JPS6149144A - Control device of air-fuel ratio in engine - Google Patents

Abstract

PURPOSE:To detect a level of deterioration in each constitutional part, by providing an air-fuel ratio correction value setting means setting an air-fuel ratio correction value of a mixture and a means setting a correction value of an engine condition. CONSTITUTION:A hot-wire intake air quantity sensor 5 is mounted to the upstream part of an intake passage 4 reaching from an air cleaner 2 of an engine 1 to an intake manifold 3. An O2 sensor 9 detecting concentration of oxygen in exhaust gas is mounted to an exhaust passage 8. A control device 12 provides an air-fuel ratio correction value setting means, engine condition correction value setting means and an air-fuel ratio control means. The control device 12 outputs a driving signal to the intake air quantity sensor 5 and an injector 6. In this way, the basic injection quantity can be high accuracy corrected by including aged deterioration of each constitutional part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air-fuel ratio control device for an engine, and more particularly to an air-fuel ratio control device for an engine that uses a hot-wire type intake air amount sensor and corrects it by 02 feedback. .

(Prior Art) Air-fuel ratio (A/F) control is extremely important in taking measures against engine exhaust gas, saving fuel consumption, and preventing fluctuations in rotational speed. Therefore, it is necessary to accurately detect the amount of intake air.

Conventionally, when using a hot wire intake air amount sensor as an intake air amount sensor, oil mist, dust, etc. adhere to the hot wire, and the detection accuracy decreases over time. The one using 02 feed bank and correcting it using
As described in Publication No. 9, it is known that correction is made using the atmospheric point output of the intake air amount sensor when the engine is in the initial 1υ1 state and the detected output of the intake air amount sensor in the engine operating state. It is being

The air-fuel ratio control using the 02 field bank method in the former case has the following problems.

In other words, if the intake air amount and fuel injection amount can be controlled correctly, it is possible to control the air-fuel ratio to an appropriate value (A/F = 14.7), but the hot wire type intake air amount sensor can control the intake air amount. Detection errors occur due to the shadow 9 of foreign matter attached to the sensor, and detection errors occur due to gradual changes in the characteristics of the component parts (resistive elements, etc.) of the sensor described above over a long period of time. It is inevitable that errors in injection amount will occur due to gradual changes in the characteristics of component parts (coils, springs, valves, etc.) over a long period of time.

Conventionally, the air-fuel ratio correction value is set using a detection signal from an Oz sensor that detects the oxygen concentration in exhaust gas, and the air-fuel ratio correction value is used to correct the influence of changes over time in various sensors and injectors. An engine condition correction value is set approximately every predetermined operating time, and the basic injection amount is corrected using both of the above correction values.

In this case, the effect of foreign matter adhering to the hot wire of the hot-wire intake air amount sensor and the influence of aging degradation of the intake air amount sensor and injector components, which is an order of magnitude smaller than this, can be compensated for using the same engine condition correction value. Therefore, the effects of aging deterioration of the above-mentioned components are not apparent, and it is not possible to reflect the effects and make corrections with high accuracy, and it is not possible to detect the degree of aging deterioration. There is a problem.

(Object of the Invention) The present invention is capable of correcting the basic injection amount with high precision by taking into account the influence of deterioration over time of each component such as a hot-wire intake air amount sensor and an injector, and detects the degree of the deterioration. The purpose of the present invention is to provide an engine air-fuel ratio control device that can control the engine air-fuel ratio.

(Structure of the Invention) The air-fuel ratio control device for an engine according to the present invention includes a hot-wire type intake air amount sensor and a hot wire portion of the hot-wire type intake air amount sensor that is heated at a predetermined timing to burn out foreign matter attached to the hot wire portion. an oxygen concentration detector that detects the oxygen concentration in the exhaust gas; and an air-fuel mixture that uses the detection signal from the oxygen concentration detector to set a correction value for the air-fuel ratio of the air-fuel mixture supplied to the engine. a fuel ratio correction value setting means; an engine condition correction value setting means for setting an engine condition correction value using the air-fuel ratio correction value within a predetermined period after the operation of the foreign matter burning-off means; The air-fuel ratio control means controls the air-fuel ratio by setting the basic injection amount based on the detection signal and correcting this basic injection amount with both of the above correction values.

