JPH11107966A - Air conditioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the state where oil is transitionally collected in an oil separator and to improve the reliability by detecting the temperature and pressure on a coolant on a pressure reducing device downstream side of an oil returning circuit for connecting the oil separator to the low pressure side of a refrigerator cycle, and then returning the oil. SOLUTION: The pressure and temperature of a medium on a pressure reducing device 8 downstream side of an oil returning circuit 13 for connecting an oil separator 2 to the low pressure side of a refrigerating cycle are detected by a pressure sensor 9 and a temperature sensor 10. A control means 11 calculates the temperature difference between the saturated temperature of the coolant at the detected pressure and the detected temperature, and performs an oil returning operation when the temperature difference is a set temperature difference or less. Since the state where the oil is transitionally collected in the oil separator 2 because of the starting in the state where the coolant is stayed in a compressor 1 or a liquid backing can be detected, the reliability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner.

[0002]

2. Description of the Related Art FIG. 17 is a system diagram showing a conventional air conditioner. In the figure, 1 is a compressor, 2 is an oil separator, 3 is a condenser, 4 is a first opening / closing valve, 5 is a throttle device, 6 is an evaporator, 7 is an accumulator, and 8 is provided in a first oil return circuit 13. 13 is a first oil return circuit, 12 is a second on-off valve provided in the first oil return circuit 13, and 19 is a flow direction of a medium made of refrigerant and refrigerating machine oil flowing through the pipe. Arrows shown are connected by pipes to form an air conditioner.

The gas refrigerant which has been compressed by the compressor 1 and has become high temperature and high pressure is separated by the oil separator 2 into the gas refrigerant and the refrigerating machine oil. The gas refrigerant flows into the condenser 3, while the refrigerating machine oil is returned to the refrigerant pipe on the inlet side of the accumulator 7 through the second on-off valve 12 and the first pressure reducing device 8 provided in the first oil return circuit 13, The oil is returned to the compressor 1 through the accumulator 7.

The gaseous refrigerant is condensed in the condenser 3 to become a liquid refrigerant, passes through the first on-off valve 4, and becomes a low-pressure gas-liquid two-phase refrigerant in the expansion device 5. The gas-liquid two-phase refrigerant is sent to the evaporator 6, where it absorbs heat to become a gas refrigerant. The gas refrigerant returns to the compressor 1 via the accumulator 7, and the refrigeration cycle is completed.

[0005]

In the above-described air conditioner, the specifications of the oil return circuit, the state of the refrigerant oil and the refrigerant flowing through the oil return circuit, and the condition of the refrigerant, regardless of the amount of the oil stored in the oil separator. The amount of oil returned was determined under pressure conditions. For this reason, when a large amount of refrigerating machine oil of the compressor 1 is transiently taken out to the oil separator 2 due to a liquid back, a start-up in a state where the refrigerant is laid in the compressor 1, or a forming, etc. In the compressor 1, the oil shortage sometimes occurred.

The present invention has been made to solve such a problem, and detects the pressure and temperature at the outlet of the oil return circuit, converts the pressure into a saturation temperature, and uses the temperature difference to determine the oil separator 2. It is intended to improve the reliability of the air conditioner by judging that a large amount of oil is transiently present in the air conditioner and adjusting the oil return amount or stopping the air conditioner.

[0007] Further, when refrigeration oil that does not dissolve in the refrigerant is used, the oil is likely to stay in the piping. Therefore, the amount of oil in the piping is detected and the oil is returned to reduce the amount of oil in the compressor. The purpose is to secure and improve the reliability of the air conditioner.

[0008]

In order to achieve the above object, an air conditioner according to a first aspect of the present invention provides a refrigeration system in which a compressor, an oil separator, a condenser, a throttle device, and an evaporator are sequentially connected by piping. An air conditioner equipped with a cycle, a recirculation circuit connecting the oil separator and a low pressure side of the refrigerating cycle, a decompression device provided in the recirculation circuit, and A temperature detecting means provided in the oil circuit, for detecting the temperature of the oil return circuit, a pressure detecting means for detecting the pressure of the refrigerant in the oil return circuit, and calculating a saturation temperature of the refrigerant at the pressure detected by the pressure detecting means. And
Calculating a temperature difference between the saturation temperature and the temperature detected by the temperature detection means, and when the temperature difference is equal to or less than a set temperature difference, a control means for issuing an oil return command; and the oil separator according to a command from the control means. Oil returning means for returning the refrigerating machine oil to the compressor side.

In the air conditioner of the second invention, the oil return means is provided when the control means stops the compressor and closes an opening / closing device for shutting off the high pressure side and the low pressure side of the refrigeration cycle. It is constituted by the oil return circuit.

[0010] In the air conditioner of the third invention, the oil return means includes a pressure reducing device having a smaller flow resistance than the pressure reducing device of the oil return circuit, and a bypass provided in parallel with the pressure reducing device of the oil return circuit. It is composed of piping.

The air conditioner according to a fourth aspect of the present invention is the air conditioner according to the first aspect of the present invention, wherein heat is exchanged between the refrigerant downstream of the temperature detecting means and the pressure detecting means and the refrigerant flowing out of the condenser. It has exchange means.

