JPH03267656A - Freezer - Google Patents

Abstract

PURPOSE:To control overheating degree with high precision at a low cost by a compact system by a method wherein a discharge temperature sensor detects the temperature of refrigerant delivered from a compressor and controls the opening degree of an electric expansion valve so as to make the refrigerant delivery temperature come up to a desired level. CONSTITUTION:An outdoor heat exchanger 3 and a room heat exchanger 5 are provided respectively with temperature sensors 10 and 11, and detection signals from these sensors 10 and 11 and a detection signal from an outdoor air temperature sensor 12 are input into a desired delivery temperature setting means 21. The means 21 calculates a desired delivery temperature corresponding to, for example, a condensation temperature measured by the temperature sensors 10 and 11 based on a desired delivery temperature calculation table for every operation frequency Hf. On the other hand, a delivery piping 1a is provided with a delivery temperature sensor 13 which detects refrigerant delivery temperature. The refrigerant delivery temperature and the desired delivery temperature are input into an opening degree controlling means 22, which has a function to adjust the opening degree of an electric expansion valve 4 so as to make the refrigerant delivery temperature come up to the desired level.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a refrigeration system having an electric expansion valve for controlling the degree of superheat.

(Prior art) In a refrigeration system that is constructed by connecting a condenser, an electric expansion valve, and an evaporator to a compressor with variable compression capacity, it is important to ensure the capacity of the refrigeration system and improve compressor reliability by refluxing liquid refrigerant. To prevent deterioration, the degree of superheat (S) of the refrigerant is adjusted by adjusting the opening degree of the electric expansion valve.
, H,) has been conventionally practiced. In the first conventional example of superheat degree control, a bypass circuit having a capillary tube is provided in the refrigerant circuit to detect the evaporation saturation temperature of the refrigerant, and the suction temperature of the compressor is detected, and the suction temperature and the evaporation saturation temperature are detected. Based on this, the degree of superheating is determined and the opening degree of the electric expansion valve is controlled to keep the degree of superheat within a predetermined range.

In addition, in the second conventional example, Utility Model Application Publication No. 59-79777, if conditions such as the internal and external temperatures and the amount of air blown to the condenser and evaporator are constant, the discharge temperature of the refrigerant can be estimated from the operating frequency of the compressor. Therefore, the above degree of superheating can be achieved by determining the target discharge temperature of the refrigerant from the operating frequency of the compressor and adjusting the opening degree of the electric expansion valve so that the discharge temperature from the compressor reaches the determined target discharge temperature. was under control.

(Problems to be Solved by the Invention) However, in the first conventional example, the structure is complicated, such as the need to provide a bypass circuit, and there are problems in that the cost and space required increase. Not suitable for

In addition, in the second conventional example, the target discharge temperature is determined only by the operating frequency of the compressor, so for example, if the amount of air blown to the condenser fluctuates and the condensing pressure changes, the amount of air blown to the evaporator changes. or when the outside temperature changes, the discharge temperature of the refrigerant also changes, and there is a problem that it is not possible to set an accurate target discharge temperature to obtain a constant degree of superheat using only the above operating frequency.

This invention was made to solve the above-mentioned conventional problems, and its purpose is to provide a refrigeration system that is inexpensive, compact, and highly accurate in controlling the degree of superheating by adjusting the opening of an electric expansion valve. An object of the present invention is to provide a refrigeration device that can control the degree of superheat.

(Means for Solving the Problems) Therefore, the refrigeration system of the present invention is a refrigeration system comprising a variable compression capacity compressor 1, a condenser 3, an electric expansion valve 4, and an evaporator 5 connected to it. Compression capacity grasping means 20 grasps the compression capacity If of the compressor 1, detects the condensation temperature Tc in the condenser 3, the evaporation temperature Te in the evaporator 5, and the outside temperature T (all of which are detected). Temperature sensor 10.11
．． 12, target discharge temperature setting means 21 for setting a target discharge temperature of the refrigerant discharged from the compressor 1 based on the compression capacity Hf and the detected temperature Tc, and detecting the refrigerant discharge temperature TO from the compressor 1. It is equipped with a discharge temperature sensor 13 and an opening degree control means 22 that controls the opening degree of the electric expansion valve 4 in order to bring the refrigerant discharge temperature To closer to the target discharge temperature Tll1.

