JP3161219B2 - Evaporative fuel treatment system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing system for an internal combustion engine, and more particularly to an evaporative fuel treatment system for an internal combustion engine that performs learning control of an air-fuel ratio. TECHNICAL FIELD The present invention relates to an evaporative fuel treatment apparatus for an internal combustion engine, which can update the concentration of air to prevent the air-fuel ratio from becoming rough.

[0002]

2. Description of the Related Art In general, in an internal combustion engine, an evaporative fuel treatment device (evaporation fuel treatment device) is provided to prevent fuel vapor (HC) evaporating from a fuel storage unit such as a fuel tank or a carburetor from being released to the atmosphere when the internal combustion engine is stopped. System) is provided. In this evaporation system, evaporated fuel (hereinafter referred to as vapor) evaporated from a fuel storage unit is adsorbed to a canister, and the vapor adsorbed by the canister is sucked into an intake side by using a suction negative pressure during operation of the engine. (Purge).

An air-fuel ratio sensor is provided in the exhaust passage, and the fuel injection amount is corrected by a feedback correction coefficient (FAF) based on the output signal of the sensor so that the air-fuel ratio becomes the target air-fuel ratio. In an electronically controlled fuel injection type internal combustion engine equipped with an air-fuel ratio control device, if the vapor adsorbed in the canister is purged toward the intake side, the air-fuel ratio will be deviated, so the fuel injection amount must be corrected with the purged vapor amount. is there. For this correction, it is necessary to accurately know the concentration of the vapor to be returned to the intake passage.

On the other hand, in the air-fuel ratio control device, learning control of the air-fuel ratio is generally performed in order to correct a characteristic deviation due to a temporal change of an actuator such as an air-fuel ratio sensor and a fuel injection valve. In this learning control, it is common practice to divide the operating state of the engine into regions according to the load of the engine, provide a learning value for each region, and update the learning value based on the deviation of the feedback correction coefficient from the reference value. I have.

When the purge control of the vapor is combined with the air-fuel ratio control device having the learning value for each operation region of the engine, in the operation region of the engine where the learning control of the base air-fuel ratio is completed, the air-fuel ratio at the time of performing the purge is determined. Reference value (target air-fuel ratio)
Deviation from (hereinafter simply referred to as the deviation of the air-fuel ratio) can be calculated all vapor concentration as the influence of purge. However, in the engine operating region where the learning control of the base air-fuel ratio has not been completed, it cannot be determined whether the deviation of the air-fuel ratio at the time of performing the purge is a deviation of the air-fuel ratio learning or the influence of the purge. In such a case, if the deviation of the air-fuel ratio is taken in as the deviation of the air-fuel ratio learning, there is a risk of erroneous learning. Since the adverse effect of the erroneous learning is very large, the deviation of the air-fuel ratio is taken in as the vapor concentration.

Therefore, in the conventional air-fuel ratio control device, when purging is performed in the operating region of the engine in which the learning control of the base air-fuel ratio is not completed, the deviation of the feedback correction coefficient is slowly taken as the vapor concentration, or the purge is performed. The vapor concentration learning speed at the time of execution is made faster than the base air-fuel ratio learning.

[0007]

However, in the control in which the deviation of the feedback correction coefficient is slowly taken in as the vapor concentration at the time of purging in the engine operating region where the learning control of the base air-fuel ratio is not completed, the vapor concentration is , The feedback correction coefficient is greatly roughened, and drivability may be deteriorated. Further, in the control in which the vapor concentration learning speed is made faster than the base air-fuel ratio learning at the time of performing the purge, there is a possibility that the vapor concentration learning may be erroneously learned.
In this case, if the speed of the vapor concentration learning is reduced, the possibility of erroneous learning is reduced, but the air-fuel ratio feedback correction coefficient may be greatly changed.

Accordingly, the present invention solves the above-described problems in the conventional evaporative fuel processing apparatus for an internal combustion engine, and in an internal combustion engine that performs learning control of an air-fuel ratio, whether the air-fuel ratio learning is completed or not completed is determined by the canister. It is an object of the present invention to provide an evaporative fuel treatment device for an internal combustion engine that can prevent the air-fuel ratio from becoming rough by updating the vapor concentration of the fuel.

