JPH0339330B2 - - Google Patents

Description

Detailed Description of the Invention: Industrial Field of Application The present invention relates to a bias magnet for magnetic transfer, which is used when magnetically recording recorded contents on a magnetic recording medium to another magnetic recording medium. Related to heads.

BACKGROUND TECHNOLOGY AND PROBLEMS This kind of magnetic transfer usually transfers a blank recording medium having a magnetic layer with a low coercive force to a mother recording medium in which recording has been made in a magnetic layer having a high coercive force. A method is used in which both magnetic layers of a magnetic medium are superimposed in close contact with each other, and in this state, a bias magnetic field is applied from the outside to transfer the magnetic recording on the mother recording medium to a blank recording medium.

When performing magnetic transfer, both the mother and blank recording media are stably running at a high speed, for example, 2 to 4 m/sec, while the magnetic layers of both media are passed through a bias magnetic field for the transfer. It is desired that the transfer be performed by passing the two in close contact and without causing any positional deviation between the two.

As a bias magnetic head for magnetic transfer that provides a bias magnetic field for performing such magnetic transfer,
The present applicant previously proposed a structure as shown in FIG.

This magnetic head H is shown in a perspective view in FIG.
Fig. 2 shows the top view, and Fig. 3 shows the A-A of Fig. 2.
As shown in a cross-sectional view along the line, and as shown in FIG.
2, and a non-magnetic cylindrical body 13 rotatably arranged around the front core part 11.

As shown in FIG. 5 in a top view, FIG. 6 in a front view, and FIG. 7 in a side view, the front core part 11 has a cylindrical surface part 11A having a regular cylindrical outer circumferential surface in the middle part in the axial direction. and cylindrical or cylindrical shaft portions 11B and 11C, which are provided integrally with, for example, a cylindrical surface portion 11A at both ends in the axial direction. The front core portion 11 is constructed by joining and combining a pair of core halves 11a and 11b, which are split into two in a cross section including the axis across the cylindrical surface portion 11A and the shaft portions 11B and 11C. be done.

A nonmagnetic material is interposed between these core halves 11a and 11b to form a magnetic gap. This magnetic gap is formed as a bias magnetic field generating magnetic gap g extending in a straight line along the axial direction in a portion facing the outer peripheral surface of the cylindrical surface portion 11A. This magnetic gap g has a portion deeper than the required depth and a shaft portion 11B and 1 at both ends.
1C, the magnetic gap G has a gap length that is sufficiently larger than the gap length of the gap g.

These magnetic gap g and magnetic gap G are formed by forming a core half 1 made of a non-magnetic material such as forsterite, copper, or bronze, for example, of high-density sintered magnetic ferrite.
It is filled between 1a and 11b, and these are combined by glass fusing or epoxy resin adhesive.

The shaft portions 11B and 11C are narrower than the outer diameter of the cylindrical surface portion 11A, and may be formed into, for example, a prismatic shape with a cylindrical front surface.

On the other hand, the rear core section 12 is connected to the paired front core section 11.
A pair of core parts 12a and 1 corresponding to a and 11b
2b, both core parts 12a and 12b are the second core parts 12a and 12b.
As shown in the figure, for example, each has a U-shape, both rear parts are magnetically closely joined to each other, and the front part is a pair of core halves 11a, 11b to sandwich these halves 11a and 11b. Also, the core portion 12 of the rear core portion 12
As shown in FIGS. 3 and 4, U-shaped notches 12a ₁ and 12b ₁ are provided in the front parts of each of a and 12b.
is provided, and the cylindrical surface portion 11A of the front core portion 11
A required gap 14 exists between the rear core portion 12 and the rear core portion 12.

A winding 15 is wound around the rear core portion 12 . This winding 15 can be wound around each core part 12a and 12b, or one core part 1
It is possible to wrap only around 2a or 12b, or it can be wrapped across between them. Therefore, the arrangement position of the winding 15 can be arbitrarily selected.

