CA1269424A - Insulated conductor for a wire harness - Google Patents
Insulated conductor for a wire harnessInfo
- Publication number
- CA1269424A CA1269424A CA000530172A CA530172A CA1269424A CA 1269424 A CA1269424 A CA 1269424A CA 000530172 A CA000530172 A CA 000530172A CA 530172 A CA530172 A CA 530172A CA 1269424 A CA1269424 A CA 1269424A
- Authority
- CA
- Canada
- Prior art keywords
- conductor
- insulation
- wire harness
- insulated conductor
- insulated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000004020 conductor Substances 0.000 title claims abstract description 150
- 238000009413 insulation Methods 0.000 claims abstract description 104
- 239000004433 Thermoplastic polyurethane Substances 0.000 claims abstract description 24
- 229920002803 thermoplastic polyurethane Polymers 0.000 claims abstract description 22
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 claims description 18
- 229920005992 thermoplastic resin Polymers 0.000 claims 2
- 235000019589 hardness Nutrition 0.000 description 14
- 238000007790 scraping Methods 0.000 description 12
- 238000005299 abrasion Methods 0.000 description 9
- 230000007423 decrease Effects 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229920005862 polyol Polymers 0.000 description 2
- 150000003077 polyols Chemical class 0.000 description 2
- 239000004721 Polyphenylene oxide Substances 0.000 description 1
- 239000012190 activator Substances 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 210000002445 nipple Anatomy 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920000570 polyether Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
Landscapes
- Insulated Conductors (AREA)
- Organic Insulating Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
An insulated conductor for a wire harness comprises a conductor and an insulation with which the conductor is covered. The insulation formed of thermoplastic polyurethane having shore D hardness of more than 50 and a thickness of less than 0.2 mm. The adherence of the insulation to the conductor is less than 2 kg/10 mm, being measured as the required force to pull 10 mm of the insulation off the conductor.
An insulated conductor for a wire harness comprises a conductor and an insulation with which the conductor is covered. The insulation formed of thermoplastic polyurethane having shore D hardness of more than 50 and a thickness of less than 0.2 mm. The adherence of the insulation to the conductor is less than 2 kg/10 mm, being measured as the required force to pull 10 mm of the insulation off the conductor.
Description
The present invention relates to an insulated conductor for a wire harness comprising a conductor and an insulation of thermoplastic polyurethane with which the con-ductor ls covered.
A conventional insulated conductor for a wire harness for a car, comprises a bundle of a plurality of insulated conduc-tors having a predetermined length with a covering of tape wound on the bundle holding it together. Each of the insulated conductors has ends exposed and parts such as connectors connected to the exposed ends.
Lately, there have been various specifications of a car, which increases the number of parts and the number of wiring circuits. Accordingly, a wire harness has the diameter enlarged and the weight increased. For example, the diameter of the wire harness for the car changes from 20 through 30 mm of the prior art harness to 50 through 60 mm. It will be noted that this is contrary to the requirement of enlargement of a space wlthin the car and of lightness of the car. Also, this causes the ~eight of the wire harness to increase and the number of operators for assembl:Lng the wire harness to increase.
Thus, it will be noted that the smaller diameter and lighter weight of the wire harness are required for meeting the re-quirement of car design and for assembling the wire harness without any decrease in efEectiveness of operation.
One of the prior art insulated conductors for a wire harness comprises an insulation of vinyl chloride provided on a conductor. The conductor comprises a twisted conductor formed by twisting a plurality of copper wire elements while the insulation is formed by extruding vinyl chloride on the twisted conductor. The thickness of the insulation normally ranges from 0.6 mm to 1.1 mm and is 0.4 mm in case of thinnest insulation.
In order to make the diameter of the wire harness smaller, it is effective to thin the insulation of the ~;9~
insulated conductor. ~lowever, if the insulation is thinned, the abrasion resistance oE the insulated conductor is lowered, which disadvantageously causes the insulation of the insulated conductor to be damaged when the wire harness is assembled, installed and treated thereafter.
The conductor of twisted wires provides flexibility and softness to the insulated conductor, which preferably aids the conductor to be compressively secured to terminals, but the twisted conductor tends to have wire elements untwisted and protruded, which causes the cross section of the insulation on the conductor to have an out-of-round excursion with the result that the insulation of vinyl chloride tends to have a thick portion as indicated by t (max) and a thin portion as indicated by t (min). In case that terminals are compres-sively secured to the ends of the insulated conductor, the insulation at the ends of the insulated conductor has to be removed. This is accomplished by stripplng blades into the insulation, so that the blades never contact the conductor whlle they are moved.
