Turbocharger Bearing Housing with Non-Circular Bearing Bores

A turbocharger includes a compressor wheel, a shaft, a bearing housing, and a floating ring. The shaft is coupled to the compressor wheel and extends through the bearing housing. The bearing housing includes an inner housing surface extending circumferentially around the shaft. The floating ring rotatably supports the shaft in the bearing housing and rotates relative to the bearing housing and the shaft. The floating ring includes an outer bearing surface that extends circumferentially around the shaft and that faces the inner peripheral housing surface. The inner housing surface is formed of a rigid material and has an inner housing cross-sectional shape that in a first axially outer region of the inner housing surface is non-circular perpendicular to the axis, decreases in area moving axially toward a first axial end, and forms a first outer fluid film interface with the outer bearing surface of the floating ring.

CROSS-REFERENCE TO RELATED APPLICATION(S)

TECHNICAL FIELD

This disclosure relates to turbochargers and, in particular, bearing housings for turbochargers.

BACKGROUND

A turbocharger is a forced induction device, which supplies compressed air to an internal combustion engine associated therewith. A turbocharger may include a turbine, which is rotated by exhaust gas from the engine, and a compressor, which is rotated by the turbine to compress the air supplied to the engine. The turbine and the compressor are connected to each other by a shaft and rotate at high rotational speeds, which may create vibrations and/or heat.

SUMMARY

Disclosed herein are implementations of a turbocharger. In an implementation, a turbocharger includes a compressor wheel, a shaft, a bearing housing, and a floating ring. The shaft is coupled to the compressor wheel and extends through the bearing housing. The bearing housing includes an inner housing surface extending circumferentially around the shaft. The floating ring rotatably supports the shaft in the bearing housing and rotates relative to the bearing housing and the shaft. The floating ring includes an outer bearing surface that extends circumferentially around the shaft and that faces the inner peripheral housing surface. The inner housing surface is formed of a rigid material and has an inner housing cross-sectional shape that in a first axially outer region of the inner housing surface is non-circular perpendicular to the axis, decreases in area moving axially toward a first axial end, and forms a first outer fluid film interface with the outer bearing surface of the floating ring.

In an implementation, a turbocharger includes a turbine, a compressor, a shaft, a bearing housing, and a floating journal bearing. The turbine includes a turbine housing and a turbine wheel in the turbine housing. The compressor includes a compressor housing and a compressor wheel in the compressor housing. The shaft rotatably couples the turbine wheel to the compressor wheel, and includes an outer shaft surface. The bearing housing is positioned between the turbine housing and the compressor housing, and has the shaft extending therethrough. The bearing housing has an inner housing surface with a cross-sectional shape that is non-circular and that varies in size moving along an axis of the shaft. The floating journal bearing is positioned radially between and is rotatable independent of the inner housing surface and the outer shaft surface. The floating journal bearing includes an outer bearing surface. A first fluid film interface is formed between the inner housing surface and the outer bearing surface.

In an implementation, a turbocharger includes a shaft, a bearing housing, and a bearing. The shaft is coupled to a turbine wheel and a compressor wheel at opposite ends thereof. The bearing housing includes an inner housing surface with a radial dimension that varies moving circumferentially about an axis thereof and moving axially therealong. The inner housing surface defines a first bore. The bearing includes an outer bearing surface with another radial dimension that is constant moving circumferentially about another axis thereof and moving axially therealong. The inner bearing surface defines a second bore. The bearing is positioned in the first bore. The shaft extends through the second bore. A first fluid film interface is formed between the inner housing surface and the outer bearing surface. A second fluid film interface is formed between the inner housing surface and the shaft. The bearing rotates independent of the bearing housing and the shaft.

DETAILED DESCRIPTION

As discussed in further detail below, the present disclosure is directed to a bearing system for a turbocharger and a turbocharger comprising the same. The bearing system generally includes a bearing housing and a journal bearing, which cooperatively support a rotatable shaft. The bearing housing forms a fluid film interface with the journal bearing therein using a bore geometry that varies in radial dimension moving circumferentially about an axis thereof (e.g., being non-circular in cross-section) and moving axially therealong. By varying the radial dimension moving axially, the bearing system may provide improved stability and reduce noise as compared to bearing systems that do not vary in radial dimension moving axially, and may also control fluid flow for cooling and/or lubrication. The journal bearing forms another fluid film interface with the shaft therein, which may also use a bore geometry that varies in radial dimension moving circumferentially about an axis thereof and/or varies in radial dimension moving axially therealong.

Referring toFIG. 1, a turbocharger100generally includes a turbine110and a compressor120. The turbine110generally includes a turbine housing112and a turbine wheel114. The compressor120generally includes a compressor housing122and a compressor wheel124. The compressor wheel124is connected to the turbine wheel114with a shaft130to be rotated thereby. More particularly, the turbine110receives exhaust gas from an internal combustion engine (not shown), which rotates the turbine wheel114and, in turn, rotates the compressor wheel124to compress air for supply to the engine.

The turbocharger100additionally includes a bearing system having a bearing housing140and a journal bearing150. The bearing housing140and the journal bearing150cooperatively rotatably support the shaft130. The bearing housing140is arranged axially (e.g., in an axial direction) between and is coupled to turbine housing112and the compressor housing122, for example, with threaded fasteners (not shown). The journal bearing150is arranged radially (i.e., in a radial direction) between the shaft130and the journal bearing150. The axial direction is parallel with an axis134of the shaft130(and/or axes of the bearing housing140and the journal bearing150, which are generally the same as the axis134of the shaft130), while the radial direction is perpendicular to the axis134.

