JPH0528732Y2 - - Google Patents

Description

[Detailed explanation of the idea]

INDUSTRIAL APPLICATION FIELD The present invention relates to a rotary transformer, and particularly to a rotary transformer that can improve signal transmission performance. 2. Description of the Related Art In general, recording and reproducing equipment using a rotating head, such as a video tape recorder and a digital audio tape recorder, uses a rotary transformer to exchange signals between an electronic circuit body and the rotating head. This rotary transformer consists of a rotor core and a stator core of the same configuration, and each core has an annular groove formed in a disk-shaped core body made of a magnetic material, and a coil is disposed within this annular groove. ing. Furthermore, recently, a technique has been proposed in which a copper coil pattern is directly formed in the annular groove of the core body using thin film technology instead of a wire-shaped coil. Problems that the invention aims to solve In a rotary transformer in which a coil pattern is formed using the above-mentioned thin film technology, through holes are formed at both ends of the coil, and a through hole is formed at each end of the coil, so that the coil pattern is formed in a different plane from the rotating magnetic head. The structure is such that a lead wire or a lead wire from the electronic circuit body is connected to the coil through this through hole. Conventionally, this pair of through holes were formed with a large distance between them. Further, since the diameter of this through hole is small and the thickness of the copper film at the inner periphery of the through hole is small, magnetic flux becomes dense and self-inductance increases.
Generally, the current applied to a rotary transformer is a minute current, and the signal current is obstructed by the increase in self-induced electromotive force that accompanies the increase in inductance, and the signal cannot be transmitted appropriately, resulting in a decrease in signal transmission efficiency. There was a problem with putting it away. Therefore, an object of the present invention is to provide a rotary transformer that solves the above problems by having a structure in which the self-induction generated in a pair of through holes cancels each other out. Means for Solving the Problems In order to solve the above problems, in the present invention, a rotor and a stator, which are formed by patterning a thin film coil having a through hole at the end on a core made of ferrite, are arranged facing each other. arranged,
In a rotary transformer that transmits and receives signals between the two, both ends of the thin film coil are placed close to each other, a conductor is connected to one end, and the conductor is inserted into a through hole formed at the other end. The core is characterized in that it is drawn out to a surface different from the surface on which the thin film coil is disposed, and the other terminal portion is drawn out to a surface different from the surface on which the thin film coil of the core is disposed through a through hole. Embodiment FIGS. 1, 2 and 3 show an embodiment of a rotary transformer according to the present invention. As mentioned above, the rotary transformer 1 is composed of a rotor core and a stator core that are arranged opposite to each other, but since each core has the same configuration, for convenience of explanation,
Only one core 2 will be illustrated and explained. Figure 1 also shows the coil arrangement surface (hereinafter surface 2a).
2 shows a surface (hereinafter referred to as back surface 2b) in which a groove portion (to be described later) is formed, and FIG. 3 shows a cross section taken along line A--A in FIG. 1. The core 2 is a disc-shaped member made of ferrite (for example, NiZn ferrite material), and has four concentric grooves 3 to 6 formed on its surface 2a, as shown in FIG. Thin film coils 7 to 10 are formed inside the concentric grooves 3 to 6 using thin film forming techniques such as etching and photolithography. By forming the coil of the rotary transformer 1 into a thin film, there are various advantages such as eliminating the troublesome winding process, reducing the thickness of the core, and improving the yield. In addition, through holes 11a to 14a, 11 are provided at each terminal end of each thin film coil 7 to 10.
