System for detecting and adjusting for variation in cylinder pressure in internal combustion engine

• US 5,276,625 A
• Filed: 07/31/1990
• Issued: 01/04/1994
• Est. Priority Date: 07/31/1989
• Status: Expired due to Fees

• Current Assignee: Japan Electronic Control Systems Company Limited
• Original Assignee: Japan Electronic Control Systems Company Limited
• Inventors: Nakaniwa, Shinpei
• Primary Examiner(s): Trans, Vincent N.
• Application Number:
  US07/559,943
• Time in Patent Office: 1,253 Days
• Field of Search: 73/115, 73/117.3, 73/118.2, 364/558, 364/571.01, 364/571.02, 364/571.03, 364/571.04, 364/571.05, 364/571.06, 364/571.07, 364/571.08, 364/551.01, 364/431.01 , 364/431.03, 364/431.04, 364/431.07, 364/431.08, 123/425, 123/435
• US Class Current: 701/111
• CPC Class Codes: F02D 35/023 by determining the cylinder pressure
• CPC Class Codes: G01L 23/08 operated electrically G01L23/22 takes precedence
• CPC Class Codes: G01M 15/08 by monitoring pressure in cylinders

Abstract

A cylinder pressure detecting system includes a plurality of pressure sensors, each of which is provided for monitoring pressure in one of plurality of cylinders. The system performs data sampling of detection values produced by one of the pressure sensors corresponding to a cylinder in an intake stroke, and compares each of the sampled detection values and a predetermined reference minimum value to respectively set differences therebetween as offset correction values. These processes are performed for the respective cylinders. The detection values of the pressure sensors for the respective cylinders are corrected on the basis of the offset correction values so that the detection values detected by the respective pressure sensors coincide with each other.

Claims

1. A system for determining cylinder pressure in a cylinder of an internal combustion engine, said cylinder performing an intake stroke under suction, said system comprising:

pressure detecting means for monitoring pressure in said cylinder and for producing an output signal indicative of said monitored pressure;

means for monitoring said internal combustion engine and for producing at least one reference signal at regular predetermined crankshaft angle intervals of the internal combustion engine;

means, responsive to said at least one reference signal, for detecting an occurrence of said intake stroke of said cylinder;

means for reading a first value of said output signal upon detection of said occurrence of said intake stroke of said cylinder and for storing said first value as a stored first detection value;

offset value setting means for setting a difference between said stored first detection value and a predetermined reference value as an offset correction value;

first correction means for reading a second value of said output signal at a predetermined crankshaft angular position, for storing said second value as a stored second detection value and for correcting said stored second detection value on the basis of said offset correction value for producing a corrected detection value;

means for sampling said corrected detection value to produce sampled corrected values and for processing said sampled corrected values for producing an output signal indicative of the cylinder; and

control means for controlling ignition timing of the engine in response to said output signal.

2. An apparatus comprising:

(a) an internal combustion engine having a cylinder which, in operation, performs an intake stroke under suction, a compression stroke, an expansion stroke; and

(b) a control system for said internal combustion engine, responsive to cylinder pressure in said cylinder, said control system comprising

(i) means for monitoring said cylinder pressure in said cylinder and for producing a sensor output signal indicative of said cylinder pressure;

(ii) means for monitoring said internal combustion engine and producing at least one reference signal at regular predetermined crankshaft angle intervals of said internal combustion engine;

(iii) means responsive to said at least one reference signal for detecting an occurrence of said intake stroke of said cylinder;

(iv) means for reading a first value of said sensor output signal upon detection of an occurrence of said intake stroke of said cylinder and for storing said first value as a stored first detection value;

(v) means for setting a difference between said stored first detection value and a predetermined reference value as an offset correction value;

(vi) means for reading a second value of said sensor output signal at a predetermined crankshaft angular position, for storing said second value as a stored second detection value and for correcting said stored second detection value, on the basis of said offset correction value, for producing a corrected detection value;

(vii) means for sampling said corrected detection value for producing sampled correction values, for calculating an average of said sampled corrected values and for outputting said average as indicative of said cylinder pressure; and

(viii) control means for controlling ignition timing of said engine in response to said average.

3. An apparatus comprising:

(a) an internal combustion engine having a cylinder which, in operation, performs an intake stroke under suction, a compression stroke, an expansion stroke and an exhaust stroke;

(b) pressure sensor means for monitoring pressure in said cylinder and for producing a sensor output signal indicative of said pressure;

(c) crank angle sensor means for monitoring said internal combustion engine and producing at least one reference signal at regular predetermined crankshaft angle intervals of said internal combustion engine; and

(d) a control unit operatively coupled with said internal combustion engine, said pressure sensor means and said crank angle sensor means, said control unit comprising

(i) means responsive to said at least one reference signal for detecting said occurrence of said intake stroke of said cylinder;

(ii) means for reading a first value of said sensor output signal upon detection of said occurrence of said intake stroke of said cylinder and storing said first value as a stored first detection value;

(iii) means for setting a difference between said stored first detection value and a predetermined reference value as an offset correction value;

(iv) means for reading a second value of said sensor output signal at a predetermined crankshaft angular position, for storing said second value as a stored second detection value and for correcting said stored second detection value on the basis of said offset correction value for producing a corrected detection value;

(v) means for sampling said corrected detection value to produce sampled corrected values, for calculating an average of said sampled corrected values and for outputting said average as indicative) of said cylinder pressure; and

(vi) control means for controlling ignition timing of said engine in response to said average.

