JPS6345030B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention controls an expansion valve by calculating the superheat amount of suction refrigerant based on the difference between the refrigerant temperature at the open end on the inlet side of the compressor and the refrigerant temperature in this inlet refrigerant pipe. This invention relates to a superheat detection system for a refrigeration cycle.

Conventionally, a thermostatic automatic expansion valve has been used as a pressure reducing device in the refrigeration cycle, but since a thermosensitive cylinder is brought into contact with the piping in the section that controls the amount of superheat, and changes in temperature are converted into changes in pressure, the response is is delayed. For this reason, it has the disadvantage that it cannot follow sudden load fluctuations, causing liquid backlash or hunting.

Furthermore, since superheat is not directly detected, it has been impossible to arbitrarily control the amount of superheat to be optimal for the operating conditions of the air conditioner.

Furthermore, as a control signal for conventional electric expansion valves,
The device that detects the amount of superheat detects the temperature at the inlet or middle part of the evaporator (Te) and the temperature at the inlet of the compressor (Ts), and simply calculates the amount of superheat (SH) by SH = Ts - Although it is set as Te, there is a pressure drop at the evaporator inlet, middle part, and compressor inlet. Since this amount of decrease changes depending on the operating conditions, it has been impossible to accurately detect the amount of superheat.

In addition, there is a system that detects the amount of superheat by installing a pressure sensor and a temperature sensor at the inlet of the compressor. However, since the pressure sensor is expensive, it has the disadvantage of increasing the cost of the equipment.

This invention was made to eliminate the above-mentioned conventional drawbacks, and provides a refrigeration cycle superheat detection system that can accurately detect the absolute value of the amount of superheat in the refrigerant sucked into a compressor and can precisely control the expansion valve. The purpose is to

Embodiments of the superheat detection system for a refrigeration cycle according to the present invention will be described below with reference to the drawings. FIG. 1 is a refrigeration circuit diagram of one embodiment, and FIG. 2 is an enlarged view of the vicinity of the bypass path in FIG. 1. In both Fig. 1 and Fig. 2, 1 is a compressor, and the high-temperature, high-pressure refrigerant gas discharged from the compressor 1 passes through a four-way valve 2. It is sent to the exchanger 3, where it is condensed and liquefied, and then passed through the capillary tubes 4a and 4b, reduced in pressure by the electric expansion valve 5, and sent to the indoor heat exchanger 6, where it is evaporated and gasified. Four-way valve 2 becomes low-pressure refrigerant gas
The air is sent to the accumulator 7 via the .

As is clear from the enlarged view of FIG. 2, a bypass path 9 is provided between the electric expansion valve 5, the indoor heat exchanger 6, and the suction pipe 15.
A capillary tube 10 is provided in the middle of this bypass path 9.

In addition, the suction pipe 15 of the compressor 1 in the bypass path 9
Temperature sensor 1 that detects the temperature of the refrigerant at the open end of the side
1 is provided, and a temperature sensor 8 is also attached to the suction pipe 15 to detect the temperature of the refrigerant in the suction pipe 15. Both temperature sensors 8
The detection outputs of and 11 are sent to a controller 12.

This controller 12 receives the detection outputs of both temperature sensors 8 and 12, calculates the amount of superheat of the refrigerant sucked into the compressor 1, and thereby calculates the superheat amount of the refrigerant sucked into the compressor 1.
It is designed to control the opening of the valve.

Further, FIG. 3 is an enlarged view of another embodiment of the bypass path 9 portion. FIG. 3 shows an example in which the bypass path 9 is routed from both ends of the inlet and outlet of the electric expansion valve 5 via capillary tubes 13 and 14. and 14 have been added.

In the refrigeration cycle superheat detection system of the present invention configured as described above, especially in the case shown in FIG. 3, refrigerant flows into the bypass path 9 from the high pressure side during both cooling and heating operations. .

Further, FIG. 4 shows an outline of the system of the present invention on a Mollier diagram. In FIG. 4, the horizontal axis H represents enthalpy, and the vertical axis P represents pressure. In FIG. 4, Td indicates the compressor discharge refrigerant temperature, and A indicates the high-pressure refrigerant liquid at the inlet of the electric expansion valve 5. This liquid passes through the capillary tube 13 or 14 shown in FIG. 3, further passes through the capillary tube 10, and generates a temperature T ₁₁ corresponding to the suction pressure at the open end 16 opened to the suction pipe 15 on the low pressure side. .

By detecting this saturation temperature with the temperature sensor 11 and further detecting the temperature T ₈ of the suction refrigerant with the temperature sensor 8, the controller 12 can detect the superheat amount (T ₈ −T ₃ ). .

As described above, according to the superheat detection system for a refrigeration cycle of the present invention, a bypass path is provided from the inlet and/or outlet of the electric expansion valve to the compressor inlet or the accumulator inlet via the capillary tube, The controller detects the temperature corresponding to the suction pressure of the refrigerant gas at the open end of this bypass path and the temperature of the refrigerant gas introduced from the indoor heat exchanger into the accumulator and sucked into the compressor. Since the electric expansion valve is controlled by calculating the amount of superheat of the refrigerant gas sucked into the compressor based on the difference between the two temperatures, the absolute value of the amount of superheat can be detected, and the amount of superheat can be detected from the indoor heat exchanger (evaporator) inlet. Even if there is a pressure loss up to the outlet, it is possible to accurately control the electric expansion valve, improving protection and controllability of the compressor, and enabling detailed energy-saving operation.

[Brief explanation of drawings]

Fig. 1 is a refrigeration circuit diagram showing an embodiment of the superheat detection system for the refrigeration cycle of the present invention, Fig. 2 is an enlarged view of the vicinity of the bypass passage in the superheat detection system for the above refrigeration cycle, and Fig. 3 is an enlarged view of the vicinity of the bypass passage in the superheat detection system for the above refrigeration cycle. FIG. 4, which is an enlarged view of an embodiment of each bypass path in the superheat detection system, is a Mollier diagram showing refrigerant behavior in the superheat detection system of the refrigeration cycle. 1... Compressor, 2... Four-way valve, 3... Outdoor heat exchanger, 4a, 4b, 10... Capillary tube, 5... Electric thermal expansion valve, 6... Indoor heat exchanger, 7... Accumulator, 8, 11... Temperature sensor, 9... Bypass path, 12... Controller, 15
...Suction piping, 16...Open end. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a refrigeration cycle in which a compressor, a condenser, an electric expansion valve, an evaporator, etc. are connected in series, the compressor inlet or accumulator is connected from the expansion valve inlet or outlet, or both, via a capillary tube. a bypass path leading to the inlet; a first temperature sensor that detects the refrigerant temperature at the open end of the bypass path on the compressor inlet side or the accumulator inlet side; and a first temperature sensor in the suction pipe that sucks refrigerant into the compressor inlet a second temperature sensor that detects refrigerant temperature;
A controller that controls the opening degree of the electric expansion valve by calculating the amount of superheat of the refrigerant sucked into the compressor using the difference between the detection outputs of the first and second temperature sensors. A superheat detection system for refrigeration cycles.