JPH0772514B2 - Secondary air introduction abnormality detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for warming up an engine three-way catalyst at low engine temperatures.
The present invention relates to an abnormality detection device for a secondary air introduction device that introduces secondary air from an intake system to an exhaust system.

[Conventional technology and problems]

For example, in a so-called air-fuel ratio feedback device that detects the residual O ₂ concentration in exhaust gas with an air-fuel ratio detector such as an O ₂ sensor and feeds back the signal to the control unit to control the fuel supply amount to the engine. As a post-treatment, an exhaust gas converter, that is, a three-way catalyst, having a high purification rate for exhaust gases such as CO and HC in the range of the theoretical air-fuel ratio is installed. However, this three-way catalyst has a low purification rate when the engine is at a low temperature, and as a result, exhaust gas tends not to be sufficiently purified. Therefore, as a measure to warm up the three-way catalyst at low temperatures, for example, air (secondary air) is bypassed from the intake system such as an air cleaner and introduced into the exhaust system, and HC, C
There is known a secondary air introducing device that oxidizes O and heats the three-way catalyst in a warmed-up state. This secondary air introducing device is roughly divided into an air supply source, an air injection method using an air pump, and an air suction (AS) method that directly draws air from the atmosphere through a check valve (called AS valve) by utilizing pulsation of exhaust gas. However, both have a secondary air control valve that activates or deactivates the secondary air introduction device and is controlled by the output from the computer according to the engine temperature.

In an internal combustion engine equipped with such a secondary air introducing device, the secondary air control valve remains closed due to sticking or the like, even though an operation signal is output to the secondary air introducing device, or If the valve is not opened to the intended opening degree, or if the air pump of the secondary air introducing device malfunctions, the desired amount of secondary air is not supplied to the exhaust system,
Since the three-way catalyst is not warmed up early, there is a problem that unpurified exhaust gas is discharged in a relatively long period until it is warmed up, and exhaust emission deteriorates. The driver needs to know such an abnormality of the secondary air introducing device at an early stage and repair it. Therefore, an object of the present invention is to provide a secondary air introduction abnormality detection device capable of detecting an abnormality of the secondary air introduction device in which a desired amount of secondary air is not supplied to the exhaust passage.

[Means for solving problems]

The secondary air introduction abnormality detection device according to the present invention is an air-fuel ratio feedback device that determines an air-fuel ratio correction coefficient based on an air-fuel ratio signal from an air-fuel ratio detector installed in an exhaust system and controls a fuel supply amount to an engine. An internal combustion engine provided with a secondary air introducing device for introducing secondary air to the upstream side of the air-fuel ratio detector of the exhaust system at a low engine temperature,
A secondary air introducing device operation determining means for determining whether or not an operating signal is issued to the secondary air introducing device, and an operating signal is issued to the secondary air introducing device by the secondary air introducing device operation determining means. When the average value of the air-fuel ratio correction coefficient when it is determined that the secondary air introduction device is abnormal is included, the secondary air introduction device is determined to be abnormal.

[Action]

When it is determined by the secondary air introducing device operation determining means that the operating signal is being issued to the secondary air introducing device,
If a desired amount or more of secondary air is introduced into the exhaust system upstream of the air-fuel ratio detector by the secondary air introduction device, it is determined by the air-fuel ratio feedback control device based on the air-fuel ratio signal from the air-fuel ratio detector. The average value of the air-fuel ratio correction coefficient is
In order to increase the fuel supply amount with respect to this secondary air, it should be larger than a predetermined value, so that at this time, if the average value of the air-fuel ratio correction coefficient is equal to or smaller than the predetermined value, Either no secondary air is supplied or only less than the desired amount of secondary air is introduced,
The abnormality determining means determines that the secondary air introducing device is abnormal.

〔Example〕

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

FIG. 1 is a block diagram showing the entire secondary air introduction abnormality detecting device for an internal combustion engine of the present invention.

Reference numeral 1 denotes an internal combustion engine (combustion chamber), 2 denotes an intake passage, 3 denotes an exhaust passage, an air-fuel ratio detector 4 is provided in the exhaust passage 3, and sends an air-fuel ratio signal to an air-fuel ratio feedback device 5. As a result, the device 5 controls the fuel supply amount. 6
Is a secondary air introduction device for bypassing the engine 1 from the intake passage 2 and introducing secondary air into the exhaust passage 3,
The secondary air control valve 8 that connects and disconnects the bypass 7 is controlled to open and close. Further, 9 is a secondary air introducing device operation judging means for judging the presence or absence of a control valve operating signal from the secondary air introducing device 6, and the abnormality judging means 10 is an air-fuel ratio correction coefficient FAF from the air-fuel ratio feedback device 5. The warning signal is transmitted based on the average value of the above and the signal from the secondary air introducing device operation determining means 9.

