Thrust bearing assembly for engine crankcase

Methods and systems are provided for a thrust bearing assembly for a crankcase of an engine. In one example, a thrust bearing may comprise a semicircular curved plate mounted on a main bearing. At least two holes may be asymmetrically positioned on the surface of the thrust bearing to allow attachment with a flywheel housing in a unique manner.

FIELD

Embodiments relate to engine systems. Other embodiments relate to thrust bearing assemblies for engine crankcases.

BACKGROUND

Crankshafts are journaled in engine blocks by a series of axially spaced engine bearing assemblies. These assemblies include one or more rotary bearings that permit rotation of the crankshaft while supporting an axial load of the crankshaft. For example, the crankshaft includes a thrust bearing that provides a fore/aft gap-control for axial movement (also known as endplay) of the crankshaft. The thrust bearing is typically located at a terminal location, such as at a back end of an engine block, where a crankcase cover meets the crankshaft.

Incorrect assembly and mounting of the thrust bearing assembly during engine manufacture can result in premature engine degradation. For example, if the thrust bearing is mounted with the opposite side (than intended) facing the crankshaft, the crank surface may be affected under conditions of high thrust loading, especially during buff or coupling events, as well as during dynamic operation. If the thrust bearing is mounted using a grub screw and a counter sunk, the thrust bearing may need to be thicker than desired, resulting in additional weight and manufacturing cost. If the thrust bearing is made thinner, as desired, the grub screw surface may damage the thrust surface.

BRIEF DESCRIPTION OF THE INVENTION

Methods and systems are provided for enabling reliable mounting of a crankcase thrust bearing assembly. In one embodiment, a thrust bearing assembly includes an arcuate plate having a concave inner edge and a convex outer edge extending radially from the inner edge to form a thrust surface, at least two holes in the plate positioned asymmetrically with reference to a central axis of the arcuate plate, a plurality of parallel grooves formed on one face of the arcuate plate. For example, in an embodiment, positions of the holes and parallel grooves are selected/configured, e.g., relative to one another and/or to first and second planar surfaces of the arcuate plate, to establish a particular pattern that distinguishes the first surface of the plate from the second surface of the plate.

In one example, a thrust bearing assembly may include a main bearing and a thrust bearing. The thrust bearing assembly may be positioned at an interface of a crankshaft housing and a flywheel. The main bearing may include two semicircular half bearings coupled to each other and to the crankshaft housing via tabs housed in flange walls of the main bearing. A first tab housed in the upper half bearing may align with a second tab housed in the lower half bearing to ensure effective coupling of the two halves. The thrust bearing may be mounted on a surface of the lower half of the main bearing. The thrust bearing may include asymmetric holes to couple the bearing assembly to a flywheel housing via a poka-yoke feature.

In this manner, the use of asymmetric dowel holes on the thrust bearing assembly better ensures that that a thrust bearing is mounted with the correct surface facing the crankshaft. In particular, it may be ensured that the bearing can only be mounted in one direction. Further, the off-centered holes may be positioned on the bearing surface such that an incorrectly assembled thrust bearing is clearly visible to a technician, allowing for any mounting error to be rapidly identified and addressed. By relying on a simple poka-yoke feature, the thrust bearing assembly may be made easy to manufacture without relying on additional production and tooling costs.

DETAILED DESCRIPTION

FIG. 1is a block diagram of an example vehicle system100. In the depicted example, the vehicle system is a locomotive configured to run on a track. Vehicle system100includes an internal combustion engine10. Engine10includes one or more combustion chambers wherein air and fuel is burned to generate torque that enables vehicle propulsion. As depicted herein, in one example, the locomotive is a diesel electric vehicle operating a diesel engine10located within a main engine housing102. However, in alternate embodiments of vehicle system100, alternate engine configurations may be employed, such as a gasoline engine or a bio diesel or natural gas engine, for example.

