JPS6212385B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an engine control method that performs feedback control to optimize engine control elements such as ignition timing and air-fuel ratio, which are elements that determine the combustion state of an internal combustion engine. In this type of feedback control of an engine, a value corresponding to the feedback control amount of a control element such as ignition timing is rewritten and stored in a storage device as a feedback map value for each engine operating state classification,
Among the stored map values, the map value corresponding to the engine operating state at that time is used to evaluate the feedback factor of the control element and calculate the feedback control amount to control the control element.
It has begun to be proposed for the reason of improving control responsiveness during engine transients. However, in the above control method, the stored feedback map value does not change unless it is newly modified or rewritten by the feedback factor evaluation process of the control element. Therefore, old past values remain as map values for operating state categories that are not operated for a long time. However, the optimum value of the air-fuel ratio including the ignition timing and the amount of fuel supplied as control elements changes depending on engine conditions such as cooling water temperature and environmental conditions such as atmospheric conditions. Therefore, past map values that remain unmodified may not be compatible with current engine and environmental conditions. Therefore, the present invention is characterized in that the stored feedback map value is rewritten so that it converges to the target value as time or engine rotation progresses, regardless of the feedback factor. It is desirable that the target value be a value that can provide the quickest feedback control to the optimum value of a control element such as engine ignition timing, which changes due to various factors with the passage of time or engine rotation. For example, if the memorized feedback map value has positive and negative values, and the optimal value of the control element (feedback control amount) takes positive and negative values in a completely chaotic manner as time passes, the map value may change due to long-term feedback. If it is not changed, it is preferable to set the target value to 0 because by setting this map value to 0, the average time required to bring the feedback control amount close to the optimum value of the control element can be minimized. Hereinafter, an embodiment will be described in which the present invention is applied to a device that performs feedback control of ignition timing as a control element that determines the combustion state using an engine knocking signal as a feedback factor. In Fig. 1, 1 is a 4-cylinder 4-stroke engine;
2 is a knock detector fixed to the engine 1 and detects the characteristic engine vibration when knocking occurs; 3;
is a starter, and 31 is a starter switch. 4 is a rotation sensor that measures the rotation angle position of the engine 1, which generates a top dead center signal when the engine 1 rotates and reaches the top dead center position, and also divides one engine rotation equally from the top dead center position. A rotation angle signal is generated each time the crank angle is rotated by a certain crank angle (for example, 7.5 degrees in this embodiment). A pressure sensor 21 is built into the control computer 6, and pressure is transmitted from the intake manifold 12 of the engine 1 to a pressure input port through a pipe 13 to measure the intake manifold pressure Pm. 5 is a known fuel supply device. Reference numerals 7 and 8 designate an ignition coil and an igniter, respectively, as ignition actuators that use two coils and eliminate a distributor. The control computer 6 determines the engine rotation speed N from the time interval at which the rotation angle pulses generated by the rotation sensor 4 occur, and also calculates the intake manifold pressure from the output voltage of the pressure sensor 21 to determine the operating state of the engine. At the same time, the knocking occurrence state is detected from the output signal of the knock sensor (knock detector) 2, and the ignition timing is controlled. Also,
In order to control the ignition timing to a specific value when starting the engine, the voltage supplied from the starter switch 31 to the starter 3 is input to the control computer 6 as a starter signal. In addition, since the energization time of the ignition coil is changed according to the battery voltage, the battery voltage is sent to the control computer 6 as a battery voltage signal.
be taken into account. Reference numeral 15 denotes a power source that generates power at a voltage required by the control computer 6 from the voltage of a battery 19 mounted on the vehicle. Next, according to FIG.
will be explained in detail. 60 is a central processing unit (CPU) that calculates the ignition timing, and uses TMS9900 manufactured by _TI with a 16-bit configuration. Reference numeral 70 indicates a read-only memory unit (ROM) that stores control programs and control constants, and 69 indicates a temporary memory unit (RAM) that is used to store control data while the CPU 60 is operating according to the control program. 61 is an interrupt control unit which notifies the CPU of the occurrence of an interrupt with three levels of priority. The interrupt factors in this embodiment include an interrupt caused by the generation of a rotation angle signal pulse from the engine rotation sensor 4;
There are three types of interrupts: a program interrupt which is caused by the CPU 60 itself setting the level of the program interrupt output port of the digital input/output port 64 to "0" level, and a timer interrupt which is caused by the timer every 8 milliseconds (ms). The timer section 62 is composed of a 16-bit counter that counts an 8 μs clock signal and a latch that stores and holds the counter value every time a rotation angle signal pulse of the rotation sensor 4 is generated. Therefore, in the interrupt processing for generation of rotation angle pulses, the CPU 60 reads the value of the crank angle counter section 63 to know the rotation angle position of the engine, reads the latch value of the timer section 62, and repeats this operation for two rotations. By determining the difference between the latch values at each angular position, it is possible to measure the time it takes for the engine to rotate between two rotational angular positions, and also to measure the engine speed. The crank angle counter section 63 is a counter with a lower digit in decimal notation and an upper digit in 4 decimal notation, and counts up based on the rotation angle signal of the rotation sensor 4, and when the next rotation angle signal is generated after the generation of the top dead center signal. The counter is reset to the value "0" and synchronized with the engine rotation. Therefore, the value of the crank angle counter is
By reading it out by the CPU, the engine rotational angular position can be determined in units of 7.5 degrees of crank angle. The digital input/output port 64 is a port used for inputting and outputting logic signals, and in order to recognize that the starter switch 31 is turned on when starting the engine, the digital input/output port 64 is a port used for inputting and outputting logic signals. Enter your level. It is also used to generate a program interrupt signal to be supplied to the interrupt control section 61. As is well known, the knock detection circuit 65 internally generates a knock detection pulse signal when the instantaneous value of the knock signal greatly exceeds the average level, and counts the number of pulses for a period designated by the CPU 60. The analog input port 67 is for measuring the voltage value of an analog signal, and is connected to the output voltage signal of the pressure sensor 21 that measures the intake manifold pressure of the engine 1 and the battery voltage for correcting the energization time of the ignition coil 7. Analog-to-digital (A/D) conversion of voltage. The energization ignition control section 68 energizes the two coil current actuator circuits of the igniter 8 and generates an ignition signal. This energization ignition control section 68
has several down counters, and is instructed by the CPU to determine which ignition coil 7 should be energized and ignited, and to determine the crank angle counter value and down count value at which the down counter should start counting. When the value becomes "0", the #1 coil energization signal and the #2 coil energization signal are set to level "0" for energization and to level "1" for ignition. 71 is a common bus,
The CPU carries control and data signals on this bus signal line to control peripheral circuits and send and receive data. The configuration, operation, and control method of the control program of this embodiment will be explained below.

