JPH0384366A - Freezing device - Google Patents

Abstract

PURPOSE:To prevent the unnecessary stop of running of a compression and to reliably prevent the occurrence of a damage accident of the compressor by providing an operation controller which outputs a command to stop the compressor when the degree of overheat of discharge gas is an abnormal value and the temperature of discharge gas is abnormally high. CONSTITUTION:The temperature and the pressure of discharge gas are detected by a temperature detector 6 and a pressure detector 7 and based on the detecting results, the degree of overheat is computed by an operation controller 8. When the computed degree of overheat is increased to an abnormal value exceeding a given value and a discharge gas temperature is increased to an abnormal value, a stop command is outputted from the operation controller 8 to stop a compressor 1. In a case except the above, operation of the compres sor 1 is continued. Based on a computing result of the degree of overheat, an opening command is outputted from an opening output part 81 of the opera tion controller 8 to a motor-operated expansion valve 52 of a degree of over heat control mechanism 5. A liquid refrigerant is injected to the compression process part of the compressor 1 from a liquid injection piping 51 to control the degree of overheat of discharge gas to a specified value.

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). (D)
are sequentially connected, and a liquid injection pipe (E) leading to the screw rotor (a) of the compressor (A) is connected to the high-pressure liquid section between the condenser (B) and the expansion mechanism (C). , a temperature-sensitive expansion valve (
F), and the expansion valve (F) is connected to the discharge side of the compressor (A) via a pressure equalization pipe (G), while a temperature sensor (f) of the expansion valve (F) is connected to the discharge side of the compressor (A). is arranged on the discharge side of the compressor (A), and the discharge gas pressure from the pressure equalization pipe (G) and the discharge gas temperature detected by the temperature detector (f),
By controlling the opening degree of the expansion valve (F), the piping (E)
By injecting liquid refrigerant into the screw rotor (a), the degree of superheat of the discharged gas is always kept constant. The reason for maintaining the degree of superheat 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 refrigerant is supplied to the refueling point of the compressor (A), a flash will occur, resulting in a reduction in the refueling capacity.

In addition, the above compressor (A) usually operates when the discharged gas reaches an abnormally high temperature (for example, 100°C or higher).
A temperature detector (H) for emergency stop of the compressor (A) is separately provided, and the temperature detector (H) is used to prevent damage accidents due to abnormally high temperature of the compressor (A). There is.

(Problem to be Solved by the Invention) The above-described refrigeration apparatus includes a temperature detector (H) that makes an emergency stop of the compressor (A) when the discharged gas is at an abnormally high temperature;
Since the temperature sensor (f) for controlling the degree of superheating of the discharged gas is used, the structure is not only complicated but also costly. (A), it is formed with high precision and has good response characteristics. On the other hand, the temperature detector (f) for controlling the degree of superheating eliminates hunting etc. of the expansion valve (F). Therefore, as shown in Figure 3, which will be described later, the engine is operated in an operating range where the degree of superheating can be controlled, for example, with a degree of superheating of 25°C. When the pressure of the discharged gas temporarily increases by 1 even though the pressure is high, for example, when a sudden pressure increase occurs as shown in peak (a) in the same figure, the detector (f) Prior to the opening degree control of the expansion valve (F), the emergency temperature detector (H) is activated, and even though the compressor (A) is operating within a controllable operating range,
This causes the system to stop. Furthermore, when the discharge gas pressure is low and the expansion valve (F) is uncontrollable, or when the amount of refrigerant is insufficient, even if the discharge gas temperature has not reached the abnormally high temperature, If the operation continues, the compressor (A) may be damaged.

The present invention was made in view of the above-mentioned problems, and its purpose is to eliminate unnecessary suspension of operation of the compressor, and to reliably prevent damage accidents to the compressor. The object of the present invention is to provide a refrigeration system that can be manufactured at a low cost.

(Means for Solving the Problems) In order to achieve the object 1, the present invention provides a compressor (1
), in which the compressor (1) is provided with one temperature detector (1) for detecting the temperature of the discharged gas. 6) and one pressure detector (7) for detecting the discharge gas pressure, and these detectors (6) (7)
The degree of superheating of the discharged gas is calculated based on the detection results from the compressor (1), and when this degree of superheating is an abnormal degree of superheating that is higher than the constant degree of superheating, or when the temperature of the discharged gas is abnormally high, the compressor (1) is stopped. It is characterized by being provided with an operation controller (8) that outputs commands.

The superheat degree control mechanism (5) includes a liquid injection pipe (51) that injects liquid refrigerant into the compression process section of the compressor (1), and an electric expansion valve (52) interposed in the middle of this pipe (51). The operation controller (8) also includes a temperature detector (6) and a pressure detector (7).
The expansion valve is provided with an opening degree output section (81) that outputs an opening degree command to the expansion valve (52) so that the degree of superheating calculated based on the detection result from the expansion valve (52) becomes a constant degree of superheating.

