JP2003028000A - Diagnostic system for intake air temperature sensor for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve diagnostic accuracy by diagnosing an intake air temperature sensor in consideration of an engine room temperature. SOLUTION: An execution condition flag is referred to (S51), and if the execution condition flag is set, a difference (TAMAX-TAMIN) between a maximal intake air temperature TAMAX and a minimal intake air temperature TAMIN is compared with a determination threshold kTA indicative of characteristic degradation of the intake air temperature sensor (S52). If TAMAX-TAMIN>=kTA, the intake air temperature sensor is determined to be normal and an intake air temperature sensor characteristic NG flag is cleared (S53). If TAMAX-TAMIN<kTA, on the other hand, whether a room warm-up end flag is set or not is checked (S54). If the room warm-up end flag is set, the intake air temperature sensor is determined to be abnormal and the intake air temperature sensor characteristic NG flag is set (S55). A misdiagnosis of the intake air temperature sensor due to an influence of an engine room temperature is prevented, and diagnostic accuracy is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for an engine intake air temperature sensor that takes into consideration the temperature inside an engine chamber.

[0002]

2. Description of the Related Art Conventionally, in the diagnosis of an intake air temperature sensor for measuring the temperature of intake air of an engine, the difference between the intake air temperature detected by the intake air temperature sensor under two different conditions is compared with a predetermined judgment value. Therefore, the presence or absence of abnormality is determined. For example, in Japanese Patent Application Laid-Open No. 9-303191, the intake air temperature detected by an intake air temperature sensor under the first operating condition depending on the outside air temperature and the intake air temperature under the second operating condition depending on the heat generation of the internal combustion engine. A technique has been disclosed in which a difference from the intake air temperature detected by the sensor is obtained, and the difference is compared with a predetermined determination value to determine whether or not there is an abnormality in the intake air temperature sensor.

[0003]

However, the temperature of the intake system to which the intake air temperature sensor is attached is greatly influenced by the temperature inside the engine chamber, and the vehicle travels down a long downhill in an environment where the outside air temperature is low such as in winter. In such a case, since the engine load is small and the exhaust temperature is low, the temperature in the engine chamber becomes low, and the temperature in the engine chamber becomes low due to the traveling wind depending on the vehicle speed. Therefore, under such a condition, the difference between the output values of the intake air temperature sensor is small, and if the compensation for the temperature inside the engine chamber is not performed as in the prior art, the diagnostic accuracy is reduced.

The present invention has been made in view of the above circumstances, and a diagnostic device for an intake air temperature sensor for an engine which can improve the diagnostic accuracy by diagnosing the intake air temperature sensor in consideration of the temperature inside the engine chamber. Is intended to provide.

[0005]

In order to achieve the above object, the invention according to claim 1 is a condition for executing a diagnosis of an intake air temperature sensor for measuring a temperature of intake air of an engine based on an engine cooling water temperature and a vehicle speed. The exhaust gas temperature is estimated based on the engine operating state and the diagnostic execution condition determining means for determining whether or not is satisfied, and the estimated value of the exhaust temperature is used to determine the warm-up completion state in the engine chamber above the set temperature. An engine chamber warm-up completion determining means for determining whether or not there is, and a determination threshold value preset with a difference between the maximum value and the minimum value of the intake temperature measured by the intake temperature sensor when the diagnosis execution condition is satisfied. And a diagnostic means for determining that the intake air temperature sensor is abnormal when the difference between the maximum value and the minimum value of the intake air temperature is smaller than the determination threshold value and the inside of the engine chamber is in the warm-up completion state. To And it said that there were pictures.

According to a second aspect of the present invention, in the first aspect of the present invention, the engine bunch warm-up completion determining means sets a basic estimated value of the exhaust temperature based on the engine speed and the engine load, This basic estimated value is corrected by a smoothing coefficient based on the engine cooling water temperature to obtain an estimated value of the exhaust temperature.

According to a third aspect of the invention, in the second aspect of the invention, the intake pipe pressure or the intake air amount is used as the engine load.

