JPH0714133A - Magnetic tape-head-actuator device - Google Patents

Abstract

PURPOSE: To index a tape head during a seek operation for a track and to rapidly control with servo a head position to accurately follow up the head during an access operation to the track. CONSTITUTION: A head actuator assembly 30 has a base member 302, a beam member 304 which can move against the base member 302 along a 1st axis, an upper flexibility member 60 and a lower flexibility member which are arranged in parallel planes with each other and face each other in order to connect top and bottom end parts of the base member 302 with top and bottom end parts of the beam member 304 respectively and also an electromagnetic drive means. The beam member 304 has a supporting part on which a reluctance converter 308 is mounted, on a surface of the converter 308, plural sets of pair of read/write elements are provided which access a multi-track magnetic tape, and the tape is moved in parallel with the surface of the converter 308 and also along a perpendicular pass to the 1st axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a magnetic tape head,
Regarding actuators. More specifically, the present invention indexes a multi-track magnetoresistive transducer across a track in track seek mode and servo-controlled track following.
Head for quick adjustment of transducer position in mode
A magnetic drive assembly for an actuator.

[0002]

BACKGROUND OF THE INVENTION In the field of information storage, increasing storage capacity of tapes has been achieved by thinning the tape substrate and by various data compression techniques. The capacity of data increases due to the increase in the number of tracks on the magnetic tape (narrower width of each track) and the increase in the number of read / write elements of the head due to the advancement of magnetic tape media and tape head technology. Has increased further. For example, the IBM 3490-E magnetic tape subsystem for a 12.7 mm (1/2 inch) wide tape uses a head with 36 read / write elements and has a tape capacity of 800 megabytes (MB). The 3490-E tape drive performs bidirectional linear recording (as opposed to helical recording) and reduces the number of tape windings, which improves performance and allows multiple head elements. The sets are interleaved. In interleaved heads, the read / write element ordered element pairs (as viewed toward the face of the head) alternate with the write element / read element ordered element pair. , And each pair of elements is associated with a track on the tape. As the tape moves in one direction, a pair of elements arranged in one order access the corresponding tracks (eg, even-numbered tracks) to write, then read, and the tape moves in the opposite direction. When doing so, the pair of elements arranged in another order accesses another corresponding track (odd-numbered track) to read after writing. To improve the performance of such a large number of tracks, which also requires a large number of closely spaced elements, the 3490-E drive tape head uses thin film deposition techniques. It is a magnetoresistive converter formed.

However, the number of tracks formed on a tape medium is limited by the number of read / write elements formed on the head for writing / reading narrower tracks. Therefore, tape drives have been designed that process tapes using heads that have a smaller number of sets of read / write elements than tracks on the tape. The tracks are divided into groups and each group has the same number of tracks as the read / write element pairs of the head. To access all groups, the head is indexed into a number of discrete positions, corresponding to the number of groups of tracks, across the direction of tape travel, for example by springs driven by step motors or voice coils. . For example, a head with 8 read / write pairs corresponds to a tape with 24 tracks if the tracks are divided into 3 groups with 8 tracks each and the head has 3 index positions. it can. It is desirable that each group be interleaved to reduce the distance that the head travels between index positions. In this example, each of the three groups has 8 tracks. If the tracks are numbered sequentially from 0 to 23, the result of group interleaving is track 0,
, 3, 21 are the first group and can be accessed by the head indexed at position 0. Similarly, tracks 1, 4, 7, ...
, 22 is the second group and is accessed by the head at index position 2 and tracks 2, 5, 8, ..., 23 are the third group and is accessed by the head at index position 2 It

[0004]

Despite having achieved the advantage of increasing the data capacity in this way, there are, for example, 64 or even 128 tracks.
Further increase in data capacity is desired so that a tape with a width of 7 mm can be used. However, even if the heads are indexed, a multi-track head is limited in that it cannot accurately and reliably record and read data on such a very small number of tracks. Causes of this problem are, for example, uneven tape edges, thermal expansion due to ambient atmosphere, inaccurate tape passage in the tape drive, and inaccurate format of the tracks on the tape itself. Misalignment of the track with the converter due to, for example. Even if the tape wobble is minimal, if the 12.7 mm tape has 128 tracks (each track approximately 80 microns wide), then signals such as crosstalk and dropouts. Note that the deterioration of the

Therefore, the tape head can be indexed into one of several positions during a track seek operation, and the position of the head is adjusted so that the head accurately follows the track during a track access operation. There has been a demand for a tape head actuator capable of quickly servo-controlling the head. Furthermore, such actuators must be reliable and relatively simple in construction so that they can be manufactured on a commercial high volume basis.

