JPH01237336A - Detecting device for abnormality in air-fuel ratio - Google Patents

Abstract

PURPOSE:To make it possible to detect abnormality early and accurately by accumulating outputs from a means for deciding oxygen concentration in exhaust gas at a predetermined times per each cylinder and detecting deviation of respective accumulating values in the distribution of all accumulating values. CONSTITUTION:There is provided a fuel supply means M2 per each cylinder (or each cylinder group) of a multi-cylinder internal combustion engine M1 for performing a control corresponding to the engine operating state. There are provided a means M3 for detecting oxygen concentration in exhaust gas and a means M4 for judging a proper fuel supply quantity based on the level of output from the means M3. Then, the judged result is feedbacked to a control means M4. In this case, there is further provided a means M5 for accumulating the output from the oxygen detecting means M3 at predetermined times per each cylinder for detecting the deviation of respective accumulating values in a distribution of the all accumulating values by a deviation detecting means M5. In detecting a cylinder having the large deviation, the air-fuel ratio is judged as being abnormal by a judged output means M7, to thereby inform the abnormality.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides accurate and quick correction of abnormal air-fuel ratios for each cylinder or cylinder group of a multi-cylinder internal combustion engine. This invention relates to an air-fuel ratio abnormality detection device that detects air-fuel ratio abnormalities.

[Conventional technology] Currently, in order to reduce and suppress fuel consumption and improve and improve emissions, fuel injection valves are used to precisely control the amount of fuel supplied to the amount of intake air to obtain appropriate output. Fuel ratio control II systems exist.

This system is an air-fuel ratio feedback control as shown in FIG. 5(B), which detects the oxygen concentration in the exhaust gas and feeds back the result to realize precise control.

In such a system, if the fuel supply system, for example a fuel injection valve, malfunctions and there is an excess or shortage of fuel, if left as is, the air-fuel ratio in the relevant cylinder will simply become inappropriate and the output will be reduced. Is the scale causing a shortage or deterioration of emissions?
Due to the above feedback, air-fuel ratios were inappropriate even in other cylinders, causing various problems in terms of output and emissions.

Such an abnormality in the air-fuel ratio for each cylinder does not occur due to an abnormality in the fuel supply system of each cylinder or cylinder group, but also occurs when the opening/closing valve timing is incorrect due to an abnormality in the valve clearance of the intake and exhaust valves in the combustion chamber. .

For this reason, it has been necessary to use some method to detect that the air-fuel ratio of one of the cylinders is abnormal, and have the manager of the internal combustion engine (in the case of a car, the driver) take countermeasures.

As a device that takes this issue into consideration, the output of internal combustion engines is being increased (
When a lean air-fuel ratio (lean) state periodically occurs during air-fuel ratio feedback control, the system determines that the fuel injection valve of the cylinder corresponding to the lean crank angle is abnormal (Japanese Patent Laid-Open No. No. 62-107252) has been proposed.

[Problems to be solved by the invention] However, if the air-fuel ratio deviation caused by various abnormalities is a slight deviation, the
(2 sensors) output deviation also becomes smaller, making detection difficult. If the sensitivity is increased, a single peak will be observed, and noise will be falsely detected as a deviation. For this reason, in order to make an accurate judgment, it is necessary to wait until the degree of abnormality becomes large enough to clearly determine that there is a deviation in ζ, which may have an effect on the internal combustion engine itself. Furthermore, if the abnormality is on the rich side, detection itself is impossible.

Structure of the Invention Therefore, the present invention employs the following structure for the purpose of solving the above problems.

