Bearing systems for turbochargers used on internal combustion engines

Abstract

A bearing system for a turbocharger rotor assembly that includes an elongated bearing carrier with anti-friction bearings on each end carried in a stationary housing. The elongated bearing carrier is supported within the housing by axially spaced elastomeric bands in grooves in the outside diameter of the bearing carrier that cooperate with grooves in the bore of the stationary housing within which the elastomeric bands are seated to carry the axial thrust of the rotor assembly in both axial directions.

Claims

1. A bearing system for a rotating assembly carried in a housing of a turbocharger for an internal combustion engine, wherein the bearing system and housing combine to form a coolant cavity by an elongated bearing carrier whose outer surface forms one surface defining the coolant cavity and is sealed with said housing by an elastomeric band on each end of said one surface, each said elastomeric band being seated in a groove formed into a housing bore and a peripheral groove formed into the outer surface to coincide with the groove in the housing bore to carry rotor thrust in both axial directions.

2. The bearing system of claim 1 wherein said outer surface of the elongated bearing carrier is cylindrical, and wherein each peripheral groove is a peripheral “O”-ring groove formed into said outer surface at each end of said one surface, and said elastomeric bands are “O”-rings seated in each said peripheral “O”-ring groove that are located to coincide with said grooves in said housing bore when said elongated bearing carrier is assembled to a position within said housing bore.

3. The bearing system of claim 1 wherein the elastomeric bands seated in said peripheral “O”-ring grooves and concurrently seated in said grooves in said housing bore, function to carry rotor thrust in both axial directions.

4. A turbocharger for use on internal combustion engines, comprising: a bearing housing carrying a turbocharger rotating assembly including a rotatable shaft with a compressor wheel at one end rotatably drivable by an engine exhaust gas turbine wheel at the opposite end, said rotatable shaft being rotatably carried within a tubular bearing carrier by ball bearings adjacent opposite ends of the tubular bearing carrier, said ball bearings being adapted to carry thrust forces in both axial directions to the tubular bearing carrier, said tubular bearing carrier being carried within a housing bore within the bearing housing by elastomeric bands engaged with and carried by correspondingly spaced grooves formed into both the housing bore of the bearing housing and the tubular bearing carrier, whereby axial rotor thrust forces imparted to the tubular bearing carrier are carried by the elastomeric bands to the bearing housing.

5. The turbocharger of claim 4, wherein the bearing housing includes a central cooling jacket around the tubular bearing carrier connectible with a source of cooling fluid from an internal combustion engine, and wherein the elastomeric bands carried by said correspondingly spaced grooves provide seals between the housing bore of the bearing housing and an outer surface of the tubular bearing carrier confining the cooling fluid adjacent the outer surface of the tubular bearing carrier.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view taken along a plane through the axis of rotation of a turbocharger, utilizing a grease-lubricated ball bearing version of this invention:

(2) FIG. 2 is a cross-sectional view taken along a plane through the axis of rotation of a turbocharger, utilizing an embodiment of this invention with an alternate arrangement of grease-lubricated ball bearings.

MORE DETAILED DESCRIPTION OF THE INVENTION

(3) The bearing system of this invention is adapted to support, within stationary elements of a turbocharger, a high-speed rotating assembly.

(4) As set forth above, FIG. 1 illustrates the center section of a turbocharger 10, wherein stationary elements, such as bearing housing 11 and end housing 12, enclose a rotating shaft 13, a turbine wheel 14 at one end and a compressor wheel 15 at the other end. The bearing system 16 of the invention carries the rotating shaft 13 and is carried by the bearing housing 11. As is well known in the art, the rotor assemblies of the turbochargers can attain speed up to 200,000 RPM and are exposed to very high temperatures of engine exhaust gas at their turbine ends.

(5) The bearing system 16 of this invention, which is illustrated in FIG. 1, comprises an elongated cylinder 17 with a deep groove ball bearing 18 at its compressor end, capable of carrying rotor thrust in both axial directions, and an angular contact ball bearing 19 slidably mounted at its turbine end. In one embodiment of this invention, the angular contact ball bearing 19 comprises a full compliment of ceramic balls and is mounted against a pre-load spring 19a slidably in its bore. This allows it to move axially when the shaft 13 expands axially due to heat conducted to it from the hot turbine wheel 14.

