JP2015087076A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner which increases rotational frequency of a compressor and shortens defrosting operation time by boosting a DC current during a defrosting operation.SOLUTION: An air conditioner includes: an indoor unit having an indoor heat exchanger and an indoor fan; a compressor; and an outdoor unit having an outdoor heat exchanger and an outdoor fan. In the air conditioner, the compressor, a four-way valve, the outdoor heat exchanger and the indoor heat exchanger are connected by a refrigerant pipe, and the air conditioner can switch a cooling operation, a heating operation and a defrosting operation by the switching of the four-way valve. The outdoor unit has a driving control device 18 including: a rectifying circuit 2 for converting an input AC power into a DC voltage; a booster 3 for boosting the DC voltage; an inverter 4 for driving the compressor by converting the DC voltage from the booster 3 into the AC power; and a control unit 13 for controlling the booster 3 and the inverter 4. The control unit 13 boosts the DC voltage irrespective of the size of a load of the air conditioner at the starting time of the defrosting operation.

Description

  The present invention relates to an air conditioner that defrosts frost formed on an outdoor heat exchanger by a defrosting operation.

  When a conventional air conditioner continues heating operation in a state where the outside air temperature is low and frost forms on the outdoor heat exchanger of the outdoor unit (frost formation), the heat exchange capacity of the heat exchanger decreases and the heating capacity is reduced. In order to lower the temperature, the frost that has formed on the outdoor heat exchanger is melted by switching the refrigeration cycle from the heating operation to the cooling operation and performing the defrosting operation (reverse defrosting). In general, during the defrosting operation, the fan of the outdoor unit is stopped in order to increase the defrosting effect, and the indoor unit side is also in the cooling operation, so the fan of the indoor unit is also stopped so as not to feel cold, and the indoor temperature is lowered. It is preventing. However, when the defrosting operation becomes longer, the cooling operation time becomes longer, the room temperature decreases, and the comfort may be impaired.

  Therefore, in the conventional air conditioner, during the defrosting operation, it has been conventionally performed to increase the voltage applied to the compressor in order to increase the rotation speed of the compressor and shorten the defrosting operation time. For example, Patent Document 1 discloses a defrosting operation in an air conditioner that drives a compressor motor by converting a DC voltage obtained by rectifying an AC power supply voltage using a converter into AC power having a predetermined frequency and voltage using an inverter. It has been disclosed that sometimes the drive voltage supplied from the inverter to the compressor motor is made higher than usual so as to increase the capacity (rotation speed) of the compressor and shorten the defrosting operation time.

Japanese Patent Laid-Open No. 62-29869

  However, although the air conditioner of Patent Document 1 sets the drive voltage supplied to the compressor motor by the inverter to a higher voltage than usual, the drive voltage cannot be increased beyond the DC voltage supplied to the inverter. There was a limit to increasing the rotation speed of the compressor.

  Therefore, in order to drive the compressor at a high rotational speed, as a method for increasing the DC voltage supplied to the inverter, a boost chopper is provided in the converter, and the DC voltage obtained by rectifying the AC power supply voltage is converted by switching the boost chopper. There is one that boosts and supplies it to the inverter. For example, in order to increase the operating efficiency of the compressor, the winding of the compressor motor is increased, but if the winding is increased, the counter electromotive force generated when the compressor motor is rotated increases. In order to drive the compressor at a high speed, it is necessary to increase the drive voltage supplied from the inverter to the compressor motor. In such a case, a converter using a boost chopper is effective.

  In a normal operation of an air conditioner using such a boost chopper, it is desirable that switching of the boost chopper is not performed as much as possible in view of a reduction in efficiency due to swivel loss of the boost chopper and generation of harmonic noise. For this reason, when the air conditioner has a low load and a high DC voltage is not required, the DC voltage is not boosted by the boost chopper. The magnitude of the load of the air conditioner is detected by monitoring the input current of the air conditioner, and when it exceeds a predetermined value (for example, 3A), it is determined that the load has increased, and the boost chopper is switched. Start and boost DC voltage.

