JPH0723816B2 - Air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an air conditioner capable of switching between a heating cycle and a cooling cycle, and particularly to an oil recovery operation for recovering oil in a refrigerant circuit to a compressor. To improve what you do.

(Prior Art) Conventionally, in a refrigeration system equipped with a variable-capacity compressor, if a low-capacity operation is continued, the refrigerant circulation amount during the refrigeration cycle decreases and the refrigerant is discharged together with the refrigerant discharged from the compressor. The efficiency of recovering the lubricating oil is deteriorated, and the oil in the compressor becomes insufficient. When the oil is significantly insufficient, the compressor may be burned out.

Therefore, in order to prevent the oil shortage of the compressor, for example,
As disclosed in Japanese Patent Laid-Open No. 57-41416, a changeover switch for switching the operating capacity of the compressor between a low capacity side and a high capacity side is provided, and when low capacity operation is performed for a certain period of time, the compressor is switched to the high capacity side during the refrigeration cycle. There is an attempt to increase the circulation amount of the refrigerant to accelerate the recovery of oil.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional one, particularly when the capacity of the indoor exchanger serving as the condenser during the heating operation is small, a high capacity operation of the compressor is performed in the heating cycle for the purpose of recovering oil. If this is done, the discharge gas pressure will rise too high and the high-pressure holding switch will operate, and the oil recovery operation may become impossible. Further, in the case of a multi-type air conditioner in which indoor units are connected in parallel, the flow rate is small in the branch pipe of the indoor unit having a small capacity during heating operation, and oil is not sufficiently collected. further,
Even if the oil circulation amount is increased, there is a problem that the recovery efficiency may be poor if the oil viscosity is high.

(Object of the first invention) The first invention of the present application is made in view of such a point, and an object thereof is to switch to a cooling cycle after heating the compressor for a predetermined time. At the same time, the amount of circulation of the refrigerant is increased and the viscosity of the oil that accumulates in the refrigerant circuit is reduced to promptly and reliably recover the oil.

(Object of the second invention) Further, when performing the oil recovery operation by switching to the cooling cycle, the condensation pressure in the outdoor heat exchanger may not be sufficiently increased when the outdoor air temperature is particularly low. When it occurs, the increase of the circulation amount of the refrigerant becomes insufficient,
It may not be possible to recover the oil sufficiently.

In order to solve this problem, an object of the second invention of the present application is to stop the operation of the air conditioner due to the excessive rise of the condensation pressure regardless of the outdoor air temperature when the oil recovery operation is performed by switching to the cooling cycle. While preventing it, the condensation pressure in the outdoor heat exchanger is quickly increased to secure a sufficient refrigerant circulation amount,
This is to prevent the efficiency of oil recovery operation from decreasing.

(Means for Solving the Problems) In order to achieve the above object, the solution means of the first invention of the present application is, as shown in FIG. 1, a compressor (1) whose operating capacity is variably adjusted. , A indoor heat exchanger (12), a pressure reducing mechanism (8 or 13) and an outdoor heat exchanger (6) are sequentially connected, and a cycle switching for switching the refrigerant circuit between a cooling cycle and a heating cycle is provided. The object is an air conditioner provided with the mechanism (5). Then, in such an air conditioner, a measuring means (31) for measuring and integrating the operating time of the compressor (1) during the heating operation, and the measuring means (31).
The cycle switching mechanism (5) is switched to the cooling cycle side for a set time when the calculated value of (1) reaches a predetermined value, and the operating capacity of the compressor (1) and the opening degree of the pressure reducing mechanism (8 or 13) are set. Control means for controlling to increase (51)
And a compressor (1) for removing oil in the refrigerant circuit.
Is to be collected.

Further, in addition to the above-mentioned configuration, the solution means of the second invention of the present application has the function of the control means (51) until the condensing pressure in the outdoor heat exchanger (6) reaches a predetermined value. The outdoor fan (6a) is stopped, and when the condensing pressure reaches a predetermined pressure, a function is added to control the operation of the outdoor fan (6a).

