JP2016065655A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner capable of simplifying a pipe design around compressors, restricting unbalanced state of lubricant oil at the compressors even if the piping design around the compressors is simplified and performing an efficient distribution of lubricant oil to the compressors.SOLUTION: An air conditioner 10 comprises an outdoor unit 11 including a plurality of compressors 13, 14, an outdoor heat exchanger 17 and an expansion valve 18. A freezing cycle 31 of the air conditioner 10 is carried out in such a way that discharging pipes 35a, 35b of each of the compressors 13, 14 are connected to a high-pressure side refrigerant pipe 35; the suction pipes 38a, 38b of each of the compressors 13, 14 are connected to a low pressure side refrigerant pipe 38 at a merging point through a suction pipe branch part 40; suction pipes 38a, 38b branched from the suction pipe branched part 40 are connected to one compressor 13 where oil is easily returned and the other compressor 14 where oil is hardly returned back to form a returned oil displacing structure and an oil supplying pipe 46 for supplying a surplus oil from a prescribed height position of one compressor 13 where oil is easily returned back to a refrigerant suction side of the other compressor 14 where oil is hardly returned back is connected.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an air conditioner that includes a plurality of compressors in an outdoor unit.

  In an air conditioner provided with a plurality of compressors in an outdoor unit, the discharge pipe and the suction pipe of these compressors are connected to each other to constitute a refrigeration cycle apparatus. In the refrigeration cycle apparatus, an imbalance occurs between the amount of lubricating oil discharged from each compressor and the amount of lubricating oil returning to each compressor, which may cause a shortage of oil in the compressor. When oil shortage occurs, the compressor runs out of oil, which may adversely affect the life of the compressor.

  Therefore, in order to prevent running out of oil in the compressor, each compressor is connected with an oil level detection circuit having an oil leveling pipe at a predetermined height position on the side of the case, and each temperature sensor of each oil level detection circuit is connected. And the temperature sensor of the bypass pipe, the oil level of the lubricating oil in the case of each compressor is detected. If the oil level of the lubricating oil in the case is lowered in any of the compressors, oil return control is performed to return the lubricating oil in the oil separator evenly to the compressor suction pipe, and the oil is supplied to each compressor. Prevents cutting.

Japanese Patent No. 4323484

  In the refrigeration cycle apparatus described in Patent Literature 1, the refrigerant discharged from the compressor is returned from the suction pipe to the refrigerant suction port of each compressor via the outdoor unit, the transition pipe, the indoor unit, and the transition pipe from the discharge pipe. . In a refrigeration cycle with multiple compressors, the oil return balance may be lost due to the effects of piping design, suction pipe mounting angle, and refrigerant circulation rate, and each compressor may be biased in the oil return of the circulating oil in the case. .

  If there is a bias in the oil return of the lubricating oil, the oil return balance between the compressors is lost, and there is a risk that any compressor will be adversely affected by the lack of lubricating oil due to the bias in the oil return.

  In the refrigeration cycle apparatus, each compressor is provided with an oil level detection circuit that detects the level of the lubricant level in the case. However, the oil level detection circuit is provided with a check valve, a pressure reducer, and an oil temperature sensor in each first oil leveling pipe connected to each compressor and connected to the buffer tank, while the buffer tank has a pressure reducing pipe, The second oil leveling pipe provided with the temperature sensor and the bypass pipe connecting the buffer tank to the high-pressure side refrigerant pipe of the compressor need to be provided with a decompressor and a temperature sensor, and the piping configuration around the compressor becomes complicated. Moreover, the oil level detection circuit has a large number of parts. For this reason, the oil level detection circuit has complicated piping operation such as oil equalizing pipes around each compressor, and the discharge refrigerant is reduced by the bypass amount. there were.

  The embodiment of the present invention has been made in consideration of the above-described circumstances, and simplifies the piping design around the compressor. Even if the simplification is performed, the lubricant unbalance between the compressors is suppressed, and the compressors are evenly distributed. It aims at providing the air conditioning apparatus which can perform oil efficiently.

