JPS6399460A - Refrigerant controller for refrigerator - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a control method for an expansion valve of a heat pump type refrigeration system formed of a compressor, a condenser, an expansion valve, and an evaporator as main components. In particular, the present invention relates to a method for controlling the opening degree of an expansion valve depending on the degree of superheating of gas discharged from a compressor.

[Conventional technology]

Conventionally, the method of controlling the opening degree of the expansion valve according to the degree of superheating of the refrigerant on the high pressure side of the refrigeration cycle was developed in Utility Model Application No. 55-14847.
No. 0 has been proposed, but this prior art is designed to open and close the expansion valve according to the difference between the discharge pipe temperature and the high pressure side saturated refrigerant temperature in the condenser. child,
This method detects the saturation level in the condenser as the high-pressure side saturation temperature, and does not take into account the saturation range at the refrigerant discharge part of the compressor. No consideration was given to the method.

In addition, as another conventional example, the opening degree of the expansion valve is controlled according to the degree of superheating on the suction side of the compressor, as disclosed in Japanese Patent Laid-Open No. 49-128.
No. 850, JP-A-59-191854, or 1%
There is a patent publication No. 59-205559, etc., but there is no description of a system for controlling an expansion valve depending on the degree of superheating of discharged gas.

[@Problems that Ming tries to solve]

The above-mentioned conventional technology does not consider a method for detecting the degree of superheating of the refrigerant at the refrigerant discharge section of the compressor. That is,
In the conventional technology, the refrigerant temperature Tc of the condenser is detected as the saturation temperature on the high pressure side, the temperature Td of the discharge pipe section of the compressor is detected, and the expansion valve is controlled according to the temperature difference (TcL-Tc). Ta.

For this reason, first, when the connecting pipe between the compressor and the condenser is long, the saturation pressure in the condenser decreases due to pressure loss at the connecting pipe, and the saturation temperature also decreases. In this way, the degree of superheat of the discharged refrigerant that is detected and calculated varies depending on the length of the piping, and there is a problem in that an accurate degree of superheat at the compressor discharge section cannot be obtained.

An object of the present invention is to accurately detect the degree of superheat of a discharged refrigerant and to provide a correspondence between the set degree of superheat and the detected degree of superheat.
Comer.

(Sixth means to solve the problem) The above purpose is to provide a pipe with one end closed in the discharge piping near the compressor, and cool the pipe to cool the discharge gas within the pipe. Detect the saturation temperature corresponding to this discharge pressure, detect the discharged gas m degree and the detected saturation temperature above), detect the accurate degree of superheat of the discharged refrigerant, and compare this detected degree of superheat with the set degree of superheat. Control the expansion valve (2),
In addition, we also calculated the temporal change of the above difference and the temporal integration of the difference.
If the above superheat degree is lower than the set superheat degree, adjust the valve opening degree in the closing direction.
If it is high, the refrigeration system can be stabilized by controlling the valve opening in the opening direction.

[Effect]

One end was closed to the discharge gas atmosphere of the compressor. By providing a pipe and cooling it, the discharge gas is cooled and condensation occurs. s in the area where condensation occurs within the above technique.
By providing a temperature sensor, it is possible to detect an accurate saturation temperature corresponding to the pressure of the discharge gas atmosphere. The detected saturation temperature and discharge gas temperature 1 The degree of superheat of the refrigerant discharged from the trowel is detected and controlled, and the amount of refrigerant in circulation is controlled. Therefore, the expansion valve opening degree can eliminate abnormal closing operation of the expansion valve from the transient state after the start-up of the refrigeration equipment to the steady state. is optimized.

