Ignition timing control system and method for an internal combustion
Contents
1. _ RETARD i ANGLE Exo CORRECTION 1 ABRUPT ADVANCE d ANGLE CORRECTION I SAm WHEN KNOCKING IS PRESENT I TIME Dn 112 113 tu 4 658 789 1 IGNITION TIMING CONTROL SYSTEM AND METHOD FOR AN INTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION 1 Field of the Invention The present invention relates generally to an ignition timing control system for a vehicular internal combus tion engine which prevents the occurrence of engine knocking 2 Description of the Prior Art It is desirable to prevent occurrence of engine knock ing which is due mainly to accelerated violent burning of uncombusted gas since knocking brings about energy losses reduction of engine output and applies shocks to all parts of the engine and furthermore increases fuel consumption A conventional system for controlling ignition timing so as to suppress knocking is exemplified by Engine Service Manual 1983 published by Nissan Motor Co Ltd on June 1983 FIGS 1 through 4 show the construction and action of the conventional ignition timing control system dis closed in the above identified Japanese document In FIG 1 1 denotes an engine Intake air is supplied to each engine cylinder via an intake air pipe 3 from an air cleaner 2 while fuel is supplied thereto via a fuel injector 4 according2. d fourth means for correcting the basic timing ad vance angle by a retardation angle so that no knocking will occur during the predetermined transient state when said third means produces said transient indication indicating that the engine is starting to operate in the predetermined transient state and e fifth means for igniting air fuel mixture supplied to the engine at a timing corresponding to the cor rected ignition timing angle 2 The system according to claim 1 which further comprises sixth means for recording the value of retar dation angle correction when knocking is suppressed during the predetermined transient state and storing the recorded value in conjunction with the current engine operating conditions and wherein said fourth means corrects the basic advance angle by a retardation angle value derived from the value stored in said sixth means in conjunction with the current engine operating condi tions 3 The system according to claim 1 which further comprises sixth means for returning the corrected igni tion advance angle toward the basic advance angle side by adding thereto a predetermined advance angle re turn value after said third means determines that the predetermined transient state has ended 4 The system according to claim 3 wherein said predetermined advance angle return value is of the same magnitude as the retardation angle immediately before the end of the predetermined transient state but of t
3. LUY HOSN3S MI X 0MX 9 el 1931 NOIL VHHIA 5NDIOONDI tl 92518 SNDIOONDI Sheet 3 of 11 4 658 789 U S Patent Apr 21 1987 1 000 N 03309 0007 000 0002 0001 I 5555 55 55 52 Ton X UV 20792 DSLT 0S j Gg 9 N 9 3 IV V 319NV ONVAQV 01678 U S Patent Apr 21 1987 Sheet 4 of11 4 658 789 FIG 4 a FUEL d INTAKE AIR FIG 4 b x INTAKE AIR AMOUNT AIR FUEL MIXTURE RATIO RICH FIG 4 c INTENSITY eee 2221 REFERENCE FIG 4 d RETARD ANGLE CORRECTION TIME t3 4 658 789 Sheet 5 of 11 U S Patent 21 1987 HOSN3S gl 315NV 64 p N 8 CC HOLVH3N35 SNVAW 1VNDIS NOILINDE ds NOILINDI i 2 ES MO13HIV z 1 2 1M9I5MVVL 2 NINIL NOILIN I I 1 1 H0123HHO2 I 1 TVAH3LNI AN3ISNVHL HOLV10091V9 NOI103HHOOD HOSN3S 01 9130 NOILVHSIA U S Patent Apr 21 1987 Sheet6of11 4 658 789
4. FIG 6 START Pi CALCULATE SAo YES lt 1 1 NO T YES 1 20 SAm P 5 CALCULATE SA 14 OUTPUT Sp U S Patent 21 1987 Sheet7 of 11 4 658 789 FIG 6 b 2 1 Pe 2 1 YES Pug 0 0 6 SAm lt 0 15 KNOCKING YES PRESENT P20 P19 CORRECT BY CORRECT BY ADVANCE RETARD ANGLE ANGLE Gp U S Patent Apr 21 1987 Sheet 8 of 11 4 658 789 FIG 7 a BASIC FUEL INJECTION AMOUNT Tp FIG 7 75 COUNT VALUE C2 FIG 7 0 RETARD ANGLE CORRECTION SAm ii SAk TIME tu t U S Patent Apr21 1987 Sheet90f11 4 658 789 FIG 8 a START SP1 CALCULATE 540 N SP7 C YES f NO 6 SP 1 SP 10 NO 5 11 1 C2 20 SP 12 SAm SP 3 CALCULATE SA 5 14 OUTPUT Sp 7 U S Patent Apr 21 1987 Sheet 10 of 11 4 658 789 FIG 8 b SP 31 SAm ADF 1 1S NO KNOCKING YES PRESENT 2 SP 35 CORRECT RETARD ANGLE ADF 0 CORRECT BY SLOW ADVANCE ANGLE CORRECT BY ABRUPT ADVANCE ANGLE ep U S Patent Apr 21 1987 Sheet 11 of 11 4 658 789 FIG 9 a BASIC FUEL INJECTION AMOUNT Tp FIG 9 b COUNT VALUE Ci C2 FIG 9 c
5. and if the ignition timing angle reaches the predetermined limit value the control unit resets the flag ADF ADF 0 Hence the ignition timing is corrected slowly thereafter Conversely if ADF 0 in the step SP32 the routine goes to the step SP34 in which the value SAk is updated in accordance with the equation 3 hereinafter referred to as slow advance angle correction and the routine then ad vances to the step 5 13 On the other hand if knocking is detected in the step SP 6 the control unit corrects the angle for retardation in accordance with the equation 2 in the step SP35 in order to suppress knocking and the flag ADF is reset to zero ADF 0 in order to select the slow advance angle correction due to the possibility of knocking and the routine then goes to the step P13 In this way in the third preferred embodiment the correction of the advance angle is carried out appropri ately with the possible occurrence of knocking taken into consideration after the end of the knock induction time interval Tn The engine performance can be fur ther improved by suppressing abrupt changes in engine torque as compared with the first embodiment de Scribed above FIGS 9 a through 9 c are timing charts for the ignition timing control mode based on the above described program flowcharts in FIGS 8 a and 8 5 The processing at the beginning of acceleration transfer is the same as in the first preferred embodiment At the end of
