JP2001241779A - Refrigerant flow rate controller for air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a refrigerating cycle by preventing or reducing an overheat of an intermediate part of an indoor heat exchanger when cooled and to control to an optimum refrigerant flow rate under the stabilized control of a valve travel of an expansion valve. SOLUTION: A refrigerant flow rate controller 11 controls a valve lift of an electronic expansion valve 4 so that a superheat degree becomes a predetermined target value. In this case, the superheat degree is obtained by a difference between a lower temperature by comparing a temperature of an intermediate part of an evaporator detected by an evaporator intermediate part temperature sensor 10 at the time of cooling in the refrigerating cycle with an evaporator inlet temperature detected by an evaporator inlet temperature sensor 9 and a compressor suction temperature detected by a compressor suction temperature sensor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant flow control device for an air conditioner, which has an improved superheat control method for a refrigeration cycle of a heat pump type air conditioner.

[0002]

2. Description of the Related Art Conventionally, in a heat pump type air conditioner of this type, an intermediate portion between a refrigerant inlet and an outlet of an indoor heat exchanger acting as an evaporator during a cooling operation is excessively throttled, and the branch flow of the indoor heat exchanger is deteriorated. In order to prevent the overheating, the temperature difference ΔT between the indoor air suction temperature Ts and the temperature Tc of the intermediate portion from the refrigerant inlet to the refrigerant outlet of the indoor heat exchanger (evaporator) is used to prevent the overheating. ΔT = Ts−Tc), and
If the temperature difference [Delta] T is less than the predetermined temperature difference [Delta] T _1, the expansion valve consisting of an electronic control valve in a predetermined time go open by a predetermined opening degree, the indoor heat exchanger to increase the refrigerant circulation flow rate of the refrigeration cycle Prevents overheating of the middle part. And
When the temperature difference [Delta] T (Ts-Tc) reaches ₁ or more predetermined temperature difference [Delta] T, the compressor suction temperature and the indoor heat exchanger based on the degree of superheat resulting from the difference between the inlet temperature of (evaporator) The control is returned to the normal superheat control for controlling the opening of the electronic expansion valve.

[0003]

However, in such a conventional method of controlling the degree of superheat, the intermediate portion of the indoor heat exchanger (evaporator) may be overheated again even when the control is returned to the normal degree of superheat control. . In this case, there is a problem that the refrigeration cycle becomes unstable because the electronic expansion valve repeatedly opens and closes.

[0004] In particular, when the compressor is of a variable capacity type driven by an inverter, or when a split type indoor / outdoor unit connection pipe is long, many problems such as the above-mentioned refrigeration cycle instability occur. Was.

The present invention has been made in view of such circumstances, and an object of the present invention is to prevent or reduce overheating of an intermediate portion of an indoor heat exchanger during a cooling operation, thereby stabilizing a refrigeration cycle. Accordingly, it is an object of the present invention to provide a refrigerant flow control device for an air conditioner that can control the refrigerant flow to an optimum flow by controlling the opening of the expansion valve stably.

The invention according to claim 1 is
A refrigeration cycle for circulating the refrigerant by connecting at least a compressor, an outdoor heat exchanger, an expansion valve capable of controlling the flow rate of a refrigerant, and an indoor heat exchanger by a refrigerant pipe, and an evaporator for detecting an inlet temperature of the indoor heat exchanger An inlet temperature sensor, an evaporator intermediate portion temperature sensor for detecting an intermediate temperature between an inlet and an outlet of the indoor heat exchanger, a compressor suction temperature sensor for detecting a suction temperature of the compressor, and During the cooling operation, the evaporator intermediate temperature detected by the evaporator intermediate temperature sensor is compared with the evaporator inlet temperature detected by the evaporator inlet temperature sensor. Control means for determining the degree of superheat of the difference from the compressor suction temperature detected by the temperature sensor, and controlling the degree of opening of the expansion valve so that the degree of superheat becomes a predetermined target value;
A refrigerant flow control device for an air conditioner, comprising:

According to the present invention, the temperature difference (Ts-Tc) between the lower one of the intermediate temperature Tc and the inlet temperature Tcj of the indoor heat exchanger acting as an evaporator during the cooling operation and the compressor suction side temperature Ts. Alternatively, since the opening degree control of the expansion valve is performed based on the degree of superheat of Tcj), the intermediate portion of the indoor heat exchanger is overheated due to over-throttlement of the expansion valve or deterioration of the branch flow of the indoor heat exchanger during cooling operation. Even when the accurate evaporation temperature cannot be detected, the superheat control can be performed based on the inlet temperature Tcj of the indoor heat exchanger.

