JP3365935B2 - Evaporative fuel treatment system for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine, which controls the purge of evaporated fuel stored in a canister of a vehicle equipped with the internal combustion engine into an intake system of the internal combustion engine, and more particularly to a load fluctuation of the internal combustion engine. The present invention relates to an evaporated fuel processing device for an internal combustion engine, which suppresses air-fuel ratio fluctuations due to changes in the purge flow rate during operation.

[0002]

2. Description of the Related Art Conventionally, vapor (evaporated fuel) generated in a fuel tank is stored in a canister, and when the stored vapor is purged into an intake system of an internal combustion engine, the purge flow rate of the vapor is used as a load of the internal combustion engine. In order to prevent a sudden large change in the air-fuel ratio when starting the purge or adjusting the purge flow rate, the purge amount is gradually changed when the purge flow rate is changed. (Japanese Patent Publication No. 5-69986).

[0003]

However, when the load of the internal combustion engine fluctuates, the purge flow rate changes due to the change in the negative pressure in the intake pipe, but the purge flow rate changes abruptly, especially during idle when the negative pressure in the intake pipe is large. To do. Therefore, the method of correcting the air-fuel ratio fluctuation by the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor provided in the exhaust system of the internal combustion engine cannot immediately correct the air-fuel ratio fluctuation caused by the change in the purge flow rate. The time during which the air-fuel ratio deviates from the target air-fuel ratio (theoretical air-fuel ratio) becomes long, which causes deterioration of exhaust gas characteristics and drivability.

The present invention has been made to solve the above problems, and quickly suppresses air-fuel ratio fluctuations due to changes in the purge flow rate when the load of the internal combustion engine fluctuates, and thus deteriorates exhaust gas characteristics and drivability. An object of the present invention is to provide an evaporated fuel processing device for an internal combustion engine, which can be prevented.

[0005]

To achieve the above object, the invention according to claim 1 is supplied to an internal combustion engine based on the output of an air-fuel ratio sensor for detecting the oxygen concentration in the exhaust gas of the internal combustion engine. An evaporative fuel processing apparatus for an internal combustion engine, comprising an air-fuel ratio feedback control means for feedback-controlling an air-fuel ratio of an air-fuel mixture to a target air-fuel ratio, the evaporative fuel storage means storing evaporative fuel, and the evaporative fuel storage means storing the evaporated fuel. In an evaporated fuel processing apparatus for an internal combustion engine, comprising: a purge control means for controlling the purge of the evaporated fuel into the intake system of the internal combustion engine, a load fluctuation amount detection means for detecting a fluctuation amount of the load of the internal combustion engine , Depending on the operating state of the internal combustion engine
A fuel amount calculator that calculates the amount of fuel supplied to the internal combustion engine.
And a purge control means, when the variation amount of the load detected by the load variation amount detecting means is large,
Of the purged evaporated fuel amount and the calculated fuel amount
Calculated before each value of the load change and after the load change
The amount of evaporated fuel to be purged based on
It is characterized by calculating .

With this configuration, purging of the evaporated fuel stored by the evaporated fuel storage means into the intake system of the internal combustion engine is controlled based on the load fluctuation amount detected by the load fluctuation amount detection means, so that the internal combustion engine It is possible to quickly suppress the air-fuel ratio fluctuation caused by the change in the purged amount of the evaporated fuel when the load changes, thereby preventing deterioration of the exhaust gas characteristics and drivability.

[0007]

[0008] With this arrangement, when the amount of variation of the load detected by the load fluctuation amount detection means is larger than a predetermined value, each of the previous variation of the load of the purged fuel vapor amount and the calculated fuel quantity Since the amount of evaporated fuel to be purged is calculated based on the value and the amount of fuel calculated after the change in the load, the amount of evaporated fuel to be purged can be changed by the amount of change in the fuel amount due to the change in load. Therefore, it is possible to quickly and effectively suppress the air-fuel ratio variation caused by the change in the purged fuel vapor amount.