(Function) In the refrigeration system of the present invention having the above configuration, the refrigerant discharged from the compressor 1 is first condensed in the condenser 3, then reduced in pressure by the electric expansion valve 4, and evaporated in the evaporator 5. Return flow to In such an operating state of the refrigeration system, for example, the temperature sensor 10 detects the condensing temperature Tc of the condenser 3, and the target temperature setting means 21 calculates the detected temperature Tc and the compression capacity of the compressor 1 from the compression capacity grasping means 20. A target discharge temperature TII+ of the discharge refrigerant is set based on Hf. On the other hand, the discharge temperature sensor 13 indicates the discharge refrigerant temperature T from the compressor 1.
.

Detect. The opening control means 22 controls the electric expansion valve 4 so that the discharge refrigerant temperature To approaches the target discharge temperature Tm.
The degree of superheating is controlled by controlling the degree of opening.

(Example) Next, a specific example of the refrigeration apparatus of the present invention will be described in detail with reference to the same page.

In FIG. 2 showing the case where the present invention is applied to an air conditioner, this air conditioner has an outdoor unit X and an indoor unit Y.
A discharge pipe 1a and a suction pipe 1b of the compressor 1 are connected to a refrigerant pipe 9 via a four-way switching valve 2. An outdoor heat exchanger 3, an electric expansion valve 4, a closing valve 6, an indoor heat exchanger 5, and a closing valve 7 are sequentially installed in this refrigerant pipe 9. Further, an accumulator 15 is interposed in the suction pipe 1b. Further, the outdoor unit X is provided with an outdoor fan 16, and the indoor unit Y is provided with an indoor fan 1.
7 is provided.

Each of the outdoor heat exchanger 3 and the indoor heat exchanger 5 is provided with a temperature sensor 10.11, and the detection signal of these temperature sensors 10.11 and the detection signal of the outside air temperature sensor 12 are determined by the target discharge temperature. It is input into the setting means 21. Also connected to the compressor 1 is a compression capacity grasping means 20 that grasps the compression capacity of the compressor 1 by detecting the operating frequency Hf of the compressor 1. Hf, the opening control means 22
and is output to the target discharge temperature setting means 21. Then, the target discharge temperature setting means 21 sets the condensing temperature Tc measured by the temperature sensor 10 or 11 for each operating frequency If based on the target discharge temperature calculation table shown in FIG. 4 during heating and FIG. 5 during cooling. The target discharge temperature T- corresponding to the target discharge temperature T- is calculated. On the other hand, a discharge temperature sensor 13 is attached to the discharge pipe 1a, and the discharge temperature sensor 13 detects the refrigerant discharge temperature To. The refrigerant discharge temperature To and the target discharge temperature Tm are input to the opening degree control means 22, and the opening degree control means 22 controls the refrigerant discharge temperature T.
.

It has a function of adjusting the opening degree of the electric expansion valve 4 so that the temperature approaches the target discharge temperature Tm.

The control block with the above configuration is explained with reference to FIG.
In step S1, the operating frequency Hf, condensing temperature Tc, evaporation temperature Te, and outside air temperature T are detected, in step S2 the target discharge temperature Ts+ is calculated, and on the other hand, in step S3, the discharge refrigerant temperature To is detected. and discharge refrigerant temperature T.

In order to bring the temperature closer to the target discharge temperature TII+, step S
Step S4 controls the opening degree of the electric expansion valve 4, and step S5 controls the degree of superheating of the refrigerant in the air conditioner.

Next, to explain the operating state of the above-mentioned air conditioner during heating operation, first, the four-way switching valve 2 is switched opposite to the state shown in FIG. 2 to flow the refrigerant in a counterclockwise direction. is condensed in the indoor heat exchanger 5, which functions as a condenser, and evaporated in the outdoor heat exchanger 3, which functions as an evaporator, and is returned to the compressor 1. Then, superheat degree control during heating operation will be explained with reference to the flowchart in FIG. (YES)
Proceeding to step Sll, the compression capacity grasping means 20 inputs the operating frequency Hf of the compressor 1 to the opening control means 22. Then, in step 512, the opening control means 22 reads the number of pulses corresponding to the operating frequency Hf from the table of operating frequency Hf and the number of pulses, and outputs the corresponding number of pulses to the electric expansion valve 4 in the next step S13. Then, the opening degree of the electric expansion valve 4 is adjusted. On the other hand, when it is determined that the transition period is not in step SIO (NO), the process proceeds to step S14 and subsequent steps. The outside air temperature T and the condensing temperature Tc from the temperature sensor 10 are input to the target discharge temperature setting means 21 in steps 515 and S16. and step 517
, the target discharge temperature setting means 21 sets the operating frequency I of the compressor 1.
f, depending on the condensing temperature Tc and the outside air temperature T, the optimal target discharge temperature Tm at that time, that is, the discharge temperature Ta+ at which the optimal degree of superheating is obtained on the Mollier diagram, is determined using the table shown in FIG. 4 above. Calculated based on. In this case, a plurality of the above tables may be provided for each outside temperature T, or
Alternatively, the temperature read from the table as described above may be corrected according to the outside temperature T. And step S18
After the discharge temperature sensor 13 detects the discharge temperature To at
The process advances to step S19. In step S19, the electric expansion valve 4 for bringing the discharge temperature To closer to the target discharge temperature Tm
It is determined whether or not the opening adjustment pulse is included in the preset upper and lower limit ranges of the number of pulses, and if it is included (YES), the process proceeds to step 513, and the above A number of pulses corresponding to the temperature difference are output, and the same control is repeated thereafter to perform control such that the discharge temperature To from the compressor 1 approaches the target discharge temperature Tl1l.

