JP2004301452A - Refrigeration circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the injection of a refrigerant to a compressor to achieve the maximum refrigeration efficiency at all times. <P>SOLUTION: A discharge temperature of a compressor 4 is detected by a discharge temperature detector 35, a temperature of an evaporator 7 is detected by an evaporation temperature detector 34, and the outside air temperature is detected by an outside air temperature detector 32, when the refrigerant condensed by a condenser 5 is partially injected into the compressor 4 to cool the compressor 4, so that the injection amount to maximize the refrigeration efficiency is operated on the basis of these temperatures, and an injection control valve 31 is controlled by an injection control part 36 on the basis of a result of the operation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refrigeration circuit in which a part of a refrigerant condensed in a condenser is injected into a compressor, and when the compressor is cooled, an injection amount is controlled so that refrigeration efficiency is maximized. .
[0002]
[Prior art]
Conventionally, in a refrigeration circuit, a refrigerant is compressed by a compressor and circulated through the circuit. At this time, if the temperature of the refrigerant or the temperature of the compression chamber during the compression process increases, the compression efficiency decreases, or the members constituting the compression chamber become more worn.
[0003]
Therefore, a configuration has been proposed in which a part of the refrigerant liquefied in the refrigeration circuit is extracted to cool a compression chamber or the like of the compressor (see Patent Document 1).
[0004]
FIG. 2 is a diagram illustrating a configuration in which a part of a liquefied refrigerant is extracted from a receiver tank 101 (a liquid receiver) provided in a refrigeration circuit and supplied to a compressor 102, thereby forming a compression chamber or the like (not shown) of the compressor 102. FIG. 3 is a diagram illustrating a partial configuration diagram of a refrigeration circuit configured to cool.
[0005]
The refrigerant compressed by the compressor 102 is liquefied by the condenser 103 and is temporarily stored in the receiver tank 101 before being supplied.
[0006]
Therefore, a part of the liquefied refrigerant is extracted by the extraction pipe 104 and injected into the compressor 102 through the thermo valve 105.
[0007]
The opening of the thermo valve 105 is controlled by a temperature-sensitive cylinder 107 provided in a discharge pipe 106 of the compressor 102, and a refrigerant amount corresponding to the opening is injected into the compressor 102. I have.
[0008]
That is, that the temperature of the refrigerant discharged from the compressor 102 is high means that the temperature of the compression chamber and the like in the compressor 102 is also high. When the temperature of the compression chamber is high, the refrigerant drawn into the compression chamber is heated by the heat, so that the suction amount is reduced and the compression efficiency is reduced.
[0009]
Therefore, in such a case, the opening of the thermo valve 105 is increased to increase the injection amount of the refrigerant into the compressor 102, and when the temperature of the refrigerant is low, the opening of the thermo valve 105 is reduced, The injection volume is reduced.
[0010]
However, since the temperature-sensitive cylinder 107 is configured to control the opening of the thermo-valve 105 by utilizing the fact that gas is sealed inside and the volume of the gas changes in accordance with the temperature change, the response to the temperature change is reduced. Slowly, for example, when the compressor 102 is started, it takes time from the room temperature to the temperature of the discharged refrigerant (the time required for components such as the temperature-sensitive cylinder 107 to reach this temperature). Cannot be controlled properly.
[0011]
For this reason, the capillary tube 108 is connected in parallel with the thermo valve 105 so that the refrigerant can be injected through the capillary tube 108 even when the thermo valve 105 is closed when the compressor 102 is started.
[0012]
[Patent Document 1]
JP 2001-280760 A
[Problems to be solved by the invention]
However, in the above-described configuration, the amount of refrigerant to be injected into the compressor is controlled only by the discharge temperature of the compressor, and thus the amount of refrigerant may not always be such that the refrigeration efficiency is in an optimum state. Was.
[0014]
In other words, the temperature of the compression chamber is cooled by cooling the compressor, and the degree of heating of the refrigerant drawn into the compression chamber from the members constituting the compression chamber is reduced.
[0015]
For this reason, a large amount of refrigerant can be sucked and compressed, and the compression efficiency is improved.This means that the amount of refrigerant that can be used in the refrigeration circuit is reduced, and as a result, even if the compression efficiency is improved. The refrigeration efficiency does not always improve (it does not reach the maximum value).
