KR20130135132A - Heat pump type air conditioner - Google Patents

Abstract

Provided is a heat pump type air conditioner capable of improving the estimation accuracy of supercooling by improving the reliance of the refrigerant used in estimation of supercooling. The present invention provides a heat pump type air conditioner comprising an external heat exchanger (1); multiple indoor units (2, 3); a first fluid path (91) combining the ejection ports in heating of multiple indoor heat exchanger (21, 31) and connecting the joint portion and an air suction port in heating the external heat exchanger (1); and a refrigerant circuit (A) having compressors (51, 52). The heat pump type air conditioner has a temperature estimation unit (102) estimating the temperature of the refrigerant after joining in the first fluid path (91) when heating, based on the value corresponding to the maximum flux of the refrigerant of indoor expansion valves (23, 33) and the openness of the indoor expansion valves (23, 33) as a result of detecting temperature sensors (24, 34) of indoor fluid pipes; and a supercooling estimation unit (103) calculating the supercooling of the refrigerant circuit (A) by using the estimated temperature estimated in the temperature estimation unit (102). [Reference numerals] (AA) Air heating;(BB) Air cooling

Description

Heat Pump Air Conditioning Unit {HEAT PUMP TYPE AIR CONDITIONER}

The present invention relates to a heat pump type air conditioner.

In a heat pump type air conditioner having an outdoor heat exchanger, an indoor heat exchanger, and a compressor, control of an adjustment valve or the like is performed to calculate the supercooling degree from the temperature of the refrigerant circulating in the refrigerant circuit and to bring the subcooling degree within an appropriate range. It is done. The refrigerant temperature used for the calculation of the supercooling degree measures the detected value of the outdoor liquid pipe temperature sensor installed in the outdoor unit on the flow path connecting the indoor heat exchanger and the outdoor heat exchanger, or the temperature of the refrigerant circulating in the indoor heat exchanger installed in the indoor unit. The detection value in the room liquid pipe temperature sensor is used. As controlling an adjustment valve based on subcooling degree, Unexamined-Japanese-Patent No. 8-219572 (patent document 1) is mentioned, for example.

Japanese Patent Application Laid-open No. Hei 8-219572

However, in the flow path near the outdoor liquid pipe temperature sensor, there is a possibility that the refrigerant flowing through is in a two-phase state of gas liquid. During the heating operation, the refrigerant flowing out from the indoor heat exchanger through the expansion valve is condensed in the indoor heat exchanger, and thus is in a liquid state. However, the flow path connecting the indoor heat exchanger and the outdoor heat exchanger may be several meters or more for home use or 100 meters or more for business use. Therefore, when the coolant in the liquid state passes through the flow path and reaches the vicinity of the outdoor liquid pipe temperature sensor, there is a fear that the phase state of the coolant changes due to the pressure loss caused by the flow path, resulting in a two-phase state of the gas phase and the liquid phase. As a result, the temperature of the liquid phase refrigerant flowing out from the indoor heat exchanger must be detected as a value necessary for the calculation of the degree of supercooling, thereby detecting the temperature of the refrigerant in the two-phase state. The temperature of the refrigerant lost in pressure and brought into the two phase state is lower than the temperature of the refrigerant in the liquid state before the pressure loss. Thereby, there exists a problem that an overcooling degree is calculated excessively and the calculation precision of a subcooling degree falls.

In patent document 1, when an overcooling degree is calculated excessively, the opening degree of an outdoor expansion valve will become larger than an appropriate opening degree as a control to reduce a subcooling degree. As a result, the refrigerant downstream of the outdoor heat exchanger does not evaporate completely, resulting in a wet state, and there is a fear that breakage of the compressor due to liquid compression may occur.

On the other hand, when the detection value of the indoor liquid pipe temperature sensor is used to calculate the supercooling degree, when a plurality of indoor units are connected to one refrigerant circuit, the temperature of the refrigerant after flowing out from the plurality of indoor heat exchangers and joining is detected. It is difficult.

This invention is made | formed in view of such a situation, and it aims at providing the heat pump type air conditioner which can improve the reliability of the refrigerant temperature used for calculation of a supercooling degree, and can improve the calculation precision of a subcooling degree. do.

