Motor drive device

Abstract

A motor drive device (100) comprises: a housing (1) of which the internal space is partitioned into an upper space (11) and a lower space (12) by a partition part (10); an electronic component (30) that is disposed in the lower space (12) of the housing (1); and an internal fan (2) that is disposed in the upper space (11) of the housing (1) and discharges air from the internal space of the housing (1) to the outside. A first ventilation hole (14) that communicates the upper space (11) and the outside of the housing (1) is formed in the upper surface (1a) of the housing (1), and a second ventilation hole (15) that communicates the upper space (11) and the lower space (12) is formed in a portion of the partition part (10) that faces the upper surface (1a). The internal fan (2) is disposed so as to face the first ventilation hole (14) and is disposed such that at least a portion thereof does not overlap the second ventilation hole (15) when the housing (1) is viewed from the upper surface (1a) side.

Description

Motor drive device

[0001] The present disclosure relates to a motor drive device provided in a control panel.

[0002] Conventionally, a motor drive device having a fan for cooling electronic components inside a housing is known. The motor drive device may be installed, for example, in a control panel of an industrial device. In a factory where an industrial device is installed, oil used for cooling and processing the industrial device evaporates, filling the air with oil mist, or the environment is often humid. In such an environment inside the factory, if the control panel is not sufficiently sealed, there is a risk that oil mist or water vapor may enter the inside of the control panel. At this time, the oil mist or water vapor enters the inside of the housing and circulates by the air flow generated by the fan. When the oil mist or water vapor is cooled by the action of the fan and condensation occurs near the fan, and the droplets fall onto the electronic components arranged inside the housing, there is a risk that the electronic components may cause a short circuit failure or malfunction due to oxidation or corrosion of the wiring pattern or components.

[0003] For example, the motor drive device disclosed in Patent Document 1 has a configuration including a heat sink for cooling a power element inside a housing. Electronic components are arranged below the heat sink inside the housing. The edge of the heat sink facing the electronic components is inclined with respect to the horizontal plane. Droplets collected by a fan arranged above the heat sink adhere to the heat sink and move along the inclined edge, and fall to a position avoiding the electronic components.

[0004] Japanese Unexamined Patent Application Publication No. 2016 - 154242

[0005] However, since the technique disclosed in Patent Document 1 is configured to drop droplets inside the housing, there is a risk that liquid condensed in the middle of the inclined portion of the heat sink or droplets blown by the air flow circulating inside the housing may adhere to the electronic components.

[0006] The present disclosure has been made in view of the above, and an object thereof is to obtain a motor drive device capable of suppressing droplets falling into the housing while cooling electronic components arranged inside the housing.

[0007] To solve the above-mentioned problems and achieve the objective, the motor drive device according to this disclosure is a motor drive device installed in a control panel and comprises a housing whose internal space is divided into an upper space and a lower space by a partition, electronic components arranged in the lower space of the housing, and an internal fan arranged in the upper space of the housing for discharging air from the internal space of the housing to the outside. A first ventilation hole is formed on the upper surface of the housing to connect the upper space and the outside of the housing, and a second ventilation hole is formed in a part of the partition facing the upper surface to connect the upper space and the lower space. The internal fan is arranged opposite the first ventilation hole and is positioned such that at least a part of it does not overlap with the second ventilation hole when the housing is viewed from the top side.

[0008] The motor drive device described herein has the effect of cooling the electronic components placed inside the housing while suppressing the falling of liquid droplets into the housing.

[0009] A perspective view showing a motor drive device according to Embodiment 1. An explanatory diagram showing the internal structure of a control panel housing the motor drive device according to Embodiment 1. A perspective view showing a disassembled motor drive device according to Embodiment 1. A cross-sectional view showing the interior of the motor drive device according to Embodiment 1. A vertical cross-sectional view showing the interior of the motor drive device according to Embodiment 1 from a different position than in Figure 4. An enlarged view showing the upper space of the housing of the motor drive device according to Embodiment 1. A perspective view schematically showing the interior of the housing of the motor drive device according to Embodiment 1. A cross-sectional view showing a modified electronic component 1 consisting of a capacitor component of the motor drive device according to Embodiment 1. A cross-sectional view showing a modified electronic component 2 consisting of a capacitor component of the motor drive device according to Embodiment 1. A perspective view showing a partially disassembled motor drive device according to Embodiment 2. A perspective view showing a modified motor drive device 1 according to Embodiment 2, partially disassembled. A perspective view showing a modified motor drive device 2 according to Embodiment 2. A perspective view showing a modified motor drive device 3 according to Embodiment 2.

