JPH0494444A - Vaporized fuel processing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To control air-fuel ratio so as to obtain the theoretical air-fuel ratio by at any time providing a purge correcting means which corrects a release amount of vaporized fuel released by a purge means in accordance with concentration of the vaporized fuel. CONSTITUTION:A purge means M3 releases vaporized fuel, generated in a fuel system, to an intake system, and an arithmetic means M4 calculates a fuel injection amount supplied to an internal combustion engine M1 in accordance with a detection signal of a detecting means M2. The first injection amount correcting means M5 variably corrects an air-fuel ratio feedback correction coefficient so that air-fuel ratio of a suction mixture obtains the theoretical air-fuel ratio in accordance with the detection signal of the detecting means M2, to correct the fuel injection amount calculated in the arithmetic means M4. The second injection amount correcting means M6 corrects the fuel injection amount calculated in the arithmetic means in accordance with concentration of the vaporized fuel obtained from the air-fuel ratio feedback correction coefficient, and a purge correcting means M7 corrects a release amount of vaporized fuel released by the purge means M3 in accordance with concentration of the vaporized fuel.

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.

Further, there is 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 Unexamined Patent Publication 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.

[Invention or problem to be solved]

In the conventional device described above, when the evaporated fuel concentration is high, the correction amount by purge of the fuel injection amount becomes large and the actual fuel injection amount becomes small, or the actual fuel injection amount has a lower limit, that is, a minimum fuel injection amount. Therefore, when the concentration of evaporated fuel is extremely high, it becomes impossible to set the correction amount of the fuel injection amount by purging to an accurate value, resulting in a problem that the air-fuel ratio deteriorates.

The present invention has been made in view of the above points, and is an internal combustion engine in which the air-fuel ratio is always controlled to be the stoichiometric air-fuel ratio by correcting both the fuel injection amount and the vaporized fuel emission amount according to the vaporized fuel concentration. An object of the present invention is to provide a vaporized fuel processing control device.

[Means to solve the problem]

FIG. 1 shows a diagram of the principle of the present invention.

In the figure, a detection means M2 detects the operating state of the internal combustion engine M1.

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

The calculating means M4 calculates the internal combustion engine f! according to the detection signal of the detecting means M2. Calculates the fuel injection amount to be supplied to IMI.

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 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.

[Effect]

In the present invention, as the evaporated fuel is discharged by the purge means M3, the second injection amount correction means M6 corrects the fuel injection amount according to the evaporated fuel concentration, and the purge correction means M7
Since the amount of evaporated fuel discharged by the purge means M3 is corrected according to the evaporated fuel concentration, even when the evaporated fuel concentration is too high to correct the fuel injection amount by the second injection amount correction means M6, the purge correction means M7 The emission amount is corrected by this, and the air-fuel ratio can be controlled to be 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 an intake passage 11 of an internal combustion engine 10, and a throttle position sensor 13 for detecting the opening degree of the throttle valve 12 is provided on the shaft of this throttle valve I2. A pressure sensor I4 for detecting intake pressure is provided in the intake passage 11 on the downstream side of the throttle position sensor 13, and a pressure sensor I4 is provided downstream for supplying pressurized fuel from the fuel supply system to the intake boat for each cylinder. An injection valve (injector) 15 is provided. Further, an intake temperature sensor 16 is provided in the intake passage 11, and an analog electrical signal corresponding to the intake temperature is supplied to the A/D converter 31. The pressure sensor 14 generates an analog voltage electrical signal corresponding to the intake pressure, and this output is supplied to an A/D converter 31 in the electronic control circuit 30.

The distributor 2o has crank angle sensors 21 and 30 degrees that generate a reference position detection pulse signal every 720 degrees 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. The pulse signals from these crank angle sensors 21 and 22 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.
Or 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.

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

The 02 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 4 of the electronic control circuit 30 outputs different output voltages.
0 to the A/D converter 31. 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) 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.
It is equipped with The charcoal canister 42 is connected to the upper bottom of the fuel tank 41 with a vapor collection pipe 44.
Adsorbs vapor that evaporates from 1. The VSV 43 transfers the vapor adsorbed to the charcoal canister 42 to the intake passage 11.
The VSV 43 is a solenoid valve that opens and closes in response to an electric signal from the electronic control circuit 30.

