JPH0498053A - Air conditioning plant - Google Patents

Abstract

PURPOSE:To prevent cold air from being blown into a room at a defrosting operation during heating operation and at the same time to prevent liquid from returning back to a compressor by a method wherein an air conditioner is constructed such that a heat exchanging operation can be carried out between a refrigerant circuit and a suction side pipe branched from a discharging side pipe of a compressor and connecting between an accumulator and the compressor, a three-way transfer valve is changed over to release the fourth bypassing circuit to perform a defrosting operation. CONSTITUTION:During defrosting operation, the fourth bypassing circuit 14 is opened by a three-way transfer valve 13, thereby gaseous refrigerant of high temperature and high pressure from a compressor 1 is sent to an outdoor side heat exchanger 3, resulting in that not only an efficient defrosting operation can be carried out within a short period of time, but also during cooling or heating operation, refrigerant in a suction pipe 1a for the compressor 1 is heated through a suction heat exchanger 11 by a part of the discharged gas of high temperature and high pressure from the compressor 1 with the first bypassing circuit 10 and then the compressor 1 can be efficiently controlled in its operation. With such an arrangement, it is possible to prevent a phenomenon of liquid returning to the compressor and at the same time it is also possible to prevent a heat loss and further it becomes possible to eliminate problems of blowing of cold air into a room.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an air conditioner that performs heating and cooling operations using a refrigeration cycle circuit.

[Conventional technology]

Conventionally, this type of air conditioner has a configuration such as that shown in Figure 4.12 of ``Heat Pumps - Project I Star Meter and Its II-J P122'', published by Japan Technology and Economic Center, July 5, 1981. is well known.

The schematic structure of such an air conditioner will be briefly explained using FIG. 5. In the figure, reference numeral 1 is a compressor, 2 is a four-way switching valve, 3 is an outdoor heat exchanger, and 4.5 is a cooling operation. The first and second parts each function as an expansion mechanism during heating operation.
6 is an indoor heat exchanger, and 7 is an accumulator. A refrigeration cycle circuit is constructed by sequentially connecting these devices through refrigerant piping. In addition, 8 and 9 are on the indoor side,
Indoor and outdoor air blowers respectively blow air to the outdoor heat exchanger 6.3, and 4a and 4b are the first pressure reducing device (capillary tube) constituting the first restrictor W4 and the circuit that bypasses this. a first check valve provided in;
5a and 5b are a second pressure reducing device (capillary tube) constituting the second throttle device 5 and a second check valve provided in a circuit that bypasses the second pressure reducing device (capillary tube).

In an air conditioner with such a configuration, during cooling operation (the flow of the refrigerant is indicated by the thick solid line arrow in the figure), the high temperature and high pressure gas refrigerant discharged from the compressor 1 passes through the four-way switching valve 2. In the outdoor heat exchanger 3, the gas refrigerant is condensed and liquefied by exchanging heat with outdoor air blown by the outdoor fan 9.

Then, the first throttle device in the bypass circuit on the side of the first throttle device 4
through the check valve 4b and forming the second throttle device 5.
The refrigerant is introduced into the pressure reducing device 5a and is depressurized, becoming a low-temperature, low-pressure liquid refrigerant. After that, this liquid refrigerant enters the indoor heat exchanger 6 and exchanges heat with the indoor air blown by the indoor blower 8 to cool the indoor air. 2. Accumulator 7
A refrigeration cycle during cooling is configured in which the refrigerant passes through the refrigerant and returns to the compressor 1, and thereafter the refrigerant is circulated through the above-mentioned refrigeration cycle path while repeating liquefaction and vaporization in sequence.

On the other hand, during heating operation (the flow of refrigerant is shown by the thin solid arrow in the figure), the high temperature and high pressure gas refrigerant discharged from the compressor 1 passes through the four-way switching valve 2 which is switched to the heating side.
The gas refrigerant enters the indoor heat exchanger 6 and exchanges heat with the indoor air blown by the indoor blower 8 to heat the indoor air, and thereby condenses and liquefies the gas refrigerant. Then, this liquid refrigerant passes through the second check valve 5b in the circuit that bypasses the second throttle device 5, is led to the first pressure reducing device fi4a that constitutes the first throttle device W4, and is depressurized. , it becomes a low-temperature, low-pressure liquid refrigerant. After that, the liquid refrigerant enters the outdoor heat exchanger 3, exchanges heat with the outdoor air blown by the outdoor fan 9, collects heat from the outdoor air and cools the outdoor air, and as a result, the liquid refrigerant evaporates into gas. It passes through the four-way switching valve 2 and the accumulator 7 and returns to the compressor 1, thereby forming a refrigeration cycle during heating.

