Patent ID: 7429839
Filing Date: 2008-09-30
Classification: F04B,H02P

Abstract:
1. A collision prevention unit for use in a linear compressor including a reciprocating piston, a linear motor driving the piston, and a motor controller controlling the linear motor to vary magnitude of a stroke of the piston according to power, the unit comprising: a near-collision detector detecting whether the piston passes a near-collision position spaced from a top dead center according to a predetermined high power with a predetermined high power distance; a collision return time calculator calculating a near-collision position return time for the piston to return to the near-collision position based on the detection of the near-collision detector according to compression and expansion cycles; an entry position detector detecting whether the piston passes an entry position detection position spaced from the top dead center according to a predetermined low power with a predetermined low power distance; and an entry return time calculator calculating an entry detection position return time for the piston to return to the entry detection position according to the compression and expansion cycles based on the detection of the entry position detector, wherein the motor controller decreases a driving force of the linear motor when the near-collision position return time is greater than a predetermined allowance time per power, and increases the driving force of the linear motor when the near-collision position return time is less than the predetermined allowance time per power when controlling according to the high power, and the motor controller further decreases the driving force of the linear motor when the entry detection position return time is greater than a predetermined criterion time per power, and increases the driving force of the linear motor when the entry detection position return time is less than the criterion time.