Noise filter

Abstract

To provide a noise filter that is highly safe and easy to maintain. [Solution] The noise filter 5' is an LC filter mainly comprising a capacitor 11 and an inductor 21, and includes a capacitor 11, an inductor 21, a sealed section 10 housing the capacitor 11, and an unsealed section 20 housing the inductor 21 and at least partially open to the outside air.

Description

Technical Field

[0001] This disclosure relates to a noise filter.

Background Art

[0002] When a power conversion device, such as a motor drive device, is operating, high-frequency noise is generated from the built-in switching elements. In order to remove the high-frequency noise, a filter, such as a noise filter, is provided at the input section of the power conversion device. Such a noise filter includes a capacitor and an inductor (for example, Japanese Unexamined Patent Application Publication No. 2021-121143).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the heat generation of the capacitor during the use of the noise filter is relatively small, the capacitor often contains combustible substances, such as electrolytic paper, plastic film, and insulating oil. Further, in a capacitor having a structural portion provided with a thin metal film, such as a vapor deposition electrode film or a metallicon, the metal is oxidized by external temperature and humidity, and the performance of the capacitor deteriorates over time. Therefore, when the inductor generates heat in the noise filter and its influence extends to the capacitor over a long period, the capacitor may malfunction and, in the worst case, may catch fire.

[0005] For this reason, a noise filter with high safety and easy maintenance is desired.

Means for Solving the Problems

[0006] According to a first aspect of the present disclosure, a noise filter is provided, comprising a capacitor, an inductor, a sealed section housing the capacitor, and an unsealed section housing the inductor and at least partially open to the outside air.

[0007] The purposes, features, and advantages of this disclosure will become even clearer from the following description of embodiments related to the accompanying drawings. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of the noise filter in the first embodiment. [Figure 2] Figure 1 is a decomposed perspective view of the noise filter shown. [Figure 3A] This is a cross-sectional view of the noise filter in a modified example. [Figure 3B] This is a cross-sectional view of a noise filter in another modified example. [Figure 4A] This is a perspective view of the noise filter in the second embodiment. [Figure 4B] This is an objective view of the noise filter in the third embodiment. [Figure 4C] This is a perspective view of the noise filter in the fourth embodiment. [Figure 4D] This is a perspective view of the noise filter in the fifth embodiment. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described below with reference to the attached drawings. Throughout all drawings, corresponding components are denoted by the same reference numerals. Figure 1 is a perspective view of the noise filter in the first embodiment, and Figure 2 is an exploded perspective view of the noise filter shown in Figure 1. As shown in these drawings, the noise filter 5 is an LC filter mainly comprising a capacitor 11 and an inductor 21. The noise filter 5 is connected to a power conversion device, such as a motor drive device, through its connector 30.

[0010] Figures 1 and 2 show multiple capacitors 11 arranged in a line on a substrate 12, but the noise filter 5 may also include a single capacitor. The number of capacitors 11 can be changed as appropriate depending on the required capacitance. A typical capacitor 11 includes two conductors (not shown) insulated by a dielectric.

[0011] Furthermore, in Figures 1 and 2, multiple inductors 21 are arranged side by side. However, the noise filter 5 may also include a single inductor. The inductor 21 mainly consists of a coil. A core made of a magnetic material may be placed at the center of the coil. In other words, the inductor 21 may also be a reactor.

[0012] These capacitors 11 and inductors 21 are electrically connected to each other by a connector 39. The connector 39 may be a flexible conductor, such as a conductive wire, or a rigid conductor, such as a busbar. Typically, the connector 39 includes a resistor (not shown) between the capacitor 11 and the inductor 21. In other embodiments, the connector 39 may not be shown. Since the noise filter 5 including the capacitor 11 and the inductor 21 is well known, no further explanation is provided.

[0013] As shown in Figures 1 and 2, the capacitor 11 is housed in the sealed section 10. The sealed section 10 is preferably a rectangular parallelepiped as shown, but it may take other forms, such as a cylindrical shape. The sealed section 10 is preferably made of a flame-retardant material, such as metal. However, the sealed section 10 may be made of a resin to which an organic or inorganic flame retardant has been added.

