Tube material

Abstract

To provide an electric wire with a terminal capable of enhancing water cut-off performance of a resin coating part coating an electric connection part between a terminal fitting and an insulated wire without using a liquid adhesive.SOLUTION: A wire portion 6 in which a fitting 5 and an insulated wire 2 are electrically connected at an 6a of an electrical connecting portion, a tube material 7 covering an outer periphery of the insulating covering 4 at a portion along an axial direction of the insulated wire 2, and a portion including the 6a of the electrical connecting portion of the wire portion 6, and a resin cover portion 8 that is formed in contact with at least a portion of an outer circumferential surface of the tube material 7, wherein the tube material 7 is configured as a single-layer tubular member that contains a crosslinked polyolefin-based resin, and at least one of an acid-modified resin constituting 5 mass% or more and 40 mass% or less of a resin component, and a thermoplastic elastomer constituting 20 mass% or more and 40 mass% or less of the resin component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a terminal-attached electric wire. [Background technology]

[0002] Insulated electric wires installed in vehicles such as automobiles often have terminal fittings connected to the conductor at their ends. If an electrolyte liquid such as water comes into contact with the electrical connection between the terminal fitting and the electric wire conductor, electrical problems such as short circuits and corrosion of metal materials may occur. To prevent these electrical problems and corrosion, it is necessary to waterproof the electrical connection.

[0003] It is well known to cover electrical connections with a resin coating such as a molding material to seal the electrical connections. The resin coating is formed in an area extending from the electrical connection to a portion of the end of the insulated electric wire. However, if a gap is formed between the resin coating and the insulated electric wire, liquids such as water may penetrate through the gap, potentially causing electrical problems such as short circuits or corrosion of the metal material at the electrical connection. To prevent liquids from penetrating through such gaps, a method of interposing an adhesive layer between the insulated electric wire and the resin coating is sometimes used. For example, Patent Document 1 discloses a configuration in which an adhesive layer is formed on the surface of the insulating coating at the end of the insulated electric wire, and a waterproof resin portion (resin coating portion) is formed including the portion where the adhesive layer is formed. Alternatively, a tubing material such as a heat-shrinkable tube may be used instead of an adhesive. For example, Patent Document 2 discloses a configuration in which an adhesive tube is provided to cover the end of the insulating material of the insulated electric wire, and then a molded portion (resin coating portion) is formed including a region that covers a portion of the adhesive tube. The adhesive tube of Patent Document 2 is made of a thermoplastic resin having a cross-linked structure and has heat shrinkability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-187041 [Patent Document 2] Japanese Patent Application Publication No. 2019-091639 Summary of the Invention [Problem to be solved by the invention]

[0005] As disclosed in Patent Document 1, when a liquid adhesive is used to supplement the waterproofing properties of the resin coating, disadvantages can arise, such as variations in the thickness of the liquid adhesive and the long drying time required for the solvent contained in the liquid adhesive. Furthermore, a thick adhesive layer is required to accommodate the difference in thermal expansion between the insulating coating of the insulated wire and the resin coating, but forming a thick layer using a liquid adhesive is difficult. In contrast, as disclosed in Patent Document 2, by using a tubing material such as a heat-shrinkable tube instead of an adhesive, a layer with sufficient thickness and excellent thickness uniformity can be easily disposed between the resin coating and the insulated wire.

[0006] Patent Document 2 lists a synthetic resin containing a cross-linked thermoplastic resin, particularly a polyolefin resin such as cross-linked polyethylene or cross-linked polypropylene, as a constituent material of the adhesive tube. It is said that the outer surface of this adhesive tube can be adhered to the inner surface of the molded part to prevent liquid penetration. However, in automobiles and other applications, depending on the application of the terminal-attached electric wire and the location where the terminal-attached electric wire is routed, a particularly high level of watertightness may be required. Further investigation of the constituent materials of the adhesive tube beyond those described in Patent Document 2 may enable a higher level of watertightness to be achieved.

[0007] In view of the above, an object of the present invention is to provide an electric wire with a terminal that can improve the waterproofing properties of a resin coating that covers an electrical connection between a terminal fitting and an insulated electric wire without using a liquid adhesive. [Means for solving the problem]

[0008] The terminal-attached electric wire of the present disclosure comprises an electric wire portion in which a terminal fitting and an insulated electric wire having an insulating coating covering the outer periphery of a conductor are electrically connected at an electrical connection portion; a tube material covering the outer periphery of the insulating coating at a portion along the axial direction of the insulated electric wire; and a resin coating portion covering the portion of the electric wire portion including the electrical connection portion and formed in contact with at least a portion of the outer periphery of the tube material, wherein the tube material is configured as a single-layer tubular member containing a cross-linked polyolefin resin and at least one of an acid-modified resin in an amount of 5% by mass to 40% by mass of the resin component and a thermoplastic elastomer in an amount of 20% by mass to 40% by mass of the resin component. [Effects of the Invention]

[0009] The electric wire with terminal according to the present disclosure is an electric wire with terminal that can improve the waterproofing properties of the resin coating that covers the electrical connection between the terminal fitting and the insulated electric wire without using a liquid adhesive. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective side view showing a terminal-attached electric wire according to one embodiment of the present disclosure, in which a tube material is indicated by a dashed line. [Figure 2] FIG. 2 is a partial cross-sectional view of the terminal-attached electric wire, showing the tube material and the resin coating portion cut away. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Description of the embodiments of the present disclosure] First, an embodiment of the present disclosure will be described. (1) The terminal-attached electric wire of the present disclosure comprises an electric wire portion in which a terminal fitting and an insulated electric wire having an outer periphery of a conductor covered with an insulating coating are electrically connected at an electrical connection portion; a tube material covering the outer periphery of the insulating coating at a portion along the axial direction of the insulated electric wire; and a resin coating portion covering a portion of the electric wire portion including the electrical connection portion and formed in contact with at least a portion of the outer periphery of the tube material, wherein the tube material is configured as a single-layer tubular member containing a cross-linked polyolefin resin and at least one of an acid-modified resin in an amount of 5% by mass to 40% by mass of the resin component and a thermoplastic elastomer in an amount of 20% by mass to 40% by mass of the resin component.

