JP3349398B2 - Evaporative fuel treatment system for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel processing apparatus for an internal combustion engine, and more particularly to a fail-safe technique thereof.

[0002]

2. Description of the Related Art A conventional evaporative fuel processing apparatus for an internal combustion engine is:
The fuel tank includes a canister that adsorbs fuel vapor generated in the fuel tank, and a purge control valve that is interposed in a purge passage of the fuel vapor from the canister to the intake system and controls a purge amount of the fuel vapor. Then, an operation unit by the microcomputer calculates an opening control amount (valve opening duty) of the purge control valve according to the engine operating condition, and drives the purge control valve with a signal corresponding to the opening control amount. .

On the other hand, as a fail-safe technique, the presence or absence of a system failure is determined, and in the event of a failure, the opening control amount (valve opening duty) is set to 0 and the purge control valve is fully closed, thereby reducing the purge rate. Is controlled to 0.

[0004]

However, in such a conventional fail-safe technique for an evaporative fuel treatment apparatus for an internal combustion engine, even in the case of a failure of the arithmetic unit of the microcomputer, the failure can be reduced.
If the purge rate is set to 0, gasoline odor is generated due to overflow of the canister, and the capacity of the canister must be increased in order to prevent this, leading to an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to secure a minimum purge function in the event of a failure in an arithmetic unit of a microcomputer. It is a further object of the present invention to provide a direct injection spark ignition type internal combustion engine that has been receiving attention in recent years, and that it can well cope with switching control between stoichiometric combustion and lean combustion.

[0006]

According to the first aspect of the present invention, there is provided an evaporative fuel processing apparatus for an internal combustion engine .
1 is configured.

[0007]

On the main microcomputer side and the sub microcomputer side,
Each of the opening control amount calculating means for calculating the opening control amount of the purge control valve based on the engine operating conditions, the opening control amount calculated by the opening control amount calculating means on the main microcomputer side, and the opening control amount on the sub microcomputer side. Failure determination means for determining a failure based on consistency with the opening control amount calculated by the opening control amount calculation means is provided.

The main microcomputer is provided with an opening control amount to be output to the purge control valve when one of the failure determination means on the main microcomputer side and the failure determination means on the sub-microcomputer side determines that a failure has occurred. From the opening control amount calculated by the opening control amount calculating means on the main microcomputer side,
Of the opening control amount calculated by the opening control amount calculating means on the main microcomputer side and the opening control amount calculated by the opening control amount calculating means on the sub-microcomputer side, the control amount on the small opening side is set. Fail-safe driving means is provided.

[0010] In the invention according to claim 2 , the failure determination means calculates the opening control amount calculated by the opening control amount calculation means on the main microcomputer side and the opening control amount calculation means on the sub-microcomputer side. If the difference from the opening control amount is equal to or more than a predetermined value and continues for a predetermined time or more, it is determined that a failure has occurred. In the invention according to claim 3 , the internal combustion engine includes a fuel injection valve that injects fuel directly into the combustion chamber of the engine, and at least stoichiometric combustion at a stoichiometric air-fuel ratio and lean air-fuel ratio according to engine operating conditions. A direct injection spark ignition type internal combustion engine including a combustion mode switching control means for switching control to lean combustion, when the control amount of the small opening degree by the fail-safe drive means,
Lean combustion inhibiting means for inhibiting lean combustion is provided.

According to a fourth aspect of the present invention, the combustion mode switching control means is configured to perform at least a homogeneous stoichiometric combustion in which fuel is injected in an intake stroke and a stoichiometric air-fuel ratio is performed according to an engine operating condition, and a fuel in an intake stroke. And a stratified lean combustion in which fuel is injected during the compression stroke to perform at a lean air-fuel ratio. When the control amount on the small opening side is set by the safe drive means, homogeneous lean combustion and stratified lean combustion are prohibited.

[0012]

According to the first aspect of the present invention, the opening control amount of the purge control valve is calculated on each of the main microcomputer side and the sub-microcomputer side. If it is determined that a failure has occurred, the control amount is set to the small opening degree side, and purging of the fuel vapor can be continued on the safe side,
An effect is obtained that generation of gasoline odor due to canister overflow can be prevented without increasing the capacity of the canister.

