JP2700128B2 - Evaporative fuel processing control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing control apparatus for an internal combustion engine that discharges and processes evaporative fuel from an internal combustion engine to an intake system.

[Conventional technology]

2. Description of the Related Art Conventionally, in an internal combustion engine, evaporative fuel generated from a fuel tank or the like is adsorbed on activated carbon and purged (discharged) to an intake system for processing.

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

For example, the apparatus described in JP-A-63-289243 performs a correction by purging the fuel injection amount separately from the feedback correction at the time of performing the purge, and obtains the purge correction amount 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 the air-fuel ratio control.

[Problems to be solved by the invention]

In the above conventional apparatus, when the fuel vapor concentration is high, the correction amount by purging the fuel injection amount becomes large and the actual fuel flow injection amount becomes small. However, the actual fuel injection amount has a lower limit, that is, the minimum fuel injection amount. When the fuel vapor concentration is extremely high, there is a problem that the correction amount by purging the fuel injection amount cannot be set to an accurate value and the air-fuel ratio deteriorates.

The present invention has been made in view of the above points, and an internal combustion engine that constantly controls an air-fuel ratio to be a stoichiometric air-fuel ratio by correcting both a fuel injection amount and an emission amount of evaporated fuel in accordance with an evaporated fuel concentration. It is an object of the present invention to provide an evaporative fuel processing control device.

[Means for solving the problem]

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

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

The purge means M3 discharges the evaporated fuel generated in the fuel system to the intake system.

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

The first injection amount correcting 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 in accordance with the detection signal of the detecting means M2, and calculates the fuel injection amount calculated by the calculating means M4. Is corrected.

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

The purge correction means M7 corrects the amount of fuel vapor released by the purge means M3 according to the fuel vapor concentration obtained from the air-fuel ratio feedback correction coefficient.

[Action]

In the present invention, the fuel injection amount is corrected in accordance with the evaporated fuel concentration by the second injection amount correcting means M6 in accordance with the release of the evaporated fuel by the purging means M3, and the evaporated fuel concentration is corrected by the purge correcting means M7. Therefore, even when the fuel injection amount cannot be completely corrected by the second injection amount correction means M6 due to the high concentration of the evaporated fuel, the discharge amount is corrected by the purge correction means M7. Thereby, the air-fuel ratio can be controlled to be the stoichiometric air-fuel ratio.

〔Example〕

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

In FIG. 1, a throttle valve 12 is provided in an intake passage 11 of an internal combustion engine 10.
A throttle position sensor 13 for detecting the opening of the throttle valve 12 is provided on the shaft of the throttle valve 12. A pressure sensor 14 for detecting an intake pressure is provided in the intake passage 11 on the downstream side of the throttle position sensor 13, and a fuel for supplying pressurized fuel to the intake port from a fuel supply system for each cylinder further downstream. An injection valve (injector) 15 is provided. An intake air temperature sensor 16 is provided in the intake passage 11, and an analog electric signal corresponding to the intake air temperature is supplied to the A / D converter 31. The pressure sensor 14 generates an analog voltage electric 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 20 has a crank angle sensor 21 whose axis converts a crank angle (CA) to generate a reference position detecting pulse signal at every 720 ° CA, and generates a reference position detecting pulse signal at every 30 ° CA. A crank angle sensor 22 is provided. The pulse signals of the 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 the input / output interface 32 of the electronic control circuit 30.

Further, the cooling water passage 23 of the cylinder block of the internal combustion engine 10
Is provided with a water temperature sensor 24 for detecting the temperature of the cooling water. The water temperature sensor 24 generates an analog voltage electric signal corresponding to the cooling water temperature THW, and this output is supplied to the A / D converter 31.

The exhaust manifold 25 downstream of the exhaust system, the three harmful components HC in the exhaust gas, CO, three-way catalytic converter 26 to simultaneously purify NO _X is provided. An O ₂ sensor, which is a type of air-fuel ratio sensor, is provided on the exhaust pipe 27 downstream of the exhaust manifold 25 and upstream of the catalytic converter 26.
28 are provided. The O ₂ sensor 28 generates an electric signal according to the concentration of the oxygen component in the exhaust gas. That is, the O ₂ sensor 28 supplies a different output voltage to the A / D converter 31 via the signal processing circuit 40 of the electronic control circuit 30 depending on whether the air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio. I do. An on / off signal of a key switch (not shown) is supplied to the input / output interface 32, and an analog signal of a vehicle speed sensor (not shown) is supplied to the A / D converter 31.

