JPH0460106A - Control device of engine - Google Patents

Abstract

PURPOSE:To judge an actual condition of a catalyst with accuracy and ease by calculating a temperature increasing gradient from a catalyst temperature detected at a normal operation and a catalyst temperature detected after an air-fuel ratio is corrected to a rich side at the normal operation, and judging the deterioration of the catalyst when the temperature increasing gradient is not in a specified allowable range. CONSTITUTION:An air-fuel ratio adjusting means B which is able to change the supplying air-fuel ratio is provided on an intake passage A of an engine E, while a catalyst device D for purifying exhaust gas is provided on an exhaust passage C. There are also provided an operational condition judging means F for detecting a normal operational condition of the engine E and a catalyst temperature detecting means G for detecting a catalyst temperature. Further, there is provided a temperature gradient calculating means H which calculates the temperature increasing gradianet from the catalyst temperature detected at the normal operation and the catalyst temperature detected after the air-fuel ratio is corrected to a rich side at the normal operation. A deterioration judging means J is provided for judging the deterioration of the catalyst when the calculated temperature increasing gradient is not in a specified allowable range. When the deterioration is judged, generation of alarm or control of an intake amount is commanded as required.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine control device that determines deterioration of a catalyst device disposed in an exhaust system.

(Prior Art) Conventionally, it has been common practice to install a catalyst device in the exhaust passage of an engine to react and purify harmful components of exhaust gas, but if the temperature of this catalyst device rises abnormally, the catalyst Since the catalytic converter itself melts and becomes impossible to purify, there is a known technology in which a temperature sensor is installed in the catalytic device to issue an alarm when the temperature rises above a predetermined temperature. As seen in eO-27756, when the catalyst temperature stops below a predetermined value during deceleration fuel cut based on the signal from the catalyst temperature sensor, fuel supply is started to improve the purification performance of the catalyst. Techniques are known in the art.

(Problem to be solved by the invention) However, in the catalyst device installed in the exhaust system as described above, if the reaction purification performance of the catalyst decreases due to thermal deterioration after long-term use, the amount of exhaust gas will decrease. There is a problem that when the amount of water increases, harmful components that cannot be completely purified are released as they are.

It is difficult to easily detect the deterioration state of the catalyst as described above, and in the low intake air volume range such as during idling, the amount of exhaust gas is small and sufficient purification performance is obtained. The actual degree of catalyst deterioration cannot be determined by detecting the components, and there is a risk that emissions performance will decrease due to insufficient purification ability when the amount of exhaust gas increases.

Additionally, in order to judge the purification performance of a catalyst by detecting the components of exhaust gas, a special measuring device is required, and this can only be done during periodic inspections. This has the problem of being operated for a long period of time without sufficient fuel.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to provide an engine control device that can easily and accurately detect and determine the deterioration state of a catalyst.

(Means for Solving the Problems) In order to achieve the above object, the control device of the present invention has an air-fuel ratio that can change the supplied air-fuel ratio, as shown in the basic configuration in FIG. An adjustment means B is provided, and
A catalyst device for purifying exhaust gas is disposed in the exhaust passage C. Further, operating state determining means F for detecting the steady operating state of the engine E and catalyst temperature detecting means G for detecting the catalyst temperature are installed.

On the other hand, upon receiving the signals from the operating state determining means F and the catalyst temperature detecting means G, the catalyst temperature detected during steady operation and the catalyst temperature detected after the air fuel ratio is corrected to the rich side by the air fuel ratio adjusting means B during the steady operation. A temperature gradient calculation means H is provided for calculating a temperature rise gradient from The deterioration determining means J issues commands to issue an alarm, limit the amount of intake air, etc. as necessary when determining deterioration.

