WO2001019549A1

WO2001019549A1 - Bond bearing and method of making

Info

Publication number: WO2001019549A1
Application number: PCT/US2000/024940
Authority: WO
Inventors: Rosario Quatrochi
Original assignee: Federal-Mogul Corporation
Priority date: 1999-09-13
Filing date: 2000-09-12
Publication date: 2001-03-22

Abstract

A connecting rod (12) is fitted with metallic sliding bearings (22, 26) which are bonded to the connecting rod (12). The bond is achieved without the application of heat to either the connecting rod (12) or the bearings (22, 26) by adhesive bonding or magnetic pulse welding. The same technique can be employed for bonding sliding bearings to other support structures, such as bonding journal bearing to an engine block.

Description

Bond Bearing and Method of Making BACKGROUND OF THE INVENTION 1. Technical Field

This invention relates generally to connecting rods for piston assemblies, and more particularly to the bearings and bushes used to journal the crank shaft and wrist pin within the large and small end openings of such connecting rods. This disclosure incorporates the connecting rods for piston assemblies disclosed in provisional application 60/153,498, filed September 13, 1999, whose priority is claimed for this application. 2. Related Prior Art

Connecting rods of piston assemblies are typically formed with a small end into which a bushing is press-fitted. The opposite large end of the connecting rod is typically split to define a removable bearing cap which is typically bolted to the companion part of the connecting rod to define an opening in the large end of the connecting rod. Normally, this split large end of the connecting rod is fitted with a corresponding set of split bearings which typically comprise a relatively soft bearing metal applied to a semi-circular steel backing layer. The backings of the bearings are seated in the opening of the split large end, and are clamped under high pressure of the bolts which join the bearing cap to the complimenting part of the large end.

U.S. RE 21,495 discloses a method of bonding a bearing layer in the large end opening of a connecting rod by heating the bearing to a high temperature by means of an electric current. It will be appreciated that heating bearing material to an elevated temperature could have a detrimental effect on its bearing properties and performance for the intended purpose. U.S. 1,768,529 discloses a method for bonding a bearing within the large end opening of a connecting rod using an intermediate coating material such as tin. U.S. 1,834,746 similarly employs tin to unite the bearing to the connecting rod. Both involve heating the bearing and connecting rod to achieve bonding which adds costing complexity to the manufacturing process and may be detrimental to the properties of the bearing.

SUMMARY OF THE INVENTION AND ADVANTAGES

A method of bonding bearings to a support structure according to the invention overcomes or greatly minimizes the foregoing limitations of the prior art methods.

According to the invention, a method of joining a metal sliding bearing to a metal support structure includes fabricating the bearing separately from the support structure with the bearing and support structure having mutual surfaces to be joined. The surface of the bearing is positioned adjacent the surface of the support structure and the surfaces are bonded together to fix the bearing in position on the support structure substantially without heating the bearing and

support structure.

According to a further aspect of the invention, the heatless joining is

achieved by adhesively bonding the bearing to the support structure.

According to a further aspect of the invention, the heatless joining is achieved by magnetic pulse welding the bearing to the support structure.

The invention further contemplates a connecting rod and bearing assembly wherein the sliding bearing or bearings in the bearing seats of the connecting rod are joined by such a heatless bond. THE DRAWINGS

Figure 1 is an exploded perspective view of a piston assembly constructed according to the invention;

Figure 2 is a front elevation view of a connecting rod constructed according to the invention;

Figure 3 is an enlarged fragmentary cross-sectional view schematically showing one embodiment of the bond between the sliding bearing and support structure;

Figure 4 is a view like Figure 3 but of an alternative bonding embodiment;

Figure 5 is a schematic cross-sectional view taken along lines 5-5 of Figure 4;

Figure 6 is a view like Figure 3 but of an alternative bonding embodiment of the invention;

Figure 7 is a view like Figure 3 but has still a further embodiment of the invention; and

Figure 8 is a fragmentary cross-sectional view showing another application of the invention to an engine block.

DETAILED DESCRIPTION Figures 1 and 2 of the drawings illustrate a piston assembly 10 generally indicated by reference numeral 10 of the type for use in internal combustion engine applications and the like, including a connecting rod 12 having a small end 14 for mounting a piston 15 and a large end 16 for journalled connection to a crankshaft (not shown). The ends 14,16 are joined by a longitudinally exteding arm or shank 18 of the rod 12. The small end 14 is formed with a bore or eye 20 in which a bearing bush 22 is disposed for journalling a wrist pin 23 used to couple the piston 15 removably to the connecting rod.

The large end 16 includes a relatively larger opening or eye 24 for receiving a split bearing 26. The large end 16 is split along transverse parting plane P to define a separable lower bearing cap portion 28. The splitting of the bearing cap 28 from the rod 12 is preferably carried out by known fracture separation techniques, to provide irregular surfaces 30 at the ends of the legs of the bearing cap portion 28 that mate with uniquely cooperating mating surfaces of the connecting rod 12 according to known principles for restricting lateral movement of the bearing cap 28 in service.

