Air conditioning apparatus

Abstract: An air conditioning apparatus comprising: a single heat source device (A) including a compressor (l), a reversing valve (2), an outdoor heat exchanger (3) and an accumulator (4); a plurality of indoor units (B,C,D) including indoor heat exchangers (5) and first flow controllers (9); a first main pipe (6) and a second main pipe (7) for connecting between the heat source device (A) and the indoor units (B,C,D); a first branch joint (l0) which can selectively connect one end of the indoor heat exchanger (5) of each indoor unit (B,C,D) to either one of the first main pipe (6) and the second main pipe (7); a second branch joint (ll) which is connected to the other end of the indoor heat exchanger (5) of each indoor unit (B,C,D) through the first flow controllers (9), and which connects the other end to the second main pipe (7) through a second flow controller (l3); the first branch joint (l0) and the second branch joint (ll) connected together through the second flow controller (l3); the second branch joint (ll) connected to the first main pipe (6) through a third flow controller (l5); a junction device (E) which includes the first branch joint (l0), the second flow controller (l3), the third flow controller (l5) and the second branch joint (ll), and which is interposed between the heat source device (A) and the indoor units (B,C,D); the first main pipe (6) having a greater diameter than the second main pipe (7); and a switching arrangement (40) which can be arranged between the first main pipe (6) and the second main pipe (7) in the heat source device (A) to switch the first main pipe (6) and the second main pipe (7) to a low pressure side and to a high pressure side, respectively, when the outdoor heat exchanger (3) works as a condenser or as an evaporator; characterized in that it comprises: a first timer (6l) for changing the setting of the second flow controller (l3) at a first cycle during operation of the compressor (l); a second timer for returning the setting of the second flow controller (l3) to its initial setting at a second cycle longer than the first cycle; and determination means (63) for changing the setting of the second flow controller (l3) by a predetermined value at a time based on outputs from the first timer (6l), and for returning the setting of the second flow controller (l3) to the initial setting based on an output from the second timer (62).

Description: The present invention relates to a multi-room heat pump type of air conditioning apparatus wherein a single heat source device is connected to a plurality of indoor units. More particularly, the present invention relates to an air conditioning apparatus wherein cooling and heating can be selectively carried out for each indoor unit, or wherein cooling can be carried out in one or some indoor units, and simultaneously heating can be carried out in the other indoor unit(s). Such an apparatus is disclosed for example in EP-A-0 421 459. Now, a prior art reference as disclosed in EP-A-0 453 271 will be explained. Referring now to Figure 7, there is shown a schematic diagram of the entire structure of a conventional air conditioning apparatus, which is depicted on the basis of the refrigerant system of the apparatus. Referring to Figures 8-10, there are shown the operation states in cooling or heating in the conventional device shown in Figure 7. Figure 8 is a schematic diagram showing the operation states of the conventional device wherein solo cooling or solo heating is performed; Figures 9 and 10 are schematic diagrams showing the operation states of cooling and heating concurrent operation; Figure 9 is a schematic diagram showing the operation state of the conventional device wherein heating is principally performed under cooling and heating concurrent operation (total heating load is greater than total cooling load); and Figure 10 is a schematic diagram showing the operation state of the conventional device wherein cooling is principally performed under cooling and heating concurrent operation (total cooling load is greater than total heating load). Explanation of the prior art will be made for the case wherein a single heat source device is connected to three or two indoor units. The following explanation is also applicable to the case wherein a single source device is connected to more than three indoor units. In Figure 7, reference numeral A designates a heat source device. Reference numerals B, C and D designate the indoor units which are connected in parallel as described later on, and which have the same structure. Reference numeral E designates a junction device which includes a first branch joint, a second flow controller, a second branch joint, a gas-liquid separator, and first and second heat exchanging portions. Reference numeral 1 designates a compressor. Reference numeral 2 designates a four port reversing valve which can switch the flow direction of a refrigerant in the heat source device. Reference numeral 3 designates an outdoor heat exchanger which is installed on the side of the heat source device. Reference numeral 4 designates an accumulator which is connected to the compressor 1, the reversing valve 2 and the outdoor heat exchanger 3 to constitute the heat source device A. Reference numeral 5 designates three indoor heat exchangers in the indoor units B, C and D. Reference numeral 6 designates a first main pipe which has a large diameter and which connects the four way reversing valve 2 and the junction device E. Reference numerals 6b, 6c and 6d designate first branch pipes which connect the junction device E and the indoor heat exchangers 5 of the respective indoor units B, C and D, and which correspond to the-first main pipe 6. Reference numeral 7 designates a second main pipe which has a smaller diameter than the first main pipe 6, and which connects the junction device E and the outdoor heat exchanger 3 of the heat source device A. Reference numerals 7b, 7c and 7d designate second branch pipes which connect the junction device E and the indoor heat exchangers 5 of the respective indoor units B, C and D, and which correspond to the second main pipe 7. Reference numeral 8 designates three way switching valves which can selectively connect the first branch pipes 6b, 6c and 6d to either the first main pipe 6 or the second main pipe 7. Reference numeral 9 designates first flow controllers which are connected to the respective indoor heat exchangers 5 in close proximity to the same, which are controlled based on degree of superheat in cooling and degree of subcooling in heating at refrigerant outlet sides of the respective indoor heat exchangers, and which are connected to the second branch pipes 7b, 7c and 7d, respectively. Reference numeral 10 designates the first branch joint which includes the three way switching valves 8 which can selectively the first branch pipes 6b, 6c and 6d to either the first main pipe 6 or the second main pipe 7. Reference numeral 11 designates the second branch joint which includes the second branch pipes 7b, 7c and 7d, and a confluent portion thereof. Reference numeral 12 designates the gas-liquid separator which is arranged in the second main-pipe 7, and which has a gaseous phase zone connected to first ports 8a of the respective switching valves 8 and a liquid phase zone connected to the second branch joint 11. Reference numeral 13 designates the second flow controller which is connected between the gas-liquid separator 12 and the second branch joint 11, and which can be selectively opened and closed. Reference numeral 14 designates a bypass pipe which connects the second branch joint 11 to the first main pipe 6. Reference numeral 15 designates a third flow controller which is arranged in the bypass pipe 14. Reference numerals 16b, 16c and 16d designate third heat exchanging portions which are arranged in the bypass pipe 14 downstream of the third flow controller 15, and which carry out heat exchange with the respective second branch pipes 7b, 7c and 7d in the second branch joint 11. Reference numeral 16a designates the second heat exchanging portion which is arranged in the bypass pipe 14 downstream of the third flow controller 15 and the third heat exchanging portions 16b, 16c and 16d, and which carries out heat exchanging with the confluent portion where the second branch pipes 7b, 7c and 7d join in the second branch joint. Reference numeral 19 designates the first heat exchanging portion which is arranged in the bypass pipe 14 downstream of the third flow controller 15 and the second heat exchanging portion 16a, and which carries out heat exchanging with the pipe which connects between the gas-liquid separator 12 and the second flow controller 13. Reference numeral 17 designates a fourth flow controller which is arranged in a pipe between the second branch joint 11 and the first main pipe 6, and which can be selectively opened and closed. Reference numeral 32 designates a third check valve which is arranged between the outdoor heat exchanger 