JPH10153355A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a proper amount of oil of each compressor in the case where a plurality of compressors include different volumes or a variable volume system-based compressor. SOLUTION: An oil equalizer pipe connection pipelines 12a to 12c are provided near the shell standard oil level elevation of each of compressors 2a to 2c where there are provided an oil equalizer pipe 11 communicated with one end of each of the oil equalizer pipe connection pipelines 12a to 12c and a communication pipeline which is communicated with the upper part in an accumulator 20 and the oil equalizer pipeline 11 in structure. This construction makes it possible to increase the pressure of the oil equalizer pipe 11 higher than the pressure in the shell of each of the compressors 2a to 2c and eliminate the movement of oil by way of the oil equalizer pipe during the operation of the compressors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner having a plurality of low-pressure shell type compressors.

[0002]

2. Description of the Related Art A conventional air conditioner of this type is disclosed in Japanese Utility Model Laid-Open No. 19675/1992.

Hereinafter, the air conditioner described above will be described with reference to the drawings. In FIG. 8, the outdoor unit 1 of the air conditioner includes a plurality of low-pressure shell-type compressors 2, four-way valves 3, outdoor heat exchangers 4, outdoor expansion valves 5, and accumulators 20. The indoor unit 6 includes an indoor expansion valve 7 and an indoor heat exchanger 8. Further, the outdoor unit 1 and the indoor unit 6 are connected to form an annular refrigerant circuit. The outlet pipe of the accumulator 20 has a U-shape, and an oil return hole is provided below the outlet pipe. An oil equalizing pipe connection pipe 12 is provided near the standard oil level of the shell of each compressor 2, and one end of each oil equalizing pipe connection pipe 12 communicates with the oil equalizing pipe 11.
Incidentally, three compressors 2 are connected in the conventional example, and suffixes a, b, and c are added to distinguish them.

Next, a method of controlling the oil amount of each compressor in the air conditioner having the above configuration will be described. First, the compressor 2
When the oil amount in the shell increases and the oil level rises, the pressure at the connection of the oil equalizing pipe connection pipe 12 of the compressor 2 increases.
Further, when the oil amount in the shell of the compressor 2 decreases and the oil level decreases, the pressure at the connection part of the oil equalizing pipe connection pipe 12 of the compressor 2 decreases. Therefore, for example, when the oil amount of the compressor 2a decreases due to oil forming or the like at the time of startup, the oil level height of the compressor 2a decreases, and the pressure of the connection portion of the oil equalizing pipe connection pipe 12a of the compressor 2a decreases. However, the pressure becomes lower than the pressure at the connection between the oil equalizing pipe connection pipes 12b and 12c of the compressors 2b and 2c. For this reason, the oil in the shells of the compressors 2b and 2c moves into the shell of the compressor 2a via the oil equalizing pipe 11, and the shortage of the oil amount of the compressor 2a can be prevented. Thus, the oil amount of each compressor can be controlled to an appropriate amount.

[0005]

However, in the above configuration, a plurality of compressors include compressors of different capacities, or a plurality of compressors include a variable capacity compressor. In this case, the pressure in the shell of the high-capacity compressor is low, and the pressure in the shell of the low-capacity compressor is high because each compressor is of the low-pressure shell type. Therefore, for example, the compressor 2a
When the capacity is lower than b and 2c, the pressure in the shell of the compressor 2a becomes higher than the pressure in the shell of the compressors 2b and 2c, and the pressure at the connection part of the oil equalizing pipe connection pipe 12a of the compressor 2a is reduced. Oil equalizing pipe connection pipes 12b, 12 of the compressors 2b, 2c
The pressure is higher than the pressure at the connection point c. For this reason, the compressor 2a
The oil in the shell of the compressor 2b, 2c
And the oil amount of the compressor 2a decreases. At this time, in the shell of the compressor 2a, the oil stirred by the rotating parts or the oil dropped from the compression chamber floats in the form of a mist, and the mist-like oil is cooled together with the refrigerant in the compressor 2b. , 2c. Therefore, the compressor 2
Even if the oil level height a becomes lower than the connection position of the oil equalizing pipe connection pipe 12a, the oil amount continues to decrease, and eventually the oil amount becomes insufficient. As described above, there is a problem that the oil amount of the compressor on the low capacity side becomes insufficient.

SUMMARY OF THE INVENTION The present invention solves the conventional problem. In the case where a plurality of compressors include compressors having different capacities,
Alternatively, it is another object of the present invention to provide an air conditioner capable of adjusting a proper oil amount of each compressor even when a plurality of compressors include a variable displacement compressor.

[0007]

SUMMARY OF THE INVENTION The present invention provides an equalizing pipe connecting pipe near a standard oil level of a plurality of low pressure shell type shells, and an equalizing pipe connected to one end of each of the equalizing pipe connecting pipes. An oil pipe, a communication pipe communicating the upper part in the accumulator and the oil equalizing pipe, and the pressure of the oil equalizing pipe is higher than the pressure of the shell of each of the compressors.

Further, the present invention provides an oil equalizing pipe connecting pipes near one of the standard oil level of a plurality of low pressure shell type compressor shells, and one end of each oil equalizing pipe connecting pipe, and an accumulator. A communication pipe communicating the upper part of the inside and the oil equalizing pipe, a two-way valve provided in the communication pipe, and cooling, or, when the continuous operation time of heating becomes a predetermined time or more,
There is provided a two-way valve control means for closing the two-way valve for a predetermined time, and when the two-way valve is closed, the pressure of the oil equalizing pipe is higher than the pressure of the shell of each compressor.

Further, the present invention provides an oil equalizing pipe connecting pipe near the standard oil level of a plurality of low pressure shell type compressor shells, and an oil equalizing pipe communicating with one end of each oil equalizing pipe connecting pipe, and an accumulator. A communication pipe that communicates the upper part of the inside with the oil equalizing pipe, a two-way valve provided in the communication pipe, and a differential pressure detection device that detects a differential pressure between a shell upper part and a shell lower part of each compressor. When the differential pressure between the upper shell and the lower shell detected by the differential pressure detecting device of one compressor is less than a predetermined lower differential pressure, the two-way valve is closed, and then the differential pressure detection of all the compressors is performed. When the differential pressure between the upper shell portion and the lower shell portion detected by the device is equal to or greater than a predetermined standard differential pressure, a two-way valve control means for opening the two-way valve is provided, and when the two-way valve is closed, the pressure of the oil equalizing pipe is increased. Is higher than the shell pressure of each compressor. That.

