Insulated conductor wire, terminal wire and wire harness

Abstract

To provide a coated conducting wire or the like, which can suppress a rupture of a coating part even when the coated conducting wire is bent.SOLUTION: A coated conducting wire 23 is formed of a conducting wire 25 that is coated with an insulative coating part 27. A terminal 1 includes a terminal body 3 and a crimping part 5. The crimping part 5 is a part at which the terminal body is crimped on the coated conducting wire, and includes a conducting wire crimped part 7 at which the terminal body is crimped on a conducting wire part that is exposed from a coating part on a tip side of the coated conducting wire, and a coating crimped part 9 at which the terminal body is crimped on a part of the coating part of the coated conducting wire. In a stress-strain curve of the coating part 27, a stress lowering part which accompanies the increase of strain is not formed between a yield stress and the rupture stress.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a covered conductor wire, an electric wire with terminal, and a wiring harness for use in, for example, an automobile. [Background technology]

[0002] Conventionally, in the fields of automobiles, office automation equipment, home appliances, etc., electric wires made of copper-based materials with excellent electrical conductivity have been used as power lines and signal lines. In particular, in the field of automobiles, the performance and functionality of vehicles are rapidly improving, and the number of various electric devices and control devices installed in vehicles is increasing. Accordingly, the number of electric wires with terminals used is also on the rise.

[0003] Generally, in such electric wires with terminals, a covered conductor in which the conductor is covered with an insulating resin to ensure insulation and protect the internal conductor is connected to a terminal. The covered conductor needs to be durable enough that the covering is not damaged when bent, etc.

[0004] As an example of an electric wire with terminal in which such a covered conductor wire and a terminal are connected, there has been proposed an electric wire with terminal in which one end along the longitudinal direction is sealed and a crimp terminal having a crimping portion formed into a cross-sectional hollow cylindrical shape with a welded portion along the longitudinal direction is crimped to the covered conductor wire (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-107149 A Summary of the Invention [Problem to be solved by the invention]

[0006] In an electric wire with terminal as disclosed in Patent Document 1, the coating is crimped together with the conductor. During this process, the coating is compressed from the outer periphery, so that the coating is partially stretched at the crimped portion with the terminal. In this state, when the coated conductor is bent relative to the terminal, the coating is stretched due to compression and bending, which overlap, and the coating may break.

[0007] In particular, as described in Patent Document 1, when a convex shape is formed on part of the inner surface of a cylindrical crimped portion due to welding, a part with a large amount of compression is locally generated in a part in the circumferential direction. Therefore, the condition of this part is more severe than that of the surrounding area, and the coating part is easily damaged. This phenomenon can be explained as follows.

[0008] FIG. 10 is a diagram showing a stress-strain curve of a general polyvinyl chloride resin to which a plasticizer or the like has been added. In the elastic region of a general resin, the strain increases in an approximately linear manner as the stress increases. The slope of this curve is the Young's modulus. When the stress reaches the yield stress (X in the figure), plastic deformation begins, and the strain increases with smaller stress. That is, a region where the stress decreases (Z in the figure, hereinafter referred to as the stress drop portion) is generated. If the strain increases further, the stress increases and the resin breaks. The stress at this time is the breaking stress Y. Details will be described later, but in this way, a stress drop portion where the stress drops once is usually formed between the yield stress X and the breaking stress Y.

[0009] In this way, if there is a stress drop portion where the stress decreases when the strain (elongation) increases, the elongation will increase even more with a small stress when the yield stress is exceeded. For example, if there is a protrusion due to welding as described above, the elongation due to compression will be relatively large in that portion compared to the surrounding area. Therefore, if the covered conductor is bent around the terminal in this state, the elongation will easily progress in that portion with a smaller stress, so the local elongation will increase even more compared to the surrounding area, making it more likely to break.

[0010] This phenomenon is more noticeable when there are protrusions, etc., on the inner surface of the terminal due to welding, as described above, but it can also occur even in the absence of welding due to partial compression variations, etc. If the coating breaks in this way, it becomes impossible to ensure insulation and watertightness.

[0011] In contrast, if the compression ratio of the coating is increased (the amount of compression is reduced) and the amount of elongation is reduced by compressing the coating, the adhesive strength between the coating and the coating crimped portion will decrease, and the removal force of the coating will decrease and the water-stopping ability of the crimped portion will decrease. For this reason, a coated conductor is required in which the coating is less likely to break even when crimped at a compression ratio below a certain level.

