JPH09159329A - Heat pump type air-conditioning apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable ice to be removed at the outdoor heat exchanger produced during the heating operation of a cooling-heating air conditioner. SOLUTION: Refrigerant heated to high temperature under pressure by a compressor 1 is fed to an outdoor heat exchanger 5 or an indoor heat exchanger 3 by switching by a four-way valve 2 to effect the cooling or heating of the operation. A temperature sensor 7 for detecting freeze at the outdoor heat exchanger 5 is attached to the two heat exchangers 3, 5 or to the refrigerant piping 6 in a setup to effect defrosting by switching of the four-way valve 2 during heating operation. A bypass pipe 8 is connected one end to a point between the outdoor heat exchanger 5 and a capillary tube 4 and the other end to a point between the outdoor heat exchanger 5 and the suction side of the compressor 1, an opening-closing valve 9 is attached to the bypass pipe 8, and a pressure sensor 10 is attached to the suction side of the compressor 1. When the pressure sensor 10 has detected unusually low pressure, the opening- closing valve 9 is opened and the refrigerant having passed through the outdoor heat exchanger 5 is forced back into the compressor 1 to normalize its operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting operation when an outdoor heat exchanger is frozen during a heating operation of a cooling and heating air conditioner.

[0002]

2. Description of the Related Art A refrigerant that has been heated to a high temperature by a compressor is switched to an outdoor heat exchanger and an indoor heat exchanger by a four-way valve and supplied, and the indoor heat exchanger is directly fed with a high temperature refrigerant to perform heating operation. In addition, the refrigerant is sent through the outdoor heat exchanger and the capillary to perform the cooling operation.

During the heating operation, the high temperature and high pressure refrigerant radiates heat in the indoor heat exchanger and is liquefied. The high pressure liquid refrigerant is decompressed by the capillary and sent to the outdoor heat exchanger. Low-temperature outdoor air is blown to the outdoor heat exchanger, the refrigerant is vaporized while further lowering the temperature of the low-temperature air, and the vaporized refrigerant is sent again to the compressor to be pressurized. .

The water vapor contained in the outdoor air passing through the outdoor heat exchanger is liquefied when cooled, and water droplets adhere to the outdoor heat exchanger. When the outdoor air has a low temperature, the adhered water becomes frost and becomes ice. It grows. In this state, the passage of air in the outdoor heat exchanger is blocked, and heat exchange cannot be effectively performed.Therefore, the refrigerant sent to the outdoor heat exchanger does not vaporize as in the normal state, and the temperature and pressure are low. Then it is returned to the compressor and the refrigeration cycle cannot operate as expected.

When the outdoor heat exchanger freezes during the heating operation as described above, the temperature and pressure of the refrigerant in the refrigerant pipe line are lower than in the normal state, and the temperature sensor detects the freezing of the outdoor heat exchanger. it can. Therefore, when a refrigerant temperature abnormality occurs during the heating operation, the four-way valve is switched to send the high temperature / high pressure refrigerant discharged from the compressor to the frozen outdoor heat exchanger, and the defrosting operation is performed again. Heating operation can be performed.

[0006]

By the way, since the indoor heat exchanger is cooled during the defrosting operation, the operation of the indoor fan is stopped to make it difficult to perform heat exchange, and the temperature of the indoor air drops. I try not to. However, the temperature of outdoor air in the middle of winter is low, and the refrigerant pressurized by the compressor to reach a high temperature
Since the frost adhering to the outdoor heat exchanger is melted and sent to the indoor heat exchanger through the capillary, the temperature of the refrigerant has already become quite low at the inlet side of the indoor heat exchanger, and the indoor heat exchanger was touched. Water vapor contained in indoor air may freeze on the surface of the indoor heat exchanger.

When the indoor heat exchanger freezes in this way, the refrigerant sent to the compressor does not become a complete gas body, but is in a wet state or a state in which the liquid is mixed and is not a gas body. The refrigerant pipe has a large flow resistance for the refrigerant, and the pressure on the suction side becomes low when the compressor operates. Also, because the capacity of the compressor does not change,
The pressure on the discharge side also decreases and the pressure on the entire refrigeration cycle decreases, and liquid refrigerant accumulates in the refrigerant pipe of the outdoor unit up to the capillary, causing a shortage of refrigerant from the indoor heat exchanger to the suction side of the compressor. Was likely to run out of compressor oil due to lack of lubricating oil.

