JPH0432935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an engine fuel control device, particularly an O ₂
An engine that controls fuel using the output of an air-fuel ratio sensor such as a sensor as a feedback signal, stores the control results as a learned value, and starts the next fuel control based on the learned value. The present invention relates to a fuel control device.

(Prior art) In order to improve the responsiveness of fuel control to so-called aging of engines, variations in performance among individual engines, and transient engine operation,
A so-called learning control method has been proposed. This learning control method for fuel control uses an O ₂ sensor installed in the engine's exhaust system to judge from time to time whether the air-fuel ratio is correctly controlled to the stoichiometric air-fuel ratio and uses the output signal of the O ₂ sensor. Feedback controls the fuel amount based on the information, and learns (memorizes) the correct fuel amount in each operating zone of the engine, which is basically determined by intake negative pressure (engine load) and engine speed, at an appropriate timing through sampling. Then, when the operating state is changed, the learned value corresponding to the changed operating zone is read out, and the current fuel control is performed using this learned value as a reference (Japanese Patent Laid-Open No. 1983-1999).
(See Publication No. 96339).

However, in this learning control method, the O ₂ sensor that determines whether the control is correct or not only determines whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio, so it cannot be operated with the air-fuel ratio enriched. In the high-load operating range of the engine (the so-called enrichment zone) where it is necessary to carry out the fuel injection, there is a problem in that even if it is possible to determine that the air-fuel ratio is rich, it is not possible to determine whether or not the fuel is appropriate.

For this reason, in the conventional learning control system, open loop control is currently used in the high load operating range, and fixed map control that is preset in accordance with the operating state is currently performed.

In view of the current situation, the applicant of this application has filed a patent application
In the patent application No. 164698 (Japanese Unexamined Patent Publication No. 59-54750) (title of the invention: "Engine fuel control device"), the value learned during closed-loop air-fuel ratio control is An engine fuel control device that can achieve optimal control of fuel (air-fuel ratio) that takes into account aging and variations in the engine over the entire operating range of the engine by reflecting it in the fuel control of each operating state in the load operating range. is proposed.

(Object of the Invention) The present invention has been made based on the above-mentioned invention, and provides two cases in which secondary air for purifying exhaust gas is supplied to the exhaust system of an engine even under the same operating condition. Next, when the air supply is stopped, that is, 2
This method focuses on the fact that the engine condition correction value is different at the time of the next air cut.

In other words, in the operating range (feedback zone) where closed-loop control of the air-fuel ratio is performed, secondary air is normally supplied to the engine's exhaust system and is controlled by an exhaust gas purification device such as a catalyst type installed in the exhaust passage. The unburned components in the exhaust gas are purified by reacting with oxygen in the secondary air. On the other hand, in the high-load operating range (enrich zone) where open-loop control is performed, the air-fuel ratio is set to the rich side to ensure high engine output, and the amount of exhaust gas also increases compared to the operating range with closed-loop control. Therefore, when secondary air is supplied to the exhaust system, there is a problem in that excessive reaction heat is generated within the exhaust gas purification device, leading to thermal deterioration of the catalyst and the like. Therefore, in high-load operating ranges where open-loop control is performed, secondary air is usually cut off.

Now, if we consider the case where secondary air is being supplied, in this case, the oxygen contained in the secondary air will greatly affect the output of the O ₂ sensor installed in the exhaust system. In reality, the secondary air supply position is O ₂
It may be upstream or downstream of the sensor setting position in the exhaust gas flow direction, but even if it is downstream, a part of the secondary air may be The flow is reversed to the ₂ sensor position,
The output of the _O2 sensor will be affected thereby. On the other hand, during operation with the secondary air cut off, the output of the O ₂ sensor is naturally not affected by the secondary air.

