JP2014090102A - Dew condensation prevention structure of electrical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dew condensation prevention structure of an electrical device that prevents dew condensation on a printed circuit board without complicating a structure and without a difficult control.SOLUTION: A dew condensation prevention structure 10 of an electrical device 12 includes: a heating part 38 provided on a substrate 14; sensors 40a and 40b for detecting dew on the substrate 14; and a controller for controlling the heating part 38. Surface temperature of the substrate 14 and temperature of ambient atmosphere of the substrate 14 are measured with the two sensors 40a and 40b. Surrounding of the heating part 38 as a center is heated. Dew is prevented by making temperature higher than that of the ambient atmosphere.

Description

  The present invention relates to a dew condensation prevention structure for an electrical device on which an electronic component such as a power device is mounted.

  Conventionally, a power device such as an IPM (Intelligent Power Module) or a diode bridge is mounted on a printed circuit board to constitute an electrical equipment such as an inverter. Since power devices are highly heat-generating parts, they need to be cooled. An example of the cooling method is cooling using a refrigerant. The piping through which the refrigerant flows is covered with a refrigerant jacket, and the power device is cooled via the heat transfer plate. By using the refrigerant, the cooling capacity is increased, and the degree of freedom of the downsizing and arrangement of the electrical equipment is increased.

  Although the power device is cooled from the refrigerant jacket via the heat transfer plate, when the refrigerant temperature becomes lower than the air temperature, the printed circuit board may be cooled below the ambient air temperature via the lead of the power device. For example, when the output of the power device is small, there are cases where a plurality of electrical devices and power devices are provided and some of them are stopped. If the printed circuit board is condensed, problems such as defective insulation between the conductive patterns and corrosion of the printed circuit board occur.

  In Patent Document 1, an auxiliary cooler capable of exchanging heat with respect to an electrical component box of an air conditioner is provided, and the auxiliary cooler is connected to the compressor via a bypass circuit. The flow rate adjusting means adjusts the flow rate of the refrigerant to the auxiliary cooler to prevent dew condensation in the electrical component box. However, an actuator or the like is necessary for adjusting the flow rate of the refrigerant, which is not preferable because the apparatus becomes large.

  Patent Document 2 discloses a heat pump device in which a refrigerant circuit having two parallel flow paths is provided and the thermal resistance of each flow path with respect to a power semiconductor is different. The flow path switching means switches the flow path according to the operating state of the heat pump device to prevent dew condensation of the power semiconductor. However, the configuration for switching the flow path becomes complicated, and the apparatus is increased in size.

  Patent Document 3 discloses a technique for preventing condensation by covering a component mounting surface of a printed board with a resin. However, it takes time to cure the resin, and the manufacturing time becomes long. Since parts are covered with resin, repairs that replace parts are not possible.

  Patent Document 4 discloses a configuration in which a semiconductor package is mounted on a substrate and a portion where condensation occurs due to cooling of the refrigerant is hermetically covered. However, it is difficult to form a complete airtight structure to prevent condensation. Even if a complete hermetic structure can be formed, the cost is considerably increased.

  Patent Document 5 discloses a configuration in which a heater is disposed on a pipe, and cooling water is heated using a dew point temperature inside and outside the apparatus and a pipe surface temperature. However, since the cooling water is heated, a large amount of heat is required, which is not preferable in terms of energy efficiency.

  Patent Document 6 discloses a configuration in which an intermediate pressure refrigerant in a refrigeration cycle absorbs heat from a heat generating device and evaporates. By controlling the degree of opening and closing of the electric expansion valve, the intermediate pressure is changed, the amount of cooling from the heating device is adjusted, and condensation is prevented. However, since the amount of cooling changes depending on the operating state of the heat generating device, control becomes difficult.

JP-A-5-157372 JP 2009-281602 A Japanese Utility Model Publication No. 1-86295 JP 2000-349484 A JP-A-1-169615 Japanese Patent Laid-Open No. 11-23081

  SUMMARY OF THE INVENTION An object of the present invention is to provide a dew condensation prevention structure for an electrical device that does not cause dew condensation on a printed circuit board without complicating the configuration and difficult control.

  The electrical equipment includes a substrate, a power device mounted on the substrate, a cooling member to which a pipe through which a refrigerant flows is attached, and an attachment for attaching the substrate to the cooling member.

  A dew prevention structure for an electrical device according to the present invention includes a heat generating portion provided near a lead of a power device on the board, a fixture, or both, a sensor for detecting the possibility of dew condensation on the board, And a control unit that switches on and off the heat generating unit from the value measured by the sensor.

  The sensor detects whether or not condensation occurs, and if it is determined that condensation occurs, the control unit causes the heat generating unit to generate heat. Prevents condensation due to temperature rise. If there is no condensation, the heat generating part will not generate heat.

