JP7748859B2 - Wires with terminals, wire harnesses - Google Patents

Description

The present invention relates to terminal-attached electric wires, etc., used in automobiles, etc.

Typically, automotive wiring harnesses are made by connecting crimp terminals to the conductors of covered conductors, then bundling them together and routing them as signal wires in automobiles and other applications. A typical covered conductor and crimp terminal is made by removing the covering from the tip of the covered conductor, crimping the exposed conductor to the conductor crimping portion, and then crimping the covering to the crimping portion. During this process, an oxide film that impairs conductivity forms on the surface of the conductor, but strong compression when crimping the conductor crimping portion destroys this oxide film and ensures reliable contact between the conductor and the crimping portion. As a result, the conductor wires that make up the conductor come into contact with the conductor crimping portion of the crimping terminal, ensuring conductivity between the crimping terminal and the conductor.

However, particularly in wiring harnesses used in automobiles, thinner wires than conventional ones are sometimes used to reduce weight, and there is a demand for wires with a diameter of 0.35 sq (sq: ^mm2 ) or less. In the case of thin wires, excessive compression can cause wire breakage or damage, resulting in a significant decrease in the tensile strength of the connection. However, as mentioned above, weakening the compression does not sufficiently destroy the oxide coating, and the contact between the conductor and the conductor crimping portion is insufficient, resulting in an increase in the resistance of the connection.

In other words, strong compression can damage the wires and reduce the strength of the crimped portion, while weak compression can insufficiently ensure the contact area between the conductor crimped portion and the conductor or destroy the oxide film, increasing the resistance of the crimped portion and causing pullout due to insufficient crimping, thereby failing to ensure the strength of the crimped portion. As such, it is difficult to control the balance between conductivity and tensile strength using compression ratio alone, especially with small-diameter insulated wires. For this reason, there is a demand for a connector that makes it easy to control the balance between conductivity and tensile strength using compression ratio with a single crimping operation.

In response to this, electric wires containing tension members are being considered. For example, when using an electric wire made of a conductor with a tensile strength of around 30 N, in order to ensure a tensile strength exceeding 80 N required for automotive electric wires, a proposed electric wire containing tension members has been constructed in which the conductor is wound spirally around the outer periphery of a metallic or non-metallic tension member. One method for producing such electric wires involves stripping the conductor in stages, exposing the tension member and inserting it into a sleeve, crimping the tension member with a steel clamp, and then integrating the components with a curable resin such as an adhesive, while crimping the conductor portion with an aluminum clamp or other material (Patent Document 1).

In addition, a coated electric wire has been proposed that includes a conductor section made up of multiple bundled strands, and fibrous tensile strength members arranged in the valleys between the strands on the outer periphery of the conductor section and the inner periphery of the coating material (Patent Document 2).

However, in both Patent Document 1 and Patent Document 2, for example, when connecting a crimp terminal using a thick-diameter coated conductor wire, the conductor crimping portion can be crimped at a compression rate that achieves both connection strength and connection resistance. However, as the diameter of the wire becomes smaller, the range of appropriate crimping conditions for both connection strength and electrical resistance becomes narrower. This is because, as mentioned above, attempting to ensure connection strength causes the conductor to break, increasing connection resistance, and prioritizing connection resistance makes it impossible to obtain sufficient connection strength, which can lead to the wire coming loose. In this way, the smaller the wire diameter, the more difficult it becomes to achieve both connection strength and electrical resistance.

For example, Patent Document 1 uses a method in which a conductor is inserted into a sleeve and crimped. However, when a thinner electric wire is inserted into a tubular terminal and crimped, strong compression can damage the wire due to the thinness of the conductor, making it more likely to lose tensile strength. On the other hand, weak compression does not adequately destroy the oxide film on the conductor surface, weakening the metallic bond and reducing conductivity.

In particular, when crimping is performed in an open barrel shape, the conductor and the tension member dissipate during crimping, reducing tensile strength and increasing resistance at the crimped portion. Furthermore, connecting conventional electric wires with tension members requires separate crimping processes for crimping the tension member and the conductor, as well as a step stripping operation. This increases the number of parts and the number of man-hours required, resulting in high costs. The step stripping process itself becomes particularly difficult as the diameter of the electric wire becomes smaller. As such, Patent Document 1 has the problem of increased processing costs due to the complex manufacturing process.

Patent Document 2 also discloses an example in which fibrous tension members are provided between the conductor wires, thereby improving strength without reducing electrical properties. However, when the electric wire in Patent Document 2 is crimped, the tension members get between the conductor wire and the terminal, which can increase the resistance of the crimped portion. Even if the tension members are conductors, when temperature changes occur, gaps will form between the tension members and the conductor wire due to differences in thermal expansion coefficients, resulting in an increase in the resistance of the crimped portion.

