Abrading – Abrading process – Roll – roller – shaft – ball – or piston abrading
Patent
1997-11-14
2000-11-21
Eley, Timothy V.
Abrading
Abrading process
Roll, roller, shaft, ball, or piston abrading
451 62, 451251, 451399, B24B 100, B24B 500
Patent
active
061495034
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention concerns crankpin grinding machines and in particular apparatus and methods for supporting crankshafts in such machines for grinding of the crankpins around the crankshaft.
BACKGROUND TO THE INVENTION
In the grinding of crankpins, drive is transmitted to the crankshaft in conventional manner from the headstock and as the crankshaft rotates so a grinding wheel mounted on a wheelhead is advanced in registry with first one and then another of the crankpins so as to grind the crankpin. The wheelhead is advanced and retracted during rotation of the crankshaft so as to maintain grinding contact between the grinding wheel and the crankpin as the latter is rotated eccentrically around the axis of rotation of the crankshaft.
It has been proposed to use end journals to assist in mounting a crankshaft for grinding of crankpins.
Since the circularity of the crankpins will determine the wear characteristics of the crankshaft and the big end bearings associated therewith, it is highly desirable that whatever method of mounting is employed, it should maintain the highest possible accuracy as regards circularity of grinding surfaces of the crankpins. It has been found that whip, and distortion of the crankshaft during grinding may introduce errors in the circularity of the ground surfaces of the crankpins, resulting in accelerated wear and unreliability of crankshafts ground in this manner.
Conventionally when mounted in an engine block, a crankshaft is supported by journal bearings at opposite ends and at intervals along its length. Typically a journal bearing is provided intermediate each crankpin, so that every part of the crankshaft is supported in a journal bearing. Thus a four cylinder engine will typically have five journal bearings for the crankshaft and a six cylinder engine could have as many as seven crankshaft journal bearings.
It is an object of the present invention to provide an improved method and apparatus for mounting such crankshafts in a crankpin grinder to facilitate the grinding of crankpins thereon in a manner which will reduce the circularity errors characteristic of prior art methods, and apparatus for supporting crankshafts in such machines.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a method of supporting a workpiece having journal and eccentric regions, in a grinding machine for grinding the eccentric regions thereof, comprises the steps of: for rotating the workpiece about its main axis (ie the axis of the journal regions thereof); and headstock, a pair of members which cooperate to form at least part of a journal bearing, complementary to the said region, and supporting at least one of the said two members, thereby in turn providing support for the workpiece at the said position remote from the headstock.
The workpiece may be a crankshaft in which event the remote support may be provided by a plurality of said complementary journal bearings, each situated at, and each surrounding, a respective journal bearing region of the crankshaft.
Preferably a lower one of the two members of the or each complementary support bearing is movable into a position in which it is aligned with the crankshaft, and includes an upwardly open curved surface which is of complementary radius to, and in its aligned position cradles the underside of, a journal region of the crankshaft when the latter is fitted to the headstock.
Preferably the other (upper) member of the or each complementary support bearing comprises a closure which is movable between an open position to allow for insertion and removal of a crankshaft, and a closed position in which it bridges the upwardly open cradle so as to restrain movement of the crankshaft in an upward sense out of the cradle provided by the lower member.
The or each closure for bridging the cradle may comprise a finger which when urged towards the crankshaft provides a reaction surface to prevent the said upward movement of the crankshaft.
Alternatively the or each cradle closure may include a downwardly facing curv
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patent: 4003721 (1977-01-01), Price et al.
patent: 4023937 (1977-05-01), Smith
patent: 4269001 (1981-05-01), Bottomley
Eley Timothy V.
Unova UK Limited
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