Further, the internal combustion engine 10 is provided with an evaporative purge system for preventing evaporated fuel (vapor) evaporated from the fuel tank 41 from escaping into the atmosphere. This system includes a charcoal canister 42 and an electric negative pressure switching valve (VSV) 43 as a purge means M3. The charcoal canister 42 is connected to the upper bottom of the fuel tank 41 by a vapor collecting pipe 44,
Vapor evaporating from the fuel tank 41 is adsorbed. The VSV 43 passes the vapor adsorbed on the charcoal canister 42 to the intake passage
The VSV 43 is an on-off valve provided in the middle of the vapor recirculation pipe 45 returning to the downstream of the throttle valve 12 and receiving and receiving 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 to start a program, take in outputs from each sensor, and control the injector 15 and other actuators.

The electronic control circuit 30 is configured by using, for example, a microcomputer, and in addition to the above-described A / D converter 31, input / output interface 32, and CPU 33, a ROM 34, a RAM 35, and a backup RAM 36 that retains information even after a key switch is turned off. , Clock (CLK) 3
7 and the like are provided, and these are connected by a bus 38.

In the electronic control circuit 30, an injection control circuit 39 including a down counter, a flip-flop, and a drive circuit controls 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 speed in 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 set, and the drive circuit starts energizing the fuel injection valve 15. On the other hand, when the down counter counts a clock signal (not shown) and its carry-out terminal finally becomes "1" level, the flip-flop is reset and the drive circuit starts to operate the fuel injection valve 15.
Stop urging. That is, the fuel injection valve 15 is energized by the above-described fuel injection amount TAU.
Is sent into the combustion chamber of the internal combustion engine 10.

Next, a control program of an embodiment of the present invention will be described.

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 a high level period of the pulse signal. That is, the amount of vapor to be purged is proportional to the duty ratio DPG of the pulse signal.

FIG. 3 shows a flowchart of one embodiment of the VSV control routine as the purge correction means M7. This routine
As a precondition, the average value FAF of the feedback correction coefficient FAF
When av satisfies 0.95 <FAFav <1.05, for example, 1se
It is executed by an interrupt for each c. However, once the execution condition of the VSV control is satisfied, the execution of this routine is not hindered even if the precondition is subsequently not satisfied.

In the figure, at step 50, it is determined whether or not the feedback control condition is satisfied. Here, 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, the feedback control conditions such as those at the time of fuel cut are not satisfied, the purge duty ratio DPG is set to zero at step 51 to stop the purge.

If the feedback condition is satisfied in step 50, it is determined whether the purge condition is satisfied (step 5).
2), 30 seconds have not elapsed after the start, or 5 seconds have not elapsed since the idle switch was turned on, or the vehicle speed was less than 2 km / h,
Alternatively, if the purge condition such as the intake air temperature is lower than 45 ° C. is not satisfied, the routine proceeds to step 51, where the duty ratio DPG is set to zero.

When the feedback condition and the purge condition are satisfied, it is determined whether or not the value of the feedback correction coefficient FAF exceeds 1.0 (step 53). If the value of the FAF exceeds 1.0, O ₂
It is determined whether or not the output of the sensor 28 indicates lean (step 54). Here, in the case of lean, the value of the duty ratio DPG is increased by a predetermined value a (step 5).
Five). The predetermined value a is, for example, a value corresponding to 10% of the duty ratio DPG. O ₂ sensor output to maintain the value of the duty ratio DPG proceeds to step 56 if rich in the step 54.

That is in the lean side value of the feedback correction coefficient FAF is increased controls the amount of fuel injection at 1.0 or more and the duty ratio only when the O ₂ sensor output is instructed lean
The DPG is increased by a predetermined value a to increase the purge amount.

If the value of the feedback correction coefficient FAF is less than 1.0 in step 53, the value of the FAF is compared with a predetermined value KFAFL (step 53).
57). The predetermined value KFAFL is, for example, 0.95, and when the value of the FAF is equal to or larger than the predetermined value KFAFL, that is, when 0.95 ≦ FAF ≦ 1.0, step 5 is performed.
Proceed to 6 to maintain the value of the duty ratio DPG. The value of FAF is in the case of less than the predetermined value KFAFL to determine whether the output of the O ₂ sensor 28 is pointing rich (step 58),
If lean, proceed to step 56 to change the duty ratio DPG
Maintain the value of.

O ₂ sensor output decreases the value of the duty ratio DPG proceeds to step 59, if the rich predetermined value b in step 58 (step 59). The predetermined value b is, for example, a value corresponding to 2% of the duty ratio DPG.

That is, the value of the feedback correction coefficient FAF is
The purge amount is reduced by reducing the duty ratio DPG by a predetermined value b only when the fuel injection amount is on the rich side where the fuel injection amount is controlled to be reduced below FL and the output of the O ₂ sensor indicates rich.

