EP3315877A1

EP3315877A1 - Air conditioning system

Info

Publication number: EP3315877A1
Application number: EP16857220.4A
Authority: EP
Inventors: Takahiro Kato
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2015-10-22
Filing date: 2016-09-21
Publication date: 2018-05-02
Anticipated expiration: 2036-09-21
Also published as: EP3315877B1; JP6552939B2; JP2017078561A; WO2017068902A1; CN107850352A; ES2732660T3; EP3315877A4

Abstract

An air conditioning system (1) includes a backup operation control unit (61A, 61B) configured to perform backup operation on an operational outdoor unit of a plurality of outdoor units (2A, 2B) when a compressor (10) of any of the plurality of outdoor units (2A, 2B) becomes non-operational; and the backup operation control unit (61A, 61B) is provided with a four-way selector valve synchronization control unit (62A, 62B) configured to operate a four-way selector valve (13) in backup operation to switch from a cooling cycle position to a heating cycle position, such that the four-way selector valve synchronization control unit (62A, 62B) operates the four-way selector valve (13) of the operational outdoor unit temporarily in a cooling cycle position so as to reduce a low pressure of the non-operational outdoor unit and to secure an operating pressure difference of the four-way selector valve (13) of the non-operational outdoor unit, and then operates the four-way selector valve (13) of the non-operational outdoor unit to switch to a heating cycle position, and subsequently operates the four-way selector valve (13) of the operational outdoor unit to switch to a heating cycle position, and synchronizes the four-way selector valves (13).

Description

Technical Field

The present invention relates to an air conditioning system including a refrigeration cycle having a plurality of outdoor units each provided with a compressor, a four-way selector valve, and an outdoor heat exchanger and connected in parallel.

Background Art

In the related art, an air conditioning system is known that includes a backup operation function for preventing a complete shutdown of the air conditioning system and for operating operational compressors or outdoor units to continue air conditioning operation, when any one of compressors becomes non-operational in an air conditioning system having a plurality of compressors installed in an outdoor unit, or when a compressor of any of outdoor units becomes non-operational in an air conditioning system including one refrigeration cycle having a plurality of outdoor units connected in parallel.
Among such air conditioning systems, in the air conditioning system having the plurality of outdoor units connected in parallel, in backup operation, positions of four-way selector valves need to be synchronized to be cooling cycle positions or heating cycle positions, in order that the outdoor units operate in the same operation mode. In such a case, when a plurality of compressors are installed in the outdoor unit and even any of the plurality of compressors becomes non-operational, the remaining compressors can operate the four-way selector valve to switch the positions. However, when only one compressor is installed in the outdoor unit or when all of the installed compressors become non-operational, the compressor(s) of the outdoor unit cannot operate. As a result, the four-way selector valves cannot be synchronized.
In other words, in order to switch from the non-energized cooling cycle position to the energized heating cycle position of the four-way selector valve, a slide valve is operated to slide. As a result, it is necessary to secure a high/low pressure difference equal to or greater than a predetermined value (typically, 0.3 MPa, though this depends on the specifications of the four-way selector valve). However, in the outdoor unit with a non-operational compressor, this high/low pressure difference cannot be secured. As a result, the four-way selector valves cannot be operated to synchronously switch to the heating cycle position and thus the system may not be able to operate.
Even when the four-way selector valve of the operational outdoor unit is in the heating cycle position and operation is possible in the heating cycle, the four-way selector valve on the outdoor unit side with the non-operational compressor cannot switch to the heating cycle position and remains in the cooling cycle position. In such a case, a high pressure generated by operation of the operational outdoor unit is applied via the refrigerant gas line to a low pressure intake channel from the four-way selector valve to the compressor on the non-operational outdoor unit side. In order to prevent such a situation, the air conditioning system is configured to stop operation.
As described above, when problems such as the non-operational compressor occur, the orientations of the four-way selector valves differ between the outdoor units. When operation is continued in this state, a high-pressure refrigerant and a low-pressure refrigerant cause a short circuit that shuts down the system. When this is repeated, the outdoor unit may be damaged. In order to solve such problems, Patent Document 1 describes a system including a control unit configured to temporarily shut down operation of the system when problems occur, and then synchronize four-way selector valves of the outdoor units to be orientated in the same orientation, and subsequently reactivate the system.

Citation List

Patent Document

Patent Document 1: JP 06-341742 A ( JP 3203096 B )

Summary of Invention

Technical Problems

However, in the system described in Patent Document 1, operation of the system has to be temporarily shut down when problems occur. As a result, for example, when cooling operation is performed in a cooling cycle to switch to heating operation, it is not possible to directly operate the four-way selector valve of the non-operational to switch from the cooling cycle position to the heating cycle position, and the system has to be temporarily shut down. Furthermore, a method or means for synchronizing the orientations of the four-way selector valves of the outdoor units are not specifically described.
In light of such circumstances, an object of the present invention is to provide an air conditioning system that can reliably synchronize four-way selector valves and perform backup operation when a compressor of any of a plurality of outdoor units connected in parallel becomes non-operational.

Solution to Problems

In order to solve the above-described problem, an air conditioning system according to an embodiment of the present invention adopt the following.
An air conditioning system according to an embodiment of the present invention includes:

a refrigeration cycle including a refrigerant circuit on an indoor unit side and an outdoor unit side connected via a refrigerant liquid line and a refrigerant gas line;
a plurality of outdoor units each including at least one compressor, a four-way selector valve configured to operate the refrigeration cycle to switch to any of a cooling cycle and a heating cycle, and an outdoor heat exchanger, and connected in parallel in the refrigeration cycle; and
a backup operation control unit configured to perform backup operation on another operational outdoor unit to continue air conditioning operation when the compressor of any of the plurality of outdoor units becomes non-operational;
wherein the backup operation control unit includes a four-way selector valve synchronization control unit configured to operate the four-way selector valve in backup operation to switch from a cooling cycle position to a heating cycle position, such that the four-way selector valve synchronization control unit operates the four-way selector valve of the operational outdoor unit temporarily in a cooling cycle position so as to reduce a low pressure of the non-operational outdoor unit and to secure an operating pressure difference of the four-way selector valve of the non-operational outdoor unit, and then operates the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position, and subsequently operates the four-way selector valve of the operational outdoor unit to switch to a heating cycle position and synchronizes the four-way selector valves so as to operate in a heating cycle.

