Claims:We claim
1. A turbocharger bearing assembly with asymmetric support pad width for journaling rotor shafts of high-speed rotary machines with increased load bearing capacity, comprising of: a fluid bearing ring (121) with an outer diameter surface (122) and a inner diameter surface (123), wherein said fluid bearing ring is provided with a circumferential oil feed groove (124) disposed on the said outer diameter surface (122), Wherein said oil feed groove (124) is provided with a plurality of oil feed holes (125) positioned equidistantly around the periphery of the said oil feed groove (124), wherein said inner diameter surface is provided with the corresponding exit points (130) of the said plurality of oil feed holes, wherein said fluid bearing is provided with a pair of support pads (126a, 126b), where each one of the said support pads is positioned on either side of the said oil feed ring groove (124), wherein width (y) of the support pad (126a) positioned on first side of the circumferential oil feed groove is larger than the width (x) of the support pad (126b) positioned on the second side of the circumferential oil feed groove.

2. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 1, wherein said oil feed holes (125) are positioned vertically at 90° with respect to the length of the fluid bearing, wherein said entry point (125) of the oil feed holes positioned on oil feed groove (124) at the outer diameter surface (122) is arranged linearly with the corresponding exit points (130) of the oil feed holes positioned on the inner diameter surface (123).

3. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 1, wherein said oil feed holes (125) are positioned at an inclination with respect to the length of the fluid bearing, wherein said angle of inclination ranges from 10° to 70°.

4. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 1, wherein said circumferential oil feed groove (124) is formed by a cut out oil feed ring groove along the circumference of the outer diameter surface (122).

5. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 1, increasing the width (y) of the support pad (126a) positioned on first side of the oil feed groove with respect to the width (x) of the support pad (126b) positioned on second side of the oil feed groove provides an unequal support pad length (y > x) on the outer diameter surface (122) of the floating bearing (121), improving the load bearing capacity of the bearing assembly.

6. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 1, wherein said overall length (L) of the fluid bearing bush is increased.

7. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 1, wherein the increased width portion (y-x) of the support pad (126a) on first side of the oil feed groove is equivalent to the width (z) of the cut-out portion (125) of the oil-feed groove from the circumferential outer diameter surface (122) of the fluid bearing.

8. A turbocharger assembly including a bearing bush assembly with asymmetric support pad width, is provided with a pair of radial bearing bushes (132a,132b, 136a,136b) with asymmetric support pad widths, wherein said first radial bearing bush (132a, 136a) with asymmetric support pad widths is disposed at the compressor side and second radial bearing bush (132b, 136b) with asymmetric support pad widths is disposed at the turbine side, the said first side of the first bearing bush with increased width (133a, 137a) at the compressor side faces the said first side of the second bearing bush with increased width (133b,137b) disposed at the turbine side.

9. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 8, wherein said oil feed holes (125) of the bearing bushes (132a,132b) are positioned vertically at 90° with respect to the length of the fluid bearing.

10. A turbocharger bearing assembly with asymmetric support pad width, as claimed in claim 8, wherein said oil feed holes (125) of the bearing bushes (136a,136b) are positioned at an inclination with respect to the length of the fluid bearing, wherein said angle of inclination ranges from 10° to 70°.

11. A turbocharger assembly including a bearing bush assembly with asymmetric support pad width, as claimed in claim 8, wherein said central axial spacing (A) between the said pair of radial bearing bushes (132a,132b, 136a,136b) with asymmetric support pad widths is unaltered.