[0010] Hereinafter, a motor drive device according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0011] Embodiment 1. Figure 1 is a perspective view showing a motor drive device according to Embodiment 1. Figure 2 is an explanatory diagram showing the internal structure of a control panel housing the motor drive device according to Embodiment 1. The white arrows shown in Figure 2 indicate the airflow passing through the heat sink 4. The motor drive device 100 shown in Figure 1 controls the current flowing to a motor used in industrial equipment such as robots, machine tools, and conveying machines, and realizes a desired motor motion. As shown in Figure 2, the motor drive device 100 is installed in a control panel 200 of the industrial equipment. The control panel 200 is, for example, a high-voltage panel. In addition to the motor drive device 100, the control panel 200 is equipped with devices for utilizing electrical energy, such as relays, transformers, switches, circuit breakers, and switches (not shown). The devices arranged inside the control panel 200 are isolated from the outside of the control panel 200. The motor drive unit 100 has a housing 1 containing an internal fan and multiple electronic components, which is placed inside the control panel 200, while the heat sink 4 and external fan 5 are exposed to the outside of the control panel 200.

[0012] Figure 3 is a perspective view showing an exploded view of the motor drive device according to Embodiment 1. Figure 4 is a cross-sectional view showing the inside of the motor drive device according to Embodiment 1. Figure 5 is a longitudinal cross-sectional view of the inside of the motor drive device according to Embodiment 1, shown from a different position than in Figure 4. The white arrows shown in Figures 4 and 5 indicate the airflow passing through the inside of the housing 1. As shown in Figures 3 to 5, the motor drive device 100 comprises a housing 1, an internal fan 2, a plurality of electronic components 30, 31, a heat sink 4, and an external fan 5.

[0013] The housing 1 is, for example, roughly rectangular in shape, with a top surface 1a, a bottom surface 1b, and four sides 1c, 1d, 1e, and 1f. An opening is formed on one of the four sides 1f of the housing 1, and this opening is covered by a heat sink 4. The internal space of the housing 1 is divided into an upper space 11 and a lower space 12 by a plate-shaped partition 10 located opposite the top surface 1a of the housing 1. The upper space 11 of the housing 1 is the space enclosed by the top surface 1a and sides 1c, 1d, 1e, and 1f of the housing 1 and the partition 10, and functions as a duct that forms an airflow. An internal fan 2 is housed in the upper space 11 to expel the air heated inside the housing 1 to the outside and cool the internal space of the housing 1. The lower space 12 of the housing 1 is the space enclosed by the bottom surface 1b and sides 1c, 1d, 1e, 1f of the housing 1 and the partition 10, and houses multiple electronic components 30, 31 such as a power module and capacitor components. Note that the shape of the housing 1 is not limited to the rectangular parallelepiped shown in the figure, and may be other shapes. Also, there are not limited to multiple electronic components, and one or more are sufficient.

[0014] An opening 13a for inserting and removing the internal fan 2 is formed on the top surface 1a of the housing 1, and an internal fan cover 13 that covers the opening 13a is detachably provided. The internal fan cover 13 constitutes a part of the top surface 1a of the housing 1. The opening 13a is formed over almost the entire upper space 11. The opening 13a may be configured to be the same size as the internal fan 2. In this case, the internal fan cover 13 will also be the same size as the internal fan 2. By removing the internal fan cover 13 from the housing 1, maintenance of the internal fan 2 and the inside of the housing 1 in the upper space 11 can be performed. The internal fan cover 13 has a first ventilation hole 14 that connects the upper space 11 of the housing 1 to the outside of the housing 1. The first ventilation hole 14 is composed of a plurality of small holes, for example. The internal fan 2 is positioned in the upper space 11 of the housing 1, facing the first ventilation hole 14. The upper surface 1a of the housing 1 does not necessarily need to have an opening 13a to provide an internal fan cover 13; it may be configured without an internal fan cover 13. In this case, the first ventilation hole 14 is formed on the upper surface 1a of the housing 1.