  In order to solve the above-described problems, an embodiment of the present invention includes an outdoor unit having a plurality of compressors, an outdoor heat exchanger, and an expansion valve, and a discharge pipe of each compressor is connected to a high-pressure side refrigerant pipe. On the other hand, the suction pipe of each compressor is connected to the low pressure side refrigerant pipe on the merging side via the suction pipe branching section, and the suction pipe branched from the suction pipe branching section is one compressor that is easy to return oil. Are connected to the other compressor that is hard to return to oil and are configured to have an oil return eccentric structure, and the refrigerant of the other compressor that is hard to return to oil from a predetermined height position of the one compressor that easily returns to oil An oil supply pipe for supplying surplus oil is connected to the suction side.

The refrigeration cycle figure of the air conditioning apparatus which shows 1st Embodiment. (A), (B) and (C) are figures which show each example of composition of a suction piping branch part of a compressor suction piping (arranged in an outdoor unit of an air harmony device), respectively. The refrigeration cycle figure which represented the air conditioning apparatus of 1st Embodiment on the ph diagram. The refrigeration cycle figure by the side of the outdoor unit of the air conditioning apparatus of 2nd Embodiment.

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

[First Embodiment]
FIG. 1 is a refrigeration cycle diagram showing a first embodiment of an air conditioner.

  The air conditioner 10 includes an outdoor unit 11 and an indoor unit 12, and the outdoor unit 11 includes a plurality of, for example, two compressors 13 and 14. The outdoor unit 11 includes compressors 13 and 14, an oil separator 15, a four-way valve 16, an outdoor heat exchanger 17, an expansion valve 18, an accumulator 19, and an outdoor fan 20.

  The outdoor unit 11 includes an outdoor control unit 22 that controls the operation thereof, and inverters 23 and 24 that perform frequency control of the operation of the compressors 13 and 14. The inverters 23 and 24 rectify the voltage of the commercial AC power supply 25, convert the rectified voltage into a frequency according to a command from the outdoor control unit 22, and output the converted voltage. The compressors 13 and 14 are variable capacity type and are operated with frequency controlled by the outputs of the inverters 23 and 24.

  Further, the indoor unit 12 includes an indoor control unit (not shown) that controls the operation of the expansion valve 27, the indoor heat exchanger 28, the indoor fan 29, and the indoor unit 12. The expansion valve 27 of the indoor unit 12 and the expansion valve 18 of the outdoor unit 11 are configured by an expansion mechanism such as an electronic expansion valve that can easily adjust the valve opening degree. The expansion valve is provided in at least one of the outdoor unit 11 and the indoor unit 12. May be good.

  The compressors 13 and 14 of the outdoor unit 11, the oil separator 15, the four-way valve 16, the outdoor heat exchanger 17, the expansion valve 18, the expansion valve 27 and the indoor heat exchanger 28 of the indoor unit 12, and the oil of the outdoor unit 12 The separators 15 are sequentially connected by a refrigerant pipe 30 to constitute a refrigeration cycle 31. The refrigerant pipe 30 that connects the outdoor unit 11 and the indoor unit 12 is a liquid-side or gas-side transition pipe, and packed valves 32 and 33 are provided in the transition pipe.

[Piping around the compressor]
The plurality of compressors 13 and 14 are compressors in which the inside of the case becomes high pressure during operation, and the refrigerator oil (lubricating oil) for lubrication is accommodated in the case. Discharge pipes 35 a and 35 b are respectively connected to the refrigerant discharge ports of the compressors 13 and 14, and these discharge pipes 35 a and 35 b are joined and connected to the high-pressure side refrigerant pipe 35. A four-way valve 16 is connected to the high-pressure side refrigerant pipe 35 via an oil separator 15 that separates the gas refrigerant and the oil content of the lubricating oil. The high pressure side refrigerant pipe 35 is provided with a discharge temperature sensor 36 and a high pressure sensor 37.

  Further, suction pipes 38a and 38b are connected to the refrigerant suction ports of the compressors 13 and 14, respectively, and a low-pressure side refrigerant pipe 38 is connected to the suction pipes 38a and 38b. The low-pressure refrigerant pipe 38 is connected to the four-way valve 16 via a low-pressure sensor 39 and an accumulator 19 that is a gas-liquid separator.