In other words, for example, even if the engine operating state specified by the intake negative pressure and engine speed is the same, the difference between when secondary air is supplied and when it is cut is
The feedback signal, which is the output of the O ₂ sensor, will show different values. Therefore, it is important to use the engine condition correction value obtained during closed-loop control that supplies secondary air as the basic data for setting the engine condition correction value during open-loop control that cuts off secondary air. This is not preferable because it includes errors.

The present invention specifically aims to solve this problem, and seeks an engine condition correction value during open loop control (enrich zone) in which the supply of secondary air to the exhaust system is stopped. In this case, calculate the engine condition correction value during closed-loop control with the secondary air cut to the exhaust system, and calculate the engine condition correction value in the feedback zone with the secondary air cut to the exhaust system. It is an object of the present invention to provide an engine fuel control device that calculates an engine condition correction value in an enrichment zone using an engine condition correction value as basic data.

(Structure of the Invention) For this reason, the present invention learns the engine condition correction value in the feedback zone while supplying secondary air to the exhaust system and cutting off the secondary air to the exhaust system. Calculates the engine condition correction value in the enrichment zone using the learned value (engine condition correction value) when the supply of secondary air is stopped, and executes open-loop control of the air-fuel ratio based on this engine condition correction value. I try to do that.

As shown in the block diagram of the invention in FIG. 1, the present invention includes an air-fuel ratio sensor 1 that outputs a signal corresponding to the air-fuel ratio of the air-fuel mixture taken into the engine E, and an operating state sensor that detects the engine operating state. 2
a first storage device 3 in which a basic control value for controlling the air-fuel ratio of the air-fuel mixture taken into the engine is given in advance in accordance with the engine operating state; a second storage device 4 for storing engine condition correction values corresponding to respective operating conditions; and a second storage device 4 for calculating an air-fuel ratio correction value based on the output signal of the air-fuel ratio sensor during closed-loop air-fuel ratio control, and processing the air-fuel ratio correction value. The engine state correction value is determined and the engine state correction value corresponding to the engine operating state at the time of processing is updated in the second storage device 4, and the air-fuel ratio sensor is installed during closed-loop air-fuel ratio control and in a state where secondary air is cut off. An air-fuel ratio correction value is determined by the signal No. 1, and an engine condition correction value is calculated at the time of open-loop air-fuel ratio control and secondary air cut based on the engine condition correction value obtained by processing the air-fuel ratio correction value. The engine state correction value is stored in correspondence with the engine operating state during open loop air-fuel ratio control in the second storage device 4 and during secondary air cut, and the basic control value in the first storage device 3; A control device that controls the air-fuel ratio of the air-fuel mixture taken into the engine based on the engine condition correction value stored in the second storage device 4 and the air-fuel ratio correction value obtained based on the output signal of the air-fuel ratio sensor 1. 5 is a fuel control device for an engine.

(Effects of the Invention) According to the present invention, during closed loop control in the feedback zone, an engine condition correction value is obtained with the secondary air cut off, and the engine condition correction value thus obtained is used as basic data. Since the engine condition correction value in the enrichment zone is calculated as follows, the engine condition correction value calculated in the operating condition of the enrichment zone can be calculated without being affected by secondary air. This can be reflected in the fuel control of the zone (feedback cut zone), and the fuel control in the enrichment zone can be made more accurate.

(Example) Hereinafter, an example of the present invention will be described in more detail.

As shown in FIG. 2, the fuel control system for the engine E according to the present invention commands the discharge amount to the injector 8 that injects fuel into the intake passage 7 downstream of the air cleaner 6, and also instructs the injector 8 to inject fuel into the intake passage 7 downstream of the air cleaner 6. is pressurized by air pump 9,
turning on an electromagnetically actuated secondary air control valve 12 interposed in a secondary air supply passage 11 that supplies secondary air upstream of the exhaust passage 10 of the engine E;
It basically consists of a microcomputer 5 as a control device for controlling off, and the following sensors that provide various data necessary to this microcomputer 5.