A compressor, an oil separator, a condenser, a first on-off valve,
An air conditioner using a refrigerating machine oil that does not mix with a refrigerant is provided with a refrigeration cycle in which a throttle device and an evaporator are sequentially connected to a pipe. A first bypass circuit provided between a pipe connecting the
A first decompression device provided in a bypass circuit, a second bypass circuit for bypassing the first decompression device, a second on-off valve and a second decompression device provided in the second bypass circuit, At the outlet of the 1 bypass circuit, a pressure detecting means for detecting the pressure of the refrigerant, a temperature detecting means for detecting the temperature of the refrigerant, and converting the detected pressure into a saturation temperature, and calculating a temperature difference from the refrigerant temperature, When the calculated temperature difference becomes equal to or larger than the set temperature difference, a control means for performing control for opening the second on-off valve for a predetermined time is provided.

The air conditioner according to a sixth aspect of the present invention is provided with a refrigeration cycle in which a compressor, an oil separator, a condenser, a first on-off valve, a throttle device, and an evaporator are sequentially connected to a pipe. In air conditioners using machine oil, the first
A first bypass circuit provided between an upper portion of the pipe at a horizontal location of the pipe for leading the refrigerant from the on-off valve and the pipe connecting the expansion device and the evaporator; and a first bypass circuit provided in the bypass circuit. A first decompression device, a second bypass circuit bypassing the first decompression device and connected to an evaporator outlet, a second on-off valve and a second decompression device provided in the second bypass circuit, At the outlet of the first bypass circuit, pressure detecting means for detecting the pressure of the refrigerant, temperature detecting means for detecting the temperature of the refrigerant, and converting the detected pressure to the saturation temperature of the refrigerant at that pressure, the saturation temperature and Control means for calculating a temperature difference from the temperature detected by the temperature detection means, and when the calculated temperature difference is equal to or more than a set temperature difference, controlling to open the second on-off valve for a predetermined time; Are provided.

In the air conditioner according to a seventh aspect of the present invention, in the air conditioner according to the fifth or sixth aspect, the heat exchange between the refrigerant flowing out of the condenser and the refrigerant downstream of the temperature detecting means and the pressure detecting means is performed. Exchange means.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a configuration diagram of an air-conditioning apparatus according to Embodiment 1 of the present invention. In the figure, 1 is a compressor, 2 is an oil separator, 3 is a condenser, 4 is a first on-off valve, 5 is a throttle device, 6 is an evaporator, 7 is an accumulator, 13 is a first oil return circuit, and piping To form an air conditioner. Reference numeral 19 denotes an arrow indicating a flowing direction of a medium composed of a refrigerant and refrigerating machine oil flowing through the pipe. 23 is a reservoir.

A compressor 1, an oil separator 2, a condenser 3, a reservoir 23, a first opening / closing valve 4, a throttle device 5, an evaporator 6, an accumulator 7, and the like are sequentially connected by pipes. A first oil return circuit 13 is connected to a pipe connecting the accumulator 7 and the evaporator 6 to return the refrigerating machine oil accumulated in the oil separator 2 from the bottom of the second oil return line 2.

The first oil return circuit 13 includes a second on-off valve 1
2 and a first pressure reducing device 8 are provided. As the second on-off valve 12, for example, an electromagnetic valve is used. First oil return circuit 13
The first depressurizing device 8 for decompressing the refrigerant flowing through the device has a resistance. For example, a capillary is used as the first depressurizing device 8. As the first pressure reducing device 8, an expansion valve or an electronic expansion valve may be used.

In the first oil return circuit 13, for example, a pressure sensor 9 is provided downstream of the first capillary 8 as pressure detection means 9 for detecting the pressure of the medium flowing through the first oil return circuit 13. Similarly, downstream of the first capillary 8, for example, a temperature sensor 10 is provided as temperature detecting means 10 for detecting the temperature of the medium flowing through the first oil return circuit 13. Further, control means 11 for performing calculations based on the results detected by the temperature sensor 10 and the pressure sensor 9
It has. Then, an electromagnetic valve is used as the first on-off valve 4.

As the refrigerating machine oil, one that dissolves in the refrigerant is used.
When the air conditioner is operated in a state where the refrigerant is laid down in the compressor 1 or a liquid back occurs, a large amount of the refrigerating machine oil of the compressor 1 is taken out into the refrigerating cycle, and Refrigerator oil containing a large amount of refrigerant accumulates in the separator 2. When the refrigerating machine oil collected in the oil separator 2 returns to the low-pressure gas side via the first oil return circuit 13, there is provided a material having a large resistance such as the first capillary 8.
The oil return process takes a considerable amount of time. For this reason, the amount of oil returned to the compressor is reduced, and the compressor 1 is operated in a state where the refrigerating machine oil is insufficient. In some cases, the original performance cannot be exhibited due to the lack of the refrigerating machine oil. There was a risk of impairing the properties.

In such a state, a considerable amount of refrigerant is dissolved in the refrigerating machine oil stored in the oil separator 2, and the pressure P detected by the pressure sensor 9 is saturated by the control means 11 at the pressure P. Convert to temperature Tsat.

Next, the temperature difference T-Tsat is calculated by the control means 11 using the temperature T detected by the temperature sensor 10. If a large amount of refrigerant is dissolved in the refrigerating machine oil, the temperature T indicates a value close to the saturation temperature Tsat. Conversely, during normal operation or the like, the amount of the refrigerant dissolved in the refrigerating machine oil is very small, and the temperature of the refrigerating machine oil is dominant, or the refrigerant gas flows through the oil return circuit 13, so that the temperature T
And the saturation temperature Tsat.