3 and the second main pipe 7, and which allows the refrigerant only to flow from the outdoor heat exchanger 3 to the second main pipe 7. Reference numeral 33 designates a fourth check valve which is arranged between the four way reversing valve 2 of the heat source device A and the first main pipe 6, and which allows the refrigerant only to flow from the first main pipe 6 to the reversing valve 2. Reference numeral 34 designates a fifth check valve which is arranged between the reversing valve 2 and the second main pipe 7, and which allows the refrigerant only to flow from the reversing valve 2 to the second main pipe 7. Reference numeral 35 designates a sixth check valve which is arranged between the outdoor heat exchanger 3 and the first main pipe 6, and which allows the refrigerant only to flow from the first main pipe 6 to the outdoor heat exchanger 3. The third to sixth check valves 32-35 constitute a switching valve arrangement 40. Reference numeral 41 designates a liquid purging pipe which has one end connected to the gas-liquid separator 12 and the other end connected to the first main pipe 6. Reference numeral 42 designates a fifth flow controller which is arranged in the liquid purging pipe 41 between the gas liquid separator 12 and the first main pipe 6. Reference numeral 43 designates a fourth heat exchanging portion which is arranged in the liquid purging pipe 41 downstream of the fifth flow controller 42, and which carries out heat exchange with the pipe connecting between the gas-liquid separator 12 and the first branch joint 10. Reference numeral 23 designates a first temperature detector which is attached to the pipe connecting between the second flow controller 13 and the first heat exchanging portion 19. Reference numeral 25 designates a first pressure detector which is attached to the same pipe as the first temperature detector 23. Reference numeral 26 designates a second pressure detector which is attached to the second branch joint 11. Reference numeral 52 designates a third pressure detector which is attached to the pipe connecting between the first main pipe 6 and the first branch joint 10. Reference numeral 51 designates a second temperature detector which is attached to the liquid purging pipe 41 at a refrigerant outlet of the fourth heat exchanging portion 43. Reference numeral 53 designates a third temperature detector which is attached to the bypass pipe 14 at a refrigerant outlet of the first heat exchanging portion 19. The operation of the prior art as constructed above will be explained. Firstly, the case wherein only room cooling is performed will be explained with reference to Figure 8. In this case, the flow of the refrigerant is indicated by arrows of solid line. The refrigerant gas which has discharged from the compressor 1 and been a gas having high temperature under high pressure passes through the four way reversing valve 2, and is heat exchanged and condensed in the outdoor heat exchanger 3. Then, the refrigerant passes through the third check valve 32, the second main pipe 7, the separator 12 and the second flow controller 13 in that order. The refrigerant further passes through the second branch joint 11 and the second branch pipes 7b, 7c and 7d, and enters the indoor units B, C and D. The refrigerant which has entered the indoor units B, C and D is depressurized to low pressure by the first flow controllers 9 which are controlled based on degree of superheat at the outlet refrigerants of the respective indoor heat exchanger 5. In the indoor heat exchangers 5, the refrigerant thus depressurized carries out heat exchanging with indoor air to be evaporated and gasified, thereby cooling the rooms. The refrigerant so gasified passes through the first branch pipes 6b, 6c and 6d, the three way switching valves 8, and the first branch joint 10. Then the refrigerant is inspired into the compressor 1 through the first main pipe 6, the fourth check valve 33, the four way reversing valve 2, and the accumulator 4. In this way, a circulation cycle is formed to carry out cooling. At this mode, the three way switching valves 8 have the first ports 8a closed, and second ports 8b and third ports 8c opened. At the time, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is at high pressure in it, which necessarily make the third check valve 32 and the fourth check valve 33 to conduct for the refrigerant. In addition, in this mode, the refrigerant, which has passed through the second flow controller 13, partly enters the bypass pipe 14 where the entered part of the refrigerant is depressurized to low pressure by the third flow controller 15. The refrigerant thus depressurized carries out heat exchanging with the second branch pipes 7b, 7c and 7d at the third heat exchanging portions 16b 16c and 16d of the indoor units, with the confluent portion of the second branch pipes 7b, 7c and 7d at the second heat exchanging portion 16a in the second branch joint 11, and at the first heat exchanging portion 19 with the refrigerant which enters the second flow controller 13. The refrigerant is evaporated due to such heat exchanging, and enters the first main pipe 6. Then the refrigerant is inspired into the compressor 1 through the fourth check valve 33, the first four way reversing valve 2 and the accumulator 4. On the other hand, the refrigerant, which has heat exchanged at the first heat exchanging portion 19, at the second heat exchanging portion 16a and at the third heat exchanging portions 16b, 16c and 16d, and has been cooled so as to get sufficient degree of subcooling, enters the indoor units B, C and D which are expected to carry out room cooling. When the amount of the refrigerant which is sealed in the air conditioning apparatus is not enough to fill the second main pipe in cooling with a liquid refrigerant having high pressure, the refrigerant which has been condensed in the outdoor heat exchanger 3 and has a two phase state under high pressure passes through the second main pipe 7 and the gas-liquid separator 12. Then the two phase refrigerant carries out heat exchange, at the first heat exchanging portion 19, at the second heat exchanging portion 16a, and at the third heat exchanging portions 16b, 16c and 16d, with the refrigerant which has been depressurized to low pressure by the third flow controller 15 and flows through the bypass pipe. The refrigerant which has liquefied and cooled due to such heat exchange to obtain sufficient degree of subcooling, and flows into the indoor units B, C and D which are expected to carry out cooling. Secondly, the case wherein only heating is performed will be described with reference Figure 8. In this case, the flow of the refrigerant is indicated by arrows of dotted line. The refrigerant which has been discharged from the compressor 1 and been a gas having high temperature under high pressure passes through the four way reversing valve 2, the fifth check valve 34, the second main pipe 7, and the gas-liquid separator 12. Then the refrigerant passes through the first branch joint 10, the three way switching valves 8, and the first branch pipes 6b, 6c and 6d. After that, the refrigerant enters the respective indoor units B, C and D where the refrigerant carries out heat exchanging with indoor air. The refrigerant is condensed to be liquefied due to such heat exchanging, thereby heating the rooms. The refrigerant thus liquefied passes through the first flow controllers 9 which are controlled based on degree of subcooling at the refrigerant outlets of the respective indoor heat exchangers 5. Then the refrigerant enters the second branch joint 11 through the second branch pipes 7b, 7c and 7d, and joins there. Then the joined refrigerant passes through the fourth flow controller 17. The refrigerant is depressurized by either the first flow controllers 9 or the fourth flow controller 17 to take a two phase state having low pressure. The refrigerant thus depressurized enters the outdoor heat exchanger 3 through the first main pipe 6 and the sixth check valve 35 of the heat source device A, and carries out heat exchanging to be evaporated and gasified. The refrigerant thus gasified is inspired into the compressor 1 through the four way reversing valve 2, and the accumulator 4. In this way, a circulation cycle is formed to carry out room heating. In this mode, the switching valves 8 have the second ports 8b closed, and the first and the third ports 8a and 8c opened. In this mode, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is at high pressure in it, which necessarily causes the fifth check valve 34 and the sixth check valve 35 to conduct for the refrigerant. Thirdly, the case wherein heating is principally performed in cooling and heating concurrent operation will be explained with reference to Figure 9. Explanation will be made for the case wherein the indoor units B and C are expected to carry out heating, and the indoor unit D is expecting to carry out cooling. In Figure 9, arrows of dotted line indicate the flow of the refrigerant. The