JPH06264725A - Deterioration detecting device of catalytic converter - Google Patents

Abstract

PURPOSE:To accurately detect deterioration by providing air-fuel ratio sensors on the upstream side and the downstream side of a catalytic converter, judging the catalyst deterioration from at least the air-fuel ratio sensor on the downstream side, and judging the case where the detected value of the deterioration is more than the fixed valve as the deterioration when the load accumulated value is more than the fixed value. CONSTITUTION:Air-fuel ratio sensors 12, 13 are respectively provided on the upstream side and the downstream side of a catalytic converter. An electric control units performs the deterioration judgement of the catalytic converter on the basis of the output of at least the air-fuel ratio sensor 13. The electronic control unit detects the deterioration of catalyst by means of deterioration detecting means 23, 24. On the other hand, load of an internal combustion engine is detected by a load detecting means 6A, and the detected value is accumulated in a load accumulating means 25. When the accumulated value exceeds the fixed accumulated value, it is judged that the deterioration level of the catalytic converter reaches the fixed value when the detected value calculated by the deterioration detecting means 23, 24 is more than the fixed value. Thus, the deterioration diagnosis is precisely performed without unnecessarily repeating the deterioration judgement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic converter deterioration detecting device capable of accurately detecting deterioration of a catalytic converter.

[0002]

2. Description of the Related Art Conventionally, there is known a deterioration detecting device for a catalytic converter using an air-fuel ratio sensor used for air-fuel ratio feedback control of an internal combustion engine. In the air-fuel ratio feedback control (single O2 sensor system) of such an internal combustion engine, an air-fuel ratio sensor for detecting the oxygen concentration is provided upstream of the catalytic converter, but the air-fuel ratio is controlled due to variations in the output characteristics of the air-fuel ratio sensor. There is a problem in improving accuracy. Therefore, in order to compensate for variations in the output characteristics of the air-fuel ratio sensor, variations in parts such as the fuel injection valve, and changes over time or over time, a second air-fuel ratio sensor is provided downstream of the catalytic converter and the upstream air-fuel ratio sensor is used. In addition to the air-fuel ratio feedback control, a dual O2 sensor system that performs air-fuel ratio feedback control by a downstream side air-fuel ratio sensor has already been proposed.

On the other hand, the catalytic converter is designed so that its function is not significantly deteriorated as long as it is used within the range of normally considered use conditions. However, if there is any cause during use, such as misfire, the function of the catalyst may be significantly reduced. As a result, if the engine is operated while the exhaust gas is not sufficiently purified by the catalytic converter, the behavior of the output of the downstream side air-fuel ratio sensor is affected by unburned gas such as HC, CO, NOX and the like. There is a problem in that, as a result of the change, the degree of output of the downstream air-fuel ratio sensor becomes large, resulting in a reduction in emissions.

Therefore, it is important to detect the deterioration of the catalytic converter. For example, Japanese Patent Application No. 3-264 has been used in the past.
As disclosed in 312, the area equivalent value S of the figure formed by the air-fuel ratio sensor signal and the predetermined signal and the output inversion period T of the signal obtained by comparing the air-fuel ratio sensor signal and the predetermined signal are calculated. , A device for determining deterioration of the catalytic converter at predetermined time intervals by a combination of S and T obtained by air-fuel ratio sensors upstream and downstream of the catalytic converter.

[0005]

However, in such a conventional catalytic converter deterioration detecting device, deterioration is judged every predetermined time. Therefore, when the total intake air amount varies depending on the engine state, the catalyst enters the catalyst. Since the exhaust gas flow rate is different, the purification performance of the catalyst is not constant, and the calculated values of the parameters S and T required for deterioration determination vary greatly, which makes it difficult to accurately determine the deterioration.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is to obtain a deterioration detecting device for a catalytic converter capable of accurately detecting deterioration of the catalytic converter.

[0007]

According to a first aspect of the present invention, there is provided a deterioration detecting device for a catalytic converter, which is provided in an exhaust system of an internal combustion engine and is provided downstream of a catalytic converter for purifying exhaust gas. An air-fuel ratio sensor that detects the concentration of a specific component in the exhaust gas downstream of the converter, a deterioration detection unit that detects deterioration of the catalytic converter based on the output of the air-fuel ratio sensor, and a load that detects the load of the internal combustion engine. Detecting means, load value accumulating means for accumulating the detection values obtained by the load detecting means, and when the accumulated value obtained by the load value accumulating means exceeds a predetermined accumulated value, by the deterioration detecting means, Deterioration determination means for determining that the degree of deterioration of the catalytic converter has reached a predetermined value when the obtained detected value is equal to or greater than a predetermined value. A.

