JP5716102B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly to a cooling and heating simultaneous multi-type air conditioner including a plurality of indoor units.

Conventionally known methods for controlling a cooling and heating simultaneous multi-type air conditioner include those disclosed in the following patent documents, for example.
In Patent Document 1, air conditioning is performed by controlling the capacity of the compressor and the rotational speed of the outdoor unit side blower from the discharge pressure and suction pressure of the compressor.
In patent document 2, in order to adjust the capacity | capacitance of the utilization unit of the driving | operation with which the load of air_conditionaing | cooling operation and heating operation becomes subordinate, air conditioning is performed by controlling the air volume of the outdoor unit side air blower.

Japanese Patent No. 2716559 JP 2011-112233 A

  In recent years, there is an increasing need for a simultaneous heating and cooling multi-type air conditioner that can air-condition buildings such as high-rise buildings that have large indoor and outdoor height differences. However, in any of the above patent documents, the liquid pipe pressure on the indoor unit side is not actively controlled. In the air conditioner described in the above-mentioned patent document, when the outdoor unit is installed on the upper side and the indoor unit is installed on the lower side with a predetermined height difference, when the outdoor heat exchanger functions as a condenser with a large cooling load, The liquid head for the height difference and the liquid density is applied to the indoor liquid pipe. Then, if the height difference is further enlarged, it is assumed that the pressure in the indoor liquid pipe becomes equal to or higher than the discharge pressure of the compressor. That is, the refrigerant pressure (liquid pipe pressure) on the outlet side of the indoor unit that performs the heating operation becomes equal to or higher than the refrigerant pressure (high pressure gas pipe pressure) on the inlet side, and the high pressure gas refrigerant flows through the indoor heat exchanger of the indoor unit. There is no fear.

  Here, in the outdoor fan air volume control described in Patent Document 1 and Patent Document 2, the discharge pressure can be adjusted, but the liquid pipe pressure cannot be adjusted.

  Therefore, in the cooling and heating simultaneous multi-type air conditioner described in Patent Document 1 and Patent Document 2, when the outdoor unit is installed on the upper side and the indoor unit is installed on the lower side, the difference in height between them is a predetermined value or more. In such a case, there is a possibility that the refrigerant does not flow to the indoor unit that performs the heating operation and the heating operation capability cannot be exhibited.

  Therefore, the present invention aims to improve the heating capacity by allowing the refrigerant to flow into the indoor unit that performs the heating operation even in the case of the elevation difference construction in the simultaneous cooling and heating multi-type air conditioner. To do.

In order to achieve the above object, according to the present invention, at least one outdoor unit, the first indoor unit and the second indoor unit are connected by a refrigerant pipe, and the outdoor unit exchanges heat with the compressor. The first indoor unit includes a first indoor heat exchanger, and the second indoor unit includes an air conditioner including a second indoor heat exchanger. When the indoor unit performs a heating operation and the second indoor unit performs a cooling operation, and when the outdoor heat exchanger acts as a condenser, the refrigerant from the compressor is used as the outdoor heat exchanger. On the other hand, the refrigerant pipe is configured to flow to the first indoor heat exchanger, and the opening of the expansion valve disposed on the refrigerant outlet side of the outdoor heat exchanger is reduced, thereby reducing the first the outlet side of the liquid refrigerant pressure in the indoor heat exchanger inlet-side gas refrigerant pressure of the first indoor heat exchanger And controlling so remote higher.

According to the present invention, it is possible to improve the heating capacity by allowing the refrigerant to flow through the indoor unit that performs the heating operation even in the case of the elevation difference construction in the simultaneous cooling and heating multi-type air conditioner. It becomes.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

The refrigeration cycle system diagram of Example 1 is shown. The Mollier diagram of Example 1 is shown. It is a figure which shows an example of the control flowchart of the outdoor expansion valve 15 of Example 1. FIG. FIG. 3 is an excerpt of a part of the refrigeration cycle diagram of Example 1. It is a figure for demonstrating the outdoor expansion valve control flowchart of Example 2. FIG. It is a figure for demonstrating the outdoor expansion valve control flowchart of Example 3. FIG. 6 is a diagram for explaining a refrigeration cycle structure of Example 4. FIG. It is a figure for demonstrating the control flowchart of the outdoor expansion valve of Example 5. FIG. 6 is a system diagram of a refrigeration cycle in Example 6. FIG.

  Hereinafter, an embodiment of an air conditioner of the present invention will be described with reference to the drawings.

