JP2007163012A - Outdoor unit of refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an outdoor unit of a refrigerating cycle device capable of securing ample cooling action for reverse voltage application circuits, thus enabling stable operation of the reverse voltage application circuits. <P>SOLUTION: The outdoor unit 50 has enclosed therein an electrical component box 60 for mounting an inverter device 1 therein, and also has enclosed therein a compressor 20, an outdoor heat exchanger 22 and the like. A hybrid IC 62 is placed upright on an air supply passage, on a circuit board 61 inside the electrical component box 60. The hybrid IC 62 has a plurality of reverse voltage application circuits 5u, 5v, 5w, 6u, 6v, 6w. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an outdoor unit of a refrigeration cycle apparatus such as an air conditioner.

  In an inverter device that outputs driving power to a compressor motor by turning on and off a plurality of switching elements, each switching element has a reflux diode. Recently, IGBTs and FETs are often used as the switching elements.

  FETs have a merit that high-frequency switching is possible because of their high on / off speeds, and are frequently used when driving a motor with a small output such as a fan motor because the loss at the time of low voltage output is small.

  However, the free-wheeling diode of the FET, that is, the parasitic diode that is naturally formed in the manufacturing process has a problem that the reverse recovery characteristic is poor. For this reason, when the forward current due to the energy stored in the motor winding (inductive load) is flowing through the freewheeling diode of the FET and the other switching element paired with the FET is turned on, the freewheeling diode has a large amount. A reverse current flows, resulting in a large power loss. For this reason, it is very difficult to adopt an FET in an inverter device that drives a compressor motor that requires a larger current than a fan motor.

  On the other hand, a reverse voltage application circuit for applying a reverse voltage to the freewheeling diode of the MOSFET is provided prior to turning on the other switching element paired with the MOSFET, and the reverse current is applied to the freewheeling diode when the other switching element is on. An inverter device that suppresses reverse current and reduces power loss is known (for example, Patent Document 1).

By adopting such an inverter device having a reverse voltage application circuit, even an air conditioner compressor motor that requires a large current can be driven taking advantage of the merit of FET.
Japanese Patent Laid-Open No. 10-327585

  The inverter device for driving the compressor motor as described above is accommodated in the outdoor unit of the air conditioner. Accordingly, the reverse voltage application circuit is mounted on the circuit board of the inverter device.

  However, the reverse voltage application circuit has, for example, an FET as a switch means for applying the reverse voltage, and the FET generates heat when the reverse voltage is applied. This heat generation makes the operation of the reverse voltage application circuit unstable. As a result, there is a concern that it is difficult to appropriately suppress the reverse current flowing through the freewheeling diode.

  In consideration of the above circumstances, the present invention provides an outdoor unit for a refrigeration cycle apparatus capable of ensuring a sufficient cooling action for a reverse voltage application circuit and thereby enabling stable operation of the reverse voltage application circuit. The purpose is to do.

  An outdoor unit of a refrigeration cycle apparatus according to a first aspect of the present invention is for driving a compressor to a motor by turning on and off a plurality of switching elements having a refrigeration cycle having a compressor and a heat exchanger and a reflux diode. An refrigeration cycle apparatus comprising an inverter device for outputting electric power, wherein an FET is used for at least a part of the switching elements of the inverter device, and an electrical component box containing a circuit board on which these switching elements are mounted A hybrid IC that is housed together with the compressor and the heat exchanger and has a plurality of reverse voltage application circuits for applying reverse voltage to the reflux diode of the FET at a predetermined timing is provided on the ventilation path on the circuit board. Has been established.

  The outdoor unit of the refrigeration cycle apparatus of the present invention can ensure a sufficient cooling action for the reverse voltage application circuit. Thereby, the stable operation | movement of a reverse voltage application circuit is attained, and the reverse current which flows into a free-wheeling diode can be suppressed appropriately.

[1] A first embodiment of the present invention will be described below with reference to the drawings.
In FIG. 1, M is a brushless DC motor (load) used as a compressor motor of an air conditioner, and is fixed with three phase windings Lu, Lv, and Lw that are star-connected around a neutral point C. A rotor and a rotor having permanent magnets are included. The rotor rotates due to the interaction between the magnetic field generated by the current flowing through the stator phase windings Lu, Lv, and Lw and the magnetic field generated by the permanent magnet of the rotor.