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

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 CPTJ33, ROM34. RAM
35. A backup RAM 36, a clock (CLK) 37, etc., which retain information even after the key switch 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, when the fuel injection amount TAU is calculated by correcting the basic injection amount Tp calculated from the intake pressure and the engine rotational speed based on the operating state of the engine, the fuel injection amount TAU is preset in the down counter of the injection control circuit 39. At the same time, the flip-flop is also set and the drive circuit starts energizing the fuel injection valve 15. On the other hand, when the down counter counts the clock signal (not shown) and the carrier voltage terminal finally reaches 1 level, the flip-flop is reset and the drive circuit stops energizing the fuel injection valve 15. In other words, the fuel injection valve 15 with the fuel injection amount TAU is energized, and therefore an amount of fuel corresponding to the fuel injection amount TAU is injected into the internal combustion engine 1.
It will be sent into the combustion chamber of 0.

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 amount of vapor to be purged is the duty ratio DP of this pulse signal.
Proportional to G.

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

This routine has a precondition that the average value FAFav of the feedback correction coefficient FAF is 0.95<FAFav<
When 1.05 is satisfied, it is executed with an interrupt every 1 sec, for example. However, once the execution condition for the ■S■ control is satisfied, the execution of this routine is not prevented even if this precondition is not satisfied thereafter.

In the figure, in step 50, it is determined whether a feedback control condition is satisfied. Here, if the feedback control conditions are not satisfied, such as when the coolant temperature is low, or when starting, when running under high load, or when fuel is cut, the purge duty ratio DPG is set to zero in step 51, and the purge is stopped.

If the feedback condition is satisfied in step 50, it is determined whether the purge condition is satisfied in step 52.
), if the purge conditions are not met, such as 30 seconds have not passed since the engine was started, or 5 seconds have not passed since the idle switch was turned on, or the vehicle speed is less than 2km/h, or the intake temperature is less than 45℃. Proceeding to step 51, the duty ratio DPG is set to zero.

When the feedback condition and the purge condition are met, it is determined whether the feedback correction coefficient FAFO value exceeds 1.0 (step 53), and if the FAF value exceeds 1.0, the output of the 02 sensor 28 indicates lean. It is determined whether or not (step 54). In the case of lean, the value of the duty ratio DPG is increased by a predetermined value a (step 55). The predetermined value a is, for example, a value corresponding to 10% of the duty ratio DPG. If the above step 54 is 0□ sensor output or rich, step 5
Proceed to step 6 to maintain the value of the duty ratio DPG.

In other words, the value of the feedback correction coefficient FAF is on the side where the fuel injection amount is increased when it is 1.0 or more, and 0.
Only when the two sensor output indicates lean, the duty ratio DPG is increased by a predetermined value a to increase the purge amount.

In step 53, the value of the feedback correction coefficient FAF is 1.
．． If it is less than 0, the value of FAF is compared with a predetermined value KFAFL (step 57). The predetermined value KFAFL is, for example, 0.
95, and if the value of FAF is greater than or equal to the predetermined value KFAFL, that is, 0.95≦FAF≦1.0, the process proceeds to step 56 and the value of the duty ratio DPG is maintained. Also, if the value of FAF is less than the predetermined value KFAFL, 02 sensor 28
In step 58), if the output is lean, the process proceeds to step 56 and the value of the duty ratio DPG is maintained.

If the 02 sensor output is positive in step 58, the process proceeds to step 59 and the value of the duty ratio DPG is decreased by a predetermined value (step 59).

This predetermined value is, for example, a value corresponding to 2% of the duty ratio DPG.

In other words, the value of the feedback correction coefficient FAF is set to the predetermined value K.
The purge amount is reduced by decreasing the duty ratio DPG by a predetermined value only when the fuel injection amount is controlled to be reduced below the FAFL, and when the sensor output indicates rich.

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 64m5ec.

