JP2022149384A - Coated conducting wire, electric wire with terminal, and wire harness - Google Patents

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 The present invention relates to coated conductors, terminal-equipped conductors, and wire harnesses used in, for example, automobiles.

2. Description of the Related Art Conventionally, in the fields of automobiles, OA equipment, home electric appliances, and the like, 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 advancing, and the number of various electric devices and control devices to be mounted on vehicles is increasing. Therefore, along with this, the number of electric wires with terminals used tends to increase.

In general, such a terminal-equipped electric wire is connected to a terminal and a covered conductor whose conductor is covered with an insulating resin in order to ensure insulation and protect the internal conductor. A coated conductor must have durability to the extent that the coated portion is not damaged when it is bent.

An electric wire with a terminal in which such a coated conductor and a terminal are connected is, for example, one end along the longitudinal direction is sealed, and a cross-sectional hollow cylindrical shape having a welded portion along the longitudinal direction There has been proposed an electric wire with a terminal in which a crimp terminal having a crimp portion formed in a gap and a covered conductor are crimped (Patent Document 1).

JP 2018-107149 A

In an electric wire with a terminal as disclosed in Patent Document 1, the coating is crimped together with the conductor. At this time, since the covering portion is compressed from the outer periphery, the covering portion is partially stretched due to the compression at the crimping portion with the terminal. If the coated conductor is bent with respect to the terminal in such a state, elongation due to compression and elongation due to bending are superimposed on the coated portion, and there is a risk that the coated portion will break.

In particular, as described in Patent Document 1, when a convex shape is formed along with welding on a part of the inner surface of the cylindrical crimping part, the amount of compression is localized in a part of the circumferential direction. A large part of For this reason, the conditions are more severe at the site than at the surroundings, and damage to the coated section is likely to occur. This phenomenon is explained as follows.

FIG. 10 is a diagram showing a stress-strain curve of a general vinyl chloride resin to which a plasticizer or the like is added. In general resins, strain increases substantially linearly as stress increases in the elastic region. The slope at this time is the Young's modulus. When the stress reaches the yield stress (X in the figure), plastic deformation begins and the strain increases at lower stresses. That is, a region where the stress is reduced (Z in the figure, hereinafter referred to as a stress reduced region) is generated. When the strain further increases, the stress increases and fracture occurs. The stress at this time is the breaking stress Y. Although the details will be described later, in this way, a stress-lowering portion where the stress drops once is usually formed between the yield stress X and the breaking stress Y.

In this way, if there is a stress drop portion where stress decreases when strain (elongation) increases, when the yield stress is exceeded, elongation will further increase with a small stress. For example, if there is a convex portion due to welding as described above, elongation due to compression is relatively large at that portion compared to the surrounding area. Therefore, if the coated conductor is bent with respect to the terminal in this state, the portion in question tends to expand with a smaller stress, so that the portion expands more locally than the surrounding area, and breakage is likely to occur. .

Such a phenomenon appears conspicuously in the presence of protrusions and the like due to welding on the inner surface of the terminal as described above, but it can also occur due to partial compression variations and the like even when there is no welding. If the covering portion is broken in this way, it becomes impossible to ensure insulation and water stoppage.

On the other hand, if the compressibility of the covering portion is increased (the amount of compression is reduced) and the elongation amount is reduced by compressing the covering portion, the adhesion between the covering portion and the crimping portion decreases, and the covering portion comes off. This results in a decrease in force and a decrease in the waterproofness of the crimped portion. Therefore, there is a demand for a coated conductor whose coated portion is less likely to break even if it is crimped at a compression ratio of a predetermined value or less.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to provide a coated conductive wire or the like that can suppress breakage of the coated portion even when the coated conductive wire is bent.

In order to achieve the above-mentioned object, a first invention is a coated conductive wire coated with a resin-made coating, wherein the stress-strain curve of the coating has a strain between the yield stress and the breaking stress. The covered conductor is characterized in that no stress-lowering portion is formed as the stress increases.

It is desirable that the yield stress of the covering portion is 30 MPa or more.

It is desirable that the Young's modulus of the covering portion is 3.5 MPa or more.

According to the first invention, in the stress-strain curve of the resin constituting the covering portion, since a clear stress-lowering portion is not formed between the yield stress and the breaking stress, when the covering conductor is bent with respect to the terminal, , local elongation as described above is less likely to occur, and breakage of the covering portion due to such elongation can be suppressed.

