Noise suppression cable

A noise suppression cable includes an insulated electric wire including an insulator that covers an outer periphery of a conductor wire, and a magnetic tape layer formed by transversely winding a magnetic tape on an outer periphery of the insulated electric wire. A magnetic body constituting the magnetic tape is cut out from a rolled material in such a manner that a width direction of the magnetic tape corresponds to a rolled direction, and the magnetic body has a magnetic property that is different between the width direction and an orthogonal direction to the width direction.

TECHNICAL FIELD

The present invention relates to a noise suppression cable in which a magnetic tape is used to suppress electromagnetic wave noise.

BACKGROUND ART

A noise suppression cable, which does not have a ferrite core around the cable but has a magnetic tape wrapped around an electric wire, is known (see e.g. PTL 1).

In this noise suppression cable, magnetic metal tapes (or simply called magnetic tapes) having a predetermined width are wrapped around an insulated wire formed by covering a conductor with an insulation and are arranged at a predetermined distance along a cable longitudinal direction. In general, magnetic tapes are formed by a slitting process, i.e., by continuously cutting a long and wide rolled material to a certain width and rewinding onto a roll or reel. A noise suppression effect of the conventional noise suppression cable is controlled by adjusting a tape length and a tape width. In addition, since plural narrow magnetic tapes are arranged at appropriate intervals, flexibility of the cable is improved.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the above-mentioned noise suppression cable, the magnetic tape cut out from a rolled material may not provide a desired electromagnetic wave noise suppression effect depending on the rolled direction.

It is an object of the invention to provide a noise suppression cable that achieves an improvement in the effect of electromagnetic wave suppression.

Solution to Problem

According to one embodiment, provided is a noise suppression cable, comprising an insulated electric wire comprising an insulator that covers an outer periphery of a conductor wire and a magnetic tape layer formed by transversely winding a magnetic tape on an outer periphery of the insulated electric wire, wherein a magnetic body constituting the magnetic tape is cut out from a rolled material in such a manner that a width direction of the magnetic tape corresponds to a rolled direction, and the magnetic body has a magnetic property that is different between the width direction and an orthogonal direction to the width direction.

The magnetic body may have a magnetic permeability in the orthogonal direction to the width direction greater than that in the width direction. A plurality of magnetic tape layers may be formed at predetermined intervals along a cable longitudinal direction. The magnetic tape may comprise a single magnetic body or a plurality of magnetic bodies that are joined in the orthogonal direction to the width direction. The magnetic tape layer may be formed by transversely winding the magnetic tape multiple times.

Advantageous Effects of Invention

According to an embodiment of the invention, a noise suppression cable can be provided that achieves an improvement in the effect of electromagnetic wave suppression.

DESCRIPTION OF EMBODIMENT

An embodiment of the invention will be described below in reference to the drawings. Constituent elements having substantially the same functions are denoted by the same reference numerals in each drawing and the overlapping explanation thereof will be omitted.

FIG. 1is a schematic front view showing a configuration of a noise suppression cable in an embodiment of the invention.FIG. 2is a cross sectional view showing the noise suppression cable shown inFIG. 1. InFIG. 1, illustration of fillers9is omitted.

A noise suppression cable1is provided with plural insulated electric wires4(three in the present embodiment) each formed by covering an outer periphery of a conductor wire2with an insulator3, a resin tape layer5A formed by wrapping a resin tape around the plural insulated electric wires4with fillers9interposed therebetween, a shield layer6provided around the resin tape layer5A, a resin tape layer5B provided around the shield layer6, plural magnetic tape layers7having a predetermined width W and formed around the resin tape layer5B at a predetermined distance D along a cable longitudinal direction, a resin tape layer5C provided around the plural magnetic tape layers7and the resin tape layer5B, and a sheath8as an insulating protective layer formed of a resin, etc.

The insulated electric wire4transmits power or a signal at a frequency of, e.g., 100 kHz to 1 MHz. Although plural insulated electric wires4are provided in the present embodiment, the number of the insulated electric wires4may be one. The insulated electric wire4may alternatively be a twisted pair wire which transmits differential signals.