On the other hand, on the outer periphery of the cylindrical surface portion 11A of the front core portion 11, a non-magnetic cylindrical body 13 made of alumina ceramics or the like is arranged so as to be rotatable about the cylindrical surface portion 11A. This non-magnetic cylindrical body 13 is rotatably supported by bearing portions 17 such as ball bearings provided in small diameter portions 11B ₁ and 11C ₁ located at both ends of the cylindrical surface portion 11A, respectively.

In order to perform transfer from a mother recording medium (mother tape) to a blank recording medium (blank tape) using the magnetic head H configured in this way, both tapes are stacked so that their magnetic layers are in close contact with each other. state, the magnetic gap g of the magnetic head H
This can be done by placing the tapes in contact with each other via the non-magnetic cylindrical body 13, and moving the superposed tapes and the magnetic head H relatively.

For example, as shown in FIG. 8, a magnetic head H is fixed, a non-magnetic cylindrical body 13 and a rolling large-diameter drive roller 18 are arranged in front of a gap g, and tapes 1 and 2 are passed between them. The magnetic layers are pressed against each other in a state where they face each other in close contact with each other.

19 is a guide roller, 20 is a roller 18 is a drive motor, and the roller 20 is driven by a belt mechanism, for example.
The rotation is transmitted to the pulley 22 of the roller 20.
The tapes 1 and 2 are caused to run at a constant speed.

During constant speed running, the winding 15 of the magnetic head H is supplied with alternating current at a required frequency f, for example 10 KHz, thereby generating alternating magnetic flux in the rear core portion 12. In this case, the magnetic head H has a rear core portion 1.
Both core parts 12a-12b of 2 - Core half 11b of front core part 11 - Magnetic gap g - Core half 11
b- A closed magnetic path of the rear core portion 12a is formed, and the alternating current magnetic flux concentrated in the magnetic gap g is transferred to the non-magnetic cylindrical body 1.
3 to the tapes 1 and 2 which are in close contact with each other, thereby performing magnetic transfer.

Even when the mother recording medium 1 is a sheet-like recording medium such as a magnetic card, the blank recording medium 1
If a sheet-like recording medium is used as well, and the two are run in close contact with each other, magnetic transfer can be performed using the above-mentioned magnetic head H.

According to the magnetic head H configured in this way,
Since the media 1 and 2 are superimposed on the non-magnetic rotating cylindrical body 13 that moves in front of the magnetic gap g and are caused to run in contact with each other, the resistance due to friction with the head H can be sufficiently reduced. As a result, accurate transfer can be performed without any positional deviation occurring between the two media 1 and 2 that are running in close contact with each other.

Furthermore, since the non-magnetic cylinder 13 may be large enough to surround the cylindrical surface portion 11A, its mechanical strength can be maintained sufficiently even if its thickness is made sufficiently thin. Therefore, even if the magnetic medium is brought into contact with the magnetic gap g via the non-magnetic cylindrical body 13, a decrease in transfer efficiency can be prevented.

That is, as shown in FIG. 9, let the gap length of the magnetic gap g formed between the pair of core halves 11a and 11b be l, and the front surface of the magnetic gap g be Let d be the distance from the center of the gap g of the close contact area of the media 1 and 2 to the non-magnetic cylinder 13, When the width is L, the relative velocity between the head H and media 1 and 2 is v [m/s], and the bias current frequency is f [Hz], that is, when the virtual wavelength λ = v/f [m] , in order to effectively utilize the magnetic field in the magnetic gap g,
ld ...(1), and under the condition of equation (1) above, it is possible to bring the magnetic medium into close contact with the center of the magnetic gap g to a position where it is attenuated to about 5/1 or less of the maximum magnetic field. Therefore, it is desirable to select L2.5l...(2). Furthermore, during transfer, it is desirable that a reversal magnetic field of 5 cycles or more be applied to the media 1 and 2 that are in close contact with each other before the applied magnetic field attenuates, and for this reason, Lf/v5...(3) is selected, and In order to cause recording demagnetization so that the bias signal is not recorded on media 1 and 2, it is desirable to select l2v/f (4). Now, if we choose L=2.5l...(5) as the limit condition for equation (2) and substitute this into equation (4), we get Lf/v5...(6). This equation (6) is consistent with equation (3), so in the end,
The conditions for satisfying all equations (1) to (4) are as follows:
Equations (1), (5), and (3) l=d...(1) L=2.5l...(5) Lf/v5...(3) Now, for example, if the gap length l and thickness d of the magnetic gap g are selected to be 1 mm, then the contact distance L should be greater than L = 2.5 mm, and the distance between the head H and the media 1 and 2. If the relative velocity v of is v=4 [m/s], Lf5×4 [m/s] f5×4 [m/s]/2.5×10 ^-3 [m]=8×10 ³
All you have to do is select [Hz].

