JP5414482B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner in which one outdoor unit and a plurality of indoor units are combined. In particular, the refrigerating machine oil circulating in the refrigerating cycle of the air conditioner is separated, and the refrigerating machine oil is returned to the compressor. It is related with the air conditioner provided with the oil quantity adjustment function which makes the quantity of the refrigerating machine oil in a compressor appropriate.

  Generally, refrigerating machine oil is enclosed in an air conditioner for lubrication of a compressor. The required amount of refrigerating machine oil varies depending on the length of the refrigerant pipe to be used. When the amount of refrigerating machine oil is small compared to the length of the refrigerant pipe, the oil becomes insufficient. For this reason, when an outdoor unit of an air conditioner is manufactured, a sufficient amount of oil that does not cause a shortage of oil is sealed even in the case of the expected maximum pipe length.

  Another conventional technique is described in Patent Document 1. In this document, a sensor for detecting the oil level in the compressor is provided, and an open / close valve and a throttle are provided in an oil return pipe connecting the oil separator and the compressor. Thus, the return control of oil to each compressor is performed.

JP 2001-349644 A

  As described above, in the conventional one, the amount of the refrigerating machine oil enclosed in the outdoor unit constituting the air conditioner is set to a sufficient oil amount so that the oil amount does not become insufficient even at the maximum pipe length. For this reason, when the pipe length is short, the amount of refrigeration oil is always excessive, a large amount of refrigeration oil is discharged into the cycle pipe, and the oil is accumulated in the heat exchanger on the low pressure side to form an oil film in the pipe. Thereby, the heat transfer performance of the heat exchanger was reduced, and the cooling capacity and the heating capacity were reduced.

  In addition, if the amount of oil that returns to the compressor cannot be controlled properly, a large amount of refrigeration oil will return to the compressor, causing liquid compression by the refrigeration oil, leading to increased compressor input and compressor failure. It was.

  Furthermore, in the thing of the said patent document 1, the refrigerating machine oil discharged | emitted from the compressor is isolate | separated from a refrigerant | coolant with an oil separator, and has a structure which returns to a compressor. However, the control of the return amount of the refrigeration oil is an open / close control by a solenoid valve, and it is difficult to optimize the amount of oil in the compressor by finely adjusting the return amount of the refrigeration oil.

  In addition, during a transitional cycle such as when starting or switching the number of rooms (when changing the number of air-conditioned rooms), the refrigeration oil in the compressor will temporarily flow into the refrigeration cycle. Of refrigeration oil. However, conventionally, no consideration has been given to oil amount control that keeps the refrigerating machine oil in the compressor constant according to the operating state of the outdoor unit.

  An object of the present invention is to prevent so-called oil shortage in the compressor due to oil rising, in which refrigeration oil is discharged from the compressor to the refrigeration cycle, and to maintain the oil amount in the compressor appropriately to ensure the reliability of the compressor. It is to obtain an air conditioner capable of improving the performance.

  Another object of the present invention is to prevent a large amount of refrigerating machine oil from being released into the refrigerating cycle, and to prevent a large amount of refrigerating machine oil from staying in the refrigerant pipes and heat exchangers in the refrigerating cycle. The object is to obtain an air conditioner that can prevent a drop.

To achieve the above object, the present invention provides an outdoor unit comprising a compressor, a four-way valve, an outdoor heat exchanger and an outdoor expansion valve, an indoor unit comprising a heat exchanger and an indoor expansion valve, the outdoor unit and the In an air conditioner including a refrigerant pipe connecting an indoor unit, an oil separator provided on the discharge side of the compressor, a low-pressure pipe between the four-way valve and the compressor, and the oil separator and oil connecting return pipe, the adjustment and the electronic expansion valve provided in the oil return pipe, the opening degree of the electronic expansion valve of the oil return pipe based on the discharge gas super heater preparative discharged from at least the compressor A control device for controlling the amount of oil in the compressor , and the control device detects the temperature of the discharge gas from the compressor or the temperature of the high-temperature portion near the compressor discharge pipe such as the top of the compressor. Sensors and Calculate the superheat of the compressor discharge gas based on the detection value by the pressure sensor on the compressor discharge side, control the opening degree of the electronic expansion valve of the oil return circuit based on the calculated superheat, and If the calculated superheat is in an allowable range, the opening degree of the electronic expansion valve is maintained, and if the superheat is lower than the allowable range, the opening degree of the electronic expansion valve is further opened by a specified pulse, When the superheat is higher than the allowable range, the opening degree of the electronic expansion valve is closed by a specified pulse, and thereafter the superheat is calculated every time a predetermined time elapses to control the electronic expansion valve opening degree. .

