JPH0544581A - Abnormality detecting method for exhaust gas reflux system for engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of erroneous diagnosis by accurately detecting abnormality of an exhaust gas reflux system, being in a state that reflux of exhaust gas is executed, without being influenced by an open air temperature. CONSTITUTION:When, after an output change DELTATS of an output voltage TSEGR 0 of an EGR temperature sensor during establishment of a diagnosis condition and a present output voltage TSEGR of an EGR temperature sensor is calculated at S216, a state that the output change DELTATS is lower than a set value is continued for a given time, it is decided from close stick of an EGR valve that a trouble where exhaust gas does not reversely flow to a suction system occurs. Namely, only when, after establishment of a diagnosis condition, the temperature of an EGR passage is below a set temperature and besides a slight temperature change is produced even when a given time elapses, it is decided that a close stick trouble occurs. Thereby, even when an open air temperature is low and an exhaust gas reflux gas temperature detected by the EGR temperature sensor is lower than an actual temperature, accurate decision of a trouble is practicable and erroneous decision can be prevented from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas recirculation system abnormality detection method capable of accurately detecting an exhaust gas recirculation system abnormality.

[0002]

2. Description of the Related Art Conventionally, a technique has been widely adopted in which exhaust gas recirculation (EGR), which recirculates a part of engine exhaust gas to the intake side, lowers the combustion temperature of an air-fuel mixture to reduce nitrogen oxides in the exhaust gas. ing.

In this EGR, generally, an exhaust gas recirculation amount adjusting valve is provided in the middle of an exhaust gas recirculating passage connecting the exhaust passage and the intake passage, and the valve opening degree of the exhaust gas recirculating amount adjusting valve is set to the operating condition of the engine. When the exhaust gas recirculation amount adjusting system including the exhaust gas recirculation amount adjusting valve fails, the combustion state of the engine becomes unstable and misfires increase, resulting in a decrease in output and deterioration of fuel efficiency.

For this reason, for example, Japanese Patent Laid-Open No. 3-23355.
In the publication, when the target valve opening value of the exhaust gas recirculation amount adjustment valve interposed in the exhaust gas recirculation passage is a predetermined value or more, the temperature of the EGR gas (exhaust gas recirculation gas) before and after the exhaust gas recirculation amount adjustment valve is detected. There has been proposed a technique for diagnosing that the valve opening control system is out of order when the temperature difference is below a predetermined value.

[0005]

However, in general,
In order to detect the temperature of the EGR gas passing through the exhaust gas recirculation passage, it is necessary to install a temperature sensor at a predetermined distance from the exhaust port of the engine to prevent destruction by heat.

Therefore, the detected temperature of the EGR gas is easily influenced by the outside air temperature, and the detected EGR gas temperature is unique to the EGR executed when the engine is warmed up, especially when the outside air temperature is low. There is a possibility that an erroneous determination may occur when compared with the threshold value that is set in advance.

The present invention has been made in view of the above circumstances, and an abnormality of the exhaust gas recirculation system in the exhaust gas recirculation execution state can be accurately detected without being affected by the outside air temperature, and erroneous diagnosis is prevented. It is an object of the present invention to provide a method for detecting an abnormality in an exhaust gas recirculation system of an engine, which is capable of doing so.

[0008]

SUMMARY OF THE INVENTION An engine exhaust gas recirculation system abnormality detection method of the present invention is an engine exhaust gas recirculation system abnormality detection system in which exhaust gas is recirculated from an exhaust system to an intake system via an exhaust gas recirculation amount adjusting valve. In the method, the temperature of the exhaust gas recirculation gas detected on the upstream side of the exhaust gas recirculation amount control valve is below a preset temperature threshold value under a predetermined diagnostic condition, and the time change of the detected temperature is preset. When the temperature is within the temperature change threshold, it is determined that the exhaust gas recirculation amount adjustment system including the exhaust gas recirculation amount adjustment valve is abnormal.

[0009]

According to the abnormality detecting method for the exhaust gas recirculation system of the present invention, the temperature of the exhaust gas recirculation gas detected on the upstream side of the exhaust gas recirculation amount adjusting valve is below a preset temperature threshold value under a predetermined diagnostic condition. When the detected time change of the temperature is within the preset temperature change threshold value, the exhaust gas is not normally recirculated from the exhaust system to the intake system, and the exhaust gas including the exhaust gas recirculation amount adjustment valve is included. It is determined that the reflux adjustment system is abnormal.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The drawings show an embodiment of the present invention, and FIG. 1 is a flow chart (part 1) of the EGR valve stick determination procedure,
2 is a flowchart of the EGR valve stick determination procedure (Part 2), FIG. 3 is a flowchart of the EGR valve stick determination procedure (Part 3), FIG. 4 is a flowchart of the EGR valve stick determination procedure (Part 4), and FIG.
GR control procedure flowchart (part 1), FIG.
Flowchart of R control procedure (No. 2), FIGS.
Is an explanatory view showing hysteresis during EGR cut, FIG.
2 is a schematic diagram of the engine control system, FIG. 13 is a circuit configuration diagram of the control device, and FIG. 14 is a characteristic diagram of the EGR gas temperature sensor.