(Operation) Due to the abnormal configuration, in the first invention of the present application, the operating time of the compressor (1) is measured and integrated by the measuring means (31) during the heating operation of the air conditioner. When the integrated value reaches a predetermined value, the control means (51) causes
While switching the cycle switching mechanism (5) to the cooling cycle side, the capacity of the compressor (1) and the pressure reducing mechanism (8 or 13)
Is controlled so as to increase, the circulation amount of the refrigerant increases without increasing the discharge gas pressure, and the wet operation is performed to reduce the viscosity of the oil accumulated in the refrigerant circuit. Therefore, due to the increase in the circulation amount of the refrigerant and the decrease in the oil viscosity, the oil accumulated in the refrigerant pipe of the air conditioner, the indoor heat exchanger (12) and the outdoor heat exchanger (6) flows together with the refrigerant flow. It will be easier and the oil will be recovered promptly and reliably.

In the second invention of the present application, when the oil recovery operation is performed by switching to the cooling cycle as described above, the control means (5
Due to 1 '), the outdoor fan (6a) is stopped in the outdoor heat exchanger (6) until the condensing pressure reaches a predetermined value, so that heat is not exchanged in the outdoor heat exchanger (6) and the condensing pressure is reduced. It rapidly rises to ensure a sufficient circulation amount of the refrigerant, and effectively prevents a decrease in the efficiency of the oil recovery operation even when the outdoor air temperature is low. Then, when the condensing pressure reaches a predetermined value, the outdoor fan (6a) is operated by the control means (51 ') to secure a necessary heat exchange amount in the outdoor heat exchanger (6), and the condensing pressure rises. Therefore, even when the outdoor air temperature is high, the high pressure protection switch does not operate and the oil recovery operation becomes impossible due to the excessive rise of the discharge gas pressure.

(Embodiment of the first invention) An embodiment of the first and second inventions of the present application will be described below with reference to the drawings starting from FIG.

FIG. 2 shows a refrigerant piping system of a multi-type air conditioner to which the first invention of the present application is applied, (A) is an outdoor unit,
(B) to (F) are indoor units connected in parallel to the outdoor unit (A). Inside the outdoor unit (A), a first compressor (1a) whose capacity is adjusted by an inverter (2a) whose output frequency is variably switched in 10 Hz steps within a range of 30 to 70 Hz, and a pilot pressure The capacity is adjusted in two stages of full load (100%) and unload (50%) by the unloader (2b) which is differential at the second compressor (1b) and the check valve (1e). A compressor (1) configured to be connected in parallel, an oil separator (4) for separating oil in gas discharged from the compressor (1), and switching during heating operation as indicated by the solid line in the figure. A four-way switching valve (5) as a cycle switching mechanism that switches as shown by a wavy line in the cooling operation, an outdoor heat exchanger (6) that serves as a condenser during the cooling operation and an evaporator during the heating operation, and its fan (6a). And the supercooling coil (7) and the refrigerant flow rate during cooling operation An outdoor electric expansion valve (8) as a pressure reducing mechanism for heating that performs a throttle action of the refrigerant during operation, a receiver (9) that stores the liquefied refrigerant, and an accumulator (10) are built in as main devices. Each device (1) to (10)
Are connected to each other through a refrigerant communication pipe (11) so that the refrigerant can flow. Further, the indoor units (B) to (F) have the same configuration, and each has an indoor heat exchanger (12) ... And a fan (12a) ... which become an evaporator during cooling operation and a condenser during heating operation. In addition, the liquid refrigerant branch pipes (11a) of the indoor heat exchangers (12) ... In-room electric expansion valve as a pressure reducing mechanism for cooling that regulates the flow rate of the refrigerant during heating operation and throttles the refrigerant during cooling operation. (13) are respectively interposed and connected to the outdoor unit (A) by a connecting pipe (11b) via a main closing valve (17) after joining. Further, (TH1) ... is a room temperature thermostat that detects each room temperature, (TH2) ... and (TH3) ... are temperatures that detect the temperature of the refrigerant in the liquid side and gas side piping of the indoor heat exchanger (12), respectively. A sensor, (TH4) is a temperature sensor that detects the temperature of the refrigerant in the discharge pipe of the compressor (1), and (TH5) is a temperature sensor that detects the evaporation temperature of the outdoor heat exchanger (6) (evaporator) during heating operation. , (TH6) is a temperature sensor that detects the temperature of the intake gas drawn into the compressor (1), and (P1) is a pressure sensor that detects the pressure of the discharge gas during heating operation and the pressure of the intake gas during heating operation. is there.