[0012] In the above-described electric wire with terminal, a tube material is interposed between the insulated electric wire and a resin coating portion that covers the electrical connection portion between the terminal fitting and the insulated electric wire. The tube material contains, in addition to a cross-linked polyolefin resin, the predetermined amount of at least one of the acid-modified resin and the thermoplastic elastomer, thereby exhibiting high adhesion to the insulating coating and the resin coating portion. Therefore, the resin coating portion is firmly bonded to the insulated electric wire via the tube material, making it less likely that liquids such as water will penetrate between the resin coating portion and the insulated electric wire. As a result, the tube material effectively improves the water-stopping properties provided by the resin coating portion in the electric wire with terminal. The tube material also has excellent manufacturability.

[0013] (2) In the above aspect (1), the tube material may contain both the acid-modified resin and the thermoplastic elastomer, which enhances adhesion between the tube material and the insulating coating and resin-coated portion, thereby enhancing the water-stopping effect.

[0014] (3) In the above-mentioned (1) or (2), the thermoplastic elastomer and the resin material constituting the resin coating may have the same type of skeleton, which will particularly enhance the adhesion of the tube material to the resin coating and provide a significant improvement in watertightness.

[0015] (4) In any one of the above aspects (1) to (3), the thermoplastic elastomer may include at least one of a polyester-based elastomer and a polyamide-based elastomer. This allows the tube material to exhibit high adhesion to the insulating coating and the resin coating portion. Polyester-based resins and polyamide-based resins are often used as constituent materials for molding materials provided on terminal-attached electric wires. When the resin coating portion is configured as a molding material made of such a resin material, if the tube material contains the above-mentioned elastomer, the tube material will exhibit particularly high adhesion to the molding material, effectively preventing liquid from penetrating between the resin coating portion and the insulated electric wire.

[0016] (5) In any one of the above aspects (1) to (4), the acid-modified resin may include an acid-modified polyolefin resin, which makes it easier to form a tube material that exhibits high adhesion to the insulating coating and the resin-coated portion together with the cross-linked polyolefin resin.

[0017] (6) In any one of the above aspects (1) to (5), the resin coating may cover the entire outer circumferential surface of the tubing. This means that the entire tubing is located between the resin coating and the insulated wire, which can contribute to improving adhesion between the resin coating and the insulated wire.

[0018] [Details of the embodiments of the present disclosure] Hereinafter, a terminal-attached electric wire according to an embodiment of the present disclosure will be described in detail with reference to the drawings. Hereinafter, various properties are values ​​measured at room temperature in the atmosphere unless otherwise specified.

[0019] <Overall composition> First, the overall configuration of an electric wire with terminal 1 according to one embodiment of the present disclosure will be described with reference to Figures 1 and 2. The electric wire with terminal 1 has an electric wire portion 6, a tube member 7, and a resin coating portion 8. Figure 1 shows the electric wire with terminal 1 in a perspective side view. Here, the tube member 7 is indicated by a dashed line. Figure 2 shows the electric wire with terminal 1 in a partial cross-sectional view in which only the tube member 7 and the resin coating portion 8 are cut away.

[0020] In the electric wire portion 6, an insulated electric wire 2 having a conductor 3 covered with an insulating covering 4 is electrically connected to a terminal fitting 5 at an electrical connection portion 6a. The terminal fitting 5 has a terminal connection portion 51 and a barrel portion formed integrally and extending from the rear end side of the terminal connection portion 51 and consisting of a first barrel portion 52 and a second barrel portion 53. The terminal connection portion 51 is configured as a bolt-fastened connection portion and can be electrically connected to a mating conductive member using a bolt inserted into a bolt insertion hole 51a.

[0021] At the electrical connection portion 6a, the insulating coating 4 at the end of the insulated wire 2 is removed, exposing the conductor 3. This end of the insulated wire 2 with the exposed conductor 3 is crimped and fixed to one side (the upper side in FIGS. 1 and 2 ) of the barrel portions 52, 53 of the terminal fitting 5, thereby connecting the insulated wire 2 to the terminal fitting 5. Specifically, the first barrel portion 52 electrically connects the conductor 3 to the terminal fitting 5 and physically fixes the conductor 3 to the terminal fitting 5. Meanwhile, the second barrel portion 53 fixes the insulated wire 2 behind the first barrel portion 52, thereby assisting in physically fixing the insulated wire 2 to the terminal fitting 5. In this specification, along the axial direction (longitudinal direction) of the terminal-attached electric wire 1, the side where the terminal fitting 5 is arranged is referred to as the front, and the side where the insulated wire 2 is arranged is referred to as the rear.