According to an embodiment of the present invention, the air conditioning system includes the backup operation control unit configured to perform backup operation on an operational outdoor unit of the plurality of outdoor units when the compressor of any of the plurality of outdoor units becomes non-operational; and the backup operation control unit is provided with the four-way selector valve synchronization control unit configured to operate the four-way selector valve in backup operation to switch from the cooling cycle position to the heating cycle position, such that the four-way selector valve synchronization control unit operates the four-way selector valve of the operational outdoor unit temporarily in the cooling cycle position, so as to reduce a low pressure of the non-operational outdoor unit and to secure an operating pressure difference of the four-way selector valve of the non-operational outdoor unit, and then operates the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position, and subsequently operates the four-way selector valve of the operational outdoor unit to switch to the heating cycle position, and synchronizes the four-way selector valves so as to operate in a heating cycle. As a result, in backup operation, even when the four-way selector valve is operated to switch from the cooling cycle position to the heating cycle position, an operating pressure difference can reliably be secured so as to operate the four-way selector valve of the non-operational outdoor unit to switch from the cooling cycle position to the heating cycle position, and can synchronize the four-way selector valve to be in the heating cycle position so as to perform backup operation. This solves problems such as application of high pressure refrigerant gas to the low pressure channel of the non-operational outdoor unit and a complete shutdown of the air conditioning system caused by the four-way selector valve of the non-operational outdoor unit that cannot be operated to synchronously switch to a heating cycle position because the operating pressure difference required for the four-way selector valve of the non-operational outdoor unit to switch from the cooling cycle position to the heating cycle position cannot be secured. As a result, the operational outdoor unit can reliably be operated to perform backup operation.
Further, according to another embodiment of the present invention, in the air conditioning system described above, the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a rotational speed of the compressor of the operational outdoor unit reaches a predetermined rotational speed.
According to this embodiment of the present invention, the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a rotational speed of the compressor on the operational outdoor unit side reaches a predetermined rotational speed. As a result, when the rotational speed of the compressor of the operational outdoor unit reaches a predetermined value, the low pressure of the non-operational outdoor unit reduces, the pressure difference required for the four-way selector valve to switch to the heating cycle position is determined to be secured, and a switch command is output. This enables the four-way selector valve of the non-operational outdoor unit to switch to the heating cycle position. Accordingly, in backup operation, the four-way selector valve of the non-operational outdoor unit can be operated to reliably switch from the cooling cycle position to the heating cycle position for synchronization, and backup operation can be performed only with software changes and without hardware changes on a current system.
Additionally, according to another embodiment of the present invention, in the air conditioning system described above, the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a detection value of a low pressure of the non-operational outdoor unit is equal to or less than a predetermined value.
According to this embodiment of the present invention, the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a detection value of a low pressure on the non-operational outdoor unit side is equal to or less than a predetermined value. As a result, when the detection value of the low pressure on the non-operational outdoor unit is equal to or less than a predetermined value, the low pressure of the non-operational outdoor unit reduces, the pressure difference required for the four-way selector valve to switch to the heating cycle position is determined to be secured, and a switch command is output. This enables the four-way selector valve of the non-operational outdoor unit to switch to the heating cycle position. Accordingly, in backup operation, the four-way selector valve of the non-operational outdoor unit can be operated to reliably switch from the cooling cycle position to the heating cycle position for synchronization, and backup operation can be performed only with software changes and without hardware changes on a current system.
Further, according to another embodiment of the present invention, in the air conditioning system described above, the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a difference between detection values of a high pressure and a low pressure of the non-operational outdoor unit is equal to or greater than a predetermined value.
According to this embodiment of the present invention, the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a difference in detection values of a high pressure and a low pressure on the non-operational outdoor unit side is equal to or greater than a predetermined value. As a result, when the difference in detection values of the high pressure and the low pressure on the non-operational outdoor unit is equal to or greater than a predetermined value, the low pressure of the non-operational outdoor unit reduces, the pressure difference required for the four-way selector valve to switch to the heating cycle position is determined to be secured, and a switch command is output. This enables the four-way selector valve of the non-operational outdoor unit to switch to the heating cycle position. Accordingly, in backup operation, the four-way selector valve of the non-operational outdoor unit can be operated to reliably switch from the cooling cycle position to the heating cycle position to synchronize, and backup operation can be performed only with software changes and without hardware changes on a current system.
Further, according to another embodiment of the present invention, in the air conditioning system described above, low pressure channels between the four-way selector valves of the plurality of outdoor units and the compressors are connected to one another via a low pressure communication line.
According to this embodiment, the low pressure channels between the four-way selector valves and the compressors of the plurality of outdoor units are connected to one another via the low pressure communication line. As a result, in backup operation, when the four-way selector valve of the non-operational outdoor unit is operated to switch from the cooling cycle position to the heating cycle position to synchronize and the operational outdoor unit operates in the cooling cycle and the low pressure on non-operational outdoor unit side reduces, it is possible to reduce the low pressure promptly via the low pressure communication line. Accordingly, the reliability and certainty on the switching of the four-way selector valve can be enhanced, and the time needed for the switching can be shortened.
Further, according to another embodiment of the present invention, in the air conditioning system described above, the low pressure communication line is an oil equalizing line or a pressure equalizing line connecting the low pressure channels of the compressors of the plurality of outdoor units to one another.
According to this embodiment, the low pressure communication line is an oil equalizing line or a pressure equalizing line connecting the low pressure channels of the compressors of the plurality of outdoor units to one another. As a result, in the air conditioning system including the plurality of outdoor units, the compressors of the plurality of outdoor units or the low pressure channels of the compressors may be connected via an oil equalizing line or a pressure equalizing line. In such a case, the oil equalizing line or the pressure equalizing line also function as the low pressure communication line. In backup operation, the low pressure on the non-operational outdoor unit side reduces via the oil equalizing line or the pressure equalizing line, and the four-way selector valve of the non-operational outdoor unit can be operated to switch to the heating cycle position to synchronize. Accordingly, the four-way selector valve of the non-operational outdoor unit can reliably be operated to synchronously switch the positions with use of existing oil equalizing lines and pressure equalizing lines and without cost increase.
Additionally, an air conditioning system according to an embodiment of the present invention includes:

