JPH07294385A - Diagnostic device of egr device of internal engine - Google Patents

Abstract

PURPOSE:To obtain an accurate diagnosis device while suppressing cost increase by providing a sensor, etc., for detecting the pressure of an intake path. CONSTITUTION:An intake path 106 of an engine body 101 is provided with an air flow sensor 108, a pressure sensor, etc., for detecting the pressure of an intake pipe. The output signal of each sensor is input to a control unit 112 and a rotary speed, the amount of intake air, etc., are measured or calculated. Also, an air/fuel ratio sensor 118, etc., are laid out at an exhaust path 116. Then, the target pressure of the intake pipe is obtained from an engine rotary speed and the amount of intake air and the difference with the actually measure pressure of the intake pipe is calculated. The integrated value obtained by multiplying a differential constant and that obtained by multiplying an integral constant are added to calculate the deviation of the amount of exhaust reflux. At this time, the amount of difference between a target pressure and the actually measured pressure of the intake pipe is compared with a failure criterion reference value as a diagnosis. When the amount of difference is larger exceeding a specific amount, it is judged that a failure occurred. When an internal engine is functioning normally, the difference between the target pressure and the actually measured pressure is extremely small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for an EGR device that recirculates exhaust gas from an internal combustion engine, and detects a highly accurate exhaust gas recirculation amount based on an engine intake air amount and an actually measured value in an intake pipe, while Accurate diagnosis of the EGR device is performed by detecting holes in the exhaust gas recirculation path by monitoring the fuel ratio.
The present invention relates to a diagnostic device that reports failure information of a GR device.

[0002]

2. Description of the Related Art As a basic technique relating to a diagnostic device for an EGR device, there is, for example, a device provided with a means for detecting a pressure in an intake pipe and performing a failure diagnosis by a pressure difference when the EGR passage is opened and closed. As a known example of this, Japanese Patent Laid-Open No. 4-1
There is a publication such as 1625. Further, there is one that includes means for detecting the temperature of the recirculated exhaust gas and performs a failure diagnosis based on a temperature difference when the EGR passage is opened and closed. As a known example of this, there is JP-A-2-227544. In addition, JP-A-63
A means for detecting the pressure in the intake pipe and the temperature of the recirculated exhaust gas as in Japanese Patent No. 125157 is provided, and the recirculated exhaust gas temperature under a predetermined pressure condition when the EGR passage is opened is used to perform a failure diagnosis. There is a diagnostic technique that uses the pressure in the intake pipe and the temperature of the recirculated exhaust gas.

[0003]

However, in the above prior art, for example, in the method of detecting the pressure in the intake pipe,
By storing a large amount of intake pipe pressure value data corresponding to the opening / closing amount of the EGR passage and the operating state in the memory, even if the flow rate of the recirculated exhaust gas can be detected, a failure such as a hole in the recirculation path of the exhaust gas will occur. However, there is a problem in that this cannot be detected accurately. In addition, a memory for holding a large amount of pressure data in the intake pipe is required, which is uneconomical. Further, even with the method of detecting the temperature of the recirculation exhaust gas, even if the presence or absence of the supply of the recirculation exhaust gas can be determined, it cannot be said that the supply amount is accurately detected. In addition, even if a method of detecting the pressure in the intake pipe and the temperature of the recirculated exhaust gas is combined, when the failure such as a hole in the recirculation path of the exhaust gas occurs, the temperature of the air sucked from the holed portion is There is a problem that it is affected by disturbance and accurate diagnosis cannot be performed.

In view of the above problems, the present invention can accurately detect the flow rate of the recirculated exhaust gas without requiring a large amount of memory, and has a failure such as a hole in the recirculation path of the exhaust gas. Even in such a case, it is an object of the present invention to provide a diagnostic device capable of accurately determining the failure of the EGR device.