6. transient state when the rate of change of engine load per unit time detected by said first means exceeds a predetermined positive value and there after the rate of change drops to a negative value d fourth means for correcting the basic timing ad vance angle by a retardation angle so that no knocking will occur during the predetermined transient state when said third means determines that the engine is starting to operate in the prede termined transient state and e fifth means for igniting air fuel mixture supplied to the engine at a timing corresponding to the cor rected ignition timing angle 9 The system according to claim 8 wherein said first means comprises sixth means for detecting the number of engine revolutions per unit time seventh means for detecting an intake air quantity and eighth means for calculating a basic fuel injection quantity on the basis of the detection results of said sixth and seventh means 10 A system for controlling the ignition timing of an internal combustion engine comprising a first means for detecting engine operating condi tions b second means for determining a basic ignition advance angle on the basis of the detected engine operating conditions c third means for determining on the basis of the detected engine operating conditions whether the engine operates in a predetermined transient state having a causal relation to the occurrence of knocking wherein said third means det
7. FIGS 6 a and 6 b show a second preferred embodi ment in which a microcomputer using a given program is applied to the present invention It should be noted that the hardware is substantially the same as shown in FIG 1 except that the control unit 16 is embodied by the microcomputer The microcom puter comprises a Central Processing Unit CPU a Random Access Memory RAM a Read Only Mem ory ROM and an Input output Port I O In this embodiment the control unit microcom puter functionally comprises means for detecting the transient state means for setting the advance angle value of ignition timing means for calculating the cor rection value storing means and ignition signal gener s ating means the data used for various calculations being held after the engine 1 stops FIGS 6 a and 6 b together form a program flow chart by which the control unit microcomputer exe cutes the ignition timing control in each ignition cycle First in a step P1 the control unit calculates the basic advance angle value SAo in accordance with the oper ating conditions of the engine 1 This calculation is e g carried out by looking up a corresponding optimum value in a table map plotted versus N and Tp as shown in FIG 2 and as described with regard to the first pre ferred embodiment Next in a step P5 the control unit determines whether the rate of change ATp of the basic fuel injection amount Tp per ignition cycle
8. IGN is equal to or more than 2 msec IGN If ATp 2 msec IGN the control unit recognizes that the engine is operating in a transient state and the control unit sets a count value C of a first counter to 4 C1 4 in a step P3 Thereafter the control unit resets a knock zone flag NF NF 0 and the routine advances to a step On the other hand if ATp 2 msec IGN the routine goes directly to the step P4 The first counter is used in con junction with a second counter to be described later to recognize the knock induction time interval Tn and its set value 4 represents two revolutions of the en gine In addition the knock zone flag NF indicates whether or not there is currently a knock induction time interval Tn When set NF 1 the flag NF means that 20 25 40 45 60 65 8 we are in a knock induction interval Tn and when reset 0 it means that there is no current interval Tn The control unit then checks the value of the first counter in a step If Ci 0 when the first counter is cleared the control unit resets the knock zone flag NF and continues to the step Pe If C1740 the routine goes to the step P7 in which it checks the knock zone flag NF If NF 1 the routine goes to a step Pg If NF 0 the routine goes to a step Po wherein the control unit decrements the count value of the first counter by and then to a step Pio In the step P10 the control unit deter
9. ignition timing is retarded to a value by which knocking can immediately be prevented Conse quently knocking can be prevented even at the zone start timing The interval during which the count value C2 of the second counter drops decrementally from 20 to 0 is defined as the knock induction time interval Tn and specifically corresponds to 10 revolutions of the engine 1 Hereafter the execution flow will normally progress through the normal knocking control processing as only in extreme case will further retard angle correction be necessary since the ignition timing is sufficiently retarded at the zone start timing 112 When the count value of the second counter reaches zero C2 0 at time 113 the control unit recognizes that the knock induction time interval Tn is over and stores the current value SAk into the corresponding memory area as the value SAm and immediately carries out the advance angle correction by updating SAk to 0 FIGS 8 and 8 b together form a program flow chart for the control unit in a third preferred embodi ment in which the advance angle correction is different from that in the second preferred embodiment In FIGS 8 0 and 8 b the contents of steps 5 1 through SP are the same as those steps Pi through P17 in FIGS 6 a and 6 b of the second preferred embodi ment The steps SP3 through 5035 are different from the steps P16 P2o of FIGS 6 Therefore only these different steps will be described bel
