Magnetic head with medium sliding surface having varied curvature and recording/reproducing apparatus

A magnetic head includes core blocks having a medium sliding surface formed on one surface of the core blocks, the medium sliding surface having a slender convex curved shape formed along a sliding direction of a recording medium from the upstream side of the sliding direction to the downstream side, and the medium sliding surface having a magnetic gap formed thereon, wherein the medium sliding surface is shaped along a longitudinal direction thereof like a circular arc with a radius of curvature R while being shaped along a width direction like a circular arc with a radius of curvature r, which is smaller than the radius of curvature R, so that the radius of curvature r is continuously reduced with closer distance to the downstream end of the recording medium sliding direction from a vicinity of the magnetic gap, so that by employing the above magnetic head, a long life magnetic head with small damage due to foreign material adhesion as well as small abrasion can be provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to magnetic heads, and in particular relates to a magnetic head for use in VTR equipment and a tape storage device such as a DDS (digital data storage, digital tape streamer).

2. Description of the Related Art

In a magnetic head for use in VTR equipment, the track width has been decreased year after year in consistency with the recording density improvement and the digitizing a signal recording pattern.

From such a background, an MIG (metal in gap) type magnetic head has been used, in which a pair of magnetic core half-pieces, which are made of ferrite or ceramic so as to have metallic magnetic thin films formed thereon and being excellent in soft magnetic characteristics, are integrated together with an insulating film therebetween by a bonding member such as deposited glass.

Recently, in order to reduce the track width further than that of the MIG type magnetic head, a thin-film magnetic head having a thin-film coil is tried to incorporate it into a magnetic head for VTR equipment.

FIG. 13shows a perspective view of a thin-film magnetic head200as an example of a magnetic head. The thin-film magnetic head200is built by bonding side faces of plate-like core half-pieces202and203together with a core-embedded layer205therebetween so as to have a plate-like integrated structure on the whole. The core half-pieces202and203are made of a hardwearing ceramic material such as CaTiO3and AlTiC (Al2O3—TiO2ceramic), or Ni—Zn ferrite.

As shown inFIG. 13, one surface of the thin-film magnetic head200is also shaped like a slender convex curved surface so as to have a medium sliding surface210, and on both sides of the medium sliding surface210in the width direction, steps212and213are continuously formed so as to sandwich the medium sliding surface210. That is, in an upper portion of the half-pieces202and203, a projection215cramped by the steps212and213is constructed, and the top surface of the projection215constitutes the medium sliding surface210while surfaces neighboring both the side surfaces of the medium sliding surface210in the width direction constitute side faces207and207.

A medium sliding surface210is to be a curved surface (a curved surface along a sliding direction of a recording medium) along a circular arc with a radius of curvature R on a surface including large side surfaces202aand203aof the core half-pieces202and203and furthermore, the medium sliding surface210is to be a curved surface along a circular arc with a radius of curvature r existing on a side face202b(a surface perpendicularly neighboring on the side surface202a) of the core half-piece202.

The radius of curvature r is set to be smaller than the radius of curvature R, and is also set to be substantially constant along a longitudinal direction of the medium sliding surface210. For example, if in the core half-pieces202and203, the width is 1.0 mm, the height is 1.8 mm, the depth is 0.28 mm, and the with of the medium sliding surface210is between from 150 to 200 μm, the radius of curvature R can be between from 3 to 5 mm, and the radius of curvature r can be between from 1 to 2 mm.

The core-embedded layer205arranged at the center of the medium sliding surface210is provided with a magnetic head211built therein, and at the substantial center of the medium sliding surface210, a magnetic gap G of the magnetic head211is exposed.

In the thin-film magnetic head200mentioned above, the radius of curvature r is set to be substantially constant along a longitudinal direction of the medium sliding surface210, so that the width of an actual contact part with a recording medium of the medium sliding surface210is substantially constant along a longitudinal direction (a sliding direction of a recording medium) of the medium sliding surface210.

Therefore, during the traveling of a medium, a foreign material, for example, adhering to a tape-shaped recording medium is readily caught up between the medium sliding surface210and the recording medium, possibly resulting in damage of the medium sliding surface210due to the foreign material.

