JPH0436550A - Refrigerator - Google Patents

Abstract

PURPOSE:To enable an operating range of a compressor to be expanded by a method wherein when a temperature of discharged gas is increased up to a predetermined temperature which is approximate to a setting temperature for stopping an operation of the compressor, a degree of opening of an electrical expansion valve is increased in such a way as the temperature becomes an over-heating temperature not exceeding the predetermined temperature. CONSTITUTION:An electrical expansion valve 6 is installed in the midway part of a liquid injection pipe 5. A temperature sensor 7 for sensing a discharged gas temperature and a pressure sensor 8 for sensing a discharged gas pressure are installed at a discharging side of a compressor 1. In turn, an over-heating degree of the discharged gas is calculated based on a result of sensing from each of the sensors 7 and 8, a command of degree of opening is outputted to the expansion valve 6 in such a way as the overheating degree of the discharged gas becomes a constant over-heating degree. When the discharged gas temperature becomes a predetermined temperature which is approximate to the set temperature for stopping the operation of the operation of the compressor 1, an overheating degree controller 9 for outputting an command of degree of opening for increasing a degree of opening of the electrical expansion valve 6 in such a way as the discharged gas temperature becomes the degree of overheating not exceeding the predetermined temperature is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention mainly relates to a refrigeration system equipped with a screw compressor.

(Prior art) Conventionally, this type of refrigeration equipment has been developed, for example, by
5, and as shown in FIG. 5, a condenser (B), an expansion mechanism ('C), and an evaporator are installed on the refrigerant discharge side of a compressor (A) equipped with a screw rotor (a). vessel('
D) are sequentially connected, and the condenser (B) and expansion mechanism (C
) is connected to the liquid injection pipe (E) leading to the screw rotor (a) of the compressor (A).
) T-connection, and a temperature-sensitive expansion valve (F) is interposed in the middle of this pipe (E), and the expansion valve (F) is connected to a pressure equalizing pipe (G) on the discharge side of the compressor (A). ) while connecting via
The temperature-sensitive cylinder (f) of the expansion valve (F) is disposed on the discharge side of the compressor (A), and the discharge gas pressure from the pressure equalization pipe (G) and the temperature-sensitive cylinder (f) are arranged at the discharge side of the compressor (A). By controlling the opening degree of the expansion valve (F) based on the detected discharge gas temperature and injecting liquid refrigerant from the pipe (E) into the screw rotor (a), the degree of superheating of the discharge gas is always kept constant. I try to keep it that way. The reason why the degree of superheat is kept constant is that when the degree of superheat exceeds a certain level, decomposition of the oil stored in the compressor (A) occurs; If this occurs, the refrigerant will be dissolved in the oil, and when the oil is supplied to the oil supply point of the compressor (A), a flash will occur, resulting in a reduction in the oil supply capacity.

(Problems to be Solved by the Invention) However, in the above-mentioned refrigeration system, the following problem occurred.

In Figure 6, the vertical axis represents the discharge gas temperature (Td), and the horizontal axis represents the saturated condensation temperature (Tc) corresponding to the discharge pressure.
The graph shows the relationship between c and the degree of superheating, and in the same figure, the straight line (a) indicates a superheat degree of 0°C, and the straight line (b) shows a superheat degree of 25°C relative to the straight line (a). The discharge gas temperature in each case is shown.

As described above, when the degree of superheat is 25 degrees Celsius compared to the degree of superheat 0 degrees Celsius, the operating range of the high temperature switch that stops the operation of the compressor when the discharge gas temperature becomes, for example, 100 degrees Celsius or higher, is: In relation to the compressor stop setting temperature, the upper limit of the condensing temperature is low, that is, when the degree of superheat is 0°C,
The upper limit of condensation temperature is (Tc1), whereas 25℃
When the degree of superheating is reached, the upper limit value decreases to (T c 2). If the degree of superheat is set to a predetermined degree of superheat in this way, the operating temperature range of the compressor, that is, the operating range of the compressor is limited in accordance with the degree of superheat, and the operation of the condenser in a high temperature range is restricted. There have been problems such as insufficient heat recovery when heat recovery operation is required.

