Up to now, various compressor models for automotive air conditioners have been manufactured to answer the needs of car manufacturers for fuel economy and quietness. The 10PC20 compressor, developed for automotive air conditioners, is the world's first swash plate type compressor having a continuously variable displacement mechanism.The 10PC20 is aimed at realizing a large displacement compressor with a continuously variable displacement mechanism, which has not been achieved until today. To achieve this goal, the 10PC20 design is based on the swash plate type compressor, consisting of double-headed pistons, which is adaptable to a large displacement and has excellent rotating balance and durability. The 10PC20 changes its displacement continuously by changing the inclination of the swash plate (swash plate angle) continuously. (See photo. 1 and 2) The 10PC20 adopts two variable displacement principles. The first controls the displacement by changing the piston stroke, and the second controls the displacement by changing the piston top volume. Structurally, the 10PC20 features a swash plate angle regulation mechanism which changes the swash plate angle along a specified locus, and a swash plate angle control mechanism which controls the displacement so that the suction pressure of the compressor equals a specified pressure. As a result, the 10PC20 is able to react quickly to maintain the most favorable air conditioning cycle constantly, against changes in the vehicle cooling load and engine speed. Therefore, the 10PC20 provides comfortable air conditioning, excellent fuel economy and NVH characteristics.This report covers the structure, principle and mechanism of variable displacement, and the evaluation results of the 10PC20.