Torque generated by fuel combustion in engine10is transferred to crankshaft110positioned in crankshaft housing108(also referred to herein as the crankshaft block). In particular, the crankshaft housing108is coupled to the engine at a front end104of the housing. The crankshaft110may extend out of the housing108at a rear end106of the housing. The protruding crankshaft at the rear end106of the housing is covered via flywheel covering112. In the depicted example, flywheel covering112is hollow and included recesses for receiving the protruding end of the crankshaft, as well as for housing a flywheel114. A (single) thrust bearing assembly116is provided at the interface of the crankshaft housing108and the flywheel covering112. Specifically, the thrust bearing assembly116is provided at the rearmost end of the crankshaft housing. This allows the crankshaft110to be journaled into the crankshaft housing108and further into an engine block. The thrust bearing assembly116is made up of at least a main bearing and a thrust bearing, as described with reference toFIGS. 4-5. In addition to the thrust bearing assembly116, one or more additional radial bearings118may be positioned along crankshaft housing108to journal the crankshaft110. For example, additional radial bearings118may be positioned equidistantly along the length of the crankshaft housing. In one example, each of the radial bearings118may include an upper half bearing and a lower half bearing.

During operation of engine10, loads on the crankshaft tend to force the crankshaft in axially opposite directions. The axial thrust may be significantly high during selected engine operating conditions, such as during periods of rapid acceleration and deceleration. Large axial thrusts can also be generated by the action of a torque converter in an engine transmission. This causes thrust loads to be imparted on the bearings. The thrust bearing is required to absorb such thrust forces to reduce engine damage and vibrations. Since the thrust bearing absorbs all the thrust force (relative to other radial bearings), the unit area pressure on the thrust bearing surface is high. By including a thrust bearing assembly at the end of the crankshaft furthest from the engine, the thrust force applied on the crankshaft can be better absorbed while enabling the crankshaft to remain seated and journaled on the crankshaft housing. In addition, sufficient oil film support can be provided at the bearing to maintain a desired separation between the crankshaft and the thrust bearing. A view of the crankshaft along axis A-A′ (y-axis of the Cartesian coordinate system130), when observed from the rearmost end of crankshaft housing, is described atFIG. 2.

FIG. 2shows a perspective view200of a crankshaft journaled in an engine block. The depicted view200shows the rear end of the engine housing with the crankshaft journaled on a thrust bearing assembly in an engine housing. In the view shown inFIG. 2, the crankshaft housing has been separated from the flywheel housing. Components previously introduced inFIG. 1are numbered similarly and not reintroduced for brevity.

Perspective view200shows a face of the rear end106of crankshaft housing108with crankshaft110protruding out of it. While not shown, it will be appreciated that at the front end of the engine housing, the crankshaft is coupled to the engine and is configured to receive and transfer engine torque. View200also shows a face of the flywheel housing112with a recess220for receiving the crankshaft110. Once mated, the flywheel housing covers the crankshaft end and the entire length of the crankshaft is contained and substantially no part of the crankshaft is exposed.

The crankshaft110protrudes out from the face of the crankshaft housing to mate into a recess220sized to receive the crankshaft. One or more threaded holes218may be provided along a periphery of the crankshaft housing108and flywheel housing112for coupling the two blocks. In particular, the threaded holes218may be positioned and sized such that when the crankshaft housing108is juxtaposed on the flywheel housing112with the crankshaft110inserted into recess220, the threaded holes218on the crankshaft housing108line up with corresponding holes (that is, corresponding in size and position) on the flywheel housing112and the two can be mechanically bolted to each other via nuts, bolts, screws, or other fastening devices, and the crankshaft is securely mounted within a cavity defined by a combination of the crankshaft housing and the flywheel housing.