  The brushless DC motor M is housed in such a manner that the compression mechanism of the compressor 20 and the rotary shaft are directly connected. An outdoor heat exchanger 22 is connected to the refrigerant discharge port of the compressor 20 via a four-way valve 21, and an indoor heat exchanger 24 is connected to the outdoor heat exchanger 22 via an expansion valve 23. A refrigerant suction port of the compressor 20 is connected to the heat exchanger 24 via the four-way valve 21 by piping. Thus, a heat pump refrigeration cycle capable of cooling and heating is configured. During cooling, the refrigerant discharged from the compressor 20 flows in the direction of the solid arrow, and the outdoor heat exchanger 22 functions as a condenser and the indoor heat exchanger 24 functions as an evaporator. At the time of heating, the refrigerant discharged from the compressor 20 flows in the direction of the broken line arrow by the switching operation of the four-way valve 21, and the indoor heat exchanger 24 functions as a condenser and the outdoor heat exchanger 22 functions as an evaporator.

  The inverter device 1 is connected to the brushless DC motor M. The inverter device 1 includes a rectifier circuit 31 that rectifies an AC voltage of a commercial AC power supply 30, input terminals P and N to which an output voltage (DC voltage Vd = 280 V) of the rectifier circuit 31 is applied via a smoothing capacitor 32, A switching circuit 2 is provided which receives the DC voltage Vd between the input terminals P and N and energizes the phase windings Lu, Lv and Lw and switches the energization. A control unit 10 is provided for driving control of the switching circuit 2.

  The switching circuit 2 has a series circuit of low-loss power MOSFETs (superjunction MOSFETs, etc.) for three phases U, V, and W as upstream and downstream switching elements along the application direction of the DC voltage Vd. MOSFET 3u upstream of U phase, MOSFET 4u and resistor 7u downstream of U phase, MOSFET 3v upstream of V phase, MOSFET 4v and resistor 7v downstream of V phase, MOSFET 3w upstream of W phase, downstream of W phase A MOSFET 4w and a resistor 7w are provided on the side. Each MOSFET is driven on and off at a predetermined timing by the controller 10. The free-wheeling diodes Du +, Dv +, and Dw + are connected in reverse parallel to the MOSFETs 3u, 3v, and 3w, respectively. The free-wheeling diodes Du−, Dv−, and Dw− are connected in reverse parallel to the MOSFETs 4u, 4v, and 4w, respectively. These free-wheeling diodes are incorporated in corresponding MOSFETs as so-called parasitic diodes.

  The unconnected ends of the phase windings Lu, Lv, and Lw are respectively connected to the interconnection point between the MOSFET 3u and the MOSFET 4u, the interconnection point between the MOSFET 3v and the MOSFET 4v, and the interconnection point between the MOSFET 3w and the MOSFET 4w.

  In addition, the switching circuit 2 is provided on the downstream side when forward currents (return currents) flow through the free-wheeling diodes Du +, Dv +, and Dw + by the energy stored in the phase windings Lu, Lv, and Lw that are inductive loads. In order to suppress reverse current flowing through the free-wheeling diodes Du +, Dv +, and Dw + when the MOSFETs 4u, 4v, and 4w are turned on, reverse voltages are applied to the free-wheeling diodes Du +, Dv +, and Dw + before the MOSFETs 4u, 4v, and 4w are turned on. Reverse voltage application circuits 5u, 5v, 5w for applying are provided.

  Further, when the forward current (return current) flows through the free-wheeling diodes Du−, Dv−, and Dw− due to the energy stored in the phase windings Lu, Lv, and Lw, the switching circuit 2 has the upstream side MOSFETs 3u, In order to suppress the reverse current flowing through the free-wheeling diodes Du−, Dv−, and Dw− when 3v and 3w are turned on, the free-wheeling diodes Du−, Dv−, and Dw− are turned on before the MOSFETs 3u, 3v, and 3w are turned on. Reverse voltage application circuits 6u, 6v, 6w for applying a reverse voltage are provided.

