GB2175958A

GB2175958A - Improvements in or relating to turbochargers

Info

Publication number: GB2175958A
Application number: GB08612714A
Authority: GB
Inventors: Jr Joe Albert Mceachern; James William Brogdon
Original assignee: Teledyne Industries Inc
Current assignee: TDY Industries LLC
Priority date: 1985-05-30
Filing date: 1986-05-23
Publication date: 1986-12-10
Also published as: JPS6213732A; AU5786586A; SE8602322L; DE3617402A1; BR8602584A; FR2582728A1; GB8612714D0; GB2175958B; IT8683622A0; NZ216321A; IT1204246B; SE8602322D0

Abstract

A turbocharger has a main housing (12) with a throughbore through which a tubular bearing carrier (40) is coaxially positioned. A shaft (14) extends through the bearing carrier (40) and is rotatably secured to the bearing carrier by a pair of axially spaced bearing assemblies (48, 50), each having an inner race (58, 60), an outer race (74, 80) and bearing elements entrapped therebetween. A pair of spacers (70, 76) are coaxially positioned around the shaft between the bearing assemblies so that an outer axial end (72, 78) of each spacer abuts against the outer race of each bearing assembly. A helical compression spring (86) in a state of compression urges the spacers (70, 76) axially away from each other to equalise the axial compressive load on each bearing assembly and thereby minimise bearing skidding and uneven wear. <IMAGE>

Description

SPECIFICATION Improvements in or relating to turbochargers Background of the Invention Field of the Invention The present invention relates generally to turbochargers and, more particularly, to a turbocharger with a preloaded bearing assembly.

Description of the PriorArt There are a number of previously known turbochargers having a housing in which a shaft is rotatably mounted. A turbine is attached to one end of the shaft and a compressor is attached to the opposite end of the shaft. Bearing assemblies, such as one or more ball bearing assemblies, rotatably mount the shaft to the housing.

In operation, the output from the compressor is connected to the intake of an internal combustion engine while the exhaust from the engine is connected to the inlet ofthe turbine. Thus, during operation of the engine, exhaust products from the engine rotatably drive the turbine which, in turn, drives the compressor which inducts fresh air, compresses the air and supplies the compressed air to the engine.

For effective operation of the turbocharger, the turbocharger shaft, and thus the turbine and the compressor, necessarily rotate at high rotational speeds. As a result, any vibration or play in the bearing assembly not only creates excessive noise but also results in rapid deterioration of the bearing assembly and its associated components.

There have, however, been a number of previously known devices which impose a load on the bearing assemblies in order to minimise any mechanical play within the bearing assemblies.

These previously known devices, however, have been complicated and complex in construction and not wholly effective in operation. Furthermore, many of these previously known devices which preload the bearing assemblies impose uneven loads on the bearing assemblies which results in uneven wear.

The present invention aims to provide a turbocharger construction which can overcome or at least reduce at least some of the above mentioned disadvantages of the previously known devices.

Summary of the Present Invention According to the present invention there is provided a turbocharger comprising: a main housing having a throughbore, a tubular bearing carrier coaxially positioned within said throughbore, a shaft extending through said bearing carrier, said shaft having a turbine at one end and a compressor at its other end, a pair of bearing assemblies for rotatably mounting said shaft to said bearing carrier, each bearing assembly comprising an inner race, an outer race, and bearing elements entrapped between said races, said bearing assemblies being axially spaced from each other and contained between said turbine and said compressor, means for securing said inner races against axial movement to said shaft, means contained between said bearing assemblies for urging the outer races of said bearing assemblies axially away from each other.

The inner races of the bearing assemblies are preferably secured against axial movement to the shaft by an inner spacer tube and two annular slingers. The slingers are conveniently secured to the shaft so that one slinger abuts against the outer axial end of each bearing assembly inner race.

First and second annular spaces are conveniently positioned coaxially around the shaft in between the bearing assemblies. Each spacer may include an outer axial end which abuts against the inner axial end of the outer race for each bearing assembly. The inner axial end of the second spacer preferably abuts against a radially inwardly extending flange on the bearing carrier so that the second spacer is sandwiched in between the bearing carrier flange and the outer race of adjacent bearing assembly. A helical compression spring in a state of compression is preferably then disposed around the shaft in between the inner axial end of the first spacer and the radially inwardly extending portion of the bearing carrier.

