Patent Description:
In a refrigeration cycle using a refrigerant circuit including a compressor, a heat source-side heat exchanger, an expansion valve, and a usage-side heat exchanger that are interconnected, heretofore, a refrigerant leak has sometimes occurred at the usage-side heat exchanger and its vicinity for any reason.

In this respect, for example, Patent Literature <NUM> (<CIT>) discloses a technique of, upon detection of a refrigerant leak, controlling a compressor and valves to automatically operate a pump down operation, and recovering a refrigerant into the heat source-side heat exchanger, thereby suppressing the refrigerant leak into a space where a usage-side heat exchanger is placed, as much as possible. The content of the earlier application <CIT> as filed is comprised in the state of the art according to Article <NUM>(<NUM>) EPC.

This earlier application shows a refrigeration apparatus with a plurality of usage units wherein when one of the usage units is in a refrigerant leak situation, the control unit closes a usage-side valve of the leak unit and continues to open a usage-side valve of the non-leak units and performs pressure control to reduce a refrigerant pressure at a portion on the side of the liquid-refrigerant connection pipe with respect to each usage-side valve below a refrigerant pressure at the portion at the time when the leak unit is detected.

Document <CIT>discloses a refrigeration apparatus comprising a plurality of usage units wherein when the leakage of refrigerant is detected, the apparatus operates with the usage-side valves all closed.

As to a refrigerant circuit including a plurality of usage-side heat exchangers that are interconnected, for example, if a refrigerant leak occurs at one of the usage-side heat exchangers, it has been considered to close a valve on a passage for supplying a refrigerant to the usage-side heat exchanger at which the refrigerant leak occurs, and to allow the refrigerant to continuously circulate through the remaining usage-side heat exchangers at which no refrigerant leak occurs.

This configuration suppresses the refrigerant leak at the leak spot, and continues temperature control by the remaining usage-side heat exchangers at which no refrigerant leak occurs.

In the case of closing the valve on the passage for supplying the refrigerant to the usage-side heat exchanger at which the refrigerant leak occurs, however, the valve may not be completely closed, resulting in a slight clearance at the valve. In such a case, when the compressor is continuously driven after the occurrence of the refrigerant leak, a refrigerant pressure is continuously applied to the closed valve, which may allow the refrigerant to pass through the clearance at the valve. The amount of the refrigerant passing through the clearance at the valve increases as the refrigerant pressure to be applied to the valve is high.

In view of the aspects described above, the present invention provides a refrigeration apparatus capable of, even in occurrence of a refrigerant leak, suppressing the extent of the refrigerant leak in continuously operating a usage unit other than a usage unit at which the refrigerant leak occurs.

The invention solves the problem by means of three alternative solutions defined respectively by the features of the refrigeration apparatus according to one of the appended independent claims <NUM>, <NUM> or <NUM>.

Examples of the case where the refrigerant leak situation satisfies the predetermined condition according to appended claims <NUM>, <NUM> or <NUM> may include, but not limited to, a case where a sensor detects that a leakage refrigerant concentration in a usage unit is equal to or more than a predetermined concentration, and a case where a sensor detects a change or reduction in value of a pressure or temperature of a portion, through which a refrigerant flows, of a usage unit.

In the apparatuses according to appended claims <NUM>, <NUM> or <NUM>, when one of the usage units is in a refrigerant leak situation satisfying the predetermined condition, the control unit closes the usage-side valve of the leak unit. This configuration makes the refrigerant discharged from the compressor and passing through the heat source-side heat exchanger hard to flow toward the usage-side heat exchanger of the leak unit via the usage-side valve, and reduces the leakage of the refrigerant from the leak unit.

In addition, the control unit continues to open the usage-side valve of the non-leak unit operated. This configuration avoids circulation of the refrigerant in the leak unit, but allows circulation of the refrigerant in the usage-side heat exchanger of the non-leak unit. Consequently, the usage-side heat exchanger is continuously used as an evaporator for the refrigerant. This configuration therefore causes the non-leak unit to continuously cool a target to be cooled.

In a typical usage-side valve, the valve may not be completely closed even in a fully closed state, and may be slightly opened as unintended in some instances. If the valve is slightly opened as unintended, the refrigerant may pass through the usage-side valve of the leak unit to flow toward the usage-side heat exchanger, so that the refrigerant leak lasts as unintended. The leakage of the refrigerant passing through the usage-side valve of the leak unit tends to increase when a refrigerant pressure at the usage-side valve of the leak unit on the side of the liquid-refrigerant connection pipe is high. In allowing continuous circulation of the refrigerant in the non-leak unit, since the non-leak unit and the leak unit are connected to the heat source unit in parallel, the refrigerant pressure is continuously applied to the usage-side valve of the leak unit on the side of the liquid-refrigerant connection pipe.

In this respect, in the refrigeration apparatus according to appended claims <NUM>, <NUM> or <NUM> the control unit performs the pressure control to reduce the refrigerant pressure at each usage-side valve on the side of the liquid-refrigerant connection pipe below the refrigerant pressure at the time when the leak unit satisfies the predetermined condition. This configuration therefore reduces the leakage of the refrigerant passing through the usage-side valve of the leak unit while allowing continuous circulation of the refrigerant in the non-leak unit even when the usage-side valve of the leak unit is slightly opened as unintended.

The refrigeration apparatus thus suppresses, even in occurrence of a refrigerant leak, the extent of the refrigerant leak in continuously operating a usage unit other than a usage unit at which the refrigerant leak occurs.

According to the first alternative solution defined by the refrigeration apparatus comprising the features of appended claim <NUM>, the heat source unit includes a heat source-side expansion valve configured to reduce a pressure of the refrigerant radiating heat in the heat source-side heat exchanger. The control unit performs the pressure control by controlling the heat source-side expansion valve such that an extent of decompression in the heat source-side expansion valve after the leak unit has satisfied the predetermined condition is greater than an extent of decompression in the heat source-side expansion valve at the time when the leak unit satisfies the predetermined condition.

In this tlw refrigeration apparatus, the control unit performs the pressure control using the heat source-side expansion valve, thereby reducing the pressure of the refrigerant flowing toward the usage-side heat exchanger after the heat radiation in the heat source-side heat exchanger. This configuration eliminates a necessity of significantly reducing the pressure of the refrigerant flowing through the heat source-side heat exchanger serving as a radiator.

According to a further embodiment of the first alternative solution defined by the refrigeration apparatus comprising the features of appended claim <NUM>, the refrigeration apparatus further includes a subcooling pipe, a subcooling expansion valve, and a subcooling heat exchanger. The subcooling pipe is configured to shunt the refrigerant radiating heat in the heat source-side heat exchanger, from a refrigerant passage through which the refrigerant flows toward each of the usage units, and is configured to guide the refrigerant to the compressor. The subcooling expansion valve is disposed at a middle of the subcooling pipe and is configured to decompress the refrigerant passing therethrough. The subcooling heat exchanger is configured to cause the refrigerant decompressed by the subcooling expansion valve, of the refrigerant flowing through the subcooling pipe, to exchange heat with the refrigerant flowing through the refrigerant passage.

Guiding the refrigerant to the compressor may involve guiding the refrigerant to a suction side of the compressor, and guiding the refrigerant to the compressor in an intermediate state of a compression process.

The refrigeration apparatus subcools the refrigerant flowing toward the heat source-side expansion valve. This configuration therefore suppresses a flush of the refrigerant flowing from the heat source-side expansion valve toward the non-leak unit even when the control unit performs the pressure control by reducing the pressure of the refrigerant which has passed through the heat source-side heat exchanger, using the heat source-side expansion valve.

According to the second alternative solution defined by the refrigeration apparatus comprising the features of appended claim <NUM>, the control unit performs the pressure control by controlling the compressor such that a driving frequency of the compressor after the leak unit has satisfied the predetermined condition is lower than a driving frequency of the compressor at the time when the leak unit satisfies the predetermined condition.

In this tlw refrigeration apparatus, the control unit lowers the driving frequency of the compressor, thereby easily reducing the refrigerant pressure at each usage-side valve on the side of the liquid-refrigerant connection pipe.

According to the third alternative solution defined by the refrigeration apparatus comprising the features of appended claim <NUM>, the heat source unit further includes a heat source-side fan configured to provide an air flow for the heat source-side heat exchanger. The control unit performs the pressure control by controlling the heat source-side fan such that an airflow volume of the heat source-side fan after the leak unit has satisfied the predetermined condition is larger than an airflow volume of the heat source-side fan at the time when the leak unit satisfies the predetermined condition.

In this refrigeration apparatus, the control unit increases the airflow volume of the heat source-side fan, thereby easily reducing the refrigerant pressure at each usage-side valve on the side of the liquid-refrigerant connection pipe.

