Patent GB-1409143-A (GB)
Title: Internal combustion engine spark timing control system
IPC: F02P5/10
Filed: 1973-10-01
Abstract: 1409143 Timing ignition FORD MOTOR CO Ltd 1 Oct 1973 [4 Oct 1972] 45713/73 Heading F1B A spark timing control system for an engine has a carburetter induction passage 18 with a spark port 36 above the idle speed position of the throttle valve 30, a distributer breaker plate 12 spring- biased in a spark timing retarded setting direction, vacuum servo means 14 normally moving the breaker plate in an advanced timing direction as a function of increases in spark port vacuum applied thereto, conduit means 16 connecting the spark port to the servo means and control means momentarily advancing the timing to a spark setting advanced above that which would normally be called for according to the level of vacuum at the spark port in response to accelerative opening movement of the throttle valve 30 and subsequently returning the timing to the spark timing setting called for by the spark port pressure level. The control system includes a one piece valve body structure having first and second axially aligned valves 98, 76 movable therein between open and closed positions and spring-biased to open and  closed positions respectively, the first valve variably controlling communication of pressure between a first line 114 connected to a manifold vacuum reservoir 120 and a first portion 116 of the conduit means connected to the servo means 14. The second valve controls communication of pressure between the first portion 16 and a second portion 52 of the conduit means connected to the carburetter spark port, the second valve having means providing at all times a slow bleed down of pressure between the servo means and the spark port while being movable to an open position in response to spark port pressure above the force of the spring means 84 and the servo means pressure. Means 62 connects manifold vacuum to act on the first valve in opposition to the spring means 102 whereby steady state and light acceleration operation vacuum levels connect the first and second portions while disconnecting the vacuum reservoir from the first portion so that changes in carburetter spark port vacuum level cause a corresponding change in spark timing and whereby heavy accelerations, reducing manifold vacuum to a low level, connect the reservoir vacuum to the servo means 14 to temporarily advance the timing beyond the setting called for by spark port pressure level until the servo means vacuum is bled to the spark port level. Other means 106, 108 is axially aligned with and acts on the first valve to limit reservoir vacuum and thereby the temporary advance and responsive to manifold vacuum levels above a predetermined level indicative of deceleration conditions moves the first valve to temporarily connect reservoir vacuum to the servo means to decay the reservoir vacuum to the servo means pressure level. As shown the second valve comprises a combination flexible non-return flap valve and flow regulating valve. The valve incorporates a built in orifice (not shown) to provide a controlled leakage in both directions at all times. Specification 1409142 is referred to.