JP2001336438A - Device of controlling air-to-fuel ratio for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To steadily control the air-fuel ratio at a time when an engine provided with a port-purge type fuel-vapor treating device, is started in a cold state even after the learning value of air-to-fuel control is changed influenced by the purged fuel flow rate immediately before the engine stop. SOLUTION: Fuel vapor occurring in a fuel take 1 is collected by a canister 12 and is purged into air-intake path 8 through purge passage 13. An electronic control unit(ECU) 30 adjusts the amount of fuel injected from an injector 4 so that the air-fuel ratio detected by an oxygen sensor 24 becomes the target air-fuel ratio, thus controlling the air-fuel ratio. ECU 30 learning-corrects the air-fuel ratio control based on the learning value obtained by learning the air-to- fuel ratio control results for the running conditions. ECU 30 corrects the control of the air-to-fuel ratio based on a standard value in place of the learned value, when the learning value learned immediately before the last stop becomes smaller than the specific threshold value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an engine which controls the air-fuel ratio of the engine and learns and corrects the amount of fuel supplied to the engine based on the results of the air-fuel ratio control.

[0002]

2. Description of the Related Art Conventionally, for example, in order to control an air-fuel ratio of a combustible mixture of air and fuel supplied to an automobile engine, a fuel amount supplied from an injector to an intake passage is provided in an exhaust passage. There is an air-fuel ratio control device that performs control based on a detected value of an oxygen sensor. In this type of air-fuel ratio control device, the supplied fuel amount is controlled based on the deviation between the detected air-fuel ratio and the target air-fuel ratio so that the detected air-fuel ratio becomes a predetermined target air-fuel ratio. In addition, learning correction of the amount of fuel supplied to form a combustible air-fuel mixture is generally performed based on the results of air-fuel ratio control.
In this learning correction, for example, a plurality of learning regions are partitioned in accordance with the throttle opening and the engine rotation speed, which are operating parameters of the engine, and the results of air-fuel ratio control are calculated as learning values in accordance with the learning regions. Then, each learning value is stored in the nonvolatile memory. Then, by appropriately reflecting these learning values on the amount of fuel supplied to the engine, optimal air-fuel ratio control is started immediately. The air-fuel ratio control including such learning correction functions particularly effectively for adapting the air-fuel ratio control in accordance with individual differences of the engine, aging, use environment conditions, and the like.

[0003] On the other hand, as a device provided with the engine, there is known a fuel vapor processing device for processing fuel vapor generated in a fuel tank without releasing it to the atmosphere. As shown in FIG. 7, in this type of processing apparatus, fuel vapor generated in a fuel tank 71 is collected by a canister 72. The collected fuel is used when the engine 73 operates.
Intake passage 7 from canister 72 through purge passage 74
Purged to 5. The purged fuel is supplied to the fuel tank 7
1 through an injector or the like (not shown) to the engine 73.
Together with the fuel supplied to the combustion chamber for combustion. Purge control valve 76 provided in purge passage 74
In order to control the flow rate (purge flow rate) of the fuel vapor purged to the intake passage 75, the opening / closing or the opening degree is controlled according to the operating state of the engine 73. This type of processing apparatus is disclosed in, for example, JP-A-6-26385, JP-A-6-26386, JP-A-6-74068, JP-A-6-101528 and JP-A-6-22.
No. 9333.

When the air-fuel ratio control including the learning correction is applied to an engine equipped with this type of processing device, the amount of fuel purged from the purge passage 74 is added to the original amount of fuel supplied through the injector. Will be.
For this reason, in the air-fuel ratio control, it is necessary to control the total fuel amount supplied to the engine 73 in consideration of the purge flow rate in order to prevent the air-fuel ratio from becoming unnecessarily rich. That is, the amount of fuel supplied through the injector is reduced in anticipation of the purge flow rate, or the amount of fuel supplied through the purge control valve 76 is reduced.
It is necessary to adjust the purge flow rate as needed.

By the way, in the processing apparatus provided with the purge control valve 76, the purge flow rate can be adjusted and the fuel purge can be cut off as necessary by controlling the control valve 76 with a computer. Thus, the suitability of the fuel purge for the air-fuel ratio control can be improved. On the other hand, there are problems that the entire processing apparatus becomes complicated by the amount of the purge control valve 76, the production cost increases, and the program of the air-fuel ratio control becomes complicated.

Therefore, it is conceivable to reduce the above-mentioned problems by adopting a port purge type fuel vapor processing apparatus having no purge control valve and reexamining the contents of the air-fuel ratio control on the premise of its existence. Port purge type processing equipment
The purge flow rate flowing from the port of the purge passage to the intake passage is determined according to the throttle opening of the intake passage and the magnitude of the negative intake pressure generated in the passage. I don't have anything.

[0007]

However, in an air-fuel ratio control device for an engine equipped with the port purge type processing device, the purge flow rate changes irregularly depending on the temperature condition of the processing device, and the purge flow rate in the combustible air-fuel mixture varies. The fuel concentration may fluctuate. For example, when the temperature of the fuel tank or the canister is high, the amount of generated fuel vapor increases, and the concentration of the purge fuel in the combustible mixture increases. Further, if the temperature of the fuel tank or the canister is low, the purge flow rate decreases, and the purge fuel concentration in the combustible mixture decreases. Therefore, from the fluctuation of the purge fuel concentration, the air-fuel ratio control device may cause the following problems.

