Patent Description:
Refrigerants such as HFC-<NUM> (difluoromethane) and HFC-410A, which is a mixture of HFC-<NUM> and HFC-<NUM> (pentafluoroethane), are conventionally used as refrigerants sealed in the refrigerant circuits of air conditioners to prevent the destruction of the ozone layer. However, these refrigerants have a problem in that they have high global warming potentials (GWPs).

In contrast, refrigerants containing HFO-<NUM> (<NUM>,<NUM>,<NUM>-trifluoroethylene), which are disclosed in <CIT>, are known to have less effect on the ozone layer and global warming. <CIT> discloses that such a refrigerant is sealed into a refrigerant circuit to constitute an air conditioner.

Further air conditioners are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

However, the refrigerants disclosed in <CIT> have the property of undergoing a disproportionation reaction (self-decomposition reaction) when given some energy under high-pressure and high-temperature conditions. A disproportionation reaction of a refrigerant in a refrigerant circuit results in a rapid pressure and temperature rise. In an air conditioner in which an outdoor unit and an indoor unit are connected, a disproportionation reaction tends to occur in a portion of the refrigerant circuit within the outdoor unit. If such a disproportionation reaction occurs one after another, the disproportionation reaction and the resulting pressure rise may propagate from the outdoor unit side to the indoor unit side and may thus cause the refrigerant to be ejected into the indoor space.

An object of the present invention is to reduce the likelihood that an air conditioner having a refrigerant circuit in which a refrigerant containing a hydrofluorocarbon having the property of undergoing a disproportionation reaction causes the refrigerant to be ejected into the indoor space when the refrigerant undergoes a disproportionation reaction.

The invention provides an air conditioner according to claim <NUM>.

An air conditioner according to a first aspect has a refrigerant circuit which is formed by connecting an outdoor unit and an indoor unit, and a control unit. A refrigerant containing a hydrofluorocarbon having a property of undergoing a disproportionation reaction is sealed in the refrigerant circuit. Here, the refrigerant circuit includes a refrigerant shutoff mechanism and the control unit is configured to control the devices that constitute the outdoor unit and the indoor unit, so that refrigerant shutoff mechanism shuts off the flow of the refrigerant from the outdoor unit side to the indoor unit side when the refrigerant in a portion of the refrigerant circuit within the outdoor unit meets a predetermined condition.

Here, the air conditioner includes the refrigerant shutoff mechanism as described above. Therefore, when a disproportionation reaction occurs in the portion of the refrigerant circuit within the outdoor unit, the refrigerant shutoff mechanism can shut off the flow of the refrigerant from the outdoor unit side to the indoor unit side so as to inhibit the propagation of the disproportionation reaction and the resulting pressure rise to the indoor unit.

Thus, here, even when the refrigerant undergoes a disproportionation reaction, a likelihood that the devices and pipes that constitute a portion of the refrigerant circuit within the indoor unit is damaged can be reduced, thereby reducing the likelihood of the refrigerant being ejected into the indoor space.

An air conditioner according to a second aspect is the air conditioner according to the first aspect, in which the outdoor unit includes a compressor and an outdoor heat exchanger, and the indoor unit includes an indoor heat exchanger. The refrigerant circuit is configured to circulate the refrigerant through, in sequence, the compressor, the outdoor heat exchanger, the indoor heat exchanger, and the compressor. Here, the refrigerant shutoff mechanism includes a gas-side refrigerant shutoff mechanism configured to shut off the flow of the refrigerant from the intake side of the compressor to the indoor unit side and a liquid-side refrigerant shutoff mechanism configured to shut off the flow of the refrigerant from the liquid side of the outdoor heat exchanger to the indoor unit side.

Here, the refrigerant circuit is configured to circulate the refrigerant through, in sequence, the compressor, the outdoor heat exchanger, the indoor heat exchanger, and the compressor (cooling operation). Therefore, when a disproportionation reaction occurs in the portion of the refrigerant circuit within the outdoor unit, it is necessary to shut off the flow of the refrigerant from the intake side of the compressor to the indoor unit side and the flow of the refrigerant from the liquid side of the outdoor heat exchanger to the indoor unit side.

Accordingly, here, the gas-side refrigerant shutoff mechanism and the liquid-side refrigerant shutoff mechanism as described above are provided as refrigerant shutoff mechanisms in the refrigerant circuit.

Thus, here, when a disproportionation reaction occurs in the portion of the refrigerant circuit within the outdoor unit while the refrigerant is being circulated in the refrigerant circuit through, in sequence, the compressor, the outdoor heat exchanger, the indoor heat exchanger, and the compressor, the gas-side refrigerant shutoff mechanism and the liquid-side refrigerant shutoff mechanism can shut off the flow of the refrigerant from the outdoor unit side to the indoor unit side.

An air conditioner according to a third aspect is the air conditioner according to the second aspect, in which the gas-side refrigerant shutoff mechanism is a check valve.

Here, as described above, the gas-side refrigerant shutoff mechanism is a check valve. The check valve therefore can shut off the flow of the refrigerant from the intake side of the compressor to the indoor unit side without electrical control.

An air conditioner according to a fourth aspect is the air conditioner according to the first aspect, in which the outdoor unit includes a compressor and an outdoor heat exchanger, and the indoor unit includes an indoor heat exchanger. The refrigerant circuit is configured to circulate the refrigerant through, in sequence, the compressor, the indoor heat exchanger, the outdoor heat exchanger, and the compressor. Here, the refrigerant shutoff mechanism includes a gas-side refrigerant shutoff mechanism configured to shut off the flow of the refrigerant from the discharge side of the compressor to the indoor unit side and a liquid-side refrigerant shutoff mechanism configured to shut off the flow of the refrigerant from the liquid side of the outdoor heat exchanger to the indoor unit side.

Here, the refrigerant circuit is configured to circulate the refrigerant through, in sequence, the compressor, the indoor heat exchanger, the outdoor heat exchanger, and the compressor (heating operation). Therefore, when a disproportionation reaction occurs in the portion of the refrigerant circuit within the outdoor unit, it is necessary to shut off the flow of the refrigerant from the discharge side of the compressor to the indoor unit side and the flow of the refrigerant from the liquid side of the outdoor heat exchanger to the indoor unit side.

Thus, here, when a disproportionation reaction occurs in the portion of the refrigerant circuit within the outdoor unit while the refrigerant is being circulated in the refrigerant circuit through, in sequence, the compressor, the indoor heat exchanger, the outdoor heat exchanger, and the compressor, the gas-side refrigerant shutoff mechanism and the liquid-side refrigerant shutoff mechanism can shut off the flow of the refrigerant from the outdoor unit side to the indoor unit side.

An air conditioner according to a fifth aspect is the air conditioner according to the second or fourth aspect, in which the gas-side refrigerant shutoff mechanism is an electromagnetic valve.

Here, as described above, the gas-side refrigerant shutoff mechanism is an electromagnetic valve. Therefore, when the refrigerant in the portion of the refrigerant circuit within the outdoor unit meets the predetermined condition, the electromagnetic valve can be closed by electrical control to shut off the flow of the refrigerant from the intake side of the compressor or the discharge side of the compressor to the indoor unit side.

An air conditioner according to a sixth aspect is the air conditioner according to any one of the second to fifth aspects, in which the liquid-side refrigerant shutoff mechanism is an expansion valve configured to decompress the refrigerant flowing between the outdoor heat exchanger and the indoor heat exchanger.

