COMPOSITE MAGNETIC HEAD DEVICE

Abstract: A composite magnetic head device consisting of a recording magnetic head and a reproducing magnetic head as a unitary structure, wherein the magnetic gap is narrowed to improve relation relative to a magnetic medium and to offer advantage in regard to reducing the size, facilitating assembly, and increasing the precision, on a first magnetic shield plate (SH1) are mounted a recording magnetic head element (1R), an accompanying integrated circuit (32) and the like to constitute a recording head portion. On a second magnetic shield plate (SH2) are mounted a reproducing magnetic head element (1P), an accompanying integrated circuit (35) and the like to constitute a reproducing head portion. The two portions are joined at the back surfaces of the first and second shield plates, and are held in a shield case (80). Surfaces to oppose to the magnetic medium are generated on the recording head portion and the reproduc­ ing head portion by the cylindrical grinding.

Description: The present invention relates to a combination magnetic head apparatus with a combination magnetic head apparatus comprising a recording head portion with a recording magnetic head element portion, a recording intergrated circuit and a capacitor and a reproducing head portion with a reproducing magnetic head element portion, a reproducing integrated circuit and a capacitor, whereby said recording magnetic head element portion includes thin film magnetic head elements formed on a magnetic substrate and a protective substrate is bonded thereto so as to cover the same and said reproducing magnetic head element portion includes thin film magnetic head elements formed on a substrate and a protective substrate is bonded thereto so as to cover the same. The GB-A-2 130 425 discloses a combination magnetic head apparatus in which a recording magnetic head and a reproducing magnetic head are integrated in one body. In Fig. 1 which is a schematic representation of its location and construction, respective magnetic gaps GR and GP of a recording magnetic head HR and a reproducing magnetic head HP are arranged along the direction as shown by an arrow a in Fig. 1 along which a recording medium is transported. The GB-A-1 339 091 relates to a bidirectional magnetic head for use with magnetic tape drives. This head comprises a first portion having a contour defined by a first constant radius extending from a first center of radius on a base line and a second portion having a contour defined by a second contant radius extending from a second center of radius on said base line. Transducing elements for reading information and writing information are placed perpendicular to the base line provided parallel with each other. The contact surfaces of the recording and reproducing head portions are polished around a reading circle center and a writing circle center. The read gap arc and write gap arc are different so that the surface of the bidirectional magnetic head is asymmetric. Thus, the manufacturing of head is not easy and the contact of the heads with the tape is poor. The JP-A-5924418 discloses a thin film magnetic head with a thin film recording and a thin film reproducing head. Each head comprises a basis, substrates, a thin film channel each head provided with a gap. The recording head and the reproducing head is bonded on one common field plate provided between the heads. For exactly positioning the heads on the shield plate it is necessary, to provide a frame in wich the heads and the shield plate are provided during manufacturing the magnetic thin film head. For securing the localisation of the heads and the shield plate resin is filled in the free space between the frame and the recording and the reproducing head, whereby the recording head and the reproducing head are arranged parallel to each other. This way for producing combined magnetic heads is rather expensive. Producing combination magnetic heads with more than one thin film for each reproducing head or recording head respectively ist difficult. It is the object of the invention to provide a combination magnetic head apparatus of the above type which allowes easy manufacturing and guarantees good contact of the recording magnetic head element portion and the reproducing magnetic head element portion with the magnetic medium, whereby a compact structure of such an combination magnetic head apparatus is possible. The combination magnetic head apparatus of the present invention with the above discribed features is characterized in that said recording head portion is bonded on one surface of a first magnetic shield plate, said reproducing head portion is bonded on one surface of a second magnetic shield plate, said recording head portion and said reproducing head portion are bonded together on the other surfaces of said first and second magnetic shield plates and the overall arrangement thereof is incorporated into a shield case, the depth direction of said recording head portion and the depth direction of said reproducing head portion are provided parallel with each other, said recording head portion is provided with a magnetic medium contact surface by cylindrical polishing around a polishing center displaced from an extension of the depth direction of the magnetic gap in one direction by a predeterminded length and said reproducing head portion is respectively provided with a magnetic medium contact surface by cylindrical polishing around a polishing center displaced from an extension of the depth direction of the magnetic gap by said predetermined length in a direction opposite to the direction of the length of the recording head portion. The recording magnetic head element portion