[Table] As shown in Table 1, the control program consists of four levels of processing: three types of interrupt processing routines that have a priority relationship and a base routine that is constantly executed when no interrupt processing is performed. In the interrupt processing routine, processing that needs to be performed in synchronization with engine rotation and elapsed time is performed. First, the gear interrupt processing routine shown in FIG. 14 will be explained. The gear interrupt signal is generated every 7.5 degrees of crank rotation angle, with the top dead center position of cylinder #1 or #4 being 0 degrees. In the gear interrupt processing routine, first, in step 1100, the value of the crank angle counter is read from the crank angle counter section 63, and the rotational angular position of the engine 1 is determined. Next, in the energization ignition processing at step 1200, data is supplied to the energization ignition control unit 68 for control in accordance with energization ignition control data calculated by a program interrupt to be described later. Next, in step 1300, fixed position processing is performed to perform processing at a fixed angular position. FIG. 15 shows a flowchart of the energization ignition process in step 1200. First step 12
At 05, it is determined whether the engine has currently reached the angular position at which to start counting down to start energizing the #1 coil of the two ignition coils 7,
If the judgment is “YES”, step 1210 #1
At the same time as setting the initial value of the down counter for coil energization, down counting is started. In this embodiment, this down counter counts down the clock signal for 8 μs and when the value reaches "0", it sets the #1 coil energization signal to "0" and starts energizing. In step 1215, it is determined whether the engine has reached the angular position to start counting down for ignition of the #1 coil, and if the determination is "Yes",
At step 1220, the initial value of the down counter for energizing the #1 coil is set and at the same time down counting is started. In this embodiment, this down counter counts down with an 8 μs clock signal, and when the value reaches "0", stopping the energization of the ignition coil corresponds to ignition, so the energization signal of the #1 coil is When set to logic "1", energization of ignition coil #1 is stopped. Steps 1225 and 12 for #2 coil as well.
Similarly, energization ignition control is performed at 30, 1235, and 1240. Next, the fixed position processing in step 1300 will be explained. In the energization ignition process, the angular position at which the process effectively operates varies depending on the value calculated by the program interrupt, whereas in the fixed position process, the process is performed at a predetermined angular position. FIG. 4 shows at which rotational angular position the fixed position process 1300 is performed. Crank angle 0~60
Measure the rotation time to rotate a 60 degree crank angle at 180 to 240 degrees. Measure the intake manifold pressure at 0 and 180 degrees. Angle 22.5~60 degrees,
Count the knock detection pulses from 202.5 to 240 degrees. Also, a program interrupt is generated at 60 and 240 degrees, and the program interrupt processing routine is activated. 16th
A flowchart of this fixed position processing 1300 is shown in the figure. In step 1310, the crank angle is determined,
0, TDC treatment 1320 at 180 degrees, 22.5,
Perform 22.5 degree processing 1330 at 200.5 degrees, 60 degrees,
Perform 60 degree processing 1340 at 240 degrees, and do nothing else. FIG. 17 shows a flowchart of the TDC processing 1320. In step 1321, the timer section 6
The timer latch value of step 2 is taken in as TP1, and then in step 1321, the A/D converted value of the intake manifold pressure Pm is taken in. FIG. 18 shows a flowchart of the 225 degree processing 1330. In step 1331, the signal port of the digital input/output port 64 is set to "0". As a result, the knock detection circuit 65 starts counting knock detection pulses. FIG. 19 shows a flowchart of the 60 degree process 1340. At step 1341, the timer latch value is fetched and set as TP2. In step 1342, the 60 degree crank angle rotation time Tm is determined using equation (1). Tm=TP2-TP1...(1) Digital input/output port 6 in step 1343
The signal output port No. 4 is set to level "1" and counting of the knock detection pulses is completed. Further, in step 1344, the program interrupt output port of the digital input/output port 64 is set to level "0" and then set to level "1" again to generate a program interrupt signal and start the program interrupt processing routine. FIG. 20 shows a flowchart of program interrupt processing. At step 2100, the ignition timing to be applied to the current operating condition is calculated based on the feedback results calculated in the base routine described below. Actual control of the energization ignition control section is performed by the gear interrupt processing routine as described above. In step 2200, when the feedback flag _fFB is "1", the start of feedback is instructed in the check evaluation process in step 2300, and the feedback process such as map rewriting, which will be described later, has not yet been completed. Therefore, the program interrupt processing is ended without performing the check evaluation in step 2300. When the flag _fFB is not "1", the value is "0", and at this time, the start of feedback is not instructed,
Since the feedback processing is not in progress, the knock evaluation processing of step 2300 is performed. Flag f _FB
The reason why nok evaluation is not performed when is "1" is because the control conditions are not clear even if nok evaluation is performed while map rewriting is in progress.