12. A turbocharger assembly including a bearing bush assembly with asymmetric support pad width, as claimed in claim 8, wherein the spacer length (B) between the said pair of radial bearing bushes (132a,132b, 136a,136b) with asymmetric support pad widths is decreased. , Description:FIELD OF THE INVENTION
The present invention is related to a bearing assembly for journaling rotor shafts of high-speed rotary machines. In particular, the present invention relates to a fluid journal bearing assembly for turbochargers with asymmetric pad widths with increased load bearing capacity and reduced bearing wear rate.
BACKGROUND OF THE INVENTION
Turbochargers are generally used to increase the performance of an internal combustion engine. An IC engine works by burning fuel in the cylinder. The amount of fuel input is limited by the amount of air sucked into the cylinder, and this also limits the power output by the engine. To increase the output power, the amount of fuel is increased by compressing more air into the cylinder to improve the combustion function. Turbocharger is actually an air compressor that extracts energy from engine exhaust via a turbine to drive a compressor that compresses the intake air to increase its volume and direct it to the engine. Turbochargers generally supplies air at a higher pressure than the atmosphere creating a forced induction / charging system allowing more amount of air into the internal combustion engine than the naturally aspirated engine. With this higher air mass flow rate, the fuel is burned effectively and results in higher engine power output along with lower engine out emissions. Thus it can increase the output power of the engine under the same working efficiency. Higher power output is achieved for a given engine size or reverse is also possible achieving target power output with smaller engine size known as “engine downsizing”, both are advantageous in view of cost effectiveness and less space requirement for engine installation.
Turbochargers typically comprises of a radial turbine wheel at one of the shaft and a centrifugal compressor wheel at another end of the shaft forming a rotating rotor assembly, and a bearing system to support the rotating rotor assembly. The bearing housing connects the compressor housing and turbine housing. The exhaust gas from the engine drives the turbine wheel. As the turbine wheel rotates, coaxially positioned compressor wheel also rotates sucking in the air from the atmosphere into the compressor and delivering the air at higher pressure to the engine intake system. When the engine speed increases, the exhaust gas discharge speed and the turbine speed are also increased simultaneously. The compressor compresses more air into the engine cylinder, and the pressure and density of the air increase, which can burn more fuel, correspondingly increase the fuel quantity and adjust the engine speed. Usually a turbocharger is provided with bearings bushes for journalling a rotor shaft against the radial load and the thrust load applied thereto.
In recent years there has been an increased demand for increasing the speed of the turbocharger and obtaining a compact size therein. Several attempts have been made to increase the speed of the turbocharger by using various types of bearing bushes. Since the operating temperature of the turbocharger is very high, and the speed of the rotor also very high during turbocharger working, the common mechanical needle roller or ball bearing becomes inefficient in handling the load experienced by the rotor assembly. Therefore, the turbocharger on the market generally uses fully floating bearings, but this bearing has high lubrication requirements and needs special lubricating oil for lubrication, plus supercharging but it has been impossible to attain the end because of increased vibration and acoustics, limited load bearing capacity, reduced rotor stability, bearing frictional and burning loss during high-speed rotation.
A conventional floating bearing bush includes a floating bush rotatably provided in the space between the rotor shaft and the bearing housing. The floating bush bearing is configured so as to supply pressurized lubricating oil from the bearing housing to the space between an inner peripheral surface of the bearing housing and an outer peripheral surface of the floating bush and also to the space between an inner peripheral surface of the floating bush and the rotor shaft via an oil supply path provided in the floating bush. The floating bush bearing is configured to support the rotor shaft stably while suppressing its oscillation by a damping effect of the oil film of the lubricating oil. The use of fluid bearings requires equipment to supply pressurized fluid, but bearing friction is small and problems with heat generation and lubrication management are eliminated. There is no solid contact between the sliding surfaces, so there is no concern about flaking due to repeated loading during operation, and the service life is long.
In spite of the above advantages of the floating bearing, owing to the structural arrangement whereby the inner and outer peripheral portions of a floating bush are as closely spaced apart as possible from adjacent parts for minimizing vibration, the inner peripheral portion experiences a higher peripheral velocity which results in an increased frictional loss and inevitable scoring. Conventional fluid bearings have a limited load capacity, as a common issue. Further the bearing spacing, which is the spacing between the axial center of the two bearing bushes has a significant influence on the rotor stability, which is also determined to a large extent by the design of the bearing bush assembly. Therefore there exists a need in the art for a bearing bush assembly with increased load bearing capacity and reduced bearing wear rate, vibration and acoustic properties, without affecting the rotor stability and the axial bearing spacing while maintaining the same bearing housing dimensions thereof.
