Refrigeration cycle apparatus and outdoor heat source unit

There is provided a refrigeration cycle apparatus in which an outdoor heat source unit, an indoor unit, and a water heating unit are connected, and an air conditioning operation and a water heating operation can be performed separately, and an exhaust-heat recovery operation can be performed by simultaneously performing air cooling and water heating. The outdoor heat source unit includes a compressor for compressing refrigerant, a refrigerant air-heat exchanger that performs heat exchange between the refrigerant and outside air, a fan for cooling the refrigerant air-heat exchanger, a control device that includes an inverter device for driving the compressor, and a heat sink for dissipating heat of the inverter device, and a switching element in the inverter device is constituted by an element formed by a wide bandgap semiconductor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a refrigeration cycle apparatus in which an exhaust-heat recovery operation can be performed by simultaneously operating air cooling and water heating.

2. Description of the Related Art

Conventionally, there is a type of refrigeration cycle apparatus that includes an outdoor heat source unit and a refrigerant circuit formed by connecting an indoor unit and a water heating unit by piping. The refrigeration cycle apparatus is capable of operating air cooling and water heating separately in a single system, and also capable of operating air cooling and water heating simultaneously (see, for example, Japanese Patent Application Laid-open No. 2010-196950). In this system, exhaust heat generated at the time of air cooling can be recovered for water heating by simultaneously performing an air cooling operation and water heating. Thus, a highly efficient operation can be achieved.

In such type of refrigeration cycle apparatus, by controlling the capacity by using an inverter device as a control device for driving a compressor of an outdoor heat source unit, energy saving is further improved. The inverter device is constituted by a plurality of switching elements, and because a high voltage and a large current flow through the switching elements, a heat loss occurs. The heat loss is forcibly air-cooled by a fan for a refrigerant air-heat exchanger through radiating fins (see, for example, Japanese Patent Application Laid-open No. 5-196262).

However, according to the above conventional techniques, when exhaust heat is recovered by a simultaneous operation of air cooling and water heating, although the compressor of the outdoor heat source unit is required to be operated, the fan of the outdoor heat source unit is not required to be operated because heat exchange is not necessary in the refrigerant air-heat exchanger. On the other hand, when the compressor is driven by the inverter device, it is necessary to operate a fan to radiate the heat in the inverter device. Therefore, there has been a problem in that the operation efficiency is degraded by the power input to the fan.

The present invention has been achieved in view of the above problems, and an object of the present invention is to obtain a refrigeration cycle apparatus that can achieve a high efficiency operation at the time of an exhaust-heat recovery operation.

SUMMARY OF THE INVENTION

There is provided a refrigeration cycle apparatus according to an aspect of the invention in which an outdoor heat source unit, an indoor unit, and a water heating unit are connected, and an air conditioning operation and a water heating operation can be performed separately, and an exhaust-heat recovery operation can be performed by simultaneously performing air cooling and water heating, wherein the outdoor heat source unit includes a compressor for compressing refrigerant, a refrigerant air-heat exchanger that performs heat exchange between the refrigerant and outside air, a fan for cooling the refrigerant air-heat exchanger, a control device that includes an inverter device for driving the compressor, and a heat sink for dissipating heat of the inverter device, and a switching element in the inverter device is constituted by an element formed by a wide bandgap semiconductor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of a refrigeration cycle apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments.

First Embodiment

FIG. 1is a configuration example of an outdoor heat source unit that is included in a refrigeration cycle apparatus according to a first embodiment of the present invention. An outdoor heat source unit1includes a refrigerant air-heat exchanger11, a fan12, a compressor13, an inverter device14for driving the compressor13, a switching element15in the inverter device14, a temperature detection unit16in the inverter device14, control device17that is an electric part including the inverter device14, a separator sheet metal18, a heat sink19, and a sheet metal duct20.

In the first embodiment, the switching element15in the inverter device14is constituted by a wide bandgap semiconductor made of a material such as SIC (silicon carbide) or GaN (gallium nitride). As the material of the wide bandgap semiconductor, besides SiC or a GaN based material, diamond and the like can be used.

