Arcuately offset pairs of juxtapositioned pin journals of an internal combustion engine crankshaft have their fillets pressure rolled for fatigue strengthening by opposing inclined rollers carried in cages at the lower ends of a pair of relatively rotatable tool housings supported in a side-by-side relationship by a pair of jaws of floating clamping structure. This structure allows the rollers to follow the crank pin journals as the crankshaft is being turned so that arcuately offset crank pin fillets can be simultaneously pressure worked and strengthened. Opposing roller reaction loads are cancelled at load receiving bearings operatively interposed between the pair of tool housings.
William P. Gottschalk, Hans T. Lauten
Original Assignee: Hegenscheidt Corporation
BACKGROUND OF THE INVENTION
This invention relates to deep rolling of fillets of engine crankshafts or other annular areas of metallic work pieces subject to operating high stress loads, and more particularly, to a new and improved machine, rolling tool and method to simultaneously deep roll the fillets of arcuately offset, juxtapositioned crank pin journals to increase their fatigue strength and surface layer hardness.
DESCRIPTION OF RELATED ART
In internal combustion engines such as V-6 engines found in many modern automobiles the left bank of cylinders of the engine block is set slightly forward of the right bank. This cylinder arrangement allows the connecting rods of paired pistons mounted in the cylinders in opposite banks of the engine to be connected side-by-side to adjacent or juxtapositioned journal portions of a common crank pin. To provide for even firing, in which the cylinders fire at 120 degree intervals, the centerline of each such journal portion radiating from the axis of rotation of the crankshaft are arcuately spaced from one another by an included angle of 30 degrees, for example. Other V-block engines with different cylinder arrangements, "V-10" for example, may have a different crank pin journal offset.
Because of crankshaft design and such crank pin journal offset, the crankshaft may be operationally stressed at the crank pin journal fillet areas to such an extent that fillet cracking and crankshaft bending may occur during engine operation to materially decrease crankshaft service life. To improve durability, the crankshaft may be strengthened by increasing crank pin journal diameter and by heat-treating (quenched and tempered) the crankshaft to increase yield and fatigue strength. Fatigue strength and durability of crank pins and main bearing journals can importantly be increased by deep rolling compressive stresses into the metal of the annular fillets between the pin journals and adjacent counterweights or bearing collars.
Furthermore, with downsizing of automotive vehicles and their components for reducing weight and improving fuel efficiency, smaller engines and crankshafts are needed. To improve fatigue strength and durability of downsized crankshafts, deep rolling of fillets and other circular joint areas is increasingly important with fatigue strength improvements ranging from 20%-150%.
Before the present invention, such fillet rolling of arcuately offset journals of crank pins was difficult and time consuming particularly since the fillets of side-by-side and arcuately offset crank pin journals had to be independently rolled with high-load fillet rolling machines in a time consuming and tedious operation. The side loads resulting from independent rolling could cause the rolling tool to "self center" and move off of the fillet so that desired compressive fillet stresses and fatigue strength were reduced or not obtained.
Examples of equipment, tooling and procedures generally related to the present invention can be found in prior art patents such as U.S. Pat. Nos.: 5,138,859 issued Aug. 18, 1992 for "Method and Apparatus For Smooth Rolling and Deep Rolling Multi-Stroke Crankshafts"; 4,785,537 issued Dec. 4, 1984 for "Machine For the Machining of Crankshafts"; and 4,766,753 issued Aug. 30, 1988 for "Rolling Apparatus For Surface Hardening or Smoothing" all assigned to Wilheim Hegenscheidt GmbH, Bernhard-Schondorfp Platz, D-5140 Erkenlenz, Germany and hereby incorporated by reference.
In contrast to the above identified prior art patent disclosures, the present invention is drawn to new and improved fillet rolling methods, tooling and machinery for the tooling that provides for the new and improved simultaneous deep rolling and fatigue strengthening of the fillets of contiguous arcuately offset crank pin journals and other annuluses.
The upper tooling of this invention comprises side-by-side main housings in which back up rollers are mounted. Secured to the lower or work end of each housing is a cage which carries an angulated or inclined work roller that has rolling contact with a peripheral surface of the back up roller so that loads applied to the housings will be transmitted by the back up roller to the inclined metal working roller and then to the grain structure of metallic fillets of crankshaft pins being deep rolled for fatigue strengthening.
The crankshaft whose pin fillets are being rolled is mounted in a chuck or other work piece holder and driven about its rotational axis by a motor drivingly connected to the chuck so that the work rollers pressure roll the annular fillets of the crank pins.
A caged annular thrust bearing unit operatively mounted between the tool housings maintains their orientation in parallel planes while they are being relatively rotated and turned about the axis of an engine crankshaft. This thrust bearing unit importantly provides structure to accommodate and neutralize the opposing resulting lateral thrust loads generated by the opposing and outwardly inclined rollers during deep rolling operation. With opposing lateral thrust loads being cancelled, the tooling remains on center even though the journal portions of each pin are arcuately offset from one another.
In addition to the upper tooling, a pair of lower support tools is provided, each having two back up rollers that support the pin journals as the work rollers of the upper tooling deep roll the fillets of the crank pins. These back up rollers are strategically located beneath the pin journals to receive rolling loads transmitted through the pin journals so that no appreciable bending loads will be applied to the crankshaft when being rolled.
The upper and lower pairs of tools are respectively supported in parts of upper and lower jaws of "floating" clamping structures, each comprising a pair of levers which are pivotally connected together by an intermediate pivot. Hydraulic power cylinders interconnecting end portions of the clamping levers are operable to generate the working force transmitted through the jaws for the fillet rollers by the powered expansion of the cylinders. To provide for the individual operation of each pair of jaws, the clamping structure is pivotally mounted for "floating operation" by supporting swing arms that swing back and forth or oscillate pendulum fashion during deep rolling operation.
In this invention a new and improved method of fillet rolling of a metallic component, such as a pin journal of a crankshaft, is provided in which arcuately offset annular fillets of side-by-side pin journal portions are simultaneously deep rolled to compressively stress the metal of the fillets and thereby increase the fatigue strength of the component.
It is another feature, object and advantage of this invention to provide a new and improved metal rolling machine comprising pairs of pivotally connected levers with metal working rollers in tooling mounted in clamping jaws of the levers which float around axis of an internal combustion engine crankshaft for simultaneously deep rolling of pairs of offset annular fillets of offset pins of the crankshaft.
Another feature, object and advantage of this invention is to provide new and improved tooling for rolling annular and arcuately offset work areas such as crankshaft pin journal fillets featuring side-by-side relatively rotatable housings each having a fillet rolling device mounted thereto so that laterally spaced and arcuately offset fillets can be simultaneously deep rolled and metal worked to improve their fatigue strengths.
These and other features objects and advantages of this invention will become more apparent from the following detailed description and drawings in which: