JPH0451744B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a refrigeration cycle for a heat pump type air conditioner such as a separate air conditioner having an indoor side unit and an outdoor side unit.

[Prior art]

Conventionally, there has been a refrigeration cycle for an air conditioner as described above, as shown in FIG.

In Fig. 1, 1 is a compressor, 2 is a four-way valve, and 3 is a compressor.
is an outdoor heat exchanger, 4 is a distributor, and 5 is an outdoor heat exchanger.
is an expansion valve, 6 is a connecting pipe, 7 is an indoor heat exchanger,
8 is a connection pipe, 9 is an accumulator, and in a separate air conditioner, at least the indoor heat exchanger 7
are provided in the indoor unit, and each member not provided in the indoor unit is provided in the outdoor unit.

In such a refrigeration cycle, high-temperature, high-pressure refrigerant discharged from the compressor 1 during cooling operation of the air conditioner and refrigerating machine oil for lubrication mixed with this refrigerant pass through the four-way valve 2 and enter the outdoor heat exchanger 3. Here, heat is exchanged to become a high-temperature, high-pressure liquid refrigerant, and this liquid refrigerant passes through a distributor 4, is depressurized by an expansion valve 5, and reaches an indoor heat exchanger 7 through a connecting pipe 6.
Here, it evaporates, passes through the connecting pipe 8, passes through the four-way valve 2, the accumulator 9, and is sucked into the compressor 1 again, forming a circulation cycle.

However, in such a refrigeration cycle, if the connecting pipes 6 and 8 become long, the refrigerant that has been mixed into the refrigerating machine oil and is in a so-called stale state when the compressor is started will form, causing a large amount of refrigeration to occur. Even when machine oil is discharged and the compressor 1 is in continuous operation,
Refrigerating machine oil mixed with refrigerant is constantly discharged, and it takes time for the discharged refrigerating machine oil to circulate through the refrigeration cycle and return to the compressor 1.
The problem is that the amount of refrigerating machine oil in the compressor decreases, causing poor lubrication of the compressor and seizure of the sliding parts. Moreover, such drawbacks also occur during heating operation. Furthermore, when performing compressor capacity control operation or low-load operation, the amount of refrigerant circulated decreases and the speed of refrigerant flowing in the piping decreases, making it difficult for the refrigerant oil to return to the compressor. However, there is a drawback that lubrication failure of the compressor similar to that mentioned above occurs.

When defrosting the outdoor heat exchanger 3, the high-temperature, high-pressure refrigerant gas discharged from the compressor 1 passes through the four-way valve 2 and reaches the outdoor heat exchanger 3 to remove the frost attached to it. It is melted and removed, becomes a refrigerant liquid through this heat exchange, passes through the distributor 4, is depressurized by the expansion valve 5, and is transferred to the connecting pipe 6, the indoor heat exchanger 7, the connecting pipe 8, the four-way valve 2, and the accumulator 9. In addition to forming a circulation cycle in which the air is sucked into the compressor 1 through the
When it is operated, cold air is blown into the room, so it is stopped and a reverse cycle defrost is performed. However, during this defrosting, the low temperature and low pressure 2 that is depressurized by the expansion valve 5
Since the phase flow refrigerant is not heat exchanged in the indoor heat exchanger 7, the pressure of the low-pressure refrigerant gas decreases and enters the accumulator 9, where the refrigerant liquid accumulates, reducing the amount of refrigerant circulation. However, there is also the disadvantage that the input to the compressor 1 becomes smaller, and therefore the defrosting time becomes longer.

In addition, when the heating temperature is low, the evaporation temperature is low and frost quickly forms, which further lowers the evaporation temperature.As a result, the suction pressure of the compressor is greatly reduced, the compression function is reduced, and the heating capacity is reduced. There are also drawbacks.

[Summary of the invention]

This invention has a refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, a throttling device, an indoor heat exchanger, and an accumulator are connected in a ring, and the discharge side of the compressor and the four-way valve It consists of an oil separator installed between the two, a bypass path connecting the oil separator and the above-mentioned accumulator via a solenoid valve, and a control device. A defrost start thermostat that closes the contacts at ₁ , a circuit that opens the above solenoid valve and switches a 4-way valve to perform reverse cycle defrosting, and a heating operation forced timer that allows continuous heating operation for a certain period of time. When heating is performed at a low temperature, the contact is closed at an evaporation temperature t ₂ lower than the defrosting start temperature t ₁ , and this evaporation temperature t ₂
The thermostat opens the contact at the evaporation temperature _t3 , which is just before the defrosting start temperature _t1 is reached, and in conjunction with this, the solenoid valve opens at the evaporation temperature _t2 , and the solenoid valve opens at the evaporation temperature _t3 . The present invention attempts to solve the above-described drawbacks of the conventional air conditioner by providing a refrigeration cycle for an air conditioner, which is characterized by having a circuit that closes the air conditioner.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

