1. Field of the Invention
The present invention relates to magnetic disk data storage systems, and more particularly to systems utilizing multiple disks and multiple read/write heads.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In FIGS. 1A and 1B, a magnetic disk data storage system of the art is illustrated which includes a sealed enclosure 12 and a plurality of magnetic disks 14 each of which has an upper surface 16 and a lower surface 18. The disks are supported for rotation by a spindle 20 of a motor 22.
An actuator 24, includes an E-block 25 having at a distal end a plurality of actuator arms 26. The actuator 24 also includes a bearing 27 which mounts the actuator 24 pivotally within the enclosure 12 and further includes a voice coil 28 at its proximal end. The voice coil 28 is disposed between a pair of magnets 30 which are fixedly connected with respect to the enclosure 12. Generating an electrical current in the coil 28 induces a magnetic field about the coil. Interaction between the magnetic fields of the coil 28 and the magnets 30 provides a desired, controlled pivotal movement of the actuator about a pivot point 31 of the bearing.
The actuator arms 26 support a plurality of suspensions 32, each of which supports at its distal end a magnetic head 34. Each suspension 32 holds its corresponding magnetic head 34 in close proximity to a surface of one of the disks 14 to facilitate reading and recording data to and from the disk 14.
With reference now also to FIGS. 2A and 2B, as well as to FIGS. 1A and 1B, the suspension 32 includes suspension trace circuitry 36 which conducts electrical signals from the head 34 to a set of contacts 38 along an edge of the suspension 32. A bridge flex connector 40, having trace circuitry 41, electrically connects the suspension trace circuitry 36 with circuitry 42 (see FIG. 1A) attached to the E-block 25. The heads 34, suspensions 32, bridge flex connectors 40 and E-block 25 with E-block circuitry 42 together form a Head Stack Assembly 44 (HSA).
The motor 22 and spindle 20 cause the disks 14 to rotate. As the disks 14 rotate, the air immediately adjacent the disks 14 moves with the disks 14 as a result of friction and the viscosity of the air. This moving air passes between each of the heads 34 and its adjacent disk surface 16, 18 forming an air bearing. This air bearing causes the head to fly a very small distance from the disk surface 16, 18.
With reference to FIGS. 2C and 2D, as well as FIGS. 1A and 1B, each of the heads 34 includes a read element 46 and a write element 48 (FIG. 2E). As the disk surface 16 or 18 moves past the head 34 the write element 48 generates a magnetic field leaving magnetic data on the passing disk 14. Such write elements are generally in the form of an electrical coil 50 passing through a magnetic yoke 52. As a current passes through the coil 50 it induces a magnetic field which in turn generates a magnetic flux in the yoke 52. A gap (not shown) in the yoke causes the magnetic flux in the yoke to generate a magnetic field which fringes out from the gap. Since the gap is purposely located adjacent the disk, this magnetic fringing field imparts a magnetic data onto the passing magnetic disk 14.
With continued reference to FIGS. 2C and 2D, to read data from a disk 14, the read element 46 detects changes in surrounding magnetic fields caused by the disk 14 passing thereby. Several read elements have been used to read such data. A very effective read element currently in use is a GMR Spin Valve sensor. Such sensors take advantage of the changing electrical resistance exhibited by some materials when a passing magnetic field affects the magnetic orientation of adjacent magnetic layers. At its most basic level, a GMR spin valve includes a free magnetic layer and a pinned magnetic layer separated by a non-magnetic layer such as copper. The pinned layer has magnetization which is pinned in a pre-selected direction. The free layer, on the other hand, has a direction of magnetization which is perpendicular with the pinned layer, but is free to move under the influence of an external magnetic field such as that imparted by a passing magnetic recording medium. As the angle between the magnetic directions of the free and pinned layers changes, the electrical resistance through the sensor changes as well. By sensing this change in electrical resistance, the magnetic signal passing by the read element can be detected.
With continued reference to FIGS. 2A and 2C, in order to deliver an electrical signal to the write element or to receive an electrical signal from a read element, a set of electrical head contacts 54 are provided in the surface at the distal end of the head 34. These contacts 54 connect with the suspension trace circuitry 36 at the distal end of the suspension 32. The suspension 32 and the actuator arm 26 together form an arm assembly 33.(see FIGS. 1A and 1B).
The process of manufacturing the heads 34 and assembling them onto an arm assembly 33 causes slight variations in the magnetic directions of free and pinned layers of the spin valve. These changes can have devastating effects on the performance of the read element. In order to ensure correct alignment of the magnetic layers, after all of the Head Stack Assemblies (HSAs) 44 have been assembled the assemblies are passed through a carefully controlled magnetic field which ensures proper alignment of the magnetization within the read element. This process is known as Head Stack Assembly Reinitialization (HSA Reinitialization).
