JP2022096001A - Diagnostic device - Google Patents

Abstract

To provide a diagnostic device capable of diagnosing a device through which exhaust gas from an engine passes without deteriorating the exhaust gas.SOLUTION: A catalyst deterioration diagnostic device (diagnostic device) includes a device 102, a simulation device 105 and an MPU (processor). Exhaust gas from an engine passes through the device 102. The simulation device 105 comprises a function identified from a first signal indicating a state of the exhaust gas before the device 102 and a second signal indicating a state of the exhaust gas after the device 102. The MPU inputs a third signal obtained through a shift of an air-fuel ratio of the first signal to the simulation device 105, and diagnoses the device 102 from a fourth signal and the third signal output from the simulation device 105.SELECTED DRAWING: Figure 2

Description

The present invention relates to a diagnostic device.

As a means for reducing harmful exhaust gas from automobiles and improving fuel efficiency and drivability, a feedback type air-fuel ratio control device that controls the air-fuel ratio based on information on the exhaust gas component of an internal combustion engine such as an engine has been put into practical use. ing.

In the above engine control system, most of the diagnostic devices of the exhaust gas purification device are in a deteriorated state of the catalyst due to the relationship between the detection information of the air-fuel ratio detecting means attached upstream of the catalyst and the detection information of the air-fuel ratio detecting means attached downstream of the catalyst. (See, for example, Patent Document 1). The above relationship is the ratio of the cross-correlation function and the autocorrelation function calculated from the detection information of the air fuel ratio detecting means upstream of the catalyst and the detection information of the air fuel ratio detecting means downstream of the catalyst, or the periodic ratio, the fluctuation frequency ratio in a predetermined period, and the like. Diagnosis is performed as a catalyst deterioration index.

In the above air-fuel ratio control device, the three-way catalyst, which is an example of the catalyst, is installed immediately after the engine exhaust, and is easily deteriorated because it is affected by high temperature, high pressure, vibration, poor fuel, and the like. ..

In particular, automobiles destined for North America need to comply with OBDII regulations (laws that require the installation of in-vehicle self-diagnosis devices, etc.), and failures such that the purification rate of the three-way catalyst exceeds the exhaust regulation value by 1.5 times. If this occurs, it is necessary to promptly warn the driver of the abnormality and urge him to repair it. Therefore, when the purification rate of the three-way catalyst drops for some reason, it is necessary to take appropriate measures such as replacement of the three-way catalyst.

Japanese Unexamined Patent Publication No. 2005-256702

The catalyst deterioration diagnosis is performed from the cross-correlation function of the air fuel ratio sensor signal upstream of the catalyst and the air fuel ratio sensor signal downstream of the catalyst when the air fuel ratio shift is applied. However, since the air-fuel ratio shift is executed at the time of diagnosis, there is a problem that the exhaust gas deteriorates during that time, although it is a short time. The present invention proposes a method for diagnosing catalyst deterioration that does not deteriorate exhaust gas.

That is, an object of the present invention is to provide a diagnostic device capable of diagnosing a device through which exhaust gas from an engine passes without deteriorating the exhaust gas.

In order to achieve the above object, the present invention presents a device through which exhaust from the engine passes, a first signal indicating the state of the exhaust in front of the device, and a second signal indicating the state of the exhaust after the device. A simulated device composed of a function identified from a signal, a third signal obtained by shifting the air fuel ratio of the first signal to the simulated device, and a fourth signal and a third signal output from the simulated device are input to the simulated device. It comprises a processor for diagnosing the device from.

According to the present invention, it is possible to diagnose a device through which the exhaust gas from the engine passes without deteriorating the exhaust gas. Issues, configurations and effects other than those described above will be clarified by the following description of the embodiments.

It is an example of the internal combustion engine system which is the object of this invention. It is a basic block diagram of the catalyst deterioration diagnosis apparatus by embodiment of this invention. It is a block diagram of the catalyst deterioration diagnosis apparatus by Embodiment 1 of this invention. This is an example of diagnosing catalyst deterioration by combining system identification using the sequential least squares method and frequency analysis (conventional example). This is a proposal to deal with the problem of catalyst diagnosis by frequency analysis. Air-fuel ratio shift (rich → lean) control using a first-order lag filter. It is the air-fuel ratio sensor signal before the simulated catalyst and the air-fuel ratio sensor signal after the simulated catalyst at the time of the air-fuel ratio shift of the first embodiment. This is the result of the catalyst deterioration diagnosis of Form 1. It is a block diagram of the catalyst deterioration diagnosis apparatus by Embodiment 2 of this invention. It is the air-fuel ratio sensor signal before the simulated catalyst and the air-fuel ratio sensor signal after the simulated catalyst at the time of the air-fuel ratio shift of the second embodiment. This is the result of the catalyst deterioration diagnosis of Form 2. This is an example of the identification mechanism of a simulated catalyst. This is the identification result of the air-fuel ratio sensor signal (O2 sensor) after the simulated catalyst. It is a flowchart (1) common to the embodiment of this invention. It is a flowchart (2) common to the embodiment of this invention. It is a flowchart of Embodiment 1 of this invention. It is a flowchart of Embodiment 2 of this invention. It is a block diagram of the catalyst deterioration diagnostic apparatus which is a comparative example. It is an air-fuel ratio sensor signal before the actual catalyst and an air-fuel ratio sensor signal after the actual catalyst at the time of shifting the air-fuel ratio at the time of catalyst diagnosis. It is a calculation diagram of the cross-correlation function using the air-fuel ratio sensor signal before and after the catalyst. It is the result of the catalyst deterioration diagnosis of the comparative example.

Hereinafter, the configuration and operation of the catalyst deterioration diagnostic apparatus (diagnosis apparatus) according to the first and second embodiments of the present invention will be described with reference to the drawings.

(Internal combustion engine system configuration)
First, the configuration of the internal combustion engine system including the catalyst deterioration diagnostic apparatus according to the first and second embodiments of the present invention will be described with reference to FIG.

