JPS63129159A - Air-fuel ratio control device - Google Patents

Abstract

PURPOSE:To prevent a canister from large forming its size while to perform a proper engine control, by constituting a device such that a study value for the amount of fuel, contained in a mixture supplied to an engine, is updated on the basis of detected air-fuel ratio when a purge passage is placed in a closed condition. CONSTITUTION:A solenoid valve 33 is controlled by a control circuit 20 so that a purge passage 30 is opened and closed in a predetermined period, and this causes purge gas to be interruptedly introduced to an intake system. And when the purge passage 30 is closed by the control circuit 20, in short, when no purge gas is introduced to the intake system, updating of a study value is executed by an updating executing means on the basis of air-fuel ratio detected by an air-fuel ratio sensor 14. In short, introduction of the purge gas to the intake system is executed prior to updating the study value. Accordingly, a proper engine control can be performed by sufficiently ensuring the introduction time of the purge gas to the intake system and enabling a canister 32 to be prevented from large forming its size while updating of the study value to be surely executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device used in a vehicle internal combustion engine.

[Conventional technology]

Conventionally, the engine exhaust system detects the deviation of the air-fuel ratio of the air-fuel mixture drawn into the engine from the design target value due to machine differences in the amount of air taken into the internal combustion engine, changes in the characteristics of the intake air amount sensor over time, etc. Learning control is generally known in which the air-fuel ratio of the air-fuel mixture taken into the engine is detected from a signal from an air-fuel ratio sensor installed in the engine, and the air-fuel ratio is corrected based on the detection result.

On the other hand, in order to reduce the amount of HC emitted from vehicles,
Evaporated fuel (hereinafter also referred to as purge gas) from within the fuel tank is introduced into the intake system of the engine.

For this reason, the air-fuel ratio detected by the signal of the air-fuel ratio sensor is influenced by the amount of purge gas introduced.
Therefore, while the purge gas is being introduced, it becomes impossible to detect the machine difference variation that is to be corrected by the learning control, or changes in the air-fuel ratio due to changes in sensor characteristics over time, etc.

To address this problem, the air-fuel ratio control method disclosed in Japanese Patent Application Laid-Open No. 57-165644 prohibits the introduction of purge gas when the conditions for performing learning update in learning control are met.

[Problem that the invention seeks to solve]

However, in this case, the engine state at the time of updating the learning value in learning control and the engine state at the time of introducing purge gas are independent, and updating the learning value is given priority over the introduction of purge gas. Therefore, the engine operating conditions for introducing purge gas are limited to a narrow range,
It was not possible to secure enough time to introduce purge gas, and as a result, the purge gas had to be temporarily stored (the canister had to be made larger), and a high concentration of purge gas was supplied to the engine when purge gas was introduced. As a result, the air-fuel ratio of the air-fuel mixture temporarily becomes overrich, causing an increase in harmful components in the exhaust gas.

Therefore, in view of the above-mentioned problems, the present invention provides an air-fuel ratio control device that can solve the above-mentioned problems by providing an opportunity to update a learned value without being affected by the purge gas while ensuring sufficient purge gas introduction time. is intended to provide.

[Means for solving problems]

In order to solve the above-mentioned problems, in the present invention, the update speed of the learning value in learning control does not need to be made faster because it takes into account variations in engine differences, changes over time in the characteristics of the intake air amount sensor, etc. Focusing on this, as shown in Fig. 9, there is a detection means for detecting the operating state of the engine, including the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, and a detection means for detecting the operating state of the engine, including the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine. a purge passage for guiding the purge passage; an opening/closing means provided in the purge passage for opening and closing the purge passage; and based on the operating state of the engine detected by the detection means,
a control means for controlling the opening/closing means so that the purge passage is opened and closed at a predetermined period to introduce the evaporated fuel into the intake system; and based on the air-fuel ratio detected by the detection means, and update execution means for updating the learned value for the amount of fuel contained in the air-fuel mixture supplied to the engine by the control means when the purge passage is closed by the opening/closing means. This is an air-fuel ratio control device.

[Effect]

According to the above configuration, the opening/closing means is controlled by the control means so that the purge passage is opened and closed at a predetermined period, so that purge gas is continuously introduced into the intake system. Then, when the purge passage is closed by the control means, that is, when purge gas is not introduced into the intake system, the learning value is updated by the update execution means based on the air-fuel ratio detected by the detection means. be done.

