JPS61223243A - Surging controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve drivability and fuel consumption rate by open-loop- controlling the air-fuel ratio and controlling other operation condition factors so as to be fitted with the open-loop control when surging is judged in an internal-combustion engine utilizing a lean-burn system. CONSTITUTION:During engine revolution, the output value of a lean sensor 6 is taken in at each prescribed time interval and accommodated into the RAM107 in a control circuit 10, and the absolute value S of the difference from the output value in the preceding time is calculated, and added into the integration value DELTALN. Then, it is judged if the engine operation state is normal or not from the engine revolution speed, intake pressure, etc., and if the judgment is 'YES', the average value of the DELTALN in the past several times is calculated, and the result is compared with a prescribed value, and the generation of surging is detected. When the generation of surging is detected, air-fuel ratio feedback control is prohibited, and the air-fuel ratio is open-loop-controlled, and other operation condition factors are controlled so as to be fitted with the open-loop control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an internal combustion engine using a lean burn system.

[Prior art]

In recent years, lean burn systems have been adopted in which internal combustion engines are operated at a lean air-fuel ratio to prevent exhaust pollution and to reduce fuel consumption. That is, there is a system in which a lean sensor is provided in the exhaust pipe of the engine, and an output signal of this lean centimeter is used to perform feedback control of the air-fuel ratio of the engine to an arbitrary value on the lean side. In such a lean burn system, an air-fuel ratio that does not have enough margin for the misfire limit due to NOx constraints is adopted, and therefore,
Considering the worst tolerance of the lean sensor's durability, it may lead to deterioration in operating performance such as misfires and surging.

[Problem that the invention seeks to solve]

In order to solve the above-mentioned problems in lean burn, Kanto Motoyama proposed a method for detecting surging by integrating the fluctuation signals of lean sensors and increasing the amount of fuel when surging is determined in the patent application No. 59-89248. We are proposing something that suppresses sanitizing. However, this sequential method has a problem in that engine operation is not optimized when surging is detected. That is,
By increasing the amount of fuel, the air-fuel ratio is corrected to the rich side, but other factors such as ignition timing and injection timing remain at the original air-fuel ratio before correction, and do not correspond to the corrected air-fuel ratio. This is because they are not.

[Means for solving problems]

According to the present invention, as shown in FIG. 1, there is a means 1 for generating a signal according to fluctuations in the combustion state of the internal combustion engine, a steady state determining means 2 for determining the steady state of the engine, and a signal generating means l in the steady state. Means 3 for comparing the signal level, LE from 1 with a predetermined value, means 4 for open-loop control of the air-fuel ratio when surging is determined by this comparison, and means 4 for controlling other operating condition factors when surging is determined by the comparison. A surging control device for an internal combustion engine is provided comprising control means 5 adapted to open-loop control.

〔Example〕

In FIG. 2 showing the entire internal combustion engine according to the present invention, a surge tank 3 of an intake passage 2 of an engine body 1 has an intake passage 2.
A pressure sensor 4 is provided to detect the absolute pressure of intake air, and its output is supplied to an A/D converter 101 with a built-in multiplexer of a control circuit 10. A lean (mixture) sensor 6 is provided in the exhaust passage 5 of the engine body l. Since the output of the lean sensor 6 is obtained as a current output as shown in the output characteristics in Fig. 3, the control circuit lO
A/D
is supplied to converter 101.

The distributor tough has a crank angle sensor 8 whose shaft generates a pulse signal for detecting a reference position every 720 degrees in terms of crank angle, and a pulse signal for detecting angular position every 30 degrees in terms of crank angle. A crank angle sensor 9 is provided to generate pulse signals from the crank angle sensors 8 and 9. Pulse signals from these crank angle sensors 8 and 9 are supplied to an input/output interface 103 of a control circuit 10.

Further, the intake passage 2 is provided with a fuel injection valve 11 for supplying pressurized fuel from a fuel supply system to the intake boat for each cylinder. Reference numeral 21 denotes an igniter, which is connected to the spark plug 22 via a distributor.

