JPH0135261B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves the starting characteristics of a refrigeration circuit used in an air conditioner or a refrigerator and the control of a pressure reducing device, thereby enabling highly efficient operation.

Conventionally, a capillary reach tube has generally been used as a pressure reducing device for a refrigeration circuit. When the situation changes, the decompression function cannot sufficiently follow the situation, resulting in a decrease in capacity.

In addition, refrigeration circuits that use electric expansion valves as pressure reducing devices have a large time constant, take a long time to start up, and have low efficiency until steady operation is reached.

This invention eliminates the drawbacks of the conventional refrigeration circuit device as described above, performs subcool control and superheat control on the refrigeration circuit, uses an electric expansion valve in the pressure reducing device, and adjusts the opening degree of the expansion valve. In addition to keeping the difference between the wall temperature of the inlet pipe of the electric expansion valve and the wall temperature of the suction pipe of the compressor within a predetermined range to ensure efficient operation, the refrigerant flowing into the electric expansion valve is controlled by the compressor using the opening/closing means. The system stops when the compressor is stopped, maintains the high-low pressure difference in the refrigeration circuit when the compressor is stopped, speeds up the start-up time at startup, improves startup characteristics, and improves efficiency from this perspective.

That is, the configuration of the present invention is to construct a refrigeration circuit by sequentially connecting a compressor, a condenser, an electric expansion valve, an evaporator, and an accumulator in series, and to exchange heat between the refrigerant at the outlet of the condenser and the refrigerant at the inlet of the compressor. means for exchanging heat between the refrigerant exiting the condenser and the refrigerant at the outlet of the evaporator, which have been heat exchanged by the heat exchange means;
an opening/closing means that opens when the compressor is started and closes when the compressor is stopped to control the flow of refrigerant to the electric expansion valve; a first temperature sensor that detects the temperature of the wall of the electric expansion valve inlet; The second temperature sensor detects the machine suction pipe wall temperature, and the electric sensor calculates the difference between the temperatures detected by the first and second temperature sensors, and maintains this temperature difference within a predetermined range. The device is equipped with a controller that issues a signal to adjust the opening degree of the expansion valve.

The action is to perform super heat control by exchanging heat between the refrigerant at the condenser outlet and the refrigerant at the compressor inlet, and after exiting the condenser, the refrigerant that has undergone heat exchange for super heat control and the refrigerant at the evaporator outlet are heated. Perform subcool control by means of exchange. In a refrigeration circuit that performs super heat control and subcool control in this way, the refrigerant temperature at the inlet of the electric expansion valve and the compressor inlet are used to operate the electric expansion valve most efficiently even if the outside temperature of the heat exchanger on the user side and the heat source side changes. The difference with the refrigerant temperature is constant. Figure 2 shows the electric expansion valve inlet refrigerant temperature T ₁ when this refrigeration circuit is used in an air conditioner and the pressure is reduced to the maximum capacity when the heating operation is performed.
Temperature difference ΔT between and compressor inlet refrigerant temperature T ₂ = T ₁ −
The value of T ₂ is shown using the outside air temperature T ₀ as a parameter.

Note that the △ marks in the figure indicate variations in experimental values.

As can be seen from FIG. 2, in a refrigeration circuit that performs super heat control and subcool control, ΔT is maintained within a predetermined range even if the outside temperature T ₀ (° C.) changes. Therefore, conversely, if the difference ΔT between the inlet refrigerant temperature T ₁ (° C.) of the electric expansion valve and the inlet refrigerant temperature of the compressor is kept within the above range, a pressure reduction value that provides the highest performance can be obtained.