FIG. 2 shows a specific embodiment of the present invention in which the present invention is applied to an internal combustion engine equipped with an air-fuel ratio feedback device equipped with an electronically controlled fuel injection device (fuel injector) and an air suction type secondary air introduction device. FIG.

A piston is installed in the cylinder bore 12 formed in the engine body 11.
13 is slidably accommodated, and a combustion chamber 14 is formed above the piston 13. Intake port 15 connected to combustion chamber 14
And exhaust port 16 have intake valve 17 and exhaust valve, respectively.
Opened and closed by 18.

The intake passage 21 communicating with the intake port 15 has an air cleaner 22 on the most upstream side, and an air flow meter 23 on the immediate downstream side. The throttle valve 24 is an air flow meter
It is arranged on the downstream side of 23. The fuel injection valve 25 is provided on the downstream side of the throttle valve 24 and in the vicinity of the intake port 15, and fuel is pumped from the tank 27 by the pump 26 so that the intake port 15
Fuel is injected into the inside. On the other hand, an exhaust passage 31 communicating with the exhaust port 16 is provided with a three-way catalyst (exhaust gas converter) 32, and an O ₂ sensor 33 for detecting the oxygen concentration in the exhaust gas is provided upstream of the exhaust gas converter 32. That is, an air-fuel ratio detector is provided. An opening 34 formed in the exhaust passage 31 on the upstream side of the O ₂ sensor 33 is connected to a secondary air control valve 35 connected to the air cleaner 22 via a supply pipe 36. A temperature sensor 37 that detects the temperature of the catalyst is attached to the three-way catalyst 32. Distributor 38
It has a shaft 39 connected to a crank shaft (not shown) provided in the engine body 11, and also has a rotation speed sensor 40 for detecting the engine rotation speed via the shaft 39.

The electronic control (ECU) 41 equipped with a microcomputer
The fuel injection amount is controlled based on the intake air amount Q detected by the air flow meter 23, the engine speed Ne detected by the rotation speed sensor 40, the air-fuel ratio of the exhaust gas detected by the O ₂ sensor 33, and the like. Further, the ECU 41 opens the secondary air control valve 35 when the temperature of the catalyst is lower than a predetermined value, and closes the control valve 35 after warming up the catalyst. Also, ECU4
1 performs feedback control so that the air-fuel mixture has a stoichiometric air-fuel ratio.

The ECU 41 is a central processing unit (CO
U) 42, read only memory (ROM) 43 for storing programs and various constants, random access memory (RAM) 44 for temporarily storing data, and analog signals output from the air flow meter 23 etc. as digital signals. I / O for inputting the digital signal output from the rotation speed sensor 40 and the like and outputting the command signal to the fuel injection valve 25 and the secondary air control valve 35 (I / O) port 46 and a bus line 47 interconnecting them, and drive circuits 48, 4 for driving and controlling the fuel injection valve 25 and the secondary air control valve 35 based on a command signal.
Having 9.

Now, the fuel injection amount τ is calculated by τ = K × FAF × T _P. Here, T _P represents the basic injection amount, and is calculated by (intake air amount Q) / (engine speed Ne). FAF represents an air-fuel ratio correction coefficient, which changes around 1.0 based on the output signal from the O ₂ sensor 33. K is a correction coefficient and is determined by the cooling water temperature, the intake air temperature, and the like.