[0012] The present invention has been made in consideration of such problems, and has an object to provide a covered conductor etc. that is capable of preventing breakage of the covering even when the covered conductor is bent. [Means for solving the problem]

[0013] In order to achieve the above object, a first aspect of the present invention is a coated conductor in which a conductor is coated with a resin coating, the resin is a polyvinyl chloride resin to which a plasticizer and an impact modifier are added, the amount of the impact modifier added is 5 to 20 parts by mass per 100 parts by mass of the polyvinyl chloride resin, and the impact modifier is a core-shell type having a graft layer on the outside of a particulate rubber, The coated conductor is characterized in that in the stress-strain curve of the coating, no portion of the coating that reduces stress due to an increase in strain is formed between the yield stress and the breaking stress. It is preferable that the particle diameter of the rubber particles of the impact resistance improver dispersed in particulate form is 10 μm or less, and the rubber component is 7.3 parts by mass or less per 100 parts by mass of the vinyl chloride resin.

[0014] The yield stress of the coating is 30 MPa or more 40MPa or less It is desirable that:

[0015] It is desirable that the covering portion has a Young's modulus of 3.5 MPa or more.

[0016] According to the first aspect of the present invention, in the stress-strain curve of the resin constituting the coating, no clear stress drop section is formed between the yield stress and the breaking stress. Therefore, when the coated conductor is bent relative to the terminal, the localized elongation as described above is unlikely to occur, and therefore breakage of the coating can be suppressed.

[0017] Furthermore, if the yield stress is 30 MPa or more, it is possible to prevent the covering portion from being excessively stretched during compression or the like.

[0018] Furthermore, if the Young's modulus of the covering portion is 3.5 MPa or more, sufficient wear resistance can be ensured.

[0019] A second invention is an electric wire with terminal in which the covered conductor wire of the first invention is connected to a terminal, the terminal having a terminal body and a crimping portion, the crimping portion comprising a conductor crimping portion to which the conductor wire is crimped and a coating crimping portion to which the coating is crimped, and the minimum thickness of the coating at the crimping portion is 50% or less of the thickness of the coating at a portion other than the crimping portion.

[0020] It is desirable that in the area other than the crimped portion, the size of the conductor is 3 sq. or less and the thickness of the covering portion is 0.3 mm or less.

[0021] It is desirable that the compression rate of the covering portion at the covering compression-bonding portion be 50% or less.

[0022] The crimping portion may be formed into a generally tubular shape by rolling the ends of a flat material so that they butt together, and welding the butt joints together, with all portions sealed except for the portion where the coated conductor wire is inserted.

[0023] According to the second aspect of the present invention, the compression rate is 50% or less at the portion with the greatest compression, so that sufficient crimping can be performed. Furthermore, if the compression rate of the coating at the coating crimping portion is 50% or less, crimping can be performed more reliably. Even in this case, as described above, breakage of the coating when the coated conductor is bent relative to the terminal can be suppressed.

[0024] It is particularly effective when the size of the coated conductor is 3 sq. or less and the thickness of the coating is 0.3 mm or less.

[0025] In addition, if the crimping portion is cylindrical with one end sealed, the coating crimping portion can ensure watertightness. In addition, since a weld is formed, a protrusion may be generated on the inner surface of the crimping portion, but even in such a case, as described above, breakage of the coating portion when the coated conductor is bent relative to the terminal can be suppressed.

[0026] A third aspect of the present invention is a wire harness comprising a plurality of electric wires with terminals according to the second aspect of the present invention bundled together.

[0027] In the present invention, a plurality of electric wires with terminals can also be bundled together for use. Effect of the Invention

[0028] According to the present invention, it is possible to provide a covered conductor etc. capable of suppressing breakage of the covering even when the covered conductor is bent. [Brief description of the drawings]