  Here, an accumulator may be provided in the low-pressure pipe on the suction side of the compressor, and the oil return pipe may be connected to the low-pressure pipe between the four-way valve and the accumulator. Further, the oil return pipe may be directly connected to an accumulator provided in the low pressure pipe.

  Further, the oil return pipe includes an oil return pipe connecting the low pressure pipe between the four-way valve and the accumulator and the oil separator, a suction pipe between the accumulator and the compressor, and the oil. An oil return pipe connecting the separator may be provided, and an electronic expansion valve may be provided in each of the oil return pipes.

A plurality of the compressors are provided in parallel, and a plurality of the oil return pipes are provided so as to connect the suction pipes of the compressors and the oil separator. each provided with the electronic expansion valve, wherein the control device adjusts the opening degree of the electronic expansion valve of each oil return pipes on the basis of the discharge gas super heater preparative discharged from at least the respective compressor each compression If the in-machine oil amount is controlled, the oil amount in each compressor can be appropriately controlled even when a plurality of compressors are provided.

  In the above, the control device can be shared by controlling the opening degree of the electronic expansion valve of the oil return pipe by the control device that controls each component of the outdoor unit installed in the outdoor unit.

Moreover, the includes a compressor oil level sensor for detecting the oil level height of Rutotomoni, the oil level sensor, and an intermediate position of the oil surface of the optimum oil amount, more when the oil amount is reduced It detects the lower limit position of the oil level that will cause the compressor failure, and the oil level sensor controls the oil level in the compressor so that the amount of oil in the compressor does not become excessive or excessive. Is maintained in an appropriate predetermined range, an air conditioner having a small oil amount fluctuation in the compressor can be obtained.

  Even if the superheat is lower than the allowable range, the electronic expansion valve opening is already the upper limit opening, or even if the superheat is higher than the allowable range, the electronic expansion valve opening is already the lower limit opening. In some cases, it is preferable not to perform control to further open and close the opening of the electronic expansion valve.

  According to the present invention, refrigeration oil is released from the compressor into the refrigeration cycle, so-called oil shortage due to rising oil can be prevented, and the amount of oil in the compressor can be appropriately maintained. The reliability of the compressor can be improved. In addition, since a large amount of refrigerating machine oil is released into the refrigeration cycle and a large amount of refrigerating machine oil stays in the refrigerant piping and heat exchanger in the refrigeration cycle, it is possible to prevent the cooling capacity and heating capacity from deteriorating. There is an effect that an air conditioner that can be obtained can be obtained.

It is a refrigerating cycle block diagram which shows Example 1 of the air conditioner of this invention. It is a refrigerating cycle block diagram which shows the other example of Example 1 of the air conditioner of this invention. It is a flowchart explaining the control in Example 1 of the air conditioner of this invention. It is a flowchart explaining the control in Example 2 of the air conditioner of this invention. It is a flowchart explaining the control in Example 3 of the air conditioner of this invention. It is a refrigerating cycle block diagram which shows the reference example with respect to the air conditioner of this invention.

  Before describing an embodiment of the present invention, a reference example for the present invention will be described with reference to FIG.