This is because the feedback method becomes complicated,
This is because the stability of feedback control may be impaired. In the knock evaluation process of step 2300, it is determined whether or not feedback processing should be started based on the count value of the knock detection pulses of the knock detection circuit 65 and the ignition circuit in which no knock is detected, and the base routine processing actually performs the feedback processing. Activate the routine. To activate, set flag _fFB to “1”. Here, a method of calculating ignition timing in this embodiment will be explained. FIG. 3 shows a graph of a torque curve with respect to ignition timing at a certain engine speed. Ignition timing is expressed in angle before top dead center (degrees BTDC), and the larger the value, the more advanced the ignition timing is. Torque curve 1 indicates a state where the throttle valve is close to fully open, and MBT1 is MBT (M _I
N _I MUM ADVANCE FOR BEST TORQUE)
The ignition timing at which knock starts to occur in this case is indicated as knock limit 1. M.B.T.
It is best from the standpoint of engine efficiency and fuel efficiency to ignite the ignition at this point, but if knocking occurs, it will have a negative effect on the engine itself, and the unique sound produced will not be good for the driver's hearing, so the knocking limit or knocking limit should be set. It is customary to set the ignition timing to a slightly more retarded side. Torque curve 2 shows the relationship between torque and ignition timing when the throttle valve is in a half-open state. Display MBT and Knock Limit as MBT2 and Knock Limit 2. In this case, the knock limit is
Since it is on the advance side of MBT, it is best to ignite at MBT. Therefore, in this embodiment, MBT is set as the maximum advance ignition timing, and feedback control is performed from this value to the retard side using the output signal of the knock sensor. The ignition timing calculation formula is shown in equation (2). θx=θ _PP -θ _FM -Pxθ _T ...(2) θx: Final ignition timing (degrees BTDC) θ _PP : Fixed map advance angle θ _FM : Feedback map value P: Learning coefficient θ _T : Feedback retard amount Hereinafter, how to obtain each term in equation (2) will be explained according to the flowchart of the ignition timing calculation process 2100 in FIG. 21. In step 2105, the engine rotational speed N is determined from the 60 degree crank angle rotation time Tm calculated in the gear interrupt process using equation (3). N (rpm) = 10 ⁷ × 1/Tm (microseconds) ... (3) In step 2110, the A/D conversion value Vpm of the intake manifold pressure taken in by the gear interrupt processing is
Find the intake manifold pressure from equation (4). Pm (mmHg) = A ₁ × Vpm + A ₂ ... (4) A ₁ , A ₂ : Conversion coefficient In step 2115, it is determined whether the starter is activated when starting the engine, and if "YES", the ignition timing is changed to 7.5 in step 2120. degree (energizing time 11.5
Set it to a fixed value of milliseconds and proceed to step 217.
