JPS58210380A - Parallel compression system refrigerator - Google Patents

Abstract

PURPOSE:To hold always oil surface properly in running a compressor by arranging two compressors in parallel to supply a portion of gas separated by a separator from lubricating oil to one compressor and the remaining gas to the other compressor and providing a check valve in a pressure and oil equalizing pipe for interconnecting both compression element chambers. CONSTITUTION:When compressors 1, 2 are run in parallel, oil separated by a separator 5a enters a compression element chamber 2d and is supplied to a compression element chamber 1d through a pressure and oil equalizing pipe 3 and a check valve 4 because of (pressure in motor chamber 2c)>(pressure in motor chamber 1c). In running only the compressor 1, a portion of oil entering a compression element chamber 2d from a suction pipe 5 is supplied to the compression element chamber 1d by the differential pressure between the compression element chambers 2d, 1d. In running only the compressor 2, gas flow from the compressor 1 to the compression element chamber 2d is blocked by the check valve 4 so that oil returned to the motor chamber 2c cannot be sent to the chamber 2d and oil surface is stabilized.

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 conventional parallel compression type refrigeration equipment using two compressors, pressure equalization and oil piping is installed between the measuring compressors, and these piping 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 independent operation, the suction pipe, motor room, compression element chamber, and pressure equalization pipe of the stopped compressor are passed through the Because pressure is applied to the compression element chamber of the compressor inside, the oil equalizing check valve of the compressor during operation closes, and the oil that has returned to the suction chamber does not return to the compression element chamber.
It is difficult to maintain the oil level in the compression chamber at a normal level, which can cause seizures due to insufficient supply of lubricating oil to the moving parts of the compressor, decrease in refrigeration capacity due to excessive oil flow from the compressor during operation, and oil leakage. There was a risk of damage to the valve part due to compression. 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 condensed in the low-temperature separator is returned to the compressor, causing the 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, a pressure difference occurs in the compression element chamber of a surface compressor, 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 was 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 the first and second semi-hermetic compressors, and (1a) and (2a) are the compressors (1) (
2) crankcase, inside which is the bulkhead (lb) (2).
b), the motor chambers (1c) (2c) and the compression element chamber (l
d) It is sectioned as (2d). (le) (2
e), (If) (2f) are each motor chamber (lc) (2c
), the motor and compression element housed in the compression element chamber (ld) (2d) - (1g82g) are both elements (1eX
2e), (1f
It closes when the pressure in cX2c) becomes significantly lower than the pressure in the compression element chambers (1d) (2d).

(li) (2i) is a check valve for oil equalization installed at the bottom of the partition wall (lb) (2b), which allows the oil to flow from the oil sump (1jX2j) at the bottom of the motor chamber (1c Only 02k)-"s in 1 is allowed to inflow oil. (3) is a pressure equalizing oil pipe that communicates the compression element chambers (ld) (2d') of the surface compressor (1) (2), (4
) is provided in this pressure equalizing oil pipe (3), and the first compressor (
This is a check valve that blocks the flow of gas from the compression element chamber (1d) of 1) to the compression element chamber (2d)-S of the second compressor Q).

(5) is connected to the evaporator (
refrigeration cycle suction pipe connected to (not shown), (6)
is a suction branch pipe of the first compressor (1) that connects the upper part of this suction pipe (5) and the motor chamber (1c) of the first compressor (1), and (7) is a suction pipe (5). and the second compressor (2
) and the second compressor (2) connected to the motor chamber (2c) of
The suction branch pipe (5) connects the surface compressor (
1) The pressure loss to the motor chamber (IC) (2c) inlet of (2) (pressure loss of the suction branch pipe (6) of the first compressor (1)) ≧ (second compressor (2) (pressure loss of the suction branch pipe (7)).

In addition, the suction branch pipes (6) and (7) are connected to the suction pipe (5),
As mentioned above, the suction pipe (
5) It constitutes a separation means (5a) that separates the refrigerant gas flowing therein into lubricating oil and gas. (8) is a surface compressor (
1) The common discharge pipe of (2) is connected to the condenser (A) via the oil separator OQ, and to the evaporator (not shown) via the expansion valve (not shown). The oil separator a0 is equipped with a float (1oa) 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 sent to the suction side through the oil return pipe (b). Connected into the accumulator (9). The oil return pipe (b) is connected to a piping device α trench that injects liquid refrigerant from the condenser μs into the accumulator (9) on the suction side via a valve and expansion device controlled by the temperature of the suction pipe (5). has been done.

