JPS6346274B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention maintains the oil level of the compressor at an appropriate level whether the compressors connected in parallel are operating in parallel or any compressor is operating independently. This invention relates to a parallel compression device.

Figure 1 shows the structure of a conventional parallel compressor. In the figure, 1 and 2 are parallel hermetic compressors;
a, 2a are the crankcases of this compressor, 1b,
Reference numeral 2b denotes a partition wall, which divides the inside of the compressor into motor chambers 1c, 2c and compression element chambers 1d, 2d. 1e and 2e are the motors housed in the motor chambers 1c and 2c, and 1f and 2f are the compression element chambers 1.
This is a compression element housed in d and 2d. 1g, 2
g represents the motors 1e, 2e and compression elements 1f, 2f.
The crankshafts 1h and 2h are connected to the above partition wall 1.
The pressure equalizing differential pressure valve is provided at the upper part of the motor chambers 1c and 2b, and is closed when the pressure in the motor chambers 1c and 2c becomes significantly lower than the pressure in the compression element chambers 1d and 2d, such as during startup. 1i, 2i are check valves for oil equalization, which connect the motor chambers 1c, 2c to the compression element chambers 1d,
This allows oil to flow into 2d. 8 is an accumulator, one of its piping is connected to the suction pipes 3 and 4 of the compressors 1 and 2, and the other one is connected to an evaporator (not shown). 9 is a pressure equalizing pipe, and 10 is an oil equalizing pipe, and these pipes are always in a state of communication during operation, regardless of parallel operation or individual operation. Also 1
j and 2j are respective discharge pipes of the compressors 1 and 2, and these are connected to a condenser (not shown) via a common discharge pipe 12.

A conventional parallel compression device is configured as described above, and during partial operation, the pressure of the suction pipe is transferred to the compression element chamber of the operating compressor through the suction pipe, motor chamber, compression element chamber, and pressure equalization pipe of the compressor on the stop side. As a result, the pressure in the motor chamber becomes extremely low compared to the pressure in the compression element chamber, and the oil that returned to the motor chamber along with the suction gas cannot be returned to the compression element chamber. It was difficult to maintain the oil level, and there was a risk of seizure and abrasion due to insufficient supply of lubricating oil to the compressor sliding parts, reduction in capacity due to excessive oil flow, and damage to valve parts due to oil compression. Another method is to install an oil separator on the discharge side to separate the oil contained in the discharged gas and return it to the compressor in order to prevent excessive oil flow during partial operation. In this case, high-temperature oil returns to the crankcase of the compressor, raising the oil temperature, and when restarting after a long shutdown, condensed liquid refrigerant is returned to the cooler crankcase, causing the oil to bubble and lubricate. There was a risk of defects occurring.

This invention was made to solve the above problems, and it separates the oil from the gas taken into the compressor and returns only the gas to the motor room to cool the motor. The object of the present invention is to obtain a parallel compression device that can reliably return the compressor to the compression element chamber of the compressor, and one embodiment of the present invention will be described below with reference to FIG. In FIG. 2, parts corresponding to the conventional apparatus shown in FIG. 1 are designated by the same reference numerals and will be explained. In the figure,
1 and 2 are semi-hermetic compressors, 1a and 2a are crankcases of this compressor, and inside this are partition walls 1b,
2b provides motor chambers 1c, 2c and compression element chamber 1.
It is divided into d and 2d. 1e, 2e, 1f,
2f is a motor and a compression element housed in a motor chamber and a compression element chamber, respectively. 1g and 2g are crankshafts connecting both elements, 1h and 2h are partition walls 1b and 2
A pressure equalizing differential pressure valve installed at the upper part of the motor chamber 1c and 2c adjusts the pressure of the motor chambers 1c and 2c to the compression element chamber 1 at the time of startup.
It closes when the pressure becomes significantly lower than d and 2d. 1i, 2i are check valves for oil equalization, which connect the motor chambers 1c, 2c to the compression element chambers 1d,
This allows oil to flow into 2d.

The suction pipes 3 and 4 of the compressors 1 and 2 configured in this way are connected to the upper part of the suction header 5, with the suction pipe 3 being connected to the downstream side and the suction pipe 4 being connected to the upstream side with respect to the gas flow direction. There is. Reference numerals 6 and 7 indicate oil return pipes that communicate the lower opening of the suction header 5 with the compression element chambers 1d and 2d of the respective compressors 1 and 2, and the oil return pipe 6 for the first compressor 1 is connected to the flow of gas. upstream side, second
An oil return pipe 7 for the compressor 2 is connected to the downstream side of the gas flow. 8 is an accumulator, one end is connected to the suction header 5, and the other end is connected to the evaporator (not shown)
It is connected to the. 9 is a pressure equalizing pipe, 10 is an oil equalizing pipe,
1j and 2j are discharge pipes of each compressor, which are connected to a common discharge pipe 12 and also to a condenser (not shown).