That is, in the above-mentioned air-fuel ratio control device, since the individual correction is not performed for the fluctuation of the purge fuel concentration, the deviation of the air-fuel ratio due to the purge fuel is corrected by the learning value. However, since the learned value can change reflecting the change in the purge fuel concentration, the learned value greatly deviates from the learned value required by the engine, and the actual air-fuel ratio largely deviates from the target air-fuel ratio.

The effect of such fluctuations in the purge fuel concentration is particularly noticeable when the engine is operated at a high temperature, stopped, left standing for a predetermined time, and then started in a cold state. That is, during the high-temperature operation, the learned value is updated to the lean value by the purge fuel, but the influence of the purge fuel on the learned value is reduced at the subsequent cold start. Here, at the time of cold start, since the learned value at the time of high temperature operation learned immediately before the engine is stopped is reflected in the air-fuel ratio control, the amount of fuel supplied from the injector is reduced by reflecting the lean side learned value. Will be. As a result, the actual air-fuel ratio becomes significantly lean, and the operation of the engine becomes unstable, which may cause vibration or engine stall.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine equipped with a port purge type fuel vapor processing apparatus, wherein a learning value learned by air-fuel ratio control during high-temperature operation is purged. An object of the present invention is to provide an air-fuel ratio control device for an engine that can stably control the air-fuel ratio regardless of a learning value immediately before stop even when a cold start is performed, even if the air-fuel ratio changes under the influence of a flow rate change.

[0011]

According to one aspect of the present invention, a fuel supply means for supplying fuel stored in a fuel tank to an engine, and a fuel supply means for generating fuel in the fuel tank. A port purge type fuel vapor processing device that collects fuel vapor and purges the fuel vapor into an intake passage through a purge passage to burn and process the fuel vapor together with the supplied fuel in an engine; Air-fuel ratio detecting means for detecting the air-fuel ratio of the air-fuel ratio, and controlling the supplied fuel amount based on a deviation between the detected air-fuel ratio and the target air-fuel ratio so that the detected air-fuel ratio becomes a predetermined target air-fuel ratio. -Fuel ratio control means and the result of air-fuel ratio control are learned as learning values for each of a plurality of learning regions set for the operating state of the engine, and the supplied fuel amount is corrected based on the learning values. An engine air-fuel ratio control device provided with a learning correction means for learning when the learned value learned immediately before the previous stop is smaller than a predetermined threshold value when the engine is started, a predetermined standard value instead of the learned value. And a start-time correction means for correcting the supplied fuel amount based on the above.

[0012] In the configuration of the present invention, when the temperature of the fuel tank or the fuel vapor processing device increases during the operation of the engine,
A large amount of fuel vapor is generated in the fuel tank, and the flow rate of the fuel vapor purged from the purge passage to the intake passage (purge flow rate)
And the concentration of purge fuel in the combustible mixture supplied to the engine increases. At this time, the deviation between the air-fuel ratio detected by the air-fuel ratio detection unit and the predetermined target air-fuel ratio increases, and the amount of fuel supplied by the fuel supply unit is controlled by the air-fuel ratio control unit based on the deviation. Is controlled so that the detected air-fuel ratio becomes the target air-fuel ratio. The results of the air-fuel ratio control are learned by the learning correction means as learning values for each of a plurality of learning areas. When the operating state of the engine becomes an operating state corresponding to each learning area, the learned values are supplied to the supplied fuel. It will be reflected in the amount correction. The learning value at this time is learned as a value on the lean side for reducing the supplied fuel amount, that is, a small value. Here, if the operation of the engine is stopped from the high temperature state and the engine is started in a cold state after being left for a predetermined time, in the conventional air-fuel ratio control, a small learning value learned immediately before the stop is a small learning value in the air-fuel ratio control. Was to be reflected in. For this reason, the amount of fuel supplied to the engine at the time of starting is significantly reduced from the normal amount, and the actual air-fuel ratio is significantly leaned. On the other hand, according to the configuration of the present invention, at the time of starting the engine, the starting correction means operates, and when the learning value learned immediately before the previous stop is smaller than the predetermined threshold value, the predetermined correction value is substituted for the learning value. The supplied fuel amount is corrected based on the standard value of. Therefore, at the time of cold start, the supplied fuel amount is not greatly reduced with respect to the normal amount, and the actual air-fuel ratio is not significantly leaned.

According to a second aspect of the present invention, in the first aspect of the present invention, the starting correction means corrects the supplied fuel amount initially based on the standard value itself. Thereafter, the fuel supply amount is corrected based on the standard value that is gradually changed until the learning value is simultaneously learned.

According to the configuration of the present invention, in the initial stage of the correction by the start-time correction means, the supplied fuel amount is corrected based on the standard value itself as in the first aspect of the invention, and thereafter, simultaneously. The supplied fuel amount is corrected based on a standard value gradually changed until the learned value to be learned is matched. Therefore, after the start of the engine is completed, the standard value is gradually changed toward the learning value and is not changed abruptly, so that the supplied fuel amount does not change abruptly.