The crankshaft is journaled into crankshaft housing108through the use of one or more radial engine bearing assemblies positioned along a length of the crankshaft (seeFIG. 1) and a single thrust bearing assembly116at the rear-most end106of the crankshaft housing. The thrust bearing assembly116includes a thrust bearing216positioned external to a main bearing214. In order to maintain the axial load, the thrust bearing has to be mounted with a specified first surface facing the main bearing, and an opposite second surface facing the flywheel housing. This second surface is the surface of the thrust bearing that is visible upon mounting in the depicted view200. A bearing222, provided on the flywheel housing112, lines up against the second surface of the thrust bearing216when the flywheel housing is connected to the crankshaft housing, with the crankshaft110inserted into recess220.

To ensure that the thrust bearing216is correctly mounted, as elaborated with reference toFIG. 4, the thrust bearing may be configured with a plurality of grooves and holes that, taken together, generate a particular pattern that distinguishes the first surface of the thrust bearing from the second surface. In the depicted view, holes212are visible. The holes and grooves on the thrust bearing are arranged such that when the thrust bearing is mounted correctly, an asymmetric arrangement of the holes is clearly visible to a service technician.

The asymmetric arrangement of the holes may be such that holes212in the thrust bearing216can mate with a corresponding poka-yoke feature224, also asymmetrically arranged, on bearing222of the flywheel housing112. As a result of the correct mounting, the poka-yoke features224may align and couple with holes212, as depicted inFIG. 3.

FIG. 4shows a front view400of the thrust bearing assembly116when viewed from one end of the crankcase casing, in the direction of the crankshaft casing108. In the view shown inFIG. 4, the crankshaft housing has been separated from the flywheel housing and the crankshaft has been removed. Components previously introduced inFIGS. 1 and 2are numbered similarly and not reintroduced for brevity. Upon assembly of the crankshaft casing108with the flywheel housing, the threaded holes218on the crankshaft housing108may align with corresponding holes (that is, corresponding in size and position) on the flywheel housing and the two sets of holes may be mechanically bolted to each other via nuts, bolts, screws, or other fastening devices. Axis Y-Y′ denotes the central longitudinal axis of the thrust bearing assembly116while axis X-X′ denotes the central lateral axis of the thrust bearing assembly116.

Cavity408in the center of the crankshaft casing108denotes the region through which the crankshaft passes. The thrust bearing assembly116includes a main radial bearing214encircling the cavity408. In the presence of the crankshaft (within cavity408), the main bearing214radially supports the crankshaft. The main bearing214may comprise a first semicircular half bearing403and a second semicircular half bearing405. Each of the first semicircular half bearing403and a second semicircular half bearing405are arcuate including a concave inner surface and a convex outer surface. The radius of the first semicircular half bearing403(distance from the center of the cavity408to the concave edge of the semicircular half bearing403) may be equal to the radius of the second semicircular half bearing405(distance from the center of the cavity408to the concave edge of the semicircular half bearing405). As elaborated in relation toFIG. 5, in each of the first semicircular half bearing403and the second semicircular half bearing405, the concave inner surface may include one or more tabs to mutually couple the two half bearings and also to couple the main bearing to the crankshaft casing108. By locking the main bearing214to the crankshaft housing108, rotation of the main bearing214may be averted.

The thrust bearing assembly116may include a thrust bearing216positioned external to the second semicircular half bearing405of the main bearing214. The thrust bearing may be a semi-circular arcuate plate comprising two surfaces, a first surface facing the main bearing214and a second surface facing the flywheel (not shown here). The thrust bearing216may be positioned on the surface of the second semicircular half bearing405facing the flywheel. The thrust bearing216may include a concave inner edge, a convex outer edge, and two straight side edges. In one example, the arc length of the convex outer edge may be equal to that of the convex outer edge of the second semicircular half bearing405and the thrust bearing216may extend from a first interface where the second semicircular half bearing405meets the first semicircular half bearing403to a second interface where the second semicircular half bearing405meets the first semicircular half bearing403. In another example, the arc length of the convex outer edge may be shorter than that of the convex outer edge of the second semicircular half bearing405. The thrust bearing216may be of uniform thickness and may include one or more tabs along the lengths of the two straight edges. The tabs may facilitate in mounting the thrust bearing216on the second semicircular half bearing405of the main bearing214. In one example, thickness of the thrust bearing216may be 4.47 mm.

