JPS6345443A - Abnormality deciding method for air-fuel ratio controller - Google Patents

Abstract

PURPOSE:To decide that a fuel supply system is abnormal if feedback correction is not carried out for more than predetermined time in each learning area, by splitting an air-fuel ratio feedback control area into a plurality of learning areas and updating the learning value with an average value of air-fuel ratio feedback correction factor for each learning area. CONSTITUTION:A control circuit 26 operates a basic fuel injection based on an intake air flow fed from an air flow meter 2 and a rotation fed from a crank angle sensor 30. Then said basic fuel injection is corrected by a learning value for each operating area splitted on the basis of the intake air flow and the rotation and by an air-fuel ratio feedback correction factor in an operating area where feedback correction is made, thus carrying out the air-fuel ratio control. The learning value in each operating area is updated such that the average value of feedback correction factor in that operating area will have a predetermined value. On the other hand, guard is set in the feedback correction factor and the learning value in order to prevent erroneous control and erroneous learning. It is decided that an injection valve is defective if the feedback correction is not made for longer than a predetermined time in each learning area because of said guard.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for determining an abnormality in an air-fuel ratio control device, and in particular, a method for determining an abnormality in an air-fuel ratio control device '4B that controls the air-fuel ratio by controlling the amount of fuel injection. Regarding the method.

(Prior Art) An air-fuel ratio control method using an air-fuel ratio control device, which is the basis of the present invention, will be explained with reference to FIGS. 2 and 3. The second leap is executed every predetermined time (for example, 64 m5ec). In step 200, it is determined whether the engine cooling water temperature is above a predetermined temperature (for example, 60 degrees Celsius), whether the 0□ sensor is activated, and whether the fuel injection amount has been increased. It is determined whether the air-fuel ratio feedback control conditions are satisfied by determining whether the 1.0 and ends this routine. When it is determined in step 200 that the air-fuel ratio feedback control condition is satisfied, it is determined in step 204 whether or not the 02 sensor output ○X indicates an air-fuel ratio rich. When it is determined that the 0□ sensor output OX indicates a rich air-fuel ratio, in step 208, fog is calculated from the air-fuel ratio feedback correction coefficient FAF to an integral constant, and the 02 sensor output oX indicates a lean air-fuel ratio. If so, in step 206, the integral constant is added to the air-fuel ratio feedback correction coefficient FAF, and the process proceeds to step 210.

In step 210, it is determined whether the 02 sensor output OX has reversed from rich to lean or from lean to rich. If this determination is affirmative, in step 212, the average value FA of the air-fuel ratio feedback correction coefficient calculated last time is determined.
Using FAV and the air-fuel ratio feedback correction coefficient FAF integrated in step 2.6 and step 208, the air-fuel ratio feedback correction coefficient F is calculated based on the following 2.
Calculate the AF average value FAFAV.

In the next step 214, the engine rotational speed NE and the intake air i
In step 216, a learning area corresponding to the current engine speed NE and intake air amount Q is determined. This learning area is determined by the engine speed NE and the engine load Q/NE as shown in Fig. 4, and ranges from the low intake air amount area to the high intake air amount area to the learning area A, the learning area B, and the learning area B. It is divided into areas C and defined. Note that the region where the intake air amount is higher than learning region C is the air-fuel ratio open loop control region, and the region between learning region A and learning region B and the region between learning region B and learning region C is the air-fuel ratio open loop control region. This is a canister purge area that supplies adsorbed blow-by gas to the intake system.

In the next step 218, the average value FAFAV of the air-fuel ratio feedback correction coefficient calculated in step 212 is stored as the average value FAFAV(X) of the air-fuel ratio feedback correction coefficient of the learning area determined in step 216. Note that X indicates one of learning area A, learning area B, and learning area C. In the next step 220, the average value FAFAV (x) of all air-fuel ratio feedback correction coefficients is 1.0.
In step 224, it is determined whether the
It is determined whether the average value FAFAV (x) of all the air-fuel ratio feedback correction coefficients is less than 1.0. In step 220, all of the average values FAFAV(X) are
If it is determined that the value exceeds O, step 222
, set the learning value FGHAC to a predetermined amount (for example, 0.05
), and in step 224 the average value FAFAV (x
) is 1. If it is determined that it is less than 0, step 226
, set the learning value FGHAC to a predetermined value (for example, 0.05
), and in the next step 228 the average value FAFAV
Set all of (x) to 1.0 and end this routine.