According to a third aspect of the present invention, in order to achieve the above object, a standard value is calculated based on a learning value learned immediately before a previous stop in the first or second aspect of the invention. It is intended that a standard value calculating means for performing the calculation is provided.

According to the configuration of the present invention, in addition to the operation of the invention described in claim 1 or 2, the standard value used in place of the learned value at the time of starting the engine is learned immediately before the previous stop. Since it is calculated based on the learning value, the correction by the starting correction means is performed in accordance with the magnitude of the learning value at that time.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying an air-fuel ratio control apparatus for an engine according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a gasoline engine system including a fuel vapor processing apparatus according to the present embodiment. The engine system mounted on the vehicle includes a fuel tank 1 for storing fuel. A fuel pump 1 is built in the fuel tank 1. The fuel discharged by the fuel pump 2 is supplied to a plurality of injectors 4 provided in the engine 3, a fuel passage 5, a pressure regulator 6, and a delivery pipe 7.
Is distributed and supplied. When each injector 4 operates, fuel is injected into the intake passage 8. Each injector 4 corresponds to a fuel supply unit of the present invention for supplying the fuel stored in the fuel tank 1 to the engine 3 through a formal route. Air introduced from the outside into the intake passage 8,
The fuel injected from the injector 4 forms a combustible air-fuel mixture and is supplied to each combustion chamber of the engine 3. The surplus fuel without being distributed to each injector 4 is returned to the fuel tank 1 through the pressure regulator 6 and the return passage 9. The exhaust gas after combustion in the engine 3 is discharged to the outside through the exhaust passage 10. When the crankshaft 3a rotates with the combustion of the fuel in each combustion chamber, the driving force for running the automobile is increased by the engine 3
Is obtained.

The fuel vapor processing apparatus according to this embodiment is of a port purge type, which collects and processes the fuel vapor generated in the fuel tank 1 without releasing it to the atmosphere. This processing device includes a canister 12 that collects fuel vapor generated in the fuel tank 1 through a vapor passage 11. The canister 12 contains an adsorbent made of activated carbon or the like.

A purge passage 13 extending from the canister 12
Communicates with the intake passage 8. A purge port 13 a of the purge passage 13 is opened near a throttle valve 14 provided in the intake passage 8. The canister 12 collects only the fuel component in the fuel vapor introduced through the vapor passage 11, and discharges only the gas containing no fuel component to the outside through the outlet passage 15. During operation of the engine 3, the intake negative pressure generated in the intake passage 8 acts on the canister 12 from the purge port 13 a through the purge passage 13. Due to the negative pressure of the intake air, the fuel collected in the canister 12 is drawn into the purge passage 13, and is purged from the purge port 13 a to the intake passage 8. Thus, the vapor passage 11, the canister 12, and the purge passage 1
3 constitutes the port purge type fuel vapor processing apparatus of the present invention.

Each ignition plug 16 provided corresponding to each combustion chamber of the engine 3 operates upon receiving an ignition signal output from an ignition coil 17.

Various sensors 20, 21, 22, 23, 24
Is for detecting various operation parameters related to the operation state of the engine 3. That is, the throttle valve 14
The throttle sensor 20 provided in correspondence with the above detects the opening degree TA of the throttle valve 12 operated by the driver, and outputs an electric signal corresponding to the detected value. An intake pressure sensor 21 provided for the intake passage 8 detects a pressure (intake pressure) PM of the air taken into the intake passage 8 and outputs an electric signal corresponding to the detected value. A water temperature sensor 22 provided in the engine 3 detects the temperature (cooling water temperature) THW of the cooling water flowing inside the engine 3 and outputs an electric signal corresponding to the detected value. A rotation speed sensor 23 provided in the engine 3 detects a rotation speed (engine rotation speed) NE of the crankshaft 3a, and outputs an electric signal corresponding to the detected value. In this embodiment, the rotation speed sensor 23 detects a change in the rotation angle (crank angle) of the crankshaft 3a every 30 ° and outputs it as a rotation pulse signal every 30 °. The oxygen sensor 24 provided in the exhaust passage 10 detects the oxygen concentration (output voltage) Ox in the exhaust gas discharged from each combustion chamber to the exhaust passage 10 and outputs an electric signal corresponding to the detected value. The oxygen sensor 24 corresponds to an air-fuel ratio detection unit of the present invention used to detect an air-fuel ratio A / F between air and fuel supplied to the engine 3.

In addition, the vehicle is provided with a well-known ignition switch IG operated to start the engine 3 and an engine starter (both not shown) activated by operation of the switch IG.

In this embodiment, an electronic control unit (EC
U) 30 inputs various signals output from the various sensors 20 to 24 described above. The ECU 30 controls each of the injectors 4 and the ignition coil 17 and the like to execute fuel injection control including air-fuel ratio control and ignition timing control based on these input signals. In this embodiment, the ECU 30 constitutes the air-fuel ratio control means, the learning correction means, the start-time correction means, and the standard value calculation means of the present invention.

As is well known, the ECU 30 includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), a backup RAM, an external input circuit, an external output circuit, and the like. The ECU 30
A logical operation circuit is configured by connecting a CPU, a ROM, a RAM, a backup RAM, an external input circuit, an external output circuit, and the like by a bus. The ROM stores in advance a predetermined control program related to the air-fuel ratio control of the engine and the like. The RAM temporarily stores the calculation results of the CPU. The backup RAM stores data stored in advance. The CPU executes the above-described various controls and the like according to a predetermined control program based on detection signals of the various sensors 20 to 24 input via the input circuit.

