Hydrodynamic bearing

A hydrodynamic bearing includes an annular washer having an annular face configured to form a hydrodynamic thrust bearing. The annular face defines a plurality of circumferentially spaced oil grooves having opposing first and second lips extending between inner and outer diameters of the face. The annular face further defines a plurality of circumferentially spaced thrust segments alternating with the grooves such that each of the thrust segments is disposed between an associated pair of first and second ones of the grooves. Each of the thrust segments includes a land that is raised on the face relative to the first and second lips of the associated pair, a first ramp extending from the second lip of the first groove to a first side of the land, and a second ramp extending from the first lip of the second groove to a second side of the land.

TECHNICAL FIELD

The present disclosure relates to hydrodynamic bearings.

BACKGROUND

A bearing is a device that reduces friction between components having relative movement. Two main categories of bearings are thrust bearings and radial bearings. Thrust bearings are typically used to restrain axial movement of one or more components while reducing friction between surfaces, whereas radial bearings typically support a component for rotation. Thrust bearings and radial bearings may be of the hydrodynamic type. A hydrodynamic bearing utilizes oil to form a load-carrying film that separates the two surfaces rotating relative to each other.

SUMMARY

According to one embodiment, a hydrodynamic bearing includes an axially extending sleeve defining a central bore and an annular washer extending radially outward from the sleeve. The washer has an annular bearing face that defines a plurality of circumferentially spaced oil grooves each having opposing first and second lips extending between inner and outer diameters of the washer. The bearing face further defines a plurality of circumferentially spaced thrust segments arranged about the washer in alternating arrangement with the grooves such that each of the thrust segments is disposed between an associated pair of first and second ones of the grooves. The thrust segments are bi-directionally ramped and configured carry a wedge-shaped thrust-load oil film. Each of the thrust segments includes a land that is raised on the bearing face relative to the first and second lips of the associated pair, the land having first and second opposing sides, a first ramp extending from the second lip of the first groove to the first side of the land, and a second ramp extending from the first lip of the second groove to the second side of the land.

According to another embodiment, a hydrodynamic bearing includes an axially extending sleeve defining a central bore and an annular washer extending radially outward from the sleeve. The washer has an annular bearing face that defines a plurality of circumferentially spaced oil grooves extending between inner and outer diameters of the face. The bearing face further defines a plurality of circumferentially spaced lands that are each circumferentially disposed between a pair of the grooves and a plurality of first ramps. Each first ramp extends from a corresponding one of the grooves to a corresponding one of the lands. Each of the first ramps slopes outwardly from the corresponding one of the grooves to the corresponding one of the lands. The bearing face also defines a plurality of second ramps that each extend from a corresponding one of the grooves to a corresponding one of the lands. Each of the second ramps slopes outwardly from the corresponding one of the grooves to the corresponding one of the lands.

According to yet another embodiment, a hydrodynamic bearing includes an annular washer having an annular face configured to form a hydrodynamic thrust bearing. The annular face defines a plurality of circumferentially spaced oil grooves having opposing first and second lips extending between inner and outer diameters of the face. The annular face further defines a plurality of circumferentially spaced thrust segments alternating with the grooves such that each of the thrust segments is disposed between an associated pair of first and second ones of the grooves. Each of the thrust segments includes a land that is raised on the face relative to the first and second lips of the associated pair, a first ramp extending from the second lip of the first groove to a first side of the land, and a second ramp extending from the first lip of the second groove to a second side of the land.

DETAILED DESCRIPTION

Directional terms used herein are made with reference to the views and orientations shown in the exemplary figures. A central axis is shown in the figures and described below. Terms such as “outer” and “inner” are relative to the central axis. For example, an “outer” surface means that the surfaces faces away from the central axis, or is outboard of another “inner” surface. Terms such as “radial,” “diameter,” “circumference,” etc. also are relative to the central axis. The terms “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made.