[0010] The present invention also provides an oil equalizing pipe connecting pipes near the standard oil level of a plurality of low pressure shell type compressor shells, one end of each of the oil equalizing pipe connecting pipes, and an accumulator. A communication pipe that communicates the upper part of the inside and the oil equalizing pipe, a two-way valve provided in the communication pipe, and an oil level detection device that detects an oil level of each compressor, and at least one When the oil level detected by the oil level detector of the compressor is less than a predetermined lower limit oil level, the two-way valve is closed, and then the oil level detection of all compressors is performed. When the oil level detected by the device is equal to or higher than the predetermined oil level,
There is provided two-way valve control means for opening the two-way valve, and when the two-way valve is closed, the pressure of the oil equalizing pipe is higher than the pressure of the shell of each of the compressors.

According to the present invention, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a variable capacity compressor,
The oil amount of each compressor can be controlled to an appropriate amount.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to an outdoor unit comprising a plurality of low-pressure shell-type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator; An annular refrigerant circuit is formed by connecting an inner expansion valve and an indoor unit including an indoor heat exchanger, and an oil equalizing pipe connection pipe is provided near a standard oil level of a shell of each of the compressors. An oil pipe connected to one end of an oil pipe connection pipe; and a communication pipe connecting the suction gas pipe upstream of a suction gas branch section to each of the compressors and the oil equalization pipe. Higher than the shell pressure of the machine.

Therefore, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a compressor of a variable capacity system, during operation of the compressor, Oil does not move from the shell of the compressor on the low-capacity side to the compressor on the high-capacity side via the oil equalizing pipe, and it is possible to prevent shortage of oil in the compressor on the low-capacity side.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to the compressors via the oil equalizing pipe connection pipes. At this time, the amount of the gas refrigerant to be distributed is proportional to the square root of the differential pressure in the oil equalizing pipe and the shell of each of the compressors, and the amount of the oil to be distributed is also the same as that of the oil equalizing pipe and the shell of each of the compressors. Is proportional to the square root of the differential pressure. However, since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil distributed is determined by the ratio of the discharge oil amount determined by the capacity of each compressor. And different. Therefore,
In some of the compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing tube to the ratio of the amount of discharged oil is small, and if the continuous operation is continued for a long time, the oil amount decreases. The oil will eventually run out.

However, since the inlet of the communication pipe is located in the upper part of the accumulator in which oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, it is possible to prevent shortage of the oil amount after a long operation because the ratio of the oil amount distributed from the communication pipe through the oil equalizing pipe to the oil discharge amount ratio of the compressor is small.

In general, the high-capacity compressor has a larger amount of oil supply to the compression chamber than the low-capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low-capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the compressor on the high capacity side, the amount of oil returned is smaller than the amount of discharged oil, and the amount of oil decreases as continuous operation is continued.

However, when all the compressors stop,
The pressure in the cycle is equalized, and the oil level of the compressors is adjusted by the oil equalizing pipe so that the oil level is equal.
Therefore, it is possible to prevent an oil shortage due to the oil return amount being smaller than the oil discharge amount of the compressor on the high capacity side. Thus, the oil amount of each compressor can be controlled to an appropriate amount.

According to a second aspect of the present invention, there is provided an outdoor unit comprising a plurality of low pressure shell type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator; An annular refrigerant circuit is formed by connecting an indoor unit including an indoor heat exchanger, and an oil equalizing pipe connection pipe is provided near a standard oil level of a shell of each of the compressors. An oil equalizing pipe having one end connected thereto, a communication pipe communicating the suction gas pipe upstream of a suction gas branch to each of the compressors and the oil equalizing pipe, and a two-way valve provided in the communication pipe,
When the continuous operation time of the cooling or the heating is equal to or longer than a predetermined time, a two-way valve control unit that closes the two-way valve for a fixed time is provided, and when the two-way valve is closed, the pressure of the oil equalizing pipe is increased. The pressure is higher than the shell pressure of each compressor.

Therefore, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a compressor of a variable capacity type, the compressor having the lower capacity is used. No oil moves from the shell through the oil equalizing pipe to the compressor on the high-capacity side, and the shortage of oil in the compressor on the low-capacity side can be prevented.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to the compressors via the oil equalizing pipe connection pipes. At this time, the amount of the gas refrigerant to be distributed is proportional to the square root of the differential pressure in the oil equalizing pipe and the shell of each of the compressors, and the amount of the oil to be distributed is also the same as that of the oil equalizing pipe and the shell of each of the compressors. Is proportional to the square root of the differential pressure. However, since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil distributed is determined by the ratio of the discharge oil amount determined by the capacity of each compressor. And different. Therefore,
In some of the compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing tube to the ratio of the amount of discharged oil is small, and if the continuous operation is continued for a long time, the oil amount decreases. The oil will eventually run out.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, it is possible to prevent shortage of the oil amount after a long operation because the ratio of the oil amount distributed from the communication pipe through the oil equalizing pipe to the oil discharge amount ratio of the compressor is small.

In general, the higher capacity compressor has a larger oil supply amount to the compression chamber than the lower capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the compressor on the high-capacity side, the amount of oil returned is small with respect to the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the continuous operation time of cooling or heating is equal to or longer than a predetermined time, the two-way valve is closed for a predetermined time, so that when the two-way valve is closed, the pressure in the shell becomes high and low. Oil moves from the compressor on the capacity side to the compressor on the high capacity side where the pressure in the shell is low via the oil equalizing pipe. Therefore, it is possible to prevent an insufficient amount of oil after a long-time continuous operation because the amount of oil returned is smaller than the amount of oil discharged from the compressor on the high capacity side. Thus, the oil amount of each compressor can be controlled to an appropriate amount.

According to a third aspect of the present invention, there is provided an outdoor unit including a plurality of low-pressure shell type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator; An annular refrigerant circuit is formed by connecting an indoor unit including an indoor heat exchanger, and an oil equalizing pipe connection pipe is provided near a standard oil level of a shell of each of the compressors. An oil equalizing pipe having one end connected thereto, a communication pipe communicating the suction gas pipe upstream of a suction gas branch to each of the compressors and the oil equalizing pipe, and a two-way valve provided in the communication pipe,
A differential pressure detector for detecting a differential pressure between a shell upper part and a shell lower part of each of the compressors, wherein a differential pressure between the shell upper part and the shell lower part detected by the differential pressure detector of at least one of the compressors is a predetermined value; When the pressure difference is less than the lower limit differential pressure, the two-way valve is closed, and thereafter, when the differential pressure between the upper shell and lower shell detected by the differential pressure detectors of all the compressors is equal to or more than a predetermined standard differential pressure, Two-way valve control means for opening the two-way valve is provided, and when the two-way valve is closed, the pressure of the oil equalizing pipe is higher than the pressure of the shell of each of the compressors.