[0015] The partition 10 has a second ventilation hole 15 that connects the upper space 11 and the lower space 12 of the housing 1. The second ventilation hole 15 is composed of a plurality of small holes, for example. The second ventilation hole 15 is formed in a position where the projected surface of the first ventilation hole 14 does not overlap when the housing 1 is viewed from the top surface 1a. It is preferable that the second ventilation hole 15 is formed in a position where the projected surface of the first ventilation hole 14 does not overlap when the housing 1 is viewed from the top surface 1a, but it is also acceptable for a part of the projected surface of the first ventilation hole 14 to overlap. When performing maintenance on the motor drive unit 100, the internal fan cover 13 can be removed from the housing 1, allowing for easy visual inspection of the lower space 12 of the housing 1 through the second ventilation hole 15.

[0016] As shown in Figures 4 and 5, in the internal space of the housing 1, by driving the internal fan 2, air from the lower space 12 of the housing 1 flows through the second vent 15 to the upper space 11 and is discharged to the outside of the housing 1 through the first vent 14. At this time, the upper space 11 of the housing 1 functions as a duct that forms the airflow from the second vent 15 to the first vent 14, so that the airflow is not dispersed and weakened, and the airflow can be strengthened. In addition, since the second vent 15 is formed in a part of the partition 10 that faces the upper surface 1a where the first vent 14 is formed, there is less bending in the air passage from the lower space 12 through the second vent 15 to the first vent 14. As a result, changes in the direction of the airflow can be suppressed, wind loss can be suppressed, and the air inside the housing 1 can be effectively discharged to the outside of the housing 1.

[0017] Furthermore, a third ventilation hole 16 is formed on the lower surface 1b of the housing 1, connecting the lower space 12 of the housing 1 with the outside of the housing 1. The third ventilation hole 16 is, for example, composed of a plurality of small holes. Preferably, the third ventilation hole 16 is formed in a range that includes the position where the projected surface of the second ventilation hole 15 overlaps when the housing 1 is viewed from the upper surface 1a side. If the second ventilation hole 15 and the third ventilation hole 16 are on a straight line, the air flows in a straight line from the third ventilation hole 16 to the second ventilation hole 15 without being dispersed, thus improving cooling efficiency. However, the third ventilation hole 16 may be formed in a position where the projected surface of the second ventilation hole 15 does not overlap when the housing 1 is viewed from the upper surface 1a side. Furthermore, considering cooling efficiency, it is preferable that the third ventilation hole 16 is formed only on the bottom surface 1b, but for example, it may be formed only on at least one side surface 1c, 1d, 1e, or it may be formed on at least one side surface 1c, 1d, 1e and the bottom surface 1b. Also, the third ventilation hole 16 may be formed over a wider area than the second ventilation hole 15. For example, the third ventilation hole 16 may be formed over the entire bottom surface 1b.

[0018] Figure 6 is an enlarged view showing the upper space of the housing in a motor drive device according to Embodiment 1. As shown in Figure 6, the internal fan 2 is positioned opposite the first ventilation hole 14 and is positioned so as not to overlap with the second ventilation hole 15 when the housing 1 is viewed from the top surface 1a side. That is, the internal fan 2 is positioned away from the second ventilation hole 15. The internal fan 2 is supported on the upper surface of the partition 10. The internal fan 2 draws in air from the lower space 12 and generates an airflow that is discharged from the second ventilation hole 15 of the partition 10 through the first ventilation hole 14 formed on the upper surface 1a of the housing 1 to the outside of the housing 1. It is preferable that the internal fan 2 is positioned so as not to completely overlap with the second ventilation hole 15 when the housing 1 is viewed from the top surface 1a side, but it may be positioned so that at least a part of it does not overlap with the second ventilation hole 15. That is, it may be positioned so that at least a part of it avoids the second ventilation hole 15.