A plurality of oil groves412,414,416, and418may be etched on the second surface of the thrust bearing216. The oil groves412,414,416, and418may not extend to the first surface of the thrust bearing216. In this example, the oil groves are symmetrically distributed around the central longitudinal Y-Y′ axis with two groves412and414(first set of groves) on a first side of the thrust bearing216(on a first side of the Y-Y′ axis) and the remaining two groves416and418(second set of groves) on a second side of the thrust bearing (on a second side of the Y-Y′ axis), the second side of the thrust bearing opposite to the first side. In this example, the oil groves are parallel to each other. In alternate examples, the oil groves may be differently distributed and may be transverse to each other. In one example, the thickness and depth of each oil grove may be 10 mm and 1.45 mm respectively. The oil grooves412,414,416, and418channel a lubricant (not shown) for developing a protective hydrodynamic oil film across the face of the thrust bearing216during crankshaft operation, to reduce friction and wear.

A pair of holes212are formed on the thrust bearing to enable coupling of the thrust bearing assembly116to the flywheel via a poka-yoke feature. Relative to the central longitudinal Y-Y′ axis, the two holes212are positioned asymmetrically. A first of the at least two holes is positioned closer to the first set of parallel grooves (414and414) on the first side of the thrust bearing216, and wherein a second of the at least two holes is positioned further from the second set of parallel grooves (416and418) on a second, opposite side of the thrust bearing216.

By positioning the holes212in an asymmetric manner, during assembly, it may be ensured that the thrust bearing is mounted on the second surface of the main bearing. If the thrust bearing is incorrectly assembled, due to the presence of the asymmetric holes, a technician would be able to identify and rectify the error at the manufacturing site.

In this way, the arrangement of the two holes212relative to the central longitudinal Y-Y′ axis and relative to the plurality of grooves412,414,416, and418distinguishes the one face of the arcuate plate of the thrust bearing from another opposite face of the arcuate plate.

In this way, the components ofFIG. 4enable a thrust bearing assembly for a crankshaft, comprising: a main radial bearing including a pair of semicircular half bearings, each with a concave inner surface, a convex outer surface, and a pair of flange walls extending from the convex surface, the radial bearing configured to encircle a crankshaft in a crankshaft housing; and a thrust bearing including a semi-circular plate with a concave inner edge, a convex outer edge extending radially from the inner edge to form a thrust surface, a pair of asymmetrically positioned holes along the thrust surface, and parallel grooves on one face of the plate.

FIG. 5shows an exploded view500of the thrust bearing assembly116including a main bearing214. In this view, an inner shell of the main bearing has been projected outside of the thrust bearing assembly for better understanding of the interlocking mechanism of the main bearing214and the crankshaft casing108. Components already introduced in previous figures are numbered similarly and not reintroduced for brevity.

The main bearing214may comprise a first semicircular half bearing403and a second semicircular half bearing405. Each of the first semicircular half bearing403and the second semicircular half bearing405are arcuate including a concave inner surface and a convex outer surface. A first flange wall503(also refereed herein as first flange) may radially extend from the edge of the convex surface508of the first semicircular half bearing403while a second flange wall505(also refereed herein as second flange) may radially extend from the edge of the convex surface510of the second semicircular half bearing405. Each of the flange walls503and505may be arcuate bearing shells with a concave inner surface and a convex outer surface. In this exploded view, the flange walls503and505are shown to be protruding out of the thrust bearing assembly116, however, upon assembly, the flange walls503and505extend radially inwards (away from the face of the main bearing in contact with the flywheel housing) and encircle the crankshaft positioned within the cavity408. The flange walls503and505may include one or more openings507to improve alignment of the flanges with the crankshaft casing108. The width and thickness of the flange wall503may be equal o that of the flange wall505. In one example, the width of the flange walls503and505may be 53 mm.