Therefore, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a compressor of a variable capacity type, the compressor having a lower capacity is used. No oil moves from the shell through the oil equalizing pipe to the compressor on the high-capacity side, and the shortage of oil in the compressor on the low-capacity side can be prevented.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to the compressors via the oil equalizing pipe connection pipes. At this time, the amount of the gas refrigerant to be distributed is proportional to the square root of the differential pressure in the oil equalizing pipe and the shell of each of the compressors, and the amount of the oil to be distributed is also the same as that of the oil equalizing pipe and the shell of each of the compressors. Is proportional to the square root of the differential pressure. However, since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil distributed is determined by the ratio of the discharge oil amount determined by the capacity of each compressor. And different. Therefore,
In some of the compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing tube to the ratio of the amount of discharged oil is small, and if the continuous operation is continued for a long time, the oil amount decreases. The oil will eventually run out.

However, since the inlet of the communication pipe is located in the upper part of the accumulator in which oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, it is possible to prevent shortage of the oil amount after a long operation because the ratio of the oil amount distributed from the communication pipe through the oil equalizing pipe to the oil discharge amount ratio of the compressor is small.

In general, a high-capacity compressor has a larger amount of oil supply to the compression chamber than a low-capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low-capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the compressor on the high-capacity side, the amount of returned oil is small relative to the amount of discharged oil, and if the continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the differential pressure between the upper shell portion and the lower shell portion detected by the differential pressure detecting device of at least one of the compressors becomes less than a predetermined lower limit differential pressure, thereafter, the differential pressure of all the compressors is reduced. In order to close the two-way valve until the differential pressure between the upper shell and the lower shell detected by the detection device is equal to or higher than a predetermined standard differential pressure, when the two-way valve is closed, the pressure in the shell is high and the low-capacity side is closed. The oil moves from the compressor through the oil equalizing pipe to the compressor on the high capacity side where the pressure in the shell is low. Therefore, it is possible to prevent an insufficient amount of oil after a long-time continuous operation because the amount of oil returned is smaller than the amount of oil discharged from the compressor on the high capacity side.

Further, since the shortage of the oil amount of each of the compressors is detected from the differential pressure between the upper shell and the lower shell, the oil discharge amount and the oil return amount of the compressor due to the difference in the operating conditions are affected. , The two-way valve can be controlled with high accuracy. Therefore, the closing of the two-way valve is too late, or
Insufficient oil amount of the compressor on the high capacity side because the opening after closing of the two-way valve is too early, and the opening after closing of the two-way valve is early, or after the closing of the two-way valve. Of the compressor on the low capacity side due to the opening of the compressor being too slow can be prevented. Thus, the oil amount of each compressor can be controlled to an appropriate amount.

According to a fourth aspect of the present invention, there is provided an outdoor unit including a plurality of low pressure shell type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator; An annular refrigerant circuit is formed by connecting an indoor unit including an indoor heat exchanger, and an oil equalizing pipe connection pipe is provided near a standard oil level of a shell of each of the compressors. An oil equalizing pipe having one end connected thereto, a communication pipe communicating the suction gas pipe upstream of a suction gas branch to each of the compressors and the oil equalizing pipe, and a two-way valve provided in the communication pipe,
An oil level detector for detecting the oil level of each of the compressors, wherein the oil level detected by the oil level detector of at least one of the compressors is a predetermined lower limit oil level When the oil level is less than the predetermined standard oil level, the two-way valve is closed, and thereafter, when the oil level detected by the oil level detectors of all the compressors is equal to or more than a predetermined standard oil level. It is provided with two-way valve control means for opening the valve, and when the two-way valve is closed, the pressure of the oil equalizing pipe is higher than the pressure of the shell of each compressor.

Therefore, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a compressor of a variable capacity type, the compressor having a lower capacity is used. No oil moves from the shell through the oil equalizing pipe to the compressor on the high-capacity side, and the shortage of oil in the compressor on the low-capacity side can be prevented.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to the compressors via the oil equalizing pipe connection pipes. At this time, the amount of the gas refrigerant to be distributed is proportional to the square root of the differential pressure in the oil equalizing pipe and the shell of each of the compressors, and the amount of the oil to be distributed is also the same as that of the oil equalizing pipe and the shell of each of the compressors. Is proportional to the square root of the differential pressure. However, since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil distributed is determined by the ratio of the discharge oil amount determined by the capacity of each compressor. And different. Therefore,
In some of the compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing tube to the ratio of the amount of discharged oil is small, and if the continuous operation is continued for a long time, the oil amount decreases. The oil will eventually run out.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where oil is separated and only the gas refrigerant is present, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, it is possible to prevent shortage of the oil amount after a long operation because the ratio of the oil amount distributed from the communication pipe through the oil equalizing pipe to the oil discharge amount ratio of the compressor is small.

In general, the high-capacity compressor has a larger oil supply amount to the compression chamber than the low-capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low-capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the compressor on the high capacity side, the amount of oil returned is small relative to the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil will decrease,
Eventually, the amount of oil will be insufficient.

However, when the oil level detected by the oil level detector of at least one of the compressors is less than a predetermined lower limit oil level, thereafter, the oil level of all the compressors is reduced. In order to close the two-way valve until the oil level detected by the height detection device is equal to or higher than a predetermined oil level, when the two-way valve is closed, the pressure in the shell is higher on the low-capacity side. Oil moves from the compressor via the oil equalizing pipe to the compressor on the high capacity side where the pressure in the shell is low. Therefore, it is possible to prevent an insufficient amount of oil after a long-time continuous operation because the amount of oil returned is smaller than the amount of oil discharged from the compressor on the high capacity side.

Further, in order to detect the shortage of the oil amount of each of the compressors from the oil level, variations in the oil discharge amount and the oil return amount of the compressor due to the difference in operating conditions, and in the shell of the compressor. The two-way valve can be accurately controlled without being affected by the variation in the pressure distribution. Therefore, the closing of the two-way valve is too late, or the opening after the closing of the two-way valve is too early, the oil amount of the compressor on the high capacity side is insufficient, and after the closing of the two-way valve. Opening too early, or
Insufficient oil amount of the compressor on the low-capacity side due to too late opening of the two-way valve after closing can be prevented. Thus, the oil amount of each compressor can be controlled to an appropriate amount.

[0038]

FIG. 1 to FIG. 7 show an embodiment of the present invention.
This will be described with reference to FIG. The same parts as those in the related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIG.

FIG. 1 is a refrigeration cycle diagram of an air conditioner according to Embodiment 1 of the present invention. In FIG. 1, a communication pipe 13 communicates the upper part of the accumulator 20 with the oil equalizing pipe 11. The pressure of the oil equalizing pipe 11 is higher than the pressure of the shell of each compressor 2. Incidentally, three compressors 2 are connected in the conventional example, and suffixes a, b, and c are added to distinguish them.