That is, according to the first aspect of the present invention, it is determined whether or not the diagnosis execution condition of the intake air temperature sensor for measuring the temperature of the intake air of the engine is satisfied on the basis of the engine cooling water temperature and the vehicle speed. The temperature of the exhaust gas is estimated based on the operating state, and it is determined from the estimated value of the exhaust temperature whether or not the engine compartment is in the warm-up completion state at the set temperature or higher. Then, when the diagnosis execution condition is satisfied, the diagnosis is executed by comparing the difference between the maximum value and the minimum value of the intake air temperature measured by the intake air temperature sensor with a preset determination threshold value,
As a result, when the difference between the maximum value and the minimum value of the intake air temperature is smaller than the determination threshold and the inside of the engine chamber is in the warm-up completed state, it is determined that the intake air temperature sensor is abnormal. Compensation for the temperature in the engine chamber is performed without using, and the diagnostic accuracy of the intake air temperature sensor is improved.

At this time, as the estimated value of the exhaust temperature, the basic estimated value of the exhaust temperature is set on the basis of the engine speed and the engine load, and this basic estimated value is set to the engine. It is desirable to obtain it by correcting with a moderating coefficient based on the cooling water temperature, and as the engine load,
As in the invention described in claim 3, the intake pipe pressure or the intake air amount can be used.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 9 relate to an embodiment of the present invention, FIG. 1 is an overall view of an engine system, FIG. 2 is a circuit configuration diagram of an electronic control system, FIG. 3 is a flowchart of a determination parameter initialization routine, and FIG. 5 is a flowchart of an execution condition determination routine, FIG. 6 is a flowchart of an estimated exhaust temperature calculation routine, FIG. 7 is an explanatory diagram of an estimated exhaust temperature calculation search map, and FIG. 8 is a smoothing coefficient table. FIG. 9 is a flowchart of the diagnosis determination routine.

In FIG. 1, reference numeral 1 is an engine, and in the figure, a DOHC horizontally opposed four-cylinder gasoline engine is shown. Cylinder block 1 of this engine 1
A cylinder head 2 is provided in each of the left and right banks of a, and an intake port 2a and an exhaust port 2b are formed in each cylinder head 2 for each cylinder. An intake cam shaft 3 and an exhaust cam shaft 4 are provided in each cylinder head 2 of the left and right banks, and a crank pulley 5, a timing belt 6, and an intake cam shaft 3 fixed to the crank shaft 1b are provided. The rotation of the crankshaft 1b is transmitted to the intake camshaft 3 and the exhaust camshaft 4 via the intake cam pulley 7 and the exhaust cam pulley 8 fixed to the exhaust camshaft 4 and the like, and is 1/2 of the crankshaft 1b. Rotate.

Further, as an intake system of the engine 1, an intake manifold 9 is communicated with each intake port 2a, and a throttle valve 11a is provided in the intake manifold 9 via an air chamber 10 in which intake passages of each cylinder are gathered. The throttle chamber 11 is also in communication. An intercooler 12 is provided upstream of the throttle chamber 11, the intercooler 12 is in communication with a compressor 14b of a turbocharger 14 via an intake pipe 13, and an air intake chamber 16 is further provided with an air cleaner 15. Are in communication.

Further, the throttle chamber 11 is provided with a bypass passage 17 for bypassing the throttle valve 11a, and an idle for controlling the idle speed by adjusting the amount of bypass air flowing through the bypass passage 17 in the bypass passage 17. A control valve (ISC valve) 18 is provided. Further, an injector 19 is provided immediately upstream of the intake port 2a of each cylinder of the intake manifold 9, and an ignition plug 20 is provided for each cylinder of the cylinder head 2. The spark plug 20 is connected to the secondary winding side of the ignition coil 21 with a built-in igniter (see FIG. 2).

