JP5402027B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner, and more particularly, to a technique for returning refrigeration oil separated from a refrigerant discharged by an oil separator from the oil separator to a compressor.

  Conventionally, in an air conditioner, for example, in the case of cooling, the refrigerant discharged from the compressor is condensed in the outdoor heat exchanger, exhausted to the outdoor air, then becomes low temperature and low pressure in the expansion device, and the indoor heat exchanger The refrigerant that has flowed into and cooled to evaporate and evaporate, and the evaporated and vaporized refrigerant is subjected to a refrigeration cycle in a refrigerant circuit that performs a process of being drawn into the compressor again. This compressor is filled with refrigerating machine oil to lubricate the internal mechanism, but a small amount of refrigerating machine oil is contained from the compressor and refrigerant is discharged. For this reason, in order to ensure that the discharged refrigeration oil is returned to the compressor and the compressor operates normally, the conventional air conditioner has an oil separator and flow rate adjustment between the discharge port and the suction port of the compressor. An oil return circuit having a means is provided so as to bypass the refrigerant circuit, and the refrigerating machine oil contained in the refrigerant discharged from the compressor is separated by an oil separator, and the separated refrigerating machine oil is supplied to the compressor through the flow rate adjusting means. The mechanism to return to is adopted.

JP-A-8-189732

  A part of the refrigerant circulating in the refrigerant circuit (main circuit) flows into the oil return circuit, and the oil return circuit separates the refrigeration oil from the flowed refrigerant. If it is always fully open, the amount of refrigerant flowing into the oil return circuit increases, the amount of refrigerant flowing in the refrigerant circuit decreases, and the refrigeration cycle operation cannot be performed efficiently. On the other hand, if the oil return circuit is simply closed in order to increase the efficiency of the refrigeration cycle operation, the amount of refrigeration oil returned to the compressor is reduced, which hinders the lubricating operation of the internal mechanism of the compressor.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to perform a refrigeration cycle operation more efficiently than in the past while appropriately returning refrigeration oil to the compressor.

The invention according to claim 1 of the present invention includes a refrigerant circuit that performs a vapor compression refrigeration cycle by circulating a refrigerant,
A compressor provided in the refrigerant circuit;
An oil separator for separating oil from refrigerant discharged from the compressor;
An oil return pipe for returning the oil separated by the oil separator to the suction side of the compressor;
An on-off valve that can freely open and close the oil return pipe, and an oil return circuit that returns oil to the suction side of the compressor by opening and closing the on-off valve;
A rotational speed detector for detecting the rotational speed of the compressor;
A temperature load calculating unit that calculates a temperature load that is a difference between a room temperature that is a target of air conditioning control by the air conditioner and a set target room temperature;
When the condition that the rotation speed detected by the rotation speed detection unit is smaller than a predetermined rotation number and the temperature load calculated by the temperature load calculation unit is smaller than a predetermined value, in the opening and closing valve of the oil return circuit and closed so as not to supply the oil in the oil separator to the compressor, the said detected by the rotation number detection unit speed is a predetermined rotational speed or more Or an air conditioner including a control unit that opens an on-off valve of the oil return circuit when the temperature load calculated by the temperature load calculation unit satisfies a condition that the temperature load is equal to or greater than a predetermined value. is there.

According to the present invention, less than the rotational speed of the rotational speed is predetermined for the detected compressor by the rotation speed detecting unit, that the temperature load calculated by the temperature load calculation unit is smaller than a predetermined value satisfies case, for example, to an intermediate operation or the like in a state where the rotational speed of the compressor is lowered in accordance with the thermal load, the oil of the on-off valve of the control unit is an oil return circuit and the closed state in the oil separator Is not supplied to the compressor . In situations such as during the intermediate operation, the amount of refrigerant discharged from the compressor and the amount of oil contained in the refrigerant is small, and even if the oil return operation by the oil return circuit is interrupted, there is little trouble on the operation of the compressor. Thus, the control according to the present invention suppresses the amount of refrigerant flowing into the oil return circuit in situations such as during the intermediate operation, suppresses the reduction in the amount of refrigerant circulating in the refrigerant circuit, and enables efficient refrigeration cycle operation. Prioritize. Moreover, when the said rotation speed of a compressor is more than a predetermined rotation speed, or when the said temperature load is more than a predetermined value, ie, it is contained in the refrigerant | coolant discharged from a compressor, and the said refrigerant | coolant When the amount of oil is assumed to be large, the control unit opens the on-off valve of the oil return circuit and causes the oil return circuit to return the oil to the compressor, thereby lubricating the internal mechanism of the compressor. Prioritize operation. As a result, according to the present invention, it is possible to perform the refrigeration cycle operation more efficiently than before, while appropriately returning oil to the compressor and ensuring the lubrication operation of the internal mechanism of the compressor ( For example, energy efficiency can be improved throughout the year).

  The invention according to claim 2 is the air conditioner according to claim 1, wherein the oil return circuit further includes a pressure reducing mechanism connected in series to the on-off valve in the oil return pipe. It is what you have.