Referring toFIG. 1, a hydrodynamic bearing20supports a rotary member22. The bearing20may be fixed to a housing or other structure. The bearing20may be a combination thrust (axial) and radial bearing with hydrodynamic features for supporting both thrust (axial) and radial loads. In other embodiments, the hydrodynamic bearing20may be only a thrust bearing or only a radial bearing. The rotary member22includes a shaft24and a flange26. The shaft24extends through the bearing20. The bearing20includes a sleeve28that radially supports the shaft24for rotation about the centerline32and an annular washer30that supports thrust loads of the flange26. The bearing20and the rotary member22may be concentric with each other and centered on the centerline32or may be offset from the centerline32. The sleeve28and the washer30may be integrally formed as a solid body. The bearing20may be formed of plastic.

The hydrodynamic bearing20is configured to create a load-carrying oil film between the washer30and the flange26and between the sleeve28and the shaft24. During rotational operation, oil34is fed into the contact between washer30and flange26to create a wedge-shaped thrust-load carrying oil film. Oil is also fed into the contact between shaft24and sleeve28to create a wedge-shaped radial-load oil film.

Referring toFIGS. 1, 2, and 3, the sleeve28extends axially and has an inner diameter36that defines a central bore40sized to receive the shaft24. The annular washer30may be centered on the centerline32and extends radially outward from an end42of the sleeve28. The annular washer30has an annular bearing face44configured to form a hydrodynamic thrust bearing. The bearing face44has an outer diameter46and an inner diameter48. The inner diameter48may be continuous with the inner diameter36of the sleeve28, or a transition may be present. The bearing face44may be an axial face that is oriented radially, i.e., perpendicular, to the centerline32. The bearing face44defines a plurality of oil grooves50. The grooves50are circumferentially spaced around the face44and may be equally spaced relative to each other. The face44is shown with ten grooves, but the number may vary depending upon the specific requirements of the bearing20. The grooves50extend radially across the face44. The grooves50may extend partially or may extend completely from the outer diameter46to the inner diameter48. The face44further defines a plurality of circumferentially spaced thrust segments52alternating with the grooves50such that each of the thrust segments52is disposed between an associated pair of first and second ones of the grooves50, e.g., grooves50aand50b. The thrust segments52are bi-directionally ramped and configured carry a wedge-shaped thrust-load oil film in both rotational directions of the rotary member22.

Referring toFIGS. 2 and 4, the grooves50have opposing lips60,62that may extend radially between the inner and outer diameters of the face44. Each thrust segment52includes a land54, a first ramp56, and a second ramp58. The land54is flat and represents the highest point of the face44. That is, the land54is raised on the bearing face44relative to the first and second lips60,62. The ramp56extends from the lip62of the groove50ato a first side64of the land54. The other ramp58extends from the lip60of the groove50bto a second side66of the land54. The ramps56,58extend and slope from their lowest positions at the lips60,62to their highest positions at the land54. The ramps56,58slope in opposite directions making the thrust segments52bi-directional. That is, the ramps58are sloped outwardly in the clockwise direction of the washer30and the ramps56are sloped outwardly in the counterclockwise direction of the washer30.

The bi-directional thrust segments52allow the bearing20to be functional for both rotational directions of the rotary member22. The ramps58and the lands54cooperate to provide a wedge-shaped thrust-load oil film when the flange26rotates clockwise, and the ramps56and the lands54cooperate to provide a wedge-shaped thrust-load oil film when the flange26rotates counterclockwise.

The grooves50each have a circumferential width (W) measured between the lips60and62, and a depth (D). The depth D is measured at the deepest point of the groove. The land54has first circumferential length80measured between the first and second sides64,66. The first ramp56has a circumferential length82measured between the second lip62and the first side64. The second ramp58has a circumferential length84measured between the first lip60and the second side66. (When comparing the width W and the lengths80,82,84the measurements should be at a same radial position of the face44.)

In the illustrated embodiment, the ramps56and58are circumferentially longer than the land54, and the ramps56,58are the same length. In other embodiments, however, the lands54can be longer than the ramps56,58and/or the ramps may be of different lengths. The relative dimensions of the components of the thrust segments52can be tuned to provide optimum performance for particular applications. According to one or more embodiments, the ratio between the length80of the land54and the length(s)82,84, or both is between 1:1 to 1:5; the ratio between the width W of the groove50and the length(s)82,84, or both is between 1:1 to 1:15; and the depth D is between 0.025 to 1.5 millimeters (mm). The angles Alpha and Beta may be between 0.25 to 3 degrees. These relative lengths, the depth D, and the angles are of course merely examples and may vary according to application of the bearing20.