[Means for Solving the Problems] That is, the gist of the present invention is, as illustrated based on the basic configuration diagram in FIG. a fuel supply means M2 which is provided and supplies fuel according to a target supply fuel amount set according to the operating state of the internal combustion engine M1; and an oxygen detection means M3 which detects the oxygen concentration in the exhaust gas of the internal combustion engine M1. , a supply amount control means M4 that determines whether the fuel supply amount is excessive or insufficient based on the output value level of the oxygen detection means M3, and feeds back to the fuel supply amount by the fuel supply means M2 according to the determination result. An air-fuel ratio abnormality detection device used in a supply control device, comprising an accumulation device M5 that accumulates the output value of the oxygen detection device M3 a predetermined number of times for each cylinder or each cylinder group, and a total accumulation of each of the cumulative values. A bias detection means M6 detects a bias in the distribution of values, and if a cylinder or cylinder group with a large bias is detected from the detection result of the bias detection means M6, the air-fuel ratio is determined to be abnormal and the abnormality is detected. An air-fuel ratio abnormality detection device characterized by comprising: determination output means M7 that outputs a notification signal.

[Operation] The accumulating means M5 accumulates the output value of the oxygen detecting means M3, which is output to the supply amount controlling means M4, a predetermined number of times for each cylinder or each cylinder group. For example, for each cylinder - once per cycle
Accumulates 200 times.

Then, this cumulative value accumulates a steady, subtle deviation (lean bias or rich bias) in the air-fuel ratio of each cylinder. If it is just a noise-like error, it will be averaged out during accumulation and will no longer appear.

The bias detection means M6 detects the bias of each cumulative value in the distribution of all cumulative values. For example, the cumulative value for each cylinder or each cylinder group is compared with the total cumulative value for all cylinders or all cylinder groups, and the extent to which there is a deviation compared to the whole is detected.

If a cylinder or cylinder group with a large bias is detected based on the detection result of the bias detection unit M6, the determination output unit M7 determines whether the cylinder or cylinder group has a large bias is detected.
It determines that the air-fuel ratio is abnormal and outputs a signal notifying the abnormality. In this way, it becomes possible to perform appropriate processing for abnormalities.

Next, the present invention will be explained in detail. The present invention is not limited to these, but includes various embodiments without departing from the gist thereof.

Embodiments Next, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a system configuration diagram of a gasoline internal combustion engine equipped with an air-fuel ratio abnormality detection device according to an embodiment of the present invention.

In the figure, a four-cylinder internal combustion engine 1 has a combustion chamber 6 formed by a cylinder 2, a piston 3, a cylinder block 4, and a cylinder head 5 for each cylinder. A spark plug 7 is disposed in each combustion chamber 6. The output from the piston 3 is transmitted to drive wheels (not shown) via various transmission mechanisms such as an automatic transmission (not shown).

The intake system of the internal combustion engine 1 is provided with an intake pipe 9 that communicates with the fuel chamber 6 via an intake valve 8, and a surge tank 10 upstream of the intake pipe 9 that absorbs pulsation of intake air. A throttle valve 11 is disposed upstream of this surge tank 1-7=0.

Further upstream is an air flow meter 1 that detects the amount of intake air.
4, and an air cleaner 15 for introducing dust-free outside air into the air flow meter 14.

On the other hand, the exhaust system of the internal combustion engine 1 is provided with an exhaust pipe 17 that communicates with the combustion chamber 6 via an exhaust valve 16.

The fuel system includes a fuel supply source consisting of a fuel tank and a fuel pump (not shown), a fuel supply pipe that derives fuel from this fuel supply source, and a fuel injection pipe arranged for each cylinder in the branched intake pipe 9. A valve 18 is provided.

The ignition system also includes an igniter 19 that outputs a high voltage necessary for ignition, and a distributor 20 that distributes and supplies the high voltage generated by the igniter 19 to the spark plug 7 in conjunction with a crankshaft (not shown). It is provided.

In addition to the air flow meter 14, the internal combustion engine 1 also includes a vehicle speed sensor 32, which is installed on the axle and outputs a pulse signal according to the rotation amount of the axle, and a throttle valve 11.
a throttle position sensor 33 that detects the opening degree of the throttle valve in conjunction with the cylinder block 4; a water temperature sensor 34 that is installed in the cooling system of the cylinder block 4 and detects the cooling water temperature;
The oxygen seismic intensity sensor (02 sensor) 35, which is installed in the exhaust pipe 17 and detects the residual oxygen concentration in the exhaust gas as an analog signal, works in conjunction with the accelerator pedal 36a, and when the accelerator pedal 36a is not depressed, "○N" is displayed. An idle switch 36 that outputs a signal is provided. Further, a warning device 37 is provided to notify the driver of a predetermined abnormality, and a warning is issued by lighting a warning lamp 37a.

