JPH02122402A - Rotary transformer - Google Patents

Abstract

PURPOSE:To decrease an induced voltage, and to improve an S/N in an RF transmission system in a wide range by setting a signal current in a reverse direction between a first coil and a second coil formed with folding one edge of the first coil. CONSTITUTION:A coil 1 consists of a coil 1a at a radius ra, and a coil rb at a radius rb, which is formed by folding one edge of the coil 1a, formed so as to have the reverse winding direction to the coil 1a and so as to be concentric (radius rb > radius ra), and the coil 1a is concentrically arranged inside the coil 1b, and a signal currents 'is' are applied in mutually reverse directions between the coils 1b and 1a. Further, a coil 2 has the same constitution, and the signal currents is are applied in the mutually reverse directions between coils 2d and 2c. Thus, the induced voltage is offset, and the influence of unnecessary radiation on a rotary transformer can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary transformer applied to, for example, a rotating drum type VTR.

[Summary of the invention]

This invention provides a rotary transformer including a first coil and a second coil formed by folding back one end of the first coil.
The first coil and the second coil are
By arranging the two coils so that the signal current is in opposite directions, the influence of unnecessary radiation can be significantly reduced.

[Prior Art] Recently, as the recording band of a VTR has expanded, the band of the recording/reproducing amplifier system, the so-called RF band, has also been expanding. For example, the RF band of a conventional NTSC VTR is as follows:
The frequency was ~7 to 10MHz for home use, and ~15MHz for commercial use, but HDTV (High Definition)
The RF band in VTRs for ion TV has become wider, extending from 20 to 40 MH2.

Due to this widening of the band, it is no longer possible to expect the low-pass filter characteristics that the RF transmission system of VTRs had in the past, and the influence of unnecessary radiation may occur on the rotary transformer from outside the VTR and inside the VTR. It has become.

An example of unnecessary radiation from outside the VTR is, for example, 80
FM broadcasting near MHz, amateur radio (CB is 27M
Hz) etc.

On the other hand, as an example of unnecessary radiation inside a VTR, for example, M
V that handles sampling analog signals such as USE signals
In a TR, the sampling frequency [or oversampling frequency] is used, and in a VTR that handles digital signals, the clock frequency (4f sc' = 14.3MHz
~74.25 MHz (HD)), etc.

[Problem to be solved by the invention]

In such a situation, there is a problem in that the unnecessary radiation not only has a bad influence on the signal through the rotary transformer, but also that the influence of the unnecessary radiation differs between channels, especially in a planar rotary transformer.

The above-mentioned problems will be explained below in the conventional example shown in FIG.

In FIG. 4, B is placed on the outside of the coil 21 for the A channel.
A coil 22 for the channel is arranged.

Let the radius of each coil 21,22 be r1, r2, respectively (r
2>rl). In addition, 23 and 24 are coils 21 and 22, respectively.
This is the terminal connected to.

If the magnetic flux density from the outside is B(t), then the coil 21.
The magnetic fluxes Φ1 and Φ2 interlinking with 22 are the (21)th and (21)th, respectively.
22) It becomes as follows.

Φl=π・rl2・B(t)...(21) Φ2=π・
r2t-B(t) (22) The induced voltage E per turn generated by this electromagnetic induction is expressed by the following formula.

And its absolute value is as shown in the following equation.

E2>El (25) Therefore, if the number of turns is constant, the outer coil 22 will definitely be greatly affected by unnecessary radiation.

The actual output due to the influence of unnecessary radiation is expressed by the following formula, assuming that the number of turns of the coil 21 is N1 and the number of turns of the coil 22 is N2.

Therefore, the number of turns N1, N
By selecting 2, it is possible to eliminate the level difference in the influence of unnecessary radiation between channels.

