JPH09126066A - Evaporated fuel treating device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of controllability of the air fuel ratio while the purge capacity of a large amount of mixture of the evaporated fuel is secured. SOLUTION: The low purge map of relatively low purge ratio with throttled purge volume between the two maps containing the opening (duty ratio) of a CPC valve for each operation range by a purge ratio switching part 52 so that the controllability of the air fuel ratio can be secured even under the condition of high concentration immediately after the purge is started. When the set time is elapsed, controllability of the air fuel ratio is secured in the normal evaporation concentration after the fuel vapor of high concentration is purged, and at the same time, the high ratio purge map in which the purge ratio capable of a large amount of purge is relatively high is selected to switch the purge ratio is switched, and a large amount of purge is realized while the over-rich of the air fuel ratio due to the high concentration of evaporation immediately after the purge is started is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel processing apparatus for an engine, which prevents fluctuations in an air-fuel ratio when purging evaporated fuel generated in a fuel tank.

[0002]

2. Description of the Related Art Generally, in vehicles such as automobiles, in order to prevent the vaporized gas of fuel generated in a fuel tank from being discharged to the atmosphere, the vaporized fuel gas is temporarily adsorbed on activated carbon in a canister or the like. A so-called evaporative purge system is provided for storing and sucking the evaporated fuel gas in the canister from the intake passage into the combustion chamber of the engine under set operating conditions.

In this evaporative purge system, for example, as disclosed in Japanese Patent Laid-Open No. 63-85249, the purge control valve provided in the purge passage between the canister and the intake passage is controlled to control the purge amount. When the purge is executed, the fuel injection amount is corrected and controlled by the output from the air-fuel ratio sensor provided in the exhaust system, and the deviation of the air-fuel ratio from the target air-fuel ratio is corrected.

[0004]

By the way, in recent years, with the stricter regulation of the emission of vaporized fuel to the atmosphere, the purge rate, which is the flow rate ratio of the intake air amount sucked into the engine and the vaporized fuel mixture, is changed to the air-fuel ratio. There is an increasing need to set the value as large as possible within the range where the control followability by the feedback control is secured and to perform a large amount of purge.

However, regardless of the filling state of the canister, when a large amount of purge is suddenly started, when the adsorbed amount of evaporated fuel in the canister is large, overrich of the air-fuel ratio occurs at the initial stage of purging, and conversely, the evaporated fuel in the canister is contaminated. When the adsorbed amount is small, over lean of the air-fuel ratio occurs at the initial stage of purging, so that it becomes difficult to realize the air-fuel ratio control to stoichio, and the controllability may be significantly deteriorated.

The present invention has been made in view of the above circumstances, and while ensuring the purging ability for a large amount of evaporated fuel mixture,
An object of the present invention is to provide an evaporated fuel processing device for an engine, which can prevent deterioration of air-fuel ratio controllability.

[0007]

According to the first aspect of the present invention,
In an evaporative fuel treatment apparatus for an engine, which purges an evaporative fuel mixture through a purge passage that communicates a canister that stores evaporative fuel from a fuel tank with an intake system, the evaporative fuel mixture is purged at a high concentration. A purge control means for switching to a purge at a purge rate higher than the above-mentioned purge rate when the purge rate corresponding to the mixture concentration is started and the elapsed time after the start of the purge reaches a set time To do.

According to a second aspect of the present invention, there is provided an evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage that connects a canister that stores evaporative fuel from a fuel tank and an intake system. When the purge of the air-fuel mixture is started at the purge rate that corresponds to the high-concentration evaporated fuel-air mixture concentration, and when the integrated value of the intake air amount after the start of purge reaches the set value, the purge rate higher than the above-mentioned purge rate It is characterized in that it is provided with a purge control means for switching to the purge.

According to a third aspect of the present invention, there is provided an evaporated fuel treatment apparatus for an engine, wherein an evaporated fuel mixture is purged through a purge passage that connects a canister for storing evaporated fuel from a fuel tank and an intake system. The purging of the air-fuel mixture is started at the purge rate corresponding to the high concentration of the evaporative fuel mixture, and the evaporative fuel mixture concentration calculated based on the smoothed value of the air-fuel ratio feedback correction coefficient after the start of the purge is the set value. When the above-mentioned purge rate is reached, purge control means for switching to purge at a purge rate higher than the above-mentioned purge rate is provided.

According to a fourth aspect of the present invention, there is provided an evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage that connects a canister that stores evaporative fuel from a fuel tank and an intake system. Purge control means for starting the purge of the air-fuel mixture at a purge rate corresponding to the concentration of the high-concentration evaporated fuel mixture, and then switching to the purge at a higher purge rate than the above-mentioned purge rate based on the concentration of the evaporative fuel mixture. And a fuel injection control means for correcting the fuel injection amount based on the vaporized fuel mixture concentration and the purge rate for each operation region when the purge control means performs the purge.

According to a fifth aspect of the present invention, there is provided an evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage that connects a canister that stores evaporative fuel from a fuel tank and an intake system. The purge of the air-fuel mixture is started at a purge rate corresponding to the concentration of the high-concentration evaporative fuel mixture, and after the purge is started, the evaporative-fuel mixture concentration is purged based on the smoothed value of the air-fuel ratio feedback correction coefficient. When it is determined that the concentration is lower than the concentration corresponding to the purge rate, a purge control means for switching to purge at a purge rate lower than the purge rate is provided.