  FIG. 1 is a system diagram of a refrigeration cycle of the air conditioner of the first embodiment. This air conditioner is composed of one outdoor unit 10 installed on the roof and indoor units 40a and 40b used for air conditioning on the lower floor with a refrigerant high / low pressure gas pipe 31, a low pressure gas pipe 32, and a liquid main pipe 33. Connected and configured. One outdoor unit 10 or a plurality of outdoor units 10 may be connected in parallel. Two indoor units (40a, 40b) may be connected or a plurality of indoor units may be connected.

The operation state of each indoor unit in the present embodiment is that the indoor unit 40a performs heating operation and the indoor unit 40b performs cooling operation, and is in a state of simultaneous cooling and heating operation. Further, assuming that the cooling load is greater than the heating load, the outdoor heat exchanger 14 is a condenser.
The refrigerant flow in the cooling main mode (cooling load> heating load state) in the simultaneous cooling and heating operation will be described. First, a case where the height difference between the outdoor unit 10 and the indoor units (40a, 40b) is equal to or less than a predetermined value (in the case of current product specifications) will be described. The high-pressure gas refrigerant compressed by the compressor 11 is discharged to the high-low pressure switching four-way valve 12 and the heat exchanger switching four-way valve 13. The high-pressure gas refrigerant sent to the high-low pressure switching four-way valve 12 is sent through the high-low pressure gas pipe 31 to the indoor unit 40 a that performs heating operation. Here, since the high pressure side opening / closing mechanism 51a is opened and the low pressure side opening / closing mechanism 52a is closed on the gas pipe side of the indoor unit 40a, the high pressure gas refrigerant flowing from the high / low pressure gas pipe 31 is sent to the indoor heat exchanger 41a, It exchanges heat with the indoor air, condenses into high-pressure liquid refrigerant, and is sent to the indoor expansion valve 42a and the liquid branch pipe 35a.

  On the other hand, the high-pressure gas refrigerant discharged to the heat exchanger switching four-way valve 13 is condensed by the outdoor heat exchanger 14 to become high-pressure liquid refrigerant, and is slightly throttled by the outdoor expansion valve 15 and sent to the liquid blocking valve 23 and the liquid main pipe 33. It is done. Then, it merges with the high-pressure liquid refrigerant sent from the indoor unit 40a via the liquid branch pipe 35a, and is sent via the liquid branch pipe 35b to the indoor unit 40b performing the cooling operation. The high-pressure liquid refrigerant sent to the indoor unit 40b is throttled and depressurized by the indoor expansion valve 42b, evaporates by exchanging heat with the indoor air in the indoor heat exchanger 41b, becomes a low-pressure gas refrigerant, and the high-pressure side opening / closing mechanism 51b is closed. Since the side opening / closing mechanism 52b is opened, it is sent to the low-pressure gas pipe 32 and returns to the compressor 11 to circulate again.

  Next, the case where the height difference between the outdoor unit 10 and the indoor units (40a, 40b) is equal to or greater than a predetermined value will be described. The outdoor unit 10 and the indoor unit 40b that performs cooling operation have the same refrigerant flow, and the description will be limited to the vicinity of the indoor unit 40a that performs heating operation. The refrigerant pressure (gas pipe side pressure) on the inlet side of the indoor heat exchanger 41a of the indoor unit 40a is the same as that of the high and low pressure gas pipe 31 because the high pressure side opening / closing mechanism 51a is opened and the low pressure side opening / closing mechanism 52a is closed. . Further, when the high / low pressure gas pipe 31 is used at a high pressure, the gas flow rate is slow and the pressure loss of the pipe is small compared to when the high / low pressure gas pipe 31 is used at a low pressure. It can be said that it is almost equivalent. That is, the refrigerant pressure (gas pipe side pressure) on the inlet side of the indoor heat exchanger 41a of the indoor unit 40a is substantially the discharge pressure of the compressor 11.

  On the other hand, the refrigerant pressure (liquid pipe side pressure) on the outlet side of the indoor heat exchanger 41a of the indoor unit 40a will be described in order. The liquid blocking valve 23 with respect to the discharge pressure of the compressor 11 is connected to the outdoor heat exchanger 14 and The pressure is reduced by the pressure loss of the outdoor expansion valve 15. However, since the head due to gravity and liquid refrigerant density is applied to the liquid main pipe 33, the pressure increases as it goes downward. For this reason, in the liquid branch pipe 35a, when the height difference between the outdoor unit 10 and the indoor unit 40a is large, the pressure may increase to be equal to or higher than the discharge pressure of the compressor 11. As the refrigerant flow of the indoor unit 40a, if the refrigerant pressure (liquid pipe side pressure) on the outlet side is not larger than the refrigerant pressure (gas pipe side pressure) on the inlet side of the indoor heat exchanger 41a, Since the high-pressure gas refrigerant does not flow into the indoor unit 40a, the indoor unit 40a cannot generate heating capacity.