In addition, in FIG. 2, various auxiliary devices are provided in addition to the above main devices. (1f) is installed in the bypass circuit (11c) of the second compressor (1b) and is "open" when the second compressor (1b) is stopped and in the unload state, and "closed" in the full load state. Solenoid valve for unloader, (1g) is a capillary tube, (1h) and (1i) are oil separators (4), oil return pipes (11u) and first compressor (1a)
And a branch pipe (11v) that returns lubricating oil to the second compressor (1b)
And (11w) are capillary tubes that control the amount of oil returned, and (21) are installed in a pressure equalizing hot gas bypass circuit (11d) that connects the discharge pipe and the suction pipe, and the room during cooling operation. This is a hot gas solenoid valve that opens when the heat exchanger (12) (evaporator) is in a low load state and during defrosting. Further, (11e) is a heating overload control bypass circuit, and the bypass circuit (11e) is
Auxiliary condenser (22), first check valve (23), high-pressure control valve (24) and second check valve that open when the indoor heat exchanger (12) (condenser) during heating operation is under low load (25) are connected in series one after another, and part of them are equipped with a liquid-sealing prevention bypass circuit (11f) for preventing liquid-sealing when the operation is stopped, the third check valve (27) and the capillary tube (CP3). It is provided through. Further, (11g) is a liquid injection bypass for connecting the liquid refrigerant side pipe of the heating overload bypass circuit (11e) and the suction gas pipe of the main pipe to adjust the superheat degree of the suction gas during the heating and cooling operation. The liquid injection bypass circuit (11g) includes a solenoid valve (29) for injection that opens and closes in conjunction with turning on and off of the compressor (1), and a temperature sensing tube (TP).
An automatic expansion valve (30) whose opening is adjusted according to the degree of superheat of the intake gas detected by 1) is interposed.

Further, in FIG. 2, (F1) to (F6) are liquid purification filters provided in the refrigerant circuit or the oil return pipe, (HPS) is a high pressure switch for protecting the compressor, and (SP) is It is a service port.

The solenoid valves and sensors are connected to the outdoor control unit (15), which will be described later, together with the main equipment by signal lines,
The outdoor control unit (15) is an indoor control unit (16)
It is connected to ... by a communication wire so that signals can be exchanged.