The invention according to claim 2 relates to an internal combustion engine.
Based on the output of the air-fuel ratio sensor that detects the oxygen concentration in the exhaust gas
The air-fuel ratio of the mixture supplied to the internal combustion engine.
Air-fuel ratio feedback control hand for feedback control to
An evaporative fuel processing system for an internal combustion engine, comprising:
Evaporated fuel storage means for storing fuel and the evaporated fuel storage device
Of the evaporated fuel stored by the stages to the intake system of the internal combustion engine
Of an internal combustion engine equipped with a purge control means for controlling the
In the fuel-emission processing device, the fluctuation amount of the load of the internal combustion engine
A load fluctuation amount detecting means for detecting
The feedback control means controls the mixing supplied to the internal combustion engine.
In order to control the air-fuel ratio of the air to the target air-fuel ratio, the air-fuel ratio
The air-fuel ratio correction coefficient is calculated based on the output of the sensor.
The load control means is detected by the load variation detection means.
When the amount of load fluctuation is small, the air-fuel ratio correction coefficient
The purged fuel vapor amount is gradually reduced until it falls below a predetermined value.
And the air-fuel ratio correction coefficient falls below the predetermined value.
The amount of the evaporated fuel to be purged is gradually reduced .

With this configuration, when the load fluctuation amount detected by the load fluctuation amount detecting means is smaller than the predetermined value, the evaporated fuel amount purged by the purge control means is
Since it is gradually increased or decreased while referring to the control amount of the feedback control by the air-fuel ratio feedback control means, it is possible to suppress the control instability due to the individual difference of the solenoid valve or the like which constitutes the purge control means.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an internal combustion engine including an evaporated fuel processing apparatus according to an embodiment of the present invention and a control system therefor. Reference numeral 1 is, for example, a four-cylinder internal combustion engine (hereinafter referred to as “engine”). ), A throttle body 3 is provided in the middle of the intake pipe 2 of the engine 1, and a throttle valve 4 is arranged inside the throttle body 3. A throttle valve opening (θTH) sensor 5 is connected to the throttle valve 4,
An electronic control unit (hereinafter referred to as “ECU”) 6 that outputs an electric signal according to the opening degree of the throttle valve 4
Supply to.

The fuel injection valve 7 is provided for each cylinder between the engine 1 and the throttle valve 4 and slightly upstream of an intake valve (not shown) of the intake pipe 2, and each fuel injection valve 7 is provided with a fuel pump 8. Is connected to the fuel tank 9 and is electrically connected to the ECU 6, and the valve opening time (fuel injection time) Tout is controlled by a signal from the ECU 6.

An intake pipe absolute pressure (PBA) sensor 11 is provided immediately downstream of the throttle valve 4 via a pipe 10. The absolute pressure signal converted into an electric signal by the absolute pressure sensor 11 is sent to the ECU 6. Supplied.

An intake air temperature (TA) sensor 12 is attached to the intake pipe 2 downstream of the absolute pressure sensor 11.
EC is detected by detecting the intake air temperature TA and outputting the corresponding electric signal.
Supply to U6. An engine water temperature (TW) sensor 13 including a thermistor or the like is mounted on a cylinder block of the engine 1, detects the engine water temperature (cooling water temperature) TW, outputs a corresponding temperature signal, and supplies the ECU 6 with the temperature signal.

An engine speed (NE) sensor 14 is mounted around a cam shaft (not shown) or around a crank shaft of the engine 1, and a signal pulse (hereinafter referred to as "hereinafter referred to as" a signal pulse "at a predetermined crank angle position every 180 degrees rotation of the crank shaft of the engine 1). TDC
Signal pulse ”), and the TDC signal pulse is supplied to the ECU 6.

The LAF sensor 16 as an air-fuel ratio sensor is attached to the exhaust pipe 15 of the engine 1, detects the oxygen concentration in the exhaust gas, and outputs a signal corresponding to the concentration E
Supply to CU6.