Here, as described above, the liquid-side refrigerant shutoff mechanism is the expansion valve. The expansion valve is used for decompression while the refrigerant is being circulated in the refrigerant circuit. When the refrigerant in the portion of the refrigerant circuit within the outdoor unit meets the predetermined condition, the expansion valve can be closed by electrical control to shut off the flow of the refrigerant from the liquid side of the outdoor heat exchanger to the indoor unit side.

An air conditioner according to a seventh aspect is the air conditioner according to any one of the first to sixth aspects, in which the refrigerant circuit further includes a refrigerant relief mechanism configured to release the refrigerant out of the refrigerant circuit when the refrigerant in the portion of the refrigerant circuit within the outdoor unit meets a predetermined condition.

Here, as described above, a refrigerant relief mechanism is further provided in addition to the refrigerant shutoff mechanism. Thus, when a disproportionation reaction occurs, the refrigerant shutoff mechanism can shut off the flow of the refrigerant from the outdoor unit side to the indoor unit side, and the refrigerant relief mechanism can release the refrigerant out of the refrigerant circuit.

Thus, here, the propagation of the disproportionation reaction and the resulting pressure rise to the indoor unit can be further inhibited.

An air conditioner according to an eighth aspect is the air conditioner according to the seventh aspect, in which the outdoor unit includes a compressor, and the refrigerant relief mechanism is a relief valve disposed on the discharge side of the compressor.

An air conditioner according to a ninth aspect is the air conditioner according to the seventh aspect, in which the outdoor unit includes a compressor, and the refrigerant relief mechanism is a terminal cover covering a terminal portion of the compressor.

An air conditioner according to a tenth aspect is the air conditioner according to the seventh aspect, in which the outdoor unit includes an outdoor heat exchanger, and the refrigerant relief mechanism is a protective cover covering a brazed portion of the outdoor heat exchanger.

An air conditioner according to an eleventh aspect is the air conditioner according to any one of the first to tenth aspects, in which the refrigerant contains HFO-<NUM>.

HFO-<NUM> is a hydrofluorocarbon having the property of undergoing a disproportionation reaction and has properties, such as boiling point, close to those of HFC-<NUM> and HFC-410A. Thus, a refrigerant containing HFO-<NUM> can be used as an alternative refrigerant to HFC-<NUM> or HFC-410A.

Thus, here, a refrigerant containing HFO-<NUM> is used as an alternative refrigerant to HFC-<NUM> or HFC-410A. Even when the refrigerant undergoes a disproportionation reaction, the likelihood that the portion of the refrigerant circuit within the indoor unit is damaged can be reduced, thereby reducing the likelihood of the refrigerant being ejected into the indoor space.

Embodiments of air conditioners according to the present invention will hereinafter be described with reference to the drawings. The specific configurations of the embodiments of the air conditioners according to the present invention are not limited to the following embodiments and modifications thereof.

<FIG> is a schematic diagram of an air conditioner <NUM> according to a first embodiment of the present invention.

The air conditioner <NUM> is an apparatus capable of cooling the indoor space of a building or other place through a vapor-compression refrigeration cycle. The air conditioner <NUM> mainly includes an outdoor unit <NUM>, an indoor unit <NUM>, a liquid-refrigerant connection pipe <NUM> and a gas-refrigerant connection pipe <NUM> that connect the outdoor unit <NUM> and the indoor unit <NUM> together, and a control unit <NUM> that controls the devices that constitute the outdoor unit <NUM> and the indoor unit <NUM>. The outdoor unit <NUM> and the indoor unit <NUM> are connected together via the refrigerant connection pipes <NUM> and <NUM> to form a vapor-compression refrigerant circuit <NUM> of the air conditioner <NUM>.

The indoor unit <NUM> is installed indoors and constitutes part of the refrigerant circuit <NUM>. The indoor unit <NUM> mainly includes an indoor heat exchanger <NUM> and an indoor fan <NUM>.

The indoor heat exchanger <NUM> is a heat exchanger that exchanges heat between indoor air and the refrigerant circulated between the indoor unit <NUM> and the outdoor unit <NUM> through the liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM>.

A liquid side of the indoor heat exchanger <NUM> is connected to the liquid-refrigerant connection pipe <NUM>, whereas a gas side of the indoor heat exchanger <NUM> is connected to the gas-refrigerant connection pipe <NUM>.

The indoor fan <NUM> is a fan that blows indoor air to the indoor heat exchanger <NUM>. The indoor fan <NUM> is driven by an indoor fan motor 32a.

The outdoor unit <NUM> is installed outdoors and constitutes part of the refrigerant circuit <NUM>. The outdoor unit <NUM> mainly includes a compressor <NUM>, an outdoor heat exchanger <NUM>, an expansion valve <NUM>, and an outdoor fan <NUM>.

The compressor <NUM> is a device for compressing the refrigerant. For example, the compressor <NUM> is a compressor in which a positive-displacement compression element (not shown) is driven to rotate by a compressor motor 21a. An intake pipe <NUM> is connected to an intake side of the compressor <NUM>, whereas a discharge pipe <NUM> is connected to a discharge side of the compressor <NUM>. The intake pipe <NUM> is connected to the gas-refrigerant connection pipe <NUM>.

The outdoor heat exchanger <NUM> is a heat exchanger that exchanges heat between outdoor air and the refrigerant circulated between the indoor unit <NUM> and the outdoor unit <NUM> through the liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM>. A liquid side of the outdoor heat exchanger <NUM> is connected to a liquid refrigerant pipe <NUM>, whereas a gas side of the outdoor heat exchanger <NUM> is connected to the discharge pipe <NUM>. The liquid refrigerant pipe <NUM> is connected to the liquid-refrigerant connection pipe <NUM>.

The expansion valve <NUM> is an electric valve that decompresses the refrigerant and is disposed in the liquid refrigerant pipe <NUM>.

The outdoor fan <NUM> is a fan that blows outdoor air to the outdoor heat exchanger <NUM>. The outdoor fan <NUM> is driven by an outdoor fan motor 25a.

The outdoor unit <NUM> also includes various sensors. Specifically, the outdoor unit <NUM> includes a discharged-refrigerant sensor <NUM> that detects the pressure of the refrigerant on the discharge side of the compressor <NUM>.

The refrigerant connection pipes <NUM> and <NUM> are refrigerant pipes constructed on site when the air conditioner <NUM> is installed at an installation site in a building or other place. The refrigerant connection pipes <NUM> and <NUM> constitute part of the refrigerant circuit <NUM>.

The control unit <NUM> is composed of control boards and other components (not shown) disposed in the outdoor unit <NUM> and the indoor unit <NUM> and connected in communication with each other. In <FIG>, the control unit <NUM> is shown as being located apart from the outdoor unit <NUM> and the indoor unit <NUM> for illustration purposes. The control unit <NUM> controls the devices <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> that constitute the air conditioner <NUM> (here, the outdoor unit <NUM> and the indoor unit <NUM>), that is, controls the operation of the overall air conditioner <NUM>.

In the refrigerant circuit <NUM>, a refrigerant containing a hydrofluorocarbon having a property of undergoing a disproportionation reaction is sealed. Examples of such refrigerants include ethylenic hydrofluorocarbons (hydrofluoroolefins), which have less effect on both the ozone layer and global warming and which has carbon-carbon double bonds that are readily decomposed by OH radicals. Here, among hydrofluoroolefins (HFOs), a refrigerant containing HFO-<NUM> is used. HFO-<NUM> has properties, such as boiling point, close to those of HFC-<NUM> and HFC-410A and provides high performance. Thus, a refrigerant containing HFO-<NUM> can be used as an alternative refrigerant to HFC-<NUM> or HFC-410A.