a refrigeration cycle including a refrigerant circuit on an indoor unit side and an outdoor unit side connected via a refrigerant liquid line and a refrigerant gas line;
a plurality of the outdoor units each including at least one compressor, a four-way selector valve configured to operate the refrigeration cycle to switch to any of a cooling cycle and a heating cycle, and an outdoor heat exchanger, and connected in parallel in the refrigeration cycle; and
a backup operation control unit configured to perform backup operation on another operational outdoor unit to continue air conditioning operation when the compressor of any of the plurality of outdoor units becomes non-operational;
wherein discharge lines between the compressors and the four-way selector valves of the plurality of outdoor units are provided with a high pressure bypass circuit including a solenoid valve communicating the discharge lines to one another; and
the backup operation control unit is provided with a four-way selector valve synchronization control unit configured to operate the four-way selector valve in backup operation to switch from a cooling cycle position to a heating cycle position, such that the four-way selector valve synchronization control unit opens the solenoid valve provided in the high pressure bypass circuit so as to operate the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position, and synchronizes the four-way selector valves so as to operate in a heating cycle.

According to this embodiment, the air conditioning system includes the backup operation control unit configured to perform backup operation on the operational outdoor unit of the plurality of outdoor units when the compressor of any of the plurality of outdoor units becomes non-operational; and the discharge lines between the compressors and the four-way selector valves of the plurality of outdoor units are provided with the high pressure bypass circuit including the solenoid valve communicating the discharge lines to one another; and the backup operation control unit is provided with the four-way selector valve synchronization control unit configured to operate the four-way selector valve in backup operation to switch from the cooling cycle position to the heating cycle position, such that the four-way selector valve synchronization control unit opens the solenoid valve provided in the high pressure bypass circuit so as to operate the four-way selector valve of the non-operational outdoor unit to switch to the heating cycle position, and synchronizes the four-way selector valves so as to operate in the heating cycle. As a result, in backup operation, when the four-way selector valve is operated to switch from the cooling cycle position to the heating cycle position, the high pressure refrigerant gas discharged from the operational outdoor unit is applied to the discharge line of the non-operational outdoor unit, and an operating pressure difference can reliably be secured so as to operate the four-way selector valve of the non-operational outdoor unit to switch from the cooling cycle position to the heating cycle position, and can synchronize the four-way selector valve to be in the heating cycle position so as to perform backup operation. This solves problems such as application of the high pressure refrigerant gas to the low pressure channel of the non-operational outdoor unit and a complete shutdown of the air conditioning system caused by the four-way selector valve of the non-operational outdoor unit that cannot be operated to synchronously switch to the heating cycle position because the operating pressure difference required for the four-way selector valve of the non-operational outdoor unit to switch from the cooling cycle position to the heating cycle position cannot be secured. As a result, the operational outdoor unit can reliably be operated to perform backup operation.

Advantageous Effects of Invention

According to an embodiment of the present invention, in backup operation, even when the four-way selector valve is operated to switch from the cooling cycle position to the heating cycle position, an operating pressure difference can reliably be secured so as to operate the four-way selector valve of the non-operational outdoor unit to switch from the cooling cycle position to the heating cycle position, and can synchronize the four-way selector valve to be in the heating cycle position so as to perform backup operation. This solves problems such as application of the high pressure refrigerant gas to the low pressure channel of the non-operational outdoor unit and a complete shutdown of the air conditioning system caused by the four-way selector valve of the non-operational outdoor unit that cannot be operated to synchronously switch to a heating cycle position because the operating pressure difference required for the four-way selector valve of the non-operational outdoor unit to switch from the cooling cycle position to the heating cycle position cannot be secured. As a result, the operational outdoor unit can reliably be operated to perform backup operation.

Brief Description of Drawings

FIG. 1 is a refrigerant circuit diagram of an air conditioning system according to a first embodiment of the present invention operating in a cooling cycle.
FIG. 2 is a configuration diagram of a four-way selector valve installed in a refrigerant circuit of the system described above.
FIG. 3 is a refrigerant circuit diagram of the system described above operating in a heating cycle.
FIG. 4 is a refrigerant circuit diagram of the system described above in backup operation with the four-way selector valve of a non-operational outdoor unit unable to be operated to synchronously switch to a heating cycle position.
FIG. 5 is a refrigerant circuit diagram of the system described above in backup operation with the four-way selector valve of the non-operational outdoor unit operated to synchronously switch to the heating cycle position.
FIG. 6 is a refrigerant circuit diagram in which the four-way selector valve on the non-operational outdoor unit side is correctly operated to synchronously switch positions after the state of FIG. 5.
FIG. 7 is a flowchart illustrating an example of switching control of the four-way selector valve when the air conditioning system described above is in backup operation.
FIG. 8 is a flowchart illustrating another example of switching control of the four-way selector valve when the air conditioning system described above is in backup operation.
FIG. 9 is a refrigerant circuit diagram of an air conditioning system according to a second embodiment of the present invention.