The control circuit 10 is configured as a microcomputer, for example, and includes a C
A PU 105, a ROM 106, and a RAM 107 are provided. 104 is a drive circuit for driving the fuel injection valve 11. Note that the interrupt generation of the CPU 105 is caused by A/
This occurs when the A/D conversion of the D converter 101 is completed, when the input/output interface 103 receives a pulse signal from the crank angle sensor 8.9, etc.

The intake pressure data PM of the intake pressure sensor 4 and the output current value lJ of the lean sensor 6 are captured by an A/D conversion routine executed at predetermined time intervals and stored in a predetermined area of the RAM 107. In other words, the data PM, I in the RAM 107 are updated at predetermined intervals.

41m (A) and (B) are diagrams for explaining the principle of surging measurement in the present invention. When traveling at a constant speed and the air-fuel ratio is relatively richer than the misfire limit, the output signal waveform of the lean sensor 6 hardly changes, as shown in Figure 4 (A). On the other hand, when the air-fuel ratio approaches the misfire limit while driving at a constant speed, the output signal waveform of the lean sensor 6 has a part that protrudes toward the lean side, as shown in FIG. 4 (B). do.

In other words, the change in waveform becomes large. The present invention detects surging by distinguishing between changes in the output waveform of the lean sensor, and when surging is detected, performs open-loop control of the air-fuel ratio, and also controls the air-fuel ratio in open-loop control based on other operating factors. Control to fit.

The operation of the apparatus shown in FIG. 2 will be explained with reference to the flowcharts shown in FIGS. 5 to 8.

FIG. 5 shows an A/D conversion routine, which is part of the main routine and is executed every predetermined period of time, for example, every 12 m5. That is, in step 501, the output value LNSR of the lean sensor 6 is taken in from the A/D converter 101 and stored in the RAM 107. In addition, at this time, other A
/D conversion value For example, intake pressure data PM is also converted to A/D converter 1.
01 and stored in the RAM 107.

In step 502, the absolute value S of the difference between the previously captured output value LNSRO of the lean sensor 6 and the current output value LNSR is calculated. In other words, S-I LNSR-LNSROl - However, -1 is the output value L of the lean sensor 6 due to air-fuel ratio feedback.
This is to eliminate changes in NSR as a dead zone. Therefore, -1 is not necessarily necessary, and S is guarded with 0 in steps 503 and 504. In step 505, the value S is converted into its integrated amount Δ
Add to LN.

In step 506, it is determined whether the state is in a steady state.

Conditions for a steady state include, for example, that the current air-fuel ratio A/F is above a predetermined value, that the engine rotation speed Ne is within a predetermined range, that the intake pressure PM is within a predetermined range, and that the change in intake pressure PM is For example, it must be within a predetermined range. As a result, if the state is not steady, the process proceeds to step 514 and the timer counter T is cleared.

Note that the timer counter T is, for example, a 32ss counter, and in this case measures the duration of a steady state. Next, the process advances to step 515 to clear the integrated amount ΔLN, and in step 516, LNSR is set to LNSRO to prepare for the next execution, and in step 517, this routine ends.

If it is before 0.53 has elapsed since the steady state has been reached, the process advances from step 506 to step 507, and then to step 515. In other words, since the timer counter T is not cleared, the measurement of the duration of the steady state continues.

Next, when 0.53 elapses after the steady state is reached, the process proceeds from step 506 to step 507, then to step 508, and then to step 516. In other words, since the integrated amount ΔLN is not cleared, integration of the absolute value S calculated in step 502 is started.

Furthermore, when 1.53 elapses after the steady state is reached, the process proceeds from step 506 to step 509 through steps 507 and 508, and -ALN-(ALNX 15+ALN)/16 is calculated. Here, ΔLN indicates the average value of ΔLN for the past 15 times, that is, the value ΔLN calculated this time is multiplied by step 509.