(Function) In the above-mentioned engine control device, when the operating condition is stable and steady, the air-fuel ratio is corrected to the rich side to increase the amount of unburned components introduced into the catalyst device, thereby controlling the catalyst device. It utilizes the fact that the temperature of the catalyst increases as the purification reaction is promoted, and this temperature increase is also related to the degree of deterioration of the catalyst. Therefore, by measuring the catalyst temperature before and after the rich correction of the air-fuel ratio, calculating the temperature increase slope, and comparing this temperature increase slope with a predetermined tolerance range, it is determined that the catalyst has deteriorated. , accurately and easily determines the actual state of the catalyst, issues an alarm, and limits the amount of intake air to prevent it from increasing, thereby suppressing the emission of harmful components, and increasing the frequency of catalyst monitoring to encourage replacement of the catalyst device. This makes it possible to maintain good exhaust purification performance by performing the cleaning at the appropriate time.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is an overall configuration diagram of a rotary piston engine according to an embodiment.

In the engine body 1, a rotor 3 rotates planetarily within a casing 2, and intake air is supplied to a working chamber 4 from an intake port 5, and after compression and explosion, exhaust gas is discharged from an exhaust port 6. In the intake passage 7 connected to the intake port 5, an air cleaner 8, an air flow sensor 9, and a throttle valve 10 are arranged from the upstream side, and an injector 11 is interposed in the downstream part. Also, exhaust port 6
In the exhaust passage 13 connected to the 02 sensor 14, a pre-catalyst device 15 and a main catalyst device 16 are arranged in series on the downstream side of the 02 sensor 14 to remove HC and Co from the exhaust gas.

Reactive purification of harmful components such as NOx is performed.

The main catalyst device 16 includes a catalyst temperature sensor 1.
7 is arranged to detect the catalyst temperature. The signal from this catalyst temperature sensor 17 is transmitted to the control unit 2.
0, the temperature increase gradient is calculated from the catalyst temperature detected during steady operation and the catalyst temperature detected after the fuel injection amount from the injector 11 is increased by a predetermined amount and the air-fuel ratio is corrected to the rich side during the steady operation. The deterioration state of the catalyst is determined based on whether the temperature increase gradient is within a predetermined allowable range.

Further, an alarm lamp 21 connected to the control unit 20 to warn the driver of catalyst deterioration is installed on the instrument panel 22, and a throttle lamp 21 that regulates the maximum opening of the throttle valve 10 in the intake passage 7 of the engine is installed. A limiter 23 is attached, and a signal is output from the control unit 20 to the throttle limiter 23.

The control unit 20 includes an intake air amount signal from the air flow sensor 9, an engine rotation speed signal from the rotation sensor 24, a throttle opening signal from the throttle opening sensor 25, and a throttle opening signal from the throttle opening sensor 25, in order to detect the operating state of the engine. The air-fuel ratio signal etc. from the 02 sensor 14 are respectively input.

The process of determining catalyst deterioration by the control unit 20 will be explained with reference to the flowchart in FIG. 3. After the control is started, it is determined in step S1 whether air-fuel ratio feedback execution conditions are satisfied. Is this the verdict?
If S is in a feedback region where fuel increase or fuel cut is not performed, such as a high load region, it is determined in step S2 whether the operating state is in a stable steady state based on changes in throttle opening, etc. do. If the catalyst is in a steady state, it is determined in step S3 whether the catalyst temperature is within a set temperature range suitable for determining deterioration.

If the catalyst deterioration determination condition is satisfied in step S3 (YES), first, in step S4, the catalyst temperature is measured and stored as the first detected value Ta. Subsequently, in step S5, the air-fuel ratio is corrected to the rich side by a predetermined amount, and it is determined in step S6 whether or not the steady state continues for a predetermined period of time after this rich correction.
Judge by.

If the determination in step S6 is YES and the steady state has been maintained for a predetermined period of time, the catalyst temperature after rich correction is measured in step S7 and stored as the second detected value Tb.

Next, in step S8, the temperature increase gradient is calculated by dividing the temperature difference between the first and second detected values Ta, Tb before and after the rich correction by the measurement time difference (predetermined time) between the two. Calculated by And this step S
The temperature increase gradient obtained in step 8 is compared with the set value of the allowable range in step S9, and it is determined in step S1.0 whether this temperature gradient is within the allowable range.

