JPH038307A - Rotary transformer - Google Patents

Abstract

PURPOSE:To contrive a broad-band transformer, miniaturization and multi-channeling of a transformer by forming magnetic thin films consisting of an alloy magnetic material at respective winding grooves and stepped parts and allowing each radial length at the stepped parts to be larger than the whole thickness of the magnetic thin films which are formed at the base faces of each winding groove. CONSTITUTION:Both side faces of each winding groove 23 are formed into tapering shapes and stepped parts 29 and 29 are formed so that magnetic reluctance can be reduced at a surface part where a groove width is close to an opposite face 21a. Further, magnetic thin films 25... consisting of an alloy material are formed to constant thickness through insulating layers 26 and 26 at each winding groove 23 and stepped part 29. Each radial length (t3) at each stepped part 29 is set so that its length is larger than the whole thickness (t2) of the magnetic thin films 25... which are formed at base faces of the winding grooves 23 and 23. In this way, when a rotary transformer is installed at the rotary cylinder of a magnetic recording device, magnetic reluctance decreases at each stepped part 29 that is opposite to the other stepped part, even though subtle shift in terms of dimensions occurs between respective fixed and rotation parts. Thus, inductance changes in the transformer are not affected very much by the above shift.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to home VTR [video tape]
The present invention relates to a rotary transformer that transmits signals between the rotating head side and the fixed device side in a magnetic recording/reproducing device using a rotating head such as a recorder.

[Conventional technology]

A rotary transformer consists of a stator fixed to the main body of the device and a rotor that rotates with a rotating head. In the conventional rotary transformer, both the stator and the rotor were constituted by a core 11 as shown in FIG.

This core 11 is made of an oxide magnetic material made of N1-Zn ferrite and formed into a disk shape, and has a hole 12 in the center thereof through which a rotating shaft passes. Furthermore, annular winding grooves 13 that are concentric with the hole 12 are provided on the opposing surface 11 a that is one end surface of the core 11 . Note that since a two-channel rotary transformer is illustrated here, two winding grooves 13 are formed on the inner circumferential side and the outer circumferential side.

The core 11 is manufactured by molding Ni--Zn ferrite powder to which a binder is added under high pressure, firing it at a high temperature (1200° C.), and then subjecting it to predetermined machining.

In each of the winding grooves 13, 13 of this core 11, windings 14, 14 are provided.

The stator has a core 11 configured as described above fixed to the main body of the device, and each winding 14 of this core 11.
is connected to the recording/reproducing circuit on the device main body side. In addition, the rotor has a core 11 of the same configuration as the core 11 of the stator.
The central axis is bent, and the opposing surfaces 11a are arranged to face each other with a small gap between them, and are rotated along with the rotating head. Each winding 14 on the rotor side is connected to each magnetic head of the rotary head.

As a result, the rotating magnetic head and the fixed recording/reproducing circuit are magnetically coupled by the rotary transformer.
It becomes possible to transmit signals between the two.

(Problems to be Solved by the Invention) The transmission efficiency E, /aE, of the rotary transformer is determined by the following formula (2).

Here, K is the coupling coefficient, L3 is the combined inductance seen from the rotor side, and L is the inductance of the magnetic head. Also, general garlic.

<L.

From this equation (2), it can be seen that in order to increase the transmission efficiency El/aE6, the inductance LII should be made high enough to prevent the resonance frequency from dropping to the system band.

By the way, the inductance in the magnetic circuit is expressed by the following equation (2).

K.

Here, N is the number of turns of the winding, and R is the magnetic resistance of the magnetic path.

Moreover, this magnetic resistance R1 is represented by the following ⑐.

Here, μ is the magnetic path i! ! i magnetic flux, S is the cross-sectional area of the magnetic path,
! It is the length of the evacuation route.

Therefore, by substituting this 2〇 into formula (■), the following 2〇 can be obtained.

! Therefore, it can be seen that the inductance is proportional to the magnetic permeability μ and the cross-sectional area S. The inductance in equation (2) is also proportional to the magnetic permeability and cross-sectional area of the core 11 shown in FIG.

As a result, the transmission efficiency of the rotary transformer is
It depends on the magnetic permeability and cross-sectional area of , and as these become smaller, the inductance increases, and the transmission efficiency also deteriorates as .