[0014] The sealed portion 10 does not have any connecting parts, such as openings, notches, or valves, that connect the internal space of the sealed portion 10 to the external space. It is preferable that the boundary portions of adjacent outer surfaces of the sealed portion 10 be sealed with a seal or the like, but sealing is not necessarily required.

[0015] Note that the connecting portion 39 is connected to the capacitor 11 through a hole (not shown) formed in the sealing portion 10. The size of the hole formed in the sealing portion 10 is sufficient to allow the connecting portion 39 to pass through. The space between the hole and the connecting portion 39 may be sealed.

[0016] The inductor 21 is stored in the non-sealing portion 20. The non-sealing portion 20 is preferably a rectangular parallelepiped, but may be in other forms, such as a cylindrical shape. At least one opening 29 is formed in the non-sealing portion 20. Therefore, the internal space and the external space of the non-sealing portion 20 communicate with each other through the opening 29. The non-sealing portion 20 is also preferably formed of the same material as the sealing portion 10.

[0017] In FIGS. 1 and 2, the opening 29 is formed in one end face 27 of the non-sealing portion 20. However, other openings 28 or the like may be formed in other faces of the non-sealing portion 20, such as the other end face 26 and the side faces. Alternatively, the opening 29 may be formed in a part of the upper surface of the non-sealing portion 20 where the sealing portion 10 is not disposed.

[0018] As can be seen from FIG. 2, a plate-like portion 25 is disposed horizontally between the sealing portion 10 and the non-sealing portion 20. The plate-like portion 25 may be formed of the same material as the sealing portion 10, or the plate-like portion 25 may be formed of a heat insulating material. As shown in the figure, the plate-like portion 25 may serve as a lid for the non-sealing portion 20 together with the covers 30a and 30b for the connector 30. The covers 30a and 30b are also formed of the same material as the sealing portion 10.

[0019] Furthermore, the sealing portion 10 and the non-sealing portion 20 are preferably fixed to each other by a fixture 35, such as a screw. In FIG. 2, the flange portion of the sealing portion 10 is fixed to the non-sealing portion 20 including the plate-like portion 25 by the fixture 35. Each of the sealing portion 10 and the non-sealing portion 20 is preferably made replaceable.

[0020] As described above, the capacitor 11 of the noise filter 5 in the present disclosure is stored in the sealed portion 10, and the inductor 21 is stored in the non-sealed portion 20. When a power conversion device, for example, a motor drive device is driven, high-frequency noise is generated from the switching element of the power conversion device. The noise filter 5 connected to the power conversion device functions to cut high-frequency noise.

[0021] By the way, due to the power conversion device itself or other reasons, the capacitor 11 may experience aging deterioration, and its temperature may rise due to self-heating. Also, due to the heat of the inductor 21 of the noise filter 5 and the influence of the humidity of the outside air, the metal electrodes inside the capacitor 11 may oxidize, deteriorating the various characteristics of the capacitor, and as a result, the temperature of the capacitor may rise due to self-heating. And the capacitor 11 may include a laminate of electrolytic paper or plastic film and metal foil, or a metallized film obtained by vapor-depositing metal on a plastic film. In the case of a large capacitor, such a laminate or metallized film is often impregnated with electrical insulating oil. That is, the capacitor 11 may contain a plurality of types of combustible substances. In such a case, under the influence of the heat of the inductor 21, the deterioration of the capacitor 11 is promoted, and in the worst case, the combustible substances of the capacitor 11 may catch fire.

[0022] In the present disclosure, the capacitor 11 is sealed by the sealed portion 10. That is, the capacitor 11 is isolated from the inductor 21 in the non-sealed portion 20. Therefore, the capacitor 11 in the sealed portion 10 is hardly affected by the heat of the inductor 21.

[0023] Also, even when the combustible substances of the capacitor 11 catch fire, since the capacitor 11 is stored in the sealed portion 10, the influence of the ignition of the capacitor 11 hardly reaches the inductor 21.

[0024] Therefore, even if the capacitor 11 in the sealed section 10 is damaged, there is little possibility that the inductor 21 in the unsealed section 20 will be damaged. Thus, if the capacitor 11 is damaged, the fixing device 35 can be removed to separate the sealed section 10, including the capacitor 11, from the unsealed section 20, and a new sealed section 10 with a similar configuration can be assembled to the unsealed section 20.

