Studies on Gear Pumps with 2 to 5 Teeth

Abstract

In order to obtain as large a delivery as possible without changing the inner space VC of a gear pump casing, the authors introduced a method of designing and producing gear pumps with the number of teeth from 𝒵₁ = 𝒵₂ = 2 to 5. They presented a new tooth profile of helical gears suitable for pumps producing no fluctuations in delivery. Equations were derived for calculating the theoretical delivery V_th of the gear pumps and also the thrust which occurs on the gears. Experiments were conducted using four kinds of trial gear pumps with 𝒵₁ = 𝒵₂ = 3 or 4. In the case of the gear pumps with 𝒵 = 3 and a transverse module of 15.65 mm, the volumetric efficiency was about 98% and the total efticiency was about 90% when the pump was operated at about 1.5 MPa using a machine oil as the pumping fluid. The volume ratio V_th/V_c of the trial gear pump was about 0.5, while it was about 0.2 in the case of a conventional gear pump with almost the same delivery.