JPH0742588A - Fuel vaproized gas processing system - Google Patents

Abstract

PURPOSE:To perform processing of fuel vaporized gas of a large quantity through purging and to improve a vaporization dispersion preventing effect by method wherein when fuel vaporized gas is purged, an air-fuel ratio of air- fuel mixture is shifted to a lean region and a purge amount of the fuel vaporized gas is increased to compensate for a fuel injection amount equivalent to an amount shifted to a lean region. CONSTITUTION:Based on detecting signals from an airflow sensor 17 and a crank angle sensor 24, an injector solenoid 9a is controlled by the fuel control means 42 of an electronic control unit 25 and a fuel injection amount is controlled. Based on a detecting signal from an O2 sensor 22, a fuel injection amount is corrected by an air-fuel ratio correcting means 43 so that an air-fuel ratio is adjusted to a theoretical value. Further, when fuel vaporized gas generated in a fuel tank 11 and adsorbed to a canister 12 is purged to the intake system of an internal combustion engine by means of a purge solenoid valve 13, a fuel injection amount is decreased by a shifting-to-lean-region means 44 to shift an air-fuel ratio to a lean region. When feedback control of an air-fuel ratio is effected, a purge is controlled by a purge control means 45 according to operation of a purge timer 45a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine (internal combustion engine).
The present invention relates to a fuel evaporative gas treatment system for processing (evaporating) an evaporative variable in the intake system by purging it.

[0002]

2. Description of the Related Art Conventionally, in an engine used in an automobile or the like, fuel evaporative gas generated from a fuel tank or the like is once adsorbed on activated carbon in a canister, and then the intake air of the engine is introduced from the canister through a purge solenoid valve. The system is purged (released) and processed.

As a technique for controlling the discharge flow rate (purge air flow rate) of the fuel evaporative gas to the intake system during such a purging process, an apparatus as disclosed in, for example, Japanese Patent Laid-Open No. 4-112959 has been conventionally proposed. ing. In this device, the purge air flow rate is adjusted according to the detection result of the air-fuel ratio sensor (O ₂ sensor), and the fuel injection amount is adjusted according to the purge air flow rate so that the air-fuel ratio always becomes the theoretical air-fuel ratio. Have control over.

[0004]

By the way, in recent years, from the viewpoint of environmental protection, in order to reliably prevent leakage of fuel evaporative emission from a fuel tank or the like, it is strongly desired to improve the performance of preventing evaporation of fuel evaporative emission. It is rare. Therefore, it is conceivable to increase the capacity of the canister that stores the activated carbon to surely capture most of the fuel evaporative emission gas generated from the fuel tank or the like.

However, even if the capacity of the canister is increased in this way, in the above-mentioned conventional apparatus, the fuel evaporative gas trapped in the canister cannot be purged and processed in a large amount within a certain period of time. However, there is a problem in that the fuel evaporative gas leaks from the canister and the improvement of the evaporation preventive performance of the fuel evaporative gas cannot be realized.

The present invention was devised in view of the above-mentioned problems, and a large amount of fuel evaporative emission can be purged within a certain period of time so that the evaporation prevention performance of the fuel evaporative emission is greatly improved. It is an object to provide an evaporative gas treatment system.

[0007]

Therefore, in the fuel evaporative emission gas treatment system of the present invention (claim 1), the detection means for detecting the operating state of the engine, and the engine based on the detection result of the detection means are used. Fuel control means for controlling the fuel injection amount to be supplied, air-fuel ratio detecting means for detecting the air-fuel ratio of the intake air-fuel mixture in the engine, and air-fuel ratio of the intake air-fuel mixture in the engine based on the detection result of the air-fuel ratio detecting means. Air-fuel ratio correction means for correcting the fuel injection amount controlled by the fuel control means so that the fuel ratio becomes the stoichiometric air-fuel ratio, adsorption means for adsorbing the fuel evaporative gas generated in the engine, and adsorption by the adsorption means The purge means for releasing the fuel vaporized gas to the intake system of the engine, and reducing the fuel injection amount controlled by the fuel control means at the time of introducing the purge to reduce the air-fuel ratio of the engine. And leaning means for over emissions reduction, and characterized by including a purge control means for controlling the release rate of the fuel vapor by the purge means based on an output of the air-fuel ratio correction means.

Further, the discharge flow rate of the fuel evaporative gas by the purge means controlled by the purge control means is preset according to the first value obtained from the air-fuel ratio correction means and the operating state of the engine. It may be determined based on the second value (claim 2). Further, when the flow rate of the fuel evaporative gas released by the purge means is not 0 at the end of the introduction of the purge, the purge control means causes the tailing control to gradually bring the flow rate of the fuel evaporative gas released by the purge means closer to zero. May be performed (Claim 3), and when at least one of the start of purge introduction and the end of purge introduction, the leaning means sets the fuel injection amount controlled by the fuel control means to a target value. The lamp control may be performed so as to gradually change to (Claim 4).

Further, an upper limit value may be set for the discharge flow rate of the fuel evaporative gas by the purge means controlled by the purge control means (claim 5), and the upper limit value may be controlled by the purge control means. The rate of change of the discharge flow rate of the fuel evaporative gas by the purging unit may be switched according to the detection result of the detecting unit (claim 6).

[0010]

In the above-described fuel evaporative emission gas treatment system of the present invention, when the purge is introduced, the leaning means reduces the fuel injection amount controlled by the fuel control means, thereby leaning the air-fuel ratio of the intake air-fuel mixture in the engine. It Then, in such a lean state, by the purge control means,
The discharge flow rate of the fuel vaporized gas by the purging unit is controlled based on the output of the air-fuel ratio correcting unit (claim 1).