refrigerant which has been discharged from the compressor 1, and been a gas having high temperature under high pressure passes through the four way reversing valve 2, and then reaches the junction device E through the fifth check valve 34 and the second main pipe 7. The refrigerant flows through the gas-liquid separator 12. In addition, the refrigerant passes through the first branch joint 10, the three way switching valves 8 connected to the indoor units B and C, and the first branch pipes 6b and 6c in that order, and enters the indoor units B and C which are expected to carry out heating. In the indoor heat exchangers 5 of the respective indoor units B and C, the refrigerant carries out heat exchange with indoor air to be condensed and liquefied, thereby heating the rooms. The refrigerant thus liquefied passes through the first flow controllers 9 of the indoor units B and C, the first controllers 9 of the indoor units B and C being almost fully opened under the control based on degree of subcooling at the refrigerant outlets of the corresponding indoor heat exchangers 5. The refrigerant is slightly depressurized by these first flow controllers 9 to have a pressure (medium pressure) between the high pressure and the low pressure, and flows into the second branch joint 11 through the second branch pipes 7b and 7c. After that, a part of the refrigerant passes through the second branch pipe 7d of the indoor unit D which is expected to carry out cooling, and enters the indoor unit D. The refrigerant flows into the first flow controller 9 of the indoor unit D, the first flow controller 9 being controlled based on degree of superheat at the refrigerant outlet of the corresponding indoor heat exchanger 5. After the refrigerant is depressurized by this first flow controller 9, it enters the indoor heat exchanger 5, and carries out heat exchange to be evaporated and gasified, thereby cooling the room. Then the refrigerant enters the first main pipe 6 through the three way switching valve 8 which is connected to the indoor unit D. On the other hand, another part of refrigerant passes through the fourth flow controller 17 which is selectively opened and closed, and which is controlled in such a way to make constant the difference between the high pressure in the second main pipe 7 and the medium pressure in the second branch joint 11. Then the refrigerant joins with the refrigerant which has passed the indoor unit D which is expected to carry out cooling. After that, the refrigerant thus joined passes through the first main pipe 6 having such a larger diameter, and the sixth check valve 35, and enters the outdoor exchanger 3 where the refrigerant carries out heat exchange to be evaporated and gasified. The refrigerant thus gasified is inspired into the compressor 1 through the reversing valve 2 and the accumulator 4. In this way, a circulation cycle is formed to carry out the cooling and heating concurrent operation wherein heating is principally performed. At this time, the difference between the evaporation pressure in the indoor heat exchanger 5 of the cooling indoor unit D and that of the outdoor heat exchanger 3 lessens because of switching to the first main pipe 6 having such a greater diameter. At that time, the three port switching valves 8 which are connected to the heating indoor units B and C have the second ports 8b closed, and the first and third ports 8a and 8c opened. The three port switching valve 8 which is connected to the cooling indoor unit D has the second port 8a closed, and the first port 8b and the third port 8c opened. In this mode, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is at high pressure in it, which necessarily causes the fifth check valve 34 and the sixth check valve 35 to conduct for the refrigerant. At this circulation cycle, the remaining part of the liquefied refrigerant goes into the bypass pipe 14 from the confluent portion where the second branch pipes 7b, 7c and 7d join together. The refrigerant which has gone into the bypass pipe 14 is depressurized to low pressure by the third flow controller 15. The refrigerant thus depressurized carries out heat exchange with the refrigerant in the confluent portion of the second branch pipes 7b, 7c and 7d in the second branch joint 11 at the second heat exchanging portion 16a, and at the first heat exchanging portion 19 with the refrigerant which flows into the second flow controller 13. The refrigerant is evaporated by such heat exchange, and enters the first main pipe 6. After that, the refrigerant flows into the sixth check valve 35 and then into the outdoor heat exchanger 3 where it performs heat exchange to be evaporated and gasified. The refrigerant is inspired into the compressor 1 through the four way reversing valve 2 and the accumulator 4. On the other hand, the refrigerant in the second branch joint 11 which has carried out heat exchange and cooled at the first heat exchanging portion 19, at the second heat exchanging portion 16a, and at the third heat exchanging portions 16b, 16c and 16d to obtain sufficient degree of subcooling flows into the indoor unit D which is expected to cool the room. Fourthly, the case wherein cooling is principally performed in cooling and heating concurrent operation will be described with reference to Figure 10. Explanation will be made for the case wherein the indoor units B and C are expected to carry out cooling, and the indoor unit D is expected to carry out heating. In Figure 10, arrows of solid lines indicate the flow of the refrigerant. The refrigerant which has been discharged from the compressor 1 and been a gas having high temperature under high pressure carries out heat exchange at an arbitrary amount in the outdoor heat exchanger 3 to take a two phase state having high temperature under high pressure. Then the refrigerant passes through the third check valve 32 and the second main pipe 7, and is forwarded to the gas-liquid separator 12 in the junction device E. The refrigerant is separated into a gaseous refrigerant and a liquid refrigerant there, and the gaseous refrigerant thus separated flows through the first branch joint 10, and the three way switching valve 8 and the first branch pipe 6d which are connected to the indoor unit D, in that order, the indoor unit D being expected to heat the room. The refrigerant flows into the indoor unit D, and carries out heat exchange with indoor air to be condensed and liquefied, thereby heating the room. In addition, the refrigerant passes through the first flow controller 9 connected to the heating indoor unit D, this first flow controller 9 being almost fully opened under control based on degree of subcooling at the refrigerant outlet of the indoor heat exchanger 5 of the heating indoor unit D. The refrigerant is slightly depressurized by this first flow controller 9 to have a pressure (medium pressure) between the high pressure and the low pressure, and flows into the second branch joint 11. On the other hand, the remaining liquid refrigerant enters the second branch joint 11 through the second flow controller 13 which is controlled in such a way to make constant the difference between the high pressure and the medium pressure. Then the refrigerant joins there with the refrigerant which has passed through the heating indoor unit D. The refrigerant thus joined passes through the second branch joint 11, and then the second branch pipes 7b and 7c, respectively, and enters the respective indoor units B and C. The refrigerant which has flowed into the indoor units B and C is depressurized to low pressure by the first flow controllers 9 of the indoor units B and C, these first flow controllers 9 being controlled based on degree of superheat at the refrigerant outlets of the corresponding indoor heat exchangers 5. Then the refrigerant flows into the indoor heat exchangers 5, and carries out heat exchange with indoor air to be evaporated and gasified, thereby cooling these rooms. In addition, the refrigerant thus gasified passes through the first branch pipes 6b and 6c, the three way switching valves 8 connected to the indoor units B and C, and the first branch joint 10. Then the refrigerant is inspired into compressor 1 through the first main pipe 6, the fourth check valve 33, the four way reversing valve 2, and the accumulator 4. In this way, a circulation cycle is formed to carry out the cooling and heating concurrent operation wherein cooling is principally performed. In this mode, the three way switching valves 8 which are connected to the indoor units B and C have the first ports 8a closed, and the second and third ports 8b and 8c opened. The three way switching valve 8 which is connected to the indoor unit D has the second port 8b closed, and the first and third ports 8a and 8c opened. At that time, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is a high pressure in it, which necessarily causes the third check valve 32 and the fourth check valve 33 to conduct for the refrigerant. In this circulation cycle, the liquid refrigerant