JP2595139B2 - Failure detection device for exhaust gas recirculation control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation (hereinafter abbreviated as EGR) device for recirculating a part of exhaust gas of an internal combustion engine (hereinafter abbreviated as an engine) to an intake pipe of the engine. The present invention relates to a failure detection device that detects a failure of an EGR control device that controls the failure.

[0002]

2. Description of the Related Art Heretofore, this type of EGR control device has been widely applied to an engine as a means for reducing NOx in exhaust gas, and an exhaust pressure control using an exhaust pressure transducer (hereinafter abbreviated as BPT). An EGR control device of a system has been put to practical use.

[0003] Further, as a failure detecting device of the EGR control device, for example, there is a device described in Japanese Patent Application Laid-Open No. 62-51746. Detected values of the operating state of the engine at the time of the closing operation are respectively stored, and a failure of the EGR control device is detected from a difference between these two stored values.

[0004]

As described above, the conventional EGR control device failure detecting device is as described above. During the failure diagnosis of the EGR control device, the operating state and the load state of the engine must be stable. There is a problem that the frequency of performing is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and increases the frequency of performing a failure diagnosis of an EGR control device and eliminates erroneous detection due to a load change during the failure diagnosis of the EGR control device. EG that can
An object of the present invention is to obtain a failure detection device for an R control device.

[0006]

According to the present invention, there is provided a failure detecting device for an EGR control device, comprising: a recirculation pipe for exhaust gas; an EGR control valve for controlling a flow rate thereof;
Operating state detecting means, load state detecting means, first storing means for storing a first operating state and a load state detected value when the EGR control valve is opened, and second storing means for storing the EGR control valve when the EGR control valve is closed. Second storage means for storing the operating state and load state detection values of the first and second EGR control devices according to the difference between the first and second load detection values, and calculates the difference between the normal engine operation state standard values; A correction unit that corrects one of the first and second operation state detection values based on the difference and a comparison is made as to whether the difference between the corrected and uncorrected operation state detection values is inside or outside a predetermined range. Accordingly, a failure determination means for determining a failure of the EGR control device is provided.

[0007]

The failure detecting device of the EGR control device according to the present invention detects the first and second operating states and the load state when the EGR control valve is opened and closed, and determines the detected values of the first and second load states. A difference between the engine operating state standard values corresponding to the difference is calculated, and one of the first and second operating state detected values is corrected by the correction means based on the difference, and the corrected operating state detected value and the other operating state are corrected. Only when it is determined by the failure determination means that the difference value from the detected value is outside the predetermined range, it is determined that the EGR control device has failed.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus configuration according to this embodiment,
In FIG. 1, a well-known four-cycle spark ignition type engine 1 mounted on a vehicle mainly sucks combustion air through an air cleaner 2, an intake pipe 3, and a throttle valve 7. Fuel is supplied from a fuel system (not shown) via an injector 5 provided on the intake pipe 3 upstream of the throttle valve 7. The throttle sensor 8 detects the throttle valve opening Θ of the throttle valve 7 and outputs a signal corresponding to Θ.

An intake manifold section 4 downstream of the intake pipe 3
At the inlet, the absolute pressure PB in the intake pipe 3 is
Is detected by The pressure sensor 6 detects the intake pipe pressure P
A signal corresponding to B is output.

The ignition coil 12 has a primary side connected to a power supply and a transistor at the last stage of the igniter 13, and supplies a high voltage from a secondary side to an ignition plug (not shown) provided for each cylinder of the engine 1.

The exhaust gas of the engine 1 is at least partially discharged outside through an exhaust pipe 14 and a catalytic converter 15 for removing harmful components.

A part of the exhaust gas diverted to the exhaust branch pipe which is a recirculation pipe connected to the exhaust pipe 14 flows into the intake pipe 3 via the EGR control valve 9 and is returned to the engine 1.

An EGR negative pressure port is provided in the intake pipe 3 slightly upstream from the end when the throttle valve 7 is fully closed. The BPT 10 has a negative pressure P from its EGR negative pressure port.
_EGR and exhaust pressure from exhaust gas branch pipe are introduced. The BPT 10 introduces the negative pressure P _EGR or the atmospheric pressure to the EGR control valve 9 according to the state of the introduction pressure.