Proceed to step 5. If the starter is not operating, the process advances to step 2125. The fixed map advance angle (θ _PP ), the feedback map value (θ _FM ), and the number of feedbacks (N _FB ) for determining the learning coefficient P are calculated using the engine speed (N) and intake manifold pressure Pm as two axes. Fixed advance angle map (θ _PP map, see Figure 5), Feedback map (θ _FM map, see Figure 6)
(See figure) It is determined from the feedback frequency map ( _NFB map, see Figure 7). The θ _PP map is a fixed data map that stores MBT, and the θ _FM map and N _FB map are variable data maps that are rewritten by feedback or the like as control progresses. The θ _FM map stores the amount of retardation from the MBT for each operating state classification, and the N _FB map shows how much each value in the θ _FM map has been rewritten as a result of past feedback. The horizontal axis of the θ _PP map in Figure 5 is the engine speed N
In the low rotation range of less than 1000 rotations, the increment of the engine rotation speed N is small with respect to the column number X corresponding to the horizontal axis, and there is no overall proportional relationship (single linear function type). The vertical axis of the θ _PP map is the intake manifold pressure Pm, and the line number Y corresponding to the vertical axis
The relationship is proportional to (single linear function type). The θ _FM map in Fig. 6 and the N _FB map in Fig. 7 are defined only for the high load region of the θ _PP map in Fig. 5, but for the defined region, engine rotation, intake manifold The relationship between pressure, column number X, and row number Y is the same as the θ _PP map. θ _PP map, θ _FM map, N _FB map to θ _P
When determining the values of _P , θ _FM and N _FB , use X and Y. Therefore, in step 2125 of FIG. 21, the number of revolutions (N) is converted into column number X according to equation (5). Xi is a column number and is an integer, and the decimal point of X indicates the middle rotation speed between the rotation speeds specified on the horizontal axis of the map. In step 2130, the intake manifold pressure
It is converted from pm to line number Y according to equation (6). Yi is a row number and an integer. The decimal point part of Y indicates the intake manifold pressure that is between the intake manifold pressures specified on the vertical axis of the map. In step 2135, the fixed map advance angle θ _PP is set as
The X and Y values obtained in steps 2125 and 2130 are read from the fixed advance angle map (θ _PP map), and are determined by 4-point interpolation calculation using equation (7). In step 2140, a feedback map value θ _FM is calculated from the feedback map (θ _FM map) in X and Y by four-point interpolation using equation (8). In step 2145, the number of feedbacks N _FB is calculated from the feedback number map (N _FB map) in X and Y by four-point interpolation using equation (9). Each value in the feedback count map represents how much the value of the θ _FM map with the same (X, _Y ) number has been feedbacked in the past. The procedure for rewriting each value of the _NFB map will be explained in the base routine section below. In step 2150, the number of feedback N
Learning coefficient map (P map) as shown in Figure 9 on _FB
Search for learning coefficient P. As is clear from the learning coefficient map (P map) in FIG. 9, the learning coefficient P becomes smaller as the number of feedback increases. This is because it is thought that as feedback is performed, each map value of the θ _FM map approaches the optimum feedback value, and the amount of feedback is reduced to improve control stability. In step 2155, a feedback angle _θFB map as an ignition timing feedback control amount is determined using equation (10). θ _FB = θ _FM + Pxθ _T ……(10) The term Pxθ _T exists because, as will be explained later, the distribution of engine speed and intake manifold pressure during the knock evaluation period is within a certain range, such as during acceleration/deceleration. This is because if the term does not exist, there will be no feedback to the feedback map value _θFM , so feedback is provided by this term. In order to prevent the ignition timing from advancing beyond MBT, it is checked in step 2160 that _θFB is not negative, and if it is negative, it is set to 0 in step 2165. In step 2170, the final ignition timing θx is set to (11)
Calculate by formula. θx=θ _PP −θ _FB (11) In step 2175, in the case from step 2170, the calculation is performed using the 8 ms interrupt processing routine described later. Calculate the coil energization angle from the coil energization time To _N and the engine speed to determine the final ignition timing θ.
Find the energization start angle θo _N from x, coil #1,
Regarding #2, the starting angular position of the down-count for energization and the initial value to be set to the down counter, and the starting angular position of the down-counting for ignition and the initial value to be set to the down counter are calculated. FIG. 22 shows the knock evaluation processing step 230.
0 is shown. In step 2305, the knock interval, which is a software counter of the number of ignitions since the start of knock evaluation in the base routine described later, is set.
Increase WNO by 1. In steps 2310 and 2315, it is determined whether the engine speed N and intake manifold pressure Pm are in a steady state within a certain difference △N, △Pm from the comparison reference values Ns, Pms, respectively, and the answer is "NO".
If so, in step 2325, the steady state flag _fST is set to the value "0". If it is in a steady state, in step 2320, in order to calculate the average value of the column number X corresponding to the engine rotation speed N during the knock evaluation period and the row number Y corresponding to the intake manifold pressure Pm, the integrated value Σx of X and Y is calculated.
Add the current X and Y to Σy. In step 2335, 22.5
-60 degrees and between 200.5 and 240 degrees, the knock pulse count value Nkpls is taken from the knock detection circuit 65 that counts the knock detection pulses, and in step 2340, the knock pulse count value Nkpls is acquired.
It is determined whether the value of Nkpls is larger than the comparison reference value kp, and if "YES", it is assumed that a knock has been detected and the feedback flag _fFB is set to "1" in step 2350. If “NO” in the judgment step 2340, the number of ignitions after the start of knock evaluation in step 2345 is equal to the predetermined number of ignitions Nmax (for example,
100 ignitions) has elapsed, and if it has elapsed, the feedback start flag _fFB is set to "1" in step 2350, and the base processing routine starts feedback. Step 2
If the determination at step 345 is "NO", no action is taken and the knot evaluation process is ended. FIG. 23 shows a flowchart of the 8 millisecond (ms) interrupt processing routine. In step 3100, the battery voltage V _B is taken from the analog input port 67, and in step 3200, the battery voltage V _B is taken in.
According to the energization time characteristics shown in FIG. 13, the coil energization time To _N is calculated. Next step 33
00, 1 is added to the counter _C1M on the software for creating a time signal every minute. FIG. 24 shows a flowchart of base processing. In step 4100, initialization processing is performed to clear the θ _FM map and N _FB map, clear the counters on the software, and set initial values of parameters and the like. In step 4200, interrupts are enabled. In step 4300, it is determined whether the feedback flag _fFB , which is set by the program interrupt processing and instructs the start of feedback processing, is "1". If "Yes", the feedback processing is performed in step 4400. . If “NO”, do nothing and proceed to step 450.
