A pump control system for an automatic transmission

摘要

A system for temperature compensating and regulating secondary pressure in a hydraulic circuit for an automatic transmission, includes a viscosity insensitive fixed orifice (64) and a relatively high resistance laminar orifice (60) connected in series relationship between a vent port and a control pressure supplied to a secondary regulated pressure SRP valve (52). At relatively low temperature, flow through the laminar orifice (60) is negligible; therefore, the steady-state differential pressure across the fixed orifice (64) is negligible. At relatively higher temperatures, flow through the laminar orifice increases. A pressure divider is established and the feedback differential pressure is reduced in proportion to the hydraulic resistance of the two orifices (60,64). Flow to friction elements from a primary pump (16) and auxiliary pump (22) and return of fluid to the inlets of the pumps (16,22) is controlled through a clutch capacity pressure regulator valve (212) acting in cooperation with the SRP valve (52).