Here, the ignition timing control is to control the ignition timing of each ignition plug 16 by controlling the ignition coil 17 according to the operating state of the engine 3.

The fuel injection control is to control the amount of fuel injected by each injector 4 and its injection timing in accordance with the operating state of the engine 3. In this embodiment, the ECU 30 calculates the basic fuel injection amount TAUBSE based on the throttle opening TA and the engine rotational speed NE, and corrects the basic fuel injection amount TAUBSE according to various conditions to obtain the final fuel injection amount TAUBSE. The injection amount TAU is determined.

The air-fuel ratio control means that at least the oxygen sensor 2
That is, the air-fuel ratio of the combustible air-fuel mixture supplied to the engine 3 is feedback-controlled based on the detection value of the engine 4. That is, the air-fuel ratio control is performed by the injector 4 based on the deviation between the actual air-fuel ratio and the target air-fuel ratio so that the actual air-fuel ratio obtained from the value detected by the oxygen sensor 24 becomes the predetermined target air-fuel ratio. This controls the fuel injection amount.

Hereinafter, the air-fuel ratio control will be briefly described. FIG. 2 shows the behavior of the oxygen concentration Ox detected by the oxygen sensor 24 in the air-fuel ratio control, the determination of the air-fuel ratio by the ECU 30, and the air-fuel ratio correction coefficient FAF.

The ECU 30 corrects the air-fuel ratio based on the value of the oxygen concentration (output voltage) Ox detected by the oxygen sensor 24 so that the air-fuel ratio of the combustible mixture supplied to the engine 3 becomes a predetermined target air-fuel ratio. Calculate the coefficient FAF. Further, E
The CU 30 controls the amount of fuel injection from each injector 4 based on the calculated value of the air-fuel ratio correction coefficient FAF.
Here, when the air-fuel ratio is rich, the ECU 30 calculates the air-fuel ratio correction coefficient FAF as a subtraction value (shown by a downward-sloping straight line in FIG. 2) for decreasing the fuel injection amount from each injector 4. When the air-fuel ratio is lean, the ECU 30 calculates the air-fuel ratio correction coefficient FAF as an added value for increasing the fuel injection amount from each injector 4 (shown by a straight line rising to the right in FIG. 2).

That is, the ECU 30 compares the output voltage of the oxygen concentration Ox corresponding to the air-fuel ratio A / F detected by the oxygen sensor 24 with a predetermined reference voltage.
It is determined whether the air-fuel ratio is rich or lean.
When the ECU 30 determines that the air-fuel ratio is rich, the ECU 30 reduces the air-fuel ratio correction coefficient FAF at a fixed rate,
When it is determined that the air-fuel ratio is lean, the air-fuel ratio correction coefficient FAF is increased at a constant rate. When the determination of the air-fuel ratio changes from lean to rich or from rich to lean, the ECU 30 skips the air-fuel ratio correction coefficient FAF stepwise. This skip is a calculation method for increasing the responsiveness of the air-fuel ratio feedback control and bringing the air-fuel ratio closer to the target air-fuel ratio. That is, the ECU 3
0 is set based on the difference between the detected air-fuel ratio A / F and the target air-fuel ratio so that the detected value corresponding to the air-fuel ratio A / F detected by the oxygen sensor 24 becomes a predetermined target air-fuel ratio. 4 controls the fuel injection amount supplied. In this embodiment, an EC for executing the air-fuel ratio control is described.
U30 corresponds to the air-fuel ratio control means of the present invention.

In this embodiment, the ECU 30 performs learning correction of the air-fuel ratio. The learning correction of the air-fuel ratio is to learn the result of the air-fuel ratio control as a learning value for each of a plurality of learning regions set with respect to the operating state of the engine 3 and to determine the fuel injection amount by the injector 4 based on the learning value. Is to be corrected. That is, the ECU 30 corrects the basic fuel injection amount TAUBSE based on a learning value learned for each of a plurality of divided learning regions set corresponding to the throttle opening TA and the engine rotation speed NE. By
Correct the air-fuel ratio control. In this embodiment, the ECU 30 that executes the learning correction corresponds to learning correction means of the present invention.

Next, among the various controls executed by the ECU 30, the processing for air-fuel ratio control including learning correction will be described. FIG. 3 shows a flowchart relating to the air-fuel ratio control. FIG. 4 is a flowchart showing a routine for calculating the final reflection value KGX and the like.

The ECU 30 periodically executes the routine shown in FIG. 3 every predetermined period. First, in step 100, E
The CU 30 reads the values of the throttle opening TA, the oxygen concentration Ox, the engine speed NE, and the coolant temperature THW based on the detection signals of the various sensors 20, 22, 23, and 24, respectively.

Next, in step 200, the ECU 30
The basic fuel injection amount TAUBSE is calculated and determined based on the read values of the throttle opening TA and the engine speed NE. The ECU 30 calculates the basic fuel injection amount TA
The calculation of UBSE is performed by referring to predetermined function data.

