JP2838448B2 - Failure detection device for exhaust gas recirculation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detecting device for an exhaust gas recirculation device for diagnosing an operating state of an exhaust gas recirculation device in an internal combustion engine of an automobile or the like and detecting a failure.

[0002]

2. Description of the Related Art In an internal combustion engine of an automobile or the like, exhaust gas is recirculated into an intake air-fuel mixture in accordance with an operation state of the engine.
An exhaust gas recirculation system (hereinafter referred to as EGR) that reduces NOx in exhaust gas by reburning unburned gas in exhaust gas or slowing down combustion in a cylinder to lower combustion temperature. ).

[0003]

As a device for diagnosing the operation of this type of EGR device, conventionally, the temperature of exhaust gas in a recirculation pipe circulated to an intake pipe is detected, and the EGR amount is adjusted while opening a throttle valve. A device for diagnosing whether or not the EGR device is operating by detecting a point at which the temperature of the recirculated exhaust gas sharply rises when increasing it has been proposed (Japanese Patent Laid-Open No. 51-94025). reference).

[0004] However, this type of conventional EGR diagnostic apparatus can roughly detect whether or not the EGR operation is being performed. When the passage is narrowed, an abnormal EGR operation (EGR) due to the narrowed passage is performed.
(Displacement of the amount) cannot be detected accurately.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an abnormal EGR operation (deviation of EGR amount).
It is an object of the present invention to provide a failure detection device for an exhaust gas recirculation device capable of accurately detecting the same.

[0006]

For this purpose, one of the failure detecting devices for an exhaust gas recirculation system according to the present invention detects the engine speed as shown in the block diagram of FIG. , An air flow meter 9 that detects the amount of intake air of the engine and outputs a signal indicating the amount of intake air, detects an intake pipe pressure of the engine, and detects the intake pipe pressure. An intake pipe pressure sensor 8 that outputs a signal indicating the intake pipe pressure, an intake pipe pressure data corresponding to the number of revolutions and the amount of intake air when the engine normally performs exhaust gas recirculation, as a data table, and a revolution number sensor 7. Using the rotation speed data from the air flow meter 9 and the intake air amount data from the air flow meter 9
An expected intake pipe pressure is obtained by searching a data table stored in the storage means 17, and a ratio between the expected intake pipe pressure and the measured intake pipe pressure detected by the intake pipe pressure sensor 8 is calculated. Is smaller than a predetermined width, a failure determination unit 16 that determines that the exhaust gas recirculation device has failed and outputs a failure signal, and a failure indicator 15 that receives a failure signal from the failure determination unit 16 and displays a failure. And, it comprises.

[0007]

In a steady operation state in which the internal combustion engine performs exhaust gas recirculation, the failure judging means 16 uses the rotational speed data from the rotational speed sensor 7 and the intake air amount data from the air flow meter 9 to store it in the storage means 17. The expected intake pipe pressure is obtained by searching the data table obtained. Next, the failure determination means 16 calculates a ratio between the expected intake pipe pressure and the measured intake pipe pressure detected by the intake pipe pressure sensor 8, and when the ratio deviates from a preset width, the exhaust recirculation device. Is determined to have failed, and a failure signal is output to the failure indicator 15. The failure indicator 15 receives the failure signal and performs a failure display.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of a failure detection device of the EGR device. Reference numeral 2 denotes a diaphragm type EGR valve mounted on the internal combustion engine 1.

The EGR valve 2 has a valve 2b connected to a diaphragm 2a in a casing, and a recirculation passage 3 on the intake side connected to a valve chamber of the valve 2b is connected to an exhaust pipe (exhaust) of the internal combustion engine 1. The discharge side recirculation passage 4 connected to the manifold 11 is connected to the surge tank 13 of the intake pipe, and the diaphragm chamber is provided near the throttle valve 6 in the intake pipe 12. And connected to the EGR port 5 via a pipeline.

This EGR device operates during the operation of the internal combustion engine.
When the throttle valve 6 is opened above the position of the EGR port 5, a negative pressure in the intake pipe 12 is applied to the diaphragm chamber of the EGR valve 2 through a pipe line, and the valve is adjusted according to the negative pressure and the opening of the throttle valve 6. 2b is opened, and the exhaust gas sucked from the exhaust pipe through the circulation passage 3 is returned to the circulation passage 4
Through the surge tank 13.

Reference numeral 7 denotes a rotation speed sensor for detecting the rotation speed of the engine, which is provided opposite to the rotor of the distributor.
A signal having a cycle corresponding to the crank angle of the engine, that is, the rotation speed is output. Reference numeral 8 denotes an intake pipe pressure sensor for detecting an intake pipe pressure in the surge tank 13 in which the exhaust gas is recirculated. For example, a piezo-type semiconductor pressure sensor is used, and outputs a voltage signal corresponding to the intake pipe pressure.