  On the other hand, the load of the air conditioner immediately after switching the refrigeration cycle from the heating operation to the cooling operation to start the defrosting operation is almost zero. This is because when switching the refrigeration cycle, the pressure difference between the high-pressure side and the low-pressure side applied to the four-way valve included in the refrigeration cycle is switched to zero after switching the four-way valve. This is because the pressure difference on the discharge side becomes almost zero, and as a result, the load on the compressor becomes almost zero. Therefore, in the conventional air conditioner that determines the switching operation / non-operation of the boosting chopper according to the size of the load, it tries to boost the DC voltage in order to drive the compressor motor at a high speed at the start of the defrosting operation with a small load. However, since the step-up chopper does not operate, a necessary rotational speed cannot be obtained, and there is a problem that it takes a long time to defrost.

  The present invention has been made in view of the above problems, and regardless of the load of the air conditioner during defrosting operation, the DC voltage is boosted by a boost chopper to increase the rotational speed of the compressor. It aims at providing the air conditioner which shortens defrost operation time.

  In order to solve the above problems and achieve the object of the present invention, the present invention includes an indoor unit having an indoor heat exchanger and an indoor fan, a compressor, an outdoor heat exchanger, and an outdoor fan. An outdoor unit, and the compressor, the four-way valve, the outdoor heat exchanger, and the indoor heat exchanger are connected by a refrigerant pipe, and switching between the cooling operation, the heating operation, and the defrosting operation is possible by switching the four-way valve. In the outdoor unit, the outdoor unit includes a rectifying unit that converts an input AC power source into a DC voltage, a load detection unit that detects a load of the air conditioner, and a boosting unit that boosts the DC voltage. A drive control device comprising: an inverter that converts the DC voltage from the booster unit into AC power to drive the compressor; and a control unit that controls the booster unit and the inverter. At the start of the defrosting operation Characterized by boosting the DC voltage regardless of the magnitude of the load of the air conditioner.

  According to the present invention, since the DC voltage is boosted and supplied to the inverter at the boosting unit regardless of the load size during the defrosting operation, the defrosting operation is performed by increasing the rotation speed of the compressor at the start of the defrosting operation. There is an effect that the time can be shortened.

FIG. 1 is a block diagram showing a schematic configuration of an air conditioner according to an embodiment of the present invention. FIG. 2 is a block diagram of a drive control device in the outdoor unit of FIG. FIG. 3 is a flowchart for explaining the operation of the air conditioner according to the embodiment of the present invention. FIG. 4 is a block diagram showing a configuration example according to another embodiment of the boosting unit in FIG.

  Embodiments of an air conditioner according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

[Configuration of air conditioner]
FIG. 1 is a block diagram showing a schematic configuration of an air conditioner according to an embodiment of the present invention. The indoor unit, the outdoor unit, and the remote controller of the air conditioner according to the present embodiment are configured as shown in FIG. The remote controller 50 is used by the user to perform operations such as turning the power on and off and switching the operation mode. In the indoor unit 40, an indoor heat exchanger 42 and an indoor fan 42a are incorporated. Here, a cross flow fan is used as the indoor fan 42a, and this rotates to generate an air flow. Indoor air is sucked into the indoor unit 40 by the action of the indoor fan 42a, and the sucked indoor air passes through the indoor heat exchanger 42 to exchange heat with the refrigerant, thereby generating cold air or warm air. The cold or warm air flow after passing through the indoor heat exchanger 42 is blown out into the room from a blower outlet (not shown).

  As shown in FIG. 1, the outdoor unit 30 includes a four-way valve 34, a compressor 32, an outdoor heat exchanger 36, an outdoor fan 36a, an expansion valve 38, and the like, and the four-way valve 34, the compressor 32, and the outdoor heat exchange. 36, an expansion valve 38, and an indoor heat exchanger 42 are sequentially connected by a refrigerant pipe 60 to constitute a refrigeration cycle 39. The refrigerant flowing in the refrigerant pipe 60 is compressed by the compressor 32, and then flows into the outdoor heat exchanger 36 or the indoor heat exchanger 42 by the switching of the four-way valve 34 to exchange heat, whereby the air conditioner 20 Can be cooled or heated.

