Coil type high-voltage resistive cable for preventing noise

Abstract: There is provided a coil type noise suppressing high voltage resistance wire wherein, without applying a releasing agent to the coil core, by reducing the viscosity of the fluororubber in unvulcanized state to a moderate degree, winding work of the resistance wire can be smoothly carried out. On the coil core 12 covered by extrusion coating with a fluororubber mixed with ferrite powder, a resistance wire 13 is wound widthwise, and the coil core 12 on which the resistance wire 13 is wound widthwise is gradually covered with an insulating layer 14, braid for reinforcement 15 and a sheath 16 . The fluororubber is a blend polymer blended as a polymer for reinforcement with an ethylene-vinyl acetate copolymer (EVA) which has compatibility with the fluororubber and is co-vulcanized in vulcanizing. The blend ratio is 5 to 25 % by weight of the EVA to the blend polymer.

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to a coil type noise suppressing high voltage resistance wire to be used for example as an ignition cable for an internal engine of automobile and the like. Description of the Related Art: A high voltage resistance wire for transmitting the high voltage generated in the ignition coil through a distributor or directly to an ignition plug is required to have small transmission loss, excellent noise suppressing effect, and excellent heat resistance and voltage resistance. At present, there are generally used a cord type high voltage resistance wire made by impregnating carbon in a fiber and a coil type high voltage resistance wire made by winding a metal fine wire having high inherent resistance on a core such as a magnetic material. As the aforedescribed coil type high voltage resistance wire there is disclosed, as shown in Fig. 2, a product made by such steps that a resistance wire 53 is wound by burying on a coil core 52 which is formed by extrusion coating a fluororubber made by mixing ferrite powder on a reinforced cord 51 formed of Aramid fiber or glass fiber, on which an insulating layer 54 is extrusion coated, and further coating is made sequentially by a braid 55 and an outermost sheath 56. (ref. to Japanese Utility Model Publication No. 32253/1989 and to US-A-4 435 692). When the resistance wire 53 is wound on the coil core 52 in a snapped state, there are effects such that there is no case for the wound resistance wire 53 to slide sideways and there occurs no damaging of the resistance wire 53 by free beating or bending at the time of the connection of the end part to the terminal fitting. With respect to further details of providing such a wire, reference is made to US-A-4 894 490 the disclosure of which is incorporated herewith into this application. In DE-A-4034197 a coil type noise suppressing high voltage resistance wire comprises a resistance wire being wound on a coil core formed by flourorubber mixed with a magnetic material, and an insulation layer being coated on the outside thereof. The coil core is formed by a blend polymer blended with a polymer for chemical reinforcement which is compatible with the flourorubber and is co-vulcanized therewith. The lower limit for the blend ratio is disclosed to be 10%. The object technial teaching of this document is to provide an igintion cable having an outer diameter of not more than 5 mm, having a destributed capacity of not more than 80 pF/m, if the cable is subject to water and having the chance in the resistance value being lowered by ± 5%. Problems that the invention is to solve: Now, in manufacturing the aforedescribed coil type high voltage resistance wire, the general practice is such that firstly, ferrite mixed fluororubber is extrusion coated on the reinforced cord 51 and cooled to form a coil core 52; the coil core 52 is once taken up onto a bobbin, and then the resistance wire 53 is wound while reeling out the coil core 52. The coiling work of the resistance wire 53 onto the coil core is normally made by burying the resistance wire 53 in the coil core 52 by winding the resistance wire 53 sideways on the coil core 52 under the inelastic and unvulcanized state of the fluororubber, and thereafter vulcanizing the resultant, by which the resistance wire 53 is held in a state of snapping into the coil core 52. Accordingly, the aforedescribed work of taking up the coil core 52 onto the bobbin is to take place inevitably under the unvulcanized state. However, as the fluororubber in the unvulcanized state has high viscosity, when the coil core 52, taken up onto the