Therefore, the start-up in a state in which the refrigerant is stagnation in the compressor 1 and the state in which the oil is temporarily accumulated in the oil separator 2 due to the liquid back and the like are calculated by calculating the temperature difference T-Tsat. Can be determined from

Next, a specific control method will be described. When the temperature difference T-Tsat is equal to or smaller than the set temperature difference, the control means 11 determines that the refrigerating machine oil is present in the oil separator 2 due to a transient phenomenon, and stops the air conditioner, and at the same time, the electromagnetic valve 4 Close. With this control, the solenoid valve 4
Since the high-pressure side and the low-pressure side are shut off, a pressure difference is generated between the high-pressure side and the low-pressure side, and the refrigerating machine oil stored in the oil separator 2 is sent to the low-pressure side by using the pressure difference. When the air conditioner is stopped, a predetermined time is set. When the stop time exceeds the set time, the air conditioner is automatically restarted. Since the operation is restarted in a state where oil is present on the low pressure side, the time during which the compressor is operated due to lack of oil can be reduced.

According to the first embodiment, the pressure and temperature on the downstream side of the pressure reducing device 8 of the oil return circuit 13 connecting the oil separator 2 and the low pressure side of the refrigeration cycle are detected, and the refrigerant at the detected pressure is detected. The temperature difference between the saturation temperature and the detected temperature is calculated, and if the temperature difference is equal to or less than the set temperature difference, the oil return operation is performed. Since the state in which oil is accumulated in the oil separator due to liquid back or the like can be detected transiently, an air conditioner with improved reliability can be provided.

Embodiment 2 FIG. 2 is a configuration diagram of an air conditioner according to Embodiment 2 of the present invention. As a switching valve for switching between cooling and heating, for example, a four-way valve 4 is provided.
By incorporating a refrigerating device, a refrigerating device capable of coping with cooling and heating can be provided.

The heat exchanger acting as the condenser 3 during cooling becomes an evaporator (6) during heating. Conversely, the heat exchanger acting as the evaporator 6 during cooling acts as the condenser (3) during heating. The control method is the same as described above, but since the solenoid valve 4 is not used in this circuit,
By fully closing the expansion device 5, high pressure and low pressure are shut off.

According to the second embodiment, the control means 11
When the opening / closing device including the expansion device 5 for shutting off the high-pressure side and the low-pressure side of the refrigeration cycle is closed when the compressor is stopped, the oil return operation is performed by the oil return circuit 13. It is possible to detect a state where oil is accumulated in the oil separator 2 due to a start-up in a state where the refrigerant is laid in the refrigerant 1 or a liquid back, etc., and to operate the compressor 1 due to a shortage of refrigeration oil. It is possible to provide an air conditioner with reduced reliability and improved reliability.

Embodiment 3 FIG. 3 is a configuration diagram of an air-conditioning apparatus according to Embodiment 3 of the present invention. In addition to the first oil return circuit 13 of Embodiment 1, a second return line that bypasses the solenoid valve 12 and the first capillary 8 is used. An oil circuit 14 is provided.
The second oil return circuit 14 is provided with an electromagnetic valve as the third on-off valve 15, and is provided with a second capillary 16 having a smaller resistance than the first capillary 8.

Downstream from the junction of the first oil return circuit 13 and the second oil return circuit 14, for example, a pressure sensor 9 is provided as pressure detection means 9 for detecting the pressure of the medium flowing through the junction circuit. Further, as a temperature detecting means 10 for detecting the temperature of the medium flowing through the merging circuit, for example, a temperature sensor 10
It has. Further, a temperature sensor 10, a pressure sensor 9
Control means 1 for performing calculations based on the results detected by
1 is provided.

The refrigerating machine oil accumulated in the oil separator 2 for the same reason as in the first embodiment is used to control the temperature difference T-Tsat by the control means 1.
Calculate by 1. If the temperature difference T-Tsat is equal to or larger than the set temperature difference, it can be determined that almost no oil is accumulated in the oil separator 2, and it is not necessary to return the oil immediately. As a result, since only the first oil return circuit 13 having the larger resistance is used for the purpose of reducing the high and low pressure bypass amounts, the control means 11 opens the solenoid valve 12 and closes the solenoid valve 12. The refrigeration oil collected in the oil separator 2 is returned using the first oil return circuit 13.

When the temperature difference T-Tsat is equal to or less than the set temperature difference, the state where the oil is transiently accumulated in the oil separator 2 due to the start-up of the compressor 1 in a state where the refrigerant is laid down and the control means 11 judges, while operating the air conditioner,
In order to quickly return the refrigerating machine oil to the low pressure side, the solenoid valve 15 of the second oil return circuit 14 having a small resistance is opened. The solenoid valve 12 of the first oil return circuit 13 may be either open or closed. When the temperature difference T-Tsat becomes equal to or greater than the set temperature difference, the solenoid valve 14 of the second oil return circuit 14 is closed, and the first oil return circuit 1
The third solenoid valve 12 is opened.

As a result, the time during which the compressor is operated due to lack of refrigerating machine oil can be shortened, and the reliability of the air conditioner is improved.

The electromagnetic valve 15 of the second oil return circuit 14 is opened, the electromagnetic valve 12 of the first oil return circuit 13 is opened or closed, and the electromagnetic valve 4 is closed. May be.