[0019] As shown in Figure 4, the electronic component 30 is a power module that is mounted on, for example, a power module mounting plate 30a and constitutes a circuit for supplying power to a motor. The power module mounting plate 30a has heat transfer characteristics. Also, as shown in Figure 5, the electronic component 31 is a capacitor component mounted on a printed circuit board 31a. Note that the electronic components may include other electronic components in addition to the electronic components 30 and 31 consisting of the power module and capacitor component. The electronic component 30 consisting of the power module and the electronic component 31 consisting of the capacitor component are heat sources and are electronic components that require cooling. As shown in Figure 4, at least a portion of the electronic component 30 consisting of the power module is located directly below the second ventilation hole 15. The electronic component 30 is located near the second ventilation hole 15, above the lower space 12, as shown in Figure 4. Note that if multiple electronic components 30 consisting of power modules are arranged, they may be provided from the upper to the lower part of the lower space 12. As shown in Figure 5, at least a portion of the electronic component 31 consisting of the capacitor component is located directly below the second ventilation hole 15. Furthermore, the electronic component 31 is positioned above the lower space 12, which is near the second ventilation hole 15. These electronic components 30 and 31 are located in the air passage from the third ventilation hole 16 to the second ventilation hole 15. The airflow velocity increases near the second ventilation hole 15. Therefore, by positioning the electronic components 30 and 31 near the second ventilation hole 15, the heated electronic components 30 and 31 can be efficiently cooled. In addition, the air heated by cooling the electronic components 30 and 31 can be immediately discharged to the second ventilation hole 15 without affecting other electronic components. Moreover, by positioning the electronic components 30 and 31 in the air passage from the third ventilation hole 16 to the second ventilation hole 15, a large amount of air flows to the electronic components 30 and 31, allowing them to be cooled efficiently. In addition, considering cooling efficiency, it is preferable that the electronic components 30 and 31 be placed directly below the second vent hole 15, but they do not necessarily have to be placed directly below the second vent hole 15. However, even in this case, it is preferable that the multiple electronic components 30 and 31 be placed in the air passage from the third vent hole 16 to the second vent hole 15.

[0020] Figure 7 is a schematic perspective view showing the inside of the housing of a motor drive device according to Embodiment 1. As shown in Figure 7, the electronic component 30 consisting of a power module may be supported by a vertically elongated power module mounting plate 30a. In this case, the longitudinal direction of the mounting surface on which the power module is installed is positioned along the side surface 1d or side surface 1e of the housing 1, which is along the air passage from the third ventilation hole 16 to the second ventilation hole 15. The electronic component 30 consisting of the power module is then positioned in the air passage from the third ventilation hole 16 to the second ventilation hole 15. The side surface of the housing 1 along the air passage from the third ventilation hole 16 to the second ventilation hole 15 is perpendicular to the side surface 1f of the housing 1 attached to the wall portion 201 of the control panel 200, and also perpendicular to the top surface 1a of the housing 1. By positioning the longitudinal direction of the mounting surface of the vertically elongated power module mounting plate 30a along the side 1d or side 1e of the housing 1, which is in line with the airflow path from the third ventilation hole 16 to the second ventilation hole 15, the area on which electronic components 30 can be installed along the third ventilation hole 16 to the second ventilation hole 15 can be increased, allowing many electronic components 30 to be cooled efficiently.

[0021] Figure 8 is a cross-sectional view showing a modified example 1 of an electronic component consisting of a capacitor component in a motor drive device according to Embodiment 1. The electronic component 32 shown in Figure 8 is a large capacitor component and is positioned directly below the second ventilation hole 15. When the electrolyte of the electronic component 32, which is a large capacitor component, evaporates at high temperatures, there is a risk that its lifespan will be shortened. By positioning the electronic component 32, which is a large capacitor component, directly below the second ventilation hole 15, the electronic component 32 can be cooled efficiently.

[0022] Figure 9 is a cross-sectional view showing a modified example 2 of an electronic component consisting of a capacitor component in a motor drive device according to Embodiment 1. The electronic component 33 shown in Figure 9 is a large capacitor component, and is a vertically elongated electrolytic capacitor whose longitudinal mounting surface is arranged along an air passage from the third ventilation hole 16 to the second ventilation hole 15. By arranging the electronic component 33 in this way, the surface area exposed to air is increased, and it can be arranged without obstructing the airflow, so that the electronic component 33, which consists of a large capacitor component, can be cooled efficiently.

[0023] The heat sink 4 dissipates the heat generated by the electronic components 30 and 31. As shown in Figures 4 and 5, the heat sink 4 has a flat heat sink base 40 and a plurality of flat fins 41 arranged in parallel at intervals on one surface of the heat sink base 40. The heat sink 4 is made of a metal material with relatively high thermal conductivity so that it can dissipate the heat generated by the electronic components 30 and 31. For example, the heat sink 4 is made of a corrosion-resistant metal material such as aluminum or an aluminum alloy. The heat sink 4 is fixed to the housing 1 such that the heat sink base 40 closes an opening formed in the side surface 1f of the housing 1. The area around the fins 41 is covered by a fin cover 42 with open top and bottom surfaces.

