JPS6111853Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention is a high-voltage resistance electric wire (hereinafter abbreviated as ignition cable) that suppresses the noise disturbance caused by the noise propagation generated by electric ignition in internal combustion engines such as automobiles and propagating into the air through the electric wire itself. ) related to improvements. Conductive substances such as salt (for preventing freezing on roads in cold regions) and sludge adhere to the outer periphery of the sheath of the ignition cable, and when this becomes an impedance to the ground potential, the resistance conductor core wire (hereinafter abbreviated as "core wire") and the outer periphery of the sheath The charging current is dissipated depending on the capacitance between the two. Therefore, if the capacitance is large, the ignition voltage will drop significantly, causing ignition failure. In order to prevent such ignition failures, an ignition cable with a low capacitance of about 80 PF/m or less is required. On the other hand, increasing the outer diameter to reduce the capacitance is not preferable because the outer diameter of the ignition cable is usually 7 mm or 8 mm, which causes problems such as lack of compatibility with conventional products and space problems. In order to reduce the capacitance while keeping the outer diameter constant, it is necessary to reduce the diameter of the core wire, but simply making the core wire of a conventional product thinner will cause various problems. The present invention aims to solve various problems caused by reducing the diameter of the core wire, and to obtain an ignition cable that has the required low capacitance and is less likely to cause poor conductivity. The present invention will be explained below along with its background. For ignition cables, it is necessary to add a resistance value of about 16KΩ/m to the core wire in order to prevent radio interference caused by ignition discharge, so generally carbon paint is applied to a glass fiber bundle, impregnated, and dried to form the core wire. The diameter of about 1.8mm is used. If an attempt is made to reduce the diameter while using a glass fiber bundle as a tension member, the core wire will break during the extrusion or vulcanization process for insulation, sheathing, etc., resulting in the disadvantage that it cannot be used on an industrial production line. This drawback could be overcome by using strong aramid fiber bundles. For example, use a 1500 denier aramid fiber bundle, coat it with carbon paint, impregnate it, dry it, finish it to an outer diameter of 0.6 mm, extrude coat it with a semiconductive compound, and use a resistance conductor core wire with a diameter of 1.0 mm. By sequentially applying cross-linked polyethylene insulation, glass braid, and ethylene propylene rubber (EP rubber) or silicone rubber sheath to the cable, an ignition cable with a low capacitance of about 80 PF/m could be obtained. However, it has been found that the low capacitance ignition cable thus obtained has an unstable withstand voltage and cannot withstand long-term use. That is, it was found that an ignition coil withstand voltage test in which 30KV DC was repeatedly applied to simulate an ignition cycle caused a withstand voltage failure. We continued various studies to improve this defective withstand voltage, and found that instead of using a 1500 denier aramid fiber bundle, we used a strand of three 400 denier aramid fiber bundles to improve the withstand voltage, as mentioned above. The present invention was completed after discovering that the ignition coil withstanding voltage test was good. That is, three 400-denier aramid fiber bundles are twisted together, semi-conductive paint and peeling paint are applied on top of the bundle, impregnated and dried, and finished to an outer diameter of 0.6 mmφ.
The ignition cable has a capacitance of approximately 80 PF/cm, which is made by extrusion coating a semiconductive compound to create a resistance conductor core wire with a diameter of 1.0 mm, and then sequentially applying cross-linked polyethylene insulation, glass braiding, and EP rubber or silicone rubber sheathing. It was found that the capacitance was as low as m, and it did not cause any defects even in the ignition coil withstand voltage test. In order to achieve the target of 80PF/m or less, it is necessary to make the core wire outer diameter 1.2mmφ or less. FIGS. 1a and 1b show cross-sectional views of the resistance conductor core wires used in the examples and comparative examples of the present invention. 1
is a semiconductive extruded layer made of a semiconductive compound such as rubber plastic mixed with a conductive substance such as carbon black. 2 is a semiconductive paint layer. This semiconductive paint is made by mixing conductive substances such as carbon black, graphite, or silver powder into rubber plastic, etc., and dissolving it in a solvent.The paint is repeatedly coated, impregnated, and dried as described later, and is used to prevent noise. This is to obtain the required high resistance. In addition, between 1 and 2, conductive silicone paint (e.g. rubber, plastic, carbon, graphite,
A release layer 8 is provided, which is made of a semi-conductive paint mixed with a conductive substance such as silver or copper powder and dissolved in a solvent or the like, mixed with silicone, or the like. The presence of this release layer also allows it and the semiconducting compound coated on the outside to prevent the coating and impregnation of the dried semiconductive paint on the inside of the release layer from occurring in the longitudinal direction, which may occur when tension is applied to the tension member. Compensate for and ensure poor conductivity caused by cutting. 3 is an aramid fiber bundle, but the one in Example (a) is
Three strands of 400 denier fiber bundles, i.e. 3
Comparative example (b) is a real twisted one.