In FIG. 2, parts that are the same as those in FIG. 1 are given the same reference numerals, and their explanation will be omitted. Reference numeral 10 denotes an oil separator, and the oil separator 10 is provided between the discharge side of the compressor 1 and the four-way valve 2 of the refrigeration cycle, with the upper portion connected thereto. 11 is a bypass path connecting the lower part of the oil separator 10 and the accumulator 9, and 12 is a solenoid valve provided in the middle of the bypass path 11.

FIG. 3 shows the electrical circuit of the control device according to this embodiment. In Fig. 3, CM is the electric motor for the compressor 1, F ₁ M is the electric blower motor for blowing air to the outdoor heat exchanger 3, and F ₂ M is the electric blower motor for blowing air to the indoor heat exchanger 7. , SW ₁ is an operation switch, SW ₂ is an air conditioning/heating switch, and 23W is an indoor temperature thermoswitch.When the indoor temperature is higher than the set value, the contact of the thermoswitch 23W is (c)-
In (a), when the value is lower than the set value, the contact is switched between (b) and (c). 52F is a coil of a contactor for the blower motor F ₂ M, and when this coil 52F is energized and energized, its contact 52f is closed, and the blower motor F ₂ M is energized and operated, and is deenergized and demagnetized. Then, the contact 52f is opened and the blower electric motor F ₂ M is stopped. Also,
52C is the compressor motor CM and blower motor
F ₁ M contactor coil, this coil 52
When C is energized and excited, its contact 52C closes, and the compressor motor CM and blower motor
When F ₁ M is operated and deenergized, contact 52
c is opened, and the compressor motor CM and blower motor F ₁ M are stopped. 21C is a coil of the electromagnetic valve 12. When the coil 21C is energized and excited, the electromagnetic valve 12 is opened, and when the coil 21C is deenergized and deenergized, the electromagnetic valve 12 is closed. _21S4 is a coil of the four-way valve 2. When this coil _21S4 is energized and excited, it becomes a heating operation where the refrigerant flows as shown by the broken arrow in FIG. The four-way valve 2 is switched to perform a cooling operation (or a defrost operation) in which the refrigerant flows.
TM is a timer motor, which rotates when energized and stops rotating when de-energized. t _n is a timer contact, and the timer motor rotates once in the set time (t _n1 + t _n2 ), and at this time, the contact t _n is open during the set time t _n1 and is closed during the next set time t _n2 . Contact t _n is closed and this process is repeated.
Y is a time-limited relay, and when the time-limited relay Y is energized, its contact y is closed for a certain period of time t _n3 , and after that, the contact y is open as long as it is energized.

TM ₁ is a heating operation forced timer motor.
It rotates when energized and stops rotating when de-energized. t _na and t _nb are the contacts of the timer, and the timer motor rotates once in the set time (t _n4 + t _n5 ), and during this set time t _n4 , the contact t _na is open and t _nb is closed. . During the next set time t _n5 , contact t _na is closed, t _nb is open, and this is repeated.

X4 is the coil of the auxiliary relay, which is connected in series to the contact T _nb of the heating operation forced timer (TM ₁ ), and when energized and energized, its contact 4x _a opens, and when it is deenergized and deenergized, its contact 4x _a closes. .

Then, the timer 52C of the contactor, the coil 21C of the solenoid valve 12, the timer motor TM, the heating operation forced timer motor TM1, and the auxiliary relay coil X.
4. Time-limited relay Y is indoor temperature thermo switch 23
It is connected in parallel to the W contact (c). 26S
is a contact of the thermostat attached to the suction pipe, which closes when the temperature falls below a certain set value t ₂ [°C] and opens when it rises above the set value t ₃ [°C]. 26D ₁
is a contact point of the defrost start thermostat installed at the same location as 26S, which closes when the temperature falls below the set value t ₁ [°C] and opens when it rises above the set value.