For example, the refrigerant containing HFO-<NUM> includes HFO-<NUM> alone or a mixture of HFO-<NUM> with other refrigerants. An example of the mixture of HFO-<NUM> with other refrigerants is a mixture of HFO-<NUM> with HFC-<NUM>. Here, HFO-<NUM> and HFC-<NUM> are mixed in a ratio (wt%) of <NUM>:<NUM>. Another example is a mixture of HFO-<NUM> with HFC-<NUM> and HFO-1234yf (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene). Here, HFO-<NUM>, HFC-<NUM>, and HFO-1234yf are mixed in a ratio (wt%) of <NUM>:<NUM>:<NUM>.

HFC-<NUM>, which is a type of HFC, is mixed in such refrigerants containing HFO-<NUM> as a constituent for improving performance. HFCs having <NUM> or less carbon atoms are preferred to minimize the effect on the ozone layer and global warming. Specific examples other than HFC-<NUM> include difluoroethane, trifluoroethane, tetrafluoroethane, HFC-<NUM>, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, and heptafluorobutane. Of these, those that have less effect on both the ozone layer and global warming include HFC-<NUM>, <NUM>,<NUM>-difluoroethane (HFC-152a), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (HFC-<NUM>), and <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (HFC-134a). HFO-<NUM> may be mixed with one or more of these HFCs. HFO-<NUM> may also be mixed with a hydrochlorofluoroolefins (HCFO), which are less combustible because of their higher proportion of halogen in the molecule. Specific examples include <NUM>-chloro-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (HCFO-1224yd), <NUM>-chloro-<NUM>,<NUM>-difluoroethylene (HCFO-<NUM>), <NUM>,<NUM>-dichlorofluoroethylene (HCFO-<NUM>), <NUM>-chloro-<NUM>-fluoroethylene (HCFO-<NUM>), <NUM>-chloro-<NUM>,<NUM>,<NUM>-trifluoropropene (HCFO-1233xf), and <NUM>-chloro-<NUM>,<NUM>,<NUM>-trifluoropropene (HCFO-1233zd). Of these, those that provide high performance include HCFO-1224yd, and those that have high critical temperature, durability, and coefficient of performance include HCFO-1233zd. HFO-<NUM> may be mixed with one or more of these HCFOs and HCFCs. HFO-<NUM> may also be mixed with other refrigerants such as other hydrocarbons and CFOs.

The hydrofluorocarbon having the property of undergoing a disproportionation reaction is not limited to HFO-<NUM>, but may be another HFO. For example, an ethylenic hydrofluorocarbon having the property of undergoing a disproportionation reaction may be selected from <NUM>,<NUM>,<NUM>-trifluoropropene (HFO-1243zf), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (HFO-1234ze), <NUM>-fluoropropene (HFO-1261yf), HFO-1234yf, <NUM>,<NUM>,<NUM>-trifluoropropene (HFO-1243yc), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropene (HFO-1225ye), trans- <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (HFO-1234ze(E)), and cis-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (HFO-1234ze(Z)). The hydrofluorocarbon having the property of undergoing a disproportionation reaction need not be an ethylenic hydrofluorocarbon, which has a carbon-carbon double bond, but may be an acetylenic hydrofluorocarbon, which has a carbon-carbon triple bond, having the property of undergoing a disproportionation reaction.

The air conditioner <NUM> performs cooling operation as the basic operation. Cooling operation is executed by the control unit <NUM>.

During cooling operation, in the refrigerant circuit <NUM>, gas refrigerant at the low pressure of the refrigeration cycle is taken into the compressor <NUM>, where the gas refrigerant is compressed to the high pressure of the refrigeration cycle before and is then discharged therefrom. The high-pressure gas refrigerant discharged from the compressor <NUM> enters the outdoor heat exchanger <NUM>. The high-pressure gas refrigerant entering the outdoor heat exchanger <NUM> releases heat in the outdoor heat exchanger <NUM> by heat exchange with outdoor air supplied as a cooling source by the outdoor fan <NUM>, thus becoming high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has released heat in the outdoor heat exchanger <NUM> is sent to the expansion valve <NUM>. The high-pressure liquid refrigerant sent to the expansion valve <NUM> is decompressed by the expansion valve <NUM> to the low pressure of the refrigeration cycle, thus becoming low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the expansion valve <NUM> passes through the liquid-refrigerant connection pipe <NUM> and enters the indoor heat exchanger <NUM>. The low-pressure gas-liquid two-phase refrigerant entering the indoor heat exchanger <NUM> evaporates in the indoor heat exchanger <NUM> by heat exchange with indoor air supplied as a heating source by the indoor fan <NUM>. In this way, the indoor air is cooled. The indoor air is then supplied to the indoor space to cool the indoor space. The low-pressure gas refrigerant evaporated in the indoor heat exchanger <NUM> passes through the gas-refrigerant connection pipe <NUM> and is taken into the compressor <NUM> again.

Refrigerants containing a hydrofluorocarbon having the property of undergoing a disproportionation reaction as described above may undergo a disproportionation reaction when given some energy under high-pressure and high-temperature condition. <FIG> is a graph showing the relationship between the pressure and temperature at which a refrigerant undergoes a disproportionation reaction. The curve in <FIG> shows the pressure and temperature limit at which the refrigerant undergoes a disproportionation reaction, indicating that the refrigerant undergoes a disproportionation reaction on the curve and in the region above the curve and does not undergo a disproportionation reaction in the region below the curve. When the pressure and temperature of the refrigerant in the refrigerant circuit <NUM> rise to the curve or the region above the curve where the refrigerant undergoes a disproportionation reaction in <FIG>, the refrigerant in the refrigerant circuit <NUM> undergoes a disproportionation reaction that results in a rapid pressure and temperature rise. Here, in the air conditioner <NUM> composed of the outdoor unit <NUM> and the indoor unit <NUM> that are connected together, a disproportionation reaction tends to occur in a portion of the refrigerant circuit <NUM> within the outdoor unit <NUM>, which includes the compressor <NUM>. If such a disproportionation reaction occurs in a chain reaction manner, the disproportionation reaction and the resulting pressure rise may propagate from the outdoor unit <NUM> side to the indoor unit <NUM> side. This may damage the devices and pipes that constitute a portion of the refrigerant circuit <NUM> within the indoor unit <NUM> and may thus cause the refrigerant to be ejected into the indoor space.

Accordingly, here, refrigerant shutoff mechanisms are provided, as described below. The refrigerant shutoff mechanisms shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets a predetermined condition.

The portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> includes a check valve <NUM> and an expansion valve <NUM> as refrigerant shutoff mechanisms.

The check valve <NUM> is a gas-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side. The check valve <NUM> is a valve mechanism that allows the refrigerant flow from the gas-refrigerant connection pipe <NUM> to the intake side of the compressor <NUM> while shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side. Here, the check valve <NUM> is disposed in the intake pipe <NUM>.