As shown in FIG. 1, the internal combustion engine system includes an internal combustion engine, an intake system, and an exhaust system, and the internal combustion engine is equipped with an ignition device 201, a fuel injection device 202, and a rotation speed detection device 203. The air flowing in from the air cleaner 200 is adjusted in flow rate by the throttle valve 213, then measured by the flow rate detecting means 204, mixed with the fuel injected from the fuel injection device 202 at a predetermined angle, and mixed with each cylinder. It is supplied to 214. Further, an air-fuel ratio sensor 205 and a three-way catalyst 206 are attached to the exhaust system, and the exhaust gas is purified by the three-way catalyst 206 and then discharged to the atmosphere.

The internal combustion engine control device 207 takes in the rotation speed Ne of the ring gear or the plate 208 by the output signal Qa of the flow rate detecting means 204 and the rotation speed detecting means 203, calculates the fuel injection amount Ti, and calculates the injection amount of the fuel injection device. Control. Further, the internal combustion engine control device 207 detects the air-fuel ratio in the internal combustion engine from the air-fuel ratio sensor 205, and corrects the fuel injection amount Ti so that the air-fuel ratio in the internal combustion engine becomes the theoretical air-fuel ratio. I do. Further, the air-fuel ratio after the catalyst is detected by the oxygen sensor 215.

On the other hand, the fuel in the fuel tank 209 is sucked and pressurized by the fuel pump 210 and then guided to the fuel inlet of the fuel injection device 202 through the fuel pipe 212 provided with the pressure regulator 211, and the excess fuel is used. Is returned to the fuel tank 209. The above is the target internal combustion engine system.

(Comparative example)
Next, in order to facilitate understanding of the present invention, FIG. 18 shows a block diagram of a catalyst deterioration diagnostic apparatus as a comparative example. The block 301 is an engine control system, and is composed of fuel control, ignition control, air-fuel ratio control, and the like. The output of the block 301 is the air-fuel ratio, and is input to the air-fuel ratio shift amount calculation means of the block 302. The air-fuel ratio of the block 302 is input to the actual catalyst of the block 303, and the air-fuel ratio after the actual catalyst, which is the output of the block 303, the air-fuel ratio, which is the output of the block 302, and the diagnostic conditions are satisfied in the block 304. At that time, block 305 calculates the intercorrelation function.

At this time, since the diagnostic condition of the block 304 is satisfied, the air-fuel ratio shifted (rich → lean) in the block 302 is input to the actual catalyst of the block 303. In block 307, the calculated cross-correlation function and the threshold value (constant) are compared, and when the return value of the cross-correlation function is larger than the threshold value, block 308 determines that it is NG. On the contrary, when the return value of the cross-correlation function is smaller than the threshold value, the block 308 determines that it is OK.

Next, FIG. 19 shows an operation example of the air-fuel ratio before the actual catalyst (here, the O2 sensor signal) and the air-fuel ratio after the actual catalyst (here, the O2 sensor signal) at the time of shifting the air-fuel ratio of the comparative example. show.

When the actual catalyst is deteriorated to some extent, the O2 sensor signal before the actual catalyst is shifted to the lean side on average because the air-fuel ratio shift is executed (not shown). At this time, when the initial state is rich, the O2 sensor signal after the actual catalyst gradually swings and shifts to the lean side. When the initial state is lean, the air-fuel ratio after the actual catalyst is enriched once, and then the air-fuel ratio is shifted to the lean side.

At this time, the air-fuel ratio is gradually shifted for each predetermined number of ignitions, and the cross-correlation function is calculated for each number of ignitions. Shifting the air-fuel ratio (rich → lean) indicates that the air-fuel ratio is moved from the ternary point of the three-way catalyst from rich to lean, and the air-fuel ratio is moved to the ternary point having the best purification rate. Will not be controlled. Therefore, there is a problem that the exhaust gas increases during that time.

Next, the calculation of the cross-correlation function, which is a deterioration index of the catalyst deterioration diagnosis, will be described with reference to FIG. The DC component of the O2 sensor signal before and after the actual catalyst is cut, and the convolution integrated value of the O2 sensor signal before the actual catalyst and the O2 sensor signal after the actual catalyst is calculated as a molecule. Further, the convolution integral value of the square of the O2 sensor signal before the actual catalyst is calculated as the denominator. The cross-correlation function is calculated from the ratio of the numerator to the denominator.

Based on the above, FIG. 21 shows the results of the catalyst deterioration diagnosis of the comparative example obtained. New catalysts and durable catalysts are almost new level (cross-correlation function value: 0 to 0.05), and in the case of catalysts corresponding to 80% of the OBD regulation value, the cross-correlation function value is 0.1. It becomes ~ 0.15. In the case of a catalyst corresponding to the OBD regulation value of 100%, it is 0.35 to 0.45. Therefore, by setting the threshold value to 0.3 as an example, the deterioration catalyst can be accurately determined. However, as described above, there remains a problem that the exhaust gas deteriorates during the air-fuel ratio shift at the time of diagnosis.

Therefore, in the embodiment of the present invention described later, it is an object to accurately determine the deterioration catalyst after preventing the deterioration of the exhaust gas generated in the above-mentioned catalyst deterioration diagnosis.

(Basic configuration)
Hereinafter, the catalyst deterioration diagnostic apparatus using the system identification according to the embodiment of the present invention will be described based on the examples.

FIG. 2 shows a block diagram of the catalyst deterioration diagnostic apparatus according to the embodiment of the present invention. This block diagram is conceptual, and a specific block diagram will be described with reference to FIG. 3 (form 1). First, the block 101 of FIG. 2 represents an engine control system, and the inside thereof is composed of fuel control, ignition control, air-fuel ratio control, and the like. The output of the block 101 is the air-fuel ratio and is input to the device of the block 102. Further, the air-fuel ratio is input to the air-fuel ratio shift amount calculating means of the block 104, but if the diagnostic conditions are not satisfied by the diagnostic condition determining means of the block 103, the air-fuel ratio shifts from rich to lean. Not done. When the diagnostic condition of block 103 is satisfied, the air-fuel ratio is shifted from rich to lean.

In the block 105, the output signal of the block 102 and the air fuel ratio not shifted are input, and the output signal of the block 102 and the output signal of the block 105 are input from the output signal of the block 102 and the output signal of the block 104. , Sequential minimum squares and other system identifications are used for matching.

