Noise filter

Abstract

This noise filter includes a capacitor, an inductor, a sealed unit that contains the capacitor, and an unsealed unit that contains the inductor and is at least partially open to outside air.

Description

Noise Filter

[0001] The present disclosure relates to noise filters.

[0002] When a power conversion device, such as a motor drive device, is operated, high-frequency noise is generated from the built-in switching elements. To remove high-frequency noise, a filter, such as a noise filter, is provided at the input of the power conversion device. Such a noise filter includes a capacitor and an inductor (see, for example, JP 2021-121143 A).

[0003] Japanese Patent Publication No. 2021-121143

[0004] Although capacitors generate relatively little heat when used in a noise filter, they often contain flammable materials, such as electrolytic paper, plastic film, and insulating oil. Furthermore, capacitors with structural components that include thin metal films, such as vapor-deposited electrode films or metallicon, can oxidize due to external temperature and humidity, causing the capacitor's performance to deteriorate over time. Therefore, if an inductor generates heat within a noise filter and this influence extends to the capacitor over a long period of time, the capacitor may fail and, in the worst case, catch fire.

[0005] For this reason, there is a demand for a noise filter that is highly safe and easy to maintain.

[0006] According to a first aspect of the present disclosure, there is provided a noise filter comprising a capacitor, an inductor, a sealed portion that houses the capacitor, and a non-sealed portion that houses the inductor and is at least partially open to the outside air.

[0007] The objects, features, and advantages of the present disclosure will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.

[0008] FIG. 1 is a perspective view of a noise filter according to a first embodiment; FIG. 2 is an exploded perspective view of the noise filter shown in FIG. 1; FIG. 3 is a cross-sectional view of a noise filter according to a modified example; FIG. 4 is a cross-sectional view of a noise filter according to another modified example; FIG. 5 is a perspective view of a noise filter according to a second embodiment; FIG. 6 is a perspective view of a noise filter according to a third embodiment; FIG. 7 is a perspective view of a noise filter according to a fourth embodiment; and FIG. 8 is a perspective view of a noise filter according to a fifth embodiment.

[0009] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. Corresponding components are designated by common reference numerals throughout the drawings. FIG. 1 is a perspective view of a noise filter according to a first embodiment, and FIG. 2 is an exploded perspective view of the noise filter shown in FIG. 1. As shown in these drawings, the noise filter 5 is an LC filter mainly including a capacitor 11 and an inductor 21. The noise filter 5 is connected to a power conversion device, for example, a motor drive device, via its connector 30.

[0010] 1 and 2 show a plurality of capacitors 11 arranged in an array on the substrate 12, the noise filter 5 may 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] 1 and 2, multiple inductors 21 are arranged in parallel. However, the noise filter 5 may include a single inductor. The inductor 21 mainly includes a coil. A core made of a magnetic material may be disposed at the center of the coil. In other words, the inductor 21 may be a reactor.

[0012] The capacitor 11 and the inductor 21 are electrically connected to each other by a connecting portion 39. The connecting portion 39 may be a flexible conductor, such as a conductive wire, or a rigid conductor, such as a bus bar. Typically, the connecting portion 39 includes a resistor (not shown) between the capacitor 11 and the inductor 21. In other embodiments, the connecting portion 39 may be omitted from illustration. The noise filter 5 including the capacitor 11 and the inductor 21 is well known, and therefore further description will be omitted.

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

[0014] The sealed portion 10 does not have a communicating portion, such as an opening, a notch, a valve, or the like, that connects the internal space of the sealed portion 10 with the external space. It is preferable that the boundary portions of the adjacent external surfaces of the sealed portion 10 are sealed with a seal or the like, but sealing is not necessarily required.

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

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

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

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

[0019] Furthermore, the sealing portion 10 and the non-sealing portion 20 are preferably fixed to each other by fasteners 35, such as screws. 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 fasteners 35. It is preferable that the sealing portion 10 and the non-sealing portion 20 are made interchangeable.

[0020] As described above, the capacitor 11 of the noise filter 5 according to the present disclosure is housed in the sealed portion 10, and the inductor 21 is housed in the non-sealed portion 20. When a power conversion device, such as a motor drive device, is operating, high-frequency noise is generated from the switching elements of the power conversion device. The noise filter 5 connected to the power conversion device functions to cut out high-frequency noise.