10. that it is not in a knock induc tion time interval Tn and the routine goes to a step P16 following which the normal knock control based on the output state of the knocking detecting means is exe cuted In the step P15 the control unit determines whether or not the count value C2 of the second counter is zero If C240 the control unit recognizes that the engine is still operating within the knock induction time interval Tn and control passes to the step Die at which the nor mal knocking control process starts If C 0 in the step Pis the control unit recognizes that the knock induc tion time interval Tn is over In the subsequent step the control unit resets the knock zone flag NF NF 0 and clears the first counter 0 In the next step Pig the final retard angle correction value SAk is stored as the value SAm into the corresponding memory area To correct the advance angle the control unit updates the value SAk to zero SAk 0 in order to return the igni tion timing angle to the basic advance angle value SA SAo and thereafter goes to the step P13 In the normal knocking control process after the routine passes through the step or Pis the control unit determines whether or not knocking has occurred If the engine is currently knocking the routine goes to a step wherein the ignition timing is retarded in accordance with the equation 2 If there is no knock ing No the routine goes to a step P29 wher
11. United States Patent Morita 4 658 789 Apr 21 1987 111 Patent Number 45 Date of Patent ________ gt _ lt _ _ 54 IGNITION TIMING CONTROL SYSTEM AND METHOD FOR AN INTERNAL COMBUSTION ENGINE 75 Inventor Tatsuo Morita Yokosuka Japan Nissan Motor Company Limited Yokohama Japan 73 Assignee 21 Appl No 809 733 22 Filed Dec 17 1985 30 Foreign Application Priority Data Jan 31 1985 JP 4 60 18058 Jan 31 1985 JP Japan 60 18059 51 Int e EE F02P 5 145 52 U S Ch 123 422 123 425 58 Field of Search 123 415 416 417 422 123 423 425 56 References Cited U S PATENT DOCUMENTS 4 428 343 1 1984 Schweikert et al 123 425 4 448 163 5 1984 Yoshida 123 422 4 508 079 4 1985 Komurasaki et al 123 422 4 513 716 4 1985 Haraguchi et al 123 422 KNOCKING DETECTOR KNOCKING SENSOR FOREIGN PATENT DOCUMENTS 3309947 7 1984 Fed Rep of Germany 123 422 58 217775 12 1983 Japan we 123 425 59 168266 9 1984 Japan 123 422 OTHER PUBLICATIONS VG Series Engine Service Manual 1983 Jun 1983 by Nissan Motor Company Limited Primary Examiner Andrew M Dolinar Attorney A
12. and engine 30 40 45 50 60 65 4 performance is degraded at the initial stage of accelera tion In addition since the process of returning ignition timing toward the advance side upon completion of the knock induction time interval Tn is carried out only with small increments ASAa a prolonged reduction of torque injurious to the output performance of the en gine 1 cannot be prevented Therefore the correction of the ignition advance angle needs to be carried out with an improvement in output performance in mind SUMMARY OF THE INVENTION With the above described problem in mind it is an object of the present invention to provide an ignition timing control system which achieves an improvement in engine performance during and or immediately after the above described knocking induction time interval This can be achieved by a system for controlling an ignition timing of an internal combustion engine com prising a first means for detecting engine operating conditions b second means for determining a basic ignition advance angle on the basis of the detected en gine operating conditions c third means for determin ing on the basis of the detected engine operating condi tions whether the engine is starting to operate in a pre determined transient state having a causal relation to the occurrence of knocking d fourth means for correcting the basic timing advance angle by a retardation angle so that no knocking
13. d the exhaust temperature and thus the temperature at the exhaust valve s are increased so that the engine cylin der is subjected to knocking At this time the ignition timing starts to be corrected in a series of steps of value ASAr toward the retardation side for each ignition timing starting at the ignition timing following time t as shown in FIG 4 d The above described correction process continues until the knocking is suppressed at time t3 as shown in FIG 4 c Hence the interval Tn between times ti and ts is the interval during which knocking occurs After knocking intensity drops to an acceptable level at the time 13 the ignition timing starts to be returned toward the advance side The interval Tn is practically limited to within several engine revolu tions after the accelerator pedal is depressed That is to say knocking due to acceleration occurs only within the interval Tn For convenience Tn is referred to as a knock induction time interval It should be noted that although during the time interval Tn knocking actually occurs in the conventional system as shown in FIG 4 c the knock induction time interval also refers to an interval during which there is a possibility of inducing knocking due to a lean air fuel mixture immediately following the onset of acceleration Thus even if engine knocking is suppressed within the knock induction time interval Tn the influence of knocking cannot be eliminated completely
14. d 8 b are integrally a program flow chart of the ignition timing control system in a third preferred embodiment and FIGS 9 a through 9 c are timing charts for explain ing the action of the third embodiment 4 658 789 5 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will be made to the drawings in order to facilitate understanding of the present invention First FIG 5 shows a first preferred embodiment of the present invention In FIG 5 a control unit 1 comprises functionally a transient detector 32 a transient control interval detec tor 33 and a memory 34 in addition to the conventional elements shown in FIG 2 The transient detector 32 calculates the rate of change of engine load ATp rate of change Tp per ignition cycle IGN or per unit time from the output of the Tp calculator 25 If at first ATp gt 2 msec IGN and thereafter ATp drops to nega tive value within a predetermined number of engine revolutions e g 2 revolutions a high level transient determination signal Sk is outputted to the transient control interval detector 33 In other cases non tran sient or stable states the signal Sk is at a low level L In other words when a predetermined initial accelera tion state is detected the signal Sk goes high When no predetermined initial acceleration state is detected the signal Sk goes low It should be noted that detection of the initial acceleration state may be based on changes in