[0022] The tube material 7 is configured as a single-layer tubular member made of a predetermined material, which will be described later. The tube material 7 covers the outer periphery of the insulating coating 4 at some locations along the axial direction of the insulated wire 2. In the illustrated embodiment, the tube material 7 covers the entire periphery of the region near the end of the insulated wire 2.

[0023] The resin coating portion 8 is configured as a coating layer made of a resin material such as a molding material, and coats a portion of the electric wire portion 6, including the electrical connection portion 6a. The resin coating portion 8 is in contact with at least a portion of the outer circumferential surface of the tube material 7. In the illustrated embodiment, the resin coating portion 8 coats the entire outer circumferential surface of the tube material 7. The resin coating portion 8 is formed along the axial direction of the terminal-attached electric wire 1, from a position forward of the tip 3a of the conductor 3 exposed at the end of the insulated electric wire 2 to a position rearward of the tip of the insulating coating 4 of the insulated electric wire 2, and coats the entire electrical connection portion 6a and a portion of the area where the insulating coating 4 of the insulated electric wire 2 remains, over the entire circumference. The area where the resin coating portion 8 coats the insulating coating 4 of the insulated electric wire 2 also includes the area where the tube material 7 is provided.

[0024] In this way, the tube material 7 is disposed so as to cover the outer periphery of the insulating coating 4 of the insulated wire 2, and the outer periphery of the tube material 7 is further covered by the resin coating portion 8. The tube material 7 is composed of a single layer of material, and no other material, such as an adhesive, is interposed between the tube material 7 and the insulating coating 4 or between the tube material 7 and the resin coating portion 8. The inner periphery of the tube material 7 is adhered to the surface of the insulating coating 4, and the outer periphery is adhered to the inner periphery of the resin coating portion 8. Here, the adhesion of the inner and outer surfaces of the tube material 7 to the insulating coating 4 and the resin coating portion 8 occurs by welding (fusion). In other words, the material constituting the single layer of tube material 7 melts and then re-solidifies on the inner and outer periphery and in the depth regions nearby, thereby adhering to the insulating coating 4 and the resin coating portion 8, respectively, over the entire circumference.

[0025] In the electric wire with terminal 1 according to this embodiment, the entire electrical connection portion 6a of the electric wire portion 6 is covered with a resin coating 8. Therefore, the resin coating 8 protects the electrical connection portion 6a from contact with liquids such as water. Furthermore, a tube material 7 is interposed between the resin coating 8 and the insulated electric wire 2, and the tube material 7 is bonded to both the resin coating 8 and the insulated electric wire 2. Therefore, the resin coating 8 is tightly adhered to the outer periphery of the insulating coating 4 via the tube material 7, and the presence of the tube material 7 prevents liquids such as water from penetrating between the resin coating 8 and the insulating coating 4 and into the electrical connection portion 6a. In other words, the tube material 7 serves to improve the watertightness of the electric wire with terminal 1. In particular, since the tube material 7 is made of a specific material described below, it exhibits excellent adhesion to the insulating coating 4 and the resin coating 8, and is highly effective in improving watertightness. The resin coating 8 and the tube material 7 prevent electrolytes such as water from penetrating into the electrical connection 6a, making electrical problems such as short circuits and corrosion of metal materials less likely to occur at the electrical connection 6a.

[0026] <Configuration of each part> Specific configurations of the electric wire portion 6, the resin coating portion 8, and the tube material 7 that constitute the electric wire with terminal 1 will be described below in order.

[0027] (Electrical Wire Section) As described above, the electric wire portion 6 has a structure in which the terminal fitting 5 is connected to the end portion of the insulated electric wire 2 via the electrical connection portion 6a.

[0028] The conductor 3 constituting the insulated wire 2 may be made of a single metal wire, but is preferably made of a stranded wire in which multiple wires are twisted together. In this case, the stranded wire may be made of one type of metal wire, or two or more types of metal wire. Examples of materials for the metal wires constituting the conductor 3 include copper, copper alloys, aluminum, aluminum alloys, and these materials plated with various platings.

[0029] Examples of materials for the insulating coating 4 constituting the insulated wire 2 include rubber, polyolefin resins such as polyethylene (PE) and polypropylene (PP), halogen-based polymers such as polyvinyl chloride (PVC), and thermoplastic elastomers. These may be used alone or in combination of two or more. The resin material may be crosslinked. Various additives may be added to the constituent materials of the insulating coating 4 as appropriate. Examples of additives include flame retardants, fillers, and colorants.

[0030] Examples of materials (base materials) for the terminal fitting 5 include commonly used brass, various copper alloys, copper, etc. A part of the surface (e.g., the contact points) or the entire surface of the terminal fitting 5 may be plated with various metals such as tin, nickel, gold, or alloys containing these.

[0031] As described above, the conductor 3 and the terminal fitting 5 may be made of any metal material, but when dissimilar metals are in contact at the electrical connection 6a, such as when the terminal fitting 5 is made of a common terminal material in which a base material made of copper or a copper alloy is tin-plated, and the conductor 3 includes a wire made of aluminum or an aluminum alloy, corrosion is particularly likely to occur at the electrical connection 6a due to contact with electrolytes such as moisture. However, in the terminal-attached wire 1 according to this embodiment, the resin coating 8 covers the electrical connection 6a, and a tube material 7 is interposed between the resin coating 8 and the insulated wire 2, providing a waterproof structure, thereby suppressing corrosion such as bimetallic corrosion.