The invention as set forth in claim 1 is an indoor heat exchanger, an indoor heat exchanger, an indoor expansion valve connected to an outlet for heating the indoor heat exchanger, and an indoor heat exchanger installed between the indoor heat exchanger and the indoor expansion valve to detect a temperature of a refrigerant. A refrigerant circuit comprising a plurality of indoor units having a liquid pipe temperature sensor, a first flow path for joining a discharge port during heating of the plurality of indoor heat exchangers and communicating a joining portion and a suction port during heating of the outdoor heat exchanger; And a temperature of the refrigerant after confluence in the first flow path during heating, based on a value corresponding to the maximum refrigerant flow rate of the indoor expansion valve and the opening degree of the indoor expansion valve, as a result of the detection of the indoor liquid pipe temperature sensor. A temperature estimating unit for estimating a and a temperature estimated by the temperature estimating unit; A subcooling degree calculating part which calculates a subcooling degree is provided.

The invention according to claim 2, further comprising: an outdoor liquid pipe temperature sensor provided in the outdoor first flow path for detecting a temperature of the refrigerant, wherein the subcooling degree calculation unit is configured to estimate the temperature and the outdoor liquid pipe temperature. The detection result of the sensor is compared, and when the detection result of the outdoor liquid pipe temperature sensor is lower than the estimated temperature by a predetermined temperature or more, the estimated temperature is determined as the refrigerant temperature, otherwise the detection result of the outdoor liquid pipe temperature sensor is determined. And a coolant temperature determination unit determining a coolant temperature, and a calculation unit calculating a supercooling degree of the coolant circuit based on the coolant temperature determined by the coolant temperature determining unit.

The invention according to claim 3 is based on the subcooling control valve according to claim 1 or 2, wherein the subcooling adjustment valve is provided with respect to the first flow path and the subcooling degree can be adjusted according to the opening degree, and the subcooling degree calculated by the subcooling calculation unit. A subcooling degree adjusting part for controlling the subcooling adjusting valve is further provided.

According to the invention described in claim 1, in the refrigerant circuit having a plurality of indoor heat exchangers, it is possible to estimate the refrigerant temperature of the liquid phase after joining the first flow path during heating. The refrigerant at the time of heating normally becomes a liquid state when it joins out of an indoor unit. The liquidus temperature is used as the refrigerant temperature used in the calculation of the subcooling degree. However, the coolant may be in the gas-liquid two-phase state due to pressure loss or the like during the flow of the flow path, and the coolant temperature is lowered by being in the gas-liquid two-phase state. According to the present invention, by estimating the refrigerant temperature and using it for the calculation of the subcooling degree, it is possible to suppress the occurrence of an error or deviation between the liquid phase refrigerant temperature by detecting the refrigerant temperature in the gas-liquid two-phase state. Thereby, the reliability of the refrigerant temperature used for calculation of the subcooling degree can be improved, and the calculation precision of the subcooling degree can be improved.

According to the invention as set forth in claim 2, by setting a predetermined temperature as a predetermined value for determining whether or not a gas-liquid two-phase state is determined based on it, the estimated temperature is determined as the refrigerant temperature in the gas-liquid two-phase state, and the liquid phase In the case of a state, the detection temperature of the outdoor liquid pipe temperature sensor may be determined as the refrigerant temperature. As a result, the refrigerant temperature can be more accurately determined, and the calculation accuracy of the supercooling degree can also be improved.

According to invention of Claim 3, the subcooling degree can be adjusted based on the subcooling degree calculated with high precision.

BRIEF DESCRIPTION OF THE DRAWINGS The conceptual diagram which shows the structure of the heat pump type air conditioner of this embodiment.
2 is a flowchart showing a flow relating to the subcooling degree calculation of the present embodiment.

Next, an embodiment is given and this invention is demonstrated in detail. As shown in FIG. 1, the heat pump type air conditioner of the present embodiment mainly includes an outdoor heat exchanger 1, indoor units 2 and 3, a switching valve 4, a compressor 5, And an accumulator 6, a subcooling control valve 7, various sensors 81 and 82, flow paths 91 to 98, and a control unit 10. The refrigerant circuit A mainly includes the outdoor heat exchanger 1, the indoor units 2 and 3, the switching valve 4, the compressor 5, the accumulator 6, and the supercooling control valve 7. And various sensors 81 and 82 and flow paths 91 to 98.