If the blades contact the condutor by any chance, then the conductor is damaged, which causes the insulated conductor to be cut due to vibration applied thereto from the car. If the insulation is thicker, the conductor is never damaged even though the wire elements are slightly untwisted or protruded, but if the insulation is thinner, and the wire elements are untwisted or protruded, this causes the conductor to be possibly damaged when the insulation is removed.
Accordingly~ it is a principal object of the inven-tion to provide an insulated conductor for wire harness adapted to have a smaller diameter by thinning an insulation without any decrease in abrasion resistance of the insulation.
It is another object of the invention to provide an insulated conductor for wire harness wherein a conductor is not damaged when an insulation is removed.
9~
According to the present invention, there is provided an insulated conductor Eor a wire harness~comprising a conductor and an insulation witl- which the conductor is cov-ered, the insulation characterized by being formed of thermoplastic polyurethane having shore D hardness of more than 50 and a thickness of less than 0.2 mm and wherein the adherence of the insulation to the conductor is less than 2 kg/lO mm, being measured as the required force to pull lO mm of the insulation off the conductor.
With the insu]ation formed of thermoplastic polyurethane having shore D hardness of more than 50, the abrasion resistance of the insulation is larger, which allows the insulation to be thlnner and the diameter of the insulatecl conductor,to be smaller.
The conductor may be either a single conductor or a twLsted body of wire elements, and may be preEerably a com-pressed conductor formed by compress:Lvely cleEorming a twisted body oE wire Lnto a body having a substantially round cross section. With the conductor compressed, the wire elements are neither untwLsted nor prodruded, less insulation is embecl(led into the space between the wire elements of the twisted body, whlcll eases the removal of the insulation .
ThUS~ it will be noted that the d:Lameter oE the insulation becomes uniform, whLcll causes the conductor to be never damaged.
It has been Eound by the :Lnventors that a failure to remove all oE the insulation depends on the thickness differ-ence of the insulation ,that is, a difference between the maximum and minimum thicknesses, and on the adherence of the conductor to the insulation. According to the invention, with the thickness difference of less than ~0 ~m, no failure of removal is caused and also with the adherence of the insu-lation to the conductor of less than 2 Kg/lOmm~ as above indicated, no failure of removal is caused.
The above and other objects and features of the invention will be apparent from the description of the ~ i9~29~
"
embodiments taken along with reference to the accompanying drawings in which;
Fig. 1 is a perspective view of a conventional wire harness;
Fig. 2 is a cross sectional view of a prior art insulated conductor for a wire harness;
Fig. 3 illustrates an insulation of tile insulated conductor for a wire harness being removed;
Fig. 4 is a cross sectional view of an insulated conductor for a wire harness constructed in accordance with one embodiment of the invention;
Fig. 5 is a front view of a scraping tester for determining an abrasion resistance of the insulated conductor for a wire harness;
Fig. 6 illustrates curves oE scrapLng character-istic of the insulation of the insulated conductor for a wire harlless;
Fig. 7 i:LIustrates a curve of fai:Lure of removal of tlle Lnsulation re:Lat:Lve to the tllickness d-lEEerence thereof;
Fig. 8 Lllustrates a curve oE failure oE removal oE the insulat:Lon re:LatLve to the adherence oE the insulation;
Fig. 9 :Ls a cross sectional view of an insulated conductor constructed in accordance with another embodiment of the invention;
and Fig. 10 is a cross sectional view of an insu-lated conductor constructed in accordance with a further embodiment of the envention.
Fig. 1, shows an insulated conductor for a wire harness for a car, which comprises a bundle 2 of a plurality of insulated conductors l having a predetermined length with a covering 3 of tape wound on the bundle holding it together.
Each of the insulated conductors 1 has ends exposed and parts 7 such as connectors connected to the exposed ends.
Fig- 2, shows one of the prior art insulated conductors 4;~
for a wire harness,comprises an insulation 5 of vinyl chloride provided on a conductor 4. The condutor 4 comprises a twisted conductor formed by twisting a plurality of copper wire elements 4a while the insulatlon 5 is formed by extruding vinyl chloride on the twisted conductor. The thickness of the insulation 5 normally ranges from 0.6 mm to 1.1 mm and is 0.4 mm in case of thinnest insulation.
In order to make the diameter of ~he wire harness smaller, it is effective to thin the insulation 5 oE tlle insulated conductor. However, iE the insulation 5 is thinned, the abrasion resistance of the insulated conductor is lowerd, which disadvantageously causes the insu~ation of the insulated conductor to be dama8ed when the wire harness is assembled, installed and treated thereafter.