Further, a deterioration detecting device for a catalytic converter according to a second aspect of the present invention is provided on a downstream side of a catalytic converter which is provided in an exhaust system of an internal combustion engine and purifies exhaust gas, and exhaust gas downstream of the catalytic converter is provided. An air-fuel ratio sensor for detecting the concentration of a specific component in the gas, based on the output of this air-fuel ratio sensor, deterioration detection means for detecting the deterioration of the catalytic converter, load detection means for detecting the load of the internal combustion engine, The load value accumulating means for accumulating the detected load values obtained by the load detecting means, and the output of the air-fuel ratio sensor crosses the predetermined value every time the cumulative value obtained by the load value accumulating means exceeds the predetermined cumulative value. Based on the number of times calculating means for calculating the number of times and the value obtained by the number of times calculating means, a deterioration judgment for judging that the degree of deterioration of the catalytic converter has reached a predetermined value It is obtained by a means.

According to a third aspect of the present invention, there is provided a catalytic converter deterioration detecting device according to the second aspect, wherein the number of times calculating means is the detected load value obtained by the load detecting means. The comparison signal calculating means for calculating and outputting the predetermined value as a comparison signal based on

A deterioration detecting device for a catalytic converter according to a fourth aspect of the present invention is the deterioration detecting device for a catalytic converter according to any one of the first to third aspects, wherein the deterioration determining means is the internal combustion engine. The deterioration determination is performed when the rotation speed is within a predetermined range and the detected load value is within a predetermined range.

A catalytic converter deterioration detecting device according to a fifth aspect of the present invention is the catalytic converter deterioration detecting device according to any one of the first to fourth aspects, wherein the load detecting means is a fuel consumption device for an internal combustion engine. It is to detect the quantity.

According to a sixth aspect of the present invention, there is provided a deterioration detecting device for a catalytic converter according to any one of the first to fourth aspects, wherein the load detecting means determines the traveling distance of the vehicle. It is something to detect.

Further, a deterioration detecting device for a catalytic converter according to a seventh aspect of the present invention is the deterioration detecting device for a catalytic converter according to any one of the first to sixth aspects, wherein the deterioration determining means is A warning means is provided for issuing a warning when it is determined that the degree of deterioration has reached a predetermined value.

[0014]

According to the deterioration detecting device for a catalytic converter according to the first aspect of the present invention, since the deterioration of the catalytic converter is detected based on the accumulated value by the load value accumulating means, the deterioration determination of the catalytic converter is repeated unnecessarily. It is possible to detect the deterioration of the catalytic converter more accurately and surely.

Further, according to the deterioration detecting device for the catalytic converter of the second aspect of the present invention, the number of times the output signal of the air-fuel ratio sensor crosses the predetermined value is calculated every time the accumulated value of the load values exceeds the predetermined value. Since it is decided to do so, it is possible to surely detect the performance deterioration of the catalytic converter.

Further, according to the deterioration detecting device of the catalytic converter of the third aspect of the present invention, since the predetermined value is the value calculated according to the load value as the comparison signal, the deterioration degree of the catalytic converter is relatively small. Even in that case, the degree of deterioration can be accurately determined.

Further, according to the deterioration detecting device of the catalytic converter of the fourth aspect of the present invention, the deterioration of the catalytic converter is judged when the rotational speed of the internal combustion engine and the output value of the load are within a predetermined range. Therefore, it is possible to prevent the variation of the parameters required for the deterioration detection and to improve the accuracy of the deterioration detection.

Further, according to the deterioration detecting device for a catalytic converter of the fifth aspect of the present invention, the load can be easily detected by setting the load to the fuel consumption amount.

Further, according to the deterioration detecting device of the catalytic converter of the sixth aspect of the present invention, the load can be easily detected as in the fifth aspect by setting the load as the traveling distance.

Further, according to the deterioration detecting device of the catalytic converter of the seventh aspect of the present invention, the warning means can notify the driver of the abnormality of the catalytic converter.

[0021]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram conceptually showing Embodiment 1, and FIG.
FIG. 3 is a block diagram specifically showing the first embodiment. In FIG. 2, 1 is an internal combustion engine, 2 is an intake pipe, 3 is an exhaust pipe, 4 is an intake manifold connected to the intake pipe 2, 5 is an air cleaner provided at an intake port of the intake pipe 2, and 6 is an intake pipe 2.
A hot-wire intake air amount sensor (hereinafter referred to as AFS) provided in the intake pipe, 7 an injector provided in the intake pipe 2, 8 a throttle valve provided downstream of the injector 7 in the intake pipe 2, 9 a throttle opening sensor, 10 Is an idle switch, and 11 is a catalytic converter provided in the exhaust pipe 3.

Further, 12 is a first air-fuel ratio sensor provided upstream of the catalytic converter 11, 13 is a second air-fuel ratio sensor provided downstream of the catalytic converter 11, and these air-fuel ratio sensors 12, 13 are provided. Respectively detect the air-fuel ratio in the exhaust gas in the upstream and downstream of the catalytic converter 11.