[0009]

According to a first aspect of the present invention, there is provided an evaporative fuel processing apparatus for an internal combustion engine which detects the concentration of residual oxygen in exhaust gas by a sensor provided in an exhaust passage and performs feedback learning of an air-fuel ratio. In an internal combustion engine that performs control, fuel vapor from a fuel system is adsorbed in a canister,
An evaporative fuel processor for purging evaporative fuel adsorbed in the canister into an intake passage by a purge passage provided with a flow control valve during operation of the engine, wherein the feedback learning control of the air-fuel ratio is performed in an operating region of the internal combustion engine. Is performed for each region by dividing into a plurality of regions, and in each of the operating regions having a learned value of the air-fuel ratio, in the region where the learning is completed, the calculation is performed based on the detected value of the oxygen concentration in the exhaust gas. Air-fuel ratio and air-fuel ratio feedback during purge control
Vapor concentration calculating means for calculating the concentration of the evaporated fuel gas based on the shift amount of the correction coefficient to the rich side or the lean side ,
In the learning non-completion region, the concentration of the evaporative fuel gas calculated in the learning completion region is subtracted by using a subtraction value corresponding to the decrease in the amount of the evaporative fuel adsorbed in the canister, thereby obtaining the evaporative fuel gas. Vapor concentration estimating means for estimating the concentration, and fuel injection amount correcting means for correcting the fuel injection amount based on the concentration of the evaporated fuel gas obtained by the vapor concentration calculating means or the vapor concentration estimating means. Features.

The vapor concentration estimating means calculates the subtraction value as a true vapor concentration in the base A / F learning completion region.
Degree, the accumulated purge flow rate and the decay rate of the vapor concentration.
Alternatively, the subtraction value may be determined according to the difference between the vapor concentration and the accumulated vapor flow rate calculated by the integrated purge flow rate calculation means. Further, the vapor concentration estimating means has a map for storing the subtraction value in association with a representative value of the amount of evaporated fuel adsorbed on the canister, and in a learning completion area,
The map of the map value may be learned and updated if the concentration of the evaporated fuel obtained by the oxygen concentration detection sensor is compared with the concentration of the evaporated fuel obtained by the subtraction operation and the difference is equal to or more than a predetermined value.

[0011]

According to the evaporative fuel processing apparatus for an internal combustion engine of the present invention, in the region where the learning is completed, the air-fuel ratio calculated by the vapor concentration calculating means based on the detected value of the oxygen concentration in the exhaust gas, and the purge control. Air-fuel ratio feedback supplement during execution
The concentration of the evaporated fuel gas is calculated based on the shift amount of the positive coefficient to the rich side or the lean side . In the learning-uncompleted region, the vapor concentration estimating means subtracts the concentration of the evaporated fuel gas obtained in the learning-completed region using a subtraction value corresponding to a decrease in the amount of the evaporated fuel adsorbed on the canister. Thus, the concentration of the evaporated fuel gas is estimated. Then, the fuel injection amount correcting means corrects the fuel injection amount based on the concentration of the evaporated fuel gas obtained by the vapor concentration calculating means or the vapor concentration estimating means. As a result, the vapor concentration from the canister is updated irrespective of whether the learning of the air-fuel ratio is completed or not completed, so that the roughening of the air-fuel ratio is prevented.

Here, the vapor concentration estimating means calculates the subtraction value as a true vapor concentration in the base A / F learning completion region.
Degree, the accumulated purge flow rate and the decay rate of the vapor concentration.
It is determined according to the difference from the vapor concentration , or the subtraction value is determined according to the integrated amount of evaporated fuel calculated by the integrated purge flow rate calculating means. Further, when the vapor concentration estimating means has a map for storing the subtracted value in correspondence with the representative value of the amount of evaporated fuel adsorbed on the canister, the map is obtained by the oxygen concentration detecting sensor in the learning completion region. The concentration of the evaporated fuel is compared with the concentration of the evaporated fuel obtained by the subtraction operation, and when the difference is equal to or more than a predetermined value,
The map value is learned and updated.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 schematically shows an electronically controlled fuel injection type internal combustion engine 1 provided with an evaporative fuel treatment device 20 according to one embodiment of the present invention. In FIG. 1, a throttle valve 18 is provided in an intake passage 2 of an internal combustion engine 1, and a throttle opening sensor 19 for detecting an opening of the throttle valve 18 is provided on a shaft of the throttle valve 18. . A surge tank 3 is provided in the intake passage 2 on the downstream side of the throttle opening sensor 19, and a pressure sensor 17 for detecting a pressure of intake air is provided in the surge tank 3. Further, on the downstream side of the surge tank 3, a fuel injection valve 7 for supplying pressurized fuel from a fuel supply system to an intake port is provided for each cylinder.

