DESCRIPTION
Title of Invention
WIRE CONNECTING METHOD OF ALUMINUM WIRE AND COPPER WIRE AND
ELECTRIC MOTOR USING THE WIRE CONNECTING METHOD
Technical Field
[0001]
The present invention relates to a wire connecting method of an aluminum wire and a copper wire and an electric motor using the wire connecting method. Background Art
[0002]
In a conventional electric motor mounted, for example, in a hermetic type compressor, an aluminum wire is used as a winding wire and a copper wire is used as a crossover wire to reduce the cost. In such an electric motor, the aluminum wire and the copper wire are connected each other using a crimp terminal having two conductive grooves provided side by side. That is, an end of the aluminum wire and an end of the copper wire are press-fitted into two conductive grooves provided side by side on both sides of a central piece portion of a crimp terminal. Thus, the conductive grooves of the crimp terminal are expanded, the elastic force acts, as crimp stress, on the end of the aluminum wire and the end of the copper wire, and reliability can be ensured (see, for example, Patent Literature 1). Citation List Patent Literature
[0003]
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2010-166643 (Fig. 5) Summary of Invention Technical Problem
[0004]
However, the wire connection by press-fitting an end of an aluminum wire and an end of a copper wire into two conductive grooves provided side by side on both

sides of a central piece portion of a crimp terminal has the following problems (1) and (2).
(1) When an aluminum wire is press-fitted into one of two conductive grooves provided side by side on both sides of a central piece portion of a crimp terminal, and a copper wire is press-fitted into the other one of the conductive grooves, because the aluminum wire is lower in stiffness than the copper wire, the central piece portion of the crimp terminal is inclined toward the aluminum wire, the entrance of the conductive groove into which the aluminum wire is press-fitted is narrowed, and the inner part of the conductive groove into which the aluminum wire is press-fitted is wide. Because the aluminum wire is deformed at the entrance of the conductive groove and is press-fitted to the inner part of the conductive groove, the crimp stress decreases compared to the case of crimp of a copper wire.
(2) When this method is used in a device whose atmospheric temperature around a wire connection portion increases during operation, such as a hermetic type compressor, stress relaxation progresses owing to thermal creep. Consequently, the crimp stress to the aluminum wire by the crimp terminal decreases as time proceeds. When the initial crimp stress is low, contact resistance increases owing to the above-described chronological change, and at worst, electric connection is lost.
[0005]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a wire connecting method of an aluminum wire and a copper wire by which the long-term reliability in the case of connecting an aluminum wire and a copper wire can be ensured, and an electric motor in which the wire connecting method is used. Solution to Problem
[0006]
A wire connecting method of an aluminum wire and a copper wire of an embodiment of the present invention uses a crimp terminal in which two conductive grooves are provided side by side, and an insulating member having a cavity housing the crimp terminal and two anvils protruding in the cavity. The two anvils correspond

to the two conductive grooves. The wire connecting method of an aluminum wire and a copper wire includes placing an end of an aluminum wire on one of the two anvils, placing an end of a copper wire on the other of the two anvils, and press-fitting each of the end of the aluminum wire and the end of the copper wire into a corresponding one of the two conductive grooves of the crimp terminal being housed in the cavity. The end of the aluminum wire is press-fitted into one of the two conductive grooves of the crimp terminal before the end of the copper wire is press-fitted into the other one of the two conductive grooves of the crimp terminal.
In an electric motor of an embodiment of the present invention, an aluminum wire is used as a winding wire of a stator and a copper wire is used as a crossover wire. A wire connection portion of the winding wire and the crossover wire is made using the above wire connecting method of an aluminum wire and a copper wire. Advantageous Effects of invention
[0007]
In the wire connecting method of an aluminum wire and a copper wire of an embodiment of the present invention, the end of the aluminum wire is press-fitted into one of the two conductive grooves before the end of the copper wire is press-fitted into the other one of the two conductive grooves. If the copper wire is press-fitted into one of the conductive grooves of the crimp terminal first, the entrance part of the other one of the conductive grooves into which the aluminum wire is press-fitted is narrowed, the aluminum wire is deformed at the entrance part, and the inner part is wider than the entrance. Consequently, the crimp stress between the crimp terminal and the aluminum wire decreases. However, by first press-fitting the aluminum wire into one of the conductive grooves of the crimp terminal and then press-fitting the copper wire into the other one of the conductive grooves of the crimp terminal, the problem can be solved in that the aluminum wire is deformed at the entrance of the conductive groove to decrease the crimp stress. Also, the increase in contact resistance with the crimp terminal can be minimized, and the long-term reliability can be ensured against thermal creep.

In the electric motor according to an embodiment of the present invention, the
wire connection portion of the winding wire and the crossover wire is achieved by the
above-described wire connecting method of an aluminum wire and a copper wire to
easily ensure reliability.
Brief Description of Drawings
[0008]
[Fig. 1] Fig. 1 is a top view showing an electric motor in which a wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used.

[Fig. 2] Fig. 2 is an exploded perspective view showing a wire connection portion in which the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used.

[Fig. 3] Fig. 3 is a sectional view showing the relationship between heights of the anvils and two conductive grooves of a crimp terminal of the wire connection portion in which the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used.

[Fig. 4] Fig. 4 illustrates a method for obtaining sizes in the wire connection portion in which the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used so that an aluminum wire comes into contact with the crimp terminal before a copper wire comes into contact with the crimp terminal.