However, in recent years, magnetic recording and reproducing apparatuses are required to have rotary transformers with higher bandwidths in order to record high-quality, high-definition video signals in, for example, VTRs. Here, the Ni-Z used for the core 11
The frequency characteristics of magnetic permeability of n-type ferrite are shown in curve B in Figure 2.
Shown below. As is clear from this curve B, the magnetic permeability of the core 11 decreases as the frequency increases;
At frequencies exceeding lOMHz, which is the band of

Therefore, the transmission efficiency of the rotary transformer is also
This problem worsens as the magnetic permeability of 1.1 decreases, making it difficult to increase the bandwidth of the device using conventional rotary transformers.

Furthermore, it is desired that magnetic recording and reproducing devices be made smaller in terms of installation space, etc., and as a result, there is a need for rotary transformers to be made smaller in size as well. Moreover, for example, household V
With the adoption of FM audio recording and flying erase heads in TRs, the number of channels in rotary transformers is increasing.As rotary transformers become smaller, the area of the opposing surface 11a of the core 11 (the area of a circle with diameter ] - "Area of the circle with diameter") becomes smaller.

Also, when the number of channels of the rotary transformer increases, the opposing surface 11 of the core 11 assigned to one channel
The area of a becomes smaller. As a result, the transmission efficiency of the rotary transformer also deteriorates as the rotary transformer becomes smaller and the number of channels increases. In addition, such miniaturization and multichannelization will increase crosstalk due to the proximity of channels, so it is also possible to use conventional rotary transformers to miniaturize the device and increase the number of channels. It was difficult.

Therefore, the conventional rotary transformer has the problem that it is not easy to increase the bandwidth, reduce the size, and increase the number of channels.

[Means to solve the problem]

In order to solve the above problems, the rotary transformer according to the present invention includes a fixed part and a rotating part that rotates with respect to the fixed part with a gap therebetween. In a rotary transformer that transmits signals between the rotating head side and the fixed device side by forming winding grooves and winding wires in each winding groove, the rotating part and the fixed part are made of non-magnetic material. Each winding groove and a stepped portion formed on the side surface of each winding groove are respectively formed on these substrates, and each winding groove and each stepped portion is made of an alloy magnetic material. A magnetic thin film is formed, and the stepped portion is characterized in that the length in the radial direction is larger than the total thickness of the magnetic thin film formed on the bottom surface of each winding groove.

[For production]

According to the above configuration, the winding on the fixed part side and the winding on the rotating part side are magnetically coupled through a magnetic circuit consisting of the respective magnetic thin films and the gap between them, and the magnetic thin film Since it is made of an alloy magnetic material, its magnetic permeability is higher than that of an oxide magnetic material even in a high frequency range.

Therefore, since the transmission efficiency can be increased by improving the magnetic permeability in this magnetic circuit, it is possible to increase the bandwidth of the rotary transformer. In addition, when the magnetic permeability is improved in this way, it becomes possible to compensate for the decrease in transmission efficiency due to the decrease in the cross-sectional area of the magnetic path, so it becomes possible to downsize the rotary transformer and increase the number of channels. Furthermore, the magnetic thin film formed in each winding groove and the magnetic thin film formed in other winding grooves are magnetically insulated by the nonmagnetic material of the substrate. Therefore, crosstalk between channels can also be reduced, making it easier to downsize and increase the number of channels.

Further, the stepped portions formed in the fixed portion and the rotating portion are formed to have a radial length larger than the total thickness of the magnetic thin film formed on the bottom surface of the winding groove. Therefore, when the fixed part and the rotating part are made to face each other, the magnetic resistance between the facing step parts is reduced.

As a result, when a rotary transformer is installed in the rotating cylinder of a magnetic recording device, changes in inductance in the rotary transformer will not be affected by this misalignment, even if there is a slight dimensional misalignment between the fixed part and the rotating part. The magnetic resistance becomes smaller due to the decrease in magnetic resistance.

[Embodiment J] An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

The rotary transformer of this embodiment has a disk-shaped stator and rotor, and the stator is fixed to the main body of the device. Further, the rotor is adapted to rotate with the rotating head, and these stator and rotor are constituted by a substrate 21 shown in FIG.

The substrate 21 is made of a disc-shaped non-magnetic material, and is provided with a hole 22 in the center for passing the rotating shaft.

Further, on the opposing surface 21a, which is one end surface of the substrate 21, an annular winding groove 23 and 2 concentric with the hole 22 are formed.
3 is provided. Note that since a two-channel rotary transformer is illustrated here, the winding grooves 23 and
Two 23 are formed on the inner circumferential side and the outer circumferential side.