  In such a state, although the discharge pressure of the compressor 11 rises even if the air volume of the outdoor fan 19 is reduced, the pressure of the liquid main pipe 33 also rises, so that the pressure is increased between the inlet side and the outlet side of the indoor unit 40a. A pressure difference cannot be applied, and the refrigerant does not flow into the indoor unit 40a. Even if the frequency of the compressor 11 is increased, the discharge pressure of the compressor 11 and the pressure of the liquid main pipe 33 are both increased, so that the refrigerant does not flow into the indoor unit 40a.

  Therefore, in the present embodiment, the high-pressure gas refrigerant from the high-low pressure gas pipe 31 can be flowed to the indoor unit 40a that performs the heating operation by reducing the opening of the outdoor expansion valve 15. More specifically, in the air conditioner of the present embodiment, at least one outdoor unit 10, the first indoor unit 40a and the second indoor unit 40b are connected by a refrigerant pipe, and the outdoor unit 10 is compressed. The first indoor unit 40a includes a first indoor heat exchanger 41a, and the second indoor unit 40b includes a second indoor heat exchanger 41b. Yes.

  When the first indoor unit 40a performs the heating operation and the second indoor unit 40b performs the cooling operation, and when the outdoor heat exchanger 14 acts as a condenser, the refrigerant from the compressor 11 is While flowing to the outdoor heat exchanger 14, the refrigerant pipe is configured to flow to the first indoor heat exchanger 41a. Further, by reducing the opening of the expansion valve (outdoor expansion valve 15) arranged on the refrigerant outlet side of the outdoor heat exchanger 14, the refrigerant pressure on the inlet side of the first indoor heat exchanger 41a is changed to the first indoor heat. It controls so that it may become higher than the refrigerant | coolant pressure of the exit side of the exchanger 41a. In this case, the first indoor heat exchanger 41a acts as a condenser, and the refrigerant from the outdoor heat exchanger 14 is combined with the refrigerant flowing from the first indoor heat exchanger 41a to generate the second indoor heat. It flows to the exchanger 41b.

  By adopting such a configuration, since the discharge pressure of the compressor 11 does not change and only the pressure of the liquid main pipe 33 can be lowered, the outdoor unit 10 is on the upper side and the indoor unit 40a is on the lower side. Even if there is a difference, the refrigerant from the high / low pressure gas pipe 31 can be allowed to flow through the indoor unit 40a, and the heating capacity of the indoor unit 40a can be exhibited.

  The control target is where the liquid pipe pressure connected to the heating indoor unit is lower than the discharge pressure, and a pressure sensor may be attached to the liquid pipe side of the heating indoor unit. Alternatively, when the heating capacity of the heating indoor unit is not generated, it may be estimated that the liquid pipe pressure is higher than the discharge pressure, and the outdoor expansion valve may be throttled until the heating capacity is generated. The presence or absence of the heating capacity may be estimated from the difference between the air intake and blow-out temperature of the indoor unit. The saturation temperature estimated from the discharge pressure and the gas pipe temperature are compared, and a predetermined superheat level is obtained in the refrigerant in the gas pipe section. You may estimate by whether or not. Alternatively, the pressure loss at the outdoor expansion valve may be estimated from the outdoor expansion valve flow rate characteristics and the appropriate liquid main pipe flow rate, and the pressure loss corresponding to the separately obtained height difference head may be given by narrowing the outdoor expansion valve in advance. Alternatively, the height difference may be estimated from the operating pressure and the refrigerant circulation rate, the indoor expansion valve flow rate characteristic, and the outdoor expansion valve flow rate characteristic. In this simultaneous cooling and heating multi, the connection pipe may be constituted by one liquid pipe and two gas pipes, or may be constituted by two gas pipes. In addition, this control is a multi-cooling simultaneous multi-unit, when the outdoor heat exchanger is a condenser, the indoor unit performing cooling operation and the indoor unit performing heating operation coexist, and both indoor units start operation. Instead of starting the control, control may be performed to throttle the outdoor expansion valve when the heating indoor unit liquid pipe pressure is higher than the discharge pressure during operation or when the capacity of the heating indoor unit is insufficient.

  FIG. 2 shows a Mollier diagram of this embodiment. 2 is a simplified diagram of the refrigeration cycle diagram of FIG. As for the operation state of the unit, heating operation and cooling operation are mixed in the indoor units (40a, 40b), the outdoor heat exchanger 14 of the outdoor unit 10 acts as a condenser, and the outdoor unit 10 is connected to the indoor unit ( 40a, 40b) is a case where construction is performed with a height difference of a predetermined value or more installed on the lower side.