Note that when all of the average values FAFAV (x) are 1.0, this routine ends without updating the learned value FGHAC.

As a result of the above, the air-fuel ratio feedback correction coefficient corresponds to the stoichiometric air-fuel ratio through integral processing so that it gradually decreases when the 02 sensor output indicates rich and gradually increases when the Oz sensor output indicates lean air-fuel ratio. It changes around the value, that is, 1.0. In addition, the learning value FGHAC
is updated to increase or decrease in accordance with the magnitude of the average value of the air-fuel ratio feedback correction coefficient calculated each time the 02 sensor output is reversed. Note that upper and lower limits of the above-mentioned air-fuel ratio feedback correction coefficient FAF and learning value FGHAC are generally determined as shown below in consideration of fail-safes due to erroneous learning and the like.

0.8≦FAF≦1.2... 2) -〇, 2≦FGHAC≦0.2... (3) Figure 3 shows the fuel flow rate executed at predetermined time intervals (for example, every 4 m5ec). This shows an injection amount calculation routine. In step 300, the engine rotation speed NE and intake air IQ are taken in, and in step 302, the basic fuel injection time TP (=Q/λ・NE (where λ is the air-fuel ratio) is calculated, and in step 304, the fuel injection time TAU is calculated based on the following formula.

TAU=TP (FAF 1 FGHAC)・K...(4
) However, K is an increase correction coefficient for increasing the fuel injection amount according to the intake air temperature, engine cooling water temperature, etc.

After calculating the fuel injection time TAU as shown in equation (4) above, the air-fuel ratio is feedback-controlled by opening each fuel injection valve for a time corresponding to the fuel injection time at every predetermined crank angle.

In the above air-fuel ratio control method, for example, if one of the fuel injection valves in a four-cylinder internal combustion engine is disconnected and fuel injection is no longer performed, the theoretical air-fuel ratio will be Since the feedback correction coefficient FAF changes around 4/3-1, 33, . . . , the air-fuel ratio moves to the air-fuel ratio rich side by 33% due to the air-fuel ratio feedback control. For this reason, conventionally, in order to detect abnormalities in the fuel injector, the sum of the air-fuel ratio feedback correction coefficient FAF and the learning value FGHAC is used to determine whether the following equation (5) or (6) holds true. By making such judgments, abnormalities such as short circuits, clogging, etc. of the fuel injector UI line were detected.

Note that equations (5) and (6) are obtained from the above (2) and (3) II.

FAF+FGHAC≦0.6...(5) FAF1FG
HAC≧1.4...(6) That is, fuel injection for the basic fuel injection amount! When the amount is corrected to the rich or lean side by 40% or more, it is determined that the correction amount is caused by a disconnection or short circuit of the fuel injection valve, and that the fuel injection valve is abnormal.

Also, JP-A-57-72054 and JP-A-59
As shown in Publication No. 96451, it was determined that the 02 sensor was abnormal when the 02 sensor output did not reverse in all operating ranges.

[Problem that the invention seeks to solve]

However, as explained above, in a four-cylinder internal combustion engine, when fuel injection is no longer executed from one of the fuel injection valves, the air-fuel ratio feedback correction coefficient FAFO value theoretically changes to 1.
33..., which exceeds the upper limit of 1.2 explained in equation (2) above. Therefore, the air-fuel ratio feedback correction coefficient is limited by the upper limit value to 1.2, and air-fuel ratio feedback control is no longer performed, and therefore the learning value FGHAC is no longer updated, so the FA
There was a problem in that the state of +FC;HAC=1.2 continued, and the above equation (6) could not determine whether there was an abnormality in the fuel injection valve or the like. Conversely, if the wiring of the fuel injector is short-circuited and the valve remains open, the air-fuel ratio feedback correction coefficient FAF is limited to the lower limit value 0.8 according to equation (2) above. It is not possible to determine whether there is an abnormality in the injection valve, etc.