(Effects of the Invention) In the present invention, as explained above, after burning off the foreign matter attached to the hot wire of the intake air amount sensor, the engine condition correction value is set using the air-fuel ratio correction value at a predetermined period, and the above correction value is set. Since the basic injection amount is corrected using the value, the influence of deterioration over time of each component of the hot-wire intake air amount sensor and the injector is reflected in the engine condition correction value.

Therefore, to take into account the effects of aging mentioned above, the air-fuel ratio should be controlled at high I+'7 degrees. In addition, the degree of the deterioration over time can be detected from the engine condition correction value as needed.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

As shown in Fig. 1, a vertical four-cylinder fuel injection engine 1
A hot wire type intake air amount sensor 5 is installed at the upstream side of the intake passage 4 leading from the air cleaner 2 to the intake manifold 3, an injector 6 for fuel injection is installed at the downstream side of the intake passage 4, and a The exhaust passage 8 is equipped with an 02 sensor 9 that detects the oxygen concentration in the exhaust gas.
A crank angle sensor 11 is provided near the gear 10 at the end of the crankshaft to detect the top dead center (TDC) of the piston of the base f4% cylinder.

Detection signals from the sensors 5, 9, and 11 are output to the control device 12, and drive signals are output from the control device 12 to the intake air amount sensor 5 and the injector 6.

The hot wire type intake air sensor 5 is an existing hot wire type intake air amount sensor that detects the air flow rate based on the principle that a hot wire is cooled by the air flow flowing through the intake passage 4 and its resistance value changes. be.

In the hot wire type intake air amount sensor 5, the engine 1
As the operating time passes, foreign matter such as dust or oil mist adheres to the surface of the hot wire and gradually cools down, causing the difference between the actual intake air amount and the detected intake air amount to increase over time. (Thus, the correction amount added to the basic injection HT (basic injection pulse) set from the intake air iQa detected by the intake air amount sensor 5 and the engine rotation speed n8 gradually increases over time. I'm going to go there.

In addition to foreign matter adhering to the hot wire of the hot-wire type intake air amount sensor, the components of the intake air amount sensor (such as resistors) and the components of the injector (such as coils, springs, and valves) may deteriorate over time. The correction will be made as described below, taking into account the effects of changes in characteristics due to deterioration.

The air-fuel ratio control device for the engine 1 is configured as shown in the block diagram in FIG. , time (
For example, a free running counter 15 that outputs mS vehicle position time), a ROM 16 that stores various preset calculation programs, a RAM 17 that exchanges and stores various data with the MPU 14, and an injection signal from the MPU 14. an output timer 18 that receives T, and an output timer 18 that receives
an injector WIJ circuit 19 that receives an injection pulse from the injector 6 and outputs an injection drive pulse to the injector 6;
A burn-off current drive circuit 20 receives a burn-off current energization signal from A 4 and outputs a burn-off current to the hot wire of the intake air amount sensor 5;
An A/D converter 21 converts the 02 signal into a square pulse and outputs it to the MPU 14; a waveform shaping circuit 22 receives the 02 signal from the 02 sensor 9 and shapes the waveform into a square pulse; and a waveform shaping circuit 22 receives the 02 signal from the 02 sensor 9 and shapes the waveform into a square pulse; It is composed of a waveform shaping circuit 23 that shapes the waveform into pulses.

However, the MPU 14 also has the function of an input/output interface.

Next, an outline of the air-fuel ratio control performed by the above air-fuel ratio control device will be explained with reference to FIGS. 3 to 6.

First, since the following 02 feedback control is performed only within the feedback region where the engine speed n8 and the engine load are each within a predetermined value range, the following is the control within this feedback region.

The intake air amount Q1 detected by the intake air amount sensor 5 and the engine speed l giant number n detected by the crank angle sensor 11.
The basic injection amount Tn is calculated based on a predetermined map input and stored in advance based on
T B is corrected by correction coefficient crs, Ct2 and CLI, T□=CFil' CL2・CL I・TIl
The injection amount T obtained in step 2 is injected.