The distributor 4 has crankshaft sensors 5 and 30 ° CA whose axes generate pulse signals for detecting a reference position every 720 ° CA in terms of, for example, crank angle (CA).
A crank angle sensor 6 for generating a pulse signal for detecting a reference position is provided every time. These crank angle sensors 5,
The pulse signal 6 functions as a fuel injection timing interrupt request signal, an ignition timing reference timing signal, a fuel injection amount calculation control interrupt request signal, and the like. These signals are sent to the control circuit 1
0, and the output of the crank angle sensor 6 is supplied to an interrupt terminal of the CPU 103.

In the cooling water passage 8 of the cylinder block of the internal combustion engine 1, a water temperature sensor 9 for detecting the temperature of the cooling water is provided. Water temperature sensor 9 is the temperature of cooling water
Generates analog voltage electric signal according to THW. This output is supplied to the A / D converter 101 of the control circuit 10. The exhaust system downstream of the exhaust manifold 11 is provided with a three-way catalytic converter 12 that simultaneously purifies three harmful components HC, CO, and NOx in the exhaust gas. An O ₂ sensor 13, which is a type of air-fuel ratio sensor, is provided in the exhaust pipe 14 downstream of the exhaust manifold 11 and upstream of the catalytic converter 12. The O ₂ sensor 13 generates an electric signal according to the concentration of the oxygen component in the exhaust gas. That is, the O ₂ sensor 13 supplies a different output voltage to the A / D converter 101 via the signal processing circuit 111 of the control circuit 10 depending on whether the air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio. . The input / output interface 102 is supplied with an on / off signal of a key switch (not shown).

[0016] In this case, based evaporating from the fuel tank 21
Evaporative fuel processing device 20 Pas is prevented from escaping into the atmosphere
Has a charcoal canister 22 and an electric purge flow control valve (VSV) 26. The charcoal canister 22 is connected to the upper bottom of the fuel tank 21 by a vapor collecting pipe 25 and adsorbs vapor evaporated from the fuel tank 21. In the middle of the vapor collection pipe 25, the fuel tank 21
A tank internal pressure control valve 23 is provided which opens when the pressure of the vapor inside the tank becomes equal to or higher than a predetermined pressure. This internal pressure control valve 23
, A switch is attached, and the open / close state of the internal pressure control valve 23 is input to the input / output interface 102. The VSV 26 converts the vapor adsorbed by the charcoal canister 22 into the throttle valve 1 of the intake passage 2.
An electromagnetic on-off valve provided in the middle of the vapor recirculation pipe 27 returning to the downstream side of 8, and opens and closes in response to an electric signal from the control circuit 10. The VSV 26 can perform duty control on the amount of vapor flowing into the intake passage 2.

In the above-described configuration, when a key switch (not shown) is turned on, the control circuit 10 is energized to start a program and capture the output from each sensor.
It controls the fuel injection valve 7 and other actuators. The control circuit 10 is configured using, for example, a microcomputer, and in addition to the above-described A / D converter 101, input / output interface 102, CPU 103, ROM 104, RA
M1 0 5, after off the key switch also for holding information backup RAM 106, and the clock (CLK) 107 and the like are provided, which are connected to each other by a bus 113. In this control circuit 10, an injection control circuit 11 including a down counter, a flip-flop, and a driving circuit is provided.
0 is for controlling the fuel injection valve 7. That is,
Basic injection amount T calculated from intake air amount and engine speed
When the fuel injection amount TAU obtained by correcting p in the operating state of the engine is calculated, the fuel injection amount TAU is preset in the down counter of the injection control circuit 110 and the flip-flop is set, so that the drive circuit of the fuel injection valve 7 Start biasing. On the other hand, when the down counter counts a clock signal (not shown) and the carry-out terminal finally becomes "1" level, the flip-flop is reset and the drive circuit stops energizing the fuel injection valve 7. I do. That is, the fuel injection valve 7 is energized by the above-described fuel injection amount TAU, so that an amount of fuel corresponding to the fuel injection amount TAU is sent to the combustion chamber of the internal combustion engine 1.

