JPS6151156B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is designed to maintain 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. The present invention relates to a parallel compression type refrigeration system. In a conventional parallel compression type refrigeration system using two compressors, a pressure-equalizing and oil-equalizing piping is installed between both compressors, and these pipings are always in communication during operation, regardless of parallel operation or individual operation. I was driving in this condition. As a result, in a semi-hermetic refrigerator that is divided into a suction chamber element and a compression chamber element, during individual operation, compressor air is passed through the suction pipe, motor room, compression element chamber, and pressure equalization pipe of the stopped compressor. As pressure builds up in the compression element chamber of the machine, the oil equalizing check valve of the operating compressor closes, allowing the oil that has returned to the suction chamber to return to the compression element chamber, maintaining the oil level in the compression chamber at a normal level. It is difficult to do so, and there is a risk of seizure due to insufficient supply of lubricating oil to the sliding parts of the compressor, reduction of refrigeration capacity due to excessive oil flow from the compressor during operation, and damage to valve parts due to oil compression. It was hot. In addition, in order to prevent excessive oil rise during partial operation, there is a method of installing an oil separator on the discharge side of the compressor to separate the oil contained in the discharged gas and return it directly to the compressor. The oil returns to the crankcase and raises the oil temperature, and when restarting after a long stop, the liquid refrigerant that has condensed in the separator, where the temperature is low, is returned to the compressor, causing oil to bubble and cause lubrication failure. There was a risk that this could occur. In addition, due to slight differences in compressor capacity and suction piping resistance, differential pressure occurs in the compression element chambers of both compressors, which tends to cause the oil level of the compressor to become unbalanced during operation. There were drawbacks such as difficulty in checking the oil level position through the oil window and maintenance work. This invention has been made to eliminate the above-mentioned drawbacks, and one embodiment of the invention will be described below with reference to the drawings. That is, in the figure, 1 and 2 are first and second semi-hermetic compressors, 1a and 2a are crankcases of these compressors 1 and 2, and motor chambers 1c and 2c are connected to each other by partition walls 1b and 2b. and compression element chambers 1d and 2d. 1
e, 2e, 1f, 2f are motor chambers 1c, 2, respectively.
c, a motor and a compression element housed in compression element chambers 1d and 2d. 1g and 2g are both elements 1e and 2
Crankshaft connecting e, 1f, 2f, 1h, 2
h is a pressure equalizing differential pressure valve provided at the upper part of the partition walls 1b, 2b, and is closed when the pressure in the motor chambers 1c, 2c becomes significantly lower than the pressure in the compression element chambers 1d, 2d, such as during startup. .

1i and 2i are check valves for oil equalization provided at the bottom of the partition walls 1b and 2b, and the oil sump 1 at the bottom of the motor chambers 1c and 2c
From j, 2j to compression chamber 1d, oil sump 1k at the bottom of 2d,
This allows oil to flow only into 2k.

Reference numeral 3 denotes a pressure equalizing oil pipe that communicates the compression element chambers 1d and 2d of both compressors 1 and 2, and 4 is provided in this pressure equalizing oil pipe 3 to connect the compression element chamber 1d of the first compressor 1 to the second compressor element chamber 1d. This is to block the flow of gas to the compression element chamber 2d of the compressor 2. 5 is a suction pipe of a refrigeration cycle connected to an evaporator (not shown) via a well-known accumulator 9; 6 is a suction pipe connecting the upper part of this suction pipe 5 and the motor chamber 1c of the first compressor 1; 1 is a suction branch pipe of the compressor 1; 7 is a suction branch pipe of the second compressor 2 that connects the lower part of the suction pipe 5 and the motor chamber 2c of the second compressor 2; The pressure loss from the inlet to the motor chamber 1c, 2c inlet of both compressors 1, 2 (pressure loss in the suction branch pipe 6 of the first compressor 1) ≧ (pressure in the suction branch pipe 7 of the second compressor 2) (Loss). In addition, the suction branch pipes 6 and 7 are branched from the upper and lower parts of the suction pipe 5 as described above, thereby separating the refrigerant gas flowing through the suction pipe 5 into lubricating oil and gas.
It consists of Reference numeral 8 denotes a common discharge pipe for both compressors 1 and 2, which is connected to a condenser via an oil separator 10 and an evaporator (not shown) via an expansion valve (not shown).