On the other hand, in the exhaust system of the engine 1, the exhaust manifold 22 communicating with each exhaust port 2b of the cylinder head 2 joins the exhaust, and an exhaust pipe 23 is connected to the exhaust manifold 22. The turbine 14a of the turbocharger 14 is installed in the exhaust pipe 23, and downstream thereof,
A catalyst 24 and a muffler 25 are provided and opened to the atmosphere.
In the turbocharger 14, the compressor 14b is rotationally driven by the energy of the exhaust gas introduced into the turbine 14a to suck and pressurize air for supercharging.
A waste gate valve 27 having a waste gate valve actuating actuator 26 composed of a diaphragm type actuator is provided on the a side.

Actuator 2 for operating the wastegate valve
6 is divided into two chambers by a diaphragm, one of which is a duty solenoid valve D.D. A pressure chamber communicating with the SOL is formed, and the other accommodates a spring that biases the wastegate valve 27 in the closing direction and forms a spring chamber in which a rod connecting the diaphragm and the wastegate valve 27 is extended. And the spring chamber is open to the atmosphere.

Further, the duty solenoid valve D.D. The SOL is a port that communicates with the pressure chamber of the wastegate valve actuating actuator 26, the intake pipe 13 downstream of the compressor 14b of the turbocharger 14 via the orifice 28, and the port that communicates with the intake pipe 13 upstream of the compressor 14b. And a valve opening degree of a port of a port communicating with the intake pipe 13 upstream of the compressor 14b according to a duty ratio of a control signal output from an electronic control unit 40 (see FIG. 2) described later. Then, the pressure on the upstream side and the pressure on the downstream side of the compressor 14b are adjusted to supply control pressure to the pressure chamber of the waste gate valve operating actuator 26, and the opening degree of the waste gate valve 27 is adjusted to supercharge. The pressure is controlled.

Here, the sensors for detecting the engine operating state will be described. Immediately downstream of the air cleaner 15 of the intake pipe 13, an intake air amount sensor 30a for measuring the intake air amount and an intake air amount sensor 30b for measuring the temperature of the intake air are integrally incorporated.
An intake air temperature measurement unit 30 is installed. Further, a throttle opening sensor 31 is connected to a throttle valve 11a provided in the throttle chamber 11,
At 0, an intake pipe pressure sensor 32 for measuring the pressure in the intake pipe as an absolute pressure is exposed. Further, a knock sensor 33 is attached to the cylinder block 1a of the engine 1, and a cooling water temperature sensor 34 is exposed to a cooling water passage 1c that connects the left and right banks of the cylinder block 1a.

An air-fuel ratio sensor 35 is arranged in the exhaust pipe 23 at the confluence of the exhaust manifolds 22 of each bank. Further, a crank angle sensor 37 for detecting a protrusion for crank angle detection formed on the outer periphery of the crank rotor 36 is provided on the outer periphery of the crank rotor 36 axially attached to the crank shaft 1b of the engine 1, and the crank angle sensor 37 is provided in one bank. On the rear surface of the intake cam pulley 7, a cylinder discrimination sensor 38 for detecting a protrusion for cylinder discrimination formed on the outer peripheral side of the rear surface of the intake cam pulley 7 is provided oppositely.

Next, the structure of the electronic control system for controlling the engine 1 will be described. The signals from the various sensors described above are processed by the electronic control unit (ECU) 40 shown in FIG. 2, the control amounts for the various actuators are calculated, and fuel injection control, ignition timing control, idle speed control, and overspeed control are performed. Engine control such as supply pressure control is performed.

The ECU 40 includes a CPU 41, a ROM 42,
A RAM 43, a backup RAM 44, a counter / timer group 45, and an I / O interface 46 are mainly configured by a microcomputer connected via a bus line, and a constant voltage circuit 47 that supplies a stabilized power supply to each unit,
Drive circuit 4 connected to I / O interface 46
8. A peripheral circuit such as A / D converter 49 is built in.
The counter / timer group 45 is a free-run counter,
Input of cylinder discrimination sensor signal (cylinder discrimination pulse) Various counters such as counter, fuel injection timer, ignition timer, periodic interrupt timer for generating periodic interrupt, input of crank angle sensor signal (crank pulse) Various timers such as the interval timer and the watchdog timer for monitoring the system abnormality are collectively referred to for convenience, and various software counters and timers are used.