According to the third embodiment, the pressure reducing device including the second capillary 16 having a smaller flow resistance than the pressure reducing device including the first capillary 8 of the oil return circuit 13 is provided.
Since the oil return operation is performed by the second oil return circuit 14 composed of a bypass pipe provided in parallel with the pressure reducing device composed of the first capillary of the oil return circuit 13, the refrigerant is laid down in the compressor 1. Since the state where oil is accumulated in the oil separator 2 can be detected transiently due to the start-up and forming of the compressor, the compressor is operated due to lack of refrigerating machine oil without stopping the air conditioner. The time can be reduced, and an air conditioner with improved reliability can be provided.

Embodiment 4 FIG. FIG. 4 is a configuration diagram of an air-conditioning apparatus according to Embodiment 4 of the present invention. As a switching valve for switching between cooling and heating, for example, a four-way valve 2
By incorporating a refrigerating device in No. 4, a refrigerating device capable of coping with cooling and heating can be provided.

The heat exchanger acting as the condenser 3 during cooling becomes an evaporator (6) during heating. Conversely, the heat exchanger acting as the evaporator 6 during cooling acts as the condenser (3) during heating. The control method is the same as described above, but since the solenoid valve 4 is not used in this circuit, the expansion device 5 is fully closed.

According to the fourth embodiment, a pressure reducing device comprising the second capillary 16 having a smaller flow resistance than the pressure reducing device comprising the first capillary 8 of the oil return circuit 13 is provided.
The oil return means is constituted by a second oil return circuit 14 comprising a bypass pipe provided in parallel with a pressure reducing device comprising a first capillary of the oil return circuit 13 and a pressure detecting means comprising a pressure sensor 9 and a temperature sensor 10 The control means 11 receiving the detection result of the temperature detection means stops the compressor,
Further, when the switching device including the expansion device 5 for shutting off the high pressure side and the low pressure side of the refrigeration cycle is closed, the oil return circuit 13
In addition, since the oil return operation is performed by the oil return circuit 14, the oil is transiently accumulated in the oil separator 2 due to the start-up in a state where the refrigerant is laid in the compressor 1 or the liquid back. It is possible to detect the state, reduce the time during which the compressor 1 is operated due to lack of refrigerating machine oil, and provide an air conditioner with improved reliability.

Embodiment 5 FIG. 5 is a configuration diagram of an air-conditioning apparatus according to Embodiment 5 of the present invention. Oil separator 2
An oil return circuit 13 and an oil return circuit 14 are provided between the bottom portion of the pump and a pipe connecting the expansion device 5 and the evaporator 6. A control method similar to that of the third embodiment is performed.

The temperature difference T calculated by the control means 11
When -Tsat is equal to or less than the set temperature difference,
A large amount of refrigerant is dissolved.

According to the fifth embodiment, a large amount of refrigerant mixed with the refrigerating machine oil is evaporated by the evaporator 6, so that the amount of the refrigerant in the refrigerating machine oil is reduced, that is, liquid back is prevented. As a result, the reliability of the compressor is improved.

Embodiment 6 FIG. FIG. 6 is a configuration diagram of an air-conditioning apparatus according to Embodiment 6 of the present invention. The air-conditioning apparatus includes, for example, a four-way valve 24 as a switching valve, and is capable of coping with cooling and heating by installing two throttle devices. The present invention can be applied to an air conditioner.

The heat exchanger that has worked with the condenser 3 during cooling becomes an evaporator (6) during heating. Conversely, the heat exchanger acting as the evaporator 6 during cooling acts as the condenser (3) during heating. During cooling, the expansion device 5a is fully opened, and the expansion device 5b depressurizes the refrigerant and adjusts the flow rate. During heating, the expansion device 5b is fully opened, and the expansion device 5a depressurizes the refrigerant and adjusts the flow rate.

According to the sixth embodiment, a large amount of refrigerant mixed with refrigeration oil is evaporated by evaporator 6 to reduce the amount of refrigerant in refrigeration oil, that is, to prevent liquid back. As a result, the air conditioner that can improve the reliability of the compressor can be adapted to cooling and heating.

Embodiment 7 FIG. FIG. 7 is a configuration diagram of an air-conditioning apparatus according to Embodiment 7 of the present invention. The heat exchange means 17 for exchanging heat between the refrigerant flowing out of the condenser 3 and the refrigerant downstream of the pressure sensor 9 and the temperature sensor 10 provided in the merging circuit of the oil return circuit 13 and the oil return circuit 14 of the third embodiment. For example, as shown in FIG. 8, a heat exchanger 17 for contacting an oil return pipe with a high-pressure liquid pipe is used. The heat exchange means 17 may be a double tube heat exchanger. Further, the oil return circuit 13 shown in the first embodiment may be provided with the heat exchange means 17.

The control method is the same as in the third embodiment. Temperature difference T-Tsa calculated by control means 11
If t is equal to or less than the set temperature difference, a large amount of refrigerant is dissolved in the refrigerating machine oil, and the temperature of the oil return circuit is lower than that of the high-pressure liquid discharged from the reservoir. By exchanging heat between the refrigerant flowing in the oil return circuit and the high-pressure liquid, it is possible to recover the heat loss of the refrigerant flow by the bypass and to evaporate the refrigerant dissolved in the refrigerating machine oil.

As a result, according to the seventh embodiment, the degree of supercooling of the refrigerant can be increased upstream of the expansion device 5, so that a decrease in refrigeration performance can be prevented and the reliability of the compressor can be improved. It is possible to do.