The oil separator 10 is provided with a float 10a that detects the oil level and a needle valve 10b that opens and closes according to the movement of the float 10a, and the return oil is connected to the suction-side accumulator 9 through an oil return pipe 11. .

Next, the operation will be explained. When both compressors 1 and 2 are in operation, the first compressor 1
The relationship between the operating pressure of the second compressor 2 and the operating pressure of the second compressor 2 is (motor chamber 2c pressure of the second compressor 2) - (first compressor 1
motor chamber 1c pressure) = approximately 100 to 400 mmAq. Further, normally, oil containing about 0.5% of the refrigerant circulation amount returns to the compressors 1 and 2 together with the refrigerant gas that has evaporated inside the suction pipe 5 of the refrigerant cycle. At this time, the refrigerant gas is separated into lubricating oil and gas by the separation means 5a, and most of this oil flows into the suction branch pipe 7 of the second compressor 2 under the influence of gravity, and the second
It passes through the motor chamber 2c of the compressor 2 and the oil equalizing check valve 2i, and is supplied to the compression element chamber 2d. The oil is supplied to the compression element chambers 1d and 2d of both compressors 1 and 2 through pressure equalizing oil pipes 3.
Since there is a pressure difference between the motor chambers 1c and 2c of both compressors 1 and 2 as described above, the pressure of the first compressor 1 is Since it flows together with the gas that has flowed into the compression element chamber 1d, it is supplied to the compression element chamber 1d of the first compressor 1 through the pressure equalization pipe 3 and the check valve 4, and can perform its lubrication function normally.

Next, when only the first compressor 1 is operated, the refrigerant gas flows from the suction pipe 5 into the motor chamber 1c through the suction branch pipe 6 of the first compressor 1. During this time, the pressure will drop by approximately 600mmAq due to pressure loss in the piping. In addition, the pressure in the compression element chamber 1d is also equalized by the differential pressure valve 1.
It decreases due to the action of b. On the other hand, oil is supplied from suction pipe 5.
Suction branch pipe 7 of second compressor 2, motor chamber 2c,
The oil flows into the compression element chamber 2d via the oil equalizing check valve 2i, but since the second compressor 2 is not operating, the pressure loss in the suction branch pipe 7 is extremely small. The pressure P ₁ d in the chamber 1 d and the pressure P ₂ d ⁴ in the compression element chamber 2 d of the second compressor 2 become P ₁ d < P ₂ d, and the oil accumulated in the compression element chamber 2 d of the second compressor 2 A part of the compressor is supplied to the compression element chamber 1d of the first compressor 1 due to the pressure difference, allowing normal operation to continue.

Next, when only the second compressor 2 is operated, the refrigerant gas and oil flow from the suction pipe 5 into the motor chamber 2c via the suction branch pipe 7 of the second compressor 2. During this time, the pressure in the motor chamber 2c of the second compressor 2 decreases by about 600 mmAg due to pressure loss in the piping.
On the other hand, if there is no check valve 4 in the pressure equalization pipe 3, the suction branch pipe 6 of the stopped first compressor 1 is connected to the motor chamber 1c of the first compressor 1, the oil equalization check valve 1i, and the compressor. Gas flows into the compression element chamber 2d of the second compressor 2 in operation through the element chamber 1d and the oil equalization pipe 3, increases the pressure, and closes the oil equalization check valve 2i of the second compressor 2. Therefore, it was impossible to move the oil that had returned to the motor chamber 2c to the compression element chamber 2d, and there was a possibility that lubrication failure would occur due to lack of oil in a short period of time. Since the working check valve 4 is provided in the oil equalizing pipe 3, gas is prevented from flowing from the first compressor 1 to the compression element chamber 2d of the second compressor 2, and the pressure in the compression element chamber 2d is equalized. The pressure is maintained at approximately the same level as the motor chamber 2c by the action of the pressure differential valve 2h. Therefore, it is possible to send the oil returned to the motor chamber 2c to the compression element chamber 2d, and even if the second compressor 2 is operated continuously, the oil level can be kept relatively stable. .