The upper portion of the closed fuel tank 9 is provided with a passage 20.
The canister (evaporated fuel storage means) 21 communicates with the canister 21 via the purge passage 23.
Is connected to the downstream side of the throttle valve 4. The canister 21 contains an adsorbent 22 for adsorbing the evaporated fuel generated in the fuel tank 9 and has an outside air intake 21a. A two-way valve 20 composed of a positive pressure valve and a negative pressure valve is disposed in the middle of the passage 20a, and a purge control valve 24 which is a duty control type solenoid valve is disposed in the middle of the purge passage 23.
Is provided. The solenoid of the purge control valve 24 is E
The purge control valve 24 is connected to the CU 6 and is controlled according to a signal from the ECU 6 to change the temporal ratio of the valve opening time (valve opening duty).

When the vaporized fuel generated in the fuel tank 9 reaches a predetermined set pressure, the positive pressure valve of the two-way valve 20 is pushed open to flow into the canister 21 and the canister 21.
It is adsorbed by the adsorbent 22 inside and stored. Purge control valve 2
4 is opened by a duty control signal from the ECU 6
The evaporated fuel that has been closed and temporarily stored in the canister 21 is sucked through the purge control valve 24 together with the outside air sucked from the outside air intake port 21a provided in the canister 21 due to the negative pressure in the intake pipe 2. It is sucked into the pipe 2 and sent to each cylinder of the internal combustion engine. Further, when the fuel tank 9 is cooled by the outside air and the negative pressure in the fuel tank increases, the 2-way valve 2
The negative pressure valve of 0 is opened, and the evaporated fuel temporarily stored in the canister 21 is returned to the fuel tank 9. In this way, the fuel vapor generated in the fuel tank 9 is prevented from being released to the atmosphere.

The ECU 6 shapes the input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, a central processing circuit (hereinafter referred to as "the central processing unit"). "CPU"),
It is composed of a storage means for storing various calculation programs executed by the CPU and calculation results, an output circuit for supplying a drive signal to the fuel injection valve 7, the purge control valve 24, and the like.

Further, the CPU of the ECU 6 determines the engine operating conditions such as the air-fuel ratio feedback control region and the open-loop control region in which the air-fuel ratio feedback control is not performed based on the output signals from the various engine parameter sensors described above. The fuel injection time Tout of the fuel injection valve 7 is calculated in synchronization with the TDC signal pulse based on the following equation (1) according to the determined engine operating state.

Tout = Ti × KAF × K1 + K2 (1) Here, Ti is the basic fuel injection time, specifically, the basic fuel injection time determined according to the engine speed NE and the intake pipe internal pressure PB. A Ti map for determining the Ti value is stored in a storage unit (not shown) provided in the ECU 6.

KAF is an air-fuel ratio correction coefficient, and the air-fuel ratio of the air-fuel mixture supplied to the engine by the feedback control means stored in the storage means when the engine is in the air-fuel ratio feedback control region is the target air-fuel ratio (theoretical). It is calculated by the PID control theory based on the output signal from the LAF sensor 16 so as to match the air-fuel ratio). Also,
The smoothed value of the KAF is stored in the storage means as KAFPG. K1 and K2 are other correction coefficients and correction variables that are calculated according to various engine parameter signals, and values that optimize various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to the engine operating state. Is set to.

Next, referring to FIG. 2, a purge control process (purge control means) for optimally controlling the purge flow rate of the evaporated fuel from the canister 21 to the intake pipe 2 in accordance with the fuel injection amount and the evaporated fuel concentration. ) Is explained. FIG. 2 is a flowchart showing a schematic flow of the entire purge control process,
Each process shown in FIG. 2 and the flowcharts of FIGS. 3 to 5 described later is repeatedly executed at predetermined time intervals (for example, every 81.92 ms).

In FIG. 2, first, it is determined whether or not the engine water temperature TW detected by the TW sensor 13 is in a predetermined high water temperature region in which the evaporated fuel from the canister 21 can be purged (step S101). Engine water temperature T
If W is in the predetermined high water temperature region, it is further determined whether the engine 1 is in the fuel cut (step S102). If not in the fuel cut, LA
It is determined whether or not the state of the F sensor 16 satisfies a predetermined air-fuel ratio feedback control execution condition capable of executing the air-fuel ratio feedback control based on the output of the LAF sensor 16 (step S103). If the air-fuel ratio feedback control execution condition is satisfied, it is further determined whether or not the engine 1 is idle (step S10).
4).

