JP3138031B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus in which compressors are arranged in parallel.

[0002]

2. Description of the Related Art Generally, a building in which a plurality of indoor heat exchangers (indoor units) are arranged in parallel and a plurality of compressors are arranged in parallel with respect to a refrigerant pipe connected to each indoor heat exchanger. Multi-type air conditioners are known. Although this type of multi-type air conditioner has the advantage that a large-capacity system can be achieved, since multiple compressors are connected in parallel, the lubrication inside each compressor depends on the operating state of each compressor. The amount of oil (hereinafter “oil”) becomes unbalanced.

For this reason, the applicant has filed Japanese Patent Application No. 3-11412.
The oil return pipes connected from the oil separator to the compressor in No. 5 are connected by a connecting pipe, and a valve is provided on the oil return pipe and / or the connecting pipe, and the valve is opened and compressed as necessary. It was proposed that the oil volume in the machine not be unbalanced.

[0004]

According to this proposal, one oil return oil is connected to the oil separator, and is connected to a lower portion of the oil separator. Therefore, when the oil is returned to one of the compressors by opening the above-described valve, the oil does not easily accumulate in the oil separator. As described above, even if oil is returned to one compressor and oil is returned to the other compressor, oil is not accumulated in the oil separator as described above. It was difficult to get the oil back on the plane.

An object of the present invention is to supply oil to a compressor that is short of oil in a short time.

[0006]

SUMMARY OF THE INVENTION To achieve this object, the present invention provides an oil separator for each of the compressors connected in parallel, and an oil separator connected to the upper and lower portions of each of these oil separators. Connect return pipes to each compressor in parallel,
The lower oil return pipes are connected to each other by a connecting pipe, and the lower oil return pipe and / or the connecting pipe are provided with a valve which is opened when the amount of oil in the compressor becomes a predetermined value or less.

[0007]

Normally, a fixed amount of oil is always kept in the oil separator by returning the oil to the compressor via the upper oil return pipe connected to the oil separator. Then, when the amount of oil in the compressor becomes equal to or less than a predetermined value, the valve is opened, and the oil reserved in the oil separator is allowed to flow in a short time to the compressor having insufficient oil.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, A and B indicate outdoor units, and C and D indicate indoor units. The outdoor unit A includes an accumulator 1a, a scroll or reciprocating compressor 2a, an oil separator 3a, a four-way valve 4a,
It comprises an outdoor heat exchanger 5a and an outdoor electric expansion valve 6a. The above-mentioned compressor 2a and the compressor 2b of the outdoor unit B are of variable capacity type whose capacity is changed according to the load (the number of rotations of the electric motor in the compressor is changed).

The outdoor unit B is the same as the outdoor unit A, and will not be described. Indoor unit C
Is composed of an indoor heat exchanger 7c and an indoor electric expansion valve 8c.

[0010] The indoor unit D is the same as the indoor unit C, and a description thereof will be omitted. These are connected via pipes 9 and 10 to form a refrigeration cycle. Needless to say, by increasing or decreasing the number of the indoor units C and D and the number of the outdoor units A and B in accordance with the increase or decrease of the air conditioning load, a refrigeration apparatus optimal for the air conditioning load can be configured.

Next, the oil return circuit of the outdoor unit A will be described. Reference numeral 11a denotes an upper oil return pipe connected to the upper part of the oil separator 3a, which is connected to the compressor 2a. Reference numeral 12a denotes a lower oil return pipe connected to the lower part of the oil separator 3a, which is also connected to the compressor 2a. Therefore, two oil return pipes 11a and 12a are connected in parallel to the compressor 2a.
13a and 14a are decompression elements connected to the upper oil return pipe 11a and the lower oil return pipe 12a, and the resistance value of the pressure reduction element 13a is set to be larger than the resistance value of the pressure reduction element 14a. The lower oil return pipe 12a has valves 15a, 16
a is incorporated, and the opening and closing operations of these valves 15a and 16a are determined by the controller 17a. Reference numerals 18a and 19a denote two oil level detection sensors provided above and below the compressor.
The output from these detection sensors 18a and 19a is
7a. These sensors 18a, 19
The valves 15a and 16a are controlled to open and close in accordance with the output from a. The control will be described later. Further, the oil return circuit of the outdoor unit B is the same as the oil return circuit of the outdoor unit A, and the description is omitted.