However, in the case of a refrigeration circuit that uses a capillary reach tube as a pressure reducer and does not perform subcool control or superheat control, the refrigerant temperature at the inlet of the electric expansion valve, which exhibits the maximum capacity due to changes in the outside air temperature T ₀ (°C), decreases to T _{1 .} The difference ΔT between the refrigerant temperature T2 and the compressor inlet refrigerant temperature _T2 changes significantly. Therefore, even if this ΔT is controlled within a predetermined range, the maximum performance will not always be exhibited regardless of the outside temperature. Therefore, in order to control this temperature difference ΔT within a predetermined range and operate the refrigeration circuit at its maximum capacity regardless of the outside temperature, that is, the external conditions, subcool control and superheat control are required.

Electric expansion valves reduce the pressure of condensed refrigerant liquid, and can freely change the pressure reduction value using electrical signals.In capillary reach tubes, the pressure reduction value is left to change depending on changes in external conditions, and cannot be intentionally controlled. cannot be changed to the target value.

The first and second temperature sensors detect the wall temperature of the electric expansion valve inlet pipe and the wall temperature of the compressor suction pipe, respectively, and indirectly detect the temperature of the refrigerant flowing in the pipe. .

The controller detects a temperature difference ΔT between the electric expansion valve inlet refrigerant temperature T ₁ and the compressor inlet refrigerant temperature T ₂ which are indirectly detected by the first and second temperature sensors.
=T ₁ -T ₂ is calculated, and an electric signal is output to adjust the valve opening of the electric expansion valve so that this value falls within a predetermined range.

In addition, the opening/closing means opens when the compressor starts up and closes when it stops.When the compressor stops, the high-pressure side and low-pressure side of the refrigeration circuit are separated and this high-low pressure difference is maintained, and steady operation is maintained when the compressor is restarted. This aims to shorten the startup time and improve efficiency during startup.

The details of this invention will be further explained below based on the illustrated embodiments.

Figure 1 shows the basic refrigeration circuit of this invention.
In the figure, 1 is a compressor, 2 is a condenser, 3 is an electric expansion valve, 4 is an evaporator, and 5 is a function for exchanging heat between the high-pressure, high-temperature refrigerant leaving the condenser 2 and the refrigerant at the outlet of the evaporator 4. 6 is a heat exchange pipe that exchanges heat with the refrigerant that exits the condenser and enters the accumulator heat exchanger, and the refrigerant that exits the accumulator heat exchanger 5 and enters the compressor 1. , 7 is a solenoid valve that is equipped with a relay (not shown) in the circuit of the motor section of the compressor 1 and operates in synchronization with the driving and stopping of the motor, and is opened when the compressor 1 is started and closed when it is stopped. It's controlled like that. Reference numeral 8 is provided in the pipe on the inlet side of the compressor 1, and detects the pipe wall temperature to determine the refrigerant temperature T ₂ at the inlet of the compressor 1.
A second temperature sensor 9 that indirectly detects the refrigerant temperature at the inlet of the electric expansion valve 3 is provided on the inlet side pipe of the electric expansion valve 3, and detects the pipe wall temperature to determine the refrigerant temperature at the inlet of the electric expansion valve 3.
a first temperature sensor that indirectly detects T ₁ ;
0 is inputted with the detected values of the temperature sensors 8 and 9, calculates the temperature difference T ₁ −T ₂ =ΔT, and operates the electric expansion valve 3 so that this temperature difference ΔT falls within a predetermined range.
This is a controller that emits a signal to adjust the valve opening of the valve.

In the refrigeration circuit control device configured as shown in FIG. A signal is sent to the controller 10, and when the temperature difference ΔT is outside the predetermined range and is larger than the upper limit of the predetermined range, the valve opening of the electric expansion valve 3 is reduced, and when it is smaller than the lower limit of the predetermined range, the valve opening is reduced. A signal is sent to the electric expansion valve 3 to increase the value. The opening degree of the electric expansion valve 3 is adjusted according to the signal, and the pressure reduction value is adjusted by adjusting the amount of refrigerant flowing therein.

Since this embodiment is configured as described above, even if the outside air temperature T ₀ (℃) changes, the electric expansion valve inlet refrigerant temperature T ₁ and the compressor inlet refrigerant temperature T ₂ is maintained within a predetermined range (7.5°C±1°C in this example), allowing for the most efficient operation.