Please note that as used in the following discussion, and throughout this specification, the term xe2x80x9cconfigurationxe2x80x9d will be used to refer to the sequence of read elements and write elements and their contacts in a given head, and this configuration shall not chance regardless of the direction that this head is facing. The term xe2x80x9corientationxe2x80x9d will refer to the order or sequence of elements or contacts presented by a head as it faces in different directions, i.e. facing upwards or downwards.
Note also that there will be a distinction made between an xe2x80x9cup headxe2x80x9d of the prior art and an xe2x80x9cupward facing headxe2x80x9d, and likewise a distinction between a xe2x80x9cdown headxe2x80x9d of the prior art and a xe2x80x9cdownward facing headxe2x80x9d, so that an up head may be used as a downward facing head, or a down head as an upward facing head. In the prior art, up heads and down heads required usually mirror image configurations. For example, an up head 34a facing downward may have a configuration of Rxe2x88x92, R+, Wxe2x88x92 and W+, as shown by the symbols in boxes in FIG. 2D, and a down head 34B, also facing downward in the figure, would then have a configuration of W+, Wxe2x88x92, R+ and Rxe2x88x92, as also shown by the symbols in boxes in FIG. 2C. The xe2x80x9cconfigurationsxe2x80x9d of the up and down heads do not change when the up heads and down heads are turned to face downward. In terms of their xe2x80x9corientationxe2x80x9d, however, the sequences do change, so that an up head now facing upward would now have an orientation of W+, Wxe2x88x92, R+ and Rxe2x88x92, shown by the symbols in parentheses in FIG. 2D, while a down head, now facing upward, would have an orientation of Rxe2x88x92, R+, Wxe2x88x92 and W+, as shown by the symbols in parentheses in FIG. 2C.
Simply put, for this discussion, xe2x80x9cconfigurationxe2x80x9d is fixed by manufacture and xe2x80x9corientationxe2x80x9d is achieved by turning the head rightside-up or upside-down.
Also, please note that for the sake of clarity in this discussion, the term xe2x80x9cmatchingxe2x80x9d will be used in describing a configuration of head, especially in the prior art, which is used in the same orientation for which its configuration is named (i.e., an up head facing upward or a down head used facing downwards). The term xe2x80x9cnon-matchingxe2x80x9d shall be used for the opposite cases (i.e. an up head facing downwards or a down head facing upwards).
With continued reference to FIGS. 1A and 2C, prior art systems require that two sets of heads 34 be used. One set of heads 34a is designed to face upward to read the lower surface of the disk 14, while the other set 34b is designed to face downward to read the upper surface of the disk 14. This required production of two sets of magnetic heads increases production and inventory costs but has been necessitated by several factors.
First, the HSA reinitialization of all heads simultaneously requires that the read elements 46, all face in the same directions in the assembly. This requires that the configuration of the read element 46 in an up head 34a be manufactured in an opposite sequence than that of a sensor in a down head 34b. Simply flipping a head 34 about its longitudinal axis would result in a read element 46 being oriented in the wrong direction.
Second, the orientation of a head 34 is dictated in part by the topography of an air bearing surface 56. FIG. 2E shows an air-bearing surface of a head 34, enlarged. The air-bearing surface includes a pair of rails 58 and has a leading edge 60 and a trailing edge 62. In order to maintain proper flight characteristics it is necessary to have the leading edge oriented into the direction of the oncoming air stream. For this reason it is not possible to simply flip a head about its lateral axis, as this would cause the trailing edge 62 of the air-bearing surface 56 to be oriented into the oncoming air stream.
Third, with reference to FIGS. 1A, 2A and 2C, signals from the contact pads 54 connect electrically with circuitry on the bridge flex connector 40 and circuitry 42 on the E-block 25. This requires that two different sets of heads 34a and 34b be used to ensure that the contacts 54 of both the up head 34a and the down head 34b connect with the appropriate circuitry 42 on the E-block 25.
This use of two different heads 34a and 34b adds to manufacturing expense and time as well as inventory cost. Additionally, oftentimes a manufacturing run will be more successful for one set of heads than another, leading to, for example, a greater inventory of up heads 34a than down heads 34b. Since the prior art requires that an equal number of each type of head be used, many heads become wasted. Valuable time is wasted as well while additional heads are manufactured. Therefore there remains a need for a system for allowing the use of a single configuration of head to be used in either the upward or downward orientation.