If the air-fuel ratio feedback control execution condition is not satisfied in step S103, it is further determined whether the engine load is in the WOT (throttle fully open) region (step S105). If so, the process proceeds to step S104.

When the engine is idle at step S104, a vehicle speed (VP) sensor (not shown) is further added.
It is determined whether or not the vehicle speed VP detected by is greater than or equal to a predetermined value VQPGIDLE (step S106), and VP <
If it is VQPGIDLE, it is determined that the vehicle is in a predetermined low vehicle speed range, and the intake pipe pressure PBA is further set to the predetermined pressure PBQPG.
It is determined whether it is smaller than IDL (step S10).
7). If PBA <PBQPGIDL, it is determined that the engine is in a predetermined low load region, and the process proceeds to step 108.

In step 108, the purge control switching flag FQPGIDLE is indicated by the value "1" indicating that the purge control is executed by the valve opening duty ratio control described later.
Is set to the value "1". Steps S101 to S10
As a result of each determination process of step 7, the process proceeds to step S108 when it is determined that the purge flow rate is relatively low, and in such a case, the purge control is executed by the valve opening duty ratio control. This is because it is difficult to directly calculate the valve opening duty according to the target purge flow rate, because the error becomes large especially when the purge flow rate is relatively low due to the variation among the purge control valves 24.

If the engine water temperature TW is not within the predetermined high water temperature range in step S101, then step S
If the fuel cut is being performed in step 102, or if the engine load is not in the WOT region in step S105, after setting both the valve opening duty DOUTPG and the purge flow rate QPG to the value “0” (step S
109, 110), the purge control switching flag FQPG
IDLE is set to the value "0" (that is, the purge control is executed based on the purge flow rate) (step S111), and the process proceeds to step S114.

If it is not idle in step S104, VP ≧ VQPGI in step S106.
In the case of DLE, or in the above step S107, PBA ≧
In either case of PBQPGIDL, the purge control switching flag FQPGIDLE is set to the value "0" (step S112).

When the processing of step S108 or S112 is completed, DOUTPG (valve opening duty ratio) described later.
Is calculated (step S113), and then step S114
Proceed to.

In step S114, DOUTP
It is determined whether the G value is a negative value, and the DOUTPG value is
If it is a negative value , the DOUTPG value is set to "0" (step S115), and the process ends. Also, DOUTP
If the G value exceeds 100 (%), it is set to "100" (steps S116 and S117), and the process ends.

Next, referring to FIG. 3, the above step S1
The DOUTPG (valve opening duty ratio) calculation processing of No. 13 will be described. FIG. 3 is a flowchart showing a DOUTPG calculation process for calculating the valve opening duty ratio according to the set target purge flow rate.

First, in step S201, the gauge pressure PBG calculated from the pressure PBA detected by the PBA sensor 11 is calculated.
According to (atmospheric pressure (PA) -PBA), as shown in FIG. 6, a DPGOn table (flow rate rising duty ratio table) (FIG. 6A) and a QPGBRKn table (purge flow rate at duty break point (DPGBRK)). Value table) (the same figure (b)), and QPGFn table (the purge flow rate value table at the valve opening duty ratio of 100%) (the same figure (c)) are searched for the flow rate rising duty ratio DPGOn and the duty break point, respectively. The purge flow rate QPGBRKn and the purge flow rate value QPGFn at the valve opening duty ratio of 100% are calculated. This is the purge control valve 24
Since the purge flow rate-valve opening duty ratio characteristic curve of 1 shows the characteristic of one point break as shown in FIG. 7, the flow rate rising duty ratio DPGOn and the duty ratio break point (DP
(GBRK), the purge flow rate QPGBRKn, and the purge flow rate QPGFn at a valve open duty ratio of 100%, the valve open duty ratio DOUTPG corresponding to the purge flow rate QPG.
Is calculated.

