JP3241483B2 - Evaporative fuel processor for engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an evaporative fuel processing apparatus for an engine, and more particularly to an engine constituting a power plant of a vehicle together with an automatic transmission. The present invention relates to an evaporative fuel processing device for an engine which is supplied to an engine.

[0002]

2. Description of the Related Art In an engine of an automobile or the like, for example, in order to prevent air pollution caused by emission of fuel vapor generated in a fuel supply system to the atmosphere, the fuel vapor evaporated in a fuel tank is referred to as purge. In this case, the evaporated fuel is generally once adsorbed in a canister and then supplied into an intake passage during operation of the engine.

In recent years, in order to reduce the size of the canister, for example, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent Laid-Open Publication No. 1-107, there is an engine in which the fuel vapor is purged even when the engine is idling.

[0004] On the other hand, in a vehicle equipped with an automatic transmission, creep running may be performed in which the vehicle is moved forward at a very low speed only by the driving force generated when the engine is idling without depressing the accelerator pedal.

[0005]

However, if the fuel vapor is purged during the idling operation of the engine as described above, the following problem occurs during the creep running of the vehicle.

That is, since the creep running is performed in an idling state in which the throttle valve is fully closed, the amount of air taken into the combustion chamber of the engine is small, and accordingly, the regular amount of fuel supplied to the intake system is also reduced. Is running low.
If the unmetered fuel vapor is introduced into the intake system, the actual air-fuel ratio of the air-fuel mixture in the combustion chamber becomes richer than the required air-fuel ratio, and misfires easily occur. Becomes unstable.

In that case, during creep running,
Since the brake operation is frequently performed to fine-tune the vehicle speed or stop the vehicle,
The engine load transiently fluctuates due to the braking force applied to the wheels at the time of the braking operation, and the probability of causing an engine stall increases.

The present invention addresses the above-mentioned problem in introducing fuel vapor from a fuel tank into an intake system during idling in an engine constituting a power plant of a vehicle together with an automatic transmission. It is an object to surely prevent engine stall from occurring during braking from a creep running state.

[0009]

That is, the evaporative fuel processing apparatus for an engine according to the first aspect of the present invention is applied to an engine used with an automatic transmission, and operates in a predetermined operating state including an idle operation. A throttle valve fully-closed state detecting means for detecting a fully-closed state of a throttle valve provided in an intake system of the engine in the engine in which the fuel vapor in the fuel tank is introduced into the intake system; Range detecting means for detecting the range of the vehicle, vehicle speed detecting means for detecting the vehicle speed of the vehicle, the range of the automatic transmission detected by the range detecting means indicates the D range, and the throttle valve fully closed state detecting means When the fully closed state of the throttle valve is detected, the vehicle speed of the vehicle detected by the vehicle speed detecting means exceeds a predetermined vehicle speed. Lever, characterized in that a and evaporative fuel introduction inhibiting means for inhibiting the introduction of fuel vapor into the intake system.

[0010]

According to the above arrangement, the following operation can be obtained.

That is, even if fuel vapor is introduced into the intake system during idling operation of the engine, when the range of the automatic transmission is the D range and the opening of the throttle valve is fully closed, When the vehicle is in an operating state in which the vehicle speed exceeds a predetermined vehicle speed, the evaporated fuel is not introduced into the intake system. As a result, the air-fuel ratio of the air-fuel mixture in the combustion chamber of the engine is maintained at an appropriate air-fuel ratio according to the operating state of the engine, and in a creep running state in which the vehicle speed of the vehicle exceeds the predetermined vehicle speed, For example, even if a brake operation is performed to stop the vehicle, the engine can be operated stably without causing engine stall.

[0012]

Embodiments of the present invention will be described below.

