Busbar connection method, busbar connection structure

Abstract

Laser irradiation provides a good weld condition when welding and joining busbars together. [Solution] The tip of busbar 2 is inserted into a through hole formed in busbar 1 and connected by welding. Step 1 involves irradiating the tip of busbar 2 protruding from the through hole with a laser to melt it. Step 2 involves irradiating the area near the through hole into which the tip of busbar 2 is inserted with a laser to remelt both busbars 1 and 2.

Description

Technical Field

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[0001] The present invention relates to a technique for connecting busbars by laser welding.

Background Art

[0002] As is well known, high efficiency is required in power conversion devices, and busbars with low impedance are often used instead of electric wires for connecting electrical components (such as capacitors and IGBTs) within the power conversion device.

[0003] When processing such busbars, it is not uncommon to join a pair of busbars by laser welding. For example, in Non-Patent Document 1, a method for connecting busbars is proposed in which a through-hole is formed in one busbar, and the tip of the other busbar is inserted therein and laser welded in a T shape. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​In this regard, Non-Patent Document 1 describes inserting the tip into the through hole, and then melting the tip (protruding portion) that protrudes from the through hole by laser irradiation to bring the busbars into close contact. However, in this state, the penetration between the busbars may be insufficient, and a good weld condition may not be obtained.

[0007] This invention was made to solve the problems of the conventional method, and aims to achieve a good weld condition when joining busbars together by laser irradiation. [Means for solving the problem]

[0008] (1) One aspect of the present invention is a method of connecting two busbars by welding, in which the tip of one busbar is inserted into a through hole formed in one busbar, A first step involves irradiating the tip of the other busbar protruding from the through hole with a laser to melt it, A second step involves remelting both busbars by irradiating the area near the through hole into which the tip of the other busbar is inserted with a laser, It is characterized by having [this feature].

[0009] (2) Another aspect of the present invention is a structure in which the busbars are connected by welding by inserting the tip of one busbar into a through hole formed in one busbar and irradiating it with a laser, The aforementioned through hole is While it is formed in a horizontally elongated, roughly rectangular shape, The aforementioned tip portion is It is formed in a roughly convex shape, An insertion portion formed to be narrower than the longitudinal direction of the through hole, A main body portion formed wider than the longitudinal direction of the through hole, The stepped portion between the insertion portion and the main body portion, Equipped with, When the insertion portion is inserted from one side of the through hole to the other side and protrudes from the other side of the through hole, The main body is positioned on one side of the through hole. The invention is characterized in that when a laser is irradiated along the width direction of the insertion portion, the gap between the insertion portion and the through hole is closed by the stepped portion.

[0010] (3) The present invention can also be configured as a power conversion device equipped with the busbar connection structure described above. [Effects of the Invention]

[0011] According to the present invention, a good weld condition can be obtained when welding and joining busbars together by laser irradiation. [Brief explanation of the drawing]

[0012] [Figure 1] A perspective view showing a busbar connection method (connection structure) according to an embodiment of the present invention, in which one busbar is inserted into the other busbar. [Figure 2] (a) is a plan view showing the laser irradiation in the first step of Example 1, (b) is a cross-sectional view of line AA in Figure 1 before laser irradiation in (a), and (b) is a cross-sectional view of line AA in the same figure after laser irradiation. [Figure 3] (a) is a plan view showing the laser irradiation in the second step of Example 1, (b) is a cross-sectional view of line AA in Figure 1 before laser irradiation in (a), and (b) is a cross-sectional view of line AA in the same figure after laser irradiation. [Figure 4] (a) is a partial view showing the tip of the other busbar in Example 2, and (b) is a plan view showing the laser irradiation in the first step of the same example. [Modes for carrying out the invention]

[0013] The following describes a busbar connection method (connection structure) according to an embodiment of the present invention. This connection method is used, for example, in an inverter device for controlling the power supplied to an electric motor mounted on an electric vehicle (EV) or hybrid vehicle (HV).

[0014] That is, the inverter device includes a semiconductor module incorporating a power semiconductor device such as an insulated gate bipolar transistor (IGBT) as described above, a drive circuit for driving the semiconductor module, a control circuit for controlling the drive circuit, and various electrical components such as a capacitor for current smoothing.

[0015] Not only the connection between the electrical components in such an inverter device, but also as the power wiring supplied from the battery and the power wiring supplied to the motor, it is not uncommon to use a bus bar with low impedance instead of an electric wire, and the above connection method is applied.

[0016] As shown in FIG. 1, the connection method is to connect the bus bar 1 of one electrical component to be connected and the bus bar 2 of the other electrical component in a T shape. Here, a horizontally long rectangular through hole 3 (see FIG. 2) along the width direction is formed in the bus bar 1.

[0017] The tip 2a of the bus bar 2 is inserted into the through hole 3 from one side (D side) toward the other side (U side). As a result, the tip 2a protrudes from the through hole 3 to the other side, and in this state, welding is performed by irradiating with a laser P.

Example

[0018] Example 1 of the connection method will be described based on FIGS. 2 and 3. The connection method of this example has the first step in FIG. 2 and the second step in FIG. 3, and the first step is substantially the same as in Non-Patent Document 1. In this example, a high-power solid-state laser or the like described in Non-Patent Document 2 can be used for the irradiation of the laser P.

[0019] (1) In the first step, as shown in FIG. 2(b), after inserting the tip 2a of the bus bar 2 into the through hole 3, the tip 2a is irradiated with a laser P. At the stage before this irradiation, a gap S occurs between the inner peripheral surface 3a of the through hole 3 and the outer peripheral surface 2b of the tip 2a.