[Structure of Engine Control System] In FIG. 12, reference numeral 1 in the drawing is an engine body, and in the drawing, a 6-cylinder horizontally opposed engine is shown. This engine body 1
Indicates that the cylinder block 2 has banks on both sides with the crankshaft 1a as the center (in the figure, the right bank is the left bank,
The left side is divided into two, and each cylinder head 3 of each bank is formed with an intake port 4, and an intake manifold 5 is connected to each intake port 4.

Further, upstream of the intake manifold 5, the throttle chambers 6a and 6b are provided corresponding to each bank.
Of the throttle chambers 6a, 6b
The air chamber 7 is connected to the upstream side of the. An air cleaner 9 is attached to the upstream side of the air chamber 7 via an intake pipe 8, and an intake air amount sensor (a hot film type air flow meter in the figure) 10 is provided immediately downstream of the air cleaner 9. ing.

The throttle chambers 6a, 6 are also
Throttle valves 11a and 11b are respectively provided between b and the air chamber 7, and one throttle valve 11b is provided with a throttle opening sensor 12a and an idle switch 12b for detecting the throttle valve fully closed. Has been done.

Further, each throttle chamber 6a, 6b
A variable intake valve 11c is interposed in a passage 6c that communicates with the throttle valve 11a and 11b. The throttle valve 11a and the throttle valve 11b are connected to each other by a passage 6d. The idle speed control valve (ISCV ) 13 is interposed.

An injector 14 is arranged immediately upstream of each intake port 4 of each cylinder of the intake manifold 5, and the tip of each injector of each cylinder head 3 is exposed to the combustion chamber. A spark plug 15 is attached. The ignition coil 15 a is directly attached to the terminal portion of the ignition plug 15 and connected to the igniter 16.

The injector 14 includes a fuel tank 1
Fuel is pressure-fed from an in-tank type fuel pump 18 provided inside 7 through a fuel filter 19 and regulated by a pressure regulator 20.

A cooling water temperature sensor 21 is exposed to a cooling water passage (not shown) formed in the cylinder block 2, and a right bank knock sensor 22a and a left bank knock sensor 22a are provided in the banks of the cylinder block 2, respectively. A bank knock sensor 22b is attached, and the exhaust ports 23 of the cylinder heads 3 communicate with the exhaust pipes 24a and 24b provided for each bank.

Each of the knock sensors 22a and 22b includes, for example, a vibrator having substantially the same natural frequency as the knock vibration,
This is a resonance type knock sensor composed of a piezoelectric element that detects the vibration acceleration of this vibrator and converts it into an electric signal, and detects the vibration transmitted to the cylinder block etc. by the combustion pressure wave in the explosion stroke of the engine. The detection signal according to the vibration waveform is output.

The exhaust pipes 24a and 24b are provided with
The right bank O2 sensor 25a and the left bank O2 sensor 25b are exposed respectively, and the catalytic converters 26a and 26b are respectively provided on the downstream sides of the O2 sensors 25a and 25b, and further downstream of the catalytic converters 26a and 26b. A catalytic converter 27 is provided at the side confluence portion.

An exhaust gas recirculation (EGR) passage 28 is connected to the exhaust port 23 of the right bank, and is composed of a diaphragm actuator E as an exhaust gas recirculation amount adjusting valve.
A passage 6e that connects the downstream sides of the throttle valves 11a and 11b to each other via the valve body 29a of the GR valve 29.
Is in communication with. Exhaust port 2 of the EGR passage 28
A temperature sensor (EGR gas temperature sensor) 30 that detects the temperature of the exhaust gas recirculation gas is provided on the third side.
The EGR passage 28 immediately upstream of the valve 29 communicates with the EGR vacuum modulator 31.

The EGR vacuum modulator 31
Is divided into a back pressure chamber 31a communicating with the EGR passage 28 and a diaphragm chamber 31b communicating immediately upstream of the throttle valve 11b of the left bank. This diaphragm chamber 31b is connected via a valve 31c. Above EGR
It communicates with the diaphragm chamber 29b of the valve 29 and immediately upstream of the throttle valve 11a of the right bank.

In addition, an EGR solenoid valve 32 is provided in a passage that connects the diaphragm chamber 29b of the EGR valve 29 and the upstream side of the throttle valve 11a of the right bank.
The valve body 32a is inserted. Then, the EGR solenoid valve 32, the EGR valve 29, and the EGR
The vacuum modulator 31 constitutes an exhaust gas recirculation amount adjusting system for adjusting the recirculation amount of the exhaust gas, and when EGR is performed, the solenoid coil 32b of the EGR solenoid valve 32 is energized to open the valve element 32a, and the vacuum modulator The valve opening degree of the EGR valve 29 is controlled by 31.

On the other hand, the crankshaft 1a of the engine body 1 has a first crank rotor 33 for detecting a crank angle.
And the second crank rotor 34 for discriminating the cylinders of each group (groups of # 1, # 2 cylinders, # 3, # 4 cylinders, # 5, # 6 cylinders) with a predetermined interval in the axial direction. First and second crank angle sensors 35, which are axially mounted in close proximity to each other and are formed on the outer circumferences of the first and second crank rotors 33 and 34, such as electromagnetic pickups for detecting protrusions that are the objects to be detected, 36 are provided opposite to each other.