As shown in FIG. 1, an engine 1 has an intake passage 5 communicating with a combustion chamber 4 through intake and exhaust valves 2 and 3, respectively.
And an exhaust passage 6. The intake passage 5 is provided with an air cleaner 7 from the upstream side, an air flow sensor 8 for detecting the amount of intake air to the combustion chamber 4, and a throttle valve 9 for adjusting the amount of intake air or the engine output. 4, a fuel injection valve 10 for injecting fuel into
It is installed downstream of a surge tank 11 provided downstream of the throttle valve 9. On the other hand, a three-way catalytic catalytic converter 12 is provided in the exhaust passage 6, and a residual oxygen concentration in the exhaust gas is detected on the upstream side of the catalytic converter 12 so that the inside of the combustion chamber 4 is detected. An O ₂ sensor 13 for detecting the air-fuel ratio of the air-fuel mixture is provided.

The engine 1 is provided with a fuel supply system for supplying fuel to the fuel injection valve 10. The fuel supply system includes a fuel tank 14 for storing fuel, a fuel pump 15 installed in the tank 14, a fuel supply passage 16 for guiding fuel discharged from the pump 15 to a fuel injection valve 10, a fuel supply passage 16, A fuel recovery passage for recovering excess fuel not injected by the injection valve; The fuel recovery passage 17 is provided with a pressure regulator 18 for adjusting the fuel injection pressure.
In other words, when the negative pressure of the intake air is introduced into the pressure regulator 18 from the surge tank 11 in the intake passage 5 through the negative pressure passage 19, the fuel injection from the fuel injection valve 10 is performed in accordance with the negative pressure. The pressure is adjusted.

An upper portion of the fuel tank 14 is connected to an evaporative fuel collecting passage 21 which collects the evaporative fuel evaporated in the tank 14 and guides the fuel to a canister 20. The connected purge passage 22 is connected to the surge tank 11 in the intake passage 5 through a purge control valve 23 that opens when the power is supplied.
It is connected to the. The atmosphere opening passage 24 connected to the lower portion of the canister 20 is guided to the surge tank 11 via a check valve 25. The check valve 25 is configured to shut off the atmosphere opening passage 24 when the surge tank 11 is in a negative pressure state. Therefore, the evaporated fuel guided to the canister 20 through the evaporated fuel collecting passage 21 is supplied to the canister 2.
After the gas is once adsorbed by the activated carbon contained in the purge gas, it is supplied to the intake passage 5 through the purge passage 22 when the purge control valve 23 is opened.

Further, the engine 1 is provided with an electronic control type control unit (hereinafter referred to as ECU) 30. The ECU 30 includes an intake air amount signal from the air flow sensor 8, an engine speed signal from a rotation sensor 31 for detecting the engine speed, and an idle switch 3 for detecting a fully closed state of the throttle valve 9.
2, a water temperature signal from a water temperature sensor 33 for detecting the engine water temperature, an air-fuel ratio signal from the O ₂ sensor 13, and the engine 1 together with the automatic transmission 26 constituting a power plant of the vehicle. A shift position signal from the shift position sensor 34 and a vehicle speed signal from a vehicle speed sensor 35 for detecting the vehicle speed of the vehicle are input, and based on these signals, fuel injection control from the fuel injection valve 10 and purge The purge control of the evaporated fuel using the control valve 23 is performed.

Here, the fuel injection control performed by the ECU 30 will be described. This fuel injection control is generally performed as follows.

That is, the ECU 30 determines, based on the intake air amount Q indicated by the signal from the air flow sensor 8 and the engine speed Ne indicated by the signal from the rotation sensor 31, the amount of intake air drawn into the combustion chamber 4 per cycle. Is calculated, the basic injection pulse width Tp corresponding to the value is set, and when a predetermined feedback condition is satisfied, O
_A feedback correction coefficient Cfb is calculated based on the air-fuel ratio signal from the _two sensors 13. That is, the ECU 30
For example, the engine water temperature T indicated by a signal from the water temperature sensor 33
When w is higher than a predetermined value and the engine speed Ne indicated by the signal from the rotation sensor 31 and the basic injection pulse width Tp as a representative characteristic of the engine load, as shown in FIG. When it is determined that the injection pulse width and the injection pulse width belong to the feedback zone Zfb set as a parameter, it is determined that the feedback condition is satisfied, and the feedback is performed when the air-fuel ratio signal from the O ₂ sensor 13 indicates the rich state of the air-fuel ratio. The correction coefficient Cfb is subtracted, and the feedback correction coefficient Cfb is added when the air-fuel ratio signal indicates a lean state of the air-fuel ratio.