It uses 1500 denier fiber bundles. As shown in FIG. 2, an insulator 4 made of cross-linked polyethylene is provided on the resistance conductor core wire 7, and a reinforcing layer such as a glass braid 5 is further provided, and an EP rubber or silicone rubber sheath 6 is extruded around the outer periphery of the insulator 4, as shown in Table 1. A low capacitance ignition cable was fabricated with dimensions of . As shown in Table 1, the ignition cables thus obtained all exhibited a capacitance of 80 PF/m or less. The capacitance was measured using the capacitance test method of JISC3004-1975 Rubber Insulated Wire Test Method. That is, the conductor was immersed in grounded water, and the capacitance between the conductor and the water was measured using the AC bridge method at a frequency of 1000 Hz, and the capacitance was calculated per 1 m of wire length. Thereafter, the cables of the embodiments and comparative examples of the present invention were subjected to an ignition coil withstand voltage test as shown in FIG. Although this test is not prescribed by any standards, it is a practical and useful test method. In Fig. 3, 11 is a frame, 12 is a motor, and 13 is a frame.
is the coil, 14 is the igniter, 15 is the distributor (1000RPM), 16 is the drive belt, 17, 17' is the ground, 18, 18' is the ignition cable, the surface of the ignition cable is treated with silver paint etc. and ground 17, 18', 1
Discharge 30KV for 7'. The test results are shown in Table 2. As is clear from Table 2, the tension members made of three 400 denier aramid fiber bundles shown in Examples 1 to 4 were compared with those shown in Comparative Examples 1 to 4. The withstand voltage characteristics are clearly improved in the withstand voltage test method. The above-mentioned improvement in the withstand voltage characteristics is presumably due to the fact that the core wire is well-tightened, and it is difficult for the core wire surface to be crushed and become uneven when the insulator is crosslinked. The low capacitance ignition cable of the present invention thus obtained is extremely excellent for preventing salt damage, especially in cold regions. In the present invention, the insulating layer may be a crosslinked product of not only crosslinked polyethylene but also a blend containing polyethylene (such as polyethylene and ethylene propylene, or polyethylene and ethylene-α-olefin copolymer, etc.). In addition to braiding, the reinforcing layer may be a perforated tape or the like, and this reinforcing layer may be provided not only inside the sheath layer but also between the inner and outer sheath layers. Alternatively, the reinforcing layer may not be provided.

【table】

【table】 [Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the resistance conductor core wire, Figure a is an example of the present invention, Figure b is a comparative example, and Figure 2 is a perspective view of an ignition cable using the resistance conductor core wire of Figure 1. , and FIG. 3 respectively illustrate explanatory diagrams of the ignition coil withstand voltage test method. DESCRIPTION OF SYMBOLS 1... Semi-conductive extrusion layer, 2... Semi-conductive paint layer, 3... Aramid fiber bundle, 4... Insulator, 5...
...Reinforcement layer, 6... Sheath, 7... Resistance conductor core wire.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In an electric wire comprising a resistive conductor core wire, an insulating layer, and a sheath, the resistive conductor core wire is coated with semiconductive paint on a tension member made of a plurality of aramid fiber bundles twisted together. A low capacitance high voltage resistance electric wire characterized by being coated, impregnated and dried, and coated with a semiconductive compound via a semiconductive peeling layer to have an outer diameter of 1.2 mmφ or less. (2) The low-capacitance, high-voltage resistance wire according to claim (1) of the utility model registration claim, in which the number of twisted wires is three. (3) The low-capacitance, high-voltage resistance electric wire according to claim (1), wherein the insulating layer is a layer made of polyethylene or a crosslinked blend containing polyethylene.