[0021] However, due to factors such as the power conversion device itself, capacitor 11 may deteriorate over time, causing self-heating and resulting in an increase in capacitor temperature. Furthermore, the heat from inductor 21 of noise filter 5 and the influence of ambient humidity can cause the metal electrodes inside capacitor 11 to oxidize, degrading the capacitor's characteristics and resulting in an increase in capacitor temperature due to self-heating. Capacitor 11 may include electrolytic paper or a laminate of plastic film and metal foil, or a metallized film in which metal is vapor-deposited on plastic film. In large capacitors, such laminates and metallized films are often impregnated with electrical insulating oil. In other words, capacitor 11 may contain multiple types of flammable materials. In such cases, the heat from inductor 21 accelerates the deterioration of capacitor 11, and in the worst case, the flammable materials in capacitor 11 may ignite.

[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 less susceptible to the heat of the inductor 21.

[0023] Furthermore, even if the combustible material in the capacitor 11 ignites, the capacitor 11 is housed in the sealed portion 10, so that the effects of the ignition of the capacitor 11 are unlikely to reach the inductor 21.

[0024] Therefore, even if the capacitor 11 in the sealed portion 10 is damaged, there is little possibility that the inductor 21 in the non-sealed portion 20 will be damaged. Therefore, if the capacitor 11 is damaged, the fixing device 35 can be removed, the sealed portion 10 itself including the capacitor 11 can be separated from the non-sealed portion 20, and a new sealed portion 10 having a similar configuration can be assembled to the non-sealed portion 20.

[0025] From the above, it will be understood that in the first embodiment, it is possible to significantly improve the safety of the noise filter 5 and also improve the maintainability of the noise filter 5.

[0026] Fig. 3A is a cross-sectional view of a noise filter according to a modified example. The noise filter 5' shown in Fig. 3A includes a housing 6, and a horizontally disposed plate-like portion 25a divides the interior 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 in which a capacitor 11 and the like are disposed. Furthermore, the lower portion of the housing 6 functions as a non-sealed portion 20 in which an inductor 21 and the like are disposed. For this purpose, an opening 29 is formed in an end surface 27 of the lower portion of the housing 6.

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

[0028] Fig. 3B is a cross-sectional view of a noise filter according to another modification. In the noise filter 5a shown in Fig. 3B, two parallel plate-shaped portions 25b, 25c are arranged horizontally within the housing 6. These plate-shaped portions 25b, 25c divide the interior space of the housing 6 into three sections. The uppermost space functions as the sealed portion 10 in which the capacitor 11 and other components are arranged. Furthermore, the lowermost space functions as the non-sealed portion 20 in which the inductor 21 and other components are arranged. For this purpose, an opening 29 is formed in an end surface 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 isolated space portion 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 isolated space portion 40. The intermediate space shown in Fig. 3B is configured as a non-sealed portion, and an opening 38 is formed in the wall portion 36 of the housing 6. However, the isolated space portion 40 may be configured as a sealed portion, and the opening 38 may not be formed.

[0030] In the modified example shown in Figure 3B, an isolated space 40 is disposed between the uppermost space in which the capacitor 11 is disposed and the lowermost space in which the inductor 21 is disposed. Because the isolated space 40 itself has a thermal insulating effect, even if the inductor 21 generates heat, the capacitor 11 in the sealed portion 10 is less susceptible to the effects of the heat from the inductor 21. Similarly, it can be seen that even if the flammable material in the capacitor 11 ignites, the inductor 21 is less susceptible to the effects of the ignition of the capacitor 11. This further enhances the safety of the noise filter 5a. The internal space of the isolated space 40 may be filled with a thermal insulating material.

[0031] 3B , a sensor 32 serving as a detection unit is further disposed in the internal space of the sealed portion 10. The sensor 32 is 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 portion 10 has reached a predetermined temperature or higher, or that smoke has been generated in the internal space of the sealed portion 10, the sensor 32 outputs the detected information via the output unit 33. The output unit 33 may be a lamp or a speaker provided on the outer surface of the noise filter 5. Alternatively, the operation screen of a power conversion device connected to the noise filter 5, such as an NC device that controls a motor drive device, may be used as the output unit 33 to display the information described above.