Go to 0. At step 4500, the counter _C1M on the software for 1 minute becomes _K1M (=60 seconds/8ms=750)
Determine whether it is larger than the
Since the number of minutes has elapsed, forgetting processing in step 4600 is performed. FIG. 25 shows a flowchart of the feedback processing 4400. In this process, the θ _FM map feedback does not immediately feed back the map feedback data generated from the data of a certain knot evaluation period, but feeds back to the map after the next knot evaluation period ends, and is delayed by one knot evaluation period. Let's do it. This is because the feedback angle θ _{FB is}
It is expressed as = θ _FM +P×θ _T , and as described later, θ _FM
This is because approximately an amount of P×θ _T is fed back to the θ FM map, so the feedback angle θ _FB is approximately twice as much as when it is not fed back to the θ _FM map. In step 4405, the operating state during the knock evaluation period is determined by the average value of the column number X and line number Y used in the ignition timing calculation 2100 of the program interrupt processing using equations (12) and (13). = ΣX / WNO ... (12) = ΣY / WNO ... (13) Σ (number of ignitions) θ The point at coordinates (,) on _{the FM} map is used as the feedback center when performing map feedback. In step 4410, the center of the operating state ()
is within the defined _feedback region of the θ _FM map as shown in FIG. In step 4425, the steady state flag f _ST
is “1”, and if “YES”, step 44
At 30, the map feedback flag f _MFB is set to "1". If "NO", the process advances to step 4435, and the map feedback flag _fMFB is set to "0". Therefore, in this case, the feedback amount _.theta.T is calculated, but it is not fed back to the map because the map feedback flag _fMFB , which indicates whether map feedback is to be performed, is not "1". If it is determined in step 4410 that it is not within the feedback region, θ _T is set to "0" in step 4420, and the process proceeds to step 4435, in which the flag _fMFB is set to 0. In step 4440, it is determined whether the value of the map feedback flag 2f _MFB2 to which the value of the flag f _MFB of the previous feedback processing has been transferred is "1". If "YES", the map feedback flag is transferred in step 4445. Process. At this time, the data used for map feedback is the data calculated in the previous feedback process. Step 4
If the determination at 440 is "NO", the process proceeds to step 4450 without performing map feedback. In step 4450, the map feedback data calculated this time is set as a parameter for map feedback in the next feedback process. ₂ : X coordinate of the feedback center used for map feedback ₂ : Y coordinate of the feedback center used for map feedback θ _T2 : Feedback amount f used for map feedback _MFM2 : Map feedback flag 2 Step At step 4455, processing for starting the knot evaluation is performed. That is, the knock interval
WNO, ΣX, ΣY are cleared to "0", feedback flag f _FB is set to "0", steady state flag f _ST is set to "1", steady state judgment comparison reference value Ns, Pms is the current engine rotation speed N, intake manifold pressure
Configure Pm settings. FIG. 26 shows a flowchart of the feedback amount θ _T calculation process in step 4415. In this example, the knock interval is the number of ignitions from the start of the knock evaluation to the end of the knock evaluation.
The feedback amount θ _T is determined by WNO. The knock evaluation period ends when a knock is detected or the number of aborts Nmax has elapsed. FIG. 8 shows a graph of the relationship in which the feedback amount θ _T is determined from the knock interval WNO. _θT
When the value of θ T is positive, it is feedback toward the retard side, and when the value of θ _T is negative, it is feedback toward the advance side. Basically, the retard side is a straight line a ₂ and the advance side is a straight line b ₂
determined by the graph of Actually, the straight lines a ₂ , c,
The values of WNO and _θT at the end points of _b2 are stored as a basic feedback amount θf map, and θf is obtained by linear interpolation calculation from this map using the knock interval WNO. This θf is multiplied by a correction coefficient, which will be described later, to obtain _θT . Also, when a large angle must be retarded, the larger the value of the _a2 part of the graph in Figure 8, the faster the response to the retard side, and when a large angle must be advanced, The larger the value of _b2 in the graph, the faster the response to the advance angle side. Therefore, in this example, if the retardation continued in the past,
If the retard angle characteristic is changed from a ₂ to a ₃ and the advance angle has continued in the past, the advance angle characteristic is changed from b ₂ to b ₃ to speed up control responsiveness. Further, when the feedback target value is reached where the advance angle and the retard angle continue alternately, the stability of the ignition timing is improved by reducing the amount of feedback of the retard angle and the advance angle. Therefore, in this embodiment, when the advance angle and the retard angle continue alternately, the retard angle characteristic is changed from a ₂ to a ₁ , and the advance angle characteristic is changed from b ₂ to b ₁ to improve control stability. . This will be explained using the flowchart of the feedback amount θ _T calculation process 4415 shown in FIG. 26. In step 4415-1, the knock interval
θf is determined by interpolation calculation from the θf map using WNO. In step 4415-2, it is determined whether the steady state flag f _ST managed by the program interrupt processing is "0" or "1", and if it is unsteady at "0", the retardation characteristic is determined in steps 4415-3 and 4415-4. Both the parameter ia and the lead angle characteristic parameter ib are set to 0, and in step 4415-5, the basic feedback amount θf is directly set as the feedback amount _θT . If it is determined in step 4415-2 that the value of the steady state flag f _ST is "1" indicating steady state, the value of the current feedback amount θf is checked in step 4415-6. If θf>0 and the angle is retarded, the process proceeds to step 4415-7, where the value of fl indicating the previous feedback history is determined. When fl > 0, the previous time was a retard When fl < 0, the previous time was a lead When fl = 0 There was no lead or retard last time When fl>0 and the previous time was also a retard, step 4415
Determine the value of the advance and retard characteristic parameter ia of −8. ia = 1: Retard angle characteristic is a in Fig. 8. ₃ ia = 0: Retard angle characteristic is a in Fig. 8. ₂ ia = -1: Retard angle characteristic is a in Fig _{. 8.} If ia≦0, step 2223-9 to ia
is added to enhance the retardation characteristic, and step 4415
Proceed to -12. If ia > 0, the retard characteristic cannot be further enhanced, so proceed to step 4415.
