Electric wire for high frequency, high voltage and large current

Abstract

An electric wire contains a conductive wire having at least a groove structured on the surface of the conductive wire, and an additional wire to be filled into the groove. The groove is provided on an outer surface of the conductive wire along a longitudinal direction of the conductive wire. The additional wire is inserted in the groove.

Description

TECHNICAL FIELD

This application claims priority under 35 U.S.C. §119 from Japanese patent application Serial No. 2009-245345, filed Oct. 26, 2009, entitled “Electric wire for high frequency, high voltage and large current”, which is incorporated herein by reference in its entirety.

Here, t is a temperature in ° C., at which a resistance of the electric wire is measured. R is a ratio of a resistance at the measured temperature to a resistance measured at 50° C.

It is optimal that resistances of the electric wire 0 fulfill the above equation when the resistances of the electric wire 0 are measured at every 10° C. between 50° C. and 200° C. Such electric wire 0 has lower resistance in a wide range of temperature. Therefore, electric power consumptions of a motor containing such electric wire 0 become more consistent in a wide range of temperature. Although not limited, the equation may be set as ‘1≤R≤0.0028t+0.86’. It is not to mention that the above preferred value, slope, area and equation is not only applied to the electric wire 0 in the present embodiments but also any other electric wire.
<Modification Examples>

FIG. 14 shows a first modification example of the third embodiment. As shown in this figure, a conductive wire 1, grooves 2 and additional wires 3 have square cross-sectional shapes. Square shapes are easy to reduce dead spaces and increase contact areas. Since the grooves 2 and the additional wires 3 have square cross-sectional shapes, dead spaces inside of the electric wire 1 is reduced and the contact areas between the additional wires 3 and the conductive wire 1 are increased. Furthermore, when a coil is wound with the electric wire 0 of the first modification example, the electric wire 0 is packed more densely. FIG. 15 shows a second modification example of the third embodiment. An electric wire 0 of the second modification has a rectangular cross-sectional shape. Grooves 2 and additional wires 3 are placed on one long edge of the rectangular. FIG. 16 shows a third modification example of the third embodiment. An electric wire 0 of the third modification has a rectangular cross-sectional shape. A groove 2 and an additional wire 3 is placed on each short edge of the rectangular so that the two grooves 2 and the two additional wires 3 face to each other. The advantages of these electric wires 0 are the same as described before.

<Fourth Embodiment>

FIG. 14 shows a fourth embodiment of the electric wire. Here, the same explanations as in the previous embodiments are omitted and the different things are mainly explained. As shown in this figure, an electric wire 0 is composed of a conductive wire 1. The conductive wire 1 has an approximately square cross-sectional shape. Each corner of the conductive wire 1 is cut out along the longitudinal direction of the conductive wire 1. Thereby, on each corner of the conductive wire 1, a groove (cutout) 7 is formed along the longitudinal direction of the conductive wire 1. The groove 7 has a square cross-sectional shape. In the groove 7, an insulator 6 is placed. In other word, the groove 7 is filled with the insulator 6. The insulator 6 also has a square cross-sectional shape. The outer surface of the conductive wire 1 is coated with an insulator sheath 4.

In the case of an electric wire that has a quadrilateral cross-sectional shape, the inventor has discovered that the electric discharge mainly occurs at the corner of the electric wire when the electric wires are packed densely. Then, the inventor also discovered that if insulators are placed at the corners of the quadrilateral along the longitudinal direction of the electric wire, the electric discharges are effectively prevented. Thus, the electric wire 0 of this embodiment can prevent electric discharge effectively even when the electric wire 0 is packed densely. Therefore, when a coil is wound with the electric wire 0, a higher voltage can be applied to this coil.

The discharge is well prevented even if a width W1 of the insulator 6 is less than one third of a width W2 of the conductive wire 1. If the width W1 of the insulator 6 is set less than one third of a width W2 of the conductive wire 1, an cross-sectional area of the conductive wire 1 doesn't have to become so small that the conductive wire 1 can still conduct a large current. Because of the same reason, it is also preferable that a width W1 of the groove 7 is less than one third of a width W2 of the conductive wire 1.

It is preferable that the insulator 6 is made of a synthetic resin. Synthetic resin provides an excellent insulation even if the insulator 6 is thin. Furthermore, synthetic resin adheres well to many metals.

The insulator sheath 4 may be made of the same or different material from the material of the insulator 6. However, if the insulator sheath 4 is made of the same material as the material of the insulator 6, adhesiveness between the insulator 6 and the insulator sheath 4 is improved.