Reference numeral 14 is an ignition coil, 15 is an igniter connected to the ignition coil 14, 16 is a water temperature sensor attached to the internal combustion engine 1, 17 is a battery, and 18 is an ignition key switch connected to the battery 17.
9 is an electronic control unit, 20 is an electronic control unit 1
A warning lamp connected to 9 and a crank angle sensor 21 for detecting the crank angle.

In FIG. 2, the AFS 6 is a hot wire type AFS for measuring the amount of air taken into the internal combustion engine 1 from the intake pipe 2 through the intake manifold 4. The injector 7 is arranged upstream of the throttle valve 8 and injects fuel.
Is for detecting the opening of the throttle valve 8
Is attached to. The water temperature sensor 16 is a thermistor type sensor that detects the cooling water temperature of the internal combustion engine 1. Further, the ignition coil 14 ignites by a signal from the igniter 15 and sends the generated ignition signal to the electronic control unit 19.

Next, the electronic control unit 19 operates the AFS.
6, a water temperature sensor 16, a throttle opening sensor 9, an ignition coil 14, and air-fuel ratio sensors 12, 1 for detecting the air-fuel ratio.
The respective signals from 3 are input to perform air-fuel ratio control and catalyst deterioration detection.

FIG. 3 is a detailed block diagram of the electronic control unit 19. In the figure, 100 is a microcomputer, and this microcomputer 100
Is a CPU 200 that performs air-fuel ratio control and the like according to the outputs of the air-fuel ratio sensors 12 and 13 according to a predetermined program, a free-running counter 201 that measures the rotation cycle of the internal combustion engine 1, and various controls. A timer 202 for measuring time, an A / D converter 203 for converting an analog input signal into a digital signal, a RAM 205 used as a work memory, a ROM 206 in which a program is stored, and a drive signal for outputting. It is composed of an output port 207 and a common bus 208.

A first input interface circuit 101 shapes the primary ignition signal of the ignition coil 14 into an interrupt signal and outputs it to the microcomputer 100. When this interrupt signal is generated, the CPU
Reference numeral 200 reads the value of the counter 201, calculates the cycle of the rotation speed of the internal combustion engine 1 from the difference between the read value and the previous read value, and stores it in the RAM 205.

Reference numeral 102 denotes a second input interface circuit, which inputs signals from the air-fuel ratio sensors 12, 13 and the AFS 6, the throttle opening sensor 9 and the water temperature sensor 16 and outputs them to the A / D converter 203. It is a thing. An output interface circuit 104 amplifies the drive output signal from the output port 207 and outputs it to the injector 7 and the warning lamp 20.

Next, regarding the operation of the CPU 200 of the deterioration detecting device for the catalytic converter configured as described above, a control block diagram of FIG. 4, a diagram showing the behavior of the air-fuel ratio sensor when the catalyst is normal, and FIG. 6 are shown. The behavior of the air-fuel ratio sensor when the catalyst deteriorates will be described with reference to the flowcharts of FIGS. 7 to 8 and the behavior of the air-fuel ratio sensor of FIG. 9. First, the air-fuel ratio control in the apparatus shown in this embodiment will be described with reference to the behavior of the air-fuel ratio sensor shown in FIG. 9 based on the control block diagram shown in FIG.

A block 401 indicates a preset second predetermined signal (target value of air-fuel ratio control), and an adder a
First, the output signal V2 of the second air-fuel ratio sensor 13 and the output signal of the block 401 are compared. The output deviation V2S
Based on the above, the second PI controller 402 PI-controls the output deviation V2S to obtain a predetermined correction output signal V2SH.
Is output. Next, a block 403 indicates a preset first predetermined signal, which is added to the correction output signal V2SH in the adder b and used as the determination value VTH of the second air-fuel ratio sensor 13.

Next, in the adder c, the output signal V1 of the first air-fuel ratio sensor 12 is compared with the above-mentioned judgment value VTH, and the first PI controller 404 is based on this comparison value.
Then, the correction amount CFB of the air-fuel ratio feedback is calculated.

Here, the air-fuel ratio feedback correction amount CFB
Indicates that the magnitude of the output signal of the first air-fuel ratio sensor 12 is substantially equal to the number of times the cycle crosses the determination value VTH and the period. Next, in the multiplier d, this correction amount CFB is multiplied by the basic fuel amount calculated from the intake air amount detected by the AFS 6 shown in block 405. The multiplication result is further multiplied by the output signal from the block 406 in the multiplier e to calculate the final fuel discharge amount. In this block 406, the correction amount corresponding to the warm-up state of the internal combustion engine calculated based on the signal of the water temperature sensor 16 and the acceleration / deceleration state are detected from the signal of the throttle opening sensor 9 to respond to this acceleration / deceleration state. The fuel correction amount such as the corrected amount is output. In order to calculate the drive time of the injector 7 from the fuel amount obtained by the multiplier e, the injector 7 is respectively calculated in blocks 407 and 408.
Of the injection time and the dead time of the injector 7 are calculated, and the outputs thereof are multiplied by the fuel amounts by the multipliers f and g, respectively. As described above, the air-fuel ratio control is performed by correcting the determination value of the first air-fuel ratio sensor 12 using the output signal of the second air-fuel ratio sensor 13.