Still referring to Figures 1 and 2, the large end 16 incorporates bolt bosses 38 on either side of the opening 24 which are tapped to receive suitable fastening bolts 42 for securing the bearing cap 28 to the upper half of the connecting rod 12. According to the invention, the split bearing 26 is bonded integrally within the opening 24 of the large end 16, such that a lower half 44 of the split bearing 26 is bonded permanently to the bearing cap 28, and an upper half 46 of the splint bearing 26 is united permanently to the remainder of the connecting rod 12 via a permanent bond interface, designated generally by the reference numeral 48 in Figure 2. The bearing bush 22 may likewise be permanently united within the eye 20 of the small end 14 of the connecting rod 12 via a permanent bond interface indicated generally at 50 in Figure 2 in the same manner to be described below with respect to the bonding of the split bearing 26.

The split bearing 26 of the invention preferably comprises at least a functional layer of bearing material of either aluminum or copper-based bearing alloys of the type typically used in crankshaft engine bearing applications. As will become apparent from the exemplary embodiments of the invention below, the invention contemplates bonding such bearing layers to the connecting rod 12 with or without inclusion of the usual steel backing that is common with such bearings. Exemplary aluminum-based bearing alloys include those available commercially from Federal-Mogul Corporation, Southfield, Michigan sold under the product designations A-500, A-400, TR-20, G-74, G-174, TR-153, G-272, A-100 and A- 250. Exemplary copper-based bearing alloys available from the same manufacturer include product designations H-24, H-116, H-14 and G-41. Turning now to the bonding of the bearing 26 to the connecting rod

12, two general approaches are contemplated. First, a process wherein the aluminum or copper-based bearing 26 is united to the connecting rod 12 across a weld surface 52, as illustrated in Figure 3, and secondly where the bearing 26 is united to the connection rod 12 by an adhesive interface 54, as illustrated in Figures 4 and 5.

Considering first the weld interface 52, a principal consideration to be taken into account when selecting the welding process is to unite the split bearing 26 to the connecting rod 12 in a way that does not impair the desirable bearing properties of the bearing 26 or the integrity of the surrounding connecting rod 12. Of particular challenge is the welding of an aluminum-based bearing 26 to a ferrous-based connecting rod 12. The dissimilar materials have different coefficients of expansion, and heating aluminum to high temperature produces undesirable aluminum oxide which impairs the ability of the aluminum to bond metallurgically to a mating component, including ferrous components. Also of concern is the formation of intermetallics which can occur if the aluminum is heated to a molten state and allowed to alloy with the iron. Such intermetallics are inherently brittle and detrimental to the achievement of a load-bearing bond between the bearing 26 and connecting rod 12.

Still another problem to be addressed when considering heating the bearing 26 to achieve metallurgical bonding between the bearing 26 and connecting rod 12 is that such heat may undesirably anneal or soften the bearing 26, changing its properties to the detriment of the desirable bearing properties of the lining 26.

The invention contemplates use of low temperature welding techniques that achieve metal-to-metal bonding between the bearing 26 and connecting rod 12 across the weld interface 52 while minimizing or eliminating the foregoing concerns with high temperature welding processes. A presently preferred low temperature welding technique that may be used to weld the bearing 26 to the connecting rod 12 is magnetic pulse welding. In magnetic pulse welding, no heat is applied to the bearing 26 or connecting rod 12 that would cause localized melting and fusion at the interface, as in the heat-induced welding techniques discussed above. Rather, the bearing 26 is installed in the opening 24 and the

assembled bearing 26 and connecting rod 12 are placed within a field of a

discharge coil in which current is discharged. The discharging current creates an eddy current in the bearing 26 and connecting rod 12, setting up a magnetic field in the assembly which powerfully opposes the magnetic field of the discharging current with a force equal to the square of the discharge current. The resultant opposing fields effectively "hammer" the bearing liner 26 with high frequency, high application force pulses of energy, causing the bearing 26 to move away from the coil at tremendously high speed, pushing the bearing lining 26 well beyond its yield strength into the plastic region. As a result, the bearing 26 yields plastically at the interface and is forcibly driven in to the mating surfaces 56,58 of the upper half of the connecting rod 12, and the bearing cap 28, generating a solid-state weld at the interface between the bearing lining 26 and the connecting rod 12, without application of heat.

