Air-conditioning system

Abstract: An air conditioning system in which a single heat source unit (A) comprising a compressor (1), a four-way valve (2), a heat source unit side heat exchanger (3) and an accumulator (4) is connected to a plurality of indoor units (B, C, D) through a first and a second connection pipes (6, 7). Each indoor unit (B, C, D) comprises a suction air temperature detecting device (50) for detecting a suction air temperature of the indoor unit, an opening degree setting device for setting a minimum valve opening degree of the first flow rate controller 9 in accordance with the difference between the target temperature and the suction air temperature and a first valve opening degree control device (52) for controlling the valve opening degree of the first flow rate controller 9 at a predetermined rate to the minimum valve opening degree.

Description: BACKGROUND OF THE INVENTION This invention relates to an air-conditioning system in which a plurality of indoor units are connected to a single heat source unit and particularly to a refrigerant flow rate control unit so that a multi-room heat pump type air conditioning system is provided for selectively operating the respective indoor units in cooling or heating mode of operation, or wherein cooling can be carried out in one or some indoor units while heating can be concurrently carried out in other indoor units. Fig. 4 is a general schematic diagram illustrating one example of a conventional heat pump type air-conditioning system. In the figure, reference numeral 1 designates a compressor, 2 is a four-way valve, 3 is a heat source unit side heat exchanger, 4 is an accumulator, 5 is an indoor side heat exchanger, 6 is a first connection pipe, 7 is a second connection pipe, and 9 and is a first flow rate controller. The operation of the above-described conventional air-conditioning system will now be described. In the cooling operation, a high-temperature, high-pressure refrigerant gas supplied from the compressor 1 flows through the four-way valve 2 and is heat-exchanged with air in the heat source unit side heat exchanger 3, where it is condensed into a liquid. Then, the liquid refrigerant is introduced into the indoor unit through the second connection pipe 7, where it is pressure-reduced by the first flow rate controller 9 and heat-exchanged with air in the indoor side heat exchanger 5 to evaporate into a gas thereby cooling the room. The refrigerant in the gaseous state is then supplied from the first connection Pipe 6 to the compressor 1 through the four-way valve 2 and the accumulator 4 to define a circulating cycle for the cooling operation. In the heating operation, the high-temperature, high-pressure refrigerant gas supplied from the compressor 1 is flowed into the indoor unit through the four-way valve 2 and the first connection pipe 6 so that it is heat-exchanged with the indoor air in the indoor side heat exchanger 5 to be condensed into liquid thereby heating the room. The refrigerant thus liquidified is pressure-decreased in the first flow rate controller 9 until it is in the low-pressure, gas-liquid phase state and introduced into the heat source unit side heat exchanger 3 through the second connection pipe 7, where it is heat-exchanged with the air to evaporate into a gaseous state, and is returned to the compressor 1 through the four-way valve 2 and the accumulator 4, whereby a circulating cycle is provided for carrying out the heating operation. Fig. 5 is a general schematic diagram illustrating another example of a conventional heat pump type air-conditioning system, in which reference numeral 24 designates a low-pressure saturation temperature detection means. In the above conventional air-conditioning system, when the cooling operation is to be carried out, the compressor 1 is controlled in terms of the capacity so that the detected temperature of the low-pressure saturation temperature detecting means 24 is in coincidence with the predetermined value. However, in the conventional air-conditioning system, all of the indoor units are coincidentally operated in either cooling or heating mode of operation, so that a problem where an area to be cooled is heated and, contrary, where an area to be heated is cooled. As an improvement of this, an air conditioning system which allows the concurrent cooling and heating operations has been developed, as illustrated in GB-A-2194651 and in EP-A-453271. The latter system is illustrated in Fig. 6. In Fig.6, A is a heat source unit, B,C and D are indoor units of the same construction and connected in parallel to each other as described later. E is a junction unit comprising therein a first junction portion, a second flow rate controller, a second junction portion, a gas/liquid separator, a heat exchanger, a third flow rate controller and a fourth flow rate controller. Reference numeral 20 is a heat source side fan of a variable flow rate for blowing air to the heat source side heat exchanger 3, 6b, 6c and 6d are indoor unit side first connection pipes corresponding to the first connection pipe 6 and connecting the junction unit E to the indoor side heat exchangers 5 of the indoor units B, C and D, respectively, and 7b, 7c and 7d are indoor unit side second connection pipes corresponding to the second connection pipe 7 and connecting the junction unit E to the indoor unit side heat exchangers 5 of the indoor units B, C and D, respectively. Reference numeral 8 is a three-way switch valve for selectively connecting the indoor unit side first connection pipes 6b, 6c and 6d to either of the first connection pipe 6 or to the second connection pipe 7. Reference numeral 9 is a first flow rate controller disposed close to the exchanger 5 and connected to the indoor unit side second connection pipes 7b, 7c and 7d and is controlled by the superheating amount at the outlet side of the indoor unit side heat exchanger 5 in the cooling mode of operation, and is controlled by the subcooling amount in the heating mode of operation. Reference numeral 10 is a first junction portion including three-way valves 8 connected for switching between the indoor unit side first connection pipes 6b, 6c and 6d, the first connection pipe 6 and the second connection pipe 7. Reference numeral 11 is a second junction portion comprising the indoor unit side second connection pipes 7b, 7c and 7d, and the second connection pipe 7. Reference numeral 12 designates a gas-liquid separator disposed midpoint in the second connection pipe 7, the gas phase portion thereof being connected to a first opening 8a of the three-way valve 8, the liquid phase portion thereof being connected to the second junction portion 11. Reference numeral 13 designates a second flow rate controller (an electric expansion valve in this embodiment) connected between the gas-liquid separator 12 and the second junction portion 11. Reference numeral 14 designates a bypass pipe connecting the second junction portion 11 and the first connection pipe 6, 15 is a third flow rate controller (an electric expansion valve in this embodiment) disposed in the bypass pipe 14, 16a is a second heat exchanging portion disposed downstream of the third flow rate controller 15 inserted in the bypass pipe 14 for the heat-exchange in relation to the junctions of the indoor unit side second connection pipes 7b, 7c and 7d in the second junction portion 11. 