JPH06288281A - Self-diagnostic device in fuel supplying device for internal combustion engine - Google Patents

Abstract

PURPOSE:To avoid erroneous diagnosis accompanying canister purge while ensuring occasion of erroneous self-diagnosis using learned result in rich condition of an air-fuel ratio by judging whether it is actually in purge (separating) condition or not according to the temperature in a canister, and supplying separated evaporation fuel in an engine. CONSTITUTION:In an evaporation gas treatment device 21 in an engine 1, evaporation gas of fuel generated in a fuel tank 20 is absorbed and collected on adsorbent 23 in a canister 22, and supplied in the intake passage positioned downstream of a throttle valve 4 through a purge passage 24. A diaphragm valve 28 provided with a pressure chamber in which throttle negative pressure or the atmospheric pressure is led through a reference pressure leading-in passage on the purge passage 24 is controlled in its electrification through a solenoid 29 by a control unit 6. Calculating treatment is carried out following a program on a ROM by a CPU housed in the control unit 6, and a fuel injection amount is set while making correcting-control of air-fuel ratio feedback and air-fuel ratio learning control per an operating range. It is controlled to supply fuel in the engine 1, and self-diagnosis is carried out by a result of the air-fuel ratio learning in relation to a fuel supplying system. However, canister separating condition is judged on the basis of a temperature in the canister 22, and then self-diagnosis is inhibited so as to ensure diagnosis occasion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis device for a fuel supply system for an internal combustion engine, and more particularly, in a fuel supply system having an air-fuel ratio learning correction function, a fuel supply system using the result of the air-fuel ratio learning. Device for diagnosing abnormalities in

[0002]

2. Description of the Related Art Conventionally, as a self-diagnosis device in a fuel supply system for an internal combustion engine, for example, Japanese Patent Laid-Open No. 4-318244.
There is one disclosed in Japanese Patent Publication No. This one is
The air-fuel ratio of the engine intake air-fuel mixture is detected via the oxygen concentration in the exhaust gas detected by the oxygen sensor, the detected air-fuel ratio and the target air-fuel ratio are compared, and the air-fuel ratio for approaching the target air-fuel ratio While setting the feedback correction coefficient, in the fuel supply device having the air-fuel ratio learning function for learning the required correction amount by the air-fuel ratio feedback correction coefficient for each learning region having the engine load and the rotation as parameters, based on the learning value, Self-diagnosis of the fuel supply device.

[0003]

By the way, after the evaporated fuel in the fuel tank is once adsorbed (charged) in the canister, the evaporated fuel desorbed (purged) from the canister is supplied to the intake system of the engine. In the engine equipped with the fuel evaporative emission control device, when the vaporized fuel desorbed from the canister is supplied to the engine, the vaporized fuel becomes an excessive fuel supply to enrich the air-fuel ratio. Then, the air-fuel ratio learning is performed in a direction to eliminate the enrichment of the air-fuel ratio due to the desorption of the evaporated fuel from the canister, and even if the self-diagnosis is performed using the learned region, the fuel supply system Since the turbulence of the air-fuel ratio due to the component failure of (1) and the turbulence of the air-fuel ratio due to the supply of the evaporated fuel from the canister cannot be distinguished, there is a possibility of causing a false diagnosis.

If the self-diagnosis based on the air-fuel ratio learning value learned with the purge control valve provided in the purge passage from the canister learned in the open state is prohibited, the supply of evaporated fuel (canister purge). It is possible to avoid erroneous diagnosis based on the learning value in the rich state. However, in such a configuration, the self-diagnosis is not performed even when the evaporated fuel is not actually supplied, so that the self-diagnosis prohibited area becomes too wide, and the learning area used for the self-diagnosis is set. Had the problem of losing the opportunity for self-diagnosis.

The present invention has been made in view of the above problems, and in the self-diagnosis of the fuel supply system using the air-fuel ratio learning result for each operation region, the error caused by the canister purge is ensured while ensuring the opportunity of self-diagnosis. It is an object of the present invention to provide a self-diagnosis device that can avoid diagnosis.