The outdoor heat exchanger (1) is a device for performing heat exchange between the refrigerant passing through the inside and the outside air. The outdoor heat exchanger 1 receives air from the fan 11 arranged adjacently. The outdoor heat exchanger 1 functions as a condenser at the time of cooling operation, and functions as an evaporator at the time of heating operation.

Here, the first flow path 91 is a pipe, one end of the outdoor heat exchanger 1 (suction inlet during heating), one end of the indoor heat exchanger 21 of the indoor unit 2 (discharge port during heating) and the indoor unit. One end (discharge port at the time of heating) of the indoor heat exchanger 31 of (3) is connected. The first flow path 91 includes an oil supply passage 911 extending to the vicinity of the outdoor heat exchanger 1 and the indoor units 2 and 3, and a first branch branched from the oil passage 911 and extending into the indoor unit 2. It consists of the flow path 912 and the 2nd branch flow path 913 extended from the fuel flow path 911 into the indoor unit 3, and the like. That is, the main flow passage 911 communicates the confluence point of the first branch flow passage 912 and the second branch flow passage 913 with one end of the outdoor heat exchanger 1. The outdoor liquid pipe temperature sensor 81 which detects the coolant (liquid) temperature in a flow path is provided in the site | part arrange | positioned in the outdoor unit 100 in the main flow path 911.

The indoor unit 2 is disposed indoors and includes an indoor heat exchanger 21, a fan 22, an indoor expansion valve 23, and an indoor liquid pipe temperature sensor 24. The indoor heat exchanger 21 is a device that performs heat exchange between the refrigerant passing through the inside and the outside air. The first branch flow path 912 is connected to one end (discharge port during heating) of the indoor heat exchanger 21. The fan 22 is disposed adjacent to the indoor heat exchanger 21 and blows toward the indoor heat exchanger 21. The wind blown toward the indoor heat exchanger 21 is sent indoors.

The indoor expansion valve 23 is an electromagnetic expansion valve that can electrically adjust the opening degree of the valve. The indoor expansion valve 23 is interposed in the first branch flow path 912. The indoor liquid pipe temperature sensor 24 is a temperature sensor that detects the temperature of the refrigerant in the pipe. The indoor liquid pipe temperature sensor 24 is disposed between the indoor heat exchanger 21 and the indoor expansion valve 23 in the first branch flow path 912.

The indoor unit 3 has the same configuration as the indoor unit 2, and includes an indoor heat exchanger 31, a fan 32, an indoor expansion valve 33, and an indoor liquid pipe temperature sensor 34. The indoor heat exchanger 31 is a device that performs heat exchange between the refrigerant passing through the inside and the outside air. One end (discharge port during heating) of the indoor heat exchanger 31 is connected to the second branch flow path 913. The fan 32 is arranged adjacent to the indoor heat exchanger 31 and blows toward the indoor heat exchanger 31.

The indoor expansion valve 33 is an electromagnetic expansion valve that can electrically adjust the opening degree of the valve. The indoor expansion valve 33 is interposed in the second branch flow path 913. The indoor liquid pipe temperature sensor 34 is a temperature sensor that detects the temperature of the refrigerant. The indoor liquid pipe temperature sensor 34 is disposed between the indoor heat exchanger 31 and the indoor expansion valve 33 in the second branch flow passage 913. The indoor liquid pipe temperature sensors 24 and 34 are disposed downstream of the indoor heat exchangers 21 and 31 at the time of heating, and detect the discharge refrigerant temperature of the indoor heat exchangers 21 and 31 at the time of heating. Can be. The indoor liquid pipe temperature sensors 24 and 34 are configured to attach a temperature sensor to a pipe surface, for example, and surround the temperature sensor with a heat insulating material so as not to detect ambient air temperature.

The switching valve 4 is a four-side switching valve provided with four ports 41 to 44. The switching valve 4 is controlled by the control unit 10 and switches the flow path of the coolant during the cooling operation and the heating operation. The switching valve 4 forms a flow path in which the coolant flow becomes a flow indicated by the solid arrow in Fig. 1 during the cooling operation, and a flow path in which the coolant flow becomes a flow indicated by the broken arrow in Fig. 1 during the heating operation. Form.

