JP5223873B2 - Air conditioner - Google Patents

Description

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

  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, and then cooled to low temperature and low pressure in the expansion device. 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 sucked 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. Therefore, in order to reliably return the discharged refrigeration oil to the compressor and operate the compressor normally, in the conventional air conditioner, as shown in Patent Document 1 below, the discharge port and the suction port of the compressor An oil return circuit having an oil separator and an open / close valve is provided in between, and the refrigerating machine oil contained in the refrigerant discharged from the compressor is separated by the oil separator, and the separated refrigerating machine oil is supplied to the open / close valve. And the mechanism which returns to a compressor through a pressure reduction mechanism is employ | adopted.

JP-A-8-189732

  In the conventional air conditioner, by controlling the opening / closing operation of the on-off valve, the circuit is switched between the circuit open state in which the refrigerant is allowed to pass through the oil return circuit and the circuit closed state in which the refrigerant is not allowed to pass. The amount of refrigerating machine oil to be returned is controlled. From the viewpoint of energy saving (low power consumption), it is desired to further reduce the electric power required for controlling the opening / closing operation of the opening / closing valve. Furthermore, even when opening / closing operation control of the on-off valve becomes impossible due to disconnection or the like, there is a need for reliability that can reliably return the refrigeration oil from the oil return circuit to the compressor.

  The present invention has been made to solve the above-described problem, and is used for controlling the opening / closing operation of an on-off valve for controlling the amount of refrigeration oil returned to the compressor while appropriately returning the refrigeration oil to the compressor. The purpose is to further reduce the power required.

The invention according to claim 1 of the present invention comprises a refrigerant circuit (15) for performing a vapor compression refrigeration cycle by circulating a refrigerant,
A compressor (40) provided in the refrigerant circuit (15);
An oil separator (51) for separating refrigeration oil from refrigerant discharged from the discharge side of the compressor (40);
An oil return pipe (52) for returning the refrigeration oil separated by the oil separator (51) to the suction side of the compressor (40);
An on-off valve (53) provided downstream of the oil separator (51) in the oil return pipe (52), the oil return pipe (52) being closed when energized and opened when not energized; ,
An air conditioner (1) provided with a pressure reducing mechanism (54) that is provided in series with the on-off valve in the oil return pipe (52) and depressurizes the refrigerant after passing through the on-off valve (53). is there.

  In the present invention, the on-off valve is provided in the oil return pipe on the downstream side of the oil separator, and the oil return pipe is closed when energized and opened when not energized. Generally, the compressor discharges more refrigeration oil in the high rotation range.In the present invention, the oil return pipe can be opened without energizing the on-off valve in the high rotation range. Refrigerating machine oil can be reliably returned to the compressor without consumption.

  In addition, when the compressor is in the low rotation range, the amount of refrigeration oil discharged is small, and even if the on-off valve is closed, the amount of refrigeration oil that returns to the compressor is unlikely to be insufficient, so the compressor will run at low speed. It is possible to close the on-off valve in the case of a region, and even if power consumption is required for energization to close the on-off valve, Due to the closed state of the on-off valve, the refrigerant circulation amount of the main refrigerant circuit is increased, so that the capacity of the compressor can be efficiently extracted in the intermediate performance (region in the low rotation range). As a result, it can contribute to improving APF (annual energy consumption efficiency), which is an index of annual power consumption.

  On the other hand, even if energization to the on / off valve becomes impossible due to disconnection or the like, the on / off valve is opened by the de-energized state at this time, so the reliability of returning the refrigeration oil to the compressor is ensured. Is done. For example, in the case of the prior art in which the on-off valve is opened when energized, it is necessary to provide two systems of oil return pipes in order to avoid a state in which the compressor oil does not return to the compressor due to a failure of the on-off valve due to disconnection or the like. In the present invention, as described above, even when the disconnection occurs, the on-off valve is open, and a state in which the refrigeration oil cannot be returned to the compressor is avoided. Therefore, one oil return pipe is sufficient.

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

  In general, the refrigeration oil discharged from the compressor is surely returned to the compressor to keep the compressor operating normally, so that it is not necessary to return the oil (that is, the on-off valve is closed). The good period) is shorter than the period during which the oil is returned in the open state. In the present invention, since the on-off valve is closed by energization only when necessary, it takes less time to energize the conventional on-off valve that is de-energized only in the closed state, leading to energy saving. .

