JPS63143362A - Anomaly detecting device for introduction of secondary air - Google Patents

Abstract

PURPOSE:To rapidly detect the anomaly of a secondary air introducing device by judging the generation of anomaly if the average value of the air fuel ratio correction coefficient supplied from an air fuel ratio feedback device is below a prescribed value, when the secondary air introducing device for supplying the secondary air into an exhaust system operates. CONSTITUTION:An air fuel ratio controller is equipped with an air fuel ratio feedback device 5 which controls the fuel quantity supplied into an engine on the basis of the air fuel ratio signal supplied from an air fuel ratio detector 4 arranged din an exhaust passage 3. Further, the controller is equipped with a secondary air introducing device 6 equipped with a secondary air control valve 8 which supplies the secondary air into the exhaust passage 3 from an intake passage 2, bypassing an engine 1, in the case when the engine temperature is low. In this case, an operation judging means 9 for judging the presence of the control valve operation signal supplied from the secondary air introducing device 6 is provided. When the secondary air introducing device operates, an anomaly judging means 10 judges anomaly when the average value of the air fuel ratio correction coefficient which is supplied from an air fuel ratio feedback device 5 is below a prescribed value, and an alarm signal is generated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a three-way catalyst warm-up for an engine when the engine temperature is low.
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.

[Prior art and problems]

For example, in a so-called air-fuel ratio feedback device that detects the residual 02 concentration in exhaust gas using an air-fuel ratio detector such as an 02 sensor and feeds back the signal to a control unit to control the amount of fuel supplied to the engine, As a treatment, an exhaust gas converter, that is, a three-way catalyst, is installed which has a high purification rate for exhaust gases such as Co and IC within the range of returning the stoichiometric air-fuel ratio. However, this three-way catalyst
When the engine is at a low temperature, the purification rate decreases, and as a result, the exhaust gas tends to not be sufficiently purified. Therefore, as a measure to warm up the three-way catalyst at low temperatures, air (secondary air) is bypassed from the intake system of an air cleaner, etc., and introduced into the exhaust system, where it is oxidized with HC and Co in the exhaust gas, and the reaction heat is A secondary air introduction device that warms up a three-way catalyst is known.

This secondary air introduction device can be roughly divided into two types depending on the air supply source: an air injection method using an air pump, and a near suction (As) method that draws air directly from the atmosphere through a check valve (called an As valve) using the pulsation of exhaust air. Both types have a secondary air control valve that activates or deactivates the secondary air introduction device, and are controlled by output from a computer depending on the engine temperature.

By the way, regarding the internal combustion engine equipped with the secondary air introduction device described above, even though the computer outputs a signal to activate the secondary air introduction device when the engine is low temperature, due to troubles during durability, etc., the air pump or AS pulp and other mechanisms do not operate, and therefore secondary air is not supplied to the exhaust system and HC and Co in the exhaust gas may increase. In addition to the current situation, there has been no abnormality detection device that can determine whether or not the secondary air introduction device is operating normally, which is not desirable in terms of exhaust gas countermeasures. In view of the current situation, it is an object of the present invention to provide an abnormality detection device for determining whether or not a secondary air introduction device is operating normally.

[Means for solving problems]

In order to solve the above problems, the present invention provides an air-fuel ratio feedback device that controls the amount of fuel supplied to the engine based on an air-fuel ratio signal from an air-fuel ratio detector, and an air-fuel ratio feedback device that controls the amount of fuel supplied to the engine based on an air-fuel ratio signal from an air-fuel ratio detector, and a secondary air supply system that supplies secondary air to the exhaust system when the engine is low temperature. In an internal combustion engine equipped with a secondary air introduction device, the secondary air introduction device operation determination means is configured to check whether or not the secondary air introduction device is in an operating state; A secondary air introduction abnormality detection device is provided, comprising abnormality determination means for determining an abnormality and generating a signal when the average value of the air-fuel ratio correction coefficient is less than or equal to a predetermined value in the air-fuel ratio feedback device. .

[For production]

When the engine is cold, even though the secondary air introduction device is operating, the average value of the air-fuel ratio correction coefficient FAF in the air-fuel ratio feedback device is less than a predetermined value, that is, the basic air-fuel ratio is corrected to the rich side. If there is, some kind of structural trouble has occurred in the secondary air introduction device, and the
It is expected that C, Co, etc. will not be oxidized. The present invention utilizes the above phenomenon to detect an abnormality in the operation of the secondary air introduction device.