The EGR control valve 9 comprises a valve including a diaphragm, a negative pressure chamber, and a spring. The BPT 10 has a discharge port, a diaphragm, a port opposed to the diaphragm, and a port communicating with the EGR negative pressure port and the negative pressure chamber. It is composed of an atmospheric pressure introducing chamber adjacent to the pressure chamber, a spring, and a filter for introducing atmospheric pressure. These constitute an EGR device of a so-called exhaust pressure control system together with an EGR solenoid 11 described later.

An EGR solenoid 11 is provided between the BPT 10 and the EGR negative pressure port. This E
When the GR solenoid 11 is turned on, the BPT 10
A three-way solenoid that introduces a negative pressure P _EGR from the GR negative pressure port and shuts off the negative pressure to introduce atmospheric pressure to the BPT 10 when turned off. The warning lamp 16 is turned on when a failure in the EGR control device is detected, and the warning lamp 16 informs the driver of EGR.
This is for notifying an abnormality of the control device.

Reference numeral 19 denotes a key switch 17 from the battery 18.
The control device receives power from the throttle sensor 8, the pressure sensor 6, and the ignition coil 12 and processes the signals. The injector 5, the EGR solenoid 11
And the warning lamp 16 and the like are driven and controlled.

FIG. 2 shows the internal configuration and the like of the control device 19 in FIG.
Are a CPU 200 for performing various calculations and determinations, a counter 201 for measuring a rotation period, and a timer 20 for measuring a driving time.
2. A / D to convert analog input signal to digital signal
It comprises a converter 203, a RAM 204 as a work memory, a ROM 205 storing a main flow program shown in FIG. 3, etc., an output port 206 for outputting a command signal of the CPU 200, a common bus 207, and the like.

The ignition signal from the primary side of the ignition coil 12 is subjected to waveform shaping and the like by a first input interface circuit 101, turned into an interrupt command signal INT, and input to the microcomputer 100.

Each time this interrupt is issued, the CPU 200 of the microcomputer 100 reads the value of the counter 201 and calculates the rotation period from the difference from the previous value. After this, the microcomputer 100 calculates the rotational speed data Ne representing the engine speed N _E from the rotation period. Analog output signals from the throttle sensor 8 and the pressure sensor 6 are removed or amplified by a second input interface circuit 102 for noise components, and are given to an A / D converter 203, where a throttle representing a throttle valve opening Θ is obtained. It is converted into digital data of a valve opening value θ (Θ∝θ) and an intake pipe pressure value Pb (PB∝Pb) representing the intake pipe pressure PB. Reference numeral 104 denotes an output interface circuit.
The drive signal from the controller 06 is subjected to processing such as amplification and the like, and is output to the injector 5, the EGR solenoid 11, the warning lamp 16, and the like to control the drive.

The power supply circuit 103 turns on the key switch 17
Sometimes, the voltage of the battery 18 is made constant and supplied to the microcomputer 100, whereby the microcomputer 100 starts operating. The control device 19 has the reference
It is composed of 0 to 104 elements.

The ROM 205 stores the rotational speed data N
e and the intake pipe pressure standard value Pb _im (Ne, θ) without EGR divided two-dimensionally by the throttle valve opening value θ.
Is stored in advance as a two-dimensional map. In this case, the standard value of the intake pipe pressure Pb _im (Ne, θ) is set to a standard value obtained by an experiment.

In FIG. 8, the curve indicates a standard intake pipe pressure value Pb _im without EGR (OFF) using the throttle opening value θ as a variable when the rotational speed data Ne is constant.
4 shows a map of (Ne, θ). There is EGR (O
Of the engine state detection values Ne _ON , θ _ON , and Pb _ON at the time of N), the intake pipe pressure standard value Pb _im1 (Ne _ON , θ _ON ) is _obtained by the rotation speed data Ne _ON and the throttle valve opening value θ _ON. Find by map. Similarly, of the state detection values Ne _OFF , θ _OFF , and Pb _OFF of the engine when the EGR is OFF, Ne _{OFF is selected.}
And θ _OFF , the intake pipe pressure standard value Pb _im2 (Ne _OFF ,
θ _OFF ) is obtained from a map. However, in FIG. 8, Ne = Ne _ON = Ne _OFF = constant in order to simplify the description. The obtained standard values of both intake pipe pressures Pb _im1 , Pb
The difference ΔPb _im of _im2 is due to the change in load, that is, Ne _ON
Indicates the estimated value of the change in the intake pipe pressure caused by the change to Ne _OFF and the change of θ _ON to θ _OFF . This difference ΔPb
_im only intake pipe pressure value Pb _OFF during OFF of the EGR load variation correction to seek Pb _OFF 'as an estimate of the intake pipe pressure, the difference between Pb _ON, i.e. the engine load state Ne _ON, theta
ON the same as EGR at _ON, it is possible to determine the difference between a value corresponding Pb _EGR intake pipe pressure during OFF. This difference value Pb
The failure diagnosis of the EGR device can be performed by determining whether the _EGR is inside or outside the predetermined range. The rotation speed data N
e and throttle valve opening value θ correspond to the operating state detection value
And the intake pipe pressure value Pb corresponds to the load state detection value.
Needless to say.