The compressors 51 and 52 are compressors for compressing a refrigerant in a gaseous state and are driven using an engine (not shown) as a drive source. The suction ports of the compressors 51 and 52 are connected to the discharge port of the accumulator 6 through the second flow path 92. The compressors 51 and 52 are connected in parallel in the refrigerant circuit A. FIG. In addition, the capacitive electromagnetic valve B and the buffer C are provided for the compressors 51 and 52.

The discharge ports of the compressors 51 and 52 are connected to the port 41 of the switching valve 4 via the third flow passage 93. On the third flow path 93, an oil separator D is disposed. The pressure sensor 82 is arrange | positioned between the oil separator D and the switching valve 4. The pressure sensor 82 is a sensor which detects the pressure in the 3rd flow path 93. The pressure sensor 82 detects the discharge pressure from the compressors 51 and 52. In addition, the oil separator D is connected to a fourth flow path 94 which connects itself with the second flow path 92 (between the branch point and the accumulator 6). An adjustment valve 94a is interposed in the fourth flow path 94.

The port 42 of the switching valve 4 is connected to the other end (discharge port at the time of heating) of the outdoor heat exchanger 1 via the 5th flow path 95. As described above, the first flow path 91 is connected to one end of the outdoor heat exchanger 1. The port 43 of the switching valve 4 is connected to the inlet port of the accumulator 6 via the sixth flow path 96.

The accumulator 6 is a liquid separator and prevents the refrigerant in the liquid state from flowing into the compressors 51 and 52. The port 43 of the switching valve 4 is connected to the other end (intake port at the time of heating) of the indoor heat exchangers 21 and 31 via the seventh flow path 97. The seventh flow path 97 branches in the vicinity of the indoor units 2 and 3 similarly to the first flow path 91.

The supercooled heat exchanger E is interposed between the outdoor liquid pipe temperature sensor 81 and the outdoor heat exchanger 1 in the first flow path 91. The subcooling heat exchanger (E) further cools the refrigerant flowing in the main oil passage 911, and mainly improves the refrigeration cycle efficiency during the cooling operation and the heating operation by increasing the subcooling degree of the refrigerant.

A subcooling bypass flow path 71 connected to the sixth flow path 96 is connected to one end (discharge port during heating) of the subcooling heat exchanger E. FIG. The subcooling control valve 7 is an electromagnetic expansion valve which can adjust the degree of opening electrically, and is interposed in the subcooling bypass flow path 71. A part of the part between the subcooling control valve 7 and the 6th flow path 96 in the subcooling bypass flow path 71 distribute | circulates the inside of the subcooling heat exchanger E. As shown in FIG.

When the subcooling control valve 7 is opened and the refrigerant flows through the subcooling bypass flow path 71, the main oil passage 911 and the subcooling bypass flow path 71 exchange heat in the subcooling heat exchanger E. FIG. The refrigerant circulated in the subcooling bypass flow path 71 is expanded by the subcooling adjustment valve 7 to have a lower temperature and a lower pressure than the refrigerant circulating in the oil passage 911. Therefore, the refrigerant circulating in the oil passage 911 at the time of cooling and heating operation is supercooled in the subcooling heat exchanger (E). By increasing the opening degree of the subcooling control valve 7, the subcooling degree in a system becomes large.

In addition, a heating bypass flow path 914 is provided in the vicinity of the outdoor heat exchanger 1 (between the outdoor heat exchanger 1 and the supercooled heat exchanger E) in the oil passage 911. The heating bypass flow path 914 branches from one end side of the liquid pipe check valve 911a interposed in the oil passage 911 and joins the other end side. The adjustment valve 914a is interposed in the heating bypass flow path 914. The adjustment valve 914a is an electromagnetic expansion valve that can electrically control the degree of opening.