Moreover, if the yield stress is 30 MPa or more, it is possible to suppress excessive stretching of the coating during compression or the like.

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

A second invention is an electric wire with a terminal to which the coated conductor wire according to the first invention and a terminal are connected, wherein the terminal has a terminal body and a crimping part, and the crimping part has a A conductor crimping portion to be crimped and a covering crimping portion to which the covering portion is crimped, wherein the minimum thickness of the covering portion in the crimping portion is 50 times the thickness of the covering portion in a portion other than the crimping portion. % or less.

In a portion other than the crimping portion, it is preferable that the size of the conducting wire is 3 sq or less, and the thickness of the covering portion is 0.3 mm or less.

It is desirable that the compressibility of the covering portion in the covering crimping portion is 50% or less.

The crimping portion is formed into a substantially tubular shape by rolling the ends of a flat plate-shaped material so that they are butted together, and welding the butt portions to form a substantially tubular shape. may have been

According to the second invention, since the compressibility is 50% or less at the portion where the amount of compression is the largest, sufficient crimping can be performed. Furthermore, if the compressibility of the covering portion in the covering crimping portion is 50% or less, crimping can be performed more reliably. Even in this case, as described above, breakage of the coated portion when the coated conductor is bent with respect to the terminal can be suppressed.

Moreover, it is particularly effective when the size of the coated conductor is 3 sq or less and the thickness of the coated portion is 0.3 mm or less.

Moreover, if the crimped portion is cylindrical with one end sealed, the covering crimped portion can ensure waterproofness. In addition, since the welded portion is formed, there is a possibility that a convex portion will be formed on the inner surface of the crimping portion. It is possible to suppress breakage of the covering portion in.

A third aspect of the invention is a wire harness comprising a bundle of a plurality of wires with terminals according to the second aspect of the invention.

In the present invention, a plurality of electric wires with terminals can be bundled and used.

ADVANTAGE OF THE INVENTION According to this invention, the covered conductor etc. which can suppress the breakage of a covering part when bending a covered conductor can be provided.

The perspective view which shows the electric wire 10 with a terminal. Sectional drawing which shows the electric wire 10 with a terminal. (a) is a cross-sectional view taken along the line CC of FIG. 2, and (b) is an enlarged view of part D of (a). The figure which shows the stress-strain curve of the resin of a coating part. The figure which shows the terminal 1 and the coated conductor 23 before crimping. FIG. 4 is a cross-sectional view showing a state in which a crimping portion 5 is arranged between molds 31a and 31b, where (a) is a view before crimping, and (b) is a view after crimping. The figure which shows the stress-strain curve of each coating part used for the Example. (a), (b) is a figure which shows the bending test method of a coated conductor. The figure which shows the test method of the electric wire 10 with a terminal. The figure which shows the stress-strain curve of the resin of the conventional covering part.

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

The covered conducting wire 23 is configured by covering the conducting wire 25 with a covering portion 27 made of insulating resin. Conductor 25 is made of, for example, copper, a copper alloy, aluminum, or an aluminum alloy. When the covered conductor 23 is inserted into the crimping portion 5 of the terminal 1, the covering portion 27 of the tip of the covered conductor 23 is partially peeled off to expose the conductor 25. As shown in FIG. Details of the covering portion 27 will be described later.

A terminal 1 is made of, for example, copper, a copper alloy, aluminum, or an aluminum alloy, and comprises a terminal body 3 and a crimp portion 5 . The terminal main body 3 is formed by forming a plate-shaped material having a predetermined shape into a tubular body having a rectangular cross section. The terminal body 3 has an elastic contact piece 15 inside which is formed by folding a plate material into a rectangular cylindrical body. The terminal body 3 is connected by inserting a male terminal or the like from the front end portion. In the following description, an example in which the terminal body 3 is a female terminal that allows insertion of an insertion tab (not shown) of a male terminal or the like will be shown. is not particularly limited. For example, instead of the female terminal main body 3, for example, an insertion tab for a male terminal may be provided.

The crimping part 5 is a part to be crimped with the covered conductor, and includes a conductor crimping part 7 for crimping the conductor part exposed from the covering part on the tip side of the covered conductor, and a covering crimping part for crimping a part of the covering part of the covered conductor. Part 9. The conductor crimping portion 7 and the covering crimping portion 9 are integrally formed.