In operation, the helical compression spring exerts an outward force at one end to the first spacer and thus on the outer race of the first bearing assembly. This force is then transmitted to the opposite end of the helical spring through the shaft second bearing assembly second spacer and the bearing carrier flange. Consequently, the outward forces exerted by the compression spring on the outer races for both bearing assemblies are precisely equal to each other.

A primary advantage of the present invention is that the spring not only eliminates any mechanical play present in the bearing assemblies and thus vibration during operation of the turbocharger, but is also simple and efficient in construction.

Furthermore, the entire means for preloading the bearing assembly is wholly contained in between the bearing assemblies thus resulting in a compact and lightweight construction.

Brief Description of the Drawings A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawings wherein like reference characters refer td like parts throughout the several views, and in which: Figure lisa diagrammatic view illustrating a preferred embodiment of the present invention; and Figure 2 is a fragmentary longitudinal sectional view illustrating the embodiment of Figure 1, shown to an enlarged scale.

Detailed Description of the Drawings With referencefirstto Figure 1 a preferred embodiment of the turbocharger 10 of the present invention isthereshown and comprises a main housing 12 having a shaft 14 rotatably mounted to it in a fashion which will be subsequently described in greater detail. A compressor 16 is secured to one end of the shaft while a turbine 18 is secured to the other end of the shaft 14. The compressor 16 is contained within a compressor casing 17 while, similarly, the turbine 18 is contained within a turbine casing 9.

Upon rotation of the compressor 16, the compressor 16 inducts air from its inlet 20 (illustrated diagrammatically) and supplies the compressed air at its outlet 22 to the intake 24 of an internal combustion engine 26. The internal combustion engine 26 has its exhaust 28 secured to the inlet 30 of the turbine 18 and the exhaust 32 from the turbine 18 is open to the atmosphere. In the conventional fashion, the exhaust from the engine 26 rotatably drives the turbine which in turn rotatably drives the compressor 16 through the shaft 14 to supply compressed air to the engine 26.

With reference now particularly to Figure 2, the housing 12 includes a throughbore 34 which is coaxial with the shaft 14. Atubular bearing housing 36 having an outwardly flanged end 38 is press fit into the throughbore 34 until the flanged end 38 of the bearing housing 36 abuts against the main housing 12. Preferably the housing 12 is constructed of aluminium for lightweight construction while the bearing housing 12 is constructed of steel for durability.

A tubular cylindrical bearing carrier 40 having an outwardly extending flange 42 at one end is then positioned within the bearing housing 36 so that the flanges 38 and 42 flatly abut against each other. A retaining ring assembly 44 secures the bearing housing 36 and bearing carrier 40 to each other, and thus to the housing 12, against axial movement.

First and second axially spaced bearing assemblies 48 and 50, respectively, rotatably mount the turbocharger shaft 14 to the bearing carrier 40.

Each bearing assembly 48 and 50 preferably comprises a ball bearing assembly having its inner race 58 and 62, respectively, secured for rotation with the shaft 14 and its outer race 74 and 80, respectively, secured against radial movement to the inner periphery 52 ofthe bearing carrier 40. For a reason to be shortly described, however, some axial movement ofthe outer races of the bearing assemblies 48 and 50 is permitted. In addition, the bearing assemblies 48 and 50 are mounted between the shaft 14 and the bearing carrier 40 adjacent each end ofthe bearing carrier 40.

Still referring to Figure 2, a tubular and cylindrical spacer 54 is positioned coaxially around the shaft 12 in between the bearing assemblies 48 and 50. The spacer 54 is dimensioned so that one end 56 abuts against an inner axial end of the inner race 58 of the first bearing assembly 48. Similarly, the other end 60 ofthe spacer 54 abuts against the inner'axial end of the inner race 62 of the second bearing assembly 50. A first slinger 64 is then secured to the shaft 2 so that it abuts against the outer axial end of the first bearing assembly inner race 58 and, similarly, a second slinger 66 is secured to the shaft 14 so that it abuts against the outer axial end of the second bearing assembly inner race 62.Consequently, the slingers 64 and 66, together with the spacer 54, secure the inner races 58 and 62 ofthe bearing assemblies 48 and 50, respectively, against axial movement with respect to the shaft 14.