15. ein the ignition timing angle is advanced in accordance with the equation 3 Thereafter the routine goes to the step 4 658 789 9 It should be noted that the lower limit of the cor rection angle value is 15 and the upper limit of the correction angle value is 0 FIGS 7 a through 7 b are timing charts for explain ing the ignition timing control procedure based on the above described program the flowchart of which is shown in FIGS 6 a and 6 b When the acceleration pedal is depressed at a time t11 the basic fuel injection amount Tp is increased so that ATp becomes equal to or greater than 2 msec IGN as shown in FIG 7 a Therefore as shown in FIG 76 the first counter is set to 4 C1 4 and decremented in each of the next few ignition cycles Before the count value C of the first counter reaches zero however i e before the engine 1 has completed two revolutions the value ATp changes to a negative value and the control unit recognizes that the engine is starting to operate in a knock induction time interval Tn and sets the count value C of the second counter to 20 representing an interval Tn of 10 engine revolutions Thereafter the value C2 of the second counter is decremented in each ignition cycle Hence time 112 in FIGS 7 represents the zone start timing The stored value SAm is retrieved for use as the retard angle cor rection value at the time 112 as shown in FIG 7 so that the
16. ermines that the engine is starting to operate in the predeter mined transient state when the rate of change of engine load in each ignition cycle detected by said first means first exceeds a predetermined positive value and thereafter the rate of change drops to a negative value d fourth means for correcting the basic timing ad vance angle by a retardation angle so that no 4 658 789 13 knocking will occur during the predetermined transient state when said third means determines that the engine is starting to operate in the prede termined transient state and e fifth means for igniting air fuel mixture supplied to the engine at a timing corresponding to the cor rected ignition timing angle 11 A method for controlling an ignition timing of an internal combustion engine comprising the steps of a detecting engine operating conditions b determining a basic ignition advance angle on the basis of the detected engine operating conditions c determining on the basis of the detected engine operating conditions whether the engine is starting to operate in a predetermined transient state having a causal relationship to the occurrence of knocking by determining that the engine is starting to operate in the predetermined transient state when the rate of change of engine load per unit time exceeds a predetermined positive value and thereafter the rate of change drops to a negative value d correcting the basic ignition ti
17. esent ignition timing and ASAr a correction value toward the retardation side per ignition cycle On the other hand when the signal Sn is at a low L level no knocking the value is updated in the following equation 3 SAk SAk ASAa 3 where ASAa denotes a correction value toward the advance side per ignition cycle The upper limit of SAk when updating toward the advance side is zero degrees 0 and will never be a positive value exceeding zero degrees The corrector 22 corrects the basic advance angle value SAo with the retardation angle correction value SAk and calculates a final advance angle value SA expressed in the following equation 4 SA SAo SAk 4 The ignition signal generator 23 outputs the ignition signal Sp to the ignition means 8 at a timing correspond 4 658 789 3 ing to the final advance angle SA The high voltage pulse Pi is generated at the same timing to ignite the air fuel mixture Hence if knocking is detected the ignition timing is repeatedly retarded in small increments to suppress knocking and thereafter once the knocking stops the ignition timing is again slowly advanced to hold the optimum combustion state In this case the correction value ASAr is set approximately to 1 and the value of ASAa is approximately set as follows ASAa A SArX 1 10 to 1 15 The reason for this difference in value is that although knocking must be immediately suppressed the return from the reta
18. gent or Firm Schwartz Jeffery Schwaab Mack Blumenthal amp Evans 57 ABSTRACT A system and method for controlling the ignition timing of an internal combustion engine in which a predeter mined transient state which increase the probability of engine knocking is detected a basic ignition advance angle value determined by an engine operating condi tion is corrected by a retardation angle value which is stored when knocking is suppressed during the prede termined transient state and is returned quickly toward the basic advance angle while ensuring that engine knocking will not recur after the predetermined tran sient state is over 13 Claims 18 Drawing Figures DISCRIMINATOR KNOCKING TRANSIENT CONTROL VIBRATION INTERVAL CORRECTION CALCULATOR DETECTOR TRANSIENT STATE DETECTOR TIMING CALCULATOR IGNITION SIGNAL GENERATOR GNITION 4 658 789 Sheet 1 of 11 U S Patent Apr 21 1987 1 d LINN LUY 4 658 789 Sheet 2 of 11 U S Patent 21 1987 8 SNV3W ds HOSN3S Sl ue MO13HIV XMV Ol uo1v1ino1voa di ve YOLVHANAD TWNOIS NOILINODI YOLVINITWS ovs 22 VS HO123HHO2 Xvs 2 HOLVIND1V9 LNNOWY NOIL23HHO2 7 LINN 91