  FIG. 2-1 shows a Mollier diagram when the outdoor expansion valve 15 of this embodiment is not controlled. From the outlet (●) of the compressor 11, the refrigerant passes through the outdoor heat exchanger 14, the specific enthalpy decreases, and the pressure drops slightly due to the pressure loss of the outdoor heat exchanger 14. Although there is an outdoor expansion valve 15 at the outlet of the outdoor heat exchanger 14, the differential pressure ΔPvo before and after the outdoor expansion valve 15 is small because control for reducing the expansion valve opening degree is not performed. The state from the outlet side of the outdoor heat exchanger 14 to the outdoor liquid blocking valve (□) hardly changes and enters the liquid main pipe 33. In the liquid main pipe 33, the specific enthalpy of the refrigerant remains unchanged, the head ΔPH is applied, and the refrigerant pressure rises, resulting in a state of the heater liquid pipe (liquid branch pipe 35a) (◯) of the indoor unit 40a that performs the heating operation. Here, if the pressure of the gas pipe of the indoor unit 40a that performs the heating operation, that is, the pressure of the gas pipe flowing from the high / low pressure gas pipe 31 to the indoor unit 40a (pressure of the heating machine gas pipe) is PGih, Since the pressure PLih ≧ the pressure PGih of the heater gas pipe, the refrigerant does not flow into the indoor unit 40a that performs the heating operation.

  Next, FIG. 2-2 shows a Mollier diagram when the outdoor expansion valve 15 of this embodiment is controlled. From the outlet (●) of the compressor 11, the refrigerant passes through the outdoor heat exchanger 14, the specific enthalpy decreases, and the pressure drops slightly due to the pressure loss of the outdoor heat exchanger 14. Since the opening degree of the outdoor expansion valve 15 is controlled at the outlet of the outdoor heat exchanger 14, the front-rear differential pressure ΔPvo of the outdoor expansion valve 15 is increased. As a result, the pressure from the outlet side of the outdoor heat exchanger 14 to the outdoor liquid blocking valve (□) is lower than that in FIG. 2-1, so the pressure of the heater liquid pipe (liquid branch pipe 35a) (◯) is also the same. Compared to Fig. 2-1. Then, since the pressure PLih of the heater liquid pipe <the pressure PGih of the heater gas pipe, the refrigerant flows into the heater (indoor unit 40a), and the refrigerant condensed in the heater (indoor unit 40a) is the outdoor heat exchanger 14. Then, the refrigerant is condensed with the refrigerant and sent to the indoor unit 40b that performs the cooling operation. And the pressure reduction and heat exchange are made in the indoor unit 40b, and it sends to the compressor 11 again, and a refrigerating cycle is formed.

  FIG. 3 is a diagram illustrating an example of a control flowchart of the outdoor expansion valve 15 of the present embodiment. After starting the operation of the air conditioner, some indoor units perform cooling operation and heating operation, and when the outdoor heat exchanger 14 acts as a condenser, the control proceeds to the outdoor expansion valve 15. As shown in FIG. 3, when the refrigerant pressure on the discharge side of the compressor 11 is higher than the refrigerant pressure in the liquid branch pipe 35a (in the case of True in FIG. 3), the outdoor expansion valve 15 is not particularly operated, and the compressor 11 When the refrigerant pressure on the discharge side becomes equal to or lower than the refrigerant pressure in the liquid branch pipe 35a, the outdoor expansion valve is throttled. In addition, although demonstrated using the refrigerant | coolant pressure of the liquid branch pipe 35a here, you may use the refrigerant | coolant pressure of the piping which is a part of liquid main pipe | tube 33 and is arrange | positioned below.

  The control shown in FIG. 3 is event-like control in the specific case described above. When the operation mode changes (such as when the indoor unit operation state changes), or when a predetermined condition is satisfied (discharge pressure> liquid pipe pressure). When the refrigerant circulation amount, the outdoor fan air amount, etc. change, the throttle valve opening degree that has been throttled may be restored to the original state as appropriate. Alternatively, the opening degree of the outdoor expansion valve 15 may be controlled so that the differential pressure between the discharge pressure and the liquid pipe pressure is within a predetermined range.