The resin tape layer5A is formed by wrapping a resin tape around the plural insulated electric wires4with the fillers9interposed therebetween throughout the cable longitudinal direction. The resin tape layer5B is formed by wrapping a resin tape around the shield layer6throughout the cable longitudinal direction. The resin tape layer5C is formed by wrapping a resin tape around the resin tape layer5B and the magnetic tape layers7throughout the cable longitudinal direction. Tapes made of, e.g., a resin such as polyethylene terephthalate (PET) or polypropylene-based resin can be used as the resin tapes constituting the resin tape layers5A to5C.

The shield layer6is formed by, e.g., braiding conductive wires and is connected to a ground. Alternatively, the shield layer6may be formed by wrapping a tape with a conductor attached thereto.

(Configuration of Magnetic Tape Layer7)

The magnetic tape layer7is formed by transversely wrapping a magnetic tape70having the width W around the resin tape layer5B several times. The magnetic tape layer7is formed of two layers of the magnetic tapes70in the present embodiment, but may be formed of a single or three or more layers of the magnetic tapes70. The width W is preferably, e.g., 5 to 50 mm. The distance D between the magnetic tape layers7is preferably, e.g., 5 to 50 mm. The magnetic tape70is composed of, e.g., plural magnetic bodies extending in a direction orthogonal to the width direction (in a wrapping direction) and joint sheets joining the plural magnetic bodies. Alternatively, the magnetic tape may be formed of a single magnetic body. The magnetic body is cut out from a rolled material in such a manner that the width direction of the magnetic tape70coincides with the rolled direction, and magnetic permeability in the direction orthogonal to the width direction is higher than magnetic permeability in the width direction. In other words, the magnetic body has different magnetic properties (induced magnetic anisotropies) between the width direction and a direction orthogonal to the width direction.

The magnetic body constituting the magnetic tape70is preferably a soft magnetic material having low magnetic coercivity and high magnetic permeability to reduce electromagnetic wave noise. The soft magnetic material used can be, e.g., an amorphous alloy such as Co-based amorphous alloy or Fe-based amorphous alloy, a ferrite such as Mn—Zn ferrite, Ni—Zn ferrite or Ni—Zn—Cu ferrite, or a soft magnetic metal such as Fe—Ni alloy (permalloy), Fe—Si—Al alloy (sendust) or Fe—Si alloy (silicon steel), etc. The detailed configuration of the magnetic tape70will be described later.

(Method of Forming Magnetic Tape Layer7)

FIGS. 3A to 3Dare explanatory diagrams illustrating an example of a method of forming the magnetic tape layer7.

Firstly, two first rolled materials71, which have a relatively wide band shape and are long along a rolled direction10, and two second rolled materials72, which have a relatively narrow band shape and are long along a rolled direction10, are prepared. The first rolled material71is a magnetic body of, e.g., 10 to 25 μm in thickness and 30 mm in width, and the second rolled material72is a magnetic body of, e.g., 10 to 25 μm in thickness and 10 mm in width.

Next, as shown in FIGS.3B1and3B2, the first and second rolled materials71and72are arranged with an overlap of about 5 mm and joined by joint tapes73to form a magnetic sheet74as a rolled material. The joint tape73can be, e.g., a Teflon adhesive tape (Teflon is a registered trademark) having a thickness of about 10 to 25 μm. Next, the magnetic sheet74is cut along cutting lines11into the magnetic tapes70shown inFIG. 3Cwhich have a predetermined width W and a predetermined length L. The length L of the magnetic tape70is substantially the same as the circumferential length of the resin tape layer5B.

Next, as shown inFIGS. 3C and 3D, plural sets of two stacked magnetic tapes70are transversely wrapped around the resin tape layer5B. The magnetic tape layers7each composed of two magnetic tapes70are thereby formed.

