Hydraulic steering unit

• US 5,097,920 A
• Filed: 08/30/1990
• Issued: 03/24/1992
• Est. Priority Date: 09/09/1989
• Status: Expired due to Fees

• Current Assignee: Danfoss Fluid Power A/S
• Original Assignee: Danfoss A/S
• Inventors: Holm-Pedersen, Poul H., Rasmussen, Ivar
• Primary Examiner(s): HILL, MITCHELL
• Application Number:
  US07/574,883
• Time in Patent Office: 572 Days
• Field of Search: 180/132, 384/607, 277/6, 277/7, 277/8, 277/215, 277/71, 277/79, 277/212 F, 277/212 R
• US Class Current: 180/441
• CPC Class Codes: B62D 5/062 Details, component parts
• CPC Class Codes: B62D 5/093 Telemotor driven by steering wheel movement hydraulic steering gear B62D3/14
• CPC Class Codes: F16J 15/004 forming of recuperation chamber for the leaking fluid

Abstract

Hydraulic steering mechanism is extended through an aperture in an end wall in a housing that has a pressure chamber, the steering mechanism including a slide rotatable with the steering column. An axial bearing is mounted by the end wall for rotatably mounting the steering mechanism while the aperture axially opposite end portion mounts a sealing ring between the housing and the steering mechanism. Axially between the sealing ring and the bearing there is a pressure reduction ring providing an annular gap with the slide for throttling the flow of fluid from the pressure chamber to a fluid collecting chamber that at least in part is defined by the pressure reduction and sealing rings. Fluid can flow from the collecting chamber through a housing outlet. The pressure reduction ring has an enlarged diameter flange for sealingly engaging the end wall and being clamped between the wall and the axial bearing. Increased pressure in the pressure chamber results in the flow of fluid through the gap increasing to automatically increase the pressure drop created by the throttle effect of the pressure reduction ring and thereby keeping the load on the sealing ring small.

Claims

1. A hydraulic steering unit comprising a housing having an end wall, a pressure chamber and a bore opening through the end wall to the pressure chamber, an axially extending steering control mechanism rotatably mounted by the housing and extending axially through the bore into the pressure chamber, a sealing ring in the bore for forming a fluid seal between the steering mechanism and the housing, a one piece pressure reduction ring surrounding the steering mechanism and at least in part being located axially between the pressure chamber and the sealing ring to provide a small annular gap between the pressure reducing ring and the steering mechanism that constitutes a throttle, and an annular fluid collecting chamber at least in part defined by the pressure reduction ring and the sealing ring and extending axially between the pressure reduction ring and the sealing ring, the pressure reduction ring having a part surrounded by the fluid collecting chamber, the housing having a fluid outlet opening to the fluid collecting chamber, the pressure reduction ring having a circumferential flange sealingly abutting against the end wall.

2. A steering unit according to claim 1, characterized in that the pressure reduction ring has an inner circumferential surface and at least one circumferential groove opening through the inner surface to the steering mechanism, the steering mechanism and the reduction ring providing an annular throttle axially between the collecting chamber and the pressure chamber.

3. A steering unit according to claim 2, characterized in that the groove is rectangular in cross section.

4. A hydraulic steering unit comprising a housing having an end wall, a pressure chamber and a bore opening through the end wall to the pressure chamber, an axially extending steering control mechanism rotatably mounted by the housing and extending axially through the bore into the pressure chamber, a sealing ring in the bore for forming a fluid seal between the steering mechanism and the housing, a one piece pressure reduction ring surrounding the steering mechanism and at least in part being located between the pressure chamber and the sealing ring, and a fluid collecting chamber that in part is defined by the pressure reduction ring and the sealing ring, the housing having an outlet opening to the fluid collecting chamber, the pressure reduction ring having a circumferential flange sealingly abutting against the end wall, the pressure reduction ring having an axially extending annular ring part extending axially between the circumferential flange and the sealing ring and being of an outer diameter substantially smaller than the outer diameter of the circumferential flange, and a central annular projection projecting axially away from the circumferential flange in a direction axially opposite the annular ring part, the central annular projection being of an outer diameter substantially smaller than the outer diameter of the circumferential flange.

5. A hydraulic steering unit comprising a housing having an end wall, a pressure chamber and a bore opening through the end wall to the pressure chamber, an axially extending steering control mechanism rotatably mounted by the housing and extending axially through the bore into the pressure chamber, a sealing ring in the bore for forming a fluid seal between the steering control mechanism and the housing, a one piece pressure reduction ring surrounding the steering control mechanism and at least in part being located between the pressure chamber and the sealing ring, and a fluid collecting chamber that in part is defined by the pressure reduction ring and the sealing ring, the housing having an outlet opening to the fluid collecting chamber, the pressure reduction ring having a circumferential flange sealingly abutting against the end wall, the pressure reduction ring having an annular part that has a first end opening to the pressure chamber and an annular part that has an end opening to the fluid collecting chamber, the annular ring part that opens to the pressure chamber having an inner circumferential surface that in an axial direction throughout its length is conical, and the annular ring part that opens to the fluid collecting chamber having an inner circumferential surface that is of a constant internal diameter throughout its axial length.

6. A steering unit according to claim 5 characterized in that the circumferential inner surface of the annular ring part that opens to the pressure chamber has a conical internal diameter enlargement of a gradient in the order of about 1,100.

7. A hydraulic steering unit comprising a housing having an end wall, a pressure chamber and an bore opening through the end wall to the pressure chamber, an axially extending steering control mechanism rotatably mounted by the housing and extending axially through the bore into the pressure chamber, a sealing ring in the bore for forming a fluid seal between the steering mechanism and the housing, a one piece pressure reduction ring surrounding the steering control mechanism and at least in part being located between the pressure chamber and the sealing ring, and a fluid collecting chamber that in part is defined by the pressure reduction ring and the sealing ring, the housing having an outlet opening to the fluid collecting chamber, the pressure reduction ring having a circumferential flange sealingly abutting against the end wall, and an axial bearing in the housing adjacent to the end wall for supporting the steering mechanism, the circumferential flange being clamped between the end wall and the axial bearing.

8. A steering unit according to claim 7, characterized in that the axial bearing comprises a roller element and a roller plate of stiff material between the pressure reduction ring and the roller element.

9. A steering unit according to claim 8, characterized in that the pressure reduction ring has centering means for ensuring the axial bearing is centered relative to the projection ring.