JPH01170739A - Air-fuel ratio controller for engine - Google Patents

Abstract

PURPOSE:To improve the responsive property of air-fuel ratio control by setting a fuel injection amount on the basis of a basic air-fuel ratio correction value for correcting the dispersion of a fuel injection valve proper and an ineffective injection correction value for correcting a time lag from the beginning of current supply to said fuel injection valve to the beginning of injection. CONSTITUTION:A feed-back correction value is calculated B on the basis of deviation of actual air-fuel ratio detected by an air-fuel ratio detecting means A from a desired air-fuel ratio. A basic air-fuel ratio correction value CK for correcting the dispersion of a fuel injection valve proper to set the air-fuel ratio to a desired one and an ineffective injection correction value TV for correcting a time lag from the beginning of current supply to a fuel injection valve to the beginning of injection are set C. The fuel injection amount is set D on the basis of these three correction values. Also then, the respective correction valued CK, TV are varied under a plurality of different running conditions to set the feed-back correction value substantially to zero so that a plurality of correction value properties correlated with both correction values are calculated E and the correction values CB, TV approximate to the intersection point of these correction value properties are set as new correction values.

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 in particular to a basic air-fuel ratio correction value and an invalid injection correction value for correcting variations inherent in injection valves in a fuel-injected engine. This article relates to a system that allows for optimal settings.

[Prior art]

Among recent automobile engines, fuel injection type engines generally perform feedback correction of the air-fuel ratio using the output of a 0□ sensor so that the air-fuel ratio becomes a target air-fuel ratio (stoichiometric air-fuel ratio). For example, Japanese Patent Application Laid-Open No. 58-18074 discloses that while the air-fuel ratio is feedback-controlled, past operating conditions and feedback correction amounts are memorized in order to improve responsiveness in transient conditions. An air-fuel ratio feedback control device is described which corrects the fuel injection amount based on the above-mentioned stored operating state and feedback correction amount when the above-mentioned condition is present.

By the way, in a fuel injection engine that performs feedback correction of the air-fuel ratio, the fuel injection amount after warming up (this is the pulse width of the fuel injection pulse) is generally determined as follows. .

T i = T P ・CK -C11-CA -C3
X (1+cm)+'rv (1) Ti: Fuel injection amount, TP: Basic fuel injection amount determined based on engine speed N and intake air tQ, CK: Caused by manufacturing error of fuel injection valve, etc. Basic air-fuel ratio correction coefficient, CD, which corrects variations inherent in the injection valve: CA, a coefficient set according to the number of injections per crankshaft (one or two times)
: Intake temperature correction coefficient, CB Two-person pressure correction coefficient, CFI
: Feedback correction term, Tv: Invalid injection correction term that corrects the delay period from the start of energization to the fuel injection valve until it actually opens.

Conventionally, in order to set the basic air-fuel ratio correction coefficient Cx and the invalid injection correction term Tv, an actual prototype engine (however, a fuel injection valve with an average manufacturing error and invalid injection time is used) is used to set the basic air-fuel ratio correction coefficient Cx and the invalid injection correction term Tv. The C engineering and TvO values were determined, and the C1 and Tv values were applied to all engines of the same type.

[Problem that the invention seeks to solve]

When the basic air-fuel ratio correction coefficient CK and the invalid injection correction term TV obtained experimentally using an actual prototype engine are uniformly applied to all engines of the same type as in the above-mentioned conventional technology, it is necessary to Manufacturing errors specific to fuel injection valves and variations in invalid injection time cannot be corrected individually, and any deviations in the air-fuel ratio (deviations from the target air-fuel ratio) caused by these variations can be corrected by air-fuel ratio feedback correction. I will do it. As a result, there are problems such as the reference zero point in the air-fuel ratio feedback correction being significantly deviated, increasing the burden of calculation processing for the feedback correction, and reducing the responsiveness of the feedback correction.

[Means for solving problems]

As shown in the functional block diagram of FIG. 1, the air-fuel ratio control device for an engine according to the present invention includes an air-fuel ratio detection means for detecting the air-fuel ratio of an air-fuel mixture supplied to the engine, and a detection means for detecting the air-fuel ratio by the air-fuel ratio detection means. a feedback correction value calculation means for calculating a feedback correction value based on the deviation between the determined air-fuel ratio and a preset target air-fuel ratio; A correction value setting means for setting a basic air-fuel ratio correction value to be corrected, an invalid injection correction value for correcting a delay period from the start of energization to the fuel injection valve to the start of injection, and at least the feedback correction value calculation means. a fuel injection amount setting means for setting a fuel injection amount supplied from the fuel valve based on the feedback correction value and the basic air-fuel ratio correction value and the invalid injection correction value set by the correction value setting means; and the feedback correction value. The basic air-fuel ratio correction value and the invalid injection correction value are each arbitrarily changed in a plurality of different operating conditions so that correction value characteristic calculating means to be obtained; and correction value changing means for setting a basic air-fuel ratio correction value and an invalid injection correction value near the intersection of the plurality of correction value characteristics obtained by the correction value characteristic calculating means as new correction values. It is equipped with the following.