[0025] From the above, it can be seen that in the first embodiment, the safety of the noise filter 5 can be greatly enhanced, and the maintainability of the noise filter 5 can also be improved.

[0026] Figure 3A is a cross-sectional view of a modified noise filter. The noise filter 5' shown in Figure 3A includes a housing 6, and a horizontally positioned plate-like portion 25a divides the internal space of the housing 6 into an upper portion and a lower portion. The upper portion of the housing 6 functions as a sealed portion 10 where capacitors 11 and the like are located. Furthermore, the lower portion of the housing 6 functions as an unsealed portion 20 where inductors 21 and the like are located. For this purpose, an opening 29 is formed in the end face 27 of the lower portion of the housing 6.

[0027] In other words, the plate-like portion 25a is part of the wall portion that constitutes the sealed portion 10, and also part of the wall portion that constitutes the unsealed portion 20. The plate-like portion 25a can also function as a partition plate that separates the sealed portion 10 and the unsealed portion 20 from each other within the housing 6. An opening 28 may be additionally formed on the end face 26 of the lower portion of the housing 6. In the modified example shown in Figure 3A, in addition to the effects described above, the effect of easily forming the sealed portion 10 and the unsealed portion 20 can be obtained by simply placing the plate-like portion 25 inside the housing 6 in which the opening 29 etc. is formed.

[0028] Figure 3B is a cross-sectional view of a noise filter in another modified form. In the noise filter 5a shown in Figure 3B, two parallel plate-like portions 25b and 25c are arranged horizontally within the housing 6. These plate-like portions 25b and 25c divide the internal space of the housing 6 into three sections. The uppermost space functions as a sealed section 10 where a capacitor 11 and the like are placed. Furthermore, the lowermost space functions as an unsealed section 20 where an inductor 21 and the like are placed. For this purpose, an opening 29 is formed in the end face 27 of the corresponding lower portion of the housing 6.

[0029] Furthermore, the intermediate space sandwiched between the plate-like portions 25b and 25c is an isolation space 40 that isolates the capacitor 11 and the inductor 21 from each other. A control printed circuit board 13 for the noise filter 5a and the like are arranged in the isolation space 40. The intermediate space shown in Figure 3B is configured as an open space, and an opening 38 is formed in the wall portion 36 of the housing 6. However, the isolation space 40 may be configured as an open space, and the opening 38 may not be formed.

[0030] In the modified example shown in Figure 3B, an isolation space 40 is placed between the uppermost space where the capacitor 11 is located and the lowermost space where the inductor 21 is located. Since the isolation space 40 itself has an insulating effect, even if the inductor 21 generates heat, the capacitor 11 inside the sealed section 10 will be less affected by the heat from the inductor 21. Similarly, even if the flammable material in the capacitor 11 ignites, the inductor 21 will be less affected by the ignition of the capacitor 11. Therefore, the safety of the noise filter 5a can be further enhanced. The internal space of the isolation space 40 may be filled with insulating material.

[0031] In Figure 3B, a sensor 32, acting as a detection unit, is further positioned in the internal space of the sealed section 10. The sensor 32 is assumed to be a temperature sensor or a smoke sensor, and is connected to the control printed circuit board 13. When the sensor 32 detects that the temperature in the internal space of the sealed section 10 has risen above a predetermined temperature, or that smoke has been generated in the internal space of the sealed section 10, this information is output through the output unit 33. The output unit 33 may be a lamp or speaker provided on the outer surface of the noise filter 5. Alternatively, the operation screen of an NC device that controls a power conversion device, such as a motor drive device, to which the noise filter 5 is connected may be used as the output unit 33 to display the aforementioned information.

[0032] The output unit 33 is preferably located in a place other than the sealed unit 10, for example, on the outer surface of the unsealed unit 20, or on the outer surface of the isolated space unit 40 as shown in Figure 3B. If the capacitor 11 inside the sealed unit 10 is damaged by heat, it is sufficient to separate the entire sealed unit 10, assemble a new sealed unit 10, and connect the signal line (not shown) extending from the output unit 33 to the sensor 32. Therefore, even if the capacitor 11 inside the sealed unit 10 is damaged, damage to the output unit 33 located outside the sealed unit 10 can be avoided.