  6 is provided with an oil separator 7 on the discharge side of the compressor 1, oil is sent from the oil separator 7 through an oil return pipe 21 to the accumulator 8, and the compressor is passed through the accumulator 8. This is a reference example for returning oil to 1. The oil return pipe 21 is provided with an electromagnetic valve 10a, and an oil amount is adjusted by opening / closing control, and a capillary tube 17 is provided to reduce the high pressure. In FIG. 6, A is an outdoor unit, B1 and B2 are indoor units, 2 is a four-way valve, 3 is an outdoor heat exchanger, 4 is an outdoor expansion valve, 5 is an indoor heat exchanger, 6 is an indoor expansion valve, 9 Is a receiver tank, 10 is a solenoid valve, 11 is a check valve, 12 is a gas blocking valve, 13 is a liquid blocking valve, 15 is a control device, and 16 is a refrigerant pipe.

  However, even in this reference example, the solenoid valve 10a simply performs opening / closing control of full open / close, and fine adjustment of the amount of refrigeration oil cannot be made. In a typical cycle state, it is difficult to optimally control the amount of refrigerating machine oil returned to the compressor.

On the other hand, the present invention can appropriately control the amount of refrigerating machine oil returned to the compressor or the quantity of refrigerating machine oil in the compressor, thereby improving the cooling performance and heating performance. It is intended to improve the reliability.
Embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 is a refrigeration cycle configuration diagram showing Embodiment 1 of an air conditioner of the present invention. As an air conditioner, a twin-type air conditioner (with two indoor units for one outdoor unit) is used. An example when the present invention is applied will be described. In the present embodiment, the number of indoor units is not limited to two, and the present invention can be similarly applied to three or more indoor units or one.

  In the figure, A is an outdoor unit, and B1 and B2 are indoor units connected to the outdoor unit A by a refrigerant pipe 16. In the outdoor unit A, reference numeral 1 denotes a compressor that compresses low-temperature and low-pressure refrigerant vapor into high-temperature and high-pressure refrigerant vapor. In this embodiment, a plurality of compressors 1 are provided in parallel. 2 is a four-way valve for reversing the refrigerant flow during cooling and heating, and 3 is an outdoor heat exchanger that functions as a condenser during cooling and an evaporator during heating. In this embodiment, one outdoor unit A Two outdoor heat exchangers 3 are provided, and each outdoor heat exchanger 3 is provided with an outdoor expansion valve 4 for controlling the flow rate of the refrigerant flowing in the refrigerant pipe of the refrigeration cycle. 7 is provided on the discharge side of the compressor 1 and is an oil separator for separating refrigeration oil mixed with refrigerant discharged from the compressor, and 8 is provided on the suction side of the compressor 1. An accumulator for separating the liquid refrigerant from the gas-liquid mixed refrigerant, 12 is a gas blocking valve, 13 is a liquid blocking valve, and the gas blocking valve 12 and the liquid blocking valve 13 allow the refrigerant and refrigeration oil in the refrigeration cycle to be supplied to the outdoor unit. A can be sealed.

  In the indoor units B1 and B2, 5 is an indoor heat exchanger that becomes an evaporator during cooling and a condenser during heating, and 6 is an indoor expansion valve that adjusts the flow rate of the refrigerant flowing in the refrigerant piping of the refrigeration cycle. .

  Further, the outdoor unit A is provided with a control device 15 that controls each device such as an expansion valve, a solenoid valve, a compressor, and a fan of the indoor / outdoor unit.

  The outdoor unit A and the indoor units B1 and B2 are connected by a local refrigerant pipe 16 in which an air conditioner is installed in accordance with the local construction conditions.

  Reference numeral 21 denotes an oil return pipe. The oil return pipe 21 connects the oil separator 7 and a low-pressure pipe 22 upstream of the accumulator 8 (between the accumulator and the four-way valve). An electronic expansion valve 14 is provided. The oil return pipe 21 may be directly connected to the accumulator 8.

  As in this embodiment, by providing the electronic expansion valve 14 that is a throttle device in the oil return pipe 21, it becomes possible to finely adjust the valve opening, and an appropriate amount of oil can be returned to the compressor. Therefore, it becomes possible to always keep a certain amount of oil in the compressor. Therefore, according to the present embodiment, the amount of refrigeration oil in the compressor can be appropriately maintained even under transient cycle operation conditions such as when the air conditioner is started up or when the number of indoor units operated changes. Insufficient lubrication due to a decrease in the amount of oil and liquid compression due to the return of a large amount of refrigerating machine oil into the compressor can be prevented, and failure of the compressor 1 can be prevented. In addition, the amount of oil discharged from the compressor into the refrigeration cycle piping can be minimized, and heat transfer performance is reduced due to refrigeration oil stagnation in the heat exchanger, and the cooling capacity and heating capacity associated therewith are reduced. The decline can also be suppressed. The control of the electronic expansion valve 14 can also be controlled by the control device 15.

