Abstract:
A head suspension assembly including a head and a suspension coupled to the head to support the head to fly above the disc surface for operation. The head includes a slider having a bearing surface and a transducer having a transducer element. The suspension supports the head at a pitch angle determined so that close point between the head and disc surface is located at the slider spaced from the transducer. In one embodiment of the head suspension, the suspension supports the head during operation at a pitch angle θ P ≦(d R −d W )/d A-B −4 d C /l to avoid transducer contact with media asperities with mean roughness.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. Provisional Application Ser. No. 60/067,696, entitled “PROXIMITY MR CONCEPT: DISPLACED CONTACT CONCEPT,” filed Dec. 4, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to data storage systems. In particular, the present invention relates to a head suspension assembly for supporting transducers for reading and writing information to a data disc. 
     Data storage systems are known which include transducers supported relative to a disc surface for reading and writing information. Known transducer elements include inductive-type transducers and magnetoresistive (“MR”) transducer elements. The transducers are supported via a slider coupled to a suspension assembly. The slider includes a bearing surface for lifting the slider above the disc surface. As the disc spins, air flows under the bearing surface to raise the slider (and transducer elements) relative to the disc surface to fly over the disc surface for read and write operations. The suspension assembly includes a load beam which supplies a load force to counter the hydrodynamic lifting force to provide a stable lift height and pitch angle for operation of the slider. 
     It is important for operation that the slider fly in close proximity to the data surface to provide the desired resolution. During operation of a disc drive, the slider may contact or slap the disc media due to vibration or shock. Contact of a slider with a disc surface may wear the slider and may damage the transducer elements of the slider. Contact between a magnetoresistive head and a disc surface may cause thermal asperities corrupting signals read from the disc surface. Thus it is desirable to limit contact of transducer elements supported at a trailing edge of the slider while providing desired read/write resolution for operation of the disc drive. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a head suspension assembly including a head having a transducer and suspension means for supporting the head to fly above the disc surface for operation of a transducer element of the transducer. The suspension means supports the head to limit contact interface between the transducer and disc surface of the disc. In a preferred embodiment of the head, the suspension means supports the head during operation at a pitch angle θ P ≦(d R −d W )/d A-B −4d C l to avoid transducer contact with media asperities with mean roughness. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a data storage system. 
     FIG. 2 is a perspective view of an actuator block supporting heads for operation of a data storage system. 
     FIG. 3 is a perspective view of a head. 
     FIG. 4 is a side illustrative view of a head suspension assembly. 
     FIG. 5 is a side illustrative view of a trailing edge portion of a head illustrating a recessed transducer supported via a slider. 
     FIG. 6 is similar to FIG. 5 with the head shown at a pitch angle θp. 
     FIG. 7 is similar to FIGS. 5-6 with the head shown at a pitch angle θp=θ A-B . 
     FIG. 8 is a side illustrative view of a trailing end portion of a head having a crown. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention relates to a data storage system and, in particular, has applications to a disc drive  50  for storing digital information as shown in FIG.  1 . As shown, disc drive  50  includes a base  52 , a disc stack  54 , and rotary actuator  56 , which supports heads  58  relative to surfaces of discs of disc stack  54  to read and write information to and from discs. Heads  58  are coupled to a flex circuit  60 , which is coupled to circuitry  61  of the disc drive for read and write operations. 