In order to prevent the damage of the medium sliding surface210, the contact part with a recording medium of the medium sliding surface210may be reduced by tapering the medium sliding surface210with the radius of curvature r reduced to be as small as possible; however, in this case, there is a problem that the contact pressure of the recording medium is concentrated on an edge extremity of the medium sliding surface210so that the abrasion of the medium sliding surface210is increased.

SUMMARY OF THE INVENTION

The present invention has been made in view of the situation described above, and it is an object thereof to provide a long life magnetic head with small damage due to adhesion of foreign materials as well as small abrasion.

In order to achieve the above object, the present invention is incorporated into the following configurations.

A magnetic head according to the present invention comprises a core block having a medium sliding surface formed on one surface of the core block, the medium sliding surface having a slender convex curved shape formed along a sliding direction of a recording medium from the upstream side of the sliding direction to the downstream side, and the medium sliding surface having a magnetic gap formed thereon, wherein the medium sliding surface is shaped along a longitudinal direction thereof like a circular arc with a radius of curvature R while being shaped along a width direction like a circular arc with a radius of curvature r, which is smaller than the radius of curvature R, so that the radius of curvature r is continuously reduced with closer distance to the downstream end of the recording medium sliding direction from a vicinity of the magnetic gap.

According to such a magnetic head, since the radius of curvature r of the medium sliding surface is continuously reduced with closer distance to the downstream end of the recording medium sliding direction from the vicinity of the magnetic gap, the width of the contact part of the medium sliding surface to the recording medium is gradually reduced with closer distance to the downstream end from the vicinity of the magnetic gap. Therefore, a foreign material once caught up on the medium sliding surface can be discharged therefrom, enabling the damage of the medium sliding surface to be reduced.

Also, since the radius of curvature r is set to be comparatively large in the vicinity of the magnetic gap, the medium sliding surface cannot be tapered in the vicinity of the magnetic gap, thereby reducing the abrasion due to the recording medium.

A magnetic head according to the present invention is the magnetic head described above, in which the radius of curvature r of the medium sliding surface may be continuously reduced with closer distance to the upstream end of the recording medium sliding direction from a vicinity of the magnetic gap.

According to such a magnetic head, since the radius of curvature r of the medium sliding surface is continuously reduced with closer distance to the upstream end of the recording medium sliding direction from the vicinity of the magnetic gap, the width of the contact part of the medium sliding surface to the recording medium is gradually increased with closer distance to the vicinity of the magnetic gap from the upstream end. Therefore, only the foreign material stuck on the recording medium is flicked off when it contacts on the medium sliding surface together with the recording medium, so that the foreign material cannot be caught up on the medium sliding surface, enabling the damage of the medium sliding surface to be reduced.

Also, since the radius of curvature r is set to be comparatively large in the vicinity of the magnetic gap, the abrasion due to the recording medium can be reduced in the same way as the above.

A magnetic head according to the present invention is the magnetic head described above, in which if it is defined that the radius of curvature r in the vicinity of the magnetic gap is r1; the radius of curvature r of at least one of the downstream end and the upstream end of the recording medium sliding direction is r2; and Δr=r1−r2, the Δr may range from 0.1 mm to 0.5 mm.

Also, the respective radii of curvature r (=r2) in the downstream end and the upstream end may be equal to or different from each other.

According to such a magnetic head, since the Δr is set to be in the above range, a magnetic head with small damage and abrasion due to the recording medium can be obtained.

A magnetic head according to the present invention is also the magnetic head described above, in which a cut-out is provided at a position adjacent to the downstream end of the medium sliding surface so that the width of the medium sliding surface is continuously reduced with closer distance to the downstream end.

According to such a magnetic head, since the width of the medium sliding surface at the downstream end becomes smaller by providing the cut-out at a position adjacent to the downstream end of the medium sliding surface, so that the radius of curvature r adjacent to the downstream end is more reduced, and a foreign material once caught up on the medium sliding surface is liable to be discharged therefrom, enabling the damage of the medium sliding surface to be further reduced.

A magnetic head according to the present invention is also the magnetic head described above, in which a cut-out is provided at a position adjacent to the upstream end of the medium sliding surface so that the width of the medium sliding surface is continuously reduced with closer distance to the upstream end.

