JPH04112959A - Evaporated fuel process controller - Google Patents

Abstract

PURPOSE:To control an air/fuel ratio so as to constantly be a theoretical air/fuel ratio in a process where an evaporated fuel of an internal combustion engine is emitted to a suction system by controlling the amount of evaporated fuel emission according to the correction amount due to the purging of fuel injection amount. CONSTITUTION:A fuel injection amount to be supplied to an internal combustion engine M1 is calculated by a calculation means M4 according to a detection signal of a detection means M2 for detecting a driving condition of the internal combustion engine M1, while an air/fuel ratio feedback correction coefficient is varied so as to define the air/fuel ratio of an intake mixed air as a theoretical air/fuel ratio according to the detection signal of the detection means M2, and the fuel injection amount calculated by the calculation means M4 is corrected, by a first injection amount correction means M5. The fuel injection amount calculated by the calculation means M4 is corrected according to the evaporated fuel concentration obtained from the air/fuel ratio feedback correction coefficient by a second injection amount correction means M6, while the emission amount of the evaporated fuel emitted by a purging means M3 is corrected according to the evaporated fuel concentration as well as to the correction amount by the second correction means M6, by a purging correction means M7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an evaporated fuel processing control device for an internal combustion engine that discharges evaporated fuel from the internal combustion engine into an intake system for treatment.

[Conventional technology]

BACKGROUND ART Conventionally, in internal combustion engines, vaporized fuel generated from a fuel tank or the like has been adsorbed onto activated carbon and then purged (discharged) into the intake system for treatment.

There is also an internal combustion engine in which a fuel injection control device performs feedback control of the air-fuel ratio so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio.

For example, the device described in Japanese Patent Application Laid-Open No. 63-289243 corrects the fuel injection amount by purging in addition to feedback correction when executing purge, and this purge correction amount is obtained from the average value of the feedback correction coefficient of the air-fuel ratio. It is set according to the evaporated fuel concentration (vapor concentration) to improve the followability of air-fuel ratio control.

In the conventional device described above, when the evaporated fuel concentration is high, the correction amount by parity of the fuel injection amount becomes a dog, and the actual fuel injection amount becomes smaller. If the evaporated fuel concentration is extremely high, it becomes impossible to set the correction amount by purging of the fuel injection amount to an accurate value, which causes a problem that the air-fuel ratio deteriorates.

In order to solve this problem, the present applicant applied for a patent dated August 8, 1990, entitled "Evaporative Fuel Processing Control Device for Internal Combustion Engine," etc., and decided to change the fuel injection amount and evaporated fuel according to the evaporated fuel concentration. We proposed a device that controls the air-fuel ratio to always be the stoichiometric air-fuel ratio by correcting both the amount of fuel released.

C Invention or problem to be solved] The above device uses an electric negative pressure switching valve (V S
An output sensor located downstream of the intake passage from the purge port communicating with V) measures the intake pressure, and controls to increase the purge amount when the air-fuel ratio is lean.

However, in internal combustion engines of the type that measure the amount of intake air with an air flow meter located upstream of the intake passage than the purge port communicating with VSv, increasing the purge amount when the air-fuel ratio is lean will cause the amount of air in the purge air to increase. When the vapor concentration is low, the air-fuel ratio of the air-fuel mixture becomes even leaner, posing a problem that accurate air-fuel ratio control cannot be performed.

The present invention has been made in view of the above points, and the present invention controls the amount of evaporated fuel released according to the amount of correction by purging of the amount of fuel injection, or the amount of correction of the amount of fuel injection by purging according to the amount of emitted fuel vapor. An object of the present invention is to provide an evaporated fuel processing control device that controls the air-fuel ratio to always be the stoichiometric air-fuel ratio by controlling the air-fuel ratio.

[Failure to solve the problem]

FIGS. 1(A) and 1(B) show diagrams of the principle of the present invention.

In FIG. 1(A), the detection means M2 detects the internal combustion engine M1.
Detects the operating status of the

The purge unit M3 discharges evaporated fuel generated within the fuel system to the intake system.

The calculating means M4 calculates the amount of fuel injection to be supplied to the internal combustion engine M1 in response to the detection signal of the detecting means M2.

The first injection amount correction means M5 varies the air-fuel ratio feedback correction coefficient so that the air-fuel ratio of the intake air-fuel mixture becomes the stoichiometric air-fuel ratio according to the detection signal of the detection means M2, and the fuel injection amount is calculated by the calculation means M4. Correct.