Further, the discharge flow rate of the fuel evaporative gas by the purge means is set to a first value obtained from the air-fuel ratio correction means and a second value preset according to the operating state of the engine in the purge control means. It is determined based on (claim 2). Further, when the discharge flow rate of the fuel evaporative gas by the purge means is not 0 at the end of the introduction of the purge, the tailing control is performed by the purge control means, and the discharge flow rate of the fuel evaporative gas by the purge means gradually approaches 0. (Claim 3).

Further, at least at one of the start of purge introduction and the end of purge introduction, the lean control unit performs the ramp control so that the fuel injection amount controlled by the fuel control unit gradually changes to the target value. (Claim 4). Further, the purge evacuation gas discharge flow rate by the purging means is controlled by the purging control means so as not to exceed the upper limit value (Claim 5), and the detection result of the detecting means, that is, the operation of the engine. Control is performed while switching the rate of change of the discharge flow rate according to the state (claim 6).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel evaporative gas treatment system as an embodiment of the present invention will be described below with reference to the drawings.
Is a block diagram showing its configuration, FIG. 2 is a hardware block diagram showing a control system for the system, FIG. 3 is an overall configuration diagram showing an engine system to which the system is applied, and FIG. 4 is a control procedure by the system. 5 is a flow chart for explaining, and FIG. 5 is a timing chart for explaining the operation of the system.

An automobile engine system to which the system of this embodiment is applied is as shown in FIG. 3. In FIG. 3, an engine (internal combustion engine) 1 is used.
Is an intake passage 3 and an exhaust passage 4 communicating with the combustion chamber 2.
The intake passage 3 and the combustion chamber 2 are controlled to communicate with each other by the intake valve 5, and the exhaust passage 4 and the combustion chamber 2 are controlled to communicate with each other by the exhaust valve 6.

Further, the intake passage 3 is provided with an air cleaner 7, a throttle valve 8 and an electromagnetic fuel injection valve (injector) 9 in this order from the upstream side, and the exhaust passage 4 is provided in order from the upstream side. An exhaust gas purifying catalytic converter (three-way catalyst) 10 and a muffler (silencer) not shown are provided. The intake passage 3 is provided with a surge tank 3a. Further, the throttle valve 8 is connected to an accelerator pedal (not shown) via a wire cable, and its opening degree is adjusted according to the depression amount of the accelerator pedal.

In the engine system of this embodiment, in order to prevent the fuel evaporative gas generated in the fuel tank 11 from evaporating into the atmosphere,
A canister (adsorption means) 12 is connected to the fuel cell via a fuel evaporative gas collection pipe 40. The activated carbon 12a is built in the canister 12, and the activated carbon 12a is adapted to adsorb the fuel evaporative gas flowing from the fuel tank 11 through the fuel evaporative gas collecting pipe 40.

Further, in order to purge (release) the fuel evaporative gas adsorbed in the canister 12 into the intake system of the engine 1 for processing, the fuel evaporative gas recirculation pipe capable of releasing the fuel evaporative gas into the intake passage 3 41 is provided so as to communicate between the canister 12 and the intake passage 3 downstream of the throttle valve 8. Further, a purge solenoid valve (purge means) 13 is provided in the fuel vaporized gas recirculation pipe 41. The purge solenoid valve 13 includes a valve body 13a that can come into contact with a valve seat portion 13c formed in the fuel vaporized gas recirculation pipe 41, and a purge solenoid 13b for adjusting the position of the valve body 13a with respect to the valve seat portion 13c. It consists of and.

When the valve body 13a is in contact with the valve seat portion 13c (closed state), the fuel evaporative gas recirculation pipe 41 is closed,
The canister 12 and the intake passage 3 are separated from each other, and the fuel evaporative gas from the canister 12 is not discharged to the intake passage 3. On the other hand, when the purge solenoid 13b is excited, the valve body 13a is separated from the valve seat portion 13c (open state), and the canister 12 and the intake passage 3 are in communication with each other through the fuel evaporative gas recirculation pipe 41. The fuel evaporative emission gas is released from the canister 12 to the intake passage 3.

The purge solenoid 13b is an EC which will be described later.
The canister 1 is excited by receiving an electric signal from U, and by opening and closing the purge solenoid valve 13 with a predetermined drive duty D _PRG described later, the canister 1
The flow rate of the fuel vaporized gas discharged from 2 to the intake passage 3 (hereinafter referred to as the purge air flow rate) is controlled.

In FIG. 3, reference numeral 15 denotes a fuel pressure regulator, which operates by receiving a negative pressure in the intake passage 3 and operates from a fuel pump (not shown) to the fuel tank 11
The fuel pressure injected from the injector 9 is adjusted by adjusting the amount of fuel returning to. With such a configuration, the air taken in through the air cleaner 7 according to the opening degree of the throttle valve 8 is mixed with the fuel from the injector 9 in the intake manifold portion so as to have an appropriate air-fuel ratio, and the spark plug is provided in the combustion chamber 2. By igniting 16 at an appropriate timing, the intake air-fuel mixture is burned and engine torque is generated.
The air-fuel mixture is discharged as exhaust gas to the exhaust passage 4, and the catalytic converter 10 mixes CO, HC, and NOx in the exhaust gas.
After purifying the two harmful components, the muffler silences them and releases them to the atmosphere.