The refrigeration apparatus according to to appended claims <NUM>, <NUM> or <NUM> suppresses, even in occurrence of a refrigerant leak, the extent of the refrigerant leak in continuously operating a usage unit other than a usage unit at which the refrigerant leak occurs.

The refrigeration apparatus according to the first alternative solution eliminates a necessity of significantly reducing a pressure of the refrigerant flowing through the heat source-side heat exchanger serving as a radiator.

The refrigeration apparatus according to the further embodiment of the first alternative solution suppresses a flush of the refrigerant flowing from the heat source-side expansion valve toward a non-leak unit.

The refrigeration apparatus according to the second alternative solution easily reduces a refrigerant pressure at each usage-side valve on the side of the liquid-refrigerant connection pipe.

The refrigeration apparatus according to the third alternative solution increases an airflow volume of the heat source-side fan, thereby easily reducing a refrigerant pressure at each usage-side valve on the side of the liquid-refrigerant connection pipe.

A refrigeration apparatus <NUM> according to an embodiment of the present invention will be described below with reference to the drawings. It should be noted that the following embodiments are merely specific examples of the present invention, do not intend to limit the technical scope of the present invention, and may be appropriately modified without departing from the scope of the appended claims.

<FIG> is a schematic configuration diagram of a refrigeration apparatus <NUM> according to an embodiment of the first alternative solution of the present invention. The refrigeration apparatus <NUM> employs a vapor compression refrigeration cycle to cool a usage-side space such as the interior of a cold storage warehouse or the interior of a showcase in a store.

The refrigeration apparatus <NUM> mainly includes: a heat source unit <NUM>; a plurality of (two in this embodiment) usage units, that is, a first usage unit <NUM> and a second usage unit <NUM>; a liquid-refrigerant connection pipe <NUM> and a gas-refrigerant connection pipe <NUM> each connecting the heat source unit <NUM> to the first usage unit <NUM> and the second usage unit <NUM>; a refrigerant leak sensor configured to detect a refrigerant leak in a corresponding one of the usage units, that is, a first refrigerant leak sensor <NUM> configured to detect a refrigerant leak in the first usage unit <NUM>, and a second refrigerant leak sensor <NUM> configured to detect a refrigerant leak in the second usage unit <NUM>; a plurality of remote controllers, that is, a first remote controller 50a and a second remote controller 60a each functioning as an input device and a display device; and a controller <NUM> configured to control operation of the refrigeration apparatus <NUM>.

In the refrigeration apparatus <NUM>, the heat source unit <NUM> as well as the first usage unit <NUM> and the second usage unit <NUM> connected to the heat source unit <NUM> in parallel via the liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM> constitute a refrigerant circuit <NUM>. The refrigeration apparatus <NUM> performs a refrigeration cycle to compress, cool or condense, decompress, heat or evaporate, and then compress again a sealed-in refrigerant in the refrigerant circuit <NUM>. In this embodiment, the refrigerant circuit <NUM> is filled with R32 as a refrigerant for a vapor compression refrigeration cycle.

The heat source unit <NUM>, to which the first usage unit <NUM> and the second usage unit <NUM> are connected in parallel via the liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM>, constitutes a part of the refrigerant circuit <NUM>. The heat source unit <NUM> mainly includes a compressor <NUM>, a heat source-side heat exchanger <NUM>, a heat source-side fan <NUM>, a receiver <NUM>, a subcooler <NUM>, a heat source-side expansion valve <NUM>, a hot gas bypass pipe <NUM>, a hot gas bypass valve <NUM>, an injection pipe <NUM>, an injection valve <NUM>, a liquid-side shutoff valve <NUM>, and a gas-side shutoff valve <NUM>.

The heat source unit <NUM> also includes a discharge-side refrigerant pipe <NUM>, a heat source-side liquid refrigerant pipe <NUM>, and a suction-side refrigerant pipe <NUM>. The discharge-side refrigerant pipe <NUM> connects a discharge side of the compressor <NUM> to a gas-side end of the heat source-side heat exchanger <NUM>. The heat source-side liquid refrigerant pipe <NUM> connects a liquid-side end of the heat source-side heat exchanger <NUM> to the liquid-refrigerant connection pipe <NUM>. The suction-side refrigerant pipe <NUM> connects a suction side of the compressor <NUM> to the gas-refrigerant connection pipe <NUM>.

The heat source unit <NUM> includes: the hot gas bypass pipe <NUM> configured to shunt part of the refrigerant flowing through the discharge-side refrigerant pipe <NUM> back to the suction side of the compressor <NUM> via the suction-side refrigerant pipe <NUM>; and the hot gas bypass valve <NUM> disposed at the middle of the hot gas bypass pipe <NUM>.

The heat source unit <NUM> includes: the injection pipe <NUM> (a subcooling pipe) configured to shunt part of the refrigerant flowing through the heat source-side liquid refrigerant pipe <NUM> back to the compressor <NUM>; and the injection valve <NUM> (a subcooling expansion valve) disposed at the middle of the injection pipe <NUM>. The injection pipe <NUM> branches off the heat source-side liquid refrigerant pipe <NUM> at a portion downstream of the subcooler <NUM>, passes through the subcooler <NUM>, and is connected to the compressor <NUM> in an intermediate state of a compression process.

The compressor <NUM> is a device configured to change by compression a low-pressure refrigerant to a high-pressure refrigerant in the refrigeration cycle. The compressor <NUM> used herein is a closed compressor in which a displacement compression element, such as rotary or scroll, (not illustrated) is driven to rotate by a compressor motor M21. Although not illustrated in the drawings, the compressor <NUM> in this embodiment includes one or more constant-speed compressors and a variable displacement compressor that are connected in parallel. The variable displacement compressor includes the compressor motor M21 and has an operating frequency controllable by an inverter. In decreasing the capacity of the compressor <NUM>, the operating frequency of the variable displacement compressor is lowered. In further decreasing the capacity of the variable displacement compressor even though the operating frequency of the variable displacement compressor has been lowered, the constant-speed compressors are stopped. However, the method of decreasing the capacity is not limited thereto.

The heat source-side heat exchanger <NUM> functions as a radiator for the high-pressure refrigerant in the refrigeration cycle. The heat source unit <NUM> includes the heat source-side fan <NUM> for sucking outside air (heat source-side air) into the heat source unit <NUM>, causing the heat source-side air to exchange heat with the refrigerant in the heat source-side heat exchanger <NUM>, and then discharging the heat source-side air to the outside. The heat source-side fan <NUM> is configured to supply to the heat source-side heat exchanger <NUM> the heat source-side air for cooling the refrigerant flowing through the heat source-side heat exchanger <NUM>. The heat source-side fan <NUM> is driven to rotate by a heat source-side fan motor M34. The heat source-side fan <NUM> has an airflow volume controlled by adjusting the number of rotations of the heat source-side fan motor M34.

The receiver <NUM> temporarily stores therein the refrigerant condensed in the heat source-side heat exchanger <NUM>. The receiver <NUM> is disposed at the middle of the heat source-side liquid refrigerant pipe <NUM>.

The subcooler <NUM> is a heat exchanger for further cooling the refrigerant temporarily stored in the receiver <NUM>. The subcooler <NUM> is disposed on the heat source-side liquid refrigerant pipe <NUM>. Specifically, the subcooler <NUM> is disposed downstream of the receiver <NUM>.

The heat source-side expansion valve <NUM> is an electric expansion valve whose opening degree is controllable. The heat source-side expansion valve <NUM> is disposed on the heat source-side liquid refrigerant pipe <NUM>. Specifically, the heat source-side expansion valve <NUM> is disposed downstream of the subcooler <NUM>.

The injection valve <NUM> is disposed on the injection pipe <NUM>. Specifically, the injection valve <NUM> is disposed between a branched portion of the heat source-side liquid refrigerant pipe <NUM> and an inlet of the subcooler <NUM>. The injection valve <NUM> is an electric expansion valve whose opening degree is controllable. The injection valve <NUM> decompresses, in accordance with its opening degree, the refrigerant flowing through the injection pipe <NUM> before the refrigerant flows into the subcooler <NUM>.

The liquid-side shutoff valve <NUM> is a manual valve disposed at a joint between the heat source-side liquid refrigerant pipe <NUM> and the liquid-refrigerant connection pipe <NUM>.

The gas-side shutoff valve <NUM> is a manual valve disposed at a joint between the suction-side refrigerant pipe <NUM> and the gas-refrigerant connection pipe <NUM>.

