Variable displacement compressor control valve arrangement

Claim 1

In a variable displacement wobble plate type compressor having compression chambers each with a suction valve for admitting fluid thereto at a suction pressure and a discharge valve for delivering the fluid therefrom at a discharge pressure, a sealed crankcase containing a variable angle wobble plate mechanism whose angle and thereby the piston stroke and thus displacement of the compression chambers is made to vary by pressurizing the crankcase using fluid at discharge pressure wherein the displacement is at its minimum when crankcase pressure rises to discharge pressure and is at its maximum when crankcase pressure falls to suction pressure, and a displacement control valve continuously acted upon and normally responsive to at least compressor suction pressure for controlling the pressure in the compressor's crankcase relative to suction pressure so as to normally increase the piston stroke and thereby displacement with increasing suction pressure: the improvement comprising speed responsive control means for directly acting on and positively conditioning said displacement control valve irrespective of the suction pressure so as to increase the crankcase pressure to discharge pressure above but not below a prescribed compressor life limiting speed and thereby decrease the piston stroke and thus displacement to its minimum above but not below said speed.