The present invention relates to bearings for connecting rods. More specifically, the invention relates to a bearing capable of supporting radial and axial loads.
In reciprocating engines, a piston reciprocates within a cylinder. The piston is connected to a crankshaft by a connecting rod such that movement of the piston drives the crankshaft. A bearing is provided between the connecting rod and the crankshaft to absorb radial forces generated by the relative movement between the connecting rod and the crankshaft. The axial ends of the bearing contact a surface of the crankshaft. This contact (i.e., rubbing against each other) of the bearing and the crankshaft can cause the interface surface to wear poorly. Also, the friction generated between the connecting rod and the bearing and between the crankshaft and the bearing generates heat that can cause damage to the bearing or the components themselves. Misalignment of the components can result in the uneven distribution of forces and sometimes cause very large axial and radial forces to be exerted between the connecting rod and the crankshaft in a single location.
The prior art includes different attempts designed to decrease the amount of friction generated between the connecting rod and the crankshaft. One attempt includes lubricating the connecting rod. However, the lubricant eventually collects in an oil sump at the bottom of the engine block and must be replenished periodically. Some attempts have been made to increase the amount of lubricant that is retained in the bearing by forming lubrication scallops on the thrust surfaces of the bearing, increasing spray lubrication on rotating assemblies, and adding special coatings to the components. Although the methods described above aid in the reduction of friction and heat, these methods can fail to provide sufficient lubrication means for the bearing and undesirable amounts of friction and heat are still generated.
In one construction, the invention provides a bearing for a connecting rod. The bearing includes a retainer that defines a retainer axis. The retainer includes a plurality of pockets spaced about a circumference of the retainer, a first axial flange on a first end of the retainer, and a second axial flange on a second end of the retainer opposite the first end. The bearing also includes a plurality of radial rolling elements, each of the plurality of radial rolling elements retained in one of the plurality of pockets. The bearing further includes means for absorbing forces directed in an axial direction substantially parallel to the retainer axis. The means are positioned on the first axial flange and the second axial flange.
In another construction, the invention provides a bearing for a connecting rod. The bearing includes a retainer having a plurality of pockets spaced about a circumference of the retainer, a first end that defines a first flange, and a second end that defines a second flange opposite the first flange. The bearing also includes a plurality of radial bearing elements that support a radial load, and each of the plurality of radial bearing elements is positioned in one of the plurality of pockets. A first plurality of axial bearing elements is positioned on the first flange and receives at least a portion of an axial load, and a second plurality of axial bearing elements is positioned on the second flange and receives at least a portion of the axial load.
In yet another construction, the invention provides a connecting rod assembly that includes a connecting rod and a bearing. The connecting rod includes a first end and a second end. The first end is configured to be coupled to a piston, and the second end is configured to be coupled to a crankshaft. The connecting rod assembly also includes a bearing coupled with the second end. The bearing includes a retainer having a plurality of pockets spaced about a circumference of the retainer, a first retainer end that defines a first flange, and a second retainer end that defines a second flange opposite the first flange. The bearing also includes a plurality of radial bearing elements that receives a radial load. Each of the plurality of radial bearing elements is positioned in one of the plurality of pockets. A first plurality of axial bearing elements is positioned on the first flange and receives at least a portion of an axial load, and a second plurality of axial bearing elements is positioned on the second flange and receives at least a portion of the axial load.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
Referring generally to
As illustrated in
The bearing 14 includes a retainer 42 having a first axial flange 46, a second axial flange 50, and bridge members 52. The first axial flange 46, second axial flange 50, and bridge members 52 are formed together as one piece. The bridge members 52 extend between the first axial flange 46 and the second axial flange 50 to define a plurality of pockets 53 arranged circumferentially about the retainer 42. Each pocket 53 is defined between two adjacent bridge members 52, the first axial flange 46, and the second axial flange 50. Each of a plurality of radial rolling elements 54 is retained within a corresponding one of the pockets 53. The retainer 42 has a snap-fit retention feature such that the radial rolling elements 54 are pressed into the pockets 53 and are retained therein. The snap-fit retention feature does not inhibit the rotational movement of the radial rolling elements 54.
In the illustrated embodiment, the retainer 42 is formed as one piece. Thus the illustrated bearing 14 is used with an assembled crankshaft 12. The assembled crankshaft 12 includes a plurality of pieces that are assembled together to form the crankshaft 12. The assembled crankshaft includes a plurality of crank pins 13 (one is shown in
In other constructions, the retainer 42 can have a split cage design and be formed as two separate pieces. Alternatively, the retainer 42 can be formed as one piece and later split or cut along a planar surface such that two substantially equal, semi-cylindrical halves are formed. The split cage retainer can be used with either an assembled crankshaft or a solid crankshaft 12. The two pieces of the retainer are positioned around the crankshaft 12, and the connecting rod is mounted thereto to retain the two pieces of the retainer around the crankshaft 12. In addition, the two separate pieces of the retainer can be joined together after being positioned around the crankshaft 12. For example, if the retainer is formed of a polymer, then each half of the retainer can be formed separately with one or more locking tabs. Thus, the retainer can have a snap fit interface that includes a locking tab on one or both halves of the retainer.