The present invention was created in view of the above problems, and its purpose is to maintain the degree of superheat constant until the discharge gas temperature reaches the set stop temperature of the compressor, and to maintain a constant degree of superheating until the discharge gas temperature reaches a predetermined temperature close to the set stop temperature. The object of the present invention is to provide a refrigeration system that can expand the operating range of a compressor by controlling the degree of superheat to a small value and maintaining the discharge gas temperature at the predetermined temperature.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a compressor (1).
, comprising a condenser (2), an expansion mechanism (3), and an evaporator (4), and a high-pressure liquid section between the condenser (2) and the expansion mechanism (3) is provided with a compressor in the compressor (1). Refrigeration a connected to the liquid injection scene piping (5) that communicates with the process section
In g, the liquid injection pipe (5)
An electric expansion valve (6) is interposed in the middle of the compressor (1), and a temperature detector (7) for detecting the discharge gas temperature and a pressure detector (8) for detecting the discharge gas pressure are installed on the discharge side of the compressor (1). ), and the degree of superheating of the discharged gas is calculated based on the detection results from each of these detectors (7) and (8), and the degree of superheating of the discharged gas is set at a constant superheating degree in the expansion valve (6). When the opening command is output so that the temperature of the discharge gas rises to a predetermined temperature close to the stop temperature of the compressor (1), the discharge gas temperature does not exceed the predetermined temperature. The present invention is characterized by being provided with a superheat degree controller (9) that outputs an opening command for increasing the opening degree of the electric expansion valve (6) so that the opening degree of the electric expansion valve (6) is increased.

(Function) The discharge gas temperature and pressure from the compressor (1) are detected by each of the detectors (7) and (8), and a command from the superheat degree controller (9) is issued based on the detection results. The opening degree of the electric expansion valve (6) is controlled, that is, until the discharge gas temperature reaches a predetermined temperature near the stop temperature of the compressor (1), a constant degree of superheat is imparted to the discharge gas, By applying this constant degree of superheating, refrigeration operation can be performed in a well-balanced manner without decomposing the oil in the compressor (1) or reducing the refueling capacity due to refrigerant dissolving into the oil. Furthermore, when the discharge gas temperature rises and reaches a predetermined temperature close to the stop set temperature, the degree of superheating is controlled to be small and the discharge gas temperature is maintained at the predetermined temperature over a certain range. Therefore, the upper limit of the condensing temperature becomes large, and the operating range of the compressor (1) is expanded.

(Example) The refrigeration system shown in Fig. 1 includes a condenser (2) and a temperature-sensitive expansion mechanism (3) on the refrigerant discharge side of a screw compressor (1).
and the evaporator (4) are connected in sequence, and the temperature sensing tube (3a) of the expansion mechanism (3) is connected to the evaporator (4).
The expansion mechanism (3) is arranged on the discharge side of the thermosensor (3a), and the expansion mechanism (3) is controlled to open and close based on the detection result of the thermosensor (3a). A liquid injection pipe (5) leading to the refrigerant compression process section of the compressor (1) is connected to the high pressure liquid section of the compressor (1).

The compressor (1) has a screw rotor (11) inside.
and a compressed refrigerant discharge chamber (
12), an oil reservoir chamber (13) is formed at the bottom of the discharge chamber (12), and the rotor (11), etc. is supplied from this oil reservoir chamber (13) via an oil supply pipe (not shown). At the same time, the tip of the liquid injection pipe (5) is made to face the rotor (11), and the high pressure liquid refrigerant from this pipe (5) is injected into the rotor (11). , the degree of superheating of the discharged gas is always kept constant.