Referring additionally toFIG. 2, the bearing housing140defines a bore142in which the journal bearing150and the shaft130are positioned and rotate. More particularly, the bearing housing140includes an inner housing surface144that defines at least a portion of the bore142and that rotatably supports the journal bearing150therein. The inner housing surface144extends circumferentially entirely around an axis of the bearing housing140. Fluid, such as oil received from the engine, forms outer fluid film interfaces (e.g., oil film interface) between the inner housing surface144and an outer bearing surface156of the journal bearing150(as discussed in further detail below) on left and right sides of the bearing system to, thereby, rotatably support the journal bearing150within the bearing housing140. As discussed in further detail below, the inner housing surface144includes a geometry that may provide various functional benefits relating, for example, to stability, noise, vibration, speed, and/or fluid routing. The inner housing surface144may also be referred to as an inner peripheral surface, an inner circumferential surface, an inner peripheral housing surface, or an inner circumferential housing surface. The outer bearing surface156may also be referred to as an outer peripheral surface, an outer circumferential surface, an outer peripheral bearing surface, or an outer housing circumferential surface. The bore142may also be referred to as a cavity or a housing bore. The inner housing surface144may also be referred to as an inner peripheral surface, an inner peripheral housing surface, an inner housing bearing surface, or similar.

The bearing housing140is additionally configured to receive and distribute a fluid (e.g., oil from the engine) for lubricating and/or cooling various components within the bearing housing140, such as the shaft130and the journal bearing150. A fluid circuit may be cooperatively formed by various features of the bearing housing140and the journal bearing150. For example, the bearing housing140includes a fluid passage146that is connectable to a fluid source (not shown), such as an oil pump associated with an oil circulation system of the engine, for receiving the fluid into the bearing housing140. The fluid passage146extends radially inward to form a fluid outlet by which the fluid flows through the inner housing surface144into the bore142. The outlet of the fluid passage146may be referred to as a housing outlet. The fluid passage146thereby communicates the fluid into the bore142of the bearing housing140to form the outer fluid film interfaces between the inner housing surface144of the bearing housing140and the outer bearing surface156of the journal bearing150. As discussed in further detail below, the outlet of the fluid passage146may be located in an intermediate region between a first axial end150a(e.g., near the turbine110) and a second axial end150b(e.g., near the compressor120) of the journal bearing150. The fluid received in the bore142may then flow between the inner housing surface144and the outer bearing surface156in opposite axial directions toward a first axial end150aof the journal bearing150and a second axial end150bof the journal bearing150and/or may flow radially inward through the journal bearing150to radially between the journal bearing150and the shaft130.

The bearing housing140is a singular component or may be a multi-piece assembly, for example, being formed from a cast metal material (e.g., an aluminum, aluminum alloy, iron alloy, or steel alloy). The inner housing surface144is formed by a rigid material, such as the cast metal material otherwise forming the bearing housing140, so as to not deflect under radial loading thereof by the journal bearing150(e.g., the inner housing surface144generally does not provide compliance for radial movement of the shaft130). Alternatively, the inner bearing surface144may include an inner lining that is formed separate from and coupled to the bearing housing140, such lining being formed of aluminum, aluminum alloy, iron alloy, steel alloy, bronze, or brass.

The journal bearing150is configured as a floating journal bearing that surrounds the shaft130and is arranged radially between the shaft130and the bearing housing140. The journal bearing150is generally cylindrical and includes a bore152through which the shaft130extends. The journal bearing150, by being a floating journal bearing, may rotate independent of the shaft130and the bearing housing140. The outer fluid film interfaces are formed between the inner housing surface144and the outer bearing surface156of the journal bearing150, and inner fluid film interfaces are formed between an inner bearing surface154that defines the bore152of the journal bearing150and an outer shaft surface132of the shaft130. The outer bearing surface156and the inner bearing surface154each extend circumferentially entirely around an axis of the journal bearing150. As discussed in further detail below, the inner bearing surface154includes a geometry that may provide various functional benefits relating, for example, to stability, noise, vibration, speed, and/or fluid routing. The inner bearing surface154may also be referred to as an inner peripheral surface, an inner circumferential surface, an inner peripheral bearing surface, or an inner circumferential bearing surface.

As referenced above, the journal bearing150rotates independent of the shaft130and the bearing housing140. Rotation of the journal bearing150is caused by rotation of the shaft130(e.g., at high speeds) as torque is transferred therebetween (e.g., from shearing of the fluid forming the second fluid film interface therebetween). The journal bearing150rotates at a slower speed relative to the bearing housing140than does the shaft130, for example, at 15-20% of the speed of the shaft130depending on operating conditions (e.g., temperature and/or speed). The journal bearing150may also be referred to as a floating ring, floating bearing, or floating ring bearing.

The journal bearing150is additionally configured to receive and distribute fluid for lubricating and/or cooling various components, such as the shaft130and the journal bearing150. The journal bearing150may include a fluid passage158athat extends radially from the outer bearing surface156to the inner bearing surface154. The fluid may thereby flow from the bore142of the bearing housing140(i.e., from between the inner housing surface144and the outer bearing surface156) into the bore152of the journal bearing150to form the inner fluid film interfaces between inner bearing surface154and the outer shaft surface132of the shaft130. The journal bearing150may, in some embodiments, additionally include a circumferential channel158bin the outer bearing surface156extending circumferentially therearound. The circumferential channel158bmay be axially aligned with both the outlet of the fluid passage146of the bearing housing140and the fluid passage158aof the journal bearing150, so as to maintain fluidic communication between the fluid outlet146c and the fluid passage158aeven as the journal bearing150rotates relative to the bearing housing140. The fluid received in the bore152of the journal bearing150may then flow between the inner bearing surface154and the outer shaft surface132in opposite axial directions toward the first axial end150aof the journal bearing150and the second axial end150bof the journal bearing150.

The journal bearing150is a singular component, or may be a multi-piece assembly, formed by a rigid material, such as an extruded or cast metal material (e.g., brass and/or bronze). For example, the journal bearing150may be machined from a bar stock of material (e.g., extruded brass or bronze). The inner bearing surface154is formed by a rigid material, such as the extruded or cast metal material otherwise forming the journal bearing150(e.g., to generally not deflect under radial loading from the shaft130). The journal bearing150may also be referred to as a ring, a floating bearing, a floating journal bearing, or a floating ring.