In addition, in the method of determining an abnormality based on whether or not the 0□ sensor output reverses during all operating conditions, it is determined that there is an abnormality even if the 0□ sensor output does not reverse due to tolerances of the 0□ sensor, weather conditions, etc. Therefore, there was a problem in that it was not possible to accurately determine the abnormality of the O2 sensor or the like.

The present invention has been made to solve the above-mentioned problems, and even when the air-fuel ratio feedback correction coefficient is limited to the upper and lower limits and the learned value is not updated, it is possible to accurately detect abnormalities in the air-fuel ratio control device including the fuel injection valve. It is an object of the present invention to provide a method for determining abnormalities in air-fuel ratio control mZ that can be accurately determined.

[Means for solving problems]

In order to achieve the above object, the present invention divides the air-fuel ratio feedback control region into a plurality of learning regions, calculates the average value of the air-fuel ratio feedback correction coefficient obtained from the 02 sensor output for each learning region, and calculates the basic fuel injection amount. In determining an abnormality in the air-fuel ratio control device that performs feedback control of the air-fuel ratio using the air-fuel ratio feedback correction coefficient and the learning value that is updated so that the average value becomes a predetermined value, determines whether air-fuel ratio feedback control is being executed when the has been operated for a predetermined time or longer, and determines that the air-fuel ratio control device is abnormal when air-fuel ratio feedback control is not executed in each learning area. Features.

[Effect]

According to the present invention, as explained above, the average value FAFAV of the air-fuel ratio feedback correction coefficient is obtained for each learning 9N range, and the average value of the basic fuel injection amount, the air-fuel ratio feedback correction coefficient FAF, and the air-fuel ratio feedback correction coefficient F.A.
Learning value FGHA that is updated so that FAV becomes a predetermined value
The air-fuel ratio is feedback-controlled using C. In addition, when the engine has been operated for a predetermined time or longer within each learning area, it is determined whether or not air-fuel ratio feedback control is being executed, and when air-fuel ratio feedback control is not being executed within each learning area, that is, when the air-fuel ratio When air-fuel ratio feedback control is not performed within the learning region where feedback control is performed, it is determined that an abnormality has occurred in the air-fuel ratio control device. Note that whether or not air-fuel ratio feedback control is being executed can be determined by measuring the number of reversals of the 0□ sensor output, and when the number of reversals in each learning area is less than a predetermined value, that is, air-fuel ratio feedback is detected. When control is no longer being performed and learning is no longer being performed, air-fuel ratio control including the fuel injection valve! It can be determined that the A position has become abnormal. By appropriately determining the number of reversals, it can be determined that the air-fuel ratio control device has become abnormal when the number of reversals is less than a predetermined value, and also when the air-fuel ratio feedback control is being performed normally, the number of reversals of the 02 sensor output is the predetermined value. If the value of the air-fuel ratio feedback correction coefficient is sometimes limited to the upper and lower limits due to changes in the fuel injection amount due to tolerances of the fuel T4 injector, etc., the value of the air-fuel ratio feedback correction coefficient is sometimes limited to the upper and lower limits. If it is less than the number of times but exceeds the above prescribed value,
It can be determined that the air-fuel ratio control device including the fuel injection valve is normal.

