JP3561972B2 - Engine fuel vapor treatment system - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an evaporative fuel processing apparatus for an engine in which evaporative fuel generated from a fuel tank is collected by evaporative fuel collecting means such as a canister, and the collected evaporative fuel is purged in a predetermined operation region and supplied to an intake system. It is about.
[0002]
[Prior art]
Generally, in a fuel injection engine for an automobile, in order to adjust an air-fuel ratio to a target value (target air-fuel ratio), a basic fuel injection amount (basic pulse) corresponding to an intake air amount detected by an air flow sensor is basically used. (Width), the fuel is injected from the fuel injection valve into the intake system or the combustion chamber. However, there is a limit to the accuracy of the injection amount control by the fuel injection valve, and a part of the fuel injected from the fuel injection valve does not immediately enter the combustion chamber because it adheres to the intake passage wall. Further, the injection characteristics of the fuel injection valve may change with time. For this reason, it is difficult to match the air-fuel ratio with the target air-fuel ratio with high accuracy simply by injecting the fuel at the basic fuel injection amount corresponding to the intake air amount.
[0003]
Therefore, usually, in a fuel injection type engine, in a predetermined operation region (feedback region), the linear O₂O in exhaust gas with sensor₂The concentration is detected and the O₂The air-fuel ratio is calculated from the concentration, a feedback correction value acting in a direction to eliminate the air-fuel ratio deviation is calculated according to a deviation of the air-fuel ratio from the target air-fuel ratio (air-fuel ratio deviation), and the feedback correction value is used to calculate the basic fuel. The air-fuel ratio control that corrects the injection amount and causes the air-fuel ratio to follow the target value, that is, feedback control of the air-fuel ratio is performed. Outside the feedback region, the feedback correction value is fixed to a neutral value, and the open-loop control is performed.
[0004]
Further, if the fuel vapor generated in the fuel tank in the automobile is directly discharged into the atmosphere, air pollution is caused and the fuel is lost. Therefore, a car is usually provided with a canister for collecting the evaporated fuel contained in the air in the fuel tank by adsorption. The canister is provided with evaporative fuel purging means for appropriately purging the evaporative fuel collected in the canister into the intake system. The evaporative fuel purging means usually comprises a purge passage connecting the canister and the intake system, and a purge control valve for appropriately opening and closing the purge passage. When the purge control valve is opened, the evaporation inside the canister is stopped. Fuel is purged into the intake system (canister purge).
[0005]
By the way, when the canister purge is performed, the fuel vapor in the canister is supplied to the intake system.Therefore, when the fuel injection by the open loop control is performed with the basic fuel injection amount corresponding to the intake air amount, the canister purge is performed. Then, the air-fuel ratio greatly deviates from the target value. Therefore, in an engine in which the feedback control of the air-fuel ratio is performed in the feedback region, the canister purge is usually performed during the feedback control. However, when the canister purge is performed during the feedback control of the air-fuel ratio, the evaporated fuel supplied to the intake system by the canister purge becomes a disturbance when viewed from the air-fuel ratio control side, and the evaporated fuel is trapped in the canister. In this case, this disturbance is compensated by a feedback operation that changes the feedback correction value to a leaner side than the neutral value. In this case, when the amount of evaporative fuel supplied to the intake system by the canister purge (evaporative fuel purge amount) is constant and the engine is in a steady state, disturbance caused by the canister purge is almost completely compensated. You. However, when the fuel vapor purge amount changes suddenly, for example, when the purge control valve changes from a closed state to an open state, or when it changes from an open state to a closed state, or when the differential pressure across the purge control valve changes suddenly, or When the engine is in a transient state during canister purging, for example, during acceleration / deceleration, disturbance due to canister purging is not sufficiently compensated due to air-fuel ratio detection delay (time lag) or feedback operation delay, and the air-fuel ratio deviates from the target value. There is a problem that it shifts. Such a phenomenon occurs for the following reason.
[0006]
That is, during the feedback control of the air-fuel ratio, for example, when the purge control valve is changed from the closed state to the open state, the air-fuel ratio is enriched according to the evaporated fuel purge amount. The enrichment of the air-fuel ratio is caused by the linear O₂After being detected by the sensor, the feedback correction value is changed in the lean direction based on this, and the enrichment of the air-fuel ratio is corrected. In other words, the canister purge enriches the air-fuel ratio.WasIn some cases, there is a time lag and the enrichment is linear O₂Until the air-fuel ratio is actually detected by the sensor, no enrichment of the air-fuel ratio is corrected.
[0007]
Conversely, when the purge valve changes from the open state to the closed state, the air-fuel ratio becomes lean, but also in this case, there is also a time lag, and after the canister purge is stopped, the air-fuel ratio becomes lean, and then this lean state is achieved. Is linear O₂Until actually detected by the sensor, the leaning of the air-fuel ratio will not be corrected at all.
[0008]
Further, when the engine is in a transient state during canister purging, for example, during acceleration, the differential pressure across the purge control valve sharply drops, so that the amount of evaporated fuel supplied to the combustion chamber in one suction stroke ( The ratio of the inflow of the evaporated fuel to the inflow of the evaporated fuel in the total inflow of the fuel is sharply reduced, and the air-fuel ratio becomes lean. On the other hand, the air-fuel ratio becomes rich during deceleration. However, also in this case, there is a time lag, and the lean or rich air-fuel ratio is not linear O₂No correction will be made until it is actually detected by the sensor.
[0009]
For this reason, when the engine is in a transient state at the time of a sudden change of the evaporated fuel purge amount or the canister purge, the air-fuel ratio is temporarily enriched, fuel is wasted, fuel efficiency is reduced, and HC emission increases. This causes problems such as a reduction in emission performance, and conversely, a problem that the air-fuel ratio becomes lean and a sufficient engine output cannot be obtained.
[0010]
Further, when the rapid increase and decrease of the evaporated fuel purge amount are frequently repeated, or when the acceleration and deceleration are frequently repeated during the canister purge, the correction of the air-fuel ratio is caused by the time lag or the delay of the feedback operation. A problem arises in that the hunting or cycling occurs and the stability of the feedback control of the air-fuel ratio is deteriorated.
[0011]
In the case where the evaporated fuel is processed as a disturbance of the air-fuel ratio feedback control, when the evaporated fuel purge amount is very large, the feedback correction value sticks to the lean limit value in order to compensate for the disturbance caused by the purge amount. It may not be possible to cope with other disturbances.
[0012]
On the other hand, the fuel vapor purge amount is detected, and the final fuel injection amount originally required, that is, the final fuel injection amount required when there is no canister purge (hereinafter referred to as the required fuel injection amount) Is corrected by the amount of the evaporated fuel purge, thereby eliminating the influence of the canister purge from the feedback control of the air-fuel ratio. In other words, the evaporative fuel supplied to the intake system by the canister purge is reduced by the air-fuel ratio feedback control. Attempts have been made to avoid disturbance, but no practical means has been found at this time that can directly detect the fuel vapor purge amount with high accuracy.
[0013]
In view of this, there has been proposed an engine in which an evaporative fuel purge amount is indirectly estimated and the required fuel injection amount is reduced by the estimated value (for example, see Japanese Patent Application Laid-Open No. 2-245441). In such a conventional engine, for example, the engine disclosed in Japanese Patent Application Laid-Open No. 2-245441, the fuel vapor purge amount is estimated based on the difference between the feedback correction value and the neutral value. In this conventional engine, the estimated value of the fuel vapor purge amount is divided by the engine speed to calculate the fuel vapor purge amount per rotation, and the basic fuel injection amount is divided by the fuel vapor purge amount per rotation. Only weight loss correction is performed.
[0014]
[Problems to be solved by the invention]
Generally, the evaporated fuel purge amount fluctuates in a very short cycle in accordance with a change in the operating state of the engine such as a change in the intake air amount, a change in the intake pressure, a change in the engine speed, and the like. By the way, in the conventional engine disclosed in, for example, Japanese Patent Application Laid-Open No. 2-245441, the amount of fuel vapor purge is estimated based on the feedback correction value. However, as described above, the feedback correction value is₂Since there is a time lag due to the relationship calculated based on the air-fuel ratio detected by the sensor, if the actual amount of evaporative fuel purge changes in a short cycle with a change in the operating state of the engine, the estimation accuracy of the evaporative fuel purge amount And the air-fuel ratio deviates from the target value. Therefore, the inventor of the present application first calculates the average feedback correction value by averaging the feedback correction value of the air-fuel ratio control during canister purging, and indirectly estimates the trap amount based on the average feedback correction value. Then, the actual fuel injection amount is set by calculating the evaporative fuel inflow amount based on the trap amount estimation value and subtracting the evaporative fuel inflow amount from the required fuel injection amount. A proposal was made to compensate for the effect of canister purge on control. In this case, specifically, the evaporative fuel release amount is calculated based on the trap amount estimation value, and the evaporative fuel inflow amount is calculated based on the evaporative fuel release amount. Then, a pulse width of the injection corresponding to the evaporated fuel inflow amount, that is, a purge pulse width is calculated, and the required fuel injection amount (pulse width) is corrected by the purge width to drive the fuel injection valve. The resulting deviation of the actual air-fuel ratio from the target value is prevented. At this time, a purge control valve differential pressure is calculated based on the intake charging efficiency, a purge air amount is calculated based on the purge control valve differential pressure and the purge control valve opening, and the calculated purge air amount and The amount of evaporative fuel release is calculated based on the estimated trap amount. By doing so, the actual air-fuel ratio does not deviate from the target value due to the canister purge, and the purge can be sufficiently performed even at idle.
[0015]
However, for example, when purging is performed in this manner, the trap amount is estimated based on the feedback correction value of the air-fuel ratio.₂If an abnormal value is obtained due to factors such as noise to the sensor or deterioration of the sensor, the estimation of the trap amount is inappropriate and erroneous, and therefore, the evaporative fuel calculated based on the estimated trap amount is calculated. The inflow amount is far from the actual evaporative fuel inflow amount. Then, the evaporative fuel inflow amount (fuel reduction value) to be subtracted from the required fuel injection amount is not appropriate, and is too large or too small, so that the air-fuel ratio deviates from the target value. Therefore, aside from the region where the air-fuel ratio deviation does not significantly affect such as at the time of high load, in the low load region such as idling, the flammability deteriorates due to the air-fuel ratio deviation due to such erroneous estimation of the trap amount. , Especially at high altitudes, is more likely to stall.