Also, if you continue to use this type of heating operation,
For example, when the outdoor air temperature is low, frost forms on the outdoor heat exchanger 3. When such frost formation increases, the heat exchange efficiency deteriorates, and the amount of heat extracted from the outdoor air decreases, resulting in a significant decrease in the heating capacity of the air conditioner. Therefore, in such cases, it is necessary to perform defrosting.

Such a defrost operation is performed as described in PL21 in the above-mentioned document "Heat Pump - Actual Meter and Volume 6". That is, during such a defrost operation (the flow of refrigerant is indicated by the dashed arrow in the figure), the high temperature and high pressure gas refrigerant discharged from the compressor 1 is switched from the heating side to the cooling side. It passes through valve 2 and enters outdoor heat exchanger 3. Here, the outdoor side blower 9 is stopped. And this outdoor heat exchanger 3
The frost formed on the surface of the refrigerant is melted by a high-temperature gas refrigerant, and this refrigerant is condensed and liquefied, passes through the first check valve 4b that bypasses the first throttling device W4, and passes through the second throttling device 5. The refrigerating cycle operation is performed in which the pressure is reduced by the second pressure reducing device 5a, and the liquid refrigerant enters the indoor heat exchanger 6, then returns to the compressor 1 through the four-way switching valve 2 and the accumulator 7. It was something to do.

[Problem to be solved by the invention]

By the way, some problems occur when a low temperature, low pressure liquid refrigerant is introduced into the indoor heat exchanger 6 during the defrost operation during the above-mentioned heating operation. That is, the indoor blower 8 disposed opposite to the indoor heat exchanger 6 is
During this defrost operation, the defrost operation is normally performed or is stopped. For example, when operating in a breeze, the low-temperature, low-pressure liquid refrigerant and the indoor air exchange heat, cool the indoor air, and the liquid refrigerant evaporates and gases, causing the four-way switching valve 2 and the accumulator 7
and returns to compressor 1. Therefore, in such a case, cold air is blown toward the indoor side, resulting in a problem that the air conditioning effect is significantly reduced.

Furthermore, when the indoor blower 8 is stopped, heat cannot be collected from the low-temperature, low-pressure liquid refrigerant, and the refrigerant enters the accumulator 7 as a liquid and returns to the compressor 1, so the compressor 1 compresses the liquid and compresses it. Machine troubles sometimes occurred.

Further, according to the above-mentioned conventional apparatus, since the high pressure is low especially during defrosting, the low pressure also decreases, making it impossible for the compressor 1 to fully utilize its capacity, and the defrosting time also takes a long time. Furthermore, since the four-way switching valve 2 is switched to the cooling side during the heating operation to perform the defrost operation, there is also a problem in that heat loss occurs during the switching.

The present invention was made in view of the above-mentioned circumstances, and therefore, it prevents cold air from being blown into the room during defrost operation during heating operation, and performs defrost operation with the four-way switching valve set to the heating side, thereby reducing the pressure. The air conditioner is configured to increase the compression function by increasing the air flow rate, and also prevents liquid from returning to the compressor by exchanging heat between the high-temperature, high-pressure gas refrigerant from the compressor and the suction side piping. The purpose is to obtain.

[Means to solve the problem]

The air conditioner according to the present invention has a first bypass circuit that exchanges heat with the suction side piping and bypasses the high temperature, high pressure gas refrigerant from the compressor to the piping side between the first expansion device and the second expansion device. and a second and third bypass circuit having a check valve that bypasses the first pressure reducing device and the second pressure reducing device, and a three-way switching valve from the discharge side piping of the compressor to the first and third bypass circuits having check valves that bypass the first and second pressure reducing devices. A fourth bypass circuit is provided on the piping side between the second throttling device and is connected by bypass and has an inner diameter smaller than the discharge side piping,
Furthermore, a fifth bypass circuit is provided which is connected from between the discharge side piping of the compressor and the three-way switching valve to the piping side between the first and second throttle devices via a pressure regulating valve. This is what I did.