FIG. 3 is an electric circuit diagram showing a wiring relationship between the inside of the outdoor control unit (15) arranged on the outdoor unit (A) side and each connected device. In the figure, (MC1) is the first connected to the frequency conversion circuit (INV) of the inverter (2a).
The compressor (1a) motor, (MC2) the second compressor (1b) motor, (MF) the outdoor fan (6a) motor, (52
F), (52C ₁ ) and (52C ₁₂ ) are fan motors (M
F), a magnetic contactor that operates a frequency conversion circuit (INV) and a motor (MC ₁₂ ). The above devices are connected to a three-phase AC power source via a fuse box (FS) and an earth leakage breaker (BR1). , The outdoor control unit (15) is connected by a single-phase AC power supply. Next, inside the outdoor control unit (15), the normally open contact (R
Y ₁ ) to (RY ₇ ) are connected in parallel to the single-phase alternating current, and these are in turn connected to the electromagnetic relay (20) of the four-way switching valve (5).
S), an electromagnetic contactor of the frequency converting circuit (INV) (52C _1), an electromagnetic contactor of the second compressor (1b) (52C _2), an electromagnetic contactor for outdoor fan (52F), the solenoid valve unloader (1f ) Solenoid relay (SV _L ), hot gas solenoid valve (21) solenoid relay (SV _P ) and injection solenoid valve (29) solenoid relay (SV _T ) coils connected in series to the outdoor control unit. Room temperature thermostat (TH1) input to (15)
And the contact of each of the electromagnetic contactor or the electromagnetic relay is opened / closed by being opened / closed according to the signals of the temperature sensors (TH2) to (TH6). A coil of a pulse motor (EV) that adjusts the opening of the outdoor electric expansion valve (8) is connected to the terminal CN. In the circuit on the right side of FIG. 3, (CH ₁ ) and (CH ₂ ) are heaters for preventing oil forming of the first compressor (1a) and the second compressor (1c), respectively.
They are connected in series with electromagnetic contactors (52C ₁ ) and (52C ₂ ), respectively, so that current flows when the compressors (1a) and (1b) are stopped. Furthermore, (51C ₂ ) is a motor (M
C ₂₎ of the over-current _{relays, (49C 1), (49C} 2) the first compressor, respectively I (1a), temperature protection switch of the second compressor _{(1b), (63H 1)} , (63H ₂ ) is the first compressor (1
a), switch for pressure rise protection of the second compressor (1b), (5
1F) is a fan motor (MF) overcurrent relay, which is connected in series and is an electromagnetic relay (30F _X ) at startup.
A protection circuit is configured to turn on the switch and turn it off in case of a failure. The outdoor control unit (15) has a built-in outdoor control device (15a) indicated by a broken line, and the outdoor control device (15a) integrates the operation time of the compressor (1) with an integration timer ( 31) and with
Each outdoor control unit (1
6) ... Or the operation of each device is controlled according to the signal input from each sensor.

Next, FIG. 4 is an electric circuit diagram showing the main wiring of the inside of the indoor control unit (16) and each connected device. In Fig. 4, (MF) is an indoor fan (12a) motor, which receives a single-phase AC power source and switches between strong wind and weak wind by the relay terminals (RY ₁ ) to (RY ₃ ) in order of increasing air volume and heating. During operation, the room temperature thermostat (TH1) signal is used to make a slight breeze only when stopped. The terminal CN of the printed circuit board of the indoor control unit (15) is connected to the indoor electric expansion valve (1
While the pulse motor (EV) that adjusts the opening of 3) is connected, signals from the room temperature thermostat (TH1) and temperature sensors (TH2) and (TH3) are input. Further, each indoor control unit (16) is connected to the outdoor control unit (15) via a signal line so that signals can be transmitted and received, and is also connected so as to be input from a remote control switch (RCS). The indoor control unit (16) has a built-in indoor control device (16a) indicated by a broken line, and the indoor control device (16a) operates in response to a signal from each sensor or the outdoor control unit (15). The operation of the electric expansion valve (13) or the indoor fan (12a) is controlled.

In FIG. 2, during the heating operation of the air conditioner, the refrigerant is compressed in the gas state by the compressor (1) and is branched to each indoor unit (B) to (F) via the four-way switching valve (5). Sent. In each of the indoor units (B) to (F), heat is exchanged in each of the indoor heat exchangers (12) and condensed and then merged, and the outdoor unit (A) stores the liquid in the receiver (9). In the liquid state, it is subjected to a throttling action by the outdoor electric expansion valve (8) and evaporated in the outdoor heat exchanger (6) to be in a gas state and returned to the compressor (1). Further, during the cooling operation, the four-way switching valve (5) is switched as shown by the dotted line, the flow of the refrigerant is opposite to that during the heating operation, the refrigerant is condensed in the outdoor heat exchanger (6), and the indoor electric expansion valve (13). ) ... receives a throttling action and evaporates in the indoor heat exchanger (12), and then returns to the compressor in a gas state.

