JPS6143629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for returning oil mixed in refrigerant in a low pressure section to the compressor in a refrigeration system using a positive displacement compressor such as a screw compressor.

Note that in this specification, "oil refrigerant liquid" refers to a refrigerant liquid containing oil.

For example, in a refrigeration system using an oil injection type screw compressor, oil injected into the rotor of the screw compressor is discharged from the compressor together with refrigerant gas and enters an oil separator. Oil is separated in an oil separator, cooled in an oil cooler, and supplied to a compressor for recycling. However, it is impossible to separate 100% of the oil that enters the oil separator, and a very small portion of the oil remains unseparated, dissolves in the refrigerant, and passes through the condenser to the low-pressure section of the refrigeration system (generally a flooded evaporator, low pressure receiver). If oil continues to flow into the low pressure section, it will cause a lack of oil in the compressor and adversely affect heat transfer in the heat exchanger.
Therefore, oil mixed into the low pressure section of the refrigeration system needs to be returned to the compressor.

On the other hand, in a conventional screw refrigerator, for example, as shown in FIG.
2. In a refrigerator in which a refrigeration cycle is formed by an outlet pipe 33, a steam pipe 42, and an intake pipe 30,
In order to return the oil accumulated in the evaporator 17 to the screw compressor 1, the section from the discharge pipe 31 to the suction pipe 30 is connected to bypass pipes 40, 41, the ejector 14 is provided in the bypass path, and the suction part 38 of the ejector 14 is connected to the bypass pipe 40, 41. and the evaporator 17 are connected by an oil return pipe 37. The oil-containing refrigerant liquid in the evaporator 17 is transferred to the bypass pipe 4
0.41 is sucked into the ejector 14 and returned to the screw compressor 1 via the suction pipe 30.

However, in conventional systems with this type of structure, the refrigerant gas pressurized by the screw compressor is returned to the suction side and sucked, which increases wasteful compression work that is useless for the refrigeration cycle, reducing efficiency. This also has the disadvantage of considerably reducing the effective suction capacity of the screw compressor.

SUMMARY OF THE INVENTION An object of the present invention is to provide an oil return device for a refrigeration system that eliminates the above-mentioned drawbacks of the conventional ones, reduces wasteful compression work, secures an effective suction amount, and improves efficiency. It is something.

The present invention provides a refrigeration system that forms a refrigeration cycle with a positive displacement compressor, a condenser, an evaporator, and a refrigerant path connecting these, and includes an oil return container at a position lower than the evaporator, The refrigerant liquid storage part and the oil return container are connected by a communication path for oil recovery, and the oil refrigerant liquid storage part of the oil return container and the through hole communicating with the rotor working space of the compressor are connected by the oil return path. A pressurizing mechanism is provided which makes the inside of the oil return container high pressure by heating the oil refrigerant or introducing high pressure gas on the discharge side, and when the oil return operation is performed, the communication path is cut off, the oil return path is opened, and the oil return path is opened. This oil return device for a refrigeration system is characterized in that the oil refrigerant liquid in the oil return container is returned to the rotor working space of the compressor by high pressure created by a pressurizing mechanism.

The operation of the present invention will be explained.

In conventional examples, an ejector installed in the bypass connecting the discharge port and suction port of the compressor is used as the driving force to return the oil in the evaporator to the compressor, so the oil refrigerant liquid sucked up is The air was introduced into the suction port of the compressor, and had the drawbacks mentioned above.

In the present invention, an oil return container for recovering oil from the evaporator is provided separately from the evaporator, and the driving force for guiding the oil from the oil return container to the compressor is used to heat the oil refrigerant liquid or to increase the refrigerant gas on the high pressure side. Using a pressurizing mechanism that increases the internal pressure of the oil return container by introduction,
Furthermore, when returning oil, the communication circuit between the evaporator and the oil return container is cut off, and the oil return circuit is separated from the compressor's normal suction path. Instead, it is returned to the rotor working space of the compressor.

By doing this, in the present invention, the compression work can be reduced without wastefully compressing and circulating refrigerant gas that does not contribute to the refrigeration effect, and the efficiency can be improved by ensuring the effective suction amount. can.

To explain an embodiment of the present invention using a screw compressor using drawings, in FIG. 2, an oil separator 11 is provided between discharge pipes 31 and 32, and the separated liquid oil is separated from the oil 34, is pressurized by the oil pump 12, cooled by the oil cooler 13, and then sent to the bearing oil supply hole 3 by the oil pipe 35 for lubrication of the bearing part, and is injected into the rotor action chamber to cool the rotor. Used for lubrication and sealing as well as compressor absorption.

