JPS6065245A - Air-fuel ratio controller for internal-combustion engine - Google Patents

Abstract

PURPOSE:To keep off any influence on a coefficient of storing control compensation due to evaporative fuel, by installing an on-off valve in position between a canister and a suction passage as well as installing a driving device closing the on-off valve by means of a judging device which judges a storing condition. CONSTITUTION:An on-off valve 10 is installed interposingly between a canister 12 and a suction passage 8. When a strong condition is satisfied, a signal S8 out of a control circuit 61 is set down to a high level and thereby the on-off valve is energized with current. With this constitution, the canister 12 is intercepted from the suction passage and evaporative fuel is made so as not to be led into the suction passage. Thus, during storing control, a variation in the air- fuel mixture due to the evaporative fuel is preventable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an air-fuel ratio control device for a vehicle internal combustion engine having an electronically controlled fuel injection device, and in particular, to an air-fuel ratio control device for an internal combustion engine for a vehicle having an electronically controlled fuel injection device, and in particular to an air-fuel ratio control device for altitude compensation of the air-fuel ratio and for air-fuel ratio control due to aging of parts. The present invention relates to an air-fuel ratio control device suitable for a vehicle internal combustion engine that performs learning control designed to compensate for the fuel ratio and introduces evaporated fuel stored in a canister into an intake passage.

[Background of the invention]

In an electronically controlled fuel injection system, for example, engine speed NK detected by a speed sensor, intake pipe pressure, QPM
The basic fuel injection time TP is calculated based on this, and the final fuel injection time τ in seconds is calculated by making various corrections to the basic fuel injection time TP according to the operating state of the engine. The injection valve is opened for the fuel injection time τ to inject fuel.

On the other hand, in this type of fuel injection control device that uses a three-way catalytic converter to simultaneously remove Go, HC, and NOx from exhaust gas as a measure against exhaust emissions, It is desired to control the fuel ratio near the stoichiometric air-fuel ratio. Therefore, an oxygen sensor is installed in the exhaust passage, and under certain conditions, a feedback correction coefficient FAF is calculated so that the air-fuel ratio becomes close to the stoichiometric air-fuel ratio based on the air-fuel ratio signal from the oxygen sensor. Feedback control is being executed.

In an electronically controlled fuel injection system that performs such air-fuel ratio feedback control, the air-fuel ratio is learned under predetermined conditions during the feedback control in order to compensate for changes in the air-fuel ratio due to variations in parts over time. Then, the learning correction coefficient FG is calculated.

When learning the air-fuel ratio, the fuel that has evaporated in the fuel tank and is stored in the canister (hereinafter referred to as evaporated fuel)
However, it must be taken into consideration that the air-fuel ratio is supplied to the combustion chamber under certain conditions, including at least that the throttle valve is not fully closed, and that this causes a temporary change in the air-fuel ratio.

That is, when learning temporary fluctuations in the air-fuel ratio due to evaporated fuel, the following problems occur.

(1) For example, in fuel injection control that performs so-called partial lean control, in which the air-fuel ratio is controlled to be leaner than the stoichiometric air-fuel ratio under predetermined conditions, in addition to the feedback control described above, the various coefficients described above are used. In addition, calculate the lean correction coefficient FLEAN, where X is a correction coefficient based on water temperature, intake air temperature, etc.

Then, during lean control, the feedback correction coefficient F
AF is set to rlJ, lean correction coefficient FLInAN
is set to a value of "1" or less, whereby the air-fuel ratio is controlled to be leaner than the stoichiometric air-fuel ratio within a range that does not cause problems in a certain operating state.

However, temporary fluctuations in the air-fuel ratio due to evaporated fuel depend on the amount of fuel introduced from the canister into the intake passage and the operating conditions at that time, and the influence of evaporated fuel on the learning correction coefficient FG is not uniform. Therefore, the range of variation in the learning correction coefficient FG due to the influence of evaporated fuel becomes large, and even if you plan to operate under a predetermined lean air-fuel ratio using lean control, the air-fuel ratio will deviate from the desired value, resulting in a lean There is a tendency to adversely affect drivability, fuel efficiency, and exhaust emissions during control.

(2) On the other hand, the air-fuel ratio may temporarily become quite rich due to evaporated fuel, and in that case, the learning correction coefficient FG
becomes quite small.

Therefore, if the vehicle is stopped immediately after learning such changes in the air-fuel ratio due to evaporated fuel, the next time the vehicle is started, the air-fuel ratio becomes too lean, resulting in problems such as poor startability.