Next, the purge control switching flag FQPG is set.
It is determined whether IDLE has the value "1" (step S202). If the flag FQPGIDLE is the value "1", the purge control by the valve opening duty ratio (DUTY) control process (control for gradually increasing or decreasing the valve opening duty ratio while referring to the KAF value) to be described later is executed in step S.
On the other hand, if the FQPGIDLE value is “0” while proceeding to 203, the process is ended to execute the purge control by the flow rate control (the valve opening duty ratio is directly calculated from the target purge flow rate to control the purge flow rate).

Next, the valve opening duty ratio control processing of step S203 will be described with reference to FIGS. 4 and 8.
FIG. 4 is a flow chart showing the valve opening duty ratio control processing, and FIG. 8 is a time chart showing changes in flags, coefficients, and valve opening duty ratio during execution of the valve opening duty control processing.

First, a load change process for suppressing a change in the air-fuel ratio due to a change in the purge flow rate when the engine load changes during execution of the valve opening duty ratio control is executed (step S301). This load variation process will be described later in detail.

Next, the purge control switching flag FQPGID
It is determined whether LE has the value "1" in the previous time (step S302). If the flag FQPGIDLE is not the value "1", the valve opening duty ratio control is started from this time (time t1 in FIG. 8), and the predetermined value DPGIDINI is set as the initial value of the target valve opening duty ratio DPGIDLE during idling. Along with (step S303), the smoothed value KAFPG of the air-fuel ratio correction coefficient KAF is set in KAFPGIDL (step S304), and the process ends. The predetermined value DPGIDINI is set to such a value that the evaporated fuel can be purged at the time of idling even if the purge control valve 24 varies.
The DPGIDINI value is the purge control valve 24 when the purge control valve 24 varies to the maximum purge flow side.
Is set to the valve opening duty value when the flow rate of rises.

In step S302, the flag FQPGI is set.
If the DLE is the value "1", it is determined that the valve opening duty ratio control is continued, and the transient correction execution flag that is set to the value "1" during execution of the transient correction process to be described later in the load variation process of step S301. It is determined whether FDLOADPG has a value of "1" (step S305).
If the flag FDLOADPG has a value of "1", the transient correction process is executed, and the process is ended without executing the valve opening duty ratio control by gradually increasing or decreasing after step S306. If the flag FDLOADPG is not the value "1", the transient correction process is not executed, and the process proceeds to step S306 and the subsequent steps.

In step S306, the air-fuel ratio correction coefficient KAF is set to the KAF set in step S304.
It is determined whether it is larger than PGIDL by a predetermined width (DKAFPGIL) or more. KAF> KAFPG I DL-DK
If APGGI L (time t1 to t2 in FIG. 8), the target valve opening duty ratio DPGIDLE is assumed to have a small effect of the purge on the air-fuel ratio correction coefficient KAF.
Is increased by a predetermined amount DDPGIDLE (step S30
7). The increased DPGIDLE value is a predetermined upper limit value DP
When it exceeds GIDLEH, the DPGIDLE value is set to the upper limit value D.
Set to PGIDLEH (steps S308, S30
9). The upper limit value DPGIDLEH is the purge control valve 2
The value is set so that the evaporated fuel can be purged at the time of idling even if there is a variation of 4.
The GIDLEH value is set to a valve opening duty value that becomes an idle target flow rate when the purge control valve 24 varies to the maximum side where the purge flow rate is small.

In step S306, KAF≤
If KAFPGIDL-DKAFPGIL, further K
The AF value has a predetermined width DKAFPG than the KAFPGIDL value.
It is determined whether it is smaller than IH (DKAFPGIH> DKAFPGIL) or more (step S310 ). KAF ≧ K
If AFPGLDL-DKAFPGIH (state from time t2 to t3 in FIG. 8), it is determined that an appropriate amount of evaporated fuel has been purged, and the process ends, and KAF <KAFPGL.
If DL-DKAFPGIH (state after time t3 in FIG. 8), the DPGIDLE value is set to a predetermined amount DDP, assuming that the influence of the purge on the air-fuel ratio correction coefficient KAF is too large.
GIDLE is reduced (step S311 ). When the reduced DPGIDLE value falls below a predetermined lower limit value DPGIDINI, the DPGIDLE value is reduced to the lower limit value DPGIDINI.
Is set (steps S312 and S313).

