JP2005235447A - Wire for wire harness and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire for a wire harness capable of suppressing generation of partial discharge and a water tree and of enhancing adhesiveness of a semiconductive layer to an insulation layer; and to provide its manufacturing method. <P>SOLUTION: This wire for a wire harness has a conductor 10 and the insulation layer 30 formed outside the conductor 10. The wire has semiconductive layers 20 and 40 on an interfacial surface between the conductor 10 and the insulation layer 30 and at least either of the surfaces of the insulation layer 30. The semiconductive layers comprise adjacent layers 20B and 40B in contact with the insulation layer 30 and separated layers 20A and 40A separated from the insulation layer. The adjacent layers have volume resistivity different from that of the separated layers. For instance, the resistivity of the adjacent layers 20B and 40B is set larger than that of the separated layers 20A and 40A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wire harness wire and a method for manufacturing the same. In particular, the present invention relates to a wire harness wire capable of improving adhesion between a semiconductive layer and an insulating layer, and a method for manufacturing the wire harness.

  Conventionally, the wire shown in FIG. 4 is known as an electric wire for a wire harness of an automobile. This includes a conductor 10, an insulating layer 30, a shield layer 50, and a sheath 60 in order from the center side (see, for example, Patent Document 1). Such electric wires are used not only for automobiles using ordinary internal combustion engines but also for electric cars and hybrid cars. For example, in a hybrid vehicle, a direct current of about 200 V is supplied from a battery, and the voltage is raised to 500 V by a converter and supplied to an inverter. The inverter converts it into three-phase alternating current and supplies power to the vehicle drive motor. When the vehicle decelerates, the motor functions as a generator, and the generated regenerative power is supplied to the inverter, converted into direct current, and used for charging the battery.

JP-A-6-124608 (Fig. 17)

  However, the above-described electric wires have the following problems, particularly when considering high voltage response.

(1) Partial discharge may occur, leading to deterioration of insulation.
Conventional wire harness wires are considered to be used at a voltage of about 500 V, and are not configured to be used at higher voltages. Therefore, when considering the use of electric wires at a higher voltage, if there is a minute gap at the interface between the conductor and the insulating layer and the interface between the insulating layer and the shield layer, partial discharge occurs at that gap. Therefore, it is assumed that insulation deterioration will occur in the long term.

(2) Water trees are generated, which may lead to insulation deterioration.
If power is continuously applied while water is in contact with the electric wire, a water tree that penetrates as the tree grows in the insulating layer is generated due to the influence of the electric field, and the breakdown of the water tree progresses. Sometimes. Water trees are generated and propagated starting from any location where electric field concentrates inside the electric wire, such as voids or protrusions, in an environment where water exists. In particular, if a minute gap exists at the interface between the conductor and the insulating layer and the interface between the insulating layer and the shield layer, the gap may become the starting point of the water tree. For this reason, considering the use of electric wires at a higher voltage, the electric wires are required to be devised to suppress the generation of water trees.

(3) Even if a semiconductive layer is formed as a countermeasure against occurrence of partial discharge or water tree, it is difficult to adhere to the insulating layer with sufficient strength.
The provision of an internal semiconductive layer at the interface between the conductor and the insulating layer, or the provision of an external semiconductive layer on the outer peripheral surface of the insulating layer is performed with a power cable or the like. Usually, these semiconductive layers are formed by extruding a conductive resin in which carbon black is mixed with a base resin. However, due to the blending of carbon black, the viscosity at the time of extrusion differs between the inner and outer semiconductive layers and the insulating layer, and it is difficult to adhere the semiconductive layer to the insulating layer with sufficient strength. In particular, once the internal semiconductive layer is formed, the insulating layer is formed, and then the external semiconductive layer is formed by extrusion, so that the outer layer is formed after the base layer is formed. The decline is even more pronounced. As a result, there may be a case where water tree and partial discharge cannot be sufficiently suppressed.