Negative pressure sensor 13...Detects the intake negative pressure downstream of the throttle valve 14 in the intake passage 7.

Rotation sensor 15...Detects the rotation speed of the engine E. This rotation sensor 15 is the negative pressure sensor 13
Together, they constitute the driving state sensor 2 referred to in the present invention.

_O2 sensor 1: Located upstream of the catalyst device 16 in the exhaust passage 10 of the engine E, it detects whether the air-fuel ratio of the air-fuel mixture taken into the engine E is rich or lean based on the oxygen concentration in the exhaust gas.

Intake temperature sensor 17...Detects the temperature of intake air.

Water temperature sensor 18...Detects the cooling water temperature of the engine cooling water passage 19.

As shown in FIG. 3, the microcomputer 5 constituting the control device according to the present invention inputs the outputs of the sensors 1, 13, 15, 17, and 18, or inputs the outputs of the injector 8 and the secondary air control valve 12. I/ for outputting commands
O interface 20, central processing unit (CPU) 21, read-only memory (ROM)
22. Random access memory (RAM) 2
3, and has a basic structure in which these are connected by a data bus 24 and an address bus 25.

Each address of the read-only memory 22 is
Each engine operating state specified by the engine speed r and the intake negative pressure V, more specifically, as shown in FIG. 6, the engine speed r and the intake negative pressure V=
Corresponding to the engine operating states z1 to z10 and zA to zC divided by the curves of V ₁ , V ₂ , V ₃ , and V ₄ , the basic fuel discharge amount for each engine operating state is shown at each corresponding address. By storing Q′(r,V) in advance,
Create a basic control map and use this read-only
A part of the memory 22 is used as the first storage device 3 according to the present invention.

Similarly, the random access memory 23
Each address corresponds to each engine operating state specified by the engine speed r and intake negative pressure V, and the corresponding address can be updated with an engine state correction value _K3 , which will be explained in detail below, as a learned value. memorize it,
A part of this random access memory 23 is used as the second storage device 4 according to the present invention.

And CPU21 of microcomputer 5
The pulse width is determined during execution of the main routine as shown in the flowchart of FIG. Then, the pulse is outputted by an interrupt signal during execution of the main routine.

This fuel control routine initializes the I/O interface 20 and necessary data by a start signal, and then performs the following step 1.
Execute steps 7 to 7 and repeat.

In step 1, the rotation sensor 15, negative pressure sensor 13, water temperature sensor 18, intake temperature sensor 17, and
The engine speed r, intake negative pressure V, cooling water temperature θw, intake air temperature θa, and O ₂ sensor signal P are read from the O ₂ sensor 1 via the I/O interface 20 .

In step 2, the read engine speed r
Then, the engine operating state at that time is detected from the intake negative pressure V, and the basic discharge amount Q'(r, V) corresponding to the detected engine operating state is read from the basic control map in the first storage device 3.

Next, in step 3, a temperature correction coefficient K ₁ (θw, θa) for the basic discharge amount Q' is calculated from the read cooling water temperature θw and intake air temperature θa. Calculation of this temperature correction coefficient K ₁ can be performed using the map as described above, but it is possible to calculate the temperature correction coefficient K 1 without using the map.
A formula may also be used. In any case, the temperature correction coefficient _K1 is set to be a larger value than during normal operation when the engine is cold, when the cooling water temperature θw is low, or when the intake temperature θa is low, in cold weather.

Furthermore, in step 4, an air-fuel ratio correction value _K2 is calculated based on the _O2 sensor signal P.

For example, if the previous output signal P of the O ₂ sensor 1 was lean and the current output signal P is also lean, this air-fuel ratio correction value K ₂ is the discharge amount that is the previous discharge amount increased by an appropriate amount. The increase amount ΔK ₂ is calculated so that the calculated increase amount ΔK ₂ is added to the previous air-fuel ratio correction value K ₂ and set as the value K ₂ ←K ₂ +ΔK ₂ . Also, when the output signal P changes from lean to rich, it is considered that the previous discharge amount was too large, so the current reduction amount Δ′K ₂ is calculated based on the previous air-fuel ratio correction value K ₂ The air-fuel ratio correction value of is set as K ₂ ←K ₂ −Δ′K ₂ .

