JP6061665B2 - Oil return structure of air conditioner and air conditioner - Google Patents

Description

  The present invention relates to an oil return structure for an air conditioner and an air conditioner.

  Generally, refrigerator oil (hereinafter simply referred to as oil) is used in a compressor constituting a refrigeration cycle of an air conditioner in order to lubricate a scroll portion and the like. Since this oil is often selected to be compatible with the refrigerant, during the operation of the compressor, the oil flows out of the compressor and circulates in the pipe together with the refrigerant. In general, the refrigeration cycle apparatus is provided with an accumulator between the evaporator and the compressor in order to prevent liquid back to the compressor. The accumulator is configured so that the liquid refrigerant and the gas refrigerant are separated, and only the gas refrigerant is sent to the compressor, and the liquid refrigerant is accumulated in the accumulator.

  Here, oil is dissolved in the liquid refrigerant accumulated in the accumulator, and the oil accumulated in the accumulator is returned to the compressor by an oil return structure. As a result, an appropriate amount of oil is held in the compressor.

  Various oil return structures have been proposed in the past, and there is a technique in which an oil return pipe is connected to the bottom of the accumulator and the oil is returned to the compressor through the oil return pipe (see, for example, Patent Document 1). ). In Patent Document 1, one end on the upstream side of the oil return pipe projects upward from the bottom surface of the accumulator, and when the oil in the accumulator exceeds the height of the opening end of the oil return pipe, the oil return pipe is And is returned to the compressor.

Japanese Utility Model Laid-Open No. 3-13075 (page 5, FIG. 1)

  By the way, in a multi-type air conditioner including a plurality of indoor units and outdoor units such as a building multi-air conditioner, a maximum pipe length (for example, a maximum of 100 m) that can be connected is determined in advance according to the model. And when the system is assembled with the maximum pipe length, the amount of oil sealed in the air conditioner is determined so that an appropriate amount of oil can be held by the compressor. That is, the amount of oil is determined according to the case where the system is assembled with the maximum pipe length regardless of the pipe length of the actually assembled system.

  For this reason, for example, in a system that can connect up to 20 units, when the number of indoor units connected is small, for example, 3 units, that is, when the pipe length is short, surplus oil accumulates in the compressor. The compressor is provided with an electric motor mechanism that drives a compression mechanism that compresses the refrigerant. When oil accumulated in the compressor reaches the rotor portion of the electric motor mechanism, it becomes a resistance of the rotor during operation of the compressor, and power consumption There was a problem that became high.

  In recent years, energy efficiency indexes that take into account intermediate periods and partial loads such as APF (year-round energy consumption efficiency) and IPLV (period performance coefficient) are compared, which is disadvantageous when power consumption increases.

  For this reason, when the increase in power consumption accompanying the increase in the oil in the compressor is observed, it is required to stop returning the oil to the compressor and store the oil in the accumulator. However, in Patent Document 1, since the oil is returned when the amount of oil in the accumulator becomes higher than the opening end of the oil return pipe, the oil cannot be stored more than that height. .

  The present invention has been made to solve the above-described problems, and provides an oil return structure for an air conditioner and an air conditioner that can prevent an increase in power consumption due to an increase in oil in the compressor. For the purpose.

  An oil return structure of an air conditioner according to the present invention is an oil return structure of an air conditioner that returns oil from an accumulator to a compressor, and includes a first oil return portion that constitutes a path for returning oil from the accumulator to the compressor; Each of the first oil return portion and the second oil return portion has an oil return hole that opens at a different height position in the accumulator, and the lower oil return hole. The 1st oil return part which has is equipped with the solenoid valve closed when the compressor input increases by the oil amount increase in a compressor.

  ADVANTAGE OF THE INVENTION According to this invention, the oil return structure of the air conditioning apparatus which can aim at the increase prevention of the power consumption by the increase in the oil in a compressor can be obtained.

It is a schematic circuit block diagram which shows an example of the circuit structure of the multi-type air conditioning apparatus to which the oil return structure which concerns on one embodiment of this invention is applied. It is a refrigerant circuit figure which shows the flow of the refrigerant | coolant in the air conditioning apparatus of FIG. It is a figure which shows the structure of the principal part containing the oil return structure which concerns on one embodiment of this invention. It is a flowchart which shows the flow of the oil return control in the air conditioning apparatus of one embodiment of this invention. It is a figure which shows the result of having measured the relationship between the oil quantity in the compressor in driving | operation, and a compressor input, making a compressor frequency different. It is a figure which shows the modification of the accumulator of FIG.