If the output signal of the block 102 and the output signal of the block 105 match in the block 105, when the diagnostic condition of the block 103 is satisfied, the air-fuel ratio, which is the output of the block 104, is shifted from the rich to the lean side. It also stops system identification that makes the simulated device in block 105 equivalent to block 102. Then, in the block 106, the deterioration of the device of the block 102 and the like are determined from the air-fuel ratio shifted from the rich to the lean of the block 104 and the output signal of the block 105.

That is, the catalyst deterioration diagnostic device (diagnosis device) includes at least a device 102, a simulated device 105, and an MPU (processor). Exhaust gas from an engine (internal combustion engine) passes through the device 102. The simulated device 105 has a first signal (signal of the first air fuel ratio sensor) indicating the exhaust state before the device 102 and a second signal (signal of the second air fuel ratio sensor) indicating the exhaust state after the device 102. It consists of functions identified from the signal). The MPU (processor) inputs a third signal obtained by shifting the first signal to the air-fuel ratio to the simulated device 105, and diagnoses the device 102 from the fourth signal and the third signal output from the simulated device 105.

As a result, the air-fuel ratio does not shift with respect to the device 102, so that the exhaust does not deteriorate. Further, since the device 102 is diagnosed without using frequency analysis, the calculation load can be reduced.

The device 102 is composed of a catalyst for purifying the exhaust gas, as will be described later. This makes it possible to diagnose the deterioration of the catalyst without deteriorating the exhaust gas. Further, the first signal and the second signal are signals output from the O2 sensor (air-fuel ratio sensor), respectively. As a result, deterioration of the catalyst can be diagnosed using the output signal of the O2 sensor, which is an inexpensive air-fuel ratio sensor.

(Embodiment 1)
Next, Embodiment 1 of the present invention will be described. FIG. 3 is a block diagram of the catalyst deterioration diagnostic apparatus according to the first embodiment of the present invention.

The block 701 is an engine control system, and is composed of fuel control, ignition control, air-fuel ratio control, and the like. The output of the block 701 is the air-fuel ratio (a signal indicating the state of the air-fuel ratio), and the fluid corresponding to this air-fuel ratio is input to the actual catalyst of the block 702. If the diagnostic condition is not satisfied by the diagnostic condition determining means of the block 707, the air-fuel ratio shift is not permitted in the block 705, and the air-fuel ratio, which is the output of the 701 in the block 704, is not shifted by the air-fuel ratio and is output as it is. Will be done.

The air-fuel ratio that is not shifted is input to the simulated catalyst of 703, and the air-fuel ratio after the actual catalyst, which is the output of 702, is also input to the simulated catalyst of 703. The transfer characteristics in the simulated catalyst are varied so that the air-fuel ratio and the air-fuel ratio after the actual catalyst of 702 have the same operation.

The simulated catalyst of 703 is composed of a transfer function of a second-order lag system + a waste time system, and the air-fuel ratio after the actual catalyst of 702 and the air-fuel ratio after the simulated catalyst of 703 have the same operation. The incoming coefficients (parameters) are calculated by the sequential least squares method.

That is, the MPU (processor) identifies the transfer function (function) constituting the simulated catalyst 703 (simulated device) by the sequential least squares method. As a result, the simulated catalyst 703 (simulated device) is sampled for each sampling of the O2 sensor signal (first signal) before the actual catalyst 702 (device) and the O2 sensor signal (second signal) after the actual catalyst 702 (device). ) Is identified (approximate).

On the other hand, when the diagnostic condition is satisfied in the block 707, the air-fuel ratio shift is permitted in the block 705, the air-fuel ratio shift amount is calculated in the block 704, and the air-fuel ratio shifted air-fuel ratio is input to the simulated catalyst of 703, and 702. The air-fuel ratio after the actual catalyst, which is the output of, is also input to the simulated catalyst of 703. At this time, since the diagnostic condition of the block 707 is satisfied, the coefficients of the transfer function of the second-order lag system + the wasted time system are not calculated by the sequential least squares method in the simulated catalyst of the block 703, and the update is performed. It is stopped.

In this state, the simulated catalyst is in a state equivalent to that of the actual catalyst because the system identification by the sequential least squares method is stopped immediately before the diagnostic conditions are satisfied. In this state, the air-fuel ratio shifted air-fuel ratio is input to the simulated catalyst of the block 703, so that the air-fuel ratio sensor signal after the simulated catalyst corresponding to the deterioration can be detected. Since the simulated catalyst has the same response characteristics as the actual catalyst, it can be determined that the deterioration of the simulated catalyst is the same as the deterioration of the actual catalyst.

After that, the cross-correlation function calculation unit of the block 706 calculates the cross-correlation function from the air-fuel ratio before the simulated catalyst and the air-fuel ratio after the simulated catalyst. By comparing the calculated cross-correlation function in block 709 with the threshold value set in block 708, block 710 determines whether the actual catalyst is OK or NG.

In other words, by using a simulated catalyst that operates in the same way as the actual catalyst instead of the actual catalyst, it is possible to determine the deterioration of the actual catalyst without deteriorating the exhaust even if the input air-fuel ratio is shifted. can.

FIG. 4 is an example of diagnosing catalyst deterioration by combining system identification using the sequential least squares method and frequency analysis (conventional example). FIG. 4 is a method of determining the deterioration of the actual catalyst from the identification parameters calculated by the sequential least squares method in the simulated catalyst without focusing on the air-fuel ratio which is the output of the simulated catalyst. Up to the simulated catalyst, the structure is the same as described above, except that the identification parameters are used to determine the deterioration of the actual catalyst.

The calculation of the simulated catalyst can be performed online with a microcomputer or the like, but in order to judge the deterioration of the actual catalyst from the identification parameters, it is necessary to use frequency analysis or the like and make a judgment from the result. Therefore, it is not possible to perform online calculation with a microcomputer or the like, and it is necessary to obtain it from the frequency analysis result on the desk, and it is difficult to mount all the diagnostic logic on the microcomputer.