partly enters the bypass pipe 14 from the confluent portion where the second branch pipes 7b, 7c and 7d join together. The liquid refrigerant which has entered into the bypass pipe 14 is depressurized to low pressure by the third flow controller 15. The refrigerant thus depressurized carries out heat exchange at the second heat exchanging portion 16a with the refrigerant in the confluent portion of the second branch pipes 7b, 7c and 7d in the second branch joint 11, and at the first heat exchanging portion 19 with the refrigerant which flows into the second flow controller 13. The refrigerant is evaporated by such heat exchange, and enters the first main pipe 6. The refrigerant which has entered the first main pipe 6 is inspired into the compressor 1 through the fourth check valve 33, the four way reversing valve 2, and the accumulator 4. On the other hand, the refrigerant in the second branch joint 11 which has carried out heat exchange and cooled at the first heat exchanging portion 19, at the second heat exchanging portion 16a, and at the third heat exchanging portions 16b, 16c and 16d to obtain sufficient degree of subcooling flows into the indoor units B and C which are expected to carry out room cooling. When the liquid level at which the gaseous refrigerant and the liquid refrigerant separated in the gas liquid separator 12 are divided is below the liquid purging pipe 41 of the gas-liquid separator 12, the gaseous refrigerant enters the liquid purging pipe 41, and is depressurized to low pressure by the fifth flow controller 42. The amount of the refrigerant which is flowing through the fifth flow controller 42 is small because the refrigerant at the inlet of the fifth flow controller 42 is in the form of gas. As a result, the refrigerant which is flowing through the liquid purging pipe 41 carries out heat exchange, at the fourth heat exchanging portion 43, with the gaseous refrigerant which goes from the gas-liquid separator 12 to the first branch joint 10 and has high pressure. The refrigerant in the liquid purging pipe 41 becomes a superheated gas having low pressure due to such heat exchange, and enters the first main pipe 6. Conversely, when the liquid level at which the gaseous refrigerant and the liquid refrigerant separated in the gas-liquid separator 12 are divided is above the liquid purging pipe 41 of the gas liquid separator 12, the liquid refrigerant enters the liquid purging pipe 41, and is depressurized to low pressure by the fifth flow controller 42. Because the refrigerant at the inlet of the fifth flow controller 42 is in the form of liquid, the amount of the refrigerant which is flowing through the fifth flow controller 42 is greater in comparison with the case wherein the refrigerant at the fifth flow controller 42 is in the form of gas. As a result, even when the refrigerant which is flowing through the liquid purging pipe 41 carries out heat exchanger, at the fourth heat exchanging portion 43, with the gaseous refrigerant which goes from the gas liquid separator 12 into the first branch joint 10 and has high pressure, the refrigerant in the liquid purging pipe 41 enters the first main pipe 6 in the form of two phase state without becoming a superheated gas having low pressure. The conventional air conditioning apparatuses involve the following problems: Because the conventional apparatus does not have a ventilating function as one of air conditioning functions, a ventilating device is required. In addition, the conventional apparatus involves a problem in that it can not cope with load which is occurred by introducing outdoor air. An object of the present invention is to provide an air conditioning apparatus wherein cooling and heating can be selectively carried out for each indoor unit, or wherein cooling can be carried out in one or some indoor units, and simultaneously heating can be carried out in the other indoor unit(s), and which can have a ventilating function, and cope with load caused by ventilation in accordance with the operation states of driving indoor units. The features of the present invention are set out in claims 1 to 3. The invention will be further described, by way of example, with reference to the drawings in which:- Figure 1 is a schematic diagram showing the entire structure of an embodiment which is depicted on the basis of the refrigerant system of the apparatus; Figure 2 is a schematic diagram showing the operation states of the embodiment of Figure 1 wherein solo cooling or solo heating is performed; Figure 3 is a schematic diagram showing the operation state of the embodiment of Figure 1 wherein heating is principally performed under cooling and heating concurrent operation; Figure 4 is a schematic diagram showing the operation state of the embodiment of the Figure 1 wherein cooling is principally performed under cooling and heating concurrent operation; Figure 5 is is a flowchart showing the operation of a first indoor unit in accordance with the embodiment; Figure 6 is a schematic diagram of the entire structure of a modification, which is depicted on the basis of the refrigerant system of the apparatus; Figure 7 is a schematic diagram of the entire structure of a conventional air conditioning apparatus, which is depicted on the basis of the refrigerant system of the apparatus; Figure 8 is a schematic diagram showing the operation states of the conventional apparatus of Figure 7 wherein solo cooling or solo heating is performed; Figure 9 is a schematic diagram showing the operation state of the conventional apparatus of Figure 7 wherein heating is principally performed under cooling and heating concurrent operation; Figure 10 is a schematic diagram showing the operation state of the conventional apparatus of the Figure 7 wherein cooling is principally performed under cooling and heating concurrent operation. Now, the present invention will be described in detail with reference to preferred embodiments illustrated in the accompanying drawings. An embodiment of the present invention will be described. Figure 1 is a schematic diagram of the entire structure of an embodiment of the air conditioning apparatus according to the present invention, which is depicted on the basis of the refrigerant system of the apparatus. Figures 2 to 4 are schematic diagram showing the operation states in cooling or heating in the embodiment of Figure 1; Figure 2 being a schematic diagram showing the operation states wherein solo operation on cooling or solo operation on heating is performed; and Figures 3 and 4 being schematic diagrams showing the operation states in cooling and heating concurrent operation, Figure 3 being a schematic diagram showing the operation state wherein heating is principally performed under cooling and heating concurrent operation (total heating load is greater than total cooling load), and Figure 4 being a schematic diagram showing the operation state wherein cooling is principally performed under cooling and heating concurrent operation (total cooling load is greater than total heating load). Although explanation on the embodiment will be made in reference to the case wherein a single outdoor unit as a heat source device is connected to three indoor units, the explanation is also applicable to the case wherein the outdoor unit is connected to two or more indoor units. In Figure 1, reference A designates an outdoor unit as a heat source device. Reference B designates a first indoor unit, and references C and D designate second indoor units. The indoor units B, C and D which are connected in parallel as described later and have the same structure as each other in terms of a refrigeration cycle. Reference E designates a junction device which includes a first branch joint 10, a second flow controller 13, a second branch joint 11, a gas-liquid separator 12, and first and second exchanging portions 19 and 16a, as described later. Reference numeral 1 designates a compressor. Reference numeral 2 designates a four port reversing valve which can switch the flow direction of a refrigerant in the heat source device. Reference numeral 3 designates an outdoor heat exchanger which is installed on the side of the heat source device. Reference numeral 4 designates an accumulator which is connected to the devices 1-3 to constitute the heat source device A. Reference numeral 5 designates the indoor heat exchangers of the first and second indoor units B, C and D. Reference numeral 6 designates a first main pipe which has a large diameter and which connects the four way reversing valve 2 of the heat source device A and the junction device E. Reference numerals 6b, 6c and 6d designate first branch pipes which connect the junction device E and the indoor heat exchangers 5 of the respective indoor units B, C and D, and which correspond to the first main pipe 6. Reference numeral 7 designates a second main pipe which has a smaller diameter than the first main pipe 6, and which connects the junction device E and the outdoor heat exchanger 3 of the heat source device