The heat source unit <NUM> includes various sensors. In the heat source unit <NUM>, specifically, a suction pressure sensor <NUM> and a discharge pressure sensor <NUM> are disposed around the compressor <NUM>. The suction pressure sensor <NUM> is configured to detect a suction pressure that is a pressure of the refrigerant at the suction side of the compressor <NUM>. The discharge pressure sensor <NUM> is configured to detect a discharge pressure that is a pressure of the refrigerant at the discharge side of the compressor <NUM>. On the heat source-side liquid refrigerant pipe <NUM>, a receiver outlet temperature sensor <NUM> is disposed between an outlet of the receiver <NUM> and the inlet of the subcooler <NUM>. The receiver outlet temperature sensor <NUM> is configured to detect a receiver outlet temperature that is a temperature of the refrigerant at the outlet of the receiver <NUM>. Moreover, a heat source-side air temperature sensor <NUM> is disposed around the heat source-side heat exchanger <NUM> or the heat source-side fan <NUM>. The heat source-side air temperature sensor <NUM> is configured to detect a temperature of heat source-side air to be sucked into the heat source unit <NUM>.

The heat source unit <NUM> also includes a heat source unit control unit <NUM> configured to control operations of the respective components constituting the heat source unit <NUM>. The heat source unit control unit <NUM> includes a microcomputer including, for example, a central processing unit (CPU) and a memory. The heat source unit control unit <NUM> is connected to a first usage unit control unit <NUM> of the first usage unit <NUM> and a second usage unit control unit <NUM> of the second usage unit <NUM> via a communication line to exchange, for example, a control signal with the first usage unit control unit <NUM> and the second usage unit control unit <NUM>.

The first usage unit <NUM> is connected to the heat source unit <NUM> via the liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM>, and constitutes a part of the refrigerant circuit <NUM>.

The first usage unit <NUM> includes a first usage-side expansion valve <NUM> and a first usage-side heat exchanger <NUM>. The first usage unit <NUM> also includes: a first usage-side liquid refrigerant pipe <NUM> connecting a liquid-side end of the first usage-side heat exchanger <NUM> to the liquid-refrigerant connection pipe <NUM>; and a first usage-side gas refrigerant pipe <NUM> connecting a gas-side end of the first usage-side heat exchanger <NUM> to the gas-refrigerant connection pipe <NUM>.

The first usage-side expansion valve <NUM> is a restrictor functioning as means for decompressing the refrigerant to be supplied from the heat source unit <NUM>. In this embodiment, the first usage-side expansion valve <NUM> is a thermostatic expansion valve including a feeler bulb, and operates in accordance with a change in temperature of the feeler bulb. In other words, the first usage-side expansion valve <NUM> has an opening degree automatically set in accordance with a change in temperature of the feeler bulb.

The first usage-side heat exchanger <NUM> functions as an evaporator for the low-pressure refrigerant in the refrigeration cycle to cool inside air (usage-side air). In this embodiment, the first usage unit <NUM> is used for cooling the interior of a door-equipped case such as a reach-in case; however, the use of the first usage unit <NUM> is not limited thereto.

The first usage unit <NUM> includes a first usage-side fan <NUM> for sucking usage-side air into the first usage unit <NUM>, causing the usage-side air to exchange heat with the refrigerant in the first usage-side heat exchanger <NUM>, and then supplying the usage-side air to the usage-side space. The first usage-side fan <NUM> is configured to supply to the first usage-side heat exchanger <NUM> the usage-side air for heating the refrigerant flowing through the first usage-side heat exchanger <NUM>. The first usage-side fan <NUM> is driven to rotate by a first usage-side fan motor M53.

The first usage unit <NUM> also includes a first on-off valve <NUM> configured to interrupt an inflow of the refrigerant into the first usage unit <NUM>. The first on-off valve <NUM> is disposed on the side of a liquid refrigerant inlet (the liquid-refrigerant connection pipe <NUM> side) of the first usage unit <NUM>. Specifically, the first on-off valve <NUM> is disposed closer to the liquid refrigerant inlet than the first usage-side heat exchanger <NUM> is. More specifically, the first on-off valve <NUM> is disposed closer to the liquid refrigerant inlet than the first usage-side expansion valve <NUM> is. In this embodiment, the first on-off valve <NUM> is an electromagnetic valve whose open state and closed state are switchable. The first on-off valve <NUM> is switched to the closed state so as to interrupt an inflow of the refrigerant into the first usage unit <NUM>, more specifically into the first usage-side heat exchanger <NUM>. However, even the first on-off valve <NUM> is in the fully closed state, the valve opening degree may not be completely closed, and may be slightly opened as unintended in some instances. The first on-off valve <NUM> is normally in the open state.

The first usage unit <NUM> also includes a first check valve <NUM> configured to interrupt an inflow, that is, a backflow of the refrigerant into the first usage unit <NUM> through an outlet of the first usage unit <NUM>. The first check valve <NUM> is disposed on the gas refrigerant outlet (the gas-refrigerant connection pipe <NUM> side) of the first usage unit <NUM>. Specifically, the first check valve <NUM> is disposed closer to the gas refrigerant outlet than the first usage-side heat exchanger <NUM> is. The first check valve <NUM> permits a flow of the refrigerant from the first usage-side gas refrigerant pipe <NUM> toward the gas-refrigerant connection pipe <NUM>. On the other hand, the first check valve <NUM> interrupts a flow of the refrigerant from the gas-refrigerant connection pipe <NUM> toward the first usage-side gas refrigerant pipe <NUM>, more specifically toward a portion closer to the first usage-side heat exchanger <NUM> than the first check valve <NUM> is.

The first usage unit <NUM> also includes a first usage unit control unit <NUM> configured to control operations of the respective components constituting the first usage unit <NUM>. The first usage unit control unit <NUM> includes a microcomputer including, for example, a CPU and a memory. The first usage unit control unit <NUM> is connected to the heat source unit control unit <NUM> via the communication line to exchange, for example, a control signal with the heat source unit control unit <NUM>. The first usage unit control unit <NUM> is electrically connected to the first refrigerant leak sensor <NUM> to receive a signal from the first refrigerant leak sensor <NUM>.

The second usage unit <NUM> is similar in configuration to the first usage unit <NUM>. The second usage unit <NUM> is also connected to the heat source unit <NUM> via the liquid-refrigerant connection pipe <NUM> and the gas-refrigerant connection pipe <NUM>, and constitutes a part of the refrigerant circuit <NUM>. The second usage unit <NUM> and the first usage unit <NUM> are connected in parallel.

The second usage unit <NUM> includes a second usage-side expansion valve <NUM> and a second usage-side heat exchanger <NUM>. The second usage unit <NUM> also includes: a second usage-side liquid refrigerant pipe <NUM> connecting a liquid-side end of the second usage-side heat exchanger <NUM> to the liquid-refrigerant connection pipe <NUM>; and a second usage-side gas refrigerant pipe <NUM> connecting a gas-side end of the second usage-side heat exchanger <NUM> to the gas-refrigerant connection pipe <NUM>.

The second usage-side expansion valve <NUM> is a restrictor functioning as means for decompressing the refrigerant to be supplied from the heat source unit <NUM>. In this embodiment, as in the first usage-side expansion valve <NUM>, the second usage-side expansion valve <NUM> is a thermostatic expansion valve including a feeler bulb, and operates in accordance with a change in temperature of the feeler bulb. In other words, the second usage-side expansion valve <NUM> has an opening degree automatically set in accordance with a change in temperature of the feeler bulb.

The second usage-side heat exchanger <NUM> functions as an evaporator for the low-pressure refrigerant in the refrigeration cycle to cool inside air (usage-side air). In this embodiment, the second usage unit <NUM> is used for cooling the interior of a doorless case with a large upper open end, such as an open case; however, the use of the second usage unit <NUM> is not limited thereto.

As in the first usage unit <NUM>, the second usage unit <NUM> also includes a second usage-side fan <NUM> to be driven to rotate by a second usage-side fan motor M63.

The second usage unit <NUM> also includes a second on-off valve <NUM> configured to interrupt an inflow of the refrigerant into the second usage unit <NUM>. The second on-off valve <NUM> is disposed on the side of a liquid refrigerant inlet (the liquid-refrigerant connection pipe <NUM> side) of the second usage unit <NUM>. Specifically, the second on-off valve <NUM> is disposed closer to the liquid refrigerant inlet than the second usage-side heat exchanger <NUM> is. More specifically, the second on-off valve <NUM> is disposed closer to the liquid refrigerant inlet than the second usage-side expansion valve <NUM> is. In this embodiment, the second on-off valve <NUM> is an electromagnetic valve whose open state and closed state are switchable. The second on-off valve <NUM> is switched to the closed state so as to interrupt an inflow of the refrigerant into the second usage unit <NUM>, more specifically into the second usage-side heat exchanger <NUM>. However, even the second on-off valve <NUM> is in the fully closed state, the valve may not be completely closed, and may be slightly opened as unintended in some instances. The second on-off valve <NUM> is normally in the open state.