The constant voltage circuit 47 is connected to the battery 51 via a first relay contact of a power supply relay 50 having two relay contacts. The power relay 50 has one end of its relay coil grounded and the other end of the relay coil connected to the drive circuit 48. A power supply line for supplying power from the battery 51 to each actuator is connected to the second relay contact of the power supply relay 50.

Further, one end of an ignition switch 52 is connected to the battery 51, and the other end of the ignition switch 52 is connected to an input port of the I / O interface 46. The constant voltage circuit 47 is directly connected to the battery 51, and when ON of the ignition switch 52 is detected and the contact of the power supply relay 50 is closed, power is supplied to each part in the ECU 40 while the ignition switch is turned on. Regardless of whether 52 is ON or OFF, backup power is always supplied to the backup RAM 44.

The knock sensor 33 and the crank angle sensor 3 are connected to the input port of the I / O interface 46.
7, a cylinder discrimination sensor 38, a vehicle speed sensor 39 for detecting a vehicle speed, etc. are connected, and further, an intake air amount sensor 30a, an intake air temperature sensor 30b, a throttle opening sensor 31, via an A / D converter 49, The intake pipe pressure sensor 32, the cooling water temperature sensor 34, the air-fuel ratio sensor 35, etc. are connected, and the battery voltage VB is input and monitored. On the other hand, the output port of the I / O interface 46 has an I
SC valve 18, injector 19, duty solenoid valve D. SOL, an alarm lamp 53 for notifying the driver of an abnormality when an abnormality occurs, and a relay coil of the power supply relay 50 are connected via a drive circuit 48, and
An ignition coil 21 with a built-in igniter is connected.

The I / O interface 46 also includes
An external connection connector 55 is connected. By connecting a serial monitor (portable failure diagnosis device) 60 to the external connection connector 55, the serial monitor 60 causes input / output data in the ECU 40 and the ECU 40.
With the self-diagnosis function, the failure portion (including the intake air temperature sensor characteristic NG flag indicating an abnormality of the intake air temperature sensor 30b described later) stored in the backup RAM 44 and the trouble data indicating the failure content can be read and diagnosed.
Further, the serial monitor 60 allows the initial setting (clearing) of trouble data. The diagnosis of trouble data by the serial monitor 60 and the initial set are described in detail in Japanese Patent Publication No. 7-76730 by the applicant.

The CPU 41 processes the detection signals from the sensors and switches input via the I / O interface 46, the battery voltage, etc. in accordance with the control program stored in the ROM 42, and stores them in the RAM 43. Based on the data, the various learning value data stored in the backup RAM 44, the fixed data stored in the ROM 42, and the like, the injector 19, the ignition coil 21 with the built-in igniter, the ISC valve 18, the duty solenoid valve D.D. A control amount for SOL or the like is calculated, and engine control such as fuel injection control, ignition timing control, ISC control, supercharging pressure control is performed.

In this case, in the fuel injection control by the ECU 40, when the fuel injection amount commensurate with the intake air amount is determined according to the engine operating state, the density change due to the temperature change of the intake air is compensated, and the proper fuel is injected. In order to maintain the injection amount, the reliability of the intake air temperature sensor 30b that measures the intake air temperature is important. Therefore, the ECU 40 monitors the intake air temperature sensor 30b and the peripheral system for any abnormality by executing the diagnosis of the intake air temperature sensor 30b every predetermined time.

In diagnosing the intake air temperature sensor 30b, first, it is determined whether or not the conditions for executing the diagnosis of the intake air temperature sensor 30b are satisfied based on the engine cooling water temperature and the vehicle speed. It is determined whether or not a diagnosis condition that the vehicle is traveling at a speed equal to or higher than a set vehicle speed with the machine completed is satisfied. At the same time, the temperature of the exhaust gas is estimated based on the engine operating state, and from this estimated value of the exhaust temperature, whether or not the temperature in the engine chamber has reached a temperature sufficient to raise the intake temperature in the warm-up completed state above the set temperature. To determine.

