the disk is accelerating or slowing down, so that the lift of the pneumatic bearing of the head is weakened and that, under the effect of vibrations, the head can come into contact with the disk Also, when the disc is stopped, the head rests on the surface of the disc Normally, during a slowdown, most commercial discs allow the head to come into contact with the surface of the disc until the disc is again accelerated and the pneumatic bearing is restored This condition is not appropriate for a military-type product that is subject in operation to shocks, to vibrations

  as well as brutal manipulations.

  As a result, at the first appearance of a slowing down, the head must be moved away from the surface of the disc The arm assembly 111 allows the heads to be

completely removed from the disc.

  With reference to Figs. 9A-B, the actuator arm assembly is generally designated 111. This arm assembly includes a central arm assembly 112, an upper arm 114, and a lower arm 116.

  central arm has a housing portion 118.

  The arm assembly 111 is dynamically balanced about the pivot axis such that impacts, vibrations, and stresses applied to the cartridge do not produce a twisting effect in the arm. head on the track

  during strong disturbances by acceleration initiation.

  The housing 118 has a cylindrical opening 250 having a diameter sufficient to receive the bearings 110 and 126 The housing 118 also has opposed pairs of rectangular openings 252, 254 which define inside the housing 118 a cavity into which can be inserted the voice coil 120 The housing 118 further comprises another opening 256 in which a magnetic assembly 258 is fixed on the housing 118 by means of fasteners 260 Also with reference to FIGS. 1 OA-B, the magnetic assembly 258 comprises a block 262 provided with a precise front surface 264, opposite side surfaces 266, 268, a rear surface 270 having extensions 272 on each side 266, 268 and two opposite top and bottom surfaces 274, 276 A hole 278 is arranged in each extension 272 Fixing members 260 pass through

  the mounting holes 278 The surface 274 has a platform

  A permanent magnet 284 is fixed in the channel 282 with the aid of a suitable adhesive. The magnet 284 has opposed precise front and rear surfaces 286, 287. 284, 290 and upper surfaces 292 and lower 294 The magnet 284 has a north pole 296, designated by (N), at one end 288 and a south pole

  opposite 298, designated (S), at the end 290.

  Referring to Figs. 4A and 11A-D, a charging detection assembly is shown at 106. This assembly 106 includes a printed circuit board 300 having

  opposing lower and upper surfaces 302 and 304.

  A magnetic flux detector 306 (i.e., a Hall effect detector) having conductors 308 is mounted on the surface 302 with a suitable adhesive. The detector 306 is positioned on a focus member having a Hall effect 310 which is disposed in an opening 312 formed through the wafer 300 A plurality of contact pins 314 pass through the wafer 300 The wafers 314 constitute connection means with a set 166 forming a flexible spindle motor circuit Resistors 316, 318 and a capacitor 320 are mounted on the surface 304 of the wafer 300. The detector 306 is preferably a Hall effect type magnetic flux detector having a ceramic substrate provided with a hermetically sealed element. The detector 306 detects a flow. Magnet from the magnet 284 in the actuator arm assembly 111 The assembly 111 is shown in the full storage or retracting position in FIG. 4A, protuberances 122 on the flexible portions 121 are arranged in recesses 140 of feed ramps 138, the heads 124 being arranged between corresponding feed shoes 142. In this position, the heads and This completely retracted position of the arm and head assembly is an important feature. In this fully retracted position, the magnetic flux from the magnet 284 and sensed by the detector 306 When the arm assembly 111 is rotated to position heads 124 above corresponding disks 168, the magnet 284 moves away from the detector 306 by reducing the magnetic flux from the magnet 284. detected by the detector 306 It has been determined that the output signal of the detector 306 allows the positioning of the arm assembly 111 in a linear fashion ( that is, the position of a head) In correspondence, the detector 306 detects a magnetic flux coming from the magnet 284 to

determine a leading position.

  Also an automatic head retraction is performed in normal or abnormal operating situations In the case of a normal operating situation, the heads are retracted by

  report to the disc each time the spindle is stopped.

  A retraction is performed in less than 100 milliseconds so that it does not significantly increase the duration of a normal shutdown Abnormal operations occur during a loss of primary system power or when the operator inadvertently removes the cartridge while the spindle is still rotating In response to a loss of primary power, which produces a stop of the rotation of the disc, the electronic system detects a power failure and uses the counter-electromotive force of the spindle motor to produce the power necessary to retract the heads by moving them away from the disk and to bring them to the rest pads. As a result, the energy resulting from the rotational inertia of the assembly formed by the motor and the disk is converted into a retracting movement unloading the heads and protecting them, as well as the disc, against exposures to shocks and vibrations The second abnormal sequence if the operator removes the cartridge while the spindle is rotating In this case, a detector in the handle of the cartridge detects that the trigger system of the handle has been actuated The electronic system responds to this signal by rapid retraction of the heads up on the support pad Again, this process is performed in less than 100 milliseconds, and it

  before the cartridge has cleared the connector.