Description of Embodiments

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 8.
FIG. 1 is a refrigerant circuit diagram of an air conditioning system according to the present embodiment operating in a cooling cycle. FIG. 2 is a configuration diagram of a four-way selector valve installed in a refrigerant circuit of the air conditioning system. FIG. 3 is a refrigerant circuit diagram of the air conditioning system operating in a heating cycle.
An air conditioning system 1 of the present embodiment includes a refrigeration cycle 6 including a plurality of outdoor units 2A, 2B and a plurality of indoor units 3A, 3B connected in parallel via so-called connecting refrigerant liquid lines 4 and refrigerant gas lines 5.
The plurality of outdoor units 2A, 2B each include an outdoor refrigerant circuit 21 in which a compressor 10, an oil separator 11, a check valve 12, a four-way selector valve 13, an outdoor heat exchanger 14, an expansion valve for heating (EEVH) 15, a receiver 16, a liquid-side operation valve 17, a gas-side operation valve 18, an accumulator 19, and the like are connected in a known manner via a refrigerant line 20; and an oil return circuit 24 including a solenoid valve 22 and a capillary tube 23 connected between the compressor 10 and the oil separator 11. The plurality of outdoor units 2A, 2B are connected in parallel in the refrigeration cycle 6 via the refrigerant liquid lines 4A, 4B and the refrigerant gas lines 5A, 5B.
In the outdoor refrigerant circuit 21, a refrigerant discharge line 20A from the compressor 10 to the four-way selector valve 13 is provided with a high pressure pressure sensor 25, and a refrigerant intake line 20B from the four-way selector valve 13 to the compressor 10 is provided with a low pressure pressure sensor 26. Additionally, the compressors 10 of the outdoor units 2A, 2B are connected via an operation valve 28 by an oil equalizing line 27 for equalizing oil levels of oil filling the compressors 10. The oil equalizing line 27 or a pressure equalizing line disposed parallel with the oil equalizing line 27 connects the low pressure channels (refrigerant intake line 20B) of the outdoor units 2A, 2B between the four-way selector valve 13 and the compressor 10 and functions as a low pressure communication line for equalizing a low pressure of the low pressure channels.
Note that here, the compressor 10 is a low pressure housing type compressor with a low-pressure refrigerant atmosphere inside the housing.
Further, the four-way selector valves 13 installed in the outdoor refrigerant circuits 21 of the outdoor units 2A, 2B are configured to switch the cooling cycle illustrated in FIG. 1 and the heating cycle illustrated in FIG. 3 of the refrigeration cycle 6, and includes the following.
As illustrated in FIG. 2, the four-way selector valve 13 includes a valve body 30; a wall surface on one side of the valve body 30 is provided with a high-pressure port 31 that the refrigerant discharge line 20A from the compressor 10 is connected to; a valve seat portion on a wall surface on the other side is provided with a low-pressure port 32 that the refrigerant intake line 20B to the compressor 10 is connected to; both sides of the low-pressure port 32 are provided with a first port 33 and a second port 34, respectively, that a refrigerant gas line 20C connected to an indoor heat exchanger 50 (described below) and a refrigerant gas line 20D connected to the outdoor heat exchanger 14 are connected to; and further, a slide valve 36 configured to slide on the valve seat portion on the wall surface on the other side is incorporated in an inner channel 35 of the valve body 30.
Additionally, a sliding surface side of the slide valve 36 is provided with a switching channel 37 configured to communicate the low-pressure port 32 to any of the first port 33 and the second port 34; a pair of pistons 38, 39 are joined to both end portions of the slide valve 36; and a left and right pair of a first pilot chamber 40 and a second pilot chamber 41 defined inside the inner channel 35 by the pistons 38, 39 are formed. Note that refrigerant gas can flow in small amounts between the inner channel 35 and the first and second pilot chambers 40 and 41 inside the valve body 30 via small gaps located between the valve body 30 and the pistons 38 and 39.
Further, the four-way selector valve 13 includes a pilot valve 42 configured to switch connection states of the low-pressure port 32 to the first pilot chamber 40 and the second pilot chamber 41. The four-way selector valve 13 is configured such that when a pressure difference between high and low pressure is generated between the first pilot chamber 40 and the second pilot chamber 41, the pressure difference causes the slide valve 36 to slide in the valve body 30 together with the pistons 38, 39. This switches the connection states of the high-pressure port 31 and the low-pressure port 32 to the first port 33 and the second port 34.
The pilot valve 42 includes a valve body 43, an electromagnetic coil 44 disposed at an end on one side of the valve body 43, a plunger 45 configured to be drawn back when the electromagnetic coil 44 is excited, a spring 46 configured to push the plunger 45 when the electromagnetic coil 44 is not excited, and a valve 47 for switching communication of either the first pilot chamber 40 or the second pilot chamber 41 to the low-pressure port 32 in response to movement of the plunger 45.
On the other hand, the plurality of indoor units 3A, 3B each include an indoor refrigerant circuit 52 including the indoor heat exchanger 50 and an expansion valve for cooling (EEVC) 51, and are connected in parallel in the refrigeration cycle 6 via the refrigerant liquid lines 4A, 4B and the refrigerant gas lines 5A, 5B.
When the air conditioning system 1 is in cooling cycle operation, in the four-way selector valve 13, the pilot valve 42 is not energized and the electromagnetic coil 44 is not excited. As a result, as illustrated in FIG. 2, the plunger 45 and the valve 47 are pushed by the spring 46 to communicate the first pilot chamber 40 to the low-pressure port 32. As a result, when the compressor 10 is driven, and a high pressure is applied to the inner channel 35 from the refrigerant discharge line 20A via the high-pressure port 31, the high/low pressure difference between the first pilot chamber 40 and the inner channel 35 brings the slide valve 36 to a cooling cycle position illustrated in FIG. 2. As a result, the high-pressure port 31 is communicated to the second port 34, and the low-pressure port 32 is communicated to the first port 33.
Thus, the refrigerant discharged from the compressor 10 to the refrigerant discharge line 20A circulates through the cooling cycle as indicated by a solid line and arrows in FIG. 1, traveling through the oil separator 11, the check valve 12, the four-way selector valve 13, the outdoor heat exchanger 14, the expansion valve for heating (EEVH) 15, the receiver 16, the liquid-side operation valve 17, the refrigerant liquid line 4, 4A, 4B, the expansion valve for cooling (EEVC) 51, the indoor heat exchanger 50, the refrigerant gas line 5, 5A, 5B, the gas-side operation valve 18, the four-way selector valve 13, the refrigerant intake line 20B, and the accumulator 19 before returning to the compressor 10.