When the above-mentioned air-fuel ratio control is carried out, the first and second air-fuel ratio sensors 12, 13 mounted upstream and downstream of the catalyst.
Behavior will be described with reference to FIGS. Figure 5
(A) and FIG. 5 (B) show the first and second (catalyst upstream / downstream) air-fuel ratio sensors 12, 1 when the catalytic converter 11 is normal.
3 output is shown. FIG. 5A shows the first air-fuel ratio sensor 1
2 shows the relationship between the second output and the first predetermined signal, and the output of the first air-fuel ratio sensor 12 changes at an appropriate cycle by the air-fuel ratio feedback control. FIG. 5B shows the relationship between the second air-fuel ratio sensor 13 and the second predetermined signal when the catalytic converter 11 is in a normal state. Here, since the purification performance of the three-way catalyst is high, the air-fuel ratio of the gas entering the catalyst is rich /
Even if the lean width is large, the air-fuel ratio of the discharged gas is averaged over time, so there is little change compared to the output of the first air-fuel ratio sensor 12. This tendency increases as the purification performance of the three-way catalyst increases.

Next, FIGS. 6A and 6B show the outputs of the first and second (catalyst upstream / downstream) air-fuel ratio sensors 12 and 13 when the degree of deterioration of the catalyst is large. Here, FIG. 6A is similar to FIG. FIG. 6B shows the relationship between the second air-fuel ratio sensor 13 and the second predetermined signal. As shown in FIG. 6C, when the intake air amount Q becomes large, the gas flow velocity at the catalyst becomes fast. Therefore, the purification rate of the catalyst decreases, and as a result, the output level and frequency of the second air-fuel ratio sensor 13 increase. Here, when the comparison signal obtained by calculating the second predetermined signal according to the intake air amount Q and the respective sensor outputs (when the catalyst is normal and when the catalyst is deteriorated) are compared, the catalyst shown in FIG. In the normal state, there is almost no difference in magnitude between the comparison signal and the sensor output signal, but when the catalyst deterioration is large as shown in FIG. 6B, the difference between the comparison signal and the sensor output is large.

Focusing on this difference in behavior, a deterioration detecting device for a catalytic converter will be described with reference to FIGS. FIG. 7 is a flowchart illustrating the calculation of the comparison signal of the air-fuel ratio sensor and the deterioration determination. First, step S701
Then, depending on whether or not the operating state of the internal combustion engine is a predetermined state, for example, the operating state parameters detected by the AFS 6, the water temperature sensor 16, the crank angle sensor 21, etc. of the internal combustion engine, the operating state of the internal combustion engine 1 is in the idle state, acceleration / deceleration. It is determined whether or not the set condition for determining the deterioration of the catalytic converter 11 is satisfied in the steady state excluding the state and the like. For example, the water temperature of the internal combustion engine 1, the exhaust gas temperature, the rotation speed of the internal combustion engine, When the basic fuel injection amount and the like are within the set range, it is considered that the vehicle is in the predetermined operation state, and the process proceeds to step S702. If it is not in the predetermined operation state, step S712
The warning lamp goes off when the deterioration judgment is stopped.
Next, in step S702, the engine load, for example, the intake air amount (q) is read, and this is accumulated in step S703.

Here, as the cumulative value, the same effect can be obtained by using the opening degree of the throttle valve 8 and the intake pipe pressure in addition to the intake air amount. The cumulative value of the intake air amount of the vehicle is substantially proportional to the cumulative value of the fuel discharge amount, that is, the consumed fuel amount, and the consumed fuel amount increases as the traveling distance increases. The cumulative value of the intake air amount and the traveling distance are not exactly proportional, but it can be said that they are roughly proportional under the same operating conditions. Then, in order to calculate the cumulative value of the intake air amount, the instantaneous intake air amount as an analog amount has to be integrated over time, but the fuel consumption amount can be easily calculated by integrating the drive time of the injector 7. Further, since the traveling distance can be obtained only by counting up the signal of the vehicle speed sensor which is an ON / OFF signal, for example, when the calculation is performed inside the microcomputer 100, the microcomputer 100 does not become a burden and a smaller ROM, It can be realized with RAM capacity. Further, it can be realized without using the microcomputer 100, only by configuring the counter with a simple external circuit. Therefore, in this embodiment, the cumulative value of the intake air amount is obtained, which is used as the fuel consumption amount (fuel supply amount).
Even if it is replaced with the cumulative value of, the same effect can be obtained. Further, the cumulative value of the intake air amount is the same as the cumulative value of the detection signal of the vehicle wheel speed sensor (vehicle speed sensor).