16b, 16c and 16d are third heat exchanging portions disposed downstream of the third flow rate controller 15 inserted in the bypass pipe 14 for the heat-exchange in relation to the junctions of the indoor unit side second connection pipes 7b, 7c and 7d in the second junction portion 11. Reference numeral 19 is a first heat exchanging portion disposed downstream of the third flow rate controller 15 inserted in the bypass pipe 14 and downstream of the second heat exchanging portion 16a for the heat-exchange in relation to the pipe connected between the gas-liquid separator 12 and the second flow rate controller 13, and 17 is a fourth flow rate controller (an electric expansion valve in this embodiment) connected between the second junction portion 11 and the first connection pipe 6. Reference numeral 32 is a third check valve disposed between the heat source unit side heat exchanger 3 and the second connection pipe 7 for allowing the flow of the refrigerant only from the heat source unit side heat exchanger 3 to the second connection pipe 7. Reference numeral 33 is a fourth check valve disposed between the four-way valve 2 of the heat source unit A and the first connection pipe 6 for allowing the flow of the refrigerant only from the first connection pipe 6 to the four-way vale 2. Reference numeral 34 is a fifth check valve disposed between the four-way valve 2 and the second connection pipe 7 for allowing the flow of the refrigerant only from the four-way valve 2 to the second connection pipe 7. Reference numeral 35 is a sixth check valve disposed between the heat source unit side heat exchanger 3 and the first connection pipe 7 for allowing the flow of the refrigerant only from the first connection pipe 6 to the heat source unit side heat exchanger 3. The above-described third, fourth, fifth and sixth check valves 32, 33, 34 and 35, respectively, constitutes a flow path change-over unit 40. Reference numeral 21 designates a takeoff pipe connected at one end thereof to the liquid outlet pipe of the heat source unit side heat exchanger 3 and to the inlet pipe of the accumulator 4, 22 is a throttle disposed in the takeoff pipe 21, and 23 designates a second temperature detection means disposed between the throttle 22 and the inlet pipe of the accumulator of the takeoff pipe 21. The conventional air-conditioning system capable of a concurrent heating and cooling operation has the above-described construction. Accordingly, when only the cooling operation is being carried out, the high-temperature, high-pressure refrigerant gas supplied from the compressor 1 flows through the four-way valve 2 and is condensed into a liquid in the heat source unit side heat exchanger 3 with the air supplied from the variable capacity heat source unit side fan 20. Then, the liquid refrigerant is introduced into the respective indoor units B, C and D through the third check valve 32, the second connection pipe 7, the gas-liquid separator 12, the second flow rate controller 13, the second junction portion 11 and through the indoor unit side second connection pipes 7b, 7c and 7d. The refrigerant introduced into the indoor units B, C and D is decreased in pressure by the first flow rate controller 9 controlled by the superheating amount at the outlet of the indoor unit side heat exchanger 5, where it is heat-exchanged in the indoor unit side heat exchanger 5 with the indoor air to be evaporated into a gas to cool the room. The gaseous refrigerant is flowed through the indoor unit side first connection pipes 6b, 6c and 6d, the three-way change-over valve 8, the first junction portion 10, the first connection pipe 6, the fourth check valve 33, the four-way valve 2 of the heat source unit and the accumulator 4 into the compressor 1 to define a circulating cycle for the cooling operation. At this time, the first opening 8a of the three-way change-over valve 8 is closed while the second opening 8b and the third opening 8c are opened. At this time, the first connection pipe 6 is at a low pressure and the second connection pipe 7 is at a high pressure, so that the refrigerant inevitably flows toward the third check valve 32 and the fourth check valve 33. Also, in this cycle, one portion of the refrigerant that passes through the second flow rate controller 13 is introduced into the bypass pipe 14 and is pressure-reduced in the third flow rate controller 15 and heat-exchanged in the third heat exchanging portions 16b, 16c and 16d in relation to the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11. Thereafter, the heat-exchanging is carried out in the second heat exchanging portion 16a in relation to the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11, and a further heat-exchanging is carried out in the first heat exchanging portion 19 in relation to the refrigerant flowing into the second flow rate controller 13 to evaporate the refrigerant, which then is supplied to the first connection pipe 6 and the fourth check valve 33 to be returned into the compressor 1 through the four-way valve 2 of the heat source unit and the accumulator 4. On the other hand, the refrigerant within the second junction portion 11 which is heat-exchanged and cooled at the first, second and third heat-exchanging portions 19, 16a, 16b, 16c and 16d and is introduced into the indoor units B, C and D to be cooled. In the mode of operation in which cooling is mainly carried out in the concurrent cooling and heating operations, the refrigerant gas supplied from the compressor 1 is flowed into the heat source unit side heat exchanger 3 through the four-way valve 2, where it is heat-exchanged in relation to the air supplied by the variable capacity heat source unit side fan 20 to become a high-temperature and high-pressure ga-liquid phase. At this time, the pressure obtained on the basis of the saturation temperature detected by the second temperature detecting means 23 is used to adjust the air flow rate of the heat source unit side fan 20 and the capacity of the compressor 1. Thereafter, this refrigerant in the high-temperature, high-pressure gas-liquid phase state is supplied to the gas-liquid separator 12 of the junction unit E through the third check valve 32 and the second connection pipe 7. Then, the refrigerant is separated into the gaseous refrigerant and the liquid refrigerant, the separated gaseous refrigerant is introduced into the indoor unit D to be heated through the first junction portion 10, the three-way valve 8 and the indoor unit side first connection pipe 6d, where it is heat-exchanged in relation to the indoor air in the indoor unit side heat exchanger 5 to be condensed into a liquid to heat