Electric Noise Absorber

(i) Field of the Invention

The present invention relates to an electric noise absorber which is attached around an electric wire of electronic apparatus to absorb electric noises generated inside the electronic apparatus or electric noises transmitted to the electronic apparatus from the outside via the electric wire.

(ii) Description of the Related Art

In a conventional art for removing or suppressing electric noises flowing through the electric wire, a magnetic body, for example, of ferrite is attached around the electric wire to attenuate the electric noises flowing through the wire. Examples of such known electric noise absorber include a non-divided type absorber in which an annular closed magnetic path is formed only by a magnetic body, a divided type absorber in which the closed magnetic path is formed when the electric wire is surrounded with a plurality of divided magnetic body parts, and the like. When an annular magnetic flux is generated by electric noises in the closed magnetic path formed by the magnetic body, the electromagnetic energy of the electric noise is converted to a heat energy inside the magnetic body. As a result, the electric noises are attenuated. When the electric wire is wound around the magnetic body in such a manner that the electric wire passes plural times inside the closed magnetic path formed by the magnetic body, i.e., a hollow in the magnetic body, the electric noises can more effectively be absorbed.

However, the number of windings of the electric wire passed through the hollow of the magnetic body is limited by the relationship between the thickness of the electric wire and the size or thickness of the hollow formed in the magnetic body. The electric noise absorbing performance cannot be enhanced further. The ability of preventing the operation error or failure of the electronic apparatus from being caused by the electric noises is also limited.

Wherefore, an object of the present invention is to provide an electric noise absorber which can effectively absorb electric noises.

According to a first aspect of the invention, there is provided an electric noise absorber comprising a magnetic body having a first and second openings extending therethrough to encompass an electric wire serially extending through the first and second openings to absorb electric noise flowing though the wire. Preferably, the first and second openings are disposed in parallel; the magnetic body comprises a plurality of magnetic body parts defining abutting faces, dividing at least one of the openings to define two open faced hollows together forming the opening, by which the parts may be joined to form the magnetically unitary magnetic body; and the parts comprise at least two different magnetic materials.

Each of the first and second openings may be divided into two open faced hollows by magnetic body parts having abutting faces by which the associated body parts may be joined as specified.

Also according to the invention, there is provided an electric noise absorber comprising a magnetic body defined by at least two magnetic body parts which together define parallel openings spaced by magnetic material of at least one of the parts, through which openings an electric wire may extend in series for absorption of electric noise, flowing through the wire, by the absorber, the parts defining abutting faces by which the body parts may be joined to form the magnetically unitary magnetic body.

Preferably, there are three magnetic body parts and the openings are spaced by one of these body parts which defines abutting faces by which the three body parts are joined as specified; and housing parts housing the body parts connectable together ensure the joining of the body parts at the abutting faces to ensure the formation of the magnetically unitary magnetic body.

The magnetic body is preferably formed of a ferrite of a nickel--zinc (Ni--Zn) material or a manganese--zinc (Mn--Zn) material. A soft or hard ferrite can be used. Instead of using the ferrite itself, ferrite powder may be mixed in plastic, synthetic rubber, or the like. Besides the ferrite body, a silicon steel magnetic core, a powder compact of molybdenum or other metal, or the like may be used as the magnetic body. The material of the magnetic body is not limited to these examples.

According to further aspect of the present invention, the electric noise absorber is provided with a plurality of magnetic body parts formed of different magnetic materials. Each of the magnetic body parts is provided with the hollow. Specifically, since the magnetic materials differ with the magnetic body parts, the frequency characteristic of the electric noise absorbing performance can differ with the magnetic body parts and the electric noise absorbing characteristic is enhanced over a wide bandwidth.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGS. 1A and 1B are explanatory views showing the structure of an electric noise absorber according to the first embodiment of the present invention;

FIGS. 2A and 2B are schematic views showing the state of the electric noise absorber of FIGS. 1A and 1B when in use;