The second injection amount correction means M6 corrects the fuel injection amount calculated by the calculation means M4 according to the vaporized fuel concentration obtained from the air-fuel ratio feedback correction coefficient.

The purge correction means M7 corrects the amount of evaporated fuel released by the purge means M3 according to the evaporated fuel concentration and the correction amount of the second correction means M6.

In FIG. 1(B), the second injection amount correction means M6 adjusts the calculation means M4 according to the evaporated fuel concentration obtained from the air-fuel ratio feedback correction coefficient and the correction amount of the purge correction means M7.
Correct the fuel injection amount calculated by

[Effect]

In the first invention, when correcting the amount of evaporated fuel released, the correction amount of the second injection amount correction means M6 is taken into account, and if the cause of the fluctuation in the air-fuel ratio is due to overcorrection of the amount released, Since the emission amount is controlled to prevent this overcorrection, the air-fuel ratio can be accurately maintained at the stoichiometric air-fuel ratio.

Further, in the second invention, the second injection amount correction means M
When correcting the fuel injection amount in step 6, purge correction means M7
If the cause of fluctuations in the air-fuel ratio is due to over-correction of the injection amount due to the purge of the fuel injection amount, the amount of correction due to the purge of the fuel injection amount is controlled to prevent this over-correction. Therefore, the air-fuel ratio can be accurately maintained at the stoichiometric air-fuel ratio.

〔Example〕

FIG. 2 shows a configuration diagram of an embodiment of an internal combustion engine to which the device of the present invention is applied.

In the figure, a throttle valve 12 is provided in the intake passage 11 of the internal combustion engine IO, and a throttle position sensor 13 for detecting the opening degree of the throttle valve 12 is provided on the shaft of the throttle valve 12. An air flow meter 14 for measuring the amount of intake air is installed in the intake passage 11 upstream of the throttle position sensor 13, and an air flow meter 14 is installed downstream for supplying pressurized fuel from the fuel supply system to the intake port for each cylinder. A fuel injection valve (injector) 15 is provided. In addition, an intake air temperature sensor 1 is provided in the intake passage 11.
6 are provided, and the analog electrical signal according to the intake temperature is A.
/D converter 31. The air flow meter 14 generates an analog voltage electrical signal according to the amount of intake air,
This output is supplied to an A/D converter 31 within the electronic control circuit 30.

The distributor 20 is equipped with a crank angle sensor 21 and a 30° crank angle sensor that generates a reference position detection pulse signal every 720° CA in terms of crank angle (CA).
A crank angle sensor 22 that generates a reference position detection pulse signal is provided for each CA. These pulse signals from the crank angle sensor 2122 function as an interrupt request signal for fuel injection timing, a reference timing signal for ignition timing, an interrupt request signal for fuel injection amount calculation control, and the like. These signals are supplied to an input/output interface 32 of an electronic control circuit 30.

Also, the cooling water passage 2 of the cylinder block of the internal combustion engine 10
3 includes a water temperature sensor 24 for detecting the temperature of the cooling water.
is provided. The water temperature sensor 24 indicates the cooling water temperature TH.
An analog voltage electric signal corresponding to W is generated, and this output is supplied to an A/D converter 31.

A three-way catalytic converter 26 is provided in the exhaust system downstream of the exhaust manifold 25 to simultaneously purify three harmful components HC, Co, and NO in the exhaust gas.

Further, an 02 sensor 28, which is a type of air-fuel ratio sensor, is provided in the exhaust pipe 27 downstream of the exhaust manifold 25 and upstream of the catalytic converter 26.

The 0□ sensor 28 generates an electrical signal depending on the concentration of oxygen components in the exhaust gas. In other words, the 02 sensor 28 changes depending on whether the air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio.
The signal processing circuit 40 of the electronic control circuit 30
The signal is supplied to the A/D converter 31 via the A/D converter 31. Further, the input/output interface 32 is supplied with an on/off signal from a key switch (not shown), and is further supplied with an analog signal from a vehicle speed sensor (not shown) to the A/D converter 31.

Further, the internal combustion engine 10 is provided with an evaporative purge system that prevents evaporated fuel (vapor) evaporated from the fuel tank 41 from escaping into the atmosphere.