Inside the distributor 2o, there is a rotation angle sensor 38 that also serves as a rotation speed sensor that outputs a rotation angle signal every 1/24 rotation of the camshaft of the distributor 20, that is, every time the crankshaft rotates 30 degrees, and A cylinder discrimination sensor 39 is provided that outputs a reference signal once for each rotation of the camshaft of the distributor 2°, that is, for every two rotations of the crankshaft.

Incidentally, the signals from each of the above-mentioned sensors are manually inputted to an electronic control unit (hereinafter simply referred to as ECU) 50, and also
3O controls each part of the internal combustion engine 1 mentioned above.

Next, the configuration of the ECU 3O will be explained based on FIG. 3.

ECU3O is CPU50a, ROM50b, RAM5
0c, a backup RAM 50d, a clock 51, etc. as a logic operation circuit, and a common bus 50e.
It is connected to an input/output port 50f, a human-powered boat 50g, and an output port 50h via the input/output port 50f for input/output with the outside.

The ECU 3O includes buffers 50i, 50j, 50, 50m, 50q for the detection signals of the sensors described above, a multiplexer 50n, and an A/D converter 50p. Among these, the analog signal buffer 50i of the air flow meter 14
, an analog signal buffer 50j of the water temperature sensor 34, and an analog signal buffer 50k of the oxygen temperature sensor 35.
The analog signal from the input terminal is A/D converted by an A/D converter 50p via a multiplexer 50n, and then inputted from a human output boat 50f.

In addition, ECU3O has both cylinder discrimination and rotation angle sensors 38.3
This signal and the signal from the throttle position sensor 33 are input manually to an input capacitor 50g.

Furthermore, the ECU 3O includes drive circuits 50t, 50u, and
50v, and the CPU 50a outputs a control signal to the drive circuits 50t, 50u, and 50v via the output capacitor 50h.

Next, the air-fuel ratio abnormality detection control and fuel injection amount control of the present invention executed by the ECU 3O will be explained based on the flowcharts shown in FIG. 4 and below. In addition to this, the ECU 3O also performs ignition timing control in accordance with the air-fuel ratio and the like.

FIG. 4(A) is a flowchart showing the processing of the air-fuel ratio abnormality detection routine which is executed by interruption at sufficiently short time intervals.

First, when the process starts, two conditions are determined. That is, it is determined whether (1) it is in a steady state (step 110) and (2) whether or not it is the A/D conversion timing for the output signal of the oxygen concentration sensor (hereinafter referred to as 02 sensor) (step 120). Steady state refers to an engine state in which there are no drastic changes in the fuel injection amount or intake air amount, and applies to a wide range of operating conditions, such as during idle rotation control using feedback after warm-up, and during constant speed operation. . Further, the timing of A/D conversion of the 02 sensor output signal is every 180'CA because it is performed for each of the four cylinders.

If either of the conditions in ■ or ■ above are not met,
As shown in FIG. 4(B), the process is temporarily terminated.

If both of the above conditions (1) and (2) are satisfied, the 02 sensor output signal is subjected to A/D conversion processing, and the converted value is read (step 150).

After the process of step 150, the process branches depending on the content of n representing the cylinder number (step 160).

This n is set by the 30' interrupt routine shown in FIG. 4(C). The 30° interrupt routine is started by the manual input ζ of the rotation angle signal from the rotation angle sensor 38. When the interrupt is executed, first, the variable 81 representing the rotation angle phase is increased by 30 degrees (step 510).
. Subsequently, it is determined whether θ1 is greater than or equal to 180° (step 520). If the angle is less than 180°, the process is immediately terminated. If the angle is 180° or more, the counter m is incremented (step 530). Next, it is determined whether m is greater than 4 (step 540). If it is larger, "1" is set to n, which is the cylinder number (step 550). If m is less than 4, nicom is set (step 560).