  FIG. 1 is a schematic circuit configuration diagram showing an example of a circuit configuration of a multi-type air conditioner to which an oil return structure according to an embodiment of the present invention is applied. A detailed circuit configuration of the air conditioner will be described with reference to FIG. FIG. 1 shows an example in which four indoor units B are connected. In addition, in the following drawings including FIG. 1, the relationship of the size of each component may be different from the actual one.

  The air conditioner 100 includes an outdoor unit A and a plurality of indoor units B1, B2, B3, and B4 (hereinafter sometimes collectively referred to as an indoor unit B), and includes a gas-side main pipe 101a and a liquid-side main. The pipe 101b, the gas side branch pipe 101c and the liquid side branch pipe 101d are connected. That is, in the air conditioner 100, a plurality of indoor units B are connected to the outdoor unit A in parallel. The gas side main pipe 101a, the liquid side main pipe 101b, the gas side branch pipe 101c, and the liquid side branch pipe 101d are refrigerant pipes that conduct the refrigerant (heat source side refrigerant), and R410A is enclosed as the refrigerant. . Note that a low GWP refrigerant such as R32 or HFO1234yf may be used as the refrigerant. Moreover, although FIG. 1 demonstrates as an example the structure in case the indoor unit B is four units (B1, B2, B3, B4), this invention is not limited to this number.

  The outdoor unit A includes a compressor 1, an oil separator 2, a flow path switching device 3 such as a four-way valve, a heat source side heat exchanger (outdoor heat exchanger) 4, and an accumulator 5. The indoor units B1, B2, B3, and B4 include use-side heat exchangers (indoor heat exchangers) 6a, 6b, 6c, and 6d (hereinafter sometimes collectively referred to as use-side heat exchangers 6) and expansion devices. 7a, 7b, 7c, 7d (hereinafter sometimes collectively referred to as expansion device 7), and the use side heat exchanger 6 and expansion device 7 are connected in series. The compressor 1, the oil separator 2, the flow path switching device 3, the heat source side heat exchanger 4, the expansion devices 7a, 7b, 7c, 7d, the use side heat exchangers 6a, 6b, 6c, 6d, and the accumulator 5 A refrigerant cycle is formed in which the refrigerant is circulated by being sequentially connected by piping.

  The heat source side heat exchanger 4 is provided with a blower 4a for blowing air such as a fan. The use side heat exchangers 6a, 6b, 6c, and 6d are also provided with a blower 4a (not shown) that similarly blows air.

  Next, each device provided in the outdoor unit A and the indoor unit B will be described.

[Outdoor unit A]
The compressor 1 sucks a refrigerant, compresses the refrigerant to be brought into a high-temperature and high-pressure state, and conveys the refrigerant to a refrigerant circuit. For example, the compressor 1 may be composed of an inverter compressor capable of controlling capacity.

  The flow path switching device 3 is provided on the downstream side of the oil separator 2 and switches between a refrigerant flow in the heating operation mode and a refrigerant flow in the cooling operation mode.

  The oil separator 2 is provided on the discharge pipe 1a of the compressor 1 and separates oil discharged from the compressor 1 together with the refrigerant (hereinafter simply referred to as oil). The oil separator 2 communicates with the suction pipe 1 b of the compressor 1 through an oil return capillary 8 so that the oil is returned to the compressor 1 through the oil return capillary 8. By returning the oil to the compressor 1 in this way, seizure of the compressor 1 due to a shortage of oil in the compressor 1 is prevented.

  The heat source side heat exchanger 4 functions as a condenser during the cooling operation, functions as an evaporator during the heating operation, and performs heat exchange between the air supplied from the blower 4a and the refrigerant.

  The accumulator 5 is provided on the suction side of the compressor 1 and stores excess refrigerant due to a difference between the cooling operation mode and the heating operation mode, or changes in transient operation (for example, the number of indoor units B operated). Excess refrigerant for

  Since oil flows into the accumulator 5 together with the refrigerant, an oil return pipe 10 for returning the oil to the compressor 1 is connected between the accumulator 5 and the suction pipe 1b. The oil return pipe 10 is provided with an electromagnetic valve 9 that opens and closes the flow path of the oil return pipe 10. Thus, the oil is returned to the compressor 1 not only from the oil separator 2 but also from the accumulator 5. The oil return pipe 10 corresponds to the first oil return pipe of the first oil return portion of the present invention.