〔Example〕

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

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

1 is an internal combustion engine (combustion chamber), 2 is an intake passage, and 3 is an exhaust passage. An air-fuel ratio detector 4 is provided in the exhaust passage 3, and transmits an air-fuel ratio signal to an air-fuel ratio feedback device 5. Thereby, the device 5 controls the fuel supply amount. 6
is a secondary air introduction device for introducing secondary air from the intake passage 2 to the exhaust passage 3 bypassing the engine 1,
Opening/closing control of the secondary air control valve 8 that communicates/cuts off the bypass path 7 is performed. Reference numeral 9 denotes a secondary air introduction device operation determination means for determining the presence or absence of a control valve operation signal from the secondary air introduction device 6, and an abnormality determination means 1o detects the air-fuel ratio correction coefficient FAF from the air-fuel ratio feedback device 5. A warning signal is issued based on the average value of and the signal from the secondary air introduction device operation determination 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. This is an overall diagram of the organization.

A piston 13 is slidably housed in a cylinder bore 12 formed in the engine body 11, and a combustion chamber 14 is formed above the piston 13. An intake boat 15 and an exhaust boat 16 connected to the combustion chamber 14 are opened and closed by an intake valve 17 and an exhaust valve 18, respectively.

The intake passage 21 communicating with the intake boat 15 has an air cleaner 22 at its most upstream side, and an air flow meter 23 is provided immediately downstream thereof.

It is arranged downstream of the throttle valve 24 and the air flow meter 23. The fuel injection valve 25 is provided downstream of the throttle valve 24 and near the intake boat 15 , and injects fuel into the intake boat 15 by pressure-feeding fuel from a tank 27 by a pump 26 . On the other hand, a three-way catalyst (exhaust gas converter) 32 is disposed in the exhaust passage 31 communicating with the exhaust boat 16, and an 01 sensor 33 for detecting the oxygen concentration in the exhaust gas is located upstream of the exhaust gas converter 32. An air/fuel ratio detector is provided. An opening 34 formed in the exhaust passage 31 on the upstream side of the Ot sensor 33 is connected to a secondary air control valve 35 connected to the air cleaner 22 via a supply pipe 36. Note that a temperature sensor 37 is attached to the three-way catalyst 32 to detect the temperature of the catalyst. The distributor 3.8 includes a shaft 39 connected to a crankshaft (not shown) provided within the engine body 11,
It also has a rotation speed sensor 40 that detects the engine rotation speed via this shaft 39.

Electronic control (ECU) 41 with microcomputer
controls the fuel injection amount based on the intake air amount Q detected by the air flow meter 23, the engine rotation speed Nes detected by the rotation speed sensor 40, the air-fuel ratio of exhaust gas detected by the 02 sensor 33, etc. Also ECU
41 is 2 when the temperature of the catalyst is lower than a predetermined value.
Next, the air control valve 35 is opened, and after warming up the catalyst, the control valve 35 is closed. Further, the llIC041 performs feedback control so that the air-fuel mixture reaches the stoichiometric air-fuel ratio.

The ECU 41 includes a central processing unit (COU) 42 that performs various types of arithmetic processing, a ROM 43 that stores programs and various constants, and a random access memory (RAM) 4 that temporarily stores data.
4, an A/D converter 45 that converts the analog signal output from the air flow meter 23 etc. into a digital signal, and an A/D converter 45 which inputs the digital signal output from the rotation speed sensor 40 etc. It includes an input/output (I10) boat 46 for outputting a command signal to the control valve 35, and a pass line 47 that interconnects these, and also controls the fuel injection valve 25 and secondary air control based on the command signal. Drive circuits 48 and 4 for driving and controlling the valves 35
It has 9.

Now, the fuel injection amount τ is calculated by r=KXFAFXTP. Here, T indicates the basic injection amount, and (
It is determined by intake air amount Q)/(engine rotation speed Ne). FAF indicates air-fuel ratio correction coefficient, 0, sensor 33
It changes around 1.0 based on the output signal from. K is a correction coefficient, which is determined by the cooling water temperature, intake air temperature, etc.