Next, a method of adjusting an appropriate oil amount of each compressor in the air conditioner having the above configuration will be described. Here, whether the multiple compressors include compressors with different capacities,
Alternatively, it is assumed that a compressor of a variable capacity system is included, and the compressor 2a has a lower capacity than the compressors 2b and 2c.

First, during the operation of the compressor 2, the pressure of the oil equalizing pipe 11 which is communicated with the upper part in the accumulator 20 by the communication pipe 13 becomes higher than the pressure of the shell of the compressor 2. Therefore, oil does not flow out from the low-capacity compressor 2a to the oil equalizing pipe connection pipe 12a.

Since the inlet of the communication pipe 13 is located in the upper part of the accumulator 20 where oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe 13.

When all the compressors 2 are stopped, the pressure in the cycle is equalized, and the oil can be moved between the compressors 2 through the oil equalizing pipe 11. The oil amount is adjusted so that the oil level of all the compressors 2 becomes equal.

According to this embodiment, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a variable capacity compressor, During the operation, the oil does not move from the compressor on the low capacity side to the compressor on the high capacity side via the oil equalizing pipe. Therefore, it is possible to prevent the low-capacity compressor from running out of oil due to the oil moving to the high-capacity compressor via the oil equalizing pipe.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed to each compressor together with the gas refrigerant from the oil equalizing pipe through each oil equalizing pipe connection pipe. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, it is possible to prevent shortage of oil amount after long-time continuous operation because the ratio of the amount of oil distributed from the pipe through the oil equalizing pipe to the ratio of the oil discharge amount of the compressor is small.

In general, the high-capacity compressor has a larger oil supply amount to the compression chamber than the low-capacity compressor, and therefore has a higher oil content of the discharged refrigerant than the low-capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is smaller than the amount of discharged oil, and the amount of oil decreases as continuous operation is continued.

However, when all the compressors are stopped, the pressure in the cycle is equalized, and the oil level is adjusted by the oil equalizing pipe so that the oil level of each compressor becomes equal. Therefore, it is possible to prevent an oil shortage due to the oil return amount being smaller than the oil discharge amount of the compressor on the high capacity side. Thus, each compressor can be maintained at an appropriate oil amount.

(Embodiment 2) Embodiment 2 of the present invention will be described with reference to FIGS.

FIG. 2 is a refrigeration cycle diagram of an air conditioner according to a second embodiment of the present invention. In FIG. 2, reference numeral 13 denotes a communication pipe that communicates with the upper part of the accumulator 20 and the oil leveling pipe 11, and reference numeral 14 denotes a communication pipe. The pressure in the oil equalizing pipe 11 is higher than the pressure in the shell of each compressor 2 when the two-way valve 14 is closed. Here, the two-way valve control means 15 closes the two-way valve 14 for a fixed time when the continuous operation time of cooling or heating reaches a predetermined time. Incidentally, three compressors 2 are connected in the conventional example,
To distinguish them, subscripts a, b, and c are added.

FIG. 3 is a flowchart showing a method for controlling the two-way valve 14 of the air conditioner according to the second embodiment of the present invention. From FIG. 3, first, in Step 1, cooling or
The continuous operation time Tr of heating is detected. In step 2,
If the continuous operation time Tr detected in step 1 is shorter than the predetermined upper limit continuous operation time Tro, the process returns to step 1. If the continuous operation time Tr is longer than the predetermined upper limit continuous operation time Tro, the process proceeds to step 3. In step 3, the two-way valve 14 is closed. In step 4, the closing time Tv of the two-way valve 14 is detected. In step 5, when the two-way valve closing time Tv detected in step 4 is shorter than the predetermined upper limit two-way valve closing time Tvo, the process returns to step 4, and when it is longer than the predetermined upper limit two-way valve closing time Tvo, the process proceeds to step 6. move on. In step 6, the two-way valve 14 is opened. In step 7, the continuous operation time Tr is returned to 0, and the process returns to step 1.

Next, a description will be given of a method for adjusting an appropriate oil amount of each compressor in the air conditioner having the above configuration. Here, whether the multiple compressors include compressors with different capacities,
Alternatively, it is assumed that a compressor of a variable capacity system is included, and the compressor 2a has a lower capacity than the compressors 2b and 2c.

First, when the compressor 2 starts operating, since the two-way valve 14 is open, the pressure of the oil equalizing pipe 11 connected to the upper part in the accumulator 20 by the communication pipe 13 is reduced. Higher than the shell pressure. Therefore,
Oil does not flow out from the low-capacity compressor 2a to the oil equalizing pipe connection pipe 12a.

Since the inlet of the communication pipe 13 is located in the upper part of the accumulator 20 where oil is separated and only the gas refrigerant is present, only the gas refrigerant containing no oil flows through the communication pipe 13.

When the continuous operation time of the cooling or the heating reaches a predetermined time, the two-way valve 14 is closed, and the compressor 2a on the low-capacity side where the pressure in the shell is high passes from the oil equalizing pipe 1
1, a high-capacity compressor 2 with a low pressure in the shell
Oil moves to b and 2c. And, after the two-way valve 14 is closed,
After a lapse of a certain time, the two-way valve is opened, and the movement of oil through the oil equalizing pipe 11 is eliminated.

According to this embodiment, even when a plurality of compressors include compressors having different capacities, or when a plurality of compressors include a variable capacity compressor,
During operation of the compressor, while the two-way valve is open, no oil moves from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. Therefore, it is possible to prevent the low-capacity compressor from running out of oil due to the oil moving to the high-capacity compressor via the oil equalizing pipe.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to each compressor via each oil equalizing pipe connection pipe. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator in which oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, since the ratio of the amount of oil distributed from the communication pipe via the oil equalizing pipe to the ratio of the oil discharge amount of the compressor is small,
Insufficient oil amount after long continuous operation can be prevented.

In general, the compressor on the high capacity side has a larger amount of oil supply to the compression chamber than the compressor on the low capacity side, so that the oil content of the discharged refrigerant is larger than that of the compressor on the low capacity side. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is small with respect to the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the continuous operation time reaches the upper limit continuous operation time, the two-way valve is closed for a fixed time, and the oil moves from the compressor on the low capacity side to the compressor on the high capacity side via the oil equalizing pipe. I do. Therefore, it is possible to prevent an insufficient oil amount after a long-time continuous operation because the oil return amount is smaller than the oil discharge amount of the high-capacity compressor. Thus, each compressor can be maintained at an appropriate oil amount.

(Embodiment 3) Embodiment 3 of the present invention will be described with reference to FIGS.