and the reproducing magnetic head element portion of the inventive combination magnetic head apparatus can be brought in contact with the magnetic medium satisfactorily and can be attached easily. The magnetic gaps can be narrowed and the apparatus can be made small in size. Fig. 1 is a layout representation of a prior art combinatoin magnetic head apparatus, Fig. 2 is a partly sectioned side view of an embodiment of a combination magnetic head apparatus according to the present invention, Figs. 3 and 4 are a cross-sectional view and a plan view of an example of a recording head portion thereof, Figs. 5 and 6 are like cross-sectional view and plan view of a reproducing magnetic head portion thereof and Fig. 7 is an explanatory diagram showing a polishing state of a contact surface of a magnetic gap of a magnetic head apparatus according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a combination magnetic head apparatus according to the present invention will be described with reference to Fig. 2 and the followings. In the figure, reference numeral 31 designates an overall arrangement of the combination magnetic head apparatus of the present invention. In the present invention, a recording head portion and a reproducing head portion are formed on a first magnetic shield plate SH₁ and a second magnetic shield plate SH₂. Each of the first and second magnetic shield plates SH₁ and SH₂ is formed of a plate-shaped member having a highly accurate flatness and made of high magnetic permeability soft magnetic material, such as permalloy. A recording magnetic head element portion 1R is attached to a front end of one surface of the first magnetic shield plate SH₁, while a ceramic substrate 34 on which accompanying electrical parts such as a capacitor 33 for stabilizing a voltage source of a recording integrated circuit 32 and so on are mounted is attached to the rear end thereof. Also, a reproducing magnetic head element portion 1P is attached to a front end of one surface of the second magnetic shield plate SH₂, while a ceramic substrate 37 on which accompanying electrical parts, such as an integrated circuit 35 for reproducing, a capacitor array 36 for deriving a signal and so on are mounted is attached to the rear end portion. Conductive patterns are formed on these ceramic substrates 34 and 37 to interconnect the respective integrated circuits 32 and 35 and the circuit elements, that is, capacitors 33 and 36 and so on with predetermined patterns. Respective parts are connected through, for example, lead wires 70 and 71 with a predetermined interconnection relationship, whereby to form the circuits accompanying with the respective heads. The recording magnetic head element portion 1R is, as shown in, for example, Fig. 3 which is an enlarged plan view thereof and Fig. 4 which is a plan pattern view thereof, formed such that electromagnetic induction type thin film magnetic head elements hr corresponding to a large number of channels are arranged in parallel to each other on a magnetic substrate 11 made of Mn-Zn ferrite, Nn-Ni ferrite and so on. In this case, on the substrate 11, there is formed a groove 12 which is filled with a non-magnetic material 13, for example, glass. The grove 12 is formed in the substrate and filled by the glass to form a common planar surface 11a with the substrate 11 and extended along the longitudinal direction of the substrate 11. When the substrate 11 has conductivity, on the major surface 11a of the substrate 11, there is deposited a non-magnetic insulating layer 14 such as SiO₂ and the like on which conductor means 15 is deposited. This conductor means 15 is formed of, for example, a band-shaped thin film conductive member 16 which becomes a bias coil common to all channels (tracks) and a band-shaped thin film conductive member 17 which becomes a signal coil prepared to each channel. These conductive members 16 and 17 are arranged at least partly to be laid along the groove 13. A thin film magnetic layer 18 made of such as permalloy and the like is formed across the groove 13 and the conductor means 15 formed thereon in association with each channel. In this case, an insulating layer 19 such as SiO₂ and the like is deposited on the conductor means 15 to electrically insulate the same from the thin film magnetic layer 18. One end of each magnetic layer 18 forms an operational magnetic gap GR through a non-magnetic gap spacer 20 formed, for example, by the insulating layer 19 between it and the substrate 11, while the other end thereof is magnetically and tightly coupled to the surface 11a of the substrate 11 via a window 21 bored, for example, through the insulating layers 19 and 14. In this way, the common substrate 11 and each magnetic layer 18 constitute each closed magnetic path and thereby the magnetic head element hr of each channel is formed. On each magnetic head element hr , there is bonded a protective substrate 22 having excellent wear-proof property through a bonding agent 23 in opposing relation to the substrate 11. These substrates 11 and 22 are polished to form a magnetic medium contact surface 4R to which the magnetic gap GR is faced. Both end portions 16a, 16b and 17a, 17b of the thin film conductive members 16 and 17 of the conductor member 15 are, on the other hand, extented to the rear side edge of the substrate 11 to form terminals which are respectively connected to the external circuits, for example, to the recording integrated circuit 32 mounted on the aforesaid ceramic substrate 34. In this case, the width of the protective substrate 22 is selected to be narrower than that of the magnetic substrate 11 to thereby expose the respective terminals 16a, 16b and 17a, 17b outside the protective