Next, the load variation process of step S301 will be described with reference to FIGS. 5 and 9. FIG. 5 is a flow chart showing the load variation process, and FIG. 9 is a time chart showing how the flag, coefficient, and valve opening duty ratio change during execution of the load variation process.

This load change process is a process for suppressing the change in the air-fuel ratio caused by the change in the purge flow rate when the engine load changes. In FIG. 5, first, the purge control switching flag FQPGIDLE has the value "1" at the previous time. It is determined whether or not (step S401). Flag FQPG
If IDLE is not the value "1" previously, it is assumed that the valve opening duty ratio control is started this time, and the purge flow rate QPGD is set.
In order to calculate the LD, the target valve opening duty ratio DPGIDLE at idle is set to the initial value DPGIDINI (step S402), and the purge flow rate QPGDLD is obtained by searching the DPGIDLE value and step S201 according to the following equation (2). DPGOn value, QP
GBRKn value and valve opening duty ratio DPG at break point
It is calculated using the BRK value (step S403).

[0044]

[Equation 1] Next, the current fuel amount (injected fuel amount + purged fuel amount) TI
M is set as the fuel amount TIMDLD before load change (step S404), and the transient correction execution flag FDLOA is set.
The DPG is set to the value "0" (step S405), and the process ends.

In step S401, the flag FQPGI is set.
If DLE is the value "1", it is determined that the valve opening duty ratio control is continuing, and the purge flow rate QPGDLD calculated in accordance with the above equation (2) or (3) in step S403 or step S412 described later is zero. It is determined whether or not the following (step S406). QPGDLD>
If it is 0, the fluctuation rate KTI of the fuel amount before and after the load fluctuation
The DLD value is set to TIM (current fuel amount) / TIMDLD (previous fuel amount) (step S407), while Q
If PGDLD ≦ 0, the purge flow rate does not actually take a negative value, so the KTIDLD value is set to “1” so that the valve opening duty ratio is not corrected in the reverse direction based on the calculated QPGDLD value. .0 ”(uncorrected value) (step S409).

Next, the load fluctuation amount DPBA obtained by the difference in the intake pipe pressure PBA between the two rotations of the crankshaft.
CYL is calculated, and the DPBACYL value is the upper threshold value DPB.
Whether or not it is larger than ALDP, that is, whether or not the fluctuation of the PBA value to the increasing side is large, or the lower threshold value-DPBALD
It is determined whether or not it is smaller than M, that is, whether or not the fluctuation of the PBA value toward the decreasing side is large (steps S409 and S).
410). FIG. 9 shows an example in which the PBA value fluctuates toward the decreasing side. Lower threshold-DPBALDM (upper threshold DPBALD
P is also the same), a hysteresis is provided in consideration of the stability of control, and in FIG. 9, -DPBALDML, -DP
Shown as BALDMH.

As described above, the threshold value is set to the upper threshold value DPBALDP depending on whether the change in the PBA value (engine load) to the increasing side is large or the change in the PBA value to the decreasing side is large.
And the lower threshold-DPBALDM
This is because the influence of the fluctuation of the purge flow rate on the air-fuel ratio correction coefficient differs between the increasing side and the decreasing side of the engine load. In other words, the degree of engine rich / lean toughness (air-fuel ratio variation due to fuel amount variation) and the degree of purge flow rate variation due to engine load variation differ between the engine load increasing side and the engine load reducing side.

Further, the load fluctuation amount DPBACYL is used to detect the fluctuation of the intake pipe pressure PBA.
The load fluctuation during idling is caused by on / off of the air conditioner and does not occur rapidly. Therefore, when the difference ΔPBA between the previous PBA value and the current PBA value is used as the PBA fluctuation, This is because the difference in PBA is so small that load fluctuations during idle cannot be detected accurately.