(Function) The temperature and pressure of the discharge gas are detected by the temperature detector (6) and the pressure detector (7), and based on the detection results, the operation controller (8) controls the overheating of the discharge gas. degree is calculated, and when the calculated degree of superheat becomes an abnormal degree of superheat equal to or higher than a predetermined degree, and when the discharge gas temperature becomes an abnormally high temperature, a stop command is output from the operation controller (8). At other times, the compressor (1) is stopped, and at other times, the compressor (1) continues to operate. Furthermore, based on the calculation results of the degree of superheat by each of the detectors (6) and (7), the electric expansion valve of the degree of superheat control mechanism (5) is transmitted from the opening degree output section (81) of the operation controller (8). An opening command is output to (52), and the liquid injection pipe (51
) is injected into the compression process section of the compressor (1), and the degree of superheat of the discharged gas is controlled to be constant.

(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 placed 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 temperature-sensitive tube (3a). A superheat degree control mechanism (5) for controlling the superheat degree of the discharged gas to a constant superheat degree is disposed between the liquid section and the compressor (1).

The compressor (1) has a screw rotor (11) inside.
and a compressed refrigerant discharge chamber (for example) of the rotor (11).
12), an oil reservoir chamber (13) is formed at the bottom of the discharge chamber (12), and the oil reservoir chamber (13) is connected to the rotor (11) via an oil supply pipe (not shown). At the same time, by injecting high-pressure liquid refrigerant from the superheat degree control mechanism (5) into the rotor (11), the degree of superheat of the discharged gas is always maintained at a constant degree of superheat. There is.

Therefore, in the above refrigeration apparatus, the compressor (1)
In the discharge chamber (12), one temperature detector (6) for detecting the discharge gas temperature and one pressure detector (7) for detecting the discharge gas pressure are arranged, and each of these detection Connect the devices (8) and (7) to the operating level controller (8),
Based on the detection results from each of the detectors (6) and (7), the controller (8) calculates the degree of superheating of the discharged gas, and this degree of superheating is greater than the constant degree of superheating controlled by the control mechanism (5). When the degree of superheat is abnormally high and when the discharge gas temperature is abnormally high, the controller (8) outputs a stop command to the compressor (1) to stop the compressor (1). .

Further, the superheat degree control mechanism (5) is configured to control the condenser (2).
and the expansion mechanism (3) from the high pressure liquid section between the compressor (1) and the expansion mechanism (3).
It consists of a liquid injection pipe (51) for injecting liquid refrigerant into the screw rotor (11), and an electric expansion valve (52) interposed in the middle of the pipe (51). ), the electric expansion valve (
52) is provided with an opening output section (81) that outputs an opening command.

Specifically, as shown in FIG. 2, a central processing unit of a computer is used as the operating level controller (8), and the temperature detector (6) and the temperature detector (6) are connected to the input side of the controller (8). The pressure detector (7) is connected to the controller (8).
An electric expansion valve (52) is connected to the output side of the opening output section (81), and the detection results from each of the detectors (8) and (7) are calculated by the controller (8). The degree of superheating
Outputting a command from the output section (81) of the controller (8) to the expansion valve (52) so that the degree of superheat is constant;
The opening degree of the expansion valve (52) is adjusted, and the compressor (52) is connected to the output side of the controller (8).
1) is connected, and when the degree of superheat calculated by the controller (8) is an abnormal degree of superheat higher than the constant degree of superheat, and when the discharge gas temperature is abnormally high, the controller (8) ) outputs a stop command to the motor switch of the compressor (1) to stop the compressor (1).

Next, the control mode by the above operation controller (8) is changed to the third mode.
This will be explained based on the diagram. This Figure 3 shows a graph of the relationship between Td-Tc and degree of superheat, with the vertical axis representing the discharge gas temperature (Td) and the horizontal axis representing the saturated condensing temperature (Tc) corresponding to the discharge pressure. , the straight line (a) is when the superheat degree is O''C, and the straight line (b) is 25°C with respect to the above straight line (a).
If we take the superheat degree of
The discharge gas temperature is shown when the degree of superheating is 45°C for (a).

Therefore, in the refrigeration system, as shown by the straight line (b) in FIG. The degree of opening of the electric expansion valve (52) is adjusted in the device (8) to always give a constant degree of superheat (25°C) to the discharged gas, and by giving this constant degree of superheat, the compressed gas Refrigeration operation is performed in a well-balanced manner without decomposing the oil in the machine (1) or reducing the refueling capacity due to refrigerant dissolving in the oil.
When operating at °C, 45 °C as indicated by the straight line (c) above
When the superheat suddenly rises to the abnormal superheat range of
Further, when the discharge gas temperature rises to the abnormally high temperature range (100'C), a stop command is output from the controller (8) to the compressor (1), and the compressor (1) The operation of the controller (8) is stopped, and at other times, the controller (8
) The compressor (1) continues to operate while the opening degree of the expansion valve (52) is adjusted based on the opening degree command from the compressor (1).