  FIG. 4 is an excerpt from a part of the refrigeration cycle diagram of the first embodiment, in which pressure sensors (71, 72, 73) are attached to the liquid main pipe 33, the liquid branch pipe 35a, or 35b of the indoor unit. The pressure sensor on the indoor unit side allows the liquid pipe pressure to be controlled by the outdoor expansion valve 15 when the outdoor unit 10 and the indoor units (40a, 40b) are installed with a height difference of a predetermined value or more. It becomes easy. Here, the mounting position of the pressure sensor may be the same indoor liquid pipe assembly (a part of the liquid main pipe 33) as the floor where the indoor unit is located, as in the pressure sensor 71, and the liquid branch pipes (35a, 35b) of the indoor unit. Alternatively, a pressure sensor may be attached to the liquid pipe inside the indoor unit.

  As an example, when it demonstrates using the pressure sensor 72 installed in the liquid branch pipe 35a of the indoor unit 40a which performs heating operation, the 1st indoor unit 40a performs heating operation and the 2nd indoor unit 40b performs cooling operation. In the case where the outdoor heat exchanger 14 acts as a condenser, and the detected pressure on the discharge side of the compressor 11 becomes equal to or lower than the detected pressure of the pressure sensor 72, the refrigerant outlet of the outdoor heat exchanger 14 The refrigerant pressure on the inlet side of the first indoor heat exchanger 41a becomes higher than the refrigerant pressure on the outlet side of the first indoor heat exchanger 41a by reducing the opening of the outdoor expansion valve 15 arranged on the side. To control. As a result, the high-pressure gas refrigerant from the high-low pressure gas pipe 31 can flow through the indoor heat exchanger 41a.

Hereinafter, the present embodiment will be described with reference to FIG.
FIG. 5 is a diagram for explaining an outdoor expansion valve control flowchart of this embodiment. The difference from FIG. 3 of the first embodiment is that the outdoor expansion valve 15 is throttled when the temperature difference between the intake air temperature and the blown air temperature of the indoor unit 40a that performs the heating operation becomes equal to or less than a set value. is there. Although not shown, the indoor unit 40a includes a first temperature sensor that detects the temperature on the air suction side and a second temperature sensor that detects the temperature on the air blowing side. When the temperature difference between the temperature on the air blowing side detected by the second temperature sensor and the temperature on the air suction side detected by the first temperature sensor becomes equal to or less than the set value, the outdoor expansion valve 15 is opened. By reducing the degree, the refrigerant pressure on the inlet side of the indoor heat exchanger 41a is controlled to be higher than the refrigerant pressure on the outlet side of the indoor heat exchanger 41a. Thereby, the heating capability of the indoor unit 40a can be exhibited similarly to the first embodiment. Since the other points are the same as those in the first embodiment, detailed description thereof is omitted.

  Thereby, it is not necessary to attach the pressure sensor which measures a liquid pipe pressure to the indoor unit side. The temperature difference between the intake air temperature and the blown air temperature of the indoor unit 40a that performs heating operation is an index for determining the heating capacity of the indoor unit 40a, but the set value here may be as small as 2K or 3K. What is to be determined here is whether or not high-pressure gas is flowing through the indoor unit 40a that performs heating operation, and does not control the outdoor expansion valve 15 in order to further increase the heating capacity that has already been generated. Different from expansion valve control. The heating capacity is generally controlled by controlling the outdoor fan 19. Here again, the outdoor expansion valve 15 may be controlled so that the temperature difference between the intake air temperature and the blown air temperature of the indoor unit 40a falls within a predetermined range.

Hereinafter, the present embodiment will be described with reference to FIG.
FIG. 6 is a diagram for explaining an outdoor expansion valve control flowchart of this embodiment. The difference from FIG. 3 of the first embodiment and FIG. 5 of the second embodiment is that the outdoor expansion valve 15 is throttled when the gas pipe temperature of the indoor unit 40a that performs the heating operation becomes lower than the set value. It is. More specifically, when the temperature difference between the refrigerant temperature on the inlet side of the indoor unit 40a and the saturation temperature in the refrigerant pressure on the discharge side of the compressor 11 is equal to or less than a set value, the opening degree of the outdoor expansion valve 15 is set. By restricting, the refrigerant pressure on the inlet side of the indoor heat exchanger 41a is controlled to be higher than the refrigerant pressure on the outlet side of the indoor heat exchanger 41a. Thereby, the heating capability of the indoor unit 40a can be exhibited similarly to the first embodiment.

  Moreover, by controlling in this way, it is not necessary to attach a pressure sensor for measuring the liquid pipe pressure on the indoor unit side as in the second embodiment. Further, since the set value is considered based on the saturation temperature obtained from the discharge pressure, if the gas pipe side temperature of the indoor unit 40a is substantially equal to or lower than the saturation temperature, it is determined that no gas refrigerant is flowing in the indoor unit 40a. Then, the outdoor expansion valve 15 is throttled. Here again, the outdoor expansion valve may be controlled so that the gas pipe temperature falls within a predetermined range.