  On the contrary, when attention is paid to the return of the refrigerant to the compressors 13, 13, the low-pressure side refrigerant (merged suction) pipe 38 from the four-way valve 16 is a gas refrigerant pipe, and passes through the accumulator 19 at the suction pipe branch 40. It branches and is guide | induced to each branch suction piping 38a, 38b. The branch suction pipes 38a and 38b are connected to the refrigerant suction ports of the compressors 13 and 14 through suction pipes 41 and 41, respectively.

  In the suction pipe branching section 40, the branch suction pipe 38a connected to one compressor 13 on one side is more than the branch suction pipe 38b connected to the other compressor 14, and the return refrigerant amount (to the compressor) is extended. The oil return eccentric structure is configured to increase the amount of oil return. Specifically, the suction pipe branching section 40 is configured in an oil return eccentric structure as shown in FIG. 2 (A), (B) or (C), and one branch suction pipe 38a is the other branch suction pipe. From 38b, it is comprised in the refrigerant | coolant branch structure which increases a refrigerant | coolant amount and by extension, an oil return amount.

  FIG. 2A shows a pipe branching structure using inertial force, and the suction pipe branching section 40 is configured such that one branch suction pipe 38a is substantially linear from the low-pressure side refrigerant (merged suction) pipe 38 on the accumulator 19 side. A refrigerant branch passage 43 is formed which extends smoothly and has the other branch suction pipe 38b connected at an angle of a predetermined angle or more, for example, a right angle. The suction pipe branch section 40 is a refrigerant branch flow path 43 that uses inertial force, so that one compressor 13 on one side is the refrigerant of the other compressor 14 (gas) regardless of the operating state of the refrigeration cycle 31. The amount is large, and as a result, an oil return eccentric structure is formed in which oil is easy to return.

  FIG. 2B shows a pipe branching structure using gravity, and the suction pipe branching section 40 divides the branch from the accumulator 19 into the low pressure side refrigerant (merged suction) pipe 38 on the merging side up and down in the direction of gravity. A gravity-use refrigerant branch flow path 44 is arranged such that the pipe that is easy to return oil is directed downward as one branch suction pipe 38a and the pipe that is difficult to return oil is directed upward as the other branch suction pipe 38b. It is.

  FIG. 2C shows a pipe branching structure in which a refrigerant branching channel 45 is formed in which the inner pipe diameters of the branching suction pipes 38 a and 38 b are increased or decreased from the suction pipe branching portion 40, and the merging from the accumulator 19. For the low-pressure side refrigerant (combined suction) pipe 38 on the side, the pipe that is easy to return oil is used as one branch suction pipe 38a, the pipe that has a small flow resistance and a large inner pipe diameter, and the pipe that is difficult to return oil is the other pipe. The branch suction pipe 38b is a pipe having a large flow path resistance and a small inner pipe diameter.

[Compressor oil level adjustment]
As shown in FIGS. 2A, 2B, or 2C, in the suction pipe branching portion 40 of the refrigeration cycle 31, one compressor 13 on one side is easy to return to oil, and the other compressor 14 is returned to oil. Constructed in an oil-returning oil structure that is difficult to perform. An excess oil discharge pipe 46 is provided as an oil supply pipe for supplying excess oil to one of the compressors 13 and 14 having an oil return eccentric structure, which easily returns to oil. The surplus oil discharge pipe 46 is connected to a predetermined height position on the case side surface of the one compressor 13, and functions as an oil equalizing pipe that keeps the oil level height of the lubricating oil in the one compressor 13 at an optimum constant level. .

  A surplus oil discharge pipe 46 connected to one compressor 13 also serves as an oil supply pipe. A decompressor 48 which is a pressure drop means such as a check valve 47 and a capillary tube is provided on the way, and a temperature detection means downstream thereof. The temperature sensor 49 is provided to constitute the compressor oil level detection means 50. The surplus oil discharge pipe 46 is connected to a branch suction pipe 38b which is the refrigerant suction port side of the other compressor 14.