[0020] In this state, as shown in Figure 2(a), the laser P is irradiated onto the tip 2a of the busbar 2 protruding from the through hole 3, melting the tip 2a. At this time, the laser P is irradiated along the width direction (L side → R side) of the tip 2a, as shown by arrow X in Figure 2(a).

[0021] As a result, as shown in Figure 2(c), the molten material 2c of the tip portion 2a flows into the gap S, creating a state in which the busbars 1 and 2 are in close contact. However, in this state, only the busbar 2 is molten and the penetration is insufficient, which may result in an unsatisfactory weld. Therefore, the connection method aims to achieve a strong weld by performing a second step.

[0022] (2) In the second step, as shown in Figure 3(b), the material 2c of the tip portion 2a flows in to fill the gap S and the busbars 1 and 2 are in close contact, and the laser P is irradiated again. Here, as shown in Figure 3(a), the laser P is irradiated near the boundary between the through hole 3 and the material 2c of the tip portion 2a.

[0023] At this time, the laser P is irradiated over the entire circumference of the boundary, as shown by arrow Y, remelting the inner circumferential surface 3a of the through hole 3 and the material 2c of the tip portion 2a. As a result, as shown in Figure 3(c), the materials 3b and 2c of both 2a and 3a are sufficiently melted, and a good and strong weld state can be obtained for the busbars 1 and 2.

[0024] Furthermore, since process 2 is performed with busbars 1 and 2 in close contact during process 1, there is no need to use jigs or other fixtures to press busbars 1 and 2 together, nor is there a need to pre-reduce the gap S by requiring high dimensional accuracy for busbars 1 and 2. Consequently, effects such as equipment omission in the welding process and relaxation of part dimensional tolerances (improved yield) can be obtained, enabling low-cost and high-quality laser welding. [Examples]

[0025] An embodiment 2 of the connection method will be described with reference to Figure 4. In this embodiment, as shown in Figure 4(a), the tip portion 2a of the busbar 2 is formed in a substantially convex shape.

[0026] Specifically, the tip portion 2a comprises an insertion portion 13 formed to be narrower than the longitudinal direction of the through hole 3, and a main body portion 12 formed to be wider than the longitudinal direction of the through hole 3. The insertion portion 13 is formed continuously with the tip side of the main body portion 12, and a stepped portion 14 is formed between the two 12 and 13.

[0027] Here, the insertion portion 3 is inserted into the through hole 3 from one side to the other and protrudes to the other side. At this time, the stepped portion 13 abuts the inner periphery of the through hole 13 and the main body portion 12 is positioned on one side, so as shown in Figure 4(b), one side of the left and right ends (R and L sides) of the gap S is closed by the stepped portion 14.

[0028] In the first step of Example 1, since the laser P is irradiated in the direction of arrow X, there is a risk that the laser P may escape from the left and right ends (R and L sides) of the gap S and affect the electrical equipment.

[0029] In contrast, in this embodiment, one side of the left and right ends (R and L sides) of the gap S is closed by the stepped portion 14, thereby preventing the laser P from escaping. In this respect, it is possible to avoid the impact on electrical equipment due to laser escaping.

[0030] It should be noted that the present invention is not limited to the embodiments described above, and can be implemented with modifications within the scope of each claim. For example, the present invention is not limited to inverter devices for electric vehicles or hybrid vehicles, but can be applied to inverter devices in general. [Explanation of symbols]

[0031] 1, 2... Bus bar 2a...Tip 3b…Outer surface 3…Through hole 3a…Inner peripheral surface 12...Main body 13…Insertion part 14…Step section

Claims

1. A method of connecting two busbars by welding, in which the tip of one busbar is inserted into a through hole formed in one busbar, A first step involves irradiating the tip of the other busbar protruding from the through hole with a laser to melt it, A second step involves remelting both busbars by irradiating the area near the through hole into which the tip of the other busbar is inserted with a laser, A method for connecting busbars, characterized by having the following features.

2. The second step is, By irradiating the area near the boundary between the inner circumference of the through hole and the outer circumference of the tip with a laser, the two are made to fuse together. The busbar connection method according to claim 1, characterized by the features described above.

3. The second step is, The busbar connection method according to claim 2, characterized in that a laser is irradiated over the entire circumference of the through hole.

4. The aforementioned through hole is While it is formed in a horizontally elongated, roughly rectangular shape, The aforementioned tip portion is It is formed in a roughly convex shape, An insertion portion formed to be narrower than the longitudinal direction of the through hole, A main body portion formed wider than the longitudinal direction of the through hole, The stepped portion between the insertion portion and the main body portion, Equipped with, In the first step described above, The insertion portion protrudes to the other side of the through hole, The main body is positioned on one side of the through hole, When a laser is irradiated along the width direction of the insertion portion, the gap between the insertion portion and the through hole is closed by the stepped portion. A method for connecting busbars according to any one of claims 1 to 3.

5. A structure in which the two busbars are connected by welding by inserting the tip of one busbar into a through hole formed in one busbar and irradiating it with a laser, The aforementioned through hole is While it is formed in a horizontally elongated, roughly rectangular shape, The aforementioned tip portion is It is formed in a roughly convex shape, An insertion portion formed to be narrower than the longitudinal direction of the through hole, A main body portion formed wider than the longitudinal direction of the through hole, The stepped portion between the insertion portion and the main body portion, Equipped with, When the insertion portion is inserted from one side of the through hole to the other side and protrudes from the other side of the through hole, The main body is positioned on one side of the through hole. When a laser is irradiated along the width direction of the insertion portion, the gap between the insertion portion and the through hole is closed by the stepped portion. A busbar connection structure characterized by the following features.

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