[0029] [Figure 1] FIG. 2 is a perspective view showing a terminal-fitted electric wire 10. [Diagram 2] FIG. 2 is a cross-sectional view showing the electric wire 10 with a terminal. [Diagram 3] (a) is a cross-sectional view taken along line CC in Figure 2, and (b) is an enlarged view of part D in (a). [Figure 4] FIG. 4 is a diagram showing the stress-strain curve of the resin of the coating portion. [Diagram 5] FIG. 2 is a diagram showing the terminal 1 and the coated conductor wire 23 before crimping. [Figure 6] 5A and 5B are cross-sectional views showing a state in which a pressure-bonding section 5 is disposed between metal molds 31a and 31b, where (a) is a view showing the state before pressure-bonding, and (b) is a view showing the state after pressure-bonding. [Figure 7] FIG. 4 is a diagram showing stress-strain curves of each coating portion used in the examples. [Figure 8] 1(a) and (b) are diagrams showing a bending test method for a coated conductor. [Figure 9] 4 is a diagram showing a method for testing the electric wire with terminal 10. FIG. [Figure 10] FIG. 13 is a diagram showing a stress-strain curve of resin of a conventional coating portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing an electric wire with terminal 10, and Fig. 2 is a cross-sectional view. The electric wire with terminal 10 is configured by connecting a terminal 1 and a coated conductor wire 23.

[0031] The coated conductor wire 23 is formed by coating a conductor wire 25 with a coating portion 27 made of insulating resin. The conductor wire 25 is made of, for example, copper, a copper alloy, aluminum, or an aluminum alloy. When the coated conductor wire 23 is inserted into the crimping portion 5 of the terminal 1, a part of the coating portion 27 at the tip of the coated conductor wire 23 is peeled off to expose the conductor wire 25. The details of the coating portion 27 will be described later.

[0032] The terminal 1 is made of, for example, copper, copper alloy, aluminum, or aluminum alloy, and is composed of a terminal body 3 and a crimping portion 5. The terminal body 3 is a plate material of a predetermined shape formed into a cylindrical body with a rectangular cross section. The terminal body 3 has an elastic contact piece 15 formed by folding the plate material into the rectangular cylindrical body inside. The terminal body 3 is connected by inserting a male terminal or the like from the front end. In the following description, an example is shown in which the terminal body 3 is a female terminal that allows the insertion of an insertion tab (not shown) of a male terminal or the like, but in the present invention, the detailed shape of the terminal body 3 is not particularly limited. For example, an insertion tab of a male terminal, for example, may be provided instead of the female terminal body 3.

[0033] The crimping portion 5 is a portion that is crimped to the coated conductor wire, and is made up of a conductor crimping portion 7 that crimps the conductor portion exposed from the coating at the tip side of the coated conductor wire, and a coating crimping portion 9 that crimps a part of the coating of the coated conductor wire. The conductor crimping portion 7 and the coating crimping portion 9 are integrally formed.

[0034] Incidentally, serrations (not shown) may be provided in the circumferential direction on a part of the inner surface of the conductor crimping portion 7. By forming serrations in this manner, the oxide film on the surface of the conductor can be easily destroyed when the conductor is crimped, and the contact area with the conductor can be increased.

[0035] The crimping portion 5 is formed by rolling the ends of a flat plate-shaped material so that they butt against each other to form a cylindrical body with a circular cross section, and the butt joints are joined and integrated by welding or the like to form a joint 21. A covered conductor wire 23 is inserted from the rear end (the side opposite the terminal body 3) of the cylindrically formed crimping portion 5. A sealing portion 11 is provided at the front end (the terminal body 3 side) of the crimping portion 5. That is, the crimping portion 5 is substantially cylindrical with one end closed, and the other portions are sealed except for the rear end where the covered conductor wire is inserted. The joint 21 and the sealing portion 11 are welded by, for example, laser welding or the like.

[0036] Fig. 3(a) is a cross-sectional view taken along line CC in Fig. 2, and Fig. 3(b) is an enlarged view of part D in Fig. 3(a). As described above, the cylindrical coating crimping part 9 has a joint 21 formed along the axial direction. Since the joint 21 is joined by laser welding or the like, a protrusion 22 protruding toward the inner surface may be formed as shown in Fig. 3(b). In this case, the coating part 27 at the site of the protrusion 22 is compressed more strongly than the surrounding coating part 27.

[0037] Next, the coating 27 in this embodiment will be described in detail. Since vinyl chloride resin is generally used for the coating of a coated conductor, the following description will be given of the case where vinyl chloride resin is used, but other resins are equally applicable.