  In this invention, since the adjustment mechanism of the oil return circuit further includes a pressure reducing mechanism connected in series with the on-off valve in the oil return pipe, even if a relatively expensive motorized valve or the like is not used as the on-off valve, For example, the amount of oil passing through the oil return circuit can be controlled at a low cost by a combination of an inexpensive on-off valve such as a solenoid valve and a pressure reducing mechanism such as a capillary tube.

  Further, the invention according to claim 3 is the air conditioner according to claim 1 or 2, wherein the control unit performs the detected rotation at least during start-up control of the air conditioner. The valve opening / closing control of the oil return circuit based on the number and the calculated temperature load is not performed.

  In this invention, when the load applied to the compressor is relatively small, the control unit performs opening / closing control of the oil return circuit based on the detected rotation speed and the calculated temperature load, In a situation where the load applied to the compressor is relatively large, such as during start-up control of the air conditioner, the oil return circuit based on the detected rotational speed and the calculated temperature load Open / close control is not performed, that is, by selecting control that keeps the open / close valve of the oil return circuit in an open state, the oil is returned from the oil return circuit to the compressor, and the internal operation of the compressor is lubricated. By preferentially securing, smooth refrigeration cycle operation can be ensured.

  The invention according to claim 4 is the air conditioner according to any one of claims 1 to 3, wherein the control unit determines whether or not predetermined protection control is being performed. And the protection control is performed when the condition that the detected rotational speed is smaller than the predetermined rotational speed and the calculated temperature load is smaller than a predetermined value is satisfied. When it is determined that the oil return circuit has not been entered, the on-off valve of the oil return circuit is closed.

  According to the present invention, when the control unit performs a predetermined protection control, for example, a control such as defrosting or out-of-gassing protection, the detected rotational speed is greater than the predetermined rotational speed. Even if the condition that the calculated temperature load is smaller than the predetermined value is satisfied, the on-off valve of the oil return circuit is kept open, but the protection control is not entered. Only when it is determined that the on-off valve of the oil return circuit is closed, the predetermined protection control is performed, and the capacity of the compressor increases and the refrigerant and oil discharged from the compressor Under increasing conditions, the oil return circuit is made to return the oil to the compressor, and the lubrication operation of the internal mechanism of the compressor is preferentially ensured, thereby ensuring a smoother refrigeration cycle operation.

The invention according to claim 5 is the air conditioner according to any one of claims 1 to 4, further comprising a timer unit that measures a time during which the conditions are satisfied.
The control unit opens and closes the on-off valve of the oil return circuit only when the time measured by the timer unit reaches a predetermined time, assuming that the condition to be measured by the timer is satisfied. Control is performed.

  According to the present invention, the control unit determines that the condition to be measured by the timer is satisfied only when the time measured by the timer unit reaches a predetermined time. Since the on-off valve control is performed, the on-off valve of the oil return circuit is prevented from hunting repeatedly switching between the open state and the closed state within a short period of time, ensuring the lubrication operation of the internal mechanism of the compressor and improving the efficiency. When the opening / closing control of the opening / closing valve of the oil return circuit is to be performed in order to perform the refrigeration cycle well, the opening / closing valve can be switched between the open state and the closed state.

The invention according to claim 6 is the air conditioner according to claim 5, further comprising an on / off switching timer unit for measuring an elapsed time when the on-off valve of the oil return circuit is closed,
The control unit opens the on-off valve of the oil return circuit when the elapsed time measured by the on-off switching timer unit reaches a predetermined elapsed time.

  In situations such as during intermediate operation, the amount of oil discharged from the compressor is small, so the on-off valve of the oil return circuit is closed to reduce the amount of refrigerant circulating in the refrigerant circuit. If the oil is not returned to the compressor over a long period of time even if it is time, etc., the lubrication operation of the internal mechanism of the compressor may be hindered. When the elapsed time when the on-off valve of the oil return circuit is closed (the elapsed time measured by the on / off switching timer unit) reaches a predetermined elapsed time, the detected rotational speed and the calculated Even if the temperature load satisfies any of the above conditions, the on-off valve of the oil return circuit is opened to ensure the lubrication operation of the internal mechanism of the compressor. This makes it possible to more accurately determine which of the lubrication operation of the internal mechanism of the compressor and the efficient refrigeration cycle operation operation should be prioritized.

  According to the present invention, it is possible to perform the refrigeration cycle operation more efficiently than before, while appropriately returning the oil (refrigeration oil) to the compressor and ensuring the lubrication operation of the internal mechanism of the compressor. .

It is a refrigerant circuit figure showing a schematic structure of an air harmony machine concerning an embodiment of the present invention. It is a block diagram which shows schematic structure of a controller. It is a flowchart which shows the flow of the process at the time of the oil return control in an air conditioner. It is a flowchart which shows the control at the time of returning a solenoid valve from a closed state to an open state.

  Hereinafter, an air conditioner according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a refrigerant circuit diagram showing a schematic configuration of an air conditioner according to an embodiment of the present invention.