  In FIG. 1, 18 is an oil level sensor for detecting the oil level (oil amount) in each compressor 1, and 19 is a compressor discharge such as a discharge gas temperature from the compressor or the top of the compressor. Compressor temperature sensor for detecting the temperature of the high-temperature portion near the pipe, 20a is a pressure sensor for detecting the pressure on the discharge side of the compressor provided in the high-pressure pipe 23, and 20b is provided in the low-pressure pipe 22 for suctioning the compressor This is a pressure sensor for detecting the side pressure.

  Reference numeral 24 denotes a bypass pipe that connects the high-pressure pipe 23 downstream of the oil separator 7 and the liquid pipe 25 provided with the receiver tank 9. The bypass pipe 24 includes a solenoid valve 10 and a check valve 11. Is provided. Reference numeral 26 denotes a check valve provided in parallel with each of the outdoor expansion valves 4 provided in each of the plurality of outdoor heat exchangers 3.

  FIG. 2 shows a modified example of FIG. 1, and in this example, the same reference numerals as those in FIG. 1 denote the same or corresponding parts. As shown in the present embodiment, when a plurality of compressors 1 are used in one outdoor unit A, the operating conditions are different for each compressor 1, so that the required refrigeration in each compressor 1 is used. The machine oil amount is also different. That is, even when the oil amount of one compressor is appropriate, if the oil amount of the other compressor is excessive or too low, as described above, the compressor failure or refrigeration cycle may occur. It leads to performance degradation.

  The example shown in FIG. 2 is such that all of the plurality of compressors have an appropriate oil amount. In this example, the oil separator 7 and the suction pipes 22a and 22b of the respective compressors are used. Are connected by a plurality of oil return pipes 21a and 21b, and an electronic expansion valve 14 is provided in each of the oil return pipes 21a and 21b. Thereby, the return amount of oil can be controlled for each compressor according to the operating state of each compressor. It becomes possible to keep the oil level in each compressor constant.

  In the embodiment shown in FIG. 1, the oil return pipe 21 is connected to the low-pressure pipe 22 upstream of the accumulator 8, so that depending on the refrigerant circulation amount and the amount of liquid refrigerant in the accumulator 8, the accumulator 8 is sufficient for the compressor 1. It may not be possible to return the correct amount of oil. On the other hand, in the example shown in FIG. 2, since the oil separator 7 returns directly to the suction pipes 22a and 22b of the compressor 1 via the oil return pipes 21a and 21b, the refrigerant circulation amount and the accumulator 8 An appropriate amount of refrigerating machine oil can be returned into each compressor by controlling the opening of each electronic expansion valve 14 without being affected by the state or characteristics.

  In the example of FIG. 2, the oil return pipe 21 and the electronic expansion valve 14 shown in FIG. That is, an oil return pipe for connecting the low pressure pipe 22 between the four-way valve 2 and the accumulator 8 and the oil separator 7, and suction pipes 22 a and 22 b between the accumulator 8 and the compressor 1. And an oil return pipe for connecting the oil separator 7 and an electronic expansion valve 14 may be provided in each oil return pipe.

  Next, a specific example of the oil amount control in the compressor will be described with reference to the flowchart of FIG. This control example is based on controlling the opening of the electronic expansion valve 14 based on the frequency of the compressor, and further detecting the amount of oil in the compression to correct the opening of the electronic expansion valve 14. An example of control is shown.