[0006]

Therefore, a self-diagnosis device in a fuel supply system for an internal combustion engine according to the present invention is shown in FIG.
It is configured as shown in. In FIG. 1, the air-fuel ratio detecting means detects the air-fuel ratio of the engine intake air-fuel mixture, and the air-fuel ratio learning means learns the air-fuel ratio for obtaining the target air-fuel ratio based on the air-fuel ratio detected by the air-fuel ratio detecting means. The correction value is learned for each operating area.

Then, the air-fuel ratio control means corrects the fuel supply amount to the engine based on the air-fuel ratio learning correction value for each operating region learned by the air-fuel ratio learning means. On the other hand, the canister adsorbs and collects the evaporated fuel in the fuel tank,
The means for desorbing the adsorbed and collected evaporated fuel and supplying it to the intake passage of the internal combustion engine. Here, the self-diagnosis means performs self-diagnosis of the fuel supply device based on the air-fuel ratio learning value learned by the air-fuel ratio learning means.

Further, the desorption state determination means determines the desorption state of the evaporated fuel in the canister based on at least the temperature inside the canister detected by the canister temperature detection means. The self-diagnosis prohibiting means prohibits the self-diagnosis by the self-diagnosis means at least on condition that the desorption state determination means determines the desorption state.

[0009]

According to this structure, the self-diagnosis is performed using the result of the air-fuel ratio learning for each operating region, but the temperature inside the canister is detected, and the desorption state (purge state) in the canister is detected based on this temperature inside the canister. ) Is determined.
Then, self-diagnosis using the air-fuel ratio learning result is prohibited, at least on condition that the desorption state is determined based on the canister internal temperature.

That is, it is determined whether or not desorption is actually performed according to the temperature condition in the canister, and learning is performed in a state where the desorbed evaporated fuel is supplied to the engine to enrich the air-fuel ratio. Avoid false self-diagnosis using the results.

[0011]

EXAMPLES Examples of the present invention will be described below. In FIG. 2 showing an embodiment, air is drawn into the internal combustion engine 1 through a throttle chamber 2 and an intake manifold 3. The throttle chamber 2 is provided with a throttle valve 4 interlocking with an accelerator pedal (not shown), and controls the intake air flow rate Q of the engine 1. The intake manifold 3 is provided with an electromagnetic fuel injection valve 5 for each cylinder, and injects fuel into the intake manifold 3 which is fed under pressure from a fuel pump (not shown) and is controlled to a predetermined pressure by a pressure regulator. The control of the fuel injection amount by the fuel injection valve 5 is performed by the control unit 6 with a built-in microcomputer.

Further, each cylinder of the internal combustion engine 1 is provided with an ignition plug 7, to which a high voltage generated by an ignition coil 8 is sequentially applied via a distributor 9, whereby sparks are generated. Ignite and ignite the air-fuel mixture. Here, the ignition coil 8 is configured such that the generation timing of the high voltage is controlled via the attached power transistor 10.

The throttle valve 4 has an opening TVO.
Sensor that detects the pressure with a potentiometer
11 is attached, and the distributor 9
The crank angle sensor 12 built in the engine outputs a detection signal at every predetermined crank angle. A cooling water jacket of the engine 1 is provided with a water temperature sensor 13 for detecting a cooling water temperature Tw representing the engine temperature, and an exhaust manifold 14 is provided with an air-fuel ratio of an intake air-fuel mixture of the engine 1. An oxygen sensor 15 is provided as an air-fuel ratio detecting means for detecting the oxygen concentration in the exhaust gas which is in a close relationship.

Further, the engine 1 is provided with an evaporative gas treatment device 21 for the fuel tank 20. The evaporative gas treatment device 21 causes the adsorbent 23 such as activated carbon filled in the canister 22 to adsorb and collect the evaporative gas of the fuel generated in the fuel tank 20 to collect the fuel adsorbed by the adsorbent 23. The air is supplied to the intake passage downstream of the throttle valve 4 via the purge passage 24.