A. Reference numerals 7b, 7c and 7d designate second branch pipes which connect the junction device E and the indoor heat exchangers 5 of the respective indoor units B, C and D, and which correspond to the second main pipe 7. Reference numeral 8 designates three way switching valves which can selectively connect the first branch pipes 6b, 6c and 6d to either the first main pipe 6 or the second main pipe 7. Reference numeral 9 designates the first flow controllers which are connected to the respective indoor heat exchangers 5 in close proximity to the same, which are controlled based on degree of superheat in cooling and on degree of subcooling in heating at refrigerant outlet sides of the respective indoor heat exchangers, and which are connected to the second branch pipes 7b, 7c and 7d, respectively. Reference numeral 10 designates the first branch joint which includes the three way switching valves 8 which can selectively the first branch pipes 6b, 6c and 6d to either the first main pipe 6 or the second main pipe 7. Reference numeral 11 designates the second branch joint which includes the second branch pipes 7b, 7c and 7d, and the second main pipe 7. Reference numeral 12 designates the gas-liquid separator which is arranged in the second main pipe 7, and which has a gas phase zone connected to first ports 8a of the respective switching valves 8 and a liquid phase zone connected to the second branch joint 11. Reference numeral 13 designates the second flow controller which is connected between the gas-liquid separator 12 and the second branch joint 11, and which can be selectively opened and closed. Reference numeral 14 designates a bypass pipe which connects the second branch joint 11 to the first main pipe 6. Reference numeral 15 designates the third flow controller which is arranged in the bypass pipe 14. Reference numerals 16b, 16c and 16d designate third heat exchanging portions which are arranged in the bypass pipe 14 downstream of the third flow controller 15, and which carry out heat exchange with the respective second branch pipes 7b, 7c and 7d in the second branch joint 11. Reference numeral 16a designates the second heat exchanging portion which is arranged in the bypass pipe 14 downstream of the third flow controller 15 and the third heat exchanging portions 16b, 16c and 16d, and which carries out heat exchanging with the confluent portion where the second branch pipes 7b, 7c and 7d join in the second branch joint. Reference numeral 19 designates the first heat exchanging portion which is arranged in the bypass pipe 14 downstream of the third flow controller 15 and the second heat exchanging portion 16a, and which carries out heat exchanging with a pipe which connects between the gas-liquid separator 12 and the second flow controller 13. Reference numeral 17 designates the fourth flow controller which is arranged in a pipe between the second branch joint 11 and the first main pipe 6, and which can be selectively opened and closed. Reference numeral 32 designates a third check valve which is arranged between the outdoor heat exchanger 3 and the second main pipe 7, and which allows a refrigerant only to flow from the outdoor heat exchanger 3 to the second main pipe 7. Reference numeral 33 designates a fourth check valve which is arranged between the four way reversing valve 2 of the heat source device A and the first main pipe 6, and which allows the refrigerant only to flow from the first main pipe 6 to the reversing valve 2. Reference numeral 34 designates a fifth check valve which is arranged between the reversing valve 2 and the second main pipe 7, and which allows the refrigerant only to flow from the reversing valve 2 to the second main pipe 7. Reference numeral 35 designates a sixth check valve which is arranged between the outdoor heat exchanger 3 and the first main pipe 6, and which allows the refrigerant only to flow from the first main pipe 6 to the outdoor heat exchanger 3. These check valves 32-35 constitute a switching valve arrangement 40. Reference numeral 41 designates a liquid purging pipe which has one end connected to the gas-liquid separator 12 and the other end connected to the first main pipe 6. Reference numeral 42 designates a fifth flow controller which is arranged in the liquid purging pipe 41 between the gas liquid separator 12 and the first main pipe 6. Reference numeral 43 designates a fourth heat exchanging portion which is arranged in the liquid purging pipe 41 downstream of the fifth flow controller 42, and which carries out heat exchange with a pipe connecting between the gas-liquid separator 12 and the first branch joint 10. Reference numeral 23 designates a first temperature detector which is attached to the pipe connecting between the second flow controller 13 and the first heat exchanging portion 19. Reference numeral 25 designates a first pressure detector which is attached to the same pipe as the first temperature detector 23. Reference numeral 26 designates a second pressure detector which is attached to the pipe connecting the second flow controller 13 and the second branch joint 11. Reference numeral 52 designates a third pressure detector which is attached to the pipe connecting between the first main pipe 6 and the first branch joint 10. Reference numeral 51 designates a second temperature detector which is attached to the liquid purging pipe 41 at a refrigerant outlet of the fourth heat exchanging portion 43. Reference numeral 53 designates a third temperature detector which is attached to the bypass pipe 14 at a refrigerant outlet of the first heat exchanging portion 19. The first indoor unit B can be constructed so that, for e.g. aiming at ventilating, outdoor air is introduced, and be caused to pass through the indoor heat exchanger 5 of the first indoor unit B, and then the air as primary air is supplied to the indoor heat exchangers 5 of the second indoor units C and D. Reference numeral 36 designates a fan for introducing the outdoor air, which introduces the outdoor air, causes the outdoor air to pass through the indoor heat exchanger 5 of the first indoor unit B, and supplies the air to the second indoor units C and D. Reference numeral 37 designates fans which are arranged in the second indoor units C and D, and which introduces the indoor air, and causes the indoor air to pass through the indoor heat exchangers 5 of the second indoor units C and D to circulate the indoor air. Reference numeral 38 designates an air path which is arranged to supply the second indoor units C and D with the air that has passed through the indoor heat exchanger 5 of the first indoor unit B. The flow of the outdoor air which is introduced into the first indoor unit B is indicated by a white arrow of a chain line. The flow of the air which is supplied from the first indoor unit B to the second indoor units C and D is indicated by white arrows of solid lines. The flow of the indoor air which is introduced into the second indoor units C and D is indicated by black arrows. The flow of the air which is supplied indoors from the second indoor units C and D is indicated by white arrows of broken lines. The operation of the embodiment as constructed above will be explained. Firstly, the case wherein only cooling is performed will be explained with reference to Figure 2. In this case, the flow of the refrigerant is indicated by arrows of solid line. The refrigerant gas which has discharged from the compressor 1 and had high temperature under high pressure passes through the four way reversing valve 2, and is heat exchanged and condensed in the outdoor heat exchanger 3. Then, the refrigerant passes through the third check valve 32, the second main pipe 7, the separator 12 and the second flow controller 13 in that order. The refrigerant further passes through the second branch joint 11 and the second branch pipes 7b, 7c and 7d, and enters the indoor units B, C and D. The refrigerant which has entered the indoor units B, C and D is depressurized to low pressure by the first flow controllers 9 which are controlled based on degree of superheat at the outlets of the respective indoor heat exchanger 5. In the indoor heat exchangers 5, the refrigerant thus depressurized carries out heat exchanging with air to be evaporated and gasified, thereby cooling the rooms. The refrigerant so gasified passes through the first branch pipes 6b, 6c and 6d, the three way switching valves 8, and the first branch joint 10. Then the refrigerant is inspired into the compressor 1 through the first main pipe 6, the fourth check valve 33, the four way reversing valve 2, and the accumulator 4. In this way, a circulation cycle is formed to carry out cooling. At this mode, the three way switching valves 8 have the first ports 8a closed, and second ports 8b and third ports 8c opened. At the time, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is at high pressure in it, which necessarily make the third check valve 32 and the fourth check valve 33 to conduct for the refrigerant. In addition, in this