If it is within the allowable range (YES), the air-fuel ratio is returned to normal control in step Sll, while if it is out of the allowable range (No), it is determined that the catalyst has deteriorated in step S12. In step S13, an on signal is output to the alarm lamp 21 to light it up and issue an alarm, and in step S14, a drive signal is output to the throttle limiter 23 to regulate the maximum opening of the throttle valve 10 and limit the intake air amount. Suppress the increase in exhaust gas volume.

Further, if the determination in step S6 is No and the steady operation after richly correcting the air-fuel ratio does not continue for a predetermined period of time, the first detected value Ta of the catalyst temperature measured in step S4 is determined in step S15. Cancel and step Sl
After returning the air-fuel ratio to normal control at step S1,
~Wait for the condition in S3 to be met.

FIG. 4 shows an example of setting the allowable range for the rising slope of the catalyst temperature, which is set according to the time after rich correction and the catalyst temperature. In a deteriorated catalyst, the purification reaction is slow and the temperature rise is small.

According to the above embodiment, when steady-state operating conditions suitable for determining catalyst deterioration are established, the catalyst temperature before and after rich correction of the air-fuel ratio is detected, the temperature increase gradient is calculated in relation to the elapsed time, and the permissible range is determined. If a good purification reaction is not taking place, it is determined that the catalyst has deteriorated, and an alarm is issued and the amount of intake air is restricted to prevent a large amount of exhaust gas from flowing into the catalyst device. Regulations (-) are aimed at preventing the discharge of harmful components that cannot be purified.

(Effects of the Invention) According to the present invention as described above, the temperature gradient calculation means calculates the temperature increase gradient from the catalyst temperature detected during steady operation and the catalyst temperature detected after correcting the air-fuel ratio to the rich side during the steady operation. By being equipped with a deterioration determination means that determines that the catalyst has deteriorated when the temperature increase gradient is not within a predetermined tolerance range, the actual catalyst condition can be accurately and easily determined and an alarm can be issued. In addition to suppressing the emission of harmful components by restricting the amount of air emitted or intake air from increasing, the frequency of monitoring the catalyst is increased so that even if catalyst deterioration progresses rapidly, it can be determined early and the catalyst can be replaced. It is possible to maintain good exhaust purification performance and prevent air pollution.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the basic configuration of the present invention, FIG. 2 is an overall configuration diagram of a concrete example of an engine control device, FIG. 3 is a flowchart diagram for explaining the processing of the controller, and FIG. FIG. 3 is a characteristic diagram illustrating an example of setting an allowable range for an increase gradient of catalyst temperature. E, 1...Engine, A, 7...Intake passage, B...Air-fuel ratio adjustment means, C213...
・Exhaust passage, D16... Catalyst device, F...
...Operating state determination means, G...Catalyst temperature detection means, H...Temperature gradient calculation means, J...
Deterioration determination means, 11...Injector, 17.
... Catalyst temperature sensor, 20 ... Control unit, 21 ... Alarm lamp, 23 ...
...Throttle limiter. Figure 2 Figure 1

Claims (3)

[Claims] (1) In an engine control device equipped with an operating state determining means for detecting the steady operating state of the engine and a catalyst temperature detecting means for detecting the catalyst temperature, the catalyst temperature detected during steady operating and the air-fuel ratio during the steady operating a temperature gradient calculation means for calculating a temperature rise gradient from the detected catalyst temperature after correcting the temperature to the rich side; A control device for an engine, comprising: deterioration determining means for determining. (2) The engine control device according to claim 1, wherein an alarm is issued when the deterioration determining means determines that the catalyst has deteriorated. (3) The engine control device according to claim 1, wherein the intake air amount is limited to a predetermined amount or less when the deterioration of the catalyst is determined by the deterioration determining means.