Peak combustion pressure timing detector for internal combustion

Details Peak combustion pressure timing detector for internal combustion Peak combustion pressure timing detector for internal combustion

1985-07-12

1986-07-22

Levy, Stewart J.

Measuring and testing

Vehicle chassis

Steering

G01M 1500

Patent

active

046011978

ABSTRACT:
Apparatus for sensing the timing of peak combustion pressure in an internal combustion engine includes a capacitive piezoelectric element adapted for flexure in response to variations in combustion chamber pressure and connected in parallel with a first resistance, a constant current generator connected to establish a predetermined voltage across the first resistance and thereby across the piezoelectric element when the capacitance of the latter remains constant, a second resistance, a source of the predetermined voltage, and an operational amplifier effective to compare the voltage across the piezoelectric element with the predetermined voltage and source or sink current through the second resistance to maintain the predetermined voltage across the piezoelectric element. The output voltage of the operational amplifier is an analog of the current through the second resistance and thus of the rate of change of capacitance of the piezoelectric element. The crankshaft angle after ignition at which this voltage crosses the predetermined reference corresponds to the timing of peak combustion pressure. In order to reduce noise in the 6 to 9 kilohertz range, the first and second resistances may be reduced, the second resistance bypassed at high frequencies and the output voltage amplified with low pass filtering.

REFERENCES:
patent: 3820013 (1974-06-01), Gaudette, Jr. et al.
patent: 4231091 (1980-10-01), Motz
patent: 4406265 (1983-09-01), Brandt et al.
patent: 4481925 (1984-11-01), Karau et al.
patent: 4491010 (1985-01-01), Brandt et al.

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