JP3201129B2 - Evaporative fuel processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor processing apparatus for an automobile, and more particularly to a fuel vapor processing apparatus capable of suppressing disturbance of an air-fuel ratio when a purge is resumed after returning from a fuel cut state.

[0002]

2. Description of the Related Art Fuel evaporating from a fuel tank of an automobile is once absorbed by a canister to improve fuel efficiency and prevent air pollution, and is purged into an intake pipe at an appropriate timing to be used as fuel. However, when the internal combustion engine is in a so-called fuel cut state, for example, when descending a slope, it is necessary to interrupt the purge, and the purge is restarted after the fuel cut state is released.

Therefore, it is an object to prevent the air-fuel ratio of the internal combustion engine from being greatly disturbed when the purge is restarted.
To solve this problem, Japanese Patent Laying-Open No. 4-370359 discloses an apparatus in which a purge valve control signal immediately before fuel cut is stored, and when the purge is restarted, the stored purge valve control signal is used as an initial value. ing.

Further, Japanese Patent Application Laid-Open No. 5-79410 discloses that
When the purge valve is open, the accumulated value of the purge flow rate is increased, and when the purge valve is closed, the accumulated value of the purge flow rate is decreased. When the accumulated value of the purge flow rate is small, fuel is accumulated in the canister. A device that controls the opening degree of a purge valve to be small has been proposed.

[0005]

SUMMARY OF THE INVENTION
In the device disclosed in JP-A-370359, since the amount of evaporated fuel stored in the canister during the closing of the purge valve is not considered, a large amount of evaporated fuel is accumulated during the closing of the purge valve. In such a case, it is impossible to avoid a large change in the air-fuel ratio due to the restart of the purge.

In Japanese Patent Application Laid-Open No. Hei 5-79410, the integrated value of the purge flow rate is determined according to the opening / closing time of the purge valve and does not reflect the actual fuel evaporation amount. May give. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an evaporative fuel processing apparatus capable of reducing disturbance to the air-fuel ratio even when purge is restarted after fuel cut is released.

[0007]

An evaporative fuel processing apparatus according to a first aspect of the present invention is provided in a canister for adsorbing evaporative fuel evaporating from a fuel tank of an internal combustion engine and a purge pipe connecting the canister and an intake pipe. A purge valve for controlling the amount of evaporated fuel purged into the intake pipe; an air-fuel ratio detecting means provided in an exhaust pipe of the internal combustion engine; and an air-fuel ratio detected by the air-fuel ratio detecting means being controlled to a predetermined target air-fuel ratio. Air-fuel ratio feedback control means for calculating the air-fuel ratio correction coefficient, purge rate control means for controlling the purge rate based on the air-fuel ratio correction coefficient calculated by the air-fuel ratio feedback control means, and air-fuel ratio feedback control means A fuel injection valve control means for controlling the opening time of the fuel injection valve based on the corrected air-fuel ratio correction coefficient, and a state representative of the amount of fuel vapor generated in the fuel tank. A fuel vapor generation amount detecting means for detecting the amount, a purge inhibition time integrating means for accumulating the purge prohibited time, and a fuel vapor generation amount in the fuel tank detected by the fuel vapor generation amount detecting means. And a restart purge rate setting means for setting an initial value of a purge rate at the time of restarting the purge based on the state quantity to be performed and the purge prohibition time integrated by the purge prohibition time integrating means.

According to a second aspect of the present invention, there is provided an evaporative fuel processing apparatus.
The fuel vapor generation amount detecting means is a pressure detecting means for detecting the pressure in the fuel tank.

[0009]

In the fuel vapor processing apparatus according to the first invention, the fuel cut time and the state quantity representing the amount of fuel vapor generated per unit time in the fuel tank, such as the fuel temperature and the fuel tank internal pressure, are calculated. The amount of evaporated fuel adsorbed to the canister during the fuel cut is estimated based on the estimated fuel amount, and the purge valve opening at the time of restarting the purge is determined based on the estimated value of the evaporated fuel amount.