[Purpose of the invention]

An object of the present invention, in order to solve such conventional problems, is to provide an internal combustion engine that prohibits the introduction of evaporated fuel into the intake passage when the above-mentioned conditions for calculating the learning control correction coefficient FG are satisfied. An object of the present invention is to provide an air-fuel ratio control device.

[Structure and effect of the invention]

In the present invention, an on-off valve is interposed between the canister and the intake passage, and under a predetermined learning condition V, the on-off valve is closed to prevent evaporated fuel from being introduced into the intake passage. This feature makes it possible to prevent the influence of evaporated fuel on the learning control correction coefficient FG.

〔Example〕

The present invention will be explained below based on the drawings.

FIG. 1 shows an example of the configuration of an internal combustion engine for an automobile having an air-fuel ratio control device according to the present invention. Air filter 1 is throttled through inlet Paizo 3? It is connected to D5. Slot Sin 3? On Day 5, a fuel injection valve 7 is provided upstream of the fuel injection valve 7, and an intake throttle valve 9 is provided downstream of the fuel injection valve 7 to adjust the amount of intake air in conjunction with an accelerator pedal (not shown). An intake pipe absolute pressure sensor 11 is provided downstream of the throttle valve 9 to measure the absolute pressure at that location. Furthermore, there is a valve opening position sensor 2 that measures the opening position of the intake throttle valve 9, an idle switch 4 that is turned on only when the intake throttle valve 9 is fully closed, and a valve opening position sensor 2 that measures the opening position of the intake throttle valve 9. Turns on only when the temperature is 40 degrees or higher・9
A power switch 6 is installed in conjunction with the intake throttle valve 9.

The &-) 8 provided on the upstream side of the intake throttle valve 9 is connected to the canister 12 via a solenoid valve 10, and the solenoid valve 10 is normally open and the canister 12 and port 8 are connected. are communicated.

throttle? The intake manifold 13 is connected to an intake manifold 13 having a branch pipe connected to each cylinder of the engine.
The intake manifold 13 is provided with an intake temperature sensor 15 that measures the temperature of intake air therein. The bottom wall 13a of the intake manifold 13 before branching has a live part 17 through which engine cooling water is circulated to heat the air-fuel mixture.
is provided.

Reference numeral 19 designates a well-known engine body, which includes a piston 21, a cylinder 23, and a cylinder head 25, and a combustion chamber 27.
The air-fuel mixture is drawn into the combustion chamber 27 via the intake valve 29 and then ignited by the ignition glove 31. A water jacket 33 is formed around the cylinder 23, and engine cooling water is circulated through the water jacket 33 to cool parts including the cylinder 23. An engine coolant temperature sensor 37 is provided on the outer wall of the cylinder block 35 to measure the temperature of the engine coolant in the water jacket 33.

An exhaust manifold 39 is connected to an exhaust port (not shown) of the cylinder head 25, and an 02 sensor 41 for measuring the residual oxygen concentration in the exhaust gas is provided downstream of the exhaust manifold 39. The exhaust manifold 39 is connected to an exhaust pipe 45 via a three-way catalyst 43.

Further, 51 is a key switch, 53 is an igniter, and 55 is a distributor. The distributor 55 is provided with an Nθ sensor 57 that outputs an on/off signal at every predetermined crank angle θ1, and the output signal determines the engine rotational speed. It is possible to know the predetermined crank angle position, and also to turn on/off at every angle θ2 larger than the above angle θ1.
A G sensor 59 that outputs an off signal is provided, and cylinder discrimination and top dead center position detection are performed based on the output signal.

Further, 60 indicates a battery.

The control circuit 61 includes a valve opening position sensor 2, an idle switch 4, an armpit switch 6, an intake pressure sensor 11, an intake temperature sensor 15, an engine cooling water temperature sensor 37, a sensor 41. Solenoid valve 10. Key switch 51, N8 sensor 57
, G sensor 59, and battery 60, and are connected to a valve opening signal s1, an idle signal S2, a power signal S3, an intake pressure signal S4, an intake temperature signal S5, a water temperature signal S6, an air-fuel ratio signal S7, and a start signal. S9, an engine rotational speed signal 810, a cylinder discrimination signal 811, and a battery voltage signal 814 are input from each sensor.

Also, Mal m times 1m 61 H-'tWat bar Fi
M4th I n 1m sharp m injection valve and igniter 53
It is also connected to the fuel introduction prohibition signal s8, the fuel injection signal 812 and the ignition signal 81 based on predetermined calculations.
Outputs 3.

As shown in FIG. 2, the control circuit 61 is a central processing unit (CPU) 61a that controls various devices.

