JPH0245796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a capacity control refrigeration circuit in which the amount of superheat can be arbitrarily set using an electronic signal in a refrigeration cycle in which the capacity of a compressor can be controlled by an inverter or the like.

FIG. 1 is a schematic diagram showing a refrigerant flow path to a conventional expansion valve. In the figure, 1 is an expansion valve, 2 to 5 are check valves, and the flow direction of the refrigerant during heating operation is shown by a broken line, and the flow direction of the refrigerant during cooling operation is shown by a solid line.

By the way, conventionally, a temperature-type automatic expansion valve is used as an expansion valve in this type of refrigeration cycle, but a temperature-sensitive tube is brought into contact with the piping in the section that controls the amount of superheat to convert temperature changes into pressure changes. Because of this, the response will be slow. For this reason, it is not possible to follow sudden changes in load and compression operation capacity, and has the drawback of easily causing liquid back-up or hunting. In addition, since the amount of superheat is not directly detected, such as through a temperature-sensitive cylinder that is activated by the expansion of gas or liquid, it is not possible to arbitrarily control the amount of superheat to the optimum amount that matches the operating condition of the air conditioner. It was impossible.

In addition, conventional electric expansion valves that detect the amount of superheat as a control signal detect the temperature Te at the inlet or intermediate part of the evaporator and the temperature Ti at the compressor inlet, and easily detect the amount of superheat. Amount SH
is assumed to be SH=Ti−Te, but there is a pressure drop in these parts. Since this amount of reduction varies depending on air conditions and compressor operating capacity, it has been impossible to accurately detect the amount of superheat.

Therefore, some systems install a pressure sensor and a temperature sensor at the compressor inlet to detect the amount of superheat, but the amount of superheat cannot be changed arbitrarily when controlling the capacity of the compressor. The circuit could not be operated efficiently.

This invention has been made to solve the above-mentioned problems, and aims to provide a control device for a capacity-controlled refrigeration circuit that can arbitrarily switch between high-capacity operation and high-efficiency operation of the capacity-controlled refrigeration circuit. purpose.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a circuit diagram of the refrigeration cycle in this embodiment, where A indicates the indoor unit and B indicates the outdoor unit. First, outdoor unit B
, 11 is a compressor whose capacity can be controlled.
This compressor 11 is connected to an outdoor heat exchanger 13 through a four-way valve 12 for switching between air conditioning and heating. This outdoor heat exchanger 13 is a distributor 14
a, 14b to an electric reversible expansion valve 15, and the electric reversible expansion valve 15 is connected to an indoor heat exchanger 16 of the indoor unit A.
Further, the indoor heat exchanger 16 is connected to an accumulator 17 through a four-way valve 12, and the accumulator 17 is connected to the compressor 11. A temperature sensor 18 and a pressure sensor 19 are provided near the refrigerant suction side of the compressor 11. The temperature sensor 18 detects the suction temperature of the refrigerant of the compressor 11, and its detected power is sent to the controller 20. Further, the pressure sensor 19 detects the refrigerant suction pressure of the compressor 11, and this detected force is also sent to the controller 20. The controller 20 receives these detected forces and controls the opening and closing of the electric reversible expansion valve 15.

Next, the operation of the above configuration will be explained. Compressor 11
During cooling operation, the compressed high-temperature, high-pressure refrigerant gas flows into the outdoor heat exchanger 13 through the four-way valve 12, where it is condensed and liquefied, and then transferred to the distributor 1.
4a and 14b, the refrigerant reaches the electric reversible expansion valve 15, where it expands adiabatically and becomes a low-temperature, low-pressure two-phase refrigerant.In the indoor heat exchanger 16, the refrigerant liquid absorbs heat from the surroundings and evaporates, turning into gas. The water then flows into the accumulator 17 via the four-way valve 12. Furthermore, the refrigerant gas is sucked into the compressor 11 through the suction pipe,
The refrigerant is compressed by the compressor 11 and circulated within the system again. The pressure P of this suction refrigerant is determined by the pressure sensor 19.
The temperature T is detected by the temperature sensor 18 and sent to the controller 20. Controller 20
is the superheat amount SH from these two detection forces
is calculated, and an expansion valve opening signal that optimizes the superheat amount SH is sent to the electric reversible expansion valve 15.

Also, during heating operation, the flow path of the four-way valve 12 is switched, and the high-temperature, high-pressure refrigerant gas compressed by the compressor 11 flows into the indoor heat exchanger 16 via the four-way valve 12, and becomes a low-temperature, high-pressure refrigerant liquid. It is liquefied, flows into the electric reversible expansion valve 15 from the opposite direction, expands into a low-temperature, low-pressure two-phase refrigerant, and flows into the distributors 14a and 14b.
It is evaporated in the outdoor heat exchanger 13, enters the accumulator 17 again via the four-way valve 12, and is sucked into the compressor 11.

In the above embodiment, by making the inlet and outlet of the expansion valve 15 reversible, the refrigerant circuit itself can be simplified and its reliability can be improved. In addition, Figure 3 shows the capacity characteristics and efficiency (COP to EER) during heating operation.
Indicates the relationship between heating capacity Q and superheat amount SH,
As is clear from this Figure 3, which shows the relationship between the coefficient of performance COP and the superheat amount SH, the superheat amount and the coefficient of performance that maximize the heating capacity Q
It does not match the amount of super heat that maximizes COP,
The former is larger. Therefore, for example, when the room temperature is considerably lower than the set temperature, the expansion valve 15 is adjusted so that the amount of super heat is determined so that the heating capacity Q is maximized.
By controlling the opening of the expansion valve 15 so that the amount of superheat is determined so that the coefficient of performance COP is maximized when the room temperature approaches the design temperature, both comfort and energy-saving operation can be achieved. can be satisfied.

As described above, according to the present invention, the pressure and temperature of the refrigerant at the inlet of the compressor are detected, the amount of superheat is detected based on the detection signal, and the opening degree of the expansion valve is controlled so that the amount of superheat is optimized. In particular, during heating operation, the superheat amount is appropriately switched to perform maximum capacity operation and maximum performance efficiency operation as appropriate, making it possible to satisfy both heating comfort and energy-saving operation.

[Brief explanation of the drawing]

Fig. 1 is a refrigerant flow path diagram of a conventional expansion valve, Fig. 2 is a capacity control refrigeration circuit diagram including a control device according to the present invention, and Fig. 3 is the relationship between the superheat amount, heating capacity, and coefficient of performance of the capacity control refrigeration circuit. It is a diagram. 11...Compressor, 12...Four-way valve, 13...Outdoor heat exchanger, 15...Electric reversible expansion valve, 16
... Indoor heat exchanger, 18 ... Temperature sensor, 19
...output sensor, 20...controller.

Claims (1)

[Claims] 1 A compressor with capacity control, an outdoor heat exchanger installed on the outdoor side, an indoor heat exchanger installed on the indoor side, a four-way valve for switching between air conditioning and heating, and an electric reversible expansion with reversible entrance and exit. In a capacity control refrigeration circuit equipped with a valve, there is a detection means for detecting the pressure and temperature of the refrigerant at the inlet of the compressor, and an electric reversible expansion valve that calculates the amount of superheat from the output of this detection means and optimizes the amount of superheat. In addition to controlling the opening of the electric reversible expansion valve, during heating operation, the amount of super heat is switched according to the difference between the set temperature and the room temperature, and the opening of the electric reversible expansion valve is switched between maximum capacity operation and maximum coefficient of performance operation. 1. A control device for a capacity control refrigeration circuit, comprising: means.