  As shown in FIG. 1, an air conditioner 1 as a refrigeration apparatus according to this embodiment includes one outdoor unit 2 and one indoor unit 3. Among these, the air conditioner 1 also includes a refrigerant circuit 15 that performs a vapor compression refrigeration cycle by circulating the refrigerant.

  The refrigerant circuit 15 includes an outdoor circuit 20, an indoor circuit 30, a liquid side communication pipe 16, and a gas side communication pipe 17. The indoor circuit 30 is connected to the outdoor circuit 20 via the liquid side communication pipe 16 and the gas side communication pipe 17.

  The outdoor circuit 20 is housed in the outdoor unit 2. The outdoor circuit 20 is provided with a compressor 40, a four-way switching valve 21, an outdoor heat exchanger 22, an expansion valve 24, a receiver 23, a liquid side closing valve 25, and a gas side closing valve 26.

  The compressor 40 is a hermetic scroll compressor. The compressor 40 is configured by housing a compression mechanism and an electric motor that drives the compression mechanism in a cylindrical housing. The compression mechanism and the electric motor are not shown. The compressor 40 is configured to be variable in capacity by changing the rotational speed of the motor stepwise or continuously by control by a control unit described later.

  A suction pipe 43 that is a low-pressure gas pipe and a discharge pipe 44 that is a high-pressure gas pipe are respectively connected to the compressor 40. The suction pipe 43 is configured so that the refrigerant sucked into the compressor 40 flows, while the discharge pipe 44 is configured so that the refrigerant discharged from the compressor 40 flows. The suction pipe 43 has an inlet end connected to the first port of the four-way switching valve 21 and an outlet end connected to the suction side of the compressor 40. The discharge pipe 44 has an inlet end connected to the discharge side of the compressor 40 and an outlet end connected to the second port of the four-way switching valve 21.

  The four-way switching valve 21 has a third port connected to the gas-side shutoff valve 26 by piping, and a fourth port connected to the upper end of the outdoor heat exchanger 22 by piping. The four-way switching valve 21 includes a state in which the first port and the third port communicate with each other and a state in which the second port and the fourth port communicate with each other (a state indicated by a solid line in FIG. 1), the first port, The state is switched to a state (state indicated by a broken line in FIG. 1) in which the four ports communicate with each other and the second port and the third port communicate with each other. By the switching operation of the four-way switching valve 21, the refrigerant circulation direction in the refrigerant circuit 15 is reversed.

  The outdoor heat exchanger 22 is configured by a cross fin type fin-and-tube heat exchanger. In the outdoor heat exchanger 22, the refrigerant circulating in the refrigerant circuit 15 and the outdoor air exchange heat.

  One end of the outdoor heat exchanger 22 is connected to the liquid side communication pipe 16 via a bridge circuit 28. The bridge circuit 28 is configured by connecting the first pipeline 281, the second pipeline 282, the third pipeline 283, and the fourth pipeline 284 in a bridge shape. In the bridge circuit 28, the outlet end of the first pipe line 281 is connected to the outlet end of the second pipe line 282, the inlet end of the second pipe line 282 is connected to the outlet end of the third pipe line 283, and the third pipe The inlet end of the passage 283 is connected to the inlet end of the fourth conduit 284, and the outlet end of the fourth conduit 284 is connected to the inlet end of the first conduit 281. In the bridge circuit 28, the inlet end of the first conduit 281 and the outlet end of the fourth conduit 284 are on the outdoor heat exchanger 282 side, and the inlet end of the second conduit 282 and the outlet end of the third conduit 283 are liquid. It is arranged on the side communication pipe 16 side.

  Each of the first to fourth pipelines 281 to 284 is provided with one check valve. The first conduit 281 is provided with a check valve CV-1 that allows only the refrigerant to flow from the inlet end to the outlet end. The second pipe 282 is provided with a check valve CV-2 that allows only the refrigerant to flow from the inlet end to the outlet end. The third pipe 283 is provided with a check valve CV-3 that allows only the refrigerant to flow from the inlet end to the outlet end. The fourth pipe 284 is provided with a check valve CV-4 that allows only the refrigerant to flow from the inlet end to the outlet end.

  The receiver 23 is a cylindrical container and stores a refrigerant. One end of the receiver 23 is connected to the outlet end of the first pipeline 281 and the outlet end of the second pipeline 282 in the bridge circuit 28 by piping. The other end of the receiver 23 is connected by piping to the inlet end of the third pipeline 283 and the inlet end of the fourth pipeline 284 in the bridge circuit 28. An expansion valve 24 is provided in the pipe connecting the lower end of the receiver 23 and the bridge circuit 28. The expansion valve 24 is a so-called electric expansion valve.

  The outdoor circuit 20 is further provided with a gas vent pipe 35 and a pressure equalizing pipe 37. The gas vent pipe 35 has one end connected to the receiver 23 and the other end connected to the suction pipe 43. The degassing pipe 35 is provided to introduce the gas refrigerant of the receiver 23 to the suction side of the compressor 40 and depressurize the receiver 23. The gas vent pipe 35 is provided with a gas vent solenoid valve 36.