A connecting pipe 20 connects the lower oil return pipes 12a and 12b of both outdoor units A and B.
The valves 15a, 16a, and 15a depend on the amount of oil in the compressors 2a and 2b of the outdoor units A and B, respectively.
The opening and closing of b and 16b are controlled as shown in the table below.

The four valves 15a, 16a, 15
Instead of b and 16b, a three-way valve or the like may be provided at the connecting portion 23 between the lower oil return pipes 12a and 12b and the connecting pipe 20, or a valve may be provided at the connecting pipe 20.

[0014]

[Table 1]

In this table, in the column of oil amount, "normal" means that none of the sensors 18a, 19a, 18b, and 19b operate, and "decrease" means that the sensors 18a and 18b operate and the oil amount is low. This is a state in which the oil amount has dropped below a predetermined amount, and “extremely reduced” is a state in which all of the sensors 18a, 19a, 18b, and 19b operate and the oil amount has dropped extremely.

Next, the operation of this embodiment will be described.

When the four-way valves 4a and 4b are in the state shown by the solid lines in FIG. 1, the refrigerant flows as shown by the arrows in the figure. The outdoor electric expansion valves 6a and 6b are almost fully opened, and the indoor electric expansion valves 8c and 8d are adjusted in opening according to the load. In this case, the two outdoor units A and B are operated simultaneously,
The outdoor heat exchangers 5a and 5b function as condensers, and the indoor heat exchangers 7c and 7d function as evaporators. That is, cool air is sent from the indoor heat exchangers 7c and 7d, and the cooling operation is performed.

When the four-way valves 4a and 4b are switched as shown by the dotted lines in FIG. 1, the refrigerant flows in the direction opposite to the arrow in FIG. The opening degree of the indoor electric expansion valves 8c and 8d and the outdoor electric expansion valves 6a and 6b is adjusted according to the load. In this case, the two outdoor units A and B are operated simultaneously,
The outdoor heat exchangers 5a and 5b function as evaporators, and the indoor heat exchangers 7c and 7d function as condensers. That is,
Warm air is sent from the indoor heat exchangers 7c and 7d, and a heating operation is performed.

When any one of the cooling or heating operation states is performed, the valves 15a, 15a
6a and the valves 15b and 16b are closed, so that the amount of oil separated by the oil separators 3a and 3b exceeds the position of the upper oil return pipes 11a and 11b. As shown by a dotted line in FIG.
It is always returned to the scroll or reciprocating compressors 2a, 2b through 1a, 11b.

If, for example, the capacity of one of the compressors 2a is reduced (rotational speed is reduced) due to a temporary decrease in the cooling or heating load, the amount of oil returned to the one compressor 2a is reduced by the other. The amount of oil returned to the compressor 2b of
Only the sensor 18a is activated and the valves 15a, 16a, 15
The open / close states of b and 16b are as shown in (b) of the table.
That is, since the oil amount in one compressor 2a has become equal to or less than a predetermined value, the lower oil return pipe 12 is connected to the one compressor 2a.
a to the other compressor 2b via the upper oil return pipe 13b
The oil is returned to the respective compressors 2a and 2b via.

Here, the oil level 2 in one oil separator 3a
Reference numeral 1 denotes a position slightly lower than the position of the upper oil return pipe 11a, and the oil 22 is stored in the state of the hatched portion in FIG. Therefore, the accumulated oil 22 is transferred to the lower oil return pipe 12a.
, Is immediately returned to one compressor 2a. Also, since the resistance value of the pressure reducing element 14a of the lower oil return pipe 12a is set smaller than the resistance value of the pressure reducing element 13b of the upper oil return pipe 11b, one of the compressors 2a whose oil amount is decreasing
To prevent the two compressors 2a and 2b from being unbalanced. On the other hand, when the oil amount of the other compressor 2b decreases below a predetermined amount, the valves 15a, 16a, 15b, 16b
The opening and closing operation is performed so that the oil stored in the other oil separator 3b is quickly returned to the other compressor 2b via the lower oil return pipe 12b.