Still referring to Figure 2, a first annular spacer nozzle 70 is contained within the interior of the bearing carrier 40 and has one axial end 72 which abuts against the inner axial end ofthe first bearing assembly race 74. Similarly, a second annular spacer nozzle 76 is contained within the interior of the bearing carrier 40 and has its outer axial end 78 in abutment with the inner axial end of the second bearing assembly outer race 80. An inner axial end of the spacer nozzle 76 abuts against a radially inwardly extending portion of flange 84 on the bearing carrier 40.

A helical compression spring 86 is sandwiched in between the inner axial end 88 of the spacer nozzle 70 and the inner axial end of the bearing carrier flange 84. The compression spring 86 is in a state of compression, for example at 50 pounds pressure.

In operation, the compression spring 86 exerts an outward axial force on the spacer nozzle 70 which in turn exerts an outward axial force on the first bearing assembly outer race 74. This outward axial force is transmitted through the shaft 14 to the other bearing assembly 50 so that an outward axial force is exerted on the second outer race 80. This outward force is in turn transmitted through the spacer nozzle 76 and bearing carrier flange 84 to the opposite end of the helical spring 86. Consequently, the outward axial force exerted on the outer races 74 and 80 of the ball bearing assemblies 48 and 50, respectively, are equal but opposite in direction.

From the foregoing, it can be seen that a primary advantage of the present invention is that the bearing assemblies 48 and 50 are preloaded by the spring 86 in equal but opposite directions; thus eliminating any mechanical play which may be present in the bearing assemblies 48 and 50.

Furthermore, since the outward forces exerted on the outer races of the bearing assembly are equal to, but opposite of, each other, any wear ofthe bearing assemblies is equally distributed between the bearing assemblies 48 and 50.

A still further advantage of the present invention is that the spacer nozzles, together with the helical springs are wholly contained in between-the bearing assemblies 48 and 50. This results in not only an inexpensive but also compact construction for the turbocharger.

Claims

1. A turbocha rger comprising: a main housing having athroughbore, a tubular bearing carrier coaxially positioned within said throughbore, a shaft extending through said bearing carrier, said shaft having a turbine at one end and a compressor at its other end, a pair of bearing assemblies for rotatably mounting said shaft to said bearing carrier, each bearing assembly comprising an inner race, an outer race, and bearing elements entrapped between said races, said bearing assemblies being axially spaced from each other and contained between said turbine and said compressor, means for securing said inner races against axial movement to said shaft, means contained between said bearing assemblies for urging the outer races of said bearing assemblies axially away from each other.

2. A turbocharger as defined in claim 1, wherein said bearing carrier includes a radially inwardly extending flange and wherein said urging means comprises: a first annular spacer position around said shaft and having an outer end in abutment with an inner axial end of the outer race of one bearing assembly, a second annular spacer positioned around said shaft and having an outer end in abutment with an inner axial end of the outer race of the other bearing assembly, said second spacer having an inner axial end in abutment with one axial end of said flange, and means for resiliently urging said first annular spacer and the other axial end of said flange away from each other.

3. Aturbochargeras defined in claim 2, wherein said resilient urging means comprises a compression spring in a state of compression.

4. A turbocharger as defined in claim 1,2 or 3, and comprising a spacer tube positioned around said shaft so that opposite ends of said tube abut against the inner axial ends of said inner races, and means secured to said shaft which abut against the outer axial ends of said inner races.

5. Aturbocharger as defined in claim 4, wherein said last mentioned means comprises a pair of annular slingers, said slingers being secured to said shaft so that each slinger abuts against an outer axial end of each inner race.

6. A turbocharger substantially as herein described with reference to, and as shown in, the accompanying drawings.