FIGS. 3A and 3B are explanatory views showing the structure of an electric noise absorber according to the second embodiment;

FIGS. 4A and 4B are explanatory views showing the structure of an electric noise absorber according to the third embodiment;

FIG. 5 is an explanatory view showing the structure of an electric noise absorber according to the fourth embodiment;

FIGS. 6A and 6B are explanatory views showing modifications of the electric noise absorber;

FIGS. 7A to 7D are explanatory views showing modifications of the electric noise absorber;

FIGS. 8A to 8C show samples for use in measuring the impedance-frequency characteristic; and

FIGS. 9A and 9B are graphs showing the impedance-frequency characteristic to compare the samples shown in FIGS. 8A to 8C.

Embodiments of the present invention will be described hereinafter with reference to the accompanying drawings.

A. A first embodiment of the invention will now be described.

FIGS. 1A and 1B are explanatory views showing the structure of an electric noise absorber 2 according to the first embodiment of the present invention. The electric noise absorber 2 is provided with a magnetic body 4 and its support casing. The magnetic body is divided into three pieces. Specifically, the magnetic body 4 is formed of a first magnetic body part 4a, a second magnetic body part 4b and a third magnetic body part 4c. The magnetic body parts are collectively termed the magnetic body 4. The magnetic body parts 4a, 4b and 4c are contained in first, second and third housing sections 6a, 6b and 6c, respectively. For material, Mn--Zn soft ferrite is used in the first magnetic body part 4a, while Ni--Zn soft ferrite is used in the second and third magnetic body parts 4b, 4c.

Abutting faces 8a, 8b which can abut each other without any gap therebetween are formed in an area where the first and second magnetic body parts 4a and 4b are opposed. Grooves 12a, 12b are formed in the magnetic body parts 4a, 4b, respectively, to form a first hollow 10a in which an electric wire may be positioned between the magnetic body parts when the magnetic body parts are interconnected without any gap therebetween by the abutting faces 8a, 8b. Abutting faces 8c are also formed opposite to the abutting faces 8b of the second magnetic body part 4b, and abutting faces 8d are formed on the third magnetic body part 4c. Grooves 12c, 12d are formed in the magnetic body parts 4b, 4c, respectively, to form a second hollow 10b in which an electric wire is positioned between the magnetic body parts 4b and 4c when the second and third magnetic body parts 4b, 4c are interconnected without any gap by the abutting faces 8c, 8d. The magnetic body parts 4a to 4c are provided with recesses 20a to 20c to engage the inner walls of the housing sections 6a to 6c when the magnetic body parts 4a to 4c are housed in the housing sections 6a to 6c, respectively.

Each of the first and third housing sections 6a, 6c is a box shape having an opening via which each of the first and third magnetic body parts 4a, 4c are contained, respectively. The inner walls of the first and third housing sections 6a, 6c are provided with fixed protrusions 22a, 22c which can engage the recesses 20a, 20c of the first and third magnetic body parts 4a, 4c, respectively. When the first and third magnetic body parts 4a, 4c are housed in the first and third housing sections 6a, 6c in such a manner that the abutting faces 8a, 8d are exposed, the fixed protrusions 22a, 22c engage in the recesses 20a, 20c to prevent the first and third magnetic body parts 4a, 4c from falling out of the housing sections 6a, 6c, respectively.

The second housing section 6b is a substantially square frame shape which encompasses the side wall of the second magnetic body part 4b and has openings via which the second magnetic body part 4b can be inserted. The inner wall of the second housing section 6b is also provided with a fixed protrusion 22b which engages the recess 20b of the second magnetic body part 4b. When the second magnetic body part 4b is housed in the second housing section 6b to expose the abutting faces 8b, 8c, the fixed protrusion 22b engages the recess 20b to prevent the second magnetic body part 4b from falling out of the second housing section 6b.

Additionally, notches 16a to 16d are formed in the housing sections 6a to 6c through which the electric wire can be passed and corresponding to the sectional shapes of the grooves 12a to 12d when the magnetic body parts 4a to 4c are housed in the housing sections 6a to 6c, respectively.