the room. The refrigerant is then controlled by the subcooling amount at the outlet of the indoor unit side heat exchanger 5, flows through the substantially fully opened first flow rate controller 9 where it is slightly pressure-decreased and enters into the second junction portion 11. On the other hand, the liquid refrigerant is supplied to the second junction portion 11 through the second flow rate controller 13, where it is combined with the refrigerant which passes through the indoor unit D to be heated and introduced into each indoor units B and C through the indoor unit side second connection pipes 7b and 7c. The refrigerant flowed into the respective indoor units B and C is pressure-reduced by the first flow rate controller 9 controlled by the superheating amount at the outlet of the indoor unit side heat exchangers B and C and is heat-exchanged in relation to the indoor air to evaporate into vapor to cool the room. The vaporized refrigerant then flows through a circulating cycle of the indoor unit side first connection pipes 6b and 6c, the three-way valve 8 and the first junction portion 10 to be suctioned into the compressor 1 through the first connection pipe 6, the fourth check valve 33, the four-way valve 2 of the heat source unit and the accumulator 4, thereby to carry out the cooling-dominant operation. The conventional air-conditioning system constructed as above-described has a problem in that, a disturbance of the refrigerant cycle is generated due to the variation in pressure of the refrigeration cycle and a stable detection of the low-pressure saturation temperature in the heat source unit cannot be achieved due to the variation of the indoor cooling load when the operation is cooling only or due to the variation of the indoor cooling load or heating load when the operation is cooling-dominant. When the operation is cooling-dominant, the refrigerant which passed thorugh the heat source unit side heat exchanger becomes vapor-liquid phase state, preventing a stable detection of the saturation temperature of the refrigerant. Alternatively, when the number of indoor units in the cooling operational mode, when the units are started for cooling operation after a long period of stoppage or when the cooling operation is started immediately after heating operation, a large amount of liquid refrigerant stays in the accumulator or the like, so that a vapor-liquid two-phase state due to lack of refrigerant takes place at the inlet of the first flow rate controller 9, increasing the flow path resistance of the first flow rate controller 9, which causes the decrease in refrigerant pressure, the decrease in the refrigerant circulating amount and the decrease in the low pressure saturation temperature whereby the cooling capacity is disadvantageously decreased and the heating and cooling cannot be selectively carried out by each indoor unit and a stable concurrent cooling and heating operation in which some of the indoor units carry out cooling and some other of the indoor units carry out heating. In particular, when the air-conditioning system is installed in a large-scale building, the air-conditioning load is significantly different between the interior portion and the perimeter portion, and between the general offices and the OA (office automated) room such as a computer room. This invention has been made in order to solve the above-discussed problems and has as its object the provision of an air-conditioning system generally as shown in Fig. 6, in which the cooling and heating can be selectively carried out for each indoor units or some of the indoor units can be cooling-operated while other of the indoor units are being heating-operated, and the l-p saturation temperature in the heat source unit can be reliably detected. The present system has the features set out in claim 1. Specifically, the air-conditioning system of the invention is provided with a takeoff pipe connected at one end thereof to a liquid outlet side pipe of the heat source unit side heat exchanger and at the other end thereof to an inlet pipe of the accumulator through a throttle device, the takeoff pipe extending through cooling fins of the heat source unit side heat exchanger, and a temeprature detector is disposed in the takeoff pipe between the throttle device and the inlet pipe of the accumulator. The takeoff pipe is arranged to extend through cooling fins of the heat source unit side heat exchanger, so that even when the refrigerant in the vapor-liquid two phase state is supplied from the heat source unit side heat exchanger due to the air flow rate control conditions of the heat source unit side fan, and even when the refrigerant evaporates or fails to condense due to a high air temperature, the refrigerant is heat-exchanged again to become liquid at the takeoff pipe coiled in the fins, whereby a stable and accurate detection can be realized by the temperature detector. The heat source unit side heat exchanger may be provided at a refrigerant inlet and outlet portions with first and second valves, respectively, and a heat source unit side bypass pipe bypassing the heat source unit side heat exchanger through a third valve is connected at one end thereof to a liquid outlet side pipe positioned between the heat source unit side heat exchanger and the takeoff pipe connection portion. The present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which: Fig. 1 is a general schematic diagram illustrating the refrigeration lines of the air-conditioning system of a first embodiment of the present invention; Fig. 2 is a schematic diagram generally illustrating the refrigerant lines of the air-conditioning system of a second embodiment of the present invention; Fig. 3 is a flow chart illustrating the control of the first to third solenoid valves in the cooling-dominant operation in the air-conditioning system of the second embodiment of the present invention; Fig. 4 is a schematic diagram illustrating one example of a conventional air-conditioning system; Fig. 5 is a schematic diagram illustrating another example of a conventional air-conditioning system; and Fig. 6 is a schematic diagram illustrating a further example of a conventional air-conditioning systenm. DESCRIPTION OF THE PREFERRED EMBODIMENTS The description of the embodiments of the air-conditioning system of the present invention will now be made in terms of the drawings. Embodiment 1 Fig. 1 is a general schematic diagram of the refrigerant lines in one embodiment of the first invention. Figs. 2 to 4 illustrate the operational state in the cooling and the heating operations of the first embodiment illustrated in Fig. 1, and Fig. 2 illustrates the cooling or heating only operational states, Figs. 3 and 4 illustrate the concurrent cooling and heating operation, Fig. 3 being operational state diagram for the heating dominant operation (where the heating operation capacity is larger than the cooling operation capacity) and Fig. 4 being operational state diagram for the cooling dominant