Inverter device and method for manufacturing inverter device

Abstract

This inverter device comprises: a housing; a switching element that is attached to an inner surface of the housing; a capacitor that is attached to the inner surface alongside the switching element in a first direction, and that is connected to the switching element; a first bus bar that extends along the first direction to connect the switching element and the capacitor; a second bus bar that is positioned on a side opposite the inner surface with the first bus bar therebetween, and that extends along the first direction to connect the switching element and the capacitor; a first welding trace that extends on the first bus bar in a second direction intersecting the first direction; and a plurality of second welding traces that extend on the second bus bar in the second direction, and that are positioned on both sides sandwiching the first welding trace when viewed in a normal direction of the inner surface.

Description

Inverter device and method for manufacturing the same

[0001] The present invention relates to an inverter device and a method for manufacturing the inverter device.

[0002] Conventionally, inverter devices that drive high-power motors include inverter devices equipped with large-capacity capacitors, such as several hundred μF. The large-capacity capacitor is realized as a capacitor module in which a plurality of capacitor elements are connected, and is connected by bus bars to a power module, which is a switching element in the inverter circuit.

[0003] When connecting using bus bars, it is necessary to suppress the occurrence of loop inductance, but when bus bar connections are made using fastening screws or other fasteners, there are areas where the P-side and N-side bus bars cannot face each other, increasing loop inductance. One bus bar connection that suppresses loop inductance is welding.

[0004] For example, U.S. Patent Application Publication No. 2017 / 0133316 discloses a technique for connecting a capacitor and a semiconductor device by welding a bus bar from both the front and back sides of the bus bar.

[0005] US Patent Application Publication No. 2017 / 0133316

[0006] However, when connecting a switching element and a capacitor using the technology of U.S. Patent Application Publication No. 2017 / 0133316, the switching element and the capacitor are attached to the housing after being connected by a bus bar. This places stress on the welded portion of the bus bar during attachment, which may result in distortion or damage. Meanwhile, due to mounting space and other factors, the switching element and the capacitor are attached in a position where either the front or back side of the flat bus bar faces the inner wall of the housing, making it difficult to weld them from both the front and back sides after attachment.

[0007] Therefore, an object of the present disclosure is to enable busbar welding after a switching element and a capacitor are attached to a housing.

[0008] One aspect of an inverter device according to the present disclosure includes a housing, a switching element attached to an inner surface of the housing, a capacitor attached to the inner surface alongside the switching element in a first direction and connected to the switching element, a first bus bar extending along the first direction to connect the switching element and the capacitor, a second bus bar located on the opposite side of the first bus bar from the inner surface and extending along the first direction to connect the switching element and the capacitor, a first weld mark extending on the first bus bar in a second direction intersecting the first direction, and a plurality of second weld marks extending on the second bus bar in a direction along the second direction and located on both sides of the first weld mark when viewed in a normal direction to the inner surface.

[0009] One aspect of a manufacturing method for an inverter device according to the present disclosure includes an attachment step of attaching switching elements and capacitors connected to the switching elements to an inner surface of a housing, arranged in a first direction; a first welding step of welding a first portion of a first bus bar that extends along the first direction to connect the switching elements and the capacitor to the switching elements on the inner surface, the first portion of the first bus bar being on the switching element side, and a second portion of the second bus bar that extends along the first direction to connect the switching elements and the capacitor, the first portion of the second bus bar being on the switching element side, and the second portion of the second bus bar being on the capacitor side, and a third portion that connects the first portion and the second portion, at locations on both sides of a welding point of the first bus bar when viewed in a normal direction to the inner surface.

[0010] According to the present disclosure, busbar welding is possible after the switching element and capacitor are attached to the housing.

[0011] FIG. 1 is a perspective view showing an inverter device. FIG. 2 is a schematic side view showing the inside of a housing of the inverter device. FIG. 3 is a view showing an attachment step in a manufacturing method of the inverter device. FIG. 4 is a view showing a first welding step in a manufacturing method of the inverter device. FIG. 5 is a view showing a second welding step in a manufacturing method of the inverter device. FIG. 6 is a view showing an inverter device of a first modified example. FIG. 7 is a view showing an inverter device of a second modified example. FIG. 8 is a partially enlarged view showing the second welding step in the second modified example.

