GB1316527A - Vacuum spark advance cutoff - Google Patents

Abstract

1316527 Timing ignition FORD MOTOR CO Ltd 13 Sept 1971 [2 Dec 1970] 42606/71 Heading F1B An ignition timing control system comprises an engine carburetter 10 having an induction passage 18 containing a spark port 28 located above the idle speed position of a throttle valve 26 controlling flow through the passage and subject to the depression in the carburetter as a function of the movement of the throttle valve from its idle speed position, an engine distributer having a breaker plate 12 pivotally movable in opposite directions to advance and retard the spark timing vacuum controlled servo means 14 connected to the breaker plate for moving the same and flow-rate control means between the spark port and servo means to control the rate of change of application of vacuum from the spark port to the servo means, the control means including conduit means 16 connecting the vacuum at the spark port to the servo means for effecting variable movement of the breaker plate 12 from a maximum retard setting at closed throttle valve idle speed position to a maximum advance setting at high spark port off idle vacuum levels. An air bleed means 52 is openable upon a decrease in the pressure level at the spark port 28 from essentially atmospheric pressure conditions, in response to an accelerative movement of the throttle valve, to momentarily bleed air to the servo means 14 to maintain the breaker plate at a maximum retard setting. Subsequently the breaker plate setting can advance upon an increase in vacuum level at the spark port. As shown the air bleed means 52 comprises a diaphragm 68 connected to a valve member 66. The chamber 74 is connected to the chamber 72 by a metering orifice 76.