Further, according to the present invention, if the indoor temperature is below a predetermined value during the defrost operation, the three-way switching valve is returned to the heating operation mode at regular time intervals.

Furthermore, according to the invention, indoor l! A sixth bypass circuit is provided that bypasses the piping between the heat exchanger and the second throttling device to the accumulator via a solenoid valve, and when the indoor temperature is below a predetermined value during defrost operation,
The sixth bypass circuit is opened by a solenoid valve at regular time intervals.

Further, according to the present invention, the first bypass circuit configured to be able to exchange heat with the suction side piping of the compressor and bypass-connected to the piping side between the first and second expansion devices is connected to the compressor. The valve is installed on the discharge side piping of the machine between a three-way switching valve that switches the circuit to the fourth bypass circuit and a four-way switching valve located downstream of the three-way switching valve.

[Effect]

According to the present invention, during defrost operation during heating operation, the blowers to the indoor and outdoor heat exchangers are stopped while the four-way switching valve remains in the heating operation state, the three-way switching valve is switched, and the fourth By opening the bypass circuit and performing defrost operation, it prevents heat loss when switching the conventional four-way switching valve, prevents cold air from blowing into the room, and increases compressor capacity. Heat exchange between the high-temperature, high-pressure gas refrigerant from the compressor and the suction side piping can also prevent liquid from returning to the compressor.

Further, according to the present invention, when the indoor temperature falls below a predetermined value during the defrost operation, by detecting the temperature, the heating operation is performed after a certain period of time, and the indoor heat exchanger This prevents refrigerant from accumulating in the air.

Furthermore, according to the present invention, when the indoor temperature falls below a predetermined value during defrost operation, by detecting the temperature, the solenoid valve is controlled to open and close, and the sixth bypass circuit is opened. The refrigerant accumulated in the indoor heat exchanger is returned to the accumulator side.

Further, according to the present invention, during defrost operation, by opening the fourth bypass circuit by the three-way switching valve,
The high-temperature, high-pressure gas refrigerant from the compressor is sent to the outdoor heat exchanger, and defrosting can be performed efficiently and in a short time.However, during cooling and heating operations, a portion of the high-temperature, high-pressure discharged gas from the compressor generates suction heat. By heating the refrigerant in the suction side piping to the compressor via the exchanger, the liquid returns to the compressor. This suppresses overheating near the end of operation and prevents compressor trouble.

〔Example〕

FIG. 1 shows an embodiment of an air conditioner according to the present invention, and in this figure, the same or corresponding parts as in FIG. 5 described above are given the same numbers and the explanation thereof will be omitted.

Now, according to the present invention, the compressor 1, the four-way switching valve 2, the outdoor heat exchanger 3, the first expansion device 4, the second expansion device 5,
In an air conditioner including a refrigerant circuit in which an indoor heat exchanger 6 and an accumulator 7 are sequentially connected by refrigerant piping, a refrigerant circuit is branched from the discharge side piping of the compressor 1 and connects the accumulator 7 and the compressor 1. Suction side piping 1a to be connected
A first bypass pipe that passes through a suction heat exchanger 11 configured to be able to exchange heat with the auxiliary capillary tube 12 and is connected to the pipe side between the first and second throttle devices 4.5 in a bypass manner. 10 and provided with a check valve 4b that bypasses the first pressure reducing device f4a, and a third bypass circuit 5C provided with a check valve 5b that bypasses the second pressure reducing device 5a. and the inner diameter of the discharge side piping 1b which is connected from the discharge side piping 1b of the compressor 1 via the three-way switching valve 13 to the piping side between the first and second throttle devices W4 and 5 in a bypass manner. A fourth tube having at least a portion thereof a thin tube 15 having an inner diameter smaller than that of the fourth tube.
A bypass path 14 is provided for the compression I! A pressure regulating valve 16 is inserted between the discharge side pipe 1b of No. 1 and the three-way switching valve 13.
The present invention is characterized in that a fifth bypass circuit 17 is provided, which is connected to the piping between the first and second throttle devices 4 and 5 in a bypass manner.

