JP5038201B2 - Crimping method of terminal to electric wire - Google Patents

Description

  The present invention relates to a method for connecting a wire and a terminal made of different metals, and more particularly to a method for crimping that is effective when a copper terminal is crimped to an aluminum wire.

  Conventionally, the electric wire used for the wire harness for automobiles is generally a copper electric wire, but recently, there is a movement to replace it with an aluminum electric wire because of its light weight and good recyclability.

  Aluminum has a conductivity of about 60% compared to copper, but it can be expected to be significantly lighter because it only weighs 1/3. Further, since the melting point of copper is 1083 ° C., the melting point of aluminum is 660 ° C., there is an advantage that the metal can be easily recovered.

When the electric wire of the automobile wire harness is an aluminum electric wire, there are the following problems when a copper terminal is used as the crimp terminal. Aluminum has a larger coefficient of linear expansion than copper. The linear expansion coefficient of aluminum is 23.5 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of copper is 17.0 × 10 ⁻⁶ / ° C., so aluminum expands according to the temperature change by about 1.4 times that of copper. Easy to shrink. Therefore, when the copper terminal is crimped to the aluminum electric wire, there arises a problem that the contact resistance between the aluminum conductor and the copper terminal becomes unstable under heat cycle or thermal shock conditions.

  This will be described in detail.

  FIG. 2 shows a general example in which a crimp terminal for an aluminum wire is crimped to a conductor of an aluminum wire. A terminal 10 as a crimp terminal for an aluminum electric wire has a connection plate portion 11 with a hole 11a at the front portion and a crimp portion 12 at the rear portion. The crimping portion 12 has a U-shape having a bottom plate 13 and a pair of crimping pieces 14, 14 extending upward from both lateral edges of the bottom plate 13, and has a serration 15 on the inner surface. The electric wire 1 is formed by covering the outer periphery of a conductor 2 made of stranded wire or the like with an insulation coating 3. When crimping the terminal 10, the exposed conductor 2 of the end of the peeled electric wire 1 is inserted on the bottom plate 13. Then, the crimping pieces 14 on both sides are bent inward by a crimping device, and crimped so as to wrap the conductor 2. Thereby, the terminal 10 can be crimped to the conductor 2.

  By the way, when a copper terminal is used for the terminal 10 and an aluminum wire is used for the electric wire 1 and crimping is performed at room temperature (23 ° C.), the cross section of the crimping portion 12 is as shown in FIG. . In the cross section in this state, the reaction force acts on the interface between the conductor 2 and the terminal 10 toward the center of the thickness of each other and balances. However, this balance is due to the volume ratio at the temperature at which the terminal 10 is crimped to the conductor 2, and when there is a temperature change, the contact state of the interface changes due to volume expansion. Specifically, the interface when crimped at room temperature 23 ° C. is affected by volume change in a temperature range −40 ° C. to 120 ° C. where the use of the wire harness is assumed.

  For example, as shown in FIG. 3C, when the ambient temperature rises to a higher temperature side than normal temperature, the inner aluminum conductor 2 has a larger volume expansion than the outer copper terminal 10, The reaction force from the outer copper terminal 10 acts on the aluminum conductor 2, and there is no gap at the interface between the terminal 10 and the conductor 2. In this case, since the copper terminal 10 has higher hardness than the aluminum conductor 2, stress in the direction of the arrow acts on the conductor 2. Incidentally, when the temperature rises to 120 ° C., the strain due to thermal expansion is about 0.06%, and the proof stress slightly decreases, but remains within the range of elastic deformation.

  On the other hand, as shown in FIG. 3 (b), when the ambient temperature falls to a lower temperature side than normal temperature, the inner aluminum conductor 2 has a larger volume shrinkage than the outer copper terminal 10, The contact pressure at the interface between the outer copper terminal 10 and the aluminum conductor 2 decreases, and in the worst case, a gap 5 may be formed at the interface between the terminal 10 and the conductor 2 as shown. When the gap 5 occurs, the contact resistance increases. Therefore, especially in low temperature conditions, the electrical connection performance is greatly reduced.

Therefore, conventionally, in order to avoid such a problem, when an aluminum electric wire is used, an aluminum terminal is also used as the terminal (see Patent Documents 1 and 2). Alternatively, when it is necessary to connect a copper terminal and an aluminum terminal, copper (including a copper alloy) and aluminum (including an aluminum alloy) are metal-bonded by solid phase bonding using ultrasonic waves.
Japanese Patent Laying-Open No. 2003-249284 (FIG. 7)

  However, when an aluminum terminal is used, aluminum is inferior to copper in comparison with copper, so that when the terminal has a spring portion, there is a problem that the portion is easily sag. Moreover, when a copper terminal is used and a terminal and a conductor are solid-phase bonded by ultrasonic waves, there is a problem that the crimping operation becomes troublesome.

