IC engine idle speed control appts. - has idle speed normally controlled within set dead-band, whilst during service, speed is controlled manually

摘要

A main inlet air passage (4) is provided, with a throttle valve (10) positioned in the passage. A control valve (36) is positioned in the bypass air passage, with an auxiliary bypass air passage (38) bypassing both the throttle valve and the control valve. The control valve (36) is responsive to a control signal to regulate the idle speed of the engine. A manually operable mechanism (40) is provided in the auxiliary air passage (38) for adjusting the engine idle speed. - The idle speed is normally controlled within a set dead-band. To facilitate manual adjustment of the idel speed e.g. during servicing, an arrangement is provided which permits manual generation of a selection signal indicating that manual adjustment of the idle speed is desired. In response to the selection signal, the idle speed is instead controlled within a narrower dead-band and perhaps with reduced gain.