[0006]

SUMMARY OF THE INVENTION The present invention is a transducer for indexing a multi-track magnetoresistive transducer across a track in track seek mode and servoing the transducer in track following mode. To provide a tape drive actuator assembly for controlling the position of the. More specifically, the head actuator assembly of the present invention comprises a base member; a beam member spaced from the base member and movable relative to the base member along a first axis;
An upper elastic member and a lower elastic member which are arranged in parallel surfaces and face each other for connecting the upper end and the lower end of the base member to the upper end and the lower end of the beam member, respectively; Have. The beam member has a support for mounting a magnetoresistive transducer, and the transducer surface is provided with a plurality of pairs of read / write elements for accessing a multi-track magnetic tape, and the tape Are moved along a path parallel to the surface of the transducer and perpendicular to the first axis.

The electromagnetic drive means or assembly is a support; two pairs of electromagnetics separated from each other by an air gap and fixed to the support; movable in the air gap and fixed to the inner surface of the beam member. A substantially flat electrical coil; and a magnet and a magnetic shield that substantially surrounds the coil but is spaced therefrom. The coils are arranged in a plane orthogonal to the plane of the elastic member and in a plane defined by the tape passage and the first axis. The two magnets of each of the pair of magnets are preferably separated by a second air gap. The above structure produces a leakage flux of less than about 1 Gauss in the direction of the magnetoresistive transducer.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A magnetic tape drive in which the head actuator assembly of the present invention may be incorporated is shown in FIG. The magnetic tape drive 10 includes a base unit 12 to which a power supply 14, various electronic circuit cards 16, a deck assembly 18 and an air assembly 20 are mounted. Mounted on the deck assembly 18 are a loader mechanism 22, a drive motor (not specifically shown in the figure), a punt cam assembly 24 and a "D" bearing assembly 26. The head actuator assembly 30 is mounted on the D bearing assembly 26. The circuit card 16 contains, among other things, a drive controller, a read / write processor and a control and data interface. Magnetic tape drive 10 can operate independently and in an automated tape loader system connected to a host computer, and also in an automated data storage and retrieval system (library) having multiple drives. Can be incorporated.

For reference, the magnetic tape drive 10
The operation of will be briefly described. A removable tape cartridge 28, with magnetic tape wrapped around a supply reel, is inserted into the loader mechanism or assembly 22 through a slot 32 in the front of the base unit 12.
The loader assembly 22 retracts the cartridge and lowers it to the deck assembly 18.
The punt cam assembly 24 engages a leader block attached to the free end of the tape and pulls the tape around the D-bearing assembly 26 so that the tape is placed in the tape passage and the head It can be moved across the tape head mounted on the actuator assembly 30. The leader block is then engaged by the take-up reel of the deck assembly 18, and the magnetic tape drive 10 can record information on and read it from the tape. The magnetic tape drive 10 shown in FIG.
Is designed to accept a tape cartridge that contains a take-up reel and only a supply reel.
The present invention is not limited to use with such drive / cartridge combinations, but may also be used with drive / cartridge combinations, for example, where the tape cartridge includes both supply reels and take-up reels.

FIG. 2A shows, for example, IBM3490-.
7 shows a track layout of a typical conventional tape having 36 recording tracks, such as E's 12.7 mm wide tape. Associated with each track is a pair of read and write elements on a fixed tape head. For example, write element 50 is paired with read element 51 and associated with odd tracks, and read element 52 is paired with write element 53 and associated with even tracks. As the tape moves from left to right in FIG. 2A, the pairs of elements 50 and 51 associated with odd tracks become active and simultaneously record on those tracks. The tape first passes under the write element 50 and it records information in the track, then the tape passes under the read element 51 which reads and verifies the information just recorded. When the tape moves in the opposite direction, the pair of elements 52 and 53 associated with the even tracks become active and simultaneously record on those tracks in the same manner as described above. Each read element of such a head has a length of about 195 microns, each track has a width of about 285 microns (each write element has a slightly shorter length), and there are 30 tracks between each track. There is a micron direction buffer, and there is a 670 micron edge guard band between the first and last tracks and each edge of the tape.

In contrast to the above, FIG.
2 shows a layout of tracks on a tape having a width of 12.7 mm having recording tracks of FIG. The width of each track is approximately 80 microns, there is a 2 micron direction buffer every 4 tracks, and there are 756 micron edge guard bands. The track size has been significantly reduced and the number of tracks has been increased to 3490-E.
It is clear that the recording capacity has increased compared to tape systems. For high performance, the tape head is preferably a thin film magnetoresistive (MR) transducer. The thin-film photography technology has formed small elements arranged at narrow intervals, increasing the number of tracks for recording data and increasing the recording capacity.

