JPS62153546A - Anomaly detector for engine - Google Patents

Abstract

PURPOSE:To speedily detect the anomaly and deterioration of an engine control system on the basis of the output of exhaust sensors for detecting the concentration of the exhaust harmful components in exhaust gas which are installed onto the downstream side of catalyst. CONSTITUTION:An NOX sensor 15 which utilizes SnO2 and a CO sensor 16 are installed into an exhaust system 12 on the downstream side of a three- component catalyst 14. During the air fuel ratio control by the detection signal of an O2 sensor 13, a control unit 25 reads each output signal of the NOX sensor 15 and the CO sensor 16 during the stationary operation, and compares these output values with the judgment levels corresponding to the number N of revolution and the fundamental injection time TP. When the NOX concentration or CO concentration is higher than each judgment level, the control unit 25 drives an anomaly alarm means.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine abnormality detection device, and more particularly to a device for detecting an abnormality in an engine control system that controls the operating state of an engine.

[Conventional technology]

In recent years, many control devices have been proposed that are equipped with an oxygen concentration sensor (hereinafter referred to as "Ot sensor") and control the air-fuel ratio of an engine, as disclosed in Japanese Patent Application Laid-Open No. 54-57029.

In such an air-fuel ratio control device, a 0□ sensor installed in the exhaust system adjusts the temperature according to the residual oxygen concentration in the exhaust gas as shown in Figure 3 (a).
The stoichiometric air-fuel ratio (air-fuel ratio, i.e., A/F = approximately 15) is detected using this output, and the air-fuel ratio of the air-fuel mixture supplied to the engine is feedback-controlled to the stoichiometric air-fuel ratio based on this detection signal. It is something to do.

By combining this air-fuel ratio control device with a catalyst, especially a three-way catalyst, it can eliminate harmful components in exhaust gas, such as NoX.
, Co, and HC can be purified extremely efficiently.

[Problem that the invention seeks to solve]

However, even if feedback control of the air-fuel ratio is performed by the air-fuel ratio control device, the output characteristics of the 02 sensor itself may deviate due to aging etc., or the control means for controlling the amount of air-fuel mixture given to the engine (e.g. In the case of a fuel injection system, the control characteristics of the fuel control computer and fuel injection valve, or in the case of a carburetor, the carburetor body and air-fuel ratio feedback control computer, etc.) may be incorrect, or the exhaust gas purification catalyst may be out of order. If the purification performance of the exhaust gas deteriorates, effective exhaust gas purification will not be achieved, resulting in
X, Co, HC) may be emitted into the atmosphere in larger amounts than the standard level.

In view of the above points, an object of the present invention is to prevent the concentration of harmful components in the exhaust gas discharged into the atmosphere from exceeding a set range due to some kind of deterioration or abnormality in the engine control system.
An object of the present invention is to provide an engine abnormality detection device capable of quickly detecting the state.

[Means for solving problems]

Therefore, in the present invention, as shown in FIG. 7, in an engine control system having a control means for controlling the amount of air-fuel mixture given to the engine according to the operating state of the engine, and an exhaust gas purifying catalyst in the exhaust system, an exhaust sensor installed on the side to detect the concentration of harmful components discharged in the exhaust gas;
The present invention is characterized by comprising a detecting means for detecting that the concentration of exhaust harmful components in the exhaust gas detected by the exhaust sensor exceeds a set range.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. This example is an example in which the present invention is applied to a fuel injection system, but of course it can also be applied to a carburetor using an air-fuel ratio feedback control method.

FIG. 1 shows a schematic configuration of an internal combustion engine equipped with an air-fuel ratio control device. The intake system of an engine 1 includes an air flow j-';'2 with a potentiometer 18, a throttle valve 3, and a throttle valve opening. A throttle sensor 4, an intake air temperature sensor '17, and the like are provided to detect the temperature. The air taken in from this intake system is supplied to an intake manifold 6 via a surge tank 5, and is mixed with fuel injected from a fuel injection valve 7 activated in response to an electric pulse signal to form an air-fuel mixture with a predetermined air-fuel ratio. It is supplied to the combustion chamber 8 of the engine 1 as a fuel.

In this combustion chamber 8, a mixture of fuel and air is ignited and burned by a spark plug 10 provided in a cylinder head 9, and the combustion gas is passed through an exhaust system 11 to an exhaust system 12.
is discharged.