As such, in both Patent Document 1 and Patent Document 2, if the compression rate during crimping is low (i.e., strong compression), the tensile strength of the reinforcing member is damaged and decreases, and if the compression rate during crimping is high (i.e., weak compression), the resistance of the crimped portion increases. In other words, it is difficult to control the balance between conductivity and tensile strength with the compression rate in a single crimping operation.

On the other hand, in the case of aluminum conductors in particular, an oxide film forms on the surface, and methods have been proposed to form serrations on the inner surface of the conductor crimping section to reduce connection resistance (e.g., Patent Documents 3 to 5). Such serrations destroy the oxide film on the conductor, reducing connection resistance, and are formed either extending perpendicular to the conductor's axial direction, or as intermittent irregularities along the conductor's axial direction, to provide a catch in the pulling direction.

Japanese Utility Model Application Laid-Open Publication No. 61-046827 Japanese Patent Application Laid-Open No. 2012-3856 JP 2017-84485 A JP 2015-32542 A International Publication No. 2019/167714

However, with methods in which serrations are formed perpendicular to the longitudinal direction of the insulated conductor wire or intermittently along the longitudinal direction of the insulated conductor wire, the conductor wire located on the outer periphery of the insulated conductor wire intersects all of the serrations arranged along the longitudinal direction. At the intersections between the conductor wire and the serrations, the conductor wire is formed with alternating thin and thick sections due to the unevenness of the serrations. For conductor wires of a certain thickness, such changes in cross-sectional shape can contribute to an increase in tensile strength. However, with particularly thin wires, such cross-sectional changes may become flaws that can cause the conductor wire to break. Therefore, applying conventional serrations may actually decrease tensile strength. Furthermore, when serrations are perpendicular to the longitudinal direction or in the opposite direction to the conductor wire twisting direction (i.e., when there are many intersections between the serrations and the conductor strands), the conductor wire may slip into the recesses of the serrations, applying an unnatural tensile load to the conductor wire and potentially causing it to break.

The present invention was made in consideration of these problems, and aims to provide a terminal-attached electric wire or the like that can achieve both connection strength and connection resistance.

In order to achieve the above-mentioned object, a first invention is an electric wire with terminal in which a covered conductor wire and a terminal are electrically connected, the covered conductor wire having a tension member and a conductor wire arranged on the outer periphery of the tension member and made of a plurality of conductors, the terminal having a conductor crimping portion to which the conductor wire exposed from the coating at the tip of the covered conductor wire is crimped, and a coating crimping portion to which the coating of the covered conductor wire is crimped, and the inner surface of the conductor crimping portion has serrations arranged in the circumferential direction, the serrations extending at a predetermined angle other than the longitudinal direction of the conductor wire or a direction perpendicular to the longitudinal direction. the angle at which the serrations are formed relative to the longitudinal direction of the conductor is within ±60 degrees relative to the extension direction of the conductor relative to the longitudinal direction of the conductor, the conductor is formed by twisting a plurality of conductors around the outer periphery of the tension member, the serrations are formed on the inner surface of the conductor crimping portion at a predetermined angle relative to the longitudinal direction of the conductor, and the spiral direction in which the serrations extend relative to the longitudinal direction of the conductor is the same as the spiral direction in which the conductor extends relative to the longitudinal direction of the conductor.

At least the tip of the conductor may be compressed from the outer periphery.

The conductor may be plated.

The conductor is formed by twisting multiple conductor wires around the outer periphery of the tension member, and it is desirable that the width of the serrations be between 0.5 and 2 times the diameter of the conductor wires.

According to the first invention, in a cross section perpendicular to the longitudinal direction of the covered conductor, the conductor is disposed around the outer periphery of the tension member. This ensures that when the conductor is crimped by the conductor crimping portion, the conductor and the conductor crimping portion come into contact with each other, ensuring electrical continuity, and the tension member increases tensile strength.

In this case, serrations are provided in the conductor crimping section, which increases the contact area between the conductor and the conductor crimping section, thereby reducing connection resistance. For example, without serrations, the conductor's Young's modulus is lower than that of the strength member, which could cause the conductor to elongate first, resulting in breakage. However, providing serrations increases the contact area between the terminal and conductor, increasing the frictional force between the terminal and conductor. As a result, the increased frictional force suppresses the elongation of the conductor, and the load generated during a tensile test is distributed to the strength member, thereby increasing the tensile strength of the electric wire.

Furthermore, because the serrations are not formed in a direction perpendicular to the longitudinal direction of the covered conductor, the number of intersections between the conductor and the serrations can be reduced. In this way, by forming the serrations so that they extend in the longitudinal direction of the covered conductor or at a specified angle to the longitudinal direction, rather than in a direction perpendicular to the longitudinal direction of the covered conductor, it is possible to prevent scratches on the conductor and a decrease in tensile strength.