[0032] The output unit 33 is preferably provided at a location other than the sealed unit 10, for example, on the outer surface of the non-sealed unit 20, or on the outer surface of the isolated space unit 40 as shown in Figure 3B. If the capacitor 11 in 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 a signal line (not shown) extending from the output unit 33 to the sensor 32. Therefore, even if the capacitor 11 in the sealed unit 10 is damaged, it is possible to avoid damage to the output unit 33 provided at a location other than the sealed unit 10.

[0033] The predetermined temperature is, for example, a value that is lower by a predetermined temperature than the ignition temperature of the combustible material contained in capacitor 11. Because sensor 32 is provided, it is possible to recognize in advance that capacitor 11 may catch fire and issue a warning to the outside via output unit 33. Therefore, it is possible to prevent capacitor 11 from actually catching fire.

[0034] 3B, a fan 31 is disposed on the end face 26 side of the housing 6 in the internal space of the non-sealed portion 20. The fan 31 draws external air into the internal space of the non-sealed portion 20 through an opening 28 in the end face 26, cools the inductor 21, and discharges the air from an opening 29 in the other end face 27. Since the inductor 21 can be air-cooled by the fan 31, the influence of heat on the capacitor 11 can be reduced. Naturally, the fan 31 can also be disposed in the noise filter of other embodiments.

[0035] However, it is possible that the capacitor may catch fire while the inductor is being air-cooled by a fan. If such an event occurs, because the capacitor is not housed in a sealed compartment in the prior art, the flame generated in the capacitor is blown inside the noise filter by the fan. As a result, the flame may overheat the inductor and cause it to be damaged. Furthermore, the flame may spread to the outside of the noise filter through the opening on the end face where the fan is not located (corresponding to opening 29), which could cause the fire to spread to objects located around the noise filter.

[0036] However, in the present disclosure, because the capacitor 11 is housed in the sealed portion 10, even if the capacitor 11 catches fire, the flame will not reach the inductor 21 located in the internal space of the non-sealed portion 20. Furthermore, because the flame does not reach the internal space of the non-sealed portion 20, the fan 31 will not cause the flame to spread to the outside of the noise filter 5 through the opening 29. In other words, even if the noise filter 5 includes the fan 31 inside the non-sealed portion 20, there will be no risk of the fire spreading to objects located around the noise filter 5. Therefore, even when the fan 31 is included, a highly safe noise filter 5 can be provided.

[0037] 4A is a perspective view of the noise filter according to the second embodiment. The connection portion 39 in the second embodiment is a flexible conductor, such as a wire. Therefore, in the second embodiment, the positional relationship between the sealed portion 10 and the non-sealed portion 20 can be freely changed within the range of the length of the connection portion 39 (conductive wire). Therefore, the overall layout of the noise filter 5b can be flexibly changed depending on the environment in which the power conversion device or the like is installed.

[0038] For example, when only a long, narrow space is available, the sealed portion 10 and the non-sealed portion 20 may be arranged in series in the horizontal direction, as shown in Fig. 4A. In a space where the vertical distance is relatively long and no horizontal distance can be ensured, the sealed portion 10 and the non-sealed portion 20 may be arranged so as to be stacked on top of each other (see Fig. 1, etc.). Alternatively, in an environment where there is a step (not shown in the drawings), the sealed portion 10 may be arranged above the step, and the non-sealed portion 20 may be arranged below the step.

[0039] Fig. 4B is a perspective view of a noise filter according to a third embodiment. A vertically extending plate-shaped portion 25d is disposed in the housing 6 of a noise filter 5c shown in Fig. 4B. In Fig. 4B, the plate-shaped portion 25d is disposed in the center of the horizontal width of the housing 6, but the plate-shaped portion 25d may be disposed in a location other than the center.

[0040] The left portion of the housing 6 functions as the sealed portion 10 in which the capacitor 11 and the like are arranged. Furthermore, the right portion of the housing 6 functions as the non-sealed portion 20 in which the inductor 21 and the like are arranged. For this purpose, an opening 28 is formed in an end surface 26 of the lower portion of the housing 6. In other words, the plate-like portion 25d is a part of the wall that constitutes the sealed portion 10, and is also a part of the wall that constitutes the non-sealed portion 20.

[0041] The configuration shown in Figure 4B is a modified example of the configuration shown in Figure 3A. Therefore, it is possible to obtain the same effect as that described in Figure 3A. In the third embodiment, two parallel plate-like portions 25 may be arranged vertically within the housing 6, with the rightmost portion being the sealed portion 10, the leftmost portion being the non-sealed portion 20, and the middle portion being the isolated space portion 40 described above.