[0024] As shown in Figure 2, the external fan 5 is, for example, positioned above the heatsink 4, drawing in air from the bottom of the heatsink 4 and pushing it out from the top of the heatsink 4. Alternatively, the external fan 5 may be positioned above the heatsink 4, drawing in air from the top of the heatsink 4 and pushing it out from the bottom of the heatsink 4. Furthermore, the external fan 5 may be positioned below the heatsink 4, drawing in air from either the top or bottom of the heatsink 4 and pushing it out from either the bottom or top of the heatsink 4. In addition, if the heat generated by the electronic components constituting the motor drive unit 100 is small, a structure that cools using only the internal fan 2 without the heatsink 4 and external fan 5 may be used.

[0025] As shown in Figure 2, the motor drive unit 100 according to Embodiment 1 is mounted on a wall portion 201 that separates the inside of the control panel 200 from the outside of the control panel 200, with the fins 41 and the external fan 5 exposed to the outside of the control panel 200 through mounting holes (not shown) formed in the wall portion 201. During operation, the motor drive unit 100 generates heat from the electronic components 30 and 31 located inside the control panel 200. This heat is transmitted to the outside of the control panel 200 via the fins 41 and released into, for example, a factory where industrial equipment is installed, through heat exchange with the air supplied by the external fan 5. On the other hand, the heat that is not transmitted to the fins 41 remains in the internal space of the housing 1. The heat remaining in the internal space of the housing 1 is released into the control panel 200 by creating an airflow inside the housing 1 with the internal fan 2. The heat released into the control panel 200 is then released to the outside of the control panel 200 by a heat exchanger (not shown) or the like.

[0026] For example, factories where industrial equipment is installed are often filled with oil mist from the evaporation of oil used for cooling and processing the industrial equipment, and are also in environments with high humidity. In such environments, if the control panel 200 installed in the factory is not properly sealed, there is a risk that oil mist or water vapor may enter the inside of the control panel 200.

[0027] At this time, the oil mist or water vapor enters the interior of the housing 1 and circulates due to the airflow generated by the internal fan 2. When the oil mist or water vapor is cooled by the action of the internal fan 2, condensation occurs near the internal fan 2, and if the droplets become large, they may fall into the lower space 12 of the housing 1 due to gravity. If droplets form in the lower space 12, electronic components 30, 31 and other electronic components on the circuit board may short-circuit and fail, or the wiring patterns or components may fail due to oxidation or corrosion.

[0028] Therefore, in the motor drive device 100 according to Embodiment 1, the internal fan 2 is positioned opposite the first ventilation hole 14, and is configured such that at least a part of the internal fan 2 does not overlap with the second ventilation hole 15 when the housing 1 is viewed from the top. When oil mist or water vapor passes through the internal fan 2, it condenses and forms droplets on the blades of the internal fan 2, for example. When the droplets become large, they fall due to gravity. At this time, if the second ventilation hole 15 is directly below the internal fan 2, the droplets will fall into the lower space 12 of the housing 1. However, in the motor drive device 100 according to Embodiment 1, since at least a part of the internal fan 2 is positioned so as not to overlap with the second ventilation hole 15, the droplets fall onto the upper surface of the partition 10 directly below the internal fan 2. As a result, it is possible to prevent droplets from entering the lower space 12 of the housing 1, and thus protect the electronic components 30, 31 and other electronic components located in the lower space 12. Preferably, the second ventilation hole 15 is formed in a position where, when the housing 1 is viewed from the top surface 1a, the projected surface of the first ventilation hole 14 does not overlap with the second ventilation hole 15 at all. However, by shifting the positions of the first ventilation hole 14 and the second ventilation hole 15, even if the second ventilation hole 15 partially overlaps with the projected surface of the first ventilation hole 14, it is possible to suppress the entry of liquid droplets. In particular, since there is a high possibility that liquid droplets will fall from the center of the internal fan 2, by positioning the internal fan 2 so that its center does not overlap with the second ventilation hole 15, the possibility of liquid droplets falling into the lower space 12 can be greatly reduced.

[0029] Furthermore, the electronic components include electronic components 30 and 31 positioned such that at least a portion of their outer surface is located directly below the second ventilation hole 15. Near the second ventilation hole 15, the airflow velocity increases. Therefore, the heated electronic components 30 and 31 can be efficiently cooled. In addition, the air heated by cooling the electronic components 30 and 31 can be immediately discharged to the second ventilation hole 15 without affecting other electronic components.