Note that the CPU 103 generates an interrupt at A / D
After the A / D conversion of the converter 101, when the input / output interface 102 receives the pulse signal of the crank angle sensor 6, when it receives the interrupt signal from the clock generation circuit 107, and the like. Next, the calculation of the air-fuel ratio feedback correction coefficient (FAF) and the base air-fuel ratio learning value in the evaporative fuel processing apparatus 20 of the embodiment configured as described above will be described with reference to FIG. In this internal combustion engine, the operating range of the engine is divided into n according to the operating state of the engine.
It is assumed that base air-fuel ratio learning control having a learning value for each region is performed.

First, in step 201, the operating state parameters (water temperature, load, engine speed, etc.) of the internal combustion engine are read, and in the following step 202, the operating range of the internal combustion engine (D
1 to Dn: n is a natural number) is determined based on the load of the engine. Then, in step 203, it is determined whether or not the operating state of the engine is a base air-fuel ratio (A / F) learning condition. If not, the routine proceeds to step 208, where the vapor concentration FGPG is set to 0, and this routine is executed. To end. On the other hand, when the base A / F learning condition is satisfied in step 203, the process proceeds to step 204, where the known base A / F learning (FAF calculation, base A / F for each operation area (D1 to Dn)) is performed.
/ F learning value).

When step 204 is completed, step 20
At 5, it is determined whether or not there is an area for which the base A / F learning has been completed. If there is no area in which the base A / F learning has been completed, the purge control is not executed. Therefore, if there is no area in which the base A / F learning has been completed in step 205, the process proceeds to step 208, where the vapor concentration FGPG is set to 0, and this routine ends. On the other hand, if it is determined in step 205 that there is an area in which the base A / F learning has been completed, the process proceeds to step 206, and it is determined whether the purge control is being performed.

When it is determined in step 206 that the purge control is not being executed, the routine proceeds to step 208, where the vapor concentration FGPG is set to 0, and this routine is terminated. On the other hand, when it is determined in step 206 that the purge control is being executed, the routine ends after calculating the purge rate described later in step 207. FIG. 3 shows an embodiment of the calculation of the purge rate in step 207 of FIG. 2 in detail.

In step 301, first, in step 202
The current operation range (D1 to Dn) determined in step (1) is read, and in step 302, the integrated purge flow rate is calculated. The calculation of the integrated purge flow rate is performed based on the time when the VSV 26 is opened and the negative pressure in the intake passage 2 at that time, but the detailed description is omitted here. Next step 3
In 03, it is determined whether or not the current operation area read in step 301 is the base A / F learning completion area. In this embodiment, the base A
In the / A learning completed area, all deviations of the FAF are calculated by calculating the vapor concentration FGPG from the influence of the purge. In the base A / F learning not completed area, step 302 is executed.
The vapor concentration FGPG is calculated from the integrated purge flow rate determined in step (1) and the vapor concentration attenuation rate KFGPGDEC previously determined and stored in the ROM 104 of the control circuit 10.

First, a case will be described in which the current operation area is the completion area of the base A / F learning. In this case, in step 304, the current FAF value calculated based on the output signal from the air-fuel ratio sensor is read, and in subsequent step 305, it is determined whether or not the deviation due to the purge of the FAF value is shifted to the rich side by a predetermined value b or more. To 1−FAF ≧ b
Determined by This determination is based on the fact that the value of FAF is 1 in the base A / F learning completion area. If 1−FAF ≧ b (the FAF is shifted by b or more to the rich side), the process proceeds to step 306, where the value of the vapor concentration FGPG (R) in the base A / F learning completion region is calculated by the following equation. , And then proceeds to step 310.

FGPG (R) = FGPG-B On the other hand, if 1-FAF <b in step 305, the process proceeds to step 307, in which it is determined whether or not the deviation of the FAF value due to the purge is more than a predetermined value b toward the lean side. 1-FAF ≦ −b
Determined by Then, when 1−FAF ≦ −b (F
(AF is shifted to the lean side by b or more).
The process proceeds, the base A / F learning completion value of the vapor concentration FGPG (R) in the region determined by increasing the vapor concentration FGPG by the predetermined value B by the following equation Step 3 0
Go to 9 .