Furthermore, in the control device of the present invention, a solenoid valve 7 is provided on the inlet side of the electric expansion valve 3, and a relay is provided in the circuit of the motor section of the compressor 1, so that it is activated by starting and stopping the motor. Since the control is such that it opens at startup and closes at stop, the solenoid valve 7 closes at the same time as the compressor 1 stops, closing the pipeline, and the high-pressure side and low-pressure side are almost in operation while the compressor 1 is stopped. Since the compressor 1 is maintained in a steady state as soon as it is started, it can quickly start up. Furthermore, in the above embodiment, the solenoid valve 7 is opened and closed by detecting the start and stop of the compressor 1. However, the signal for opening and closing the solenoid valve 7 can be used, for example, to connect this refrigeration circuit to an air conditioner. When used, it may be based on an on-off signal of a room temperature detector that detects the room temperature and starts and stops the compressor 1. Furthermore, when water is heated or cooled and this water is used as a medium for various purposes. Alternatively, an on/off signal from a water temperature detector that detects the water temperature and starts/stops the compressor 1 may be used. Further, in the above embodiment, a solenoid valve is used as a means for opening and closing the refrigeration circuit, but even if an electric valve is used, exactly the same effect can be obtained. Further, in the above embodiment, the opening and closing operations are performed in synchronization with the start and stop of the compressor, but the same effect can be obtained by opening and closing with a slight time delay from the start and stop of the compressor.

As described above, the present invention provides a refrigeration circuit that performs subcool control and superheat control, and the electric expansion valve is operated so that the difference between the refrigerant temperature at the inlet of the electric expansion valve and the refrigerant temperature at the compressor inlet is within a predetermined range. The degree of opening is adjusted, and an opening/closing means is provided at the inlet of the electric expansion valve, which opens when the compressor is started.
Since it closes when stopped, it not only provides high capacity but also enables quick startup and highly efficient operation.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a refrigeration circuit control device showing an embodiment of the present invention, and Fig. 2 is a characteristic showing the relationship between the difference ΔT between the refrigerant temperature at the electric expansion valve inlet and the compressor inlet temperature and the outside air temperature. It is a diagram. The same symbols in the figures indicate the same or corresponding parts, 1
is a compressor, 2 is a condenser, 3 is an electric expansion valve, 4 is an evaporator, 5 is an accumulator heat exchanger, 6 is a heat exchange pipe, 7 is a solenoid valve, 8 and 9 are temperature sensors,
10 is a controller.

Claims (1)

[Scope of Claims] 1. In a refrigeration circuit comprising a compressor, a condenser, an electric expansion valve, an evaporator, and an accumulator connected in series, the condenser outlet refrigerant and the compressor inlet refrigerant a means for exchanging heat between the refrigerant exiting the condenser and the refrigerant at the outlet of the evaporator, and a means for exchanging heat between the refrigerant exiting the condenser and the refrigerant at the outlet of the evaporator; an opening/closing means that opens when the compressor is started and closes when the compressor is stopped; a first temperature sensor that detects the temperature of the walls of the inlet pipes of the electric expansion valve; and a second temperature sensor that detects the temperature of the walls of the suction pipes of the compressor. a controller that calculates a temperature difference detected by the sensor and the first and second temperature sensors and issues a signal to the electric expansion valve to adjust the valve opening so that the temperature difference is maintained within a predetermined range; A refrigeration circuit control device comprising: 2. The control device for a refrigeration circuit according to claim 1, wherein the opening/closing means is constituted by a solenoid valve. 3. A patent characterized in that the opening/closing operation of the electromagnetic valve is performed by the output of a temperature detector that detects the temperature of a controlled object heated or cooled by the refrigeration circuit and starts or stops the compressor. A control device for a refrigeration circuit according to claim 2.