[0016]
Therefore, an object of the present invention is to provide a refrigeration circuit in which the amount of refrigerant injected into a compressor can be controlled so that the maximum refrigeration efficiency is always obtained.
[0017]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides at least a compressor that compresses a refrigerant, a condenser that condenses the refrigerant, and a refrigeration circuit including an evaporator that evaporates the refrigerant. When cooling the compressor by injecting it into the compressor, the injection amount is controlled to maximize the refrigeration efficiency based on the discharge temperature of the compressor, the evaporation temperature in the evaporator, and the outside air temperature. It is characterized.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a refrigeration circuit applied to the present invention. The refrigeration circuit 1 includes an outdoor unit 2 provided with a compressor 4 and a condenser 5 and the like, and an outdoor unit 2 and an expansion valve 6. And an indoor unit 3 which is provided on the side of the heat utilization space and includes an evaporator 7 and the like.
[0019]
In the present embodiment, the case where cold heat is used by the refrigeration circuit 1 will be described, but it goes without saying that the case where warm heat is used is also applicable. In addition, a description will be given of an example of a conventionally used HFC refrigerant or the like as a refrigerant, but a carbon dioxide refrigerant may be used.
[0020]
Then, the refrigerant compressed by the compressor 4 in the outdoor unit 2 is condensed by the condenser 5 and liquefied. The liquefied refrigerant is sent to the indoor unit 3 through the refrigerant pipe, expanded by the expansion valve 6 and evaporated by the evaporator 7 to generate cold heat. Thereafter, the refrigerant returns to the outdoor unit 2 through the refrigerant pipe and is compressed by the compressor 4.
[0021]
FIG. 2 is a diagram showing the configuration of such an outdoor unit 2 in detail. The outdoor unit 2 includes a strainer 11, an accumulator 12, a compressor 4, an oil separator 13, a condenser 5, a receiver tank 14, a filter dryer. 15 and the like, the refrigerant circulates in this order.
[0022]
Further, the outdoor unit 2 includes a refrigerant injection device 20 so that a part of the liquefied refrigerant stored in the receiver tank 14 can be injected into the compressor 4.
[0023]
The strainer 11 removes impurities (dust such as abrasion powder) contained in the refrigerant returned from the indoor unit 3 to the outdoor unit 2. The accumulator 12 separates the refrigerant from the strainer 11 into gas and liquid so that only gaseous refrigerant can be supplied to the compressor 4 so that liquid compression does not occur in the compressor 4.
[0024]
The compressor 4 includes a compression chamber and a motor (not shown), and expands the space volume of the compression chamber by the power of the motor to draw in the gaseous refrigerant supplied from the accumulator 12, and then reduces the space volume of the compression chamber. It compresses the refrigerant by reducing the size.
[0025]
The compressor 4 is provided with a high-pressure sensor 21, a low-pressure sensor 22, and a high-pressure manometer 23 for detecting the pressure in the case, and a control circuit 24 is connected to the high-pressure sensor 21 and the low-pressure sensor 22.
[0026]
Then, the control circuit 24 controls the operation stop of the compressor 4 based on the signal from the low pressure sensor 22, and forcibly stops the compressor 4 when the signal from the high pressure sensor 21 exceeds a predetermined level. It does not exceed the set abnormal pressure. The pressure at this time can be visually recognized by the high pressure manometer 23.
[0027]
The oil separator 13 is a lubricating oil that has been discharged together with the refrigerant among the lubricating oil that has lubricated various sliding portions in the compressor 4 (for example, a contact portion between a plurality of members forming a rotating shaft of a motor and a compression chamber). The separated lubricating oil returns to the compressor 4 via the lubricating oil return pipe 25.
[0028]
The condenser 5 exchanges heat between the compressed high-temperature and high-pressure refrigerant and the outside air to condense the refrigerant, and the outside air is blown by the blower 26.
[0029]
When an HFC refrigerant or the like is used as the refrigerant, the refrigerant is condensed by the condenser 5 to be condensed and liquefied.
[0030]
The receiver tank 14 stores the refrigerant liquefied in the condenser 5, and is able to supply the refrigerant without excess or shortage with respect to the fluctuation of the heat load on the indoor unit 3 side.