The invention according to claim 2 is the air conditioner (1) according to claim 1, wherein the on-off valve (53) is switched between energized and de-energized states, and the on-off valve (53) A control unit (91) for driving and controlling the opening and closing operation;
A rotation speed detector (78) for detecting the rotation speed of the compressor (40),
When the rotational speed detected by the rotational speed detection section (78) belongs to a predetermined high rotational speed range, the controller (91) opens the on-off valve (53), and When the rotational speed detected by the rotational speed detector (78) belongs to a predetermined low rotational speed range, the on-off valve (53) is closed.

  According to this invention, the rotational speed detected by the rotational speed detection unit belongs to a predetermined low rotational speed range, the amount of refrigerant discharged from the compressor and the amount of refrigerating machine oil contained in the refrigerant is small, and the oil return In the situation such as during the intermediate operation where there is little hindrance to the compressor operation even if the oil return operation by the pipe is interrupted, the control unit closes the on-off valve so that the amount of refrigerant flowing into the oil return pipe is reduced. By reducing, it is possible to suppress a reduction in the amount of refrigerant circulating through the refrigerant circuit, which is the main circuit of refrigerant circulation, and to prioritize efficient refrigeration cycle operation. On the other hand, when the rotation speed detected by the rotation speed detection unit belongs to a predetermined high rotation speed range and the amount of refrigerant discharged from the compressor and the amount of oil contained in the refrigerant is large. The control unit prioritizes and secures the lubricating operation of the internal mechanism of the compressor by returning the refrigerating machine oil to the compressor by opening the on-off valve. As a result, according to the present invention, it is possible to perform the refrigeration cycle operation more efficiently than before, while appropriately returning the refrigeration oil to the compressor and ensuring the lubrication operation of the internal mechanism of the compressor. .

The invention according to claim 3 is the air conditioner (1) according to claim 2, further comprising a refrigerant pressure adjusting mechanism (40) for adjusting the refrigerant pressure in the oil return pipe (52). Prepared,
The controller (91) drives and controls the refrigerant pressure adjusting mechanism (40, 24) when opening and closing the on-off valve (53), and determines the refrigerant pressure in the oil return pipe (52) in advance. Then, the valve (53) is opened / closed after being temporarily lowered to a predetermined value.

In the present invention, the control unit drives and controls the refrigerant pressure adjusting mechanism to temporarily lower the refrigerant pressure in the oil return pipe to a predetermined value, and then causes the on-off valve to perform an opening / closing operation. The opening / closing operation of the opening / closing valve provided in the oil return pipe is reliably performed. The on-off valve that is closed when energized and opened when de-energized is greatly affected by the pressure of the refrigerant passing through the oil return pipe due to its mechanism. Therefore, in the present invention, the refrigerant pressure in the oil return pipe Is reduced for a certain period of time during which the on-off valve performs the on-off operation, and the on-off valve performs the on-off operation, thereby reducing the influence of the refrigerant pressure on the on-off operation and ensuring the on-off operation of the on-off valve. To do.
Further, the control unit (91), the rotation number detected by the rotation number detection unit (78) belongs to a predetermined low rotation speed range, and when the on-off valve (53) is closed, Control may be performed to return the on-off valve (53) to an open state when a predetermined time has elapsed.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to further reduce the electric power required for opening / closing operation control of the on-off valve for controlling the quantity of the refrigerating machine oil returned to a compressor, returning a refrigerating machine oil appropriately with respect to a compressor. .

It is a refrigerant circuit figure showing a schematic structure of an air harmony device concerning an embodiment of the present invention. It is a block diagram which shows schematic structure of a controller. It is a conceptual diagram which shows the oil return control in an air conditioning apparatus. It is a flowchart which shows the flow of the process at the time of the oil return control in an air conditioning apparatus. It is a sectional side view which shows schematic structure of the solenoid valve closed at the time of electricity supply.

  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 illustrating a schematic configuration of an air-conditioning apparatus 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 outdoor circuit 20 and the indoor circuit 30 are connected via a liquid side communication pipe 16 and a 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, an accumulator 23, a liquid side closing valve 25, and a gas side closing valve 26.