Embodiment 8 FIG. FIG. 9 is a configuration diagram of an air-conditioning apparatus according to Embodiment 8 of the present invention. The air-conditioning apparatus includes, for example, a four-way valve 24 as a switching valve, and is capable of coping with cooling and heating by installing two throttle devices. The present invention can be applied to an air conditioner.

The heat exchanger that has been working with the condenser 3 during cooling becomes an evaporator 6 during heating. Conversely, during cooling, the evaporator 6
Acts as the condenser 3 during heating. During cooling, the expansion device 5b is fully opened, and the expansion device 5a depressurizes the refrigerant and adjusts the flow rate. During heating, the expansion device 5a is fully opened, and the expansion device 5b depressurizes the refrigerant and adjusts the flow rate.

According to the eighth embodiment, the aperture devices 5a and 5
It is possible to increase the degree of supercooling of the refrigerant upstream of b, so that the refrigeration performance can be prevented from deteriorating, and the air conditioner that can improve the reliability of the compressor can be adapted to cooling and heating. it can.

Embodiment 9 FIG. FIG. 10 is a configuration diagram of an air conditioner showing a ninth embodiment of the present invention, in which a compressor 1, an oil separator 2, a condenser 3, a reservoir 23, a first on-off valve 4, a throttle device 5, and an evaporator. In order to detect the amount of accumulated oil between the upper part of the horizontal pipe that has exited the condenser and the pipe connecting the accumulator 7 and the evaporator 6, the vessel 6, the accumulator 7 and the like are sequentially connected by pipes. First bypass circuit 1
8 are provided.

The inlet side of the first bypass circuit 18 must be so constructed as to be drawn from above. Regardless of the direction of the connection on the outlet side, oil flows with a pressure difference between high pressure and low pressure. The first bypass circuit 18 includes a first pressure reducing device 8. The first pressure reducing device 8 has a resistance and uses, for example, the first capillary 8 (expansion valve, electronic valve, etc.). An expansion valve may be used).

A second bypass circuit 22 for bypassing the first capillary 8 is provided.
For example, a second solenoid valve 12 is provided as the second on-off valve 12, and a second capillary 16 is provided as the second decompression device 16, and the second capillary 16 has a smaller resistance than the first capillary 8.

At the outlet of the first bypass circuit 18, for example, a pressure sensor 9 is provided as a means 9 for detecting pressure, and a temperature sensor 10 is provided as a means 10 for detecting temperature, and the temperature is detected by the temperature sensor 10 and the pressure sensor 9. Control means 20 for performing an operation based on the result is provided.

As the refrigerating machine oil, a refrigerating machine oil that does not dissolve in the refrigerant is used. For example, a combination of R404A and hard alkyl benzene, or a combination of R407C and hard alkyl benzene. When the refrigeration cycle is operated in such a combination, the refrigerant and the refrigerating machine oil do not dissolve, so that the refrigerant is in a liquid state, for example, a reservoir 23.
In the high-pressure liquid section after exiting, the liquid phase and the refrigerant phase are divided into a liquid-liquid two-phase state. In this combination, the refrigerating machine oil has a lower specific gravity than the refrigerant liquid, so that the oil phase is upper and the refrigerant liquid phase is lower.

By using this property, a bypass circuit 18 for taking out oil from above a horizontal pipe which becomes a high-pressure liquid part is constructed as shown in FIG.
Install as follows. As described above, by installing the bypass circuit 18 between the upper part of the pipe at the horizontal location of the pipe for leading the medium from the first on-off valve 21 and the pipe connecting the evaporator 6 and the accumulator 7, Refrigeration oil can be returned to the low pressure side.

From the pressure P detected by the pressure sensor 9,
The temperature is converted into the saturation temperature Tsat by the control means 20 and the temperature difference T−T is calculated using the temperature T detected by the temperature sensor 10.
Calculate sat. When the refrigerating machine oil is taken out of the compressor for some reason and the amount of the refrigerating machine oil retained in the piping increases, the thickness of the oil phase in the horizontal piping increases, so that the refrigerating oil flows into the oil return circuit 18. The amount of the machine oil increases, and as a result, the temperature difference increases because the temperature of the refrigerating machine oil becomes dominant. Conversely, when the amount of the refrigerating machine oil retained in the liquid pipe is small, the thickness of the refrigerating machine oil layer in the horizontal pipe is small, and as a result, the ratio of the refrigerant flowing to the oil return circuit 18 increases, The temperature difference becomes smaller.

By utilizing this principle, when the temperature difference is larger than the reference temperature difference, it is determined that the amount of retained oil in the liquid pipe is above the reference amount, and the amount of retained oil above the reference value is detected. It is possible to do. In other words, when the temperature difference is greater than or equal to the setting,
Since it can be determined that the amount of oil present in the liquid pipe is large, the second solenoid valve 12 is opened by the control means 20 for a certain time.

As a result, it is possible to increase the bypass amount of the refrigerant for a fixed time and reduce the time for returning the oil present in the high pressure liquid to the low pressure side, thereby improving the reliability of the compressor. Become.

In such a refrigeration cycle of a refrigerant and a refrigerating machine oil system, the limit oil return speed exists not only in the rising gas pipe but also in the descending liquid pipe. Since the specific gravity of the refrigerating machine oil is smaller than the specific gravity of the refrigerant liquid, buoyancy is generated in the refrigerating machine oil. By installing the horizontal liquid pipe provided with the bypass circuit 18 at the highest position relative to the other liquid pipes, the refrigerating machine oil which cannot be lowered at the speed lower than the oil return limit speed is frozen to the horizontal liquid pipe. Since the machine oil accumulates and the thickness of the phase of the refrigerating machine oil increases, it can be determined from the temperature difference T-Tsat that the liquid pipe is at or below the oil return limit speed.

