JPS63172411A - Rotary transformer - Google Patents

Abstract

PURPOSE:To make it possible to miniaturize a rotary transformer, without deterioration in transmission gain and increase in reduced cutoff frequency, by a structure wherein the facing magnetic surfaces of a primary transformer and a secondary transformer, which are magnetically coupled, cover parts of grooves, in which coils are provided so that parts of the grooves are made to remain as gaps. CONSTITUTION:Grooves 9 for providing coils are formed in the facing surfaces of a rotary transformer on the primary side and the secondary side in the circumferential direction. The surface of each groove is covered so that a part is made to remain as gaps 13. The facing areas of the magnetic surfaces of a primary transformer 1 and the secondary transformer 2 in the rotary transformer, which are magnetically coupled, are secured. When the length of the gap 13 is equal to that of a conventional transformer, the magnetoresistance of the gap part can be reduced by the increment of the facing area. Even if the rotary transformer is made compact, the specified values of the inductance and the coupling coefficient in operation can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotating transformer used in a magnetic recording/reproducing device.

BACKGROUND OF THE INVENTION In recent years, magnetic recording and reproducing devices have become smaller in size at a remarkable rate, and the components constituting these devices are also required to have smaller volumes. In particular, in recording systems using rotating heads such as video tape recorders, the size of the device is limited by the size of the cylinder used, and the main volume of this cylinder is occupied by the internal rotating transformer. is large. Therefore, in order to downsize magnetic recording and reproducing devices, it has become an important issue to find out how to downsize the rotary transformer without deteriorating its mechanical characteristics.

4A, B, and C show a side view, a plan view, and a sectional view of a conventional rotary transformer. In Fig. 4, 1 is a primary transformer of a rotating transformer made of magnetic material, 2 is a secondary transformer, 3 is an air gap separating the primary and secondary transformers of the rotating transformer, and 4 is a magnetic material through the air gap. 6.6 is the primary coil for applying or reproducing signals, 7.8 is 2 for reproducing or reproducing signals.
This is the next coil.

A magnetic head is connected to the beginning and end of the primary coil 6.6, and an amplifier for applying or reproducing a signal is connected to the beginning and end of the secondary coil 7.8. In such a configuration, the primary transformer 1 of the rotary transformer
rotates, and the reproduction signal from the magnetic head is transmitted to the primary coil 6.
．． 6, the air gap 3 between the rotating transformer 1.2
Generates magnetic flux through the This magnetic flux generates an induced voltage in the coil 7.8 installed in the secondary transformer 2, and the reproduction output can be transmitted to the amplifier without rotating the secondary transformer 2.

Problems to be Solved by the Invention However, when trying to miniaturize such a rotating transformer, if the external shapes of the coils 5, 6, 7.8 do not change,
Since the groove width dimension necessary for installing these does not change, the opposing area of the magnetic surfaces 4 that are magnetically coupled becomes smaller. This increases the magnetic resistance of the air gap 3, which means that the inductance and coupling coefficient required for the rotating transformer can be reduced.
This will degrade the transmission gain and low-frequency cutoff frequency, which are important transmission characteristics of a rotating transformer.

The present invention provides a rotary transformer that is free from the problems of deterioration of transmission characteristics and increase in low cutoff frequency that occur when the rotary transformer is downsized.

Means for Solving the Problems In order to achieve the above object, the rotary transformer according to the present invention has the following features:
The opposing magnetic surfaces of the next-side and secondary-side transformers are structured so that the groove in which the coil is installed is closed, leaving a part of the gap.

Function: In a rotary transformer having such a configuration, the area of the magnetic surfaces that are magnetically coupled through the air gap can be increased. Therefore, if the length of the gap is kept the same as in the conventional case, the magnetic resistance of the gap can be reduced by the increase in the facing area. As a result, even if the rotary transformer is downsized, it is possible to maintain predetermined values for the inductance and coupling coefficient during operation. Therefore, the problems of a reduction in transmission gain and an increase in the low cutoff frequency of the rotary transformer are eliminated.

Embodiment As an embodiment of the present invention, FIGS. 1A, 1B, and 1C show a side view, a plan view, and a sectional view of a rotary transformer, respectively. In FIG. 1, 1 is the primary transformer of the rotary transformer, 2 is the secondary transformer of the rotary transformer, 3 is the air gap 1 separating the primary transformer 1 and the secondary transformer 2 of the rotary transformer;
4 is the magnetic surface of the primary transformer 1 and the secondary transformer 2 that are magnetically coupled; 6, 6 are the primary coils a, b for applying or reproducing signals; and 7.8 are the magnetic surfaces for reproducing signals. The secondary coils a, b, and 9 are grooves provided on the inner and outer circumferences for installing the primary coil and the secondary coil. Reference numerals 10, 11, and 12 are concentric disk-shaped lids that close the six grooves 9 with some concentric gaps remaining. 13 is a gap between the lids 10, 11.12. Primary coil 6
．． A magnetic head is connected to the beginning and end of the secondary coil 7.8, and a recording/reproducing amplifier is connected to the beginning and end of the secondary coil 7.8. A groove 9 for installing the coil is formed in the circumferential direction on the opposing surfaces of the primary and secondary sides of the rotary transformer, and the surface of this groove is filled with a part of the air gap as shown in Figure 1B. This is to ensure the facing area of the magnetic surfaces of the primary transformer 1 and the secondary transformer 2 of the rotary transformer that are magnetically coupled to each other.

