JPH0447564Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a control device for an electric expansion valve in a refrigeration system, and is particularly designed to prevent wet operation at the start of operation and to quickly reach stable operation. The present invention relates to a control device for controlling.

(Prior Art) In a conventional refrigeration system consisting of a compressor 1, an outdoor heat exchanger 3, an electric expansion valve 4, and an indoor heat exchanger 5 shown in FIG. It is started by giving a predetermined valve opening degree, and after that, the degree of heating is controlled based on the temperature difference on the side of the indoor heat exchanger 5, which acts as an evaporator, based on the opening degree (Japanese Patent Application Laid-Open No. 1985-1918). .

(Problems to be Solved by the Invention) However, since the above conventional device gives a predetermined valve opening at the start of operation, the amount of liquid accumulated in the indoor heat exchanger 5 and the valve opening of the electric expansion valve 4 are Depending on the relationship, the refrigerant liquid in the indoor heat exchanger 5, which functions as an evaporator, returns to the compressor 1 without being evaporated, resulting in wet operation, which can cause the compressor 1 to malfunction. .

Furthermore, in the conventional device described above, the opening degree of the electric expansion valve 4 is controlled based on the temperature difference on the indoor heat exchanger 5 side (the temperature difference measured by the temperature sensors 6 and 7). , 7 to stabilize, and during that time, the opening degree of the electric expansion valve 4 is not stable, which may cause abnormal phenomena such as hunting.

(Means for Solving the Problems) Therefore, the present invention provides a refrigeration system having a compressor 1, an outdoor heat exchanger 3, an electric expansion valve 4, and an indoor heat exchanger 5 as a means for solving the above problems. , an operation start means 11 of the refrigeration system, a start control means 12 that fully closes the electric expansion valve 4 and starts the compressor 1 based on the operation signal of the operation start means 11, and detects the suction pressure of the compressor 1. Suction pressure detection means 1
3, a first pressure determining means 14 that outputs a signal when the pressure detected by the suction pressure detecting means 13 falls to a predetermined lower limit set pressure, and the first pressure determining means 14
an initial control means 15 that outputs a valve opening signal at a predetermined opening speed according to a signal from the valve, and a suction pressure detection means 1
a second pressure determination means 16 that outputs a signal when the pressure detected by 3 reaches a predetermined upper limit setting pressure;
superheat degree detection means 17 for detecting the degree of superheat; and superheat degree control means 18 for commanding the opening degree control of the electric expansion valve 4 based on the degree of superheat detected by the superheat degree detection means 17 based on the output signal of the second pressure determination means 16; , has an electric expansion valve driving means 20 that drives the electric expansion valve 4 in response to commands from the activation control means 12, the initial control means 15, and the degree of superheat control means 18, and the electric expansion valve driving means 20 drives the electric expansion valve 4. , which controls the electric expansion valve 4.

(Function) The present invention achieves the following effects by the above means. When the refrigeration equipment starts operating, the electric expansion valve is fully closed, and it starts opening only when the suction pressure reaches the lower limit set value. control,
Instead of relying on the temperature difference on the indoor heat exchanger side, which is not stable for a relatively long period of time, as in the past, it is based on the suction pressure of the compressor, which is stable for a relatively short period of time. Since superheat degree control is performed only after the suction pressure reaches the upper limit set value after startup, safe operation is reached quickly and abnormal phenomena such as hunting do not occur.

(Embodiment) A control device for an electric expansion valve of a refrigeration system as a preferred embodiment of the present invention will be described in detail below with reference to FIGS. 2 and 3.

The refrigeration system shown in Fig. 2 includes a compressor 1, a four-way switching valve 2, an outdoor heat exchanger 3, an electric expansion valve 4, an indoor heat exchanger 5, a four-way switching valve 2, and a compressor 1 connected in order in an annular manner. The refrigerant circuit has a refrigerant circuit configured as shown in FIG. That's what I do.

6 is a temperature sensor disposed on the suction side of the compressor 1, and 7 and 8 are temperature sensors disposed on the inlet sides of the indoor heat exchanger 5 and the outdoor heat exchanger 3, which act as evaporators during cooling operation and heating operation, respectively. A temperature sensor is provided. Reference numeral 9 denotes a thermostat that starts and stops the compressor 1 depending on the room temperature.