FGPG (R) = FGPG + B Then, in step 309, the value of the vapor concentration FGPG (R) in the base A / F learning completion region is calculated by the vapor concentration F
This routine is replaced with GPG and this routine ends. Also, F
When the shift of the AF value to the rich side or lean side due to the purge is smaller than the predetermined value b (NO in both steps 305 and 307), the value of the vapor concentration FGPG (R) in the base A / F learning completion region is changed. Without executing this routine.

Next, a case will be described in which the determination of the current operation area in step 303 is an area where the base A / F learning has not been completed. In this case, the process proceeds to step 310, where the attenuation rate KFGPGDEC of the vapor concentration in the base A / F learning incomplete area is interpolated from the map stored in the ROM 104 of the control circuit 10 based on the integrated purge flow rate calculated in step 302. Ask. Then, in the following step 311, the vapor concentration FGPG (K) in the base A / F learning uncompleted region is calculated by the following equation, and the value of the vapor concentration FGPG (K) in the base A / F learning uncompleted region is calculated as the vapor concentration. This routine is replaced with FGPG, and this routine ends. Here, the right side of the following equation
The initial value of FGPG of one term was calculated in the learning completion area.
Things are used.

FGPG (K) = (FGPG-1) × KF
GPGDEC + 1 In the embodiment described above, the control circuit 1 shown in FIG.
The amount of vapor adsorbed on the canister 22 is calculated and stored in the RAM 105 according to the open / closed state of the internal pressure control valve 23 input to the input / output interface 102 of 0, and the canister before the purge is started is stored in the ROM 104. A plurality of attenuation rate maps may be stored according to the amount of vapor adsorbed on the canister 22, and the plurality of attenuation rate maps may be selectively used according to the amount of vapor adsorbed on the canister 22 at the start of purging.

FIG. 4 shows a routine for calculating the fuel injection amount TAU, which is executed at every predetermined crank angle, for example, 360 ° CA. In step 401, the basic injection amount TP is calculated. That is, data of the intake air amount Q and the rotation speed Ne of the engine is read from the RAM 105, and the equation TP = KQ /
The calculation is performed using Ne (where K is a constant). Then, a correction amount FW according to the operating state of the engine, such as a warm-up increase correction amount, an intake air temperature correction amount, a water temperature correction amount, and a transient correction amount, is calculated. In the following step 402, the fuel injection amount TAU is calculated by using the feedback correction amount FAF, the correction amount FW, and the vapor concentration FGP.
It is calculated by the equation including G TAU = TP × (FW + FAF−FGPG). Next, at step 403, the injection amount TAU is set to the down counter and the flip-flop of the injection control circuit 110. Fuel injection is executed by this set.

As described above, in the evaporative fuel treatment apparatus of the present invention, the concentration of vapor from the canister is updated regardless of whether the learning of the air-fuel ratio is completed or not completed in the internal combustion engine that performs the learning control of the air-fuel ratio. It is possible to prevent the air-fuel ratio from becoming rough. FIG. 5 shows a modification of the purge rate calculation routine of FIG. 3, and the same steps as those of FIG. 3 are denoted by the same step numbers. The difference between the routine of FIG. 5 and the routine of FIG.
The only difference is that the step 501 is provided. In the embodiment of FIG. 3, when the operating region of the engine is the learning-incomplete region, the attenuation rate KFG of the vapor concentration is always calculated from the integrated purge flow rate.
Although the PGDEC is calculated to calculate the vapor concentration in the learning uncompleted region, if the accumulated purge flow rate has not increased from the previous time, there is no change in the vapor concentration. Therefore, in this embodiment, the control in steps 310 and 311 is not performed. Omitted. That is,
In step 501, it is determined whether or not the accumulated purge flow rate has increased by a predetermined value AI or more from the previous accumulated purge flow rate.
If it has increased, the process proceeds to step 310 and the subsequent steps.
The same control as that described above is performed, but if it is less than AI, this routine is terminated as it is, and steps 311 and 312 are not executed.

The embodiment described above is the basic structure and operation of the evaporative fuel treatment apparatus for an internal combustion engine according to the present invention. The characteristics of the separation of the vapor from the canister 22 shown in FIG. For example, it varies depending on deterioration, vapor adsorption state, and product variation of the canister.
Therefore, an embodiment in which control of the control accuracy of the above-described embodiment is improved, which can cope with a change in the characteristic of desorption of vapor from the canister 22, will be described next with reference to FIG. In the routine of FIG. 6, the same steps as those of the routine of FIG. 3 are denoted by the same reference numerals, and some of the steps of FIG. 3 are omitted.