In addition, in the case of a conductor in which multiple conductors are twisted together, the number of intersections between the conductors and the serrations can be more efficiently reduced by aligning the spiral direction of the serrations with the spiral direction of the twisted conductors relative to the longitudinal direction of the conductor.

The above-mentioned effect is particularly effective when the angle at which the serrations are formed relative to the longitudinal direction of the conductor is within ±60 degrees of the twist angle of the conductor relative to the longitudinal direction of the conductor.

In addition, by compressing the tip of the conductor from the outer periphery to form the terminal processing section, it is possible to prevent the conductor from coming apart when the tip of the conductor is inserted into the tubular conductor crimping section.

In addition, plating the surface of the conductor with a conductive metal is effective in improving conductivity and tensile strength. It also improves workability by reducing variation in the conductor wires when crimping the wire.

Furthermore, if the width of the serrations is between 0.5 and 2 times the diameter of the conductor wire, the contact area between the conductor wire and the conductor crimping portion can be ensured.

The second invention is a wire harness characterized by integrating multiple terminal-equipped electric wires, including the terminal-equipped electric wire of the first invention.

According to the second invention, a wire harness can be obtained in which multiple small-diameter electric wires are bundled together.

The present invention makes it possible to provide terminal-attached electric wires and the like that achieve both high connection strength and low connection resistance.

FIG. 2 is a perspective view showing the electric wire with terminal 10. 1A is an axial cross-sectional view showing the terminal-attached electric wire 10, and FIG. 1B is a radial cross-sectional view of the conductor crimping portion 7. FIG. FIG. 2 is a diagram showing the terminal 1 and the coated conductor wire 11 before crimping. 1A is a diagram showing the tip of a conductor 13, and FIGS. 1B to 1D are diagrams showing the configuration of a terminal processing portion 19. FIG. 10A and 10B are diagrams showing other configurations of the terminal processing unit 19. 1A and 1B are development views of the terminal 1 before crimping. 1A is a development view of the terminal 1 before crimping, and FIG. 1B is a development view of the conductor 13. FIG. 1A is a perspective view showing a terminal-attached electric wire 10a, and FIG. 1B is a radial cross-sectional view of a conductor crimping portion 7. FIG. 1A is a perspective view showing a terminal-attached electric wire 10b, and FIG. 1B is a radial cross-sectional view of a conductor crimping portion 7. FIG.

(First embodiment)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing a terminal-fitted wire 10, Fig. 2(a) is an axial cross-sectional view of the terminal-fitted wire 10, and Fig. 2(b) is a radial cross-sectional view of the conductor crimping portion 7. The terminal-fitted wire 10 is configured by electrically connecting a terminal 1 and a covered conductor wire 11.

The coated conductor wire 11 consists of a strength member 17 located approximately in the center of the cross section, a conductor wire 13 consisting of multiple conductors arranged around the periphery of the strength member 17, and a coating 15 that coats the conductor wire 13. The conductor wire consisting of the strength member 17 and the conductor wire 13 is referred to as a composite conductor 12. The coated conductor wire 11 has the conductor wire 13 exposed from the tip of the coating 15. The conductor may be made of annealed copper wire, hardened copper wire, copper alloy wire, Corson alloy wire, aluminum wire, or aluminum alloy wire, but from the standpoints of cost and wire conductivity, annealed copper wire, hardened copper wire, or copper alloy wire is preferable. In this case, the surface of the conductor 13 may be plated with tin or other plating.

The tension member 17 is a member that receives tension in response to a tensile load. Furthermore, as will be described in more detail below, the conductor wires 13 (multiple conductor strands) may be twisted spirally around the outer periphery of the tension member 17 in the longitudinal direction of the coated conductor wire 11. In this case, each of the conductor wires 13 (conductor strands) arranged around the outer periphery of the tension member 17 may be made of a conductor of the same shape and cross-sectional area.

The terminal 1 is made of, for example, copper, copper alloy, aluminum, or aluminum alloy. The terminal 1 is composed of a terminal body 3 and a crimping portion 5 connected via a transition portion 4. A covered conductor wire 11 is connected to the crimping portion 5 of the terminal 1.

The terminal body 3 is formed by forming a plate material of a predetermined shape into a cylindrical body with a rectangular cross section. The terminal body 3 has an internal resilient contact piece formed by folding the plate material into the rectangular cylindrical body. A male terminal or the like is inserted into the front end of the terminal body 3 to connect it. Note that the following explanation shows an example in which the terminal body 3 is a female terminal that allows the insertion of an insertion tab (not shown) of a male terminal or the like, but the detailed shape of this terminal body 3 is not particularly limited in the present invention. For example, the female terminal body 3 may be replaced with an insertion tab of a male terminal, or a bolt fastening portion like a round terminal may be provided.