FIG. 3 is a flowchart of an example program for implementing the present invention in the engine configuration diagram shown in FIG. Note that this routine is interrupted at predetermined intervals. Step 5
0, the ECU 4 based on the signal from the temperature sensor 37
It is determined whether or not there is a valve opening signal for the secondary air control well 35 from the input/output boat 46 of No. 1, that is, whether or not the air sax is in operation (secondary air introduction device operation determination means). If it is in operation, step 51 If it is not in operation, the routine advances to step 46, where the rich counter X, which will be described later, is set to O (clear) and this routine ends. Generally, near-suction type secondary air introduction uses suction by negative pressure waves, so when the engine is under high load and rotation, the exhaust pressure becomes high and suction becomes difficult. Therefore step 51 and step 52
Then, it is determined whether the area is such that sufficient secondary air can be introduced into the exhaust system. That is, in step 51, the intake air i1Q from the air flow meter 23 and the distributor 38
The engine load Q/Ne is calculated based on the engine rotation speed Ne from the rotation speed sensor 40 of If so, the process advances to step 52, and if it is greater than A, the counter X is cleared and the routine ends. Generally, air-fuel ratio feedback control is stopped when the engine speed is high to ensure drivability. Therefore, in step 52, it is determined whether the engine rotation speed Ne is below a predetermined value B, that is, whether it is low rotation or high rotation. If it is below B, the process proceeds to step 53, and if it is greater than B, it is determined The tobacco counter X is cleared and the routine ends. Generally, the 02 sensor 33 does not operate unless the zirconia element (not shown) in which it is housed reaches a certain temperature (for example, 450° C.) or higher, so in step 53 it is determined whether the 0□ sensor 33 is activated. Activation of the 02 sensor 33 is determined by the magnitude of the voltage generated by passing a small current from the ECU 41, for example. If it is activated, the process proceeds to step 54; if it is not activated, the counter X is cleared and the routine end. In step 54, the average value (FAF) of the air-fuel ratio correction coefficient FAF when performing feedback control based on the signal of the activated 02 sensor 33 is determined.
is below a predetermined value C, that is, the air-fuel ratio is rich (excessively rich), resulting in a decrease in FAF, and the FAF becomes below a predetermined value C, or is it in a lean condition (H)? Therefore, it is determined whether FAF increases and FAF becomes larger than a predetermined value C. That is, if FAF is larger than the predetermined value C, near suction (secondary air introduction) is normal.
Further, in order to indicate that HC and Co generated when the engine temperature is low is oxidized, the routine proceeds to step 56, where the counter X is cleared and the routine is terminated. On the other hand, if FAF is less than the predetermined value C, it is determined that the air suction is abnormal, and the process proceeds to step 55, where the rich counter X is incremented by 1. In general, if a near suction abnormality is determined by just one rich determination, an erroneous determination may occur. Therefore, in this routine, air suction abnormality is determined only when the rich determination continues a predetermined number of times. Therefore, in step 57, it is determined whether the value of the rich counter
If it is below, this routine is ended without clearing the counter X, and the routine proceeds to the next execution.

After memorizing the near suction abnormality, proceed to step 59, clear the rich counter X as in step 56, and
At step 60, a diagram lamp is turned on to warn the driver of the air suction abnormality.

FIG. 4 shows a flowchart of an example program different from that shown in FIG. This routine is a program that determines air suction abnormality based on the number of rich determinations within a certain time t0, whereas the routine shown in Figure 3 determines air suction abnormality based on the number of consecutive rich determinations. . Note that this routine lasts for 4 fixed times t. Interrupt processing is performed at predetermined intervals within the time period.

Steps 61 to 64 are the same as the determinations from step 50 to step 53 in FIG. 3, but if the determination is NO at each step, the routine ends without clearing the rich counter X up to that point. do.

In step 65, the current execution time t is 4 fixed time t.
It is determined whether or not it exceeds 0. If it does, the process proceeds to step 66, and if it is less than a certain time t0, the process proceeds to step 67. In step 66, step 57 (third
Figure) Similarly, it is determined whether the value of the rich counter X is greater than the set value, and if it is greater than the set value, step 6
8, the air suction abnormality is stored, and then, in step 69, the rich counter X is cleared, and in step 71, the diagram lamp is turned on to warn of the abnormality, and this routine ends. On the other hand, if it is less than the set value in step 66, it is determined that the near suction is normal, and in step 70, the rich counter X is cleared and this routine is ended.

In step 65, if it is less than 4 predetermined time t0, the process proceeds to step 67, and the FAF advances to below a predetermined value, for example 1, according to the signal from the 02 sensor 33 (Fig. 2), and 1 is added to the rich counter X. This routine is terminated, and if the predetermined value C is exceeded, the routine proceeds to step 73, and this routine is terminated while maintaining the current stretch counter X.