  In this example, an oil level sensor 18 (see FIGS. 1 and 2) is attached to the compressor 1 so that the amount of oil in the compressor can always be detected and kept constant. That is, a hole is provided in the container of the compressor 1, the detection part of the oil level sensor 18 is inserted into the container from the outside of the container, and the sensor body is installed outside the container of the compressor 1. The mounting position of the oil level sensor 18 is controlled so that the amount of oil in the compressor does not become excessive or too small. Therefore, if the oil amount becomes smaller than this, the compressor will fail. An oil level sensor 18 is installed at each of the lower limit positions causing the problem.

Next, the control of the oil level in the compressor in this embodiment will be described along the flowchart of FIG.
First, the air conditioner is turned on (step S1). When the power is turned on, zero reset (reference point adjustment) is performed in order to detect the exact opening degree of the electronic expansion valve 14 that controls the oil return amount (step S2). Next, the compressor 1 of the outdoor unit is started (step S3). When the compressor is started, the refrigeration oil in the compressor is temporarily discharged into the refrigeration cycle piping and the amount of oil becomes insufficient, so that the opening of the electronic expansion valve 14 is fully opened to prevent the oil amount from being insufficient. The amount of oil is increased (step S4). Next, the timer is set to 0 seconds, and after a lapse of A seconds, the process proceeds to step S7 (steps S5 and S6). In step S7, the frequency of the compressor is detected, and based on the detected compressor frequency, the electronic expansion valve 14 is opened from the "compressor frequency-expansion valve opening characteristic diagram (a)" obtained in advance. The degree Xpls is calculated (step S8), and the opening degree of the electronic expansion valve 14 is controlled to Xpls (step S9).

Next, if the oil level in the compressor detected by the oil level sensor 18 is lower than the lower limit value, the process returns to step S4 and the opening degree of the expansion valve 14 is fully opened, and becomes higher than the lower limit value. To step S11. In step S11, if the oil level height is between the intermediate value and the lower limit value, this state is the optimum oil amount, and the opening degree of the electronic expansion valve 14 is maintained at the current opening degree. In step S11, when the oil level becomes equal to or greater than the intermediate value, the process proceeds to step S12, the opening of the electronic expansion valve 14 is closed by the designated pulse Ypls, and the amount of oil introduced into the compressor is reduced, and the process proceeds to step S5. Return.
By controlling as described above, the oil level in the compressor can be maintained within an appropriate predetermined range.

  Generally, in an air conditioner, the refrigerant circulation rate is increased by increasing the operating frequency of the compressor, thereby improving the cooling / heating capacity. However, when the refrigerant circulation amount increases, the amount of refrigeration oil flowing out from the compressor also increases, and as a result, the amount of oil in the compressor decreases. In this embodiment, the relationship of the amount of oil supplied to the compressor according to the opening degree of the electronic expansion valve 14 with respect to the compressor frequency is obtained in advance (see “compressor frequency-expansion valve opening characteristic diagram (a)” in FIG. 3). ) When the operating frequency of the compressor is high, the opening degree of the electronic expansion valve 14 is increased to increase the supply amount of refrigeration oil to the compressor. When the operating frequency of the compressor is low, the electronic expansion valve 14 The amount of oil supplied to the compressor can be quickly accommodated in accordance with the change in the operating frequency by controlling the amount of refrigerating oil supplied to the compressor to be decreased by reducing the opening of the compressor.

  According to the present embodiment, the opening degree of the electronic expansion valve 14 is controlled to an appropriate opening degree based on the compressor frequency, and the opening degree is corrected by detecting the oil level in the compressor. Therefore, the compressor oil can be prevented from being discharged from the compressor 1 to the refrigeration cycle, that is, the amount of oil in the compressor due to rising oil can be prevented, and the amount of oil in the compressor can be appropriately maintained. In addition, it is possible to prevent a large amount of refrigerating machine oil from being released into the refrigeration cycle, and to prevent cooling capacity and heating capacity from being lowered.

  Next, a second embodiment of the present invention will be described with reference to the flowchart of FIG. In this embodiment, the basic configuration of the air conditioner is the same as that shown in FIGS. 1 and 2, and only the method of controlling the opening degree of the electronic expansion valve 14 is different.