The ECU 30 calculates another correction coefficient Co based on a water temperature signal from the water temperature sensor 33 and the like, and calculates the basic injection pulse width Tp, the feedback correction coefficient Cfb, the other correction coefficient Co, and a predetermined value. The final injection pulse width Ti is obtained by substituting the learning correction coefficient Clrn obtained under the condition (1) into the following relational expression.

Ti = Tp (1 + Cfb + Co + Clrn) + Tv Here, Tv represents an invalid injection time in consideration of an operation delay of the fuel injector 10.

Then, the ECU 30 outputs a drive signal corresponding to the final injection pulse width Ti to the fuel injection valve 10.

The purge control, which is a feature of the present invention, is specifically performed as follows in accordance with the flowchart shown in FIG.

That is, after reading various signals, the ECU 30 determines whether or not the above-described air-fuel ratio feedback condition is satisfied (steps S1 and S2). When it is determined that the air-fuel ratio feedback condition is satisfied, the routine proceeds to step S3, where it is determined whether or not the operating state of the engine 1 is the idle operating state based on the idle signal from the idle switch 32, and the idle operating state is determined. If not, step S4 is executed, and a standard frequency fo (for example, 10 Hz) is set as the drive frequency f of the purge control valve 23. Then, after setting a purge rate Rp according to the operating state of the engine 1, a duty drive signal according to the drive frequency f is sent to the purge control valve 23 so that the fuel vapor is purged at the purge rate Rp. (Steps S5 and S5)
6). Here, in the ECU 30, for example, as shown in FIG. 4, a map of the duty ratio D linearly corresponding to the purge ratio Rp is set.
If N is turned off, the fuel vapor adsorbed by the canister 20 is purged at the purge rate Rp corresponding to the duty rate D.

Returning to the flowchart of FIG.
When it is determined in step S2 that the air-fuel ratio feedback condition is not satisfied, the flow branches to step S7 to set 0 as the purge rate Rp. Therefore, the purge control valve 23 is completely closed, and the purge of the fuel vapor is stopped.

When the ECU 30 determines in step S3 that the operation state of the engine 1 is the idling operation state, it proceeds to step S8 and sets the range of the automatic transmission 26 indicated by the signal from the shift position sensor 34 to the D range. If it is determined that the vehicle is in the D range, the process proceeds to step S9, and the vehicle speed Vs of the vehicle indicated by the signal from the vehicle speed sensor 35 is set to the set vehicle speed Vo (for example,
km / h). And EC
If U30 determines that the vehicle speed Vs is lower than the set vehicle speed Vo, it checks in step S10 the value of the learning flag Flrn to determine whether the learning processing of the learning correction coefficient Clrn used for fuel injection control has been completed. Then Y
If it is determined to be ES, it is determined in step S11 whether or not the learning process has been completed last time. That is, the learning correction coefficient Cl
It is determined whether or not the learning process of rn has just been completed.

When NO is determined in step S11, that is, when it is determined that the learning process has just been completed, the ECU 30 sets a predetermined value To as a timer value Ts of a purge start timer in step S12. In the following step S13, the timer value Ts is set.
Is determined to be 0 or not, and if NO, step S14
After decrementing the timer value Ts in step S15, the drive frequency f of the purge control valve 23 is determined in step S15.
, An initial frequency fs (for example, 5 Hz) lower than the standard frequency fo (10 Hz) is set, and a predetermined initial value α is set as the purge rate Rp in step S16. Therefore, the purge control valve 23 is opened and closed at a longer cycle than usual until the decrement process of the timer value Ts of the purge start timer ends.