  Accordingly, a main object of the present invention is to provide a wire harness wire and a method for manufacturing the same, which can suppress the occurrence of partial discharge and water tree and can improve the adhesion between the semiconductive layer and the insulating layer.

  The present invention achieves the above object by providing a semiconductive layer on an electric wire and configuring the semiconductive layer with two layers having different volume resistivity.

  The electric wire for wire harness of the present invention is an electric wire for wire harness having a conductor and an insulating layer formed outside the conductor. A semiconductive layer is provided on at least one of the interface between the conductor and the insulating layer and the surface of the insulating layer. The semiconductive layer is composed of a proximity layer in contact with the insulating layer and a separating layer separated from the insulating layer. The proximity layer and the separation layer are characterized by having different volume resistivity.

  For the semiconductive layer, a semiconductive resin in which a conductive filler is mixed with a base resin is usually used. The semiconductive resin has a higher viscosity at the extrusion temperature as the content of the conductive filler is larger, that is, as the volume resistivity is lower. Therefore, if the semiconductive layer is formed of two layers having different volume resistivity, materials having different conductive filler contents can be used in the adjacent layer in contact with the insulating layer and the separation layer separated from the insulating layer. The adhesion of the semiconductive layer can be improved.

  Specific examples of the semiconductive layer include an internal semiconductive layer and an external semiconductive layer. For example, when the semiconductive layer is an internal semiconductive layer formed at the interface between the conductor and the insulating layer, the volume resistivity of the separation layer (inner layer) of this internal semiconductive layer is determined from the volume resistivity of the adjacent layer (outer layer). It is preferable to reduce the size.

  When the semiconductive layer is an external semiconductive layer formed on the surface of the insulating layer, the volume resistivity of the proximity layer (inner layer) of the external semiconductive layer is made larger than the volume resistivity of the separating layer (outer layer). It is possible.

  On the other hand, the manufacturing method of the wire harness for wire harness of the present invention includes a step of forming an insulating layer by extrusion on the outside of the conductor, and a step of forming a semiconductive layer by extrusion on at least one of the inside and outside of the insulating layer The manufacturing method of the electric wire for wire harnesses which has these. The semiconductive layer is composed of a proximity layer that is in contact with the insulating layer and a separation layer that is separated from the insulation layer, and the volume resistivity is different between the proximity layer and the separation layer. The viscosity at the time of extruding the adjacent layer is an intermediate value between the viscosity at the time of extruding the separation layer and the viscosity at the time of extruding the insulating layer. And it is characterized by performing extrusion coating of a proximity layer and a separation layer by tandem extrusion.

  A typical example of the electric wire manufactured by this method is an electric wire including a conductor, an internal semiconductive layer, an insulating layer, an external semiconductive layer, a shield layer, and a sheath in order from the inside. Among these constituent members, the internal semiconductive layer and the external semiconductive layer correspond to the semiconductive layer, and either one of them may be omitted.

  When forming this semiconductive layer, the viscosity of the adjacent layer is set to an intermediate value between the viscosity of the insulating layer and the viscosity of the separating layer. For example, a material in which the content of a conductive filler such as carbon black contained in the base resin is reduced is used as the material of the proximity layer. If the content of the conductive filler is small, a material having a viscosity close to that of the insulating layer not containing the filler can be obtained, and adhesion between the insulating layer and the proximity side can be improved. Moreover, since the viscosity at the time of extrusion of a proximity layer is also close to the same viscosity of a separation layer, the adhesiveness of a proximity layer and a separation layer can also be improved.

  On the other hand, the separation layer has a volume resistivity lower than that of the adjacent layer and has a high conductivity, so that the separation layer can retain most of the function as a semiconductive layer. For example, the isolation layer can be made of a material with a high content of conductive filler, such as carbon black, and even if the viscosity at the time of extrusion deviates from the viscosity of the insulating layer, the adhesion to the insulating layer is the proximity layer. Can be secured. In particular, by tandem extruding the proximity layer and the separation layer, the outer layer is formed before the inner layer of these two layers is completely cured, and the adhesion between the proximity layer and the isolation layer Can also be increased.