Here, the set values are determined so that t ₁ > t ₃ > t ₂ . _t1 is selected and set to a temperature at which frost forms on the outdoor heat exchanger 3 and the heating capacity begins to drop.
_26D2 is a contact point of the defrost end thermostat, which closes when the temperature falls below the set value and opens when the temperature rises above the set value. Note that the set value _t1 of the defrost start thermostat is lower than the set value of the defrost end thermostat. X2 is the coil of the auxiliary relay, which is connected in series with the thermostats 26D ₁ , 26D ₂ and the contact t _na of the forced heating operation timer, and when energized, the contact 2x _a closes and the contacts 2x _b , 2x _c , 2x _d ,2
When x _e is opened and deenergized, contact 2x _a is opened and contacts 2x _b , 2x _c , 2x _d , and 2x _e are closed. X3 is a coil of an auxiliary relay connected in series with the contact 26S of the thermostat, and when energized and energized, the contact 3x _a closes, and when deenergized and deenergized, the contact 3x _a opens. X1 is the coil of the auxiliary relay, which is connected in series with the thermostat contacts 26D ₁ and 26D ₂ and the heating operation forced timer contact _tna .
When energized _and energized, the contacts 1x _a and 1x c are closed, and when energized and demagnetized, the contacts 1x _a and 1x _c are opened and _{1x b is} closed. Further, a contact t _na of a timer, a contact y of a time-limited relay Y, and contacts 2x _a and 3x _a of auxiliary relays X2 and X3 are connected in parallel to the coil 21 of the solenoid valve 12 .

When the indoor temperature is higher than the set value of the thermo switch 23W during cooling, when the operation switch SW ₁ is turned on, the coil 52F of the contactor is energized and the contact 52f is closed, and the blower motor F of the indoor heat exchanger is turned on. ₂ M is activated and the heating/cooling switch is turned on.
Since SW ₂ is on the cooling side (d) and the contacts (a) and (c) of the thermo switch 23W are connected, the contactor coil 52C is energized and the contact 52c is closed, and the compressor motor CM is turned on. The compressor 1 starts to drive.

In addition, since the time-limited relay Y is also energized, the contact y
is closed, the coil 21C of the solenoid valve is excited, the solenoid valve 12 is opened, and the bypass path 11 is opened. Further, after the set time t _n3 has elapsed, the time-limited relay Y is demagnetized, the contact y is opened, the coil 21C of the solenoid valve is demagnetized, the solenoid valve 12 is closed, and the bypass path 11 is closed. Note that this also applies to startup during heating. The timer motor TM is energized and continues to rotate, and when the set time t _n1 elapses, the contact t _n closes, the solenoid valve coil 21C is energized, the solenoid valve 12 opens, and the set time t _n2 elapses.
After , the contact t _n is opened, the coil 21C is demagnetized, the solenoid valve 12 is closed, and the above-described operation is repeated. Note that this also applies during heating.

During heating, when the room temperature is lower than the set value of the thermo switch 23W, when the operation switch SW ₁ is turned on, the contactor coil 52F is energized and the contact 52 is turned on.
f is closed, and the blower motor for the indoor heat exchanger
F ₂ M is started, the air conditioning/heating changeover switch SW ₂ is set to the heating side (E), the coil 21S ₄ of the four-way valve 2 is excited and the heating operation is started, and the contacts (B) and (C) of the thermo switch 23W are connected. Therefore, the coil 52C of the contactor is excited, the contact 52c is closed, and the compressor 1 is started.

Since the time-limited relay Y is also energized, the contact y is closed and the coil 21C of the solenoid valve is energized, and the solenoid valve 12 is opened and the bypass path 11 is formed. Furthermore, after the set time t _n3 , the time-limited relay Y is demagnetized, the contact y is opened, the coil 21C is demagnetized, the solenoid valve 12 is closed, and the bypass path 11 is closed.

The timer motor TM is energized and continues to rotate.
Similarly to the cooling operation described above, the coil 21C is energized after the set time t _n1 has elapsed, and demagnetized after the set time t _n2 has elapsed, and the operation of opening and closing the solenoid valve 12 is repeated.