In the fuel vapor processing apparatus according to the second aspect of the present invention, since the internal pressure in the fuel tank increases in proportion to the amount of fuel vaporized, the fuel temperature is detected by detecting the fuel tank internal pressure to generate fuel vapor at that time. Detect the amount.

[0011]

FIG. 1 is a block diagram of an embodiment of an evaporative fuel treatment apparatus according to the present invention. One cylinder 10 of an internal combustion engine has an intake passage 11 and an exhaust valve 10 via an intake valve 101.
The exhaust passage 12 is connected via the second exhaust passage 12. Intake channel 1
A fuel injection valve 111 is disposed near one intake valve 101.

The fuel injected into the fuel injection valve 111 is stored in the fuel tank 13, and the fuel pressurized by the fuel pump 131 is supplied through a fuel pipe 132. Evaporated fuel generated in the fuel tank 13 is supplied to the canister 1 through a vapor pipe 133.
It is led to 4. The canister 14 and the intake passage 11 are connected by a purge pipe 141, and a purge control valve 142 is installed in the purge pipe 141.

An air-fuel ratio sensor 121 for detecting an air-fuel ratio of exhaust gas is provided in the exhaust passage 12. The evaporative fuel processing device is controlled by the control unit 15.
Is configured as a microcomputer system, for example. That is, the control unit 15 controls the CPU
152, a memory 153, an input interface 154, and an output interface 155.

The air-fuel ratio sensor 121 is connected to the input interface 154 and takes the air-fuel ratio of the exhaust gas into the control unit 15. The control unit 15 is connected to the fuel injection valve 111 and the purge control valve 142 via the output interface 155. FIG. 2 is a flowchart of an air-fuel ratio control routine executed by the evaporated fuel processing apparatus according to the present invention, which is executed at every constant cam angle.

In step 201, it is determined whether the air-fuel ratio feedback control is permitted. (1) Not during start-up (2) Not during fuel cut (3) Cooling water temperature (THW) ≧ 40 ° C (4) Air-fuel ratio feedback control when all conditions for air-fuel ratio sensor activation completion are satisfied Is permitted, and if any one of the conditions is not satisfied, the air-fuel ratio feedback control is not permitted.

When an affirmative determination is made in step 201, the process proceeds to step 202, where the output voltage V _{OX of the} air-fuel ratio sensor 121 is output.
Is read, and in step 203, a predetermined reference voltage V
_R (for example, 0.45 V) or less is determined.
If an affirmative determination is made in step 203, it is determined that the air-fuel ratio of the exhaust gas is lean, and the process proceeds to step 204, where an air-fuel ratio flag XOX is set to "0".

In step 205, it is determined whether or not the air-fuel ratio flag XOX and the state maintaining flag XOXO match. If an affirmative determination is made in step 205, it is determined that the lean state is continuing, and in step 206, the air-fuel ratio correction coefficient FAF is increased by the lean integral amount "a", and this routine ends.

If a negative determination is made in step 205,
Assuming that the state has been reversed from the rich state to the lean state, the routine proceeds to step 207, where the air-fuel ratio correction coefficient FAF is increased by the lean skip amount “A”. Note that the lean skip amount “A” is set sufficiently larger than the lean integral amount “a”.

Next, at step 208, the state maintaining flag XO
XO is reset and this routine ends. If a negative determination is made in step 203, it is determined that the air-fuel ratio of the exhaust gas is rich, and the process proceeds to step 209, where the air-fuel ratio flag XOX is set to "1". In step 210, it is determined whether or not the air-fuel ratio flag XOX and the state maintaining flag XOXO match.

If the determination in step 210 is affirmative,
Assuming that the rich state continues, step 211
Then, the air-fuel ratio correction coefficient FAF is reduced by the rich integral amount "b", and this routine is terminated. When a negative determination is made in step 210, it is determined that the lean state has been reversed to the rich state, and the routine proceeds to step 212, where the air-fuel ratio correction coefficient FAF is reduced by the rich skip amount “B”.