Next, the operation of this embodiment (operation of the control device 19) will be described with reference to FIG. First, in step S1, and determines a rotation speed data Ne representing the engine speed N _E on the basis of the rotation cycle already determined. Step S
In step 2, input information such as an intake pipe pressure value Pb representing the intake pipe pressure PB and a throttle valve opening value θ representing the throttle valve opening Θ are read.

In the next step S3, based on the previously obtained rotational speed data Ne and the previously read intake pipe pressure value Pb and throttle valve opening value θ, control other than those described later (control of fuel supply and ignition timing The details will be omitted for control and the like.)

In step S4, an EGR control process whose details are shown in FIG. 4 is performed based on the rotational speed data Ne obtained earlier, the intake pipe pressure value Pb and the throttle valve opening value θ read earlier.

In step S5, based on the previously obtained rotational speed data Ne and the previously read throttle valve opening value θ, a process for determining a steady operation state, the details of which are shown in FIG. 5, is performed.

In step S6, the previously obtained rotational speed data Ne, the previously read intake pipe pressure value Pb and throttle valve opening value θ, the ON / OFF signal of the EGR solenoid 11 controlled in step S4, FIGS. 6 and 7 show details based on the flag information set in S5.
A GR failure determination process is performed. After the process in step S6, the process returns to step S1 to repeat the above operation.

Next, the detailed processing of step S4 in FIG. 3 will be described with reference to FIG. First, in step S401, it is determined whether input information representing the operating state of the engine, such as the previously obtained rotational speed data Ne and the previously read intake pipe pressure value Pb, is within the preset and stored EGR control zone. That is, it is determined whether or not the operating state of the engine 1 is in a zone where EGR is required. If it is outside the EGR control zone, the process proceeds to step S402, and the EGR failure diagnosis execution flag used in step S6 is cleared. That is, even during the EGR failure diagnosis, E
Stop GR failure diagnosis. Then, the EGR solenoid 11 is turned off, the atmospheric pressure is introduced into the BPT 10, and the EG
The R control valve 9 is closed, and the EGR control process in step S4 ends.

On the other hand, if it is determined in step S401 that the vehicle is within the EGR control zone, the flow advances to step S403 to determine whether or not the EGR failure diagnosis execution flag used in step S6 is set. When it is not set, that is, when it is determined that the EGR failure diagnosis is not being performed, the process proceeds to step S404, and the EGR solenoid 11 is turned on. That is, the pressure P of the EGR negative pressure port is applied to the BPT 10.
_{The EGR} is introduced to control the exhaust pressure of the EGR control valve 9, and the process of step S4 is completed. Also, in step S403, the EGR failure diagnosis execution flag is set and the EGR
If it is determined that the failure is being diagnosed, the process of step S4 ends.

Next, the detailed processing of step S5 in FIG. 3 will be described with reference to FIG. First, step S50
In step 1, the previously obtained rotational speed data Ne is compared with the previously obtained rotational speed data to determine whether the change value of the rotational speed data is within a predetermined value, that is, the amount of change in the rotational speed of the engine 1 from the previous time to the present time. Is determined to be within a predetermined number of revolutions, and if it is determined not to be within the predetermined value, the process jumps to step S504.