The conductor 4 oE twisted wires provides flexibility and softness to tlle insulated conductor, wh:Lch preEerably aids the conductor to be compressively secured to terminals, but the twisted conductor tends to have wLre elements untwisted and protrucled, wh:Lcll causes the cross section oE the insulation on the conductor to have an out-of-round excursion as indica-ted by dotted line oE Fig. 2 with the result that the insula-tion 5 of vLnyl chlorLde tends to have a tllick portion as indicated by t (max) and a thin portion as indicated by t(min).
In case that terminals are compressively secured to the ends of the insulated conductor, the insulation at the ends of the insulated conductor has to be removed. This is accomplished by stripping blades 6 into the insulation 5, as shown in Fig.3, so that the blades 6 never contact the conductor 4 while they are moved as indicated by an arrow in Fig. 3. If the blades 6 contact the conductor by any chance, then the conductor 4 is damaged, which causes the insulated conductor to be cut due to vibration applied thereto from the car. If the insulation 5 is thicker, the conductor 4 is never damaged even though the wire elements 4a are slightly untwisted or protruded, but if 9~
the insulation is thinner, and the wire elments 4a are untwisted or protruded, this causes the conductor 4 to be possibly damaged when the insulation is removed.
Referring now to Fig. 4, there is shown an insulated conductor 10, which comprises a conductor 12 and an insulation 14 provided on the conductor 12.
The insulation 14 comprises thermoplastic polyurethane having shore D hardness of more than 50 and has the thickness of average less 0.2 mm. Thermoplastic polyurethane is formed by polycondensing long-chain polyo:L having polyester or polyether bond and short-chain polyol by aromatic or aliphatic diisocianate~ Thermoplasticity is produced by arranging urethane-bond (-NHC00-) substantially in series to each other and has a mouldabLe property by melting material at high temperature. Various - hardnesses may be provided by selecting polyol and diisocianate.
Thermoplastic polyurethane has a higher abrasion resistance than vinyl chloride has and the thermoplastic polyurethane has shore D hardness greater than 50 with the result that thermoplastic polyurethane of thickness of less than 0.2 mm can have the abraslon resistance equal to that of vinyl chloride of thickness of 0.6 mm, which is generally used for a conventional insulated conductor.
The conductor 12 may comprise a twisted body formed by twisting a plurality of copper wire elements 12a or may comprise a compressed conductor formed by compressively deforming the twisted body into one having a substantially round cross section as shown in Fig. 4. The compressed conductor 12 can be produced by passing the twisted body through a die or through a shaping roll to decrease the diameter thereof. In this manner, the wire elements 12a are deformed into non-round cross section so as to fill the space within the twisted body, which prevents the wire elements from being untwisted or protruded so that the twisted body 9~2~
is deformed into round cross section. Thus, it will be noted that be thickness oE the insulation 1~ never varies, although it is less than 0.2 mm.
For example, with the insulation of 0.15 mm thickness provided on the conductor of 0.5 mm diameter, the thickness difference H is determlned by the following expression;
H = ~(t max - t min ) (t max ~ t min)~ x 100%
In this expression, t max designates the maximum thickness while t min designates the minimum thickness. It was acknowledged that the ~hickness difference H was about 15 when the conductor 12 was not compressed, but decreased to about 5~ when the conductor 12 was compressed.
With the insulation of thermoplastic polyurethane having shore D hardness of more than S0, the abrasion resist-ance of the insulation becomes larger, which allows the thickness of the insulation to be thinner and the diameter of the insulated conductor to be smaller.
The conductor 12 may be either a single conductor or a twisted body o~ wlre elements, and may be preferably a compressed conductor 12 Eormed by compressing the twisted body into one having a round cross section. With the conduc-tor 12 compressed, the w:Lre elements 12 are neither untwisted nor protruded to make the surface of the conductor 12 smooth and less insulation is embedded into the space between the wire elements 12a of the twisted body. Thus, it will be noted that the diameter of the insulation becomes uniform and that the adherence of the conductor to the insulation decreases, which causes the conductor not to be damaged upon removal of the insulation even though the thickness of the insulation is smaller.
The abrasion resistance of the insulated conductor for a wire harness can be expressed by the number of scraping ~9~;~4 , times of the scraping test. This test can be accomplished by a scraping tester as shown in Fig. 5. A sample lOA of the insulated conductor is secured on a stand 18 by clamps 20 in a horizontal manner while scraping blades 22 having a diameter of edge oE 0.125 mm are mounted on the sample lOA
with a weight 24 mounted on the scraping blades 22 in accordance with the size of the insulated conductor. The scraping blades 22 are moved by a stroke of about 10 mm by reciprocationg means 26. In this manner, when the sample lOA
is scraped by the scraping blades 22 to damage the insulation until the scraping blades 22 contact with the conductor 12, the reciprocating movement stops and the number of recipro-cations (number of scraping times) is indicated on a coulnter, not shown.