[0033] The predetermined temperature mentioned above is, for example, a value that is a predetermined temperature lower than the ignition temperature of the flammable material contained in the capacitor 11. Since the sensor 32 is located there, it is possible to recognize in advance that the capacitor 11 may ignite and to warn the outside through the output unit 33. Therefore, it is possible to prevent the capacitor 11 from actually igniting.

[0034] Furthermore, in Figure 3B, the fan 31 is positioned on the end face 26 side of the housing 6 within the internal space of the unsealed section 20. The fan 31 draws outside air into the internal space of the unsealed section 20 through the opening 28 on the end face 26, air-cools the inductor 21, and discharges it through the opening 29 on the other end face 27. Since the inductor 21 can be air-cooled by the fan 31, the thermal impact on the capacitor 11 can be reduced. Naturally, the fan 31 can also be placed in the noise filter of other embodiments.

[0035] Incidentally, it is possible for a capacitor to catch fire while the inductor is being air-cooled by a fan. In such a situation, since the capacitor is not housed in a sealed compartment in conventional technology, the flame generated in the capacitor will be blown into the noise filter by the fan. As a result, the inductor may be overheated by the flame and damaged. Furthermore, the flame may extend to the outside of the noise filter through the opening on the end face where the fan is not located (corresponding to opening 29), thereby posing a risk of spreading fire to objects placed around the noise filter.

[0036] However, in this disclosure, since the capacitor 11 is housed in the sealed section 10, even if the capacitor 11 ignites, the flame will not reach the inductor 21 located in the internal space of the unsealed section 20. Furthermore, since the flame does not reach the internal space of the unsealed section 20, the fan 31 will not cause the flame to spread outside the noise filter 5 through the opening 29. In other words, even if the noise filter 5 is equipped with a fan 31 inside the unsealed section 20, there will be no situation where objects placed around the noise filter 5 catch fire. Therefore, even when equipped with a fan 31, a highly safe noise filter 5 can be provided.

[0037] Figure 4A is a perspective view of the noise filter in the second embodiment. In the second embodiment, the connecting portion 39 is a flexible conductor, such as a wire. Therefore, in the second embodiment, the positional relationship between the sealed portion 10 and the unsealed portion 20 can be freely changed within the range of the length of the connecting portion 39 (conductive wire). Accordingly, the arrangement of the entire noise filter 5b can be flexibly changed according to the environment in which the power converter and the like are located.

[0038] For example, if only a long, narrow space is available, the sealed section 10 and the unsealed section 20 can be arranged in series horizontally, as shown in Figure 4A. In a space where the height is relatively long and there is no space to be secured horizontally, the sealed section 10 and the unsealed section 20 can be arranged so that they are stacked on top of each other (see Figure 1, etc.). Alternatively, although not shown in the drawings, in environments where there are steps, the sealed section 10 can be placed above the step and the unsealed section 20 can be placed below the step.

[0039] Figure 4B is a perspective view of a noise filter in a third embodiment. The housing 6 of the noise filter 5c shown in Figure 4B has a vertically extending plate-shaped portion 25d. In Figure 4B, the plate-shaped portion 25d is located in the center of the horizontal width of the housing 6, but the plate-shaped portion 25d may be located in a place other than the center.

[0040] The left portion of the housing 6 functions as a sealed section 10 where capacitors 11 and the like are located. Furthermore, the right portion of the housing 6 functions as an unsealed section 20 where inductors 21 and the like are located. For this purpose, an opening 28 is formed in the end face 26 of the lower portion of the housing 6. In other words, the plate-like portion 25d is part of the wall portion that constitutes the sealed section 10, and also part of the wall portion that constitutes the unsealed section 20.

[0041] The configuration shown in Figure 4B is a modified version of the configuration shown in Figure 3A. Therefore, the same effects as those described in Figure 3A can be obtained. In the third embodiment, two parallel plate-shaped portions 25 may be arranged vertically within the housing 6, with the rightmost portion being a sealed portion 10, the leftmost portion being an unsealed portion 20, and the middle portion being the aforementioned isolated space portion 40.