[0008]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and includes a compressor 1, a four-way valve 2, an indoor heat exchanger 3, a capillary 4, and an outdoor heat exchanger 5 as a refrigerant. A refrigeration cycle connected by the pipe 6 is configured, and a temperature sensor 7 for detecting freezing is provided in both the heat exchangers 3 and 5 or the refrigerant pipe 6, and the temperature sensor 7 detects the freezing of the outdoor heat exchanger 5 during heating operation. In the air conditioner that switches the four-way valve 2 to defrost by the temporary cooling operation, the bypass connecting the refrigerant pipe 6 that connects the outdoor heat exchanger 5 and the capillary 4 to the suction side of the compressor 1 A pipe 8 is provided, an opening / closing valve 9 is attached to the bypass pipe 8, and a pressure sensor 10 is attached to the refrigerant pipe 6 on the suction side of the compressor 1. The pressure sensor 10 is used for heating by a signal from the temperature sensor 7. Low pressure detected during defrosting operation That as the on-off valve 9 intended to open.

[0009]

When the temperature sensor 7 detects a temperature lower than the refrigerant temperature during the normal heating operation by switching the four-way valve 2 and heating operation, it is determined that the outdoor heat exchanger 5 has frozen, and the four-way valve 2 is temporarily switched to cooling operation. Therefore, the compressor 1
The high-temperature and high-pressure refrigerant compressed by is the frozen outdoor heat exchanger 5
Can be melted to remove the frost attached to the surface. Then, when the outdoor temperature is low, the refrigerant cooled by melting frost is depressurized by the capillary 4 while being kept at a low temperature and sent to the indoor heat exchanger 3 to be vaporized and cool the indoor heat exchanger 3. .

The heated room has a higher absolute humidity than the outdoor air, and when the cooled air near the indoor heat exchanger 3 comes into contact with the indoor heat exchanger 3, water vapor is liquefied. When the temperature is low, freezing occurs in the indoor heat exchanger 3. In this state, the refrigerant liquefied in the outdoor heat exchanger 5 cannot be gasified and becomes liquid or liquid-mixed in the compressor 1
However, the flow path resistance increases and the amount of refrigerant returned decreases drastically, causing troubles in the compressor 1.

According to the present invention, the refrigerant pipe 6 between the capillary 4 and the outdoor heat exchanger 5 is branched to connect the bypass pipe 8 to the suction side of the compressor 1, and the suction side of the compressor 1 becomes an abnormal negative pressure. At this time, the pressure sensor 10 opens the on-off valve 9 of the bypass pipe 8. By directly returning the refrigerant that has not been depressurized by the capillary 4 to the compressor 1, the refrigerant and the compressor oil return to the compressor 1, and the compressor 1 The temperature and pressure of the refrigerant on the discharge side are increased to enable stable operation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the piping diagram of an air conditioner shown in the figure. 1 is a compressor, 2 is a compressor 1
Is a four-way valve in which the discharge side and the suction side are connected, 3 is an indoor heat exchanger for air conditioning the indoor air, and 5 is an outdoor heat exchanger that is installed outdoors and through which process air for air conditioning flows. The capillary 4 for reducing the pressure of the refrigerant is installed between the indoor heat exchanger 3 and the outdoor heat exchanger 5, and the other side of both the heat exchangers 3 and 5 is connected to the four-way valve 2.

Reference numeral 6 denotes a refrigerant pipe for circulating a refrigerant through the compressor 1, the four-way valve 2, the outdoor heat exchanger 5, the capillary 4, and the indoor heat exchanger 3 and is compressed to a high pressure and high temperature by the compressor 1. During the heating operation, the refrigerant is sent to the indoor heat exchanger 3 by the four-way valve 2 through the refrigerant pipe 6 and exchanges heat with the indoor air to be liquefied. Then, the high-pressure liquid refrigerant is depressurized by the capillary 4, sent to the outdoor heat exchanger 5, vaporized, and returned to the compressor 1 via the four-way valve 2. At this time, when the outdoor air is cold and has high humidity, water vapor is condensed by the outdoor heat exchanger 5.