The evaporative gas in the fuel tank 20 is introduced into the canister 22 through an evaporative gas passage 26 provided with a check valve 25 that opens when the positive pressure in the fuel tank 20 becomes a predetermined value or more. The purge passage 24 is provided with a diaphragm valve 28 having a pressure chamber into which the throttle negative pressure or the atmospheric pressure is introduced via the reference pressure introduction passage 27.

The diaphragm valve 28 opens the purge passage 24 against the valve closing force of the spring 28a when a negative pressure is applied to the pressure chamber, and closes the spring 28a when the pressure chamber becomes atmospheric pressure. The purge passage 24 is closed by closing the valve by the valve biasing force. Here, in order to selectively apply a throttle negative pressure to the pressure chamber of the diaphragm valve 28, a normally open type purge control solenoid 29, whose current is controlled by the control unit 6 in the reference pressure introducing passage 27, is installed. Has been done.

The purge control solenoid 29 is
In the off state, the negative pressure introduction path 30 for introducing the throttle negative pressure
And the reference pressure introducing passage 27 are communicated with each other, and in the ON state, the atmospheric pressure introducing passage 31 for introducing atmospheric pressure from the upstream side of the throttle valve 4 is communicated with the reference pressure introducing passage 27. . Therefore, this purge control solenoid
By turning on / off 29, the throttle negative pressure and the atmospheric pressure can be switched and introduced into the pressure chamber of the diaphragm valve 28, whereby the opening / closing of the purge passage 24 can be electronically controlled by the control unit 6. .

The control unit 6 controls the cooling water temperature T
The purge control solenoid 29 is turned on / off according to operating conditions such as w and vehicle speed to control the canister purge. Further, in this embodiment, the canister is further added.
A temperature sensor 32 in the canister as a canister temperature detecting means for detecting the temperature (temperature of the adsorbent 23) Tc in 22;
A canister ambient temperature sensor 33 for detecting the ambient temperature Ta of the canister 22 is provided in order to determine a change in the canister internal temperature Tc due to adsorption / desorption.

Here, the CPU of the microcomputer incorporated in the control unit 6 performs arithmetic processing according to the programs on the ROM shown in the flow charts of FIGS. 3 to 5, and performs air-fuel ratio feedback correction control and emptying for each operating region. While executing the fuel ratio learning correction control, the fuel injection amount Ti is set and the fuel supply to the engine 1 is controlled, while the self-diagnosis of the fuel supply system including the fuel injection valve 6, the fuel pump, the pressure regulator and the like is performed. This is performed using the result of the air-fuel ratio learning.

In this embodiment, the air-fuel ratio learning means,
The functions of the air-fuel ratio control means, the self-diagnosis means, the desorption state determination means, and the self-diagnosis prohibition means are provided in software by the control unit 12 as shown in the flow charts of FIGS. The program shown in the flowchart of FIG. 3 has a basic fuel injection amount (basic fuel supply amount) Tp.
The air-fuel ratio feedback correction coefficient LMD multiplied by
This program is set by proportional / integral control.

First, in step 1 (denoted as S1 in the drawing; the same applies hereinafter), a voltage signal output from the oxygen sensor 15 according to the oxygen concentration in the exhaust gas is read. Then, in the next step 2, the oxygen sensor read in step 1 is read.
The voltage signal from 15 is compared with a slice level (for example, 500 mV) corresponding to the theoretical air-fuel ratio which is the target air-fuel ratio.

When it is judged that the voltage signal from the oxygen sensor 15 is larger than the slice level and the air-fuel ratio is richer than the stoichiometric air-fuel ratio, the routine proceeds to step 3, where it is judged whether or not this rich judgment is the first time. Determine. When the rich determination is the first time, the routine proceeds to step 4, where the air-fuel ratio feedback correction coefficient LMD set up to the previous time is set to the maximum value a.