Further, provided on the cylinder head 3,
A cam rotor 37 is connected to a cam shaft 1c that makes a half rotation with respect to the crankshaft 1a, and an electromagnetic field for determining the compression top dead center of a specific cylinder (for example, # 1 cylinder) is provided on the outer periphery of the cam rotor 37. A cam angle sensor 38 composed of a pickup or the like is provided oppositely, and the crank angle of each cylinder can be determined by signals from the cam angle sensor 38 and the first and second crank angle sensors 35, 36. You can

Incidentally, the first and second crank rotors 3
3, 34, or the outer circumference of the cam rotor 37,
A slit may be provided as a detected body instead of the protrusion, and further, the first and second crank angle sensors 3 may be provided.
5, 36 and the cam angle sensor 38 are not limited to magnetic sensors such as electromagnetic pickups, but may be optical sensors or the like.

[Circuit Configuration of Control Device] In FIG.
Reference numeral 40 denotes a control device (ECU) including a microcomputer. The ECU 40 includes, for example, a main computer 41 that performs ignition timing control, fuel injection control, and the like, and a dedicated sub computer 42 that performs knock detection processing, for example. It is composed of two computers.

Further, the constant voltage circuit 4 is provided in the ECU 40.
3 is built in, and a stabilizing voltage is supplied from this constant voltage circuit 43 to each part. This constant voltage circuit 43
Is directly connected to the battery 45 via the relay contact of the ECU relay 44, and the relay coil of the ECU relay 44 is connected to the battery 45 via the key switch 46. Further, the fuel pump 1 is connected to the battery 45 via a relay contact of a fuel pump relay 47.
8 is connected.

The main computer 41 is a main C
PU48, ROM49, RAM50, back-up RA
M50a, timer 51, serial interface (S
The CI) 52 and the I / O interface 53 are connected to each other via a bus line 54.

The input port of the I / O interface 53 has an intake air amount sensor 10, a throttle opening sensor 12a, a cooling water temperature sensor 21, a right bank O2 sensor 25a, a left bank O2 sensor 25b, and an EGR gas temperature sensor. 30 is connected via the A / D converter 55, the idle switch 12b, the starter switch 56, the first and second crank angle sensors 35 and 36, and the cam angle sensor 38 are connected, and the battery is further connected. 45
Is connected and the battery voltage is monitored.

The I / O interface 53 is also provided.
An igniter 16 is connected to an output port of the ISCV 13, an injector 14, an EGR solenoid valve 32, and an engine check lamp (ECS lamp) 5 for displaying an abnormality occurrence via a drive circuit 57.
8. The relay coil of the fuel pump relay 47 is connected.

On the other hand, the sub-computer 42 is a sub-CP.
U59, ROM60, RAM61, timer 62, SCI
63 and an I / O interface 64 are connected to each other via a bus line 65.

At the input port of the I / O interface 64, the first and second crank angle sensors 35, 36,
Also, the cam angle sensor 38 is connected, and the right bank knock sensor 22a and the left bank knock sensor 22b are connected.
, Respectively, an amplifier 66, a frequency filter 67, and A /
It is connected through the D converter 68.

The main computer 41 and the sub computer 42 are connected by a serial line via SCIs 52 and 63, and the output port of the I / O interface 64 of the sub computer 42 is
It is connected to the input port of the I / O interface 53 of the main computer 41.

The detection signals from the knock sensors 22a and 22b are amplified to a predetermined level by the amplifier 66, and then the necessary frequency components are extracted by the frequency filter 67, and are analogized by the A / D converter 68. Data is converted to digital data, and the sub computer 4
At 2, it is determined whether knock has occurred.

The result of determination as to whether or not the knock has occurred is output to the I / O interface 64 of the sub computer 42, and when the knock has occurred, the sub computer 42 sends the main computer 41 through a serial line via the SCIs 63 and 52. The knock data is read in, and the main computer 41 immediately delays the ignition timing of the corresponding cylinder based on the knock data to avoid knock.

Further, the main computer 41 self-diagnoses the abnormality of the ERG valve 29 during the ERG control in the medium load region of the engine, and if the abnormality is diagnosed, E
The CS lamp 58 is turned on to give a warning to the driver and trouble data is stored in the backup RAM 50a. The trouble data stored in the backup RAM 50a is stored in the I / O of the main computer 41.
When the failure diagnosis device 70 is connected to the O interface 53 via the external connector 69, the failure diagnosis device 70 can be read and the failure diagnosis can be easily performed.

[Operation] Next, the operation of the EGR control system will be described with reference to the flowcharts of the EGR control procedure shown in FIGS. 5 and 6.

The flow chart of this EGR control procedure is as follows.
An interrupt routine executed every predetermined time is shown. In step S101, it is determined whether or not the starter switch 56 is ON, that is, whether or not the engine is being cranked, and the starter switch 56 is ON and cranking is being performed. Sometimes, the process branches from step S101 to step S125, and the set value S is set to the count value COUNT of the post-start elapsed time counter.
Set ET (COUNT ← SET), step S126
Then, the EGR solenoid ON determination flag FLAGEGR for determining whether or not the EGR solenoid valve 32 is ON.
Is cleared (FLAGEGR ← 0), and in step 127, EG
The R solenoid valve 32 is turned off to cut the EGR, and the routine ends.

