Piston assembly
The present disclosure relates to a piston assembly, the piston assembly comprising a cylinder extending along an axis and having an open axial end, a cap assembly closing the cylinder at its open axial end, wherein the cap assembly comprises an insertion portion received in the cylinder at its open axial end, and a piston axially movably disposed within the cylinder and partially received in the insertion portion of the cap assembly. The present disclosure further relates to a variable displacement hydraulic unit including said piston assembly.
1. A piston assembly, comprising:
a cylinder extending along an axis and having an open axial end,
a cap assembly closing the cylinder at its open axial end, the cap assembly comprising an insertion portion received in the cylinder at its open axial end, and
a piston axially movably disposed within the cylinder and partially received in the insertion portion of the cap assembly;
a first biasing member for biasing the piston in a first direction along the axis, and
an axially displaceable zeroing member limiting axial movement of the first biasing member; and
a worm screw or leadscrew engaged with the zeroing member so that the zeroing member is displaceable along the axis by rotating the worm screw.
2. The piston assembly of claim 1 , wherein a cylinder wall enclosing the cylinder has a cylindrical shape and includes no machined portion or portions in or on the cylinder wall.
3. The piston assembly of claim 1 , wherein the cap assembly comprises an outer sealing member disposed radially in between the insertion portion of the cap assembly and a cylinder wall enclosing the cylinder, wherein the outer sealing member is mounted on the insertion portion of the cap assembly.
4. The piston assembly of claim 3 , wherein a radially outer surface of the insertion portion of the cap assembly comprises an outer annular indentation, wherein the outer sealing member is received in the outer annular indentation.
5. The piston assembly of claim 1 , wherein the cap assembly comprises an inner sealing member disposed radially in between the insertion portion of the cap assembly and the piston, wherein the inner sealing member is mounted on the insertion portion of the cap assembly.
6. The piston assembly of claim 5 , wherein a radially inner surface of the insertion portion of the cap assembly comprises an inner annular indentation, wherein the inner sealing member is received in the inner annular indentation.
7. The piston assembly of claim 1 , further comprising a hydraulic chamber formed axially in between the cap assembly and the piston, wherein a hydraulic pressure in the hydraulic chamber is configured to bias the piston in the first direction along the axis.
8. The piston assembly of claim 1 , further comprising a housing, wherein the cylinder is formed in the housing and the cap assembly is fixed to the housing.
9. The piston assembly of claim 1 , wherein the first biasing member is axially supported on the cap assembly.
10. The piston assembly of claim 1 , further comprising
a second biasing member for biasing the piston in a second direction along the axis, opposite the first direction,
wherein the zeroing member limits axial movement of the first biasing member in the first direction along the axis and wherein the zeroing member limits axial movement of the second biasing member in the second direction along the axis, opposite to the first direction.
11. The piston assembly of claim 10 , wherein the piston comprises a body portion and a protrusion extending from the body portion in a lateral direction perpendicular to the axis, wherein the first biasing member is configured to be axially supported on the protrusion and to bias the piston in the first direction along the axis when at least a portion of the protrusion extends beyond the zeroing member in the second direction along the axis, and wherein the second biasing member is configured to be axially supported on the protrusion and to bias the piston in the second direction along the axis when at least a portion of the protrusion extends beyond the zeroing member in the first direction along the axis.
12. The piston assembly of claim 11 , wherein an axial extension of the protrusion is equal to an axial extension of the zeroing member.
13. The piston assembly of claim 11 , further comprising:
a first thrust ring axially disposed in between the zeroing member and the first biasing member and in between the protrusion and the first biasing member so that the first biasing member is configured to be supported on the protrusion via the first thrust ring and to move the piston in the first direction until the first thrust ring hits the zeroing member, and
a second thrust ring axially disposed in between the zeroing member and the second biasing member and in between the protrusion and the second biasing member so that the second biasing member is configured to be supported on the protrusion via the second thrust ring and to move the piston in the second direction until the second thrust ring hits the zeroing member.
14. The piston assembly of claim 10 , wherein the first biasing member and/or the second biasing member at least partially enclose/encloses the piston.
15. A variable displacement hydraulic unit, comprising:
a swashplate, and
the piston assembly of claim 1 ,
wherein the piston is coupled to the swashplate for rotating the swashplate.
16. A piston assembly, comprising:
a cylinder extending along an axis and having an open axial end,
a cap assembly closing the cylinder at its open axial end, the cap assembly comprising an insertion portion received in the cylinder at its open axial end, and
a piston axially movably disposed within the cylinder and partially received in the insertion portion of the cap assembly;
a first biasing member for biasing the piston in a first direction along the axis, and an axially displaceable zeroing member limiting axial movement of the first biasing member; and
a rotatable gudgeon including an eccentric pin engaged with the zeroing member so that the zeroing member is displaceable along the axis by rotating the rotatable gudgeon.