  The use of a magnetic flux detector 308 of a magnet 284 as a position detector corresponds to an important characteristic.

  can be used to correct positional errors.

  With reference to FIG. 12, an example of such a system

  Closed loop is generally represented at 322.

  A commanded position signal is transmitted via a line 324 to a summing junction 326 The output signal of the junction 326 transmitted by a line 328 is a position error and is used by an actuating system The position of the heads is detected by a position detector (i.e., the detector 308 and the magnet 284) at 332. A head position indicator signal is transmitted by a line. The actuating arm position 322 determined by the Hall effect sensor 332 (for example, the detector 306) is returned to 334 and is subtracted from the commanded position at 324 to produce the error signal.

position transmitted by line 328.

  With reference to FIG. 13, the electronic controller interface system 84 comprises an input / output controller 336, for example an Intel 8 OC 186 microprocessor (operating at 12.5 MHz) as the main control element. The Intel microprocessor 8 OC 186 is a highly integrated 16-bit microprocessor with chip selection logic, two channel DMA controllers,

  three timers and one built-in interrupt controller.

  A control program is stored in the memory 338 of the electronic system 84, for example a 64 K × 16 bit EPROM memory or an E 2 PROM memory. There are also two 32 K × 8 bit static RAM memories (SRAM) 340 In addition, twelve discrete system input signals and sixteen discrete output signals are used to fulfill various communication functions with the input / output controller and the drive controller. The input / output section 344 of this device is arranged as a state sequencer which receives commands from the input / output combination and disk data 342 (for example a component 8496 supplied by National Semiconductor). from the processor These commands control the execution of various functions, such as data input phasing and state phasing. n is terminated, an interrupt is transmitted to the input / output controller The different control state registers are used to store conditions relating to error states The disk data controller 346 is also a state sequencer which executes commands issued by the input / output controller The commands control the read and write operations on the disk. Again, different control, status and error registers provide the possibility to correct errors or to determine if a restart is needed The I / O and disk data controller uses its own privileged data buffer,

  which consists of two fast SRAM memories of 32 K x 8.

  Three disk channels introduced into the data buffer are controlled by the input / output controller and disk data The three channels correspond to input / output, disk and processor The disk channel has the highest priority and the channel processor has the lowest priority This principle allows a simultaneous transfer of data between the input / output interfaces, and disk Thirty-one analog voltage channels provide control of various system functions for automatic testing An analog digital component eight-bit 348 measures these channels and the BIT software determines if there is

a fault in the system.

  The disk drive cartridge 52 utilizes both a preferred surface and an integrated servo system. This means that none of the five drives are fully assigned to servo track information. Servo information is also incorporated into all other surfaces at the beginning of each sector of each track This servo system provides the best combination of fine positioning that is required to perform fast operations in extreme environments. The disk drive circuit 80 fulfills the critical functions that are necessary for performing the fast disk drive operations. The disk drive circuit provides positioning of the read / write heads (motor and motor control). actuation, i.e., voice coil 120 movement in the inductor assembly 104), selection of read / write heads, pin motor start / stop operations, BIT functions, and as current interruption and transient recovery control functions. The drive controller 350 is the main drive element of the drive drive circuit 80. The drive controller uses a high-speed digital signal processor (eg Texas Instruments TMS 320 32-bit digital signal processor). C 30) for controlling the position of the heads via a closed loop digital control algorithm. The disk drive control program utilizes a preferred and integrated servo-information complement system to provide optimal control of positioning of the read / write heads during

  track search, read and write operations.

  A track determination is made by means of the closed-loop control 352 of the rotating actuating device.

  coarse position is written on a dedicated surface (that is,

  ie one of the five disks 168) and is composed alternately of tracks transmitting signals of 0.70 M Hz and 1.00 M Hz The midpoint between each of said tracks defines the center of each cylinder and accordingly, the Data tracks located on the remaining disk surfaces When a search command is received, the training controller uses the coarse position information to control the speed and acceleration of the device

  head actuation during the search operation.

  Once the runway determination is complete, information on servos integrated at 354 on the defined runway is used to perform centering and tracking. Referring to FIGS. 14 and 15, a new peak detector (described in FIG. continued) is used to retrieve amplitude information for each of the four servo bursts, designated respectively by A, B, C, D This information is processed by the drive controller 350 to determine an exact head position as well as the amount of current to be applied to the rotating actuator (i.e. voice coil 120)

  to correct and maintain the leading position.