A read-only memory (ROM) 61b in which various numerical values and programs are written in advance, and a random access memory (R
AM) 61c, analog input (i No. e? A/D converter (ADC) for converting into isotal signal) 61d, input/output interface (Ilo') 6113 where various digital signals are input and various digital signals are output.
．． Buffer lag memory (BU-RAM) (51f
, and a path line 6 to which each of these devices is connected.
It is made up of 1g.

ROM6 Ib contains the main processing routine Grodaram, fuel r@injection Ff! 8f, mon/zf russ d 100) Sodeshida Ha-11 Durham, programs for calculating the air-fuel ratio feedback correction coefficient' and the learning correction coefficient described later, and various other programs, as well as various data necessary for these calculation processes. is stored in advance.

Then, the opening sensor 2, the intake pipe pressure sensor 11, the intake temperature sensor 15, the water temperature sensor 37, 0 . The controller 41 and battery 60 are connected to the A/D controller 61d, and the voltage signals S1, S4, S5, S6,
S7.51475f, the signals are sequentially converted into binary signals in accordance with instructions from the CPU 61a.

・9 every 30 degrees of crank angle from the crank angle sensor 57
The pulse signal S10, the t4 pulse signal 811 for every 360 degrees of crank angle from the crank angle sensor 59, the idle signal s2 from the idle switch 4, the /4 power signal S3, and the start signal S9 are transmitted through the machine/061e, respectively. The signal is taken into the control circuit 61.

A binary signal representing the engine rotational speed is formed based on the Norse signal 810;
cooperate to generate a request signal for fuel injection/main pulse width calculation,
An interrupt signal for starting fuel injection, a cylinder discrimination signal, and the like are generated. Also, the throttle valve 9 is activated by the idle signal S2.
It is determined whether or not it is substantially fully closed.

From engineering/06 '1 e, fuel introduction prohibition signal S8,
A fuel injection signal 812 and an ignition signal 813 formed by various calculations are sent to the electromagnetic valve 10. fuel injection valve 7,
and is output to the igniter 53.

The fuel injection time (
The injection amount) can be determined, for example, as follows.

τ: (TP+TAG)X(1+FG)XFAFXFLE
iAN'XK・・・・・・・・・・・・・・・ (1)
Here, τ=final fuel injection time TP=basic fuel injection time FAF=feedback correction coefficient TAG=learning correction amount 1? 'G = Learning correction coefficient' FLΣM N = Lean correction coefficient = Correction coefficient due to water temperature, intake temperature, etc. The basic fuel injection time TP is predetermined based on the intake pipe negative pressure PM and the engine speed NlIC. Read from a table or calculated.

The feedback correction coefficient FAF is 0.0 under feedback control conditions. Air-fuel ratio signal S7 from sensor 41
If it is determined that the air-fuel ratio is lean, the injection amount is increased, for example, 1.05, and if the air-fuel ratio is determined to be rich from the air-fuel ratio signal BYK, the injection amount is decreased. If the value is 0.95, for example, and the correction coefficient FAIF is not under the foot-no-guk-side split condition, the correction coefficient FAIF will be 1.0.
As shown in the figure.

At step ++1iif S1, it is determined whether the feedback condition is satisfied. For example, the engine coolant temperature THW is 50°C when the engine is not in the starting state or in the bed after starting.
As described above, if the conditions for hook control are not satisfied when the arm arm is not being increased, the feedback correction coefficient FAF is set to 1.0 in step S2 so that feed page control is not executed, and this procedure is ended. If the conditions are met, the process advances to step S3. In step S3, the air-fuel ratio signal 87 is read.

In step S4, the voltage value represented by the air-fuel ratio signal S7 is filtered, and #1# is applied when the air-fuel ratio signal is rich, and 1O when the air-fuel ratio signal is lean.
If the flag is 111 in step S4, it is determined that the air-fuel ratio is too rich, and the procedure is executed to make the air-fuel ratio lean.

That is, in step S5, flub CAFL is set to zero, and step S
Proceeding to step 6, it is determined whether the flag CAFR is zero. Since the flag CAFR is zero when shifting to the over-concentration side for the first time, the process proceeds to step S8, where a predetermined value α1 is subtracted from the correction coefficient FAF stored in the RAM 610, and the result is set as a new correction coefficient FAF. In step S9, flag C
Let AFR be 1. Therefore, if excessive concentration is determined twice or more in succession in step 84, a negative determination will always be made in step S6 passed from the second time onwards, and in step 87, a predetermined value β1 is subtracted from the correction coefficient FAF'. The FAXI' calculation is completed using the result as a new correction coefficient FAI'.