The post-start elapsed time counter is a subtraction counter for counting the elapsed time after the engine is started, and the countdown starts when the starter switch 56 is turned from ON to OFF.

On the other hand, when the starter switch 56 is OFF and the engine is already started in step S101, the process proceeds from step S101 to step S102 to determine whether the count value COUNT of the post-start elapsed time counter is 0 or not. To do. Then, when COUNT = 0, the process jumps to step S104, and when COUNT ≠ 1, the counter is counted down in step S103 (COUNT
NT ← COUNT-1), and in step S104, the value of the EGR solenoid ON determination flag FLAGEGR is referred to.

In step S104, FLAGEGR = 1,
That is, if the EGR solenoid valve 32 is still in the ON state at the time of executing the previous routine, step S1
In 05, the cooling water temperature (hereinafter referred to as E
Set the set value TWEGRL to TWEGR (set to GR water temperature) (TWEGR ← TWEGRL) and proceed to step S107 to set FLAGE
When GR = 0, that is, when the EGR solenoid valve 32 is in the OFF state at the time of the previous routine execution, in step S106, the set value TWEGRH is set to the EGR water temperature TWEGR (TWEGR ← TWEGRH; where TWEGRL <TWEGR
H) Go to step S107.

In step S107, the cooling water temperature TW and ERG are set.
The water temperature is compared with TWEGR. When TW <TWEGR, the routine is exited through steps S126 and S127, and TW ≧ TWE
When the warm-up is completed at GR, the routine proceeds to step S108, and the value of the EGR solenoid ON determination flag FLAGEGR is referred to.

When FLAGEGR = 1, the EGR solenoid valve 32 was ON last time,
The process proceeds from step S108 to step S109, and the vehicle speed (hereinafter, referred to as EGR vehicle speed) V that satisfies the EGR execution condition V
Set the set value VSEGRH to SEGR (VSEGR ← VS
EGRH) Proceed to step S111, FLAGEGR = 0, that is, EGR solenoid valve 3 at the time of the previous routine execution.
When 2 is OFF, the above step S108
To step S110, the set value VSEGRL is set to the EGR vehicle speed VSEGR (VSEGR ← VSEGRL;
VSEGRL <VSEGRH) The process proceeds to step S111.

In step S111, the vehicle speed VSP and the EGR vehicle speed VSEGR are compared, and when VSP> VSEGR, similarly, the routine exits through steps S126 and S127,
When VSP≤VSEGR, in step S112, the value of the EGR solenoid ON determination flag FLAGEGR is referred to, and F
When LAGEGR = 1, in step S113, the set value NEGRH is set to the engine speed NEGR (hereinafter referred to as EGR speed) NEGR that satisfies the EGR execution condition (NEGR ← NEG
RH) and FLAGEGR = 0, in step S114, EG
Set the set value NEGRL to the R speed NEGR (NEGR ← N
EGRL; provided that NEGRL <NEGRH).

Then, the process proceeds from step S113 or step S114 to step S115, and the engine speed NE and the EGR speed NEGR are compared. And NE> NEGR
If, then the routine exits through steps S126 and S127, and if NE ≦ NEGR, then in step S116, the count value COUNT of the post-start elapsed time counter is referred to,
When COUNT ≠ 0, that is, when the engine is started (after the starter switch 56 is turned from ON to OFF) and is less than the predetermined time, the value of the EGR solenoid ON determination flag FLAGEGR is referred to in step S117.

In step S117, FLAGEGR = 1
If so, the routine proceeds to step S118, where the basic fuel injection pulse width TP as the engine load is within the set range (TPEGRL ≦ TP
<TFEGRH), and if FLAGEGR = 0, in step S119, the basic fuel injection pulse width TP
Is within the set range (TPEGRH≤TP <TFEGRL).

Then, as a result of the determination in the above step S118 or step S119, if the engine operating state is within the setting range, it is determined that the engine operating state is in the medium load range, and the process proceeds from step to step S123. Exit the routine through S126 and S127.

On the other hand, in step S116, the count value COUNT of the post-start elapsed time counter is COUNT = 0.
When, that is, after the engine is started (after the starter switch 56 is turned from ON to OFF) and a predetermined time has elapsed, the process branches from step S116 to step S120, and the value of the EGR solenoid ON determination flag FLAGEGR is referred to. If FLAGEGR = 1, step S121
Then, the basic fuel injection pulse width TP is within the set range (TPEGRL ≦
It is determined whether or not TP <TEGRH2), and FLAGEGR =
When it is 0, in step S122, the basic fuel injection pulse width TP
Is within the set range (TPEGRH≤TP <TEGRL2).

Similarly, as a result of the determination in step S121 or step S122, if the engine operating condition is within the set range, it is determined that the engine operating state is in the medium load range and the process proceeds from step to step S123. The routine exits through steps S126 and S127.

At step S123, the EGR solenoid is turned on.
Set the discrimination flag FLAGEGR (FLAGEGR ←
1) In step S124, the EGR solenoid valve 32 is turned on to perform EGR, and the routine ends.