When the diagnosis execution condition of the intake air temperature sensor 30b is satisfied and it is estimated from the exhaust gas temperature estimated value that the temperature inside the engine chamber is equal to or higher than the set temperature, the intake air temperature sensor 30b measures the intake air temperature. The difference between the maximum value and the minimum value of the temperature is compared with a preset determination threshold value, and the diagnosis of the intake air temperature sensor 30b is executed. As a result, when the difference between the maximum value and the minimum value of the intake air temperature is equal to or more than the determination threshold value, it is determined that the intake air temperature sensor 30b is normal, and the difference between the maximum value and the minimum value of the intake air temperature is greater than the determination threshold value. The intake air temperature sensor 3 is small, and when the temperature inside the engine chamber is in the warm-up completion state, that is, although the intake air temperature surely changes.
If a predetermined output change is not obtained from 0b, it is determined that the sensor itself of the intake air temperature sensor 30b or the wiring system is abnormal.

That is, the ECU 40 realizes the functions of the diagnostic execution condition determining means, the engine interior warm-up completion determining means, and the diagnostic means according to the present invention. Below, ECU4
FIG. 3 shows the diagnosis process of the intake air temperature sensor 30b based on 0.
~ It demonstrates using the flowchart shown in FIG. 6, FIG.

In FIG. 3, the ignition switch 52 is turned on.
The determination parameter initialization routine is executed only once after the ECU 40 is turned on, the ECU 40 is powered on, and the CPU 41 is power-on reset. In this routine, the maximum intake air temperature T which is a memory value for detecting the maximum value and the minimum value of the intake air temperature TA measured by the intake air temperature sensor 30b.
Initialize AMAX and minimum intake air temperature TAMIN.

That is, first, in step S11, the minimum data value 0000H is stored as the initial value in the maximum intake air temperature TAMAX, and then in step S2, the minimum intake air temperature TAMAX is stored.
The maximum data value FFFFH is stored in MIN as an initial value and the routine exits. That is, the maximum intake air temperature TAMA
By initializing X with the minimum data value 0000H and the minimum intake air temperature TAMIN with the maximum data value FFFFH, as described below, as long as the intake air temperature sensor 30b is normal,
The maximum intake air temperature TAMAX and the minimum intake air temperature TAMIN can be updated by the measured intake air temperature TA.

Next, when the initialization process for diagnosis is completed, the determination parameter calculation routine of FIG. 4 is executed every predetermined time (for example, every 512 msec) and the minimum value of the intake air temperature measured by the intake air temperature sensor 30b. And the maximum value are recorded, and it is determined whether the condition for executing the diagnosis of the intake air temperature sensor 30b is satisfied by executing the execution condition determination routine of FIG. 5 at every predetermined time (for example, every 1024 msec). It Further, the estimated exhaust gas temperature calculation routine of FIG. 6 is executed every predetermined time (for example, every 128 msec), and the temperature in the engine chamber reaches a temperature sufficient to raise the intake air temperature based on the estimated value of the exhaust gas temperature. It is determined whether or not. Then, the diagnosis determination routine of FIG. 9 is executed every predetermined time (for example, every 1024 msec), and the change of the intake air temperature measured by the intake air temperature sensor 30b under the condition of execution of the diagnosis (difference between the maximum value and the minimum value). Is judged to have reached the judgment threshold value.

In the determination parameter calculation routine of FIG.
First, in step S21, the current maximum intake air temperature T stored in the intake air temperature TA measured by the intake air temperature sensor 30b is stored.
Check whether it is higher than AMAX. And TA> T
In the case of AMAX, the routine proceeds to step S22, the maximum intake air temperature TAMAX is updated by the intake air temperature TA by the intake air temperature sensor 30b (TAMAX = TA), and the routine is exited.