[Fig. 5] Fig. 5 is a sectional view showing the relationship between heights of the anvils, diameters, and the two conductive grooves of the crimp terminal of the wire connection portion in which a wire connecting method of an aluminum wire and a copper wire according to Embodiment 2 of the present invention is used.

[Fig. 6] Fig. 6 illustrates the shape of two conductive grooves of a crimp terminal of a wire connection portion in which a wire connecting method of an aluminum wire and a copper wire according to Embodiment 3 of the present invention is used. Description of Embodiments

[0009] Embodiment 1
The present invention will be described below with reference to embodiments shown in the drawings.

Fig. 1 is a top view showing an electric motor in which a wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used.
Fig. 2 is an exploded perspective view showing a wire connection portion in which the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used.
Fig. 3 is a sectional view showing the relationship between heights of the anvils and two conductive grooves of a crimp terminal of the wire connection portion in which the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used.
The wire connection portion in which the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used is disposed on one end face of a stator core 10 of an electric motor as shown in Fig. 1 to Fig. 3. That is, the wire connection portion includes crimp terminals 1 each in which two conductive grooves 1a and 1b are provided side by side with a central piece portion 1c between the two conductive grooves 1a and 1b, and an insulating member 2 having cavities 6 and 7 capable of housing the crimp terminals 1.
[0010]
The cavities 6 and 7 are each provided with two lead-wire binding grooves 8a and 8b. In the lead-wire binding grooves 8a and 8b, anvils 9 corresponding to the two conductive grooves 1a and 1b of the crimp terminal 1 are provided to protrude upward from the bottom surfaces. The anvils 9 include an aluminum-wire-side anvil 9a on which an end of an aluminum wire, namely, a winding start end 3 of a winding wire or a winding finish end 4 of another winding wire is placed, and a copper-wire-side anvil 9b on which an end of either one of copper wires, namely, crossover wires 5 that connect the winding wires is placed. The protruding height of the aluminum-wire-side anvil 9a is formed to be higher than the protruding height of the copper-wire-

side anvil 9b. Thus, the end of the aluminum wire (the winding start end 3 of the winding wire or the winding finish end 4 of the other winding wire) can be press-fitted into the conductive groove 1 a of the crimp terminal 1 before the end of the copper wire (the crossover wire 5) is press-fitted into the conductive groove 1b.
[0011]
Next, the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention will be described with reference to Fig. 1 to Fig. 3.
First, the aluminum wires, namely, the winding start end 3 of the winding wire and the winding finish end 4 of the other winding wire, and the copper wires, namely, the crossover wires 5 are placed on the cavities 6 and 7. Next, from above these ends and the crossover wires 5 (hereinafter also collectively referred to as "lead wires"), crimp terminals 1 each having conductive grooves 1a and 1b having a smaller width than the diameter of these lead wires, are press-fitted into the cavities 6 and 7 with the conductive grooves 1a and 1b facing the respective lead wires. Then, the aluminum wires, namely, the winding start end 3 of the winding wire and the winding finish end 4 of the other winding wire, and the copper wires, namely, the crossover wires 5 are bound by the lead-wire binding grooves 8a and 8b provided in the cavities 6 and 7, and insulating layers of the aluminum wires and the copper wires are removed by the edges of the conductive grooves 1a and 1b of the crimp terminals 1. Thus, the aluminum wires, namely, the winding start end 3 of the winding wire and the winding finish end 4 of the other winding wire, and the copper wires, namely, the crossover wires 5 are electrically connected.
[0012]
To ensure crimp stress necessary for long-term reliability, the heights of the anvils 9 are changed so that the aluminum wires are press-fitted into the crimp terminals 1 before the copper wires are press-fitted into the crimp terminals 1 to make the height of the aluminum-wire-side anvils 9a higher than the height of the copper-wire-side anvils 9b so that the copper wires having higher stiffness than the crimp terminal 1 are press-fitted into the conductive grooves 1 b after the aluminum wires

are press-fitted into the conductive grooves 1a. In other words, the press-fitting depth of the copper wires, which has higher stiffness than the crimp terminal 1, into the conductive grooves 1b is shallower than the press-fitting depth of the aluminum wires into the conductive grooves 1a. Thus, crimp stress on the aluminum wire side can be increased with pressing force to the conductive grooves 1a of the aluminum wires generated with the expansion of the conductive grooves 1b of the crimp terminals 1 due to press-fitting of the copper wires, and therefore increase in contact resistance can be minimized. Consequently, the long-term reliability of the wire connection between the crimp terminals 1 and the aluminum wires, namely, the winding start end 3 of the winding wire and the winding finish end 4 of the other winding wire can also be ensured against thermal creep. An electric motor having a wire connection portion of winding wires and crossover wires that is made using such a wire connecting method of an aluminum wire and a copper wire has an improved reliability.
[0013]
Fig. 4 illustrates a method for obtaining sizes in the wire connection portion in which the wire connecting method of an aluminum wire and a copper wire according to Embodiment 1 of the present invention is used so that the aluminum wire comes into contact with the crimp terminal before the copper wire comes into contact with the crimp terminal.
In Fig. 4, the height from the lower surfaces of the cavities 6 and 7 of the crimp terminal 1 to the upper surfaces of the aluminum-wire-side anvils 9a is denoted by A, the height from the lower surfaces of the cavities 6 and 7 of the crimp terminal 1 to the upper surfaces of the copper-wire-side anvils 9b is denoted by B, the diameter of the aluminum wires is denoted by