According to such a magnetic head, since the width of the medium sliding surface at the upstream end becomes smaller by providing the cut-out at a position adjacent to the upstream end of the medium sliding surface, so that the radius of curvature r adjacent to the upstream end is more reduced, and a foreign material stuck to the recording medium is more liable to be flipped therefrom, enabling the damage of the medium sliding surface to be further reduced.

Next, a recording and reproducing apparatus according to the present invention comprises a tape loading route, in which a tape-like recording medium derived from a tape reel is wound about a rotary drum; and any one of the magnetic heads described above and disposed in the rotary drum.

According to such a recording and reproducing apparatus, since it is provided with the magnetic head described above with small damage due to foreign material adhesion as well as small abrasion, a low noise and long life recording/reproducing apparatus can be obtained.

The tape loading route may preferably comprise the rotary drum to be driven and rotated; guide posts respectively disposed on the upstream side and the downstream side of the rotary drum for guiding a tape-like recording medium derived from the tape reel so as to wind it around the rotary drum; and a capstan disposed on the downstream side of the rotary drum for allowing the recording medium to travel.

As described above in detail, according to a magnetic head of the present invention, a curvature radius r of a medium sliding surface is formed to continuously decrease from the vicinity of the magnetic gap toward the downstream end in a recording medium sliding direction, and a contact part of the medium sliding surface to a recording medium gradually decreases from the vicinity of the magnetic gap toward the downstream end, so that a foreign material once caught up on the medium sliding surface can be discharged therefrom by being stuck to the recording medium again, enabling the damage of the medium sliding surface to be reduced.

The radius of curvature r is also set to be comparatively large in the vicinity of the magnetic gap, so that the medium sliding surface cannot be tapered in the vicinity of the magnetic gap, thereby reducing the abrasion due to a recording medium.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments according to the present invention will be described below with reference to the drawings.

FIG. 1is a schematic plan view of a tape-loading route of a recording/reproducing apparatus according to the embodiment of the present invention. The recording/reproducing apparatus shown in FIG.1and comprising a rotary drum1is used for instruments such as VTR equipment. The rotary drum1rotationally driven by a motor is equipped with two magnetic heads100according to the present invention. In the recording/reproducing apparatus shown inFIG. 1, a magnetic tape (a recording medium) T derived from a feeding tape reel11of a tape cassette and guided along a guide post13ais wound about the rotary drum1by a predetermined angle; furthermore, the magnetic tape T guided along a guide post13bis clamped between a capstan14and a pinch roller15so as to travel in the arrow direction of the drawing by the rotation of the capstan14; finally the magnetic tape T is wound about a winding tape reel12. In such a manner, the rotary drum1having the magnetic heads100and the magnetic tape T constitute the tape-loading route.

There are also provided an overall-width erase head Ha and a sound head Hb in the tape-loading route.

FIG. 2is a perspective view of the magnetic head100;FIG. 3is a side view of the magnetic head100;FIGS. 4Ato4D are a front view and side views of the magnetic head100; andFIG. 5is a plan view of the magnetic head100.

The magnetic head100shown inFIGS. 2to5is built by bonding side faces of plate-like core half-pieces (core blocks)102and103together with a core-embedded layer105therebetween so as to have a plate-like integrated structure on the whole. The core half-pieces102and103are made of a hardwearing ceramic material such as CaTiO3and AlTiC (Al2O3—TiO2ceramic), or Ni—Zn ferrite. The core-embedded layer105is provided with a reproducing MR head and a recording inductive thin-film head built therein.

As shown inFIGS. 2to5, one surface of the magnetic heads100is formed like a slender convex curved surface so as to have a medium sliding surface110, and on both sides of the medium sliding surface110in the width direction, steps112and113are continuously formed so as to sandwich the medium sliding surface110. That is, in an upper portion forming the core blocks102and103, a projection115is constructed so as to cramp the steps112and113, and the top surface of the projection115constitutes the medium sliding surface110while surfaces neighboring both the side surfaces of the medium sliding surface110in the width direction constitute side faces107and107. Also, at the substantial center of the medium sliding surface110, a magnetic gap G of the recording inductive thin-film head mentioned above is exposed at a position corresponding to the core-embedded layer105.