operation (where the cooling operation capacity is larger than the heating operation capacity). While this first embodiment will be described in terms of a heat source unit having three indoor units, the heat source unit having at least two indoor units will equally be applicable. In Fig. 1, reference character A designates a heat source unit, B, C and D designate similarly constructed heat source units connected in parallel to each other as will be described in more detail later. E, which will be described in more detail later, is a junction unit including a first junction portion, a second flow rate controller, a second junction portion, a vapor-liquid separator, a heat exchanger, a third flow rate controller and a four flow rate controller. Also, reference numeral 1 designates a compressor, 2 is a four-way valve for changing the refrigerant flow direction of the heat source unit, 3 designates a heat source unit side heat exchanger, 4 designates an accumulator connected to the compressor 1 through the four-way valve 2, and the heat source unit A comprises the compressor 1, the four-way valve 2, the heat source unit side heat exchanger 3 and the accumulator 4. Also, reference numeral 5 designate indoor unit side heat exchangers disposed in three indoor units B, C and D, 6b, 6c and 6d are indoor unit side first connection pipes corresponding to the first connection pipe 6 for connecting the junction unit E to the respective indoor unit side heat exchangers 5 of the indoor units B, C and D, 7 is a second connection pipe thinner than the first connection pipe 6 for connecting the junction unit E to the heat source unit side heat exchanger 3 of the heat source unit A. Also, reference characters 7b, 7c and 7d are indoor unit side second connection pipes corresponding to the second connection pipe 7 for connecting the junction unit E to the indoor unit side heat exchanger 5 of the respective indoor units B, C and D. Reference numeral 8 designates three-way change-over valve which is a valve unit capable of selectively connecting the indoor unit side first connection pipes 6b, 6c and 6d to either of the first connection pipe 6 and the second connection pipe 7, and isolating the indoor unit side first connection pipes 6b, 6c and 6d from the first connection pipe 6 and the second connection pipe 7. Reference numerals 9 designate first flow rate controllers connected to the indoor unit side second connection pipes 7b, 7c and 7d for being controlled by the superheat amount at the outlet side of the indoor unit side heat exchanger 5 during the cooling operation (by a first valve opening degree control means 52 which will be described later, in this embodiment) and by the subcooling amount at the outlet side of the indoor unit side heat exchangers 5 during the heating operation. The first flow rate controllers 9 are connected to the indoor unit side second connection pipes 7b, 7c and 7d. Reference numeral 10 designates a first junction portion comprising the three-way valves for selectively connecting the indoor unit side first connection pipes 6b, 6c and 6d to either the first connection pipe 6 or the second connection pipe 7. Reference numeral 11 designates a second junction portion comprising the indoor unit side second connection pipes 7b, 7c and 7d and the second connection pipe 7. Reference numeral 12 designates a vapor-liquid separator inserted into the second connection pipe 7, a vapor phase region thereof being connected to a first opening 8a of the three-way valve 8 and a liquid phase region thereof being connected to the second junction portion 11. Reference numeral 13 designates a second flow rate controller (an electrical expansion valve in this embodiment) capable of closing and opening and connected between the vapor-liquid separator 12 and the second junction portion 11. Reference numeral 14 designates a bypass pipe connecting the first connection pipe 6 to the second junction portion 11, 15 is a third flow rate controller (an electrical expansion valve in this embodiment) inserted into the bypass pipe 14, 16a is a second heat exchanging portion disposed downstream of the third flow rate controller 15 inserted into the bypass pipe 14 for carrying out heat-exchange with respect to the indoor unit side second connection pipes 7b, 7c and 7d in the second junction portion 11. Reference numerals 16b, 16c and 16d are third heat-exchanging portions disposed downstream of the third flow rate controller 15 inserted into the bypass pipe 14 for heat-exchanging in relation to the respective indoor unit side second connection pipes 7b, 7c and 7d in the second junction portion 11. Reference numeral 19 designates a first heat exchanging portion disposed downstream of the third flow rate controller 15 of the bypass pipe 14 and the second heat exchanging portion 16a for carrying out heat-exchanging in relation to the pipe connecting the vapor-liquid separator 12 and the second flow rate controller 13, and reference numeral 17 designates a fourth flow rate controller (an electrical expansion valve in this embodiment) capable opening and closing the connection between the second junction portion 11 and the first connection pipe 6. On the other hand, reference numeral 32 is a third check valve disposed between the heat source unit side heat exchanger 3 and the second connection pipe 7 for allowing the refrigerant to flow only from the heat source side heat exchanger 3 to the second connection pipe 7. Reference numeral 33 is a fourth check valve disposed between the four-way valve 2 of the heat source unit A and the first connection pipe 6 for allowing the refrigerant to flow only from the first connection pipe 6 to the four-way valve 2. Reference numeral 34 designates a fifth check valve disposed between the four-way valve 2 of the heat source unit A and the second connection pipe 7 for allowing the refrigerant to flow only from the first connection pipe 6 to the four-way valve 2. Reference numeral 35 designates a sixth check valve disposed between the heat source unit side heat exchanger 3 and the first connection pipe 6 for allowing the refrigerant to flow only from the heat source unit side heat exchanger 3 to the first connection pipe 6. The above-described third, fourth, fifth and sixth check valves 32, 33, 34 and 35, respectively, constitute a flow path change-over unit 40. The high temperature, high pressure refrigerant gas supplied from the compressor 1 flows through the four-way valve 2, heat-exchanged in relation to outdoor air in the heat source unit side heat exchanger 3 to be condensed into liquid, and flows through the third check valve 32, the second connection pipe 7, the vapor-liquid separator 12, the second flow rate controller 13, the second junction portion 11 and indoor unit side second connection pipes 7b, 7c and 7d to be supplied into the respective indoor units B, C and D. The refrigerant flowed into the respective indoor units B, C and D is pressure-reduced by the respective first flow rate controllers 9 and