At the next step 5, the correction coefficient LM is obtained by subtracting a predetermined proportional constant P from the correction coefficient LMD up to the previous time.
Control the decrease of D. Further, in step 6, 1 is set in the flag FP indicating that proportional control has been executed. On the other hand, when it is determined in step 3 that the rich determination is not the first time, the process proceeds to step 7, and the value obtained by multiplying the integration constant I by the latest fuel injection amount Ti is used as the correction coefficient LM up to the previous time.
The correction coefficient LMD is updated by subtracting from D.

When it is determined in step 2 that the air-fuel ratio is lean with respect to the target, similarly to the rich determination, first, in step 8, it is determined whether or not this lean determination is the first time. If it is determined that it is the first time, the routine proceeds to step 9, where the correction coefficient LMD up to the previous time is set to the minimum value b. In the next step 10, the proportional constant P is added to the correction coefficient LMD up to the previous time to update, and in step 11, the flag FP is set to 1.

When it is determined in step 8 that the lean determination is not the first time, the process proceeds to step 12, and a value obtained by multiplying the integration constant I by the latest fuel injection amount Ti is added to the correction coefficient LMD up to the previous time. The program shown in the flowchart of FIG. 4 is an air-fuel ratio learning program for each operating region.

In step 21, the flag FP is discriminated, and when FP is 1, the process proceeds to step 22 and FP
Is reset to zero, then various processes are performed by this program, and when it is zero, this program is terminated as it is. When the FP is reset to zero in step 22, in the next step 23, the basic fuel injection amount T representing the engine load is
On the air-fuel ratio learning map that rewritably stores the air-fuel ratio learning correction coefficient KBLRC for each operating region divided into plural with p (= K × Q / Ne; K is a constant) and engine speed Ne as parameters, The latest basic fuel injection amount Tp and the engine speed Ne are read in order to specify the region to which the operating conditions of No.

Then, in the next step 24, step 23
The basic fuel injection amount Tp and the engine speed Ne read in
Stored in the area on the air-fuel ratio learning map corresponding to
Read the air-fuel ratio learning correction coefficient KBLRC and load it to KBLRC.
_OLDSet to. In step 25, the air-fuel ratio fee
Average of maximum and minimum values a and b of the feedback correction coefficient LMD
(= (A + b) / 2) and the convergence target value (correction coefficient LMD
This is the initial value, and in the present embodiment, a predetermined ratio of deviation from 1.0)
X is the air-fuel ratio learning correction coefficient KBLRC _OLDValue added to
Is the new air-fuel ratio learning correction coefficient KBLRC for the relevant area.
_NEW(← KBLRC_OLD+ X ・ {(a + b) /2-1.0})
Set as.

By this learning, the correction amount by the air-fuel ratio feedback correction coefficient LMD is converted into the air-fuel ratio learning correction coefficient KBLRC for each operating region, and the deviation between the air-fuel ratio feedback correction coefficient LMD and the convergence target value can be reduced. While stabilizing the air-fuel ratio feedback correction coefficient LMD near the target convergence value, it becomes possible to meet different correction requests depending on the operating region.

In step 26, the air-fuel ratio learning correction coefficient
The map data is rewritten by using KBLRC _NEW as update data corresponding to the corresponding area on the air-fuel ratio learning map.
The final fuel injection amount Ti (fuel supply amount) is calculated from the intake air flow rate Q and the engine speed Ne by the basic fuel injection amount Tp.
On the other hand, various correction coefficients CO are set according to the operating conditions such as the cooling water temperature Tw, a correction amount Ts is set according to the battery voltage, and further the air-fuel ratio feedback correction coefficient LMD and the learning map are set. The air-fuel ratio learning correction coefficient KBLRC stored in the relevant operating region is read and calculated as Ti = Tp × CO × LMD × KBLRC + Ts.

Then, at the predetermined injection timing synchronized with the engine rotation, the fuel injection amount Ti calculated most recently is calculated.
The fuel supply to the engine is controlled by outputting the injection pulse signal having the pulse width corresponding to the above to the fuel injection valve 6. In step 27, self-diagnosis of the fuel supply system is performed based on the air-fuel ratio learning correction coefficient KBLRC (air-fuel ratio learning correction value) for each operating region stored in the air-fuel ratio learning map.