FIG. 4 is a refrigeration cycle diagram of the air conditioner according to the third embodiment of the present invention. In FIG. 5, reference numeral 13 denotes a communication pipe for connecting the upper part of the accumulator 20 to the oil equalizing pipe 11, and reference numeral 14 denotes a communication pipe. The pressure in the oil equalizing pipe 11 is higher than the pressure in the shell of each compressor 2 when the two-way valve 14 is closed. Reference numeral 16 denotes a differential pressure detecting device (for example, a differential pressure sensor or two pressure sensors) that detects a differential pressure between the upper shell and the lower shell of the compressor 2. Here, the two-way valve control means 17 starts the two-way valve 14 when the differential pressure between the upper shell portion and the lower shell portion detected by the differential pressure detecting device 16 of at least one compressor 2 becomes lower than a predetermined lower limit differential pressure. Then, when the differential pressure between the upper shell and the lower shell detected by the differential pressure detectors 16 of all the compressors 2 becomes equal to or higher than a predetermined standard differential pressure, the two-way valve 14 is opened. Incidentally, three compressors 2 are connected in the conventional example, and suffixes a, b, and c are added to distinguish them.

FIG. 5 is a flowchart showing a method for controlling the two-way valve 14 of the air conditioner according to the third embodiment of the present invention. As shown in FIG. 5, first, at step 11, the differential pressure detecting device 16 detects the differential pressure P between the upper shell portion and the lower shell portion of the compressor 2. In step 12, at least one compressor 2
The differential pressure P detected in the step 11 of the above is the predetermined lower limit differential pressure P
If it is 1 or more, the process returns to step 11, and the predetermined lower limit differential pressure P
If it is less than 1, the process proceeds to step 13. In step 13, the two-way valve 14 is closed. In step 14, the differential pressure detecting device 16 detects the differential pressure P between the upper part and the lower part of the shell of the compressor 2. In step 15, if the differential pressure P detected in step 14 of all the compressors 2 is less than the predetermined standard differential pressure Ps, the process returns to step 14, and if it is equal to or more than the predetermined standard differential pressure Ps, the process proceeds to step 16. In step 16, the two-way valve is opened, and the process returns to step 1.

Next, a description will be given of a method for adjusting an appropriate oil amount of each compressor in the air conditioner having the above configuration. Here, whether the multiple compressors include compressors with different capacities,
Alternatively, it is assumed that a compressor of a variable capacity system is included, and the compressor 2a has a lower capacity than the compressors 2b and 2c.

First, when the compressor 2 starts operating, since the two-way valve 14 is open, the pressure of the oil equalizing pipe 11 connected to the upper part in the accumulator 20 by the communication pipe 13 is reduced. Higher than the shell pressure. Therefore,
Oil does not flow out from the low-capacity compressor 2a to the oil equalizing pipe connection pipe 12a.

Since the inlet of the communication pipe 13 is located in the upper part of the accumulator 20 where oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe 13.

When the oil amount of the compressor decreases, the oil level decreases, the pressure difference between the upper shell and the lower shell decreases, and when the oil amount of the compressor increases, the oil level decreases. As a result, the pressure difference between the upper shell and the lower shell increases. Accordingly, when the oil amount of the compressors 2b and 2c decreases and the pressure difference between the upper shell and the lower shell becomes less than the lower limit pressure, the two-way valve 14 is closed, and the compression in the low capacity side where the pressure in the shell is high. Oil moves from the compressor 2a via the oil equalizing pipe 11 to the compressors 2b and 2c on the high capacity side where the pressure in the shell is low. Then, when the oil amount of the compressors 2b and 2c increases and the differential pressure between the upper shell and the lower shell becomes higher than the standard, the two-way valve 14 is opened, and the movement of oil through the oil equalizing pipe 11 is eliminated.

According to this embodiment, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a variable capacity compressor,
During operation of the compressor, while the two-way valve is open, no oil moves from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. Therefore, it is possible to prevent the low-capacity compressor from running out of oil due to the oil moving to the high-capacity compressor via the oil equalizing pipe.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed to the compressors together with the gas refrigerant from the oil equalizing pipe via each oil equalizing pipe connection pipe. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where the oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, since the ratio of the amount of oil distributed from the communication pipe via the oil equalizing pipe to the ratio of the oil discharge amount of the compressor is small,
Insufficient oil amount after long continuous operation can be prevented.

In general, the higher capacity compressor has a larger oil supply to the compression chamber than the lower capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is small with respect to the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the oil amount of the compressor on the high-capacity side decreases and the differential pressure between the upper shell and the lower shell becomes less than the lower differential pressure, the oil amount increases and the differential pressure between the upper shell and the lower shell becomes the standard differential. Until the pressure exceeds the pressure, the two-way valve is closed, and oil moves from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. Therefore, it is possible to prevent an insufficient oil amount after a long-time continuous operation because the oil return amount is smaller than the oil discharge amount of the high-capacity compressor.

Further, since the shortage of the oil amount of each compressor is detected from the differential pressure between the upper shell and the lower shell, the oil discharge amount and the oil return amount of the compressor due to the difference in the operating conditions are not affected. The two-way valve can be controlled accurately. Therefore, the closing of the two-way valve is too slow, or the opening after the closing of the two-way valve is too early, and the amount of oil in the compressor on the high capacity side is insufficient, and the opening after the closing of the two-way valve is too early. Alternatively, the shortage of the oil amount of the compressor on the low-capacity side due to the opening of the two-way valve after closing is too slow can be prevented. Thus, each compressor can be maintained at an appropriate oil amount.

Embodiment 4 Embodiment 4 of the present invention will be described with reference to FIGS.

FIG. 6 is a refrigeration cycle diagram of an air conditioner according to a fourth embodiment of the present invention. In FIG. 6, reference numeral 13 denotes a communication pipe that connects the upper part of the accumulator 20 with the oil equalizing pipe 11, and reference numeral 14 denotes a communication pipe. The pressure in the oil equalizing pipe 11 is higher than the pressure in the shell of each compressor 2 when the two-way valve 14 is closed. Reference numeral 18 denotes an oil level detector (for example, a plurality of float switches) for detecting the oil level of the compressor 2. Here, when the oil level detected by the oil level detector 18 of at least one of the compressors 2 becomes less than a predetermined lower limit oil level, the two-way valve controller 19 controls the two-way valve 14. Is closed, and when the oil level detected by the oil level detectors 18 of all the compressors 2 becomes equal to or higher than a predetermined standard oil level, the two-way valve 14 is opened.
Incidentally, three compressors 2 are connected in the conventional example, and suffixes a, b, and c are added to distinguish them.