[0016]
The present invention has been made to solve such a problem, and the air-fuel ratio shifts because the purge amount actually sucked when the trap amount is erroneously estimated does not correspond to the fuel reduction value. The purpose is to prevent
[0017]
Another object of the present invention is to prevent engine stall from being repeated due to a purge.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes an air-fuel ratio detecting means for detecting an air-fuel ratio of an air-fuel mixture supplied to a combustion chamber of an engine, as shown in FIG. Feedback correction value setting means for setting a feedback correction value based on a deviation of the air-fuel ratio from a target value detected by the detection means; and controlling the air-fuel ratio based on the feedback correction value set by the feedback correction value setting means. Air-fuel ratio control means, evaporative fuel collecting means for collecting evaporative fuel generated from a fuel tank, and evaporative fuel purging means for purging evaporative fuel from the evaporative fuel collector means and supplying the evaporative fuel to an intake system in a predetermined operation region. A feedback correction value set by the feedback correction value setting means during execution of the purge by the fuel vapor purge means. Evaporative fuel trapping amount estimating means for estimating the amount of evaporative fuel trapping by the evaporative fuel trapping means; Evaporative fuel inflow amount calculating means for calculating the evaporative fuel inflow amount to be calculated, and a required fuel for obtaining the target value of the air-fuel ratio by reducing the amount corresponding to the evaporative fuel inflow amount calculated by the evaporative fuel inflow amount calculating means. What is claimed is: 1. An evaporative fuel processing apparatus for an engine, comprising: a fuel supply amount reducing unit configured to reduce a supply amount from a supply amount. And purge limiting means for restricting purging of the fuel vapor by the fuel vapor purging means when a state in which the estimation of the amount of evaporative fuel collection is incorrectly detected by the false estimation detecting means is detected. Providing evaporated fuel treatment device for an engine according to symptoms.
[0019]
Also,Claim 1The invention ofthe aboveIn the configuration, the erroneous estimation detecting means is constituted by stalling detecting means for detecting stalling, and when the stalling is detected by the stalling detecting means, the erroneous estimation is determined to be in the erroneous estimation state of the amount of trapped fuel vapor.Characterized by.
[0020]
Also,Claim 2The invention ofClaim 1The present invention also provides an evaporative fuel processing device for an engine, wherein the engine stall detecting means detects engine stall during purging by the fuel vapor purging means.
[0021]
Also,Claim 3The invention of,The purge limiting means limits the purge of the evaporated fuel when a state in which the estimation of the amount of collected fuel vapor is erroneously estimated by the erroneous estimation detection means in a predetermined low load region of the engine. An evaporative fuel processing device is provided.
[0022]
Also,Claim 4The invention ofClaim 3The present invention also provides an evaporative fuel processing device for an engine, wherein the predetermined low load region is at idle.
[0023]
Also,Claim 5The invention of,The evaporative fuel trapping amount estimating means estimates the amount of evaporative fuel trapping during purging in an operation region other than the idling state, and the evaporative fuel purging means estimates the evaporative fuel trapping amount estimating means during idling. The present invention provides an evaporative fuel processing device for an engine, which executes purge after estimation of the amount of evaporative fuel trapped by the engine is completed.
[0024]
Also,Claim 6The present invention is directed to an evaporative fuel collecting means for collecting evaporative fuel generated from a fuel tank, and an evaporative fuel purge for purging evaporative fuel from the evaporative fuel collective means and supplying the evaporative fuel to an intake system in a predetermined operation region including an idling state. An engine stall detecting means for detecting engine stall, and a purge restricting means for restricting purging of the fuel vapor by the fuel vapor purging means when the engine stall is detected by the engine stall detecting means. The present invention provides an evaporative fuel processing device for an engine.
[0025]
[Action]
According to the first aspect of the invention, an air-fuel ratio is detected, a feedback correction value is set based on a deviation of the detected air-fuel ratio from a target value, and feedback control of the air-fuel ratio is performed based on the set feedback correction value. Is performed. Further, the evaporated fuel generated from the fuel tank is collected by the evaporated fuel collecting means, and the evaporated fuel is purged from the evaporated fuel collecting means in a predetermined operation region and supplied to the intake system. At this time, during the execution of the purge, the amount of trapped evaporative fuel (trap amount) is estimated based on the feedback correction value, and the amount of evaporative fuel flowing into the engine is calculated based on the estimated value of the amount of trapped evaporative fuel. Then, the reduced value corresponding to the calculated evaporated fuel inflow amount is reduced from the required fuel supply amount, thereby preventing the deviation of the air-fuel ratio from the target value due to the canister purge. Further, when an erroneous estimation of the evaporative fuel trapping amount is detected, the purge of the evaporative fuel is limited, and the deviation of the air-fuel ratio due to the fact that the purge amount actually sucked does not correspond to the fuel reduction value as a result of the erroneous estimation. Be suppressed.
[0026]
Also,Claim 1According to the invention, an erroneous estimation of the trap amount is detected by the engine stall. That is, if an engine stall occurs, purging is prohibited because there is a high possibility that the engine stall has occurred due to erroneous estimation of the trap amount. Also,Claim 2According to the invention, it is highly probable that the cause of the engine stall is the erroneous estimation of the trap amount only when the engine stall occurs during the execution of the purge. Is detected.
[0027]
Also,Claim 3According to the invention, in the low load region where the erroneous estimation of the trap amount has a large effect on the flammability, the purging is limited when the erroneous estimation is detected, thereby preventing the deterioration of the flammability at the low load. Further, on the high load side where the influence of the erroneous estimation is relatively small, normal purging is performed.
[0028]
Also,Claim 4According to the invention, when the erroneous estimation is detected at the time of idling, the purge is limited, thereby preventing the engine from stalling particularly at high altitude.
[0029]
Also,Claim 5According to the invention, the estimation of the trap amount is performed in off-idle. The purge at the time of idling is performed after the estimation of the trap amount is completed. Therefore, even when the erroneous estimation of the trap amount is detected and the purge is limited, the trap amount is estimated, and the idle purge can be returned after the estimation is completed again.
[0030]
Also,Claim 6According to the invention, when the engine stalls, the purge of the evaporated fuel may be caused by the purge, and the purge of the evaporated fuel is limited.
[0031]
【Example】
Hereinafter, examples of the present invention will be specifically described.
[0032]
FIG. 2 is a system diagram of an engine provided with the evaporated fuel processing apparatus according to one embodiment of the present invention. The engine of this embodiment shown by CE in FIG. 2 is an in-line four-cylinder gasoline injection engine, and each cylinder 1 (only one cylinder is shown) burns from an intake port 3 when an intake valve 2 is opened. The air-fuel mixture is sucked into the chamber 4, compressed by the piston 5, ignited by a spark plug (not shown), burned, exploded and expanded, and the combustion gas is exhausted by opening the exhaust valve 6. The gas is discharged to the exhaust passage 8 via the exhaust port 7 as gas.
[0033]
The exhaust passage 8 contains O 2 in the exhaust gas.₂Linear O to detect concentration₂A sensor 9 is provided. Linear O₂O detected by the sensor₂The concentration is input to the control unit CU. In the control unit CU, this O₂The air-fuel ratio of the air-fuel mixture sucked into the combustion chamber 4 is calculated based on the concentration. Where linear O₂O detected by the sensor 9₂The concentration and the air-fuel ratio of the air-fuel mixture have a unique correspondence. Therefore, hereafter, O₂The air-fuel ratio calculated based on the concentration is referred to as “linear O₂It is referred to as "the air-fuel ratio detected by the sensor 9" or "actual air-fuel ratio".
[0034]
The engine CE is provided with an intake system 10 for supplying combustion air to the combustion chamber 4 of each cylinder 1. The intake system 10 has a common intake passage 11 whose upstream end is opened to the atmosphere via an air cleaner (not shown). The common intake passage 11 has a throttle valve which is opened and closed in conjunction with an accelerator pedal (not shown). 12 are interposed. A surge tank 13 for stabilizing the flow of the intake air is connected to a downstream end of the common intake passage 11. The surge tank 13 has an independent intake passage 14 (only one independent intake passage 14) for individually supplying air to each cylinder 1. The downstream end of each of the independent intake passages 14 is connected to the corresponding intake port 3 of the cylinder 1.
[0035]
In the independent intake passage 14 of each cylinder 1, a fuel injection valve 15 for injecting fuel into the intake port 3 or into the combustion chamber 4 in the vicinity of the respective intake port 3 so that the injection port is directed to the downstream side. It is provided. The fuel injection amount (injection pulse width) and the injection timing of these fuel injection valves 15 are controlled by the control unit CU as described later.
[0036]
Further, the engine CE is provided with an assist air supply device (hereinafter, referred to as AMI) 16 for supplying assist air to each fuel injection valve 15 in order to promote vaporization and atomization of fuel. Although not shown in detail, the AMI 16 is provided with an assist air introduction passage 17 having an upstream end upstream of the throttle valve 12 and communicating with the common intake passage 11. A solenoid assist air control valve 18 that is opened and closed by the unit CU is provided. Further, a bypass assist air passage 19 for bypassing the assist air control valve 18 and passing air is provided. The bypass assist air passage 19 has an orifice 20 for regulating a flow rate by generating a predetermined pressure loss (pressure drop). Is interposed.
[0037]
The downstream end of the assist air introduction passage 17 is connected to a mixing chamber 21, and the mixing chamber 21 is further connected to an assist air supply passage 22. The assist air supply passage 22 branches to four branch assist air supply passages 23 on the downstream side, and each branch assist air supply passage 23 is connected at its downstream end to the fuel injection valve 15 of the corresponding cylinder 1. I have. Assist air is individually supplied to the fuel injection valve 15 of each cylinder 1 from the corresponding branch assist air supply passage 23.
[0038]
The engine CE is provided with an evaporative fuel processing device 24 that collects evaporative fuel (gasoline vapor) evaporated from a fuel tank (not shown), purges the collected evaporative fuel as appropriate, and supplies the evaporative fuel to the intake system 10. ing.
[0039]
The evaporative fuel processing device 24 includes a canister 25 filled with an adsorbent (for example, activated carbon) capable of collecting evaporative fuel by adsorption. The canister 25 has a relief passage 26 having a distal end communicating with the upper space of the fuel tank to relieve air and evaporative fuel in the upper space of the fuel tank into the canister 25, and an atmosphere opening passage having a distal end open to the atmosphere. 27 and a purge passage 28 whose tip is connected to the mixing chamber 21. The open-to-atmosphere passage 27 may be connected at its tip to the common intake passage 11 upstream of the throttle valve 12. In addition, the canister 25 is not filled with an adsorbent, but uses a material other than adsorption (e.g., absorption, reaction, etc.) to collect evaporated fuel (but can be purged with air). It may be filled.