As described above, according to the ninth embodiment,
Refrigeration oil can be returned by stopping the air conditioner or increasing the refrigerant flow rate by detecting the amount of retained oil above the reference or below the oil return limit speed, thereby improving the reliability of the air conditioner. The flow rate of the refrigerant can be increased by increasing the opening of the expansion device, or by increasing the air volume (water volume) of the condenser 3 and the evaporator 6.

Embodiment 10 FIG. FIG. 12 is a configuration diagram of an air-conditioning apparatus according to Embodiment 10 of the present invention. For example, a four-way valve 24 is provided as a switching valve, and
The present invention can be applied to a refrigerating apparatus that can cope with cooling and heating, for example, by installing individual components.

The heat exchanger functioning as the condenser 3 during cooling becomes the evaporator (6) during heating. Conversely, the heat exchanger acting as the evaporator 6 during cooling acts as the condenser (3) during heating. Squeezing device 5b during cooling
Is fully opened, and the pressure of the refrigerant is reduced and the flow rate is adjusted by the expansion device 5a. During heating, the expansion device 5a is fully opened, and the expansion device 5b depressurizes the refrigerant and adjusts the flow rate.

According to the tenth embodiment, the refrigerating machine oil can be returned by stopping the air conditioner or increasing the refrigerant flow rate by detecting the amount of retained oil above the reference or below the oil return limit speed. The air conditioner that can improve the reliability of the air conditioner can be adapted to cooling and heating.

Embodiment 11 FIG. FIG. 13 is a configuration diagram of an air-conditioning apparatus according to Embodiment 11 of the present invention. The oil return circuit 18 composed of a bypass circuit is connected between the upper part of the pipe at a horizontal location of the pipe for leading the medium from the first on-off valve 21 and the pipe connecting the evaporator 6 and the accumulator 7. I have.

The oil retention amount detection method, principle, control method, and the like are the same as those in the fifth embodiment. As shown in FIG. 8, by connecting the bypass circuit 18 to the inlet of the evaporator 6, the loss of the refrigerant flow rate can be reduced, and finally, the deterioration of the refrigeration performance can be reduced.

According to the eleventh embodiment, the oil return circuit 18 composed of a bypass circuit connects the upper part of the pipe, the evaporator 6 and the accumulator 7 at the horizontal position of the pipe for leading the medium from the first on-off valve 21. Since it is connected between the pipes to be connected, the loss of the refrigerant flow rate can be reduced, and finally, the deterioration of the refrigeration performance can be reduced.

Embodiment 12 FIG. FIG. 14 is a configuration diagram of an air-conditioning apparatus according to Embodiment 12 of the present invention. Electromagnetic valves 27a and 27b are used as opening / closing valves 27a and 27b, a bypass circuit 18 is taken out from two positions, and two expansion devices 5a and 5b are further provided. As switching valves for switching between cooling and heating, for example, By incorporating the four-way valve 24 into the refrigerating device, a refrigerating device capable of coping with cooling and heating can be provided.

The heat exchanger acting as the condenser 3 during cooling becomes an evaporator (6) during heating. Conversely, the heat exchanger acting as the evaporator 6 during cooling acts as the condenser (3) during heating. Squeezing device 5 for cooling
a is fully opened, the refrigerant is depressurized and the flow rate is adjusted by the expansion device 5b. The solenoid valve 27b is opened and the solenoid valve 27a is closed by the control means 20. During heating, the expansion device 5b is fully opened,
The pressure of the refrigerant is reduced and the flow rate is adjusted by the expansion device 5a.
Are controlled by the control means 20 so as to open and the electromagnetic valve 27b to be closed.

According to the twelfth embodiment, the oil return circuit 18 composed of a bypass circuit is connected to the upper part of the pipe at a horizontal position of the pipe for leading the medium from the first on-off valves 27a and 27b and the expansion devices 5a and 5b. By connecting between the pipe and the pipe connecting the evaporator 6, the loss of the refrigerant flow rate can be reduced,
Eventually, an air conditioner that can reduce a decrease in refrigeration performance can be adapted for cooling and heating.

Embodiment 13 FIG. FIG. 15 is a configuration diagram of an air conditioner showing a thirteenth embodiment of the present invention. As means 17 for exchanging heat between the refrigerant flowing out of the condenser 3 and the refrigerant downstream of the pressure sensor 9 and the temperature sensor 10 of the bypass circuit 18 of the ninth embodiment, as shown in FIG.
A heat exchange 17 for bringing the high pressure liquid pipe 8 into contact with the high pressure liquid pipe 8 is used.
The means 17 for exchanging heat may be a double tube heat exchanger. The oil retention amount detection method, principle, control method, and the like are the same as those in the ninth embodiment.

According to the thirteenth embodiment, bypass circuit 1
By exchanging heat between the refrigerant flowing through 8 and the high-pressure liquid, the degree of supercooling at the inlet of the expansion device can be increased, so that the loss of the refrigerant flow rate due to the bypass can be recovered as heat. Can be prevented.

Embodiment 14 FIG. FIG. 16 is a configuration diagram of an air-conditioning apparatus according to Embodiment 13 of the present invention. As a switching valve, for example, a four-way valve 24 and two squeezing devices are installed to provide a refrigerating device capable of coping with cooling and heating.
The present invention can be provided.