〔Effect of the invention〕

As explained above, according to the present invention, the abnormality of the air-fuel ratio control device is determined within each learning region, and when it is determined that there is an abnormality in each learning region, it is determined that the air-fuel ratio control device is abnormal.
Even if the air-fuel ratio feedback correction coefficient is continuously limited to the upper and lower limits, it is possible to determine an abnormality in the air-fuel ratio control device, and the air-fuel ratio feedback correction coefficient can be adjusted only in a specific learning area due to changes in weather conditions, etc. An effect can be obtained in that when the value is temporarily limited to the upper and lower limit values, it is not determined to be abnormal.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A four-cylinder internal combustion engine equipped with an air-fuel ratio control device to which the present invention is applicable will be described in detail below with reference to the drawings. As shown in FIG. 5, an air flow meter 2 that directly detects intake air iQ is arranged downstream of an air cleaner (not shown). This air flow meter 2 is
It is composed of a compensation plate 2A rotatably arranged in a damping chamber, a measuring plate 2B connected to two compensation motion plates, and a potentiometer 2C that generates a voltage according to the opening degree of this measuring plate 2B. has been done. Therefore, the intake air iQ can be detected by the voltage output from the potentiometer. A throttle valve 4 is arranged downstream of the air flow meter 2, and the throttle valve 4 has an idle switch 6 that outputs an on signal when the throttle valve is fully closed, and outputs a voltage proportional to the opening degree of the throttle valve 4. A throttle opening sensor 8 is attached. A surge tank 10 disposed downstream of the throttle valve 4 communicates with a combustion chamber of an engine body 25 via an intake manifold 12. A fuel injection valve 14 is arranged in each of the intake manifolds 12 so as to correspond to each cylinder.The combustion chamber of the engine main body 25 has an exhaust gas equipped with a catalyst device filled with a three-way catalyst via an exhaust manifold 16. connected to the tube. A 0□ sensor 18 is attached to the exhaust manifold 16 to detect the residual oxygen concentration in the exhaust gas and output an inverted signal at the residual oxygen concentration corresponding to the stoichiometric air-fuel ratio. Further, a thermistor-type water temperature sensor 20 is attached so as to protrude into a water jacket formed in the cylinder block of the engine body 25.

An ignition plug is attached so as to protrude into a combustion chamber formed in the engine body 25, and this ignition plug is connected to a control circuit 26 via a distributor 22 and an igniter 24. Attached to the distributor 22 are a cylinder discrimination sensor 2B and a rotation angle sensor 30, which each include a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing. This cylinder discrimination sensor 2
8 generates a reference position signal every 72Q@CA (crank angle), and the rotation angle sensor 30 outputs a crank angle signal every 30'CA.

The control circuit 26 is composed of, for example, a microcomputer, and includes a central processing unit (CPU) 32, an analog-to-digital (A/D) converter 34, and a read-only memory (RO).
M) 36, a random access memory (RAM) 38, and a random access memory (Ilo) 40 are provided. Signals output from the throttle opening sensor 8, water temperature sensor 20, and air flow meter 2 are input to the A/D converter 34, and an idle switch 6 and a cylinder discrimination sensor are input to the input/output port 40. 28, rotation angle sensor 30
The signal output from the 02 sensor 18 is inputted via the buffer 42 and the comparator 44. And input/output boat 40
is connected to the fuel injection valve 14 via a down counter 46, a flip-flop 48, and a driver 50, and is also connected via a driver 52 to the other end of a check clamp 54 whose one end is grounded. This down counter 46
, the flip-flop 48 and the driver 50 control the opening time of the fuel injection valve 14 to control the fuel injection amount, and when the fuel injection time TAU is calculated, this fuel injection time TAU is counted by the down counter 46. It is also set in the flip-flop 48. As a result, the driver 50 energizes the fuel injection valve 14 to start fuel injection. On the other hand, the down counter 46 counts a clock signal (not shown) and sets the fuel injection time TA.
When the value corresponding to U is reached, the flip-flop 48 is reset and the driver 50 stops energizing the fuel injection valve 14 and stops injecting fuel. Therefore,
The fuel injection valve 14 is opened for a time corresponding to the fuel injection time TAU, and fuel corresponding to the fuel injection time TAU is supplied into the combustion chamber of the engine body 25.

FIG. 6 is a circuit diagram showing details of the 0□ sensor 18, buffer 42, and comparator 44 shown in FIG. buffer 4
2 consists of a parallel circuit consisting of a capacitor C1 and a resistor R1, one end of which is grounded, and the comparator 44 is a series circuit consisting of an operational amplifier OP, a resistor R2 that generates a comparison voltage v, (=0.45 volts), and a resistor R3. It is made up of.

Note that the resistor R1 is used to limit the maximum level of the output voltage VOX when the element temperature of the 02 sensor 18 becomes excessive. As a result, the voltage ■ output from the Oz sensor 18. 8 is called once to the buffer 42, converted into a digital signal by the comparator 44, and inputted to the human output port 40 as the 02 sensor output OX. Note that ■cc indicates the voltage a of the control circuit 26 (for example, 5 ports). The ROM stores in advance a control routine program to be described below and a learning area map shown in FIG.