Details of the self-diagnosis in step 27 are shown in the flow chart of FIG. In the flowchart of FIG. 5, first, in step 31, the ambient temperature Ta of the canister 22 detected by the canister ambient temperature sensor 33 is read. In step 32, the canister internal temperature Tc detected by the canister internal temperature sensor 32 is read.

Then, in step 33, the ambient temperature T
deviation between the temperature a and the temperature Tc in the canister ΔT (← Ta−T
c) is calculated. In step 34, the temperature deviation ΔT is compared with a predetermined temperature to determine whether the canister internal temperature Tc is lower than the ambient temperature Ta by a predetermined value or more. The adsorbent 23 used in the canister 22 has a property that the temperature rises when adsorbing (charging) the vaporized fuel and decreases when desorbing (purging) the adsorbed vaporized fuel. Is generally known.

Therefore, in the desorbed state, the canister internal temperature Tc should be lower than the ambient temperature Ta, and when it is determined that the deviation ΔT exceeds the predetermined temperature,
When the desorption state in the canister 22 is estimated, and conversely, when it is determined that the deviation ΔT is below the predetermined temperature,
The non-detached state of the canister 22 is estimated. Here, when the canister 22 is in the desorbed state and the desorbed evaporated fuel is supplied to the engine through the purge passage 24, the fuel injected and supplied from the fuel injection valve 5 is supplied to the engine in accordance with the engine required amount. As a result, the fuel supplied through the purge passage 24 is additionally added, so that the air-fuel ratio becomes rich. Then, the air-fuel ratio feedback correction is performed to eliminate the enrichment of the air-fuel ratio, and the result of the feedback correction is learned.

On the other hand, in the present embodiment, as will be described later, the self-diagnosis of the fuel supply system is carried out based on the learning value on the air-fuel ratio learning map, so that the above-mentioned factors other than the failure of the fuel supply system are caused. If a large air-fuel ratio deviation occurs and the air-fuel ratio deviation is learned, there is a risk of erroneous diagnosis.
Therefore, when it is determined in step 34 that the deviation ΔT is less than or equal to the predetermined temperature, the process proceeds to step 36 to perform self-diagnosis, but the deviation ΔT exceeds the predetermined temperature and the desorption state of the canister 22 is estimated. Sometimes step
35. Based on the ON / OFF (open / close) state of the purge control solenoid 29, it is determined whether the desorbed evaporated fuel is actually being supplied to the engine 1 through the purge passage 24. judge.

That is, even if the desorption occurs in the canister 22, the purge control solenoid is
If 29 is closed, desorbed fuel canister 22
Since the air does not stay inside and is not supplied to the engine 1, the air-fuel ratio is not affected by the desorbed fuel, and the self-diagnosis can be normally performed as in the non-desorbed state. Therefore, when it is determined in step 35 that the purge control solenoid 29 is in the on state (closed state), the process proceeds to step 36 to perform self-diagnosis, but when it is determined in the off state (open state), the canister purge is involved. To avoid erroneous diagnosis, this routine is terminated without performing self-diagnosis.

If the desorbed fuel is not supplied due to the closed state of the solenoid 29 even when the canister 22 is in the non-disengaged state or the desorbed state, the routine proceeds to step 36 and thereafter to self-diagnose the fuel supply system. Therefore, according to the present embodiment, it is possible to avoid self-diagnosis based on the learned result of the air-fuel ratio deviation accompanying the canister purge, and it is possible to maintain the accuracy of self-diagnosis, while maintaining the temperature Tc in the canister.
Since the diagnosis is canceled only when the desorbed fuel is actually supplied to the engine, the chance of the diagnosis can be secured sufficiently.

In step 36, the air-fuel ratio learning value in the preset diagnostic regions A and B on the air-fuel ratio learning map is read. The diagnostic areas A and B are 1 on the learning map.
Although it may be an area, it may be configured to obtain a representative value of a plurality of adjacent areas. In the next step 37, the absolute value ΔMR of the deviation of the air-fuel ratio learning values in the read two diagnostic regions A and B is calculated.