In other words, the introduction of purge gas into the intake system is executed with priority over updating of the learned value.

〔Example〕

The present invention will be described below with reference to an embodiment shown in the drawings.

In FIG. 1, an engine 1 is a known four-stroke spark ignition engine mounted on an automobile, and intakes combustion air through an air cleaner 2, an intake pipe 3, and a throttle valve 4. Further, fuel is supplied from a fuel system (not shown) through electromagnetic fuel injection valves 5 provided corresponding to each cylinder. The exhaust gas after combustion is released into the atmosphere through an exhaust manifold 6, an exhaust pipe 7, a three-way catalytic converter 8, and the like. The intake pipe 3 includes a potentiometer-type intake air amount sensor 11 that detects the amount of intake air taken into the engine 1 and outputs an analog voltage according to the amount of intake air; A thermistor-type intake air temperature sensor 12 that outputs a corresponding analog voltage (or analog detection signal) is installed. In addition, the engine 1 detects the cooling water temperature,
A thermistor-type water temperature sensor 13 that outputs an analog voltage (analog detection signal) according to the cooling water temperature is installed, and the exhaust manifold 6 detects the air-fuel ratio based on the oxygen concentration in the exhaust gas, and the air-fuel ratio is determined by the theoretical air-fuel ratio. smaller than the air-fuel ratio (
i.e. rich), about 1 volt (high level in this case),
An air-fuel ratio sensor 14 is installed that outputs a voltage of about 0.1 volt (low level in this case) when the air-fuel ratio is higher than the stoichiometric air-fuel ratio (that is, lean). The rotational speed (or rotational speed) sensor 15 detects the rotational speed of the crankshaft of the engine 1 and outputs a pulse signal with a frequency corresponding to the rotational speed. For example, an ignition coil of an ignition device may be used as the rotation speed (rotation speed) sensor 15 (an ignition pulse signal from the primary terminal of the ignition coil may be used as the rotation speed signal).
An idle switch (IDLESW) 16 detects the throttle fully closed position.

17 is a starter switch that is turned on when the starter is operating. The fuel tank 31 stores fuel such as gasoline, and the evaporated fuel generated from this is temporarily transferred to the purge passage 30.
It is stored in a canister 32 via a purge passage 30 and supplied from the throttle section to the engine via a solenoid valve 33 provided in a purge passage 30 depending on the state of the engine. The control circuit 20 calculates the fuel injection amount based on the detection signals of the sensors 11 to 17 to control the opening time of the electromagnetic fuel injection valve 5,
Is it the opening/closing side of the solenoid valve 33 that supplies evaporated fuel? 111.

Next, the control circuit 20 will be explained with reference to FIG. 1
00 is a microprocessor (i.e., CPU) that calculates the fuel injection amount. 101 is a rotation number counter that indicates the rotation speed (
This is a rotational speed counter that counts the engine rotational speed based on the signal from the rotational speed sensor 15. In addition, this rotation number counter 101 is synchronized with the engine rotation and interrupts the interrupt control unit 1.
Send an interrupt command signal to 02. Interrupt control unit 102
When receiving this signal, it outputs an interrupt signal to the microprocessor 100 via the common bus 150. 10
A digital input port 3 transmits digital signals such as the signal from the air-fuel ratio sensor 14, the signal from the idle switch 16, and the signal from the starter switch 17 to the microprocessor 100. Reference numeral 104 is an analog input port consisting of an analog multiplexer and an A-D converter, and has the function of A-D converting each signal from the intake air amount sensor 11, intake air temperature sensor 12, and water temperature sensor 13 and sequentially reading it into the microprocessor 100. . Each of these units 101゜10.2, 103
, 104 is transmitted to the microprocessor 100 through the common bus 150.

A power supply circuit 105 supplies power to a RAM 107, which will be described later. 18 is a battery, and 19 is a key switch, but the power supply circuit 105 is directly connected to the battery 18 without passing through the key switch 19.

Therefore, power is always applied to the RAM 107, which will be described later, regardless of the key switch 19. 106 is also a power supply circuit, which is connected to the battery 18 through a key switch 19. The power supply circuit 106 supplies power to parts other than the RAM 107, which will be described later.