  In the present embodiment, an oil return eccentric structure is adopted in the suction pipe branching portion 40 installed on the refrigerant suction side of the compressors 13 and 14 of the refrigeration cycle 31, and the oil returning to the one compressor 13 together with the gas refrigerant is supplied to the other. The compressor 14 is configured to have an oil return eccentric structure that is easier to return oil than the compressor 14 of. A surplus oil discharge pipe 46 is connected to the case side surface of one compressor 13 that is easy to return oil, and the surplus oil that flows in is supplied to the other compressor 14. By supplying the surplus oil from one compressor 13 to the other compressor 14, the oil level can be adjusted so as to achieve leveling between the compressors 13,14.

[Compressor oil level detection]
For oil level detection in the compressor 13 by the compressor oil level detection means 50, a pressure reducer 48, which is a pressure reduction means for the capillary tube, is installed in the surplus oil discharge pipe 46 installed in one compressor 13, A temperature sensor 49, which is a temperature detection means, is installed downstream of the temperature sensor 49. The temperature sensor 49 detects the temperature of excess oil or refrigerant passing through the excess oil discharge pipe 46 as an actual measurement value.

Further, from the discharge gas temperature, the condensation (saturation) temperature, and the evaporation (saturation) temperature detected by the discharge temperature sensor 36, the high pressure sensor 37 and the suction low pressure sensor 39 of the refrigeration cycle 31, the low pressure superheated gas temperature. The estimated value of T _gas is estimated, and the estimated value of the low pressure superheated gas temperature T _gas is compared with the actually measured value from the temperature sensor 49 installed in the surplus oil discharge pipe 46, so that The oil level of the lubricating oil can be detected.

For example, when the in-case lubricating oil of one compressor 13 has a required height or more, surplus lubricating oil that is refrigeration oil flows in the surplus oil discharge pipe 46. Even if surplus oil passes through the capillary tube decompressor 48, the temperature change due to decompression is small, and the actually detected temperature detected by the temperature sensor 49 is the temperature T of the lubricating oil in the case of one compressor 13. The oil temperature T _oil1 is substantially equal to the _oil1 and is substantially equal to the discharge gas temperature detected by the discharge temperature sensor 36 of the refrigeration cycle 31. Therefore, when the measured value of the temperature sensor 49 detects the oil temperature _Toil1 , the lubricating oil in the case of the one compressor 13 has a proper lubricating flow rate and the required lubricating flow rate exists. It can be detected.

  On the other hand, when the oil level of the lubricating oil in the case of the compressor 13 decreases and the lubricating oil does not flow into the surplus oil discharge pipe 46, the gas refrigerant in the compressor 13 flows through the surplus oil discharge pipe 46. Become. When the refrigerant flows into the surplus oil discharge pipe 46 and the refrigerant flows through the pressure reducer 48 of the capillary tube, the refrigerant drops in pressure and a large temperature drop occurs. The temperature drop of the refrigerant is detected by the temperature sensor 49 as an actual measurement value.

On the other hand, as shown in FIG. 3, the condensation (saturation) temperature detected by the high pressure sensor 37 of the refrigeration cycle 31, the evaporation (saturation) temperature detected by the low pressure sensor 39, and the discharge detected by the discharge temperature sensor 36. The low pressure superheated gas temperature T _gas can be estimated from the gas temperature, and the actual measured value by the temperature sensor 49 installed in the surplus oil discharge pipe 46 is compared with the estimated value of the low pressure superheated gas temperature T _gas estimated in the refrigeration cycle 31. Thus, the oil level of the in-case lubricating oil of one compressor 13 can be detected.

  Therefore, by detecting the temperature of the actually measured value by the temperature sensor 49 that is a temperature detecting means installed in the surplus oil discharge pipe 46, the oil level of the lubricating oil in the case of one compressor 13 can be detected. .

  And when the excess oil flows into the surplus oil discharge pipe 46 from one compressor 13 among the plurality of compressors 13, 14, the oil level height of the lubricating oil in the case of one compressor 13 Is kept at the required oil level. At this time, the other compressor 14 is supplied with the excess oil of one compressor 13 added to the suction refrigerant of the other branch suction pipe 38b, and therefore the in-case lubricating oil of each of the compressors 13 and 14 is supplied. As for the oil level, the required amount is kept effective, and no problem occurs.