FIG. 1 shows a routine that is executed every predetermined time (for example, 24 m5 ec). First, in step 100, it is determined whether or not the check lamp 54 is lit. When the check clamp 54 is lit, this routine is ended, and when the check clamp 54 is not lit, the routine proceeds to step 102, where the engine rotational speed NE and intake air amount Q obtained from the crank angle signal are acquired. In step 104, a learning area corresponding to the current driving state is determined from the map shown in FIG. 4 in the same manner as described above. In the next step 106, it is determined whether or not the learning area has changed due to a change in the driving condition. If the learning area has changed, in step 108, it is determined whether the driving condition has been in a specific learning area or not. Count to count (i
CN_T is cleared and set to 0 in step 110.
The inversion count value COX, which counts the number of inversions of the two sensor outputs, is cleared and the process proceeds to step 118.

On the other hand, when it is determined in step 106 that the learning area has not changed, the count value CNT is incremented in step 112, and in step 114 it is determined whether the 02 sensor output OX has reversed from rich to lean or from lean to rich. to decide. 02 sensor output O
If X is inverted, the inversion count value CoX is incremented in step 116.

In the next step 118, based on the count value CNT, the institution spends a predetermined period of time (for example, 35ec) within a specific learning area.
It is determined whether or not the vehicle has been driven. When the judgment in step 118 is negative, the process proceeds to step 126, and step 11
If the determination in step 8 is affirmative, it is determined in step 120 whether the inverted count value COX is greater than or equal to a predetermined value (for example, 2). If it is determined that the inversion count value COX is greater than or equal to the predetermined value, the flag F(x
), and if it is determined that the inverted count value COX is less than a predetermined value, the flag F (
Set x). Note that X in the flag F (x) corresponds to learning areas A to C in FIG. 5.

In the next step 126, the sum ΣF of the flags F (x)
It is determined whether or not (x) is a predetermined value corresponding to the number of learning regions, that is, 3 or more. If the sum ΣF (x) is 3 or more, it is determined that a disconnection or short circuit of the fuel injector has occurred, and step 128 At this point, a signal is output to the check clamp 54 via the driver 52 to turn on the check clamp 54. On the other hand, if the total sum ΣF (x) is less than the predetermined value, this routine is immediately terminated.

As a result of the above, if the engine has been operated for a predetermined time or longer within a specific learning region, and the number of reversals of the OX sensor while operating within this learning region is determined to be less than the predetermined value in all learning regions, fuel injection is performed. It is determined that the valve is abnormal and the check clamp is turned on.

The number of times the O If an abnormality occurs, the number of reversals will be smaller than in the above case, so it is possible to determine whether the fuel injection valve is abnormal from the number of reversals. Also, in all learning areas, that is, learning SR area A, learning area B, and learning area C, 0□
The reason why the fuel injector is determined to be abnormal when the number of reversals of the sensor output is less than a predetermined value is because the number of reversals of the 02 sensor within the above predetermined time is normal in a specific learning area due to changes in weather conditions, etc. This is because it may be less than the state.

Next, referring to FIG. 7, the flags F (x) (=F (A), F (B), F
(C) Changes in ) and changes in air-fuel ratio feedbank correction coefficient FAF and learned value FGHAC when fuel injection valve is abnormal
Explain the changes in

In a 4-cylinder internal combustion engine, all four fuel injection valves are operating normally, and when one of the fuel injection valves is closed due to a disconnection at time T2, the difference between time T1 and time T2 is centered around 1.0. The air-fuel ratio feedback correction coefficient FAF, which has been changing, is gradually increased because the fuel injection amount decreases and the 0□ sensor output indicates a lean air-fuel ratio. Then, when the upper limit value shown in (2) 2 above is reached, it is limited to this upper limit value. A predetermined period of time from time T2 (
At time T3, when 35 ec) have elapsed as explained above,
0□Since the number of reversals of the sensor output is O, the flag F (
A) is set. Similarly, flag F (B) is set at time T when driving in learning area B for a predetermined time or more, and flag F (C) is set at time T when driving in learning area C for a predetermined time or more. Ru. As a result, at time T1, flags F (A), F (B
) and F (C) are all set, thereby lighting the check lamp.

