Power converter

Abstract

To provide a power conversion device that can avoid or suppress the effects of condensation on water-vulnerable parts of electrical equipment and other devices with a simple configuration. [Solution] A power converter 1 has a fragile component 2, which includes an electronic circuit vulnerable to water, housed inside a housing 3. A textured surface treatment area 4 is provided on the inner surface of the housing 3, away from the fragile component 2. Condensation preferentially occurs at the textured surface treatment area 4, and because the surface tension at the textured surface treatment area 4 is high, water droplets are retained at the textured surface treatment area 4. As a result, condensation at the fragile component 2 can be avoided or suppressed, and water droplets can be prevented or suppressed from dripping onto the fragile component 2.

Description

Technical Field

[0001] The present invention relates to a power conversion device such as an inverter mounted on an electric vehicle, and particularly to a power conversion device provided with measures against condensation.

Background Art

[0002] This type of power conversion device is usually cooled below the upper limit temperature in order to ensure its operation, and measures against condensation occurring at low temperatures may be taken. For example, Patent Document 1 describes a device configured to warm the inside of the power conversion device with the heat of a heating element such as an engine. In the device described in Patent Document 1, a bypass path that bypasses the cooling device is provided in a path through which a heat medium circulates between the power conversion device and the cooling device, and the heat medium flowing through the cooling path passing through the inside of the power conversion device is switched by a switching valve to flow through the cooling device and the bypass path, and heat is supplied to the bypass path from a heating part such as an engine. When the temperature is low, the heat medium is made to flow through the bypass path to raise the temperature of the heat medium, thereby setting the temperature inside the power conversion device above the dew point temperature to prevent condensation.

[0003] Further, Patent Document 2 describes a device configured to suppress condensation on the inner surface of the inverter housing even when the temperature around the power conversion device rapidly decreases. In the device described in Patent Document 2, a temperature adjustment part for circulating a heat medium inside is provided between the heat radiation surface of the power semiconductor module and the inner surface of the housing. Therefore, even when the housing is suddenly exposed to a low-temperature atmosphere, since the heat medium is interposed between the inner surface of the housing and the power semiconductor module, a rapid decrease in the temperature of the power semiconductor module is avoided, and as a result, condensation on the power semiconductor module is avoided or suppressed.

[0004] Furthermore, Patent Document 3 describes a device configured to prevent the conditions for condensation from occurring in the first place. In the device described in Patent Document 3, the conditions for condensation are predetermined, and when those conditions are met, the number of switching cycles per unit time of the semiconductor switching element is increased. According to Patent Document 3, increasing the number of switching cycles per unit time increases the amount of heat generated, thus eliminating the conditions for condensation and preventing or suppressing condensation. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-111526 [Patent Document 2] Japanese Patent Publication No. 2024-093978 [Patent Document 3] Japanese Patent Publication No. 2013-158181 [Overview of the project] [Problems that the invention aims to solve]

[0006] As illustrated by Patent Documents 1 to 3, conventional methods prevent condensation by raising the internal temperature of the power converter. Specifically, in the device described in Patent Document 1, a bypass path is heated by a heat source such as an engine, and a heat transfer medium is flowed through it to transfer heat to the inside of the power converter, raising the temperature inside the power converter to above the dew point temperature. As a result, valves and control devices are required to switch between the bypass path and the path through which the heat transfer medium flows, which can lead to a larger or more complex overall configuration of the device. Furthermore, in the device described in Patent Document 1, since heat from a heat source is utilized, condensation cannot be prevented when the temperature of the heat source is not high enough.

[0007] In the apparatus described in Patent Document 2, a temperature control unit that exchanges heat by flowing a heat transfer medium is required to be interposed between the inner surface of the housing and the power semiconductor module. Therefore, similar to the apparatus described in Patent Document 1, the overall configuration of the apparatus may become larger or more complex. Furthermore, since the heat transfer medium needs to be heated, not only is equipment required for this purpose, but energy consumption for heating may also increase.

[0008] On the other hand, the device described in Patent Document 3 generates heat using the switching elements that make up the inverter, and this heat prevents condensation, thus eliminating the need for new parts. In this respect, it can avoid increasing the size and complexity of the device. However, there are concerns about reduced durability due to the misuse of the switching elements, as well as energy consumption or deterioration of energy efficiency.