In addition, when the temperature of the thermostat attached to the suction pipe falls below the set value t ₂ [°C] during low temperature heating, its contact 26S closes, the auxiliary relay coil X3 is energized, and the contact 3x _a closes. The coil 21C of the solenoid valve is excited, the solenoid valve 12 is opened, and the bypass path 11 is opened. 26S for t ₃ or more
is open, 3X _a is open, 21C is demagnetized,
The solenoid valve 12 is closed and the bypass path 11 is closed.
Furthermore, in defrosting, when the heating time has passed the set time t _n4 , t _na is closed, t _nb is opened, and the timer motor (TM ₁ ) for forcing heating operation is de-energized and stops rotating. . Next, when the set temperature falls below the set value of the higher defrost end thermostat, that contact 26D ₂ closes, and then when the set temperature falls below the set value t ₁ [°C] of the defrost start thermostat, that contact 26D ₁ closes. is closed, the coil X2 of the auxiliary relay is energized, and the contact _2xc is opened, so the coil (21S ₄ ) of the four-way valve 2 is demagnetized and defrosting begins. At the same time, contact 2 of coil X2 of the auxiliary relay
When x _d and 2x _e are opened, the electric motor of outdoor heat exchanger 3
F ₁ M is stopped, the contact 2x _a is closed, the solenoid valve coil 21C is energized, the solenoid valve 12 is opened, and the bypass path 11 is opened. Further, the coil X1 of the auxiliary relay is energized, contacts 1x _a and 1x _c are closed, and 1x _b is opened, and is connected in parallel with the contact 26D ₁ of the defrosting start thermostat. Also, 4x _a , 1
The heating operation forced timer motor (TM ₁ ) connected in series with x _c starts rotating, and when the set time t _n5 elapses, t _na opens, t _nb closes, and the auxiliary relay ( It is energized, the contact _4xa is opened, and the heating operation forced timer motor (TM ₁ ) has stopped rotating. When defrosting starts, the temperature immediately rises above the set value t ₁ [°C] of the defrost start thermostat, and its contact 26D ₁ opens, and the defrost end thermostat contacts 26D ₂ and 1x _a , a circuit of auxiliary relay coils X2 and X1 is formed.
When the temperature rises above the set value of the defrosting thermostat, its contact _26D2 opens, the coils X2 and X1 of the auxiliary relay are demagnetized, and defrosting is completed. The heating operation forced timer motor (TM1) starts rotating.

Next, the operation of the refrigeration cycle shown in FIG. 2 will be explained. In Figure 2, the solid arrows indicate the flow of refrigerant during cooling and defrosting operations, and the dashed arrows indicate the flow of refrigerant during heating.
The dashed dotted line indicates the flow of refrigerant and refrigerating machine oil in the bypass path.

During cooling operation, high-temperature, high-pressure refrigerant gas and refrigerating machine oil discharged from the compressor 1 enter the oil separator 10 from above, and the refrigerating machine oil is separated from the refrigerant gas and collected at the bottom of the oil separator 10. . The refrigerant gas separated from the refrigeration oil exits from the upper part of the oil separator 10, passes through the four-way valve 2, reaches the outdoor heat exchanger 3, where it exchanges heat and becomes a high-temperature, high-pressure refrigerant liquid, which passes through the distributor 4. It is depressurized by the expansion valve 5, evaporated in the indoor heat exchanger 7 via the connecting pipe 6, and then returns to the compressor via the connecting pipe 8, the four-way valve 2, and the accumulator 9.

During this operation, the solenoid valve 12 located in the middle of the bypass path 11 is closed, but when refrigerating machine oil accumulates in the oil separator 10, the solenoid valve 12 is opened by a signal and the oil accumulates in the lower part of the oil separator 10. The refrigerating machine oil passes through the bypass path 11, is returned to the accumulator 9 via the solenoid valve 12, and is returned to the compressor 1 together with the low-temperature, low-pressure refrigerant gas that has returned from the indoor heat exchanger 7. This greatly shortens the refrigerating machine oil circulation circuit. This operation is almost the same during heating operation.

Therefore, even if the indoor unit and outdoor unit of the air conditioner are far apart, that is, even if the connecting pipes 6 and 8 are long, the refrigerating machine oil circulation circuit is short and passes through the bypass path 11, so the compression There is no possibility of a shortage of refrigerating machine oil in machine 1. In addition, when the compressor 1 is of the capacity control type, even when the circulating amount of refrigerant discharged from the compressor is significantly reduced and becomes small, that is, when the speed at which the refrigerant moves in the piping becomes low, There will be no shortage of refrigeration oil returned.

When the compressor 1 is started, the time-limited relay Y
As a result, the solenoid valve 12 is kept open for a certain period of time t _n3 after the compressor 1 is started, so that the refrigerant that has been mixed in the refrigerating machine oil when the compressor 1 is stopped will form when the compressor starts. Even if a large amount of refrigerating machine oil is discharged from the compressor 1 compared to during normal continuous operation, the refrigerating machine oil is separated from the refrigerant by the oil separator 10 and does not circulate through the refrigerant circuit. It returns to the accumulator 9 via the path 11 through the open electromagnetic valve 12, and returns to the compressor 1 together with the low-pressure gas, making it possible to compensate for the shortage of refrigerating machine oil in the compressor in a short time.