This system uses a charcoal canister 42. and an electric negative pressure switching valve (VSV) 43 as purge means M3. The charcoal canister 42 is the fuel tank 41
The upper bottom of the fuel tank 41 is connected to the vapor collection pipe 44 to adsorb vapor evaporated from the fuel tank 41. VSV43 is an on-off valve provided in the middle of a vapor return pipe 45 that returns the vapor adsorbed to the charcoal canister 42 to the downstream of the throttle valve 12 in the intake passage 11.
This is a solenoid valve that opens and closes in response to an electrical signal from 0.

In the above configuration, when a key switch (not shown) is turned on, the electronic control circuit 30 is energized, a program is started, and outputs from each sensor are taken in to control the injector 15 and other actuators.

The electronic control circuit 30 is configured using, for example, a microcomputer, and includes the aforementioned A/D converter 31, input/output interface 32 . In addition to the CPU 33, the ROM 34. RAM3
5. A backup RAM 36, a clock (CLK) 37, etc., which retain information even after the key switch 0) is turned off, are provided, and these are connected by a bus 38.

In this electronic control circuit 30, an injection control circuit 39 including a down counter, a flip-flop, and a drive circuit is for controlling the fuel injection valve 15. That is, the basic injection amount Tp calculated from the intake air amount and the engine speed
When the fuel injection amount TAU corrected based on the engine operating condition is calculated, the fuel injection amount TAtJ is preset to the down counter of the injection control circuit 39, and a flip-flop is also set, and the fuel injection amount TAtJ is preset to the down counter of the injection control circuit 39. start the movement. On the other hand, when the down counter counts the clock signal (not shown) and finally reaches 11 levels, the flip-flop is set and the drive circuit stops energizing the fuel injection valve 15. In other words, the fuel injection valve 15 is energized by the aforementioned fuel injection amount TA[J,
Therefore, an amount of fuel corresponding to the fuel injection amount TAU is sent into the combustion chamber of the internal combustion engine 10.

Next, a control program for an embodiment of the apparatus of the present invention will be explained.

The electronic control circuit 30 supplies a pulse signal whose duty ratio changes at a constant frequency to the VSV 43, and opens the VSV 43 during the high level period of this pulse signal. In other words, the purge amount is proportional to the duty ratio DPG of this pulse signal.

FIG. 3 shows a flowchart of one embodiment of the VSv control routine as the purge correction means M7.

This routine is executed by interrupting, for example, every 1 sec, when the average value FAFav of the feedback correction coefficient FAF satisfies 0, 95<FAFav<1.05 as a precondition. However, once the execution condition for the ■S■ control is satisfied, the execution of this routine is not prevented even if the precondition is not satisfied thereafter.

In the figure, in step 50, it is determined whether the purge execution flag XPRG is 11' and purge is being executed. Here, the feedback control conditions such as when the cooling water temperature is low, at startup, at high load driving, or at fuel cut are not satisfied, and 30 seconds have not passed after startup, or the idle switch is turned on. 5 seconds have not passed or the vehicle speed is 2.
If the purge conditions such as less than km/h or less than 45° C. of the intake air temperature are not satisfied, the flag XPRG is 101 and the process proceeds to step 51, where the duty ratio DPG is set to zero.

If the purge execution flag
If the value is within this range, increase the duty ratio DPG value to 10%.
(step 53).

In step 52, the value of the feedback correction coefficient FAF is set to 1.
．． If it is outside the range of 0 to 1.05, it is determined in step 54 whether the feedback correction coefficient FAFO value exceeds 1.05, and if it is, it is determined in step 55.
It is determined whether the purge correction amount KPG is zero.

If the purge correction amount KPG is zero, it has not been reduced by the actual fuel injection amount or purge correction amount, and the reason why the air-fuel ratio is lean is because low-concentration vapor is being purged. , in step 51 the duty ratio DPG
Set to zero and stop the purge.

Furthermore, since the reason why the purge correction amount KPG is not zero but only one is due to both the purge amount and the purge correction amount, the duty ratio DPG is decreased by 2% in step 56.

In step 54, the value of the feedback correction coefficient FAF is set to 1.
．． If the value does not exceed 05, the process proceeds to step 57, and it is determined whether the value of the feedback correction coefficient FAF is within the range of 0.95 to 1.0. If it is within this range, the process is terminated without changing the duty ratio DPG. do. Outside this range, that is, the feedback correction coefficient FAFO value is 0.95.
If the rich state is as follows, the duty ratio DPG is decreased by 5% in step 56.