An oil return container 46 is provided at a position lower than the evaporator 17. An oil recovery pipe 4 is provided between the evaporator 17 and the oil return container 46 as a communication path for oil recovery.
7 and a pressure equalizing pipe 49 are provided. Oil recovery pipe 47
connects the oil-rich refrigerant liquid storage section of the evaporator 17 and the oil return container 46, and an on-off valve 48 is provided in the middle. The pressure equalizing pipe 49 connects the upper part of the evaporator 17 and the upper part of the oil return container 46, and an on-off valve 50 is provided in the middle. Furthermore, an on-off valve 53 is provided at the lower part of the oil return container 46, which is connected to the introduction hole 2 of the screw compressor 1 through oil return pipes 51 and 52 as an oil return path.

As will be described later, the introduction hole 2 is connected to the rotor working space through an oil injection passage 39 provided in the slide valve 5 which is axially distant from the low pressure control edge 10 of the slide valve 5 by more than one land of the teeth of the rotor. The suction port is connected to the roller action space after the suction port is closed, and is designed not to communicate with the suction port even under partial load, thereby preventing a decrease in the effective suction amount of the compressor.

The lower part of the oil return container 46 is a heat exchanger, and the high temperature, high pressure refrigerant liquid from the condenser 15 is passed through the tube to heat the oil refrigerant liquid, and the oil return container 46 is heated.
The internal pressure is now high. In other words, the oil refrigerant liquid pressurizing mechanism is configured to heat the oil refrigerant liquid using a high-temperature, high-pressure refrigerant liquid.

The oil return container 46 is provided with a float 54 and a limit switch 55. The float 54 and the limit switch 55 are interlocked, and when the liquid level rises and the liquid level reaches H, the limit switch 55 is turned on, closing the on-off valves 48 and 50 and opening the on-off valve 53, thereby lowering the liquid level. When the liquid level decreases and the liquid level reaches L, the limit switch 55 is turned off, the on-off valves 48 and 50 are opened, and the on-off valve 53 is closed. (Not shown, and the contact opening and closing of the limit switch may be reversed).

Therefore, when the liquid level in the oil return container 46 decreases to L, the limit switch 55 is turned off, the on-off valves 48 and 50 are opened, and the oil recovery pipe 47 and the oil recovery pipe 47 as a communication path for oil recovery are opened. A pressure equalization pipe 49 communicates between the evaporator 17 and the oil return container 46, the on-off valve 53 is closed, and the oil-rich refrigerant liquid in the evaporator 17 flows into the oil return container 46 by gravity.

When the liquid level rises to H, limit switch 5
5 is turned on, the on-off valves 48 and 50 are closed, and the on-off valve 53 is opened. That is, the oil recovery pipe 47 and the pressure equalization pipe 49, which serve as communication paths for oil recovery, are cut off.
The oil return path is separated from the normal suction path of the compressor 1.

Since the high-pressure, high-temperature refrigerant liquid is passed through the oil return container 46, the oil-containing refrigerant liquid that has flowed into the oil return container 46 is heated to vaporize a portion of the refrigerant liquid, and the internal pressure of the oil return container 46 is reduced. gradually increases, and when the pressure in the oil return container 46 becomes higher than the intermediate pressure portion where the oil return pipe 52 communicates with the rotor working space, the oil return container 46 is removed from the evaporator 17 due to the pressure difference.
The oil-containing refrigerant liquid that has flowed into the compressor 1 is returned to the compressor 1.

At this time, the refrigerant liquid passing through the oil return container 46 is supercooled, increasing the refrigeration effect and increasing the refrigeration capacity.

Then, the refrigerant liquid containing oil in the oil return container 46 returns to the compressor 1, and the liquid level in the oil return container 46 decreases.
When the liquid level reaches L, the limit switch 55 is turned off, the on-off valves 48 and 50 are opened, and the opening valve 53 is closed, allowing the refrigerant liquid containing oil to flow from the evaporator 17 into the oil return container 46 again. The oil mixed into the low pressure part is automatically returned to the compressor 1.

Further, when the liquid level in the oil return container 46 is L and the limit switch 55 is open, the on-off valve 48,
50 is open, the on-off valve 53 is closed, and the evaporator 1
The oil-containing refrigerant liquid that has flowed into the oil return container 46 from 7 is also heated by the high-pressure refrigerant liquid, partially evaporates, and is sucked from the suction port of the compressor 1, but at this time, the high-pressure refrigerant liquid is overheated. Since it is cooled, the refrigeration capacity of the refrigerator is not reduced.