Since magnetic pulse welding is a cold process, the properties of the bearing liner 26 and connecting rod 12 are not undesirably altered from heating, as with other welding techniques involving the application of heat to achieve melting at the interface. In fact, the plastic deformation that occurs in the bearing lining 26 has the beneficial effect of work hardening the bearing liner 26, such that it has improved hardness and strength following welding as compared to that of the bearing liner 26 prior to welding. The resultant weld joint is as strong if not stronger than the material being welded. No filler material or intermediate bond material, such as tin, is needed at the interface to achieve bonding between the bearing liner 26 and the connecting rod 12, as with other heat-induced welding processes.

The invention contemplates other equivalent low temperature

welding processes that achieve the same or similar end results as that of the

magnetic pulse welding of uniting the dissimilar aluminum bearing liner 26 with

the ferrous connecting rod 12 without application of heat in order to preserve and preferably enhancing the strength and hardness of the bearing liner 26 through plastic deformation.

The same process may be carried out with bearing liners fabricated of copper-based alloys, as well as aluminum and copper-based liners 26 that are initially bonded to a steel backing 60, as illustrated in Figure 6. In the case of the 9

-8-

steel-backed liner illustrated in Figure 6, the welding occurs at the interface between the backing 60 and the connecting rod 12 according to the same principals described above with respect to the bearing liner 26 alone, with the welding occurring between two similar metals, namely the steel backing 60 and the ferrous- based connecting rod 12 which often is of a steel alloy.

Turning now to the alternative process of bonding the liner 26 to the connecting rod 12 via an adhesive bond, Figure 4 illustrates an enlarged fragmentary section of the large end 16, wherein the aluminum-based bearing liner 26 is permanently fixed to the ferrous-based connecting 12 via the adhesive interface 54. The adhesive interface 54 in this basic embodiment is one that can withstand bearing compressive loading of about 33,000 psi, shear loads tending to rotate the bearing liner 26 relative to the connection rod 12 of about 5,000 psi, and thermal cycling in the operating range of -46°C to 190°C. The adhesive interface 54 should also exhibit high impact resistance, should not excessively inhibit the conduction of heat from the bearing 26 to the connecting rod 12, should withstand an operating environment exposed to petroleum lubricants, their additives, water, sulfides and other contaminants, and should provide an operating life of at least ten

million cycles at 100 HZ. Contemplated adhesives include high strength/high temperature epoxies and phenolics with extra flexibilizers. Figure 5 illustrates a further variant in which the surfaces 56,58 preferably are formed to include alternating peaks 64 and valleys 66 across the surfaces (shown greatly exaggerated for purpose of illustration), with the adhesive 54 residing in the valley 66 and the liner 26 making metal-to-metal contact with the connecting rod 12 across the peaks 64. Such an arrangement enables the adhesive 54 to provide the necessary holding force to secure the liner 26 against rotation on the connecting rod 12 in service, while providing significant metal-to- metal contact at the interface of the liner 26 and the connecting rod 12 to promote good heat transfer. Such direct metal-to-metal contact at the interface of the liner 26 with the connecting rod 12 across the peaks 64 effectively isolates the adhesive 54 within the valleys 66 from bearing the full compressive loads. In turn, the adhesive 54 does not break down or degrade over time from exposure to excessive compressive loading, enabling it to retain its integrity despite the high compressive loading of the bearing liner 26 that takes place across the peaks 64, and the possibility of using adhesives with lower load bearing capacity than that called for by the Figure 1-4 embodiment is contemplated..

The alternating peaks and valleys 64,66 can be provided in a number of ways. The invention contemplates finishing the surfaces 56,58 of the opening 24 in a machine turning operation to impart a helical pattern (single or multiple lead) of the peaks and valley across the surface. The lead and depth of such peaks and valleys can be controlled according to known machining principals, including varying the feed rate and cutting depth of the tool.

Such peaks 64 and valleys 66 can alternatively be formed by generating cross-machining opposing helix patterns across the surface to provide a

generally knurled, criss-crossing surface profile, with the peaks 64 comprising pyramidal islands separated by criss-crossing channels or grooves constituting the valleys 66. It will be appreciated that other patterns and techniques, such as etching, can also be used to achieve the same end result of providing a series of valleys or pockets 66 in which the adhesive 54 is resides together with lands or peaks 64 that make metal-to-metal contact with the connecting rod 12. It will be appreciated also that less than full metal-to-metal contact could also be employed, with there being a thin layer of the adhesive extending across the peaks, but not so thick as to significantly impair the integrity of the adhesive or the beneficial heat transfer characteristics of the metal-to metal contact in operation.

The same adhesive bonding techniques could be used with copper- based liners described above, as well as aluminum or copper-based liners with a steel backing, as illustrated in Figure 7.

