JPH09243213A - Air conditioning equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a deviation of a refrigerating machine oil in air conditioning equipment in which a plurality of compressors are arranged in parallel by arranging oil separators on delivery pipings of the compressors to connect oil return tubes respectively to suction pipings of adjacent compressors sequentially. SOLUTION: Compressors 1a-1c are arranged in parallel and oil separators 1a-2c are connected respectively to delivery pipings thereof. Oil return tubes 6a-6c of the oil separators are connected to suction pipings of the adjacent compressors 1. For example, the oil return piping 6a is connected to the suction piping of the compressor 1b. Outlet pipings of the oil separators 2 are grouped into one and connected to a condenser 3. The temperature of a fluid to be cooled as cooled by an evaporator 5 is detected by a sensor 7 to control the number of operating units of the compressors 1. The individual oil return pipes 2 are connected to suction pipings of the adjacent compressors 1 sequentially to prevent the deviation of a refrigerating machine oil. The compressors 1 to be started or stopped during the control of the operating units thereof are set at random by utilizing random number, thereby achieving a leveling of the operation time of the compressors 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner that controls the temperature of a fluid to be cooled so as to approach a set temperature.

[0002]

2. Description of the Related Art In the prior art of an air conditioner having a plurality of compressors of this type, first of all, each compressor forms an independent refrigeration cycle, that is, each cycle is
It has a refrigeration cycle in which a compressor, a condenser, a decompression mechanism, and an evaporator are sequentially connected, and a common pipe for the fluid to be cooled of each of the evaporators is used to form one air conditioner. Secondly, the compressors are installed in parallel, the discharge pipe and the suction pipe of each compressor are common, and the condenser,
An air conditioner is formed by one refrigeration cycle that is sequentially connected to the decompression mechanism and the evaporator. In this second air conditioner, an oil equalizing pipe for balancing the oil of each compressor is installed in order to prevent the bias of the refrigerating machine oil.

As a known example of this prior art,
The first is Japanese Patent Application No. 5-99354, and the second is National Technical Report Vol.41 No.5.
Oct. 1995 (attached).

[0004]

Among the above-mentioned conventional techniques, the first one uses a condenser, a pressure reducing mechanism, and an evaporator for each refrigeration cycle, which leads to a cost up and a cooling target. The fluid piping becomes complicated,
When controlling the number of compressors, the evaporator could freeze.

In the second type, a compressor must be provided with an oil equalizing pipe, and a special compressor is required.

Further, when controlling the number of compressors, if the order of starting and stopping the compressors is determined in advance, the operating time of each compressor is biased and the operating life of the compressor is long. Will be short.

[0007]

In order to make the independent multiple refrigeration cycle of the plural compressors an independent refrigeration cycle of the plural compressors among the above-mentioned problems, each of the compressors according to claims 1 and 2. An oil separator is provided in each of the discharge pipes, and each oil return pipe is sequentially connected to the suction pipe of the adjacent compressor, thereby forming a refrigeration cycle that prevents uneven distribution of oil. This cycle prevents the oil from being biased, so that the number of compressors can be controlled.

Further, in order to prevent a bias in the operating time of the compressor in controlling the number of compressors, random numbers are used as in claims 3 and 4, and compression for starting and stopping when controlling the number of compressors is performed. By randomly setting the compressors, the operating hours of the compressor are leveled and the life of the air conditioner is extended.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An 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 pipes of the respective compressors. The oil return pipes 6a, 6b, 6c of the oil separator are connected to the suction pipes of the adjacent compressors, respectively. That is, the oil return pipe 6a is connected to 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 and 2c are integrated into one and connected to the condenser 3. afterwards,
The pressure reducing mechanism and the evaporator are sequentially connected, and then the pipe is branched and connected to the suction side of the compressors 1a, 1b, 1c.

The temperature of the fluid to be cooled, which is cooled by the evaporator 5, is detected by the sensor 7, and the number of compressors is controlled.