Therefore, as shown in FIG. 5, the air-fuel ratio after the actual catalyst and the air-fuel ratio after the simulated catalyst are the same operation in order to enable the online deterioration judgment instead of using the identification parameter for the judgment of the catalyst deterioration. At this stage, the system identification by the sequential minimum square method was stopped, and when the diagnostic conditions were satisfied, the deterioration of the catalyst was judged from the relationship between the air-fuel ratio input to the simulated catalyst and the air-fuel ratio after the simulated catalyst.

However, when diagnosing, it is necessary to shift the air-fuel ratio to the air-fuel ratio input to the simulated catalyst in order not to deteriorate the exhaust, and the air-fuel ratio shifted air-fuel ratio is input to the simulated catalyst before the simulated catalyst. The method of diagnosis is based on the relationship between the air-fuel ratio of the above and the air-fuel ratio after the simulated catalyst.

(Air-fuel ratio shift)
FIG. 6 shows a method of air-fuel ratio shift. Normally, the air-fuel ratio is controlled in the engine control system, but with that method, the air-fuel ratio shifts the air-fuel ratio input to both the actual catalyst and the simulated catalyst, and it is not possible to prevent exhaust deterioration.

Therefore, the first-order lag filter is applied only to the air-fuel ratio before the simulated catalyst so that the air-fuel ratio shift is applied only to the simulated catalyst. In order to apply the air-fuel ratio shift from rich to lean of the three-way catalyst, a high time constant first-order lag filter is applied only when the differential value of the air-fuel ratio is negative.

That is, the MPU (processor) applies a first-order lag filter to the signal (first signal) of the O2 sensor in front of the actual catalyst 702 (device) and increases the fall time constant to execute the air-fuel ratio shift. This makes it possible to perform an air-fuel ratio shift that shifts from rich to lean with respect to the simulated catalyst 703 (simulated device) without shifting the air-fuel ratio with respect to the actual catalyst 702 (device).

Specifically, for example, the MPU (processor) increases the falling time constant during the period in which the time derivative of the signal (first signal) of the O2 sensor in front of the actual catalyst 702 becomes negative. Thereby, the air-fuel ratio shift that shifts from rich to lean with respect to the simulated catalyst 703 (simulated device) can be reproduced in the same manner as the air-fuel ratio shift when the air-fuel ratio shifts with respect to the actual catalyst 702 (device). ..

It is possible to apply the air-fuel ratio shift in the lean → rich direction, but it is known empirically that there is a large variation in the air-fuel ratio sensor (O2 sensor) when shifting from lean to rich, and the rich → lean direction. It is supposed to be.

That is, the air-fuel ratio shift of the present embodiment is a lean shift that changes the air-fuel ratio from rich to lean. As a result, according to the empirical rule that the signal variation of the O2 sensor (air-fuel ratio sensor) is smaller when the air-fuel ratio is changed from rich to lean than when it is changed from lean to rich, the simulated catalyst 703 (simulated device) is empty. A fuel ratio shift can be performed.

Next, FIG. 7 will be described. FIG. 7 is an example at the time of diagnosis of a moderately deteriorated actual catalyst (≈ simulated catalyst). The three timing charts on the upper side of FIG. 7 show the air-fuel ratio shifted (rich → lean) before the simulated catalyst and the air-fuel ratio after the simulated catalyst when the air-fuel ratio sensor signal after the simulated catalyst is in a rich state. An example of determining the deterioration of the actual catalyst from the mutual correlation function of the sensor signal is shown.

On the other hand, the three timing charts on the lower side of FIG. 7 show the case where the air fuel ratio sensor signal after the simulated catalyst is in a lean state. In that case, the air fuel ratio sensor signal after the simulated catalyst is enriched once and then simulated. An example in which the air-fuel ratio before the catalyst is lean-shifted (rich → lean) and the deterioration of the actual catalyst is judged from the mutual correlation function with the air-fuel ratio sensor signal after the simulated catalyst is shown.

That is, the MPU (processor) calculates an index showing the similarity between the air-fuel ratio-shifted third signal and the fourth signal output from the simulated catalyst 703 (simulated device) every time the air-fuel ratio shift is executed. The actual catalyst 702 (device) is diagnosed from the index.

As a result, since the device is diagnosed based on the similarity between the third signal and the fourth signal, the calculation load can be suppressed as compared with the case where the actual catalyst 702 (device) is diagnosed by using frequency analysis. ..

In the present embodiment, the index showing the similarity between the third signal and the fourth signal is a cross-correlation function. Thereby, an index showing the similarity between the third signal and the fourth signal can be calculated by integration.

Further, in the present embodiment, as shown in FIG. 7, the MPU (processor) executes the air-fuel ratio shift for each predetermined number of ignitions, and calculates a cross-correlation function (correlation value) for each predetermined number of ignitions. do. As a result, the air-fuel ratio shift can be gradually shifted.

The MPU (processor) diagnoses that the actual catalyst 702 (device) has deteriorated when the load mean value (mean value) of the maximum value of the cross-correlation function and the second largest value exceeds the threshold value. Thereby, the deterioration of the device can be diagnosed from the signals of the upper two periods having high similarity among the third signal and the fourth signal.

An example of the result of the catalyst deterioration diagnosis of Form 1 is shown in FIG. Basically, the result is almost the same as that in FIG. However, the major difference is that the exhaust does not deteriorate. Since the air-fuel ratio shift is applied to the simulated catalyst equivalent to the actual catalyst, the cross-correlation function is calculated, and the determination is made by comparing with the threshold value, the exhaust gas does not deteriorate by not applying the air-fuel ratio shift to the actual catalyst.

Specifically, when the MPU (processor) indicates that the value of the cross-correlation function (correlation value) exceeds the threshold value and the similarity between the third signal and the fourth signal is high, the actual catalyst 702 (device) is deteriorated. Diagnose that. Thereby, the deterioration of the actual catalyst 702 (device) can be easily diagnosed by comparing the cross-correlation function with the threshold value.