That is, according to the first and second aspects of the invention,
At the time of purging the vaporized fuel mixture, the purge is started at a purge rate corresponding to the concentration of the vaporized fuel mixture having a high concentration immediately after the start of the purge. When it is determined that the air concentration has become a normal state, the purge is switched to a purge at a higher rate, and in the invention according to claim 2, the concentration of the evaporated fuel mixture is determined from the integrated value of the intake air amount after the start of the purge. When it is determined that the normal state has been reached, the purge is switched to a purge at a higher rate.

According to the third aspect of the invention, the purge is started at the purge rate corresponding to the high concentration of the evaporated fuel mixture immediately after the purge is started, and then the air-fuel ratio feedback correction coefficient is based on the smoothed value. In the state where it is determined that the concentration of the evaporated fuel mixture calculated by the above is in the normal state, the purge is switched to the purge at a higher ratio. Further, at that time, in the invention described in claim 4, the fuel injection amount is corrected based on the concentration of the evaporated fuel mixture and the purge rate for each operation region.

On the other hand, according to the fifth aspect of the present invention, after the purge is started at the purge rate corresponding to the high concentration of the evaporated fuel mixture, the purge is started at the start of the purge based on the smoothed value of the air-fuel ratio feedback correction coefficient. If it is determined that the concentration is lower than the vaporized fuel mixture concentration corresponding to the purge rate of, the purge rate is switched to a lower rate.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention.
1 is a block diagram showing a functional configuration relating to the evaporative purge control, FIG. 2 is a flowchart of a purge control routine, FIG. 3 is a schematic configuration diagram of an engine control system, and FIG. 4 is a circuit configuration diagram of an electronic control system. .

In FIG. 3, reference numeral 1 is an engine,
An intake passage 3 communicates with each intake port 2a formed in the cylinder head 2 of the engine 1. A throttle valve 4 is interposed in the intake passage 3, and a throttle opening sensor 6 for detecting a throttle opening is connected to the throttle valve 4. An intake air amount sensor 7 is interposed on the upstream side of the throttle valve 4 in the intake passage 3, and an air cleaner 8 is attached upstream of the intake air amount sensor 7.

An unillustrated spark plug whose tip is exposed to the combustion chamber is attached to the cylinder head 2 for each cylinder, and an injector 9 is exposed immediately upstream of each intake port 2a of each cylinder. . This injector 9
The fuel tank 10 is in communication with a fuel tank 10 via a fuel pipe (not shown), and is configured to inject fuel adjusted to a specified pressure into the intake port 2a.

A discharge passage 11 for discharging the evaporated fuel generated in the fuel tank 10 extends from the upper portion of the fuel tank 10 and communicates with an upper portion of a canister 12 having an adsorption portion made of activated carbon or the like. Has been done. The canister 12 is provided with a fresh air introduction port communicating with the atmosphere at a lower portion thereof, and a purge passage 13 for introducing a mixture of fresh air from the fresh air introduction port and the evaporated fuel gas stored in the adsorption section.
Is extended from the top.

The purge passage 13 communicates with the intake passage 3 on the downstream side of the throttle valve 4, and in the middle thereof, a canister as a purge control valve for controlling the flow rate (purge flow rate) of the evaporated fuel mixture. A purge control valve (CPC valve) 14 is installed.
The CPC valve 14 is a duty solenoid valve whose valve opening is proportionally controlled according to the duty ratio of a drive pulse signal output from an electronic control unit 30 described later. In the present embodiment, the duty ratio is 0%. That is, when the drive pulse signal is OFF, it is fully closed and the duty ratio is 100%.
That is, it is fully opened by continuous energization.

A water temperature sensor 19 is provided in a cooling water passage 18 formed in the cylinder block 1a of the engine body 1.
Further, an O2 sensor 21 is exposed to an exhaust passage 20 communicating with the exhaust port 2b of the cylinder head 2, and a catalytic converter 2 is provided downstream of the O2 sensor 21.
2 are interposed.

On the other hand, in FIG. 4, reference numeral 30 is an electronic control unit (ECU), and this ECU 30 is a CPU 3
1. A microcomputer in which a ROM 32, a RAM 33, an input port 34, and an output port 35 are connected to each other via a bus line 36, and peripheral circuits thereof. The throttle opening sensor 6, the intake air amount sensor 7,
Signals from sensors such as the water temperature sensor 19, the O2 sensor 21, and the crank angle sensor 23 for detecting a crank angle are processed, and the injector 9 and the CPC valve 1 are processed.
A control signal is output to actuators such as 4.

The O 2 sensor 21 and the crank angle sensor 23 are connected to the input port 34 via waveform shaping circuits 37 and 38, respectively, and the throttle opening sensor 6, the intake air amount sensor 7, and the intake air amount sensor 7, respectively. Water temperature sensor 1
9 are connected via A / D converters 39, 40 and 41, respectively. The injector 9 and the CPC valve 14 are connected to the output port 35 via drive circuits 45 and 46, respectively.

A control program and various fixed data for control are stored in the ROM 32, and output signals of the sensors and switches after data processing are performed in the RAM 33 and calculations by the CPU 31. The processed data is stored. In the CPU 31, the R
In accordance with a control program stored in the OM 32, fuel injection control, ignition timing control, purge control of evaporated fuel mixture (hereinafter abbreviated as "evaporation"), etc. are executed.