  The present invention is characterized by an oil return structure for returning the oil accumulated in the accumulator 5 to the compressor 1, and the structure of the characteristic portion will be described again.

  In the outdoor unit A, a pressure sensor 21 that detects the suction pressure Ps of the compressor 1 is provided on the suction side of the compressor 1. In addition, the outdoor unit A is usually provided with a pressure sensor and a temperature sensor, but they are omitted here because they are not related to the gist of the present invention.

[Indoor unit B]
The use side heat exchanger 6 functions as an evaporator during cooling operation and functions as a condenser during heating operation. The use side heat exchanger 6 performs heat exchange between air supplied from a blower (not shown) and the refrigerant, and generates heating air or cooling air to be supplied to the air-conditioning target space.

  The throttling device 7 has a function as a pressure reducing valve or throttling device, and expands the refrigerant by depressurizing it. The throttling device 7 may be constituted by a device whose opening degree can be variably controlled, for example, an electronic throttling device.

  In the indoor unit B, the temperature sensors 22a, 22b, 22c, and 22d (hereinafter sometimes collectively referred to as the temperature sensor 22) that detect the temperature of the refrigerant are provided at the entrance and exit of the use-side heat exchanger 6 and the temperature sensor. 23a, 23b, 23c, and 23d (hereinafter collectively referred to as temperature sensor 23) are provided.

  The air conditioner 100 configured as described above can be cooled or heated by switching the flow path switching device 3, but the air conditioner 100 to which the oil return mechanism of the present invention is applied is the cooling operation. Or what is necessary is just to be able to perform heating operation. Further, the configuration of the refrigerant circuit is not limited to the illustrated one.

  The air conditioner 100 is further provided with a control device 30 that controls the entire air conditioner. The control device 30 is composed of a microcomputer and includes a CPU, a RAM, a ROM, and the like. The ROM stores a control program and a program corresponding to the flowcharts shown in the drawings.

  The control device 30 is connected so as to receive detection signals from various sensors in the air conditioner, and controls the driving frequency of the compressor 1 and opens the throttle device 7 based on these detection signals. Perform degree control. Further, the control device 30 performs opening / closing control of the electromagnetic valve 9 of the oil return pipe 10 so that the amount of oil in the compressor 1 becomes an appropriate amount based on detection signals from various sensors. Details of this control will be described again. In addition, although the example which provided the control apparatus 30 in the outdoor unit A was shown in FIG. 1, you may make it the structure divided into the outdoor unit A and the indoor unit B, and mutually performing a cooperation process.

Next, each operation mode executed by the air conditioner 100 will be described.
FIG. 2 is a refrigerant circuit diagram illustrating a refrigerant flow in the air-conditioning apparatus of FIG. In FIG. 2, the case where all the indoor units B are driven will be described as an example. In FIG. 2, the solid arrow indicates the refrigerant flow in the cooling operation mode, and the dotted arrow indicates the refrigerant flow in the heating operation mode.

[Cooling operation mode]
The low-temperature and low-pressure refrigerant is compressed by the compressor 1 and discharged as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the oil separator 2. In the oil separator 2, the refrigerant and the oil mixed in the refrigerant are separated. The high-temperature and high-pressure refrigerant separated in the oil separator 2 passes through the flow path switching device 3 and flows into the heat source side heat exchanger 4.

  The high-temperature and high-pressure gas refrigerant flowing into the heat source side heat exchanger 4 radiates heat to the air by exchanging heat with the air supplied from the blower 4a. The refrigerant that has exchanged heat with the air enters a liquid state and flows out of the heat source side heat exchanger 4. This liquid refrigerant flows out of the outdoor unit A. The refrigerant flowing out of the outdoor unit A flows into each of the indoor units B1 to B4 through the liquid side main pipe 101b and the liquid side branch pipe 101d.

  The refrigerant that has flowed into the indoor unit B1 to the indoor unit B4 is expanded (depressurized) by each of the expansion devices 7a to 7d to be in a low-temperature and low-pressure gas-liquid two-phase state. The refrigerant in the gas-liquid two-phase state flows into the use side heat exchanger 6a to the use side heat exchanger 6d. The refrigerant in a gas-liquid two-phase state that has flowed into the use side heat exchanger 6a to the use side heat exchanger 6d absorbs heat from the air by exchanging heat with air (indoor air) supplied from a blower (not shown), It becomes a low-pressure gas refrigerant and flows out from the use side heat exchanger 6a to the use side heat exchanger 6d.