Moreover, not only the opening control amount calculation means, so provided on both the main microcomputer side and the sub-microcomputer side the failure determining means, in addition to the above effects, if any defect of the malfunction determining unit Also, the effect that the purge of the evaporated fuel can be continued on the safe side can be obtained. According to the invention of claim 2, since the difference between the opening control amount by two microcomputers is higher than the predetermined value state is determined as a failure when the predetermined time or longer, it is possible to perform the failure determination accurately .

According to the third aspect of the present invention, it is possible to prevent lean combustion with a large torque sensitivity due to the evaporated fuel to prevent the deterioration of drivability even though the purging of the evaporated fuel is continued on the safe side at the time of failure. it can. In the invention according to claim 4 , when the switching control is performed between the homogeneous stoichiometric combustion, the homogeneous lean combustion, and the stratified lean combustion, the deterioration of the drivability is reliably prevented by prohibiting the homogeneous lean combustion and the stratified lean combustion. Can be.

[0015]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of an internal combustion engine showing an embodiment. First, this will be described. Air is sucked into the combustion chamber of each cylinder of the internal combustion engine 1 mounted on the vehicle from the air cleaner 2 through the intake passage 3 under the control of the electronically controlled throttle valve 4.

An electromagnetic fuel injection valve (injector) 5 is provided so as to directly inject fuel (gasoline) into the combustion chamber. The fuel injection valve 5 is energized by a solenoid in response to an injection pulse signal output in an intake stroke or a compression stroke from the control unit 20 in synchronization with engine rotation, opens the valve, and injects fuel adjusted to a predetermined pressure. It has become. The injected fuel diffuses into the combustion chamber in the case of the intake stroke injection to form a homogeneous mixture, and in the case of the compression stroke injection, forms a stratified mixture around the ignition plug 6. , Control unit 20
Is ignited by the ignition plug 6 based on the ignition signal from
Combustion (homogeneous combustion or stratified combustion). The combustion method is
In combination with air-fuel ratio control, it is divided into homogeneous stoichiometric combustion, homogeneous lean combustion (air-fuel ratio of 20 to 30), and stratified lean combustion (air-fuel ratio of about 40).

Exhaust gas from the engine 1 is discharged from an exhaust passage 7, and an exhaust purification catalyst 8 is interposed in the exhaust passage 7. Further, a canister 10 is provided as an evaporative fuel processing device for processing the evaporative fuel generated from the fuel tank 9. The canister 10 is a sealed container filled with an adsorbent 11 such as activated carbon, and is connected to an evaporative fuel introduction pipe 12 from the fuel tank 9. Therefore, engine 1
Evaporated fuel generated in the fuel tank 9 during the stop of
The evaporative fuel is introduced into the canister 10 through the evaporative fuel introduction pipe 12 and is adsorbed there.

The canister 10 also has a fresh air inlet 13.
Are formed, and the purge passage 14 is led out. The purge passage 14 is connected to the intake passage 3 downstream of the throttle valve 4 (intake manifold) via a purge control valve 15. The purge control valve 15 is opened by a signal output under predetermined conditions from the control unit 20 during operation of the engine 1. Accordingly, when the engine 1 is started and the purge permission condition is satisfied, the purge control valve 15 is opened, and the suction negative pressure of the engine 1 acts on the canister 10. As a result, the canister 10 is blown by the air introduced from the fresh air inlet 13. The fuel vapor adsorbed by the adsorbent 11 is desorbed, and the purge gas containing the desorbed fuel vapor passes through the purge passage 14 and the throttle valve 4 of the intake passage 3
It is sucked downstream, and thereafter burned in the combustion chamber of the engine 1.

The control unit 20 includes a CPU, an R
A microcomputer including an OM, a RAM, an A / D converter, an input / output interface, and the like is provided. The microcomputer receives input signals from various sensors, performs arithmetic processing based on the input signals, And the operation of the purge control valve 15 and the like. The microcomputer is a main microcomputer 20a.
And a sub-microcomputer 20b (see FIG. 3).

