This application claims priority to Japanese Patent Application No. P2000-092638 filed on Mar. 30, 2000 which is hereby incorporated by reference in its entirety.
The present invention relates to a magnetic head used in a magnetic storage device, particularly a hard disk drive, and a method for manufacturing the magnetic head.
A magnetic head used in a magnetic storage device such as a hard disk drive, etc., basically comprises a reading unit for reading out information recorded on a magnetic storage medium and a writing unit for writing information on a magnetic storage medium. Both the reading unit and the writing unit are composed of, for example, plural core members stacked to form a multi-layered structure to produce a magnetic gap portion, a coil portion wound on the outer periphery of the stacked core members and other components.
Conventionally, the writing unit usually comprises a core member made of ferrite, and a coil wound around the core member. Since the core member of the writing unit is made of ferrite, magnetic permeability of the ferrite is as low as about 20 at an operating frequency of about 1 MHz to 2 MHz, and accordingly, eddy current loss is large. Therefore, the eddy current loss generates heat to result in thermal expansion of the core member of the writing unit. When the magnetic head is mounted on the magnetic storage medium, especially a hard disk drive, etc., with high accuracy in positioning on tracks formed on the magnetic storage medium, a change in temperature in the writing unit (thermal distortion) due to the heat generated in the writing unit causes an off-track amount and an amount of track width fluctuation to increase. As a result, the magnetic head is not positioned precisely on the track, and therefore, information cannot be written precisely.
To solve the above-mentioned problem, there have been proposed magnetic heads each comprising a core member composed of magnetic material having large saturation magnetization and small magnetic permeability, such as sendust, etc., and a coil wound around the core member. However, such a magnetic head has disadvantages in that a sufficient high frequency response cannot be obtained as compared to the magnetic head made of ferrite, etc., and in that the core member made of sendust, etc., has a low electroconductivity, resulting in an increase in resistance of the coil, which is not preferable in terms of performance characteristics.
As described above, in the conventional magnetic head, the coil is wound around the core member formed of the magnetic material having a small magnetic permeability to achieve reduction in size and heat radiation. In such a magnetic head, however, it is very difficult to achieve sufficient heat radiation. Therefore, in view of the manufacturing efficiency, it is difficult to manufacture a magnetic head having such small size and weight.
As described above, in the conventional magnetic head, the coil wound around the core member has relatively large resistance, and heat loss is increased due to a large difference in thermal expansion coefficient between the core member and the coil, which causes an increase in temperature of the coil. As a result, the magnetic permeability of the core member made of the magnetic material having a small magnetic permeability is reduced due to increase in temperature of the core member, so that a predetermined electroconductivity cannot be obtained.
A method for solving the above problem may include disposing the coil away from the core member composed of the magnetic material having a low magnetic permeability and electrically connecting the coil and the core member. This method, however, has a problem in that since the coil and the core member are independent members from each other, it is difficult to accurately wind the coil around the core member.
Accordingly, an object of the present invention is to provide a magnetic head having an improved heat radiation, particularly a magnetic head comprising a core member composed of magnetic material having large saturation magnetization and small magnetic permeability and a coil wound around the core member, as well as a method for manufacturing the magnetic head.
In order to achieve the object, there is provided a magnetic head comprising:
a core member made of magnetic material having saturation magnetization of 80 emu/cm3 or more and large magnetic permeability; and
a coil wound around the core member,
the core member including a first portion and a second portion having a sectional area different from that of the first portion.
Also, there is provided a magnetic head comprising:
a core member made of magnetic material having saturation magnetization of 80 emu/cm3 or more and large magnetic permeability;
a coil wound around the core member; and
a conductive connection element connected to the coil and made of electrically conductive material so as to be integral with the coil.
Also, there is provided a magnetic head comprising:
a core member made of magnetic material having saturation magnetization of 80 emu/cm3 or more and large magnetic permeability; and
a coil wound around the core member;
the core member having a first portion and a second portion having a sectional area different from that of the first portion;
a first bonding layer made of electrically conductive material disposed between the first portion and the second portion of the core member; and
a second bonding layer made of insulating material disposed between the first portion and the second portion of the core member so as to provide electrical insulation between the first portion and the second portion.
Also, there is provided a method for manufacturing a magnetic head comprising the steps of:
forming a core member including a first portion and a second portion by cutting a bulk body of magnetic material;
forming a first bonding layer and a second bonding layer on the first portion and the second portion of the core member so as to provide electrical insulation therebetween; and
winding a coil around the core member including the first portion and the second portion with the first portion and the second portion being electrically insulated from each other.
Also, there is provided a method for manufacturing a magnetic head comprising the steps of:
forming a core member by cutting a bulk body of magnetic material;
forming a first bonding layer and a second bonding layer on the first portion and the second portion of the core member so as to provide electrical insulation therebetween;
winding a coil around the core member including the first portion and the second portion with the first portion and the second portion being electrically insulated from each other; and
forming a conductive connection element made of electrically conductive material so as to be integral with the coil by filling a conductive connection element forming hole formed in the core member with the conductive material.
The magnetic head of the present invention comprises a core member made of magnetic material having saturation magnetization of 80 emu/cm3 or more and large magnetic permeability, and a coil wound around the core member.
The core member has two portions, i.e., the first portion composed of a large sectional area and the second portion composed of a small sectional area different from that of the first portion. Thus, it is possible to heat the core member in a very short time upon energization of the coil.
Further, since the core member has the first portion and the second portion made of the same magnetic material, and the first bonding layer and the second bonding layer having a substantially uniform thickness and disposed between the first portion and the second portion, the core member has an improved thermal conductivity as compared to a core member composed of different materials or a core member composed of only one material. In other words, the core member has a good thermal conductivity.
Also, since the core member is formed from a single bulk body of magnetic material, it is possible to obtain sufficient electroconductivity of the core member even though the core member has low saturation magnetization. Therefore, a magnetic head including such a core member provides a higher electroconductivity than a magnetic head including a core member composed of only one material. Further, since the core member includes the first portion and the second portion with a different sectional area, it is possible to maintain a predetermined thermal expansion coefficient even though the core member has low saturation magnetization.
In addition, since the core member has the first portion and the second portion made of magnetic material having large magnetic permeability, it is possible to suppress heat generation caused by eddy current loss.
Further, since the core member is formed by cutting the bulk body of magnetic material, a magnetic head is obtained without involving heat treatment such as sintering, etc. Therefore, it is possible to reduce heat treatment, resulting in a reduction in manufacturing cost.
Furthermore, since the magnetic head comprises the core member made of magnetic material having large saturation magnetization and having two portions, i.e., the first portion and the second portion having different sectional areas and different properties. It is possible to maintain a predetermined thermal expansion coefficient even though the magnetic material has a low magnetic permeability. It is also possible to obtain an excellent electroconductivity and a sufficiently large electromagnetic conversion efficiency.
Further, since the core member is formed by cutting the bulk body of magnetic material, it is possible to obtain a magnetic head having a simple structure as compared to a magnetic head comprising a coil wound around a ferrite core. As a result, it is possible to obtain a magnetic head having small size and weight as compared to a conventional magnetic head.
According to the present invention, it is possible to provide a magnetic head having small size and weight and having small heat generation, resulting in improved heat radiation.
Also, it is possible to obtain a magnetic head having good heat radiation by forming a large magnetic head core with small thickness, i.e., by forming a magnetic head having small overall size.
Further, it is possible to obtain a magnetic head having a uniform thickness for the entirety of a core member.
The coil