Next, the operation will be explained. When the plane compressor CI) (2) is in operation, due to the difference in piping resistance between the suction branch pipes (6) and (7) of the plane compressors (1) and (2), The relationship between the operating pressure of the second compressor (2) is (
Second compressor (2) motor chamber (2c madness) - (first compressor (1) motor chamber (IC) pressure) = approximately 100 to 4
00 mmAq. In addition, oil containing about 0.5% of the refrigerant circulation amount is normally contained in the refrigerant cycle suction pipe (5.
) returns to the compressor (1) and (2) side together with the evaporated refrigerant gas. 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. The oil is supplied to the compression element chamber (2d) through the motor chamber (2c) and oil equalizing check valve (21) of the second compressor (2).

The oil is in the compression element chamber of the surface compressor (1) (2) = (ld)
(2d reproduction: The pressure is equalized by the pressure equalization oil pipe (3), and there is a pressure difference between the motor chambers (lc) and (2c) of the surface compressors (1) and (2) as described above, so the second The pressure equalizing pipe (3) flows together with the gas flowing from the compression element chamber (2d) of the compressor (2) to the compression element chamber (1d) of the first compressor (1).
) and the check valve (4), the compression element chamber (1d) of the first compressor (1) is supplied to the compression element chamber (1d), so that the lubricating function can be performed normally.

Next, when only the first compressor (1) is operated, refrigerant gas flows into the motor chamber (1c) from the suction pipe (5) through the suction branch pipe (6) of the first compressor (1). During this time, the pressure decreases by about 600 rrmAQ due to pressure loss in the piping.

In addition, the pressure in the compression element chamber (1d) is also controlled by the equalization differential pressure valve (1h).
It decreases due to the action of On the other hand, oil is supplied from the suction pipe (5) to the second
Suction branch pipe (7) of compressor (2), motor room (2c)
, flows out of the compression element chamber (2d) through the oil equalizing check valve (21), but since the second compressor (2) is not operating, the pressure loss in the suction branch pipe (7) is extremely small. The pressure Pld in the compression element chamber (1d) of the first compressor (1) and the pressure Pgd in the compression element chamber (2d) of the second compressor (2) are Pld
<P! 6, and the compression element chamber (2) of the second compressor (2)
d) Some of the oil accumulated in the first compressor (1
) is supplied to the compression element chamber (1d), allowing normal operation to continue.

Next, when only the second compressor (2) is operating, the refrigerant gas and oil are passed from the suction pipe (5) to the motor room (2c) through the suction branch pipe (7) of the second compressor (2). During this time, due to pressure loss in the piping, the motor chamber of the second compressor (2) (
The pressure in 2c) decreases by about 400 mnAq. On the other hand, if the pressure equalizing oil pipe (3) does not have a check valve (4), the suction branch pipe (6) of the stopped first compressor (1) is connected to the motor chamber of the first compressor (1). (1c), oil equalizing check valve (li
), the compression element chamber (ld), and the oil equalizing pipe (3), gas flows into the compression element chamber (2) of the second compressor (2) in operation, increasing the pressure and increasing the pressure in the second compressor. (2) Oil equalizing check valve (2
1), it was impossible to move the oil that had returned to the motor chamber (2c) to the compression element chamber (20), and there was a possibility that lubrication failure would occur due to lack of oil in a short period of time. In this invention, a check valve (4) that operates at about 10 ormIAq is provided in the oil equalizing pipe (3), so that there is no flow from the first compressor (1) to the compression element chamber (20) of the second compressor (2). The inflow of gas is blocked, and the pressure in the compression element chamber (2d) is maintained at approximately the same level as the motor chamber (2c) by the action of the equalizing differential pressure valve (2h).Therefore, the oil returned to the motor chamber (2υ) is It becomes possible to feed the oil into the compression element chamber (20), and even if the second compressor (2) is operated continuously, the oil level can be kept relatively stable.