Next, the operation will be explained. When both compressors 1 and 2 are in operation, the refrigerant evaporated in the evaporator (not shown) flows into the accumulator 8 as refrigerant gas and 0.5 to 1% oil. Unevaporated liquid refrigerant may be mixed into this inflow gas when there is a load change. The gas-liquid refrigerant separated into gas and liquid by the accumulator 8 is sucked into the U-shaped tube 81, and the oil-liquid refrigerant is sucked in little by little through a small hole at the lower end of the U-shaped tube and flows into the suction header 5. The gas flowing into the suction header 5 is separated into gas and liquid because the gas flow rate decreases, and the gas is sucked into each compressor 1 and 2 from the upper part of the header 5, and the oil accumulates in the lower part of the header 5.
When the suction gas flows into the suction pipes 3 and 4 between this header 5 and each compression element chamber 1d, 2d, a
Since a pressure difference on the order of mmAg is generated, oil flows into the compression element chambers 1d and 2d of each compressor 1 and 2 due to this pressure difference and gravity, helping to ensure smooth operation. In this case, since the first compressor 1 is connected from the downstream side of the suction header 5 and the second compressor 2 is connected from the upstream side, the pressures in both compression element chambers 1d and 2d are slightly lower on the 1d side. On the other hand, since the oil return pipe of the second compressor 2 is connected from the upstream side of the suction header 5, the amount of oil returned is large. The excess oil returned to the second compressor 2 is automatically supplied to the compression element chamber 1d of the first compressor 1, which has a lower pressure.

Next, in the case of partial operation, the case where the first compressor 1 stops will be explained first. First compressor 1
is stopped, so the suction header 5 and the compression element chamber 1
No pressure difference occurs between d. On the other hand, since the second compressor 2 is being operated, due to the pressure difference between the suction header 5 and the compression element chamber 2d and gravity, the oil accumulated in the lower part of the suction header 5 is compressed on the driving side where there is a pressure difference. It flows into the compression element chamber 2d of the machine 2.

Next, when the second compressor 2 stops, as in the previous case, the compression element chamber 1 of the operating compressor 1
Due to the pressure difference between d and the suction header 5 and gravity,
The oil accumulated in the lower part of the suction header 5 is returned to the compression element chamber 1d. Furthermore, the oil flowing into the oil return pipe 7 of the second compressor 2 connected to the upstream side of the suction header 5 flows into the compression element chamber 2d due to the influence of gravity.
The pressure difference between the first compression element chamber 1d and the second compression element chamber 2d (during partial operation, the equalizing pressure differential pressure valve 1 is applied from the compression element chamber 1d of the first compressor 1 to the motor chamber 1c
Due to the pressure difference caused by the gas flowing through the
is supplied to the compression element chamber 1d of the compressor 1.

As described above, according to the present invention, oil is separated from the gas taken into the compressor, only the gas is returned to the motor chamber, where it is used for cooling the motor, and the oil is separated, allowing the compressor to be operated. Since the high pressure side and low pressure side are not connected like in conventional oil separators, there is no possibility of abnormalities in oil return due to failure of the oil separator float or needle valve. This enables stable operation without causing any problems.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional parallel compression device;
The figure is a configuration diagram showing an embodiment of the present invention. In the figure, 1 and 2 are compressors, 1c and 2c are motor chambers, 1d and 2d are compression element chambers, 3 and 4 are gas suction pipes, 5 is a suction header, 6 and 7 are oil return pipes, 8 is an accumulator, and 9 1 is a pressure equalizing pipe, and 10 is an oil equalizing pipe.

Claims (1)

[Claims] 1 In a system in which multiple compressors are connected in parallel and equipped with pressure equalization pipes and oil equalization pipes connecting these compressors, and capacity is controlled by stopping a specified compressor, there is no connection between the evaporator and the compressor. A parallel compression device characterized in that a suction header is provided, an oil return pipe is provided from the suction header to each compressor, and the oil return pipes are connected to the upstream side of the gas suction pipe in order of decreasing resistance.