  Tracks A 1, B 1, A 2, B 2, A 3 and B 3 are shown in FIG. 14 The information on integrated servos is designated respectively by A, B, C and D. The amplitude peak information indicated at 356, is detected by the new peak detector circuit which will be described in the following This information on servos is a burst of four temporally offset pulses (for example a burst can comprise a sine wave of 2.5 M Hz during 4 microseconds) Heads can be held in the center of a track by equalizing the magnitudes between overlapping servo bursts For example, the bursion 358 designated by A and the bursal 360 designated by B overlap on the center line 362 of the track A 1 The line 362 corresponds to equal amplitudes for A and B, as designated by VA and VB (ie VA = VB) In correspondence, the heads can be held in the center of a track by setting the positio n of the head so that amplitudes between overlapping servo bursts are equal (i.e., VA = VB).

  quadruple burst assures linear track-to-line positioning

  track with a tolerance of + / a track Also, these bursts of integrated servos are used for track positioning to track as well as for a

  precise positioning, as described above.

  Each sector (0-54, FIG. 15) comprises a data segment 364 which is preceded by the burst of integrated servos A, B, C and D. The synchronization sequence for the integrated servo sector is indicated in FIG. synchronization operations indicated in the following: zero; affected area index; sector marker detection window; data reading signal of the head; detected sector mark; multiplexers A, A 1 and A 2;

  servos CS, WR, INT and RD; and recall of integrated servos.

  A rotating actuator drive circuit 365 comprises a twelve-bit digital-to-analog converter 366 and an amplifier 368. The actuator drive circuit 365 receives positioning data from the drive controller 350 and which are converted into an analog voltage for the drive motor of the rotary actuating member Velocity profiles and excitation currents of the rotating actuating member are kept constant, independently of variations of resistors for optimal performance

severe environments.

  The drive controller 350 is assisted by a memory that uses both a RAM 370 and a PROM 372. The RAM 370 is a 64 Kbits CMOS static RAM, organized as a 2K x 32 memory and is incorporated in the drive controller It is used to temporarily store and process program data elements The PROM 372 is a 1Mbit CMOS EPROM, organized as a 32K x 32 memory and which stores the controller management program

drive.

  The drive controller 350 communicates with the disk data processor via a parallel communication port. The input / output ports for discrete signals are also provided. The discrete signals are from other parts of the system. 80 of the cartridge 52 and include the following states: "retracted heads", "closed handle", communication access indicator, state of the analog / digital converter and power state Output signals are also incorporated and include the signals following: spindle motor validation, rotary actuator validation, head selection, analog / digital and digital / analog converter signals. The closed-loop spindle control circuit 374 described above uses a Hall signal return device.

  to control the spindle speed.

  Analog read / write signal processing circuit 378 produces high density coding / decoding for disk data read / write operations. The data is encoded from NRZ and the length between synchronization and unwrapping is limited.

by an encoder 380.

  During the writing process, NRZ formatted data and timing information are encoded and applied to the write executing members. During the reading operation, encoded data which is stored on the disc is recovered by amplification. and analog detection, with subsequent synchronization recovery and decoding via a data synchronizer, a phase lock loop (PLL) 381 and with a run length

  limited (RLL) for the NRZ 382 decoder.

  The first stage of the analog circuits comprises an automatic gain control amplifier, which maintains a constant signal amplitude at the output of a Bessel filter provided in the read line. The Bessel filter band limits the read signal which is supplied to the equalizing member and the detector The equalizing member restores the critical amplitude and the phase information for the purpose of detecting the data transitions by the

detector circuit.

  The output signal of the data detector is applied to the phase comparator of the phase-locked loop via a data synchronizer. The synchronizer is used to ensure rapid determination of a phase lock by passing the signal. PLL in a reference clock when the system does not operate in the read mode The limited run length data that was synchronized as well as the phase locked clock signal is applied to a decoder 182 for conversion to NRZ data and in clock signal. Writing lock and cartridge file protection capabilities are incorporated in the 384 circuitry to provide user selectable protection against loss of stored information through overwriting.

inadvertently performed.