A portion of the inner surface of the conductor crimping portion 7 may be provided with serrations (not shown) in the circumferential direction. By forming the serrations in this way, when the conductive wire is crimped, the oxide film on the surface of the conductive wire can be easily destroyed, and the contact area with the conductive wire can be increased.

The crimping portion 5 is formed by rolling the ends of a flat material so that the ends thereof are butted against each other so as to form a cylindrical body having a circular cross section, and the butting portions are joined by welding or the like to be integrated, thereby forming the joint portion 21 . be. The coated conductor 23 is inserted from the rear end portion (on the side opposite to the terminal main body 3) of the crimping portion 5 formed in a cylindrical shape. A sealing portion 11 is provided at the front end portion (on the terminal main body 3 side) of the crimping portion 5 . That is, the crimping portion 5 has a substantially tubular shape with one side closed, and the rest of the portion is sealed except for the rear end portion into which the coated conductor is inserted. Note that the joint portion 21 and the sealing portion 11 are welded by, for example, laser welding.

3(a) is a cross-sectional view taken along the line CC of FIG. 2, and FIG. 3(b) is an enlarged view of a portion D of FIG. 3(a). As described above, the joint portion 21 is formed along the axial direction in the tubular covering pressure-bonding portion 9 . Since the joint portion 21 is joined by laser welding or the like, as shown in FIG. In this case, the covering portion 27 at the portion of the convex portion 22 is compressed more strongly than the surrounding covering portion 27 .

Next, the covering portion 27 in this embodiment will be described in detail. Since vinyl chloride resin is used for the covering portion of a general covered conductor, the case where vinyl chloride resin is used will be described below, but other resins are similarly applicable.

Vinyl chloride resin is originally a hard resin, but plasticizers are widely used as additives to make vinyl chloride resin flexible. The reason why the vinyl chloride resin is hard at room temperature is that the intermolecular force of the vinyl chloride polymer strongly attracts the molecules and shortens the distance between the molecules. Therefore, when a plasticizer is added, the plasticizer molecules intervene between the molecules of the vinyl chloride polymer, hindering the interaction between the polymer molecules. can be held. It is the function of the plasticizer to soften the PVC resin in this way, and the more the plasticizer is added, the softer it becomes, and this softening phenomenon is called plasticization.

On the other hand, in recent years, there has been a demand for smaller diameter electric wires for automobiles, and in some cases, coated conductor wires having a thinner coating portion and a smaller outer diameter are used. However, when a soft vinyl chloride polymer containing a large amount of plasticizer is used as the covering portion as described above, not only is the abrasion resistance lowered, but also the heat resistance, which has been highly demanded in recent years, is deteriorated. Therefore, it is necessary to reduce the amount of plasticizer or change to a plasticizer with high heat resistance (the plasticizing effect is reduced). However. In this way, the intermolecular interaction is reduced, so that the coating material becomes harder and wear resistance and heat resistance are improved, but there is a problem of embrittlement such as cracking at low temperatures.

On the other hand, in applications where improved impact resistance is required, vinyl chloride resin is often mixed with impact-resistant resins (reinforcing agents) having rubber properties, such as ABS, MBS, acrylic rubber, chlorinated polyethylene, and EVA. be. For example, by mixing 5 to 20 parts by mass of reinforcing agent with 100 parts by mass of vinyl chloride resin, practically sufficient impact strength can be imparted to vinyl chloride products. This reinforcing agent is dispersed as fine particles in the vinyl chloride resin, and when the product is impacted, the presence of these fine particles absorbs the impact energy and prevents damage to the product.

As a result of the inventors' intensive research, the present invention has found that, although different from the instantaneous impact resistance as described above, when bending stress is applied in an environment where it is used as an electric wire with a terminal, especially at low temperatures, In addition, we have found a combination of materials that has the effect of preventing breakage of the coating.

A description will be given below using a stress-strain curve. As shown in FIG. 10, when a tensile stress is applied to general polyvinyl chloride, loose molecular chains are extended, and the stress rises during the extension process. When the molecular chain is fully extended and reaches the limit (yield stress), the effect of the plasticizer present between the molecules increases the effect of slippage occurring between the molecules, and after passing the yield stress X, Once the stress drops (Z in the figure). The degree of reduction in stress at this time is determined by the type of plasticizer used, the amount added, and the molecular weight of polyvinyl chloride. In other words, if a plasticizer with a large plasticizing power or a large amount is added, the degree of reduction in this stress will be large. growing.