A retainer axis 66 is defined through the center of the retainer 42, which generally coincides with the center of the second aperture 38 of the connecting rod 10. The retainer axis 66 is substantially parallel to the pivot axis 34. As the piston pump reciprocates and the crankshaft 12 is driven by the connecting rod 10, radial and axial forces are generated. Radial forces are defined as forces directed in a direction substantially perpendicular to the retainer axis 66. Thus, radial forces are directed in a radial direction with respect to the bearing 14. Axial forces are defined as forces directed in a direction substantially parallel to the retainer axis 66. Thus, axial forces are directed in an axial direction with respect to the bearing 14. The plurality of radial bearing elements 54 are configured and positioned to provide radial support. The bearing 14 also includes a means for absorbing axial loads. The means includes axial bearing elements on the retainer 42 configured and positioned to provide axial support. The axial bearing elements can include rolling elements, a low-friction material coupled to the bearing, planar surfaces of the bearing, or other suitable means.
The means for absorbing axial loads of the bearing 14 of
The first and second axial flanges 46 and 50 define inner thrust faces 70 and outer thrust faces 74. When the connecting rod 10 is mounted with the bearing 14, the outer surfaces of the connecting rod 10 are positioned adjacent the inner thrust faces 70 of the axial flanges 46 and 50. Similarly, when the connecting rod 10 and bearing 14 assembly are mounted on the crankshaft 12, the outer thrust faces 74 of the axial flanges 46 and 50 are positioned adjacent surfaces such as walls 16 (see
The lubrication grooves 62 allow oil, grease, or other lubricants to flow between the lubrication grooves 62 and into contact with the bearing 14, the connecting rod 10, and the crankshaft 12. The lubrication decreases the frictional forces generated between the inner thrust faces 70 and the connection rod 10 and between the outer thrust faces 74 and the crankshaft 12 by reducing or preventing metal-to-metal contact. The lubrication grooves 62 also aid in retention of lubricant and thus decrease the amount of lubrication necessary and decrease the frequency with which lubrication is reapplied to the bearing 14.
The radial rolling elements 54 are evenly spaced around the circumference of the retainer 42 and are retained in the pockets 53. Each radial rolling element 54 is substantially cylindrical with a radial rolling element axis 78 (
The bearing 14 also includes means for absorbing axial forces exerted on the connecting rod 10. The first and second axial flanges 46 and 50 extend radially outwardly from the retainer 42. The first axial flange 46 is positioned at a first end of the retainer 42, and the second axial flange 50 is positioned at an opposite second end of the retainer 42. The first and second axial flanges 46 and 50 are integrally formed as one piece with the retainer 42. The first and second axial flanges 46 and 50 include the plurality of axial rolling elements 58, which are positioned near an outboard edge 80 of the flanges 46 and 50. The axial rolling elements 58 allow the bearing 14 to dissipate axial loads, even while under radial loading. Each of the axial rolling elements 58 are positioned in one of a plurality of pockets 55 formed in the first and second axial flanges 46 and 50. The retainer 42 has a snap-fit retention feature such that the axial rolling elements 58 are pressed into the pockets 55 and are retained therein. The snap-fit retention feature does not inhibit the rotational movement of the axial rolling elements 58. The axial rolling elements 58 extend through the first and second axial flanges 46 and 50 and roll against the surfaces of the connecting rod 10 and the crankshaft 12 to reduce the amount of friction generated between the surfaces. Thus, the lubrication demand and the amount of heat generated are reduced.
With reference to
In the illustrated embodiment, thirty-six axial rolling elements 58 are evenly distributed around the circumference of the bearing 14, with eighteen axial rolling elements 58 evenly distributed around the circumference of each of the first and second axial flanges 46 and 50. The number of axial rolling elements 58 on the first axial flange 46 is equal to the number of axial rolling elements 58 on the second axial flange 50. Furthermore, each axial rolling element 58 on the first flange 46 is directly opposed by a corresponding axial rolling element 58 on the second axial flange 50 (best illustrated in
The presence of the radial rolling elements 54 and the axial rolling elements 58 allows the retainer 42 to be formed of a variety of different materials. As described above, the surfaces of the retainer 42 do not rub against the surfaces of the connecting rod 10 or the surfaces of the crankshaft 12. Thus, the retainer 42 may formed of a hard metal that might otherwise cause damage to the connecting rod 10 and the crankshaft 12. If desired, the retainer 42 may be formed of other materials, such as soft metals, plastics, engineering polymers, or a different suitable material. This allows the retainer 42 to be formed of materials chosen for specific properties such as high heat tolerance.
