READ AND WRITE HARD DISK BY MULTIPLE AND PARALLEL MAGNETIC HEADS

Field of the Invention

The present invention relates to the filed of computers hardware. More particularly, the present invention relates to an apparatus for reading and writing on magnetic hard disks by using an array of multiple and parallel read and write heads.

Background of the Invention

The hard disk, or any other storage device that comprises magnetic disks, consist of many concentric tracks, in which information can be stored on, or from which information can be extracted. The information is stored/extracts by a corresponding read/ write head, comprises one or more read/write heads for each side. The read/write head consists of a magnetic sensor constructed on a slider that guides the head by keeping it in a fix height and position above the disk surface. The head is normally installed on the distal end of an arm while the proximal end of the arm is connected to an actuator that rotates around an actuator axis, thereby allowing the head to be located above each track of the disk.

The hard disk platter may have a radius of about 30 mm, and consists thousands of tracks, with a very small scale width, making the accuracy of tracking an important parameter. The tracks, like any other shaped material, have a certain tolerance, and are not exactly concentric. Furthermore, the actuator axis and the arm also have a certain tolerance, making accurate tracking even harder. Another problem that makes the tracking difficult is the thermal instability of the platter and the tracks, which may expand or shrink according to the ambient temperature. This thermal effect changes the tracks' diameter and makes it even more difficult for the arm and the read/write head to follow the tracks' center.

Many read and write systems that comprise a plurality of heads for reading and writing information, are described in the art. Generally, they do not offer ways to overcome the lack of accuracy during reading and writing process due to the above mentioned reasons.

WO 01/41142 describes a reading/recording apparatus with a number of angularly spaced brackets, each carrying a number of reading/recording heads, radial positioned corresponding to the disk platter. This apparatus provides a fix positioned heads in the brackets, making it hard to follow in changing diameter tracks.

Another example is US 7,102,842, in which a multi-head actuators device is disclosed. However, this device relates to the tracks as symmetrical and coincident tracks, and do not deal with the problem of changing diameter of tracks. Furthermore, the plurality of actuators mounted on a single platter increases the tolerance and decreases the level of accuracy.

It is therefore an object of the invention to provide an apparatus with multiple read/write heads that can accurately track on the center of tracks while overcoming their changing diameter.

It is another object of the invention to provide an apparatus with multiple read/write heads that includes a mechanism for achieving high accuracy during read/write processes.

It is a further object of this invention to provide an apparatus with multiple read/write heads that can achieve maximum transfer rate within its structural limits.

Other objects and advantages of present invention will appear as description proceeds.

Summary of the Invention

The present invention is directed to an apparatus for performing read/write operations of data to/from data tracks of a disk, such as a magnetic disk, for storing data, that comprises: an array of read/write heads, each of which connected to a gripping clip; a radial arm for carrying the array above the surface of the disk, such that each clip can be individually displaced in a radial direction that essentially coincides with the radius of the disk; an actuator for providing a moving force to each clip, required for the displacement; and a controller, for continuously keeping heads of the array essentially above their corresponding data tracks, by individually and continuously controlling the transfer of the moving force to each head in the direction.

Each head may consist of a sensor (e.g., that may be magnetic and employ GMR materials) for reading/writing data and a vertical displacement control device for carrying the sensor in a fix height above the surface of the disk.

The arm may consist of:

a first controllable common shifting mechanism connected to all clips by a common member, for concurrently shifting all heads up to a predefined displacement in a first radial direction by shifting the member; and a plurality independently controllable shifting mechanisms, each of which connected to a clip, for individually shifting each head up to the predefined displacement in a similar or an opposite radial direction.

The first controllable common shifting mechanism may comprise a damping mechanism like a spring or an actuator (such as an electric motor or a piezoelectric element, or ), locked at one side for pushing the common member to one direction and a damping mechanism like a spring or an actuator locked at the other side for pushing the common member to the opposite direction.

Each independently controllable second shifting mechanism may be locked at one side to the common member.

The actuator may be made of elements that move by controlling their temperature and may be made from materials (e.g., metals) with an appropriate thermal expansion coefficient.

Brief Description of the Drawings

The above and other characteristics and advantages of the invention will be more readily apparent through the following examples, and with reference to the appended drawings, wherein: Fig. 1. is a schematic top view of the array of heads above the disk's platter, forming the multiple heads apparatus, according to one embodiment of the apparatus ; Fig. 2. is a schematic side view of the array of heads according to one embodiment of the invention; Fig. 3. is a schematic side view of the array of heads and the heads compound in it possible course of movement, in relation to the disk's radius;

Fig. 4. is a schematic plan view of prior art tracks of the disk; Fig. 5. is a schematic plan view of prior art tracks of the disk divided into sectors;

Fig. 6. is a schematic perspective view of prior art hard disk formation; Fig. 7A (prior art) schematically illustrates data management on a conventional disk; and

Fig. 7B schematically illustrates data management on a disk, according to one embodiment of the apparatus.