The outdoor heat source unit1is divided by the separator sheet metal18to form a fan cabin21and a machine cabin22. In the fan cabin21, the refrigerant air-heat exchanger11and the fan12are arranged. In the machine cabin22, the compressor13, the inverter device14, the control device17, the heat sink19, and the sheet metal duct20are arranged.

The inverter device14is connected to the heat sink19arranged at a side of the machine cabin22, and the heat sink19is configured to be covered by the sheet metal duct20such that sufficient airflow is provided to a fin portion. As long as sufficient airflow is provided to the fin portion, an air guiding structure such as a duct is not necessary, and it suffices that only the heat sink19is arranged.

The separator sheet metal18has a hole with the size of the heat sink19. By driving the fan12of the outdoor heat source unit1, air is taken out of from a side of the machine cabin22through this hole via the heat sink19, thereby forcibly air-cooling the heat sink19.

A configuration of the refrigeration cycle apparatus including the outdoor heat source unit1is explained next.FIG. 2is a configuration example of the refrigeration cycle apparatus. The refrigeration cycle apparatus is constituted by the outdoor heat source unit1, an indoor unit2, and a water heating unit3. The refrigeration cycle apparatus has a refrigerant circuit that is formed by connecting the outdoor heat source unit1, the indoor unit2, and the water heating unit3by piping. The refrigeration cycle apparatus is a system in which an air conditioning operation (a cooling operation and a heating operation) and a water heating operation can be performed separately in a single system, and also these operations can be performed simultaneously. Because a four-way valve, an accumulator, a linear expansion valve (LEV), and the like shown inFIG. 2are general components, detailed explanations thereof will be omitted.

A connection state in the refrigeration cycle apparatus at the time of an exhaust-heat recovery operation is explained.FIG. 3depicts a connection state in the refrigeration cycle apparatus when an exhaust-heat recovery operation is in progress. As shown inFIG. 3, because refrigerant circulates between the indoor unit2and the water heating unit3to establish a refrigeration cycle, heat exchange by the refrigerant air-heat exchanger11of the outdoor heat source unit1is not necessary, and therefore, as a refrigerant circuit, it is not necessary to perform any operation of the fan12of the outdoor heat source unit1.

However, as described above, the compressor13of the outdoor heat source unit1is in operation also during the exhaust-heat recovery operation. At this time, a large current flows through the switching element15of the inverter device14to cause a heat loss, and thus the fan12of the outdoor heap source unit1is required to be operated only to dissipate heat of the inverter device14.

Therefore, by forming the switching element15in the inverter device14with a wide bandgap semiconductor made of a material such as SiC or GaN instead of a conventional Si based element, the heat resistance of the switching element15is improved. The control device17suppresses the operation or the fan12during the exhaust-heat recovery operation in which the operation of the fan12of the outdoor heat source unit1is not necessary as a refrigerant cycle. The power consumed by the fan12of the outdoor heat source unit1accounts for 2 to 4% of the total input power even in a high efficient direct-current (DC) type, and therefore, if the operation can be stopped when the operation is not required, the energy saving property can be improved.

By replacing the switching element15of the inverter device14from an Si based element to a wide bandgap semiconductor made of a material such as SiC or GaN, in addition to the improvement of the heat resistance of the element itself, reduction of a heat loss caused by switching such as a recovery loss and a switching loss can be achieved. As for the heat resistance, while a general heat resistance of the switching element15formed by a conventional Si based element is up to 150° C. or lower for a semiconductor chip temperature, a wide bandgap semiconductor made of a material such as SiC or GaN realizes a high heat resistance such as that up to around 250° C. for a chip temperature. Therefore, an exhaust-heat recovery operational range while stopping the operation of the fan12can be extended.