Next, at step 300, the ECU 30
As described above, the value of the air-fuel ratio correction coefficient FAF is calculated based on the read value of the oxygen concentration Ox.

Next, at step 400, the ECU 30
Based on the read values of the throttle opening TA and the engine speed NE, a final reflection value KGX of a learning value KG described later is calculated. Learning value KG and its final reflection value K
GX is a basic fuel injection amount TAUBSE to be supplied to the engine 3 due to individual variations or dimensional variations of various components of the engine 3 and aging of the components.
This is for correcting an error in the air-fuel ratio caused by an error.

Next, at step 500, the ECU 30
Based on the value of the read cooling water temperature THW, the engine 3
The warm-up correction coefficient KTHW for correcting the basic fuel injection amount TAUBSE is calculated in accordance with the warm-up state.

Next, at step 600, the ECU 30
The basic fuel injection amount TAUBSE calculated as described above,
Based on the air-fuel ratio correction coefficient FAF, the final reflection value KGX, and the warm-up correction coefficient KTHW, the value of the final fuel injection amount TAU is calculated according to the following equation (1). TAU = TAUBSE * FAF * KGX * KTHW (1)

Thereafter, at step 700, the ECU 30
Controls each injector 4 based on the calculated value of the final fuel injection amount TAU, thereby controlling the fuel injection amount supplied to each combustion chamber of the engine 3. That is, the air-fuel ratio of a combustible mixture of fuel and air supplied to each combustion chamber is controlled.

Here, the calculation of the final reflection value KGX of the learning value KG in step 400 will be described with reference to the flowchart of FIG.

First, in step 401, the ECU 30
It is determined whether or not the value of the throttle opening TA is smaller than a predetermined reference value θ1. This determination is for determining the effect of the fuel purge by the fuel vapor processing device on the learning value KG of the air-fuel ratio control and its final reflection value KGX. Here, for example, an angle of “8 to 10 °” can be applied as the reference value θ1. If this determination is negative,
The ECU 30 jumps the processing to step 413, assuming that the fuel purge has little effect on the final reflection value KGX. If this determination is affirmative, the ECU 30 proceeds to step 402.

In step 402, the ECU 30 determines whether or not the guard processing execution flag XKGPRG for the final reflection value KGX after the engine is started is "0". Here, the guard process means a process of setting the final reflection value KGX to a certain upper limit when the final reflection value KGX becomes larger than necessary. If this determination is negative, the guard process is not executed, and the ECU 30 jumps the process to step 407. If this determination is affirmative, the guard process has been executed, and the ECU 30
Shifts the processing to step 403.

In step 403, the ECU 30 determines that the previously reflected final reflection value KGX is equal to the predetermined threshold value KG.
It is determined whether it is smaller than PRG. This threshold value KGP
RG is a reference value for determining whether or not the final reflection value KGX has changed under the influence of the fuel purge. This threshold value KGPRG is a value that is not stable on the rich side or lean side and is a certain level, and corresponds to the threshold value of the present invention. If this determination is negative, the final determination value K
Assuming that GX is not affected by the fuel purge,
The CU 30 jumps the processing to step 413. If this determination is affirmative, the ECU 30 proceeds to step 404 assuming that the final determination value KGX has changed due to the effect of the fuel purge.

At step 404, the ECU 30 determines whether or not the ignition switch IG has been turned from "OFF" to "ON", that is, whether or not starting of the engine 3 by cranking has been started. If this determination is negative, the ECU 30 does not start the engine 3, and the ECU 30 proceeds to step 4
Jump to 13. If this determination is affirmative, the ECU 30 proceeds to step 405 because the engine 3 is being started.

In step 405, the ECU 30 changes the final reflection value KGX to its guard value KGPGRD because the final reflection value KGX has changed due to the influence of the fuel purge.
Set to. The guard value KGPGRD indicates a standard value that is not biased excessively or excessively as the learning value KG to be used for the air-fuel ratio control, and corresponds to the standard value of the present invention.

Next, at step 406, the ECU 30
It is determined whether the post-start increase FSE is “0”. The post-start increase FSE is set after the engine 3 is started. For a while after the start of the engine 3, by increasing the fuel injection amount after the start, it is possible to prevent fluctuations in idle speed due to a lean air-fuel ratio or a large frictional force of the engine 3 after the start. Can be.
If the determination here is negative, the ECU 30 executes the processing in step 41 because the post-start increase FSE has been performed.
Jump to 3. If the determination here is affirmative, the ECU 30 shifts the processing to step 407 since the post-start increase is not performed.

After shifting from steps 402 and 406, in step 407, the ECU 30 determines that the guard value KGPGRD
Is subtracted from the predetermined value β to calculate a new guard value KGPGRD. In the following step 408, the ECU 30 sets the newly calculated guard value KGPGRD as the final reflection value KGX of the learning value KG.

The ECU 30 determines in steps 407 and 408
After the final reflection value KGX is corrected based on the guard value KGPGRD itself, the learning value K that is simultaneously learned is
By gradually changing the guard value KGPGRD until it matches G, and correcting the final reflection value KGX based on the changed guard value KGPRD, the injector 4
The amount of fuel supplied from is corrected.