[0007] For this reason, it is possible to prevent the intermediate portion of the indoor heat exchanger from being overheated again, so that repeated opening and closing of the expansion valve due to reheating of the intermediate portion and the instability of the refrigeration cycle due to the repeated overheating can be prevented. It can be prevented or reduced.

According to a second aspect of the present invention, the control means includes:
2. The refrigerant flow control device for an air conditioner according to claim 1, wherein the superheat degree target value is changed depending on a case where the superheat degree is obtained by using the evaporator intermediate temperature or the evaporator inlet temperature. is there.

According to the present invention, an indoor heat exchanger which acts as an evaporator during cooling operation generally has a considerably large pressure loss between the inlet and the middle thereof due to its shape and the flow rate of the refrigerant. Intermediate temperature Tc rather than Tcj
Is much lower.

Therefore, the target superheat degree when the evaporator intermediate temperature Tc is used to calculate the superheat degree and the target superheat degree when the evaporator inlet temperature Tcj is used are the same target superheat degree α. Then, the degree of superheat calculated using the evaporator inlet temperature Tc becomes larger, and the opening of the expansion valve tends to be narrowed.

Therefore, when the superheat degree is calculated using the evaporator inlet temperature Tcj, a value smaller than the target superheat degree α when the superheat degree is calculated using the evaporator intermediate temperature Tc is calculated. The optimum superheat control can be performed by changing the target superheat degree β (α> β).

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
It will be described based on.

FIG. 1 is a refrigeration cycle diagram of an air conditioner 1 according to one embodiment of the present invention. In FIG. 1, an air conditioner 1 includes a compressor 2, an outdoor heat exchanger 3, an electronic expansion valve 4 including a pulse motor drive valve (PMV) and the like, which can control the flow of a refrigerant, and an indoor heat exchanger 5 in this order. 6 constitute a closed refrigeration cycle in which the refrigerant is circulated in order and the refrigerant is circulated in the direction of the arrow in the drawing to perform the cooling operation.

On the refrigerant suction side of the compressor 2, a compressor suction temperature sensor 7 for detecting the temperature Ts on the suction side of the compressor 2 is provided, and outside air is blown to the outdoor heat exchanger 3. An outdoor fan 8 such as a propeller fan is provided to promote heat exchange.

On the other hand, the indoor heat exchanger 5 functions as an evaporator during the cooling operation, and an evaporator inlet temperature sensor 9 for detecting the evaporator inlet temperature Tcj during the cooling operation is provided on the refrigerant inlet side. At the same time, an evaporator intermediate temperature sensor 10 installed at an intermediate portion between the refrigerant inlet and the outlet and detecting the temperature Tc of the intermediate portion is provided, and indoor air is blown to the indoor heat exchanger 5 to exchange heat. An indoor fan 11 made up of, for example, a cross flow fan or the like is provided.

The electronic expansion valve 4, the compressor suction temperature sensor 7, the evaporator inlet temperature sensor 9, and the evaporator intermediate temperature sensor 10 are controlled by a microprocessor or the like via signal lines shown by broken lines in the figure. It is electrically connected to the refrigerant flow control device 11 as a means.