(Effects Obtained by Forming Magnetic Tape70to have Width Direction Along Rolled Direction)

FIGS. 4A and 4Bare explanatory diagrams respectively illustrating methods of making a test piece-A and a test piece-B which are used to test for induced magnetic anisotropy of rolled materials. To form a test piece-A12a,a rolled material12having a width of 20 mm is cut along the cutting lines11into a 20 mm square piece. To form a test piece-B13a,a rolled material13having a width of 30 mm is cut along the cutting lines11into a 20 mm square piece.

FIG. 5Ais an explanatory diagram illustrating a system for measuring inductance of a coil in which the test pieces-A and -B are placed so that the rolled direction of the pieces-A and -B coincides with a magnetic field direction of the coil.FIG. 5Bis an explanatory diagram illustrating a system for measuring inductance of a coil in which the test pieces-A and -B are placed so that the rolled direction of the pieces-A and -B is orthogonal to the magnetic field direction of the coil. The measuring systems have a coil14of 5 mm depth by 50 mm width by 100 mm length.FIG. 5Ashows a measuring system a andFIG. 5Bshows a measuring system b. The measuring system a is a system for measuring inductance of the coil14when the test piece-A12aand the test piece-B13aare placed inside the coil14so that the rolled direction10coincides with a magnetic field direction14a,as shown inFIG. 5A. The measuring system b is a system for measuring inductance of the coil14when the test piece-A12aand the test piece-B13aare placed inside the coil14so that the rolled direction10is orthogonal to the magnetic field direction14a,as shown inFIG. 5B.

FIG. 6is a graph showing the measurement results from the coil inductance measuring systems shown inFIGS. 5A and 5B.

The test piece-A12aor the test piece-B13awas placed in the coil14and inductance of the coil14was measured. As a result, with the test piece-B13a,there is substantially no difference in inductance of the coil14between when measured by the measuring system a and when measured by the measuring system b, which shows that the test piece-B13adoes not have induced magnetic anisotropy. On the other hand, with the test piece-A12a,inductance of the coil14measured by the measuring system a is significantly smaller than inductance of the coil14measured by the measuring system b in a frequency range of not less than 100 kHz. This shows that the test piece-A12ahas induced magnetic anisotropy.

FIG. 7is an explanatory diagram to explain a difference in induced magnetic anisotropy between the test piece-A12aand the test piece-B13a.In widthwise edge regions (shaded regions)12band13bof the rolled materials12and13, internal stress generated by rolling is present along the rolled direction10and it is considered that magnetic permeability of the edge regions12band13bis low. The edge region13bof the rolled material13is cut off during the slitting process and it is considered that the test piece-B13atherefore has little or no induced magnetic anisotropy. On the other hand, the edge region12bof the rolled material12remains without being cut off during the slitting process and it is considered that the test piece-A12atherefore has induced magnetic anisotropy.

(Functions and Effects of the Embodiment)

The following functions and effects are obtained in the present embodiment.

(1) By cutting out the magnetic tapes70from the magnetic sheet74as a rolled material so that the width direction of the magnetic tapes70coincides with the rolled direction, inductance is increased as compared to when the width direction of the magnetic tape coincides with the direction orthogonal to the rolled direction. This allows a desired electromagnetic wave noise suppression effect to be obtained.

(2) Since the magnetic tape layers7having a predetermined width are provided at a predetermined distance in the cable longitudinal direction, excellent flexibility is obtained as compared to when providing a magnetic tape layer throughout the cable longitudinal direction.

(3) Since plural magnetic bodies are joined by the joint tapes73to provide a required length corresponding to cable diameter, it is adaptable to various cable diameters without increasing the types of the rolled materials71and72.

(4) Since a ferrite core is not used, an appearance is excellent, problems during handling such as cracks on the ferrite core do not arise, and it is possible to suppress electromagnetic wave noise emission without increasing the outer diameter of the cable.

EXAMPLE

FIGS. 8A to 8Dare explanatory diagrams respectively illustrating Samples S1to S3in Comparative Examples 1 to 3 and Sample S4in Example of the invention. Samples S1to S4were formed using a Co-based amorphous alloy as a magnetic body and had a cable length of 1500 mm.