After step 550 or step 560, θ1
is set to 0° (step 570).

In this manner, the cylinder number n in the exhaust stroke is determined. However, when starting the internal combustion engine 1, in the initial setting by the ECU 50, n and θ1 are determined by the cylinder discrimination sensor 39.
It is determined accurately based on the relationship between the output of the cylinder discrimination signal output by the rotation angle sensor and the output of the rotation angle signal output by the rotation angle sensor 3.

Returning to FIG. 4(A), in step 160, if ■n=1, the A of the 02 sensor output signal for the exhaust of the first cylinder
The /D conversion value Ox+ is the cumulative value ΣOx of the 199 A/D conversion values Ox+ detected for the first cylinder up to the previous time.
+, and the cumulative value A1 for 200 times is calculated (
step 170). Similarly, ■ When n=2, the A/D conversion value OX2 of the 02 sensor output signal for the second cylinder exhaust gas is 199, which was detected for the second cylinder until the previous time.
It is added to the cumulative value ΣOX2 of the same A/D conversion value OX2 for 200 times, and the cumulative fi A 2 for 200 times is obtained (step 180). The A/D conversion value ○
The cumulative 1st shift A3 for 0 times is calculated (step 190),
■ When n=4, the A/D conversion value ○X4 of the 02 sensor output signal for the 4th cylinder exhaust is the cumulative value of the 199 A/D conversion values ○X4 detected for the 4th cylinder up to the previous time. It is added to the value ΣOX4, and the cumulative value of 200 times (aAA
is determined (step 200).

When the calculation of any one of the accumulation (i A 1 to A4 (steps 170 to 200) is completed, step 170 is completed.
The calculation of cumulative value A I-A a at ~210 is 200 each
It is determined whether or not the process has been performed more than once (step 21).
0). This is 200 A/D conversion data○X1～○
This is a process for attempting to make a determination based on X4. If 200 or more A/D conversions have not been performed for each cylinder and the data has not been accumulated in A1-A4, the process is temporarily terminated.

If the cumulative fffl A + to A4 have been accumulated 200 times or more, the arithmetic mean value Y of A1-A4 is calculated as shown in the following formula (step 220).

A++A2+A3+A4 Y= □ Next, moving to FIG. 4(B), the magnitude of the ratio between the cumulative values A1 to A4 and Y is determined (steps 230 to 300).
. That is, in steps 230 and 240, it is determined whether the value of AI/Y is between the upper limit S and the lower limit S2, and in steps 250 and 260, it is determined whether the value of A2/Y is between the upper limit S1 and the lower limit S2. It is determined whether or not there is, step 270
, 280, it is determined whether the value of A3/Y is between the upper limit S and the lower limit S2, and in steps 290 and 300, it is determined whether the value of A, /Y is between the upper limit S1 and the lower limit S2. It is determined whether or not. All cumulative values A1 to A4 are Sl and S2
If the air-fuel ratio is between the two, the air-fuel ratio is determined to be compact for all cylinders (step 310). For example, the upper limit S1 is 1.2,
For example, the lower limit S2 is set to 0°8.

■If the ratio of A1-A4 and Y is larger than 81, it is determined that the air-fuel ratio of that cylinder is too rich and cannot be controlled to an appropriate range, and that R11 is rich abnormality (steps 320 to 32). 350). Subsequently, a signal indicating a rich abnormality is output (Step 15 = 360). This signal is output, for example, as a signal that causes the warning lamp 37a on the dash board in the driver's seat to blink. Alternatively, the fuel injection control system may be notified of the abnormality and the injection of the corresponding injector may be stopped for one day.

Further, data indicating whether the cylinder or cylinder group is rich abnormal may be written in the backup RAM 50d. In this case, during repair, back-up RAM 50d
By examining the data inside, you can immediately find out which cylinder or group of cylinders is abnormal.