  In this embodiment, the opening degree of the electronic expansion valve 14 is controlled using the compressor discharge gas superheat (superheat degree). The compressor discharge gas superheat TdSH is calculated from the temperature obtained from the compressor temperature sensor 19 provided at the top of the compressor and the pressure obtained from the pressure sensor 20a provided on the discharge side of the compressor. Can do. When the compressor discharge gas superheat TdSH is low, since the compressor temperature is usually lowered, the temperature of the portion where the refrigerating machine oil is accumulated at the lower part of the compressor is also lowered. For this reason, the amount of liquid refrigerant in the compressor increases, and a large amount of liquid refrigerant is mixed into the refrigeration oil in the compressor. For this reason, since the viscosity of refrigerating machine oil falls, it is necessary to control the opening degree of the electronic expansion valve 14 and supply more refrigerating machine oil in a compressor.

Hereinafter, the control of this embodiment will be described with reference to the flowchart of FIG.
In the flowchart of FIG. 4, steps S1 to S6 are the same as those of the embodiment shown in FIG. In this embodiment, in steps S7 and S8, the controller discharge temperature and discharge are controlled by the control device 15 based on the detected values from the compressor temperature sensor 19 of the outdoor unit and the pressure sensor 20a provided on the discharge side of the compressor. While detecting the pressure, the compressor discharge gas superheat TdSH is calculated. In step S9, it is calculated whether or not the calculated compressor discharge gas superheat TdSH is within an allowable range with respect to the target temperature. If the calculated temperature is within the allowable range, the opening degree of the electronic expansion valve 14 that controls the oil return amount is calculated. Maintain and return to step S5. If the compressor discharge gas superheat is outside the allowable range of the target temperature in step S9, the process proceeds to step S10.

  In step S10, when the calculated compressor discharge gas superheat TdSH is lower than the target temperature TdSH by an allowable range or more (in the case of Yes), the process proceeds to step S11, and the opening degree of the electronic expansion valve 14 is set by the designated pulse Ypls. Further open and return to step 5. At this time, when the electronic expansion valve opening is already the upper limit opening, control for further opening the electronic expansion valve opening is not performed, and the upper opening is maintained.

  On the other hand, when the calculated compressor discharge gas superheat TdSH is higher than the target temperature TdSH by an allowable range or more (in the case of No), the process proceeds to step S12, and the opening of the electronic expansion valve 14 is larger than the lower limit opening (Yes) If so, the process proceeds to step S13 and the opening of the electronic expansion valve 14 is closed by the designated pulse Zpls. If the expansion valve opening is not more than the lower limit opening in step S12 (in the case of No), the opening is maintained and the process returns to step S5.

  Here, since the speed of the temperature change of the compressor discharge gas superheat TdSH is smaller than the speed of the opening / closing control of the electronic expansion valve 14, the opening degree of the electronic expansion valve 14 is excessively opened and closed, and the inside of the compressor It is conceivable that the amount of oil becomes excessive or excessive. For this reason, in this embodiment, the amount of oil in the compressor is prevented from becoming excessive or low by controlling using the timer set in steps S5 and S6.

  According to the present embodiment, since the opening degree of the electronic expansion valve 14 is controlled based on the compressor discharge gas superheat, even if the cycle operation state fluctuates, the compressor discharge gas superheat is accommodated in the compressor. The amount of refrigerating machine oil can be controlled to an appropriate amount. Therefore, it is possible to improve the reliability of the compressor, and to prevent a large amount of refrigeration oil from being released into the refrigeration cycle, thereby ensuring the cooling capacity and the heating capacity.

  A third embodiment of the present invention will be described with reference to the flowchart of FIG. Also in this embodiment, the basic configuration of the air conditioner is the same as that shown in FIGS. 1 and 2, and only the method of controlling the opening degree of the electronic expansion valve 14 is different.

  In this embodiment, the opening degree of the electronic expansion valve 14 is controlled by using a pressure ratio which is a ratio between the discharge pressure and the suction pressure of the compressor 1.

  The pressure ratio, which is the ratio between the discharge pressure and the suction pressure of the compressor 1, has a limited operating range for ensuring the quality of the compressor 1. For example, when the outside air temperature is low during the heating period, the suction pressure of the compressor is reduced, so that the high pressure ratio operation is performed. Further, since the discharge pressure of the compressor is reduced when the outside air temperature is low during the cooling period, the operation is performed at a low pressure ratio.