Comparative Example 1

Sample S1in Comparative Example 1 shown inFIG. 8Ais configured based on the noise suppression cable1shown inFIG. 2, but the magnetic tape layers7, the resin tape layer5C and the sheath8are not provided around the shield layer6.

Comparative Example 2

Sample S2in Comparative Example 2 shown inFIG. 8Bis configured that the magnetic sheet74shown inFIG. 3Bwhich is not cut to the width W is longitudinally wrapped around the resin tape layer5B. In Sample S2, a length in the cable longitudinal direction was 80 mm and a length in the wrapping direction was 65 mm.

Comparative Example 3

Sample S3in Comparative Example 3 shown inFIG. 8Cis configured that second rolled materials72of 10 mm width and 80 mm in length, which are cut out so that the width direction is orthogonal to the rolled direction10, are stacked in pairs and transversely wrapped around the resin tape layer5B at 10 mm intervals. In Sample S2in Comparative Example 2, two first rolled materials71of 30 mm in width and two second rolled materials72of 10 mm in width are used and the total of the lengths in the wrapping direction is 80 mm. Therefore, Sample S3is formed using the second rolled materials72having a length of 80 mm in the wrapping direction so as to be consistent with the total of the lengths in the wrapping direction in Sample S2.

Sample S4in Example shown inFIG. 8Dcorresponds to the present embodiment and is configured that the magnetic tapes70of 10 mm in width and 80 mm in length, which are cut out so that the width direction coincides with the rolled direction10, are stacked in pairs and transversely wrapped around the resin tape layer5B at 10 mm intervals.

FIG. 9is an explanatory diagram illustrating a common-mode noise measuring device. In a measuring device100, an inverter120covered with a shield box121and a motor130covered with a shield box131were placed on an aluminum base plate110, and Samples S1to S4shown inFIG. 8were connected between the inverter120and the motor130. Then, common-mode current Ic (common-mode noise) was detected by a current transformer (CT)140and analyzed by a frequency analyzer150.

FIG. 10are graphs showing the results of measuring common-mode noise by the measuring device100shown inFIG. 9.FIG. 10Ais a graph showing the results of a receive level of common-mode current Ic measured by the measuring device100inFIG. 9, andFIG. 10Bis a graph showing the inductance measurement results of Samples S1to S4.

It is understood fromFIG. 10Athat the common-mode current Ic of the Sample S4in Example is the smallest across frequency from 100 Hz to 1 MHz. Meanwhile, it is understood fromFIG. 10Bthat inductance of Sample S4in Example is higher than inductance of other Samples S1to S3in Comparative Examples across frequency from 100 Hz to 700 Hz. That is, this shows that Sample S4in Example, in which the magnetic tapes70are formed so that the width direction coincides with the rolled direction and such magnetic tapes70are provided around the insulated electric wires4at a predetermined distance, has a higher electromagnetic wave noise suppression effect than other Samples S1to S3in Comparative Examples.

The embodiment of the invention is not limited to that described above and various embodiments can be implemented. For example, although plural magnetic tape layers7are provided in the present embodiment, the number of the magnetic tape layers7may be one. The one magnetic tape layer7may have a width of 5 to 50 mm or may be continuously formed throughout the longitudinal direction. In addition, the magnetic tape70is formed by joining plural magnetic bodies in the present embodiment but may be formed of a single magnetic body. In addition, the outer conductor may be a smooth metal pipe such as copper pipe. Frequency characteristics for suppressing electromagnetic wave noise may be different for each of the magnetic tape layers.

In addition, some of the constituent elements in the embodiment can be omitted or changed without changing the gist of the invention. For example, the inclusion9may be omitted as long as no problem arises when wrapping a resin tape around the plural insulated electric wires4.

INDUSTRIAL APPLICABILITY

The invention is applicable to a noise suppression cable in which a magnetic tape is used instead of ferrite core to suppress electromagnetic wave noise.

REFERENCE SIGNS LIST