JPH116657A - Air-conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce temperature change in fluid to be cooled by closing the oil-returning piping of the oil separator at the discharge side of a compressor being stopped, and by switching to an oil-returning piping for returning refrigerating machine oil to intake piping of the compressor being stopped when operation state is switched to unloader control. SOLUTION: The temperature of fluid to be cooled that is cooled by an evaporator 5 is detected by a sensor 7 and the number of compressors 1a, 1b, and 1c is controlled (unloader control). Also, solenoid valves 8a, 8b, and 8c are arranged in oil-returning pipes 6a, 6b, and 6c. Then, immediately when operation state is switched to the unloader control, the solenoid valves such as the solenoid valves 8a and 8b are closed, and the solenoid valve 8c is opened, thus preventing refrigerating machine oil from flowing into the compressor 1c being stopped, and at the same time successively returning the refrigerating machine oil to the compressors 1b and 1c via the oil-returning pipes 6b and 6a. As a result, the unbalance of the refrigerating machine oil and the adhesion and seizure of the compressors 1a-1c can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for controlling the temperature of a fluid to be cooled to a set temperature,
In particular, an object of the present invention is to reduce the temperature change of the fluid to be cooled by controlling the number of compressors.

[0002]

2. Description of the Related Art The prior art of this type of air conditioner having a plurality of compressors is such that a compressor is installed in parallel, a discharge pipe and a suction pipe are commonly used, and a condenser, a decompression mechanism, an evaporation Some air conditioners are formed by one refrigeration cycle formed by connecting the air conditioner sequentially. Also, in the refrigeration cycle of this air conditioner, an oil separator is provided in each discharge pipe of the plurality of compressors to prevent bias of the refrigerating machine oil, and an oil return pipe of the oil separator is connected to each of the adjacent compressors. Some have a structure that returns to the suction pipe.

Further, in order to prevent the bias of the refrigerating machine oil,
There are a pressure equalizing pipe method in which a pressure equalizing pipe is provided between a plurality of compressors to prevent bias of the refrigerating machine oil, and an external refueling method in which refrigerating machine oil is supplied from outside the compressor.

As a known example of this kind of technology,
Japanese Patent Application No. 5-99354 is an example.

[0005]

In the above prior art, when the unloader control is performed, the compressor oil that has been stopped is stopped by the oil return pipe because of the structure that returns the refrigerating machine oil to the suction pipe. When the refrigerating machine oil stays and the running side of the refrigerating machine oil runs short, there is a problem that the compressor is hardened or damaged. In addition, among the conventional technologies, a compressor having a special structure must be used as the compressor used in the equalizing pipe system or the external refueling system, and a compressor having the same structure as that used in a general air conditioner cannot be used. And that the refrigeration cycle becomes complicated.

[0006]

In order to prevent the refrigerating machine oil from returning to the suction pipe of the stopped compressor, at the time when the operation state shifts to the unloader control, the discharge side of the stopped compressor is selected. The oil return pipe of the oil separator is closed and switched to the oil return pipe that returns the refrigeration oil to the suction pipe of the stopped compressor. That is, the stopped compressor is skipped, and the oil is sequentially returned to the next compressor. When two compressors are air conditioners, the refrigerating machine oil of one operating compressor returns to its own suction pipe by the oil separator during unloader control.

[0007] Alternatively, by operating the compressor that is stopped during unloader control at a constant interval for a fixed time, it is possible to eliminate the bias of the refrigerating machine oil between the compressors. In addition, an increase in the cooling capacity at this time can be prevented by bypassing the high pressure side and the low pressure side.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG.

A plurality of compressors 1a, 1b, 1c (three in FIG. 1) are installed in parallel, and oil separators 2a, 2b, 2c are connected to the discharge pipe of each compressor. The oil return pipes 6a, 6b, 6c of the oil separator are respectively connected to suction pipes of adjacent compressors. That is, the oil return pipe 6a is connected to the suction pipe of the compressor 1b, the oil return pipe 6b is connected to the suction pipe of the compressor 1c, and the oil return pipe 6c is connected to the suction pipe of the compressor 1a. The outlet pipes of the oil separators 2a, 2b, 2c are integrated into one and connected to the condenser 3. Thereafter, the pressure reducing mechanism and the evaporator are sequentially connected, and thereafter, the pipe is branched and connected to the suction sides of the compressors 1a, 1b, 1c. Evaporator 5
The temperature of the fluid to be cooled is detected by the sensor 7, and the number of compressors is controlled (unloader control). Also, the solenoid valves 8a, 8b, 8c are installed on the oil return pipe. In the normal operation state, the compressors 1a, 1b, 1c
Is operated, the solenoid valves 8a and 8b are opened, the solenoid valve 8c is closed, and the refrigerating machine oil is sequentially returned to the adjacent compressor. Thereby, since the refrigerating machine oil circulates through each compressor, bias of the refrigerating machine oil is prevented. In this state, if it is assumed that the process shifts to the unloader control based on the temperature of the fluid to be cooled detected by the sensor 7, the number of compressors is controlled by controlling the number of compressors.
For example, the compressor 1c stops. At this time, if the state of the oil return pipe remains normal operation, the refrigerating machine oil returning from the compressor 1b will accumulate in the stopped compressor 1c, and the operating compressors 1a, 1b Will run out of refrigerating machine oil. In order to prevent this, the solenoid valves 8a and 8b are closed at the same time as the
Open c. Thus, it is possible to prevent the refrigerating machine oil from flowing into the stopped compressor 1c, and to return the refrigerating machine oil to the next compressor in sequence.