N1・r12=N2・r22...(28) According to the above-mentioned technique, although it is possible to eliminate the level difference in the influence of unnecessary radiation between channels, it is possible to eliminate the inductance L of the coil of each channel as a rotary transformer. There was a problem in that it was difficult to match the signals, and the matching conditions for recording and reproducing signals, such as the head and recording/reproducing amplifier, were impaired. In other words, although it is possible to eliminate the level difference in the influence of unnecessary radiation between channels, there is a problem in that the influence of unnecessary radiation itself cannot be reduced.

Therefore, an object of the present invention is to provide a rotary transformer that is less susceptible to unnecessary radiation.

[Means to solve the problem]

This invention consists of a first coil and a second coil formed by folding back one end of the first coil, and a signal current flows in opposite directions between the first coil and the second coil. The structure is arranged so that

[Effect]

In a rotary transformer, the signal current is in opposite directions between the first coil and the second coil, so the polarity of the induced voltage electromagnetically induced by unnecessary radiation is different from that in the first coil. and the second coil are opposite to each other, and the induced voltages cancel each other out. Therefore, the influence of unnecessary radiation on the rotary transformer can be significantly reduced.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. This first embodiment is applied to a planar facing type rotary transformer.

FIG. 1 shows a coil of a rotary transformer according to a first embodiment, and FIG. 2 shows a cross-sectional view of a part of the rotary transformer.

In FIG. 1, for example, a coil 2 for the B channel is provided outside the coil 1 for the A channel. Although not shown, these coils 1 and 2 are wound in grooves formed on one surface of a disk-shaped core, and cores having coils similar to those in FIG. 1 are provided facing each other. There is. still,
A signal current is is supplied from each terminal 3.4.

Coil 1 includes a coil 1a with radius ra and this coil 1a.
A coil lb with a radius rb (radius rb>
radius ra). And coil 1b
A coil la is arranged concentrically inside the coil 1b, and the signal current is is directed in opposite directions between the coil 1b and the coil 1a. Incidentally, the radius difference (radius ra - radius rb) between the coils 1as1b is set to an interval that does not cancel the magnetic field formed by each coil 1a, 1b.

The coils 2 have a similar configuration, and include a coil 2c with a radius re, and a coil 2d with a radius rd (radius rd > radius rc). A coil 2c is arranged concentrically inside the coil 2d, and a signal current i is generated between the coil 2d and the coil 2c.
s are arranged in opposite directions. Note that the radius difference (radius rd - radius rc) between the coils 2c and 2d is set to such an extent that the magnetic fields formed by the coils 2c and 2d are not canceled.

The reduction of induced voltage will be described below using the coil 1 (1a, lb) as an example.

If the external magnetic flux density is B(t), the coil la,
The magnetic fluxes Φa and Φb interlinking with lb are respectively expressed by equation (1),
It is expressed as in equation (2).

Φa = π ・ra2 ・B(t) ・ ・ ・(1
) Φb = π ・rbt −B(t) ・ ・ ・(2
) The induced voltage E per 1 turn generated by this electromagnetic induction is expressed by the following formula.

of by the way, Therefore, the induced voltage E is as follows.

If the radii ra and rb are selected so that the radius difference (rb-ra) is smaller than the radius ra or rb (i.e., rb -
ra≠0), the following equation holds.

Moreover, as a result, the voltage induced by unnecessary radiation can be significantly reduced, and a rotary transformer that is hardly affected by unnecessary radiation can be constructed. In addition, it is possible to improve the S/N in a wideband RF transmission system,
A planar facing type rotary transformer can also be used for a wideband VTR. Although the coils 2 (2c, 2d) will not be described in detail, similarly to the coil 1, the influence of unnecessary radiation can be significantly reduced.

As shown in FIG. 2, there is a gap g between the rotor 6 and the stator 7 of the rotating drum 5, and the coils la and lb for the A head on the rotor 6 side are
Coils 8a and 8b for the head are compatible. In this case, if the radius difference (rb-ra) is too small, there is a problem that the magnetic fields formed by the two coils 1a and 1b cancel each other out. Therefore, it is preferable that the relationship radial difference (rb-ra)≧gear g be satisfied between the gap g and the radius difference (rb-ra).