Reference numeral 17 denotes a degree of superheat detection means, which detects the degree of superheat by determining the temperature difference between the temperature sensors 6 and 7 during cooling operation and by using temperature sensors 6 and 8 during heating operation. It should be noted that the superheat degree detection means 17 may be any other known means other than the one based on the temperature difference described above.

Reference numeral 11 denotes an operation start means, which includes an operation start push button (not shown), an operation relay, and the like. Reference numeral 13 denotes a suction pressure detection means that detects the suction pressure of the compressor 1 and outputs it as an electric signal. When the suction pressure detected by the suction pressure detection means 13 falls to the lower limit set pressure of 3 kg/cm ² , a first pressure determination is made. The means 14 outputs a signal to the initial control means 15, and the initial control means 15 outputs a signal to the electric expansion valve driving means 20 to open the electric expansion valve 4 at a predetermined opening speed.

When the suction pressure detected by the suction pressure detection means 13 rises by 4 kg/cm ² of the upper limit setting pressure, the second
The pressure determination means 16 outputs a signal to the degree of superheat control means 18, and outputs a command to the electric expansion valve drive means 20 to control the opening degree of the electric expansion valve 4 based on the degree of superheat detected by the degree of superheat detection means 17. The opening degree of the electric expansion valve 4 is controlled.

Further, in addition to the initial control means 15 and superheat degree control means 18, a valve closing amount control means 19 is provided. When the compressor 1 is stopped by the thermostat 9, the valve closing amount control means 19 closes the valve at a slow speed until the thermostat 9 is turned on next time. Therefore, the amount of valve closing is proportional to the time the thermostat 9 is OFF, and when this time is extremely long (for example, 30 minutes), the valve is fully closed.

The electric expansion valve driving means 20 receives commands from the initial control means 15, the degree of superheat control means 18, and the valve closing amount control means 19, and drives the electric expansion valve 4 with respective control signals.

Regarding the above-mentioned refrigeration system, control during cooling operation will be explained based on the flowchart shown in FIG. In FIG. 3, for example, step 1 is abbreviated as SP1, and the same applies hereafter.

At the start of the cooling operation (SP1), a command from the operation start means 11 is outputted to the electric expansion valve drive means 20 via the activation control means 12, and the electric expansion valve 4 is fully closed (SP2). The compressor 1 is operated (SP3), the pressure on the suction side decreases, and the electric expansion valve 4 continues to operate fully closed until the pressure detected by the suction pressure detection means 13 reaches 3 kg/ ^cm2 . When it comes to cm ² , the first
The pressure determination means 14 outputs the first pressure signal ON to the initial control means 15 (SP5), and the electric expansion valve driving means 20 outputs a continuous valve opening output to the electric expansion valve 4 (SP6), and the valve is opened at a predetermined opening speed. Electric expansion valve 4
The degree of opening increases.

This predetermined opening speed increases the degree of opening of the electric expansion valve 4 from fully closed to fully open in proportion to the passage of time, for example, in 3 minutes.

When the suction pressure increases and the detected pressure of the suction pressure detection means 13 reaches the upper limit setting pressure 4Kg/cm ² , the second
The pressure determination means 16 outputs the second pressure signal ON to the superheat degree control means 18 (SP8), and the superheat degree control means 18 sets the degree of superheat to the set value based on the degree of superheat detected by the degree of superheat detection means 17. Perform opening control (SP9). If the upper limit set pressure of 4 kg/cm ² is not reached even after the set time has elapsed (SP10), it is determined that there is a refrigerant shortage or other abnormality, and the compressor 1 is stopped. (SP11) During superheat control operation, its opening (number of pulses)
is controlled while memorizing (SP12), and when the room temperature reaches the set value, thermostat 9 is turned off (SP13).
Stop compressor 1 (SP14). Therefore, the electric expansion valve 4 is moved in the closing direction by the valve closing amount control means 19, but the control pulse speed for this valve closing is changed to a very slow one, and the thermostat 9 is
The valve closes at a slow speed until it turns ON (SP15). The valve closing speed is set to, for example, 30 minutes from fully open to fully closed.