Fig. 6 shows the number of scraping times relative to the thickness of tlle insulation when various insulated conductors were tested by such a tester. The load of the weight 24 used for the tests was 1.2 kg. In Fig. 6, a curve A is the number of scraping times of the insulated conductor comprislng the compressed conductor covered with the insula-tion of thermoplast:Lc polyurethane having shore D hardness of 60, a curve B that of the insulated conductor comprising the compressed conductor covered with the insulation of thermoplastic polyurethane having shore D hardness of 50, a curve C that of the insulated conductor comprising the compressed conductor covered with the insulation of thermo-plastic polyurethane having shore D hardness of 40, and a curve D that of the prior art insulated conductor comprising the twisted conductor covered with the insulation of vinyl chloride. As noted from Fig. 6, shore D hardness of 40-60 of thermoplastic polyurethane is essentially required for providing to the insulated conductor the abrasion resistance of the insulated conductor identical to or higher than that of the prior vinyl chloride insulated conductor although the thickness of the insulation of thermoplastic polyurethane is 4~4 g less than 0.2 mm, wl~ich is sufficlent to make the diameter of wire harness appreciably smaller.
It should be noted that the effectiveness of removal of the insulation 14, where needed to connect to a part 7, depends on the difference in thickness thereof, that is, the difference between the maximum thickness (t max) and the minimum ~hickness (t min). Fig. 7 shows the relation between the difference in thickness and a failure of removal of the insulation when there was removed the insulation of the insulated conductor which was formed by covering with the insulation of thermoplastic polyurethane of 0.15 mm thickness the conductors of concentrically twisted seven wires having a section of 0.3 mm2 through 0.85 mm2. As noted from Fig., 8, with the difference in thickness of the insulation of thermo-plastic polyurethane being less than 40 ~m, there was nofailure of removal of insulation.
It should be also noted that the effectiveness of removal of the lnsulatLon depends on the adherence of the conductor 12 to bhe insulation 14. The adherence of the conductor to the insulation can be expressed by a force required to pull the remaining insulation of 10 mm length off the conductor after the sample of the insulated conductor of 35 mm length has the insulation of 25 mm length removed.
In other words, the adherence is measured as the required pulling out force of the conductor per 10 mm length of the insulation.
Fig. 8 shows a relation between the adherence of - the conductor relative to the insulation and the failure of removal of the insulation from the conductor when the insulated conduc-tor had the insulation of thermoplastic polyurethane having the difference in thickness of less than 40 ~m. ~s noted from Fig. 8, with the adherence of the conductor to the insulation being less than 2 kg/lOmm, there was no failure of removal of the insulation. Decreasing the adherence of the conductor to the insulation may be effected by omitting to preheat the ~~
the conductor, passing the conductor through a pipe-type die or nipple and coating the conductor with activator.
Fig. 9 shows another embodiment of the invention in which there is a middle layer 15A of vinyl chloride resin between the insulation 14 of thermoplastic polyurethane and the conductor 12. With this embodiment, since there i5 disposed the mlddle layer 15A of smaller pulling force between the conductor and the insulation, the adherence of the conductor 12 to the insulation 14 is lower, which causes removal of the insulation 14 to be more easily made and softness to be provided to the insulated conductor. In one example, a wire harness including the insulated conductors, which had the middle layer 15A of vinyl chloride of 0.05 mm thickness covered on the conductors having a cross section of 0.3 through 0.85 mm and the insulation 14 of thermoplastic polyurethane of 0.15 mm thickness covered on the middle layer 15A had the diameter decreased 25 through 30% and the weight decreased about 20% in comparison with those oE
prior wire harness including the insulated conductors which had only the insulation oE vinyl chloride.
Fig. 10 shows a further embodiment of the invention in wlch there is a layer 15B oE non-combustible vinyl chloride covered on the insulation 14 of thermoplastic ployurethane.
With this embodiment, combustibility of thermoplastic polyurethane is obstructed by non-combustibility of the layer 15B of vinyl chloride to provide non-combustibility to the insulated conductor. It should be noted that the total thickness of the insulation of thermoplastic polyurethane and the layer of non-combustible vinyl chloride can be less than 0.2 mm by selecting proper hardness of the insulation of thermoplastic polyurethane. In examples, the thickness of the insulation of thermoplastic polyurethane was 0.18 mm (shore D hardness of 60), 0.15 mm (shore D hardness of 60) and 0.10 mm (shore D hardness of 65) while the thickness of ~9~2~
the layer of non-combustible vinyl chloride was 0.02 mm, 0.05 mm and 0.10 mm, respectively.