The various sensors include a crank angle sensor 21 for detecting rotation of a crankshaft or a camshaft of the engine 1,
22 are provided. These crank angle sensors 2
1, 22 are 720 ° crank angle, where n is the number of cylinders.
/ N, outputs a reference pulse signal REF at a predetermined crank angle position (for example, 110 ° before compression top dead center) and outputs a unit pulse signal POS every 1 to 2 °. From the REF cycle etc., the engine speed N
e can be calculated.

In addition, an air flow meter 23 for detecting the intake air flow rate Qa upstream of the throttle valve 4 in the intake passage 3,
Accelerator sensor 24 for detecting the amount of accelerator pedal depression (accelerator opening) ACC, opening TV of throttle valve 4
A throttle sensor 25 for detecting O (including an idle switch that is turned on when the throttle valve 4 is fully closed), a water temperature sensor 26 for detecting the cooling water temperature Tw of the engine 1, and a rich / lean exhaust air-fuel ratio in the exhaust passage 7. An O ₂ sensor 27 that outputs a signal corresponding to the vehicle speed, a vehicle speed sensor 28 that detects a vehicle speed VSP, and the like are provided.

Next, the purge control of the evaporated fuel (control of the purge control valve 15) performed by the microcomputer in the control unit 20 will be described with reference to the flowcharts of FIGS. The evaporative fuel purge control uses the main microcomputer 20a and the sub-microcomputer 20b as shown in FIG. 3 and executes the routine of FIG.
The routine of FIG. 5 is executed on the side b.

FIG. 4 shows a purge control routine on the main microcomputer side, which is executed every predetermined time (for example, 10 ms). In step 1 (referred to as S1 in the figure, the same applies hereinafter),
Reference flow baseQ for purging based on intake air flow Qa
= Qa × PRATE # (where PRATE # is a constant).

In step 2, the equivalent ratio correction is performed. That is, if the target equivalent ratio is TFBYA (14.6 / corresponding to the target air-fuel ratio), the corrected flow rate Qevp = baseQ × TFB
YA is calculated. This is to reduce the purge flow rate when the air-fuel ratio is lean. In step 3, differential pressure correction is performed. That is, the throttle opening TVO and the engine speed N
The value KPB corresponding to the differential pressure before and after the throttle is obtained by referring to the map allocated by e, and the purge control valve required opening EVPSS is obtained.
Calculate T = Qevp × KPB.

In step 4, the required purge control valve opening E
Based on VPSST, this is used as the valve opening duty EVPOUT1 = f (EVPSS) which is the opening control amount of the purge control valve.
T). Here, the steps 1 to 4 correspond to the opening degree control amount calculating means on the main microcomputer side.

The valve opening duty EVPOUT1 calculated on the main microcomputer side is transmitted to the sub microcomputer side, and conversely, the valve opening duty EVP calculated on the sub microcomputer side is calculated.
VPOUT2 is received by the main microcomputer. In step 5, the consistency between the valve opening duty EVPOUT1 calculated on the main microcomputer side and the valve opening duty EVPOUT2 calculated on the sub microcomputer side is determined. That is, it is determined whether or not they are substantially equal. Specifically, the difference | EVPOUT1−EVPOUT
2 | is smaller than a predetermined value.

When EVPOUT1 = EVPOUT2,
Specifically, if | EVPOUT1−EVPOUT2 | is less than the predetermined value, the process proceeds to step 6, where the failure counter C
1 is cleared (C1 = 0). EVPOUT1 @ EVP
In the case of OUT2, for details, | EVPOUT1-EVP
If OUT2 | is equal to or greater than the predetermined value, the process proceeds to step 7, where the failure counter C1 is incremented (C1 = C
1 + 1).

In step 8, the failure counter C1 is compared with a predetermined value to determine whether or not C1 ≧ the predetermined value. And
It is determined that C1 <predetermined value is normal, and that C1 ≧ predetermined value is failure. Here, the steps 5 to 8 correspond to the failure determination means on the main microcomputer side.