The medium sliding surface110is to be a curved surface (a curved surface along a sliding direction of a magnetic tape) along a circular arc with a radius of curvature R along a surface including large area side surfaces102aand103aof the core half-pieces102and103. That is, the medium sliding surface110is formed like a slender convex curved surface along the sliding direction of the magnetic tape (the recording medium) from the upstream side to the downstream side, as shown by the arrow in the drawing, so as to have a circular arc with a radius of curvature R along the longitudinal direction thereof.

Also, the medium sliding surface110is to be a curved surface along a circular arc with a radius of curvature r existing on a side face102b(a surface perpendicularly neighboring on the side surface102a) of the core half-piece102. That is, the medium sliding surface110is formed so as to have a circular arc with a radius of curvature r, which is smaller than the radius of curvature R, along the width direction thereof.

Furthermore, as shown inFIGS. 3to5, the radius of curvature r is arranged so as to continuously decrease from a vicinity110aof the magnetic gap G to the downstream end110bin the sliding direction of the recording medium. Similarly, the radius of curvature r is arranged so as to continuously decrease from the vicinity110aof the magnetic gap G to the upstream end110cin the sliding direction of the recording medium. That is, the radius of curvature of the medium sliding surface110is comparatively large in the vicinity110aof the magnetic gap G, and the radius of curvature is reduced with further distance from the magnetic gap G.

Therefore, when the magnetic tape is sliding on the medium sliding surface110, the width of an actual contact part is small adjacent to the upstream end110cof the medium sliding surface110; the width of the actual contact part gradually increases toward the vicinity110aof the magnetic gap G; then, the width of the contact part is reduced again with closer distance to the downstream end110b.

Therefore, if a foreign material is stuck to the magnetic tape T, the foreign material is once brought into contact with the medium sliding surface110together with the magnetic tape; however, only the foreign material is flicked off by the sliding of the magnetic tape so that the foreign material cannot be caught up on the medium sliding surface110.

Even if the foreign material is caught up on the medium sliding surface110, since the width of the contact part of the medium sliding surface110is gradually reduced with closer distance to the downstream end110b, the foreign material is separated from the medium sliding surface110by being stuck to the magnetic tape again.

In such a manner, since opportunity of the foreign material to contact with the medium sliding surface110is reduced, damage due to the foreign material is reduced and the damage of the medium sliding surface110can be consequently prevented.

The radius of curvature r is set to be comparatively large in the vicinity110aof the magnetic gap G, so that the medium sliding surface110cannot be tapered in the vicinity of the magnetic gap G, thereby dispersing the contact pressure of the magnetic tape and reducing the abrasion of the medium sliding surface110.

Regarding to the radius of curvature r, as shown inFIGS. 4Bto4D, if it is defined that the radius of curvature r in the vicinity110aof the magnetic gap G is r1; the radius of curvature r of the downstream end 110band/or the upstream end110cin the sliding direction of the recording medium is r2; and Δr=r1−r2, it is preferable that Δr range from 0.1 mm to 0.5 mm.

The respective radii of curvature r (=r2) in the downstream end110band the upstream end110cmay be equal to or different from each other within the range of the condition mentioned above.

If Δr is less than 0.1 mm, the radius of curvature difference between the vicinity110aof the magnetic gap G and the upstream end110c/the downstream end110bis reduced, so that the width difference of the contact part between the medium sliding surface110and the magnetic tape becomes smaller. Thereby, that is not preferable because the foreign material is liable to contact with the medium sliding surface110so that the damage cannot be prevented from being produced.

Whereas if Δr is more than 0.5, it is not preferable because the medium sliding surface110is tapered in shape on the whole so that the abrasion by the magnetic tape sliding is increased.

In addition, as a specific example of the radius of curvature r, it is preferable that the radius of curvature r (=r1) in the vicinity110aof the magnetic gap G range from 0.9 mm to 1.5 mm, and 1.2 mm may be more preferable. If the radius of curvature r is 1.6 mm or more, the tape traveling is unstable.