  One end of the pressure equalizing pipe 37 is connected between the gas venting electromagnetic valve 36 and the receiver 23 in the gas venting pipe 35, and the other end is connected to the discharge pipe 44. The pressure equalizing pipe 37 is provided with a pressure equalizing check valve 38 that allows only the refrigerant to flow from one end to the other end. The pressure equalizing pipe 37 prevents the receiver 23 from bursting by allowing the gas refrigerant to escape when the outside air temperature rises abnormally and the pressure of the receiver 23 becomes too high while the air conditioner 1 is stopped. Therefore, the refrigerant does not flow through the pressure equalizing pipe 37 during the operation of the air conditioner 1.

  The air conditioner 1 according to the present embodiment is provided with an oil separator 51 and an oil return pipe 52. The oil separator 51 is provided in the discharge pipe 44 of the compressor 40 and separates refrigeration oil (hereinafter referred to as oil) from the refrigerant discharged from the compressor 40. The oil return pipe 52 is provided by connecting the oil separator 51 and the suction pipe 43 of the compressor 40 in order to return the oil separated by the oil separator 51 to the suction side of the compressor 40. Further, the oil return pipe 52 is provided with an electromagnetic valve 53 as an open / close valve that allows the oil separator 51 and the suction side of the compressor 40 to be in a communication state or a communication cut-off state by making the oil return pipe 52 freely openable and closable. It has been. The oil return pipe 52 is further provided with a capillary tube 54 as an example of a pressure reducing mechanism connected in series to the electromagnetic valve 53. The oil return circuit 55 includes the electromagnetic valve 53 and the capillary tube 54, and controls whether oil is returned to the suction side of the compressor 40 by opening and closing the electromagnetic valve 53. That is, the oil return circuit 55 supplies the oil in the oil separator 51 to the compressor 40 when the electromagnetic valve 53 is in the open state, and the oil return circuit 55 in the oil separator 51 when the electromagnetic valve 53 is in the closed state. Oil is not supplied to the compressor. That is, the amount of oil that the oil return circuit 55 returns to the compressor 40 is controlled by opening / closing the electromagnetic valve 53 and restricting the oil return pipe 52 by the capillary tube 54.

  The indoor circuit 30 is provided in the indoor unit 3. The indoor circuit 60 is provided with an indoor heat exchanger 61. The indoor heat exchanger 61 is configured by a cross fin type fin-and-tube heat exchanger. In the indoor heat exchanger 61, the refrigerant circulating in the refrigerant circuit 15 and the room air exchange heat.

  One end of the liquid side communication pipe 16 is connected to the liquid side closing valve 25, and the other end is connected to one end of the indoor heat exchanger 61 in the indoor circuit 60. One end of the gas side communication pipe 17 is connected to the gas side closing valve 26, and the other end is connected to the other end of the indoor heat exchanger 61.

  The outdoor unit 2 is provided with an outdoor fan 70. The outdoor fan 70 sends outdoor air to the outdoor heat exchanger 2. On the other hand, the indoor unit 3 is provided with an indoor fan 80. The indoor fan 80 sends room air to the indoor heat exchanger 61.

  The outdoor unit 2 is provided with various sensors. Specifically, the outdoor unit 2 is provided with an outside air temperature sensor 71 for detecting the temperature of the outdoor air. In the outdoor unit 2, an outdoor heat exchanger temperature sensor 72 for detecting the heat transfer tube temperature is provided below the outdoor heat exchanger 22. The outdoor heat exchanger 22 is provided with an outdoor heat exchanger pressure sensor 76 for detecting the internal refrigerant pressure. The outdoor heat exchanger pressure sensor 76 detects the condensation pressure during the cooling operation described later, and detects the evaporation pressure during the heating operation.

  The suction pipe 43 of the compressor 40 is provided with a suction pipe temperature sensor 73 for detecting the suction refrigerant temperature of the compressor 40. Each discharge pipe 44 is provided with a discharge pipe temperature sensor 75 for detecting the discharge refrigerant temperature of the compressor 40. Further, the compressor 40 is provided with a drive current sensor 77 that detects a drive current value of the compressor 40 and a frequency sensor (an example of a rotation speed detection unit) 78 that detects a drive frequency of the compressor 40. ing.

  The indoor unit 3 is provided with sensors for temperature and humidity. Specifically, the indoor unit 3 is provided with a suction air temperature sensor 81 and a blown air temperature sensor 82. The intake air temperature sensor 81 detects the temperature of the indoor air sucked into the indoor unit 3, that is, the intake air temperature of the indoor unit 3. The blown air temperature sensor 82 detects the temperature of the air blown from the indoor unit 3, that is, the blown air temperature of the indoor unit 3. Furthermore, in the indoor unit 3, an indoor heat exchanger temperature sensor 84 for detecting the heat transfer tube temperature is provided below the indoor heat exchanger 61. Furthermore, the indoor heat exchanger 61 is provided with an indoor heat exchanger pressure sensor 85 for detecting the internal refrigerant pressure. The indoor heat exchanger pressure sensor 85 detects the evaporation pressure during the cooling operation described later, and detects the condensation pressure during the heating operation.