  Referring to FIGS. 16A, the new peak detection circuit has been shown generally in FIG. 16AA schematically represents the track servo electronic servo system 354 as well as the coarse servo positioning system 352. The diagram also shows a preferred servo detection circuit 388, an index detection circuit 390, and a sector marker detection circuit 392. The peak detection circuit 386 includes a precision rectifier 394 having an input connected by the The amplifier 398 comprises a feedback loop having resistors 400, 402 and a diode 404. The output of the amplifier 398 is connected to a diode 406. A capacitor 410 and an inductor 412 are also connected to the amplifier. amplifier 398 An output signal of rectifier 394 is applied to a line 408 This output signal is a rectified signal of The accuracy of the input signal (i.e., a burst of servos) applied to line 396 An integrator 414 receives the signal applied to line 408 This signal is transmitted through

  a resistor 416 to an input in the amplifier 418.

  A resistor 420 is connected between the ground and the other input of the amplifier 418. A capacitor 422 and a

  inductor 424 are also connected to amplifier 418.

  The output signal of the amplifier 418 is applied to the line 426. This output signal is an integrated signal of the

signal introduced by line 408.

  An integrating output member 428 receives the signal transmitted by the line 426. The output member 428 comprises two fast analog switches 430, 432 and a resistor 434. The integrated signal is then transmitted by a line 436 to an amplifier 438 having a The other input of the amplifier 438 is connected by a resistor 442 to the ground. The output signal of the amplifier 438 transmitted via the line 444 is applied to a multiplexer 446. Capacitors 448 and inductors 450 are also connected to the multiplexer 446 A selected input of the multiplexer 446 is presented at its output in a line 452 The signal applied to the line 452 is transmitted to an amplifier 454 The output signal of the amplifier 454, which is an analog signal, is converted to a digital signal (i.e., an eight-bit word) by an analog / digital converter 456 A voltage regulator 458applies a digital The capacitors 460, 462 and the resistor 464 are connected to the regulator 458. The capacitors 466, 468 and the inductor 470 are connected to the capacitor 458.

456 converter.

  This single peak fast sensing circuit 386 is used in cooperation with a fast analog-to-digital converter 456 to retrieve information about magnetically recorded, spatially shifted and spatially shifted servo bursts. This recovery method is different from the methods used. in the prior art o individual detectors are used for the recovery of each burst of servos The advantage obtained with a single recovery circuit is that it can operate in extreme temperature conditions, where it would occur drifts Parameters, individual circuits The parameter variations of the single recovery circuit as a function of temperature will be identical for each burst of servos, and this will result in

  removal of all negative effects.

  With reference to FIG. 17, this represents a high-level structural flowchart of the software. The software for the input / output control 336 performs the following functions: it accepts commands from the input / output bus and produces the signals of command necessary for execution of orders; it controls the transmission of data between the input / output bus and the drive of disks; it checks the drive status and reports existing faults in the input / output bus; and it establishes and transmits commands according to the state of the disks The software for the drive control 350 performs the control of the following functions: position of the read / write heads; switching on and off the spindle motor; head retraction upon loss of power or cartridge removal; selection of read / write head; power interruption and recovery command for both controllers; automatic test functions; and control and transmission of drive states to the input / output controller The functions performed by the software will be illustrated here by the

  description of reading operations, operations

  write and automatic test function (BIT).

  An order is received by the I / O bus and it is decoded as a read command by the input / output command The state of the drive is checked for the installed cartridge and the disk rotation If these conditions are satisfied, the order is determined as

  being valid and the reading operation is engaged.

  The address information received with the reading order is translated into a head and cylinder number. This information is transmitted in a search order to the drive command which decodes the search order and selects the required head. The drive control 350 then positions the heads on the required cylinder by driving the rotating actuator. This movement may involve acceleration and deceleration depending on the number of cylinders with respect to which the heads are to be moved after termination. of this open-loop motion, the servo error voltage is read and is used to center the heads on the track using a closed-loop digital control algorithm. After the heads have been centered, a response for termination command is returned to the input / output command. The input / output control loads the disk data controller registers 346 with the correct information to perform a read operation. This information contains the number of the starting sector on the track as well as the number of sectors to be read. the read operation, the input / output control checks the initial information to determine if the heads were centered on the correct track by the open-loop motion If the heads are located on an incorrect track, the input / output command calculates correction required for correct positioning of the heads The input / output command sends another search order to the drive command to correctly position the heads When this operation is completed, order termination information is sent again by the drive command to the command input / output Another read operation is performed by the com input / output control During data transfer from a disk to the RAM, under the control of the disk data controller 346, an error detection is performed. If a data error occurs, the disk data controller 346 sends syndrome bytes to the input / output command to enable it to correct the error The input / output command performs an "exclusive OR" operation on the data using the syndrome bytes to correct the data error After a data sector has been loaded into the RAM, the input / output command signals it to the drive control so that its disk controller can transfer data from the RAM to the input / output bus. Consequently, data transfers occur simultaneously from a disk to the RAM memory and from the RAM memory to the input / output bus. It should be noted that the drive command can not determine a real head position. Upon receiving a search command, it loads a cylinder address register with the number of cylinders and performs a movement of open loop If the input / output command determines an incorrect positioning, it must send a special command to the drive command, so as to reposition the heads without changing the contents of its cylinder address register.

  synchronization between the two controllers.