19. he opposite sign 15 20 25 30 40 45 50 55 65 12 5 The system according to claim 3 wherein said predetermined advance angle return value is smaller than the retardation angle immediately before the end of the predetermined transient state but of the opposite sign and said sixth means adds said return value to said corrected ignition angle value in each ignition cycle 6 The system according to claim 3 which further comprises seventh means for detecting knocking after said third means determines that the predetermined transient state has ended and wherein said sixth means determines the advance angle return value in accor dance with the presence or absence of knocking 7 The system according to claim 6 wherein said advance angle return value first has a negatively large value less than zero and thereafter has a negatively small value 8 A system for controlling the ignition timing of an internal combustion engine comprising a first means for detecting engine operating condi tions b second means for determining a basic ignition advance angle on the basis of the detected engine operating conditions c third means for determining on the basis of the detected engine operating conditions whether the engine operates in a predetermined transient state having a causal relation to the occurence of knock ing wherein said third means determines that the engine is starting to operate in the predetermined
20. lculator 21 determines that the engine has entered a knock induction time inter 4 658 789 7 val Tn and so reads the initial correction value SAm from the memory 34 adopting it as the initial retard angle correction value SAk The basic advance angle value SAo is immediately corrected in accordance with the above described equation 4 so as to start retarding the ignition timing Hence actually the ignition timing is retarded immediately following the onset of accelera tion so that no knocking will occur during the knock induction time interval Tn This means that knocking can be prevented even when the engine is most suscepti ble the knock induction time interval Tn which con trasts noticeably with conventional ignition timing con trol methods and thus engine performance can be im proved remarkably without the ill effects of knocking Since in this embodiment the ignition timing is immedi ately updated to 0 to return the ignition timing angle to the optimum advance angle upon expiration of the knock induction interval Tn the reduction of engine output can be minimized It should be noted that although in this embodiment the correction of the advance angle is carried out imme diately by setting the value SAk to 0 0 the ignition timing angle value may be updated incremen tally toward the advance angle side by a predetermined value per ignition cycle for example in increments of 1 or greater
21. load in each ignition cycle first exceeds a predetermined positive value and there after the rate of change drops to a negative value d correcting the basic ignition timing advance angle by a retardation angle so that no knocking occurs during the predetermined transient state and re turning the corrected ignition timing advance angle immediately toward the basic advance angle after the predetermined transient state is over and e igniting air fuel mixture supplied to the engine at a timing corresponding to the corrected ignition timing angle
22. mines whether or not the rate of change ATp is negative If ATp lt 0 the control unit recognizes that the engine has just entered hereinafter referred to as a zone start timing a predetermined transient state 1 knock induction time interval Tn Thereafter the con trol unit executes a retard angle processing routines at steps through On the other hand if ATpZO in the step the control unit recognizes that it is not the zone start timing and the routine goes to the step During the zone start timing the knock zone flag NF is set NF 1 and the count value C2 of the second counter is set to 20 C2 20 in the step P11 In the step the stored correction value SAm is retrieved from memory for use as the initial retard angle correction SAk In the step Pis the ignition timing value SA is derived and the corresponding ignition signal Sp is generated and output in the final step P14 Hence the ignition timing is immediately retarded by the value SAm so that the knocking can immediately be prevented even at the very start of the knock induction interval Tn On the other hand in cases where the routine branches from the steps Ps or to the step Pe the control unit first checks for knocking zone flag NF If NF 1 the routine goes to the step wherein the count value of the second counter is decremented by one and then to step P15 If NF 0 in the step the control unit recognizes
23. ming advance angle by a retardation angle so that no knocking occurs during the predetermined transient state and re turning the corrected ignition timing advance angle immediately toward the basic advance angle after the predetermined transient state is over and e igniting air fuel mixture supplied to the engine at a timing corresponding to the corrected ignition timing angle 12 The method according to claim 11 further com prising the step f of recording the value of retardation 20 25 30 35 45 50 55 65 14 angle correction when knocking is suppressed during the predetermined transient state and storing the re corded correction value in conjunction with the current engine operating conditions and wherein the retarda tion angle is derived from the stored correction value corresponding to the current engine operating condi tions 13 A method for controlling an ignition timing of an internal combustion engine comprising the steps of a detecting engine operating conditions b determining a basic ignition advance angle on the basis of the detected engine operating conditions c determiming on the basis of the detected engine operating conditions whether the engine is starting to operate in a predetermined transient state having a causal relationship to the occurrence of knocking by determining that the engine is starting to operate in the predetermined transient state when the rate of change of engine