  The low-pressure gas refrigerant that has flowed out of the use side heat exchanger 6a to the use side heat exchanger 6d flows out of the indoor unit B1 to the indoor unit B4, passes through the gas side branch pipe 101c and the gas side main pipe 101a to the outdoor unit A. Flows in. The refrigerant flowing into the outdoor unit A flows through the flow path switching device 3 and into the accumulator 5. The refrigerant flowing into the accumulator 5 is separated from the liquid refrigerant and the gas refrigerant, and the gas refrigerant is sucked into the compressor 1 again through the suction pipe 1b.

  By the way, the control device 30 adjusts the refrigerant supply amount to the use side heat exchanger 6 by using detection values from the temperature sensors 22 and 23 provided at the refrigerant inlet / outlet of the use side heat exchanger 6. Yes. Specifically, the degree of superheat (refrigerant temperature at the outlet side of the use-side heat exchanger 6-refrigerant temperature at the inlet) is calculated based on detection values from the temperature sensors 22 and 23, and the degree of superheat is 2 to 5 ° C. The degree of opening of the expansion device 7 is determined so as to be approximately, and the amount of refrigerant supplied to the use-side heat exchanger 6 is adjusted.

  Thus, in the cooling operation mode, since the superheat degree control is performed so that the superheat degree of the outlet of the use side heat exchanger 6 of each operating indoor unit B is 2 to 5 ° C., the refrigerant in the liquid state is It does not flow into the accumulator 5. However, when there is an indoor unit B that is in a transitional state, the degree of superheat cannot be temporarily reduced to 2 to 5 ° C., and the refrigerant in a small amount of liquid state (dryness level of about 0.95) May flow into the accumulator 5.

[Heating operation mode]
The low-temperature and low-pressure refrigerant is compressed by the compressor 1 and discharged as a high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the oil separator 2. In the oil separator 2, the refrigerant and the oil mixed in the refrigerant are separated. The high-temperature and high-pressure refrigerant separated in the oil separator 2 passes through the flow path switching device 3 and flows out of the outdoor unit A.

  The refrigerant that has flowed out of the outdoor unit A flows into the use side heat exchanger 6a to the use side heat exchanger 6d of the indoor units B1 to B4 through the gas side main pipe 101a and the gas side branch pipe 101c. . The refrigerant in the gas state that has flowed into the use side heat exchanger 6a to the use side heat exchanger 6d exchanges heat with air (indoor air) supplied from a blower (not shown), thereby radiating heat to the air. It becomes a liquid refrigerant and flows out from the use side heat exchanger 6a to the use side heat exchanger 6d.

  The liquid refrigerant flowing out from the use side heat exchanger 6a to the use side heat exchanger 6d is expanded (depressurized) in each of the expansion devices 7a to 7d to be in a low-temperature / low-pressure gas-liquid two-phase state. The refrigerant in the gas-liquid two-phase state flows out of the indoor units B1 to B4, and flows into the outdoor unit A through the liquid side main pipe 101b and the liquid side branch pipe 101d.

  The gas-liquid two-phase refrigerant flowing into the outdoor unit A flows into the heat source side heat exchanger 4 and absorbs heat from the air by exchanging heat with the air supplied from the blower 4a to become a low-pressure gas refrigerant. It flows out from the heat source side heat exchanger 4. The refrigerant that has flowed out of the heat source side heat exchanger 4 passes through the flow path switching device 3 and flows into the accumulator 5. The refrigerant flowing into the accumulator 5 is separated from the liquid refrigerant and the gas refrigerant, and the gas refrigerant is sucked into the compressor 1 again through the suction pipe 1b.

  In such a heating operation mode, surplus refrigerant is always present in the accumulator 5. The liquid refrigerant that has flowed into the accumulator 5 is evaporated and sucked into the compressor 1, or is sucked into the compressor 1 through an oil return hole 53 a provided in the refrigerant outlet pipe 52 of the accumulator 5.

