JPS6155022B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in refrigerant flow rate control methods.

Conventionally, capillary tubes and thermostatic expansion valves have been mainly used as refrigerant circulation amount control devices. However, although the capillary tube has the advantage of having a simple structure and low cost, its use is limited to small-sized devices because of its narrow control range. On the other hand, thermostatic expansion valves have a certain control range and can meet most requests, but they usually require superheat of about 5°C between the refrigerant evaporation temperature and the temperature sensor, so the evaporation outlet The refrigerant will completely gasify in the vicinity, making it impossible to utilize the evaporation heat transfer area in that area. Furthermore, since thermostatic expansion valves are mechanical, they do not have a sufficiently wide control range, and their response speed is slow.As they are simple feedback systems, they can cause excessive hunting depending on the length of the evaporator system. have.

As a conventionally used electric expansion valve,
Some systems use a float to detect the refrigerant level and activate a solenoid valve, but this is only applicable to completely flooded evaporators.

There is also an electric expansion valve that can be used in dry or semi-full conditions, but this type has only one liquid refrigerant detector, which is simply combined with an electric valve, so the evaporator system is long. In this case, excessive hunting is unavoidable, similar to the case with thermostatic expansion valves.

The present invention aims to overcome the drawbacks of the above-mentioned conventional methods. That is, in the present invention, in a refrigerant circuit such as a heat pump, the control target for the refrigerant flow rate is the amount of superheat ((heated steam temperature) minus (saturation temperature)), which is normally 5 degrees), but the liquid level in the low pressure receiver.

As a result, the second half of the refrigerant evaporator does not function as a superheater as in the conventional case, but the entire heat exchanger operates as an evaporator, which increases the refrigerant evaporation temperature and improves the coefficient of performance. In order to keep this liquid level stable, two liquid refrigerant detectors are installed inside the low-pressure liquid receiver, one above the other.

The present invention provides a method for setting the opening degree of a refrigerant flow rate control valve based on two detection signals (the presence or absence of liquid) from these liquid refrigerant detectors.

That is, the present invention provides a liquid refrigerant detector for detecting the upper limit of liquid refrigerant and a liquid refrigerant detector for detecting the lower limit of liquid refrigerant, in a low-pressure liquid receiver or liquid separator located between an evaporator and a compressor. In a refrigerant flow control method for a refrigerant circuit such as a refrigerator or a heat pump, in which the upper liquid refrigerant detector or the lower liquid refrigerant detector simultaneously detects liquid refrigerant, the setting of the refrigerant flow control valve is changed. gradually decrease the refrigerant flow rate per unit time over time, and if the upper liquid refrigerant detector does not detect liquid refrigerant and the lower liquid refrigerant detector detects liquid refrigerant, the setting of the refrigerant flow control valve remains unchanged. If the liquid refrigerant detectors at the top and bottom or only at the bottom do not detect liquid refrigerant, the setting of the refrigerant flow control valve is changed to gradually increase the refrigerant circulation amount per unit time over time. There is a refrigerant flow control method.

The present invention also provides a liquid refrigerant detector for detecting the upper limit of liquid refrigerant and a liquid refrigerant detector for detecting the lower limit of liquid refrigerant, which are installed in the low-pressure liquid receiver or liquid separator located between the evaporator and the compressor. In a refrigerant flow control method for refrigerant circuits such as refrigerators and heat pumps, when the upper liquid refrigerant detector detects liquid refrigerant, the setting of the refrigerant flow control valve is changed to control the refrigerant flow rate per unit time. gradually decreases over time (hereinafter referred to as the first case), and when the upper liquid refrigerant detector does not detect liquid refrigerant and the lower liquid refrigerant detector detects liquid refrigerant, the refrigerant flow rate control valve is set. (hereinafter referred to as the second case), and if the upper and lower liquid refrigerant detectors or the lower liquid refrigerant detector do not detect liquid refrigerant, change the setting of the refrigerant flow control valve to increase the amount of refrigerant per unit time. The amount of circulation is gradually increased over time (hereinafter referred to as the third case), and the refrigerant control valve is substantially closed for a short time when the second case shifts to the first case. The feature lies in the refrigerant flow rate control method.

