JPH02683Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a refrigerant state detection device that is inserted into the compressor suction side of a refrigeration cycle or other refrigerant piping to detect the refrigerant state. In refrigeration cycles, etc., insufficient heating may occur due to condensate freezing on the cooler coils, or due to other external factors or malfunctions in the equipment or control system that make up the cycle. Refrigerant that is not present, or even in liquid phase, may enter the suction line of the compressor intermittently or continuously, adversely affecting the cycle and preventing its high efficiency operation, and in the worst case, causing the compressor to fail. This may lead to damage to the product. Various control methods have been proposed in the past in order to prevent such compressor accidents in refrigeration cycles and to ensure stable cycle operation.
A typical method is to maintain the degree of heating at the outlet of the cooler constant within a predetermined range. This method generally uses a temperature-activated automatic expansion valve to detect the temperature and pressure of the refrigerant near the outlet of the cooler and automatically adjust the valve opening. Since the temperature and pressure are mechanically calculated and fed back to the valve, the response speed is usually slow, and for this reason the degree of superheat of the refrigerant at the outlet of the cooler must always be set to an excessive value. Therefore, the cooler cannot be used effectively, the cooler has to be enlarged, and the amount of refrigerant in the refrigeration cycle has to be increased. And especially in heat pump refrigeration cycles,
Since the degree of superheating is set high as mentioned above,
As the outdoor coil unit becomes larger and the refrigerant sucked into the compressor is superheated gas, separation of the refrigerating machine lubricating oil tends to be promoted and it tends to accumulate in the cooler. Oil does not return, which tends to cause damage and accidents, and it is necessary to add a complicated device to promote this oil return. Furthermore, such an excessive setting of the degree of superheating inevitably promotes an increase in the discharge temperature, which leads to a decrease in economic index coefficients such as the cycle growth coefficient. Furthermore, apart from the above, there is also a method of adjusting the degree of subcooling at the condenser outlet, but this method is a secondary control for the refrigerant condition at the condenser outlet, and it is determined by the load fluctuation on the condenser side. Therefore, the effectiveness could not be recognized. In this way, conventional refrigeration cycles have been able to keep up with daily load fluctuations on the cooler side, if you ignore the economical efficiency, larger size of the equipment, and complexity. However, the behavior of the refrigerant during the refrigeration cycle is extremely dynamic, and the mechanical refrigerant state detection mechanism found during conventional cycles cannot completely follow this dynamic behavior of the refrigerant. Ta. In view of the various shortcomings of the conventional refrigerant state detection mechanism as described above, this invention improves this by converting the instantaneous state of the refrigerant into electrical capacity and detecting it accurately and continuously. be. Embodiments of the refrigerant state detection device according to this invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment of this invention. In FIG. 1, 1 is a metal tube forming a part of the refrigerant circulation circuit, and 2 and 3 are arranged inside the metal tube 1 to face each other. The refrigerant is connected to the electrodes 2 and 3 with the
A capacitive element passing between the two is formed. 4,
5 is a conductor drawn out from both electrode plates 2 and 3 through insulators 8 and 9 of the tube wall, and 6 and 7 are terminals thereof. When the refrigerant state detection device configured as described above is inserted into the compressor suction side pipe of the refrigeration cycle so that the A end is on the evaporator side and the B end is on the compressor side, the refrigerant state during cycle operation can be detected. The flow is in the direction of the arrow. When a voltage is applied between the electrode plates 2 and 3, if certain conditions are satisfied, this can be made to act as a capacitor. In general, the capacitance of a capacitor is, when the electrode plates are parallel plates, C=ε _p・K・S/d...(1) However, ε _p : Dielectric constant of vacuum [F/m] C: Electrostatic Capacity [F] S: Electrode area [m ² ] d: Electrode spacing [m] K: Relative dielectric constant (material between electrodes). From this equation (1), it is clear that the capacitance of a parallel plate capacitor is proportional to the dielectric constant of the interelectrode material. Then, the relative dielectric constant depending on the state of the refrigerant is determined as “Refrigerant R-
22 (CHF ₂ Cl)'' is as follows.