Now, when the sensor 7 is a thermostat and controls the number of compressors at the inlet temperature of the fluid to be cooled, the compressors 1a, 1b, 1c are all operated and the temperature of the fluid to be cooled drops, and When the point (B) is reached, the compressor 1c changes from the on state to the off state, and the cooling capacity becomes 66%. When the load is smaller, the temperature drops further, and when the temperature reaches point (C), the compressor 1b changes from the on state to the off state,
Cooling capacity drops to 33%. Similarly, when the point (D) is reached, the compressor 1a is stopped and all the compressors are stopped.

On the contrary, when the temperature rises, point (C),
The compressors are sequentially turned on at points (B) and (A), and the cooling capacity also increases from 0 to 33%, 66%, 100%.

As described above, since the cooling power can be changed according to the load, the temperature change of the fluid to be cooled can be reduced.

Next, the embodiments of claims 3 and 4 will be described with reference to FIGS.
A description will be given using Equation 1.

When the cycle of FIG. 1 is operated by controlling the number of compressors shown in FIG. 2, the compressor 1a among the three compressors is stopped last when the temperature drops and first started when the temperature rises. Will be done. That is, the compressor 1a has a longer operating time and a shorter life than the other two compressors. By leveling the operation time of the compressor, it is possible to prevent the life of the compressor from being unbalanced and to extend the life of the air conditioner. Now in FIG.
It is assumed that point (B) is reached when the temperature drops. At this time, the operation of Equation 1 is performed to determine the stop compressor No. No. by a random number.

[0018]

[Equation 1] N = R-INT (R / Nmax) * Nmax (Equation 1) where N: No. 1 of compressor to be started (stopped) ... Compressors 1a, 2 ... Compressors 1b, 3 ... Compressor 1c R: Random number Nmax: Total number of compressors INT (): Function for converting the number in () to an integer Similarly, for the point (C), which one of the remaining two compressors is to be stopped is calculated. It is determined by the calculation of.

On the contrary, even when the temperature rises, the arithmetic operation of the equation 1 is performed to determine which of the stopped compressors should be started.

[0020]

According to claim 1 of the present invention, it is possible to prevent the bias of the refrigerating machine oil when a plurality of compressors are used as a single refrigeration cycle, and the number of compressors according to claim 2 is controlled. It has become possible. Further, since the control of a plurality of units is performed in a single refrigeration cycle, there is no fear of partial freezing of the evaporator when controlling the number of compressors. Thirdly, since the number of units is controlled, the temperature change of the cooled fluid becomes small.

As the effects of the third and fourth aspects, since the operating time of the compressor can be leveled, the respective installed compressors will reach the end of their lives at substantially the same time, and the compressor will be used as an air conditioner. It has become possible to extend the life. In a specific example, an air conditioner equipped with two compressors has zero cooling load.
In the case of ˜50%, if the compressor rotation is not controlled and the life of the compressor is set to 20,000 hours, only one of the compressors always operates at this cooling load. That is, when the operating time of one compressor reaches the end of its life of 20,000 hours, the other compressor may be hardly operated. In this case, the life of the air conditioner is 20,000 hours.

On the contrary, when the rotation control according to claims 3 and 4 is employed, the operating time of both compressors is leveled, so that the operating time of each compressor is 20,000 hours at almost the same time. Welcome. That is, the life of the air conditioner is 40,000 hours. As described above, in this specific example, the life of the air conditioner is approximately doubled with and without rotation control.

The method of determining the starting compressor based on this random number can be applied not only when controlling the number of compressors, but also when starting the compressor when the air conditioner is started.

[Brief description of drawings]

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

FIG. 2 is an on-off state diagram of a compressor showing an embodiment of control of the number of compressors 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.

Front page continued (72) Inventor Masanori Uekura 390 Muramatsu, Shimizu City, Shizuoka Hitachi Air Conditioning Systems Division (72) Inventor Koji Ito 390 Muramatsu Shimizu City Shizuoka Prefecture Hitachi Systems Air Conditioning Systems Division

Claims (1)

[Claims] 1. In an air conditioner in which a plurality of compressors are installed in parallel and a refrigeration cycle is constituted sequentially by a condenser, a pressure reducing mechanism and an evaporator, an oil separator is provided in the discharge pipe of each compressor. An air conditioner that is provided, and that oil return pipes are sequentially connected to the suction pipes of the adjacent compressors to eliminate the bias of refrigerating machine oil.