Japanese patent document 2009-156333 provides a bearing device for a rotary machine capable of reducing noise, comprising of : a pair of floating bush type sliding bearings positioned on the rotor shaft of a supercharger and the like supply of lubricating oil between a shaft and the bearings and between the bearings and a bearing housing, and the shaft is rotated via an oil film. To decrease the self-excited vibration arising from rocking of the oil film, specifically, the width of the inside bearing of the compressor-side floating bush bearing is made smaller than the width of the inside bearing of the turbine-side floating bush bearing. However, the floating bush bearing on the compressor side and the floating bush bearing on the turbine side have different shapes and thus, the number of components increases. This results in increase in management cost and higher risk of misassembling.
US patent 4640630 discloses a supercharger bearing assembly including floating bushes journaling a rotor shaft interposed between the rotor shaft and a housing assembly, the floating bushes each have an inner peripheral portion of a smaller length than an outer peripheral portion, to reduce the amplitude of vibration of the floating bush, reduce the loss of power due to a frictional loss and increase resistance to seizure.
Japanese patent document 2006207668 provides provide an asymmetrical fluid bearing having simple construction for increasing the load capacity of the fluid bearing and reducing the loss of the bearing. The radial fluid bearing has a cutout portion on part of a single side of the shaft which gives asymmetrical load thereto during rotation. The fluid bearing also has a cutout portion which gives asymmetrical load thereto, on the bearing surface. The bearing surface on the counter load side where a cutout is provided is formed narrower than the bearing surface on the load side where the cutout is not provided. In this case, the cutout is formed extending from the side of the fluid bearing into the bearing surface of the fluid bearing, or the cutout is formed at the middle of the fluid bearing. This asymmetrical fluid bearing is used as a precision control source for generating elastic waves artificially to monitor and observe underground structures and conditions mainly for early detection of earthquakes and transmitting them to the ground.
US patent application 2013108483 relates to an exhaust-gas turbocharger having a compressor; a turbine; a bearing housing connected at one end to the compressor and at the other to turbine-side end and which has an oil collecting chamber at the turbine-side end and which has a plain bearing arrangement for a rotor shaft. The plain bearing arrangement comprises a compressor-side bearing and a turbine-side bearing which is spaced apart axially from the compressor-side bearing, wherein the compressor-side bearing and the turbine-side bearing are of different design. Difference in design includes differing outer diameter of the rotor shaft in the compressor side region and turbine side region; difference in outer/inner diameter of the turbine-side bearing bush and compressor-side bearing bush; difference is inner and/or outer bearing widths of the bearing bushes; presence of grooves on the inner bearing surfaces and/or the outer bearing surfaces of the bearing bushes; difference in receiving bores for the bearing bushes in the bearing housing.
European patent 2728212 discloses a first floating bush bearing disposed on a compressor housing side and a second floating bush bearing disposed on a turbine housing side, to improve oscillation stability when a turbine rotor revolves at a high speed, reduce the number of parts, and facilitate processing and assemblability. The inner bearing width of the first and second floating bushes is formed to be smaller than the outer bearing width by the same proportion in both bushes.
All of the above cited prior-art documents relate to bearing bush assembly which mainly focuses on dampening the oscillation and vibration noise due to high speed rotor rotation. Few documents disclose modification and improvement in the bearing bush design for achieving reduced vibration, reduced frictional and rotor stability. None of the documents addresses the problem of load bearing capacity of the rotor shaft and bearing bush assembly thereof by means of improvement in the bearing bush design without comprising the rotor stability, bearing wear rate, vibrational and acoustic properties of rotor shaft. The present invention provides a floating bush bearing assembly with asymmetric pad widths. The present invention provides a fluid journal bearing assembly for journaling rotor shafts of high-speed rotary machines such as turbochargers, wherein said bearing assembly includes unequal support pad length on the outer diameter surface which increases load bearing capacity of the rotor assembly with reduced bearing wear rate and reduced vibration and acoustics properties during high-speed rotation. The present invention also provides a simple bearing construction with reduced number of parts without affecting the rotor stability and the axial bearing spacing while maintaining the same bearing housing dimensions thereof. The present invention provides an asymmetric fluid bearing that can be suitably used as a radial bearing for devices that operates with a large impact load.