FIG. 4 shows a flowchart of an embodiment of the purge correction amount calculation routine as the second injection amount correction means M6. This routine is executed with an interrupt every 65m5ec.

In the figure, in step 60, it is determined whether the purge execution flag XPRG is +1' and the purge is being executed. If the purge execution flag XPRG is +0', the process advances to step 61 and the purge correction amount KPG is set to zero.

If the purge execution flag XPRG is 111, it is determined whether the value of the feedback correction coefficient FAF is in the range of 1.0 to 1.05 (step 62), and if the value of FAF is within this range, the purge correction amount KPG is The process ends without changing the value of .

In step 62, the value of the feedback correction coefficient FAF is 1.
．． If it is outside the range of 0 to 1.05, step 63 determines whether the feedback correction coefficient FAFO value exceeds 1.05, and if it does, step 64
It is determined whether the duty ratio DPG is less than a predetermined value somewhat larger than zero.

If the duty ratio DPG is less than the predetermined value, the purge amount is extremely small and the reason why the air-fuel ratio is lean is because the purge correction amount KPGO value is too large, so in step 61, the purge correction amount KPG is set to zero. shall be.

If the duty ratio DPG is greater than or equal to the predetermined value, the cause of the lean condition is both the purge amount and the purge correction amount, so in step 65, the purge correction amount KPG is set to 5μSe.
Decrease by C.

In step 63, the feedback correction coefficient FAFO value is 1.
．． If it does not exceed 05, that is, the feedback correction coefficient F
If the AFO value is less than 1.0 and is in a rich state, proceed to step 6.
6, the purge correction amount KPG is increased by 5 μsec.

FIG. 5 shows a flowchart of an embodiment of the fuel injection amount calculation routine as the calculation means M4.

In the figure, in step 71, a basic fuel injection amount Tp is calculated based on the intake air amount Q and the engine rotational speed NE. Next, this basic fuel injection amount Tp and the feedback correction coefficient F
Calculate the fuel injection amount τ using the following formula using AF and a constant (
Step 72).

r=TpXFAFXK This step 72 corresponds to the first injection amount correction means M5.

Further, the actual fuel injection amount TAU is determined using the fuel injection amount τ, the purge correction amount KPG, the reference idle rotation speed NE, and the rotation speed NE using the following equation.

TAU=r-(KPGXNE0/NE) As shown in FIG. 6, the feedback correction coefficient FAF is 1.05 by the above vSV control routine and purge correction amount calculation routine.
In the first region exceeding KPG, the duty ratio DPG is
When KPG is zero, it becomes zero, and when KPG is not zero, it decreases.
Further, the purge correction amount KPG becomes zero when DPG is less than a predetermined value, and is decreased when DPG is greater than a predetermined value.

In the second region where the feedback correction coefficient FAF is in the range of 1.0 to 1.05, the duty ratio DPG is increased;
The purge correction amount KPG is maintained. In the third region where the feedback correction coefficient FAF is in the range of 0.95 to 1.0, the duty ratio DPG is maintained and the purge correction amount KPG
is increased. Feedback correction coefficient FAF is 0.9
In the fourth region of less than 5, the duty ratio DPG is decreased and the purge correction amount KPG is increased.

Here, if the vapor generation is small and the amount of vapor in the charcoal canister 42 is small, the duty ratio DPG is adjusted according to the feedback correction coefficient FAF shown in FIG. 7(B).
The purge correction amount KPG is varied as shown in FIGS. 7(C) and 7(D), and the vapor amount is gradually decreased as shown in FIG. 7(A). Here, at a time T when the feedback correction coefficient FAF exceeds 1.05 after the purge correction amount KPG becomes zero, the duty ratio DPG becomes zero and the purge is temporarily stopped.

Here, if the vapor generation is large and the amount of vapor in the charcoal canister 42 is large, the duty ratio DPG and the purge correction amount KPG are adjusted according to the feedback correction coefficient FAF shown in FIG. 8(B). ) and (D), and the amount of vapor is gradually decreased as shown in FIG. 8(A). Here, at time T when the feedback correction coefficient FAF exceeds 1.05 and the duty ratio DPG becomes less than a predetermined value, the purge correction amount KPG is set to zero, and thereafter the feedback correction coefficient FAF becomes 1.0.
At a time point T when the value exceeds 5, the duty ratio DPG becomes zero and the purge is temporarily stopped.