Reference numeral 9 denotes an air flow meter which is attached to the intake pipe 12 and detects the amount of intake air. For example, a potentiometer connected to a measuring plate or a heating wire type detection circuit outputs a voltage signal corresponding to the amount of intake air. Output. 1
Reference numeral 0 denotes an atmospheric pressure sensor for detecting the atmospheric pressure, and a semiconductor pressure sensor outputs a voltage signal corresponding to the atmospheric pressure.

Each of the rotational speed sensor 7, the intake pipe pressure sensor 8, the air flow meter 9, and the atmospheric pressure sensor 10 is connected to an electronic control unit 20. Reference numeral 15 denotes a failure indicator which is connected to the electronic control unit 20 and indicates when the EGR device has failed.

As shown in the block diagram of FIG. 3, the electronic control unit 20 is mainly composed of a microcomputer, and includes a CPU 21, a read only memory ROM 22,
A random access memory (RAM) 23 and an input / output circuit 24 are provided, and the units are interconnected via a bus.

The CPU 21 executes an EGR device failure detection operation described later based on program data stored in the ROM 22 in advance. The RAM 23 is provided with an area for temporarily storing detected rotation speed data, intake air amount data, intake pipe pressure data, and the like.

Table data for retrieving an expected intake pipe pressure from engine speed data and intake air amount data is stored in the ROM 22 in advance. These data are created based on data obtained by actually measuring the number of revolutions, the amount of intake air, and the intake pipe pressure when the EGR operation is normally performed in the internal combustion engine. The ROM 22 stores various set values and constants used for the calculation.

The input / output circuit 24 includes a sensor amplifier,
An A / D converter and the like are built in, and the above-mentioned rotation speed sensor 7, intake pipe pressure sensor 8, air flow meter 9, atmospheric pressure sensor 10, and failure indicator 15 are connected to an input / output circuit 24, and input / output of signals Is performed.

Next, the operation of the failure detection device will be described with reference to the flowchart of FIG.

When this processing routine is entered during operation of the engine, the CPU 21 first takes in the crank angle signal N from the rotation speed sensor 7 and reads in the intake air amount data Qa from the air flow meter 9 in step 100. Then, in step 110, the engine speed Ne is calculated by counting the time intervals of the crank angle signals or by counting the number of those signals within a certain time.

Next, in step 120, the difference between the currently read intake air amount Qa and the previous intake air amount Qa0 is calculated, and the absolute value of the difference is set as the intake air amount difference DQa. Next, at step 125, the currently read intake air amount data Qa
Is stored in a predetermined area of the RAM 23 as the intake air amount Qa0, and the data is updated.

Next, in step 130, the CPU 21
The atmospheric pressure detection data Pat from the atmospheric pressure sensor 10 is read. Then, in step 140, it is determined whether or not the read data of the atmospheric pressure Pat is higher than the atmospheric pressure (for example, 650 mmHg) at which a failure can be detected. If the data is lower than the atmospheric pressure (650 mmHg), an accurate EGR is performed. This processing is terminated assuming that the failure cannot be detected.

On the other hand, if the detected atmospheric pressure Pat is higher than the set atmospheric pressure (650 mmHg), the routine proceeds to the next step 160.

Next, the CPU 21 proceeds to step 160
Absolute value DQ of the difference between the intake air amounts calculated in step 120
a is larger than a certain value (for example, 10 m ³ / h), and the absolute value DQa of the difference between the intake air amounts is made a certain value (10 m ³ / h).
If it is greater than ³ / h), the process is terminated because the engine is in a transient operation state such as during acceleration or deceleration, and accurate failure detection cannot be performed.

On the other hand, if the absolute value DQa of the difference between the intake air amounts is equal to or smaller than a predetermined value (10 m ³ / h), then, at step 170
Then, the CPU 21 searches the table data of the estimated intake pipe pressure with respect to the rotational speed data and the intake air amount data stored in the ROM 22, and thereby, according to the rotational speed data Ne and the intake air amount data Qa read as described above. The estimated intake pipe pressure data Pa is determined.

Next, at step 180, the CPU 21
A detection signal from the intake pipe pressure sensor 8 is read, and the detected data is stored in a register as measured intake pipe pressure data Po.