Here, in the evaporative purge control, when performing a large amount of purging, the purge rate, which is the mixing ratio of the evaporative purge amount to the intake air amount of the engine, is set as much as possible within the range where stable air-fuel ratio feedback control is possible. It is desirable to increase the CP value so that a constant purge rate is usually maintained in the entire purge operation range where the evaporative purge is executed.
Although the opening degree of the C valve 14 is varied to control the purge flow rate, immediately after the start of the purge, the fuel vapor containing a high concentration of hydrocarbons is purged from the canister 12 into the purge passage 13 and the air-fuel ratio is overrich. There is a risk that Therefore, in the present embodiment, the air-fuel ratio controllability is ensured by performing the purge at the low purge rate immediately after the start of the evaporation purge and switching to the purge at the high purge rate after the elapse of the set time.

FIG. 1 shows the main structure of the function relating to the evaporation purge control by the ECU 30. The air-fuel ratio detecting section 50,
The operating state detection unit 51, the purge ratio switching unit 52 as the purge control unit, the purge control unit 53, and the fuel injection control unit 5
4 can be represented.

In the air-fuel ratio detecting section 50, based on the signal from the O2 sensor 21, an air-fuel ratio feedback correction coefficient LAMB for correcting the fuel injection amount by the air-fuel ratio feedback.
Calculate DA.

In the operating state detecting section 51, the coolant temperature TW, the throttle opening θ,
Parameters representing operating conditions such as the intake air amount Q and engine speed Ne are calculated, and the operating conditions are detected.

The purge ratio switching unit 52 stores the opening of the CPC valve 14, that is, the duty ratio CPCMAP of the drive pulse signal for each operating region when the operating condition detected by the operating condition detecting unit 51 satisfies the evaporative purge condition. Of the two maps, immediately after the start of purging, the low-ratio purge map with a relatively low purge rate corresponding to the high evaporative concentration is selected, while when the set time has elapsed, the high-ratio purge map with a relatively high purge rate is selected. Therefore, the purge ratio is switched.

In the above low ratio purge map, the purge amount is narrowed so that the air-fuel ratio control can be ensured even under a high concentration of evaporation, and a constant purge rate (for example, 1).
%) Is a map storing the opening degree (duty ratio) of the CPC valve 14, the basic fuel injection amount (basic fuel injection pulse width) Tp (the intake air amount Q and the intake pipe pressure P may be used) and the engine speed. Ne and Ne are configured as a lattice.

Further, the above high ratio purge map enables a large amount purge while ensuring air-fuel ratio control under a normal evaporation concentration after the evaporation purge is started and the high concentration fuel vapor is almost completely purged. It is a map that stores the opening degree (duty ratio) of the CPC valve 14 so that the purge rate (for example, 3%) is stored. Similarly, the basic fuel injection pulse width Tp and the engine speed Ne are configured as a grid. There is.

That is, when a high concentration of the evaporation concentration is expected immediately after the start of the purge, the purge ratio is first lowered to prevent the air-fuel ratio from being overrich. When it is determined that the purge rate is low, the purge rate is switched to a high purge rate.

The opening (duty ratio) of the CPC valve 14 may be calculated by calculation instead of referring to the above map.

In the purge control unit 53, the purge map (low ratio purge map or high ratio purge map) selected by the purge ratio switching unit 52 and the basic fuel injection pulse width Tp calculated by the fuel injection control unit 54, which will be described later, are compared with the operation. The duty ratio CPCD is set by interpolation calculation from the map value CPCMAP based on the engine speed Ne detected by the state detection unit 51, and is output to the CPC valve 14 to control the purge flow rate of the purge passage 13.

The fuel injection control section 54 calculates the basic fuel injection pulse width Tp from the intake air amount Q and the engine speed Ne as shown in the following equation (1) (Tp = K × Q / N).
e; where K is an injector characteristic correction constant), and this basic fuel injection pulse width Tp is related to various corrections corresponding to the engine state, that is, cooling water temperature correction, acceleration / deceleration correction, full throttle increase correction, idle post-increase correction, etc. The effective injection pulse width Te is obtained by performing the feedback correction with the air-fuel ratio feedback correction coefficient LAMBDA while correcting with the various increase amount correction coefficient COEF, and further, the effective injection pulse width Te is added to the effective injection pulse width Te based on the battery voltage. The final fuel injection amount (fuel injection pulse width) Ti is calculated by adding the voltage correction coefficient TB for interpolating
The corresponding signal is output to the injector 9. Ti = Te + TB (1) where Te = Tp × COEF × LAMBDA

Next, the purge control routine executed by the ECU 30 will be described with reference to the flowchart of FIG. The purge control routine shown in FIG. 2 is a routine process routine executed every predetermined time after system initialization accompanying engine startup. First, in step S101, it is checked whether the evaporative purge condition is satisfied. The evaporative purge conditions are that the set time or more has elapsed since the engine was started, the cooling water temperature is the set water temperature or more, and the like.
When the evaporative purge condition is not satisfied, the routine is exited, and when the evaporative purge condition is satisfied, the process proceeds to step S102.

In step S102, it is checked whether the elapsed time after the start of purging (purge time) has reached the set value, and if it has not reached the set value, the low ratio purge map is selected in step S103, and this low purge map is selected. The duty ratio CPC based on the map value CPCMAP that refers to the ratio purge map based on the basic fuel injection pulse width Tp and the engine speed Ne
The drive pulse signal of D is output to the CPC valve 14, low-rate purge is executed, and the routine exits. The purge time is measured by setting a loop counter or a timer of the program at the start of execution of the low ratio purge, and thereafter measuring the elapsed time.