In such a configuration, during the defrost operation, the blower 8.9 that blows air to the indoor and outdoor heat exchangers 6.3 is stopped while the four-way switching valve 2 remains in the heating operation state, and the three-way switching valve 13 is stopped. is switched to open the fourth bypass circuit 14 to enable defrost operation.

In the air conditioner configured as described above, during cooling operation, the refrigerant flows in the direction of the arrow indicated by the thick solid line in the figure. The heat exchanger 3 exchanges heat with the outdoor air blown by the outdoor blower 9, and thereby the gas refrigerant is condensed and liquefied. Then, the pressure is reduced by the first pressure reducing device 4a in the first throttle device W4, and the refrigerant becomes a low-temperature, low-pressure liquid refrigerant. On the other hand, a part of the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 passes through the first bypass circuit 10 and exchanges heat with the low-pressure refrigerant sucked into the compressor 1 in the suction heat exchanger 11, thereby converting the suction refrigerant into It is heated to completely vaporize it, condenses and liquefies itself, is depressurized by the auxiliary capillary tube 12, becomes a low-temperature, low-pressure liquid refrigerant, joins the piping between the first and second throttle devices 4.5, and flows into the second Passing through the third bypass circuit 5C in the expansion device 5, the indoor heat exchanger 6
In this refrigeration cycle, the liquid refrigerant enters the room and exchanges heat with the indoor air blown from the indoor blower 8 to cool the indoor air, and the liquid refrigerant evaporates into gas and returns to the compressor 1 through the four-way switching valve 2 and the accumulator 7. The circuit is configured.

In addition, during heating operation (the flow of refrigerant is in the direction of the arrow indicated by the thin solid line in the figure), the high temperature and high pressure gas refrigerant discharged from the compressor 1 passes through the four-way switching valve 2, which is switched to the heating side, to the indoor side. The gas refrigerant enters the heat exchanger 6 and exchanges heat with the indoor air blown from the indoor blower 8 to heat the indoor air, and thereby condenses and liquefies the gas refrigerant. Then, the pressure is reduced by the second pressure reducing device 5a in the second expansion device 5,
It becomes a low temperature, low pressure liquid refrigerant. On the other hand, a part of the high temperature and high pressure gas refrigerant discharged from the compressor 1 is transferred to the first bypass circuit 1.
0, the suction heat exchanger 11 exchanges heat with the low-pressure refrigerant sucked into the compressor 1, heats the suction refrigerant, and completely vaporizes the refrigerant, which condenses and liquefies itself and is depressurized by the auxiliary capillary tube 12 to become a low-temperature, low-pressure refrigerant. It becomes a liquid refrigerant, joins the piping side, passes through the second bypass circuit 4c in the first throttle device 4, enters the outdoor heat exchanger 3, and flows into the outdoor blower 9.
In this refrigeration system, the liquid refrigerant evaporates into gas, passes through the four-way switching valve 2, the accumulator 7, and returns to the compressor 1. A cycle circuit is constructed.

In addition, during such a heating operation, for example, during a defrost operation that is required when the outdoor air temperature is low and frost forms on the outdoor heat exchanger 3 (refrigerant flow is in the direction of the arrow indicated by the broken line in the figure). In this case, the high-temperature, high-pressure gas refrigerant discharged from the compressor 11!1 passes through the three-way switching valve 13, which is switched to the defrost side, and passes through the first and second throttle devices 4.5.
It flows into the piping side through the fourth bypass circuit 14 connected to the piping side between them.

On the other hand, a part of the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 passes through the first bypass circuit 10 and is compressed by the suction heat exchanger 11! 11, the suction refrigerant is heated and completely vaporized, and it condenses and liquefies itself and is depressurized by the auxiliary capillary tube 12 to become a low-temperature, low-pressure liquid refrigerant, which is then transferred to the fourth bypass circuit. It is mixed with the high-temperature, high-pressure gas refrigerant that has passed through the 15 portions of the thin tubes 14 and 15. These combined gas refrigerants are then transferred to the second bypass circuit 4 in the first restrictor W4.
C and enters the outdoor heat exchanger 3. At this time, the outdoor fan 9 is stopped. Then, the high-temperature gas refrigerant melts the frost that has formed on the surface of the outdoor heat exchanger 3, and this refrigerant is condensed and liquefied, passes through the four-way switching valve 2, enters the accumulator 7, and returns to the compressor 1. It will be.