The heating bypass flow path 914 is provided with a low temperature heating bypass flow path 915 branched from the upstream side of the regulating valve 914a at the time of heating and joining to the sixth flow path 96. In the low temperature heating bypass flow path 915, an adjustment valve 915a and a sub heat exchanger F are interposed in order from the heating bypass flow path 914 toward the sixth flow path 96. The adjustment valve 915a is an electromagnetic expansion valve which can electrically control the opening degree. The flow rate of the refrigerant flowing through the heating bypass flow passage 914 and the low temperature heating bypass flow passage 915 is determined according to the opening degree of the adjustment valves 914a and 915a.

The sub heat exchanger F causes heat exchange between the refrigerant passing through the low-temperature heating bypass flow path 915 and the cooling water cooling the engine (not shown). As a result, the refrigerant flowing through the low temperature heating bypass flow path 915 is vaporized to become a refrigerant in a gaseous state, and flows into the sixth flow path 96 and flows into the accumulator 6. These adjustment valves 914a and 915a adjust the flow rate of the refrigerant flowing into the outdoor heat exchanger 1 during heating operation. The supercooling degree in a system can also be adjusted with adjustment valve 914a, 915a.

Closing valves 911b and 97a are interposed in the oil passage 911 and the seventh flow passage 97 of the first flow passage 91, respectively, near the entrance and exit of the outdoor unit 100. In addition, the outdoor unit 100 mainly includes an outdoor heat exchanger 1, a switching valve 4, compressors 51 and 52, a supercooling control valve 7, an accumulator 6, a control unit 10, and various flow paths. And a housing (not shown) for accommodating them. In addition, an eighth flow path 98 that connects the third flow path 93 and the sixth flow path 96 is provided in the refrigerant circuit A, and the hot gas bypass valve 98a is provided in the eighth flow path 98. Is interposed.

The control unit 10 is an electronic control unit (ECU), and is mainly an apparatus for switching the cooling operation and the heating operation or adjusting the supercooling degree based on a command of a remote controller or the like. The control unit 10 is based on various information, the opening degree of each valve 23, 33, 7, 914a, 915a, 911b, 94a, 97a, 98a, B, etc. which are provided in the flow path, Switch the flow path configuration.

Specifically, the control unit 10 includes an operation switching unit 101 for switching between cooling and heating operations, a temperature estimating unit 102, a subcooling degree calculating unit 103, and a subcooling degree adjusting unit 104. Equipped. The temperature estimating unit 102 determines the value corresponding to the maximum refrigerant flow rate of the indoor expansion valves 23 and 33 and the opening degree of the indoor expansion valves 23 and 33 as a result of the detection of the indoor liquid pipe temperature sensors 24 and 34. Based on this, the temperature of the coolant in the oil passage 911 (near the downstream of the indoor units 2 and 3 at the time of heating) is estimated.

The temperature estimating unit 102 receives temperature information from the indoor liquid pipe temperature sensors 24 and 34 and acquires the opening degree information of the indoor expansion valves 23 and 33 controlled by the self (control unit 10). . As a value corresponding to the maximum refrigerant flow rate of the indoor expansion valves 23 and 33, in the present embodiment, the capacity of the indoor heat exchangers 21 and 31 and the size t of the indoor expansion valves 23 and 33 (t). ) Is used.

There is a correlation between the maximum refrigerant flow rate of the indoor expansion valves 23 and 33, the capacity of the indoor heat exchangers 21 and 31 (indoors 2 and 3) and the size of the indoor expansion valves 23 and 33, From the said capacity | capacitance and a size, the weighting | weighting corresponded to the maximum refrigerant flow volume is possible. Moreover, in general, there is a correlation between the capacity of the indoor heat exchangers 21 and 31 and the size of the indoor expansion valves 23 and 33 provided for the indoor heat exchangers 21 and 31, so that the weighting value is given. As the capacity, it can be calculated using either value as the size.

As calculations, for all the indoor units in the refrigerant circuit A, a value corresponding to the detection result of the indoor liquid pipe temperature sensor x the maximum refrigerant flow rate of the indoor expansion valve (in this embodiment, the size of the indoor expansion valve or the capacity of the indoor heat exchanger). The opening degree of the indoor expansion valve = the first calculation result and the value corresponding to the maximum refrigerant flow rate of the indoor expansion valve (in this embodiment, the size of the indoor expansion valve or the capacity of the indoor heat exchanger) x The opening degree of the indoor expansion valve = A 2nd calculation result is computed, and the value which divided the sum of a 1st calculation result by the sum of a 2nd calculation result is made into estimated temperature. The opening degree may be a ratio (%) or a pulse, and what is necessary is just to be unified by the 1st calculation result and the 2nd calculation result. Generally, in the expansion valve, the opening degree of the valve is adjusted by the number of pulses. That is, the pulse is correlated with the opening of the expansion valve. For example, for 0-1600 pulses, the opening of the expansion valve is from fully closed to fully open.