Therefore, in the above refrigeration system, an electric expansion valve (6) is interposed in the middle of the liquid injector piping (5), and in the discharge chamber (12) of the compressor (1),
A temperature detector (7) for detecting the discharge gas temperature and a pressure detector (8) for detecting the discharge gas pressure are respectively provided, and each of these detectors (7) and (8) is connected to a superheat degree controller ( 9
), the controller (9) calculates the degree of superheating of the discharged gas based on the detection results of the respective detectors (7) and (8),
Based on this calculation result, an opening command is output to the expansion valve (6) so that the degree of superheating of the discharged gas always remains constant, and when the temperature of the discharged gas reaches a certain value, the operation of the compressor (1) is stopped. The operating range of the high temperature switch, that is, the compressor (1)
When the temperature rises to a predetermined temperature close to the set stop temperature of the motor-driven expansion valve ( 6) is configured to output an opening degree command that increases the opening degree.

Specifically, as shown in FIG. 2, a central processing unit of a computer is used as the superheat degree controller (9), and the temperature detector (7) and the temperature detector (7) are connected to the input side of the controller (9). A pressure detector (8) is connected to the output side of the controller (9), and the electric expansion valve (6) is connected to the output side of the controller (9).
The opening degree of the electric expansion valve (6) is adjusted by an output signal from the controller (9).

Next, the electric expansion valve (8) is operated by the superheat degree controller (9).
) will be explained based on FIG. This third
In the figure, the vertical axis is the discharge gas temperature (similar to Figure 6 above).
Td) is plotted on the horizontal axis, and the saturated condensation temperature (T
A graph of the relationship between Td-Tc and the degree of superheat obtained by taking c) is shown. In the same figure, the straight line (A) is for the case where the degree of superheat is 0°C as in the case of Fig. 6, while the line (C) is for the above-mentioned straight line. In the case where the degree of superheat is set to 25° C. with respect to (a), the discharge gas temperature is shown when the degree of superheat is controlled by the controller (9).

As is clear from the line (c) in Figure 3, the discharge gas temperature is
The opening degree of the electric expansion valve (6) is adjusted by the controller (9) until the compressor (1) reaches a predetermined temperature (for example, 95°C) near the stop temperature (for example, 100°C). , the discharged gas is always kept at a constant degree of superheat (25°C),
By applying this constant degree of superheat, the compressor (
Refrigeration operation is performed in a well-balanced manner without decomposing the oil in the oil tank or reducing the refueling capacity due to refrigerant dissolving into the oil.
5°C), the opening degree of the electric expansion valve (6) is greatly controlled by a command from the controller (9), and the degree of superheat is lower than the set superheat degree (25'C), for example, 10'C. As a result, the discharge gas temperature is maintained at the predetermined temperature, that is, on the 95° C. line, over a certain range, and therefore, the upper limit of the condensation temperature (Tc) is increased compared to the conventional method. That is, in the case of FIG. 6, the upper limit of the condensation temperature was (Tc2), but the upper limit of the condensation temperature was (Tc3).
) is increased to nearly the upper limit value (Tc 1) when the degree of superheat is 0°C, and the operating temperature range of the compressor (1), that is, the operating range of the compressor (1) is expanded. . Note that the degree of superheat to be controlled is not limited to the above-mentioned 10''C, but may be a degree of superheat lower than that.

Next, the operation of the refrigeration system configured as above will be explained based on the flowchart shown in FIG. 4.