  The compressor 40 is, for example, 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 detailed illustration of the compression mechanism and the electric motor is omitted. 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. In the suction pipe 43, the refrigerant sucked into the compressor 40 flows. The refrigerant discharged from the compressor 40 flows through the discharge pipe 44. The suction pipe 43 has an inlet end connected to the first port of the four-way switching valve 21 via the accumulator 23, 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 via the oil separator 51.

  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 and the second port and the third port communicate. 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, for example, 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 by piping.

  The accumulator 23 is a cylindrical container, and stores the refrigerant so that the liquid refrigerant and the gas refrigerant are separated and the gas refrigerant is sucked into the compressor 40. The accumulator 23 is provided in a suction pipe 43 that connects the four-way switching valve 21 and the compressor 40.

  An oil return circuit 55 is provided in the outdoor circuit 20 provided in the air conditioner 1 according to the present embodiment. The oil return circuit 55 is provided so as to branch from the main refrigerant circuit 15 (outdoor circuit 20) and circulate the refrigerant. An oil separator 51, an oil return pipe 52, a solenoid valve 53, and a capillary tube 54 are provided.

  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 can be opened and closed freely so that the oil separator 51 and the suction side of the compressor 40 are in a refrigerant communication state (the oil return circuit 55 is open) or the refrigerant communication is cut off. An electromagnetic valve (an example of an on-off valve) 53 is provided as an on-off valve that is in a state (the oil return circuit 55 is closed). The electromagnetic valve 53 is provided in an oil return pipe 52 that is downstream of the oil separator 51 in the oil return circuit 55. The electromagnetic valve 53 is closed when energized and opened when not energized. Become.

  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 controls whether or not to return oil 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.

  Furthermore, the outdoor unit 2 is provided with an outdoor fan 70. The outdoor fan 70 sends outdoor air to the outdoor heat exchanger 22.

  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 low pressure sensor 791 is a sensor that detects the refrigerant pressure before compression by the compressor 40, and outputs the detected low pressure value (value of the refrigerant pressure before compression by the compressor 40) to the control unit 91.

  The high pressure sensor 792 detects the refrigerant pressure after being compressed by the compressor 40, and outputs the detected high pressure value (the value of the refrigerant pressure after being compressed by the compressor 40) to the control unit 91.

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

  The indoor unit 3 is provided with an indoor circuit 30. The indoor circuit 30 is provided with an indoor heat exchanger 31. The indoor heat exchanger 31 is configured by, for example, a cross fin type fin-and-tube heat exchanger. In the indoor heat exchanger 31, heat is exchanged between the refrigerant circulating in the refrigerant circuit 15 and the room air. 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 31.

  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 side of the indoor heat exchanger 31 in the indoor circuit 30. 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 side of the indoor heat exchanger 31.

  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. Further, 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 31. Furthermore, the indoor heat exchanger 31 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.

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

  The controller 90 includes a control unit 91, a timer 93, and an input receiving unit 94.

  The controller 91 adjusts the opening degree of the expansion valve 24, switches the four-way switching valve 21, and the like. Further, the control unit 91 performs drive control (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 opening / closing operation of the electromagnetic valve 53 according to the driving frequency (rotation speed) of the compressor 40 detected by the frequency sensor 78. Details of the opening / closing control of the electromagnetic valve 53 by the controller 91 will be described later.

  The timer 93 performs various time measurements. For example, the timer 93 measures the elapsed time that the electromagnetic valve 53 of the oil return circuit 55 is in an open state or a closed state.

  The input receiving unit 94 receives inputs such as a start instruction for starting the air conditioner 1 and an instruction for a target indoor temperature, which are input from 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 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 31 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 degree 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. The discharged refrigerant passes through the oil separator 51, passes through the four-way switching valve 21, and flows into the outdoor heat exchanger 22. In the outdoor heat exchanger 22, the refrigerant dissipates heat to the outdoor air and condenses. The refrigerant is then sent to the compressor 40 from the liquid side communication pipe 16 to the indoor circuit 30.

