Lubrication strategy for dry run pump system

A method of operating a gerotor pump assembly for an automotive transmission of a motor vehicle in a loss-of-prime mode, the method comprising:

• rotating an inner drive gear in a first direction about an axis of rotation, the inner drive gear having a plurality of projections extending outwardly along an outer periphery thereof, an outer driven gear surrounding the inner drive gear and defining a plurality of recessions along an inner surface configured to engage with the plurality of projections of the inner drive gear, the outer driven gear and the inner drive gear further defining at least one dynamically-changing fluid cavity therebetween, each projection being configured to engage with a recession of the plurality of recessions in a fully engaged position, the inner drive gear and the outer driven gear defining an oil transfer volume clearance between a projection and a recession in the fully engaged position;
• maintaining oil within the oil transfer volume clearance as the inner drive gear is rotated in the first direction;
• lubricating a pump running face of the inner drive gear via a plurality of lubrication cavities defined within the pump running face, each lubrication cavity of the plurality of lubrication cavities extending within the pump running face from a central aperture of the inner drive gear, the central aperture extending along the axis of rotation;
• rotating the inner drive gear in a second direction about the axis of rotation, the second direction being opposite the first direction;
• maintaining oil within the oil transfer volume clearance as the inner drive gear is rotated in the second direction;
• adding oil into a forward outlet fluid reservoir when the inner drive gear is rotated in the first direction;
• adding oil into a forward inlet fluid reservoir when the inner drive gear is rotated in the second direction;
• lubricating a bearing surface disposed along an outer periphery of the outer driven gear via at least one of a first port in fluid communication with the forward inlet fluid reservoir and a second port in fluid communication with the forward outlet fluid reservoir;
• collecting oil within a shaft cavity defined between a seal, a cover, a ball bearing arrangement, and a shaft upon which the inner drive gear is mounted;
• and
• collecting oil within a hollow space defined between the shaft and a bushing cap attached to an end of the shaft.

A system for providing lubrication to a gerotor pump assembly, the system comprising:

• a shaft;
• an inner drive gear coupled to the shaft, the shaft and the inner drive gear being rotatable about an axis of rotation defined along a length of the shaft, the inner drive gear having a plurality of projections extending outwardly along an outer periphery thereof;
• an outer driven gear surrounding the inner drive gear and defining a plurality of recessions along an inner surface configured to engage with the plurality of projections of the inner drive gear, the outer driven gear and the inner drive gear further defining at least one dynamically-changing fluid cavity therebetween, each projection being configured to engage with a recession of the plurality of recessions in a fully engaged position, the inner drive gear and the outer driven gear defining an oil transfer volume clearance between a projection and a recession in the fully engaged position,
• wherein the inner drive gear is configured to be rotated in a first direction about the axis of rotation and a second direction about the axis of rotation, the first direction being opposite the second direction, the inner drive gear and the outer driven gear being configured to maintain oil within the oil transfer volume clearance as the inner drive gear is rotated in the first direction and in the second direction;
• and
• a housing structure defining a forward inlet fluid reservoir therein and a first port connecting the forward inlet fluid reservoir with the at least one dynamically-changing fluid cavity, the housing structure further defining a forward outlet fluid reservoir therein and a second port connecting the forward outlet fluid reservoir with the at least one dynamically-changing fluid cavity, at least a portion of the forward outlet fluid reservoir being located on an upper side of the second port, the first port being located on a lower side of the second port, the forward outlet fluid reservoir having an outlet opening defined on an upper side of the second port, the forward inlet fluid reservoir having an inlet opening defined on an upper side of the first port, the inlet opening being located on an upper side of the second port, the inner drive gear defining a pump running face along a side of the inner drive gear, the pump running face defining a plurality of lubrication cavities therein, the outer driven gear having a bearing surface along an outer periphery thereof, the system being configured to:
• lubricate the pump running face of the inner drive gear via the plurality of lubrication cavities;
• add oil into the forward outlet fluid reservoir when the inner drive gear is rotated in the first direction;
• add oil into the forward inlet fluid reservoir when the inner drive gear is rotated in the second direction;
• and
• lubricate the bearing surface via the first port and the second port,
• the housing structure comprising a main body portion and a cover attached to the main body portion, the system further comprising:
• a ball bearing arrangement having an inner race fixed to the shaft and an outer race fixed to the cover;
• a seal disposed between the shaft and the cover, a shaft cavity being defined between the shaft, the cover, the ball bearing arrangement, and the seal, the shaft cavity being configured to collect oil therein;
• and
• a bushing cap disposed over an end of the shaft, the gerotor pump assembly defining a hollow space between the bushing cap and the end of the shaft, the hollow space configured to collect oil therein.