Next, in step S704, it is determined whether the cumulative value Σq is larger or smaller than the predetermined cumulative value Q. If it is smaller, the process proceeds to step S712, and if it is larger, the process proceeds to step S705. Next, in step S705, the comparison signal is interpolated for the read intake air amount using a one-dimensional map.
Here, for example, if the intake air amount q is large, the comparison signal value is increased, and conversely, if the intake air amount q is small, the comparison signal value is decreased. Therefore, when the intake air amount q is large, the comparison voltage as the comparison signal is calculated on the rich side. As the load, the throttle valve opening and the intake pipe pressure can be used in addition to the intake air amount, and the comparison signal may be obtained from a map or calculation of these loads and the internal combustion engine rotation speed.

In step S706, the obtained comparison signal is read, and in step S707, the output of the second air-fuel ratio sensor 13 is read. Then, step S708
In, the read values are compared and calculated. Next, in step S709, a comparison is made with a predetermined value (the judgment value may be varied depending on the operating state), and if the comparison result is equal to or more than the predetermined value, the deterioration of the catalytic converter 11 is judged in step S713. It is determined that the degree has reached a predetermined value or more (the catalyst has deteriorated), and the warning lamp is turned on in step S714 to notify the driver of the abnormality.

Then, in step S715, the cumulative value Σq is cleared and the determination is performed again. If the comparison result is less than or equal to the predetermined value, it is determined in step S710 that the catalyst is normal and the cumulative value Σq is cleared in step S711.
In step S712, the warning lamp is turned off.

Deterioration determination calculation is performed based on the above processing. For the warning lamp 20, except for the case shown in FIG. Will continue to light the warning lamp 20 over a predetermined number, or if a simple external circuit is installed such that the warning lamp 20 will continue to light after the ignition key switch is turned off, the driver will be notified of the abnormality more reliably. be able to.

Next, FIG. 8 shows a flow chart of the comparison calculation process. First, in step S801, the output of the second air-fuel ratio sensor 13 is compared with the comparison signal. If the output of the sensor 13 is larger than the comparison signal, the current flag is set to 1 in step S802, that is, the sensor output is considered to be slightly rich, If the output of the sensor 13 is smaller than the comparison signal, the present flag is set to 0 in step S803, and the process proceeds to step S804. In step S804, it is determined whether or not it is the first comparison after the power is turned on, and if it is the first determination, step S80.
In step 5, the previous flag is initialized. If it is not the first determination, the process proceeds to step S806.

In step S806, step S in FIG.
The same determination as in step 701 is performed, and if the result of the determination is not the predetermined state, the counter is reset to 0 in step S807. If it is in the predetermined state, the counter is not operated and step S808 is performed.
Go to and increment the counter. Steps S808 to S8
In 10, the current flag and the previous flag are combined to determine whether or not the current and previous flags are reversed. When the flags are reversed, the output of the second air-fuel ratio sensor 13 crosses the comparison signal, and the counter is set in step S811. increase. When not inverted, the counter is not operated.

Subsequently, in step S812, it is determined whether or not the same load output cumulative value as in step S704 of FIG. 7 has reached a predetermined cumulative value.
At 813, the comparison calculation result is output from the counter value and the counter value is set to 0. If the cumulative value of the load output is less than the predetermined cumulative value, the process ends.

As described above, as shown in FIG. 8, the number of times the second air-fuel ratio sensor 13 as the comparison calculation process crosses the comparison voltage value is counted. As described above, since the determination is performed only in the predetermined operating state, it is possible to reduce the variation in the parameters required for the deterioration determination. In addition, since the deterioration is determined for each predetermined intake air amount, the determination is performed according to the flow rate of exhaust gas passing through the catalyst.Therefore, the number of determinations should be increased as the gas flow velocity at which the performance of the catalyst decreases becomes faster. Therefore, efficient and reliable determination can be performed. Then, as described above, the deterioration of the catalytic converter can be detected according to FIG. Further, in the flowchart shown in FIG. 7, the intake air amount is accumulated only in the predetermined operating state, but it may be accumulated in all the operating states.

In FIG. 1 conceptually showing the embodiment described above, the load detecting means 6A is the AFS 6 in FIG.
Comparing signal calculating means 23, comparing means 24, load value accumulating means 25, and deterioration determining means 26 are composed of electronic control unit 19, and warning means 20A is a warning lamp 20.
It is composed by. Further, the deterioration detecting means in the claims is composed of a comparison signal calculating means 23 and a comparing means 24 in FIG. Incidentally, 22 is the air-fuel ratio sensor 1
2 and 13 are air-fuel ratio control devices.