Furthermore, when the heating operation changes to the defrosting operation, the auxiliary _relay coil
2 opens, and at the same time, the four-way valve 2 is switched.
Therefore, the high-temperature, high-pressure refrigerant gas compressed by the compressor 1 passes through the oil separator 10, the four-way valve 2, and reaches the outdoor heat exchanger 3, and after defrosting it, the distributor 4 The pressure is reduced by the expansion valve 5, and the connection pipe 6, the indoor heat exchanger 7, and the connection pipe 8
It passes through the four-way valve 2 and returns to the accumulator 9. At the same time, a portion of the high-temperature, high-pressure refrigerant gas discharged from the compressor 1 is returned to the accumulator 9 from the lower part of the oil separator 10 via the bypass path 11 and through the electromagnetic valve 2 . In the accumulator 9, the low-temperature, low-pressure refrigerant gas that has passed through the indoor heat exchanger 7, which functions as an evaporator, is mixed with the high-temperature, high-pressure refrigerant gas that has passed through the bypass path 11. The pressure increases and returns to the compressor 1. As a result, it is possible to create a state in which the storage volume of the refrigerant gas is small and the amount of circulation is large, so that the outdoor heat exchanger 3
Frost that adheres to the surface can be melted and removed in a short time.

In addition, when the heating temperature is low and the outside air temperature is extremely low, the temperature of the thermostat to start defrosting will be set at _t1.
If the temperature is lower than [°C] and the heating operation is being performed using the forced heating operation timer, frost will form on the outdoor heat exchanger 3, which acts as an evaporator, and the evaporation temperature will further drop, resulting in an extremely low heating capacity. temperature
When it becomes less than t ₂ , the contact 26S is closed, the auxiliary relay coil X3 is energized, and the contact 3x _a
is closed, the solenoid valve coil 21C is energized, the solenoid valve 12 is opened, and a portion of the high temperature and high pressure refrigerant gas discharged from the compressor 1 is bypassed to the accumulator 9 via the oil separator 10 and the bypass path 11. The low-temperature, low-pressure refrigerant gas that has passed through the outdoor heat exchanger 3, which functions as an evaporator, is mixed with the high-temperature, high-pressure refrigerant gas that has passed through the bypass passage 11, so that the low-pressure refrigerant rises and reaches the compressor. Return to 1. This increases the amount of refrigerant circulated in the compressor 1, increasing the heating capacity at low temperatures. Furthermore, when the evaporation temperature rises to t ₃ [°C] before the defrosting start temperature t ₁ becomes higher, the contact 26S is opened, the auxiliary relay coil X3 is demagnetized, and the contact 3x _a is opened, and the electromagnetic The valve coil 21C is demagnetized and the solenoid valve 12 is closed.

When a variable capacity compressor 1 is used, the above-mentioned solenoid valve 1 for defrosting and heating at low temperatures is used.
By operating the compressor at its maximum capacity while 2 is open, it is more effective to increase the defrosting capacity and heating capacity.

During cooling or heating operation, after starting the compressor 1, continuous operation is performed for a certain period of time t _n1 , and then the contact t _n of the timer motor TM is closed, and the timer motor TM
As the continues to rotate, the coil 21C is excited for a set time t _n3 at set time intervals t _n2 and the solenoid valve 12 is opened, so that the refrigerating machine oil stored in the oil separator 10 is bypassed from the oil separator 10. Road 11
via the solenoid valve 12 to the accumulator 9
The refrigerating machine oil is returned to the compressor 1 along with the low-temperature, low-pressure refrigerant gas returned from the heat exchanger serving as the evaporator, and the compressor is replenished with refrigerating machine oil, so there is no shortage of refrigerating machine oil.

Furthermore, since the refrigeration cycle of this embodiment is configured as described above, when the air conditioner is stopped, the refrigerant that has accumulated in the connecting pipe 8 returns to the discharge port side of the compressor 1 due to its own weight. Also, it is possible to prevent oil from being accumulated in the oil separator 10 and entering the discharge port of the compressor 1, thereby preventing damage to the valve of the compressor 1 at the time of startup.