4. A method of determining cylinder pressure in a cylinder of an internal combustion engine, the cylinder performing an intake stroke under suction, a compression stroke, an expansion stroke and an exhaust stroke, said method comprising the steps of:

monitoring pressure in said cylinder and producing a sensor output signal indicative of said pressure;

detecting an occurrence of said intake stroke of said cylinder;

reading a first value of said sensor output signal upon detection of said occurrence of said intake stroke of said cylinder and storing said first value as a stored first detection value;

setting a difference between said stored first detection value and a predetermined reference value as an offset correction value;

reading a second value of said sensor output signal at a predetermined crankshaft angular position and storing said second value as a stored second detection value;

correcting said stored second detection value, on the basis of said offset correction value for producing a corrected detection value;

sampling said correction detection value for producing sampled corrected detection values, calculating an average of said sampled corrected detection values and outputting said average as indicative of said cylinder pressure; and

controlling ignition timing of the engine in response to said average.

5. A method of determining cylinder pressure in a cylinder of an internal combustion engine, said cylinder performing an intake stroke under suction, a compression stroke, an expansion stroke and an exhaust stroke, said method comprising the steps of:

monitoring pressure in said cylinder and producing a sensor output signal indicative of said monitored pressure;

detecting an occurrence of the intake stroke of the cylinder;

reading a first value of said sensor output signal upon detection of said occurrence of said intake stroke of said cylinder and storing said first value as a stored first detection value;

setting a difference between said stored first detection value and a predetermined reference value as an offset correction value;

reading a second value of said sensor output signal at a predetermined crankshaft angular position and storing said second value as a stored second detection value;

sampling said stored second detection value during a period of time, when no combustion takes place in said cylinder when the engine operates, for producing sampled second detection values;

calculating a weighted average of said sampled second detection values;

calculating a ratio of said weighted average to said stored second detection value outside of said period of time and updating a gradient correction coefficient with said ratio;

calculating a product of said stored second correction value and said gradient correction coefficient and a sum of said product and said offset correction value to produce a corrected detection value;

sampling said corrected detection value for sampled correction detection values and calculating an average of said sampled corrected detection values and outputting said average as indicative of said cylinder pressure; and

controlling ignition timing of the engine in response to said average.

6. In an internal combustion engine having a plurality of cylinders, each of the plurality of cylinders performing an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke, comprising:

a plurality of pressure sensors, corresponding in number to the plurality of cylinders, each of said pressure sensors mounted in one of the plurality of cylinders, respectively, each of said pressure sensors being constructed and arranged to produce, as a sensor signal, a voltage signal indicative of a positive cylinder pressure developed within a corresponding one of the plurality of cylinders, and producing a zero voltage signal in response to a negative cylinder pressure developed therewithin;

a crank angle sensor constructed and arranged to generate a crank angle reference signal (REF) at every predetermined angular position of a crankshaft in the engine and a crank position signal (POS) at every unit angular displacement of the crankshaft;

a first multiplexer operatively coupled with said plurality of pressure sensors;

a second multiplexer operatively coupled with said plurality of pressure sensors;

an analog-digital converter operatively coupled with said first and second multiplexers and with said crank angle sensor, said analog-digital converter being constructed and arranged to generate a digital signal indicative of a result of an analog to digital conversion at timings determined by said crank angle reference signal and said crank position signal; and

a control unit operatively coupled with said analog-digital converter and said crank angle sensor,

wherein said control unit comprises;

means for generating a first select signal to render said first multiplexer operable for supplying said analog-digital converter with the sensor signal of a specific one of said plurality of pressure sensors, which is mounted on one of the plurality of cylinders for performing compression and expansion strokes, and a second select signal to render said second multiplexer operable for supplying said analog-digital converter with the sensor output signal of a specific one of said plurality of pressure sensors which is mounted on one of the plurality of cylinders for performing an intake stroke;

means for storing said digital signal of said analog-digital converter at a timing determined by said crank angle reference signal, whenever each of the plurality of cylinders performs the intake stroke, as an offset correction value for a specific cylinder performing said intake stroke;

means for repeatedly storing said digital signal of said analog-digital converter at an interval determined by said crank position signal whenever each of the plurality of cylinders performs a compression stroke and an expansion stroke, as a set of sampled values for the cylinder performing said compression and expansion strokes;

means for converting said set of sampled values for the cylinder performing said compression and expansion strokes into a set of cylinder pressure values, correcting said set of cylinder pressure values with said correction value for the cylinder performing said compression and expansion strokes, and storing the result as a set of corrected cylinder pressure values for the cylinder performing said compression and expansion strokes;

means for processing said set of corrected cylinder pressure values for each of the plurality of cylinders and generating an output signal; and

means for controlling the combustion in the plurality of cylinders in response to said output signal.