  Hereinafter, the configuration of the present invention will be described in more detail.

  The conductor is not particularly limited in material and configuration as long as the necessary power transmission capacity can be secured. Examples of the material include copper wire, tin-plated copper wire, aluminum wire, aluminum alloy wire, steel core aluminum wire, copper fly wire, nickel-plated copper wire, silver-plated copper wire, and copper-covered aluminum wire. As the configuration of the conductor, a single wire and a stranded wire are conceivable, but generally a stranded wire structure in which a plurality of strands are combined is preferable.

  The semiconductive layer, that is, the internal semiconductive layer and the external semiconductive layer are preferably composed of a mixture of a base resin and a conductive filler. Predetermined conductivity can be imparted to the semiconductive layer by mixing conductive fillers. The base resin is preferably at least one selected from the group consisting of polyethylene, polyvinyl chloride, and polyvinyl acetate. Carbon black can be suitably used as the filler.

The volume resistivity of the adjacent layer in the semiconductive layer is preferably 10 ⁷ to 10 ⁹ Ω · cm. If it is a material of such a volume resistivity, there may be little content of an electroconductive filler, and it can be set as the viscosity near an insulating layer. The volume resistivity of the separation layer is preferably 10 ³ to 10 ⁵ Ω · cm. By securing such a resistivity, most of the functions as the semiconductive layer can be performed by the adjacent layer, which is desirable in terms of suppressing partial discharge. Below the lower limit of the resistivity, it tends to cause Joule heat due to current flowing through the semiconductive layer. On the contrary, if the upper limit is exceeded, the resistivity becomes too high, and the potential gradient mitigating effect at the interface between the conductor and the insulating layer or between the insulating layer and the shield layer may not be sufficient.

  This semiconductive layer may be formed by extrusion. If each semiconductive layer is formed by extrusion, unlike the case where the conductive cloth tape is used, there is no irregular portion such as an end portion or an edge of the conductive cloth tape, and the origin of the water tree can be eliminated. . In particular, if the proximity layer and the separation layer are formed by tandem extrusion, the adhesion between the proximity layer and the separation layer can be increased.

  The insulating layer is configured to have voltage resistance according to the voltage of the electric wire. Examples of the material for the insulating layer include ethylene propylene rubber, vinyl resin (for example, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, etc.), polystyrene, polyethylene, chlorosulfonated polyethylene rubber, silicon rubber, polytetrafluoroethylene, and the like. In particular, a cross-linked polyolefin, particularly a cross-linked polyethylene is preferred. This insulating layer is preferably coextruded or tandemly extruded with the semiconductive layer. For example, the proximity layer / separation layer of the inner semiconductive layer, the insulating layer, and the proximity layer / separation layer of the outer semiconductive layer may be sequentially tandem extruded. By extruding each of these layers simultaneously or continuously, it is possible to prevent foreign matter from entering between the layers or generating a gap.

  Usually, the electric wire of the present invention forms a shield layer on the outer semiconductive layer and further provides a sheath on the shield layer. It is desirable to use a braided material of metal wire such as copper wire for the shield layer. By providing the shield layer, guidance prevention shielding and danger prevention shielding can be performed. The sheath is generally made of chloroprene rubber, vinyl resin, polyethylene or the like. By providing the sheath, the insulating layer (shield layer) can be mechanically protected.

  The electric wire for a wire harness of the present invention is preferably used for high voltage applications. In particular, utilization at 600 V or higher, more preferably 800 V or higher, and further preferably 1 kV or higher can be expected.

According to the present invention, the following effects can be obtained.
According to the electric wire for a wire harness of the present invention, it is possible to fill a minute gap at the interface between the conductor and the insulating layer and the interface between the insulating layer and the shield layer, thereby suppressing the occurrence of partial discharge.

  By eliminating these minute gaps, the starting point of water tree generation can be eliminated, and insulation deterioration due to the generation of water trees can be suppressed.