Proceed to -12. If fl=0 as determined in step 4415-7, the process directly advances to step 4415-12. If the judgment in step 4415-7 is fl<0, that is, the previous angle was advanced and the current angle is retarded. In this case, the value of the advance angle characteristic coefficient ib is determined in step 4415-10, and ib≧ If it is 0, subtract 1 from ib in step 4415-11 and proceed to step 44.
Proceed to 15-12. In step 4415-12, the feedback amount θ _T is calculated using equation (15): θ _T =θf×2 ^ia (15). The process then proceeds to step 4415-20. Step 4415-
If θf = 0 in step 6, set θ _T = 0 and proceed to step 4.
Proceed to 415-20. If θf<0 in step 4415-6, that is, the current feedback amount is on the advance side, the process advances to step 4415-13. Step 4415-1
3, if fl>0 and the previous feedback was delayed, the process advances to step 4415-14. Step 4
If the retard characteristic coefficient ia is ia≧0 in step 415-14, 1 is subtracted from ia in step 4415-15.
The process then proceeds to step 4415-18. If ia<0 in step 4415-14, the process proceeds to step 4415-18 without doing anything. In step 4415-13, if fl=0 and the advance/lag amount in the previous feedback is 0, the process immediately proceeds to step 4415-18. In step 4415-13, if fl<0 and the previous feedback was advanced, step 4415-13
Proceed to step 16 and check the value of the advance angle characteristic coefficient ib. ib=1: The retard characteristic is b in Fig. 8. ₃ ib=0: The retard characteristic is b in Fig. 8. ₂ ib=-1: The retard characteristic is b in Fig. 8. If ₁ ib≦0, then 1 Increase the lead angle feedback amount. And step 4415-1
Proceed to step 8. If ib>0 in step 4415-16, the advance angle feedback amount cannot be increased any further, so the process directly advances to step 4415-18. θ _T ← θf×2 ^ib (16) Then, the process proceeds to step 4415-20. In step 4415-20, the feedback amount θ _T calculated this time is transferred to fl. FIG. 27 shows a flowchart of the map feedback processing step 4445. In this embodiment, the map feedback includes the previous average value ₂ of column number X corresponding to the rotation speed N during the knock evaluation period, and the previous average value ₂ of row number Y corresponding to the intake manifold pressure Pm. Feedback is performed for each element of the θ _FM map within two columns or two lines from the feedback center ( ₂ , ₂ ), which is defined as two coordinates. In steps 4445-1 to 4445-4 _, the lower limit value X of the column number
_L , upper limit value X _H , lower limit value Y _L of line number Y, upper limit value Y _H
is obtained using equations (17) to (20). X _L = ( ₂ - 1) integer part or
₂ -2 (when ₂ is an integer value) or X _FML (when the above value is smaller than _{the lower limit of
2} - 2 (when ₂ is an integer value) or Y _FML (when the above value is smaller than the Y lower limit value Y _FML of the θ _FM map) ...... (18) Integer part of X _H = ( ₂ + 2) or X _FMH (When the above value is larger than the θ _FM map's X upper limit X _FMH )
...(19) Y _H = Integer part of ( ₂ + 2) or Y _FMH (When the above value is larger than the Y upper limit value Y _FMH of the θ _LM map)
...(20) Set X _L in column number X _J and Y _L in line number Y _J of the element to be rewritten in step 4445-5. In step 4445-6, the feedback center ( ₂ ,
₂ ) Find the X-direction deviation △X and Y-direction deviation △Y between the points (X _J , Y _J ). However, △X and △Y are the actual deviations multiplied by 4 to include only the integer part. In step 4445-7, the distance L map is searched using ΔX and ΔY to find the distance l. 10th
An example of a distance map is shown in FIG. In the example of FIG. 10, the distance l increases with equal weight for ΔX and ΔY. In example 2 of FIG. 11, the distance increases with ΔY weighing twice as much as ΔX. The amount of feedback decreases as the distance increases, so the first
In the case of Example 2 in FIG. 1, the amount of feedback decreases rapidly as it moves away from the feedback center in the ΔY direction, that is, in the intake manifold pressure direction. Step 4445-8 searches the feedback rate k from the feedback rate map (K map) using the distance l. The relationship between the distance l and the feedback rate k is shown in the characteristics of the k map in FIG. In step 4445-9, the feedback frequency N _FB (X _J , Y _J ) of the N _FB map is searched. In step 4445-10, the learning coefficient P is searched from the P map shown in FIG. 9 using N _FB (X _J , Y _J ). In step 4445-11, it is determined whether the previous feedback amount θ _T2 is positive or negative, and if θ _T2 ≧0,
At step 4445-13, the map value θ _FM (X _J , Y _J ) is rewritten using equation (21). θ _FM (X _J X _J ) = minimum value {θ _PP (X _J , Y
_J ), θ _FM (X _J , Y _J )+k×P×θ _T2 }
...(21) If θ _T2 <0, in step 4445-12, θ _FM (X _J , Y _J ) is rewritten according to equation (22). θ _FM (X _J , Y _J ) = maximum value {0,
θ _FM (X _J , Y _J ) + K×P×θ _T2 }
...(22) After that, in step 4445-14, the number of times of feedback N _FB corresponding to the rewritten map value θ _FM (X _J , Y _J ) of the θ _FM map _is determined.