Next, when it is determined from the determination results of steps S409 and S410 that the variation amount of the intake pipe internal pressure PBA is larger on either the increase side or the decrease side (the answer to step S409 is NO, or step S410). The answer is YES), which means that the so-called load fluctuation is large in the scope of claims, and the purge flow rate Q before the load fluctuation.
Variation value KTI of fuel amount before and after load variation in PGDLD
By multiplying the DLD, it calculates the purge flow QPGDLDC after the load change (steps S411), the valve opening duty value DPGIDLE the formula after the load change from QPGDLDC value issued the calculated (3), in the step S201 DPBOn value, Q obtained by the search
PGBRKn value and valve opening duty ratio D at the break point
It is calculated using PGBRK (step S412), the calculated DPGIDLE value is subjected to predetermined limit processing (step S413), and the transient correction execution flag FD is calculated.
Set LOADPG to the value "1" (step S41
4), the process ends.

[0050]

[Equation 2] The answer to step S409 or S410 is NO.
If it is, it is assumed that the so-called load fluctuation is small in the scope of claims, and the process proceeds to step S403 and subsequent steps.

When the variation in the intake pipe pressure PBA is relatively large, the valve opening duty ratio control by the gradual increase and decrease as shown in FIG. 8 is stopped, and the variation in the fuel amount before and after the load variation is stopped. The valve opening duty ratio is directly calculated in accordance with the above because the change of the purge flow rate with respect to the fluctuation of the intake pipe pressure PBA is rapid at the time of idling, which causes a large fluctuation of the air-fuel ratio. In this case, the correction of the air-fuel ratio fluctuation cannot be made in time, which causes deterioration of the exhaust gas characteristics and operability.Therefore, the valve opening duty ratio is set appropriately in anticipation of the change in the purge flow rate when the load changes, and the evaporated fuel to be purged By controlling the amount,
It is intended to prevent the above-mentioned problems from occurring.

Further, in FIG. 9, the valve opening duty ratio D
In PGIDLE, the load fluctuation amount DPBACYL of the intake pipe pressure PBA is the lower threshold value-DPBALDM (H).
Since the rapid change of the purge flow rate does not occur until the time t1 below which the valve opening duty ratio control shown in FIG. 4 is performed (normal control).
It is changing by gradually increasing or decreasing by. In addition, the load change process is being executed from time t1 (time t1-t2).
The valve opening duty ratio DPGIDLE during this period is based on the change of the purge flow rate QPGDLD and the fuel amount change KTIDLD during execution of the load change process so that the influence on the air-fuel ratio becomes the same as when the load does not change. QPGDLD value (fixed value at time t1) corresponding to the change in fuel amount
It is calculated based on the QPGDLDC value calculated from

When the differential value DPBACYL exceeds the lower threshold value -DPBALDM (L) at time t2, the change in the intake pipe pressure PBA ends, and since the rapid change in the purge flow rate does not occur thereafter, the above-mentioned gradual increase / decrease The valve opening duty ratio control is restarted. At this time, the QPGDLD value is updated to the value calculated based on the intake pipe internal pressure PBA at time t2.

As described above, according to the evaporated fuel processing apparatus for the internal combustion engine of this embodiment, the purge flow rate is directly changed so that the purge flow rate appropriately changes according to the change of the fuel amount before and after the change of the engine load. Since the valve opening duty ratio is calculated,
It is possible to quickly and effectively suppress a large change in the air-fuel ratio due to a change in the purge flow rate when the engine load changes, and prevent deterioration of exhaust gas characteristics and drivability.

[0055]

According to the evaporative fuel processing apparatus for an internal combustion engine of the first aspect, the internal combustion engine for the evaporative fuel stored by the evaporative fuel storage means is based on the load variation amount detected by the load variation amount detecting means. Since the purge to the intake system is controlled, the air-fuel ratio fluctuation caused by the change in the purged amount of the evaporated fuel when the load of the internal combustion engine changes can be quickly suppressed, thereby preventing the deterioration of exhaust gas characteristics and drivability. be able to.