Each of the above-mentioned winding grooves 23 is formed in a tapered shape on both side surfaces, and the groove width is widened at a portion close to the opposing surface 21a. Step portions 29 are formed on both side surfaces of each of the winding grooves 23 so as to reduce magnetic resistance in the surface portion near the opposing surface 21a. Further, as shown in FIG. 6(b), in each winding groove 23 and each stepped portion 29, a magnetic thin film 25 made of an alloy magnetic material is coated with a constant thickness through insulating layers 26, 26. It is formed.

Each of the above step portions 29 is shown in FIGS. 3(a) and 3(b).
), it is formed parallel to the opposing surface 21a. Each stepped portion 29 is set so that its radial length is greater than the total thickness t2 of the magnetic thin films 25 formed on the bottom surfaces of the winding grooves 23.

As a result, when a rotary transformer is installed in the rotating cylinder of a magnetic recording device, changes in inductance in the rotary transformer will occur even if there is a slight dimensional misalignment between the fixed part and the rotating part. Since it is reduced at the stepped portion 29, the influence of this shift is reduced.

Here, curve A in FIG. 2 shows the frequency characteristic of magnetic permeability when two Sendust thin films having a thickness of 4.5 μm are laminated as the magnetic thin film 25 made of an alloy magnetic material. As is clear from this curve A, the Sendust thin film is
Compared to the Ni-Zn ferrite shown in curve B above, magnetic permeability is higher in all bands, and I is the upper limit of the band for home VTRs.
There is also a difference of about 10 dB in OMI (z). Therefore, if this magnetic thin film 25 is used as a core, higher magnetic permeability can be obtained in a wider band than a core made of a conventional oxide magnetic material. .

The magnetic yl film 25 is formed by sputtering or vapor deposition, as will be explained later. For this reason, Figure 3 (
As shown in a), when both side surfaces of the winding groove 23 are formed in a cylindrical shape and are perpendicular to the opposing surface 21a, the magnetic thin film 25 formed on both side surfaces Thickness t1
・T is thinner than the bottom film, and it is difficult to form it to a constant thickness. Therefore, in this embodiment, both side surfaces of the winding groove 23 are formed into a tapered shape as described above. Then, as shown in FIG. 3(b), even when a magnetic thin film 25 is formed on the inner surface of this winding groove 23 by sputtering or vapor deposition, the film thickness t on both sides is
1. It can be formed so that tl and the total thickness t2 of the bottom surface are approximately equal and constant. The magnetic thin film 25 formed in this manner has a lower magnetic resistance than the case shown in FIG. 3(a), and can reduce variations in magnetic resistance.

Further, the magnetic thin film 25 is formed on the inner surface of the winding groove 23 with a base layer 28 interposed therebetween, as shown in FIG. This underlayer 28 is formed to improve the adhesion between the substrate 21 and the magnetic thin film 25, alleviate stress differences, prevent chemical reactions during heat treatment, and improve the orientation of the magnetic thin film 25. .

Further, as shown in FIG. 4, the magnetic thin film 25 is formed of three
It is formed to have a layered structure. This is because the magnetic thin film 25 has a laminated structure with an insulator interposed therebetween to reduce eddy current loss caused by magnetic flux.

Therefore, the thickness t of each layer of this magnetic thin film 25 is determined under conditions that satisfy the following formula.

Here, μ. is the vacuum permeability, μ. is the relative magnetic permeability at the upper limit frequency f of the usage band, and ρ is the electrical specific resistance. Further, ω=2πfC. The thickness of each insulating layer 26 is approximately several hundred to several thousand. Note that this magnetic yI film 25 is
Although it is better to have a larger number of laminated layers, a three-layered structure is used here in consideration of processing time.

As shown in FIG. 4, the substrate 21 has a protective film 27 covering the entire surface of the magnetic thin film 25 formed on the opposing surface 21a and in the winding groove 23. This protective film 27 is for electrical insulation on the facing surface 21a side and for protecting the magnetic thin film 25.

Further, as shown in FIG. 1, a winding 24 is wound within each winding groove 23 in the substrate 21. As shown in FIG. Note that the winding 24 may be patterned or may be formed of a thin film.

The stator of the rotary transformer has a board 21 having the above structure fixed to the main body of the apparatus, and each winding 24 of this board 21 is connected to a recording/reproducing circuit on the main body of the apparatus. In addition, the rotor is arranged such that the substrate 21 having the same structure is aligned with the substrate 21 of the stator so that its central axis coincides with the substrate 21 of the stator, and the opposing surfaces 21a face each other with a small distance therebetween. This is what I did. Each winding 24 on the rotor side is connected to each magnetic head of the rotary head.