In such a configuration, the operation of the rotary transformer of the present invention during regeneration will be described below. When a signal current generated from the magnetic head is applied to the primary coil 6.6, alternating magnetic flux is generated in the air gap and the primary side 1 and secondary side 2 of the transformer via the air gap 3 and the lids 10, 11.12. occurs. This AC magnetic flux induces a signal voltage in the secondary coil 7.8, and one signal on the primary side is transmitted to the secondary side.

At this time, set the inductance and loss resistance of the magnetic head to L
Let h and Rh be the self-inductance and loss resistance of the primary transformer 1 of the combined rotating transformer. R
1, and the primary side transformer 1 and the secondary side transformer 2
If the winding ratio is n and the coupling coefficient is k, then this is the low cutoff frequency of the rotary transformer, and the gain G in the middle range is as follows. Therefore, by increasing the self-inductance L1 of the primary transformer 1, the cutoff frequency f can be increased. It can be seen that the gain G decreases and the gain G increases. By the way, such self-inductance can be considered as follows. FIG. 2 shows an enlarged cross-sectional view of the main parts of the rotary transformer of this embodiment shown in FIG. The magnetic flux induced by the current in the primary transformer flows as indicated by the arrow in FIG. Since it is extremely small in comparison, it is the magnetic resistance of the air gap 3 that determines the self-inductance of the primary transformer. here,
The reason why the gap 13 is provided between each of the lids 10, 11 and 12 that close the groove 9 is to prevent the magnetic flux generated in the primary transformer from turning into a closed magnetic flux inside the primary transformer. Therefore, the width l of this gap 13 needs to be larger than the width 2 of the gap 3 to some extent. Now, the radial widths of the lids 10, 11 and 12 having magnetic surfaces that are magnetically coupled are Wl, W2, respectively. W3, the average radius is rl, r2, r3, and the width of the void 30 is 2.
If the number of turns of the primary coil is N, then the self-inductance L1 is as follows. However, μ. is the magnetic permeability in air. In the conventional technology, the radial width w1. lol
2. W3 can only take a size limited by the groove 9, but the lids 10, 11.
W2. W3, and if the external dimensions are the same as the conventional one, the self-inductance on the primary side can be increased by the proportion derived from the above equation. Furthermore, by making the self-inductance the same, it is possible to downsize the rotary transformer without deteriorating the transmission characteristics.

In this embodiment, in order to close the groove in which the coil is installed, leaving a part of the gap, a disc-shaped lid is provided, but as shown in FIG. The structure may be such that it is incorporated in the next-side transformer and the secondary-side transformer. In the case of the embodiment shown in FIG. 3A, the lid 30
, 31 can be reduced to two, which has the effect of reducing manufacturing costs. In the case of the embodiment shown in FIG. 3B, by rounding the cross-sectional shape of the grooves 19 and 20 in which the coils are installed, the lid part can be made thinner, which has the effect of reducing the overall thickness of the rotating transformer. There is.

Effects of the Invention The present invention has a structure in which the opposing magnetic surfaces of the primary transformer and the secondary transformer that are magnetically coupled are closed, leaving a part of the gap in which the coil is installed, thereby increasing the transmission gain. This makes it possible to downsize the rotary transformer without deteriorating the frequency or increasing the low-frequency cutoff frequency.It also has the effect of improving the transmission characteristics if the external dimensions of the rotary transformer are kept the same. are doing. Of course, if the rotating transformer of the present invention is used, the magnetic recording device itself can be downsized, and its characteristics will not deteriorate due to the downsizing.

[Brief explanation of the drawing]

FIG. 1A is a side view of a rotary transformer according to an embodiment of the present invention, FIG. 1B is a plan view of magnetic surfaces that are magnetically coupled, and FIG.
Figure C is a sectional view of the same, Figure 2 is a sectional view of the main part showing the operation of the rotary transformer of the present invention, Figures 3A and B are sectional views of the main part showing the rotary transformer of another embodiment of the present invention, 4A and 4C are a side view, a plan view, and a sectional view showing a conventional rotary transformer. 1... Primary side transformer, 2... Secondary side transformer, 3... Air gap, 4... Magnetic surface, 6, 6...・Primary coil a, b, 7.8...
...Secondary coil a, b, 9...Groove, 10
, 11.12... Circular void, 13...
・Void. Name of agent: Patent attorney Toshio Nakao and one other person Figure 2 Figure 4 (A)?

Claims (1)

[Claims] A rotary transformer characterized in that opposing magnetic surfaces of a primary transformer and a secondary transformer that are magnetically coupled close a groove in which a coil is installed, leaving a part of the gap.