The crimping portion 5 of the terminal 1 is the part that is crimped to the insulated conductor wire 11, and includes a conductor crimping portion 7 that crimps the conductor wire 13 exposed from the insulation portion 15 at the tip of the insulated conductor wire 11, and a insulation crimping portion 9 that crimps the insulation portion 15 of the insulated conductor wire 11. That is, the conductor wire 13 exposed when the insulation portion 15 is stripped is crimped by the conductor crimping portion 7, electrically connecting the conductor wire 13 to the terminal 1. The insulation portion 15 of the insulated conductor wire 11 is also crimped by the insulation crimping portion 9 of the terminal 1. In this embodiment, the conductor crimping portion 7 and insulation crimping portion 9 are so-called open barrel types.

The inner surface of the conductor crimping portion 7 is provided with multiple serrations 18 extending in the axial direction of the conductor crimping portion 7 (i.e., the longitudinal direction of the conductor 13 crimped by the conductor crimping portion 7) or at a predetermined angle other than a direction perpendicular to the axial direction of the conductor crimping portion 7 (the longitudinal direction of the conductor 13). As shown in Figure 2(b), the multiple serrations 18 are arranged at predetermined intervals around almost the entire circumferential direction of the conductor crimping portion 7. Note that the open barrel crimping portion 5 has at least one pair of opposing barrel pieces folded in to crimp the insulated conductor 11. In this case, serrations 18 do not necessarily need to be formed in the portion of the conductor crimping portion 7 that is folded in to the insulated conductor 11 (i.e., near the tips of the barrel pieces).

The serrations 18 may be recessed portions that are thinner than the other portions, or may be protruding portions that are thicker than the other portions. "Extending at a predetermined angle to the longitudinal direction" does not mean extending in a direction perpendicular to the longitudinal direction. The extension direction of the serrations 18 will be described in detail later.

The serrations 18 are effective in destroying the oxide film on the surface of the conductor 13, for example, when the conductor 13 is made of aluminum (or an aluminum alloy). Even when the conductor 13 is made of copper (or a copper alloy), the cross-sectional shape of the conductor 13 changes at the intersection between the conductor 13 and the serrations 18, increasing the contact area between the conductor 13 and the conductor crimping portion 7. This reduces the connection resistance.

The present invention demonstrates the benefits of the serrations 18 when the cross-sectional area of the composite conductor 12 (the total cross-sectional area of the conductor 13 and the strength member 17) is 2.5 sq. or less, and is particularly effective when it is 0.35 sq. or less. Furthermore, it is desirable that the cross-sectional area of the composite conductor 12 (the total cross-sectional area of the conductor 13 and the strength member 17) be 0.3 sq. or less. Furthermore, because the conductor 13 is used together with the strength member 17, the total cross-sectional area of the conductor 13 and the strength member 17 may be 0.05 sq. or less. The smaller the cross-sectional area of the conductor 13, the greater the effect of this embodiment. From the perspective of ensuring the strength of the crimped portion, the total cross-sectional area of the conductor 13 and the strength member 17 is preferably 0.01 sq. or more, and more preferably 0.03 sq. or more.

The tension member 17 may be a metal wire such as a steel wire, or may be made of resin or fiber-reinforced resin, or may be made of multiple strands bundled together. For example, the strands that make up the tension member 17 can be made of PBO (polyparaphenylene benzobisoxazole) fiber, aramid fiber, carbon steel wire, stainless steel wire, liquid crystal polyester fiber, glass fiber, or carbon fiber, but non-metallic wire is preferable in terms of corrosion resistance.

Furthermore, it is desirable that the tensile strength of the reinforcing member 17 be higher than that of the conductor 13. Note that tensile strength refers to the maximum stress that leads to breakage when subjected to tensile stress, but in this embodiment, it is used as a relative indicator of the ease with which the material breaks due to crushing during crimping. In other words, the reinforcing member 17 is made of a material that is less likely to deform during crimping than the conductor 13. Furthermore, it is desirable that the Young's modulus of the reinforcing member 17 be higher than that of the conductor 13, and that the yield stress (or proof stress) of the reinforcing member 17 be higher than the yield stress (or proof stress) of the conductor 13.

Next, we will explain the manufacturing method of the terminal-attached electric wire 10. Figure 3 is a perspective view showing the terminal 1 and the covered conductor wire 11 before crimping. As mentioned above, the terminal 1 has a terminal body 3 and a crimping portion 5. The crimping portion 5 is a so-called open barrel type.

First, as described above, the coating 15 at the tip of the coated conductor wire 11 is stripped to expose the conductor wire 13 at the tip. Next, as shown in Figure 4(a), a terminal processing section 19 may be formed at the tip of the conductor wire 13 before insertion into the crimping section 5 of the terminal 1. The terminal processing section 19 is a processing section that integrates the individual wires of the conductor wire 13 to prevent them from coming apart.

