JPH11354348A - Isolation transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an isolation transformer wherein, when both electric power and electric signal are transmitted, the interference between adjoining coils in the same core is suppressed with no increase in size of the primary side core and the secondary side core. SOLUTION: An isolation transformer 1 comprises at least first coils 2a and 3a and second coils 2b and 3b wound with electric wire, and cores 2c and 3c of soft magnetic material, in non-contact manner for transmission of an electric power and electric signal under electromagnetic induction between a primary side core 2 and a secondary side core 3 provided to face each other for free relative rotation. Here, related to the primary side core 2 and the secondary side core 3, magnetism shielding parts 2f and 3f for suppressing interference between both coils are formed at such positions across the coupling magnetic flux between the first and second coils, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation transformer for electrically connecting a fixed member and a rotating member which rotate relative to each other in a non-contact manner, and for transmitting electric power or an electric signal between the two members in a non-contact manner. .

[0002]

2. Description of the Related Art Separation transformers are opposed to each other with a predetermined gap therebetween. A primary core and a secondary core each having a coil formed by winding an electric wire around a core made of a synthetic resin containing a soft magnetic material are arranged. have. The separation transformer is as described in 1 above.
A connector for rotating the secondary core and the secondary core relatively about a common axis and coupling the two cores by electromagnetic induction, and electrically connecting the rotating body and the fixed body in a non-contact manner. Has been used as

[0003]

When both power and electric signals are transmitted in the separating transformer, power and signal coils are radially provided in the primary and secondary cores. It is necessary to arrange them at a predetermined distance.

In this case, arranging different coils on the same core has various advantages because the size of the separation transformer is small, but there is a problem that interference occurs between different coils as described below.

That is, in a separation transformer in which a power coil and a signal coil are arranged in a core, a primary core and a secondary core are usually opposed to each other with a predetermined gap therebetween, and a power coil is arranged. The coils and the signal coils are coupled by electromagnetic induction, and electric power and signals are transmitted in a non-contact manner.

For this reason, when the distance between the power and signal coils in the radial direction is small, or when the gap between the opposed cores is large, etc., the power coil and the signal coil are separated from each other. Interference occurs between That is, in the separation transformer having such a structure, for example, the AC magnetic flux due to the current flowing in the power coil interlinks with the signal coil, resulting in signal transmission noise and reduced signal transmission reliability.

In particular, when the gap between the primary core and the secondary core that are opposed to each other is increased, the coupling efficiency between the opposed coils is reduced, and the adjacent power and signal coils within the same core are reduced. The coupling between the coils becomes stronger, and accurate signal transmission is hindered.

As a countermeasure against this, conventionally, a primary side core and two
In each of the secondary cores, the distance between adjacent cores in the radial direction is increased. However, this increases the size of the core, and loses the advantage of miniaturization described above by disposing the power and signal coils in one core.

The present invention has been made in view of the above points, and when transmitting both electric power and electric signals, the primary and secondary cores are not enlarged, An object of the present invention is to provide a separation transformer capable of suppressing interference between adjacent coils.

[0010]

In order to achieve the above object, the present invention has at least first and second coils wound with an electric wire and a core made of a soft magnetic material, and is relatively rotatable relative to each other. A separation transformer for transmitting electric power and an electric signal in a non-contact manner by electromagnetic induction between a primary side core and a secondary side core that are opposed to each other, wherein the primary side core and the secondary side core are respectively The configuration is such that a magnetic shielding portion for suppressing interference between the two coils is formed at a position crossing the interlinkage magnetic flux generated between the first and second coils.

Preferably, the magnetic shielding portion is a groove formed in a circumferential direction.

Preferably, the magnetic shield is formed of a ring-shaped synthetic resin.

[0013] More preferably, the magnetic shielding portion is formed by a plurality of electric conductors arranged intermittently in a ring shape in the circumferential direction.

[0014]

The magnetic shielding section magnetically shields between the adjacent first and second coils and suppresses interference between the two coils.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described in detail with reference to FIGS.

As shown in FIG.
The secondary core 2 and the secondary core 3 are opposed to each other with a predetermined gap G. For example, the primary core 2 is used as a fixing member,
The secondary core 3 is attached to a rotating member to electrically connect the two members, and is used when electric power and an electric signal are transmitted between the two members in a non-contact manner.

Since the secondary core 3 has the same configuration as the primary core 2, the primary core 2 will be described, and the secondary core 3 will be described in the following description and the corresponding configuration in the drawings. The description is omitted by using the reference numerals corresponding to the parts.

The primary core 2 has a power coil 2a, a signal coil 2b, and a core 2c. Each of the power coil 2a and the signal coil 2b is formed into a ring shape by winding an electric wire such as a winding in which a polyamide-based fusion coating is overcoated on a polyurethane-based insulation coating a predetermined number of times. Here, as long as the electric wire can be formed in a ring shape, the cross section of the conductor may be circular, rectangular or any shape. The power coil 2a is set to have a larger cross-sectional area than the signal coil 2b in consideration of the fact that the transmitted current is larger than that of the signal coil 2b.

