Axial piston pump neutral centering mechanism

A variable displacement pump assembly of the type comprising a pump housing defining a pumping chamber, a rotating group disposed in said pumping chamber, and a tiltable swashplate operably associated with said rotating group to vary the fluid displacement thereof;

• said swashplate defining a tilt axis and including a trunnion member having its axis of rotation coincident with said tilt axis, said trunnion member being rotatably supported relative to said pump housing;
• and a neutral centering mechanism operably associated with said pump housing and with said swashplate;
• characterized by:
• (a) said neutral centering mechanism comprising a cam member having an axis of rotation, and being fixed to rotate with said trunnion member;
• said axis of rotation of said cam member being coincident with said axis of rotation of said trunnion member;
• (b) said cam member defining a cam surface oriented generally parallel to said axis of rotation of said cam member, said cam surface including a minimum displacement portion and a maximum displacement portion;
• (c) said neutral centering mechanism further including a cam follower assembly fixed relative to said pump housing, and including a cam follower element, and means biasing said cam follower element into engagement with said cam surface, whereby, when said cam follower element is in engagement with said maximum displacement portion of said cam surface, said biasing means and said cam follower element bias said cam member toward a neutral position in which said cam follower element is in engagement with said minimum displacement portion of said cam surface.