However, such closely spaced small tracks and devices increase the likelihood of unwanted crosstalk. In addition, it is difficult and costly to form 128 sets of read / write elements in the transducer as required in a fixed head system, and the element format is not perfect and the track format is not perfect. Not, and if there is wobble or some disturbance in the movement of the tape through the transducer, the information recorded on adjacent tracks will interfere with each other. Therefore, the number of sets of elements formed in the transducer is reduced, the spacing between each set is increased, and the transducer is moved between some small number of index positions in track seek mode. It is desirable to move the transducer in a direction transverse to the tape as it does. In the example shown in FIG. 2B, the transducer has 32 pairs of read / write elements and is driven between four index positions. The read and write element lengths are 35 and 79 microns, respectively. In order to reduce the crosstalk between the elements, as shown in FIG. 2B, the pair of elements should be a read / write pair in the forward direction and then a read / write pair in the reverse direction. It must be separated by 4 tracks in the transverse direction. Thus, when the transducer is in the first index position as shown, if the tape is moved in the forward direction (ie, the direction indicated by the arrow from left to right as shown), Tracks 1, 9, 1
, ..., 121 are recorded and read by 16 read / write elements 54 and 55, and the tape is moved in the opposite direction (ie, the direction indicated by the arrow from right to left). In this case, the 16 read / write elements 56 and 57 provide tracks 5, 13, 21,
..., 125 is recorded and read. When the transducer is moved to the second index position, tracks 2, 10, 18, ... If the tape is moved in the forward direction.
.., 126 are recorded and read by elements 54 and 55, and when the tape is moved in the reverse direction, tracks 6, 14, 22, ..., 126 are elements 5
Recorded and read by 6 and 57. Similarly, the remaining tracks can be accessed by positioning the transducer at the appropriate index position and properly selecting the direction of tape travel.

When the dimensions of the device and the track are small as described above, even a slight misalignment of the track (TRM:
(Relative deviations in alignment between track and device) significantly reduce performance and even prevent recording or reading on the correct track. Thus, the magnetic tape drive 10 has a servo-controlled track following mode that controls the transducer elements to maintain proper alignment with the tracks on the tape. The tape has dedicated servo tracks (at least one for each index position), while the transducer has dedicated servo elements. To accurately follow the servo track under servo control, the head actuator assembly 30 causes the transducer to move very quickly and extremely across the width of the tape in response to signals from the servo elements. It must be able to drive back and forth by a small amount. The present invention is
To access the information on the 128-track tape,
A good tracking frequency of about 500 Hz and a good tracking movement of about ± 4 microns or less in the direction across the tape as indicated by arrow 58 can be achieved without head skew.

FIG. 3 is an exploded view of each element of the head actuator assembly 30 of the present invention, and FIG. 4 is an assembled head mounted on the D bearing assembly 26 of the magnetic tape drive 10. -Shows the actuator assembly 30. The head actuator assembly 30 has a base member 302, on which the beam member 304 and the electromagnetic assembly 40 are mounted. The electromagnetic assembly 40 includes a support 404, one or more magnets 406 and a magnetic shield 4.
Including 08. Affixed to beam member 304, but positioned between magnets 406 and in the magnetic field generated therefrom, is a substantially flat moving coil 402 (as opposed to a cylindrical voice coil coaxial with the yoke). Yes). Mounted on the outer surface of beam member 304 is a multi-track magnetoresistive transducer 308. Upper and lower ends of the beam member 304 and the base member 302
The upper and lower parts of the bracket are interconnected by the bracket 3
14 and elastic members 60 and 6 fixed by screws 316
2 (other mounting methods may also be used), thereby suspending the beam member 304 from the base member 302.
A hose 318 is secured to the beam member 304 and provides air to the transducer 308 that acts as a puffer device that lifts the tape from the surface of the transducer 308 during rapid forward feed and winding to prevent the tape from sticking to this surface. Give to the output section. Also included in the head actuator assembly 30 is an optical tachometer which provides a feedback signal of the beam member position to the drive controller during head index. This tachometer includes an optical sensor 320 and a sensor 32 mounted on a base member 302.
Positioned through slot 0 and beam member 3
A code strip 322 mounted on and moving with 04. Various brackets and screws
Various cables secure the elements of the actuator assembly 30, and various cables attach the transducer 308, moving coil 402 and tachometer sensor 320 to the magnetic tape.
Connect to the circuit card 16 of the drive 10. To prevent the ribbon cable 310 from interfering with the movement of the beam member 304, the ribbon cable 310 is attached to the beam member 3
Guided upwards along side 04 and base member 30
It is desirable that the curved surface 322 inside 2 removes the base member 302 to the outside.

In operation, when it is desired to access a particular set of tracks on the tape, the servo loop of the drive controller supplies current to moving coil 402. The electromagnetic field generated by the moving coil 402 interacts with the magnetic field of the magnet 406 to try to hold the beam member 304 in its initial position.
It produces a force opposite to the bias force of 0 and 62. This force pushes the beam member 304 to which the moving coil 402 is fixed and moves along an axis AA perpendicular to the tape travel path (which is shown by axis BB in FIG. 4). Let Head actuator assembly 3
When 0 is in seek or index mode, the magnitude of the current supplied to moving coil 402 traverses the beam member over a relatively large distance of 1 to 3 tracks (up to about ± 240 microns). It is relatively large so as to shift in direction and hold each element of the transducer in a position facing the desired track. When the head actuator assembly 30 is in the track following mode, the servo loop responds to the position error signal from the servo following element of the transducer 308 to accurately align the transducer and the track (approximately ± 4). The moving coil is supplied with a very slight and high frequency conditioning current (which causes the movement of the beam member in the micron order).