[0040]
The purge passage 28 is provided with a duty solenoid-type purge control valve 29 that can be arbitrarily opened and closed by controlling the opening degree by the control unit CU. The opening of the purge control valve 29 is controlled by the drive duty ratio applied from the control unit CU. For example, the purge control valve 29 is fully closed when the drive duty ratio is 0 and fully open when the drive duty ratio is 100%. During this period, the valve opening degree is controlled to increase as the drive duty ratio increases.
[0041]
In this evaporative fuel processor 24, when the purge control valve 29 is fully closed (drive duty ratio is 0), the air in the fuel tank is relieved into the canister 25 through the relief passage 26, and is discharged into the atmosphere through the atmosphere opening passage 27. Is done. However, the evaporative fuel in the relieved air is collected by the adsorbent when passing through the adsorbent layer in the canister 25 and is not discharged into the atmosphere.
[0042]
When the purge control valve 29 is open, the air in the atmosphere is sucked into the canister 25 through the atmosphere opening passage 27 by the negative pressure of the intake system 10, passes through the adsorbent layer, and passes through the purge passage 28. The air enters the mixing chamber 21 of the AMI 16, flows from the assist air supply passage 22 to the branch assist air supply passage 23, and is purged into the combustion chamber 4 via the intake system 10. The flow rate of the purged air (hereinafter, referred to as the purge air amount) changes according to the degree of opening of the purge control valve 29 (ie, the drive duty ratio). At that time, a part of the evaporated fuel collected by the adsorbent in the canister 25 is separated from the adsorbent, and is passed through the intake system 10 together with the purged air (hereinafter, referred to as purge air). To the combustion chamber 4. Hereinafter, the flow rate of the evaporated fuel purged into the combustion chamber 4 via the intake system 10 in this manner is referred to as “evaporated fuel purge amount”.
[0043]
The transportation path of the purge air or the evaporated fuel from the canister 25 to the combustion chamber 4 has a considerable capacity. Therefore, there is a transport delay corresponding to the volume and shape (transport characteristics) of the transport path before the evaporated fuel discharged from the canister 25 to the purge passage 28 actually flows into the combustion chamber 4. Therefore, at a certain time, the flow rate of the vaporized fuel discharged from the canister 25 to the purge passage 28 (hereinafter, referred to as the vaporized fuel discharge amount) and the flow rate of the vaporized fuel actually flowing into the combustion chamber 4 (hereinafter, referred to as the Is generally not the same except in a special case such as in a steady state. For this reason, the evaporated fuel purge amount will be separately described below for the evaporated fuel discharge amount and the evaporated fuel inflow amount.
[0044]
When the volume of the transport path of the purge air or the evaporated fuel from the canister 25 to the combustion chamber 4 is very small, the transport delay can be ignored. Even if the concept of the evaporated fuel purge amount is used without distinction, no particular problem occurs.
[0045]
By the way, in the engine CE shown in FIG. 2, the downstream end of the purge passage 28 is connected to the mixing chamber 21, and the fuel vapor collected in the canister 25 is purged to the intake system 10 through the AMI 16. , AMI is not provided, the downstream end of the purge passage 28 may be branched and connected to each independent intake passage 14. Further, in the case of the engine CE having no AMI, the downstream end of the purge passage 28 is connected to the surge tank 13 so that the fuel vapor collected in the canister 25 is directly purged to the intake system 10. You may.
[0046]
The control unit CU is a general engine CE control device composed of a microcomputer.₂The air-fuel ratio (actual air-fuel ratio) detected by the sensor 9, the throttle opening detected by the throttle opening sensor 31, the intake air amount detected by the air flow sensor 32, the engine speed detected by the speed sensor 33, Various control of the engine CE, control of the evaporative fuel processor 24, control of the evaporative fuel collected by the canister 25 are performed by using the idle signal output from the idle switch 34, the atmospheric pressure detected by the atmospheric pressure sensor 35, and the like as control information. (Hereinafter, referred to as a trap amount), an evaporative fuel release amount calculation, an evaporative fuel inflow amount calculation, and the like.
[0047]
FIG. 3 is a control block diagram showing basic functions of the control unit CU. As shown in FIG. 3, the control unit CU functionally includes an engine control block SL for performing air-fuel ratio control (fuel injection amount control) and canister purge control, and a trap amount estimation block SM for estimating a trap amount. And an evaporative fuel purge amount calculation block SN which calculates an evaporative fuel release amount and an evaporative fuel inflow amount based on the trap amount.
[0048]
The engine control block SL basically controls the injection pulse width of the fuel injection valve 15, that is, the fuel injection amount by feedback or open loop depending on the operation state (air-fuel ratio control) so that the air-fuel ratio becomes the target air-fuel ratio. At the same time, the canister purge control according to the operation state is performed in the operation region where the canister purge should be performed.
[0049]
In the air-fuel ratio control, if the operating state of the engine CE falls within a predetermined feedback region (for example, a region excluding a high load region and a high rotation region), the deviation of the actual air-fuel ratio from the target air-fuel ratio (hereinafter, this is referred to as The feedback control is performed based on the air-fuel ratio deviation, and if not in the feedback region, the open-loop control is performed based on the air-fuel ratio deviation. In the feedback control of the air-fuel ratio, a basic pulse width of a pulse (injection pulse) for driving the fuel injection valve 15, that is, a basic fuel injection amount is calculated according to the intake air amount and the engine speed (base calculation). Then, on the other hand, the feedback correction amount cfb is calculated based on the air-fuel ratio deviation (for example, a value obtained by subtracting the actual air-fuel ratio from the target air-fuel ratio) (stage S1). Here, the feedback correction amount cfb is a neutral value, that is, a neutral value that does not correct the air-fuel ratio in any direction is 0, and when cfb> 0, the fuel injection amount is corrected so that the air-fuel ratio is corrected in the fuel-rich direction. When cfb <0, the air-fuel ratio (fuel injection amount) is corrected in the fuel lean direction.
[0050]
Then, based on the basic pulse width and the feedback correction value cfb, for example, the basic pulse width is multiplied by cfb, so that the basic pulse width is corrected in the direction in which the air-fuel ratio deviation decreases, and the required pulse width, that is, the required fuel injection The amount is calculated (stage S2). For example, when the actual air-fuel ratio is leaner than the target air-fuel ratio, cfb> 0. Accordingly, the fuel injection amount is corrected to increase, the air-fuel ratio is corrected in the rich direction, and the air-fuel ratio deviation is reduced. Conversely, when the actual air-fuel ratio is richer than the target air-fuel ratio, cfb <0. Accordingly, the fuel injection amount is corrected to be reduced, the air-fuel ratio is corrected in the lean direction, and the air-fuel ratio deviation is reduced. Thus, the air-fuel ratio (fuel injection amount) is feedback-controlled so as to eliminate the air-fuel ratio deviation according to the air-fuel ratio deviation.
[0051]
When the open-loop control of the air-fuel ratio is performed, the feedback correction value cfb is fixed to 0. In this case, the basic pulse width becomes the required pulse width without being corrected according to the air-fuel ratio deviation, and open loop control without feedback is performed.
[0052]
Further, a pulse width (hereinafter, referred to as a purge correction pulse width) corresponding to a later-described evaporated fuel inflow amount is subtracted from the required pulse width, that is, the required fuel injection amount, and an actual injection pulse width of the fuel injection valve 15 (hereinafter, referred to as a purge correction pulse width). , Which is referred to as an actual injection pulse width), that is, the actual fuel injection amount (actual fuel injection amount) is calculated. Then, with the actual injection pulse width, that is, the actual fuel injection amount, the fuel injection valve 15 is driven at a predetermined timing to inject fuel. Thus, the actual air-fuel ratio is maintained at the target air-fuel ratio.
[0053]
The canister purge control is performed by a well-known ordinary method according to the operating state of the engine CE when a canister purge condition, for example, the water temperature is equal to or higher than a predetermined value is satisfied. That is, a duty ratio according to the operation state of the engine CE is applied to the purge control valve 29, thereby performing the canister purge.
[0054]
The trap amount estimation block SM calculates an average feedback correction value cfbave by averaging the feedback correction value cfb calculated in the stage S1 of the engine control block SL at the time of canister purging (stage S3), and furthermore, this average feedback. The trap amount is indirectly estimated based on the correction value cfbave (stage S4). That is, the trap amount is grasped by using the average feedback correction value cfbave as an index for determining whether the currently grasped trap amount (trap amount estimated value) is larger or smaller than the true trap amount.
[0055]
As will be described later, the control unit CU calculates the fuel vapor inflow amount based on the trap amount estimation value by a predetermined calculation formula, and further subtracts the fuel vapor inflow amount from the required fuel injection amount to calculate the actual fuel injection amount. Set. Here, if the trap amount estimation value is accurate, that is, if it matches the true trap amount, the evaporative fuel inflow amount is accurately calculated, so that the evaporative fuel supplied to the combustion chamber 4 by the canister purge is It does not cause disturbance in the feedback control, and does not particularly affect the feedback correction value cfb. In this case, if there is no other large disturbance, the feedback correction value cfb only slightly fluctuates around the neutral value (that is, 0). Therefore, the average feedback correction value cfbave becomes almost the neutral value 0. In other words, if the average feedback correction value cfbave is 0, the trap amount estimation value matches the true trap amount.
[0056]
However, if the trap amount estimation value is larger than the true trap amount, the calculated value of the evaporated fuel inflow amount becomes larger than the true value, and accordingly, the actual fuel injection amount becomes smaller than the proper value. The amount of fuel actually supplied is smaller than the required fuel amount (required fuel injection amount), so that the actual air-fuel ratio becomes lean. In this case, in order to correct this leaning, the feedback correction value cfb changes in the rich direction and becomes larger than 0, and accordingly, the average feedback correction value cfbave becomes larger than 0. In other words, if cfbave> 0, the trap amount estimate is larger than the true trap amount.
[0057]
As described above, since the feedback correction value cfb fluctuates, even if the trap amount estimation value is larger than the true trap amount, cfb> 0 is not always satisfied. Therefore, even if cfb> 0. The trap amount estimation value is not always larger than the true trap amount. Therefore, if the trap amount is estimated based on the feedback correction value cfb, the estimation accuracy is considered to be extremely low. In view of such circumstances, in the present embodiment, the trap amount is estimated based on the average feedback correction value cfbave.
[0058]
Conversely, if the estimated trap amount is smaller than the true trap amount, the calculated evaporative fuel inflow amount becomes smaller than the true value, and accordingly, the actual fuel injection amount becomes larger than the proper value. The amount of fuel supplied to the chamber 4 becomes larger than the required amount of fuel, and the actual air-fuel ratio becomes rich. In this case, in order to correct this enrichment, the feedback correction value cfb changes in the lean direction and becomes smaller than 0, and accordingly, the average feedback correction value cfbave becomes smaller than 0. In other words, if cfbave <0, the trap amount estimated value is smaller than the true trap amount.
