JPH04203852A - Air conditioning apparatus - Google Patents

Abstract

PURPOSE:To eliminate the shortage and/or excess of refrigerant for an operating indoor machine smoothly by a method wherein the degree of overheating of the suction port of a compressor and the change of overheating degree with respect to the change of the unit valve travel of an expansion valve for the operating indoor machine are detected while the expansion valve of a stopping indoor machine is controlled based on the detecting results to control the amount of refrigerant. CONSTITUTION:A suction temperature sensor 13 and a suction pressure sensor 14 for detecting the overheating degree of a suction temperature are provided at the suction port of a compressor 1 while these detecting signals are sent to a control unit 15 to operate the overheating degree of the suction port of the compressor 1. The control unit 15 detects the overheating degree of the suction port of the compressor 1 and the change of the overheating degree with respect to the change of the unit valve travel of an electronic expansion valve for an operating indoor machine among three sets of indoor machines 4, 5, 6 and controls the opening and/or closing of the electronic expansion valve of a stopping indoor machine based on the results of detection to control the amount of refrigerant in the stopping indoor machine. When the refrigerant in the operating indoor machine is short, a valve at the outlet port of refrigerant of the stopping indoor machine is controlled so as to be opened and when the refrigerant is excessive, an expansion valve at the inlet port side of the refrigerant is controlled so as to be opened. According to this method, the shortage and/or excess of refrigerant in the operating indoor machine can be eliminated smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an air conditioner, and particularly to the adjustment control of the amount of refrigerant in a multi-system air conditioner.

(Prior Art) Generally, in a multi-system air conditioner, a refrigeration cycle is configured by a compressor, a four-way valve, an outdoor unit, a plurality of indoor units connected in parallel, and the like.

In such a multi-system air conditioner, if the number of operating indoor units decreases, refrigerant may accumulate in the stopped indoor unit (mainly caused by valve leakage), or the cycle of the operating indoor unit may There may be a shortage of refrigerant in the tank, resulting in insufficient capacity or a significant increase in the degree of superheating. Normally, to eliminate this inconvenience, the solenoid valve on the gas side of the stopped indoor unit is closed and the solenoid valve on the liquid side is opened to recover the accumulated refrigerant.
Alternatively, attempts are made to prevent the refrigerant from accumulating, or to recover the refrigerant using a bypass capillary. However, when taking these measures, conventional air conditioners do not control the amount of refrigerant recovered, and considering the wide range of operating conditions in multi-system air conditioners,
In some cases, the liquid may return suddenly, it may take time to return the liquid, or there is a risk that the liquid may be returned too much.

Furthermore, if all indoor units are not operated at startup, a phenomenon of excess refrigerant may occur in the cycle of the operating indoor unit. Normally, this is temporarily absorbed by the receiver (eventually, it leaks out to other stopped indoor units, eliminating the excess refrigerant), but it is not necessarily absorbed efficiently under a wide range of operating conditions in multi-system air conditioners. Not that you can.

(Problems to be Solved by the Invention) In a multi-system air conditioner, the amount of refrigerant in the refrigeration cycle changes frequently and over a fairly wide range. When such an air conditioner has an operating indoor unit and a stopped indoor unit, it is difficult to resolve refrigerant shortage or refrigerant excess in the operating indoor unit using conventional methods of adjusting the amount of refrigerant, and the efficiency of the refrigeration cycle decreases. There was a problem that the reliability of the compressor could be reduced.

This invention was made in view of the above-mentioned circumstances, and can extremely smoothly resolve refrigerant shortages and refrigerant excesses in operating indoor units under a wide range of operating conditions, and improves the efficiency of the refrigeration cycle and the reliability of the compressor. The purpose is to provide an air conditioner that can.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides an air conditioner having a compressor, an outdoor unit, and a plurality of indoor units each equipped with an expansion valve at a refrigerant inlet/outlet. The degree of superheat of the compressor suction port and the change in the degree of superheat with respect to the unit opening degree change of the expansion valve of the operating indoor unit among the plurality of indoor units are detected, and based on the detection result, the indoor unit is stopped. The gist of the present invention is to include a refrigerant amount adjusting means for controlling the expansion valve and adjusting the amount of refrigerant in the stopped indoor unit.