[0012] Hereinafter, embodiments of an inverter device and a manufacturing method for an inverter device according to the present disclosure will be described in detail with reference to the accompanying drawings. However, to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or redundant description of substantially identical configurations may be omitted. Furthermore, elements shown in earlier-described figures may be appropriately referenced in the description of later figures.

[0013] (Structure of inverter device 100) Fig. 1 is a perspective view showing the inverter device 100, and Fig. 2 is a schematic side view showing the inside of the housing of the inverter device 100. For convenience in explaining directions, XYZ coordinates are shown in Fig. 1 and Fig. 2.

[0014] The inverter device 100 is a device that converts DC power supplied from, for example, a battery into AC power and supplies it to, for example, a motor. The inverter device 100 may be incorporated into an electromechanical integrated motor, or may be a device separate from the motor or other device that it supplies power to. The inverter device 100 includes a housing 101, a power module 102, and a film capacitor 103.

[0015] The housing 101 holds and protects the elements disposed therein, and the internal space may be closed by a lid, or the internal space may be open without a lid. FIG. 1 shows an example in which the lid is not provided. The power module 102 is a modularized version of multiple switching elements in an inverter circuit. The power module 102 is disposed within the housing 101 and attached to the inner surface of the housing 101. In FIGS. 1 and 2, as an example, the power module 102 is attached to the bottom surface 108 located on the −Z side of the inner surface. Note that FIG. 2 shows only the bottom surface 108 of the housing 101.

[0016] The power module 102 may be attached directly to the inner surface of the housing 101 with screws or the like, or indirectly via a spacer or jig. The film capacitor 103 is a smoothing capacitor in the inverter circuit, and is formed by modularizing multiple capacitor elements to increase capacity. While an electrolytic capacitor may be used as the smoothing capacitor, the film capacitor 103, which has excellent durability, is used here. The film capacitor 103 is also disposed within the housing 101 and attached directly or indirectly to the inner surface of the housing 101.

[0017] The power module 102 and the film capacitor 103 are arranged side by side in the X direction within the housing 101, for example, and are connected to each other by bus bars 104 and 105 to form an inverter circuit. Therefore, the bus bars 104 and 105 extend along the X direction to connect the power module 102 and the film capacitor 103. For example, each of the bus bars 104 and 105 is a flat bus bar that extends along the bottom surface 108 to which the power module 102 and the film capacitor 103 are attached. Therefore, loop inductance is suppressed compared to when the bus bars are not flat and extend along the bottom surface 108.

[0018] As an example, of the bus bars 104, 105, the one located on the −Z side is the N (Negative) bus bar 104, and the one located on the +Z side is the P (Positive) bus bar 105. In other words, of the bus bars 104, 105, the one closer to the bottom surface 108 is the N bus bar 104, and the one located on the opposite side of the N bus bar 104 from the bottom surface 108 is the P bus bar 105.

[0019] The N bus bar 104 is formed by welding a first portion 41 on the power module 102 side to a second portion 42 on the film capacitor 103 side. Therefore, a weld mark 106 on the N bus bar 104 extends on the N bus bar 104 in, for example, the Y direction that intersects with the direction in which the power module 102 and the film capacitor 103 are arranged.

[0020] The P bus bar 105 is formed by welding a first portion 51 on the power module 102 side, a second portion 52 on the film capacitor 103 side, and a third portion 53 connecting the first portion 51 and the second portion 52. That is, the third portion 53 of the P bus bar 105 is located between the first portion 51 and the second portion 52. The weld marks 107 on the P bus bar 105 extend on the P bus bar 105 in the same direction as the weld marks 106 on the N bus bar 104, and are located on both sides of the weld marks 106 on the N bus bar 104 when viewed in the normal direction to the bottom surface 108. For this reason, as will be described later, the N bus bar 104 and the P bus bar 105 can be welded after the power module 102 and the film capacitor 103 are attached to the inner surface of the housing 101.