[0030] A third ventilation hole 16 is formed on the lower surface of the housing 1. The electronic components 30 and 31 include components that are placed in an air passage that extends from the third ventilation hole 16 to the second ventilation hole 15. As a result, a large amount of air flows to the electronic components 30 and 31, allowing them to be cooled efficiently.

[0031] The electronic component 30 includes a power module supported on a power module mounting plate 30a. The mounting surface of the power module mounting plate 30a is positioned along side 1d or side 1e of the housing 1, which is aligned with the airflow path from the third vent 16 to the second vent 15. The electronic component 30, consisting of the power module, is positioned within the airflow path from the third vent 16 to the second vent 15. By positioning the mounting surface of the power module mounting plate 30a along side 1d or side 1e of the housing 1, which is aligned with the airflow path from the third vent 16 to the second vent 15, the area on which the electronic component 30 is installed along the airflow path from the third vent 16 to the second vent 15 can be increased, allowing for efficient cooling of a large number of electronic components 30.

[0032] The electronic component 33 includes an electrolytic capacitor whose mounting surface is positioned along an air passage from the third ventilation hole 16 to the second ventilation hole 15. By positioning the electronic component 33 in this manner, the surface area exposed to air is increased, and the component can be positioned without obstructing the airflow, thus efficiently cooling the electronic component 33, which consists of a large capacitor component.

[0033] Embodiment 2. Next, the motor drive device 101 according to Embodiment 2 will be described. Figure 10 is a perspective view showing the motor drive device according to Embodiment 2 in a partially disassembled state. As shown in Figure 10, the motor drive device 101 according to Embodiment 2 has a droplet fall prevention unit 6 in the upper space 11 of the housing 1 to catch droplets generated on the internal fan 2. The other configurations are the same as in Embodiment 1.

[0034] The droplet fall prevention unit 6 shown in Figure 10 is a filter positioned below the internal fan 2 that adsorbs droplets. The filter can be made of, for example, urethane, felt, superabsorbent polymer, nylon, polyester, or wool. The droplet fall prevention unit 6, which consists of a filter, is positioned between the internal fan 2 and the partition 10. By having the droplet fall prevention unit 6, even if many droplets accumulate on the upper surface of the partition 10, or if evaporation of droplets is difficult, the droplets can be adsorbed by the filter, thereby suppressing the dripping of droplets into the lower space 12 of the housing 1.

[0035] Figure 11 is a perspective view showing a modified example 1 of the motor drive device according to Embodiment 2, with parts disassembled. The droplet fall prevention section 6A shown in Figure 11 is formed on the upper surface of the partition section 10 and is configured as a wall-shaped projection that blocks droplets from flowing into the second ventilation hole 15. The droplet fall prevention section 6A, consisting of a wall-shaped projection, is provided between the upper surface of the partition section 10 facing the internal fan 2 and the second ventilation hole 15. By having the droplet fall prevention section 6A, even when many droplets accumulate on the upper surface of the partition section 10, or when evaporation of droplets is difficult, the flow of droplets can be blocked by the wall-shaped projection, thereby suppressing the falling of droplets into the lower space 12 of the housing 1. Alternatively, in addition to providing the droplet fall prevention section 6A, a droplet fall prevention section 6 consisting of a filter as shown in Figure 10 may be installed on the upper surface of the partition section 10.

[0036] Figure 12 is a perspective view showing a modified example 2 of the motor drive device according to Embodiment 2. In Figure 12, the upper part of the housing 1 is omitted, and the partition 10 is exposed. The droplet fall prevention section 6B shown in Figure 12 is formed on the upper surface of the partition 10 and is configured as a recess for storing droplets. The droplet fall prevention section 6B, which consists of a recess, is formed in a position opposite the internal fan 2. By having the droplet fall prevention section 6B, even when many droplets accumulate on the upper surface of the partition 10, or when evaporation of droplets is difficult, the droplets can be stored in the recess, thereby suppressing the dripping of droplets into the lower space 12 of the housing 1. Alternatively, a droplet fall prevention section 6 consisting of a filter as shown in Figure 10 may be installed inside the recess of the droplet fall prevention section 6B. In addition, a droplet fall prevention section 6A consisting of a wall-shaped projection as shown in Figure 11 may be provided together with the droplet fall prevention section 6B.