Since the temperature of the outdoor air during the heating operation is low,
The water formed by dew condensation becomes frost and grows into ice, and the outdoor heat exchanger 5 deteriorates the heat exchange efficiency, and the expected heating operation cannot be performed. Reference numeral 7 is a temperature sensor for detecting the freezing of the outdoor heat exchanger 5, and in the embodiment shown in the figure, it is attached to the refrigerant pipe 6 facing the capillary 4 on the outlet side of the indoor heat exchanger 3.

That is, when the outdoor heat exchanger 5 freezes during the heating operation, the refrigerant is returned to the compressor 1 in a wet state, so that the amount of the gaseous refrigerant is small and the pressure / temperature of the refrigerant after pressurization becomes low. Further, since the refrigerant having a low pressure and temperature is completely liquefied in the indoor heat exchanger 3 and the heat has been radiated, the temperature of the refrigerant on the outlet side becomes lower than that in the normal operation, and the temperature sensor 7 causes the outdoor heat exchange. Freezing of the container 5 can be detected.

When the temperature sensor 7 detects the freezing of the outdoor heat exchanger 5, the four-way valve 2 is switched to temporarily perform defrosting by the cooling operation even during the heating operation. Therefore, the refrigerant that has been compressed by the compressor 1 and has become high temperature and high pressure is sent to the outdoor heat exchanger 5, so that the ice energy adhering to the outdoor heat exchanger 5 is melted by the thermal energy of the refrigerant.

Then, the defrosting operation is stopped by detecting the rise in the refrigerant temperature by the time control or the temperature sensor 7, the four-way valve 2 is switched, and the heating operation is restarted.

By the way, when the outdoor air is at a low temperature, even if the blower facing the outdoor heat exchanger 3 is stopped during the defrosting operation, the cold outdoor air enters the outdoor heat exchanger 5 to reduce the refrigerant temperature. The pressure and temperature of the refrigerant passing through the capillary 4 are lower than normal values. Because of this,
When the refrigerant takes heat of vaporization in the indoor heat exchanger 3 to be gasified, the indoor air is rapidly cooled and water vapor in the air freezes on the surface of the indoor heat exchanger 3. At this time, both the indoor and outdoor heat exchangers 3 and 5 were frozen, and the air conditioner became a serious problem that completely disabled it.

Reference numeral 8 denotes a bypass pipe which branches a refrigerant pipe 6 which connects the capillary 4 and the outdoor heat exchanger 5, and the other part of the bypass pipe 8 is connected to the suction side of the compressor 1.
Reference numeral 9 is an opening / closing valve attached to the bypass pipe 8, and 10 is a pressure sensor attached to the refrigerant pipe 6 on the suction side of the compressor 1.

If freezing of the indoor heat exchanger 3 occurs during the defrosting operation of the outdoor heat exchanger 5 during the heating operation, the outdoor heat exchanger 5
The refrigerant liquefied in 1. cannot be vaporized in the indoor heat exchanger 3, and the liquid refrigerant in the refrigerant pipe 6 is difficult to return to the compressor 1 due to the large flow path resistance. Since the refrigerant has less gas component than usual, the compressor 1 that compresses the gas cannot compress a sufficient amount of refrigerant, the suction side of the compressor 1 becomes a large negative pressure, and the pressure on the discharge side is also normal. The refrigeration cycle generally goes to low temperature and low pressure in a short time.

The fact that the refrigerant sucked into the compressor 1 is small means that the compressor oil for lubricating the inside does not return, which may cause an emergency situation where the compressor 1 suddenly locks and becomes unusable. there were.

In the present invention, if the pressure sensor 10 detects an abnormal negative pressure on the suction side of the compressor 1, the open / close valve 9 of the bypass pipe 8
Therefore, a part of the refrigerant liquefied in the outdoor heat exchanger 5 directly returns from the bypass pipe 8 to the suction side of the compressor 1.