If it is determined that the value is within the predetermined value, the process proceeds to step S502, and the previously read throttle valve opening value θ
Is compared with the previously read throttle valve opening value, and whether the change amount of the throttle valve opening value is within a predetermined value, that is, the change amount of the opening degree of the throttle valve 7 changed from the previous time to the current time is the predetermined opening value. It is determined whether it is within the degree.

If it is determined in step S502 that the value is within the predetermined value, the process proceeds to step S503. If it is determined that the value is not within the predetermined value, the process proceeds to step S504. In step S503, the steady operation state flag used in step S6 is set, and the steady operation state processing in step S5 ends. That is, it is determined that the engine is in a steady operation in which the rotation speed data Ne and the throttle valve opening value θ are within a predetermined value.

In step S504, step S504
The steady operation state flag used in step 6 is cleared, and the steady operation state determination process in step S5 ends. That is, the rotation speed data Ne or the throttle opening value θ fluctuates,
It is determined that the operation is other than the steady operation.

Next, the detailed processing of step S6 in FIG. 3 will be described with reference to FIGS. First, in step S601, it is determined whether or not the EGR solenoid 11 is controlled to be ON in the EGR control process in step S4. If it is ON control, the process proceeds to step S602, and if it is not ON control, the process proceeds to step S607.

In step S602, it is determined whether or not the steady operation state flag set in step S5 is set, and if it is set, step S603 is performed.
If not, the EGR failure determination processing in step S6 is terminated.

In step S603, the previously obtained rotational speed data and the previously read throttle valve opening value θ and intake pipe pressure value Pb are used to detect the operating state detection values Ne _ON , θ of the engine 1 when the EGR is ON. _ON , Pb _ON and stored in step S60.
Proceed to 4.

In step S604, the EGR failure diagnosis execution flag used in step S4 is set. That is,
This indicates that the EGR solenoid 11 is forcibly turned off during the EGR failure diagnosis, and the process proceeds to step S605, where the EGR solenoid 11 is turned off, that is, the atmospheric pressure is set to B
Then, the EGR control valve 9 is forcibly closed and the EGR control valve 9 is closed.

On the other hand, in step S607 after the negative determination in step S601, it is determined whether or not the EGR failure diagnosis execution flag is set. If it is determined that the flag has not been set, that is, if the EGR failure diagnosis is not being performed, the EGR failure determination processing in step S6 ends. If it is determined that the flag is set, that is, if the EGR failure diagnosis is being performed, the process proceeds to step S608.

In step S608, it is determined whether a predetermined time has elapsed after the EGR failure diagnosis execution flag is set. That is, it is determined whether or not the time during which the EGR solenoid 11 is turned off for the diagnosis of the EGR failure is sufficient. If it is determined that the time is not sufficient, the process proceeds to step S6.
When the GR failure determination processing is completed and it is determined that the processing is sufficient, the process proceeds to step S609.

In step S609, the previously obtained rotational speed data Ne, the previously read intake pipe pressure value Pb and the throttle valve opening value .theta.
_OFF , Pb _OFF , and θ _OFF are stored in step S61.
Go to 0.

In step S610, the previously stored EG
A two-dimensional map is mapped by the rotation speed data Ne _ON and the throttle valve opening value θ _ON which are the operation state detection values when the R solenoid 11 is ON and in the steady operation state, and the intake pipe pressure standard value Pb _im1 (Ne _ON , θ _ON ), the rotation speed data Ne _OFF and the throttle valve opening value θ stored in step S609.
_{When OFF} , the intake pipe pressure standard value Pb _im2 (N
e _OFF , θ _OFF ). Then, the intake pipe pressure value Pb _OFF stored in step S609 is corrected with the difference ΔPb between the obtained Pb _im1 and Pb _im2 as a correction value, and is set to Pb _OFF ′. This Pb _OFF 'has a load state of N
e _ON and θ _ON indicate intake pipe pressure values (actually, intake pipe pressure estimated values) at the time of EGR OFF. That is, the intake pipe pressure value Pb _ON stored above and the intake pipe pressure value Pb _OFF ′ obtained above become the same load state (Ne _ON , θ _ON ) (see FIG. 8).

[0042] In the next step S611, the step of asking Figure 7 the difference value Pb _EGR intake pipe pressure value Pb _OFF after correction of the intake pipe pressure value Pb _ON and Pb _OFF previously stored 'S6
Proceed to 12. This difference value Pb _EGR is equal to E
Measured intake pipe pressure value Pb _ON and EGR O at GR ON
This shows the amount of deviation from the estimated intake pipe pressure value Pb _OFF 'at the time of FF.

