Apparatus and method for recognizing misfire occurrence in multi-cylinder internal combustion engine

• US 5,670,713 A
• Filed: 03/22/1996
• Issued: 09/23/1997
• Est. Priority Date: 03/22/1995
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd., Robert Bosch Gbmh
• Original Assignee: Unisia Jecs Corporation (Hitachi, Ltd.), Robert Bosch GmbH
• Inventors: Machida, Kenichi, Ries-Muller, Klaus
• Primary Examiner(s): Dombroske, George M.
• Application Number:
  US08/620,334
• Time in Patent Office: 550 Days
• Field of Search: 73/116, 73/117.2, 73/117.3, 364/431.07, 364/431.08, 123/419, 123/425, 123/436
• US Class Current: 73/114.03
• CPC Class Codes: G01M 15/11 by detecting misfire

Abstract

Apparatus and method for recognizing an absence or presence of a misfire in each of cylinders of a multi-cylinder internal combustion engine without influences of a mechanical deviation in a crank angle sensor and of a combustion state deviation between each of the cylinders. A period of each reference signal (REF) is generated from the crank angle sensor and a fuel combustion state deviation between each of the cylinders. The period of each reference signal (REF), which is generated from the crank angle sensor whenever an engine crankshaft has rotated through a predetermined crank angle expressed as 720°/n (n denotes a number of engine cylinders), is measured by a timer. A determination of the absence or presence of the misfire in each cylinder is made based on the measured period of the reference signal for each corresponding one of the cylinders. The measured period being corrected with either or both of first and second correction coefficients (KT_i KKT_i) derived by learning the corresponding first correction coefficient for the mechanical deviation and by learning the corresponding second correction coefficient for the combustion state deviation.

Claims

1. A misfire recognizing apparatus for a multi-cylinder internal combustion engine, comprising:

a) a reference signal generating sensor for generating and outputting a reference signal (REF) for each predetermined crank angle rotation of an engine crankshaft, which angle rotation is expressed by 720°

/n, where n denotes a number of engine cylinders within the engine, and said reference signal including a cylinder number identifying signal indicative of one of the engine cylinders;

b) a second sensor for detecting an engine driving condition other than an engine revolution speed; and

c) a control unit including;

d) period measuring means for measuring a period of the reference signal for each predetermined crank angle rotation, the reference signal period corresponding to a combustion state of a corresponding one of the engine cylinders;

e) misfire occurrence determining means for determining a presence or absence of misfire in each cylinder based on the measured period of the reference signal for the corresponding one of the engine cylinders;

f) first determining means for determining whether a fuel supply to the engine is cut off or carried out based on the detected engine driving condition;

g) first correction coefficient setting means for setting a first correction coefficient (KT_i, where i=1to n in increments of

     1) for each measured period of the reference signals so that stepwise variations (Δ

T) in the periods of the reference signals consecutively measured for all of the cylinders are mutually equal to one another when said first determining means determines that the fuel supply to the engine is cut off;

h) second determining means for determining whether the misfire occurrence determining means has determined the absence of misfire in any the engine cylinders; and

i) second correction coefficient determining means for setting a second correction coefficient (KKT_i, where i=1 to n in increments of

     1) for each measured period of the reference signals so that the respective periods of the reference signals for all of the engine cylinders, which are corrected according to the first correction coefficients set by the first correction coefficient setting means, are equal to an average value (T_AVE) of the respective periods of the reference signals when the first determining means determines that the fuel supply to the engine is carried out and when said second determining means determines that the misfire occurrence determining means has determined the absence of misfire in any of the engine cylinders,

wherein said misfire occurrence determining means comprises;

j) correction means for correcting the periods of the respective reference signals continuously measured for all of the engine cylinders according to either or both of the first and second correction coefficients set by said first and second correction coefficient setting means and said misfire occurrence determining means determines the absence or presence of misfire in any engine cylinder based on the corrected periods of the reference signals by said correction means.

2. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 1, wherein said first correction coefficient setting means comprises:

k) ideal stepwise variation calculating means for calculating a stepwise variation Δ

T of one of the periods of the reference signals corresponding to the combustion state of each corresponding one of the cylinders representing a previously set learning representative cylinder within a given crank angle of 720°

corresponding to four strokes of the engine and dividing the calculated stepwise variation Δ

T by the number of the cylinders (n) to calculate an ideal stepwise variation (S); and

l) first correction coefficient calculating means for calculating the first correction coefficient KT_i for each cylinder from a ratio between the measured period (Ti, where i=1 to n in increments of

     1) of the reference signal for the corresponding one of the cylinders within the given crank angle of 720° and

an ideal period derived by adding the measured period of one of the reference signals for the previously set learning representative cylinder at a first interval of the given crank angle of 720°

to a product of the ideal stepwise variation S and of the cylinder number counted from the previously set learning representative cylinder.

3. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 2, wherein n=4 and wherein the first correction coefficient for each cylinder is expressed as:

KT_i-3 =(T5+1·

S)/T4,

KT_i-2 =(T5+2·

S)/T3,

KT_i-1 =(T5+3·

S)/T2, and

KT₁ ! KT_i =(T5+4·

S)/T1=T1/T1=1,

where i-3 denotes (i-3)-th cylinder, i-2 denotes (i-2)-th cylinder, i-1 denotes (i-1)-th cylinder, and i denotes the previously set learning representative cylinder and i=1.

4. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 3, wherein said second correction coefficient setting means comprises:

m) average value calculating means for calculating the average value T_AVE of the periods of the respective reference signals for all of the engine cylinders corrected according to the first correction coefficients while said misfire occurrence determining means has determined the absence of misfire in all of the engine cylinders; and

n) second correction coefficient calculating means for calculating the second correction coefficients for the respective cylinders from a ratio between the corrected periods of the reference signals according to the first correction coefficients for the respective periods of the reference signals for the cylinders and the average value T_AVE calculated in the average calculating means.

5. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 4, wherein the average value T_AVE is expressed as:

space="preserve" listing-type="equation">T.sub.AVE =(HT2+HT3+HT4+HT5)/4

where HT2 is expressed as HT2=!T2×

KT_i-1, HT3 is expressed as T3×

KT_i-2, HT4 is expressed as T4×

KT_i-3, and HT5 is expressed as T5×

KT_i, and

wherein the second correction coefficients for the respective cylinders are expressed as;

space="preserve" listing-type="equation">KKT.sub.i =HT1/T.sub.AVE

where HT1 is expressed as HT1=!T1×

KT_i.

6. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 5, wherein said first correction coefficient setting means further comprises first correction coefficient storing means for storing the first correction coefficients for the respective cylinders in respective memory regions corresponding to the engine revolution speed derived according to the reference signals from the reference signal generating sensor.

7. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 6, wherein said second sensor comprises a sensor arranged for detecting an engine load and wherein said second correction coefficient setting means comprises second correction coefficient storing means for storing the second correction coefficients for the periods of the respective reference signals in respective memory regions corresponding to the detected engine load and the engine revolution speed.

8. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 7, wherein said misfire occurrence determining means comprises:

o) first correction coefficient learning determining means for determining whether the first correction coefficients have been learned according to the first correction coefficients storing means;

p) second correction coefficient learning determining means for determining whether the first correction coefficients for determining whether the second correction coefficients have been learned according to the second correction coefficients storing means;

q) misfire occurrence determination value calculating means for calculating a misfire occurrence determination value (MISA) according to the periods of the reference signals corrected by the first correction coefficients and by the second correction coefficients according to results of learning determinations of said first correction coefficients and second correction coefficients learning determining means; and

r) misfire occurrence comparing means for comparing the calculated misfire occurrence determination value (MISA) with a reference value (SL) and determining whether the misfire occurs in any one of the cylinders according to a result of the comparison between the misfire occurrence determination value and the reference value (SL).

9. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 8, wherein said misfire occurrence determination value calculating means calculates the misfire occurrence determination value (MISA) as follows:

space="preserve" listing-type="equation">MISA= 3×

(HHT4-HHT5)+(HHT4-HHT1)!/HHT5.sup.3

where HHT4 is expressed as HT4/KKT_i-3, HHT5 is expressed as HT5/KKT_i, and HHT1 is expressed as HT1/KKT_i.

10. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 9, wherein when said misfire occurrence determining means determines that the misfire in any one of the cylinders occurs according to the result of the comparison between the misfire occurrence determination value and the reference value, a warning signal is output to a warning lamp indicating that the misfire occurs.

11. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 8, wherein said misfire occurrence determination value calculating means calculates the misfire occurrence determination value (MISA) as follows when said first and second correction coefficients learning determining means determines that the first and second correction coefficients have not been learned, respectively.:

MISA= 3×

(H4-T5)+(T4-T1)!/T5³.

12. A misfire recognizing apparatus for a multi-cylinder internal combustion engine as claimed in claim 8, wherein said misfire occurrence determination value calculating means calculates the misfire occurrence determination value (MISA) as follows when the first correction coefficients learning determining means determines that the first correction coefficients have been learned and when said second correction coefficient learning means determines that the second correction coefficients have not been learned:

space="preserve" listing-type="equation">MISA= 3×

(HT4-HT5)+(HT4-HT1)!/HT5.sup.3.

13. A method for recognizing a misfire occurrence in a multi-cylinder internal combustion engine, comprising the steps of:

a) generating and outputting a reference signal (REF) for each predetermined crank angle rotation of an engine crankshaft, which angle rotation is expressed by 720°

/n, where n denotes a number of engine cylinders within the engine, and said reference signal including a cylinder number identifying signal indicative of one of the engine cylinders;

b) detecting an engine driving condition other than an engine revolution speed;

c) measuring a period of the reference signal for each predetermined crank angle rotation, the reference signal period corresponding to a combustion state of a corresponding one of the engine cylinders;

d) determining a presence or absence of misfire in each cylinder based on the measured period of the reference signal for each corresponding one of the engine cylinders;

e) determining whether a fuel supply to the engine is cut off or carried out based on the detected engine driving condition;

f) setting a first correction coefficient (KT_i, where i=1 to n in increments of

     1) for each measured period of the reference signals so that stepwise variations (Δ

T) in the periods of the reference signals consecutively measured for all of the cylinders are mutually equal to one another when determining, at the step e), that the fuel supply to the engine is cut off;

g) determining whether, at the step d), the absence of misfire occurs in any of the engine cylinders; and

h) setting a second correction coefficient (KKTi, where i=1 to n in increments of

     1) for each measured period of the reference signals so that the respective periods of the reference signals for all of the engine cylinders, which are corrected according to the first correction coefficients, are equal to an average value (T_AVE) of the respective periods of the reference signals when determining, at the step d), that the fuel supply to the engine is carried out and when determining, at the step e), the absence of misfire in any of the engine cylinders,

wherein said step d) further comprises the steps of;

i) correcting the periods of the respective reference signals continuously measured for all of the engine cylinders according to either or both of the second and first correction coefficients, and

j) determining whether misfire occurs in any of the engine cylinders based on the corrected periods of the reference signals at the step i).