  The sensor measures the temperature and / or humidity of the substrate and the ambient atmosphere around the substrate. Detects whether condensation occurs due to temperature and humidity.

  The heat generating portion is a conductor pattern formed on the substrate or a heater attached to the substrate. The heat generating part uses a conductor pattern of the substrate or is attached to the substrate.

  There are a plurality of the electrical equipment or power devices. When the electric device or power device is stopped or driven at low power, the substrate is easily cooled, but is heated by the heat generating portion to prevent dew condensation.

  The control unit uses hysteresis control to switch the heat generating unit on and off. Prevents the heat generating part from switching on and off frequently.

  In the present invention, it is only necessary to detect whether or not condensation occurs with a sensor and to turn on or off the heat generating portion, and condensation can be prevented with a simple configuration and control. When the heat generating portion is formed of a conductor pattern, the heat generating portion can be manufactured in the process of manufacturing the substrate, and the manufacturing is not complicated.

It is a figure which shows the structure of the dew condensation prevention structure of the electrical equipment of this invention. (A) is a figure which shows the heat generating part formed with the conductor pattern, (b) is the figure which made the heat generating part meander. It is a figure which shows the structure of a control part. It is a figure which shows the structure of the dew condensation prevention structure of the electrical equipment which provided the heat-emitting part in the attachment vicinity. It is a figure which shows the structure of the dew condensation prevention structure of the electrical equipment which provided the heat generating part in the lead vicinity and the attachment vicinity. It is a figure which shows the structure of the control part which uses a humidity sensor. It is a figure which shows the heat-emitting part of a planar heater.

  A dew condensation preventing structure for an electrical equipment according to the present invention will be described with reference to the drawings. The electrical equipment uses high heat-generating parts such as power devices including an inverter circuit.

  As shown in FIG. 1, the electrical device 12 includes a substrate 14, a power device 16 mounted on the substrate 14, a cooling member 20 including a pipe 18 through which a refrigerant flows, and an attachment for attaching the substrate 14 to the cooling member 20. 22.

  The substrate 14 is a printed circuit board in which a conductor pattern 26 is formed on the surface of the resin substrate 24 with a conductor such as copper foil. Instead of the resin substrate 24, a metal substrate in which an insulator is laminated on the surface of a metal plate may be used. The surface on the cooling member side of the substrate 14 will be described as an opposing surface 28, and the opposite surface will be described as an opposing surface 30. In FIG. 1, a conductor pattern 26 is formed on the facing surface 28 of the substrate 14. A conductor pattern 26 is also appropriately formed on the opposite surface 30 of the substrate 14.

  The lead 32 of the power device 16 is connected to the conductor pattern 26. The power device 16 is a highly heat-generating electronic component such as an IPM or a diode bridge. The lead 32 of the power device 16 is connected to the conductor pattern 26 of the substrate 14 by soldering or the like.

  The power device 16 is cooled by the cooling member 20. The cooling member 20 includes a pipe 18 through which a refrigerant flows, a refrigerant jacket 34 and a heat transfer plate 36. The pipe 18 is covered with a rectangular parallelepiped refrigerant jacket 34, and a plate-shaped heat transfer plate 36 is attached to the refrigerant jacket 34. The refrigerant is chlorofluorocarbon, ammonia, water or the like. The heat transfer plate 36 and the power device 16 are in contact with each other. The substrate 14 and the cooling member 20 are attached by a fixture 22. The attachment tool 22 is a screw or the like, and is preferably made of a material that hardly thermally expands.

  The dew condensation prevention structure 10 of the electrical device 12 of the present invention shown in FIGS. 1, 2, and 3 includes a heat generating portion 38 provided on the substrate 14, sensors 40a and 40b for detecting the possibility of condensation on the substrate 14, and a heat generating portion. The control part 42 which controls 38 is provided.

  The heat generating portion 38 is provided in the vicinity of the lead 32 of the power device 16 on the substrate 14. In the vicinity of the lead 32 of the power device 16, when the power device 16 stops or is driven at low power, the lead 32 is also cooled, and the vicinity of the substrate 14 is also cooled. For this reason, a portion that is cooled and easily dewed is heated by the heat generating portion 38.

  The heat generating portion 38 uses a conductor such as a copper foil on the surface of the substrate 14 that is the same as the conductor pattern 26. For example, as shown in FIG. 2A, a linear conductor pattern 26 ′ that becomes a heat generating portion 38 is formed near the conductor pattern 26 to which the leads 32 are connected. The line width of the conductor pattern 26 'is narrowed, and a resistor is formed by the conductor pattern 26'. Both ends of the heat generating unit 38 are connected to the control unit 42. Since the conductor pattern 26 'serving as the heat generating portion 38 is a resistor, it generates heat when a current is passed.