In the embodiment shown in FIG. 6, since the decay rate KFGPGDEC of the vapor concentration is changed by successive calculations,
The vapor concentration decay rate KFGPGDEC is determined by the RA of the control circuit.
It is stored in M105. In the routine of FIG. 6, the control after step 309 when it is determined in step 303 that the area is the learning completion area is different. That is, step 60
In step 1, as in the non-learned region, the attenuation rate KFGPGDEC of the vapor concentration is calculated from the accumulated purge flow rate by interpolation from the map stored in the RAM 105 of the control circuit 10. Then, in the subsequent step 602, the vapor concentration FGPG equivalent to the base A / F learning incomplete area
(K) is calculated by the following equation.

FGPG (K) = (FGPG-1) × KF
GPGDEC + 1 In the subsequent step 603, steps 305 to 3
It is determined whether the difference between the vapor concentration FGPG (R) in the base A / F learning completion region calculated in step 09 and the vapor concentration FGPG (K) calculated in step 602 is larger than a predetermined value a, and FGPG (R If FGPG (K)> a, the process proceeds to step 604. Then, step 604
In the equation, the vapor concentration FGPG (K) calculated from the integrated purge flow rate and the attenuation rate DFGPGDEC is a predetermined value a higher than the vapor concentration FGPG (R) in the base A / F learning completion region.
The smaller value is the decay rate of vapor concentration DFGPGDEC
Is determined to be too large, and the decay rate KFGPG of the vapor concentration is determined.
The value of DEC is reduced by a predetermined value A, and the RAM
The attenuation factor KFGPGDEC of 5 is updated.

On the other hand, at step 603, FGPG (R)-
If FGPG (K) ≦ a, the routine proceeds to step 605, where the vapor concentration FGPG in the base A / F learning completion region
The difference between (R) and the vapor concentration FGPG (K) calculated from the accumulated purge flow rate and the attenuation rate DFGPGDEC is a predetermined value−
It is determined whether or not FGPG (R) -FGP
If G (K) <− a, the process proceeds to step 606. Then, in step 606, the integrated purge flow rate and the attenuation rate DFG
The vapor concentration FGPG (K) calculated from PGDEC is the vapor concentration FGPG in the base A / F learning completion region.
The reason why the value is larger than (R) by the predetermined value a is that the attenuation rate DFGPGDEC of the vapor concentration is determined to be too small, the value of the attenuation rate KFGPGDEC of the vapor concentration is increased by the predetermined value A, and the attenuation rate KFGPGDEC of the RAM 105 is increased by this value. Update. When the difference between the vapor concentration FGPG (K) and the vapor concentration FGPG (R) is less than a predetermined value a, the value of the vapor concentration attenuation rate KFGPGDEC is determined to be an appropriate value, and the vapor concentration attenuation rate KFGPGDEC is determined. This routine ends without updating the value.

As described above, in this embodiment, the true vapor concentration FGPG in the base A / F learning completion region
(R), the accumulated purge flow rate and the decay rate DPG of the vapor concentration
Since the decay rate DFGPGDEC of the vapor concentration is learned and corrected from the difference between the PGDEC and the vapor concentration FGPG (K), the deterioration of the canister 22, the product variation,
Alternatively, even if the adsorption state of the vapor to the canister 22 is different, the correct vapor concentration can always be calculated.

As described above, the problem of the prior art is solved by the evaporative fuel processing apparatus for an internal combustion engine according to the present invention, and the following can be performed. (1) Regardless of whether the learning of the air-fuel ratio is completed or not completed, the concentration of vapor from the canister is updated to prevent the air-fuel ratio from becoming rough. (2) The feedback learning control of the air-fuel ratio is performed for each region by dividing the operation region of the internal combustion engine into a plurality of regions, and in the case of having the learning value of the air-fuel ratio for each operation region, erroneous learning is prevented and learning is performed. The accuracy is improved. (3) By learning the attenuation rate so as to eliminate the error of the vapor concentration calculated based on the actual air-fuel ratio deviation and the vapor concentration calculated based on the integrated purge flow rate and the attenuation rate, it is possible to cope with the deterioration with time of the canister and the like. (4) If a plurality of attenuation rate maps are prepared according to the amount of vapor adsorbed by the canister, the vapor concentration is estimated according to the amount of adsorbed fuel vapor to the canister when the learning of the air-fuel ratio is not completed. be able to.