On the other hand, if the ratio of A1-A4 to Y is smaller than 82, it is determined that the air-fuel ratio of that cylinder is too lean and cannot be controlled within an appropriate range, that is, a lean abnormality occurs (steps 370 to 400). . Subsequently, a signal indicating lean abnormality is output (step 410). The lighting of the warning lamp 37a and the notification to the fuel injection control system are the same as in the case of rich abnormality.

In this case as well, as described above, data indicating whether the cylinder or cylinder group has a rich abnormality may be written in the backup RAM 50d and used at the time of repair.

In this way, the process is once terminated and repeated at predetermined time intervals.

The fuel injection amount control process and its feedback process executed in the system of this embodiment are shown in FIG. 5(A).
, (B).

Each control is executed at predetermined time intervals. First, in the fuel injection amount control routine of FIG. 5(A), the detection signal Q from the air flow meter 14 and the rotation angle sensor 38 is detected.

A NE is captured (step 610). Next, based on this, the basic fuel injection amount (time) TP is determined from the map f (Q/NE) prepared in the ROM 5, Ob (step 620). Next, the actual fuel injection amount (time) TAU is calculated based on the formula below (step 630).

TAtJ=TPXFAFXα+β Here, α is a correction coefficient set to a value other than 1.0 when the engine is cold or accelerated, and β is a correction value for invalid injection time, etc. FAF is a feedback correction coefficient, and is set as shown in the FAF setting interrupt routine of FIG. 5(B).

That is, when the process is started at predetermined time intervals, it is determined whether the feedback condition is satisfied (step 7).
10). If not established, FAF is fixed at 1.0 (step 720). If it is true, take in the A/D conversion value of the 02 sensor output signal (step 730).
, it is determined whether the head is greater than 0°45V (step 740).

(2) If the A/D conversion value is thicker than 0.45V, it is considered rich, and it is further determined whether or not it was rich last time (step 750). If it was rich last time, FAF is decreased by a predetermined value K1 in order to gradually reduce the fuel injection amount (step 760). If it was lean last time,
Since the switch has been made to rich this time, the FAF is decreased by a value of skip (straight R5) which is larger than Ki for reasons such as responsiveness (step 770).

(2) If the A/D conversion value is 0.45V or less, it is considered lean, and it is further determined whether or not it was lean last time (step 780). If it was lean last time, FAF is increased by a predetermined value Ki in order to gradually increase the fuel injection amount (
step 790).

If it was rich last time, it has switched to lean this time, so FAF is increased by the skip value R9, which is a value greater than 1 (step 800).

The process is thus completed and repeated at predetermined time intervals, and if the feedback condition is satisfied, the FAF is constantly updated.

Returning to FIG. 5(A), this TAU is set to the output port 50h (step 640). This causes the drive circuit 50t to operate at a predetermined timing to open the fuel injector for a period of time TAU. In this way, the process is once terminated and repeated at predetermined time intervals.

FIG. 6 shows the 02 sensor output value when the fuel injection amount control and its feedback process are executed. Of these, (A) is a timing chart when the fuel injection valve 1 and the valve clearances of the supply and exhaust valves 8 and 16 are normal and the air-fuel ratio is controlled normally; (B)
The valve clearance of the fuel injection valve 18 of one cylinder or the intake/exhaust valve 8° 16 of one cylinder is abnormal,
It is a timing chart when the air-fuel ratio of that cylinder is excessively rich. That is, in the normal timing chart (A), the trajectory is smooth, but in the abnormal timing chart (B), a peak is formed in the exhaust stroke of the relevant cylinder.
Not smooth.

Therefore, for example, if the second cylinder has a rich abnormality,
In step 180 of FIG. 4(A), A corresponding to the peak is
Only the /D conversion value is accumulated in A2 200 times, and the other accumulated values AI + A3 + A, l are normal values,
Alternatively, under the condition that the feedback control after step 730 in FIG. 5(B) is being executed, a value lower than the normal value is set for the feedback control. Therefore, for A2, a negative determination is made in step 250 of FIG. 4(B) that the upper limit S1 has been exceeded, and the second cylinder is determined to have a rich abnormality (step 330), and a rich abnormal signal is output. (step 360
).