FIG. 7 is a flowchart showing a method for controlling the two-way valve 14 of the air conditioner according to the fourth embodiment of the present invention. As shown in FIG. 7, first, in step 21, the oil level detector 18 detects the oil level H of the compressor 2. In step 22, when the oil level H detected in step 21 of at least one of the compressors 2 is equal to or more than the predetermined lower limit oil level Ho, the process returns to step 21 and is smaller than the predetermined lower limit oil level Ho. If so, the process proceeds to step 23. In step 23, the two-way valve 14 is closed. In step 24, the oil level detector 18 detects the oil level H of the compressor 2. In step 25, if the oil level H detected in step 24 of all the compressors 2 is less than the predetermined standard oil level Hs, the process returns to step 24 and is equal to or more than the predetermined standard oil level Hs. And proceeds to step 26. In step 26, the two-way valve is opened, and the process returns to step 21.

Next, a method of adjusting an appropriate oil amount of each compressor in the air conditioner having the above configuration will be described. Here, whether the multiple compressors include compressors with different capacities,
Alternatively, it is assumed that a compressor of a variable capacity system is included, and the compressor 2a has a lower capacity than the compressors 2b and 2c.

First, when the compressor 2 starts operating, since the two-way valve 14 is open, the pressure of the oil equalizing pipe 11 connected to the upper part in the accumulator 20 by the communication pipe 13 is reduced. Higher than the shell pressure. Therefore,
Oil does not flow out from the low-capacity compressor 2a to the oil equalizing pipe connection pipe 12a.

Since the inlet of the communication pipe 13 is located in the upper part of the accumulator 20 where oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe 13.

Further, the oil amount of the compressors 2b and 2c decreases,
When the oil level becomes lower than the lower limit oil level, the two-way valve 14 is closed, and the pressure in the shell from the compressor 2a on the low capacity side where the pressure in the shell is high is increased via the oil equalizing pipe 11. The oil moves to the compressors 2b and 2c on the high capacity side where the pressure is low. When the oil amount of the compressors 2b and 2c increases and the oil level becomes equal to or higher than the standard oil level, the two-way valve 14 is opened, and the movement of the oil through the oil level pipe 11 is eliminated.

According to this embodiment, even when a plurality of compressors include compressors of different capacities, or when a plurality of compressors include a variable capacity compressor,
During operation of the compressor, while the two-way valve is open, no oil moves from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. Therefore, it is possible to prevent the low-capacity compressor from running out of oil due to the oil moving to the high-capacity compressor via the oil equalizing pipe.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to each compressor via each oil equalizing pipe connection pipe. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, since the ratio of the amount of oil distributed from the communication pipe via the oil equalizing pipe to the ratio of the oil discharge amount of the compressor is small,
Insufficient oil amount after long continuous operation can be prevented.

In general, the compressor of the high capacity side has a larger amount of oil supply to the compression chamber than the compressor of the low capacity side, so that the oil content of the discharged refrigerant is larger than the compressor of the low capacity side. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is small with respect to the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the oil amount of the compressor on the high capacity side decreases and the oil level becomes lower than the lower limit oil level, the oil level increases and the oil level becomes higher than the standard oil level. Until the two-way valve is closed, the oil moves from the compressor on the low capacity side to the compressor on the high capacity side via the oil equalizing pipe. Therefore, it is possible to prevent an insufficient oil amount after a long-time continuous operation because the oil return amount is smaller than the oil discharge amount of the high-capacity compressor.

Further, since the shortage of the oil amount of each compressor is detected from the oil level, variations in the oil discharge amount and the oil return amount of the compressor due to the difference in the operating conditions, and in the shell of the compressor, The two-way valve can be accurately controlled without being affected by variations in the pressure distribution. Therefore, the closing of the two-way valve is too late,
Alternatively, the opening of the two-way valve after closing is too early, the oil amount of the compressor on the high-capacity side is insufficient, and the opening after closing of the two-way valve is early, or after the closing of the two-way valve. Insufficient oil amount of the compressor on the low capacity side due to the opening being too slow can be prevented. Thus, each compressor can be maintained at an appropriate oil amount.

[0088]

As described above, the present invention provides an outdoor unit including a plurality of low-pressure shell type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator, an indoor expansion valve, and an indoor side. An annular refrigerant circuit is formed by connecting an indoor unit comprising a heat exchanger, an oil equalizing pipe connection pipe is provided near a standard oil level of a shell of each compressor, and one end of each oil equalizing pipe connection pipe is connected. An oil equalizing pipe communicated with the oil equalizing pipe and a communication pipe communicating the upper part of the accumulator with the oil equalizing pipe are provided, and a pressure of the oil equalizing pipe is higher than a pressure of a shell of each of the compressors.

Accordingly, even when a plurality of compressors include compressors having different capacities, or when a plurality of compressors include a compressor of a variable capacity type, the compressor is operated during operation. The oil does not move from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. Therefore, it is possible to prevent the low-capacity compressor from running out of oil due to the oil moving to the high-capacity compressor via the oil equalizing pipe.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to each compressor via each oil equalizing pipe connection pipe. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, since the ratio of the amount of oil distributed from the communication pipe via the oil equalizing pipe to the ratio of the oil discharge amount of the compressor is small,
Insufficient oil amount after long continuous operation can be prevented.

In general, the compressor on the high capacity side has a larger amount of oil supply to the compression chamber than the compressor on the low capacity side, so that the oil content of the discharged refrigerant is larger than that of the compressor on the low capacity side. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is small relative to the amount of discharged oil, and the amount of oil decreases as continuous operation is continued.

However, when all the compressors are stopped, the pressure in the cycle is equalized, and the oil level of each compressor is adjusted by the oil equalizing pipe so that the oil level becomes equal. Therefore, it is possible to prevent an oil shortage due to the oil return amount being smaller than the oil discharge amount of the compressor on the high capacity side. Thus, each compressor can be maintained at an appropriate oil amount.

An outdoor unit comprising a plurality of low-pressure shell compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve and an accumulator, and an indoor unit comprising an indoor expansion valve and an indoor heat exchanger. Are connected to each other to form an annular refrigerant circuit, an oil equalizing pipe connection pipe is provided near the standard oil level of the shell of each of the compressors, and an oil equalizing pipe communicating one end of each of the oil equalizing pipe connecting pipes; and the accumulator. A communication pipe that communicates the upper part of the inside with the oil equalizing pipe, a two-way valve provided in the communication pipe, and when the continuous operation time of cooling or heating reaches a predetermined time, the two-way valve for a predetermined time A two-way valve control means for closing the two-way valve, wherein when the two-way valve is closed, the pressure of the oil equalizing pipe is higher than the pressure of the shell of each of the compressors.

Thus, even when a plurality of compressors include compressors of different capacities, or a plurality of compressors include a variable capacity compressor, the operation of the While the two-way valve is open, oil does not move from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. Therefore, it is possible to prevent the low-capacity compressor from running out of oil due to the oil moving to the high-capacity compressor via the oil equalizing pipe.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed from the oil equalizing pipe to the compressors via the oil equalizing pipe connecting pipes together with the gas refrigerant. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator in which oil is separated and only the gas refrigerant exists, only the gas refrigerant containing no oil flows through the communication pipe. Therefore, since the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the oil discharge force of the compressor is small,
Insufficient oil amount after long continuous operation can be prevented.