Several advantages are recognized by bonding the bearing liner 26 permanently to the connecting rod 12, rather than relying on the crush force of the bearing cap 28 to hold the liners 26 against rotation during operation. With a permanent bond, the high crush loads are not necessary, and thus the size and weight of the connecting rod can be reduced accordingly. Further, it is not necessary when bonding the bearing liner 26 according to either process described above to go through the multiple-stage finishing operations to prepare the surfaces

56,58 to receive the lining. In a normal crush bearing application, the surfaces 56,58 are finished in at least three passes, including rough bore, finish bore, and a final honed or microsized finish to ensure that proper crushing of the lining is achieved between the bearing cap and connecting rod. According to the present invention, the first stage rough bore would be adequate and the invention contemplates the bonding of the bearing liner 26 to the surfaces 56,58 in an as- formed condition, such as that which results from a powder metal forging operation. Eliminating the need for the usual multi-stage machining operation of the large end opening 24 saves considerable time and cost in the manufacture of connecting rods. According to a further advantage of the invention, the final finishing of the running surface 68 of the bearing lining 26 preferably takes place after the lining 26 has been bonded permanently to the connecting rod 12. Any variations due to manufacturing tolerance of the connecting rod or the bonding of the liner 26 to the connecting rod 12 can be compensated for in the finishing of the running surface 68 to assure that the running surface 68 is true to shape and location required to generally mating crankshaft. It is contemplated that excess lining material would be provided beyond that which is required to journal the crankshaft, which is subsequently removed and the final machining operation to properly size the running surface 68. In each of the above examples, the bearing liner 26 may be provided with a suitable overlay of tin, lead or other soft-based metals or alloys thereof in conventional manner to provide good initial running-in characteristics. The invention contemplates that excess overlay could be initially applied and subsequently machined during the final sizing operation. In both cases, the final sizing operation is greatly simplified at far less than traditional techniques.

In view of the above description, it will be further appreciated that the same principals can be applied to other applications where a sliding bearing is used to journal a relative rotatable member. In Figure 8, for example, the same linings as discussed above are bonded by the same techniques to the bearing seats of an engine block 70 and the mating bearing blocks 72, which may be ferrous or aluminum-based materials, wherein the bearing liners 28 serve as the main bearings journalling the crankshaft of an engine relative to the block. The disclosed embodiments are representative of presently preferred forms of the invention, but are intended to be illustrative rather than definitive thereof. The invention is defined in the claims.

Claims

What is claimed is:

1. A method of joining a metal sliding bearing to a metal support structure, comprising: fabricating the bearing separately from the support structure with the bearing and structure having mutual surfaces to be joined; positioning the surface of the bearing adjacent the surface of the support structure; and bonding the surfaces together to fix the bearing in position on the support structure substantially without heating the bearing and support structure.

2. The method of claim 1 wherein the surfaces are bonded together with an adhesive.

3. The method of claim 1 wherein the surfaces are bonded together by magnetic pulse welding.

4. The method of claim 1 wherein the bearing is fabricated from a bearing material selected from the group of bearing materials consisting of aluminum and bronze alloy bearing alloy materials.

5. The method of claim 4 wherein the bearing material is bonded directly to the support structure without a steel backing.

6. The method of claim 5 wherein the support structure is fabricated of an iron based material.

7. The method of claim 6 wherein the support structure comprises a connecting rod.

8. The method of claim 6 wherein the support structure comprises an engine block.

9. The method of claim 1 wherein the bearing is fabricated from a layer of bearing material bonded to a steel backing layer.

10. The method of claim 9 wherein the steel backing is bonded to the support structure.

11. The method of claim 10 wherein the support structure is fabricated of an iron based material.

12. The method of claim 11 wherein the support structure comprises a connecting rod.

13. The method of claim 11 wherein the support structure comprises an engine block

14. The method of claim 2 wherein at least one of the joining surfaces is formed with a series of peaks and valleys, and including providing the adhesive in the valleys and exposing tips of the metal peaks to provide and adhesive bond at the interface in the area of the valleys while providing metal-to-metal contact between the bearing and support structure across the peaks.

15. The method of claim 14 wherein the peaks and valleys are formed in the joining surface of the support structure.

16. The method of claim 2 including providing a variable thickness layer of the adhesive bonding material at the interface.

17. A connecting rod and bearing assembly comprising:

a connecting rod of iron-based metal having at least one bearing seat; a sliding bearing fabricated of at least a layer of bearing metal, said bearing having a backing surface to be bonded to said bearing seat; and a bond fixing said backing surface of said bearing to said bearing seat of said support structure substantially without the presence of a melted and resolidified metal bond at the interface of said backing surface and said bearing seat.

18. The assembly of claim 17 wherein said bearing is bonded adhesively to said support structure.

19. The assembly of claim 17 wherein said bearing is magnetic pulse welded to said support structure to provide a cold fusion bond between said bearing and support structure.

20. The assembly of claim 17 wherein said sliding bearing includes a steel backing layer.

21. The assembly of claim 18 wherein one of said backing surface and said bearing seat is formed with peaks and valleys and said adhesive is disposed in said valleys.