However, in the tubular covering pressure-bonding portion 9 as in the present embodiment, a predetermined or more pressing force is required between the covering pressure-bonding portion 9 and the covering portion 27 in order to secure the retaining force and the water stoppage. In this manner, a certain amount of compression is required in order to secure a predetermined or more pressing force against the covering portion 27 . However, if there is a stress drop as described above, the strain (elongation) will be greater for the same compressive force than if there is no stress drop. Moreover, the difference between the yield stress and the breaking stress becomes smaller due to the existence of the stress-reduced portion. Therefore, when a bending force is applied, the covering portion 27 may break. In particular, when the convex portion 22 is formed on the inner surface of the covering pressure-bonding portion 9 , the local compression increases the possibility of fracture at that portion compared with the surrounding area.

On the other hand, in the present invention, a resin having a stress-strain curve (characteristics) as shown in FIG. In addition, the tensile test for performing the stress-strain curve is performed, for example, at 0° C. and at a tensile speed of 25 mm/min.

As described above, this resin is elastically deformable up to the yield stress A, but even if the yield stress A is exceeded, there is no stress drop portion as seen in the stress-strain curve of the general resin described above. . That is, between the yield stress A and the breaking stress B, the stress increases as the strain increases.

In this resin, when it is further stretched beyond the yield stress A, the polyvinyl chloride matrix, which is the matrix, increases the stress due to the entanglement points between the molecules, but the impact resistance improvement that is dispersed in the vinyl chloride resin Tensile stress is transmitted to the rubber molecules of the agent, and when the rubber particles are stretched, the stress rises further in the stress-strain curve, ie, the so-called strain hardening property is enhanced. As a result, the stress-lowering portion is reduced, and the stress difference between the yield stress and the breaking stress (tensile strength) can be increased.

For example, when the electric wire 10 with a terminal is bent, the strongly compressed portion and the vicinity of the scratch of the covering portion 27 are first stretched. . Therefore, the stress is distributed to the surrounding covering portion 27 such as the highly compressed portion which is more likely to stretch, and as a result, breakage is less likely to occur. By optimally setting the strain hardening property in this way, breakage of the covering portion 27 can be suppressed.

As the plasticizer used for the coating portion 27 of the present embodiment, there are many types such as phthalic acid, adipic acid, phosphoric acid, fatty acid, trimellitic acid, epoxy, and polyester. Although 20 to 30 kinds of plasticizers are generally used, trimellitic acid-based, epoxy-based, and polyester-based plasticizers are preferably used from the viewpoint of heat resistance. In particular, trimellitic acid-based and polyester-based materials are more preferable for exhibiting strain hardening properties in the stress-strain curve in the tensile test.

For example, tri-normal octyl trimellitate (Kao Corporation product Trimex N-08), trimellitic acid 2-ethylhexyl ester (Kao Corporation Trimex T-08LP), trimellitic acid mixed linear alkyl ester (stock Company ADEKA product Adekaiser C-880), isononyl trimellitate (ADEKA product C-9N), dipentaerythritol ester (ADEKA product UL-6), pyromellitic acid 2-ethylhexyl ester (ADEKA company) product UL-80), pyromellitic acid mixed linear alkyl ester (ADEKA Co., Ltd. product UL-100), and the like.

The above preferred plasticizers may be used alone or in combination, and conventional phthalic acid-based, adipic acid-based, phosphoric acid-based, fatty acid-based, You may use it in combination with other plasticizers, such as.

As an impact modifier, a core-shell type impact modifier having a graft layer on the outside of particulate rubber is used as an impact modifier that is effective in expressing strain hardening in a stress-strain curve in combination with the above-mentioned preferred plasticizer. Among them, those having butadiene-based rubber or acrylic-based silicone/acrylic composite rubber in the core are preferable.

Examples of butadiene-based rubber (MBS) include METABLEN C-223A and C-215A manufactured by Mitsubishi Chemical Corporation, and Kaneace B-11A and B-22 manufactured by Kaneka Corporation. Examples of acrylic rubber-based rubbers include METABLEN W-300A and W-450A manufactured by Mitsubishi Chemical Corporation, Kaneace FM-21, FM-40, PA-20 and PA-40 manufactured by Kaneka Corporation. Examples of silicone-acrylic composite rubber include S-2001, S-2006, S-2501 and S-2030 manufactured by Mitsubishi Chemical Corporation.