FIG. 18 shows a part of a coil, in which the electric wire 0 is wound with a best arrangement. This figure shows an enlarged longitudinal cross-sectional view of the coil. More specifically, the electric wire 0 is wound on an outer surface of a cylindrical bobbin 11. After the coil 10 is sectioned in a longitudinal direction of the cylindrical bobbin 11 and one end section is magnified, the coil 10 is seen as FIG. 18. In this figure, a right and left direction is the longitudinal direction of the cylindrical bobbin 11. An upward direction is the circumferential direction of the cylindrical bobbin 11. And, a downward direction is the center direction of the cylindrical bobbin 11. For convenience, the right and left direction of the FIG. 18 is called longitudinal direction and the upward and downward direction is called circumferential direction.

As shown in FIG. 18, the electric wire 0 is arranged so that the electric wire 0 aligns on one line in both longitudinal and circumferential directions. In other words, the electric wire 0 is arranged so that it forms columns and rows in cross-sectional view. This arrangement maximizes the density of the electric wire 0. As shown in FIG. 18, each edge of the electric wire 0 is arranged to be on one line in both longitudinal and circumferential directions. Thus, one corner of one square is adjacent to one corner of next three squares. In other word, four corners come together at a junction of a grid formed by edges of the quadrilateral. In this arrangement, the four insulators 6 become adjacent to one another at the junction. This arrangement effectively prevents electric discharge from the corner of the electric wire 0. Therefore, a higher voltage can be applied to the coil 10. Thus, a larger power can be generated if the coil 10 is used for a motor. In addition, since the wire density is high, the coil 10 can be compact to obtain a sufficient inductance or to generate a sufficient magnetic force.

<Modification Examples>

FIG. 19 shows a first modification example of the fourth embodiment. As shown in this figure, in an electric wire 0, an insulator 6 that fills grooves 2 and an outer surface of the conductive wire 1 is formed together. In other word, in this modification example, the insulator sheath 4 is united into the insulator 6. This arrangement makes the manufacturing process of the electric wire 0 simpler.

FIG. 20 shows a second modification example of the fourth embodiment. An electric wire 0 of the second modification has a rectangular cross-sectional shape. When a conductive wire 1 has a rectangular cross-sectional shape, width W2 of the conductive wire 1 may be based on a longer edge of the conductive wire 1.

FIG. 21 shows a third modification example of the fourth embodiment. As shown in this figure, on each corner of the conductive wire 1, a groove 7 is formed along the longitudinal direction of the conductive wire 1. In addition, grooves 2 are formed on the edges of the square. The position of these grooves 2 are approximately at the middle of the edge and distant from the corner. In the groove 7, an insulator 6 is placed. In the groove 2, an additional wire 3 is placed. Therefore, in the electric wire 0 of this modification example, an increase of the resistance is well suppressed at high temperature. In addition, electric discharge from the corner of the electric wire 0 is well prevented. Therefore, at a high temperature not only a motor containing the electric wire 0 of this modification example can suppress the elevation of the electric power consumption effectively, but a high voltage can also be applied to the motor. Accordingly, such motor can generate a larger mechanical power with a relatively lower electric power consumption at a high temperature.

FIG. 22 shows a fourth modification example of the fourth embodiment. As shown in this figure, all the grooves 2 and 7, additional wires 3 and insulators 6 have square cross-sectional shapes. Like this example, if the grooves 2 and the grooves 7 have a similar cross-sectional shape, a process of forming grooves becomes simpler.

FIG. 23 shows a fifth modification example of the fourth embodiment. An electric wire 0 of the fourth modification has a rectangular cross-sectional shape. Grooves 7 and insulators 6 are placed at all the corners of the rectangular. Grooves 2 and additional wires 3 are placed on one long edge of the rectangular. The advantages of electric wires 0 are a combination of the advantages described before.

In the above embodiments, the quadrilateral shapes are rectangular or square. In other embodiments, a quadrilateral shape may be a quadrilateral shape that is not rectangular or square. In other embodiment, the insulator 6 may be placed at one, two or three corners of the quadrilateral. In other embodiment, a cross-sectional shape of the groove 7 and the insulator 6 may be other shape such as circular.

<Example>

An electric wire 0 as shown in FIG. 13 was made. As a conductive wire 1, an aluminum (Al) wire (Φ2 mm) was prepared. And, as additional wires 3, copper (Cu) wires (Φ0.2 mm) were prepared. On the aluminum wire, four grooves 2 were formed by a blade. Then, the copper wires were put into the groove 2.

Then, the temperature of the electric wire 0 was slowly raised. And, resistances of the electric wire 0 were measured between 50° C. and 200° C. at every 10° C., applying a direct current (DC). Then, ratios of the resistances at the measured temperature to the resistance at 50° C. were calculated. The result is shown in FIG. 24.

As a comparison, resistances of an aluminum wire (Φ2 mm) and a copper wire (Φ2 mm) were measured in the same way. And, ratios of the resistances at the measured temperature to the resistance at 50° C. were also calculated. The results are also shown in FIG. 24.