Further, the discharge pipes 31, 32, the oil pipe 34, or an external heat source may be used as a heat source for the oil-containing refrigerant liquid. In this case, when the liquid level is L, the limit switch 55 opens and the on-off valves 48, 50 open. is open and the on-off valve 53 is closed, the heated and evaporated gas is sucked in from the suction port of the compressor 1, so unlike the case where the refrigerant is supercooled as in the previous example, the effective suction of the compressor 1 is reduced. However, in order to prevent this, the heating source is connected to the discharge pipes 31 and 32.
Alternatively, in the case of the oil pipe 34, as shown in FIG. 3, a bypass passage 57 with an on-off valve 56 provided in the middle is provided so that the heat exchange of the heating source is performed in the bypass passage 57, and when the limit switch 55 is open, the on-off valve 56 is opened. If the limit switch 55 is closed or an external heat source (such as a heater) is used, the effective suction amount of the compressor 1 can be prevented from decreasing by not supplying the external heat source when the limit switch 55 is open. .

When the liquid level reaches H and the limit switch 55 is closed, the on-off valves 48 and 50 are closed, and the on-off valve 53 is open, the oil-containing refrigerant liquid is returned to the rotor working space after the suction port is closed. Therefore, the effective suction amount of the compressor 1 is not reduced.

Furthermore, a float 54 provided in the oil return container 46
and limit switch 55, on-off valve 4
8, 50, 53 may be operated by a timer, the on-off valves 48, 50 are opened for a certain period of time, and the on-off valves 5
3 is closed to allow the refrigerant liquid containing oil to flow from the evaporator 17 into the oil return container 46, and then the on-off valves 48 and 50 are closed for a certain period of time and the on-off valve 53 is opened to remove the oil accumulated in the oil return container 46. The refrigerant liquid may be returned to the compressor 1. The timer can be set arbitrarily depending on the oil return condition.

Furthermore, a liquid level gauge for the oil return container 46 may be provided, and the on-off valves 48, 50, 53 may be operated manually, and the manual valves may be operated while checking the liquid level. Further, heat exchange between the oil-containing refrigerant liquid and the heat source may be performed between the oil return container 46 and the on-off valve 53.

To explain the structure of the screw compressor 1, the fourth
As shown in the figure, a male rotor 4 and a female rotor (parallel to the male rotor 4, on the other side, not shown) are supported so as to mesh with each other and rotate in reverse. The sucked refrigerant gas is compressed and discharged from the high pressure port 7. 5 is a slide valve for volume adjustment, which is operated by a hydraulic piston 8. The capacity is increased when the low-pressure control lip 10 of the slide valve 5 rests against the fixed end 9 of the casing, and the slide valve 5 moves towards the high-pressure port 7 so that the low-pressure control lip 10 and the fixed end 9 If the distance between the two increases, the capacity will decrease.

The slide valve 5 is provided with an oil injection passage 39. The space 45 allows the oil injection passage 39 to
Even when the slide valve 5 moves, it always communicates with the introduction hole 2, and the oil sent to the introduction hole 2 is injected into the working space of the rotor. Since the oil injection passage 39 is separated from the low-pressure control edge 10 by a distance of one teeth-to-tooth ride of the rotor or more, the oil injection passage 39 does not communicate with the suction port 6 .

In a screw compressor that does not use the slide valve 5, if the inlet hole 2 is provided at a distance of one land or more from the suction port confinement edge 19, the action chamber after confinement during suction can be Since it is open, there is no communication on the suction side.

FIG. 5 shows another embodiment, in which the pressurizing mechanism is configured to guide refrigerant vapor from the high-pressure refrigerant system into the cooling-back container 46 to make the internal pressure high. The oil return container 46 is connected to the oil return container 46 by a pressurizing pipe 59 having an on-off valve 58 in the middle. The refrigerant vapor for pressurization may be extracted at any point in the high-pressure refrigerant system, for example, the pressurizing pipes 60, 61,
It is also possible to extract by 62 or 63.

In addition, a heat exchanger 18 is provided between the oil return container 46 and the oil return pipe 52 returning to the compressor 1 to exchange heat between the oil-containing refrigerant liquid from the low-pressure part and the high-pressure refrigerant liquid. supercooling to increase the freezing effect,
Increases the coefficient of performance of refrigerators.

The effects of this embodiment are almost the same as those of the previous embodiment.

However, the on-off valve 58 is designed to open and close together with the on-off valve 53.

Since the above embodiment is constructed as described above, it has the following remarkable effects.

(1) By connecting the oil return passage to the rotor working space after the suction port of the compressor is closed, a reduction in the effective suction amount of the compressor due to oil-containing refrigerant from the low pressure section is prevented.

(2) By providing an oil return passage in the slide valve, the amount of refrigerant containing oil from the low pressure section communicated to the suction side is reduced even during partial loads, thereby reducing the effective suction amount during partial loads. Make it smaller. (When partially connected to the suction side) (3) Provide the oil return passage in the slide valve at a position axially away from the low-pressure control edge of the slide valve to the high-pressure side by at least one land between the teeth of the rotor. This prevents the oil-containing refrigerant from the low-pressure section from communicating with the suction port even during partial load, thereby preventing a decrease in the effective suction amount during partial load.