As described above, according to the present embodiment, it is possible to diagnose the actual catalyst 702 (device) through which the exhaust gas from the engine passes without deteriorating the exhaust gas.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. FIG. 9 is a block diagram of the catalyst deterioration diagnostic apparatus according to the second embodiment of the present invention. The major difference between Form 1 and Form 2 is that Form 1 is identified using the sequential least squares method for identifying the simulated catalyst, and a large computational load is applied such as calculating the cross-correlation function for determining deterioration. Because the cross-correlation function is not used for the deterioration determination, the calculation load can be expected to decrease accordingly. Now, let's get into the explanation of the block diagram.

The block 1301 is an engine control system, and is composed of fuel control, ignition control, air-fuel ratio control, and the like. The output of the block 1301 is the air-fuel ratio (a signal indicating the state of the air-fuel ratio), and the fluid corresponding to this air-fuel ratio is input to the actual catalyst of the block 1302. If the diagnostic condition is not satisfied by the diagnostic condition determining means of the block 1307, the air-fuel ratio shift is not permitted in the block 1305, and the air-fuel ratio, which is the output of the 1301 in the block 1304, is not shifted and is output as it is. Will be done.

The air-fuel ratio that is not shifted is input to the simulated catalyst of 1303, and the air-fuel ratio after the actual catalyst, which is the output of 1302, is also input to the simulated catalyst of 1303. The transfer characteristics in the simulated catalyst are varied so that the air-fuel ratio and the air-fuel ratio after the actual catalyst of 1302 have the same operation.

The simulated catalyst of 1303 is composed of a transfer function of a second-order lag system + a waste time system, and the air-fuel ratio after the actual catalyst of 1302 and the air-fuel ratio after the simulated catalyst of 1303 are put out there so as to have the same operation. The coefficients (parameters) that come are calculated by the sequential minimum square method.

On the other hand, when the diagnostic condition is satisfied in the block 1307, the air-fuel ratio shift is permitted in the block 1305, the air-fuel ratio shift amount is calculated in the block 1304, and the air-fuel ratio shifted air-fuel ratio is input to the simulated catalyst of 1303 and 1302. The air-fuel ratio after the actual catalyst, which is the output of, is also input to the simulated catalyst of 1303. At this time, since the diagnostic conditions of block 1307 are satisfied, the coefficients of the transfer function of the second-order lag system + wasted time system are not calculated by the sequential least squares method in the simulated catalyst of block 1303, and the update is performed. It is stopped.

In this state, the simulated catalyst is in a state equivalent to that of the actual catalyst because the system identification by the sequential least squares method is stopped immediately before the diagnostic conditions are satisfied. In this state, the air-fuel ratio shifted air-fuel ratio is input to the simulated catalyst of the block 703, so that the air-fuel ratio sensor signal after the simulated catalyst corresponding to the deterioration can be detected. Since the simulated catalyst has the same response characteristics as the actual catalyst, it can be determined that the deterioration of the simulated catalyst is the same as the deterioration of the actual catalyst.

After that, the average value for each air-fuel ratio shift of the block 1306 is calculated. By comparing the calculated average value for each air-fuel ratio shift in block 1309 with the threshold value calculated (set) from the air-fuel ratio shifted in block 1308, block 1310 determines whether the actual catalyst is OK or NG. do.

That is, even in the second form, by using a simulated catalyst that performs the same operation instead of using the actual catalyst as the diagnosis target, the actual catalyst deteriorates without deteriorating the exhaust even if the input air-fuel ratio is shifted. Can be determined.

Specifically, the MPU (processor) performs an air-fuel ratio shift for each predetermined number of ignitions, and is empty from the average value of the fourth signal for each predetermined number of ignitions output from the simulated catalyst 703 (simulated device). The average value of the fourth signal (for example, 0.57, FIG. 10) during the period in which the fuel ratio shift is executed is calculated as a deterioration index. Then, when the deterioration index is smaller than the threshold value (for example, 0.7, FIG. 10) corresponding to the average value of the air-fuel ratio-shifted third signal, the MPU (processor) diagnoses that the actual catalyst 702 (device) has deteriorated. do.

Thereby, the deterioration of the device can be diagnosed from the average value of the third signal and the fourth signal without using the cross-correlation function. As a result, the calculation load can be further suppressed.

Next, FIG. 10 will be described. FIG. 10 is an example at the time of diagnosis of a moderately deteriorated actual catalyst (≈ simulated catalyst). The three timing charts on the upper side of FIG. 10 show the air-fuel ratio shifted (rich → lean) before the simulated catalyst and the air-fuel ratio after the simulated catalyst when the air-fuel ratio sensor signal after the simulated catalyst is in a rich state. An example of determining the deterioration of the actual catalyst from the average value for each air-fuel ratio shift of the sensor signal is shown.

On the other hand, the three timing charts on the lower side of FIG. 10 show the case where the air-fuel ratio sensor signal after the simulated catalyst is in a lean state. In that case, the air-fuel ratio sensor signal after the simulated catalyst is once enriched and then simulated. An example is shown in which the air-fuel ratio before the catalyst is lean-shifted (rich → lean), and the deterioration of the actual catalyst is determined from the average value of the air-fuel ratio sensor signal after the simulated catalyst for each air-fuel ratio shift.

In this method, in the case of a normal catalyst, the air-fuel ratio sensor (O2 sensor) after the simulated catalyst hardly swings, so that the average value shows about 1.0 V. On the other hand, in the case of the deteriorated catalyst, when the air-fuel ratio shift (rich → lean) is performed, the air-fuel ratio sensor (O2 sensor) after the simulated catalyst gradually shifts to the lean side while swinging. Therefore, the average value for each air-fuel ratio shift is smaller than 1.0V. Therefore, in the case of OK, the average value is around 1.0V, and in the case of NG, it is less than that.

An example of the result of the catalyst deterioration diagnosis of the second form is shown in FIG. Basically, the results are almost the same as those in FIGS. 21 and 8. However, as described above, if the threshold value is higher than the threshold value, the value is OK, and if the value is lower than the threshold value, the value is NG.