[0046]

As described above in detail, the deterioration detecting device for a catalytic converter according to claim 1 of the present invention is provided in the exhaust system of an internal combustion engine downstream of a catalytic converter for purifying exhaust gas. And an air-fuel ratio sensor for detecting a specific component concentration in exhaust gas downstream of the catalytic converter, a deterioration detecting unit for detecting deterioration of the catalytic converter based on an output of the air-fuel ratio sensor, and a load of the internal combustion engine. The load detection means for detecting the load value, the load value accumulation means for accumulating the detection values obtained by the load detection means, and the cumulative value obtained by the load value accumulation means exceeding a predetermined cumulative value, Deterioration determining means for determining that the degree of deterioration of the catalytic converter has reached a predetermined value when the calculated value obtained by the deterioration detecting means is equal to or greater than a predetermined value. And therefore, an effect that it is possible to perform the deterioration detection of the catalytic converter accurately.

A deterioration detecting device for a catalytic converter according to a second aspect of the present invention is provided on the downstream side of a catalytic converter which is provided in an exhaust system of an internal combustion engine and purifies exhaust gas, and exhaust gas at the downstream of the catalytic converter. An air-fuel ratio sensor for detecting the concentration of a specific component in the gas, based on the output of this air-fuel ratio sensor, deterioration detection means for detecting the deterioration of the catalytic converter, load detection means for detecting the load of the internal combustion engine, The load value accumulating means for accumulating the detected load values obtained by the load detecting means, and the output of the air-fuel ratio sensor crosses a predetermined signal every time the accumulated value obtained by the load value accumulating means exceeds a predetermined accumulated value. Deterioration for judging that the degree of deterioration of the catalytic converter has reached a predetermined value based on the number of times calculating means for calculating the number of times and the value obtained by the number of times calculating means Due to a constant unit, in addition to the effect, also Kanade effect that performance degradation of the catalytic converter can also be detected.

A catalytic converter deterioration detecting device according to a third aspect of the present invention is the catalytic converter deterioration detecting device according to the second aspect, wherein the number-of-times calculating means is the detected load value obtained by the load detecting means. Since the comparison signal calculating means for calculating and outputting the predetermined value as the comparison signal based on the above is provided, the deterioration degree can be accurately determined even when the deterioration degree of the catalytic converter is relatively small. .

Further, a deterioration detecting device for a catalytic converter according to a fourth aspect of the present invention is the deterioration detecting device for a catalytic converter according to any one of the first to third aspects, wherein the deterioration determining means is the internal combustion engine. Since the deterioration determination is performed when the rotation speed is within the predetermined range and the detected load value is within the predetermined range, it is possible to prevent the variation in the parameters required for the deterioration detection and to improve the accuracy of the deterioration determination. There is an effect that can be.

According to a fifth aspect of the present invention, there is provided a deterioration detecting device for a catalytic converter according to any one of the first to fourth aspects, wherein the load detecting means is a fuel consumption device for an internal combustion engine. Since the amount is detected, the load can be easily detected.

Further, a deterioration detecting device for a catalytic converter according to a sixth aspect of the present invention is the deterioration detecting device for a catalytic converter according to any one of the first to fourth aspects, in which the load detecting means determines a traveling distance of the vehicle. Since the detection is performed, the load can be easily detected and the load can be detected at a lower cost, as in the fifth aspect.

Further, a deterioration detecting device for a catalytic converter according to claim 7 of the present invention is the deterioration detecting device for a catalytic converter according to any one of claims 1 to 6, wherein the deterioration determining means is Since the warning means for issuing a warning when it is determined that the degree of deterioration has reached a predetermined value is provided, it is possible to notify the driver of the deterioration of the catalytic converter.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing the structure of a first embodiment.

FIG. 2 is a block diagram specifically showing the configuration of the first embodiment.

FIG. 3 is a block diagram showing a configuration of an electronic control device.

FIG. 4 is a block diagram of air-fuel ratio control.

FIG. 5 is a diagram showing a behavior of a catalyst normal air-fuel ratio sensor.

FIG. 6 is a diagram showing the behavior of the air-fuel ratio sensor when the catalyst deteriorates.

FIG. 7 is a flowchart of comparison signal calculation means and deterioration determination calculation.

FIG. 8 is an example of a flowchart of comparison calculation processing.

FIG. 9 is a diagram showing the behavior of the air-fuel ratio sensor during air-fuel ratio control.

[Explanation of symbols]

 1 Internal Combustion Engine 3 Exhaust Pipe 6 AFS 11 Catalytic Converter 19 Electronic Control Unit

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[Procedure amendment]

[Submission date] July 7, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

A deterioration detecting device for a catalytic converter according to claim 1 of the present invention is an exhaust system for an internal combustion engine.
Upstream of the catalytic converter for exhaust gas purification inserted in the
Is installed in the first air-fuel
A first air-fuel ratio sensor for detecting a ratio signal, and the catalyst
It is provided on the downstream side of the converter to specify the exhaust gas.
Second air-fuel ratio for detecting concentration as second air-fuel ratio signal
A sensor and at least based on the second air-fuel ratio signal
Deterioration determining means for determining the deterioration of the catalyst, load detecting means for detecting the load of the internal combustion engine, load value accumulating means for accumulating the detection values obtained by the load detecting means,
When the accumulated value obtained by the load value accumulating means exceeds the predetermined accumulated value, and the detected value obtained by the deterioration detecting means becomes equal to or larger than the predetermined value, the degree of deterioration of the catalytic converter is predetermined. And a deterioration determining means for determining that the value of has reached.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