Conversely, if the previous output signal P was rich and the current output signal P is also rich, the reduction amount Δ″K ₂ is calculated and the current air-fuel ratio correction value K ₂ −K ₂ −
If Δ″K ₂ is reversed from rich to lean, the increase amount ΔK ₂ is calculated and the current air-fuel ratio correction value K ₂ is set to K ₂ ←K ₂ +ΔK ₂ .

Note that the air-fuel ratio correction value K ₂ is calculated during open-loop control.
That is, in the high-load operating range of the engine (the operating range indicated by diagonal lines in FIG. 5, hereinafter referred to as the enrichment zone), K 2 is set to a constant value, that is, K ₂ =1.

In the next step 5, an engine condition correction value _K3 corresponding to each engine operating condition is calculated based on the air-fuel ratio correction value _K2 .

The calculation (learning) of this engine condition correction value _K3 is as follows:
This is carried out according to the flowchart shown in FIG. This will be explained in detail below with reference to FIG.

In step 501, at the start of learning, the learning state value IF, which takes "1" when learning _K3 with the supply of secondary air stopped and "0" otherwise, is set to "0". Next, it is determined in which operating zone the current engine operating state is located based on the engine rotational speed r and the intake negative pressure V. As shown in FIG. 6, the normal operating range of the engine (excluding the acceleration/deceleration operating range) is divided into feedback zones z1, . . . for each engine operating state specified by engine speed r and intake negative pressure V. ..., z10 and enrichment zones zA, zB, zC shown by diagonal lines,
From the engine speed r and intake negative pressure V read in step 1, it is determined to which zone the current engine operating state belongs.

The feedback zones z1 to z10 are zones where learning control, that is, closed loop control, is performed based on the output signal P of the O ₂ sensor 1, and in this zone, the secondary air control valve 12 is normally in the open state. While holding the position, secondary air supplied by the air pump 9 is supplied to the exhaust passage 10 via the secondary air supply passage 11, and the exhaust gas is purified by the catalyst device 16. On the other hand, enrichment zone zA,
zB and zc are open-loop control zones corresponding to the high-load operating range of engine E, that is, zones where control based on the output signal P of O ₂ sensor 1 cannot be performed, and the air-fuel ratio of the mixture is equal to the stoichiometric air-fuel ratio. The fuel ratio is controlled to be richer, and secondary air is cut off in this zone to prevent thermal deterioration of the catalyst device 16.

Next, in step 502, the determined zone m
It is determined whether or not the zone belongs to the enrichment zones zA, zB, zC, and if any of the enrichment zones zA, zB, zC, for example zA, is stored in the memory in the second storage device 4 in step 529. A certain previous engine condition correction value K ₃ (zA) is read out and used as a correction value for the discharge amount Q.

In steps 503 and 504, it is determined whether the acceleration/deceleration operation is being performed or not.
It is determined whether or not the machine is in cold operation, and in step 505,
If the operating state belongs to the feedback zone, it is determined whether it belongs to any of the feedback zones z8, z9, and z10 adjacent to the enrichment zones zA to zC.

() If the feedback zone is other than z8, z9, or z10 (m = z1 to z7) In this case, proceed to step 516 and basically repeat the routine of steps 516 to 529. Then, the engine condition correction value _K3 is calculated by learning by sampling the air-fuel ratio correction value _K2 .

That is, when the number of sampling times I reaches I=8, I=0, k=0 (k is the addition value of _K2 ) are set (step 517), and the output signal P of the _O2 sensor 1 changes from rich to rich. Every time there is a reversal from lean to rich, sampling (see FIG. 7) is performed and the air-fuel ratio correction value _K2 at that time is added (steps 518, 519). Sampling number I
When the value reaches "8", after confirming that IF=0, in step 528, the engine condition correction value K ₃ (m) is determined from the following equation.