[0059]
Therefore, after initially setting an appropriate initial value for the trap amount estimation value, if cfbave> 0, the trap amount estimation value is reduced by a predetermined correction amount σ, and if cfbave <0, the trap amount estimation value is corrected. By repeating the operation of increasing the amount by the amount σ, the estimated trap amount eventually converges (attains) to the true trap amount, and the trap amount is grasped. Thus, the trap amount is estimated based on the average feedback correction value cfbave.
[0060]
Here, whether or not the estimated trap amount substantially matches the true trap amount, that is, whether or not the estimation of the trap amount is almost completed, is determined by determining whether the absolute value | cfbave | of the average feedback correction value cfbave is a predetermined value. It is preferable to make a determination based on whether the difference is equal to or less than the limit value ε. If | cfbave | is very small, it is considered that the estimated trap amount substantially matches the true trap.
[0061]
If the correction amount σ is large, the time required for convergence of the trap amount estimation value after the estimation starts, that is, the time required for estimating the trap amount can be shortened, but the accuracy of the trap amount estimation value decreases. In addition, when the correction amount σ is small, the time required for convergence of the trap amount estimation value increases, but the accuracy of the trap amount estimation value can be improved. Therefore, it is preferable to set the correction amount σ to an appropriate value so that the requirement for the time required for convergence and the requirement for the accuracy of the trap amount estimation value are compatible.
[0062]
The correction amount σ does not need to be a constant value, and may be changed during the estimation of the trap amount according to, for example, the progress of the estimation of the trap amount, or may be set according to the value of the average feedback correction value cfbave. Is also good. For example, when the estimation of the trap amount is started, the correction amount σ may be increased to speed up the convergence, and after the trap amount estimation value has converged to some extent, the correction amount σ may be decreased to increase the accuracy of the trap amount estimation value. If the correction amount σ is increased as the average feedback correction value cfbave is increased, the convergence is accelerated when the estimated trap amount is far from the true trap amount, and the accuracy is improved when the estimated trap amount is close to the true trap amount. Can be increased.
[0063]
This trap amount estimating method is based on the premise that the above-described correlation (correlation) is established between the trap amount or the evaporated fuel purge amount and the feedback correction value cfb or the average feedback correction value cfbave. I have. Therefore, the trap amount cannot be estimated with high accuracy in a situation where the correlation is low or a situation where the correlation does not exist. Therefore, it is preferable to prohibit the estimation of the trap amount in a situation where the correlation is low or a situation where the correlation does not exist. Here, the situation where the correlation is low includes, for example, when the intake air amount is extremely large, when the intake pressure is extremely low, and the like, as described later. Examples of the situation where the correlation does not exist include, for example, when the canister purge is stopped, when the air-fuel ratio feedback control is stopped (at the time of open loop control), and the like. It is needless to say that the estimation of the trap amount may be prohibited only when there are several situations where the correlation is low or there is no correlation.
[0064]
In addition, this trap amount estimating method uses the feedback correction value cfb if the evaporative fuel inflow amount is accurately grasped, that is, if the supply of the evaporative fuel by the canister purge does not affect the feedback correction value cfb. It is assumed that the value fluctuates around the neutral value 0, and therefore the average feedback correction value cfbave becomes the neutral value 0. By the way, in the engine, the air-fuel ratio learning such that the control output characteristic, that is, the injection characteristic of the fuel injection valve is automatically corrected by learning so that the feedback correction value cfb becomes a neutral value 0 on average is widely performed. However, when estimating the trap amount in an engine that performs the air-fuel ratio learning, it is preferable that the trap amount is estimated after the air-fuel ratio learning is completed. However, if the air-fuel ratio learning has been completed, the average feedback correction value cfbave will surely reach the neutral value 0 if there is no influence of the canister purge.
[0065]
If the estimation of the trap amount is prohibited in this way and the prohibition period continues for a certain period of time or more, the estimated trap amount may deviate from the true trap amount. Even when it is determined that the processing has been completed, it is preferable to cancel (reset) the determination.
[0066]
In this embodiment, the trap amount is calculated based on the average feedback correction value cfbave by calculating the average feedback correction value cfbave by averaging the feedback correction value cfb of the air-fuel ratio. The feedback correction value cfb of the air-fuel ratio is determined by some factor (for example, linear O₂If an abnormal value is detected due to noise to the sensor or deterioration of the sensor, etc.), the estimation of the trap amount is inappropriate and erroneous learning is performed. Therefore, the inflow amount of the fuel vapor calculated based on the estimated trap amount is calculated. Is very different from the actual amount of fuel vapor inflow (erroneous learning of the trap amount), and the fuel for setting the actual fuel injection amount by subtracting the amount of fuel vapor inflow (reduced fuel value) from the required fuel injection amount The weight loss value is not appropriate, and is too large or too small, so that the air-fuel ratio deviates from the target value. In a low load region such as when idling, the flammability deteriorates due to the air-fuel ratio deviation caused by such an erroneous learning of the trap amount, aside from a region where the deviation of the air-fuel ratio does not significantly affect such as at a high load. , Especially at high altitudes. Therefore, at the time of idling where the erroneous learning of the trap amount has a large effect on the combustibility, the canister purge is prohibited when the erroneous learning of the trap amount is detected.
[0067]
Here, erroneous learning of the trap amount is detected based on whether or not an engine stall has occurred. When an engine stall occurs, purging is prohibited because there is a high possibility that the engine stall has occurred due to erroneous learning of the trap amount. The learning of the trap amount itself is performed at the time of off-idle purging. Even if erroneous learning is detected, the purging is executed as it is at the off-idle, the learning of the trap amount is redone, and the idle purge is performed after the redo is completed. By resuming, the purge can be performed again without impairing the combustion stability during idling.
[0068]
In this embodiment, when the erroneous learning of the trap amount is detected, the idle purge is completely stopped. However, in this case, the idle purge amount may be reduced instead of the complete stop. In addition, the erroneous learning of the trap amount is indirectly detected by the engine stall determination. However, when the phenomenon that the feedback correction amount cfb of the air-fuel ratio deviates even under the same operation state occurs, the trap amount is erroneously learned. May be determined to be erroneous learning.
[0069]
The evaporative fuel purge amount calculation block SN basically calculates an evaporative fuel release amount based on the trap amount estimation value estimated at the stage S4 of the trap amount estimation block SM, and further calculates the evaporative fuel release amount based on the evaporative fuel release amount. The evaporative fuel inflow amount is calculated, the pulse width of the fuel injector 15 corresponding to the evaporative fuel inflow amount, ie, the purge correction pulse width is calculated, and the purge correction pulse width is output to the engine control block SL. That is, the influence of the canister purge on the air-fuel ratio control is compensated by the feedforward control (estimated control) without causing a time lag, and thus without causing a deviation of the air-fuel ratio.
[0070]
More specifically, first, a differential pressure across the purge control valve 29 in the purge passage 28, that is, a pressure difference between immediately upstream and downstream of the purge control valve 29 (hereinafter, referred to as a differential pressure across the purge control valve). Is calculated (stage S5), while the purge control valve opening (purge SOL opening) is calculated from the drive duty ratio applied to the purge control valve 29 (stage S6). The purge air amount (canister degassing Air amount) is calculated based on the purge control valve opening (stage S7).
[0071]
In this embodiment, the pressure difference before and after the purge control valve is calculated based on the intake charging efficiency. The reason is as follows. That is, the intake pressure can be calculated from the charging efficiency by a well-known method, and the pressure immediately downstream of the purge control valve 29 is substantially the same as the intake pressure. On the other hand, the pressure immediately upstream of the purge control valve 29 can be regarded as a substantially constant value (atmospheric pressure). The differential pressure before and after the purge control valve is the difference between the pressure immediately upstream of the purge control valve 29 and the pressure immediately downstream thereof, that is, the difference between the atmospheric pressure and the intake pressure. Therefore, by performing a predetermined calculation process on the charging efficiency, the differential pressure across the purge control valve can be obtained. By doing so, it is not necessary to provide an intake pressure sensor, and the intake system 10 is simplified. Of course, the pressure immediately downstream of the purge control valve 29 may be detected using an intake pressure sensor. Further, a differential pressure sensor for directly detecting the differential pressure across the purge control valve may be provided.
[0072]
The purge air amount is calculated by a well-known method based on the differential pressure across the purge control valve and the opening degree of the purge control valve. That is, generally, between the pressure difference ΔP between the front and rear of a device interposed in a gas closed passage, ie, a pressure loss, and a flow velocity u of a gas flowing through the device, a constant value well known in the field of fluid dynamics is used. A functional relationship holds (for example, ΔP = ku²). Therefore, it is possible to calculate the flow velocity of the gas in the device based on the pressure difference between the front and rear. Then, the volume flow rate of the gas flowing through the flow path can be obtained by multiplying the flow velocity by the flow cross-sectional area of the device. Therefore, in view of the general principle, in the present embodiment, the flow cross-sectional area of the purge control valve 29 can be easily obtained from the purge control valve opening. (Drive duty ratio) and the purge air amount (volume flow rate) can be obtained. Note that a flow rate detection sensor capable of directly detecting the purge air amount may be provided, and the flow rate detection sensor may detect the purge air amount.
[0073]
Then, the evaporative fuel release amount (purge gas mass flow rate, that is, mass flow rate of the evaporative fuel) is calculated based on the purge air amount calculated in the stage S7 and the trap amount estimation value (stage S8). Next, the engine speed is measured (Stage S9), and the purge gas ratio is calculated based on the engine speed and the amount of evaporative fuel release calculated in Stage S8 (Stage S10). Here, the purge gas ratio is a ratio of the evaporated fuel discharged from the canister 25 to the purge passage 28 in the required total fuel (required fuel injection amount), and is a contribution ratio of the evaporated fuel to the combustion. It represents.
[0074]
Thereafter, a transport delay characteristic (intake air amount model) of a purge air or evaporative fuel transport path from the canister 25 to the combustion chamber 4 (hereinafter, referred to as an evaporative fuel transport path) is set (stage S11). The net purge gas ratio is calculated based on the purge gas ratio calculated at the stage 10 and the intake air amount model set at the stage S11 (stage S12). The net purge gas ratio is a ratio of the evaporated fuel flowing into the combustion chamber 4 to the total required fuel (required fuel injection amount), that is, a ratio of the evaporated fuel inflow amount to the required fuel injection amount. Therefore, the fuel amount to be injected from the fuel injection valve 15 is obtained by multiplying the required fuel injection amount by (the difference between 1 and the net purge gas ratio).