[0032] (Resin coated part) As described above, the resin coating 8 covers the electrical connection 6a between the terminal fitting 5 and the conductor 3, thereby preventing the intrusion of liquids such as water into the electrical connection 6a from the outside. As shown in Figures 1 and 2, the resin coating 8 contacts the surface of the terminal fitting 5 at its front side and contacts the insulating coating 4 of the insulated wire 2 and the tube material 7 at its rear side, thereby covering the entire area of ​​the electrical connection 6a.

[0033] The specific range of the resin coating 8 is not particularly specified, as long as it covers the entire electrical connection portion 6a along the axial direction of the electric wire portion 6 and is positioned in contact with at least a portion of the outer circumferential surface of the tube material 7. That is, the resin coating 8 may cover only a portion of the outer circumferential surface of the front side of the tube material 7 along the front-rear direction, or it may cover the entire outer circumferential surface of the tube material 7 along the front-rear direction. However, as in the illustrated embodiment, it is preferable that the resin coating 8 cover the entire outer circumferential surface of the tube material 7 along both the front-rear direction and the circumferential direction. In this case, the tube material 7 contacts and is bonded to the resin coating 8 over the entire outer circumferential surface, thereby enhancing adhesion between the resin coating 8 and the insulated electric wire 2 and effectively preventing liquid from penetrating between them.

[0034] The material constituting the resin coating portion 8 is not particularly limited, and various resin materials can be used, but polyester resins such as polybutylene terephthalate (PBT) and polyamide resins such as aromatic nylon are preferably used. These resins can firmly prevent the penetration of liquids such as water and exhibit high mechanical strength. The resin material constituting the resin coating portion 8 may be a single type or a mixture of two or more types. Various additives may be added to the material constituting the resin coating portion 8 as appropriate. Examples of additives include flame retardants, fillers, and colorants.

[0035] The resin coating portion 8 made of polyester-based resin or polyamide-based resin exhibits high adhesiveness to the surfaces of metal materials such as the terminal fitting 5 and the wire conductor 3. Therefore, in the electrical connection portion 6a, the resin coating portion 8 directly adheres to the surfaces of these metal materials, thereby firmly preventing the intrusion of liquid from outside. On the other hand, the resin coating portion 8 made of these resins often does not exhibit high adhesiveness to the insulating coating 4 made of polyolefin, PVC, or the like. However, in the terminal-attached electric wire 1 according to this embodiment, a tube material 7 that exhibits adhesiveness to both the insulating coating 4 and the resin coating portion 8 is interposed between the insulating coating 4 and the resin coating portion 8 in the rear portion of the resin coating portion 8, and the insulating coating 4 and the resin coating portion 8 are mutually adhered via the tube material 7.

[0036] The resin coating portion 8 may be disposed at a predetermined position by any method, such as applying or molding a molten resin. However, it is preferable to form the resin coating portion 8 as a molding material formed by molding a molten resin. A resin coating portion 8 containing a polyester-based resin or a polyamide-based resin can be suitably formed as a molding material.

[0037] (tube material) The tube material 7 is configured as an insulating resin member that is pre-formed into a cylindrical shape before being placed around the insulated wire 2. The tube material 7 is configured as a single-layer cylindrical member, and does not include any layers other than the cylindrical member, such as a layer of liquid adhesive, on the inner and outer peripheral surfaces.

[0038] The constituent material of the tube material 7 includes a cross-linked polyolefin resin and at least one of an acid-modified resin and a thermoplastic elastomer. Preferably, the tube material 7 includes at least an acid-modified resin in addition to the cross-linked polyolefin resin. More preferably, the tube material 7 includes both an acid-modified resin and a thermoplastic elastomer in addition to the cross-linked polyolefin resin. As described above, the tube material 7 is composed of a single layer, and the resins are uniformly mixed and molded.

[0039] Crosslinked polyolefin resins are those in which a crosslinked structure is formed between the polymer chains of polyolefin resins. Examples of polyolefin resins constituting crosslinked polyolefin resins include homopolyolefins such as polyethylene (PE) and polypropylene (PP), block polyolefins such as ethylene-propylene copolymers, and ethylene copolymers. In particular, it is preferable to use polyolefins such as PE. As the polyolefin resin, only one type may be used, or two or more types may be mixed and used. Unlike the acid-modified resin described below, polyolefin resins are not acid-modified. Crosslinked polyolefin resins exhibit a certain degree of adhesion to the insulating coating 4 and the resin coating portion 8 by welding.

[0040] The crosslinking of the polyolefin resin is preferably carried out by irradiation with ionizing radiation, particularly electron beams. However, crosslinking methods other than crosslinking by ionizing radiation, such as silane crosslinking, may also be used. Note that in the tube material 7, crosslinking may be carried out on a mixture of the polyolefin resin described above and an acid-modified resin and / or a thermoplastic elastomer.

[0041] By including a cross-linked polyolefin resin in the tube material 7, the tube material 7 can be configured as a heat-shrinkable tube. That is, a resin composition containing an olefin resin is extruded into a small-diameter tube, cross-linked by electron beam irradiation or the like, and then the small-diameter tube is heated and expanded in diameter, thereby imparting heat-shrinkability to the tube material 7. By placing the tube material 7 configured as a heat-shrinkable tube at a predetermined position on the insulated wire 2 and heating it to shrink, the tube material 7 can be positioned in close contact with the outer peripheral surface of the insulated wire 2. During this heating process, the inner peripheral surface of the tube material 7 can be simultaneously welded to the surface of the insulating coating 4.

