Butterfly valve return controller for IC engine - uses two vacuum feeds on either side of throttle and solenoid valve to apply vacuum to alter throttle stop position

摘要

The throttle stop gives progressive closure reduces atmospheric pollution from a motor vehicle exhaust without the need for catalytic converters. The throttle stop is coupled to a piston in a vacuum cylinder. The piston is spring loaded to drive the stop to the throttle fully closed position. The vacuum to operate the piston is derived directly from a point on the atmosphere side of the throttle butterfly and from a second point on the engine side of the throttle via a solenoid valve, which is closed at low engine speed and opened at high engine speed, and a pressure regulator. If the throttle is closed when the engine speed is high and the solenoid valve open the regulated pressure is supplied to the vacuum cylinder holding the throttle part open until the speed falls and the solenoid valve closes. At low engine speed (solenoid valve closed) the depression in the vacuum cylinder reduces as the air pressure on the inlet side of the throttle rises back to atmospheric pressure, which is communicated to the vacuum cylinder through a restrictor value giving progressive closing of the throttle.