The correction coefficient (air-fuel ratio correction value) CFII is an Oz feedback coefficient calculated based on the detection signal from the Oz sensor, and can be qualitatively represented by a diagram as shown in FIG.

The above correction coefficients Ct and Z are the second learning terms for correcting the influence of foreign matter adhering to the hot wire of the hot wire type intake air amount sensor, and are predetermined values separated by 1st period, 2nd period, 2nd period, etc. It increases in a stepwise manner for each operating time (in the predetermined period (first period) after the hot wire of the intake air amount sensor burns out the foreign matter), the shadow of the foreign matter is small, so Ct, Z = 1.0 is set.

However, as the amount of foreign matter adhering increases with the passage of time after burning out, the value of CFII also increases accordingly. Set cL□ to a constant value.

Then, as time passes in the second period, CFI+ increases as above, so the CFII at the end of the second period is the CFI of the second period.
It is added to the values of t and Z to set Ct2 of the second period to a constant value.

Since such operations are repeated, CF and Ct2 become as shown in FIGS. 3 and 4, respectively.

The above correction coefficient (engine condition correction value) CLI is the first learning term that corrects the influence of aging deterioration of the components of the hot wire type intake air amount sensor and injector. Although it is set before time has elapsed, its value is set as described below. That is, this first learning term CLI is held at a constant value during the period from burnout to burnout, and changes stepwise for each burnout.

The qualitative relationship between the correction amount by the correction coefficient and the basic injection amount is illustrated in FIG. 6 when the engine operating condition is constant. In this figure, the injection pulse T is the injection pulse that provides the optimal A/F value (A/F = 14.7), but since the correction amount ΔT increases as the operating time increases, the appropriate timing Foreign matter is burned off by applying electricity to the hot wire.

In addition, the 1st period, 2nd period, etc. in Figures 3 and 4 may be divided by a predetermined driving time, a predetermined mileage, or other parameters equivalent to these. It may be separated, but in the flowchart described later, 02
Time 8 when the A/F obtained from the detection signal of sensor 9 reversed from rich to lean! It is divided every time (learning counter NL) reaches a predetermined number of times (NLE).

Regarding the setting of the first learning term in Fig. 5, it is desirable to set it immediately after the burnout, but in the flowchart described later, the 1st learning term corresponding to the operating time is set to the set value (
NBI).

The burnout in FIG. 6 may also be performed every predetermined driving time or mileage as described above, but in flowchart 1, which will be described later, the burnout counter NB corresponding to the driving time is set to the set value ( NB2) and it is burnt out during cranking.

Hereinafter, each step knob executed by the control device 12 will be explained based on the flowchart 1- in FIG. 7. However, the reference numeral 5100 and S1 to S45 indicate each step.

First, after control is started at 5100, S1 is initialized, and S1 is initialized.
In Step 2, it is determined whether or not the engine 1 is cranking based on the signal from the Stark 5W13. If the engine 1 is cranking, the process goes to S3; otherwise, the process goes to S9.

In S3, the burnout counter NB counted in S9
The burn-out time is determined based on whether or not the burn-out time is greater than the set value NB2, and when the burn-out time has come, the process moves to S4, and otherwise the process moves to S2.

In other words, the control flow of the burnout counter NB is, for example, L.
Since it is counted moment by moment in S9 every time it goes around every msec, the above set value NB2
corresponds to approximately a predetermined time, and the burnout is performed at every predetermined operating time and during cranking of the engine 1.

In S4, a pulse signal of "1" is output as the burn-off current energization signal 1b, and the burn-off current is outputted from the burn-off current drive circuit 20 to the hot wire of the intake air amount sensor 5 to burn off the foreign matter.

In S5, it is determined whether or not cranking is in progress based on the signal from the starter 5W13 again, and the process is repeated until the cranking is completed to continue the burnout, and when the cranking is completed, the process moves to S6. In S6, rOJ is outputted as the burn-off current energization signal (2) to stop the burn-off, the burn-off counter NB is cleared in S7, and the first learning term and the second learning term are initialized in S8.