FIG. 4 shows a flowchart of one embodiment of a purge correction amount calculation routine as the second injection amount correction means M6. This routine is executed by interruption every 64mesc.

In the figure, at step 60, it is determined whether or not the feedback control condition is satisfied. Here, when the cooling water temperature is low, at the time of starting, at the time of high-load running, or when the feedback control condition such as at the time of fuel cut is not satisfied, in step 61, the correction amount of the fuel injection amount by purging, that is, the purge correction amount KPG Is set to zero. This purge correction amount KPG is a correction amount at a reference idle speed (for example, 600 rpm).

If the feedback condition is satisfied in step 60, it is determined whether the purge condition is satisfied (step 6).
2), 30 seconds have not elapsed after the start, or 5 seconds have not elapsed since the idle switch was turned on, or the vehicle speed was less than 2 km / h,
Alternatively, if the purge condition such as the intake air temperature is lower than 45 ° C. is not satisfied, the routine proceeds to step 61, where the purge correction amount KPG is set to zero.

When the feedback conditions and purge condition is satisfied, the value of the feedback correction coefficient FAF is to determine whether less than 1.0 (step 63), O ₂ sensor when the value of FAF is less than 1.0
It is determined whether the output of 28 indicates rich (step 64). Here, if rich, purge correction amount
The value of KPG is increased by a predetermined value c (step 65). The predetermined value c is a value corresponding to, for example, 4 μsec. If the O ₂ sensor output is lean at step 64 Step 66
Then, the value of the purge correction amount KPG is maintained.

That is in the rich side value of the feedback correction coefficient FAF is reduced controls the fuel injection amount is less than 1.0, and only the purge correction amount when the O ₂ sensor output is instructed rich
The fuel injection amount is decreased by increasing KPG by a predetermined value c.

If the value of the feedback correction coefficient FAF is equal to or greater than 1.0 in step 63, the value of the FAF is compared with a predetermined value KFAFH (step 63).
67). The predetermined value KFAFH is, for example, 1.05, and if the value of the FAF is equal to or less than the predetermined value KFAFH, that is, if 1.0 ≦ FAF ≦ 1.05, step 6
Proceeding to 6, the value of the purge correction amount KPG is maintained. Also in the case where the value of FAF exceeds a predetermined value KFAFH to determine whether the output of the O ₂ sensor 28 is instructed to lean (Step 6
8) If rich, proceed to step 66 to maintain the value of the purge correction amount KPG.

O ₂ sensor output at step 68 proceeds to step 69 if lean, reduces the value of the purge correction amount KPG predetermined value d (step 69). The predetermined value d is, for example, 4 μse
This is a value corresponding to c.

That is, the value of the feedback correction coefficient FAF is
The fuel injection amount is increased by decreasing the purge correction amount KPG by a predetermined value d only when the fuel injection amount is on the lean side where the fuel injection amount is controlled to increase beyond FH and the output of the O ₂ sensor indicates lean. .

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

In the figure, at step 71, the intake pressure PM and the engine speed
The basic fuel injection amount Tp is calculated based on NE. Next, the fuel injection amount τ is obtained from the basic fuel injection amount Tp, the feedback correction coefficient FAF, and the constant K by the following equation (step 7).
2).

τ = Tp × FAF × K This step 72 corresponds to the first injection amount correction means M5.

Further, the actual fuel injection amount TAU is obtained by the following equation using the fuel injection amount τ, the purge correction amount KPG, the reference idle speed NE _0, and the speed NE.

TAU = τ− (KPG × NE ₀ / NE) According to the VSV control routine and the purge correction amount calculation routine, as shown in FIG.
In a region where the FAF is less than the predetermined value KFAFL, the duty ratio DPG is reduced and the purge correction amount KPG is increased. In a region where the feedback correction coefficient FAF is equal to or larger than KFAFL and smaller than 1.0, the duty ratio DPG is maintained, and the purge correction amount KPG is increased.

When the feedback correction coefficient FAF is 1.0 or more,
In a region equal to or lower than KFAFH, the duty ratio DPG is increased, and the purge correction amount KPG is maintained. Feedback correction factor FAF
In the region where exceeds KFAFH, the duty ratio DPG is increased,
The purge correction amount KPG is reduced.

Here, when the amount of vapor generated is small and the amount of vapor in the charcoal canister 42 is small, as shown in FIG.
The value of the feedback correction coefficient FAF indicated by a exceeds 1.0,
And when the O ₂ sensor output indicates lean (solid line Ib indicates air-fuel ratio A / F), the duty ratio DPG is increased and the solid line
The purge flow rate indicated by I c increases and the charcoal canister 4
The vapor in 2 is released. In this case, since the vapor concentration is low, the feedback correction coefficient FAF does not fall below the predetermined value KFAFL.
DPG, or barge flow, increases steadily. Further, the feedback correction coefficient FAF hardly exceeds the predetermined value KFAFH, the purge correction amount KPG hardly increases, and the TAU
The correction amount FPURGE FPURGE = KPG × NE ₀ / NE hardly increases as shown by the solid line Id and maintains a low value.