This exhaust system 12 is provided with an oxygen concentration sensor (0□ sensor) 13 that uses a solid electrolyte, for example, Zr01, and generates a voltage signal according to the residual oxygen concentration in the exhaust gas. As shown in , this 0□ sensor 13
The air-fuel ratio is detected by the output signal of. Also, the exhaust system 12
On the downstream side of the position where the 02 sensor 13 is installed, harmful components contained in the exhaust gas, such as HC, Go, NOX, etc.
A three-way catalyst 14 is provided for purification. Furthermore, the exhaust system 12 on the downstream side of the three-way catalyst 14 includes an NOX sensor 15 that uses a semiconductor, for example, SnO2, and whose resistance value changes depending on the NOx concentration, and a resistor that also uses, for example, SnO2 and whose resistance value changes according to the CO concentration. A CO sensor 16 whose value changes is provided, and a NO OX sensor 15 and a C
As shown in FIGS. 4(a) and 4(b), the resistance value of the O sensor 16 is NOx? 74 degrees D (NOx > and Co?f
It is known that the resistance value changes depending on the fi degree D (Co), and this change in resistance value is detected as voltage signals V9 and ■ゎ, and these output signals ■8 and ■ are used for the downstream side of the three-way catalyst 14. NOx concentration NOX) and CO concentration D (
Co) is detected.

Further, the cylinder block 19 of the engine 1 is provided with a water temperature sensor 20 that detects the engine cooling water temperature, and the distributor 22 that distributes the ignition signal from the igniter 21 to each cylinder is provided with a cylinder discrimination sensor 23 and a rotation angle sensor 24. Built-in. The air flow meter 2.0□ sensor 13, NoX sensor 15, CO sensor 16, water temperature sensor 20, cylinder discrimination sensor 23, and rotation angle sensor 2 detect each operating condition of the engine 1.
The detection signal from the 4th etc. is supplied to the control unit 25. The control unit 25 is configured using, for example, a microcomputer, and FIG. 2 shows its configuration. That is, a random access memory (hereinafter referred to as rRAMj) that performs temporary storage etc. for the central processing unit (hereinafter referred to as rcPtJJ) 27 that executes arithmetic processing.
28, read-only memory (hereinafter referred to as rROMJ) 29 used as program memory, etc.
PU27, RAM28, ROM29, etc. are connected to data bus 30.
connected by. This data bus 30 is connected to input/output ports 31, 32, and output boats 26, 33, and 34. take out the signal via multiplexer 36;
The A/D converter 37 converts it into a digital signal and supplies it.

The signals from the cylinder discrimination sensor 23 and the rotation angle sensor 24 are waveform-shaped by a waveform shaping circuit 38 and sent to the input/output port 32.
Further, the detection signal from the throttle sensor 4 is appropriately A/D converted by the input circuit 40 and sent to the input/output board 3.
2. The output signals from the output ports 26, 33.34 are supplied to the igniter 21, the fuel injection valve 7, and the abnormality warning means 39 via the drive circuits 35, 41.42, and are used for ignition control, fuel injection amount, and notification. Control takes place. 43 is a clock oscillation mill, which provides a timing clock signal to the CPU 27 and the like.

The operation of the above configuration will be described below.

First, the CPU 27 of the control unit 25 uses the intake air amount obtained from the detection signal from the potentiometer 18 in the air flow meter 2 and the engine rotational speed obtained from the detection signal from the rotation angle sensor 24 to store information in the ROM 29 in advance. The basic injection time TP is read from the map.

Furthermore, the fuel injection time TAU is calculated by correcting the basic injection time TP according to the detection signals from each sensor.

TAU=TP* Here, K is a correction coefficient.

These correction coefficients include, in addition to 1 for correction coefficients including warm-up increase, start-up increase, and acceleration increase, and 2 for air-fuel ratio feedback correction coefficients based on the detection signal of the 0□ sensor 13.

A fuel injection signal corresponding to the fuel injection time TAU determined in this way is output to the injection valve 7 via the drive circuit 42, and the injection valve 7 is opened for the fuel injection time TAU in synchronization with the engine rotation. Engine 1 intake manifold 6
Fuel is injected inside.

By injecting fuel in this manner, an air-fuel mixture with a predetermined air-fuel ratio is supplied into the combustion chamber 8.

The above is a general description of the engine control system, and next, the features of the present invention will be described.

Even if the engine control system is configured and operating as described above, the output characteristics of the 0□ sensor 13 and the control characteristics of the control system including other sensors and fuel injection valves 7 may be incorrect, or the exhaust gas purification catalyst If the purification performance of the exhaust gas is degraded, sufficient purification of the exhaust gas will not be achieved, and as a result, a large amount of harmful components (NOX, C○, HC) in the exhaust gas will exceed the predetermined standard level and enter the atmosphere. There is a risk of being ejected inside.