That is, after the engine is started, the cooling water temperature T
When W, the vehicle speed VSP, and the engine speed NE satisfy the EGR condition and the engine operating state is in the medium load range, E
The solenoid coil 32b of the GR solenoid valve 32 is energized to open the valve body 32a.

Then, suction negative pressure leaks from the EGR passage 28 through the valve 31c of the EGR vacuum modulator 31 in accordance with the back pressure applied to the back pressure chamber 31a of the EGR vacuum modulator 31 and into the diaphragm chamber 29b of the EGR valve 29. The suction negative pressure introduced is regulated. As a result, the lift position of the valve element 29a of the EGR valve 29, that is, the valve opening degree is controlled, and the recirculation of exhaust gas to the intake side is controlled.

At this time, a hysteresis is provided for the EGR execution and the EGR cut, and for the cooling water temperature TW, as shown in FIG. 7, when EGR solenoid valve 32 is ON and EGR is being executed, TW <TWEGRL is satisfied. , EGR is cut, EGR solenoid valve 32 is OFF, and E
When TW ≧ TWEGRH during GR cut, EGR is executed.

For the vehicle speed VSP, as shown in FIG. 8, when VSP> VSEGRH during EGR execution,
EGR is cut, and VSP ≤ VSE during EGR cut
When it becomes GRL, EGR is executed. Engine speed NE
As shown in FIG. 9, during the EGR execution, NE
When> NEGRH, EGR is cut, and when NE ≦ NEGRL is satisfied during EGR cutting, EGR is executed.

For the basic fuel injection pulse width TP, when the elapsed time after engine start is less than a predetermined value, as shown in FIG. 10, when EGR is executed, TP <TPEGRL or TP ≧ TFEGRH. , EGR is cut, EG
When the area of TPEGRH≤TP <TFEGRL is entered during R cut, EGR is executed. Further, when a predetermined time elapses after the engine is started, as shown in FIG. 11, when TP <TPEGRL or TP ≧ TEGRH2 during EGR execution, E
GR is cut and TPEGRH≤TP <during EGR cutting
When the area of TEGRL2 is entered, EGR is executed.

With respect to the above EGR control, it is diagnosed whether or not a failure of the exhaust gas recirculation amount adjusting system has occurred. The most likely failure of the exhaust gas recirculation amount adjusting system is a valve stick failure in which the valve element 29a of the EGR valve 29 is stuck due to carbon adhesion in the exhaust gas.
There is a malfunction of the GR solenoid valve 32 or the EGR vacuum modulator 31.

Any of these malfunctions in the exhaust gas recirculation amount adjusting system results in an abnormality of the EGR valve 29, and can be detected by the EGR valve stick determination procedure described below.

The flowcharts of FIGS. 1 to 4 show a routine executed every predetermined time after the key switch 46 is turned on, and a judgment is made of a close stick failure in which the valve body 29a of the EGR valve 29 remains closed. Close stick determination (steps S201 to S228) and EGR
The open stick determination (after step S229) is for determining an open stick failure in which the valve element 29a of the valve 29 remains open.

First, in step S201, the value of the close stick clear determination flag FLAGCLC stored at a predetermined address of the RAM 50 is referred to. The close stick clear determination flag FLAGCLC is set to 1 when the clear determination without abnormality is made in the close stick determination, and the initial value is
FLAGCLC = 0. If the clear stick determination is once made in the close stick determination, the close stick determination is not performed until the key switch 46 is turned off.

That is, in step S201, FLAG
When CLC = 1, jump to step S229 to shift to open stick determination, and when FLAGCLC = 0, proceed from step S201 to step S202 above, and in steps S202 to S207, diagnosis for performing close stick determination. Check whether the condition is met.

In order to check whether or not this diagnostic condition is satisfied, in step S202, the cooling water temperature TW is set to the set water temperature EGRT.
It is determined whether or not W (for example, 60 ° C.) or more, and TW ≧ EG
When RTW, in step S203, it is determined whether or not the EGR solenoid valve 32 is ON by referring to the value of the EGR solenoid ON determination flag FLAGEGR. As a result, FL
AGEGR = 1 and the EGR solenoid valve 32 is O
If it is N, it is determined in step S204 whether the output voltage TSEGR of the EGR gas temperature sensor 30 is equal to or higher than a set value MEGRT1 (for example, 1.0 V).

As shown in FIG. 14, the EGR gas temperature sensor 30 has a characteristic that the output voltage is high when the detected temperature is low, and the output voltage is decreased as the detected temperature rises.
For example, when the detected temperature is 15 ° C, the output voltage is about 4.5.
The output voltage is approximately 2.8 V when V and 50 ° C., and the output voltage is approximately 1.0 V when the detected temperature is 90 ° C. When TSEGR <MEGRT1, the EGR passage 2 is output.
The temperature of 8 is about 90 ° C or higher.