  If the conductor pattern 26 ′ is too thin, a region that generates heat is reduced, and the substrate 14 may not be heated. Therefore, as shown in FIG. 2 (b), the linear conductor pattern 26 'serving as the heat generating portion 38 may be meandered to enlarge the region where heat is generated. The amount of heat of the heat generating portion 38 is increased, and the substrate 14 is easily heated.

  When the conductor pattern 26 of the substrate 14 is formed by etching or the like, a conductor pattern 26 'that becomes the heat generating portion 38 can be formed at the same time. Therefore, a special manufacturing process for forming the heat generating portion 38 is not added.

  In FIG. 1, since the facing surface 28 of the cooling member 20 in the substrate 14 is easier to cool than the opposite surface 30, a heating portion 38 is provided on the facing surface 28 of the substrate 14. When the opposite surface 30 of the substrate 14 is also cooled, a heat generating portion 38 may be provided on the opposite surface 30. The number of the heat generating portions 38 is not limited, and is appropriately formed at a place to be cooled.

  As the sensors 40a and 40b, temperature sensors that measure the temperature of the substrate 14 and the ambient atmosphere of the substrate 14 are used. Examples of the sensors 40a and 40b include white silver resistance thermometers, thermistors, thermocouples, and IC temperature sensors. The sensors 40 a and 40 b include a first sensor 40 a that measures the temperature of the substrate 14 and a second sensor 40 b that measures the temperature in the ambient atmosphere of the substrate 14.

  The values measured by the sensors 40a and 40b are used to determine the possibility of condensation on the substrate 12. The first sensor 40 a is attached in the vicinity of the lead 32 of the power device 16 on the substrate 14. Measure the temperature of the part where condensation is likely to occur. The second sensor 40b may be attached to the substrate 14 and measure the temperature of the surrounding atmosphere, or may be arranged around the substrate 14 by another member to measure the temperature. In FIG. 1, the second sensor 40 b is disposed in the space on the opposite surface 30 side of the substrate 12, but may be disposed in the space on the opposite surface 28 side of the substrate 12.

  The control unit 42 in FIG. 3 is a circuit or a program for switching on and off the heat generating unit 38 from the values measured by the sensors 40a and 40b. For example, the control unit 42 compares the values of the power supply 44 for flowing current to the heat generating unit 38, the control relay 46 for connecting or disconnecting the heat generating unit 38 and the power supply 44, and the values of the two sensors 40a and 40b. Is provided with a comparison circuit 48 for outputting an ON or OFF signal. When the electrical device 12 is an inverter circuit or the like, the control unit 42 may be incorporated in a microcomputer used for the inverter circuit or the like.

  The surface temperature of the substrate 14 and the temperature of the ambient atmosphere of the substrate 14 are measured by the two sensors 40a and 40b. The comparison circuit 48 compares the two values, and if the value of the first sensor 40a is high, there is no possibility of condensation, the control relay 46 is turned off, and the power supply 44 and the heat generating portion 38 are disconnected. No current flows through the heat generating portion 38 and no heat is generated.

  If the value of the 2nd sensor 40b is higher than the value of the 1st sensor 40a, the board | substrate 14 has cooled from the surrounding atmosphere and there exists a possibility of dew condensation. The control relay 46 is turned on to connect the power supply 44 and the heat generating unit 38. A current flows through the heat generating portion 38 to generate heat. The periphery of the heat generating part 38 is heated. Since the heat generating part 38 is provided in the vicinity of the lead 32 of the power device 16 or the like, a place where condensation easily occurs is heated. The temperature of the substrate 14 is set higher than that of the surrounding atmosphere to prevent condensation.

  As described above, the present invention has a simple configuration, and there is no increase in the size of the apparatus as shown in the prior art. The heat generating portion 38 can be formed at the same time as the substrate 14, and the manufacturing is not complicated. Only the values of the two sensors 40a and 40b are compared, and the control is simple.

  There is a case where the substrate 14 is cooled via the attachment 22 and dew condensation occurs. As shown in FIG. 4, the heat generating portion 38 and the first sensor 40 a may be disposed near the fixture 22 on the substrate 14. The first sensor 40a and the second sensor 40b may be provided for each heat generating part 38, or the first sensor 40a and the second sensor 40b may be provided only for one of the heat generating parts 38. When there are a plurality of first sensors 40a or second sensors 40b, an average value of the values measured by the sensors 40a and 40b may be used.