After that, the routine is repeated, and when the purge time becomes the set value or more in step S102,
The process proceeds from step S102 to step S104, the high ratio purge map is selected, and the drive pulse of the duty ratio CPCD obtained by referring to this high ratio purge map based on the basic fuel injection pulse width Tp and the engine speed Ne. A signal is output to the CPC valve 14 to switch from the low rate purge to the high rate purge and exit the routine.

As a result, the followability in the air-fuel ratio feedback control can be secured immediately after the start of the evaporation purge, where a high concentration of the evaporation concentration is expected, and a large amount of the evaporation purge can be performed after the evaporation concentration decreases, and the air-fuel ratio controllability can be improved. It is possible to enable large-scale purging while maintaining the above.

FIG. 5 is a flow chart of a purge control routine according to the second embodiment of the present invention.

The present embodiment differs from the above-described first embodiment in that the criterion for determining whether to switch from the low ratio purge to the high ratio purge in the purge ratio switching unit 52 is changed from the purge time to the integrated value of the intake air amount. is there.

That is, in the present embodiment, under the condition that the purge rate is constant, the evaporation purge amount is proportional to the intake air amount, and there is a strong negative correlation between the total purge amount after the start of the evaporation purge and the evaporation concentration. Because there is
The purge ratio switching unit 52 integrates the intake air amount Q after the start of the low ratio purge to obtain an integrated value (purge integrated value) of the total purge amount after the start of the purge, and this integrated value is adopted as an index representing the evaporation concentration. Then, when this integrated purge value exceeds the set value, it is determined that the high-concentration fuel vapor is almost completely purged and the normal evaporation concentration is low, and the low-ratio purge is switched to the high-ratio purge. .

Therefore, in the purge control routine of the present embodiment, as shown in FIG. 5, step S102 of the above-described purge control routine of the first embodiment (see FIG. 2) is changed to step S102.
In step S102A, it is checked in step S102A whether or not the integrated purge value after the start of purging has reached the set value, and if it has not reached the set value, in step S103 the low rate purge map is selected to execute the low rate purge. Then, when the value becomes equal to or larger than the set value, the high ratio purge map is selected in step S104 to execute the high ratio purge.

Also in this embodiment, as in the case of the first embodiment described above, the followability in the air-fuel ratio feedback control is secured immediately after the start of the evaporation purge in which a high evaporation concentration is expected, and a large amount of the evaporation purge is obtained after the evaporation concentration decreases. It can be performed.

6 to 9 relate to the third embodiment of the present invention, FIG. 6 is a block diagram showing a functional configuration relating to the evaporation purge control / air-fuel ratio control, and FIG. 7 relates to the smoothing processing of the air-fuel ratio feedback correction coefficient. FIG. 8 is a flowchart of the evaporation concentration calculation routine, and FIG. 9 is a flowchart of the purge control routine.

In the present embodiment, the low ratio purge and the high ratio purge are switched according to the evaporation concentration. As shown in FIG. 6, the purge ratio switching unit 52A and the fuel injection control unit 54A are different from the first embodiment. The function of is slightly changed, and the evaporation concentration calculation unit 55 is added.

The evaporative emission concentration calculating section 55 first calculates a value (average value or first-order lag value) N_LAMBDA obtained by smoothing the air-fuel ratio feedback correction coefficient LAMBDA, and the center value (1.0) of this smoothing processing value N_LAMBDA. ) Evaporation concentration Φ (equivalent ratio)
Is calculated.

For example, when the smoothed processing value N_LAMBDA is used as the first-order lag value, as shown in FIG. 7, the average value B_LAMBD of the maximum value MAX and the minimum value MIN of the air-fuel ratio feedback correction coefficient LAMBDA at a predetermined time point.
A_OLD (B_LAMBDA_OLD = (MAX + M
IN) / 2) is calculated and then the next average value B_LA is calculated.
MBDA_NEW (B_LAMBDA_NEW = (MA
X '+ MIN) / 2) is calculated and average value B is calculated.
_LAMBDA is updated, and the first-order delay value N_L
The latest first-order delay value N_LAMBDA_NEW is calculated from AMBDA_OLD according to the following equation (2). N_LAMBDA_NEW = {(a-1) × N_LAMBDA_OLD + B_LAMBDA_NEW} / a (2) where a is a raw constant

Then, during execution of the evaporation purge, the smoothing processing value N_ of the air-fuel ratio feedback correction coefficient LAMBDA
When LAMBDA is smaller than the lower limit value of the control target range (for example, 0.99) with respect to the center value, it is determined that the evaporation concentration is high, and the smoothing processing value N_LAMBDA is the upper limit value of the control target range (for example, 1.01). ) Is exceeded, the evaporative concentration is judged to be low. More specifically, the routine of FIG. 8 described later performs a process of gradually increasing and decreasing from the initial value (Φ = 1.0) according to the deviation from the center value of the smoothing process value N_LAMBDA of the air-fuel ratio feedback correction coefficient LAMBDA. , The evaporation concentration Φ is calculated.

In the purge ratio switching unit 52A, the evaporation concentration Φ calculated by the evaporation concentration calculating unit 55 is compared with the set value, and when the evaporation concentration Φ is higher than the set value, the low ratio map is selected. To perform a low percentage purge,
When the evaporation concentration Φ becomes lower than the set value, the high ratio map is selected to switch to the high ratio purge.