K ₃ (m) = K ₃ ′ (m) + (k/8-1)・α Note that K ₃ ′ (m) is the previous engine condition correction value currently stored in the second storage device 4, α is a suitable constant smaller than 1.

Engine condition correction value K ₃ obtained in this way
(m) is read into the corresponding address of the second storage device 4 in step 528, and is the previous engine condition correction value.
K ₃ ′ (m) is the engine condition correction value K ₃ obtained this time.
Rewrite it as (m).

() If the feedback zone is one of z8, z9, or z10 In this case, for example, the feedback zone
After transitioning to z8, learning when supplying secondary air,
Learning with secondary air supply temporarily stopped, 2
Next, a total of three stages of learning are performed, including learning after restarting the air supply.

That is, as shown in Fig. 8, the supply of secondary air is continued until the first set time _t1 , which is set appropriately in advance, is reached, where T is the time from the time when the feed back zone z8 is entered. Then, during the period from the first set time t ₁ to the second set time t ₂ set in consideration of the transient time and until the third set time t ₃ is reached, 2
Learning is performed according to a time chart in which the supply of secondary air is temporarily stopped and the supply of secondary air is restarted after the third set time _t3 .

Note that in FIG. 8, t ₄ is a fourth set time t ₄ that is preset as a transition time when the supply of secondary air is restarted.

The learning at each stage above will be explained below.

()-1 When T<t ₁ (when secondary air is supplied) In this case, the steps described above are repeated until T reaches the first set time t ₁ (step 514).
Through steps 516 to 529, the engine operating state correction value K ₃ (z8), which is in feedback zones z8, z9, and z10 and when secondary air is supplied, is determined by sampling.
Calculate K ₃ (z9) and K ₃ (z10). That is, as mentioned above, each feedback zone z8, z9 or z10
In step 528, the air-fuel ratio correction value K ₂ is added each time the output signal P of the O ₂ sensor 1 is inverted, and after confirming that the secondary air is being supplied, the current engine operating state correction value is added in step 528. _K3 (m)
is determined, and the memory at the corresponding address in the second storage device 4 is updated in step 528.

()-2 t ₂ ≦ T < t ₃ (during secondary air cut) First, when the time T reaches the first set time t ₁ , the sampling number I and the addition value k are calculated in the path from step 514 to step 517. Set to “0”.

Then, in the path of steps 507, 508, and 509, t ₁
When <T< _t2 , a secondary air stop command is output in step 510 to temporarily stop the supply of secondary air.
This secondary air is cut by applying an off signal to the secondary air control valve 12 shown in FIG.
This is done by blocking the next air supply passage 11.

Next, in step 511, an engine condition correction value K ^t ₃ (z8) during the transition period is determined by interpolation calculation. That is, the latest engine condition correction value at T<t ₁
When K ₃ (z8) is Q ₁ and the previous engine condition correction value K ₃ '(z8) at T=t ₂ is Q ₂ , the engine condition during the transition period (t ₁ < T < t ₂ ) Correction value K ^t ₃
(z8) is calculated using the following formula.

K ^t ₃ (z8) = Q ₁ - (Q _{1 -} Q ₂ ) x (T - t ₁ / t ₂ - t ₁ ) This K ^t ₃ (z8) is used as a correction value for the discharge amount Q during the transition period. do.