While some preEerred embodiments of the invention have been described and illustrated with reference to the accompanying drawings, it will be inderstood by those skilled in the art that they are by way of example and that various changes and modifications may be made without departing from the spirit and scope of the invention, which is intended to be defined only by the appended claims.
A conventional insulated conductor for a wire harness for a car, comprises a bundle of a plurality of insulated conduc-tors having a predetermined length with a covering of tape wound on the bundle holding it together. Each of the insulated conductors has ends exposed and parts such as connectors connected to the exposed ends.
Lately, there have been various specifications of a car, which increases the number of parts and the number of wiring circuits. Accordingly, a wire harness has the diameter enlarged and the weight increased. For example, the diameter of the wire harness for the car changes from 20 through 30 mm of the prior art harness to 50 through 60 mm. It will be noted that this is contrary to the requirement of enlargement of a space wlthin the car and of lightness of the car. Also, this causes the ~eight of the wire harness to increase and the number of operators for assembl:Lng the wire harness to increase.
Thus, it will be noted that the smaller diameter and lighter weight of the wire harness are required for meeting the re-quirement of car design and for assembling the wire harness without any decrease in efEectiveness of operation.
One of the prior art insulated conductors for a wire harness comprises an insulation of vinyl chloride provided on a conductor. The conductor comprises a twisted conductor formed by twisting a plurality of copper wire elements while the insulation is formed by extruding vinyl chloride on the twisted conductor. The thickness of the insulation normally ranges from 0.6 mm to 1.1 mm and is 0.4 mm in case of thinnest insulation.
In order to make the diameter of the wire harness smaller, it is effective to thin the insulation of the ~;9~
insulated conductor. ~lowever, if the insulation is thinned, the abrasion resistance oE the insulated conductor is lowered, which disadvantageously causes the insulation of the insulated conductor to be damaged when the wire harness is assembled, installed and treated thereafter.
The conductor of twisted wires provides flexibility and softness to the insulated conductor, which preferably aids the conductor to be compressively secured to terminals, but the twisted conductor tends to have wire elements untwisted and protruded, which causes the cross section of the insulation on the conductor to have an out-of-round excursion with the result that the insulation of vinyl chloride tends to have a thick portion as indicated by t (max) and a thin portion as indicated by t (min). In case that terminals are compres-sively secured to the ends of the insulated conductor, the insulation at the ends of the insulated conductor has to be removed. This is accomplished by stripplng blades into the insulation, so that the blades never contact the conductor whlle they are moved.
If the blades contact the condutor by any chance, then the conductor is damaged, which causes the insulated conductor to be cut due to vibration applied thereto from the car. If the insulation is thicker, the conductor is never damaged even though the wire elements are slightly untwisted or protruded, but if the insulation is thinner, and the wire elements are untwisted or protruded, this causes the conductor to be possibly damaged when the insulation is removed.
Accordingly~ it is a principal object of the inven-tion to provide an insulated conductor for wire harness adapted to have a smaller diameter by thinning an insulation without any decrease in abrasion resistance of the insulation.
It is another object of the invention to provide an insulated conductor for wire harness wherein a conductor is not damaged when an insulation is removed.
9~
According to the present invention, there is provided an insulated conductor Eor a wire harness~comprising a conductor and an insulation witl- which the conductor is cov-ered, the insulation characterized by being formed of thermoplastic polyurethane having shore D hardness of more than 50 and a thickness of less than 0.2 mm and wherein the adherence of the insulation to the conductor is less than 2 kg/lO mm, being measured as the required force to pull lO mm of the insulation off the conductor.
With the insu]ation formed of thermoplastic polyurethane having shore D hardness of more than 50, the abrasion resistance of the insulation is larger, which allows the insulation to be thlnner and the diameter of the insulatecl conductor,to be smaller.
The conductor may be either a single conductor or a twLsted body of wire elements, and may be preEerably a com-pressed conductor formed by compress:Lvely cleEorming a twisted body oE wire Lnto a body having a substantially round cross section. With the conductor compressed, the wire elements are neither untwLsted nor prodruded, less insulation is embecl(led into the space between the wire elements of the twisted body, whlcll eases the removal of the insulation .
ThUS~ it will be noted that the d:Lameter oE the insulation becomes uniform, whLcll causes the conductor to be never damaged.
It has been Eound by the :Lnventors that a failure to remove all oE the insulation depends on the thickness differ-ence of the insulation ,that is, a difference between the maximum and minimum thicknesses, and on the adherence of the conductor to the insulation. According to the invention, with the thickness difference of less than ~0 ~m, no failure of removal is caused and also with the adherence of the insu-lation to the conductor of less than 2 Kg/lOmm~ as above indicated, no failure of removal is caused.