Further, the point that the exhaust gas, which is the original purpose, does not deteriorate is a big difference from the result of the comparative example (FIG. 21). Since the average value for each air-fuel ratio shift is calculated for the air-fuel ratio sensor signal input to the simulated catalyst equivalent to the actual catalyst and compared with the threshold value, the exhaust is exhausted by not applying the air-fuel ratio shift to the actual catalyst. It will not get worse.

(Identification of simulated catalyst)
FIG. 12 is an example of the identification mechanism of the simulated catalyst. The simulated catalyst is described by a model (transmission function) of the second-order lag system + wasted time system, and its coefficients such as wasted time, intrinsic angular frequency, attenuation coefficient, and steady gain are described by the air-fuel ratio sensor signal after the actual catalyst and the simulated catalyst. This is a method of obtaining by the sequential minimum square method so that the difference between the later air-fuel ratio sensor signals becomes zero.

That is, the MPU (processor) wastes time +2 by using the deviation between the signal (second signal) of the O2 sensor after the actual catalyst 702 (device) and the fourth signal output from the simulated catalyst 703 (simulated device). By identifying the waste time, natural angular frequency, attenuation coefficient, and steady gain, which are the factors of the next lag factor, by the sequential minimum square method, the transfer function (function) constituting the simulated catalyst 703 (simulated device) is identified. ..

This makes it possible to identify the transfer function (function) constituting the simulated catalyst 703 (simulated device) as a physical model of the wasted time + second-order lag system.

When the catalyst deterioration diagnosis condition is satisfied, the above system identification is stopped, the air-fuel ratio shift (rich → lean) is applied to the air-fuel ratio sensor signal before the simulated catalyst, and the diagnosis is made from the relationship with the air-fuel ratio sensor signal after the simulated catalyst. Run.

FIG. 13 shows the results of the air-fuel ratio sensor signal (O2 sensor) after the actual catalyst and the air-fuel ratio sensor signal (O2 sensor) after the simulated catalyst calculated by the identification mechanism of the simulated catalyst shown in FIG. It can be seen that the O2 sensor signal after the actual catalyst and the O2 sensor signal after the simulated catalyst operate almost in the same manner. This example is a deterioration catalyst, but in the case of a normal catalyst, it can be inferred that the O2 sensor signal after the actual catalyst and the O2 sensor signal after the simulated catalyst do not swing.

Therefore, from now on, the flowchart of the embodiment of the present invention will be described. FIG. 14 is a flowchart of the diagnostic condition determination means of the first and second forms.

In step 1801, it is checked whether the rotation speed of the internal combustion engine is within a predetermined range. In step 1802, it is checked whether the load of the internal combustion engine is within a predetermined range. In step 1803, it is checked whether the water temperature (cooling water temperature) is within a predetermined range. In step 1804, it is checked whether the vehicle speed is within the predetermined range. In step 1805, it is checked whether the intake air temperature is within the predetermined range.

In step 1806, it is checked whether the atmospheric pressure is equal to or higher than the predetermined value. In step 1807, it is checked whether the battery voltage is within the predetermined range. Check if the fuel is being cut in step 1808. In step 1809, it is checked whether the air-fuel ratio control feedback is in progress. In step 1810, it is checked whether the actual catalyst is activated. Check if the sensor used in step 1811 is faulty.

If all the conditions of steps 1801 to 1811 are satisfied in step 1812, it is determined that the diagnostic conditions are satisfied. If even one is out of the range, it is determined in step 1813 that the diagnostic condition is not satisfied.

In other words, the MPU (catalyst) has an engine speed (speed) within a predetermined range, an engine load within a predetermined range, a water temperature within a predetermined range, a vehicle speed within a predetermined range, an intake air temperature within a predetermined range, and an atmospheric pressure. Diagnoses the actual catalyst 702 (device) when the battery voltage is within the specified range, the fuel is not cut, the air-fuel ratio is fed back, the actual catalyst is active, and the sensor used is not failed. ..

Thereby, the timing for diagnosing the actual catalyst 702 (device) can be appropriately set.

Next, the flowchart of FIG. 15 will be described. FIG. 15 is also a flowchart common to Form 1 and Form 2.

FIG. 15 is a process of storing the air-fuel ratio sensor signal before the actual catalyst and the air-fuel ratio sensor signal after the actual catalyst in the RAM of the microcomputer. In step 1901, it is checked whether the air-fuel ratio sensor in front of the actual catalyst is activated. If it is active, the process proceeds to step 1902, and if it is not activated, the process returns to step 1901. Next, if the air-fuel ratio sensor before the actual catalyst is activated, in step 1902, it is checked whether the air-fuel ratio sensor after the actual catalyst is activated. If it is activated, the process proceeds to step 1903, and if it is not activated, the process returns to step 1902.

Next, in step 1903, the air-fuel ratio sensor signal before the actual catalyst is stored in the RAM of the microcomputer. Further, in step 1904, the air-fuel ratio sensor signal after the actual catalyst is stored in the RAM of the microcomputer, and this is repeated for each predetermined task. In this embodiment, the task is set every 10 ms, but this is not the case.

Next, the flowchart of FIG. 16 will be described. FIG. 16 corresponds to the flowchart of Form 1. In step 2001, it is checked by the sequential minimum square method whether the air-fuel ratio sensor signal (O2 sensor) after the actual catalyst and the air-fuel ratio sensor signal (O2 sensor) after the simulated catalyst are substantially the same. If they are almost the same, the process proceeds to step 2002, and if they are not the same, the process returns to 2001. If they are almost the same, it is checked in step 2002 whether the diagnostic conditions are satisfied. If the diagnostic condition is not satisfied, the process proceeds to return, and if the diagnostic condition is satisfied, the process proceeds to step 2003.

In step 2003, the air-fuel ratio shift (rich → lean) is executed on the air-fuel ratio sensor signal (O2 sensor) before the simulated catalyst. In step 2004, the cross-correlation function of the air fuel ratio sensor signal (O2 sensor) before the simulated catalyst and the air fuel ratio sensor signal (O2 sensor) after the simulated catalyst is calculated.

In step 2005, the constant threshold value and the cross-correlation function are compared, and if the cross-correlation function is equal to or less than the threshold value, it is determined to be OK in step 2006, and if the cross-correlation function is larger than the threshold value, it is determined to be NG in step 2007.