When the ECU 30 determines in step S13 that the timer value Ts of the purge start timer is 0, the ECU 30 proceeds to step S17 and sets the drive frequency f of the purge control valve 23 to the standard frequency fo. Then, step S18 is executed, and the feedback correction coefficient Cfb is set to the predetermined feedback lower limit value Fmn (eg, -0.5) set in the negative region.
It is determined whether or not the value is larger than the threshold value. If the determination is YES, the process proceeds to step S19 to determine whether or not the value of the purge increase flag Fz is 1. Here, the purge increase flag Fz is normally set to 1 and the flag Fz
This flag is set to 1 again when the increase timer that starts operating when the value of z is cleared to 0 counts a preset operation time.

When the ECU 30 determines in step S19 that the value of the purge increase flag Fz is 1, the ECU 30 proceeds to step S20 and proceeds to step S20.
A value obtained by adding a predetermined incremental value β to p and a predetermined upper limit value Rmx
Are compared with each other, and the smaller one of the two is replaced with a new purge rate Rp, and the value of the purge increase flag Fz is cleared to 0 in step S21.

On the other hand, when the ECU 30 determines in step S18 that the feedback correction coefficient Cfb is not larger than the feedback lower limit value Fmn, the ECU 30 proceeds to step S22 to determine whether the value of the purge reduction flag Fg is 1 or not. . Here, the purge reduction flag Fg
Is set to 1 in normal times, and is set to 1 again when the weight loss timer that starts operating when the value of the flag Fg is cleared to 0 counts a preset operation time. Flag.

When the ECU 30 determines in step S22 that the value of the purge reduction flag Fg is 1, the ECU 30 proceeds to step S23 to execute the current purge rate R.
The value obtained by subtracting the predetermined gradual decrease value γ from p is compared with 0, the larger value of both is replaced with a new purge rate Rp, and the process proceeds to step S24 to set the value of the purge decrease flag Fg. Is cleared to 0.

If the ECU 30 determines in step S9 that the vehicle speed Vs of the vehicle is not lower than the set vehicle speed Vo, that is, determines that the vehicle is in a creep running state, the ECU 30 executes step S7 to perform a purge. Set 0 as the rate Rp.

Next, the operation of the embodiment will be described with reference to the time chart shown in FIG.

At the end of deceleration of the vehicle, the throttle valve 9
Are fully closed, and when the idle switch 32 switches from OFF to ON, the learning flag Flrn is set to 1 and the learning process of the learning correction coefficient Clrn is started. Then, the learning process is completed and the learning flag Fl
When rn is cleared to 0, the drive frequency of the purge control valve 23 is set to an initial frequency fs lower than the standard frequency fo, and a predetermined initial value α is set as the purge rate Rp. Therefore, the purge control valve 23 is opened / closed at a longer opening / closing cycle than usual, whereby the introduction amount of the evaporated fuel is suppressed, and the canister 2 is opened at the beginning of the purge.
A large amount of evaporated fuel adsorbed to zero is prevented from flowing into the intake passage 5 rapidly. Since that time, so that the fuel that is not metered is introduced into the intake passage 5, the air-fuel ratio of the mixture in the combustion chamber 4 becomes rich state than the stoichiometric air-fuel ratio, O ₂ sensor in the exhaust passage 6 with it 1
3 also reflects the air-fuel ratio and becomes a rich state. In order to make the air-fuel ratio in the combustion chamber 4 converge to the stoichiometric air-fuel ratio, the feedback correction coefficient Cfb is linearly changed as shown in FIG. Will decrease.