(Embodiment) Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. Fig. 1 shows the configuration of a refrigeration cycle of the present invention. In Fig. 1, 1 is a compressor, 2 is a condenser, 8 is an evaporator, 4 is an electrically driven expansion valve, 5 is a discharge gas pipe of the compressor, and 6 is a technical pipe whose one end is closed and the other end is open to the discharge gas pipe 5;
7 is a first sensor that detects the temperature of the tube 6; 8 is a second sensor that detects the temperature of the discharged gas; 9 is a sensor that detects the temperature Tea of the first sensor 7 and the temperature Ta of the second sensor 8. A control device 10 is an intake gas pipe which calculates the degree of superheat B'fi (=Td-Teat) and drives the opening degree of the expansion valve 4. The tip of the technical tube 6 is attached so as to be able to exchange heat with the suction tube 10.

In the refrigeration cycle shown in FIG. 1, refrigerant discharged from the compressor 1 circulates through the discharge gas pipe 5, the condenser 2, the expansion valve 4, the evaporator 8, and the suction gas pipe. Next, FIG. 2 shows the details of the tube 6. The down pipe 6 is installed perpendicularly to the discharge gas pipe 51 (see FIG. 2). As shown in FIG. , condensation occurs at a certain position in the pipe 6, and the temperature becomes constant in the length direction of the branch g6.In the pipe 6, the liquid refrigerant near the tip of the branch v6 falls, and the liquid refrigerant that has fallen is , discharge gas (
This causes a circular flow of evaporation, and the temperature remains constant in the area within the tube 6 where the liquid refrigerant exists. The first sensor 7 is attached to a region f where the temperature of the tube 6 is constant, and detects the saturation temperature Tsat corresponding to the pressure of the discharged gas atmosphere.

On the other hand, the second sensor 8 detects the discharge gas temperature Td,
The control device 9 opens and closes the expansion valve according to the temperature difference (Td-Tsat), that is, the superheat degree SHd of the discharged gas.

Figure 8 (This shows the relationship between the degree of superheating SHd and the degree of superheating and humidity on the suction side of the compressor. If the degree of superheating SHd of the discharge gas is small, the suction side will be in a wet state containing liquid refrigerant, and if SHa is large, the suction side will be in a wet state. The refrigerant is in a superheated state.The refrigerating capacity reaches its maximum when the degree of superheat of the suction refrigerant is around Qdeg.Therefore, in the example shown in FIG. This allows the refrigeration cycle to utilize its full potential.

As explained above, according to this embodiment, it is possible to reliably detect the discharge gas superheat degree SHd near the compressor, and by giving an appropriate setting value for the discharge gas superheat degree. , the performance of the refrigeration cycle can be maximized.Also, by changing the setting of the discharge gas superheat degree depending on the rotation speed of the compressor, the temperature of the heat medium of the condenser, and the evaporator, etc., the refrigeration cycle can be maximized. Even if the operating conditions of the system change, it is possible to control the capacity to the maximum.

Further, even if the connecting pipe between the compressor 1 and the condenser 2 is long, according to this embodiment, there is no effect on the discharge gas superheat degree BHJ.

Although FIG. 2 shows an embodiment in which the vibro is cooled through the suction pipe f, it is also possible to cool the vibro with a refrigerant flowing from the condenser to the pressure a machine input section.

In addition, by inserting the first sensor 7 into the vibro, it is possible to detect the saturation temperature even more accurately. The effect of control (I mentioned this in detail).

Next, a specific example of the opening/closing control method of the expansion valve will be described.

First, the adjustment amount ΔV of the expansion valve opening is expressed by the following formula.

6 is the difference between the detected and calculated discharge gas superheat degree 5H (t) and the set superheat degree EIHds at; the first term on the right side of the above equation represents the current error, and the second term represents the integral value of the error. , the eighth term represents the differential value of the error. This control force formula is the so-called P i D IIJ control method. The coefficient Kl is 2
s K3 is a constant, and this coefficient is 1, K2 . By optimizing 3, the degree of superheating of the discharged gas to be controlled can be stably controlled, and the heat pump type refrigeration cycle can be stably operated.