Further, in the fuel injection control unit 54A, the correction of the fuel injection amount based on the evaporation concentration Φ is added to the fuel injection control unit 54 in the first embodiment described above. That is, based on the evaporation concentration Φ calculated by the evaporation concentration calculation unit 55, the effective injection pulse width T of the excess fuel due to the evaporation purge is
e ′ is calculated, the effective injection pulse width Te ′ of this excess fuel is subtracted from the normal effective injection pulse width Te, the voltage correction coefficient TB is added, and the final fuel injection shown by the following equation (3) is performed. The pulse width Ti is calculated. The effective injection pulse width Te 'based on the excess fuel amount due to the evaporation purge is the basic fuel injection pulse width Tp and the coefficient (1-Φ) based on the purge rate Kevp and the evaporation concentration Φ in the actual low ratio purge or high ratio purge. It is calculated by multiplying by. Ti = Te−Te ′ + TB (3) where Te ′ = Tp × Kevp × (1-Φ)

FIG. 8 shows an evaporation concentration calculation routine executed every predetermined time. First, in step S201, it is checked whether or not purging is being executed. When the purging is not being executed, the routine is exited, and when purging is being executed, In step S202, the smoothing processing value N_LAMBDA of the air-fuel ratio feedback correction coefficient LAMBDA is the control target lower limit value LD (for example,
0.99).

As a result, N_LAMBDA <LD, and when it is estimated that the evaporation concentration is high and the air-fuel ratio is rich, the routine proceeds from step S202 to step S203, and the evaporation concentration ΦOLD calculated at the time of executing the previous routine.
Is increased by a set value ΔΦ to calculate a new evaporation concentration Φ (Φ = ΦOLD + ΔΦ; the initial value of Φ is 1.0), and the routine ends.

In step S202, N_LAMBD
When A ≧ LD, the process proceeds to step S204, where the smoothing processing value N_LAMBDA is the control target upper limit value LU (for example,
1.01) Check whether or not the following, N_LAMBDA ≦ LU
When the smoothing processing value N_LAMBDA is within the target control range (LD ≦ N_LAMBDA ≦ LU), the routine proceeds to the routine while keeping the evaporation concentration ΦOLD calculated at the time of the previous routine execution in step S205 (Φ = ΦOLD). Get out.

Further, in step S204, N_LAMB
When DA> LU, and it is estimated that the evaporation concentration is low and the air-fuel ratio is lean, a new evaporation concentration Φ is calculated by decreasing the evaporation concentration ΦOLD calculated during the previous routine execution by the set value ΔΦ. = ΦOLD-ΔΦ), exit the routine.

On the other hand, in the purge control routine of FIG. 9, it is checked in step S301 whether the evaporative purge condition is satisfied. If the evaporative purge condition is not satisfied, the routine is exited. If the evaporative purge condition is satisfied, step S302 is performed.
Proceed to.

In step S302, it is checked whether or not the evaporation concentration Φ exceeds the set value, and if it exceeds the set value, the low ratio purge map is selected in step S303, and this low ratio purge map is used as the basic fuel injection. The drive pulse signal having the duty ratio CPCD obtained by referring to the pulse width Tp and the engine speed Ne is used as the CPC valve 1
4 is output, low ratio purge is executed, and the routine exits.

After that, the routine is repeated, and when the evaporation concentration Φ becomes equal to or less than the set value, the process proceeds from step S302 to step S304, the high ratio purge map is selected, and the high ratio purge map is set to the basic fuel injection pulse width Tp. The drive pulse signal of the duty ratio CPCD obtained by referring to the engine rotation speed Ne is output to the CPC valve 14, and the low ratio purge is switched to the high ratio purge to exit the routine.

In the present embodiment, even when the evaporation concentration in the fuel tank 10 increases due to a rise in the fuel temperature and the like after the evaporation concentration once decreases, the evaporation concentration becomes higher again, which is more reliable. Correspondence becomes possible.

In this embodiment, the evaporation concentration Φ is calculated from the smoothing processing value N_LAMBDA of the air-fuel ratio feedback correction coefficient LAMBDA, but a concentration sensor is attached to the purge passage 13 to directly detect the evaporation concentration. Alternatively, it may be applied to a system in which the fuel injection amount is not corrected by the evaporation concentration.

10 to 12 relate to the fourth embodiment of the present invention, FIG. 10 is a block diagram showing a functional configuration relating to the evaporation purge control / air-fuel ratio control, FIG. 11 is a flowchart of an evaporation concentration calculation routine, and FIG. 12 is a purge. It is a flowchart of a control routine.

In this embodiment, a low ratio purge that secures air-fuel ratio controllability by narrowing the purge amount under a high evaporation concentration condition and a normal condition where the evaporation concentration is not high concentration are used. While enabling a large amount of purge, it switches between high-rate purge in which the area where the purge rate is constant is limited, and a purge rate map that stores different purge rates depending on the operating area in this high-rate purge It is prepared for correcting the injection amount.

Therefore, the functional configuration relating to the evaporation purge control in the present embodiment, as shown in FIG.
The evaporation concentration calculation unit 55 and the purge ratio switching unit 52A in the embodiment are changed so that the evaporation concentration calculation unit 55A,
The purge ratio switching unit 52B is configured so that the evaporation concentration calculation unit 55A determines the switching timing from the low ratio purge to the high ratio purge.

That is, in the evaporation concentration calculating section 55A,
Similar to the third embodiment described above, the evaporation concentration Φ is calculated based on the smoothing processing value N_LAMBDA of the air-fuel ratio feedback correction coefficient LAMBDA, and the fuel injection control unit 54A corrects the fuel injection amount based on this evaporation concentration Φ. As a result of the progress of the air-fuel ratio feedback control, when the air-fuel ratio converges in the vicinity of stoichiometry and the smoothing processing value N_LAMBDA falls within the target range, the concentration determination for switching from the low ratio purge to the high ratio purge is completed, and the concentration determination is completed. The completion flag FΦ is set to 1.

