Compressor pulse width modulation

Abstract

A scroll compressor includes a capacity modulation system. The capacity modulation system has a piston that is connected to the non-orbiting scroll that disengages the non-orbiting scroll from the orbiting scroll when a pressure chamber is placed in communication with the suction chamber of the compressor. The non-orbiting scroll member moves into engagement with the orbiting scroll when the chamber is placed in communication with the discharge chamber. The engagement between the two scrolls is broken when the pressure chamber is placed in communication with fluid from the suction chamber. A solenoid valve controls the communication between the pressure chamber and the suction chamber. By operating the valve in a pulsed width modulated mode, the capacity of the compressor can be infinitely varied between zero and one hundred percent.

Description

FIELD OF THE INVENTION[0001]The present invention is related to scroll-type machinery. More particularly, the present invention is directed towards capacity modulation of scroll-type compressors.BACKGROUND AND SUMMARY OF THE INVENTION[0002]Scroll machines are becoming more and more popular for use as compressors in refrigeration systems as well as air conditioning and heat pump applications. The popularity of scroll machinery is primarily due to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit with respect to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor is normally provided which operates to drive the scroll members via a suitable drive shaft. During normal operation, these scroll machines are designed to have a fixed compression ratio.[00...

AI Technical Summary

Benefits of technology

[0004]The present invention, however, overcomes these deficiencies by enabling an infinitely variable capacity modulation system which has the capability of modulating the capacity from 100% of full capacity down to virtually zero capacity utilizing only a single set of controls. Further, the system of the present invention enables the operating efficiency of the compressor and / or refrigeration system to be maximized for any degree of compressor unloading desired.

[0005]In the present invention, compressor unloading is accomplished by cyclically effecting axial separation of the two scroll members during the operating cycle of the compressor. More specifically, the present invention provides an arrangement wherein one scroll member is moved axially with respect to the other scroll member by a solenoid valve which operates in a pulsed width modulation mode. The pulsed width modulation operating mode for the solenoid valve provides a leakage path across the tips of the wraps from the higher compression pockets defined by the intermeshing scroll wraps to the lower compression pockets and ultimately back to suction. By controlling the pulse width modulation frequency and thus the relative time between sealing and unsealing of the scroll wrap tips, infinite degrees of compressor unloading can be achieved with a single control system. Further, by sensing various conditions within the refrigeration system, the duration of compressor loading and unloading for each cycle can be selected for a given capacity such that overall system efficiency is maximized.

[0006]The various embodiments of the present invention detailed below provide a wide variety of arrangements by which one scroll member may be axially reciprocated with respect to the other to accommodate a full range of compressor unloading. The ability to provide a full range of capacity modulation with a single control system as well as the ability to select the duration of loaded and unloaded operation cooperate to provide an extremely efficient system at a relatively low cost.

Problems solved by technology

Using a fixed compression ratio compressor to meet this wide range of loading requirements can present various problems to the designer of the system.

This delayed suction method of capacity modulation actually reduces the compression ratio of the compressor.

While such systems are effective at reducing the capacity of the compressor, they are only capable of providing a predetermined or stepped amount of compressor unloading.

While it is possible to provide multiple stepped unloading by incorporating a plurality of unloading ports at different locations along the compression process, this approach becomes more and more costly as the number of ports is increased and it requires additional space to accommodate the separate controls for opening and closing each individual on each set of ports.

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