The second usage unit <NUM> also includes a second check valve <NUM> configured to interrupt an inflow, that is, a backflow of the refrigerant flowing into the second usage unit <NUM> through an outlet of the second usage unit <NUM>. The second check valve <NUM> is disposed on the side of the gas refrigerant outlet (the gas-refrigerant connection pipe <NUM> side) of the second usage unit <NUM>. Specifically, the second check valve <NUM> is disposed closer to the gas refrigerant outlet than the second usage-side heat exchanger <NUM> is. The second check valve <NUM> permits a flow of the refrigerant from the second usage-side gas refrigerant pipe <NUM> toward the gas-refrigerant connection pipe <NUM>. On the other hand, the second check valve <NUM> interrupts a flow of the refrigerant from the gas-refrigerant connection pipe <NUM> toward the second usage-side gas refrigerant pipe <NUM>, more specifically toward the second usage-side heat exchanger <NUM> from the second check valve <NUM>.

The second usage unit <NUM> also includes a second usage unit control unit <NUM> configured to control operations of the respective components constituting the second usage unit <NUM>. The second usage unit control unit <NUM> includes a microcomputer including, for example, a CPU and a memory. The second usage unit control unit <NUM> is connected to the heat source unit control unit <NUM> via the communication line to exchange, for example, a control signal with the heat source unit control unit <NUM>. The second usage unit control unit <NUM> is electrically connected to the second refrigerant leak sensor <NUM> to receive a signal from the second refrigerant leak sensor <NUM>.

The first refrigerant leak sensor <NUM> is configured to detect a refrigerant leak in the first usage unit <NUM>. The second refrigerant leak sensor <NUM> is configured to detect a refrigerant leak in the second usage unit <NUM>. The first refrigerant leak sensor <NUM> is disposed in a casing of the first usage unit <NUM>. The second refrigerant leak sensor <NUM> is disposed in a casing of the second usage unit <NUM>. Each of the first refrigerant leak sensor <NUM> and the second refrigerant leak sensor <NUM> to be used in this embodiment is a well-known general-purpose product.

Upon detection of a refrigerant leak, the first refrigerant leak sensor <NUM> (or the second refrigerant leak sensor <NUM>) outputs an electric signal (hereinafter, referred to as a "refrigerant leak signal") indicative of occurrence of the refrigerant leak, to the first usage unit control unit <NUM> (or the second usage unit control unit <NUM>) connected thereto.

The first remote controller 50a is an input device that causes a user of the first usage unit <NUM> to input various instructions for switching an operating state of the refrigeration apparatus <NUM>. The first remote controller 50a also functions as a display device for displaying the operating state of the refrigeration apparatus <NUM> and predetermined notification information. The first remote controller 50a is connected to the first usage unit control unit <NUM> via a communication line to exchange signals with the first usage unit control unit <NUM>.

As in the first remote controller 50a, the second remote controller 60a is an input device that causes a user of the second usage unit <NUM> to input various instructions for switching an operating state of the refrigeration apparatus <NUM>, and a display device for displaying the operating state of the refrigeration apparatus <NUM> and predetermined notification information. The second remote controller 60a is connected to the second usage unit control unit <NUM> via a communication line to exchange signals with the second usage unit control unit <NUM>.

In the refrigeration apparatus <NUM>, the heat source unit control unit <NUM>, the first usage unit control unit <NUM>, and the second usage unit control unit <NUM> are connected via the communication lines to constitute the controller <NUM> for controlling operation of the refrigeration apparatus <NUM>.

<FIG> is a schematic block diagram of a schematic configuration of the controller <NUM> and the components connected to the controller <NUM>.

The controller <NUM> has a plurality of control modes, and controls the operation of the refrigeration apparatus <NUM> in accordance with a control mode in which the controller <NUM> is to be stated. Examples of the control modes of the controller <NUM> include: a normal operating mode in which the controller <NUM> is stated in a normal situation; and a refrigerant leak control mode in which the controller <NUM> is stated upon occurrence of a refrigerant leak.

The controller <NUM> is electrically connected to the actuators (i.e., the compressor <NUM> (the compressor motor M21), the heat source-side expansion valve <NUM>, the injection valve <NUM>, the hot gas bypass valve <NUM>, and the heat source-side fan <NUM> (the heat source-side fan motor M34)) and the various sensors (i.e., the suction pressure sensor <NUM>, the discharge pressure sensor <NUM>, the receiver outlet temperature sensor <NUM>, the heat source-side air temperature sensor <NUM>, and the like) in the heat source unit <NUM>. The controller <NUM> is also electrically connected to the actuators (i.e., the first usage-side fan <NUM> (the first usage-side fan motor M53), the first usage-side expansion valve <NUM>, and the first on-off valve <NUM>) in the first usage unit <NUM>. The controller <NUM> is also electrically connected to the actuators (i.e., the second usage-side fan <NUM> (the second usage-side fan motor M63), the second usage-side expansion valve <NUM>, and the second on-off valve <NUM>) in the second usage unit <NUM>. The controller <NUM> is also electrically connected to the first refrigerant leak sensor <NUM>, the second refrigerant leak sensor <NUM>, the first remote controller 50a, and the second remote controller 60a.

The controller <NUM> mainly includes a storage unit <NUM>, a communication unit <NUM>, a mode control unit <NUM>, an actuator control unit <NUM>, and a display control unit <NUM>. These units in the controller <NUM> are implemented in such a manner that the components in the heat source unit control unit <NUM> and/or each of the first usage unit control unit <NUM> and the second usage unit control unit <NUM> integrally function.

The storage unit <NUM> includes, for example, a read only memory (ROM), a random access memory (RAM), and a flash memory. The storage unit <NUM> has a volatile storage region and a nonvolatile storage region. The storage unit <NUM> stores therein a control program that defines processing to be performed by each unit of the controller <NUM>. Also in the storage unit <NUM>, the respective units of the controller <NUM> appropriately store predetermined information (e.g., values detected by the respective sensors, commands input to the first remote controller 50a, commands input to the second remote controller 60a) in a predetermined storage region.

The communication unit <NUM> is a functional unit that plays a role as a communication interface for exchanging signals with the respective components connected to the controller <NUM>. The communication unit <NUM> receives a request from the actuator control unit <NUM>, and transmits a predetermined signal to a designated one of the actuators. The communication unit <NUM> also receives signals from the various sensors <NUM> to <NUM>, the first refrigerant leak sensor <NUM>, the second refrigerant leak sensor <NUM>, the first remote controller 50a, and the second remote controller 60a, and stores the received signals in the predetermined storage region of the storage unit <NUM>.

The mode control unit <NUM> is a functional unit that switches a control mode, for example. In a state in which none of the first refrigerant leak sensor <NUM> and the second refrigerant leak sensor <NUM> detects a refrigerant leak, the mode control unit <NUM> sets the control mode at the normal operating mode.

When one of the first refrigerant leak sensor <NUM> and the second refrigerant leak sensor <NUM> detects a refrigerant leak, the mode control unit <NUM> switches the control mode to the refrigerant leak control mode according to the sensor, which has detected the refrigerant leak, of the first refrigerant leak sensor <NUM> and the second refrigerant leak sensor <NUM>.

The actuator control unit <NUM> controls, on the basis of the control program, the operations of the respective actuators (e.g., the compressor <NUM>, a first on-off valve <NUM> and a second on-off valve <NUM>) in the refrigeration apparatus <NUM>, in accordance with a situation.

In the normal operating mode, for example, the actuator control unit <NUM> controls the number of rotations of the compressor <NUM>, the number of rotations of the heat source-side fan <NUM>, the number of rotations of the first usage-side fan <NUM>, the number of rotations of the second usage-side fan <NUM>, and the opening degree of the injection valve <NUM> in real time, in accordance with, for example, set temperatures and values detected by the various sensors. In the normal operating mode, the actuator control unit <NUM> brings the heat source-side expansion valve <NUM> into the fully open state. Also in the normal operating mode, the actuator control unit <NUM> sets a target value of a suction pressure in accordance with cooling loads to be required for the first usage unit <NUM> and the second usage unit <NUM>, and controls the operating frequency of the compressor <NUM> so as to acquire the suction pressure with the target value. Also in the normal operating mode, the actuator control unit <NUM> brings the hot gas bypass valve <NUM> into the fully closed state to interrupt an inflow of the refrigerant into the hot gas bypass pipe <NUM>.

