Hydraulic Gerotor pump for automatic transmission

A hydraulic system for an automatic transmission, the system comprising:

• a hydraulic gerotor pump comprising:
• a housing having an inlet and an outlet, and defining a cavity in fluid communication with the inlet and the outlet thereof;
• and
• a gear set rotatably disposed within the cavity of the housing, the gear set comprising an inner gear and an outer gear, the inner gear and the outer gear having radially opposed intermeshing teeth that together define a plurality of circumferentially disposed variable volume pumping chambers therebetween,
• wherein the housing is made of a first aluminum-based material and the inner gear and the outer gear of the gear set are made of a second aluminum-based material, and
• wherein a linear coefficient of thermal expansion of the first aluminum-based material is substantially the same as that of the second aluminum-based material such that an axial clearance between the gear set and the housing is in a range of 0.03 millimeters to 0.09 millimeters at temperatures in a range of −40° C. to 160° C., and
• wherein surfaces of the inner gear and the outer gear are (i) coated with an iron alloy, ceramic, cermet, or diamond-like carbon material and/or (ii) treated by boridinq and/or carburizing;
• and
• an electric motor including a rotor coupled to a drive shaft and a stator surrounding the rotor, the rotor including multiple circumferentially disposed permanent magnets,
• wherein the drive shaft of the electric motor is mechanically coupled to the inner gear of the gear set of the hydraulic gerotor pump and is operable to drive rotation of the gear set.

An automatic transmission comprising:

• a hydraulic gerotor pump comprising:
• a housing having an inlet and an outlet, and defining a cavity in fluid communication with the inlet and the outlet thereof;
• and
• a gear set rotatably disposed within the cavity of the housing,
• wherein the housing is made of a first aluminum-based material and the inner gear and the outer gear of the gear set are made of a second aluminum-based material, and
• wherein a linear coefficient of thermal expansion of the first aluminum-based material is substantially the same as that of the second aluminum-based material such that an axial clearance between the gear set and the housing is in a range of 0.03 millimeters to 0.09 millimeters at temperatures in a range of −40° C. to 160° C., and
• wherein surfaces of the inner gear and the outer gear are (i) coated with an iron alloy, ceramic, cermet, or diamond-like carbon material and/or (ii) treated by boridinq and/or carburizing;
• an electric motor including a rotor coupled to a drive shaft and a stator surrounding the rotor, wherein the drive shaft of the electric motor is mechanically coupled to the inner gear of the gear set of the hydraulic gerotor pump and is operable to drive rotation of the gear set;
• a hydraulic fluid sump in fluid communication with the inlet of the housing;
• a transmission control system in fluid communication with the outlet of the housing;
• and
• a gear and clutch arrangement that transmits torque between an input shaft and an output shaft, wherein the gear and clutch arrangement selectively receives pressurized hydraulic fluid from the transmission control system.