During this circulation, the refrigerant condensed and liquefied at the outdoor heat exchanger 14 undergoes adiabatic expansion at the expansion valve for cooling (EEVC) 51, absorbs heat from the air subjected to heat exchange at the indoor heat exchanger 50, and is changed to evaporated gas to be supplied for indoor cooling and the like. Note that in the cooling cycle, bold lined portions of the refrigeration cycle 6 illustrated in FIG. 1 indicate high pressure regions, and thin lined portions indicate low pressure regions.
On the other hand, when the air conditioning system 1 is in heating cycle operation, in the four-way selector valve 13, the pilot valve 42 is energized and the electromagnetic coil 44 is excited. As a result, the plunger 45 and the valve 47 resist the spring 46 and are pulled toward the electromagnetic coil 44, and the second pilot chamber 41 is communicated to the low-pressure port 32. As a result, when the compressor 10 is driven, and high pressure is applied to the inner channel 35 from the refrigerant discharge line 20A via the high-pressure port 31, the high/low pressure difference between the second pilot chamber 41 and the inner channel 35 causes the slide valve 36 to move and slide from a position on the left to a position on the right as illustrated in FIG. 2 to be in a heating cycle position. As a result, the high-pressure port 31 is communicated to the first port 33, and the low-pressure port 32 is communicated to the second port 34.
Switching to the heating cycle position of the four-way selector valve 13 causes the refrigerant discharged from the compressor 10 to the refrigerant discharge line 20A to circulate through the heating cycle as indicated by a solid line and arrows in FIG. 3, traveling through the oil separator 11, the check valve 12, the four-way selector valve 13, the gas-side operation valve 18, the refrigerant gas line 5, 5A, 5B, the indoor heat exchanger 50, the expansion valve for cooling (EEVC) 51, the refrigerant liquid line 4, 4A, 4B, the receiver 16, the expansion valve for heating (EEVH) 15, the outdoor heat exchanger 14, the four-way selector valve 13, the refrigerant intake line 20B, and the accumulator 19 before returning to the compressor 10.
During this circulation, the refrigerant condensed and liquefied by releasing heat via heat exchange with air at the indoor heat exchanger 50 undergoes adiabatic expansion at the expansion valve for heating (EEVH) 15, and is changed to evaporated gas at the outdoor heat exchanger 14 to be supplied for indoor heating and the like. Note that in the heating cycle, bold lined portions of the refrigeration cycle 6 illustrated in FIG. 3 indicate high pressure regions, and thin lined portions indicate low pressure regions.
The operation in the cooling cycle or the heating cycle of the air conditioning system 1 is executed via outdoor controllers 60A, 60B and indoor controllers (not illustrated) receiving an operation command from a remote control or the like and appropriately controlling a rotational speed of the compressor 10, switching of the four-way selector valve 13, opening amounts of the expansion valve for cooling (EEVC) 51 and the expansion valve for heating (EEVH) 15, rotational speeds of the non-illustrated indoor fan and outdoor fan, and the like.
Additionally, in order to control the plurality of outdoor units 2A, 2B depending on air conditioning loads and also to avoid a complete shutdown of the air conditioning system 1 when the compressor 10 of any of the outdoor units 2A, 2B becomes non-operational, the outdoor controllers 60A, 60B include backup operation control units 61A, 61B configured to operate the operational outdoor units 2A, 2B to continue air conditioning operation.
Further, the backup operation control units 61A, 61B are provided with four-way selector valve synchronization control units 62A, 62B configured to reliably synchronize the four-way selector valves 13 of the non-operational outdoor units 2A, 2B to switch to the heating cycle positions when the four-way selector valves 13 are operated to switch from the cooling cycle position to the heating cycle position in backup operation.
The four-way selector valve synchronization control units 62A, 62B include control functions of operating the four-way selector valves 13 in backup operation to switch from the cooling cycle position to the heating cycle position, such that, for example, the four-way selector valve synchronization control units 62A, 62B operate the four-way selector valve 13 of the operational outdoor unit 2A temporarily in the cooling cycle position so as to reduce pressure in the low pressure regions of the non-operational outdoor unit 2B and to secure a pressure difference for the four-way selector valve 13 of the non-operational outdoor unit 2B to operate, and then operate the four-way selector valve 13 of the non-operational outdoor unit 2B to switch the heating cycle position, and subsequently operate the four-way selector valve 13 of the operational outdoor unit 2A to switch to the heating cycle position and thus synchronize the four-way selector valves 13 of both the outdoor units 2A, 2B to be in the heating cycle position.
In other words, in the non-operational outdoor unit 2B, since the compressor 10 is non-operational, the pressure difference of a predetermined value or greater (typically, approximately 0.3 MPa, though this may depend on the specifications of the four-way selector valve 13) required for the four-way selector valve 13 to switch from the cooling cycle position to the heating cycle position cannot be secured. As a result, when the four-way selector valve 13 of the operational outdoor unit 2A is operated to switch from the cooling cycle position to the heating cycle position in backup operation, the four-way selector valve 13 of the non-operational outdoor unit 2B cannot be synchronized to switch to the heating cycle position. As illustrated in FIG. 4, this causes problems such as application of the high pressure refrigerant gas discharged from the operational outdoor unit 2A via the refrigerant gas line 5B to a low pressure intake channel from the four-way selector valve 13 to the compressor 10 of the non-operational outdoor unit 2B. The four-way selector valve synchronization control units 62A, 62B are configured to resolve this problem.
As described above, when the four-way selector valve 13 of the operational outdoor unit 2A is operated to switch from the cooling cycle position to the heating cycle position in backup operation, for example, the four-way selector valve synchronization control units 62A, 62B operate the four-way selector valve 13 of the operational outdoor unit 2A temporarily in the cooling cycle position as illustrated in FIG. 5. In this case, the four-way selector valve 13 of the non-operational outdoor unit 2B is not energized and is in the cooling cycle position. As a result, when the operational outdoor unit 2A operates, a low pressure of the intake channel (refrigerant intake line 20B) from the four-way selector valve 13 to the compressor 10 of the non-operational outdoor unit 2B via the refrigerant gas line 5B reduces, and thus the pressure difference of 0.3 MPa or greater required for the four-way selector valve 13 to switch the positions is secured.
Then, the four-way selector valve synchronization control units 62A, 62B are configured to determine that the pressure difference of 0.3 MPa or greater is secured, and output a switch command for the four-way selector valve 13 of the non-operational outdoor unit 2B to switch to the heating cycle position so as to operate the four-way selector valve 13 to switch to the heating cycle position, by any of the following (1) to (3).