OBJECT OF THE INVENTION
The primary objective of the present invention is to provide a turbocharger bearing assembly with asymmetric pad widths with increased load bearing capacity and reduced bearing wear rate.
Another objective of the present invention is to provide a turbocharger bearing assembly with unequal support pad length on the outer diameter surface of the float bearing bush which efficiently sustain both the radial load and impact load on the high speed rotor shaft.
Another objective of the present invention is to provide a turbocharger bearing assembly with reduced outer gap whirl and increased rotor stability without affecting the axial bearing spacing and inner gap whirl.
Still another objective of the present invention is to provide a turbocharger bearing assembly with simple bearing construction for use in high speed rotor with reduced vibration and acoustics.
SUMMARY OF THE INVENTION

The present invention overcome the deficiencies of the prior art and provide a floating radial bearing bush with asymmetric support pad widths capable of improving its load bearing capacity with reduced bearing wear rate. The bearing has a new structural configuration, which improves the stability of rotor rotation, without affecting the axial bearing spacing and inner gap whirl.

The present invention provides a turbocharger bearing assembly with asymmetric pad widths with increased load bearing capacity and reduced bearing wear rate, comprising of : a fluid bearing ring with an outer diameter surface and a inner diameter surface, wherein said fluid bearing ring is provided with a circumferential oil feed groove positioned on the said outer diameter surface, wherein said inner diameter surface is provided with oil feed holes, wherein said fluid bearing is provided with a pair of support pads each disposed on either side of the said oil feed ring groove, wherein width of the support pad positioned on first side of the circumferential oil feed groove is larger than the width of the support pad positioned on the second side of the circumferential oil feed groove. Increasing the width of the support pad positioned on first side of the oil feed groove with respect to the width of the support pad positioned on second side of the oil feed groove provides an unequal support pad length on the outer diameter surface of the floating bearing. Further this also increases the overall length of the fluid bearing bush, thus improving the load bearing capacity of the bearing assembly.
In an embodiment of the present invention, a turbocharger assembly is provided with a pair of radial bearing bushes with asymmetric support pad widths, each of which are disposed, first radial bearing bush at the compressor side and the second radial bearing bush at the turbine side. The first and second radial bearing bush on the rotor shaft is positioned such that the first side of the first bearing bush with increased width disposed at the compressor side faces the first side of the second bearing bush with increased width disposed at the turbine side. This decreases the spacer length between the two radial bearing bushes without altering the central axial spacing and the eccentricity ratio of the rotor shaft.
The present invention provides a bearing assembly for journalling rotor shafts of high-speed rotary machines such as turbochargers, wherein said bearing assembly is provided with a increased support pad width on first side of the circumferential oil feed groove when compared to the second side of the oil feed groove, this increases the overall length of the radial journal bearing improving the load bearing capacity. The bearing configuration also reduces the bearing wear rate and vibrational acoustics of the radial journal bearing assembly without affecting the rotor stability, inner gap whirl and friction.
BRIEF DESCRIPTION OF THE DIAGRAM
Figure 1 shows the turbocharger bearing assembly with asymmetric pad widths with increased load bearing capacity according to the present invention.
Figure 2 shows whirl vibration run-up tests with conventional journal bearing bush (132) and asymmetric journal bearing bush (133) with unequal support pad widths according to the present invention.
Figure 3 illustrates the turbocharger assembly with a pair of radial bearing bushes (132a,132b) with asymmetric pad widths, each one of which is disposed at the compressor side and turbine side. The oil feed holes (125) are positioned vertically at 90° with respect to the length of the fluid bearing
Figure 4 illustrates the turbocharger assembly with a pair of radial bearing bushes (136a,136b) with asymmetric pad widths, each one of which is disposed at the compressor side and turbine side. The oil feed holes (125) are positioned at an inclined angle with respect to the length of the fluid bearing