Then, the ratio between the expected intake pipe pressure Pa and the actually measured intake pipe pressure Po is calculated, and in step 190, it is determined whether or not the ratio Pa / Po is smaller than a lower limit set value (for example, 0.97). And the ratio Pa / Po is the set value (0.9
7) If it is smaller, the process proceeds to step 220, where it is determined that a failure has occurred in the EGR device, and a failure is displayed on the failure indicator 15.

Further, at step 200, the ratio Pa /
It is determined whether Po is larger than an upper limit set value (for example, 1.03). If the ratio Pa / Po is larger than the set value (1.03), the process similarly proceeds to step 220, and a failure occurs in the EGR device. Assuming that a fault has occurred, a fault is displayed on the fault indicator 15.

On the other hand, if the ratio Pa / Po is equal to or higher than the lower limit set value (0.97) and equal to or lower than the upper limit set value (1.03) in steps 190 and 200, it is determined that the EGR device is operating normally. In step 210, the failure display is turned off.

Such processing is repeated, for example, at a constant crank angle (180 ° CA) or at a constant time interval. As described above, the calculated or detected expected intake pipe pressure Pa and the measured intake air pressure are measured. The pipe pressures Po are compared, and if the measured intake pipe pressure Po deviates from the expected intake pipe pressure Pa by a predetermined ratio or more, it is determined that the narrowing of the circulation passages 3 and 4 and the opening / closing failure of the EGR valve 2 have occurred. A fault is detected and displayed.

FIG. 5 shows a flowchart of another embodiment. In this example, table data for retrieving expected intake air amount data from engine speed data and expected intake pipe pressure data is stored in the ROM 22 in advance. The failure of the EGR device is detected by checking the difference between the actually measured intake air amount data and the expected intake air amount data.

That is, as shown in FIG.
In step 300, the crank angle signal N is fetched from the rotation speed sensor 7, and the intake pipe pressure data Pb is read from the intake pipe pressure sensor 8. Then, at step 310, the engine speed Ne is calculated by counting the time intervals of the crank angle signals or by counting the number of those signals within a predetermined time.

Next, at step 320, the difference between the intake pipe pressure Pb read this time and the previous intake pipe pressure Pb0 is calculated, and the absolute value of the difference is set as the intake pipe pressure difference DPb. Next, in step 125, the currently read intake pipe pressure data Pb is stored in a predetermined area of the RAM 23 as the intake pipe pressure Pb0, and the data is updated.

Next, the CPU 21 proceeds to step 330.
The atmospheric pressure detection data Pat from the atmospheric pressure sensor 10 is read. Then, in step 340, it is determined whether or not the read data of the atmospheric pressure Pat is higher than the pressure (for example, 650 mmHg) at which a failure can be detected accurately. This processing is terminated assuming that the failure cannot be detected.

On the other hand, if the detected atmospheric pressure Pat is higher than the set atmospheric pressure (650 mmHg), the routine proceeds to the next step 360.

Next, the CPU 21 determines in step 360 that
It is determined whether the absolute value DPb of the difference between the intake pipe pressures calculated in step 320 is larger than a certain value (for example, 10 mmHg), and if the absolute value DPb of the difference between the intake pipe pressures is larger than a certain value (10 mmHg). Since the engine is in a transient operation state such as at the time of acceleration or deceleration and accurate failure detection cannot be performed, this processing is terminated.

On the other hand, if the absolute value DPb of the difference between the intake pipe pressures is equal to or less than the fixed value (10 mmHg), then, at step 37
Then, the CPU 21 searches the rotational speed data Ne and the intake pipe pressure data Pb, which have been read as described above, by searching the rotational speed data and the intake pipe pressure data stored in the ROM 22 for table data of the expected intake air amount. The corresponding expected intake air amount data Qb is determined.

Next, at step 380, the CPU 21
The detection signal from the air flow meter 9 is read, and the detection data is stored in a register as the measured intake air amount data Qo.

Then, the ratio between the expected intake air amount Qb and the actually measured intake air amount Qo is calculated, and in step 390, it is determined whether the ratio Qb / Qo is smaller than a lower limit set value (for example, 0.97). And the ratio Qb / Qo is equal to the set value (0.9
7) If it is smaller, the process proceeds to step 420, where it is determined that a failure has occurred in the EGR device, and a failure is displayed on the failure indicator 15.

Further, in step 400, the ratio Qb /
It is determined whether or not Qo is greater than an upper limit set value (for example, 1.03). If the ratio Qb / Qo is greater than the set value (1.03), the process similarly proceeds to step 420, and a failure occurs in the EGR device. Assuming that a fault has occurred, a fault is displayed on the fault indicator 15.

On the other hand, if the ratio Qb / Qo is equal to or more than the lower limit set value (0.97) and equal to or less than the upper limit set value (1.03) in steps 390 and 400, it is determined that the EGR device is operating normally. In step 410, the fault display is turned off.