The purge ratio switching unit 52B refers to the value of the concentration determination completion flag FΦ, and when FΦ = 0,
When the low ratio purge map is selected and FΦ = 1, the high ratio purge map is selected, and the purge ratio map is selected correspondingly to switch from the low ratio purge to the high ratio purge.

The purge rate map is constructed with the basic fuel injection pulse width Tp and the engine speed Ne as a grid.
A preset purge rate is stored for each operation region in which the high ratio purge is executed, and the opening (duty ratio) of the CPC valve 14 is stored in each region of the high ratio purge map corresponding to this purge ratio. Has been done.

As described in the third embodiment, the fuel injection control section 54A corrects the fuel injection amount according to the evaporation concentration Φ. At that time, the purge rate Kevp in the equation (3) is corrected.
Is set to a constant purge rate Kevpl (for example, 1%) irrespective of the operating region when the low ratio purge is executed, and is set to a purge ratio Kevpmap (for example, 1%) for each operating region obtained from the purge ratio map when the high ratio purge is executed. 0.8% to 3%).

The evaporation concentration calculation routine in this embodiment is different from the evaporation concentration calculation routine in the third embodiment (see FIG. 8) in the air-fuel ratio feedback correction coefficient LAMBD.
In addition to the process of calculating the evaporation concentration Φ according to the degree to which the smoothing processing value N_LAMBDA of A deviates from the control target range, it is determined whether the evaporation concentration is within the target range for switching from the low ratio purge to the high ratio purge. The processing will be described below, and will be described below with reference to the flowchart of FIG.

In this evaporation concentration calculation routine, it is checked in step S401 if purging is being executed. If purging is not being executed, the concentration completion flag FΦ is cleared in step S402 (FΦ = 0) and the routine is exited. During execution, the routine proceeds to step S403, and it is checked whether or not the smoothing processing value N_LAMBDA of the air-fuel ratio feedback correction coefficient LAMBDA is below the control target lower limit value LD1 (for example, 0.99).

As a result, when N_LAMBDA <LD1, and it is estimated that the evaporation concentration is high and the air-fuel ratio is rich, the routine proceeds from step S403 to step S404, and the evaporation concentration ΦOLD calculated at the time of the previous routine execution.
Is increased by a set value ΔΦ to calculate a new evaporation concentration Φ (Φ = ΦOLD + ΔΦ; the initial value of Φ is 1.0), and the process proceeds to step S408.

In step S403, N_LAMBD
When A ≧ LD1, the routine proceeds to step S405, and it is checked whether or not the smoothing processing value N_LAMBDA is equal to or less than the control target upper limit value LU1 (for example, 1.01), and N_LAMBDA ≦.
LU1, and when the smoothing processing value N_LAMBDA is within the target control range (LD1 ≦ N_LAMBDA ≦ LU1), the evaporation concentration ΦOLD calculated at the time of the previous routine execution in step S406 is held (Φ = ΦOL
D), and proceeds to step S408.

Further, in step S405, N_LAMB
When DA> LU1 and it is estimated that the evaporation concentration is low and the air-fuel ratio is lean, a new evaporation concentration Φ is calculated by decreasing the evaporation concentration ΦOLD calculated during the previous routine execution by the set value ΔΦ. = ΦOLD−ΔΦ),
It proceeds to step S408.

At step S408, the smoothing processing value N_LA
It is checked whether MBDA is lower than the target range lower limit value LD2 (for example, 0.95) for the completion of the density determination, and N_LAMBD is determined.
When A <LD2, it is determined that the concentration is not enough to be switched from the low ratio purge to the high ratio purge, the concentration completion flag is cleared (FΦ = 0) in step S411, the routine is exited, and N_LAMBDA ≧ LD2 is satisfied. At this time, the process proceeds to step S409, and it is checked whether or not the smoothing processing value N_LAMBDA is equal to or less than the target range upper limit value LU2 (for example, 1.05) for the completion of the density determination.

When N_LAMBDA> LU2, similarly, the concentration completion flag FΦ is cleared in step S411 and the routine is exited. When N_LAMBDA≤LU2, that is, LD2≤N_LAMBDA≤LU2, the low ratio purge is performed. Then, it is judged that the concentration has reached a level that can be switched to the high ratio purge, and the concentration determination completion flag FΦ is set in step S410 (FΦ = 1), and the routine is exited.

In contrast to the above-mentioned evaporative concentration calculation routine, in the purge control routine of FIG. 12, it is checked in step S501 if the evaporative purge condition is satisfied. If the evaporative purge condition is not satisfied, the routine is exited and the evaporative purge condition is satisfied. At this time, the value of the density determination completion flag is referred to in step S502.

When FΦ = 0 in step S502, the flow advances to step S503 to select a low ratio purge map, and the low ratio purge map is referred to based on the basic fuel injection pulse width Tp and the engine speed Ne. Drive pulse signal of duty ratio CPCD obtained by
The low ratio purge is executed by outputting to the valve 14 and correcting the fuel injection amount based on the evaporation concentration Φ and the constant purge rate Kevpl, and the routine is exited.