Generally, elastic members or springs 60 and 62 connecting the beam member 304 to the base member 302.
Should be flexible enough to move the transducer 308 the desired amount across the tape, but as the tape passes through the transducer 308, the servo loop and transducer 308 track and track. It is neither desirable nor too rigid in order not to diminish the ability to quickly guarantee alignment errors with the transducer. If the connecting elastic member is too stiff, excessive current must be applied to the moving coil 402 to move the beam member 304, which causes extra stress and fatigue of the elastic member. It causes early failure. In addition, the resilient member allows the indexing and following movement of the transducer 308 to be undistorted so that the beam member 304, the magnetic tape drive 10 and the resilient member maintain parallelism during indexing and tracking operations. It has to be done almost linearly. Further, the entire head actuator assembly 30 includes a transducer 3
It must be highly resistant to shock, vibration and other forces that cause twisting and other unwanted vibrations and movements in 08 which reduce the ability of transducer 308 to accurately record and read information from the tape. I won't.

Instability if the natural frequency / resonance frequency or vibration mode of the head actuator assembly 30 is close to or within the operating frequency range of the servo loop controlling the movement of the beam member 304. This happens. FIG. 5 shows the beam member 304.
And a frequency response plot of a head actuator assembly using a conventional standard thin rectangular leaf spring to interconnect base member 302.
The first natural vibration occurs at about 30 Hz, which represents a combined spring and mass system of the actuator, and the second natural frequency occurs at about 500 Hz, showing only the spring system as if each end of the spring were Represents a fixed state. As previously mentioned, a tracking frequency of about 500 Hz is required for the head actuator assembly 30 to accurately track 128 tracks of tape. The first natural frequency of 30 Hz of the standard spring system shown in FIG. 5 is well below and apart from the operating frequency which must be guaranteed or filtered out by the servo loop. However, the second natural frequency of 500 Hz is in the range of the operating frequency of the servo and cannot be guaranteed or eliminated without degrading the required information. Thus, vibrations occur that interfere with accurate tracking.

In addition, standard springs also experience torsional forces which prevent accurate tracking. Stiffening the spring or elastic member can reduce the first natural frequency, but this does not increase resistance to torsional forces,
And, as mentioned above, it reduces the overall actuator responsiveness and increases the current flowing through the moving coil and increases the stress associated therewith. If the elastic member is made thinner, the second natural frequency tends to increase,
It tends to weaken the elastic member itself and receive stress, resulting in failure due to fatigue. The head actuator assembly 30 of the present invention uses a conventional standard leaf spring, as described above, to servo tape a tape having a number of narrow tracks, such as 128 tracks having a width of 80 microns. It solves the problem of being unable to use. The head actuator assembly 30 is mechanically decoupled from the balance of the magnetic tape drive 10 and the external vibration is applied to the beam member 3.
04, and beam member 304
In order to reduce the adverse effects of vibrations from the other components of the magnetic tape drive 10, the base member 3
02 must be made of large and heavy material.
However, the base member 302 is
The base member 302 must be non-magnetic to prevent it from magnetically interacting with and interfering with the operation of the transducer 308. The beam member 304 must also be non-magnetic, but the moving coil 4 required to increase the responsiveness of the beam member 304 and drive the beam member 304 and the components attached thereto.
02 to reduce the amount of current flowing through the beam member 3.
04 must be very lightweight. Therefore, it is desirable to form the base member 302 from brass and weigh for example 300 grams, and the beam member 304 from aluminum or magnesium and weigh less than 4 grams, for example.

FIGS. 6A and 6B show the top and bottom surfaces of one embodiment of the upper resilient member 60. The same applies to the lower elastic member 62. In the illustrated embodiment, the elastic member 60 is a restraining member 60 formed in a corrugated shape.
Have two. An opening 616 extends through the restraint member 602 to increase rigidity, increase resistance to torsional forces, and increase the second natural frequency. A top sheet or top plate 604 and / or bottom plate 606 (shown cut away) may be provided to increase strength and stiffness. Top plate 604 and bottom plate 606
Is a restraint member 602, the top plate 604 and the bottom plate 6
06 is connected to the restraining member 602 by spot welding or an adhesive in order to prevent the 06 from moving with respect to other elements.