Since the thickness d is 1 mm, the thickness of the non-magnetic cylindrical body 13 must be 1 mm or less, but since the cylindrical surface portion 11A is very small, the mechanical strength is sufficient even with a thickness of 1 mm or less. Therefore, even if the non-magnetic cylindrical body 13 is present, the transfer efficiency does not decrease.

Now, in order to make the non-magnetic cylindrical body 13 rotatable in such a magnetic head H, it is necessary to provide the above-mentioned bearing part 17 between this cylindrical body 13 and the front core part 11. . In order to make the cylindrical body 13 as small as possible, the bearing part 17 should be arranged in small diameter parts 1 near both ends of the cylindrical surface part 11A as shown in the figure.
1B ₁ , 13C ₁ , but when a part of the bearing part 17 is brought into contact with both the upper and lower end surfaces of the cylindrical body 13 in this way, a gap (hereinafter referred to as this gap) facing both the upper and lower end surfaces of the cylindrical body 13 is formed. (referred to as an end face gap) is magnetically short-circuited by the bearing portion 17.

Therefore, when trying to downsize the cylindrical body 13,
It is necessary to take measures to prevent magnetic short circuits caused by the bearing portion 17.

On the other hand, the front core part 11 has a cylindrical surface part 1 as shown in the figure.
Since the gap g formed in the cylindrical surface portion 11A acts as a substantial gap, the alternating current magnetic flux for transfer also concentrates on the end face gap. Under such circumstances, the above-mentioned bearing portion 17 is usually made of steel, such as a ball bearing.
Hysteresis loss and eddy current loss occur in the bearing 17 due to the leakage magnetic flux crossing the end face gap passing through the bearing 17.

Since all of these iron losses are heat losses, there is a risk that the magnetic properties of the front core portion 11 in particular may deteriorate due to the heat generated by the iron losses.

Purpose of the Invention Therefore, the present invention prevents the end face gap from being magnetically short-circuited by the bearing portion 17, and at least reduces the hysteresis loss, which is a large loss, out of the iron loss caused by the leakage magnetic flux around the end face gap. This prevents deterioration of magnetic properties due to heat generation in the bearing section.

Summary of the Invention Therefore, in this invention, the outside of the bearing part 17 is covered with a non-magnetic metal whose magnetic permeability μ is substantially 1 or less, or the bearing part 17 itself is made of a non-magnetic metal with μ<1, or μ≒1. It is made of non-magnetic non-metal.

Embodiment Next, an example of the present invention will be described in detail with reference to FIG. 10 and subsequent figures.

In the example of FIG. 10, as is clear from FIG. 11, which is a longitudinal cross-sectional view, the bearing portion 17 is connected to the small diameter portions 11B ₁ , 1 through a ring 25 made of non-magnetic metal.
Mounted on 3C ₁ . Since the figure shows a case where a ball bearing is used as the bearing portion 17, the inner race 17a is attached to the ring 25.

The ring 25 is configured as a cylindrical body having a flange 25a as shown in the figure, and the flange 25a is attached so as to be in contact with each of the upper and lower end surfaces of the cylindrical surface portion 11A. Flange 25a provided on ring 25
The outer diameter of the bearing portion 17 is selected to be slightly shorter than the outer diameter of the outer race 17b of the bearing portion 17. As a result, the end face gap is substantially covered by this flange 25a.

As the non-magnetic metal constituting the ring 25, brass, copper, aluminum, etc. can be used.