[0038] PVC resin is originally a hard resin, but plasticizers are widely used as additives to make it flexible. PVC resin is hard at room temperature because the intermolecular forces of the vinyl chloride polymer strongly attract each other, shortening the distance between the molecules. When a plasticizer is added, the plasticizer molecules enter between the vinyl chloride polymer molecules, preventing the interaction between the polymer molecules, and as a result, the distance between the molecules remains wide even at room temperature, allowing the resin to maintain its soft state. In this way, it is the function of the plasticizer to soften PVC resin, and the more plasticizer is added, the softer it becomes. This phenomenon of softening is called plasticization.

[0039] On the other hand, in recent years, there has been a demand for thinner electric wires for automobiles, and coated conductors with thinner coatings and smaller outer diameters are sometimes used. However, when the coating is made of soft vinyl chloride polymers containing a lot of plasticizer as described above, not only does it reduce wear resistance, but it also results in poor heat resistance, which has been in high demand in recent years. For this reason, it is necessary to reduce the amount of plasticizer or to change to a plasticizer with high heat resistance (which reduces the plasticizing effect). However, doing so reduces the intermolecular interaction described above, making the coating harder and improving wear resistance and heat resistance, but it also causes problems with embrittlement, such as being prone to cracking at low temperatures.

[0040] In contrast, in applications requiring improved impact resistance, impact-improving resins (reinforcements) with rubber properties, such as ABS, MBS, acrylic rubber, chlorinated polyethylene, and EVA, may be mixed into polyvinyl chloride resin. For example, mixing 5 to 20 parts by mass of a reinforcing agent with 100 parts by mass of polyvinyl chloride resin can impart sufficient impact strength for practical use to polyvinyl chloride products. The reinforcing agent is dispersed as fine particles in the polyvinyl chloride resin, and when an impact is applied to the product, the presence of these fine particles absorbs the impact energy, preventing damage to the product.

[0041] As a result of extensive research by the inventors, the present invention has discovered a combination of materials that, although different from the instantaneous impact resistance described above, has the effect of preventing the coating from breaking even when bending stress is applied in an environment in which the wire is used as an electric wire with a terminal, particularly at low temperatures.

[0042] Below, we will use the stress-strain curve to explain. As shown in Figure 10, when tensile stress is applied to ordinary polyvinyl chloride, the loosened molecular chains are stretched, and stress rises in the process of stretching. When the molecular chains are fully stretched and reach their limit (yield stress), the effect of slippage between molecules increases due to the influence of the plasticizer present between the molecules, and once the yield stress X is passed, the stress drops (Z in the figure). The degree of stress drop at this time is determined by the type of plasticizer used, the amount added, and the molecular weight of polyvinyl chloride. In other words, the degree of stress drop is greater when a plasticizer with a large plasticizing power is used or when a large amount is added, and the intermolecular force also decreases when the molecular weight of polyvinyl chloride is small, so the stress drops more.

[0043] However, in the case of the cylindrical coating crimping portion 9 as in this embodiment, a pressing force of more than a predetermined value between the coating crimping portion 9 and the coating portion 27 is required to ensure the anti-pullout force and water-stopping property. In this way, a certain amount of compression is required to ensure a pressing force of more than a predetermined value against the coating portion 27. However, when there is a stress drop portion as described above, the strain (elongation) is larger even with the same compressive force compared to when there is no stress drop portion. In addition, the presence of the stress drop portion reduces the difference between the yield stress and the breaking stress. Therefore, there is a risk of the coating portion 27 breaking when a bending force is applied. In particular, when a convex portion 22 is formed on the inner surface of the coating crimping portion 9, the possibility of breaking of the portion is higher than the surrounding area due to local compression.

[0044] In contrast, in the present invention, a resin having a stress-strain curve (characteristics) as shown in Fig. 4 is used for the covering portion 27. The tensile test for obtaining the stress-strain curve is performed, for example, at 0°C and at a tensile speed of 25 mm / min.

[0045] As mentioned above, this resin is elastically deformable up to the yield stress A, but even if the yield stress is exceeded, there is no stress drop section as seen in the stress-strain curve of the general resin mentioned above. In other words, between the yield stress A and the breaking stress B, the stress increases with increasing strain.

[0046] When this resin is stretched beyond the yield stress A, the stress on the matrix polyvinyl chloride increases as the entanglement points between the molecules are pulled, but the tensile stress is transmitted to the rubber molecules of the impact modifier dispersed in the polyvinyl chloride resin, and when these rubber particles are stretched further, the stress rises further in the stress-strain curve, enhancing the so-called strain hardening. As a result, the stress drop area decreases, and the stress difference between the yield stress and the breaking stress (tensile strength) can also be increased.