The expansion valve <NUM> is a liquid-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. The expansion valve <NUM>, as described above, is an electric valve that decompresses the refrigerant. Thus, the expansion valve <NUM> functions both as an expansion mechanism that decompresses the refrigerant flowing between the outdoor heat exchanger <NUM> and the indoor heat exchanger <NUM> and as a liquid-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

Here, during the basic operation (here, cooling operation), when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets a predetermined condition (when the refrigerant meets a condition for a disproportionation reaction to occur), the check valve <NUM>, serving as the gas-side refrigerant shutoff mechanism, operates to shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side, thereby shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side. Also, the expansion valve <NUM>, serving as the liquid-side refrigerant shutoff mechanism, operates to switch from an open state to a fully closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

Here, the predetermined condition for the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> (the condition for the refrigerant to undergo a disproportionation reaction) may be a threshold pressure PH corresponding to the lower pressure limit at which the refrigerant on the discharge side of the compressor <NUM>, which tends to reach the highest pressure and temperature, undergoes a disproportionation reaction. For example, as shown in <FIG>, the threshold pressure PH may be the lower pressure limit (i.e., the value on the curve indicating the pressure and temperature limit at which the refrigerant undergoes a disproportionation reaction) at which the refrigerant undergoes a disproportionation reaction at the maximum operating temperature TX of the refrigerant circuit <NUM>. If this pressure value is close to the maximum operating pressure PX of the refrigerant circuit <NUM>, the threshold pressure PH may be the maximum operating pressure PX. The maximum operating temperature TX and the maximum operating pressure PX of the refrigerant circuit <NUM> are the upper operating pressure and temperature limits prescribed in view of the design strength of the refrigerant circuit <NUM> (i.e., the devices and pipes that constitute the refrigerant circuit <NUM>).

Until the pressure of the refrigerant on the discharge side of the compressor <NUM> (here, the pressure of the refrigerant detected by the discharged-refrigerant sensor <NUM>) reaches the threshold pressure PH, the refrigerant flows from the gas-refrigerant connection pipe <NUM> toward the intake side of the compressor <NUM> through the check valve <NUM>, and the refrigerant flows from the liquid side of the outdoor heat exchanger <NUM> toward the liquid-refrigerant connection pipe <NUM> through the expansion valve <NUM>, which is in an open state (see the region where the refrigerant shutoff mechanisms do not operate in <FIG>). That is, until the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> does not meet the predetermined condition (does not meet the condition for a disproportionation reaction to occur). Thus, the basic operation continues without shutting off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side.

However, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant on the discharge side of the compressor <NUM> undergoes a disproportionation reaction. The disproportionation reaction and the resulting pressure rise propagate from the discharge side of the compressor <NUM> toward other parts of the refrigerant circuit <NUM>. Consequently, the disproportionation reaction of the refrigerant and the resulting pressure rise propagate through the compressor <NUM> to the intake side of the compressor <NUM>. Thus, the check valve <NUM>, serving as the gas-side refrigerant shutoff mechanism, operates to shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side, thereby shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side (see the region where the refrigerant shutoff mechanisms operate in <FIG>). The disproportionation reaction of the refrigerant and the resulting pressure rise also propagate through the outdoor heat exchanger <NUM> to the liquid side of the outdoor heat exchanger <NUM>. Thus, the expansion valve <NUM>, serving as the liquid-side refrigerant shutoff mechanism, operates to switch from an open state to a fully closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side (see the region where the refrigerant shutoff mechanisms operate in <FIG>). Here, the expansion valve <NUM> is operated by the control unit <NUM>. That is, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the control unit <NUM> controls the expansion valve <NUM> so that it switches from an open state to a fully closed state. The control unit <NUM> also stops the compressor <NUM>. That is, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (meets the condition for a disproportionation reaction to occur). Thus, the refrigerant shutoff mechanisms <NUM> and <NUM> operate to shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, and the basic operation is stopped.

Here, as described above, the refrigerant shutoff mechanisms <NUM> and <NUM> are provided in the air conditioner <NUM> in which the refrigerant circuit <NUM> is composed of the outdoor unit <NUM> and the indoor unit <NUM> that are connected together and a refrigerant containing a hydrofluorocarbon having the property of undergoing a disproportionation reaction is sealed in the refrigerant circuit <NUM>. The refrigerant shutoff mechanisms <NUM> and <NUM> shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur). In particular, here, the refrigerant circuit <NUM> is configured to circulate the refrigerant through, in sequence, the compressor <NUM>, the outdoor heat exchanger <NUM>, the indoor heat exchanger <NUM>, and the compressor <NUM> (cooling operation). Therefore, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM>, it is necessary to shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side and the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. Accordingly, here, the gas-side refrigerant shutoff mechanism <NUM> and the liquid-side refrigerant shutoff mechanism <NUM> as described above are provided as refrigerant shutoff mechanisms in the refrigerant circuit <NUM>.

Thus, here, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM>, the refrigerant shutoff mechanisms <NUM> and <NUM> can shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, thereby inhibiting the propagation of the disproportionation reaction and the resulting pressure rise to the indoor unit <NUM>.

Thus, here, even when the refrigerant undergoes a disproportionation reaction, a likelihood that the devices and pipes that constitute the portion of the refrigerant circuit <NUM> within the unit <NUM> is damaged can be reduced, thereby reducing the likelihood of the refrigerant being ejected into the indoor space. In particular, here, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> while the refrigerant is being circulated in the refrigerant circuit <NUM> through, in sequence, the compressor <NUM>, the outdoor heat exchanger <NUM>, the indoor heat exchanger <NUM>, and the compressor <NUM>, the gas-side refrigerant shutoff mechanism <NUM> and the liquid-side refrigerant shutoff mechanism <NUM> can shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side.

It is also possible to provide the refrigerant shutoff mechanisms in the refrigerant connection pipes <NUM> and <NUM>, rather than in the outdoor unit <NUM>. However, since portions of the refrigerant connection pipes <NUM> and <NUM> are disposed inside a building, it is undesirable to provide the refrigerant shutoff mechanisms in the refrigerant connection pipes <NUM> and <NUM> in view of the possibility of the refrigerant being ejected into the indoor space due to damage to the refrigerant connection pipes <NUM> and <NUM>. Thus, it is preferred to provide the refrigerant shutoff mechanisms in the outdoor unit <NUM>.

Here, as described above, the gas-side refrigerant shutoff mechanism is the check valve <NUM>. The check valve <NUM> can therefore shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side without electrical control.

Here, as described above, the liquid-side refrigerant shutoff mechanism is the expansion valve <NUM>. The expansion valve <NUM> can be used for decompression while the refrigerant is being circulated in the refrigerant circuit <NUM>. Further, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the expansion valve <NUM> can be closed by electrical control to shut off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

If a refrigerant containing HFO-<NUM> is used as the refrigerant containing a hydrofluorocarbon having the property of undergoing a disproportionation reaction, it can be used as an alternative refrigerant to HFC-<NUM> or HFC-410A. Even when the refrigerant undergoes a disproportionation reaction, it can be inhibited that the portion of the refrigerant circuit <NUM> within the indoor unit <NUM> is damaged, thereby reducing the likelihood of the refrigerant being ejected into the indoor space.

Although, in the first embodiment, the check valve <NUM> is used as the gas-side refrigerant shutoff mechanism, the gas-side refrigerant shutoff mechanism is not limited thereto; rather, as shown in <FIG>, an electromagnetic valve <NUM> may be used as a gas-side refrigerant shutoff mechanism.

The electromagnetic valve <NUM> is a valve mechanism whose opening and closing state is electrically controlled by the control unit <NUM>. Here, the electromagnetic valve <NUM> is disposed in the intake pipe <NUM>.

The electromagnetic valve <NUM> is controlled so that it is in an open state during the basic operation. When the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (e.g., when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH), the electromagnetic valve <NUM> is controlled so that it switches to a closed state.

Thus, here, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the condition for a disproportionation reaction to occur, the electromagnetic valve <NUM>, serving as the gas-side refrigerant shutoff mechanism, operates to shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side, thereby shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM>.

In this configuration, as in the first embodiment, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the refrigerant shutoff mechanisms <NUM> and <NUM> can shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, thereby inhibiting the propagation of the disproportionation reaction and the resulting pressure rise to the indoor unit <NUM>.