Next, when the time T becomes more than the second set time _t2 ,
This time, go through steps 508, 512, and 513.
Engine condition correction value K ^s ₃ (z8) on the route 514 to 529, in the feedback zone and when the secondary air is cut
Learn. That is, when Tt ₂ is reached, the supply of secondary air is stopped in step 512 so as to continue to step 510, and the state function IF is changed in step 513.
is set to 1, and the learning begins with the secondary air stopped. As described above, this learning involves determining the air-fuel ratio correction value as an extreme value at each lean/rich reversal.
_K2 is sampled and added sequentially, and when the number of samplings reaches "8" (step 520), the state function IF is not "0", so the process moves to step 522, and when m=z8, 523 performs the substitution m←zA, and similarly when m=z9, z10, m←zB, zC in steps 525 and 527, respectively.
Perform the following replacement.

This substitution is based on the engine condition correction values in enrichment zones zA, zB, and zC that perform open-loop control.
K ₃ (zA), K ₃ (zB), K ₃ (zC) are engine condition correction values K ^s ₃ (z8), K ^s ₃ (z9) during secondary air cut in feedback zones z8, z9, z10. , K ^s ₃
This is because (z10) is used. That is, step 528
For example, the correction value found in zone zA corresponds to calculating K ^s ₃ (z8)←K ^s ′ ₃ (z8) + (k/8-1)・α, and m is At the time zA
Since it has been rewritten as , the second step by step 528
When replacing storage device 4, replace the memory at the address corresponding to zone zA (engine condition correction value K ₃ ′ (zA))
It is carried out about. Through the above learning process, the previous engine condition correction values K ₃ ′ (zA), K ₃ ′
(zB), K ₃ ′ (zC) (=K ^s ′ ₃ (z8), K ^s ′ ₃ (z9), K ^s
' ₃
(z10)) is the current engine condition correction value K ₃ (zA),
..., K ₃ (zC).

()-3 t ₃ T (in the case of restarting the supply of secondary air) During the transition period of t ₃ ≦T < t ₄ , when T = t ₃ , steps 507, 508, 509, and 511 are followed. Release the stoppage of the secondary air (see Figure 8).

Then, in step 511, in order to prevent thermal shock _{of the catalyst device 16 when the supply of secondary air is resumed, the latest engine condition correction value K 3 (} m) (m = zA ,zB or
zC) as Q ₁ , the previous engine condition correction value K ₃ ' (m) at T = t ₄ as Q ₂ , perform interpolation calculations in the same way as the interpolation calculations when the secondary air is stopped, and calculate the transition period. Find the engine condition correction value K ^t ₃ (m) at
The discharge amount during the transition period is set using this correction value.

Next, at the stage when t ₄ T is reached, the normal
In other words, the learning returns to the feedback zone and when the secondary air is being supplied.

Returning to FIG. 4, in the next step 6, the basic discharge amount Q' corresponding to the engine operating state (specifically, zone m) obtained in the previous step,
In addition to using the temperature correction coefficient K ₁ and the current air-fuel ratio correction value K ₂ , the latest engine condition correction value currently stored in the address corresponding to the engine operating condition is used.
K ₃ (m) is read from the second storage device 4, and the discharge amount is calculated by the following calculation.

Q=Q'×K ₁ ×K ₂ ×K _3The determined discharge amount Q is converted into a pulse to be applied to the injector 8 in step 7, and the injector 8 injects fuel according to the pulse corresponding to the discharge amount Q. It is discharged into the intake passage 7.

In the above embodiment, the enrichment zone zA,
Engine condition correction value K ₃ (zA) at zB, zC,
K ₃ (zB), K ₃ (zC) are the engine condition correction values K ^s ₃ (z8), ^K s ₃ (z9), K at the time of secondary air cut in the adjacent feedback zones z8, z9, z10, respectively. ^s ₃
(z10), but the point is that the engine condition correction value K ^s ₃ (m) (m = z1 to z10) at the time of secondary air cut in the feedback zone is used as basic data to calculate the engine condition in the enrichment zone. What is necessary is to calculate a state correction value. For example, the engine condition correction value in the enrichment zone zA
K ₃ (zA) is the engine condition correction value K ^s ₃ (z2), K ^s ₃ (z5),
As in the case where the average value of K ^s ₃ (z8) is used, a value obtained by appropriately manipulating the learning value of the feedback zone may be used.