Therefore, during such defrosting, the defrost operation can be started without switching the four-way switching valve 2 from the heating side to the cooling side, and thereby there is no heat loss due to switching. In addition, the low temperature liquid refrigerant is transferred to the indoor heat exchanger 6.
Since the air does not pass through the interior, the problem of conventional cold air being blown into the interior of the room is also resolved.

Furthermore, the inner diameter of the piping 15 constituting a part of the fourth bypass circuit 14 is made smaller than that of the discharge side piping 1b, which causes pressure loss, increases the pressure on the high pressure side of the compressor 1, and reduces the input. This increases the capacity of the compressor 1, making it possible to shorten the defrost time.

In addition, the defrost end signal detects the outlet side temperature of the outdoor heat exchanger 3 during defrost operation using a detection device such as a thermistor, but since the high pressure side pressure is increased,
Due to the sudden rise in pressure on the high pressure side just before the end of defrost,
There are cases where the outdoor heat exchanger 3 is abnormally stopped due to high pressure cut before the temperature on the outlet side reaches the end temperature, but this can be resolved by the presence of the fifth bypass circuit 17. That is, by opening the pressure regulating valve 16 in this fifth bypass circuit 17 due to the above-mentioned sudden increase in the high pressure side pressure, it becomes possible to maintain the high pressure side pressure constant, thereby preventing abnormal stoppage due to high pressure cut. Here, the pressure regulating valve 16 of this fifth bypass circuit 17 can prevent this pressure regulating valve 16 even if the high pressure side pressure becomes abnormally high for some reason during cooling or heating operation, for example. 16 is opened and the pressure on the high pressure side is maintained constant, thereby preventing abnormal stoppage due to high pressure cutting.

In addition, since the suction heat exchanger 11 is configured to exchange heat between the suction side piping 1a to the compressor 1 and the high temperature and high pressure gas refrigerant discharged from the compressor 1, the compressor 1
It is possible to prevent the phenomenon of liquid returning to the compressor, and it is possible to prevent problems with the compressor.

Note that if the electric heater is installed facing the indoor heat exchanger 6 as indicated by 20 in the figure, the refrigerant will not pass through the indoor heat exchanger 6 during the defrost operation.
This has the advantage that the indoor blower 8 can be operated and the heating operation can be continued even during the defrosting operation.

FIG. 2 shows another embodiment of the present invention. In this embodiment, an indoor temperature detector 30 is provided to detect the indoor temperature in which the indoor heat exchanger 6 is installed, and the defrost operation is performed. It is characterized in that the three-way switching valve 13 is returned to the heating operation mode at fixed time intervals when the indoor temperature is below a predetermined value.

In other words, during defrost operation, the indoor temperature is below the predetermined value (
For example, if the temperature is below 5°C), the pressure inside the indoor heat exchanger 6 will be about 5 kg/cniG, and the pressure inside the pipe between the first and second restrictors W4.5 (normally intermediate pressure, approximately (approximately 10 to 15 kg/cnG), refrigerant accumulates in the indoor heat exchanger 6 during the defrost operation. Therefore, if there is a shortage of refrigerant circulating in the refrigerant circuit, or if too much refrigerant accumulates, it will act as a condenser when heating operation returns, so the refrigerant will be full in the condenser and the high pressure will be cut off. may occur.

Therefore, in this example device, the indoor temperature is detected by the indoor temperature detector 30 during the defrost operation, and the indoor temperature is detected to be below a predetermined value (
For example, if the temperature is below 5 degrees Celsius), return to heating operation after a certain time interval. For example, after performing defrost operation for 5 minutes, return to heating operation for 1 minute, and then re-entering defrost operation) , it is possible to prevent the refrigerant from accumulating in the indoor heat exchanger 6.