As referenced above, the inner housing surface144of the bearing housing140includes a geometry (e.g., a housing bore geometry) that may provide various advantages as compared to a conventional geometry. The inner bearing surface154of the journal bearing150may also include a geometry (e.g., a bearing bore geometry) that may also provide various advantages as compared to the conventional geometry. A conventional bore geometry may instead be constant in radial dimension moving circumferentially (i.e., being entirely circular) and axially (i.e., being cylindrical).

Bearing Housing Geometry

Referring toFIG. 1and additionally toFIGS. 2-6, the inner housing surface144has a geometry that varies in radial dimension moving circumferentially about the axis of the bearing housing140and also moving axially therealong. The inner bearing surface154of the journal bearing150may also vary in radial dimension moving circumferentially about the axis thereof and/or moving axially therealong.

For example, referring toFIGS. 1 and 2, the bearing housing140may include a axially central region140c(e.g., a non-bearing region) that does not support the journal bearing150(e.g., does not form the outer fluid film interface) that is surrounded by first and second axially outer regions140d,140e(e.g., bearing regions) that support the journal bearing150by forming the outer fluid film interfaces (e.g., left and right fluid film interfaces as shown). In the axially central region140cof the bearing housing140, the inner housing surface144may have an inner dimension and define a cross-sectional area that is larger than dimensions of the first and second axially outer regions140d,140e.For example, the inner housing surface144may have a radius RHIM that is constant moving circumferentially around the axis134and moving axially therealong (e.g., between 25% and 75% of an axial length of the journal bearing150, such as between 40% and 60% (e.g., approximately 50%). Moving axially from the axially central region140cto each of the first and second axially outer regions140d,140e,the inner housing surface144may change in radial dimension abruptly, such as in a stepped manner.

In the dimensional nomenclature below for radial dimensions R, the first letter of the suffix generally refers to the component (e.g., “H” refers to the bearing housing140, “B” refers to the journal bearing150, and “S” refers to the shaft130), the second letter generally refers to the surface (e.g., “I” refers to an inner surface, such as the inner housing surface144, and “0” refers to an outer surface, such as the outer bearing surface156of the journal bearing150), the third character generally refers to the axially-extending region (e.g., “M” refers to the central region or position between the turbine110and the compressor120; “1” refers to a first axially outer region, such as the first axially outer region140d,on a first, left, or turbine side of the journal bearing150relative to the middle position; “2” refers to a second axially outer region, such as the second axially outer region140e,on a second, right, or compressor side of the journal bearing150relative to the middle position), the fourth character generally refers to the axial position within a region (e.g., “E” refers to a position at or near an end, such as the first and second axial ends150a,150b;“C” refers to a central position, such as at or near the axially central region140c), and “max” and “min” refer to the maximum and minimum radial dimensions of the component at the specified location. Similarly, in the dimensional nomenclature below for the cross-sectional areas A, the first letter refers to the component (see above), the second letter refers to the surface (see above), and the third character refers to the axial region (see above). Letters, numbers, or characters may be omitted where not applicable, such as when referring to radial dimensions or areas more generally (e.g., over a side as opposed to end and central locations) or if there is no variation (e.g., having a constant value over different positions).

Circumferentially-Varying Geometry of the Bearing Housing

With the radial dimension of the bore geometry varying moving circumferentially, the bore geometry may also be referred to as having a circumferentially-varying radial dimension, which results in the cross-sectional shape (e.g., the cross-sectional area) of the inner housing surface144being non-circular. The cross-sectional shapes discussed herein are taken perpendicular to the axis of the shaft130. For example, the inner housing surface144(e.g., the cross-sectional shape or cross-sectional area thereof) may include a series of peaks144aand valleys144bhaving smaller and larger radial dimensions, respectively, measured from the axis134of rotation of the shaft130. The radial dimension of the peaks144amay be referred to as a peak radial dimension or minimum radial dimension, and the radial dimension of the valleys144bmay also be referred to as a valley radial dimension or maximum radial dimension. The peaks144aand the valleys144balternate circumferentially and extend axially over a majority (e.g., an entirety) of the axial distance of the first axially outer region140d(e.g., between the first axial end150aof the journal bearing150and the axially central region140cof the bearing housing140, such as on the turbine side) and also the second axially outer region140e(e.g., between the second axial end150band the axially central region140c,such as on the compressor side of the journal bearing150). As a result, each of the peaks144aforms an axially-extending ridge, and each of the valleys144bforms an axially-extending trough. The outer fluid film interfaces are formed between the peaks144aof the inner housing surface144and the outer bearing surface156(e.g., two outer film interfaces, one in the first axially outer region140dand another in the second axially outer region140e).

As shown, the inner housing surface144may include three of the peaks144aand three of the valleys144btherebetween, but may include fewer (e.g., two) or more (e.g., four, five, or more). The peaks144aand/or the valleys144bmay also be referred to as lobes. For illustrative purposes, the radial dimensions of the bearing housing140are depicted in an exaggerated manner, andFIG. 6superimposes the cross-sectional shape of the various components of the turbocharger100to illustrate the different radial dimensions at different axial positions. As discussed blow, the radial dimension may vary at each axial location (e.g., the difference between the radial dimensions of the peak144aand the valley144bat one axial position) by between 2 and 50 microns, or other suitable amount.

This circumferentially-varying radial dimension of the inner housing surface144may, as compared to the conventional geometry, reduce vibrations (e.g., sub-synchronous vibrations), reduce noise, control bearing temperature, increase rotational speed of the shaft130, and/or increased stability at high rotational speeds of the shaft130, as compared to conventional geometries of bearing housings and/or journal bearings. Sub-synchronous vibrations refer to vibrations causes by the journal bearing150rotating at a slower speed than the shaft130.