  The outdoor unit 2 is provided with a controller 90. The controller 90 controls the operation of the air conditioner 1 in response to a signal from the sensors and a command signal from a remote controller or the like.

  FIG. 2 is a block diagram illustrating a schematic configuration of the controller 90.

  The controller 90 includes a control unit 91, a temperature load calculation unit 92, a timer 93, and an input reception unit 94.

  The controller 91 adjusts the opening degree of the expansion valve 24, switches the four-way switching valve 21, and opens / closes the gas vent solenoid valve 36. In addition, the control unit 91 performs capacity control of the compressor 40 and air volume control of the outdoor fan 70 and the indoor fan 80. Further, the control unit 91 controls the open / close state of the electromagnetic valve 53 according to the driving frequency of the compressor 40 detected by the frequency sensor 78 and the temperature load calculated by the temperature load calculation unit 92. Details of the opening / closing control of the electromagnetic valve 53 by the controller 91 will be described later.

  The temperature load calculation unit 92 receives the temperature of the indoor air detected by the suction air temperature sensor 81 (the temperature of the room subject to air conditioning control by the air conditioner 1) and the input receiving unit 94 receives from the operator. The difference from the target room temperature is calculated as a temperature load.

  A timer (timer unit, open / close switching timer unit) 93 measures various times. For example, the timer 93 measures the time during which the drive frequency of the compressor 40 detected by the frequency sensor 78 and the temperature load calculated by the temperature load calculation unit 92 are in a state that satisfies a predetermined condition described later. To do. The timer 93 measures the elapsed time that the electromagnetic valve 53 of the oil return circuit 55 is closed.

  The input receiving unit 94 receives inputs such as a start instruction for starting the air conditioner 1 and an instruction for a target room temperature, which are input by an operator to an operation panel (not shown) provided in the indoor unit 3 or the outdoor unit 2. is there.

  Next, the operation of the air conditioner 1 will be described. During the operation of the air conditioner 1, the refrigerant circulates while changing phase in the refrigerant circuit 15 to perform a vapor compression refrigeration cycle. The air conditioner 1 performs a cooling operation and a heating operation.

  << Cooling Operation >> During the cooling operation, the indoor heat exchanger 61 functions as an evaporator and a cooling operation is performed. During the cooling operation, the four-way switching valve 21 is in a state indicated by a solid line in FIG. The expansion valve 24 is adjusted to a predetermined opening. The degas solenoid valve 36 is appropriately opened and closed. These valves 24 and 36 are controlled by the controller 91 of the controller 90.

  When the compressor 40 is operated, the refrigerant compressed by the compressor 40 is discharged to the discharge pipe 44. This discharged refrigerant flows into the outdoor heat exchanger 22 through the four-way switching valve 21. In the outdoor heat exchanger 22, the refrigerant dissipates heat to the outdoor air and condenses. The refrigerant condensed in the outdoor heat exchanger 22 flows into the first pipe 281 of the bridge circuit 28, passes through the check valve CV-1, and flows into the receiver 23.

  Only the liquid refrigerant flows out from the receiver 23 toward the expansion valve 24. The refrigerant that has flowed out of the receiver 23 is depressurized by the expansion valve 24, and then flows into the third conduit 33 of the bridge circuit 28. Thereafter, the refrigerant passes through the check valve CV-3 and the outflow check valve 34 and is sent to the indoor circuit 60 through the liquid side communication pipe 16.

  The refrigerant that has flowed into the indoor circuit 60 is introduced into the indoor heat exchanger 61. In the indoor heat exchanger 61, the refrigerant absorbs heat from the indoor air and evaporates. That is, the refrigerant introduced into the indoor circuit 60 evaporates in the indoor heat exchanger 61, and as a result, the indoor air is cooled.

  The refrigerant evaporated in the indoor heat exchanger 61 flows into the outdoor circuit 20 through the gas side communication pipe 17. Thereafter, the refrigerant passes through the four-way switching valve 21 and is sucked into the compressor 40 through the suction pipe 43. The compressor 40 compresses the sucked refrigerant and discharges it again. In the refrigerant circuit 15, such refrigerant circulation is repeated.

  As described above, the controller 91 of the controller 90 adjusts the opening degree of the expansion valve 24. At that time, the control unit 91 adjusts the opening degree of the expansion valve 24 so that the degree of superheat of the gas refrigerant flowing out of the indoor heat exchanger 61 becomes constant. Specifically, the opening degree of the expansion valve 24 is appropriately changed so that the difference between the detected temperature of the suction pipe temperature sensor 73 and the detected temperature of the indoor heat exchanger temperature sensor 84 is maintained at a predetermined value.