Therefore, through the above steps S202 and S203, the process proceeds to step S204, and when TSEGR <MEGRT1, the cooling water temperature TW is the temperature (60 ° C. or more) above the completion of warming up, and the EGR solenoid valve 32 is turned on. In this state, since the temperature of the EGR passage 28, which indicates the temperature of the exhaust gas recirculation gas, is approximately 90 ° C. or higher, it is determined that the exhaust gas is normally recirculating to the intake side, and the process jumps to step S222.

In step S222, the backup RAM 5
Clear the close stick determination data CLST stored at a predetermined address of 0a (CLST ← 0) EC
The S lamp 58 is kept off, the close stick clear determination flag FLAGCLC is set (FLAGCLC ← 1) in step S223, and the process proceeds to the open stick determination in step S229 and subsequent steps.

On the other hand, in step S204, TSEGR ≧ MEG
When the temperature is RT1 (when the temperature of the EGR passage 28 is lower than about 90 ° C.), the steps S204 to S205 are performed.
To the output voltage TSEGR of the EGR gas temperature sensor 30.
Is lower than the set value EGRCTS (for example, 4.5V).

As a result, when TSEGR <EGRCTS, that is, when the temperature of the EGR passage 28 is higher than approximately 15 ° C., the routine proceeds from step 205 to step S206, where the engine speed NE is within the set range (ERPML≤NE < ER
PMH; For example, ERPML = 1500 rpm, ERPM
H = 2500 rpm), and if it is within the setting range, in step S207, the basic fuel injection pulse width TP as the engine load is within the setting range (ERGTPL).
≤TP <EGRTPH; for example, ERGTPL = 3.0 ms,
EGRTPH = 4.5 ms).

When the basic fuel injection pulse width TP is within the set range, the steps S207 to S207 are performed.
The process proceeds to S208, and the value of the diagnosis condition satisfaction determination flag FLAGCON is referred to. This diagnostic condition satisfaction determination flag FLAGCON
When FLAGCON = 1, the above steps S202, S2
The conditions of 03, S205, S206, S207 are satisfied, and the cooling water temperature TW is 6
At 0 ° C or higher, the EGR solenoid valve 32 is in the ON state, the temperature of the EGR passage 28 is higher than about 15 ° C, and the engine speed NE and the basic fuel injection pulse width TP are in a predetermined operating range. It means that the diagnosis condition is satisfied within the range, and when FLAGCON = 0, the condition is not satisfied in any step,
Indicates that the diagnostic conditions are not met.

Therefore, the above steps S202, S203, S20 are performed.
After going through 5, S206 and S207, proceed to the above step S208, where FLAGC
When ON = 0, since it is the first time that the diagnostic condition is not satisfied and the diagnostic condition is satisfied, the diagnostic condition satisfaction determination flag FLAGCON is set (FLAGCON) in step S209.
← 1), when FLAGCON = 1, the condition is not satisfied for the first time, and therefore the process jumps to step S213.

After setting the diagnostic condition satisfaction determination flag FLAGCON in step S209, step S21 is performed.
Going to 0, the output voltage TSEG of the EGR gas temperature sensor 30
Let R be the output voltage TSEGR0 after the diagnosis condition is satisfied (TSEGR
0 ← TSEGR).

Next, in step S211, it is determined whether or not the output voltage TSEGR0 of the EGR gas temperature sensor 30 after the diagnosis condition is satisfied is equal to or higher than a set value EGRETS (for example, 2.8V), and when TSEGR0 ≧ EGRETS, that is, When the temperature of the EGR passage 28 is about 50 ° C. or lower, the failure determination execution determination flag FLAGTS is set (FLAGTS ← 1) in step S212, and the process proceeds to step S213.

Failure determination execution determination flag FLAGTS
When FLAGTS = 1, the above steps S202, S20
Since the temperature of the EGR passage 28 is about 50 ° C. or less after the diagnosis condition is satisfied through 3, S205, S206, and S207, and after this diagnosis condition is satisfied in step S211, a failure determination is made. And in step S211 above, TSEGR0 <E
When it is GRETS (the temperature of the EGR passage 28 is approximately 50 °
If it is higher than C), the failure judgment is not performed and the step
The process branches from S211 to step S225 to clear the failure determination execution determination flag FLAGTS (FLAGTS ← 0).

Further, each step S202, S203, S205, S206, S2
If the condition is not satisfied in any of the steps 07, the process branches from the corresponding step to step S224 to clear the diagnosis condition satisfaction determination flag FLAGCON (FLAGCON ←
0), and then in step S225, the failure determination execution determination flag FLAGTS is cleared (FLAGTS ← 0).

Then, from step S225 to step S2
26, and the first counter is displayed for a predetermined time (for example, 7se
c) Set value EGRTMR corresponding to count value COUNT
Set as CLC (COUNT CLC ← EGR
TMR), in step S227, the set value EGRTMR is set as the count value COUNTCLS in the second counter (COUNTCLS ← EGRTMR).

The first and second counters are both down counters, and when the count value becomes 0,
It can be seen that the time corresponding to the set value has elapsed.

After that, the above steps S227 to S2
Proceed to 28, and close stick clear determination flag FLA
Clear GCLC (FLAGCLC ← 0) and step S229
The process shifts to the subsequent open stick determination.