The series of processes in steps 402 to 408 is performed when the final reflection value KGX of the learning value KG learned immediately before the previous stop at the time of starting the engine 3 becomes smaller than the threshold value KGPRG at that time. Injector 4 based on guard value KGPRD instead of final reflection value KGX
This is a process for correcting the amount of fuel supplied from the controller. In this embodiment, the ECU 30 that executes the processes of steps 402 to 406 corresponds to a start-up correction unit of the present invention.

Then, at step 409, the ECU 30
Determines whether the final reflection value KGX set this time is smaller than the learning value KG learned during this time. Here, the learning value KG is calculated by normal learning control separately performed by the ECU 30. The normal learning control is to calculate a learning value KG for each of a plurality of learning regions set from the slot opening TA and the engine speed NE. In this embodiment, an average value of a plurality of air-fuel ratio correction coefficients FAF previously calculated for each learning region is calculated as a learning value KG for each learning region.

If the determination here is affirmative, the ECU 30 determines that the final reflection value KGX has returned to the learning value KG.
In step 410, the guard processing execution flag XKGPR
Set G to “0”. In the following step 411, the ECU
30 is a learning value K when the ignition switch IG changes from ON to OFF, that is, when the engine is stopped.
The stop learning value KGIGOFF which is G is changed to the guard value KGP.
GRD is set, and the process proceeds to step 413. That is, in step 411, the guard value KGPGRD is calculated based on the learning value KG (final reflection value KGX) learned immediately before the previous stop. In this embodiment, the ECU 3 that executes the process of step 411
0 corresponds to the standard value calculating means of the present invention.

On the other hand, if the determination in step 409 is negative, since the final reflection value KGX has not returned to the learning value KG, the ECU 30 sets the guard processing execution flag XKGPRG to “1” in step 412, and To step 413.

Steps 401-406, 411, 412
In step 413, the ECU 30 determines whether the ignition switch IG has been turned “ON → OFF”, that is, whether the engine 3 has been stopped. If this determination is negative, since the engine 3 is not stopped,
The ECU 30 once ends the subsequent processing. If this determination is affirmative, since the engine 3 has been stopped, E
The CU 30 shifts the processing to step 414.

Then, in step 414, the ECU 30 sets the final reflection value KGX as the stop time learning value KGIGOFF. This stop learning value KGIGOFF is the final reflection value KGX when the engine is stopped, and does not change until the next engine start.

In the following step 415, the ECU 30 calculates a new threshold value KGPRG by subtracting a predetermined value α from the stop learning value KGIGOFF, and terminates the subsequent processing once. In this embodiment, step 41
The ECU 30 executing the processing of No. 5 corresponds to a threshold value updating means for updating the threshold value KGPRG.

In the routine for calculating the final reflection value KGX, at step 401, the throttle opening T
If A is larger than the reference value θ1, the influence of the purge fuel on the final reflection value KGX is small.
GX is not corrected. And steps 413-4
At 15, the final reflection value KGX of the learning value KG learned immediately before the previous engine stop is set to the stop learning correction value KGIGO.
Set as FF, and its stop learning value KGIGOFF
Is reduced by a predetermined value α from a new threshold value KGP.
Set as RG and stored in memory.

On the other hand, in step 401, if the throttle opening TA is smaller than the reference value θ1 at the time of cold start, the influence of the purge fuel on the final reflection value KGX is large. The process proceeds to step 402. If it is determined in step 402 that guard processing has not been performed, steps 403 to 406 are performed.
Therefore, the guard value KG is obtained only when the final reflection value KGX is smaller than the threshold value KGPRG and the engine 3 is started.
If PGRD is set as the final reflection value KGX and the amount is not increased after starting, the process proceeds to step 407. If the guard process is performed in step 402, the process proceeds to step 407 as it is. Then, in steps 407 and 408, the final reflection value KGX is set to the learning value KG.
Guard value KG reduced by a predetermined value β to approach
PGRD is set as a new final reflection value KGX and stored in the memory.

Further, in steps 409 to 412, when the final reflection value KGX has not reached the learning value KG, the guard processing execution flag XKGPRG is set to "1". When the same value KGX reaches the learning value KG, the same flag XKGPR
G is set to “0” and the stop learning value KGIGOFF obtained immediately before the previous engine stop is set to the guard value KGPGR.
D and stored in memory. Thereafter, in steps 413 to 415, the learning value at stop KGIGOFF and the threshold value KGPRG are updated, respectively, after waiting just before the engine stop as described above.

Here, an example of the behavior of various parameters related to the calculation of the final reflection value KGX is shown in FIGS.
(F).

When the temperature of the fuel tank 1 or the canister 12 increases during the operation of the engine 3 and the purge flow rate flowing from the purge passage 13 to the intake passage 8 increases, the purge fuel concentration in the combustible mixture supplied to the engine 3 increases. Get higher.
For this reason, in the air-fuel ratio control executed by the ECU 30, the learning value KG and its final reflection value KGX are set to the lean side in accordance with the change in the air-fuel ratio correction coefficient FAF in order to suppress the air-fuel ratio A / F from becoming rich. Turns into a value. As a result, FIG.
As shown in (b), the final reflection value KGX falls below the threshold value KGPRG at time t1, and gradually decreases the value.