A deterioration detecting device for a catalytic converter according to a second aspect of the present invention is inserted in an exhaust system of an internal combustion engine.
Installed upstream of the catalytic converter for exhaust gas purification
The specific component concentration of the exhaust gas as the first air-fuel ratio signal
First air-fuel ratio sensor for detecting by the above, and the catalytic converter
Is installed on the downstream side of the
A second air-fuel ratio sensor for detecting the second air-fuel ratio signal,
At least based on the second air-fuel ratio signal
Deterioration determining means for determining deterioration, load detecting means for detecting the load on the internal combustion engine, load value accumulating means for accumulating the detected load values obtained by the load detecting means, and load value accumulating means. The number of times the output of the air-fuel ratio sensor crosses a predetermined value each time the cumulative value exceeds a predetermined cumulative value , or a number-of-times calculating means for calculating the cycle equivalent , and the catalyst based on the value obtained by the number of times calculating means. And a deterioration determining means for determining that the degree of deterioration of the converter has reached a predetermined value.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Further, according to the deterioration detecting device of the catalytic converter of the second aspect of the present invention, the number of times the output signal of the air-fuel ratio sensor crosses the predetermined value each time the cumulative value of the load values exceeds the predetermined value , or Since we decided to calculate the period equivalent ,
Performance deterioration of the catalytic converter can be reliably detected.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

Next, FIGS. 6A and 6B show the outputs of the first and second (catalyst upstream / downstream) air-fuel ratio sensors 12 and 13 when the degree of deterioration of the catalyst is large. Here, FIG. 6A is similar to FIG. FIG. 6B shows the relationship between the second air-fuel ratio sensor 13 and the second predetermined signal. As shown in FIG. 6C, when the intake air amount Q becomes large, the gas flow velocity at the catalyst becomes fast. Therefore, the purification rate of the catalyst decreases, and as a result, the output level and frequency of the second air-fuel ratio sensor 13 increase. Here, when the comparison signal obtained by calculating the second predetermined signal according to the intake air amount Q and the respective sensor outputs (when the catalyst is normal and when the catalyst is deteriorated) are compared, the catalyst shown in FIG. In the normal state, there is almost no difference in magnitude between the comparison signal and the sensor output signal. However, when the catalyst deterioration shown in FIG. 6 (B) is large , the difference between the comparison signal and the sensor output becomes large .
Sensor output is the first upstream side air-fuel ratio shown in FIG.
It approaches the frequency (cycle) of the ratio sensor.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

In step S706, the obtained comparison signal is read, and in step S707, the output of the second air-fuel ratio sensor 13 is read. Then, step S708
In, the read values are compared and calculated. Next, in step S709, a comparison is made with a predetermined value (the judgment value may be varied depending on the operating state), and if the comparison result is equal to or more than the predetermined value, the deterioration of the catalytic converter 11 is judged in step S713. It is determined that the degree has reached a predetermined value or more (the catalyst has deteriorated), and the warning lamp is turned on in step S714 to notify the driver of the abnormality. It should be noted that the predetermined value is other than changing the judgment value in the operating state.
In step S707, the second air-fuel ratio sensor
At the same time that the output of the service 13 is read, the first air-fuel ratio sensor
Read the output and display the output shown in FIG. 5 (A) or FIG. 6 (A).
The number of times the predetermined signal of 1 is crossed or the period equivalent value as a function
There is a method of calculating and making the judgment value variable. For example, in FIG.
The output of the first air-fuel ratio sensor shown in 0 crosses the first predetermined signal.
Based on the number of cuts N ₁ , the one-dimensional map stored in the ROM 206
The predetermined value Nda is calculated from the calculated value. This predetermined value Nda
Is set to increase proportionally up to N ₁ = 100 (times).
It is fixed.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

As described above, as shown in FIG. 8, the number of times the second air-fuel ratio sensor 13 as the comparison calculation process crosses the comparison voltage value is counted. In addition, in FIG.
Measurement can be easily done by using the timer function of the CPU.
The same effect can be obtained. As described above, since the determination is performed only in the predetermined operating state, it is possible to reduce the variation in the parameters required for the deterioration determination. In addition, since the deterioration is determined for each predetermined intake air amount, the determination is performed according to the flow rate of exhaust gas passing through the catalyst.Therefore, the number of determinations should be increased as the gas flow velocity at which the performance of the catalyst decreases becomes faster. Therefore, efficient and reliable determination can be performed. Then, as described above, the deterioration of the catalytic converter can be detected according to FIG. Further, in the flowchart shown in FIG. 7, the intake air amount is accumulated only in the predetermined operating state, but it may be accumulated in all the operating states.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