During the cooling operation, the refrigerant flow controller 11 controls the compressor suction temperature Ts detected by the compressor suction temperature sensor 7, the evaporator inlet temperature Tcj detected by the evaporator inlet temperature sensor 9, and the evaporator intermediate portion. The evaporator intermediate temperature Tc detected by the temperature sensor 10 is read, and the evaporator inlet temperature Tcj and the evaporator intermediate temperature Tc are constantly compared to be lower, for example, the evaporator intermediate temperature Tc and the compressor suction. The difference (Ts-Tc) from the temperature Ts, that is, the degree of superheat is obtained, and the number of control pulses applied to the electronic expansion valve 4 is controlled so that the degree of superheat becomes a predetermined target degree of superheat α. Are controlled to be opened by predetermined degrees.

When the refrigerant flow controller 11 determines that the evaporator inlet temperature Tcj is lower than the evaporator intermediate temperature Tc (Tc> Tcj), the evaporator inlet temperature Tcj and the compressor suction pressure are used. Difference from temperature Ts (Ts-Tcj)
The degree of superheat is determined by the following formula, and the opening degree of the electronic expansion valve 4 is controlled so that the degree of superheat reaches the target degree of superheat β.

The target superheat degree β is set to a smaller value (β <α) than the target superheat degree α. The reason is that the indoor heat exchanger 5 acting as an evaporator during the cooling operation has a considerably large pressure loss in the indoor heat exchanger 5 due to its shape and the circulation flow rate of the refrigerant.
Is significantly lower than the inlet temperature Tcj.

For this purpose, while calculating the degree of superheat using the evaporator intermediate section temperature Tc, the superheat degree target value α is set to the evaporator inlet temperature higher than the evaporator intermediate section temperature Tc. This is because, if the superheat control is performed using the target value of the superheat calculated using Tcj, the opening of the electronic expansion valve 4 is excessively reduced. Therefore, the superheat degree target value β is set to a smaller value (β <α) than α.

Therefore, when the air conditioner 1 is operated for cooling, the refrigerant in the refrigeration cycle circulates in the direction of the arrow in FIG. For this reason, the high-temperature and high-pressure gaseous refrigerant compressed by the compressor 2 flows into the outdoor heat exchanger 3 and radiates heat while condensing and liquefying. The liquid refrigerant is decompressed by the electronic expansion valve 4 and controlled to a required flow rate and then flows into the indoor heat exchanger 5, where it evaporates and vaporizes, absorbs heat from the outside air and cools the surrounding air, The room is cooled by blowing the cooling air into the room by the indoor fan 11.

The gaseous refrigerant vaporized in the indoor heat exchanger 5 is separated into liquid components by a gas-liquid separator (not shown), and then returned to the compressor 2 from the suction side again. .

If the opening of the electronic expansion valve 4 is too narrow during the cooling operation and the inflow of the liquid refrigerant flowing into the indoor heat exchanger 5 is too small, a large amount of the refrigerant from the outside air is generated by the insufficient refrigerant. Because it absorbs heat, it may overheat.

Therefore, in order to prevent the overheating, the refrigerant flow controller 11 controls the degree of superheating. That is, the refrigerant flow rate control device 11 controls the compressor suction temperature Ts detected by the compressor suction temperature sensor 7 and the evaporator inlet temperature sensor 9.
, The evaporator middle temperature Tc detected by the evaporator middle temperature sensor 10
And the evaporator inlet temperature Tcj is constantly compared with the evaporator intermediate temperature Tc to determine the lower temperature. Further, the lower temperature (Tcj or Tc) and the compressor suction temperature Ts are calculated. The temperature difference ΔT (Ts−Tc or Tcj) is calculated as the degree of superheat.

When the evaporator intermediate temperature Tc is lower than the evaporator inlet Tcj (Tc <Tcj), the refrigerant flow control device 11 sends the electronic control signal from the refrigerant flow control device 11 so that the superheat degree ΔT becomes the superheat degree target value α. A control pulse is applied to the expansion valve 4 to open it by a predetermined opening, and the refrigerant circulation flow rate is increased to prevent overheating of the refrigerant.