The rich skip amount "B" is set to be sufficiently larger than the rich integral amount "b". Then step 2
At step 13, the state maintaining flag XOXO is set to "b", and this routine ends. If a negative determination is made in step 201, the routine proceeds to step 214, where the air-fuel ratio correction coefficient F
AF is set to "1.0" and this routine ends.

FIG. 3 is a flowchart of a purge rate control routine executed by the control unit 15 of the evaporated fuel processing apparatus according to the present invention. In step 301, it is determined whether air-fuel ratio feedback control is being performed. Step 3
When an affirmative determination is made in 01, the routine proceeds to step 302, where it is determined whether or not fuel cut is being performed.

If a negative determination is made in step 302, the routine proceeds to step 303, where the normal purge rate control is performed, and the routine proceeds to step 304. In step 304, the purge stop flag X
The IPGR is reset, the fuel cut counter C _cut is reset in step 305, and this routine ends.
If an affirmative determination is made in step 302, step 306
To perform the correction purge rate calculation at restart,
In step 7, the purge stop flag XIPGR is set to "1", and this routine ends.

If a negative determination is made in step 301, the routine proceeds to step 308, where the purge rate PGR is reset. In step 309, the purge stop flag XIPGR is set to "1", and this routine ends. FIG. 4 shows FIG.
6 is a flowchart of a normal purge rate control process executed in step 303 of the purge rate control routine shown in FIG.

That is, in step 3031 it is determined in which region the air-fuel ratio correction coefficient FAF is located. FIG. 5 is a graph showing an area of the air-fuel ratio correction coefficient FAF, where 1 ± F
If it is within 1 ± G, it is determined that it belongs to the area II, and if it is outside 1 ± G, it belongs to the area III. Note that 0 <F <G.

If it is determined in step 3031 that the purge rate belongs to the region I, the process proceeds to step 3032, where the purge rate PGR
Is increased by a predetermined purge rate increasing amount D, and the routine proceeds to step 3034. If it is determined in step 3031 that the purge rate belongs to the region III, the process proceeds to step 3033, in which the purge rate PGR is decreased by a predetermined purge rate down amount E, and the process proceeds to step 3034.

If it is determined in step 3031 that the image belongs to the area II, the flow directly proceeds to step 3034. In Step 3034, a restart-time correction purge rate PGR _comp, which will be described later, is subtracted from the purge rate PGR.
Proceed to. In step 3035, the restart correction purge rate PGR _comp is subtracted by a predetermined constant value F, and in step 3036, it is determined whether the restart correction purge rate PGR _comp is positive.

If a negative determination is made in step 3036, the correction purge rate at restart PGR _comp is reset in step 3037.
Is set to the lower limit value “0”, and the routine proceeds to step 3038. If an affirmative determination is made in step 3036, the flow directly proceeds to step 3038, where the upper and lower limits of the purge rate PGR are checked, and this routine ends. FIG. 6 is a flowchart of the restart-time correction purge rate calculation executed in step 306 of the purge rate control routine shown in FIG.

That is, in step 3061, the pressure _PT in the fuel tank detected by the pressure sensor 134 for detecting the pressure in the fuel tank 13 is read. The fuel tank internal pressure is a function of the amount of evaporated fuel in the fuel tank, and the amount of evaporated fuel in the fuel tank is an indication of an equilibrium state such as evaporation of fuel, release to the canister, and liquefaction of the evaporated fuel. The internal pressure _PT can be considered to represent the degree of evaporation of the fuel in the fuel tank. The degree of fuel evaporation is substantially determined by the fuel temperature and the pressure acting on the fuel surface, and may be represented by detecting the fuel temperature instead of the fuel tank internal pressure _PT . However, when the pressure in the fuel tank is used as a parameter as in the present embodiment, the effects of changes in the atmospheric pressure and the like are canceled out, so that more accurate detection can be easily performed.

In step 3062, the fuel cut counter C _cut is incremented, and the flow advances to step 3063. Note that the fuel cut counter C _cut indicates the duration of the fuel cut state. In step 3063,
Fuel tank pressure _PT and fuel cut counter C _cut
Is determined as a function of the fuel vapor amount VAPOR adsorbed on the canister 14 during the fuel cut.