Next, the oil return structure which is a characteristic part of the present invention will be described.
FIG. 3 is a diagram showing a configuration of a main part including the oil return structure according to the embodiment of the present invention. Hereinafter, the oil return structure will be described with reference to FIG.
Here, first, the configuration of the compressor 1 will be described, and then the oil return structure will be described.

  The compressor 1 includes a rotor 12a and a stator 12b, and transmits to the compression mechanism 11 a compression mechanism 11 that compresses refrigerant, an electric motor mechanism 12 that drives the compression mechanism 11, and a rotational force generated by the electric motor mechanism 12. And a main shaft 13, which are housed in a sealed container 14. And the oil reservoir 15 which stores oil is provided in the lower part of the airtight container 14, and the oil level position at the time of normal time is a position lower than the rotor 12a. 3 of FIG. 3 has shown the height position of the minimum required oil amount. The oil in the oil reservoir 15 rises in the vertical hole in the main shaft 13 due to the pump action by the rotation of the main shaft 13, and slides of the main shaft 13 and the compression mechanism 11 (main bearing 61, sub-bearing 63, compression described later) To each sliding portion of the mechanism 11).

  Part of the oil after sliding on each sliding part falls and returns to the oil reservoir 15, and the rest flows into the compression mechanism 11 together with the refrigerant and is discharged out of the compressor together with the compressed refrigerant. The oil discharged from the compressor 1 together with the refrigerant to the outside of the compressor is separated from the refrigerant by the oil separator 2, passes through the oil return capillary 8 and the suction pipe 1 b, and is returned to the compressor 1.

  In the oil return structure of the present embodiment, when the amount of oil in the compressor 1 is appropriate, the oil is returned from the accumulator 5 to the compressor 1, and the amount of oil in the compressor 1 becomes larger than the appropriate amount so that the rotor 12a When it begins to soak in oil (when the amount of compressor oil increases), the structure is such that the accumulator 5 can be used as an oil reservoir container by stopping the return of oil from the accumulator 5 to the compressor 1. The determination as to whether the rotor 12a of the compressor 1 has begun to be immersed in oil is made according to the flowchart of FIG.

Next, an oil return structure for returning oil from the accumulator 5 to the compressor 1 will be described.
The accumulator 5 includes a refrigerant inlet pipe 51 and a refrigerant outlet pipe 52, and the oil return pipe 10 is connected to the bottom surface of the accumulator 5 as described above. One end of the refrigerant inlet pipe 51 is connected to a pipe 101 e (see FIG. 1) through which the refrigerant flowing out from the use-side heat exchanger 6 and going to the compressor 1 passes, and the other end is opened in the accumulator 5. The refrigerant outlet pipe 52 is formed of a U-shaped pipe, one end is connected to the suction pipe 1 b, and the other end is opened in the accumulator 5.

  The oil return pipe 10 is connected to the bottom of the accumulator 5 so that the opening (oil return hole) of the opening end 10 a in the accumulator 5 is located at a position off from just below the refrigerant inlet pipe 51. This is because when the opening end 10 a of the oil return pipe 10 is located directly below the refrigerant inlet pipe 51, the oil level in the accumulator 5 is disturbed by the suction refrigerant flowing into the accumulator 5 from the refrigerant inlet pipe 51, and the oil return pipe 10 This is because there is a possibility that the oil cannot be successfully returned to the compressor 1.

  The solenoid valve 9 of the oil return pipe 10 is normally opened, and when the oil accumulated in the compressor 1 becomes higher than the opening end 10a of the oil return pipe 10, the oil return pipe 10 is connected to the compressor 1. Oil is returned. The height h1 in the accumulator of the opening end 10a of the oil return pipe 10 is set to a height at which the compressor 1 does not run out of oil when the system is assembled with the maximum pipe length. That is, since the oil is returned to the compressor 1 only after the height of the oil exceeds the height of the opening end 10a, if the height of the opening end 10a is too high, the compressor 1 may fall short of oil. . For this reason, when the system is assembled with the maximum pipe length, the height position of the opening end 10a is determined so that the compressor 1 does not run out of oil.

  Further, the accumulator 5 is provided with an oil return portion 53 as an oil return path for increasing the amount of compressor oil, which is different from the oil return path by the oil return pipe 10. The oil return portion 53 has an oil return hole 53a provided at the bottom of the U-shape of the refrigerant outlet pipe 52, one end connected to the refrigerant outlet pipe 52, and the other end at the same height as the oil return hole 53a in the accumulator 5. An oil return pipe 53b opened at h2. The oil return portion 53 corresponds to a second oil return portion of the present invention, and the oil return pipe 53b corresponds to a second oil return pipe.

