Patent ID: 7380492
Filing Date: 2008-06-03
Classification: F04B

Abstract:
1. A hydrostatic variable displacement unit having a swash plate ( 3 ) which serves to adjust the stroke of displacement pistons ( 1 ) in a cylinder block ( 2 ) and can be pivoted in its angular position with respect to the stroke direction of the displacement pistons ( 1 ) by means of a servo system ( 4 ), the servo system ( 4 ) comprising at least one servo piston ( 5 ) having two servo-piston end surfaces ( 6 ) which are in each case assigned a servo cylinder ( 7 ) and a servo-piston rear surface ( 8 ), the servo cylinders ( 7 ), by means of the assigned servo-piston end surfaces ( 6 ), in each case bounding a servo-cylinder pressure space ( 9 ), and the servo piston ( 5 ) being acted upon by a spring arrangement ( 10 ) which comprises at least one spring ( 11 ), which is arranged outside the servo-cylinder pressure space ( 9 ) and is clamped between two spring plates ( 12 ), wherein the two spring plates ( 12 ) are acted upon by the springs ( 11 ) in each case in the direction of a stop ( 13 ) of the particular servo cylinder ( 7 ) that is situated on its side, in such a manner that, in the neutral position, the spring plates ( 12 ) bear against the servo-piston rear surfaces ( 8 ) and against the stop ( 13 ) of the particular servo cylinder ( 7 ) in a manner essentially free from play, with the distance between the spring plates ( 12 ), and the spring prestress being determined by the distance between the two stops ( 13 ) of the servo cylinders ( 7 ).