VAPOR = VAPOR (P _T , C _cut ) As a function for obtaining the evaporated fuel amount VAPOR, for example, the following can be used. That is, the fuel evaporation amount α per unit time can be determined as a function of the fuel tank pressure _PT .

Α = α (P _T ) Therefore, the evaporated fuel amount VAPOR can be obtained by multiplying the fuel evaporation amount α per unit time by the count value of the fuel cut counter C _cut corresponding to the elapsed time. VAPOR = α (P _T ) · C _{cut In} step 3064, the restart correction purge rate PGR _comp is determined as a function of the evaporated fuel amount VAPOR and the intake air amount GA detected by the air flow meter 112.

PGR _comp = β · VAPOR / GA where β is a coefficient. FIG. 7 is a flowchart of a purge control valve driving routine in which the opening of the purge valve 142 is controlled by so-called duty ratio control. That is, in step 71, it is determined whether or not the purge stop flag XIPGR is "1". If an affirmative determination is made, it is determined that purge is being stopped, and the duty ratio Duty is set to "0" in step 72, and this routine is ended I do.

If a negative determination is made in step 71, it is determined that purging is in progress, and the routine proceeds to step 73, where the duty ratio Duty is calculated based on the following equation. Duty = γ · PGR / PGR ₁₀₀ + δ Here, PGR ₁₀₀ is a full open purge rate which is a purge amount when the purge valve is fully opened, and is set in advance as a map of the internal combustion engine speed _Ne and the throttle valve opening TA. I have.

FIG. 8 is an example of setting a map for determining the full open purge rate. γ and δ are correction coefficients determined by the battery voltage and the atmospheric pressure. FIG. 9 is a flowchart of the fuel injection valve control routine,
In step 1, the basic fuel injection time Tp is determined as a function of the internal combustion engine speed _Ne and the intake air amount GA.

Tp = Tp ( _Ne , GA) In step 92, a purge correction coefficient FPG is calculated based on a purge rate PGR and an evaporative fuel concentration index FGPG described later. FPG = (FGPG-1) .PGR In step 93, the fuel injection valve opening time TAU is determined by the following equation using the air-fuel ratio correction coefficient FAF and the purge correction coefficient FPG calculated by the air-fuel ratio control routine shown in FIG. .

TAU = α · Tp · (FAF + FPG) + β Here, α and β are correction coefficients including a warm-up increase, a start-up increase, and the like. In step 94, the fuel injection valve opening time T
AU is output and this routine ends. FIG. 10 is a flowchart of a fuel vapor concentration learning routine for calculating the fuel vapor concentration index FGPG.

In step 1001, it is determined whether or not the purge stop flag XIPGR is "1". If the determination is affirmative, it is determined that the purge is being stopped, and this routine is directly terminated. When an affirmative determination is made in step 1001, the process proceeds to step 1002, and it is determined whether or not the evaporative fuel concentration learning condition is satisfied.

That is, when (1) during the air-fuel ratio feedback control, (2) cooling water temperature ≧ 80 ° C., (3) starting fuel increase = 0, and (4) warm-up fuel increase = 0, all conditions are satisfied. Learning is performed, and if any of the conditions is not satisfied, learning is not performed.

When a negative determination is made in step 1002,
That is, when learning is not performed, this routine is directly terminated. When an affirmative determination is made in step 1002, that is, when learning is performed, the process proceeds to step 1003. Step 100
In step 3, a time average value FAFAV of the air-fuel ratio correction coefficient FAF calculated in the air-fuel ratio control routine of FIG.
Proceed to step 1004.

In step 1004, the average value FAFA
V is "0.98" or less, exceeds "0.98" and "1.0
It is determined which area is less than “2” or greater than “1.02.” If it is determined that the average value FAFAV is less than “0.98,” the process proceeds to step 1005, where the evaporated fuel concentration index FGPG Is reduced by a predetermined amount “Q” (for example, 0.4%), and the routine proceeds to step 1007.