Then, during the cooling and heating operation, the lubricating oil discharged from the compressor (1) together with the refrigerant accumulates on the pipe or the wall of the pipe such as the heat exchanger, so that the outdoor control device (15a) causes An oil recovery operation is performed to recover the oil. The procedure will be described based on the flowchart of FIG.

In the flowchart of FIG. 5, when the power is turned on, the integrated value of the integration timer (31) whose set time is set to 8 hours in step S ₁ is set to 7 hours to perform normal operation, and in step S ₂ . Determine if the compressor is running. The determination in step S ₂ is NO when the compressor (1) is stopped.
In case of, the integration timer (31) is stopped, and when the time has elapsed and the compressor (1) is in operation, YES, the integration timer (31) is operated and the process proceeds to step S ₃ to perform the defrost operation. Whether NO is performed or not, and if NO is not performing the defrost operation, the process proceeds to step S ₄ . Then, in step S ₄ , it is determined whether or not the integrated value of the integration timer (31) has reached 8 hours, and if NO, the steps S ₂ and S ₃ are repeated until the integrated value reaches 8 hours. When it reaches, the determination becomes YES and the process moves to step S ₅ . In step S ₅ , if heating is in progress, the four-way switching valve (5), which is a cycle switching mechanism, is switched to the cooling side, and the capacity of the compressor (1) is maximized (70 Hz for the first compressor (1a), Set the second compressor (1b) to full load, start the outdoor blower fan (6a), fully open the outdoor electric expansion valve (8), open the indoor electric expansion valve (13) ... (Note that the injection solenoid valve (29) and the hot gas solenoid valve (21) are closed). Next, in step S _6, the step S is before proceeding to ₅ to determine whether an in heating, the indoor fan in operation at the time of YES is an oil-recovery operation during the heating operation at step S ₇ a (12a) Stop to prevent cold air from blowing indoors. In addition, NO during cooling operation
Oil proceeds to step S ₈ in a state of operating the indoor fan (12a), it is determined whether or not subjected to oil recovery operation of step S ₅ to S ₇ 3 minutes, if the YES passed 3 minutes at The recovery operation is ended, and the normal operation is performed, returning to step S ₂ . Note that steps S ₅ by the defrosting operation If YES the determination in step S ₃ is performed defrosting operation
Since there is the oil recovery operation similar to oil recovery effect of to S _8, performs the normal operation by resetting the integrating timer (31) in step S _9.

In the above flow, control means for performing oil recovery operation between the air conditioner set time at step S ₅ ~S ₈ (51)
Are configured.