If C1 <predetermined value, as a result of the failure judgment,
Although it is considered normal, a failure determination result (failure determination flag) FSUBNG is received from the sub-microcomputer side. And
In step 9, it is determined whether or not the sub microcomputer has determined that a failure has occurred (failure determination flag FSUBNG = 1). When the failure determination flag FSUBNG = 0, it is determined that there is no failure on both the main microcomputer side and the sub-microcomputer side, and the routine proceeds to step 12, where the valve opening duty EVPOUT output to the purge control valve is set to the main microcomputer. The valve opening duty EVPOUT1 calculated on the side is set to (E
VPOUT = EVPOUT1), and this routine ends.

If it is determined in step 8 that C1 ≧ predetermined value, as a result of the failure determination, it is determined that a failure has occurred.
Go to 0,11. Also, in the determination in step 9, the FSU
If BNG = 1, that is, if the main microcomputer determines that there is no failure but the sub-microcomputer determines that there is a failure, the process also proceeds to steps 10 and 11.

In step 10, lean combustion is prohibited (lean combustion prohibition flag = 1). In step 11, the valve opening duty EVPOU calculated by the main microcomputer is calculated.
T1 and valve opening duty EV calculated on the sub-microcomputer side
Compare the magnitude with POUT2. As a result of comparison, EVPO
If UT1 ≦ EVPOUT2, the routine proceeds to step 12, where the smaller EVPOUT1 is selected, and the valve opening duty EVPOUT output to the purge control valve is set to the valve opening duty EVPOUT1 calculated on the main microcomputer side (EVPOUT = EVPOUT1). ), End this routine.

Conversely, if EVPOUT1> EVPOUT2, the process proceeds to step 13, where the smaller EVPOU
T2 is selected, and the valve opening duty EVPOUT output to the purge control valve is set to the valve opening duty EVPOUT2 calculated on the sub-microcomputer side (EVPOUT = EVPO
UT2), end this routine. As described above, when a failure is determined by either the failure determination on the main microcomputer side or the failure determination on the sub-microcomputer side, the valve opening duty EVPOUT output to the purge control valve is calculated by the main microcomputer side. Valve duty EVPOUT1
And the valve opening duty EVPO calculated by the sub microcomputer
The purge of evaporated fuel is continued on the safe side with the smaller one of UT2. Therefore, step 11
13 correspond to fail-safe driving means.

FIG. 5 shows a purge control routine on the sub-microcomputer side, which is executed at predetermined time intervals. Steps 21 and 2
In step 4, as in steps 1-4 on the main microcomputer side,
A valve opening duty, which is an opening degree control amount of the purge control valve, is calculated, and is calculated as EVPOUT2.

Here, the steps 21 to 24 correspond to the opening control amount calculating means on the sub-microcomputer side. And
Valve opening duty EVPOU calculated on the sub microcomputer side
T2 is transmitted to the main microcomputer side, and conversely, the valve opening duty EVPOUT1 calculated by the main microcomputer side is received by the sub microcomputer side.

In step 25, the consistency between the valve opening duty EVPOUT1 calculated on the main microcomputer side and the valve opening duty EVPOUT2 calculated on the sub microcomputer side is determined. That is, it is determined whether or not these are substantially equal. Specifically, the difference | EVPO
It is determined whether UT1-EVPOUT2 | is less than a predetermined value.

When EVPOUT1 = EVPOUT2,
Specifically, if | EVPOUT1−EVPOUT2 | is less than the predetermined value, the routine proceeds to step 26, where the failure counter C2 is cleared (C2 = 0). EVPOUT1 @ EV
In the case of POUT2, for details, | EVPOUT1-EV
If POUT2 | is equal to or greater than the predetermined value, the process proceeds to step 27, where the failure counter C2 is incremented (C2 =
C2 + 1).

In step 28, the failure counter C2 is compared with a predetermined value to determine whether or not C2 ≧ the predetermined value. C2 <
If the value is the predetermined value, the result of the failure determination is regarded as normal, and in step 29, a failure determination flag FSUBNG = 0 is set.
On the other hand, if C2 ≧ predetermined value, as a result of the failure determination, it is determined that a failure has occurred, and in step 30, a failure determination flag FSUBNG = 1 is set.