In this way, the end face gap is covered with the ring 25 made of non-magnetic metal, and this ring 25
When the bearing portion 17 is attached to the small diameter portions 11B ₁ and 13C ₁ via the small diameter portions 11B 1 and 13C 1 , even if the bearing portion 17 is placed close to the end gap, the end gap will not be magnetically short-circuited.

When the alternating current magnetic flux concentrated in the end face gap passes through the inside of the ring 25, an eddy current is generated inside the ring 25, and the alternating current magnetic flux due to this eddy current is oriented in such a way that it cancels out the external alternating magnetic flux. Therefore, the external magnetic flux passing through the ring 25 is reduced, and therefore the iron loss due to the external magnetic flux reaching the shaft striking portion 17 can be ignored. In this manner, the magnetic permeability μ of the ring 25 becomes 1 or less in an alternating magnetic field, and as a result, a magnetic shielding effect can be imparted to the bearing portion 17.

Note that although eddy current loss occurs in the ring 25, the amount is extremely small, and therefore no heat is generated to the extent that it affects the magnetic properties.

In addition, in this invention, a non-magnetic metal is used to provide a magnetic shielding effect, and a magnetic metal is not used. If the latter metal is used, the end face gap will be magnetically short-circuited by the magnetic metal. This is because the alternating current magnetic flux no longer concentrates on the gap g of the cylindrical surface portion 11A, and the head ceases to function as a magnetic head.Also, when it is pivoted away from the end face gap, the alternating current magnetic flux passes through the magnetic metal. This is because hysteresis loss and eddy current loss occur, making it impossible to achieve the object of the present invention.

In the embodiment shown in FIG. 12, an outer ring 26 is provided in addition to the inner ring 25 in order to further improve the magnetic shielding effect. It is designed to cover. Therefore, outer ring 2
6 is also made of the above-mentioned non-magnetic metal material, and as shown in the figure, a bottomed cylindrical body having a shaft cylinder inside is used.

By using this outer ring 26,
Cylindrical surface portion 11 of the end gap and gap g
The alternating current magnetic flux from the gaps existing at the upper and lower ends of A will not pass through the cylindrical body 13 and wrap around the bearing portion 17, and the magnetic shielding effect will be more reliable.

When the bearing portion 17 is made of non-magnetic hard metal or non-magnetic non-metal instead of steel, the ring 25 or 26 can be omitted.

FIG. 13 and subsequent figures show an embodiment in that case. 1st
In the example shown in FIG. 3, a bearing portion 17 made of a non-magnetic metal such as a non-magnetic metal such as beryllium copper, ceramics (such as silicon carbide), or a hard plastic made of Teflon resin is used.

In the case of the bearing portion 17 using non-magnetic metal, some eddy current loss occurs, but hysteresis loss, which is a large loss, does not occur. When a non-magnetic non-metal is used, no eddy current loss occurs, so the iron loss becomes almost zero.

FIG. 14 shows an example of the bearing portion 17 that does not use a ball bearing, and this example is a case where an oil-less metal is used. That is, the bearing portion 17 is constituted by a ring-shaped shaft cylinder 27A with a flange and a ring-shaped bearing 27B attached to the cylindrical body 13, and the shaft cylinder 27A is made of a non-magnetic metal material for oilless metal such as brass. In addition, the bearing 27
A hard chrome plating layer 27C is formed on the surface in contact with B to improve wear resistance and sliding resistance. The bearing 27B is made of oilless metal such as a copper alloy.

In this configuration as well, magnetic short-circuiting of the end face gap due to the bearing portion 17 can be prevented, and hysteresis loss does not occur.

FIG. 15 shows a ring-shaped shaft cylinder 27 similar to FIG. 14.
The bearing part 17 is composed of a ring-shaped bearing 27B and a ring-shaped bearing 27B, both of which are made of nonmagnetic and nonmetallic materials (for example, ceramic materials such as silicon carbide and silicon nitride).
It consists of In this case, the plating layer 27C as shown in FIG. 14 is unnecessary.