[Table] In this way, there is a difference of about 6 times in relative dielectric constant between the gas phase and the liquid phase of the refrigerant, and as a result, the capacitance of the capacitor formed by the electrode plates 2 and 3 consisting of the parallel plates is different from that of the refrigerant. It can be seen that there is a similar difference of about 6 times between the gas phase and the liquid phase. This idea takes advantage of this property. FIG. 2 shows a block diaphragm of a control device to which this invention is applied, where 11 is a detector such as a resonant circuit including the capacitance element, 12 is a first comparator, and 13 is this first comparator 12.
The comparator 12 and the integrator 13 form a control signal circuit.
14 is a second comparator which is an emergency control signal circuit; 15 is a first output obtained through the integrator 13, which is a control output that is fed back to, for example, an expansion mechanism; and 16 is a control output when the compressor is damaged. A second output is an emergency control signal that triggers the cycle to take emergency action when expected. As a usage example, the refrigeration cycle mentioned in the conventional example,
In other words, the operation will be described when the detection device of this invention and the control device are applied to a refrigeration cycle that maintains the degree of superheat at the cooler outlet constant and uses an automatic expansion valve. When the cycle is working well and the refrigerant passing between the electrode plates is maintained at an appropriate level of dryness,
In other words, when load fluctuations and other disturbance factors in the cooler are small, and the so-called stable operation is being performed except for steady refrigerant pulsations, and the adjustment function of the automatic expansion valve is working correctly, at this time, the above-mentioned The detector 11 generates an output corresponding to the pulsation of the refrigerant, but by adjusting so that the control outputs 15 and 16 are not equal at this level of output, the cycle continues to operate stably. However, when the condition of the refrigerant passing between the electrodes exceeds the appropriate set value due to load fluctuations in the cooler or other factors, for example, the dryness may fluctuate to such an extent that it cannot be considered as a steady pulsation. , when the automatic expansion valve cannot follow this, the output of the detector 11 naturally increases, and this output is transmitted to the first comparator 1.
2. The output becomes 15 after passing through the integrator 13, which biases the cycle to encourage the refrigerant state to return to its proper condition. Since the detector output of this level does not reach the set value of the second comparator 14, there is no output 16. When the cycle mechanism itself is expected to be damaged due to abnormally large values, the detector 11 generates a correspondingly large output and output 16 is output, which triggers emergency measures for the cycle, and the measures are executed. will be done. Therefore, when using the refrigerant condition detection device of this invention, it is possible to take safety measures for the refrigeration cycle as described above, and unlike conventional mechanical detection devices, it is possible to take instantaneous values of the refrigerant condition. Since it can output accurately and continuously, there is no need to set the degree of superheat of the refrigerant excessively, and at the same time, it is possible to downsize the cooler, reduce the amount of refrigerant, and ensure smooth oil return, eliminating cycle damage accidents. becomes possible. Moreover, this invention can be easily installed in an existing refrigeration cycle, and since the structure is simple, it can be provided at low cost. In the explanation of the above embodiment, the electrode shape was a parallel flat plate, but for example, as shown in FIG. Cylindrical electrode 2
2 may be used as the other electrode, and may have any shape as long as it forms an electrical capacitance. Furthermore, the location of the equipment in the refrigerant circuit is not limited.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view and longitudinal sectional view showing the configuration of one embodiment of the refrigerant state detection device according to this invention, Fig. 2 is a circuit block diagram explaining the usage state of the same, and Fig. 3 is another embodiment. FIG. In the figure, 1 is a metal tube, 2, 3, 22 are electrodes,
11 is a detector, 12 and 13 are control signal circuits, 14
is the emergency control signal circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] A capacitive element is formed in the refrigerant circulation path of the refrigeration cycle so that the refrigerant passes between both electrodes, and a detection signal is generated in response to a change in the capacitance value of the capacitive element due to a change in the state of the refrigerant. a control signal circuit that outputs the detection signal via an integrator;
and a refrigerant state detection device comprising an emergency control signal circuit that detects an abnormal value of the detection signal and outputs an emergency control signal.