Post-fitting shield member, shielded wire, manufacturing method of shielded wire, and manufacturing method of post-fitting shield member

Abstract

A post-fitting shield member to be post-fitted with an electric wire is a plated fiber bundle wound in coil form and formed by performing metal plating on a high-strength fiber member. A manufacturing method of a shielded wire includes an insertion step of inserting an electric wire into the post-fitting shield member having a coil shape; a first fixing step of fixing one end portion of the post-fitting shield member into which the electric wire was inserted in the insertion step; an expansion step of expanding the post-fitting shield member that was fixed in the first fixing step toward the side of its other end portion; and a second fixing step of fixing the other end portion of the post-fitting shield member that was expanded in the expansion step.

Claims

1. A post-fitting shield member to be post-fitted with an electric wire comprising: a plated fiber bundle with metal plating on a high-strength fiber member, wherein the plated fiber bundle is wound in a coil shape, and wherein the high-strength fiber member is larger than or equal to 1 GPA in breaking tensile strength and is from 1% to 10% in breaking extension ratio.

2. The post-fitting shield member according to claim 1, wherein the plated fiber bundle is thin and flat, and has a flat surface being one of an upper surface and a bottom surface in a thickness direction of the plated fiber bundle, the flat surface facing a center line of the coil shape.

3. The post-fitting shield member according to claim 1, wherein in state that the plated fiber bundle is wound on the electric wire spirally, d.sup.2={(D).sup.2+P.sup.2}/.sup.2 is satisfied, where d is an inner diameter of the plated fiber bundle, D is an outer diameter of the electric wire, and P is a pitch P after the post-fitting shield member is post-fitted with the electric wire.

4. A shielded wire comprising: the post-fitting shield member according to claim 1; and an electric wire which is inserted in the post-fitting shield member having the coil shape, wherein the post-fitting shield member is in a state that it is elongated so as to be longer than its natural length and wound on the electric wire spirally.

5. The shielded wire according to claim 4, wherein TN/D0.5 is satisfied, where T is the width of each plated fiber bundle, N is a number of plated fiber bundles, and D is the outer diameter of the electric wire.

6. A manufacturing method of a shielded wire comprising: an insertion step of inserting an electric wire into the post-fitting shield member according to claim 1 having the coil shape; a first fixing step of fixing one end portion of the post-fitting shield member into which the electric wire was inserted in the insertion step; an expansion step of expanding the post-fitting shield member that was fixed in the first fixing step toward a side of another end portion of the post-fitting shield member; and a second fixing step of fixing the other end portion of the post-fitting shield member that was expanded in the expansion step.

7. A manufacturing method of a post-fitting shield member comprising: a plating step of performing metal plating on a high-strength fiber member; a heat treatment step of winding a plated fiber bundle obtained by the plating step into a coil shape and subjecting the wound plated fiber bundle to heat treatment of a prescribed temperature or higher and a prescribed time or longer; and a cooling step of cooling the wound plated fiber bundle as subjected to the heat treatment.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows the structure of a shielded wire including a post-fitting shield member according to an embodiment of the present invention.

(2) FIG. 2 shows the structure of the post-fitting shield member.

(3) FIG. 3 is a sectional view of a plated fiber bundle used in the post-fitting shield member shown in FIG. 2.

(4) FIGS. 4A-4C show an insertion step, a first fixing step, and an expansion step, respectively, of a manufacturing method of a shielded wire according to the embodiment.

(5) FIG. 5 is a graph showing a relationship between tensile elastic modulus and temperature of fiber.

DESCRIPTION OF EMBODIMENTS

(6) A preferred embodiment of the present invention will be hereinafter described. The present invention is not limited to the embodiment described below, and various modifications are possible without departing from the spirit and scope of the invention. In the embodiment described below, part of the constituent elements will not be shown in the drawings or will be omitted in the description. It goes without saying that known techniques are applied to those constituent elements as appropriate within the confines that no contradictions to the following description will occur.

(7) FIG. 1 shows the structure of a shielded wire 1 including a post-fitting shield member 20 according to the embodiment. As shown in FIG. 1, in the shielded wire 1, the post-fitting shield member 20 is provided as a shield layer around an electric wire 10.

(8) The electric wire 10 is formed in such a manner that a conductor 10a made of a conductive metal is covered with an insulator 10b. Although in the embodiment the conductor 10a is twisted element wires, the invention is not limited to that case; the conductor 10a may be a single wire, for example Plural electric wires may be used instead of the single electric wire 10.

(9) The post-fitting shield member 20 is a conductive member and is disposed around the electric wire 10 to exhibit a shielding effect. FIG. 2 shows the structure of the post-fitting shield member 20. As shown in FIG. 2, the post-fitting shield member 20 is formed in such a manner that a bundle B of plural plated fiber members each of which is formed by subjecting a high-strength fiber member to metal plating is wound in coil form. Alternatively, the post-fitting shield member 20 may have a single high-strength fiber member.