As previously described in relation toFIG. 4, a thrust bearing216may be mounted external to the second semicircular half bearing405of the main bearing214. The thrust bearing216may include a plurality of holes212to facilitate mating with a poka-yoke feature on the flywheel. Further, the surface on the thrust bearing216that is not in contact with the main bearing214may include a plurality of grooves412and414to channel lubricant across the face of the thrust bearing216during crankshaft operation.

The flange walls503and505may include alignments tabs (also referred herein as tabs) such that the first semicircular half bearing403and a second semicircular half bearing405may be mutually coupled, and the main bearing214may be coupled to the crankshaft casing108. A first alignment tab512may be positioned on the flange wall503while a second alignment tab514may be positioned on the flange wall505. Each of the two alignment tabs512and514may be positioned at an interface of the first flange wall503and the second flange wall505such that upon aligning the first semicircular half bearing403and the second semicircular half bearing405, the first alignment tab512and the second alignment tab514abuts one another. Said another way, upon juxtaposition of the first semicircular half bearing403and the second semicircular half bearing405, the first alignment tab512may align with the second alignment tab514. If during assembly, the first semicircular half bearing is positioned in place of the second semicircular half bearing, the tabs will not align (not be adjacent), thereby making it obvious to a technician that the assembly has been erroneous (which can then be rectified). In this way, the tab positioning enables a unique assembly of the two semicircular half bearings.

The first alignment tab512includes a first triangular prism512awith a right angled surface and a first sloped surface512band the second alignment tab514includes a second triangular prism514awith a right angled surface and a second sloped surface514b. Upon aligning of the first semicircular half bearing403and the second semicircular half bearing405, the alignment tab from each half bearing may be juxtaposed next to each other such that the right angled surface of each half bearing abuts one another, and the sloped surface of each half bearing slopes away from one another. The tabs512and514also couple each of the first semicircular half bearing403and the second semicircular half bearing405to the crankshaft housing108. Once the first semicircular half bearing403and the second semicircular half bearing405are attached to each other and to the crankshaft housing108, the tab assembly155comprising tabs512and514may hold the main bearing414in position encircling the crankshaft.

In this way, the components ofFIG. 5enable a starter system, comprising: a thrust bearing assembly for a crankshaft, comprising: a radial bearing including a pair of semicircular half bearings, each with a concave inner surface, a convex outer surface, an alignment tab on the inner surface, and a pair of flange walls extending from the convex surface, the pair of half bearings configured to encircle an outer surface of the crankshaft, journaled within a crankcase, via aligning of the alignment tab, and a thrust bearing supporting a lower surface of the crankshaft, the thrust bearing including a semi-circular plate with a concave inner edge abutting the lower surface of the crankshaft, a convex outer edge extending radially from the inner edge to form a thrust surface, parallel grooves formed on the plate, and a pair of alignment holes positioned asymmetrically along the thrust surface relative to the parallel grooves.

FIG. 6Ashows a cross sectional view600of the bearing assembly601including a first example alignment tab arrangement. As seen inFIG. 6A, the bearing assembly may be visible through the thrust bearing and the main bearing in the direction of the main engine housing. In one example, the cross sectional view600may be a cross section of the crankshaft housing108(as seen inFIG. 1) along the X-Y plane.