In step S21, TA≤TA
In the case of MAX, the routine proceeds to step S23, where the intake air temperature TA detected by the intake air temperature sensor 30b is the current minimum intake air temperature TA.
Check whether it is lower than MIN. And TA ≧ TAM
In the case of IN, the routine exits from step S23,
When TA <TAMIN, the routine proceeds from step S23 to step S24, where the intake air temperature T detected by the intake air temperature sensor 30b is T.
The minimum intake air temperature TAMIN is updated at A (TAMIN = T
A), exit the routine. After that, the routine is repeated, and the maximum value of the intake air temperature TA by the intake air temperature sensor 30b is the maximum intake air temperature TAMAX, and the minimum value is the minimum intake air temperature TA.
Each is recorded as MIN.

On the other hand, the execution condition judging routine of FIG. 5 judges whether or not the diagnosis can be executed, and operates the execution condition satisfaction flag. In other words, when the vehicle is running at a speed equal to or higher than the set vehicle speed with the engine cold start to warm-up completed, the execution condition satisfaction flag is set as the diagnosis execution condition is satisfied, and when the diagnosis execution condition is not satisfied, the execution condition is satisfied. Clear the flag.

Therefore, in the execution condition determination routine, first, at step S31, the cooling water temperature TW at the time of engine start is started.
ST is compared with a preset determination value kTWST1 to check whether the engine is started in a cold state. And T
If WST> kTWST1, it is determined that the diagnostic condition is not satisfied, the execution condition flag is cleared in step S35, and the routine exits. If TWST ≦ kTWST1, step S35 is executed.
It progresses from 31 to step S32.

In step S32, the current cooling water temperature TW
Is compared with a preset determination value kTW1 to determine whether or not the engine warm-up is currently completed. And step S
If TW <kTW1 in 32, it is determined that the diagnostic condition is not satisfied, the execution condition flag is cleared in step S35, and the routine exits. If TW ≧ kTW1 and the engine warm-up is completed, the process proceeds to step S33 and the vehicle speed VSPD is It is checked whether or not a preset vehicle speed kVSPD1 or more is set.

As a result, when VSPD <kVSPD1, it is determined that the diagnostic condition is not satisfied, and the process proceeds from step S33 to step S35 to clear the execution condition flag and exit the routine. If VSPD ≧ kVSPD1, that is, if TWST1 ≦ kTWST1 and TW ≧ kTW1 and VSPD ≧ kVSPD1, and the engine is started in the cold state and warming up is completed and the vehicle is in the running state, the diagnostic condition is satisfied. The process proceeds from S33 to S34, sets the execution condition flag, and exits the routine.

Next, in the estimated exhaust temperature calculation routine of FIG. 6, first, in step S41, it is checked whether or not the in-room warm-up completion flag is cleared. The indoor warm-up completion flag indicates that the temperature inside the engine compartment has risen to a temperature sufficient to raise the intake air temperature, and warm-up inside the engine compartment is based on the estimated value of the exhaust temperature described below. Judge completion.

Then, in step S41, if the warm-up completion flag in the chamber is already set and the warm-up in the engine chamber is completed, the routine is exited as it is, and the warm-up completion flag in the chamber is cleared. If so, the process proceeds to step S42, and the estimated value of exhaust temperature (estimated exhaust temperature) TEXR is calculated based on the engine speed and the engine load. The estimated exhaust temperature TEXR is the engine speed N
The basic exhaust temperature TEXR0, which is the basic estimated value of the exhaust temperature, is calculated by referring to the estimated exhaust temperature calculation search map with E and the engine load as a grid with interpolation calculation, and the basic exhaust temperature T
The present estimated exhaust gas temperature TEXRn is calculated from EXR0 and the previous estimated exhaust gas temperature TEXRn-1 as a first-order delay using the moderating coefficient NTEX based on the engine cooling water temperature TW. TEXRn = TEXRn-1 + (TEXR0-TEXR
n-1) x NTEX