substrate 22. The terminals 16a, 16b and 17a, 17b extended on this substrate 11 are respectively connected through the lead wires 70 to the circuit portions formed on the ceramic substrate. While, the reproducing magnetic head element portion 1P is formed, as shown in Fig. 5 which is an enlarged cross-sectional view thereof and Fig. 6 which is an enlarged plan view thereof, such that in response to the respective head elements hr of the aforesaid recording magnetic head element portion 1R, reproducing magnetic head elements hp corresponding to the respective channels are arranged on a common substrate 41. The substrate 41 is made of, for example, Ni-Zn ferrite or Mn-Zn ferrite and the like. When this substrate 41 has conductivity, through an insulating layer 42 such as SiO₂ or the like on this substrate and then on a bias conductive member 43 made of a band-shaped conductive film which becomes a bias magnetic field generating current path for applying a bias magnetic field to an MR thin film element 45 which will be described later, there is formed through an insulating layer 44 the MR thin film element 45 made of such as Ni-Fe alloys, Ni-Co alloys or the like and having a magneto-resistance effect. On this MR thin film element 45, there are respectively formed through a thin insulating layer 46 a pair of magnetic layers 47 and 48 made of, for example, M₀ permalloy which becomes a part of magnetic cores of magnetic circuits and one ends of which are extended in the direction across the bias conductive member 43 and the MR thin film element 45. A protective substrate 50 is bonded to the substrate 41 via a bonding agent 49. Between the front end of one magnetic layer 47 and the substrate 41, there is interposed a non-magnetic gap spacer layer 51 made of, for example, the insulating layer 46 and having a predetermined thickness to form a front magnetic gap GP. In facing relation to this magnetic gap GP, a magnetic medium contact surface 4P is formed over the substrates 41 and 50 by polishing. While the rear end of the magnetic layer 47 forming the magnetic gap GP and the front end of the other magnetic layer 48 are formed on the MR thin film element 45 via the insulating layer 46 to ride thereon, respectively, a discontinuous portions 53 with a predetermined width is formed between both the ends to make the same distant apart. While the rear end and the front end of both the magnetic layers 47 and 48 are electrically insulated from the MR element 45 by the insulating layer 46 at both sides thereof, they are coupled to each other magnetically. As described above, both the magnetic layers 47 and 48 through the discontinuous portions 53 are magnetically coupled by the MR elements 45 and thus the MR type head elements hp are formed, in which the magnetic circuit is formed of the substrate 41, the magnetic gap GP, the magnetic layer 47, the MR element 45, the magnetic layer 48 and the substrate 41. Also in this case, respective end portions 43a and 43b of the bias conductive member 43 and both ends of each MR thin film element 45 in each head element hp are respectively extended to the end portion of the substrate 41 that is not covered with the protective substrate 50 to thereby form on predetermined portions of the circuit portions on the ceramic substrate 37 terminal portions which are connected, for example, by lead wires 71 as shown in Fig. 2. On the head element portions 1R and 1P respectively attached to the first and second shield plates SH₁ and SH₂, there are formed magnetic medium contact surfaces 4R and 4P as mentioned before. Particularly the magnetic medium contact surfaces 4R and 4P are formed by a special mode. In the first place, the magnetic medium contact surface 4R of one magnetic head element portion 1R will be described with reference to Fig. 7. In this case, the contact surface 4R is polished around the center which is a position displaced inside from the extension of the depth direction of the magnetic gap GR of the head element portion. Specifically, in the prior art magnetic head described in connection with Fig. 1, the polishing of the magnetic medium contact surface is carried out such that as shown by a chain line in Fig. 7, a central axis c of the cylindrical polishing is placed on the extension of the depth direction of the operational magnetic gap GR and upon its attaching it is located with an inclination of a predetermined angle ϑ. According to the arrangement of this embodiment, the magnetic medium contact surface 4R with the operational magnetic gap GR being faced is formed such that as shown by a solid line in Fig. 7, regarding the surface along the relative movement direction of the magnetic medium is cylindrically polished around the polishing center of the position c which is displaced from the extended direction (extended surface) SR of the depth direction of the gap GR by a predetermined length ℓs and along an arc b of a predetermined radius of curvature R. Though not shown, the magnetic medium contact surface 4P of the other head, i.e., the reproducing head element portion 1P is formed such that it is cylindrically polished around the polishing center of the position displaced from the extended direction of the depth direction of the magnetic gap to the direction opposite to that of the recording element portion 1R by length - ℓs. The first and second magnetic shield plates SH₁ and SH₂ having the magnetic head element portions 1R and 1P on which the magnetic medium contact surfaces 4R and 4P are respectively formed as described above are bonded or spot-welded together at their back surfaces by a laser, for example, irradiating a laser spot from the side surfaces thereof for 0.1 to 0.5 seconds and so on. As