(1) When the operational outdoor unit 2A operates in the cooling cycle and the rotational speed of the compressor 10 reaches a predetermined rotational speed, a low pressure on the non-operational outdoor unit 2B side reduces to a predetermined value or less, the pressure difference of the predetermined value (0.3 MPa) or greater is determined to be secured, and a switch command for the four-way selector valve 13 is output to the non-operational outdoor unit 2B.
(2) When the operational outdoor unit 2A operates in the cooling cycle and a low pressure is detected to be equal to or less than a predetermined value by the low pressure pressure sensor 26 on the non-operational outdoor unit 2B side, the pressure difference of the predetermined value (0.3 MPa) or greater is determined to be secured, and a switch command for the four-way selector valve 13 is output to the non-operational outdoor unit 2B.
(3) When the operational outdoor unit 2A operates in the cooling cycle and the difference (high pressure-low pressure) between detection values of the high pressure pressure sensor 25 and the low pressure pressure sensor 26 on the non-operational outdoor unit 2B side is detected to be equal to or greater than a predetermined value, the pressure difference of the predetermined value (0.3 MPa) or greater is determined to be secured, and a switch command for the four-way selector valve 13 is output to the non-operational outdoor unit 2B.

Subsequently, the four-way selector valve 13 of the operational outdoor unit 2A is operated to switch to the heating cycle position, and thus the four-way selector valves 13 of operational outdoor unit 2A and the non-operational outdoor unit 2B are synchronized in the heating cycle position. FIG. 6 illustrates the four-way selector valve 13 of the non-operational outdoor unit 2B and the four-way selector valve 13 of the operational outdoor unit 2A synchronized in the same heating cycle position. The four-way selector valve 13 of the non-operational outdoor unit 2B is in the heating cycle position, and thus the high pressure refrigerant gas can be prevented from being applied to the low pressure intake channel (refrigerant intake line 20B) from the four-way selector valve 13 to the compressor 10.
FIGS. 7 and 8 are flowcharts illustrating the control functions of the four-way selector valve synchronization control units 62A, 62B described above. In the air conditioning system 1 including the plurality of outdoor units 2A, 2B connected in parallel, control functions are provided such that when any of the outdoor units (outdoor unit 2B) becomes non-operational due to the non-operational compressor 10, the operational unit (outdoor unit 2A) operates the four-way selector valve 13 of the non-operational outdoor unit 2B to synchronously switch from the cooling cycle position to the heating cycle position. These control functions will be described in detail below with reference to FIGS. 7 and 8.
FIG. 7 is a flowchart for (2) and (3) described above. At step S1, when the non-operational outdoor unit 2B is non-operational due to the non-operational compressor 10 or the like, the process proceeds to step S2 at which a backup operation heating operation command is output to the operational outdoor unit 2A. In this case, at step S3, the operational outdoor unit 2A operates the four-way selector valve 13 in the cooling cycle position in which the high-pressure port 31 and the second port 34 are communicated and the low-pressure port 32 and the first port 33 are communicated.
In this state, the process proceeds to step S4, and, as described in (2) and (3) described above, it is determined whether the detection value detected by the low pressure pressure sensor 26 is equal to or less than a predetermined value, or whether the difference (high pressure-low pressure) in detection values of the high pressure pressure sensor 25 and the low pressure pressure sensor 26 is equal to or greater than a predetermined value. When the determination is YES, the process proceeds to step S5 at which a switch command is output to the four-way selector valve 13 of the non-operational outdoor unit 2B. Thus, the process proceeds to step S6 at which the four-way selector valve 13 of the non-operational outdoor unit 2B has a reduced low pressure and the operating pressure difference for the slide valve 36 to slide from the cooling cycle position to the heating cycle position as described above is secured. As a result, even during a complete shutdown of the compressor 10, switching to the heating cycle position can be achieved.
Subsequently, the process proceeds to step S7 at which a switch command is output for the four-way selector valve 13 of the operational outdoor unit 2A operating in the cooling cycle position. At step S8, switching to the heating cycle position causes the operational outdoor unit 2A to operate in the heating cycle, and backup heating operation at step S9 starts.
On the other hand, FIG. 8 is a flowchart for (1) described above.
In this case, as described above, steps other than steps at which whether the low pressure on the non-operational outdoor unit 2B side is reduced to equal or less than a predetermined value, and whether the pressure difference of 0.3 MPa or greater required for switching of the four-way selector valve 13 is secured are determined by determining, at step S14 illustrated in FIG. 8, whether the rotational speed of the compressor 10 of the operational outdoor unit 2A operating in the cooling cycle has reached a predetermined rotational speed, that is, steps S11 to S13 and steps S15 to S19, are the same as steps S1 to S3 and steps S5 to S9 described with reference to FIG. 7, and as such the description will be omitted.