[0075]
Then, a pulse width of the fuel injection valve 15 corresponding to the net purge gas ratio (evaporated fuel inflow amount) calculated in the stage S12, that is, a purge correction pulse width is calculated (stage 13), and the purge correction pulse width is determined by the engine control block. Output to SL.
[0076]
Hereinafter, a specific method of estimating the trap amount by the control unit CU (trap amount estimation routine) will be described in accordance with the flowchart shown in FIG. 4 and appropriately referring to FIG. 2 and FIG.
[0077]
This trap amount estimation routine is executed at a predetermined time period. In step # 1, initialization is performed, and 0 is set as an initial value in each of a trap amount estimation completion flag xtraplrn and a trap amount estimation possible flag xtlex. Here, the trap amount estimation completion flag xtraplrn is a flag that is set to 1 when the estimation of the trap amount is completed, and is reset to 0 when prohibition of the estimation of the trap amount continues for a predetermined time or more. The trap amount estimation possible flag xtex is a flag that is set to 1 when the trap amount estimation condition is satisfied, and is reset to 0 when the trap amount estimation condition is not satisfied.
[0078]
Next, in step # 2, the engine stall is determined by checking whether the engine speed ne is lower than the engine stall determination speed KSENST (for example, 300 rpm). If ne <KSENST, it means that engine stall has occurred, and in this case, the trap amount estimation completion flag xtraplrn is forcibly reset to 0 in step # 3. Here, if xtraplrn is set to 0, the idle purge is forcibly stopped even when the trap amount estimation has been completed and the idle purge has been performed, and the trap amount estimation is performed again in steps # 4 to # 12, and the process is completed. Until the idle purge is performed, the idle purge will not be restarted. On the other hand, if ne ≧ KSENST, it is not an engine stall, and the process directly proceeds to step # 4..
[0079]
Next, in step # 4, it is determined whether a predetermined trap amount estimation condition is satisfied, that is, whether the operating state of the engine CE is in a state where the trap amount can be estimated with high accuracy. I do. Here, when all of the following four conditions are satisfied, it is determined that the trap amount estimation condition is satisfied.
(1) Canister purge has been performed
(2) Feedback control of air-fuel ratio is performedhandBeing
(3) The amount of intake air is less than a predetermined value
(4) The intake pressure exceeds a predetermined value
In other words, when the canister purge is stopped, when the feedback control of the air-fuel ratio is stopped, when the intake air amount is equal to or more than a predetermined value, or when the intake pressure is equal to or less than a predetermined value, the trap amount is reduced. Estimation is prohibited. The reason for this is as follows.
[0080]
That is, as described above, when the canister purge (at the time of off idling) or the feedback control is stopped, there is no correlation between the trap amount and the feedback correction value or the average feedback correction value. Therefore, the estimation of the trap amount is prohibited.
[0081]
Also, when the intake air amount is very large, the differential pressure across the purge control valve becomes very small, the intake pulsation becomes severe, and the feedback correction value fluctuates. Therefore, the purge air amount can be calculated with high accuracy. Therefore, the estimation of the trap amount is prohibited.
[0082]
Further, when the intake pressure is very low, the differential pressure across the purge control valve becomes too large, and it becomes impossible to calculate the purge air amount with high accuracy. Therefore, the estimation of the trap amount is prohibited.
[0083]
Thus, if it is determined in step # 4 that the trap amount estimating condition is satisfied (YES), the trap amount estimable flag xtex is set to 1 in step # 5, and the trap amount estimating prohibition counter ct is set to the initial value ct.₀Is set. Here, the trap amount estimation prohibition counter ct is a counter for counting a period (time) during which the trap amount estimation condition is not satisfied and the estimation of the trap amount is prohibited.
[0084]
Subsequently, in step # 6, the average feedback correction value cfbave is calculated by the following equation 1, and the number-of-calculations counter P for counting the number of calculations of the average feedback correction value cfbave is incremented by 1 (P = P + 1). .
cfbave = Σ (k = 0 → n−1) [cfb (ik)] / n Equation 1
cfbave: average feedback correction value
cfb (i): current feedback correction value
cfb (ik): feedback correction value k times before
n: number of cfb samples to be averaged
In Expression 1, １ (k = α → β) [f (k)] represents a sigma operation (Σ) from K = α to k = β of the function f (k).
[0085]
Next, in step # 7, the number-of-operations counter P is set to a predetermined set value P.₀It is determined whether or not P <P₀(NO), skip all the following steps, that is, return to step # 2 without estimating the trap amount. In this trap amount estimation routine, the count value of the number-of-operations counter P is equal to the set value P₀If the value is less than the value, it is considered that the average feedback correction value cfbave is not yet sufficiently stable (the effect of the fluctuation of the feedback correction value cfb remains), so that the trap amount is not estimated. .
[0086]
On the other hand, in step # 7, P ≧ P₀(YES), it is determined in step # 8 whether the absolute amount | cfbave | of the average feedback correction value cfbave is equal to or larger than a predetermined limit value ε. Here, if | cfbave | <ε, it is determined that the estimation of the trap amount has been completed. In this case, the estimated trap amount is considered to substantially match the true trap amount. The estimated trap amount trap is kept unchanged without change.
[0087]
For example, as schematically shown in FIG.₂When the trap amount estimated value trap is a₁~ A₃It is determined that the estimation of the trap amount has been completed when the value falls within the range. The graph G in FIG.₁Represents | cfbave |. Also, trap> a₂Cfbave> 0 and trap <a₂Is within the range of cfbave <0.
[0088]
On the other hand, if | cfbave | ≧ ε, the trap amount estimation value trap is increased or decreased by the correction amount σ depending on whether the average feedback correction value cfbave is equal to or less than 0 or greater than 0, and the trap amount estimation value trap To approach the true trap volume. The method of setting the correction amount σ is as described above. Specifically, if it is determined in step # 8 that | cfbave | <ε is satisfied (NO), the trap amount estimation completion flag xtraplrn is set to 1 in step # 12, and the process returns to step # 2. On the other hand, if it is determined in step # 8 that | cfbave | ≧ ε (YES), it is determined in step # 9 whether cfbave is 0 or less. Then, when it is determined that cfbave ≦ 0 (YES), the trap amount estimated value trap is increased by the correction amount σ (trap = trap + σ) in step # 10, and when it is determined that cfbave> 0 (NO). Reduces the trap amount estimated value trap by the correction amount σ in step # 11 (trap = trap−σ).
[0089]
If it is determined in step # 4 that the trap amount estimation condition is not satisfied (NO), the trap amount estimation prohibition counter ct is decremented by 1 in step # 13, and the trap amount estimation is prohibited. (Time) is counted (ct = ct-1), and the number-of-operations counter P is reset to 0 (P = 0).
[0090]
Next, at step # 14, it is determined whether or not the trap amount estimation prohibition counter ct is equal to or smaller than 0, that is, a predetermined time ct after the trap amount estimation is prohibited.₀Is determined, and if it is determined that ct ≦ 0 (YES), the predetermined time ct has already been reached.₀Has elapsed, the trap amount estimation completion flag xtraplrn is reset to 0 in step # 15, and thereafter, the process returns to step # 2. In this case, as described above, since the trap amount estimation value trap may deviate from the true trap amount, the trap amount estimation completion flag xtraplrn is reset. On the other hand, if it is determined in step # 14 that ct> 0 (NO), the ct is still ct.₀Does not elapse, the process skips step # 15 and returns to step # 2.
[0091]
FIG. 10 shows a case where the trap amount estimation routine is executed, and the purge execution flag xpg, the engine speed (a), the average feedback correction value cfbave (b), and the trap amount estimation when each routine described later is executed. Completion flag xtraplrn (c), idle purge execution flag xpgid (d), purge control valve drive duty dpg (e), trap amount trap (f), evaporative fuel release amount (l / s) prg (g), evaporative fuel release FIG. 4 is a term chart showing an example of changes over time of the amount (g / s) prg (h), the purge gas ratio cpg0 (i), and the actual pulse width ta (j), separately for running and idling.
[0092]
As apparent from FIG. 10, when the engine stalls, the trap amount estimation completion flag xtraplrn is reset, the idle purge execution flag xpgid is cleared to zero, and the drive duty dpg is set to zero. Then, the estimated value trap of the trap amount is held as it is at the previous value, and the feedback of the air-fuel ratio is started when the feedback condition is satisfied after the restart. The purge gas ratio cpg0 can be smoothed from the broken line to the solid line at the time of rising. Also, the shaded portion in the graph of the actual pulse width ta corresponds to the amount of decrease due to the purge.
[0093]
Incidentally, when the control unit CU has an air-fuel ratio learning function, it is preferable to estimate the trap amount after the air-fuel ratio learning is completed as described above. The advantage in the case of estimating the trap amount after the completion of the air-fuel ratio learning is as described above. Therefore, a preferred method of estimating the trap amount in the case where the air-fuel ratio learning function is provided will be described below with reference to FIGS. 2 and 3 according to the flowchart shown in FIG. In this routine, the air-fuel ratio learning is basically performed when a predetermined air-fuel ratio learning condition is satisfied at the time of idling, while the predetermined trap amount estimation is performed at the time of non-idling after the air-fuel ratio learning is completed. When the condition is satisfied, the trap amount is estimated.
[0094]
Specifically, as shown in FIG. 5, this routine is executed at a predetermined time period, first, initialization is performed in step # 21, and an initial value 0 is set to an air-fuel ratio learning completion flag xlrnnd. The air-fuel ratio learning completion flag xlrnd is a flag that is set to 1 when the air-fuel ratio learning is completed.
[0095]
Next, in step # 22, it is determined whether or not the idle determination flag xidle is 1. The idle determination flag xidle is a flag that is set to 1 when the engine CE is in an idle state, and is reset to 0 when the engine CE is in a non-idle state. If it is determined that xidle = 1 (YES), an idling routine for performing air-fuel ratio learning in steps # 23 to # 29 is executed, and xidle ≠ 1 (xidle = 0) (NO) ), A non-idle time routine for estimating the trap amount in steps # 30 to # 35 is executed.
[0096]
When executing the idling time routine, first, in step # 23 and step # 24, it is determined whether the air-fuel ratio feedback control execution flag xfb is 1 and the idling duration time counter tidl exceeds a predetermined value α. Is determined. Here, the air-fuel ratio feedback control execution flag xfb is set to 1 when the air-fuel ratio feedback control is being performed, and is reset to 0 when the feedback control is not being performed (at the time of open loop control). It is. The idle continuation time counter tidl is a counter for counting the elapsed time after the start of the idle operation at the time of idling. In this routine, if the idle operation continues for a predetermined period α or less during the feedback control of the air-fuel ratio during idling, it is considered that the engine CE has not reached a stable idle state. I try not to do it.