Thereafter, at time t2, when the ignition switch IG is switched from ON to OFF and the engine 3 is stopped, the final reflection value KGX immediately before the stop is significantly smaller than the threshold value KGPRG. The value KGIGOFF and the threshold value KGPRG are not updated.

Thereafter, when the engine 3 is left for a predetermined time and the cold start is performed at time t3, the final reflection value KGX is corrected by the guard value KGPRGD and the threshold value KGPRG is corrected.
And at the same time, the guard processing execution flag XKGPR
G switches from “0” to “1”.

Thereafter, at time t3 to t4, the post-start increase F
While SE is performed, the final reflection value KGX is corrected by the guard value KGPGRD itself. At time t4, when the increase after startup is completed, a guard value KGPG that is gradually reduced until it coincides with an original learning value KG that is separately learned at the same time.
The final reflection value KGX is corrected by RD. During this time, the final reflection value KGX is reduced by gradually reducing the guard value KGPGRD.

Then, at time t5, when the final reflection value KGX to be corrected matches the original learning value KG, the guard processing execution flag XKGPRG is switched from "1" to "0", and at the same time, the guard value KGPGRD is restored. Is returned to the value of Here, the period shown from time t3 to time t5 in FIG.
This is a correction period for correcting the final reflection value KGX when the engine 3 starts cold operation.

Thereafter, at time t6, the final reflection value KGX exceeds the threshold value KGPRG. At time t7, the ignition switch IG is switched from ON to OFF, and when the engine 3 is stopped, learning is performed immediately before the stop. The stop learning value KGIGOFF is set by the learned reflection value KGX. At the same time, the stop learning value KGIGOFF
, The guard value KGPRG is corrected, and the threshold value KGPRG is updated with a value obtained by subtracting a predetermined value α from the stop learning value KGIGOFF.

Thereafter, at times t9 and t11, the engine 3
Is stopped, the final reflection value KGX becomes the threshold value KGP
If it is larger than RG, the final reflection value KG at those times
Learning value at stop KGIGOFF, threshold value KG based on X
The PRG and the guard value KGPGRD are updated and calculated, respectively.

FIG. 6 shows the behavior of the air-fuel ratio A / F reflecting the effect of the correction of the final reflection value KGX, corresponding to times t3 to t5 in FIG.

As described above, in the air-fuel ratio control device of the present embodiment, the fuel tank 1 is operated while the engine 3 is operating.
When the temperature of the canister 12 increases, a large amount of fuel vapor is generated in the fuel tank 1 and the concentration of purge fuel in the combustible mixture supplied to the engine 3 increases. At this time, the deviation between the air-fuel ratio A / F detected by the oxygen sensor 24 and the target air-fuel ratio increases, and the fuel injection amount that is formally supplied from the injector 4 is controlled by the ECU 30 based on the deviation. Control is performed so that the air-fuel ratio A / F becomes the target air-fuel ratio. The result of the air-fuel ratio control is learned by the ECU 30 as a learning value KG for each of a plurality of learning regions, and the operating state of the engine 3, that is, a state in which the throttle opening TA and the engine rotational speed NE correspond to each learning region. Then, those learning values KG are reflected in the correction of the fuel injection amount injected from the injector 4. The learning value KG at this time is learned as a value on the lean side for reducing the fuel injection amount from the injector 4, that is, a small value.

Here, the engine 3
Is stopped and the engine 3 is started in a cold state after being left for a predetermined time, in the conventional air-fuel ratio control, the small learning value KG learned immediately before the stop is only reflected in the air-fuel ratio control. Met. For this reason, the amount of fuel supplied to the engine 3 at the time of cold start is significantly reduced from the normal amount, and the actual air-fuel ratio A / F is largely leaned.

On the other hand, according to the air-fuel control system of the present embodiment, when the engine 4 is started in a cold state, the correction by the ECU 30 is activated, and the learning value K learned immediately before the previous stop is obtained.
When G (final reflection value KGX) is smaller than a predetermined threshold value KGPRG, the fuel injection amount from injector 4 is corrected based on a predetermined guard value KGPRD instead of final reflection value KGX. Therefore, when the engine 3 is started in a cold state, the fuel injection amount from the injector 4 is not greatly reduced with respect to the normal amount, and the actual air-fuel ratio A
/ F is not significantly leaned. Accordingly, in the engine 3 including the port purge type fuel vapor processing device, the learning value KG (final reflection value KGX) learned in the air-fuel ratio control during the high-temperature operation is greatly affected by the change in the purge flow rate. Even if it decreases, the learning value KG immediately before the previous stop (the final reflection value KG) is obtained at the time of the subsequent cold start.
Regardless of the magnitude of X), the air-fuel ratio A / F can be stably controlled. As a result, it is possible to prevent the engine 3 from oscillating unstably or the engine from stalling at the time of cold start.

According to the air-fuel ratio control device of this embodiment, in the initial stage of the correction by the ECU 30, the fuel injection amount by the injector 4 is corrected based on the guard value KGPRD itself, and thereafter, the final reflection value KGX
Is gradually changed until it coincides with the learning value KG learned at the same time, and the fuel injection amount is corrected based on that. Therefore, after the cold start of the engine 3 is completed, the guard value KGPGRD is gradually changed toward the learning value KG, and is not changed abruptly.
The fuel injection amount from the engine does not change rapidly. From this, it is possible to prevent the rotation of the engine 3 from changing suddenly after the start is completed, and it is possible to secure stable drivability.