  The refrigerant that has flowed into the indoor circuit 30 is introduced into the indoor heat exchanger 31. In the indoor heat exchanger 31, the refrigerant absorbs heat from the indoor air and evaporates. That is, the refrigerant introduced into the indoor circuit 30 evaporates in the indoor heat exchanger 31, and as a result, the indoor air is cooled.

  The refrigerant evaporated in the indoor heat exchanger 31 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 and the accumulator 23. 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 from the indoor heat exchanger 31 is 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 closed and the oil return pipe 52 is closed, the oil circulation in the oil return pipe 52 is blocked. On the other hand, when the solenoid valve 53 is opened and the oil return pipe 52 is opened, 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 31 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.

  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 31. In the indoor heat exchanger 31, 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 31, and as a result, the indoor air is heated.

  The refrigerant condensed in the indoor heat exchanger 31 flows into the outdoor circuit 20 through the liquid side communication pipe 16. Thereafter, the refrigerant is decompressed by the expansion valve 24 and then introduced into the outdoor heat exchanger 22.

  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 (open / close control of the electromagnetic valve 53 of the oil return circuit 55) in the air conditioner 1 will be described. FIG. 3 is a conceptual diagram showing oil return control in the air conditioning apparatus 1. FIG. 4 is a flowchart showing the flow of processing during oil return control in the air conditioning apparatus 1.

  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 solenoid valve 53 is left in an open state (S10) as a state in which the solenoid valve 53 of the oil return circuit 55 is not energized. When the compressor 40 is driven in a high rotation range at the time of start-up and the like and is not in a steady operation, it is necessary to return oil to the compressor 40. Therefore, the control unit 91 opens the electromagnetic valve 53 opened in S10. Maintain the state.

  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).

  Here, the control unit 91 (1) the drive frequency is smaller than a predetermined value B, or (2) steady control (compressed in a high rotation range at the time of start-up or when the indoor / outdoor temperature difference is large) It is determined whether the control state is other than the control state in which the compressor 40 is driven (the control state in which the compressor 40 is driven in a relatively low rotation range) (S3). The control unit 91 repeats the S2 and S3 processes while the condition (1) or (2) is not satisfied (NO in S3).

  On the other hand, when the condition (1) or (2) is satisfied (YES in S3), the control unit 91 maintains the open state of the electromagnetic valve 53 as a state in which the electromagnetic valve 53 is not energized. On the other hand, the timer 93 is used to measure the elapsed time from when the condition (1) or (2) is satisfied (S4). Thereafter, the control unit 91 (3) the drive frequency is equal to or higher than a predetermined value A (the predetermined value A> the predetermined value B), or (4) the steady control is not being performed. Judgment is made (S5). If either of the conditions (3) or (4) is met, the process returns to the process of opening the electromagnetic valve 53 in S10 at that time, and the processes after S2 are performed.

  In S5, when the control unit 91 determines that none of the above (3) or (4) applies (NO in S5), the measurement time by the timer 93 reaches a predetermined time a. It is determined whether or not (S6). Here, when the time measured by the timer 93 has not reached the predetermined time a (NO in S6), the control unit 91 returns to the process of S5.

  On the other hand, when the time measured by the timer 93 has reached a predetermined time a (YES in S6), the control unit 91 sets the electromagnetic valve 53 in a closed state by energizing the electromagnetic valve 53. At the same time, the timer 93 causes the passage of time from the time when the electromagnetic valve 53 is closed (S7). As described above, the electromagnetic valve 53 is closed (1) the drive frequency is lower than the predetermined value B, or (2) the electromagnetic valve 53 is kept for a certain period of time in the state of steady control. After the oil is sufficiently returned to the compressor 40 in the open state, it is not necessary to return the oil for a predetermined period (predetermined time b in the present embodiment). When the state 2) continues, the solenoid valve 53 is closed, and the refrigerant circulation amount in the refrigerant circuit 15 which is the main circuit of the refrigerant circulation is increased to increase the intermediate performance (the state (1) or (2) In order to efficiently draw out the capacity of the compressor 40.