     In particular, in the embodiment shown, the rotary actuator  56  includes an actuator block  62  and a voice coil motor  64  for movement. Heads  58  are supported relative to the actuator block  62  via a plurality of stacked actuator arms  66 . The heads  58  are coupled to the actuator arms  66  via suspension assemblies  68  in a known manner. Operation of the disc drive rotates the actuator block  62  about an axis  70  for positioning heads  58  relative to selected data tracks on the disc surface via operation of the voice coil motor  64 . FIG. 2 is a detailed perspective view of the actuator block  62 , which illustrates heads  58  supported via suspension assemblies  68  coupled to actuator arms  66  to define head suspension assemblies. As shown, heads  58  include a slider  72 , which supports transducer elements for read and write operations. 
     FIG. 3 illustrates an embodiment of a head  58  including slider  72 . Slider  72  includes an upper surface  74 , an air bearing  76 , a leading edge  78 , and a trailing edge  80 . As shown, bearing  76  includes raised side rails  82 ,  84 , and center rail  86  forming the bearing surfaces of the bearing  76 . Raised side rails  82 ,  84  and center rail  86  are elevated above a recessed bearing cavity or base  88 . The bearing  76  also includes a tapered edge  90  at leading edge  78  for providing lift for “take-off” from the disc surface in a known manner. The slider is formed of a ceramic substrate material, such as a mixture of TiC (Titanium Carbide) and Alumina (Al 2 O 3 ), or other known slider materials. The bearing surfaces (side rails  82 ,  84 ; center rail  86 ; and surface  90 ) are formed by known subtractive masking techniques such as milling or chemical etching. 
     Transducer elements  92  (illustrated diagrammatically) are supported proximate to the trailing edge  80  of the slider to form head  58 . Transducers may be inductive-type transducers or magnetoresistive-type (“MR”) transducers. Preferably, transducer elements  92  are embedded in an Alumina layer to form the transducer  94  which is deposited on the trailing edge  80  of the slider via known deposit techniques. 
     Slider  72  is coupled to suspension assembly  68  at upper surface  74  of the slider so that air bearing  76  faces the disc surface. As the disc rotates, the disc pulls a very thin layer of air beneath the air bearing surface, which develops a lifting force that causes the slider  72  to lift and fly several microinches above the disc surface. In particular, skin friction on the air bearing surfaces causes air pressure to develop between the disc and the air bearing surfaces to provide lift to the slider to raise the slider to fly above the disc surface for proximity recording. The disc rotates as illustrated by arrow  96  of FIG. 1 to cause air to flow from leading edge  78  to trailing edge  80  for flying operations of heads  58 . 
     The slider is supported via the suspension assembly to fly at a pitch angle relative to the disc surface  54 . FIG. 4 illustrates the slider  72  supported via a load beam  98 . Load beam  98  is secured to actuator arm  66  (not shown in FIG. 4) to form a portion of the suspension assembly  68 . The slider  72  is flexibly supported relative to the load beam  98  via a gimbal spring  100  in a known manner. In particular, the gimbal spring  100  includes a portion  102  coupled to load beam  74  and a tab portion  104  coupled to slider  72 . Tab  104  is flexibly coupled to portion  102  to flexibly support the slider  72  secured to tab portion  104  to allow the slider to pitch and roll relative to the disc surface. An extended end  106  of load beam defines a load point for loading slider  72  to bias the slider toward the disc surface. End  106  defines a point about which the slider  72  pitches. Thus, pitch angle of slider may be adjusted by shifting the load point position of the load beam  98  on the slider  72   
     FIGS. 5-7 are exaggerated views of a trailing end portion of the head  58 . The transducer  94  is recessed from the bearing surfaces (side rails  82 ,  84  and center rail  86 ) a distance d R  as illustrated in FIG.  5 . The trailing edge portions of the lower surface of the slider and transducer  94  are referenced as Point A and Point B respectively. The longitudinal distance between Point A and Point B is defined as d A-B . 
     The angle θ A-B  defining the relationship between Point A of the slider and Point B of the recessed transducer as illustrated in FIG. 5 is provided by: 
     