Various sensors are provided to control the operating state of the engine 1. As shown in FIG. 3, first, the intake air that has passed through the air cleaner 7 is introduced into the intake passage 3
An air flow sensor (intake air amount sensor) 17 for detecting the intake air amount from the Karman vortex information,
An intake air temperature sensor 18 for detecting the intake air temperature and an atmospheric pressure sensor 19 for detecting the atmospheric pressure are provided.

Further, the throttle valve 8 in the intake passage 3
A potentiometer-type throttle position sensor 20 for detecting the opening of the throttle valve 8,
Throttle valve 8 fully closed (that is, idling)
Is provided with an idle switch 21 for mechanically detecting the position from the position of the throttle valve 8. Further, on the exhaust passage 4 side, on an upstream side portion of the catalytic converter 10, an oxygen concentration sensor (air-fuel ratio detection) that detects the oxygen concentration in the exhaust gas (O ₂ concentration, that is, the air-fuel ratio of the intake air-fuel mixture in the engine 1). Means; hereinafter, simply referred to as an O ₂ sensor) 22. Other sensors include a water temperature sensor 23 for detecting the temperature of the cooling water 14 for the engine 1 and a crank angle sensor 24 for detecting the crank angle of the engine 1.
(The crank angle sensor 24 also has a function as a rotation speed sensor for detecting the engine rotation speed Ne) and the like.

Detection signals from these sensors and switches are input to an electronic control unit (ECU) 25 having a hardware structure as shown in FIG. The ECU 25 has a CPU (arithmetic unit) 26 as its main part, and the CPU 26 includes an intake air temperature sensor 18, an atmospheric pressure sensor 19, a throttle position sensor 20, an O ₂ sensor 22, and a water temperature sensor 23.
The detection signal from is input through the input interface 27 and the analog / digital converter 28.

The CPU 26 has an air flow sensor 17, an idle switch 21, a crank angle sensor 24,
Detection signal (digital signal) from the vehicle speed sensor 30
An on / off signal from an ignition switch (key switch) 34 or the like is input via the input interface 29. Further, the CPU 26 stores program data and fixed value data via a bus line, and stores a basic duty D _T and feedback integral gains G _PUP and G _PDN which will be described later as a map R.
Data is exchanged between the OM 32, the RAM 33 that is updated and sequentially rewritten, and the battery backup RAM (not shown) that is backed up by holding the stored contents while the battery is connected. It is like this.

The data in the RAM 33 is erased and reset when the ignition switch 34 is turned off. In addition, as a result of the calculation by the CPU 26,
From the ECU 25, signals for controlling the operating state of the engine 1 such as fuel injection control signal, fuel pump control signal, ignition timing control signal, engine check lamp lighting signal, alarm lamp lighting signal, purge air flow rate control signal, etc. Various control signals are output.

Of these control signals, the fuel injection control (air-fuel ratio control) signal is sent from the CPU 26 to the injection driver 3
4 is output to an injector solenoid 9a for driving the injector 9 (correctly, a transistor for the injector solenoid 9a). Further, the ignition timing control signal is outputted from the CPU 26 to the power transistor 36 via the ignition driver 35, and the power transistor 36 causes the distributor 38 via the ignition coil 37 to sequentially generate sparks on the respective spark plugs 16. ing. Further, the purge air flow rate control signal is output from the CPU 26 to the purge solenoid 13b of the purge solenoid valve 13 via the purge driver 39.

Now, focusing on the fuel injection control (air-fuel ratio control) and the purge air flow rate control during this air-fuel ratio control, the ECU 2 is used for these controls.
As shown in FIG. 1, 5 is a fuel control means 42, an air-fuel ratio correction means 43, a leaning means 44, and a purge control means 4.
Have five. The fuel control means 42 controls the fuel injection amount supplied to the combustion chamber 2 of the engine 1 on the basis of the detection results of the air flow sensor 17 and the crank angle sensor 24 as the detection means, and the intake air from the air flow sensor 17 is controlled. The intake air amount A / Ne information per one engine revolution (engine load information) is obtained from the amount A information and the engine speed Ne information from the crank angle sensor 24, and the basic pulse width set according to this information is set to the density. By correcting, the basic drive time T _B for the injector 9
(That is, the fuel injection amount by the injector 9) is determined.

Further, the air-fuel ratio correction means 43 controls the fuel controlled by the fuel control means 42 so that the air-fuel ratio of the intake air-fuel mixture in the engine 1 becomes the stoichiometric air-fuel ratio based on the detection result of the O ₂ sensor 22. The injection amount, that is, the basic drive time T _B for the injector 9 described above is corrected, and the feedback correction coefficient K _AF of the air-fuel ratio to be multiplied by the basic drive time T _B is calculated.

This feedback correction coefficient K _AF is O ₂
When the air-fuel ratio detected by the sensor 22 becomes rich, it becomes smaller than 1 in order to make the air-fuel ratio lean, and conversely,
When the air-fuel ratio detected by the O ₂ sensor 22 becomes lean, it becomes larger than 1 in order to make the air-fuel ratio rich. By controlling the injection time (valve opening time) of the injector 9 by multiplying the basic drive time T _B set by the fuel control means 42 by such a feedback correction coefficient K _AF , the air-fuel ratio becomes theoretically empty. It is controlled so that the fuel ratio is obtained.