Detailed Description of Preferred Embodiment

The apparatus proposed by present invention comprises an array of heads which contains read and write units that is controlled by an appropriate controller. Each unit is assembled from a lock, a gripping clip, an independently controllable shifting mechanism, a spring and a read/write head. The array of heads substitutes the standard actuator arm, common in regular hard disks. The array of heads forms a type of a radial arm that is placed along the radius of the disk platter, between the center of the platter by a horizontal spring or any other damping mechanism, and its outside perimeter, by a small motor or any other mechanism. The array of heads will perform a radial movement towards the center of the disk and back in response to a moving force, for enabling the heads to follow the tracks on the platter.

When the disk starts to operate and revolve, the array of head or only the heads can be lowered so that the heads, are placed and stabilized at the desired height above the disk surface by an appropriate vertical displacement control device. The heads can move along the vertical axis by a spring or any other mechanism. The heads can be moved in radial direction, individually in every read and write units or simultaneously with the array of heads. The heads comprises a slider which slides on the disk platters, and on it or in it, a sensor for transmitting information from/to the tracks. When the disk stops to operate, the array of heads or

only the heads can be raised from the disk surface, preventing physical contact with the disk. Each side of the disk platter has its own array of heads. Each array of heads can be driven by a separate motor.

The array of heads can be pushed by the a common motor for all platters and arrays thereof.

The engine of the array of heads can be realized by any type of motor.

The information is arranged and divided to little fragments called sectors. The sectors are then written on the disk. In this invention, the arrangement of the information is made by dividing the sector in such manner that enables each read/write head to "handle" a part of the sector. However, the sector can be divided to unequal parts so that each head handles a different amount of information. This can be because the inner heads have to pass less circumferential distance around the center of the disk than the distance of the outer heads at the same time. So the outer heads can pass more information than the inner heads thereof.

The data can be written in parallel, not only to heads on each side of a platter but also to all sides of the whole platter.

Fig. 1 illustrates a disk's platter (10), preferably magnetic hard disk, that enables reading and writing information capability. Disk's platter (10) rotates around axis (16), by conventional drive spindle (not illustrated). The array of heads (15),is placed in radial orientation to the disk platter (10), held horizontally optionally between spring house(ll) and motor house (12). The array of heads (15) preferably comprises read and write heads within read and write units (not shown). The array of heads (15) can be displaced in a radial direction by a first controllable common shifting mechanism, pushed by motor (14), housed in motor house (12), towards the center (16) of disk platter (10), and retreats back in a radial direction by spring (13), housed in spring house (11). This radial movement, enables the array of heads (15) to cover any track within the disk platter (10) radius, and enables the read and write heads to access the area that stores information at disk platter (10).

When disk (10) is inactive and is not rotating, the array of heads (15) or only the heads can be raised from the disk surface(lθ) in order to prevent a physical contact with disk surface (10). When disk (10) is active and rotates around axis (16), the array of heads (15) can be lowered, to thereby enable the read/write heads to be stabilized at desired height from disk (10) surface.

Fig. 2 illustrates by a cross-section view of the array of heads (15), according to an embodiment of the invention. The array of heads (15) can comprise 10 read/write units (21) in this illustration. Each read/write unit (21) comprises read/write head (20) which is perpendicularly attached to gripping clip (23) by a spring, preferably "vertical spring" (22). Clip (23) can be horizontally moved by a shifting mechanism (24) in order to place the head above the center of each desired track (not shown) of the disk. Lock (25) serves as a fixed mechanical point that the shifting mechanism (24) is horizontally attached to.

The shifting mechanism (24) enables a relatively small horizontal displacement of each read/write head (20), that also simultaneously moves with the array of heads (15). By using the small displacement, each head (20) can be placed exactly above the center of it's track. This small displacement is needed because of the changing temperature of the disk and of the array of heads, causing a certain amount of deformation, linear expansion and a change in structure dimension with temperature. Shifting mechanism (24) can be any type of motor or material with elastic features and displacing capabilities of objects such as a piezoelectric mechanism or a thermal mechanism.

Spring (22) holds the read/write head (20) at horizontal axis firmly above the track (not shown), and allows vertical displacement for setting the

height above the disk surface. Spring (22) is preferably a flat spring, that enables a firm holding of the read/write head (20) slider, thereby preventing horizontal deviation, and allows said slider to adjust its height above varying heights of the disk's surface.

The read/write head (20) preferably comprises a slider and a sensor (not shown). Said sensor can be Giant Magneto Resistive (GMR) materials, materials made up of very thin, alternating layers of various metallic and nonmetallic elements with significant variations in resistance. These properties help controlling a sensor that responds to very small rotating on the disk. The magnetic rotation yields a very large change in sensor resistance, which in turn provides a signal that can be picked up by the electric circuits in the disk or any other type of sensor. The slider orientation in the read/write head (20) sets the position of the sensor according to the position of the slider. The radial position of head (20) on its corresponding tracks, is set by two parameters: coarse movement that occurs when the read/write heads (20) moves simultaneously with the array of heads (15), and fine movement that occurs when each head (20) moves independently by the shifting mechanism (25).