On the other hand, when FΦ = 1 in step S502, the process proceeds to step S504 to select the high ratio purge map and the purge ratio map, and set the high ratio purge map to the basic fuel injection pulse width Tp and the engine speed Ne. The drive pulse signal having the duty ratio CPCD obtained by referring to the basic fuel injection pulse width T is output to the CPC valve 14 and the evaporation concentration Φ and the purge rate map are used as the basic fuel injection pulse width T.
The fuel injection amount is corrected based on the actual purge rate Kevpmap obtained by referring to p and the engine speed Ne, and the routine is exited by switching from the low rate purge to the high rate purge.

In this embodiment, as in each of the above-described embodiments, when the evaporation concentration is high at the start of the evaporation purge, deterioration of the air-fuel ratio controllability can be prevented. When it becomes possible to correct the fuel injection amount based on the purge rate different for each operating region and the evaporation concentration at that time, it is possible to further improve the air-fuel ratio controllability.

The determination of switching from the low ratio purge to the high ratio purge is made based on the elapsed time after the start of the low ratio purge described in the first embodiment or the integrated value of the intake air amount described in the second embodiment. Alternatively, the detected value of the evaporation concentration by the concentration sensor attached to the purge passage 13 may be used.

When the low ratio purge is executed, the purge ratio K
Depending on the operating region, evpl is not set to a constant value, and a higher purge rate is adopted. As with the case of executing the high ratio purge, fuel consumption is reduced in accordance with the low ratio purge map that determines the basic opening (duty ratio) of the CPC valve 14. A purge rate map for injection correction may be prepared.

13 and 14 relate to the fifth embodiment of the present invention, FIG. 13 is a block diagram showing a functional configuration relating to the evaporation purge control / air-fuel ratio control, and FIG. 14 is a flowchart of the purge control routine.

In each of the first to fourth embodiments described above, in order to deal with the case where a high concentration of evaporation is expected at the start of the evaporation purge, the low ratio purge is executed in a state where the evaporation concentration is high and the evaporation concentration is high. In contrast to switching to a high ratio purge after it becomes low, this embodiment reduces the evaporative purge amount, which is a disturbing factor that affects the air-fuel ratio controllability, earlier and improves the air-fuel ratio controllability. As shown in FIG. 13, the function of the purge ratio switching unit 52 in the above-described first embodiment is changed to a purge ratio switching unit 52C.

Therefore, in the purge ratio switching unit 52C in this embodiment, when the operating condition satisfies the evaporative purge condition, first, the high ratio purge map having a relatively high purge ratio is selected and the high ratio purge is executed. After that, the smoothing processing value N of the air-fuel ratio feedback correction coefficient LAMBDA
_LAMBDA is adopted as an index representing the amount of evaporated fuel adsorbed by the canister 12, and the canister 1 is used by this index.
When it is determined that the amount of adsorbed fuel vapor in No. 2 is small, the low ratio purge map having a relatively low purge ratio is selected and switched to the low ratio purge.

In this case, the low ratio purge map shows that the purge amount is improved in order to improve the controllability of the air-fuel ratio when a large amount of purge is not required under the condition that the evaporated fuel adsorption amount of the canister 12 is small and the evaporation concentration is low. The opening degree (duty ratio) of the CPC valve 14 so as to obtain a constant purge rate by reducing the basic fuel injection pulse width Tp and the engine speed Ne.
Are stored for each area having a grid of, and the high ratio purge map has a CPC that provides a constant purge rate that enables a large amount of purge while ensuring air-fuel ratio control under normal evaporation concentration. Similarly, the opening degree (duty ratio) of the valve 14 is stored for each region having the basic fuel injection pulse width Tp and the engine speed Ne as a lattice.

The purge control routine in this embodiment is shown in FIG.
4, first, in step S601, it is checked whether or not the evaporative purge condition is satisfied. When the purge condition is not satisfied, the routine is exited. When the purge condition is satisfied, the purge flag FP for switching the purge ratio in step S602.
Refer to the value of. The purge flag FP indicates a high rate purge execution when the value is 0 and a low rate purge execution when the value is 1, and is cleared to 0 at the time of system initialization.

Therefore, at the first time of the routine, FP =
Therefore, the duty ratio CPCD obtained by referring to the high ratio purge map based on the basic fuel injection pulse width Tp and the engine speed Ne is selected from the above step S602 to step S603. Is output to the CPC valve 14 to execute the high ratio purge.

In the following step S604, the smoothing processing value N_LAMB of the air-fuel ratio feedback correction coefficient LAMBDA.
Check whether DA is lower than the set value SET1, N_LA
When MBDA <SET1, it is determined that the evaporative fuel adsorption amount of the canister 12 is relatively high in a normal state, and the purge flag FP is cleared (FP = 0) in step S605 in order to continue high rate purge (FP = 0). Exit through N_
When LAMBDA ≧ SET1, it is determined that the evaporated fuel adsorption amount of the canister 12 has decreased and the evaporation concentration has decreased, and the purge flag FP is set in step S606 to switch to the low ratio purge (FP = 1) routine. Get out.

The routine is then repeated, step
When FP = 1 in S602, steps from S602
The routine proceeds to S607, the low ratio purge map is selected, and the duty ratio C obtained by referring to this low ratio purge map based on the basic fuel injection pulse width Tp and the engine speed Ne.
The drive pulse signal of PCD is output to the CPC valve 14,
Perform a low percentage purge.