Hereinafter, the present embodiment will be described with reference to FIG.
FIG. 7 is a diagram for explaining the refrigeration cycle structure of the present embodiment. In the embodiment described so far, the liquid pipe pressure of the indoor unit 40a that performs the heating operation is lowered by restricting the outdoor expansion valve 15, but in FIG. 7, the liquid refrigerant in the liquid pipe that causes the liquid head is reduced. Thus, an increase in the liquid pipe pressure is suppressed.

  First, the left figure of FIG. 7 shows the state of the liquid main pipe 33 and the low-pressure gas pipe 32 in normal operation. The vertical pipe portions of the low-pressure gas pipe 32 and the liquid main pipe 33 are shown in cross-section and the internal refrigerant state is described. The low-pressure gas pipe 32 is used as a gas single phase, and the liquid main pipe 33 is used as a liquid single phase. Here, the head in the liquid single phase can be obtained by liquid density ρL × height difference ΔH × gravity acceleration.

  Next, the right figure of FIG. 7 is an example in which the liquid head is reduced. A part of the refrigerant in the liquid main pipe 33 is moved to the low-pressure gas pipe 32 by opening the indoor expansion valve 42b of the indoor unit 40b that performs the cooling operation with respect to the left figure. Since the low-pressure gas pipe 32 has a larger volume than the liquid main pipe 33, such a movement of the refrigerant can be easily performed. Further, the refrigerant may be moved to an auxiliary device such as an accumulator or a receiver. By setting the refrigerant in the liquid main pipe 33 in the two-phase state in this manner, the two-phase head density ρGL <liquid density ρL, so that the head ρGL × ΔH × g in the two-phase state can be reduced. It is also possible to generate heating capacity during simultaneous operation.

Hereinafter, the present embodiment will be described with reference to FIG.
FIG. 8 is a view for explaining a control flowchart of the outdoor expansion valve of the present embodiment. This embodiment is different from the first to third embodiments in that the pressure loss of the difference in height between the outdoor unit 10 and the indoor units (40a, 40b) is throttled by the outdoor expansion valve 15 in advance. Here, the indoor / outdoor height difference may be stored in the control circuit by the contractor, or may be estimated from an operating state such as a trial operation.

The degree of opening of the outdoor expansion valve 15 to be throttled is determined by determining the pressure applied to the liquid main pipe 33 in consideration of the physical properties of the refrigerant with respect to the height difference, and then the amount of refrigerant circulating through the outdoor heat exchanger 14 acting as a condenser, the outlet of the condenser It is determined from the state (liquid single phase or two phase) and expansion valve flow rate characteristics. For example, in order to generate an equivalent pressure loss, the expansion valve opening degree is opened when the refrigerant circulation amount is large, and when the condenser outlet state is two-phase, the expansion valve opening degree is opened and the expansion valve aperture is For small models, it is recommended to open the expansion valve opening. The obtained opening is always taken into account when calculating the outdoor expansion valve. These outdoor expansion valve opening calculations are set in the control circuit 28.
In addition, this throttling may be always entered when the indoor unit cooling operation and the heating operation are mixed and the outdoor heat exchanger becomes a condenser as shown in the flowchart of FIG. 8, as shown in FIGS. When the outdoor expansion valve is throttled when the determination condition is satisfied, it may be used as a guide for the opening degree to be throttled.

  FIG. 9 is a system diagram of the refrigeration cycle of Example 6. The number of outdoor units 10 and indoor units 40a and 40b is the same as in Example 1, but the number of connecting pipes is only two (low pressure gas pipe 32 and high pressure gas pipe 34) corresponding to gas pipes, and the liquid pipe is a gas pipe. Omitted by flowing refrigerant along with gas in the tube. Furthermore, a gas-liquid separator 61 for separating the two-phase refrigerant sent to the indoor units 40a and 40b into liquid and gas, a first decompression mechanism 62 for adjusting the refrigerant pressure of the liquid refrigerant after separation, and the gas refrigerant There is a second pressure reducing mechanism 63 that adjusts the refrigerant pressure.