As mentioned above, the tensile member 17 is positioned approximately in the center, with the conductor wire 13 positioned around it. The conductor wire 13 is made up of multiple conductors. In such a case, as shown in Figure 4(b), the terminal processing portion 19 can be formed by compressing at least the tip of the conductor wire 13 from the outer periphery. In this way, compressing the tip of the conductor wire 13 from the outer periphery prevents the wire from unraveling, making it easier to insert the wire into the tubular crimping portion 5.

Alternatively, as shown in Figure 4(c), at least the tip of the conductor 13 may be plated all at once to form the terminal processing portion 19 with a plating layer 21. In this way, plating the tip of the conductor 13 all at once from the outer periphery prevents the wire from coming apart, making it easier to insert into the tubular crimping portion 5.

Note that when plating the conductor wires 13 en bloc from the outer periphery, the temperature may become very high depending on the plating method. If plating is performed en bloc after twisting the conductor wires 13 using this plating method, the tensile strength of the reinforcing members 17 may be deteriorated by the heat, resulting in a decrease in tensile strength.

In such cases, as shown in Figure 4(d), a plating layer 21 may be formed on each conductor before twisting them around the outer periphery of the tension member 17. Alternatively, as shown in Figure 5, a plating layer 21 may be formed on each conductor, and then the tips of multiple conductors may be plated together starting from the outer periphery. In this case, the type of plating for each conductor may be different from the type of plating performed on the entire conductor. As mentioned above, plating the conductors together can prevent them from coming apart, but if the conductors are bundled and plated together, there is a risk that thick or thin areas of plating may occur due to the shape of the conductors, etc. In contrast, performing a primer plating process on each conductor in advance can reduce this effect and enable approximately uniform plating to be achieved all at once.

Note that the terminal processing section 19 is not limited to methods using compression or plating. For example, the tip of the conductor 13 may be soldered or welded to prevent the wires from coming apart. It is also possible to combine multiple terminal processing methods, such as compression from the periphery and batch plating.

Next, the coated conductor wire 11, whose tip has been treated in this manner, is placed in the crimping section 5. At this time, the exposed portion of the conductor wire 13 is located in the conductor crimping section 7, and the coating portion 15 is located in the coating crimping section 9.

Here, Figure 6(a) is a developed view of the conductor crimping portion 7 before crimping. As mentioned above, the conductor crimping portion 7 is provided with serrations 18. In the example shown, the serrations 18 are formed to extend in the longitudinal direction of the covered conductor wire 11 to be crimped (direction A in the figure, also referred to as the axial direction of the terminal 1). In other words, multiple serrations 18 are formed approximately parallel to the axial direction of the terminal 1. Note that "extending" the serrations 18 means that they are formed continuously, without being separated, so that their direction is the longitudinal direction.

The height (if convex) or depth (if concave) of the serrations 18 is preferably between 0.03 mm and 0.08 mm. If the height or depth of the serrations 18 is too small, the effect of increasing the contact area provided by the serrations 18 is small. Furthermore, if the height or depth of the serrations 18 is too large, the conductor may not reach the bottom of the serrations 18 during crimping, potentially creating a gap between the conductor and the conductor crimping portion 7. This reduces the contact area between the conductor 13 and the terminal 1, increasing connection resistance. Furthermore, the amount of change relative to the conductor wire diameter is large, raising the risk of conductor wire breakage.

Furthermore, it is desirable that the width of the serrations 18 be between 0.5 and 2 times the diameter of the conductor that makes up the conducting wire 13. If the width of the serrations 18 is too wide, two or more conductors will be placed on one serration 18, reducing the effect of increasing the contact area provided by the serrations 18. If the width of the serrations 18 is too wide, the conductor wires will not come into contact with the serrations 18, reducing the effect of providing the serrations.

As mentioned above, the conductor wire 13 is made up of multiple conductors. In this case, if the individual conductors are not twisted together but are arranged approximately straight relative to the longitudinal direction of the covered conductor wire 11 (i.e., if the direction in which each conductor strand extends is approximately straight relative to the longitudinal direction of the covered conductor wire 11), the extension direction of the conductor strands will coincide with the longitudinal direction of the covered conductor wire 11.

In this case, the extension direction of the serrations 18 and the extension direction of the conductor wires that make up the conductor 13 are approximately parallel. As a result, the individual conductor wires that make up the conductor 13 do not intersect with multiple serrations 18. In other words, the conductor wires that make up the conductor 13 have a substantially constant cross-sectional shape, except for the leading and trailing ends of the serrations 18. This reduces cross-sectional variations that are a cause of flaws that reduce the tensile strength of the conductor 13, and suppresses the reduction in tensile strength.

