Servo arrangement

Patent metadata

Field	Value
Publication number	US-2024026867-A1
Application number	US-202118249146-A
Country	US
Kind code	A1
Filing date	Dec 15, 2021
Priority date	Jan 22, 2021
Publication date	Jan 25, 2024
Grant date	—

Abstract

A variable displacement hydraulic unit with a housing in which a rotating group is housed, wherein the displacement volume of the rotating group is variably adjustable by means of a swivel element able to tilt around a tilt axis perpendicular to the rotational axis of the rotating group. The swivel element can be actuated by at least one servo unit including a servo cylinder integrated in the housing and a servo piston moveably within the servo cylinder. The head of the servo piston can be pressurized in the servo cylinder such that a movement of the servo piston coupled to the swivel element via a servo piston shaft tilts the swivel element; wherein the servo unit is located within the housing on that side of the swivel element on which no rotating group is located, and follow a working direction substantially parallel to the rotational axis of the rotating group.

First claim

What is claimed is:

1 . A variable displacement hydraulic unit with a housing in which a rotating group is housed, wherein the displacement volume of the rotating group is variably adjustable by means of a swivel element tiltable around a tilt axis perpendicular to the rotational axis of the rotating group, which swivel element can be actuated by at least one servo unit comprising:
a servo cylinder integrated in the housing; a servo piston moveably within the servo cylinder, wherein the head of the servo piston can be pressurized in the servo cylinder, such that a movement of the servo piston, which is coupled to the swivel element via a servo piston shaft, tilts the swivel element; wherein the servo unit is arranged within the housing on that side of the swivel element on which no rotating group is located, and follows a working direction substantially parallel to the rotational axis of the rotating group.

2 . The hydraulic unit according to claim 1 , wherein the hydraulic unit comprise more than one servo unit with working directions substantially parallel to each other.

3 . The hydraulic unit according to claim 1 , comprising two servo units arranged symmetrically with regard to the swivel element tilt axis, such that the movement of one servo piston towards the rotating group causes the other servo piston to enter into the respective servo cylinder.

4 . The hydraulic unit according to claim 3 , comprising two pairs of servo units, with each pair having one servo unit on either side of the swivel element tilt axis.

5 . The hydraulic unit according to one of the preceding claims, wherein a skirt of the servo piston head shows a convex or spherical shape.

6 . The hydraulic unit according to claim 1 , wherein the servo piston shaft is connected to the swivel element in an articulated manner.

7 . The hydraulic unit according to claim 1 , wherein the connection of the servo piston shaft to the swivel element is a kind of ball joint, hinge joint, pin joint or similar, comprising a calotte on the swivel element into which a convex end of the servo piston shaft can be inserted, such that linear forces in direction of the servo piston shaft can be transmitted to the swivel element and vice versa.

8 . The hydraulic unit according to claim 1 , wherein the servo cylinder is a bore in the housing or a cylinder fixed to the inner side of the housing.

9 . The hydraulic unit according to claim 1 , wherein, in a neutral position of the swivel element, the rotating group do not show a displacement volume and the servo piston(s) are at half way of their possible stroke in the servo cylinder.

10 . The hydraulic unit according to claim 1 wherein a tilt movement is provided by means of a stop surface stationary at the housing.

11 . The hydraulic unit according to claim 1 , wherein the servo cylinder can be pressurized by a servo pressure provided by a pressure source internal or external to the hydraulic unit and controlled by a control unit.

12 . The hydraulic unit according to claim 11 , wherein the external pressure source is a bolt-on pressure source having hydraulic fluid or air as working fluid.

13 . The hydraulic unit according to claim 11 , wherein the height of the servo pressure is provided in a load dependent manner.

14 . The hydraulic unit according to claim 1 , wherein a servo spring is located at the swivel element opposite to a servo unit and on the sliding surface side of the swivel element, in order to provide a restoring force to the swivel element when the swivel element is tilted away from an initial position by the allotted servo unit.

15 . The hydraulic unit according to claim 1 , wherein to each servo unit at least one servo spring is allotted.

16 . The hydraulic unit according to claim 1 , comprising restoring means for holding or restoring the swivel element into a neutral position, in which the stroke of the displacement pistons is zero, wherein the restoring means comprise at least two servo springs arranged with a first end on the sliding surface side of the swivel element, such that in neutral position of the swivel element the servo spring forces are balanced, and wherein the servo springs are attached with their second end to a fixing point stationary within the housing, preferably at the end cap of the hydraulic unit.

17 . The hydraulic unit according to claim 16 , wherein the servo springs are arranged symmetrically with respect to the tilt axis on the sliding surface side of the swivel element.

18 . The hydraulic unit according to claim 16 , wherein the restoring means provide for an end stop of a maximum tilt angle of the swivel element in either direction of tilt.

19 . The hydraulic unit according to claim 14 , wherein, in the initial position of the swivel element, the servo spring(s) is/are pre-tensioned.

20 . The hydraulic unit according to claim 14 , wherein the servo spring(s) is/are guided by internal or external guiding means and/or is/are attached with a first end in an articulated manner to the swivel element and with the second end to the fixing point, wherein the guiding means comprise at least at their first end a spring seat on which the servo spring can abut.

Assignees

• Danfoss Power Solutions Gmbh & Co Ohg

Inventors

• Fiebing Carsten
• Laffrenzen Heiko
• Reinhardt Thoms

Classifications

• F04B1/2078

  Swash plates · CPC title

• F04B1/324 Primary

  by changing the inclination of the swash plate · CPC title

• F15B15/1447

  Pistons; Piston to piston rod assemblies · CPC title

• F15B15/1476

  Special return means · CPC title

• F15B15/1428

  Cylinders (F15B15/1438 takes precedence) · CPC title