In the first embodiment and the first modification, the refrigerant shutoff mechanisms are used as a measure against the disproportionation reaction of the refrigerant. It is preferred to use, in addition to the refrigerant shutoff mechanisms, another measure against the disproportionation reaction of the refrigerant.

Accordingly, here, as shown in <FIG>, a relief valve <NUM> is further provided as a refrigerant relief mechanism. The relief valve <NUM> releases the refrigerant out of the refrigerant circuit <NUM> when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (e.g., when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH).

The relief valve <NUM> is connected between the discharge side of the compressor <NUM> and the gas side of the outdoor heat exchanger <NUM> (here, in the discharge pipe <NUM>) in a branched manner via a discharge branch pipe <NUM>. The relief valve <NUM> releases the refrigerant out of the refrigerant circuit <NUM> from the discharge side of the compressor <NUM> when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur). Here, the relief valve <NUM> is a valve mechanism that operates when the pressure on the primary side (here, on the discharge side of the compressor <NUM>) reaches a prescribed pressure or higher. For example, the relief valve <NUM> is a mechanical valve mechanism such as a spring-loaded relief valve or a rupture disk. Here, the prescribed pressure for the relief valve <NUM> is set to the threshold pressure PH, which is a predetermined condition for the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> (the condition for a disproportionation reaction to occur).

The relief valve <NUM> does not operate during the basic operation. When the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the relief valve <NUM> operates to release the refrigerant out of the refrigerant circuit <NUM>.

Thus, here, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the refrigerant shutoff mechanisms <NUM>, <NUM>, and <NUM> can shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, and the refrigerant relief mechanism <NUM> can release the refrigerant out of the refrigerant circuit <NUM>, thereby further inhibiting the propagation of the disproportionation reaction and the resulting pressure rise to the indoor unit <NUM>.

If a mechanical valve mechanism as described above is provided as the refrigerant relief mechanism <NUM>, a limit switch or other device may be provided on the refrigerant relief mechanism <NUM> so that it sends an operating signal to the control unit <NUM> when the refrigerant relief mechanism <NUM> operates. In response to the operating signal from the refrigerant relief mechanism <NUM>, the control unit <NUM> may operate the refrigerant shutoff mechanisms <NUM> and <NUM> to shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side.

Instead of a mechanical valve mechanism, a valve mechanism that is electrically controlled by the control unit <NUM>, such as an electromagnetic valve, may be used as the refrigerant relief mechanism <NUM>. In this case, as with the refrigerant shutoff mechanisms <NUM> and <NUM>, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the control unit <NUM> can operate the refrigerant relief mechanism <NUM> so that it switches from a closed state to an open state.

Configurations different from the relief valve disposed on the discharge side of the compressor <NUM> may also be used as refrigerant relief mechanisms <NUM>. For example, as shown in <FIG>, the compressor <NUM> may have a metal terminal cover covering a terminal portion of the compressor <NUM>. In this case, the refrigerant can be released out of the refrigerant circuit <NUM> through the terminal portion of the compressor <NUM>. In addition, as shown in <FIG>, the outdoor heat exchanger <NUM> may have a protective cover covering a brazed portion of the outdoor heat exchanger <NUM>. In this case, the refrigerant can be released out of the refrigerant circuit <NUM> through the brazed portion of the outdoor heat exchanger <NUM>. These refrigerant relief mechanisms <NUM> may be used alone or in combination.

Although, in the first embodiment and the first and second modifications, the expansion valve <NUM>, which decompresses the refrigerant flowing between the outdoor heat exchanger <NUM> and the indoor heat exchanger <NUM>, is used as the liquid-side refrigerant shutoff mechanism, the liquid-side refrigerant shutoff mechanism is not limited thereto; rather, an additional valve mechanism capable of opening and closing, such as an electromagnetic valve, may be provided as the liquid-side refrigerant shutoff mechanism somewhere in the path of the refrigerant circuit <NUM> from the discharge side of the compressor <NUM> through the outdoor heat exchanger <NUM> and the expansion valve <NUM> to the liquid-refrigerant connection pipe <NUM>. In this case, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the control unit <NUM> can control the additional valve mechanism so that it switches from an open state to a closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

Although examples in which the present invention is applied to the cooling-only air conditioner <NUM>, which performs cooling operation as the basic operation, are described in the first embodiment and the modifications thereof, the present invention is not limited thereto, but can also be applied to an air conditioner <NUM> capable of switching between cooling and heating that performs cooling operation and heating operation as the basic operation, as shown in <FIG>.

The air conditioner <NUM> is an apparatus capable of cooling and heating the indoor space of a building or other place through a vapor-compression refrigeration cycle. The air conditioner <NUM> mainly includes an outdoor unit <NUM>, an indoor unit <NUM>, a liquid-refrigerant connection pipe <NUM> and a gas-refrigerant connection pipe <NUM> that connect the outdoor unit <NUM> and the indoor unit <NUM> together, and a control unit <NUM> that controls the devices that constitute the outdoor unit <NUM> and the indoor unit <NUM>. The outdoor unit <NUM> and the indoor unit <NUM> are connected together via the refrigerant connection pipes <NUM> and <NUM> to constitute a vapor-compression refrigerant circuit <NUM> of the air conditioner <NUM>.

The indoor unit <NUM> is installed indoors and constitutes part of the refrigerant circuit <NUM>. The configuration of the indoor unit <NUM> is the same as that of the first embodiment and the modifications thereof; therefore, a description thereof is omitted here.

The outdoor unit <NUM> is installed outdoors and constitutes part of the refrigerant circuit <NUM>. The outdoor unit <NUM> mainly includes a compressor <NUM>, a four-way switching valve <NUM>, an outdoor heat exchanger <NUM>, an expansion valve <NUM>, and an outdoor fan <NUM>.

The compressor <NUM> is a device for compressing the refrigerant. For example, the compressor <NUM> is a compressor in which a positive-displacement compression element (not shown) is driven to rotate by a compressor motor 21a. An intake pipe <NUM> is connected to the intake side of the compressor <NUM>, whereas a discharge pipe <NUM> is connected to the discharge side of the compressor <NUM>. The intake pipe <NUM> is connected to the four-way switching valve <NUM>.

The outdoor heat exchanger <NUM> is a heat exchanger that exchanges heat between outdoor air and the refrigerant circulated between the indoor unit <NUM> and the outdoor unit <NUM> through the liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM>. The liquid side of the outdoor heat exchanger <NUM> is connected to a liquid refrigerant pipe <NUM>, whereas the gas side of the outdoor heat exchanger <NUM> is connected to a first gas refrigerant pipe <NUM>. The liquid refrigerant pipe <NUM> is connected to the liquid-refrigerant connection pipe <NUM>. The first gas refrigerant pipe <NUM> is connected to the four-way switching valve <NUM>.

The four-way switching valve <NUM> is a valve mechanism that switches the circulation direction of the refrigerant in the refrigerant circuit <NUM>. When the refrigerant is circulated through, in sequence, the compressor <NUM>, the outdoor heat exchanger <NUM>, the expansion valve <NUM>, the indoor heat exchanger <NUM>, and the compressor <NUM> (hereinafter referred to as "heat release state"), the four-way switching valve <NUM> connects the discharge side of the compressor <NUM> (here, the discharge pipe <NUM>) and the gas side of the outdoor heat exchanger <NUM> (here, the first gas refrigerant pipe <NUM>) and connects the intake side of the compressor <NUM> (here, the intake pipe <NUM>) and the gas-refrigerant connection pipe <NUM> side (here, a second gas refrigerant pipe <NUM>) (see the solid lines in the four-way switching valve <NUM> in <FIG>). Here, the second gas refrigerant pipe <NUM> is connected to the four-way switching valve <NUM> and the gas-refrigerant connection pipe <NUM>. When the refrigerant is circulated through, in sequence, the compressor <NUM>, the indoor heat exchanger <NUM>, the expansion valve <NUM>, the outdoor heat exchanger <NUM>, and the compressor <NUM> (hereinafter referred to as "evaporation state"), the four-way switching valve <NUM> connects the discharge side of the compressor <NUM> (here, the discharge pipe <NUM>) and the gas-refrigerant connection pipe <NUM> side (here, the second gas refrigerant pipe <NUM>) and connects the intake side of the compressor <NUM> (here, the intake pipe <NUM>) and the gas side of the outdoor heat exchanger <NUM> (here, the first gas refrigerant pipe <NUM>) (see the dashed lines in the four-way switching valve <NUM> in <FIG>).