Here, steps 25 to 30 correspond to the failure determination means on the sub-microcomputer side. Then, the value of the failure determination flag FSUBNG is transmitted to the main microcomputer side, and this routine ends. If the sub-microcomputer determines that a failure has occurred and the failure determination flag FSUBNG is set to 1, lean combustion is unconditionally prohibited by the routine of the main microcomputer in FIG. 4 (step 1).
0), the smaller valve opening duty is output (steps 11 to 13).

Next, the switching control of the combustion system performed by the microcomputer in the control unit 20 will be described with reference to FIG.
This will be described with reference to the flowchart of FIG. FIG. 6 shows a combustion mode switching routine, which is executed every predetermined time (for example, 10 ms). This routine corresponds to combustion mode switching control means. In step 41, engine operating conditions such as the engine speed Ne, the basic fuel injection amount Tp (or the target engine torque tTe), and the water temperature Tw are read.

In step 42, a combustion mode switching map is referred to based on the engine operating conditions. That is, the engine speed Ne and the basic fuel injection amount Tp (or the target engine torque t
Te) as a parameter, and a plurality of maps in which the combustion method (and the basic target equivalent ratio TFBYA0) is determined for each condition such as the water temperature Tw and the time after the start, and the actual engine is determined based on the map selected from these conditions. The combustion mode (and the basic target equivalent ratio TFBYA0) is set to one of the homogeneous stoichiometric combustion, the homogeneous lean combustion, and the stratified lean combustion according to the parameters of the operating state. The map illustrated in FIG. 6 is after the warm-up is completed (the water temperature Tw is high and the time after starting is large).

In step 43, the process branches according to the determination of the combustion system. In the case of homogeneous stoichiometric combustion, step 46
Go to and perform the corresponding control. That is, the fuel injection amount is set to be equivalent to the stoichiometric air-fuel ratio (14.6), and the air-fuel ratio feedback control by the O ₂ sensor is performed, while the injection timing is set to the intake stroke to perform homogeneous stoichiometric combustion.

In the case of homogeneous lean combustion, the routine proceeds to step 47, where corresponding control is performed. That is, the fuel injection amount is set to a value corresponding to the lean air-fuel ratio of the air-fuel ratio of 20 to 30, and the open control is performed, while the injection timing is set to the intake stroke to perform homogeneous lean combustion. In the case of stratified lean combustion, the routine proceeds to step 48, where the corresponding control is performed. That is, the fuel injection amount is set to a value corresponding to a lean air-fuel ratio of about 40, and the open control is performed, while the injection timing is set to the compression stroke to perform stratified lean combustion.

However, immediately before each of the homogeneous lean combustion control in step 47 and the stratified lean combustion control in step 48, steps 44 and 45 are provided. Here, it is determined whether lean combustion is inhibited (lean combustion inhibition flag = 1) or not. If lean combustion is prohibited, step 4 is performed without performing homogeneous lean combustion control and stratified lean combustion control.
The program proceeds to step 6, where the homogeneous stoichiometric control is performed.

Therefore, step 10 in FIG. 4 and steps 44 and 45 in FIG. 6 correspond to lean combustion inhibiting means. When it is determined that a malfunction has occurred, lean combustion (homogeneous lean combustion control and stratified lean combustion control) with high torque sensitivity due to the evaporated fuel is prohibited to prevent deterioration in drivability. The calculation formula of the fuel injection amount is as follows.

TI = Tp × TFBYA × α + Ts Here, Tp is a basic fuel injection amount corresponding to the stoichiometric air-fuel ratio, and is obtained by Tp = K0 × Qa / Ne (K0 is a constant). TFBYA is a target equivalence ratio, which is obtained by correcting the basic target equivalence ratio TFBYA0 obtained from the map by the combustion efficiency or the like and giving a first-order delay. The target equivalence ratio TFBYA is also called a target fuel-air ratio correction coefficient, and is expressed as 14.6 / tAF, where the target air-fuel ratio is tAF.

