System for detecting combustion state in internal combustion engine

• US 5,339,245 A
• Filed: 12/23/1991
• Issued: 08/16/1994
• Est. Priority Date: 12/26/1990
• Status: Expired due to Fees

• Current Assignee: Nippendenso Company Limited
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Hirata, Yoshihiko, Sakakibara, Koji
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US07/812,109
• Time in Patent Office: 967 Days
• Field of Search: 364/431.08, 364/431.07, 123/425, 123/117, 123/115, 123/419, 123/435, 123/422, 123/480, 73/115, 73/116, 73/117, 73/35
• US Class Current: 701/111
• CPC Class Codes: F02D 2041/281 between sensors and control unit
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: F02D 35/027 using knock sensors
• CPC Class Codes: F02D 41/28 Interface circuits
• CPC Class Codes: F02P 5/152 dependent on pinking detecting or indicating knocks in internal-combustion engines G01L23/22
• CPC Class Codes: G01L 23/225 circuit arrangements therefor
• CPC Class Codes: G01M 15/08 by monitoring pressure in cylinders
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A combustion state detecting system for an internal combustion engine which is equipped with a combustion state detector for detecting a combustion state of said engine. The system also includes an amplifier having a plurality of amplification factors to amplify or attenuate a combustion signal obtained by the combustion state detector, the amplification factor of the amplifier being arranged to be switchable plural times on the basis of a detection result of the combustion state detector within a predetermined time period of a combustion cycle of the engine. The decision of the combustion state of the engine is made on the basis of an output of the amplifier generated within the predetermined time period. This arrangement allows an A/D converter to input a signal having as great as possible without overflow to improve the detection accuracy of the combustion state of the engine.

Claims

1. A combustion state detecting system for an internal combustion engine, comprising:

combustion state detecting means for detecting a combustion state of said engine and for outputting a continuous detection signal being indicative thereof, where said detection signal includes a plurality of detection signal portions per combustion cycle;

amplifying means for amplifying said detection signal with one of a plurality of selectable different amplification factors;

amplification-factor switching means for selecting an amplification factor for said amplifying means on the basis of a value of a current portion of said detection signal within a continuous time period of a combustion cycle of said engine, where said amplifying means uses said amplification factor corresponding to said current portion of said detection signal within a current combustion cycle for amplifying a next portion of said detection signal within said current combustion cycle, thereby changing said amplification factor more than once per combustion cycle; and

combustion state decision means for performing an analog-to-digital conversion on each of said amplified portions of said detection signal, thereby obtaining a local maximum value corresponding to each of said amplified portions, and for deciding about the combustion state of said engine on the basis of a comparison between each of said local maximum values within said continuous time period and a threshold value,

wherein said local maximum value is compared with said first and second predetermined values so that a gain for the next analog-to-digital conversion is decreased when said local maximum value is greater than said first predetermined value in a high-gain state and increased when said local maximum value is smaller than said second predetermined value in a gain-decreased state, said second predetermined value being set to be smaller than said first predetermined value, and the analog-to-digital conversion value and information relating to the gain are stored and used for calculation.

2. A system as claimed in claim 1, wherein said decision signal at the time of the next analog-to-digital conversion is estimated on the basis of whether the detection signal has a decreasing or increasing tendency so that the estimated decision signal is compared with a third predetermined value so as to switch the gain on the basis of the comparison result.