As an example, in the indoor unit 2, the detection result of the indoor liquid pipe temperature sensor 24 is 20 ° C., the size of the indoor expansion valve 23 is 1.5t, and the opening degree of the indoor expansion valve 23 is 200. In the indoor unit 3, the detection result of the indoor liquid pipe temperature sensor 34 is 30 ° C., the size of the indoor expansion valve 33 is 3t, and the opening degree of the indoor expansion valve 33 is 400 pulses. In this case, the sum of the first calculation results is 42000, the sum of the second calculation results is 1500, and the estimated temperature is 42000/1500 = 28 ° C.

In the above specific example, when the value corresponding to the maximum refrigerant flow rate of the indoor expansion valve is the capacity of the indoor heat exchanger (indoor), the capacity of the indoor heat exchanger 21 is 3.6 kPa, and the The capacity is 8 kPa, and 110400 (sum of the first calculation result) / 3920 (sum of the second calculation result) # 28.16 占 폚. As described above, in the present embodiment, the size of the indoor expansion valve or the capacity of the indoor heat exchanger (indoor) is used as a value corresponding to the maximum refrigerant flow rate of the indoor expansion valve. Naturally, if the maximum refrigerant flow rate of the indoor expansion valve can be grasped, the value can be used.

The temperature estimating unit 102 calculates the refrigerant temperature (that is, the estimated temperature in the vicinity of the confluence point in the oil passage 911 where the first branch passage 912 and the second branch passage 913 join by the above calculation). ) Is calculated.

The subcooling degree calculation unit 103 includes a coolant temperature determination unit 103a and a calculation unit 103b. The coolant temperature determination unit 103a receives the detection result of the outdoor liquid pipe temperature sensor 81 and the estimated temperature calculated by the temperature estimating unit 102, and compares the detection result with the estimated temperature. In the refrigerant temperature determining unit 103a, a predetermined temperature is set in advance with respect to the temperature difference between them. In this embodiment, predetermined temperature is set to 3 degreeC.

The coolant temperature determination unit 103a determines the estimated temperature as the coolant temperature (system liquid temperature) when the estimated temperature-the outdoor liquid pipe temperature sensor 81 detects ≥ a predetermined temperature (3 ° C). The refrigerant temperature determining unit 103a determines the detection result as the refrigerant temperature (system liquid temperature) when the estimated temperature-the outdoor liquid pipe temperature sensor 81 is a detection result <predetermined temperature (3 ° C). The predetermined temperature may be set by experiment or simulation in consideration of the length, pressure loss, and the like of the oil passage 911.

The calculator 103b receives the pressure information from the pressure sensor 82. The calculation unit 103b calculates the condensation temperature of the refrigerant based on the pressure information. The condensation temperature of the refrigerant is determined by the type of refrigerant and the pressure in the flow path. The calculation unit 103b calculates the subcooling degree by subtracting the refrigerant temperature determined by the refrigerant temperature determining unit 103a from the calculated condensation temperature (condensation temperature-refrigerant temperature = subcooling degree).

The subcooling degree adjusting part 104 controls the opening degree of the subcooling adjustment valve 7 based on the calculated subcooling degree. The subcooling degree adjusting unit 104 determines whether the subcooling degree is within a predetermined range (predetermined above the first predetermined temperature and below the second predetermined temperature). If the subcooling degree is within a predetermined range, the opening degree of the subcooling regulating valve 7 is not adjusted. When the subcooling degree is lower than the first predetermined temperature (for example, 19 ° C), the subcooling degree adjusting unit 104 controls the subcooling adjusting valve 7 to the side that closes the subcooling adjusting valve 7. That is, the supercooling degree adjusting unit 104 reduces the opening degree of the supercooling angle adjusting valve 7. As a result, the supercooling degree is increased, and the supercooling degree is controlled to fall within a predetermined range. Moreover, when the subcooling control valve 7 is closed, the subcooling degree at the inlet side at the time of heating of the subcooling heat exchanger E becomes large. By closing the subcooling control valve 7, excess refrigerant of the system stored in the accumulator 6 is stored in the indoor heat exchangers 21 and 31 (condenser), so that the refrigerant is more likely to flow in the indoor heat exchangers 21 and 31. Cold.