[0046]

As described in detail above, the deterioration detecting device for a catalytic converter according to claim 1 of the present invention is an internal combustion engine.
Converter for purification of exhaust gas inserted into the exhaust system of automobiles
It is installed on the upstream side of the
A first air-fuel ratio sensor that detects the air-fuel ratio signal of 1;
The exhaust gas provided downstream of the catalytic converter
The second detecting the specific component concentration of the second air-fuel ratio signal
Air-fuel ratio sensor and at least the second air-fuel ratio signal
Deterioration determination means for determining the deterioration of the catalyst based on the above, load detection means for detecting the load of the internal combustion engine, load value accumulation means for accumulating the detection values obtained by the load detection means, and this load value accumulation When the cumulative value obtained by the means exceeds the predetermined cumulative value and the calculated value obtained by the deterioration detecting means becomes equal to or greater than the predetermined value, the degree of deterioration of the catalytic converter reaches the predetermined value. Since the deterioration determining unit that determines that the deterioration has occurred is provided, it is possible to accurately detect the deterioration of the catalytic converter.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

A deterioration detecting device for a catalytic converter according to a second aspect of the present invention is inserted in an exhaust system of an internal combustion engine.
Installed upstream of the catalytic converter for exhaust gas purification
The specific component concentration of the exhaust gas as the first air-fuel ratio signal
First air-fuel ratio sensor for detecting by the above, and the catalytic converter
Is installed on the downstream side of the
A second air-fuel ratio sensor for detecting the second air-fuel ratio signal,
At least based on the second air-fuel ratio signal
Deterioration determining means for determining deterioration, load detecting means for detecting the load on the internal combustion engine, load value accumulating means for accumulating the detected load values obtained by the load detecting means, and load value accumulating means. The number of times the output of the air-fuel ratio sensor crosses a predetermined signal each time the cumulative value exceeds a predetermined cumulative value , or a number of times calculating means for calculating the cycle equivalent , and the catalyst based on the value obtained by the number of times calculating means. Since the deterioration determining means for determining that the degree of deterioration of the converter has reached a predetermined value is provided, in addition to the above-mentioned effect, there is an effect that deterioration of the performance of the catalytic converter can be detected.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 10

[Correction method] Added

[Correction content]

FIG. 10 is a diagram showing a first air-fuel ratio sensor output.

[Procedure Amendment 12]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Added

[Correction content]

[Figure 10]

Claims (7)

[Claims] 1. An air-fuel ratio sensor which is provided in an exhaust system of an internal combustion engine and is provided on a downstream side of a catalytic converter for purifying exhaust gas, and which detects a concentration of a specific component in exhaust gas downstream of the catalytic converter, and the air-fuel ratio sensor. Deterioration detection means for detecting deterioration of the catalytic converter based on the output of the fuel ratio sensor, load detection means for detecting the load of the internal combustion engine, and load value accumulation for accumulating detection values obtained by the load detection means. Means and the accumulated value obtained by the load value accumulating means exceeds a predetermined accumulated value, and when the detected value obtained by the deterioration detecting means becomes a predetermined value or more, deterioration of the catalytic converter A deterioration detecting device for a catalytic converter, comprising: deterioration determining means for determining that the degree has reached a predetermined value. 2. An air-fuel ratio sensor which is provided in an exhaust system of an internal combustion engine and is provided on a downstream side of a catalytic converter for purifying exhaust gas, and which detects a concentration of a specific component in exhaust gas downstream of the catalytic converter. Based on the output of the fuel ratio sensor, deterioration detecting means for detecting deterioration of the catalytic converter, load detecting means for detecting the load of the internal combustion engine, and load value for accumulating the detected load value obtained by the load detecting means. Accumulating means, a number-of-times calculating means for calculating the number of times the output of the air-fuel ratio sensor crosses a predetermined value each time the cumulative value obtained by the load value accumulating means exceeds the predetermined cumulative value, And a deterioration determining unit that determines that the degree of deterioration of the catalytic converter has reached a predetermined value based on the measured value. 3. The catalyst according to claim 2, wherein the number-of-times calculation means comprises comparison signal calculation means for calculating the predetermined value based on the detected load value obtained by the load detection means and outputting it as a comparison signal. Converter deterioration detection device. 4. The deterioration determining means determines the deterioration when the rotational speed of the internal combustion engine is within a predetermined range and the detected load value is within a predetermined range. Deterioration detection device for any catalytic converter. 5. The deterioration detecting device for a catalytic converter according to claim 1, wherein the load detecting means detects a fuel consumption amount of the internal combustion engine. 6. The deterioration detecting device for a catalytic converter according to claim 1, wherein the load detecting means detects a traveling distance of the vehicle. 7. The catalyst according to claim 1, wherein the deterioration determining means includes warning means for issuing a warning when it is determined that the degree of deterioration of the catalytic converter has reached a predetermined value. Converter deterioration detection device.