The feedback correction coefficient K _AF set by the air-fuel ratio correction means 43 as described above is the same as when the air-fuel ratio deviates from the theoretical air-fuel ratio due to variations in the injector 9 or changes in various conditions. It is a learning value corresponding to long-term fluctuations. Further, the real-time or short-term fluctuation of the air-fuel ratio can be viewed as a feedback integral value K _I of the air-fuel ratio calculated to be reflected in the learning value described above, and in this embodiment, in the purge air flow rate control described later, This feedback integral value K _I (actually, for example, an average value of about 10 seconds) is used as a control judgment criterion. That is, in this embodiment, the feedback integrated value K
_{When I} is smaller than 1, it is determined that the air-fuel ratio is in a short-term rich state, and when the feedback integral value K _I is larger than 1, it is determined that the air-fuel ratio is in a short-term lean state. . Also, this feedback integral value K
_I is the evaporated fuel gas (purge air) in the canister 12.
There is a correlation with the concentration (air-fuel ratio), purge air in the state feedback integral value K _I is less than 1 is in the enrichment tendency, purge air is in the lean tendency feedback integration value K _I is a large state than 1 .

The leaning means 44 is provided with the fuel control means 4 when the purge is introduced by the operation of the purge control means 45 described later.
This is for reducing the fuel injection amount controlled by 2 and making the air-fuel ratio of the intake air-fuel mixture in the engine 1 lean. Specifically, FIG. 4, as described later with reference to FIG. 5, leaning means 44, when the purge introduction start, only the target lean coefficient P _OBJ (%) with respect to the basic air-fuel ratio determined by the basic drive time T _B lean The leaning coefficient P _L (%) is given so that the air-fuel ratio becomes a better value.
By gradually changing the feedback correction coefficient K _AF set in 3, ramp control is performed to gradually reduce the fuel injection amount to a target value corresponding to the air-fuel ratio _leaned by the target leaning coefficient P _OBJ. It has a function. Here, the target leaning coefficient P _OBJ is set based on the maximum value of the purge air flow rate by the purge solenoid valve 13 which is the original purpose.

[0032] Incidentally, the lean means 44, during a period from a predetermined time before T _P of purge introduction end (the purge completion of the introduction time is defined by the purge timer 45a to be described later) until the end purge introduced, target lean _Conversion factor P _OBJ
The fuel injection amount is increased by giving the leaning coefficient P _L and gradually changing the feedback correction coefficient K _AF set by the air-fuel ratio correcting means 43 so that the basic air-fuel ratio becomes the basic air-fuel ratio from the lean air-fuel ratio. Is also provided with the function of performing a ramp control to gradually increase to a target value corresponding to the basic air-fuel ratio.

The purge control means 45 is the air-fuel ratio correction means 4
3, the purge solenoid valve 1 is operated based on the output of the air-fuel ratio correction means 43 in accordance with the off-timer operation and the on-timer operation by the built-in purge timer (down counter) 45a with the start of the air-fuel ratio feedback control operation.
3 is used to control the flow rate of purge air. More specifically, the purge control means 45 of this embodiment is
A predetermined drive duty D _PRG for opening and closing the purge solenoid valve 13 is calculated, and the drive duty D _PRG is calculated.
By outputting an electric signal for exciting the purge solenoid 13b of the purge solenoid valve 13 according to _PRG , the purge air flow rate discharged from the canister 12 to the intake passage 3 is controlled.

The drive duty D _PRG described above is given, for example, by the following equation (1). D _PRG = K _PFB * K * D _T (1) where K _PFB is the duty feedback correction coefficient,
K is a correction coefficient given by intake air temperature correction, correction immediately after starting, and D _T is a basic duty. Here, the duty feedback correction coefficient K _PFB is updated every sampling cycle, and when the feedback integral value K _I from the air-fuel ratio correction means 43 is larger than 1, the purge air in the canister 12 is as described above. The air-fuel ratio is judged to be lean and increased by a preset feedback control gain G _PUP, and when the feedback integral value K _I is 1, it is judged that the air-fuel ratio is in the ideal air-fuel ratio state. If the feedback integral value K _I is kept constant and is smaller than 1, it is determined that the air-fuel ratio of the purge air in the canister 12 is enriched as described above, and the feedback control gain _GPDN set in advance is set.
It is supposed to be reduced only.

The basic duty D _T is, for example, the engine speed Ne information from the crank angle sensor 24,
This engine speed Ne information and air flow sensor 1
It is given as map data by the engine load information (A / Ne) obtained from the intake air amount A information from 7, and is preset in the ROM 32. Therefore, the purge air flow rate (driving duty D _PRG ) is the feedback integrated value K which is the output from the air-fuel ratio correction means 43.
_{It is determined based on I} (first value) and a basic duty D _T (second value) preset according to the operating state of the engine 1.

The duty feedback correction coefficient K set in the purge control means 45 of this embodiment.
_An upper limit value K _B is set in _PFB , whereby the upper limit value is set in the purge air flow rate controlled by the purge control means 45. Further, when the purge air flow rate by the purge solenoid valve 13 is not 0 at the end of the introduction of the purge, the purge control means 45.
As will be described later with reference to FIGS. 4 and 5, tailing control is performed so that the purge air flow rate by the purge solenoid valve 13 gradually approaches 0 based on a preset tailing gain D _PLT .

Further, the above-mentioned gains G _PUP and G
_{The PDN} is stored in the ROM 32 as a map in advance and can be switched according to the detection result of the idle switch 21, for example. Specifically, when the idle switch 21 is in the ON state (idling state), the gains G _PUP and G _PDN are set to the idle switch 21.
Switch to a smaller value than when is off. As a result, the rate of change of the purge air flow rate controlled by the purge control means 45 is switched according to the detection result (whether in the idling state or not) of the idle switch 21 as the detection means.