24. n be minimized when and or after the knock induction time interval due to a lean air fuel mixture ratio the engine performance can be improved In addition since the ignition timing is immediately retarded in accordance with the previous learning value when the engine enters a knock induction time interval knocking can be prevented immediately and engine performance can be improved Furthermore since an appropriate advance angle correction is carried out after the end of the knock induction interval in each embodiment the reduction of engine output can be minimized and the engine perfor mance can be improved It will clearly be appreciated by those skilled in the art that the foregoing description has been made in terms of the preferred embodiments and various changes can be made without departing from the scope of the present invention which is to be defined by the appended claims What is claimed is 1 A system for controlling the ignition timing of an internal combustion engine comprising a first means for detecting engine operating condi tions including engine load b second means for determining a basic ignition advance angle on the basis of the detected engine operating conditions c third means for producing a transient indication on the basis of the detected engine operating condi tions when the rate of change of engine load first increases by a predetermined amount and then decreases by a predetermined amount
25. n of the knock vibration detector 13 to a determinating reference value Vo If Vn gt Vo the knock discriminator 14 outputs a knock determina tion signal Sn having a high logic level H If Va Vo the knock determination signal Sn turns to the lower level In addition the engine revolutional speed N of the engine 1 is monitored by a crank angle sensor 15 built into the distributor 6 The electrical signals from the air flow meter 10 the knock discriminator 14 and the crank angle sensor 15 are inputted to a control unit 16 The control unit 16 carries out the ignition timing control on the basis of the information from the sensors described above although the control unit 16 also con 20 30 40 45 50 55 60 65 2 trols the fuel injection amount injected by the fuel injec tor 4 the detailed description thereof is omitted FIG 2 is a block diagram of the major functional element of the ignition timing control system The con trol unit 16 comprises functionally a correction amount calculator 21 a corrector 22 an ignition signal genera tor 23 an ignition timing calculator 24 and a Tp calcu lator 25 The Tp calculator 25 receives signals from the air flow meter 10 and crank angle sensor 15 and derives the basic fuel injection amount Tp The basic fuel injec tion amount Tp in units of milliseconds since the fuel injector 4 opens to inject fuel at a fixed rate for an open ing duration determined by a p
26. occur transiently In addi tion the retard angle correction value SAk obtaining immediately before the end of the knock induction in terval of time Tn is stored for later reference i e learned and the learned value is used as the subse quent retard angle correction amount to prevent knocking before it actually occurs thus fully eliminat ing the ill effects of knocking Another consideration is that when the ignition tim ing angle is adjusted to a region in which the frequency of occurrence of knocking is extremely rare as part of the knock suppression process engine output perfor mance is sacrificed if the return to the normal ignition timing angle is slow Therefore in this embodiment since the knock induction time interval Tn is detected on the basis of engine operating conditions and the frequency of occurrence of knocking will always be extremely low upon expiration of the interval Tn en gine output performance is improved by returning the ignition timing to the basic advance immediately after the end of the knock induction time interval Tn That is to say during acceleration the transient state detector 32 detects the initial state of acceleration when the accelerator pedal is depressed and turns the tran sient state determination signal Sk to the high H level Therefore the means for calculating the correction value 43 made up of the transient control interval de tector 33 and the correction ca
27. ow After C2 0 so that the control unit recognizes that the knock induction time interval Tn has ended in the step 515 the routine goes via step SP17 to the step SP3 wherein the current value SAk is stored into the memory as SAm and an advance flag ADF is set ADF 1 Then the routine goes to the step SP16 The advance flag ADF indicates the magnitude of the required advance angle correction after the end of the knock induction time interval Tn If ADF 0 the control unit uses a small value ASAal for the advance angle correction value and if ADF 1 the control unit uses a large value ASAa2 therefor Next the control unit determines whether knocking has occurred in the step 5 16 If no knocking occurs 5 20 35 40 45 55 60 65 10 the control unit checks the status of advance flag ADF in the step SP32 If ADF 1 the routine goes to the step SP33 in which the retard angle correction value SAk is updated in accordance with the following equation 5 hereinafter referred to as abrupt advance angle correc tion and then to the step SP13 SAk SAk ASAa2 5 It should be noted that the advance angle correction value ASAa2 is set as follows ASAa1 ASAa2 SASAr ASAr is the correction value toward the retardation side shown in the equation 2 In the advance angle processing in the step SP33 the ignition timing angle is limited to a predetermined upper limit value a prede termined value less than 0