heat-exchanged in the indoor unit side heat exchangers 5 in relation to the indoor air to evaporate into vapor to cool the room. The refrigerant in the vapor state follows the circulating cycle from the indoor unit side first connection pipes 6b, 6c and 6d to the compressor 1 through the three-way valve 8, the first junction portion 10, the first connection pipe 6, the fourth check valve 33, the heat source side four-way valve 2 and the accumulator 4 to achieve the cooling operation. At this time, the first opening 8a of the three-way valve 8 is closed, and the second opening 8b and the third opening 8c are opened, and since the first connection pipe 6 is at a low pressure and the second connection pipe 7 is at a high pressure, the refrigerant flows through the third check valve 32 and the fourth check valve 33. In this cycle, a portion of the refrigerant passed through the second flow rate controller 13 enters into the bypass pipe 14 and is pressure-reduced to a low pressure at the third flow rate controller 15. The refrigerant then is heat-exchanged in the third heat exchanging portions 16b, 16c and 16d in relation to the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11, and is heat-exchanged in the second heat exchanging portion 16a in relation to the meeting portions of the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11, and is further heat-exchanged in the first heat exchanging portion 19 in relation to the refrigerant flowing into the second flow rate controller 13, the evaporated refrigerant being suctioned into the compressor 1 through the first connection pipe 6, the fourth check valve 33, the four-way valve 2 of the heat source unit and the accumulator 4. On the other hand, the refrigerant at the second junction portion 11 which is heat-exchanged and cooled at the first, the second and the third heat exchanging portions 19, 16a, 16b, 16c and 16d and sufficiently subcooled flows into the indoor units B, C and D to be operated for cooling. Next, the heating-only operation will be described. The high temperature, high pressure refrigerant gas supplied from the compressor 1 flows through the four-way valve 2, the fifth check valve 34, the first connection pipe 6, the vapor-liquid separator 12, the first junction portion 10, the three-way valve 8 and the indoor unit side first connection pipes 6b, 6c and 6d to flow into the indoor units B, C and D to be heat-exchanged in relation to indoor air into liquid to heat the room. The refrigerant in the liquid state flows through the first flow rate controller 9 which is controlled in the substantially fully-opened state by the subcooling amount at the outlet of the respective indoors unit side heat exchanger 5, flows through the indoor unit side second connection pipes 7b, 7c and 7d into the second junction portion 11 to joint together to further flow through the fourth flow rate controller 17. At this time, the refrigerant is pressure-reduced to a low-pressure vapor-liquid two phase state at either of the first flow rate controllers 9 or the third and the fourth flow rate controllers 15 and 17. The refrigerant pressure-reduced to a low pressure follows the circulating cycle from the first connection pipe 6 to the compressor 1 through the sixth check valve 6 of the heat source unit A, the heat source unit side heat exchanger 3, where it is heat-exchanged in relation to the outdoor air to evaporate into a gaseous state and further flows through the four-way valve 2 and the accumulator 4. At this time, the second opening 8b of the three-way valve 8 is closed, and the first opening 8b and the third opening 8c are opened, and since the first connection pipe 6 is at a low pressure and the second connection pipe 7 is at a high pressure, they are communicated to the fifth check valve 34 and the sixth check valve 35 because it is in communication with the suction side of the compressor 1 and the outlet side of the compressor 1, respectively. The heating-dominant operation in the concurrent cooling and heating operation will now be described. In this case, the description will be made as to where the two indoor units B and C are to be operated for heating and the indoor unit D is to be operated for cooling. As shown by the dotted arrows in the figure, the high temperature, high pressure refrigerant gas supplied from the compressor 1 is supplied to the junction unit E through the four-way valve 2, the fifth check valve 34 and the second connection pipe 7, and then introduced into the indoor units B and C to be operated for heating through the vapor-liquid separator 12, the first junction portion 10, the three-way valve 8 and the indoor unit side first connection pipes 6b and 6c, and the refrigerant is heat-exchanged in the indoor unit side heat exchanger 5 in relation to the indoor air to be condensed into liquid to heat the room. The condensed liquid refrigerant flows through the first flow rate controller 9, which is controlled to the substantially fully opened state by the subcooling amount at the outlet of the indoor unit side heat exchangers 5 of the indoor units B and C, to be slightly pressure-reduced and introduced into the second junction portion 11. One portion of this refrigerant flows through the indoor unit side second connection pipe 7d to enter into the indoor unit D to be operated for cooling, and flows through the first flow rate controller 9 to be pressure-reduced, and then flows into the indoor unit side heat exchanger 5 to be heat-exchanged to evaporate into a gaseous state to cool the room, and then flows into the first connection pipe 6 through the first connection pipe 6d and the three-way valve 8. On the other hand, the other refrigerant flows through the fourth flow rate controller 17, and is combined with the refrigerant flowed through the indoor unit D to be operated for cooling, to flow into the heat source side heat exchanger 3 through the thick first connection pipe 6 and the sixth check valve 35 of the heat source unit A, where it is heat-exchanged in relation to the outdoor air to evaporate into the gaseous state. This refrigerant follows a circulating cycle extending to the compressor 1 through the four-way valve 2 of the heat source unit and the accumulator 4, whereby the heating-dominant operation is carried out. At this time, the vapor pressure of the indoor unit side heat exchanger 5 of the indoor unit D to be operated for cooling and the pressure difference of the heat source unit side heat exchanger 3 is reduced because the thick first connection pipe 6 is substituted. Also, at this time, the second opening 8b of the three-way valve 8 connected to the indoor units B and C is closed and the first opening 8a and the third opening 8c are opened, and the first opening 8a of the indoor unit D is closed and the second opening 8b and the third opening 8c are opened. Also, at this time, since first connection pipe 6 is at a low pressure and the second connection pipe 7 is at a high pressure, the refrigerant flows into the fifth check valve 34 