Next, an embodiment of a control method during a transient state such as during startup will be described. FIG. 4 shows the operating state of the heat pump device after it has been started. While the engine is stopped, the degree of superheat of the discharged gas is 0, so according to the above equation, the correction amount becomes 0, and a signal to open the expansion valve cannot be issued.

In the present invention, the expansion valve is forcibly opened by a predetermined amount at the same time as the heat pump device is started or after a predetermined period of time after the start of the heat pump device. After the circuit is opened, the opening is maintained at a constant degree for a predetermined time, and the above-mentioned PiD control is performed after the predetermined time has elapsed. In other words, the superheat degree of the discharged gas after startup is smaller than the set superheat degree, and ε
is negative, so depending on how the coefficients, K2 and K3 are selected, the expansion valve remains closed and does not open. In the present invention, until the above error ε exceeds a predetermined width, the coefficient is
ft thicker, and after ε reaches a predetermined width, reduce the coefficient by 3. As a result, after startup, if the superheat degree EIH (t) suddenly decreases, that is, the discharge gas temperature suddenly increases, the eighth term in the previous equation is positive, and the coefficient is 3d larger, so the expansion valve is commanded to open. Therefore, the expansion valve does not open to an abnormally small degree after startup.When the error is within a predetermined range, 3 becomes small, and the heat pump device can operate stably.

(Effects of the Invention) As explained above, according to the present invention, it is possible to detect the degree of saturation corresponding to the pressure of the discharge gas atmosphere near the compressor, and the degree of superheat of the refrigerant discharged from the compressor can be detected. It is possible to accurately detect the degree of superheating and control the degree of superheat to approximately the set value, and the performance of the refrigeration equipment can be operated efficiently and stably. It is possible to eliminate the abnormal closing operation of the expansion valve from the subsequent transient state to the steady state I, and has the effect of improving startup operation when starting up the refrigeration system.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a refrigeration cycle showing an embodiment of the present invention, Fig. 2 is an enlarged detailed view of the at part in Fig. 1, Fig. 8 is a custom-made drawing of the refrigeration cycle, and Fig. 4 is a diagram at startup. It is a diagram explaining the operating state and showing the relationship between elapsed time, discharge gas temperature, discharge gas superheat degree, and expansion valve opening degree. 1... Compressor 2... Condenser 8... Evaporator 4
...Expansion valve 5...Discharge pipe 6...Technical pipe 7...
・First sensor 8...Second sensor 9...Saliva suppressor rod 145

Claims (4)

[Claims] 1. In a heat pump equipped with a refrigerant circuit formed by connecting a compressor, a condenser, an evaporator, and an expansion valve in sequence as main components, the first sensor detects the refrigerant temperature at the discharge part of the compressor; It is equipped with a technical pipe branched from the discharge part and closed at the tip, and a second saturation temperature detection sensor that detects the temperature of this pipe, and calculates the degree of superheating of the discharge part from the detection signals of the first sensor and the second sensor. , a means for calculating the difference between the set degree of superheat and the detected superheat part and a temporal change in the degree of superheat, and a means for controlling the opening degree of the expansion valve based on the result of this calculation, (SHd) and the set superheat degree (SHdset), the temporal change of this difference, and the temporal integration of the difference in the superheat degree A refrigerant control device for a refrigeration system, characterized in that, if the opening degree is higher, the opening degree of the expansion valve is controlled in the opening direction. 2. Detected superheat degree (SBd) and set superheat degree (SHds)
et) has a coefficient K_1, (SHd-SHdset)
A refrigerant control device for a refrigeration system according to claim 1, which calculates the expansion valve opening degree by weighting the time integral term of (SHdset) with a coefficient K_2 and the temporal change of (SHdset) with a coefficient K_3; 3. 3. A refrigerant control device for a refrigeration system according to claim 1, wherein the opening degree of the expansion valve is fixed at a predetermined value for a predetermined period of time after the refrigeration system is started. 4. The coefficients K_1, K_2, and
A refrigerant control device for a refrigeration system according to any one of claims 1 to 3, characterized in that K_3 is changed.