FIG. 3 shows yet another embodiment of the present invention,
In this embodiment, similarly to the embodiments described above, in order to prevent refrigerant from accumulating in the indoor heat exchanger 6, which would be a problem if the indoor temperature falls below a predetermined value during defrost operation, A sixth bypass circuit 18 is provided that bypasses the piping between the heat exchanger 6 and the second throttle device W5 to the accumulator 7 side via a solenoid valve 19, and the indoor temperature is below a predetermined value during defrost operation. , the sixth bypass circuit 18 is opened by the solenoid valve 19 at fixed time intervals by detecting this with the indoor temperature detector 30.

That is, when the indoor temperature falls below a predetermined value (for example, below 5 degrees Celsius) during defrost operation, by detecting that temperature, the solenoid valve 19 is controlled to open and close at regular intervals, and the sixth bypass is activated. By opening the circuit 18, the refrigerant accumulated in the indoor heat exchanger 6 is returned to the accumulator 7fi (for example, 5
After performing the defrost operation for one minute, the sixth bypass circuit 18 is opened for one minute, and the accumulated refrigerant is transferred to the accumulator 7.
(control the operation to return it to If such a configuration is adopted, it is possible to solve problems caused by accumulation of refrigerant in the indoor heat exchanger 6 during the defrost operation.

FIG. 4 shows another embodiment of the invention, in which:
A suction heat exchanger 11 is configured to exchange heat between a portion of the high-temperature, high-pressure gas refrigerant discharged from the compressor 1 and the suction side pipe 1a, and the first and second expansion devices 4.
A first bypass circuit 10 that is bypass-connected to the piping side between the compressor 1 and the three-way switching valve 13 that switches the circuit to the fourth bypass circuit 14 on the discharge side piping lb of the compressor 1 is arranged downstream of the three-way switching valve 13 that switches the circuit to the fourth bypass circuit 14. The branch part 10 is connected to the four-way switching valve 2.
The feature is that it is configured to branch at point a.

According to such a configuration, during defrost operation, by opening the fourth bypass circuit 14 using the three-way switching valve 13, the high temperature and high pressure gas refrigerant from the compressor 1 is sent to the outdoor heat exchanger 3, and the defrost operation is performed. Not only can you operate efficiently and in a short time, but during cooling and heating operation,
The first bypass circuit 10 heats the refrigerant in the suction side piping 1a to the compressor 1 via the suction heat exchanger 11 with a part of the high-temperature, high-pressure discharge gas from the compressor 1.
This prevents the phenomenon of liquid returning to the compressor 1 and enables efficient operation control of the compressor 1. Furthermore, since heat exchange by the suction heat exchanger 11 is not performed during the defrost operation,
It is possible to suppress the rise of the high pressure and low pressure valves in the compressor 1 and the tendency towards overheating in the compressor 1 near the end of the defrost operation, thereby making it possible to prevent compressor troubles.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part of the air conditioner may be modified and changed as necessary. For example, as shown by the broken line in FIGS. 2 to 4, a check valve or the like is installed in the middle of the fourth bypass circuit 14 to ensure only the required flow direction of the refrigerant. Various modifications may be considered, including the following.

〔Effect of the invention〕

As explained above, according to the air conditioner according to the present invention, a part of the high temperature and high pressure gas refrigerant from the compressor is configured to exchange heat with the suction side piping via the suction heat exchanger. In addition to preventing the phenomenon of liquid returning to the compressor, it is also possible to perform defrost operation by switching the three-way switching valve while the four-way switching valve remains in heating mode, eliminating heat loss, etc. caused by switching the four-way switching valve as in the past. It has various excellent effects such as being able to prevent the problem and also eliminating the conventional problems such as blowing of cold air toward the indoor side. Furthermore, during defrost operation, the discharge side gas refrigerant from the compressor passes through a bypass circuit having a pipe with an inner diameter smaller than that of the discharge side pipe, so the high pressure increases, thereby improving the compression function. There are advantages such as being able to shorten the defrost time.

In addition, if high pressure rises too much during cooling, heating, or defrosting operation, the problem of abnormal stoppage due to high pressure cut can be appropriately and reliably prevented by maintaining the high pressure constant with a pressure regulating valve. Another advantage is that it can be prevented.

Further, even when the indoor temperature is low, the refrigerant does not accumulate in the indoor heat exchanger, and it is possible to prevent a refrigerant shortage phenomenon and a high pressure cut when switching heating operation, etc.

