Compact multiple magnetic head apparatus

The present invention is to construct a combination magnetic head apparatus in which thin film type magnetic head element portions, circuits and circuit parts accompanying therewith are mounted on first and second magnetic shield plates to thereby construct a recording head and a reproducing head and both the magnetic shield plates are bonded together at the back surfaces thereof with the result that the apparatus can be made small in size, the assembling thereof can be simplified and the accuracy thereof can be improved.

TECHNICAL FIELD 
The present invention relates to a combination magnetic head apparatus in 
which a recording magnetic head or, in some case, a recording magnetic 
head including an erase magnetic head for erasing a recording previously 
recorded on a magnetic recording medium and a reproducing magnetic head 
are sequentially arranged along the relative transportation direction of 
the magnetic recording medium so as to be integrated in one body, more 
particularly, to a combination magnetic head apparatus that is made by 
combining, for example, a thin film electromagnetic induction type 
magnetic head and a reproducing magnetic head of a thin film 
magneto-resistance effect (hereinafter referred to as MR) type. 
BACKGROUND ART 
A combination magnetic head apparatus in which a recording magnetic head 
and a reproducing magnetic head are integrated in one body is made such 
that, as shown, for example, 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. 
In this case, in the respective recording magnetic head HR and the 
reproducing magnetic head HP, magnetic head element portions 1R and 1P 
each having magnetic head elements prepared for a single or a plurality of 
channels are located at their front portions and resinous mold bodies 2R 
and 2P incorporating circuit portions, such as, integrated circuits 
accompanying therewith or the like respectively construct block bodies and 
they are bonded together with a reference plane fs as the center abutting 
surfaces 3R and 3P provided on these block bodies, or resinous mold 
members 2R and 2P and each of which constructs a reference flat plane. The 
magnetic gaps GR and GP of the recording magnetic head HR and the 
reproducing magnetic head HP are respectively located such that their 
depth directions SR and SP have symmetrical inclinations of a 
predetermined angle .theta., for example, .theta.=4.degree. relative to 
the reference central plane fs. Contact surfaces 4R and 4P of the 
respective magnetic heads HR and HP with the magnetic medium are formed 
by, for example, cylindrical polishing with a predetermined radius of 
curvature around respective points on the depth directions SR and SP of 
the magnetic gaps GR and GP. 
In the combination magnetic head thus being arranged, since it is difficult 
that the distance between the magnetic gaps GR and GP of the respective 
recording and reproducing magnetic heads HR and HP is made short enoughly, 
it is therefore difficult that a contact relation or so-called abutting of 
the magnetic gaps GR and GP with the magnetic medium is maintained 
satisfactorily. There is further such a defect that the outer dimension of 
the overall arrangement thereof becomes large. Further, there are defects 
that its humidity-proof property and environment-proof property for the 
integrated circuits are low and that when the magnetic heads are 
assembled, the number of bonding wires required by the integrated circuit 
or the like is increased. 
The present invention is to improve the afore-said defects encountered with 
the above mentioned combination magnetic head apparatus. 
DISCLOSURE OF INVENTION 
A recording head portion is constructed in which a recording magnetic head 
element portion, a recording integrated circuit and a capacitor are 
arranged on one surface of a first magnetic shield plate. While, a 
reproducing head portion is constructed in which a reproducing magnetic 
head element portion, a reproducing integrated circuit and a capacitor are 
arranged on one surface of a second magnetic shield plate. These head 
portions are bonded together at the other surfaces of the respective 
magnetic shield plates and the whole thereof is incorporated in a shield 
case. 
The magnetic head element portion is formed of a thin film magnetic head 
element formed on a magnetic substrate bonded on the first magnetic shield 
plate and a protective substrate is bonded thereto to cover its upper 
side. 
The reproducing magnetic head element portion is formed of a thin film 
magnetic head element formed on a magnetic substrate bonded on the second 
magnetic shield plate and a protective substrate is bonded thereto to 
cover its upper side. 
On these recording head and reproducing head, there are formed magnetic 
medium contact surfaces by the cylindrical polishing in which the center 
of the polishing is provided at the position displaced from the line on 
the depth direction of the respective magnetic gaps.

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 SH.sub.1 and a second 
magnetic shield plate SH.sub.2. Each of the first and second magnetic 
shield plates SH.sub.1 and SH.sub.2 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 SH.sub.1, 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 SH.sub.2, 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 SiO.sub.2 and the like on which conductor means 15 is 
deposited. This conductor means 15 is formed of, fo 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 SiO.sub.2 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 11a 
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 SiO.sub.2 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, M.sub.0 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 43 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 SH.sub.1 and SH.sub.2, 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 .theta.. 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 4R 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 
SH.sub.1 and SH.sub.2 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 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 SH.sub.1 and SH.sub.2, 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 SH.sub.1 and 
SH.sub.2 as the center. 
In this case, if the above mentioned distance ls is selected as 
EQU ls=R sin .theta. (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=3 mm and .theta.=4.degree. are established in the prior art structure, 
from Eq. (1), it is sufficient that ls=200 .mu.m 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. 
EQU Pg=P cos .theta. (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. W 
Therefore, if now .theta.=4.degree. 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 SH.sub.1 and SH.sub.2 is inserted into a metal can, that is, 
a magnetic shield case or can, 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 SH.sub.1 and 
SH.sub.2 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 SH.sub.1 and SH.sub.2 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 SH.sub.1 and SH.sub.2 
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.