  When the electromagnetic valve 53 is closed as described above, the control unit 91 determines whether (3) the drive frequency is equal to or higher than a predetermined value A, or (4) whether steady control is not being performed (S8). If the condition (3) or (4) is satisfied (YES in S8), the process returns to the process of opening the electromagnetic valve 53 in S10, and the processes after S2 are performed. That is, when the electromagnetic valve 53 is closed, the control unit 91 sets the compressor 40 at a rotational speed up to a predetermined upper limit rotational speed based on the driving frequency of the compressor 40 detected by the frequency sensor 78. When the rotation speed of the compressor 40 reaches the upper limit rotation speed, the electromagnetic valve 53 is opened.

  In S8, when the control unit 91 determines that none of the above (3) or (4) is applicable (NO in S8), the time b measured in advance by the timer 93 (predetermined) It is determined whether or not the predetermined time b <the predetermined time a) has been reached (S9). If the control unit 91 determines that the time measured by the timer 93 has not reached the predetermined time b (NO in S9), the process returns to S8.

  In other words, in the present embodiment, the controller 91 determines that the drive frequency of the compressor 40 detected by the frequency sensor 78 corresponds to a predetermined high rotation speed range (the above condition (3) or (4)). In the case of indicating the rotation speed of the compressor 40 belonging to the region to be operated), the electromagnetic valve 53 is opened, and the drive frequency of the compressor 40 detected by the frequency sensor 78 is set to a predetermined low rotation speed range (the above ( When the rotational speed of the compressor 40 belonging to the region 1) or (2) corresponding to the condition (1) is indicated, the control for closing the electromagnetic valve 53 is performed.

  On the other hand, if the control unit 91 determines that the time measured by the timer 93 has reached a predetermined time b (YES in S9), the process proceeds to S4. That is, the control unit 91 sets the electromagnetic valve 53 in an open state so that the electromagnetic valve 53 is not energized, and the time elapsed from the time when the condition (1) or (2) is satisfied by the timer 93. Is measured (S4). In this way, the electromagnetic valve 53 is closed only for a certain period (predetermined time b in the present embodiment), and when the certain time elapses with the electromagnetic valve 53 being closed, the electromagnetic valve 53 is opened and the compressor is opened. The reason why the oil is returned to 40 is that if the oil does not return to the compressor 40 for a long time, the operation of the compressor 40 is hindered.

  In other words, in the above embodiment, the oil return circuit 55 is provided on the downstream side of the oil separator 51, and the oil return circuit 55 (oil return pipe 52) is closed when energized and opened when not energized. The controller 91 controls the drive of the opening / closing operation of the solenoid valve 53 by switching between energization and non-energization of the solenoid valve 53.

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

  For example, when the control unit 91 causes the electromagnetic valve 53 to perform an opening / closing operation, if the refrigerant pressure in the oil return pipe 52 is high, the control unit 91 temporarily reduces the refrigerant pressure to a value that allows the electromagnetic valve 53 to be opened / closed. Then, it may be opened and closed. The controller 91 returns the reduced refrigerant pressure to the original refrigerant pressure before the opening / closing operation of the electromagnetic valve 53 after the opening / closing operation of the electromagnetic valve 53 is completed. For example, the controller 91 temporarily reduces the refrigerant pressure in the oil return pipe 52 by temporarily lowering the drive frequency (the number of revolutions) of the compressor 40 in advance when executing S4, S7, and S10 shown in FIG. After being lowered, the electromagnetic valve 53 is opened and closed. Thereby, the opening / closing operation | movement of the solenoid valve 53 is performed reliably.

  That is, when opening and closing the electromagnetic valve 53, the controller 91 has a pressure difference between the front and rear of the compressor 40 (refrigerant pressure before being sucked into the compressor 40 (so-called low pressure) due to the characteristics of the electromagnetic valve 53 that is closed when energized. And a pressure difference between the refrigerant pressure (so-called high pressure) after being discharged from the compressor 40 and a constant value (determined from the performance of the solenoid valve 53), the open / close operation of the solenoid valve 53 that is closed when energized is not hindered. Value) or less, and it is necessary to instruct the solenoid valve 54 to open or close. Therefore, the control unit 91 calculates the high / low differential pressure based on the low pressure value obtained from the low pressure sensor 791 and the high pressure value obtained from the high pressure sensor 792, monitors the high / low pressure difference, and compresses as described above. By temporarily lowering the drive frequency (the number of rotations) of the machine 40, the high / low differential pressure is set to a certain value or less, and then the solenoid valve 53 is instructed to perform an opening / closing operation. In this case, the compressor 40 is an example of the refrigerant pressure adjusting mechanism in the claims.