[0042] The content of the cross-linked polyolefin resin in the tube material 7 is not particularly limited. However, from the viewpoint of ensuring the manufacturability of the tube material 7, it is preferable that the cross-linked polyolefin resin be the main component of the resin components constituting the tube material 7. In other words, it is preferable that the cross-linked polyolefin resin account for 50% by mass or more of the resin components constituting the tube material 7. In particular, it is preferable that the cross-linked polyolefin resin account for 60% by mass or more and 95% by mass or less of the resin components constituting the tube material 7. Furthermore, it is preferable that the cross-linked polyolefin resin account for the remainder of the resin components constituting the tube material 7, excluding the acid-modified resin and the thermoplastic elastomer. Note that in this specification, the content of each component constituting the tube material 7, expressed in units of mass%, refers to the amount of that component in the resin components (polymer components) of the materials constituting the tube material 7.

[0043] As described above, the material constituting the tube material 7 preferably contains an acid-modified resin. The type of resin constituting the acid-modified resin is not particularly limited, and polyolefin-based resins or other thermoplastic resins can be suitably used. Examples of polyolefin-based resins include homopolyolefins such as polyethylene (PE) and polypropylene (PP), block polyolefins such as ethylene-propylene copolymers, and ethylene-based copolymers. Examples of thermoplastic resins other than polyolefin-based resins include styrene-based resins such as styrene-ethylene-butylene-styrene block copolymers (SEBS). In particular, polyolefins such as PP are preferred from the viewpoint of compatibility with crosslinked polyolefin-based resins. The acid-modified resins may be used alone or in combination of two or more.

[0044] The constituent material of the tube material 7 contains an acid-modified resin in addition to a cross-linked polyolefin resin, which increases the adhesion of the tube material 7 to the insulating coating 4 and the resin coating portion 8. In particular, when the resin coating portion 8 contains a polar structure such as a polyester resin or a polyamide resin, the interaction between the polar structure and the acid-modified portion of the acid-modified resin causes the tube material 7 to exhibit high adhesion to the resin coating portion 8.

[0045] The content of the acid-modified resin in the constituent material of the tube material 7 is preferably 5% by mass or more, from the viewpoint of obtaining a sufficient adhesiveness-improving effect. It is further preferable that it be 10% by mass or more, or even 20% by mass or more. On the other hand, if the content of the acid-modified resin is too high, the constituent material of the tube material 7 becomes brittle, and damage such as tearing may occur during manufacturing processes such as extrusion molding and diameter expansion, making it difficult to manufacture the tube material 7. From the viewpoint of ensuring the manufacturability of the tube material 7, it is preferable that the content of the acid-modified resin be limited to 40% by mass or less, or even 30% by mass or less.

[0046] Furthermore, the constituent material of the tube material 7 may contain a thermoplastic elastomer in addition to or instead of the acid-modified resin. The thermoplastic elastomer is not particularly limited to a specific type as long as it is an elastomer, that is, a polymer type having hard and soft segments. The soft segments contained in the thermoplastic elastomer mainly contribute to improving the adhesion of the tube material 7 to the insulating coating 4 and the resin coating portion 8. Unlike the acid-modified resin, the thermoplastic elastomer is not acid-modified.

[0047] In particular, it is preferable that the thermoplastic elastomer contains at least one of a polyester-based elastomer whose hard segments are composed of polyester units and a polyamide-based elastomer whose hard segments are composed of polyamide units. These thermoplastic elastomers are highly effective in improving the adhesion of the tube material 7. In particular, it is preferable that the thermoplastic elastomer has the same skeleton as the resin material constituting the resin coating portion 8. For example, when the resin coating portion 8 contains a polyester-based resin such as PBT, a polyester-based elastomer can be used for the tube material 7. Also, when the resin coating portion 8 contains a polyamide-based resin such as aromatic nylon, a polyamide-based elastomer can be used for the tube material 7. In this way, when the thermoplastic elastomer contained in the tube material 7 and the resin material constituting the resin coating portion 8 have the same skeleton, the adhesion of the tube material 7 to the resin coating portion 8 can be particularly effectively improved.

[0048] The content of the thermoplastic elastomer in the constituent material of the tube material 7 is preferably 20% by mass or more from the viewpoint of obtaining a sufficient effect of improving adhesiveness, and more preferably 30% by mass or more. On the other hand, from the viewpoint of ensuring the manufacturability of the tube material 7, the content of the thermoplastic elastomer is preferably kept to 40% by mass or less.

[0049] Both the acid-modified resin and the thermoplastic elastomer are effective in improving the adhesion of the tube material 7 to the insulating coating 4 and the resin-coated portion 8, particularly to the resin-coated portion 8. The inclusion of at least one of these in the materials constituting the tube material 7 provides the effect of improving adhesion. However, the inclusion of at least the acid-modified resin is preferable because even a relatively small amount can be highly effective in improving the adhesion of the tube material 7. Furthermore, it is most preferable for the tube material 7 to contain both the acid-modified resin and the thermoplastic elastomer. In this case, the contributions of both the acid-modified resin and the thermoplastic elastomer are particularly effective in improving the adhesion of the tube material 7. It is particularly preferable for the total content of the acid-modified resin and the thermoplastic resin in the materials constituting the tube material 7 to be 30% by mass or more and 45% by mass or less.