  When the semiconductive layer is composed of two layers, a proximity layer and a separation layer, and these two layers are made of materials having different volume resistivity, a semiconductive layer having high adhesion to the insulating layer can be formed.

  According to the method for manufacturing an electric wire for a wire harness of the present invention, a semiconductive layer composed of two layers, a proximity layer and a separation layer, can be formed with good adhesion to the insulating layer.

  Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view of the electric wire of the present invention. The electric wire includes a conductor 10, an inner semiconductive layer 20, an insulating layer 30, an outer semiconductive layer 40, a shield layer 50, and a sheath 60 in this order from the center.

  Here, 19 strands of 0.32 mm diameter annealed copper wire were combined to form a twisted strand, and further, 19 strands were combined to form a conductor 10 having a nominal cross-sectional area of 30 sq.

An internal semiconductive layer 20 is formed immediately above the conductor 10. The inner semiconductive layer 20 was formed by extrusion. The material used was a mixture of soft polyethylene base resin and acetylene black, which is a conductive filler. As shown in FIG. 2, the internal semiconductive layer 20 includes a separation layer 20A (inner layer) that is in contact with the conductor and is separated from the insulating layer, and a proximity layer 20B (outer layer) that is in contact with the insulating layer. For the separation layer 20A, a material in which 20 parts by weight of acetylene black was blended with 100 parts by weight of the base resin was used. For the proximity layer 20B, a material in which 60 parts by weight of acetylene black was blended with 100 parts by weight of the base resin was used. The separation layer 20A has a thickness of 0.5 mm and a volume resistivity of about 10 ³ to 10 ⁵ Ω · cm, and the proximity layer 20B has a thickness of 0.5 mm and a volume resistivity of about 10 ⁷ to 10 ⁹ Ω · cm.

  The separation layer 20A and the proximity layer 20B were formed by tandem extrusion. As shown in FIG. 3, using an extruder in which the extrusion head 70A of the separation layer 20A and the extrusion head 70B of the proximity layer 20B are arranged in series in this order from the upstream side, the conductor 10 is pulled out in the direction of the arrow in the figure, thereby Layer formation is performed. First, the separation layer 20A is formed on the conductor 10 by the conductive resin extruded from the separation layer extrusion head 70A. Subsequently, the proximity layer 20B is formed on the separation layer 20A by the conductive resin extruded from the extrusion head 70B of the proximity layer. During this extrusion, the melt flow rate (JIS K 6922-1) of each layer material at the extrusion temperature (170 ° C.) is 0.7 g / 10 min for the separating layer 20A and 1.0 g / 10 min for the adjacent layer 20B.

  An insulating layer 30 is formed on the inner semiconductive layer 20. This insulating layer 30 was also formed by extrusion. Although this extrusion state is not shown, an insulating layer extrusion head may be provided downstream of the proximity layer extrusion head 70B in FIG. 3, and the insulation layer may be extrusion coated onto the proximity layer (see FIG. 2). By co-extrusion of the internal semiconductive layer 20 and the insulating layer 30, there is little possibility that foreign matter is mixed or a gap is formed between the layers, which is more effective in suppressing partial discharge. The material of the insulating layer 30 was cross-linked polyethylene, and the thickness thereof was 1.1 mm. In this extrusion, the melt flow rate (JIS K 6922-1) of the insulating layer material at the extrusion temperature (170 ° C.) was 1.4 g / 10 min.

  Subsequently, an external semiconductive layer 40 is formed on the insulating layer 30. Similar to the internal semiconductive layer 20, the external semiconductive layer 40 is also composed of two layers, a proximity layer 40B and a separation layer 40A. However, in the outer semiconductive layer 40, the inner layer is the proximity layer 40B and the outer layer is the separation layer 40A. The proximity layer 40B and the separation layer 40A are made of the same material, the same volume resistivity, and the same thickness as those of the internal semiconductive layer 20. Further, the method for forming the outer semiconductive layer 40 is also performed in accordance with the inner semiconductive layer 20. Here, the outer semiconductive layer 40 was formed by tandem extrusion with the insulating layer 30. That is, the extrusion head of the proximity layer 40B is disposed downstream of the extrusion head of the insulating layer 30, and the extrusion head of the separation layer 40A is disposed further downstream, so that the proximity layer 40B and the separation layer 40A are sequentially extruded.