The above and other objects and features of the invention will be apparent from the description of the ~ i9~29~
"
embodiments taken along with reference to the accompanying drawings in which;
Fig. 1 is a perspective view of a conventional wire harness;
Fig. 2 is a cross sectional view of a prior art insulated conductor for a wire harness;
Fig. 3 illustrates an insulation of tile insulated conductor for a wire harness being removed;
Fig. 4 is a cross sectional view of an insulated conductor for a wire harness constructed in accordance with one embodiment of the invention;
Fig. 5 is a front view of a scraping tester for determining an abrasion resistance of the insulated conductor for a wire harness;
Fig. 6 illustrates curves oE scrapLng character-istic of the insulation of the insulated conductor for a wire harlless;
Fig. 7 i:LIustrates a curve of fai:Lure of removal of tlle Lnsulation re:Lat:Lve to the tllickness d-lEEerence thereof;
Fig. 8 Lllustrates a curve oE failure oE removal oE the insulat:Lon re:LatLve to the adherence oE the insulation;
Fig. 9 :Ls a cross sectional view of an insulated conductor constructed in accordance with another embodiment of the invention;
and Fig. 10 is a cross sectional view of an insu-lated conductor constructed in accordance with a further embodiment of the envention.
Fig. 1, shows an insulated conductor for a wire harness for a car, which comprises a bundle 2 of a plurality of insulated conductors l having a predetermined length with a covering 3 of tape wound on the bundle holding it together.
Each of the insulated conductors 1 has ends exposed and parts 7 such as connectors connected to the exposed ends.
Fig- 2, shows one of the prior art insulated conductors 4;~
for a wire harness,comprises an insulation 5 of vinyl chloride provided on a conductor 4. The condutor 4 comprises a twisted conductor formed by twisting a plurality of copper wire elements 4a while the insulatlon 5 is formed by extruding vinyl chloride on the twisted conductor. The thickness of the insulation 5 normally ranges from 0.6 mm to 1.1 mm and is 0.4 mm in case of thinnest insulation.
In order to make the diameter of ~he wire harness smaller, it is effective to thin the insulation 5 oE tlle insulated conductor. However, iE the insulation 5 is thinned, the abrasion resistance of the insulated conductor is lowerd, which disadvantageously causes the insu~ation of the insulated conductor to be dama8ed when the wire harness is assembled, installed and treated thereafter.
The conductor 4 oE twisted wires provides flexibility and softness to tlle insulated conductor, wh:Lch preEerably aids the conductor to be compressively secured to terminals, but the twisted conductor tends to have wLre elements untwisted and protrucled, wh:Lcll causes the cross section oE the insulation on the conductor to have an out-of-round excursion as indica-ted by dotted line oE Fig. 2 with the result that the insula-tion 5 of vLnyl chlorLde tends to have a tllick portion as indicated by t (max) and a thin portion as indicated by t(min).
In case that terminals are compressively secured to the ends of the insulated conductor, the insulation at the ends of the insulated conductor has to be removed. This is accomplished by stripping blades 6 into the insulation 5, as shown in Fig.3, so that the blades 6 never contact the conductor 4 while they are moved as indicated by an arrow in Fig. 3. If the blades 6 contact the conductor by any chance, then the conductor 4 is damaged, which causes the insulated conductor to be cut due to vibration applied thereto from the car. If the insulation 5 is thicker, the conductor 4 is never damaged even though the wire elements 4a are slightly untwisted or protruded, but if 9~
the insulation is thinner, and the wire elments 4a are untwisted or protruded, this causes the conductor 4 to be possibly damaged when the insulation is removed.
Referring now to Fig. 4, there is shown an insulated conductor 10, which comprises a conductor 12 and an insulation 14 provided on the conductor 12.
The insulation 14 comprises thermoplastic polyurethane having shore D hardness of more than 50 and has the thickness of average less 0.2 mm. Thermoplastic polyurethane is formed by polycondensing long-chain polyo:L having polyester or polyether bond and short-chain polyol by aromatic or aliphatic diisocianate~ Thermoplasticity is produced by arranging urethane-bond (-NHC00-) substantially in series to each other and has a mouldabLe property by melting material at high temperature. Various - hardnesses may be provided by selecting polyol and diisocianate.
Thermoplastic polyurethane has a higher abrasion resistance than vinyl chloride has and the thermoplastic polyurethane has shore D hardness greater than 50 with the result that thermoplastic polyurethane of thickness of less than 0.2 mm can have the abraslon resistance equal to that of vinyl chloride of thickness of 0.6 mm, which is generally used for a conventional insulated conductor.
