Capacity control of a compressor

Abstract

A linear compressor that is operated at a frequency greater than the natural frequency of the spring-mass system of the compressor. Operating the compressor at such a frequency can increase the output of the compressor. In one embodiment, the linear compressor includes a cylinder block having a cylinder bore, a piston positioned within the cylinder bore, first and second springs for positioning the piston where the piston and the first and second springs comprise the spring-mass system, and an armature operably engaged with the piston to drive the piston at a frequency greater than the natural frequency of the spring-mass system. The linear compressor can also include a controller which monitors the instantaneous natural frequency of the spring-mass system and modulates the frequency of the current passing through the armature such that it exceeds the natural frequency of the spring-mass system.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to compressors, and more particularly, to the capacity control of linear compressors. [0003] 2. Description of the Related Art [0004] Compressors can include a piston which is reciprocated within a cylinder bore to compress refrigerant, for example, in the cylinder bore. The compressor can further include a spring, or springs, which bias the piston into position. In some linear compressors, the piston is positioned intermediate two springs which hold the piston in a substantially stationary position until the piston is moved by an electromagnetic armature or motor, for example. The piston and springs comprise a spring-mass system having a natural, or resonant, frequency, as known in the art. If the piston is driven, via the armature or motor, at the natural frequency of the spring-mass system, the spring-mass system will resonate. Driving the piston of the compressor at, or very close t...

AI Technical Summary

Benefits of technology

[0008] The present invention includes a linear compressor that is operated at a frequency greater than the natural frequency of the spring-mass system of the compressor. Operating the compressor at such a frequency can increase the output of the compressor. In one embodiment, the linear compressor includes a cylinder block having a cylinder bore, a piston positioned within the cylinder bore, first and second springs for positioning the piston where the piston and the first and second springs comprise a spring-mass system having a natural frequency, and an armature operably engaged with the piston to drive the piston at a frequency greater than the natural frequency of the spring-mass system.

[0009] In another embodiment, the linear compressor includes a controller which monitors the instantaneous natural frequency of the spring-mass system and modulates the frequency of the current passing through the armature. As discussed above, the natural frequency of the spring-mass system can change as a result of fluctuati

Problems solved by technology

However, modulating the capacity of the compressor in this way has some limitations.

For example, increasing the magnitude of the current flowing through the armature can increase the resistance losses in the armature windings, thereby reducing the efficiency of the compressor.

Further, large displacements of the piston draws large quantities of refrigerant into the cylinder bore which may bog down or overpower the compressor.

However, when these compressors were required to produce a greater output of compressed refrigerant, their output was limited to that generated at the natural frequency of the compressor.

However, these larger-capacity compressors are typically more expensive and may become less efficient when lower demands of the compressor are required.

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