  A shield layer 50 is formed on the outer semiconductive layer 40. As the shield layer 50, a braided material made of a tin-plated copper wire having a diameter of 0.3 mm was used.

  Then, a sheath 60 is formed on the shield layer 50. Here, the sheath 60 was formed by extruding polyvinyl chloride to a thickness of 1.0 mm.

  The partial discharge test was done about such an electric wire and the conventional electric wire of FIG. The test method was performed based on the provisions of JEC-0401. As a result, it was confirmed that the electric wire of the present invention was superior in partial discharge characteristics as compared with the conventional electric wire.

Furthermore, each of the inner semiconductive layer and the outer semiconductive layer in the electric wire of the present invention has a single layer structure, and a comparative electric wire in which the volume resistivity of each semiconductive layer is 10 ³ to 10 ⁴ Ω · cm was produced. And the peeling test of a semiconductive layer and an insulating layer was done, and the load required for peeling was measured about both this invention electric wire and a comparison electric wire. As a result, it was confirmed that the electric wire of the present invention having a two-layer structure of the semiconductive layer had an increase in peel strength of about 30% compared to the comparative electric wire.

  The electric wire of the present invention can be used for a wire harness of an electric vehicle or a hybrid vehicle as well as a conventional vehicle having an internal combustion engine. Moreover, it is anticipated that the manufacturing method of this invention electric wire will be utilized in the manufacture field | area of the electric wire for wire harnesses.

It is a cross-sectional view of the electric wire for the wire harness of the present invention. It is a fragmentary longitudinal cross-sectional view of the electric wire for this invention wire harness. It is explanatory drawing which shows the formation process of the semiconductive layer of the electric wire for this invention wire harness. It is sectional drawing of the electric wire for conventional wire harnesses.

Explanation of symbols

10 conductor
20 Internal semiconductive layer 20A Separation layer 20B Proximity layer
30 Insulation layer
40 External semiconductive layer 40A Separation layer 40B Proximity layer
50 Shield layer
60 sheath
70A, 70B extrusion head

Claims (4)

A wire harness electric wire having a conductor and an insulating layer formed outside the conductor,
Having a semiconductive layer on at least one of the interface between the conductor and the insulating layer and the surface of the insulating layer;
This semiconductive layer is composed of a proximity layer that is in contact with the insulating layer and a separation layer that is separated from the insulating layer,
An electric wire for a wire harness, wherein the proximity layer and the separation layer have different volume resistivity. An internal semiconductive layer formed at the interface between the conductor and the insulating layer,
The wire harness wire according to claim 1, wherein the volume resistivity of the separation layer of the inner semiconductive layer is smaller than the volume resistivity of the adjacent layer. An external semiconductive layer formed on the surface of the insulating layer,
The wire harness wire according to claim 1, wherein the volume resistivity of the proximity layer of the outer semiconductive layer is larger than the volume resistivity of the separation layer. Forming an insulating layer by extrusion on the outside of the conductor;
A method of manufacturing an electric wire for a wire harness comprising a step of forming a semiconductive layer by extrusion on at least one of an inner side and an outer side of the insulating layer,
This semiconductive layer is composed of a proximity layer that is in contact with the insulating layer and a separation layer that is separated from the insulation layer, and the volume resistivity is different between the proximity layer and the separation layer,
The viscosity at the time of extruding the adjacent layer is an intermediate value between the viscosity at the time of extruding the separation layer and the viscosity at the time of extruding the insulating layer,
A method for producing an electric wire for a wire harness, wherein the adjacent layer and the separation layer are subjected to extrusion coating by tandem extrusion.

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