Here, when determining the abnormality of the fuel injection valve using the above formulas (5) 2 and (6) as in the past, after the air-fuel ratio feedback correction coefficient FAF is limited to 1.2, the 0□ sensor output Since it is not inverted, the learning value F G HAC is not learned and the state of F G HAC = O continues, and as a result, the state of FAF + FGHAC = 1.2 continues.
No abnormality in the fuel injection valve is detected, and as a result, the check lamp is not lit. In order to solve this problem, it is possible to greatly change the upper and lower limits of the air-fuel ratio feedback correction coefficient FAF, but in reality it is impossible to change these upper and lower limits considering the possibility of erroneous learning due to failure of the 02 sensor. It is.

In addition, in the above embodiment, the abnormality of the fuel injector is determined within the learning region, that is, the learning region and the fuel injector abnormality determination region are made to match, so that the flow rate change due to the tolerance of the fuel injector and the weather conditions Even if the air-fuel ratio feedback correction coefficient FAF is temporarily limited to the upper and lower limits due to changes in the flow rate due to changes in Therefore, the effect that the check lamp is not turned on in such a case can be obtained. Further, since a plurality of determination areas are provided, it is possible to prevent erroneous determination when the 02 sensor output is no longer inverted due to the above-mentioned flow rate change.

Note that in the above, it was determined that an abnormality in the fuel injection valve had occurred when all of the flags F (x) were 3 or more, but in step 124, the number of times the inversion count value COX became less than a predetermined value Count n and step 126
The check lamp may be turned on when ΣF (x) becomes 3n or more. By doing so, erroneous determination of fuel injection valve abnormality can be more effectively prevented. Furthermore, although the example in which the learning area is divided into three parts has been described above, the present invention is not limited to this, and the learning area can be divided into a plurality of parts exceeding three or a plurality of parts less than three. Good too. In this case, values equal to the number of learning areas are selected for 3 in step 126 and 3 in 3n described above. Further, although an example in which the learning area and the abnormality determination area are the same has been described above, the learning area and the abnormality determination area may be different. Further, in the above, it is determined that the air-fuel ratio is not being fed back by counting the number of times the O2 sensor is reversed, but the present invention is not limited to this, and the air-fuel ratio feedback correction coefficient FAF is set to the upper and lower limits. It may be determined whether or not feedback is not being executed by detecting the time limited to . In addition, although the abnormality of the fuel injection valve is determined in the above, it is also possible to determine the abnormality of the 02 sensor.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the abnormality determination routine of the present invention, and FIG.
Figure 3 is a flowchart showing the learning routine of the air-fuel ratio control method that is the basis of the present invention, Figure 3 is a flowchart showing the fuel injection amount calculation routine, Figure 4 is a diagram showing the learning area, and Figure 5 is the invention of the present invention. Equipped with an applicable air-fuel ratio control device! ! FIG. 6 is a schematic diagram showing engine A, FIG. 6 is a circuit diagram showing the buffer and comparator of FIG. 5, and FIG. 7 is a diagram showing changes in the air-fuel ratio feedback correction coefficient, learning value, and flag with respect to the course of engine operation. 14...Fuel injection valve, 18...02 sensor, 26...Control circuit, 54...Check clamp.

Claims (1)

[Claims] (1) Divide the air-fuel ratio feedback control region into multiple learning regions, find the average value of the air-fuel ratio feedback correction coefficient obtained from the O_2 sensor output for each learning region, and calculate the basic fuel injection amount and the air-fuel ratio feedback correction coefficient. In determining an abnormality in the air-fuel ratio control device that performs feedback control of the air-fuel ratio using the learned value that is updated so that the average value becomes a predetermined value, the engine is operated for a predetermined time or more within each learning region. An abnormality determination method for an air-fuel ratio control device, which determines whether or not air-fuel ratio feedback control is being executed at certain times, and determines that the air-fuel ratio control device is abnormal when air-fuel ratio feedback control is not executed in each learning region.