As shown in Figure 6(b), the extension direction of the serrations 18 may be formed at a predetermined angle (excluding those extending in a direction perpendicular to the longitudinal direction of the covered conductor wire 11) with respect to the longitudinal direction (A in the figure) of the covered conductor wire 11. Even in this case, the multiple serrations 18 are formed approximately parallel to each other. In this state, when the conductor wire 13 is crimped by the conductor crimping unit 7, the serrations 18 are formed in a spiral shape at a predetermined angle with respect to the longitudinal direction of the covered conductor wire 11.

In this case, the angle θ1 between the axial direction of the terminal 1 (A in the figure) and the extension direction of the serrations 18 (B in the figure) is preferably ±60 degrees or less, and more preferably ±40 degrees or less. In other words, the extension direction of the conductor wires that make up the conductor 13 coincides with the longitudinal direction of the covered conductor wire 11, so the angle between the extension direction of the conductor wires that make up the conductor 13 and the extension direction of the serrations 18 is ±60 degrees or less. This sufficiently reduces the number of intersections between the conductor wires and the serrations 18, thereby suppressing a decrease in tensile strength.

As mentioned above, the conductor wires 13 (multiple conductor wires) may be twisted together around the outer periphery of the tension member 17. Figure 7(a) is an exploded view of the conductor crimping portion 7 when the conductor wires 13 are twisted together, and Figure 7(b) is a conceptual diagram showing the conductor wires 13 further expanded (with the tension member 17 in a perspective view).

In this case, when the conductor 13 is crimped by the conductor crimping portion 7, the serrations 18 and the conductor strands are formed into a spiral at a predetermined angle relative to the longitudinal direction of the covered conductor 11. It is desirable that the spiral direction in which the serrations 18 extend relative to the longitudinal direction of the conductor 13 is the same as the spiral direction in which the conductor extends relative to the longitudinal direction of the conductor 13. For example, when viewed from the terminal body side, clockwise and counterclockwise spiral shapes are conceivable from the front to the back (from the tip to the rear end of the terminal 1). However, it is desirable that the spiral direction in which the serrations 18 extend and the spiral direction in which the conductor constituting the conductor 13 extends are both clockwise or counterclockwise.

By ensuring that the spiral direction is the same in this way, the number of intersections between the conductor wires and the serrations 18 is sufficiently reduced, which has the effect of preventing a decrease in tensile strength.

Even in this case, the angle θ1 of the direction in which the serrations 18 are formed (B in the figure) relative to the longitudinal direction of the coated conductor 11 (A in the figure) is preferably within ±60 degrees, and even more preferably within ±40 degrees, of the angle θ2 of the extension direction of the conductor constituting the conductor 13 (C in the figure) relative to the longitudinal direction of the coated conductor 11 (A in the figure). Here, the extension direction of the conductor constituting the conductor 13 refers to the longitudinal direction of the conductor wires in a developed view of the conductor twisted together in a spiral shape. The twist angle θ2 of the conductor 13 is, for example, 25 degrees or less.

As described above, the conductor wire 13 is crimped with the conductor crimping portion 7 having serrations 18, and the insulation portion 15 is crimped with the insulation crimping portion 9, thereby obtaining an electric wire with terminal 10. Furthermore, a wire harness can be obtained in which multiple electric wires with terminals are integrated, including the obtained electric wire with terminal 10.

Here, if the total cross-sectional area of the conductor 13 before the crimping process is A0 and the total cross-sectional area of the conductor 13 after compression is A1, then the compression rate of the conductor 13 = A1/A0 (%). In this case, it is desirable that the compression rate of the conductor 13 at the conductor crimping portion 7 is 70-80%. This weak compression can prevent breakage of the conductor wires, and the serrations 18 increase the contact area, increasing tensile strength due to frictional resistance and reducing connection resistance. For example, the increased friction between the conductor and the conductor crimping portion 7 due to the serrations can prevent elongation of the conductor and distribute the load generated during a tensile test to the tension member 17, thereby increasing the tensile strength of the electric wire.

As described above, according to this embodiment, serrations 18 are formed in the conductor crimping portion 7, which increases the contact area with the conductor 13 (conductor), thereby achieving the effects of lowering connection resistance and improving tensile strength.

In this case, the serrations 18 are not formed in the circumferential direction of the conductor crimping portion 7, nor are they arranged intermittently in the axial direction of the conductor crimping portion 7, thereby reducing the number of intersections between the conductor wires and the serrations 18. By forming the serrations 18 in this way so that they extend in the longitudinal direction of the conductor 13 or at a specified angle to the longitudinal direction, rather than in a direction perpendicular to the longitudinal direction of the covered conductor wire, it is possible to prevent scratches on the conductor wires and a decrease in tensile strength, especially in small-diameter covered conductor wires 11.

For example, if the conductor wire 13 is formed by twisting together multiple conductor wires, the spiral direction in which the serrations 18 extend and the spiral direction in which the conductor wires extend can be made the same, thereby efficiently reducing the number of intersections between the conductor wires and the serrations 18.