28. rdation angle to the normal advance angle is best carried out slowly so that the ignition timing angle does not quickly approach the knocking region again However since the conventional ignition timing con trol system is so constructed that once knocking is actu ally detected the ignition timing is retarded it is inevi table that engine performance e g of torque is re duced at the initial stages of knocking Furthermore since the conventional system is so constructed that after the knocking is suppressed the ignition timing is slowly returned to the advance side the ignition timing may be retarded more than is necessary when knocking occurs for example due to a especially lean air fuel mixture Consequently it is necessary to improve the conventional ignition timing control system in order to enhance engine driving performance In more detail when acceleration is ordered via an accelerator pedal at a time t as shown in FIG 4 a the increase in the fuel supply lags slightly behind the change in the supply amount of intake air e g the in crease in the fuel supply starts at a time t following the time ty This delay introduces a temporary leanness to the air fuel mixture ratio the air fuel mixture becomes leaner than the stoichiometric ratio as shown in FIG 4 b Consequently this causes relatively intense knock ing as shown in FIG 4 c This is because the combus tion speed is slower for such lean air fuel mixtures an
29. s for detecting transient states such as brief acceleration Numeral 43 denotes means for calculating the correc tion value which comprises the correction calculator 21 and transient control interval detector 33 The memory 34 serves as data storing means Numeral 44 denotes means for setting an advance angle which comprises the corrector 22 the ignition timing calculator 24 and the Tp calculator 25 The ignition signal generator 23 serves as means for generating the ignition signal Sp The operation of the ignition timing control system shown in FIG 5 will be described below In general proper ignition timing control can prevent or at least quickly suppress knocking In one such igni tion timing control method the ignition timing angle is advanced in the absence of knocking When knocking occurs however the ignition timing is retarded Conse quently the combustion state is so controlled as to pro vide an optimum state of combustion with a low proba bility of engine knocking However since it is a prerequisite to detect the occurrence of knocking in such an ignition timing control system it is very diffi cult to eliminate the ill effects of knocking at the initial stage of knock suppression However if occurrences of knocking can be pre dicted knocking can be prevented even from the initial stages The knock induction time interval Tn in this embodiment is accurately predicted by detecting situa tions in which knocking may
30. t waiting for the change in the knock determination signal Sn to the high H level The correction calculator 21 outputs the stored value SAm to the corrector 22 as a retard angle correction SAk In addition during the knock induction time interval Tn the value of SAk is updated in accordance with the knock determination signal Sn from the knock discriminator 14 as shown in equations 2 and 3 Upon expiration of the knock induction time interval Tn the ignition timing value SA is immediately returned to the basic advance angle value SAo with a predetermined return angle in this embodiment the absolute value thereof equals that of SAk immediately before the knock induction time interval Tn is ended but with the sign reversed That is to say the value of SAk 25 35 40 45 55 65 6 is updated to zero 0 immediately after the end of the knock induction time interval Tn Furthermore immediately before the knock induction time interval Tn expires the retard angle correction value SAk is stored in the memory 34 as the correction value SAm It is noted that in FIG 5 numeral 41 denotes means for detecting engine operating conditions comprising an airflow meter 10 and a crank angle sensor 15 Numeral 42 denotes means for detecting engine knocking which comprises a knocking sensor 12 a knocking vibration detector 13 and a knocking discriminator 14 It is also noted that the transient state detector 32 serves as mean
31. the knock induction time interval Tn at the time 113 the current value of SAk is stored as SAm as indicated in FIG 9 c Then begins the abrupt ad vance angle correction at each ignition cycle so that is updated sequentially toward the initial value of 0 relatively quickly Hence after the knock time interval Tn the ignition timing angle is quickly and incrementally advanced so that a shock due to return of the ignition timing angle to the advance side can appro priately be reduced so that the consequent abrupt change in engine torque can be suppressed Since the conventional ignition timing control method corrects the advance angle slowly at increments of ASAa as shown in FIG 4 d the engine torque remains signifi cantly reduced for a relatively long period of time which contrasts sharply with this embodiment In addition when knocking occurs e g at a timing ot during the return of the ignition timing to the ad vance angle side the ignition timing can be corrected so as to suppress the recurrence of knocking as indicated in broken lines in FIG 9 c In this way since knocking is suppressed immediately upon detection even during the abrupt advance angle correction reduction of engine performance can be minimized and the ignition timing 4 658 789 11 can be advanced to the greatest possible advance angle so that the output performance of the engine 1 can be guaranteed Since the drop in torque ca