_J , X _J ) according to equation (23). N _FB (X _J , Y _J )=N _FB (X _J , Y _J )+k
...(23) As a result _, the map value θ _FM (X _J ,
Y _J ) remembers how much feedback has been received. In step 4445-15, 1 is added to X _J to change the position of the rewritten element. In step 4445-16, the magnitude relationship between X _J and X _H is determined, _and if X _J
Proceed to step 6 to continue the rewriting operation. If X _J >X _H , set X _L to X _J in step 4445-17, and add 1 to Y in step 4445-18. Then, in step 4445-19, the magnitude relationship between X _J and Y _H is determined, and if Y _J Y _H , step 4445-6
Go to and continue the rewrite operation. If Y _J > Y _H , map feedback processing is ended. In the above-described map feedback processing step 4445 of FIG. 27, the range and distribution of feedback to the θ _FM map are determined by the deviation △ between the feedback center ( ₂ , ₂ ) and the column number X of the rewritten element (X _J , Y _J ). Deviation between X and line number Y △ Distance l from Y
Searching for this has the following advantages: The intake manifold pressure and engine speed corresponding to each row and each column of the θ _FM map and the θ _PP map are the same for the sake of computational advantages. In this embodiment, the θ _PP map stores the MBT, but in the low-speed portion where the value changes suddenly, the difference between the engine speeds in adjacent columns is reduced to accurately represent the MBT. In such an operating range, the feedback control value also fluctuates rapidly, so rather than determining the amount of feedback for that element based on the difference in engine speed from the feedback center, it is better to determine the amount of feedback based on the deviation of the column number. Harmonizes with the map structure. In addition, in this map feedback processing step 4445, the feedback center (
₂ , ₂ ) and the rewritten map value θ _FM of the θ _FM map
Search the distance l from the distance map (L map) using the X direction deviation △X and Y direction deviation △Y, which are obtained by multiplying the deviation of the actual coordinates of (X _J , Y _J ) by 4 and using only the integer part,
The feedback coefficient k is searched from the feedback coefficient map (K map) at l. Therefore 1/
Feedback coefficients can be specified for deviations for each column number and line number. Feedback performance is improved by being able to specify the feedback amount distribution in such a fine manner. FIG. 28 shows a flowchart of forgetting processing step 4600 in the base processing of FIG. 24.
In this embodiment, feedback control is performed to retard the angle when the trigger interval is small and advance the angle when it is large, and the control speed to the advance side is slower than the control speed to the retard side. Furthermore, each map value of the operating state category that is not used for a long time in the θ _FM map may be far away from the current feedback target value. Therefore, there is a possibility that the feedback target value will be reached more quickly if each map value is forgotten than if it is left as is. Therefore, in this embodiment, since the control speed to the retard side is fast, all map values of the θ _FM map are subtracted by a predetermined amount every minute to act as a forgetting effect. In step 4605, it is determined whether the subtraction amount calculation completed flag _F1M is set to "1". If it is "0", the subtraction amount has not been calculated yet, so step 4610 is performed.
Then, the subtraction amount θfgt is calculated according to the formula (24), and in step ₄₆₁₅ , the elapsed time on the software in minutes _is calculated. Add 1 to T. In step 4620 _, the column number Xk _of the map value of the θ _FM map to be rewritten for forgetting is set to the lower limit _of
Set the Y lower limit value Y _FML of the map. Then, in step 4625, the subtraction amount calculated flag _F1M is set to "1". Then, _in step 4630, the map value θ FM (Xk, Yk) of the θ _FM map is subtracted by θfgt, and if θ _FM (Xk, Yk) < 0 in step 4640, θ _FM (Xk, Yk) is subtracted in step 4645. Set to 0.
In step 4650, Xk is added by 1, and in step 4655, the magnitude relationship between Xk and the upper _limit of X of the θ _{FM map} When the forgetting process is executed in , the forgetting operation is performed on the next element of the θ _FM map. If Xk > X _FMH in step 4655, set X _FML to Xk in step 4660, and then
At 665, add 1 to Yk. Step 467
If Yk is 0 and Y _FMH is compared in size, if Yk≦Y _FMH , this forgetting process is terminated and the next time the forgetting process is executed, the forgetting operation is performed on the next element of the θ _FM map. It will be done. If Yk> _YFMH in step 4670, step 4675 subtracts a one-minute software counter _C1M by a time _K1M corresponding to one minute of elapsed time. Further, in step 4680, the subtraction amount flag _F1M is set to "0". Therefore, when the value of K _1M is added to C _1M again, the next forgetting process is started. In the above embodiment, the map value is rewritten or forgotten so that it converges to the target value after a predetermined time has elapsed regardless of the feedback factor. It is also possible to perform forgetting processing in conjunction with this. The outline is almost the same as the above embodiment, and the following will mainly explain the changes from the above embodiment. That is, step 3300 in the 8ms interrupt processing routine of FIG. 23 is abolished, and instead, step 2199 as shown in FIG. 29 is inserted in the program interrupt processing of FIG. 20. As a result, a program interrupt is activated every 180 degrees of engine rotation, so C _1M is 1 every 180 degrees of engine rotation.