[0050] The constituent material of the tube material 7 may contain polymer components other than the cross-linked polyolefin resin, acid-modified resin, and thermoplastic elastomer resins described above. However, it is preferable to keep the content lower than that of each resin so as not to impair the properties of those resins. Preferably, the polymer material constituting the tube material 7 does not contain any polymer components other than the cross-linked polyolefin resin, acid-modified resin, and thermoplastic elastomer. Furthermore, the constituent material of the tube material 7 may contain additives in addition to the polymer material. Examples of additives include flame retardants, fillers, and colorants.

[0051] The thickness of the tube material 7 is not particularly limited, but from the viewpoint of enhancing the effect of improving watertightness and from the viewpoint of sufficiently following the difference in thermal expansion between the insulating coating 4 and the resin coating portion 8, it is preferable to make it 50 μm or more, or even 100 μm or more. On the other hand, from the viewpoint of preventing the watertight portion of the terminal-attached electric wire 1 from becoming excessively large, it is preferable to keep the thickness of the tube material 7 to 2 mm or less, or even 1 mm or less. Note that the thickness described here refers to the thickness after the tube material has been heat-shrunk.

[0052] As described above, in the terminal-attached electric wire 1 according to this embodiment, the tube material 7 is disposed between the resin coating 8, which covers the region including the electrical connection portion 6a, and the insulating coating 4 of the insulated wire 2. The tube material 7 exhibits adhesive properties to the insulating coating 4 and the resin coating 8. Therefore, the resin coating 8 is bonded to the insulated wire 2 via the tube material 7. The tube material 7 contains at least one of an acid-modified resin and a thermoplastic elastomer in addition to a cross-linked polyolefin resin, thereby improving the adhesive properties of the tube material 7, and exhibiting particularly high adhesive properties to the resin coating 8. The high adhesive properties of the tube material 7 prevent liquids such as water from penetrating between the resin coating 8 and the insulating coating 4 toward the electrical connection portion 6a. Protecting the electrical connection portion 6a from contact with electrolytes such as water prevents electrical problems such as short circuits and corrosion of metal materials in the electrical connection portion 6a, thereby maintaining a good electrical connection in the electrical connection portion 6a for a long period of time. Because the tube material 7 is configured as a single-layer tubular member with high adhesiveness, it is not necessary to use a liquid adhesive to improve watertightness. Unlike liquid adhesives, the use of the tube material 7 makes it easy to uniformly apply a sufficient thickness of resin material to a predetermined location on the terminal-attached electric wire 1.

[0053] Furthermore, as described above, in the tube material 7, from the viewpoint of ensuring manufacturability in the manufacturing process involving extrusion molding and diameter expansion, it is preferable that the contents of the acid-modified resin and the thermoplastic elastomer are each limited to 40 mass% or less. The breaking elongation of the constituent material of the tube material 7 can be used as an indicator of the manufacturability of the tube material 7. Specifically, the constituent material of the tube material 7 preferably has a breaking elongation of 150% or more, and even 300% or more. The breaking elongation can be evaluated by a tensile test in accordance with JIS K 7161.

[0054] <Method of manufacturing terminal-attached electric wire> Finally, a method for manufacturing the terminal-attached electric wire 1 according to this embodiment will be described. First, a method for manufacturing the tube material 7 will be described. To manufacture the tube material 7, a resin composition is first prepared by kneading at least one of a polyolefin resin, an acid-modified resin, and a thermoplastic resin, and, if necessary, various additives. The resin composition is then extruded into a cylindrical shape. The resulting cylindrical body is crosslinked by electron beam irradiation or the like to obtain the tube material 7. When the tube material 7 is configured as a heat-shrinkable tube, it is extruded to a small diameter, crosslinked by electron beam irradiation or the like, expanded while heated, and then cooled. This allows the shape before expansion to be memorized, and the tube material 7 acquires heat-shrinkability. The inner diameter of the heat-shrinkable tube is set smaller than the outer diameter of the insulated electric wire 2 before expansion, and expanded to a larger diameter than the outer diameter of the insulated electric wire 2 by expansion.

[0055] When manufacturing the electric wire with terminal 1, the electric wire portion 6 is first manufactured. That is, the barrel portions 52, 53 of the terminal fitting 5 are crimped and fixed to the end of the insulated electric wire 2 from which the insulating coating 4 has been stripped. This results in a structure in which the electric wire conductor 3 and the terminal fitting 5 are connected at the electrical connection portion 6a. Note that, depending on the specific configuration of the terminal fitting 5, the electric wire conductor 3 and the terminal fitting 5 may be connected by ultrasonic welding, soldering, or the like instead of crimping. In either case, before or after fixing the terminal fitting 5 to the insulated electric wire 2, the insulated electric wire 2 is inserted into the hollow portion of a tube material 7 cut to the required length, thereby arranging the tube material 7 around the outer periphery of the insulated electric wire 2.

[0056] Next, the tube material 7 is heated while being positioned at a predetermined position near the end of the insulated wire 2. The heating causes the tube material 7, which is configured as a heat-shrinkable tube, to shrink and come into close contact with the outer periphery of the insulated wire 2. At the same time, the heating causes the constituent material of the inner periphery of the tube material 7 to weld to the insulating coating 4, thereby bonding the tube material 7 to the insulating coating 4. The tube material 7 can be heated by ultrasonic welding, vibration welding, high-frequency welding, laser welding, infrared welding, friction welding, hot plate welding, hot air welding, or the like.