Therefore, in this embodiment, a NoX sensor 15 and a CO sensor 16 are provided downstream of the three-way catalyst 14 in order to detect the concentration of harmful components in the exhaust gas just before it is discharged into the atmosphere. The system monitors the output of the system, and if the concentration of harmful components exceeds a set range, it will immediately notify the driver and give the driver an opportunity to take corrective action.

Specifically, the CPU 27 causes an abnormality determination routine as shown in FIG. 5 to be performed by timer processing.

First, if air-fuel ratio feedback control is being performed based on the detection signal of the 02 sensor 13 and the engine is in steady operation (that is, not in transient operation) (steps 101 and 102), the process proceeds to step 103.

In this step 103, the output signals V, , V, of the NoX sensor 15 and CO sensor 16 are read, and the next step 1
04, NOX concentration (N
OX) and CO concentration (Co). On the other hand, the current engine operating condition 2. G is specified from, for example, the engine speed N and the basic injection time TP, and both parameters (N
, TP) as a function, and a determination level lap of NoxfNt degree and a CO concentration determination level map are set in advance.

Therefore, in step 105, the determination level of Nox concentration [)o+
and CO concentration determination level D. Read 2. Subsequently, in steps 106 and 107, the detected NOx concentration D (
When NOx) is lower than the judgment level D61 and the CO concentration (Co) is lower than the judgment level Dog, that is, when it is in the shaded area in Figure 3, it is determined that the discharged harmful component concentration is within the permissible range. (Yes) The abnormality determination routine ends.

On the other hand, when it is outside the area indicated by diagonal lines in Fig. 3, that is, No.
When the X concentration (NOx) is higher than the judgment level Dot, or the CO concentration (Co) is at the judgment level I)oz
If it is higher than that, it is determined that it is abnormal and steps 106 and 10
7) In step 108, the non-volatile memory
(part of RAM 28) and output port 2.
6. Drives the abnormality warning means 39 via the drive circuit 35,
The driver will be notified to that effect.

Incidentally, as the abnormality warning means 39, a lamp is lit.

Various means such as voice and text warnings can be used.

Here, NOx? M degree and co? The determination level of fs degree is determined based on engine speed N and basic injection time TP, but other factors such as intake air iQ and intake pipe pressure Pm
or a combination with the above N, TP, Q.

The configuration may be one-dimensionally determined using any one of Pm.

Moreover, in the above embodiment, NOx? fi degree and coty
Normality was determined when both NOx and CO satisfied predetermined conditions (that is, in the shaded area in Figure 3), but for example, as shown in Figure 6, either NOx or CO There are two determination levels for each determination level. + H, D o
z L (D o + H > D o z L ), within its setting range (D o
If it is within the range (tH), it is considered normal, whereas if it is outside the range, it is considered abnormal and a predetermined process may be performed.

〔Effect of the invention〕

As described above, the present invention utilizes the detection signal from the exhaust sensor installed downstream of the exhaust purification catalyst to detect harmful substances in the exhaust gas that are emitted into the atmosphere when some kind of deterioration or abnormality occurs in the engine control system. If the concentration of a component exceeds a set range, the condition can be quickly detected and, for example, the driver can be notified of this, thereby prompting repair of the engine control system.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing the configuration of an engine equipped with the configuration of the present invention and its peripheral equipment, FIG. 2 is a block diagram showing the configuration of the control unit in FIG. 1, and FIG. 3 is a 02 No. 4 is a graph showing changes in sensor output and discharged harmful component concentration. A characteristic diagram showing the characteristics of the sensor and the CO sensor, FIGS. 5 and 6 are flow charts of a program showing the operation according to the embodiment of the present invention, and FIG. 7 is a block diagram showing the schematic configuration of the present invention. 1...Engine, 2...Air flow meter, 7...
・Fuel injection valve, 12... Exhaust system, 13... 0□ sensor, 14... Three-way catalyst, 15... NOX sensor, 1
6...CO sensor, 26...mlJ? Wholesale unit, 27...CPU, 28...RAM, 29...R
OM.

Claims (1)

[Scope of Claims] An engine control system including a control means for controlling the amount of air-fuel mixture given to the engine according to the operating state of the engine, and an exhaust gas purifying catalyst in the exhaust system, wherein the exhaust gas purifying catalyst is provided on the downstream side of the catalyst. An engine comprising: an exhaust sensor that detects the concentration of harmful components discharged in the exhaust gas; and a detection means that detects that the concentration of harmful components discharged in the exhaust gas detected by the exhaust sensor exceeds a set range. Anomaly detection device.