  In the write operation, the same head positioning operations are performed as during the read operation. Data transfers between the input / output bus and the RAM are performed at the same time as the initial positioning operation. heads. During the execution of the BIT test, a visual indication is provided to indicate progress in the test. Upon entering the test, both BIT indicators are activated. Next, the light-emitting diode, indicating that the cartridge is ready, is lit, to indicate that both processors are operational The LED is off when terminating the ROM total control tests, regardless of the test results When terminating the BIT test, the I / O control processor will disable only the BIT indicators representing a replaceable online unit (LRU) that is

completely functional.

  The system includes a BIT test capability to detect and locate a fault at a time, for maintenance levels in and out of the aircraft. BIT test operations can be initiated by a combination of commands. manual, automatic or remote; a self-check of normal operating modes is also included A fault status indication is provided remotely via the bus or locally via

fault indicators.

  A fault control device is provided remotely via the bus or locally by

  through fault indicators.

  A current control device for BIT test is used to control the BIT indicators This control device directly supplies the activation elements of the BIT indicators directly from the + 28 V DC input and applies a pulse of increase in power to enable both BIT indicators to be activated when power is increased despite a power supply failure The current controller is power sequenced to prevent normal subroutines of increasing and reducing power to produce

incorrect BIT indications.

  Two BIT indicators 79 are provided to provide a visual indication of the operating condition of the LRU they represent. One indicator represents the electronic unit 54 and the other indicator represents the disk drive cartridge. are magnetically locked so that the last tested operating condition remains thereon after a power reduction. Once enabled, the indicators will remain on until the indicated LRU passes successively to the execution of the BIT program. The BIT switch 77 is provided to allow a manual activation of the routine BIT This switch engages only the routine BIT when the system

  is not performing a controlled function.

  Loopback functions are provided to test the data path in expanding loops. These loopback tests loop the data locally in the controller, in the encoder / decoder system, and

  finally in the disk itself.

  The system has the ability to monitor test points during the BIT subroutine Embedded test circuits consisting of an analog-to-digital converter operating with a multiplexed input, perform discrete measurements at reference test points, which are located in the data channel of

36 2699719

  read / write, in the spindle drive circuit,

  In the drive of the rotating actuator and in the power supply The measured values are compared with values recorded in ROM for determining the validity of the signals.

Claims (7)

  A disk drive comprising: a support plate; a spindle shaft attached to said support plate at one end of said spindle shaft; a stator disposed around said spindle shaft; mounting means for mounting said stator on said spindle shaft; a rotor disposed around said stator; a first bearing positioned between said spindle shaft and said rotor for rotatably supporting said rotor to rotate about said stator and said spindle shaft; a plurality of disks mounted spaced from each other on said unit rotor characterized in that biasing means are disposed between said spindle shaft and said first bearing. Disk drive according to claim 1, characterized in that it further comprises a second bearing disposed about one end of said spindle shaft in a position adjacent to said support plate, said second bearing being disposed between said spindle pin and said rotor for rotatably supporting said rotor to allow rotation thereof about said stator and said spindle shaft; and in that said first bearing is disposed around the other end of said shaft pin.   Disk unit according to Claim 1 or 2, characterized in that: said biasing means comprise at least one   curved spring disposed around said spindle shaft.   4 disk unit according to one of claims 1 to   3, characterized in that said at least one curved spring comprises two curved springs, one of said curved springs being disposed longitudinally over the other on said spindle shaft.   Disk unit according to any one of   Claims 1 to 4, characterized in that said   pin comprises a recess in which is disposed said curved spring at least provided.   6 Disk drive according to any one of   Claims 1 to 5, characterized in that said first   bearing has a floating ring that leans against said biasing means.   7 Disk unit according to any one of   Claims 1 to 6, characterized in that it comprises in   in addition: a preloading means for exerting a preload on   said first and second bearing means.   8 Disk drive according to any one of   Claims 1 to 7, characterized in that said means for   preload comprises: an elastic washer disposed about said spindle shaft; and retaining means located at one end of said spindle shaft for exerting a precharging force on said elastic washer.   9 Disk drive according to any one of   Claims 1 to 8, characterized in that said means for   mounting comprises at least one sleeve fixed on said stator   and held around said spindle shaft.