  The reverse voltage application circuit 5 u applies a voltage (for example, 15 V) of the DC power supply 40 to the reverse voltage application capacitor 42 via the resistor 41, and uses the voltage of the reverse voltage application capacitor 42 as the drain of the reverse voltage application MOSFET 43. A reverse voltage is applied to the free-wheeling diode Du + between the sources and via the diode 44. Further, the reverse voltage application circuit 5 u includes a pulse generation circuit 45 and a gate drive circuit 46 for driving the reverse voltage application MOSFET 43. The pulse generation circuit 45 generates a pulse signal for turning on / off the reverse voltage application MOSFET 43 at a predetermined timing in accordance with a command from the control unit 10. The gate drive circuit 46 supplies the pulse signal generated by the pulse generation circuit 45 to the gate of the reverse voltage application MOSFET 43.

  Other reverse voltage application circuits 5v, 5w, 6u, 6v, and 6w have the same configuration as the reverse voltage application circuit 5u. Therefore, the description is omitted.

  An example of the current path in the switching circuit 2 is shown in FIG. When the U-phase MOSFET 3u and the V-phase MOSFET 4v are on, a current flows through the path of the input terminal P, the MOSFET 3u, the phase windings Lu and Lv, the MOSFET 4v, and the input terminal N as indicated by the solid line. When the U-phase MOSFET 3u is turned off and the V-phase MOSFET 4v is on, the current based on the energy stored in the phase windings Lu and Lv passes through the MOSFET 4v from the phase windings Lu and Lv as shown by the broken line. Flows in the forward direction through the freewheeling diode Du-. Thus, in the state where the forward current (return current) flows through the freewheeling diode Du− on the MOSFET 4u side, when the upstream MOSFET3u paired with the MOSFET4u is turned on, the freewheeling diode Du− is connected between the terminals P and N through the MOSFET3u. (= 280V) is applied. At this time, a large reverse current (also called a spike current) Irr such as a short-circuit current flows through the freewheeling diode Du−. The reverse current Irr causes a large power loss, and a reverse voltage application circuit 6u is provided to suppress the reverse current Irr.

  Here, the operation of the inverter device 1 will be described. As shown in FIG. 3, the voltage of the three-phase sine wave voltage Eu and the triangular wave signal Eo is compared. The three-phase sine wave voltage Eu changes in proportion to the speed (number of rotations) of the brushless DC motor M. By this voltage comparison, an upper element drive signal for driving the MOSFET 3u on and off and a lower element drive signal for driving the MOSFET 4u on and off are created.

  By the upper element drive signal and the lower element drive signal thus created, the upstream MOSFET of at least one series circuit in the switching circuit 2 is turned on and off, and the downstream MOSFET of another at least one series circuit is turned on. The multi-phase energization is sequentially switched. By switching the multiphase energization, three interphase voltages are generated, and the interphase voltages are applied to the phase windings Lu, Lv, and Lw of the brushless DC motor M. Thereby, a sinusoidal current flows through Lu, Lv, and Lw, and the brushless DC motor M operates.

  A dead time td is ensured between the timing when the MOSFET 4u is turned off and the timing when the MOSFET 3u is turned on. The dead time td is also secured between the timing when the MOSFET 3u is turned off and the timing when the MOSFET 4u is turned on. The dead time td is generated by using a delay circuit that delays only the ON signal to the basic signal for the upper and lower elements generated from the PWM signal. By securing the dead time td, a short circuit of the series circuit of the U-phase MOSFET 3u and the MOSFET 4u is prevented. Similarly, the dead time is secured in the series circuits of other phases.

  By the way, as described in FIG. 2, when the MOSFET 3u is turned off (MOSFET 4v is turned on), the current based on the energy stored in the phase windings Lu and Lv passes through the MOSFET 4v from the phase windings Lu and Lv to the MOSFET 4u side. It flows through the freewheeling diode Du− in the forward direction. In a state where this so-called reflux current flows, the reverse voltage application signal from the control unit 10 to the reverse voltage application circuit 6u is set to a high level prior to turning on the upstream side MOSFET 3u. As a result, the reverse voltage application MOSFET 43 of the reverse voltage application circuit 6u is turned on, and the voltage stored in the reverse voltage application capacitor 42 is applied as a reverse voltage to the freewheeling diode Du−. The reverse voltage application period from the reverse voltage application circuit 6u to the free-wheeling diode Du− is a predetermined period that starts after the MOSFET 4u is turned off and includes the ON timing of the MOSFET 3u, and is predetermined. Also, the timing of starting application of the reverse voltage from the reverse voltage application circuit 6u to the freewheeling diode Du− is set with reference to the off timing of the MOSFET 4u (the falling timing of the lower element drive signal), for example.