Therefore, in the present embodiment, the oil recovery operation is performed 1 hour after the air conditioner is started at the time of starting the air conditioner and every 8 hours during the operation. At this time, if the four-way switching valve (5) is switched to the cooling cycle side during the heating operation, the flow of the refrigerant becomes the flow during the cooling operation described above. The capacity of the compressor (1) is maximized and the opening degree of the outdoor electric expansion valve (8) is fully opened, so that the circulation amount of the refrigerant is increased and the oil recovery efficiency is improved. Furthermore, since the opening degree of the indoor electric expansion valves (13) is forcibly controlled to be larger than the maximum opening degree during normal operation, that is, the degree of pressure reduction is controlled to be small, the heat exchange amount in the indoor heat exchanger (12) is reduced. The refrigerant in the refrigerant circuit becomes damp,
The viscosity of the oil that has accumulated in the refrigerant circuit is reduced, making the oil flow smoother and promoting oil recovery. Moreover, the discharge gas pressure does not rise unlike the oil recovery operation in the heating cycle, and the oil recovery operation can be reliably performed. Therefore, it is possible to effectively prevent seizure of the compressor (1) that causes an oil shortage. Further, during the cooling operation, it is not necessary to switch the four-way switching valve (5), and the oil recovery is promoted similarly to the above. In particular, even in the multi-type air conditioner as in this embodiment, each of the internal heat exchangers (12) ...
The oil remaining in the branch pipe can also be collected, which is more effective than the conventional method. When the defrost operation is performed during the heating operation, the cooling cycle is also switched to perform the full capacity operation of the compressor (1) by maximizing the opening degree of the indoor electric expansion valves (13) ... Outdoor electric expansion valve (8) ...
Since the opening of is also fully opened), it has the same effect as the oil recovery operation. Therefore, when the defrost operation is performed, the next oil recovery operation is set to be 8 hours later. The above oil recovery operation (or defrost operation) is forcibly made to be wet, but the time is as short as 3 minutes (5 minutes in the case of defrost operation), so the liquid refrigerant in the intake gas refrigerant is set by the accumulator (10). Are reliably removed and there is no risk of liquid compression in the compressor (1).

(Embodiment of the Second Invention) FIGS. 6 to 8 show an embodiment of the second invention of the present application.
Since the basic structure of the air conditioner is the same as that shown in FIGS. 2 and 4 of the first embodiment of the present invention, its illustration and description will be omitted. However, in this embodiment, (TH5) in FIG. 2 is the outdoor heat exchanger (6) during the oil recovery operation.
2 is a temperature sensor for detecting the condensation temperature corresponding to the condensation pressure of the refrigerant.

FIG. 6 is an outdoor control unit (15) arranged on the outdoor unit (A) side of an air conditioner according to an embodiment of the second invention.
FIG. 3 is an electric circuit diagram showing the wiring relationship between the inside and each of the connected devices, and has substantially the same configuration as in FIG. 3 described above, and a description of common parts will be omitted. In this embodiment, normally open contacts (RY ₂ ), (RY ₃ ) and (RY ₄ )
, But the protection switches (51C ₁ ), (51C ₂ ) on the right side of the figure,
It is connected to a protection circuit composed of (63H ₁ ) and (63H ₂ ) via an electromagnetic relay (30F _X ), and when an abnormal condition occurs during the operation of the air conditioner, the first compressor (1a ), The second compressor (1b), and the fan motor (MF) are designed to be in an emergency stop. And the outdoor control unit (1
5) includes an indoor control device (15a) as in the first embodiment.
The outdoor controller (15a) has a compressor (1)
The built-in integration timer (31) is provided as a measuring means for integrating the operating time of. The outdoor control device (15a) controls the operation of each device according to a signal input from each indoor control unit (16) ... Or each sensor.

The flow of the refrigerant during the cooling and heating operation of the air conditioner is the same as that in the first embodiment, and the description thereof will be omitted.