Thus, according to the present embodiment, the following effects are achieved.
When the air conditioning system 1 described above operates one or both of the plurality of outdoor units 2A, 2B to perform air conditioning operation, and the compressor 10 of the outdoor unit 2A or 2B (here, the outdoor unit 2B) in operation become non-operational, the backup operation control units 61A, 61B operate the operational outdoor unit 2A to continue air conditioning operation.
In this case, when the cooling cycle operation or the heating cycle operation is performed and a cooling mode or a heating mode is continued to perform backup operation, the four-way selector valve 13 of the non-operational outdoor unit 2B is maintained in the cooling cycle position or the heating cycle position, while the four-way selector valve 13 of the operational outdoor unit 2A is brought to the cooling cycle position or the heating cycle position, and thus the positions of the four-way selector valves 13 of the outdoor units 2A, 2B can be synchronized to perform backup operation.
However, in backup operation, the four-way selector valve 13 may have to be operated to switch to the cooling cycle position or the heating cycle position. In a case, since the four-way selector valve 13 of the operational outdoor unit 2A can secure the operating pressure difference, the four-way selector valve 13 of the operational outdoor unit 2A can switch as usual to the heating cycle position, but the four-way selector valve 13 of the non-operational outdoor unit 2B cannot secure a high/low pressure difference (for example, 0.3 MPa) of a predetermined value or greater because of the non-operational compressor 10. This may prevent the four-way selector valves 13 from synchronizing in the heating cycle position.
However, according to the present embodiment, in such a case, the four-way selector valve synchronization control units 62A, 62B operate the four-way selector valve 13 of the operational outdoor unit 2A temporarily in the cooling cycle position so as to reduce a low pressure of the operational outdoor unit 2A and concurrently reduce a low pressure on the non-operational outdoor unit 2B side via the refrigerant gas line 5. Thus, it is determined by any of (1) to (3) described above that the pressure difference of 3 MPa or greater is secured, and a switch command is output for the four-way selector valve 13 of the non-operational outdoor unit 2B to switch to the heating cycle position, and the four-way selector valve 13 of the non-operational outdoor unit 2B is operated to switch to the heating cycle position. Subsequently, the four-way selector valve 13 of the operational outdoor unit 2A is operated to switch to the heating cycle position, and thus the four-way selector valves 13 of the outdoor units 2A, 2B can be synchronized in the heating cycle position.
Accordingly, this solves problems such as application of the high pressure refrigerant gas to the low pressure channel of the non-operational outdoor unit 2B and a complete shutdown of the air conditioning system caused by the four-way selector valve 13 of the non-operational outdoor unit 2B that cannot be operated to synchronously switch to the heating cycle position because the operating pressure difference required for the four-way selector valve 13 of the non-operational outdoor unit 2B to switch from the cooling cycle position to the heating cycle position cannot be secured. Also, the operational outdoor unit 2A can reliably be operated to execute backup operation.
Additionally, in backup operation, it can be determined by any of (1) to (3) described above that the pressure difference equal to or greater than the predetermined value (0.3 MPa) required for switching of the four-way selector valve 13 is secured. As a result, even when the four-way selector valve 13 of the non-operational outdoor unit 2B is non-operational because of the non-operational compressor 10, the operating pressure difference can reliably be secured, and the four-way selector valve 13 can be operated to switch from the cooling cycle position to the heating cycle position. Furthermore, such switching of the four-way selector valve 13 can be achieved with software changes and without hardware changes on a current system. As a result, a cost increase can be suppressed. Note that of (1) to (3) described above, the enhancement in reliability can increase in order from (1), (2), and (3).
Further, in the present embodiment, the low pressure channels (refrigerant intake lines 20B) between the four-way selector valves 13 and the compressors 10 of the plurality of outdoor units 2A, 2B are communicated via the oil equalizing line 27 or a low pressure communication line such as a pressure equalizing line. As a result, as described above, when the operational outdoor unit 2A operates to reduce a low pressure of the non-operational outdoor unit 2B, the low pressure on the non-operational outdoor unit 2B side can promptly reduce, and the reliability and certainty on the switching of the four-way selector valve 13 can be enhanced, and the time needed for the switching can be shortened.