In addition, when the subcooling degree computed by the calculating part 103b was more than 2nd predetermined temperature, the subcooling degree adjusting part 104 controls to the side which opens the subcooling adjustment valve 7. That is, the subcooling degree adjusting part 104 enlarges the opening degree of the subcooling control valve 7. Thereby, subcooling degree becomes small and it is controlled so that subcooling degree may fall in predetermined range. The opening degree of the subcooling control valve 7 may be controlled according to the degree to which the subcooling degree deviates from a predetermined range. In addition, the subcooling degree adjusting part 104 may adjust the subcooling degree by adjusting the opening degree of the control valve 914a, 915a instead of the subcooling control valve 7. The subcooling degree adjusting unit 104 may adjust the subcooling degree by controlling the opening degree of at least one of the subcooling regulating valve 7 and the regulating valves 914a and 915a.

The control flow regarding the supercooling degree at the time of heating is demonstrated with reference to FIG. First, the temperature estimating unit 102 detects the indoor liquid pipe temperature sensors 24 and 34 and, as a result, the value corresponding to the maximum refrigerant flow rate of the indoor expansion valves 23 and 33 and the opening of the indoor expansion valves 23 and 33. Based on the figure, the temperature of the refrigerant | coolant after joining in the 1st flow path 91 (near the joining area | region) is estimated (S101).

Subsequently, the refrigerant temperature determination unit 103a compares the estimated temperature with the detection result of the outdoor liquid pipe temperature sensor 81, and estimates when the detection result of the outdoor liquid pipe temperature sensor 81 is lower than the estimated temperature by a predetermined temperature or more. The temperature is determined as the refrigerant temperature, and in other cases, the detection result of the outdoor liquid pipe temperature sensor 81 is determined as the refrigerant temperature (S102).

Subsequently, the calculation unit 103b calculates the condensation temperature from the detection result of the pressure sensor 82, and calculates the subcooling degree from the condensation temperature and the determined refrigerant temperature (S103). The subcooling degree adjusting unit 104 determines whether the subcooling degree is within a predetermined range (S104). If the subcooling degree is outside the predetermined range (No at S104), the subcooling degree is adjusted by controlling the opening degree of at least one of the subcooling regulating valve 7 and the regulating valves 914a and 915a (S105). If the subcooling degree is within a predetermined range (S104: YES), the process ends. The control unit 10 performs this control regularly.

As described above, according to the present embodiment, the temperature estimator 102 exits the plurality of indoor heat exchangers 21 and 31 so that the refrigerant in the oil passage 911 after joining (for example, immediately after joining) is obtained. The temperature can be estimated. By using this for the calculation of the subcooling degree, in calculating the subcooling degree, it is possible to suppress an error or deviation due to a temperature drop when the refrigerant enters the gas-liquid two-phase state due to pressure loss while flowing in the main oil passage 911. . That is, in this embodiment, since the temperature of the liquid state refrigerant | coolant after joining can be used as the refrigerant temperature used for calculation of a subcooling degree, the reliability of the refrigerant temperature used for calculation of a subcooling degree is improved, and a subcooling degree Can improve the accuracy of calculation. According to this embodiment, it can also respond to the refrigerant circuit which has several indoor unit.

In addition, in this embodiment, the detection result of the outdoor liquid pipe temperature sensor 81 is compared with the estimated temperature computed by the temperature estimation part 102, and the detection result of the outdoor liquid pipe temperature sensor 81 is lower than predetermined temperature. In this case, it is determined that the gas-liquid is in a two-phase state at the point of the outdoor liquid pipe temperature sensor 81, and the estimated temperature is adopted as the refrigerant temperature. And in other cases, the detection result of the outdoor liquid pipe temperature sensor 81 which is the value measured directly is employ | adopted as refrigerant temperature. As a result, it is possible to suppress the use of the refrigerant temperature in the gas-liquid two-phase state for the calculation of the subcooling degree, and the estimated temperature or measured value of the liquid phase can be used for the calculation of the subcooling degree. That is, calculation of the supercooling degree with higher precision becomes possible.