  In addition, as shown in FIG. 5, the heat generating portion 38 and the first sensor 40 a may be arranged in both the vicinity of the lead 32 of the power device 16 and the vicinity of the fixture 22 on the substrate 14. As shown in FIGS. 1, 4, and 5, a heat generating portion 38 is provided where condensation is likely to occur for each electrical device 12, and sensors 40 a and 40 b for detecting condensation are arranged.

  In the first embodiment, temperature sensors are used as the sensors 40a and 40b, but humidity sensors may be used. Examples of the humidity sensor include a capacitive sensor using porous ceramics or a hygroscopic polymer film. The humidity sensor is also attached to the substrate 14 or disposed in the ambient atmosphere of the substrate 14. Since it is a humidity sensor, the number of sensors 40a, 40b may be one.

  As shown in FIG. 6, when the humidity sensor 40 c is used, the control unit 42 ′ has a power supply 44 for flowing current to the heat generating unit 38 and a control relay 46 for connecting or disconnecting the heat generating unit 38 and the power supply 44. Prepare. The control relay 46 is turned on or off depending on the value of the humidity sensor 40c. Since condensation occurs when the humidity reaches 100%, the control relay 46 is turned on at a predetermined value before the humidity reaches 100%.

  Moreover, you may use both temperature sensor 40a, 40b and the humidity sensor 40c as a sensor for detecting dew condensation. The temperature sensor uses the first sensor 40a and the second sensor 40b as in the first embodiment. For example, when the value of the second sensor 40b is higher than that of the first sensor 40c and the humidity sensor 40c becomes equal to or higher than a predetermined value, the control unit 42 turns on the heat generating unit 38.

  The configuration for heating the substrate 14 is not limited to the heat generating portion 38 formed of a conductor pattern. For example, as shown in FIG. 7, a heating unit 38 ′ of a planar heater can be mentioned. A rubber heater or a ribbon heater can be used as the heating portion 38 'of the planar heater. The planar heater may be attached to the conductor pattern 26. The planar heater and the conductor pattern 26 are insulated.

  In FIG. 7, the heat generating portion 38 ′ is provided on the conductor pattern 26, but this is not a limitation. As in the first embodiment, a heating portion 38 ′ of a planar heater may be provided on the resin substrate 24.

  There may be a plurality of power devices 16. When some of the power devices 16 are stopped, the stopped power devices 16 are easily cooled, the substrate 14 is cooled via the leads 32, and the portion is likely to be condensed. Condensation is prevented by the heat generating portion 38.

  Moreover, there may be a plurality of electrical devices 12 such as an air conditioner including a plurality of inverters. When some of the electrical devices 12 are stopped, the power device 16 of the electrical device 12 is cooled, and the substrate 14 is easily cooled via the leads 32. A place that is easily cooled is heated by the heat generating portion 38 to prevent condensation.

  When switching the control relay 46 on and off, hysteresis control may be used. If the temperature and humidity fluctuate finely and the values measured by the sensors 40a, 40b, and 40c are not constant, on and off may be frequently switched. A circuit for performing hysteresis control is incorporated in the control relay 46 to prevent frequent switching between on and off.

  In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Each embodiment is not independent or exclusive, and may be implemented in combination as appropriate.

DESCRIPTION OF SYMBOLS 10: Dew condensation prevention structure 12 of an electrical equipment 12: Electrical equipment 14: Board | substrate 16: Power device 18: Piping 20: Cooling member 22: Mounting tool 24: Insulating board 26: Conductive pattern 28: Opposite surface 30: Opposite surface 32: Lead 34 : Refrigerant jacket 36: Heat transfer plate 38: Heat generating parts 40a, 40b, 40c: Sensors 42, 42 ': Control part 44: Power supply 46: Control relay 48: Comparison circuit

Claims (5)

A substrate,
A power device mounted on the substrate;
A cooling member provided with a pipe through which the refrigerant flows;
An attachment for attaching the substrate to the cooling member;
An anti-condensation structure for an electrical equipment comprising:
Near the lead of the power device on the substrate, near the fixture, or both, and
A sensor for detecting the possibility of condensation of the substrate;
From the value measured by the sensor, a control unit that switches the heating unit on and off,
Condensation prevention structure for electrical equipment equipped with The dew condensation prevention structure for an electrical equipment device according to claim 1, wherein the sensor measures the temperature and / or humidity of the substrate and the ambient atmosphere around the substrate. The dew condensation preventing structure for an electrical equipment according to claim 1 or 2, wherein the heat generating portion is a conductor pattern formed on the substrate or a heater attached to the substrate. The dew condensation preventing structure for an electrical equipment according to any one of claims 1 to 3, wherein there are a plurality of electrical equipment or power devices. The dew condensation preventing structure for an electrical device according to any one of claims 1 to 4, wherein the control unit uses hysteresis control to switch the heat generating unit on and off.

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