(Function) When refrigerant accumulates in a stopped indoor unit among multiple indoor units and the refrigerant in the cycle of the working indoor unit becomes insufficient, the expansion valve of the working indoor unit controls the degree of superheating. Despite this, the change in superheat for a unit change in valve opening shows a positive correlation (that is, the superheat does not decrease even though the valve is open), and the superheat at the compressor suction It's increasing.

Furthermore, since the capacity of the operating indoor unit is insufficient, the compressor frequency increases, and the degree of superheat tends to increase.

This indicates that refrigerant shortage can be determined from the change in the degree of superheating with respect to a unit change in the opening degree of the expansion valve of the operating indoor unit, and the value of the degree of superheating.

In addition, if all indoor units are not operated at startup, and an excessive amount of refrigerant occurs in the cycle of the operating indoor unit, the compression The machine suction port takes on the appearance of a liquid bag, the degree of superheating decreases, and the change in degree of superheating with respect to a unit change in the opening degree of the expansion valve has a positive correlation or becomes zero. This means that
This shows that refrigerant excess can be determined from the change in the degree of superheating and the value of the degree of heating with respect to a unit change in the degree of opening of the expansion valve.

As described above, the degree of superheating of the compressor suction port and the change in the degree of superheating with respect to the unit opening change of the expansion valve of the operating indoor unit are detected, and based on the detection results, if the operating indoor unit is short of refrigerant,
The valve at the refrigerant outlet of the stopped indoor unit is controlled to open, and if there is an excess of refrigerant, the expansion valve on the refrigerant population side is also controlled to open. As a result, the problem of refrigerant shortage or refrigerant excess in the operating indoor unit is resolved very smoothly. Since the operating range of a multi-system air conditioner is quite wide, if the expansion valve is controlled by fuzzy control, it becomes possible to control the amount of refrigerant with high precision.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 4. This embodiment is applied to a three-room air conditioner.

First, the configuration of an air conditioner is explained using Figure 1. In the figure, 1 is a compressor, 2 is a four-way valve, and 3 is an outdoor unit. Three indoor units 4, 5, and 6 equipped with electronic expansion valves 7 to 12 are connected in parallel to form a multi-system heat pump refrigeration cycle. Further, the suction port of the compressor 1 is provided with a suction temperature sensor 13 and a suction pressure sensor 14 for detecting the degree of superheating of the suction temperature.

The detection signals of both sensors 13 and 14 are sent to the control unit 15,
This control unit calculates the degree of superheat at the suction port of the compressor 1. The control unit 15 detects the superheat degree of the suction port of the compressor 1 and the change in the superheat degree with respect to a unit opening degree change of the electronic expansion valve of the operating indoor unit among the three indoor units 4.5.6. Based on the detection results, the electronic expansion valve of the stopped indoor unit is controlled to open and close, and the amount of refrigerant in the stopped indoor unit is adjusted. The suction temperature sensor 13, the suction pressure sensor 4, and the control section 15 constitute a refrigerant amount adjusting means.

Next, the operation of the air conditioner configured as described above will be explained using the control flowchart of FIG. 2 and FIGS. 3 and 4.

The microcomputer installed in the indoor unit to be operated or the compressor frequency (HzA, Hz
B 5HzC) to the outdoor unit 3 (step 21.
22.23). The outdoor unit 3 operates at a frequency expressed by the following formula based on the horsepower of the indoor unit and outdoor unit (step 24).
.

ΣHziX Indoor unit external force/outdoor unit horsepower 1) Here, i - Indoor unit number A, B, C In addition, the detection signals of the suction temperature sensor 13 and suction pressure sensor 14 are sent to the control unit 15 and the compressor 1 The superheat degree of the suction port is calculated, and the superheat degree TSH and the target superheat degree TS are calculated.
The superheat degree deviation SH, which is the difference between the two temperatures, is detected (step 25).

Then, based on the value of this superheat degree deviation SH, the opening degree of the electronic expansion valve of the operating indoor unit is controlled to perform superheat degree control.