FIGS. 7A and 7B show another embodiment 70 of the elastic member of the present invention. This elastic member 70
Includes a thin resilient plate 702 and a stiff plastic restraining member 704 adhered to the resilient plate 702, eg, with an adhesive. The opening 716 through the restraint member 704 is
The weight of this restraint member 704 is reduced to increase the second natural frequency and increase the stiffness to increase resistance to torsion and other unwanted forces. Other aperture shapes can be used, such as a honeycomb or porous shape formed of multiple holes through the restraint member 704.

The thickness of the restraint members 602 and 702 is about 2 m.
It has been found that a satisfactory actuator performance can be obtained when formed to m. The restraint or rigid member 602 of the first embodiment has extensions 608 provided at opposite ends thereof and projecting from a central portion thereof. It is desirable to have three extensions. Alternatively, the extension can be formed as part of either top plate 604 or bottom plate 606. The resilient plate 702 of the second embodiment includes extensions 708 and 710 formed at each end thereof that project beyond the restraining member 704. Three
It is desirable to have two extensions. Extensions 608 and 708 have respective connection pads 612 and 712 for receiving mounting screws. The connection pads have a spade-like shape with one open end to facilitate accurate alignment of the beam member 304 when the screws are tightened and to reduce extension sticking, twisting and other deformations. Have. However, it is also possible to use a shape with closed ends.

Extensions 6 at the ends of the elastic members 60 and 70
08 and 708 have narrowed neck regions 614 and 714. This resulting structure confines the elastic movement of the elastic member to the neck region of the extension,
On the other hand, the balance of each elastic member covered by the restraint member 602 or 702 is maintained substantially rigid even when subjected to a twisting force. Since each elastic member bends only at the inner and outer end neck regions, the beam member 304 causes the base member 30 to move during indexing and track following operations.
2 is maintained substantially parallel to 2, which reduces the twist angle of the transducer as shown in FIG.

By using the neck regions 614 and 714, the second natural frequency can be adjusted without changing the thickness of the extension. It has been found that reducing the width of the neck regions 614 and 714 increases the second natural frequency of the head actuator assembly 30. Although depending on the material forming the extensions 608 and 708, good response characteristics, strength characteristics, and fatigue resistance characteristics can be obtained with the following characteristics. The length, width and thickness of the extension are about 3.5 mm, about 3.5 mm and about 0.1 m, respectively.
m. The length and width of the neck region are each about 1.6.
mm and about 0.5 mm. Spring constant K is about 0.3N
/ Mm and the weight of the extension is a few milligrams. By providing one or more, preferably three extensions, the extension at each end of each resilient member improves resistance to twisting. However, the use of four or more extensions does not improve performance significantly and makes manufacturing difficult.

The type of material used for the resilient members 60 and 70 also affects their performance. Beryllium copper is a good material, has very good resistance to fatigue, and exhibits a nearly linear force / deflection relationship even at very small deflections (eg 4 microns or less). Further, beryllium copper passes the magnetic field well and does not deflect or concentrate the leakage flux from electromagnetic assembly 40 toward magnetoresistive transducer 308. Blue tamper (spring) steel is also suitable, and 30
The same applies to 3 stainless steel, but the latter is about 8
It exhibits some non-linearity (ie, softer than normal operation) during deflections of less than 0 micron.

FIG. 9 shows a head actuator assembly 30 having resilient members 60 and 70 according to the present invention interconnecting a beam member 304 and a base member 302.
4 is a plot of the frequency response of. The first natural frequency occurs at about 20 Hz and represents the spring / mass system of the head actuator assembly 30,
Then, the second natural frequency occurs at about 1150 Hz and represents only the elastic member system. The first natural frequency 20 Hz is well below and far from the operating frequency to be compensated or filtered by the servo loop. The second natural frequency of 1150 Hz is
It is well outside the operating frequency range of the system and can be properly compensated and does not significantly interfere with index and servo tracking. Therefore, oscillations that interfere with accurate tracking have been largely reduced or eliminated.

As is well known, the magnetoresistive converter 308 is
It requires a bias field to produce magnetoresistance and is very sensitive to external magnetic fields. Especially the converter 3
If the external magnetic field in the vertical direction is sufficiently strong with respect to 08, the bias point of the converter 308 will change, degrading its performance. Transverse magnetic fields also affect the bias of the transducer 308, but generally this is small. Therefore, almost complete magnetic field interruption to the transducer 308 must be provided.

The magnet structure of a typical magnetic driver produces a magnetic field of uneven magnetic flux density that decreases significantly towards the edges of the magnet. For example, having a magnet surface area of 10 mm × 10 mm and a gap between facing magnets of 4
In the structure of mm, the magnetic flux density at the center is about 6.5K.
Gaussian, and magnetic flux density near the edge is about 4.5
It is K Gauss. Increasing the size of the magnet can increase the density towards the edges, but such an increase does not improve the homogeneity of the magnetic field and is a new impediment to the transducer 308 and valuable storage space. Is not feasible.