[0047] For example, when the electric wire with terminal 10 is bent, the strongly compressed parts and the vicinity of scratches in the coating 27 are stretched first, but when strain hardening occurs, the stress increases and resists stretching. Therefore, the stress is dispersed to the coating 27 around the strongly compressed parts that are more likely to stretch, and as a result, the coating 27 is less likely to break. In this way, by optimally setting the strain hardening property, it is possible to suppress breakage of the coating 27.

[0048] The plasticizers used in the covering portion 27 of this embodiment include many types such as phthalic acid, adipic acid, phosphoric acid, fatty acid, trimellitic acid, epoxy, and polyester, and 20 to 30 types of plasticizers are generally used, but from the viewpoint of heat resistance, trimellitic acid, epoxy, and polyester are preferably used. In particular, trimellitic acid and polyester are more preferable in order to express strain hardening in the stress-strain curve in the tensile test.

[0049] For example, tri-normal octyl trimellitate (Trimex N-08, Kao Corporation), 2-ethylhexyl trimellitate (Trimex T-08LP, Kao Corporation), mixed linear alkyl trimellitate (ADEKA C-880, ADEKA Corporation), isononyl trimellitate (ADEKA C-9N, ADEKA Corporation), dipentaerythritol ester (ADEKA UL-6), 2-ethylhexyl pyromellitic acid ester (ADEKA UL-80), mixed linear alkyl pyromellitic acid ester (ADEKA UL-100), etc. may be mentioned.

[0050] The above-mentioned preferred plasticizers may be used alone or in combination. Furthermore, they may be used in combination with other conventional plasticizers such as phthalic acid-based, adipic acid-based, phosphoric acid-based, and fatty acid-based plasticizers, so long as the deterioration of heat resistance and abrasion resistance is minimal.

[0051] As the impact modifier, a core-shell type impact modifier having a graft layer on the outside of the particulate rubber is preferred, as it is effective in expressing strain hardening in a stress-strain curve when combined with the above-mentioned preferred plasticizers, and those having butadiene rubber, acrylic rubber, or silicone-acrylic composite rubber in the core are preferred.

[0052] Examples of butadiene rubber (MBS) include Mitsubishi Chemical Corporation's products Metablen C-223A and C-215A, and Kaneka Corporation's products Kaneace B-11A and B-22. Examples of acrylic rubber include Mitsubishi Chemical Corporation's products Metablen W-300A and W-450A, and Kaneka Corporation's products Kaneace FM-21, FM-40, PA-20, and PA-40. Examples of silicone-acrylic composite rubber include Mitsubishi Chemical Corporation's products S-2001, S-2006, S-2501, and S-2030.

[0053] The impact modifier is dispersed in particulate form when mixed into the vinyl chloride polymer. The impact modifier dispersed in particulate form is called rubber particles. The particle size of the dispersed rubber particles is preferably 10 μm or less, more preferably 0.8 to 1.0 μm. The above-mentioned preferred impact modifiers may be used alone or in combination, and may be used in combination with other impact modifiers having rubber properties, such as chlorinated polyethylene and EVA, as long as the strain hardening property is not reduced.

[0054] As mentioned above, in order for the strain hardening property to appear in the stress-strain curve, it is necessary for the stress to be transmitted to the rubber particles. Since the generation of strain in the resin matrix due to tension is considerably slower than the strain due to impact, the part of the resin matrix with the lowest elastic modulus is stretched intensively. In this case, if the above-mentioned preferable plasticizer is used and the amount of the plasticizer added is appropriately limited, the elastic modulus of the rubber particles becomes smaller than that of the resin matrix, so that the tensile stress is concentrated on the rubber particles.

[0055] The rubber particles to which the stress is transmitted are stretched with the maximum stress acting on the equator, but at that time, fine cracks called crazes are generated in the matrix resin near the rubber particles in a direction perpendicular to the stress direction. These cracks differ from normal cracks in that they contain many microvoids inside and expand in volume, absorbing the stress, and at the same time, in combination with the resistance due to the presence of the rubber particles, they exhibit strain hardening.