mode, the refrigerant, which has passed through the second flow controller 13, partly enters the bypass pipe 14 where the entered part of the refrigerant is depressurized to low pressure by the third flow controller 15. The refrigerant thus depressurized carries out heat exchanging with the second branch pipes 7b, 7c and 7d at the third heat exchanging portions 16b 16c and 16d, with the confluent portion of the second branch pipes 7b, 7c and 7d at the second heat exchanging portion 16a in the second branch joint 11, and at the first heat exchanging portion 19 with the refrigerant which enters the second flow controller 13. The refrigerant is evaporated due to such heat exchanging, and enters the first main pipe 6 and the fourth check valve 33. Then the refrigerant is inspired into the compressor 1 through the first four way reversing valve 2 and the accumulator 4. On the other hand, the refrigerant, which has heat exchanged at the first heat exchanging portion 19, the second heat exchanging portion 16a, and the third heat exchanging portions 16b, 16c and 16d, and has been cooled so as to get sufficient subcooling, enters the indoor units B, C and D which are expected to carry out cooling. In cooling, when the amount of the refrigerant which is sealed in the air conditioning apparatus is not enough to fill the second main pipe 7 with a liquid refrigerant having high pressure, the refrigerant which has been condensed in the outdoor heat exchanger 3 and has a two phase state under high pressure passes through the second main pipe 7 and the gas-liquid separator 12. Then the two phase refrigerant carries out heat exchange, at the first heat exchanging portion 19, at the second heat exchanging portion 16a, and at the third heat exchanging portions 16b, 16c and 16d, with the refrigerant which has been depressurized to low pressure by the third flow controller 15 and flows through the bypass pipe. The refrigerant which has left the gas-liquid separator 12 is liquefied and cooled due to such heat exchange to obtain sufficient supercooling, and flows into the first and second indoor units B, C and D which are expected to carry out cooling. Secondly, the case wherein only heating is performed will be described with reference Figure 2. In this case, the flow of the refrigerant is indicated by arrows of dotted line. The refrigerant which has been discharged from the compressor 1 and been a gas having high temperature under high pressure passes through the four way reversing valve 2, the fifth check valve 34, the second main pipe 7, and the gas-liquid separator 12. Then the refrigerant passes through the first branch joint 10, the three way switching valves 8, and the first branch pipes 6b, 6c and 6d in that order. After that, the refrigerant enters the first and second indoor units B, C and D where the refrigerant carries out heat exchanging with indoor air. The refrigerant is condensed to be liquefied due to such heat exchanging, thereby heating the rooms. The refrigerant thus liquefied passes through the first flow controllers 9 which are controlled based on degree of subcooling at the refrigerant outlets of the respective indoor heat exchangers 5. Then the refrigerant enters the second branch joint 11 through the second branch pipes 7b, 7c and 7d, and joins there. Then the joined refrigerant passes through the fourth flow controller 17. The refrigerant is depressurized by either the first flow controllers 9 or the fourth flow controller 17 to take a two phase state having low pressure. The refrigerant thus depressurized enters the outdoor heat exchanger 3 through the first main pipe 6 and the sixth check valve 35, and carries out heat exchanging to be evaporated and gasified. The refrigerant thus gasified is inspired into the compressor 1 through the four way reversing valve 2, and the accumulator 4. In this way, a circulation cycle is formed to carry out room heating. In this mode, the switching valves 8 have the second ports 8b closed, and the first and the third ports 8a and 8c opened. In this mode, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is at high pressure in it, which necessarily causes the fifth check valve 34 and the sixth check valve 35 to conduct for the refrigerant. Thirdly, the case wherein heating is principally performed in cooling and heating concurrent operation will be explained with reference to Figure 3. Explanation will be made for the case wherein the first indoor unit B and the second indoor unit C are expected to carry out heating, and the second indoor unit D is expecting to carry out cooling. In Figure 3, arrows of dotted line indicate the flow of the refrigerant. The refrigerant which has been discharged from the compressor 1, and been a gas having high temperature under high pressure passes through the four way reversing valve 2, and then reaches the junction device E through the fifth check valve 34 and the second main pipe 7. The refrigerant flows through the gas-liquid separator 12. In addition, the refrigerant passes through the first branch joint 10, the three way switching valves 8 connected to the first and second indoor units B and C, and the first branch pipes 6b and 6c in that order, and enters the indoor units B and C which are expected to carry out heating. The refrigerant which has flowed into the heating indoor units B and C carries out heat exchange with air in the corresponding indoor heat exchangers to be condensed and liquefied, thereby heating the room(s(. The refrigerant thus liquefied passes through the first flow controllers 9 of the indoor units B and C, the first controllers 9 of the indoor units B and C being almost fully opened under control based on degree of subcooling at the refrigerant outlets of the corresponding indoor heat exchangers 5. The refrigerant is slightly depressurized by these first flow controllers 9 to have a pressure (medium pressure) intermediate between high pressure and low pressure, and flows into the second blanch joint 11 through the second branch pipes 7b and 7c. After that, a part of the refrigerant passes through the second branch pipe 7d of the second indoor unit D which is expected to carry out cooling, and enters the indoor unit D. The refrigerant flows into the first flow controller 9 of the indoor unit D, the first flow controller 9 being controlled based on degree of superheat at the refrigerant outlet of the corresponding indoor heat exchanger 5. After the refrigerant is depressurized by this first flow controller 9, it enters the indoor heat exchanger 5, and carries out heat exchange to be evaporated and gasified, thereby cooling the room. Then the refrigerant enters the first main pipe 6 through the three way switching valve 8 which is connected to the indoor unit D. On the other hand, another part of the refrigerant passes through the second branch joint 11, and through the fourth flow controller 17 which is controlled so that a difference between the high pressure in the second main pipe 7 and the medium pressure in the second branch joint 11 falls into a predetermined range. Then the refrigerant joins with the refrigerant which has passed the indoor unit D which is expected to carry out cooling. After that, the refrigerant thus joined passes through the first main pipe 6 having such a larger diameter, and the sixth check valve 35, and enters the outdoor exchanger 3 where the refrigerant carries out heat exchange to be evaporated and gasified. The refrigerant thus gasified is inspired into the compressor 1 through the reversing valve 2 and the accumulator 4. In this way, a circulation cycle is formed to carry out the cooling and heating concurrent operation wherein heating is principally performed. At this time, the difference between the evaporation pressure in the indoor heat exchanger 5 of the cooling second indoor unit D and that of the outdoor heat exchanger 3 lessens because of switching to the first main pipe 6 having such a greater diameter. At that time, the three port switching valves 8 which are connected to the heating indoor units B and C have-the second ports 8b closed, and the first and third ports 8a and 8c opened. The three port switching valve 8 which is connected to the cooling indoor unit D has the first port 8a closed, and the second port 8b and the third port 8c opened. In this mode, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is at high pressure in it, which necessarily causes the fifth check valve 34 and the sixth check valve 35 to conduct for the refrigerant. At this circulation cycle, the remaining part of the liquefied refrigerant goes into the bypass pipe 14 from the confluent portion where the second branch pipes 7b and 7c join together. The refrigerant which has gone into the bypass pipe 14 is depressurized to low pressure by the third flow controller 15. The refrigerant thus depressurized carries out heat exchange with the refrigerant in the confluent portion of the second branch pipes 7b and 7c in the second branch joint 11 at the second heat exchanging portion 16a, and