On the other hand, if the lean flag based on the voltage value represented by the signal S7 is "0" in step S4, it is determined that the air-fuel ratio is lean, and the procedure is executed to make the air-fuel ratio rich.

That is, in step BIO, the flag CA/PR is set to zero and the process proceeds to step Stt, where it is determined whether or not the flag CAFL is zero. Flag CAF when moving to the dilute side for the first time
Since L is zero, the process proceeds to step 812, where a predetermined value α2 is added to the correction coefficient FAV, and the result is set as a new correction coefficient FA.
Let it be F. Move 11 [In s13, set hula QAFL to 1
shall be. Therefore, if it is determined that the move is thin twice or more consecutively in step 84, move 1 [E+11
Then, the determination is always negative, and in step 814, a predetermined value β2 is added to the correction coefficient IPAIF, and the result is set as a new correction coefficient IP'A'IP? AIF calculation ends.

In addition, α1 in steps S7, S8, s12.814,
α2, β1 and β2 are predetermined values.

Feedback correction coefficient F determined by this calculation means
AII' is shown in FIG. 4 together with the air-fuel ratio A/F lean rich flag, which is expressed by filtering the voltage value represented by the air-fuel ratio signal s7. Referring to this figure, when the air-fuel ratio switches from lean to rich or rich to lean, the correction coefficient FAF is skipped by α1 or α2, and if it remains lean, a predetermined number β1 is subtracted sequentially, and it remains rich. Then, a predetermined number β2 is added one after another.

Next, an example of the calculation procedure for the learning control amount TAG and the learning control correction coefficient FG is shown in FIG.

First, in step P21, it is determined whether the intake throttle valve 9 is fully closed or not using the idle signal S output from the idle switch 4.
The determination is made based on whether or not 2 is on. Intake throttle valve 9
If the is fully closed and an affirmative determination is made, in step P22, for example, the engine speed No. is 1000 rpm or less and the intake pipe pressure PM is 200tlIHI!
Determine whether or not the above is true. If the determination is affirmative, the process advances to step P24 to perform learning control.

On the other hand, if the intake throttle valve 9 is not in a fully closed state and a negative determination is made in step P21, then in step P23, for example, the intake pipe pressure
Determine whether the following is true or not. If a positive determination is made, the process proceeds to step P24 to perform learning control.0 If a negative determination is made in step P22 or P23, learning control is not performed.

Next, in step P24, it is determined whether the learning condition is satisfied or not. For example, if the air-fuel ratio feedback control is being executed, the engine coolant temperature THW is 80°C or higher, and the intake air temperature THA is 40°C or higher and 90°C or lower. to learn. If it is determined that the learning condition is satisfied, it is determined in step P25 whether the feedback correction coefficient FAF has been skipped, and if it is skipped and an affirmative determination is made, the process proceeds to step P26.

In step P25, the flags CAFL and CAFR described above are y.
This is determined based on the change in lt-+l0IVC. In step P26, the value of the correction coefficient 11'AIF immediately before skipping is read, and in step P27, the currently read correction coefficient II'AIT'n and the previously read correction coefficient FAF are read.
The arithmetic average value E'AIAV with n1 is stored in a predetermined area.Next, in step P28, the arithmetic average value FA
It is determined whether FAV is 1 or more.

If the arithmetic average value FATAV is 1.0 or more, step P28
-1, it is determined whether the intake throttle valve 9 is fully closed, and if it is fully closed, the process proceeds to step P29 and the learning control amount TA is determined.
Add "10" to G and use the result as the new learning control amount T
AG. If it is not fully closed, the process proceeds to step P30, where [o, oOsJ is added to the learning control correction coefficient FG, and the result is set as a new learning control correction coefficient IFG.

If the arithmetic average value FAX1'AV is less than 1.0, it is determined in step P28-2 whether the intake throttle valve 9 is fully closed, and if it is fully closed, the process proceeds to step p3i and the learning control amount is Subtract "10" from TAG and use the result as a new learning control 1TAG. If it is not fully closed, proceed to step P31 and subtract [o, oosJ from the learning control correction coefficient FG, and use the result as the new learning control correction coefficient pa. In this way, the learning control tTA() adjusts the intake throttle. The air-fuel ratio when the throttle valve 9 is fully closed is learned, and the air-fuel ratio when the intake throttle valve 9 is open is learned using the learning control correction coefficient FG. Therefore, when the intake throttle valve is fully closed, the evaporated fuel in the canister is not introduced into the intake passage, so the learning control fitTA
G is not affected by this. On the other hand, the learning control correction coefficient FG may be affected by the evaporated fuel.