FIG. 3 is a flow chart of a program example for implementing the present invention in the engine block diagram shown in FIG. Incidentally, this routine is interrupted every predetermined time. Step 50
Then, based on the signal from the temperature sensor 37, it is determined whether or not there is a secondary air control valve 35 opening signal from the input / output port 46 of the ECU 41, that is, whether or not the air suction operation is in progress (secondary air introduction device operation determination means). ), If it is in operation, the routine proceeds to step 51, and if it is not in operation, the routine proceeds to step 56, where a rich counter X, which will be described later, is set to 0 (clear), and this routine ends. Generally, in suction of secondary air of the air suction system, suction by negative pressure wave is used, so when the engine is under high load and high rotation, exhaust pressure becomes high and suction becomes difficult. Therefore, in steps 51 and 52, it is determined whether or not the secondary air is in a region sufficiently introduced into the exhaust system. That is, at step 51, the engine load Q / Ne is calculated from the intake air amount Q from the air flow meter 23 and the engine speed Ne from the speed sensor 40 of the distributor 38, and whether or not it is below a predetermined value A, that is, It is determined whether the load is low or high. If it is A or less, the routine proceeds to step 52, and if it is larger than A, the counter X is cleared and the routine is ended. Generally, when the engine speed is high, the air-fuel ratio feedback control is
Stop to ensure drivability. Therefore, in step 52, it is determined whether the engine speed Ne is less than or equal to a predetermined value B, that is, whether it is low speed or high speed. If it is B or less, the process proceeds to step 53, and if it is higher than B. For example, the counter X is cleared and the routine ends. Generally O ₂ sensor 33
Does not operate unless the temperature of a zirconia element (not shown) to be stored exceeds a certain temperature (for example, 450 ° C.), so it is determined in step 53 whether the O ₂ sensor 33 is activated. The activation of the O ₂ sensor 33 is determined by the magnitude of the voltage generated by, for example, passing a minute current from the ECU 41. If activated, the process proceeds to step 54, and if not activated, the counter X is cleared and the routine is executed. To finish. At step 54, the air-fuel ratio correction coefficient FA when feedback control is performed by the signal of the activated O ₂ sensor 33
Whether the average value of F (▲ ▼) is less than or equal to the predetermined value C, that is, the air-fuel ratio is rich (rich condition), and as a result FAF decreases, whether ▲ ▼ is less than or equal to the predetermined value C, or lean. FAF increases because it is in a (diluted state), ▲
It is determined whether ▼ is larger than the predetermined value C. That is, if ▲ ▼ is larger than the predetermined value C here, it means that the air suction (secondary air introduction) is normal and that HC and CO generated at low engine temperature are oxidized, so the routine proceeds to step 56 and the counter X Is cleared and the routine ends. On the other hand, if ▲ ▼ is equal to or less than the predetermined value C, it is determined that the air suction is abnormal, the process proceeds to step 55, and 1 is added (incremented) to the rich counter X. In general, it may be erroneous if the air suction abnormality is determined by only one rich determination. Therefore, in this routine, the abnormality of the air suction is determined only after the rich determination continues for a predetermined number of times. Therefore step
At 57, it is judged whether or not the value of the rich counter X is larger than the set value, and if it is larger than the set value D, the routine proceeds to step 58 to store the air suction abnormality, and if it is D or less, the counter X is not cleared and this is not cleared. Exit the routine and proceed to the next run.

After memorizing the air suction abnormality, proceed to step 59,
Similar to step 56, the rich counter X is cleared and the diagnostic lamp is turned on in step 60 to warn the driver of the abnormal air suction.

FIG. 4 shows a flowchart of a program example different from that of FIG. This routine is a program for judging whether or not the air suction is abnormal by the number of times the rich judgment is continued, whereas the routine shown in FIG. 3 judges by the number of times of the rich judgment within a certain time t ₀ . It should be noted that this routine is interrupted at regular intervals within a fixed time t ₀ . Steps 61 to 64 are the same as the steps 50 to 53 in FIG. 3, but if NO in each step, the rich counter X is not cleared and the routine ends. To do.

In step 65, it is judged whether or not the currently executed time t exceeds a certain time t _0, and if it exceeds, it proceeds to step 66, and if it is less than the certain time t ₀ , it proceeds to step 67. In step 66, similarly to step 57 (FIG. 3), it is determined whether the value of the rich counter X is greater than the set value D,
If it is larger than the set value D, the routine proceeds to step 68, the air suction abnormality is stored, then the rich counter X is cleared at step 69, and the diagnostic lamp is lit at step 71 to warn of the abnormality and this routine ends. To do. One step
If it is equal to or less than the set value D at 66, it is determined that the air suction is normal, and at step 70, the rich counter X is cleared and this routine is finished.

If it is less than the certain time t _{0 in} step 65, the step
Proceed to 67 and respond to the signal from the O ₂ sensor 33 (Fig. 2) ▲ ▼
Is less than or equal to a predetermined value of 1, for example, it is determined whether rich or lean. If ▲ ▼ is equal to or less than the predetermined value C, the routine proceeds to step 72, where 1 is added to the rich counter X to end this routine, and if it is equal to or greater than the predetermined value C, the routine proceeds to step 73 and the rich counter X till then is set. This routine is terminated while maintaining the value.

As described above, in the flowchart of the program example of the present invention described above, an example of the state until it is determined that the air suction is abnormal is shown in FIG. 5 for the flowchart of FIG. 3, and FIG. 6 for the flowchart of FIG. Shown in.

As described above, in this embodiment, when the secondary air control valve 35 is opened,
If the air-fuel ratio is in the rich state, the air-fuel mixture is changed to the lean side, and if it is in the lean state, the air-fuel mixture is changed to the rich side, and feedback control is performed, so this FAF increases / decreases accordingly. Therefore, in this graph, the feedback control center value ▲ ▼ after warming up the three-way catalyst is set to 1, and this value is set as the lean-rich boundary value of the basic air-fuel ratio.