[Effect]

In the air-fuel ratio control device for an engine according to the present invention, the air-fuel ratio of the air-fuel mixture is detected by the air-fuel ratio detection means, and the feedback correction value is calculated based on the deviation between the detected air-fuel ratio and the target air-fuel ratio. It is calculated by

The fuel injection amount setting means sets the fuel injection amount based on at least the feedback correction value, the basic air-fuel ratio correction value and the invalid injection correction value set by the correction value setting means.

The correction value characteristic calculation means arbitrarily changes the basic air-fuel ratio correction value and the invalid injection correction value in a plurality of different operating states so that the feedback correction value becomes substantially zero, and adjusts the basic air-fuel ratio correction value and the invalid injection correction value. A plurality of correction value characteristics correlated with the correction value are determined.

The correction value changing means sets, as a new correction value, the basic air-fuel ratio correction value and the invalid injection correction value near the intersection of the plurality of correction value characteristics obtained by the correction value characteristic calculation means.

That is, when calculating the basic air-fuel ratio correction value and the invalid injection correction value in the correction value characteristic calculating means, if the above-mentioned positive values on both sides are changed so that the feedback correction value becomes substantially zero, the above equation (1) As can be seen, the fuel injection amount at that time is determined using the basic air-fuel ratio correction value and the invalid injection correction value as parameters, but as shown in FIG. 6 according to the embodiment, the correction value characteristics obtained under a certain operating condition LA will necessarily pass through the point P determined by the actual positive values on both sides, subject to the constraints of the actual basic air-fuel ratio correction value and the invalid injection correction value. Therefore, the correction value characteristics LA obtained under each of a plurality of operating conditions
``The intersection P of Lm provides the actual basic air-fuel ratio correction value and invalid injection correction value.

In this way, based on the plurality of correction value characteristics obtained by the correction value characteristic calculating means, the correction value changing means sets the actual basic air-fuel ratio correction value given at the intersection P and the invalid injection correction value as new correction values. do.

As a result, the errors included in the basic air-fuel ratio correction value and the invalid injection correction value are minimal, and the feedback correction value only reflects the effects of variable factors such as clogging of the fuel injector. The effects caused by inherent variations no longer appear. In this way, the deviation in the reference zero point of the feedback correction value is eliminated, the burden of calculation processing for feedback correction control is reduced, and the original feedback correction is realized, improving the responsiveness of the air-fuel ratio feedback correction.

〔Effect of the invention〕

According to the engine air-fuel ratio control device according to the present invention, as explained above, by determining the actual basic air-fuel ratio correction value and the invalid injection correction value and setting those values as the new correction value, Effects such as being able to reduce the burden of calculation processing required for air-fuel ratio feedback correction and improving the responsiveness of air-fuel ratio feedback control can be obtained.

〔Example〕

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

Figure 2 shows the overall configuration of an automotive vertical engine E and its air-fuel ratio control device. A combustion chamber 4 is formed by a cylinder block 1, a cylinder head 2, and a piston 3. A plug 5 is installed, the intake port 6 is opened and closed by an intake valve 7, and the exhaust port 8 is opened and closed by an exhaust valve 9. An air cleaner 11 is provided at the upstream end of an intake passage 10 extending from the intake port 6, and an air cleaner 11 is provided in the intake passage 10. are the air flow meter 12 and the throttle valve 13 in order from the upstream side.
and a surge tank 14, and an injector 15 that injects fuel toward the intake port 6 is provided downstream of the intake passage 10.

A catalytic converter 17 is interposed in an exhaust passage 16 extending from the exhaust port 8 .