One or more radial bearings118may be positioned along crankshaft housing108to journal the crankshaft passing through the cavity621. The radial bearings118may be positioned equidistantly along the length of the crankshaft housing. InFIG. 6A, two such radial bearings620and640are shown. The first radial bearing620may comprise an upper half bearing622and a lower half bearing624. The two half bearings622and624may be joined via tabs602and604. In the first example of alignment tab arrangement, a first tab602coupled to the upper half bearing622may be positioned at a first edge of the upper half bearing622, proximal to a left wall612of the upper half bearing622while a second tab604coupled to the lower half bearing624may be positioned at a second edge of the lower half bearing624proximal to a right wall614of the lower half bearing624. Upon coupling of the upper half bearing622with the lower half bearing624, the first edge of the upper half bearing622abuts the second edge of the lower half bearing624. Similarly, the second radial bearing640may comprise an upper half bearing642and a lower half bearing644. The two half bearings642and644may be joined via tabs606and606. In the first example of alignment tab arrangement, a first tab606coupled to the upper half bearing642may be positioned at a first edge of the upper half bearing642, proximal to a left wall616of the upper half bearing642while a second tab608coupled to the lower half bearing644may be positioned at a second edge of the lower half bearing644proximal to a right wall618of the lower half bearing644. Upon coupling of the upper half bearing642with the lower half bearing644, the first edge of the upper half bearing642abuts the second edge of the lower half bearing644.

However, during assembly of the radial bearings, if the lower half bearing is erroneously swapped with the upper half bearing, based on the alignment of the tabs (after the assembly), it would not be visible to the technician. Such inaccurate assembly may cause increased stress on the bearings, thereby causing degradation. In order to avert any possibilities of erroneous assembly, the tabs may be positioned differently on the flange walls.

FIG. 6Bshows a cross sectional view650of the bearing assembly601including a second example alignment tab arrangement. As an example, cross sectional view650may be the window630as seen inFIG. 6A. In this tab arrangement, a first tab652coupled to an upper half bearing642(of radial bearing640) may be positioned at a first edge of the upper half bearing622, proximal to a left wall615of the upper half bearing652. While, a second tab654coupled to a lower half bearing644(of radial bearing640) may be positioned at a second edge of the lower half bearing624, also proximal to the left wall615. Upon juxtaposition of the first semicircular half bearing642and the second semicircular half bearing644, the first tab652may align with the second tab654. If during assembly, the first semicircular half bearing is positioned in place of the second semicircular half bearing, the tabs will not align, thereby making it obvious to a technician that the assembly has been erroneous (which can then be rectified). In this way, by positioning the two tabs652and654proximal to the same wall616, manufacturing errors for a bearing assembly601may be reduced.

In this way, by using asymmetric holes in the thrust bearing, possibility of incorrectly attaching the thrust bearing to the main bearing may be reduced. Due to the orientation of the holes, an erroneously mounted thrust plate may be identified at the manufacturing facility and may be rectified. Also, by aligning the tabs on the two half bearings of a main bearing, the half bearings may be installed in a single arrangement, thereby reducing the possibility of manufacturing errors.

A thrust bearing comprises: an arcuate plate having a concave inner edge and a convex outer edge extending radially from the inner edge to form a thrust surface, at least two holes in the plate positioned asymmetrically with reference to a central axis of the arcuate plate, a plurality of parallel grooves formed on one face of the arcuate plate. In any preceding example, additionally or optionally, the plurality of parallel grooves are arranged symmetrically with reference to the central axis of the arcuate plate. In any or all of the preceding examples, the circuit further comprising, additionally or optionally, a first of the at least two holes is positioned closer to a first set of parallel grooves on a first side of the central axis, and wherein a second of the at least two holes is positioned further from a second set of parallel grooves on a second, opposite side of the central axis. In any or all of the preceding examples, additionally or optionally, an arrangement of the at least two holes relative to the central axis and relative to the plurality of grooves distinguishes the one face of the arcuate plate from another opposite face of the arcuate plate. In any or all of the preceding examples, additionally or optionally, the bearing is mounted on a rear end of a crankshaft at a location where the crankshaft is journaled within a crankcase housing. In any or all of the preceding examples, additionally or optionally, the thrust bearing, when mounted, abuts a main bearing coupled to the crankshaft. In any or all of the preceding examples, the circuit further comprising, additionally or optionally, when the thrust bearing is mounted, the first set of parallel grooves are not in contact with the main bearing. In any or all of the preceding examples, further comprising, additionally or optionally, a flange extending from the convex outer edge, in a radial direction, away from the one face of the arcuate plate, the flange abutting the main bearing. In any or all of the preceding examples, additionally or optionally, the bearing is mounted on a lower surface of the crankcase, and wherein the mounted thrust bearing abuts one half bearing of the main bearing. In any or all of the preceding examples, additionally or optionally, the at least two holes are configured to mate with an alignment feature arranged on a crankcase cover.