[0031]
The receiver tank 14 is provided with a fusible plug 27 to prevent the refrigerant in the refrigeration circuit 1 from being heated and ruptured, for example, when a house housing the outdoor unit 2 has a fire. Meanwhile, when the temperature reaches a predetermined temperature (the melting point of the fusible plug 27), the refrigerant is melted and the refrigerant in the refrigeration circuit 1 is released to the atmosphere, thereby preventing rupture.
[0032]
The filter dryer 15 removes the water so that when the refrigerant contains moisture, when the evaporator 7 in the indoor unit 3 evaporates, the moisture freezes and does not clog the refrigerant circuit. The moisture indicator 28 is used for visually confirming the circulating refrigerant.
[0033]
The refrigerant injection device 20 includes an extraction pipe 29, a strainer 30, an injection amount control valve 31, an outside air temperature detector 32, an evaporation temperature detector 34, an injection amount control unit 36, a discharge temperature detector 35, an injection control valve 37, and the like. And a part of the liquefied refrigerant stored in the receiver tank 14 is injected into the compressor 4 as described above.
[0034]
The extraction pipe 29 is connected to the receiver tank 14 to extract the liquefied refrigerant stored in the receiver tank 14, and the strainer 30 removes dust contained in the extracted refrigerant.
[0035]
Since the extraction pipe 29 is for extracting a part of the liquefied refrigerant and allowing it to be injected into the compressor, the extraction pipe 29 is connected not only to the receiver tank 14 but also to the refrigerant on the indoor unit 3 side from the condenser 5. It may be connected to piping.
[0036]
As described above, when the condenser 5 is connected to the refrigerant pipe on the indoor unit 3 side, the present invention can be applied to a refrigeration circuit having no receiver tank 14, and there is an advantage that the use range is widened.
[0037]
The outside air temperature detector 32 detects the outside air temperature, the evaporation temperature detector 34 detects the evaporation temperature in the evaporator 7, and the discharge temperature detector 35 detects the discharge temperature of the compressor 4. Things. Although the evaporating temperature is detected by the evaporating temperature detector 34, it can be obtained by converting the temperature of the low-pressure sensor 22.
[0038]
The outside air temperature from the outside air temperature detector 32, the evaporation temperature from the evaporation temperature detector 34, and the discharge temperature of the compressor 4 from the discharge temperature detector 35 are input to the injection amount control unit 36, respectively. The refrigerant temperature and the discharge temperature are calculated such that the maximum refrigeration efficiency is obtained based on the evaporation temperature, and the injection amount control valve 31 is controlled based on the discharge temperature.
[0039]
As described above, the injection amount control unit 36 controls the injection amount control valve 31, so that the compressor 4 can be cooled while maintaining the maximum refrigeration efficiency.
[0040]
【The invention's effect】
As described above, according to the present invention, when a part of the refrigerant condensed in the condenser is injected into the compressor and the compressor is cooled, the discharge temperature of the compressor, the temperature of the condenser, Since the injection amount is controlled so that the refrigeration efficiency is maximized based on the temperature, the maximum refrigeration efficiency can always be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a refrigeration circuit applied to an embodiment of the present invention.
FIG. 2 is a partial configuration diagram of a refrigeration circuit applied to a description of a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Refrigeration circuit 2 Outdoor unit 3 Indoor unit 4 Compressor 5 Condenser 6 Expansion valve 20 Refrigerant injection device 29 Extraction pipe 31 Injection amount control valve 32 Outside temperature detector 33 Evaporation temperature detector 34 Evaporation temperature detector 35 Discharge temperature detection Device 36 injection amount control unit 37 injection control valve

Claims (1)

At least a compressor that compresses the refrigerant, a condenser that condenses the refrigerant, a refrigeration circuit including an evaporator that evaporates the refrigerant,
When a part of the refrigerant condensed in the condenser is injected into the compressor and the compressor is cooled, the refrigeration efficiency is determined based on the discharge temperature of the compressor, the evaporation temperature in the evaporator, and the outside air temperature. The refrigeration circuit, wherein the injection amount is controlled so that the maximum value is obtained.

Images