[0021] If the bus bars 104, 105 are welded to the inner surface of the housing 101 before the power module 102 and the film capacitor 103 are attached, stress during attachment may cause distortion or damage to the bus bars 104, 105. For this reason, it is required that the bus bars 104, 105 be welded after the power module 102 and the film capacitor 103 are attached.

[0022] As an example, the weld mark 106 of the N bus bar 104 is located at the center of the N bus bar 104 in the X direction in which the power module 102 and the film capacitor 103 are aligned. Therefore, welding is easier than when the weld mark 106 is biased toward either the power module 102 or the film capacitor 103.

[0023] In addition, the welding mark 106 on the N bus bar 104 is present in one location on the N bus bar 104, for example, and the welding mark 107 on the P bus bar 105 is present in two locations on the P bus bar 105, for example, so the loop inductance is suppressed by the minimum number of welding marks 106 and 107.

[0024] (Manufacturing Method of Inverter Device 100) Next, a description will be given of a manufacturing method of the inverter device 100. Figures 3 to 5 are diagrams showing the steps in the manufacturing method of the inverter device 100. Figure 3 shows the mounting step, Figure 4 shows the first welding step, and Figure 5 shows the second welding step.

[0025] 3, the power module 102 and the film capacitor 103 are attached, for example, side by side in the X direction, to, for example, the bottom surface 108 of the inner surface of the housing 101. At this time, the power module 102 and the film capacitor 103 are arranged so that the tips of the first portion 41 and the second portion 42 that form the N bus bar 104 butt against each other or partially overlap each other.

[0026] 4 , the first portion 41 and the second portion 42 are welded together to form the N bus bar 104. In the first welding step, laser welding is used as an example. That is, the welding is performed by irradiating the welded portion of the first portion 41 and the second portion 42 that will become the N bus bar 104 with laser light L. The laser light L is irradiated onto the N bus bar 104 from the side facing the bottom surface 108, and is irradiated through between the first portion 51 and the second portion 52 that will become the P bus bar 105. Laser welding is easier to perform inside the housing 101 than other types of welding.

[0027] 5 , the third portion 53 is disposed between the first portion 51 and the second portion 52 that will become the P bus bar 105, and the first portion 51, the second portion 52, and the third portion 53 are welded together. The welding points in the second welding step are on both sides of the welding point in the first welding step when viewed in the normal direction of the bottom surface 108. In the second welding step, laser welding, which is easy to perform welding within the housing 101, is also used as an example. That is, the welding point between the first portion 51 and the third portion 53 is irradiated with laser light L to weld them, and the welding point between the third portion 53 and the second portion 52 is also irradiated with laser light L to weld them.

[0028] The inverter device 100 shown in Figures 1 and 2 is obtained by performing the attachment step, the first welding step, and the second welding step. Conversely, with the inverter device 100 having the structure shown in Figures 1 and 2, the first welding step and the second welding step can be performed after the attachment step, as described above. Therefore, distortion and damage to the bus bars 104, 105 are suppressed.

[0029] (Modifications) Next, modifications of the inverter device 100 described above will be described. Fig. 6 is a diagram showing an inverter device 110 of a first modification. The inverter device 110 of the first modification differs from the inverter device 100 shown in Figs. 1 and 2 in that it includes insulating materials 111 and 112. The insulating materials 111 and 112 insulate the bus bars 104 and 105 from each other. In the example shown in Fig. 6, the insulating materials 111 and 112 cover both the front and rear surfaces of the bus bars 104 and 105, but it is sufficient that the insulating materials 111 and 112 cover only the surfaces of the bus bars 104 and 105 that face each other.

[0030] The insulating material 111 of the N bus bar 104 covers a portion of the overall width in the X direction. The insulating material 112 of the P bus bar 105 covers the remaining portion of the overall width of the P bus bar 105 where the insulating material 111 of the N bus bar 104 is not present. The insulating material 111 of the N bus bar 104 and the insulating material 112 of the P bus bar 105 are arranged alternately in the direction in which the power modules 102 and the film capacitors 103 are arranged. Note that the insulating material 111 of the N bus bar 104 and the insulating material 112 of the P bus bar 105 may partially overlap.