The axial rolling elements 58 aid in alignment between the connecting rod 10 and the crankshaft 12. For example,
Although the previous construction was described with respect to a reciprocating engine that includes a piston, connecting rod 10, and a crankshaft 12, the bearing 14 may be used in other suitable applications for absorbing radial and axial loads simultaneously. For example, bearing 14 may alternatively be used as a bearing for a connection rod journal, a main bearing journal of a crankshaft 12, or on a cam shaft.
Furthermore, the direct contact and rubbing together of the inner and outer thrust surfaces 270 and 274 with the surfaces of the connecting rod 10 and the surfaces of the crankshaft 12 during relative movement causes the softer material to be worn and removed over time. Thus, the retainer 242 is formed of a material that is softer than the material of the connecting rod 10 and softer than the material of the crankshaft 12. The retainer 242 acts as a sacrificial washer that dissipates thrust load and thus must be properly maintained during the lifetime of the engine. When the retainer 242 wears a specified amount, the bearing 214 is removed and replaced. The sacrificial surface reduces heat generation when composed of materials such as soft metals (e.g., bronze, tin, etc.).
In addition, the lifetime of the bearing 214 is extended with sufficient lubrication between the surfaces. As illustrated, lubricating grooves 262 extend in the radial direction away from the retainer axis 266. The lubricating grooves 262 are present on both the inner thrust surfaces 270 and the outer thrust surfaces 274 of the first and second axial flanges 246, 250. Adjacent lubricating grooves 262 define planar bearing surfaces 263 therebetween, and the plurality of planar bearing surfaces 263 define the inner and outer thrust surfaces 270, 274 of the first and second axial flanges 246, 250. The lubricating grooves 262 may be used alone or in combination with other methods for providing a sufficient supply of lubricant to the bearing 214. The lubricating grooves 262 allow the formation of a flat connecting rod 10 and crank because other lubricating features (e.g., scallops or channels formed on one or both of the connecting rod 10 and the crankshaft 12) are not required.
Similar to the bearing 14 of
As illustrated, the low-friction material is in the form of material inserts 358. As used herein, the term insert defines a piece of material that is at least partially inserted into an aperture. Apertures 359 in the first and second axial flanges 346 and 350 are through apertures 359 that each contain one material insert 358. The material inserts 358 are thicker than the first and second axial flanges 346, 350 such that they extend through the apertures 359 and protrude from both the inner and outer thrust faces 370, 374. In other constructions, the apertures may be cavities or holes formed in one or both of the inner and outer thrust faces 370, 374 that do not extend through the first and second axial flanges 346, 350. The material inserts 358 may be retained in the cavities on one or both of the inner and outer thrust faces 370, 374 using an adhesive. In yet other constructions, the first and second axial flanges 346 and 350 may not contain apertures. Rather, low-friction material may be attached directly to the inner and outer thrust faces 370, 374 using an adhesive. If the retainer is formed of plastic, the material inserts 358 may be molded in the retainer 342. The low-friction material may take other forms. For example, a ring of low-friction material may be coupled to one or both of the inner and outer thrust faces 370, 374 of the first and second axial flanges 346,350. The ring of low-friction material may be a thin strip of material that does not substantially cover the thrust faces, or the ring of low-friction material may be shaped and sized to substantially cover the thrust faces.
The low-friction material (e.g., material inserts 358) can be metallic or plastic. Examples of suitable metallic materials include bronze, tin, and other soft metals, and an example of a suitable plastic or polymer is polytrimellitamide-imide, commonly known as PAI. The material can also be a lubricious material. Thus, the material wears better and has better friction reduction than the material used to form the retainer 342. This reduces the amount of friction and heat generated due to sliding contact between adjoining surfaces (e.g., between the material inserts 358 and the surfaces of the connecting rod 10, and between the material inserts 358 and the surfaces of the crankshaft 12). The material acts as a sacrificial wear surface because it is meant to wear out and be ground down slowly as the material slides against the surfaces of the connecting rod 10 and the crankshaft 12. The sacrificial surface erosion, or lubricity, lowers friction and interface temperatures.
In the illustrated embodiment, the material inserts 358 are arcuate pieces of material that generally follow the curvature of the first and second axial flanges 346 and 350. Each material insert 358 extends across at least one lubrication groove 362. A pitch circle is defined by the plurality of radial bearing element axes 378, similar to the pitch circle 83 of
Thus, the invention provides, among other things, a bearing for a connecting rod that carries radial and axial forces simultaneously. Various features and advantages of the invention are set forth in the following claims.
This application claims priority to U.S. Provisional Application No. 61/226,009, filed Jul. 16, 2009, the entire disclosure of which is incorporated by reference herein.
Number | Date | Country | |
---|---|---|---|
61226009 | Jul 2009 | US |