The heat exchanger functioning as the condenser 3 during cooling becomes the evaporator (6) during heating. Conversely, the heat exchanger acting as the evaporator 6 during cooling acts as the condenser (3) during heating. Squeezing device 5b during cooling
Is fully opened, and the pressure of the refrigerant is reduced and the flow rate is adjusted by the expansion device 5a. During heating, the expansion device 5a is fully opened, and the expansion device 5b depressurizes the refrigerant and adjusts the flow rate. The control method and the detection method are the same as described above.

According to the fourteenth embodiment, bypass circuit 1
By exchanging heat between the refrigerant flowing through 8 and the high-pressure liquid, the degree of supercooling at the inlet of the expansion device can be increased, so that the loss of the refrigerant flow rate due to the bypass can be recovered as heat. The air conditioner that can be prevented can be adapted to cooling and heating.

[0075]

According to the air conditioner of the first invention, the pressure and the temperature on the downstream side of the pressure reducing device of the oil return circuit connecting the oil separator and the low pressure side of the refrigeration cycle are detected,
The difference between the saturation temperature of the refrigerant at the detection pressure and the detection temperature is calculated, and when the temperature difference is equal to or less than the set temperature difference, the oil return operation is performed, so the refrigerant is stagnant in the compressor. Since it is possible to detect a state where the oil separator has accumulated oil transiently due to startup in the state or due to liquid back, it is possible to provide an air conditioner with improved reliability.

According to the air conditioner of the second invention,
When the control means stops the compressor and closes an opening / closing device including a throttle device that shuts off the high pressure side and the low pressure side of the refrigeration cycle, the oil return operation is performed by the oil return circuit. It is possible to detect the state where oil is accumulated in the oil separator transiently due to the start-up in the state where the refrigerant is laid down in the refrigerant, the liquid back, etc. It is possible to provide an air conditioner that can be reduced and has improved reliability.

According to the air conditioner of the third invention,
A state in which the refrigerant is stagnated in the compressor because a pressure reducing device having a smaller flow resistance than the pressure reducing device in the oil return circuit is provided, and the oil return operation is performed by a bypass pipe provided in parallel with the pressure reducer in the oil return circuit. The compressor can be operated with a shortage of refrigerating machine oil without stopping the air conditioner, because it is possible to detect the state of oil accumulation in the oil separator transiently due to start-up or forming, etc. The time can be reduced, and an air conditioner with improved reliability can be provided.

According to the air conditioner of the fourth invention,
In the air conditioner according to the first aspect of the present invention, since the refrigerant downstream of the pressure detecting means and the temperature detecting means and the refrigerant flowing out of the condenser are heat-exchanged, the compressor is started in a state where the refrigerant is laid down. Oil can be detected transiently in the oil separator due to liquid back, etc., reducing the time the compressor is running due to lack of refrigerating machine oil, improving reliability It is possible to provide an air conditioner in which a supercooling degree at a condenser outlet is increased by performing heat exchange and a decrease in refrigeration performance is reduced.

According to the air conditioner of the fifth invention,
Through a bypass circuit provided between the upper part of the pipe at a horizontal position of the pipe for drawing out the medium from the first on-off valve through which the medium flows from the condenser and the pipe connecting the accumulator and the evaporator. An air conditioner that has improved reliability by detecting the reference oil stagnant flow rate in the liquid piping and reducing the time that the compressor is running due to lack of refrigerating machine oil. Can be provided.

According to the air conditioner of the sixth aspect,
A bypass circuit provided between the upper part of the pipe at a horizontal position of the pipe for drawing out the medium from the first on-off valve through which the medium flows from the condenser and the pipe connecting the expansion device and the evaporator is provided. Since the oil return operation is performed via the refrigeration oil, the reference oil stagnation flow rate of the liquid pipe can be detected, the time during which the compressor is operated due to lack of refrigeration oil can be reduced, and the oil is mixed with the refrigeration oil. By evaporating the refrigerant liquid by the evaporator, the liquid back can be prevented, and an air conditioner with improved reliability can be provided.

According to the air conditioner pertaining to the seventh aspect, in the fifth or sixth aspect, heat exchange is performed between the refrigerant downstream of the pressure detecting means and the temperature detecting means and the refrigerant flowing out of the condenser. As a result, the reference oil stagnation flow rate in the liquid pipe can be detected, the time during which the compressor is operating due to lack of refrigerating machine oil can be reduced, the reliability of the air conditioner can be improved, and heat exchange can be further improved. By doing so, it is possible to provide an air conditioner in which the degree of supercooling at the outlet of the condenser is increased and the decrease in refrigeration performance is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an air-conditioning apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram of an air-conditioning apparatus according to Embodiment 2 of the present invention.

FIG. 3 is a configuration diagram of an air-conditioning apparatus according to Embodiment 3 of the present invention.

FIG. 4 is a configuration diagram of an air conditioner showing a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of an air-conditioning apparatus according to Embodiment 5 of the present invention.

FIG. 6 is a configuration diagram of an air-conditioning apparatus according to Embodiment 6 of the present invention.

FIG. 7 is a configuration diagram of an air-conditioning apparatus according to Embodiment 7 of the present invention.

FIG. 8 is a cross-sectional view showing a heat exchanger that brings an oil return pipe and a high-pressure liquid pipe into contact with each other in a seventh embodiment of the present invention.