bobbin, is allowed to stand for a long period of time, the wound parts of the coil core 52 stick together to provide an obstacle to the subsequent step of winding the resistance wire 53. In order to dissolve such drawback, it may be proposed to coat a releasing agent such as talc powder, silicon oil, or the like on the surface of the unvulcanized coil core 52. However, if a releasing agent is applied, the surface of the coil core 52 becomes excessively slippery to give rise to a problem that no adequate burying of the resistance wire 53 in the coil core 52 is made in the winding work of the resistance wire 53. Accordingly, the subject of this invention is to provide a coil type noise suppressing high voltage resistance wire in which the winding work of the resistance wire can be smoothly carried out by moderately reducing the viscosity of the fluororubber of unvulcanized state without applying a releasing agent onto the coil core. The above problems are solved by the measures indicated in the characterising part of claim 1. Means of solving the problems: In order to solve the above problems, this invention provides a coil type noise suppressing high voltage resistance wire comprising a resistance wire wound widthwise on a core formed by fluororubber mixed with a magnetic material, with an insulating layer formed by coating on the outside thereof, characterized by forming the core by a blend polymer blended with a polymer for reinforcement which has good compatibility with the fluororubber and is co-vulcanized therewith, with the blend ratio of the polymer for reinforcement to the blend polymer being made between 5 % by weight and 10 % by weight. Further, as the above polymer for reinforcement, there may be used an- ethylene-vinyl acetate copolymer or a chlorinated polyethylene. Operation: As the coil type noise suppressing high voltage resistance wire constituted as above has such characteristics as good compatibility with the fluororubber and being co-vulcanized therewith, with the polymer for reinforcement having characteristics close to those of plastics, the fluororubber of unvulcanized state with moderate mixing shows improved strength and lower viscous strength. After the vulcanization, due to the co-vulcanization between the fluororubber and the polymer for reinforcement, no lowering in vulcanizing physical property occurs. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 is a perspective view to show an embodiment of the present invention. Fig. 2 is a perspective view to show prior art. DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, the preferred embodiment will be explained with reference to the drawings. As shown in Fig. 1, in the coil-type noise suppressing high voltage resistance wire 10, a coil core 12 of 1.3 mm in outer diameter is formed by extrusion coating fluororubber of unvulcanized state mixed with ferrite powder on the reinforced core 11 made by three plies of 1000 denier aramid yarn. The above fluororubber is blended with an ethylene-vinyl acetate copolymer (EVA) which has compatibility with the fluororubber and is co-vulcanized in vulcanizing. Its blend ratio is required to be set in the range of 5 to 25 parts by weight of EVA based on 100 parts by weight of fluororubber. Further, the mixing ratio of the ferrite powder is 400 parts by weight based on 100 parts by weight of fluororubber. On the coil core 12 there is wound in widthwise direction Ni-Cr resistance wire 13 of 50 µm in 7200 times/m under the unvulcanized state of the blend polymer. On the coil core 12 on which the resistance wire 13 is wound widthwise, there is formed an insulation layer 14 having an outer diameter of 4.6 mm by extrusion coating the ethylene-propylene diene copolymer (EPDM), and further, on the insulation layer 14 there is coated a reinforcing braid 15 formed by glass yarn, and on the outside thereof there is coated a sheath 16 having an outer diameter of 7.0 mm formed by EPDM. As the polymer for reinforcement, there can be used, not only the abovementioned EVA but also for example chlorinated polyethylene. Experiment: Table 1 shows the physical properties of the coil core 12 before and after vulcanizing in the case where the addition amounts of EVA to the fluororubber to form a coil core 12 are varied. The test object A is a conventional coil type noise suppressing high voltage resistance wire having no addition of EVA at all to the fluororubber which is a base polymer of the coil core 12, and the test objects B, C, D, E and F are those in which respectively the coil core 12 is formed by