In the above embodiment, a split-type air conditioner in which the compressor is located outside the room has been described, but the present invention can also be applied to a remote-type air conditioner in which the compressor is located inside the room. Further, in the above embodiment, an expansion valve was used as the throttle device, but in the present invention, a throttle device such as a capillary tube, an electric expansion valve, or an orifice can be used, and the mounting position of the throttle device is also on the indoor side. It may be placed anywhere between the heat exchanger and the outdoor heat exchanger.

〔Effect of the invention〕

As explained above, according to the present invention, an oil separator is provided between the discharge side of the compressor and the four-way valve, and the oil separator and the accumulator are connected via a solenoid valve by a bypass path. By opening the above solenoid valve, the refrigerating machine oil and high-temperature, high-pressure refrigerant gas are returned to the accumulator via the bypass path. Furthermore, even when a variable capacity compressor is used and the refrigerant discharge amount is significantly reduced, refrigerating machine oil can be easily and sufficiently returned to the compressor. Then, during defrosting, a circuit is provided to perform reverse cycle defrosting by switching the four-way valve as the solenoid valve opens in conjunction with the contact of the defrost start thermostat of the control device closing at the defrost start temperature _t1 . Therefore, the defrosting ability can be greatly improved and defrosting can be completed in a short time. In addition, the defrosting start temperature t ₁ [°C], the opening temperature t ₂ [°C], and the closing temperature t ₃ [°C] at low heating temperatures were set to t ₁ > t ₃ > t ₂ , so that the outside air If the temperature is extremely low and the temperature of the thermostat that starts defrosting is lower than the set value _t1 , and heating operation is being performed using the heating operation forced timer, frost will form on the outdoor heat exchanger that acts as an evaporator. When the evaporation temperature further decreases to a temperature _t2 at which the heating capacity is extremely reduced, the solenoid valve opens in conjunction with the closing of the thermostat contacts in the control device, increasing the low pressure and reducing the compressor capacity. becomes large, the evaporation temperature rises, and when the evaporation temperature rises to _t3 before becoming higher than the defrosting start temperature _t1 , the contact of the thermostat opens and the solenoid valve is closed. By doing this, when the heating operation forced timer operation ends, the defrosting operation starts once.
Since it is possible to remove frost that has formed on the outdoor heat exchanger, it is possible to provide a heat pump with a simple configuration and a low cost refrigeration cycle with high heating characteristics, comfort, and reliability.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing a refrigeration cycle of a conventional air conditioner, FIG. 2 is a configuration explanatory diagram showing a refrigeration cycle according to an embodiment of the present invention, and FIG. 3 is a control device according to an embodiment of the present invention. FIG. 1... Compressor, 2... Four-way valve, 3... Outdoor heat exchanger, 4... Distributor, 5... Expansion valve, 6, 8... Connection piping, 7... Outdoor heat exchanger , 9...Accumulator, 10...Oil separator, 11...Bypass path, 12...Solenoid valve, CM
...Compressor motor, F ₁ M, F ₂ M...Outdoor side,
Indoor heat exchanger blower electric motor, SW ₁ ...operation switch, SW ₂ ...air conditioning/heating selector switch, 23W
...Indoor temperature thermo switch, 52C, 52F...
...Contactor coil, 21C...Solenoid valve coil,
21S ₄ ...Four-way valve coil, TM...Timer motor, TM ₁ ...Heating operation forced timer, Y...
...Time-limited relay, 26D ₁ , 26D ₂ ...Start defrosting,
Defrost end thermostat contact, 26S... Thermostat contact, X1, X2, X3, X4...
Auxiliary relay coil. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. It has a refrigeration cycle in which a compressor, a four-way valve, an outdoor heat exchanger, a throttling device, an indoor heat exchanger, and an accumulator are connected in a ring, and between the discharge side of the compressor and the four-way valve. It consists of an oil separator provided, a bypass path connecting this oil separator and the above-mentioned accumulator via a solenoid valve, and _a control device. A defrost start thermostat that closes the circuit, a circuit that opens the solenoid valve and switches the four-way valve to perform reverse cycle defrosting, and a heating operation forced timer that operates the heating system continuously for a certain period of time. A thermostat that closes a contact at an evaporation temperature _t2 lower than the defrost start temperature _t1 at low temperatures and opens a contact at an evaporation temperature _t3 higher than the evaporation temperature _t2 and just before _the defrost start temperature t1. A refrigeration cycle for an air conditioner, comprising a circuit that opens the solenoid valve at the evaporation temperature _t2 and closes the solenoid valve at the evaporation temperature _t3 in conjunction with this.