On the other hand, the core 2c is made of a soft magnetic resin obtained by mixing a soft magnetic ferrite powder (Ni—Zn ferrite or Mn—Zn ferrite) in a synthetic resin (nylon or polyphenylene sulfide (PPS) or the like). Step 2d provided on the surface facing the secondary core 3
Has a through hole 2e formed at the center. The core 2c is made of a soft magnetic ferrite sintered body (for example, N
i-Zn-based ferrite or Mn-Zn-based ferrite mixed with a binder agent and sintered) may be used. As shown in FIG. 2, the core 2c suppresses interference between the power coil 2a and the signal coil 2b on the back side of the surface facing the secondary core 3 between the power coil 2a and the signal coil 2b. A magnetic shielding groove 2f having a rectangular cross section is formed over the entire circumference.

The magnetic shielding groove 2f is, as shown in FIG.
Since it is a mere space formed between the power coil 2a and the signal coil 2b, the magnetic permeability in this portion is
The magnetic permeability in this portion is much smaller than that without the groove. Therefore, the magnetic shielding groove 2f can reduce interference between the power coil 2a and the signal coil 2b. Here, if the magnetic shielding groove 2f is not formed over the entire circumference, but is provided intermittently, the mechanical strength of the core 2c is improved, and the magnetic shielding groove 2f can be formed deeper than when it is formed over the entire circumference.

At this time, the greater the width W and the depth D of the cross-sectional shape of the magnetic shielding groove 2f, the greater the effect of preventing interference. However, if the installation position of the magnetic shielding groove 2f between the power coil 2a and the signal coil 2b is incorrect or the width W is too large, the following problem occurs. That is, the interlinking magnetic fluxes BP and BS between the power coils 2a and 3a and the signal coils 2b and 3b are cut off between the primary core 2 and the secondary core 3 that are opposed to each other, and the power coils 2a and 3a The transmission efficiency between the signal coils 2b and 3b is impaired. The magnetic shielding groove 2f has a greater magnetic shielding effect in this portion as the relative permeability of the cores 2c and 3c is larger, and the width W
Is too large, the mechanical strength of the core 2c decreases.

Therefore, considering the interference between the power coil 2a and the signal coil 2b due to the increase in the gap G, the magnetic shield groove 2f is formed in the allowable range of the gap G, the installation position, the positions of the cores 2c, 3c. It is necessary to design the arrangement and size in consideration of factors such as the relative magnetic permeability, the mechanical strength of the cores 2c and 3c, the noise resistance of the separation transformer 1, and the like.

Since the separating transformer 1 is configured as described above, for example, in order to transmit power and a signal from the primary core 2 to the secondary core 3, predetermined power is applied to each of the power coil 2a and the signal coil 2b. 2, a flux linkage BP for electric power and a flux linkage BS for signal are generated as shown in FIG. Then, in the separation transformer 1, a current based on a predetermined coupling efficiency flows through the power coil 3 a and the signal coil 3 b of the secondary core 3 due to the electromagnetic induction by these currents, and the power and the signal are transmitted from the primary core 2 to It is transmitted to the secondary core 3.

At this time, if the above factors relating to the magnetic shielding groove 2f are not properly designed, as shown in FIG. 2, the separating transformer 1 generates the AC magnetic flux BN due to the current flowing in the power coil 2a. , And it becomes signal transmission noise.

Therefore, the thickest portions of the cores 2c and 3c are approximately three times the thinnest portions, the outer diameters are approximately 11 times the thickest portions, and the magnetic shielding grooves 2
The separation transformer 1 having the structure shown in FIG. 1 in which the width W of the power coils f and 3f is 1/5 of the radial distance between the power coils 2a and 3a and the signal coils 2b and 3b is manufactured.
N ratio) was measured. For comparison, the magnetic shielding grooves 2f,
Except that 3f was not formed, a separation transformer having the same structure as the separation transformer 1 was produced, and the same measurement was performed.

At this time, in each separation transformer, 1
In order to transmit power and signals from the secondary core 2 to the secondary core 3, 30 KHz and 5 A currents are continuously applied to the power coil 2a and 128, 143 and 174 KHz are applied to the signal coil 2b.
, A current of 20 mA was applied, and the gap G was set to 0.1.
It was appropriately changed in the range of ２2 mm. At this time, the signal waveform transmitted to the signal coil 3b of the secondary side core 3 is converted to a DL70 signal from Yokogawa Electric Corporation having an analyzer function.
Analysis was performed using an oscilloscope of type 8, and it was determined that signal transmission was possible if the S / N ratio of the transmitted signal was 5 or more, and that signal transmission was impossible if the S / N ratio was less than 5. The measurement results (S / N ratio) are shown in Table 1 together with the value of the gap G.

