초록 ▼

An on-board diagnostic system for an evaporative emission control system of an internal combustion engine powered vehicle employs a leak detection module that is fluid connected in a vent passage for the evaporative emission space. The leak detection module contains an electric motor driven impeller

An on-board diagnostic system for an evaporative emission control system of an internal combustion engine powered vehicle employs a leak detection module that is fluid connected in a vent passage for the evaporative emission space. The leak detection module contains an electric motor driven impeller, a solenoid operated valve assembly that is selectively operable to three positions, and a pressure-responsive switch whose switching characteristic possesses hysteresis corresponding to an upper regulating limit and a lower regulating limit. The valve assembly operates to allow the prime mover to pump gaseous fluid with respect to the evaporative emission space to attain a test pressure in the evaporative emission space corresponding to the upper regulating limit, to close the evaporative emission space and prevent the prime mover from pumping gaseous fluid with respect to the evaporative emission space upon initially attaining the upper regulating limit test pressure within the evaporative emission space, and which allows the prime mover to pump gaseous fluid with respect to the evaporative emission space at a pre-defined volumetric flow rate to rebuild pressure in the evaporative emission space to the upper regulating limit when the pressure has changed to the lower regulating limit due to a leak in the evaporative emission space.

대표청구항 ▼

[ What is claimed is:] [1.] In an engine-powered automotive vehicle evaporative emission control system comprising an evaporative emission space for containing volatile fuel vapors, and a leak detection system for detecting leakage from the evaporative emission space, the improvement in said leak de

[ What is claimed is:] [1.] In an engine-powered automotive vehicle evaporative emission control system comprising an evaporative emission space for containing volatile fuel vapors, and a leak detection system for detecting leakage from the evaporative emission space, the improvement in said leak detection system which comprises:a prime mover for pumping gaseous fluid with respect to the evaporative emission space;a selectively operable valve assembly which operates to a first condition for allowing the prime mover to pump gaseous fluid with respect to the evaporative emission space, which operates to a second condition for closing the evaporative emission space upon attainment of an initial test pressure within the evaporative emission space that differs sufficiently from atmospheric pressure to allow a leak in the evaporative emission space to be detected, and which operates to a third condition different from its first and second conditions;a control, including a pressure-responsive electric device, for controlling operation of the prime mover and the valve assembly;wherein the pressure-responsive electric device is disposed to provide an electric signal related to pressure in the evaporative emission space;wherein the pressure-responsive electric device allows the valve assembly to assume its first condition while the prime mover is operated to pressurize the evaporative emission space to an initial test pressure at the beginning of a test;wherein a signal from the pressure-responsive device causes the valve assembly to assume its second condition upon attainment of the initial test pressure; andwherein a signal from the pressure-responsive device causes the valve assembly to assume its third condition when the initial test pressure has changed by a pre-defined amount due to a leak in the evaporative emission space.