However, when both compressors 1 and 2 are operating, due to the difference in suction resistance between the suction pipes 6 and 7 of both compressors 1 and 2, and when only the first compressor 1 is operating, the The pressure of the suction pipe 5 is applied to the compression element chamber 1d of the first compressor 1 through the suction pipe 7 of the second compressor 2, and the pressure is applied to the compression element chamber 1d of the first compressor 1 and the motor chamber 1c. A larger pressure difference than usual occurs before and after the oil equalizing check valve 1h, and more lubricating oil droplets in the compression element chamber 1d flow into the motor chamber 1c, where the pressure is lower, and the compression element along with the suction gas. There is a tendency for the oil to be sucked in and discharged together with the gas into the discharge pipe 8, increasing the amount of oil coming up. This increase in oil flow increases the oil content in the refrigerant during the refrigerant cycle, increases the amount of oil accumulated in the suction pipe 5, and has a large effect on fluctuations in the compressor oil level due to load fluctuations. In refrigerant equipment with large load fluctuations such as cooling equipment, the oil level fluctuates widely, which poses a serious problem in operation, but in this invention, an oil separator 10 is installed in the discharge pipes 8 of the compressors 1 and 2. By separating and returning excess oil under the above conditions, the compressors 1 and 2 can be operated with a stable oil level at all times. Generally, this oil return pipe 11 is normally returned to the compression element chambers 1d and 2d of the crankcases of the compressors 1 and 2, but under the above conditions, the oil return pipe 11 is Under conditions where the amount of oil is larger than the amount of oil, the amount of high-temperature oil returned is large, causing the oil temperature of compressors 1 and 2 to rise, which poses a major problem in the operation of compressors 1 and 2. However, in the present invention, the suction gas is returned to the suction side. and cooled to almost the same temperature as the intake gas,
Since the oil is returned to the compressor, it always maintains a stable oil temperature and provides sufficient lubrication even under the above conditions.
It is possible to ensure reliability. Furthermore, as shown in the figure, if the return pipe 11 of the oil separator 10 is connected to the accumulator 9, the condensed liquid refrigerant will be returned to the cooled oil separator 10 in the event of a restart after a long-term shutdown. Even if something happens, the liquid refrigerant returns to the accumulator 9, so it is safe.

As described above, according to the present invention, while actively returning oil in the refrigeration cycle to one compressor, both compressors can perform full operation and either compressor can perform partial operation under all conditions. It is possible to maintain an appropriate oil level in the compressor, and it is possible to prevent seizure of sliding parts, reduction in refrigeration capacity due to excessive oil volume, and damage to valve parts as in the past.
Further, since the lubricating oil from the oil separator is cooled in the suction pipe and then returned to the compressor, a sufficient lubricating effect can be exerted.

[Brief explanation of the drawing]

The figure is a piping diagram showing an embodiment of the present invention. In the figure, 1 and 2 are the first and second semi-hermetic compressors, 1c and 2c are motor chambers, 1d and 2d compression element chambers, 3 is pressure equalization oil piping, 4 is a check valve, and 5 is suction pipe, 5a is separation means, 6 and 7 are suction branch pipes, 10
is an oil separator.

Claims (1)

[Claims] 1. A pressure equalizing hole at a predetermined position of a partition wall that divides the inside of the crankcase into a motor chamber side and a compression element chamber side, and an oil equalizing check valve that allows oil flow only from the motor chamber side to the compression element chamber side. In a system in which the first and second compressors are connected in parallel with each other via piping, a separating means is provided at the end of the suction pipe of the refrigeration cycle to separate the refrigerant gas flowing through the suction pipe into lubricating oil and gas; A first piping device that supplies a portion of the gas to the first compressor, a second piping device that supplies the remaining separated gas and lubricating oil to the second compressor, and both compressors. A valve provided in a pressure equalizing oil piping communicating between the compression element chambers and allowing flow only from the second compressor to the first compressor, and an oil provided in the discharge piping of both compressors. A parallel compression type refrigeration system comprising a separator and an oil return pipe that sends the lubricating oil separated by the oil separator to the suction pipe.