|Title of Invention||
"A POWER TURBINE"
|Abstract||A turbocharger ia which a drive shaft supports at ons end a turbine driven by exhaust gases from an internal combustion engine. The end of the drive shaft remote from the turbine supports & drive connection which is couple! to an outpui; shaft of the driving engine. The shaft is supported in a housing by a first bearing adjacent the turbine and a second bearing adjacent the drive coupling. The first and second bearings each define an inner bearing surface relative to which the shaft rotates and an outer bearing surface which rotates relative to the housing. The first and second bearings are mechanically coupled together such hat th«;y rotate relative to the housing at the same speed. Coupling the two bearing together (insures that directional forces applied to the bearing at the end adjacent the drive connection which might cause that bearing to seize are resisted by torque delivered from the bearing at the other end of the shaft.|
|Full Text||Ihe present invention relates to a turbine, and in particular to a power turbine of the type found in lurbocompoxmd engines,
A turbocharger comprises a drive shaft one end of which supports a turbine arranged to be driven by exhaust gases from an internal combustion engine. In automotive heavy duty diesel engines turbocharger shafts are supported in a housing usually by two separate floating bearings which are retaiaec in position by circtips or some other conventional mechanical configuration. In a filly floating bearing, the shaft rotates relative to an inner bearing surface defmed by i. bearing body which also defines an outer bearing surface which itself rotates relative to & surrounding housing. The turbocharger shaft is generally located axially by a separate bearing. In a turboe:harger the end of the shaft remote from the turbine sinply drives 8 compressor which is used to deliver air to the engine.
In turbocompourtd engines, two turbines are provided in series, both driven by the exhaust gases of the engine. One of the turbines drive.; a compressor to deliver pressviised air to the engine and the other, a power turbine, is used to generate additional power which is transmitted via a mechanical connection. For example, in a power turbine a gear wheel may be fixed to the end of Hie shaft remote from the turbine and the gear wheel is used to transmit power into an appropriate coupling, for example a fluid coupling or other drive mechanism into the crankshaft of the engine. The power may however be transmitted by otber mejins, for exwnple hydraulically or electrically.
In a power turbine, in which additional power generated is fed hack into the crankshaft of the engine via a gear wheel on the turbine shift, different loadings are applied to the shaft bearing system as compared with loadixigs in a conventional turbocharger which does uo more than drive a compressor In a conventional turbocharger, out of balance forces and shaft vibration forcus are resisted by journal oil films distributed equally around 1he circumference of the inner and outer bearings as there are no off axis external forces on the system. In a power turbine in contrast, the gear drive supported on the end of the shaft remote from the turbine generates a reaction, force which gives rise to an external directional ftrce on the turbine ahaft.
This uxtemal force significantly Increases the load, particuUirly on the bearing closest to the gear. As a result conventional floating bearing arrangements are not suitable for use at the gear end (or other drive connection) of a power turbine. This is because load carrying oil films in folly floating bearings require relative rotation at both the inner and outer bearing surfaces. However, the directionalload at the gear end of the shaft causes the shaft to be displaced such that the oil film an me side of the bearing opposite the applied force can become very thin. At high powsr transmission levels, the directional load can become so great that, in the limit, ihe floating bearing stops
rotating within Uw housing. As a result, tlia load drops aad Xailurc of the shaft bearing system can occur. Consequently conventional power turbines have some form of fixed bearing amngemeat at the drive connection
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Accordingly there is provide a power turbine comprising a drive shaft supporting at one end a turbine arranged in use to be driven by exhaust gases rom an internal combustion engine and supporting at the other end a drive jonnection which in use\ is coupled to an output shaft of the i.e. engine, vherein the shaft is supported in a housing by a first bearing adjacent to the :urbine and a second bearing adjacent the drive coupling, the first and second Dearings each define an inner bearing surface relative to which the shaft rotates ind an outer bearing surface which rotates relative to the housing characterized in that the first and second bearings are mechanically coupled :ogether ouch that they rotate relative to the housing at the same speed.
to embodiments of the present invention, the drivrng effect of the bearing adjacent the turbine end of the shaft is used to maintain the rotational speed of the more highly directionally loaded gear at the other end of the shaft As a result, when high gear loads are applied to the shaft, the bearing at the enc of the shaft remote from the turbine is prevented from slowing and losing load eazrying capacity by driving torque which is delivered from the less directionally loaded bcering at ths end of the shaft adjacent the turbine.