  When the oil height position becomes higher than the oil return hole 53a, the oil-containing refrigerant returns to the compressor 1 little by little through the suction pipe 1b. In the accumulator 5, when the oil level is sufficiently higher than the height position of the oil return hole 53a, the liquid head is applied and the oil return hole 53a is easily returned. However, when the oil return hole 53a is slightly higher, the oil is difficult to return from the oil return hole 53a. For this reason, the oil return hole 53a and the oil return pipe 53b are provided separately. Specifically, the oil return hole 53a and the oil return pipe 53b are selectively used from the oil return hole 53a when the flow rate is low and from the oil return pipe 53b when the flow rate is high. In addition, the oil return part 53 of this invention is not limited to the case where both the oil return hole 53a and the oil return piping 53b are used, The case where it is set to one side is also included.

The height h2 is set as follows.
h2 = (Qmax−Qmin) / S
Qmax: Total oil amount of the air conditioner (maximum pipe length predetermined in the system configuration)
(The amount of oil set so that there is no oil shortage when the system is configured with
Qmin: Minimum amount of oil required for the compressor Qmin
S: Cross-sectional area of the AA cross section of the accumulator 5 of FIG.

  By setting in this way, when the amount of oil in the compressor 1 increases and the oil return path is switched from the oil return pipe 10 to the oil return portion 53 side, the accumulator 5 does not accumulate too much oil, Lubrication of the compressor 1 can be maintained.

Here, the flow of oil will be described.
When oil is sucked into the accumulator 5 together with the refrigerant gas, gas and liquid are separated by the accumulator 5, and the oil accumulates at the bottom of the accumulator 5. When the solenoid valve 9 is in the open state, when oil becomes higher than the opening end 10a of the oil return pipe 10, the oil is returned from the oil return pipe 10 to the compressor 1 through the suction pipe 1b. On the other hand, when the solenoid valve 9 is in the closed state, the oil level rises with time and reaches the oil return hole of the oil return portion 53 (the opening of the opening end 53c of the oil return hole 53a and the oil return pipe 53b). Then, the oil that has reached the oil return hole of the oil return portion 53 is returned from the oil return portion 53 to the compressor 1 through the suction pipe 1b.

[Control method]
FIG. 4 is a flowchart showing a flow of oil return control in the air-conditioning apparatus according to the embodiment of the present invention.
When the cooling or heating operation is started, the control device 30 first opens the electromagnetic valve 9 (STEP 1). And the control apparatus 30 judges whether the driving | running state was stabilized (STEP2). In this determination, for example, it is determined whether 20 minutes have elapsed after the start of operation. As another determination method, various sensors such as a temperature sensor and a pressure sensor may be provided in the refrigerant circuit, and the detection value may be determined. The reason for determining whether or not the operation state is stable is as follows. That is, for example, when the refrigerant circuit state is not stable, such as immediately after the start of operation, it is impossible to accurately determine whether or not the solenoid valve 9 needs to be closed.

  Then, it is determined whether or not the pipe length of the air conditioner 100 is short enough to easily collect oil in the compressor 1 (STEP 3). If it is determined that the pipe length is short, the process proceeds to STEP 4 and it is determined that the pipe length is long. If so, proceed to STEP7. This pipe length determination is made based on, for example, the number of connected indoor units B. Specifically, when the total number of connectable indoor units B is 20, for example, when the number of connectable units of the current system is 4 or less, for example, it is determined that the piping length is short, and the number of connectable units is 5 or more Judge that the pipe length is long.

  In addition to the determination method based on the number of connected indoor units B, the pipe length is determined by pressure loss in the refrigerant pipes (the gas-side main pipe 101a and the liquid-side main pipe 101b) that connect the outdoor unit A and the indoor unit B. You may judge based on Pm. The pressure loss Pm is obtained by the difference between the suction pressure Ps of the compressor 1 of the outdoor unit A and the saturation pressure Pi of the use side heat exchanger 6 of the indoor unit B.