(10) The term high-strength fiber means a fiber material that is synthesized chemically from such a material as petroleum and that is larger than or equal to 1 GPa in breaking tensile strength and from is 1% to 10% in breaking extension ratio. Examples of such fiber is aramid fiber, polyacrylate fiber, and PBO fiber.

(11) FIG. 3 is a sectional view of the plated fiber bundle B that constitutes the post-fitting shield member 20 shown in FIG. 2. As shown in FIG. 3, the plated fiber bundle B (i.e., a bundle of plated fiber members MF) is thin and flat in cross section. The plated fiber bundle B is composed of plural high-strength fiber members F, first metal plating layers M1, and a second metal plating layer M2.

(12) Each first metal plating layer M1 is a metal plating layer that is formed on a high-strength fiber member F. In the embodiment, each first metal plating layer M1 is made of copper, for example Each plated fiber member MF is produced by forming a first metal plating layer M1 on a high-strength fiber member F.

(13) The second metal plating layer M2 is a metal plating layer that is formed by plating the plural plated fiber member MF together. In the embodiment, the second metal plating layer M2 is made of tin, for example.

(14) Although in the plated fiber bundle B shown in FIG. 3 the plural plated fiber members MF are arranged parallel with each other so as to form a single layer in the thickness direction, the invention is not limited to this case; plural plated fiber member MF may be arranged in plural layers in the thickness direction. Furthermore, the invention is not limited to the case that the plural plated fiber members MF are arranged parallel with each other; they may be slanted within the width of the plated fiber bundle B.

(15) The structure of the plated fiber bundle B is not limited to the one shown in FIG. 3. For example, the first metal plating layers M1 may be omitted. Another example is possible in which the second metal plating layer M2 is omitted and separate plated fiber members MF are twisted together into a thin and flat bundle B. Furthermore, a plated fiber bundle B is possible that is produced by forming a third metal plating layer (and a further metal plating layer or layers) on the plated fiber bundle B shown in FIG. 3.

(16) Again referring to FIG. 2, the post-fitting shield member 20 is formed by winding the plated fiber bundle B shown in FIG. 3 into a coil shape. In particular, in the post-fitting shield member 20 according to the embodiment, one of flat surfaces FS (top and bottom surfaces in the thickness direction; see FIG. 3) of the plated fiber bundle B faces the coil center line CC, that is, the flat surfaces FS are approximately perpendicular to a straight line drawn from the coil center line (coil axis) CC to the plated fiber bundle B.

(17) The post-fitting shield member 20 shown in FIG. 1 is formed by expanding the post-fitting shield member 20 shown in FIG. 2 along the coil axis. The post-fitting shield member 20 has a natural length in the state shown in FIG. 2. As a result of the expansion, the post-fitting shield member 20 is reduced in diameter and wound on the outer surface of an electric wire 10 spirally in such a manner that prescribed gaps are formed in the longitudinal direction between its adjacent portions. In addition, since the one of the flat surfaces FS of the plated fiber bundle B faces the coil center line CC, when the post-fitting shield member 20 is expanded, the one flat surface FS is brought into surface contact with the outer surface of the electric wire 10.

(18) In the post-fitting shield member 20 according to the embodiment, in a state that the plated fiber bundle B is wound on the electric wire 10 having an outer diameter D (see FIG. 1) spirally at a pitch P (see FIG. 1) after the post-fitting shield member 20 is post-fitted with the electric wire 10, it is preferable that the inner diameter d (see FIG. 2) of the plated fiber bundle B satisfies the following formula 1
[Formula 1]
d.sup.2={(D).sup.2+P.sup.2}/.sup.2. (1)

(19) This is because the inner diameter d that satisfies the above formula (1) allows the plated fiber bundle B to be wound on the electric wire 10 having the outer diameter D spirally at the pitch P.

(20) Furthermore, it is preferable that the shielding ratio of the shielded wire 1 according to the embodiment be larger than or equal to 0.5. The shielding ratio is defined by (the area of the plated fiber bundle B per unit length)/(the surface area of the electric wire 10 per unit length). It is preferable that the following formula 2 is satisfied.
[Formula 2]
(TNL)/(DL)0.5 (2)
T is the width of each plated fiber bundle B (see FIG. 3), N is the number of plated fiber bundles B, L is the length of the electric wire 10 (see FIG. 1), and D is the outer diameter of the electric wire 10.

(21) That is, the following formula 3 is satisfied.
[Formula 3]
TN/D0.5 (3)

(22) This is because the shielding ratio in the above range makes it possible to secure a shielding effect that is larger than or equal to 30 dB which is, in general, considered a minimum allowable value.