Next, the flowchart of FIG. 17 will be described. FIG. 16 corresponds to the flowchart of Form 2. In step 2101, it is checked by the sequential minimum square method whether the air-fuel ratio sensor signal (O2 sensor) after the actual catalyst and the air-fuel ratio sensor signal (O2 sensor) after the simulated catalyst are substantially the same. If they are substantially the same, the process proceeds to step 2102, and if they are not the same, the process returns to 2101. If they are almost the same, step 2102 checks whether the diagnostic conditions are satisfied. If the diagnostic condition is not satisfied, the process proceeds to return, and if the diagnostic condition is satisfied, the process proceeds to step 2103.

In step 2103, the air-fuel ratio shift (rich → lean) is executed on the air-fuel ratio sensor signal (O2 sensor) before the simulated catalyst. In step 2104, a table is used from the average value of the air-fuel ratio sensor signal (O2 sensor) before the simulated catalyst, and the threshold value is calculated. Specifically, for example, the CPU (processor) reads out the threshold value corresponding to the average value of the signals (voltages) output from the air-fuel ratio sensor (O2 sensor) from the table. The table is stored in, for example, a non-volatile memory.

In step 2105, the catalyst deterioration index is calculated from a plurality of average values for each air-fuel ratio shift of the air-fuel ratio sensor signal (O2 sensor) after the simulated catalyst. In step 2106, the calculated threshold value and the catalyst deterioration index are compared, and if the catalyst deterioration index is equal to or more than the calculated threshold value, it is determined to be OK in step 2107, and if the catalyst deterioration index is less than the calculated threshold value, NG is determined in step 2108. judge.

According to the above examples, the deterioration of the three-way catalyst can be determined without deteriorating the exhaust gas by using the system identification such as the sequential least squares method.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

For example, if the sensor in front of the catalyst is an air-fuel ratio sensor, F / B control is performed centered on the stoichiometric sensor, so learning on the lean side and rich side cannot be performed. In that case, it is necessary to apply dither control to the simulated catalyst.

Further, each of the above configurations, functions and the like may be realized by hardware by designing a part or all of them by, for example, an integrated circuit. Further, each of the above configurations, functions, and the like may be realized by software by the processor (microcomputer) interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be placed in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

The embodiment of the present invention may have the following aspects.

(1). In the diagnostic device, the air-fuel ratio shift is applied to the simulated device generation unit that generates a simulated device that outputs a signal corresponding to the output signal related to the device attached to the engine by system identification, and the signal input to the simulated device. A diagnostic device including a calculation unit for diagnosing the device.

(2). The arithmetic unit is a diagnostic device that executes the air-fuel ratio shift by applying a first-order lag filter to the input signal of the simulated device and increasing the fall time constant.

(3). The simulated device generation unit is a diagnostic device that generates the simulated catalyst by a sequential least squares method based on the output signal related to the device.

(4). A diagnosis for diagnosing the device by calculating a cross-correlation function indicating the similarity between the output signal related to the device and the output signal from the simulated device on which the air-fuel ratio shift is executed for each air-fuel ratio shift. Device.

(5). In the catalyst deterioration diagnosis device, the simulated catalyst generator that generates a simulated catalyst that outputs a signal corresponding to the output signal of the sensor located on the downstream side of the actual catalyst by system identification, and the signal input to the simulated catalyst are empty. A catalyst deterioration diagnostic device equipped with a calculation means for diagnosing deterioration of the actual catalyst by applying a fuel ratio shift.

(6). The calculation unit is a catalyst deterioration diagnosis device that executes the air-fuel ratio shift by applying a first-order lag filter to the input signal of the simulated catalyst and increasing the fall time constant.

(7). The simulated catalyst generation unit is a catalyst deterioration diagnosis device that generates the simulated catalyst by a sequential least squares method based on the output signal of the sensor.

(8). The calculation unit calculates a cross-correlation function indicating the similarity between the output signal of the sensor and the output signal from the simulated catalyst in which the air-fuel ratio shift is executed for each air-fuel ratio shift, and performs averaging processing. A catalyst deterioration diagnostic device that diagnoses deterioration of the actual catalyst by performing the above.

(9). An air-fuel ratio shift is executed on the air-fuel ratio sensor signal input to the simulated catalyst, a threshold value is calculated from the average value of the air-fuel ratio-shifted air-fuel ratio sensor signal, and each air-fuel ratio shift of the output signal of the simulated catalyst is calculated. The diagnostic device for an exhaust gas purification device according to (1), characterized in that deterioration of the catalyst is determined by comparing the average value with the threshold value.

(10). The simulated catalyst uses the deviation between the output signal of the actual catalyst and the output signal of the simulated catalyst to obtain the wasted time + the factor of the second-order lag factor, the wasted time, the natural angle frequency, the attenuation coefficient, and the steady gain. The diagnostic device for an exhaust purification device according to (1), wherein the output signal of the simulated catalyst is calculated so as to match the output signal of the actual catalyst by calculating by the sequential minimum square method.

(11). The diagnostic condition determining means has a rotation speed within a predetermined range, an engine load within a predetermined range, a water temperature within a predetermined range, a vehicle speed within a predetermined range, an intake air temperature within a predetermined range, an atmospheric pressure of a predetermined value or more, and a battery voltage. The internal combustion engine according to (1). Air-fuel ratio sensor diagnostic device.

According to (1) to (11), the air-fuel ratio sensor signal downstream of the actual catalyst and the air-fuel ratio sensor signal downstream of the simulated catalyst are equivalent to each other by the sequential minimum square method of the simulated catalyst equivalent to the actual catalyst. By applying an air-fuel ratio shift to the air-fuel ratio sensor signal upstream of the simulated catalyst, the exhaust is deteriorated due to the relationship between the air-fuel ratio sensor signal of the simulated catalyst and the air-fuel ratio sensor signal upstream of the simulated catalyst. It is possible to determine the deterioration of the actual catalyst without causing the reaction.