[0097]
Thus, if it is determined in step # 23 that xfb ≠ 1 (xfb = 0) (NO), or if it is determined in step # 24 that tidl ≦ α (NO), the air-fuel ratio learning is not performed. Then, the following steps # 25 to # 29 are skipped, and the process returns to skip # 22.
[0098]
On the other hand, if it is determined in step # 23 that xfb = 1 (YES) and if it is determined in step # 24 that tidl> α (YES), the air-fuel ratio learning execution counter Clrn is set to a predetermined value in step # 25. It is determined whether it is less than β. The air-fuel ratio learning execution counter Clrn is a counter for counting the number of times the air-fuel ratio learning has been performed after the start of the idling operation. Here, it is determined that the air-fuel ratio learning has been completed when the number of executions of the air-fuel ratio learning becomes equal to or more than the predetermined value β.
[0099]
Thus, if it is determined in step # 25 that Clrn <β (YES), the air-fuel ratio learning has not yet been completed, so the air-fuel ratio learning is continued in step # 26, and then the air-fuel ratio learning is performed in step # 27. The execution counter Clrn is incremented by one (Clrn = Clrn + 1), and then in step # 28, the idle duration counter tidl is incremented by one (tidl = tidl + 1), and thereafter, the process returns to step # 22. The air-fuel ratio learning is performed by an ordinary method such as changing the injection characteristic of the fuel injection valve 15 so that the feedback correction value cfb becomes a neutral value 0 on average when the air-fuel ratio deviation is 0.
[00100]
On the other hand, if it is determined in step # 25 that Clrn ≧ β (NO), the air-fuel ratio learning has been completed, and the air-fuel ratio learning completion flag xlrnnd is set in step # 29.
After that, the process returns to step # 22.
[0101]
When executing the non-idle time routine, the air-fuel ratio learning execution counter Clrn and the idle duration time counter tidl are first reset to 0 in step # 30. Then, it is determined in steps # 31 to # 34 whether or not the trap estimation condition is satisfied. Here, when all of the following four conditions are satisfied, it is determined that the trap amount estimation condition is satisfied. If any one of these conditions is not satisfied, the trap amount estimation condition is not satisfied. It is determined that there is.
(1) Canister purge has been performed
(2) Air-fuel ratio feedback control is being performed
(3) The amount of intake air per unit time is less than a predetermined value
(4) Air-fuel ratio learning has been completed
The reason for providing (1) to (3) among these four conditions is the same as in the case of the trap amount estimation routine shown in the flowchart of FIG. The reason why the trap amount is estimated after the air-fuel ratio learning is completed is that the accuracy of the trap amount estimation becomes extremely high after the air-fuel ratio learning is completed, as described above.
[0102]
Specifically, in four steps from step # 31 to step # 34, it is sequentially determined whether or not the purge execution flag xpg is 1, that is, whether or not the canister purge is being performed, and the air-fuel ratio feedback control is performed. It is determined whether or not the flag xfb is 1, that is, whether or not the air-fuel ratio feedback control is being performed, and whether or not the intake air amount qav per unit time is less than a predetermined value γ. It is determined whether or not the learning completion flag xlrnnd is 1, that is, whether or not the air-fuel ratio learning has been completed. Then, when it is determined that xpg = 1, xfb = 1, qav <γ, and xlrnnd = 1 (all of steps # 31 to # 34 are YES), that is, the trap amount estimation condition is Since it is established, the trap amount is estimated in step # 35, and thereafter, the process returns to step # 22. Note that a specific method of estimating the trap amount is based on a trap amount estimation routine shown in the flowchart of FIG.
[0103]
When it is determined that xpg = 0, xfb = 0, qav ≧ γ, or xlrnnd = 0 (any one of step # 31 to step # 34 is NO), Since the condition for estimating the trap amount is not satisfied, the process skips step # 35 and returns to step # 22.
[0104]
According to the trap amount estimating method shown in the flowchart of FIG. 5, since the trap amount is estimated after the air-fuel ratio learning is completed, the accuracy of estimating the trap amount is greatly increased.
[0105]
Hereinafter, a method of calculating the purge gas ratio (evaporated fuel release amount) and the net purge gas ratio (evaporated fuel inflow amount) by the control unit CU and the air-fuel ratio control will be described with reference to FIGS. The control method of (fuel injection amount control) will be specifically described.
[0106]
This routine includes steps # 41 to # 47. In step # 41, a purge control valve differential pressure dp is calculated based on the intake charging efficiency ce by searching the purge control valve differential pressure table table1. . Here, sipol (table1, ce) means dp corresponding to a certain ce in table1, which represents a predetermined functional relationship in which ce is an independent variable and dp is a dependent variable. The purge control valve differential pressure table table1 is a table showing a functional relationship between the intake charging efficiency ce and the purge control valve differential pressure dp. The reason why the pressure difference dp before and after the purge control valve can be calculated based on the intake charging efficiency ce is as described above. It should be noted that the pressure difference dp before and after the purge control valve is determined not by such a table search but by a function f representing the relationship between ce and dp.₁(Dp = f)₁(Ce)).
[0107]
Next, in step # 42, the purge air amount qpg is calculated based on the purge control valve differential pressure dp and the drive duty ratio dpg applied to the purge control valve 29 by searching the purge air amount map map1. Here, map (map1, dpg, dp) means qpg corresponding to a certain dpg and dp in map1, which represents a predetermined functional relationship in which dpg and dp are independent variables and qpg is a dependent variable. The purge air amount map1 is a map showing a functional relationship among the drive duty ratio dpg, the differential pressure dp before and after the purge control valve, and the purge air amount qpg. The reason why the purge air amount qpg can be calculated based on the drive duty ratio dpg and the purge control valve differential pressure dp is as described above. It should be noted that the purge air amount qpg is determined not by such a map search but by a function f representing the interrelation of dpg, dp and qpg.₂The calculation may be performed directly using (dpg, dp) (qpg = f₂(Dpg, dp)).
[0108]
Next, in step # 43, the evaporative fuel release amount gpg is calculated based on the purge air amount qpg and the trap amount trap by searching the evaporative fuel release amount map map2. Here, map (map2, qpg, trap) means a gpg corresponding to a certain qpg and trap in map2 that represents a predetermined functional relationship in which qpg and trap are independent variables and gpg is a dependent variable. The purge air amount map2 is a map showing a functional relationship among the purge air amount qpg, the trap amount trap, and the evaporated fuel release amount gpg.
[0109]
FIG. 11 shows an example of the dependence characteristic on the evaporated fuel release amount gpg, the purge air amount qpg, and the trap amount trap. The evaporative fuel release amount map map3 is obtained by mapping a functional relationship as shown in FIG. 11, for example. It is to be noted that the evaporated fuel emission amount gpg is not obtained by such a map search, but by a function f representing the interrelationship between qpg, trap and gpg.₃The calculation may be performed directly using (gpg, trap) (gpg = f₃(Gpg, trap)).
[0110]
Next, in step # 44, the purge gas ratio cpgo is calculated by the following equation (2).
cpgo = Ys ｛120 / (γ₀・ Vc)｝ ・ (gpg / ne) ... Equation 2
cpgo: purge gas ratio
Ys: conversion coefficient for converting the intake air amount into the fuel injection amount
γ₀:density
Vc: Effective cylinder volume
gpg: Evaporated fuel release amount
ne: engine speed [r. p. m. ]
In Equation 2, 120 / (γ₀Vc · ne) is the reciprocal of the amount of intake air (mass flow rate) into the combustion chamber 4 per unit time (second), and thus Ys · 120 / (γ) obtained by multiplying this by the conversion coefficient Ys.₀Vc · ne) is the reciprocal of the required fuel injection amount per unit time. Accordingly, the purge gas ratio cpgo is a value obtained by dividing the amount of fuel vapor release by the required fuel injection amount, that is, the ratio of the amount of fuel vapor release to the total fuel flow rate.
[0111]
Next, in step # 45, the net purge gas ratio cpg is calculated by the following equation (3).
cpg = λ · cpg + (1−λ) · cpgo Equation 3
cpg: net purge gas ratio
λ: primary filter coefficient (0 <λ <1)
cpgo: purge gas ratio
Equation 3 is a model equation representing the transport delay characteristic of the evaporated fuel transport path. By preferably setting the primary filter coefficient λ according to the shapes of the intake system 10, the AMI 16 and the purge passage 28 of the engine CE, it is possible to accurately calculate the net purge gas ratio cpg (evaporated fuel inflow amount) using Expression 3. it can.
[0112]
Next, at step # 46, the actual pulse width ta (actual fuel injection amount), that is, the fuel injection amount to be actually injected from the fuel injection valve 15 is expressed by the following equation 4.
ta = K · (ce · total−cpg) ··············· Equation 4
ta: actual pulse width
K: Conversion factor
ce: intake charging efficiency
ctotal: correction coefficient
In Expression 4, K · ce · total corresponds to a required pulse width (required fuel injection amount), that is, a fuel amount actually required in the combustion chamber 4. K · cpg is a value obtained by converting the amount of fuel supplied by purging into an injection pulse width. Therefore, in Expression 4, the injection pulse width corresponding to the amount of fuel to be actually injected from the fuel injection valve 15 (actual fuel injection amount), that is, the actual pulse width ta is calculated.
[0113]
Then, in step # 47, fuel is injected from the fuel injection valve 15 with the actual pulse width ta calculated in step # 46, and thereafter, the flow returns to step # 41.
[0114]
By doing so, the required amount of fuel is accurately supplied to the combustion chamber 4 according to the operation state even when the canister purge is performed, and the air-fuel ratio control (fuel injection amount control) is performed. The control accuracy is improved, and the actual air-fuel ratio is maintained at the target value. In this case, a process for determining the required fuel injection amount according to the operating state is performed.WhatThat is, the air-fuel ratio control itself is feedback control, but the process of subtracting the evaporated fuel inflow amount from the required fuel injection amount to eliminate the influence of the canister purge is feedforward control. Therefore, the calculation of the net purge gas ratio or the evaporated fuel inflow amount does not involve a time lag. Therefore, there is no deviation of the actual air-fuel ratio from the target value due to the canister purge.
[0115]
FIG. 12 shows the time when such control is performed.taThe drive duty ratio dpg when the canister purge is started in (H₁), Purge gas ratio cpgo (Graph H)₂), Net purge gas ratio cpg (Graph H)₃) And the actual pulse width ta (graph H₄4) shows an example of the change characteristic with respect to time.