[0009] This invention has been made in view of the above-mentioned technical problems, and aims to provide a power conversion device that can avoid or suppress the effects of condensation on water-vulnerable parts of electrical equipment and the like with a simple configuration. [Means for solving the problem]

[0010] To achieve the above objective, the present invention provides a power conversion device in which a fragile component, including an electronic circuit vulnerable to water, is housed inside a casing, characterized in that a textured surface treatment is provided on the inner surface of the casing at a location away from the fragile component.

[0011] In the present invention, the area where the textured surface treatment is provided may be an area on the inner surface of the housing that covers the area above the fragile component.

[0012] In the present invention, the textured surface area may protrude or recess inward toward the interior of the housing to increase its surface area. [Effects of the Invention]

[0013] In this invention, moisture inevitably present in the air inside the housing may condense due to the low temperature. On the other hand, the textured surface area is larger than other inner surfaces due to the fine irregularities, and the fine protrusions act as nuclei, thus promoting condensation in the textured surface area. As a result, condensation in other areas, including fragile parts, is suppressed, and ultimately, condensation in fragile parts can be avoided or suppressed. Furthermore, since water droplets are held in the textured surface area, it is prevented from dripping or flowing onto fragile parts, and in this respect as well, exposure of fragile parts to water can be avoided or suppressed.

[0014] Furthermore, since the textured surface is superior to a simple flat surface in its ability to retain water droplets, if the textured surface is provided in a location that covers the top of a fragile component, it can more effectively prevent or suppress water droplets formed by condensation from dripping onto the fragile component.

[0015] Furthermore, if the textured surface protrudes or recesses inward into the housing, the surface area of ​​the textured surface is larger compared to a simple flat surface. This increases the amount of moisture that condenses on the textured surface, further suppressing condensation in other areas, including fragile components. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the present invention, with the internal structure omitted. [Figure 2] (a) is a schematic cross-sectional view similar to Figure 1, showing another embodiment, and (b) is a top view of its cover seen from below. [Figure 3] This is a schematic cross-sectional view similar to Figure 1, showing an example where the textured surface area is curved to increase its surface area. [Figure 4] This is a schematic cross-sectional view similar to Figure 1, showing another example where the textured surface area is curved to increase its area. [Modes for carrying out the invention]

[0017] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0018] The power conversion device according to the present invention may have substantially the same configuration as an inverter, converter, etc. conventionally known in Patent Documents 1 to 3, etc. In short, it is a device mainly having functions such as conversion between direct current and alternating current, conversion of voltage, current, or frequency. FIG. 1 shows an example of a power conversion device 1 according to the present invention in a schematic cross-sectional view with the internal structure omitted. The power conversion device 1 shown here is configured by housing an electronic circuit 2 such as an inverter including a large number of switching elements inside a casing (housing) 3 made of a predetermined material such as metal.

[0019] The electronic circuit 2 is vulnerable to moisture, such as short - circuiting due to getting wet with water, and corresponds to a vulnerable component in the present invention. The casing 3 is composed of a main body part (body) 3a that fixes the electronic circuit 2 and a lid body (cover) 3b that closes the body 3a. In the example shown in FIG. 1, the electronic circuit 2 is fixed to a predetermined inner wall surface 3c of the body 3a.

[0020] The casing 3 is basically sealed by covering the opening of the body 3a with the cover 3b, but in order to prevent changes in internal pressure, a passage membrane (not shown) may be provided. Therefore, moisture inevitably enters the inside of the casing 3. The casing 3 has a structure that causes condensation at a specific location when the moisture inside it condenses due to a temperature drop. Specifically, a satin - finished part 4 is provided at a location on the inner surface of the casing separated from the electronic circuit 2.