The exhaust-heat recovery operation is a refrigeration cycle such that the indoor unit2performs an air cooling operation and the water heating unit3uses exhaust heat thereof for water heating. Accordingly, the exhaust-heat recovery operation is basically performed under a high temperature condition in which an outdoor temperature exceeds 30° C. Therefore, when a heavily-loaded state continues or some abnormalities occur in the refrigeration cycle to increase the current in the compressor13, even if a wide bandgap semiconductor made of a material such as SiC or GaN is used as the switching element15, there is a possibility that the temperature increases to exceed the allowable temperature of a semiconductor chip when the operation of the fan12is stopped.

As a protection control for such cases, there is prepared a control such that the temperature detection unit16arranged on the heat sink19or incorporated in the inverter device14detects the temperature of the switching element15in the outdoor heat source unit1, and when the temperature exceeds a predetermined threshold, the operation of the fan12is performed in a stepwise manner to protect the semiconductor chip from damage from heat.

FIG. 4depicts a relationship between a temperature of the switching element15and an operation state of the fan12. An example of a heat protection control is shown inFIG. 4. When the exhaust-heat recovery operation is performed while the fan12of the outdoor heat source unit1is stopped, upon the temperature of the heat sink19or a detected temperature of the temperature detection unit16incorporated in the inverter device14reaching T2, the control device17drives the fan12having been stopped to operate at a medium speed. Thereafter, the control device17stops the operation of the fan12again to return to a power saving operation when the detected temperature decreases to T1, and drives the fan12to operate at a high speed when the detected temperature continues to increase to reach T3even after the operation of the fan12is started. Similarly, thereafter, when the detected temperature decreases to T2, the control device17drives the fan12back to operate at a medium speed, and stops the fan12when the detected temperature decreases to T1. In this manner, in the outdoor heat source unit1, it is possible to extend the operational range and the operation time while the operation of the fan12is stopped during the exhaust-heat recovery operation.

If the increase of the detected temperature continues even though the fan12is operated at a high speed and reaches T4, the control device17recognizes a temperature abnormality and stops the operation of the compressor13for protection. As an example, an explanation has been made with four steps of temperatures, which are T1to T4; however, the present invention is not limited thereto. As long as damage of a semiconductor chip from heat can be avoided, the number of steps can be less or more than four steps.

As explained above, according to the first embodiment, in a refrigeration cycle apparatus in which the outdoor heat source unit1, the indoor unit2, and the water heating unit3are connected, an air cooling operation and a water heating operation can be performed separately, and an exhaust-heat recovery operation by a simultaneous operation of the air cooling operation and the water heating operation can be performed, the switching element15in the inverter device14is constituted by an element formed by a wide band gap semiconductor to increase heat resistance of the switching element15to reduce a heat loss in the outdoor heat source unit1. With this configuration, in the outdoor heat source unit1, the operation of the fan12to dissipate heat of the switching element15can be suppressed, and therefore the power consumption by the fan12can be reduced and a highly efficient operation can be achieved.

Second Embodiment

FIG. 5is a configuration example of an outdoor heat source unit according to a second embodiment of the present invention. An outdoor heat source unit1aincludes the refrigerant air-heat exchanger11, the fan12, the compressor13, the inverter device14for driving the compressor13, the switching element15in the inverter device14, the temperature detection unit16in the inverter device14, a control device17athat is an electric part including the inverter device14, a separator sheet metal lea, and a heat sink19a. Similarly to the first embodiment, the switching element15in the inverter device14is constituted by a wide bandgap semiconductor made of a material such as SiC or GaN.

The outdoor heat source unit1ais divided by the separator sheet metal18ato form a fan cabin21aand a machine cabin22a. In the fan cabin21a, the refrigerant air-heat exchanger11, the fan12, and the heat sink19aare arranged. In the machine cabin22a, the compressor13, the inverter device14, and the control device17aare arranged. The inverter device14is configured to be connected to the heat sink19aarranged at a side of the fan cabin21a.