Sensors for controlling the air-fuel ratio of the engine E include the air flow meter 12 and the intake temperature sensor 18 installed in the upstream part of the intake passage 10, the atmospheric pressure sensor 24 for detecting atmospheric pressure, and the The 02 sensor 19 installed in the upstream part detects the oxygen concentration in the exhaust gas, the water temperature sensor 20 detects the cooling water temperature of the water jacket, and the distributor 21 incorporates the rotation angle signal of the crankshaft, that is, the crank angle signal (however, A crank angle sensor 21a that outputs a signal (including an engine rotation speed signal), and an idle switch 13a that detects that the throttle valve 13 is in a substantially fully closed state during idling are provided, and signals from these sensors and an ignition switch are provided. Signals from the starter switch 22 and the starter switch 23 are input to the control unit 25.

The control unit 25 includes a waveform shaping circuit that shapes the waveform of the engine speed signal, an intake air amount signal from the air flow meter 12, an exhaust temperature signal from the exhaust temperature sensor 19, and an intake temperature signal from the intake temperature sensor 18. An A/D converter that A/D converts the atmospheric pressure signal from the atmospheric pressure sensor 24 and the water temperature signal from the water temperature sensor 20, an input/output interface, a CPU (central processing unit), and a ROM (read memory).
It is equipped with a microcomputer consisting of a RAM (random access memory) and a RAM (random access memory), a drive circuit that drives the injector 15 according to control signals from the microcomputer, a drive circuit that outputs an ignition drive signal to the detox repeater 21, etc. ing.

At least a control program for air-fuel ratio control (including correction value detection and update control), which will be described later, and maps and tables associated with the control are manually stored in the ROM of the micro combinator mentioned above, and also in the RAM. is the temporary memory (memory, counter,
flags, etc.) are provided.

First, an overview of the air-fuel ratio control of this embodiment will be explained. In the air-fuel ratio feedback control performed based on the output of the 0□ sensor 19, when setting the fuel injection amount T, The basic air-fuel ratio correction value Cx that corrects variations and the invalid injection correction value TV that corrects the delay period from the start of energization to the injector 15 to the actual start of injection are detected as accurately as possible and these correction values are used. This reduces the burden on the CPU in the air-fuel ratio feedback correction control and improves the responsiveness of the correction control.

Next, the routine for this air-fuel ratio control is shown in Figures 3 and 4.
This will be explained based on the flowchart shown in the figure.

In the figure, S□ (i=1.2.3...) indicates each step.

Figure 3 shows, for example, the crankshaft 2 based on the crank angle signal θ.
If the engine injects once per revolution, the pressure is N T D
This shows an interrupt processing routine for air-fuel ratio control (assuming a warm-up state) that is executed by the CPU for each CPU.When control is started when the ignition switch 22 is turned on, necessary initialization is executed. (S 1 ), and then the engine rotation speed N, which has been calculated in advance in an interrupt process and stored in the memory, is calculated based on the intake air IQ signal from the air flow meter 12 and the engine rotation speed signal from the crank angle sensor 21a. The engine speed N and intake air t are read (S2), and then the engine speed N and intake air t are determined from a map stored in the ROM with the engine speed N and intake air amount Q set in advance as parameters.
A basic injection amount TP (which corresponds to the pulse width of the fuel injection pulse) corresponding to Q is calculated (S3).

Next, at 54, the basic air-fuel ratio correction value Cx is read from the RAM memory (S4).

As the above-mentioned basic air-fuel ratio correction value C, a provisional value obtained experimentally using an actual prototype engine at the time of engine production is initially input and set in the memory of the above-mentioned RAM. According to the routine shown in the figure, the actual value of the basic air-fuel ratio correction value C is determined and sequentially updated.

Next, the injection number correction value CD, which is included as a constant in the program, is read (S5). The correction value CD is determined depending on the number of injections per revolution of the crankshaft (one or two times). Next, the intake temperature sensor 18
The intake air temperature TA signal is read from (S6), and then an intake air temperature correction value CA is calculated based on the intake air temperature TA (S7).
), Next, the signal of the atmospheric pressure PA is read from the atmospheric pressure sensor 24 (S8), the atmospheric pressure correction value C3 is calculated based on the atmospheric pressure Pa (S9), and then the output of the 0□ sensor 19 ■. 2 is read (SIO) and its output ■. 2, a feedback correction value CFI is calculated using a predetermined calculation formula (Sll).

Next, in 312, the invalid injection correction value Tv is read from the RAM memory (512). Above invalid injection correction value TV
As such, a provisional value obtained experimentally using an actual prototype engine at the time of engine manufacture is initially input and set in the RAM memory, and thereafter, after the engine starts to be used, the invalid injection correction value is set by the routine shown in Figure 4. Tv is determined and updated sequentially.

