| 摘要 |
<p>Ignition control system (10). Crankshaft advance (15, 16) and reference (17, 18) sensors are utilized to determine positions of maximum and minimum possible spark ignition advance. for each maximum advance pulse (tA) a main counter (41) starts sequentially counting clock pulses (C1) wherein the maximum count obtained by the counter (41) is related to engine crankshaft speed. The count of the main counter (41) is utilized by a dwell circuit (121) to determine the time (tDW) prior to the maximum advance pulse (t-A) at which spark coil excitation should occur. The main counter count also determines several inputs to a read-only-memory (ROM) circuit (48) whose output controls a rate multiplier (53) which receives input clock signals (C2) and provides selective frequency division for these clock signals in accordance with the ROM output. The output of the rate multiplier is coupled to an accumulator means (80, 81, 82) which provides an accumulated count which is utilized to determine spark occurrence. Pulse width modulation circuitry (56) receives an analog signal related to the amount of sensed engine vacuum pressure and produces a corresponding periodic digital two-state signal which has a duty cycle related to the magnitude of the analog vacuum signal. This signal is coupled as an input to the ROM (53) which controls the rate multiplier. In this manner the accumulator count is made to depend upon the magnitude of the analog vacuum signal. </p> |