In general, the high-capacity compressor has a larger amount of oil supply to the compression chamber than the low-capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low-capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is small with respect to the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the continuous operation time reaches the continuous operation upper limit time, the two-way valve is closed for a fixed time, and the oil moves from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. I do. Therefore, it is possible to prevent an insufficient oil amount after a long-time continuous operation because the oil return amount is smaller than the oil discharge amount of the high-capacity compressor. Thus, each compressor can be maintained at an appropriate oil amount.

An outdoor unit comprising a plurality of low-pressure shell type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve and an accumulator, and an indoor unit comprising an indoor expansion valve and an indoor heat exchanger. Are connected to each other to form an annular refrigerant circuit, an oil equalizing pipe connection pipe is provided near the standard oil level of the shell of each of the compressors, and an oil equalizing pipe communicating one end of each of the oil equalizing pipe connecting pipes; and the accumulator. A communication pipe that communicates the upper part of the inside and the oil equalizing pipe, a two-way valve provided in the communication pipe, and a differential pressure detection device that detects a differential pressure between a shell upper part and a shell lower part of each of the compressors. Closing the two-way valve when the differential pressure between the shell upper part and the shell lower part detected by the differential pressure detecting device of one of the compressors is less than a predetermined lower limit differential pressure,
Thereafter, a two-way valve control means for opening the two-way valve when the differential pressure between the upper shell portion and the lower shell portion detected by the differential pressure detecting devices of all the compressors is equal to or more than a predetermined standard differential pressure, When the direction valves are closed, the pressure of the oil equalizing pipe is set higher than the pressure of the shell of each compressor.

Thus, even when a plurality of compressors include compressors of different capacities, or a plurality of compressors include a compressor of a variable capacity type, the operation of the compressor is not affected. While the two-way valve is open, oil does not move from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe. Therefore, it is possible to prevent the low-capacity compressor from running out of oil due to the oil moving to the high-capacity compressor via the oil equalizing pipe.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed from the oil equalization pipe to the compressors via the oil equalization pipe connection pipes together with the gas refrigerant. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where oil is separated and only gas refrigerant exists, only gas refrigerant containing no oil flows through the communication pipe. Therefore, since the ratio of the amount of oil distributed from the communication pipe via the oil equalizing pipe to the ratio of the oil discharge amount of the compressor is small,
Insufficient oil amount after long continuous operation can be prevented.

In general, the high-capacity compressor has a larger oil supply amount to the compression chamber than the low-capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low-capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is smaller than the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the oil amount of the compressor on the high capacity side decreases and the differential pressure between the upper shell and the lower shell becomes smaller than the lower differential pressure, the oil amount increases and the differential pressure between the upper shell and the lower shell becomes equal to the standard pressure difference. The two-way valve is closed until the pressure becomes higher than the pressure, and oil moves from the compressor on the low capacity side to the compressor on the high capacity side via the oil equalizing pipe. Therefore, it is possible to prevent an insufficient oil amount after a long-time continuous operation because the oil return amount is smaller than the oil discharge amount of the high-capacity compressor.

Further, since the shortage of the oil amount of each compressor is detected from the differential pressure between the upper shell and the lower shell, the oil discharge amount and the oil return amount of the compressor due to the difference in the operating conditions are not affected. The two-way valve can be controlled accurately. Therefore, the closing of the two-way valve is too slow, or the opening after the closing of the two-way valve is too early, and the amount of oil in the compressor on the high capacity side is insufficient, and the opening after the closing of the two-way valve is too early. Alternatively, the shortage of the oil amount of the compressor on the low-capacity side due to the opening of the two-way valve after closing is too slow can be prevented. Therefore, each compressor can be maintained at an appropriate oil amount.

An outdoor unit comprising a plurality of low-pressure shell type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve and an accumulator, and an indoor unit comprising an indoor expansion valve and an indoor heat exchanger. Are connected to each other to form an annular refrigerant circuit, an oil equalizing pipe connection pipe is provided near the standard oil level of the shell of each of the compressors, and an oil equalizing pipe communicating one end of each of the oil equalizing pipe connecting pipes; and the accumulator. A communication pipe that communicates the upper part of the inside with the oil equalizing pipe, a two-way valve provided in the communication pipe, and an oil level detector that detects the oil level of each of the compressors, and at least one When the oil level detected by the oil level detector of the compressor is less than a predetermined lower limit oil level, the two-way valve is closed, and then the oil level of all the compressors is closed. When the oil level detected by the sensor is equal to or higher than a predetermined oil level, Comprising a two-way valve control means for opening the-way valve, when closed the two-way valve is obtained by higher than the pressure of the shell of the pressure the compressors of the oil equalizing tube.

Thus, even when a plurality of compressors include compressors of different capacities, or a plurality of compressors include a variable capacity compressor, the operation of the compressor is not possible. While the two-way valve is open, the oil does not move from the low-capacity compressor to the high-capacity compressor via the oil equalizing pipe, so that the high-capacity compression via the oil equalizing pipe does not occur. Insufficient oil amount of the compressor on the low capacity side due to the movement of oil to the compressor can be prevented.

The oil contained in the gas refrigerant flowing through the communication pipe is distributed together with the gas refrigerant from the oil equalizing pipe to each compressor via each oil equalizing pipe connection pipe. At this time, the amount of gas refrigerant to be distributed is proportional to the square root of the differential pressure between the oil equalizing pipe and the shell of each compressor, and the amount of oil to be distributed is also the same as the differential pressure between the oil equalizing pipe and the shell of each compressor. It is proportional to the square root of. But,
Since the pressure difference between the oil equalizing pipe and the shell of each compressor fluctuates due to the pressure loss of the communication pipe, the ratio of the amount of oil to be distributed is different from the ratio of the amount of discharged oil determined by the capacity of each compressor. Therefore, in some compressors, the ratio of the amount of oil distributed from the communication pipe through the oil equalizing pipe to the ratio of the amount of discharged oil is small, and if continuous operation is continued for a long time, the oil amount decreases. Suddenly, the amount of oil will run short.

However, since the inlet of the communication pipe is located in the upper part of the accumulator where oil is separated and only gas refrigerant exists, only gas refrigerant containing no oil flows through the communication pipe. Therefore, since the ratio of the amount of oil distributed from the communication pipe via the oil equalizing pipe to the ratio of the oil discharge amount of the compressor is small,
Insufficient oil amount after long continuous operation can be prevented.