Next, the amount of fuel actually injected and supplied from the injector 15 is T, = T, ・C8・CD'CA・Cm
Calculated using the formula (1+C□)+Tv (313)
, next, the injection start timing θ is calculated using the above fuel injection amount T (S14), then the crank angle θ is read from the crank angle sensor 21a (S15), and then the above given value is read. It is determined whether or not it is time to start injection based on the count value of the soft timer set when the engine angle signal θ is input (316).
), when the injection start time comes, a control signal is output to the drive circuit of the injector 15, and an injection drive pulse with a pulse width corresponding to the fuel injection amount Ti is output from the drive circuit to the injector 15, and fuel injection is executed (S17 ), S17
to return to the main routine.

Figure 4 shows that the starter switch signal is OFF after the engine starts.
This shows a correction value detection and update control routine that is executed by the CPU every time F is reached.

To give an overview of this control, fuel injection iiT,
As mentioned above, Ti””Tr ・CK −CIll −CA −CB
X(1+CFl)+TV (1) When controlling so that the feedback correction value Cym=0, in one operating state (region A in Figure 5), the above equation (1) is as follows: Ti=a, T, ・CD -CA・c,=b
Then, a=b-CK+TV... (2) Also, in another operating state different from the above operating state (region B in Fig. 5), the above equation (1) becomes 'r,= c, T
, -CD -CA-C,=d, then c=d-CK+
TV... (3) Above a, b, c,
d is a known value since the respective operating conditions, CDs intake temperature and intake pressure are known. Then, equation (2) and (3)
Determining Cx and Tv from the formula, CD = (ac)/(b d), Ty =
(b c a d) / (b d), since the above CK and TvO values give the actual 08 and TV, the CK and TV values in the RAM memory are updated sequentially using these values, and used for air-fuel ratio control. provide

Next, to explain the routine of this control, the control starts when the starter switch signal turns OFF, and necessary initialization such as resetting the flags Fa-, Fm, and FeK is performed (S30). The water temperature T. The signal is read (S31), and then the water temperature Tw is 8.
It is determined whether the temperature is 0°C or higher, that is, whether the engine is warmed up (S32), and when the temperature is T and 580°C, the engine speed N and basic injection amount Tp are read from each memory of the RAM (S33). ), then it is determined whether the flag F is in the set state (334), and if FA=0, then N.

<N<Nz and Tpl<Tp <Trz In other words, it is determined whether the operating state of the engine is in the region A of FIG. 5 (335), and if YES, the process moves to S37. On the other hand, when the flag FA is not 0 or when the determination result in S35 is NO, the process moves from S34 to 336, and N s
< N < Na and T, , <T.

< T Pa In other words, it is determined whether the operating state of the engine is in the region B of FIG. 5 (S36), and when the answer is Yes, the process moves to S37, and when the answer is No, the process returns to S333.

337, the difference between the current engine speed Ni and the previous engine speed Nt-+ is a sufficiently small tolerance value N.
0 or less, and it is determined whether the difference between the current basic injection amount TPi and the previous basic injection amount 'rrt-+ is less than or equal to a sufficiently small allowable value TPO. If Yes, the process moves to S38, and if No, the process moves to S33. return.

This is to perform the control after 338 while the engine operating state is stable in region A or B.

In 33B, CFI, Cm from each memory of RAM
and TV are read, and at the same time, the CD stored as a program constant is read, and then it is determined whether CFil is 0 (S39), and if Cym is not 0 initially, steps 340 to S46 are executed. That is, it is determined whether the flag FCK is not set (S40).
, when FCK=0, Cx is given a predetermined coefficient α(
However, the value is changed to a value obtained by multiplying 0<α by 1, e.g., α=0.95 (341), and then the TV multiplies a predetermined coefficient (however, by 1 multiplied by β, e.g., β=1.10). It is then changed to the multiplied value (S42), and then it is determined whether or not CK has become less than the set value CKO (S43). If Cx≦CKO, the process returns to S31, and if C≦CKO, the process proceeds to S44, where the flag F is set. 'cx is set and the process returns to S31.

As described above, when CK is changed to the decreasing side and Tv is changed to the increasing side and CFll=0, the process moves from S39 to 347.

However, Cx is decreased again until C≦C8°.
If C3 does not become 0 even if V is changed to the increasing side, the flag F'cx is set and CK is changed to the increasing side and TV
is changed to the decreasing side (.

That is, when FCK=1, the transition is from 340 to 345, C is changed to CK/α (S45), and then TV is changed to T.
It is changed to v/β (S46), and the process returns to 331.