[0056] The amount of the impact resistance improver added is, for example, 5 to 20 parts by mass, more preferably 5 to 15 parts by mass, relative to 100 parts by mass of vinyl chloride resin. If it is 5 parts by mass or less, the effect of strain hardening is small and the improvement of coating breakage is insufficient, and if it exceeds 20 parts by mass, the heat resistance decreases. A suitable amount of the plasticizer added is 15 to 35 parts by mass relative to 100 parts by mass of vinyl chloride resin. If the amount added is 15 parts by mass or less, the flexibility and cold resistance decrease, and if it exceeds 35 parts by mass, the abrasion resistance and strain hardening expression decrease.

[0057] As described above, by appropriately combining the type of plasticizer and the impact modifier and appropriately setting the blending amounts of these, the present application can obtain a resin having a stress-strain electrode as shown in Fig. 4. This makes it possible to obtain a covered conductor with terminal that is excellent in flexibility, cold resistance, abrasion resistance, and strain hardening expression, and that is less likely to break in the coating even if the terminal crimped portion is scratched due to bending tensile stress, especially at low temperatures.

[0058] In addition, in the stress-strain curve of the covering portion 27 shown in Fig. 4, the fact that a stress drop portion is not formed between the yield stress A and the breaking stress B due to an increase in strain is not limited to the case where the amount of stress drop is zero at any portion due to an increase in strain. As shown in Fig. 10, the effect of the present invention can be obtained as long as the yield stress does not peak. In other words, the stress drop portion means a stress drop portion where the yield stress in the stress-strain curve peaks, and the absence of a stress drop portion means that, taking into account variations and the like, there is no portion between the yield stress A and the breaking stress B where the stress is 1% or more lower than the yield stress A.

[0059] Moreover, in order to prevent breakage of covering portion 27, it is desirable that the yield stress A of covering portion 27 is 30 MPa or more. If the yield stress A is too high, covering portion 27 becomes too hard and difficult to stretch, so the yield stress A is preferably 40 MPa or less. In addition, in consideration of the wear resistance of covering portion 27, it is desirable that the Young's modulus of covering portion 27 is 3.5 MPa or more.

[0060] This embodiment is particularly effective when the coated conductor wire 23 has a small diameter and the thickness of the coating portion 27 is thin. For this reason, the conductor size of the coated conductor wire 23 is set to 3sq (sq: mm 2 It is particularly effective when the thickness of the covering portion 27 is 0.3 mm or less. Note that the minimum thickness of the covering portion 27 is desirably, for example, 0.15 mm or more.

[0061] Next, a method for manufacturing the electric wire with terminal 10 will be described. Fig. 5 is a perspective view showing the terminal 1 and the covered conductor wire 23 before crimping. As described above, the terminal 1 has the terminal body 3 and the crimping portion 5. First, the covering portion 27 at the tip of the covered conductor wire 23 is peeled off to expose the conductor wire 25 at the tip.

[0062] Next, the coated conductor wire 23 whose tip has been treated in this manner is inserted from the rear end side of the tubular crimping portion 5 of the terminal 1. When the tip of the coated conductor wire 23 is inserted into the crimping portion 5, the exposed portion of the conductor wire 25 is located inside the conductor crimping portion 7, and the coating portion 27 is located inside the coating crimping portion 9. The inner diameter of the conductor crimping portion 7 is smaller than the inner diameter of the coating crimping portion 9.

[0063] Fig. 6(a) is a cross-sectional view showing the mold 31a, mold 31b, etc. before crimping for manufacturing the electric wire with terminal 10, and Fig. 6(b) is a cross-sectional view showing the crimping portion 5 during crimping. The mold 31a and mold 31b have a substantially semi-cylindrical cavity extending in the longitudinal direction. The mold 31a also includes a large diameter portion 34 corresponding to the insulation crimping portion 9 and having a diameter slightly smaller than the radius of the insulation crimping portion 9, and a small diameter portion 32 corresponding to the conductor crimping portion 7 and having a diameter smaller than that of the large diameter portion 34. That is, the large diameter portion 34 and the small diameter portion 32 are formed so that both the portions corresponding to the conductor crimping portion 7 and the insulation crimping portion 9 have a substantially circular cross section when the terminal 1 is crimped.