The conductor 12 may comprise a twisted body formed by twisting a plurality of copper wire elements 12a or may comprise a compressed conductor formed by compressively deforming the twisted body into one having a substantially round cross section as shown in Fig. 4. The compressed conductor 12 can be produced by passing the twisted body through a die or through a shaping roll to decrease the diameter thereof. In this manner, the wire elements 12a are deformed into non-round cross section so as to fill the space within the twisted body, which prevents the wire elements from being untwisted or protruded so that the twisted body 9~2~
is deformed into round cross section. Thus, it will be noted that be thickness oE the insulation 1~ never varies, although it is less than 0.2 mm.
For example, with the insulation of 0.15 mm thickness provided on the conductor of 0.5 mm diameter, the thickness difference H is determlned by the following expression;
H = ~(t max - t min ) (t max ~ t min)~ x 100%
In this expression, t max designates the maximum thickness while t min designates the minimum thickness. It was acknowledged that the ~hickness difference H was about 15 when the conductor 12 was not compressed, but decreased to about 5~ when the conductor 12 was compressed.
With the insulation of thermoplastic polyurethane having shore D hardness of more than S0, the abrasion resist-ance of the insulation becomes larger, which allows the thickness of the insulation to be thinner and the diameter of the insulated conductor to be smaller.
The conductor 12 may be either a single conductor or a twisted body o~ wlre elements, and may be preferably a compressed conductor 12 Eormed by compressing the twisted body into one having a round cross section. With the conduc-tor 12 compressed, the w:Lre elements 12 are neither untwisted nor protruded to make the surface of the conductor 12 smooth and less insulation is embedded into the space between the wire elements 12a of the twisted body. Thus, it will be noted that the diameter of the insulation becomes uniform and that the adherence of the conductor to the insulation decreases, which causes the conductor not to be damaged upon removal of the insulation even though the thickness of the insulation is smaller.
The abrasion resistance of the insulated conductor for a wire harness can be expressed by the number of scraping ~9~;~4 , times of the scraping test. This test can be accomplished by a scraping tester as shown in Fig. 5. A sample lOA of the insulated conductor is secured on a stand 18 by clamps 20 in a horizontal manner while scraping blades 22 having a diameter of edge oE 0.125 mm are mounted on the sample lOA
with a weight 24 mounted on the scraping blades 22 in accordance with the size of the insulated conductor. The scraping blades 22 are moved by a stroke of about 10 mm by reciprocationg means 26. In this manner, when the sample lOA
is scraped by the scraping blades 22 to damage the insulation until the scraping blades 22 contact with the conductor 12, the reciprocating movement stops and the number of recipro-cations (number of scraping times) is indicated on a coulnter, not shown.
Fig. 6 shows the number of scraping times relative to the thickness of tlle insulation when various insulated conductors were tested by such a tester. The load of the weight 24 used for the tests was 1.2 kg. In Fig. 6, a curve A is the number of scraping times of the insulated conductor comprislng the compressed conductor covered with the insula-tion of thermoplast:Lc polyurethane having shore D hardness of 60, a curve B that of the insulated conductor comprising the compressed conductor covered with the insulation of thermoplastic polyurethane having shore D hardness of 50, a curve C that of the insulated conductor comprising the compressed conductor covered with the insulation of thermo-plastic polyurethane having shore D hardness of 40, and a curve D that of the prior art insulated conductor comprising the twisted conductor covered with the insulation of vinyl chloride. As noted from Fig. 6, shore D hardness of 40-60 of thermoplastic polyurethane is essentially required for providing to the insulated conductor the abrasion resistance of the insulated conductor identical to or higher than that of the prior vinyl chloride insulated conductor although the thickness of the insulation of thermoplastic polyurethane is 4~4 g less than 0.2 mm, wl~ich is sufficlent to make the diameter of wire harness appreciably smaller.
It should be noted that the effectiveness of removal of the insulation 14, where needed to connect to a part 7, depends on the difference in thickness thereof, that is, the difference between the maximum thickness (t max) and the minimum ~hickness (t min). Fig. 7 shows the relation between the difference in thickness and a failure of removal of the insulation when there was removed the insulation of the insulated conductor which was formed by covering with the insulation of thermoplastic polyurethane of 0.15 mm thickness the conductors of concentrically twisted seven wires having a section of 0.3 mm2 through 0.85 mm2. As noted from Fig., 8, with the difference in thickness of the insulation of thermo-plastic polyurethane being less than 40 ~m, there was nofailure of removal of insulation.
It should be also noted that the effectiveness of removal of the lnsulatLon depends on the adherence of the conductor 12 to bhe insulation 14. The adherence of the conductor to the insulation can be expressed by a force required to pull the remaining insulation of 10 mm length off the conductor after the sample of the insulated conductor of 35 mm length has the insulation of 25 mm length removed.