  On the other hand, the oil separator 51 separates oil from the refrigerant discharged from the compressor 40. At this time, if the solenoid valve 53 is in a closed state, the flow of the refrigerating machine oil in the oil return pipe 52 is blocked. On the other hand, when the electromagnetic valve 53 is open, the separated oil in the oil separator 51 flows through the oil return pipe 52 to the suction side of the compressor 40. The electromagnetic valve 53 is opened and closed by the control unit 91 as described above.

  << Heating Operation >> During the heating operation, the indoor heat exchanger 61 functions as a condenser, and a heating operation is performed. During the heating operation, the four-way switching valve 21 is in a state indicated by a broken line in FIG. The expansion valve 24 is adjusted to a predetermined opening. The degas solenoid valve 36 and the solenoid valve 53 are appropriately opened and closed. These valves 24, 36, 53 are operated by the control unit 91.

  When the compressor 40 is operated, the refrigerant compressed by the compressor 40 is discharged to the discharge pipe 44. The refrigerant flows from the four-way switching valve 21 toward the gas-side closing valve 26 and flows into the indoor circuit 30 through the gas-side communication pipe 17.

  The refrigerant that has flowed into the indoor circuit 30 is introduced into the indoor heat exchanger 61. In the indoor heat exchanger 61, the refrigerant dissipates heat to the indoor air and condenses. That is, the refrigerant introduced into the indoor circuit 30 is condensed in the indoor heat exchanger 61, and as a result, the indoor air is heated.

  The refrigerant condensed in the indoor heat exchanger 61 flows into the outdoor circuit 20 through the liquid side communication pipe 16. Thereafter, the refrigerant once flows into the receiver 23 through the second pipe 282 of the bridge circuit 28. The liquid refrigerant flowing out from the receiver 23 is decompressed by the expansion valve 24 and then introduced into the outdoor heat exchanger 22 through the fourth pipe 284 of the bridge circuit 28.

  In the outdoor heat exchanger 22, the refrigerant absorbs heat from the outdoor air and evaporates. The refrigerant evaporated in the outdoor heat exchanger 22 passes through the four-way switching valve 21 and is sucked into the compressor 40 through the suction pipe 43. The compressor 40 compresses the sucked refrigerant and discharges it again. In the refrigerant circuit 15, such refrigerant circulation is repeated.

  As described above, the controller 91 of the controller 90 adjusts the opening degree of the expansion valve 24. At that time, the controller 91 adjusts the opening degree of the expansion valve 24 so that the degree of superheat of the gas refrigerant flowing out of the outdoor heat exchanger 22 is constant. Specifically, the opening degree of the expansion valve 24 is appropriately changed so that the difference between the temperature detected by the suction pipe temperature sensor 73 and the temperature detected by the outdoor heat exchanger temperature sensor 72 is maintained at a predetermined value.

  Further, as in the case of the cooling operation, the oil separator 51 separates oil from the refrigerant discharged from the compressor 40. When the solenoid valve 53 is closed, the oil flow in the oil return pipe 52 is blocked. On the other hand, when the electromagnetic valve 53 is in the open state, the separated oil in the oil separator 51 is supplied to the suction side of the compressor 40 through the oil return pipe 52.

  Next, oil return control (opening / closing control of the electromagnetic valve 53 of the oil return circuit 55) in the air conditioner 1 will be described. FIG. 3 is a flowchart showing the flow of processing during oil return control in the air conditioner 1. FIG. 4 is a flowchart showing control when the electromagnetic valve 53 is returned from the closed state to the open state.

  In the oil return control (open / close control of the electromagnetic valve 53 of the oil return circuit 55), the input receiving unit 94 receives an instruction to start the air conditioner 1 from the operator, and the control unit 91 controls the outdoor unit 2 and the indoor unit 3 to operate. This is performed after starting the air conditioning operation.

  That is, the timer 93 measures an elapsed time after the start start control is finished and outputs the measured time to the control unit 91. The control unit 91 passes a predetermined time (elapsed time after the start start control is finished). For example, it is determined from the output from the timer 93 whether it has reached 10 minutes (S1). When the elapsed time since the end of the start start control has not reached the predetermined time, that is, during the start start control or after the end of the start start control, (YES in S1), the oil return control according to the drive frequency and temperature load of the compressor 40 described later is not performed, and the electromagnetic valve 53 of the oil return circuit 55 is left open (S9).

  On the other hand, when the elapsed time after the end of the start-up control has reached a predetermined time (NO in S1), the control unit 91 acquires the drive frequency of the compressor 40 from the frequency sensor 78 (S2), and further The temperature load calculation unit 92 calculates the difference between the temperature of the room air detected by the intake air temperature sensor 81 and the target room temperature received from the operator by the input receiving unit 94 as a temperature load (S3). ).

  Here, the control unit 91 (1) the drive frequency is smaller than a predetermined value (for example, 120 Hz), and (2) the temperature load is based on a predetermined value (for example, 3.0 ° C.). Is also smaller (S4).

