JPS6151155B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control method for a refrigeration system that operates multiple compressors in parallel, and is particularly suitable for equalizing lubricating oil held by each compressor. be.

A cycle diagram of a conventional refrigeration system will be explained with reference to FIG. The refrigerant discharged by the compressors 1a and 1b passes through the discharge gas pipe 8, is condensed and liquefied in the condenser 2, passes through the expansion valve 3, is evaporated in the evaporator 4, and passes through the suction gas pipe 7 and returns to the compressor 1a. , 1b, the oil equalizing pipe 5 and the pressure equalizing pipe 6 connect the crankcases of the two compressors to equalize the pressure in the crankcases and equalize the oil amount.

However, it is extremely difficult to perfectly balance this crankcase internal pressure, and
Balance below Aq is difficult to achieve even with large diameter pressure equalizing pipes.

The causes of this unbalance in the internal pressure of the crankcase include variations in the performance of each compressor and differences in the resistance of the suction piping and suction gas strainer, but it is extremely difficult to completely eliminate these causes.

In particular, when compressors of different capacities are combined, this pressure difference becomes larger.

The inside of the compressor crankcase is agitated and some oil exists in a mist state, so if there is a difference in the crankcase internal pressure, it will flow together with the gas refrigerant to the lower pressure crankcase through the oil equalization pipe or pressure equalization pipe. ,
This mist of oil also moves, and as a result, the high-pressure crankcase runs out of oil in a short period of time, creating a risk of accidents such as seizure of bearing metal.

The present invention has been made based on the above-mentioned matters, and is aimed at equalizing the oil in each compressor without equalizing the pressure in the crankcase.

The present invention is characterized by increasing the resistance of the oil equalizing pipe so that the oil does not move more than necessary even if there is a differential pressure in the crankcase.
Furthermore, the operation control circuit is configured to stop one compressor and increase the differential pressure to the opposite compressor to move oil when the oil amount becomes unbalanced.

An embodiment of the present invention will be described in detail below with reference to FIG. The oil equalizing pipe 10 connecting the crankcases of each compressor 1a, 1b is composed of a thin pipe, and its connection port is located at a position slightly higher than the proper oil level of the compressor.

Conventional oil equalizing pipes were constructed with pipes of as large a diameter as possible in order to reduce resistance as much as possible, but as a result, when a differential pressure of several tens of mmAq was created in the crankcase, the gas refrigerant flowed 2 to 4 m inside the oil equalizing pipe. /s
It flows at a relatively fast speed, and the mist of oil moves along with it.

For this reason, even if the outlet of the oil equalizing pipe was formed at a high position, there was a problem that the oil level would drop to a considerably lower position than the oil equalizing pipe. If the diameter and length of the oil equalizing pipe are determined so that the oil pressure is 1 m/s or less, and the resistance is increased, the mist-like oil will not be drawn in with the gas, so there will be no oil level below the installation position of the oil equalizing pipe. does not decrease.

However, if there is a large difference in the amount of oil in each compressor, the above method alone may not be sufficient.

FIG. 3 shows an embodiment of a compressor operation control system that takes such a case into consideration.

The contacts 23b and 24b of the timer 23 and 24 for time-limited operation and time-limited return are set to repeat the operation of closing for 60 minutes and opening for 1 minute, for example, and the operations of the two timers are set to be delayed for example by 30 minutes. This causes each compressor to alternately and periodically stop operating for short periods of time.

When one compressor stops operating, the differential pressure in the crankcase becomes extremely large, ranging from 100 mmAq to several
Since there is a pressure difference of 100mmAq, oil moves easily even through the small diameter oil equalizing pipe mentioned above. If the oil level of the compressor that has stopped operation is higher than the oil leveling pipe connection port, the oil up to that position will move to one compressor through the oil leveling pipe.

If the oil level of the compressor that has stopped operation is lower than the oil leveling pipe connection port, there is no mist-like oil in this compressor, so oil does not move, and only gas refrigerant flows in the oil leveling pipe. . (That is, no more oil is moved than necessary.) Then, after a certain period of time, another compressor shuts down and there is a similar oil movement.

Since each compressor replenishes oil alternately in this way, a constant amount of oil can always be ensured even if either compressor runs out of oil.

As explained above, according to the present invention, the resistance of the oil equalizing pipe is increased, so even if the differential pressure in the crankcase becomes large, the oil does not move more than necessary, and the oil is periodically alternately moved to one side. Since the compressors are stopped, each compressor replenishes oil with each other, so a constant amount of oil can always be secured.

[Brief explanation of the drawing]

Fig. 1 is a cycle system diagram of a conventional refrigeration system, Fig. 2 is a partial diagram showing an example of the installation state of an oil equalizing pipe of the refrigeration system of the present invention, and Fig. 3 is a diagram of the control circuit of the refrigeration system of the present invention. It is a partial diagram. 1a, 1b...compressor, 2...condenser, 3...expansion valve, 4...evaporator, 10...oil equalizing pipe.

Claims (1)

[Claims] 1 Connect multiple compressors in parallel, connect the condenser, expansion valve, and evaporator in sequence to form a refrigerant circuit, connect the crankcases of each compressor with oil equalizing pipes, and connect the oil equalizing pipes to the crankcases of each compressor. , the pipe diameter is such that the gas flow velocity between the crankcases of each compressor is 1 m/s or less due to the differential pressure between the crankcases that occurs in each compressor during normal operation, and each compressor is alternately shortened at regular intervals. A refrigeration device characterized by stopping operation for a certain period of time.