It is preferable that the radius of curvature r (=r2) of the downstream end110band the upstream end110cbe 0.7 mm or more.

The specific example mentioned above may be appropriately modified by the size of the magnetic head100and applications not by being limited to the example.

As described above, according to the magnetic head100, damage due to foreign materials is reduced and abrasion is also decreased.

Next, a magnetic head300shown inFIGS. 6 and 7may be used as another example of a magnetic head according to the present invention.

In a similar way to the magnetic head100described above, the magnetic head300shown inFIGS. 6 and 7is built by bonding side faces of plate-like core half-pieces302and303together with a core-embedded layer305therebetween so as to have a plate-like integrated structure on the whole. The core half-pieces302and303are made of the same material as that of the core half-pieces102and103. The core-embedded layer305also has a similar structure to that of the core-embedded layer105.

As shown inFIGS. 6 and 7, one surface of the magnetic heads300is formed like a slender convex curved surface so as to have a medium sliding surface310, and on both sides of the medium sliding surface310in the width direction, steps312and313are continuously formed so as to sandwich the medium sliding surface310. A projection315is constructed by being cramped with the steps312and313, and the top surface of the projection315constitutes the medium sliding surface310while surfaces neighboring both sides of the medium sliding surface310in the width direction constitute side faces307and307. Also, at the substantial center of the medium sliding surface310, the magnetic gap G is exposed at a position corresponding to the core-embedded layer305.

The medium sliding surface310is formed like a slender convex curved surface along the sliding direction of the recording medium from the upstream side to the downstream side, as shown by the arrow in the drawing, so as to have a downstream-side sliding surface311in the downstream side of the magnetic gap G as a boundary and an upstream-side sliding surface312in the upstream side of the magnetic gap G as the boundary.

The downstream-side sliding surface311is to be a curved surface (a curved surface along a sliding direction of a magnetic tape) along a circular arc with a radius of curvature R along a surface including a side surface303aof the core half-piece303. That is, the downstream-side sliding surface311is formed like a circular arc with the radius of curvature R along the longitudinal direction thereof.

Also, the downstream-side sliding surface311is to be a curved surface along a circular arc with a radius of curvature r existing on a side face303b(a surface perpendicularly neighboring on the side surface303a) of the core half-piece303. That is, the downstream-side sliding surface311is formed so as to have a circular arc with a radius of curvature r, which is smaller than the radius of curvature R, along the width direction thereof.

Furthermore, as shown inFIGS. 6 and 7, a cut-out320is provided on the downstream-side of the projection315in the sliding direction. The cut-out320is formed so that the width of the projection315(the downstream-side sliding surface311) continuously decreases from the magnetic gap G to the downstream end310b. Therefore, the radius of curvature r in the downstream-side sliding surface311is arranged so as to continuously decrease from a vicinity310aof the magnetic gap G to the downstream end310bin the sliding direction of the recording medium.

Since the width of the downstream-side sliding surface311is continuously decreased especially with the cut-out320, the radius of curvature r at the downstream end310bcan be reduced smaller than that of the case of the magnetic head100described above.

Next, the upstream-side sliding surface312is to be a curved surface along a circular arc with a radius of curvature r existing on a side face302b(a surface perpendicularly neighboring on the side surface302a) of the core half-piece302. The radius of curvature r of the upstream-side sliding surface312is constant from the magnetic gap G until the upstream end310c.

In addition, the radius of curvature r of the upstream-side sliding surface312, in the same way as in the downstream-side sliding surface311, may be formed so as to continuously decrease to the upstream end310c.

Therefore, when the magnetic tape is sliding on the medium sliding surface310, the width of a contact part is substantially constant from the upstream end310cto the vicinity310aof the magnetic gap G, and the width of the contact part gradually decreases from the vicinity310atoward the downstream end310b.

Therefore, if a foreign material is stuck to the magnetic tape T, the foreign material is once brought into contact with the medium sliding surface310together with the magnetic tape; however, since the width of the contact part gradually decreases toward the downstream end310bafter crossing the magnetic gap G, the foreign material is again stuck to the magnetic tape so as to separate from the medium sliding surface310.

In such a manner, since opportunity of the foreign material to contact with the medium sliding surface310is reduced, damage due to the foreign material is reduced and the damage of the medium sliding surface310can be consequently prevented.