Next, the above steps S607 to S608
Then, the smoothing processing value N_LAMBDA is set to the set value SET.
Check if it is lower than 2, N_LAMBDA <SET2
At this time, it is determined that the evaporation concentration is relatively high, and the purge flag FP is cleared in step S609 to switch to the low ratio purge, and the routine is exited, and N_LAMBDA ≧ SET2.
If it is, it is determined that the evaporation concentration is low, the purge flag FP is set in step S610 to continue the low ratio purge, and the routine exits.

In this embodiment, the purge amount is switched according to the amount of evaporated fuel adsorbed by the canister, so that the amount of evaporation purge, which is a disturbing factor affecting air-fuel ratio controllability, can be reduced early, and the air-fuel ratio can be reduced. A large amount of purge can be enabled while maintaining controllability.

[0090]

As described above, claims 1, 2, and
According to the inventions of 3 and 4, purging is performed at a relatively low purge rate in a state where the concentration of the evaporated fuel mixture is high immediately after the start of the purge, and the purge ratio is increased after the normal concentration of the evaporated fuel mixture is reached. Therefore, it is possible to enable a large amount of purge while preventing deterioration of air-fuel ratio controllability.
According to the fourth aspect of the invention, the fuel injection amount is corrected based on the vaporized fuel mixture concentration and the actual purge rate for each operating region, so the air-fuel ratio controllability can be further improved. Further, according to the invention of claim 5, even if the purge is started at a relatively high purge rate, when it is determined that the concentration of the evaporated fuel mixture is low, the purge is switched to the low purge rate. It is possible to enable the large-scale purge while preventing the deterioration of the air-fuel ratio controllability due to the large-scale purge performed in the state where the evaporated fuel adsorption amount of the canister is small.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a functional configuration related to evaporation purge control according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a purge control routine same as above.

FIG. 3 is a schematic configuration diagram of an engine control system of the above.

FIG. 4 is a circuit diagram of the electronic control system of the above.

FIG. 5 is a flowchart of a purge control routine according to the second embodiment of the present invention.

FIG. 6 relates to a third embodiment of the present invention and relates to evaporation purge control /
Block diagram showing the functional configuration related to air-fuel ratio control

FIG. 7 is an explanatory diagram relating to the smoothing process of the air-fuel ratio feedback correction coefficient.

FIG. 8 is a flowchart of an evaporation concentration calculation routine of the same as above.

FIG. 9 is a flowchart of a purge control routine of the above.

FIG. 10 is a block diagram showing a functional configuration relating to evaporation purge control / air-fuel ratio control according to a fourth embodiment of the present invention.

FIG. 11 is a flowchart of an evaporation concentration calculation routine of the same as above.

FIG. 12 is a flowchart of a purge control routine of the above.

FIG. 13 is a block diagram showing a functional configuration relating to evaporation purge control / air-fuel ratio control according to a fifth embodiment of the present invention.

FIG. 14 is a flowchart of a purge control routine same as above.

[Explanation of symbols]

10 ... Fuel tank 12 ... Canister 52 ... Purge ratio switching section (purge control means) 53 ... Purge control section (purge control means) Kevp, Kevpl, Kevpmap ... Purge rate Φ ... Evaporation concentration (evaporated fuel mixture concentration) LAMBDA ... Empty Fuel ratio feedback correction coefficient N_LAMBDA ... Smoothing processing value of air-fuel ratio feedback correction coefficient

Claims (5)

[Claims] 1. An evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage communicating between a canister for storing evaporative fuel from a fuel tank and an intake system. A purge control means is provided for starting at a purge rate corresponding to the concentration of a high-concentration evaporative fuel mixture, and when the elapsed time after the start of purge has reached a set time, switching to purge at a purge rate higher than the above-mentioned purge rate. An evaporated fuel processing device for an engine characterized by the above. 2. An evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage that communicates a canister that stores evaporative fuel from a fuel tank with an intake system. The purge starts at a purge rate that corresponds to the concentration of the high-concentration evaporated fuel mixture, and when the integrated value of the intake air amount after the start of purge reaches the set value, the purge is switched to a purge at a higher rate than the above purge rate. An evaporative fuel treatment system for an engine, comprising a control means. 3. An evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage communicating with a canister for storing evaporative fuel from a fuel tank and an intake system. When the evaporative fuel mixture concentration calculated based on the value obtained by smoothing the air-fuel ratio feedback correction coefficient after the start of the purge rate corresponding to the high concentration evaporative fuel mixture concentration reaches the set value, An evaporated fuel processing apparatus for an engine, comprising: a purge control means for switching to a purge at a purge rate higher than the purge rate. 4. An evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage communicating between a canister for storing evaporative fuel from a fuel tank and an intake system, A purge control means for starting at a purge rate corresponding to the concentration of the evaporated fuel mixture having a high concentration, and thereafter switching to a purge at a purge rate higher than the purge rate based on the concentration of the evaporated fuel mixture, and the purge control means. And a fuel injection control unit that corrects the fuel injection amount based on the evaporative fuel mixture concentration and the purge rate for each operation region when the purging is performed. 5. An evaporative fuel treatment apparatus for an engine, wherein an evaporative fuel mixture is purged through a purge passage that communicates a canister that stores evaporative fuel from a fuel tank with an intake system. Start with a purge rate that corresponds to the high concentration of the evaporated fuel mixture, and after starting the purge, based on the smoothed value of the air-fuel ratio feedback correction coefficient, the concentration of the evaporated fuel mixture is higher than the concentration that corresponds to the above purge rate. An evaporative fuel treatment system for an engine, comprising purge control means for switching to a purge at a purge rate lower than the above purge rate when it is judged to be low.