[0116]
In the engine CE of this embodiment, the amount of trapped fuel is estimated in this way, the amount of fuel vapor inflow (net purge gas ratio) is accurately calculated based on the amount of trap, and the amount of fuel vapor inflow is calculated from the required fuel injection amount. Since the actual fuel injection amount is set by subtracting, the evaporated fuel flowing into the intake system 10 or the combustion chamber 4 due to the canister purge does not become a disturbance in the feedback control of the air-fuel ratio. For this reason, when the estimation of the trap amount is completed, the deviation of the air-fuel ratio from the target value does not occur depending on the canister purge. However, when the estimation of the trap amount is not completed, that is, when the trap amount estimation completion flag xtraplrn is 0, the net purge gas ratio or the inflow amount of the evaporated fuel is not accurately grasped. Therefore, when the estimation of the trap amount is not completed, it is preferable to regulate the canister purge.
[0117]
For example, the following can be considered as a specific method of regulating the canister purge.
[0118]
That is, the canister purge may be prohibited or the purge speed (purge air amount) may be reduced until the estimation of the trap amount is completed. When prohibiting canister purging, the prohibition may be performed only during idle time.
[0119]
When the purge control valve 29 changes from the closed state to the open state and the canister purge is started, the drive duty ratio of the purge control valve 29 is set to prevent a sudden change in the fuel supply characteristic to the combustion chamber 4. It is preferable that the (purge air amount) be gradually increased, instead of being increased all at once to a target drive duty ratio set according to the operating state. In the case where the drive duty ratio is gradually increased until the target drive duty ratio is reached, when the estimation of the trap amount is not completed, the increasing speed of the drive duty ratio at the start of the canister purge is reduced. Is preferred. That is, when the estimation of the trap amount is completed, the increasing speed of the driving duty ratio is increased, and when the estimation of the trap amount is not completed, the increasing speed of the driving duty ratio is decreased.
[0120]
Hereinafter, a method of controlling the increasing speed of the driving duty ratio when the driving duty ratio is gradually increased at the start of the canister purge will be described with reference to FIGS. 2 and 3 as appropriate according to the flowchart shown in FIG.
[0121]
In this control routine, it is first determined in step # 51 whether or not the canister purge is being executed. If the canister purge is not being executed (NO), the purge correction value cmod is set to 0 in step # 52, and thereafter, in step # 51 Return to. The purge correction value cmod is a correction value from 0 to 1 for correcting a target drive duty ratio set according to the operating state of the engine CE when the canister purge is started. And the purge correction value cmod becomes the drive duty ratio dpg actually applied to the purge control valve 29. The purge correction value cmod is set to 0 before the start of the canister purge, and is gradually increased by the increment SP after the start of the canister purge, so that the purge air amount is gradually increased. After the purge correction value cmod reaches 1, it is kept at 1. When the purge correction value cmod is 0, the canister purge is stopped regardless of the value of the target drive duty ratio. When the purge correction value cmod is 1, the target drive duty ratio is applied to the purge control valve 29 as it is. Will be.
[0122]
On the other hand, when it is determined in step # 51 that the canister purging is being performed (YES), it is determined whether the purge correction value cmmod is 1 in step # 53. If it is determined that cmod ≠ 1 (that is, cmod <1) (NO), it is determined that the purge correction value cmod is to be gradually increased after the start of the canister purge, and thus, steps # 54 to # 54 are performed. In # 57, the purge correction value cmod is gradually increased in consideration of whether or not the estimation of the trap amount has been completed.
[0123]
Specifically, in step # 54, it is determined whether or not the trap amount estimation completion flag xtraplrn is 1, that is, whether or not the trap amount estimation has been completed. If it is determined that xtraplrn = 1 (YES), the increment SP is set to a relatively large value KM1 in step # 55, and thereafter, the process proceeds to step # 57. In this case, since the estimation of the trap amount has been completed, the net purge gas ratio or the evaporated fuel inflow amount can be accurately calculated. Therefore, the influence of the canister purge can be reliably compensated for by the feedforward control. That is, even if the canister purge is started to some extent suddenly, the effect is sufficiently compensated and the air-fuel ratio control is not disturbed. Therefore, by increasing the increment SP, that is, by increasing the increasing speed of the purge correction value cmod, the canister purge is performed at an early target drive duty ratio. In this case, the change characteristic of the drive duty ratio dpg actually applied to the purge control valve 29 with respect to time is, for example, a graph L in FIG.₁become that way. In FIG. 13, a graph L₁, L₂The portion where is parallel to the time axis represents the target drive duty ratio.
[0124]
If it is determined in step # 54 that xtraplrn ≠ 1 (xtraplrn = 0) (NO), the increment SP is set to a relatively small value KM2 (KM2 <KM1) in step # 56, and thereafter, the process proceeds to step # 57. . In this case, since the estimation of the trap amount has not been completed, the net purge gas ratio or the evaporated fuel inflow amount cannot be accurately calculated. Therefore, since the feed forward function does not work sufficiently, if the canister purge is started abruptly, the effect is not sufficiently compensated and the air-fuel ratio control is disturbed. Therefore, the increment SP is reduced, that is, the increasing speed of the purge correction value cmod is reduced. In this case, the change characteristic of the drive duty ratio dpg actually applied to the purge control valve 29 with respect to time is, for example, a graph L in FIG.₂become that way.
[0125]
In step # 57, the current purge correction value cmod is calculated by adding SP to the previous purge correction value cmod. If the current purge correction value cmod exceeds 1, as a result of the addition, the purge correction value cmod is kept at 1. Here, addclip (cmod, SP, 1) represents an arithmetic process in which SP is added to cmod, but the upper limit value is set to 1. Thus, the purge correction value cmod is gradually increased.
[0126]
Next, in step # 58, the drive duty ratio dpg to be actually applied to the purge control valve 29 is calculated by the following equation 5, and thereafter, the flow returns to step # 51.
dpg = cmod · smap (map3, ne, ce) Equation 5
dpg: drive duty ratio
cmod: purge correction value
smap (map3, ne, ce): target drive duty ratio
ne: engine speed
ce: intake charging efficiency
In Equation 5, smap (map3, ne, ce) means dpg corresponding to a certain ne and ce in a duty ratio map3 representing a predetermined functional relationship in which ne and ce are independent variables and dpg is a dependent variable. The duty ratio map3 is a map representing a functional relationship among the engine speed ne, the intake charging efficiency ce, and the drive duty ratio dpg.
[0127]
In this manner, when the canister purge is started, the drive duty ratio dpg, that is, the purge air amount is gradually increased.
[0128]
If it is determined in step # 53 that cmod = 1 (YES), it is determined that cmod has already reached 1 after the start of the canister purge, and thus steps # 54 to # 57 are skipped. In step # 58, the drive duty ratio dpg is calculated by setting the purge correction value cmod to 1. Then, the process returns to step # 51.
[0129]
Hereinafter, the control method of the canister purge at the time of idling will be described with reference to FIGS. 2 and 3 as appropriate according to the flowchart shown in FIG.
[0130]
In this control routine, first, in step # 61, various signals such as a throttle opening, an intake air amount, an engine speed, a water temperature, an idle signal, and an atmospheric pressure are read. Then, in step # 62, it is determined whether the air-fuel ratio feedback execution condition is satisfied. Here, the operating state of the engine CE is within a predetermined feedback range, and the water temperature is, for example, 40 ° C. or higher.₂When the temperature is equal to or higher than the activation temperature of the sensor 9, it is determined that the air-fuel ratio feedback execution condition is satisfied.
[0131]
If the air-fuel ratio feedback execution condition is satisfied, it is checked in step # 63 whether the water temperature is equal to or higher than the canister purge execution condition, for example, 50 ° C. If the water temperature is equal to or higher than 50 ° C., for example, it is determined that the engine is idling at step # 64 because purging may be performed, and when it is determined that the engine is idling (YES). Determines in step # 65 to step # 67 whether or not the canister purge condition during idling is satisfied. Here, when air-fuel ratio learning is completed, trap amount estimation (learning) is completed, and the atmospheric pressure is equal to or lower than the atmospheric pressure at an altitude of 1000 m, the canister purge is executed (idle purge). In other cases, the canister purge is prohibited (purge cut).
[0132]
In this embodiment, as described above, at the time of canister purging, the average feedback correction value cfbave is calculated by averaging the feedback correction value cfb of the air-fuel ratio control, and indirectly based on the average feedback correction value cfbave. The trap amount is estimated, the evaporative fuel inflow amount is calculated based on the trap amount estimation value, and the actual fuel injection amount is set by subtracting the evaporative fuel inflow amount from the required fuel injection amount. That is, the influence of the canister purge on the air-fuel ratio control is compensated by the feedforward control. Specifically, an evaporative fuel release amount is calculated based on the trap amount estimation value, and an evaporative fuel inflow amount is calculated based on the evaporative fuel release amount. The fuel injection valve 15 is operated by calculating the injection pulse width, that is, the purge pulse width corresponding to the evaporated fuel inflow amount, and correcting the required fuel injection amount (pulse width) with the purge width. The deviation of the actual air-fuel ratio from the target value due to the above is prevented. At this time, a purge control valve differential pressure is calculated based on the intake charging efficiency, a purge air amount is calculated based on the purge control valve differential pressure and the purge control valve opening, and the calculated purge air amount and The amount of evaporative fuel release is calculated based on the estimated trap amount. By doing so, the actual air-fuel ratio does not deviate from the target value due to the canister purge, and the purge can be sufficiently performed even at idle. However, when performing the idle purge in this manner, there is a problem that when the vehicle equipped with the engine CE is operated at a high altitude, an engine stall occurs due to the idle purge. That is, at high altitudes, the atmospheric pressure decreases and the intake density decreases, so that idle stability deteriorates. For this reason, the output is normally secured by density correction by ISC (idle speed control). However, if a load such as an air conditioner is input as a disturbance during idling at such a high altitude, the density correction is performed even for such load input. Cannot be properly matched, and idle stability deteriorates during a transient, causing engine stall. In the purge control, the purge air amount is calculated based on the pressure difference between the purge control valve and the purge control valve opening, and the evaporative fuel release amount is calculated based on the purge air amount and the estimated trap amount. However, when the atmospheric pressure decreases at a high altitude, the pressure difference across the purge control valve decreases, and the control accuracy deteriorates. In particular, the purge passage 28 is connected to the mixing chamber 21 of the AMI 16. In this case, when the atmospheric pressure changes, the state of the air flowing on the AMI 16 side also changes, which affects the differential pressure across the purge control valve. Therefore, the decrease in the atmospheric pressure does not linearly reflect the differential pressure, and therefore, It is difficult to cope with such a change in the atmospheric pressure by setting, and a deviation occurs in the air-fuel ratio. Therefore, idle purging is prohibited under the atmospheric pressure corresponding to a high altitude of 1000 m or higher.