[0005]

In order to achieve the above object, first, a means for detecting an intake air amount of an internal combustion engine, a means for detecting an engine operating state, and an intake based on the information obtained by the detecting means. Means for calculating the partial pressure of air in the intake pipe, means for detecting the pressure in the intake pipe, means for calculating the flow rate of the recirculated exhaust gas from the detected values of the partial pressure in the intake pipe and the pressure in the intake pipe, and the air arranged in the exhaust path By means for detecting the engine air-fuel ratio by the fuel ratio sensor or oxygen concentration sensor, means for calculating the air-fuel ratio correction coefficient based on the information obtained by the detecting means, and means for detecting the intake air temperature, E
The GR device can be diagnosed. Further, a means for notifying the information of the diagnosis result of the EGR device is provided.

In another aspect, in order to achieve the above object, first, a means for detecting the intake air amount of the internal combustion engine, a means for detecting the engine operating state, a means for detecting the recirculated exhaust gas temperature, and an exhaust passage are provided. The air-fuel ratio sensor or the oxygen concentration sensor, the means for detecting the engine air-fuel ratio, the means for calculating the air-fuel ratio correction coefficient based on the information obtained by the detecting means, and the means for detecting the intake air temperature To E
The GR device can be diagnosed. Further, a means for notifying the information of the diagnosis result of the EGR device is provided.

[0007]

According to the above-described EGR device diagnostic apparatus for an internal combustion engine of the present invention, the mass flow rate of intake air is detected, the air partial pressure in the intake pipe is calculated, and the exhaust gas is recirculated by comparison with the measured pressure in the intake pipe. Since the gas flow rate is obtained, an accurate recirculation exhaust gas flow rate can be immediately obtained without requiring a large amount of memory and without being affected by the operating state of the engine. At the same time, since the air-fuel ratio is monitored using the air-fuel ratio correction coefficient of the engine, even if a failure such as a hole in the exhaust gas recirculation path occurs, an accurate failure determination of the EGR device can be performed. You can Therefore, when a failure occurs in the EGR device, the driver or maintenance person can be immediately alerted of the situation.
Further, since the recirculation exhaust gas supply port is not intentionally opened / closed during diagnosis of the EGR device, there is no adverse effect on drivability or malfunction.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining the overall system configuration of an embodiment of the present invention. A water temperature sensor 102 is provided on the engine body 101, a position sensor 104 of a type that detects the tooth profile of the starter ring gear 103 with an electromagnetic pickup, and a signal at a constant crank angle position for each rotation of the crankshaft are obtained. Further, the camshaft is provided with a reference sensor 105 using a projection provided on the ring gear and an electromagnetic pickup, and a phase sensor (not shown) for generating a signal once every two rotations of the crankshaft for cylinder identification. An air cleaner 107 is provided in an intake path 106 of the engine body 101, and an air flow sensor 108, a throttle actuator and a throttle sensor 109, an idle speed control valve 110, and a pressure sensor 111 for detecting an intake pipe pressure are provided on the downstream side (engine body side) thereof. I have it. The output signals of the above sensors are input to the control unit 112, and the crank angle, rotation speed, intake air amount, etc. are measured or calculated,
Ignition based on the parameters indicating the engine operating state,
The control amount of fuel etc. is determined, and the power switch, the ignition coil 113, the spark plug 114, and the injector 1
15. The engine operation is controlled through various parts such as the idle speed control valve 110.

Further, in the exhaust passage 116, an EGR inlet 117 and an air-fuel ratio sensor 118 (an oxygen concentration sensor is used in this embodiment. Hereinafter, the oxygen concentration sensor is abbreviated as an O ₂ sensor, and this sensor is used for control. The example used will be described). In this system example, in order to improve the purification efficiency of harmful exhaust components, the exhaust upstream side O ₂ of the catalytic converter 119 is increased.
Based on the output signal of the sensor 117, feedback control is performed to keep the air-fuel ratio of the engine near the stoichiometric air-fuel ratio.

The EGR device aims to reduce fuel consumption by, for example, reducing pump loss by recirculating exhaust gas and cooling loss by lowering combustion gas temperature.
Further, the purpose is to reduce nitrogen oxides in the exhaust gas by lowering the combustion temperature, for example.