[0027]

[Table 1]

As is clear from the results shown in Table 1, the separation transformer 1 using the primary core 2 and the secondary core 3 in which the magnetic shielding grooves 2f and 3f are formed has a gap G of 2 mm. Also, interference between adjacent power coil 2a and signal coil 2b is suppressed, and signal coil 2b and signal coil 3
b can be reliably transmitted. On the other hand, the separation transformer using the primary core and the secondary core without the magnetic shielding grooves 2f and 3f has a gap G
Exceeds 1 mm, signal transmission becomes impossible, and the effect of forming the magnetic shielding grooves 2f and 3f is remarkably exhibited.

Here, the magnetic shielding grooves 2f and 3f may be formed in a trapezoidal cross-sectional shape whose width decreases in the depth direction, as shown in FIG. 3, in addition to a rectangular cross-sectional shape. Magnetic shielding groove 2
When f and 3f are formed in such a shape, there is an advantage that when the cores 2c and 3c are molded using a mold, the cores 2c and 3c are easily removed from the mold.

Further, it is needless to say that the magnetic shielding portion is not limited to the above-mentioned groove. For example, as shown in a separation transformer 1 shown in FIG. 4, an electrically insulating portion is provided at a position corresponding to the magnetic shielding groove 2f, 3f. Nylon (PA), polypropylene (PP), polyphenylene sulfide (PP
Resin rings 4 and 5 made of synthetic resin such as S), polyolefin, and polybutylene terephthalate (PBTP) may be embedded. By doing so, the primary core 2 and the secondary core 3 have improved mechanical strength as compared with the case where the magnetic shielding grooves 2f and 3f are used.

Further, both the primary and secondary cores 2 and 3 of the separation transformer 1, for example, the secondary core 3 shown in FIG.
A plurality of electric conductors 6 made of copper, copper alloy or the like having a circular, elliptical or rectangular cross section are intermittently arranged in the circumferential direction at positions corresponding to the magnetic shielding grooves 3f as shown in FIG. Is also good. At this time, the plurality of electric conductors 6 are embedded in the core 3c, for example, when the core 3c is formed by insert molding. By doing so, similarly to the case where the resin rings 4 and 5 are embedded in the cores 2c and 3c,
The mechanical strength of the primary core 2 and the secondary core 3 is improved.

[0032]

According to the first and second aspects of the present invention, when transmitting both electric power and electric signals, the primary and secondary cores do not increase in size, and are adjacent to each other in the same core. The present invention can provide a separation transformer capable of suppressing interference between coils.

According to the third and fourth aspects of the invention, the mechanical strength of the primary and secondary cores can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional front view of a separation transformer of the present invention cut along a diameter.

FIG. 2 is an enlarged sectional view of the left half of the separation transformer shown in FIG. 1, showing a groove for magnetic shielding.

3 is a cross-sectional view showing another form of the magnetic shielding groove in a state where the left half side of the separation transformer in FIG. 1 is enlarged.

FIG. 4 is a cross-sectional view showing an enlarged state of a left half side of the separation transformer of FIG. 1 using a ring-shaped synthetic resin as a magnetic shielding portion.

FIG. 5 shows a separation transformer using a plurality of conductors intermittently arranged in a ring shape in the circumferential direction of a core as a magnetic shielding part.
FIG. 2 is a plan view of the separation transformer of FIG. 1 as viewed from a secondary core side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Separation transformer 2 Primary core 2a Power coil 2b Signal coil 2c Core 2f Magnetic shielding groove 3 Secondary core 3a Power coil 3b Signal coil 3c Core 3f Magnetic shielding groove 4,5 Resin ring (magnetic shielding part) 6 Electric conductor (Magnetic shield)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Fumihiko Abe, Inventor Furukawa Electric Co., Ltd. 2-6-1 Marunouchi, Chiyoda-ku, Tokyo (72) Inventor Yasunori Hahiro 2-6-1 Marunouchi, Chiyoda-ku, Tokyo No. Furukawa Electric Co., Ltd.

Claims (4)

[Claims] At least first and second windings of an electric wire
And a core that is made of a soft magnetic material and has a core that is made of a soft magnetic material. The primary and secondary cores are rotatably opposed to each other. A transformer, wherein said primary side core and 2
A separation transformer, wherein a magnetic shielding portion for suppressing interference between the two coils is formed on each of the secondary cores at a position crossing a linkage magnetic flux generated between the first and second coils. 2. The separation transformer according to claim 1, wherein the magnetic shield is a groove formed in a circumferential direction. 3. The separation transformer according to claim 1, wherein the magnetic shielding portion is formed of a ring-shaped synthetic resin. 4. The separation transformer according to claim 1, wherein the magnetic shield is formed by a plurality of electric conductors intermittently arranged in a ring shape in a circumferential direction.