JPS6336433B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a parallel compression system that maintains the oil level of a compressor at an appropriate level in either the parallel operation of compressors connected in parallel or the independent operation of any compressor. This relates to a type refrigeration system. [Prior art] In a conventional parallel compression type refrigeration system using three compressors, pressure equalizing oil piping is installed between both compressors, and these pipings are always in communication regardless of whether they are operated in parallel or individually. I was driving in this condition. As a result, in a semi-hermetic compressor that is divided into the motor room side to which the suction branch pipe is connected and the compression element side, the suction pipe of the compressor that stopped during capacity control operation, the motor room side,
By connecting the compression element chamber and the pressure equalization pipe, pressure is applied to the compression element chamber of the operating compressor, and the pressure equalization/oil equalization check valve of the operating compressor closes, causing the pressure of the operating compressor to close. The oil that has returned to the motor room does not return to the compression element chamber, making it difficult to maintain the oil level in the compression element chamber at a normal level. There was a risk that the refrigeration capacity would decrease due to excessive oil coming up from the machine, and that the valves would be damaged due to oil compression. In addition, slight differences in compressor capacity,
Due to the difference in the resistance of the suction piping, a pressure difference occurs in the compression element chamber of each compressor, which tends to cause the oil level of the compressor to become unbalanced during operation, so it is necessary to confirm the oil level position from the oil window during maintenance. There were drawbacks such as difficult maintenance work. [Summary of the Invention] This invention provides a pressure equalizing hole at a predetermined position in a partition wall that divides the inside of the crankcase into a motor chamber side and a compression element chamber side, and allows oil to flow only from the motor chamber to the compression element chamber side. In one in which first to third compressors each having a pressure equalizing check valve are connected in parallel to each other,
An oil separation means is provided in the suction system of each compressor, and each suction branch pipe is provided to connect the suction system with each suction chamber of each compressor, and the suction branch pipe of the first compressor is connected to the suction branch pipe of the first compressor. The oil separating means and each of the suction branch pipes are arranged so that the gas and separated oil from the oil separation device are sucked through the suction line, and only gas is sucked into the suction branch pipes of the second and third compressors. The oil reservoirs of the first compressor and the second compressor and the oil reservoirs of the first compressor and the third compressor are connected to each other by pressure equalizing oil pipes, and the oil reservoirs of the first compressor and the second compressor are connected to each other by pressure equalizing oil pipes, A valve is provided in the pressure equalization pipe to block the flow of gas from the second compressor to the first compressor and the flow of gas from the third compressor to the first compressor, and It is an attempt to eliminate defects. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the figure, 1, 2, and 3 are the first, second, and third
The semi-hermetic compressor 11, 21, 31 is the crank case of the compressor 1, 2, 3, and the motor chamber 14, 24, 3 is separated by the partition wall 12, 22,
4. Compartmented into compression element chambers 13, 23, and 33. 15, 25, 35, and 16, 26, 3
Reference numeral 6 denotes a motor and a compression element housed in each motor chamber and compression element chamber. 17, 27, 37
are pressure equalizing holes provided above the partition walls 12, 22, and 32, and reference numbers 18, 28, and 38 are check valves for oil equalization provided at the bottom of the partition walls, and only allow oil to flow from the motor chamber side to the compression element chamber side. This allows for 4 are compression element chambers 13 and 23 of the first compressor 1 and the second compressor 2;
A pressure equalizing oil pipe 5 communicating with the pressure equalizing oil pipe 4 is provided with a check valve 6 that allows gas and oil to flow only from the first compressor 1 to the second compressor 2 side.
7 is a pressure equalizing oil pipe that communicates the compression element chambers 13 and 33 of the first compressor 1 and the third compressor 3; 8 is a suction line for each compressor 1 to 3 in the refrigeration cycle (not shown); 9 is a suction branch of this suction line 8; Low-pressure side oil separator installed at the pipe connection port,
10 is a suction branch pipe that communicates the lower part of the oil separator 9 with the motor chamber 14 of the first compressor 1, and supplies the separated oil and gas to the first compressor 1. 41 is a suction branch pipe of the second compressor 2 connected to the upper part of the oil separation device 9, and 42 is a suction branch pipe to the third compressor 3. 44 is a discharge pipe common to the first, second, and third compressors 1 to 3, and 45 is an outlet pipe of a high-pressure side oil separation device, which will be described later.This pipe 45 connects to a condenser (not shown) in the refrigeration cycle. It is connected. 46 is a high pressure side oil separation device provided in the discharge pipe 44;
47 is an oil return pipe that communicates this oil separation device 46 with the compression element chamber 11 of the first compressor 1. Next, the operation will be explained. All compressors 1,
When 2 and 3 are operating, the normal refrigerant circulation amount is 0.5w
The oil contained in the refrigerant cycle returns to the oil separator 9 together with the refrigerant gas that evaporated inside the suction pipe 8 of the refrigerant cycle. Here, part of the separated oil and gas is supplied to the motor chamber 14 of the first compressor 1 through the suction branch pipe 10, and the oil is supplied to the compression element chamber 13 through the oil equalizing check valve 18. Ru. Here, the pressure loss in the suction branch pipes of each compressor 1 to 3 is greater than the pressure loss in the branch pipe 10 of the first compressor 1, the suction branch pipe 41 of the second compressor 2, and the suction branch of the third compressor 3. Since the pressure drop of the pipe 42 is large, the pressure in the motor chamber of each compressor 1 to 3 is the motor chamber pressure P _M1 of the first compressor 1, the motor chamber pressure P M2 of the second compressor 2, and the pressure P _M2 of the second compressor 2. If the motor chamber pressure P _M3 of the compressor 3 in No. 3 is reduced, P _M1 > P _M2 and P _M1 > P _M3 . In addition, the pressure in each crank chamber is determined by each pressure equalization hole 1.
7, 27, and 37, the pressure in the compression element chamber of each compressor 1 to 3 is equalized with the motor chamber.
Assuming P _c1 , P _c2 , and P _c3 , P _c1 > P _c2 and P _c1 > P _c3 . Therefore, the excess amount of oil supplied to the compression element chamber of the first compressor 1 is supplied to the second compressor 2 and third compressor 3 through the pressure equalizing oil pipes 4 and 6. Can perform normal lubrication function. In addition, an oil separator 46 provided on the high pressure side discharge pipe
The separated oil is also transferred to the compression element chamber 1 of the first compressor 1.
However, since the above-mentioned pressure relationship holds true, the excess oil is supplied to the second and third compressors 2 and 3, and can perform the lubricating function normally. Next, when the third compressor 3 is stopped by the capacity control signal, gas does not flow through the suction branch pipe 42 of the third compressor 3, so the motor chambers 14, 24, Comparing the pressure of 34, P _M3
＞P _M1 ＞P _M2 . Therefore, when comparing the pressures of this motor chamber and the equalized compression element chamber, P _c3 > P _c1 > P _c2 and if there is no check valve 7, the pressure of P _c3 will be applied to P _c1 , and the first Although the oil that has returned to the motor chamber 14 of the compressor 1 will not return to the compression element chamber 13, according to the present invention, the influence of this pressure is eliminated by the check valve 7, so that normal operation can be achieved. Similarly, the following table summarizes the pressure relationship, check valve movement, and oil flow for all combinations of compressor operation and stop signals caused by the capacity control signal. In addition, the mark ◯ indicates that the compressors 1 to 3 are in operation, and the mark x indicates that the compressors 1 to 3 are stopped.