The first and third housing sections 6a and 6c are openably connected to the second housing section 6b by two pairs of hinges 24. Each pair of hinges 24 are arranged on the opposite outer surfaces of the second housing section 6b at upper and lower positions thereon, respectively. When the first and third housing sections 6a and 6c can rotate about the hinges 24, and the openings in the second housing section 6b can be closed by the first and third housing sections 6a and 6c. Therefore, when the first and third housing sections 6a and 6c are closed while the magnetic body parts 4a to 4c are housed in the housing sections 6a to 6c, respectively, the first and second magnetic body parts 4a and 4b are interconnected via the abutting faces 8a, 8b to form the first hollow 10a, and a closed magnetic path is formed around the hollow 10a. Then, the second and third magnetic body parts 4b and 4c are interconnected via the abutting faces 8c, 8d to form the second hollow 10b, and a closed magnetic path is formed around the hollow 10b. Moreover, the opening edges of the first and third housing sections 6a and 6c opposite to the hinges 24 are provided with engaging frames 26, while the opening edges of the second housing section 6b opposite to the hinges 24 are provided with protrusions 28 which can engage in the engaging frames 26 when the first and third housing sections 6a and 6c are closed. The frames 26 and protrusions 28 form resilient latches. Therefore, when the first and third housing sections 6a and 6c are closed, the engaging frames 26 are locked by the protrusions 28 and the first and third magnetic body parts 4a and 4c abut closely the second magnetic body part 4b.

In use the electric noise absorber 2 having the abovementioned structure, the electric wire 30 is wound a desired times around the periphery of the second housing section 6b with the second magnetic body part 4b housed therein, along the grooves 12b and 12c formed in opposite surfaces of the second magnetic body part 4b as shown in FIG. 2A. Then, the first and third housing sections 6a and 6c are closed onto housing section 6b. The engaging frames 26 are engaged with the protrusions 28 so that the electric noise absorber 2 is attached to the electric wire as shown in FIG. 2B.

The electric noise absorber 2 of the first embodiment is provided with the first and second hollows 10a and 10b through which the electric wire 30 passes. By winding the electric wire 30 around the second magnetic body part 4b between the hollows 10a and 10b, the electric wire 30 is passes through the hollows 10a and 10b a plurality of times and the portion of the electric wire 30, which is exposed to the outside of the conventional electric noise absorber, is surrounded by the magnetic body parts. As a result, the electric noise flowing through the electric wire is absorbed more effectively than in the prior art. As a result, the operation error or failure of the electronic apparatus attributed to electric noises is greatly reduced.

Additionally, the electric noise absorber 2 can easily be attached to an already placed electric wire by winding the wire around the second magnetic body part 4b and subsequently closing the first and third magnetic body parts 4a and 4c.

As the first magnetic body part 4a is formed of Mn--Zn ferrite, while the second and third magnetic body parts 4b and 4c are each formed of Ni--Zn ferrite, the electric noise absorbing ability of the electric noise absorber 2 is enhanced and extends over a wide bandwidth.

In order to confirm the above-mentioned effect, the following experiment was conducted.

As shown in FIG. 8A, there was prepared sample A of the conventional type electric noise absorber provided with only one hollow and wound with an electric wire L1 exposed on the outer periphery of a magnetic body. As shown in FIG. 8B, the inventors prepared sample B by bonding semi-cylindrical magnetic body parts to both surfaces of a magnetic body formed in a plate shape to form a magnetic body with two hollows arranged in parallel and by winding the electric wire L1 the same times as in sample A around the plate-shaped magnetic body between the hollows to pass the wire through both hollows. The impedance-frequency characteristic of both sample A and B were measured in a range of 1 MHz to 100 MHz. The results are shown graphically in FIG. 9A with the impedance characteristic of sample A being shown by a broken line and the impedance characteristic of sample B being shown by a solid line. Although the same number of turns of electric wire is wound around samples A and B, sample B is superior to the sample A in electric noise absorbing ability. Each of the magnetic body parts of sample A and B, shown in FIGS. 8A and 8B, is formed of nickel--zinc soft ferrite.