First, with the start of operation (step 1), the temperature detector (7) and the pressure detector (8) detect the discharge gas temperature (Td) and the discharge pressure (Pc), and the controller (9) detects the discharge gas temperature (Td) and the discharge pressure (Pc). (Step 2), and then, in Step 3, the controller (9) determines whether the discharge gas temperature (Td) is equal to or higher than the predetermined temperature (95°C), and if no That is, if the discharge gas temperature (Td) has not yet reached 95° C., the discharge pressure (Pc) of the discharge gas is converted to the equivalent saturation condensation temperature (Tc) (step 4), and
Based on the discharge gas temperature (Td) and condensation temperature (Tc), the controller (9) calculates the degree of superheat (SH) (step 5), and further, in step 6, the degree of superheat (SH) is calculated by the controller (9).
) is 25°C or higher, and if the answer is yes, that is, the degree of superheat (S H) has reached 25°C or higher, an open signal is sent to the expansion valve (6) in step 7. Output and said liquid inject scene piping (
5) supplies liquid refrigerant to the compressor (1) and is controlled to reduce the degree of superheating.After this, after waiting for a response from the system (step 8), in step 9,
It is determined whether or not the vehicle is in operation. If yes, the process returns to step 2; if no, the control is terminated in step 10. In addition, in the case of YES in step 3, that is, if the discharge gas temperature (Td) has reached 95°C or higher, step 1
1, an open signal is output to the expansion valve (6), and the compressor (1) is output from the liquid injection pipe (5).
) is supplied with liquid refrigerant and controlled to lower the degree of superheat and discharge gas temperature, and further, if the answer in step 6 is NO, that is, if the degree of superheat (SH) is 25° C. or less In step 12, a close signal is output to the expansion valve (6) to restrict the supply of liquid refrigerant from the liquid injection pipe (5) to the compressor (1), thereby reducing the degree of superheating. High predetermined superheat setting (25@C)
After the above steps 11 and 12 are completed, the control from step 8 is performed.

(Effects of the Invention) As explained above, in the refrigeration system of the present invention, the electric expansion valve (6
), a temperature detector (7) and a pressure detector (8) are provided on the discharge side of the compressor (1), and the detection results from each of these detectors C7) and (8) are calculates the degree of superheat of the discharged gas, outputs an opening command to the expansion valve (6) so that the degree of superheat of the discharged gas becomes a constant degree of superheat, and
When the discharge gas temperature rises to a predetermined temperature close to the set stop temperature of the compressor (1), the electric expansion valve (6 ) is provided, so that the operating temperature range of the compressor (1), that is, the operating range of the compressor (1) can be expanded. This not only makes it possible to operate the condenser (2) in a high temperature range, but also enables sufficient heat recovery when performing heat recovery operation.

[Brief explanation of the drawing]

FIG. 1 is a piping diagram of a refrigeration system according to the present invention, FIG. 2 is a control block diagram for controlling the refrigeration system, and FIG. 3 is a graph showing the relationship between discharge gas temperature Td, condensation temperature Tc, and degree of superheat. FIG. 4 is a flowchart explaining the control mode of the refrigeration system, FIG. 5 is a piping diagram showing the conventional refrigeration system, and FIG.
The figure shows the discharge gas temperature Td and condensation temperature T of the same refrigerated VTLF.
It is a graph which shows the relationship between c and superheat degree. (1) --- Compressor (2) Condenser (3) Restrictive expansion mechanism (4) Fist/evaporator (5) Liquid injection piping (6)・
...Electric expansion valve (7) ...Temperature detector (8) ...Pressure detector (9) ...Superheat degree controller Fig. 3 Condensation 6 temperature/k ( TO Fig. 1 4-layer generator 3-layer (Zhangfanchiang Fig. 4

Claims (1)

[Claims] 1) Comprising a compressor (1), a condenser (2), an expansion mechanism (3), and an evaporator (4), the condenser (2) and the expansion mechanism (3)
), a liquid injection pipe (5) that communicates with the compression process section of the compressor (1).
In the refrigeration system, an electric expansion valve (8) is interposed in the middle of the liquid injection pipe (5), and a temperature detector (8) is installed on the discharge side of the compressor (1) to detect the discharge gas temperature. 7) and a pressure detector (8) for detecting the discharge gas pressure.
The degree of superheat of the discharged gas is calculated based on the detection result from (8), and an opening degree command is output to the expansion valve (6) so that the degree of superheat of the discharged gas becomes a constant degree of superheat, and When the discharge gas temperature rises to a predetermined temperature close to the set stop temperature of the compressor (1), the electric expansion valve (6) is configured such that the discharge gas temperature reaches a degree of superheat that does not exceed the predetermined temperature. A superheat degree controller (9) that outputs an opening degree command to increase the opening degree of
).