FIG. 9 is a configuration diagram of an air conditioner showing a ninth embodiment of the present invention.

FIG. 10 is a configuration diagram of an air conditioner showing a ninth embodiment of the present invention.

FIG. 11 is a diagram showing an attached state of a bypass circuit 19 according to a ninth embodiment of the present invention.

FIG. 12 is a configuration diagram of an air conditioner showing a tenth embodiment of the present invention.

FIG. 13 is a configuration diagram of an air-conditioning apparatus according to Embodiment 11 of the present invention.

FIG. 14 is a configuration diagram of an air conditioner showing a twelfth embodiment of the present invention.

FIG. 15 is a configuration diagram of an air conditioner showing a thirteenth embodiment of the present invention.

FIG. 16 is a configuration diagram of an air conditioner showing a fourteenth embodiment of the present invention.

FIG. 17 is a configuration diagram showing a conventional air conditioner.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 compressor, 2 oil separator, 3 condenser, 4 first on-off valve, 5, 5a, 5b expansion device, 6 evaporator, 7 accumulator, 8 decompression device or first decompression device, 9 pressure sensor, 10 temperature sensor , 11 control means, 12
2nd on-off valve, 13 1st oil return circuit, 14 2nd oil return circuit, 15 3rd on-off valve, 16 2nd capillary, 17
Heat exchange means, 18 bypass circuit, 19 refrigerant flow,
20 control means, 21 first on-off valve, 22 second bypass circuit, 23 liquid reservoir, 24 switching valve, 25 on-off valve, 26 capillary, 27a, 27b first on-off valve.

Claims (7)

[Claims] 1. A compressor, an oil separator, a condenser, a throttle device,
An air conditioner including a refrigerating cycle in which evaporators are sequentially connected to a pipe, a recirculation circuit connecting the oil separator and a low pressure side of the refrigerating cycle, a decompression device provided in the recirculation circuit, and the decompression. Downstream of the device, provided in the oil return circuit,
Temperature detection means for detecting the temperature of the oil return circuit and pressure detection means for detecting the pressure of the refrigerant in the oil return circuit; and calculating the saturation temperature of the refrigerant at the pressure detected by the pressure detection means, and calculating the saturation temperature and Calculating a temperature difference from the temperature detected by the temperature detecting means, and when the temperature difference is equal to or less than a set temperature difference, a control means for issuing an oil return command; and a refrigerating machine oil of the oil separator according to a command of the control means. An air conditioner comprising: oil return means for returning oil to a compressor side. 2. The oil return circuit according to claim 1, wherein the oil return circuit is provided when the control means stops the compressor and closes an opening / closing device that shuts off a high pressure side and a low pressure side of the refrigeration cycle. The air conditioner according to claim 1, wherein 3. The oil return means includes a pressure reducing device having a smaller flow resistance than the pressure reducing device of the oil return circuit, and is a bypass pipe provided in parallel with the pressure reducing device of the oil return circuit. Item 7. The air conditioner according to Item 1. 4. The air conditioner according to claim 1, further comprising a heat exchange unit that exchanges heat between a refrigerant downstream of the temperature detection unit and the pressure detection unit and a refrigerant that has exited a condenser. . 5. An air conditioner comprising a refrigeration cycle in which a compressor, an oil separator, a condenser, a first opening / closing valve, a throttle device, and an evaporator are sequentially connected to each other, and using refrigeration oil that does not mix with the refrigerant. A first bypass circuit provided between an upper portion of the pipe at a horizontal location of the pipe for leading the refrigerant from the first on-off valve and the pipe connecting the accumulator and the evaporator; and a first bypass circuit provided in the first bypass circuit. A first decompression device, a second bypass circuit that bypasses the first decompression device, and a second on-off valve and a second decompression device provided in the second bypass circuit. At the outlet, pressure detecting means for detecting the pressure of the refrigerant, temperature detecting means for detecting the temperature of the refrigerant, and converting the detected pressure into a saturation temperature, calculating the temperature difference with the temperature of the refrigerant, and calculating Temperature difference is set temperature An air conditioner, further comprising: control means for performing control to open the second on-off valve for a predetermined time when the difference becomes equal to or greater than the difference. 6. An air conditioner comprising a refrigeration cycle in which a compressor, an oil separator, a condenser, a first on-off valve, a throttle device, and an evaporator are sequentially connected to a pipe, and using refrigeration oil that does not mix with the refrigerant. A first bypass circuit provided between the upper part of the pipe at a horizontal location of the pipe for leading the refrigerant from the first on-off valve and the pipe connecting the expansion device and the evaporator; and a first bypass circuit provided in the bypass circuit. A first decompression device,
A second bypass circuit bypassing the first pressure reducing device and connected to an evaporator outlet; a second on-off valve and a second pressure reducing device provided in the second bypass circuit;
At the outlet of the bypass circuit, a pressure detecting means for detecting the pressure of the refrigerant, a temperature detecting means for detecting the temperature of the refrigerant, and converting the detected pressure into a saturation temperature of the refrigerant at the pressure, the saturation temperature and the temperature detection. Control means for calculating a temperature difference from the temperature T detected by the means, and controlling to open the second on-off valve for a predetermined time when the calculated temperature difference is equal to or more than the set temperature difference. An air conditioner characterized by being provided. 7. A heat exchange means for exchanging heat between a refrigerant downstream of the temperature detection means and the pressure detection means and a refrigerant flowing out of a condenser. Air conditioner.