The radius of curvature r is set to be comparatively large in between the upstream end310cand the vicinity310aof the magnetic gap G, so that the medium sliding surface310cannot be tapered in the vicinity of the magnetic gap G, thereby dispersing the contact pressure of the magnetic tape and reducing the abrasion of the medium sliding surface310.

Regarding to the radius of curvature r, as shown inFIGS. 6 and 7, if it is defined that the radius of curvature r in the vicinity310aof the magnetic gap G is r1; the radius of curvature r of the downstream end310bin the sliding direction of the recording medium is r2; and Δr=r1−r2, it is preferable that Δr range from 0.1 mm to 0.5 mm.

If Δr is less than 0.1 mm, the radius of curvature difference between the vicinity310aof the magnetic gap G and the downstream end310bis reduced, so that that is not preferable because the foreign material is liable to remain on the medium sliding surface310so that the damage cannot be prevented from being produced.

Whereas if Δr is more than 0.5, it is not preferable because the medium sliding surface310is tapered in shape on the whole so that the abrasion by the sliding magnetic tape is increased.

In addition, a specific example of the radius of curvature r (=r1, r2) is similar to the case of the magnetic head100described above.

As described above, according to the magnetic head300, damage due to foreign materials is reduced and abrasion can be also decreased.

Next, a magnetic head400shown inFIGS. 8 and 9may be used as another example of a magnetic head according to the present invention.

In a similar way to the magnetic head100described above, the magnetic head400shown inFIGS. 8 and 9is built by bonding side faces of plate-like core half-pieces402and403together with a core-embedded layer405therebetween so as to have a plate-like integrated structure on the whole. The core half-pieces402and403are made of the same material as that of the core half-pieces102and103. The core-embedded layer405also has a similar structure to that of the core-embedded layer105.

As shown inFIGS. 8 and 9, one surface of the thin-film magnetic heads400is formed like a slender convex curved surface so as to have a medium sliding surface410, and on both sides of the medium sliding surface410in the width direction, steps412and413are continuously formed so as to sandwich the medium sliding surface410. A projection415is constructed by being cramped with the steps412and413, and the top surface of the projection415constitutes the medium sliding surface410while surfaces neighboring both sides of the medium sliding surface410in the width direction constitute side faces407and407. Also, at the substantial center of the medium sliding surface410, the magnetic gap G is exposed at a position corresponding to the core-embedded layer405.

The medium sliding surface410is formed like a slender convex curved surface along the sliding direction of the recording medium from the upstream side to the downstream side, as shown by the arrow in the drawing, so as to have a downstream-side sliding surface411in the downstream side of the magnetic gap G as a boundary and an upstream-side sliding surface412in the upstream side of the magnetic gap G as the boundary.

The downstream-side sliding surface411is to be a curved surface (a curved surface along a sliding direction of a magnetic tape) along a circular arc with a radius of curvature R along a surface including a side surface403aof the core half-piece403. That is, the downstream-side sliding surface411is formed like a circular arc with the radius of curvature R along the longitudinal direction thereof.

Also, the downstream-side sliding surface411is to be a curved surface along a circular arc with a radius of curvature r existing on a side face403b(a surface perpendicularly neighboring on the side surface403a) of the core half-piece403. That is, the downstream-side sliding surface411is formed so as to have a circular arc with a radius of curvature r, which is smaller than the radius of curvature R, along the width direction thereof.

Furthermore, as shown inFIGS. 8 and 9, a cut-out420is provided on the downstream-side of the projection415in the sliding direction. The cut-out420is formed adjacent to the step412so that the width of the projection415(the downstream-side sliding surface411) continuously decreases from the magnetic gap G to the downstream end410b. Therefore, the radius of curvature r in the downstream-side sliding surface411is arranged so as to continuously decrease from a vicinity410aof the magnetic gap G to the downstream end410bin the sliding direction of the recording medium.

Since the width of the downstream-side sliding surface411is continuously decreased especially with the cut-out420, the radius of curvature r at the downstream end410bcan be reduced smaller than that of the case of the magnetic head100described above.