The suction pressure of the compressor 1 of the outdoor unit A is detected by the pressure sensor 21. The saturation pressure Pi of the use side heat exchanger 6 is a pressure-converted value using the detected value of the temperature sensor 23 of the indoor unit B in operation (refrigerant evaporation temperature in the use side heat exchanger 6). . The pressure loss Pm increases as the lengths of the gas-side main pipe 101a and the liquid-side main pipe 101b connecting the outdoor unit A and the indoor unit B increase. For this reason, when the pressure loss Pm is not more than a preset threshold value (for example, 2 kg / cm ² ), it is determined that the pipe length is short, and when the pressure loss Pm is larger than the threshold value, it is determined that the pipe length is long.

  The pipe length determination may be made based on both the number of connected indoor units B and the pressure loss Pm. That is, when the number of connected units is 4 or less and the pressure loss Pm is less than or equal to the threshold value, it may be determined that the pipe length is short.

  Subsequently, the control device 30 determines whether the compressor input has deteriorated from the set value (STEP 4). The input value Wc of the compressor 1 is obtained by conversion from the secondary current value (current value between the control device 30 and the compressor 1) detected by the outdoor unit A. The compressor input set value Ws is preset in the control device 30 for each frequency, and the set value Ws is determined based on the current frequency of the compressor 1. Here, if the current input value Wc of the compressor 1 becomes 105% of the set value Ws, for example, the process proceeds to the next STEP5, and if it is less than 105%, the process proceeds to STEP7. Note that the set value Ws of the compressor 1 differs depending on the type of the compressor 1 and needs to be determined as to the type of the compressor 1, but is omitted in the flowchart because it is determined when the power is turned on.

  Then, it is determined whether or not the current compressor frequency is equal to or higher than a preset threshold frequency (STEP 5). This determination is intended to determine whether the frequency of the compressor input is likely to deteriorate due to the oil in the compressor 1. This threshold frequency is set based on the following experimental results.

  FIG. 5 is a diagram showing a result of measuring the relationship between the amount of oil in the compressor during operation and the compressor input by changing the compressor frequency. FIG. 5 shows a case where the horizontal axis represents the operating oil amount [L] in the compressor, the vertical axis represents the compressor input [W], and the frequency of the compressor 1 is 13 Hz, 40 Hz, and 100 Hz. In FIG. 5, L1 indicates the amount of oil when the rotor 12a is immersed in oil. FIG. 5 shows test data for the compressor alone.

  In the case of 13 Hz, no increase in the compressor input is observed even if the oil amount increases, but in the case of 40 Hz and 100 Hz, the compressor input tends to increase as the oil amount increases. The increase in the compressor input is increased at 40 Hz with the oil amount L1 in which the rotor 12a is immersed in the oil. At 100 Hz, the increase in the compressor input increases before the rotor 12a is immersed in oil. That is, when the frequency is 40 Hz or more, the compressor input is deteriorated due to the rotor 12a being immersed in oil, and this 40 Hz is used as the threshold frequency for the determination in STEP5.

  And when it is judged that the control apparatus 30 satisfy | fills all the conditions of STEP1-STEP5, the solenoid valve 9 is closed (STEP6), and the oil return path | route is switched from the oil return piping 10 to the oil return part 53. FIG.

  By switching the oil return path from the oil return pipe 10 to the oil return portion 53, the oil does not return from the accumulator 5 to the compressor 1 until the amount of oil in the accumulator 5 reaches the oil return portion 53. Oil will accumulate. On the other hand, since the oil is discharged together with the refrigerant in the compressor 1, the oil in the compressor 1 gradually decreases, and the amount of oil in the compressor 1 can be properly maintained.

  If any one of STEP1 to STEP5 is not satisfied, the control device 30 proceeds to STEP7 and keeps the electromagnetic valve 9 open.

  The control device 30 repeats the above processing until the operation stop is instructed (STEP 8), and when the operation stop is instructed, the operation ends.

  As described above, in the present embodiment, the oil return pipe 10 and the oil return portion 53 are provided as paths for returning the oil from the accumulator 5 to the compressor 1, and the oil return to the accumulator 5 is started first. The solenoid valve 9 provided in the oil return pipe 10 is closed when the amount of oil in the compressor 1 increases, so that the oil does not return from the accumulator 5 to the compressor 1. For this reason, the oil amount increasing state in the compressor 1 can be eliminated and an appropriate amount of oil can be held in the compressor 1.