When both compressors 2a and 2b have reduced oil amounts, valves 15a, 16a, and 1b are used as shown in FIG.
5b and 16b are opened and closed, and each oil separator 3
The oil in a and 3b is returned to the respective compressors 2a and 2b via the lower oil return pipes 12a and 12b, respectively.

At the start of operation, for example, one of the compressors 2
If the oil stagnation amount (the amount of oil mixed in the refrigerant) in the a is large, the oil is discharged together with the refrigerant discharged at the start of operation, and the oil amount in one compressor 2a is extremely reduced ( Both sensors 18a and 19a operate). In this case, the valves 15a, 16a, 15b,
The opening / closing control of 16b is performed, and the oil in the other oil separator 3b is guided to one compressor 2a via the connecting pipe 20. When the amount of oil in the other compressor 2b is extremely reduced, the valves 15a, 16a,
The opening and closing control of 15b and 16b is performed, and the oil in one oil separator 3a is guided to the other compressor 2b via the connecting pipe 20.

FIG. 2 mainly shows the oil return circuit of the refrigeration apparatus described above. Here, the lower oil return pipe 12
Since both a and b have pressure reducing elements 13a and 13b, the refrigerant pressure in the lower oil return pipes 12a and 12b and the connecting pipe 20 is reduced by the discharge pipe 3 of the compressors 2a and 2b.
0a and 30b are lower than the refrigerant pressure. By doing so, even if the discharge refrigerant pressure differs in the compressors 2a, 2b, the lower oil return pipes 12a, 1
2b and the inside of the connecting pipe 20 are always at a low pressure, so that oil can easily flow into this pipe.

On the other hand, if there is no pressure reducing element on the oil separators 41a, 41b side of the lower oil return pipes 40a, 40b as shown in FIG.
The refrigerant pressure in the discharge pipes 44a and 44b of the a and 43b is substantially uniform. Therefore, for example, the refrigerant discharge pressure of one compressor 43a is higher than the refrigerant pressure of the other compressor 43b, and the oil in the other oil separator 41b is returned to the one compressor 43a via the connecting pipe 42. In some cases (solid arrows), the refrigerant could not flow reliably from the discharge pipe 44a having a high refrigerant pressure to the discharge pipe 44b having a low refrigerant pressure (dashed arrow).

[0026]

As described above, according to the present invention, oil separators are provided for each of the compressors connected in parallel, and oil return pipes respectively connected to the upper and lower parts of the oil separators are connected in parallel to each other. At the same time, the lower oil return pipes are connected to each other by connecting pipes, and the lower oil return pipes and / or connecting pipes are provided with valves that are opened when the amount of oil in these compressors becomes lower than a predetermined value. When these valves were opened, the oil stored in the oil separator was quickly returned to the compressor when these valves were opened,
The oil balance can be properly maintained in a short time.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram focusing on an oil return circuit in the refrigerant circuit shown in FIG.

FIG. 3 is an explanatory diagram focusing on a conventional oil return circuit.

[Explanation of symbols]

 2a, 2b Compressor 3a, 3b Oil separator 11a, 11b, 12a, 12b Oil return pipe 15a, 15b, 16a, 16b Valve 20 Connecting pipe

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F25B 1/00 387 F25B 13/00

Claims (1)

(57) [Claims] 1. A refrigeration system in which a plurality of compressors are connected in parallel, an oil separator is provided for each of the plurality of compressors, and the operation of these compressors is controlled simultaneously and individually according to load. Connecting the oil return pipes led from the upper and lower parts of each of these oil separators to the respective compressors in parallel, and connecting the lower oil return pipes to each other with a connecting pipe,
A refrigeration system characterized in that the lower oil return pipe and / or the connecting pipe are provided with a valve which is opened when the oil amount in the compressor becomes a predetermined value or less.