  In addition, the detection of the oil level of the in-case lubricating oil of each of the compressors 13 and 14 is provided with a single surplus oil discharge pipe 46 that also serves as an oil equalizing pipe and an oil supply pipe in one of the compressors 13 that easily returns to the oil. With a simple piping configuration in which a pressure reducer 48 as a pressure drop means and a temperature sensor 49 as a temperature detection means are installed in the surplus oil discharge pipe 46 and the downstream side is connected to the refrigerant suction side of the other compressor 14, The compressor oil level detection means 50 can be configured. The compressor oil level detection means 50 can adjust the oil leveling between the compressors 13 and 14 only by constituting an oil level detection circuit on the one compressor 13 side.

  Unlike the refrigeration cycle of the conventional air conditioner disclosed in Patent Document 1, an oil level detection circuit or bypass pipe having a complicated piping configuration is not required around the compressor.

  Therefore, in the present embodiment, the refrigeration cycle 31 including the plurality of compressors 13 and 14 employs an oil return eccentric structure in which one compressor 13 is more likely to return oil than the other compressor 14. By deviating the oil return to the compressor 13 and returning a large amount of lubricating oil, there is no need to provide an oil level detection circuit for each of the compressors 13 and 14, and a bypass pipe is not required, so the number of parts is small. The piping configuration around the compressors 13 and 14 can be greatly simplified.

[Returning lubricating oil to the compressor]
When the excess oil does not flow into the excess oil discharge pipe 46, there is a risk that the oil level in the case of each of the compressors 13 and 14 is lowered. In this case, the temperature sensor 49 detects that excess oil does not flow, and the normally closed control valve 53 of the oil return pipe 52 is controlled to open from the oil separator 15. The lubricating oil in the oil separator 15 is returned from the oil return pipe 52 to the refrigerant suction side of one compressor 13. The oil separator 15 has a first oil return pipe 52a connected to the tank bottom wall side and a second oil return pipe 52b connected to the case side wall, and both oil return pipes 52a and 52b are pressures of capillary tubes or the like. After joining the single oil return pipe 52 via the pressure reducers 54a and 54b of the descending means, the lubricating oil is supplied to the branch suction pipe 38 to the one compressor 13 to return the lubricating oil. .

  And in this embodiment, the surplus oil discharge pipe 46 which is an oil supply pipe is provided in one compressor 13 which is easy to return oil, and this surplus oil discharge pipe 46 is connected to the refrigerant suction side of the other compressor 14. In addition, by supplying the excess oil to the other compressor 14, the oil leveling between the compressors 13 and 14 is performed.

[Refrigerant flow in refrigeration cycle]
In the refrigeration cycle 31 shown in FIG. 1, the cooling operation and the heating operation are selected by the switching operation of the four-way valve 16.

  During the cooling operation, the refrigerant discharged from the compressors 13 and 14 flows in the refrigeration cycle 31 as indicated by a solid arrow A.

  When the compressors 13 and 14 are operated during the cooling operation, the high-temperature and high-pressure gas refrigerant compressed from the point a in FIG. 3 by the compressors 13 and 14 becomes high temperature and pressure and is discharged from the point b. The discharged refrigerant is guided to the high-pressure side refrigerant pipe 35 through the discharge pipes 35a and 35b, and is separated into refrigerant and oil by the oil separator 15, and the separated lubricating oil is stored in the oil separator 15. The refrigerant in the oil separator 15 flows through the four-way valve 16 to the outdoor heat exchanger 17 and is condensed by exchanging heat with the outdoor air in the outdoor heat exchanger 17 and reaches a point c as a liquid refrigerant.