On the other hand, if the middle portion of the indoor heat exchanger 5 is overheated due to over-throttling of the electronic expansion valve 4 or deterioration of the branch flow of the indoor heat exchanger 5, the accurate evaporating temperature cannot be detected. Since the temperature Tcj is lower than the evaporator intermediate temperature Tc (Tcj <Tc), the difference (Ts-Tc) between the evaporator inlet temperature Tc and the compressor suction temperature Ts is obtained as the degree of superheat. Then, the opening degree of the electronic expansion valve 4 is opened by a predetermined opening degree by the refrigerant flow control device 11 so that the superheat degree becomes the superheat degree target value β, thereby increasing the refrigerant circulation flow rate.
Prevent overheating of refrigerant.

Therefore, according to this air conditioner 1,
During the cooling operation, even if the intermediate portion of the indoor heat exchanger 5 is overheated, the overheat can be prevented. Therefore, the reheating of the intermediate portion can be prevented, so that the occurrence of instability of the refrigeration cycle due to the repeated opening and closing of the electronic expansion valve 4 due to the reheating can be prevented.

When calculating the superheat degree of the refrigerant, the target superheat degree α in the case of using the evaporator intermediate temperature Tc in the intermediate part of the indoor heat exchanger 5 is calculated by using the evaporator intermediate temperature Tc.
Since the evaporator inlet temperature Tcj is set to a value (α> β) larger than the superheat target value β when the evaporator inlet temperature Tcj is used, optimal superheat control can be performed.

The present invention relates to a refrigerating cycle apparatus such as a refrigerating apparatus having a refrigerating cycle substantially similar to the refrigerating cycle and an air conditioner having a four-way valve provided in the air conditioner 1 so as to be capable of cooling and heating. May be applied.

[0030]

As described above, according to the present invention, the intermediate temperature T of the indoor heat exchanger acting as an evaporator during the cooling operation is provided.
The superheat control is performed based on the superheat of the temperature difference (Ts-Tc or Tcj) between the lower one of the compressor c and its inlet temperature Tcj and the compressor suction side temperature Ts. Even if the middle part of the indoor heat exchanger is overheated due to deterioration of the branch flow of the indoor heat exchanger and the accurate evaporation temperature cannot be detected, the superheat degree control can be performed based on the inlet temperature of the indoor heat exchanger. it can.

For this reason, it is possible to prevent the intermediate portion of the indoor heat exchanger from being overheated again, so that repeated opening and closing of the expansion valve due to reheating of the intermediate portion and the instability of the refrigeration cycle due to this are prevented. It can be prevented or reduced.

[Brief description of the drawings]

FIG. 1 is a refrigeration cycle diagram of an air conditioner according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Compressor 3 Outdoor heat exchanger 4 Electronic expansion valve 5 Indoor heat exchanger 6 Refrigerant piping 7 Compressor suction temperature sensor 9 Evaporator inlet temperature sensor 10 Evaporator middle temperature sensor

Claims (2)

[Claims] 1. A refrigeration cycle in which at least a compressor, an outdoor heat exchanger, an expansion valve capable of controlling the flow rate of a refrigerant, and an indoor heat exchanger are connected by a refrigerant pipe to circulate a refrigerant, and an inlet temperature of the indoor heat exchanger. An evaporator inlet temperature sensor for detecting the temperature of the evaporator, an evaporator intermediate temperature sensor for detecting a temperature of an intermediate portion between the inlet and the outlet of the indoor heat exchanger, and a compressor suction temperature sensor for detecting a suction temperature of the compressor. During the cooling operation of the refrigeration cycle, comparing the evaporator intermediate temperature detected by the evaporator intermediate temperature sensor with the evaporator inlet temperature detected by the evaporator inlet temperature sensor, Control means for determining the degree of superheat of the difference from the compressor suction temperature detected by the compressor suction temperature sensor, and controlling the degree of opening of the expansion valve so that the degree of superheat becomes a predetermined target value; Refrigerant flow control device for an air conditioner which is characterized in that it comprises. 2. The control means sets the superheat degree target value as follows:
2. The refrigerant flow control device for an air conditioner according to claim 1, wherein the degree of superheat is determined using the evaporator intermediate temperature or the evaporator inlet temperature.