[0031] That is, the insulating material 111 of the N bus bar 104 covers a portion of the entire width of the surface of the N bus bar 104 facing the P bus bar 105, from the power module 102 to the film capacitor 103. The insulating material 112 of the P bus bar 105 covers the remaining portion of the surface of the P bus bar 105 facing the N bus bar 104, which is complementary to the portion of the N bus bar 104. As a result, the bus bars 104, 105 are insulated from each other by a minimum amount of insulating materials 111, 112.

[0032] The insulating material 111 of the N bus bar 104 is provided in the first portion 41 and the second portion 42 of the N bus bar 104 at a location facing the weld mark 107 of the P bus bar 105, but does not reach the weld mark 106 of the N bus bar 104. The insulating material 112 of the P bus bar 105 is provided in the third portion 53 of the P bus bar 105 at a location facing the weld mark 106 of the N bus bar 104, but does not reach the weld mark 107 of the P bus bar 105.

[0033] That is, the insulating material 111 of the N bus bar 104 is provided in a location that does not overlap the welding mark 106 of the N bus bar 104, and the insulating material 112 of the P bus bar 105 is provided in a location that does not overlap the welding mark 107 of the P bus bar 105. Therefore, the insulating materials 111, 112 insulate the bus bars 104, 105 from each other without interfering with the welding in the first welding step and the second welding step described above.

[0034] FIG. 7 is a diagram showing an inverter device 120 of a second modified example. Like the first modified example, the inverter device 120 of the second modified example also has insulating materials 111 and 121. However, in the second modified example, the insulating material 121 of the P bus bar 105 is thicker in the Z direction than in the first modified example. Furthermore, a surface 122 of the insulating material 121 of the P bus bar 105 that faces the N bus bar 104 reaches the N bus bar 104. In other words, the insulating material 121 of the P bus bar 105 contacts the N bus bar 104 at the surface 122. From another perspective, the thickness of the insulating material 121 of the P bus bar 105 on the N bus bar 104 side corresponds to the distance between the P bus bar 105 and the N bus bar 104. As a result, as described below, the insulating material 121 of the P bus bar 105 serves as a support in the second welding step.

[0035] Fig. 8 is a partially enlarged view showing the second welding step in the second modified example. Fig. 8 shows an enlarged view of the periphery of the welded portion between the first portion 51 and the third portion 53 of the P bus bar 105. In the second modified example, the second welding step is performed with the third portion 53 of the P bus bar 105 supported on the N bus bar 104 by the insulating material 121 of the P bus bar 105. This eliminates the need to prepare a separate support tool or the like to support the third portion 53 in the Z direction, making it easier to perform the second welding step.

[0036] Furthermore, by sandwiching the insulating material 121 of the P bus bar 105 between the insulating material 111 of the N bus bar 104, the third portion 53 of the P bus bar 105 is automatically positioned in the X direction, which also makes it easier to carry out the second welding step. The above-described embodiment should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0037] The present technology can be configured as follows: (1) An inverter device including: a housing; a switching element attached to an inner surface of the housing; a capacitor attached to the inner surface alongside the switching element in a first direction and connected to the switching element; a first bus bar extending along the first direction to connect the switching element to the capacitor; a second bus bar located on the opposite side of the first bus bar from the inner surface, extending along the first direction to connect the switching element to the capacitor; a first weld mark extending on the first bus bar in a second direction intersecting the first direction; and a plurality of second weld marks extending on the second bus bar in a direction along the second direction and located on both sides of the first weld mark when viewed in a normal direction to the inner surface.

[0038] (2) The inverter device according to (1), wherein the first bus bar and the second bus bar are flat bus bars extending along the inner surface.

[0039] (3) The inverter device according to (1) or (2), wherein the first welding mark is present at one location on the first bus bar, and the second welding mark is present at two locations on the second bus bar.

[0040] (4) The inverter device according to (3), wherein the first welding mark is located at a center on the first bus bar in the first direction.

[0041] (5) The inverter device according to any one of (1) to (4), further comprising: a first insulating material covering a portion of the entire width of the first bus bar from the switching element to the capacitor on the surface of the first bus bar facing the second bus bar; and a second insulating material covering a remaining portion of the second bus bar on the surface facing the first bus bar that is complementary to the portion.