Therefore, the amount of valve closing becomes proportional to the time that the thermostat 9 is OFF, and when it finally becomes fully closed (SP16), the valve closing output is stopped (SP17).

When the room temperature rises and the thermostat 9 turns on (SP18), the control pulse speed is switched to the original speed (SP19), the electric expansion valve 4 is stopped (SP20), and the compressor 1 is operated (SP21). ), the suction pressure detection means 13 detects the pressure (SP22), and when the first pressure determination means 14 indicates that the first pressure signal is ON (SP23), the continuous valve opening output (SP6), the second pressure determination means 16 When the second pressure signal is ON (SP8)
The system switches to superheat degree control (SP9) and continues operation.

Here, if the first pressure signal does not turn ON even after restarting the compressor 1 (SP23), after a predetermined period of time has passed (SP24), the pressure is detected (SP25) and the first pressure signal turns ON and OFF. (SP26), and if it is ON, performs continuous valve opening output (SP6) and repeats the operation from (SP7) onwards. If it is OFF, after the predetermined time has elapsed (SP24), the first pressure signal is
The ON/OFF judgment (SP26) is repeated.

(Effect of the invention) As described above, according to the invention, when starting the operation of the refrigeration system, the electric expansion valve 4 is fully closed and activated, and the electric expansion is started after the suction pressure of the compressor 1 reaches the lower limit set value. Since valve 4 starts to open, it prevents the liquid refrigerant stored in the heat exchanger that acts as an evaporator from evaporating at the start of operation, which is a defect of conventional devices, from returning to the compressor and resulting in wet operation. It is something that will be done.

In addition, superheat degree control is performed after the suction pressure reaches the upper limit set value, which provides more stable control than the conventional initial control based on the temperature difference on the indoor heat exchanger side. It will arrive faster.

In addition, as in the embodiment, when the thermostat 9 restarts the compressor 1, if the valve closing amount is proportional to the length of the stop time (that is, the longer the stop time is, the larger the valve closing amount is), the thermostat 9 can prevent wet operation at startup.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of the present invention, Figure 2 is an overall configuration diagram including a refrigerant circuit diagram of a refrigeration system according to an embodiment of the present invention, and Figure 3 is the operation of the refrigeration system shown in Figure 2. 4 is a refrigerant circuit diagram of a conventional refrigeration system. 1... Compressor, 2... Four-way switching valve, 3... Outdoor heat exchanger, 4... Electric expansion valve, 5... Indoor heat exchanger, 6, 7, 8... Temperature sensor, 9... Thermostat, 11...Operation start means, 12...Start control means, 13...Suction pressure detection means, 14...First pressure determination means, 15...Initial control means, 16...
...Second pressure determination means, 17...Superheat degree detection means,
18... Superheat degree control means, 19... Valve closing amount control means, 20... Electric expansion valve drive means.

Claims (1)

[Scope of utility model registration request] In a refrigeration system having a compressor 1, an outdoor heat exchanger 3, an electric expansion valve 4, and an indoor heat exchanger 5, an operation start means 11 of the refrigeration apparatus and an operation signal from the operation start means 11 cause the electric expansion valve 4 to be fully activated. A start control means 12 for starting the compressor 1 by closing the compressor 1, a suction pressure detection means 13 for detecting the suction pressure of the compressor 1, and a signal when the pressure detected by the suction pressure detection means 13 falls to a predetermined lower limit set pressure. a first pressure determining means 14 that outputs a valve opening signal at a predetermined opening speed based on a signal from the first pressure determining means 14; a second pressure determining means 16 that outputs a signal when the upper limit setting pressure is reached; a superheating degree detecting means 17 that detects the degree of superheat; superheat degree control means 18 for commanding the opening degree control of the electric expansion valve 4 according to the temperature; and the start control means 1
2 and an electric expansion valve driving means 20 for driving the electric expansion valve 4 in response to commands from the initial control means 15 and the degree of superheat control means 18.