A second embodiment of the invention will be described below.

The difference between this second embodiment and the first embodiment is that even if the number of turns of each coil is different, as long as the following conditions are satisfied, the influence of unnecessary radiation can be eliminated for each channel. Furthermore, the unbalance of the inductance L of the coil for each channel can be eliminated.

■Inductance La of coil 1 (A channel)
If the number of turns of the coil 1a is Na, the area of the portion formed by the radius ra of the coil 1a is Sa, the number of turns of the coil lb is Nb, and the area is sb, then in general, the inductance L
Since the number of turns N is proportional to N, the following equation holds true.

5a-Na=Sb-Nb...(9)π-ra"
・Na=tt −rb”−Nb・−・(10) ■For the inductance b of coil 2 (B channel), the number of turns of coil 2c is Nc, the area of the part formed by the radius rc of coil 2c is Sc, If the number of turns of the coil 2d is Nd and the area is Sd, then the inductance L is set to -S.
Since the number of turns N is proportional to N, the following equation holds true.

5c-Nc=Sd-Nd...(11)π-rc"
・Nc=z −rd" ・Nd...(12)■ Regarding inductance La and Lb, LaζLb...(
13) (It is sufficient if the impedance can be made equal between the two channels.) Therefore, if a rotary transformer is formed based on the configuration and conditions as described above, the influence of unnecessary radiation can be eliminated for each channel, and The inductances La, Lb in each channel can be made equal, and the unbalance of inductance between the channels can be eliminated.

Other details are the same as in the first embodiment,
Omit duplicate explanations.

FIG. 3 shows a third embodiment of the invention. The third embodiment differs from the first embodiment in that the present invention is applied to a cylindrical rotary transformer.

In the configuration shown in FIG. 3, for example, the coil 10 for the A head
are arranged as shown. Note that a signal current is is supplied from the terminal 11. The coil 10 is composed of a coil 10e and a coil 10f, which is formed by folding back one end of the coil 10e so that the winding direction is opposite, and both coils 10e and lof have the same cross-sectional area. and the radii from the center are the same. The signal current is is arranged to be in the opposite direction between the coil LOe and the coil 10f.

Other details are the same as in the first embodiment,
Omit duplicate explanations.

In the first to third embodiments, a two-channel rotating drum type VTR is described, but the invention is not limited to this example, and can be similarly applied to, for example, a four-channel rotating drum type VTR. .

Further, the present invention can be similarly applied to a rotary transformer in which a coil is formed on a printed circuit board.

〔Effect of the invention〕

According to the rotary transformer according to the present invention, the rotary transformer includes the first coil and the second coil formed by folding back one end of the first coil. Since the structure is such that the signal current is in the opposite direction between the two, there is an effect that the influence of unnecessary radiation from the outside or inside the VTR on the rotary transformer, that is, the induced voltage can be significantly reduced. The above-described effects have the effect of improving the S/N in a wideband RF transmission system.

According to the embodiment, there is an effect that the influence of unnecessary radiation on the rotary transformer can be eliminated.

This has the effect that the inductance of the coil between channels can be made equal, and that unbalance of inductance can be prevented. This has the effect of preventing loss of matching conditions for recording and reproducing signals. Further, due to the various effects described above, there is an effect that the planarly opposed rotary transformer can be applied to a wideband VTR.

[Brief explanation of drawings]

FIG. 1 is a perspective explanatory view showing a first embodiment of the present invention;
The figure is a partial sectional view for explaining the formation of a magnetic field, FIG. 3 is a perspective explanatory view showing a third embodiment, and FIG. 4 is a perspective explanatory view of a conventional example. Explanation of main symbols in the drawings 1.1a, lb, 2.2c, 2d, 21.22: coil, is: signal current.

Claims (1)

[Claims] Consisting of a first coil and a second coil formed by folding back one end of the first coil, a signal is transmitted between the first coil and the second coil. A rotary transformer characterized by being arranged so that the current flows in the opposite direction.