  If both conditions (1) and (2) are not satisfied (NO in S4), the controller 91 does not satisfy both conditions (1) and (2) based on the output from the timer 93. It is determined whether the elapsed time from the time when the state is reached has reached a predetermined time (S8). That is, after entering the processing of S2 and S3, the control unit 91 always obtains the driving frequency of the compressor 40 from the frequency sensor 78, calculates the temperature load by the temperature load calculation unit 92, and 1) It is determined whether or not a state where both conditions of (2) are not satisfied continues for the predetermined time. When the elapsed time reaches a predetermined time (for example, 5 minutes) (YES in S8), the controller 91 changes or maintains the electromagnetic valve 53 of the oil return circuit 55 to an open state (S9). If the control unit 91 determines that the state has been changed to a state satisfying both conditions (1) and (2) before the elapsed time is reached (NO in S8), the process returns to S2.

  In addition, when both of these conditions (1) and (2) are satisfied (YES in S4), the control unit 91 performs predetermined protection control (for example, defrost or gas shortage protection) in the refrigeration cycle operation being performed. Etc.) is determined (S5). When it is determined that the predetermined protection control is being performed (YES in S5), control unit 91 returns the process to S2.

  When it is determined that the predetermined protection control is not performed (NO in S5), the control unit 91 satisfies both the conditions (1) and (2) based on the output from the timer 93, And it is judged whether the elapsed time from the time it reached the state which has not entered into the predetermined protection control has reached a predetermined time (S6). That is, after entering the processes of S2 and S3, the control unit 91 always obtains the driving frequency of the compressor 40 from the frequency sensor 78, calculates the temperature load by the temperature load calculation unit 92, and further determines the predetermined value. Is in a state where both of the conditions (1) and (2) are satisfied and the predetermined protection control is not performed. It is determined whether or not the predetermined time is continued. When the elapsed time reaches a predetermined time (for example, 5 minutes) (YES in S6), the controller 91 changes or maintains the electromagnetic valve 53 of the oil return circuit 55 in the closed state (S7). In addition, the control unit 91 does not satisfy both conditions (1) and (2) (the condition that does not satisfy at least one of the conditions (1) and (2)) before the elapsed time is reached. ), Or if it is determined that the predetermined protection control has been performed (NO in S6), the process returns to S2.

  That is, the control unit 91 satisfies the above conditions (1) and (2), and the condition that the protection control such as defrost or out-of-gas protection is not performed is continued for a certain period of time. The electromagnetic valve 53 of the return circuit 55 is closed. As a result, in a situation where the amount of refrigerant and oil discharged from the compressor 40 is small, the amount of refrigerant in the refrigerant circuit 15 passing through the oil return pipe 52 is suppressed, and the internal mechanism of the compressor 40 is lubricated. A smooth refrigeration cycle operation is ensured without hindering and preventing the amount of refrigerant flowing through the refrigerant circuit 15 from decreasing. On the other hand, in a situation where the capacity of the compressor 40 is increased or the above-described predetermined protection control is performed and the refrigerant and oil discharged from the compressor 40 increase, the electromagnetic valve 53 is opened. By causing the oil return circuit 55 to return the oil to the compressor 40 and giving priority to the lubricating operation of the internal mechanism of the compressor 40, a smooth refrigeration cycle operation is ensured.

  However, as shown in FIG. 4, when the electromagnetic valve 53 is in the closed state (S11), the control unit 91 has elapsed time after switching the electromagnetic valve 53 to the closed state based on the output from the timer 93. Is determined to have reached a predetermined time (for example, 30 minutes) (S12), and if the elapsed time after switching the electromagnetic valve 53 to the closed state has reached the predetermined time (YES in S12) Then, the electromagnetic valve 53 is switched to the open state (S13).

  In other words, the amount of oil discharged from the compressor 40 is small in situations such as during an intermediate operation in which the rotational speed of the compressor is reduced in accordance with the temperature load, so the solenoid valve 53 of the oil return circuit 55 Can be improved by reducing the amount of the refrigerant circulating in the refrigerant circuit 15 and the refrigeration cycle operation efficiency can be improved. If the oil return is not performed, the lubrication operation of the internal mechanism of the compressor 40 may be hindered. Therefore, when the solenoid valve 53 remains in the closed state for a long time, the driving frequency of the compressor 40 and the calculation are calculated. Even if the applied temperature load satisfies both of the above conditions, the solenoid valve 53 of the oil return circuit 55 is opened, and the amount of oil returned to the compressor 40 is increased, so that the internal mechanism of the compressor 40 is lubricated. Secure.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made.

  In short, according to the present invention, the control unit 91 controls the electromagnetic valve 53 of the oil return circuit 55 to be closed when the conditions satisfying both the above conditions (1) and (2) have continued for a certain period of time. Is to do.

