Rotary expansible chamber devices – Moving cylinder – Rotating
Reexamination Certificate
1999-03-19
2001-02-06
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Moving cylinder
Rotating
C403S359600, C464S089000
Reexamination Certificate
active
06183230
ABSTRACT:
TECHNICAL FIELD
The invention is directed to an engine oil pump and drive assembly.
BACKGROUND OF THE INVENTION
The gerotor pump has emerged as a preferred means of providing lubrication for internal combustion engines attributable to its efficiency and packaging benefits. The pump is placed on center with the crankshaft axis and is generally driven by a coarse splined hub mounted on the crankshaft. The crankshaft's coarse splined hub extends through a central opening in the pump's rotor to engage female splines of the pump rotor, transferring rotational energy therebetween. Adequate clearance within the spline drive is required because tight tolerances impede assembly.
As the gerotor oil pump has become more common place in the field, unsatisfactory noise levels have been observed. Root causing the source unveiled noise introduced as a result of longitudinal crankshaft flexure during high engine loading. This longitudinal bending imparts a radial impact between the top flat of the male spline and the receiving female spline surface. Torsional shaft deflections also occur, causing tangential impacts between the radial faces of mating male and female splines. In addition, large tolerances between the mating splines generate a rattling noise from torsional spline-to-spline impacts at lower engine speeds due to pump pressure pulsations and instantaneous engine speed fluctuations. Simply increasing the clearance between the splines eliminates crankshaft motion-induced noise but aggravates drive “rattle”. Resolving noise concerns will increase customer satisfaction with the engine package.
SUMMARY OF THE INVENTION
To resolve the discovered noise source concern, the present invention provides a pump drive system which can accommodate motion of the crankshaft, relative to the pump, without generating gear impact noise. An isolator is interposed between the pump rotor and the driving splined hub to minimize noise generation upon impact of the male splines with the female splines. All faces, arc and radial, of the splines are isolated to absorb radial impacts as well as tangential impacts. This isolator provides a forgiving system which accommodates crankshaft flexure and torsion without resulting noise. In addition, the system maintains the fail-safe feature inherent in a spline drive system because if the isolator should deteriorate, the splines will still engage to drive the pump.
REFERENCES:
patent: 2443688 (1948-06-01), McFarland
patent: 2872872 (1959-02-01), Quintilian
patent: 2887063 (1959-05-01), Aspelin
patent: 2956187 (1960-10-01), Wood
patent: 3650361 (1972-03-01), Fossum
patent: 4098096 (1978-07-01), Chard et al.
patent: 5314319 (1994-05-01), Nilsson et al.
patent: 5927149 (1999-07-01), Moody
Beardmore John Meade
Tucker Bruce Alan
General Motors Corporation
Hargitt Laura C.
Vrablik John J.
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