b to 14b are formed. Pairs of through holes 11a and 11b, 12a and 12b, and 13a formed at each terminal end of each of the thin film coils 7 to 10
and 13b, 14a and 14b are formed so as to be on the same straight line with respect to the radial direction of the core 2, respectively, and are located at the side edge positions of the central circular grooves 3 to 6 that sandwich the corresponding thin film coils 7 to 10. It is formed. Therefore, each pair of through holes 11a, 11b, 12
a and 12b, 13a and 13b, and 14a and 14b are formed in extremely close proximity. Attention is now paid to the back surface 2b of the core 2 shown in FIG. As shown in the figure, grooves 15 to 18 are formed on the back surface 2b, and each groove 15 to 1
Through holes 11a to 14a, 11b to 1 in 8
4b is formed. Therefore, the thickness of the core 2 is reduced at the positions where the through holes 11a to 14a, 11b to 14b are formed and the positions in the vicinity thereof due to the formation of the grooves 15 to 18. Also back side 2
b has through holes 11a to 14a, 11b to 1
conductive pattern 19 electrically connected to 4b
Conductive patterns 19a to 22a to which jumper wires b to 22b, 19c to 22c and jumper wires to be described later are connected are formed. Incidentally, 23 and 24 are mounting recesses in which a Hall element (not shown) for detecting the rotational speed of the core 2 is mounted when the rotary transformer 1 is incorporated into a video tape recorder or the like, and 25a to 25d, 26a to 26d is a conductive pattern to which the lead wire of the Hall element is connected. Next, a structure in which the terminal ends of the thin film coils 7 to 10, which are the main part of the present invention, are drawn out to the back surface 2b will be explained. Incidentally, since the structure in which each of the thin film coils 7 to 10 is drawn out to the back side is the same, for convenience of explanation, only the drawing structure in the thin film coil 7 will be explained using FIG. 3, and the other thin film coils 8 to 10
The explanation will be omitted. As mentioned above, the pair of through holes 11a, 1
1b is formed integrally with the conductive patterns 19b and 19c on the back surface 2b during pattern formation, so both ends of the thin film coil 7 are connected to the through holes 11.
It is pulled out to the back surface 2b via a and 11b. Among the terminal ends of the thin film coil 7, the terminal end on the inner circumferential side is connected to the back surface using a conductor wire 27 such as a jumper wire (conductor wires 28 to 30 disposed in the thin film coils 8 to 10 are shown in FIG. 1). It is pulled out to 2b.
This conductive wire 27 has one end connected to the through hole 11a.
The other end is inserted through the through holes 11a and 11b, drawn out to the back side 2b, and soldered to the conductive pattern 19a. Here, the through holes 11a, 11b and the conductor 2
Consider the self-inductance within the through holes 11a and 11b of No.7. As described above, the generated magnetic flux becomes denser in the through holes 11a and 1b, and there is a tendency for the self-inductance to increase. However, through holes 11a and 11b
By inserting the conductor 27 through the through holes 11a and 11b, the current flowing through the through holes 11a and 11b and the conductor 2
The currents flowing through hole 7 are in opposite directions (through hole 1
1a, 11b and the conducting wire 27 are connected to each end of the thin film coil 7), and the magnetic flux generated by the current flowing through the through holes 11a, 11b and the magnetic flux generated by the current flowing through the conducting wire 27 cancel each other out. Therefore, the self-inductance in the thin film coil 7 is reduced, and the signal transmission efficiency of the rotary transformer 1 can be improved. Incidentally, in order to demonstrate that the self-inductance is reduced as described above, Table 1 shows the results of an experiment conducted by the present inventor. The inductances of a rotary transformer having a thin film coil configured according to the present invention (example) and a rotary transformer having a conventional thin film coil configured (comparative example) were measured. Further, the number of coils was 4 (1CH to 4CH), and the number of turns of each coil was 3 times for 1CH and 2 times for 2CH to 4CH.