In addition, in the present invention, the suction heat exchanger is configured to enable heat exchange between a part of the high temperature and high pressure gas refrigerant discharged from the compressor and the suction side piping, and between the first and second throttle devices. A three-way switching valve that switches the first bypass circuit bypass-connected to the piping side of the compressor 1 to a fourth bypass circuit on the discharge side piping of the compressor 1, and a four-way switching valve disposed downstream thereof. During defrost operation, the fourth bypass circuit is opened by the three-way switching valve, and the high-temperature, high-pressure gas refrigerant from the compressor is sent to the outdoor heat exchanger, allowing defrost to be performed efficiently and in a short time. On the other hand, during cooling and heating operations, part of the high-temperature, high-pressure discharge gas from the compressor is used to heat the refrigerant in the suction side piping to the compressor via a suction heat exchanger. It also has the advantage of preventing liquid return, and since no heat exchange is performed by the suction heat exchanger during defrost operation, it suppresses overheating near the end of defrost operation and prevents compressor trouble. be.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a refrigeration cycle circuit showing one embodiment of an air conditioner according to the present invention, and FIGS. 2 to 4 are schematic diagrams of a refrigeration cycle circuit showing other embodiments of the present invention. , FIG. 5 is a schematic configuration diagram showing a conventional example. 1... Compressor, 1a... Suction side piping, 1b...
...Discharge side piping, 2...Four-way switching valve, 3-...Outdoor heat exchanger, 4, 5...First and second throttling devices, 4a, 5a-...No. 1 and 2nd pressure reducing device (capillary tube), 4b, 5b... check valve, 4c
, 5c... second and third bypass circuits, 6...
...Indoor heat exchanger, 7...-accumulator, 8.
9... Indoor side and outdoor side blower, 10... First bypass circuit, 11... Suction heat exchanger,
12... Auxiliary capillary tube, 13... Three-way switching valve, 14... Fourth bypass circuit, 15... -
...Thin tube, 16...Pressure regulating valve, 17...5th
Bypass circuit, 18...-Sixth bypass circuit, 1
9... Solenoid valve, 20... Electric heater, 30...
Indoor temperature detector.

Claims (4)

[Claims] (1) A refrigerant circuit formed by sequentially connecting a compressor, a four-way switching valve, an outdoor heat exchanger, a first expansion device, a second expansion device, an indoor heat exchanger, and an accumulator through refrigerant piping; It is configured to be able to exchange heat with a suction side pipe that is branched from the discharge side pipe of the compressor and connects between the accumulator and the compressor, and is bypassed to the pipe side between the first and second throttle devices. a first bypass circuit connected to the first bypass circuit, and a second bypass circuit having a check valve that bypasses a first pressure reducing device constituting the first throttle device; and a third bypass circuit having a check valve that bypasses the second pressure reducing device, and piping between the first and second throttle devices from the discharge side piping of the compressor via a three-way switching valve. A fourth bypass circuit having a pipe inner diameter portion smaller than the inner diameter of the discharge side pipe connected to the side by bypass, and a pressure regulating valve from between the discharge side pipe of the compressor and the three-way switching valve. and a fifth bypass circuit connected to the piping side between the first and second throttle devices in a bypass manner,
An air conditioner characterized in that the three-way switching valve is switched to open the fourth bypass circuit to perform defrost operation. (2) The air conditioner according to claim 1, wherein the three-way switching valve is controlled to return to the heating operation mode at regular time intervals when the indoor temperature is below a predetermined value during the defrost operation. (3) In claim 1 or 2, a sixth bypass circuit is provided that bypasses the accumulator from the piping between the indoor heat exchanger and the second throttling device via the solenoid valve, and the defrost operation is performed. 1. An air conditioner characterized in that the sixth bypass circuit is opened by a solenoid valve at fixed time intervals when the indoor temperature is below a predetermined value. (4) In claim 1, the first valve is configured to be able to exchange heat between the suction side piping connecting the accumulator and the compressor, and is bypass-connected to the piping side between the first and second throttle devices. The first bypass circuit is branched from between the three-way switching valve that switches the circuit to the fourth bypass circuit on the discharge side piping of the compressor and the four-way switching valve located downstream thereof. Characteristic air conditioner.