Furthermore, the purge control means 45 performs the above-described control operation during the period when the purge timer 45a operates as an on-timer (see T _{ON in} FIG. 5).
During the tailing control period, the purge control means 4
The purge timer 45a operates as an _off timer during a predetermined period before the control operation of the control unit 5 (see T _{OFF in} FIG. 5), and the control operation by the purge control means 45 is stopped.

Next, a fuel evaporative gas treatment procedure (purge air flow rate control) by the system of the present embodiment configured as described above will be described with reference to the flowchart of FIG. 4 and the timing chart of FIG. The purge control means 45 and the leaning means 4 implemented in the procedure shown in FIG.
4 is activated when the air-fuel ratio feedback control by the air-fuel ratio correction means 43 is turned on [see time t _{1 in} FIG. 5 (c)]. In step S1, it is determined whether the purge control flag F is "2" and the tailing control is being executed. In step S2, the purge control flag F is "1".
Determine whether the purge control is being executed.

Since the purge control flag F is set to "0" at the time of activation of the purge control, steps S1 and S
In both cases, N (No) is determined, and the off-timer operation by the purge timer 45a is first executed. At the time when the purge control is started, the off period T _OFF is set in the purge timer 45a as the remaining time count T ₂ [see time t _{1 in} FIG. 5 (a)], and the remaining time count is performed every control cycle (sampling cycle). The predetermined time ΔT ₂ is subtracted (counted down) from the time T ₂ (step S
21), the remaining time T ₂ in the purge timer 45a
Is determined to be 0 or less (step S2
2).

The process in step S1, S2 and S21 are repeated until it is determined that the remaining measurement time T ₂ is less than or equal to zero at step S22, it determines that the remaining time counting time T ₂ of the purge timer 45a becomes 0 or less Then, the purge control flag F is switched from "0" to "1" (step S23), the ON period T _ON is set in the purge timer 45a as the remaining clock time T ₁ (step S24), and the purge timer 45a is turned on. It operates as an on-timer and shifts to purge control execution (timer mode introduction) by the purge control means 45 [FIG.
Refer to time point t _{2 in} (a) and (b)].

When the purge control flag F becomes '1', N is determined in step S1 and Y (Yes) is determined in step S2, and the remaining time T ₁ of the purge timer 45a is the predetermined time T before the introduction of purge is completed. _It is determined whether or not it is within _P (step S3). Immediately after the transition to the purge control execution state, of course, the remaining time count T ₁ is larger than the predetermined time T _P , so an N determination is made, and the lean coefficient P _L set by the lean means 44 is the target lean coefficient P _OBJ. It is determined whether or not (step S
4). At this time, the leaning coefficient P _L is determined by the purge timer 45.
Since it starts from 0 according to the on-timer operation of a,
The determination in step S4 is an N determination, and the leaning coefficient P _L plus a preset gain G _PL is output as a new leaning coefficient P _L from the leaning means 44 to the air-fuel ratio correcting means 43 ( Step S5).

The process of adding the gain G _{PL in} step S5 is repeated until the leaning coefficient P _L reaches the target leaning coefficient P _OBJ . As a result, at the start of introduction of purge (after time t ₂ ), the ramp control as shown in FIG. 5D is performed, and the leaning coefficient P from the leaning means 44 is performed.
The feedback correction coefficient K _AF from the air-fuel ratio correction means 43 is gradually decreased according to _L , and the fuel control means 4
The basic drive time T _B set in 2 gradually changes, and the fuel injection amount by the injector 9 gradually changes until it reaches the target value corresponding to the air-fuel ratio _leaned by the target leaning coefficient P _OBJ. Controlled as.

Note that once the leaning coefficient P _L reaches the target leaning coefficient P _OBJ , it bypasses step S5, and as will be described later, in step S4, the remaining time T ₁ of the purge timer 45a is the same as before the completion of the introduction of purge. Predetermined time T _P
The target leaning coefficient P until it is determined that
_The amount of fuel injected by the injector 9 is held in _OBJ ,
The air-fuel ratio is controlled to be lean by the target lean coefficient P _OBJ .

On the other hand, by the countdown processing in step S15 described later, the remaining time T ₁ of the purge timer 45a is reduced to within a predetermined time T _P [time t _{6 in} FIG. 5 (a)].
From within the predetermined time T _P ], it is determined in step S4 that the remaining time T ₁ of the purge timer 45a is within the predetermined time T _P before the end of the introduction of purge (Y determination), and the lean coefficient P _{L is} calculated in advance. A value obtained by subtracting the set gain G _PL is output as a new leaning coefficient P _L from the leaning means 44 to the air-fuel ratio correcting means 43 (step S6).

In the subtraction process of the gain G _{PL in} step S6, the leaning coefficient P _L becomes 0 at the same time as the introduction of the purge is completed.
Is repeated until. As a result, the ramp control as shown in FIG. 5D is performed during the predetermined time T _P before the introduction of the purge (time point t ₆ ), and according to the leaning coefficient P _L from the leaning means 44. The feedback correction coefficient K _AF from the air-fuel ratio correction means 43 is gradually changed to a large value, and the basic drive time T _B set by the fuel control means 42 is set.
Then, the fuel injection amount by the injector 9 is controlled so as to gradually change from the state of leaning by the target leaning coefficient P _OBJ to the target value corresponding to the basic driving time T _B.