In other words, the adherence is measured as the required pulling out force of the conductor per 10 mm length of the insulation.
Fig. 8 shows a relation between the adherence of - the conductor relative to the insulation and the failure of removal of the insulation from the conductor when the insulated conduc-tor had the insulation of thermoplastic polyurethane having the difference in thickness of less than 40 ~m. ~s noted from Fig. 8, with the adherence of the conductor to the insulation being less than 2 kg/lOmm, there was no failure of removal of the insulation. Decreasing the adherence of the conductor to the insulation may be effected by omitting to preheat the ~~
the conductor, passing the conductor through a pipe-type die or nipple and coating the conductor with activator.
Fig. 9 shows another embodiment of the invention in which there is a middle layer 15A of vinyl chloride resin between the insulation 14 of thermoplastic polyurethane and the conductor 12. With this embodiment, since there i5 disposed the mlddle layer 15A of smaller pulling force between the conductor and the insulation, the adherence of the conductor 12 to the insulation 14 is lower, which causes removal of the insulation 14 to be more easily made and softness to be provided to the insulated conductor. In one example, a wire harness including the insulated conductors, which had the middle layer 15A of vinyl chloride of 0.05 mm thickness covered on the conductors having a cross section of 0.3 through 0.85 mm and the insulation 14 of thermoplastic polyurethane of 0.15 mm thickness covered on the middle layer 15A had the diameter decreased 25 through 30% and the weight decreased about 20% in comparison with those oE
prior wire harness including the insulated conductors which had only the insulation oE vinyl chloride.
Fig. 10 shows a further embodiment of the invention in wlch there is a layer 15B oE non-combustible vinyl chloride covered on the insulation 14 of thermoplastic ployurethane.
With this embodiment, combustibility of thermoplastic polyurethane is obstructed by non-combustibility of the layer 15B of vinyl chloride to provide non-combustibility to the insulated conductor. It should be noted that the total thickness of the insulation of thermoplastic polyurethane and the layer of non-combustible vinyl chloride can be less than 0.2 mm by selecting proper hardness of the insulation of thermoplastic polyurethane. In examples, the thickness of the insulation of thermoplastic polyurethane was 0.18 mm (shore D hardness of 60), 0.15 mm (shore D hardness of 60) and 0.10 mm (shore D hardness of 65) while the thickness of ~9~2~
the layer of non-combustible vinyl chloride was 0.02 mm, 0.05 mm and 0.10 mm, respectively.
While some preEerred embodiments of the invention have been described and illustrated with reference to the accompanying drawings, it will be inderstood by those skilled in the art that they are by way of example and that various changes and modifications may be made without departing from the spirit and scope of the invention, which is intended to be defined only by the appended claims.
Claims (7)
1. An insulated conductor for a wire harness comprising a conductor and an insulation with which said conductor is covered, said insulation characterized by being formed of thermoplastic polyurethane having shore D hardness of more than 50 and a thickness of less than 0.2 mm, and wherein the adherence of the insu-lation to said conductor is less than 2 kg/10 mm, being measured as the required force to pull 10 mm of the insulation off the conductor.
2. An insulated conductor for a wire harness as set forth in claim 1, and wherein said conductor comprises twisted wires.
3. An insulated conductor for a wire harness as set forth in claim 1, and wherein said conductor comprises a compressed conductor formed by compressively deforming a twisted body of wires into a body having a substantially round cross section.
4. An insulated conductor for a wire harness as set forth in claim 1, and wherein said insulation has a difference of less than 40 µm between the maximum thickness and the minimum thickness thereof.
5. An insulated conductor for a wire harness as set forth in claim l, and further comprising a middle layer of vinyl chloride thinner than said insulation between said conductor and said insulation.
6. An insulated conductor for a wire harness as set forth in claim 1, and further comprising a layer of non-combustible thermoplastic resin provided on said insulation.
7. An insulated conductor as set forth in claim 6, and wherein said layer of non-combustible thermoplastic resin comprises vinyl chloride.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000530172A CA1269424A (en) | 1987-02-23 | 1987-02-23 | Insulated conductor for a wire harness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000530172A CA1269424A (en) | 1987-02-23 | 1987-02-23 | Insulated conductor for a wire harness |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1269424A true CA1269424A (en) | 1990-05-22 |
Family
ID=4135013
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000530172A Expired CA1269424A (en) | 1987-02-23 | 1987-02-23 | Insulated conductor for a wire harness |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1269424A (en) |
-
1987
- 1987-02-23 CA CA000530172A patent/CA1269424A/en not_active Expired
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| Date | Code | Title | Description |
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| MKLA | Lapsed |