Knock detecting apparatus for internal combusion engines

• US 4,476,709 A
• Filed: 08/17/1982
• Issued: 10/16/1984
• Est. Priority Date: 08/18/1981
• Status: Expired due to Fees

• Current Assignee: Nippon Soken, Inc.
• Original Assignee: Nippon Soken, Inc.
• Inventors: Hattori, Tadashi, Miura, Kazuhiko, Ozaki, Tadashi, Ootsuka, Yoshinori
• Primary Examiner(s): Birmiel, Howard A.
• Assistant Examiner(s): Chapman, Jr., John E.
• Application Number:
  US06/408,896
• Time in Patent Office: 791 Days
• Field of Search: 73/35, 123/425, 123/435
• US Class Current: 73/35.05
• CPC Class Codes: G01L 23/225 circuit arrangements therefor

Abstract

In a knock detecting apparatus for an internal combustion engine, the output signal of a knock sensor whose output signal level varies in accordance with the engine conditions, engine speed, sensor sensitivity, etc., is passed through an automatic gain control circuit (AGC) thereby stabilizing the output level. The background noise level derived by integrating the output signal and the stabilized output signal are compared to detect the occurrence of knocking. The stabilized output signal is passed through a low-pass filter or a band-pass filter and the resulting control signal is used to control the gain of the AGC circuit.

Claims

1. A knock detecting apparatus for internal combustion engines comprising:

knock detecting means for detecting the occurence of knocking in an engine;

automatic gain control means for processing an output signal of said knock detecting means to form a background noise signal having a substantially constant level and a knock signal;

comparator means responsive to said background noise signal and said knock signal to determine the presence of knocking in said engine;

said automatic gain control means having a negative feedback loop including frequency selecting means for providing the gain control of said automatic gain control means with frequency selectivity,

wherein said automatic gain control means includes voltage controlled means for effecting said gain control, and wherein said frequency selecting means comprises a low-pass filter for connecting an output of said control means to said voltage controlled means, said filter having a cutoff frequency lower than knock frequencies.

2. An apparatus according to claim 1, wherein said gain control is effected by frequency components other than knock frequencies.

3. A knock detecting apparatus for internal combustion engines comprising:

knock detecting means for detecting the occurrence of knocking in an engine;

automatic gain control means for processing an output signal of said knock detecting means to form a background noise signal having a substantially constant level and a knock signal;

comparator means responsive to said background noise signal and said knock signal to determine the presence of knocking in said engine;

said automatic gain control means having a negative feedback loop including frequency selecting means for providing the gain control of said automatic gain control means with frequency selectivity,

wherein said automatic gain control means includes voltage controlled means for effecting said gain control, and wherein said frequency selecting means comprises a band-pass filter for connecting an output of said control means to said voltage controlled means, said filter having a passband excluding frequency bands of knock frequencies, ignition frequencies and valve seating noise frequencies.

4. An apparatus according to claim 3, wherein said gain control is effected by frequency components other than knock frequencies.