In general, the higher capacity compressor has a larger oil supply to the compression chamber than the lower capacity compressor, so that the oil content of the discharged refrigerant is larger than that of the low capacity compressor. However, since the discharged refrigerant is merged after being discharged from each compressor, the oil content of the refrigerant sucked into each compressor after being branched at the suction gas branch portion is equal. Therefore, in the high-capacity compressor, the amount of oil returned is small with respect to the amount of discharged oil, and if continuous operation is continued for a long time, the amount of oil decreases, and eventually the amount of oil becomes insufficient.

However, when the oil amount of the compressor on the high capacity side decreases and the oil level becomes lower than the lower limit oil level, the oil level increases and the oil level becomes higher than the standard oil level. The two-way valve is closed until the oil moves from the compressor on the low capacity side to the compressor on the high capacity side via the oil equalizing pipe. Therefore, it is possible to prevent an insufficient oil amount after a long-time continuous operation because the oil return amount is smaller than the oil discharge amount of the high-capacity compressor.

Further, since the shortage of the oil amount of each compressor is detected from the oil level, variations in the oil discharge amount and the oil return amount of the compressor due to the difference in the operating conditions, and in the shell of the compressor, The two-way valve can be accurately controlled without being affected by variations in the pressure distribution. Therefore, the closing of the two-way valve is too late,
Alternatively, the opening of the two-way valve after closing is too early, the oil amount of the compressor on the high-capacity side is insufficient, and the opening after closing of the two-way valve is early, or after the closing of the two-way valve. Insufficient oil amount of the compressor on the low capacity side due to the opening being too slow can be prevented. Thus, each compressor can be maintained at an appropriate oil amount.

[Brief description of the drawings]

FIG. 1 is a refrigeration cycle diagram of an air conditioner according to Embodiment 1 of the present invention.

FIG. 2 is a refrigeration cycle diagram of an air conditioner according to Embodiment 2 of the present invention.

FIG. 3 is a flowchart illustrating a method for controlling a two-way valve of an air conditioner according to a second embodiment of the present invention.

FIG. 4 is a refrigeration cycle diagram of an air conditioner according to a third embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method for controlling a two-way valve of an air conditioner according to a third embodiment of the present invention.

FIG. 6 is a refrigeration cycle diagram of an air conditioner according to a fourth embodiment of the present invention.

FIG. 7 is a flowchart illustrating a method for controlling a two-way valve of an air conditioner according to a fourth embodiment of the present invention.

FIG. 8 is a refrigeration cycle diagram of a conventional air conditioner.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 outdoor unit 2 compressor 3 four-way valve 4 outdoor heat exchanger 5 outdoor expansion valve 6 outdoor unit 7 indoor expansion valve 8 indoor heat exchanger 9 intake gas pipe 10 intake gas branch pipe 11 oil equalizing pipe 12 equalizing oil pipe connection Piping 13 Communication pipe 14 Two-way valve 15 Two-way valve control means 16 Differential pressure detection device 17 Two-way valve control means 18 Oil level detection device 19 Two-way valve control means 20 Accumulator

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michimi Kusaka 4-5-2-5 Takaidahondori, Higashiosaka-shi, Osaka Matsushita Refrigeration Co., Ltd.

Claims (4)

[Claims] 1. An outdoor unit comprising a plurality of low-pressure shell compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator, and an indoor unit comprising an indoor expansion valve and an indoor heat exchanger. Are connected to each other to form an annular refrigerant circuit, an oil equalizing pipe connection pipe is provided near the standard oil level of the shell of each of the compressors, and an oil equalizing pipe communicating one end of each of the oil equalizing pipe connecting pipes; and the accumulator. An air conditioner, comprising: a communication pipe that communicates an upper portion of the inside with the oil equalizing pipe, wherein a pressure of the oil equalizing pipe is higher than a pressure of a shell of each compressor. 2. An outdoor unit comprising a plurality of low-pressure shell-type compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator, and an indoor unit comprising an indoor expansion valve and an indoor heat exchanger. Are connected to each other to form an annular refrigerant circuit, an oil equalizing pipe connection pipe is provided near the standard oil level of the shell of each of the compressors, and an oil equalizing pipe communicating one end of each of the oil equalizing pipe connecting pipes; and the accumulator. A communication pipe that communicates the upper part of the inside with the oil equalizing pipe, a two-way valve provided in the communication pipe, and a cooling or heating continuous operation time that is equal to or longer than a predetermined time, the two-way valve for a predetermined time. An air conditioner comprising a two-way valve control means for closing the oil pressure equalizing pipe when the two-way valve is closed. 3. An outdoor unit comprising a plurality of low-pressure shell compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator, and an indoor unit comprising an indoor expansion valve and an indoor heat exchanger. Are connected to each other to form an annular refrigerant circuit, an oil equalizing pipe connection pipe is provided near the standard oil level of the shell of each of the compressors, and an oil equalizing pipe communicating one end of each of the oil equalizing pipe connecting pipes; and the accumulator. A communication pipe that communicates the upper part of the inside and the oil equalizing pipe, a two-way valve provided in the communication pipe, and a differential pressure detecting device that detects a differential pressure between a shell upper part and a shell lower part of each of the compressors. When the differential pressure between the shell upper part and the shell lower part detected by the differential pressure detecting device of one of the compressors becomes less than a predetermined lower limit differential pressure, the two-way valve is closed, and then the differential pressure of all the compressors is reduced. Upper and lower shells detected by the pressure detector A two-way valve control means for opening the two-way valve when the differential pressure is equal to or higher than a predetermined standard differential pressure, and when the two-way valve is closed, the pressure of the oil equalizing pipe is determined by the pressure of the shell of each of the compressors. Air conditioner to raise. 4. An outdoor unit comprising a plurality of low-pressure shell compressors, a four-way valve, an outdoor heat exchanger, an outdoor expansion valve, and an accumulator, and an indoor unit comprising an indoor expansion valve and an indoor heat exchanger. Are connected to each other to form an annular refrigerant circuit, an oil equalizing pipe connection pipe is provided near the standard oil level of the shell of each of the compressors, and an oil equalizing pipe communicating one end of each of the oil equalizing pipe connecting pipes; and the accumulator. A communication pipe that communicates the upper part of the inside with the oil equalizing pipe, a two-way valve provided in the communication pipe, and an oil level detector that detects an oil level of each of the compressors; When the oil level detected by the oil level detector of each of the compressors is less than a predetermined lower limit oil level, the two-way valve is closed, and then the oil level of all the compressors When the oil level detected by the sensor is equal to or higher than a predetermined oil level, the two-way valve is turned off. An air conditioner comprising a two-way valve control means that opens, wherein when the two-way valve is closed, the pressure in the oil equalizing pipe is higher than the pressure in the shells of the compressors.