Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-11-04
2001-07-31
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
C384S294000, C384S912000
Reexamination Certificate
active
06267508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to multilayer sliding bearings of the type having a metal backing, a liner of bearing metal and a relatively soft metallic overlay.
2. Related Prior Art
Multilayer sliding bearings are typically used in high-load engine applications for journaling the crankshaft, connecting rods, and the like and include a rigid metal backing of steel on which a lining of bearing metal of either copper-lead or aluminum alloy is applied, over which a running layer of a relatively softer metal is overplated usually in the form of a single layer of lead-tin-copper alloy having a thickness of about 25 &mgr;m. A nickel diffusion barrier or copper bonding layer is often interposed between the lining and overplate to prevent the tin of the overplate from diffusing into the bearing liner. As a final step, the bearing is typically coated with a micro-thin layer of tin or lead-tin flash plating, giving the bearing a bright, aesthetically pleasing appearance and providing a level of corrosion protection.
The flash plating present on the concave running surface of the bearing is quickly dissipated during the initial engine break-in period.
In service, such multilayer sliding bearings are subjected to high dynamic loading that varies in magnitude and direction due to the inertial loads applied by the piston and connecting rod mechanism and by the cylinder gas. The soft overplate layer enables the bearing surface to continually change and conform under high load forces to any misalignments or changes in profile or loading of the member being journaled, so that the loads are distributed across a greater surface area of the bearing. In addition to its conformability, the overplate also has the characteristic of embedibilty, which enables the overplate to embed any foreign hard particles of dirt and/or metal that may come between the bearing surface and the member being journaled to protect the bearing and member from excessive wear or damage.
It is generally accepted that conformability and embedibilty characteristics are dependent on overplate thickness, with a thicker overplate being preferred (i.e., on the order of 25 &mgr;m or more). It is also generally known that as the thickness of the overplate increases, so does the susceptibility of the overplate to fatigue in which the overplate surface fractures under load. Resistance to fatigue cracking requires that the bearing surface exhibit sufficient tensile strength to enable it to undergo minor configuration changes without cracking. Thus, it is necessary to balance the competing properties of conformability and embedibilty with fatigue resistance when designing an engine bearing, particularly one that is subjected to high dynamic loading.
For many high load engine applications, a 25 &mgr;m overplate of lead-tin-copper has been found to exhibit good conformability and embedibilty while possessing good fatigue resistance. However, as the output and efficiency of engines continually increases, so does the dynamic loads placed on the crank shaft and connecting rod bearings, increasing the potential for bearing fatigue. While greater fatigue resistance can be achieved by simply decreasing the thickness of the conventional single layer lead-tin-copper overplate to load the 25 &mgr;m thickness, it is at the cost of the conformability and embedibilty characteristics.
In addition to the demands on bearings due to increased loading, it is environmentally advantageous to reduce or eliminate when possible the use of heavy metals, and particularly lead in sliding bearings. U.S. Pat. No. 5,056,936 discloses a sliding bearing having a multilayer overplate construction that employs conventional lead-containing alloys, namely lead-tin-copper as one of the layer materials.
Thus, their exist they need in the industry for an improved multilayer sliding bearing that can operate under extreme high dynamic loading conditions while exhibiting good fatigue resistance as well as good conformability and embedibilty characteristics without the usage of lead-containing alloys in the overplate.
SUMMARY OF THE INVENTION
According to the invention, a multilayer sliding bearing is provided a comprising a base lining member having a rigid metal backing and a lining of bearing metal formed on the backing, and is characterized by a lead-free multilayer overplate comprising a plurality of alternating soft and hard micro-thin overplate layers of lead-free metal materials electroplated onto the base lining member.
The overplate preferably has an overall thickness in the range of about 10-20 &mgr;m, and the individual layers each have a thickness equal to at least half or less of the overall thickness of the overplate.
The multilayer overplate of the invention has the advantage of providing a composite overplate for a sliding bearing having good fatigue resistance as well as good conformability and embedibility characteristics using lead-free metal layers. By controlling the selection of material and the relative thicknesses of the multiple layers of the lead-free overplate, the invention enables a controlled hardness gradient to be developed in the overplate, which further enhances the above properties. According to a particular embodiment of the invention, the alternating soft and hard layers have varying relative thicknesses such that the overall macro hardness of the overplate is softer adjacent the top running surface of the overplate and is harder near the bottom of the overplate adjacent the bearing liner.
The use of lead-free materials further has the advantage of eliminating from the overplate the presence of heavy metals, and in particularly lead, which is beneficial from a manufacturing, use and reclamation stand point.
REFERENCES:
patent: 3077285 (1963-02-01), Budininkas
patent: 3215513 (1965-11-01), Schaefer
patent: 3522974 (1970-08-01), Polti
patent: 3623205 (1971-11-01), Scott
patent: 4474861 (1984-10-01), Ecer
patent: 4553856 (1985-11-01), Bierlein
patent: 4836695 (1989-06-01), Baureis
patent: 4889435 (1989-12-01), Gojon
patent: 4999257 (1991-03-01), Imai
patent: 5056936 (1991-10-01), Mahrus
patent: 5056937 (1991-10-01), Tanaka
patent: 5185216 (1993-02-01), Tanaka
patent: 5209578 (1993-05-01), Eastham
patent: 5434012 (1995-07-01), Tanaka
patent: 5489487 (1996-02-01), Tanaka
patent: 5601371 (1997-02-01), Koroschetz
patent: 5665480 (1997-09-01), Tanaka
Bank Brian L.
Toth James R.
Federal-Mogul World Wide Inc.
Footland Lenard A.
Reising Ethington Barnes Kisselle Learman & McCulloch PC
LandOfFree
Sliding bearing having multilayer lead-free overplate and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sliding bearing having multilayer lead-free overplate and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sliding bearing having multilayer lead-free overplate and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2515142