Furthermore, the present invention provides a liquid refrigerant detector for detecting the upper limit of the liquid refrigerant and a liquid refrigerant detector for detecting the lower limit of the liquid refrigerant, which are installed in the low-pressure liquid receiver or liquid separator located between the evaporator and the compressor. In a refrigerant flow control method for refrigerant circuits such as refrigerators and heat pumps, when the upper liquid refrigerant detector detects liquid refrigerant, the setting of the refrigerant flow control valve is changed to control the refrigerant flow rate per unit time. gradually decreases over time (hereinafter referred to as the first case), and when the upper liquid refrigerant detector does not detect liquid refrigerant and the liquid refrigerant detector detects liquid refrigerant, the refrigerant flow rate control valve is set. If it continues as it is (hereinafter referred to as the second case) and the upper and lower liquid refrigerant detectors or the lower liquid refrigerant sensor do not detect liquid refrigerant, change the setting of the refrigerant flow control valve to increase the refrigerant circulation per unit time. The refrigerant control valve is gradually increased over time (hereinafter referred to as the third case), and at the time of transition from the second case to the third case, the refrigerant control valve is substantially fully opened for a short period of time. There is a refrigerant flow control method.

Hereinafter, preferred embodiments of the present invention will be described, which are illustrated in the accompanying drawings.

FIG. 1 shows a control device in a normal refrigeration cycle.

The gasified refrigerant is compressed by the compressor 3 and reaches the condenser 2 via the refrigerant pipe 8, where it is condensed to become a liquid refrigerant and stored in the liquid receiver 5. The liquid refrigerant pumped up from this liquid receiver 5 is transferred to a refrigerant heat exchanger 6.
and a refrigerant flow rate control valve 10 and a fixed or semi-fixed expansion valve (pressure reducing valve) via a liquid reservoir heat exchanger 7.
9 and reaches the evaporator 1, where it generates cold heat.
The refrigerant discharged from the evaporator 1 once enters the liquid reservoir 4, where it is completely separated into gas phase refrigerant and liquid phase refrigerant.
Only the gaseous phase component is returned to the compressor 3 via the loop-shaped pipe.

By controlling the level of the liquid phase refrigerant in the liquid reservoir 4, the flow rate of the refrigerant in the entire system is controlled. Therefore, according to the present invention, the liquid reservoir 4
An upper liquid refrigerant detector 13 that determines the upper limit of the liquid level and a lower liquid refrigerant detector 14 that determines the lower limit of the liquid level on the inner wall surface of the
has been set up. These are both connected to a controller 11 by electric wires 15, and a signal line from this controller 11 is connected to a refrigerant flow rate control valve 10. Note that reference number 12 indicates a power supply for the controller.

The detectors 13 and 14 are thermistors (U.S.
(manufactured by SINGER) was used. This thermistor self-heats in gas, increasing its temperature and decreasing its resistance. Furthermore, since the thermistor is cooled in the liquid refrigerant, the temperature decreases and the resistance increases.

Therefore, if a circuit as shown in Figure 3 is made and this thermistor is exposed in the refrigerant, the current value of the resistor 16 will change and the voltage between terminals 18 and 18' will change, so that the liquid refrigerant will change. It can be determined whether or not.

The controller 11 is a microprocessor, and some examples of its logic circuits are shown as flowcharts in FIGS. 2a-2c.

In the example of FIG. 2a, the upper detector 13 detects whether liquid refrigerant is present at this liquid level. If YES, a signal is issued to the control valve 10 to reduce the opening degree over time. If NO, that fact is input to the AND circuit 23 and the AND circuit 24.
On the other hand, the lower detector 14 detects whether or not liquid refrigerant is present at this liquid level. This result is
If NO and the detector 13 indicates NO, a signal is generated via the AND circuit 24 to increase the opening degree of the control valve 10 over time. The upper detector is NO,
If the lower detector is YES, that is, if the liquid level is between the upper detector and the lower detector, the current opening setting will be maintained.

In the case of the above-mentioned opening decrease and opening increase, the control valve 1 is activated for a short time (for example, several seconds) immediately before the operation starts.
It may be possible to perform an operation in which the opening degree of 0 is extremely reduced or completely closed, and an operation in which the opening degree is extremely increased or fully opened. It is assumed that one of these operations is performed.

If the upper detector 13 detects liquid (first case), this indicates that the supply of liquid refrigerant exceeds the evaporation capacity (excess liquid supply).

In this case, it would be better to reduce the control valve opening, but if the evaporator pipe is long, the detector has poor sensitivity, or the control valve operates slowly (in control terminology,
If there is a large amount of wasted time or delay time, you may not be able to make it in time.

Therefore, the control valve 10 is temporarily fully closed in an attempt to integrally correct this malfunction.

When the lower detector 14 detects that there is no liquid (third case), contrary to the above, it indicates that the liquid supply is insufficient.

In this case, for the same reason as above, the control valve 10 is temporarily fully opened in order to integrally correct the delay in increasing the liquid supply due to the waste time or delay time.