S9 is the time when cranking is completed or in a normal operating state where cranking is not in progress, and in S9, the burnout counter NB is counted.

In SIO, intake air is detected by sensor 5 and A/D
The A/D converted intake air amount Q1 is read by the converter 21, and the Sll uses the detection signal TDC from the crank angle sensor 11 to calculate the top dead center circumference 311 obtained by the interrupt processing in FIG. 7(b). "l" From this, the engine rotation speed n is calculated.

In S12, the intake air IQ and the engine speed n are set in advance and stored in the ROM 16.

The basic injection amount T8 is calculated based on the intake air amount Q1 and the engine rotational speed n0 using the map.

In step 513, it is determined whether the current operating state is in the 02 feed hack region by determining whether the intake air mQ and the engine speed 08 are below their respective set values, and the current operating state is determined to be in the 02 feed hack region. If so, the process moves to 514, and otherwise, the process moves to S28.

At 314, three detection signals 02 from the 02 sensor 9 are sold.

In S15, it is determined whether the air-fuel mixture supplied to the engine X is rich or not based on the detection signal 0□. In other words, depending on whether the detection signal 02 is "1" or "0", it is determined whether it is lean or lean, and when it is rich, the process goes to S16, and when it is lean, it goes to S29.

In 316, the previous 0 set in S26 and S33
2. Depending on whether the flag FO is 0 or 1, it is determined whether or not there has been a reversal from lean to rich this time, and if it has been reversed, S1
7, and if it is not reversed, the process moves to S25.

In other words, if it is reversed, it means that an approximately appropriate A/F (air-fuel ratio) is being obtained, and if it is not reversed, the rich state continues, so the 0□ feedback coefficient CFII is set to 525. This indicates that it is necessary to make a reduction in the amount.

At step 517, the current CFB is added to the rich-side learning register CFBR, which is the basis for calculating the learning term CL2•CI,I, based on the 02 feed bank coefficient CF8, and the cumulative total of the rich-side CFB is calculated.

In 518, the number of reversals from rich to lean counted in 530, that is, the learning counter NL, is the set value NL.
Whether or not learning is completed is determined based on whether or not this point has been reached. In other words, it is determined whether or not the A/F has been reversed from rich to lean and from lean to rich a sufficient number of times as a result of maintaining an appropriate A/F, resulting in highly reliable and stable data. When it becomes S1
9, otherwise it moves to 325.

In S19, it is determined whether or not the burnout counter NB is larger than a predetermined small set value NBI.
The process moves to S20, and if it is not large, the process moves to S21. This is because the first learning term is set in step 321 at a stage when almost no foreign matter is attached to the hot wire of the intake air amount sensor 5 after burnout.

In S20, in addition to the above NLE, 517 and 331
The learning register CFBR (i.e., the cumulative value of CFLI on the rich side) and CFBL (i.e., the CF on the lean side) obtained in
By weighting them using the cumulative total value of ll) and the previous second learning term CL2, the second learning term CLZ is updated, for example, using the arithmetic expression in S20.

In S21, the learning register Cvn* obtained in 317 and 531 is set in addition to the set value NLEO of the number of inversions.
(i.e., the cumulative total of CFB on the rich side (Iri and CFIIL)
(that is, the cumulative value of CFB on the lean side) and the previous first learning term CL1, and by weighting these, the first learning term CL1 is updated by, for example, a calculation formula of 321.

In 322, the CFll for the predetermined period up to the present is added to the second learning term CL□ updated in S20 or the first learning term CLl updated in S21, so the 02 feed hack coefficient aCr g is initialized to 1.0. be converted into

In 323, the learning counter NL is cleared, and in S24
Then, the learning registers CFBR and CFIIL are cleared.

In S25, the trajectory is corrected from the rich side to the lean side.
2 feedback coefficient CFI, a predetermined minute value ΔCF
CFll is reduced by subtracting II.

Then, in S26, the previous 0□ flag FO is set to 1.

In S27, the above CF6, CL2, CL l and S
Using the basic injection ff1Tffi obtained in step 12, the corrected final injection amount T is T□=CFII-CLZ
・Calculated using the formula CL 1・T.