The impact modifier is dispersed in particulate form when mixed into the vinyl chloride polymer. These particulate dispersed impact modifiers are 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 preferable impact modifiers may be used alone or in combination. As long as the expression of strain hardening is not deteriorated, other resistant materials such as chlorinated polyethylene, EVA, etc. having rubber properties may be used. An impact modifier may be used in combination.

As described above, in the stress-strain curve, stress must be transmitted to the rubber particles in order for strain hardening to occur. Since strain generation in the resin matrix due to tension is considerably slower than strain due to impact, the portion of the resin matrix with the lowest elastic modulus is intensively stretched. At that time, if the above preferred plasticizer is used and the amount added is suitably limited, the elastic modulus of the rubber particles is smaller than the elastic modulus of the resin matrix, so the tensile stress is applied to the rubber particles. to concentrate.

The maximum stress is applied to the rubber particles to which the stress is transmitted and they are stretched on the equator. At this time, fine cracks called crazes occur in the matrix resin near the rubber particles in the direction perpendicular to the stress direction. do. Unlike normal cracks, these cracks contain a large number of microvoids inside and expand in volume to absorb such stress, and at the same time develop strain hardening properties together with the resistance due to the presence of rubber particles.

The amount of the impact modifier added is, for example, 5 to 20 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of the vinyl chloride resin. If the amount is less than 5 parts by mass, the effect of developing strain hardening is small and the improvement in coating breakage is not sufficient. If the amount exceeds 20 parts by mass, the heat resistance decreases. A suitable amount of the plasticizer to be added is 15 to 35 parts by mass with respect to 100 parts by mass of the vinyl chloride resin. When the amount added is 15 parts by mass or less, the flexibility and cold resistance are lowered, and when it exceeds 35 parts by mass, the wear resistance and strain hardening development are lowered.

As described above, according to the present application, a resin having a stress-strain polar line as shown in FIG. 4 can be obtained by appropriately setting a combination of an appropriate plasticizer type and an impact resistance modifier and their compounding amounts. For this reason, it has excellent flexibility, cold resistance, wear resistance, and strain hardening, and especially against bending tensile stress at low temperatures, even if the terminal crimping part is damaged, the coated conductor with terminal does not easily break. can be obtained.

In the stress-strain curve of the covering portion 27 shown in FIG. 4, the fact that a stress-lowering portion is not formed due to an increase in strain between the yield stress A and the breaking stress B means that any It is not limited to the case where the amount of reduction in stress is 0 even at the site. As shown in FIG. 10, the effects of the present invention can be obtained unless the yield stress peaks. That is, the stress drop portion means a stress drop portion where the yield stress in the stress-strain curve becomes a peak shape, and the absence of a stress drop portion means that the yield stress A to the breaking stress It is assumed that there is no part where the stress is lower than the yield stress A by 1% or more during the period up to B.

Moreover, in order to suppress breakage of the covering portion 27, it is desirable that the yield stress A of the covering portion 27 is 30 MPa or more. Also, if the yield stress A is too high, the steel becomes too hard and becomes difficult to stretch, so the yield stress A is preferably 40 MPa or less. Moreover, considering the wear resistance of the covering portion 27, it is desirable that the Young's modulus of the covering portion 27 is 3.5 MPa or more.

Moreover, this embodiment is particularly effective when the coated conductor wire 23 has a small diameter and the thickness of the coated portion 27 is small. Therefore, it is particularly effective when the wire size of the coated wire 23 is 3 sq (meaning sq: mm ² ) or less, and the thickness of the coated portion 27 is 0.3 mm or less. The minimum thickness of the covering portion 27 is desirably 0.15 mm or more, for example.

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 coated wire 23 before crimping. As described above, the terminal 1 has the terminal body 3 and the crimp portion 5 . First, the covering portion 27 at the tip of the covered conductor 23 is peeled off to expose the conductor 25 at the tip.

Next, the covered conductor 23 whose tip is 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 covered conductor 23 is inserted into the crimping portion 5 , the exposed portion of the conductor 25 is positioned inside the conductor crimping portion 7 , and the covered portion 27 is positioned inside the covering crimping portion 9 . The inner diameter of the conductor crimping portion 7 is smaller than the inner diameter of the covering crimping portion 9 .