  The solenoid valve 53 that is closed when energized and opened when de-energized has an iron piece (plunger) 532 that is drawn to the lower bottom portion of the oil return pipe 52 by a tension spring 531 (see FIG. 5). In an open state indicated by a solid line), a magnetic force is generated by energizing an electromagnet (solenoid) 533 provided in the upper bottom portion of the oil return pipe 52, and the oil return pipe 52 is blocked by the iron piece 532 by pulling upward by the magnetic force. Then, the oil return pipe 52 is closed (the state of the two-dot chain line shown in FIG. 5). In this configuration, the operation of the iron piece 532 due to the magnetic force of the pulling spring 531 or the electromagnet 533 is greatly affected by the pressure of the refrigerant passing through the oil return pipe 52. For this reason, the controller 91 lowers the refrigerant pressure in the oil return pipe 52 during the opening / closing operation of the solenoid valve 53 (in general, the solenoid valve closed when energized has a lower refrigerant pressure than the solenoid valve opened when energized. To reduce the influence of the refrigerant pressure on the opening / closing operation.

  Moreover, in the said embodiment, although the form which used the example of the on-off valve as the solenoid valve 53 was shown, this invention is not limited to the said form, As an on-off valve, the valve which can perform the above-mentioned on-off operation is shown. In such a case, it is possible to use a valve having another configuration.

  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 conditioning apparatus 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. .

  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 conditioning apparatus 2 Outdoor unit 3 Indoor unit 15 Refrigerant circuit 20 Outdoor circuit 24 Expansion valve 40 Compressor 51 Oil separator 52 Oil return pipe 53 Electromagnetic valve 531 Spring 532 Iron piece 533 Electromagnet 54 Capillary tube 55 Oil return circuit 30 Indoor circuit 31 Indoor heat exchanger 78 Frequency sensor 90 Controller 91 Control unit 93 Timer 94 Input reception unit

Claims (4)

A refrigerant circuit (15) in which a refrigerant circulates and performs a vapor compression refrigeration cycle;
A compressor (40) provided in the refrigerant circuit (15);
An oil separator (51) for separating refrigeration oil from refrigerant discharged from the discharge side of the compressor (40);
An oil return pipe (52) for returning the refrigeration oil separated by the oil separator (51) to the suction side of the compressor (40);
An on-off valve (53) provided downstream of the oil separator (51) in the oil return pipe (52), the oil return pipe (52) being closed when energized and opened when not energized; ,
An air conditioner (1) provided with a pressure reducing mechanism (54) provided in series with respect to the on-off valve in the oil return pipe (52) and depressurizing the refrigerant after passing through the on-off valve (53). A control unit (91) that switches between energization and non-energization states of the on-off valve (53) to drive and control the on-off operation of the on-off valve (53),
A rotation speed detector (78) for detecting the rotation speed of the compressor (40),
When the rotational speed detected by the rotational speed detection section (78) belongs to a predetermined high rotational speed range, the controller (91) opens the on-off valve (53), and The air conditioner (1) according to claim 1, wherein the on-off valve (53) is closed when the rotational speed detected by the rotational speed detector (78) belongs to a predetermined low rotational speed range. 1). A refrigerant pressure adjusting mechanism (40) for adjusting the refrigerant pressure in the oil return pipe (52),
The controller (91) drives and controls the refrigerant pressure adjusting mechanism (40, 24) when opening and closing the on-off valve (53), and determines the refrigerant pressure in the oil return pipe (52) in advance. The air conditioner (1) according to claim 2, wherein the on-off valve (53) is opened and closed after being temporarily reduced to a predetermined value. The control section (91) is predetermined when the rotation speed detected by the rotation speed detection section (78) belongs to a predetermined low rotation speed range and the on-off valve (53) is in a closed state. The air conditioner (1) according to claim 2 or 3, wherein the on-off valve (53) is returned to an open state when a given time has elapsed.

Images