[0042] Figure 4C is a perspective view of a noise filter in the fourth embodiment. In the noise filter 5d shown in Figure 4C, the sealed section 10 is arranged so as to be stacked on top of the unsealed section 20. In this configuration, the bottom wall of the sealed section 10 may be common with the upper wall of the unsealed section 20. The sealed section 10 may be located at the corner of the top surface of the unsealed section 20.

[0043] Figure 4D is a perspective view of a noise filter in the fifth embodiment. In the noise filter 5e shown in Figure 4D, the sealed section 10 is located inside the unsealed section 20. In this configuration as well, the bottom wall of the sealed section 10 may be common with the bottom wall of the unsealed section 20. Alternatively, the unsealed section 20 may be located inside the sealed section 10.

[0044] Furthermore, the internal space of the sealed section 10 may be at least partially filled with a resin, such as a flame-retardant resin. This reduces the amount of oxygen in the internal space of the sealed section 10, thereby suppressing the possibility of the capacitor 11 inside the sealed section 10 igniting.

[0045] The effects of at least one embodiment and its variations described above include significantly increasing the safety of the noise filter 5 and improving its maintainability.

[0046] While embodiments of this disclosure have been described in detail, this disclosure is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, or partially deleted in various ways, without departing from the spirit of the invention or the idea and intent of the invention derived from the claims and their equivalents. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. Furthermore, combining some of the embodiments described above as appropriate is within the scope of this disclosure.

[0047] The following additional information is disclosed regarding the above embodiments and variations. (Note 1) Capacitors and, Inductor and A sealed section for housing the capacitor, A noise filter comprising an open section housing the aforementioned inductor and at least partially open to the outside air. (Note 2) The capacitor is a noise filter as described in Note 1, containing a flammable substance. (Note 3) The noise filter according to Note 1 or 2, further comprising a connection portion for electrically connecting the capacitor and the inductor, wherein the connection portion is a wire. (Note 4) A noise filter according to any one of Notes 1 to 3, which is provided in the sealed section and comprises a detection unit for detecting the state of the internal space of the sealed section. (Note 5) The noise filter according to any one of Notes 1 to 4, wherein the noise filter comprises a housing, and the sealed portion and the unsealed portion are formed by partitioning the internal space of the housing with a partition. (Note 6) The noise filter according to any one of Notes 1 to 5, wherein the internal space of the sealed part is filled with resin. (Note 7) The noise filter according to any one of Notes 1 to 6, wherein at least a portion of the wall of the sealed portion is common with the wall of the unsealed portion. (Note 8) The noise filter according to any one of Notes 1 to 7, further comprising a fan located in the non-sealed section for cooling the internal space of the non-sealed section. [Explanation of symbols]

[0048] 5, 5', 5a~5e Noise filters 6 Housing 10 Sealed part 11 Capacitors 12 circuit boards 13 Control Printed Circuit Board 20 Unsealed area 21 Inductors 25, 25a~25d Plate-like parts 28, 29, 38 Openings 31 Fans 32 Sensor (detection unit) 35 Fixtures 39 Connection part 40 Isolated Space Section

Claims

1. Capacitors and, Inductor and A sealed section for housing the capacitor, A noise filter comprising an open section housing the aforementioned inductor and at least partially open to the outside air.

2. The noise filter according to claim 1, wherein the capacitor contains a flammable substance.

3. The device further comprises a connection portion that electrically connects the capacitor and the inductor, The noise filter according to claim 1 or 2, wherein the connection part is a wire.

4. The noise filter according to any one of claims 1 to 3, comprising a detection unit provided in the sealed portion for detecting the state of the internal space of the sealed portion.

5. The noise filter comprises a housing, The noise filter according to any one of claims 1 to 4, wherein the sealed portion and the unsealed portion are formed by partitioning the internal space of the housing with a partition.

6. The noise filter according to any one of claims 1 to 5, wherein the internal space of the sealed portion is filled with resin.

7. The noise filter according to any one of claims 1 to 6, wherein at least a portion of the wall of the sealed portion is common with the wall of the unsealed portion.

8. The noise filter according to any one of claims 1 to 7, further comprising a fan disposed in the non-sealed portion for cooling the internal space of the non-sealed portion.

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