The structure of the EGR device according to the present invention comprises a pressure regulator 121 for adjusting the amount of recirculation in the exhaust gas recirculation path 120, an intake pipe pressure pipe 122 connected to the diaphragm for controlling this, and a diaphragm in the pipe 122. A duty solenoid valve 123 for adjusting the amount of pressure applied to the diaphragm is arranged, the amount of pressure applied to the diaphragm is adjusted by a pulse signal from the control unit 112, and the amount of exhaust gas recirculation is controlled.

In this embodiment, a driver circuit for converting signal inputs from various sensors shown in FIG. 1 and output signals from an arithmetic unit into actuator drivable signals and outputting them, and input / output signals into digital arithmetic processable signals. AD to convert
-EGR control by a digital arithmetic device including a DA conversion input / output circuit, a digital arithmetic processing circuit, a constant used for digital arithmetic, a variable, and a memory for storing a program (memory indicates both nonvolatile and volatile) Not only will this be explained with an example using a device with a large processing capacity that simultaneously performs fuel control, ignition timing control, etc. of the internal combustion engine.
It goes without saying that the R control, the fuel control, the ignition timing control and the like can be configured in separate digital arithmetic units or analog arithmetic units.

FIG. 2 is a diagram for explaining a control block of the EGR device. The present embodiment is an example of controlling a pulse signal (duty) from the control unit 112 that adjusts the amount of pressure on the diaphragm of the pressure regulator 121 in FIG. In block 201, the target pressure Ps of the intake pipe is searched from the table of the engine speed N of the internal combustion engine and the intake air amount Qa, and the measured pressure Pm of the intake pipe is obtained.
Then, a difference between the exhaust gas recirculation amount is calculated by summing the product of the differential constant and the integrated value of the integral constant. At this time, the retrieved target pressure Ps
The difference between the measured pressure Pm of the intake pipe and the measured pressure Pm of the intake pipe is compared with a failure determination reference value to diagnose the EGR device. If the difference amount is larger than a predetermined amount, it is determined that the EGR device has failed. This is because the difference between the retrieved target pressure Ps and the actually measured pressure Pm of the intake pipe is very small if the EGR device normally operates. In particular, Ps and Pm are substantially the same in the steady operation state.

Further, in block 202, the basic duty of the exhaust gas recirculation amount is searched from the table of the engine speed N and the intake air amount Qa, and is added to the above deviation value and output, so that an accurate feedback control of the exhaust gas recirculation amount is performed. I do.
If the motor that controls the exhaust gas recirculation amount is a motor, the step number of the drive is output.

By the way, since the EGR device normally recirculates an inert gas, it has almost no effect on the engine air-fuel ratio, and therefore the engine air-fuel ratio has not been paid attention to in the diagnostic device. However, for example, even if the valve that controls the exhaust gas recirculation amount operates normally, the effect of normal EGR is hindered especially when there is a failure such as a hole in the exhaust gas recirculation pipe between the valve and the exhaust pipe. Nevertheless, it is very unlikely that the conventional diagnostic device using the intake pipe pressure and the conventional diagnostic device using the exhaust gas recirculation temperature can accurately detect this failure. In the present invention, simultaneously with the method described with reference to FIG. 2, the EGR device is diagnosed by the air-fuel ratio correction coefficient, so that the recirculation exhaust gas supply port is not intentionally opened and closed without adversely affecting the drivability or causing a malfunction. , Accurate EG
R device diagnostics can be performed. The EGR device diagnosis using this air-fuel ratio correction coefficient will be described with reference to FIG.

Even if the EGR control valve duty 301 in FIG. 3 changes stepwise during control as shown in the figure, if there is no failure such as a hole in the exhaust gas recirculation pipe, the exhaust gas is exhausted with respect to the air-fuel ratio correction coefficient α302. The reflux has almost no effect. If there is a failure such as a hole between the valve that controls the exhaust gas recirculation amount and the exhaust pipe, air is mixed with the exhaust gas.Therefore, especially when the opening of the valve that controls the exhaust gas recirculation amount is large, the air-fuel ratio correction coefficient α302 is large and moves to the side requiring rich correction. The failure determination level y303 is set according to the exhaust gas emission level and the like, and is set as a table or a map constant depending on the operating state and the like if necessary. Further, according to the present embodiment, a failure such as a hole between the intake pipe and the valve that controls the exhaust gas recirculation amount can be eliminated even if the method using the difference between the target pressure Ps and the measured pressure Pm of the intake pipe is used. Accurate detection is also possible with the method using the fuel ratio correction coefficient α302.