(6) The inner races of both ball bearings 18 and 19 are separated by spacer 20 and are clamped between the shaft shoulder 21 and sleeve 22 and rotate with shaft 13.

(7) As illustrated in FIG. 1, the elongated cylinder 17 is supported within the bearing housing 11 by a plurality of elastic supports which are preferably elastomeric bands 23, seated in grooves 24 and 25 in the outside surface of the elongated cylinder 17. When assembled, the elastomeric bands 23 are compressed into corresponding grooves 24a and 25a, in the bearing housing bores 26 and 27, the elastomeric bands 23 serve to position the bearing system 16 and rotor assembly 28 axially within the bearing housing 11. They also carry the thrust load of the rotor, transmitted through the ball bearings 18 and 19, to the grooves 24a, 25a in the bearing housing 11. The elastomeric bands 23 also act as radial springs that allow minor orbital motion of the bearing system 16 that may result from any residual unbalance in the turbocharger rotating assembly 28, and they also cushion the rotating assembly 28 from shock and vibration.

(8) As illustrated in FIG. 1, the bearing housing 11 includes a coolant cavity 29 for engine coolant to carry away heat transferred to the bearing assembly 16 from the hot parts of the turbocharger. The inner boundary of the coolant cavity is formed by the outside diameter of the elongated cylinder 17. The coolant cavity 29 has an inlet 30 that may be connected to the cooling system of an engine and an outlet 31 that carries the coolant from the coolant jacket 29 and returns it to the cooling system of the engine.

(9) Coolant is allowed to circulate around the outside diameter of the elongated cylinder 17 and carries away heat generated in the ball bearings 18 and 19. The elastomeric bands 23 seal the portion of the outside diameter of the elongated cylinder 17 that forms the boundary of the cooling jacket cavity 29 in the bearing housing 11. The elastomeric bands 23 are preferably of a high-temperature rubber, such as Viton, and may be Viton “O” rings. A piston ring seal 32 prevents hot exhaust gas from entering the bearing system cavity and a second piston ring seal 33 prevents compressed air from entering the bearing system cavity.

(10) As illustrated in FIG. 1, the deep groove ball bearing 18, mounted in the compressor end of the elongated cylinder 17, carries the rotor axial thrust load in both axial directions.

(11) FIG. 2 illustrates an alternate method of carrying the rotor thrust by mounting two angular contact ball bearings 40 and 41 back-to-back in the compressor end of the elongated cylinder 17 in place of the deep groove ball bearing 18 that is shown in FIG. 1. The back-to-back arrangements of the angular contact bearings 40 and 41 allows bearing 40 to carry axial thrust toward the turbine end and bearing 41 to carry axial thrust toward the compressor end. Since the full compliment angular contact bearings 40 and 41 do not have a cage to position the balls, they are able to reach higher operating speeds than the deep groove ball bearing 18 that must use a cage to position the balls.

(12) The invention illustrated and described herein provides a less complicated turbocharger structure and provides an internal combustion engine turbocharger capable of at least equal operating characteristics. Comparing the invention with the prior art U.S. Pat. No. 7,025,579 82, a turbocharger of the invention eliminates the prior art radially-extending flange 31d of the bearing carrier 31 and its thrust-carrying faces 31e and 31f, their anti-friction coatings and their mating thrust-bearing surfaces in the bearing housing 11 and end housing 16. In contrast, in the invention elastomeric bands 23 are held in grooves 24 and 25 in an bearing-carrying elongated cylinder 17 and corresponding grooves 24a and 25a of a bearing housing bore 27 within the bearing housing 11 and carry axial rotor thrust in both directions while cooperating with the bearing housing 11 to form a cooling jacket for the bearings 18, 19 and handle coolant flow to and from the bearing housing 11. They also allow the entire rotating assembly of the turbocharger 10 carried by the bearing housing 11 minor orbital motion that may result from any residual unbalance in the rotating assembly.

(13) The present invention represents a signification reduction in the complexity and manufacturing cost over prior art turbochargers, such as those shown in U.S. Pat. No. 7,025,579 B2.