[0133]
Specifically, it is determined in step # 65 whether or not the air-fuel ratio learning has been completed. In step # 66, it is determined whether or not the estimation of the trap amount has been completed. It is determined whether the atmospheric pressure is as follows. If all these are YES, a canister purge (idle purge) is executed in step # 68. If any of steps # 65 to # 67 is NO, purge cut is performed in step # 70.
[0134]
If it is determined in step # 64 that the vehicle is not idling, it means that the engine is off-idle and the purge execution conditions are satisfied in steps # 62 and # 63. Perform a purge of
[0135]
In addition, when either step # 62 or step # 63 is NO and the purge execution condition is not satisfied, the purge cut is performed in step # 70.
[0136]
By doing so, the canister purge can be performed without causing disturbance in the air-fuel ratio control, that is, without causing a deviation from the target value of the air-fuel ratio even during idling, and the idle stability can be improved. It is possible to prevent engine stalling due to idle purging in a deteriorating highland.
[0137]
In the above-described embodiment, the purging is prohibited or limited when the erroneous learning of the trap amount is detected in the idle state. May be performed even in the low load region.
[0138]
【The invention's effect】
According to the first aspect of the present invention, the amount of trapped fuel vapor (trap amount) is estimated based on the feedback correction value during the execution of the purge, and the fuel vapor to the engine is estimated based on the estimated value of the trapped fuel vapor amount. When the inflow amount is calculated and the required fuel supply amount is reduced by a reduction value corresponding to the calculated evaporative fuel inflow amount, when the erroneous estimation of the evaporative fuel trapping amount is detected, the purge of the evaporative fuel is limited. As a result, it is possible to suppress the deviation of the air-fuel ratio due to the fact that the purge amount actually sucked as a result of the erroneous estimation does not correspond to the fuel reduction value.
[0139]
Also,Claim 1According to the invention, the erroneous estimation of the trap amount can be indirectly detected by the engine stall.
[0140]
Also,Claim 2According to the invention, the erroneous estimation of the trap amount can be accurately detected by detecting the engine stall during the execution of the purge.
[0141]
Also,Claim 3According to the present invention, it is possible to suppress the deviation of the air-fuel ratio in a low load region in which the erroneous estimation of the trap amount greatly affects the combustibility.
[0142]
Also,Claim 4According to the invention, by limiting the purge when an erroneous estimation is detected during idling, it is possible to prevent the deterioration of combustion stability, and particularly to prevent engine stall due to the influence of the erroneous estimation at high altitude.
[0143]
Also,Claim 5According to the invention, the trap amount is estimated in the off-idle state, and the purge at the time of idling is performed after the estimation of the trap amount is completed. Even in this state, the estimation of the trap amount itself can be performed in a high load region where the influence of the erroneous estimation is small, and the process can smoothly return to the idle purge.
[0144]
Also,Claim 6According to the invention, when the engine stalls, the purge of the evaporated fuel is restricted, so that the possibility of the engine stall occurring can be reduced.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of the present invention.
FIG. 2 is a system diagram of an engine including an evaporative fuel processing apparatus according to one embodiment of the present invention.
FIG. 3 is a functional block diagram of a control unit according to an embodiment of the present invention.
FIG. 4 is a flowchart illustrating a method for estimating a trap amount according to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating a method of estimating a trap amount when performing air-fuel ratio learning according to an embodiment of the present invention.
FIG. 6 is a flowchart showing a method of calculating an evaporative fuel inflow amount and a method of setting an actual fuel injection amount (air-fuel ratio control) in one embodiment of the present invention.
FIG. 7 is a flowchart showing a method of setting a purge speed at the start of canister purging in one embodiment of the present invention.
FIG. 8 is a flowchart showing a method of executing a canister purge at the time of idling in one embodiment of the present invention.
FIG. 9 is a diagram showing a relationship between an average feedback correction value and a trap amount according to one embodiment of the present invention.
FIG. 10 is a diagram showing an example of a temporal change of various control amounts at the time of running and at the time of idling according to one embodiment of the present invention.
FIG. 11 is a graph showing the dependence of the amount of evaporative fuel release on the purge air amount and the trap amount according to one embodiment of the present invention.
FIG. 12 is a diagram showing an example of a temporal change of a drive duty ratio, a purge gas ratio, a net purge gas ratio, and an actual pulse width according to an embodiment of the present invention.
FIG. 13 is a diagram showing an example of a temporal change of a drive duty ratio at the start of canister purging according to one embodiment of the present invention.
[Explanation of symbols]
CE: Engine
CU: Control unit
4: Combustion chamber
9: Linear O₂Sensor
10: Intake system
15: Fuel injection valve
25: Canister
29: Purge control valve

Claims (6)

Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of the engine; and a feedback correction value for setting a feedback correction value based on a deviation of the air-fuel ratio detected by the air-fuel ratio detection means from a target value. Setting means; air-fuel ratio control means for controlling an air-fuel ratio based on the feedback correction value set by the feedback correction value setting means; evaporative fuel collecting means for collecting evaporative fuel generated from a fuel tank; An evaporative fuel purging means for purging evaporative fuel from the evaporative fuel collecting means and supplying the evaporative fuel to an intake system in an operation region, and a feedback correction value set by the feedback correction value setting means during execution of purging by the evaporative fuel purge means. Evaporative fuel collection amount estimating the evaporative fuel collection amount by the evaporative fuel collection means based on the Stage, evaporative fuel inflow calculating means for calculating an evaporative fuel inflow actually sucked into the engine based on the evaporative fuel trapping amount estimated by the evaporative fuel trapping amount estimating means, and the evaporative fuel inflow An evaporative fuel processing apparatus for an engine, comprising: a fuel supply amount reducing unit configured to reduce a reduction amount according to an evaporative fuel inflow amount calculated by a calculation unit from a required fuel supply amount for obtaining the target value of the air-fuel ratio. An erroneous estimation detecting means for detecting a state in which the estimation of the amount of evaporative fuel trapped by the evaporative fuel collecting means is erroneous estimation; and an stalling detecting means for detecting an engine stall. and erroneous estimation detection means for determining an erroneous estimated state of the fuel vapor collection amount when it is, before when the state in which the estimation of the vaporized fuel trapped amount becomes erroneous estimation has been detected by said error estimated detection means Evaporative fuel processing system for an engine, characterized in that a purge limitation means for limiting the purge of the evaporative fuel by the evaporated fuel purge means. 2. The evaporative fuel processing device for an engine according to claim 1 , wherein the engine stall detecting means detects an engine stall during execution of the purge by the fuel vapor purging means. Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of the engine; and a feedback correction value for setting a feedback correction value based on a deviation of the air-fuel ratio detected by the air-fuel ratio detection means from a target value. a setting unit, and the air-fuel ratio control means for controlling the air-fuel ratio based on the set feedback correction value by the feedback correction value setting means, and fuel vapor collection means for collecting fuel vapor generated from a fuel tank An evaporative fuel purging means for purging evaporative fuel from the evaporative fuel collecting means and supplying the evaporative fuel to an intake system in a predetermined operation region; and a feedback correction value set by the feedback correction value setting means during purging by the evaporative fuel purge means. Evaporative fuel collection amount estimating the evaporative fuel collection amount by the evaporative fuel collecting means based on the value An evaporative fuel inflow calculating means for calculating an evaporative fuel inflow actually sucked into the engine based on the evaporative fuel trapped amount estimated by the evaporative fuel trapped amount estimating means; and An evaporative fuel processing apparatus for an engine, comprising: a fuel supply amount reducing unit configured to reduce a reduction value according to an evaporative fuel inflow amount calculated by an arithmetic unit from a required fuel supply amount for obtaining the target value of the air-fuel ratio. Erroneous estimation detection means for detecting a state in which the estimation of the amount of evaporative fuel collected by the evaporative fuel collection means is erroneous estimation, and estimation of the amount of evaporative fuel collection by the erroneous estimation detection means in a predetermined low load region of the engine. An evaporative fuel processing device for an engine, further comprising a purge restricting means for restricting purging of the fuel vapor by the fuel vapor purging means when a state in which the fuel gas is erroneously estimated is detected. 4. The apparatus according to claim 3 , wherein the predetermined low load region is an idle state. Air-fuel ratio detection means for detecting the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of the engine; and a feedback correction value for setting a feedback correction value based on a deviation of the air-fuel ratio detected by the air-fuel ratio detection means from a target value. Setting means; air-fuel ratio control means for controlling an air-fuel ratio based on the feedback correction value set by the feedback correction value setting means; evaporative fuel collecting means for collecting evaporative fuel generated from a fuel tank; An evaporative fuel purging means for purging evaporative fuel from the evaporative fuel collecting means and supplying the evaporative fuel to an intake system in an operation region, and a feedback correction value set by the feedback correction value setting means during execution of purging by the evaporative fuel purge means. Evaporative fuel collecting amount estimating the evaporative fuel collecting amount by the evaporative fuel collecting means on the basis of Stage, evaporative fuel inflow calculating means for calculating an evaporative fuel inflow actually sucked into the engine based on the evaporative fuel trapping amount estimated by the evaporative fuel trapping amount estimating means, and the evaporative fuel inflow An evaporative fuel processing apparatus for an engine, comprising: a fuel supply amount reducing unit configured to reduce a reduction amount according to an evaporative fuel inflow amount calculated by a calculation unit from a required fuel supply amount for obtaining the target value of the air-fuel ratio. Erroneous estimation detecting means for detecting a state in which the estimation of the amount of evaporative fuel collected by the evaporative fuel collecting means is erroneous estimation; when it is detected includes a purge limitation means for limiting the purge of the evaporative fuel by the evaporated fuel purge unit, the fuel vapor trapped amount estimation means is vaporized during the purge execution in the operating region other than the idling Is intended to estimate a fee collection amount, the fuel vapor purge means, it is the time of idling and executes the purge after the estimation of the fuel vapor trapped amount by the evaporative fuel trapped amount estimation means is completed An evaporative fuel processing device for an engine, comprising: Evaporated fuel collecting means for collecting the evaporated fuel generated from the fuel tank, and evaporated fuel purging means for purging the evaporated fuel from the evaporated fuel collecting means and supplying the fuel to the intake system in a predetermined operation region including an idling time. In the evaporative fuel processing apparatus for an engine, an engine stall detecting means for detecting engine stall, and a purge restricting means for restricting purging of fuel vapor by the fuel vapor purging means when the engine stall is detected by the engine stall detecting means are provided. Evaporative fuel processing device for an engine.

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