Next, S29 is the case of lean, and in S29, it is determined whether the previous 02 flag FO is 1 or 0 to determine whether or not it has reversed from rich to lean, and if it has reversed, S3
The learning counter NL is counted at 0, and if it is not inverted, the process moves to S32.

In S31, the lean side learning register CFIIL
The current CFn is added to calculate the cumulative total of CFll on the lean side.

In S32, in order to correct the trajectory from the lean side to the rich side, CFI+ is increased by adding a predetermined i-duration small value ΔCFB to the 02 feedback coefficient E'A CF II, and in S33, the previous 02 flag F○ is set to 0.
is set, and the process moves from S33 to 327.

Further, when the operating state of the engine is outside the 02 feed hack region in S13, the process moves to 328, and in S28, when the learning counter NL is 828', the learning registers CFBII % CFIIL are cleared, and the process moves from 328' to S27.

After passing through each step from S1 above, the process finally reaches 327 and one cycle of control ends, and the process moves from S27 to S9 again, and the same cycle is repeated thereafter.

Next, FIG. 7(b) shows a 41-inclusive processing routine that is executed for each angle TDC based on the detection signal TDC from the crank angle sensor 11.

In S40, interrupt processing is started, and in S41, the current TD is determined by the signal from the free running counter 15.
C (read time t1 of No. 8, set the above time in S42,
From the difference between the time L2 of the previous TDC signal and the time L2 of the previous TDC signal, the TDC (No. 8 lap!! JIT, immediately 311I for crankshaft rotation)
'r is calculated, the previous time t2 is updated to the current time L1 in S43, and the output timer 18 is updated in S44.
The signal of the final injection 'FET i obtained in step 527 is output, and fuel is injected via the injector drive circuit 19 and the injector 6 for a time corresponding to the injection amount T.

The above flowchart shows one embodiment, and it goes without saying that the same air-fuel ratio control can be performed by appropriately modifying each step of this flowchart. For example, S20
Various types of arithmetic expressions can also be used for the arithmetic expressions of the learning terms in step S21.

In the above embodiment, the air-fuel ratio correction value CFB, the second learning term CL2, and the first learning term, that is, the engine condition correction value CLl, were used to calculate the final injection amount T.
Learning term CL2 can also be omitted. In this case, the air-fuel ratio correction value CF[l is set to 1, taking into account the second learning term CLZ.

[Brief explanation of drawings]

Among the drawings, FIGS. 1 to 6 show embodiments of the present invention. FIG. 1 is an overall configuration diagram, FIG. 2 is a block diagram, and FIGS. 3, 4, and 5 are o2 Feedback section 81CF
FIG. 6 is a diagram showing an injection pulse consisting of a basic injection pulse and a correction amount, and FIG. 7 is a flowchart of air-fuel ratio control. 5.Hot wire type intake air amount sensor, 9..O2 Cefsu,
11...Crank angle sensor, 12...Control device, CF8...O2 feedback coefficient, CLI...
Learning value, CLQ...Initial value of CLI, TIl...Basic injection amount. Patent applicant: Mazda Motor Corporation Figure 1 procedural amendment (travel) December 8, 1982

Claims (1)

[Claims] (1) A hot wire type intake air amount sensor, a foreign matter burning means for heating the hot wire portion of the hot wire type intake air amount sensor at a predetermined timing to burn off foreign matter attached to the hot wire portion, and a foreign matter burning means for heating the hot wire portion of the hot wire type intake air amount sensor at a predetermined timing to burn off foreign matter adhering to the hot wire portion; an oxygen concentration detector for detecting the oxygen concentration, and an air-fuel ratio correction value setting means for setting a correction value for the air-fuel ratio of the air-fuel mixture supplied to the engine using the detection signal from the oxygen concentration detector;
engine condition correction value setting means for setting an engine condition correction value using the air-fuel ratio correction value within a predetermined period after the operation of the foreign matter burning-off means; An air-fuel ratio control device for an engine, comprising an air-fuel ratio control means for setting an injection amount and controlling the air-fuel ratio by correcting this basic injection amount with both of the above correction values.