and the sixth check valve 35. In this cycle, one portion of the liquid refrigerant flows from the meeting portion of the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11 to the bypass pipe 14, pressure-reduced at the third flow rate controller 15, and heat-exchanged at the third heat exchanging portions 16b, 16c and 16d in relation to the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11 and at the second heat exchanging portion 16a in relation to the meeting portions of the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11, and further heat-exchanged in the first heat exchanging portion 19 in relation to the refrigerant flowing into the second flow rate controller 13, the evaporated refrigerant being supplied to the first connection pipe 6 and the sixth check valve 35 from where it is suctioned by the compressor 1 through the heat source unit four-way valve 2 and the accumulator 4. On the other hand, the refrigerant at the second junction portion 11, which is heat-exchanged in the second and the third heat exchanging portions 16a, 16b, 16c and 16d to be sufficiently subcooled, is supplied to the indoor unit D to be operated for cooling. Next, the cooling-dominant operation in the concurrent cooling and heating operation will now be described in terms of the operation where two indoor units B and C are to be operated for cooling and the indoor unit D is to be operated for heating. The refrigerant gas supplied from the compressor 1 flows through the four-way valve 2 to the heat exchanger 3, where it is heat-exchanged in relation to outdoor air to become two phase high-pressure and high-temperature state. After this, the refrigerant in the high-temperature, high-pressure two phase state is supplied to the vapor-liquid separator 12 of the junction unit E through the third check valve 32 and the second connection pipe 7. The refrigerant is then separated into the gaseous refrigerant and the liquid refrigerant, and the separated gaseous refrigerant flows through the first junction portion 10, the three-way valve 8 and the indoor unit side first connection pipe 6d into the indoor unit D to be operated for heating, where it is heat-exchanged in the indoor unit side heat exchanger 5 in relation to the indoor air to be condensed into liquid to heat the room. The refrigerant further flows through the first flow rate controller 9 controlled by the subcooling amount at the outlet of the indoor unit side heat exchanger 5 to be a substantially fully opened state to be slightly pressure-reduced to become an intermediate pressure (intermediate) between the high and the low pressure and flows into the second junction portion 11. On the other hand, the remaining refrigerant flows through the second flow rate controller 13, flows into the second junction portion 11 to be combined with the refrigerant flowed through the indoor unit D to be operated for heating, and flows into the indoor units B and C through the indoor unit side second connection pipes 7b and 7c. The refrigerant flowed into the respective indoor units B and C is pressure-reduced to a low pressure by the first flow rate controller 9 to be heat-exchanged in relation to the indoor air to evaporate into the gaseous state to cool the room. This refrigerant in the gaseous state follows a circulating cycle extending to the compressor 1 through the indoor unit side first connection pipes 6b and 6c, the three-way valve 8, the first connection pipe 10, the first connection pipe 6, the fourth check valve 33, the four-way valve 2 of the heat source unit and the accumulator 4, whereby the cooling-dominant operation is carried out. Also, at this time, the first opening 8a of the three-way valve 8 connected to the indoor units B and C is closed and the second opening 8b and the third opening 8c are opened, and the second opening 8b of the indoor unit D is closed and the first opening 8b and the third opening 8c are opened. Also, at this time, since the first connection pipe 6 is at a low pressure and the second connection pipe 7 is at a high pressure, the refrigerant flows into the third check valve 32 and the fourth check valve 33. In this cycle, one portion of the liquid refrigerant flows from the meeting portion of the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11 to the bypass pipe 14, pressure-reduced to a low pressure at the third flow rate controller 15, and heat-exchanged at the third heat exchanging portions 16b, 16c and 16d in relation to the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11 and at the second heat exchanging portion 16a in relation to the meeting portions of the indoor unit side second connection pipes 7b, 7c and 7d of the second junction portion 11, and further heat-exchanged in the first heat exchanging portion 19 in relation to the refrigerant flowing into the second flow rate controller 13, the evaporated refrigerant being supplied to the first connection pipe 6 and the fourth check valve 33 from where it is suctioned by the compressor 1 through the heat source unit four-way valve 2 and the accumulator 4. On the other hand, the refrigerant at the second junction portion 11, which is heat-exchanged in the first, the second and the third heat exchanging portions 19, 16a, 16b, 16c and 16d to be sufficiently subcooled, is supplied to the indoor unit D to be operated for cooling. While the three-way valve 8 is provided in the above-described first embodiment in order to selectively connect the indoor unit side first connection pipes 6b, 6c and 6d to the first connection pipe 6 or to the second connection pipe 7, a switch valve such as two solenoid valves may be provided to obtain a similar effect. While an example of a multi-room heat pump type air conditioning system has been used, the present invention is equally applicable to heat pumps and coolers having a single outer unit for a single indoor unit. Reference numeral 21 designates a takeoff pipe connected at its one end to the liquid side outlet portion of the heat source unit side heat exchanger 41 and at the other end to the inlet of the accumulator 4 and extending through the fin portions of the heat source unit side heat exchanger 41, 22 is a throttle means disposed in the takeoff pipe 21, and 23 is a second temperature detection means disposed between the throttle 22 and the inlet side connection portion of the accumulator 4 of the takeoff pipe 21. In the cooling-only operation and the cooling-dominant operation, the compressor 1 is capacity controlled to supply a high-temperature and high-pressure refrigerant gas so that the detected temperature at the second temperature detection means 23 is at the predetermined value. One portion of the gas-liquid two phase refrigerant flowing from the liquid side outlet pipe of the heat source unite side heat exchanger 41 is flowed through the takeoff pipe 21, and is heat-exchanged in relation to the air supplied from the heat source unit side fan 20 into liquid refrigerant while passing through the takeoff pipe 21 intersecting with the