However, when both compressors (1) (2>) are in operation, the first compressor ( 1) is in operation, the pressure in the suction pipe (5) is transferred to the compression element chamber (1d) of the first compressor (1) via the suction pipe (7) of the second compressor (2). ) and a pressure equalizing check valve (1h) between the compression element chamber (1d) and the motor chamber (1c) of the first compressor (1).
A larger pressure difference than usual occurs before and after ), and more lubricating oil droplets in the compression element chamber (1d) flow into the motor chamber (1c), where the pressure is lower, and flow directly into the compression element along with the suction gas. The oil is inhaled and discharged together with the gas into the discharge pipe (8), which tends to increase the amount of oil coming up. This increase in oil flow increases the oil content in the refrigerant during the refrigerant cycle, and the suction pipe (
5) Increase in the amount of oil accumulated in the compressor, and fluctuations in the compressor oil level due to load fluctuations, especially in refrigeration equipment with large load fluctuations such as showcase cooling equipment in food stores, the oil level will fluctuate widely. This is a serious problem in operation, but in this invention, an oil separator 4 is installed in the discharge pipe (8) of the compressor (1) (2) to separate and return excess oil under the above conditions. , the compressor (1) (2
> can drive. Generally, this oil return pipe (b) is returned to the compressor (1) (2) compression element chamber (k) (2d) of the crankcase, but under the above conditions, the oil is returned to the compressor (1) (2). Compressor (1) (2) When the amount of oil coming up is higher than the operating condition, the amount of high temperature return oil is large, the oil temperature of compressor (1) (2) rises, and compressor (1) (2)
) Although this poses a major operational problem, in the present invention, the liquid is mixed with the suction gas by returning it to the suction side, and while the suction gas temperature is being detected, the valve is controlled by the suction gas temperature and the amount of liquid injected refrigerant is determined relative to the total refrigerant circulation amount. The liquid is pumped through an expansion device that is selected so that the ratio of the loss of refrigerating capacity due to the rise in suction gas temperature when oil is returned from the oil separator without the liquid injection piping device (2) is approximately equal. Since the refrigerant is mixed with the suction gas, the suction gas temperature is kept almost constant without loss of refrigeration capacity, and the refrigerant is returned to the compressor at almost the same temperature as the suction gas temperature, so even under the above conditions, the suction gas temperature is kept almost constant. It is possible to maintain a stable oil temperature, provide sufficient lubrication, and ensure reliability. Furthermore, as shown in the figure, if the return pipe Q]) of the oil separator ON is connected to the accumulator (9), in the event of a restart after a long-term shutdown, liquid refrigerant may condense in the cooled oil separator QO. Even if the liquid refrigerant is returned, it is safe because the liquid refrigerant returns to the accumulator (9).

As described above, according to the present invention, while actively returning oil during 9 refrigeration cycles to one compressor, full operation of both compressors, partial operation of both compressors, and all conditions. It is possible to maintain an appropriate oil level in both compressors, and it is possible to prevent seizure of sliding parts, reduction in refrigeration capacity due to excessive oil flow, and damage to valve parts as in the conventional case.

Furthermore, since the lubricating oil from the oil separator is cooled in the suction pipe and then returned to the compressor, it can exert sufficient lubricating action.

[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, (1cX2c) is the motor room, (1dX2d) is the compression element chamber, (3) is the pressure equalization oil piping, and (4) is a check valve, (5)
(5a) is the suction pipe, (5a) is the separation means, (6) (7) is the suction branch pipe, (10 is the oil separator, and (2) is the condenser. Agent: Makoto Kazuno)

Claims (1)

[Claims] A partition wall that divides the inside of the crankcase into the motor chamber side and the compression element chamber side has a pressure equalization hole at a predetermined position and an oil equalization check valve that allows oil to 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 by piping in parallel, a separation 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. and a first piping device that supplies a part of the gas separated by the separation means to the first compressor;
A second piping device that supplies the separated remaining gas and lubricating oil to the second compressor, and a pressure-equalizing oil piping that communicates between the compression element chambers of both compressors; A valve that allows flow only from the second compressor to the first compressor, an oil component installed in the discharge piping of both compressors, and a lubricating oil separated by the oil component It is characterized by the provision of a return pipe that sends oil to the suction pipe. Parallel compression refrigeration equipment.