If an air-fuel ratio correction learning device is provided, even if the air-fuel ratio learning correction coefficient is used in place of the air-fuel ratio correction coefficient α302 in the present invention, the same or greater effect can be obtained.

FIG. 4 shows an example of processing after searching for the target pressure (target pressure) of the intake pipe. The intake pipe pressure changes with the intake air temperature. Equation 1 shows that the intake pipe pressure is proportional to the intake air temperature according to the ideal gas state equation.

Pm = nRT / V (Equation 1) Here, n is the gas mole number, R is the gas constant, T is the intake temperature, and V is the intake pipe volume. Therefore, block 4
After the search for the target pressure 01, the intake air temperature compensation in block 402 is performed. Equation 2 shows the intake temperature compensation.

(T ₁ / T ₂ ) Pm = nRT ₁ / V (Equation 2) Here, T ₁ is, for example, an intake air temperature measured by an intake pipe internal temperature sensor not shown in FIG. T ₂ is the intake air temperature when the target pressure is measured. The intake air temperature compensation shown in Expression 2 can improve the accuracy of the target pressure of the block 401, which can further improve the reliability of the diagnosis result. Further, as a result, the accuracy of the deviation amount of the exhaust gas recirculation amount described in FIG. 2 is improved, and the effect that the control performance of the EGR device can be improved is obtained.

FIG. 5 shows a specific example of the intake air temperature compensation for the pressure. The current intake air temperature T ₁ is divided by the intake air temperature T ₂ when the target pressure is measured, and the target pressure correction constant K is calculated.

FIG. 6 shows an example in which the target pressure correction constant K described in FIG. 5 is searched in a table with the current intake air temperature T ₁ as an axis. Further, the current intake air temperature T ₁ can be estimated by the deviation between the throttle opening and the intake air amount obtained from the engine rotation speed. Further, for example, it can be estimated by the difference between the intake air amount actually measured by a sensor that measures the mass flow rate, and the measured or estimated intake pipe pressure and the intake air amount obtained from the engine rotation speed.

FIG. 7 is a general flow chart of an embodiment of the present invention. In step 701, the voltage value of the pressure sensor is captured by the A / D converter. Step 702
Then, take in the output of the hot wire air flow meter in the same manner. In steps 703 and 704, the basic duty in exhaust gas recirculation and the target pressure of the intake pipe for feedback control are searched for in a map. At this time, it goes without saying that if the drive system of the exhaust gas recirculation amount control valve is a step motor or the like, the search of the basic duty is the calculation of the basic step number. In step 705, the intake air temperature compensation described in FIGS. 4 to 6 is performed. In step 706, the EGR device is diagnosed by comparing the difference amount between the retrieved target pressure Ps and the measured pressure Pm of the intake pipe described in FIG. 2 with the failure determination reference value x. If the difference amount is equal to or greater than the failure determination reference value x, it is determined that the EGR device has failed, and the process proceeds to step 708.
If it is determined that the EGR device is normal, the process proceeds to step 707. In step 707, the air-fuel ratio correction coefficient α described in FIG. 3 is compared with the failure determination reference value y, so that E
The GR device is diagnosed. If the air-fuel ratio correction coefficient α is greater than or equal to the failure determination reference value y, it is determined that the EGR device has failed, and the process also proceeds to step 708. If it is determined that the EGR device is normal, the process proceeds to step 709. In step 708, EG
The storage of the R device failure information, the notification process to the driver and the maintenance person, the process for the engine operation control maintenance at the time of the EGR device failure, etc. are executed. In steps 709 and 710, feedback control amount calculation and valve opening / closing control are performed.

Further, in the above embodiment, the intake pipe pressure sensor, the means for diagnosing the EGR device by comparing the intake pipe pressure data according to the operating condition and the EGR control amount, and the air-fuel ratio explained in FIG. EGR that obtains a similar effect by using means for comparing the correction coefficient α with the failure determination reference value y
Device diagnostics can be configured.