Further, this circumferentially-varying radial geometry of the inner housing surface144may also assist in flow of the fluid. As shown by comparing the cross-sectional views inFIGS. 3-6, the peaks144aand the valleys144bof the inner housing surface144are at the same angular position at different axial positions, such that the axially-extending ridges formed by the peaks144aand the axially-extending troughs formed by the valleys144beach extend parallel with the axis.

Alternatively, the peaks144aand the valleys144bof the inner housing surface144may be at different angular positions at different axial positions, such that the axially-extending ridges formed by the peaks144aand the axially-extending troughs formed by the valleys144beach extend at least partially circumferentially around the axis134. As a result, the peaks144aand valleys144bmay function to assist in flow of the fluid toward and/or away from the first axial end150aand/or the second axial end150b.As the journal bearing150is rotated, an axial force is applied by the peaks144ato push the fluid toward or away from the first axial end150aand/or the second axial end150b.For example, the peaks144amay extend circumferentially between 5 degrees and 90 degrees from the first axial end150ato the second axial end150b.

Referring toFIGS. 7A-7E, the angular position of each peak144ais plotted against the axial position represented as a percentage of the axial distance within the first and second axially outer regions140d,140e(e.g., between the first axial end150aor the second axial end150band the axially central region140c), so as to illustrate the angular position of the ridge formed thereby relative to the axial position. As shown inFIG. 7A, the peaks144ado not extend circumferentially (i.e., as shown inFIGS. 2-6). As shown inFIG. 7B, the peaks144aextend circumferentially 20 degrees from the first axial end150ato the second axial end150bin the same direction of rotation as the journal bearing150(i.e., rolling down the page as shown), such that the fluid is pushed axially toward the second axial end150b.As shown inFIG. 7C, the peaks144aextend circumferentially 45 degrees from the second axial end150bto the first axial end150ain the same direction of rotation as the journal bearing150(i.e., rolling down the page as shown), such that the fluid is pushed axially toward the second axial end150b.As shown inFIG. 7D, the peaks144aextend circumferentially 10 degrees from an intermediate position to the first axial end150aand the second axial end150bin the direction of rotation, such that the fluid is pushed axially outward from the intermediate region to each of the first axial end150aand the second axial end150b.As shown inFIG. 7E, the peaks144aextend circumferentially 20 degrees from each of the first axial end150ato the second axial end150bin the direction of rotation, such that the fluid is pushed axially inward from the first axial end150aand the second axial end150b(e.g., to retain fluid in the bore142).

Axially-Varying Geometry of the Bearing Housing

With the radial dimension of the bore geometry varying moving axially, the bore geometry of the inner housing surface144(e.g., the inner housing cross-sectional shape) may also be referred to as having an axially-varying radial dimension. More particularly, by reducing the maximum radial dimension of the inner housing surface144(i.e., the dimension of the valleys144b) moving axially toward the first axial end150a(e.g., on the turbine side) and/or the second axial end150b,greater stability may be provided to the bearing system and reduced noise may be achieved as compared conventional bearing geometries. The minimum radial dimension of the inner housing surface144(i.e., the dimensions of the peaks144a) may be constant in the first and second axially outer regions140d,140e.Further, by having the maximum dimension of the inner housing surface144reduce to a smaller dimension on one side (e.g., the first axially outer region140d,such as the turbine side) as compared to the other (e.g., the second axially outer region140e,such as the compressor side), the bore geometry allows the flow of fluid to be biased more toward the first axial end150aor the second axial end150b.For example, with the bore geometry having an axially-varying radial dimension, the cross-sectional shape of the inner housing surface144may have an area that varies moving axially (e.g., decreases moving axially outward), which may be referred to as an axially-varying cross-sectional area. The different areas allow unequal biasing of fluid flow between the first axial end150aof the journal bearing150and the second axial end150bof the journal bearing150. That is, the fluid may flow in an axial direction between the inner housing surface144and the outer bearing surface156at uneven flow rates toward the first axial end150aand the second axial end150b.This uneven flow may be advantageous to control cooling of various components of the turbocharger100and to control a temperature of the fluid to limit rotational friction between the inner housing surface144and the outer bearing surface156(e.g., due to shearing of the fluid) and/or prevent oil burning (e.g., due to too high a temperature).

The axially-varying radial dimension and the axially-varying cross-sectional area are illustrated by comparing the cross-sectional views ofFIG. 3(taken at a central position in the first axially outer region140d),FIG. 4(taken at an end position in the first axially outer region140d),FIG. 5(taken at an end position in the second axially outer region140e,such as the right or compressor side), andFIG. 6(superimposition of the cross-sections ofFIGS. 2-5).

FIG. 3is a cross-sectional view of the turbocharger100taken in the first axially outer region140dat a at a central position adjacent to the axially central region140c(e.g., non-bearing region). The first axially outer region140dmay instead be on a compressor side of the turbocharger100. At this central axial position, the inner housing surface144has a maximum radial dimension RHI1Cmaxmeasured from the axis134at one or more of the valleys144b(e.g., all) and a minimum radial dimension RH1minat one or more (e.g., all) of the peaks144a.At the central position, the difference between the maximum radial dimension RHI1Cmaxand the minimum radial dimension RH1minmay, for example, be between 2 and 50 microns, such as between 15 and 40 microns, or other suitable dimension.

In the first axially outer region140d,the maximum radial dimension RHI1max(i.e., of the valleys144b) of the inner housing surface144may be highest at the central position as compared to any other axial position. Thus, moving axially from the central axial position toward the first axial end150a,the maximum radial dimension RHI1maxmay decrease and/or stay constant. For example, as shown, the maximum radial dimension RHI1maxdecreases moving from the central position toward the first axial end150aof the journal bearing150.

The minimum radial dimension RHI1minof the inner housing surface144may, as shown, be constant over the axial distance of the journal bearing150(i.e., be the same at each axial position).