Another example thrust bearing assembly for a crankshaft, comprises: a main radial bearing including a pair of semicircular half bearings, each with a concave inner surface, a convex outer surface, and a pair of flange walls extending from the convex surface, the radial bearing configured to encircle a crankshaft in a crankshaft housing, and a thrust bearing including a semi-circular plate with a concave inner edge, a convex outer edge extending radially from the inner edge to form a thrust surface, a pair of asymmetrically positioned holes along the thrust surface, and parallel grooves on one face of the plate. In any preceding example, additionally or optionally, the thrust bearing is coupled to a lower surface of the crankshaft. In any or all of the preceding examples, additionally or optionally, the pair of asymmetrically positioned holes are positioned at different distances and different heights relative to a central axis of the bearing assembly, the central axis running along a length of the crankshaft. In any or all of the preceding examples, additionally or optionally, the parallel grooves are formed on one face of the arcuate plate, and are arranged at equal distance and equal heights relative to the central axis such that a first hole of the pair of asymmetrically positioned holes is closer to the parallel grooves along the thrust surface while a second hole of the pair is further from the parallel grooves along the thrust surface. In any or all of the preceding examples, additionally or optionally, an arrangement of the asymmetrically positioned holes relative to the parallel grooves distinguishes a front face of the thrust bearing from a back face of the bearing. In any or all of the preceding examples, additionally or optionally, each half bearing of the main bearing has an orientation tab on the concave inner surface, and wherein the main radial bearing is mounted on the crankshaft by aligning with the orientation tab of a first of the pair of half bearings with the orientation tab of a remaining of the pair.

In yet another example, a thrust bearing assembly for a crankshaft, comprises: a radial bearing including a pair of semicircular half bearings, each with a concave inner surface, a convex outer surface, an alignment tab on the inner surface, and a pair of flange walls extending from the convex surface, the pair of half bearings configured to encircle an outer surface of the crankshaft, journaled within a crankcase, via aligning of the alignment tab, and a thrust bearing supporting a lower surface of the crankshaft, the thrust bearing including a semi-circular plate with a concave inner edge abutting the lower surface of the crankshaft, a convex outer edge extending radially from the inner edge to form a thrust surface, parallel grooves formed on the plate, and a pair of alignment holes positioned asymmetrically along the thrust surface relative to the parallel grooves. In any preceding example, additionally or optionally, the asymmetrically positioned holes and the parallel grooves define a first face of the thrust bearing, a second face of the thrust bearing, opposite the first face, in face sharing contact with the flange wall of a lower of the pair of half bearings. In any or all of the preceding examples, additionally or optionally, the first face of the thrust bearing is configured to be in face-sharing contact with a crankcase cover having a bearing with a poka-yoke feature, the thrust bearing aligned so that a protrusion of the poka-yoke feature mates with the asymmetrically positioned alignment holes. In any or all of the preceding examples, additionally or optionally, the alignment tab is configured as a triangular prism with a right angled surface and a sloped surface, and wherein when the pair of half bearings are aligned, the alignment tab from each half bearing is juxtaposed next to each other such that the right angled surface of each half bearing abuts one another, and the sloped surface of each half bearing slopes away from one another.

This written description uses examples to disclose the invention, and to enable one of ordinary skill in the relevant art to practice embodiments of the invention, including making and using the devices or systems and performing the methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the relevant art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the language of the claims.