If the amount of vapor generated in the charcoal canister 42 is too large due to the large amount of vapor generated, as shown in FIG.
The value of the feedback correction coefficient FAF indicated by a exceeds 1.0,
And when the O ₂ sensor output indicating a lean (solid line II b shows the air-fuel ratio A / F), the duty ratio DPG is increased, the solid
The purge flow rate shown in IIc increases and the charcoal canister
The vapor in 42 is released. In this case, when the vapor concentration is high but the feedback correction coefficient FAF is 1.0 or more, the duty ratio DPG, that is, the purge flow rate increases. Further, when the feedback correction coefficient FAF is less than 1.0 and the output of the O ₂ sensor indicates rich, the purge correction amount KPG, that is, the TAU correction amount FPURGE increases rapidly as shown by IId. However, due to the high vapor concentration, the feedback correction factor FA
F is O ₂ duty ratio, i.e. purge flow when the sensor output becomes rich is less than a predetermined value KFAFL reduced, this increase in purge correction amount KPG clogging TAU correction amount by is regulated.

As described above, in accordance with the purge, the fuel injection amount is changed in accordance with the vapor concentration by the purge correction amount KP in the purge correction amount calculation routine.
In order to correct only the value corresponding to G and to correct the purge duty ratio DPG, that is, the amount of vapor, in accordance with the vapor concentration in the VSV control routine, the vapor concentration is high and the fuel injection amount is regulated at the minimum fuel injection amount, and the purge correction is performed. Even when the correction cannot be completed by the correction by the amount calculation routine, the amount of vapor released is corrected by the VSV control routine, whereby the air-fuel ratio can be controlled to be the stoichiometric air-fuel ratio.

In addition, as shown in FIG.
When F is 1.0 or more and lean to the lean side, increase the duty ratio, that is, the purge amount, as much as possible.When FAF is less than 1.0 and shift to the rich side, increase the purge correction amount KPG as much as possible to increase the air-fuel ratio. Since the stoichiometric air-fuel ratio is maintained, the purge amount can be increased as much as possible, thereby improving the fuel efficiency.

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

〔The invention's effect〕

As described above, according to the evaporative fuel processing control apparatus for an internal combustion engine of the present invention, even when the concentration of the evaporative fuel is high and cannot be corrected by correcting the fuel injection amount, the amount of the evaporative fuel released is corrected, and the air-fuel ratio is always theoretically adjusted. It can be controlled to achieve an air-fuel ratio, which is extremely useful in practice.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a configuration diagram of an embodiment of an internal combustion engine to which the present invention is applied, FIG. 3 is a flowchart of a VSV control routine, and FIG. Flowchart, FIG. 5 is a flowchart of a fuel injection amount calculation routine, FIG. 6 is a diagram showing a relationship between a feedback correction coefficient, a duty ratio, and a purge correction amount, and FIGS. 7 and 8 are control by the apparatus of the present invention. 6 is a time chart illustrating an operation. M1,10 ... internal combustion engine, M2 ... detection means, M3 ... purge means, M4 ... calculation means, M5 ... first injection amount correction means, M6
... 2 injection amount correction means, M7 ... purge correction means, 14 ...
... pressure sensor, 15 ...... fuel injection valve, 28 ...... O ₂ sensor, 30
…… Electronic control circuit, 42 …… Charcoal canister, 43…
… Electric negative pressure switching valve (VSV), 50-73 …… Steps.

Claims (1)

(57) [Claims] A detecting means for detecting an operation state of the internal combustion engine; a purging means for discharging vaporized fuel generated in a fuel system to an intake system; and supplying the fuel to the internal combustion engine in accordance with a detection signal of the detecting means. Calculating means for calculating a fuel injection amount; and a fuel injection amount calculated by the calculating means by varying an air-fuel ratio feedback correction coefficient so that an air-fuel ratio of the intake air-fuel mixture becomes a stoichiometric air-fuel ratio according to a detection signal of the detecting means. First to correct
Evaporative fuel processing for an internal combustion engine, comprising: an injection amount correcting means for correcting the fuel injection amount calculated by the calculating means in accordance with the evaporated fuel concentration obtained from the air-fuel ratio feedback correction coefficient. In the control device, there is provided purge correction means for correcting the amount of evaporative fuel released by the purge means in accordance with the evaporative fuel concentration obtained from the air-fuel ratio feedback correction coefficient. apparatus.