Patent Description:
< <CIT> (disclosing the preamble of claims <NUM> and <NUM> respectively) describes a copper piece welding method comprising: in a first period of time, a first laser with a first power is used to irradiate a first preset areas and a first molten pool is formed in the first preset area. Thereafter, a second molten pool is formed by a second laser. A spots irradiated with the first and second lasers are different from each other and the portion welded by the first laser is irradiated with the second laser.

<CIT> also describes a welding method and device for copper and copper alloy materials. The known welding method is performed using composite laser light including main-band laser light and sub-band laser light.

A welding method using laser light has been widely known. For example, Patent Document <NUM> discloses that a workpiece is preheated by irradiation with a first laser light along a planned welding line, and is welded by irradiation of the preheated portion with a second laser light while a filler wire is supplied to the preheated portion.

In an electric rotating machine such as an electric motor or an electric generator, a plurality of conductor segments is respectively inserted into a plurality of slots formed at a stator core, and end portions of the conductor segments inserted into the slots are welded.

In the case where the end portions of the conductor segments are welded by arc welding, it is, due to high heat input, necessary to increase the length of an exposed conductor portion extending to the end portion of the conductor segment in order to prevent melting of an insulating coating that insulates among the conductor segments, and for this reason, it is difficult to reduce a coil end portion in size. Moreover, for arc welding, grounding is necessary.

In the case of using laser light, welding can be performed with less thermal influence because of high energy density. However, the conductor segment is generally made of copper, and copper has a low energy absorption rate in the wavelength range of the laser light used for welding. For this reason, it is difficult to perform welding with the laser light.

It is an object of the present disclosure to provide a laser welding method for welding a material containing copper as a main component with laser light.

The present invention relates to a laser welding method for welding a material (<NUM>) containing copper as a main component according to claim <NUM>. The method includes heating the material (<NUM>) by irradiation with a first laser light (L1) and welding the material (<NUM>) by irradiation of a portion, which has been irradiated with the first laser light (L1), of the material (<NUM>) with a second laser light (L2) with which an energy absorption rate of copper contained in the material (<NUM>) increases by an increase in a temperature of the material (<NUM>).

In the first aspect, the material (<NUM>) containing copper as the main component is heated by irradiation with the first laser light (L1). In addition, the portion of the material (<NUM>) irradiated with the first laser light (L1) is irradiated with the second laser light (L2). With the second laser light (L2), the energy absorption rate of copper contained in the material (<NUM>) increases by an increase in the temperature of the material (<NUM>). Thus, when the portion heated and temperature-increased by irradiation with the first laser light (L1) is irradiated with the second laser light (L2), the second laser light (L2) is absorbed by copper contained in the material (<NUM>) at a high energy absorption rate, and high energy density is applied to the material (<NUM>). Accordingly, the material (<NUM>) is melted, and can be welded. Thus, the material (<NUM>) containing copper as the main component can be welded using a combination of the first and second laser lights (L1, L2).

According to the present invention, the wavelength of the first laser light (L1) is <NUM> or less. Since the energy absorption rate of copper is increased, the temperature of the material (<NUM>) can be stably increased.

In a second embodiment of the present invention, a light source of the first laser light (L1) is a diode laser. In the fourth aspect, the first laser light (L1) can be easily obtained.

In a third embodiment of the present invention, the wavelength of the second laser light (L2) is <NUM> or more. In the fifth aspect, the material (<NUM>) can be efficiently brought into a weldable molten state.

In a fourth embodiment of the present invention, a light source of the second laser light (L2) is an infrared laser. In the sixth aspect, the second laser light (L2) can be easily obtained.

In a fifth embodiment of the present invention, the number of beams of the second laser light (L2) is one or more for one beam of the first laser light (L1). In the seventh aspect, the number of beams of the second laser light (L2) is at least one for one beam of the first laser light (L1), but if there are two or more beams of the second laser light (L2) for one beam of the first laser light (L1), the material (<NUM>) can be more uniformly melted.

In a sixth embodiment of the present invention, the material (<NUM>) is irradiated with two or more pairs of the first and second laser lights (L1, L2). In the eighth aspect, variation in welding can be reduced.

The present invention further relates to a method for manufacturing an electric rotating machine (<NUM>) according to claim <NUM>, in which a plurality of conductor segments (<NUM>) is respectively inserted into a plurality of slots formed at a stator core (<NUM>) and end portions of the plurality of conductor segments (<NUM>) inserted into the slots are made of a material (<NUM>) containing copper as a main component. The method includes welding the end portions of the plurality of conductor segments (<NUM>) by the laser welding method being described previously.