  During high pressure ratio operation, the frequency of the compressor is decreased to avoid high pressure ratio operation. However, since oil rise is reduced, the amount of refrigeration oil in the compressor becomes excessive. Further, when the pressure ratio is low, the frequency of the compressor is increased to avoid the low pressure ratio operation, but as a result, the oil rise increases and the amount of refrigeration oil in the compressor is insufficient.

Therefore, in this embodiment, as shown in the flowchart of FIG. 5, the electronic expansion valve 14 of the oil return pipe 21 is controlled based on the pressure ratio.
In the flowchart of FIG. 5, steps S1 to S6 are the same as those in the embodiment shown in FIGS.

  In this embodiment, in steps S7 and S8, the compressor discharge pressure Pd and the suction are controlled by the control device 15 based on the detected values from the discharge side pressure sensor 20a and the suction side pressure sensor 20b of the compressor of the outdoor unit. The pressure Ps is detected and the pressure ratio ε is calculated. After calculating the pressure ratio ε, the process proceeds to the next step. It is confirmed in steps S9 and S10 whether the calculated pressure ratio ε is within a predetermined compressor operating range, that is, whether the pressure ratio ε is within the range between the lower limit value β1 and the upper limit value β2. If the pressure ratio ε is “β1 ≦ ε ≦ β2,” the opening degree of the electronic expansion valve 14 is maintained and the process returns from step S10 to step S5.

  When the pressure ratio ε is larger than the upper limit value β2 of the pressure ratio in steps S9 and S10, the process proceeds to step S11, and the current opening degree of the electronic expansion valve 14 is larger than the lower limit opening degree of the electronic expansion valve. In this case, the process proceeds to step S12, the opening of the electronic expansion valve 14 is closed by a preset B pulse, and the process returns to step S5. If the current opening degree of the electronic expansion valve 14 is not more than the lower limit opening degree of the electronic expansion valve in step S11, the opening degree is maintained and the process returns to step S5.

  In step S9, when the calculated pressure ratio ε is less than the lower limit opening β1, the process proceeds to step S13. If the opening degree of the electronic expansion valve 14 is less than the upper limit opening degree in step S13, the process proceeds to step S14, and after opening the opening degree of the electronic expansion valve 14 by a predetermined C pulse, step S5 is performed. Return to. If the opening of the electronic expansion valve 14 is greater than or equal to the upper limit opening in step S13, the opening is maintained and the process returns to step S5.

  In this embodiment, since the change rate of the pressure ratio of the compressor is small relative to the opening / closing control speed of the electronic expansion valve 14, the opening degree of the electronic expansion valve 14 is excessively opened and closed, and the amount of oil in the compressor May be too large or too small. For this reason, also in the present embodiment, the amount of oil in the compressor is prevented from becoming excessive or low by controlling using the timer set in steps S5 and S6.

  According to the present embodiment, since the opening degree of the electronic expansion valve 14 is controlled based on the pressure ratio, even if the pressure ratio changes and becomes a pressure ratio outside the allowable operation range, the pressure ratio changes. The amount of refrigerating machine oil in the compressor can be controlled to an appropriate amount. Therefore, it is possible to improve the reliability of the compressor, and to prevent a large amount of refrigeration oil from being released into the refrigeration cycle, thereby ensuring the cooling capacity and the heating capacity.