[0021] The satin finish is a roughened surface with fine irregularities on the metal surface, which can be formed by mechanical methods such as spraying sand or glass, or chemical methods such as etching. Also, the satin finish treatment may be referred to as the dimpling process. Therefore, the satin finish treatment part 4 can also be called the rough surface processing part. The satin finish treatment part 4 is a location where such mechanical or chemical treatment has been performed, with many fine irregularities, and thus has a larger surface area compared to a simple flat surface location. In the example shown in Fig. 1, the satin finish treatment part 4 is provided on the inner wall surface 3c of the body 3a on the side opposite to or facing the location where the electronic circuit 2 is provided, and on almost the entire inner surface of the cover 3b. Therefore, the satin finish treatment part 4 provided on the inner surface of the cover 3b almost entirely covers the upper part of the electronic circuit 2.

[0022] The above-described power conversion device 1 is mounted on a vehicle such as an electric vehicle, and thus, when placed in the natural environment, moisture may enter inside and it may be exposed to low temperatures. When the temperature inside the casing 3 drops below the dew point temperature, condensation occurs. Condensation occurs when the moisture in the air contacts a location where the temperature is below the dew point temperature. Therefore, in the power conversion device 1 according to the present invention, condensation is promoted in the satin finish treatment part 4 where the surface area is enlarged. Also, since the surface tension of water droplets increases due to the presence of many fine irregularities, the water droplets are retained on the surface of the satin finish treatment part 4.

[0023] Therefore, in the above-described power conversion device 1, condensation can be preferentially generated in the satin finish treatment part 4 and water droplets can be retained, so that the adhesion of water droplets to the electronic circuit 2 can be avoided or suppressed. That is, according to the power conversion device 1 of the present invention, the influence of condensation on the electronic circuit 2 can be avoided or suppressed without increasing the size or complexity of the overall configuration of the device. In other words, the satin finish treatment part 4 has a hydrophilic surface and a configuration in which the irregularities are close enough that the effective capillary radius is sufficiently small.

[0024] The textured surface treatment area 4 described above is hydrophilic and has excellent water droplet retention capabilities. However, it is desirable to avoid water droplets dripping onto the electronic circuit 2 as much as possible. Therefore, in order to increase the amount of water droplets that can be retained above the electronic circuit 2, the configurations shown in Figures 2(a) and 2(b) can be used. In other words, in the example shown in Figure 2, the area of ​​the textured surface treatment area 4 above the electronic circuit 2 is increased, and the width and length of the textured surface treatment area 4 are set to be larger than the width and length of the projection plane of the electronic circuit 2 in the vertical direction.

[0025] To further increase the amount of water droplets that can be held, the textured surface area 4 can be increased by curving or bending it vertically. Examples of this are shown in Figures 3 and 4. The example shown in Figure 3 is one in which the portion of the cover 3b on which the textured surface area 4 is formed is curved upward so as to be convex, thereby curving the entire textured surface area 4 and increasing its area compared to a simple flat surface. The example shown in Figure 4 is one in which the portion of the cover 3b on which the textured surface area 4 is formed is curved downward so as to be convex (so as to be recessed inward into the casing 3), thereby curving the entire textured surface area 4 and increasing its area compared to a simple flat surface. These curved shapes may be spherical, or they may be groove-shaped (or ridge-shaped) with an arc-shaped cross-section.

[0026] Although embodiments of the present invention have been described above, the present invention is not limited to the above-described configuration and can be modified as appropriate within the scope of the object of the present invention. For example, the textured surface treatment area only needs to be provided inside the housing in a location that avoids vulnerable parts such as electronic circuits, and its location, number, or shape is not limited. Furthermore, in the present invention, it is sufficient that the textured surface treatment area is provided inside the housing, and it may be used in combination with warming means such as an appropriate heating configuration. [Explanation of Symbols]

[0027] 1. Power converter 2 Electronic circuit 3. Casing 3a Body 3b cover 3c Inner wall surface 4. Textured surface treatment

Claims

1. A power converter in which fragile components, including electronic circuits that are vulnerable to water, are housed inside a casing, A textured surface treatment area is provided on the inner surface of the housing, away from the fragile component. A power conversion device characterized by the following features.

2. A power conversion device according to claim 1, The area where the textured surface treatment is provided is the inner surface of the housing, covering the area above the fragile component. A power conversion device characterized by the following features.

3. A power conversion device according to claim 1 or 2, The aforementioned textured surface area protrudes or recesses inward toward the interior of the housing, thereby increasing its surface area. A power conversion device characterized by the following features.

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