Subsequently, as shown in FIG. 8C, the Ni--Zn soft ferrite of one semi-cylindrical magnetic body part of sample B was replaced by Mn--Zn soft ferrite to form sample C. The impedance-frequency characteristic of the sample C was measured. As a result, as shown in FIG. 9B, the impedance was further raised in the range of 1 MHz to 8 MHz. It is thus confirmed that low-frequency electric noise can be absorbed more effectively. Specifically, when the first magnetic body part 4a is formed of Mn--Zn ferrite, while the second and third magnetic body parts 4b and 4c are each formed of Ni--Zn ferrite, the electric noise absorbing ability of the electric noise absorber 2 is enhanced over a wide bandwidth.

B. A second embodiment will now be described.

FIGS. 3A and 3B are explanatory views showing the structure of an electric noise absorber 102 according to the second embodiment. The electric noise absorber 102 is provided with first to third housing sections 6a to 6c and four divided magnetic body parts 104a to 104d. These parts together form the magnetic body 104. Mn--Zn soft ferrite is used in the first and second magnetic body parts 104a and 104b, while Ni--Zn soft ferrite is used in the third and fourth magnetic body parts 104c and 104d.

Abutting faces 108a, 108b which abut each other without any gap are formed where the first and second magnetic body parts 104a and 104b meet. Grooves 112a, 112b are formed in the magnetic body parts 104a, 104b, respectively, to form a first hollow 110a in which an electric wire is positioned when these magnetic body parts are interconnected without any gap between the abutting faces 108a, 108b. Abutting faces 108c, 108d which abut each other without any gap are formed in an area where the third and fourth magnetic body parts 104c and 104d meet. Grooves 112c, 112d are formed in the magnetic body parts 104c, 104d, respectively, to form a second hollow 110b in which an electric wire is positioned when these magnetic body parts are interconnected without any gap between the abutting faces 108c, 108d.

Magnetic body parts 104a and 104d are housed in first and second housing section 6a and 6c, respectively, while parts 104b and 104c are housed in third housing 6b. Recesses 120a to 120d are formed in the side walls of the magnetic body parts 104a to 104d to engage fixed protrusions 122a to 122d formed on the inner walls of the housing sections 6a to 6c, respectively.

Since the other structure of the second embodiment is the same as that of the first embodiment, the description thereof is omitted.

The electric noise absorber 102 constituted as aforementioned is attached to the electric wire as follows:

The magnetic body parts 104a to 104d are contained in the housing sections 6a to 6c, the electric wire is wound desired times around the periphery of the third housing section 6b along the grooves 112b and 112c of the second and third magnetic body parts 104b and 104c, and the first and second housing sections 6a and 6c are closed.

The magnetic body 104 is divided by the abutting faces extended through the hollows 110a and 110b in an axial direction.

Electric noise absorbing ability of the electric noise absorber 102 is enhanced over a wide bandwidth as with the first embodiment.

In the electric noise absorbers 2 and 102 of the first and second embodiments, the first hollows 10a, 110a and the second hollows 10b, 110b are formed by connecting the dividable magnetic body parts 4, 104, but the present invention is not limited to the embodiments. The magnetic body may be formed in such a manner that it cannot be divided and only one of a plurality of hollows need by formed by abutment faces.

C. A third embodiment will be described.

FIGS. 4A and 4B show the structure of an electric noise absorber 202 according to the third embodiment. The electric noise absorber 202 is provided with first and second magnetic body parts 204a and 204b, contained in first and second housing sections 206a and 206b, respectively. The first magnetic body 204a is formed of Mn--Zn soft ferrite, while the second magnetic body 204b is formed of Ni--Zn soft ferrite.