According to the air-fuel ratio control device of this embodiment, the threshold value KGPRG to be compared with the learning value KG (final reflection value KGX) is updated in accordance with the original change of the learning value KG. Become. That is, like the learning value KG,
The threshold value KGPRG also changes in accordance with the change over time of the engine 3 and the like. Therefore, when the engine 3 needs to correct the final reflection value KGX in accordance with the aging of the engine 3 at the time of cold start of the engine 3, the correction is appropriately performed. In this sense, it is possible to increase the correction accuracy of the final reflection value KGX at the time of cold start, and thus to increase the air-fuel ratio control accuracy.

According to the air-fuel ratio control device of this embodiment, the guard value KGPGRD used in place of the learned value KG (final reflection value KGX) when the engine 3 starts cold operation.
Is the learning value KG learned immediately before the last engine stop.
(Final reflection value KGX). From this, the final reflection value KGX is corrected according to the magnitude of the learning value KG corresponding to the temporal change of the engine 3 at that time. Therefore, the correction of the final reflection value KGX is not biased too much or too little. Also in this sense, the accuracy of correcting the final reflection value KGX at the time of starting the cold can be improved, and the accuracy of air-fuel ratio control can be improved.

It should be noted that the present invention is not limited to the above-described embodiment, and a part of the configuration can be appropriately changed without departing from the spirit of the invention.

[0076]

According to the first aspect of the present invention, in an engine equipped with a port purge type fuel vapor processing apparatus, the learning value learned by the air-fuel ratio control at the time of high temperature operation is affected by the change in purge flow rate. Even if it changes greatly in response to a cold start, the air-fuel ratio can be controlled stably irrespective of the learning value immediately before the stop, and the effect that the cold start of the engine can be stabilized is exhibited. .

According to the invention described in claim 2, according to claim 1
In addition to the effects of the invention described in (1), it is possible to prevent an abrupt change in the engine rotation after the completion of the cold start, and to achieve an effect of securing stable drivability.

According to the third aspect of the present invention, a first aspect is provided.
Alternatively, in addition to the effect of the invention described in claim 2, it is possible to increase the accuracy of correction of the learning value at the time of starting the cooler, and to increase the air-fuel ratio control accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a gasoline engine system according to an embodiment.

FIG. 2 is a time chart showing behaviors of oxygen concentration, air-fuel ratio determination, and air-fuel ratio correction coefficient.

FIG. 3 is a flowchart showing the details of air-fuel ratio control.

FIG. 4 is a flowchart showing a routine for calculating a final reflection value and the like.

5A to 5F are time charts showing behaviors of various parameters relating to calculation of a final reflection value.

FIG. 6 is a time chart showing the behavior of the air-fuel ratio (A / F).

FIG. 7 is a schematic configuration diagram showing a conventional engine system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel tank 3 Engine 4 Injector (fuel supply means) 8 Intake passage 11 Vapor passage 12 Canister 13 Purge passage (11 to 13 constitute a fuel vapor treatment device) 24 Oxygen sensor (air-fuel ratio detection means) 30 ECU (Empty) Fuel ratio control means, learning correction means, start time correction means, standard value calculation means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 340 F02D 45/00 340F F-term (Reference) 3G084 BA09 BA13 BA27 CA01 DA04 DA09 DA12 EB12 EB17 FA10 FA11 FA20 FA29 FA33 FA36 FA38 3G301 HA01 HA14 JA03 KA01 KA28 MA01 MA11 ND01 ND21 ND33 PA07Z PA11Z PD03A PD03Z PE01Z PE03Z PE08Z PF16Z

Claims (3)

[Claims] A fuel supply means for supplying fuel stored in a fuel tank to an engine; and a fuel vapor generated in the fuel tank, which is collected and purged to a suction passage through a purge passage, thereby obtaining the fuel. A port-purge-type fuel vapor processing apparatus for processing the steam by burning it with the supplied fuel in the engine; an air-fuel ratio detecting means for detecting an air-fuel ratio between air and fuel supplied to the engine; Air-fuel ratio control means for controlling the supplied fuel amount based on a deviation between the detected air-fuel ratio and the target air-fuel ratio so that the air-fuel ratio to be detected becomes a predetermined target air-fuel ratio; Learning as a learning value for each of a plurality of learning regions set for the operating state of the engine, and correcting the supplied fuel amount based on the learning value. And when the learned value learned immediately before the previous stop is smaller than a predetermined threshold value at the time of starting the engine, a predetermined standard value instead of the learned value is provided. An air-fuel ratio control device for an engine, comprising: a start-time correction unit for correcting the supplied fuel amount based on the start-up amount. 2. The start-time correction means corrects the supplied fuel amount initially based on the standard value itself, and thereafter changes the supplied fuel amount to the standard value which is gradually changed until it coincides with the learned value learned simultaneously. 2. The engine air-fuel ratio control device according to claim 1, wherein the supplied fuel amount is corrected based on the amount of the supplied fuel. 3. The apparatus according to claim 1, further comprising a standard value calculating unit configured to calculate the standard value based on the learned value learned immediately before the previous stop. Engine air-fuel ratio control device.