According to the invention defined in claim <NUM>, the first and second laser lights (L1, L2) are combined so that the end portions of the conductor segments (<NUM>) made of the material (<NUM>) containing copper as the main component can be welded to each other. Since high energy density is applied to the conductor segment (<NUM>), it is not necessary to increase the length of an exposed conductor portion extending to the end portion of the conductor segment (<NUM>), and therefore, a coil end portion can be reduced in size. Further, since high-speed welding among the end portions of the conductor segments (<NUM>) can be performed, a high production capacity can be obtained. Moreover, since additional equipment for obtaining a high production capacity is not necessary, reduction in an equipment investment can be achieved.

In an embodiment of the present invention according to claim <NUM>, each of the end portions of the plurality of conductor segments (<NUM>) is irradiated with one or more pairs of the first and second laser lights (L1, L2). In the tenth aspect, variation in welding among the end portions of the conductor segments (<NUM>) can be reduced.

In the following, an embodiment will be described in detail.

In a laser welding method according to the embodiment, a material (<NUM>) containing copper as a main component is irradiated with laser light, and is welded to a bonding target metal material (<NUM>). In this case, as shown in <FIG>, a surface of the material (<NUM>) is heated by irradiation with a first laser light (L1), and is welded to the bonding target metal material (<NUM>) by irradiation of the heated surface of the portion, which has been irradiated with the first laser light (L1), of the material (<NUM>) with a second laser light (L2) with which the energy absorption rate of copper contained in the material (<NUM>) increases by an increase in the temperature of the material (<NUM>).

In the laser welding method according to this embodiment, the material (<NUM>) containing copper as the main component is heated by irradiation with the first laser light (L <NUM>). In addition, the portion of the material (<NUM>) irradiated with the first laser light (L1) is irradiated with the second laser light (L2). With the second laser light (L2), the energy absorption rate of copper contained in the material (<NUM>) increases by an increase in the temperature of the material (<NUM>). Thus, when the portion heated and temperature-increased by irradiation with the first laser light (L1) is irradiated with the second laser light (L2), the second laser light (L2) is absorbed by copper contained in the material (<NUM>) at a high energy absorption rate, and the high energy density is applied to the material (<NUM>). Accordingly, the material (<NUM>) is melted, and can be welded to the bonding target metal material (<NUM>). Thus, the material (<NUM>) containing copper as the main component can be welded to the bonding target metal material (<NUM>) by use of a combination of the first and second laser lights (L1, L2).

For example, as shown in <FIG>, for a laser light having a wavelength band of around <NUM>, the energy absorption rate of copper is high, but it is difficult to obtain a level of high energy density which can be used for welding. On the other hand, a laser light having a wavelength band of around <NUM> can provide high energy density suitable for welding, but the energy absorption rate of copper is low for such a laser light. Here, copper has such properties that when the temperature increases, the energy absorption rate for the laser light having a wavelength band of around <NUM> increases. Accordingly, the former can be suitably used as the first laser light (L1), and the latter can be suitably used as the second laser light (L2).

Here, the material (<NUM>) containing copper as the main component may be either pure copper or a copper alloy containing <NUM> mass% or more of copper. The bonding target metal material (<NUM>) may be made of the same metal as in the material (<NUM>), which contains copper as a main component, or may be made of a different type of metal.

The wavelength of the first laser light (L1) is according to the present invention <NUM> or less for efficiently increasing the temperature of the material (<NUM>), as the energy absorption rate of copper is high, for stably increasing the temperature of the material (<NUM>). The wavelength of the first laser light (L1) is according to the present invention <NUM> or more for a practical perspective. The first laser light (L1) may be a single-wavelength laser light, or may be laser light with a plurality of different wavelengths superimposed.

The energy absorption rate of copper contained in the material (<NUM>) for the first laser light (L1) at <NUM> is preferably <NUM>% or more, more preferably <NUM>% or more for efficiently increasing the temperature of the material (<NUM>).

The power density of the first laser light (L1) is preferably <NUM> W/cm<NUM> or more, more preferably <NUM> W/cm<NUM> or more, and preferably <NUM> W/cm<NUM> or less for efficiently increasing the temperature of the material (<NUM>).

A light source of the first laser light (L1) is preferably a diode laser, more preferably one having an oscillation wavelength band of <NUM> or more to <NUM> or less as described above.

The temperature of the material (<NUM>) heated by irradiation with the first laser light (L1) is preferably <NUM> or more, more preferably <NUM> or more, and preferably <NUM> or less for increasing the energy absorption rate for the second laser light (L2).

The wavelength of the second laser light (L2) is preferably <NUM> or more, more preferably <NUM> or more, and preferably <NUM> or less for efficiently bringing the material (<NUM>) into a weldable molten state. The wavelength of the second laser light (L2) is preferably <NUM> or less for a practical perspective The second laser light (L2) may be a single-wavelength laser light, or may be laser light with a plurality of different wavelengths superimposed.