at the first heat exchanging portion 19 with the refrigerant which flows into the second flow controller 13. The refrigerant is evaporated by such heat exchange, and enters the first main pipe 6. After that, the refrigerant flows into the sixth check valve 35 and then into the outdoor heat exchanger 3 where it performs heat exchange to be evaporated and gasified. The refrigerant thus gasified is inspired into the compressor 1 through the four way reversing valve 2 and the accumulator 4. On the other hand, the refrigerant in the second branch joint 11 which has carried out heat exchange and cooled at the first heat exchanging portion 19, the second heat exchanging portion 16a, and the third heat exchanging portions 16b, 16c and 16d to obtain sufficient subcooling flows into the cooling indoor unit D. Fourthly, the case wherein cooling is principally performed in cooling and heating concurrent operation will be described with reference to Figure 4. Explanation will be made for the case wherein the first indoor unit B and the second indoor unit C are expected to carry out heating, and the second indoor unit D is expecting to carry out cooling, and wherein the second indoor unit D has greater cooling load than the total heating load of the first and second indoor units B and C. In Figure 4, arrows of solid lines indicate the flow of the refrigerant. The refrigerant which has been discharged from the compressor 1 and been a gas having high temperature under high pressure flows into the outdoor heat exchanger 3 through the reversing valve 2, and carries out heat exchange at an arbitrary amount in the outdoor heat exchanger 3 to take a gas-liquid two phase state having high temperature under high pressure. Then the refrigerant passes through the third check valve 32 and the second main pipe 7, and is forwarded to the gas-liquid separator 12 in the junction device E. The refrigerant is separated into a gaseous refrigerant and a liquid refrigerant there, and the gaseous refrigerant thus separated flows through the first branch joint 10, and the three way switching valve 8 and the first branch pipes 6b and 6c which are connected to the indoor units B and C, in that order, the indoor units B and C being expected to carry out heating. The refrigerant flows into the indoor units B and C, and carries out heat exchange with air to be condensed and liquefied, thereby heating the rooms. In addition, the refrigerant passes through the first flow controllers 9 connected to the heating indoor units, this first flow controller 9 being almost fully opened under control based on degree of subcooling at the refrigerant outlets of the indoor heat exchanger 5 of the heating indoor units B and C. The refrigerant is slightly depressurized by this first flow controllers 9 to have a pressure (medium pressure) intermediate between high pressure and low pressure, and flows into the second branch joint 11. On the other hand, the remaining liquid refrigerant enters the second branch joint 11 through the second flow controller 13 which is controlled so that a difference between the high pressure and the medium pressure is kept constant. Then the refrigerant joins there with the refrigerant which has passed through the heating indoor units B and C. The refrigerant thus joined passes through the second branch joint 11, and then the second branch pipe 7d, and enters the indoor unit D. The refrigerant which has flowed into the indoor unit D is depressurized to low pressure by the first flow controller 9 of the indoor unit D, the first flow controller 9 being controlled based on degree of superheat at the refrigerant outlet of the corresponding indoor heat exchanger 5. Then the refrigerant flows into the indoor heat exchanger 5, and carries out heat exchange with indoor air to be evaporated and gasified, thereby cooling the room. In addition, the refrigerant thus gasified passes through the first branch pipe 6d, the three way switching valve 8 connected to the indoor unit D, and the first branch joint 10. Then the refrigerant is inspired into compressor 1 through the first main pipe 6, the fourth check valve 33, the four way reversing valve 2, and the accumulator 4. In this way, a circulation cycle is formed to carry out the cooling and heating concurrent operation wherein cooling is principally performed. In this mode, the three way switching valve 8 which is connected to the indoor unit D has the first port 8a closed, and the second and third ports 8b and 8c opened. The three way switching valves 8 which are connected to the indoor units B and C have the second ports 8b closed, and the first and third ports 8a and 8c opened. At that time, the first main pipe 6 is at low pressure in it, and the second main pipe 7 is a high pressure in it, which necessarily causes the third check valve 32 and the fourth check valve 33 to conduct for the refrigerant. In this circulation cycle, the liquid refrigerant partly enters the bypass pipe 14 from the confluent portion where the second branch pipes 7b and 7c join together. The liquid refrigerant which has entered into the bypass pipe 14 is depressurized to low pressure by the third flow controller 15. The refrigerant thus depressurized carries out heat exchange at the second heat exchanging portion 16a with the refrigerant in the confluent portion of the second branch pipes 7b and 7c in the second branch joint 11, and at the first heat exchanging portion 19 with the refrigerant which flows into the second flow controller 13. The refrigerant is evaporated by such heat exchange, and enters the first main pipe 6. The refrigerant which has entered the first main pipe 6 is inspired into the compressor 1 through the fourth check valve 33, the four way reversing valve 2, and the accumulator 4. On the other hand, the refrigerant in the second branch joint 11 which has carried out heat exchange and cooled at the first heat exchanging portion 19, the second heat exchanging portion 16a, and the third heat exchanging portions 16b, 16c and 16d to obtain sufficient subcool flows into the indoor unit D which is expected to carry out cooling. When the liquid level at which the gaseous refrigerant and the liquid refrigerant separated in the gas-liquid separator 12 are divided is located below the liquid purging pipe 41 in the gas-liquid separator 12, the gaseous refrigerant flows into the liquid purging pipe 41, and is depressurized to low pressure by the fifth flow controller 42. At that time, the amount of the refrigerant which flows through the fifth flow controller 42 is small because the refrigerant is in the form of gas at the inlet of the fifth flow controller 42. The refrigerant which flows through the liquid purging pipe 41 carries out heat exchange, at the fourth heat exchanging portion 43, with the gaseous refrigerant which is under high pressure and which is going to flow from the gas-liquid separator 12 into the first branch joint 10. The refrigerant in the liquid purging pipe 41 becomes a superheated gas having low pressure due to such heat exchange, and flows into the first main pipe 6. Conversely, when the liquid level at which the gaseous refrigerant and the liquid refrigerant separated by the gas-liquid separator 12 are divided is located above the liquid purging pipe 41 in the gas-liquid separator 12, the liquid refrigerant flows into the liquid purging pipe 41, and is depressurized to low pressure by the fifth flow controller 42. Because the refrigerant is in the form of liquid at the inlet of the fifth flow controller 42, the amount of the refrigerant which flows through the fifth flow controller 42 is greater in comparison with the case wherein the refrigerant is in the form of gas at the inlet of the fifth flow controller. As a result, even if the refrigerant which flows through the liquid purging pipe 41 carries out heat exchange, at the fourth heat exchanging portion 43, with the gaseous refrigerant which is under high pressure and which is going to flow from the gas-liquid separator 12 into the first branch joint 10, the refrigerant in the liquid purging pipe 41 does not become a superheated gas having low pressure. The refrigerant flows into the first main pipe 6, maintaining a two phase state. An operation of the first indoor unit B will be explained, referring to Figure 5. At Step 90, it is determined whether either the second indoor unit C or the second indoor unit D is carrying out heating. If affirmative, the program proceeds to Step 93 where the first indoor unit B carries out heating. If none of the second indoor units C and D carry out heating, the program proceeds to Step 91. At Step 91, it is determined whether either the second indoor unit C or the second indoor unit D carries out cooling. If affirmative, the program proceeds to Step 94 where the first indoor unit B carries out cooling. If none of the second indoor units C and D carry out cooling, the program proceeds to Step 92. At Step 92, it is determined whether either the second indoor unit C or the second indoor unit D carries out