blend polymer having a blend of EVA in the fluororubber, showing the case where the addition amounts of EVA are 5, 10, 20, 25, and 30 % by-weight, respectively to the blend polymer. These test objects are added at the rate of 400 parts by weight of ferrite powder, 2 parts by weight of sodium stearate as a processing auxiliary, 5 parts by weight of polyfunctional crosslinking auxiliary as a vulcanizer 1 (e.g. TAIC (registered trademark by Nippon Kasei)), and 1 part by weight of organic peroxide as a vulcanizer 2 (e.g. Percadox 14:registered trademark), respectively, based on 100 parts by weight of the blend polymer comprising a blend of the fluororubber with EVA which constitute the coil core 12. As may be observed from Table 1, the test object A without addition of EVA shows too strong adhesive strength under the unvulcanized state, so that the coil core 12, when taken up on the bobbin, becomes impossible to release. In the test objects B, C D and E having more than 5 per cent by weight of the EVA addition amount, the viscosity strength under the unvulcanized state is lowered to prevent the coil cores 12 from sticking together even when the coil cores 12 are taken up on the bobbin. On the other hand, in the test objects A, B, C, D and E each having no more than 25 % by weight of the EVA addition amount, due to the moderate elasticity of the coil core 12, no crack or the like occurs and there is no special problem as to the roll processing property. However, with respect to the test object F having the EVA addition amount in excess of 25 % by weight, a problem occurs with roll processing property. In case of the poor roll processing property, close contact between the material and the roll is unsatisfactory, so that the kneading is insufficient, giving rise to occurrence of unsatisfactory dispersion of the mixing agents such as failure of kneading in of ferrite. Accordingly, it is observed that the test objects B, C, D and E, which are the embodiments of the present invention, show low adhesive strength in unvulcanized state, and are excellent in processing property. Accordingly, in the coil type noise suppressed high voltage resistance wires of the test objects B, C, D, and E, there is no occurrence of mutual adhesion of coil cores 12 even being allowed to stand for a long period of time after being taken up on the bobbin, and no obstacle caused to the winding work of the resistance wire 13 in the subsequent step. Effect of the invention: As described above, the coil type noise suppressing high voltage resistance wire of the present invention is characterized by forming the coil core by a blend polymer blended on a fluororubber with a polymer for reinforcement which has good compatibility with the fluororubber and is co-vulcanized therewith, with the blend ratio of the polymer for reinforcement to the blend polymer being made between 5 % by weight and 10 % by weight. Accordingly, due to the lowering of the adhesivity of the coil core in the unvulcanized state, even in case of storing the coil core in unvulcanized state wound on the bobbin, the coil cores are free from sticking together and no obstacle is caused to the winding work of the resistance wire 13 in the subsequent step.

Claims: A coil type noise suppressing high voltage resistance wire (10) comprising a coil core (12) formed by fluororubber mixed with a magnetic material, a resistance wire (13) being wound on said coil core (12), and an insulating layer (14) being coated on the outside thereof, the coil core (12) comprises a blend polymer comprising a polymer for reinforcement and said fluororubber, said polymer for reinforcement having a good compatibility and is blended with the fluororubber and is co-vulcanized therewith, characterized in that the blend ratio of the polymer for reinforcement to the blend polymer is lying between 5% by weight and 10% by weight. The coil type noise suppressing high voltage resistance wire according to claim 1, wherein the polymer for reinforcement is an ethylene-vinyl acetate copolymer. The coil type noise suppressing high voltage resistance wire according to claim 1, wherein the polymer for reinforcement is a chlorinated polyethylene.

Inventors: FUJIMOTO TERUTSUGU, HIGASHIKOZONO MAKOTO, INOUE HIROSHI, FUJIMOTO, TERUTSUGU, HIGASHIKOZONO, MAKOTO, INOUE, HIROSHI, Fujimoto, Terutsugu, c/o Sumitomo Wiring Sys. Ltd, Higashikozono, Makoto, c/o Sumitomo Wiring Sys Ltd, Inoue, Hiroshi, c/o Sumitomo Wiring Sys Ltd
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1995
Main classification: H01B7
IPC codes: H01B7, H01B3