  For example, in the above embodiment, the controller 91 satisfies both the above conditions (1) and (2), and the state in which protection control such as defrost or out-of-gas protection is not performed continues for a certain period of time. However, the present invention is not limited to this embodiment, and both conditions (1) and (2) are satisfied. The control unit 91 can close the solenoid valve 53 of the oil return circuit 55 when the state that has been satisfied continues for a certain period of time.

  Moreover, in the said embodiment, although the solenoid valve 53 and the capillary tube 54 were provided in the oil return circuit 55, this invention is not limited to the said form, A capillary tube is provided in the oil return circuit 55. It is also possible to employ a configuration in which the amount of oil flowing through the oil return circuit 55 is adjusted by opening / closing control of the electromagnetic valve 53 as an example of the opening / closing valve.

  Moreover, as shown in the said embodiment, the control part 91 is based on the drive frequency of the compressor 40, and the said temperature load during starting start control of the air conditioner 1, or until fixed time passes after starting control end. Although it is preferable not to perform opening / closing control of the solenoid valve 53 of the oil return circuit 55 (S1 in FIG. 3), it is possible to grasp the present invention as not performing the control shown in S1 of FIG. .

  Further, as shown in the above embodiment, when the elapsed time after switching the electromagnetic valve 53 to the closed state reaches the predetermined time (YES in S12 in FIG. 4), the control unit 91 determines that the electromagnetic valve 53 Although it is preferable to switch 53 to the open state (S13), it is possible to grasp the present invention as not performing the control shown in S12 and S13.

  Moreover, in the said embodiment, the control part 91 acquires the drive frequency of the compressor 40 from the frequency sensor 78, and uses the drive frequency of the compressor 40 as a rotation speed of the compressor 40, S2 shown in FIG. Although the following processing is performed, the present invention is not limited to the processing using the driving frequency, and performs control for opening and closing the electromagnetic valve 53 based on the rotational speed of the compressor 40 (for example, a control unit). 91 includes control for opening and closing the electromagnetic valve 53 based on the drive current value of the compressor 40 detected by the drive current sensor 77).

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Outdoor unit 3 Indoor unit 40 Compressor 51 Oil separator 52 Oil return pipe 53 Solenoid valve 54 Capillary tube 55 Oil return circuit 60 Indoor circuit 61 Indoor heat exchanger 71 Outdoor temperature sensor 72 Outdoor heat exchanger temperature sensor 73 Intake pipe temperature sensor 75 Discharge pipe temperature sensor 76 Outdoor heat exchanger pressure sensor 77 Drive current sensor 78 Frequency sensor 81 Suction air temperature sensor 90 Controller 91 Control unit 92 Temperature load calculation unit 93 Timer 94 Input reception unit

Claims (6)

A refrigerant circuit in which a refrigerant circulates and performs a vapor compression refrigeration cycle;
A compressor provided in the refrigerant circuit;
An oil separator for separating oil from refrigerant discharged from the compressor;
An oil return pipe for returning the oil separated by the oil separator to the suction side of the compressor;
An on-off valve that can freely open and close the oil return pipe, and an oil return circuit that returns oil to the suction side of the compressor by opening and closing the on-off valve;
A rotational speed detector for detecting the rotational speed of the compressor;
A temperature load calculating unit that calculates a temperature load that is a difference between a room temperature that is a target of air conditioning control by the air conditioner and a set target room temperature;
When the condition that the rotation speed detected by the rotation speed detection unit is smaller than a predetermined rotation number and the temperature load calculated by the temperature load calculation unit is smaller than a predetermined value, in the opening and closing valve of the oil return circuit and closed so as not to supply the oil in the oil separator to the compressor, the said detected by the rotation number detection unit speed is a predetermined rotational speed or more An air conditioner comprising: a control unit that opens an on-off valve of the oil return circuit when there is a condition that the temperature load calculated by the temperature load calculation unit is equal to or greater than a predetermined value.   The air conditioner according to claim 1, wherein the oil return circuit further includes a pressure reducing mechanism connected in series to the on-off valve in the oil return pipe.   The control unit does not perform on-off valve opening / closing control of the oil return circuit based on the detected rotation speed and the calculated temperature load at least during start-up control of the air conditioner. 2. The air conditioner according to 2.   The control unit determines whether or not a predetermined protection control is being performed, the detected rotational speed is smaller than the predetermined rotational speed, and the calculated temperature load is predetermined. The on-off valve of the oil return circuit is closed when it is determined that the condition that the value is smaller than a predetermined value is satisfied and the condition that the protection control is not entered is determined. 4. The air conditioner according to any one of 3. A timer unit that measures the time in which the above conditions are satisfied is provided,
The control unit opens and closes the on-off valve of the oil return circuit only when the time measured by the timer unit reaches a predetermined time, assuming that the condition to be measured by the timer is satisfied. The air conditioner according to any one of claims 1 to 4, wherein control is performed. An open / close switching timer unit for measuring an elapsed time when the on-off valve of the oil return circuit is closed;
The air conditioner according to claim 5, wherein the control unit opens the on-off valve of the oil return circuit when the elapsed time measured by the on-off switching timer unit reaches a predetermined elapsed time. .

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