(23) Next, a manufacturing method of a shielded wire 1 according to the embodiment will be described. FIGS. 4A-4C show an insertion step, a first fixing step, and an expansion step, respectively, of the manufacturing method of a shielded wire 1.

(24) First, as shown in FIG. 4A, a worker prepares an electric wire 10 to be shielded and a post-fitting shield member 20 having a natural length. Then the worker inserts the electric wire 10 into the post-fitting shield member 20 (insertion step). Since the post-fitting shield member 20 having the natural length is as short as 50% or less of the length L of the shielded wire 1 (see FIG. 1), the electric wire 10 can be inserted easily.

(25) Then, as shown in FIG. 4B, the worker fixes one end portion of the post-fitting shield member 20 (first fixing step). In the example of FIG. 4B, the outer surface of the electric wire 10 is formed with a fixing portion FP. The invention is not limited to the case that one end portion of the post-fitting shield member 20 is fixed to the outer surface of the electric wire 10; the one end portion of the post-fitting shield member 20 may be fixed to a shell of a shield connector or a grounding member (e.g., vehicle body). As a further alternative, the one end portion of the post-fitting shield member 20 may be fixed in such a manner that a terminal of a grounding housing room of a connector is crimped onto it (before insertion of the electric wire 10 into the post-fitting shield member 20).

(26) Subsequently, as shown in FIG. 4B, the worker expands the post-fitting shield member 20 (the one end portion of which is fixed) toward the side of its other end (expansion step). As a result, the post-fitting shield member 20 is elongated so as to be as long as, for example, two or more times (preferable three or more times) its natural length. As a result, the one of the flat surfaces FS comes into close contact with the outer surface of the electric wire 10.

(27) Then, as shown in FIG. 4C, the other end portion of the expanded post-fitting shield member 20 is fixed (second fixing step). The manufacture of the shielded wire 1 is thus completed. As in the first fixing step, there are no particular limitations on the fixing location in the second fixing step.

(28) Next, a manufacturing method of a post-fitting shield member 20 according to the embodiment will be described. First, a worker prepares high-strength fiber members F and has them subjected to metal plating (plating step). As a result, a plated fiber bundle B (a bundle of plated fiber members MF) having a cross section shown in FIG. 3, for example, is obtained.

(29) Then the worker winds up the plated fiber bundle B into a coil having a prescribed diameter and has it subjected to heat treatment of a prescribed temperature or higher and a prescribed time or longer (heat treatment step). The prescribed diameter is determined according to the diameter of an electric wire 10 to be shielded (so as to be larger than the diameter of the electric wire 10).

(30) It is preferable that the prescribed temperature be 50 C. to 200 C. and the prescribed time is 3 minutes to 20 hours. If the heat treatment temperature is lower than 50 C., the degree of softening of the high-strength fiber members F is low and the plated fiber members MF cannot be compressed in a coil shape, rendering the post fitting difficult. If the heat treatment temperature is higher than 200 C., the high-strength fiber members F themselves are distorted and hence prescribed dimensions cannot be obtained.

(31) If the heat treatment time is shorter than 3 minutes, the plated fiber members MF cannot be fixed in a coil shape, rendering the post fitting difficult. If the heat treatment time is longer than 20 hours, metal atoms of the inside metal plating layers M1 diffuse into the outside metal plating layer M2, to change the resistance value and render the shielding effect unstable.

(32) More specifically, a plated fiber bundle B is obtained by performing plating on 300 members of Vectran (registered trademark) which is polyacrylate fiber produced by Kuraray Co., Ltd. and then wound on a SUS metal rod of 25 mm in diameter in coil form so that its adjacent portions have an interval that is equal to its width T. Then the plated fiber bundle B in coil form is subjected to heat treatment of 100 C. and 30 minutes in a constant-temperature bath produced by Co., Ltd. Isuzu Seisakusho.

(33) Subsequently, that is, after the heat treatment, the worker cools the plated fiber bundle B to ordinary temperature, for example (cooling step).

(34) The inventors found that high-strength fiber members F soften when subjected to heat treatment, and that when a coil-shaped plated fiber bundle B is then cooled, fiber shapes are fixed so that the plated fiber bundle B will maintain its shape.

(35) FIG. 5 is a graph showing a relationship between the tensile modulus of elasticity and temperature of each of various kinds of fiber. It is seen from FIG. 5 that the tensile modulus of elasticity of each kind of fiber decreases as temperature increases. In particular, in fiber materials other than polyester fiber and nylon fiber (high-strength fiber), the elasticity lowers fast as temperature increases.

(36) In general, molecules of fiber have orientation that varies to some extent when the fiber is heated. When the fiber is thereafter cooled, the orientation of molecules is fixed and the fiber material is fixed in shape. Thus, a post-fitting shield member 20 whose shape is fixed in coil form can be obtained by winding up a plated fiber bundle B into a coil shape, subjecting it to proper heat treatment, and then cooling it. Thus, the problem that a post-fitting shield member cannot keep a coil shape is overcome.