[0057] Furthermore, the wire portion 6 with the attached tube material 7 is coated at predetermined locations, including the electrical connection portion 6a, to form the resin coating portion 8. The resin coating portion 8 can be formed by depositing a molten resin material at a predetermined location and solidifying it. The resin material can be deposited by molding. Specifically, a mold having a cavity corresponding to the shape of the resin coating portion 8 to be formed is filled with the wire portion 6, including the electrical connection portion 6a and the portion where the tube material 7 is attached, and then the molten resin material is injected into the mold. The resin coating portion 8 configured as a molding material is obtained by solidifying the resin material. When the resin coating portion 8 is formed, the high-temperature molten resin comes into contact with the outer peripheral surface of the tube material 7. This heat causes the constituent material of the outer peripheral surface of the tube material 7 to fuse to the inner peripheral surface of the resin coating portion 8, thereby adhering the tube material 7 to the resin coating portion 8. [Example]

[0058] Examples are shown below. In these examples, the waterproofing properties of the terminal-attached electric wire were evaluated while changing the constituent materials of the tube material. However, the present invention is not limited to these examples. In these examples, the evaluation of properties was carried out at room temperature in the atmosphere.

[0059] [Sample preparation] For each of Samples A1 to A27 and B1 to B9, heat-shrinkable tubing materials containing the components listed in Tables 1 to 3 were prepared. To prepare the tubing, a resin composition containing the components listed in Tables 1 to 3 was extruded into a small-diameter tube, crosslinked by electron beam irradiation, and then expanded while heated. After expansion, the heat-shrinkable tubing had an outer diameter of 6.4 mm and a wall thickness of 0.5 mm. For samples using non-crosslinked PE as the Group a material, the resin composition was directly extruded to the above dimensions without electron beam irradiation. For samples using silane-crosslinked PE, the resin composition was extruded to the above dimensions and then silane-crosslinked. Electron-beam crosslinked PE1 and electron-beam crosslinked PE2 are both electron-beam crosslinked polyethylenes, but their crosslinking degrees are different, with electron-beam crosslinked PE2 having a lower degree of crosslinking.

[0060] An insulated wire was prepared by forming an insulating coating made of cross-linked polyethylene resin around a conductor made of stranded copper alloy wire. The outer diameter of the insulated wire was 5.3 mm. The insulating coating was removed from the end of the insulated wire to expose the wire conductor, and a male crimp terminal made of tin-plated brass, commonly used in automobiles, was crimped and fixed to the end of the wire to obtain an electric wire part. Furthermore, a 10 mm long tube material was placed around the outer periphery of the insulated wire near the end.

[0061] Next, the sample was placed in a thermostatic chamber to heat the tubing. If the tubing was heat-shrinkable, it underwent thermal shrinkage and adhered tightly to the outer periphery of the insulated wire. After thermal shrinkage, the wall thickness of the tubing was 0.6 mm.

[0062] Finally, a resin coating was formed by molding. PBT or nylon 6T (PA6T) was used as the material for the resin coating. As shown in Figures 1 and 2, the resin coating was formed to cover the entire electrical connection between the insulated wire and the terminal fitting, as well as the entire outer surface of the tube material.

[0063] [Characteristics evaluation] (1) Water-repellent The watertightness of the terminal-attached electric wires fabricated using the various tubing materials described above was evaluated by an air leak test. Specifically, the entire resin-coated portion of the terminal-attached electric wire was immersed in water, and a predetermined air pressure was applied to the end of the wire not connected to the terminal. The occurrence of air leakage was confirmed by whether or not air bubbles were visible at the interface between the wire coating and the resin coating during the application of air pressure. This test was performed while varying the applied air pressure, and the watertightness was evaluated based on the upper limit of the air pressure at which no air leakage occurred.

[0064] The waterproofing property was evaluated according to the following criteria. Very high water resistance (A+): When the upper air pressure is 200 kPa or more High water resistance (A): When the upper air pressure is between 100kPa and 200kPa Poor watertightness (B): When the upper air pressure is between 50kPa and 100kPa Very poor watertightness (B-): When the upper air pressure is less than 50 kPa

[0065] (2) Heat shrinkability of the tube material In the manufacturing process of an electric wire with terminals, when the tubing material placed around the outer periphery of the insulated electric wire is heated, whether the tubing material has heat shrinkability (A) or not (B) is determined based on whether the tubing material undergoes heat shrinkage.

[0066] (3) Manufacturability of tube materials The breaking elongation of the tube material was measured as an index of the tube material's manufacturability. If the tube material is brittle and has a low breaking elongation, damage such as tearing will occur during extrusion molding or diameter expansion, reducing the manufacturability of the tube material. Breaking elongation was measured using a tensile test in accordance with JIS K 7161.

[0067] The manufacturability of the tube material was evaluated as follows based on the measured breaking elongation value. Very high manufacturability (A+): Breaking elongation of 300% or more High manufacturability (A): Breaking elongation is 150% or more but less than 300% Poor manufacturability (B): Breaking elongation less than 150%

[0068] [Evaluation results] Tables 1 to 3 below show the evaluation results of each property for each of samples A1 to A27 and B1 to B9, along with the component composition of the tube material and the constituent materials of the resin coating. For the component composition of the tube material, the content of each component in the resin is shown in mass%. For the resin coating, a black circle indicates whether PBT or PA6T was used as a constituent material.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] All of the tubing materials, Samples A1 to A27, listed in Tables 1 and 2, contain, in addition to a crosslinked polyolefin resin (Group a), at least one of the following: an acid-modified resin (Group b) in an amount of 5% by mass to 40% by mass of the resin component; and a thermoplastic elastomer (Group c) in an amount of 20% by mass to 40% by mass of the resin component. Because the tubing materials contain a crosslinked polyolefin resin, all of the samples exhibit heat shrinkability (A). Furthermore, the inclusion of at least one of the acid-modified resin and the thermoplastic elastomer in the specified amounts results in high water-stopping properties (A or A+) and high manufacturability of the tubing material (A or A+).