In the flowchart of the program example of the present invention described above, an example of the state until a near suction abnormality is determined is shown in FIG. 5 for the flowchart in FIG. 3, and FIG. 6 for the flowchart in FIG. 4, respectively. Shown below.

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

Regarding Figure 5, while the air suction is operating normally and the FAF is correcting the basic air-fuel ratio on the rich side (a-c), the basic air-fuel ratio is maintained in a lean state by near suction. The program is executed in the order of steps 50 to 54 and 56, and the FAF indicated by the dotted line in the figure is greater than the predetermined value 1. Next, when the FAF is corrected to the lean side with respect to the basic air-fuel ratio (c-d), the FAF becomes 1 or less, steps 50 to 55, and 57 are executed in order, and the rich counter X becomes 2, but in this graph, the Since the determination between suction normal and abnormal is set as D=4, it is not determined as abnormal. Then, when the FAF is corrected to the rich side again (de), the FAF gradually increases and becomes larger than 1, and the rich counter X is also cleared. However, next time the FAF outputs a correction to the lean side between f and g with respect to the basic air-fuel ratio, the program executes steps 50 to 5.
Steps 5 and 57 are executed in this order, and when the rich counter X exceeds the value of D-4, further steps 5B, 59, and 60 are executed.
The air suction abnormality memory/warning is executed only after the above is executed.

Regarding Fig. 6, it is a program in which the FAF corrects the basic air-fuel ratio to the lean side and determines air suction abnormality based on how many times the ratio becomes less than a predetermined value 1 within a certain period of time t0. Therefore, a graph of elapsed time t is provided. In addition, in this figure as well as in Figure 5, the abnormality judgment value is D=
4. Also, FA as a boundary for determining lean/rich
Set the F value to 1.0. During air suction operation and while FAF outputs correction on the rich side (h - i),
The program is executed in the order of steps 61 to 65, 67, and 73, and the rich counter X is in the state of 0. At this time, FAF never becomes smaller than the predetermined value of 1.0.

Next, when the FAF outputs a correction on the lean side (i to j), the program is executed in the order of steps 61 to 65, 67, and 72, and the rich counter X becomes 4, but when the time t reaches the 4 fixed time t0 (k), the program is step 6
1 to 66 and 70 are executed in this order, and the rich counter X is cleared without being determined to be abnormal and the routine ends. Then, within the next 4 fixed times t0 (j”k), when the FAF outputs a correction on the lean side again, the rich counter
, 6B, 69, and 71 are executed in this order, and an air suction abnormality memorization warning is issued.

〔Effect of the invention〕

As described above, according to the present invention, an abnormality in the operation of the secondary air introduction device is warned by verifying the control center value of the correction coefficient using the output signal of the air-fuel ratio detector. The secondary air introduction device can be repaired in the future, making it possible to minimize the emissions of HC and Co into the atmosphere. This system is also capable of detecting abnormalities in the air-fuel ratio detector, and when the diagram lamp is turned on, the inspector can check the secondary air intake device and the air-fuel ratio detector to detect any abnormalities in either or both of them. It becomes possible to confirm the failure.

[Brief Description of the Drawings] Figure 1 is a configuration diagram of the present invention; Figure 2 is a sectional view showing an internal combustion engine to which an embodiment of the present invention is applied; Figure 3 is a flowchart of an abnormality determination program for the air suction device ; FIG. 4 is a flowchart of an abnormality determination program different from that in FIG. 3; FIG. 5 is a graph showing the execution state of the program in FIG. 3;
FIG. 6 is a graph showing the program execution state of FIG. 4. 1... Internal combustion engine, 4... Air-fuel ratio detector, 5...
...Air-fuel ratio feedback device, 6...Secondary air introduction device, 7...Bypass path (part 6), 8...Secondary air control valve (part 6), 9...Secondary Air introduction device operation determination means, 10... abnormality determination means.

Claims (1)

[Claims] 1.Equipped with an air-fuel ratio feedback device that controls the amount of fuel supplied to the engine based on the air-fuel ratio signal from the air-fuel ratio detector, and a secondary air introduction device that supplies secondary air to the exhaust system when the engine is low temperature. In an internal combustion engine, a secondary air introduction device operation determination means for checking whether the secondary air introduction device is in an operating state; and an average of an air-fuel ratio correction coefficient in the air-fuel ratio feedback device when the secondary air introduction device is operating. A secondary air introduction abnormality detecting device comprising abnormality determining means for determining an abnormality and generating a signal when the value is less than or equal to a predetermined value.