When the warning lamp 37a lights up in this way, the driver can recognize the abnormality and take immediate action to deal with it, thereby preventing wasted fuel due to abnormal combustion conditions, and further preventing deterioration of emissions. Furthermore, the internal combustion engine will not malfunction due to long-term abnormal conditions.

In this embodiment, the four-cylinder internal combustion engine 1 corresponds to the multi-cylinder internal combustion engine M1, and the fuel injection valve 1 corresponds to the fuel supply means M.
2, the oxygen concentration sensor (02 sensor) 35 corresponds to the oxygen detection means M3, and the electronic control unit (ECU) 50 corresponds to the supply amount control means M4, the accumulation means M5, and the bias detection means M6.
and the judgment output means M7. Incidentally, among the controls executed by the electronic control unit (ECU) 50, the processes in step 630 in FIG. 5(A) and in FIG. ~200
The processing of steps 220 to 300 corresponds to the processing of the bias detection means M6, and the processing of steps 320 to 410 corresponds to the processing of the determination outputting means M7.

Effects of the Invention In the air-fuel ratio abnormality detection device of the present invention, the accumulation means M5 accumulates the output value of the oxygen detection means M3 a predetermined number of times for each cylinder or each cylinder group. As a result, unless there is a particularly drastic change in operating conditions, abnormalities in the air-fuel ratio will clearly appear in the cumulative value.
Abnormalities in the air-fuel ratio for each cylinder or for each cylinder group can be detected early and accurately.

Therefore, it can be applied to a wide range of operating conditions, and measures can be taken early to prevent insufficient output or worsening of emissions.
This can prevent deterioration of fuel efficiency and adverse effects on the internal combustion engine.

[Brief explanation of the drawing]

Fig. 1 is a diagram illustrating the basic configuration of the present invention, Fig. 2 is a system configuration diagram of one embodiment, Fig. 3 is a block diagram of the ECU, and Fig. 4 is a diagram illustrating the basic configuration of the present invention.
Figures (A) and (B) are flowcharts 1 and 4 (C) are flowcharts 3 and 3 respectively showing the air-fuel ratio abnormality detection routine performed by the ECU.
Flowchart of 0° interrupt routine, Figure 5 (A)
is also a flowchart of the fuel injection amount control routine, FIG. 5(B) is a flowchart of the FAF setting interrupt routine, FIG. 6(A) is a timing chart of the 02 sensor output value when the air-fuel ratio is normal, and FIG. B) represents a timing chart of the 02 sensor output value when the air-fuel ratio of one cylinder is abnormal. Ml...Multi-cylinder internal combustion engine M2...Fuel supply means M3...Oxygen detection means M4...Supply amount control means M5...-Accumulation means M6...-Bias detection means M7--Judgment output means 1... Internal combustion engine 14... Air flow meter 18... Fuel injection valve 35... Oxygen concentration sensor (02 sensor) 37-... Alarm device 38-... Rotation angle sensor 50... Electronic control device (ECU)

Claims (1)

[Scope of Claims] 1. A fuel supply means that is provided for each cylinder or each cylinder group of a multi-cylinder internal combustion engine and supplies fuel according to a target fuel supply amount set according to the operating state of the internal combustion engine; an oxygen detection means for detecting the oxygen concentration in the exhaust gas of the internal combustion engine; and determining whether the amount of fuel supplied is excessive or insufficient based on the output value level of the oxygen detection means, and the amount of fuel supplied by the fuel supply means according to the determination result. an air-fuel ratio abnormality detection device for use in a fuel supply control device, comprising: a supply amount control means for feeding back to the oxygen detection means; a bias detection means for detecting a bias in the distribution of all cumulative values of each of the cumulative values; and if a cylinder or cylinder group with a large bias is detected based on the detection result of the bias detection means, the air-fuel ratio An air-fuel ratio abnormality detection device comprising: determination output means for determining that the ratio is abnormal and outputting a signal indicating the abnormality.