[0042] (6) The inverter device according to (5), wherein the first insulating material is provided at a position not overlapping the first welding mark, and the second insulating material is provided at a position not overlapping the second welding mark. (7) The inverter device according to (5), wherein the second insulating material is in surface contact with the first bus bar.

[0043] (8) A method for manufacturing an inverter device, comprising: an attachment step of attaching switching elements and capacitors connected to the switching elements to an inner surface of a housing, arranged in a first direction; a first welding step of welding a first bus bar, the first bus bar extending along the first direction to connect the switching elements and the capacitor, to a first portion of the first bus bar on the switching element side and a second portion of the first bus bar on the capacitor side to form the first bus bar; and a second welding step of welding a second bus bar, the second bus bar being located on the opposite side of the first bus bar from the inner surface, extending along the first direction to connect the switching elements and the capacitor, to the first portion of the first bus bar on the switching element side, the second portion of the capacitor side, and a third portion connecting the first portion and the second portion, at locations on both sides of a welding point of the first bus bar when viewed in a normal direction to the inner surface.

[0044] (9) The inverter device manufacturing method according to (8), wherein the first welding step and the second welding step are performed by laser welding. (10) The second bus bar has an insulating material covering a part of a surface of the third portion facing the first bus bar, and the second welding step is performed in a state where the third portion of the second bus bar is supported on the first bus bar by the insulating material.

[0045] 100, 110, 120: Inverter device 101: Housing 102: Power module 103: Film capacitor 104: N bus bar 105: P bus bar 106, 107: Welding marks 108: Bottom surface 111, 112, 121: Insulating material

Claims

1. An inverter device comprising: a housing; a switching element attached to an inner surface of the housing; a capacitor attached to the inner surface alongside the switching element in a first direction and connected to the switching element; a first bus bar extending along the first direction to connect the switching element and the capacitor; a second bus bar located on the opposite side of the first bus bar from the inner surface, extending along the first direction to connect the switching element and the capacitor; a first weld mark extending on the first bus bar in a second direction intersecting the first direction; and a plurality of second weld marks extending on the second bus bar in a direction along the second direction and located on both sides of the first weld mark when viewed in the normal direction of the inner surface.

2. The inverter device according to claim 1, wherein the first bus bar and the second bus bar are flat bus bars extending along the inner surface.

3. The inverter device according to claim 1, wherein the first weld mark is present at one location on the first bus bar, and the second weld mark is present at two locations on the second bus bar.

4. The inverter device according to claim 3, wherein the first weld mark is located at a center on the first bus bar in the first direction.

5. The inverter device according to claim 1, further comprising: a first insulating material covering a portion of the entire width from the switching element to the capacitor on the surface of the first bus bar facing the second bus bar; and a second insulating material covering the remaining portion of the surface of the second bus bar facing the first bus bar, complementary to the portion.

6. An inverter device according to claim 5, wherein the first insulating material is provided at a location not overlapping the first weld mark, and the second insulating material is provided at a location not overlapping the second weld mark.

7. The inverter device according to claim 5, wherein the second insulating material is in surface contact with the first bus bar.

8. A method for manufacturing an inverter device, comprising: an attachment step of attaching switching elements and capacitors connected to the switching elements to an inner surface of a housing in a first direction; a first welding step of welding a first bus bar, the first bus bar extending along the first direction to connect the switching elements and the capacitor, to a first portion of the first bus bar on the switching element side and a second portion of the capacitor side to form the first bus bar; and a second welding step of welding a second bus bar, the second bus bar located on the opposite side of the first bus bar from the inner surface, extending along the first direction to connect the switching elements and the capacitor, to a first portion of the first bus bar on the switching element side, a second portion of the capacitor side, and a third portion connecting the first and second portions, at portions on both sides of the welded portion of the first bus bar when viewed in the normal direction of the inner surface.

9. A method for manufacturing an inverter device according to claim 8, wherein the first welding step and the second welding step are performed by laser welding.

10. A method for manufacturing an inverter device as described in claim 8, wherein the second bus bar has an insulating material covering a portion of a surface of the third portion facing the first bus bar, and the second welding process is performed with the third portion of the second bus bar supported on the first bus bar by the insulating material.

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