On the other hand, the above step S212 or step
When step S213 is reached after step S208, the value of the failure determination execution determination flag FLAGTS is referred to in step S213, and FLA
When GTS = 0, the process proceeds to the open stick determination after step S229 through the above-described steps S226, S227, S228, and when FLAGTS = 1, at step S214, the first
It is determined whether or not the count value COUNTCLC of the counter is zero.

In step S214, COUNTCLC = 0
In case of, jump to step S216, COUNTCL
When C ≠ 0, the first counter is counted down (COUNTCLC ← COUNTCLC− in step S215).
1) In step S216, an output change ΔTS between the output voltage TSEGR0 of the EGR temperature sensor 30 when the diagnostic condition is satisfied and the current output voltage TSEGR of the EGR temperature sensor 30 is calculated (ΔTS ← TSEGR0-TSEGR).

Next, the above steps S216 to S217
Then, it is determined whether the output change ΔTS of the EGR temperature sensor 30 is smaller than the set value EGR DTS (for example, 0.1 V). If ΔTS ≧ EGR DTS, the process branches to step S221 and the count value of the first counter is increased. The value of COUNTCLC is checked, and when COUNTCLC ≦ 0, the process proceeds to step S229 through steps S227 and S228, and then COUNTCLC.
When LC> 0, even if the temperature of the EGR passage 28 is 50 ° C. or less when the diagnostic condition is satisfied, a predetermined time (for example, 7
Since the temperature of the exhaust gas recirculation gas has changed by a set value (the temperature corresponding to EGR DTS) or more within sec), the EGR clear determination is made without any abnormality, and the process proceeds to step S229 through steps S227 and S228 described above.

On the other hand, at the step S217, ΔTS <EG
In the case of RDTS, the above steps S217 to S218
Then, the process proceeds to and it is determined whether or not the count value COUNTCLS of the second counter is 0. As a result of the determination, the above step S218
When COUNTCLS = 0 and ΔTS <EGRDTS continues for a set time (for example, 7 seconds), E
Despite the fact that the GR solenoid valve 32 is ON, the valve body 29a of the EGR valve 29 remains closed, and it is determined that the exhaust gas is not recirculated to the intake system due to the close stick, and the process proceeds to step S219. Go ahead, C
When COUNTCLS ≠ 0, the process branches from step S218 to step S220 to count down the second counter (COUNTCLS ← COUNTCLS-1), and at step S228, the close stick clear determination flag FLA is obtained.
Clear GCLC (FLAGCLC ← 0).

That is, after the diagnosis condition is established, the EGR passage 2
Since the temperature of 8 is 50 ° C. or lower and the temperature change is small even after the set time (for example, 7 seconds) has elapsed, the close-stick failure is determined, so the outside air temperature is low, Even if the exhaust gas recirculation gas temperature detected by the EGR temperature sensor 30 is lower than the actual temperature,
The failure can be accurately determined and erroneous determination can be prevented.

In rare cases, the EGR solenoid valve 32
Alternatively, due to a failure of the EGR vacuum modulator 31, the valve body 29a of the EGR valve 29 may remain closed and exhaust gas may not be recirculated to the intake system.
Even in this case, the abnormality can be detected by the close stick determination.

Then, from step S218 to step S2
At step 19, the close stick determination data CLST is set to 1 (CLST ← 1), the ECS lamp 58 is turned on to inform the driver of the occurrence of an abnormality, and the step
In S228, the close stick clear determination flag FLAG
Clear CLC (FLAGCLC ← 0).

Next, the open stick determination after step S229 will be described. In step S229, RAM
The value of the open stick clear determination flag FLAGCLO stored in 50 is referred to, and when FLAGCLO = 1, the routine exits. The open stick clear determination flag FLAGCLO is set to 1 when a clear determination without any abnormality is made in the open stick determination, and the initial value is FLAGCLO = 0.

In the open stick determination, once the clear determination is made, the open stick determination is not performed until the key switch 46 is turned off, as in the above-described close stick determination.

On the other hand, in step S229, FLAGCLO
= 0, in steps S230, S231, and 232, the state of the cooling water temperature TW and the EGR solenoid valve 32 are respectively set.
It is determined whether or not the diagnosis condition is satisfied based on the driving state of 1 and the driving state of the engine.

That is, in step S230, the cooling water temperature TW
Is lower than the set water temperature EGRTW2 (for example, 40 ° C), and when TW <EGRTW2, the routine proceeds to step S231, where the EGR solenoid ON discrimination flag FLAGEGR
Value of FLAGEGR = 0, that is, E
When the GR solenoid valve 32 is OFF, the routine proceeds to step S232, where it is judged if the engine speed NE is not 0, that is, if the engine is stalled (engine stopped).

If the condition is not satisfied in any of the above steps S230, S231, S232, the diagnostic condition is not satisfied, and the process jumps from the relevant step to step S242 and the third counter, for example, 60 sec. Is set as the count value COUNTCLO (COUNTCLO ← EGRTR3), and in step S243, the set value EGRTR2 corresponding to, for example, 10 seconds is set as the count value COUNTOPS in the fourth counter (COUNTOPS ← EGRTR2). , Step S244
Then, open stick clear judgment flag FLAGCLO
To clear (FLAGCLO ← 0) and exit the routine.

The third and fourth counters are down counters like the first and second counters.