As a result of the maximum radial dimension RHImaxbeing highest at the central position and the minimum radial dimension RHIminstaying constant, the cross-sectional area AHI1of the inner housing surface144(e.g., an inner housing cross-sectional area) in the first axially outer region140dmay also be highest at the central position. Further, as a result of the maximum radial dimension RHI1maxdecreasing moving from the central position and the minimum radial dimension RHIminstaying constant, the cross-sectional area AHIMdefined within the inner housing surface144decreases moving from the central axial position axially toward the first axial end150a.Thus, the cross-sectional area of the inner housing surface144varies in size between the central position and the end position (proximate the first axial end150a) on the first (e.g., left or turbine) bearing region.

FIG. 4is a cross-sectional view of the turbocharger100taken at a first end position on a first axial side of the bore142of the bearing housing140. The first end position may be the position where the maximum radial dimension RHImaxis least on the first side of the bore142. That is, the maximum radial dimension RHImaxreduces from its greatest value RHI1Cmaxat the central position to its lowest value on the first side of the bore142, which is RHI1Emaxat the first end position (i.e., RHI1Cmax<RHI1Emax) and may be referred to as a smallest valley radial dimension or minimum valley radial dimension.

The maximum radial dimension RHImaxmay, as shown inFIG. 1, change gradually moving axially (e.g., having smooth surfaces without steps). For example, the maximum radial dimension RHI1maxmay decrease at an increasing rate moving axially outward (i.e., toward the first axial end150a), such as by following a curve having a constant or reducing radius (e.g., a parabolic curve), or may decrease at a constant rate (e.g., following a linear path). Alternatively, the maximum radial dimension RHI1maxmay stay constant moving from the central position to the first axial end (i.e., RHI1Cmax=RHI1Emax). At the first end position, a difference between the maximum radial dimension RHI1Emaxand the minimum radial dimension RHIminmay, for example, be between 2 and 50 microns, such as between 4 and 20 microns, or other suitable dimension. In some applications, at the first axial end position, the difference between the maximum radial dimension RHI1Emaxand the minimum radial dimension RHIminmay be zero, such that the inner housing surface144has a circular cross-sectional shape at the first axial end position.

In the second axially outer region140e,the maximum radial dimension RHImaxof the inner housing surface144may reduce in the same or similar manner as in the first axially outer region140d.The second axially outer region140emay be symmetric to the first axially outer region140d,or may be different (e.g., to provide different flow rates, as discussed below).FIG. 5is a cross-sectional view of the turbocharger100taken at a second end position in the second axially outer region140eof the bore142of the bearing housing140. As shown, the second axial side is on the compressor side of the turbocharger100, but may instead be on the turbine side of the turbocharger100.

The second axial end position may be the position where the maximum radial dimension RHImaxis least on the second side of the bore142(e.g., forming the minimum valley radial dimension). The maximum radial dimension RHImaxon the second axial side may reduce (e.g., from a maximum value at another central position adjacent the central region) to its lowest value on the second side of the bore142, which is RHI2Emaxat the second axial end position in the manners described previously (e.g., at increasing or constant rates moving axially toward the second axial end150b). Alternatively, the maximum radial dimension RHI2maxmay stay constant moving from the central position to the second axial end (i.e., RHI2Cmax=RHI2Emax). At the second axial end position, a difference between the maximum radial dimension RHI2Emaxand the minimum radial dimension RHIminmay, for example, be between 2 and 50 microns, such as between 4 and 20 microns, or other suitable dimension. In some applications, at the second axial end position, a difference between the maximum radial dimension RHI2Emaxand the minimum radial dimension RHIminmay be zero, such that the inner housing surface144has a circular cross-sectional shape at the second axial end position.

The maximum radial dimension RHImaxmay be least at the second axial end position as compared to all other axial positions (i.e., RHI2Emax<RHI1Emax). As a result of the maximum radial dimension RHImaxbeing least at the second axial position and the minimum radial dimension RHIminstaying constant, the cross-sectional area AHIof the inner housing surface144may also be lower in the second axially outer region140ethan in the second outer region (AHI2E>AHI1E). For example, the lowest or minimum cross-sectional area in the first axially outer region140dmay be lower than the lowest or minimum cross-sectional area of the inner housing cross-sectional shape in the second axially outer region140e.Thus, with the outer bearing surface156having a constant cross-sectional shape and area (i.e., circular shape with constant diameter moving axially, as discussed below), a net cross-sectional area (i.e., AHIminus ABO) is lower in the second axially outer region140ethan in the first axially outer region140d.This difference in net cross-sectional area provides that fluid flow (i.e., received into the bore142through the fluid passage146at an axial position between the first axial end position and the second axial end position, and flowing axially between the inner housing surface144and the outer bearing surface156) is biased more toward the first axial end150athan the second axial end150b.

For example, as shown, the first axial end150ais positioned near the turbine110, while the second axial end150bis positioned near the compressor120. Thus, with the net cross-sectional area being larger at the first axial end position near the turbine110as compared to the second axial end position near the compressor120, more fluid is biased toward the turbine110. Biasing more fluid toward the turbine110may be desirable to cool components (or portions thereof) proximate the turbine110(e.g., a back wall of the turbine housing112), which may be expected to be relatively hot due to the exhaust gas from the engine flowing therethrough, while less fluid may be biased toward the second axial end150bto cool components proximate the compressor120, which are expected to be relatively cool. Alternatively, more fluid may be biased toward the compressor120than toward the turbine110. Fluid exiting axially from between the inner housing surface144and the outer bearing surface156may be used to cool and/or lubricate still further components of the turbocharger100and may ultimately be collected in a sump (not shown) of the bearing housing140to be cooled and recirculated to the engine and/or the turbocharger100.