  Since an appropriate amount of oil can be held in the compressor 1 in this way, a load caused by the rotor 12a being immersed in the oil can be reduced, and an increase in power consumption can be suppressed. As a result, COP (coefficient of performance) and IPLPV (period coefficient of performance) can be improved.

  When the pipe length is short and the number of indoor units in operation is small (for example, when the number of operating units is half of the total number of connected units), the amount of oil in the compressor 1 is likely to increase. For this reason, in addition to the determinations of STEP 2 to STEP 5 in FIG. 4, it is further determined whether or not the number of indoor units in operation is small, and if the condition that the number of indoor units in operation is small is further satisfied, the solenoid valve 9 may be closed.

  1 and 2 show the vertical type accumulator 5, the accumulator 5 may be a horizontal type as shown in FIG. The horizontal type is the same as the vertical type.

  DESCRIPTION OF SYMBOLS 1 Compressor, 1a Discharge piping, 1b Intake piping, 2 Oil separator, 3 Flow path switching device, 4 Heat source side heat exchanger, 4a Blower, 5 Accumulator, 6 (6a-6d) Usage side heat exchanger, 7 (7a-7d) Throttle device, 8 Oil return capillary, 9 Solenoid valve, 10 Oil return pipe, 10a Open end, 11 Compression mechanism, 12 Electric motor mechanism, 12a Rotor, 12b Stator, 13 Main shaft, 14 Airtight container, 15 Oil reservoir Part, 21 pressure sensor, 22 (22a-22d) temperature sensor, 23 (23a-23d) temperature sensor, 30 control device, 51 refrigerant inlet pipe, 52 refrigerant outlet pipe, 53 oil return part, 53a oil return hole, 53b oil Return pipe, 53c Open end, 61 Main bearing, 63 Sub bearing, 100 Air conditioner, 101a Gas side main pipe, 101b Liquid side main arrangement , 101c gas side branch pipes, 101d liquid side branch pipes, 101e pipe, A outdoor unit, B (B1 to B4) indoor unit.

Claims (6)

An oil return structure of an air conditioner that returns oil from an accumulator to a compressor,
A first oil return portion and a second oil return portion constituting a path for returning oil from the accumulator to the compressor;
Each of the first oil return portion and the second oil return portion has oil return holes that open at different height positions in the accumulator, and has the oil return hole having a lower height. The oil return structure of the air conditioner is characterized in that the 1 oil return portion includes an electromagnetic valve that is closed when the compressor input increases due to an increase in the amount of oil in the compressor. The oil return structure for an air conditioner according to claim 1, wherein the height of the oil return hole of the second oil return portion is set to a height h obtained by the following equation.
h = (Qmax−Qmin) / S
Qmax: Total oil amount of the air conditioner (the maximum amount determined in advance according to the model of the air conditioner)
(Oil amount set according to the length of the large pipe)
Qmin: Minimum amount of oil required for the compressor S: Cross-sectional area of the accumulator   The first oil return portion includes a first oil return pipe, and one end of the first oil return pipe opens in the accumulator to become the oil return hole, and the oil return hole is directly below the refrigerant inlet pipe of the accumulator. The oil return structure for an air conditioner according to claim 1 or 2, wherein the first oil return pipe is connected to a bottom surface of the accumulator so as to be displaced from the position. The accumulator has a refrigerant outlet pipe configured in a U shape inside,
The second oil return portion, said a bottom oil return hole provided in the refrigerant outlet pipe, which is connected at one end to the refrigerant outlet pipe, one of the other end second oil return pipe that opens mouth with the accumulator Or when the second oil return portion is constituted by both the oil return hole and the second oil return pipe, the other end side of the oil return hole and the second oil return pipe is configured. The oil return structure for an air conditioner according to any one of claims 1 to 3, wherein the opening is at the same height position . An oil return structure for an air conditioner according to any one of claims 1 to 4,
The determination result of the length of the pipe of the air conditioner is short , the input of the compressor is 105% or more with respect to a set value determined according to the frequency of the compressor, the compressor An air conditioner comprising: a control device that closes the electromagnetic valve when all the conditions are satisfied. The air conditioner is a multi-type air conditioner in which a plurality of indoor units are connected to an outdoor unit,
The control device determines whether the length of the pipe of the air conditioner is long or short based on a determination based on the number of connected indoor units and a determination based on a pressure loss in a refrigerant pipe connecting the outdoor unit and the indoor unit. 6. The air conditioner according to claim 5, wherein the determination is made by both.

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