In the figure, in step 60, it is determined whether a feedback control condition is satisfied. Here, if the feedback control conditions are not satisfied, such as when the cooling water temperature is low, at the time of starting, at the time of high load running, or at the time of fuel cut, step 61 is performed and the correction amount of the fuel injection amount by purge, that is, the purge correction amount KPG. Let be zero. This purge correction amount K
PG is the standard idle speed (e.g. 600 rpm)
This is the amount of correction in .

If the feedback condition is satisfied in step 60, it is determined whether the purge condition is satisfied in step 62.
), 30 seconds have not passed since the start, or 5 seconds have not passed since the idle switch was turned on, or the vehicle speed is 21 an/h.
If the purge condition is not satisfied, such as the intake air temperature being less than 45° C. or the intake air temperature being less than 45° C., the process proceeds to step 61, and the purge correction amount KPG is set to zero.

If the feedback condition and purge condition are met, it is determined whether the feedback correction coefficient FAFO value is less than 1.0 (Step 63), and if the FAF value is less than 1.0, the output of the 02 sensor 28 is instructed to be rich. It is determined whether or not there is one (step 64). If it is rich, the value of the purge correction amount KPG is increased by a predetermined value C (step 65). The predetermined value C is, for example, a value corresponding to 4 μsec. 0 in step 64 above. If the sensor output is lean, proceed to step 66 and set the purge correction amount KP.
Maintain the value of G.

In other words, if the value of the feedback correction coefficient FAF is less than 1.0, it is on the rich side where the fuel injection amount is controlled to decrease, and it is 0.
Only when the second sensor output indicates rich, the purge correction amount KPG is increased by a predetermined value a to decrease the fuel injection amount.

In step 63, the value of the feedback correction coefficient FAF is 1.
．． If the value is 0 or more, the value of FAF is compared with a predetermined value KFAFH (step 67). The predetermined value KFAFH is, for example, 1.
05, and if the value of FAF is less than the predetermined value KFAFH, that is, 1.0≦FAF≦1.05, the process proceeds to step 66 and the value of the purge correction amount KPG is maintained. Also, if the value of FAF exceeds the predetermined value KFAFH, the 02 sensor 28
In step 68), it is determined whether or not the output signal is instructing the output signal to be on. If it is rich, the process proceeds to step 66 and the value of the purge correction amount KPG is maintained.

If the 02 sensor output is lean in step 68, the process proceeds to step 69, and the purge correction amount KPGO value is set to a predetermined value d.
(step 69).

This predetermined value d is, for example, a value corresponding to 4 μSeC.

In other words, the feedback correction coefficient FAFO value is set to the predetermined value K.
The fuel injection amount is increased by decreasing the purge correction amount KPG by a predetermined value d only when FAFH is exceeded and the fuel injection amount is on the lean side and ○, and the sensor output indicates lean. .

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 pressure PM and the engine 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.

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

TAU=r-(KPC; , the purge correction amount KPG is increased. In the region where the feedback correction coefficient FAF or KFAFL is greater than or equal to 1.0, the duty ratio DPG is maintained and the purge correction amount KP is
G is increased.

Furthermore, in a region where the feedback correction coefficient FAF is greater than or equal to 1.0 and less than or equal to the predetermined value KFAFH, the duty ratio DPG is increased and the purge correction amount KPG is maintained. In a region exceeding the feedback correction coefficient FAF or KFAFH, the duty ratio DPG is increased and the purge correction amount KPG is decreased.

Here, if the vapor generation is small and the amount of vapor in the charcoal canister 42 is small, as shown in FIG.
When the feedback correction coefficient FAFO value indicated by a exceeds 1.0 and the O2 sensor output indicates lean (the solid line Ib indicates the air-fuel ratio A/F), the duty ratio DPG is increased and the purge shown by the solid line Ic is performed. The flow rate increases and the vapor in the charcoal canister 42 is released. In this case, since the vapor concentration is low, the feedback correction coefficient FA
F never becomes less than a predetermined value KFAFL, and when FAF is 1.0 or more, the duty ratio DPG and the purge flow rate increase dramatically. In addition, the feedback correction coefficient FAF almost never exceeds the predetermined value KFAFH, the purge correction amount KPG hardly increases, and the TAU correction amount FPURGFPURGE=KPGXNE6/NE hardly increases and maintains a low value as shown by the solid line Id. do.