Alternatively, the maximum radial dimensions RHI1Emax, RHI2Emaxand the cross-sectional areas AHI1E, AHI2Emay be the same on each side (e.g., at each axial end) of the bearing housing140, such that fluid flow is substantially equal therethrough.

Journal Bearing Geometry

Referring still toFIGS. 2-5, the outer bearing surface156of the journal bearing150has a non-variable geometry, while the inner bearing surface154of the journal bearing150may, in some embodiments, vary in radial dimension moving circumferentially about the axis of the journal bearing150and/or moving axially therealong. For example, referring again toFIGS. 1 and 2, the journal bearing150may include an axially central region150c(e.g., a non-bearing region) that does not support the shaft130(e.g., does not form the inner fluid film interface) and that is axially between first and second axially outer regions150d,150e(e.g., bearing regions) that support the shaft130by forming the inner fluid film interfaces (e.g., left and right inner fluid film interfaces as shown). The axially central region150cand the first and second axially outer regions150d,150eof the journal bearing150may correspond to the axially central region140cand the first and second axially outer regions140d,140eof the bearing housing (e.g., being the generally same in axial length and position), or may differ (e.g., being shorter in axial length). In the axially central region150cof the journal bearing150, the inner bearing surface154may have an inner dimension and define a cross-sectional area that is larger than dimensions of the first and second axially outer regions150d,150e,and may not form the inner fluid film interface (e.g., to not radially support the shaft130therein). The radius RBIMin the axially central region150cmay be constant moving circumferentially around the axis134(e.g., being circular) and may be constant moving axially therealong (e.g., between 25% and 75% of an axial length of the journal bearing150, such as between 40% and 60% (e.g., approximately 50%). Moving axially from the axially central region150cto each of the first and second axially outer regions150d,150e,the inner bearing surface154may change in radial dimension abruptly, such as in a stepped manner.

Outer Geometry of the Journal Bearing

As referenced above, the outer bearing surface156of the journal bearing150(e.g., the cross-sectional shape and/or the cross-sectional area thereof, which may be referred to as the outer bearing cross-sectional shape) is circular and cylindrical, such that the outer bearing surface156has an outer radial dimension RBOthat is the same at generally all angular positions therearound (i.e., being circular) and generally all axial positions therealong (i.e., being cylindrical). Thus, at each of the first position and the second positions on the first and second sides of the journal bearing, the journal bearing150has an outer bearing cross-sectional area that is circular and common in size.

It should be noted that the journal bearing150may include the fluid passage158a,the circumferential channel158b,or other surface features that are minor in area (e.g., forming less than 5% of the total surface area of the outer bearing surface156) in the outer bearing surface156, while the outer bearing surface156is still considered circular and/or cylindrical. With the outer radial dimension RBOof the journal bearing150and minimum radial dimension RHIminof the inner housing surface144being the same at all axial positions, the outer fluid film interfaces may be formed similarly in the first and second axially outer regions140d,140e(e.g., between the peaks144aof the inner housing surface144and the outer bearing surface156of the journal bearing150).

Circumferentially-Varying Inner Geometry of the Journal Bearing

With the radial dimension of the bore geometry of the journal bearing150varying moving circumferentially, the bore geometry may also be referred to as having a circumferentially-varying radial dimension. The result of which is the cross-sectional shape (e.g., the cross-sectional area) of the inner bearing surface154being non-circular.

For example, the inner bearing surface154(e.g., the cross-sectional shape, or the cross-sectional area thereof, which may be referred to as the inner bearing cross-sectional shape) may include a series of peaks154aand valleys154bhaving smaller and larger radial dimensions, respectively, measured from the axis134of rotation of the shaft130. The radial dimension of the peaks154amay be referred to as a peak radial dimension or minimum radial dimension, and the radial dimension of the valleys154bmay also be referred to as a valley radial dimension or maximum radial dimension. For example, as shown, the varied radial geometry may include three peaks154aand three valleys154btherebetween. The peaks154aand the valleys154bmay also be referred to as lobes. The peaks154aand the valleys154balternate circumferentially and extend axially over a majority (e.g., an entirety) of the axial distance of the first axially outer region150d(e.g., between the first axial end150aand the axially central region150cof the journal bearing150, such as on the turbine side) and also the second axially outer region150e(e.g., between second axial end150band the axially central region150c,such as on the compressor side of the journal bearing150). As a result, each of the peaks154aforms an axially-extending ridge and each of the valleys154bforms an axially-extending trough. The inner fluid film interfaces are formed between the peaks154aof the inner bearing surface154and the outer shaft surface132of the shaft130(e.g., two inner film interfaces, one in the first axially outer region150dand another in the second axially outer region150e).

As shown, the inner bearing surface154may include three of the peaks154aand three of the valleys154btherebetween, but may include fewer (e.g., two) or more (e.g., four, five, or more). To distinguish from those of the inner housing surface144, the peaks154aand the valleys154bof the inner bearing surface154may be referred to as bearing peaks and bearing valleys, respectively, while the peaks144aand the valleys144bof the inner housing surface144may be referred to as housing peaks and housing valleys, respectively. Alternatively, the inner bearing surface154may not vary moving circumferentially (e.g., having a circumferentially non-varying radial dimension), so as to be circular in cross-section at each axial position. For illustrative purposes, the radial dimensions of the journal bearing150are depicted in an exaggerated manner, andFIG. 6superimposes the cross-sectional shape of the various components of the turbocharger100to illustrate the different dimensions at different axial positions.

The circumferentially-varying radial dimension of the inner bearing surface154may reduce vibrations (e.g., sub-synchronous vibrations), reduce noise, control bearing temperature, increase rotational speed of the shaft130, and/or increases stability at high rotational speeds of the shaft130, as compared to conventional geometries of bearing housings and/or journal bearings.

The circumferentially-varying radial dimension may also assist with axial flow of the fluid. Referring toFIGS. 7A-7E, the peaks154aand the valleys154bof the inner bearing surface154may have a constant angular position or may vary as shown for the peaks144aand the valleys144bof the inner housing surface144.