[0064] As shown in Fig. 6(b), when the metal mold 31a and the metal mold 31b are engaged with each other to compress the crimping portion 5, the conductor crimping portion 7 is crimped to the conductor wire 25, and the coating crimping portion 9 is crimped to the coating portion 27. In this manner, the electric wire with terminal 10 can be obtained. Furthermore, a wire harness in which a plurality of electric wires with terminals are integrated, including the obtained electric wire with terminal 10, can be obtained.

[0065] Here, it is desirable that the minimum thickness of covering portion 27 at crimping portion 5 is 50% or less of the thickness of covering portion 27 at a portion other than crimping portion 5 (i.e., the thickness of covering portion 27 of covered conductor wire 23 before crimping). For example, at the portion of protrusion 22 described above, it is desirable that the thickness of covering portion 27 after crimping is 50% or less of the thickness before crimping.

[0066] In addition, if the cross-sectional area of ​​the covering portion 27 before crimping is A0 and the cross-sectional area of ​​the covering portion 27 at the covering crimping portion 9 after being crimped by the dies 31a and 31b is A1, the compression ratio=A1 / A0 is preferably 50% or less. Thus, this embodiment is particularly effective when the compression ratio is small (i.e., strong compression).

[0067] As described above, according to this embodiment, the resin of the covering portion 27 is made of a resin that does not form a stress drop portion associated with an increase in strain between the yield stress and the breaking stress in the stress-strain curve, so that strain hardening occurs in the covering portion 27 when it is crimped, and resistance is exerted so that the covering portion 27 becomes more difficult to stretch. Therefore, stress is dispersed to the surrounding covering portion 27 such as the strongly compressed portion that is more likely to stretch, and the breakage of the covering portion 27 can be suppressed.

[0068] Therefore, even if the compression rate of the coating crimping portion 9 is 50% or less, it is possible to suppress breakage of the coating portion 27. In addition, since strong compression is possible, it is possible to ensure high retention force and water stoppage.

[0069] Moreover, even when crimping is performed by the crimping portion 5 having the joint portion 21, it is possible to suppress breakage of the strongly compressed portion due to the convex portion 22 on the inner surface. Moreover, this is particularly effective when the diameter of the conductor is small, the thickness of the covering portion 27 is thin, or the compression ratio is small.

[0070] Furthermore, if the yield stress of the covering portion 27 is 30 MPa or more, sufficient strength of the resin can be ensured. Furthermore, if the Young's modulus of the covering portion 27 is 3.5 MPa or more, the abrasion resistance is also excellent. EXAMPLES

[0071] Using coated conductors with different resin materials for the coating, electric wires with terminals were produced as prototypes, and bending tests, abrasion resistance tests, and water-stop tests were carried out to evaluate each of them. Figure 7 shows the stress-strain curves of the resins used in the tests. E in the figure is Example 1, F is Example 2, G is Example 3, and H is the comparative example. The stress-strain curves shown in the figure are the results of a tensile test carried out at 0°C and a speed of 25 mm / min. The components and properties of each resin are shown in Table 1.

[0072] [Table 1]

[0073] Using each resin, a covering part with a thickness of 0.15 to 0.3 mm was formed on an electric wire with a wire diameter of 1.5 sq. to 2.5 sq. to prepare a covered conductor wire. The obtained covered conductor wire was crimped to a terminal to prepare an electric wire with terminal. The covering compression rate at the covering crimped part was 48%.

[0074] First, a bending test was performed. FIG. 8 is a diagram showing a bending test method using an electric wire with terminal. As shown in FIG. 8(a), the electric wire with terminal 10 is bent at 90° in each of its width directions (direction I in the figure). As shown in FIG. 8(b), the electric wire with terminal 10 is bent at 90° in each of its height directions (direction J in the figure). The temperature was 0°C. When the electric wire was bent in each direction, the presence or absence of breakage in the coating 27 was visually confirmed. The results are shown in Table 2.

[0075] [Table 2]

[0076] The results show that in Examples 1 to 3, which used resins without stress reduction portions, no breakage of the coating was observed for any size of coated conductor wire. On the other hand, in the case of the coated conductor wire with the conventional coating, the coating broke in all cases except for the case of a small diameter (1.5 sq) electric wire with a thick coating (0.25 mm or more).