Referring to FIG. 5, the air suction is operating normally.
While the FAF is correcting the basic air-fuel ratio on the rich side (a to c), the basic air-fuel ratio is kept lean by air suction, and the program starts from step 50.
The process is executed in the order of 54 and 56, and ▲ ▼ indicated by a dotted line in the figure is larger than the predetermined value 1. Next, when the FAF is corrected to the lean side with respect to the basic air-fuel ratio, (c to d) ▲ ▼ becomes 1 or less, the steps 50 to 55, 57 are executed in order, and the rich counter X becomes 2, but in this graph, Since the determination between normal and abnormal air suction is D = 4, it is not determined to be abnormal. When the FAF is corrected to the rich side again (d to e), ▲ ▼ also gradually increases to become larger than 1 and the rich counter X is also cleared. However next FA
When F is corrected and output to the lean side between f and g with respect to the basic air-fuel ratio, the program is executed in the order of steps 50 to 55 and 57, and when rich counter X exceeds the value of D = 4, further step 58, Only when 59 and 60 are executed, the air suction abnormality memory-warning is executed.

Regarding Fig. 6, the FAF outputs a correction output to the lean side with respect to the basic air-fuel ratio, and it is a program that determines how many times it fell below a predetermined value 1 within a certain time t ₀ , and the abnormality of air suction depending on the number of times. Therefore, a graph of the elapsed time t is provided.
Also in this figure, as in FIG. 5, the abnormality determination value is D = 4.
In addition, as a boundary to judge lean rich ▲
▼ Set the value to 1.0. During air suction operation and during correction output of ▲ ▼ on the rich side (h to i),
The program is executed in the order of steps 61 to 65, 67, 73 and the rich counter X is in the 0 state. At this time, ▲ ▼ does not become smaller than the predetermined value 1.0.

Next, when ▲ ▼ is corrected and output on the lean side (i ~
j), the program is executed in the order of steps 61 to 65, 67, 72 and the rich counter X becomes 4, but the time t is a constant time t _0.
When (k) is reached, the program proceeds to steps 61-66,70.
Is executed in this order, and it is not judged to be abnormal, the rich counter X is cleared, and the routine is ended. Then, within the next fixed time t ₀ (j to k), when ▲ ▼ is again corrected and output on the lean side, the rich counter X exceeds D = 4 at this time, and when the time t ₀ is reached (k), the steps 61 to 61 are repeated. 66, 68, 69, 71 are executed in this order, and the air suction abnormality memory-warning is given.

〔The invention's effect〕

As described above, in the secondary air introduction abnormality detection device according to the present invention, since the air-fuel ratio feedback control based on the output of the air-fuel ratio detector is constantly executed, a desired amount of secondary air is exhausted from the secondary air introduction device. If it is supplied to the system, the average value of the air-fuel ratio correction coefficient should be larger than the predetermined value.
When the average value of the air-fuel ratio correction coefficient is equal to or less than the predetermined value even though the operation signal is issued to the secondary air introduction device, the secondary air is not supplied to the exhaust system at all or less than the desired amount. It is possible to determine that the abnormality in which only the secondary air is supplied has occurred in the secondary air introducing device. As a result, the driver can repair the secondary air introducing device at an early stage, and it is possible to prevent the exhaust gas from being deteriorated because the three-way catalyst is not warmed up early.

[Brief description of drawings]

1 is a block diagram of the present invention; FIG. 2 is a sectional view showing an internal combustion engine to which an embodiment of the present invention is applied; FIG. 3 is a flow chart of an abnormality determination program for an air suction device; FIG. 5 is a graph showing the program execution state of FIG. 3; FIG. 6 is a graph showing the program execution state of FIG. 1 ... Internal combustion engine, 4 ... Air-fuel ratio detector, 5 ... Air-fuel ratio feedback device, 6 ... Secondary air introduction device, 7 ... Bypass path (6 part), 8 ... Secondary air control valve (Part 6), 9 ... Secondary air introduction device operation determination means, 10 ... Abnormality determination means.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02D 43/00 310 A

Claims (1)

[Claims] 1. An air-fuel ratio feedback device for determining an air-fuel ratio correction coefficient based on an air-fuel ratio signal from an air-fuel ratio detector installed in an exhaust system to control the amount of fuel supplied to the engine, and the exhaust gas when the engine temperature is low. 2 on the upstream side of the air-fuel ratio detector of the system
In an internal combustion engine provided with a secondary air introducing device for introducing secondary air, a secondary air introducing device operation determining means for determining whether or not an operation signal is issued to the secondary air introducing device, and the above When the average value of the air-fuel ratio correction coefficient when the operation signal is issued to the secondary air introducing device by the secondary air introducing device operation determining means is less than or equal to a predetermined value, the secondary air A secondary air introduction abnormality detection device, comprising: abnormality determination means for determining that the introduction device is abnormal.