During the cooling and heating operation, the lubricating oil discharged from the compressor (1) together with the refrigerant stays on the pipe walls such as pipes and heat exchangers, so the oil in the refrigerant circuit is recovered by the outdoor control device (15a). Oil recovery operation is performed. The procedure is
As will be described with reference to the flow chart of the figure, steps S ′ _{1 to} S ′ ₄ are executed in the same flow as steps S _{1 to} S ₄ in the first embodiment, and the cumulative operating time of the air conditioner reaches 8 hours. Then, the process proceeds to step S _'5, performs oil recovery operation by the following flow. In step S _'5, and a four-way switch valve (5) to the cooling side, the operating capacity of the compressor (1) is the largest (see the time chart of FIG. 8 (iii)), the outdoor motor-operated expansion valve (8) Fully open, indoor electric expansion valve (13)
The opening of ... is controlled to the open side and the outdoor fan (6
Stop a) (time chart of Fig. 8 (ii)
(Note that the injection solenoid valve (29) and hot gas solenoid valve (21) are closed). Then, step S 'in _6, the inherent operation to determine whether it is in the heating operation, the step S when a YES in the heating operation' of the cold air to stop the indoor fan (12a) ... ₇ Prevents blowout, and remains the same when the judgment is NO during cooling operation,
The process proceeds to step S _'8. Then, a further step S _'9
When the condensing temperature corresponding to the condensing pressure in the outdoor heat exchanger (6) detected by the temperature sensor (TH5) reaches the predetermined temperature T ₁ (for example, 45 ° C.) (corresponding to the predetermined pressure) (the After the operation of the outdoor fan (6a) is started in step S ′ ₁₀ (see FIG. 8 (i)) (see FIG. 8 (ii)), once the outdoor fan (6a) is operated, the condensing temperature is then set to the above predetermined value. Do not stop the operation of the outdoor fan (6a) even if the temperature falls below T ₁ . Incidentally, 'also determine simultaneously whether _9, or during the cooling operation, when the oil-recovery operation during the cooling operation, regardless step S of the level of condensation temperature' Step S proceeds to _10, to operate the outdoor fan (6a) Has been done. Then, after a lapse of set time of 3 minutes since the beginning of the oil recovery operation to exit the oil-recovery operation, performs normal operation returns to step S _'2. Incidentally, 'If YES the determination of the _three is performed defrost operation, step S' Step S integration timer ₁₁ (31)
Reset and perform normal operation.

In the above flow, integration timer (31) by Step S '5 _{to S' 10} during the set time period when the calculated value reaches a predetermined value (measurement means), the cycle switching mechanism (5) to the cooling cycle side The switching is controlled so that the operating capacity of the compressor (1) and the opening degree of the pressure reducing mechanism (8 or 13) are increased, and the outdoor fan is kept until the condensation pressure in the outdoor heat exchanger (6) reaches a predetermined pressure. A control means (51 ') is configured to control the operation of the outdoor fan (6a) when the operation of (6a) is stopped and the condensation temperature reaches a predetermined value.

Therefore, in the present embodiment, during operation of the air conditioner,
When the oil recovery operation is performed by switching to the cooling cycle as in the first embodiment of the present invention, while the condensation temperature (condensation pressure) in the outdoor heat exchanger (6) does not reach the predetermined temperature T ₁ (predetermined pressure). The outdoor fan (6a) is controlled by the control means (51 ').
Is stopped, heat exchange between the outdoor air and the refrigerant is not performed in the outdoor heat exchanger (6), and the condensing temperature (condensing pressure) rapidly rises (see FIG. 8 (i)). A sufficient amount of circulation is secured. Therefore, it is possible to effectively prevent the efficiency of oil recovery from decreasing due to the shortage of the circulation amount of the refrigerant. Further, when the condensing temperature rises and reaches the predetermined temperature T ₁ , the operation of the outdoor fan (6a) is started, and heat exchange between the outdoor air and the refrigerant is performed in the outdoor heat exchanger (6). Even when the temperature is high, the condensing pressure does not rise too high, and the high-pressure protection switches (63H ₁ ) and (63H ₂ ) do not prevent the air conditioner from operating. That is, the effect of the first aspect of the invention can be sufficiently exerted regardless of whether the outdoor air temperature is high or low.

In the above embodiment, the temperature sensor (TH5) detects the condensation temperature corresponding to the condensation pressure, but it goes without saying that a pressure sensor may be arranged to directly detect the condensation pressure. .

(Effects of the Invention) As described above, according to the air conditioner of the first invention of the present application, the capacity of the compressor is increased by switching to the cooling cycle at every predetermined time during the heating operation, and the decompression mechanism is operated. Since the oil recovery operation that controls the wet operation by increasing the opening degree is performed for a certain period of time, the refrigerant circulation amount increases and the viscosity of the refrigerant decreases without increasing the discharge gas temperature. The oil can be quickly and surely recovered from the refrigerant circuit to the compressor, so that seizure or the like due to lack of oil in the compressor can be effectively prevented, and reliability can be improved.