As shown in 340 to 346 above, when changing the values of C6 and Tv, C
Fl = 0, transition from S39 to 347, and S4
7, the flag FCK is reset, and then fuel injection [T1, intake temperature correction value CA, and atmospheric pressure correction value C8 are read from the RAM memory (S48), and then N, <N
UN, that is, it is determined whether the engine operating state is in region A (S49), and if Yes, a=T', b=
Tp ・Co ' Ca ' Cm is set (
350), and then flag F^ is set (S51).

On the other hand, when the engine operating state is in region B, the process moves from S49 to 353, where c=Ti, d=T,
-CD ・Ca -Ca is set, then flag F
m is set.

In S52 following S51, it is determined whether the flag FB is set (that is, whether the values of c and d have already been set), and if YES, the process moves to 356, and if NO, the process returns to S31. . In step 355 following 354, it is determined whether the flag FA is set (that is, whether the values of a and b have already been set), and the answer is Yes.
If so, the process moves to S56, and if No, the process returns to S31.

When the values of a, b, c, and d are set as described above, the process moves from S52 or 355 to S56, and in S56, Cx = (ac) / (b d), TV =
(b c-a d) / (b-d), and then in 357 RA is set with the above CK value and TV value, respectively.
Cx and TV in M's memory are updated and control ends.

To give a detailed explanation of the above control, obtaining the above equation (2) for area A by controlling so that CFl = 0 is obtained by finding the characteristic line LA with Cx and TV as parameters in Fig. 6. To obtain the above-mentioned equation (3) for region B by controlling so that CFl=0 is obtained, the characteristic line L1 with Cx and TV as parameters in FIG. 6 is obtained.

From the above equations (2) and (3), Cx and T
Setting v is determined by taking the characteristic line LA in FIG.

This is to find and set the intersection POCK value and TV value, and the CX value and TV value provide the actual (true) CK value and TV value.

Incidentally, it is necessary that the above regions A and B fall within the feedback region as shown in FIG.

In addition, the accuracy can be further improved by finding characteristic lines in the same way as above for the third and fourth regions in addition to region A-B, and finding the CX value and TV value at or near the intersection of these many characteristic lines. improves.

As explained above, the actual basic air-fuel ratio correction value CK and invalid injection correction value TV are determined by the control shown in FIG.
Since Cx and TV are updated with these values, the air-fuel ratio feedback correction only needs to correct variations caused by actual fluctuation factors such as injector clogging, rather than inherent factors such as injector manufacturing errors.
The burden on the CPU due to the air-fuel ratio feedback control <H is reduced, and the responsiveness of the air-fuel ratio feedback control is improved.

[Brief explanation of the drawing]

Figure 1 is a functional block diagram showing the configuration of the present invention, Figures 2-
Fig. 6 shows an embodiment of the present invention, Fig. 2 is an overall configuration diagram of an automobile vertical engine and its air-fuel ratio control device, Fig. 3 is a flowchart of the air-fuel ratio control routine, and Fig. 4 is a flowchart of the air-fuel ratio control routine. A flowchart of the correction value detection update control routine, FIG. 5 is an explanatory diagram of the engine operating range, and FIG. 6 is a diagram of characteristic lines using the basic air-fuel ratio correction value and the invalid injection correction value as parameters. 12... Air flow meter, 15... Injector, 18... Intake temperature sensor, 19... 02 sensor, 21a... Crank angle sensor, 24... Atmospheric pressure sensor, 25... Control unit. Patent applicant Mazda Motor Corporation Figure 1

Claims (1)

[Claims] (1) an air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the engine; and a feedback correction value based on the deviation between the air-fuel ratio detected by the air-fuel ratio detection means and a preset target air-fuel ratio. a basic air-fuel ratio correction value that corrects variations inherent in the fuel injectors in order to bring the air-fuel ratio of the air-fuel mixture to the target air-fuel ratio; a correction value setting means for setting an invalid injection correction value for correcting the delay period; at least a feedback correction value calculated by the feedback correction value calculation means; a basic air-fuel ratio correction value set by the correction value setting means; a fuel injection amount setting means for setting a fuel injection amount supplied from the fuel valve based on the invalid injection correction value; and a plurality of basic air-fuel ratio correction values and invalid injection correction values so that the feedback correction value becomes substantially zero. correction value characteristic calculation means for calculating a plurality of correction value characteristics correlated with the basic air-fuel ratio correction value and the invalid injection correction value by arbitrarily changing each in different operating conditions; An air-fuel ratio control device for an engine, comprising correction value changing means for setting a basic air-fuel ratio correction value and an invalid injection correction value near an intersection of correction value characteristics as a new correction value.