JP3072995B2 - Air conditioner compressor control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a compressor capacity control method for an air conditioner having a relatively large capacity.

[Conventional technology]

As described in Japanese Utility Model Application Laid-Open No. 58-85159, the conventional apparatus operates by switching two compressors as needed. Therefore, no consideration has been given to the problems that occur during the refrigeration cycle operation when the two units start operating at the same time.

[Problems to be solved by the invention]

The above prior art does not take into account stabilization of the refrigeration cycle, such as the followability of the expansion valve that occurs when the operation of the compressor is switched, and the low pressure of the refrigeration cycle suddenly increases when the capacity is increased from one to two. There was a problem that it was lowered. For this reason, the balance of the refrigeration cycle is lost, and the one in which the low pressure switch is installed operates, and the low pressure force may be abnormally low. Further, in the absence of such a protection device, an abnormally low pressure state is repeatedly operated, so that the compressor itself is operated under adverse conditions.

It is an object of the present invention to solve such a problem, and it is another object of the present invention to provide a control method for optimizing the capacity control of a compressor employing an inverter.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an air conditioner comprising a refrigeration cycle having a heat exchanger, a blower, an expansion valve, and a plurality of compressors, and controlling an operation frequency of the compressor to control its capacity. In the compression control method of the compressor, when the operation of the compressor is shifted from one to two in order to increase the capacity, one of the compressors operated in advance is set to the frequency immediately before switching, and The operation is performed while maintaining the opening degree of the expansion valve at a value at which the refrigerant circulation amount can be ensured, and then the operation of the other compressor is started.

When increasing the capacity, the operating frequency of one of the compressors operated in advance is set to the frequency immediately before switching, and the opening of the expansion valve is maintained until the refrigerant circulation amount can be secured. The opening is synchronized with the control of the compressor capacity, there is no sharp drop in low pressure, and low pressure shutoff is prevented to ensure reliability.

[Operation] In the present invention, a plurality of compression mechanisms are incorporated in one refrigeration cycle, and the capacity of the compression mechanism is controlled by an inverter. Because of the control, the expansion valve balance openings during operation of a single compression mechanism and during operation of a plurality of compression mechanisms are significantly different, and must be adjusted to the respective degrees. In the present invention, in order to synchronize with the compressor displacement control in consideration of the opening follow-up speed of the expansion valve, when shifting from a single compression mechanism operation to a plurality of operations, the operation is performed at a frequency immediately before switching for a fixed time, and the expansion valve opening Since a following operation is awaited and a large amount of refrigerant is circulated, stable operation can be performed without a sharp decrease in low pressure.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, the horizontal axis indicates time, and the vertical axis indicates a refrigeration cycle operation state such as compressor frequency, expansion valve opening, and pressure. FIG. 2 shows a flowchart of the frequency increase control in the capacity control during the refrigeration cycle operation. In FIG. 1, when the conventional air conditioner shifts from one to two when the capacity control of the air conditioner is increased, as shown by the broken line, the conventional preceding operation and the additional compressor 3 are operated simultaneously, so that the conventional low pressure Since the low pressure, such as the pressure 9, drops to near the low pressure cut set value 10, the state becomes abnormally low, causing the protection device to operate or an undesired operation for the compressor. Although the conventional high pressure 7 gradually rises as the compressor frequency rises, it is required when two units are operated because the expansion valve follow-up speed is constant as shown in the conventional expansion valve opening 5. This indicates that the low-pressure pressure sharply drops because the frequency increases before the valve opening degree at which the amount of the circulated refrigerant circulates can be secured. In this embodiment, since the expansion valve follow-up speed and the compressor frequency rise speed are constant, the control method of the compressor is improved.
When shifting to the stand operation, the preceding operation compressor 1 is maintained at a specific value for a specific time (for example, 74 HZ for 5 minutes), and waits for the expansion valve to open as indicated by the expansion valve opening 4. In the form of a high pressure 6 according to the invention, a low pressure 8 according to the invention,
As shown by the curve, rapid pressure change is prevented. Thereafter, as shown in the additional compressor 2, the low pressure can relatively gradually shift to a normal value in order to start the additional operation. FIG. 2 is a flowchart showing this compressor starting method.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the present invention, even if the capacity is increased when controlling a plurality of compressors, it is possible to prevent a sudden low pressure drop, and to prevent low pressure pressure shutoff (protection device operation) and abnormal operation of the compressor, thereby achieving stable refrigeration. Cycle operation and compressor reliability can be ensured.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, in which a horizontal axis represents time, a vertical axis represents a compressor frequency and others, and a refrigeration cycle operation state explanatory diagram. FIG. 2 is a control of the present invention when the compressor frequency is increased. 3 shows a flowchart. 1 ... preceding operation compressor frequency 4 ... expansion valve opening 9 ... conventional low pressure.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F25B 1/00 F04B 49/06 F24F 11/02

Claims (1)

(57) [Claims] 1. A compressor control method for an air conditioner, comprising: a refrigeration cycle having a heat exchanger, a blower, an expansion valve, and a plurality of compressors, wherein an operation frequency of the compressor is controlled to control its capacity. In shifting the operation of the compressor from one to two in order to increase the capacity, one of the compressors operated in advance is set to the frequency immediately before switching, and the opening degree of the expansion valve is set. A method for controlling the compressor of an air conditioner, comprising: operating the compressor while maintaining a specific time so that the refrigerant circulation amount can be ensured, and then starting the operation of the other compressor.