The driving effect at the gear end of the bearing is produced by modifying the relative surface areas and operating clearances of the inner Jind outer oil films, and by the areas of the bearing end faces abutting the shaft s'loulders.
Preferably the first and second bearings are formed from a single tubular body through which the shaft extends, Such an approach is attractive from die point of view of ease of manufacture and for mis reason single piece Hoating bearings have been used as a low cost bearing arrangements in some sma'l turbocharges. There has however been no previous recognition of the high load bearing possibilities of one piece floating bearings which would suggest the use of such bearings in power turbines in accordance with the present invention.
It is also possible to provide a multi-part bearing ai aeribly in which the first and second bearings are interconnected by a separate tube through wh;.ch the shaft extends. The separate tube could be locked against rotation relative to the bearings by any appropriate means, for example interlocking castrations.
Radial apertures nifty be provided in the bearing assembly to provide oil drainage passageways. The first and second bearings may define axially-facing end surfaces which bear against retaining shoulders, tfce radiiJ thicknesses of the end surtiaces being equal or less than the radial spacing between the inner and outer
beanrtgsurfaces. An embodiment of the present invention
will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a sectional view through a turbocharger irt accordance with the present invention;
Figure 2 is a perspective view of a one-part bearing incorporated in the turbocharger of Figure 1;
Figure 3 is an axial section through the bearing of Figure 2;
Figure 4 is a section on the line 4-4 of Figure 3;
Figure 5 is section on the line 5-5 of Figure 3; and
Figure 6 is a flection showing one pocaiblo modification of tho baariu£ of Figure 2.
Referring to Figure I, the illustrated turbocharger comprises a shaft 1 which supports at one end a turbine 2 and supports at the other end a drive gear 3. The shaft
\ is supported in a one piece tubular bearing 4 which is supjxsrted within a housing 5. The housing S is secured to a body 6 which defines a volute 7 which exhaust gases delivered from an internal combustion engine pass to torque to the turbine 2. A heat shield 8 protects the bearing assembly from the lot gases which drive the turbir.c 2.
One end of the bearing 4 abuts a shoulder 9 definec by the shaft whereas the other end Of the bearing 4 abuts a flange 10 which part of a thrust bearing which maintains the axial position of both the bearing 4 and the shaft 1. The structure of the bearing 4 is shown in greater detail in Figures 2 to 5.
Referring to Figures 2 to 5, the bearing 4 defines a first bearing having an inner bearing surface 11 and an outer bearing surface 12 and a second bearing having an inner bearing surface 13 and an outer bearing surface 14 The surface 11,12,13 and 14 are defined at the ends of a tubular body having a central section IS the inner and outer diameters of which are less than the diameters of-he inner bearing surfaces 11,12' and the outer bearing surfaces 12,14 respectively. Oil passageways 16 extend between the inner and outer bearing surfaces and oil drainage apertures; 17 may be provided in the central section IS to ensure that oil can diain freely from the inner bearing surfaces. Axial ends 18 of the tubular bearing structure have same outer diameters as the outer bearing surfaces 12,14 and greater internal diameters than the inner bearing surfaces 11,13.
Given that the bearing 4 is formed in one piece, the bearings defined at opposite ends thereof must rotate at the same speed. Thus toe rotational speed of the bearing surfaces supporting the end of the shaft adjacent the gear 3 must be the same as the rotational speed of the bearing surfaces supporting the end of the shaft adjacent the tuibine 2. Thus high loads at the end of the shall adjacent the gear 3 are prevented from slowing down and thereby reducing the load carrying capacity of the adjacent bearing surfaces.