The electromagnetic assembly 40 of the present invention reduces magnetic flux leakage and improves magnetic flux density uniformity without increasing volume. FIG. 10 is an exploded view of the electromagnetic assembly 40. FIG. 11 is a perspective view of the electromagnetic assembly 40 partially cut and with the shield 408 removed. The electromagnetic assembly 40 has a support 404 fixed to the base member 302 and having a generally U-shaped configuration, a set of magnets 406 and a magnetic shield 408. The moving electromagnetic coil 402 (fixed to the beam member 304) is spaced from the magnets 406 but positioned within the magnetic fields of these magnets 406. Various screws
The shield 408 and crash stop spring 414 are fixed to the support 404. Axis A-A indicates the direction of reciprocal movement of moving coil 402 and beam member 304.

In the illustrated embodiment, the magnet 406 and moving coil 402 cause the transducer to have less shock than if the flux lines were substantially perpendicular to the surface of the transducer 308 and the flux lines were parallel to the surface. It is arranged to give to 308. The schematic position of the transducer 308 is shown in FIG. Four mutually spaced permanent magnets 41
0-413 are arranged in the space in the support 404 in the form of north and south pole pairs 410/411 and 412/413. The north pole of the first magnet of the first magnet pair faces the south pole of the first magnet of the second magnet pair through the first air gap, and the south pole of the two magnets of the first magnet pair is the first pole. It faces the N pole of the second magnet of the second magnet pair through one air gap. Pairs 410/411 and 412/413 are separated from each other by an air gap 415 (FIG. 12) and move through this gap with a width of about 3-4 mm.
The coil 402 reciprocates. The two magnets of each pair are separated from each other by an air gap 416 (Fig. 12).
That is, between the magnet 410 and the magnet 411, and between the magnet 4
Air gap 41 between the magnet 12 and the magnet 413, respectively.
There are six. 12 shows a cross section of the electromagnetic assembly 40 taken along line 12-12 of FIG. 11, and 4
The magnetic field (indicated by arrow 420) is shown through a magnetic circuit consisting of two magnets 410-413, support 404 and air gaps 415 and 416. The current flowing through moving coil 402 interacts with magnetic flux 420 to move moving coil 402 and beam member 304 up or down, depending on the direction of this current.
In FIG. 13, the magnetic flux lines 420 toward or away from the paper surface are indicated by the symbols “+” and “·”, respectively.

Referring again to FIG. 12, the air gap 4
By separating the magnet 410 from the magnet 411 and the magnet 412 from the magnet 413 by 16
Flow through the completed magnetic circuit including the support 404. Alternatively, if magnet 410 is in contact with magnet 411 and magnet 412 is in contact with magnet 413, magnetic flux 420
Are short-circuited and flow only slightly to the support 404. Furthermore, the magnetic domains (polar grai) of the magnets 410-413 are
n) 422 are aligned in a direction perpendicular to the axis of movement AA. Such a structure increases both the magnetic flux density and its uniformity (about 7K Gauss at the center and about 6.5K Gauss near the edges).

To magnetically protect the transducer 308,
The amount of magnetic flux reaching the transducer 308 is determined by the magnetic shield 408 that is fixed to at least the upper surface and front surface of the support 404, ie, the edge of the support 404 closest to the transducer 308.
Is reduced by. As shown in FIGS. 11 and 14 (where FIG. 14 is a cross-sectional view of electromagnetic assembly 40 taken along line 14-14 of FIG. 11), magnet 41
0-413 are set back from the top edge, bottom edge and front edge of support 404. The amount of this receding is preferably about 0.5 and 2 mm, and more preferably about 1 mm on the front surface and about 1.5 mm to 2 mm on the top and bottom surfaces. Thus, the magnetic shield 408 does not contact the magnets 410-413 but close to them so as to leave a small small slot (corresponding to the air gap 415) to allow the moving coil 402 to be attached to the beam member 304. Are placed. The magnetic shield 408 is, for example, AISI.
It is preferably manufactured from high performance materials such as 1010 low carbon steel. The electromagnetic assembly 40 includes a longitudinal magnetic field (indicated by the arrow L-L) and a lateral magnetic stray field of almost negligible magnitude below about 1 Gauss (which corresponds to the average density of the earth's magnetism). (Indicated by arrow T-T),
And to this, the converter 308 is almost insensitive and thus the performance of the converter 308 is hardly affected.

[0032]

The tape head can be indexed into one of several positions during a track seek operation, and the position of the head is adjusted so that the head accurately follows the track during a track access operation. A tape head actuator that can quickly perform servo control is realized.

[Brief description of drawings]

FIG. 1 is an exploded view of a magnetic tape drive of the present invention.

FIG. 2 is a diagram showing a track layout of a tape having 36 recording tracks and 128 recording tracks, and a track width and a head size.

FIG. 3 is an exploded view of each element of the head actuator assembly of the present invention.

FIG. 4 is a perspective view of a head actuator assembly of the present invention mounted on a "D" bearing assembly of a magnetic tape drive.