[0056] Incidentally, when the amount of variation of the detected load by load variation amount detection means is large, after the variation of the value before change of the load of the purged fuel vapor amount and the calculated fuel quantity and the load Since the amount of evaporated fuel to be purged is calculated based on the calculated amount of fuel, it is possible to change the amount of evaporated fuel to be purged by the amount of change in the amount of fuel due to load fluctuation. The change in the air-fuel ratio due to the change in the evaporated fuel amount can be swiftly and effectively suppressed.

[0057] Further, according to the evaporative fuel processing system for an internal combustion engine according to claim 2, when the amount of variation of the load detected by the load fluctuation amount detection means is small, amount of fuel vapor is purged by the purge control means Since the control amount of the feedback control by the air-fuel ratio feedback control means is gradually increased or decreased, it is possible to suppress the control instability due to the individual difference of the solenoid valve or the like constituting the purge control means.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of an evaporated fuel processing apparatus for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a schematic flow of a purge control process.

FIG. 3 is a flowchart showing a DOUTPG calculation process.

FIG. 4 is a flowchart showing a DUTY control process.

FIG. 5 is a flowchart showing a load change process.

FIG. 6 is a table showing various table values searched for determining a purge flow rate from a negative pressure in the intake pipe.

FIG. 7 is a graph showing a valve opening duty-purge flow rate characteristic.

FIG. 8 is a time chart showing how each coefficient changes during the DUTY control process.

FIG. 9 is a time chart showing how each coefficient changes during the load change process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 engine 2 intake pipe 6 ECU (feedback control means, purge control means, purge amount gradual increase / decrease means) 11 PBA sensor (load fluctuation amount detection means) 16 LAF sensor (exhaust sensor) 21 canister (evaporated fuel storage means)

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02M 25/08 301 F02D 41/02 301 F02D 41/04 305 F02D 41/14 310

Claims (2)

(57) [Claims] 1. An air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine to a target air-fuel ratio based on the output of an air-fuel ratio sensor for detecting the oxygen concentration in the exhaust gas of the internal combustion engine. An evaporated fuel processing apparatus for an internal combustion engine, comprising: evaporated fuel storage means for storing evaporated fuel; and purge control means for controlling purging of the evaporated fuel stored by the evaporated fuel storage means into an intake system of the internal combustion engine. In an evaporative fuel treatment apparatus for an internal combustion engine, the load fluctuation amount detecting means for detecting a fluctuation amount of the load of the internal combustion engine, and the internal combustion engine according to the operating state of the internal combustion engine.
And a purge amount control means for calculating the amount of fuel to be purged, wherein the purge control means is configured to control the purge amount when the load variation amount detected by the load variation amount detecting means is large.
Of the amount of evaporated fuel and the calculated amount of fuel
Before each value and the fuel amount calculated after the change of the load
An evaporated fuel processing apparatus for an internal combustion engine , wherein the amount of evaporated fuel to be purged is calculated based on the above . 2. An oxygen concentration in exhaust gas of an internal combustion engine is detected.
The mixture supplied to the internal combustion engine based on the output of the air-fuel ratio sensor
Air that performs feedback control of the air-fuel ratio of Aiki to the target air-fuel ratio
Evaporative combustion of internal combustion engine equipped with fuel ratio feedback control means
Fuel processing device for storing evaporated fuel
Means and evaporated fuel stored by the evaporated fuel storage means
Purge control hand for controlling the purging of the internal combustion engine to the intake system
In a vaporized fuel processing apparatus for an internal combustion engine, the load variation amount detecting means detecting the variation amount of the load of the internal combustion engine.
Means for controlling the air-fuel ratio feedback control means in the internal combustion engine.
To control the air-fuel ratio of the supplied mixture to the target air-fuel ratio
To the air-fuel ratio correction coefficient based on the output of the air-fuel ratio sensor
The purge control means is calculated by the load fluctuation amount detection means.
When the fluctuation amount of the detected load is small, the air-fuel ratio correction
The fuel vapor to be purged until the coefficient falls below a predetermined value
The amount is gradually increased so that the air-fuel ratio correction coefficient falls below the predetermined value.
Gradually decreasing the amount of evaporated fuel to be purged when
An evaporative fuel treatment system for an internal combustion engine.