  The refrigerant flow in the cooling main mode (cooling load> heating load state) in the simultaneous cooling and heating operation will be described. Since the outdoor expansion valve 15 does not normally exist in this product form, the case where there is no outdoor expansion valve 15 and the height difference is about the current product specification below a predetermined value will be described first. The high-pressure gas refrigerant compressed by the compressor 11 is discharged to the heat exchanger switching four-way valve 13 and flows to the outdoor heat exchanger 14. Here, the refrigerant is appropriately condensed by the outdoor fan 19 to become a high-pressure two-phase refrigerant, and is sent to the high-pressure gas pipe 34 and the gas-liquid separator 61 through the check valve. The liquid refrigerant separated here is controlled so as to be maintained at an appropriate pressure between the indoor expansion valves 42a of the indoor unit 40a that performs the cooling operation after passing through the first pressure reducing mechanism 62. The proper pressure is to make the pressure between the first decompression mechanism 62 and the indoor expansion valve 42a lower than the pressure of the gas-liquid separator 61, and to this, the saturated gas refrigerant is supplied to the indoor unit 40b that performs the heating operation. Begins to flow.

  Explaining this point, the saturated gas refrigerant separated by the gas-liquid separator 61 is condensed by being sent to the indoor unit 40b that performs the heating operation, and becomes high-pressure liquid refrigerant and sent to the indoor expansion valve 42b. Moreover, it joins between the 1st pressure reduction mechanism 62 and the indoor expansion valve 42a via the liquid branch pipe 35b. The liquid refrigerant thus joined is throttled and depressurized by the indoor expansion valve 42a, and is evaporated to become low-pressure gas refrigerant by exchanging heat with indoor air in the indoor heat exchanger 41a. At this time, since the high-pressure side opening / closing mechanism 52a is closed and the low-pressure side opening / closing mechanism 51a is opened, the high-pressure side opening / closing mechanism 51a is opened and sent to the low-pressure gas pipe 32. .

  Next, a case where the height difference between the outdoor unit 10 and the indoor units (40a, 40b) is equal to or greater than a predetermined value (when expanded to be greater than the current product specification) will be described. The refrigerant flow is the same for the vicinity of the outdoor unit 10 and the indoor unit 40b that performs cooling operation, and the description will focus on the state of the indoor unit 40b and gas-liquid separator 61 that perform heating operation. Here, assuming that the amount of outdoor heat exchange is the same, if the height difference is large, the liquid refrigerant accumulates in the gas-liquid separator 61 and becomes full, and the gas refrigerant cannot be sent to the indoor unit 40b that performs the heating operation.

  For this reason, the air volume of the outdoor fan 19 must be reduced, the outdoor heat exchange amount must be reduced, and the gas-liquid separator 61 must be in a two-phase state. However, when the outside air is low or the like, there is a limit to reducing the heat exchange amount of the outdoor heat exchanger 14 only by the air volume of the outdoor fan 19, and the gas-liquid separator 61 is an indoor unit that performs heating operation while being full. There is a possibility that the gas refrigerant cannot be sent to 40b and the heating capacity cannot be generated.

Therefore, in the present embodiment, the outdoor unit 10 is provided with the outdoor expansion valve 15, and by controlling the outdoor expansion valve 15, the heating capacity of the indoor unit 40b is exhibited. In other words, the amount of heat exchange in the outdoor heat exchanger 14 can be slightly reduced by reducing the opening of the outdoor expansion valve 15 in the above case. Further, when the pressure is reduced by isoenthalpy, the refrigerant changes from a liquid single phase to a two-phase. As a result, a saturated gas refrigerant is produced in the gas-liquid separator 61, and heating capacity can be generated.
Here, as the control of the outdoor expansion valve, the outdoor expansion valve 15 when the temperature difference between the intake air temperature and the blown air temperature of the indoor unit 40a that performs the heating operation becomes equal to or less than a set value as shown in the flowchart of FIG. You may make it squeeze. By squeezing, it is possible to create a state in which the gas-liquid separator 61 has two phases. Further, in the case where the gas pipe temperature of the indoor unit 40a performing the heating operation shown in FIG. 6 is equal to or lower than the set value, only the saturated gas flows through the heater during the cooling main operation, so the reference temperature is set to the gas pipe saturation temperature. It is good. Further, as shown in FIG. 8, the pressure loss of the difference in height may be previously throttled by the outdoor expansion valve 15.

