Piston unit

Patent metadata

Field	Value
Publication number	US-9334956-B2
Application number	US-201113811518-A
Country	US
Kind code	B2
Filing date	Jul 7, 2011
Priority date	Jul 23, 2010
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A piston unit for a radial piston machine includes a piston and a roller or a roller element. The roller or roller element has a circular cylindrical jacket apart from a chamfer. A hydrostatic pressure- or force-relief element is provided in a contact area between the piston and the roller. The hydrostatic pressure- or force-relief element forms a pressure field in the contact area. The roller or roller element also has one or two end-face holes. Due to the hole(s), the roller is slightly weakened at the associated end section such that Hertzian stress is reduced at the same associated end section.

First claim

The invention claimed is:

1. A piston unit for a radial piston machine, comprising:
a piston;
a roller having a circular cylindrical shell and a first end-side recess in a first end-side portion of the roller; and
a hydrostatic pressure relief mechanism configured to act in a region of contact between the piston and the roller;
wherein the first end-side recess does not extend to a second end-side portion of the roller, the second end-side portion opposite the first end-side portion.

2. The piston unit as claimed in claim 1 , further comprising a second end-side recess in the second end-side portion of the roller, wherein:
the second end-side recess does not extend to the first end-side portion,
the first end-side recess and the second end-side recess are approximately concentric,
each of the two end-side recesses are surrounded by an approximately concentric ring portion, and
a main portion is arranged between the two ring portions.

3. The piston unit as claimed in claim 1 , wherein:
the pressure relief mechanism has a shallow depression arranged on the piston in the region of contact, and
the depression is connected via a duct to one of an inner end face and an encircling surface of the piston.

4. The piston unit as claimed in claim 3 , wherein the depression extends substantially over an entire length of the roller.

5. A piston unit for a radial piston machine, comprising:
a piston;
a roller having a circular cylindrical shell and an end-side recess; and
a hydrostatic pressure relief mechanism configured to act in a region of contact between the piston and the roller,
wherein the end-side recess in the roller is filled with plastic.

6. The piston unit as claimed in claim 5 , wherein the plastic is an elastomer.

7. The piston unit as claimed in claim 1 , wherein:
the roller has an axis of rotation,
the piston has a main portion having a length along the axis of rotation that is longer than a width perpendicular to the axis of rotation.

8. The piston unit as claimed in claim 1 , wherein:
the piston is a stepped piston having a core and an encapsulation, and
the encapsulation has a lower hardness than the core.

9. The piston unit as claimed in claim 8 , wherein the encapsulation is formed from metal.

Assignees

• Nagel Philip
• Breuer David
• Kermode Geoffrey
• Tibari Khaled
• Bosch Gmbh Robert

Inventors

• Nagel Philip
• Breuer David
• Kermode Geoffrey
• Tibari Khaled

Classifications

• F04B1/0408 Primary

  Pistons · CPC title

• F04B1/1071

  with rotary cylinder blocks · CPC title

• F16J1/00 Primary

  Pistons; Trunk pistons; Plungers (bellows pistons F16J3/06; piston-rings or seats therefor F16J9/00; {manufacture of pistons B23P15/10}; rotary pistons, e.g. for "Wankel" type engines F01C; specific for combustion engines, i.e. constructed to withstand high temperature or modified for guiding, igniting, vaporising or otherwise treating the charge F02F; {pistons for hydraulic engines F03C}; pumps F04B; floats F16K33/00) · CPC title