US Patent 7588429 Oil pump rotor assembly

An oil pump rotor assembly is disclosed. An inner rotor formed with n external teeth is based on cycloid curves which are generated by a first circumscribed-rolling circle and a first inscribed-rolling circle by rolling the first circumscribed-rolling circle and first inscribed-rolling circle along an inner base circle. An outer rotor formed with n+1 internal teeth (n+1 is the number of teeth) is based on cycloid curves which are generated by a second circumscribed-rolling circle and a second inscribed-rolling circle by rolling the second circumscribed-rolling circle and second inscribed-rolling circles along an outer base circle.