FIG. 2 shows another embodiment of the present invention, in which a two-way valve 10 is used instead of the solenoid valves 8a and 8c of FIG.

Another embodiment of the present invention will be described with reference to FIG.

A plurality of compressors 1a, 1b, 1c (three in FIG. 1) are installed in parallel, and oil separators 2a, 2b, 2c are connected to discharge pipes of each compressor. The oil return pipes 6a, 6b, 6c of the oil separator are respectively connected to suction pipes of adjacent compressors. That is, the oil return pipe 6a is connected to the suction pipe of the compressor 1b, the oil return pipe 6b is connected to the suction pipe of the compressor 1c, and the oil return pipe 6c is connected to the suction pipe of the compressor 1a. The outlet pipes of the oil separators 2a, 2b, 2c are integrated into one and connected to the condenser 3. Thereafter, the pressure reducing mechanism and the evaporator are sequentially connected, and thereafter, the pipe is branched and connected to the suction sides of the compressors 1a, 1b, 1c. Evaporator 5
The temperature of the fluid to be cooled is detected by the sensor 7, and the number of compressors is controlled (unloader control). The high pressure side and the low pressure side are connected by a bypass pipe via the electromagnetic valve 11. In the normal operation state, the compressors 1a, 1b, 1c are operated, and the refrigerating machine oil is returned to the adjacent compressor. In this state, if it is assumed that the process shifts to the unloader control based on the temperature of the fluid to be cooled detected by the sensor 7, the number of compressors is controlled by controlling the number of compressors.
For example, the compressor 1c stops. At this time, the compressor 1b
The refrigerating machine oil returned from the compressor accumulates in the stopped compressor 1c, and the running compressor oils of the compressors 1a and 1b run short. In order to prevent this, the stopped compressor 1c is operated for a fixed time, for example, 5 minutes at regular intervals, for example, every hour after the shift to the unloader control. Compressor 1 stopped by this
The refrigerating machine oil accumulated in c is discharged from the compressor 1c, thereby eliminating the bias of the refrigerating machine oil. However, operating the stopped compressor during the unload control causes an excessive cooling capacity. Therefore, the solenoid valve 11 is opened when the stopped compressor is operated for 5 minutes. This can suppress an increase in cooling capacity due to operation of the compressor.

Therefore, in the above-described refrigeration cycle, the switching of the oil return pipe can be performed by synchronizing the opening / closing of the three solenoid valves and the operation / stop of the compressor.

In the refrigeration cycle, the switching of the oil return pipe may be performed by synchronizing the opening / closing of one two-way valve and one solenoid valve with the operation / stop of the compressor. Further, in the above-described refrigeration cycle, the stopped compressor can be started at fixed intervals for a certain period of time in order to prevent the refrigerating machine oil from staying in the stopped compressor.

Further, in the above-described method for controlling a refrigeration cycle, in order to prevent an increase in the cooling capacity due to starting the compressor in a stopped state so as not to cause stagnation of the refrigerating machine oil during unloader control, the compression in the stopped state is prevented. While the machine is running, the high and low pressure sides of the refrigeration cycle can be bypassed. Therefore, the control is a solenoid valve (two-way valve), and can be controlled by a simple relay sequence circuit using a relay and a timer.

[0016]

According to the present invention, it is possible to prevent the refrigerating machine oil from being biased in one refrigeration cycle having a plurality of compressors, thereby preventing the compressor from being stuck and burning. Accordingly, unloader control (number control) is possible in one refrigeration cycle having a plurality of compressors.

[Brief description of the drawings]

FIG. 1 is a refrigeration cycle system diagram showing one embodiment of the present invention.

FIG. 2 is a refrigeration cycle system diagram showing another embodiment of the present invention.

FIG. 3 is a refrigeration cycle system diagram showing still another embodiment of the present invention.

[Explanation of symbols]

1a, 1b, 1c compressor, 2a, 2b, 2c oil separator, 3 condenser, 4 decompression mechanism, 5 evaporator, 6a, 6
b, 6c: oil return pipe, 7: sensor, 8a, 8b, 8c ...
Solenoid valve, 10: two-way valve, 11: solenoid valve.

Claims (1)

[Claims] 1. A plurality of compressors are installed in parallel, a refrigeration cycle is constituted by a condenser, a decompression mechanism, and an evaporator, and an oil separator is provided in a discharge pipe of each compressor. The oil return pipe of the oil separator is sequentially connected to the suction pipe of the adjacent compressor, and in the air conditioner having a structure for preventing the bias of the refrigerating machine oil, several of the plurality of compressors are stopped. Control to reduce the refrigeration capacity (unloader control,
The same applies to the following), in order to prevent the refrigerating machine oil from staying in the stopped compressor, the compressor operating from the suction pipe of the stopped compressor is connected to the oil return pipe connection port of the oil separator. An air conditioner characterized by switching to a suction pipe.