fins of the heat source unit side heat exchanger 41 to flow into the throttle 22 where it is pressure-reduced to the low-pressure and flows into the accumulator 4. In the heating-only operation and the heating-dominant operation, the compressor 1 is capacity controlled to supply a high-temperature and high-pressure refrigerant gas so that the detected pressure at the fourth pressure detection means 18 is at a predetermined value. Thus, the provision is made of a takeoff pipe 21 connected at one end thereof to a liquid outlet side pipe of said heat source unit side heat exchanger 41 and at the other end thereof to an inlet pipe of said accumulator 4 through a throttle device 22, the takeoff pipe 21 extending through cooling fins of the heat source unit side heat exchanger 41, and a second temperature detector means 23 disposed in the takeoff pipe 21 between the throttle device 22 and the inlet pipe of the accumulator 4. Therefore, the refrigerant flowing through the takeoff pipe 21 is condensed into liquid refrigerant when it flows through the takeoff pipe 21 portion which intersects with the fins of the heat source unit side heat exchanger 41, pressure-reduced to the low-pressure by the throttle device 22, whereby the second temperature detection means 23 is assured to always stably detect the low-pressure side saturation refrigeration temperature. Fig. 2 is a general schematic diagram illustrating the refrigerant lines of another embodiment of the air-conditioning system of the invention. A heat source unit side heat exchanging portion 3a is composed of the heat source unit side heat exchanger 41, the heat source unit side bypass pipe 42 for bypassing the heat exchanger 41, the first and second solenoid valve 43 and 44 disposed at the refrigerant inlet and outlet portions of the heat source unit side heat exchanger 41 and the third solenoid valve 45 inserted into the bypass pipe 42. Next, the control of the heat source unit side fan 20, the first, the second and the third solenoid valves 43, 44 and 45 in the cooling-dominant operation will now be described. The heat source unit side heat exchanging portion 3a is composed of the heat source unit side heat exchanger 41, the heat source unit side bypass pipe 42 and the first, the second and the third solenoid valves 43, 44 and 45, and the capacity of the heat source unit side heat exchanger is adjustable in three levels in order to obtain a large heat source unit side heat changer capacity when the indoor cooling load is heavy, to obtain a small heat source unit side heat exchanger capacity when the indoor cooling load is small and to make the heat source unit side heat exchanger capacity unnecessary when the indoor cooling load and the heating load are equal to each other. The first level corresponds to the case where the largest heat source unit side heat exchanger capacity is required, in which the first and the second solenoid valves 43 and 44 are opened and the third solenoid valve 45 is closed, thereby to flow the refrigerant to the heat source unit side heat exchanger 41, and no refrigerant is allowed to flow through the heat source unit side bypass path 42, and the flow rate adjusting range of the heat source unit side fan 20 is set to be from the fan full-speed operation to a predetermined minimum amount, so that, even when the ambient temperature of the heat source unit A is high and the refrigerant flowing into the takeoff pipe 21 is evaporated to become the vapor refrigerant, since the takeoff pipe 21 intersects the fin portions of the heat source unit side heat exchanger 41, the refrigerant is heat-exchanged with the air, the condensed liquid refrigerant may be flowed into the throttle device 22 to reduce its pressure to the low-pressure, whereby the second temperature detector 23 can detect the low-pressure saturation temperature. The second level corresponds to the case where the next-largest heat source unit side heat-exchanging capacity is required, the first, second and third solenoid valves 43, 44 and 45 are opened to flow the refrigerant to the heat source unit side heat exchanger 41 as well as the heat source unit side bypass path 42 to regulate the air quantity of the heat source unit side fan 20. At this time, the air quantity regulating ranges from the fan full speed operation to the predetermined minimum air quantity, so that, even when the condensed liquid refrigerant from the heat source unit side heat exchanger 41 and the gas refrigerant flowing through the heat source unit side bypass path are mixed to become the vapor-liquid 2 phase refrigerant which flows into the takeoff pipe 21, the takeoff pipe 21 which intersects with the fin portion of the heat source unit side heat exchanger 41 for heat-exchanging between the refrigeration and the air can cause the refrigerant to be condensed into liquid and flowed into the throttle device 22 to pressure-decrease to the low-pressure, ensuring that the low-pressure saturation temperature can be detected by the second temperature detector 23. The third level corresponds to the case where the smallest heat source unit side heat exchanger capacity is required, in which the first and the second solenoid valves 43 and 44 are closed and the third solenoid valve 45 is opened, thereby to flow the refrigerant to the heat source unit side bypass path 42 and no refrigerant is allowed to flow through the heat source unit side heat exchanger 41 so that the amount of heat exchange in the heat source unit side heat exchanging portion 3 is zero. At this time, the air quantity of the heat source unit side fan 20 is the predetermined minimum quantity, so that, even when the gas refrigerant flowing through the heat source unit side bypass path 42 flows into the takeoff pipe 21, since the takeoff pipe 21 intersects the fin portions of the heat source unit side heat exchanger 41, the refrigerant is heat-exchanged with the air, the condensed liquid refrigerant may be flowed into the throttle device 22 to reduce its pressure to the low-pressure, whereby the low-pressure saturation temperature can be detected by the second temperature detector 23. Fig. 3 is a flow chart illustrating the control of the heat source unit side fan 20, the first, the second and the third solenoid valves 43, 44 and 45 in the cooling-dominant operation. In step 166, whether or not the heat source unit side heat changing amount should be increased (UP) is judged, and the process proceeds to step 167 if it is to be UP and the process proceeds to step 168 if it is not to be UP. In step 167, whether or not the heat source unit side fan 20 is driven at full-speed is judged and the process proceeds to step 169 when it is not at full-speed. In step 169, the air quantity is increased and the process returns to step 166. In step 170, whether or not the first and the second solenoid valves 43 and 44 are open or closed is judged, and the process proceeds to step 172 when they are open and the process proceeds to step 171 when they are closed. In step 171, the