FIG. 6(a) is a cross-sectional view showing a die 31a, a die 31b, etc. before crimping for manufacturing the electric wire 10 with a terminal, and FIG. 6(b) is a cross-sectional view showing the crimping part 5 during crimping. be. The mold 31a and the mold 31b have substantially semi-cylindrical cavities extending in the longitudinal direction. The mold 31a also includes a large diameter portion 34 corresponding to the covering crimping portion 9 and having a diameter slightly smaller than the radius of the covering crimping portion 9, and a large diameter portion 34 corresponding to the conductor crimping portion 7 and having a diameter larger than that of the large diameter portion 34. and a small diameter portion 32 . That is, the large-diameter portion 34 and the small-diameter portion 32 are formed to have a substantially circular cross section when the terminal 1 is crimped at both the wire crimping portion 7 and the coating crimping portion 9 .

As shown in FIG. 6B, when the mold 31a and the mold 31b are engaged with each other to compress the crimping portion 5, the conductor crimping portion 7 is crimped to the conductor 25, and the covering crimping portion 9 is attached to the covering portion 27. crimped. The electric wire 10 with a terminal can be obtained by the above. Furthermore, it is possible to obtain a wire harness in which a plurality of electric wires with terminals are integrated, including the obtained electric wire with terminals 10 .

Here, the minimum thickness of the covering portion 27 in the crimping portion 5 is 50% or less of the thickness of the covering portion 27 in the portion other than the crimping portion 5 (that is, the thickness of the covering portion 27 of the covered conductor 23 before crimping). is desirable. For example, it is desirable that the thickness of the covering portion 27 after crimping is 50% or less of that before crimping at the portion of the convex portion 22 described above.

Further, if the cross-sectional area of the covering portion 27 before crimping is A0 and the cross-sectional area of the covering portion 27 in the crimping portion 9 after being crimped by the molds 31a and 31b is A1, the compression ratio = A1/A0 is It is desirable to make it 50% or less. Thus, this embodiment is particularly effective when the compression ratio is small (that is, strong compression).

As described above, according to the present embodiment, since the resin of the covering portion 27 is made of a resin that does not form a stress-lowering portion due to an increase in strain between the yield stress and the breaking stress in the stress-strain curve, pressure bonding is performed. At this time, strain hardening occurs in the covering portion 27, and resistance is provided so that it becomes more difficult to extend. Therefore, the stress is distributed to the surrounding covering portion 27 such as the highly compressed portion which is more likely to stretch, and breakage of the covering portion 27 can be suppressed.

Therefore, breakage of the covering portion 27 can be suppressed even when the compressibility of the covering pressure-bonding portion 9 is 50% or less. In addition, since it can be strongly compressed, it is possible to secure a high retention force and water stoppage.

Moreover, even when crimping is performed by the crimping portion 5 having the joint portion 21, breakage of the strongly compressed portion due to the convex portion 22 on the inner surface can be suppressed. Moreover, it is particularly effective when the diameter of the conductive wire is small and the thickness of the covering portion 27 is thin, or when the compressibility is small.

Moreover, if the yield stress of the covering portion 27 is 30 MPa or more, sufficient strength of the resin can be secured. Moreover, if the Young's modulus of the covering portion 27 is 3.5 MPa or more, the abrasion resistance is also excellent.

An electric wire with a terminal was experimentally manufactured using a covered conductor with a different material for the resin of the covering portion, and evaluated by conducting a bending test, an abrasion resistance test, and a water stopping test. FIG. 7 is a stress-strain curve of the resin subjected to the test. In the figure, E is Example 1, F is Example 2, G is Example 3, and H is Comparative Example. The stress-strain curve shown is the result of a tensile test performed at 0° C. and a rate of 25 mm/min. Table 1 shows the components and properties of each resin.

Each resin was used to form a covering portion with a thickness of 0.15 to 0.3 mm on an electric wire having a wire diameter of 1.5 sq to 2.5 sq to prepare a covered conductor wire. An electric wire with a terminal was produced by crimping the obtained coated conductor wire to a terminal. In addition, the covering compressibility at the covering crimping portion was set to 48%.