In step 510, surging detection is performed based on ΔLN2:X (constant value). When surging is detected, the program moves from 510 to 511 and a feedback prohibition flag XFB is set. If surging does not occur, the flow goes from 510 to 512, and Δ] is changed to Xz(<
It is determined whether the value is smaller than X+). If Δτ100 is smaller than Xz, the process advances from 512 to 513 and the feedback prohibition flag XFB is reset.

FIG. 10 is a timing diagram showing changes in the integrated value ΔLN and the smoothed average value ΔLN due to execution of the surging detection routine of FIG. 5 described above. ΔLN is 0.5sW and 1
This is the value obtained by integrating the lean sensor output every second, while ΔL
N is the rounded average value at each end point of the integration. When the predetermined value XI is exceeded and it is determined that surging is occurring, a flag XFB is set.

Then, □Next, when the smoothed value ΔLM becomes less than or equal to X:, the feedback insufficient flag XFB is lowered.

Incidentally, when the flag XFB becomes 1, a warning means such as a lamp can be activated to notify the driver or a specific location of an abnormality.

In the 51st routine, even if 0.53 elapses after reaching the steady state, if the non-capsular state occurs before 1.53 elapses, the flow at step 506 changes to step 514.
The process returns to the initial state.

In this way, in the routine of FIG. 5, i in the steady state
Surging detection is performed during the interval s, and when surging is detected, a feedback prohibition flag XFB is set, and when the surging subsides, the same flag is set.

FIG. 6 shows an injection amount calculation routine, which is executed at every predetermined crank angle. For example, if it is a synchronous injection method, 36
G" is executed at a predetermined crank position for each CA, and in the case of a 4-cylinder independent injection system, it is executed at a predetermined crank position for every 180° CA. In step 601, the basic The injection amount τP is calculated, and the final injection amount τ is calculated in step 602. That is, τ←τp−FAF・(KLEAN + Kυ・Kg +
K.

However, 5FAF: feedback correction coefficient, KLEAN
: Lean correction coefficient, K+, Kz, and other operating state parameters. This routine then ends at step 603.

, Once the injection amount τ is calculated in this way, the injection start timing and injection end timing are calculated by a routine not shown, and these timings are
．． When set in the second comparator register, the first
．． The value of the second comparator register is subtracted and typed up at predetermined time intervals. At this time, the injection start and end flags are set and the injection execution routine is executed.
As a result, fuel injection will be performed.

The KLEANψ operation will be explained with reference to the routine shown in FIG. In step 700, it is determined whether XFB is 1 or not. 700 to 7 during feedback (XFB-〇)
01, and in step 701, KLEAN is calculated based on the intake pressure data PM and rotational speed data Ne. The calculated KLEAN is stored in the RAM 107 in step 704.
The routine ends at step 705. The lean air-fuel ratio correction coefficient KLEAN is for setting the air-fuel ratio to the lean (<1.0) side.

Since it is XFB-1 during the open loop, the KLEAN calculation for the open loop is performed in steps 700 to 702. KLEAN is less than 1.0 and the lean side air-fuel ratio is P
The setting according to M and Ne is the same as in step 701, but in the open loop mode where no feedback is performed, KLEAN is set thicker (closer to 1, 0) than in the feedback mode, and the air-fuel ratio is set in the feedback mode. Compared to time, it is said to be on the rich side.

Referring to the routine in FIG. 8, the feedback correction coefficient F is
AF calculation will be explained. This routine is executed at predetermined intervals. In step 801, it is determined whether the feedback prohibition flag XFB is 1 or not. Flag XFB is set when surging occurs as described above, but it is also set when the vehicle is idling or accelerating to execute open loop control.