If it is determined that it is not less than "1.02", the routine proceeds to step 1006, where the fuel vapor concentration index FGPG is increased by a predetermined amount "P" (for example, 0.4%).
Proceed to step 1007. Over "0.98" to "1.0
When it is less than 2 ", the evaporated fuel concentration index FGP
Proceed directly to step 1007 without updating G.

In step 1007, the fuel vapor concentration index FGPG is set to the lower limit “0.7” or more and the upper limit “1.
According to the above processing, if the fuel concentration in the purge gas purged to the intake pipe 11 is "0", the evaporated fuel concentration index FGPG is set to "1". It is set to a value smaller than "1" as the fuel concentration increases.

[0044]

According to the fuel vapor processing apparatus of the first invention, the fuel vapor amount estimated based on the fuel cut time and the representative value of the amount of fuel vapor generated per unit time in the fuel tank is reduced. Since the purge valve opening at the time of restarting the purge is determined based on this, it is possible to suppress the occurrence of disturbance in the air-fuel ratio at the time of restarting the purge.

According to the evaporative fuel processing apparatus of the second invention, the amount of fuel vapor generated per unit time is detected by the pressure in the fuel tank, so that the accurate amount of fuel vapor and the atmospheric pressure change are taken into account. Detection is possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an evaporative fuel processing apparatus.

FIG. 2 is a flowchart of an air-fuel ratio control routine.

FIG. 3 is a flowchart of a purge rate control routine.

FIG. 4 is a flowchart of a normal purge rate control process.

FIG. 5 is a graph showing an area of an air-fuel ratio correction coefficient.

FIG. 6 is a flowchart of a restart-time correction purge rate calculation.

FIG. 7 is a flowchart of a purge control valve driving routine.

FIG. 8 is a setting example of a map for determining a full-open purge rate.

FIG. 9 is a flowchart of a fuel injection valve control routine.

FIG. 10 is a flowchart of an evaporative fuel concentration learning routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Cylinder 101 ... Intake valve 102 ... Exhaust valve 11 ... Intake pipe 111 ... Fuel injection valve 112 ... Air flow meter 12 ... Exhaust pipe 121 ... Air-fuel ratio sensor 13 ... Fuel tank 131 ... Fuel pump 132 ... Fuel piping 133 ... Vapor piping 134 ... Pressure sensor 14 ... Canister 141 ... Purge pipe 142 ... Purge valve 15 ... Control unit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Yuda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kenji Harima 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Toshinari Nagai 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-5-79410 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 25/08 301 F02D 41/02 330 F02D 45/00 364

Claims (2)

(57) [Claims] 1. A canister for adsorbing evaporative fuel evaporating from a fuel tank of an internal combustion engine, and a purge valve installed in a purge pipe connecting the canister and an intake pipe for controlling an amount of evaporative fuel purged into the intake pipe. Air-fuel ratio detection means installed in an exhaust pipe of an internal combustion engine; air-fuel ratio feedback control for calculating an air-fuel ratio correction coefficient to control the air-fuel ratio detected by the air-fuel ratio detection means to a predetermined target air-fuel ratio Means, a purge rate control means for controlling a purge rate based on the air-fuel ratio correction coefficient calculated by the air-fuel ratio feedback control means, and fuel injection based on the air-fuel ratio correction coefficient calculated by the air-fuel ratio feedback control means. A fuel injection valve control means for controlling the valve opening time of the valve. A fuel vapor generation amount detecting means for detecting a state quantity to be purged; a purge prohibition time integrating means for accumulating a purge prohibited time; and a fuel vapor generation amount in the fuel tank detected by the fuel vapor generation amount detecting means. A resumption purge rate setting means for setting an initial purge rate at the time of resuming the purge by taking into account a state quantity representative of the above and the purge prohibition time integrated by the purge prohibition time integration means. . 2. The fuel vapor processing apparatus according to claim 1, wherein said fuel vapor generation amount detecting means is a pressure detecting means for detecting a pressure in a fuel tank.