Further, in the above embodiment, the enrichment zone, i.e., the secondary air cut zone, and the feedback zone, i.e., the secondary air supply zone are used.
z9 and z10 may be set as secondary air cut zones. In this case, the supply of secondary air is automatically stopped (cut) in each feedback zone z8, z9, and z10, so the secondary air supply is temporarily stopped.
There is no need to cut the next air, and the engine condition correction values obtained through learning K ₃ (z8), K ₃ (z9), K ₃
(z10) as is in enrichment zones zA, zB, zC
It can be used to calculate the engine condition correction value.

Furthermore, in the above embodiment, the present invention is applied to so-called speed density fuel control in which each operating zone is specified based on the engine speed and intake negative pressure, and fuel control is performed for each operating zone. ,
The present invention is not limited to this.

That is, the present invention provides an air flow meter (sensor) that detects the amount of intake air from time to time in the intake passage of the engine, and uses the amount of intake air detected by this sensor and the engine speed to control the engine speed. The present invention can also be applied to a fuel control method in which the operating state of the engine is specified and the fuel supply amount is set in accordance with the operating state.

In addition, in the above embodiment, the air pump 9
In place of the air pump 9, a reed valve device (not shown) that closes with the positive pressure of the exhaust pulsation and opens with the negative pressure may be used.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of the present invention, FIG. 2 is a system configuration diagram of a fuel control system according to an embodiment of the present invention, FIG. 3 is a schematic diagram of the configuration of the computer in FIG. 2, and FIG. 4 is a fuel FIG. 5 is a flowchart showing the main control routine; FIG. 5 is a flowchart showing the routine for calculating the engine condition correction value; FIG.
The figure is a graph showing the engine operating range divided into multiple zones according to engine speed and intake negative pressure, Figure 7 is a graph to explain sampling of the air-fuel ratio correction value, and Figure 8 is a graph for engine condition correction. This is a time chart showing the timing of temporary stop and restart of secondary air at a learned value. DESCRIPTION OF SYMBOLS 1... Air-fuel ratio sensor ( _O2 sensor), 2... Operating state sensor, 3... First storage device, 4... Second storage device, 5... Control device, 8... Injector,
11... Secondary air supply passage, 12... Secondary air control valve.

Claims (1)

[Claims] 1. An air-fuel ratio sensor that outputs a signal corresponding to the air-fuel ratio of the air-fuel mixture taken into the engine, an operating state sensor that detects the engine operating state, and an air-fuel ratio of the air-fuel mixture taken into the engine. a first storage device in which basic control values for controlling the engine are given in advance in accordance with engine operating conditions; and a first storage device that stores engine condition correction values respectively corresponding to engine operating conditions in order to correct the basic control values. a second storage device; during closed loop air-fuel ratio control, an air-fuel ratio correction value is obtained from the output signal of the air-fuel ratio sensor, and the air-fuel ratio correction value is processed to obtain an engine state correction value; Updates the engine condition correction value corresponding to the engine operating condition at the time of processing, and calculates the air-fuel ratio correction value from the signal of the air-fuel ratio sensor during closed-loop air-fuel ratio control and with the secondary air supplied to the exhaust system cut off. Based on the engine condition correction value obtained by processing the air-fuel ratio correction value, an engine condition correction value during open-loop air-fuel ratio control and when the exhaust system secondary air is cut is calculated, and the engine condition correction value is used as the second The basic control values in the first storage device and the engine stored in the second storage device are stored in correspondence with the engine operating state during open-loop air-fuel ratio control in the storage device and when the exhaust system secondary air is cut. A fuel control device for an engine, comprising: a control device that controls an air-fuel ratio of an air-fuel mixture taken into the engine based on a state correction value and an air-fuel ratio correction value obtained based on an output signal of an air-fuel ratio sensor.