DESCRIPTION OF SYMBOLS 10 Outdoor unit 11 Compressor 12 High / low pressure switching four-way valve 13 Heat exchanger switching four-way valve 14 Outdoor heat exchanger 15 Outdoor expansion valve 19 Outdoor fan 21 High / low pressure gas blocking valve 22 Low pressure gas blocking valve 23 Liquid blocking valve 28 Control circuit 31 High-low pressure gas pipe 32 Low-pressure gas pipe 33 Liquid main pipe 34 High-pressure gas pipes 35a, 35b Liquid branch pipes 40a, 40b Indoor units 41a, 41b Indoor heat exchangers 42a, 42b Indoor expansion valves 51a, 51b High-pressure side opening / closing mechanisms 52a, 52b Low pressure Side opening / closing mechanism 61 Gas-liquid separator 62 First decompression mechanism 63 Second decompression mechanism 71, 72, 73 Pressure sensor

Claims (10)

At least one outdoor unit;
The first indoor unit and the second indoor unit are connected by a refrigerant pipe,
The outdoor unit includes a compressor and an outdoor heat exchanger,
The first indoor unit includes a first indoor heat exchanger,
The second indoor unit is an air conditioner including a second indoor heat exchanger,
When the first indoor unit performs a heating operation, the second indoor unit performs a cooling operation, and when the outdoor heat exchanger acts as a condenser,
While refrigerant from the compressor flows to the outdoor heat exchanger, a refrigerant pipe is configured to flow to the first indoor heat exchanger,
By restricting the opening of the expansion valve disposed on the refrigerant outlet side of the outdoor heat exchanger, the gas refrigerant pressure on the inlet side of the first indoor heat exchanger is changed to the outlet side of the first indoor heat exchanger. It controls so that it may become higher than the liquid refrigerant pressure of the air conditioner characterized by the above-mentioned. In the air conditioner according to claim 1,
The first indoor heat exchanger acts as a condenser;
The air conditioner characterized in that the refrigerant from the outdoor heat exchanger flows into the second indoor heat exchanger together with the refrigerant flowing from the first indoor heat exchanger. In the air conditioner according to claim 1,
The air conditioner is characterized in that the expansion valve is an outdoor expansion valve provided in the outdoor unit. In the air conditioner in any one of Claims 1-3,
The air conditioner is characterized in that the outdoor unit is installed above the first indoor unit and the second indoor unit. In the air conditioner according to claim 1 or 2,
When the refrigerant pressure on the inlet side of the first indoor heat exchanger becomes equal to or lower than the refrigerant pressure on the outlet side, the opening of the expansion valve is reduced to reduce the pressure on the inlet side of the first indoor heat exchanger. An air conditioner characterized by controlling the refrigerant pressure to be higher than the refrigerant pressure on the outlet side of the first indoor heat exchanger. In the air conditioner according to claim 1 or 2,
A first temperature sensor for detecting a temperature on an air suction side of the first indoor unit;
A second temperature sensor for detecting the temperature of the air blowing side of the first indoor unit,
When the temperature difference between the temperature on the air blowing side detected by the second temperature sensor and the temperature on the air suction side detected by the first temperature sensor becomes a set value or less, the expansion valve is opened. The air conditioning is characterized by controlling the refrigerant pressure on the inlet side of the first indoor heat exchanger so as to be higher than the refrigerant pressure on the outlet side of the first indoor heat exchanger by reducing the degree. Machine. In the air conditioner according to claim 1 or 2,
When the temperature difference between the refrigerant temperature on the inlet side of the first indoor unit and the saturation temperature on the refrigerant pressure on the discharge side of the compressor is equal to or less than a set value, the opening of the expansion valve is reduced, An air conditioner that controls the refrigerant pressure on the inlet side of the first indoor heat exchanger to be higher than the refrigerant pressure on the outlet side of the first indoor heat exchanger. In the air conditioner according to claim 1 or 2,
An air conditioner characterized in that the outdoor expansion valve is throttled so that a pressure loss with a difference in height is generated from the refrigerant flow rate and the outdoor expansion valve flow rate characteristic. At least one outdoor unit;
The first indoor unit and the second indoor unit are connected by a refrigerant pipe,
The outdoor unit includes a compressor and an outdoor heat exchanger,
The first indoor unit includes a first indoor heat exchanger,
The second indoor unit is an air conditioner including a second indoor heat exchanger,
When the first indoor unit performs a heating operation, the second indoor unit performs a cooling operation, and when the outdoor heat exchanger acts as a condenser,
While refrigerant from the compressor flows to the outdoor heat exchanger, a refrigerant pipe is configured to flow to the first indoor heat exchanger,
By opening the opening of the expansion valve disposed on the refrigerant outlet side of the second indoor heat exchanger, the refrigerant pressure on the inlet side of the first indoor heat exchanger is changed to that of the first indoor heat exchanger. An air conditioner that is controlled to be higher than the refrigerant pressure on the outlet side. The air conditioner according to claim 9,
The first indoor heat exchanger acts as a condenser;
The air conditioner characterized in that the refrigerant from the outdoor heat exchanger flows into the second indoor heat exchanger together with the refrigerant flowing from the first indoor heat exchanger.

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