Reference numeral 107 is a temporary storage unit (i.e. RAM) used temporarily during program operation, but as mentioned above, the key switch 1
Power is always applied regardless of the key switch 19.
Even if the engine is turned to FF and the operation of the engine is stopped, the stored contents will not be lost, thus forming a non-volatile memory. A second correction amount Kt, which will be described later as a learning value, is also stored in this RAM 107. Reference numeral 108 is a read-only memory (ie, ROM) that stores programs, various constants, and the like.

The output circuit 109 consists of a latch, a down counter, a power transistor, etc., and is powered by a microprocessor (CPU).
A digital signal representing the opening time of the electromagnetic fuel injection valve 5 calculated in step 100, that is, the fuel injection amount, is used to create a pulse signal with a pulse time width that gives the actual opening time of the electromagnetic fuel injection valve 5, and this pulse size is A signal is applied to the electromagnetic fuel injection valve 5. The output circuit 110 is composed of a latch, a power transistor, etc., and the CPU 100 generates an ON or OFF control signal according to the calculation result based on each input signal, and applies this signal to the electromagnetic valve 33. The timer 111 is a circuit that generates clock pulses and measures elapsed time.
0, or outputs a clock signal to the interrupt controller 102.
Outputs a time interrupt signal.

The rotational speed counter 101 measures the engine rotational speed once per engine rotation based on the output of the rotational speed sensor 15, and supplies an interrupt command signal to the interrupt control section 102 at the end of the measurement. The interrupt control unit 102 uses the signal as a CP
Generates a rotation interrupt signal to U100.

3 to 6 show schematic flowcharts of programs executed by the CPU 100, and the functions of the CPU 100 will be explained based on these flowcharts, as well as the operation of the entire configuration.

FIG. 3 is a flowchart of a program for controlling the electromagnetic valve 33 for introducing/not introducing purge gas into the intake pipe 3, and is executed as an interrupt routine every 50 m5, for example.

In step 301, it is determined whether or not the engine 1 has been warmed up based on the signal from the water temperature sensor 13. If it is determined that the engine 1 has been warmed up, the process proceeds to step 302. Also step 3
At step 02, it is determined whether the idle switch 16 is OFF, that is, whether the throttle valve 4 is open. If the idle switch 16 is OFF, the process advances to step 303. In other words, in steps 301 and 302, it is determined whether the engine conditions are such that it is possible to introduce purge gas into the engine 1, and the engine conditions are such that the engine has warmed up and is generating a torque greater than a predetermined torque. At some point, it is determined that the conditions are good enough to introduce purge gas. Note that this condition may be determined by taking into account not only the cooling water temperature and the state of the throttle valve 4 described above, but also the intake air temperature, the rotational speed, the engine load, and the like.

In step 303, it is determined whether the solenoid valve 33 is turned on and purge gas is introduced into the intake pipe 3, and flag A is "1". If it is "1", the process proceeds to step 304. . In step 304, a counter CI built into the CPU 100 is counted down, and in step 305, it is determined whether the counter C3 is at C3>0.

If CI>O, the process proceeds to step 306, where the output circuit 1 is connected to the solenoid valve 33 in order to continue introducing the purge gas.
It outputs an ON signal via 10 and returns to the main routine. Also, if it is determined rNo in step 305,
The process advances to step 307, where flag A is set to "O". Then, in step 308, the counter CI is reset to O, and in step 309, another counter C2 built into the CPU 100 is set to 300. Then, in step 310, the solenoid valve 33 is supplied with an O
Outputs the FF signal and turns off the power to the solenoid valve 33,
Return to main routine.

Further, if it is determined in step 303 that flag A is "0", the process proceeds to step 311.

In step 311, the counter C2 is counted down. In step 312, it is determined whether the counter C2 is C2>0, and if C2>0, the process proceeds to step 313. In step 313, an output is sent to the solenoid valve 33 via the output circuit 110 in order to continue the state in which no purge gas is introduced. If rNOJ is determined in step 312, the process proceeds to step 314, where flag A is set to "1". Then, in step 315, the counter C2 is reset to O, and in step 309, the counter C7 is set to 600. Then, in step 317, an ON signal is output to the solenoid valve 33 via the output circuit 110 to start introducing the purge gas, turning on the power to the solenoid valve 33, and returning to the main routine.