described above, in the magnetic gaps GR and GP of both the magnetic head element portions 1R and 1P formed together by bonding the first and second magnetic shield plates SH₁ and SH₂, the depth directions SR and SP thereof are located in parallel to each other with the reference plane fs along the bonded surface of both the shield plates SH₁ and SH₂ as the center. In this case, if the above mentioned distance ℓ s is selected as ℓs = R sin ϑ (1) the magnetic medium contact surfaces 4R and 4P of the respective head element portions 1R and 1P according to the embodiment of Fig. 2 can be made coincident with the respective contact surfaces of the prior art shown in Fig. 1. In other words, according to the present invention, although both heads HR and HP are located in parallel to each other, the contact relationships thereof relative to the magnetic medium can be made coincident with those of the prior art structure. In this connection, when R = 3mm and ϑ = 4° are established in the prior art structure, from Eq. (1), it is sufficient that ℓs = 200µm is satisfied in the embodiment of Fig. 2. Further, an explanation will be given on a pressure of the magnetic medium relative to the magnetic gaps GR and GP in that case. A contact pressure Pg in the depth direction of the magnetic medium having the structure of the present invention shown by the solid line in Fig. 7 is given by the following equation. Pg = P cos ϑ (2) where P is the contact pressure in the depth direction of the like magnetic gap in the prior art structure shown by a chain line in the same figure. Therefore, if now ϑ = 4° is satisfied, Pg = 0.998P is established. This makes it clear that Pg is not substantially different from P. As described above, the bonded member of the first and second magnetic shield plates SH₁ and SH₂ is inserted into a metal can, that is, a magnetic shield case 80 and resin 81 is filled into the can 80 as shown in Fig. 2. According to the combination magnetic head of the present invention, since by bonding the first and second magnetic shield plates SH₁ and SH₂ at their back surfaces which are manufactured with highly-accurate flatness, the respective magnetic head element portions 1R and 1P formed thereon are made together, the positioning between both of them can be made accurately. Further, since the ceramic substrates having mounted thereon the circuit portions accompanying with the respective magnetic head element portions such as the integrated circuits, the capacitors or the like are mounted on the first and second magnetic shield plates SH₁ and SH₂ and the circuit patterns are formed on the ceramic substrates, it is possible to reduce the number of the lead wires 70 and 71 which are required to interconnect the circuit portions and the head element portions. Furthermore, since both of these head element portions 1R and 1P and the accompanying circuit element portions are covered with the can 80 and are also covered with the resin 81 filled into the can 80, it is possible to improve the humidity proof property and the environment proof property so that the reliability thereof can be improved. In addition, since both the head portions are formed together by bonding the first and second magnetic shield plates SH₁ and SH₂ and the depth directions SR and SP of the magnetic gaps GR and GP are arranged to have a parallel relationship therebetween, the spacing between both the magnetic gaps GR and GP can be made adequately small so that the overall arrangement can be made small in size and high in density.

Claims: A combination magnetic head apparatus (31) comprising a recording head portion with a recording magnetic head element portion (1R), a recording intergrated circuit (32) and a capacitor (33) and a reproducing head portion with a reproducing magnetic head element portion (1P), a reproducing integrated circuit (35) and a capacitor (36), whereby -- said recording magnetic head element portion (1R) includes thin film magnetic head elements (hr) formed on a magnetic substrate (11) and a protective substrate (22) is bonded thereto so as to cover the same and -- said reproducing magnetic head element portion (1P) includes thin film magnetic head elements (hp) formed on a substrate (41) and a protective substrate (50) is bonded thereto so as to cover the same, characterized in that said recording head portion is bonded on one surface of a first magnetic shield plate (SH₁), said reproducing head portion is bonded on one surface of a second magnetic shield plate (SH₂), said recording head portion and said reproducing head portion are bonded together on the other surfaces of said first and second magnetic shield plates (SH₁, SH₂) and the overall arrangement thereof is incorporated into a shield case (80), the depth direction (SR) of said recording head portion and the depth direction (SP) of said reproducing head portion are provided parallel with each other, said recording head portion (1R) is provided with a magnetic medium contact surface (4R) by cylindrical polishing around a polishing center (C) displaced from an extension of the depth direction of the magnetic gap (GR) in one direction by a predeterminded length (1s) and said reproducing (1P) head portion is respectively provided with a magnetic medium contact surface (4P) by cylindrical polishing around a polishing center (C) displaced from an extension of the depth direction of the magnetic gap (GP) by said predetermined length (-1s) in a direction opposite to the direction of the length (1s) of the recording head portion (1R).

Inventors: IMAMURA, HIDEKO, SEKIYA, TETSUO, SODA, YUTAKA, UCHIDA, HIROYUKI
Applicants: SONY CORPORATION
Application year: 1985
Main classification: G11B5
IPC codes: G11B5