Two control loops are used to control the displacement of each head. The first control loop is closed between one head's (preferably one of the middle heads) feedback when reading it's placement on the track beneath it, and

the motor (14) used to drive the array (15). The second control loop is closed separately on each head's (20) feedback when reading it's placement on the track beneath it, and the shifting mechanism (24).

A calibration process can be made at the time of the production of the disk, in order to map every track to its head and to its sector. Each head (20) is set to read and write from its predetermined track in a certain sector, and the two control systems will set the heads (20) at the desired place during manufacturing.

It is obvious that the number of read/write units (21) is optional, and numeral 10 designates read/write units is for illustrative means only.

Fig. 3 illustrates the preferred movement of the array of heads (lδ) in relation to the disk platter's (10) radius. According to an embodiment of the invention, array (15) length of movement Ll (29) , should be at least as the length between two consecutive heads (20). By this movement, heads (20) installed on array (15), can cover the entire hard disk (10) radius. For example, in case when 10 read/write heads (20) are included in an array of heads (15) constructed on disk platter (10) with a 30mm radius, the array's (15) movement should be 30/10 = 3 mm only. Longer length than two consecutive heads (20) of Ll (29), can be used to allow one head to

read from the tracks of its neighboring head. The main goal is to overcome problems or errors when reading from a defective head.

Figs. 4, 5a, 5b and 6 illustrate prior art implementations of hard disks. Tracks (30), sectors (40) that are divided from tracks (30), and standard actuator (51) and actuator head (52) thereof. In a conventional disk, the platter is divided into tracks (30) and tracks are divided to sectors (40). This division is used to specify locations on the hard disk and to allocate disk space to files. The number of sectors can be the same for all tracks, but usually hard disks put more sub- sectors in outer tracks. Generally all sectors have of the same physical size that holds 512 Bytes, so more sectors can fit in the longer outer tracks. The size of the sector (40) in the disk platter (10) is bigger due to error correction mechanisms and a servo data for the control loop mechanisms. Each surface of a platter is divided into tracks (30) and sectors (40) in the same way, as shown in Fig. 7A. Most of the files are fragmented (i.e., stored in several places on the disk).

Theses illustrations are provided for understanding the concepts and it's relation to the present invention.

Fig. 7B schematically illustrates the data arrangement on the disk, according to the preferred embodiment of the invention. In contradiction to conventional data arrangement shown in Fig. 7A, the arrangement of

information in disk (10) is made by dividing the sector (40), in such manner that each head gets a part of the sector (40). The sector can be divided to equal or to unequal parts. The dividing to unequal parts can be, because each head (20) can handle a different amount of information. This is because the inner heads that are closer to the center of the disk, pass less circumferential distance about the axis of disk (10) than the circumferential distance that the outer heads pass at the same time. So the outer heads can forward more information than the inner heads.

In order to allow read/write operation within a sector in a high data rate, the sector may be divided to portions, such that each head in the array of heads (15) will handle a corresponding portion and all heads will concurrently perform read/write operation. This way, the data within a sector will be distributed within sub-sectors, as shown in Fig. 7B. Sub- sector 1 will be read/written by head 1, sub- sector 2 will be read/written by head 2, and so forth. For example, if there are 10 heads in the array (15) and 1000 tracks in each surface of a platter, each head in the array (15) will be controlled to read/write 100 sub-sectors in a specific "region of sector" (70) (head 1 will read/write sub-sectors 001-100, head 2 will read/write sub-sectors 101-200 and so forth, until head 10 that will read/write sub-sectors 901-1000). During one disk revolution, the location of head 1, head 2,..., head 10 will be controlled to read/write sub- sectorOOl, sub-sector 101, , sub-sector 901, respectively. The location of

head 1, head 2,..., head 10 will be controlled at other revolution to the next sector in this "region of sectors" (70) to read/write sub-sector 002, sub- sector 102,...., sub-sector 902, respectively, and so forth. This way, the data gathered from sub-sectors 001, 101, , 901 will form sector 1, the data gathered from sub-sectors 002, 102, , 902 will form sector 2, and so forth, until 100 sectors are formed. The individual control of each head in the array, as proposed by the present invention, allows concurrent read/write operations performed by all heads within a plurality of the array of heads (15), each of which assembled above the surface of a platter. This arrangement dramatically increases the rate of read/write operations within a disk with multiple platters. The rate of read/write operations may be even further increased by using several array of heads (15) distributed above each surface of each platter, while allowing all of them to perform concurrent read/write operations.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out\ carried into practice with many notifications, variations and adaptations, and with the use of numerous equivalents or alternative solution that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.