In this case, by setting the angle of the serrations 18 relative to the longitudinal direction of the conductor wire 13 to within ±60 degrees relative to the extension direction of the conductor wire relative to the longitudinal direction of the conductor wire 13, it is possible to efficiently reduce the number of intersections between the conductor wire and the serrations 18.

Second Embodiment
Next, a second embodiment will be described. Fig. 8(a) is a perspective view showing a terminal-fitted electric wire 10a according to the second embodiment, and Fig. 8(b) is a cross-sectional view perpendicular to the axial direction of the conductor crimping portion 7. In the following description, components that perform the same functions as those in the first embodiment will be assigned the same reference numerals as in Figs. 1 to 7, and redundant description will be omitted.

The terminal-attached wire 10a has a configuration similar to that of the terminal-attached wire 10, but differs in that the crimping portion 5 is formed so that the barrels overlap each other rather than having their ends butted together. In other words, opposing barrel pieces overlap each other, and one barrel piece is crimped to encase the other. Furthermore, serrations 18 are formed on the inner surface of the conductor crimping portion 7, as in the first embodiment.

In this case, the conductor wire 13 is crimped from the entire circumferential direction of the conductor wire 13 at the conductor crimping portion 7. This also prevents the barrel tip from digging into the conductor wire 13. This prevents breakage of the conductor wire and reduces a decrease in tensile strength.

The second embodiment can achieve the same effects as the first embodiment. Furthermore, by crimping the barrel pieces so that they overlap each other, excessive deformation of the conductor 13 can be suppressed, and a decrease in tensile strength can be suppressed.

(Third embodiment)
Next, a third embodiment will be described. Fig. 9(a) is a perspective view showing a terminal-fitted electric wire 10b according to the third embodiment, and Fig. 9(b) is a cross-sectional view perpendicular to the axial direction of the conductor crimping portion 7.

The terminal-attached wire 10b has a configuration similar to that of the terminal-attached wire 10, but differs in that the crimping portion 5 uses a tubular terminal 1a rather than an open barrel type. This allows the conductor 13 to be more reliably crimped by the wire crimping portion 7 from all directions, 360°, regardless of the axial position of the wire crimping portion 7. Furthermore, serrations 18 are formed on the inner surface of the wire crimping portion 7, as in the first embodiment.

The crimping portion 5 may be formed, for example, by rolling a plate member, butting the ends together, and joining them longitudinally by welding or brazing, or by expanding a tubular member to form the terminal 1. The conductor crimping portion 7 and the insulation crimping portion 9 may have the same diameter, or, as shown in the figure, the inner diameter of the insulation crimping portion 9 may be larger than the inner diameter of the conductor crimping portion 7.

Here, if the conductor crimping portion 7 is cylindrical as in this embodiment and has a brazed portion at the joint, the brazed portion with low hardness will have a smaller compressive stress on the conductor 13, making it easier for the tensile member 17 to be pulled out. For this reason, it is desirable to either remove the brazed portion, or to eliminate the brazed portion and make the hardness of the joint formed at the conductor crimping portion 7 equal to the hardness of the material in the conductor crimping portion 7.

The third embodiment can achieve the same effects as the second embodiment. Furthermore, since the conductor 13 is crimped from all directions around its entire circumference (360°) without any steps, it is possible to prevent localized stress (deformation) from occurring in the conductor 13 during crimping.

As such, the shape of the crimping portion 5 is not particularly limited, and multiple crimping shapes may be combined. For example, the insulation crimping portion 9 may be an open barrel type, and the conductor crimping portion 7 may be tubular.

Various types of electric wires with terminals were created and the electrical properties (crimped portion resistance performance) and mechanical properties (tensile strength performance) of the crimped portion were evaluated. All of the coated conductors used had a tension member placed in the center of the cross section, with conductor wires twisted around the outer periphery. The structure of the coated conductor in the coated conductor is shown in Table 1. The cross-sectional area of the composite conductor is the sum of the cross-sectional areas of the conductor wire and the tension member. The conductor wire diameter is the diameter of the wires that make up the conductor, and the conductor cross-sectional area is the sum of the cross-sectional areas of the conductor wires. Electrical properties were evaluated by measuring the electrical resistance between the terminal and the coated conductor. Mechanical properties were evaluated by pulling the coated conductor from the terminal and measuring the load applied when the coated conductor was pulled out.

As shown in Table 2, tensile strength performance was evaluated for each cross-sectional area of the conductor, with each cross-sectional area being evaluated as "Fail" (×), "Provisional Pass" (△) (acceptable depending on the circumstances), or "Pass" (Good). As shown in Table 3, resistance performance of the crimped portion was evaluated for each cross-sectional area of the conductor, with each cross-sectional area being evaluated as "Fail" (×), "Provisional Pass" (△) (acceptable depending on the circumstances), or "Pass" (Good). Here, the criteria for an example are resistance performance of "○" and tensile strength performance of "△" or higher (as tensile strength is easily achieved by combining it with other technologies). The conditions and evaluation results are shown in Tables 4 to 19.