In the illustrated example the bearing 4 is made from a single component. The central section 15 of this single component has an internal diameter greater man that o:f the turbocharger shaft and an external diamercer less than mat of the adjacent housing so as to avoid hydrodyrucnic drag resisting rotation of the shaft. This may not, however, be necessary in all embodiments of the invention. Rather, the
proportions of the central section 15 of the bearing may be varied in ord«r to give the correct hydrodroynamic force balance on the bearing. For example, it may not be necessary to provide a recess along die inner diameter in order to maximise the bearing speed. Thus, in alternative embodiments of the invention the inner diameter of the central section 15 may be smaller or larger than that illustrated and for instance may be equal to the diameter of the surfaces 11 and 13, Similarly, the outer diameter of the central section 15 may be smaller or larger than illustrated and may for instance be equal to the diameter of the surfaces 12 and 14.
The radial thickness of the end portions of the bearin.? body 4 which define me surfaces 18 can also be adjusted as necessary to modify the «.rea of the end faces 18 to ensure suitable rotational speeds for the bearing body 4. For instance, the axial ends IS of ihc tubular bearing structure may have outer diameters which are smaller than the diameter of the outer bearing surfaces 12 and 14 and internal diameters which are equal to the inner bearing surfaces 11 and 13.
Rather than forming the bearing 4 as a one-piece tube, tie bearing could be in the form of two separate bearings linked by a tube arranged to engage the bearings such that the two bearings are constrained to rotate at the same speed.
It would be possible to axially locate the bearing 4 using circlips or the like but the use of such devices can be avoided as shown in the illustrated embodiment by arranging for the bearing 4 to bear axially against ths shoulder 9 on the vurbine shaft and against the thrust bearing flange 10 at the gear end of the shaft.
A farther possible modification of me bearing of Figure 2 is illustrated in Figuru 6 which is a cross-section corresponding to ths section ttiken on the line 4-4 of Figure 2 but of a modified bearing in which an annular groove 19 is provided in the outer surface of the bearing. The groove 19 links the openings of the oil passageways 16 and ensures that the oil supply holes in the housing 5 from which oil is supplied to the bearing are never blocked.
1. A power turbine comprising a drive shaft supporting at one end a
turbine arranged in use to be driven by exhaust gases from an internal
combustion engine and supporting at the other end a drive connection which
in use is coupled to an output shaft of the i.e. engine, wherein the shaft is
supported in a housing by a first bearing adjacent to the turbine and a
second bearing adjacent the drive coupling, the first and second bearings
each define an inner bearing surface relative to which the shaft rotates and
an outer bearing surface which rotates relative to the housing characterized
in that the first and second bearings are mechanically coupled together to
rotate relative to the housing at the same speed.
2. A power turbine as claimed in claim 1, wherein the first and second
bearings are formed from a single tubular body through which the shaft
3. A power turbine as claimed in claim 1, wherein the first and second
bearings are separate components interconnected by a tubular body through
which the shaft extends.
4. A power turbine as claimed in claim 2 or 3, wherein the tubular body
defines radial apertures to provide oil drainage passage was.
5. A power turbine as claimed in claim any of the preceding claims,
wherein the first and second bearings define axially-facing end surfaces
which bear against retaining shoulders, the radial thickness of the end
surfaces being less than or equal to the radial spacing between the inner and
outer bearing surfaces.
6. A power turbine substantially as herein described with reference to
and as illustrated in the accompanying drawings.
|Indian Patent Application Number||1045/DEL/2001|
|PG Journal Number||37/2008|
|Date of Filing||12-Oct-2001|
|Name of Patentee||HOLSET ENGINEERING CO. LIMITED|
|Applicant Address||ST. ANDREWS ROAD, HUDDERSFIELD, HD1 6RA, ENGLAND.|
|PCT International Classification Number||F01B 1/00|
|PCT International Application Number||N/A|
|PCT International Filing date|