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention as embodied by “Turbocharger bearing assembly with asymmetric pads”, succinctly fulfils the above-mentioned need(s) in the art. The present invention has objective(s) arising as a result of the above-mentioned need(s), said objective(s) being enumerated below. In as much as the objective(s) of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective(s) are not exhaustive of the present invention in its entirety, and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative(s) and/or any functional equivalent(s) even though, such structural alternative(s) and/or any functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation(s)/modification(s) applied to the structural alternative(s)/functional alternative(s) within its scope and purview. The present invention may be embodied in other specific form(s) without departing from the spirit or essential attributes thereof.
Throughout this specification, the use of the word "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
In contrast to the prior art, in which the support pads on either side of the circumferential oil groove in the floating bearing bush assembly are of identical width, the present invention is based on the realization that, to obtain an improvement in the bearing arrangement of the rotor shaft in terms of load bearing capacity, bearing wear and rotor dynamics, bearing bush with asymmetric pad width with unequal support pad length are provided at both the turbine and compressor sides of the turbocharger.
The present invention provides a turbocharger bearing assembly for journaling rotor shafts of high-speed rotary machines with increased load bearing capacity, comprising of: a fluid bearing ring (121) with an outer diameter surface (122) and a inner diameter surface (123), wherein said fluid bearing ring is provided with a circumferential oil feed groove (124) positioned on the said outer diameter surface (122), Wherein said oil feed groove (124) is provided with a plurality of oil feed holes (125) positioned equidistantly around the periphery of the oil feed groove (124), wherein said inner diameter surface (123) is provided with the corresponding exit points (130) of the said plurality of oil feed holes (125), wherein said fluid bearing is provided with a pair of support pads (126a, 126b), where each of the said support pads is positioned on either side of the said oil feed ring groove (124), wherein width (y) of the support pad (126a) positioned on first side of the circumferential oil feed groove (124) is greater than the width (x) of the support pad (126b) positioned on the second side of the circumferential oil feed groove.
In the preferred embodiment of the present invention, wherein said oil feed holes (125) are positioned vertically at 90° with respect to the length of the fluid bearing, wherein said entry point (125) of the oil feed holes positioned on oil feed groove (124) at the outer diameter surface (122) is arranged linearly with the corresponding exit points (130) of the oil feed holes positioned on the inner diameter surface (123).
In an preferred embodiment of the present invention, wherein said oil feed holes (125) are positioned at an inclination preferably ranging from 10° to 70° with respect to the length of the fluid bearing, wherein said entry point (125) of the oil feed holes positioned on oil feed groove (124) at the outer diameter surface (122) is arranged in an inclined position with the corresponding exit points (130) of the oil feed holes positioned on the inner diameter surface (123).
In the preferred embodiment of the present invention, wherein said circumferential oil feed groove (124) is formed by a cut out oil feed ring groove along the circumference of the outer diameter surface (122)
In the preferred embodiment of the present invention, wherein said overall length (L) of the fluid bearing bush is increased.
In the preferred embodiment of the present invention, wherein increasing the width (y) of the support pad (126a) positioned on first side of the oil feed groove (124) than the width (x) of the support pad (126b) positioned on second side of the oil feed groove (124) provides an unequal support pad length (y > x) on the outer diameter surface (122) of the floating bearing (121), this improves the load bearing capacity of the bearing assembly.
In an embodiment of the present invention, wherein the increased width portion (y-x) of the support pad (126a) on first side of the oil feed groove (124) is equivalent to width (z) of the cut-out portion of the oil-feed groove from the circumferential outer diameter surface (122) of the fluid bearing.
In an embodiment of the present invention, wherein the turbocharger assembly is provided with a pair of bearing bushes (132a,132b) with asymmetric support pad widths, wherein said pair of bearing bushes with asymmetric support pad widths are disposed, one at the compressor side (132a) and one at the turbine side (132b).