Also, in step 301 or step 302, rNO
If it is determined that the purge gas is not allowed to be introduced, the process proceeds to step 318. In step 318, the flag A is set to "O".
9, the counter C2 is reset to 0, and step 320
Then, an OFF signal is output to the solenoid valve 33 via the output circuit 110 so that the purge gas is not introduced.

According to the above program, when the conditions for introducing purge gas are satisfied, the solenoid valve 33 is opened for 30 seconds, the purge gas is introduced during that time, and then the purge gas is introduced.
The solenoid valve 33 is closed for 5 seconds, and the introduction of purge gas is prohibited during that time. And while the above conditions are met, 45
The solenoid valve 33 is repeatedly opened and closed every second, and the purge gas is introduced intermittently.

In addition, in this embodiment, the time during which the solenoid valve 33 is closed is set to a sufficiently long time compared to the combustion cycle of the engine, and this is because the purge gas is This is to eliminate the influence of Further, in order to sufficiently introduce the purge gas into the intake pipe 3, the time during which the solenoid valve 33 is opened is set to be sufficiently longer than the time during which the solenoid valve 33 is closed.

In FIGS. 4 to 6, 2 is calculated for the first correction iKl and the second correction amount, and +, K is calculated for the first and second correction amounts.
This is a flowchart showing a program that calculates the fuel injection amount (fuel injection time) based on z, and is executed as, for example, a main routine.

When the key switch 19 and starter switch 17 are turned on and the engine 1 is started, step 100 in FIG.
0, it is determined whether the correction amount 2 corresponds to a reset condition, which will be described later. is reset to a predetermined value and the process proceeds to step 1002.In step 1002, the analog input port 104 outputs digital values obtained by A/D conversion of cooling water temperature, intake air temperature, and intake air amount, and the rotation number counter 101 outputs digital values according to the rotation number. Read each digital value.

In step 1003, the fuel injection amount, that is, the basic injection time (1) of the electromagnetic fuel injection valve 5, is calculated from the engine rotation speed N taken from the rotation speed counter 101 and the intake air IQ taken from the analog boat 104.

The calculation formula is L=FXQ/N (F: constant).

In step 1004, it is determined whether the air-fuel ratio feedback condition is satisfied by looking at various input signals, and if the air-fuel ratio feedback condition is satisfied, the process proceeds to step 1005, and if not, the process proceeds to step 1006. Processing is performed when the air-fuel ratio feedback condition is not satisfied. In step 1005, the signal of the air-fuel ratio sensor 14 is inputted from the digital input port, and the correction amount, which will be described later, is increased or decreased as a function of the elapsed time by the timer 111, and this correction amount, that is, the integral processing information is stored in the RAMIO7.

FIG. 5 shows correction ff1K as this integral processing information.

10 is a detailed flowchart of processing step 1005 for increasing or decreasing, that is, integrating. First, in step 500, it is determined whether the air-fuel ratio sensor 14 is in an active state or whether feedback control of the air-fuel ratio can be performed based on the cooling water temperature, etc., and if feedback control is not possible, that is, in the case of open loop, the process proceeds to step 506. The advance correction amount is set to 1, and the process proceeds to step 505. If feedback control is possible, step 50
Go to 1. In step 501, it is determined whether the elapsed time has passed by a unit time Δ, and if the elapsed time has not passed, the processing step 1005 is terminated without making a correction of 1.

If the time Δ has elapsed, the process proceeds to step 502, and if the air-fuel ratio is rich and the output of the air-fuel ratio sensor 14 is a rich high-level signal, the process proceeds to step 503, where the value obtained in the previous cycle is 1. is decreased by 1 to Δ, the process proceeds to step 505, and this new correction amount is stored in the RAM 10.
Store in 7.

In step 502, if the air-fuel ratio is lean and the output of the air-fuel ratio sensor 14 is a low level signal indicating lean, the process proceeds to step 504, where Δ is increased by Δ, and the process proceeds to step 505. In this way, the correction amount Kt is increased or decreased.