Axially-Varying Inner Geometry of the Journal Bearing

With the radial dimension of the bore geometry of the journal bearing150varying moving axially, the bore geometry of the inner bearing surface154(e.g., the inner bearing cross-sectional shape) may also be referred to as having an axially-varying radial dimension. As with varying the bore geometry of the bearing housing140, by reducing the maximum radial dimension (i.e., of the valleys154b) moving axially toward the first axial end150aand the second axial end150b,greater stability may be provided to the bearing system and reduced noise may be achieved as compared to conventional bearing geometries. The minimum radial dimension (i.e., of the peaks154amay be constant moving axially). Further by having different smallest dimensions and resultant cross-sectional areas on the turbine and compressor sides, unequal biasing of fluid flow may be achieved between the first axial end150aof the journal bearing150and the second axial end150bof the journal bearing150. That is, the fluid may flow in an axial direction between the inner bearing surface154and the outer shaft surface132at uneven flow rates toward the first axial end150aand the second axial end150b.

The axially-varying radial dimension and the axially-varying cross-sectional area of the inner bearing surface154are illustrated by comparing the cross-sectional views ofFIG. 2(taken in the axially central region150c),FIG. 3(taken at a central position in the first axially outer region150d),FIG. 4(taken at an end position in the first axially outer region150d),FIG. 5(taken at an end position in the second axially outer region150e), andFIG. 6(superimposition of the cross-sections ofFIGS. 2-5).

Referring again toFIG. 3, at the central position in the first axially outer region150d,the inner bearing surface154has a maximum radial dimension RBI1Cmaxmeasured from the axis134at one or more of the valleys154b(e.g., all) and a minimum radial dimension RBIminat one or more (e.g., all) of the peaks154a.At the central position, the difference between the maximum radial dimension RBI1Cmaxand the minimum radial dimension RBIminmay, for example, be between 2 and 50 microns, such as between 15 and 40 microns, or other suitable dimension.

In the first axially outer region150d,the maximum radial dimension RBI1max(i.e., of the valleys154b) of the inner bearing surface154may be highest at the central position as compared to any other axial position. The maximum radial dimension RBI1max(i.e., of the valleys154b) of the inner bearing surface154may be highest at the same or different axial position at which the maximum radial dimension RHI1maxof the inner housing surface144is highest (e.g., being closer to one of the first axial end150aor the second axial end150b) and may be at the same or different axial position at which the fluid passage158ais located.

Moving axially from the central position toward the first axial end150a,the maximum radial dimension RBImaxmay decrease and/or stay constant. For example, as shown, the maximum radial dimension RBImaxdecreases moving from the central position toward the first axial end.

The minimum radial dimension RBIminof the inner bearing surface154may, as shown, be constant over the axial distance of the journal bearing150(i.e., be the same at each axial position therealong).

As a result of the maximum radial dimension RBImaxbeing highest at the central position and the minimum radial dimension RBIminstaying constant, the cross-sectional area ABIof the inner bearing surface154(e.g., the inner bearing cross-sectional area) in the first axially outer region150dmay also be highest at the central position. Further, as a result of the maximum radial dimension RBImaxdecreasing moving from the central position and the minimum radial dimension RHIminstaying constant, the cross-sectional area ABIdefined within the inner bearing surface154decreases moving from the central axial position axially toward the first axial end150a.Thus, the cross-sectional area of the inner bearing surface154varies in size between the central position and the first end position in the first axially outer region150d(e.g., bearing region).

Referring again toFIG. 4, the maximum radial dimension RBImaxof the inner bearing surface154may be lowest in the first axially outer region150dat the first end position. The maximum radial dimension RBImaxof the inner bearing surface154reduces from its greatest value RBI1Cmaxat the central position to its lowest value on the first axially outer region150d,which is RHI1Emaxat the first axial end position (i.e., RBI1Cmax>RBI1Emax).

The maximum radial dimension RBImaxmay, as shown inFIG. 1, change gradually moving axially. For example, the maximum radial dimension may decrease at an increasing rate moving axially outward (i.e., toward the first axial end150a), such as by following a curve having a constant or reducing radius (e.g., a parabolic curve), or may decrease at a constant rate (e.g., following a linear path). Alternatively, the maximum radial dimension RHImaxmay stay constant moving from the central position to the first axial end (i.e., RBI1Cmax=RBI1Emax). The maximum radial dimension RBI1Emax(i.e., of the valleys154b) of the inner bearing surface154may be at the same or different axial position at which the maximum radial dimension RHI1Emaxof the inner housing surface144is least on the first axial side (e.g., being closer to or further from the first axial end150a). At the first end position, a difference between the maximum radial dimension RHI1maxand the minimum radial dimension RHIminmay, for example, be between 2 and 50 microns, such as between 4 and 20 microns, or other suitable dimension.

In the second axially outer region150e,the maximum radial dimension RHBmaxof the inner bearing surface154may reduce in the same or similar manner as in the first axially outer region150d,or may differ (e.g., to provide uneven flow rates as discussed below). Referring again toFIG. 5, the maximum radial dimension RBI2maxof the inner bearing surface154may be lowest on the second axially outer region150eat the end position (e.g., at or adjacent the second axial end150b). Alternatively, the maximum radial dimension RHImaxmay stay constant moving from the central position to the second axial end (i.e., RBI2Cmax=RBI2Emax). The maximum radial dimension RBI2Emax(i.e., of the valleys154b) of the inner bearing surface154may be at the same or different axial position at which the maximum radial dimension RHI2Emaxof the inner housing surface144is least on the second axial side140e(e.g., being closer to or further from the second axial end150b). At the second end position, a difference between the maximum radial dimension RBI2Emaxand the minimum radial dimension RBIminmay, for example, be between 2 and 50 microns, such as between 4 and 20 microns, or other suitable dimension.