In the refrigerant leak control mode, the actuator control unit <NUM> controls operations of the respective actuators so as to perform a predetermined operation. Specifically, as in the normal operating mode, the actuator control unit <NUM> continuously controls the operating frequency of the compressor <NUM> so as to acquire the suction pressure with the target value. In order to stop supply of the refrigerant to the usage unit at which the refrigerant leak occurs (hereinafter, referred to as a "leak unit") of the first usage unit <NUM> and the second usage unit <NUM>, the actuator control unit <NUM> closes the on-off valve (i.e., the first on-off valve <NUM> or the second on-off valve <NUM>). On the other hand, in order to continue a cooling operation using the heat exchanger of the usage unit at which no refrigerant leak occurs (hereinafter, referred to as a "non-leak unit") of the first usage unit <NUM> and the second usage unit <NUM>, the actuator control unit <NUM> opens the on-off valve (i.e., the first on-off valve <NUM> or the second on-off valve <NUM>). The actuator control unit <NUM> maintains a driven state of the compressor <NUM> immediately after detection of the refrigerant leak as described above. However, in order to reliably suppress a reduction in suction pressure such that the refrigerant pressure on the suction side of the compressor <NUM> with respect to the check valve (i.e., the first check valve <NUM> or the second check valve <NUM>) of the leak unit is maintained to be higher than the refrigerant pressure at the check valve of the leak unit or on the side of the usage-side heat exchanger of the leak unit, the actuator control unit <NUM> causes the pressure of the high-pressure refrigerant on the discharge side of the compressor <NUM> to be applied to the suction side of the compressor <NUM> with respect to the check valve of the leak unit. In other words, the actuator control unit <NUM> opens the hot gas bypass valve <NUM>. In the refrigerant leak control mode, the actuator control unit <NUM> lowers the opening degree of the heat source-side expansion valve <NUM> so as to reduce the pressure of the refrigerant flowing through the downstream side of the heat source-side expansion valve <NUM>.

The display control unit <NUM> is a functional unit that controls operations of the first remote controller 50a and the second remote controller 60a each serving as the display device.

The display control unit <NUM> causes each of the first remote controller 50a and the second remote controller 60a to output predetermined information in order that an operating state or information on a situation are displayed for an administrator.

For example, the display control unit <NUM> causes each of the first remote controller 50a and the second remote controller 60a to display thereon various kinds of information, such as set temperatures, during the cooling operation in the normal operating mode.

The display control unit <NUM> also causes each of the first remote controller 50a and the second remote controller 60a to display thereon information specifically indicating occurrence of a refrigerant leak and a usage unit, at which the refrigerant leak occurs, of the first usage unit <NUM> and the second usage unit <NUM>, in the refrigerant leak control mode. The display control unit <NUM> also causes each of the first remote controller 50a and the second remote controller 60a to display thereon notification information indicating that a non-leak unit, which is an operable usage unit at which no refrigerant leak occurs, is continuously operated, and information urging a user to make a notification to a service engineer, in the refrigerant leak control mode.

Next, a description will be given of the flow of the refrigerant in the refrigerant circuit <NUM> in the normal operating mode.

During the operation, the refrigeration apparatus <NUM> performs the cooling operation (a refrigeration cycle operation) causing the refrigerant in the refrigerant circuit <NUM> to mainly circulate through the compressor <NUM>, the heat source-side heat exchanger <NUM>, the receiver <NUM>, the subcooler <NUM>, the heat source-side expansion valve <NUM>, the usage-side expansion valves <NUM>, <NUM>, and the usage-side heat exchangers <NUM>, <NUM> in this order.

When the cooling operation is started, the refrigerant is sucked into and compressed by the compressor <NUM>, and then is discharged from the compressor <NUM>, in the refrigerant circuit <NUM>. In the cooling operation, the low pressure in the refrigeration cycle corresponds to the suction pressure to be detected by the suction pressure sensor <NUM>, and the high pressure in the refrigeration cycle corresponds to the discharge pressure to be detected by the discharge pressure sensor <NUM>.

The compressor <NUM> is subjected to capacity control according to the cooling load to be required for each of the first usage unit <NUM> and the second usage unit <NUM>. Specifically, the operating frequency of the compressor <NUM> is controlled such that the suction pressure takes a target value set in accordance with the cooling load to be required for each of the first usage unit <NUM> and the second usage unit <NUM>.

The gas refrigerant discharged from the compressor <NUM> flows into the heat source-side heat exchanger <NUM> through the gas-side end of the heat source-side heat exchanger <NUM>, via the discharge-side refrigerant pipe <NUM>.

In the normal operating mode, the hot gas bypass valve <NUM> is brought into the fully closed state to interrupt an inflow of the refrigerant into the hot gas bypass pipe <NUM>.

When the gas refrigerant flows into the heat source-side heat exchanger <NUM> through the gas-side end of the heat source-side heat exchanger <NUM>, the heat source-side heat exchanger <NUM> causes the gas refrigerant to exchange heat with the heat source-side air supplied by the heat source-side fan <NUM>, thereby radiating heat, and then condenses the gas refrigerant to turn the gas refrigerant into the liquid refrigerant. The liquid refrigerant flows out of the heat source-side heat exchanger <NUM> through the liquid-side end of the heat source-side heat exchanger <NUM>.

When the liquid refrigerant flows out of the heat source-side heat exchanger <NUM> through the liquid-side end of the heat source-side heat exchanger <NUM>, then the liquid refrigerant flows into the receiver <NUM> through the inlet of the receiver <NUM> via a portion, extending from the heat source-side heat exchanger <NUM> to the receiver <NUM>, of the heat source-side liquid refrigerant pipe <NUM>. When the liquid refrigerant flows into the receiver <NUM>, the receiver <NUM> temporarily stores therein the liquid refrigerant in a saturated state. Thereafter, the liquid refrigerant flows out of the receiver <NUM> through the outlet of the receiver <NUM>.

When the liquid refrigerant flows out of the receiver <NUM> through the outlet of the receiver <NUM>, then the liquid refrigerant flows into the subcooler <NUM> through the inlet of the heat source-side liquid refrigerant pipe <NUM> side of the subcooler <NUM> via a portion, extending from the receiver <NUM> to the subcooler <NUM>, of the heat source-side liquid refrigerant pipe <NUM>.

When the liquid refrigerant flows into the subcooler <NUM>, the subcooler <NUM> causes the liquid refrigerant to exchange heat with the refrigerant flowing through the injection pipe <NUM>, and further cools the liquid refrigerant, thereby bringing the liquid refrigerant into a subcooled state. The resultant liquid refrigerant flows out of the subcooler <NUM> through the outlet of the heat source-side expansion valve <NUM> side of the subcooler <NUM>. The controller <NUM> controls the opening degree of the injection valve <NUM> such that the refrigerant flowing from the subcooler <NUM> toward the heat source-side expansion valve <NUM> has a predetermined positive degree of subcooling.

When the liquid refrigerant flows out of the subcooler <NUM> through the outlet of the heat source-side expansion valve <NUM> side of the subcooler <NUM>, then the liquid refrigerant flows into the heat source-side expansion valve <NUM> via a portion, between the subcooler <NUM> and the heat source-side expansion valve <NUM>, of the heat source-side liquid refrigerant pipe <NUM>. At this time, the liquid refrigerant, which has flown out of the subcooler <NUM> through the outlet of the heat source-side expansion valve <NUM> side of the subcooler <NUM>, is partly shunted to the injection pipe <NUM> from the portion, between the subcooler <NUM> and the heat source-side expansion valve <NUM>, of the heat source-side liquid refrigerant pipe <NUM>.

The refrigerant flowing through the injection pipe <NUM> is decompressed to have an intermediate pressure in the refrigeration cycle by the injection valve <NUM>. The refrigerant decompressed by the injection valve <NUM> flows through the injection pipe <NUM>, and then flows into the subcooler <NUM> through the inlet of the injection pipe <NUM> side of the subcooler <NUM>. When the refrigerant flows into the subcooler <NUM> through the inlet of to the injection pipe <NUM> side of the subcooler <NUM>, the subcooler <NUM> causes the refrigerant to exchange heat with the refrigerant flowing through the heat source-side liquid refrigerant pipe <NUM>, and then heats the refrigerant to turn the refrigerant into the gas refrigerant. The refrigerant heated by the subcooler <NUM> flows out of the subcooler <NUM> through the outlet of the injection pipe <NUM> side of the subcooler <NUM>, and then returns to the compressor <NUM> in the intermediate state of the compression process.