The cross-sectional area of an electric wire is the total cross-sectional area of the conductor. Conductor material is the material that makes up the conductor, and strength members are the material that makes up the strength members. Note that the term "fiber" in the context of strength members indicates that they are formed by bundling multiple thin wires (fibers).

The conductor compression ratio is the total cross-sectional area of the compressed conductor at the conductor crimping section compared to the conductor before compression (total cross-sectional area of the conductor wires). Conductor treatment refers to the treatment of the conductor end, and "tin plating" refers to the application of tin plating to individual conductors, as shown in Figure 4(d).

All terminal shapes are the same as terminal 1 shown in Figure 1. The serration width is the width perpendicular to the extension direction, and all serrations are recessed grooves. A serration depth of 0 means that no serrations are formed.

The serration angle is the angle of the serration extension direction relative to the twist angle of the conductor wire. That is, as shown in Figure 7(b), the serration angle is the inclination angle θ1 of the serration relative to the inclination angle θ2 of the conductor wire 13, and when θ1 and θ2 are equal, the serration angle is 0. The serration angle is defined as a positive direction in a clockwise direction and a negative direction in a counterclockwise direction relative to the inclination angle θ2 of the conductor wire 13 in a plan view. The twist angle θ2 of the conductor wire was approximately 14 degrees in all cases.

As can be seen from Tables 4 to 19, by forming the specified serration configuration within ±60° of the twist angle of the twisted wire, resistance performance and tensile strength performance were rated as passing (△ or better). Regarding resistance values, although provisionally passing (△) was observed in the comparative examples, all examples were rated as ○ and were extremely good. The criteria for the examples are resistance performance of "○" and tensile strength performance of "△" or better, but no comparative examples met these conditions. Furthermore, by forming the specified serration configuration within ±40° of the twist angle of the twisted wire, resistance performance and tensile strength performance were all rated as "○."

In contrast, for wires with a cross-sectional area of 0.35 sq. or less, the effect of the serrations was small when the serration depth was shallow, at 0.01 mm or less, and tensile strength performance in particular was slightly reduced. Furthermore, for wires with a cross-sectional area of 0.13 sq. or less, resistance performance decreased when the serration depth was too deep, at 0.1 mm. Furthermore, wires with serrations formed at 90 degrees failed the tensile strength performance test.

Although an embodiment of the present invention has been described above with reference to the attached drawings, the technical scope of the present invention is not limited to the above-described embodiment. It is clear that a person skilled in the art could conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1, 1a... Terminal 3... Terminal body 4... Transition portion 5... Crimping portion 7... Conductor crimping portion 8... Inter-barrel portion 9... Insulation crimping portion 10, 10a, 10b... Terminal-attached electric wire 11... Insulated conductor wire 12... Composite conductor 13... Conductor 15... Insulation portion 17... Tensile member 18... Serration 19... End processing portion 21... Plating layer

Claims (5)

A terminal-attached electric wire in which a coated conductor wire and a terminal are electrically connected,
The coated conductor wire includes a tension member and a conductor wire arranged around the tension member and made of a plurality of conductors,
the terminal includes a conductor crimping portion to which the conductor exposed from the coating portion at the tip of the coated conductor wire is crimped, and a coating crimping portion to which the coating portion of the coated conductor wire is crimped,
The inner surface of the conductor crimping portion is provided with serrations in a circumferential direction, the serrations extending at a predetermined angle other than the longitudinal direction of the conductor or a direction perpendicular to the longitudinal direction,
the angle of the serrations relative to the longitudinal direction of the conductor is within ±60 degrees relative to the direction in which the conductor extends relative to the longitudinal direction of the conductor,
The conductor wire is formed by twisting a plurality of conductors around the outer periphery of the tension member,
The serrations are formed on the inner surface of the conductor crimping portion at a predetermined angle with respect to the longitudinal direction of the conductor,
An electric wire with a terminal , wherein the spiral direction in which the serrations extend relative to the longitudinal direction of the conductor is the same as the spiral direction in which the conductor extends relative to the longitudinal direction of the conductor . 2. The electric wire with terminal according to claim 1 , wherein at least a tip portion of the conductor is compressed from an outer periphery side. 3. The electric wire with terminal according to claim 1 , wherein the conductor is plated. 4. The electric wire with terminal according to claim 1, wherein the conductor wire is formed by twisting a plurality of conductor wires around the outer periphery of the tension member, and the width of the serrations is 0.5 to 2 times the diameter of the conductor wires. A wire harness comprising a plurality of electric wires with terminals integrated together, the electric wire with terminal being the electric wire according to any one of claims 1 to 4 .