  In consideration of the above circumstances, the present invention makes it possible to stabilize the contact resistance of the crimping part even under heat cycle or thermal shock conditions while using a spring-rich copper terminal. It is an object of the present invention to provide a method for crimping a terminal that can be used.

  According to a first aspect of the present invention, there is provided a method for crimping a terminal against an electric wire, wherein a crimp portion of a terminal made of a first metal material is a conductor of an electric wire made of a second metal material having a larger linear expansion coefficient than the first metal material. On the other hand, in a method for crimping a terminal against an electric wire that is crimped so as to be wrapped from the outside, the terminal is crimped to a conductor of the electric wire in a temperature atmosphere lower than room temperature.

  Invention of Claim 2 is the crimping method of the terminal with respect to the electric wire of Claim 1, Comprising: In the temperature atmosphere below the lower limit of the temperature range where the use of the product after crimping is assumed, the said terminal of the said electric wire It is characterized by being crimped to a conductor.

  Invention of Claim 3 is the crimping method of the terminal with respect to the electric wire of Claim 2, Comprising: The 1st metal material which comprises the said terminal is copper or a copper alloy, The 2nd which comprises the conductor of the said electric wire The metal material is aluminum or an aluminum alloy.

  Invention of Claim 4 is the crimping | compression-bonding method of the terminal with respect to the electric wire of Claim 3, Comprising: The said electric wire is an electric wire for wire harnesses of a motor vehicle, The temperature range where the use is assumed is -40 degreeC-120. The terminal is crimped to the conductor of the electric wire in a temperature atmosphere of −40 ° C. or lower, which is a range of ° C., which is the lower limit value thereof.

  Invention of Claim 5 is the crimping method of the terminal with respect to the electric wire of Claim 4, Comprising: In the atmosphere which used at least any one among liquid carbon dioxide, liquid nitrogen, and liquid helium as a refrigerant body, The terminal is crimped to the conductor of the electric wire.

  According to the invention of claim 1, since the terminal is crimped to the conductor of the electric wire under a temperature condition lower than normal temperature, the interface between the terminal and the conductor at the crimping location even when the ambient temperature is lowered to at least the temperature at the time of crimping. In addition, a gap due to a difference in volume expansion does not occur, and the contact resistance between the terminal and the conductor can be stabilized. In addition, even if the ambient temperature is lowered to a temperature below the temperature at the time of crimping, it is possible to keep the gap generated at the interface between the terminal and the conductor small, so than when crimping at room temperature, The contact resistance between the terminal and the conductor can be stabilized. Also, if the ambient temperature rises above the temperature at the time of crimping, the inner conductor will always expand more greatly than the terminal that wraps the outer side, so there will be a gap at the interface between the terminal and the conductor. There is no. In addition, since no ultrasonic equipment or the like is required, the operation can be simplified.

  According to invention of Claim 2, since a terminal is crimped | bonded to the conductor of an electric wire under the temperature conditions below the lower limit of the temperature range where the use of the product after crimping is assumed, There is no concern that a gap due to a difference in volume expansion will occur at the interface between the terminal and the conductor, and the contact resistance between the terminal and the conductor can be stabilized. Therefore, stable performance can be exhibited even under expected heat cycle or thermal shock conditions.

  According to the invention of claim 3, even when a terminal using copper or a copper alloy having a small linear expansion coefficient is connected by crimping to a conductor using aluminum or an aluminum alloy having a large linear expansion coefficient, Since a stable contact resistance can be obtained, the connection reliability between the copper terminal and the aluminum electric wire can be enhanced while maintaining the spring performance of the terminal having the spring contact portion.

  According to invention of Claim 4, it can prevent that the clearance gap by volume expansion difference arises in the interface of a terminal and a conductor in the whole use temperature range of the wire harness of a motor vehicle, and the contact resistance of a terminal and a conductor Can be stabilized.

  According to the invention of claim 5, since the terminal is crimped to the conductor of the electric wire in an atmosphere in which at least one of liquid carbon dioxide, liquid nitrogen, and liquid helium is used as a refrigerant, particularly in an extremely cold region Also in use, it is possible to improve the connection reliability of the crimp portion between the aluminum electric wire and the copper terminal.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. Note that FIG. 2 is referred to for the configuration of the crimping portion of the terminal.

  The crimping method of this embodiment is a method in the case of crimping | bonding the copper terminal 10 as a crimp terminal for aluminum wires with respect to the aluminum wire 1 for wire harnesses used for a motor vehicle. The use temperature range of the wire harness of an automobile is in the range of −40 ° C. to 120 ° C. The material (second metal material) of the conductor 2 of the aluminum electric wire 1 is aluminum or an aluminum alloy, and the material (first metal material) of the copper terminal 10 is copper or a copper alloy. Therefore, the linear expansion coefficient of the conductor 2 is larger than the linear expansion coefficient of the terminal 10.