In step 1007, it is determined whether or not the correction amount has been calculated a predetermined number of times. If the calculation has been performed a predetermined number of times, the process proceeds to step 1008; otherwise, the process proceeds to step 1014. In step 1008, it is determined whether or not an increase in power during warm-up is being implemented. If the increase in power during warm-up is not in progress, the process proceeds to step 1009, and if it is in progress, the process advances to step 1014. In step 1009, it is determined whether or not the amount is being increased during the transient period. If the amount is not being increased during the transient period, the process proceeds to step 1010, and if it is being performed, the process proceeds to step 1014.

In step 1010, it is determined whether the engine intake air amount is large. If the engine intake air amount is not large, the process proceeds to step 1011, and if it is large, the process proceeds to step 1014. In step 1011, it is determined whether or not there has been a predetermined number of times when the engine intake air amount is not large. If so, the process proceeds to step 1014; otherwise, the process proceeds to step 1012.

In step 1012, it is determined whether flag A in the purge gas control shown in FIG. 3 is NJ, that is, whether the solenoid valve 33 is opened and purge gas is being introduced. Proceed to step 1014;
Otherwise, the process advances to step 1013. In other words, through steps 1007 to 1011, it is determined that the engine state satisfies the update condition for the second correction amount Kt as shown in FIG. 7(a), and also as shown in FIG. 7(b). Only when the flag A that is entered is not rl, that is, when the solenoid valve 33 is closed and no purge gas is introduced (step 1012), it is permitted to proceed to step 1.13.

Note that in processing step 1006 when the air-fuel ratio feedback condition is not satisfied, the integral correction ff1(K,) is set to a constant value of 1.
00 and the process proceeds to step 1014.

In step 1013 in FIG. 4, the correction fi K 2 is increased or decreased, and the result is stored in the RAM 107. FIG. 6 is a detailed flowchart of step 1014 in which this correction amount is calculated by 2 and stored, that is, stored.

In step 601, after the solenoid valve 33 is turned off and the introduction of purge gas is prohibited, that is, the flag A becomes "0".
Determine whether a unit time ΔL2 has elapsed since the change to Δ
If t2 has not yet elapsed, storage processing step 1013 is ended; if t2 has elapsed, the process proceeds to step 602.

By the way, the reason why we wait for the unit time Δt2 to elapse after the flag A changes to r□ in step 601 is that the purge gas that was introduced into the intake pipe 3 when the purge gas was introduced has completed the combustion cycle of the engine 1 a predetermined number of times. This is to prevent the calculation of the second correction amount from being executed repeatedly until no purge gas remains in the intake pipe 3, that is, to prevent the purge gas from affecting the calculation of the second correction amount. This is for the purpose of Therefore, as mentioned above, the time during which the solenoid valve 33 is closed and the introduction of purge gas is prohibited when the purge gas introduction conditions are satisfied (the time during which flag A is "0") is sufficiently longer than the combustion cycle of the engine. This is, of course, sufficiently longer than the unit time Δt2 (see FIG. 7).

Next, in step 602, the value of the first correction ffl K + is determined, and if K1=1, this processing step 1013 is ended without doing anything.

Note that the correction amount 2 forms a map as shown in FIG. 8 using the intake air ff1Q. In this case, the throttle fully closed position detection switch (i.e. IDLE SW) is turned on and off.
They are distinguished by FF, and each is divided into 32 parts based on the amount of evening air. For example, in IDLE 5WON, the nth correction amount is 2
is expressed as Kn. Considering the operating conditions, a correction amount of water is used when idling or decelerating. As a general representation, in FIG. 6, the correction it K z is expressed as .

If the result in step 602 is 1, the process proceeds to step 603, where the correction IKfi obtained in the previous cycle is decreased by 2 to Δ, and the result is stored in the RAM 107 in step 605. In step 602, if <1, step 604
Step 605 increments the correction amount obtained in the previous cycle by 7 and Δ by 2, and proceeds to step 605.
End 13. In step 1014, step 10
To the correction amount calculated in 05°1006.1013, K.

is multiplied by the basic injection time t and corrected to obtain the effective injection time T.
Then, in step 1015, the invalid injection time τ9 corresponding to the battery voltage is added to the effective injection time T, and in step 1016, the output injection time τ is set in the counter. When step 1016 in this main routine is completed, step 1000 is executed. Return to

According to the above-mentioned program shown in FIGS. 4 to 6,
In step 1012, flag A indicates whether the solenoid valve 33 is opened and purge gas is being introduced, or the solenoid valve 33 is closed and purge gas is prohibited from being introduced.
Judging from the state, the calculation processing step of the second correction fiK of step 1013 is entered only when the flag A is "0", that is, the solenoid valve 33 is closed and the introduction of purge gas is prohibited. In other words, the purge gas control 4B is set to be executed with priority over the calculation process 2 for the second correction amount.