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 (6) and the pressure detector (7) detect the discharge gas temperature (Td) and the discharge pressure (Pc), and the controller (8) detects the discharge gas temperature (Td) and the discharge pressure (Pc). (Step 2), and then, in Step 3, the controller (8) determines whether the discharge gas temperature (Td) is equal to or higher than the abnormally high temperature (100"C), and the answer is NO. In other words, if the discharge gas temperature (Td) has not yet reached 100°C, the discharge pressure (Pc) of the discharge gas is converted to the equivalent saturation condensation temperature (Tc) (step 4), and the discharge gas temperature Based on the condensation temperature (Td) and the condensation temperature (Tc), the controller (8) calculates the degree of superheat (SH) (step 5), and further, in step 6, the degree of superheat (SH)
It is determined whether or not H) has an abnormal superheat degree of 45°C or less,
If the answer is YES, that is, if the degree of superheat (SH) is 45°C or less, it is determined in step 7 whether or not the degree of superheat (SH) is less than a predetermined degree of superheat of 25°C. In this case, that is, when the degree of superheat (SH) has reached 25° C. or higher, an open signal is output to the expansion valve (52) in step 8, and the compressor ( 1), the superheating degree is controlled to be lowered and the superheating degree is maintained at a predetermined set superheating degree (25°C).After this, the system waits for a response (step 9). After that, step 1
At step 0, it is determined whether or not the vehicle is in operation. If yes, the process returns to step 2; if no, the control ends at step 11.

Further, in the case of YES in the step 3, that is, if the discharge gas temperature (Td) has reached 100° C. or higher, in the step 12, the compressor (1)
A stop signal is output to stop the operation.Furthermore, if the answer in step 6 is NO, that is, the degree of superheat (SH
) is 45°C or higher, a stop signal is output to the compressor (1) to stop operation in step 13, and if no in step 7,
In other words, if the degree of superheating (SH) is 25°C or less,
In step 14, the supply of liquid refrigerant from the liquid injection pipe (5) to the compressor (1) is restricted, the degree of superheat is increased, and the degree of superheat is controlled to be maintained at the set degree of superheat (25°C), and the above After steps 12 and 13 and step 4 are completed, the control from step 9 is performed.

(Effects of the Invention) As explained above, in the refrigeration system of the present invention, the compressor (
1), one temperature detector (6) is installed to detect the discharge gas temperature.
) and one pressure detector (7) that detects the discharge gas pressure, and calculates the degree of superheat of the discharge gas based on the detection results from these detectors (6) and (7), and calculates the degree of superheat. Since the compressor (1) is provided with an operation controller (8) that outputs a stop command to the compressor (1) when the degree of superheat is higher than a certain degree of superheat and when the discharge gas temperature is abnormally high temperature.
This makes it possible to eliminate unnecessary shutdowns of the compressor (1), reliably prevent damage to the compressor (1), and reduce costs.

In other words, the superheat degree control mechanism (5) includes a liquid injection pipe (51) for injecting liquid refrigerant into the compression process section of the compressor (1), and this pipe (5).
1) using an electric expansion valve (52) interposed between The expansion valve (52)
By providing an opening degree output section (81) that outputs an opening degree command, it is possible to control the degree of superheat to a certain degree with good response, improve the controllability, and solve the problem of the conventional example due to control delay. This eliminates unnecessary stoppage of the compressor, and also prevents damage to the compressor in the event that the degree of superheat cannot be controlled or the amount of refrigerant is insufficient.

[Brief explanation of drawings]

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, and FIG. 5 is a piping diagram showing the conventional refrigeration system. (1)...Compressor (5)...Superheat control mechanism (51)...Liquid injection piping (52)
...Electric expansion valve (6) ...Temperature detector (7) ...Pressure detector (8) ...Operation controller (81) ...Opening output Unexamined Japanese Patent Publication No. 3 84366 (7)

Claims (1)

[Claims] 1) In a refrigeration system equipped with a superheat degree control mechanism (5) that controls the superheat degree of discharged gas discharged from a compressor (1) to a constant superheat degree, the compressor (1) includes: One temperature detector (6) for detecting the discharge gas temperature and one pressure detector (7) for detecting the discharge gas pressure are provided, and the detection results from these detectors (6) and (7) are an operation controller that calculates the degree of superheating of the discharged gas and outputs a stop command to the compressor (1) when the degree of superheating is an abnormal degree of superheating higher than the constant degree of superheating or when the temperature of the discharged gas is abnormally high; A refrigeration device characterized by providing (8). 2) The superheat degree control mechanism (5) includes a liquid injection pipe (51) that injects liquid refrigerant into the compression process section of the compressor (1), and an electric expansion valve (52) interposed in the middle of the pipe (51). ). The refrigeration system according to claim 1, further comprising an opening output section (81) that outputs an opening command to the expansion valve (52).