In the above air conditioner, the temperature sensor 10.12 detects the condensing temperature Tc of the indoor heat exchanger 3 and the outside air temperature T,
Since the target temperature setting means 21 sets the target discharge temperature Tl11 of the discharged refrigerant based on the detected condensation temperature Tc, the outside air temperature T, and the compressor operating frequency If from the compression capacity grasping means 21, the operation can be performed as in the conventional manner. Compared to the case where the target discharge temperature Tm is set based only on the frequency Hf, the refrigerant superheat degree can be controlled with high accuracy.

Further, the opening degree adjustment of the electric expansion valve 4 is not limited to the control process shown in FIG.
This is also possible by omitting the control process shown in FIG. 8 or FIG. 8, that is, by omitting the detection of the outside air temperature T (FIG. 7) or by omitting the detection of the condensation temperature Tc (FIG. 8). Each of these processes can also be applied during cooling operation, and the target discharge temperature Tm may be calculated based on the table shown in FIG. 5 during cooling operation. Further, although a detailed explanation is omitted, the same degree of superheat control can be performed without using the condensing temperature Tc and the outside air temperature T as described above, or by using the evaporation temperature Te together with these.

Although specific embodiments of the refrigeration system of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented with various modifications within the scope of the present invention. For example, in the above embodiment, the case where the present invention is applied to an air conditioner is exemplified, but the present invention can also be applied to other refrigeration equipment.

Further, the temperature sensor may be any sensor that measures at least one of condensation temperature, evaporation temperature, and outside air temperature.

(Effects of the Invention) As described above, the refrigeration system of the present invention does not require bypass piping for detecting the degree of superheat, and can use an existing temperature sensor, so the structure is simple, inexpensive, and While the refrigeration system can be configured compactly, a temperature sensor detects, for example, the condensing temperature, and the target discharge temperature of the discharged refrigerant is set based on the detected temperature and the compression capacity of the compressor, so the compression function is not as high as the conventional one. The degree of superheating of the refrigerant can be controlled with high accuracy compared to the case where the target discharge temperature is set solely based on the temperature.

[Brief explanation of drawings]

Fig. 1 is a functional block diagram showing the overall configuration of this invention, Fig. 2 is a piping system diagram of an air conditioner according to an embodiment of this invention, and Fig. 3 is a control block for controlling the opening of an electric expansion valve. Figure 4 is a schematic diagram of a table of target discharge temperature during heating, Figure 5 is a diagram of a table of target discharge temperature during cooling, and Figure 6.
FIGS. 7 and 8 are flowcharts showing the control process, respectively. 1...Compressor, 3...Outdoor heat exchanger, 4...Electric expansion valve, 5...Indoor heat exchanger, 10.11.12...
・Temperature sensor, 13...Discharge temperature sensor, 20...
Compression capacity grasping means, 21...Target discharge temperature setting means,
22...Opening degree control means.

Claims (1)

[Claims] 1. A variable compression capacity compressor (1), a condenser (3),
A refrigeration system comprising an electric expansion valve (4) and an evaporator (5) connected to each other, comprising a compression capacity determining means (20) for determining the compression capacity (Hf) of the compressor (1), and the condenser. (3)
condensation temperature (Tc) at evaporator (5), evaporation temperature (Tc) at evaporator (5)
e), a temperature sensor (10) (11) (12) that detects at least one of the outside air temperatures (T), and a compressor (10) based on the compression capacity (Hf) and detected temperature (Tc).
a target discharge temperature setting means (21) for setting a target discharge temperature of the refrigerant discharged from the compressor (1); a discharge temperature sensor (13) for detecting the refrigerant discharge temperature (To) from the compressor (1); A refrigeration system comprising an opening control means (22) for controlling the opening of the electric expansion valve (4) in order to bring the discharge temperature (To) closer to the target discharge temperature (Tm).