The control unit <NUM> is composed of control boards and other components (not shown) disposed in the outdoor unit <NUM> and the indoor unit <NUM> and connected in communication with each other. In <FIG>, the control unit <NUM> is shown as being located apart from the outdoor unit <NUM> and the indoor unit <NUM> for illustration purposes. The control unit <NUM> controls the devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> that constitute the air conditioner <NUM> (here, the outdoor unit <NUM> and the indoor unit <NUM>), that is, controls the operation of the overall air conditioner <NUM>.

In the refrigerant circuit <NUM>, a refrigerant containing a hydrofluorocarbon having a property of undergoing a disproportionation reaction is sealed. The refrigerant sealed in the refrigerant circuit <NUM> is the same as that of the first embodiment and the modifications thereof, therefore, a description thereof is omitted here.

The air conditioner <NUM> performs cooling operation and heating operation as the basic operation. Cooling operation and cooling operation are executed by the control unit <NUM>.

During cooling operation, the four-way switching valve <NUM> is switched to the heat release state (the state indicated by the solid lines in <FIG>). In the refrigerant circuit <NUM>, gas refrigerant at the low pressure of the refrigeration cycle is taken into the compressor <NUM>, where the gas refrigerant is compressed to the high pressure of the refrigeration cycle and is then discharged therefrom. The high-pressure gas refrigerant discharged from the compressor <NUM> passes through the four-way switching valve <NUM> and enters the outdoor heat exchanger <NUM>. The high-pressure gas refrigerant entering the outdoor heat exchanger <NUM> releases heat in the outdoor heat exchanger <NUM> by heat exchange with outdoor air supplied as a cooling source by the outdoor fan <NUM>, thus becoming high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has released heat in the outdoor heat exchanger <NUM> is sent to the expansion valve <NUM>. The high-pressure liquid refrigerant sent to the expansion valve <NUM> is decompressed by the expansion valve <NUM> to the low pressure of the refrigeration cycle, thus becoming low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the expansion valve <NUM> passes through the liquid-refrigerant connection pipe <NUM> and enters the indoor heat exchanger <NUM>. The low-pressure gas-liquid two-phase refrigerant entering the indoor heat exchanger <NUM> evaporates in the indoor heat exchanger <NUM> by heat exchange with indoor air supplied as a heating source by the indoor fan <NUM>. In this way, the indoor air is cooled. The indoor air is then supplied to the indoor space to cool the indoor space. The low-pressure gas refrigerant evaporated in the indoor heat exchanger <NUM> passes through the gas-refrigerant connection pipe <NUM> and the four-way switching valve <NUM> and is taken into the compressor <NUM> again.

During heating operation, the four-way switching valve <NUM> is switched to the evaporation state (the state indicated by the dashed lines in <FIG>). In the refrigerant circuit <NUM>, gas refrigerant at the low pressure of the refrigeration cycle is taken into the compressor <NUM>, where the gas refrigerant is compressed to the high pressure of the refrigeration cycle and is then discharged therefrom. The high-pressure gas refrigerant discharged from the compressor <NUM> passes through the four-way switching valve <NUM> and the gas-refrigerant connection pipe <NUM> and enters the indoor heat exchanger <NUM>. The high-pressure gas refrigerant entering the indoor heat exchanger <NUM> releases heat in the indoor heat exchanger <NUM> by heat exchange with indoor air supplied as a cooling source by the indoor fan <NUM>, thus becoming high-pressure liquid refrigerant. In this way, the indoor air is heated. The indoor air is then supplied to the indoor space to heat the indoor space. The high-pressure liquid refrigerant that has released heat in the indoor heat exchanger <NUM> passes through the liquid-refrigerant connection pipe <NUM> and is sent to the expansion valve <NUM>. The high-pressure liquid refrigerant sent to the expansion valve <NUM> is decompressed by the expansion valve <NUM> to the low pressure of the refrigeration cycle, thus becoming low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant decompressed by the expansion valve <NUM> enters the outdoor heat exchanger <NUM>. The low-pressure gas-liquid two-phase refrigerant entering the outdoor heat exchanger <NUM> evaporates in the outdoor heat exchanger <NUM> by heat exchange with outdoor air supplied as a heating source by the outdoor fan <NUM>, thus becoming low-pressure gas refrigerant. The low-pressure gas refrigerant evaporated in the outdoor heat exchanger <NUM> passes through the four-way switching valve <NUM> and is taken into the compressor <NUM> again.

In the air conditioner <NUM> according to this embodiment, as in the air conditioner <NUM> according to the first embodiment and the modifications thereof, a disproportionation reaction tends to occur in a portion of the refrigerant circuit <NUM> within the outdoor unit <NUM>, which includes the compressor <NUM>. If such a disproportionation reaction occurs in a chain reaction manner, the disproportionation reaction and the resulting pressure rise may propagate from the outdoor unit <NUM> side to the indoor unit <NUM> side. This may damage the devices and pipes that constitute a portion of the refrigerant circuit <NUM> within the indoor unit <NUM> and may thus cause the refrigerant to be ejected into the indoor space.

Accordingly, in this embodiment, refrigerant shutoff mechanisms are provided, as described below. The refrigerant shutoff mechanisms shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets a predetermined condition.

The portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> includes an electromagnetic valve <NUM> and an expansion valve <NUM> as refrigerant shutoff mechanisms.

The electromagnetic valve <NUM> is a gas-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side during cooling operation being performed as the basic operation. The electromagnetic valve <NUM> is also a gas-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the discharge side of the compressor <NUM> to the indoor unit <NUM> side during heating operation being performed as the basic operation. The electromagnetic valve <NUM> is a valve mechanism whose opening and closing state is electrically controlled by the control unit <NUM>. Here, the electromagnetic valve <NUM> is disposed in a second gas refrigerant pipe <NUM> connecting the four-way switching valve <NUM> and the gas-refrigerant connection pipe <NUM>.

Here, during cooling operation being performed as the basic operation, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets a predetermined condition (when the refrigerant meets a condition for a disproportionation reaction to occur), the electromagnetic valve <NUM>, serving as the gas-side refrigerant shutoff mechanism, operates to shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side, thereby shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side. Also, the expansion valve <NUM>, serving as the liquid-side refrigerant shutoff mechanism, operates to switch from an open state to a fully closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. During heating operation being performed as the basic operation, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the electromagnetic valve <NUM>, serving as the gas-side refrigerant shutoff mechanism, operates to shut off the flow of the refrigerant from the discharge side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side, thereby shutting off the flow of the refrigerant from the discharge side of the compressor <NUM> to the indoor unit <NUM> side. Also, the expansion valve <NUM>, serving as the liquid-side refrigerant shutoff mechanism, operates to switch from an open state to a fully closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

Here, the predetermined condition for the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> (the condition for the refrigerant to undergo a disproportionation reaction) may be a threshold pressure PH corresponding to the lower pressure limit at which the refrigerant on the discharge side of the compressor <NUM>, which tends to reach the highest pressure and temperature, undergoes a disproportionation reaction. The threshold pressure PH is the same as that of the first embodiment and the modifications thereof; therefore, a description thereof is omitted here.