Abutting faces 208a, 208b which can abut on each other without any gap are formed in an area where the first and second magnetic body parts 204a and 204b meet. Grooves 212a, 212b are formed in the magnetic body parts to form a first hollow 210a in which an electric wire can extend between the magnetic body parts when the magnetic body parts are interconnected without any gap by the abutting faces 208a, 208b. Recesses 220a, 220b are formed in the side faces of the magnetic body parts 204a, 204b to engage with the inner walls of the housing sections 206a, 206b, respectively. A second hollow 210b is formed through the second magnetic body 204b.

The first and second housing sections 206a and 206b are formed as box shapes having openings via which the first and second magnetic body parts 204a and 204b can be contained, respectively. The inner walls of the housing sections are provided with fixed projections 222a, 222b which can captively engage the recesses 220a, 220b of the magnetic body parts 204a, 204b, respectively. When the first and second magnetic body parts 204a and 204b are housed in the first and second housing sections 206a and 206b in such a manner that the abutting faces 208a, 208b are exposed, the fixed protrusions 222a, 222b are engaged in the recesses 220a, 220b to prevent the magnetic body parts 204a, 204b from falling from the housing sections 206a, 206b, respectively.

Additionally, notches 216a, 216b are formed in the first and second housing sections 206a and 206b in such a manner that an electric wire can be passed corresponding to the sectional shapes of the grooves 212a, 212b when the first and second magnetic body parts 204a and 204b are housed therein, respectively. Insertion openings 216c via which the electric wire can be inserted are formed in the second housing section 206b corresponding to the second hollow 210b are formed in the second magnetic body 204b.

The first and second housing sections 206a and 206b are connected in the same manner as the first and second housing sections 6a and 6b of the first embodiment.

The electric noise absorber 202 constituted as aforementioned is attached to the electric wire by housing the magnetic body parts 204a, 204b in the housing sections 206a, 206b, respectively, winding the electric wire desired times around the second magnetic body 204b between the groove 212b and the second hollow 210b along the groove 212b and the second hollow 210b and closing the first housing section 206a.

The magnetic body is divided by the abutting faces extended through the first hollow 210a in the axial direction. The first hollow 210a is formed by connecting the first and second magnetic body parts 204a and 204b. The electric wire can be relatively easily wound around the second magnetic body 204b. Labor can thus be advantageously reduced.

In electric noise absorber 202 of the third embodiment, an abutting face extends in only one hollow.

D. A fourth embodiment will now be described.

FIG. 5 shows the structure of an electric noise absorber 302 according to the fourth embodiment. The electric noise absorber 302 is provided with divided pieces, i.e., first and third magnetic body parts 304a and 304c in a first housing section 306a and second and fourth magnetic body parts 304b and 304d in a second housing section 306b. Mn--Zn soft ferrite is used in the first and second magnetic body parts 304a and 304b, while Ni--Zn soft ferrite is used in the third and fourth magnetic body parts 304c and 304d.

Abutting faces 308a, 308b which abut each other without any gap are formed in an area in which the first and second magnetic body parts 304a and 304b meet. Grooves 312a and 312b are formed in such a manner that a hollow can be formed in which an electric wire is positioned between the magnetic body parts 304a and 304b when the magnetic body parts are connected, without any gap therebetween, by the abutting faces 308a, 308b. Moreover, abutting faces 308c, 308d which can abut on each other without any gap are formed in an area in which the third and fourth magnetic body parts 304c and 304d are opposed to each other. Grooves 312c and 312d are formed in such a manner that a hollow can be formed in which an electric wire extends between the magnetic body parts 304c and 304d when the magnetic body parts are connected without any gap therebetween by the abutting faces 308c, 308d.

The first housing section 306a is formed in a box shape having an opening in which the first and third magnetic body parts 304a and 304c are arranged and housed, while the second housing section 306b is formed in a box shape having an opening in which the second and fourth magnetic body parts 304b and 304d are arranged and housed. The first and third magnetic body parts 304a and 304c are exposed in the opening of the first housing section 306a when housed in the first housing section 306a and the second and fourth magnetic body parts 304b and 304d are exposed in the opening of the second housing section 306b when housed in the second housing section 306b.