Therefore, when the learning condition is satisfied, the solenoid valve 10
is closed to block the canister 12 and the port 8 of the intake passage.

FIG. 6 shows an example of the procedure.

FIG. 6 shows an example of the opening/closing control routine of the solenoid valve 10,
First, in step P41, it is determined whether learning conditions are satisfied. For example, the determination can be made using a flag that is set to "1" when the learning condition is satisfied and rOJ is set when the learning condition is not satisfied. If an affirmative determination is made, in step P42, the signal S8 from the control circuit 61 is set to a high level to energize the solenoid valve 10, thereby cutting off the canister 12 and the port 8 of the intake passage, so that the evaporated fuel is discharged. Prevent it from being introduced into the intake passage. If the learning conditions are satisfied, in step P43, the signal S8 to the solenoid valve 10 is set to low level, thereby deenergizing the solenoid valve 10 and communicating the canister 12 and the port 8.

In this embodiment, during learning control, the solenoid valve 10 interposed between the canister 12 and the port 8 of the intake passage
This prevents fluctuations in the air-fuel ratio due to evaporated fuel during learning control.

Next, lean correction coefficient FLI! The iAN is calculated as follows, for example.

The engine is not starting, the engine coolant temperature is not lower than 75℃, the intake pipe pressure PM is 450mwH
9 or below, when the rate of change of the vehicle speed is below a predetermined value, and when the opening degree of the intake throttle valve 9 is below a predetermined value, the lean correction coefficient FLKAM is determined according to the intake pipe pressure PM from the graph shown in FIG.

In the above embodiment, the basic fuel injection time TP is determined by the engine speed and intake pipe pressure, but the basic fuel injection time TP is determined by the engine speed, intake air amount, and K.
You may also add P.

Further, in the above embodiment, one injection valve is provided upstream of the intake throttle valve, but the present invention can also be applied to a type in which an injection valve is provided for each cylinder. The present invention can be applied to any vehicle internal combustion engine that introduces air into the intake passage and performs learning control of the air-fuel ratio. Furthermore, it can also be applied to systems that do not perform lean control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an automotive internal combustion engine to which the present invention is applied, FIG. 2 is a detailed block diagram showing an example of its control circuit, FIG. 3 is a flowchart showing an example of an FAF calculation routine, Figure 4 is a time chart showing the relationship between the lean rich flag and correction coefficient PAF, and Figure 5 is TAG.
, a flowchart showing an example of an IFG calculation routine, FIG. 6 a flowchart showing an example of a solenoid valve opening/closing control routine, and FIG. 7 a flowchart showing an example of an IFG calculation routine.
It is a graph showing the relationship with LEAN. 7... Injection valve, 8... Port, 9... Intake throttle valve, 10... Solenoid valve, 11...
Intake pipe pressure sensor, 12... Canister, 13... Intake manifold, 15... Intake temperature sensor, 17... Ripe part, 19...
... Engine body, 27 ... Combustion chamber, 33 ... Water jacket, 37 ... Engine cooling water temperature sensor, 41 ... 02 sensor, 51 ... Key switch, 53
...Igniter, 55...Distributor, 57...Nθ sensor, 59...G sensor, 61...
・Control circuit. Agent Tatsu Unuma Figure 3 Figure 4

Claims (1)

[Claims] The basic fuel injection time TP is set according to the operating state of the internal combustion engine, the feedback correction coefficient FAP is calculated so that the air-fuel ratio is equal to the stoichiometric air-fuel ratio under predetermined feedback conditions, and the feedback correction coefficient FAP is calculated under predetermined learning conditions. When the average value FAFAV of FAF is greater than a predetermined value, the learning correction coefficient F
Increase G to learn and control the air-fuel ratio to the rich side, and then set the average value? When APAV is below the predetermined value, the learning correction coefficient PG' is decreased to perform learning control on the air-fuel ratio to the lean side, and the learning correction coefficient PG' is calculated based on at least the basic fuel injection time TP, the feedback correction coefficient Fhy, and the learning correction coefficient FG. In an air-fuel ratio control device for an internal combustion engine, the fuel injection valve is driven according to the final fuel injection time τ, and evaporated fuel in the fuel system is collected in a canister and introduced into the intake passage. An air-fuel ratio control device for an internal combustion engine, characterized in that the air-fuel ratio control device for an internal combustion engine is equipped with an on-off valve provided in the on-off valve, and a drive means for closing the on-off valve when the learning condition is satisfied by the determining means for determining the learning condition.