First, the bend test was evaluated. FIG. 8 is a diagram showing a bending test method using an electric wire with a terminal. As shown in FIG. 8(a), the electric wire 10 with a terminal is bent in the width direction (I direction in the drawing) by applying tension in the direction of 90°. Further, as shown in FIG. 8(b), tension is applied in the height direction (direction J in the drawing) of the terminal-equipped wire 10 in a direction of 90° and bent. The temperature was set at 0°C. Whether or not the covering portion 27 was broken when bent in each direction was visually confirmed. Table 2 shows the results.

From the results, in Examples 1 to 3 using a resin having no stress-lowering portion, breakage of the coated portion was not observed regardless of the size of the coated conductor wire. On the other hand, all of the conventional covered conductors with covered parts were broken except for wires with a small diameter (1.5 sq) and a thick covered part (0.25 mm or more).

Next, an abrasion resistance test was further conducted. In the abrasion resistance test, a reciprocating blade method conforming to ISO 6722 was used, and a load of 7 N was applied to the blade to reciprocate the coated conductor. The braid is a metal wire with a diameter of 0.45 mm. The number of reciprocating scrapes by the blade until the internal conductor was exposed was counted, and 750 or more reciprocating times were regarded as acceptable. Table 3 shows the results.

From the results, Examples 1 and 2 with a Young's modulus of 3.5 MPa or more passed the test. In other words, Examples 1 to 3 pass the bending resistance test alone, but Examples 1 and 2 pass when abrasion resistance is also taken into consideration.

Next, using Example 1 and Comparative Example 1, the water stoppage was evaluated by changing the compressibility. FIG. 9 is a diagram showing a water stopping test method. The waterproof evaluation is performed by inserting the terminal 1 crimped with the coated conductor 23 into a water tank 41 containing 3% salt water to a depth of 100 to 300 mm, inserting the end of the coated conductor 23 into the container 45, was set to a negative pressure of -30 kPa by the pump 47 and held for 1 minute. If salt water comes out from the opposite side of the terminal during the test, or if salt water seeps inside when the covering is opened after the test, it will be rejected. did. Table 4 shows the results.

As a result, when the coating compressibility was 48%, the waterproof test was passed. That is, in Example 1, by setting the compressibility to 50% or less, both the water stopping test and the bending test were passed.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical scope of the present invention is not influenced by the above-described embodiments. It is obvious that a person skilled in the art can conceive various modifications or modifications within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. be understood to belong to

Reference Signs List 1 Terminal 3 Terminal main body 5 Crimping portion 7 Lead wire crimping portion 9 Insulated crimping portion 10 Wire with terminal 11 Sealing portion 15 Elasticity Contact piece 21 Joint portion 22 Convex portion 23 Covered wire 25 Conduct wire 27 Covered portions 31a, 31b Mold 32 Small diameter portion 34 Large Diaphragm 41 Water tank 45 Container 47 Pump

Claims (8)

A coated conductive wire in which the conductive wire is coated with a resin-made coating,
A coated conductor, wherein a stress-strain curve of the coated portion does not include a stress-lowering portion that accompanies an increase in strain between a yield stress and a breaking stress. 2. The covered lead wire according to claim 1, wherein the covering portion has a yield stress of 30 MPa or more. 3. The coated lead wire according to claim 1, wherein the Young's modulus of the coated portion is 3.5 MPa or more. An electric wire with a terminal to which the coated conductor wire according to any one of claims 1 to 3 and a terminal are connected,
The terminal has a terminal body and a crimping portion,
The crimping section includes a conductor crimping section to which the conductor is crimped, and a covering crimping section to which the covering section is crimped,
An electric wire with a terminal, wherein the minimum thickness of the covering portion in the crimping portion is 50% or less of the thickness of the covering portion in a portion other than the crimping portion. 5. The electric wire with a terminal according to claim 4, wherein the size of the conducting wire is 3 sq or less, and the thickness of the covering portion is 0.3 mm or less in the portion other than the crimping portion. 6. The electric wire with a terminal according to claim 4, wherein the compressibility of the covering portion in the covering crimping portion is 50% or less. The crimping portion is formed into a substantially tubular shape by rolling the ends of a flat plate-shaped material so that they are butted together, and welding the butt portions to form a substantially tubular shape. The electric wire with a terminal according to any one of claims 4 to 6, characterized in that the terminal is provided. A wire harness in which a plurality of electric wires with terminals including the electric wire with terminals according to any one of claims 1 to 7 are integrated.

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