Next, the upstream-side sliding surface412, in substantially the same way as in the downstream-side sliding surface411, is formed like a circular arc with the radius of curvature R along the longitudinal direction thereof.

Also, the upstream-side sliding surface412is to be a curved surface along a circular arc with a radius of curvature r existing on a side face402b(a surface perpendicularly neighboring on the side surface402a) of the core half-piece402. That is, the upstream-side sliding surface412is formed so as to have a circular arc with a radius of curvature r, which is smaller than the radius of curvature R, along the width direction thereof.

Furthermore, as shown inFIGS. 8 and 9, a cut-out421is provided on the upstream-side of the projection415in the sliding direction. The cut-out421is formed adjacent to the step413so that the width of the projection415(the upstream-side sliding surface412) continuously decreases from the magnetic gap G to the upstream end410c. Therefore, the radius of curvature r in the upstream-side sliding surface412is arranged so as to continuously decrease from the vicinity410aof the magnetic gap G to the upstream end410cin the sliding direction of the recording medium.

Since the width of the upstream-side sliding surface412is continuously decreased especially with the cut-out421, the radius of curvature r at the upstream end410ccan be reduced smaller than that of the case of the magnetic head100described above.

Therefore, when the magnetic tape is sliding on the medium sliding surface410, the width of an actual contact part is small adjacent to the upstream end410cof the medium sliding surface410; the width of the actual contact part gradually increases toward the vicinity410aof the magnetic gap G; then, the width of the contact part is reduced again with closer distance to the downstream end410b.

Therefore, if a foreign material is stuck to the magnetic tape T, in the same way as in the magnetic head100described above, the foreign material is once brought into contact with the medium sliding surface410together with the magnetic tape; however, only the foreign material is flicked off by the sliding of the magnetic tape so that the foreign material cannot be caught up on the medium sliding surface410.

Even if the foreign material is caught up on the medium sliding surface410, since the width of the contact part of the medium sliding surface410is gradually reduced with closer distance to the downstream end410b, the foreign material is separated from the medium sliding surface410by sticking to the magnetic tape again.

In such a manner, since opportunity of the foreign material to contact with the medium sliding surface410is reduced, damage due to the foreign material is reduced and the damage of the medium sliding surface410can be consequently prevented.

The radius of curvature r is set to be comparatively large in the vicinity410aof the magnetic gap G, so that the medium sliding surface410cannot be tapered in the vicinity of the magnetic gap G, thereby dispersing the contact pressure of the magnetic tape and reducing the abrasion of the medium sliding surface410.

Regarding to the radius of curvature r, as shown inFIGS. 8 and 9, if it is defined that the radius of curvature r in the vicinity410aof the magnetic gap G is r1; the radius of curvature r of the downstream end410band the upstream end410cin the sliding direction is r2; and Δr=r1−r2, it is preferable that Δr range from 0.1 mm to 0.5 mm.

If Δr is less than 0.1 mm, the radius of curvature difference between the vicinity410aof the magnetic gap G and the downstream end410bis reduced, so that a foreign material is liable to contact with the medium sliding surface410. Therefore, that is not preferable because the damage cannot be prevented from being produced.

Whereas if Δr is more than 0.5, it is not preferable because the medium sliding surface410is tapered in shape on the whole so that the abrasion by the magnetic tape sliding is increased.

In addition, a specific example of the radius of curvature r (=r1, r2) is similar to the case of the magnetic head100described above.

As described above, according to the magnetic head400, damage due to foreign materials is reduced and abrasion can be also decreased.

According to the embodiments, a magnetic head having an MR head and an inductive thin-film head has been described; however, a magnetic head according to the present invention is not limited to this, and an MIG head (a metal in gap head) may be used.

FIRST EXPERIMENTAL EXAMPLE

By using the magnetic head100shown inFIGS. 2to5, the relationship between the number of foreign materials stuck on the medium sliding surface and Δr was examined.

Three magnetic heads were manufactured, each having the space between the side faces107and107being constant from the upstream end110cto the downstream end110b, and a radius of curvature r1in the vicinity110aof the magnetic gap G of 1.2 mm; the respective three magnetic heads having radii of curvature r2at the upstream end110cand at the downstream end110bof 1.1 mm, 0.9 mm and 0.7 mm. Values Δr of the respective magnetic heads are 0.1 mm, 0.3 mm, and 0.5 mm. Although not shown, a magnetic head with a radius of curvature r2of 0.65 mm was also manufactured.