In step S612, step S611
It is determined whether or not the difference value Pb _EGR obtained in the above is a value within a range determined by a predetermined value. If it is determined that the difference value is within the predetermined range, the process proceeds to step S613, where it is determined that the value is not within the predetermined range. If so, the process proceeds to step S614.

In step S613, it is determined that the EGR control device is operating normally, the warning lamp 16 is turned off, and the flow advances to step S615.

In step S615, the EGR solenoid 11 is turned on, and the flow advances to step S616 to clear the EGR failure diagnosis execution flag and end. That is, the end of the EGR failure diagnosis is provided by the flag information, and
The processing of the EGR failure determination of No. 6 is ended.

On the other hand, in step S612, the difference value Pb _EGR
Next step S6 when it is determined that is outside the predetermined range.
At 14, it is determined that there is an abnormality in the EGR control device,
The warning lamp 16 is turned on, and the process proceeds to step S616 to perform the same processing as described above.

In the above embodiment, a map is used. However, at least a part of the map may be replaced with a function, and the value may be obtained by a function calculation. Further, the intake pipe pressure value Pb _OFF ′ at the time of EGR OFF is estimated.
The intake pipe pressure value at the time of EGR ON in the load state may be estimated.

In the above-described embodiment, the intake pipe pressure value is used for the EGR failure determination. However, the EGR failure determination may be performed in the same manner as in the above-described embodiment using the intake air amount value detected using the air flow sensor. The same effects as those of the above embodiment can be obtained.

[0049]

As described above, according to the present invention, EGR
If the load changes due to, for example, the driver's throttle operation or air conditioner operation during the failure diagnosis in which the control valve is forcibly controlled to open and close, the operating state detection value used for the failure diagnosis is corrected according to the degree of the load variation. Therefore, there is an effect that accurate failure detection can be performed and the frequency of failure diagnosis increases.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a failure detection device of an EGR control device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration and the like of a control device in FIG. 1;

FIG. 3 is a flowchart showing a main operation of the control device according to the embodiment.

FIG. 4 is a flowchart showing a process of EGR control in FIG. 3 in detail.

FIG. 5 is a flowchart showing details of a process for determining a steady operation state in FIG. 3;

FIG. 6 is a flowchart showing in detail a front process of the EGR failure determination in FIG. 3;

FIG. 7 is a flowchart showing details of a post-process of the EGR failure determination in FIG. 3;

FIG. 8 is a graph showing a relationship between a throttle opening value and an intake pipe pressure value.

[Explanation of symbols]

 Reference Signs List 1 engine 3 intake pipe 6 pressure sensor 8 throttle sensor 9 EGR control valve 10 BPT 11 EGR solenoid 12 ignition coil 18 battery 19 controller

Claims (1)

(57) [Claims] 1. A recirculation pipe for recirculating exhaust gas of an internal combustion engine to an intake pipe, an exhaust gas recirculation control valve for controlling a flow rate of exhaust gas flowing in the recirculation pipe, and a passage area of the exhaust gas recirculation control valve. Valve passage area control means, operating state detection means for detecting an operation state of the internal combustion engine, load state detection means for detecting a load state of the internal combustion engine, and a passage area of the exhaust gas recirculation control valve. First storage means for storing a first operation state detection value and a first load state detection value detected by the operation state detection means and the load state detection means during the control for widening the exhaust gas recirculation control The second operation state detection value and the second load state detection value detected by the operation state detection means and the load state detection means during the control for making the passage area of the valve relatively small or zero are stored. Two A storage means, and an exhaust gas recirculation control device according to a difference between the first and second load state detection values calculates a difference between normal engine operation state standard values, and based on the difference, calculates the first and second engine operation state standard values. Correction means for correcting any one of the operation state detection values, and a difference value between the operation state detection value corrected by the correction means and the uncorrected one of the first and second operation state detection values is determined by a predetermined value. A failure detection device for an exhaust gas recirculation control device, comprising: a failure determination unit that determines a failure of the exhaust gas recirculation control device by comparing whether the exhaust gas recirculation control device is inside or outside the range.