The maximum radial dimension RBImaxof the inner bearing surface154may be lowest at the second end position as compared to all other axial positions (i.e., RBI2Emax<RBI1Emax) in the first and second axially outer regions150d,150e.As a result of the maximum radial dimension RBImaxbeing least at the second end position and the minimum radial dimension RBIminstaying constant, the cross-sectional area ABIof the inner bearing surface154may also be lower in second axially outer region150ethan the first axially outer region150d.Thus, with the outer shaft surface132having a constant cross-sectional shape and size (i.e., circular shape with constant diameter, as discussed below), a net cross-sectional area (i.e., ABIminus ASO) is lower in the second axially outer region150ethan in the first axially outer region150d.This difference in net cross-sectional area provides that fluid flow (e.g., received into the bore152through the fluid passage158aat an axial position between the first axial position and the second axial position, and flowing axially between the inner bearing surface154and the outer shaft surface132) is biased more toward the first axial end150athan the second axial end150b.Thus, more fluid is biased toward the first axial end150a(e.g., toward the turbine110) than the second axial end150b(e.g., toward the compressor120) both between the inner housing surface144and the outer bearing surface156and between the inner bearing surface154and the outer shaft surface132.

Alternatively, the maximum radial dimension RBImaxof the inner bearing surface154may be lowest on the opposite side from which the maximum radial dimension RBImaxof the inner housing surface144is lowest. As a result, more fluid is biased toward the first axial end150athan the second axial end150bbetween the inner housing surface144and the outer bearing surface156, and more fluid is biased toward the second axial end150bthan the first axial end150abetween the inner bearing surface154and the outer shaft surface132, or vice versa.

As referenced above, the shaft130has a geometry that does not vary in radial dimension moving circumferentially or axially in regions where the second fluid film interface is formed. That is, the outer surface of the shaft130does not vary radially (i.e., is circular) or axially (i.e., is cylindrical) in the axial region coinciding with the journal bearing150.

Referring toFIG. 8, a turbocharger200may be configured substantially similar to the turbocharger100but instead includes two journal bearings250(e.g., floating rings or floating journal bearings) that are spaced apart axially along the shaft130with a spacer ring260(e.g., spacer member) arranged therebetween. In a first axially outer region240d,the inner housing surface244of a bearing housing240varies in radial dimension moving both circumferentially (e.g., having peaks and valleys as described above) and axially. For example, the maximum radial dimension (e.g., the valley radial dimension) may be greatest in a central position (e.g., at an axial midpoint of a corresponding one of the journal bearings250) and reduce therefrom moving axially toward the turbine and toward a central region240ccorresponding to the spacer ring260. An oil flow passage may be arranged at the axial position corresponding to the greatest maximum radial dimension (e.g., the midpoint). Moving from this midpoint, the maximum radial dimension reduces gradually to both axial ends thereof (e.g., following a curve, such as a parabola, or a line, as described previously). The inner housing surface244may be symmetric in the first axially outer region240dabout the midpoint, or may be asymmetric (e.g., having different maximum radial dimensions on each side to bias fluid flow unequally to each side thereof, or by having the maximum radial dimension located off-center). The minimum radial dimension (e.g., of the peaks) may be constant moving axially. The fluid film interface (e.g., the outer fluid film interface) may be formed over the entire axial length of the journal bearing250. Each of the journal bearings250may have an outer bearing surface with a constant outer diameter moving both circumferentially and axially.

In a second axially outer region240e(i.e., opposite the first axially outer region240dwith the central region240carranged therebetween), the inner housing surface244may be symmetric to the first axially outer region240d.

Each of the journal bearings250may also be configured in the manners described above with respect to the journal bearing150by having an inner bearing surface254with a cross-sectional shape that varies in radial dimension moving circumferentially (e.g., for vibrations, etc.) and moving axially (e.g., for stability and/or to control fluid flow therethrough). The maximum radial dimension (e.g., the valley dimension) may be greatest in the central position (e.g., at an axial midpoint thereof) and reduce therefrom moving axially toward the turbine (or compressor) and toward the spacer ring260. Oil flow passages through the journal bearing250may be arranged at the same axial position as the oil flow passage of the bearing housing, and the journal bearing250may additionally include a circumferential channel corresponding thereto (e.g., being recessed relative to the outer bearing surface thereof, such as with the circumferential channel158b) to ensure communication between the oil passage of the bearing housing240as the journal bearing rotates relative thereto. Moving axially from the midpoint, the maximum radial dimension reduces gradually to both axial ends thereof (e.g., following a curve, such as a parabola, or line as described previously). The inner bearing surface254may be symmetric about the midpoint, or may be asymmetric (e.g., having different maximum radial dimensions on each side thereof to bias fluid flow unequally to each side thereof, or by having the maximum radial dimension located off-center). The minimum radial dimension may be constant moving axially. The fluid film interface (e.g., the inner fluid film interface) may be formed over the entire axial length of the journal bearing250.

A second of the journal bearings250may be a duplicate of a first of the journal bearing250.

The spacer ring260is configured as a ring arranged between the two journal bearings250. The spacer ring260is able to rotate independent of the two journal bearings250, the shaft230, and the bearing housing240. The spacer ring260does not support the shaft230(e.g., does not form fluid film interfaces therebetween).

The bearing housings140,240sand the journal bearing150,250and, particularly, the bore geometries of the inner housing surfaces144,244and the inner bearing surface154,254, respectively thereof, may be formed according to any suitable method. A machine, such as a magnetically levitated machine tool and spindle assembly, may apply a rotating cutting tool to the inner surface at suitable axial and radial trajectories in a milling or boring fashion to form the bore geometry thereof. The bearing housing140and the journal bearing150may be moved axially relative to the cutting tool. For example, the inner housing surface144and/or the inner bearing surface154may be formed according to the method and with the machine300described in U.S. Pat. No. 9,777,597, the entire disclosure of which is incorporated herein by reference.