FIG. 5 is a plot of frequency response of an actuator having a conventional standard leaf spring.

FIG. 6 is a perspective view of an embodiment of the elastic member of the present invention.

FIG. 7 is a perspective view of another embodiment of the elastic member of the present invention.

FIG. 8 is a diagram showing movements of the elastic member and the beam member of the present invention.

FIG. 9 is a diagram showing a plot of frequency response of an elastic member of the present invention.

FIG. 10 is an exploded view showing an electromagnetic assembly of the head actuator assembly of the present invention.

11 is a perspective view of the electromagnetic assembly of FIG. 10 after assembly.

12 is a cross-sectional view of the electromagnetic assembly taken along line 12-12 of FIG.

FIG. 13 is a cross-sectional view of a beam member and an electromagnetic assembly.

14 is a cross-sectional view of the electromagnetic assembly taken along line 14-14 of FIG.

[Explanation of symbols]

 10 ... Magnetic tape drive 12 ... Base unit 14 ... Power supply 16 ... Electronic circuit card 18 ... Deck assembly 20 ... Air assembly 22 ... Loader mechanism 24 ... Punt cam assembly 26 ... "D" bearing assembly 30 ... Head actuator assembly 40 ... Electromagnetic assembly 60, 62 ... Resilient member 302 ... Base member 304 ... Beam Member 308 ... Magnetoresistive converter 402 ... Moving coil 404 ... Support 408 ... Magnetic shield 410, 411, 412, 413 ... Magnet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Adolfo M. Gazman 3930 N Old Sabino Canyon Road, Tucson, Arizona, USA (72) Inventor Paul Wye Hugh, Arizona, USA Fane Hill Drive 8400, Tucson (72) Inventor Royal Case Witted 10740 East Cinder Road, Tucson, Arizona, USA

Claims (24)