[0037] Figure 13 is a perspective view showing a modified example 3 of the motor drive device according to Embodiment 2. In Figure 13, the upper part of the housing 1 is omitted, and the partition 10 is exposed. The droplet fall prevention section 6C shown in Figure 13 is formed in the partition 10 and is configured as a groove that guides droplets to the outside of the housing 1. A part of the droplet fall prevention section 6C, which consists of a groove, is formed in a position facing the internal fan 2. A drain hole 17 leading to the groove is formed on the side surface 1e of the housing 1. Droplets accumulated in the droplet fall prevention section 6C are discharged to the outside of the housing 1 through the drain hole 17 and fall down the side surface 1e of the housing 1. Alternatively, a droplet fall prevention section 6 consisting of a filter as shown in Figure 10 may be installed inside the groove of the droplet fall prevention section 6C. Alternatively, a droplet fall prevention section 6A consisting of a wall-shaped projection as shown in Figure 11 may be provided together with the droplet fall prevention section 6C.

[0038] The configurations shown in the above embodiments are merely examples and can be combined with other known technologies, or the embodiments themselves can be combined. Furthermore, it is possible to omit or modify parts of the configuration without departing from the gist of the invention.

[0039] 1. Enclosure, 1a. Top surface, 1b. Bottom surface, 1c, 1d, 1e, 1f. Side surfaces, 2. Internal fan, 4. Heat sink, 5. External fan, 6, 6A, 6B, 6C. Droplet fall prevention section, 10. Partition section, 11. Upper space, 12. Lower space, 13. Internal fan cover, 13a. Opening, 14. First ventilation hole, 15. Second ventilation hole, 16. Third ventilation hole, 17. Drain hole, 30, 31, 32, 33. Electronic components, 30a. Power module mounting plate, 31a. Printed circuit board, 40. Heat sink base, 41. Fin, 42. Fin cover, 100, 101. Motor drive unit, 200. Control panel, 201. Wall section.

Claims

1. A motor drive device installed in a control panel, comprising: a housing whose internal space is divided into an upper space and a lower space by a partition; electronic components arranged in the lower space of the housing; and an internal fan arranged in the upper space of the housing for discharging air from the internal space of the housing to the outside, wherein a first ventilation hole is formed on the upper surface of the housing to connect the upper space and the outside of the housing, and a second ventilation hole is formed in a part of the partition facing the upper surface to connect the upper space and the lower space, and the internal fan is arranged opposite the first ventilation hole and is arranged such that at least a part of it does not overlap with the second ventilation hole when the housing is viewed from the top side.

2. The motor drive device according to claim 1, characterized in that the internal fan is positioned opposite the first ventilation hole and is positioned so as not to overlap with the second ventilation hole when the housing is viewed from the top side.

3. The motor drive device according to claim 1 or 2, characterized in that the electronic component is arranged such that at least a portion of its outer surface is located directly below the second ventilation hole.

4. The motor drive device according to any one of claims 1 to 3, characterized in that a third ventilation hole is formed on the lower surface of the housing, and the electronic component is located in an air passage extending from the third ventilation hole to the second ventilation hole.

5. The motor drive device according to claim 4, wherein the electronic component includes a power module supported on a power module mounting plate, the power module mounting plate has a mounting surface for mounting the power module arranged along the side of the housing along an air passage from the third vent to the second vent, and the power module is arranged in the air passage from the third vent to the second vent.

6. The motor drive device according to claim 4 or 5, characterized in that the electronic component includes an electrolytic capacitor whose mounting surface is arranged along an air passage from the third vent to the second vent.

7. The motor drive device according to any one of claims 1 to 6, characterized in that it has a droplet fall prevention part provided in the upper space of the housing for receiving droplets generated on the internal fan.

8. The motor drive device according to claim 7, characterized in that the droplet fall prevention unit is a filter that is located below the internal fan and adsorbs droplets.

9. The motor drive device according to claim 7, characterized in that the droplet fall prevention part is a wall-shaped projection provided in the partition part that blocks droplets attempting to flow into the second ventilation hole.

10. The motor drive device according to claim 7, characterized in that the droplet fall prevention part is a recess formed in the partition part for storing the droplets.

11. The motor drive device according to claim 7, characterized in that the droplet fall prevention part is a groove formed in the partition part that guides the droplet to the outside of the housing.

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