The heat source-side expansion valve <NUM> is brought into the fully open state in the normal operating mode. The liquid refrigerant, which has flown into the heat source-side expansion valve <NUM> via the heat source-side liquid refrigerant pipe <NUM>, therefore passes through the heat source-side expansion valve <NUM> without being decompressed, and flows into each of the first usage unit <NUM> and the second usage unit <NUM> that are currently operated, via the liquid-side shutoff valve <NUM> and the liquid-refrigerant connection pipe <NUM>.

When the refrigerant flows into the first usage unit <NUM>, then the refrigerant flows into the first usage-side expansion valve <NUM> via the first on-off valve <NUM> and a part of the first usage-side liquid refrigerant pipe <NUM>. When the refrigerant flows into the first usage-side expansion valve <NUM>, then the refrigerant is decompressed to have the low pressure in the refrigeration cycle by the first usage-side expansion valve <NUM>. Thereafter, the refrigerant flows into the first usage-side heat exchanger <NUM> through the liquid-side end of the first usage-side heat exchanger <NUM> via the first usage-side liquid refrigerant pipe <NUM>. When the refrigerant flows into the first usage-side heat exchanger <NUM> through the liquid-side end of the first usage-side heat exchanger <NUM>, the first usage-side heat exchanger <NUM> causes the refrigerant to exchange heat with the usage-side air supplied by the first usage-side fan <NUM>, and evaporates the refrigerant to turn the refrigerant into the gas refrigerant. The resultant gas refrigerant flows out of the first usage-side heat exchanger <NUM> through the gas-side end of the first usage-side heat exchanger <NUM>. When the gas refrigerant flows out of the first usage-side heat exchanger <NUM> through the gas-side end of the first usage-side heat exchanger <NUM>, then the gas refrigerant flows to the gas-refrigerant connection pipe <NUM> via the first check valve <NUM> and the first usage-side gas refrigerant pipe <NUM>.

As in the first usage unit <NUM>, when the refrigerant flows into the second usage unit <NUM>, then the refrigerant flows into the second usage-side expansion valve <NUM> via the second on-off valve <NUM> and a part of the second usage-side liquid refrigerant pipe <NUM>. When the refrigerant flows into the second usage-side expansion valve <NUM>, then the refrigerant is decompressed to have the low pressure in the refrigeration cycle by the second usage-side expansion valve <NUM>. Thereafter, the refrigerant flows into the second usage-side heat exchanger <NUM> through the liquid-side end of the second usage-side heat exchanger <NUM> via the second usage-side liquid refrigerant pipe <NUM>. When the refrigerant flows into the second usage-side heat exchanger <NUM> through the liquid-side end of the second usage-side heat exchanger <NUM>, the second usage-side heat exchanger <NUM> causes the refrigerant to exchange heat with the usage-side air supplied by the second usage-side fan <NUM>, and evaporates the refrigerant to turn the refrigerant into the gas refrigerant. The resultant gas refrigerant flows out of the second usage-side heat exchanger <NUM> through the gas-side end of the second usage-side heat exchanger <NUM>. When the gas refrigerant flows out of the second usage-side heat exchanger <NUM> through the gas-side end of the second usage-side heat exchanger <NUM>, then the gas refrigerant flows to the gas-refrigerant connection pipe <NUM> via the second check valve <NUM> and the second usage-side gas refrigerant pipe <NUM>.

The refrigerant, which has flown out of the first usage unit <NUM>, and the refrigerant, which has flown out of the second usage unit <NUM>, merge with each other at the gas-refrigerant connection pipe <NUM>, and then are sucked into the compressor <NUM> again, via the gas-side shutoff valve <NUM> and the suction-side refrigerant pipe <NUM>.

With reference to a flowchart of <FIG>, next, a description will be given of exemplary processing to be performed by the controller <NUM> in a case where a refrigerant leak occurs in the normal operating mode.

The following description concerns an exemplary case where, of the first usage unit <NUM> and the second usage unit <NUM>, the first usage unit <NUM> undergoes a refrigerant leak, that is, the first usage unit <NUM> corresponds to the leak unit while the second usage unit <NUM> continuously performs the cooling operation, that is, the second usage unit <NUM> corresponds to the non-leak unit. However, the same processing is performed irrespective of which usage unit undergoes a refrigerant leak.

In step S10, when the controller <NUM> receives a refrigerant leak signal from one of the first refrigerant leak sensor <NUM> and the second refrigerant leak sensor <NUM>, that is, when it is assumed that one of the first usage unit <NUM> and the second usage unit <NUM> undergoes a refrigerant leak, the processing proceeds to step S11. When the controller <NUM> receives no refrigerant leak signal from the first refrigerant leak sensor <NUM> and the second refrigerant leak sensor <NUM>, that is, when it is assumed that none of the first usage unit <NUM> and the second usage unit <NUM> undergoes a refrigerant leak, the controller <NUM> continues the normal operating mode, and makes a determination in step S10 again.

In step S11, the controller <NUM> closes the on-off valve of the usage unit (the leak unit), at which the refrigerant leak occurs, of the first usage unit <NUM> and the second usage unit <NUM>, with the compressor <NUM> driven. In this example, the controller <NUM> closes the first on-off valve <NUM>. The controller <NUM> also maintains at the open state the on-off valve of the usage unit (the non-leak unit), at which no refrigerant leak occurs, of the first usage unit <NUM> and the second usage unit <NUM>. In this example, the controller <NUM> maintains the second on-off valve <NUM> at the open state. The processing then proceeds to step S12.

The controller <NUM> closes the on-off valve of the usage unit (the leak unit) at which the refrigerant leak occurs. However, the on-off valve of the leak unit may not be completely closed, so that the on-off valve may be slightly opened as unintended in some instances.

In step S12, the controller <NUM> causes each of the first remote controller 50a and the second remote controller 60a to make a notification about occurrence of the refrigerant leak and about which usage unit is the leak unit undergoing the refrigerant leak. Each of the first remote controller 50a and the second remote controller 60a may make a notification in the form of display on a screen and in the form of output by sound.

In step S13, the controller <NUM> opens the hot gas bypass valve <NUM> to allow the refrigerant to flow into the hot gas bypass pipe <NUM>. For example, the valve opening degree of the hot gas bypass valve <NUM> may be controlled to be equal to a predetermined opening degree set in advance, or may be controlled such that a value of a suction pressure to be detected by the suction pressure sensor <NUM> is maintained at a value larger than an atmospheric pressure, or may be controlled such that a value detected by the suction pressure sensor <NUM> after the hot gas bypass valve <NUM> has opened is larger than that before the hot gas bypass valve <NUM> is opened; however, the control for the valve opening degree is not limited thereto. This configuration suppresses an inflow of the air in the atmosphere into the refrigerant circuit <NUM> through the leak spot. The processing then proceeds to step S14.

In step S14, the controller <NUM> lowers the valve opening degree of the heat source-side expansion valve <NUM> so as to reduce the pressure of the refrigerant flowing through the downstream side of the heat source-side expansion valve <NUM>. In this embodiment, the controller <NUM> lowers the valve opening degree of the heat source-side expansion valve <NUM> such that the heat source-side expansion valve <NUM> has a predetermined valve opening degree smaller than the valve opening degree in the fully open state; however, the control for the valve opening degree is not limited thereto. This configuration enables continuation of the cooling operation in the non-leak unit while suppressing supply of the refrigerant to the leak unit. The processing then proceeds to step S15.

In step S15, the controller <NUM> is in a standby state until a service engineer who receives the notification about the refrigerant leak in step S12 rushes to the site. When the service engineer inputs a new command through the first remote controller 50a or the second remote controller 60a on the site, the controller <NUM> performs processing based on the basis of this command.

(<NUM>-<NUM>)
In this embodiment, upon occurrence of a refrigerant leak, the refrigeration apparatus <NUM> closes an on-off valve of a leak unit. Specifically, the refrigeration apparatus <NUM> closes the first on-off valve <NUM> upon occurrence of a refrigerant leak at the first usage unit <NUM>, and closes the second on-off valve <NUM> upon occurrence of a refrigerant leak at the second usage unit <NUM>. The refrigeration apparatus <NUM> thus suppresses additional supply of the refrigerant to the leak unit, and also suppresses an increase in leakage of the refrigerant in the leak unit.

(<NUM>-<NUM>)
In addition, the refrigeration apparatus <NUM> continues to open an on-off valve of a non-leak unit at which no refrigerant leak occurs. Specifically, the refrigeration apparatus <NUM> continues to open the second on-off valve <NUM> upon occurrence of the refrigerant leak at the first usage unit <NUM>, and continues to open the first on-off valve <NUM> upon occurrence of the refrigerant leak at the second usage unit <NUM>. The refrigeration apparatus <NUM> thus continues the cooling operation of the non-leak unit although stopping the cooling operation of the leak unit. With this configuration, at least the non-leak unit at which no refrigerant leak occurs continuously cools a target to be cooled. This configuration therefore suppresses occurrence of, for example, a deterioration of the target due to the stop of the cooling operation.