At the start of the purge, a predetermined value T
The timer value Ts of the purge start timer in which o is set is 0
After a lapse of a predetermined time ts until the driving frequency f of the purge control valve 23 becomes equal to the initial frequency fs.
The purge rate Rp is stepped in accordance with a predetermined gradual increase value β, as indicated by reference numeral (a), provided that the standard frequency fo is switched to a higher standard frequency fo and the feedback correction coefficient Cfb is larger than the feedback lower limit value Fmn. To increase. As a result, the evaporated fuel adsorbed in the canister 20 is purged within a relatively short time without impairing the air-fuel ratio control accuracy.

When the vehicle is in a stopped state as described above, the range of the automatic transmission 26 is switched from the N range as shown by a symbol (C), and the operation state of the engine 1 is maintained at the idling state while maintaining the operation state of the engine 1. The vehicle restarts. In this case, when the vehicle speed Vs of the vehicle indicated by the signal from the vehicle speed sensor 35 has reached the set vehicle speed Vo, the purge rate Rp is set to 0 as shown by the symbol (D) (FIG. 7, step S3). , S7 to S9). Therefore, the purge control valve 23 is kept in the normally closed state, and the introduction of the fuel vapor into the intake passage 5 is prevented. As a result, the air-fuel ratio of the air-fuel mixture in the combustion chamber 4 of the engine 1 is maintained at the stoichiometric air-fuel ratio. In the creep running state described above, for example, a brake operation is performed to stop the vehicle. Even if it does, engine 1 can be operated stably without causing engine stall.

[0036]

As described above, according to the present invention, in a vehicle equipped with an automatic transmission, even if vaporized fuel is introduced into the intake system during idling of the engine, the range of the automatic transmission is the D range. When the throttle valve is in the fully closed state and the vehicle is in an operating state in which the vehicle speed exceeds a predetermined vehicle speed, the evaporated fuel is not introduced into the intake system. As a result, the air-fuel ratio of the air-fuel mixture in the combustion chamber of the engine is maintained at an appropriate air-fuel ratio according to the operating state of the engine, and in a creep running state in which the vehicle speed of the vehicle exceeds the predetermined vehicle speed, For example, even if a brake operation is performed to stop the vehicle, the engine can be operated stably without causing engine stall.

[Brief description of the drawings]

FIG. 1 is a control system diagram of an engine according to an embodiment.

FIG. 2 is an engine operating region diagram showing an air-fuel ratio feedback control region.

FIG. 3 is a flowchart illustrating purge control according to the embodiment.

FIG. 4 is a characteristic diagram showing a relationship between a purge rate and a duty rate used for controlling a purge control valve.

FIG. 5 is a time chart illustrating the operation of the embodiment.

[Explanation of symbols]

 Reference Signs List 1 engine 5 intake passage 9 throttle valve 14 fuel tank 20 canister 21 evaporative fuel collecting passage 22 purge passage 23 purge control valve 30 ECU 31 rotation sensor 32 idle switch 34 shift position sensor 35 vehicle speed sensor

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 25/08 301 F02D 29/00 F02D 41/02 301

Claims (1)

(57) [Claims] An evaporative fuel processing apparatus for an engine applied to an engine used with an automatic transmission and adapted to introduce evaporative fuel in a fuel tank into an intake system in a predetermined operation state including an idle operation. Wherein a throttle valve fully closed state detecting means for detecting a fully closed state of a throttle valve provided in an intake system of the engine, a range detecting means for detecting a range of the automatic transmission, and a vehicle speed of the vehicle are detected. When the range of the automatic transmission detected by the range detecting means indicates the D range, and the throttle valve fully closed state is detected by the throttle valve fully closed state detecting means,
An evaporative fuel introduction inhibiting means for inhibiting the introduction of evaporative fuel into the intake system when the vehicle speed of the vehicle detected by the vehicle speed detecting means exceeds a predetermined vehicle speed. Evaporative fuel processing equipment.