These magnetic heads were assembled in the tape medium recording/reproducing apparatus shown inFIG. 1, and experiments of sliding a magnetic tape were performed. After the experiments, the number of foreign materials per unit area of the medium sliding surface was counted. The results are shown in FIG.10.

As shown inFIG. 10, it is understood that the foreign material adhesion amount be reduced with increasing Δr. If Δr is 0.1 mm, the foreign material adhesion amount is about 100 pieces/(μm)2, the damage of the medium sliding surface is within the allowable limit for such an adhesion amount, so that the recording and reproducing magnetic recording information can be performed without incident.

With increasing Δr, the foreign material adhesion amount is reduced; however, if Δr is 0.5 mm, the abrasion of the medium sliding surface is increased, further increasing the abrasion with further increasing Δr. The magnetic head especially with a radius of curvature r2of 0.65 mm is unserviceable because of the abrasion resistance function. It is proved that a radius of curvature r2of 0.7 mm or more be preferable.

From the above discussion, it is preferable that Δr when the radius of curvature r1in the vicinity of the magnetic gap is 1.2 mm range from 0.1 mm to 0.5 mm.

SECOND EXPERIMENTAL EXAMPLE

The difference of the curvature radius r of the medium sliding surface between the magnetic head with the cut-out and the magnetic head without the cut-out was examined.

First, a magnetic head as shown inFIG. 2was prepared, which has the constant space between the side faces; a radius of curvature r1in the vicinity of the magnetic gap G of 1.2 mm; and a radius of curvature r2at the upstream end and at the downstream end of 1.0 mm.

Two magnetic heads were prepared, in which the cut-out is further formed adjacent to the downstream end of the above magnetic head. In these magnetic heads, the width of the medium sliding surface at the downstream end became 20 μm by forming the cut-out.

The magnetic heads with the cut-out are denoted as first and second embodiments and the magnetic head without the cut-out is denoted as a third embodiment.FIG. 11shows the relationship between the curvature radius r and the measurement point along the longitudinal distance of the medium sliding surface for each magnetic head. In addition, on the abscissa ofFIG. 11, the point 0 μm is the magnetic gap position where the curvature radius r1is 1.2 mm in design; the point 300 μm is the upstream end of the medium sliding surface; and the point −300 μm is the downstream end of the medium sliding surface.

As shown inFIG. 11, the curvature radius of the magnetic heads according to the first and second embodiments at the position adjacent to the downstream end (the −300 μm measurement point), where the cut-out is formed, is smaller by 0.1 mm or more in comparison with that of the third embodiment.

Furthermore, two magnetic heads were manufactured, in which cut-outs are further formed at positions adjacent to the upstream end and the downstream end of the magnetic head according to the third embodiment. In these magnetic heads, the widths of the medium sliding surface at the upstream end and at the downstream end are 20 μm, respectively, by forming the cut-outs.

The magnetic heads manufactured in such a manner are denoted as a fourth and a fifth embodiment.FIG. 12shows the relationship between the curvature radius r and the measurement point along the longitudinal distance of the medium sliding surface for each magnetic head. In addition, on the abscissa ofFIG. 12, the point 0 μm is the magnetic gap position where the curvature radius r1is 1.2 mm in design; the point 300 μm is the upstream end of the medium sliding surface; and the point −300 μm is the downstream end of the medium sliding surface.

As shown inFIG. 12, curvature radii of the magnetic heads according to the fourth and fifth embodiments at positions adjacent to the downstream end and the upstream end (the ±300 μm measurement points), where the cut-outs are formed, are smaller by about 0.1 mm in comparison with that of the third embodiment.

As described above, it is understood that Δr can be readily increased by providing the cut-out so as to reduce the foreign material adhesion.

As shown inFIGS. 11 and 12, it is also confirmed that in any magnetic head, the curvature radius r continuously decreases from the vicinity of the magnetic gap toward the upstream and downstream ends.