Patent ID: 8718984

Claim:
A minute flow rate controller equipped with an entrance throttle groove, said minute flow rate controller comprising an inflow passage for introducing a fluid, a valve member on which a main throttle groove is formed, for flowing the fluid introduced from said inflow passage from a starting end to a finishing end, a flow rate regulating component that hermetically seals said main throttle groove up to a desired position, a fluid outflow port that opens by said flow rate regulating component at a given cross section of said main throttle groove, an outflow passage that lead out the fluid that flows out of said fluid outflow port, and an entrance throttle groove that precedes connectively at the starting end of said main throttle groove, wherein in order to determine theoretically a length L E of said entrance throttle groove by flow theory, a momentum equation of said fluid flowing through said entrance throttle groove and said main throttle groove is expressed as uρdu/dz+λu 2 ρ/2 D H +dP/dz =0, said momentum equation is computed based upon u=G/ρA and λ=64 μA/GD H , said momentum equation is also computed under a condition that a pressure difference of said fluid between said inflow passage and said outflow passage is constant, said length L E of said entrance throttle groove is determined so that when a cross section area of said main throttle groove monotonically decreases from the starting end to the finishing end, a flow rate of the fluid that flows out from said fluid outflow port monotonically decreases, as the position of said fluid outflow port moves from the starting end to the finishing end, and said length L E which is theoretically determined above is used as said length of entrance throttle groove, where u is the flow velocity of said fluid, ρ is the density of said fluid, z is the flow direction coordinate of said fluid, λ is the friction coefficient of said fluid, D H is the equivalent diameter of throttle groove cross section area, P is the pressure of said fluid, G is the mass flow rate of said fluid, A is the cross section area of said fluid outflow port, and μ is the viscosity coefficient of said fluid.