       
         Tan θ A-B =d R /d A-B   
       
     
     where: 
     d R —is the dimension of the recess of the transducer from the bearing surface of the slider; and 
     d A-B —is the distance between the slider Point A and the transducer Point B. 
     Since θ is relatively small, tan θ≈θ so that θ A-B =d R /d A-B . For desired clarity, it is desirable that transducers elements  92  be positioned in close proximity to the disc surface  54 . This is particularly important for operation of MR transducers. During operation, the slider may contact the disc surface. The head generally contacts the disc surface at a close point of the head and disc surface. Close point refers to the lowest or closest position of the head relative to the disc surface. In past slider designs the transducer is the close point for desired operation clarity. 
     FIG. 6 illustrates a head similar to that shown in FIG. 3 flying at a pitch angle θ P . At the pitch angle θ P  shown, Point B of the transducer defines the close point relative to the disc surface, since at θ P , h B  (height of Point B) is less than h A  (height of Point A). Since the transducer defines the close point, the transducer generally contacts the disc surface during shock or head slap thus wearing the Alumina or protective layer encapsulating the transducer elements. Contact between an MR head and disc surface causes thermal asperities degrading read operations by corrupting the signal from the transducer. 
     Thus it desirable to limit contact interface between the transducer and disc surface. Various techniques have been proposed to limit damage to the transducer elements via contact between a head and disc surface. The present invention provides a head suspension assembly which supports transducer elements proximate to the disc surface for desired read and write clarity and provides increased protection for the transducer elements of a head and reduces thermal asperities for an MR head. The head suspension of the present invention includes a suspension assembly supporting the head to fly at a pitch angle θ P ≦θ A-B  determined as follows: 
     
       
         θ P ≦d R /d A-B   
       
     
     θ P  is calculated so that Point A of the slider provides a desired contact interface removed from the transducer elements as illustrated in FIG.  7 . Thus, as illustrated the height of Point B from the disc surface is greater than or equal to Point A or h B ≧h A  so that Point A provides a contact interface for reducing thermal asperities and head damage. 
     As illustrated in FIG. 8, sliders tend to have a curvature or crown  110  (which is greatly exaggerated in FIG. 8) due to stresses introduced during the fabrication process. The crown  110  is aligned along the longitudinal axis (extending from the leading end to the trailing end of the slider) so that the trailing edge  80  is arched relative to a portion of the slider. As shown in FIG. 8, angle θ C  is the angle of the crown, as provided by: 
     
       
         Tan θ C =(d C l/4) or 4d C /l 
       
     
     where: 
     d C —is the dimension of the crown as illustrated in FIG. 8; and 
     l—is the length of the slider and l/4 approximates the distance of the crown at the trailing end of the head. 
     Since θ is small, Tan θ C  is approximated by θ C  so that θ C =4d C /l. In a preferred embodiment of the head suspension assembly of the present invention, θ P  is determined to compensate for the crown, as follows: 
     
       
         θ P ≦d R /d A-B −4d C /l 
       
     
     so that h A  of Point A is equal to or less than h B  of Point B so that the slider (Point A) is the close point for contact interface. Preferably θ P  approximates d R /d A-B −4d C /l so that the transducers fly at an optimum distance from the disc surface for optimum resolution. During operation of the slider, repeat or continued contact of the slider with the disc surface at Point A tends to wear slider at Point A as illustrated by dashed line  114  in FIG.  8 . Wear of the slider at Point A alters the close point or geometry of the contact interface of the slider. Thus, the pitch angle may be designed to compensate for wear in to maintain the contact interface at Point A away from the transducer at Point B. Thus, in a preferred embodiment of the present invention, θ P  is determined as follows: 
     
       
         θ P ≦(d R −d W )/d A-B −4d C /l 
       
     
     where: 
     d R —is the dimension of the recess between Point A of slider and Point B of transducer; 
     d W —is the wear height reducing the recessed dimension of the transducer; 
     d A-B —is the longitudinal axis distance between slider Point A and transducer Point B; 
     d C —is the height of the crown; and 
     l—is the length of the slider as illustrated in FIG. B. 
     Thus, the suspension assembly supporting a head is designed to provide a pitch angle θ P  which provides a substrate close point to limit damage to the transducer elements during head slap or shock. The head suspension assembly of the present invention as described limits wear of the encapsulating material of the transducer and reduces the thermal asperities for MR heads. The pitch angle should maintain the transducer elements in sufficient proximity to the disc surface for desired resolution. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.