FIG. 16 shows still another modification of the bearing part 17,
In this example, thrust bearings are used. Note that, in view of the sliding contact with the cylindrical surface portion 11A, it is preferable to use a non-magnetic non-metal using a low-friction material such as Teflon as the material for the bearing portion 17 in this case. In addition, in the case of such a configuration, since the cylindrical body 13 itself also comes into sliding contact with the circumferential surface of the cylindrical surface portion 11A, the cylindrical body 13 is also made of a non-magnetic non-metal made of a low friction material such as Teflon, and the cylindrical surface portion 11A
If a film such as Teflon is applied to the circumferential surface of the holder, the sliding resistance can be significantly reduced.

FIG. 17 shows a case in which the present invention is applied to a gas bearing, and as shown in FIG. 17 and FIG. , and the cylindrical surface portion 11
A cylindrical surface part 1 branches almost left and right from the center part of A.
A feed hole 30 reaching the outer peripheral surface of 1A is provided. On the inner surface of the cylindrical body 13 facing the small diameter parts 11B ₁ and 13C ₁ , a ring-shaped annular body 31 is provided with a small gap between the circumferential surface of the small diameter parts 11B ₁ and 13C ₁ and the upper and lower end surfaces of the cylindrical surface part 11, respectively. It is installed so that it holds and faces each other.

When pressurized gas (air, etc.) is fed into the feed hole 30, the bearing portion 17 acts as a gas bearing. In this case, if the annular body 31 is made of a non-magnetic metal or a non-magnetic non-metal as described above, iron loss can be prevented.

Note that when the drive roller 18 shown in FIG. 8 is made of a metal material instead of an elastic material, the outer surface of the cylindrical body 13 in contact with the drive roller 18 is made of an elastic material such as rubber as shown in FIG. It may be coated with No. 33. Also in this case, the cylindrical body 13 is made of non-magnetic non-metal.

Furthermore, in each of the above-described embodiments, when a non-magnetic non-metal is used as the cylindrical body 13, the cylindrical body 13 becomes electrically charged during transfer and attracts the tapes 1 and 2. Misalignment may occur. This problem is solved by using non-magnetic but weakly conductive metals (conductive silicon carbide ceramics, conductive silicon nitride ceramics, conductive alumina, etc.).

Specifically, the surface of a non-magnetic non-metal (such as non-conductive ceramics) may be made conductive using the above-mentioned metal.

The bias magnetic field for magnetic transfer may be a direct current magnetic field instead of an alternating current magnetic field, and since no eddy current loss occurs in this case, the material may be either metal or nonmetal as long as it is nonmagnetic.

Effects of the Invention As explained above, according to the configuration of this invention,
Even if the cylindrical body 13 is made smaller, it is possible to prevent magnetic short-circuiting of the end face gap due to the bearing part 17, and also to suppress the occurrence of hysteresis loss or both hysteresis loss and eddy current loss in the bearing part 17. , deterioration of the magnetic properties of the front core section 11 due to heat generation of the bearing section 17 can be prevented.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an example of a magnetic head used for explaining the present invention, FIG. 2 is a top view thereof, and FIG.
4 is a partially sectional side view taken along line A-A in the figure; FIGS. 5, 6, and 7 are top views, front views, and side views of the front core; FIG. 8 is an arrangement diagram showing a transfer mode of the magnetic head according to the present invention, FIG. 9 is a line diagram for explaining the dimensional design of the present invention, and FIGS. 10 to 18 are respectively diagrams of the magnetic head according to the present invention. FIG. 19 is a sectional view showing another example of the cylindrical body. H is a bias magnetic head for magnetic transfer according to the present invention, 11 is a front core portion, 12 is a rear core portion, 13
is a non-magnetic cylindrical body, 15 is a winding, 1 and 2 are a mother recording medium and a blank recording medium, 17 is a bearing part,
25 and 26 are inner and outer rings.

Claims (1)

[Claims] A front core part includes a magnetic gap that generates a bias magnetic field between a pair of core halves; and a non-magnetic cylindrical body disposed around the front core part through a gap provided between the front core part and the rear core part, The magnetic cylindrical body is rotatably attached to bearings disposed above and below the cylinder, and the bearings are magnetically shielded with a non-magnetic metal or made of a non-magnetic material. magnetic head.