[Table] From Table 1 above, in contrast to the comparative example, the inductance of the example is 1.05μH for 1CH and 1.05μH for 2CH.
1.33μH, 3CH 1.18μH, 4CH
It can be seen that it has decreased by 1.14 μH. Next, a method for manufacturing the core forming the rotary transformer 1 having the above structure will be explained. In the following description, a core in which two thin film coils are formed will be described. First, as shown in FIG. 4, NiZn ferrite particles are sealed in a mold 31 and pressure-molded at a pressure of, for example, 3 t/cm ² to form a core block 32 (indicated by matte finish in the figure) shown in FIG. At this time, a hole 33 into which the cylinder shaft will be inserted later and a small hole 3 which will become a through hole.
4a, 34b, 35a, and 35b are also formed at the same time. The core block 32 is then fired at 1100°C to 1200°C. This fired core block 32
As shown in FIG.
Grooves 36, 3 are provided at the locations of b, 35a, 35b.
7 is cut. As a result, the small holes 34a, 3
4b, 35a, 35b are the front surface 32a and the back surface 32b
is penetrated. Next, using a cutting tool 38 shown in FIG. 7, concentric grooves 39 and 40 are formed between each of the small holes 34a and 34b, and between 35a and 35b, as shown in FIG. The core block 3 has grooves 36, 37 and concentric grooves 39, 40 formed therein.
In step 2, an inspection is performed to determine whether the dimensions, shape, etc. are within predetermined tolerances. As a result of the inspection, core blocks 32 that meet predetermined conditions are subjected to a copper plating process. Since copper plating cannot be performed directly on ferrite, a base layer is first formed by electroless plating, and then copper electrolytic plating is applied on top of this as shown in Figure 9.
The thickness is 50 μm (the copper film 41 is indicated by diagonal lines in the figure). Subsequently, as shown in FIG. 10, the surface 32a is flattened, and concentric grooves 39,
The copper film on the surface 32a except for the copper film 41 in 40 is removed. Next, as shown in FIG. 11, thin film coils 42 and 43 having a predetermined pattern are formed in the concentric grooves 39 and 40 using an etching technique, and a conductive pattern 44 is formed at a predetermined location on the back surface 32b.
a, 44b, 45a, 45b are formed. Next, one end of the conductor wires 46, 47 is soldered to one end of the thin film coils 42, 43 (the end on the side where the conductive patterns 44a, 45a are not formed), and the other end is connected to a small hole (through-hole). Hall) 34a, 35
The core 48 that constitutes the rotary transformer of the present invention is inserted through the core 48 and pulled out to the back side 32b and soldered to the conductive patterns 44b and 45b.
is formed. In the above embodiment, a jumper wire is used as the conductive wire inserted through the through hole, but the present invention is not limited to this. For example, after forming a thin film coil, an insulating film is formed except for the connection part where one end of the thin film coil is connected, and then a conductive pattern is formed on this insulating film to correspond to the jumper wire (i.e. inside the through hole). (Two thin film conductive patterns are formed on the core.) By doing so, one end of the thin film coil may be drawn out to the back surface of the core. Effects of the Invention As described above, according to the rotary transformer of the present invention, a conducting wire is connected to one end of the thin film coil, and this conducting wire is inserted into a through hole formed at the other end, thereby connecting both ends of the thin film coil. By using a through hole to draw out the terminal end to a surface different from the surface on which the thin film coil of the core is disposed,
The current flowing through the through-hole and the current flowing through the conductor wire are in opposite directions, and the magnetic fluxes caused by these currents cancel each other out, reducing self-inductance and thus improving transmission efficiency.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a core constituting an embodiment of a rotary transformer according to the present invention, FIG. 2 is a rear view of the core shown in FIG. 1, and FIG. 3 is a
The cross-sectional views taken along the line A and FIGS. 4 to 12 are diagrams for explaining the manufacturing method of the core constituting the rotary transformer according to the present invention along the manufacturing procedure. 1...Rotary transformer, 2...Core, 2a...
...Front surface, 2b...Back surface, 3-6...Concentric groove, 7
~10...Thin film coil, 11a~14a, 11b
~14b...Through hole, 19a~22a, 1
9b to 22b, 19c to 22c... Conductive pattern, 27 to 30... Conductive wire, 32... Core block, 34a, 34b, 35a, 35b... Small hole,
39, 40... Concentric groove, 41... Copper film, 42,
43... thin film coil, 46, 47... conducting wire, 48
……core.

Claims (1)

[Scope of Claim for Utility Model Registration] A rotor and a stator each formed by patterning a thin-film coil having a through hole at its terminal end on a core made of ferrite are disposed facing each other,
In a rotary transformer that transmits and receives signals between the two, both ends of the thin film coil are placed close to each other, a conductor is connected to one end, and the conductor is inserted into a through hole formed at the other end. The rotary transformer is configured such that the other terminal end is drawn out to a surface of the core different from the surface on which the thin film coil is disposed through a through hole.