  As described above, according to each of the above-described embodiments, appropriate refrigeration oil can always be supplied to the compressor regardless of the length of the indoor / outdoor piping. Further, even when the amount of refrigeration oil in the short pipe is excessive, it is possible to prevent the cooling capacity and the heating capacity from being lowered, and it is possible to suppress an increase in compressor input. Furthermore, the amount of refrigerating machine oil in the compressor can be kept constant even in a transient cycle state such as when starting or switching the number of rooms, and the reliability of the compressor can be improved. Further, since the refrigerating machine oil can be optimally controlled, the total oil amount can be reduced.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Four-way valve 3 Outdoor heat exchanger 4 Outdoor expansion valve 5 Indoor heat exchanger 6 Indoor expansion valve 7 Oil separator 8 Accumulator 9 Receiver tank 10 Electromagnetic valve 11 Check valve 12 Gas blocking valve 13 Liquid blocking valve 14 Electron Expansion valve 15 Control device 16 Refrigerant piping 17 Capillary tube 18 Oil level sensor 19 Compressor temperature sensors 20a, 20b Pressure sensor 21 Oil return piping 22 Low pressure piping (22a, 22b ... compressor suction piping)
23 High pressure piping 24 Bypass piping 25 Liquid pipe A Outdoor unit B1, B2 Indoor unit.

Claims (7)

Air having an outdoor unit including a compressor, a four-way valve, an outdoor heat exchanger and an outdoor expansion valve, an indoor unit including a heat exchanger and an indoor expansion valve, and a refrigerant pipe connecting the outdoor unit and the indoor unit In the harmony machine,
An oil separator provided on the discharge side of the compressor;
An oil return pipe connecting the low pressure pipe between the four-way valve and the compressor and the oil separator;
An electronic expansion valve provided in the oil return pipe;
A control device for controlling the compressor oil amount by adjusting the opening degree of the electronic expansion valve of the oil return pipe based on the discharge gas super heater preparative discharged from at least said compressor,
The control device is based on a detected value by a compressor temperature sensor for detecting a temperature of a discharge gas from the compressor or a temperature of a high temperature portion near the compressor discharge pipe such as a compressor top and a pressure sensor on the compressor discharge side. Calculate the superheat of the compressor discharge gas, and control the opening of the electronic expansion valve of the oil return circuit based on the calculated superheat,
If the calculated superheat is in an allowable range, the opening degree of the electronic expansion valve is maintained, and if the superheat is lower than the allowable range, the opening degree of the electronic expansion valve is further opened by a specified pulse, When the superheat is higher than an allowable range, the opening of the electronic expansion valve is closed by a specified pulse, and then the electronic expansion valve opening is controlled by calculating the superheat every predetermined time. Air conditioner to do. The air conditioner according to claim 1 , wherein an accumulator is provided in the low-pressure pipe on the suction side of the compressor, and the oil return pipe is connected to the low-pressure pipe between the four-way valve and the accumulator. air conditioner, characterized in that there. The air conditioner according to claim 2 , wherein the oil return pipe is directly connected to an accumulator provided in the low pressure pipe . The air conditioner according to claim 2 , wherein the oil return pipe includes an oil return pipe connecting the low pressure pipe between the four-way valve and the accumulator and the oil separator, the accumulator, and the compressor. And an oil return pipe that connects the oil separator to each other, and an electronic expansion valve is provided in each of the oil return pipes . The air conditioner according to claim 1 , wherein a plurality of the compressors are provided in parallel, and a plurality of the oil return pipes are provided so as to connect the suction pipes of the compressors and the oil separator. In addition, each of the plurality of oil return pipes is provided with the electronic expansion valve, and the control device performs electronic expansion of each of the oil return pipes based on at least a discharge gas superheat discharged from each of the compressors. An air conditioner characterized in that the amount of oil in each compressor is controlled by adjusting the opening of a valve . In the air conditioner in any one of Claims 1-5, while providing the oil level height sensor which detects the oil level height in a compressor, this oil level height sensor is an oil level used as the optimal oil amount. The lower position of the oil level that will cause a compressor failure when the oil amount decreases more than this, and the oil level in the compressor is excessive or too small by this oil level height sensor. The air conditioner is characterized in that the oil level in the compressor is maintained within an appropriate predetermined range by controlling so as not to occur. 2. The air conditioner according to claim 1 , wherein even when the superheat is lower than an allowable range, the electronic expansion valve opening is already an upper limit opening, or even when the superheat is higher than an allowable range, the electronic expansion is performed. When the valve opening degree is already the lower limit opening degree, the air conditioner is characterized in that control for further opening and closing the opening degree of the electronic expansion valve is not performed .

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