As described above, in the present invention, the electronic circuit 11 is used to operate the control valve 10 electrically, so there is no operational restriction as in the conventional thermostatic expansion valve (mechanical type). (Specifically, a pulse motor-driven valve with a capacity control range and quick operation.) Therefore, according to the present invention, although it is an alternative method to the conventional temperature-type expansion valve, capillary tube, etc.,
(a) Wide capacity and temperature control range, (b) Good steady-state characteristics (small deviation from target value), (c) High stability in control process (small overshoot), (d) Fast response (e) Simple structure and reliable operation.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a normal refrigeration cycle, Figs. 2a to 2c are circuit diagrams showing examples of logic circuits thereof, and Fig. 3 is a circuit showing an example of a refrigerant liquid detection circuit. It is a diagram. 1... Evaporator, 2... Condenser, 3... Compressor,
4...Low pressure liquid reservoir, 5...High pressure liquid receiver, 6...Refrigerant heat exchanger, 7...Reservoir internal heat exchanger, 8...Refrigerant piping, 9...Expansion valve, 10...Refrigerant flow rate control valve, 1
1... Controller, 12... Power supply, 13... Upper liquid refrigerant detector, 14... Lower liquid refrigerant detector, 1
5...Wire, 16...Resistance, 17,17'...DC
Input terminal, 18, 18'...DC output terminal, 23,
24...AND circuit.

Claims (1)

[Claims] 1. A liquid refrigerant detector that detects the upper limit of liquid refrigerant and a liquid refrigerant detector that detects the lower limit of liquid refrigerant are installed in a low-pressure liquid receiver or liquid separator located between the evaporator and the compressor. In a refrigerant flow control method for a refrigerant circuit such as a refrigerator or a heat pump that is equipped with a detector, if the upper liquid refrigerant detector or the lower liquid refrigerant detector simultaneously detects liquid refrigerant, the refrigerant flow control valve is set. the refrigerant flow rate per unit time is gradually decreased over time, and when the upper liquid refrigerant detector does not detect liquid refrigerant and the lower liquid refrigerant detector detects liquid refrigerant, the refrigerant flow rate control valve is set. If the above-mentioned upper and lower liquid refrigerant detectors or only the lower liquid refrigerant detectors do not detect liquid refrigerant, the setting of the refrigerant flow control valve is changed to gradually increase the refrigerant circulation amount per unit time over time. A refrigerant flow control method characterized by: 2 A liquid refrigerant detector that detects the upper limit of liquid refrigerant and a liquid refrigerant detector that detects the lower limit of liquid refrigerant are installed in the low-pressure liquid receiver or liquid separator located between the evaporator and the compressor. In addition, in a refrigerant flow control method for refrigerant circuits such as refrigerators and heat pumps, when the upper liquid refrigerant detector detects liquid refrigerant, the settings of the refrigerant flow control valve are changed to adjust the refrigerant flow rate per unit time over time. (hereinafter referred to as the first case), and if the upper liquid refrigerant detector does not detect liquid refrigerant and the liquid refrigerant detector detects liquid refrigerant, the setting of the refrigerant flow rate control valve is maintained as is. (hereinafter referred to as the second case), if the upper and lower liquid refrigerant detectors or the lower liquid refrigerant detector do not detect liquid refrigerant, change the setting of the refrigerant flow control valve to adjust the refrigerant circulation amount per unit time. (hereinafter referred to as the third case), and the refrigerant control valve is substantially closed for a short time at the time of transition from the second case to the first case. Flow control method. 3 A liquid refrigerant detector that detects the upper limit of liquid refrigerant and a liquid refrigerant detector that detects the lower limit of liquid refrigerant are installed in the low-pressure liquid receiver or liquid separator located between the evaporator and the compressor. In a refrigerant flow rate control method for refrigerant circuits such as refrigerators and heat pumps, when the upper liquid refrigerant detector detects liquid refrigerant, the settings of the refrigerant flow control valve are changed to gradually increase the refrigerant flow rate per unit time over time. (hereinafter referred to as the first case), and if the upper liquid refrigerant detector does not detect liquid refrigerant and the liquid refrigerant detector detects liquid refrigerant, the setting of the refrigerant flow rate control valve is maintained as it is ( (hereinafter referred to as the second case), if the upper and lower liquid refrigerant detectors or the lower liquid refrigerant detector do not detect liquid refrigerant, change the setting of the refrigerant flow control valve to adjust the refrigerant circulation amount per unit time over time. The refrigerant flow rate is gradually increased (hereinafter referred to as the third case), and the refrigerant control valve is substantially fully opened for a short time at the time of transition from the second case to the third case. Control method.