Abstract: A rotary pump device and an inner gear rotor therefore in which the inner gear rotor has a outer peripheral profile surface whose cross section perpendicular to its central axis is in the form of an inner envelope curve derived by moving a locus circle on an epitrochoidal curve. If the epitrochoidal curve is defined by a base circle of diameter A, a rolling circle of diameter B and an eccentricity of length e, and the locus circle has a diameter C, the inner rotor therefor having an eccentricity ratio f.sub.e =e/B, a locus circle ratio f.sub.c =C/B and a base circle ratio n=A/B, the ratios f.sub.e, f.sub.c and n are selected so as to make the inner envelope curve smooth without any edge portions by selecting the ratios to have values such that f.sub.c /K.sub.i .ltoreq.1.1, wherein K.sub.i =(n+1).times..vertline.1-2f.sub.e .vertline.. The inner gear rotor is rotatable in an outer gear rotor having circularly arched radially inwardly extending teeth.

Abstract: A rotary gear pump having inner and outer gear rotors of the type having respective inner and outer surfaces whose cross sections are determined utilizing the trochoidal curve, the inner gear rotor having trochoidal dimensions which either eliminate or diminish to a negligible amount the edge portion of the teeth which cause excessive wear, noise or inefficiency. In one embodiment of the invention, the dimensions of the inner gear rotor are such that C/K.sub.0 .ltoreq.1 or f.sub.c /K.sub.1 .ltoreq.1.1, where C is the rotary path diameter, K.sub.0 =(A/B+1).times..vertline.B-2e.vertline., K.sub.1 =(n+1).times..vertline.1-2f.sub.e .vertline., A is the diameter of the base circle, B is the diameter of the rolling circle, e is the eccentricity, n=A/B, f.sub.e =e/B, and f.sub.c =C/B. In accordance with a second embodiment of the invention, a comparable result can be obtained provided that the number of teeth on the inner gear rotor is equal to an integer closest to the ratio d.sub.4 /2e, wherein d.sub.

Abstract: An oil pump using internal gearing, wherein the difference in number of teeth between the internal and external gears is one, and wherein the inner rotor is directly connected to the crankshaft of the internal combustion engine or to the transmission shaft. The inner rotor is formed from a trochoidal curve and tracking circle which the outer rotor is formed from a trochoidal curve theoretically ideal for the inner rotor but modified by having circularly arched inwardly curved portions so as to decrease confinement of the inner rotor and smooth the operation thereof.

Abstract: A sintered outer rotor for a rotary pump utilizing the trochoidal curve and a manufacturing method for the rotor, the rotor being formed to make a combinational gap between an inner rotor and the outer rotor as small and constant as possible in order that both the inner and outer rotors are rotatable. The rotor is formed with an eccentricity ratio less than a limit based upon an experimentally obtained function of the ratio of the diameter of the base circle to that of the rolling circle used to form the trochoidal curve, and with corrected circular arcs of the tooth portions such that .vertline..DELTA.b.vertline.+.vertline..DELTA.c.vertline.<0.3 mm and .DELTA.b>.DELTA.c, wherein .DELTA.b and .DELTA.c are respectively the corrections to the centers of the circular arcs and the radii of the circular arcs. The ratio of the base circle to that of the rolling circle is not an integer and therefore is not equal to the number of outer rotor teeth as in the conventional outer rotor.