〔Effect of the invention〕

As explained above, according to the present invention, oil can be normally returned to the compressor in operation in combinations of operation and stop of all compressors based on the capacity control signal. Also, the first compressor has the highest reliability because oil is always returned in all combinations. Therefore, if the first compressor is set to the maximum capacity, even if there is poor oil return due to a defect in the refrigerant circuit, the first compressor will be protected by preferential oil return, so there will be no problem with oil return. Even in this case, the reduction in refrigerating capacity will be minimal. Furthermore, in order to minimize oil leakage into the refrigerant circuit, even when a high-pressure side oil separator 46 is provided, the oil return pipe 47 is returned to the first compression element chamber to prevent oil leakage during operation for the same reason as described above. It is possible to supply oil to each compressor.

[Brief explanation of the drawing]

The figure is a refrigerant piping system diagram showing one embodiment of the present invention. In the figure, 1, 2, and 3 are the first, second, and third semi-hermetic compressors, 8 is the suction line, 10, 41, and 42 are the suction branch pipes to each compressor, and 9 is the low pressure side. , 4 and 6 are pressure equalizing and oil equalizing pipes, 5 and 7 are check valves, and 46 is a high pressure side oil separation device.

Claims (1)

[Claims] 1. A pressure equalizing hole is provided at a predetermined position in a partition wall that divides the inside of the crankcase into a motor chamber side and a compression element chamber side, and an equalizing hole that allows oil to flow only from the motor chamber to the compression element chamber side. In a system in which first to third compressors each having a pressure check valve are connected in parallel, an oil separation means is provided in the suction system of each of the compressors, and an oil separation means is provided between the suction system and each of the compressors. Suction branch pipes connecting the suction chambers are provided, and gas and separated oil from the oil separation device are supplied from the suction system to the suction branch pipe of the first compressor, and separated oil from the oil separation device is supplied to the suction branch pipe of the first compressor. The oil separation means and each of the suction branch pipes are connected to the suction branch pipes so that only gas is sucked into the suction branch pipes, and between the oil reservoirs of the first compressor and the second compressor and between the first compressor and The oil reservoirs of the third compressor are communicated with each other by pressure equalizing oil pipes, and the gas flow from the second compressor to the first compressor and the third A parallel compression type refrigeration system characterized by being provided with a valve that blocks the flow of gas from the first compressor to the first compressor. 2. The parallel compression refrigeration system according to claim 1, wherein the first compressor has a large capacity, and the second and third compressors have small capacities. 3 The pressure loss of the suction branch pipe from the branch point of the suction system line of each compressor to the suction port of each compressor is calculated as follows: (Pressure loss of the suction branch pipe of the first compressor) ≤ (Suction branch of the second compressor) (Pressure loss in the suction branch piping of the first compressor)≦(Pressure loss in the suction branch piping of the third compressor) Or the parallel compression type refrigeration apparatus according to item 2.