  When a reverse voltage is applied from the reverse voltage application circuit 6u to the free-wheeling diode Du− in a state where the free-wheeling current is flowing, as indicated by a current Ia flowing through the free-wheeling diode Du− in FIG. A reverse current Irr flows. At this time, the reverse voltage applied to the freewheeling diode Du− is much lower than the voltage between the terminals P and N (= 280 V). In FIG. 3, for comparison, Irr when the reverse voltage application circuit is not operated is displayed in the first switching timing portion (A section in the drawing) in FIG. 3, and the reverse voltage is displayed in the subsequent B section in the drawing. Irr when the application circuit is operated is displayed.

  As described above, when the reverse voltage is applied from the reverse voltage application circuit 6u to the freewheeling diode Du−, even if the reverse current Irr flows through the freewheeling diode Du−, the level of the reverse current Irr is extremely small. However, the period of the reverse current Irr is longer than that when the voltage between the terminals P and N (= 280 V) is applied. In this case, the integrated power value in the freewheeling diode Du− is the product of power consumption and time. Therefore, the integrated power is greatly reduced. Therefore, the power loss in the free wheeling diode Du− can be greatly reduced, and the efficiency can be improved.

  On the other hand, the inverter apparatus 1 is mounted in the electrical component box 60 of the outdoor unit 50 in the air conditioner as shown in FIG. The outdoor unit 50 includes the outdoor heat exchanger 22 from the side surface to the back surface of the housing, sucks outside air by an outdoor fan 51 inside the outdoor heat exchanger 22, and passes the sucked outside air through the outdoor heat exchanger 22. Drain outside. The internal space of the casing of the outdoor unit 50 is divided by a partition plate 52 into a space in which the outdoor fan 51 is accommodated and a machine room. In the machine room, the compressor 20 and its peripheral mechanisms, such as piping and valves, are accommodated, and the electrical component box 60 is provided above.

  As shown in FIG. 5, the electrical component box 60 has an opening 60 a that is largely cut open and an opening 60 b for ventilation, and a circuit board (printed board) 61 at a position that becomes a ceiling surface. On this circuit board 61, a rectifier circuit (diode block) 31, a smoothing capacitor 32, each switching element of the switching circuit 2, and the like are soldered and placed.

  The MOSFETs 3 u, 4 u, 3 v, 4 v, 3 w, 4 w of the switching circuit 2 are arranged along the edge of the circuit board 61. As shown in FIG. 6, in the vicinity of the opening 60b and in the vicinity of the MOSFETs 3u, 4u, 3v, 4v, 3w, and 4w on the circuit board 61, and in parallel with the arrangement direction of these MOSFETs, the hybrid IC ( Integrated circuit) 62 is erected. The hybrid IC 62 is obtained by integrating the reverse voltage application circuits 5u, 6u, 5v, 6v, 5w, and 6w in one package.

  When the outdoor fan 51 rotates, outside air flows into the opening 60a of the electrical component box 60, as indicated by a broken line in FIG. The outside air that has flowed in flows along the plate surface of the circuit board 61 toward the opening 60b and passes through the opening 60b to the outdoor fan 51 side. The hybrid IC 62 exists in a ventilation path formed in the electric component box 60.

  The state seen from the lower side of the board surface of the circuit board 61 is shown in FIG. A plurality of conductive patterns 70 for wiring are formed on the circuit board 61 between the MOSFETs 3u, 4u, 3v, 4v, 3w, 4w and the hybrid IC 62.

  In this way, the reverse voltage application circuits 5u, 6u, 5v, 6v, 5w, 6w are constituted by one hybrid IC 62, and the hybrid IC 62 is erected on the ventilation path on the circuit board 61 in the electric component box 60. Thus, a sufficient cooling action for the hybrid IC 62 can be ensured. Therefore, when the reverse voltage is applied from the hybrid IC 62 to each freewheeling diode, even if the hybrid IC 62 generates heat, heat can be radiated smoothly, and temperature rise can be reliably suppressed. Thereby, stable operation as a reverse voltage application circuit of the hybrid IC 62 is possible, and the reverse current flowing through each freewheeling diode can be appropriately suppressed.