This forgetting process is executed every 1/2K _1M engine rotation. Further, in the above embodiments, the ignition timing as a control element is feedback-controlled, but the present invention can also be applied to an apparatus that performs feedback control on the air-fuel ratio as a control element.
This will be explained below. Here, as an example, the feedback control amount is the fuel supply amount, and in particular, the control of the time width of the injection time in an engine having an electronically controlled fuel injection device will be described. The feedback factor is an air-fuel ratio signal from an air-fuel ratio sensor that detects the air-fuel ratio based on the oxygen concentration in the exhaust pipe. Signals representing engine operating conditions include engine speed N (rpm), intake air amount Q (g/
s) is used. The amount of fuel supplied per combustion (that is, equivalent to the injection time width per combustion) M is expressed by the following equation. M=Mm(N,Q)+△M(N,Q)
...(30) Mm (N, Q): A quantity calculated from the relationship between N and Q or a fixed map with N and Q as parameters. ΔM(N, Q): A rewritable feedback map value with N and Q as parameters, which directly gives the feedback control amount. Regarding the △M map, rich lean is determined based on the signal of the air-fuel ratio sensor at regular intervals using the same method as in the above embodiment, and the map amount △M of the operating state category belonging to the rotational speed N and air amount Q at that time is determined.
(Ni, Qi) is added or subtracted by a predetermined value △Mc. Also △
The M map calculates each map value △M (Ni, Qi) by S (0<S<
1) By multiplying each map value, each map value is rewritten (forgotten) so as to approach the target value 0. Therefore, only the map value △M of the operating state classification in a predetermined region normally used such as an automobile engine is updated, and the map values in other regions become old and become values far from the optimum values for feedback control. This solves the problem of worsening control responsiveness. In the above embodiment, the rewriting (forgetting) process of the feedback map value is performed by converting the map value to a constant value (θ
fgt) subtracting or multiplying the map value by a predetermined value (s), but there are also ways to search for an updated value using the map value at that time as an index, and use this searched updated value as the new map value. You can do it like this. As described above, in the present invention, the feedback control amount is calculated so that the control element that determines the engine combustion state is optimized by evaluating the feedback factor of this control element, and the control element is controlled based on this feedback control amount. A method for controlling the engine speed, wherein a value corresponding to the feedback control amount obtained by the above calculation is stored as a feedback map value in a storage device for each operating state classification in correspondence with the operating state of the engine, and the stored value is stored in a storage device for each operating state classification. In a control method in which the feedback control amount is calculated based on a map value of an operating state category corresponding to the engine operating state at that time among the feedback map values, the stored map value is set to a predetermined value regardless of the feedback factor. It is characterized by rewriting processing so that it converges to the target value as time or a predetermined engine rotation progresses. In particular, the map value of the operating state classification in the area that has not been used for a long time takes a value close to the target value. The feedback control amount calculated from the map value has the excellent effect of shortening and improving the response time until the control element is controlled to the optimum value.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
1 is a block circuit diagram of the control computer shown in FIG. 1; FIG. 3 is an ignition timing-torque characteristic diagram for explaining the embodiment shown in FIG. 1 of the present invention;
The figures serve to explain the operation of the embodiment shown in Fig. 1. Fig. 4 is a relationship diagram between engine crank angle and fixed position processing, Fig. 5 is a fixed advance angle map, and Fig. 6 is a feedback map. Fig. 7 is a feedback number map, Fig. 8 is a knock interval-feedback amount characteristic diagram, Fig. 9 is a learning coefficient map characteristic diagram, and Fig. 10 is a distance map example 1 and 11.
12 is a characteristic diagram of a feedback rate map, FIG. 13 is a characteristic diagram of an energization time map, FIGS. 14 to 28 are a flowchart of the control program of the embodiment shown in FIG. 1, and FIG. 29 is a diagram of distance map example 2. is a flowchart of the main part of a control program according to another embodiment of the present invention. 1...Engine, 2...Knock sensor, 6...
Control computer, 7...Ignition coil.

Claims (1)

[Claims] 1. A method of calculating a feedback control amount so that a control element that determines the combustion state of an engine is optimized by evaluating feedback factors of this control element, and controlling this control element based on this feedback control amount. , and a value corresponding to the feedback control amount obtained by the above calculation is stored as a feedback map value in a storage device for each operating state category in correspondence with the operating state of the engine, and among the stored feedback map values, In a control method in which the feedback control amount is calculated based on a map value of an operating state classification corresponding to the engine operating state at that time, the stored map value is calculated for a predetermined period of time or after a predetermined engine revolution, regardless of the feedback factor. An engine control method characterized by performing rewriting processing so as to converge to a target value in accordance with the engine control method.