  When the air conditioner 20 is set to the heating operation, the four-way valve 34 is switched so as to be connected by a solid line, and the high-temperature and high-pressure refrigerant generated by the compressor 32 is exchanged with the indoor heat from the discharge pipe 32a of the compressor 32. Is supplied to the vessel 42. The refrigerant flows through the indoor heat exchanger 42, the expansion valve 38, and the outdoor heat exchanger 36 in order. In the indoor heat exchanger 42, the heat energy of the refrigerant is released to the surrounding air, and warm air is generated. The warm air is blown into the indoor space by the function of the indoor fan 42a. The refrigerant is decompressed to a low pressure by the expansion valve 38 and absorbs heat from the outdoor air in the outdoor heat exchanger 36. Thereafter, the refrigerant is returned from the suction pipe 32 b of the compressor 32 to the compressor 32 via the four-way valve 34. If the temperature of the outside air decreases during the heating operation, frost tends to be formed on the outdoor heat exchanger, and if frost is formed, the heat exchange efficiency (heating efficiency) is remarkably reduced, so it is necessary to defrost.

  When the refrigeration cycle 39 is set to the cooling operation, the four-way valve 34 is switched as shown by the dotted line in FIG. 1, whereby the high-temperature and high-pressure refrigerant generated by the compressor 32 is discharged from the discharge pipe 32a of the compressor 32 to the outdoor. It is supplied to the heat exchanger 36. The refrigerant flows through the outdoor heat exchanger 36, the expansion valve 38, and the indoor heat exchanger 42 in order. In the outdoor heat exchanger 36, it is heated by a high-temperature refrigerant. The refrigerant is decompressed to a low pressure by the expansion valve 38 and absorbs heat from the surrounding air in the indoor heat exchanger 42. The cold air thus generated is blown into the indoor space by the function of the indoor fan 42a. The refrigerant that has absorbed heat by the indoor heat exchanger 42 is returned to the compressor 32 from the suction pipe 32b of the compressor 32 via the four-way valve 34. The flow of this refrigerant is the same as that during the defrosting operation of this embodiment. That is, by reversing the flow of the refrigerant in the heating operation, the frost formed on the outdoor heat exchanger 36 can be melted by warming the outdoor exchanger 36 with a high-temperature refrigerant.

[Configuration of drive control device]
FIG. 2 is a block diagram of a drive control device in the outdoor unit of FIG. As shown in FIG. 2, the drive control device 18 according to the present embodiment includes an AC power source 1, a rectifier circuit 2 that rectifies AC supplied from the AC power source 1, a reactor 3a, a reverse blocking diode 3b, and a switching element 3c. And a step-up chopper circuit composed of a smoothing capacitor 3d, an inverter 4 that converts direct current into alternating current and drives a DC brushless motor M, a DC brushless motor M that drives a compressor 32, and an AC power source 1 A zero cross detection unit 5 that detects a zero cross, a current sensor (for example, a current detection transformer) 6 that is a detection unit for detecting an input current Ii of the boost unit 3, and an input current Ii of the boost unit 3 from the current sensor 6. Input current detection unit 10 that detects the input voltage Vi of the boosting unit 3, an input voltage detection unit 11 for detecting the input voltage Vi of the boosting unit 3, and the output voltage ( Output voltage detection unit 12 for detecting line voltage (Vo), inverter drive unit 14 for controlling inverter 4 for driving DC brushless motor M by converting direct current to alternating current, and detecting the temperature of outdoor heat exchanger 36 An outdoor heat exchanger temperature sensor 15 that detects the outside air temperature, and a storage unit 17 that stores a current command value in each operation mode in advance. The load detection means for detecting the load of the air conditioner 20 includes the current sensor 6 and the input current detection unit 10, and determines the size of the load based on the size of the input current value. Furthermore, the drive control device 18 determines outdoor heat based on the temperature of the outdoor heat exchanger 36 and the outdoor air temperature detected by the outdoor heat exchanger temperature sensor 15 and the outdoor air temperature sensor 16 in order to determine to start the defrosting operation. It is determined whether or not the exchanger 36 has been frosted, control for outputting a signal for turning on / off the switching element 3c of the boosting unit 3, and a predetermined drive signal via the inverter drive unit 14 to the inverter 4 And a control unit 13 including a microcomputer for controlling the inverter 4 by outputting to the switching elements BU, BV, BW, BX, BY, BZ.

  The boosting unit 3 includes a reactor 3a connected in series to the positive terminal (P) side of the rectifier circuit 2, a reverse blocking diode 3b connected in series to the reactor 3a, and between the reactor 3a and the reverse blocking diode 3b. 2 is connected to the negative terminal (N) side of the switching element (for example, IGBT; insulated gate transistor) 3c, the smoothing connected to the output (cathode) side of the reverse blocking diode 3b and the negative terminal (N) side of the rectifier circuit 2. And a capacitor 3d.