[0073] On the other hand, in Samples B1 to B9 listed in Table 3, the tubing material does not have a component composition containing a cross-linked polyolefin resin and at least one of the above-mentioned predetermined amounts of acid-modified resin and thermoplastic elastomer, and therefore does not fully satisfy at least one of the properties of water-stopping ability, heat-shrinkability of the tubing material, and manufacturability of the tubing material. Samples B3 and B6 use a non-cross-linked resin as the resin of group a, and the tubing material does not contain a cross-linked resin, so the tubing material does not have heat-shrinkability (B). Sample B7 uses a cross-linked silicone resin instead of a polyolefin cross-linked resin as the cross-linked resin, and although the tubing material exhibits heat-shrinkability (A), its water-stopping ability is evaluated as very poor (B-). This is thought to be because the cross-linked silicone resin does not exhibit high adhesion to the insulating coating of the insulated electric wire.

[0074] In samples B1 to B5, the tubing material does not contain either an acid-modified resin or a thermoplastic elastomer, and the evaluation result is that the water-stopping ability is very low (B-). In sample B8, the tubing material contains an acid-modified resin, but the amount is less than 10 mass%, resulting in low water-stopping ability (B). In sample B9, the tubing material contains more than 40 mass% of acid-modified resin, resulting in low manufacturability of the tubing material (B).

[0075] Here, samples A1 to A27 are compared. First, a comparison of samples A3 and A4, which are crosslinked polyolefin resins in group a, confirms that equivalent water-stopping properties (A) and manufacturability of tubing (A+) are obtained regardless of whether the crosslinking is by electron beam crosslinking or silane crosslinking. Furthermore, a comparison of samples A2 and A7 reveals that sample A2, which uses electron beam crosslinked PE1, a resin with a high crosslink density, achieves particularly high manufacturability.

[0076] In samples A1 to A11, the tubing material contains either an acid-modified resin or a thermoplastic elastomer, while samples A12 to A27 contain both. While samples A1 to A11 all received a rating of only high water-stopping ability (A), most of samples A12 to A27 achieved very high water-stopping ability (A+). This suggests that using both an acid-modified resin and a thermoplastic elastomer in tubing material is highly effective in improving water-stopping ability.

[0077] A comparison of Sample A1 and Sample A2 confirms that the use of either acid-modified SEBS or acid-modified PP as the acid-modified resin effectively improves water-stopping properties. The water-stopping evaluation results for each sample also confirm that the use of either polyester or polyamide thermoplastic elastomers effectively improves water-stopping properties. However, Samples A12 to A15, in which the thermoplastic elastomer contained in the tubing material and the resin material constituting the resin coating both have polyester backbones, and Samples A24 to A27, in which both have polyamide backbones, tend to generally achieve higher water-stopping properties than Samples A16 to A23, in which the thermoplastic elastomer contained in the tubing material and the resin material constituting the resin coating have different backbones. This suggests that using a thermoplastic elastomer with the same backbone as the resin material constituting the resin coating as the tubing material can be highly effective in improving water-stopping properties.

[0078] Although the embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0079] 1. Wire with terminal 2 electric wire 3 Conductors 3a Tip of conductor 4. Insulation coating 5 Terminal fittings 51 Terminal connection part 51a Bolt insertion hole 52 First barrel section 53 Second barrel section 6 Wire section 6a Electrical Connections 7. Tubing 8 Resin coated part

Claims

1. an electric wire portion in which the terminal fitting and an insulated electric wire having an outer periphery of a conductor covered with an insulating coating are electrically connected at an electrical connection portion; a tube member covering an outer periphery of the insulating coating at a portion along an axial direction of the insulated wire; a resin coating portion that covers a portion of the electric wire portion including the electrical connection portion and is formed in contact with at least a portion of the outer circumferential surface of the tube material, The tubing material is a cross-linked polyolefin resin; At least one of an acid-modified resin in an amount of 10% by mass or more and 40% by mass or less of a thermoplastic elastomer in an amount of 20% by mass or more and 40% by mass or less of a resin component, The cylindrical member is configured as a single layer including The terminal-attached electric wire has no layers other than the tubular member on the inner peripheral surface and the outer peripheral surface.

2. The electric wire with terminal according to claim 1 , wherein the tube material contains both the acid-modified resin and the thermoplastic elastomer.

3. The electric wire with terminal according to claim 1 , wherein the thermoplastic elastomer and the resin material constituting the resin coating portion have the same type of skeleton.

4. The electric wire with terminal according to claim 1 or 3, wherein the thermoplastic elastomer includes at least one of a polyester-based elastomer and a polyamide-based elastomer.

5. The electric wire with terminal according to claim 1 or 2, wherein the acid-modified resin includes an acid-modified polyolefin resin.

6. The electric wire with terminal according to claim 1 or 2, wherein the resin coating portion covers an entire outer peripheral surface of the tubing.

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