32. the opening angle of the engine throttle valve or changes in the intake manifold negative pressure in place of the changes in Tp described above The transient control interval detector 33 detects the knock induction time interval Tn caused by a temporar ily lean air fuel mixture ratio during the acceleration period The transient control interval detector 33 marks an interval of time starting from when the transient determination signal Sk first goes high and lasting for a predetermined number of engine revolutions e g ten revolutions the knock induction time interval Tn and outputs a signal during this period to the correction amount calculator 21 The correction calculator 21 serves to send a retard angle correction value SAk to a memory 34 after knocking has been suppressed in addition to the func tions it performed in the conventional ignition timing control system The memory 34 thus learns the up dated value of SAk corresponding to the instantaneous engine operating conditions and stores it into a corre sponding memory area as a correction memory value SAm It should be noted that the memory 34 is non volatile and therefore holds the values SAm after the engine 1 stops Furthermore the correction calculator 21 immedi ately reads the stored correction amount value SAm from a memory area of the memory 34 corresponding to the current engine operating state in response to the knock induction time interval signal Tn withou
33. to an injection signal Si Each cylinder is provided with an ignition plug 5 which re ceives a high voltage pulse Pi from an ignition coil 7 via a distributor 6 at every ignition timing The ignition coil 7 the distributor 6 and a plurality of ignition plugs 6 constitute ignition means 8 for igniting and burning the air fuel mixture supplied to the engine The ignition means 8 generates and discharges the high voltage pulse Pi in accordance with an ignition signal Sp In addition the air fuel mixture within each engine cylinder is ig nited and exploded in response to discharge of the pulse Pi and the resulting exhaust gases are exhausted to at mosphere via an exhaust pipe 9 In addition the rate of flow Qa of intake air is de tected by means of an air flow meter 10 and controlled by means of a throttle valve 11 installed within the intake air pipe 3 Vibrations Ve in the engine body 1 are detected by a knock sensor 12 An output signal from the knock sensor 12 is inputted to the knock vibration detector 13 The knock vibration detector 13 comprises a BPF Band Pass Filter which enables the passage of only a frequency range corresponding to vibrations due to knocking and an integrator which generates a volt age Vn Vn 0 through 5 V proportional to the inten sity or amplitude of knocking vibrations generated per combustion stroke and outputs this voltage to a knock discriminator 14 The knock discriminator 14 compares the output voltage V
34. ulse duration is derived from the following equation 1 and the results of this calculation are outputted to the ignition timing calcula tor 24 Tp KxQa N 1 where K is a constant The ignition timing calculator 24 receives the signal from the crank angle sensor 15 The ignition timing calculator 24 looks up a basic advance angle value SAo from a three dimensional table map using known table look up techniques and outputs the basic advance angle SAo to the corrector 22 Since the basic advance angle value SAo corresponds to an optimum ignition timing according to engine operating conditions it is repre sented by a crank angle value before top dead center in the compression stroke of a specific engine cylinder The corrector 22 furthermore receives a retard angle correction value SAk from the correction amount cal culator 21 The correction amount calculator 21 calcu lates the retard angle correction value SAk 0 to correct the basic advance angle value SAo toward the retardation side depending on the presence or ab sence of knocking The initial value of the retard angle correction value SAk is set to 0 and when the knocking discrimination signal Sn is at its high H level the value SAk is calculated from the following equation 2 for each ignition timing SAk SAk ASAr 2 where SAk denotes the retard angle correction amount from the previous ignition timing SAk a retard angle correction amount for the pr
35. will occur during the predetermined transient state when the third means determines that the engine is starting to operate in the predetermined tran sient state and e fifth means for igniting air fuel mix ture supplied to the engine at a timing corresponding to the corrected ignition timing angle BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present inven tion may be obtained from the following description taken in conjunction with the attached drawings in which like reference numerals designate corresponding elements and in which FIG 1 is a schematic drawing of an entire conven tional ignition timing control system FIG 2 is a functional block diagram of the ignition timing control system shown in FIG 1 FIG 3 is a graph of advance angle in units of BTDC with respect to an engine speed N in units of RPM and basic fuel injection amount Tp in units of msec FIG 4 a through FIG 4 d are timing charts for explaining the action of the conventional ignition con trol system shown in FIGS 1 and 2 FIG 5 is a functional block diagram of an ignition timing control system in a first preferred embodiment according to the present invention FIG 6 a and FIG 6 b are integrally a program flowchart for the ignition timing control system in a second preferred embodiment FIGS through 7 are timing charts for explain ing the action of the second preferred embodiment FIGS 8 a an
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