[Claims] 1. A mass non-magnetic base member and a lightweight non-magnetic beam member spaced from the base member and reciprocally movable relative to the base member along a first axis. The member has a support on its outer surface for mounting a magnetoresistive transducer, said magnetic transducer having a read element and a write element for accessing a track of a multi-track magnetic tape on its outer surface. A plurality of pairs of the tapes, the tape moving along a tape path perpendicular to the first axis and transverse to the paired elements,
The tape passage and the first axis define a first plane and are connected between the beam member and the upper and lower ends of the base member and the upper and lower ends of the beam member, respectively. An upper elastic member and a lower elastic member arranged to face each other in two parallel second planes, a U-shaped support fixed to an inner surface of the base member, and inside the support. A first magnet pair and a second magnet pair which are fixed and separated from each other by a first air gap, in the first air gap in a plane fixed to the beam member and orthogonal to the first plane and the second surface A positioned flat moving coil and a magnetic shield spaced apart from and surrounding the magnet pair and the moving coil, wherein the upper elastic member, the lower elastic member, and the elastic member Servo-controlled magnetic tape head for the transducer for indexing and following the track, the electromagnetic drive means being housed in a space defined by the beam member and the beam member. Actuator device. 2. The north pole of the first magnet of the first magnet pair passes through the first air gap and the S pole of the first magnet of the second magnet pair.
Facing the pole, and in the first pair of magnets, the south pole of the two magnets faces the north pole of the second magnet of the second magnet pair via the first air gap. The magnetic tape head actuator device of claim 1. 3. The first air gap is 3 mm to 4 mm.
3. The magnetic tape head actuator device according to claim 2, wherein 4. The first magnet and the second magnet of the first magnet pair are separated by a second air gap, and the second magnet.
3. The magnetic tape head actuator device of claim 2, wherein the first magnet and the second magnet of the magnet pair are separated by the second air gap. 5. The magnetic tape head actuator device of claim 4, wherein the second air gap is 2 mm. 6. The magnetic tape head actuator device according to claim 4, wherein the magnetic shield is separated from the magnet by 0.5 mm to 2 mm on the upper and front surfaces of the support. 7. The magnetic tape head actuator device of claim 6 wherein said electromagnetic drive means has a leakage flux of less than 1 Gauss in the direction of said magnetoresistive transducer. 8. The magnetic tape head actuator device of claim 2 wherein the magnetic domains of the magnet are aligned perpendicular to the plane of the moving coil. 9. The magnetic tape head actuator device according to claim 1, wherein the magnetic shield has two shield members formed of a high performance material. 10. The magnetic tape head actuator device of claim 9 wherein said high performance material is low carbon steel. 11. An electromagnetic drive means for moving said beam member along said first axis during a track indexing operation.
Driving in 0 micron steps, and during the track following operation, the electromagnetic drive means drives the beam member into the first portion.
2. The magnetic tape head actuator device of claim 1 which is driven a distance less than. +-. 4 microns along the axis. 12. A magnetoresistive transducer having a plurality of pairs of read and write elements for accessing tracks of a multi-track magnetic tape on an outer surface defining a first plane, and the paired read elements. And means for driving a magnetic tape in the path across the plurality of sets of write elements, and means for transmitting and receiving signals to and from the magnetoresistive transducer for recording and reading information from and to the magnetic tape. An actuator assembly for reciprocating the magnetoresistive transducer in a direction transverse to the passage of the tape, the actuator assembly being disposed away from the base member and in the transverse direction. A non-magnetic beam member having an outer surface on which the magnetoresistive transducer can be mounted, An upper elastic member and a lower elastic member, which are respectively connected between the upper end and the lower end of the base member and the upper end and the lower end of the beam member, and are arranged to face each other in two parallel second planes. Member, a support member fixed to the inner surface of the base member, a first magnet pair and a second magnet pair fixed inside the support member and separated from each other by a first air gap, and fixed to the beam member. A flat moving coil positioned in the first air gap in a plane orthogonal to the first plane and the second surface, and a magnet surrounding the pair of magnets and the moving coil spaced apart from them. A shield, the upper elastic member, the lower elastic member,
Electromagnetic driving means housed in a space defined by the base member and the beam member, and control means for controlling a current flowing through the moving coil during the track indexing operation and the track following operation. A magnetic tape drive device having a plurality of tracks for linear recording. 13. The magnetoresistive transducer comprises 32 pairs of read and write elements that linearly access 128 tracks on the magnetic tape, and during the track indexing operation, the electromagnetic drive means comprises: Driving the member in steps of 80 microns along the transverse direction, and during the track following operation, the electromagnetic drive means drives the beam member along the transverse direction by less than ± 4 microns. The magnetic tape drive device according to claim 12. 14. The N pole of the first magnet of the first magnet pair faces the S pole of the first magnet of the second magnet pair through the first air gap, and the first magnet pair. 13. The magnetic tape driving device according to claim 12, wherein the S pole of the two magnets faces the N pole of the second magnet of the second magnet pair through the first air gap. 15. The first magnet and the second magnet of the first magnet pair are separated by a second air gap, and the first magnet and the second magnet of the second magnet pair are separated by the second air gap. 15. The magnetic tape drive device according to claim 14, wherein the magnetic tape drive devices are separated from each other. 16. The first air gap is 4 mm,
16. The magnetic tape drive device according to claim 15, wherein the second air gap is 2 mm. 17. The magnetic shield is connected to the magnet from the magnet.
The magnetic tape drive device according to claim 15, wherein the magnetic tape drive devices are separated by 5 mm to 2 mm. 18. A magnetic drive apparatus according to claim 15, wherein said electromagnetic drive means has a leakage flux lower than 1 Gauss in the direction of said magnetoresistive converter. 19. A base member, a movable beam member disposed away from the base member, fitted with a magnetoresistive transducer, and movable along a first axis spaced from the base member, the base member. Are connected between the upper and lower ends of the beam member and the upper and lower ends of the beam member, respectively, and are perpendicular to the moving path of the magnetic tape with respect to the magnetoresistive transducer and the first plane defined by the first axis. A servo-controlled tape head actuator device having an upper elastic member and a lower elastic member disposed facing each other in two parallel second planes, the base member comprising: A support fixed to the inner surface of the support, fixed inside the support and separated from each other by a first air gap, each having a first magnet and a second magnet, A first magnet pair and a second magnet pair retracted from the edge of the support and housed inside the support, a plane fixed to the inner surface of the beam member and orthogonal to the first plane and the second surface. A flat moving coil positioned within the first air gap, and a magnetic shield surrounding and enclosing the first and second magnet pairs and the moving coil, wherein the upper resiliency is A member, the lower elastic member, an electromagnetic drive means housed in a space defined by the base member and the beam member, wherein the first magnet pair and the second magnet pair are the first air gap. Are separated from each other by a second air gap, the first magnet and the second magnet of the first magnet pair are separated from each other by a second air gap, and the first magnet and the second magnet of the second magnet pair are separated from each other. Are separated from each other by the serial second air gap, said tape head actuator device. 20. The N pole of the first magnet of the first magnet pair faces the S pole of the first magnet of the second magnet pair through the first air gap, and the first magnet pair. 20. The tape head actuator device according to claim 19, wherein the south pole of the two magnets faces the north pole of the second magnet of the second magnet pair through the first air gap. 21. The tape head actuator device of claim 20 wherein each magnetic domain of the magnet is aligned perpendicular to the plane of the moving coil. 22. The first air gap is 4 mm,
21. The tape head actuator device of claim 20, wherein the second air gap is 2 mm. 23. The magnet is recessed from the top and front edges of the support by 0.5 mm to 2 mm, and the magnetic shield produces a leakage flux of less than 1 Gauss in the direction of the magnetoresistive transducer. 23. The tape head actuator device of claim 22. 24. The tape head actuator device of claim 19, wherein the magnetic shield is formed of low carbon steel.