Α is an air-fuel ratio feedback correction coefficient based on the O ₂ sensor signal, and is clamped to = 1 during lean combustion. Ts is an invalid injection time correction amount depending on the battery voltage.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram of an internal combustion engine showing an embodiment of the present invention.

FIG. 3 is a diagram showing a microcomputer configuration.

FIG. 4 is a flowchart of a purge control routine on the main microcomputer side.

FIG. 5 is a flowchart of a purge control routine on the sub-microcomputer side.

FIG. 6 is a flowchart of a combustion mode switching routine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Intake passage 4 Throttle valve 5 Fuel injection valve 6 Spark plug 9 Fuel tank 10 Canister 14 Purge passage 15 Purge control valve 20 Control unit 20a Main microcomputer 20b Sub microcomputer

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI F02D 45/00 301 F02D 45/00 301L 372 372G (56) References JP-A-6-264834 (JP, A) JP-A-2 -42157 (JP, A) JP-A-9-88701 (JP, A) JP-A-8-177549 (JP, A) JP-A-8-312401 (JP, A) (58) Fields investigated (Int. . ^7, DB name) F02M 25/08 F02M 25/08 301 F02D 41/02 325 F02D 41/02 330 F02D 41/22 301 F02D 45/00 301 F02D 45/00 372

Claims (4)

(57) [Claims] 1. A canister for adsorbing evaporated fuel generated in a fuel tank, and a purge control valve interposed in a purge passage for evaporated fuel from the canister to an intake system to control a purge amount of the evaporated fuel. In an evaporative fuel processing apparatus for an internal combustion engine, an opening control amount calculating means for calculating an opening control amount of a purge control valve based on engine operating conditions is provided on a main microcomputer side and a sub microcomputer side, respectively. Failure determination means for performing a failure determination based on the consistency between the opening control amount calculated by the degree control amount calculating means and the opening control amount calculated by the opening control amount calculating means on the sub-microcomputer side. Output to the purge control valve when one of the failure determination means on the main microcomputer side and the failure determination means on the sub microcomputer side determines that a failure has occurred on the microcomputer side. The opening control amount calculated by the opening control amount calculating means on the main microcomputer side is calculated from the opening control amount calculated by the opening control amount calculating means on the main microcomputer side. An evaporative fuel processing apparatus for an internal combustion engine, comprising: a fail-safe drive unit that makes a control amount on the small opening side out of the opening control amount calculated by the opening control amount calculation unit. 2. The failure determination means according to claim 1, wherein said failure control means calculates an opening control amount calculated by said opening control amount calculation means on the main microcomputer side and an opening control amount calculated by said opening control amount calculation means on the sub-microcomputer side. the difference is equal to or higher than a predetermined value condition is to determine a failure when the predetermined time or longer 請
The fuel vapor treatment device for an internal combustion engine according to claim 1 . 3. The internal combustion engine includes a fuel injection valve for directly injecting fuel into a combustion chamber of the engine, and at least stoichiometric combustion at a stoichiometric air-fuel ratio and lean combustion at a lean air-fuel ratio according to engine operating conditions. A direct-injection spark ignition type internal combustion engine including a combustion mode switching control unit that performs switching control between the lean combustion prohibition unit and the lean combustion prohibition unit that prohibits the lean combustion when the fail-safe drive unit sets the control amount on the small opening side. evaporative fuel processing apparatus according to claim 1 or claim 2, wherein the internal combustion engine, characterized by comprising. Wherein said combustion mode switching control means, according to the engine operating condition, at least, the homogeneous stoichiometric combustion to take place in the stoichiometric air-fuel ratio by injecting fuel in the intake stroke, the lean air by injecting fuel in the intake stroke The lean-burn inhibiting means is controlled by the fail-safe drive means to switch between homogeneous lean combustion performed at a fuel ratio and stratified lean combustion performed at a lean air-fuel ratio by injecting fuel in a compression stroke. 4. The evaporative fuel treatment system for an internal combustion engine according to claim 3 , wherein homogeneous lean combustion and stratified lean combustion are prohibited when the control amount on the small side is set.