  The liquid refrigerant condensed in the outdoor heat exchanger 17 is then sent to the expansion valve 18. The expansion valve 18 is an electronic expansion valve, for example, and the degree of condensation of the liquid refrigerant is adjusted by the expansion valve 18 to become a supercooled liquid refrigerant. The liquid refrigerant is subsequently throttled again by the expansion valve 27 on the indoor unit 12 side to expand, and the temperature drops to become a low-temperature and low-pressure refrigerant at point d. The gas-liquid two-phase refrigerant that has become low-temperature and low-pressure is sent to the indoor heat exchanger 28, where it heat-exchanges with room air to cool the room.

  On the other hand, the refrigerant that absorbs heat and evaporates by heat exchange with room air becomes a gas refrigerant. The gas refrigerant passes from the four-way valve 16 and the accumulator 19 through the suction pipe branching section 40, and is further sucked into the compressors 13 and 14 from the branch suction pipes 38a and 38b at the point a. The sucked gas refrigerant is compressed from the point a to the point b by the compressors 13 and 14 and provided in the next refrigeration cycle 31.

  The heating operation is performed by switching the four-way valve 16, and the refrigerant flows in the opposite direction. During the heating operation, the refrigerant discharged from the compressors 13 and 14 is guided as indicated by the broken line arrow B.

  In the Mollier diagram (ph diagram) of the refrigeration cycle shown in FIG. 3, the symbol C is a saturated liquid line, the symbol D is a saturated vapor line, and the symbol E is a critical point.

  Also, between a and b, the refrigerant state change in the compressors 13 and 14 is shown. Between the points b and c, the refrigerant state change in the outdoor heat exchanger (which becomes a condenser during cooling operation), between the points cd Shows the change in the refrigerant state in the expansion valves 18 and 27, and the change in the refrigerant state of the indoor heat exchanger (which becomes an evaporator during the cooling operation) is shown between points da.

Further, reference numeral T ₁ is the supercooled liquid isotherm (vertical lines), symbols T ₂ are isotherms wet steam (horizontal lines), reference numeral T ₃ is the isotherm of superheated steam. The symbol T _gas is an estimated value of the low pressure superheated gas temperature. The low-pressure superheated gas temperature T _gas is estimated from the condensation saturation temperature, the evaporation saturation temperature, and the discharge gas temperature (detected by the high-pressure sensor 37, the low-pressure sensor 39, and the discharge temperature sensor 36). The level of the lubricating oil in one of the compressors 13 can be obtained by comparison with the actually measured value by the temperature sensor 69 installed in the discharge pipe 46.

[Effect of the first embodiment]
In the refrigeration cycle 31 including the plurality of compressors 13 and 14, the air conditioner 10 of the present embodiment returns the oil of the lubricating oil from the other compressor 14 that is less likely to return the oil to the one compressor 13 that is more likely to return the oil. Employing an oil return bias structure that deliberately returns a large amount of oil, excessive oil is supplied to the refrigerant suction side of the other compressor 14 that is difficult to return from a predetermined height position of one compressor 13 that is easy to return oil. Since the oil supply pipe 46 to be supplied is provided, the oil return to the one compressor 13 is deliberately biased more than the other compressor 14, and the surplus amount of lubricating oil in one compressor is increased in the other compressor. By supplying the refrigerant to the refrigerant suction side, oil leveling between the compressors 13 and 14 can be achieved.

  In addition, the oil supply pipe from one compressor 13 where the oil is easy to return can be made into a single surplus oil discharge pipe 46, and the surplus oil discharge pipe 46 is moved to the pressure drop means 48 and a temperature downstream thereof. Only the detection means 49 is provided and connected to the refrigerant suction side of the other compressor 14, the piping configuration around the compressor can be simplified, and the cost can be reduced. Further, since the bypass pipe as in the prior art is not required, the amount of bypass is not required, and the performance deterioration of the refrigeration cycle can be suppressed.

  Further, the suction pipe branching portion 40 constituting the oil return eccentric structure uses the suction pipe 38a that is easy to return oil as a refrigerant branch structure that uses inertial force, uses gravity, or uses the magnitude of the refrigerant flow resistance. Since it is connected to each of the compressors 13 and 14 separately from the suction pipe 38b that is hard to return to oil, dynamic equipment such as a control valve for controlling the refrigerant flow rate is unnecessary, and any operating condition is determined by a static pipe configuration. However, it is easy to return the lubricating oil to one compressor 13 on one side, and to supply the surplus amount of lubricating oil to the refrigerant suction side of the other compressor 14 so as to equalize the oil between the compressors 13 and 14. it can.