[0077] Next, an abrasion resistance test was conducted. The abrasion resistance test was conducted using the blade reciprocating method in accordance with ISO6722, in which a load of 7N was applied to the blade and it was moved back and forth over the coated conductor. The blade was a metal wire with a diameter of 0.45 mm. The number of times the blade scraped back and forth until the internal conductor was exposed was counted, and a number of reciprocations of 750 or more was deemed to have passed. The results are shown in Table 3.

[0078] [Table 3]

[0079] As a result, Examples 1 and 2, which have a Young's modulus of 3.5 MPa or more, passed the test. That is, Examples 1 to 3 passed the test if only the bending resistance test was conducted, but Examples 1 and 2 passed the test if abrasion resistance was also taken into consideration.

[0080] Next, the water stoppage was evaluated by changing the compression ratio using Example 1 and Comparative Example 1. FIG. 9 is a diagram showing a water stoppage test method. For the water stoppage evaluation, the terminal 1 with the crimped coated conductor 23 was placed in a water tank 41 containing 3% salt water to a depth of 100 to 300 mm, the end of the coated conductor 23 was inserted into a container 45, and the inside of the container 45 was made negative pressure of -30 kPa by a pump 47 and held for 1 minute. If salt water came out from the opposite side of the terminal during the test or if the coating was opened after the test and salt water was found to have infiltrated inside, the terminal was deemed to have failed, and if salt water had not infiltrated into the coated conductor, the terminal was deemed to have passed. The results are shown in Table 4.

[0081] [Table 4]

[0082] The results show that the waterproofing test was passed when the coating compression rate was 48%. That is, in Example 1, by setting the compression rate to 50% or less, both the waterproofing test and the bending test were passed.

[0083] Although the embodiment of the present invention has been described above with reference to the attached drawings, the technical scope of the present invention is not limited to the above-described embodiment. It is clear that a person skilled in the art can think of various modifications or alterations within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0084] 1...Terminal 3: Terminal body 5……… Crimping section 7………Conductor crimping section 9……Sheathing crimping part 10: Wire with terminal 11....Sealing part 15...Elastic contact piece 21……Joint part 22....Convex part 23....Covered conductor 25……Conducting wire 27... Covering part 31a, 31b………Mold 32……Small diameter part 34...Large diameter section 41………Aquarium 45……Container 47………Pump

Claims

1. A coated conductor in which the conductor is coated with a resin coating, The resin is a polyvinyl chloride resin to which a plasticizer and an impact modifier are added, The amount of the impact resistance improver added is 5 to 20 parts by mass per 100 parts by mass of the vinyl chloride resin, The impact modifier is a core-shell type having a graft layer on the outside of the particulate rubber, A coated conductor, characterized in that in a stress-strain curve of the coating, no stress drop portion accompanying an increase in strain is formed between the yield stress and the breaking stress.

2. The particle diameter of the rubber particles of the impact resistance improver dispersed in particulate form is 10 μm or less, 2. The coated conductor according to claim 1, wherein the rubber component is contained in an amount of 7.3 parts by mass or less per 100 parts by mass of the polyvinyl chloride resin.

3. 3. The coated conductor according to claim 1, wherein the coating has a yield stress of 30 MPa or more and 40 MPa or less.

4. 4. The coated conductor according to claim 1, wherein the coating has a Young's modulus of 3.5 MPa or more.

5. A terminal-attached electric wire in which the coated conductor according to any one of claims 1 to 4 and a terminal are connected, The terminal has a terminal body and a crimping portion, The crimping portion includes a conductor crimping portion to which the conductor wire is crimped, and a coating crimping portion to which the coating portion is crimped, 13. An electric wire with a terminal, wherein a minimum thickness of the coating at the crimped portion is 50% or less of a thickness of the coating at a portion other than the crimped portion.

6. 6. The electric wire with terminal according to claim 5, wherein the size of the conductor is 3 sq. or less and the thickness of the covering is 0.3 mm or less in a portion other than the crimped portion.

7. 7. The electric wire with terminal according to claim 5, wherein a compression rate of the covering portion at the covering crimping portion is 50% or less.

8. 8. The electric wire with terminal according to claim 5, wherein the crimping portion is formed into a generally tubular shape by rolling ends of a flat material so that the ends are butted together and welding the butt joints, and other portions are sealed except for a portion into which the covered conductor wire is inserted.

9. A wire harness comprising a plurality of electric wires with terminals, the electric wire with terminal being the electric wire according to any one of claims 5 to 8, integrated together.

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