[0042] Fig. 4C is a perspective view of a noise filter according to a fourth embodiment. In a noise filter 5d shown in Fig. 4C, a sealing portion 10 is arranged so as to be stacked above a non-sealing portion 20. In this configuration, the bottom wall of the sealing portion 10 may be common to the upper wall of the non-sealing portion 20. The sealing portion 10 may be arranged at a corner of the upper surface of the non-sealing portion 20.

[0043] Fig. 4D is a perspective view of a noise filter according to a fifth embodiment. In a noise filter 5e shown in Fig. 4D, a sealed portion 10 is disposed in the internal space of a non-sealed portion 20. In this configuration, the bottom wall of the sealed portion 10 may also be the same as the bottom wall of the non-sealed portion 20. Alternatively, the non-sealed portion 20 may be disposed in the internal space of the sealed portion 10.

[0044] The internal space of the sealed portion 10 may be at least partially filled with a resin, such as a flame-retardant resin, which reduces the amount of oxygen in the internal space of the sealed portion 10, thereby reducing the possibility of the capacitor 11 in the sealed portion 10 catching fire.

[0045] At least one of the embodiments and modifications described above has the effect of significantly improving the safety of the noise filter 5 and improving the maintainability of the noise filter 5 .

[0046] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments. Furthermore, appropriate combinations of several of the above-described embodiments are within the scope of the present disclosure.

[0047] The following supplementary notes are further disclosed regarding the above-described embodiments and variations. (Supplementary Note 1) A noise filter comprising: a capacitor; an inductor; a sealed portion that houses the capacitor; and a non-sealed portion that houses the inductor and is at least partially open to the outside air. (Supplementary Note 2) The noise filter according to Supplementary Note 1, wherein the capacitor contains a flammable material. (Supplementary Note 3) The noise filter according to Supplementary Note 1 or 2, further comprising a connection portion that electrically connects the capacitor and the inductor, the connection portion being a wire. (Supplementary Note 4) The noise filter according to any one of Supplements 1 to 3, further comprising a detection portion that is provided in the sealed portion and detects a state of the internal space of the sealed portion. (Supplementary Note 5) The noise filter according to any one of Supplements 1 to 4, wherein the noise filter comprises a housing, and the internal space of the housing is partitioned by a partition portion to form the sealed portion and the non-sealed portion. (Supplementary Note 6) The noise filter according to any one of Supplements 1 to 5, wherein the internal space of the sealed portion is filled with resin. (Supplementary Note 7) The noise filter according to any one of Supplementary Notes 1 to 6, wherein at least a portion of a wall of the sealed portion is common to a wall of the non-sealed portion. (Supplementary Note 8) The noise filter according to any one of Supplementary Notes 1 to 7, further comprising a fan disposed in the non-sealed portion to cool the internal space of the non-sealed portion.

[0048] 5, 5', 5a to 5e Noise filter 6 Housing 10 Sealed portion 11 Capacitor 12 Board 13 Control printed circuit board 20 Non-sealed portion 21 Inductor 25, 25a to 25d Plate-shaped portion 28, 29, 38 Opening 31 Fan 32 Sensor (detection portion) 35 Fixing device 39 Connection portion 40 Isolated space portion

Claims

1. A capacitor; An inductor; a sealed portion for housing the capacitor; a non-sealed portion housing the inductor and at least partially open to the atmosphere.

2. The noise filter of claim 1 , wherein the capacitor comprises a flammable material.

3. a connection portion electrically connecting the capacitor and the inductor, 3. The noise filter according to claim 1, wherein the connection portion is a wire.

4. 3. The noise filter according to claim 1, further comprising a detector provided in said sealed portion for detecting a state of an internal space of said sealed portion.

5. The noise filter includes a housing.

3. The noise filter according to claim 1, wherein the sealed portion and the non-sealed portion are formed by dividing an internal space of the housing by a partition portion.

6. 3. The noise filter according to claim 1, wherein an internal space of said sealed portion is filled with a resin.

7. 3. The noise filter according to claim 1, wherein at least a part of a wall of the sealed portion is common to a wall of the non-sealed portion.

8. 3. The noise filter according to claim 1, further comprising a fan disposed in the non-sealed portion for cooling an internal space of the non-sealed portion.