Now, as described above, according to step S5
If the air-fuel ratio is made lean, the air-fuel ratio correction means 43
Feedback integral value K_IIs the feedback compensator
Number K _AFTo increase the fuel injection amount of the injector 9
The size of the sensor becomes large as shown in FIG.
Move up from the data position (1.0) and correspondingly
Purging control according to the processing of steps S7 to S13
By means 45, the duty feedback correction coefficient K
_PFBIs set for each sampling period.

That is, first, the operating state (in this embodiment, the idling state information by the idling switch 21)
Depending on the feedback integration gains G _PUP and G
_{After the PDN} is read from the ROM 32 and set (step S7), it is determined whether or not the feedback integral value K _I from the air-fuel ratio correction means 43 is 1 (step S7).
8).

Feedback integrated value K_IIs 1
Is the duty feedback correction coefficient at that time.
K_PFBIs used as it is and the process proceeds to step S14 described later.
However, the feedback integral value K_IIs not 1, then
The feedback integrated value K _IWhether is greater than 1
Is determined (step S9). Feedback integral value K
_IIs determined to be greater than 1, the duty factor is
Feedback correction coefficient K_PFBFeedback integral gain to
G_PUPIs added, and the added value is added to the new duty factor.
Feedback correction coefficient K_PFBUsed as (step
S10). The duty feedback correction coefficient K
_PFBDepends on the on-timer operation of the purge timer 45a.
Start from 0.

Then, a new duty feedback
Correction coefficient K_PFBIs the upper limit K_BTo determine whether or not
(Step S11), duty feedback correction section
Number K _PFBIs the upper limit K_BIf it is above the duty
Feedback correction coefficient K_{PF B}Is the upper limit value K_BReplaced with
On the other hand (step S12), duty feedback
Correction coefficient K_PFBIs the upper limit K_BIf not exceeded,
Duty feedback calculated in step S10
Correction coefficient K_PFBTo move to step S14.

On the other hand, when it is determined in step S9 that the feedback integral value K _I is 1 or less, the feedback integral gain _{GPDN is} subtracted from the duty feedback correction coefficient K _PFB , and the subtracted value is a new duty feedback compensation. It is used as the coefficient K _PFB (step S13). The new duty feedback correction coefficient K _PFB obtained in this way is substituted into the above-mentioned equation (1), and a predetermined drive duty D _PRG for opening and closing the purge solenoid valve 13 is calculated and updated ( Step S14). Then, the purge control means 45 outputs an electric signal for exciting the purge solenoid 13b of the purge solenoid valve 13 according to the updated drive duty D _PRG, and the flow rate of purge air discharged from the canister 12 to the intake passage 3 is increased. Controlled.

Drive duty D by step S14
_PRGIs updated, the remaining time of the purge timer 45a is measured.
Interval T₁(At first T_ON) To a predetermined time ΔT₁Subtract (cow
(Step S15) and the remaining time count
T₁Is determined to be 0 or less (step S1
6). The processing in steps S3 to S15 is performed in step S
16 remaining time T ₁Is determined to be 0 or less
Until the purge timer 45a remains
Clock time T₁Is determined to be 0 or less, the
At the time point, the duty feedback correction coefficient K_PFBIs 0
It is determined whether or not there is (step S17).

Duty feedback correction coefficient K _PFB
Is 0 [see, for example, time points t ₇ and t _{11 in} FIG. 5 (f)], after the purge control flag F is set to '0' (step S19), the off period T _OFF remains in the purge timer 45a and the measured time remains. Is set as T ₂ (step S20),
The purge timer 45a operates as an off timer, as shown in FIGS.

Further, in step S17, the duty
Feedback correction coefficient K_PFBWas determined not to be 0
Case [For example, time point t in FIG.₆Reference], purge control
Set the flag F to "2" (step S18),
Control. The purge control flag F becomes "2"
Then, a Y determination is made in step S1 described above, and the current
Current duty feedback correction coefficient K_PFBFrom in advance
Set tailing gain D_PLTNew subtracted
Rack duty feedback correction coefficient K_PFBToshi (Su
Step S25), the duty feedback correction section
Number K_{PF B}To open and close the purge solenoid valve 13
Drive duty D for _PRGUpdate (step
S14), as described above, by the purge control means 45.
And updated drive duty D_PRGAccording to
It outputs an electric signal to excite the Renoid 13b,
Control the air flow rate. This step S25
The ringing control process is performed in step S17.
Feedback correction coefficient K_PFBIs determined to be 0
Repeat until

A specific control example performed according to the processing procedure shown in FIG.
Focusing on the variation of the duty feedback correction coefficient K _PFB according to _I , the description will be made with reference to FIGS. That is, when the air-fuel ratio correction means 43 starts operating and the air-fuel ratio feedback control is turned on at the time point t ₁ in FIG. 5, first, the purge timer 45a operates as an off timer (step S21), and the off period T _OFF has elapsed. Then (time point t ₂ ), the on-timer is activated (step S
22 to S24), and as shown in FIGS. 5A and 5B, the timer mode is introduced.

When the timer mode is introduced, it becomes lean
By the lamp control operation of the means 44 (steps S4 and S5)
As shown in FIG. 5D, the air-fuel ratio is
Number P _OBJOnly lean. In this way the air-fuel ratio is the target
Leaning coefficient P_OBJIf it is made lean, first, Fig. 5
Time point t of (e) and (f)₂~ T₃As shown in
Feedback integral value K_IIs the feedback correction coefficient K_AFTo
To increase the fuel injection amount of the injector 9
It changes in the direction and moves upward from the center position (1.0).