In the preferred embodiment of the present invention, wherein said pair of bearing bushes (132a,132b) with asymmetric support pad widths disposed each one at the compressor side (132a) and one at the turbine side(132b), the said first side of the bearing bush with increased width (133a) at the compressor side faces the said first side of the bearing bush with increased width (133b) disposed at the turbine side.
In the preferred embodiment of the present invention, wherein said pair of bearing bushes (132a,132b) with asymmetric support pad widths disposed each one at the compressor side (132a) and one at the turbine side (132b), wherein said central axial spacing (A) between the said pair of radial bearing bushes (132a,132b) is unaltered.
In the preferred embodiment of the present invention, with first side of the bearing bush with increased width (133a) at the compressor side facing the said first side of the bearing bush with increased width (133b) at the turbine side, the spacer length (B) between the two radial bearing bushed is decreased.
As a result, without increasing the eccentricity ratio of the rotor shaft relative to the asymmetric bearing bush disposed on the turbine side and the compressor side, equilibrium is maintained between the asymmetric bearing bush on the turbine side and the asymmetric bearing bush on the compressor side and natural frequency caused by self-excited oscillation in high frequency range decreases, thereby achieving noise reduction.
The present invention provides a bearing assembly for journaling rotor shafts of high-speed rotary machines such as turbochargers, wherein said bearing assembly includes increased support pad width on first side of the circumferential oil feed groove when compared to the second side of the oil feed groove, this increases the overall length of the radial journal bearing, which improves the load bearing capacity and reduces the bearing wear rate of the radial journal bearing assembly without affecting the inner gap whirl and friction.
EXAMPLE 1
A turbocharger with a bearing bush assembly with asymmetric pad widths according to the present invention for journaling high speed rotor shafts, includes, a bearing housing interposed between a turbine housing and a compressor housing of a turbocharger for supplying pressurized air to the combustion chamber of an internal combustion engine.
A rotor shaft (135) of a turbine rotor is arranged to pass through the bearing housing. A first bearing bush (132a) is disposed on the compressor side, in-between the bearing housing and the rotor shaft. The first floating bush having a circumferential oil feed groove (124) on the outer diameter surface (122), Wherein circumferential oil fee groove is made by cut-out portion with ring shaped on the circumference of the outer diameter surface (122) of the fluid bearing. The circumferential oil fee groove (124) is provided with a plurality of oil feed holes (125) positioned equidistantly along the periphery of the oil feed groove (124). Wherein the inner diameter surface (123) is provided with the corresponding exit points (130) of the said plurality of oil feed holes with smooth surface without any cut out oil feed groove. The plurality of oil feed holes interconnects the outer diameter surface (122) at its entry points (125) and inner diameter surface (123) at its corresponding exit points (130) and being configured to supply lubricating oil from the bearing housing to the outer diameter surface and the inner diameter surface. Wherein said oil feed holes are positioned vertically at 90° with respect to the length of the fluid bearing. Wherein said entry point (125) of the oil feed holes positioned on oil feed groove (124) at the outer diameter surface (122) is arranged linearly with the corresponding exit points (130) of the oil feed holes positioned on the inner diameter surface (123). On either side of the said oil feed ring groove (124) support pads are positioned. Wherein width (y) of the support pad positioned on first side of the circumferential oil feed groove is greater than the width (x) of the support pad positioned on the second side of the circumferential oil feed groove. The first bearing bush (132a) disposed on the compressor side is positioned such that the width (y) of the support pad (133a) positioned on first side of the circumferential oil feed groove faces the turbine side. A second bearing bush (132b) having the same configuration as the first bearing bush is disposed on a turbine side. The second bearing bush is positioned such that the width (y) of the support pad (133ba) positioned on first side of the circumferential oil feed groove faces the compressor side. Therefore the said pair of radial bearing bushes (132a,132b) positioned on the rotor shaft are positioned such that the increased width (y) of the support pads (133a,133b) positioned on the first side of the circumferential oil feed groove is placed facing each other. This reduces the spacer length (B) between the two radial bearing bushes, without altering the central axial spacing (A). Increasing the width (y) of the support pad positioned on first side of the oil feed groove than the width (x) of the support pad positioned in the second side of the oil feed groove provides an unequal support pad length (y > x) on the outer diameter surface increasing the overall length (L) of the fluid bearing. This improves the load bearing capacity of the bearing assembly without affecting the rotor stability.