On the other hand, when all the conditions in the above-mentioned steps S230, S231, S232 are satisfied and the diagnostic conditions are satisfied, the process proceeds from step S232 to step S233, and the output voltage TSEGR of the EGR gas temperature sensor 30 is set to the set value MEGRT2 ( For example, ME
It is determined whether GRT2 = 2.0V or lower (approximately 65 ° C.).

As a result of the determination in step S233, TSE
When GR <MEGRT2, that is, when the temperature of the EGR passage 28 is higher than approximately 65 ° C., the process proceeds to step S234, the count value COUNTOPS of the fourth counter is checked, and when COUNTOPS ≠ 0, the fourth value is obtained in step S236. Count down the counter of (COUNTOPS ←
COUNTOPS-1) Proceed to step S237 and proceed to COUNTO
When PS = 0, that is, when the engine is in the cold state, E
Even though the GR solenoid valve 32 is turned off and the EGR is cut, the temperature of the EGR passage 28 detected by the EGR gas temperature sensor remains higher than about 65 ° C for a predetermined time (for example, 10 seconds). If so, the valve body 29a of the EGR valve 29 remains open and it is determined that there is an open stick failure in which exhaust gas is returned to the intake system, and the routine proceeds to step S235.

Then, in step S235, the backup R
The open stick determination data OPS of the AM 50a is set to 1 (OPS ← 1), the ECS lamp 58 is turned on to inform the driver of the occurrence of an abnormality, and the repair is urged. In step S237, the set value is set in the third counter. EGRTR
When 3 is set as the count value COUNTCLO ((CO
UNCLO ← EGRTR3), in step S244, the open stick clear determination flag FLAGCLO is cleared (FLAGCLO ← 0) and the routine exits.

On the other hand, in step S233, TSEGR ≧ MEG
At RT2, that is, the temperature of the EGR passage 28 is about 65.
When the temperature is below ° C, the above steps S233 to S2
Branch to 38, and count value COUNTCL of the third counter
Examine O. Then, when COUNTCLO ≠ 0, in step S241, the third counter is counted down (COUNT
After TCLO ← COUNTCLO-1), the above step S2
When the routine exits after 43 and S244 and COUNTCLO = 0, it is determined that there is no abnormality because the temperature of the EGR passage 28 is kept at about 65 ° C. or lower for a predetermined time (for example, 60 seconds). In S239, the open stick determination data OPS is cleared and (OP
ST ← 0) Keep the ECS lamp 58 in the off state, and in step S240, open stick clear determination flag FLA
Set GCLO (FLAGCLO ← 1) and exit the routine.

A failure diagnosis device 70 is connected to the ECU 40 when a failure is diagnosed by the above EGR valve stick determination routine and a repair is carried out at a service factory. Then, with this failure diagnosis device 70, the backup RA
By reading the close stick determination data CLST and the open stick determination data OPS stored in the M50a, it is possible to immediately determine whether there is a close stick failure or an open stick failure.

[0094]

As described above, according to the present invention, the abnormality of the exhaust gas recirculation system in the exhaust gas recirculation execution state can be accurately detected without being affected by the outside air temperature, and erroneous diagnosis is prevented. It is possible to obtain an excellent effect.

[Brief description of drawings]

FIG. 1 is a flowchart (part 1) of an EGR valve stick determination procedure.

FIG. 2 is a flowchart (part 2) of an EGR valve stick determination procedure.

FIG. 3 is a flowchart (part 3) of the EGR valve stick determination procedure.

FIG. 4 is a flowchart of an EGR valve stick determination procedure (4).

FIG. 5 is a flowchart of an EGR control procedure (No. 1)

FIG. 6 is a flowchart (part 2) of the EGR control procedure.

FIG. 7 is an explanatory diagram showing hysteresis during EGR cut.

FIG. 8 is an explanatory diagram showing hysteresis during EGR cut.

FIG. 9 is an explanatory diagram showing hysteresis during EGR cut.

FIG. 10 is an explanatory diagram showing hysteresis during EGR cut.

FIG. 11 is an explanatory diagram showing hysteresis during EGR cut.

FIG. 12 is a schematic diagram of an engine control system.

FIG. 13 is a circuit configuration diagram of the control device.

FIG. 14 is a characteristic diagram of an EGR gas temperature sensor.

[Explanation of symbols]

 28 EGR passage 29 EGR valve 30 EGR gas temperature sensor 31 EGR vacuum modulator 32 EGR solenoid valve

Claims (1)

[Claims] 1. A method for detecting an abnormality in an exhaust gas recirculation system of an engine, which recirculates exhaust gas from an exhaust system to an intake system via an exhaust gas recirculation amount adjustment valve, wherein an upstream side of the exhaust gas recirculation amount adjustment valve under a predetermined diagnostic condition. When the temperature of the exhaust gas recirculation gas detected on the side is equal to or lower than a preset temperature threshold value and the time change of the detected temperature is within a preset temperature change threshold value, the exhaust gas including the exhaust gas recirculation amount adjustment valve is included. A method for detecting an abnormality in an exhaust gas recirculation system of an engine, comprising: determining that the recirculation amount adjustment system is abnormal.