As a result, the stator and rotor in this example are
A magnetic thin film 25 made of a magnetic alloy material with high magnetic permeability can be used as the core. Therefore, by improving the magnetic permeability of the core constituting the magnetic circuit, transmission efficiency can be increased even at high frequencies, making it possible to increase the frequency band of the rotary transformer. In addition, magnetic permeability across all bands is improved, making it possible to compensate for the drop in transmission efficiency due to a decrease in the cross-sectional area of the magnetic path, making it possible to downsize rotary transformers and increase the number of channels. Magnetic thin film 25 formed in wire groove 23 and other winding grooves 23
Since the magnetic thin film 25 formed on the substrate 21 is magnetically insulated by the non-magnetic material of the substrate 21, crosstalk between channels can be reduced, and the miniaturization and multichannelization described above can be facilitated. I can do it.

A method for manufacturing the substrate 21 configured as described above will be explained based on FIGS. 5 and 6.

As shown in FIG. 5(a), the substrate 21 has a hole 22 in the center.
A disc-shaped non-magnetic material with openings is used. This board 2
1 is preferably a material that has a linear expansion coefficient equivalent to that of the magnetic thin film 25 and has good workability.

The substrate 21 has holes 22 as shown in FIG. 5(b).
Two annular step portions 29 are formed which are concentric with the substrate 21 and parallel to the surface of the substrate 21. Then, as shown in FIG. 5(C), two annular winding grooves 23, 23 are formed concentrically with respect to the hole 22 and the stepped portions 29, 29. At this time, as shown in FIG. 3(b), the stepped portions 29, 29 have a radial length t that is larger than the total thickness t2 of the magnetic thin film 25 to be formed on the bottom surface of the winding groove 23 in a later step. Set it so that it also becomes larger.

In addition, the step portions 29, 29 and the winding grooves 23, 23
As mentioned above, both sides of each are formed into a tapered shape. In addition, these stepped portions 29, 29 and the winding groove 23
- 23 can be formed not only by machining but also by selective etching. Further, when the grooves are formed by machining, it is preferable to perform an etching process to reduce the surface roughness within each stepped portion 29 and each winding groove 23.

Once the winding grooves 23, 23 are formed, as shown in FIG. A stratum 28 is formed. For this base layer 2 days, depending on the purpose of improving adhesion as mentioned above,
Tags , AltO, , Cry 03 or SiO
oxygen compounds such as or composites thereof, Cr5Ta,
Non-magnetic metals such as Nb, Hf or Mo or Fe, N
A magnetic metal such as i or Ni-Fe is used.

When the base layer 28 is formed, as shown in FIG.
A magnetic thin film 25 is formed on the entire inner surface by sputtering or vapor deposition.

The magnetic thin film 25 is formed in three layers with insulating layers 26 interposed therebetween, as shown in FIG. 6(b). Each layer of this magnetic thin WA25 is N1-Fe based,
Alloy magnetic materials such as Fe-3i series, Fe-Affi series, Fe-Al-3t series or Go-Fe-Ni series, Co-
Alloy magnetic materials such as Zr-based or Co-Nb-based or Cr
, Fe, Ni, Ti, , Ta5Zr, Nb, Si, B
SY, Re.

An amorphous alloy magnetic material containing one or more elements such as Hf, Zn, Mn, Au, or Ru is used. Further, the insulating layers 26 are also formed by sputtering or vapor deposition, and are made of Sin.

, ZrO, Ta, O, or Cr.

Once the magnetic thin film 25 is formed, heat treatment is performed to stabilize the magnetic properties of the magnetic thin film 25.

This heat treatment varies depending on the material of the magnetic thin film 25, but for example, in the case of Fe-Aj2-3i alloy magnetic material,
500° (1 to 1 hour.

When the heat treatment is completed, the opposing surface 21a is polished until the substrate 21 is exposed, as shown in FIG. 5(e). Further, after this polishing process, it is preferable to perform an etching process in order to remove the process-affected layer and improve the magnetic properties.

When the polishing process is completed, as shown in FIG. 5(f), a protective film 27 is formed on the opposing surface 21a and the entire surface of the magnetic thin film 25 in each winding groove 23 by sputtering or vapor deposition. This protective film 27 is made of Si0. Alternatively, Cr or the like is used.