(37) It is desirable to use high-strength fiber. Such general-purpose fiber materials as polyester fiber and nylon fiber can keep a coil shape when subjected to the above process. However, since they lose elasticity after being subjected to the process, no shape recovery occurs (left in an expanded state) after being expanded. This may cause peeling of plated layers, resulting deterioration in shielding effect.

(38) FIG. 5 shows the characteristics of two kinds of aramid fiber (Kevlar (registered trademark) and Technora (registered trademark)), polyacrylate fiber (Vectran (registered trademark)), PBO fiber (Zylon), polyester fiber, and nylon fiber. Other kinds of aramid fiber, polyacrylate fiber, and PBO fiber exhibit characteristics that are similar to the ones shown in FIG. 5.

(39) In the post-fitting shield member 20 according to the embodiment, since the plated fiber bundle B formed by performing metal plating on the high-strength fiber members F is wound in coil form, the high-strength fiber member F in the plating layers is not easily deformed plastically even if a plated fiber member MF is hooked on a certain member when the electric wire 10 is inserted into the coil-shaped plated fiber bundle B and the plated fiber bundle B is expanded. Thus, a pitch deviation due to plastic deformation can be prevented. Furthermore, even if external force acts on the expanded post-fitting shield member 20, the high-strength fiber members F are not easily deformed plastically but maintained in shape. Thus, the post-fitting shield member 20 does not make post fitting difficult and is given a uniform pitch distribution after its expansion.

(40) Since the plated fiber bundle B is thin and flat and one of the flat surfaces FS faces the coil center line CC, when the plated fiber bundle B is used as part of the shielded wire 1, its one flat surface FS comes into contact with the electric wire 10. As a result, the close contactness between the plated fiber bundle B and the electric wire 10 is increased to stabilize the shielding effect. Furthermore, the shielded wire 1 is covered with a wide plated fiber bundle B, whereby the shielding performance can be enhanced.

(41) Since Inequality (1) is satisfied, the plated fiber bundle B can be wound spirally at the pitch P on the electric wire 10 having the outer diameter D.

(42) The shielded wire 1 according to the embodiment is equipped with the post-fitting shield member 20 and the electric wire 10. And the post-fitting shield member 20 is in a state that it is elongated so as to be longer than its natural length and wound on the electric wire 10 spirally. Since the electric wire 10 is inserted into the post-fitting shield member 20 that has not been expanded yet, the efficiency of work can be made higher than in a case that it is inserted into a post-fitting shield member that is long in its longitudinal direction.

(43) Since the shielded wire 1 satisfies the relationship of Inequality (3), it exhibits a shielding effect that is larger than or equal to 30 dB which is, in general, considered a minimum allowable level.

(44) The manufacturing method of a shielded wire 1 according to the embodiment is higher in work efficiency than in a case that the electric wire 10 is inserted into a post-fitting shield member that is long in its longitudinal direction.

(45) The present inventors found that high-strength fiber members F soften when subjected to heat treatment, and that when a coil-shaped plated fiber bundle B is then cooled, fiber shapes are fixed so that the plated fiber bundle B will maintain its shape. Thus, the manufacturing method of a post-fitting shield member 20 according to the embodiment can produce a post-fitting shield member 20 in which a coil shape is maintained by winding the plated fiber bundle B into a coil shape having a prescribed diameter, subjecting it to heat treatment, and then cooling it.

(46) Although the invention has been described above by way of the embodiment, the invention is not limited to the embodiment. Various modifications are possible without departing from the spirit and scope of the invention, and the embodiment may be combined with known techniques.

(47) For example, although in the embodiment the post-fitting shield member 20 is provided directly on the electric wire 10, the invention is not limited to this case; a certain thing may be interposed between the post-fitting shield member 20 and the electric wire 10. Although in the embodiment the post-fitting shield member 20 is provided on the single electric wire 10, the invention is not limited to this case; the post-fitting shield member 20 may be provided on plural electric wires.

(48) Although the post-fitting shield member 20 according to the embodiment is thin and flat in cross section, it may have any of various other shapes. Although in the example of FIG. 1 the post-fitting shield member 20 is wound in a Z direction (Z-twist), it may be wound in an S direction (S-twist).

(49) Furthermore, although in the shielded wire 1 according to the embodiment the one plated fiber bundle B is wound on the electric wire 10 spirally, the invention is not limited to this case; two or more plated fiber bundles B may be wound on the electric wire 10 spirally. Even where two or more plated fiber bundles B are used, since they are expanded to constitute the shield wire 1, prescribed gaps are formed between the plated fiber bundles B.