Patent ID: 6216453
Filing Date: 2001-04-17
Classification: F01N,F02B,Y02T

Abstract:
A secondary air supply system for a four-cycle internal combustion engine with one or more cylinders having a crankcase capable of experiencing pressure pulsations resulting from the reciprocating motion of the engine's pistons, and having an exhaust system through which the engine's exhaust gas must pass before being discharged into the atmosphere, said secondary air supply system comprising:(a) a diaphragm air pump having a housing defining an inner chamber,(b) a diaphragm located in said inner chamber so as to divide said inner chamber into an actuating chamber and a pumping chamber, with said actuating chamber being isolated from said pumping chamber by said diaphragm,(c) said pumping chamber having an air inlet port fitted with a one-way valve such that air may enter the pumping chamber only through said inlet port and one-way valve,(d) said pumping chamber further having an air outlet port fitted with a one-way valve such that air may exit the pumping chamber only through said outlet port and one-way valve,(e) said outlet port being in communication by a connective means to the exhaust system such that air exiting the outlet port of the diaphragm air pump is injected into the exhaust system,(f) said actuating chamber being connected to the engine crankcase such that the actuating chamber and the crankcase are in airflow communication,(g) a biasing means situated in the diaphragm air pump inner chamber such that said biasing means acts on the diaphragm, the biasing force exerted by said biasing means being selected to minimize any differential between the positive and negative pressure pulses communicated from the crankcase to the actuating chamber of the diaphragm air pump, and(h) wherein secondary air is supplied to the exhaust system by the diaphragm air pump in an amount proportional to the rotational speed of the engine and the displacement of the diaphragm caused by the engine crankcase pressure pulsations and the force exerted by the biasing means.