(4) A heat exchanger is installed in the middle of the oil return pipe to exchange heat between the oil-containing refrigerant liquid in the low-pressure part of the refrigeration system and the high-pressure refrigerant liquid before flowing into the low-pressure part, and to pass the high-pressure refrigerant liquid. Cooling increases the refrigeration effect and increases the coefficient of performance of the refrigerator.

In addition, as the compressor, other than the screw compressor, a positive displacement compressor such as a rotary vane type, a rotary piston type, or a Roots type may be used. In addition, non-oil injection type devices may also be used for collecting oil from bearings.

According to the present invention, since a part of the discharged refrigerant gas is not re-inhaled, unnecessary compression work for the refrigeration cycle is reduced, and an effective suction amount is ensured.
It is possible to provide an oil return device for a refrigeration system that can improve efficiency, and has extremely great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a flow sheet of a conventional example, Fig. 2 is a flow sheet of an embodiment of the present invention, Fig. 3 is a flow sheet of another embodiment near the oil return container, and Fig. 4 is a flow sheet of an embodiment of the present invention. Longitudinal cross-sectional view of screw compressor, No. 5
The figure is a flow sheet of another example. 1...Compressor, 2...Introduction hole, 3...Bearing oil supply hole, 4...Male rotor, 5...Slide valve, 6
... Suction port, 7 ... High pressure port, 8 ... Hydraulic piston, 9 ... Fixed end, 10 ... Low pressure control edge, 11 ...
...Oil separator, 12...Oil pump, 13...Oil cooler, 14...Ejector, 15...Condenser, 16...
...expansion valve, 17...evaporator, 18...heat exchanger,
19...Suction port confinement edge, 30...Suction pipe, 3
1... Discharge pipe, 32... Discharge pipe, 33... Outlet pipe, 34... Oil pipe, 35... Oil pipe, 37... Oil return pipe, 38... Suction part, 39... Oil injection passage, 4
0... Bypass pipe, 41... Bypass pipe, 42...
...Steam pipe, 45...Space, 46...Oil return container,
47... Oil recovery pipe, 48... On-off valve, 49... Pressure equalization pipe, 50... On-off valve, 51, 52... Oil return pipe, 53... On-off valve, 54... Float, 55...
...Limit switch, 56...Opening/closing valve, 57...
Bypass path, 58... Opening/closing valve, 59, 60, 6
1, 62, 63...pressure pipe.

Claims (1)

[Scope of Claims] 1. A refrigeration system that forms a refrigeration cycle by a positive displacement compressor, a condenser, an evaporator, and a refrigerant path connecting these, is provided with an oil return container at a position lower than the evaporator, The oil refrigerant liquid storage part of the oil refrigerant liquid storage part of the oil return container and the oil return container are connected by a communication path for oil recovery, and the oil refrigerant liquid storage part of the oil return container and the introduction hole communicating with the rotor working space of the compressor are connected to the oil return container. A pressurizing mechanism is provided which connects the oil refrigerant through a passage and makes the inside of the oil return container high pressure by heating the oil refrigerant liquid or introducing high pressure gas on the discharge side, and when the oil return operation is performed, the communication passage is cut off and the oil return passage is closed. An oil return device for a refrigeration system, characterized in that the oil return device is configured to open and return the oil refrigerant liquid in the oil return container to the rotor action space of the compressor by the high pressure created by the pressure mechanism. 2. The apparatus according to claim 2, wherein the pressurizing mechanism heats the oil refrigerant liquid using the heat of the refrigerant liquid in the high-pressure refrigerant system to create a high pressure in the pressure return container. 3. The apparatus according to claim 1, wherein the pressurizing mechanism increases the internal pressure of the oil return container by guiding refrigerant vapor in the high-pressure refrigerant system into the oil return container. 4. The apparatus according to claim 1, wherein the operation of the pressurizing mechanism is controlled by a signal from a liquid level detector of the oil refrigerant liquid in the oil return container. 5. The device according to claim 1, wherein the introduction hole communicates with a rotor working space after the suction port of the compressor is closed. 6. A patent claim in which the compressor is a screw compressor, includes a slide valve, and the introduction hole communicates from the casing of the screw compressor to the rotor working space via an oil injection passage provided in the slide valve. The device according to item 1. 7. Claim 6, wherein the oil injection passage of the slide valve is provided at a position axially distant from the low pressure control edge of the slide valve by a distance of one land between teeth of the rotor or more. equipment.