The present invention provides a system, and apparatus for using magnetoresistive heads of a single configuration in either an upward direction or a downward direction in a multiple disk magnetic storage device. The invention includes a plurality of arms each supporting a magnetic head. The arms are connected with an actuator which causes them to move about a pivot point to locate the heads in a desired location on the disks. According to the present invention, the arms are of two types. The first type of arm is for use with a head mounted in its xe2x80x9cmatchingxe2x80x9d orientation (i.e., an up head facing upward) and includes circuitry which electrically connects the contact pads of the head with a set of contact pads of a predetermined arrangement on the arm. The second arm is intended for use with a head oriented in other than its xe2x80x9cmatchingxe2x80x9d orientation, for example, an up head used in the downward direction. This second arm includes circuitry, different from that of the first arm, which directs electrical signals from the contacts of its attached head to contacts on the arm in the same predetermined arrangement as on the first arm. In this way any circuitry designed to pick up an array of signals from the first arm will be able to pick up the correct signal from the second arm in spite of the fact that the head of the second arm is being used in a xe2x80x9cnon-matchingxe2x80x9d orientation.
In a preferred embodiment of the invention, the first and second arms each include at their distal portions a suspension. The suspension is a flexible member which is attached at its proximal end, in a cantilevered fashion, to a distal end of an actuator arm and its distal end includes a gimbal for positioning the head. The actuator arm attaches at its proximal end to the actuator for arcuate movement about a pivot point of the actuator in unison with all other such arms similarly attached.
The suspension includes trace circuitry which conducts signals from the head contacts to a set of suspension contacts located on an edge of the suspension. The first and second arm assemblies both use suspensions with the same arrangement of suspension contacts.
Both the first and second arm assemblies include a Bridge Flex Connector (BFC), the BFC of the first arm assembly being unique as compared with that of the second arm assembly. The BFC used on the first arm assembly is a Standard BFC. It attaches at its distal end to the edge of the suspension and includes circuitry which picks up electrical signals from the suspension contacts located on that edge of the suspension. The circuitry of the Standard BFC routes the signals from the suspension contacts to a set of head stack assembly window contacts (HSA window contacts) located on the BFC and arranged in the aforementioned contact arrangement. From the BFC contacts, various circuitry can pick up and deliver signals as needed to record and read data.
The second arm assembly uses an Uni-Wafer BFC. Like the Standard BFC, the Uni-Waver BFC attaches at its proximal end to an edge of the actuator arm and at its distal end to an edge of the suspension. Also similar to the Standard BFC, the Uni-Wafer BFC picks up signals from the suspension contacts and includes circuitry which routes those signals to HSA window contacts arranged in the same predetermined arrangement as the Standard BFC at a location along the length of the Uniwafer BFC. The circuitry of the Uni-Wafer BFC, however, differs from the circuitry of the Standard BFC.
Because the head used on the second arm assembly has been flipped over and is not in its standard, matching orientation, the arrangement of the signals delivered to the suspension contacts from the head contacts will be different on the second arm than on the first arm. For example, if the head contacts are arranged on the head such that the suspension circuitry delivers that signal to the most distal contact in the suspension contact arrangement of the first arm assembly, that same signal would end up at the most proximal contact in the arrangement of suspension contacts on the second arm.
This is the reason that the circuitry of the Uni-Wafer BFC is different from the circuitry of the Standard BFC. The circuitry of the Uni-Wafer BFC picks up an arrangement of signals from the suspension of the second arm assembly which is essentially the mirror image of the arrangement of signals provided on the suspension of the first arm assembly. The circuitry of the Uni-Wafer BFC then routes those signals so that they appear in the same predetermined arrangement at the HSA window contacts as is delivered to the HSA window contacts of the first arm using the standard BFC.
An alternate embodiment of the invention also provides first and second arms. However this embodiment uses a Long Tail Trace Suspension Assembly (Long Tail TSA), and does not include a BFC. This embodiment includes a Standard Long Tail TSA in conjunction with an Uni-Wafer TSA. The Standard Long Tail TSA holds at its distal end a head which is mounted according to its matching orientation. The Standard Long Tail TSA includes circuitry which routs signals from the head contacts to a series of TSA window contacts, the signals arriving in a predetermined arrangement at the TSA window contacts. The circuitry resides on a thin stainless steel plate which is affixed to a suspension, thus forming the long tail trace suspension assembly. While the preferred embodiment employs a stainless steel plate, those skilled in the art will appreciate that the plate could be constructed of many other materials.
The Uni-Wafer Long Tail TSA holds at its distal end a head which is mounted opposite to its matching orientation, (i.e. flipped about its longitudinal axis). The Uni-Wafer Long Tail TSA includes circuitry which picks up signals from the contacts of this head (which are arranged as a mirror image of those of the head of the first arm) and routes those signals to a series of TSA window contacts located along the length of the Uni-Wafer TSA. As with the Standard Long Tail TSA, the circuitry of the UniWafer Long Tail TSA resides on a thin plate which is affixed to a suspension to form the TSA. The circuitry of the Uni-Wafer Long Tail TSA is routed such that the predetermined arrangement of signals at the Uni-Wafer TSA contacts is the same as the predetermined arrangement of the contacts of the Standard Long Tail TSA.
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USPTO Backgrounds