Referring toFIGS. 3 and 5, the inner diameter36of the sleeve28may form a bearing surface90configured to create a wedge-shaped radial-load oil film for supporting the shaft24for rotation within the bearing20. The bearing surface90defines a plurality of circumferentially spaced oil channels92having opposing first and second lips94,96extending axially. (The terms grooves and channels are used for reader convenience and does not necessarily denote any structural differences beyond those explicitly described.) The bearing surface90also defines a plurality of circumferentially spaced radial-bearing segments98alternating with the channels92such that each of the radial-bearing segments98is disposed between an associated pair of first and second ones of the channels92. The radial-bearing segments98may also be bi-directionally ramped and configured to carry the wedge-shaped radial-load oil film in both directions.

The radial-bearing segments98may be the same or similar to the bearing segments52. Each segment98may include a land100having first and second opposing sides102,104and being raised on the bearing surface90relative to the first and second lips94,96of the associated pair of channels. A first ramp106extends from the second lip96of the first channel92ato the first side102of the land100, and a second ramp108extends from the first lip94of the second channel92bto the second side104of the land100. The ramps106,108slope in opposite directions making the bearing segments98bi-directional. That is, the ramps106are sloped outwardly in the clockwise direction and the ramps108are sloped outwardly in the counterlockwise direction.

The bi-directional radial-bearing segments98allow the bearing surface90to be functional for both rotational directions of the shaft24. The ramps106and the lands100cooperate to provide a wedge-shaped radial-load oil film when the shaft24rotates clockwise, and the ramps108and the lands100cooperate to provide a wedge-shaped radial-load oil film when the shaft24rotates counterclockwise.

The channels92each have a circumferential width (W) measured between the lips94and96, and a depth (D). The depth D is measured at the deepest point of the channel92. The land100has first circumferential length10measured between the first and second sides102,104. The first ramp106has a circumferential length112measured between the second lip96and the first side102. The second ramp108has a circumferential length114measured between the first lip94and the second side104. In the illustrated embodiment, the ramps106and108are circumferentially longer than the land100, and the ramps106,108are the same length. In other embodiments, however, the land100can be longer than the ramps106,108and/or the ramps106,108may have different lengths. The relative dimensions of the components of the thrust segments98can be tuned to provide particular properties suitable for particular applications.

The radial-bearing segment98may be the same as the thrust segments52, i.e., have the above-described relative dimensions. Or, the radial-bearing segments98may have different dimensions than the thrust segments52to account for the differences between axial and radial loads of the rotary member22.

Referring toFIGS. 6 and 7, another hydrodynamic bearing150may have both thrust and radial bearing faces. The thrust face152has a plurality of oil grooves154and thrust segments156between the grooves. Each thrust segment156has a pair of ramps158,160and a land162. The radial-bearing face166has a plurality of oil channels168and radial-bearing segments170between the channels168. Each segment170has a pair of ramps172,174and a land176.

The grooves154and the channels168may be circumferentially aligned and may have different shapes, dimensions, or both. The channels168may be wider than the grooves154. The channels168may include a bulbous portion178and a straight-walled portion180. The bulbous portion178may be at the transition182between the thrust152and radial bearing faces166. The channels168may include dams184. The dams184may be a raised wall186that encloses one end188of the channels168. The bulbous portions178increases the flow of oil from the grooves154to the channels168, and the dams184restrict the flow of oil out of the channels168to ensure a sufficient amount of oil is stored within the channels168.

While the above-described bearings are shown having both radial and thrust bearing faces, the bearings may include only a radial bearing face or only an axial bearing face in other embodiments.

The following is a list of reference numbers shown in the Figures. However, it should be understood that the use of these terms is for illustrative purposes only with respect to one embodiment. And, use of reference numbers correlating a certain term that is both illustrated in the Figures and present in the claims is not intended to limit the claims to only cover the illustrated embodiment.

PARTS LIST