The energy absorption rate of copper contained in the material (<NUM>) for the second laser light (L2) after the temperature has increased is preferably <NUM>% or more, more preferably <NUM>% or more for bringing the heated material (<NUM>) into the weldable molten state. The energy absorption rate of copper contained in the material (<NUM>) for the second laser light (L2) at <NUM> before the temperature increases is, for example, <NUM>% or more to <NUM>% or less.

The power density of the second laser light (L2) is preferably <NUM> W/cm<NUM> or more, more preferably <NUM> W/cm<NUM> or more, and preferably <NUM> W/cm<NUM> or less for efficiently bringing the material (<NUM>) into the weldable molten state.

A light source of the second laser light (L2) is preferably an infrared laser.

Irradiation of the material (<NUM>) with the first and second laser lights (L1, L2) is according to the present invention performed such that the second laser light (L2) is contained in the first laser light (L1), as shown in <FIG>. The number of beams of the second laser light (L2) is one or more for one first laser light (L1), and as shown in <FIG>, is at least one for one first laser light (L1). However, if there are two or more beams of the second laser light (L2) for one beam of the first laser light (L1) as shown in <FIG>, the material (<NUM>) can be more uniformly melted.

Next, a method of manufacturing an electric rotating machine (<NUM>) such as an electric motor or an electric generator by the laser welding method according to the embodiment will be described.

As shown in <FIG>, in the electric rotating machine (<NUM>), a plurality of conductor segments (<NUM>) is respectively inserted into a plurality of slots (not shown) formed at a stator core (<NUM>), and end portions of the plurality of conductor segments (<NUM>) inserted into the slots are made of the material (<NUM>) containing copper as the main component. Then, in such manufacturing, each of the end portions of the plurality of conductor segments (<NUM>) is spot-irradiated with the first and second laser lights (L1, L2) by the laser welding method according to the embodiment, as shown in <FIG>. Accordingly, the end portions of the plurality of conductor segments (<NUM>) are welded to each other as shown in <FIG>. In this case, the end portions of the plurality of conductor segments (<NUM>) may be irradiated with the first and second laser lights (L1, L2) such that the first and second laser lights (L1, L2) are swept thereon, as shown in <FIG>.

As described above, the first and second laser lights (L1, L2) are combined using the laser welding method according to the embodiment so that the end portions of the conductor segments (<NUM>) made of the material (<NUM>) containing copper as the main component can be welded to each other. In this case, and according to the present invention, the first laser light (L1) having a low energy density and the second laser light (L2) having a high energy density are superimposed on each other, thus a thermally-conductive welding portion (<NUM>) welded so as to be bridged between end surfaces of the conductor segments (<NUM>) and a keyhole-shaped welding portion (<NUM>) welded by Infiltration of the material (<NUM>) into between the end portions of the conductor segments (<NUM>) are formed between the end portions of the conductor segments (<NUM>) as shown in <FIG>. Thus, a high welding strength can be obtained.

Since high energy density is applied to the conductor segment (<NUM>), it is not necessary to increase the length of an exposed conductor portion extending to the end portion of the conductor segment (<NUM>), and therefore, a coil end portion can be reduced in size. Further, since high-speed welding among the end portions of the conductor segments (<NUM>) can be performed, a high production capacity can be obtained. Moreover, since additional equipment for obtaining a high production capacity is not necessary, reduction in an equipment investment can be achieved.

In manufacturing of the electric rotating machine (<NUM>), each of the end portions of the plurality of conductor segments (<NUM>) is irradiated with one or more pairs of first and second laser lights (L1, L2). Each of the end portions of the plurality of conductor segments (<NUM>) is irradiated with at least one pair of first and second laser lights (L1, L2), as shown in <FIG>. When each end portion is irradiated with two or more pairs of first and second laser lights (L1, L2) as shown in <FIG>, variation in welding among the end portions of the conductor segments (<NUM>) can be reduced.

Claim 1:
A laser welding method for welding a material (<NUM>) containing copper as a main component, the laser welding method comprising:
heating the material (<NUM>) by irradiation with a first laser light (L1) and welding the material (<NUM>) by irradiation of a portion, which has been irradiated with the first laser light (L1), of the material (<NUM>) with a second laser light (L2) with which an energy absorption rate of the copper contained in the material (<NUM>) increases by an increase in a temperature of the material (<NUM>), wherein
a wavelength of the first laser light (L1) is <NUM> or more and <NUM> or less, the method being characterised in that:
the first laser light (L1) and the second laser light (L2) are superimposed on each other, and in that:
the second laser light (L2) is contained in the first laser light (L1).