In this embodiment, since the opening degree of at least one of the subcooling control valve 7 and the control valves 914a and 915a is controlled based on the said subcooling degree, the subcooling degree can be adjusted more appropriately.

<Modified Form>

This invention is not limited to the said embodiment. For example, the subcooling degree calculation unit 103 determines the estimated temperature as the refrigerant temperature without comparing the detection result of the outdoor liquid pipe temperature sensor 81 with the estimated temperature calculated by the temperature estimating unit 102. May be calculated based on the estimated temperature. By using the estimated temperature without comparison, the subcooling degree can be more easily calculated.

In addition, adjustment of a supercooling degree may be performed by what consists of an electromagnetic expansion valve and a bypass flow path (and a heat exchanger) as mentioned above, or may be performed by another apparatus. In addition, in the said embodiment, although the case where there exist two indoor units in the refrigerant | coolant circuit A was illustrated, three or more indoor units may be sufficient. Even if there are three or more indoor units, according to this invention, the temperature of the liquid refrigerant | coolant in the oil passage 911 after joining can be estimated. In addition, the outdoor liquid pipe temperature sensor 81 may be provided near the inlet at the time of heating of the outdoor unit 100.

In addition, the regulating valves 914a and 915a function as subcooling regulating valves, and increase the opening degree to increase the flow rate flowing into the sub-heat exchanger F, thereby lowering the subcooling degree and conversely decreasing the opening degree to reduce the subcooling degree. It can increase.

1: outdoor heat exchanger
2, 3: indoor unit
21, 31: indoor heat exchanger
23, 33: indoor expansion valve
24, 34: liquid room temperature sensor
4: switching valve
51, 52: compressor
6: accumulator
7: supercooling adjustment valve
81: outdoor liquid tube temperature sensor
91: the first euro
A: refrigerant circuit

Claims (3)

Outdoor heat exchanger,
A plurality of indoor units having an indoor heat exchanger, an indoor expansion valve connected to an outlet when heating the indoor heat exchanger, and an indoor liquid pipe temperature sensor installed between the indoor heat exchanger and the indoor expansion valve to detect a temperature of the refrigerant;
A first flow path configured to join the discharge ports when the plurality of indoor heat exchangers are heated, and to communicate the confluence portion with the suction ports when the outdoor heat exchangers are heated;
Having a refrigerant circuit comprising a compressor,
Based on the detection result of the said indoor liquid pipe temperature sensor, the temperature of the refrigerant | coolant after joining in the said 1st flow path at the time of heating is estimated based on the value corresponded to the maximum refrigerant flow volume of the said indoor expansion valve, and the opening degree of the said indoor expansion valve. Temperature estimation section
And a subcooling degree calculating unit for calculating a subcooling degree of the refrigerant circuit using the estimated temperature which is the temperature estimated by the temperature estimating unit. The method of claim 1,
It is further provided with an outdoor liquid pipe temperature sensor installed in the first flow path for detecting the temperature of the refrigerant,
The subcooling degree calculator,
The estimated temperature is compared with a detection result of the outdoor liquid pipe temperature sensor, and when the detection result of the outdoor liquid pipe temperature sensor is lower than the estimated temperature by a predetermined temperature or more, the estimated temperature is determined as the refrigerant temperature. A refrigerant temperature determination unit configured to determine a detection result of the outdoor liquid pipe temperature sensor as a refrigerant temperature,
And a calculation unit for calculating a subcooling degree of the refrigerant circuit based on the refrigerant temperature determined by the refrigerant temperature determination unit. 3. The method according to claim 1 or 2,
A subcooling control valve installed on the first flow path and capable of adjusting a subcooling degree according to an opening degree;
And a subcooling degree adjusting unit that controls the subcooling adjusting valve based on the subcooling degree calculated by the subcooling degree calculating unit.

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