Description

VDOT Refrigeration System:

Variable Displacement Orifice Tube (VDOT) Refrigeration System

The variable displacement orifice tube (VDOT) system is comprised of a variable displacement compressor and a fixed expansion tube. This system can match the air conditioning demands under all conditions without cycling. The basic compressor mechanism is a variable angle wobble-plate with five axially oriented cylinders. The center of control of the compressor displacement is a bellows actuated control valve located in the rear head of the compressor that senses compressor suction pressure. The wobble-plate angle and compressor displacement are controlled by the crankcase-suction pressure differential. When the A/C capacity demand is high, the suction pressure will be above the control point; the valve will maintain a bleed discharge gas into the crankcase and close off a passage from the crankcase to the suction plenum. The angle of the wobble-plate is controlled by a force balance on the five pistons. A slight elevation of the crankcase-suction pressure differential creates a total force on the pistons resulting in a movement about the wobble-plate pivot pin that reduces the plate angle.