Note that the second correction amount processed in step 1013 is 2, that is, the learning value targets engine machine differences, changes over time in the intake air amount sensor characteristics, etc., as described above, so the update speed is increased. Since there is no need to increase the speed, even if purge gas control is prioritized, engine control will not be affected.

Therefore, according to the above configuration, since the introduction of purge gas is given priority over the calculation process of the second correction amount (learning value), sufficient time for introducing purge gas can be secured, and the canister can be Problems such as increasing size can be solved.

In addition, the purge gas is introduced and prohibited intermittently, and when the purge gas is prohibited, the second correction amount (learned value) calculation process can be executed, so the second correction value (learned value)
updates are performed reliably to ensure proper engine control.

In the above embodiment, the intake air amount is determined by the intake air amount sensor 11, and the present invention is applied to a system in which the intake air amount is used to determine the fuel injection time. This proposal can also be applied to systems that determine the fuel injection time.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a detection means for detecting the operating state of the engine, including the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, and a detection means for detecting the operating state of the engine, including the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine; a purge passage for guiding the purge passage; an opening/closing means provided in the purge passage for opening and closing the purge passage; and based on the operating state of the engine detected by the detection means,
a control means for controlling the opening/closing means so that the purge passage is opened and closed at a predetermined period to introduce the evaporated fuel into the intake system; and based on the air-fuel ratio detected by the detection means, and update execution means for updating the learned value for the amount of fuel contained in the air-fuel mixture supplied to the engine by the control means when the purge passage is closed by the opening/closing means. Since the air-fuel ratio control device is designed to perform a Sufficient time is secured for the introduction of fuel into the intake system, which prevents the canister from increasing in size, and also temporarily suppresses the concentration of evaporated fuel when the introduction of evaporated gas into the intake system is resumed. This has the excellent effect of suppressing the increase in harmful components in the generated exhaust gas.

Further, the control means controls the opening and closing means for opening and closing the purge passage so that the purge passage is opened and closed at a predetermined period, and in the update execution means, the opening and closing means is kept in a closed state by the control means. Since the learned values are updated at the same time, sufficient update opportunities are given to the learned values that do not require much update speed, and therefore the learned values can be updated reliably. Become,
Another advantageous effect is that proper engine control can be fully guaranteed.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing an embodiment of the present invention, Fig. 2 is a block diagram of the control circuit shown in Fig. 1, and Figs. 3 and 4 are executed in the CPU shown in Fig. 2. Flowchart of the program, FIG. 5 is a detailed flowchart of step 1005 shown in FIG. 4, and FIG. 6 is a detailed flowchart of step 1005 shown in FIG. 4.
Detailed flowchart of 013, Figure 7 shows Figures 3 to 6.
FIG. 8 is a time chart showing the operation of the control circuit based on the program shown in FIG. FIG. 1 is a block diagram showing a schematic configuration of the invention. 1... Engine, 11... Intake air amount sensor, 14...
・Air-fuel ratio sensor, 15...Rotational speed sensor, 20...
- Control circuit, 31... Fuel tank, 32... Canister, 33... Solenoid valve, 100... Microprocessor (CPU) 107... RAM.

Claims (1)

[Scope of Claims] Detection means for detecting the operating state of the engine, including the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, and a purge passage for guiding evaporated fuel generated in the fuel tank to the intake system of the engine. and an opening/closing means provided in the purge passage for opening and closing the purge passage, based on the operating state of the engine detected by the detection means,
a control means for controlling the opening/closing means so that the purge passage is opened and closed at a predetermined period to introduce the evaporated fuel into the intake system; based on the air-fuel ratio detected by the detection means; and update execution means for updating the learned value for the amount of fuel contained in the air-fuel mixture supplied to the engine by the control means when the purge passage is closed by the opening/closing means. air-fuel ratio control device.