FIG. 7 shows an example of the estimated exhaust temperature calculation retrieval map. As the engine load, the map shown in FIG. 7 (a) adopts the intake pipe absolute pressure, and the map shown in FIG. 7 (b) shows the intake air. Uses pipe relative pressure. The map shown in FIG. 7C uses the intake air amount as the engine load.
In these maps, engine speed and engine load (intake pipe absolute pressure, intake pipe relative pressure, or intake air amount, etc.)
Based on the above, the exhaust temperature previously obtained by simulation or experiment is stored as the basic exhaust temperature TEXR0. Further, FIG. 8 shows an example of data in a table for obtaining the moderating coefficient NTEX, and a value obtained in advance by simulation or experiment in consideration of engine characteristics, exhaust system capacity, etc., with the engine cooling water temperature TW as a parameter. Is stored. The smoothing coefficient NTEX is
The lower the engine cooling water temperature TW, the smaller the value set.

After that, the routine proceeds to step S43, and it is checked whether or not the estimated exhaust gas temperature TEXR exceeds the preset judgment value kTEX. If TEXR ≦ kTEX, the estimated exhaust gas temperature TEXR is determined to be the judgment value k in step S44.
The exhaust temperature experience counter CTEX for measuring the time exceeding TEX is cleared, and in step S45, the in-bath warm-up completion flag is cleared and the routine is exited.
> KTEX, steps S43 to S46
Then, the exhaust temperature experience counter CTEX is incremented (CTEX ← CTEX + 1), and the process proceeds to step S47.

In step S47, it is checked whether or not the exhaust temperature experience counter CTEX has exceeded the counter judgment value kCTEX. The counter determination value kCTEX is a time equivalent value at which it can be considered that the intake air temperature has risen due to an increase in exhaust chamber temperature, that is, an increase in engine temperature, and is determined in advance by simulation or experiment and fixed in the ROM 42. It is stored as a value. Then, in step S47, CTEX ≦ kC
In the case of TEX, the routine is exited and CTEX> kCT
In the case of EX, it is determined that the warm-up in the chamber is completed, the in-room warm-up completion flag is set in step S48, and the routine is exited.

The above-mentioned execution condition flag and in-room warm-up completion flag are referred to in the diagnosis determination routine of FIG.
In this routine, the execution condition flag is referred to in the first step S51 to check whether or not the execution condition flag is set. Then, if the execution condition flag is not set and cleared, without executing the diagnosis,
If the execution condition flag is set, the routine proceeds to step S52, where the maximum intake air temperature TA
Difference between MAX and minimum intake air temperature TAMIN (TAMAX-T
AMIN) is compared with a determination threshold value kTA indicating deterioration of the characteristic of the intake air temperature sensor 30b.

As a result, in step S52, TA
If MAX-TAMIN ≧ kTA, it is determined that the intake air temperature sensor 30b is normal, and the intake air temperature sensor characteristic NG flag of the backup RAM 44 is cleared in step S53, and the routine exits. On the other hand, TAMAX-TAMI
When N <kTA, steps S52 to S52
Proceeding to 54, it is checked whether or not the indoor warm-up completion flag is set.

As a result, in step S54, if the indoor warm-up completion flag is not set, the routine exits with the determination being held, and if the indoor warm-up completion flag is set, that is, Despite the fact that the warm-up is completed from the engine cold start and it is determined that the temperature inside the engine chamber has risen to a temperature sufficient to raise the intake air temperature,
If the difference between the maximum value and the minimum value of the intake air temperature sensor 30b during this period is less than the determination threshold value indicating the characteristic deterioration, the intake air temperature sensor 30b is abnormal (including characteristic deterioration of the sensor itself, short circuit, disconnection of wiring, etc.). Therefore, the routine proceeds to step S55, the intake temperature sensor characteristic NG flag of the backup RAM 44 is set, and the routine is exited.

