Knock control apparatus equipped with altitude compensation function

Claim 1

A knock control apparatus equipped with an altitude compensation function, comprising: a knock sensor fitted to an internal combustion engine for detecting the mechanical oscillation of said internal combustion engine caused by knocking to produce a signal indicating the intensity of knock; an atmopsheric pressure sensor detecting the atmospheric pressure; means for discriminating a background level signal from the output signal from said knock sensor; means for comparing the output signal from said knock sensor with the background level signal from said discrimination means and detecting the knock of said internal combustion engine and the intensity of said knock; means for generating a signal representing a maximum advance angle position in accordance with a detected atmospheric pressure; and ignition timing control means for setting and generating a first ignition timing signal representing the maximum advance angle position corresponding to the detected atmospheric pressure when no knocking in the internal combustion engine is occurring, and for generating a second ignition timing signal representing an advance angle position retarded from the maximum advance angle position changing with a predetermined retard angle changing speed in accordance with the detected knocking intensity when knocking in the internal combustion engine is occurring, the second ignition timing singal changing gradually toward the first ignition timing signal corresponding to the detected atmospheric pressure with a predetermined advance angle changing speed while changing away from the first ignition timing signal with the predetermined retard angle changing speed in accordance with a detected knocking intensity.