Similarly to the first embodiment, by forming the switching element15in the inverter device14with a wide bandgap semiconductor made of a material such as SiC or GaN instead of forming the switching element15by a Si based element, the heat resistance of the element is improved, thereby performing a heat protection control while driving of the fan12of the outdoor heat source unit1aat the exhaust-heat recovery operation is omitted as much as possible. Therefore, detailed explanations thereof will be omitted.

FIG. 6depicts a shape of the heat sink19aaccording to the second embodiment. As shown inFIG. 6, the heat sink19ahas fin shapes that are arranged in such a matrix that airflow in a vertical direction and a horizontal direction of the outdoor heat source unit1acan be obtained, thereby enhancing heat radiation by natural convection. With such fin shapes and arrangement, air flows in a vertical direction by natural convection in the outdoor heat source unit1aeven when the fan12is stooped, and thus the heat radiation performance of the heat sink19acan be improved.

Also when the fan12of the outdoor heat source unit1aoperates such as during an air cooling operation, sufficient heat radiation performance can be obtained by airflow along the separator sheet metal18ain the outdoor heat source unit1a. Furthermore, by arranging the angle of the heat sink19ain such a manner that air flowing along the separator sheet metal18adoes not deviate from fins of the heat sink19a, it becomes unnecessary to cover the heat sink19awith the sheet metal duct20and the like for guiding air. As a result, it becomes possible to avoid natural convection from being interfered by a sheet metal. With this configuration, in the outdoor heat source unit1a, the operation time of the fan12at the exhaust-heat recovery operation can be further reduced.

The shape of the fins of the heat sink19ais not limited to that shown inFIG. 6.FIGS. 7 and 8depict other shapes of the heat sink19aaccording to the second embodiment. With such a configuration that fins have a prismatic shape or a cylindrical shape and are aligned in a dot matrix as shown inFIGS. 7 and 8, same effects can be obtained.

Generally, in a refrigeration cycle apparatus, such a phenomenon occurs that refrigerant is pooled (accumulated) in the compressor13due to the temperature difference among respective constituent elements when an operation of the refrigeration cycle apparatus is stopped. Refrigerant pooled in the compressor13can not only cause difficulty in starting the compressor13but also can damage the compressor13. Therefore, in order to prevent refrigerant from being pooled therein, the inverter device14performs energization for retaining heat, which is referred to as “constraint energization”.

The constraint energization is performed by applying a direct current or a high frequency current to a coil in the compressor13by the inverter device14to generate heat at the coil or a core of the compressor13. Although this arrangement causes a heat loss also in the inverter device14, because the fan12of the outdoor heat source unit1abecomes unnecessary to be operated as a refrigerant cycle during the constraint energization, similarly to during the exhaust-heat recovery operation. Furthermore, because an operation of the fan12only to dissipate heat of the inverter device14during the outdoor heat source unit1ais stopped may be determined as a malfunction, the constraint energization has been performed without operating the fan12with a controlled amount of energy, so that the temperature of the heat sink19adoes not become too high.

However, with the configuration according to the second embodiment, the heat radiation performance of the heat sink19ais improved, and a range in which the fan12is not required to be operated during the exhaust-heat recovery operation is extended. In addition, the amount of power supplied (input power to the compressor13) at the constraint energization can be increased, and the controllability is improved such as that a large amount of power can be applied when necessary, thereby reducing a failure of the compressor13caused by pooling of the refrigerant.

As described above, according to the second embodiment, in the outdoor heat source unit1a, the heat sink19ais arranged in the fan cabin21a, the fins of the heat sink19aare arranged in a matrix or in a dot matrix, and the shape of the fins is made into a shape that is suitable for both forced and natural convections. With this configuration, as compared to the first embodiment, the heat dissipation performance is improved in the outdoor heat source unit1a, and the operation time of the fan12during the exhaust-heat recovery operation or the constraint energization can be further reduced. As a result, power consumption by the fan12can be reduced and a highly efficient operation can be achieved.

According to the present invention, it is possible to achieve a high efficiency operation at the time of an exhaust-heat recovery operation.