(<NUM>-<NUM>)
In a typical valve such as the first on-off valve <NUM> of the first usage unit <NUM> or the second on-off valve <NUM> of the second usage unit <NUM>, the valve may not be completely closed even in a fully closed state, and may be slightly opened as unintended in some instances. If the valve is slightly opened as unintended, the refrigerant passes through an on-off valve of the leak unit to flow toward a usage-side heat exchanger, so that a refrigerant leak lasts as unintended.

The high refrigerant pressure at the on-off valve of the leak unit on the side of the liquid-refrigerant connection pipe <NUM> causes a large difference in pressure between the refrigerant before flowing into the on-off valve of the leak unit and the refrigerant which has passed through the on-off valve of the leak unit. Therefore the leakage of the refrigerant passing through the on-off valve of the leak unit tends to increase. In allowing continuous circulation of the refrigerant in the non-leak unit for the purpose of continuing the cooling operation in the non-leak unit, the refrigerant pressure is continuously applied to the on-off valve of the leak unit on the side of the liquid-refrigerant connection pipe <NUM>.

In this respect, in the refrigeration apparatus <NUM> according to this embodiment, unlike the normal operating mode, in the refrigerant leak control mode, the controller <NUM> lowers the valve opening degree of the heat source-side expansion valve <NUM> so as to reduce the pressure of the refrigerant passing through the heat source-side expansion valve <NUM> (lowers the valve opening degree of the heat source-side expansion valve <NUM> to the predetermined valve opening degree in this embodiment). This configuration reduces the pressure of the refrigerant passing through the heat source-side expansion valve <NUM> and then flowing through the liquid-refrigerant connection pipe <NUM>. This configuration therefore decreases the difference in pressure between the refrigerant before flowing into the on-off valve of the leak unit and the refrigerant which has passed through the on-off valve of the leak unit. In other words, since it is considered that an atmospheric pressure is applied to the on-off valve of the leak unit on the side of the leak spot, this configuration decreases a difference between the atmospheric pressure and the refrigerant pressure at the on-off valve of the leak unit on the side of the liquid-refrigerant connection pipe <NUM>. With this configuration, if the on-off valve of the leak unit cannot be completely closed even in the fully closed state, the refrigeration apparatus <NUM> can reduce the supply of the refrigerant flowing toward the leak spot via the on-off valve of the leak unit. This configuration hardly causes a glitch due to an increase in leakage of the refrigerant in the leak unit. For example, in a case of using a combustible refrigerant, this configuration prolongs a time until a concentration of the leaking refrigerant increases to reach a combustible range. In addition, this configuration easily ensures a time until a service engineer arrives at the site.

In addition, the refrigeration apparatus <NUM> lowers the valve opening degree of the heat source-side expansion valve <NUM>, thereby reducing the pressure of the refrigerant radiating heat in the heat source-side heat exchanger <NUM> and flowing toward each of the usage units <NUM> and <NUM>. This configuration eliminates a necessity of significantly reducing the pressure of the refrigerant in causing the refrigerant to radiate heat in the heat source-side heat exchanger <NUM>, that is, the pressure of the refrigerant flowing through the heat source-side heat exchanger <NUM> serving as a radiator.

(<NUM>-<NUM>)
In this embodiment, when the refrigeration apparatus <NUM> lowers the valve opening degree of the heat source-side expansion valve <NUM> thereby reducing the pressure of the refrigerant flowing from the heat source-side expansion valve <NUM> toward the non-leak unit, the subcooler <NUM> subcools the refrigerant before flowing into the heat source-side expansion valve <NUM>. This configuration suppresses a flush of the refrigerant decompressed in the heat source-side expansion valve <NUM>, and facilitates supply of the liquid-phase refrigerant to the non-leak unit.

(<NUM>-<NUM>)
In addition, the refrigerant continuously supplied to the non-leak unit evaporates in the usage-side heat exchanger of the non-leak unit, flows out of the non-leak unit, and flows toward the suction side of the compressor <NUM> again. In the leak unit, the check valve disposed on the suction side of the compressor <NUM> suppresses an inflow of the refrigerant into the leak unit even when the refrigerant flows from the non-leak unit toward the suction side of the compressor <NUM>. This configuration also suppresses an increase in leakage of the refrigerant in the leak unit.

(<NUM>-<NUM>)
In this embodiment, upon occurrence of a refrigerant leak, the refrigeration apparatus <NUM> opens the hot gas bypass valve <NUM> to cause the refrigerant to flow through the hot gas bypass pipe <NUM>. The refrigeration apparatus <NUM> thus increases the refrigerant pressure by causing the high pressure of the discharge refrigerant from the compressor <NUM> to be applied to a portion between the check valve of the leak unit and the suction side of the compressor <NUM>. The refrigeration apparatus <NUM> thus avoids a situation in which the refrigerant pressure at the portion between the check valve of the leak unit and the suction side of the compressor <NUM> becomes lower than the refrigerant pressure at the refrigerant leak spot upstream of the check valve of the leak unit (i.e., the usage-side gas refrigerant pipe, the usage-side heat exchanger, the usage-side liquid refrigerant pipe, the usage-side expansion valve). The refrigeration apparatus <NUM> also suppresses a situation in which the air flows through the leak spot of the leak unit into the refrigerant circuit <NUM>. This configuration suppresses damage to a device such as the compressor <NUM> which may be caused if the air flows into the refrigerant circuit <NUM>.

The foregoing embodiment may be appropriately modified as described in the following modifications. It should be noted that these modifications are applicable in conjunction with other modifications insofar as there are no inconsistencies.

According to the foregoing embodiment, the refrigeration apparatus <NUM> includes the first usage unit <NUM> and the second usage unit <NUM>. In the first usage unit <NUM>, the first on-off valve <NUM> and the thermostatic first usage-side expansion valve <NUM> are disposed on the side of the refrigerant inlet of the first usage-side heat exchanger <NUM>. In the second usage unit <NUM>, the second on-off valve <NUM> and the thermostatic second usage-side expansion valve <NUM> are disposed on the side of the refrigerant inlet of the second usage-side heat exchanger <NUM>.

As illustrated in <FIG>, alternatively, a refrigeration apparatus 100a may include: a first usage-side electronic expansion valve <NUM> provided in place of the first on-off valve <NUM> and the thermostatic first usage-side expansion valve <NUM>; and a second usage-side electronic expansion valve <NUM> provided in place of the second on-off valve <NUM> and the thermostatic second usage-side expansion valve <NUM>.

Each of the first usage-side electronic expansion valve <NUM> and the second usage-side electronic expansion valve <NUM> is electrically connected to a controller <NUM>, and the controller <NUM> controls the opening degree of each of the first usage-side electronic expansion valve <NUM> and the second usage-side electronic expansion valve <NUM>.

As to an expanding operation of each of the first usage-side electronic expansion valve <NUM> and the second usage-side electronic expansion valve <NUM> in a normal operating mode, the controller <NUM> appropriately adjusts the opening degree of each of the first usage-side electronic expansion valve <NUM> and the second usage-side electronic expansion valve <NUM>. The refrigeration apparatus 100a thus produces advantageous effects similar to those of the refrigeration apparatus <NUM> according to the foregoing embodiment.

In addition, as to an operation of each of the first usage-side electronic expansion valve <NUM> and the second usage-side electronic expansion valve <NUM> in a refrigerant leak control mode, the controller <NUM> fully closes either the first usage-side electronic expansion valve <NUM> or the second usage-side electronic expansion valve <NUM> in a leak unit. In other words, the controller <NUM> sets at a minimum the opening degree of either the first usage-side electronic expansion valve <NUM> or the second usage-side electronic expansion valve <NUM> in the leak unit. The controller <NUM> also causes either the first usage-side electronic expansion valve <NUM> or the second usage-side electronic expansion valve <NUM> in a non-leak unit to continuously perform the expanding operation. The refrigeration apparatus 100a thus produces advantageous effects similar to those of the refrigeration apparatus <NUM> according to the foregoing embodiment.

As in the refrigeration apparatus <NUM> according to the foregoing embodiment, the refrigeration apparatus 100a including the first usage-side electronic expansion valve <NUM> and the second usage-side electronic expansion valve <NUM> decreases a difference in pressure between the refrigerant before flowing into the electronic expansion valve (i.e., the first usage-side electronic expansion valve <NUM> or the second usage-side electronic expansion valve <NUM>) of the leak unit and the refrigerant which has passed through the electronic expansion valve of the leak unit, thereby reducing the leakage of the refrigerant.