In addition, the oil level of the lubricating oil in the compressor 13 can be detected by an oil level height detecting unit 50 including a pressure drop unit 48 in the oil supply pipe 46 and a temperature detecting unit 49 provided downstream thereof, In addition, the oil level height detection means 50 is low pressure from the discharge gas temperature, the condensation (saturation) temperature, and the evaporation (saturation) temperature detected by the discharge temperature sensor 36, the high pressure sensor 37, and the low pressure sensor 39 of the refrigeration cycle 31. The superheated gas temperature _Tgas can be estimated, and the estimated value of the low pressure superheated gas temperature _Tgas and the actually measured value of the temperature detecting means 49 can be compared to detect the level of the lubricating oil in the compressor 13. It is not necessary to provide an oil level detection circuit or bypass pipe for each compressor as in the conventional technology, or to provide a temperature sensor for the bypass pipe, simplifying the piping configuration around the compressor, reducing the number of parts, and cost. You can go down.

[Second Embodiment]
Next, a second embodiment of the air conditioner will be described with reference to FIG.

  The second embodiment shows an example of an air conditioner 10A having different compressor capacities, and this air conditioner 10A includes a plurality of compressors 13A, which are different from the air conditioner 10 shown in the first embodiment. Since the configuration of the entire refrigeration cycle 31 is not different only by adopting a configuration in which the compressor capacity of 14A is different, the same configuration is denoted by the same reference numeral, and redundant description is omitted.

  FIG. 4 shows an outdoor unit 11A of the air conditioner 10A. The outdoor unit 11A includes a plurality of compressors 13A and 14A having different compressor capacities in order to expand the minimum capacity operation of the refrigeration cycle 31A. It is provided.

  In the second embodiment, the compressor that easily returns to oil is configured as one compressor 13A having a large compressor capacity, and is configured to be larger than the compressor capacity of the other compressor 14A. And one compressor 13A where oil is easy to return becomes easy to return liquid refrigerant at the time of transient operation, such as at the time of defrosting or starting. In this case, since the liquid refrigerant is also biased and returned to the one compressor 13A, the reliability of the compressor 13A may be deteriorated due to the liquid back.

  For this reason, the capacity of the suction cup 41 serving as a liquid back buffer is increased and the liquid refrigerant buffer can be enlarged by making the one compressor 13A that is easy to return the liquid refrigerant into a compressor having a large compressor capacity. . For this reason, the reliability with respect to the liquid bag can be improved.

  Since it becomes difficult for the liquid refrigerant to flow to the other compressor 14A having a small capacity of the suction cup 41, the other compressor 14A can ensure reliability against the liquid back.

  By the way, during the operation of the refrigeration cycle 31, since the refrigerant gas mixed with oil flows into the suction pipes 38a and 38b to the compressors 13A and 14A, the oil return amount of the refrigeration oil is different for each compressor 13A and 14A, respectively. However, the bias of the refrigerant gas (unlike the case where liquid refrigerant is present) does not cause a problem.

  In addition, the configuration of the refrigeration cycle 31A of the outdoor unit 11A and the indoor unit 12 in the air conditioner 10A, and the flow of the refrigerant in the refrigeration cycle 31A during the cooling operation and the heating operation are the air conditioner 10 of the first embodiment. The description is omitted because it is the same as that of FIG.

[Effects of Second Embodiment]
In the air conditioner 10A of the second embodiment, the same effect as that of the air conditioner 10 of the first embodiment is achieved. In the second embodiment, a refrigeration cycle including a plurality of compressors 13A and 14A. In 31A, since the capacity of one compressor 13A in which oil easily returns is larger than the capacity of the other compressor 14A, the compressor capacity of one compressor 13A in which oil easily returns can be increased, and the liquid refrigerant buffer And the reliability of the compressors 13A and 14A against the return of the liquid refrigerant (liquid back) can be improved.