During cooling operation being performed as the basic operation, until the pressure of the refrigerant on the discharge side of the compressor <NUM> (here, the pressure of the refrigerant detected by the discharged-refrigerant sensor <NUM>) reaches the threshold pressure PH, the refrigerant flows from the gas-refrigerant connection pipe <NUM> toward the intake side of the compressor <NUM> through the electromagnetic valve <NUM>, and the refrigerant flows from the liquid side of the outdoor heat exchanger <NUM> toward the liquid-refrigerant connection pipe <NUM> through the expansion valve <NUM>, which is in an open state. That is, until the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> does not meet the predetermined condition (does not meet the condition for a disproportionation reaction to occur). Thus, the cooling operation continues without shutting off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side.

However, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant on the discharge side of the compressor <NUM> undergoes a disproportionation reaction. Then, the disproportionation reaction and the resulting pressure rise propagate from the discharge side of the compressor <NUM> toward other parts of the refrigerant circuit <NUM>. The disproportionation reaction of the refrigerant and the resulting pressure rise propagate through the compressor <NUM> to the intake side of the compressor <NUM>. Thus, the electromagnetic valve <NUM>, serving as the gas-side refrigerant shutoff mechanism, operates to shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side, thereby shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side. The disproportionation reaction of the refrigerant and the resulting pressure rise also propagate through the outdoor heat exchanger <NUM> to the liquid side of the outdoor heat exchanger <NUM>. Thus, the expansion valve <NUM>, serving as the liquid-side refrigerant shutoff mechanism, operates to switch from an open state to a fully closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. Here, the electromagnetic valve <NUM> and the expansion valve <NUM> are operated by the control unit <NUM>. That is, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the control unit <NUM> controls the electromagnetic valve <NUM> and the expansion valve <NUM> so that they switch from an open state to a fully closed state. The control unit <NUM> also stops the compressor <NUM>. That is, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (meets the condition for a disproportionation reaction to occur). Thus, the refrigerant shutoff mechanisms <NUM> and <NUM> operate to shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, and the cooling operation is stopped.

During heating operation being performed as the basic operation, until the pressure of the refrigerant on the discharge side of the compressor <NUM> (here, the pressure of the refrigerant detected by the discharged-refrigerant sensor <NUM>) reaches the threshold pressure PH, the refrigerant flows from the discharge side of the compressor <NUM> toward the gas-refrigerant connection pipe <NUM> side through the electromagnetic valve <NUM>, and the refrigerant flows from the liquid-refrigerant connection pipe <NUM> toward the liquid side of the outdoor heat exchanger <NUM> through the expansion valve <NUM>, which is in an open state. That is, until the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> does not meet the predetermined condition (does not meet the condition for a disproportionation reaction to occur). Thus, the heating operation continues without shutting off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side.

However, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant on the discharge side of the compressor <NUM> undergoes a disproportionation reaction. Then, the disproportionation reaction and the resulting pressure rise propagate from the discharge side of the compressor <NUM> toward other parts of the refrigerant circuit <NUM>. Thus, on the discharge side of the compressor <NUM>, the electromagnetic valve <NUM>, serving as the gas-side refrigerant shutoff mechanism, operates to shut off the flow of the refrigerant from the discharge side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM> side, thereby shutting off the flow of the refrigerant from the discharge side of the compressor <NUM> to the indoor unit <NUM> side. The disproportionation reaction of the refrigerant and the resulting pressure rise also propagate through the compressor <NUM> and the outdoor heat exchanger <NUM> to the liquid side of the outdoor heat exchanger <NUM>. Thus, the expansion valve <NUM>, serving as the liquid-side refrigerant shutoff mechanism, operates to switch from an open state to a fully closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. Here, the electromagnetic valve <NUM> and the expansion valve <NUM> are operated by the control unit <NUM>. The control unit <NUM> also stops the compressor <NUM>. That is, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (meets the condition for a disproportionation reaction to occur). Thus, the refrigerant shutoff mechanisms <NUM> and <NUM> operate to shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, and the heating operation is stopped.

Here, as described above, the refrigerant shutoff mechanisms <NUM> and <NUM> are provided in the air conditioner <NUM> in which the refrigerant circuit <NUM> is composed of the outdoor unit <NUM> and the indoor unit <NUM> that are connected together and a refrigerant containing a hydrofluorocarbon having the property of undergoing a disproportionation reaction is sealed in the refrigerant circuit <NUM>. The refrigerant shutoff mechanisms <NUM> and <NUM> shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur). In particular, here, the refrigerant circuit <NUM> is configured to circulate the refrigerant through, in sequence, the compressor <NUM>, the outdoor heat exchanger <NUM>, the indoor heat exchanger <NUM>, and the compressor <NUM> (cooling operation). Therefore, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM>, it is necessary to shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side and the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. The refrigerant circuit <NUM> is also configured to circulate the refrigerant through, in sequence, the compressor <NUM>, the indoor heat exchanger <NUM>, the outdoor heat exchanger <NUM>, and the compressor <NUM> (heating operation). Therefore, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM>, it is necessary to shut off the flow of the refrigerant from the discharge side of the compressor <NUM> to the indoor unit <NUM> side and the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. Accordingly, here, the gas-side refrigerant shutoff mechanism <NUM> and the liquid-side refrigerant shutoff mechanism <NUM> as described above are provided as refrigerant shutoff mechanisms in the refrigerant circuit <NUM>.

Thus, here, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM>, it is possible to shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, thereby inhibiting the propagation of the disproportionation reaction and the resulting pressure rise to the indoor unit <NUM>.

Thus, here, even when the refrigerant undergoes a disproportionation reaction, the devices and pipes that constitute the portion of the refrigerant circuit <NUM> within the indoor unit <NUM> can be inhibited from being damaged, thereby reducing the likelihood of the refrigerant being ejected into the indoor space. In particular, here, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> while the refrigerant is being circulated in the refrigerant circuit <NUM> through, in sequence, the compressor <NUM>, the outdoor heat exchanger <NUM>, the indoor heat exchanger <NUM>, and the compressor <NUM>, the gas-side refrigerant shutoff mechanism <NUM> and the liquid-side refrigerant shutoff mechanism <NUM> can shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side. Also, here, when a disproportionation reaction occurs in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> while the refrigerant is being circulated in the refrigerant circuit <NUM> through, in sequence, the compressor <NUM>, the indoor heat exchanger <NUM>, the outdoor heat exchanger <NUM>, and the compressor <NUM>, the gas-side refrigerant shutoff mechanism <NUM> and the liquid-side refrigerant shutoff mechanism <NUM> can shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side.

Here, as described above, the gas-side refrigerant shutoff mechanism is the electromagnetic valve <NUM>. When the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the electromagnetic valve <NUM> can be closed by electrical control to shut off the flow of the refrigerant from the intake side of the compressor <NUM> or the discharge side of the compressor <NUM> to the indoor unit <NUM> side.