In addition to the above embodiment, means for detecting the recirculated exhaust gas temperature to diagnose the EGR device and means for comparing the air-fuel ratio correction coefficient α explained in FIG. 3 with the failure judgment reference value y are provided. By using it, it is possible to configure the diagnosis of the EGR device that achieves the same effect.

[0027]

According to the present invention, accurate diagnosis of the EGR device can be performed while suppressing an increase in cost for diagnosis. Therefore, since it is possible to reliably warn the driver or the maintenance person of an abnormality in the EGR device, an increase in fuel consumption due to a failure of the EGR device,
It is possible to suppress the discharge of harmful components into the atmosphere due to the deterioration of the operating performance due to the combustion fluctuations and the reduction of the exhaust gas conversion efficiency caused by the air-fuel ratio fluctuations caused by the air leakage.

[Brief description of drawings]

FIG. 1 is an overall system configuration diagram of an embodiment of the present invention.

FIG. 2 is a control block diagram of an EGR device.

FIG. 3 is a diagram illustrating EGR device diagnosis using an air-fuel ratio correction coefficient.

FIG. 4 is a diagram illustrating correction of a target pressure (target pressure) of an intake pipe.

FIG. 5 is a diagram illustrating intake air temperature compensation.

FIG. 6 is a diagram illustrating intake air temperature compensation.

FIG. 7 is a general flowchart of one embodiment of the present invention.

[Explanation of symbols]

101 ... Engine body, 102 ... Water temperature sensor, 103 ...
Ring gear, 104 ... Position sensor, 105 ... Reference sensor, 108 ... Airflow sensor, 109 ...
Throttle actuator and throttle sensor, 11
0 ... Idle speed control valve, 111 ... Intake pipe pressure sensor, 112 ... Control unit, 11
3 ... Power switch and ignition coil, 114 ...
Spark plug, 115 ... Injector, 118 ... Air-fuel ratio sensor, 119 ... Catalytic converter, 121 ... Pressure regulator, 123 ... Duty solenoid valve.

Claims (6)

[Claims] 1. An apparatus comprising: means for detecting an intake air amount of an engine; means for detecting an engine operating state; and means for calculating a fuel injection amount based on information of the detecting means and supplying fuel.
In an internal combustion engine having an EGR device that recirculates exhaust gas to an intake path, means for detecting pressure in the intake path, means for detecting engine air-fuel ratio by an air-fuel ratio sensor or oxygen concentration sensor arranged in the exhaust path, An EG for an internal combustion engine, comprising: means for diagnosing an EGR device based on detection signals from the pressure detection means and the engine air-fuel ratio detection means.
R device diagnostic device. 2. An EGR device for an internal combustion engine according to claim 1, further comprising means for performing engine air-fuel ratio control by a signal from the engine air-fuel ratio detection means, and using a correction coefficient in the air-fuel ratio control for diagnosis. Diagnostic device. 3. A means for performing learning control of an engine air-fuel ratio according to a signal from the engine air-fuel ratio detecting means,
A diagnostic device for an EGR device of an internal combustion engine, wherein a correction coefficient in the air-fuel ratio learning control is used for diagnostics. 4. The method according to any one of claims 1 to 3,
A diagnostic device for an EGR device of an internal combustion engine, wherein the means for detecting the pressure in the intake passage is arranged downstream of the throttle arranged in the intake pipe. 5. An apparatus comprising means for detecting an intake air amount of an engine, means for detecting an engine operating state, means for calculating a fuel injection amount based on information of the detecting means and supplying fuel.
In an internal combustion engine having an EGR device that recirculates exhaust gas in an intake path, a means for detecting a recirculated exhaust gas temperature, a means for detecting an engine air-fuel ratio by an air-fuel ratio sensor or an oxygen concentration sensor arranged in the exhaust path, A diagnostic device for an EGR device of an internal combustion engine, comprising: means for diagnosing the EGR device based on a detection signal of the detection device. 6. The method according to any one of claims 1 to 5,
An EGR device diagnosing device for an internal combustion engine, comprising means for informing information of a diagnosis result of the EGR device.