  The booster 3 boosts the output voltage of the rectifier circuit 2 and supplies it to the inverter 4 by turning on / off the switching element 3c. The booster 3 also operates as a power factor correction circuit (PFC) that improves the power factor of the power source.

[Another configuration example of booster]
FIG. 4 is a block diagram showing a configuration example according to another embodiment of the booster 3 in FIG. In FIG. 2, an example of the booster 3 configured by the boost chopper circuit has been described. However, the present invention is not limited to this, and an interleaved booster 70 as illustrated in FIG. 4 may be used. The interleave type boosting unit 70 includes a reactor 70a1 and a reverse blocking diode 70b1 connected in series, and a reactor 70a2 and a reverse blocking diode 70b2 connected in series on the positive terminal (P) side of the rectifier circuit 2. A switching element (eg, IGBT; insulated gate transistor) 70c1 is connected between the reactor 70a1 and the reverse blocking diode 70b1 and on the negative terminal (N) side of the rectifier circuit 2, and the reactor 70a2 and the reverse blocking diode 70b2 And a negative terminal (N) side of the rectifier circuit 2 is connected to a switching element (IGBT; insulated gate transistor) 70c2, and a smoothing capacitor 70d connected to the output side and the negative terminal (N) side is provided. It is configured.

  The interleave type boosting unit 70 switches the reactor 70a1 and the reverse blocking diode 70b1, and the reactor 70a2 and the reverse blocking diode 70b2 by alternately switching on and off between the switching element 70c1 and the switching element 70c2. Loss can be halved.

[Conditions for starting / ending defrosting operation]
In the control unit 13, the outdoor heat exchanger 36 determines that there is a possibility that frost formation has occurred, and the defrosting operation start condition for starting the defrosting operation is, for example, the heating operation time (heating the air conditioner 20). The refrigerant temperature detected by the outdoor heat exchanger temperature sensor 15 is the outside air temperature after 30 minutes have elapsed since the time when the operation was started or when the heating operation was continued from the defrosting operation to the heating operation. When a state 5 ° C. or more lower than the outside air temperature detected by the sensor 16 continues for 10 minutes or more, or when a predetermined time (eg, 180 minutes) has elapsed since the last defrosting operation was completed, etc. The defrosting operation start condition is stored in the storage unit 17 in advance.

  When the air conditioner 20 is performing the defrosting operation, the controller 13 determines that the frost generated in the outdoor heat exchanger 36 has melted, and the defrosting operation end condition for ending the defrosting operation is, for example, Whether the temperature detected by the outdoor heat exchanger temperature sensor 15 is 5 ° C. or higher, or whether a predetermined time (eg 10 minutes) has elapsed since the start of the defrosting operation, etc. The defrosting operation end condition is stored in the storage unit 17 in advance.

[Air conditioner operation]
FIG. 3 is a flowchart for explaining the operation of the air conditioner according to the embodiment of the present invention. First, the air conditioner 20 is operated by heating operation or cooling operation (start). Next, the control unit 13 of the drive control device 18 determines whether or not the air conditioner 20 is operated in the heating operation (step S100), and determines that the cooling operation is not performed in the heating operation (No in step S100). If it progresses to the process of step S111 and it judges that it is drive | operating by heating operation (it is Yes at step S100), it will progress to step S101 and it will be judged whether said defrost operation start conditions are satisfied. If it is determined that the defrosting operation start condition is satisfied (Yes in step S101), the defrosting operation is started in step 102. If it is determined that the defrosting operation start condition is not satisfied (No in step S101), the process returns to step S100 and the heating operation is continued.

  When the defrosting operation is started in step S102, the four-way valve 34 is switched to switch the refrigeration cycle 39 from the heating operation to the cooling operation mode, and high-temperature and high-pressure refrigerant is discharged from the discharge pipe 32a of the compressor 32 to the outdoor heat exchanger 36. Supplied. The refrigerant flows through the outdoor heat exchanger 36, the expansion valve 38, and the indoor heat exchanger 42 in order. In the outdoor heat exchanger 36, it is heated by a high-temperature refrigerant. The refrigerant is decompressed to a low pressure by the expansion valve 38 and absorbs heat from the surrounding air in the indoor heat exchanger 42. The refrigerant that has absorbed heat by the indoor heat exchanger 42 is returned to the compressor 32 via the four-way valve 34. Thus, in the defrosting operation, by reversing the refrigerant flow in the heating operation, the outdoor exchanger 36 is warmed by the high-temperature refrigerant, and the frost that has formed on the outdoor heat exchanger 36 can be melted. During the defrosting operation, the indoor fan 42a and the outdoor fan 36a are stopped.