In addition, if the vapor generation is large and the amount of vapor in the charcoal canister 42 is too large, as shown in FIG.
Feedback correction coefficient FAFO value indicated by Ia or 1.0
exceeds 0□When the sensor output indicates lean (
The solid line I [b indicates the air-fuel ratio A/F] shows the duty ratio DP.
G is increased, the purge flow rate shown by the solid line I[c increases, and the vapor in the charcoal canister 42 is released. In this case, the vapor concentration is high, but the feedback correction coefficient F
When AF is 1.0 or more, the duty ratio DPG, that is, the purge flow rate increases. Also, the feedback correction coefficient F
When AF is less than 1.0 and the 0□ sensor output indicates rich, the purge correction amount KPG, that is, the TAU correction amount FPURGE, increases rapidly as shown in IId. However, when the feedback correction coefficient FAF is less than the predetermined value KFAFL and the sensor output becomes rich due to the high vapor concentration, the duty ratio, that is, the purge flow rate, is decreased, and as a result, the purge correction amount KPG, that is, the TAU correction amount is increased. Regulated.

In this way, along with the purge, the purge correction amount calculation routine changes the fuel injection amount to the purge correction amount KP according to the vapor concentration.
Correct only the value according to G, and in the vSV control routine,
Since the purge duty ratio DPG, that is, the vapor amount is corrected according to the vapor concentration, vSv control is performed even when the vapor concentration is high and the fuel injection amount is regulated by the minimum fuel injection amount and cannot be corrected by the purge correction amount calculation routine. The amount of vapor released is corrected by the routine, and thereby the air-fuel ratio can be controlled to be the stoichiometric air-fuel ratio.

In addition, as shown in Fig. 6, the correction coefficient F
If the AF is 1.0 or more and it is off to the lean side, increase the duty ratio, that is, the purge amount as much as possible, and set the FAF to 1.
．． If it is less than 0 and deviates to the rich side, the purge correction amount K
Since the air-fuel ratio is maintained at the stoichiometric air-fuel ratio by increasing the PG as much as possible, the purge amount can be increased as much as possible, thereby improving fuel efficiency.

Note that the ■S■ 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 pressure by referring to the map. In this case, since the amount of intake air is large, the purge correction amount calculation is not executed, and only the foot correction coefficient is used. However, the present invention is not limited to this, and the VS■ control routine and purge correction amount calculation routine shown in FIGS. 3 and 4 may be executed even when the idle switch is off, 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 for an internal combustion engine of the present invention, even when the concentration of evaporated fuel is high and cannot be corrected by correcting the fuel injection amount, the amount of evaporated fuel released is corrected, and the air-fuel ratio is always maintained at the theoretical level. The air-fuel ratio can be controlled to be the same, making it extremely useful in practice.

[Brief explanation of the drawing]

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 position.
7 and 8 are time charts showing control operations by the apparatus of the present invention. Ml, to... Internal combustion engine, M2... Detection means, M3
...Purge means, M4...Calculation means, M5...First injection amount correction means, M6...Second injection amount correction means, Ml...Purge correction means, 14...Pressure sensor,
15...Fuel injection valve, 28...02 sensor, 30...
...Electronic control circuit, 42...Charcoal canister,
43...Electric negative pressure switching valve (VSV), 50-73
... Ste Nobu. Patent applicant: Toyota Motor Corporation Figure 1 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] Detection means for detecting the operating state of the internal combustion engine; purge means for discharging evaporated fuel generated in the fuel system into the intake system; and supply to the internal combustion engine in response to a detection signal from the detection means. a calculation means for calculating the amount of fuel to be injected, and a fuel injection for calculating 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. The first to correct the amount
and a second injection amount correction means for correcting the fuel injection amount calculated by the calculation means according to the vapor fuel concentration obtained from the air-fuel ratio feedback correction coefficient. What is claimed is: 1. A control device for controlling evaporated fuel for an internal combustion engine, comprising: a purge correction means for correcting an amount of evaporated fuel discharged by the purge means in accordance with the evaporated fuel concentration.