As shown in this figure, the resistance of the aluminum wire, in which the copper wires were embedded, didn't increase as much as those of the aluminum wire and the copper wire as the temperature of the wire rose. Therefore, it is expected that a motor containing the electric wire 0 of this example will generate the same power with a lower voltage than motors containing the aluminum wire or the copper wire at a high temperature such as 100 or 200° C.

Claims

1. An electric wire comprising:

a conductive wire, which has substantially a quadrilateral cross-sectional shape; and

an insulator placed along a longitudinal direction of the conductive wire at a corner of the quadrilateral;

a groove provided along the longitudinal direction of the conductive wire at the corner of the quadrilateral;

wherein the insulator is placed in the groove.

2. The electric wire of claim 1,

wherein a width of the insulator is less than one third of a width of the conductive wire.

3. The electric wire of claim 1,

wherein the insulator is made of a synthetic resin.

4. The electric wire of claim 1,

wherein insulators are placed at all corners of the quadrilateral.

5. The electric wire of claim 1, further comprising:

an additional wire inserted in the conductive wire along the longitudinal direction of the conductive wire;

wherein the additional wire comprises a conductive member;

wherein the conductive wire and the conductive member are made of different materials; and

wherein the conductive member is in contact with the conductive wire.

6. A coil comprising the electric wire of claim 1, the electric wire being wound on a bobbin so that a corner of a quadrilateral is adjacent to a corner of a next quadrilateral in a cross sectional view.

7. An electric wire comprising:

a conductive wire having substantially a quadrilateral cross-sectional shape;

a groove provided along a longitudinal direction of the conductive wire at each corner of the quadrilateral, wherein an insulator is placed into the groove along the longitudinal direction of said conductive wire;

an additional wire, comprising a conductive member, inserted into the conductive wire along the longitudinal direction of said conductive wire, wherein said additional wire is sized to fit into another groove located around a middle point of each sides of said quadrilateral; and

an insulator sheath covering entirely an outer surface of the conductive wire, covering all sides and all corners of the quadrilateral,

8. The electric wire of claim 7, wherein the conductive wire is made of materials comprising aluminum and the conductive member is made of material comprising copper.

9. The electric wire of claim 7, a resistance of the conductive wire at 200° C. is at most 1.42 times and at least 1.00 time larger than a resistance of the conductive wire at 50° C.

10. An electric wire comprising:

a conductive wire having substantially a quadrilateral cross-sectional shape;

a groove provided along a longitudinal direction of the conductive wire;

an additional wire, comprising a conductive member, inserted into the conductive wire along the longitudinal direction of said conductive wire, said additional wire is sized to fit into the groove so as to fill entirely the groove;

an insulator placed along the longitudinal direction of the conductive wire covering entirely an outer surface of said conductive wire,

11. The electric wire of claim 10, wherein the conductive wire is made of materials comprising aluminum.

12. The electric wire of claim 10, wherein said conductive member is made of materials comprising copper.

13. The electric wire of claim 10, wherein the insulator is made of a synthetic resin.

14. The electric wire of claim 10, wherein a surface of said conductive member is coated with a conductive material different from material constituting the conductive member.

15. The electric wire of claim 12, wherein the conductive member comprises a silver-plated copper wire.

16. An electric wire comprising:

a single conductive wire having substantially a quadrilateral cross-sectional shape; and

an insulating layer placed along a longitudinal direction of said single conductive wire, covering at least one corner of said quadrilateral,

17. The electric wire of claim 16, wherein the resistance of the conductive wire at 200° C. is at least 1.00 times larger than the resistance of the conductive wire at 50° C.

18. The electric wire of claim 16, wherein a ratio of resistance of the conductive wire measured at a temperature between 50° C. to 200° C. to the resistance of conductive wire measured at 50° C. satisfies the following equation:

1≤R≤0.028T+0.86

19. The electric wire of claim 16 further comprising an additional wire inserted in the conductive wire along the longitudinal direction of the conductive wire,

20. The electric wire of claim 19, wherein the conductive wire is made of materials comprising aluminum and the conductive member is made of materials comprising copper.

21. A coil comprising the electric wire of claim 16, wherein the electric wire being wound on a bobbin so that a corner of a quadrilateral is adjacent to a corner of a next quadrilateral in a cross sectional view.

22. The electric wire of claim 16, wherein the insulating layer covers entirely an outer surface of the conductive wire, covering all corners and all sides of the quadrilateral.

23. The electric wire of claim 16, wherein the insulating layer is made of synthetic resin.

24. The electric wire of claim 16 further comprises a groove disposed along the longitudinal direction of the conductive wire at one corner of the quadrilateral, wherein the insulating layer covers the groove.

25. The electric wire of claim 24, wherein the groove is provided at all corners of the quadrilateral and the insulating layer covers entirely an outer surface of the conductive wire, including all corners and all sides of the quadrilateral.