[0036]

As described above, according to the evaporative fuel treatment system for an internal combustion engine of the present invention, in an internal combustion engine for performing learning control of an air-fuel ratio, the canister can be used regardless of whether the air-fuel ratio learning is completed or not completed. There is an effect that the concentration of the vapor from the air can be updated to prevent the air-fuel ratio from becoming rough.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an overall configuration of an embodiment of an evaporative fuel processing apparatus for an internal combustion engine of the present invention together with an internal combustion engine.

FIG. 2 is a flowchart illustrating a process of calculating a FAF and a base A / F learning value in the fuel vapor processing apparatus for an internal combustion engine according to the present invention.

FIG. 3 is a flowchart showing control of an embodiment of a purge rate calculation process in FIG. 2;

FIG. 4 is a flowchart illustrating a calculation process of a fuel injection amount.

FIG. 5 is a flowchart illustrating control of a modified example of the purge rate calculation process of FIG. 3;

FIG. 6 is a flowchart showing control of another example of the calculation process of the purge rate of FIG. 3;

FIG. 7 is a characteristic diagram showing a characteristic of separation of vapor from a canister with respect to an integrated purge flow rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake passage 3 ... Surge tank 10 ... Control circuit 18 ... Throttle valve 21 ... Fuel tank 22 ... Charcoal canister 23 ... Flow switch 25 ... Vapor collection pipe 26 ... Electric purge flow control valve (VSV) 27 … Purge passage

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/14 310 F02D 41/02 330 F02D 41/04 330

Claims (4)

(57) [Claims] In an internal combustion engine that performs feedback learning control of an air-fuel ratio by detecting a concentration of residual oxygen in exhaust gas by a sensor provided in an exhaust passage, fuel vapor from a fuel system is adsorbed to a canister to operate the engine. An evaporative fuel processing apparatus for purging evaporative fuel adsorbed in the canister into an intake passage by a purge passage provided with a flow control valve, wherein the feedback learning control of the air-fuel ratio includes a plurality of operating regions of the internal combustion engine. In the case where the learning value of the air-fuel ratio is provided for each operating region, in the region where the learning is completed, the air-fuel ratio calculated based on the detected value of the oxygen concentration in the exhaust gas is used. The fuel ratio and the rich or lean side of the air-fuel ratio feedback correction coefficient during execution of the purge control.
A vapor concentration calculating means for calculating the concentration of the evaporated fuel gas based on the deviation amount, and in a learning-incomplete region, the concentration of the evaporated fuel gas calculated in the learning-completed region is calculated by the evaporation adsorbed by the canister. A vapor concentration estimating means for estimating the concentration of the evaporated fuel gas by subtracting using a subtraction value corresponding to the decrease in the fuel amount, and a vapor concentration estimating means obtained by the vapor concentration calculating means or the vapor concentration estimating means. An evaporative fuel processing apparatus for an internal combustion engine, comprising: a fuel injection amount correction unit that corrects a fuel injection amount based on a concentration. 2. The evaporative fuel processing apparatus for an internal combustion engine according to claim 1, wherein said vapor concentration estimating means calculates the base A /
True vapor concentration in F-learning completion area and accumulated purge flow rate
And determined in accordance with the difference between the vapor concentration and the vapor concentration decay rate . 3. The apparatus according to claim 1, further comprising an evaporative fuel flowing through the purge passage.
An integrated purge flow rate calculating means for calculating an integrated amount of the fuel , wherein the vapor concentration estimating means determines the subtraction value according to the integrated amount of the evaporated fuel. 4. The evaporative fuel processing apparatus for an internal combustion engine according to claim 1, wherein the vapor concentration estimating means stores the subtraction value in association with a representative value of the amount of evaporative fuel adsorbed by the canister. In the learning completion region, the concentration of the evaporated fuel determined by the oxygen concentration detection sensor is compared with the concentration of the evaporated fuel determined by the subtraction operation, and when the difference is equal to or greater than a predetermined value, Learning and updating map values.