Once this protective film 27 is formed, the base Fi, 21 is completed. Then, as shown in FIG. 1, a rotary transformer is formed by winding a winding 24 in each winding groove 23 of this substrate 21, fixing this winding 24, and performing wire processing.

In this embodiment, the magnetic thin films 25... formed on the step portion 29 are formed parallel to the opposing surface 21a, but are not limited to this, and for example, the magnetic thin films 25...
As shown in the figure, it may be formed substantially perpendicular to the stepped portion 29.

Thereby, the magnetic flux transmission efficiency can be further improved than when the magnetic thin film 25 is formed parallel to the stepped portion 29.

Further, the magnetic thin film 25 may have either isotropy or anisotropy, for example, the step portion 29 and the winding groove 23
When the magnetic thin film 25 has anisotropy, it becomes possible to control the magnetic flux transmission efficiency.

〔Effect of the invention〕

As described above, the rotary transformer according to the present invention includes a fixed part and a rotating part that rotates with a gap with respect to the fixed part, and has winding grooves on the opposing surfaces of the fixed part and the rotating part. In a rotary transformer, the rotating part and the fixed part are made of non-magnetic material, and the rotating part and the fixed part are made of non-magnetic material. It has a substrate, and each winding groove and a stepped portion formed on the side surface of each winding groove are respectively formed on these substrates, and each of the winding grooves and each stepped portion has a magnetic material made of an alloy magnetic material. A thin film is formed, and the stepped portion is formed such that the length in the radial direction is greater than the total thickness of the magnetic thin film formed on the bottom surface of each winding groove.

This increases the magnetic permeability of the magnetic circuit and improves the transmission efficiency, making it possible to increase the bandwidth of the rotary transformer. In addition, when the magnetic permeability is improved in this way, it becomes possible to compensate for the decrease in transmission efficiency due to the decrease in the cross-sectional area of the magnetic path, so it becomes possible to downsize the rotary transformer and increase the number of channels. Furthermore, since the channels are insulated by the non-magnetic material of the substrate, it is possible to prevent an increase in crosstalk due to the miniaturization of the rotary transformer and the increase in the number of channels.

Therefore, the present invention has the effect of promoting higher bandwidth, smaller size, and multi-channel rotary transformers.

Furthermore, since the radial length of the stepped portion is larger than the total thickness of the magnetic thin film formed on the bottom of the winding groove,
Magnetic resistance at the stepped portion is reduced. Therefore, when a rotary transformer is installed in the rotating cylinder of a magnetic recording device, even if the fixed part and the rotating part are slightly misaligned in dimension, the effect on the inductance of the rotary transformer will be small due to the reduction in magnetic resistance mentioned above. It has the effect of becoming.

[Brief explanation of drawings]

1 to 6 show one embodiment of the present invention. FIG. 1 is a longitudinal sectional view of the rotary transformer. FIG. 2 is a diagram comparing the frequency characteristics of an alloy magnetic material and an oxide magnetic material. FIGS. 3(a) and 3(b) are partially enlarged vertical cross-sectional views comparing the shapes of winding grooves in a rotary transformer. FIG. 4 is a partially enlarged longitudinal sectional view of a winding groove in a rotary transformer. FIGS. 5(a) to 5(f) are longitudinal cross-sectional views showing each manufacturing process of the rotary transformer. FIGS. 6(a) and 6(b) are partially enlarged vertical cross-sectional views of the winding groove portion in each manufacturing process of the rotary transformer. FIG. 7 shows another embodiment of the present invention, and is a partially enlarged vertical sectional view of a winding groove in a rotary transformer. FIG. 8 shows a conventional example, and is a vertical sectional view of a rotary transformer. 21 is a substrate, 21a is an opposing surface, 23 is a winding groove, 24 is a winding wire, 25 is a magnetic thin film, and 29 is a stepped portion.

Claims (1)

[Claims] 1. It consists of a fixed part and a rotating part that rotates with respect to the fixed part through a gap, and a winding groove is formed on each opposing surface of the fixed part and the rotating part, and a winding is inserted into each winding groove. In a rotary transformer that transmits signals between the rotating head side and the fixed device side, the rotating part and the fixed part have a substrate made of a non-magnetic material, and each winding groove and each winding groove A step portion formed on the side surface of the substrate is formed on each of these substrates, and a magnetic thin film made of an alloy magnetic material is formed in each of the winding grooves and each step portion, and the step portion has a radial length. A rotary transformer characterized in that the thickness of each winding groove is greater than the total thickness of a magnetic thin film formed on the bottom surface of each winding groove.