Here, as described above, the liquid-side refrigerant shutoff mechanism is the expansion valve <NUM>. The expansion valve <NUM> is used for decompression while the refrigerant is being circulated in the refrigerant circuit <NUM>. When the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the expansion valve <NUM> can be closed by electrical control to shut off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

In the configuration of the second embodiment, as shown in <FIG>, a check valve <NUM> may be provided in the intake pipe <NUM>. Here, during cooling operation, the check valve <NUM> functions as a valve mechanism that allows the flow of the refrigerant from the second gas refrigerant pipe <NUM> to the intake side of the compressor <NUM> while shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the second gas refrigerant pipe <NUM> side. During heating operation, the check valve <NUM> functions as a valve mechanism that allows the flow of the refrigerant from the first gas refrigerant pipe <NUM> to the intake side of the compressor <NUM> while shutting off the flow of the refrigerant from the intake side of the compressor <NUM> to the first gas refrigerant pipe <NUM> side.

In this configuration having the check valve <NUM> added thereto, during cooling operation, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the check valve <NUM> shuts off the flow of the refrigerant from the intake side of the compressor <NUM> to the second gas refrigerant pipe <NUM> side. Thus, the check valve <NUM> functions as the gas-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side. Therefore, the electromagnetic valve <NUM> need not function as a gas-side refrigerant shutoff mechanism (that is, the electromagnetic valve <NUM> need not switch from an open state to a fully closed state). Alternatively, both the electromagnetic valve <NUM> and the check valve <NUM> may function as the gas-side refrigerant shutoff mechanisms so that they can reliably shut off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side.

During heating operation, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the check valve <NUM> shuts off the flow of the refrigerant from the intake side of the compressor <NUM> to the first gas refrigerant pipe <NUM> side. Thus, the check valve <NUM> functions as the liquid-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side. Therefore, the expansion valve <NUM> need not function as a liquid-side refrigerant shutoff mechanism (that is, the expansion valve <NUM> need not switch from an open state to a fully closed state). Alternatively, both the expansion valve <NUM> and the check valve <NUM> may function as the liquid-side refrigerant shutoff mechanisms so that they can reliably shut off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

In the configuration of the first modification of the second embodiment, as shown in <FIG>, the check valve <NUM> may be replaced by an electromagnetic valve <NUM> composed of a valve mechanism whose opening and closing state is electrically controlled by the control unit <NUM>.

In this case, during cooling operation, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the electromagnetic valve <NUM> switches from an open state to a fully closed state. Thus, as in the first modification, the electromagnetic valve <NUM> can function as the gas-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the intake side of the compressor <NUM> to the indoor unit <NUM> side. During heating operation, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the electromagnetic valve <NUM> switches from an open state to a fully closed state. Thus, as in the first modification, the electromagnetic valve <NUM> can function as the liquid-side refrigerant shutoff mechanism that shuts off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

In the second embodiment and the first and second modifications, the refrigerant shutoff mechanisms are used as a measure against the disproportionation reaction of the refrigerant. It is preferred to use, in addition to the refrigerant shutoff mechanisms, another measure against the disproportionation reaction of the refrigerant.

Accordingly, here, as shown in <FIG>, a relief valve <NUM> is further provided as a refrigerant relief mechanism, as in the second modification of the first embodiment. The relief valve <NUM> releases the refrigerant out of the refrigerant circuit <NUM> when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur). The configuration of the refrigerant relief mechanism <NUM> is the same as that of the second modification of the first embodiment; therefore, a description thereof is omitted here.

Thus, here, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the refrigerant shutoff mechanisms <NUM>, <NUM>, <NUM>, and <NUM> can shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side, and the refrigerant relief mechanism <NUM> can release the refrigerant out of the refrigerant circuit <NUM>, thereby further inhibiting the propagation of the disproportionation reaction and the resulting pressure rise to the indoor unit <NUM>.

If a mechanical valve mechanism as described above is provided as the refrigerant relief mechanism <NUM>, a limit switch or other device may be provided on the refrigerant relief mechanism <NUM> so that it sends an operating signal to the control unit <NUM> when the refrigerant relief mechanism <NUM> operates. In response to the operating signal from the refrigerant relief mechanism <NUM>, the control unit <NUM> may operate the refrigerant shutoff mechanisms <NUM>, <NUM>, and <NUM> to shut off the flow of the refrigerant from the outdoor unit <NUM> side to the indoor unit <NUM> side.

Instead of a mechanical valve mechanism, a valve mechanism that is electrically controlled by the control unit <NUM>, such as an electromagnetic valve, may be used as the refrigerant relief mechanism <NUM>. In this case, as with the refrigerant shutoff mechanisms <NUM>, <NUM>, and <NUM>, when the pressure of the refrigerant on the discharge side of the compressor <NUM> reaches the threshold pressure PH, the control unit <NUM> can operate the refrigerant relief mechanism <NUM> so that it switches from a closed state to an open state.

Configurations different from the relief valve disposed on the discharge side of the compressor <NUM> may also be used as refrigerant relief mechanisms <NUM>. For example, as shown in <FIG>, the compressor <NUM> may have a metal terminal cover covering a terminal portion of the compressor <NUM>, and the outdoor heat exchanger <NUM> may have a protective cover covering a brazed portion of the outdoor heat exchanger <NUM>, as in the second modification of the first embodiment.

In the second embodiment and the first and second modifications, the expansion valve <NUM>, which decompresses the refrigerant flowing between the outdoor heat exchanger <NUM> and the indoor heat exchanger <NUM>, is used as the liquid-side refrigerant shutoff mechanism during cooling operation. However, the liquid-side refrigerant shutoff mechanism is not limited thereto. An additional valve mechanism capable of opening and closing, such as an electromagnetic valve, may be provided as the liquid-side refrigerant shutoff mechanism somewhere in the path of the refrigerant circuit <NUM> from the discharge side of the compressor <NUM> through the outdoor heat exchanger <NUM> and the expansion valve <NUM> to the liquid-refrigerant connection pipe <NUM>. In this case, when the refrigerant in the portion of the refrigerant circuit <NUM> within the outdoor unit <NUM> meets the predetermined condition (when the refrigerant meets the condition for a disproportionation reaction to occur), the control unit <NUM> can control the additional valve mechanism so that it switches from an open state to a closed state, thereby shutting off the flow of the refrigerant from the liquid side of the outdoor heat exchanger <NUM> to the indoor unit <NUM> side.

Although examples in which the present invention is applied to a configuration in which the single indoor unit <NUM> is connected to the outdoor unit <NUM> or <NUM> are described in the first and second embodiments and the modifications thereof, the present invention may also be applied to a configuration in which a plurality of indoor units <NUM> are connected to the outdoor unit <NUM> or <NUM>.

Claim 1:
An air conditioner (<NUM>, <NUM>) comprising a refrigerant circuit (<NUM>, <NUM>) which is formed by connecting an outdoor unit (<NUM>, <NUM>) and an indoor unit (<NUM>) via refrigerant connection pipes (<NUM>, <NUM>), and a control unit (<NUM>; <NUM>) configured to control the outdoor unit and the indoor unit, the outdoor unit comprising a compressor (<NUM>), an outdoor heat exchanger (<NUM>) and an expansion valve, the indoor unit comprising an indoor heat exchanger (<NUM>),
the refrigerant circuit having the compressor, the outdoor heat exchanger, the expansion valve, the indoor heat exchanger and a refrigerant sealed therein, the refrigerant containing a hydrofluorocarbon having a property of undergoing a disproportionation reaction,
the refrigerant circuit including refrigerant shutoff mechanisms (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), wherein the refrigerant shutoff mechanisms are provided by a gas-side refrigerant shutoff mechanism and a liquid-side refrigerant shutoff mechanism,
characterized in that the control unit (<NUM>; <NUM>) is configured to shut off a flow of the refrigerant from the outdoor unit side to the indoor unit side when the refrigerant in a portion of the refrigerant circuit within the outdoor unit meets a condition for the disproportionation reaction to occur.