In the above embodiment, the atmospheric pressure sensor 10 is provided to detect the atmospheric pressure. However, a valve is provided in the detection pipe in which the intake pipe pressure sensor 8 is provided, and the valve is switched to change the atmospheric pressure. If the intake pipe pressure is selectively detected, both the intake pipe pressure and the atmospheric pressure can be detected by the intake pipe pressure sensor.

Further, in the above-described embodiment, whether the engine is in a transient operation state such as during acceleration or deceleration and accurate failure detection cannot be performed, or whether the engine is in a steady operation state and fault detection is possible. The determination as to whether or not the failure is determined based on a temporal change in the intake air amount or the intake pipe pressure, that is, the magnitudes of the absolute values DQa and DPb. May be performed.

[0044]

As described above, according to the failure detection device for an exhaust gas recirculation device of the present invention, the failure determination means uses the rotation speed data from the rotation speed sensor and the intake air amount data from the air flow meter. Then, by searching a data table stored in the storage means, an expected intake pipe pressure is obtained, and a ratio between the expected intake pipe pressure and an actually measured intake pipe pressure detected by the intake pipe pressure sensor is calculated. When the width of the exhaust gas recirculation device deviates from the preset width, it is determined that the exhaust gas recirculation device has failed and a failure signal is output to the failure indicator. In the case of stenosis, abnormal EGR operation (deviation of EGR amount) due to the stenosis can be accurately detected, and fine failure detection can be performed.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of a failure detection device of the exhaust gas recirculation device showing one embodiment of the present invention.

FIG. 3 is a block diagram of the failure detection device.

FIG. 4 is a flowchart showing the operation of the failure detection device.

FIG. 5 is a flowchart of another embodiment.

[Explanation of symbols]

7-rotation speed sensor, 8-intake pipe pressure sensor, 9-air flow meter, 15-failure indicator, 16-failure determination means, 1
7-storage means.

Claims (3)

(57) [Claims] 1. A rotation speed sensor for detecting a rotation speed of an engine and outputting a signal indicating the rotation speed, and an air flow meter for detecting a suction air amount of the engine and outputting a signal indicating the suction air amount. An intake pipe pressure sensor that detects an intake pipe pressure of the engine and outputs a signal indicating the intake pipe pressure; and intake pipe pressure data with respect to a rotation speed and an intake air amount when the engine normally performs exhaust gas recirculation. Is stored in advance as a data table, and the data table stored in the storage means is searched using the rotation speed data from the rotation speed sensor and the intake air amount data from the air flow meter, thereby obtaining the expected intake air. Determine the pipe pressure, calculate the ratio between the expected intake pipe pressure and the measured intake pipe pressure detected by the intake pipe pressure sensor, and when the ratio deviates from a preset width, it is assumed that the exhaust gas recirculation device has failed. Size A failure detection device for an exhaust gas recirculation device, comprising: a failure determination unit that outputs a fixed failure signal; and a failure indicator that receives a failure signal from the failure determination unit and displays a failure. 2. A rotation speed sensor for detecting a rotation speed of an engine and outputting a signal indicating the rotation speed, and an air flow meter for detecting a suction air amount of the engine and outputting a signal indicating the suction air amount. An intake pipe pressure sensor that detects an intake pipe pressure of the engine and outputs a signal indicating the intake pipe pressure; and an intake air amount data with respect to a rotational speed and an intake pipe pressure when the engine normally performs exhaust gas recirculation. Is stored in advance as a data table, by searching the data table stored in the storage means using the rotation speed data from the rotation speed sensor and the intake pipe pressure data from the intake pipe pressure sensor, Obtain the expected intake air amount, calculate the ratio between the expected intake air amount and the measured intake air amount detected by the air flow meter, and when the ratio deviates from a preset width, it is determined that the exhaust gas recirculation device has failed. Size A failure detection device for an exhaust gas recirculation device, comprising: a failure determination unit that outputs a fixed failure signal; and a failure indicator that receives a failure signal from the failure determination unit and displays a failure. 3. The failure detecting device for an exhaust gas recirculation device according to claim 1, wherein the atmospheric pressure is detected,
An atmospheric pressure sensor that outputs a signal indicating the atmospheric pressure; and if atmospheric pressure data from the atmospheric pressure sensor falls below a preset value, and / or a detected intake air amount, intake pipe pressure, or Failure detection stopping means for stopping the failure detection operation of the failure determination means when a transient operation state of the engine in which the change over time of the rotation speed is equal to or greater than a preset range is detected. A failure detection device for an exhaust gas recirculation device.