In this way, when correcting the duty ratio DPG, the purge correction amount KPG is taken into account, and if the cause of the air-fuel ratio fluctuation is due to overcorrection of the duty ratio DPG, the duty ratio DPG is adjusted to prevent this overcorrection. In addition, if the purge correction amount KPG is over-corrected, the purge correction amount KPG is controlled to prevent this over-correction. For example, when the air-fuel ratio is lean and the vapor concentration is low, The purge amount is reduced and the air-fuel ratio of the mixture is controlled to be rich, making it possible to accurately maintain the air-fuel ratio at the stoichiometric air-fuel ratio.

Note that the ■Sv control routine in Figure 3 above is executed when the idle switch is on, and when the idle switch is off, the duty ratio DPG is calculated from the engine speed NE and intake air amount by referring to a map. In this case, since the amount of intake air is large, the purge correction amount calculation is not executed, and only the feedback correction coefficient is used. However, this is not limited to this, and even when the idle switch is off, the
The vSV control routine and purge correction amount calculation routine shown in FIG. 4 may be executed, and the present invention is not limited to the above embodiment.

〔Effect of the invention〕

As described above, according to the evaporated fuel processing control device of the present invention,
When the air-fuel ratio is lean, the air-fuel ratio can be maintained at the stoichiometric air-fuel ratio even when the vapor concentration is low, and the air-fuel ratio can be accurately maintained at the stoichiometric air-fuel ratio at all times, which is extremely useful in practice.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of an internal combustion engine to which the device of the present invention is applied, Fig. 3 is a flowchart of the vSv control routine, and Fig. 4 is a purge correction amount calculation routine. Flowchart, FIG. 5 is a flowchart of the fuel injection amount calculation routine, FIG. 6 is a diagram showing the relationship between the feedback correction coefficient, duty ratio, and purge correction amount,
7 and 8 are time charts showing control operations by the apparatus of the present invention. Ml, 10... Internal combustion engine, M2... Detection means, M3
...Purge means, M4...Calculation means, M5...First injection amount correction means, M6...Second injection amount correction means, M7...Purge correction means, 14...Air flow Meter, 15...Fuel injection valve, 28...02 sensor,
30... Electronic control circuit, 42... Charcoal canister, 43... Electric negative pressure switching valve (VSV), 50
~73...step. Figure 1 (A) CB) Figure Figure Figure

Claims (2)

[Claims] (1) A detection means for detecting the operating state of the internal combustion engine, a purge means for releasing evaporated fuel generated in the fuel system into the intake system, and a fuel injection supply to the internal combustion engine in response to a detection signal of the detection means. a calculation means for calculating the amount; and a calculation means for correcting the fuel injection amount calculated by the calculation means by varying an air-fuel ratio feedback correction coefficient so that the air-fuel ratio of the intake air-fuel mixture becomes the stoichiometric air-fuel ratio according to the detection signal of the detection means. First thing to do
a second injection amount correction means for correcting the fuel injection amount calculated by the calculation means according to the evaporated fuel concentration obtained from the air-fuel ratio feedback correction coefficient; A evaporated fuel processing control device comprising a purge correction means for correcting the amount of evaporated fuel released by the purge means, the emission corrected by the purge correction means according to a correction amount of the second injection amount correction means. A vaporized fuel processing control device characterized by controlling the amount of fuel vapor. (2) a detection means for detecting the operating state of the internal combustion engine; a purge means for releasing vaporized fuel generated in the fuel system into the intake system; and a fuel injection supply to the internal combustion engine in response to a detection signal from the detection means. a calculation means for calculating the amount; and a calculation means for correcting the fuel injection amount calculated by the calculation means by varying an air-fuel ratio feedback correction coefficient so that the air-fuel ratio of the intake air-fuel mixture becomes the stoichiometric air-fuel ratio according to the detection signal of the detection means. First thing to do
a second injection amount correction means for correcting the fuel injection amount calculated by the calculation means according to the evaporated fuel concentration obtained from the air-fuel ratio feedback correction coefficient; A evaporated fuel processing control device having a purge correction means for correcting an emitted amount of evaporated fuel discharged by the purge means, the second injection amount correction means being corrected according to the emitted amount corrected by the purge correction means. A vaporized fuel processing control device characterized by controlling the amount of fuel vapor.