Positive displacement machines and methods of increasing load-carrying capacities thereof

Patent metadata

Field	Value
Publication number	US-10247177-B2
Application number	US-201615207889-A
Country	US
Kind code	B2
Filing date	Jul 12, 2016
Priority date	Jul 13, 2015
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

Positive displacement machines and methods therefor capable of increasing a load-carrying capacity of a piston-cylinder lubrication interface of positive displacement machines having a cylinder block, a cylindrical bore defined in the cylinder block, a piston reciprocably disposed within the cylindrical bore, and a working fluid within the piston-cylinder lubrication interface to provide a load-bearing function between the piston and the bore wall of the cylinder bore. The method includes providing at least one circumferential groove on a bore wall of the cylindrical bore within the piston-cylinder lubrication interface having an opening facing the piston and that is in fluidic communication with the piston-cylinder lubrication interface so as to contain a portion of the working fluid, and operating the positive displacement machine such that the working fluid enters the cylindrical groove and promotes hydrostatic balancing of pressure of the working fluid within the piston-cylinder lubrication interface.

First claim

The invention claimed is:

1. A positive displacement machine comprising:
a cylinder block adapted to be rotated about an axis of the positive displacement machine;
a plurality of cylindrical bores defined in the cylinder block and surrounding the axis, each of the cylindrical bores having a bore wall and a port;
a plurality of pistons reciprocably disposed within the cylindrical bores, each of the pistons defining a piston-cylinder lubrication interface with the bore wall of a corresponding one of the cylindrical bores and defining a displacement chamber within the cylindrical bore adjacent the port thereof;
a working fluid located within the displacement chambers and within the piston-cylinder lubrication interfaces to provide a load-bearing function between the pistons and the bore walls of the cylinder bores;
a circumferencially continuous radial step in a surface of each of the cylindrical bores between the piston-cylinder lubrication interface and the displacement chamber thereof that defines an end of the piston-cylinder lubrication interface, wherein distal ends of the pistons are located within the displacement chambers of the cylinder bores, do not pass the radial steps of the cylindrical bores, and do not enter the piston-cylinder lubrication interfaces as the pistons reciprocate within the cylindrical bores during operation of the positive displacement machine; and
a plurality of circumferential grooves located within the piston-cylinder lubrication interfaces, at least one of the grooves being located on the bore wall of each of the cylindrical bores, the grooves having an opening facing the pistons and in fluidic communication with the piston-cylinder lubrication interfaces so as to contain a portion of the working fluid, wherein the grooves promote hydrostatic balancing of pressure of the working fluid within the piston-cylinder lubrication interfaces and increase a load-carrying capacity of the working fluid within the piston-cylinder lubrication interfaces during operation of the positive displacement machine.

2. The positive displacement machine of claim 1 , wherein the cylinder block defines the bore wall of each of the cylindrical bores and the grooves are formed in surfaces of the cylinder block.

3. The positive displacement machine of claim 2 , wherein the radial step of each of the cylindrical bores is defined by an undercut in the surface of the cylindrical bore.

4. The positive displacement machine of claim 1 , further comprising bushings located within the cylindrical bores and surrounding the pistons, wherein the bushings define the bore walls of the cylindrical bores and the grooves are formed in surfaces of the bushings.

5. The positive displacement machine of claim 4 , wherein ends of the bushings adjacent the displacement chambers define the radial steps of the cylindrical bores.

6. The positive displacement machine of claim 1 , wherein a distance between edges of the grooves closest to the displacement chambers of the cylindrical bores and ends of the piston-cylinder lubrication interface adjacent the displacement chambers is not more than fifty percent of a total axial length of the piston-cylinder lubrication interface.

7. The positive displacement machine of claim 1 , wherein the grooves have axial widths or a sum of axial widths along longitudinal axes of the cylindrical bores that each are at least ten percent of a total axial length of the piston-cylinder lubrication interface.

8. The positive displacement machine of claim 1 , wherein the grooves have depths in directions perpendicular to longitudinal axes of the cylindrical bores of at least twenty micrometers.

9. The positive displacement machine of claim 1 , wherein the grooves are not directly connected to any high pressure source of the working fluid other than through the piston-cylinder lubrication interfaces.

10. The positive displacement machine of claim 1 , wherein the working fluid is a low viscosity fluid.

11. A method of improving a load-carrying capacity of a piston-cylinder lubrication interface of a positive displacement machine comprising a cylinder block, a cylindrical bore defined in the cylinder block and having a bore wall and a port, a piston reciprocably disposed within the cylindrical bore, the piston defining a piston-cylinder lubrication interface with the bore wall of the cylindrical bore and defining a displacement chamber within the cylindrical bore adjacent the port thereof, and a working fluid within the displacement chamber and within the piston-cylinder lubrication interface to provide a load-bearing function between the piston and the bore wall of the cylinder bore, the method comprising:
providing a circumferencially continuous radial step in a surface of the cylindrical bore between the piston-cylinder lubrication interface and the displacement chamber thereof that defines an end of the piston-cylinder lubrication interface; and
providing at least one circumferential groove located on the bore wall of the cylindrical bore within the piston-cylinder lubrication interface, the groove having an opening facing the piston and in fluidic communication with the piston-cylinder lubrication interface so as to contain a portion of the working fluid; and
operating the positive displacement machine such that a distal end of the piston located within the displacement chamber of the cylinder bore does not pass the radial step of the cylindrical bore and does not enter the piston-cylinder lubrication interface as the piston reciprocates within the cylindrical bore, and the working fluid enters the cylindrical groove and promotes hydrostatic balancing of pressure of the working fluid within the piston-cylinder lubrication interface.

12. The method of claim 11 , wherein the cylinder block defines the bore wall of the cylindrical bore and the groove is formed in surfaces of the cylindrical block.

13. The method of claim 12 , wherein the radial step of the cylindrical bore is defined by an undercut in the surface of the cylindrical bore.

14. The method of claim 11 , wherein the positive displacement machine includes a bushing located within the cylindrical bore and surrounding the piston, the bushing defining the bore wall of the cylindrical bore, the method comprising forming the groove in surfaces of the bushing.

15. The method of claim 14 , wherein an end of the bushing adjacent the displacement chamber defines the radial step of the cylindrical bore.

16. The method of claim 11 , further comprising providing a distance between an edge of the groove closest to the displacement chamber of the cylindrical bore and an end of the piston-cylinder lubrication interface adjacent the displacement chamber is not more than fifty percent of a total axial length of the piston-cylinder lubrication interface.

17. The method of claim 11 , further comprising providing the groove to have an axial width along a longitudinal axis of the cylindrical bore that is at least ten percent of a total axial length of the piston-cylinder lubrication interface, or providing the groove to have an axial width along a longitudinal axis of the cylindrical bore that in combination with the axial widths of other circumferential grooves located on the bore wall to have a combined axial width of at least ten percent of a total axial length of the piston-cylinder lubrication interface.

18. The method of claim 11 , further comprising providing the groove to have a depth in a direction perpendicular to a longitudinal axis of the cylindrical bore of at least twenty micrometers.

19.

Assignees

• Purdue Research Foundation

Inventors

• Ivantysynova Monika Marianne
• Ernst Meike H

Classifications

• F04B53/18

  Lubricating · CPC title

• F04B39/0292

  Lubrication of pistons or cylinders · CPC title

• F03C1/0652

  Cylinders · CPC title

• F01B3/0044

  Component parts, details, e.g. valves, sealings, lubrication · CPC title

• F04B27/0834

  cylinder barrel · CPC title