According to the foregoing embodiment, in the refrigerant leak control mode, the heat source-side expansion valve <NUM> reduces the refrigerant pressure, thereby reducing the pressure of the refrigerant to be supplied toward the non-leak unit (see step S14).

However, the method of reducing the pressure of the refrigerant to be supplied toward the non-leak unit is not limited thereto. As illustrated in <FIG>, for example, processing of step S14a, in which the controller <NUM> forcibly lowers the driving frequency of the compressor <NUM>, is performed instead of the processing of step S14 in the foregoing embodiment to reduce the pressure of the refrigerant.

Specifically, the controller <NUM> controls the compressor <NUM> such that the driving frequency of the compressor <NUM> in the refrigerant leak control mode becomes lower than the driving frequency of the compressor <NUM> upon detection of a refrigerant leak by the first refrigerant leak sensor <NUM> or the second refrigerant leak sensor <NUM>, for example.

This configuration also decreases a difference in pressure between the refrigerant before flowing into an on-off valve of a leak unit and the refrigerant which has passed through the on-off valve of the leak unit, thereby reducing the leakage of the refrigerant.

It should be noted that the controller <NUM> may concurrently perform the processing of step S14 in the foregoing embodiment and the processing of step S14a.

However, the method of reducing the pressure of the refrigerant to be supplied toward the non-leak unit is not limited thereto. As illustrated in <FIG>, for example, processing of step S14b, in which the controller <NUM> instead of step S14, controls the heat source-side fan <NUM> such that the airflow volume of the heat source-side fan <NUM> in the refrigerant leak control mode becomes larger than the airflow volume of the heat source-side fan <NUM> upon detection of a refrigerant leak by the first refrigerant leak sensor <NUM> or the second refrigerant leak sensor <NUM>, for example.

The increase in airflow volume of the heat source-side fan <NUM> promotes heat radiation from the refrigerant in the heat source-side heat exchanger <NUM>. The refrigeration apparatus <NUM> therefore reduces the refrigerant pressure in the heat source-side heat exchanger <NUM>, and decreases a difference in pressure between the refrigerant before flowing into an on-off valve of a leak unit and the refrigerant which has passed through the on-off valve of the leak unit. This configuration also reduces the leakage of the refrigerant.

It should be noted that the controller <NUM> may concurrently perform the processing of step S14 in the foregoing embodiment and the processing of step S14b. Alternatively, the controller <NUM> may concurrently perform all the processing of step S14 in the foregoing embodiment, the processing of step S14a in Modification B, and the processing of step S14b. This configuration also reduces the leakage of the refrigerant.

According to the foregoing embodiment, in the refrigerant leak control mode, the refrigeration apparatus <NUM> lowers the valve opening degree of the heat source-side expansion valve <NUM> to the predetermined valve opening degree.

However, the extent of reducing the pressure of the refrigerant to be supplied toward the non-leak unit is not limited to an extent of pressure reduction by lowering the valve opening degree of the heat source-side expansion valve <NUM> to the predetermined valve opening degree. For example, the controller <NUM> may reduce the pressure of the refrigerant within a range where the refrigerant which has passed through the heat source-side expansion valve <NUM> is maintained at a liquid single phase state rather than a gas-liquid two-phase state. Alternatively, the controller <NUM> may reduce the pressure of the refrigerant such that the pressure takes a minimum value in the range described above. Still alternatively, the controller <NUM> may reduce the pressure of the refrigerant to a pressure larger than the minimum value in the range described above, by a pressure loss at the time when the refrigerant flows from the heat source-side expansion valve <NUM> to the non-leak unit (i.e., a pressure loss set in advance).

According to the foregoing embodiment, in addition, the controller <NUM> brings the heat source-side expansion valve <NUM> into the fully open state in the normal operating mode. However, the control for the valve opening degree is not limited thereto. Alternatively, the controller <NUM> may lower the valve opening degree of the heat source-side expansion valve <NUM> in the normal operating mode, and may further lower the valve opening degree of the heat source-side expansion valve <NUM> in the refrigerant leak control mode as compared to the normal operating mode.

According to the foregoing embodiment, the refrigeration apparatus <NUM> includes the hot gas bypass pipe <NUM>.

However, the refrigeration apparatus <NUM> does not necessarily include the hot gas bypass pipe <NUM>. In addition, the refrigeration apparatus <NUM> does not necessarily perform the processing of step S13 in the foregoing embodiment, that is, the processing of causing the refrigerant to flow into the hot gas bypass pipe <NUM>.

According to the foregoing embodiment, the refrigeration apparatus <NUM> includes the injection pipe <NUM> for injecting the refrigerant into the compressor <NUM> in the intermediate state of the compression process.

Alternatively, the refrigeration apparatus <NUM> may include an injection pipe for injecting the refrigerant toward the suction side of the compressor <NUM>, in place of the injection pipe <NUM> described in the foregoing embodiment.

According to the foregoing embodiment, the first refrigerant leak sensor <NUM> and the second refrigerant leak sensor <NUM> are disposed to detect a refrigerant leak at each usage unit <NUM>, <NUM>. If a refrigerant leak in each usage unit <NUM>, <NUM> is detectable without the refrigerant leak sensor <NUM>, <NUM>, however, the refrigeration apparatus <NUM> does not necessarily include the refrigerant leak sensor <NUM>, <NUM>.

For example, each usage unit <NUM>, <NUM> includes a sensor such as a refrigerant pressure sensor or a refrigerant temperature sensor. If a refrigerant leak in each usage unit <NUM>, <NUM> is independently detectable on the basis of a change of a value detected by such a sensor, the refrigerant leak sensor <NUM>, <NUM> may be omitted.

According to the foregoing embodiment, the refrigeration apparatus <NUM> is configured to cool, for example, the interior of a cold storage warehouse or the interior of a showcase in a store.

However, the use of the refrigeration apparatus <NUM> is not limited thereto. For example, the refrigeration apparatus <NUM> may be configured to cool the interior of a container for transportation. Alternatively, the refrigeration apparatus <NUM> may be an air conditioning system (an air conditioner) that achieves air conditioning by cooling the interior of a building or the like.

According to the foregoing embodiment, R32 is employed as a refrigerant that circulates through the refrigerant circuit <NUM>.

However, the refrigerant for use in the refrigerant circuit <NUM> is not limited thereto. For example, HFO1234yf, HFO1234ze, and a mixture thereof may be employed in place of R32 for the refrigerant circuit <NUM>. Alternatively, a hydrofluorocarbon (HFC) refrigerant such as R407C or R410A may be employed for the refrigerant circuit <NUM>. Still alternatively, a combustible refrigerant such as propane or a toxic refrigerant such as ammonia may be employed for the refrigerant circuit <NUM>.

The present invention is applicable to a refrigeration apparatus.

Claim 1:
A refrigeration apparatus (<NUM>, 100a) comprising:
a heat source unit (<NUM>) including a compressor (<NUM>) and a heat source-side heat exchanger (<NUM>);
a plurality of usage units (<NUM>, <NUM>) connected to the heat source unit in parallel via a liquid-refrigerant connection pipe (<NUM>) and a gas-refrigerant connection pipe (<NUM>); and
a control unit (<NUM>),
wherein
each of the usage units includes:
a usage-side heat exchanger (<NUM>, <NUM>); and
a usage-side valve (<NUM>, <NUM>, <NUM>, <NUM>) disposed closer to the liquid-refrigerant connection pipe than the usage-side heat exchanger is, and
when one of the usage units is in a refrigerant leak situation satisfying a predetermined condition,
the control unit is configured to
close a usage-side valve of a leak unit which is the usage unit satisfying the predetermined condition,
continue to open a usage-side valve of a non-leak unit being operated at a time when the leak unit satisfies the predetermined condition among one or more non-leak unit which is the usage unit not satisfying the predetermined condition, and to
perform pressure control to reduce a refrigerant pressure at a portion on the side of the liquid-refrigerant connection pipe with respect to each usage-side valve below a refrigerant pressure at the portion at the time when the leak unit satisfies the predetermined condition; wherein
the heat source unit further includes a heat source-side expansion valve (<NUM>) configured to reduce a pressure of the refrigerant radiating heat in the heat source-side heat exchanger, and
the control unit is configured to perform the pressure control by controlling the heat source-side expansion valve such that an extent of decompression in the heat source-side expansion valve after the leak unit has satisfied the predetermined condition is greater than an extent of decompression in the heat source-side expansion valve at the time when the leak unit satisfies the predetermined condition.