Second Embodiment

Next, a second embodiment of the present invention will be described with reference to FIG. 9.
The present embodiment is different from the first embodiment described above in that a high pressure bypass circuit 70 including solenoid valves 71 is provided between refrigerant discharge lines 20A of a plurality of outdoor units 2A, 2B, and the solenoid valves 71 are controlled by four-way selector valve synchronization control units 63A, 63B to open and close. Since other points are similar to the first embodiment described above, the description thereof is omitted.
In other words, as illustrated in FIG. 9, in the present embodiment, the refrigerant discharge lines 20A of the plurality of outdoor units 2A, 2B are connected to one another by the high pressure bypass circuit 70 including the solenoid valves 71 via an operation valve 72 for line connection. Then, provided are four-way selector valve synchronization control units 73A, 73B configured to open the solenoid valves 71 of the high pressure bypass circuit 70 when a compressor 10 of any of the plurality of outdoor units 2A, 2B, for example the outdoor unit 2B, becomes non-operational; backup operation control units 61A, 61B operate another operational outdoor unit, for example the outdoor unit 2A, to perform backup operation such that a four-way selector valve 13 of the non-operational outdoor unit 2B is operated to switch from a cooling cycle position to a heating cycle position for synchronization.
Note that in the configuration described above, the high pressure bypass circuit 70 is provided with the two solenoid valves 71. However, this is because the configuration with the plurality of outdoor units 2A, 2B is a common configuration, and needless to say, the high pressure bypass circuit 70 may be provided with only one solenoid valve 71.
According to such a configuration, when the four-way selector valve 13 of the non-operational outdoor unit 2B is operated in backup operation to switch from the cooling cycle position to the heating cycle position for synchronization, the four-way selector valve synchronization control units 73A, 73B open the solenoid valves 71 of the high pressure bypass circuit 70. As a result, high pressure refrigerant gas discharged from the operational outdoor unit 2A is applied to the refrigerant discharge line 20A of the non-operational outdoor unit 2B, and a pressure difference (high/low pressure difference) required for the four-way selector valve 13 of the non-operational outdoor unit 2B to switch from the cooling cycle position to the heating cycle position is secured, and the four-way selector valve 13 of the non-operational outdoor unit 2B can be operated to switch to the heating cycle position for synchronization. Accordingly, this configuration can also achieve the same effects as the effects achieved by the first embodiment.
Note that the present invention is not limited to the invention according to the above-described embodiments and can be modified as necessary without departing from the spirit of the present invention. For example, in the embodiments described above, when any of the outdoor units (for example, the outdoor unit 2B) becomes non-operational due to the non-operational compressor 10, and an operational unit (for example, the outdoor unit 2A) is subjected to backup operation to continue air conditioning operation, the four-way selector valve 13 of the non-operational outdoor unit 2B is operated to synchronously switch from the cooling cycle position to the heating cycle position. However, in backup heating operation, the outdoor unit 2A in backup operation is subjected to defrosting operation or oil return operation. Thus, synchronous switching of the four-way selector valves 13 is also necessary in switching to a cooling cycle and returning to the backup heating operation after completion of the cooling cycle. The embodiments of the present invention can also be applied to such a case.
Additionally, in the embodiments described above, the one compressor 10 is installed in each of the plurality of outdoor units 2A, 2B. However, needless to say, the embodiments can also be applied to the case in which a plurality of the compressors 10 connected in parallel are installed in each of the outdoor units 2A, 2B, and all of the compressors 10 installed in the outdoor units 2A, 2B become non-operational.

Reference Signs List

1 Air conditioning system
2A, 2B Outdoor unit
3A, 3B Indoor unit
4, 4A, 4B Refrigerant liquid line
5, 5A, 5B Refrigerant gas line
6 Refrigeration cycle
10 Compressor
13 Four-way selector valve
14 Outdoor heat exchanger
20A Refrigerant discharge line
20B Refrigerant intake line (low pressure channel)
21 Outdoor coolant circuit
25 High pressure pressure sensor
26 Low pressure pressure sensor
27 Oil equalizing line (low pressure communication line)
52 Indoor refrigerant circuit
60A, 60B Outdoor controller
61A, 61B Backup operation control unit
62A, 62B, 63A, 63B Four-way selector valve synchronization control unit
70 High pressure bypass circuit
71 Solenoid valve

Claims

An air conditioning system, comprising:
a refrigeration cycle including a refrigerant circuit on an indoor unit side and an outdoor unit side connected via a refrigerant liquid line and a refrigerant gas line;

a plurality of outdoor units each including at least one compressor, a four-way selector valve configured to operate the refrigeration cycle to switch to any of a cooling cycle and a heating cycle, and an outdoor heat exchanger, and connected in parallel in the refrigeration cycle; and

a backup operation control unit configured to perform backup operation on another operational outdoor unit to continue air conditioning operation when the compressor of any of the plurality of outdoor units becomes non-operational;

wherein the backup operation control unit includes a four-way selector valve synchronization control unit configured to operate the four-way selector valve in backup operation to switch from a cooling cycle position to a heating cycle position, such that the four-way selector valve synchronization control unit operates the four-way selector valve of the operational outdoor unit temporarily in a cooling cycle position so as to reduce a low pressure of the non-operational outdoor unit and to secure an operating pressure difference of the four-way selector valve of the non-operational outdoor unit, and then operates the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position, and subsequently operates the four-way selector valve of the operational outdoor unit to switch to a heating cycle position and synchronizes the four-way selector valves so as to operate in a heating cycle.
The air conditioning system according to claim 1, wherein the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a rotational speed of the compressor of the operational outdoor unit reaches a predetermined rotational speed.
The air conditioning system according to claim 1, wherein the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a detection value of a low pressure of the non-operational outdoor unit is equal to or less than a predetermined value.
The air conditioning system according to claim 1, wherein the four-way selector valve synchronization control unit is configured to output a switch command for the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position when a difference between detection values of a high pressure and a low pressure of the non-operational outdoor unit is equal to or greater than a predetermined value.
The air conditioning system according to any one of claims 1 to 4, wherein low pressure channels between the four-way selector valves of the plurality of outdoor units and the compressors are connected to one another via a low pressure communication line.
The air conditioning system according to claim 5, wherein the low pressure communication line is an oil equalizing line or a pressure equalizing line connecting the low pressure channels of the compressors of the plurality of outdoor units to one another.
An air conditioning system, comprising:
a refrigeration cycle including a refrigerant circuit on an indoor unit side and an outdoor unit side connected via a refrigerant liquid line and a refrigerant gas line;

a plurality of the outdoor units each including at least one compressor, a four-way selector valve configured to operate the refrigeration cycle to switch to any of a cooling cycle and a heating cycle, and an outdoor heat exchanger, and connected in parallel in the refrigeration cycle; and

a backup operation control unit configured to perform backup operation on another operational outdoor unit to continue air conditioning operation when the compressor of any of the plurality of outdoor units becomes non-operational;

wherein discharge lines between the compressors and the four-way selector valves of the plurality of outdoor units are provided with a high pressure bypass circuit including a solenoid valve communicating the discharge lines to one another; and

the backup operation control unit is provided with a four-way selector valve synchronization control unit configured to operate the four-way selector valve in backup operation to switch from a cooling cycle position to a heating cycle position, such that the four-way selector valve synchronization control unit opens the solenoid valve provided in the high pressure bypass circuit so as to operate the four-way selector valve of the non-operational outdoor unit to switch to a heating cycle position, and synchronizes the four-way selector valves so as to operate in a heating cycle.