The contents of this control are as follows: First, the total opening degree increment ΔPLS of the electronic expansion valve of the operating indoor unit is calculated (step 26).
, an increment in valve opening is allocated to the electronic expansion valve of each indoor unit according to its required capacity (steps 27 and 28). This control mechanism may be of any type, such as PID control or fuzzy control.

On the other hand, in parallel with the above control, the reciprocal B of the change in superheat degree for a unit change in valve opening degree is calculated as follows (step 2, 30).

ΔSH('') −3H(') −5)I
(n −1) , (2) B=ΔPLS(n
-1)"/Δ5H(n) ,,,(3) Here, in the case of ΔSH(')-0, a large value is entered in B. Also, the subscript n is expressed as n×Δ, which is the state value at time. It shows.

Then, based on these values, the valve opening degree increment ΔPLS of the electronic expansion valve at the inlet/outlet of the stopped indoor unit is determined by the fuzzy control shown in FIGS. 3 and 4. At this time, superheat degree deviation SH
If is positive or negative, it is determined which electronic expansion valve, the inlet side or the outlet side, should be opened (steps 31, 32, and 33). Both the inlet and outlet electronic expansion valves are never open at the same time.

Next, the fuzzy control rules shown in FIG. 4 will be briefly explained. If the degree of superheating is quite large (SH-PB) and the value of B is quite large (B-PB: the electronic expansion valve on the operating indoor unit side cannot be controlled), there is a refrigerant shortage, and the refrigerant outlet side of the stopped indoor unit electronic expansion valve is opened wide (
ΔPLS-PB).

Furthermore, if the degree of superheat is close to the target value, the amount of refrigerant is considered to be appropriate regardless of the value of B, and the electronic expansion valve on the refrigerant outlet side does not operate (in this case, the electronic expansion valve is closed).

On the other hand, if a liquid back-up occurs and the superheat degree is considerably smaller than the target value (SH-NB), if the liquid back-up does not disappear even after controlling the superheat degree (B-ZO, B-NB, B-P
B) It is assumed that there is an excess of refrigerant, and the electronic expansion valve on the refrigerant inlet side of the stopped indoor unit is controlled.

In this case, in consideration of refrigerant noise, ΔPLS=PM is set in all cases so that the increment in the opening degree of the electronic expansion valve is smaller than when the refrigerant outlet side is opened.

[Effects of the Invention] As explained above, according to the present invention, the degree of superheat of the compressor suction port and the change in the degree of superheat with respect to the unit opening degree change of the expansion valve of the operating indoor unit among the plurality of indoor units are detected. Based on the detection result, the expansion valve of the stopped indoor unit is controlled and the amount of refrigerant in the stopped indoor unit is adjusted. By being able to determine if there is a refrigerant shortage or refrigerant excess in the unit, it is possible to resolve refrigerant shortages or refrigerant excesses in operating indoor units extremely smoothly under a wide range of operating conditions.
At the same time, the efficiency of the refrigeration cycle and the reliability of the compressor can be improved.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the air conditioner according to the present invention, in which FIG. 1 is a system diagram showing a refrigeration cycle, FIG. 2 is a flowchart for explaining the operation, and FIG.
Figure 4 shows the membership function of fuzzy control.
The figure shows the rules of fuzzy control. 1: Compressor, 3 Outdoor unit, 4.5.6: Indoor unit, 7-12: Electronic expansion valve, 13:
Suction temperature sensor, ]4. Suction pressure sensor; 15. A control unit that constitutes a refrigerant amount adjustment means together with the suction temperature sensor and the suction pressure sensor.

Claims (1)

[Scope of Claims] An air conditioner having a compressor, an outdoor unit, and a plurality of indoor units each equipped with an expansion valve at a refrigerant inlet/outlet, the degree of superheat of the compressor suction port and one of the plurality of indoor units Refrigerant amount adjustment that detects a change in the degree of superheat with respect to a unit opening change of the expansion valve of the operating indoor unit, controls the expansion valve of the stopped indoor unit based on the detection result, and adjusts the amount of refrigerant in the stopped indoor unit. An air conditioner characterized by having means.