If feedback is not prohibited, the process proceeds to 802 and it is determined whether the output current value 1j of the sensor 6 is equal to or higher than the reference value 11 or is distorted. If □≧I11, that is, if the air-fuel ratio is leaner than the predetermined lean air-fuel ratio, the flow goes to step 803, and a well-known process for increasing the FAF is performed. It is also well known that skip processing is performed at a change point from the rich side to the lean side. Go to step 802 again), summer□
<1m.

If so, that is, if it is richer than the predetermined lean air-fuel ratio, the process proceeds to step 804.
AF integral reduction processing is performed. If there is a change point from the lean side to the rich side, skip processing is executed.

802 means XFB-1, which means surging, then 8
05, and F^F is set to 1. Therefore, feedback control of the air-fuel ratio is not performed, and therefore the air-fuel ratio takes a value on the rich side.

FIG. 9 shows an ignition timing calculation routine, which starts execution upon detecting a predetermined crank angle of the cylinder to be ignited. In step 901, it is determined whether the feedback prohibition flag XFB is 1 or not. Feedback in progress (XF
If B=0), flow to 902, rotation speed No., intake pressure PM
The basic ignition timing θmast is calculated from the first muffler g.

This first map g is set to provide an appropriate ignition timing during feedback.

If XFB is 1 in 901, the air-fuel ratio is under open-loop control, and the process proceeds to 903, where basic ignition timing θMANK is calculated from the second map g'. This second map g' is used to set the optimization timing suitable for the open loop.In step 904 of the 0th order, another correction amount Δθ not related to this invention is subtracted from θb and t. is the ignition timing θ (note that θ can take a negative value). In step 905, the set time t1 of the igniter 21 is calculated, and C
It is set in the conveyor register of PU105.

Further, in step 906, the reset time t2 of the igniter 21 is calculated and sent to the conveyor register of the CPU 105. At time t, the ignition signal rises,
This calculation is performed so that the ignition signal falls at time t2, and the falling point corresponds to the crank angle θ calculated in step 904. FIG. 11 illustrates the timing of the ignition signal. θ is measured from top dead center TDC, and jl+j! from charging time Q and rotational speed NE so that the ignition signal falls at crank angle θ! is calculated.

In the above embodiment, when XFB is set by surging detection (Fig. 10), that is, when the air-fuel ratio feedback is stopped and the feedback correction coefficient FAF is fixed at 1 and switched to open loop, the ignition timing is changed to the closed loop map. The map is switched from g to the open loop map g'. However, it is within the scope of the present invention to change not only the ignition timing but also other operating condition factors that affect the combustion state, such as injection timing and EGR amount, to suit the open loop.

〔Effect of the invention〕

By switching from air-fuel ratio closed-loop control to open-loop control in response to the surging signal and changing other operating condition factors to suit the open-loop mode, more ideal operating control is achieved, improving driveability and fuel consumption. rate and can be improved.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram for explaining the present invention in detail, FIG. 2 is an overall schematic diagram showing an embodiment of the fuel injection amount control device for an internal combustion engine according to the present invention, and FIG. Figure 4 shows the output characteristics of the lean sensor during surging and non-surging, Figures 5 to 9
The figure is a flowchart for explaining the operation of the control circuit 10 in Figure 2, Figure 10 is a timing diagram showing lean sensor signal integrated value, smoothed average value, and changes in flags, and Figure 11 is a timing diagram of ignition signal. . l...Engine body, 2...Intake passage, 4...Intake pressure sensor, 5...Exhaust passage, 6...Lean sensor, 1G...Control circuit, 11...Fuel injection valve , 20・
...igniter. Toyota Motor Corporation patent application agent to patent ratio m

Claims (1)

[Claims] Means for generating a signal according to fluctuations in the combustion state of the internal combustion engine; steady state determining means for determining the steady state of the engine; means for comparing the signal level from the signal generating means in the steady state with a predetermined value; A surging control device for an internal combustion engine, comprising means for open-loop control of an air-fuel ratio when surging is determined by the comparison, and means for controlling other operating condition factors so as to be compatible with open-loop control when surging is determined by the comparison.