  In addition, since the hybrid IC 62 is provided in the vicinity of the MOSFETs 3u, 4u, 3v, 4v, 3w, and 4w, and in parallel with the arrangement direction of the MOSFETs 3u, 4u, 3v, 4v, 3w, and 4w, The length can be made as short as possible. Since each wiring pattern 70 can be shortened, noise radiation from each wiring pattern 70 can be suppressed. Thereby, the influence of noise on the external device can be reduced, and the efficiency of the hybrid IC 62 as a reverse voltage application circuit is improved.

[2] A second embodiment will be described.
As shown in FIG. 7, the MOSFET 3u has a drain terminal pin Pd, a source terminal pin Ps, and a gate terminal pin Pg. An inductance element such as a ferrite bead 80 is attached to the drain terminal pin Pd. Due to the inductance component of the ferrite bead 80, the start-up of the reverse current Irr flowing through the freewheeling diode Du− can be delayed. As a result, the reverse current Irr can be greatly reduced.

  The same ferrite beads 80 are attached to the drain terminal pins Pd of the remaining MOSFETs 4u, 3v, 4v, 3w, 4w.

  Other configurations, operations, and effects are the same as those in the first embodiment. Therefore, the description is omitted.

  [3] In each of the above embodiments, the MOSFET is used as the upstream switching element and the downstream switching element of each series circuit in the switching circuit 2. However, the IGBT is used as the upstream switching element, and the downstream switching element is used as the downstream switching element. A configuration using a MOSFET may also be used. In this case, a reverse voltage application circuit is provided only for the MOSFET on the downstream side. Moreover, although each said embodiment demonstrated the example applied to the outdoor unit of an air conditioner, it is applicable not only to an air conditioner but to the outdoor unit of refrigeration cycle apparatuses, such as an outdoor unit of a heat-pump water heater.

  In addition, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

The figure which shows the structure of the inverter apparatus and refrigeration cycle in connection with each embodiment of this invention. The figure which shows an example of the current pathway in the switching circuit of FIG. The time chart which shows the signal waveform of each part in the switching circuit of FIG. The figure which shows the internal structure of the outdoor unit of each embodiment. The figure which shows concretely the structure of the electrical component box in the outdoor unit of each embodiment. The figure which shows the state which looked at the circuit board in the electrical component box of FIG. 5 from the downward direction. The figure which shows the principal part of 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inverter apparatus, 2 ... Switching circuit, 3u, 3v, 3w ... MOSFET, 4u, 4v, 4w ... MOSFET, 5u, 5v, 5w ... Reverse voltage application circuit, 6u, 6v, 6w ... Reverse voltage application circuit, Du, Dv, Dw: freewheeling diode, P, N: input terminal, 10: control unit, M: brushless DC motor, Lu, Lv, Lw ... phase winding, 20 ... compressor, 22 ... outdoor heat exchanger, 50 ... outdoor 51: Outdoor fan, 52 ... Partition plate, 60 ... Electric component box, 60a ... Opening, 60b ... Opening for ventilation, 61 ... Circuit board, 62 ... Hybrid IC, 70 ... Conductive pattern, 80 ... Ferrite beads

Claims (2)

In a refrigeration cycle apparatus comprising: a refrigeration cycle having a compressor, a heat exchanger, and the like; and an inverter device that outputs driving electric power to the motor of the compressor by turning on and off a plurality of switching elements having a reflux diode ,
An FET is used for at least a part of the switching elements of the inverter device, and an electric component box containing a circuit board on which these switching elements are mounted is housed together with the compressor and the heat exchanger, and the FET An outdoor unit of a refrigeration cycle apparatus, wherein a hybrid IC having a plurality of reverse voltage application circuits for applying reverse voltages to a reflux diode at a predetermined timing is erected on a ventilation path on the circuit board. The electrical component box has an opening for ventilation,
Each of the switching elements is provided in a row on the circuit board,
The hybrid IC is erected in the vicinity of the opening and the switching elements and in parallel with the arrangement direction of the switching elements.
The outdoor unit of the refrigeration cycle apparatus according to claim 1.

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