Therefore, in the accumulator 1a for separating the gaseous refrigerant attached to the compressor 1 by the liquid refrigerant flowing from the indoor heat exchanger 3 to the compressor 1 and the liquid refrigerant sent from the bypass pipe 8. Since there is always a predetermined amount of liquid refrigerant, and the refrigerant is vaporized by receiving heat from the compressor 1 and is sucked into the compressor, the shortage of compressor oil in the compressor 1 has been completely eliminated.

Further, since the high-pressure refrigerant that is not cooled returns to the compressor 1 via the bypass pipe 8, the pressure on the inlet side and the outlet side of the compressor 1 becomes high, and the efficiency of the outdoor heat exchanger 5 is increased. Defrosting has started. And
When the refrigerant is sufficiently sent to the suction side of the compressor 1 and the pressure becomes equal to or higher than the set pressure, the pressure sensor 10 closes the open / close valve 9 and returns to the normal defrosting operation of the outdoor heat exchanger 5.

When the defrosting of the outdoor heat exchanger 5 is completed,
The temperature of the refrigerant after passing through the capillary 4 rises, the four-way valve 2 is switched by the temperature sensor 7, and the heating operation is started. At this time, even if the indoor heat exchanger 3 is frozen, the temperature of the refrigerant is increased by the high temperature refrigerant. Since it melts immediately, the start-up of heating operation is delayed a little, but it does not cause serious trouble.

[0026]

As described above, according to the present invention, the bypass pipe 8 for connecting the refrigerant pipe 6 between the capillary 4 and the outdoor heat exchanger 5 to the suction side of the compressor 1 is provided, and the bypass pipe 8 is provided. An on-off valve 9 is attached to the compressor 1, and a pressure sensor 10 is provided on the suction side of the compressor 1. When the suction side of the compressor 1 becomes an abnormal negative pressure, the pressure sensor 10 opens the on-off valve 9 of the bypass pipe 8. With the open type, the refrigerant before being decompressed by the capillary 4 can be directly returned to the compressor 1.

Therefore, the indoor heat exchanger 3 is frozen during the defrosting operation of the outdoor heat exchanger 5, and the refrigerant is not sufficiently vaporized, so that the refrigerant is less likely to return from the indoor heat exchanger 3 to the compressor 1. However, the compressor oil returns to the compressor 1 from the bypass pipe 8 together with the refrigerant, and the compressor oil of the compressor 1 is insufficient, so that the locking trouble is completely eliminated.

Further, since the refrigerant returning from the bypass pipe 8 to the compressor 1 is a high-temperature and high-pressure refrigerant before being decompressed by the capillary 4, the temperature and pressure on the suction side of the compressor 1 become high and the refrigerant on the discharge side becomes Since the temperature and the pressure also increase, the ice in the outdoor heat exchanger 5 during the defrosting operation is quickly melted, and the defrosting is completed in a short time to switch to the heating operation.

[Brief description of the drawings]

FIG. 1 is a piping diagram showing an embodiment of an air conditioner according to the present invention.

[Explanation of symbols]

 1 Compressor 2 Four-way valve 3 Indoor heat exchanger 4 Capillary 5 Outdoor heat exchanger 6 Refrigerant pipe 7 Temperature sensor 8 Bypass pipe 9 Open / close valve 10 Pressure sensor

Claims (1)

[Claims] 1. A refrigeration cycle in which a compressor 1, a four-way valve 2, an indoor heat exchanger 3, a capillary 4, and an outdoor heat exchanger 5 are connected by a refrigerant pipe 6, and both heat exchangers 3 are formed. .5 or refrigerant pipe 6 with temperature sensor 7 for detecting freezing
In the air conditioner in which the temperature sensor 7 detects the freezing of the outdoor heat exchanger 5 during the heating operation and switches the four-way valve 2 to defrost by the temporary cooling operation, the outdoor heat exchanger 5 and the capillary 4 are provided. Bypass pipe 8 that branches the refrigerant pipe 6 that connects the
Is provided, an opening / closing valve 9 is attached to the bypass pipe 8, and
A pressure sensor 10 is attached to the refrigerant pipe 6 on the suction side of the compressor 1, and when the pressure sensor 10 detects a low pressure during a defrosting operation during heating according to a signal from the temperature sensor 7, the open / close valve 9 is opened. A heat pump type air conditioner.