In response to this, duty feedback
Correction coefficient K_PFBBy the processing of steps S8 to S10.
The feedback integration gain from 0 every sampling period.
In G _PUPDrive the purge solenoid valve 13
Duty D_PRGBecomes larger and the purge air flow rate increases.
Big This allows the purge air from the canister 12 to
Is the feedback integral value K_ILed back to 1.0
Will be entered.

When the lean injection fuel injection amount is completely replaced by the purge air flow rate from the canister 12, as shown at time points t _{3 to} t ₄ in FIGS. 5E and 5F, step S 8 is performed. When the determination is Y, the duty feedback correction coefficient K _PFB at that time is held, and the purge solenoid valve 13 is controlled to be opened / closed with the drive duty D _PRG according to this duty feedback correction coefficient K _PFB .

After that, time point t in FIGS. 5 (e) and 5 (f)._Four~
t_FiveAs shown in, the feedback integrated value K_IIs 1
The duty feedback correction
Number K _PFBIs sampled by the process of step S10.
Feedback integral gain G for each cycle_PUPIncrease by
However, due to the processing of steps S11 and S12, the upper limit value K _B
Will not be larger than.

Further, time t in FIGS. 5 (e) and 5 (f)._Five~ T
₆As shown in, the purge air flow rate is too high and the air-fuel ratio is
When enriched, the feedback integral value K_IIs
Feedback correction coefficient K_AFOf the injector 9
Change to the direction of decreasing the fuel injection amount and move to the center position
Move down from (1.0). In response,
Feedback correction coefficient K_PFBAre steps S8 and S
By the processing of 9 and S13, the fee is collected every sampling cycle.
Feedback integral gain G _PDNGradually decreasing, purging solenoi
Drive duty of drive valve 13_PRGBecomes smaller and purges
The air flow rate decreases and the feedback integral value K_ITo 1.0
It works like back to.

On the other hand, the purge timer 45a turns on-time.
Time t at which the movement ends₆Time T _PJust before,
For the lamp control operation of the leaning means 44 (step S6)
From the leaning means 44 to the air-fuel ratio correcting means 43.
Coefficient P_LIs the time t when the introduction of purge is completed₆Gradually
0, and the air-fuel ratio becomes the target lean coefficient P_OBJOnly lee
The basic drive time T_BThe value corresponding to
It

When the on-timer operation by the purge timer 45a ends, the timer mode is cut as shown in FIGS. 5 (a) and 5 (b).
_{In step 6} , if the duty feedback correction coefficient K _PFB is not 0, steps S17, S18, S1, S25
Accordingly, as shown in time point t ₆ ~t ₇ of FIG. 5 (f), the tailing control until the duty feedback correction coefficient K _{PF B} 0 is performed at a constant gradient (tailing gain G _PTL).

When the duty feedback correction coefficient K _PFB becomes 0 at time t ₇ , steps S17, S19, S
At 20, the purge timer 45a starts to operate again as an off timer, and after the off period T _{OFF has} elapsed (time t ₈ ), the purge timer 45a enters the on timer operating state and enters the timer mode introduction state. In addition, time points t _{8 to} t in FIGS. 5E and 5F.
_{In the} timer mode introduction period shown in ₁₁ , the case where the purge air flow rate is controlled without the duty feedback correction coefficient K _PFB reaching the upper limit value K _B is illustrated.
During the time points t _{9 to} t ₁₀ , the feedback integral value K _I is 1.
The duty feedback correction coefficient K _PFB is increased by the feedback integral gain G _{PUP for} each sampling period during this period, but the feedback integral value K _I becomes smaller than 1.0 after the time t ₁₀ and the duty feedback correction coefficient K _PFB is increased. The coefficient K _PFB is reduced to 0 by the feedback integral gain G _PDN every sampling period.

As described above, according to the fuel evaporative emission gas treatment system of this embodiment, the leaning means 44 is introduced at the time of introducing the purge.
As a result, the fuel injection amount controlled by the fuel control unit 42 is reduced, the air-fuel ratio of the intake air-fuel mixture in the engine 1 is made lean, and the purge control unit 45 operates so as to supplement the fuel injection amount for this lean. As a result, the flow rate of purge air by the purge solenoid valve 13 increases.

Therefore, a large amount of fuel evaporative gas in the canister 12 can be purged and processed within a fixed time,
The evaporation prevention performance of fuel evaporative gas is greatly improved. Also,
Accordingly, when the capacity of the canister 12 is increased so as to reliably capture most of the fuel evaporative emission gas generated from the fuel tank or the like, it is possible to reliably prevent the fuel evaporative emission gas from leaking from the canister 12.

Further, in this embodiment, the purge control means 4
5, the purge air flow rate is controlled based on the feedback integration value K _I that reflects the air-fuel ratio of the purge air, and in particular, when the purge air air-fuel ratio is lean (feedback integration value K _I > 1), the purge air flow rate is It is controlled to be large. Therefore, it becomes possible to control the purge air flow rate according to the air-fuel ratio of the purge air in the canister 12, and it is possible to realize a large amount of purge.