  When starting the defrosting operation in step S102, the control unit 13 operates the boosting unit 3 to boost the DC voltage converted from the AC power supply by the rectifier circuit 2 (step S103). As described above, the air conditioner of the present embodiment boosts the DC voltage at the boosting unit and supplies it to the inverter regardless of the size of the load even under a small load immediately after the start of the defrosting operation. Thus, compared with the case where the voltage supplied to a compressor motor only with an inverter is raised, the rotation speed of a compressor can be raised and defrost operation time can be shortened.

  The controller 13 determines whether or not the defrosting operation end condition is satisfied in step S104. When it is determined that the defrosting operation end condition is not satisfied (No in step S104), the defrosting operation is continued, and when it is determined that the defrosting operation end condition is satisfied (Yes in step S104), the boosting unit 3 The operation is terminated (step S105).

  When the control unit 13 ends the operation of the pressure increasing unit 3 in step S105, the control unit 13 switches from the defrosting operation to the heating operation (step S106), and then the processing of the control unit 13 returns to step S100.

  Moreover, if the process of the control part 13 is not heating operation in step S100 (No in step S100), the cooling operation is continued. When switching to the heating operation mode during the cooling operation (Yes in step S111), the process returns to step S100. If the operation mode is not switched in step S111 (No in step S111), the cooling operation is continued. If there is no instruction to end the operation (No in step S112), the process returns to step S111 and the cooling operation is continued. However, if there is an instruction to end the operation, the operation of the air conditioner 20 is stopped (in step S112). Yes).

  As described above, the air conditioner according to the present embodiment boosts the DC voltage at the boosting unit and supplies it to the inverter regardless of the size of the load even under a small load immediately after the start of the defrosting operation. The number of revolutions of the compressor can be increased and the defrosting operation time can be shortened as compared with the conventional case where the voltage supplied to the compressor motor is increased only by the inverter. Therefore, it is possible to cancel the defrosting operation before the room temperature is lowered by the cold air during the defrosting operation and to return to the heating operation, and it is possible to prevent the comfort from being impaired.

1 AC power supply (input AC power supply)
2 Rectifier circuit 3 Booster 3a Reactor (choke coil)
3b Reverse blocking diode 3c Switching element 3d Smoothing capacitor 4 Inverter 5 Zero cross detection unit 6 Current sensor 10 Input current detection unit 11 Input voltage detection unit 12 Output voltage detection unit 13 Control unit 14 Inverter drive unit 15 Outdoor heat exchanger temperature sensor 16 Outdoor air Temperature sensor 17 Storage unit 18 Drive control device 20 Air conditioner 30 Outdoor unit 32 Compressor 32a Discharge pipe 32b Intake pipe 34 Four-way valve 36 Outdoor heat exchanger 36a Outdoor fan 38 Expansion valve 39 Refrigerating cycle 40 Indoor unit 42 Indoor heat exchanger 42a Indoor fan 50 Remote control 60 Refrigerant pipe 70 Boosting unit 70a1, 70a2 Reactor (boosting choke coil)
70b1, 70b2 Reverse blocking diode 70c1, 70c2 Switching element 70d Smoothing capacitor M DC brushless motor

Claims (1)

An indoor unit having an indoor heat exchanger and an indoor fan, a compressor, an outdoor heat exchanger, and an outdoor unit having an outdoor fan, the compressor, the four-way valve, the outdoor heat exchanger, and the indoor heat An exchanger is connected by a refrigerant pipe, and is an air conditioner capable of switching between cooling operation, heating operation, and defrosting operation by switching the four-way valve,
The outdoor unit includes a rectifying unit that converts an input AC power source into a DC voltage, a load detection unit that detects a load of the air conditioner, a boosting unit that boosts the DC voltage, and a DC voltage from the boosting unit. A drive control device having an inverter that converts AC power into AC power to drive the compressor, and a controller that controls the booster and the inverter,
The control unit boosts the DC voltage at the start of the defrosting operation regardless of the load of the air conditioner.

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