first and the second solenoid valves 43 and 44 are opened and the process returns to step 166. In step 172, whether the third solenoid valve 45 is open or closed is judged, and the process proceeds to step 173 when it is open and the process returns to step 166 when it is closed. In step 173, the third solenoid valve 45 is closed and the process returns to step 166. On the other hand, step 168 determines whether or not the heat source unit side heat exchanging amount should be decreased (down), and the process proceeds to step 174 if it is to be decreased and the process returns to step 166 if it is not to be decreased. Step 174 determines whether or not the heat source unit side fan 20 is at the predetermined minimum air quantity, and the process proceeds to step 176 if it is at the minimum quantity and the process proceeds to step 175 if it is not. In step 175, the air quantity is deceased and the process returns to step 166. In step 176, whether the third solenoid valve 45 is opened or closed is determined and the process proceeds to step 177 if it is closed and the process proceeds to step 178 if it is opened. In step 177, the third solenoid valve 45 is opened and returns to step 166. In step 178, whether the first and the second solenoid valve 43 and 44 are opened or closed is determined and the process proceeds to step 179 when opened and the process returns to step 166 when closed. In step 179, the first and the second solenoid valves 43 and 44 are closed and the process returns to step 166. The heat source unit side heat exchanger 41 is provided at a refrigerant inlet and outlet portions with the first and the second valves 43 and 44, respectively, and the heat source unit side bypass pipe 42 bypassing the heat source unit side heat exchanger 41 through a third valve 45 is connected at one end thereof to a liquid outlet side pipe 21 positioned between the heat source unit side heat exchanger 41 and the takeoff pipe connection portion, whereby, even when the gas refrigerant flows into the takeoff pipe 21 when the heat source unit side bypass pipe 42 is communicating, the saturation temperature can be stably detected. with the takeoff pipe connected at one end thereof to a liquid outlet side pipe of the heat source unit side heat exchanger and at the other end thereof to an inlet pipe of said accumulator through a throttle device, the takeoff pipe extending through cooling fins of the heat source unit side heat exchanger, and a second temperature detector means disposed in the takeoff pipe between the throttle device and the inlet pipe of the accumulator, even when the refrigerant is evaporated by the temperature about the heat source unit or the refrigerant is supplied from the heat source side heat exchanger in the vapor-liquid phase due to the control conditions of the fan, the refrigerant can be condensed into liquid in the takeoff pipe portion which intersects with the fin portion, whereby the second temperature detection means is assured to always stably detect the low-pressure side saturation refrigeration temperature.

Claims: An air-conditioning system wherein a single heat source unit having a compressor, a four-way valve, a heat source unit side heat exchanger and an accumulator is connected to a plurality of indoor units having an indoor side heat exchanger and a first flow rate controller through first and second connection pipes; a first branch joint including a valve device for selectively connecting one of said plurality of indoor units to said first connection pipe or said second connection pipe and a second branch joint connected to the another of said indoor side heat exchangers of said plurality of indoor units through said first flow rate controller and connected to said second connection pipe through said second flow rate controller are connected to each other through said second flow rate controller and a gas-liquid separating unit; said second branch joint and said first connection pipe are connected through a fourth flow rate controller and through a bypass pipe having a third flow rate controller therein; and said air conditioning system comprises; a first heat exchanger portion for carrying out the heat-exchanging between said bypass pipe between said third flow rate controller and said first connection pipe and pipings connecting said second connection pipe and said second flow rate controller; a flow path change over unit for allowing, when said heat source unit side heat exchanger is operated as a condenser, a flow of a refrigerant from a refrigerant outlet side of said condenser only to said second connection pipe and a flow of the refrigerant from said first connection pipe only to said four-way valve side, and allowing, when said heat source unit side heat exchanger is operated as an evaporator, a flow of the refrigerant from said first connection pipe only to a refrigerant inlet side of said evaporator and a flow of the refrigerant from said four-way valve only to said second connection pipe; and a junction unit disposed between said plurality of heat source units, said intermediate unit comprising said first branch joint, said second branch joint, said gas-liquid separator, said second flow rate controller, said third flow rate controller, said fourth flow rate controller, said first heat exchanging portion and said bypass pipes; characterized by the provision of: a takeoff pipe connected at one end thereof to a liquid outlet side pipe of said heat source unit side heat exchanger and at the other end thereof to an inlet pipe of said accumulator through a throttle device said takeoff pipe extending through cooling fins of said heat source unit side heat exchanger; and a temperature detector disposed in said takeoff pipe between said throttle device and said inlet pipe of said accumulator for controlling the compressor to maintain the detected temperature substantially constant in cooling-only and cooling-dominant operation of the system. An air-conditioning system as claimed in claim 1 wherein said heat source unit side heat exchanger is provided at a refrigerant inlet and outlet portions with first and second valves, respectively, and a heat source unit side bypass pipe bypassing said heat source unit side heat exchanger through a third valve is connected at one end thereof to a liquid outlet side pipe positioned between said heat source unit side heat exchanger and said takeoff pipe connection portion.

Inventors: HAYASHIDA NORIAKI C O MITSUBIS, KAMEYAMA JUNICHI C O MITSUBISH, KASAI TOMOHIKO C O MITSUBISHI, NAKAMURA TAKASHI C O MITSUBISH, TAKATA SHIGEO C O MITSUBISHI D, TANI HIDEKAZU C O MITSUBISHI D, HAYASHIDA NORIAKI, C/O MITSUBISHI DENKI K. K., KAMEYAMA, JUNICHI, C/O MITSUBISHI DENKI K. K., KASAI, TOMOHIKO, C/O MITSUBISHI DENKI K. K., NAKAMURA, TAKASHI, C/O MITSUBISHI DENKI K. K., TAKATA, SHIGEO, C/O MITSUBISHI DENKI K. K., TANI, HIDEKAZU, C/O MITSUBISHI DENKI K. K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1992
Main classification: F25B13
IPC codes: F25B13, F24F3, F25B41