ventilating. If affirmative, the program proceeds to Step 95 where the first indoor unit B carries out ventilation. If none of the second indoor units C or D carry out ventilation, the program proceeds to Step 96 where the first indoor unit B is stopped. As explained, the first indoor unit B can work or stop in association with the operation or the stoppage of the second indoor units C and D. If at least one of the second indoor units C and D carries out heating, the first indoor unit B carries out heating, outdoor air which has been introduced into the first indoor unit B is heated to e.g. about a room temperature by the indoor heat exchanger 5 of the first indoor unit B, and the heated air is supplied to the second indoor units C and D. In that manner, introduction of the air which has been heated by the first indoor unit B can suppress an increase in the total heating load of the second indoor units C and D. Even if the second indoor unit C carries out heating and the second indoor unit D carries out cooling, outdoor air for which heating load is required can be heated to about a room temperature by the first indoor unit B to suppress an increase in the cooling load of the cooling indoor unit D. If neither the second indoor unit C nor the second indoor unit D carries out heating and one of them carries out cooling, the first indoor unit B carries out cooling. Outdoor air which has been introduced into the first indoor unit B is cooled at the indoor heat exchanger 5 of the first indoor unit B, and is supplied to the second indoor units C and D. In that case, introduction of the air which has been cooled by the first indoor unit B can suppress an increase in the total cooling load of the second indoor units C and D. If neither the second indoor unit C nor the second indoor unit D carries out heating or cooling, and one of them carries out ventilation, the first indoor unit B carries out ventilation to introduce outdoor air. In accordance with the embodiment, when at least one of the second indoor units carries out heating, the first indoor unit carries out heating to heat outdoor air at the indoor heat exchanger of the first indoor unit, and the heated air is supplied to the second indoor units. When none of the second indoor units carries out heating, and at least one of them carries out cooling, the first indoor unit carries out cooling, and the air which has been cooled by the indoor heat exchanger at the first indoor unit is supplied to the indoor heat exchanger of the second indoor units. If none of the indoor units carries out heating or cooling, and at least of them carries out ventilation, the first indoor unit carries out ventilation. As explained, the first indoor unit is operated or stopped in association with the operation or stoppage of the second indoor units, outdoor air is introduced in association with the operation or the stoppage of the second indoor units to carry out ventilation, and a sufficient amount of ventilated air can be obtained. If at least one of the second indoor units carries out heating, the first indoor unit carries out heating. If none of the second indoor units carry out heating, and at least one of them carries out cooling, the first indoor unit carries out cooling. If none of the second indoor units carry out heating or cooling, and at least one of them carries out ventilation, the first indoor unit carries out ventilation. As a result, outdoor air can be previously heated or cooled by the first indoor unit to suppress an increase in heating load or cooling load by introduction of the outdoor air, thereby realizing a stable operation with outdoor air introduced. Although in the embodiment the three way switching valves 8 can be arranged to selectively connect the first branch pipes 6b, 6c and 6d to either the first main pipe 6 or the second main pipe 7, spared on off valves such as electromagnetic on off valves 30 and 31 as shown in Figure 6 can be provided instead of the three way switching valves to make selective switching, offering similar advantages.

Claims: An air conditioning apparatus comprising: a single heat source device (A) including a compressor (1), a reversing valve (2), an outdoor heat exchanger (3) and an accumulator (4); a plurality of indoor units (B, C, D) including indoor heat exchangers (5) and first flow controllers (9); a first main pipe (6) and a second main pipe (7) connected between the heat source device (A) and the indoor units (B, C, D); a first branch joint (10) which can selectively connect one end of the indoor heat exchanger (5) of each indoor unit (B, C, D) to either the first main pipe (6) or the second main pipe (7); and a second branch joint (11) which connects the other end of the indoor heat exchanger (5) of each indoor unit (B, C, D) to the second main pipe (7) through the first flow controllers (9); the first branch joint (10) and the second branch joint (11) being connected together through a second flow controller (13); characterized in that: the indoor units are constituted by a first indoor unit (B) and second indoor units (C,D), the first indoor unit (B) having a fan for introducing outdoor air, and carrying out heat exchange with outdoor air introduced by the fan, the second indoor units (C,D) having fans for circulating indoor air, and carrying out heat exchange with the air circulated by the fans; wherein when at least one of the second indoor units (C,D) is operative to heat the circulating indoor air the first indoor unit (B) is operative to heat the introduced outdoor air. An air conditioning apparatus comprising: a single heat source device (A) including a compressor (1), a reversing valve (2), an outdoor heat exchanger (3) and an accumulator (4); a plurality of indoor units (B, C, D) including indoor heat exchangers (5) and first flow controllers (9); a first main pipe (6) and a second main pipe (7) connected between the heat source device (A) and the indoor units (B, C, D); a first branch joint (10) which can selectively connect one end of the indoor heat exchanger (5) of each indoor unit (B, C, D) to either one of the first main pipe (6) and the second main pipe (7); and a second branch joint (11) which connects the other end of the indoor heat exchanger (5) of each indoor unit (B, C, D) to the second main pipe (7) through the first flow controllers (9); the first branch joint (10) and the second branch joint (11) being connected together through a second flow controller (13); characterized in that: the indoor units are constituted by a first indoor unit (B) and second indoor units (C,D), the first indoor unit (B) having a fan for introducing outdoor air, and carrying out heat exchange with outdoor air introduced by the fan, the second indoor units (C,D) having fans for circulating indoor air, and carrying out heat exchange with the air circulated by the fans; wherein when none of the second indoor units (C,D) is operative to heat the circulated indoor air, and at least one of the second indoor units (C,D) is operative to cool the circulated indoor air, the first indoor unit (B) is operative to cool the introduced outdoor air. An air conditioning apparatus comprising: a single heat source device (A) including a compressor (1), a reversing valve (2), an outdoor heat exchanger (3) and an accumulator (4); a plurality of indoor units (B, C, D) including indoor heat exchangers (5) and first flow controllers (9); a first main pipe (6) and a second main pipe (7) connected between the heat source device (A) and the indoor units (B, C, D); a first branch joint (10) which can selectively connect one end of the indoor heat exchanger (5) of each indoor unit (B, C, D) to either one of the first main pipe (6) and the second main pipe (7); and a second branch joint (11) which connects the other end of the indoor heat exchanger (5) of each indoor unit (B, C, D) to the second main pipe (7) through the first flow controllers (9); the first branch joint (10) and the second branch joint (11) being connected together through a second flow controller (13); characterized in that the indoor units are constituted by a first indoor unit (B) and second indoor units (C,D), the first indoor unit (B) having a fan for introducing outdoor air, and carrying out heat exchange with outdoor air introduced by the fan, the second indoor units (C,D) having fans for circulating indoor air, and carrying out heat exchange with the air circulated by the fans; wherein when none of the second indoor units (C,D) is carrying out heat exchange with circulated indoor air, and at least one of the second indoor units (C,D) is operative to circulate indoor air for ventilation, the first indoor unit is operative to introduce outdoor air for ventilation.

Inventors: HAYASHIDA NORIAKI, KAMEYAMA JUNICHI, KASAI TOMOHIKO, NAKAMURA TAKASHI, TAKATA SHIGEO, TANI HIDEKAZU, HAYASHIDA, NORIAKI, KAMEYAMA, JUNICHI, KASAI, TOMOHIKO, NAKAMURA, TAKASHI, TAKATA, SHIGEO, TANI, HIDEKAZU, 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: F24F3
IPC codes: F25B13, F25B41, F24F3