Further, according to this embodiment, the basic duty D _T and the feedback integral gains G _PUP and G _PDN are set according to the operating state of the engine 1, so that the operating state (whether idling or not) is set. There is also an advantage that the purge air flow rate can be controlled according to the flow rate. Further, in this embodiment, when the purge air flow rate is not 0 at the end of the purge introduction, the purge control means 45 performs tailing control so that the purge air flow rate gradually approaches 0, and at the start of the purge introduction and at the end of the purge introduction. Sometimes, leaning means 44
In addition to performing the ramp control so that the fuel injection amount gradually changes to the target value, the purge air flow rate is controlled so as not to exceed the upper limit value. Therefore, in the system of the present embodiment, the lean coefficient P _L and the duty factor are set. It is possible to prevent the feedback correction coefficient K _PFB from changing abruptly, and it is possible to stably control the purge air flow rate.

In the above-described embodiments, the case where the system of the present invention is applied to the engine (internal combustion engine) for automobiles has been described. However, the system of the present invention is not limited to this, and various types of power can be used. It is needless to say that it is applied to the engine used as the source in the same manner as described above, and the same operational effects as described above are obtained.

[0069]

As described above in detail, according to the fuel evaporative emission gas treatment system of the present invention (claims 1 to 6), when the purge is introduced, the fuel injection is controlled by the fuel control means by the leaning means. By reducing the amount and making the air-fuel ratio of the intake air-fuel mixture lean in the engine, the purge control means operates so as to supplement the fuel injection amount for this leaning, and the discharge flow rate of the fuel evaporative gas by the purge means increases. Therefore, a large amount of the fuel evaporative gas in the adsorbing means can be purged and processed within a fixed time, and there is an effect that the evaporation prevention performance of the fuel evaporative gas can be significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a fuel evaporative emission gas processing system as one embodiment of the present invention.

FIG. 2 is a hardware block diagram showing a control system for the system of the present embodiment.

FIG. 3 is an overall configuration diagram showing an engine system to which the system of the present embodiment is applied.

FIG. 4 is a flow chart for explaining a control procedure by the system of the present embodiment.

5A to 5F are timing charts for explaining the operation of the system of this embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 engine (internal combustion engine) 2 combustion chamber 3 intake passage 3a surge tank 4 exhaust passage 5 intake valve 6 exhaust valve 7 air cleaner 8 throttle valve 9 electromagnetic fuel injection valve (injector) 9a injector solenoid 10 catalytic converter (three-way catalyst) 11 Fuel tank 12 Canister (adsorption means) 12a Activated carbon 13 Purge solenoid valve (Purge means) 13a Valve body 13b Purge solenoid 13c Valve seat part 14 Cooling water 15 Fuel pressure regulator 16 Spark plug 17 Air flow sensor (intake amount sensor) 18 Intake temperature Sensor 19 Atmospheric pressure sensor 20 Throttle position sensor 21 Idle switch 22 Oxygen concentration sensor (O ₂ sensor, air-fuel ratio detecting means) 23 Water temperature sensor 24 Crank angle sensor 25 Electronic control unit 26 CPU (arithmetic unit) 27 Input Interface 28 analog / digital converter 29 input interface 30 vehicle speed sensor 31 ignition switch 32 ROM 33 RAM 34 injection driver 35 ignition driver 36 power transistor 37 ignition coil 38 distributor 39 purge driver 40 fuel evaporative gas collection tube 41 fuel evaporative gas recirculation tube 42 fuel control means 43 air-fuel ratio correction means 44 leaning means 45 purge control means 45a purge timer

Claims (6)

[Claims] 1. A detection means for detecting an operating state of an engine, a fuel control means for controlling a fuel injection amount to be supplied to the engine based on a detection result of the detection means, and an intake air-fuel mixture empty in the engine. Air-fuel ratio detecting means for detecting the fuel ratio, and based on the detection result of the air-fuel ratio detecting means, so that the air-fuel ratio of the intake air-fuel mixture in the engine becomes the theoretical air-fuel ratio,
Air-fuel ratio correction means for correcting the fuel injection amount controlled by the fuel control means, adsorbing means for adsorbing the fuel evaporative gas generated in the engine, and fuel evaporative gas adsorbed by the adsorbing means for the engine Purge means for discharging to the intake system, lean means for reducing the fuel injection amount controlled by the fuel control means when introducing the purge, and leaning the air-fuel ratio of the intake air-fuel mixture in the engine, and the air-fuel ratio correction A fuel evaporative gas treatment system, comprising: a purge control means for controlling a discharge flow rate of the fuel evaporative gas by the purging means based on an output of the means. 2. The discharge flow rate of the fuel evaporative gas by the purge means controlled by the purge control means is preset according to a first value obtained from the air-fuel ratio correction means and the operating state of the engine. The fuel evaporative emission gas treatment system according to claim 1, which is determined based on the second value. 3. When the discharge flow rate of the fuel evaporative gas by the purging means is not 0 at the end of the introduction of the purge,
2. The fuel evaporative gas treatment system according to claim 1, wherein the purge control means performs tailing control for gradually making the discharge flow rate of the fuel evaporative gas by the purge means approach zero. 4. The lean control means performs ramp control for gradually changing the fuel injection amount controlled by the fuel control means to a target value at least at one of the start of purge introduction and the end of purge introduction. The fuel evaporative emission gas treatment system according to claim 1, characterized in that. 5. The fuel evaporative gas treatment system according to claim 1, wherein an upper limit value is set for a discharge flow rate of the fuel evaporative gas by the purge means controlled by the purge control means. 6. The change rate of the discharge flow rate of the fuel evaporative gas by the purge means controlled by the purge control means is
The fuel evaporative emission gas treatment system according to claim 1, wherein the fuel evaporative emission gas treatment system is switched according to a detection result of the detection means.