Notches 316a to 316d via which an electric wire can be passed are formed in the housing sections 306a, 306b corresponding to the sectional shapes of the grooves 312a to 312d when the magnetic body parts 304a to 304d are housed, respectively.

The first and second housing sections 306a and 306b are connected, hinged and latched closed in similar manner to the housing sections of the first, second and third embodiments.

The electric noise absorber 302 constituted as aforementioned is attached to the electric wire by housing the magnetic body parts 304a to 304d in the housing sections 306a, 306b, placing the electric wire in an annular state along the grooves 312b, 312d of the second and fourth magnetic body parts 304b and 304d, respectively, or the grooves 312a, 312c of the first and third magnetic body parts 304a and 304c, respectively, and connecting the first and second housing sections 306a and 306b together.

As shown in FIG. 6A, a further embodiment of an electric noise absorber 402 is illustrated with multiple hollows 410a and 410b. In this case, the electric noise absorber can be simultaneously attached to multiple electric wires, and the electric noises flowing through the electric wires can be absorbed at the same time.

Moreover, the hollow can have various sectional shapes. For example, as shown in FIG. 6B, the hollows 410a and 410b may be formed to have wide sections. In this case, the electric noise absorber can be attached to a flat cable. The variation of the hollow sectional shape diversifies the types of electric wires to which the electric noise absorber can be attached.

In the first and second embodiments, the hinges 24 are provided on the opposite sides of the second housing section 6b, but the present invention is not limited to these embodiments. As shown in FIGS. 6A and 6B, the hinges 24 may be provided on the same side of the second housing section 6b.

In the above-described embodiments, the magnetic body parts are contained in housing sections and the magnetic body parts can be reinforced by the housing sections. However, even if the magnetic body parts are not contained in the housing sections, the absorbing characteristics of the electric noise absorber is still enhanced. Therefore, the magnetic body parts provided with the hollows may be attached directly to the electric wire. For example, in an electric noise absorber 502 shown in FIG. 7A, hollows 510a and 510b are formed in magnetic body parts 504a and 504b formed of two different magnetic materials, respectively. Electric noises can be effectively absorbed by winding the electric wire around the magnetic body parts 504a, 504b through the hollows 510a and 510b. If magnetic body parts 504a and 504b are formed of different magnetic materials, the superior absorbing ability can be fulfilled for the electric noises in a wide bandwidth.

FIG. 7B shows the electric noise absorber 502 of FIG. 7A, in which the magnetic body parts 504a, 504b are divided by dividing faces extending through the hollows 510a, 510b, respectively. In this case, after even the already placed electric wire may be wound around the magnetic body pieces between the hollows 510a and 510b, the divided pieces are connected by the abutting faces, so that the electric noises flowing through the electric wire can effectively be absorbed. Furthermore, as shown in FIG. 7C, a multiplicity of hollows may be formed in the magnetic body parts. By winding a multiplicity of electric wires around the magnetic body portions between the respective hollows 510a, 510b of the magnetic body parts 504a, 504b, the electric noises flowing through the electric wires can be simultaneously absorbed. In this case, the electric wire may be wound around the magnetic body portion between the hollows 510a (or 510b) of the magnetic body 504a (or 504b). The sectional shape of the hollow is not limited. For example, as shown in FIG. 7D, when the hollow has a flat shape, the electric noise absorber can be attached to a flat cable or other various electric wires.

Additionally, in the embodiments, the electric noise absorbers 2, 102, 202, 302 having the magnetic body parts formed of two types of materials have been described, but the present invention is not limited to the embodiments. The electric noise absorbing characteristic of the wide bandwidth may be enhanced, for example, by combining three or more types of magnetic body parts. The material of the magnetic body is not limited to Mn--Zn ferrite or Ni--Zn ferrite, and the magnetic material may be selected in accordance with the bandwidth of the electric noises to be eliminated.