Further, according to the second invention of the present application, when performing the oil recovery operation in the cooling cycle, the outdoor fan is stopped while the condensation temperature in the outdoor heat exchanger is lower than the predetermined temperature, and when the predetermined temperature is reached, the outdoor fan is stopped. Since the operation is started, it is possible to secure a sufficient circulation amount of the refrigerant without causing an emergency stop of the air conditioner regardless of whether the outdoor air temperature is high or low, and reduce the efficiency of oil recovery. It can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a refrigerant system diagram showing the configuration of the first and second inventions of the present application. 2 to 5 show an embodiment of the first invention of the present application, FIG. 2 is a refrigerant system diagram thereof, FIG. 3 is an electric circuit diagram of an outdoor control unit, and FIG. 4 is an indoor control unit. The electric circuit diagram, FIG. 5 is a flow chart showing the procedure of the oil recovery operation. Further, FIGS. 6 to 8 show an embodiment of the second invention of the present application, FIG. 6 is an electric circuit diagram of the outdoor control unit, and FIG. 7 is a flow chart diagram showing the procedure of the oil recovery operation. FIG. 8 is a time chart showing changes in the condensing temperature, the operation of the outdoor fan, and the operating capacity of the compressor during the oil recovery operation. (1) ... compressor, (5) ... four-way switching valve (cycle switching mechanism), (6) ... outdoor heat exchanger, (8) ... outdoor electric expansion valve (pressure reducing mechanism), (12) ...... Indoor heat exchanger, (1
3) …… Indoor electric expansion valve (pressure reducing mechanism), (31) …… Integration timer (measuring means), (51), (51 ′) …… Control means.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Norifumi Maruyama 1304 Kanaoka-machi, Sakai-shi, Osaka Daikin Industry Co., Ltd., Kanaoka Plant, Sakai Manufacturing Co., Ltd. (56) References: Showa 59-91570

Claims (2)

[Claims] 1. A refrigerant circuit in which a compressor (1) whose operating capacity is variably adjusted, an indoor heat exchanger (12), a pressure reducing mechanism (8 or 13) and an outdoor heat exchanger (6) are sequentially connected. In the air conditioner having a cycle switching mechanism (5) for switching the refrigerant circuit between a cooling cycle and a heating cycle, a measuring means for measuring and integrating the operating time of the compressor (1) during heating operation ( 31) and when the calculated value of the measuring means (31) reaches a predetermined value, the cycle switching mechanism (5) is switched to the cooling cycle side for a set time, and the operating capacity of the compressor (1) and Control means (51) for controlling the opening of the pressure reducing mechanism (8 or 13) to be large
An air conditioner comprising: and a compressor (1) for collecting oil in the refrigerant circuit. 2. A refrigerant circuit in which a compressor (1) whose operating capacity is variably adjusted, an indoor heat exchanger (12), a pressure reducing mechanism (8 or 13) and an outdoor heat exchanger (6) are sequentially connected. In the air conditioner having a cycle switching mechanism (5) for switching the refrigerant circuit between a cooling cycle and a heating cycle, a measuring means for measuring and integrating the operating time of the compressor (1) during heating operation ( 31) and when the calculated value of the measuring means (31) reaches a predetermined value, the cycle switching mechanism (5) is switched to the cooling cycle side for a set time, and the operating capacity and pressure reduction of the compressor (1) are set. The opening of the mechanism (8 or 13) is controlled to be large, and the operation of the outdoor fan (6a) is stopped until the condensation pressure in the outdoor heat exchanger (6) reaches a predetermined value, and the condensation pressure becomes a predetermined value. When the value is reached, the outdoor fan (6a) Control means for controlling to perform (51 ') and a compressor oil in the refrigerant circuit (1)
An air conditioner characterized in that the air conditioner is collected.