By setting the intake air temperature sensor characteristic NG flag, the alarm lamp 53 is turned on to notify the driver of the abnormality. Further, the intake air temperature sensor characteristic NG flag can be read by connecting the serial monitor 60, so that the failure portion can be surely grasped and quick repair can be performed.

That is, when diagnosing the intake air temperature sensor 30b, the diagnosis is performed in consideration of the temperature inside the engine chamber based on the estimated exhaust gas temperature. Therefore, the abnormality of the intake air temperature sensor 30b is surely detected to prevent erroneous diagnosis. The diagnostic accuracy can be improved. In this case, since the exhaust temperature is estimated without using the exhaust temperature sensor, it can be easily applied to a system that does not have the exhaust temperature sensor, and highly reliable diagnosis can be performed without increasing the cost.

[0049]

As described above, according to the present invention, the intake air temperature sensor is diagnosed under the condition in which the temperature of the intake air surely changes in consideration of the temperature in the engine chamber, so that the diagnostic accuracy is improved. be able to.

[Brief description of drawings]

[Figure 1] Overall view of the engine system

FIG. 2 is a circuit configuration diagram of an electronic control system.

FIG. 3 is a flowchart of a determination parameter initialization routine.

FIG. 4 is a flowchart of a determination parameter calculation routine.

FIG. 5 is a flowchart of an execution condition determination routine.

FIG. 6 is a flowchart of an estimated exhaust temperature calculation routine.

FIG. 7 is an explanatory diagram of an estimated exhaust temperature calculation search map.

FIG. 8 is an explanatory diagram of a smoothing coefficient table.

FIG. 9 is a flowchart of a diagnostic determination routine.

[Explanation of symbols]

1 engine 30b intake air temperature sensor 40 electronic control unit (diagnosis execution condition determination means, engine warm-up completion determination means, diagnostic means) TW engine cooling water temperature VSPD vehicle speed TA intake air temperature TAMAX maximum intake air temperature (maximum intake air temperature) TAMIN Minimum intake air temperature (minimum value of intake air temperature) TEXR Estimated exhaust gas temperature (estimated value of exhaust gas temperature) TEXR0 Basic exhaust gas temperature (basic estimated value of exhaust gas temperature) NTEX Smoothing coefficient kTA Judgment threshold value

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/22 301 F02D 41/22 301K F term (reference) 3G084 DA27 EA11 EB22 FA02 FA05 FA07 FA10 FA11 FA20 FA25 FA27 FA29 FA33 FA38 FA39 3G301 JB01 JB09 NE17 NE19 PA01B PA07B PA10B PA11B PC08B PD02B PD11B PE01B PE03B PE05B PE08B PF01B

Claims (3)

[Claims] 1. Based on the engine cooling water temperature and the vehicle speed,
Diagnostic execution condition determining means for determining whether or not the diagnostic execution condition of the intake air temperature sensor for measuring the temperature of the intake air of the engine is satisfied, and the temperature of the exhaust gas is estimated based on the engine operating state,
From the estimated value of the exhaust temperature, engine warm-up completion determining means for determining whether or not the engine compartment is in a warm-up completion state above a set temperature, and the intake air temperature sensor when the diagnosis execution condition is satisfied. The difference between the maximum value and the minimum value of the intake air temperature measured by is compared with a preset determination threshold value, the difference between the maximum value and the minimum value of the intake temperature is smaller than the determination threshold value, and the engine compartment is warmed up. A diagnostic device for an engine intake air temperature sensor, comprising: diagnostic means for determining that the intake air temperature sensor is abnormal when in a completed state. 2. The engine compartment warm-up completion determining means sets a basic estimated value of the exhaust temperature based on the engine speed and the engine load, and uses the basic estimated value as an annealing coefficient based on the engine cooling water temperature. 2. An engine intake air temperature sensor diagnostic device according to claim 1, wherein the estimated value of the exhaust gas temperature is corrected to obtain the estimated value. 3. The diagnostic system for an intake air temperature sensor for an engine according to claim 2, wherein the intake pipe pressure or the intake air amount is used as the engine load.