Specifically, in a catalyst that is an exhaust purification device of an internal combustion engine, by using system identification by the sequential minimum square method or the like, a simulated catalyst equivalent to the actual catalyst is calculated onboard, and the air-fuel ratio is shifted to the simulated catalyst. By inputting the air-fuel ratio sensor signal obtained by executing the above, the deterioration of the simulated catalyst is determined from the mutual correlation function for detecting the similarity of the air-fuel ratio sensor signals before and after the simulated catalyst.

At this time, since the simulated catalyst and the actual catalyst are equivalent, the result can be determined to be deterioration of the actual catalyst, and further, since the air-fuel ratio shift is not executed for the air-fuel ratio sensor signal input to the actual catalyst, the exhaust gas is exhausted. Deterioration of the actual catalyst can be determined without making it worse.

Further, as another aspect, the diagnosis can be made from the average value of the air-fuel ratio before and after the simulated catalyst, instead of calculating the cross-correlation function. In this method, since the complicated cross-correlation function is not calculated, it is expected that the processing load of the microcomputer can be reduced.

When the deterioration of the catalyst is determined by the above-mentioned determination means, the engine lamp or the like is turned on, the DTC corresponding to the detected failure mode is communicated to the failure diagnosis tool, and the driver is warned of the abnormality.

101: Engine control system 102: Device 103: Diagnostic condition determination means 104: Air fuel ratio shift amount calculation means 105: Simulation device 106: Diagnostic calculation means 200: Air cleaner 201: Ignition device 202: Fuel injection device 203: Rotation speed detection device 204: Flow detection device 205: Pre-catalyst oxygen sensor 206: Catalyst 207: Internal combustion engine control device 208: Plate or ring gear 209: Fuel tank 210: Fuel pump 211: Pressure regulator 212: Fuel pipe 213: Throttle valve 214: Cylinder 215 : Post-catalyst oxygen sensor 301: Engine control system 302: Air fuel ratio shift amount calculation means 303: Device 304: Diagnostic condition judgment means 305: Mutual correlation function calculation means 306: Threshold setting means 307: Comparison judgment means 308: OK / NG judgment Means 701: Engine control system 702: Actual catalyst 703: Simulated catalyst 704: Air fuel ratio shift amount calculation means 705: Air fuel ratio shift permission determination means 706: Mutual correlation function calculation means 707: Diagnostic condition determination means 708: Threshold setting means 709: Comparison determination means 7010: OK / NG determination means 1301: Engine control system 1302: Actual catalyst 1303: Simulated catalyst 1304: Air fuel ratio shift amount calculation means 1305: Air fuel ratio shift permission determination means 1306: Air fuel ratio shift average value calculation means 1307 : Diagnostic condition determination means 1308: Threshold table search means 1309: Comparison determination means 1310: OK / NG determination means

Claims (15)

Devices through which the exhaust from the engine passes, and
A simulated device composed of a function identified from a first signal indicating the state of the exhaust before the device and a second signal indicating the state of the exhaust after the device.
A processor in which a third signal obtained by shifting the air-fuel ratio of the first signal to the simulated device is input to the simulated device, and the device is diagnosed from the fourth signal output from the simulated device and the third signal.
A diagnostic device equipped with. The diagnostic device according to claim 1.
The processor
A diagnostic device characterized in that the air-fuel ratio shift is executed by applying a first-order lag filter to the first signal and increasing the fall time constant. The diagnostic device according to claim 2.
The processor
A diagnostic apparatus characterized in that the falling time constant is increased during a period in which the time derivative value of the first signal becomes negative. The diagnostic device according to claim 1.
The processor
A diagnostic device characterized by identifying the function by the sequential least squares method. The diagnostic device according to claim 1.
The processor
A diagnostic device characterized in that an index indicating the similarity between the third signal and the fourth signal is calculated every time the air-fuel ratio shift is executed, and the device is diagnosed from the index. The diagnostic device according to claim 5.
The index is
A diagnostic device characterized by being a cross-correlation function. The diagnostic device according to claim 6.
The processor
A diagnostic apparatus characterized in that when the value of the cross-correlation function exceeds a threshold value and the similarity between the third signal and the fourth signal is high, it is diagnosed that the device has deteriorated. The diagnostic device according to claim 6.
The processor
The air-fuel ratio shift is executed every predetermined number of ignitions, and the air-fuel ratio shift is executed.
A diagnostic device characterized in that the cross-correlation function is calculated for each predetermined number of ignitions. The diagnostic device according to claim 8.
The processor
A diagnostic device for diagnosing that the device has deteriorated when the load mean value of the maximum value and the second largest value of the cross-correlation function exceeds a threshold value. The diagnostic device according to claim 5.
The processor
The air-fuel ratio shift is executed every predetermined number of ignitions, and the air-fuel ratio shift is executed.
From the average value of the fourth signal for each predetermined number of ignitions, the average value of the fourth signal during the period in which the air-fuel ratio shift is executed is calculated as a deterioration index.
A diagnostic device for diagnosing that the device has deteriorated when the deterioration index is smaller than the threshold value corresponding to the average value of the third signal. The diagnostic device according to claim 4.
The processor
By using the deviation between the second signal and the fourth signal to identify the wasted time + the factor of the second-order lag factor, the wasted time, the intrinsic angular frequency, the attenuation coefficient, and the steady gain, by the sequential least squares method. A diagnostic device characterized by identifying the function constituting the simulated device. The diagnostic device according to claim 1.
The processor
The number of revolutions is within the specified range, the engine load is within the specified range, the water temperature is within the specified range, the vehicle speed is within the specified range, the intake air temperature is within the specified range, the atmospheric pressure is within the specified value, the battery voltage is within the specified range, and the fuel is being cut. A diagnostic device comprising diagnosing the device when not, during air-fuel ratio feedback, when the actual catalyst is active, and when the sensor used is not faulty. The diagnostic device according to claim 1.
The air-fuel ratio shift is
A diagnostic device characterized by a lean shift that changes the air-fuel ratio from rich to lean. The diagnostic device according to claim 1.
The device is
A diagnostic device characterized by being composed of a catalyst for purifying the exhaust gas. The diagnostic device according to claim 14.
The first signal and the second signal are
A diagnostic device characterized by being a signal output from an O2 sensor.

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