Fig. 2 shows the reduction in whirl vibration of the asymmetric journal bearing bush with unequal support pad widths according to the present invention during run-up tests with conventional journal bearing bush. With this Asymmetric bearing bush configuration it is possible to maintain the co-rotation of each journal bearing bush at an appropriate rotation speed with respect to the rotation speed of the rotor shaft during high-speed rotation of the rotor shaft, this improves the rotation oscillation stability of the turbocharger assembly so as to effect noise reduction.
EXAMPLE 2
A turbocharger with a bearing bush assembly with asymmetric pad widths according to the present invention for journaling high speed rotor shafts, includes, a bearing housing interposed between a turbine housing and a compressor housing of a turbocharger for supplying pressurized air to the combustion chamber of an internal combustion engine.
A rotor shaft (135) of a turbine rotor is arranged to pass through the bearing housing. A first bearing bush (136a) is disposed on the compressor side, in-between the bearing housing and the rotor shaft. The first floating bush having an circumferential oil feed groove (124) on the outer diameter surface (122), Wherein circumferential oil fee groove is made by cut-out portion with ring shaped on the circumference of the outer diameter surface (122) of the fluid bearing. The circumferential oil fee groove (124) is provided with a plurality of oil feed holes (125) positioned equidistantly along the periphery of the oil feed groove (124). Wherein the inner diameter surface (123) is provided with the corresponding exit points (130) of the said plurality of oil feed holes with smooth surface without any cut out oil feed groove. The plurality of oil feed holes interconnects the outer diameter surface (122) at its entry point (125) and inner diameter surface (123) at its corresponding exit points (130) and being configured to supply lubricating oil from the bearing housing to the outer diameter surface and the inner diameter surface. Wherein said oil feed holes (125) are positioned at an inclined angle with respect to the length of the fluid bearing, wherein inclination ranges from 10° to 70°. Wherein said entry point (125) of the oil feed holes positioned on oil feed groove (124) at the outer diameter surface (122) is arranged in an inclined position with the corresponding exit points (130) of the oil feed holes positioned on the inner diameter surface (123). On either side of the said oil feed ring groove (124) support pads are positioned. Wherein width (y) of the support pad positioned on first side of the circumferential oil feed groove is greater than the width (x) of the support pad positioned on the second side of the circumferential oil feed groove. The first bearing bush (136a) disposed on the compressor side is positioned such that the width (y) of the support pad (137a) positioned on first side of the circumferential oil feed groove faces the turbine side. A second bearing bush (136b) having the same configuration as the first bearing bush is disposed on a turbine side. The second bearing bush is positioned such that the width (y) of the support pad (137b) positioned on first side of the circumferential oil feed groove faces the compressor side. Therefore the said pair of radial bearing bushes (136a,136b) positioned on the rotor shaft are positioned such that the increased width (y) of the support pads (137a, 137b) positioned on the first side of the circumferential oil feed groove is placed facing each other. This reduces the spacer length (B) between the two radial bearing bushes, without altering the central axial spacing (A). Increasing the width (y) of the support pad positioned on first side of the oil feed groove than the width (x) of the support pad positioned in the second side of the oil feed groove provides an unequal support pad length (y > x) on the outer diameter surface (122) increasing the overall length (L) of the fluid bearing. This improves the load bearing capacity of the bearing assembly without affecting the rotor stability.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the spirit and the scope of the invention may be made by a person skilled in the art.