Then, in the next step 38, the deviation Δ
If the deviation ΔMR is equal to or more than a predetermined value, that is, if the air-fuel ratio learning value in each of the diagnostic regions A and B has a deviation equal to or more than a predetermined value, the routine proceeds to step 39, in which the fuel system Diagnose abnormalities. On the other hand, when the deviation ΔMR is less than the predetermined value, it is regarded as a normal state in which the learning for the normal component variation is performed, and this routine is ended as it is.

It should be noted that the present invention is not limited to the air-fuel ratio learning method and the diagnosis method using the learning result shown in the above embodiment, but the fuel system diagnosis is performed using the result of the air-fuel ratio learning for each operating region. Similarly, it is possible to avoid misdiagnosis while securing a diagnosis opportunity in the same manner. Further, in the diagnostic control shown in the flowchart of FIG. 5, the purge control solenoid 29 is turned on / off as the determination condition for the diagnostic cancellation. However, when the desorption state is determined based on the canister temperature, all diagnostics are canceled. It may be configured. However, it is preferable to judge whether the purge control solenoid 29 is on or off, because the diagnosis opportunity can be secured more.

Further, in the above embodiment, the desorption state is determined based on the canister internal temperature Tc and the ambient temperature Ta, but only the canister internal temperature Tc is detected,
The desorption state may be determined from the time-series change in the canister internal temperature Tc. Further, it is preferable that the self-diagnosis is prohibited even immediately after the desorption state is changed to the non-desorption state.

[0041]

As described above, according to the present invention, in the system for performing self-diagnosis of the fuel supply system using the result of the air-fuel ratio learning, the air-fuel ratio learning result influenced by the evaporated fuel desorbed from the canister. It is possible to avoid erroneous diagnosis based on, and to prohibit self-diagnosis by determining the canister detachment state based on the canister internal temperature,
This has the effect of ensuring a diagnosis opportunity.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing the air-fuel ratio feedback control of the above embodiment.

FIG. 4 is a flowchart showing air-fuel ratio learning control of the above embodiment.

FIG. 5 is a flowchart showing self-diagnosis of the fuel supply system according to the embodiment.

[Explanation of symbols]

 1 Internal Combustion Engine 4 Throttle Valve 5 Fuel Injection Valve 6 Control Unit 15 Oxygen Sensor 20 Fuel Tank 21 Evaporative Gas Treatment Device 22 Canister 23 Adsorbent 24 Purge Passage 28 Diaphragm Valve 29 Purge Control Solenoid 32 Canister Ambient Temperature Sensor 33 Canister Ambient Temperature Sensor

Claims (1)

[Claims] 1. An air-fuel ratio detecting means for detecting an air-fuel ratio of an engine intake air-fuel mixture, and an air-fuel ratio learning correction value for obtaining a target air-fuel ratio based on the air-fuel ratio detected by the air-fuel ratio detecting means. Air-fuel ratio learning means for learning separately, and air-fuel ratio control means for correcting the fuel supply amount to the engine based on the air-fuel ratio learning correction value for each operating region learned by the air-fuel ratio learning means. On the other hand, in the fuel supply apparatus for an internal combustion engine, comprising a canister that adsorbs and collects the evaporated fuel in the fuel tank and desorbs the adsorbed and collected evaporated fuel and supplies it to the intake passage of the internal combustion engine, Self-diagnosis means for performing self-diagnosis of the fuel supply device based on the air-fuel ratio learned value learned by the learning means; canister temperature detection means for detecting the temperature in the canister; and at least the canister temperature detection means. Desorption state determination means for determining the desorption state of the evaporated fuel in the canister based on the temperature detected in the stage, and at least the desorption state is determined by the desorption state determination means. A self-diagnosis device in a fuel supply device for an internal combustion engine, comprising: self-diagnosis prohibition means for prohibiting self-diagnosis in the diagnosis means.