  When crimping, the crimping portion 12 of the terminal 10 is crimped to the conductor 2 of the electric wire 1 so as to be wrapped from the outside. In that case, in the method of this embodiment, as shown to Fig.1 (a), it crimps | bonds in the temperature atmosphere below -40 degreeC which is the lower limit of the said temperature range. For example, pressure bonding is performed in a cryogenic atmosphere of liquid carbon dioxide gas, liquid nitrogen, or liquid helium.

  As described above, when the terminal 10 is crimped to the conductor 2 of the electric wire under a temperature condition considerably lower than normal temperature, even when the ambient temperature is lowered to at least the temperature at the time of crimping, the terminal 10 and the conductor 2 are brought to the interface at the crimping portion. Since no gap due to the difference in volume expansion occurs, the contact resistance between the terminal 10 and the conductor 2 can be stabilized.

  In particular, in this embodiment, since the terminal 10 is crimped to the conductor 2 of the electric wire under a temperature condition that is equal to or lower than the lower limit (−40 ° C.) of the temperature range in which the product after crimping is assumed to be used, normal use is assumed. In the temperature range, there is no concern that a gap due to a difference in volume expansion occurs at the interface between the terminal 10 and the conductor 2, and the contact resistance between the terminal 10 and the conductor 2 can be stabilized. Therefore, stable performance can be exhibited even under expected heat cycle or thermal shock conditions. Further, when the terminal 10 is pressure-bonded to the conductor 2 of the electric wire in an atmosphere using at least one of liquid carbon dioxide, liquid nitrogen, and liquid helium as a refrigerant, aluminum is used even in use in a cold region. The connection reliability of the crimping part of an electric wire and a copper terminal can be improved.

  Moreover, when the ambient temperature rises above the temperature at the time of crimping, for example, when the ambient temperature becomes 23 ° C. as shown in FIG. 1B, or the temperature rises to 120 ° C. as shown in FIG. 1C. Even in this case, the inner conductor 2 always expands more greatly than the terminal 10 that wraps the outer side, so that there is no gap at the interface between the terminal 10 and the conductor 2.

  Moreover, the connection reliability of a copper terminal and an aluminum electric wire can be improved by using a copper terminal, maintaining the spring performance of the terminal which has a spring contact part.

  In addition, even if it does not reach to severe conditions of -40 degrees C or less, since it can suppress the gap | interval produced in the interface of the terminal 10 and the conductor 2 small by performing crimping | compression-bonding in temperature atmosphere considerably lower than normal temperature, Therefore, the contact resistance between the terminal 10 and the conductor 2 can be stabilized more than when the crimping is performed. Further, in order to reduce the contact resistance, the terminal 10 may be subjected to tin plating or gold plating.

It is explanatory drawing of embodiment of this invention, (a) is the state at the time of crimping | compression-bonding at low temperature, (b) is the state at normal temperature, (c) is the state of the crimping | compression-bonding part which each shows the state when the temperature rises to 120 degreeC. It is a schematic cross section. It is explanatory drawing of the crimping method of a general terminal. It is explanatory drawing of the conventional crimping | compression-bonding method, (a) is the state at the time of crimping | crimping at normal temperature, (b) is the state at the time of becoming low temperature, (c) is the crimping | compression-bonding which shows a state when the temperature rises to 120 degreeC, respectively. It is a schematic cross section of a part.

Explanation of symbols

1 Electric wire 2 Conductor 10 Crimp terminal (terminal)
12 Crimp part 14 Crimp piece

Claims (5)

A terminal for an electric wire that crimps the crimp portion of the terminal made of the first metal material to the conductor of the electric wire made of the second metal material having a larger linear expansion coefficient than the first metal material so as to be wrapped from the outside. In the crimping method of
A method for crimping a terminal against an electric wire, wherein the terminal is crimped to a conductor of the electric wire in a temperature atmosphere lower than normal temperature. A method for crimping a terminal to an electric wire according to claim 1,
A method for crimping a terminal to an electric wire, comprising crimping the terminal to a conductor of the electric wire in a temperature atmosphere equal to or lower than a lower limit value of a temperature range in which use of the product after the crimping is assumed. A method for crimping a terminal against an electric wire according to claim 2,
A method for crimping a terminal against an electric wire, wherein the first metal material constituting the terminal is copper or a copper alloy, and the second metal material constituting the conductor of the electric wire is aluminum or an aluminum alloy. A method for crimping a terminal against an electric wire according to claim 3,
The electric wire is an electric wire for a wire harness of an automobile, and a temperature range in which the electric wire is assumed to be used is in a range of −40 ° C. to 120 ° C., and the terminal is used in a temperature atmosphere of −40 ° C. or lower which is the lower limit value. A method for crimping a terminal to an electric wire, comprising crimping the conductor of the electric wire. A method for crimping a terminal against an electric wire according to claim 4,
A terminal crimping method for an electric wire, wherein the terminal is crimped to a conductor of the electric wire in an atmosphere using at least one of liquid carbon dioxide, liquid nitrogen, and liquid helium as a refrigerant.

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