  As mentioned above, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of this invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the present invention. These embodiments and modifications thereof are included in the scope and gist of the present invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10,10A ... Air conditioning apparatus 11, 11A ... Outdoor unit, 12 ... Indoor unit, 13, 13A, 14, 14A ... Compressor, 15 ... Oil separator, 16 ... Four-way valve, 17 ... Outdoor heat exchanger, 18 ... Expansion valve, 19 ... Accumulator, 20 ... Outdoor fan, 22 ... Outdoor control unit, 23, 24 ... Inverter, 25 ... Commercial AC power supply, 27 ... Expansion valve, 28 ... Indoor heat exchanger, 29 ... Indoor fan, 30 ... Refrigerant Piping, 31, 31A ... Refrigeration cycle, 32, 33 ... Packed valve, 35 ... High pressure side refrigerant piping, 35a, 35b ... Discharge piping, 36 ... Discharge temperature sensor, 37 ... High pressure sensor, 38 ... Low pressure side refrigerant piping (confluence) Suction pipe), 38a, 38b ... suction pipe (branch suction pipe), 39 ... low pressure sensor, 40 ... suction pipe branch, 41, 41a, 41b ... suction pipe, 3 ... Refrigerant branch flow path using inertial force, 44 ... Refrigerant branch flow path using gravity, 45 ... Refrigerant branch flow path using pipe diameter in pipe, 46 ... Surplus oil discharge pipe (oil supply pipe, 48 ... Check valve, 48 ... Pressure reducer (pressure drop means, capillary tube), 49 ... Temperature sensor (temperature detection means), 50 ... Compressor oil level detection means, 52 ... Oil return pipe, 53 ... control valve, 54a, 54b ... pressure reducer (pressure drop means, capillary tube).

Claims (7)

An outdoor unit having a plurality of compressors, an outdoor heat exchanger, and an expansion valve;
The discharge pipe of each compressor is connected to the high pressure side refrigerant pipe, while the suction pipe of each compressor is connected to the low pressure side refrigerant pipe on the merging side via the suction pipe branching section,
The suction pipe branched from the suction pipe branch part is connected to one compressor that is easy to return to oil and the other compressor that is difficult to return to oil, and is configured in an oil return eccentric structure,
An air characterized in that an oil supply pipe for supplying excess oil is connected to a refrigerant suction side of the other compressor that is hard to return oil from a predetermined height position of the one compressor that is easy to return oil. Harmony device. 2. The air according to claim 1, wherein the suction pipe branch portion is configured such that the oil return eccentric structure is configured by a refrigerant branch flow path using a difference in inertia force of a return refrigerant flow with respect to a low-pressure refrigerant pipe on a merging side. Harmony device. The suction pipe branching section divides the flow of return refrigerant up and down in the direction of gravity with respect to the low-pressure refrigerant pipe on the merge side so that the pipe that is easy to return oil faces downward and the pipe that does not easily return oil faces upward The air conditioning apparatus according to claim 1, wherein an oil return bias oil structure that is branched and uses gravity is configured. A difference in flow resistance is formed in the suction pipe branched from the suction pipe branching section, and the suction pipe having a low flow resistance is easily returned to the pipe, and the suction pipe having a large flow resistance is difficult to return to the oil. The air conditioner according to claim 1, wherein the oil return eccentric structure is configured as a pipe. The oil supply pipe is provided with a pressure drop means and a temperature detection means downstream of the pressure drop means, and an oil level detection means for detecting the oil level height of the lubricating oil in the compressor by the temperature detection means. The air conditioner according to claim 1 provided. The oil level detection means is provided in the measured value by the temperature detection means, the discharge temperature sensor provided in the high pressure side refrigerant pipe, the discharge gas temperature of the high pressure sensor, the condensation temperature, and the low pressure side refrigerant pipe. The air conditioner according to claim 5, wherein the oil level in the compressor is detected by comparing with an estimated value of the low pressure superheated gas temperature estimated from the evaporation temperature of the low pressure sensor. The air conditioner according to claim 1, wherein one compressor that easily returns to oil has a larger compressor capacity than the other compressor that does not easily return to oil.

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